Yasuhito Mori

Shock Hugoniot compression curve for water up to 1 GPa by using a compressed gas gun

A shock Hugoniot compression curve for water has been measured up to less than 1 GPa. A plane and steady shock wave is produced in water by the flat plate impact of a projectile accelerated by a compressed gas gun. A new experimental procedure was proposed to detect the shock wave front sensitively, which makes it possible to measure shock Hugoniot in higher precision than the previous method. The present method is based on the very large pressure dependence of the refractive index of water upon compression. By using this method, the shock compression curve was determined within the precision of 2% to 3% of the estimated shock pressure. The precision is better than that of the previous data. It was confirmed that within the pressure range covered in this experiment, the shock-particle velocity Hugoniot can be described by a linear relation with a large slope. Shock Hugoniot states on the pressure–temperature plane were calculated by using the obtained Hugoniot data combined with the values of thermodynami...

Sensitive optical detection of the shock front and fast moving surface for shock study in condensed media in the 1 GPa stress region

Based on the light extinction of total internal reflection by triangular prisms, very sensitive detection of the shock front and fast moving free surface has been demonstrated for 1 GPa shock waves in polymers. This is the first experimental verification of the feasibility of the inclined-prism technique for the relatively low shock stress region, which was originally proposed and used by Eden and Wright for obtaining the high-explosive generated shock Hugoniot of several condensed materials. The present method has the advantage that it only requires closing the gap between the free surface of the target and the reflected surface of the prisms. The feasibility and the limitation of the method have been discussed both theoretically and experimentally. A typical streak photograph for a PMMA specimen is shown to compare with the published data. It is seen that the present method is very sensitive for shock arrival detection even in the 1 GPa shock stress region.

Simple Method of Calculating Grüneisen Parameter Based on the Shock Hugoniot Data for Solids

This paper presents a novel way of calculating Gruneisen parameter for previously proposed three theoretical models. The present method provides a simplified and reliable way of estimating Gruneisen parameter for high-pressure states for solids. A new variable is defined, and integration of the differential equation for Gruneisen parameter is carried out along the shock Hugoniot curve. The available Hugoniot compression curve for the material are all that is required for calculation. Instead of the established but complicated procedure of Gruneisen parameter estimation, a simple and efficient algorithm of calculation has been developed. Numerical examples have been given for various materials, and general discussion for the behavior of Gruneisen parameter has been made.

Shock compression experiments on several polymers in the 1 GPa stress region

Abstract We have established a reliable shock Hugoniot measurement system especially useful for the 1 GPa shock wave in polymer materials. We have developed two Hugoniot measurement methods, one of which is based on the total internal reflection of light at the bottom face of the prism placed on the specimen, while the other is the PVDF gauge method, combined with the optical prism pin. Some of the measured examples for polymer are given.

Thermal nonequilibrium of the shock-compressed state of polymers realized by 1 GPa shock waves

A thermodynamic theory has been developed to calculate the shock temperature of polymers in the 1 GPa pressure region. For this purpose, the Gruneisen parameter has been calculated based on the available nonlinear shock velocity–particle velocity Hugoniot function for polymers. The calculated large values of the parameter correspond to that of phonon frequencies in the collective motion of polymer molecules, and not to that of the intramolecular vibration frequencies. Then, the equilibrium shock temperature as well as the cold potential energy function is calculated using the calculated Gruneisen parameter and the available nonlinear shock velocity–particle velocity Hugoniot function. Shock temperature and cold potential function have also been calculated using the equilibrium thermodynamic values of the Gruneisen parameter and the specific heat. From these calculations, the following unphysical result has been derived; that is, the cold potential function for these polymers has no minimum value at zero-t...

Simultaneous measurement method of both shock state and stress profile in polymers in 1 GPa stress

A new procedure of recording both Hugoniot parameters and stress profile is proposed to study shock characteristics of polymers in 1 GPa stress region. The assembly consists of an in-material polyvinylidene fluoride (PVDF) stress gauge element and an optical prism pin. The PVDF gauge records the shock wave stress profile, while the prism pin records the arrival of shock front at the free surface of the target. Argon laser beam is focused onto the bottom face of the prism pin placed on the free surface so as to satisfy the condition of total internal reflection. Shock velocity can be estimated from the time difference of two signals, the PVDF gauge and the prism pin. The Hugoniot state can be calculated by the shock velocity and the projectile velocity regardless of the stress profile obtained by the PVDF gauge. A typical result for polytetrafluoroethylene (PTFE) specimen is shown with the impact velocity of PTFE flyer of 295 m/s. The obtained Hugoniot point coincides very well with the published data. Pre...

Shock Hugoniot curves for several polymeric materials in 0.5-GPa shock stress

Hugoniot curves for several polymeric materials in the stress region of 0.5 GPa are measured by two methods developed for this purpose. High-speed photography or in-material gauge method is used combined with new prism technique based on the principle of total internal reflection. We measured the following materials, i.e., polymethylmethacrylate (PMMA), three kinds of polyethylene (PE specimens), polytetrafluoroethylene (PTFE), nylon 6 (N6), polycarbonate (PC), polypropylene (PP), polyvinylchloride (PVC). All of the Hugoniot curves are found to be nonlinear. In particular, three kinds of PE specimens are measured in detail, which have the different density, crystallinity, molecular weight distribution and manufacturing process. It is found that these PE specimens have different Hugoniot curves, but qualitatively similar.

New water shock sensor

A new shock sensor for liquids is described in this article which is suitable for precise shock Hugoniot compression curve measurement of water in the relatively low pressure region of ⩽1 GPa. The present method is based on the fact that the refractive index of water has a very large pressure dependence. A laser beam incident on the liquid–glass boundary from the proper angle of incidence is totally reflected at the interface. The condition of total internal reflection is violated if the refractive index changes instantaneously by shock compression. The shock target assembly was designed for a gas gun experiment based on the above concept. Two examples of the shock Hugoniot measurement data of water were given.

Shock Hugoniot Compression Data for Several Bio‐Related Materials

Shock wave data for several bio‐related materials have been obtained. Plane and steady shock waves have been induced by using a modest compressed gas gun facility. Shock pressure covered in this study ranges at least up to 1 GPa. In order to realize the sensitive detection of shock front in these materials in this relatively low pressure region, an optical method has been developed by our group. Optical prism was placed on the sample such that incident laser beam is totally reflected at the prism sample interface. Samples used in the experiment include gelatin with different initial density, NaCl aqueous solution, and finally chicken breast meat. Shock data obtained in the present study are compared with the shock Hugoniot curve for water. It is found that slope of the shock velocity‐particle velocity Hugoniot compression curve for all the materials tested is almost 2. While value of the intercept of the relationship, corresponding to the sound velocity, is apparently dependent on the material and ambient...

Measurement of the slope of shock velocity-particle velocity Hugoniot curve for polymers

In case of shock waves in polymers in the stress range of less than 1 GPa, a strategy to measure the slope of shock velocity-particle velocity Hugoniot curve is proposed. The method is based on the measurement of sound velocity at the shocked state as well as shock and particle velocity. The slope of Hugoniot can be evaluated by combining these values with the shock thermodynamic equation. Experiments were conducted for two kinds of polyethylene samples exhibiting peculiar shape of Hugoniot curve. An in-material PVDF gauge detects both a plane shock wave in polyethylene target induced by impact with a flyer plate and a rarefaction wave reflected from free surface of the flyer. Slope of the Hugoniot analyzed at several Hugoniot points for the polyethylene samples are consistent with their peculiar shape of the Hugoniot curves.