Thoerner Robert P, King Jonathan D, Saunders Marnie M
Department of Biomedical Engineering, University of Akron.
Department of Biomedical Engineering, University of Akron;
J Vis Exp. 2018 Sep 19(139):58168. doi: 10.3791/58168.
In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be cost-prohibitive, often priced in the $100,000 - $200,000 price range. At the other extreme are stand-alone manual devices that often lack repeatability and accuracy (e.g., a manual crank device). However, if a single use is indicated, it is over-engineering to design and machine something overly elaborate. Nonetheless, there are occasions where machines are designed and built in-house to accomplish a motion not attainable with the existing machines in the laboratory. Described in detail here is one such device. It is a loading platform that enables pure uniaxial loading. Standard loading machines typically are biaxial in that linear loading occurs along the axis and rotary loading occurs about the axis. During testing with these machines, a load is applied to one end of the specimen while the other end remains fixed. These systems are not capable of conducting pure axial testing in which tension/compression is applied equally to the specimen ends. The platform developed in this paper enables the equal and opposite loading of specimens. While it can be used for compression, here the focus is on its use in pure tensile loading. The device incorporates commercial load cells and actuators (movers) and, as is the case with machines built in-house, a frame is machined to hold the commercial parts and fixtures for testing.
在精确的机械测试方面，各种机器贯穿整个范围。商业平台虽然具有出色的精度，但成本高昂，价格通常在10万至20万美元之间。另一个极端是独立的手动装置，这类装置往往缺乏重复性和准确性（例如手动曲柄装置）。然而，如果仅需单次使用，设计和制造过于精密的东西就属于过度设计了。尽管如此，有时还是需要自行设计和制造机器，以实现实验室现有机器无法完成的运动。这里详细描述的就是这样一种装置。它是一个能够实现纯单轴加载的加载平台。标准加载机器通常是双轴的，即线性加载沿轴发生，旋转加载围绕轴发生。在使用这些机器进行测试时，载荷施加在试样的一端，而另一端保持固定。这些系统无法进行纯轴向测试，即在试样两端施加相等的拉伸/压缩力。本文开发的平台能够对试样进行大小相等、方向相反的加载。虽然它也可用于压缩测试，但这里重点介绍其在纯拉伸加载中的应用。该装置集成了商用测力传感器和致动器（移动装置），并且与自行制造的机器一样，加工了一个框架来固定商用部件和用于测试的夹具。
