Selection Process

We have briefly discussed about the structural materials used in mechanical design. Once you are aware of all these materials existing around us the question will be which one to choose and how? There is a systematic way of selecting material - popularly known as Ashby Process. Following is the outline of Ashby Process.

• Every Material has an array of attributes : density,strength, stiffness, thermal expansion coefficient, refractive index, cost etc.
• Design demands a profile - for example, low density, high strength, in addition to a design objective of minimization cost, deflection etc.
• To begin with, you have to consider all materials.
• Apply property limits - that is maximum allowed limits of a property and reduce the number of candidate materials: for example, eliminate materials that can not work in the service temperature range.
• Use Performance Index/ Material Index to further reduce the set of materials