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R O Ritchie - One of the best experts on this subject based on the ideXlab platform.
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after fat...
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after Fatigue Failure, but no thickening after overload fracture in air or after Fatigue cycling in vacuo. We find that such oxide thickening and premature Fatigue Failure (in air) occur in devices with initial oxide thicknesses of ∼4nm (SUMMiT V™) as well as in devices with much thicker initial oxides ∼20nm (MUMPs). Such results are interpreted and explained by a reaction-layer Fatigue mechanism. Specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic Failure of the entire device. The entirety of the evidence presented here strongly indicates that the reaction-layer Fatigue mechanism is the governing mechanism for Fatigue Failure in micron-scale polycrystalline silicon thin films.
Daan Hein Alsem - One of the best experts on this subject based on the ideXlab platform.
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after fat...
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after Fatigue Failure, but no thickening after overload fracture in air or after Fatigue cycling in vacuo. We find that such oxide thickening and premature Fatigue Failure (in air) occur in devices with initial oxide thicknesses of ∼4nm (SUMMiT V™) as well as in devices with much thicker initial oxides ∼20nm (MUMPs). Such results are interpreted and explained by a reaction-layer Fatigue mechanism. Specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic Failure of the entire device. The entirety of the evidence presented here strongly indicates that the reaction-layer Fatigue mechanism is the governing mechanism for Fatigue Failure in micron-scale polycrystalline silicon thin films.
Brad L Boyce - One of the best experts on this subject based on the ideXlab platform.
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after fat...
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very high cycle Fatigue Failure in micron scale polycrystalline silicon films effects of environment and surface oxide thickness
Journal of Applied Physics, 2007Co-Authors: Daan Hein Alsem, R Timmerman, Brad L Boyce, Eric A Stach, Th J M De Hosson, R O RitchieAbstract:Fatigue Failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle Fatigue behavior of these films (up to 1012cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼40kHz in different environments, stress-lifetime data exhibit similar trends in Fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no Fatigue Failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after Fatigue Failure, but no thickening after overload fracture in air or after Fatigue cycling in vacuo. We find that such oxide thickening and premature Fatigue Failure (in air) occur in devices with initial oxide thicknesses of ∼4nm (SUMMiT V™) as well as in devices with much thicker initial oxides ∼20nm (MUMPs). Such results are interpreted and explained by a reaction-layer Fatigue mechanism. Specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic Failure of the entire device. The entirety of the evidence presented here strongly indicates that the reaction-layer Fatigue mechanism is the governing mechanism for Fatigue Failure in micron-scale polycrystalline silicon thin films.
Yukitaka Murakami - One of the best experts on this subject based on the ideXlab platform.
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small crack growth model from low to very high cycle Fatigue regime for internal Fatigue Failure of high strength steel
International Journal of Fatigue, 2016Co-Authors: Yoichi Yamashita, Yukitaka MurakamiAbstract:Abstract Fatigue Failure of high strength steels mostly originates at nonmetallic inclusions. An optically dark area (ODA) beside the inclusion can be observed in specimens fractured at very high cycle Fatigue (VHCF) regime. The present paper proposes Fatigue life prediction models from low to VHCF regime. The Fatigue life prediction model inside ODA has been constructed in the VHCF regime based on the master curve of the growth of ODA where Fatigue Failure is caused by cyclic loading assisted by hydrogen trapped by inclusion. The Fatigue crack growth law is proposed for a small crack outside ODA within the framework of the area parameter model where the concept of “continuously variable Fatigue limit” for small crack is introduced. The life and scatter of Fatigue life originating at inclusions can be well evaluated by the proposed models.
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Mechanism of Fatigue Failure in ultralong life regime
Fatigue & Fracture of Engineering Materials & Structures, 2002Co-Authors: Yukitaka Murakami, N. N. Yokoyama, Junji NagataAbstract:The Fatigue fracture surfaces of specimens of heat treated hard steels which failed in the regime of N =10 5 to 5 x 10 8 cycles , were investigated by optical microscopy and SEM. Specimens having a longer Fatigue life had a particular morphology beside the inclusion at the fracture origin. The particular morphology looked optically dark and in the previous paper it was named the Optically Dark Area, ODA. The roughness inside ODA is larger than outside ODA. The relative size of the ODA to the size of the inclusion at the fracture origin increases with increase in Fatigue life. Thus, the ODA is considered to have a crucial role in the mechanism of ultra long life Fatigue Failure. Direct evidences of existence of hydrogen at the inclusion at fracture origin are presented. It is presumed that the ODA is made by the cyclic stress coupled with the hydrogen which is trapped by the inclusion at the fracture origin. To verify the influence of hydrogen, specimens containing different levels of hydrogen were prepared by different heat treatments. The results obtained by Fatigue tests of these specimens suggest that the hydrogen trapped by inclusions is a crucial factor which causes the ultra long Fatigue Failure of high strength steels. Aspects of the double S-N curve are also discussed in terms of experimental methods, specimen size and statistical distribution of inclusions sizes.
