Statics Course Work Report
Summary

Aim and Objectives
By testing three different unknown materials with the tensile test procedure and instruments the objective is to find what material is by using all the theoretical formulae, considering all the errors that may occur during all the phases of the test, from the marking of the specimen to the final measurement, usually the errors are always made from the people working in to the laboratory so we can expect errors in all the measures.
Other than that the aim is to find a value as close as possible to the theoretical values of the materials so we can say what materials are and so justify their behaviors under certain condition of stress.

1 Introduction
1.1 What is the Tensile Test

The tensile test, tests the strength of a material by applying a pulling force to a material until the material or specimen changes shape or breaks.
Using the tensile test is a way to find a really large variety of information about the specimen.
The tensile test is usually performed on materials such a metals, plastic wood and ceramics.
The test can describe how the specimen reacts when a tension is applied and so the engineers can determine were the material will be more suitable for the researched purposes.
For the tensile test are used a number of different unit of measurement. The more used are Newton per square meter (N/m2) or the Pascal (Pa).

1.2 The Specimens

The shape shown in the picture is the typical shape that tensile test specimen usually have, as you can see the shape is not even, this is because the large diameter is for gripping. The diameter that we are interested in is the smallest or the gauge section. This section of the specimen is reduced so we can predict that the failure will happen in this section, the gauge is also the part of the specimen where the engineers are going to take all the measurements. There are various way of gripping a specimen, but for our purposes the type shown in the picture is the better choice.

1.3 The testing machines

There are several types of testing machines, and everyone has a different use, for our test we used the standard tensile test machine. The machine was an hydraulic one so it applied the tension using a series of hydraulic pistons. There was just one moving piston in our machine, and the speed was of 1mm/s.

2 The Experiment
2.1 The measurements and instruments.

Before doing any experiments with the specimens you need to measure each of the specimens because you will need these measurements to plot all the graphs and to compare your result with the standard tables of the properties for see witch material you just tested.
In particular you will need the measures of:
Length of the gauge before and after the test.
Diameter of the gauge before and after the test. For taking all the measures we used a vernier caliper. Joseph R. Brown invented this device in the 1985, and this was the first tool that had a reasonable price, so all the people could buy one. After that there were more model of caliper, in our experiment we used a caliper with a digital display so the errors in the reading of the values could be minimum. For keeping the errors at a really low level we also took three measures from the same specimens so we could do the median of the measure and hence have a really low ratio of errors.

(the measurements processed on excel)

There are not measurements for the length of the gauge before the test, because the laboratory personnel made the measurements.

2.2 The practical experiment

After taking all the measures, the experiment can start, one at the time the specimens are loaded in to the Tensile Test machine, after the specimen is loaded and the clamps are closed an extensometer is attached to the specimen. This device measures the extension