Hidehiro Hata

Using NASA Standard Breakup Model to Describe Low-Velocity Impacts on Spacecraft

The applicability is examined of the hypervelocity collision model included in the NASA standard breakup model 2000 revision to low-velocity collisions possible in space, especially in the geosynchronous regime. The analytic method used in the standard breakup model is applied to experimental data from low-velocity impact experiments previously performed at Kyushu University at a velocity range less than 300 oils. The projectiles and target specimens used were stainless steel balls and aluminum honeycomb sandwich panels with face sheets of carbon fiber reinforced plastic, respectively. It is concluded that the hypervelocity collision model in the standard breakup model can be applied to low-velocity collisions with some simple modifications.

The sterilization of dry powdered foods by successive impacts

The thermal sterilization is limited to use for fungi and bacteria in some kinds of dry powdered foods because of the heat sensitivity of their flavor. The sterilization method using impulsive loads or shock waves has the characteristic to sterilize foods without heating. Higher shock pressure can shows higher disinfecting action, but has some problems such as the degradation of foods and the hardness of handling. The proper choice of energy sources is one of points to make the method push to the industrial level. Safety and facility are also important factors to develop the practical system. In this paper as the case of the lowest limit of the impact load, the powder was impacted by mechanical hammer. It was found that the iterative impacts showed the disinfecting effect although the efficiency was low at an impact. Several processing cycles were required to show the significant decreasing of bacteria, because the apparent colony number (not actual bacteria number) increased in the impact process. The numerical model to estimate the mechanical condition in sterilizing process is also presented in this paper.

Control of variation of delay time from ignition to launch in ETC gun

Control of velocity of projectile is focused in conventional ETC gun researches. On the other hand, we pay our attention on variation of delay time from ignition signal to launch of a projectile at a muzzle. Our final goal is to reduce this variation as small as possible by combination of charged voltage and inductance of coils in a condenser bank of 10 kJ. At the first step, we conducted two kinds of experiments. The one is a discharge experiment and the other is an ignition examination. We measured current and discharge voltage profile in the discharge experiment. The mixture of NH/sub 4/NO/sub 3/, Al powder and polyoxymethylene was used as a propellant. And we measured projectile velocity and delay time in the ignition experiment.

Explosively Driven Expansion and Fragmentation Behavior for Cylinders, Spheres and Rings of 304 Stainless Steel

Explosive loading techniques are applied to expand tubular cylinders, spherical shells and rings of 304 stainless steel to fragmentation, and the effects of wall thicknesses, explosive driver diameters and the constant proportionality of the in-plane biaxial stretching rates are investigated on the deformation and fracture behavior of three basic structures experimentally and numerically. In the cylinder tests, the driver is a column of high explosive PETN, inserted coaxially into the bore of a cylinder and initiated by exploding a fine wire bundle at the column axis using a discharge current from a high-voltage capacitor bank. In case of the ring tests, ring specimens are placed onto a single cylinder filled with the PETN as a expansion driver, and for sphere tests, specimens filled with the PETN are also initiated by exploding a fine copper wire line with small length located at the central point. Two types of experiments are conducted for every specimen and test condition. The first type uses high speed cameras to observe the deformation and crack generation of expanding specimens showing the final maximum in-plane stretching rate of above , and the second uses soft capturing system recovering typically most fragments successfully. The fragments are measured and investigated using a fragmentation model. The effects of test parameters on the deformation and fracture behavior for three types of structures are discussed in need of modified fragmentation model for shell structural elements.

Spall fracture of metallic circular plates, vessel endplates and conical frustums driven by direct explosive loads

Dynamic fracture experiments are conducted for circular plates, vessel endplates and conical frustums of A2017‐7075 aluminum alloys and 304 stainless steel, using a testing apparatus developed applying wire‐row explosion technique to initiation, where tensile stress waves are generated producing spall in the specimens by the direct incidence of plane detonation waves of the explosive PETN. A VISAR system is adopted to observe the free‐surface velocity histories of the specimens. The signals for basic circular plate specimens indicate the characteristics of the failure for tested materials, effects of explosive thickness variations and the configuration of specimens. Hydro codes are satisfactorily applied to simulate the experimental signal data and observed damage phenomena of recovered specimens. Next, an explosive‐filled cylindrical vessel with an endplate at the one end is initiated at the other end surface and expanded by axially propagating explosive detonation to fracture. Both the VISAR signals and...

