Laboratory report on the tensile testing

Tensile Testing Lab Report

Abstract

The lab report provided presents the basic measurements of polycarbonate and aluminium tensile strengths. Some of the properties of the materials include the tensile strength, yield strength and the comparison of the stress-strain curves of both materials. The materials been used are both cylindrical in shape. The aim of the experiment is attained as the report shows the tensile stress-strain levels of the materials that ultimately show that aluminium has a higher ultimate tensile strength compared to the polycarbonate material. The report presents the material used in the experiment, including the procedure and results attained.

Key Words: Tensile strength, Polycarbonate, Aluminium, Stress-Strain Curve/relationship

Introduction

The Tensile experiment is carried out to determine the elongation curve or load of the specimen provided. The experiment is attained through determining the tensile strength of the specimen and ductility. The tensile experiment is conducted on two different materials; the polycarbonate and aluminium. The Polycarbonate (PC) is a polymer while Aluminium is a metal [1]. The experiment will show how the two materials react to forces when deforming as the deformation depends on the geometry of the materials. Tensile strength is the mechanical behavior of the material. Thus, since force applied on a material is perceived as either stress or strain, it is provided in the following equations:

Stress = σ = P/A

Strain = ε = Lf – Lo/ Lo = ΔL/Lo

σ = stress

ε = strain

P = axial tensile load

Ao = original Cross-section area of the material used

Lo = original length of the material

Lf= final length of the specimen

The aim of the experiment is to determine the mechanical properties of the materials provided while using the tensile testing equipment to attain the properties [3]. The tensile properties of the materials are attained through the application of the Young Modulus strain and stress factors when loading materials. According to young Modulus, the stress-strain relationship is used to form the curve and is equated as E = stress/strain

The tensile experiment involves placing sample materials between grips that will be used to clamp the material. The length and cross-sectional area of the material is used, where weight is applied to the materials on one end and another end is fixed. As weight is increased, the change in the material length is measured, where changes are perceived in the form of a graph. The graph is weight vs the stretch of the material through the experiment time.

1. Place the tensile testing machine in the appropriate form. The machines forms are varied but must be in the form of a calliper to help with the appropriate strength application.

Figure 1: Tensile Testing Machine

laboratory report on the tensile testing

2. Ensure one side of the machine is well fixed by ensurng it cannot move.

3. Measure the original thickness (cross-sectional area) and width (length) of the materials and record the data.

4. The materials will them be placed one at a time on the machine, and start to tighten the grips.

5. The original distance will be measured using the ruler once the material has been placed on the grips.

6. The changes in the material as it deforms will be recorded for the attainment of the tensile strength of the material.

Polycarbonate

Aluminium

Width (Wo)

Thickness (to)

Load at Yield point

-987.1994

Yield Strength

Ultimate Tensile Strength

% elongation

Tensile Strain

Tensile Stress

152.02608

-98.71994

Aluminium Experimental Results

Break (Standard) : Tensile strain (Extension) at Break (Standard)

Break (Standard) : Tensile stress at Break (Standard)

-98.71994

-105.8193

-65.56658

-74.4229

-71.97932

-101.85963

-69.62315

Figure 2: Aluminium Strain-Stress curve

laboratory report on the tensile testing 1

Polycarbonate Experimental Results

Break (Standard) : Tensile strain (Extension) at Break (Standard)

Break (Standard) : Tensile stress at Break (Standard)

152.02608

176.26218

147.75735

134.60406

175.67911

169.88272

139.09409

169.84561

Figure 3: Polycarbonate Stress-Strain Curve

laboratory report on the tensile testing 2

Discussion

According to the results attained, as presented above and in the attached excel sheets, as the materials are introduced to strain-stress tension, they experience a plastic deformation or elastic. The deformation leads to the development of a load relationship to the material extension over time. The stress-strain relationship presents the young modulus curve slopes. According to the slopes, the ultimate tensile strength of Aluminium is at a stress of -65.56658 with the strain at 0.08548. On the other hand, the polycarbonate ultimate tensile strength is at a strain level of 1.19845 with the stress level of 176.2218.

After the elastic deformation occurs and tension application continue, yielding will re-start at the point of deformation. Aluminium and Polycarbonate do not show any definite yielding point [2]. Thus, the yielding point could be attained through dividing a load of 0.2% with the original cross-sectional area. Strain and stress levels of materials are important to determine the behavior of a material [4]. One of the main limitation during the experiment was that unlike aluminium, the polycarbonate is dependent on pressure. The strength of the polycarbonate unlike the aluminium materials increased with increased tension of the material.

Conclusions

The aim of the report was to identify the tensile strength of polycarbonate and aluminium. The experiment presented that aluminium has a ductile behavior unlike the polycarbonate. The ultimate tensile strength of the materials is perceived as the cross sectional area of the material decreases. Aluminium decreased more than the polycarbonate. Thus, the aim of the experiment was achieved, as it showed aluminium has a higher tensile strength compared to polycarbonate. Aluminium is stronger than polycarbonate.

References

ASM, «Introduction toTensile Testing,» in Tensile Testing, NY, ASM International, 20041-, pp. 1- 12.

K. Cao, M. Xinzhong, Z. Baoshan, Y. Wang and Y. Wang, «Tensile Behavior of Polycarbonate Over a Wide Range of Strain Rates,» Material Science and ENgineering, vol. 527, pp. 4056 -61, 2010.

F. Beer, R. Johston, J. Dewolf and D. Mazurek, Mechanics of Materials, New York: McGraw-Hill Companies, 2009.

S. Hashemi, Foundations of Materials Science and Engineering, New York: McGraw-Hill Publishers, 2006.

Appendix

Figure 4: Strain-Stress curve

laboratory report on the tensile testing 3