Analysis Of Stiffness And Deformation Of Beam Structure With Damage

With the rise of damage mechanics,researchers have done a lot of research on the evolution process of material damage from the macro and micro level.They selected various damage parameters to represent the damage degree,established the constitutive equation of damage coupling to study the damage evolution of materials,and based on the theory of continuum mechanics,used irreversible thermodynamic internal variables to describe the internal structure of materials deterioration,but a careful consideration of the mechanism of the change is never made.Using damage mechanism,constitutive relation and damage model to study the degradation of materials in macro mechanical properties has always been the focus of attention.Based on the damage theory,this paper studies the stiffness and deformation of the beam structure with damage story.The main content of this study is as follows:First of all,based on the nonlinear fatigue cumulative damage evolution model and continuous damage theory,considering that the fatigue cumulative damage is affected by the current strain state and loading times,using threshold strain of damage occurrence,the corresponding damage evolution model is proposed,and the change of elastic modulus is selected as the damage variable.The parameters of the fatigue cumulative damage evolution model are determined by the experimental data,which verifies the rationality of the model.Secondly,the user material subroutine of the fatigue cumulative damage evolution model is compiled by using the user material subroutine interface of ABAQUS.According to the characteristics of fatigue analysis,a cycle-based solution process is set up to simulate the fatigue cumulative damage evolution related to loading times and deformation.In addition,three-point bending fatigue simulation of simply supported beam is carried out.The results show that with the increase of the number of cycles,some areas in the material are damaged slowly,and the damaged area is enlarged gradually;the larger the cyclic load is,the larger the damaged area is;the bending rigidity of the simply supported beam decreases gradually with the increase of the number of cycles;at the same time,the change rule of the deflection at the midpoint of the simply supported beam under three different stress amplitudes is analyzedFinally,considering the uniform and linear distribution of damage along the damage layer,the stiffness changes of beams with unilateral damage layer and bilateral damage layer are studied.The maximum deformation and rotation angle of simply supported beam and cantilever beam with damage layer are calculated and compared with that of the beam without crack.The results show that the stiffness of beams with damage layer decreases with the increases of damage degree and damage layer thickness,and the resistance to deformation of beams decreases;when the damage degree is the same as the damage layer thickness,the deformation of beams with double damage layer is larger than that of beams with single damage layer.This study can provide theoretical support for the stiffness analysis of mechanical joint,and provide reference and guidance for the practical application of mechanical engineering structure.