Showing papers on "Residual stress published in 1988"
TL;DR: In this paper, the Incremental Strain, Average Stress, Power Series, and Integral methods are examined as procedures for determining non-uniform residual stress fields using strain relaxation data from the hole drilling method.
Abstract: The Incremental Strain, Average Stress, Power Series, and Integral methods are examined as procedures for determining non-uniform residual stress fields using strain relaxation data from the hole drilling method. Some theoretical shortcomings in the Incremental Strain and Average Stress methods are described. It is shown that these two traditional methods are in fact approximations of the Integral Method. Theoretical estimates of the errors involved are presented for various stress fields. Also, some simple transformations of stress and strain variables are introduced so as to decouple the stress/strain equations and simplify the numerical solution.
490 citations
307 citations
TL;DR: In this paper, surface micromachining is used to fabricate beams, plates, sealed cavities, and linear and rotary bearings, with an emphasis on polysilicon microstructures.
Abstract: Micromechanical structures can be made by selectively etching sacrificial layers from a multilayer sandwich of patterned thin films. This paper reviews this technology, termed surface micromachining, with an emphasis on polysilicon microstructures. Micromechanical characteristics of thin‐film microstructures critically depend on the average residual stress in the film, as well as on the stress variation in the direction of deposition. The stress in low‐pressure chemical vapor deposition polysilicon varies with deposition temperature, doping, and annealing cycles. Applications of surface micromachining to fabricate beams, plates, sealed cavities, and linear and rotary bearings are discussed.
279 citations
TL;DR: In this article, a general expression for the steady-state matrix cracking stress in reinforced brittle matrix composites is derived using a J-integral analysis, expressed in terms of the stress-displacement relation that characterizes the stretching of crack bridging ligaments.
239 citations
TL;DR: In this article, the residual stresses in APC-2 cross-ply laminates have been investigated and predictions based on classical laminate theory are compared to measured levels of residual stress obtained from a number of experimen tal techniques.
Abstract: Residual stresses in composite laminates depend on thermoelastic properties of the material and processing temperatures. Their distribution in the various laminae is a func tion of stacking sequence and ply orientation. In this work residual stresses in APC-2 cross-ply laminates have been investigated. Predictions based on classical laminate theory are compared to measured levels of residual stress obtained from a number of experimen tal techniques. The analysis of the results shows that accurate predictions can be made pro vided that the changes in thermoelastic properties of the materials with temperature are taken into account.
212 citations
TL;DR: In this paper, the authors reviewed the status of understanding concerning the magnitude of this number for various types of adherent film on either brittle or ductile substrates, and important effects of elastic properties, substrate thickness, and yield strength are described.
Abstract: The cracking and decohesion of thin films can be characterized by critical values of a nondimensional parameter governed by the residual stress, the film thickness, and a fracture resistance. This article reviews the status of understanding concerning the magnitude of this number for various types of adherent film on either brittle or ductile substrates. Important effects of elastic properties, substrate thickness, and yield strength are described.
206 citations
TL;DR: In this article, the propagation of cracks in a brittle substrate, as motivated by residual stress in the film, is analyzed and the results are used to predict trends in film decohesion with film thickness, residual stress, elastic properties and substrate toughness.
185 citations
TL;DR: In this paper, an indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model.
Abstract: An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.
160 citations
TL;DR: In this article, the analytical function of crack extension to a fractional power is used to represent the fracture resistance of a vitreous-bonded 96% alumina ceramic.
Abstract: The analytical function of crack extension to a fractional power is used to represent the fracture resistance of a vitreous-bonded 96% alumina ceramic. A varying flaw size, controlled by Vickers indentation loading between 3 and 300 N, was placed on the prospective tensile surfaces of four-point bend specimens, previously polished and annealed. The lengths of surface cracks were measured by optical microscopy. Straight lines were fitted to the logarithmic functions of observed bending strength versus indentation load in two series of experiments: (I) including the residual stress due to indentation and (II) having the residual stress annealed out at an elevated temperature. Within the precision of measurement these lines have the same slope, being about 32% less than the -1/3 slope which a fracture toughness independent of crack extension would indicate. Considering the criteria for crack extension and specimen failure, the fracture mechanics equations were solved for the conditions of the two series of experiments. Approximately the same values of fracture toughness, rising as a function of indentation flaw size, were obtained from both series of experiments.
152 citations
TL;DR: In this article, the residual stresses that exist between two brittle materials bonded by a thin ductile layer are calculated and the stress intensity factors associated with interface cracks are then computed and used to address problems of cracking and bond strength.
