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Showing papers on "Fatigue limit published in 1985"



Journal ArticleDOI
TL;DR: Biomechanical stress calculations using the finite element method were made using a model that employed the use of the material implanted in alveolar bone to find the most suitable elastic modulus for the dental implant.
Abstract: Titanium powder with a granule diameter of 420–500 μm was prepared and porous titanium specimens were made from this powder. The mechanical properties of these specimens were examined. The compressive strength and low cyclic compressive fatigue strength were 182 and 40 MPa, respectively. Fractography was also observed by scanning electron microscopy. Typical fatigue characteristics of the bonding areas of the powder were observed. In addition, porous-titanium-coated dental implants with pure titanium cores were prepared. The compressive strength of the material used was 230 MPa, fatigue strength not being improved. Biomechanical stress calculations using the finite element method were made using a model that employed the use of the material implanted in alveolar bone. Shear stress at the implant–bone interface as well as compressive stress concentrations in the bone was calculated. The most suitable elastic modulus for the dental implant was then estimated from these calculations. Finally, based on these results, the use of porous titanium for dental implants was assessed.

113 citations


Journal ArticleDOI
TL;DR: In this article, five different dual-phase microstructures have been produced in a steel containing 0.11 C, 1.60 Mn, 0.73 Si and they were characterized by measurement of the mean ferrite path and the density and distribution of the extrinsic transformation accommodation dislocations in the substructure of the ferrite.
Abstract: Five different dual-phase microstructures have been produced in a steel containing 0.11 C, 1.60 Mn, 0.73 Si. By careful design of the heat treatment schedules, it was arranged that all the specimens had the same fine austenite grain size before intercritical annealing and that they all contained close to 30 vol pct martensite and a negligible fraction of retained austenite after annealing. The microstructures were characterized by measurement of the mean ferrite path and the density and distribution of the extrinsic transformation accommodation dislocations in the substructure of the ferrite. Specimens representative of each of the microstructures were tested in tension at room temperature. The strength, work-hardening, and fracture of three of them were examined in detail and correlated with the microstructural parameters. The microstructural features which most influence the tensile properties are identified. Two specimens, representative of the finest and coarsest microstructures, were the subject of a detailed exploration of the initiation of persistent slip and microcracks and of crack propagation in bending fatigue. The fatigue endurance limit was also measured. It is shown that the initiation of persistent slip is primarily influenced by the heterogeneity in the density of the dislocations in the ferrite. The microstructural features of greatest importance in controlling the formation and propagation of microcracks are the local dislocation density and the mean ferrite path.

80 citations


Journal ArticleDOI
TL;DR: The ion implantation process as shown in this study is being considered as an effective method for improving the wear performance of titanium based alloys for orthopaedic implants.
Abstract: Titanium based alloys are being considered as orthopaedic implants for a variety of reasons such as excellent corrosion resistance, high fatigue strength, low modulus of elasticity, and most importantly, excellent biocompatibility. The only questionable property of these alloys is their wear resistance. While Ti–6Al–4V has recently been introduced for construction of the femoral component in knee‐joint systems, the questionable wear performance of the Ti–6Al–4V is a barrier for a more widespread acceptance of the alloy for this application. The ion implantation process as shown in this study is being considered as an effective method for improving the wear performance of titanium based alloys for orthopaedic implants. Ion beams of carbon and nitrogen have been used to implant the surface of Ti–6Al–4V hemispherical samples. The samples were tested in a pin‐on‐disk machine against ultrahigh molecular weight polyethylene (UHMWPE) with loads representative of total joint replacements. Deionized water and Ring...

