A Fatigue Test System for a Notched Shaft in Combined Bending and Torsion

This paper describes the design of a two-channel test system that can generate combinations of torque and bending on a round notched specimen. The test frame consists of a specially designed set of hardware for the size and shape of the SAE Fatigue Design and Evaluation Committee's round specimen. The two RAM computer-controlled hydraulic closed loop system provides independent control for each RAM. Load cells and stroke transducers are mounted in-line to provide signals for control and data processing. In addition to a description of the hardware, this paper defines the software that is used to control the system and perform data analysis on five channels of data. The data consist of the two channels of load and three channels of strain from a rectangular rosette. An ultrasonic surface wave technique is used to detect a crack of defined size and automatically halt the test.