This study is aimed at validating the sensitivity and resolution of topology-based cable sensors ... more This study is aimed at validating the sensitivity and resolution of topology-based cable sensors with field testing of three columns, conducting the proof-of-concept tests of an Electrical Time-Domain Reflectometry (ETDR) measurement instrument for real-time detection of the location and time of cracks under cyclic loading, and detecting cracks in RC columns and correlating crack measurements with the strain values on nearby reinforcing bars. To achieve the project objectives, three columns were tested under ring the blast were also seen after the blast was over, indicating the "memory" feature as observed from columns. blast loads: one control specimen and two retrofitted specimens. One cable sensor was installed on the rear (tension) face of each column prior to any strengthening. Proof-of concept blast tests indicated that the sensor and ETDR measurement instrument used during the tests shows the overall distribution of cracks and the location of plastic hinges. The sensitivity of the sensors for crack detection is high in comparison with the noise level. However, the local peaks were not observed for individual cracks due to the limited spatial resolution associated with the measurement instrument used during the blast tests. In the plastic hinge area, the time history of crack opening and closing corresponds well with the strain change measured from the nearby steel reinforcing bar. The large cracks observed du slowly loaded
Run up is a factor in Linear Shaped Charge (LSC) cutting for which an account must be made. It oc... more Run up is a factor in Linear Shaped Charge (LSC) cutting for which an account must be made. It occurs on the initiation segment of the charge, and the cutting performance during this period is significantly lower. Previous investigations by the UMR Explosives Group observed that similar effects occur not only with LSCs but a wide range of other explosives applications, including explosive-driven flux-compression generators. Prior to this investigation, it was believed that the main contributing factors to run up were from the combined effects of explosive run up (detonation pressure), lack of confinement at the free, initiation end of the charge, and penetrator transition from segmented pieces to a long-rod penetrator blade. As an initial step to understanding the mechanics of LSC run up, a series of investigations was performed in which the testing series was divided into several sub-categories (explosive detonation pressure run up, lack of confinement and long-rod penetrator concept) in order to reveal the effect of each on the run up. Predominantly, commercially manufactured LSCs were used for the investigation, and the entire testing was completed by the UMR Explosives Group
The work documented herein is a portion of a multi-organizational effort lead by the University o... more The work documented herein is a portion of a multi-organizational effort lead by the University of Missouri-Rolla (UMR) Rock Mechanics and Explosives Research Center, with the following participants: Kontek Industries, the Air Force Research Laboratory Airbase Technologies Division, UMR’s Department of Civil, Architectural, and Environmental Engineering, the Department of Architectural Studies from the University of Missouri-Columbia (UMC), and UMC’s National Center for Explosion Resistant Design. The ultimate goal of this multi-year project is to establish prototypical functionality and architectural standards for blast-resistant barricade systems through applied research, design, and test efforts. This paper specifically addresses the results of efforts by UMR and Kontek to design and test barrier structures that protect other structures, and mitigate pressure loads and shock hydrodynamic effects on structural barriers, columns, beams, and bents. As a part of this effort, we are examining structural load path transfer during a blast, in order to provide additional support to portions of structure under attack. Continuation of the current close coordination among the authors in the areas of analytical modeling and blast design and test, as well as the commercial constructability, allows the design of mid-scale and full-scale experiments to populate and validate empirical models for blast barriers, to include off-axis pressure prediction and the development of empirical-based algorithm for prediction of blast pressures around structures and barriers.
