The Research On Cab Structure And Spot Weld Layout Optimization Of Heavy Duty Commercial Vehicle

In recent years, with the rapid development of China national economic construction, heavy commercial vehicles are more and more widely used,and also greatly contribute to the production of heavy-duty commercial vehicles. But as international and domestic crude oil and diesel prices have climbed, increasing the cost of using a car and shrinking the income, it leads to a directly reduction of the demand for new vehicles, especially for heavy commercial vehicles; uneven pavement, wheels, engine and transmission unbalance lead to vibration of vehicle or in part. when the vibration frequency is close to natural frequency of the cab, it will produce resonance phenomenon, resulting in severe vibration and noise, which seriously affects comfort of the cab; heavy commercial vehicle with its structural features determines that the driver and passenger may be badly injuried in front impact traffic accidents because of the cab having a short distance for the energy absorption cushion. In the accident actually occurred, cab over engine truck with weak stiffness and small space suffered severe deformation after impact, causing serious injury and death because there is not enough room for survival; also some cabs with too large stiffness only produce a small deformation in an impact.But occupants bearing a great inertial force will be easily thrown out from the cab causing serious or fatal injury; heavy commercial vehicle body manufacturing process includes four major processes, stamping, welding, painting, general assembly. Manufacturing process is complex, involving many employees.How to optimize the manufacturing process to reduce vehicle production cost and increase market competitiveness, is of great significance. Heavy commercial vehicle market is basically dominated by individual transport operators, accounting for about 90 percents. The ability of individual transport operators to resist risk is weak.They are vulnerable to environment and are price-sensitive. So controlling the cost of heavy commercial vehicles production has been throughout all aspects including product development, manufacturing and sales. Thus, reducing vehicle fuel consumption and improving vehicle comfort, safety and controlling the cost of automobile manufacturing occupy an important position in heavy commercial vehicle product development process.This paper integrated with a domestic company's national "863" project "Advanced technology for development of heavy vehicles " sub-item "Heavy-Duty truck cab development" researches heavy commercial vehicle cab structure and the optimization of solder joints to reduce vehicle weight to reduce fuel consumption, simplify the process and reduce manufacturing costs. At the same time, its comfort, safety are analyzed to ensure that the optimization don't effect the comfort and safety. The main text reads as follows:1. A finite element analysis model is built by the finite element method. In order to validate the model, rigidities of bend and torsion of the model truck cab are analyzed seperately, and analysis of emulational simulation is carried out under bending-torsional loading condition, considering the affection of moving load impacting, the real load in driving process beared by the druck cab, is reverted to get stiffness parameter .Then it is compared with the data of vehicles of the same type in the current market, to find out the improvement direction, which also supplys a reference for further structure optimization.2. Vebrition modal numerical simulation and analysis of experimental test are carried out, the comparing analysis and the relating analysis, the error between whom we compare, we obtain the simulation data of the model truck, which validates the validity of the numerical analysis model. Then we compare the data with the data of the same type in the current market. And we find out the improvement direction, which also supplys a reference for further Optimization Analysis.3.This paper discussed the basic theory of topology optimization and the application status of topology optimization in automotive. Based on analysis of factors of topology optimization, using stress, displacement, and a first-order modal frequency as constraints, the layout of the external and internal cover board, holes location and size optimization were carried out separately to minimize mass through topology optimization. According to the results of topology optimization, improvement of structure design reduced the weight of the cab. The new structure modal frequency changed on the basis of the results of topology optimization, is slightly lower, so further studies should be undertaken to enhance modal frequency, providing a reference for further structural optimization of the cross-section.4. The major load-bearing structural components were found out by analysis. Optimization model of structure cross-section is built up. By analyzing the mechanical properties of the cross-section of structure cross-section model, we found sensitivity of the stiffness and modal to the interface area, moment of inertia and so. Shape optimization of structure cross-section was carried out under the guidance of sensitivity. Structure design was changed according to optimization. The changed structure had a good performance for improving the modal and stiffness of the cab.5. According to the request to reduce production costs this topic raised, this paper established a solder joint layout optimization model and optimized layout of the solder joints of the truck cab using topology optimization technology while structural optimization. Reducing a certain amount of welding points without reducing the overall performance reduces the workload of the welding. This will reduce costs of welding production line. Through modal analysis of the optimized model, it is informed that the application of this method has spread value.6. In order to test the security of the optimized model, this paper researched safety analysis and testing technology of this type of car at home and abroad, then established analysis model after the optimization. This paper also carried out research on cab crashworthiness before and after optimization. Passenger survival space was used as evaluation index to validate safety with front impact and top pressure as two kinds of working conditions. After validation,it is proved that the cab optimization doesn't effect occupant safety.7. Finally, based on the analysis above, topology optimization applied to the overall layout of the concept development has been studied to establish a model of topology optimization under multiple loading conditions, while the concept of process constraint is introduced to carry out topology optimization analysis under multiple loading conditions with change area, making the optimization results more in line with technological requirements. By comparing the optimizied results with the car-like layout ,it is informed that the method is very effective.In summary, through the study of this topic, we master a new body structure optimization design methods to make a light weight body and reduce the number of solder joints and product manufacturing costs, improving product performance, enhancing the enterprises'competitiveness. Through the implement of this study, it can fundamentally change the passive situation of mere imitation of the domestic auto industry, and have self-development capability as soon as possible. It can simplify the product design and development process, shorten product development cycles, and reduce product development costs. This study is also exemplary for other high-tech automobile parts and components independently developed.