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Study of weld line tensile strength in plastic products when products work in different temperature environments
TABLE OF CONTENTS
GRADUATION PROJECT TASKS ....................................................................... i COMMITMENT ..................................................................................................... i TABLE OF CONTENTS ....................................................................................... ii THANK YOU ........................................................................................................ x SUMMARY .......................................................................................................... xi CHAPTER 1: INTRODUCTION .......................................................................... 1
1.1. Overview of research in the subject area:.................................................... 1 1.1.1. Domestic................................................................................................ 1 1.1.2 Foreign.................................................................................................... 3
1.2. Reason for choosing the topic...................................................................... 8 1.3. Research objectives ................................................................................... 10 1.4. Scope and limitations of the study ............................................................. 10
1.4.1. Scope and limitations of the study ...................................................... 10
1.4.2. Limitations of the study....................................................................... 10 1.5. Significance of the research....................................................................... 11 CHAPTER 2 THEORETICAL BASIS ................................................................ 13 2.1. Fabrication of product................................................................................ 13 2.1.1. Overview of PA6 Plastic ..................................................................... 13 2.1.1.1. Definition ...................................................................................... 13 2.1.1.2. Physical properties ........................................................................ 14 2.1.1.3. Chemical properties ...................................................................... 15 2.1.1.4. Application .................................................................................... 18 2.1.2. Overview of fiberglass ........................................................................ 19 2.1.2.1. Definition ...................................................................................... 19 2.1.2.2. Advantages and disadvantages of fiberglass................................. 22 2.1.2.3. Properties ...................................................................................... 23 2.1.2.4. Classification................................................................................. 23 2.1.2.5. Application .................................................................................... 24 2.1.3. PA6 enclosed with fiberglass............................................................... 25
2.1.3.1. Definition and properties of the combination of PA6 and glass fiber ............................................................................................................ 25
ii
2.1.3.2. Uses ............................................................................................... 26
2.1.3.3. Advantages and disadvantages of combining PA6 with glass fiber .................................................................................................................... 27
2.1.3.4. Application .................................................................................... 28 2.2. Injection molding method.......................................................................... 29
2.3. The method of creating tensile samples and elucidating the weld line in plastic tensile samples according to the standard ............................................. 31
2.3.1. Definition of weld line in plastic products .......................................... 29
2.3.2. Elaborating on the process of creating weld lines in the tensile sample ....................................................................................................................... 31
2.4. Tensile testing method. .............................................................................. 33 2.5. Forced Convection with Air....................................................................... 35 2.6. Taguchi Method ......................................................................................... 36 2.7. Data processing method............................................................................. 39 2.8. Neural Network ......................................................................................... 40
2.8.1. Introduction ......................................................................................... 40
2.8.2. Applications......................................................................................... 42
2.9. Machines, Equipment and Software. ......................................................... 40
2.9.1. Dryer .................................................................................................... 40
2.9.1.1. The importance of plastic drying .................................................. 40
2.9.1.2. Basic parameters of the dryer for the topic. .................................. 44
2.9.1.3. Structure of the dryer .................................................................... 45 2.9.1.4. Application of dryer ...................................................................... 45
2.9.1.5. Steps to perform drying ................................................................ 47 2.9.2. Haitian injection molding machine. .................................................... 48 2.9.2.1. Structure of plastic injection machine. ......................................... 48
2.9.2.2. Preliminary steps to perform plastic injection on a Haitian injection machine: ...................................................................................... 49
2.9.3. Tensile Testing Machine ...................................................................... 53 2.9.3.1. Tensile Testing Machine Concept. ................................................ 53 2.9.3.2. Structure and main parts ............................................................... 53 2.9.3.4. Advantages and disadvantages of tractors .................................... 56 2.9.3.5. Application .................................................................................... 57
iii
2.9.4. Thermal gun......................................................................................... 58
CHAPTER 3: EXPERIMENTAL AND SELECTION PROCESS ..................... 60
3.1. Prepare tensile samples for experiments ................................................... 60
3.1.1. Prepare materials ................................................................................. 60
3.1.2. Plastic drying ....................................................................................... 63 3.1.3. Plastic Injection molding process........................................................ 65
3.2. Experiment................................................................................................. 75 3.2.1. Tensile Testing Process for Plastic ...................................................... 75
CHAPTER 4: ANALYSIS AND EVALUATION OF RESULTS, CONCLUSION AND RECOMMEMDATIONS ........................................................................... 93
4.1. Analysis and evaluation of results ............................................................. 93 4.2. Conclusion and Recommemdations ........................................................ 106 4.2.1. Conclusion ......................................................................................... 105 4.2.2. Recommendation............................................................................... 108 REFERENCES................................................................................................... 108
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LIST OF TABLE
Table 1.1: Comparison of the tensile mechanical properties of monolayer InSe. .. 2
Table 2.1: Melting temperature and forming temperature of PA6............................ 15
Table 2.2: Special properties of PA6................................................................................. 16
Table 2.3: The detailed dimensions of the tensile sample. ......................................... 33
Table 2.4: Drying conditions of various plastics ........................................................... 44
Table 2.5: Presong process temperature, mold temperature and shrinkage coefficient................................................................................................................................. 45
Table 2.6: Technical specifications ................................................................................... 49
Table 2.7: Appendix machine specifications .................................................................. 52
Table 2.8: Tractor Specifications ....................................................................................... 55
Table 3.1: Required volume of PA6 and PA6+30% ..................................................... 61
Table 3.2: Average pressure of PA6 plastic..................................................................... 71
Table 3.3: Taguchi results .................................................................................................... 86
Table 4.1: 25 tensile testing samples made from PA6 0%GF. ................................... 94
Table 4.2: 25 tensile testing samples made from PA6 10%GF. ................................. 95
Table 4.3: 25 tensile testing samples made from PA6 20%GF. ................................. 96
Table 4.4: 25 tensile testing samples made from PA6 30%GF. ................................. 97
Table 4.5: Predict the S/N ratio and response characteristics for the newly selected factor settings to the Strain. ................................................................................ 98
................................................................................. 99 Table 4.7. The graph compare the best tensile testing. .............................................. 100 Table 4.8: The graph compare the best tensile testing ............................................... 101 Table 4.9: The graph compares the best tensile ........................................................... 102