118 citations
TL;DR: In this paper, the authors present experimental results and constitutive models for single phase ceramics, transforming ceramic and ceramic composites with the aim of developing the framework for a general theory of cyclic compression fracture in notched brittle solids.
TL;DR: In this article, a set of formulas for a generalized axial stress in diamond and zinc-blende semiconductors under axial stresses is derived to calculate stress-related Raman shifts.
Abstract: A set of formulas for a generalized axial stress in diamond and zinc-blende semiconductors under axial stress is derived to calculate stress-related Raman shifts. By analyzing known Raman data on cubic SiC under hydrostatic pressures, one of the Raman-stress coefficients was obtained, and the existing elastic stiffness constants of cubic SiC were optimized. A method for calculating the stress and strain in SiC films on (100) Si is proposed. It is suggested that the stress and strain expressions and the method of the stress and strain determinations in heterostructures are quite general and may be used for other systems.
TL;DR: In this paper, a review is made of equations that have been proposed for the design of ship plates subjected to compressive loads, and the effect of the various parameters is quantified showing that a design method should account explicitly for plate slenderness, residual stresses, initial distortions and boundary conditions.
TL;DR: In this article, the simulation of welding of shell structures is investigated, and two different problems are studied: butt-welding of two plates and a thin-walled pipe.
Abstract: The simulation of welding of shell structures is investigated in this paper. In order to verify the implementation of the shell element adopted, two different problems were studied. In the first problem the butt-welding of two plates was simulated. In the second problem the butt-welding of a thin-walled pipe was simulated. It is concluded from the analysis of the plate problem that the shell element is quite effective in the membrane state. The comparison between calculated values and experimental values for the residual stress field in the pipe shows that the shell element performs quite well in the analysis of a realistic problem.
TL;DR: In this article, a model for the relationship between critical debonding pressures and the work of adhesion of thin films in the blister test is presented, and it is shown that films which cannot be peeled using the standard blister test (due to exceeding the tensile strength limit of the film before initiating a debond) can be peeled by varying the geometric parameters of the island blister.
Abstract: This paper reports a model for the relationship between critical debonding pressures and the work of adhesion of thin films in the blister test. Previous models have neglected the possible role of residual stresses in the film on the critical pressure. The model reported here shows that these stresses may have a large effect on the relation between the critical pressure and the work of adhesion. A similar model is developed for an alternative blister geometry, the annular or “island” blister. It is shown that films which cannot be peeled using the standard blister test (due to exceeding the tensile strength limit of the film before initiating a debond) can be peeled by varying the geometric parameters of the island blister.
TL;DR: In this paper, the surface cracks experienced R-curve behavior over the first few hundred micrometers; i.e., the applied crack driving force had to be increased with crack extension.
Abstract: The resistance of coarse-grained alumina to stable crack growth, initiated from “naturally’occurring surface flaws, was studied in strength tests with a bend-bar technique. The surface cracks experienced R-curve behavior over the first few hundred micrometers; i.e., the applied crack driving force had to be increased with crack extension. Compared to R curves generated from long cracks in standard single-edge-notched-bend specimens, the surface-crack curves have lower initial values. The possible influence of localized residual stresses, counteracting the applied crack driving force, is discussed.
TL;DR: In this article, a new method is proposed for determining the general stress tensor, which considerably reduces the variances of the stresses due to counting statistics and gradients, and a new set of tilts is recommended to minimise these errors.
Abstract: The determination of residual stresses via X-ray diffraction is briefly reviewed, with particular emphasis on the triaxial stress state. A new method is proposed for determining the general stress tensor, which considerably reduces the variances of the stresses due to counting statistics and gradients. The procedure involves a generalised least-squares solution of strains measured at various tilts of the X-ray beam to the sample, and a new set of tilts is recommended to minimise these errors.
TL;DR: In this article, a method for simultaneous and in situ measurement of both coating thickness and deposition stress during thermal spraying was developed, where a strip-shaped substrate was fixed on a pair of knife edges and the displacements of the front and the rear surfaces of the sample during thermal spray were measured using a pairof displacement meters.
TL;DR: In this paper, residual thermal stresses and strains of a SiC whisker-Al2O3 composite were determined by an experimental neutron diffraction technique and the results were compared with analytically determined values.
Abstract: Residual thermal stresses and strains, developed during cooling of a SiC whisker-Al2O3 composite, were determined by an experimental neutron diffraction technique and the results were compared with analytically determined values. High compressive residual thermal stresses were generated in the whiskers during cooldown after sintering. Analytical estimates of the residual stresses were obtained by using two self-consistent models: (1) a plane strain composite cylinder model and (2) Eshelby's ellipsoidal inclusion theory. The two models gave almost identical estimates of the stresses and strains in the whiskers. The interpretation of the measured strains in the whiskers by neutron diffraction had some uncertainty because of the lack of a clearly defined crystal structure of SiC.
