Showing papers on "Vibration fatigue published in 1974"
TL;DR: In this paper, a reliability analysis of fatigue-sensi tive aircraft structures, based on the application of the approach developed in the "random vibration theory," is presented.
Abstract: A reliability analysis of fatigue-sensi tive aircraft structures, based on the application of the approach developed in the "random vibration theory," is presented. Operational service loads, composed of ground loads, ground-air-ground loads, and gust loads, are all random in nature. The fatigue process involved here consists of crack initiation, crack propagation, and strength degradation. The time to crack initiation and the ultimate strength are random variables. After a fatigue crack is initiated, fracture mechanics is applied to predict crack propagation under random loading. While the fatigue crack is propagating, the residual strength of the structure decreases progressively, thus increasing the failure rate with time. The aircraft structure is subjected to periodic inspection in service. When a fatigue crack is detected during inspection, the implicated component is either repaired or replaced, so that both the static and the fatigue strength are renewed. Such a renewal process is taken into account in the present analysis. The detection of an existing fatigue crack during inspection is also a random variable which depends on the resolution capability of the particular technique employed and the size of the existing crack. Taking into account all the random variables as well as all the random loadings, the solution for the probability of first failure in a fleet of aircraft is derived. Finally, numerical examples are given to demonstrate the effect of inspection and fleet size on the fleet reliability.
121 citations
40 citations
TL;DR: In this paper, the authors describe the properties and performance characteristics of a composite aluminum-steel conductor, where the aluminum wires are fully annealed in the factory and normally all or most of the mechanical load is carried by the steel.
Abstract: This paper describes the properties and performance characteristics of a new type of composite aluminum-steel conductor. The aluminum wires are fully annealed in the factory, and normally all or most of the mechanical load is carried by the steel. The new conductor can operate continuously at high temperatures without detriment; it sags less at high temperatures than conventional conductors; it has a high self damping capability; it has a high degree of immunity to vibration fatigue; and its final sags are not affected by long time creep of aluminum.
29 citations
TL;DR: In this article, the authors examined the decreased severity of notches in fatigue when compared with the severity predicted by deformation analysis in terms of a number of factors which may influence this behaviour.
16 citations
TL;DR: In this paper, a close-form solution, expressed in terms of the hypergeometric function, for approximating the rise and fall statistics of random processes is presented, which is very simple to compute and its accuracy is very satisfactory when the random response process is reasonably narrow band.
Abstract: Under random excitation, the fatigue crack growth of a structure depends primarily on the statistics of rises and falls of the random response process. Based on the envelope statistics, a close-form solution, expressed in terms of the hypergeometric function, for approximating the rise and fall statistics of random processes is presented. The solution is very simple to compute and its accuracy is very satisfactory when the random response process is reasonably narrow band.
12 citations
TL;DR: In this article, the authors present a general statistical model for detecting fatigue under stochastic randoms, GAUSSIAN STRESS, which requires only a limited amount of data from FATIGUE TESTS in which SPECIMENS are SUBJECTed to STATIONARY NARROW BAND, GAusSIan stress.
Abstract: A GENERAL STATISTICAL MODEL FOR FATIGUE UNDER STATIONARY RANDOM GAUSSIAN STRESS IS PRESENTED. THIS PHENOMENOLOGICAL MODEL REQUIRES ONLY A LIMITED AMOUNT OF DATA FROM FATIGUE TESTS IN WHICH SPECIMENS ARE SUBJECTED TO STATIONARY NARROW BAND, GAUSSIAN STRESSES. A THEORETICAL EXTENSION IS MADE TO PREDICT FATIGUE UNDER WIDE BAND STRESSES AND ARBITRARY MEAN VALUES. STATISTICAL VARIABILITY IN MATERIAL STRENGTH IS INCLUDED IN THE MODEL. THE MODEL HAS THE PROPERTY OF ADAPTABILITY IN THAT IT IS EASILY MODIFIED TO REFLECT NEW DATA AS IT BECOMES AVAILABLE, AND IT IS EASILY INCORPORATED INTO PROBABILISTIC DESIGN PROCEDURES WHERE RELIABILITY REQUIREMENTS ARE SPECIFIED. /AUTHOR/
10 citations
01 Feb 1974
TL;DR: In this paper, a reliability analysis of fatigue-sensitive structures, based on the application of random vibration theory, is presented, where the fatigue process involved here consists of crack initiation, crack propagation and strength degradation.
