We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses ... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses for both bulk and microscale specimens. At all sizes, plastic flow is localized in shear bands which are accompanied by sudden strain bursts in the microscale tests. We show a modest ( ...
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Public reporting burden for this collection of information is estimated to average I hour per res... more Public reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Micro- and Nanotechnology Sensors, Systems, and Applications IV, 2012
ABSTRACT Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to en... more ABSTRACT Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to enable stable flight. Existing inertial measurement units (IMUs) are incapable of accurately measuring roll-pitch-yaw within the size, weight, and power requirements of at-scale insect-inspired aerial autonomous systems. To overcome this, we have designed novel IMUs based on the biological haltere system in a microelectromechanical system (MEMS). MEMS haltere sensors were successfully simulated, designed, and fabricated with a control scheme that enables simple, straightforward decoupling of the signals. Passive mechanical logic was designed to facilitate the decoupling of the forces acting on the sensor. The control scheme was developed that efficiently and accurately decouples the three component parts from the haltere sensors. Individual, coupled, and arrayed halteres were fabricated. A series of static electrical tests and dynamic device tests were conducted, in addition to in-situ bend tests, to validate the simulation results, and these, taken as a whole, indicate that the MEMS haltere sensors will be inherently sensitive to the Coriolis forces caused by changes in angular rate. The successful fabrication of a micro-angular rate sensor represents a substantial breakthrough and is an enabling technology for a number of Army applications, including micro air vehicles (MAVs).
For the first time, we have demonstrated adiabatic shear localization in pure, ultra-fine grain (... more For the first time, we have demonstrated adiabatic shear localization in pure, ultra-fine grain (UFG) and nanocrystalline (NC) tungsten (W). Fabricated by severe plastic deformation (SPD), microstructural and mechanical property analyses of the W samples show that the combination of fine grain size, stored strain energy, ultra-high strength, little or no work hardening capacity leads to a unique flow softening behavior. It is further hypothesized that, while maintaining material ductility, grain refinement and redistribution of pre-existing impurities, segregated along grain boundaries (GBs), are equally critical for localized flow softening to occur. The UFG and SPD W results serve as minimum property benchmarks for shear localization to occur. In turn, these are used to define the experimental protocols and parameters for use in alternate fabrication procedures such as rapid consolidation of UFG or NC W powders. Preliminary results indicate that additional development of high-puri...
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
The use of optical measuring techniques for small diameter Kolsky bar experiments is discussed. T... more The use of optical measuring techniques for small diameter Kolsky bar experiments is discussed. The goal is to develop methods that can eliminate the need for more commonly used strain gages which become impractical as bar sizes decrease. The basic approach taken here is to adapt interferometer-based methods, used commonly in pressure-shear plate impact experiments, to high-rate Kolsky bar experiments. A Normal Displacement Interferometer (NDI) is used to measure the motion of the free end of the transmitter bar and provide a measurement of the transmitted pulse. Similarly, the incident and reflected pulses are measured with a Transverse Displacement Interferometer (TDI) utilizing a diffraction grating at the midpoint of the incident bar. Both techniques are applied to 1.59 mm diameter steel pressure bars. In the case of the transmitter bar, measurements are also made with the traditional strain gage instrumentation and comparisons between the two are made. The incident bar measurements made via TDI are validated with a simple bar impact against a single incident bar, i.e., without a specimen or transmitter bar. The possible application of these methods to smaller systems is also discussed.
We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses ... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses for both bulk and microscale specimens. At all sizes, plastic flow is localized in shear bands which are accompanied by sudden strain bursts in the microscale tests. We show a modest ( ...
We have used two general methodologies for the production of ultrafine grained (UFG) and nanocrys... more We have used two general methodologies for the production of ultrafine grained (UFG) and nanocrystalline (NC) tungsten (W) metal samples: top-down and bottom-up. In the first, Equal channel angular extrusion (ECAE), coupled with warm rolling has been used to fabricate UFG W, and high pressure torsion (HPT) was used to fabricate NC W. We demonstrate an abrupt shift in the deformation mechanism, particularly under dynamic compressive loading, in UFG and NC W. This novel deformation mechanism, a dramatic transition from a uniform deformation mode to that of localized shearing, is shared by other UFG and NC body-centerd cubic (BCC) metals.
