Measurement of stress using synchrotron x-rays

Area of Science:

• Materials Science
• Solid Mechanics
• Crystallography

Background:

• Polycrystalline materials exhibit heterogeneous stress distribution among grains.
• Plastic deformation leads to stress variations, with stronger grains supporting higher loads.
• This phenomenon is observed in materials such as magnesium oxide (MgO) and MgO-spinel mixtures.

Purpose of the Study:

• To investigate stress partitioning in polycrystalline MgO and MgO-spinel.
• To understand the development of grain-to-grain fabric during plastic flow.
• To analyze the impact of stress partitioning on elastic moduli measurements and high-temperature behavior.

Main Methods:

• Experimental studies on samples of MgO and MgO-spinel mixtures.
• Analysis of stress distribution across different grain subpopulations.
• Investigation of high-temperature flow mechanisms.

Main Results:

• Significant stress variations were observed among different grain subpopulations after plastic flow onset.
• A distinct grain-to-grain fabric develops, facilitating stress partitioning.
• Static measurements of elastic moduli can be invalidated due to this stress partitioning.
• High-temperature flow mechanisms demonstrated more isotropic strength behavior, leading to uniform stress variation.

Conclusions:

• Stress partitioning is a critical factor in the mechanical behavior of polycrystalline materials.
• The developed fabric significantly influences stress distribution and material response.
• Understanding high-temperature behavior is crucial for predicting material properties under varying conditions.