Optical in-situ analysis of the cavitation damage on technical alloys under repeated single bubbles

重复单气泡作用下技术合金空化损伤的光学原位分析

• 批准号: 451715773
• 负责人: Dr.-Ing. Stefanie Hanke
• 金额: --
• 依托单位: Lehrstuhl für Werkstofftechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/451715773?language=en
• 关键词: Optical; situ; analysis; cavitation; damage

With time, cavitation – that is, the formation and collapse of gas bubbles in liquids – can damage the surface even of high-strength materials. The resistance of materials to cavitation is typically investigated using ultrasound sonotrodes. Due to the large number and stochastic nature of the acoustically generated bubbles, in general the resulting damage cannot be assigned to individual bubble events. However, by means of focused laser pulses it is possible to generate individual bubbles that are precisely reproducible in location and time. Besides many studies on the fluid dynamics of the collapsing bubble, some works examine the effect of such individual bubbles on a deformable solid surface. With few exceptions, the sample is from a soft material, such that the deformation resulting from a single bubble can be correlated with its dynamics. However, it is unclear how these results can be transferred to higher-strength materials.The proposed project aims at this knowledge gap between microscopically uncontrolled damage to technical alloys by acoustic cavitation on one hand and precisely reproducible loading on soft materials by individual bubbles on the other. Series of single bubbles will provide defined, repeated stress on surfaces of technical alloys. The dynamics of each bubble are recorded by imaging, then after each bubble collapse the incremental increase in damage is recorded in situ by optical microscopy, and this is complemented by high-resolution ex-situ techniques to yield a detailed picture of the damage evolution. This enables examining the development of damage during the incubation and erosion phases in unprecedented spatio-temporal resolution, as well as correlating the details of the collapse processes with material changes. In parallel, standard tests with a sonotrode are performed to put this damage into context with what is generally known about the materials’ cavitation resistance.First, microscopy optics are integrated into an existing single-bubble experiment and synchronized with high-speed visualization of the bubbles. Using samples from a soft material, this in-situ imaging is validated by ex-situ confocal microscopy. In a second step, series of tests are carried out on NiAl bronze and 316L steel in order to develop semi-automated methods to efficiently evaluate the very large data sets and to correlate in-situ and ex-situ microscopy. Finally, these methods are used in experiments on both materials, in which the number of bubbles, their distance from the sample surface, and the bubble diameter are varied. Ex-situ, the damage mechanisms in the technical alloys are analyzed in detail by high-resolution electron microscopy and compared with samples from experiments with ultrasonic cavitation according to ASTM G32. The extensive data generated in this project will be made publicly accessible, in particular for modeling work outside of the project.

随着时间的流逝，空化（即液体中气泡的形成和崩溃）甚至会损害高强度材料的表面。通常使用超声超声波塑料研究材料对气蚀的耐药性。由于声学产生的气泡的数量和随机性很大，因此总体而言，无法分配给单个气泡事件的损害。但是，通过聚焦的激光脉冲可以产生在位置和时间上精确可重现的单个气泡。除了许多关于倒塌气泡的流体动力学的研究外，一些作品还研究了这种单个气泡对可变形固体表面的影响。除少数例外，样品是来自软材料的，因此单个气泡引起的变形可以与其动力学相关。但是，目前尚不清楚如何将这些结果转移到更高强度的材料中。拟议的项目旨在通过一方面的声学空化和通过对方的单个气泡在微型材料上通过声学空化来对微观损害对技术合金的损害进行这种知识差距。一系列单个气泡将在技术合金的表面上提供定义的重复应力。每个气泡的动力学通过成像记录，然后在每个气泡崩溃之后，通过光学显微镜在原位记录损伤的增量增加，这是通过高分辨率的Ex-Situ技术来完成的，以产生损害演化的详细情况。这使得在空前的时空分辨率中研究了在孵育和侵蚀阶段期间的损害发展，并将崩溃过程的细节与材料变化相关联。同时，执行带有Sonotrode的标准测试将这种损害与有关材料的气蚀性抗性通常所知的上下文。首先，显微镜光学器件集成到现有的单泡实验中，并与气泡的高速可视化同步。使用来自柔软材料的样品，该原位成像通过前坐骨共聚焦显微镜验证。在第二步中，对NIAL青铜和316L钢进行了一系列测试，以开发半自动化的方法，以有效地评估非常大的数据集并将其与原位和前坐骨显微镜相关联。最后，这些方法用于两种材料的实验，其中气泡的数量，与样品表面的距离和气泡直径变化。前坐骨，通过高分辨率电子显微镜详细分析了技术合金中的损伤机制，并将根据ASTM G32的超声气蚀实验的样品进行了比较。该项目中生成的广泛数据将被公开访问，尤其是用于在项目之外进行建模工作。