Determination of the Necessary Geometric Parameters of the Specimen in Ring-Core Method

Abstract

There are several measuring techniques for determining residual stress which can be divided according to the created damage in to the construction in non-destructive, semi-destructive and destructive ones. One of the most common is semi-destructive hole-drilling method. This paper deals about Ring-Core method which is based on the similar principles. Today, there is no standard for the Ring-Core method, thus it is important to consider various influential factors. One of them are the dimensions of specimen. Calibration coefficients are determined by finite element (FE) analysis using the commercial software Solidworks. These coefficients are used for residual stress evaluation by incremental method used in Ring-Core method. The influence of different specimen dimensions on the accuracy of the evaluated residual stresses is considered.

Estimation of Residual Stress Field Uniformity when Using the Ring-Core Method

“…Therefore the influence of the specimen´s thickness, width and length on the method applicability was the main part of the research. The previous research of incremental method [8] at the authors´ workplace showed, the minimal specimen´s dimensions are 30mm x 40mm x 50mm for residual stress evaluation using universal set of calibration coefficients. Now the minimal specimen´s dimensions for using the integral method are considered.…”

Comparison of Different Simulation Approaches in Ring-Core Method

“…Thus the method is suitable for the evaluation of residual stress uniformly distributed through the model thickness. The strain gage sensitivity to the inner stress is determined by the calibration coefficients K 1 , K 2 calculated by equations (2)-(5) [1,8].…”

“…From published works it is known that only one universal set of calculation coefficients is needed, which is unique for specific material parameters, type of strain gage rosette and the parameters of created notch, to determine the direction, sense and magnitude of the residual stress components inside the component [1,4,5,6,7]. Thus the simple model of a cube with sufficiently large dimensions to avoid unwanted boundary influences on calculation accuracy was chosen as a simulation model.…”

“…However the connections between experimental measurement and simulation studies is still not sufficient which is showed by lack of some international standard. Prerequisite for experimental usage of the Ring-Core method for evaluation of the residual stress components in material is the determination of adequate calculation coefficients and constants [1,2,3]. Sensing of the stress changes inside the material by the sensor attached at the top of the component is not suitable by using the classic Hook´s law.…”

Integral method coefficients for the ring-core technique to evaluate non-uniform residual stresses

“…Hole-drilling is a well-established procedure defined by internationally accepted standards. 1,2 Ring-core was introduced more than 20 years ago; [3][4][5][6] however, it was deeply investigated and developed only recently, especially in terms of sensitivity and uncertainty analysis, [7][8][9][10] and even applied at the microscale. 11,12 In hole-drilling, the material is removed at the centre of a rosette, and thus the relaxed strains are measured at the periphery of the hole, whereas in ring-core the strains are measured in the central internal region, as shown in Figure 1.…”