Table 4.10: The graph compares the best tensile testing made from PA6 30%GF with ANN data prediction.................................................................................................. 103
Table 4.6: Predict the S/N ratio and response characteristics for the newly
selected factor settings to the Stress
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APPENDIX OF FIGURE
Figure 1.1: Tensile properties of the InSe nanosheet with different loading temperatures. ............................................................................................................................. 1
Figure 1.2: (a) Load-depth curve and responding (b) true stress- true plastic strain curve ............................................................................................................................................ 5
Figure 1.3: Effect of test temperature................................................................................. 5 Figure 2.1: PA6 plastic granules ........................................................................................ 14 Figure 2.2: Application of PA6........................................................................................... 19 Figure 2.3: Fiberglass ........................................................................................................... 20 Figure 2.4 Glass fiber production process....................................................................... 21 Figure 2.5: Application of PA6 GF ................................................................................... 29 Figure 2.6.The weld line in the center of the component. .......................................... 31 Figure 2.7. Internal surface details of the molding die ................................................ 30 Figure 2.8. The formation process of the weld line...................................................... 30 Figure 2.9: Detailed drawing of the tensile sample. ..................................................... 33 Figure 2.10: Tensile testing in the laboratory............................................................... 353 Figure 2.11: Excel software ................................................................................................ 39 Figure 2.12: Dryer ................................................................................................................. 46 Figure 2.13: Plastic injection machine ............................................................................. 49 Figure 2.14: Tensile Testing Machine .............................................................................. 55 Figure 2.15: Heat gun ........................................................................................................... 60 Figure 2.16: How to use a heat gun .................................................................................. 60 Figure 3.1: Electronic scale................................................................................................. 61 Figure 3.2: Electronic scale................................................................................................. 62 Figure 3.3: Plastic weighing process ................................................................................ 63 Figure 3.4: Inside the dryer ................................................................................................. 64 Figure 3.5: Adjusting the temperature accordingly ...................................................... 60 Figure 3.6: Four trays have been divided according to the correct ratio ................ 60 Figure 3.7: PA6 plastic without mixing ........................................................................... 65 Figure 3.8: Injection Molding Machine ........................................................................... 66 Figure 3.9: Injection mold ................................................................................................... 67 Figure 3.10: Hoisting the mold into the machine.......................................................... 68
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Figure 3.11: Hoisting the mold into the machine .......................................................... 69
Figure 3.12: Pouring plastic into the molding machine............................................... 70
Figure 3.13: Performing pressing ...................................................................................... 71
Figure 3.14: Plastic injection parameters ........................................................................ 72
Figure 3.15: Working screen............................................................................................... 73
Figure 3.16: Collecting the product after injection molding...................................... 68
Figure 3.17: Record information on the product ........................................................... 74
Figure 3.18: Put the product into bag ............................................................................... 75
Figure 3. 19: Pressed product ............................................................................................. 70
Figure 3.20: Tensile testing machine ................................................................................ 76
Figure 3.21: Electrical cabinet............................................................................................ 77
Figure 3.22: LAN cable........................................................................................................ 77
Figure 3.23: Screen working on web and software ...................................................... 78
Figure 3.24: Sample jig ........................................................................................................ 78
Figure 3.25: Heat gun fixture ............................................................................................. 79
Figure 3.26: Attach the heat gun to the fixture and place it on the machine table 80
Figure 3.27: Measure the distance from the tip of the gun to the sample............... 81
Figure 3.28: Taking a sample of the tensile sample...................................................... 82
Figure 3.29: Download data file ........................................................................................ 83
Figure 3.30: Minitab Software ...............................................Error! Bookmark not defined.
Figure 3.31: Minitab Software screen .............................................................................. 80
Figure 3.32: Taguchi Design............................................................................................... 84
Figure 3.33: Diagram of the heat transfer principle using gas into the tensile test specimen................................................................................................................................... 81
Figure 3.34: Collect data...................................................................................................... 88 Figure 3.35: The excel table collecting data after tensile testing.............................. 89 Figure 3.36: The main working window while import input and output data....... 90 Figure 3.37: The working when import input data to ANN model .......................... 90 Figure 3.38: Type nnstart ..................................................................................................... 91 Figure 3.39: Result after choosing training levels ........................................................ 91 Figure 3.40: Create the ANN training with 2 layers and 20 neurals ........................ 92 Figure 3.41: Principle with hidden layer and number of neurals.............................. 92
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Figure 3.42: The 4 MSE of 1 modeling presenting. ..................................................... 93
Figure 3.43: Collect predict data after ANN to excel................................................... 93
Figure 4.1 : The mean of Strain of 4 plastic materials ................................................. 95
Figure 4.2: The mean of Stress of 4 plastic materials. ................................................. 96
Figure 4.3 The graph compare the best tensile testing made from PA6 0% GF with ANN data prediction.................................................................................................. 104
Figure 4.4 The graph compare the best tensile testing made from PA6 10% GF with ANN data prediction.................................................................................................. 105 Figure 4.5 The graph compare the best tensile testing made from PA6 20% GF with ANN data prediction.................................................................................................. 105 Figure 4.6 The graph compare the best tensile testing made from PA6 30% GF with ANN data prediction.................................................................................................. 105
Figure 4.7. The line graph of DOE strain of PA6 0% GF ......................................... 109 Figure 4.8. The line graph of DOE stress of PA6 0%GF.. ........................................ 109 Figure 4.9 The line graph of DOE strain of PA6 10%GF ......................................... 109 Figure 4.10. The line graph of DOE stress of PA6 10%GF...................................... 111 Figure 4.11. The line graph of DOE strain of PA6 20%GF...................................... 111 Figure 4.12. The line graph of DOE stress of PA6 20%GF...................................... 112 Figure 4.13. The line graph of DOE strain of PA6 30%GF ..................................... 112 Figure 4.14. The line graph of DOE stress of PA6 30%GF...................................... 112
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LIST OF ACRONYMS
PA6......................................................................................................... Poliamide 6 GF.............................................................................................................Glass Fiber SEM.......................................................................... Scanning Electron Microscope ANN ................................................................................ Artificial Neural Networks GA ............................................................................................... Genetic Algorithm
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THANK YOU
During the entire study process at Ho Chi Minh City University of Technical Education, as well as during the short time spent completing this project. We have received a lot of help, teaching, and dedicated guidance from teachers in the mechanical engineering department along with teachers and teachers from other departments, workshops, and facilities. We sincerely thank our teachers for helping us a lot with both motivation and strong knowledge so that we can complete our graduation project.
