Unconfined yield stress Failure function

Uniaxial Compression - Williams Method This method was developed by Williams, Birks and Bhatta-charya24. A compact is first formed in a split mould by applying an axial compressive force, the mould is then removed to leave a cylindrical specimen with its axis vertical. The compressive vertical stress needed to cause failure of the specimen is then found and this is the unconfined yield stress for the consolidating stress used in the compaction of the specimen. The failure function is found by forming a number of compacts under different consolidating stresses and finding the unconfined yield stress for each specimen. 

Jenike failure function (Jf) This is the reiationship between the unconfined yield strength (fa) and the major consoiidation stress (cti ). A plot of the values fa versus cti shows the possible relationship of the rate of flow of powdered material out of hopper orifices. Jenike could classify the flowability of powders from selected ratios of these values. 

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