As an important basis for its structural optimization design, the heat transfer performance has a key influence on the reliability of automobile brake. Based on the finite element method, the transient heat transfer of automobile disc brake is analyzed under the condition of dynamic convection heat transfer coefficient. According to the simulation results, the CCD (Central Composite Design) sampling scheme is used to transform the optimization variable and target variable into multiple design points in the decision space. The optimization variable includes the total thickness, the height of the ventilation slot, the angle between the sides of the ribs, the number of ribs while the target variable includes the mass and temperature peak. According to the multiple quadratic regression model, the response surface function is constructed, and the approximate model of optimization analysis is obtained. The error analysis shows that the response surface function is equipped with good fitting accuracy. In order to facilitate the extremum search, the optimization of the quality is transformed into the constraint condition, and the multi-objective optimization problem of the brake disc is transformed into the single objective optimization problem. Through the sequential quadratic programming method, the Pareto optimal solution set of the optimal mathematical model is found. The results show that the temperature peak value is reduced by 7.8 % under the condition where the quality of the ventilation plate is basically unchanged. By weighting the Pareto optimal solution sets of different quality intervals, a good result evaluation of ventilation panel optimization is achieved.

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The influences of ultrasonic vibration during cold metal transfer welding process on the microstructure, element distribution and pitting resistance of AISI 430 ferritic stainless steel joints with ER 308L as filler metal were investigated. The combined effects of mechanical vibration, acoustic streaming and cavitation of ultrasonic vibration significantly refined the primary ferrite grain in the weld metal and then impacted the subsequent solid-phase transition process, leading to the ~45% reduction of ferrite content in the weld metal. Moreover, these effects also resulted in the homogenization of alloying elements in the weld metal. The pitting corrosion resistance of the welded joints with ultrasonic vibration was increased compared with that of without ultrasonic vibration, but lower than the base metal. The pitting resistance of the weld metal with ultrasonic vibration was higher than that of the weld metal without ultrasonic vibration and base metal, while that of the one without ultrasonic vibration was lower than the base metal.