Nonlinear Stability Analysis Of Crane Boom Based On Arc-length Method

According to the development in science and technology,the crane machine is widely used in all kinds of situations.The improvement in manufacturing and the utilization of high strength alloy enables the crane to lift higher,carry more loads and lengthen the boom.For the crane boom with large slenderness,the geometrical deformation increases rapidly when losing stability,which leads to instability and causes more trouble than strength failure.In a word,the stability analysis on the boom is of significant importance to the safety of the crane system.Based on the empirical research on geometrical nonlinearity,material nonlinearity and nonlinear stability analysis from home and abroad,this paper studied the geometrical nonlinear equation,the material nonlinear constitutive relation and the stiffness matrix.In this paper,the definition and classifications of the nonlinear stability method and the influence of material nonlinearity on the boom stiffness were also studied.To insure the double nonlinear stability calculation was successfully conducted using the finite element software ANSYS,the arclength method and its irritation strategy were also studied and convergent results were achieved.Based on the parameters of 750 t crawler crane model,double nonlinear models which considered both geometrical nonlinearity and material nonlinearity as well as geometrical nonlinearity-only models were set up,insuring the models could mostly conform to its force and constraint situations.Using the proposed model,the listed research was done in this paper:(1)The nonlinear stability analysis was studied based on the double nonlinear models and geometrical nonlinearity-only models.The differences of the critical load and loaddisplacement curve of the two models under different working conditions were both studied to analyze the influence of material nonlinearity on the instability problems of the model;(2)The critical loads and load-displacement curves of double nonlinear models with different slenderness ratios and angles were calculated to study the influences on their stability;(3)The nonlinear stability analysis of double nonlinear models with different yield stress was conducted.By comparing the displacement and stress nephogram at each critical points,the influence of material's yield stress on the instability phenomenon of the boom was studied to offer improvement methods for practical uses.