The stress-strain response of a porcine muscle along and perpendicular to the muscle fiber direction was characterized over a wide range of strain rates under uniaxial tension. A modified Kolsky tension bar was used to conduct the experiments at high strain rates. Tubular specimen geometry was used to achieve uniform loading within the specimen and to minimize lateral inertia effect. Loading pulse was controlled to facilitate constant strain rates and dynamic stress equilibrium. Quasi-static experiments were also performed to explore the rate effects over a wider range of strain rates. The results show that the nonlinear tensile stress-strain responses in both directions along and perpendicular to the fibers are highly sensitive to strain rates. Compared with high-rate compression response, the strain rate sensitivity in the tensile test is less dependent on the fiber orientation to the loading direction.

This paper employs the torsional split-Hopkinson bar to investigate the dynamic shear deformation behavior and fracture characteristics of a 304L stainless steel Gas Tungsten Arc Welded (GTAW) joint at room temperature under strain rates in the range of 8 Â 10 2 s À1 to 2:8 Â 10 3 s À1 . The experimental results indicate that the strain rate has a significant influence on the mechanical properties and fracture response of the tested GTAW joints. It is found that the flow stress, total shear strain to failure, work hardening exponent and strain rate sensitivity all increase with increasing strain rate, but that the activation volume decreases. The observed dynamic shear deformation behavior is modeled using the Kobayashi-Dodd constitutive law, and it is shown that the predicted results are in good agreement with the experimental data. Observation of the fractured specimens indicates that the fracture features are closely related to the preceding flow behavior. At all values of strain rate, it is noted that the specimens all fracture within their fusion zones, and that the primary failure mechanism is one of extensive localized shearing. The fracture surfaces are characterized by the presence of many dimples, which suggests a ductile fracture mode. It is shown the strain rate has a significant influence upon the appearance of the dimpled surface. A higher strain rate tends to reduce the size of the dimples and to increase their density. Finally, it is determined that the presence of weld inclusions also influences the appearance of the fracture. These inclusions cause the initiation of micro-voids, which grow and coalesce within the fusion zone, and eventually form a continuous fracture surface.

This paper reports on the development of a MEMS capacitive microphone design with 72 dBA signal-to-noise-ratio (SNR) in a compact 3.4 × 2.3 × 0.7 mm3package. The design incorporates a circular diaphragm disc suspended on one end of the cantilever beam. The diaphragm, under the bias conditions, is supported using peripheral and center protrusions extended from the back plate. The design optimization is targeted to achieve high sensitivity and low damping noise to achieve maximum SNR possible in the mentioned footprint. Finite element modeling (FEM) combined with the lumped element circuit modeling have been implemented to realize the microphone performance. The results have been validated against the measurement with very good correlation of sensitivity, noise and total harmonic distortion (THD). With the sensitivity of −35 dBV (ref. 1 V/Pa at 1 kHz) and acoustic overload point of 134 dBSPL, this is one of the highest performing MEMS analog microphone reported today. Therefore, it is very well suited for audio applications such as mobile phones, true wireless stereo (TWS) earphones, hearing aids and automotive, which demand miniaturized size, low cost and high performance.