Wei, Q.; Pan, Z. L.; Wu, X. L.; Schuster, B. E.; Kecdkes, L. J.; and Valiev, R. Z., "Microstructu... more Wei, Q.; Pan, Z. L.; Wu, X. L.; Schuster, B. E.; Kecdkes, L. J.; and Valiev, R. Z., "Microstructure and mechanical properties at different length scales and strain rates of nanocrystalline tantalum produced by high-pressure torsion" (2011). US Army Research. Paper 159.
We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses,... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses, with specimen sizes ranging from the submicron to several millimeters in diameter. We observe no change in deformation mode over this range. At all sizes, plastic flow is localized in shear bands, which are accompanied by sudden strain bursts. This metallic glass shows only a modest increase in strength in going from bulk to micrometer-sized specimens. We show that stress gradients in tapered specimens can complicate measurement of the yield strength of metallic glasses in microcompression. Estimates of yield strength based on the minimum cross-sectional area implicitly assume that yielding is controlled by a maximum effective shear stress criterion. An alternative is the shear plane yield criterion, in which the minimum shear stress on the shear band trajectory determines yield. Application of this criterion in tapered microspecimens reinforces the notion that metallic glasses possess relatively size-independent mechanical properties. Published by Elsevier Ltd on behalf of Acta Materialia Inc.
ABSTRACT We present a methodology for concurrent Photon Doppler Velocimetry (PDV) and in-situ fla... more ABSTRACT We present a methodology for concurrent Photon Doppler Velocimetry (PDV) and in-situ flash X-ray imaging during ballistic impact of metallic penetrators into monolithic armor grade ceramic targets. Tungsten heavy alloy long rod penetrators were launched from a smooth bore cannon into silicon carbide targets at velocities of 0.753 and 1.403 mm/μs. Penetrator lengths and penetration depths were measured as a function of time using an array of four 450 kV flash X-ray sources and digital film. A four channel PDV system coupled to a 16 GHz oscilloscope was used to measure the velocity history of the penetrator and at three positions on the back surface of the target. This experimental technique shows great promise for measurements of the dwell time, penetration velocity, and the time of final break-out from the back of the target.
We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses ... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses for both bulk and microscale specimens. At all sizes, plastic flow is localized in shear bands which are accompanied by sudden strain bursts in the microscale tests. We show a modest ( ...
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Public reporting burden for this collection of information is estimated to average I hour per res... more Public reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Micro- and Nanotechnology Sensors, Systems, and Applications IV, 2012
ABSTRACT Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to en... more ABSTRACT Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to enable stable flight. Existing inertial measurement units (IMUs) are incapable of accurately measuring roll-pitch-yaw within the size, weight, and power requirements of at-scale insect-inspired aerial autonomous systems. To overcome this, we have designed novel IMUs based on the biological haltere system in a microelectromechanical system (MEMS). MEMS haltere sensors were successfully simulated, designed, and fabricated with a control scheme that enables simple, straightforward decoupling of the signals. Passive mechanical logic was designed to facilitate the decoupling of the forces acting on the sensor. The control scheme was developed that efficiently and accurately decouples the three component parts from the haltere sensors. Individual, coupled, and arrayed halteres were fabricated. A series of static electrical tests and dynamic device tests were conducted, in addition to in-situ bend tests, to validate the simulation results, and these, taken as a whole, indicate that the MEMS haltere sensors will be inherently sensitive to the Coriolis forces caused by changes in angular rate. The successful fabrication of a micro-angular rate sensor represents a substantial breakthrough and is an enabling technology for a number of Army applications, including micro air vehicles (MAVs).
For the first time, we have demonstrated adiabatic shear localization in pure, ultra-fine grain (... more For the first time, we have demonstrated adiabatic shear localization in pure, ultra-fine grain (UFG) and nanocrystalline (NC) tungsten (W). Fabricated by severe plastic deformation (SPD), microstructural and mechanical property analyses of the W samples show that the combination of fine grain size, stored strain energy, ultra-high strength, little or no work hardening capacity leads to a unique flow softening behavior. It is further hypothesized that, while maintaining material ductility, grain refinement and redistribution of pre-existing impurities, segregated along grain boundaries (GBs), are equally critical for localized flow softening to occur. The UFG and SPD W results serve as minimum property benchmarks for shear localization to occur. In turn, these are used to define the experimental protocols and parameters for use in alternate fabrication procedures such as rapid consolidation of UFG or NC W powders. Preliminary results indicate that additional development of high-puri...
