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Uniaxial Powder Tester

Uniaxial Powder Tester

Assess and rank powder flowability

The Uniaxial Powder Tester (UPT) is a stand-alone uniaxial shear tester for simple, sensitive and cost-effective powder characterisation. The instrument delivers repeatable and reliable measurements, providing a robust 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 bond together rather than moving easily relative to one another. By contrast, in non-cohesive 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.


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
  • Bespoke software

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 rotational shear testers. However, it should be noted that due to the different consolidation and failure protocols of uniaxial and biaxial rotational testers, it does not always follow that values for uUYS are identical to values of UYS.



The UPT’s level of automation and low operator input means the instrument delivers highly repeatable data

Uniaxial Consolidation Stress Range: 0 -100kPa
Normal Stress - Resolution 0.3 Pa
Double Ended Consolidation
Uniaxial Unconfined Yield Strength (uUYS) - Measurement
Real Time Stress Display / Piston Position Display
Sample Mass - Measurement
Compressibility (%)
Height / Diameter Ratio of Consolidated Sample 1.25 - 1.50
Bulk Density - Poured (g/m1)
Bulk Density - Consolidated (g/ml)
Off Instrument Consolidation
Automated Stress Control
Automated Speed Control during Consolidation & Failure
Data Logging
Data Export
Report Generation
Instrument Dimension 310 x 321 x 647mm






Product Video



Off-Instrument Consolidation

The innovative offline Consolidation Station provides users with additional testing capabilities. It allows powder samples to be subjected to a range of environmental conditions, separately from the main instrument, such as elevated temperature and humidity for extended periods under the desired MPS. This allows for the simulation of many industrial processes without occupying instruments for long periods of time.

The Consolidation Station can provide up to 100 kPa of applied stress and can be placed in an oven at temperatures up to 70°C.


Principles Of Uniaxial Testing

Sample is loaded into a cylinder and consolidated with a Major Principal Stress (σ1) to form a powder column Major Principal Stress and cylinder are removed to leave a free-standing consolidated powder column 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.


Learn more about other Freeman Technology products or Learn about powder behaviour