GH4169合金激光增材制造过程热-力发展数值模拟

Numerical simulation of thermal-mechanical development of GH4169 alloy in laser additive manufacturing process

  • 摘要: 为解决GH4169合金激光增材制造过程中变形甚至开裂的问题,采用直接耦合热弹塑性有限元方法对GH4169合金单道多层墙体激光增材制造过程温度和应力演变进行仿真分析。计算表明,激光增材过程沉积试件经过快速加热和凝固冷却过程,温度变化速率超过1×105℃/s。热循环温度峰值超过2 500℃,最高达2 876℃。激光沉积扫描过的区域因冷却收缩受到约束产生较高的应力。后道沉积时激光扫描到的区域温度再次升高,先会释放前道沉积形成的应力,随着温度降低会造成更大的应力。热源加载结束的一瞬间沉积层与基板连接的部分温度存在反常增加的现象。沉积层残余应力以拉应力为主,高达875 MPa,沿沉积方向的应力分量最大。基板在与沉积层结合部位附近残余应力达到800 MPa左右,与其相对应的远处分布有残余压应力。

     

    Abstract: In order to solve the problem of deformation and even cracking in the laser additive manufacturing process of GH4169 alloy, a direct coupled thermo-elastoplastic finite element method was used to simulate and analyze the temperature and stress evolution during the laser additive manufacturing process of GH4169 alloy single-layer multilayer wall. The results showed that the deposition specimen underwent rapid heating and cooling during the laser additive process, and the temperature change rate exceeded 1×10~5℃/s. The peak temperature of the thermal cycle exceeded 2 500 ℃, and the highest temperature reached 2 876 ℃.The area scanned by laser deposition was constrained by the cooling shrinkage, which resulted in high stress. The temperature of the area scanned by the laser during the subsequent deposition increased again,which would first release the stress formed by the previous deposition, then would cause greater stress as the temperature decreased. At the moment when the deposition was over, the temperature of the part abnormally increased where the deposited layer was connected to the substrate.The residual stress of the deposition layer was dominated by tensile stress, up to 875 MPa. The stress component along the deposition direction was the largest. The residual stress of the substrate near the junction with the deposited layer reached about 800 MPa, and the residual compressive stress was distributed in the distance.

     

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