In particular, we would like to thank PhD. Nguyen Trong Hieu, Associate Professor. Pham Son Minh and Dr. Tran Minh The Uyen for directly helping us choose the topic. Mentoring and guiding us step by step, helping us clearly understand what the goal of this graduation project is. Teachers regularly have meetings both face-to-face and online to discuss and answer questions that the group encounters during project implementation.
Thank you teachers and the school for supporting us with complete facilities, spacious workshops and suitable modern equipment to Giúp our group save time and effort. It becomes easier to work hard and carry out projects. Not only that, those facilities Giúp us to interact and experience real-life feelings, helping to improve our skills not only in the graduation project but also in other parts of the project.
Because this is a graduation project and an early life lesson for us students, it is inevitable that there will be shortcomings and lack of experience in many different things, resulting in results that may not be perfect or precise. I hope to receive valuable, sincere feedback from teachers as well as friends so that we can collect, correct, and overcome in the future to get a more accurate result.
Once again I sincerely appreciate it!
x
SUMMARY
Research the tensile strength of weld lines in plastic products when the products work in different temperature environments.
Graduation project researches the tensile strength of the weld line in plastic products when the products operate in different temperature environments. This study focuses on evaluating the load-carrying capacity of weld lines in plastic products when faced with temperature fluctuations. Different temperature environments will be experimented to determine their effects on the tensile strength of the weld line.
The implementation method includes using equipment to create plastic products with specialized weld line to measure tensile strength under different temperature conditions including independent variables such as 30% PA6 mass, mass amount of PA6 0%, air temperature around the plastic product, distance of the heat gun to the plastic product, heating time when tensile testing on a tensile testing machine. Evaluating changes in the structure and mechanical properties of plastic products after testing is an important part of research.
Using Taguchi statistical method to obtain a table of parameters during the experiment, and at the same time using linear regression in forecasting to clearly see that independent variables affect output variable (forecast): strain and stress. Then we compare and comment on the results to clearly understand how temperature affects the welding line in plastic products.
The results of the project can provide useful information for plastic product manufacturers, helping them better understand the influence of temperature environment on the tensile strength of weld line. This can lead to improvements in manufacturing processes and product quality, while reducing the risk of failure and minimizing incidents during product use in diverse temperature environments.
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CHAPTER 1: INTRODUCTION 1.1. Overview of research in the subject area:
1.1.1. Domestic
Tensile testing holds paramount significance in the realm of plastics, serving key roles in material selection, design, quality control, performance assessment, compliance, and material development. In Vietnam, companies like Bossard and IMIT stand out for their expertise in tensile testing, ensuring product quality through modern testing facilities. Research studies, such as one by Van-Trung Pham & Te- Hua Fang [1], delve into the effects of temperature on the tensile properties of InSe nanosheets, revealing temperature-induced softening phenomena and reductions in tensile strength and fracture strain. The study also explores Young's modulus, highlighting its sensitivity to temperature variations and the isotropy of single-layer InSe. These findings contribute to a deeper understanding of the mechanical characteristics of materials under tensile stress, aiding advancements in material science and engineering.
Figure 1.1: Tensile properties of the InSe nanosheet with different loading temperatures.
In the figure 1.1: (a) Stress–strain curves of the InSe nanosheet subjected to uniaxial tension along the armchair direction. (b) Stress–strain curves of the InSe nanosheet
subjected to uniaxial tension along the zigzag direction. (c) Young’s modulus.
The comparison of tensile strength, fracture strain, and Young’s modulus of single layer InSe in this research with some other 2D materials is summarized in Table 1.1. It is evident that the results of this work are very close to the results in previous studies. This study provides useful knowledge and can be used as a reference for further studies about monolayer InSe in the future. From this table, it is observed that young modulus
1
of InSe is lower than that of graphene, borophene. The fracture strain of single layer InSe is higher than that of graphene, phosphorene, borophene, which suggests that single layer InSe exhibits notable flexibility. [1]
Table 1.1: Comparison of the tensile mechanical properties of monolayer InSe.
Material
Young’s modulus (N/m)
Tensile strength (N/m)
Fracture strain (%)
Temperature (K)
References
44.8 (zigzag)
InSe
InSe
InSe
12.0 0.44
1 Chang et
0 Huet
1 This research
45.7 (armchair)
9.8
0.35
45.61 (zigzag)
45.61 (armchair)
5.9
11.96
5.2
0.25
0.27
45.42 (zigzag)
0.4437
45.83 (armchair)
9.76
0.3481
1
Graphene
350
39.5
0.2
0
Liu et
Phosphorene 92.01 (zigzag) 22.15 (armchair)
10.0 0.30 4.0 0.27
1 Huet
Borophene
162.49(zigzag)
18.48
0.3
0
Wang et
378.97 (armchair)
12.26
0.12
2
The tensile test is one of the most important engineering tests for concrete reinforcement bars. In this paper, steel tensile tests were carried out with test specimens of CB-300V rebar of VINAUSTEEL Company with diameters of 12, 14 and 16mm. The process of endurance testing according to TCVN 197-1:2014 – method B with WA-1000 testing machine. The values of “upper yield strength”, “lower yield strength”, “tensile strength” were determined through experiment with the fracture subjects respectively. The effect of loading rate (stress rate) on those values was analyzed, based on that, authors suggest the appropriate loading rate range.