TL;DR: The magnetic properties of AISI 4130 steel after eight heat treatments have been investigated as discussed by the authors, and properties such as hysteresis loss, coercivity and initial permeability were found to be closely interrelated.
Abstract: The magnetic properties of AISI 4130 steel after eight heat treatments have been investigated. Properties such as hysteresis loss, coercivity, and initial permeability were found to be closely interrelated. Furthermore, they were each dependent on the hardness of the material. A relationship between the hardness and permeability was found which was microstructure independent. These parameters were also found to change in a systematic way with plastic deformation and this result can be used for non-destructive evaluation. Correlations between the magnetic parameters were also found to change in a systematic way with plastic deformation and this result can be used for non-destructive evaluation. Correlations between the magnetic parameters revealed relationships which depended on the microstructure of the material. The residual stress in steels can be determined from the changes in maximum differential permeability.
TL;DR: In this article, an investigation into the prediction of the residual hoop stress distribution in autofrettaged thick-walled tubing of high-strength low-alloy steel with a diameter ratio of 2·07 is described.
TL;DR: In this paper, the trends in the use of hard protective coatings in WC-Co metal cutting inserts are reviewed in light of recent evaluations of mechanical and structure-sensitive properties such as elevated temperature microhardness, microfracture toughness, and internal stress.
Abstract: The trends in the use of hard protective coatings in WC–Co metal cutting inserts are reviewed in light of recent evaluations of mechanical and structure‐sensitive properties such as elevated temperature microhardness, microfracture toughness, and internal stress. A better understanding of the role of hard coatings has evolved due to development of reliable methods to measure mechanical properties of thin coatings (of the order of 5 μ thick). There are intrinsic differences in the microstructure and residual stress state of chemical and physical vapor deposited (CVD and PVD) hard coatings. High compressive residual stress and fine grain size in PVD coatings contribute to increased microhardness and microfracture toughness. However, these benefits are reduced at high temperatures. Certain well‐known structure/property concepts in bulk materials are shown to be applicable to hard coatings, which aid in interpretations of metal cutting wear behavior.
01 Dec 1988
TL;DR: In this article, the residual stresses in several ground ceramics are measured using the curvature method and four-point bend tests are conducted to measure the fracture strength of the ground specimens.
Abstract: Grinding induces residual stresses and cracks at and near the surfaces of ceramic workpieces. The residual stresses in several ground ceramics are measured using the curvature method. Four-point bend tests are conducted to measure the fracture strength of the ground specimens. A fracture mechanics analysis includes the measured residual stress to calculate the grinding-induced surface crack size. It is shown that the residual stresses sometimes have a significant effect on the strength- controlling flaw size.
TL;DR: In this paper, a system known as SPATE (stress pattern analysis by measurement of thermal emission) has been developed which can detect changes in infrared emission due to minute changes in the temperature of a dynamically stressed material.
Abstract: The term thermoelastic effect refers to the coupling between mechanical deformation and the change in thermal energy of an elastic material. The first theoretical treatment of this phenomenon is attributed to Lord Kelvin1, and the resulting law states that the rate of change in temperature of a dynamically loaded body is directly related to the rate of change of the principal stress sum under adiabatic conditions. Although Kelvin's law has been well known for over a century, it is only in the past ten years that the thermoelastic effect has been exploited as a means for dynamic stress analysis. A system known as SPATE (stress pattern analysis by measurement of thermal emission) has been developed which can detect changes in infrared emission due to minute changes in the temperature of a dynamically stressed material. Recently it was discovered that the SPATE response or, more generally, the thermal response of a cyclically loaded body is not only a function of the dynamic part of the stress, but also of the static component2. This finding has led to the suggestion that residual stresses within a material might be detected using this phenomenon, and here we present the first demonstration of such a means of residual stress measurement.
TL;DR: In this article, a new goniometer has been developed where the diffraction pattern from the entire sample is integrated such that all peaks are recorded, allowing a residual stress measurement to be made.
