| This article takes a medium-sized commercial vehicle cab as the research object to carry out fatigue life prediction and lightweight research,so that it can reduce the weight of the cab structure on the basis of not reducing the current fatigue life;It helps to reduce fuel consumption,realize goals of energy saving and emission reduction,and have a high engineering application value for improving the competitiveness of enterprise products.First,based on the three-dimensional geometry of the cab,a finite element model of the cab is established in Hyperworks.The Optistruct solver is used to perform static analysis and modal analysis on the cab.The strength and stiffness characteristics of the cab are evaluated through the stress and strain results under bending and twisting conditions,and the resonance with other systems is judged according to the modal results.The results show that the safety factor of cab is 1.9 and the bending stiffness is 5961.07 N/mm under full load bending condition;the safety factor of cab is 1.44 and the twisting stiffness is 11301.7 N m/°under full load twisting conditions.The first-order free mode frequency is higher than the road excitation frequency,and the first six natural frequencies stagger the excitation frequency of the engine at idle speed and rated speed;In summary,the static and dynamic characteristics of the cab meet the design requirements.Secondly,considering the influence of the key components’deformation on the performance of the whole system,they are processed flexibly to reduce the errors caused by the rigid frame and the cab to the virtual simulation results.According to the specific structural characteristics of the commercial vehicle,the attribute file and the communication connection between the templates,the rigid-flexible coupling model of the whole vehicle is built in ADAMS/Car;By loading the road excitation obtained by the pseudo white noise method in MATLAB,without considering the lateral factors,the load-time history of the cab mount is obtained by simulating the vehicle running in a straight line at a constant speed of 60km/h on the B-level road surface,which provides necessary load condition for the subsequent fatigue life analysis of the cab.Then,according to the stress response of the cab under unit load in the n Code software,the stress-time history is calculated using the quasi-static method;Combined with the S-N curve of cab material,based on the theory of fatigue,the fatigue life is predicted by the nominal stress method.The results show that the minimum fatigue life of the cab occurs at the door frame on the left side of the cab,where the number of fatigue cycles is8.482×10~5,which translates into a mileage of 1.0178 million kilometers.Finally,20 cab sheet metal parts are preliminarily selected to participate in Sobol sensitivity analysis,and the top 8 design factors with the greatest impact on anti-fatigue lightweight are screened out.With the constraint of not reducing cab’s fatigue life and not increasing cab’s mass as the optimization goal,the ASA adaptive simulated annealing algorithm is used for optimization;The static and dynamic characteristics of the cab before and after the optimization are compared.The results show that the fatigue life of the cab is increased by 4.2%and the weight is reduced by5.29%on premise of satisfying various performances after optimization,which shows the effect of anti-fatigue lightweight is obvious. |
