A Fatigue Reliability Assessment for Rail Tension Clamps Based on Field Measurement Data

Tension clamps play an important role in maintaining the track gauge by fixing the rails to the sleepers. Damage to the tension clamps was observed on an urban railway. The cause of the fracturing of the tension clamps was identified and reliability analyses on the fatigue failure of the tension clamps were performed. The stress ranges were estimated by measuring the strain at the locations where most of the fractures occurred during train operation. Afterward, a statistical model of the stress ranges was developed using the measured data. The statistical parameters of the stress ranges for the reliability analysis were estimated based on the field measurement data. The reliability indexes were calculated for the inner and outer rails and for the inside and outside track gauges of each rail. The variations of the reliability index for the years in service and the number of cycles were investigated. The results of the reliability analyses showed a consistency with the field observations.

FATIGUE RELIABILITY ASSESSMENT OF WELDED JOINTS OF VERY FAST FERRY ACCOUNTING FOR VEHICLE LOADS

This work deals with the fatigue reliability assessment of a welded joint in a longitudinal stiffener of trapezoidal shape in a very fast ferry. Based on the analysis of wave and cargo induced loads the ship hull structure is evaluated. The local structure is represented by a longitudinal stiffener with a trapezoidal transverse section. The critical hot-spots and the stress distributions are defined by FEM. The fatigue damage assessment of considered hot spots is analysed accounting for the combination of wave induced and car-breaking transient loadings. The formulation for the assessment of the welded steel joint is based on the S-N approach and FORM/SORM techniques are applied to evaluate the reliability against fatigue failure accounting for corrosion deterioration. The structural system composed by several hot spots is evaluated as a series system based on second order reliability bounds.

Rigid-Flexible Coupling Fatigue Life Reliability Study on Bonic Fish Driving Shaft

Due to the complex loads on a bionic robotic fish operating underwater, the reliability of its working mechanism has an important effect on its overall performance. By establishing a virtual prototype model for the rigid–flexible coupling of a bionic robotic fish, we obtained the instantaneous load on the caudal fin of the robotic fish based on the flapping-wing propulsion theory with MATLAB. A rigid–flexible coupled virtual prototype model for the caudal fin drive as a flexible member of the bionic robotic fish was established, and dynamic simulations were conducted on the model. The simulations revealed the weak links in the drive shaft and established a damage level indicator and fatigue reliability analysis method based on damage theory. The behavior of fatigue reliability for different stress cycles was established, and a dynamic reliability design method with great engineering application value was proposed for virtual prototypes of rigid–flexible coupled underwater bionic robots by combining the virtual prototype technology of rigid–flexible coupling with the theory of flapping wing propulsion and the theory of random load fatigue reliability.

Bayesian Inference under Small Sample Sizes Using General Noninformative Priors

This paper proposes a Bayesian inference method for problems with small sample sizes. A general type of noninformative prior is proposed to formulate the Bayesian posterior. It is shown that this type of prior can represent a broad range of priors such as classical noninformative priors and asymptotically locally invariant priors and can be derived as the limiting states of normal-inverse-Gamma conjugate priors, allowing for analytical evaluations of Bayesian posteriors and predictors. The performance of different noninformative priors under small sample sizes is compared using the likelihood combining both fitting and prediction performances. Laplace approximation is used to evaluate the likelihood. A realistic fatigue reliability problem was used to illustrate the method. Following that, an actual aeroengine disk lifing application with two test samples is presented, and the results are compared with the existing method.