Corrosion as the “Good Guy”


Permanent Bio-Implantable Plates and Screws (Image courtesy of Praisaeng at

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.

Corrosion as the “Bad Guy”

Corrosion of a can

Image courtesy of sakhorn38 at

The topic of corrosion makes recurring appearances in the media; it seems that when you hear about one corrosion-related problem, invariably there will be others reported-on at around the same time. There has recently been a spate of articles confirming that corrosion is currently a headache to the oil and gas sector (undersea bolt failures), as well as to the aviation sector (corrosion-induced fatigue of turbine engine blades in the new Dreamliner aircraft). Oftentimes these stories are first published by financial-leaning news outlets (Wall Street Journal, CNN Money, Bloomberg), a result of the high visibility and cost that these incidents bring in terms of replacement and downtime to their respective industries. Enough of these stories circulating over the span of a few news cycles will make any investor wary, and will prompt questions on what is being done from a regulatory standpoint to restore confidence in companies’ operations. This is particularly true when these reports of corrosion failures have impacts (real, or perceived) on public and environmental safety.

Of course, corrosion is not a new phenomenon. We have been observing the process of corrosion for centuries in our manmade structures, and have developed ways to physically mitigate its effects (painting, inspection methods, et cetera). However, it has only been in recent history that we a) have deeper understanding of the electrochemical processes that describe corrosion, and b) have the industrial engineering prowess to design and build ever greater machines and superstructures that help make modern life possible (economically-available energy sources and air travel, being prime examples). The confluence of these two factors drive the need for more development of mechanistic approaches to corrosion mitigation, through the use of computer-assisted modeling and simulation.

To that end, more and more resources are being appropriated for the research of these corrosion mechanisms in many of the materials that are used today. For example, members of the LIFT Consortium (Lightweight Innovations for Tomorrow) have begun work on the development of new models and a material properties database that will allow for more accurate simulations of corrosion in aluminum alloys used in aerospace and other transportation sectors (focusing on aluminum alloys containing copper, lithium, magnesium, manganese, and zinc). The materials database will be characterized to such a degree so that precise information is obtained about the interaction between microstructure and corrosion. The team will begin with the characterization of the industry’s workhorse alloys, and then extend work to evaluate newer alloys crated using various manufacturing techniques. The goal is to mitigate corrosion in a broad spectrum of aluminum alloys through improved simulator capabilities.

However, only half of the equation is being studied by LIFT: the corrosion impact on metals…with no discussion of how that corrosion introduces damage states, from which stress corrosion cracking and other types of corrosion-fatigue can arise. VEXTEC has pioneered development of a software for the U.S. Navy that predicts the statistical distribution of stress corrosion cracking in an alloyed aluminum microstructure that has been exposed to a corrosive environment. This software serves as a basis for all types of materials that are impacted by corrosion: the material modelers can provide the inputs of the corroded damage states into the VEXTEC software, which will in turn simulate the result of in-service loading on the durability of the critical structures of interest.

Until such time as corrosion has been completely removed as a mechanism in a critically-stressed component (and that time is not approaching anytime soon), it is enough to just model the corrosion characteristics…we must also be able to effectively model the subsequent damage growth throughout the component’s service life.


VEXTEC Presenting at Trelleborg’s 2016 Global FEA Meeting

August, 2016 – Dr. Sanjeev Kulkarni (VP, Sales & Business Development) and Dr. Robert Tryon (CTO) from VEXTEC Corporation will be presenting at the 2016 Global Finite Element Analysis (FEA) meeting for Trelleborg Sealing Solutions (TSS) to be held in Boston, MA on September 15. The presentation will discuss the “Implementation of ‘Integrated Computational Materials Engineering’ or ‘ICME’ towards Managing the Fatigue Life of Components and Assemblies”.

ICME combines computational modeling and materials engineering, and considers materials at multiple length scales, processes that produce these materials and the properties to predict and optimize the performance of components. VEXTEC characterizes materials at the microstructural level and uses its Virtual Life Management®  (VLM®) technology to understand material damage, flaw initiation and crack propagation towards estimating fatigue life in components and assemblies subject thermal / mechanical cyclic loads. The talk will discuss VLM in the context of industry recognized structural design philosophies: Safe Life and Damage Tolerance.