69 citations


Journal ArticleDOI
TL;DR: In this article, the effect of porosity on fatigue crack initiation was chosen as the thrust of the present study, where conventional powder metallurgical techniques were employed to generate various levels of porosa in a heat treatable steel of the AISI 4600 type.
Abstract: Porosity in sintered powder metals may contribute to fatigue strength degradation in two ways. First, pores will act as local stress concentrators and, second, they may act act as fatigue crack precursors. Accordingly, the effect of porosity on fatigue crack initiation was chosen as the thrust of the present study. Conventional powder metallurgical techniques were employed to generate various levels of porosity in a heat treatable steel of the AISI 4600 type. Porous steel specimens, in a modified compact tension configuration, were cyclically loaded and cycles to initiation noted. Initiation was defined as the generation of a fatigue crack 0·10 mm in length at the notch root. As expected, the greater the porosity content, the earlier the crack developed. There are two interdependent variables in porosity character for a given porosity content: these are the average interpore spacing and the average pore diameter. The region of concentrated stress around each pore is proportional to the cube of th...

62 citations


Journal ArticleDOI
TL;DR: In the case of segmented poly(urethaneurea) which did not immersed in lipids solution, their fatigue strength are sufficient for application to artificial heart systems, but fatigue strength of the TU-Mn series was decreased drastically after absorption of lipids.
Abstract: Characterization of microphase separated structure, interaction with blood components, such as lipids, and fatigue behavior after immersion in blood components were carried out for segmented poly(urethaneureas). The materials studied were Biomer and segmented poly(urethaneurea) (TU-Mn) composed of hard segment with 4,4'-diphenylmethane diisocyanate (MDI)-ethylenediamine (EDA) or 4,4'-diaminodiphenylmethane (DAM) and soft segment with MDI-polytetramethylene glycol (PTMG) [Mn of 856, 1350, and 2000]. Small-angle x-ray scattering, wide-angle x-ray diffraction, and dynamic viscoelastic measurements revealed that these materials showed the state of microphase separation. TU-Mn with PtMG of Mn = 856 shows the partial phase mixing between hard and soft segments, and phase separation was improved with an increase of Mn of PTMG. Biomer has the characteristics of stronger aggregation of hard segment than that of TU-Mn. All the specimen showed lipid absorption, but the amount of absorption decreased remarkably after precoating on the specimen surface with serum albumin. Lipid absorption of the specimen was confirmed by dynamic viscoelastic and IR measurements. In the case of segmented poly(urethaneurea) which did not immersed in lipids solution, their fatigue strength are sufficient for application to artificial heart systems. However, fatigue strength of the TU-Mn series was decreased drastically after absorption of lipids. On the other hand, Biomer did not show a decrease of fatigue strength after lipid absorption. The reduction of fatigue strength in the TU-Mn series after lipid absorption will be attributed to the weak aggregation of hard segment domain. This reduction of fatigue strength in the TU-Mn series is characterized by formation of microcrack and mirror zone in fatigue fractured specimen. As the precoating of the specimen surface with serum albumin inhibits the absorption of lipids, the reduction of fatigue strength was not observed for the specimen precoated with serum albumin even after immersing the TU-Mn series in lipids solution for 96 days.

57 citations


Journal ArticleDOI
TL;DR: A comprehensive constitutive law for a sand-asphalt mixture subjected to either compressive or tensile cyclic loading is developed in this article, where elastic, plastic, viscoelastic, and viscoplastic components are incorporated into the model as they are found to be simultaneously present during the loading process.
Abstract: A comprehensive constitutive law for a sand-asphalt mixture subjected to either compressive or tensile cyclic loading is developed. The elastic, plastic, viscoelastic, and viscoplastic strain components are incorporated into the model as they are found to be simultaneously present during the loading process. The various parameters of the model are extracted from a series of repeated uniaxial creep and creep-recovery experiments performed under either compressive or tensile constant stress. The experiments are conducted at constant temperature and at various stress levels, time periods, and number of cycles. The material law presentation is followed by a parametric study that is intended to illustrate the relative quantitative influence of various parameters on the resilient and residual strain components.

53 citations


Journal ArticleDOI
TL;DR: The effect of plate thickness on the fatigue strength of transverse fillet welds in axial loading was investigated in this article, where plate thicknesses were in the range 12.5-80 mm.

51 citations



Journal ArticleDOI
TL;DR: In this paper, a 20% fall in the saturation stress in tension and cusp formation in the compressive portion of the cycle have been identified as the two best criteria for defining the failure life of laboratory specimens in strain-controlled low cycle fatigue testing.

