Automotive – VEXTEC

VEXTEC’s Presentation at the 2017 Simulia fe-safe User Group Meeting

Vextec Corporation — Thu, 07 Dec 2017 17:50:53 +0000

Watch our recent presentation on “Computational Modeling of Complex Systems using Integrated Computational Materials Engineering (ICME)” given at this year’s Simulia fe-safe User Group Meeting:

Grain Size Matters!

Vextec Corporation — Thu, 31 Aug 2017 14:26:04 +0000

A turbocharger client of ours wanted to improve durability and reduce warranty costs on cast wheels made from a nickel superalloy with a radially-solidified (RS) microstructure. A significant portion of their previous field failures had been attributed to high cycle fatigue (HCF). Our client already had ideas about how to reduce these HCF failures by changing the wheel’s microstructure to an equiaxed (EQ) morphology. General representations of RS and EQ microstructures are shown here.

Casting microstructural comparison; source: Wikipedia.

Since design changes like these would require a hefty amount of physical validation testing, they needed a way to predictively quantify the costs/benefits to the product line, should some of these proposed changes be implemented. So they turned to VPS-MICRO®. The VPS-MICRO simulation platform combines structural finite element analysis of the component (FEA, seen below) with a 3-D spatial model of the material’s microstructure to predict component durability risk. It is a probabilistic framework, accounting for variability in microstructure and strength properties, applicable damage mechanisms, and usage over time.

The primary inputs to VPS-MICRO are the design input file (stresses from the FEA and the corresponding stressed area in terms of elemental surface area) and the material input file. VEXTEC has developed plug-ins to extract the design input information from several commercial FEA software programs. The material input file contains all the relevant material properties of the component, from macro-scale to the microstructural level. These properties include those you would normally find in an FEA analysis (material modulus and Poisson’s ratio), but also microstructural properties such as grain size, population density of variously-sized inclusions/defects, and grain-level strength and energy parameters. It is the inherent variability of these microstructural properties that is a key factor of component-level fatigue life variability. The good news is that these properties can be statistically evaluated using industry standard (ASTM) tests.

Now, back to our client’s specific issue. Their RS material microstructure was originally developed to resist the onset of damage at high temperatures. The likelihood of initiating damage is low due to fewer grain boundaries. However once damage initiates, the failure probability goes up because there aren’t as many grain boundaries to arrest crack growth. Their proposed design change, using an equiaxed (EQ) microstructure instead for the turbocharger wheels, was thought to be more damage tolerant. The likelihood of initiating damage would be higher, but so would the opportunity for fatigue crack arrest (more grain boundaries). Using VPS-MICRO, our client was able to pursue a quantitative assessment of the risk of HCF failure versus grain type (radially-solidified vs. equiaxed), before any re-designed wheels were even produced or tested.

Shown below is the VPS-MICRO simulated fatigue life comparison of the current-state RS wheel, and the proposed EQ wheel (baseline average grain size = 2.7 mils). The comparison results are presented using a simulated S-N (Stress-Life) plot. The figure shows considerable variability at each stress level for both materials. Run-outs (the points on the right marked with arrows) are predicted at every stress level. A “run-out” means the simulated specimen did not fail within the number of cycles analyzed. These results indicate the RS wheel would have a lower endurance (fatigue limit) compared to the baseline EQ wheel. Generally speaking, this would seem to indicate that the EQ material is better than the RS material. These results appeared to correlate with published industry reports.

Because the wheel was a casting, there is an expected grain size variation throughout the part. Our client’s quality group thought they could maintain the EQ grain size between 1.7 and 3.8 mils, but acknowledged that sizes as high as 15 mils could occur. So they used VPS-MICRO in a different way: to evaluate the sensitivity of grain size to the risk of wheel failure. Their virtual analysis revealed that EQ wheels are not always better than RS wheels. The figure below shows that failure probability is low for small EQ grains, but is very sensitive to grain size. At a grain size of 15 mils, the EQ wheel is actually more likely to fail than the RS wheel (which has an average grain size of 87 mils). Probability of failure is not as sensitive to grain size for the RS wheel. Did the reversing trend make sense?

