Navy Research Laboratory grants license agreement for commercial applications

WASHINGTON. George Mason University (GMU), U.S. Naval Research Laboratory (NRL) Technology Transfer Office, and NRL Computational Multiphysics Systems Laboratory (CMSL) representatives signed a licensing agreement for the commercialization of NRL-developed strain imaging technologies. The agreement grants Point Semantics Corp. rights to develop the technology for industrial and laboratory uses and to market across the globe.

Officials say, the technologies has been used to test and characterize structural composite materials, , shape , and additively manufactured components.

“This suite of technologies has been a game changer in the Navy, enabling accurate material characterization and structural for various material systems with an accuracy never before possible with conventional methods,” says Dr. John Michopoulos, head, CMSL, and co-inventor of the technology. “The new strain imaging and measurement technologies are proven to be extremely sensitive, accurate, and computationally efficient when compared to other commonly used methods, granting very high performance capabilities in deformation metrology and structural health monitoring.”

Figure: Top: Stereoscopic pair of images of a deformed coupon under combined in-plane rotation and vertical torsion. Bottom: Corresponding full field strain tensor components over the surface of the coupon as produced by DSI. Photo courtesy of U.S. Naval Research Laboratory.

The process enables the non-contact detailed measurement of the strain and displacement states of relevant materials in a manner that is spatially and temporally resolved with accuracy. This is necessary for mechanical testing, characterizing their constitutive behavior and for monitoring their structural integrity, as well as other applications.

Digital imaging methods have been used since the 1980s to measure deformation on an object under mechanical or generalized loading. CMSL has built upon this body of research focusing on ways to achieve high sensitivity, accuracy, computational efficiency, and robustness beyond what traditional techniques provide. The work completed to date has led to three distinct patents:

  • The software implementation of the 2-D Meshless Random Grid (MRG) method;
  • The development of the 3-D MRG method; and
  • The development of the Direct Strain Imaging (DSI) method.

Each employs a system comprising of digital cameras, processing hardware, and software algorithms that process captured images and calculate components of the displacement vector and strain tensor either on discrete locations or on full field areas.

When using MRG and DSI methods, distinct marks are applied randomly to the surface of an object; a camera or a pair of them is then used to capture images before and after force or displacement has been applied. Then, the software identifies the centroids of the marks and measures the relative distance between any pair of them as they have moved during deformation relative to their initial position. This enables the calculation of the precise displacement vector and strain tensor components.

“The MRG and in a greater degree the DSI methods are more sensitive, more accurate, and faster than other digital imaging techniques such as Digital Image Correlation,” says Dr. Athanasios Iliopoulos, co-inventor, and mechanical engineer, CMSL. “The great advantage of our tools is how easy they make it to measure strain, using simply a marker technique to apply dots along with a camera and a software suite that provides three-dimensional, full field strain measurements in real time.”

The MRG and DSI processes use a mesh free approximation computational algorithm after sampling to represent the displacement and strain components at every point in the material. This enables engineers to measure the strain. The DSI method also applies the mesh-free approximation directly on the strain tensor field components thus avoiding the numerical error amplification due to differentiation of the displacement fields. It also does not require the observance of the continuum hypothesis and is therefore applicable for structures containing discontinuities such as flaws and cracks.

Point Semantics Corporation, CEO and licensee, Christopher Vizas, says “While obviously the laboratory and test communities want to get their hands on it, we believe that many industrial customers that employ heavy machinery or build major infrastructure will be interested as well. By measuring strain, and strain over time, users will be able to determine various critical physical quantities associated with operational conditions such as damage, fatigue, creep, etc, that industry wants to know about their equipment and structures.”

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