Correct Answer - Option 4 : lower yield stress
Ultimate load is defined as maximum load which can be placed prior to the breaking of the specimen. Stress corresponding to the ultimate load is known as ultimate stress.
When a specimen is loaded beyond the elastic limit the stress increases and reaches a point at which the material starts yielding this stress is called yield stress.
Safe working stress is known as the maximum allowable stress that a material or object will be subjected to when in service. This stress is always lower than the Yield stress and the Ultimate Stress .
Working stress = Yield stress/Factor of safety
