Residual stresses are generated during most manufacturing processes involving material deformation, heat treatments and machining or processing operations that transform the shape or change the properties of a material.  These are originated from a number of sources and can be present in the unprocessed raw material, introduced during manufacturing or arise from in-service loading.

In rail wheels, the presence of tensile residual stresses is generally harmful since they can contribute to, and are often the main cause of fatigue failure and cracking.  Compressive residual stresses are generally induced by different means in the wheel material during manufacturing process as these are beneficial since they prevent origination and propagation of fatigue cracks and increase wear and corrosion resistance. It is also important to maintain compressive stress levels within specific safety limits in order to avoid compression stresses in excess of yield limit which would lead to inhomogeneous plastic deformations.

The Innerspec POWERBOX H is the only EMAT portable instrument capable of generating up to 1200V with 8kW of peak power at speeds of up to 300Hz, making it ideal for Stress Measurement on in-service rail wheels. The device contains a built-in transmitter/receiver switch which permits pulse-echo operation required for TOF measurements. The instrument is fully compliant with EN13262 and VPI09 requirements.

This course provides an overview of system operation and configuration for operators and technicians performin residual stress measurements on rail wheels but the knowledge acquired can also be used to evaluate residual stress levels in other metallic components such as plates, pipes, pressure vessels, etc.