DETERMINATION OF THE MECHANICAL PROPERTIES

Determination of the Mechanical Properties of Metallic Materials Using Tensile Testing



Determination of the Mechanical Properties

Introduction

Tensile analysis is one of the main key elements in choosing the correct material for its purpose. This report looks at a number of different metallic and non metallic materials and their properties, and how their actual properties stand against the theoretical properties. Analysis has been conducted through extensive laboratory testing and database evaluation, in accordance with BS EN ISO 6892-1:2009. The two machined used for the tensile testing were; non-metallic - Instron Tensile Test Machine, and metallic - Horizontal Tensile Test Machine. The theoretical properties data for the materials was collected and analyzed from various software properties programs and other online sources.

The materials tested:

Metallic

Carbon Steel - 0.1%

Carbon Steel - 0.8%

Aluminum Alloy - Annealed

Pure Aluminum - Annealed

Non Metallic

Polyethylene

Acetyl Resin

Polypropylene

Theory

The aim of this experiment was to calculate and compare the actual properties of the materials with the theoretical properties, through data analysis. The machines used to conduct this experiment, automatically calculated the maximum load, and the load at fracture. The other properties; elongation percentage, modulus of elasticity, yield strength, stress at fracture and strain at fracture, must be calculated manually.

The Objectives

Virtually any material can be exposed to a tensile test. The most widespread components assessed in this way are metals, but any thing from plastics, fibers, and even human hair can be exposed to tensile checking torealise the power and ductility of the material.

Continuum Mechanics of deformable bodies is, unlike rigid bodies. Tensions in mind in continuum mechanics are only those produced by the deformation of the body, sc. only the relative changes in stress are considered not the absolute values. A body is considered free of stress, if the only forces present are inter-atomic forces (ionic, metallic and van der Waals forces) needed to hold the body together and to maintain its shape in the absence of any external influence including the gravitational attraction. Stresses generated during manufacture of the body to a specific configuration are also excluded (Sonne, 1993, 74).

Following the classical dynamics of Newton and Euler, the movement of a body is produced by the action of externally applied forces that are supposed to be of two types. Surface forces and body forces surface forces or contact forces, can do well in the delimitation of the body surface as a result of mechanical contact with other bodies, or the imaginary surfaces required portions of the body, as a result of mechanical interaction between body parts next to the surface (Euler-Cauchy principle stress). When a body acts on the external contact forces, contact the internal forces are transmitted from one point to another within the body to balance their action, according to Newton's second law of motion of conservation of momentum and angular momentum (for continuous bodies of these laws are called Euler equations of motion). Internal contact forces are related to the deformation of the body through constitutive ...