Measurement of Fiber-scale Residual Stress Variation in a Metal-matrix Composite

Abstract

The crack compliance, or slitting, method was used to measure a localized depth profile of residual stresses in a metal-matrix composite. The composite consisted of a matrix of Kanthal, a Fe–Cr–Al refractory alloy, reinforced with continuous uniaxial tungsten fibers. The stress measurements involved successively deepening a narrow slit between the fibers in the matrix, and measuring the resulting deformations with a surface strain gage. The depth profile of the in-plane residual stress components was determined from the measured strains using an eigenstrain-based extension of the residual stress calculation scheme normally used for slitting measurements. To validate some of the eigenstrain assumptions, the measured residual stresses were compared with the predictions from a thermomechanical finite element model. The model used a mesh of the actual fiber arrangement in the composite specimen rather than the commonly used unit-cell model. Compared to other techniques for measuring residual stresses in composites, the slitting measurements provided spatial resolution to a small fraction of the fiber diameter, which is useful when validating a thermomechanical model. Coincidentally, this is the first reported slitting method measurements of shear residual stresses.

Eigenstrain modelling of residual stress generated by arrays of laser shock peening shots and determination of the complete stress field using limited strain measurements

“…ACCEPTED MANUSCRIPT 5 Korsunsky et al [5] successfully constructed the residual stress induced by welding; Prime and Hill [6] determined fibre scale residual stress variation in metal-matrix composites; and Korsunsky [7] evaluated residual stresses in autofrettaged tubes. A similar approach has been used by DeWald and Hill [8] to determine the residual stress generated by LSP.…”

Three-Dimensional Constraint Effects on the Slitting Method for Measuring Residual Stress

“…l{b)), the point load is replaced with a uniform line load at constant x, denoted ¿3 {x, a) that has a unit resultant. The strain response to Ô at the strain gauge is denoted with G. The G notation will correspond to the introduced ô notation to signify the specific problem (5) where the parameter dependence of the strain responses is specifically indicated.…”

“…In parallel to the method being applied to a broad range of materials and at various length scales [3][4][5][6][7], a series of studies have also targeted the method itself and its error sources. These studies were primarily motivated by the need to quantify systematic errors as part of writing an international standard for the slitting method.…”

Stress Relaxation in Shot-Peened Geometric Features Subjected to Fatigue: Experiments and Modelling

“…an eigenstrain). The eigenstrain technique is an efficient tool to model the residual stress state present in a component and the technique has been successfully used for other applications: for instance, modelling residual stress generated due to laser shock peening [5][6][7]; stresses induced due to welding [8]; and fibre scales residual stress variation in metal-matrix composites [9]; and etc. The current paper exploits a hybrid eigenstrain/FE approach to model residual stress relaxation in shot-peened components.…”