A double-cylinder rotary shear tester has been developed which can measure the shearing torque exerted on the inner rotating cylinder and the side wall pressure distribution on the outer stationary cylinder simultaneously. Various powders were tested by changing the powder bed height, the outer cylinder radius and the rotational speed of the inner cylinder.
The torque was shown to be proportional to the square of the powder bed height. The stress normal to the shearing plane at the inner cylinder was estimated from the relation of the side wall pressure distribution to the outer cylinder radius and the internal friction factor was evaluated without introducing Rankine's passive powder pressure coefficient.
The internal friction factors thus obtained for some of the powders tested were in good agreement with those measured by a direct shear tester.