VEXTEC Presenting at International Conference on Fatigue Damage of Structural Materials XI

August 30, 2016 -Dr. Robert Tryon, CTO of VEXTEC, will be presenting at the eleventh biennial International Conference on Fatigue Damage of Structural Materials which will be held in Hyannis, Massachusetts beginning September 18th through the 23rd. This conference will bring together delegates from around the world to discuss how to characterize, predict, and analyze the fatigue damage of structural materials. Dr. Tryon’s presentation titled, “Microscale Computational Fatigue Modeling of Structures with Surface Corrosion” will be given, Tuesday, September 20th at 11:10 a.m.

VEXTEC Presenting at Design of Medical Devices Conference

Dr. Sanjeev Kulkarni, VP of Sales and Business Development will be a featured DMD_2016_speaker at this year’s Design of Medical Devices Conference in Minneapolis, MN, April 1 1-14, 2016.  Dr. Kulkarni’s presentation titled, “Computational Durability Software as a Medical Device Development Tool (MDDT)” will be presented on Tuesday, April 12, 2:00-3:30.  VEXTEC has been working closely with the FDA and Industry and has had to develop methods and approaches in the MDDT evolution roadmap.  Dr. Kulkarni’s presentation will include what the tool specifically does, and discuss the concept of context of use and qualification, and demonstrate (with an example) its role in the current implementation as well as the tool’s potential to ultimately impact multiple device programs and support multiple device sponsors.


VPS-MICRO® Software Demonstration Now Available

VEXTEC's software VPS-MICRO®

VEXTEC’s software VPS-MICRO®

VEXTEC is pleased to announce that a demonstration is now available on our website of the proprietary software VPS-MICRO. VPS-MICRO is a patented software used for material model development and VLM predictions.  VEXTEC’s VLM technology is a computational framework that accurately accounts for a material’s reaction to the stress imparted upon it, its variability and all its various damage mechanisms, its geometry, and the conditions of its usage over time. VLM simulation software platform uniquely combines the industry standard FEA with a 3-D spatial model of the material microstructure to predict component durability and remaining useful life over time. Our patented physics-based computational methods accurately and efficiently predict lifecycle statistics. Click here to view the VPS-MICRO demonstration.

Reporting on TMS 2016 in Music City

March 2, 2016, by: Sanjeev Kulkarni, PhD–One realizes that they are in Nashville when the largest convention complex is called Music City Center, is humongous (12 million square feet) and has the shape of a guitar. And you know are at the TMS when all everyone is talking about is Metals and Materials – and how to make them, analyze / study them and use them for amazing applications. Last month, (February 14 – 18) both these came together at TMS 2016 – the annual gathering that brings together over 4000 globally located individuals (academicians, leaders, engineers, professionals and students) in the minerals, metals and materials fields. VEXTEC Corporation, based in the Metro Nashville area, participated at multiple levels – as an Exhibitor (with a booth), gave 3 presentations on a broad range of topics and hosted a reception on the 16th floor of the nearby spectacular Pinnacle building (a Nashville downtown landmark!)
Ashley Clark (Director of Operations) and Robert McDaniels (Senior Materials

VEXTEC's software VPS-MICRO®

VEXTEC’s software VPS-MICRO®

Engineer) did a phenomenal job of organizing and setting up the booth as an all hands task. Everyone at VEXTEC contributed in putting together the VEXTEC stall with the displays, projector, brochures and the give away items – and with the VEXTEC software VPS-MICRO® to demonstrate. It was fun to interact with the attendees who stopped by the booth with the curiosity to look for a product and /or service that just might help them with their next project or product or help with their research.
Some of the booth visitors came directly from the three separate presentations – one each given by VEXTEC co-founders, Dr. Bob Tryon and Dr. Animesh Dey, and one by me. Here are the presentation titles with a link to the slides.
• “Reliability-Based Methods for Rapid Certification of Metal Additive Manufactured Parts”, Dr. Sanjeev Kulkarni, VP for Sales & Business Development

• “Uncertainty Propagation in a Computational Fatigue Model of an Air frame Structure”, Dr. Animesh Dey, Chief Product Development Officer

• “Microstructural Small Flaw Fracture Mechanics for Improved Design Analysis” – Dr. Robert Tryon, Chief Technical Officer

The talks were well attended and each was followed by a series of insightful questions and comments with a couple of direct leads and possibilities. Overall, the conference had a very high quality of talks / presentations, though the size of the venue made the coverage of all talks in your specific area of interest logistically impossible. I would like to highlight three TMS Featured subject areas that align with VEXTEC technology and offering – Integrated Computational and Materials Engineering (ICME), Certification of 3-D Printed / Additive Manufactured components, and Use of Bioabsorbable Materials / Metals for Medical Devices.

