A mathematical model and software for obtaining the yield stress of complex materials

Value Proposition

Knowing the limit of elasticity, or yield stress, of materials is crucial for the design of any engineering structure and subsurface operations. Determining this point for an ideal material, such as metals, is straightforward. However, the yield stress measurement for more complex materials, like geomaterials, remains ambiguous and debatable. Rather than being based on physical principles, the current method is empirical and requires additional arbitrary input parameters from uniaxial or triaxial compression test results. There is a need for a clear, quantitative determination of yield point for complex materials.

Technology

Duke inventors have reported a mathematical model and software for obtaining the yield stress of a material. This is intended to be utilized for determining the point of yield stress of complex materials on stress-strain curves of uniaxial or triaxial compression tests, such as those utilized in the drilling and mining industries. Unlike the current empirical experimental method, this physics-based protocol relies on energy considerations. The yield stress is determined as the point on the stress-strain curve of maximum mechanical power dissipation. Since the mechanical power is computed as the time derivative of the scalar product of stress with strain, the method only needs measurements of stress and strain to be applicable. The technology has been demonstrated in the lab using 3D printed samples of porous rock and on data from compression tests of real rocks.

Advantages

  • Offers a clear, quantitative determination of yield stress for complex materials like porous rocks
  • This method does not require the use of an input parameter
  • Offers a physics-based understanding of the yield stress as an energy potential
  • No new measurements are required to be applied in conventional mechanical experiments
Example showcasing the new method used on the stress-strain curve of a uniaxial compression of a 3D printed sample
Example showcasing the new method used on the stress-strain curve of a uniaxial compression of a 3D printed sample