How to measure the angle of internal friction?

The angle of internal friction indicates the friction property between the internal powder layers. Any point in the powder interior is suffered from the interaction caused by the particles nearby, resulting in friction between the sliding particles. The measurement of the angle of internal friction can be achieved through the following methods.

Flowing test

Powder particles are poured into a cylinder with a hole at the bottom through which the powder escapes. The angle between the sloping side and the horizontal line is defined as the angle of internal friction.

Rod tension test

A rod is placed vertically at the center of a cylindrical container, which is surrounded by powder particles. The powder surface is flat. Then the rod is lifted upwards, creating an angle between the sloping side and the horizontal line, which is defined as the angle of internal friction.

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