Experimental Study on Fatigue Performance of Welded Hollow Spherical Joints Reinforced by CFRP

Abstract

The risk of fatigue failure of welded hollow spherical joints (WHSJs) under alternating loads increases due to the inherent defects, the disrepair, and the demand for tonnage upgrades, of suspension cranes. The finite element analysis results revealed that the ranking of the stress concentration factor at the WHSJ was as follows: weld toe in steel tube of tube–ball connection weld > weld toe in steel tube of tube–endplate connection weld > weld toe in sphere of tube–ball connection weld > weld toe in plate of tube–endplate connection weld. Moreover, the peak stress at the weld of the tube–sphere connection was reduced by 32.93% after CFRP bonding reinforcement, which was beneficial for improving the fatigue performance. In this study, 16 full-scale specimens of Q235B WHSJs were tested by an MTS fatigue testing machine to study the strengthening effect of CFRP on the fatigue performance. It was found that the fatigue fracture of WHSJs was transferred from the tube–sphere connection weld to the tube–endplate connection after CFRP reinforcement. According to the fitted S-N curves, the fatigue strength could be increased by 13.26%–18.19% when the cycle number increased from 10,000 to 5,000,000.

Axial Compression Bearing Capacity of Bolted Drum-Shaped Spherical Shell Joints: Experimental and Numerical Analysis

“…Zhang et al [19] embarked on analyzing the fatigue behavior at the weld toe in the steel tube of WHSJs through 20 constant-amplitude fatigue tests, utilizing an infrared thermal imager to predict the location of fatigue failure based on surface temperature variations. Similarly, Duan et al [20] conducted fatigue tests on 16 full-scale WHSJ specimens and explored the reinforcing effect of CFRP on their fatigue performance, discovering a shift in the fatigue fracture location from the tube-sphere connection to the tube-endplate connection post-reinforcement. With a foundational understanding of fatigue behavior, researchers then explored more specialized aspects and external factors affecting WHSJs.…”

Comprehensive Fatigue Analysis and Practical Design Methodology for Weld Toes in the Sphere of Welded Hollow Spherical Joints in Grid Structures

“…Transitioning to welded cross plate-hollow sphere joints, Jiao et al [21][22][23] undertook 19 constant and 14 variable amplitude fatigue tests, establishing the corresponding S-N curves. In terms of structural reinforcement, Duan et al [24] discovered that post-CFRP reinforcement shifted the fatigue fracture from the tube-sphere connection weld to the tube-endplate connection. However, there remains a void in research regarding the fatigue performance of the weld toes in the sphere of TSJs.…”