An instrument for detecting arbitrary peaks and troughs of a fluctuating stress signal

An instrument has been developed to detect arbitrary peaks and troughs of a fluctuating stress signal. This information is used to perform a fatigue life prediction. The instrument uses an analogue method of detecting peaks and troughs. This is considered to be cheaper and faster than the digital alternative. A microprocessor was employed to read peak/trough values from seven such channels and perform a ‘rainflow’ cycle count of the stress histories. The equipment has been tested on the Humber Suspension Bridge and has been shown to work satisfactorily.