The Analysis Of Tower Crane Structural Reliability And It’s Hoisting Mechanism Rope Jumping Behavior

Due to its large carrying capacity and simple structure,the slewing bearing has been widely used in cranes,fans,robots and other fields.The failure of the slewing bearing is mainly caused by cracks caused by fatigue of the raceway surface after a long time of operation.Considering that the crack of metal material usually sprouts near the grain boundary and expands along the grain boundary,this paper proposes the method of combining the grain division and cohesion unit of(Voronoi)to simulate the crack initiation and propagation behavior of the metal material under the fatigue load.On this basis,the fatigue life of the slewing bearing is predicted.The simulation analysis method studied in this paper is beneficial to the rapid prediction of the fatigue life of the slewing bearing and the safety evaluation of the structure.It has important engineering application value.In this paper,a three-dimensional model of slewing bearing is established.According to the rated load of slewing bearing,the finite element software ABAQUS is used to analyze the contact stress distribution on the raceway surface,determine the position of the dangerous section,and determine the contact area size according to Hertz theory.On this basis,through Matlab The position of the grain seed point is generated,and the two-dimensional Voronoi model of the hazard section of the raceway is established in Neper.The cohesive force element is embedded between the grains to simulate the grain boundary property,and the microscopic model of the raceway material is finally obtained.The paper gives the cohesive force unit in the intersection.Under the variable load,two stages of performance degradation and damage evolution,two damage variables are defined respectively.The fatigue damage model of cohesive unit is programmed by UMAT subroutine.The crack initiation and propagation behavior of metal materials are simulated by quasi-static loading method.The simulation results are consistent with the theory:the crack initiation depth is the same as the theoretical maximum shear stress depth;the total crack life is in accordance with the two-parameter Weibull distribution.The cohesive unit failure rate of the RVE(Representative Volume Element)in the central analysis area is used as the slewing bearing failure criterion.Based on the L-P theoretical results,it is determined that the slewing bearing fails when the failure rate of the cohesive unit in the RVE region reaches 19.13%.By calculating the life of slewing bearing under different load factors of L-P theory,compared with the proposed evaluation criteria,the results are within 3%,and when the load factor is 1.3,the life is obviously reduced.It is considered that the safety factor should be large in the selection.More than 1.3 times is safer;the influence of different raceway surface hardness on the life of the slewing bearing is analyzed by simulation.From the economic point of view,when the surface hardness of the raceway reaches 59HRC,the fatigue performance of the slewing bearing is the best.