Mind the Gap

By Michael
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Whereas virtual designs are 100% perfect – as designed, with perfect circles, perfect corners and razor-sharp edges – the real world is not.

Any manufactured part which is assembled from pieces and which consists of various materials, comes under the influence of Mr. Thermodynamics and his physical gang members Mr. Temperature and Ms. Pressure. With all those parameters and forces applied during the fabrication process the resulting product is at best close, but never fully identical with the originally designed dimensions.

Important to note: with every percentage we want to minimize these dimensional deviations, represented by gaps and misalignment in assemblies, we increase manufacturing cost due to additional investment in equipment, better materials or just more effort to optimize the machinery.

Depending on the product this will be necessary and justified: if we manufacture a submarine boat we need to take care to have the outer skin absolutely water-tight under all operating conditions and with a safety margin. Here very little deviation is allowed in order to not jeopardize security. No compromises. Building a submarine or alike is complex and expensive.

yellow-submarine-256x256

For less demanding situations the control of dimensions is less critical.

A bicycle for instance needs to meet a set of functional specifications, i.e. it needs to be durable and parts should move without friction. However the physical constraints on the product in operation are less severe than in the submarine case, which means that certain dimensional deviations of assembled parts can be accepted. This results in manufacturing process which is less demanding.

Another view is on aesthetics: we want a car to look good in every aspect. The gap between the hood and the chassis for example needs to be straight, close (but not too close) and overall needs to suite the expert’s eye. Intuitive buying decisions may depend on this feature. I am not joking. So this is important too!

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Courtesy of DCS Inc.

I guess I sufficiently hit on this point: when we manufacture a virtual model we have to expect dimensional deviations. We therefore need to understand, control and design for those deviations – preferentially before it is found out from the first product which comes off the assembly line.

dcs

This was the introduction to present the domain of competence of DCS Inc. or Dimensional Control Systems Inc., a 125+ employees company headquartered in Troy, Michigan USA, with local representations worldwide. DCS is also a Gold software partner of Dassault Systèmes and they have captured their knowhow of dimensional engineering and process capabilities into a suite of tolerance analysis software applications (3DCS CAA V5 Based) which helps designers and engineers to anticipate real life conditions put on ideal designs. Good news is: 3DCS software is fully integrated in the DS 3D PLM solution and respectively the brands CATIA, DELMIA, ENOVIA and SIMULIA.

What DCS does is clearly heavy duty engineering simulation with a lot of differential equations involved. Don’t try this alone at home. If you are a manufacturer who needs to control dimensional tolerances as a function of production cost, a good advice is to let DCS assist you.

One prominent project where DCS is already part of the competence team is ITER, the nuclear fusion reactor to be built in Cadarache in the South of France. ITER is a highly challenging endeavor with a long list of technical unknowns. With the objective to master fusion technology as an unlimited source of energy for man. DCS’ job is to watch over the design of the reactor vessel built to sustain the physics involved, boost the understanding of dimension tolerancing and gain a certain level of trust for predicting results. (For more general information about ITER, and some 3D virtual fly throughs, go here.)

Ladies and gentlemen, mind the gap.

To get in touch with DCS, find their information file here or directly on the PLM MarketPlace where 3DCS products are referenced. John Sienskowski is your contact to call for help.

Soon more from the beautiful world of applied engineering.

Best,
Michael

P.S. any questions or ideas for future posts in this series – let me know

How Do You Mend a Broken Heart?

By Tim
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Courtesy Sunshine Heart

Courtesy Sunshine Heart

While I know that I should eat well, exercise regularly, not smoke, and have regular checkups – I don’t always do these healthy things, which puts me at greater risk for developing a heart condition. 

Apparently, I am not alone. I just read some staggering statistics on Heart Failure (HF) at the US Center for Disease Control and Prevention’s website. Five million people in the United States suffer from HF and 500,000 more are expected to join their ranks each year.  According to the American Heart Association (AHA), the 2006 costs associated with HF in the U.S. was 29.6 billion dollars.