48 citations


Journal ArticleDOI
TL;DR: In this article, the effect of microstructure on the fatigue crack initiation of fully pearlitic steels was studied through independent variation of the prior austenite grain size, pearlite colony size, and the pearlite interlamellar spacing.
Abstract: The effect of microstructure on the fatigue crack initiation of fully pearlitic steels was studied through independent variation of the prior austenite grain size, pearlite colony size, and the pearlite interlamellar spacing. Increasing yield strength (controlled by decreasing the pearlite interlamellar spacing) was seen to increase the smooth and notched-bar crack initiation endurance limit. Grain and colony size variations, at constant yield strength, were seen to exhibit no effect on crack initiation. Scanning Electron Microscopy revealed smooth-bar cracks to have initiated at surface inclusions. The influence of the pearlite interlamellar spacing, reflecting a change in the effective slip length, and the differences between notched and smooth-bar fatigue specimens for studying the effects of microstructure on crack initiation are discussed.

Journal ArticleDOI
TL;DR: In this paper, the stress intensity factors for various spot welded joints such as tensile-shear, cross-tension, T type tension and bending specimens, are analyzed by finite element method.
Abstract: The stress intensity factors for various spot welded joints such as tensile-shear, cross- tension, T type tension and bending specimens, are analysed by finite element method. The fatigue strength and the fatigue crack pathes for these specimens can be well characterized by the stress intesity factors analysed and a mixed mode fracture criterion. It is found that fracture mechanics is a powerfull approach to evaluate the fatigue strength for various spot welded joint specimens with different loading systems, plate thicknesses and nugget diameters.

Journal ArticleDOI
TL;DR: In this article, the effects of inclusions on 538 °C (1000 °F) strain control low cycle fatigue life of hot isostatically pressed and heat treated powder metal Rene* 95 compacts were evaluated.
Abstract: Effects of inclusions on 538 °C (1000 °F) strain control low cycle fatigue life of hot isostatically pressed and heat treated powder metal Rene* 95 compacts were evaluated. Size and location (surface or internal for the test bar) effects along with inclusion types and sources are categorized. Five types of inclusions were identified based on fracture initiation site appearance, although only two major types commonly contribute to significant life low cycle fatigue life degradation. Prior particle boundary decoration reactive type inclusions typically cause the most severe low cycle fatigue life degradation, and those are followed by the discrete ceramic type inclusions. Known potential contaminant seeding study evaluations were used to confirm sources for specific inclusion types. Attempts to minimize the sources for introduction of these contaminants in the argon gas atomization process facilities were only partially successful. An advanced processing approach for the manufacture of Rene 95 to achieve superior low cycle fatigue life has been proposed based on the improved understanding of the inclusion problem.

Journal ArticleDOI
TL;DR: In this paper, the authors investigate the interaction of two types of crack systems in biaxial fatigue, experiments were performed on thin-wall tubular specimens in tension, torsion and combined tension-torsion loading.
Abstract: — During constant amplitude loading, two different types of crack systems have been reported In the high cycle fatigue (HCF) region, cracks nucleate on a small number of maxium shear strain amplitude planes One of these cracks becomes a dominant crack and leads to failure of the specimen In the low cycle fatigue (LCF) region, equally developed microcracks are observed over the entire gage section and grow during the majority of the life. The failure is due to a linking in which the microcracks join up during the last few cycles of the fatigue life. To investigate the interaction of these two types of crack systems in biaxial fatigue, experiments were performed on thin-wall tubular specimens in tension, torsion and combined tension-torsion loading The test program included step loading and block loading in which two equivalent strain amplitudes were employed. One of the equivalent strain amplitudes is in the HCF region and the other was in the LCF region Fatigue lives were predicted from constant amplitude damage curves when a single crack system dominated the fatigue process Two competitive crack systems were sometimes developed on the maximum shear strain amplitude planes in a single specimen under block loading This resulted in a conservative prediction of the fatigue life.

Journal ArticleDOI
TL;DR: In this paper, the authors test the hypothesis that fatigue cracks in drawn, pearlitic steel wire propagate from pre-existing surface defects which can be treated as cracks, and the fatigue limits of five different wires have been statistically determined.

