Showing papers on "Stress concentration published in 1990"
TL;DR: In this article, a fracture mechanics analysis for the growth of fatigue cracks from the pores of an aluminium casting alloy is described, and it is shown that the fatigue life can be quantitatively predicted from a knowledge of the size of casting defects: in particular it explains the lack of effect of heat-treatment and the apparent absence of a mean stress effect.
Abstract: — The fatigue properties of un-notched polished specimens of an aluminium casting alloy have been measured for various heat-treatment conditions and at various mean stresses. The relation between fatigue life and alternating stress is insensitive to heat-treatment and, apparently, to mean stress. It was observed that failure initiated at interdendritic shrinkage defects: evidence of classical crack initiation from persistent slip bands was also seen but such cracks, being less severe than the casting defects, never caused failure. A fracture mechanics analysis for the growth of fatigue cracks from the pores is described. It shows that the fatigue life can be quantitatively predicted from a knowledge of the size of casting defects: in particular it explains the lack of effect of heat-treatment and the apparent absence of a mean stress effect is shown to be caused by the variation in size of maximum defect present among the specimens tested. It is shown that reducing the size of shrinkage defects will increase the life, but only up to the stage at which initiation from persistent slip bands becomes operative.
329 citations
TL;DR: In this paper, an approximate Galerkin solution to the one-dimensional cracked beam theory developed by Christides and Barr for the free bending motion of beams with pairs of symmetric open cracks is suggested.
214 citations
TL;DR: In this paper, the shape and velocity of propagating cracks in the hydrostatic stress condition were studied by using gelatin, the physical properties of which were controlled to be constant, and the condition of a stable isolated crack formation was discussed.
Abstract: The three-dimensional shape and velocity of propagating cracks in the hydrostatic stress condition were studied by using gelatin, the physical properties of which were controlled to be constant. Various liquids (with various densities, viscosities, and volumes as the governed parameters) were injected in gelatin to form liquid-filled cracks. The directions of the crack growth and the propagation of an isolated crack are governed by the density difference between injected liquid and gelatin (Δρ), that is, a buoyancy. The propagation of a crack has two critical values: the first is the transition value to brittle fracture; the second is the value where segmentation begins to occur. The condition of a stable isolated crack formation is discussed. The crack shape of an isolated crack in the direction perpendicular to the crack plane is different from that of a growing crack with a fat tear drop form: the former has an elliptical top and a nearly flat bottom. The upper termination of an isolated crack in the vertical cross section has an elliptical shape, and the lower termination has a cusped shape. The lower part of the crack occupies the preexiting fracture which has formed by fracturing at the crack top. The crack thickness (w)/crack height (h) ratio is proportional to Δρ A, if the elastic moduli are constant. The crack length l/h ratio increase with h in the primary fracture, while the l/h ratio decreases with h in the preexisting fracture except for air-filled cracks. The ascending velocity of an isolated crack is proportional to Δρ3 h4, that is, Δρ w2, if the other physical properties are constant. The height and length of a growing penny-shaped crack are approximately proportional to A 3d1/3t4/9, so that the growth rate of height is in proportion to A3d3t−5/9 (A3d is constant injection rale). Some comparisons with the two-dimensional crack theory and applications for magma-filled cracks are discussed on the basis of these results.
168 citations
TL;DR: Neumann et al. as mentioned in this paper reported about plastic strain controlled high cycle fatigue (HCF) experiments on an austenitic stainless steel (26% Ni, 15% Cr, 23% Ti, 13% Mn, 12% Mo, 03% Al) for both annealed and age hardened conditions.
Abstract: We report about plastic strain controlled High Cycle Fatigue (HCF) experiments on an austenitic stainless steel (26% Ni, 15% Cr, 23% Ti, 13% Mn, 12% Mo, 03% Al) for both annealed and age hardened conditions Since twin boundary cracking phenomena were dominant for both conditions, most of the research focused on annealed steel The local orientation of more than 190 grains was measured by a modified electron channeling technique In a simplifying model [P Neumann and A Tonnessen, Proc Conf Fatigue, Charlottsville, USA, Vol 1, pp 3–22 (1987); P Neumann and A Tonnessen, Proc Int Conf Strength of Metals and Alloys, Tampere, Finland, Vol 1, p 743–748 (1987)] these orientation data were used to calculate the local stress concentrations near the twin boundaries By this method for 89% of the examined twin boundaries we could predict whether a crack would develop or not A laser interferometric method was used to measure the local plastic strain across different selected twin boundaries These experiments show that local plasticity is the most important parameter in HCF of fcc polycrystals
164 citations
TL;DR: In this paper, the authors developed a model for fatigue growth of matrix cracks in metals reinforced with aligned continuous elastic fibers, which provides estimates of the tip value of the stress intensity factor amplitude, ΔKTIP.
