Numerical Simulation And Temperature Information Detection Of Local Heat Treatment In Electron Beam Welding Of Titanium Alloy

In this dissertation, according to the practical environment of vacuumelectron beam weld, an infrared vacuum temperature measuring system is built,which could be used to measure the work-piece surface temperature in vacuumenvironment. The advantage of the system is obviously, such as the system couldbe wireless controlled outside the vacuum chamber, the wireless datatransmission, the independent power source, easy to operate, etc. Through thetemperature measurement testing in common environment, it is found that themeasurement error is small, the program operation is stable during measurement,and could meet the requirement of the temperature measurement in local electronbeam heat treatment.The result of the thermal effect during the electronic beam welding and localheat treatment are simulated by ANSYS software. In this dissertation, a three-dimensional finite element model and a rotational paraboloidal body heat sourcehave been established to simulate the temperature fields during electron beamwelding on2mm thick flat plate of TA15titanium alloy, while Gaussian surfacesource model is established to similate the process of the local electronic beamheat treatment.Through the simulation of the temperature field in electronic beam weldingand local heat treatment, and the analysis in the thermal cycling curve near theweld joint, it is found that the trend of the thermal cycling curve is similar,except the peak temperature, which is captured in upper and lower surface duringelectronic beam welding and local heat treatment. Besides, the peak temperaturedifference is only150℃between the upper and lower surface in local heattreatment, and the temperature gradient is small along with the thicknessdirection, which could meet the requirement of local heat treatment.Based on the results of temperature fields and thermal elastic-plasticitytheory, indirect coupling method is employed to compute the developmenthistories of thermal elastoplastic stress during welding process and local heattreatment, as well as the distribution of residual stress after welding. Thesimulated results show that the residual stress of weld zone changes mainly istensile stress during electron beam welding and heat treatment. The peak value ofthe tensile stress, which near the weld zone, is obviously lower after heat treatment than that before heat treatment. Through the testing of longitudinalresidual stress and transverse residual stress in these two state by the holedrilling method, the distribution and changed trends from siulationm areconsistent to the tested results.