What are the main methods for measuring internal friction angle?

The internal friction angle represents the friction characteristics between particle layers inside the powder. Any point inside the powder will bear the action of the surrounding particles. The relationship between the vertical stress and the tangential stress r on any plane passing through the point, in an extreme equilibrium state Below, most powders conform to Coulomb’s formula:

There are 5 simple methods for measuring internal friction angle

(1) Warehouse flow experiment. There is a small hole at the bottom of the warehouse, and the powder in the warehouse falls freely through the hole. The angle between the moving surface of the particles and the horizontal plane is the internal friction angle of the powder.

(2) Round rod tension test. A round rod is placed vertically in the center of the container. Powder is added to the container to make the surface of the powder horizontal. Then the round rod is pulled upwards. The angle between the moving surface and the horizontal plane is the internal friction angle.

(3) Piston test. Powder is loosely loaded into a tube with a diameter of D_T. There is still a piston below the tube that can drive the piston. When the height of the powder loading reaches a certain critical value L, the piston can no longer be pushed upward. Then the critical value L/D_T. is the internal friction angle.

(4) Soaring flow test. Apply the surging phenomenon in the fluidization test, that is, the powder flows upward in streams.

The interval between each strand is the air segment, and the maximum L/D_T. ratio is the internal friction angle. L is the maximum value of the length of each strand.

(5) Chamber pressure experiment. The particle pressure in the warehouse increases proportionally with the bed height. When it reaches a certain critical value of L/D_T., the pressure growth becomes smaller and finally approaches a constant value. The measured critical value is the internal friction coefficient .