Distributions Of Residual Stress Components Research Articles

Residual Stresses in Explosively Welded Plates Made of Titanium Grade 12 and Steel with Interlayer

Distributions of residual stress components in explosively welded three-layer plate composed of titanium Grade 12, titanium Grade 1 and SA516 Grade 70 steel are investigated in this paper. The study applied the sectioning and the hole-drilling strain gage methods for residual stress measurement. The results have shown an inhomogeneous residual stress distribution, approximated by fourth-order polynomial along the thickness of a three-layer plate. Biaxial compressive residual stress state is observed in titanium Grade 12 and Grade 1 layers which change to tensile type in the vicinity of the interface between titanium Grade 1 and steel. Microstructure observation reveals the presence of the adiabatic shear bands in titanium Grade 12 layer at the interface with titanium Grade 1 interlayer. The observed distribution of residual stress components is justified by the occurrence of the shock wave phenomena.

高エネルギー放射光を用いた強加工層極表面近傍での残留応力測定と組織変化挙動の考察

It is necessary to establish a measurement method that can evaluate accurate stress on the surface. However, the microstructure evolution takes place near the surface due to severe plastic deformation, since structural members have been superpositioned a lot of working processes to complete. As well known, a plane stress can't be assumed on the severe worked surface. Therefore we have been proposed the measurement method that can be measured the in-depth distribution of residual stress components by using high energy X-ray from a synchrotron radiation source. There is the combination of the constant penetration depth method and tri-axial stress analysis. Measurements were performed by diffraction planes for the orientation parameter Γ = 0.25 of which elastic constants are nearly equal to the mechanical one. The stress components obtained must be converted to the stress components in real space by using optimization technique, since it corresponds to the weighted average stress components associated with the attenuation of X-ray in materials. The predicted stress components distribution agrees very well with the corrected one which was measured by the conventional removal method. To verify the availability of the proposed method, thermal aging variation of residual stress components on the severe worked surface under elevated temperature was investigated using specimen superpositioned working processes (i.e., welding, machining, peening). It is clarified that the residual stress components increase with thermal aging, using the diffraction planes in hard elastic constants to the bulk. This result suggests that the thermal stability of residual stress has the dependence of the diffraction plane.

Residual stress distributions in ship hull specimens

This paper provides an in-depth study of residual stress distributions found in stiffened steel plate structures, such as those typically used in ship hulls. The effect of stiffener spacing on the distribution of residual stress components was studied. The welding heat input was also varied between high and moderate to study the effect of heat input level on residual stress distributions. Four specimens, resembling typical stiffened steel plate structures used in ship hulls were built and tested. Steel plates of 9.5 mm thickness were stiffened by welding L127 × 76 × 9.5 steel angles. The test was completed using the neutron diffraction method. The three normal components of residual stress were obtained in this study. It was found that a lower heat input results in higher tensile residual stress and that there exists a critical stiffener spacing somewhere beyond 250 mm that creates a maximum tensile residual stress value near the welded connection.

Measurement of Residual Stresses in Nuclear-grade Zircaloy-4(R) Tubes—Effect of Heat Treatment

Nuclear-grade Zircaloy-4(R) tubes are produced by a unique manufacturing process known as pilgering, which leaves the material in a work-hardened state containing a pattern of residual stresses. Moreover, such tubes exhibit elastic anisotropy as a result of the pilgering process. Therefore, standard equations originally proposed by Sachs (Z Met Kd, 19: 352–357, 1927; Sachs, Espey, Iron Age, 148: 63–71, 1941). for isotropic materials do not apply in this situation. Voyiadjis et al. (Exp Mech, 25: 145–147, 1985) proposed a set of equations for treating elastically anisotropic materials, but we have determined that there are discrepancies in their equations. In this paper, we present the derivation for a set of new equations for treating elastically anisotropic materials, and the application of these equations to residual stress measurements in Zr-4(R) tubes. To this end, through thickness distribution of residual stress components in as-received and heat treated (500°C) Zr-4(R) tubes was measured employing the Sachs’ boring-out technique in conjunction with electrochemical machining as the means of material removal, and our new equations. For both as-received and the heat treated materials, the axial and tangential residual stresses were significantly higher than the radial and shear residual stresses. The largest residual stress was the tangential stress component in the as-received material, showing a tensile value at the outer surface and a compressive value at the inner surface. At high values of von Mises equivalent stress, the principal directions of residual stress coincided with the principal axes of the tube for the as-received material, as well as for the material heat treated at 500°C.

Metrological justification of reflection hologram interferometry with respect to residual stresses determination by means of blind hole drilling

A description of practical implementing combined technique for residual stress determination in plane thick-walled structures is presented. The main features, which are inherent in a procedure of reconstruction and quantitative interpretation of fringe patterns arising as a result of blind hole drilling in residual stress field, are discussed in detail. Two plane aluminium specimens welded from two equal parts having dimensions 130×80 mm in-plane and thickness of 18 and 12 mm are the objects of investigation. Weld seam is performed along the shortest side of both specimens. A wide set of actual fringe patterns related to both uniform and non-uniform residual stress field is reconstructed. Most of typical fringe patterns are presented as illustrations. A whole set of available interferograms shows that a residual stress field in both thick-walled plane specimens investigated consists of both a uniform and non-uniform part. It is shown that a form of both non-uniform and uniform stress fields remains practically the same along the weld line. Moreover, non-uniform residual stress field at the proximity of weld seam is of similar form for both specimens. Emphasis is made in a choice of the transition model proceeding from a comparison of actual interferograms and reference fringe patterns. For the first time reference fringe patterns are constructed by using data obtained from corresponding actual fringe patterns, which reveal a non-coincidence between specimen's symmetry cross-sections and principal strain directions. It is shown that relations developed for a probe hole drilled in uniform 2-D stress field can be used for deriving residual stress components when fringe patterns obtained reveal a presence of local strain gradients. A good agreement between actual and reference fringe patterns is achieved in a case of local strain gradients existing. Comparing two types of interferograms related to uniform residual stress fields demonstrates their full coincidence. It is shown that the whole set of obtained fringe patterns consists of three main groups. The main evidence, which reveals an interferogram belonging to each specific class, is a typical form of fringes configuration. The main principles of creating the general fringe patterns catalogue are established and initial draft of this catalogue is developed. Distributions of residual stress components are constructed for different surfaces of both specimens under study. Quantitative results have a form that is typical for welded joints of structures bounded by plane surfaces. It is shown that fine nuances inherent in residual stress distributions over different specimen faces can be reliably derived from recorded fringe patterns of any type.

The effect of thermal history on the distribution of residual stresses in PMMA rods

AbstractA nondestructive technique based on the photoelastic properties of transparent polymers has been used to monitor the distribution of residual stress components in circular rods of poly(methyl methacrylate) (PMMA). The influence of various thermal histories on these stresses as well as on the molecular birefringence has been determined. The technique has been further simplified to obtain the values of maximum tensile and compressive residual stresses with the help of just two photoelastic measurements. The stresses so obtained are within 10% of the values obtained using detailed experimental measurements and their analysis. The simplified procedure is, therefore, suitable for “on‐line” determination of residual stresses in extrusion industry.