scispace - formally typeset
Search or ask a question

Showing papers on "Vibration fatigue published in 1983"


Book
01 Jan 1983
TL;DR: In this paper, the authors evaluate the fatigue resistance of welded attachments subjected to variable amplitude fatigue loading and show that the results obtained from these variable amplitude tests are consistent with the previously reported constant amplitude test.
Abstract: The research described in this report is intended to provide information on evaluating the fatigue resistance of welded attachments subjected to variable amplitude fatigue loading. The research consisted of laboratory studies of welded attachments under random variable amplitude load spectra defined by a Rayleigh-type distribution with most stress-cycles below the constant amplitude fatigue limit. (Some stress cycles exceeded this limit.) Eight full-size beams with web attachments and cover plates were tested during the program. Fatigue crack growth data were generated using random block variable amplitude stress spectra defined by a Rayleigh-type distribution. Also, nonload-carrying fillet-welded cruciform-type specimens were tested under simple bending using a random variable amplitude block loading to supplement the existing shorter life studies carried out on stiffener details. The results obtained from these variable amplitude tests are consistent with the previously reported constant amplitude test. However, the existence of a fatigue limit below which no fatigue cracks propagate is assured only if none of the stress range cycles exceed this constant amplitude fatigue limit. If any of the stress range cycles (as few as one per thousand cycles) exceed the limit, fatigue crack propagation will likely occur. The random variable test data from the beam specimens generally fell between the upper and lower confidence limits projected from constant cycle data. The smaller simulated details generally resulted in the random variable test data falling near the upper confidence limit of constant amplitude test results.

81 citations



Journal ArticleDOI
TL;DR: In this article, an analysis of the random decrement method and the conditions which must be satisfied in order for the method to yield consistent estimates is given. But the method is not suitable for the analysis of structural systems.
Abstract: Random decrement signatures have been introduced for use in the determination of the frequencies of oscillation, damping ratios and modes of vibration of structural systems from naturally induced vibration data. This paper gives an analysis of the random decrement method and the conditions which must be satisfied in order for the method to yield consistent estimates.

9 citations


01 Oct 1983
TL;DR: In this article, variable amplitude stress waveforms were developed by superimposing two sine wave signals, i.e., a high frequency/low amplitude signal upon a low frequency/high amplitude signal.
Abstract: The fatigue behavior of welded steel tees loaded in cantilever bending was examined using simple variable amplitude stress waveforms. These waveforms were developed by superimposing two sine wave signals, i.e., a high frequency/low amplitude signal upon a low frequency/high amplitude signal. The test program involved changing the relative size and frequency of these two sine signals. The goal of these tests was to determine the effect that smaller high frequency stress cycles would have upon the fatigue life associated with a major stress cycle. The results of the tests indicated that the damage effect of these smaller stresses was greater than anticipated. In fact, the current AASHTO method of bridge fatigue design may be inadequate because of the damage associated with these additional stresses. The current AASHTO design practice considers only one cycle per vehicle. The smaller dynamic oscillations of the structure are ignored. The impact fraction included in design only accounts for the increase in maximum stress. The influence of the smaller cycles can be included in design by increasing the impact fraction to account for their fatigue damage. The future tests in this project using measured stress histories will be used to develop this approach. (FHWA)

5 citations


Journal ArticleDOI
TL;DR: In this paper, a model is proposed which is able to explain the stress-hold and the strain-hold effects on the fatigue life in time dependent fatigue, assuming the effect of corrosion and creep to become dominant below a certain frequency.
Abstract: Interaction of fatigue with corrosion and creep has been analyzed through a parameter [Fi ] introduced at the crack propagation stage. Assuming the effect of corrosion and creep to become dominant below a certain frequency, a model is proposed which is able to explain the stress-hold and the strain-hold effects on the fatigue life in time dependent fatigue. Beyond a certain period stress-hold leads to time-dependent and strain-hold leads to cycle-dependent interaction life. By suitably evaluating the parameter [Fi ], life under any type of loading condition can be estimated. Based on the parameter, an interaction diagram is proposed for predicting the fatigue life in time dependent high temperature low cycle fatigue.

3 citations


01 Dec 1983
TL;DR: In this paper, the authors derived expressions for fatigue life in terms of functions of the PSD showing that the close relationship is due to the fact that all the signals have had a Gaussian amplitude probability distribution.
Abstract: Many of the components and structures developing cracks and failing in service have been subjected to vibration, but the exact relationship between vibration and fatigue is difficult to define. Examples are given of calculations which can be made for highly resonant structures. Responses covering a wide frequency band are more difficult to analyse. Although fatigue itself is known to be not very sensitive to frequency, tests using power spectral density (PSD) to control the loading show a strong link between life and PSD. The author derives expressions for fatigue life in terms of functions of the PSD showing that the close relationship is due to the fact that all the signals have had a Gaussian amplitude probability distribution. Fixing the PSD then fixes the whole of the peak and through distribution and so fixes the number and amplitude of the reversals in a time-domain description of the stress history. Finite element techniques can be used with a given set of dynamic input forces and a computer program to predict PSD plots at any chosen number of points on the component or structure. Frequency-domain information is then available on a component before it is made. The general trend towards lighter structures will increase the need for fatigue-life predictions from frequency-domain data. This is the fourth and final article in a series on fatigue. (TRRL)

2 citations




Proceedings ArticleDOI
Golam M. Newaz1
01 Feb 1983
TL;DR: In this article, a dimensionless fatigue life parameter is developed for the correlation of fatigue data of carburized and core material, which can be generalized to account for the fatigue strength differentials of dissimilar materials such as the core and case-core interface.
Abstract: A dimensionless fatigue life parameter is developed for the correlation of fatigue data of carburized and core material. It is shown that the Smith-Watson-Topper parameter can be generalized to account for the fatigue strength differentials of dissimilar materials such as the core and case-core interface. Fatigue data generated using circumferentially notched specimens was successfully correlated to the core material fatigue data using this parameter at low stresses. From these observations, a scheme is proposed to predict low-stress fatigue life of a carburized member experiencing multiaxial stresses based on the core material fatigue response only.

1 citations