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Micro-Raman spectroscopy was used to analyze machined germanium residual stress profiles. The results showed that the stress field in germanium semiconductors was characterized by a surface layer under compression, compressive-to-tensile transition and a deeper-lying region of tension. The transition from plastic to elastic deformation was indicated by an abrupt transformation.

The influence of residual stresses and defects on the upper strength limit of cold-formed steel columns is investigated using Jezek's method of column curve construction. The yield stress at the corners of the columns was also studied together with the buckling behavior of the column through a new concept called second reduction. Results show that the hypothetical values obtained conform to existing data andthat he changes in the yield stress at the corners could be disregarded in the analysis. The new column curve derived shows good match to the AISC LRFD columncurve.

The study of the residual stresses in Fe40Ni40(Si + B)19Mo1 and Fe40Ni38B18Mo4 amorphous ribbons is discussed. The coercivity increases linearly with the increase in stress applied on the region above 80 MPa for Fe40Ni40(Si + B)19Mo1 and 50 MPa for Fe40Ni38B18Mo4.

The probability of accelerating two-dimensional unsteady compressible flow computations with a generalized minimal residual (GMRES) technique employing a conjugate-gradient-like technique to accelerate the convergence of current solvers, was explored. A Newton iterative time-marching scheme that helped solve two-dimensional compressible Navier Stokes equations in a curvilinear body-filled coordinate system can be used as a preconditioner.

Hydraulic expansion of a tube into a grooved tubesheet is modeled as an elastic-plastic process. A special shell theory is used to obtain the tube residual stresses in the vicinity of the grooves. It is found that the maximum tensile residual stresses occur at the inside surface of the tube, but their magnitudes are lower than those in the transition region. The results also suggest the use of a higher hydraulic forming pressure for grooved joints than for ungrooved joints.

This paper presents results of a finite element study of the severe cold bending of thick, high-strength steel plates using an explicit, two-dimensional, finite element code. A parametric study was performed to study the effect of contact surface conditions and the plate's material model on the behavior of the plate during cold bending. The results of these numerical studies were compared with experimental data measured by Weng in 1984 and analytical equations proposed by Dat in 1980. It was found that the model with isotropic hardening and no friction showed the best agreement with the experimental and analytical results.

Byline: Janez Grum The paper provides a short survey of the technical literature on induction surface hardening. A general introduction is followed by a description of metallurgical aspects of induction heating, the discussion being focused on the dependence of the heating rate and the temperature required for homogeneous austenitising from the heating time. Particular attention is thus paid to temperature-time dependence in induction surface heating with reference to power density and heating time at a given high current frequency. This is followed by a description of modes of quenching and the related changes of internal stresses and occurrence of residual stresses in modelling and experimental measurement with both heat-treatment steels and case-hardening steels. Finally, the relationship between fatigue strength for finite life and fatigue strength of different steels is shown in relation to different modes of heat treatment.

Byline: Alexander Lepeshkin, Stepan Lepeshkin The features of regimes of induction heating and cooling for superficial high intensive hardening of details are considered. The opportunities of the software package developed for the calculation of parameters of an electromagnetic field, non-stationary thermal and thermo-elastic-plastic state at heating and cooling, and the residual stresses after hardening with the use of a final element method are shown. Investigations of high-frequency induction heating processes for superficial high intensive hardening with different specific superficial powers, including the definition of thermal stress at any moment in the heating and cooling process, are carried out. The distributions of residual stresses are determined in view of phase transformations into a material of a detail. The results of investigations and recommendations are given for the choice of parameters and regimes of induction superficial hardening of details in view of the restrictions on thermal and residual stresses.

The micro-Raman scattering technique is employed for the characterization of the residual stress in the freestanding GaN-based micromechanical structures on various silicon substrates, which are normally manufactured by a dry release technique. The results prove that the GaN mechanical structures on Si platforms are very important, as they can be successfully used for the fabrication of various microelectromechanical systems and sensors.

An analytical model is developed for analyzing the edge effects on the stress gradients in the film and the substrate. The closed-form solutions for the stresses in the film and the substrate are obtained by using the shear lag model in the planar geometry to analyze the stress transfer problem.

