High frequency testing machine with climate chamber

通过所要求的带气候室的高频试验系统，将开辟新的科学领域和新的方法，例如超高周疲劳（VHCF）、结构耐久性、疲劳裂纹扩展阈值的确定或阈值范围内的变幅载荷。从技术角度来看，高频测试系统填补了结构力学研究所的超声波和伺服液压测试系统之间的差距，并将专门用于需要高测试负载和高测试频率的研究项目。在VHCF制度中，将使用增材制造的试样来研究裂纹萌生，其中在制造过程中通过人工缺陷或空腔打印出人工制品。为了研究尺寸效应，将改变伪影的位置和尺寸，并且将对样本施加具有不同平均应力的弯曲和扭转载荷。因此，需要更大的样品和更高的频率。此外，还将进行疲劳测试，例如，使用增材制造的功能梯度多孔结构或组件（如医疗应用样本）。由于不同的影响因素，将研究变量的变化以及循环次数的上限，这仅适用于高频率和短测试时间。在结构耐久性领域中，为了描述剩余强度或剩余刚度方法，也需要进行大量的基本疲劳试验，例如复合材料结构，这些试验考虑不同的应力水平和应力比以及载荷方向。特别感兴趣的是，不仅是恒定的振幅载荷，而且在结构耐久性和疲劳裂纹扩展的门槛制度的背景下的服务负载。在结构耐久性研究领域，对荷载谱的处理，如省略和截断，需要进行大量的荷载循环研究。在确定模式I和特别是混合模式下的疲劳裂纹扩展阈值的领域中，新技术通过块接块的高负载循环次数进行测试。在实践中，许多部件，例如管道、船舶结构、轮对轴或风力涡轮机的转子轴，暴露在冰点以下的不同温度下。虽然低温对断裂韧性的影响是众所周知的，疲劳裂纹扩展的门槛制度，以及适当的机制很少被调查。

Through the requested high frequency testing system with a climatic chamber, new scientific fields with new methods regarding e.g. very high cycle fatigue (VHCF), structural durability, the determination of fatigue crack growth thresholds or variable amplitude loadings in the threshold regime will be opened. From technical point of view, the high-frequency testing system closes the gap between the Structural Mechanics Institute's ultrasonic and servo hydraulic testing systems and will be specifically used in research projects, where both high test loads and high test frequencies are required. In the VHCF regime, crack initiation will be investigated using additively manufactured specimen, in which artefacts by means of artificial defects or cavities are printed during the manufacturing process. In order to investigate the size effect, the artefacts will be varied in position and size as well as the specimen will be loaded with bending and torsion with different mean stresses. Therefore, larger specimen and higher frequencies are necessary. Furthermore, fatigue test e.g. with additively manufactured functionally graded porous structures or component like specimen of medical applications will be performed. Due to different influencing factors, the variety of variables as well as higher limit number of cycles will be investigated, which is only feasible with high frequencies and therewith short testing time. Also a high number of basic fatigue experiments are necessary in the field of structural durability for the description of the residual strength or residual stiffness approaches, e.g. for composite structures, which consider different stress levels and stress ratios as well as load directions. Of especial interest are not only constant amplitude loadings, but also service loads in the context of both structural durability and fatigue crack growth in the threshold regime. In the field of structural durability, manipulations of the load spectrum, like omission and truncation, need investigations with high number of load cycles. In the field of the determination of the fatigue crack growth thresholds under Mode I and particularly Mixed Mode, new techniques are tested with block by block high number of load cycles. In practice, numerous components, e.g. pipelines, ship structures, wheelset axles or rotor shafts of windturbines, are exposed different temperatures beneath the freezing point. While the influence of low temperature on the fracture toughness is well-known, fatigue crack growth in the threshold regime as well as the appropriate mechanisms are rarely investigated.