Factor of Safety:
Factor of safety is number used to determine working stress. It is fixed based on experimental works on material. It accounts all uncertainties like, material defects, manufacturing defects, unskilled workmanship, unforeseen loads, temperature effects etc. Factor of safety is dimensionless number. It is fixed based on the experimental works on each material. It can be defined as the ratio of ultimate stress to working stress for the brittle materials or yield stress working stress for the ductile materials.