In engineering applications, surface modifications of materials can greatly influence the lifetime of parts and structures. For instance, laser melt injection (LMI) of ceramic particles into a metallic substrate can greatly improve abrasive resistance. The LMI process is challenging to model due to the rapid temperature changes, which induce high mechanical stresses. Ultimately, this leads to plastification and residual eigenstresses in particles and matrix. These depend on the process parameters. In order to predict these stresses, we propose a major extension of the Nonuniform Transformation Field Analysis that enables the method to cope with strongly varying thermo-elastic material parameters over a large temperature range (here: 300 to 1300 K). The newly proposed θ-NTFA method combines the NTFA with a Galerkin projection to solve for the self-equilibrated fields needed to gain the NTFA system matrices. For that, we exploit our recent thermo-elastic reduced order model (Sharba et al., 2023) and extend it to allow for arbitrary polarization strains. An efficient implementation and a rigorous separation of the derivation of the reduced order model is proposed. The new θ-NTFA is then validated for various thermo-mechanical loadings and in thermo-mechanical two-scale simulations.

中文翻译：

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热塑性非均匀相变场分析，用于激光熔融注射材料的特征应力分析


在工程应用中，材料的表面改性会极大地影响零件和结构的使用寿命。例如，将陶瓷颗粒激光熔融注射 （LMI） 到金属基材中可以大大提高耐磨性。LMI 过程的建模具有挑战性，因为温度变化很快，会引起高机械应力。最终，这会导致颗粒和基体中的塑化和残余特征应力。这些取决于工艺参数。为了预测这些应力，我们提出了非均匀变换场分析的主要扩展，使该方法能够在较大的温度范围内（此处：300 至 1300 K）处理强烈变化的热弹性材料参数。新提出的 θ-NTFA 方法将 NTFA 与 Galerkin 投影相结合，以求解获得 NTFA 系统矩阵所需的自平衡场。为此，我们利用了我们最近的热弹性降阶模型（Sharba等人，2023 年）并将其扩展为允许任意极化应变。提出了一种高效的实现和对降阶模型推导的严格分离。然后，针对各种热机械载荷和热机械双尺度模拟验证新的 θ-NTFA。