CAJ | 학술논문

分析电火花表面强化层的应力场特点,建立三维应力场模型,并利用APDL编程实现对应力场的有限元数值模拟,给出强化层和基体在不同位置、不同方向的应力分布和变化规律.结果表明:强化过程中,熔池及附近区域存在的巨大且剧烈变化的温度梯度和不一致的冷却速率使试样产生很大的热应力;由于热导率和热膨胀系数存在差异的缘故,各节点的应力值随着位置的变化而变化;试样的应力曲线在热影响区都存在突变,有强化层时,由于强化层和基体材料的比热容C和热导率,κ不一致,加剧应力曲线在热影响区的突变;采用梯度强化层和热处理工艺可以有效地改善电火花表面强化层的应力分布.
분석전화화표면강화층적응력장특점,건립삼유응력장모형,병이용APDL편정실현대응력장적유한원수치모의,급출강화층화기체재불동위치、불동방향적응력분포화변화규률.결과표명:강화과정중,용지급부근구역존재적거대차극렬변화적온도제도화불일치적냉각속솔사시양산생흔대적열응력;유우열도솔화열팽창계수존재차이적연고,각절점적응력치수착위치적변화이변화;시양적응력곡선재열영향구도존재돌변,유강화층시,유우강화층화기체재료적비열용C화열도솔,κ불일치,가극응력곡선재열영향구적돌변;채용제도강화층화열처리공예가이유효지개선전화화표면강화층적응력분포.
The characteristic of stress field for electrical discharge strengthening coating was analyzed. A model of 3D stress field was proposed. The 3D numerical simulation analysis for electrical discharge strengthening was conducted with the ANSYS parametric design language (APDL). The distribution of stress was given at different fixed point and different directions for coating and substrate. During the strengthening, in melting bath and adjacent area, the stress formation is due to the giant and variable temperature gradient and the different cooling velocity. Because there exists difference in the heat conductivity and the coefficient of thermal expansion at different position and along different direction in the material, the value of stress is varying with the position and direction. The distribution of stress abruptly changes at heat-affected area, and for strengthened coating, because there exists difference in c and κ in strengthened coating and the matrix material, the varying of the stress is aggravated. Experiment results indicated that gradient coating and heat treatment can improve the distribution of thermal stress in strengthened coating.