Analysis Of Weld Fatigue For Steel Crane Beam Based On Equivalent Structural Stress

With the rapid development of Chinese economy, the steel crane beam has been widely applied in different trade, so many problems need to be studied and resolved. Many factories in the Heavy and Extra Heavy steel crane beams after repeated run have been varying degrees of fatigue damage, and the main beam is main load bearing element. Thus,the main beam's resistance to fatigue directly determines the service life of the crane beam.That fatigue steel crane beam damage is mostly founded in the weld through continuous study. Thus, the study of the steel crane beam weld fatigue has more realistic significance.For these reasons, the paper investigates systematically the fatigue life of crane beam steel weld.1 This paper introduces structural steel crane beam system and analyzes generation and classification and causes of fatigue crack in detail. In addition, the locations of four welds that would be analysis have been introduced.2 According to the existing regulations about crane beam, the design results of crane beam, including strength, stability, fatigue stress amplitude and deformation are checked,Checking results show that it complies with regulatory requirements.3 The preparation of the fatigue loading spectrum is a very important work. Load time history determines the fatigue strength and fatigue life of crane beams. Based on this, we do static and transient analysis for steel crane beams with ANSYS simulated working condition of crane beam to obtain the load-time history of node under different conditions. And the rain-flow counting method and probability statistics are compiled to gain load spectrum.4 This paper emphatically introduces the equivalent structural stress method which is made by professor Dong who is the Chinese American and others. Different from the nominal stress, structural stress method, notch stress-strain method and fracture mechanics method, the paper verifies the equivalent structural stress method has a non-insensitive mesh that distinguishes it from the nominal stress of structural stress method, notch stress-strain method and fracture mechanics method. In addition,it assesses the fatigue life of steel crane beam weld.5 The fatigue life of weld toes with different hf have been studied. The results show that with the increasing size of hf, the fatigue life will decrease for the higher stress concentration factor. In addition,the fatigue life of four different gap sizes(0.2mm, 0.3mm,0.4mm, 0.5mm) are studied. We found that with the increasing size of gap, the fatigue life also has decreased for the higher stress concentration factor. When the gap size increasing from 0.2mm to 0.5mm, the corresponding fatigue life increases approximately 0.1%, the fatigue life of crane beams basically keep unchanging. It is noteworthy that when the gap size is 0, the fatigue life is higher than others, and compared with 0.2mm, the fatigue life decreases about 7.56%.