The Theory And Test On Constant Amplitude Fatigue Behavior Of Grid Structure With Crossed Plate-Welded Hollow Spherical Joints

Grid structures are applied widely in industrial worckshops with suspended cranes and the fatigue of grid structure is focused in the domestic and international engineering and academia fields, but has not yet been fully resolved. Fatigue test is well-known as the direct and reliable method to reveal the fatigue performance of joints and components. However, due to the long cycle time,large cost and multiple influencing factors,the fatigue test make a slow progress at home and abroad.The fatigue of grid structure with welded hollow spherical joints is mainly the fatigue of welded hollow spherical joints. Based on fatigue test of crossed plate-welded hollow spherical joints of flatbed grid structure, the author has designed welded hollow spherical joints. In this paper,16 specimens of welded hollow spheres for KQ-4, KQ-5and KQ-7 were tested stability and efficiently under constant amplitude stress by use of self design loading equipment. According to the testing results and Regression analysis of test data, the form and mechanism of fatigue failure were felt out and the S-N curves were obtained. The fatigue design method for flatbed grid structure with crossed plate-welded hollow spherical jionts has been developed by use of allowable stress amplitude method. and some uncertain factors which have a greater influence on the fatigue test data have been analysed.The research results in the paper will supply some references for the modification of《Specification for design and construction of grid structure》with the popularization and application of grid structure with bolt-sphere joints and welded hollow spherical joints in industrial factory with suspended crane, the fatigue performance becomes the hot problem to be solved for many years in the engineering field. Fatigue test is well-known as the direct and reliable method to reveal the fatigue performance of joints and components. However, fatigue test costs so much time, money and is influenced by so many factors that it develops relatively slowly at home and abroad.The research results in the paper will supply some references for the modification of《Specification for design and construction of grid structure》.