An analytical model is developed to obtain the closed-form solutions for the interfacial stress distributions along the film width. The results have shown that the present model is more rigorous and the analytical results have agreed with finite element results, but the stress singularity occurring at the points near the edge has influenced the stress distribution.

A method was developed for the evaluation of the residual stresses and the biaxial modulus of thin films and the interfacial fracture energy of the interface between the thin film and the substrate. Micron-scale cantilever bilayer beams and a computational method were used to determine the elastic properties of the bilayer beams and it was found that the average residual stresses in the Ti thin films are tensile stresses which are independent of the layer thickness.

Byline: J. Grum, F. Ravnik The purpose of controlling the hardening process by selecting the most suitable quenching parameters is to ensure the required hardness and the residual stresses, particularly in the surface layer of a machine part. The article describes the system designed to capture acoustic emission in different quenching media, which includes the assessment of hardening efficiency during the quenching process itself. Analysis of these acoustic emission signals can give useful information and confirm the differences caused by different quenching conditions. The sound pressure signal, as the variation of time dependent amplitude at different frequencies, is presented by 3D diagrams. Analysis of the quenching results, i.e. cross-sectional hardness of the workpiece and the acoustic emission signals during the process itself, leads to a new approach in the monitoring of the hardening processes.

The ferromagnetic resonance (FMR) on a system consisting of a ferromagnetic (FM) film and antiferromagnetic films is studied. The results reveal that the system with an applied or residual stress anisotropy has some symmetrical, or equivalent, directions of the hard and easy axes.

The residual stress of Pt thin films deposited on Ti/SiO2/Si substrates cooled down from different annealing temperatures to room temperature is quantified by the x-ray diffraction (XRD) method. The relationship between residual stress and microstructural changes of Pt/Ti films, which is closely related to the diffusion and oxidation of Ti in the annealing process, is discussed.

Two significant applications of multiple coating cracking phenomenon are found. The method to define the effective substrate thickness that is useful in analytical modeling of the stress transfer phenomena in coating/ substrate systems is also proposed.

A simplified mechanical analysis is used to estimate long-range residual stresses induced by punching and a magnetoeleastic coupled model predicts their influence on the global magnetic behavior of the device. These residual stresses have a small local influence on the permeability, compared to plasticity, but they affect a larger volume of material so that at the end their global magnetic impact is as large as the one of the plasticity.

In this paper, detailed weld residual stress analyses are presented for a typical multi-pass girth weld in Type 316L stainless steel pipe with r/t ratio of 25. Advanced finite element procedures were used to simulate the residual stress development under controlled welding conditions associated with weld mock-ups. Both axisymmetric and 3-D special shell element models were used to reveal local residual stress details and global residual stress characteristics in the girth weld. Residual stress measurements using hole-drilling method were conducted for model validation on the laboratory weld mock-up welds. A good agreement between finite element predictions and experimental measurements were obtained. The major findings include: (a) Axial residual stresses within and near the weld area exhibit a strong bending feature across the pipe wall thickness, while the hoop residual stresses showed a much less variation through the wall thickness. (b) Some periodic variation of the residual stresses is present along the pipe circumference near the weld, particularly for the axial residual stress component. Such a variation tends to become more pronounced in thick wall than in thin wall girth welds. A 3-D model is essential to adequately capture such 3-D features in residual stress distributions. (c) A rapid variation in weld residual stresses can be seen at start/stop positions, where a high magnitude of axial residual stresses is present in both tension and compression. [DOI: 10.1115/1.1359527]

A. J. WHITTLLE [1] R. P. BURFORD [2] M. J. HOFFMAN [3] The effects of residual stress in modified poly(vinyl chloride) pipes upon the relationship between pressure tests and C-ring [...]

