A Microprocessor-Controlled Test System Utilizing Relevant Component Duty Cycles

The need for meaningful fatigue tests of hydraulic and mechanical components is ever-increasing. Such tests are often performed in the laboratory. Previous investigations have shown that laboratory test lives will be different than field duty lives if laboratory test cycles used have either a different load or “time at load” than the field duty cycle. Field duty cycles often consist of complex shapes. The closer that the laboratory test cycles approximate the field duty cycle, the better the correlation that can be drawn between laboratory and field lives. This paper presents a technique for predicting field endurance life from laboratory test results which capitalizes on the OSU material failure number theory. It describes a microprocessor-controlled test system which provides an inexpensive, reliable means of producing test cycles which approximate the shape of the field duty cycle. An example application is presented.