Journal ArticleDOI
TL;DR: In this article, the effects of various phenomena such as creep-induced intergranular cavitation, mean stress, material condition, and enivronment on the fatigue life of several engineering structural alloys are discussed.
Abstract: Time-dependent fatigue behaviour is of considerable interest to the designers of elevated-temperature equipment subjected to periodic thermal transients that can introduce both creep and fatigue damage In this review the effects of various phenomena such as creep-induced intergranular cavitation, mean stress, material condition, and enivronment on the fatigue life of several engineering structural alloys are discussed Materials used to illustrate these effects when subjected to various loading conditions within the creep range include 225Cr-1Mo steel (annealed), modified 9Cr-1 Mo steel (normalized and tempered), types 304 and 316 stainless steel, alloy 800H, Hastelloy X, and alloy 718 Several models used to extrapolate available data to predict cyclic life are also discussed in terms of both their strengths and apparent shortcomings No model currently available is clearly superior in its ability to predict cyclic life for all alloys under all loading conditions envisioned, particularly at lo

Journal ArticleDOI
TL;DR: In this article, a model for life prediction in low-cycle fatigue with hold time at tensile peak strain is suggested in the temperature region of 0.57Tm. This model is based on previously reported theories for creep cavitatation and they predict the creep-fatigue life.
Abstract: In high-temperature and low-cycle fatigue, creep damage reduces fatigue life. In this investigation, a model for life prediction in low-cycle fatigue with hold time at tensile peak strain is suggested in the temperature region of 0.57Tm. This model is based on previously reported theories for creep cavitatation and we predict the creep-fatigue life. It is proposed that the fatigue life may be predicted in terms of plastic strain range, test temperature, hold time and other parameters. An equation for life prediction is given and checked using other investigators' experimental results with various hold times. The predicted creep-fatigue lives are in good agreement with those observed experimentally for 304 stainless steel, 316 stainless steel, CrMoV steel and 13CrMo44 steel.

Journal ArticleDOI
TL;DR: The porous coating of femoral stems was shown to dramatically improve the load carrying capability and fatigue characteristics of the stem-cement interface.
Abstract: Porous coated surfaces for fixation of total hip replacement are a current trend in clinical orthopedics. Such devices are designed to be fixed by ingrowth of bony tissue, although in the absence of FDA approval for biologic fixation, fixation with PMMA cement is recommended by the implant manufacturers. In order to characterize the mechanical properties of the micro-interlocked stem-cement interface, we tested both porous coated and smooth femoral components in cement mantles of consistent overall geometry. Under conditions of increasing load the smooth stems demonstrated stepwise irreversible subsidence into the mantle. Axial and circumferential strains measured in the cement containment vessels with the smooth stems showed that stepwise increases in tensile hoop strain occurred concomitantly with the stepwise incidents of stem subsidence. When subjected to the same loading conditions, the porous coated stems did not undergo stepwise incidents of subsidence, and hoop strain generation was reduced. In addition, a twofold increase in the failure load of the stem-cement interface was measured with the porous coated stems. Fatigue loading for 10(7) loading cycles did not result in gross failure of either the micro-interlocked or smooth interfaces. However, the data showed that during fatigue loading, stepwise subsidence of the smooth stems again occurred. The final subsidence magnitude of the smooth stem-cement interface at 10(7) loading cycles was six times greater than the value associated with the porous coated stem. Thus the porous coating of femoral stems was shown to dramatically improve the load carrying capability and fatigue characteristics of the stem-cement interface.

Journal ArticleDOI
TL;DR: In this article, the fatigue strength of dual-phase steel was found to be similar to that of other types of steel ( eg solution hardened or microalloyed steels) of equal tensile strength.

Journal ArticleDOI
TL;DR: In this article, the authors describe a stress measuring system, which is capable of fast acquisition of stress data and can reveal the influences of tool variations en residual machining stresses, and examples are shown of how machining operations can be evaluated with the aid of residua) stresses.

