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Unformatted text preview: Experiment #1: Static Tensile Testing of Metallic Alloys Materials Science 104 Discussion 2A Introduction Tensile testing of metallic alloys is very important in determining the amount of applied force that a specimen can withstand. These tests could assist scientists in choosing the best type of material for various projects. In order to perform these tests, scientists utilize the tensile test machine which stretches out a specimen at a constant rate and also records data on factors such as the time, load strength, elongation, etc. Other concepts that are important in regards to this experiment include yield strength, ductility, elastic and plastic elongation, stress, and strain. These concepts are all very important in understanding what tensile strength is: the maximum stress that can be sustained in tension. One most note, however, that the results of tensile tests are not always completely accurate in the real world because of the controlled environment. Objective The objective of this experiment is to determine various mechanical properties of two metallic alloys: aluminum and brass. In order to determine these properties, we subject aluminum and brass rods to the tensile test machine to apply a load on the metallic alloy until the point of fracture. While this load is applied, the PLW software will be recording data such as the load and elongation so that we will be able to analyze the data during the elongation. With these data points, we will be able to then plot a stress vs. strain graph. This graph will allow us to calculate the yield strength at a 0.2% offset strain, tensile strength, ductility, and modulus of elasticity. Experimental Procedures Before placing the aluminum and brass rods into the tensile testing machine, we first need to measure the cross sectional diameter and the gage length of the specimens between the two points on the rod using calipers. Following this we then place the rod and secure it in the tensile test machine. The PLW program is then activated and a constant load is applied to the specimen. We then observe as the load cell vs. extensometer chart on the computer screen shows the specimen transitioning through elastic deformation to plastic deformation. We can visually see this occurring as the specimen becomes more deformed as time progresses. After the specimen undergoes plastic deformation for a period of time, fracture occurs and it breaks into two. The smallest cross section is then measured as is the elongated gage length between the two points. We then use the data points from the program to plot a stress vs. strain graph. This procedure is then repeated for the second metallic alloy. Results The first thing we have to do is convert the voltage readings into pounds so that we can create our stress vs. strain curve. In order to do so, we use the equation: y = -0.0017x 2 + 12.098x to convert from mV lb. Once this is converted to pounds, we can then find out the stress on the metallic alloy by using the equation σ = F/A...
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This note was uploaded on 05/08/2008 for the course MATSCI 104 taught by Professor Lan during the Spring '08 term at UCLA.
- Spring '08