148 citations
TL;DR: The current results indicate that for a given system (material properties mu and nu constant), the stress distribution is a function of the ratio of contact radius to layer thickness (a/h), and while tensile stresses are seen to occur only when a/h is small, tensile strain is observed for all a/H values.
Abstract: The stress distribution in the region of contact between a layered elastic sphere and a layered elastic cavity is determined using an analytical model to stimulate contact of articulating joints. The purpose is to use the solution to analyze the effects of cartilage thickness and stiffness, bone stiffness and joint curvature on the resulting stress field, and investigate the possibility of cracking of the material due to tensile and shear stresses. Vertical cracking of cartilage as well as horizontal splitting at the cartilage-calcified cartilage interface has been observed in osteoarthritic joints. The current results indicate that for a given system (material properties mu and nu constant), the stress distribution is a function of the ratio of contact radius to layer thickness (a/h), and while tensile stresses are seen to occur only when a/h is small, tensile strain is observed for all a/h values. Significant shear stresses are observed at the cartilage-bone interface. Softening of cartilage results in an increase in a/h, and a decrease in maximum normal stress. Cartilage thinning increases a/h and the maximum contact stress, while thickening has the opposite effect. A reduction in the indenting radius reduces a/h and increases the maximum normal stress. Bone softening is seen to have negligible effect on the resulting contact parameters and stress distribution.
129 citations
TL;DR: Based on the complex-valued "stress concentration vector" introduced by Willis, a new definition of real-valued stress intensity factors is introduced in this article, where tractions ahead of the crack and the relative crack face displacements given by Willis are rewritten into real-form expressions.
Abstract: Based on the complex-valued «stress concentration vector» introduced by Willis, a new definition of real-valued stress intensity factors is introduced. In terms of the new stress intensity factors, tractions ahead of the crack and the relative crack face displacements given by Willis are rewritten into real-form expressions. The energy release rate obtained by Willis is also expressed into a real form in terms of the stress intensity factors
120 citations
TL;DR: In this article, the authors used the optical method of reflected caustics combined with high speed photography to investigate the dynamic fracture initiation and propagation in 4340 steel. And they found that the crack tip velocity and stress intensity factor time records varied smoothly and repeatably allowing for a straightforward interpretation of the data.
Abstract: Dynamic fracture initiation and propagation in 4340 steel was investigated experimentally using the optical method of reflected caustics combined with high speed photography. A new crack propagation testing configuration consisting of a three point bend specimen loaded in a drop weight tower was used. It was found that prior to crack initiation the stress intensity factor time record calculated using the dynamic tup load and a static formula disagrees with the actual stress intensity factor measured by caustics. During crack propagation, the crack tip velocity and stress intensity factor time records varied smoothly and repeatably allowing for a straightforward interpretation of the data. The experiments show that for the particular heat treatment of 4340 steel used, the dynamic fracture propagation toughness depends on crack tip velocity through a relation that is a material property.
116 citations
TL;DR: In this article, the effects of residual stress fields on fatigue crack propagation were evaluated using two numerical methods, i.e., finite element method and the weight function method, allowing a detailed analysis of the experimental data to be obtained.
115 citations
TL;DR: In this article, the authors investigated the influence of mechanically induced martensitic transformation on the rate of fatigue crack growth in 304-type austenitic stainless steels and found that changing the composition of the austenite by changing composition or lowering temperature reduces the fatigue crack rate and increases the threshold stress intensity for crack growth.
Abstract: This research reports an investigation into the influence of mechanically induced martensitic transformation on the rate of fatigue crack growth in 304-type austenitic stainless steels. Two steels of different composition, 304L and 304LN, were used to test the influence of composition; two test temperatures, 298 and 77 K, were used to study the influence of test temperature; and various load ratios were used to determine the influence of the mean stress. It was found thadecreasing the mechanical stability of the austenite by changing composition or lowering temperature reduces the fatigue crack growth rate and increases the threshold stress intensity for crack growth. However, this beneficial effect diminishes as the load ratio increases, even though increasing the load ratio increases the extent of the martensite transformation. Several mechanisms that may influence this behavior are discussed, including the perturbation of the crack tip stress field, crack deflection, work hardening, and the relative brittleness of the transformed material. The perturbation of the stress field seems to be the most important; by modifying previous models, we develop a quantitative analysis of the crack growth rate that provides a reasonable fit to the experimental results.