VEXTEC and our turbocharger client investigated this relationship between the grain size and HCF failure risk. After analyzing the output of the VPS-MICRO simulations, we determined that competing failure mechanisms were present:

The area effect: it takes more small-sized grains to fill a given surface area compared to fewer, larger grains. A smaller average grain size means a statistically-higher probability of having a weaker grain in a given area. This is analogous to the “weakest link theory“, where increasing the number of links in a chain increases its probability of failure. This explains why larger grains are producing fewer failures compared to small grains (the downward trend of the figure above).
The grain-level strength effect: as the grain size increases, an initiating fatigue crack has a larger size as well. These larger-sized starter cracks are more likely to grow (with minimal arresting) to final failure. Therefore, the local strength properties of the grains become key gatekeepers to either prevent or allow these cracks to propagate from their initial sizes.

The final conclusions reached by our client, with the assistance of VPS-MICRO, were

Using EQ material (2.7 mils) would reduce turbocharger wheel HCF failures by at least 60%
Not all EQ materials are equal; small changes in grain size yield large changes in durability
The probability of wheel failure was not as sensitive to grain size for the RS material
Replacing RS material with EQ material requires significantly-tighter production control

Our client could now make a more-informed decision about the proposed design change (producing and testing the EQ wheel). They knew they would have to cast the wheel in a production environment to capture realistic variations, and to assess their capability to hold tighter tolerance on grain size than what was previously required on the RS wheel.

We’ve said it before, and we’ll say it again:

VEXTEC Founders to Attend 2014 Southern Automotive Conference

Ashley C. Clark — Mon, 06 Oct 2014 18:30:06 +0000

Oct. 6, 2014 – Brentwood, Tenn. — VEXTEC’s Chief Technology Officer, Dr. Robert Tryon and Chief Product Development Officer, Dr. Animesh Dey, will be attending the 2014 Southern Automotive Conference, October 9 – 10 at the Birmingham-Jefferson Convention Complex in Birmingham, Alabama.

At the conference on Thursday Oct 9th at 2:15, a panel presentation will be hosted by ArcelorMittal and Kia on “The Innovation Imperative” to discuss a study that stressed the need to innovate close to the production lines to incorporate essential technologies faster. The Brookings Institute conducted a study in 2013 titled, “DRIVE! Moving Tennessee’s Automotive Sector Up the Value Chain” which discussed the need for the South to transform its automotive manufacturing base into an definitive “advanced industry.” One of the challenges identified in the study is insufficient private research & development (R&D) resources and shortage of collaborative technology development throughout the Southern auto supply chain. This panel will explore novel approaches to identifying technology needs and to improving the ability to innovate locally.

VEXTEC is a local company in Nashville, Tennessee that has received over $25 million in Federal R&D funding specifically for advancing the manufacturing production lines of durable goods. With this funding, they have developed methods known as Virtual Life Management® (VLM®), and obtained seven patents along the way. VEXTEC now provides services in the areas of production line reliability, risk assessment and durability prediction for manufacturing companies of structural, mechanical and electronic products. At the Southern Automotive Conference Dr. Tryon and Dr. Dey will be looking for manufacturers who could benefit from this technology. Both will be available after conference hours for detailed discussions.

The Need for Speed

Michael Oja — Wed, 29 May 2013 19:01:43 +0000

In the race to get products to market, does risk-mitigation get enough time in the winner’s circle?

What do aerospace, medical device manufacturers, and auto racing all have in common? Answer: the need to minimize risk of premature/unexpected component failure while crossing the finish line first. While these industries each have vastly different stakeholders, goals, and success metrics, all look to avoid costly breakdowns in the field. And speed is key. Being the first across the finish line in auto racing gives you the largest share of the purse, not to mention first choice of lucrative endorsement deals. Being the first to market with an innovative or more reliable medical implant or a lighter aircraft component helps in marketing, product launch success, or company profitability and growth. However, pushing the design limits to gain this speed advantage must be weighed against the possible failure of the component in an unforeseen manner.

