Empirical modeling of stress concentration factors using finite element analysis and artificial neural networks for the fatigue design of tubular KT‐joints under combined loading

Abstract

The hotspot stress (HSS) approach for the fatigue design of tubular joints requires that peak HSS be known. Peak HSS in tubular joints is usually determined based on the stress concentration factor (SCF) estimated from empirical models developed through extensive experimental investigations and finite element analysis. While peak HSS usually occurs at a KT‐joint's crown and saddle points, its location may change if the tubular joint is subjected to a combination of axial, in‐plane bending, or out‐of‐plane bending loads. This study investigated the peak HSS and its location in a typical KT‐joint subjected to the combined loading. Specifically, empirical models to determine the SCF around the brace axis have been developed using extensive finite element analysis and artificial neural networks (ANN) simulations. Less than 3% error was noticed between peak HSS determined through developed models and FEA. Hence, the ANN‐based SCF equations and principle of superposition can be used to calculate peak HSS rapidly for fatigue design of tubular joints. This methodology is applicable for developing empirical models for SCF in other tubular joints and boundary conditions.

Stress Concentration Factors in KT-Joints Subjected to Complex Bending Loads Using Artificial Neural Networks

“…When bending at an angle to the orthogonal axis of the joint, the peak HSS occurs between the crown and saddle points [26]. A KT-joint was simulated for different combinations of combined bending to show this shift and as a proof of concept of the empirical models to determine peak HSS in such scenarios.…”

“…However, none of the available empirical models can determine SCF around the brace axis. Recently, Iqbal et al [26] proposed empirical models capable of determining SCF around the brace axis of a KT-joint; however, only the central brace was subjected to bending loads. In this work, the SCF around the brace axis for the KT-joint is investigated, with all braces subjected to bending.…”

Numerical Investigation of Crack Mitigation in Tubular KT-Joints Using Composite Reinforcement

“…This effect is due to a higher stress concentration at the saddle point than at the crown when a KT-joint is subjected to axial compressive load. When a tubular joint is subjected to combined load, the location of maximum stress depends on the direction and relative magnitude of load components [34]. For such situations, knowing the crack location would be critical for assessment.…”