Abstract: A method for configuring a hydraulic actuator to provide energy dissipation capabilities during low energy collisions while controlling energy dissipation during high energy collisions comprises biasing a valve member towards a closed position with a resilient member having a rigidity of between 600 and 1500 lbs/in, applying a low preload to the resilient member, and restricting the flow of fluid by using a stop to limit movement of the valve member away from the closed position.

Abstract: A hydraulic actuator comprises a cylinder, a piston reciprocatingly received within the cylinder, a piston rod connected to the piston and a pressure release mechanism which allows hydraulic fluid to pass from a first side of the piston to a second side of the piston when the actuator encounters shock loading. This permits the piston to move. The pressure relief mechanism includes a passageway extending from the first side of the piston to the second side of the piston and a valve member adjacent to the passageway which releasably engages the piston. The valve member has a closed position where the valve member closes the passageway and engages the piston. A resilient member biases the valve member towards the closed position. A valve member limiter limits movement of the valve member away from the closed position.