Through experimental research on test samples, this article presents the results of tensile experiments on CB300-V rebar steel bars according to current TCVN with different speeds and loads. Due to budget and time constraints, the authors were able to conduct testing for steel bars D12, 14, 16. Based on the experimental results, the authors recommend the loading speed for these steel types as follows: after:
- CB300-V D12 rebar steel bar: 1.0kN/s-1.5kN/s; - CB300-V D14 rebar steel bar: 2.0kN/s;
- CB300-V D16 rebar steel bar: 3.0kN/s;
The application of any loading speed range for rebars with diameter Dÿ18 needs to be further researched in the future. However, based on the results we can preliminarily choose the speed range from 3.0kN/s to a maximum of 6.0kN/s with a step of 0.5kN/s for steel bars from D18 or higher is suitable. [2]
Carbon nanotubes (CNTs) are nanostructures with exceptional mechanical, electrical, and thermal properties. This study developed high-performance composites by vertically aligning multi-walled CNT arrays and fabricating multi- layered sheets. Incorporating these sheets into an epoxy resin matrix using hot-melt
3
prepreg processing resulted in composites with superior tensile strength and modulus compared to traditional methods.
The study employed drawing and winding techniques to create highly aligned multi-layered carbon nanotube (CNT) sheets from spinnable aligned CNT arrays. These sheets were integrated into an epoxy composite using hot-melt prepreg processing with a vacuum-assisted system (VAS), ensuring effective resin infiltration while preserving CNT alignment. The resulting composite exhibited superior tensile strength and elastic modulus compared to both the prepreg and the CNT sheet alone, surpassing conventional mixing methods with an elastic modulus of 56.4 GPa and tensile strength of 217.5 MPa—21 and 2.4 times higher than epoxy resin, respectively. [3]
1.1.2 Foreign
The study explores the impact of tempering temperature on P92 steel's tensile properties using the Automated Ball Indentation Technique (ABI) in the figure 1.2. Published in Procedia Engineering (2014), the research reveals a decrease in yield strength (YS), ultimate tensile strength (UTS), and strength coefficient (K) with higher tempering and test temperatures. The reduction in strength is attributed to increased precipitate size and lath width. Strain hardening exponent (n) decreases with rising test temperature, validated by increased indentation pile-up. ABI results align well with conventional tensile tests, and load-depth curves (the figure 1.2a) are used for true stress-true plastic strain conversion (the figure 1.2b). Regression analysis yields parameters for all test temperatures, showing consistency in ABI and conventional test results.
4
Figure 1.2: (a) Load-depth curve and responding (b) true stress- true plastic strain curve
Figure 1.3: Effect of test temperature
On (a) yield strength, (b) ultimate tensile strength, (c) strength coefficient and (d) strain hardening exponent.
The data from conventional tensile tests in Figure 1.3 shows a decrease in yield strength (YS), ultimate tensile strength (UTS), and strength coefficient (K) with increasing tempering and test temperatures. This decrease is more pronounced at higher temperatures due to increased plastic deformation, attributed to larger precipitate size and lath width resulting from elevated tempering temperatures. Grain size remains unchanged, indicating no significant impact on material strength. Strain hardening exponent values differ slightly between conventional tensile and
5
automated ball indentation (ABI) tests, with ABI tests showing a lower average value due to limited strain hardening. The ABI technique yields comparable results to conventional tests, demonstrating its effectiveness in evaluating tensile properties. The study concludes that varying tempering temperatures influence the tensile properties of P92 steel, and ABI is a reliable technique for such assessments. [4]
Abstract: This paper presents an experimental and numerical investigation into the mechanical behavior of SAE 1045 steel sheet specimens during conventional tensile testing. The study proposes an experimental-numerical methodology to derive elastic and hardening parameters characterizing the material response, particularly in regions of complex stress states at the neck during high levels of axial deformation. This methodology extends established procedures used for cylindrical samples to sheet samples. Finite element simulations based on large strain elastoplasticity are employed to model the deformation process throughout the test. The experimental validation of the numerical results demonstrates the effectiveness of the proposed methodology for 3D analysis of sheet specimens. Additionally, the study discusses the range of applicability of plane stress conditions.
6
Figure 1.3. Analysis of a SAE 1045 steel sheet tension specimen. a) Engineering stress-strain relationship. Results at the section undergoing extreme necking: b) ratio of current to initial width and thickness (mean values along thickness and width, respectively) versus axial elongation, c) load versus true deformation and d) mean true axial stress versus true deformation.
Conclusion: The paper presents experimental and numerical analyses of mechanical behavior during standard tensile tests on SAE1045 steel, focusing on cylindrical and sheet specimens. Initially, material response characterization using cylindrical specimens is conducted to derive elastic and hardening parameters. A finite element elastoplasticity-based formulation is then employed to simulate tensile deformation in sheet specimens, considering derived material properties. Results from both simulations are validated with experimental data. Subsequently, successful experimental hardening characterization of sheet specimens is achieved using a correction factor obtained from simulation. The proposed methodology
7
provides an adequate description of material response during tensile testing using both cylindrical and sheet specimens. [5]
Abstract: Polymers degrade over time, especially at surface and boundary regions, affecting their mechanical properties. Under high strain, they undergo permanent deformation, transitioning from linear elasticity to plastic behavior. The yield point marks the onset of permanent deformation, followed by significant stretching in the plastic region. Strain hardening leads to ultimate rupture, determined by the ultimate strength and elongation at break. Various factors influence polymer behavior, including molecular characteristics, microstructure, strain rate, and temperature. This paper discusses high-strain behavior, failure mechanisms, and physical aging effects on polymers. Additionally, it explores the potential of composite materials, including polymers, in wind turbine blade technology for lighter, more efficient blades.
Conclusion: Tensile testing at intermediate and high strain rates is achievable but complex. In plastics, due to their lower modulus, elastic waves propagate slower, making wave propagation effects significant even at lower rates compared to metals. A high strain rate tensile test was conducted on two materials, PE and PS, at a nominal strain rate of 40/s. Results indicate that the actual strain rate experienced by the specimen varies with the material. Strain rate increases during initial loading and stabilizes at strains exceeding 10%. However, the current strain measurement setup lacks accuracy at small strains, although the range falls below the failure strain of many plastics. [6]
1.2. Reason for choosing the topic
Today, the use of plastic in everyday life and industry is increasingly common, and this is creating significant impacts on all aspects of life and production. Plastic has become a major ingredient in many consumer and industrial products. From household items such as water bottles, bags, food containers to industrial
8
applications such as packaging, automobile manufacturing, healthcare, and many other fields.
