Page 70 - Fundamental Of Design In Mechanical Engineering

Factor of safety

◦ Guideline for selection of quantities values for factor of safety

are as follow:

Table 2.1 : Types of material and the value of factor of safety

Material fs

1 Cast iron component, failure due to maximum stress 3-5

2 Ductile material (steel, Al) subjected to external 1.5-2

static force. Has proper heat treatment and small
plastic deformation

3 Ductile material subjected to external fluctuating 1.3-1.5
force, fatigue failure

4 Component cam and follower, gears, bearing. 1.8-2.5

Failure cause by small pit.

5 Component piston rod, power rod, power screw or 3-6

stud. Sudden large lateral deflection. Critical

buckling load.

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