A Constitutive Model for the Mechanical Behavior of Single Crystal Silicon at Elevated Temperature

Moon, H.-S.; Anand, Lallit; Spearing, S. Mark

doi:10.1557/proc-687-b9.6

Cited by 9 publications

(9 citation statements)

References 12 publications

(16 reference statements)

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“…Although mono-crystalline silicon is often considered brittle, plastic deformation is known to occur [52]. Plastic deformation of the silicon most likely happens during cool down between approximately 630 • C and 970 • C. This region is above the britle-to-ductile transition temperature of silicon [53] and below the viscous flow point of silicon dioxide [54], [55]. However, we have no data to confirm this.…”

Section: Discussionmentioning

confidence: 84%

Permanent Stiffness Reduction by Thermal Oxidation of Silicon

Kuppens¹,

Herder²,

Tolou³

2019

J. Microelectromech. Syst.

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Stiffness in compliant micro mechanisms can negatively affect performance. Current methods for stiffness reduction in micro electro mechanical systems (MEMS) consume power, have a large footprint or are relatively complex to manufacture. In this paper stiffness is reduced by static balancing. A building block commonly used for stiffness reduction in large scale compliant mechanisms is made compatible with MEMS. Preloading required to create negative stiffness is obtained from residual film stress by thermal oxidation of silicon. Instead of buckling a plate spring by moving its end points, a SiO 2 film 1900 nm to 2500 nm thick will stretch micro-beams 24 µm wide, while the end points are fixed. To show efficacy of our method, the building block is coupled with a simple linear stage. However, the building block can readily be combined with other compliant micro mechanisms to reduce their stiffness. Statically balanced MEMS will enable novel designs in low-frequency sensor technology, low-frequency energy harvesting and pave the way to autonomous micro-robotics. We show a stiffness reduction of a factor 9 to 46. The balancing effect remained after SiO 2 removal, due to plastic deformation of the beams. [2019-0023]

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Section: Discussionmentioning

confidence: 84%

Permanent Stiffness Reduction by Thermal Oxidation of Silicon

Kuppens¹,

Herder²,

Tolou³

2019

J. Microelectromech. Syst.

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“…In low-C steel, numerous investigations have been performed on the yield point phenomenon, [35][36][37] and the stress concentration was observed to have a strong influence on the Lu¨ders band. [37][38][39][40] Several studies assessed the microstructural origin of the Lu¨ders band propagation, [41][42][43][44] and others proposed the thermal effects associated with strain localization. [45][46][47] Dissipative thermal effects due to the Lu¨ders band propagation were observed by means of infrared image processing, for a S355MC steel grade (0.5C0.35Mn), and a low-amplitude thermal front of 2°C or 3°C was reported.…”

Section: Bh Of the Isolated Ferrite And Bainite Constituentsmentioning

confidence: 99%

Static Strain Aging of Microstructural Constituents in Transformation-Induced-Plasticity Steel

Samek

Moor

Penning

et al. 2008

Metall Mater Trans A

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A pronounced difference in static strain aging was observed between unstrained and prestrained low-alloy multiphase transformation-induced-plasticity (TRIP) steel. High bake-hardening (BH) values were obtained for prestrained TRIP steel. This aging behavior was shown to be directly related to the multiphase microstructure, by analyzing static strain aging in the ferrite and bainite separately. The ferrite in TRIP steel exhibits very limited strain aging, due to the Cottrell atmosphere formation. The bainite constituent, which contains retained austenite, has a pronounced static strain-aging response in the 2 pct prestrained condition. This is a result of internal stresses generated by the strain-induced martensite and the low-temperature aging of this phase. In the absence of strain-induced martensite, the BH values of TRIP steel are low and are due only to the Cottrell atmosphere formation. The TRIP steel exhibits an intermediate BH response, due to the composite effect of its ferrite and bainite constituents. The influence of the cross-sectional changes and volume changes during tensile tests carried out to determine the BH values is also reviewed.

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“…10 shows stress-strain curves for Si at various levels of initial dislocation density. Measurements of the upper yield strength of Si [23], [24] have also shown that the upper yield strength of Si is a function of temperature, strain rate, and initial density of dislocations. The key question is whether or not the structural design of Si-SiC hybrid structures can rely on the upper yield strength of Si, which has been adopted for the allowable stress in the analysis so far.…”

Section: Materials and Structures Issues In The Design Of Si-sic Hmentioning

confidence: 99%

“…The model developed for this purpose is described elsewhere [23]- [25]. It consists of a continuum description of the plasticity of silicon, with nominal dislocation density and shear resistance as the internal variables.…”

Section: Materials and Structures Issues In The Design Of Si-sic Hmentioning

confidence: 99%

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Development of Si–SiC Hybrid Structures for Elevated Temperature Micro-Turbomachinery

Moon

Choi

Spearing

2004

J. Microelectromech. Syst.

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Abstract-The design of the Massachusetts Institute of Technology (MIT) microengine is limited in part by the material capability of Si primarily due to the pronounced thermal-softening and strain-softening at temperatures higher than the brittle-to-ductile transition temperature (BDT), approximately 550 C. In order to circumvent this limitation, it has been proposed to reinforce the Si with chemical vapor deposited (CVD) SiC in strategic locations to create a Si-SiC hybrid microengine turbine spool. Detailed design of Si-SiC hybrid structures for high temperature micro-turbomachinery, however, has been hampered by the lack of understanding of the mechanical behavior of Si and SiC hybrid structures at elevated temperatures and by the unavailability of accurate material properties data for both Si and SiC at the temperatures of interest. In this work, a series of initial thermomechanical FE analyzes have been performed to assess the advantage of the hybrid structures, and to provide structural design criteria and fabrication requirements. Then, the feasibility of the Si-SiC hybrid structures concept for elevated temperature micro-turbomachinery was verified based on more rigorous mechanical testing at high temperatures. Finally, the Si-SiC hybrid spool design was critically reevaluated with regard to creep using a Si constitutive model developed as a separate effort.[0988]Index Terms-Finite element analysis, mechanical testing, Massachusetts Institute of Technology (MIT) microengine, Si-SiC hybrid structures.

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A Constitutive Model for the Mechanical Behavior of Single Crystal Silicon at Elevated Temperature

Cited by 9 publications

References 12 publications

Permanent Stiffness Reduction by Thermal Oxidation of Silicon

Permanent Stiffness Reduction by Thermal Oxidation of Silicon

Static Strain Aging of Microstructural Constituents in Transformation-Induced-Plasticity Steel

Development of Si–SiC Hybrid Structures for Elevated Temperature Micro-Turbomachinery

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