On the stress distribution in a spherical shell with an off-center curvilinear hole

A numerical analysis is made of the joint effect of two factors of asymmetry—ellipticity and eccentricity—on the stress distribution near a free hole in a spherical shell. The nature of deformation is determined by the predominant factor. Whether there are “fixed” points on the graphs of stress distribution around a small hole at which they intersect depends on how rigidly the outer edge is fixed. As the rigidity of fixation is increased, the points smear __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 1, pp. 113–118, January 2006.     

Residual stress determination using blind-hole drilling and digital speckle pattern interferometry with automated data processing

A combined system of blind-hole drilling and digital speckle pattern interferometry that performs automated data analysis is used to determine the magnitude of the residual stress induced in an aluminum plate subjected to uniaxial tension. The authors perform a finite element analysis of the blind-hole drilling process to adjust the analytical model commonly used for residual stress determination. The relieved displacement field due to the introduction of the blind hole is determined by the evaluation of the optical phase distribution. Using more than 300 values of this displacement field, the magnitude of the residual stress is determined and compared with the applied stress value.     

Wave field in a rectangular plate with an off-center hole

Kazakh Institute of Chemical Technology, Chimkent. Translated from Prikladnaya Mekhanika, Vol. 26, No. 5, pp. 76–81, May, 1990.     

Residual stress measurement using the hole drilling method and laser speckle interferometry part IV: Measurement accuracy

Experimental Techniques -     

Residual stress effect on fatigue striation spacing in a cold-worked rivet hole

The residual stress effect due to cold-working is studied in relation to fatigue striation spacing. Cold-working introduces a compressive stress field around the hole reducing the tendency for fatigue cracks to initiate and grow under cyclic mechanical loading. It is known that fatigue lifetime assessment requires a detailed knowledge of the residual stress profile. X-ray diffraction and 3D finite element analysis (FEA) can be used to determine the residual stress profile. Scanning electron microscopy (SEM) measurements were performed for measuring the striation spacing.     

A general form for calculating residual stresses detected by using the holographic blind-hole method

A general form used for analyzing residual stresses measured using the holographic blind-hole method is introduced in this paper. Adopting the general form presented, the residual stresses can be obtained using three relative displacements measured from a single interference fringe pattern. Even for the case in which phase-shifting holographic interferometry is not employed, interpolating calculations for determining the fringe orders are not needed, since the choice of data points becomes more flexible when using this general form. Two experiments, the first one carried out by the authors and the second one published previously, are used to illustrate the applicability and usefulness of this general form. Suggestions for the applications of this general form are also established via the upper bound error estimations.     

Residual stress evaluation by microscopic strain measurement

Experimental Techniques -     

Residual stress analysis near a cold expanded hole in a textured alclad sheet using X-ray diffraction

In this paper we present the methods of determination and the stress obtained at the periphery of a cold expanded hole in a 2024-T3 Alclad aluminum alloy sheet. The measurements in the aluminum clad were performed by the sin²Ψ method, taking experimental precautions to deal with the texture effects. In the core aluminum a special method had to be implemented to determine the stress values in a direction not accessible to the X-ray diffraction. The strains were measured in sample orientations selected according to the texture characteristics and stress factorsF _ij were used to calculate the stress tensor. TheF _ij values were determined assuming a quasi-isotropic material behavior, after concluding that the stress results were not significantly affected by factors calculated for textured material. The residual stress profile, both in the clad and in the sheet, shows a nearly axisymmetric stress state. Compressive stresses were observed near the periphery of the hole, with values that are higher on the exit than on the entrance face. Residual stresses were also higher in the hoop direction than in the radial direction. They decreased with the radial distance to the hole and affected the previous stress state over a distance of 6 mm. The plastic deformation induced by the cold expansion is well evidenced by the FWHM values, which in the affected zone decrease with increasing distance from the hole edge.     

An accurate and efficient computational method for seeking two equi-tangential stress hole shapes

Archive of Applied Mechanics - As an infinite elastic plane containing two holes subjected to uniform remote loading, the tangential stress concentration degree around the holes is related to the...     

Photoviscoelastic stress analysis of a plate with a central hole

An epoxy resin containing excessive plasticizer was developed and characterized. The material, which deforms viscously at room temperature, has optical properties that depend on stress and strain. A tensile specimen was prepared from the epoxy resin so that the mechanical and optical properties of the epoxy resin could be characterized. The elastic and plastic behavior was determined at 37°C using tensile stresses between 4 and 26 MPa. The birefringence was also recorded as a function of time and stress. From these results, a photoviscoelastic constitutive equation was constructed to describe the dependence of the birefringence on stress and strain. The constitutive equation was then applied to study the deformation of a tensile specimen containing a central circular hole. By using the isochromatic fringes in combination with the isoclinic, the time-dependent variation of the stress field in the specimen was solved.     

Maximum stress in a tensile strip with a large hole

Measurements were made to decide between two solutions of the title problem. In question was the limiting value of the stress-concentration factor at the edge of a large hole in a tensile strip as the hole diameter approached the strip width. The results indicate that the stress-concentration factor is near two and support one of the solutions with a minor qualification.     

Residual stress measurements on cold-formed profiles

Experimental Techniques -     

Non-linear least-squares solution to the moiré hole method problem in orthotropic materials. Part 1: Residual stresses

The hole method problem relates to two inverse problems of interest: the first, most commonly addressed by practitioners, is to obtain residual stresses; the other, generally neglected, inverse problem can be posed as either a stress separation problem or a material elastic properties identification problem. In both this Paper I and Paper II, we pose and solve this dual hole method problem in an orthotropic plate, using computer generated moiré isothetics, by means of a non-linear least-squares approach. In Paper I we address the residual stress problem. In Paper II we pose the use of moiré isothetics as a means to achieve separation of stresses, but we deal with the determination of the five orthotropic elastic constants, four of which are independent.     

Magneto-elastic stress induced by an electric current in an infinite thin plate with an elliptical hole

Two-dimensional magnetic field and stress analyses have been presented for soft ferromagnetic, paramagnetic, and diamagnetic materials of an infinite thin plate with an elliptical hole under steady electric current. The magnetic stress has been analyzed in the Maxwell Stress Model. Except for the approximation of the plane stress state since the plate is the thin plate, any assumption is not made for the stress analysis, though the Maxwell stress components are expressed by nonlinear terms. The boundary condition expressed by Maxwell’s stress is completely satisfied without any linear assumptions on the boundary. Two ways for the boundary condition are stated. The analysis of σ _z in the direction of the plate thickness is also carried out. Figures of the magnetic field and stress distribution are shown. Stress intensity factors are also derived, and the magnitude of the stress intensity factor for the magnetic stress and thermal stress due to the Joule heat caused by the electric current is discussed.