Residual Stresses Measurement Using an Indentation Made by an Impact Load

The impact-indentation stress measurement method makes use of the principle of superposition stress fields resulting from the residual stresses and the surface plastic deformation. The main laws measuring stress by impact-indentation method are that, in the direction of major stress, the strain increment is in direct proportion to major residual strain in same indentation sizes and the strain increment in the fixed distance from center of indentation is in direct proportion to indentation size in the same residual stress fields. The stress measuring equipment has been developed and has more advantages than the hole-drilling method, such as higher precision, nondestructive, more convenient and rapid in the measuring process. Generally, its measurement error is less than 15 MPa. It has successfully applied in measuring residual stresses of various welded structures in the field.