An experimental study was conducted to determine the influence of high-pressure waterjet (WJ) peening and abrasive waterjet (AW J) machining on the surface integrity and texture of metals. A combination of microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface texture that result from the material removal process. The measurement and evaluation of residual stress was conducted with X-ray diffraction. The residual stress fields resulting from treatment were analyzed to further distinguish the influence of material properties on the surface integrity. It was found that waterjet peening induces plastic deformation at the surface layer of metals as good as shot peening. The degree of plastic deformation and the state of material surface were found to be strongly dependent on the peening conditions applied. [S0094-9930(00)00801-5]

An analytical model for predicting the level of autofrettage following either inner, outer, or combined machining of a gun barrel is developed based on Hill's (Hill, R., 1950, The Mathematical Theory of Plasticity, Clarendon Press, Oxford, U.K.) solution for the autofrettage residual stress field. The analysis results in very simple algebraic expressions for the post-machining level of autofrettage in terms of the original level induced in the blank tube. In parallel, a finite element analysis of the machining process is performed in which the residual stress field is simulated by an equivalent thermal load. The numerical results are found to be in excellent agreement with the analytical ones. Thus, as an equivalent thermal load can always be determined, either analytically or numerically, for any other approximations to the residual stress field due to autofrettage (Perl, M., 1988, ASME J. Pressure Vessel Technol., 110, pp. 100-102), the foregoing methodology can be readily applied, enabling the determination of post-machining autofrettage level in these cases. [S0094-9930(00)00501-1]

We present a new and simplified method of estimating residual stress in welded structures by using inherent strain. The method makes use of elastic analysis by means of the finite element method and is used to calculate the residual stress in complicated three-dimensional structures efficiently. The inherent strain distribution in a welded joint of a small-diameter pipe penetrating a pressure vessel was assumed to be a simple distribution, and the residual stress was calculated. Inherent strain distributions were inferred from those of welded joints with simple shapes. The estimated residual stress using these inferred inherent strains agrees well with the measurements of a mock-up specimen. The proposed method is a simple way to estimate welding residual stress in three-dimensional structures of complicated shapes.

Crossbore intersections in liquid ends of positive displacement pumps (PDPs) have regions with high stress concentration. Due to the cyclic loading that occurs in most PDPs, these stress concentration points are susceptible to fatigue cracking. In order to prolong their life, the liquid ends are often overpressurized (autofrettaged), thus inducing beneficial compressive hoop stresses in these critical regions upon removal of the autofrettage pressure. This autofrettage process drives the region of high stress concentration beyond the elastic limit and well into the elastic-plastic region. Elastic-plastic stresses and strains due to loading and unloading were analyzed in crossbore geometries, with Bauschinger effect included, using 3-D finite element analysis of the liquid end. For comparison, an analytical approach was developed, based on the strain energy density criterion first proposed by Glinka. The approach was modified to include the Bauschinger effect for precise estimation of such stresses and strains. Good correlation was observed between elastic-plastic crossbore stresses and strains predicted by the analytical approach and the finite element analysis.

We are very pleased that the discussers have provided us with a reason to re-visit our paper. The back-calculated secant modulus relation of the Myeongji pile combined with the strain [...]

IntroductionThe authors have presented a well-documented case study of the load test interpretation of prestressed high-strength concrete (PHC) piles, which are very popular in the Far East and are often [...]

A plasma-spray thermal barrier coating (TBC) was deposited on a stainless steel substrate. Residual stresses were first measured using moire interferometry combined with a cutting relaxation method. Fringe patterns in [...]

The different problems regarding the nature of high built-up stresses in diamond like carbon (DLC) films were examined and the application of pulse plasma method in growing low residual stress DLC films were emphasized. Sufficiently thick and hard DLC films of substantially low stress were deposited by the pulse plasma enhanced chemical vapor deposition method. Stress values were observed to be less than 0.5 GPa even with wide variation in pulse parameters.

The current design practice of single bored piles in residual weathered formations is based mainly on stability consideration against shear failure, and pile deformation analysis is rarely carried out. However, the acceptance criteria of single piles during pile load tests during construction is based mainly on the permissible settlement criteria as specified in the specifications/codes. In this study, a reliable method of predicting the load deformation and load distribution curves is proposed for bored piles in a residual weathered formation (Kenny Hill Formation) in Kuala Lumpur based on: (1) considerations of the weathering profiles and the engineering characteristics of this formation; (2) field performance data of fully instrumented bored pile load tests; and (3) load transfer design characteristics of the load deformation behavior. In this deformation analysis, the pile installation methods and the nonlinear behavior of the pile material are incorporated. The proposed load deformation analysis was carried out on both the instrumented and noninstrumented piles, producing good results. Therefore, this proposed method can be used to predict the load deformation characteristics of single bored piles in weathered formation during the design stage.