Development of a biaxial tensile testing machine for pulsed neutron experiments.

A biaxial tensile testing method has been used to get macroscopic information on elastoplastic deformation of a thin steel specimen and improve the accuracy of plastic processing of steel materials. We newly developed a biaxial tensile testing machine for pulsed neutron experiments (BTM-NEU) to provide the microscopic crystallographic information of steel materials under biaxial load and correlate it with the macroscopic mechanical properties of the materials. The performance of the BTM-NEU was experimentally evaluated with cold-rolled mild steel and hot-rolled high-tensile-strength steel materials and compared with that of a standard biaxial tensile testing machine (BTM-std) as follows. •The BTM-NEU can test an ISO-standardized cruciform specimen as the BTM-std and its performance is equivalent to that of the BTM-std.•The BTM-NEU has excellent long-time reliability and stability necessary for pulsed neutron experiments, especially Bragg-edge neutron imaging experiments.•The BTM-NEU can be applied to pulsed neutron experiments using a Bragg-edge imaging method.

Interplanetary dust from the explosive dispersal of hydrated asteroids by impacts.

The Earth accretes about 30,000 tons of dust particles per year, with sizes in the range of 20-400 microm (refs 1, 2). Those particles collected at the Earth's surface--termed micrometeorites--are similar in chemistry and mineralogy to hydrated, porous meteorites, but such meteorites comprise only 2.8% of recovered falls. This large difference in relative abundances has been attributed to 'filtering' by the Earth's atmosphere, that is, the porous meteorites are considered to be so friable that they do not survive the impact with the atmosphere. Here we report shock-recovery experiments on two porous meteorites, one of which is hydrated and the other is anhydrous. The application of shock to the hydrated meteorite reduces it to minute particles and explosive expansion results upon release of the pressure, through a much broader range of pressures than for the anhydrous meteorite. Our results indicate that hydrated asteroids will produce dust particles during collisions at a much higher rate than anhydrous asteroids, which explains the different relative abundances of the hydrated material in micrometeorites and meteorites: the abundances are established before contact with the Earth's atmosphere.