Analysis of Explosion Combustion Phenomenon with Ammonium Nitrate

In this study, an explosion combustion phenomenon of ammonium nitrate (ρ=1.7kg/cm3) was used instead of the explosive PETN and the ultra-high-speed destruction phenomenon of aluminum cylinder was analyzed. The mix powder obtained by mixing aluminum powder (ρ=2.7kg/cm3) and ammonium nitrate was used instead of the explosive PETN, and an explosive combustion phenomenon was generated using copper wire explosion by high-voltage capacitor bank (40kV, 12.5 /F). Ammonium nitrate and aluminum powder are kneaded in a combination ratio of 5 : 1 in mass. An aluminum cylinder was destroyed by the phenomenon. The experiments were conducted using various diameters of ammonium nitrate particle and the photographs of the phenomenon were taken by the high-speed camera (IMACON468) and the high-speed video camera (HPV-1). The fragments of aluminum cylinder were collected and their dimensions were measured. The explosion phenomenon and fragments were compared with the result by explosive PETN. This paper presents these experiments and analysis result. And, hydro codes have been applied to simulate the deformation behavior of the aluminum cylinder.

Mechanical changes in materials caused by explosive precompression shock waves and the effects on fragmentation of exploding cylinders

Explosive driven rapid fracture in a structural body will be preceded by a compression process, and the compression effects on mechanical properties of the materials are clearly important to understand shock-induced failure such as spall or fragmentation phenomena. In this study, incident shock waves in plate specimens of aluminum A2017-T4 and 304 stainless steel are generated by plane detonation waves in the high explosive PETN initiated using wire-row explosion techniques, and the compressed specimens are successfully recovered without severe damages due to the reflected expansion waves with use of momentum trap method. A hydro code, Autodyn-2D is applied to determine test conditions: thicknesses of explosives, attenuators, specimens and momentum traps and to evaluate experimental results, simulating time-histories of stress waves in the layers of the test assembly. Microhardness distributions in cross-sections, tensile strength, fracture ductility and yield stress are measured for the recovered specimens, using miniature tensile and compression test pieces machined from them. They are compared with those of virgin specimens, showing significant increase of hardness, tensile and yield strength and remarkable reduction of elongation and ductility for shocked specimens. The results are taken into consideration for evaluation of experimental fragmentation energy in cylinder explosion tests.

Development of Gun Bullet Protect Board - Gun Bullet Experiment and Analysis -

The purpose of this study is development of gun-bullet protect board. The collision test was executed in such a way to launch a bullet and collide to the target by the air gun. The mock bullet made of brass was used as the projectile. The collision behaviors of polycarbonate (PC) target board were clarified. Next, the analysis of gun bullet collision between the bullet and PC board has been practiced by non-liner dynamic FEM commercial software (AUTODYNTM) and an effective bullet protection board is designed based on this analytical result.

A1 Development of single stage gas gun and launching experiment of various projectiles

Table A Default Closure Tables for Residential and Industrial Land Use Applications Table B Chemical/Physical Properties Table C Exposure Equations Table D Exposure Assumptions Table E Default Exposure Assumption References Table F Human Health Toxicity Parameters Table G Critical Toxic Effects and Categories This appendix provides various tables of values needed to determine default closure levels under RISC. A short narrative describing each table is provided below; the tables are provided following the text.

Explosively Driven Fragmentation Behavior for Structural Components and Shatterproof Effect of Wall Doubling

One-dimensional symmetrical explosive loadings are applied to expand structural components: tubular cylinders, spherical shells and rings of 304 stainless steel and double and single walled cylinders of an aluminum alloy, A5052 to fragmentation, and the effects of wall thicknesses, explosive driver diameters and the constant proportionality of the in-plane biaxial stretching rates are investigated on the deformation and fracture behavior of three types of single walled structures and shatterproof behavior for double walled cylinders experimentally and numerically. In the cylinder tests, the driver is a column of high explosive PETN, inserted coaxially into the bore of a cylinder and initiated by exploding a fine wire bundle at the column axis using a discharge current. In case of the ring tests, ring specimens are placed onto a cylinder charged with the PETN as an expansion driver, and for sphere tests, a specimen filled with the PETN is also initiated by exploding a fine copper wire line with small length located at the central point. Observation results of deformation have shown the final maximum in-plane stretching rate order of , and fracture evaluations on recovered fragments are discussed indicating the need of modified fragmentation model for the structural components. In the double walled cylinder tests, only for lowermost amount of the explosive the outer cylinder has almost caught the fragments of inner cylinder, revealing that the damage phenomena are much different from those for single walled ones.