Speed in Design

Auto racing is one of the world’s most expensive sporting endeavors. A recent USA Today article puts the price tag of prepping and running a car in the Indianapolis 500 at nearly $1 million, and that is already assuming that the car is owned outright. While the bulk of this cost is sunk into parts, staffing, and off-track expenses, a not-insignificant 4.5% of that is spent on controlled testing. For example, one day at a rolling wind tunnel costs $35,000…more than the MSRP of the average production vehicle on US roadways today. While the finances of auto racing and the commercial automotive industry may differ, their goals are similar: to create lighter-weight components that will aid (or at least not hinder) aerodynamic performance. Designers are constantly being tasked with pushing the envelopes of their designs, while still attempting to maintain reliability and risk targets. These designs, in turn, lead to more expensive and detailed manufacturing/machining techniques and the use of more exotic material alloys. The uncertainties in every design usually manifest themselves as restrictive knock-down or safety factors that inevitably detract from performance. Governing bodies in the various auto racing categories (F1, NASCAR, drag racing, to name a few) place additional restrictions in the form of specification limits on components such as engines, body shapes, and spoilers to maintain competitive balance. Regardless of the type of restriction, if a way to reduce the uncertainty in a design is found, it can be advantageous. VEXTEC’s Virtual Life Management (VLM) simulation technology can be that solution. Through rigorous computational analysis of design, load-induced stress, and material, VLM can efficiently identify and quantify those design uncertainties. VEXTEC has provided VLM support to many of the industry’s leading manufacturers of heavy duty engine connecting rods, engine blocks, and turbochargers. This new insight has offered engineers the ability to understand where they really are on their design envelope, and how far they can push certain parameters, even before the first test piece is built.

Speed in Optimizing Maintenance

Weight savings and aerodynamics are, arguably, even more critical in the aerospace industry, where the civilian maintenance repair & overhaul (MRO) market is expected to be $56 billion this year. Engine maintenance alone will take up about 40% of this valuation. The cost of an unexpected catastrophic failure is much higher here than in the auto world. But in order to reduce this risk, aircraft must be maintained and repaired. And while they’re being maintained, they are not in the air delivering passengers, hauling freight, or making money. So minimizing the downtime is crucial to keeping viable profit margins. VEXTEC has partnered extensively with civil and military aircraft users, employing VLM on a multitude of issues including: unitized wing structures (US Air Force), certifying weld-repaired engine blades (EB Airfoils) and resolving premature bearing failure (American Airlines). The bearing study, for example, saved American Airlines about $4 million per year by avoiding the repair/replacement of their APU bearings. The results from these and other studies provide our clients with knowledge they would not have otherwise been able to acquire, and allow for sound financial decisions to be made on fielded components.

Speed in Reliability

One of the fastest-changing industries is the medical device industry. Technology is racing forward, minimizing invasiveness is driving the miniaturization of implantable devices (especially in heart rhythm monitors), while manufacturing methods are still trying to catch-up. It seems that no other industry is as heavily scrutinized in terms of reliability and risk, at least in public perception. Medical implants are exposed to harsh internal environments, unpredictable stress and strain cycles, and oftentimes difficult installation procedures. Yet these devices are counted-on to reliably elevate our quality of life on a daily basis. The variability observed in material, vendor supply, and manufacturing all play a part in the reliability of the components that make up a medical device. Through industry-directed capability studies, the VLM technology pioneered by VEXTEC has effectively modeled these sources of variability, virtually tested millions of components, and delivered reliability answers to as many “what-if” scenarios as design and materials engineers saw fit to explore. The VLM approach reduces the number of blind alleys (ineffective combinations of material, design, and operational limits) that companies would have to travel down through the traditional design-build-test method, and focuses internal R&D resources on the combinations most likely to succeed in both manufacturing cost and operational reliability.

These three high-risk/high-reward sectors are not the only sectors that have benefited from VLM technology. Indeed, any company looking to speed-up their design phase, reduce their warranty reserves, or just wanting to make more-informed decisions on how their products can best be sourced, manufactured, and used would benefit from a conversation with us. The green flag has dropped…where are you in the field?

VEXTEC: Meeting the Need for Speed.