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Showing papers on "Fatigue limit published in 1987"


Book
01 Jan 1987
TL;DR: A summary of the six lectures presented at the session, "Modern Trends in Composite Laminates Mechanics" at CISM in Udine as discussed by the authors, is presented in this paper.
Abstract: This chapter summarizes part of the six lectures, pertaining to fatigue of composite materials, presented at the session, “Modern Trends in Composite Laminates Mechanics” at CISM in Udine The summary provided here is of introductory nature aimed at a reader who is not an expert in the subject Ample references are given to help the reader pursue the subject further

504 citations


Book
01 Jan 1987
TL;DR: In this article, the authors present a fatigue evaluation procedure for existing steel highway bridges and a compatible fatigue design procedure for new highway bridges, which realistically characterize the actual fatigue stress and cyclic conditions in bridges and use methods of calculating stress ranges that are similar to present AASHTO methods.
Abstract: This report presents a fatigue evaluation procedure for existing steel highway bridges and a compatible fatigue design procedure for new steel highway bridges. Both procedures realistically characterize the actual fatigue stress and cyclic conditions in bridges. Both procedures use the same detail categories and corresponding fatigue strength data as the present AASHTO specifications; they also use methods of calculating stress ranges that are similar to present AASHTO methods. The evaluation procedure, which is recommended for inclusion in the AASHTO Manual for Maintenance-Inspection of Bridges, gives accurate estimates of the remaining mean and safe fatigue lives and permits these estimates to be updated in the future to reflect changes in traffic conditions. An alternative procedure is also given for monitoring the accumulated fatigue damage during the life of the bridge; it is intended for use in conjunction with the routine inspections that are normally conducted at two-year intervals. An assessment of remaining fatigue life is needed in bridge management systems to assist in scheduling inspection, maintenance, rehabilitation and replacement. It is also useful in evaluating administrative and legislative policies such as truck-weight and overload policies. The design procedure, which is recommended for inclusion in the AASHTO Standard Specifications for Highway Bridges, is consistent with the evaluation procedure and utilizes many of the same concepts. However, it is presented in a format convenient for design; a calculated design stress range is compared with a permissible stress range corresponding to a desired safe design life. The procedure is much more flexible than present AASHTO fatigue procedures; it permits rigorous analysis methods and designs for any desired design life, initial truck volume, and truck-volume growth rate.

155 citations


Journal Article
TL;DR: Finite-element analysis revealed that the stress on the nail exceeded its fatigue endurance limit and that the femur had to regain 50 per cent of its original stiffness through healing to accommodate weight-bearing without the risk of fatigue failure of the nail.
Abstract: The clinical and mechanical factors predisposing to a fatigue fracture of an interlocking nail were studied in seven patients who were treated for a fracture of the distal part of the femur. In all patients, the fracture of the femur was five centimeters or less from the more proximal of the two distal screw-holes. Finite-element analysis revealed that the stress on the nail exceeded its fatigue endurance limit and that the femur had to regain 50 per cent of its original stiffness through healing to accommodate weight-bearing without the risk of fatigue failure of the nail. The risk of fatigue failure may be minimized by using nails that have a larger diameter and by avoiding early weight-bearing.

147 citations


Journal ArticleDOI
TL;DR: In this article, the static and cyclic fatigue behavior of sintered silicon nitride was investigated at room temperature, and it was shown that the minimum time to failure was almost the same, in spite of differences in loading mode or frequency.
Abstract: The static and cyclic fatigue behavior of sintered silicon nitride was investigated at room temperature. Flexure specimens, with an indentation-induced flaw at the center, were tested under a static or cyclic load applied by four-point bending. Sintered silicon nitride was shown to be susceptible to static and cyclic fatigue failure. Comparing the static and cyclic fatigue lifetimes at frequencies from 0.01 to 10 Hz, it was shown that minimum time to failure was almost the same, in spite of differences in loading mode or frequency. However, cyclic stress decreased the scatter in lifetime by reducing the upper limit. Moreover, the cyclic fatigue limit was significantly lower than the static fatigue limit. High-magnification fractography revealed a fatigue failure dominated by intergranular cracking with partial transgranular failure at perpendicularly elongated crystals. This suggests that the intergranular fatigue crack can be arrested at grain-boundary triplets, and also can be reactivated by subsequent cyclic loading. The crack growth rate, calculated from the fatigue lifetime, showed three characteristic regions having a plateau at 70% to 90% of the fracture toughness, which suggests a possible intergranular stress corrosion cracking mechanism resembling that in glass or alumina.

