Stress Measurement Introduction

Introduction

TSC have developed a unique system for measuring stress in ferromagnetic metals.

The system is based upon the ACSM (Alternating Current Stress Measurement) technique which measures small changes in the magnetic field caused by changes in stress. The technique does not require contact with the surface under investigation, allowing the operator to make stress measurements with almost no setting up time.

The application of mechanical stress to a metal changes its electrical conductivity and, more significantly, its magnetic properties. In ferromagnetic metals, stresses change the size and orientation of magnetic domains and, in turn, change the magnetic permeability.

In general magnetic, electric and stress fields are non-uniform and hence interact in a complex way. TSC have concentrated on using probes and electronics that give uniform electrical and magnetic fields. The StressProbe instrumentation is capable of measuring absolute value of electrical fields and also detect permeability changes caused by mechanical stress.

The interaction between uniform electrical and mechanical stress fields has been shown to be capable of interpretation. The directional nature of the strains and magnetic fields produces anisotropy in the material properties. A theoretical interpretation of measured electrical or magnetic properties has been developed for anisotropic behaviour and found to be capable of interpreting practical measurements. This work led to the practical use of the Stressprobe as a non-contacting stress measurement tool.

TSC's technology is marketed as TSC StressProbe.

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