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Study of weld line tensile strength in plastic products when products work in different temperature environments
TABLE OF CONTENTS
GRADUATION PROJECT TASKS ....................................................................... i COMMITMENT ..................................................................................................... i TABLE OF CONTENTS ....................................................................................... ii THANK YOU ........................................................................................................ x SUMMARY .......................................................................................................... xi CHAPTER 1: INTRODUCTION .......................................................................... 1
1.1. Overview of research in the subject area:.................................................... 1 1.1.1. Domestic................................................................................................ 1 1.1.2 Foreign.................................................................................................... 3
1.2. Reason for choosing the topic...................................................................... 8 1.3. Research objectives ................................................................................... 10 1.4. Scope and limitations of the study ............................................................. 10
1.4.1. Scope and limitations of the study ...................................................... 10
1.4.2. Limitations of the study....................................................................... 10 1.5. Significance of the research....................................................................... 11 CHAPTER 2 THEORETICAL BASIS ................................................................ 13 2.1. Fabrication of product................................................................................ 13 2.1.1. Overview of PA6 Plastic ..................................................................... 13 2.1.1.1. Definition ...................................................................................... 13 2.1.1.2. Physical properties ........................................................................ 14 2.1.1.3. Chemical properties ...................................................................... 15 2.1.1.4. Application .................................................................................... 18 2.1.2. Overview of fiberglass ........................................................................ 19 2.1.2.1. Definition ...................................................................................... 19 2.1.2.2. Advantages and disadvantages of fiberglass................................. 22 2.1.2.3. Properties ...................................................................................... 23 2.1.2.4. Classification................................................................................. 23 2.1.2.5. Application .................................................................................... 24 2.1.3. PA6 enclosed with fiberglass............................................................... 25
2.1.3.1. Definition and properties of the combination of PA6 and glass fiber ............................................................................................................ 25
ii
2.1.3.2. Uses ............................................................................................... 26
2.1.3.3. Advantages and disadvantages of combining PA6 with glass fiber .................................................................................................................... 27
2.1.3.4. Application .................................................................................... 28 2.2. Injection molding method.......................................................................... 29
2.3. The method of creating tensile samples and elucidating the weld line in plastic tensile samples according to the standard ............................................. 31
2.3.1. Definition of weld line in plastic products .......................................... 29
2.3.2. Elaborating on the process of creating weld lines in the tensile sample ....................................................................................................................... 31
2.4. Tensile testing method. .............................................................................. 33 2.5. Forced Convection with Air....................................................................... 35 2.6. Taguchi Method ......................................................................................... 36 2.7. Data processing method............................................................................. 39 2.8. Neural Network ......................................................................................... 40
2.8.1. Introduction ......................................................................................... 40
2.8.2. Applications......................................................................................... 42
2.9. Machines, Equipment and Software. ......................................................... 40
2.9.1. Dryer .................................................................................................... 40
2.9.1.1. The importance of plastic drying .................................................. 40
2.9.1.2. Basic parameters of the dryer for the topic. .................................. 44
2.9.1.3. Structure of the dryer .................................................................... 45 2.9.1.4. Application of dryer ...................................................................... 45
2.9.1.5. Steps to perform drying ................................................................ 47 2.9.2. Haitian injection molding machine. .................................................... 48 2.9.2.1. Structure of plastic injection machine. ......................................... 48
2.9.2.2. Preliminary steps to perform plastic injection on a Haitian injection machine: ...................................................................................... 49
2.9.3. Tensile Testing Machine ...................................................................... 53 2.9.3.1. Tensile Testing Machine Concept. ................................................ 53 2.9.3.2. Structure and main parts ............................................................... 53 2.9.3.4. Advantages and disadvantages of tractors .................................... 56 2.9.3.5. Application .................................................................................... 57
iii
2.9.4. Thermal gun......................................................................................... 58
CHAPTER 3: EXPERIMENTAL AND SELECTION PROCESS ..................... 60
3.1. Prepare tensile samples for experiments ................................................... 60
3.1.1. Prepare materials ................................................................................. 60
3.1.2. Plastic drying ....................................................................................... 63 3.1.3. Plastic Injection molding process........................................................ 65
3.2. Experiment................................................................................................. 75 3.2.1. Tensile Testing Process for Plastic ...................................................... 75
CHAPTER 4: ANALYSIS AND EVALUATION OF RESULTS, CONCLUSION AND RECOMMEMDATIONS ........................................................................... 93
4.1. Analysis and evaluation of results ............................................................. 93 4.2. Conclusion and Recommemdations ........................................................ 106 4.2.1. Conclusion ......................................................................................... 105 4.2.2. Recommendation............................................................................... 108 REFERENCES................................................................................................... 108
iv
LIST OF TABLE
Table 1.1: Comparison of the tensile mechanical properties of monolayer InSe. .. 2
Table 2.1: Melting temperature and forming temperature of PA6............................ 15
Table 2.2: Special properties of PA6................................................................................. 16
Table 2.3: The detailed dimensions of the tensile sample. ......................................... 33
Table 2.4: Drying conditions of various plastics ........................................................... 44
Table 2.5: Presong process temperature, mold temperature and shrinkage coefficient................................................................................................................................. 45
Table 2.6: Technical specifications ................................................................................... 49
Table 2.7: Appendix machine specifications .................................................................. 52
Table 2.8: Tractor Specifications ....................................................................................... 55
Table 3.1: Required volume of PA6 and PA6+30% ..................................................... 61
Table 3.2: Average pressure of PA6 plastic..................................................................... 71
Table 3.3: Taguchi results .................................................................................................... 86
Table 4.1: 25 tensile testing samples made from PA6 0%GF. ................................... 94
Table 4.2: 25 tensile testing samples made from PA6 10%GF. ................................. 95
Table 4.3: 25 tensile testing samples made from PA6 20%GF. ................................. 96
Table 4.4: 25 tensile testing samples made from PA6 30%GF. ................................. 97
Table 4.5: Predict the S/N ratio and response characteristics for the newly selected factor settings to the Strain. ................................................................................ 98
................................................................................. 99 Table 4.7. The graph compare the best tensile testing. .............................................. 100 Table 4.8: The graph compare the best tensile testing ............................................... 101 Table 4.9: The graph compares the best tensile ........................................................... 102
