Showing papers on "Vibration fatigue published in 1986"
TL;DR: In this paper, a model is presented which describes the influence of plastic strain and cycling frequency and temperature changes on fatigue life, which account for temperature changes, cycling waveshape, and joint geometries.
Abstract: Plastic strain versus fatigue life data are presented for tests run at -- 50, 35, 125, and 150°C. It was found that these data could be correlated by the Coffin-Manson fatigue law, with an exponent of approximately 0.5 for the tests run at -35°C to 125°C. At 150°C the exponent was reduced to 0.37. These results were obtained for plastic strain limited tests. Different results are obtained when total strain limits are employed. This difference is discussed. The influence of cycling frequency and temperature changes are also discussed. A model is presented which describes the influence of plastic strain and cycling frequency. Corrections to the model predicted fatigue life, which account for temperature changes, cycling waveshape, and joint geometries, are also discussed.
310 citations
TL;DR: In this paper, the power spectral density of the strain history and conventional fatigue strength data is used to predict the fatigue life span under variable amplitude loading for certain classes of strain history.
Abstract: Fatigue life prediction under variable amplitude loading normally involves a two stage process of cycle counting and damage summation. This paper shows that for certain classes of strain history, predictions can be made directly from a knowledge only of the power spectral density of the strain history and conventional fatigue strength data.
42 citations
01 Jan 1986
TL;DR: In this paper, a closed loop servohydraulic structural fatigue testing machine was used to evaluate the fatigue strength of rear axle housings of automobiles under constant amplitude loadings, and the results showed that the weak spot of axle housing was the heat affected zone in weldment.
Abstract: This paper presents fatigue strength evaluations of various structural components of automobiles under constant amplitude loadings with a closed loop servohydraulic structural fatigue testing machine. Structural fatigue tests of rear axle housings of automobiles were performed. Acceptance criteria for the axle housing were decided by the actual proving ground running test and statistical analysis of results. Durability evaluations of axle housings for 8-ton trucks were conducted. The weak spot of axle housings was the heat affected zone in weldment. Torsional fatigue tests on a turbocharged diesel engine crankshaft were performed. Most cracks initiate at the oil hole and propagate along the maximum tensile stress planes. Fatigue strength evaluations of automobile components were also performed for their structural reliability in service. The constant amplitude fatigue testing method is quickest when a proper acceptance criterion is decided or known.
9 citations
TL;DR: In this article, a model for predicting fatigue crack growth rate and life probabilistically under random load history is presented, which allows for random growth per cycle, and is based on experimental results of constant amplitude cyclic loads.
5 citations
TL;DR: In this paper, uncertainties in the dynamic shear modulus along with random wave loading were used to estimate the fatigue response of offshore structures against fatigue in a First-Order Second Moment (FIRM) technique.
3 citations
TL;DR: In this article, an approach is developed to fatigue and fracture phenomena based on the generalized energy concept taking into account micro-cracking damage accumulated at the crack-tip, where it is assumed that stresses at the cracks are bounded, and damage is result of the stress-state and environmental prehistory in vicinity of the crack tip.
Abstract: An approach is developed to fatigue and fracture phenomena based on the generalized energy concept taking into account microcracking damage accumulated at the crack-tip. It is assumed that stresses at the crack-tip are bounded, and damage is result of the stress-state and environmental prehistory in vicinity of the crack-tip. A fatigue crack does not grow when it is in subequilibrium state (in the Griffith sense) and advances when it reaches non-equilibrium state at a distance which order of magnitude is equal to the characteristics size of material microstructure. The model is applied to assessment of cyclic and static fatigue cracks growth in elastic and visco-elastic media, in particular, under nonstationary and random loading when jumping, kinking and branching of cracks are expected.
2 citations
TL;DR: In this paper, the authors proposed to use the concept of crack closure for examination of fatigue crack growth and fatigue behavior under random loading, which can be predicted from constant amplitude test.
Abstract: Crack extension by fatigue may sometimes cause a catastrophic failure of structure. For the safety assessment of structure, therefore, it is indispensable to estimate fatigue crack growth under service loading. In most cases actual service loads are random, and the estimating method for fatigue crack growth under random loading must be established.For practical use, it is very preferable that the prediction of fatigue behavior in real structures under random loading could be made using the data obtained by constant amplitude loading test which is simple and convenient as a conventional and routine test. Many investigations have been carried out in order to clarify the relationship between fatigue behaviors under random loading and constant amplitude loading, recently based on the concept of “crack closure” proposed by Elber. In these investigations, however, pure random load has not been applied because of its complexity, and the relationship has not been clarified yet.In this study, fatigue crack propagation tests under random loading-narrow band random for its simplicity-are carried out as well as constant amplitude loading tests for comparison. Crack closure phenomena of the specimens are automatically recorded over a long period of fatigue cycles using electric potential method aided by micro-computer system. It is shown that consideration of crack closure is essential for examination of fatigue crack growth and fatigue behavior under random loading may be predicted from constant amplitude test.
