Equipment

split-Hopkinson (Kolsky) bar

The E3M Lab utilizes a split-Hopkinson bar for performing high strain rates tests at strain rates on the order of 1,000 /s, as well as direct impact tests to induce even higher loading rates. Tests can be performed in tension, compression, or direct shear. The specimen of interest is placed between two bars, the incident and transmitter bars. Pressurized gas is used to accelerate a striker bar and impact the incident bar, generating a stress wave that travels down the bar and loads the specimen. A portion of the wave is transmitted through the specimen and into the transmitter bar, while the remainder is reflected back in the opposite direction along the incident bar. This allows for the specimen to be loaded under dynamic force equilibrium at high strain rates, enabling the full stress vs. strain material behavior up until fracture to be determined.

Servo-hydraulic load frame

The E3M Lab also has an MTS 858 MiniBionix II servo-hydraulic load frame, capable of performing low- and intermediate rate tests. The frame has independent axial and torsional control channels, with force peak axial force capacity of 5.5 kip and torsional capacity of 2,200 in-lb. The dual control channels allows for tests to be performed under tension, compression, torsion, direct shear, or combined loading states. It also has an integrated stereo DIC system, capable of measuring 3D deformation and full-field strains on the samples.

Shimadzu HPV-2 High Speed Camera

A Shimadzu HPV-2 high speed camera is used to take images during the split-Hopkinson bar tests, with a peak frame rate of 1,000,000 frames per second. These images are then utilized for Digital Image Correlation (DIC) analysis. It can be used to capture a wide range of dynamic events including split-Hopkinson bar experiments, impact testing, and high speed fluid flow.

Telops FAST M3K High Speed Infrared (IR) Camera

The lab uses a Telops FAST M3K IR camera to obtain full-field temperature measurements at high acquisition speeds, with frame rates up 100,000 fps possible. This provides in-depth measurements of the temperature changes during high-speed events such split-Hopkinson bar and impact testing, to characterize the coupled mechanical and thermal response of materials under dynamic loading conditions. It can also be used for applications such as fracture and damage identification in composite materials, assessing coupled mechanical and thermal response of batteries, and testing of energetic materials.

Digital Image Correlation (DIC)

Digital Image Correlation (DIC) is an optical measurement technique capable of resolving the full-field deformation and strain across the material specimen during tests. The E3M Lab utilizes DIC to gain a more accurate understanding of the material response during dynamic loading, including the strain localization phenomena and instantaneous true strain rate across the material. Additionally this full-field strain data is utilized as input for advanced solving methods to determine the full-field stresses across the material.

DIC image showing full-field strains during an SHB tension test, and the associated extensometer (average) true strain rate along with localized true strains at discrete points along the specimen

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