Computer-controlled mechanical testing machine for small samples of biological viscoelastic materials

Time dependency in the mechanical properties of viscoelastic materials means that a variety of tests is often required to fully characterize their properties. Computer control is the best way of controlling loads and displacements and the rate at which they are applied, as well as recording and analysing the data produced. This paper describes apparatus for measuring the viscoelastic properties of articular cartilage in compression which is readily adaptable to any small sample in which accurate strain measurements require small, carefully controlled displacements. An IBM-type microcomputer is used to control a stepper motor driving a ball screw with a positional accuracy of about 1 micron.