Development of Elevated Temperature Fatigue Testing Technique for Micro Components used in Micro Power Generating Systems

MEMS中使用的单晶硅(SCS)微元器件，由于其运动的波动，经常遭受循环疲劳损伤。评估微结构的疲劳损伤和准静态力学性能对于MEMS的安全运行和延长寿命是至关重要的。到目前为止，作者已经在高温下进行了微尺度SCS试件的单向拉伸和单向弯曲应力下的高周疲劳试验。在此基础上，提出了从纳米尺度到微米尺度的试件尺寸范围内预测SCS疲劳寿命的适用参数。然而，MEMS中的SCS元件不仅要承受拉应力，还要承受压应力。例如，硅基功率…中使用的部件，如在高温下工作的微型涡轮机械和微型往复发动机；通常由于器件启动/停止时的循环热滞后而受到较低应变率的拉伸/压缩疲劳损伤。更多的ES。光微开关还将在全反向弯曲变形中承受拉压循环载荷。为了建立可靠的硅基MEMS设计准则，需要一种新的循环拉/压载荷下损伤评估技术。本研究开发了一种可对微尺度的SCS试件施加循环拉/压载荷的全逆弯曲疲劳试验机，该试验机采用双厚悬臂梁结构。本文的主要内容是：1)微疲劳试验机的设计；2)弯曲疲劳试验程序的建立；3)微米级单晶硅试件的疲劳寿命预测。在疲劳试验中，SCS试件在两个厚悬臂梁之间往复运动，在试件的两端分别产生拉应力和压应力。这两个悬臂有两个作用：一个是弯曲的压痕，另一个是施加在试件上的循环载荷的检测器。利用基于AFM技术的激光反射系统，通过测量双悬臂梁的挠度来测量弯曲载荷。通过对微型SCS试件的准静态弯曲试验，验证了该试验机弯曲力测量的准确性和位移控制系统的可靠性。我们成功地进行了全反向循环弯曲试验，从而获得了微观SCS试件的弹性应力-应变滞后曲线。这项研究将提供一个有效的参数来预测微尺度SCS的疲劳寿命，而不受试验条件的影响。较少

Single crystal silicon (SCS) micro components used in MEMS often suffer from cyclic fatigue damage due to their fluctuating motion. Evaluating fatigue damage as well as quasi-static mechanical properties of micro SCS structures is essential for safe operation and life extension of MEMS. The authors have so far carried out high cyclic fatigue tests of microscale SCS specimens under uniaxial tensile and one-directional bending stressing at elevated temperatures. Here, the applicable parameter to predict fatigue lives of SCS was proposed on a broad-range of specimen size from nanoscale to microscale. However, SCS components in MEMS would undergo not only tensile stress but also compressive stress. For example, components used in silicon based power MEMS, such as micro turbo machinery and micro reciprocating engine operating at high temperatures ; usually receive tension/compression fatigue damage with lower strain rate attributed to cyclic thermal hysteresis at the start/stop of the devic … More es. Optical micro switches will be also subject to tension-compression cyclic loading in a full-reversed bending deformation. In order to establish a reliable design criterion for silicon-based MEMS, new damage evaluation technique under cyclic tensile/compressive loads is required. This research developed a full-reversed bending fatigue tester that can apply cyclic tensile/compressive loads to a microscale SCS specimen using twin thick-cantilevers.A novel full-reversed bending fatigue tester was developed for cyclic fatigue damage evaluation of MEMS materials. This paper focuses on ; 1)the design of the micro fatigue tester ; 2)establishment of the bending fatigue testing procedure ; and 3)revealing fatigue lives of microscale single crystal silicon (SCS) specimens. In fatigue testing, an SCS specimen was reciprocated between the twin thick-cantilevers to induce tensile and compressive stresses at both fixed ends of the specimen, respectively. The twin cantilevers played two roles ; one is as an indenter for bending and the other as a detector of cyclic loads applied to a specimen. The bending loads were measured by the deflection of the twin cantilevers using a laser reflection system based on AFM technique. Quasi-static bending tests of micro SCS specimens demonstrated the measurement accuracy of bending force and reliability of the displacement control systems of the tester. We succeeded the full-reversed cyclic bending tests, whereby the elastic stress-strain hysteresis loops of micro SCS specimen was obtained. This research will propose an effective parameter to predict fatigue lives of microscale SCS without respect to test conditions. Less