Investigation of the feasibility to characterize the properties of critical brazing joints by means of non-destructive ultrasonic testing

研究通过无损超声检测表征关键钎焊接头性能的可行性

• 批准号: 348677458
• 负责人: Professor Dr.-Ing. Wolfgang Tillmann
• 金额: --
• 依托单位: Lehrstuhl für Werkstofftechnologie (LWT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/348677458?language=en
• 关键词: Investigation; feasibility; characterize; properties; critical

It is generally important for the brazing process to avoid the formation of brittle phases in a joining process. However, in order to identify potential hazards at an early stage, reliable methods for non-destructive quality assurance, especially for safety-related components, are needed. Although ultrasonic testing is sporadically used for a non-destructive analysis of soldered seams, their potential is not yet fully exploited. Currently, the detection of striking flaws such as cracks in the joint or porosity, which show a high display due to the transition from material/air, are in the focus when using ultrasonic testing. Our own preparations, however, have revealed other unused possibilities of ultrasonic testing that can be used to detect even small changes in material properties. Thus, the aim of this proposal is structured along two decisive scientific questions. The focus of this research project is to find answers to these questions:The detection of resistance-reducing brittle phases is especially important for industrial users, as these phases affect the lifetime of the joint and can lead to catastrophic damages, especially when they occur in safety components. Therefore, the research project will examine the possibility of reliably identifying such brittle phases in different solders. Additionally, the geometric influence in the form of prolonged acoustic delay lines in the base material until the soldered seam is reached, has to be considered from a technical point of view, as this can reduce the resolution of the test method. For a reliable detection of brittle phases, the acoustic properties of the brittle structural constituents in the material to be brazed have to be distinctly different from the remaining part to be brazed. This was confirmed preliminary studies. The influences of the geometry of the component as well as the change of the acoustic characteristic values by brittle phases are determined through fundamental investigations.Based on multi-frequency testing, ultrasonic testing offers the potential to determine the gap width of a solder non-destructively. Compared to a weld, the brazed seam is composed of two interfaces, which are sometimes only a few microns apart. This can lead to severe interferences during ultrasonic examinations, which depend on the test frequency. One the one hand, these interferences make a precise examination of the brazed joints difficult and request a heightened diligence when selecting the test frequencies. On the other hand, these interferences might provide an opportunity to control the solder gap in the component non-destructively after soldering.

对于钎焊过程来说，避免在连接过程中形成脆性相通常很重要。然而，为了及早发现潜在危险，需要可靠的无损质量保证方法，尤其是与安全相关的部件。尽管超声波测试偶尔用于焊缝的无损分析，但其潜力尚未得到充分利用。目前，超声波检测的重点是检测接头裂纹或孔隙等显着缺陷，这些缺陷由于材料/空气的转变而表现出高显示度。 然而，我们自己的准备工作已经揭示了超声波测试的其他未使用的可能性，这些可能性可用于检测材料特性的微小变化。因此，该提案的目标是围绕两个决定性的科学问题构建的。该研究项目的重点是找到这些问题的答案：降低电阻的脆性相的检测对于工业用户来说尤其重要，因为这些相会影响接头的使用寿命，并可能导致灾难性的损坏，特别是当它们发生在安全部件中时。因此，该研究项目将研究可靠识别不同焊料中此类脆性相的可能性。此外，必须从技术角度考虑以基材中延长的声学延迟线形式直至到达焊缝的几何影响，因为这会降低测试方法的分辨率。为了可靠地检测脆性相，待钎焊材料中脆性结构成分的声学特性必须与待钎焊的其余部分明显不同。初步研究证实了这一点。通过基础研究确定了部件几何形状的影响以及脆性相对声学特征值变化的影响。基于多频测试，超声波测试提供了非破坏性确定焊料间隙宽度的潜力。与焊缝相比，钎焊缝由两个界面组成，有时仅相距几微米。这可能会导致超声波检查期间的严重干扰，这取决于测试频率。一方面，这些干扰使得对钎焊接头的精确检查变得困难，并且在选择测试频率时要求更加谨慎。另一方面，这些干扰可能提供在焊接后无损地控制元件中的焊接间隙的机会。