Digest of Technical Papers. 12th IEEE International Pulsed Power Conference. (Cat. No.99CH36358)
An integral part of the Explosive-Driven Power Generation Program is to enhance the quality and r... more An integral part of the Explosive-Driven Power Generation Program is to enhance the quality and resolution of photography of the surface of EDPG armatures during explosive expansion. The quality and resolution of photography are affected by the amount of illumination, its wavelength, pulse duration, shock effects from the explosive event, explosive plasmas, and surrounding atmospheric characteristics (shock generation of light, blurring, refraction, etc.). Current methods of providing illumination for very high speed photography (~1×106 frames per second) involve the utilization of intense light generated by explosive events such as so-called “argon bombs”; however, such devices reduce the maximum explosive weight in the experimental device and also generate light of a less desirable wavelength. A new system was developed in-house using inexpensive equipment that allows flash photography at 1×106 frames per second utilizing 100 ISO film. This equipment is described along with the techniques used to mitigate the deleterious effects of the explosive event on its surrounding environment. The resultant imaging maximizes resolution of phenomena at the armature surface, far surpassing any previously achieved at this facility
IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255)
Compact autonomous megawatt-power systems based on shock depolarization of ferroelectric material... more Compact autonomous megawatt-power systems based on shock depolarization of ferroelectric materials are capable of producing kiloampere currents and ultrahigh-voltage pulses with amplitudes exceeding 100 kV. Herein, we report the results of experimental investigations of the generation of ultrahigh voltage by poled Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and Pb0.99(Zr0.52Ti0.48)0.98Nb0.01O3 ferroelectrics subjected to shock loading at different shock vector/polarization vector configurations. Our experiments demonstrated that under loading perpendicular to the polarization vector (transverse stress mode) the ferroelectrics are capable of generating high voltages exceeding 400 kV, while the loading parallel to the polarization vector (longitudinal stress mode) causes a distortion of the depolarization process in ferroelectrics of large thicknesses, resulting in inefficient generation of ultrahigh voltage. It was shown that for transverse semi-planar shock waves, the presence of the longitudinal component of stress due to non-perfect planarity of the shock front can cause a complex electric field distribution in the shock front area, resulting in energy losses in ferroelectrics operating in the ultrahigh-voltage mode. The important finding is that a cylindrical, radially expanding shock wave results in no significant distortion of the depolarization process and energy losses during ultrahigh-voltage generation by transversely shock-compressed ferroelectrics. The experimental results indicate that the voltage amplitude generated by transversely shock-compressed ferroelectrics is directly proportional to the ferroelectric thickness in the range from 6 to 230 mm. We found that over the full range of investigated thicknesses the breakdown-field-on-thickness dependence of shocked ferroelectrics is described by a power law and the mechanism of initiation of electric breakdown does not significantly change with ferroelectric thickness.
This study is aimed at validating the sensitivity and resolution of topology-based cable sensors ... more This study is aimed at validating the sensitivity and resolution of topology-based cable sensors with field testing of three columns, conducting the proof-of-concept tests of an Electrical Time-Domain Reflectometry (ETDR) measurement instrument for real-time detection of the location and time of cracks under cyclic loading, and detecting cracks in RC columns and correlating crack measurements with the strain values on nearby reinforcing bars. To achieve the project objectives, three columns were tested under ring the blast were also seen after the blast was over, indicating the "memory" feature as observed from columns. blast loads: one control specimen and two retrofitted specimens. One cable sensor was installed on the rear (tension) face of each column prior to any strengthening. Proof-of concept blast tests indicated that the sensor and ETDR measurement instrument used during the tests shows the overall distribution of cracks and the location of plastic hinges. The sensitivity of the sensors for crack detection is high in comparison with the noise level. However, the local peaks were not observed for individual cracks due to the limited spatial resolution associated with the measurement instrument used during the blast tests. In the plastic hinge area, the time history of crack opening and closing corresponds well with the strain change measured from the nearby steel reinforcing bar. The large cracks observed du slowly loaded
Run up is a factor in Linear Shaped Charge (LSC) cutting for which an account must be made. It oc... more Run up is a factor in Linear Shaped Charge (LSC) cutting for which an account must be made. It occurs on the initiation segment of the charge, and the cutting performance during this period is significantly lower. Previous investigations by the UMR Explosives Group observed that similar effects occur not only with LSCs but a wide range of other explosives applications, including explosive-driven flux-compression generators. Prior to this investigation, it was believed that the main contributing factors to run up were from the combined effects of explosive run up (detonation pressure), lack of confinement at the free, initiation end of the charge, and penetrator transition from segmented pieces to a long-rod penetrator blade. As an initial step to understanding the mechanics of LSC run up, a series of investigations was performed in which the testing series was divided into several sub-categories (explosive detonation pressure run up, lack of confinement and long-rod penetrator concept) in order to reveal the effect of each on the run up. Predominantly, commercially manufactured LSCs were used for the investigation, and the entire testing was completed by the UMR Explosives Group
