Ultra High Strain Rate Nanoindentation Testing.

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Strain rate dependence of indentation hardness is crucial for understanding time-dependent plasticity.
• Existing indentation techniques have limitations in achieving a wide range of strain rates.

Purpose of the Study:

• To develop and present a novel indentation-based testing technique.
• To enable the measurement of strain rate dependence of hardness over an extended range (seven orders of magnitude).
• To validate the technique by comparing indentation data with conventional uniaxial data.

Main Methods:

• Utilized advanced nanomechanical measurement capabilities with low noise and high data acquisition rates.
• Implemented a novel testing strategy combining step load and constant load/hold tests.
• Employed a simple analysis to derive equivalent uniaxial response from indentation data.

Main Results:

• Achieved indentation strain rates approaching ballistic levels (4000 1/s).
• Successfully measured strain rate dependence of hardness across seven orders of magnitude.
• Demonstrated excellent agreement between indentation-derived uniaxial data and conventional uniaxial data for aluminum.

Conclusions:

• The novel indentation technique effectively measures strain rate-dependent hardness over a broad range.
• The method provides accurate insights into time-dependent plasticity, even at ultra-high strain rates.
• This technique offers a valuable tool for materials characterization and understanding dynamic mechanical behavior.