TENSILE TEST LAB REPORT

4Tensile Test Lab Report

TENSILE TEST LAB REPORT

Table of Contents

3Abstract

3Introduction

4Methods

4Results

5Discussion

6Conclusion

7References

Abstract

This experiment found a linear relationship between strain and stress for each of the two sample materials investigated i.e. aluminium 2000 series and polycarbonate. Hooke’s Law was generally obeyed.

Introduction

Hooke’s Law is one of the fundamental principles in any Tensile Test. According to this law, the relationship between the load and the extension exhibited by an elastic material is linear (Bhargava & Sharma, 2011) which is represented as:

TENSILE TEST LAB REPORT

Where E
refers to the ‘slope’ of the curve

ε refers to ‘strain’ also called ‘Modulus of Elasticity/Young’s Modulus’, and

σ refers to the ‘stress’

According to ……………………………., Young’s Modulus may be defined as the measure of the stiffness of a given material.

In order to investigate how a material behaves when subjected to a given amount of heat and tension, a Tensile Test is usually carried out on that material based on the aforementioned parameters i.e. stress, strain, and slope (Christensen & Bonaquist, 2004).

This experiment, therefore, sought to investigate the behaviour of two sample materials i.e. aluminium 2000 series and polycarbonate when subjected to Tensile Stress using the electromechanical testing machine.

Methods

To begin with, each of the two sample materials i.e. aluminium 2000 series and polycarbonate were loaded on the electromechanical tester which exerts a load at regular rate of strain. Secondly, the load and extension were measured for each of the two samples.

Thirdly, the load was divided by the cross-sectional area which represented the stress. Then, the extension was divided by the original gauge length for each of the two sample materials. Finally, a graph of Stress vs. Strain was plotted for each of the two samples.

Results

Figure 1: Stress-Strain curve for Aluminium 2000 series sample

TENSILE TEST LAB REPORT 1

Figure 2: Stress-Strain curve for the polycarbonate sample

TENSILE TEST LAB REPORT 2

Discussion

From both Table 1 and 2 produced above, it is evident that the two materials are indeed elastic materials as they exhibited a linear relationship for their stress and strain until a given elastic limit point was effectively reached where the stress reduced with increase in strain. This implies that each of the two materials obeyed Hooke’s Law as briefly discussed in the introduction.

From Figure 1 above, it can be seen that for the aluminium 2000 series, the sample 2 reached the elastic limit faster followed by sample 3, and finally sample 1 in that order. Specifically, sample 2, 3, and 1 each reached elastic limits at 781, 846, and 900 respectively. On average, therefore, the ultimate tensile strength for aluminium 2000 series was found to be 842. According to International Conference, JōNo, & Inoue (1992), the ultimate tensile strength for aluminium should range between at least 30 and at most 280. This implies that the approximate value obtained in this experiment varied significantly. This variation may be attributed to such human errors as inaccurate reading of thickly calibrated readings on the electromechanical tester.

From Figure 2 above, it can be seen that for the polycarbonate, the sample 3 reached the elastic limit faster followed by sample 2, and finally sample 1 in that order. Specifically, sample 3, 2, and 1 each reached elastic limits at 2800, 3200, and 3400 respectively. On average, therefore, the ultimate tensile strength for polycarbonate was found to be 3133. According to Verlinden & Cahn (2007), the ultimate tensile strength for polycarbonate should range between at least 2500 and at most 3500 suggesting that the approximate value obtained in this experiment was within the rational values presented by other literatures.

To ensure accuracy of results in future experiments of this nature, it would be prudent to use highly accurate machines (the electromechanical tester) whose calibrations are accurate and clear.

Conclusion

The aim of this experiment was to visualize the behaviour of aluminium 2000 series and polycarbonate when subjected to tensile stress. This was partly achieved as the general linear relationship between the strain and stress of each of the two materials was established as had been expected. A few errors, however, reduced the accuracy of the results found for the aluminium 2000 series material. Overall, the experiment was successful.

References

Bhargava, A. K., & Sharma, C. P. (2011). Mechanical behaviour and testing of materials. New Delhi, PHI Learning Private Ltd.

Christensen, D. W., & Bonaquist, R. F. (2004). Evaluation of indirect tensile test (IDT) procedures for low-temperature performance of hot mix asphalt. Washington, D.C., Transportation Research Board.

International Conference, JōNo, M., & Inoue, T. (1992). Mechanical behaviour of materials- VI: proceedings of the Sixth International Conference, Kyoto, Japan, 29 July-2 August 1991. http://public.eblib.com/choice/publicfullrecord.aspx?p=1838186.

Verlinden, B., & Cahn, R. W. (2007). Thermo-mechanical processing of metallic materials. Amsterdam, Pergamon. http://site.ebrary.com/id/10178530.