Book ChapterDOI
01 Jan 1985
TL;DR: In this paper, a Bayesian linear regression analysis with prior information from behavior of similar joints is used to predict the fatigue life of offshore structural joints, in particular for dynamically sensitive deep water structures.
Abstract: Fatigue failure is an important failure mode for offshore structural joints, in particular for dynamically sensitive deep water structures. To predict the fatigue life only a few test results are generally available for the actual type of joint. In addition, however, test results for joints with slightly different geometries are available. Fatigue life predictions can be based on a Bayesian linear regression analysis with prior information from behavior of similar joints. The posterior distribution of the regression parameters is then used in predicting the fatigue life. First and second order reliability methods (FORM and SORM) are applied. Besides the statistical uncertainty, also the uncertainty in the overall loading, the uncertainty in the local hot spot stress calculation and the uncertainty in the strength reduction due to increased thickness are included.

Journal ArticleDOI
TL;DR: In this paper, the Ni20Cr wire with and without carbon ion implantation was tested in tension-tension fatigue and a 17% increase in endurance limit was found with implantation.

Journal ArticleDOI
TL;DR: In this article, a cumulative damage rule for fatigue of metals under variable stress-amplitude loading is proposed, which takes into account the sequence of stress levels, i.e., high-tolow or low-to-high changes of stress amplitudes.
Abstract: A cumulative damage rule is proposed for fatigue of metals under variable stress-amplitude loading. The rule is nonlinear and takes into account the sequence of stress levels, i.e., high-to-low or low-to-high changes of stress amplitudes. To facilitate probabilistic estimates of safety of structural elements subjected to fatigue loading, a stochastic model of fatigue damage is developed. The mean value and the variance of the fatigue life of an element are determined in terms of the statistics of the material properties and of the load parameters.


Journal ArticleDOI
TL;DR: In this article, the fatigue strength of welded joints may be improved in many situations, especially in those cases where high-strength steels are used, but the use of a metho...
Abstract: Improving the fatigue strength of welded joints may be economically interesting in many situations, especially in those cases where high-strength steels are used. However, widespread use of a metho...

Journal ArticleDOI
TL;DR: In this paper, the authors evaluate the local strain conditions near the fatigue-crack starting zones in welded structures, at the toe of weld joints, characterized by steep gradients for strain and stress.
Abstract: The object of the paper is the experimental evaluation of the local strain conditions near the fatigue-crack starting zones in welded structures, at the toe of weld joints. These zones are characterized by steep gradients for strain and stress. The evaluation is performed using strain gages and finite-element techniques on real cruciform weld joints. The results illustrate the possibilities and the limitations posed by the use of local strain measurements to assess the fatigue strength of welded structures. These factors are usually estimated on the basis of a nominal stress approach.

Journal ArticleDOI
TL;DR: In this paper, the influence of texture on the deformation behavior and monotonic and cyclic properties of two recrystallized P/MX7091-T651 plates was investigated.
Abstract: The influence of texture on the deformation behavior and monotonic and cyclic properties of two recrystallized P/MX7091-T651 plates was investigated. Thermal mechanical treatments were used to produced two different textures which varied in intensity by a factor of four. The two plates had similar grain and precipitate structures. The deformation behavior and mechanical properties were correlated with grain orientation and grain boundary misorientation. Differences in fracture surface roughness and crack deflection frequencies were observed for the two texture variants during fatigue crack propagation studies. Deformation behavior, crack closure, and crack deflection affected the fatigue crack growth rates. A small but measurable improvement in tensile strength, fatigue strength, and fatigue crack growth resistance was obtained in the sharply textured material when compared with the weakly textured counterpart.


Journal ArticleDOI
01 Jan 1985-Polymer
TL;DR: In this paper, the influence of sorbed water on average fatigue life and on fracture surface morphology for unnotched samples of low and high molecular weight poly(methyl methacrylate) has been investigated.

Journal ArticleDOI
TL;DR: In this paper, the influence of outting variables including the breaching speeds, tooth rises and tool angles on the surface layer's condition and fatigue behavior of broached titanium alloy is experimentally studied.