111 citations
TL;DR: In this paper, a semi-infinite plate containing an edge crack is considered and a normal velocity is imposed on the boundary of the plate on one side of the edge crack.
Abstract: The two-dimensional elastodynamic problem of a semi-infinite plate containing an edge crack is considered. A normal velocity is suddenly imposed on the boundary of the plate on one side of the edge crack. A combination of transient mode I and mode II deformation fields is induced near the crack tip. The corresponding stress intensity factor histories are determined exactly by linear superposition of several more readily obtainable stress wave propagation solutions. The stress intensity factor histories are determined for the time interval from initial loading until the first wave scattered at the crack tip is reflected at the plate edge and returns to the crack tip
TL;DR: In this article, a systematic study of stresses in tubular Y-and T-joints has been conducted in which nearly 900 thin-shell finite-element analyses were performed.
TL;DR: In this paper, a continuum theory for non-Newtonian flow of a two-phase composite containing rigid inclusions is presented, which predicts flow suppression by a factor of (1 - V)q, where V is the volume fraction of the rigid inclusion and q depends on the stress exponent and the inclusion shape.
Abstract: A continuum theory for non-Newtonian flow of a two-phase composite containing rigid inclusions is presented. It predicts flow suppression by a factor of (1 - V)q, where V is the volume fraction of the rigid inclusion and q depends on the stress exponent and the inclusion shape. Stress concentrations in the rigid inclusion have also been evaluated. As the stress exponent increases, flow suppression is more pronounced even though stress concentration is less severe. To test this theory, superplastic flow of zirconia/mullite composites, in which zirconia is a soft, non-Newtonian superplastic matrix and mullite is a rigid phase of various size, shape, and amount, is studied. The continuum theory is found to describe the two-phase superplastic flow reasonably well.
TL;DR: In this paper, a 15 wt% SiC particulate reinforced 6061 aluminium alloy has been examined using pre-cracked specimens and detailed attention was paid to interactions between the SiC particles and the growing fatigue-crack tip.
Abstract: Fatigue crack growth behaviour in a 15 wt% SiC particulate reinforced 6061 aluminium alloy has been examined using pre-cracked specimens. Crack initiation and early growth of fatigue cracks in smooth specimens has also been investigated using the technique of periodic replication. The composite contained a bimodal distribution of SiC particle sizes, and detailed attention was paid to interactions between the SiC particles and the growing fatigue-crack tip. At low stress intensity levels, the proportion of coarse SiC particles on the fatigue surfaces was much smaller than that on the metallographic sections, indicating that the fatigue crack tends to run through the matrix avoiding SiC particles. As the stress intensity level increases, the SiC particles ahead of the growing fatigue crack tip are fractured and the fatigue crack then links the fractured particles. The contribution of this monotonic fracture mode resulted in a higher growth rate for the composite than for the unreinforced alloy. An increase in the proportion of cracked, coarse SiC particles on the fatigue surface was observed for specimens tested at a higher stress ratio.
TL;DR: In this paper, it has been established that hydrogen assisted subcritical crack growth in Fe-3wt%Si single crystals is discontinuous while accompanied by substantial plasticity, and the near crack tip stress distribution in an elastic-plastic analysis enabled insight into how dislocation shielding led to mirocrack nucleation.
Abstract: It has been established that hydrogen assisted subcritical crack growth in Fe-3wt%Si single crystals is discontinuous while accompanied by substantial plasticity. Prop osed micromechanisms of this process are addressed via observed fine-scale {100} cleavage features, acoustic emission tracking and computer simulation analysis. The near crack tip stress distribution in an elastic-plastic analysis enabled insight into how dislocation shielding led to mirocrack nucleation. Such discretized computational models include: the stress due to the dislocation self field, the stress from crack-dislocation interactions, the stress from the crack-external stress interaction and the external applied stress. Stress distributions in both macroscopic and microscopic scales of interest were also examined, appropriate to different slip systems. It was found that the stress at the crack tip became slightly compressive while the position of the maximum stress, approaching the theoretical strength shifts to about 2–30 nm from the crack tip. The high stress region may be correlated with the observed 1 μm discontinuous crack instabilities as detected by acoustic emission. The mutual feedback from experimental findings related to acoustic emission and crystallographical habits vis-a-vis theoretical aspects are analyzed. This approach results in a micromechanical model which has implications to both hydrogen embrittlement thresholds and the ductile-brittle transition.
