Reliability analysis of universal joint of a compliant platform

Abstract

A B S T R A C T The paper describes a methodology for computation of fatigue reliability of universal joint in an articulated offshore tower. Failure criteria were formulated using the conventional Palmgren-Miner rule (S-N curve approach) and the fracture mechanics (F-M) principle. The dynamic analysis of double hinged articulated tower under wind and waves is carried out in time domain. The response histories of hinge shear stresses are employed for the reliability analysis. Advanced first-order reliability method and Monte Carlo simulation method were used to estimate the reliability. Various parametric studies were carried out, which yield important information for the reliability based design. The S-N curve approach yields a significantly conservative estimate of probability of failure when compared to the F-M approach. A = fatigue strength coefficient a = crack size a • = initial crack size a c r = critical crack size B = stress modelling error C = Paris coefficient [C] = damping matrix C • , m = crack propagation parameters C d = drag coefficient D = accumulated damage da/dN = crack growth rate E[.] = expectation f i = zero crossing frequency f x (X) = probability density function of the random variable X g(X) = limit state function H s = significant wave height [I] = mass matrix K = intercept of the S-N curve at σ R equals to one [K] = stiffness matrix L = load effect {M θ } = forcing function m = slope of the S-N curve m = fatigue exponent m o = nth moment of the stress spectrum N = number of cycles to fatigue failure Correspondence: M. M. Zaheer.

Effect of current on the dynamic response of a bi-articulated offshore tower

“…It demands analysis of articulated towers under combined action of wind, wave, and current loads, Kunpeng et al (2016). The combined action may also cause fatigue damage to articulated joints as they are subjected to significant stress reversals as reported by Zaheer and Islam (2010). It shows the critical impact of the combined wind, wave, and current action on compliant platforms like articulated towers.…”

Modelling and verification of fatigue damage for compliant mechanisms

“…Different crack locations correspond to different types of vector B in Eq. (16). Equation (18) can be applied to determine the corresponding torque variations.…”

“…Nie et al 15 discussed and modelled the fatigue life of robots with flexible joints subjected to percussive impact forces. Zaheer and Islam 16 evaluated the fatigue reliability of a universal joint in an articulated offshore mechanism. The conventional Palmgren-Miner ruler and the fracture mechanics were applied to develop a fatigue model.…”

Comparative study between S-N and fracture mechanics approach on reliability assessment of offshore wind turbine jacket foundations

“…The reliability methods applied to account for inherent uncertainties with respect to selecting an optimal tool for making a proper decision, which enables a balance between design criteria, and inspection and repair plans include S-N and FM formulations. In [41,42], a methodology for the calculation of fatigue reliability (FR) of universal joint in an articulated offshore tower was presented. It was reported that the S-N curve approach yields a significantly conservative approximation of POF [Type here] when compared to the FM approach.…”