An electric-power-saving hydraulic fatigue-testing machine

An hydraulic fatigue-testing machine combining a mechanical hydraulic pulsator and a closed-loop control system has been constructed as a trial. The dynamic capacities for load and stroke ranges are 1 MN superposed by a mean load ranging from 0 to 1 MN and 5 mm, respectively, over a frequency range from 3.3 to 10 Hz. The consumption of electric power and cooling water for this machine is about one third of the servo-controlled electro-hydraulic machine. The stability of this control system is 0.5 percent of the range. Some experimental results are presented to demonstrate the excellent stability of load during fatigue testing.