Hot-forging Die Cavity Surface Layer Temperature Gradient Distribution and Determinant

Based on the car front-wheel-hub forging forming process of numerical simulation, the temperature gradient expression of forging model cavity near the surface layer was got ten, which illustrates that the forging temperature gradient is related to forging die materials thermal conductivity, specific heat and impact speed, and the correlation coefficient is 0.97. Under the different thermal conductivity, heat capacity and forging speed, the temperature gradient was compared with each other. The paper obtained the relevant laws, which illustrates the temperature gradient relates to these three parameters in a sequence of thermal conductivity 〉 impact speed〉 specific heat capacity. To reduce thermal stress in the near-surface layer of hot forging cavity, the material with greater thermal conductivity coefficient and specific heat capacity should be used.

Whole-process modeling of titanium disc forming for gradient distributions of temperature and deformation

Gradient distributions of temperature and deformation(GDTD)are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine.However,heating,cooling and deforming sequence in the whole process of the titanium disc forming,which leads to difficulties for achieving GDTD due to a lot of parameters.To solve this problem,a whole-process model of the titanium disc forming for GDTD has been established.In the model,heating and cooling via heat radiation,conduction and convection,and deforming by local loading with mold chilling are all considered.Experiments on heating and cooling as well as deforming were carried out by using a furnace and the Gleeble-3500 machine.The experimental data are used to determine thermal parameters and constitutive relations of the IMI834 titanium alloy,and then to verify the reliability of the model.Then the model was used to simulate the evolution rules of temperature and deformation of the titanium disc.The results show that the heating surface,furnace temperature,billet profile and loading rate play the core role for the control of GDTD,and thus a set of parameters were determined.Therefore,this work provides a base for developing a new forming technology of the dual-performance titanium discs with the approach of local heating and local loading.

Effect of Operation Parameters on the Thermal Characteristics in a Planar Solid Oxide Fuel Cell

Effective operation strategies in the solid oxide fuel cell(SOFC)can adjust the spatial distribution of temperature gradient favoring the long-term stability.To investigate the effects of different operating conditions on the thermal behavior inside SOFC,a three-dimensional model is developed in this study.The model is verified by comparing it with the experimental data.The heat generation rate and its variation under different operating conditions are analyzed.The combined effects of operating voltage and gas temperature are considered to be the key factor influencing the temperature gradient.Compared to the original case,the temperature of SOFC decreases by 21.4 K when the fuel velocity reaches 5 m/s.But the maximum temperature gradient increases by21.2%.Meanwhile,higher fuel velocities can eliminate about 32%of the area with higher temperature gradient.And when the oxidant velocity reaches 7.5 m/s,the peak temperature gradient effectively decreases by 16.59%.Simultaneous adjustment of the oxidant and fuel velocities can effectively reduce the peak temperature gradient and increase the safety zone.The effects of operation conditions on the temperature gradient of the cell are clarified in this study,which can be a reference for further research on the reliability of SOFCs.