117 citations


Journal ArticleDOI
TL;DR: In this article, fatigue and stress-rupture testing of unidirectional Nicalon-type silicon carbide fiber-reinforced lithium aluminosilicate glass-ceramic matrix composites is described.
Abstract: Fatigue and stress-rupture testing of unidirectional Nicalon-type silicon carbide fibre-reinforced lithium aluminosilicate glass-ceramic matrix composites is described. Tensile fatigue testing was performed at 22°C on two different composite systems to contrast the behaviour under applied stresses above and below the levels necessary to cause matrix cracking. The higher strength of the two composites was then also tested in flexural fatigue and constant-load stress rupture at 22, 600 and 900° C in air. It is shown that the level of tensile stress at which composite inelastic stress-strain behaviour begins is an important factor in the control of overall composite performance, and that properties at elevated temperature are significantly different to those at room temperature.

116 citations


Journal ArticleDOI
TL;DR: In this paper, Bilby, Cottrell and Swinden applied the crack model to simulate the blocking of the plastic zone at the grain boundary and to obtain the stress concentration ahead of the crack as it approaches the barrier.
Abstract: The behaviour of short cracks approaching growth barriers (eg grain boundaries) is considered The crack model of Bilby, Cottrell and Swinden is applied to simulate the blocking of the plastic zone at the grain boundary and to obtain the stress concentration ahead of the crack as it approaches the barrier The idea of the Hall-Petch type relationship that the transmission of slip across grain boundaries needs the previous achievement of a critical stress has been used By making the crack growth rate proportional to the plastic displacement at the root of the crack the deceleration behaviour of short cracks and the existence of non-propagating cracks may be explained The fatigue limit is related to the stress below which a crack growing in a single grain is unable to promote slip in the neighbouring grain The different behaviour in the so-called long crack period has been rationalized in terms of the plastic zone exceeding the grain size For this case, and in the grain completely included within the plastic zone, the Hall-Petch analysis must be applied Hence the maximum back-stress sustained by this grain cannot exceed the yield stress After this point the Bilby et al model is used with uy as a friction stress (ie the Dugdale model) Finally use is made of Fracture Mechanics to correlate the results in the long crack phase

112 citations


Journal ArticleDOI
TL;DR: In this article, the effect of grain size on the cyclic stress-strain response and on the fatigue life including the plastic strain fatigue limit was determined for a large number of specimens.

101 citations


Journal ArticleDOI
TL;DR: In this paper, a low carbon annealed steel has been first prestrained and then cycled in load control with zero mean stress and a new softening parameter, based on the changes in plastic strain amplitude with cycling, was defined to describe the softening process and its kinetics.

90 citations


Journal Article
TL;DR: In this article, a fatigue and fracture rating plan for riveted steel highway bridges is proposed for a specific purpose: to provide a sensible fatigue rating for highway bridges with the specific objectives of providing an adequate degree of understanding to permit rating recommendations to be developed.
Abstract: This study was carried out with the specific objectives of providing a sensible fatigue and fracture rating plan for riveted steel highway bridges. To accomplish this objective a study of existing test data was carried out and summarized. This information was then supplemented with additional test information produced during the project using beam sections from actual riveted bridges. This permitted estimates of deterioration to be assessed and fatigue and fracture data applicable to full size members to be acquired. The goal of the riveted girder tests which examined the fatigue strength and fracture resistance of the members and assessed the toughness and metallurgical characteristics of the material was to achieve an adequate degree of understanding to permit rating recommendations to be developed.

55 citations



Patent
06 Jul 1987
TL;DR: In this article, a high-strength spin-on filter of improved fatigue strength comprises a cylindrical housing (12), a unitary cover (28) and an internal filter element assembly (18).
Abstract: A high-strength spin-on filter (10) of improved fatigue strength comprises a cylindrical housing (12), a unitary cover (28) and an internal filter element assembly (18). The open end of the housing (12) is folded inwardly over the periphery of the cover (28) and into deformable engagement with radial projections (54) thereon to secure the cover and housing against both relative rotation and separation without stress concentrations that would otherwise decrease fatigue life of the filter (10) in high-pressure pulsatile hydraulic systems.