Abstract: It is well known that coatings made by physical vapor deposition are very strongly textured and, as a consequence, it is sometimes extremely difficult to measure the residual stress by the classical X-ray diffraction method A new goniometer has been developed where the diffraction pattern from the entire sample is integrated such that all peaks are recorded This permits a residual stress measurement to be made The instrumentation also allows phase analysis and pole figure determination In the present work, a number of highly textured TiN and Ti(CN) samples, taken from earlier studies, are investigated and these demonstrate the strengths of the new measurement technique Results are presented for the Ti(CN) film which show that the residual stress depends strongly on the diffraction peak chosen for study The dependence of the stress on the crystallographic orientation factor allows the X-ray elastic constants of the film to be derived These deviate from the theory and it is possible that this may not apply to highly textured samples which also have a stress gradient through the film
TL;DR: In this article, the residual stress in post cathode magnetron sputter deposited molybdenum films has been studied and it was found that the residual film stress is very sensitive to the gas pressure during sputtering and that the film stresses are highly anisotropic.
Abstract: As part of the program to develop a large‐area thin‐film pulse heater for a lithium ion source, the residual stress in post cathode magnetron sputter deposited molybdenum films has been studied. It was found that in films prepared in the low‐pressure sputtering regime, the residual film stress is very sensitive to the gas pressure during sputtering and that the film stresses are highly anisotropic. The transition pressure for changing from compressive to tensile residual stress, as defined by Thornton and Hoffman, depends on the relationship between the measurement direction in the film and the post cathode orientation. In order to deposit a nearly stress‐free film a pressure cycling technique was developed which deposited alternate film layers containing tensile and compressive stresses. Film resistivity and thermal coefficient of resistivity measurements were made during the pulse heating of the molybdenum films.
TL;DR: In this paper, an analysis of the compressive test results is given based on the mixture rule modified to apply for discontinuous randomly oriented fiber composites. But, it is shown that agreement between predictions and experimental results can only be obtained by considering the increase of the strength of the matrix as a result of the presence of the fibres.
Abstract: Composites made with Al–7 wt-%Si alloys and discontinuous Nicalon SiC fibres were prepared by compocasting followed by squeeze casting. This technique gives rise to macroscopically homogeneous materials with, however, some segregation of the fibres in the eutectic phase, especially for the lowest volume fractions. The SiC fibres appreciably improve wear resistance, hardness, and compressive strength of the matrix, both in the as cast and heat treated conditions. An analysis of the compressive test results is given based on the mixture rule modified to apply for discontinuous randomly oriented fibre composites. However, it is shown that agreement between predictions and experimental results can only be obtained by considering the increase of the strength of the matrix as a result of the presence of the fibres. This increase is discussed in terms of structural changes and residual stresses created during cooling resulting from the difference in the coefficients of thermal expansion of the components...
TL;DR: To determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips, specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface.
Abstract: The interactive influence of cooling rate and the sign and magnitude of thermal contraction difference between metals and ceramic veneers on bond strength have not been extensively analyzed, although numerous bond-test studies have been reported during the past two decades. A previous analytical study of residual incompatibility stress in bond-test specimens indicated that bond strength values may be of relatively little value if the residual stress state of the metal-ceramic specimens is not considered. The objective of this study was to determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips. Specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface. The residual stress states in the ceramic region were estimated from finite element stress analyses of the bond-test specimens by use of dilatometry data obtained at the cooling rate of 3 degrees C/min. The total stress induced from the residual stress and the applied flexural load was also determined for these specimens. Statistical analyses of the experimental data revealed that the slowly cooled specimens exhibited a significantly lower (p < 0.05) flexural strength compared with rapidly cooled specimens. Regardless of the cooling technique, metal-ceramic specimens with a negative thermal contraction difference (alpha m - alpha p < 0) failed at significantly lower (p < 0.05) flexural loads than did specimens with a positive thermal contraction difference.
TL;DR: In this article, the authors compared the indentation fracture behavior of three-layer Al2O3-ZrO2 composites with substantial compressive residual stresses compared with the behaviors of monolithic Al 2 O3 and Al 2O3 ZrO 2 ceramics without intentionally introduced residual stresses.
Abstract: Indentation fracture behavior of three-layer Al2O3-ZrO2 composites with substantial compressive residual stresses was compared with the behaviors of monolithic Al2O3 and Al2O3-ZrO2 ceramics without intentionally introduced residual stresses. The indentation cracks were smaller in the three-layer specimens relative to the monolithic specimens in agreement with the predictions of indentation fracture mechanics theory. Indentation and strength testing were used to show that a residual compressive stress of approximately 500 MPa exists in the outer layers of the three-layer composites. The three-layer specimens showed excellent damage resistance in that the strength differential between the three-layer and monolithic indented specimens was maintained at indentation loads up to 1000 N, the maximum indentation load used in the experiments.