High Strain Rate Testing Metals

Crash-worthiness is a key part of the design of a modern automobile. Under crash conditions, structural materials are subject to very high rates of strain and loading. Many material properties, including those of the steel or aluminum used in the automobile body, are strain-rate sensitive. Consequently, quasi-static stress-strain data may not produce accurate predictions of behavior at high strain rates, and the use of such data in the analysis and design of dynamically loaded structures can lead to cautious overweight designs or premature structural failure.

Our servohydraulic VHS high rate systems provides metals researchers with extensive capabilities for impact and high strain rate testing. The VHS systems are also able to be configured to perform tests from quasi-static to impact speeds, as well as providing a cyclic testing capability.

The systems incorporate a very high performance hydraulic actuator, featuring hydrostatic bearings and a seal-less piston rod. With high performance control valves, these systems can be configured for speeds up to 25 m (81 ft) per second. Combined with a high-stiffness two or four column load frame, the advanced 8800 control system and Profiler software can assist you in achieving near constant velocity. Patented ‘Fastjaw’ grips are utilized to instantaneously grip the specimen once the actuator has reached the correct velocity for the test.

Testing forces are measured using high-stiffness piezoelectric load cells and a high-speed data collection system that records the entire stress-strain curve at rates up to 5 MHz. These features allow metals researchers to evaluate their materials at a level of detail never before possible. In order to perform high rate tests, we suggest using our HighRate software program operating under Console software. These provide a single user interface for test set-up, firing, data collection and viewing. We suggest using Impulse™ Software for advanced analysis techniques.