The Comet’s legacy is not completely negative however; these early failures helped develop the backbone of fatigue and fracture mechanics that would be used, refined and evolved over the next 70 years. Indeed, it was only 20 years after that first test flight of the Comet that NASA’s engineering team supported a successful moon landing! Industries beyond aviation and space exploration have benefited from this science as well: heavy machinery, transportation, naval, energy, medical devices…all have been fundamentally changed by the furtherance of materials science principles.

VEXTEC continues this evolutionary effort, by incorporating these “physics of failure” principles into our probabilistic Virtual Life Management® technology. We differentiate ourselves from other computational fatigue methods, by combining a component’s inherent microstructural variability with physics-based damage mechanisms and realistic loading histories to accurately predict fatigue life. As structures become increasingly more complex, with continual demands for lighter-weight materials (for both manufacturing and operational cost savings) and better performance, the need for a comprehensive reliability simulation technology becomes clear. No one wants to be the next disastrous chapter in this Comet’s Tale.

Image by Praisaeng at FreeDigitalPhotos.net

While plenty of industries abhor corrosion and its consequences, another sector has welcomed it as a step in the healing process: medical devices. Devices have evolved over the decades to be less-intrusive during (and after) implantation.The bio-inert nature of titanium (along with its weight and strength characteristics) has made it the go-to material for structural orthopedic implants (hip and knee joints, bone plates and screws, etc.). These implants are made to go into the patient’s body and remain there, hopefully performing well for an extended period of time without the need for replacement. But what about implantable devices that have a finite life of medical functionality, and afterwards can become detrimental to the patient’s quality of life?

Such is the case with attaching soft tissues to bone during ACL repairs, as described in a recent issue of Advanced Materials & Processes. Stainless steel or plastic attachments have been the accepted materials in the past because of their strength and biocompatibility behaviors. However, once these devices have done their job they can be hard to remove, or can (in the case of stainless steel) cause metal sensitivity in the patient. Implanted screws made of polymer-based biocomposites have been shown to degrade at a safe rate in living bone and tissue. This allows the repaired ligament to heal, while the tool itself is slowly absorbed by the body using its own metabolic conversion system (the Krebs cycle).

Another example is the performing of a balloon angioplasty to unblock clotted arteries. The device employed in this procedure is a balloon-tipped catheter, which widens the artery. A metallic mesh stent is placed in the area where the work was performed, to keep the artery open as it heals from the procedure. The mesh stent never goes away, which can have an unintended outcome as time progresses. In an ideal world, the stent would remain properly positioned in the artery and cause no further damage. In reality, the stent has the opportunity to create major issues in the body after the artery’s healing time (localized inflammation, or structural breakdown resulting in stent fracture and arterial wall damage). A research group at Michigan Tech is looking to take the bio-corrodible nature of zinc and use it to their advantage in stent design. An alloyed zinc stent would perform the necessary function of propping the blood vessel open as it heals, and then would break down into products that are harmless to the body after its function is complete. The degradation rate for zinc in the body has been shown to be approximately 0.015 millimeters/month for the first three months (the crucial timeframe for stent functionality), with an accelerated rate after that.

VEXTEC’s past success with modeling corrosion-induced damage propagation (previously used for corrosion mitigation purposes) provides an exciting opportunity to repurpose this methodology to model the corrosion state in materials and devices in which degradation is in fact encouraged. Whether seen as detrimental or beneficial, the processes of corrosion and fatigue are interrelated. The key to merging the two phenomena lies in reducing the size of the initial flaw (as described by traditional damage tolerance analysis) to better reflect the size ranges that are observed in corroded surfaces. In the realm of bioabsorbable medical devices, the ongoing degradation due to corrosion can be explicitly accounted-for during the service life of the implanted devices. The randomized load patterns of a given virtual patient (or a population of patients) can provide the external loads necessary to perform simulated damage progression. This analysis could provide insights into the reliability of a temporary implant and its effect on a patient’s wellbeing.

A limiting factor in the current approach for predicting corrosion influenced part life is that corrosion and fatigue failure mechanisms are modeled separately rather than together. Seldom are synergistic damage processes of corrosion and fatigue explicitly modeled in commercially available software applications used by OEMs. However, recent developments in unified fatigue modeling are bringing corrosion and fatigue modeling techniques together by reducing the size of the initial surface flaw in damage tolerance analysis to create a total fatigue life approach that can address the microstructure of the corroded surface.

“We are extremely pleased to be recognized with this highly competitive award from the USAF,” said Dr. Robert Tryon (CTO, Co-Founder of VEXTEC).  “Not only is this an important step for the USAF in designing a corrosive resistant fleet of the future, but for VEXTEC as we continue to add modules and functionality to our proprietary Virtual Life Management® (VLM®) software.”

While the primary goal of Phase I is to demonstrate the conceptual design of a corrosion fatigue prediction tool, the overall goal of the SBIR program is to develop mature technologies that can be commercialized for sale in the private sector and/or military markets. To this end, VEXTEC has developed a roadmap for this technology that will take this concept from Phase I demonstration to a valuable asset for the defense and aerospace industry. Ultimately, this technology will enable alloy by design in support of all new reliable and sustainable aircraft designs.

VEXTEC’s VLM software for leads of defibrillator devices

Brentwood, TN, April 10, 2015 – Dr. Sanjeev Kulkarni, Vice President of Sales & Business Development of VEXTEC Corporation, will be presenting at the 2015 Design of Medical Devices Conference on April 15, 2015. The conference will be held in Minneapolis, Minnesota April 13 – 16. Representatives from world-class medical device designers, researchers, manufacturers, and the public sector will be in attendance to share perspectives and innovations in medical device design.

Dr. Kulkarni will be presenting, “Uncertainty Management in Computational Simulations of Medical Devices” which will discuss VEXTEC’s software based uncertainty management tool to virtually manage the life of products.  VEXTEC’s Virtual Life Management® (VLM®) software uses efficient Monte Carlo simulation with system reliability methods to analyze risk and predict failure at component, system and population level for many types of products including medical devices. Based on the tool’s maturity in other industries, the FDA has accepted the tool into the Medical Device Development Tool (MDDT) pilot program. The VLM® tool considers the uncertainty of model parameters and acquired data to serve as a framework to incorporate realism with multi-scale statistical characterization using probabilistic and parallel computational simulation techniques. VEXTEC will also participate in the Scientific Poster Session on April 15

Founded in 2000, VEXTEC Corporation has developed patented technology on virtual material modeling and predicting product durability. As a senior strategic member of VEXTEC’s Leadership Team, Dr. Kulkarni leads commercial Sales & Business Development with a focus on Healthcare/Life Sciences/Medical Devices and Strategic Alliances. Dr. Kulkarni is an industry recognized leader and expert in Computational Mechanics and Computer Aided Engineering, and has supported many industries (Automotive, Aerospace, Defense, Energy, Consumer Products and Medical Devices) and in a variety of roles that include 5 years with Boston Scientific (as R&D Fellow), 10 years with KB Engineering (as President) and 6 years with TRW Automotive (as Principal Engineer).