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MATL 3500
Tensile Lab

Abstract Tensile testing was performed on four brass rectangular samples to determine the effects of different initial conditions on material behaviour. Tensile loads were applied to brass samples until fracturing occurred. The final conditions where measured and recorded at the point of fracture. The four samples had varying sizes and it was determined that the thinner samples could withstand less total load but were able to withstand a higher strain. Completion of this experiment demonstrated the usefulness of tensile testing as well as an understanding of material properties.

Table of Contents
Abstract i
List of Figures iii
Introduction 1
Procedure 2
Results 2
Discussion 6
Conclusion 6
References 7

List of Figures
Figure 1 Typical Stress - Strain Curve 1
Figure 2 Stress Strain Curve With True Stain 2
Figure 3 Instron 8501 2
Figure 4 Sample 1…………………………………………………………………………………3
Figure 5 Sample 2…………………………………………………………………………………3
Figure 6 Sample 3…………………………………………………………………………………4
Figure 7 Sample 4…………………………………………………………………………………4

Introduction
It is important to perform tensile testing on materials to determine what applications they can be used for. By submitting material to tensile testing you can determine certain properties it has which can be very important when designing many different types of structures. When a material undergoes tensile testing it is subjected to a pulling force on each side until the material is deformed or fractures. The data obtained from this can be used to determine the ultimate strength, tensile strength, and yield point of a material. [1]
For the testing four pieces of brass that had a rectangular cross section were used. They had a section with reduced gauge, which insured that the highest stress and therefore a fracture that occurred in the middle of the specimen and inside the measured portion. Every piece of brass had slightly varying dimensions so different stresses and strains could be observed.
The data obtained from each run was used to determine the Young’s modulus, yield strength, ultimate tensile strength, percent reduction in area, elongation at failure and true strain at failure. Many of these properties can be observed in stress vs. strain graphs and are shown in fig.1, along with the general shape of the sample that can be observed at that point. The graph for true stress-strain can be seen in fig. 2.
In the linear elastic region the material will return to its original shape and maintain its original properties if the load is removed. The slope of the curve in this region is the Young’s modulus. Once the strain reaches the proportional limit permanent deformation begins. This point is typically found using the intercept of the curve and a 0.2% offset line. The ultimate tensile strength is point where the sample can withstand the largest load before necking begins. After necking begins the material cannot withstand as high of a load because the cross sectional area of the material is actually decreasing. In true stress analysis the instantaneous area of the specimen is used to calculate stress and strain as opposed to the original area.

Figure 1 Typical Stress - Strain Curve [5]

Figure 2 Stress Strain Curve With True Stain [3]
Procedure
The purpose of this test is to determine the tensile properties of a certain type of brass with different initial sizes (length, width and thickness). Four different size combinations were tested. An Instron 8501 testing device was used to test each piece until fracture; an example of this machine can be seen in fig. 3. It logged the elongation of the piece of brass as an increasing load was applied.

Figure 3 Instron 8501 [4]
Two marks were initially put on the sample piece of brass at arbitrary points in the thinner section of the brass. The distance between these marks was the initial length. The initial thickness and width at the middle of the piece of