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Comparative assessment of failure strain predictions using ductile damage criteria for warm stretch forming of IN718 alloy
International Journal of Material Forming ( IF 2.4 ) Pub Date : 2020-10-12 , DOI: 10.1007/s12289-020-01588-3
Gauri Mahalle , Nitin Kotkunde , Amit Kumar Gupta , Swadesh Kumar Singh

It is vital to envisage accurately the fracture limits of high strength superalloys when noticeable localized necking or thinning tendency is not observed during sheet-metal stretch forming process. The present study mainly focuses on fracture limits evaluation of Inconel 718 alloy (IN718) in the effective plastic strain (EPS) vs. average triaxiality space. First, uniaxial tensile test, to analyze the material properties, were instigated at different test temperatures (RT-700 °C). Subsequently, stretch forming is performed to evaluate forming and fracture forming limit diagrams (FLD and FFLD) of IN718 using Nakazima test. It is observed that forming and fractured limits of IN718 are significantly influenced by variation of processing temperatures (with approximately 65–70% improvement in major safe and fracture strains) in all deformation regions (with respect to RT). In average triaxiality (η) vs effective plastic strain (EPS) space, higher fracture limits of IN718 are noticed in the entire triaxiality path of deformation region. Seven different ductile fracture models, namely McClintock (M-Mc), Brozzo, Rice-Tracey (R-T), Ko, Oh, Cockcroft and Latham (C-L), and Clift, are formulated so as to foresee the fracture loci of IN718 in EPS vs. triaxiality space. Overall, Oh model, showed best predictability at all temperatures with least Average absolute error (AAE < 13.5%).



中文翻译:

使用延性损伤准则进行IN718合金热拉伸成形的失效应变预测的比较评估

当在钣金件拉伸成形过程中未观察到明显的局部颈缩或变薄趋势时,准确地设想高强度高温合金的断裂极限至关重要。本研究主要集中在有效塑性应变(EPS)与平均三轴空间之间的Inconel 718合金(IN718)的断裂极限评估上。首先,在不同的测试温度(RT-700°C)下进行单轴拉伸试验以分析材料性能。随后,使用中岛试验进行拉伸成形以评估IN718的成形极限和断裂成形极限图(FLD和FFLD)。可以观察到,在所有变形区域(相对于RT),IN718的成形和断裂极限受加工温度变化的影响(主要安全应变和断裂应变提高了约65-70%)。在平均三轴性(η)与有效塑性应变(EPS)空间中,在变形区域的整个三轴性路径中注意到IN718的断裂极限更高。建立了七个不同的延性断裂模型,分别是McClintock(M-Mc),Brozzo,Rice-Tracey(RT),Ko,Oh,Cockcroft和Latham(CL)和Clift,以预测EPS中IN718的断裂位与三轴空间。总体而言,Oh模型在所有温度下均显示出最佳的可预测性,并且平均绝对误差最小(AAE <13.5%)。在变形区域的整个三轴路径中,IN718的断裂极限更高。建立了七个不同的延性断裂模型,分别是McClintock(M-Mc),Brozzo,Rice-Tracey(RT),Ko,Oh,Cockcroft和Latham(CL)和Clift,以预测EPS中IN718的断裂位与三轴空间。总体而言,Oh模型在所有温度下均显示出最佳的可预测性,并且平均绝对误差最小(AAE <13.5%)。在变形区域的整个三轴路径中,IN718的断裂极限更高。建立了七个不同的延性断裂模型,分别是McClintock(M-Mc),Brozzo,Rice-Tracey(RT),Ko,Oh,Cockcroft和Latham(CL)和Clift,以预测EPS中IN718的断裂位与三轴空间。总体而言,Oh模型在所有温度下均显示出最佳的可预测性,并且平均绝对误差最小(AAE <13.5%)。

更新日期:2020-10-12
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