Abstract

Candidate tungsten armor materials in a magnetic confinement fusion device must be able to withstand thermal variation that leads to internal stresses caused by the impinging heat load. In addition, the thermomechanical properties of these materials are degraded by irradiation-induced defect accumulation. Fission reactor–based irradiation data are used to predict the fusion neutron damage and property change. This study examines the motivation and design of a custom-designed three-point bend test for neutron-irradiated disk specimens that are 3 mm in diameter to be able to define the flexural strength of advanced tungsten materials, alloys, and composites—and to the extent that embrittlement occurs after neutron irradiation. The theory provided shows a calculation for the flexural deflection and shear deflection due to the small-geometry constraints. A finite element deformation analysis is performed to evaluate the mechanical stress field of disk bend specimens. The stress values above 80% of the maximum stress are concentrated in 2.4 mm of the 3.0-mm length of the centerline across the tungsten disk diameter. A bend test fixture has been designed and fabricated to enable testing of these specimens with precisely engineered tolerance and minimal machine compliance. This fixture will be able to be placed inside a universal testing frame at elevated temperatures for the mechanical property evaluation of future neutron-irradiated disk specimens.

摘要

磁约束聚变装置中的候选钨装甲材料必须能够承受热变化，从而导致由撞击热负荷引起的内部应力。此外，这些材料的热机械性能会因辐照引起的缺陷积累而降低。基于裂变反应堆的辐照数据用于预测聚变中子损伤和性质变化。本研究检查了为直径为 3 毫米的中子辐照圆盘试样定制设计的三点弯曲试验的动机和设计，以便能够确定先进钨材料、合金和复合材料的弯曲强度——并中子辐照后发生脆化的程度。提供的理论显示了由于小几何约束引起的弯曲挠度和剪切挠度的计算。执行有限元变形分析以评估圆盘弯曲试样的机械应力场。超过最大应力 80% 的应力值集中在穿过钨盘直径的 3.0 毫米中心线长度的 2.4 毫米处。弯曲测试夹具的设计和制造能够以精确设计的公差和最小的机器顺应性测试这些样品。该夹具将能够放置在高温下的通用测试框架内，用于评估未来中子辐照盘样本的机械性能。超过最大应力 80% 的应力值集中在穿过钨盘直径的 3.0 毫米中心线长度的 2.4 毫米处。弯曲测试夹具的设计和制造能够以精确设计的公差和最小的机器顺应性测试这些样品。该夹具将能够放置在高温下的通用测试框架内，用于评估未来中子辐照盘样本的机械性能。超过最大应力 80% 的应力值集中在穿过钨盘直径的 3.0 毫米中心线长度的 2.4 毫米处。弯曲测试夹具的设计和制造能够以精确设计的公差和最小的机器顺应性测试这些样品。该夹具将能够放置在高温下的通用测试框架内，用于评估未来中子辐照盘样本的机械性能。