High-rate dynamic testing maschine

与准静态加载相比，材料、结构或结构节点在快速、高速率动态加载下的力学行为往往不同。这就是所谓的应变率效应，它可以在高测试速度下导致强度的显著增加，特别是在纤维增强复合材料的情况下。在不同的应变率下，刚度、断裂伸长率和破坏模式也可能不同。在​​结构碰撞和冲击行为领域，了解材料的这种应变率效应是必不可少的。为了进行这样的实验表征，使用了伺服液压动态高速试验机，这是本方案的主题。试件或结构试件被夹在这样的试验机中，就像在任何常规试验机中一样。然而，在突然将载荷引入试件之前，通过液压的方式强烈地加速了上部试件的夹紧。160kN高强度纤维复合材料性能等级的高速试验机速度高达20 m/S，这意味着，根据试件几何形状的不同，应变率高达约50%。典型地实现了600个1/S(作为比较：在大约的范围内进行准静态试验)。0.001 1/S).对于力-位移或应力-应变信号的数据采集和测量记录，需要一个记录频率足够高的高速数据记录器和系统的一部分，以便在仅持续几毫秒的试验期间记录足够多的数据点。基于两个高速摄像机的立体相关(数字图像相关)的光学高速测量系统通常用于应变测量。采购这种带有光学高速测量系统的高速试验机是布伦斯韦格理工学院新任命海姆斯教授的一部分，也是飞机设计与轻质结构研究所(IFL)在瞬变动力学领域的科学研究活动所必需的。Heimbs是这一领域公认的专家，在他被任命为IFL并扩大他之前广泛的研究活动后，他正在开发这一领域。许多研究项目正在规划中，一些项目已经获得批准，这些项目涉及轻质和纤维复合材料的高速动态表征以及连接技术，例如在鸟撞载荷下的创新机翼结构、新型能量吸振器或用于有限元模拟的具有应变率相关的层内和层间强度和断裂能的新材料建模方法。

The mechanical behavior of materials, structures or structural joint often differs under fast, high-rate dynamic loading compared to quasi-static loading. This is referred to as the so-called strain rate effect, which can lead to significant increases in strength at high test velocities, especially in the case of fiber-reinforced composite materials. Stiffness, elongation at break and failure modes can also differ at different strain rates. Knowledge of such strain rate effects of the materials is essential in the area of ​​structural crash and impact behavior.For such an experimental characterization, a servo-hydraulic dynamic high-rate testing machine is used, which is the subject of this proposal. A coupon or structural specimen is clamped in such a testing machine as in any conventional testing machine. However, the upper specimen clamping is strongly accelerated by means of hydraulic pressure before the load is abruptly introduced into the specimen. High-speed testing machines in the 160 kN performance class for high-strength fiber composite materials reach speeds of up to 20 m/s, which means that, depending on the specimen geometry, strain rates of up to approx. 600 1/s are typically realized (for comparison: quasi-static tests are carried out in the range of approx. 0.001 1/s ).For the data acquisition and measurement recording of force-displacement or stress-strain signals, a high-speed data recorder with a sufficiently high recording frequency is required and part of the system in order to record a sufficiently large number of data points during the test, which lasts only a few milliseconds. An optical high-speed measuring system based on the stereo correlation of two high-speed cameras (Digital Image Correlation) is typically used for the strain measurement.The procurement of this high-speed testing machine with an optical high-speed measuring system is part of the new appointment of Prof. Heimbs to the TU Braunschweig and is necessary for the scientific research activities of the Institute of Aircraft Design and Lightweight Structures (IFL) in the field of transient dynamics.Prof. Heimbs is a proven expert in this field and is developing it after his appointment at the IFL and expanding his extensive previous research activities. Numerous research projects are in planning and some have already been approved, which deal with the highz-rate dynamic characterization of lightweight and fiber composite materials as well as joining technologies, for example for innovative wing structures under bird strike loads, for new types of energy absorbers or for new methods of material modeling with strain rate-dependent intra- and interlaminar strengths and fracture energies for finite element simulations.