The work documented herein is a portion of a multi-organizational effort lead by the University o... more The work documented herein is a portion of a multi-organizational effort lead by the University of Missouri-Rolla (UMR) Rock Mechanics and Explosives Research Center, with the following participants: Kontek Industries, the Air Force Research Laboratory Airbase Technologies Division, UMR’s Department of Civil, Architectural, and Environmental Engineering, the Department of Architectural Studies from the University of Missouri-Columbia (UMC), and UMC’s National Center for Explosion Resistant Design. The ultimate goal of this multi-year project is to establish prototypical functionality and architectural standards for blast-resistant barricade systems through applied research, design, and test efforts. This paper specifically addresses the results of efforts by UMR and Kontek to design and test barrier structures that protect other structures, and mitigate pressure loads and shock hydrodynamic effects on structural barriers, columns, beams, and bents. As a part of this effort, we are examining structural load path transfer during a blast, in order to provide additional support to portions of structure under attack. Continuation of the current close coordination among the authors in the areas of analytical modeling and blast design and test, as well as the commercial constructability, allows the design of mid-scale and full-scale experiments to populate and validate empirical models for blast barriers, to include off-axis pressure prediction and the development of empirical-based algorithm for prediction of blast pressures around structures and barriers.
Digest of Technical Papers. 12th IEEE International Pulsed Power Conference. (Cat. No.99CH36358)
An integral part of the Explosive-Driven Power Generation Program is to enhance the quality and r... more An integral part of the Explosive-Driven Power Generation Program is to enhance the quality and resolution of photography of the surface of EDPG armatures during explosive expansion. The quality and resolution of photography are affected by the amount of illumination, its wavelength, pulse duration, shock effects from the explosive event, explosive plasmas, and surrounding atmospheric characteristics (shock generation of light, blurring, refraction, etc.). Current methods of providing illumination for very high speed photography (~1×106 frames per second) involve the utilization of intense light generated by explosive events such as so-called “argon bombs”; however, such devices reduce the maximum explosive weight in the experimental device and also generate light of a less desirable wavelength. A new system was developed in-house using inexpensive equipment that allows flash photography at 1×106 frames per second utilizing 100 ISO film. This equipment is described along with the techniques used to mitigate the deleterious effects of the explosive event on its surrounding environment. The resultant imaging maximizes resolution of phenomena at the armature surface, far surpassing any previously achieved at this facility
IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255)
Compact autonomous megawatt-power systems based on shock depolarization of ferroelectric material... more Compact autonomous megawatt-power systems based on shock depolarization of ferroelectric materials are capable of producing kiloampere currents and ultrahigh-voltage pulses with amplitudes exceeding 100 kV. Herein, we report the results of experimental investigations of the generation of ultrahigh voltage by poled Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and Pb0.99(Zr0.52Ti0.48)0.98Nb0.01O3 ferroelectrics subjected to shock loading at different shock vector/polarization vector configurations. Our experiments demonstrated that under loading perpendicular to the polarization vector (transverse stress mode) the ferroelectrics are capable of generating high voltages exceeding 400 kV, while the loading parallel to the polarization vector (longitudinal stress mode) causes a distortion of the depolarization process in ferroelectrics of large thicknesses, resulting in inefficient generation of ultrahigh voltage. It was shown that for transverse semi-planar shock waves, the presence of the longitudinal component of stress due to non-perfect planarity of the shock front can cause a complex electric field distribution in the shock front area, resulting in energy losses in ferroelectrics operating in the ultrahigh-voltage mode. The important finding is that a cylindrical, radially expanding shock wave results in no significant distortion of the depolarization process and energy losses during ultrahigh-voltage generation by transversely shock-compressed ferroelectrics. The experimental results indicate that the voltage amplitude generated by transversely shock-compressed ferroelectrics is directly proportional to the ferroelectric thickness in the range from 6 to 230 mm. We found that over the full range of investigated thicknesses the breakdown-field-on-thickness dependence of shocked ferroelectrics is described by a power law and the mechanism of initiation of electric breakdown does not significantly change with ferroelectric thickness.
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Papers by Jason Baird