Journal ArticleDOI
TL;DR: Measurement of the level of porosity in composite resins shows that it may be increased significantly by spatulation, and appears to have limited effect on the abrasive wear characteristics of the materials but has a considerable impact on the resistance to fatigue.

Journal ArticleDOI
TL;DR: The compressive strength, the compressive fatigue limit and the abrasion resistance rating are improved with the addition of silver particles in the glass, and the new material undergoes a more rapid setting reaction than the conventional cement and is significantly less susceptible to erosion in pH 4.0 buffer.

Journal ArticleDOI
TL;DR: The vulnerability of Luque rod constructs to implant failure, from a mechanical standpoint, is greater than is generally assumed and methods to decrease tensile stresses in the implants and increase stiffness include external immobilization, larger diameter rods, and procedures to enhance correction.

Book
01 Jun 1987
TL;DR: In this article, a systematic review of the current achievement by each author with the emphasis on important points is presented, where the elaborated experimental techniques and theoretical approaches, some of which are quite unique, are introduced by respective authors to make clear the difficulty arising in the observation of small cracks and analysis of data.
Abstract: This first volume of CJMR (Current Japanese Materials Research), contains thirteen chapters concerning the above three themes of fatigue cracks. Each chapter is not a single paper as appearing in many academic journals and transactions, but a systematic review of the current achievement by each author with the emphasis on important points. The common feature is that the elaborated experimental techniques and theoretical approaches, some of which are quite unique, are introduced by respective authors to make clear the difficulty arising in the observation of small cracks and analysis of data. Theoretical models are proposed from the viewpoint of fracture mechanics to link the two thresholds of fatigue limit and crack growth, and intensive discussions are made for further development of the theory. Threshold stress intensity factors and the growth rate of medium and long sized cracks are also discussed, together with their opening behavior. The influencing factors are plastic zone size, the stress ratio and residual stress distribution occurring in welded joints. Mode II crack growth is of great significance since the initial fatigue cracks propagate mainly in shear mode. The problems of fatigue crack growth in corrosive environment is highly important since its retardation and enhancement take placemore » in structural steels affected by the variety of factors. Life prediction in such environments poses another important problem. These are systematically discussed in this book.« less


Patent
18 Aug 1987
TL;DR: Nickel-chromium alloys consisting essentially of from 30-75 nickel, 12-30% chromium, up to 10% molybdenum and up to 8% tungsten are used to improve low cycle and thermal fatigue strength as mentioned in this paper.
Abstract: Nickel-chromium alloys consisting essentially of from 30-75 nickel, 12-30% chromium, up to 10% molybdenum, up to 8% tungsten, up to 15% cobalt, up to 5% of niobium and/or tantalum, titanium plus aluminum up to 5%, and carbon nitrogen and silicon in correlated percentages to thereby improve low cycle and thermal fatigue strength, the balance being from 0 to 50% iron.

Journal ArticleDOI
TL;DR: In this paper, a new and simple definition of the Rain Flow Cycle count method for the analysis of a random load process is presented, combined with the Palmgren-Miner damage rule, and a stochastic model for the fatigue life and fatigue limit variability.
Abstract: We present a new and simple definition of the Rain Flow Cycle count method for the analysis of a random load process. It is combined with the Palmgren-Miner damage rule, and a stochastic model for the fatigue life and fatigue limit variability. Algorithms are presented which make it possible to calculate the RFC-amplitude distribution, based on a Markov Chain approximation of local maxima and minima. The method derived would apply to structures subjected to random fatigue loads such as acoustic noise, random vibration or sea waves, etc.

