Independent of external loads, there are internal stresses inside structures and materials. These stresses are called residual stresses. Even though “stress” is an abstract term, the plural form “residual stresses” is often used. Residual stresses / Residual Stress terms were first mentioned in literature already in 1841. Since then, the importance of residual stress has become a well-known fact.

Grinding is a chip-forming process which requires high energy to remove material to specified dimensions. The high energy, in return, generates heat which is created by the interactions of the grinding wheel with the workpiece. The generated heat energy is absorbed by the workpiece which increases the temperature of the workpiece from the surface layer into the subsurface zones.

Stresstech is a world leader in developing and manufacturing non-destructive inspection equipment for grinding burn detection and residual stress measurement.

Grinding thermal damages, also known as grinding burns, will shorten the fatigue life and can cause severe failures in dynamically loaded, critical components.

Combined with dimensional inspection, hardness tests and periodic metallographic analysis, the Barkhausen noise analysis method can help close the loop on insuring product quality.

Barkhausen noise gives information from the surface and very close area beneath the surface. Compressive stresses will decrease the intensity of Barkhausen noise while tensile stresses increase it. This fact can be exploited so that by measuring the intensity of Barkhausen noise the amount of residual stress can be determined.

Barkhausen Noise Analysis (BNA) is based on a concept of inductive measurement of a noise-like signal, generated when a magnetic field is applied to a ferromagnet.

Interview with Dominik Dapprich, Managing Director of Stresstech GmbH

Robotized solutions for measuring stresses by X-ray diffraction