A Theoretical Solution for the Estimation of “Rainflow” Ranges From Power Spectral Density Data

Abstract

This report outlines a theoretical solution for the estimation of rainflow range density functions using statistics computed directly from power spectral density data. The rainflow range mechanism is broken down into a set of events which can be analyzed using Markov process theory. The dependence between extremes in this instance is modelled using an approximation of the joint distribution of peaks and troughs first proposed by Kowalewski. NOMENCLATURE dh = interval width used to discretise the stress range f., = long run transition probability f; = absorption probability in state i from originating level j h = stress range pk = transition probability of going from state i to state k P =transition probability matrix p ( i p ) = probability of a peak being at level ip PSD = power spectral density function tp = twice the mean signal value y ( t ) = signal as a function of time ps,, ( h ) = rainflow range probability density function Y , , Y,, Y, = events as described in Section 3

Steering Wheel Tie Rod Fatigue Life Determination According to Turkish Mission Profiles

“…As a result, during design and verification process automobile companies use one or several methods together on automobile parts [3]. Durability test of a car, it encounter throughout their entire lifetime loads, type of usage, environmental and operational conditions will represent the entire load spectrum is provided by the determination [3,4,6]. Such a study on the most important and difficult is that how the representative load spectrum is determined.…”

“…The most popular method used for the determination of load spectrum for the whole life of vehicle is a customer usage based method [3][4][5][6][7][8].…”

“…Without appropriate knowledge of these loads one needs large safety factors, restrictive weight or cost reduction potentials [7]. By executing real test and computer analysis fatigue life prediction and the undamaged time of a vehicle component, which is affected by load spectrum, must determine referencing customer usage in which market component run [4].…”

“…These parameters are linear analysis results, dynamic load data, and the material specifications [2,5]. For the service life of a product operational loading conditions are main importance [4]. The requirements on the strength, however, strongly depend on the loads in actual customer usage.…”

“…Hence, automobile companies uses new techniques in order to eliminate fatigue failures come out on prototype vehicles during is very important in terms of customer expectation and guarantee cost within the vehicle development time. The major parameters that effects the durability of a component are material, geometry and load spectrum [2,4,5]. The prediction of service life, reliability and safety are essential for the design process of road vehicle structures [6].…”