Abstract

The objective of this experiment is to test three specimens of different materials in a Tensile test machine and to calculate basic material characteristics such as tensile stress and Young’s Modulus. This report will explain in detail theory and procedures involved in such test and give all results obtained by group C2 on October 2013.

Introduction

Young’s Modulus, also known as Elastic Modulus is a material characteristic that represents stiffness and is defined as the stress along an axis over the strain in the range in which set material behaves according to Hooke’s Law (the elastic region).

One of the methods used for calculating this characteristic is the tensile test, where a sample is pulled apart by a Tensile Testing machine until it brakes.

The aim of this experiment is to perform tensile tests on samples of standard steel, aluminium alloy and copper in order to calculate Young’s Modulus.

In addition to this, also yield stress, tensile strength and percentage elongation and reduction of area will be calculated, only for the standard steel sample.

Theory

Young’s Modulus (E)

Stress (

Strain (

Cross sectional Area (A)

Length (L)

Young’s Modulus (measured in Pascals) is calculated as stress over strain, where stress is Force over Area (measured in Pascals) and strain is the difference in length over the initial length (no units).

Yield stress is defined as the stress at which a material starts to deform plastically.

0.1% proof stress is used for calculating the yield stress when the stress and strain graph of a test piece does not produce a significant flat line which would represent the yield stress region.

Tensile strength is the maximum stress that a material can withstand while being stretched before breaking.

Percentage elongation and percentage reduction of area after fraction is the percentage of how much the test piece’s length and area have increased/decreased after braking in comparison with the initial values.

References: All Formulas and theory 1. An introduction to Mechanical Engineering, Jonathan Wickert, 6th June 2003, Edition 1, CL-Engineering 2. Lecture Notes, Richard Goodey, 2013, London City University Appendices Values For Graphs 1,2 and 3 (Data 1), 0.1% proof Line meeting point (Data 2) , uncertainties (Data 3). Data 1