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An experimental method is presented that enables stress intensity factors due to residual stress to be determined directly, without prior determination of the residual stress. The method is based on the crack compliance method, where a narrow cut is introduced progressively into the considered component, and the resulting strain change is measured by a strain gage. The required mathematical relations to determine stress intensity factors from strain measurements are established by means of some basic relations of linear elastic fracture mechanics. They are derived explicitly for two exemplary geometrical systems, which allowed for analytical treatment. Experimental data obtained in the case of a steel roller are presented and discussed.

In previous work it has been shown that near surface residual stresses may be deduced from surface strains produced by making a cut of progressively increasing depth. The process of electric discharge wire machining (EDWM), by providing very narrow cuts, greatly improves the ability of the method to resolve a stress gradient near the surface. However, the EDWM process may also introduce residual stresses. In the present work a model for estimating the influence of EDWM is presented, and a procedure for eliminating its effect on residual stress measurement is developed. Experimental results validate the theoretical approach.

The use of thin cuts for residual stress measurement is referred to as the crack compliance method. A computational model is presented for the determination of normal and shear residual stresses near the surface by introducing shallow cuts. The optimum regions for strain measurement are obtained. This method is shown to be considerably more sensitive than the conventional hole drilling method and is capable of measuring residual stresses which vary with depth below the surface.

A new method is proposed for measuring the axial component of an axisymmetric residual stress field in thin-walled cylinders. The specific application considered is determination of the stress at the centerline of a circumferential weld. The method involves strain measurements at the outside wall while a complete circumferential slit is cut to increasing depths from the inside wall. The technique is applied to the simple case of a single pass weld. Experimental results are in good agreement with predicted values.

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A method is proposed for measurement of the hoop stress in an axisymmetric residual stress field in cylinders in which the axial stress is independent of the axial coordinate. The method involves measuring strains at the outside surface while an axial crack is cut progressively from the outside. Experimental results are presented for two short cylindrical rings cut from a long quenched cylinder. Good general agreement is obtained with X-ray and hole drilling measurements of residual stresses.

The strains on the surface near a loaded crack or cut are compared for cuts of different width to depth ratios. General solutions are obtained for an arbitrary distribution of normal and shear tractions on the faces of the crack or cut. Numerical results are presented for normal stress distributions which vary with distance from the surface as power functions of zero to third order. The results are useful for measurement of near surface residual stresses and should also be of value for crack compliance measurements of stress intensity factors.