Tamotsu Majima

Transport Coefficients and Orientational Distributions of a Dilute Colloidal Dispersion Composed of Hematite Particles: Analysis for an Applied Magnetic Field Parallel to the Angular Velocity Vector of Simple Shear Flow

We have studied the influences of the magnetic field, shear rate, and random forces on transport coefficients such as viscosity and diffusion coefficient, and also on the orientational distributions of hematite particles composed of a dilute colloidal dispersion. Hematite particles are modeled as spheroids with a magnetic moment normal to the particle axis. In the present analysis, these particles are assumed to conduct the rotational Brownian motion in a simple shear flow as well as an external magnetic field. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved by the numerical analysis method. The results obtained here are summarized as follows. With increasing the magnetic field, since the magnetic moment is strongly restricted to the magnetic field direction, the motion of the particle is forced to rotate in directions normal to the shear flow direction. In the case of a strong magnetic field and a smaller shear rate, the rodlike particles can freely rotate in the xy-plane with the magnetic moment remaining pointing to the magnetic field direction. On the other hand, for a strong shear flow, the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. Additionaly, the diffusion coefficient gives rise to smaller values than expected, since the rodlike particle sediments with the particle inclining toward directions normal to the moment direction.Copyright

The interference effect of double symmetrical cracks on general yield strength

Abstract The interference effect of double symmetrical cracks of either equal or unequal crack depth on the plane-strain general yield strength under tension is analyzed based on the upper and lower bound theorems. Theoretical results are compared with experimental results. The experimentally obtained range of crack pitch as influenced by the interference effect can be predicted accurately by the theory. The discrepancy is recognized at each crack pitch, especially for the single symmetrical crack, between the experimental value of the ratio of mean tensile stress in the net section at general yielding to the lower yield point and the constraint factor calculated from the theory. Strain figures obtained by Frys etching method show that plastic deformation occurs approximately along the line of velocity discontinuity employed in the upper bound considerations.