Table 4.10: The graph compares the best tensile testing made from PA6 30%GF with ANN data prediction.................................................................................................. 103
Table 4.6: Predict the S/N ratio and response characteristics for the newly
selected factor settings to the Stress
v
APPENDIX OF FIGURE
Figure 1.1: Tensile properties of the InSe nanosheet with different loading temperatures. ............................................................................................................................. 1
Figure 1.2: (a) Load-depth curve and responding (b) true stress- true plastic strain curve ............................................................................................................................................ 5
Figure 1.3: Effect of test temperature................................................................................. 5 Figure 2.1: PA6 plastic granules ........................................................................................ 14 Figure 2.2: Application of PA6........................................................................................... 19 Figure 2.3: Fiberglass ........................................................................................................... 20 Figure 2.4 Glass fiber production process....................................................................... 21 Figure 2.5: Application of PA6 GF ................................................................................... 29 Figure 2.6.The weld line in the center of the component. .......................................... 31 Figure 2.7. Internal surface details of the molding die ................................................ 30 Figure 2.8. The formation process of the weld line...................................................... 30 Figure 2.9: Detailed drawing of the tensile sample. ..................................................... 33 Figure 2.10: Tensile testing in the laboratory............................................................... 353 Figure 2.11: Excel software ................................................................................................ 39 Figure 2.12: Dryer ................................................................................................................. 46 Figure 2.13: Plastic injection machine ............................................................................. 49 Figure 2.14: Tensile Testing Machine .............................................................................. 55 Figure 2.15: Heat gun ........................................................................................................... 60 Figure 2.16: How to use a heat gun .................................................................................. 60 Figure 3.1: Electronic scale................................................................................................. 61 Figure 3.2: Electronic scale................................................................................................. 62 Figure 3.3: Plastic weighing process ................................................................................ 63 Figure 3.4: Inside the dryer ................................................................................................. 64 Figure 3.5: Adjusting the temperature accordingly ...................................................... 60 Figure 3.6: Four trays have been divided according to the correct ratio ................ 60 Figure 3.7: PA6 plastic without mixing ........................................................................... 65 Figure 3.8: Injection Molding Machine ........................................................................... 66 Figure 3.9: Injection mold ................................................................................................... 67 Figure 3.10: Hoisting the mold into the machine.......................................................... 68
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Figure 3.11: Hoisting the mold into the machine .......................................................... 69
Figure 3.12: Pouring plastic into the molding machine............................................... 70
Figure 3.13: Performing pressing ...................................................................................... 71
Figure 3.14: Plastic injection parameters ........................................................................ 72
Figure 3.15: Working screen............................................................................................... 73
Figure 3.16: Collecting the product after injection molding...................................... 68
Figure 3.17: Record information on the product ........................................................... 74
Figure 3.18: Put the product into bag ............................................................................... 75
Figure 3. 19: Pressed product ............................................................................................. 70
Figure 3.20: Tensile testing machine ................................................................................ 76
Figure 3.21: Electrical cabinet............................................................................................ 77
Figure 3.22: LAN cable........................................................................................................ 77
Figure 3.23: Screen working on web and software ...................................................... 78
Figure 3.24: Sample jig ........................................................................................................ 78
Figure 3.25: Heat gun fixture ............................................................................................. 79
Figure 3.26: Attach the heat gun to the fixture and place it on the machine table 80
Figure 3.27: Measure the distance from the tip of the gun to the sample............... 81
Figure 3.28: Taking a sample of the tensile sample...................................................... 82
Figure 3.29: Download data file ........................................................................................ 83
Figure 3.30: Minitab Software ...............................................Error! Bookmark not defined.
Figure 3.31: Minitab Software screen .............................................................................. 80
Figure 3.32: Taguchi Design............................................................................................... 84
Figure 3.33: Diagram of the heat transfer principle using gas into the tensile test specimen................................................................................................................................... 81
Figure 3.34: Collect data...................................................................................................... 88 Figure 3.35: The excel table collecting data after tensile testing.............................. 89 Figure 3.36: The main working window while import input and output data....... 90 Figure 3.37: The working when import input data to ANN model .......................... 90 Figure 3.38: Type nnstart ..................................................................................................... 91 Figure 3.39: Result after choosing training levels ........................................................ 91 Figure 3.40: Create the ANN training with 2 layers and 20 neurals ........................ 92 Figure 3.41: Principle with hidden layer and number of neurals.............................. 92
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Figure 3.42: The 4 MSE of 1 modeling presenting. ..................................................... 93
Figure 3.43: Collect predict data after ANN to excel................................................... 93
Figure 4.1 : The mean of Strain of 4 plastic materials ................................................. 95
Figure 4.2: The mean of Stress of 4 plastic materials. ................................................. 96
Figure 4.3 The graph compare the best tensile testing made from PA6 0% GF with ANN data prediction.................................................................................................. 104
Figure 4.4 The graph compare the best tensile testing made from PA6 10% GF with ANN data prediction.................................................................................................. 105 Figure 4.5 The graph compare the best tensile testing made from PA6 20% GF with ANN data prediction.................................................................................................. 105 Figure 4.6 The graph compare the best tensile testing made from PA6 30% GF with ANN data prediction.................................................................................................. 105
Figure 4.7. The line graph of DOE strain of PA6 0% GF ......................................... 109 Figure 4.8. The line graph of DOE stress of PA6 0%GF.. ........................................ 109 Figure 4.9 The line graph of DOE strain of PA6 10%GF ......................................... 109 Figure 4.10. The line graph of DOE stress of PA6 10%GF...................................... 111 Figure 4.11. The line graph of DOE strain of PA6 20%GF...................................... 111 Figure 4.12. The line graph of DOE stress of PA6 20%GF...................................... 112 Figure 4.13. The line graph of DOE strain of PA6 30%GF ..................................... 112 Figure 4.14. The line graph of DOE stress of PA6 30%GF...................................... 112
viii
LIST OF ACRONYMS
PA6......................................................................................................... Poliamide 6 GF.............................................................................................................Glass Fiber SEM.......................................................................... Scanning Electron Microscope ANN ................................................................................ Artificial Neural Networks GA ............................................................................................... Genetic Algorithm
ix
THANK YOU
During the entire study process at Ho Chi Minh City University of Technical Education, as well as during the short time spent completing this project. We have received a lot of help, teaching, and dedicated guidance from teachers in the mechanical engineering department along with teachers and teachers from other departments, workshops, and facilities. We sincerely thank our teachers for helping us a lot with both motivation and strong knowledge so that we can complete our graduation project.
