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Thursday, 5 February 2015

MECHANICAL AND THERMAL PROPERTIES OF MATERIALS

Summary

After study of material science we came to know that: What is ductile & brittle material?
Application areas of these materials, for example brittle material is hard so we can use it where impact loading will be high and ductile material is soft so it can be used where there is some vibration and high speed rotation.
So why we are going to read this post, let us understand what we will secure after reading this post.
  • We will come to know about the properties of such materials e.g. physical, mechanical & thermal properties after reading this post.
  • We will come to know how we can measure & express the hardness of such material.
  • We will come to know that behavior of such materials under different type of loading like bending load, shear load, tensile load & compressive load.
  • We will also come to know about insulation & its purpose.

Introduction

Material science is a study field that enable us to know which type of material & where we can use such material. It also gives information about different type of material and also tells us that how we can design of any construction element or any engineering element with high factor of safety. 

We should select material for any application after studying of all the factors related to that application.

Problems in material selection

There is some problems during materials selection, (I am giving very brief and if you require details pls. tell me I can give you the details knowledge about the issues during material selection.)
  • Environmental problems in material selection.
  • Economical and price analysis problems in material selection.
  • Design of any engineering components is limited by the materials that are available.
  • Selection of material according to Mechanical properties that we require is very crucial job.
  • Manufacturing & processing problems.
  • There are lots of materials is available and we have to select as per our customer and design requirement.
Let us brief the study of the mechanical behaviour of materials and we will also discuss the basic mechanical properties of the construction materials such as steel, concrete and timber.
 Diagram 1: Stress-strain diagram of steel
Structures are subjected with different types of load, structure are made with different types of construction & engineering materials.
The properties that calculate the behaviour of material in a structure under different types of loading is called mechanical properties .These properties are calculated by testing of specimen of materials.

Stress

When a force is acting on a object and tends to deform the object, the materials of the object exerts an internal resistance force to oppose the changing in dimensions. This internal resistance force per unit area is called as Stress. Its unit is N/m2

Strain

It is defined as change in dimension to original dimension. It is unit less 
Area = A, change in length = ∆l 
Stress = P/A and strain = ∆l/L 
Stress is directly proportional to strain- according to Hooks law.

Let us see 

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