01 Jan 1990
TL;DR: FATIGUE as discussed by the authors is the progressive, localized, and permanent structural change that occurs in a material subjected to repeated or fluctuating strains at nominal stresses that have maximum values less than (and often much less than) the tensile strength of the material.
Abstract: FATIGUE is the progressive, localized, and permanent structural change that occurs in a material subjected to repeated or fluctuating strains at nominal stresses that have maximum values less than (and often much less than) the tensile strength of the material. Fatigue may culminate into cracks and cause fracture after a sufficient number of fluctuations. The process of fatigue consists of three stages: • Initial fatigue damage leading to crack initiation • Crack propagation to some critical size (a size at which the remaining uncracked cross section of the part becomes too weak to carry the imposed loads) • Final, sudden fracture of the remaining cross section
TL;DR: In this paper, the ductile fracture of a spheroidized 1518 steel has been investigated using three types of tensile specimens: smooth tensile, notched tensile and plane-strain tensile.
Abstract: The ductile fracture of a spheroidized 1518 steel has been investigated using three types of tensile specimens — smooth tensile, notched tensile, and plane-strain tensile. It was found that void nucleation has two different modes (Type I and Type II) depending on local conditions, the most important of which are the size, shape, and distribution of the particles. By identifying the low-strain-range nucleation behavior (Type I), it was possible to determine the value of plastic strain, eN, after which void nucleation at average-sized carbide particles (Type II) begins; eN is 0.45 for the smooth tensile case, 0.30 for the notched, and 0.25 for the plane strain. The critical stress for Type II void nucleation, σc, is of the order of 1200 MPa. Void growth depends on the macroscopic stress-strain state: longitudinal growth is given by a linear function of applied plastic strain, ep, whereas lateral growth shows a linear dependence on the triaxial stress, σT. When the local value ofV f reaches a critical volume fraction of voids (V f cri = 5 ± 0.5 pct), void coalescence occurs in a catastrophic manner, leading to final separation within a highly localized zone. The stress concentration caused by the notched tensile specimen geometry and the localized mode of plastic flow caused by the constraint of the plane-strain state in a Clausing-type specimen were found to affect the substeps of void nucleation, growth, and coalescence.
TL;DR: The mechanical anisotropy of four mile gneiss has been investigated in a series of uniaxial and triaxial, compression and extension experiments performed at confining pressures Pc up to 400 MPa, constant strain rates e from 1.6×10−6 to 1.5× 10−4 s−1, and temperatures T from 25° to 800°C on cylindrical and notched samples oriented with respect to foliation (S) and lineation (L) as mentioned in this paper.
Abstract: The mechanical anisotropy of Four-mile gneiss has been investigated in a series of uniaxial and triaxial, compression and extension experiments performed at confining pressures Pc up to 400 MPa, constant strain rates e from 1.6×10−6 to 1.5×10−4 s−1, and temperatures T from 25° to 800°C on cylindrical and notched samples oriented with respect to foliation (S) and lineation (L). Differential stresses measured both at the onset of yielding and at failure vary with specimen orientation, with maximum compressive strengths exhibited by samples cored perpendicular to S and minimum strengths exhibited by samples cored at 45° to both S and L. While failure strengths are influenced most strongly by the orientation of S, they appear to depend upon the orientation of L as well. An orthorhombic failure criterion, generalized from a nonlinear Mohr-Coulomb relation, has been considered with quadratic and linear stress terms resembling those of invariants J2 and I1, respectively, and material parameters estimated by nonlinear regression methods. Satisfactory fits were achieved for results at T = 25°C as well as T = 700°C. Fracture strengths are relatively insensitive to changes in T and e and the anisotropy exhibited at T = 700°C is remarkably similar to that measured at T = 25°C. Relatively small reductions in strength observed at elevated temperatures are probably due to the influence of thermally induced microcracks. Mechanisms of deformation and sources of anisotropy have been identified by examining microstructures developed in deformed specimens and observing their relationships to those fabric elements initially present in the starting material. Throughgoing shear fractures developed in samples shortened in all orientations with respect to S and L by the coalescence of microcracks in feldspar and quartz grains, as reported for isotropic granites. However, inelastic strains within mica grains were accommodated by slip, frictional sliding, and kinking, and deformation of favorably oriented micas appears to have led to local stress concentrations in neighboring phases that result in nucleation of tensile microcracks. Both S and L are defined by the preferred orientations of micas, and a simple model involving crack nucleation around oriented mica grains is proposed to explain the anisotropy observed.
