Linear calibration of axial load fatigue testing machines (NT TR 579)

Abstract

  A method of linear calibration of axial load fatigue testing machines is proposed. It is built on the understanding obtained from a vibration analysis of the force transfer function from the load cell of the machine to a fabricated calibration bar. The results have been successfully verified on a commercial testing machine installed at SP in Borås. Static and dynamic uncertainties are taken into account and summarized into one quantity which is a function of the bandwidth of the applied test signal. Performing the dynamic characterization in practice consists of making a frequency sweep with the strain gage equipped calibration bar. All the proceeding steps of analysis required to predict an upper bound of the linear measurement error is conveniently handled by software. To make use of the calibration result in testing, the user only needs to understand the concept of test signal bandwidth and the definition of the dynamic error.