High-rate dynamic testing maschine

材料、结构或结构节点在快速、高速动载作用下的力学行为往往与准静态加载不同。这被称为所谓的应变率效应，它可以导致在高测试速度下强度的显著增加，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、断裂伸长率和失效模式也可能不同。材料的这种应变率效应的知识在以下领域是必不可少的： 结构碰撞和冲击行为。对于这样的实验表征，使用伺服液压动态高速试验机，这是本提案的主题。试样或结构样本被夹持在这种测试机器中，如在任何常规测试机器中一样。然而，在载荷突然引入试样之前，通过液压的方式强烈加速上部试样的夹紧。用于高强度纤维复合材料的160 kN性能级高速试验机可达到高达20 m/s的速度，这意味着根据试样几何形状，应变率高达约100 m/s。通常可实现600 1/s（为了比较：准静态测试在约600 1/s的范围内进行）。对于力-位移或应力-应变信号的数据采集和测量记录，需要具有足够高的记录频率的高速数据记录器，并且该高速数据记录器是系统的一部分，以便在仅持续几毫秒的测试期间记录足够大量的数据点。基于双高速摄像机立体相关的光学高速测量系统（数字图像相关）通常用于应变测量。采购这台配备光学高速测量系统的高速试验机是布伦瑞克理工大学Heimbs教授新任命的一部分，也是飞机设计和轻型结构研究所（Heimbs教授是这一领域公认的专家，在他被任命为IFL后，他正在发展这一领域，并扩大了他以前广泛的研究活动。许多研究项目正在规划中，其中一些已经获得批准，这些项目涉及轻质和纤维复合材料的高速率动态特性以及连接技术，例如用于鸟撞载荷下的创新机翼结构，对于新类型的能量吸收器或新的材料建模方法，以及用于有限元模拟的层间强度和断裂能。

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.