Journal ArticleDOI
TL;DR: In this paper, annealed low carbon steel in the extremely low cycle fatigue regime has been investigated and it was shown that the final fracture occurs at a strain cycle count less than that expected from the Manson-Coffin law for an ordinary low-cycle fatigue regime in which the development of small surface cracks leads to the fracture of the specimen.
Abstract: Attention has been focussed on the characteristics of the fatigue life of annealed low carbon steel in the extremely low cycle fatigue regime. In this regime, a transition of the fracture mode occurs from the surface to internal cracking with an increase in the plastic strain range. Results show that in this regime the final fracture occurs at a strain cycle count less than that expected from the Manson-Coffin law for an ordinary low cycle fatigue regime in which the development of small surface cracks leads to the fracture of the specimen. Such a reduction in fatigue life is caused by the cracking of pearlite inside the material at a high plastic strain range. The applicability of Miner's law to the prediction of the fatigue life under a variable plastic strain amplitude in the extremely low cycle fatigue regime has also been discussed.


Journal ArticleDOI
TL;DR: In this article, it was shown that increasing the matrix failure strain (ductility) will yield a pronounced improvement of the mechanical properties (under static and fatigue loading) and a shift of the crack initiation level to higher strain values.


Journal ArticleDOI
TL;DR: In this paper, a new theory of autofrettage is proposed for a closed-end cylinder which takes into account work-hardening in the presence of small plastic strains based upon equivalent stress-strain data.

Journal ArticleDOI
TL;DR: In this article, stress intensity factors are calculated using contact pressure and tangential stress distributions across contact surfaces using the Finite Element Method and the results of the calculated results are compared with experimental results of fretting fatigue tests.
Abstract: Fretting fatigue cracks appear very early in the fatigue life of metals. Fretting fatigue life is dominated by the propagation process of small cracks. Characteristics of fretting fatigue cracks are analysed using stress intensity factors which are obtained at the tip of cracks growing from contact edges. Stress intensity factors are calculated using contact pressure and tangential stress distributions across contact surfaces. Contact pressure and tangential stress distributions are anaysed using the Finite Element Method. Fretting fatigue limits are estimated by comparing the above mentioned calculated results of stress intensity factor ranges with the threshold stress intensity factor range of the material. These calculated results are compared with experimental results of fretting fatigue tests.

Journal ArticleDOI
TL;DR: In this article, a method for determining the rolling load that produced optimum fatigue strength improvement in deep-rolled specimens was presented, based on the surface stresses calculated using Hertzian theory and von Mises distortion energy failure criterion.


Journal ArticleDOI
TL;DR: In this paper, a series of strain controlled low-cycle fatigue tests in the simulated high-temperature gas-cooled reactor (HTGR) helium environment were conducted at 900°C on Hastelloy X and its modified version, Hastelloys XR.

01 Jan 1987
TL;DR: In this article, the long-life fatigue strength results for stress-relieved and shot-blasted mild-steel cruciform welds at four nominal mean stress levels are reported.
Abstract: Long-life fatigue strength results for stress-relieved and shot-blasted mild-steel cruciform welds at four nominal mean stress levels are reported. These results are compared with analytical predictions, which fall within 6% of the experimental values for all stress levels. This close agreement supports the validity of the local stress-strain approach for modelling the fatigue of welds. It is also concluded that performance of a notch-root set-up cycle analysis and consideration of both axial and bending stress components are crucial to obtaining accurate fatigue strength predictions for steel weldments.

Journal ArticleDOI
TL;DR: In this paper, the influence d'une pointe de pression dans un contact elastohydrodynamique sur la fatigue d'un palier de roulement is investigated.
Abstract: Influence d'une pointe de pression dans un contact elastohydrodynamique sur la fatigue d'un palier de roulement

Journal ArticleDOI
TL;DR: S-N curves of Ti-5Al-2.5Sn ELI alloy were determined at liquid helium temperature (4K) for both the base and welded materials as mentioned in this paper.
Abstract: S-N curves of Ti-5Al-2.5Sn ELI alloy were determined at liquid helium temperature (4K) for both the base and welded materials.The base material had a longer fatigue life at 4K than at 77K. Welding deteriorated the fatigue properties at 4K. Internal crack initiation was seen at lower cyclic stress in both the base and the welded materials. For the base material, internal crack initiation occurred at 4K, and there were no obvious defects near the initiation sites. On the other hand, fatigue cracks generally initiated at porosity in the weldment. Internal crack initiation is considered one of the causes of reduced fatigue life.High cyclic frequency brought about a large temperature increase in the specimen, making the testing temperature uncertain in fatigue tests at cryogenic temperature.