In particular, we would like to thank PhD. Nguyen Trong Hieu, Associate Professor. Pham Son Minh and Dr. Tran Minh The Uyen for directly helping us choose the topic. Mentoring and guiding us step by step, helping us clearly understand what the goal of this graduation project is. Teachers regularly have meetings both face-to-face and online to discuss and answer questions that the group encounters during project implementation.
Thank you teachers and the school for supporting us with complete facilities, spacious workshops and suitable modern equipment to Giúp our group save time and effort. It becomes easier to work hard and carry out projects. Not only that, those facilities Giúp us to interact and experience real-life feelings, helping to improve our skills not only in the graduation project but also in other parts of the project.
Because this is a graduation project and an early life lesson for us students, it is inevitable that there will be shortcomings and lack of experience in many different things, resulting in results that may not be perfect or precise. I hope to receive valuable, sincere feedback from teachers as well as friends so that we can collect, correct, and overcome in the future to get a more accurate result.
Once again I sincerely appreciate it!
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SUMMARY
Research the tensile strength of weld lines in plastic products when the products work in different temperature environments.
Graduation project researches the tensile strength of the weld line in plastic products when the products operate in different temperature environments. This study focuses on evaluating the load-carrying capacity of weld lines in plastic products when faced with temperature fluctuations. Different temperature environments will be experimented to determine their effects on the tensile strength of the weld line.
The implementation method includes using equipment to create plastic products with specialized weld line to measure tensile strength under different temperature conditions including independent variables such as 30% PA6 mass, mass amount of PA6 0%, air temperature around the plastic product, distance of the heat gun to the plastic product, heating time when tensile testing on a tensile testing machine. Evaluating changes in the structure and mechanical properties of plastic products after testing is an important part of research.
Using Taguchi statistical method to obtain a table of parameters during the experiment, and at the same time using linear regression in forecasting to clearly see that independent variables affect output variable (forecast): strain and stress. Then we compare and comment on the results to clearly understand how temperature affects the welding line in plastic products.
The results of the project can provide useful information for plastic product manufacturers, helping them better understand the influence of temperature environment on the tensile strength of weld line. This can lead to improvements in manufacturing processes and product quality, while reducing the risk of failure and minimizing incidents during product use in diverse temperature environments.
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CHAPTER 1: INTRODUCTION 1.1. Overview of research in the subject area:
1.1.1. Domestic
Tensile testing holds paramount significance in the realm of plastics, serving key roles in material selection, design, quality control, performance assessment, compliance, and material development. In Vietnam, companies like Bossard and IMIT stand out for their expertise in tensile testing, ensuring product quality through modern testing facilities. Research studies, such as one by Van-Trung Pham & Te- Hua Fang [1], delve into the effects of temperature on the tensile properties of InSe nanosheets, revealing temperature-induced softening phenomena and reductions in tensile strength and fracture strain. The study also explores Young's modulus, highlighting its sensitivity to temperature variations and the isotropy of single-layer InSe. These findings contribute to a deeper understanding of the mechanical characteristics of materials under tensile stress, aiding advancements in material science and engineering.
Figure 1.1: Tensile properties of the InSe nanosheet with different loading temperatures.
In the figure 1.1: (a) Stress–strain curves of the InSe nanosheet subjected to uniaxial tension along the armchair direction. (b) Stress–strain curves of the InSe nanosheet
subjected to uniaxial tension along the zigzag direction. (c) Young’s modulus.
The comparison of tensile strength, fracture strain, and Young’s modulus of single layer InSe in this research with some other 2D materials is summarized in Table 1.1. It is evident that the results of this work are very close to the results in previous studies. This study provides useful knowledge and can be used as a reference for further studies about monolayer InSe in the future. From this table, it is observed that young modulus
1
of InSe is lower than that of graphene, borophene. The fracture strain of single layer InSe is higher than that of graphene, phosphorene, borophene, which suggests that single layer InSe exhibits notable flexibility. [1]
Table 1.1: Comparison of the tensile mechanical properties of monolayer InSe.
Material
Young’s modulus (N/m)
Tensile strength (N/m)
Fracture strain (%)
Temperature (K)
References
44.8 (zigzag)
InSe
InSe
InSe
12.0 0.44
1 Chang et
0 Huet
1 This research
45.7 (armchair)
9.8
0.35
45.61 (zigzag)
45.61 (armchair)
5.9
11.96
5.2
0.25
0.27
45.42 (zigzag)
0.4437
45.83 (armchair)
9.76
0.3481
1
Graphene
350
39.5
0.2
0
Liu et
Phosphorene 92.01 (zigzag) 22.15 (armchair)
10.0 0.30 4.0 0.27
1 Huet
Borophene
162.49(zigzag)
18.48
0.3
0
Wang et
378.97 (armchair)
12.26
0.12
2
The tensile test is one of the most important engineering tests for concrete reinforcement bars. In this paper, steel tensile tests were carried out with test specimens of CB-300V rebar of VINAUSTEEL Company with diameters of 12, 14 and 16mm. The process of endurance testing according to TCVN 197-1:2014 – method B with WA-1000 testing machine. The values of “upper yield strength”, “lower yield strength”, “tensile strength” were determined through experiment with the fracture subjects respectively. The effect of loading rate (stress rate) on those values was analyzed, based on that, authors suggest the appropriate loading rate range.