TL;DR: In this article, the effect of Si and Al additions on the low temperature toughness and fracture mode of Fe-27Mn (in mass%) alloys was investigated in terms of the microstructure, heterogeneous deformation and stacking fault energy.
Abstract: The effect of Si and Al additions on the low temperature toughness and fracture mode of Fe-27Mn (in mass%) alloys was investigated in terms of the microstructure, heterogeneous deformation and stacking fault energy. The Fe-27Mn binary alloy has two constituent phases at 77 K; Epsilon martensite (e) and metastable austenite (γ). It undergoes a ductile-to-brittle transition because of an intergranular fracture associated with heterogeneous deformation. The intergranular fracture is caused by stress concentration at grain boundaries on which large e plates impinge. Silicon addition to the Fe-27Mn binary alloy is effective for refining e plates and changes the fracture mode from intergranular to transgranular. The fracture is, however, a quasi-cleavage mode along e plates so that Fe-27Mn-Si alloys also exhibit a ductile-to-brittle transition related to the formation of e. The stress concentration at the intersection of e plates results in the formation of microcracks along the e plates leading to the quasi-cleavage fracture. Fracture modes of high manganese steels containing e largely depend on the microstructure and the deformation behavior. Silicon addition probably affects not only the nucleation of e, but also the cross slip behavior of partial dislocations at the intersection of e plates through a decrease in the stacking fault energy of γ, thus leading to the change in fracture mode.Aluminum addition to high manganese steels is so effective for suppressing the γ-e transformation that the low temperature embrittlement associated with the formation of e does not occur with even a small Al addition. In an Fe-27Mn-2.5Al alloy, for example, toughness is high even at 77 K because the γ phase is so stable that the transformation to e does not occur during deformation at 77 K.
TL;DR: In this article, tensile fracture experiments were performed upon specimens of wet mature bovine Haversian bone, with short, controlled notches, and the results indicated that bone resists the effect of stress raisers such as fatigue microcracks and surgical sawcuts to a much greater extent than anticipated on the basis of its elastic or elastoplastic properties.
TL;DR: In this article, a crack resistance function is defined based on experimental data and then combined with an average state of stress in front of the cracktip to formulate a crack driver function, analogous to the safety factor.
15 Jun 1990-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an elastic shear lag analysis, which includes an interphase region, has been developed and correlated with the micro-debonding test data of Mandell et al. to determine the thickness and material properties of the interphase.
Abstract: An elastic shear lag analysis, which includes an interphase region, has been developed and correlated with the micro-debonding test data of Mandell et al. to determine the thickness and material properties of the interphase. The shear strength and the relationship between thickness and shear modulus of interphase were determined for both glass-epoxy and graphite-epoxy composites. An axisymmetric finite element model, which includes the interphase properties obtained from the shear lag analysis, was also developed. The effects of the interphase on stresses and deformation at the interface and fracture toughness of the fibrous composites were investigated. The following conclusions were drawn from the study: (1) by including an interphase, both the shear lag analysis and the finite element model provide very good predictions; (2) an interphase exists and is softer than the matrix; (3) the interphase has significant effect on stress concentration, displacement and fracture toughness of the fibrous composite.
TL;DR: In this paper, the authors investigated the behavior of fatigue crack growth and closure through a compressive residual stress field and found that partial opening of the crack occurs and this plays an important role in crack growth.
Abstract: Behaviour of fatigue crack growth and closure through a compressive residual stress field is investigated by performing fatigue crack growth tests on welded SEN specimens of a structural steel (JIS SM50A). Depending on the type of the initial residual stress in the region of crack growth, the growth and closure of the crack show different behaviour. In particular, in the transition region from a compressive residual stress field to a tensile residual stress field, the fatigue crack growth rates cannot be described by the effective stress intensity factor range ΔKeff, based on the measured crack opening stress intensity factor Kop. Also it is found that the R'-method using the data of da/dN vs ΔK for residual stress-free specimens, with the effective stress ratio R'[=(Kmax+Kr)/(Kmin+Kr)], gives non-conservative predictions of the growth rates in the transition region. Observations of crack closure behaviour in this study indicates that partial opening of the crack occurs and this plays an important role in crack growth through a compressive residual stress field. Based on the concept of a partial opening point (defined and measured in this work), fatigue crack growth behaviour can be better explained.
