Study On Thermo-elastic Deformation Of Combined Die In Precision Forging

In the precision forging, there is always a large amount of heat generated during the process due to the fierce deformation of material and the friction between die and workpiece. When the deformation temperature is high, the die is necessary to be preheated. The rise of die temperature will lead to die deformation, which affects the component dimensional accuracy. The combined die, which is widely used in precision forging, was set as an example. The relationship between die thermo-elastic deformation and temperature distribution as well as normal stress was studied by theoretical derivations, finite element simulations and experiments.Firstly, based on the classical Lame formulas and thermo-elastic mechanics theories, the thermo-elastic deformation of combined die was derived with the linear superposition of thermal and elastic deformations. The theoretical equations were applied in different combined dies to derive the thermo-elastic deformations of double-layer, three-layer and four-layer combined dies. Finite element simulations of combined dies with different layers and even temperature fields were conducted in the MSC.MARC software, which showed a good agreement between calculated values and simulated results.Then, the thermo-elastic deformation of combined die with even temperature distribution was extended into uneven temperature fields to explore the relationship between temperature distributions and die thermo-elastic deformations. The double-layer combined die was set as an example. Three kinds of uneven temperature fields, including linear one, quadratic one and exponential one, were built up to study the thermo-elastic deformation by both theoretical derivation and finite element simulation. In the comparison, there was a good agreement between the calculated values and the simulated results under the uneven temperature fields.Finally, in order to study die thermo-elastic deformation during the precision forging process and acquire the temperature distribution inside the die, the combined die temperature acquisition device was designed. The device was made up by the temperature measurement part and the data acquisition part, including a combined die with blind holes, thermal couples, the DaqBook and a computer. It was then applied in the reverse extrusion experiment. The temperature inside the combined die during the continuous process and the dimensions of extrusion components after releasing and cooling were accumulated and compared with simulation results in three deformation temperatures. The changing rules of the temperature on different check points inside the die and its influences on the extrusion components dimensions were analyzed. Meanwhile, the related parameters in the simulation were collected to predict the die thermo-elastic deformations after preheating as well as the extrusion process, which were then compared with the simulation results to verify the effectiveness of theoretical derivations. In the end, based on the theoretical derivation of die thermo-elastic deformations with uneven temperature distributions, a linear preheat temperature field, a quadratic one and an exponential one were built up for the extrusion combined die. The relationship between the thermo-elastic die deformation and different temperature distributions was analyzed through theoretical derivations and finite element simulations.