1 citations
TL;DR: In this article, the fatigue properties of a wrought Ni-base superalloy treated by laserglazing and post heat treatments have been investigated, and the results showed that the fatigue property of laserglazed specimens was obviously deteriorated because of resolution of γ′ phase and grain boundary carbide, interdendritic segregation of TiC and microcrack caused by thermal stress.
Abstract: Fatigue properties of a wrought Ni-base superalloy treated by laserglazing and post heat treatments have been investigated. Tests have been run both by the rotating bend fatigue at 700°C and the vibration fatigue of turbine blades at room temperature. The results showed that the fatigue property of laserglazed specimens was obviously deteriorated because of resolution of γ′ phase and grain boundary carbide, interdendritic segregation of TiC and microcrack caused by thermal stress. However, suitable preheating and post heat treatment added before and after laserglazing can eliminate these defects and recover the fatigue life of this superalloy. Selected laser processing technology was applied to repairing blades rejected due to microcracks at trailing edge. The vibration fatigue life of blades repaired by laserglazing and post heat treatment was over two times as high as that of normal used blades with same service time.
TL;DR: In this paper, two micro processing units are used to perform experiments with or without response compensation by FFT, and the developed soft and hardware are satisfactory and fatige crack growth tests under a stationary random stress intensity factor showed the effect of the compensation and indicated the possibility of a simplified and less time consuming test method.
Abstract: To supply data needed for a rational fatigue design of structures subject to random load there must be some appropriate testing methods which are able to reproduce a specified time history of the random variable such as load, stress, strain and stress intensity factor and also must be inexpensive to be popular ones.With a small micro computer system alone, it is very difficult to perform exact experiments considering the dynamic characters of the test system varying as the fatigue damage accumulates in the specimen. In this report, two Micro Processing Units are used to perform experiments with or without response compensation by FFT. Stationary Gaussian random processes are generated with a large computer and data are packed into special forms to be sent through TSS within a reasonable time.The developed soft and hardware are satisfactory and fatige crack growth tests under a stationary random stress intensity factor showed the effect of the compensation and indicated the possibility of a simplified and less time consuming test method without response compensation.
TL;DR: In this paper, a probability-based method for evaluating fatigue damage in a freight car is described, and the effect of uncertain boundary conditions for the car in the calculations of fatigue damage is also discussed.
Abstract: SUMMARY The critical components of railroad fraight cars are subjected to fluctuating stresses and, therefore, vulnerable to fatigue damage. These fluctuating stresses result from different motions of the car when it travels along a track and is subjected to various track irregularities. Both the track irregularities and corresponding motions are highly random. Therefore, the fatigue damage can only be determined by means of a percentage probability level. This paper describes a probability-based method for evaluating fatigue damage in a freight car. The effect of uncertain boundary conditions for the car in the calculations of fatigue damage is also discussed. The applications of the method to carbody design and assessment of fatigue life are also explained
TL;DR: In this article, the interaction of creep-hot corrosion and low cycle fatigue is analyzed based on the energy expended for the nucleation of damage at the advancing crack front, which yields a relation in terms of J-integral which is applicable to both crack propagation and final failure.
Abstract: Defects introduced in pressure vessel components during fabrication processes act as potential sources for damage accumulation and subsequent catastrophic failure. Cracks nucleate at these stress risers and propagate aided by fatigue type of loading, corrosion and creep. Analysis of crack growth under conditions of ‘time-dependent fatigue’ is very important for the life prediction of pressure vessel components. In this paper the interaction of creep-hot corrosion and low cycle fatigue is analyzed based on the energy expended for the nucleation of damage at the advancing crack front. The total damage accumulation is divided into that due to (i) fatigue, (ii) corrosion and (iii) creep for modelling purpose. The analysis yields a relation in terms ofJ-integral which is applicable to both crack propagation and final failure. A corrosion-creep parameter (F i ) has been introduced at the crack propagation stage and raw data from different sources have been analyzed for different types of loading and compared with the theoretical predictions. The total energy in tension which includes the tension going time, appears to be a good parameter for the prediction of time-dependent fatigue life.