How interfaces limit nanoscale stress concentrations and prevent catastrophic failure in single-asperity contacts

Area of Science:

• Materials Science
• Nanotechnology
• Tribology

Background:

• Contact mechanics is crucial across scientific fields.
• Quantifying stress at microscale contact points is experimentally challenging.
• Understanding stress evolution in materials under load is vital.

Purpose of the Study:

• To experimentally resolve nanoscale stress fields at material contact interfaces.
• To investigate stress distribution in single-layer and multilayered thin films under indentation.
• To elucidate energy dissipation mechanisms in artificial multilayered materials.

Main Methods:

• In situ scanning synchrotron X-ray nanodiffraction with 80 nm resolution.
• Custom indentation setup with a nanomechanical probe (diamond wedge with nanocrystalline diamond coating).
• Corroboration using X-ray scattering, SEM, micromechanical testing, and finite element modeling.

Main Results:

• Successfully mapped nanoscale stress fields on both the indenter and the thin film.
• Demonstrated that interfaces diffuse stress, influencing the overall mechanical response.
• Showcased a 30% reduction in stored elastic energy for multilayered films versus monolithic ZrN.

Conclusions:

• Interfaces play a critical role in stress diffusion and mechanical response at the asperity level.
• Artificial multilayered materials exhibit enhanced energy dissipation capabilities.
• The findings provide fundamental insights into preventing catastrophic failure through material design.