Vibration testing, particularly when performed in reliability test chambers, is very costly. Design considerations for vibration expander heads that will accept several test specimens for simultaneous testing are discussed in this report. Well-designed expander heads will provide more meaningful results and reduce test time and costs through maximum utilization of test hardware.
This article, the first of a three-part series, discusses natural frequency equations for square, constant thickness expander heads. Parts II and III will cover damping equations for square, constant thickness expander heads and the inverted truncated pyramid expander head. Complete derivations accompany each expander head equation.