About the Uniaxial Powder Tester

The Uniaxial Powder Tester

Uniaxial Powder Tester

The Uniaxial Powder Tester (UPT) is a unique stand-alone uniaxial shear tester for simple, sensitive and cost-efficient powder characterisation. The instrument delivers repeatable and reliable measurements, providing a robust, cost-effective alternative to traditional powder testing techniques.

Uniaxial testing first involves the construction of a consolidated powder column. This is then removed from its confining sleeve before being fractured through the application of a vertical stress, directly measuring the uniaxial Unconfined Yield Strength (uUYS). This technique can therefore be used to assess and rank powder flowability.

Cohesive powders have relatively strong inter-particular forces, which encourage the particles to adhere together rather than moving easily relative to one another. By contrast, in free-flowing powders, the tensile forces between particles tend to be much weaker.

Uniaxial powder testing is a direct and reliable method for measuring the uUYS and Flow Function of powders.

For further information, please contact us.

Benefits of the Uniaxial Powder Tester

  • Direct uUYS (σc) and Flow Function (FF) measurements
  • Fast
  • Repeatable
  • Low Cost
  • Versatile
  • Easy to use
  • Intuitive, easy to interpret results
  • Robust
Flow Function Plot - Uniaxial Powder Tester

The uniaxial Unconfined Yield Strength (uUYS) is a measurement of stress required to break or fail a previously consolidated, unconfined column of powder. The uUYS is similar to the Unconfined Yield Strength (UYS), a parameter derived from biaxial shear testers, but it should be noted that due to the different consolidation and failure protocols of uniaxial and biaxial testers, it does not always follow that values for uUYS are identical to values of UYS.

Uniaxial Powder Tester Consolidation Station

Off-Instrument Consolidation

The innovative Consolidation Station provides users with additional testing capabilities. It allows powders to be consolidated, separately from the main instrument, for an extended period of time or within a controlled environment, for example at a fixed relative humidity or at elevated temperatures.

The Consolidation Station can provide up to 100 kPa of applied stress and can be placed in an oven at temperatures up to 100°C.

Principles of uniaxial testing

Consolidation – Uniaxial Powder Testing

Sample is loaded into a cylinder and consolidated with a Major Principal Stress (σ1) to form a powder column

Consolidated Powder Column – Uniaxial Powder Testing

Major Principal Stress and cylinder are removed to leave a free-standing consolidated powder column

Uniaxial Unconfined Yield Strength – Uniaxial Powder Testing

Column is fractured through the application of a compressive stress, and derive uniaxial Unconfined Yield Strength

The Challenge...

Practical constraints have previously inhibited the exploitation of uniaxial testing. These include:

  • Constructing a free-standing powder column
  • Ensuring a uniform density and stress throughout the entire powder column
  • A practical, easy to use powder tester that can be used with a wide range of powders

The UPT has overcome these challenges by:

  • Developing a sleeve design enabling the creation of a free-standing column of powder
  • Using a double-ended consolidation method to ensure uniform density and stress

For further information, please contact us.