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Mechanism of superlong Fatigue Failure in the regime of N>107 cycles and fractography of the fracture surface
Transactions of the Japan Society of Mechanical Engineers. A, 2000Co-Authors: Yukitaka Murakami, Toru Ueda, Tetsushi Nomoto, Yasuo MurakamiAbstract:In order to elucidate the mechanism of superlong Fatigue Failure in the regime of N>107 cycles, the fracture surfaces of specimens of heat treated hard steel, SCM 435 and 0.46% medium carbon steel were investigated by optical microscope, SEM and AFM. It has been revealed that specimens having longer life have a particular morphology beside the inclusion at fracture origin. The particular morphology looks optically dark by the observation of optical microscope and it has been named the optically dark area, ODA. The ODA looks a rough area in the observation by SEM and AFM. The relative size of ODA to the size of inclusion at fracture origin increases with increase in Fatigue life. Thus, ODA has a crucial importance for the mechanism of superlong Fatigue Failure. It has been assumed that ODA is made by the Fatigue due to cyclic stress coupled with hydrogen which is trapped by the inclusion at fracture origin. To verify the hypothesis, specimens annealed at 300°C in a vacuum (VA specimens) and quenched in a vacuum (VQ specimens) are prepared to desorp the hydrogen trapped by inclusions. The specimens VA and VQ, had a much smaller ODA than conventionally heat treated specimens. Thus, it has been concluded that hydrogen trapped by inclusion is the crucial factor which causes superlong Fatigue Failure of high strength steels.
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On the mechanism of Fatigue Failure in the superlong life regime (N>107 cycles). Part 1: influence of hydrogen trapped by inclusions
Fatigue & Fracture of Engineering Materials & Structures, 2000Co-Authors: Yukitaka Murakami, Tetsushi Nomoto, Toru UedaAbstract:The fracture surfaces of specimens of a heat-treated hard steel, namely Cr-Mo steel SCM435, which failed in the regime of N= 10 5 to 5 x 10 8 cycles, were investigated by optical microscopy and scanning electron microscopy (SEM). Specimens having a longer Fatigue life had a particular morphology beside the inclusion at the fracture origin. The particular morphology looked optically dark when observed by an optical microscope and it was named the optically dark area (ODA). The ODA looks a rough area when observed by SEM and atomic force microscope (AFM). The relative size of the ODA to the size of the inclusion at the fracture origin increases with increase in Fatigue life. Thus, the ODA is considered to have a crucial role in the mechanism of superlong Fatigue Failure. It has been assumed that the ODA is made by the cyclic Fatigue stress and the synergetic effect of the hydrogen which is trapped by the inclusion at the fracture origin. To verify this hypothesis, in addition to conventionally heat-treated specimens (specimen QT, i.e. quenched and tempered), specimens annealed at 300 °C in a vacuum (specimen VA) and the specimens quenched in a vacuum (specimen VQ) were prepared to remove the hydrogen trapped by inclusions. The specimens VA and VQ, had a much smaller ODA than the specimen QT. Some other evidence of the influence of hydrogen on superlong Fatigue Failure are also presented. Thus, it is concluded that the hydrogen trapped by inclusions is a crucial factor which causes the superlong Fatigue Failure of high strength steels.
Jianyu Zhang - One of the best experts on this subject based on the ideXlab platform.
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multiaxial high cycle Fatigue Failure of 30crmnsia steel with mean tension stress and mean shear stress
International Journal of Fatigue, 2019Co-Authors: Jianyu ZhangAbstract:Abstract Experiments had been performed to investigate the effect of the mean tension stress and mean shear stress on the multiaxial Fatigue Failure of 30CrMnSiA steel. The crack growth path was observed under a metallographic microscope. The stage I cracks were always initiated on the MSSA planes and propagated approximately 20–100 μm for the different load conditions. The stage II crack propagated approximately 400–1000 μm along the MN plane for in-phase loading. The stage II crack initially propagated along the MN plane and quickly deviated from it for 90° out-of-phase loading. Crack initiation and early propagation (
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effect of mean shear stress on torsion Fatigue Failure behavior of 2a12 t4 aluminum alloy
International Journal of Fatigue, 2014Co-Authors: Jianyu Zhang, Qingshan XiaoAbstract:Abstract Fatigue experiments with solid cylindrical bar specimens were carried out to investigate the effects of mean shear stress on the torsion Fatigue Failure behavior of 2A12-T4 aluminum alloy. The torsion S–N curves under different values of mean shear stress were obtained. Experiment results showed that Fatigue life under the same shear stress amplitude gradually reduces with increasing the mean shear stress, when mean shear stress is lower than a threshold value. Macro-analysis and micro-analysis of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean shear stress values under torsion Fatigue loading.
