Interlaminar fracture and breakdown of fibers in rectangular-cross-section beams made of carbon-fiber-reinforced plastic (CFRP) are investigated for the case in which the midspan of the beams, which are fixed at both ends, is bombarded by small projectiles. Interest is focused on the relationship between the internal shear stress and the failure mode of the beams. Also, the effects of projectile tip shape on damage initiation are examined. The internal shear stress is calculated by use of the computer code AUTODYN-2D by employing information included in the bending strain waves which are detected experimentally by strain gauges glued on the beam surface. The fracture of CFRP is inspected by means of an ultrasonic microscope and an optical microscope.
Two kind of MD simulations of Mode I crack have been carried out to investigate the effect of micro/macro interaction on crack propagation. The one is coupling with analytical solution only on MD boundary, which in the other one, the whole system is coverd with the analytical solution. It has been found that stress field given from macro field is important in crack propagation, and has shown that the size of applied stress filed affects the size and location of voids caused during crack propagation.
A new mechanism is constructed to transport fluids by means of a progressive wavy motion of two elastic plane membranes which face each other and cover two magnetic fluid layers adjacent to both side walls in a long duct of rectangular cross section. A steady fluid flow can be induced in an inner stratum which is formed between two opposite membranes. Wavy motions of membranes (the peristaltic motion) are excited by the external magnetic field in the form of sinusoidal waves propagated along a train of electromagnets which is arranged linearly along the axis of the duct and driven by a digital electronic pulse-width-modulation circuit and a DC power supply. As a result of examinations of fundamental characteristics of intensity of the propagating magnetic field, wavy motions generated on the membranes, and flow velocity and pressure induced dynamically, the mechanism proposed here exhibits very interesting the excellent performance to be useful in the practical electromagnetopropulsion and/or fluid transportation systems.
Directional characteristics of the combustion noise are experimentally investigated on turbulent diffusion flames established in the plane shear layers of three different flow and turbulence conditions. The effects of a breakdown of the organized flame structure in the downstream direction on the spectral behavior of combustion noise are also examined by inspecting the coherence between the acoustic pressure perturbation and local temperature fluctuation. The results show that the combustion noise emitted from the objective flames bears a quadrupole nature, but not a monopole one, independent of the existence of organized structure. Also, the organized flame structure has stronger influences on the overall noise generation than the increased free stream turbulence intensity within 5-7% under the same flow conditions, which may provide a clue to the noise reduction in the industrial burner systems. It is expected that noise radiation due to organized eddies decreases relatively rapidly with their downstream disappearance.
