Abstract

Friction stir welding has the advantages of producing less material deformation and of simple joining of relatively thick materials, but the disadvantages of forming relatively large heat-affected zones around weld areas. In addition, in research on reductions in bulletproof performance in heat-affected zones, it is necessary to evaluate the ballistic limit velocity (V₅₀), which measures bulletproof performance, and this requires specimens of a certain minimum size and has only limited application to local areas such as heat-affected zones. Instrumented indentation testing (IIT), a method of measuring material properties by utilizing load-depth curves measured by a small indenter leaving fine marks on the material, has no specimen size requirements; in addition, it has simple test procedures and is nondestructive. Here a theoretical model is proposed for evaluating V₅₀ of aluminum alloys by ductile hole formation using IIT. Heat-affected zones generated after friction stir welding of for 7000-series aluminum alloys were simulated, and the model was validated through comparison with the conventional V₅₀ test. In addition, there is currently no way to directly evaluate V₅₀ for welded areas in 7000-series aluminum, but here IIT was used to assess V₅₀ for each local part of the welded specimen. The conventional V₅₀ test takes 15 min per shot and cannot be reused of specimens, but the test using IIT takes 1 min to complete one test and has benefits in terms of time, cost and safety.

Graphic Abstract

中文翻译：

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7xxx 铝合金搅拌摩擦焊后使用仪器压痕试验评估弹道极限速度

摘要

搅拌摩擦焊的优点是材料变形较小，较厚的材料连接简单，但缺点是在焊接区周围形成较大的热影响区。此外，在热影响区防弹性能降低的研究中，有必要评估弹道极限速度（V ₅₀)，它测量防弹性能，这需要一定最小尺寸的样品，并且仅适用于局部区域，例如热影响区。仪器压痕测试 (IIT) 是一种利用负载深度曲线测量材料特性的方法，该曲线由在材料上留下精细标记的小压头测量，没有试样尺寸要求；此外，它具有简单的测试程序并且是非破坏性的。这里提出了一个理论模型，用于通过使用 IIT 形成延性孔来评估铝合金的V ₅₀。模拟了7000系铝合金搅拌摩擦焊后产生的热影响区，并通过与常规V ₅₀对比验证了模型测试。此外，目前还没有办法直接评估7000 系列铝焊接区域的V ₅₀，但这里使用 IIT 评估焊接试样每个局部部分的V ₅₀。传统的V ₅₀测试每次需要 15 分钟，并且不能重复使用样品，但使用 IIT 的测试需要 1 分钟才能完成一次测试，并且在时间、成本和安全方面都有好处。

图形摘要