Abstract: : A reliability analysis of fatigue-sensitive structures, based on the application of random vibration theory, is presented. The fatigue process involved here consists of crack initiation, crack propagation and strength degradation. After a fatigue crack is initiated, fracture mechanics is applied to predict crack propagation under random loading. The aircraft structure is subjected to periodic inspection in service. When a fatigue crack is detected during inspection, the implicated component is either repaired or replaced. Such a renewal process is taken into account in the present analysis. Taking into account all the random variables as well as the random loadings, the solution for the probability of first failure in a fleet of aircraft is derived.
5 citations
Esso1
TL;DR: In this article, a model of a fixed-bottom platform is subjected to finite length synthetic wave profiles representing operational and severe sea states for a given location, and a fatigue analysis is performed.
Abstract: As the offshore oil industry moves into deeper water, fixed-bottom platforms will be found to exhibit dynamic amplification of wave-induced response. The resulting dynamic loads will have a significant effect on the cyclic stresses used in a fatigue analysis. State-of-the-art fatigue analyses require some sort of stress-history curve, which is extracted from the dynamic response indicated by a mathematical model of a platform. The mathematical model of the platform is subjected to finite length synthetic wave profiles representing operational and severe sea states for a given location.
3 citations
TL;DR: In this article, a mechanical type of random fatigue testing machine is improved so that random loads with arbitrary overall means can be applied to the specimens and random fatigue tests are then carried out by the testing machine both on hard steel (S55C) and aluminum alloy (7075-T6) in order to examine the utility of the machine and to determine the fatigue strengths or the fatigue lives of both materials under service loads.
Abstract: A mechanical type of random fatigue testing machine is improved so that random loads with arbitrary overall means can be applied to the specimens Random fatigue tests are then carried out by the testing machine both on hard steel (S55C) and aluminum alloy (7075-T6) in order to examine the utility of the machine and to determine the fatigue strengths or the fatigue lives of both materials under service loads Further, discussions are made about the appropriate methods both of load counting and of estimation of fatigue lives under service loads Consequently, the full wave count method is proved to be very useful since the fatigue lives estimated by that method are closer to the actual lives, irrespective of the material and the extent of the irregularity of the original random load
1 citations
TL;DR: In this paper, the effects of the cyclic frequency and the stress wave form on the fatigue strength have been investigated by many investigators, but the physical meaning of the frequency and wave form dependent fatigue behavior has not been elucidated.
Abstract: The effects of the cyclic frequency and the stress wave form on the fatigue strength have been investigated by many investigators, but the physical meaning of the frequency and wave form dependent fatigue behavior has not been elucidated. In the present work, an analysis of these effects was made employing a modified Johnston-Gilman's formula. The experimantal results, which were obtained from fatigue tests performed under the sinusoidal, the triangular and the rectangular stress waves and under the cyclic frequency range from 0.2 to 60c/s, were well explained by the present analysis. Particularly, the frequency effect on fatigue strength was well interpreted in terms of the dislocation motion over a wide range of cyclic frequencies.
1 citations
TL;DR: In this article, a noncontact measurement of the surface temperatures of steel specimens subjected to rotating bending was made and the temperature variation was expressed as the sum of two exponential functions with due consideration for heat transmission.
Abstract: Noncontact measurement was made of the surface temperatures of steel specimens subjected to rotating bending. The temperature variation was expressed as the sum of two exponential functions with due consideration for heat transmission. The thermal energy produced during one stress cycle could be regarded to be almost constant throughout the main fatigue process and its stress dependence was found to be expressible in an exponential function of the reciprocals of the stress amplitudes. A fatigue criterion has been obtained, which agrees with the results presented by others from the standpoint of hysteresis energy dissipation, and, being applied to the notched specimens, gives a means to determine the fatigue notch factors. The calculated values have been shown to agree satisfactorily with the data in the literature.