Through experimental research on test samples, this article presents the results of tensile experiments on CB300-V rebar steel bars according to current TCVN with different speeds and loads. Due to budget and time constraints, the authors were able to conduct testing for steel bars D12, 14, 16. Based on the experimental results, the authors recommend the loading speed for these steel types as follows: after:
- CB300-V D12 rebar steel bar: 1.0kN/s-1.5kN/s; - CB300-V D14 rebar steel bar: 2.0kN/s;
- CB300-V D16 rebar steel bar: 3.0kN/s;
The application of any loading speed range for rebars with diameter Dÿ18 needs to be further researched in the future. However, based on the results we can preliminarily choose the speed range from 3.0kN/s to a maximum of 6.0kN/s with a step of 0.5kN/s for steel bars from D18 or higher is suitable. [2]
Carbon nanotubes (CNTs) are nanostructures with exceptional mechanical, electrical, and thermal properties. This study developed high-performance composites by vertically aligning multi-walled CNT arrays and fabricating multi- layered sheets. Incorporating these sheets into an epoxy resin matrix using hot-melt
3
prepreg processing resulted in composites with superior tensile strength and modulus compared to traditional methods.
The study employed drawing and winding techniques to create highly aligned multi-layered carbon nanotube (CNT) sheets from spinnable aligned CNT arrays. These sheets were integrated into an epoxy composite using hot-melt prepreg processing with a vacuum-assisted system (VAS), ensuring effective resin infiltration while preserving CNT alignment. The resulting composite exhibited superior tensile strength and elastic modulus compared to both the prepreg and the CNT sheet alone, surpassing conventional mixing methods with an elastic modulus of 56.4 GPa and tensile strength of 217.5 MPa—21 and 2.4 times higher than epoxy resin, respectively. [3]
1.1.2 Foreign
The study explores the impact of tempering temperature on P92 steel's tensile properties using the Automated Ball Indentation Technique (ABI) in the figure 1.2. Published in Procedia Engineering (2014), the research reveals a decrease in yield strength (YS), ultimate tensile strength (UTS), and strength coefficient (K) with higher tempering and test temperatures. The reduction in strength is attributed to increased precipitate size and lath width. Strain hardening exponent (n) decreases with rising test temperature, validated by increased indentation pile-up. ABI results align well with conventional tensile tests, and load-depth curves (the figure 1.2a) are used for true stress-true plastic strain conversion (the figure 1.2b). Regression analysis yields parameters for all test temperatures, showing consistency in ABI and conventional test results.
4
Figure 1.2: (a) Load-depth curve and responding (b) true stress- true plastic strain curve
Figure 1.3: Effect of test temperature
On (a) yield strength, (b) ultimate tensile strength, (c) strength coefficient and (d) strain hardening exponent.
The data from conventional tensile tests in Figure 1.3 shows a decrease in yield strength (YS), ultimate tensile strength (UTS), and strength coefficient (K) with increasing tempering and test temperatures. This decrease is more pronounced at higher temperatures due to increased plastic deformation, attributed to larger precipitate size and lath width resulting from elevated tempering temperatures. Grain size remains unchanged, indicating no significant impact on material strength. Strain hardening exponent values differ slightly between conventional tensile and
5
automated ball indentation (ABI) tests, with ABI tests showing a lower average value due to limited strain hardening. The ABI technique yields comparable results to conventional tests, demonstrating its effectiveness in evaluating tensile properties. The study concludes that varying tempering temperatures influence the tensile properties of P92 steel, and ABI is a reliable technique for such assessments. [4]
Abstract: This paper presents an experimental and numerical investigation into the mechanical behavior of SAE 1045 steel sheet specimens during conventional tensile testing. The study proposes an experimental-numerical methodology to derive elastic and hardening parameters characterizing the material response, particularly in regions of complex stress states at the neck during high levels of axial deformation. This methodology extends established procedures used for cylindrical samples to sheet samples. Finite element simulations based on large strain elastoplasticity are employed to model the deformation process throughout the test. The experimental validation of the numerical results demonstrates the effectiveness of the proposed methodology for 3D analysis of sheet specimens. Additionally, the study discusses the range of applicability of plane stress conditions.
6
Figure 1.3. Analysis of a SAE 1045 steel sheet tension specimen. a) Engineering stress-strain relationship. Results at the section undergoing extreme necking: b) ratio of current to initial width and thickness (mean values along thickness and width, respectively) versus axial elongation, c) load versus true deformation and d) mean true axial stress versus true deformation.
Conclusion: The paper presents experimental and numerical analyses of mechanical behavior during standard tensile tests on SAE1045 steel, focusing on cylindrical and sheet specimens. Initially, material response characterization using cylindrical specimens is conducted to derive elastic and hardening parameters. A finite element elastoplasticity-based formulation is then employed to simulate tensile deformation in sheet specimens, considering derived material properties. Results from both simulations are validated with experimental data. Subsequently, successful experimental hardening characterization of sheet specimens is achieved using a correction factor obtained from simulation. The proposed methodology
7
provides an adequate description of material response during tensile testing using both cylindrical and sheet specimens. [5]
Abstract: Polymers degrade over time, especially at surface and boundary regions, affecting their mechanical properties. Under high strain, they undergo permanent deformation, transitioning from linear elasticity to plastic behavior. The yield point marks the onset of permanent deformation, followed by significant stretching in the plastic region. Strain hardening leads to ultimate rupture, determined by the ultimate strength and elongation at break. Various factors influence polymer behavior, including molecular characteristics, microstructure, strain rate, and temperature. This paper discusses high-strain behavior, failure mechanisms, and physical aging effects on polymers. Additionally, it explores the potential of composite materials, including polymers, in wind turbine blade technology for lighter, more efficient blades.
Conclusion: Tensile testing at intermediate and high strain rates is achievable but complex. In plastics, due to their lower modulus, elastic waves propagate slower, making wave propagation effects significant even at lower rates compared to metals. A high strain rate tensile test was conducted on two materials, PE and PS, at a nominal strain rate of 40/s. Results indicate that the actual strain rate experienced by the specimen varies with the material. Strain rate increases during initial loading and stabilizes at strains exceeding 10%. However, the current strain measurement setup lacks accuracy at small strains, although the range falls below the failure strain of many plastics. [6]
1.2. Reason for choosing the topic
Today, the use of plastic in everyday life and industry is increasingly common, and this is creating significant impacts on all aspects of life and production. Plastic has become a major ingredient in many consumer and industrial products. From household items such as water bottles, bags, food containers to industrial
8
applications such as packaging, automobile manufacturing, healthcare, and many other fields.
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