采用延性损伤模型和数值方法预测Ni-Cr基合金在温成形条件下的断裂极限

为了确定IN625合金的安全成形和断裂极限,在300和673 K下分别进行拉伸成形和深拉延成形实验。将实验获得的基于应力的断裂成形极限图(FFLD)转变为基于应力的σ-FFLD和有效塑性应变(EPS)跟三轴度(η)的关系曲线,以消除断裂极限对应变的过度依赖。为了预测断裂极限,校准7种不同的损伤模型。结果显示,Oh模型对断裂轨迹的预测能力最好,绝对误差最小。虽然实验得到的断裂极限仅用于数值分析,但没有一个损伤模型预测整个应力三轴度范围(0.33<η<0.66)的断裂应变。在不同的温度和润滑条件下深拉延成形圆柱杯,深拉延工艺窗口有助于确定起皱、安全和断裂区域。在润滑条件下,673 K时达到最大的拉延比2。利用Hill 1948各向异性屈服函数对拉伸成形和深拉延成形过程的数值预测结果均在可接受的误差范围内。

Influence of welding consumables on tensile and impact properties of multi-pass SMAW Armox 500T steel joints vis-a-vis base metal

In this investigation, comparative study of tensile and impact properties of multi-pass SMAW Armox500 T steel joints fabricated by austenitic stainless steel(ASS) and low hydrogen ferritic steel(LHF)consumables vis-a-vis base metal was carried out. The tensile tests were conducted on computer controlled Walter t Bai Ag UTM at a nominal strain rate of 10à3 sà1. Subsequently, charpy impact tests were carried out on an instrumented Zwick-Roell test setup to obtain load vs. displacement and maximum energy absorbed vs. displacement of the specimen. It was observed that, the joint efficiency of weldment processed by LHF consumable was 41.7% and weldment processed by ASS was 30.6% of its base metal indicating the influence of electrode consumable on tensile properties of the joints. On the contrary, impact toughness of weldment processed by ASS was 20% more and weldment processed by LHF was 12% less than that of base metal. Microstructural studies also revealed that, ASS can be considered as a candidate welding consumable for good strain hardening and toughness of the welding joint in impact applications. However, LHF steel consumable is recommended for welding joints that requires higher joint efficiency under tensile loading conditions.