The VEXTEC participation concluded with a reception for invitees, employees and well-wishers! A great event as we move into the amazing Nashville spring.

VEXTEC Exhibiting & Presenting at TMS 2016

Jan, 2016 —  VEXTEC is excited to announce that we will be attending the 145th Annual TMS 2016  in our hometown of Nashville, TN at the Music City Center.  VEXTEC will be exhibiting Feb. 15 – 17th in the exhibit hall at booth #534.  We also have three presentations scheduled:

  • Tuesday, Feb. 16th 4:40 p.m., Room 205B, Reliability-Based Methods for Rapid Certification of Metal Additive Manufactured Parts
  • Tuesday, Feb. 16th 4:40 p.m., Room 207C, Uncertainty Propagation in a Computational Fatigue Model of an Air frame Structure
  • Wednesday, Feb. 17th 9:30 a.m., Room 213, Microstructural Small Flaw Fracture Mechanics for Improved Design Analysis

TMS 2016

Presentation for the 2015 SIMULIA West Regional User Meeting

Author:  Dr. Sanjeev Kulkarni, Vice President Sales and Business Development.

Dr. Sanjeev KulkarniLast week, I was at the 2015 SIMULIA West Regional User Meeting held at the historic Hayes Mansion in San Jose, CA! VEXTEC was one of the sponsors of the event and is a partner of the Advanced Integration Program. It was the 20th anniversary of this event and I was at the first of these events held in Long Beach. The longstanding tradition of the Regional User Meeting format has continued – providing an invaluable platform for industry and academia to join together and share their knowledge and experience in advancing methods and technology for finite element analysis, multi-physics, process automation, design optimization and simulation management . It was great to catch up with old friends (the Computational Modeling community is a small and close knit community), connect with other users and learn how the latest simulation technology and methods can accelerate and improve product development. At the meeting, I learned about Simulia’s Learning Community portal which is a convenient site to keep abreast of the latest collaborations in the 3DS eco-system.

The main event included future strategies and technology/product updates from Simulia leadership as well as User Presentations and Networking opportunities. I also had the opportunity to participate as an invited speaker. My talk entitled – Computational Modeling of Complex Systems using “Digital Twin” and “Digital Thread” Frameworks – underscored of how VEXTEC’s Virtual Life Management (VLM) technology compliments and aligns with Dassault Systèmes (DS) strategy of computational modeling and uncertainty management. VEXTEC is developing this technology as part of the US Air Force’s initiative on developing a computational Digital Thread, Digital Twin eco-system.

Here is a link to the slides from my presentation: VEXTEC DS SimuliaWest 2015_Presentation

VEXTEC Seeking Analytical Engineers to Join Our Team

We are seeking enthusiastic, hard working, self motivated graduates to be a part of our engineering analysis team.

For the Analytical Engineer I Position, qualified candidates will have the following skills:

  • B.S. in Engineering (Civil, Mechanical, BME, Material Science degrees are preferred)
  • Familiarity and experience with engineering simulation tools (FEA)
  • Excellent analytical and problem solving skills
  • Ability to write engineering code is preferred
  • Technical report writing experience is a plus
  • Ability to work independently
  • Self-motivated with the ability to pick up new analytical skills

For the Analytical Engineer II Position, qualified candidates will have the following skills:

  • M.S./Ph.D. with a B.S. in Engineering (Civil, Mechanical, BME, Material Science degrees are preferred)
  • Experience in structural mechanics or fracture mechanics
  • Knowledge of probabilistic methods and statistics
  • Knowledge of finite element modeling and analysis. Deep familiarity and experience with commercial finite element software such as ANSYS, Abaqus, Nastran will be an asset
  • Familiarity and experience with engineering simulation tools
  • Excellent analytical and problem solving skills
  • Ability to write engineering code is preferred
  • Technical report writing experience is a plus
  • Good communication skills both oral & written
  • Ability to work independently
  • Self-motivated with the ability to pick up new analytical skills

To apply for a career at VEXTEC, please send your cover letter and resume to