Spot-weld Layout Optimization Regarding Fatigue Life For Commercial Vehicle Cab

As an very important part of the vehicle，auto-body is where the driver works in，whichrequires it can provide a safe and comfortable operating environment for the driver. Thismeans that the auto-body must have enough stiffness and high the low intrinsic modefrequency. Auto-body is mainly formed by sheet metal, which is connected by spot-welds.Therefore, the welding-spots have a great impact on the static and dynamic performance ofthe body.Under thealternate loads, the auto-body is susceptible to fatigue affect. Due to thesevere stress concentration emerge near the spots, the spots’ fatigue life will beshorten,comparing with the sheet metal. Thus, in the early phase of design, optimizing thelayout of welding-spot, which based on its fatigue behavior, can improving the body’sperformance and it is economically viable.Certain commercial vehicle cab is studied in this thesis, the cab’s stiffness、structuralstrength and modal frequency is analyzed to be an comparison for future research. And thefatigue life of welding-spots is analyzed. Based on the result of fatigue life, a new thecommercial vehicle cab finite element analysis model was established. Using topologyoptimization methods, the welding-spots are optimized. By analyzing crashworthinesscharacteristic ofthe optimized cab，the reasonable of spot weld layout optimization method isverified.Firstly, the BIW(body in white) is established, and its’performance is calculated.The stress and strain of frequency response of cabunder unit excitation is calculated.After that, using load spectrum which is obtained from the real vehicle test and s-ncurve, based on miner hypothesis, the spot weld of cab’s fatigue life is predicted. Throughthis result, the numbers of spot weld which will lose efficacy are73. Then, according to the result of fatigue life, a new BIW is build. Based on the stiffnessand fatigue life, the welding-spots are optimized by using topology optimization methods.Through contrast different optimized results, The final optimization results is decided.Finally, through analyzing crashworthiness characteristic of the optimized cab，thereasonable of spot weld layout optimization method is verified.