TL;DR: An analytical solution for the three-dimensional stress field in a plate of an arbitrary thickness, 2h, and weakened by a cylindrical hole of radius a is presented in this article.
Abstract: An analytical solution for the three-dimensional stress field in a plate of an arbitrary thickness, 2h, and weakened by a cylindrical hole of radius a is presented. Far away from the hole, the plate is subjected to a uniform tensile load, σ0, in a direction parallel to the plane of the plate. The solution is shown to be derivable from a general 3D solution, which the first author constructed in a previous paper. The analysis shows the stress concentration factor to vary across the thickness and to be sensitive to the value of the radius to thickness ratio, a/h. Furthermore, it is shown that for ratios of (a/h)≧4, the results predicted by plane stress theory are more than adequate for engineering applications. Finally, the transition between plane stress and plane strain appears to occur at a/h=0.5.
TL;DR: In this article, stress intensity factor solutions for coalescing coplanar semi-elliptical cracks subjected to pure bending were presented, and various models were employed for the prediction of fatigue crack growth of coalescing Coplanar cracks.
TL;DR: In this paper, the authors performed crack propagation experiments as a function of temperature on a single crystalline superalloy RENE N4 and measured crack growth rates at 21 °C, 704°C, 927°C and 1038°C on specimens with [001] and [110] directions parallel to the load axis and the machined notch, respectively.
Abstract: Crack propagation experiments were performed as a function of temperature on the single crystalline superalloy RENE N4. Crack growth rates at 21 °C, 704 °C, 927 °C, 1038 °C, and 1093 °C were measured on specimens with [001] and [110] directions parallel to the load axis and the machined notch, respectively. Fracture surfaces at each temperature were examined and discussed in terms of the crack tip stress field and the crystallographic orientation of the specimens.
TL;DR: The effect of a metal collar on stress distribution with cast post and cores was studied by using three-dimensional photoelastic models of maxillary canine teeth of average dimensions, and the greatest stress concentration was found at the lingual apex of the post.
Abstract: The effect of a metal collar on stress distribution with cast post and cores was studied by using three-dimensional photoelastic models of maxillary canine teeth of average dimensions. Standardized parallel post and cores were cemented into the models, with half of the samples incorporating a 1.5 mm metal collar. A 400 gm load was applied to the cingulum of the cores and stresses were frozen in the models. The posts were removed, the teeth were sectioned, and stresses were measured with a circular polariscope. In both groups the greatest stress concentration was found at the lingual apex of the post. On a point by point basis, stresses were higher in the collared specimens. Variation in stress magnitude among five preselected points was greater within the noncollared group.
Book•
01 Apr 1990
TL;DR: Stress and strain transformation plane elasticity theory structures with symmetry bending of beams and plates theories of torsion moment distribution flexural shear flow energy methods instability of columns and plates finite elements yield and strength criteria plasticity and collapse creep and visco-elasticity high and low cycle fatigue fracture mechanics as discussed by the authors.
Abstract: Stress and strain transformation plane elasticity theory structures with symmetry bending of beams and plates theories of torsion moment distribution flexural shear flow energy methods instability of columns and plates finite elements yield and strength criteria plasticity and collapse creep and visco-elasticity high and low cycle fatigue fracture mechanics. Appendices: properties of areas matrix algebra stress concentrations.
TL;DR: In this paper, the effect of welding residual stresses on the crack growth rate is related to the position of the crack and its orientation with respect to the weld line, and its influence on the fatigue crack closure is discussed.
TL;DR: In this paper, the authors measured fatigue crack propagation rates in tension-tension load cycling using precracked and annealed compact tension specimens in ZrO{sub 2}-12 mol% Ce-TZPs and found that fatigue crack growth behavior was strongly influenced by the history of crack shielding via the development of the crack-tip transformation zones.
Abstract: Fatigue crack propagation rates in tension-tension load cycling were measured in ZrO{sub 2}-12 mol% CeO{sub 2}-10 wt% Al{sub 2}O{sub 3} ceramics using precracked and annealed compact tension specimens. The fatigue crack growth behavior was examined for Ce-TZPs. The fatigue crack growth behavior was strongly influenced by the history of crack shielding via the development of the crack-tip transformation zones. Crack growth rates under sustained peak loads were also measured and found to be significantly lower and occurred at higher peak stress intensities as compared to the fatigue crack growth rates.