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

微机电系统中的单晶硅（SCS）微元器件经常会因其起伏运动而遭受循环疲劳损伤。评估微SCS结构的疲劳损伤以及准静态力学性能对于MEMS的安全运行和寿命延长至关重要。迄今为止，作者进行了高温下单向拉伸和单向弯曲应力下的微尺度SCS试样的高周疲劳试验。在这里，适用的参数，以预测疲劳寿命的SCS提出了一个广泛的试样尺寸从纳米尺度到微米尺度。然而，MEMS中的SCS组件不仅会受到拉应力，而且还会受到压应力。例如，在硅基功率MEMS中使用的部件，例如在高温下操作的微型涡轮机械和微型往复式发动机;通常在装置启动/停止时由于循环热滞后而以较低的应变率受到拉伸/压缩疲劳损伤。 关于我们 es.光学微型开关也将在完全反向弯曲变形中经受拉压循环载荷。为了建立可靠的硅基MEMS设计准则，需要新的循环拉/压载荷下的损伤评估技术。研制了一种可对微尺度SCS试件施加拉/压循环载荷的全反向弯曲疲劳试验机，用于MEMS材料的循环疲劳损伤评估。本论文的重点是; 1）微型疲劳试验机的设计; 2）弯曲疲劳试验程序的建立; 3）微尺度单晶硅（SCS）试样的疲劳寿命揭示。在疲劳测试中，SCS样本在双厚杠杆之间往复运动，以分别在样本的两个固定端处产生拉伸和压缩应力。双杠杆起着两个作用;一个是作为弯曲压头，另一个是作为施加到试样上的循环载荷的检测器。弯曲载荷的测量采用基于原子力显微镜技术的激光反射系统，通过双悬臂梁的偏转来实现。微型SCS试件的准静态弯曲试验验证了弯曲力测量的准确性和位移控制系统的可靠性。成功地进行了全反向循环弯曲试验，获得了微型SCS试件的弹性应力-应变滞回曲线。这项研究将提出一个有效的参数来预测微尺度SCS的疲劳寿命，而不考虑测试条件。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