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
The use of optical measuring techniques for small diameter Kolsky bar experiments is discussed. T... more The use of optical measuring techniques for small diameter Kolsky bar experiments is discussed. The goal is to develop methods that can eliminate the need for more commonly used strain gages which become impractical as bar sizes decrease. The basic approach taken here is to adapt interferometer-based methods, used commonly in pressure-shear plate impact experiments, to high-rate Kolsky bar experiments. A Normal Displacement Interferometer (NDI) is used to measure the motion of the free end of the transmitter bar and provide a measurement of the transmitted pulse. Similarly, the incident and reflected pulses are measured with a Transverse Displacement Interferometer (TDI) utilizing a diffraction grating at the midpoint of the incident bar. Both techniques are applied to 1.59 mm diameter steel pressure bars. In the case of the transmitter bar, measurements are also made with the traditional strain gage instrumentation and comparisons between the two are made. The incident bar measurements made via TDI are validated with a simple bar impact against a single incident bar, i.e., without a specimen or transmitter bar. The possible application of these methods to smaller systems is also discussed.
We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses ... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses for both bulk and microscale specimens. At all sizes, plastic flow is localized in shear bands which are accompanied by sudden strain bursts in the microscale tests. We show a modest ( ...
We have used two general methodologies for the production of ultrafine grained (UFG) and nanocrys... more We have used two general methodologies for the production of ultrafine grained (UFG) and nanocrystalline (NC) tungsten (W) metal samples: top-down and bottom-up. In the first, Equal channel angular extrusion (ECAE), coupled with warm rolling has been used to fabricate UFG W, and high pressure torsion (HPT) was used to fabricate NC W. We demonstrate an abrupt shift in the deformation mechanism, particularly under dynamic compressive loading, in UFG and NC W. This novel deformation mechanism, a dramatic transition from a uniform deformation mode to that of localized shearing, is shared by other UFG and NC body-centerd cubic (BCC) metals.
Wei, Q.; Pan, Z. L.; Wu, X. L.; Schuster, B. E.; Kecdkes, L. J.; and Valiev, R. Z., "Microstructu... more Wei, Q.; Pan, Z. L.; Wu, X. L.; Schuster, B. E.; Kecdkes, L. J.; and Valiev, R. Z., "Microstructure and mechanical properties at different length scales and strain rates of nanocrystalline tantalum produced by high-pressure torsion" (2011). US Army Research. Paper 159.
We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses,... more We present quasi-static, room temperature compression data for Pd 40 Ni 40 P 20 metallic glasses, with specimen sizes ranging from the submicron to several millimeters in diameter. We observe no change in deformation mode over this range. At all sizes, plastic flow is localized in shear bands, which are accompanied by sudden strain bursts. This metallic glass shows only a modest increase in strength in going from bulk to micrometer-sized specimens. We show that stress gradients in tapered specimens can complicate measurement of the yield strength of metallic glasses in microcompression. Estimates of yield strength based on the minimum cross-sectional area implicitly assume that yielding is controlled by a maximum effective shear stress criterion. An alternative is the shear plane yield criterion, in which the minimum shear stress on the shear band trajectory determines yield. Application of this criterion in tapered microspecimens reinforces the notion that metallic glasses possess relatively size-independent mechanical properties. Published by Elsevier Ltd on behalf of Acta Materialia Inc.
ABSTRACT We present a methodology for concurrent Photon Doppler Velocimetry (PDV) and in-situ fla... more ABSTRACT We present a methodology for concurrent Photon Doppler Velocimetry (PDV) and in-situ flash X-ray imaging during ballistic impact of metallic penetrators into monolithic armor grade ceramic targets. Tungsten heavy alloy long rod penetrators were launched from a smooth bore cannon into silicon carbide targets at velocities of 0.753 and 1.403 mm/μs. Penetrator lengths and penetration depths were measured as a function of time using an array of four 450 kV flash X-ray sources and digital film. A four channel PDV system coupled to a 16 GHz oscilloscope was used to measure the velocity history of the penetrator and at three positions on the back surface of the target. This experimental technique shows great promise for measurements of the dwell time, penetration velocity, and the time of final break-out from the back of the target.
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Papers by Brian Schuster