Piezoelectrically Controlled Actuator
The intermediate strain rate test is initiated by a piezoelectrically controlled actuator. This actuator consists a double action hydraulic cylinder, piezoelectric stack actuator, friction pads, and a bolt to apply preload. The piezoelectric stack actuator expands as a voltage is applied. When the piezoelectric element’s expansion is restricted, it applies a force. The force created by the piezoelectric element is in the normal direction to the friction pads. The friction pads restrict the motion of an extension of the hydraulic cylinder’s piston. This breaking force allows for more energy to be stored in the hydraulic cylinder. When the test is initiated, the voltage is removed from the piezoelectric element. This allows for the energy stored in the hydraulic cylinder to be released; thus, the hydraulic cylinder piston moves in the intended direction to perform a tension or compression test. The maximum force that can be applied to a specimen is 60 kN in the direction of motion. The maximum stroke length of the hydraulic cylinder is 55 mm. Interchangeable grips are used on the end of the extension of the hydraulic cylinder to hold the specimen during the test.