Thankfully, there are many bioengineering researchers in the world who are using realistic simulation technology to study the heart and associated medical devices in amazing levels of detail.

Click to view animation of Stent analysis using Abaqus FEA

Click to view animation of Stent analysis using Abaqus FEA

Performing realistic 3D simulation of the human heart and medical devices requires being able to model human tissue, blood flow, nonlinear structures, and complex contact between the devices and the heart. SIMULIA has developed robust finite element analysis (FEA) and multiphysics technology within the Abaqus Unified FEA product suite.  This technology is being used by bioengineering researchers to simulate realistic physical behavior of the medical devices interacting with the heart, arteries, and blood vessels.

One of those researchers is Dr. William Peters, a cardiothoracic surgeon and and founder of Sunshine Heart in New Zealand. His patented C-Pulse has recently been accepted for human trials in the U.S. The device consists of a cuff that wraps around the aorta that inflates and deflates a membrane against the vessel’s external walls. This process makes the aorta pulsate in time with the heart, augmenting blood flow through the circulatory system and reducing the strain on the entire heart. Check out the complete case study here.

Milton DeHerrera Ph.D of Edwards Lifesciences  is another innovative bioengineer. At the 2009 SIMULIA Customer Conference, he presented a paper on the “Numerical Study of Metal Fatigue in a Superelastic Anchoring Stent Embedded in a Hyperelastic Tube”, coauthored by Wei Sun, Ph.D from the Department of Mechanical Engineering at the University of Connecticut. Their research is intended to  improve the virtual representation of human tissue and medical device interaction.

Adding to the complexity of developing medical devices is that ‘one-size does not always fit-all’. Dr.   Ken Perry has a cool medical device simulation blog site detailing his use of FEA and associated validation processes. Check out a couple of his recent posts – Identifying Worst Case Device Sizes and FEA and the FDA .

These dedicated researchers are helping to develop amazingly innovative and effective treatments that are truly capable of ‘mending broken hearts’. Now that I am aware of the alarming heart failure statistics, I plan to take a little more initiative in trying to keep my heart healthy.

Pass the fruit, veggies, and oats…will you join me?

Take care
Tim

PS: This is part 2 of my ongoing series on how realistic simulation is being used to improve medical devices and enhance the quality of our lives, stay tuned.

Tiger Woods and my dad have something in common

By Tim
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No, it’s not below-par rounds of golf. My dad’s sport was basketball. But both golf and b-ball contributed to their common link – bad knees.  Tiger’s knee injury ended his 2008 season prematurely. Tiger had arthroscopic surgery and physical therapy and is winning at his sport once again.

My dad also had arthroscopic surgery. It helped him for a while. But in his late 50’s he underwent complete knee replacement surgery on his right knee. A few years later, he had his left knee replaced. Then about 10 years after that, he underwent a second replacement on his right knee. Though he never got back on the basketball court, the implants definitely helped him maintain his quality of life by keeping him mobile and eliminating his knee pain.

Both Tiger and my dad have been helped thanks to ongoing research of knee mechanics and orthopedic implants. Researchers at Scripps Clinic have recently published a study on patients with knee replacements.

 At the time of surgery, they implanted tiny computer chips in the patient’s knees. These chips sent data to receivers that recorded the stresses on the knee joint during various activities. They then used the data, in combination with Abaqus FEA software from SIMULIA, to make increasingly complex 3D computer models of human knees. With these realistic models they can now perform accurate virtual tests on a variety of potential knee replacement parts and surgical techniques. Check out the case study on Scripp’s research published at Design World Magazine’s website.

Other researchers, such as the team at the University of Aberdeen  in the UK, have also published a study on using realistic simulation to understand the effect of ACL reconstructive surgery. Check out their paper published at the 2009 SIMULIA Customer Conference.

Engineers at Zimmer  and the University of Wisconsin-Madison collaborated on research published at the 2008 Abaqus Users’ Conference on material modeling of a virtual biomechanical knee.

Knee biomechanics and orthopedic implants is just one area of bioengineering research that is being performed with Abaqus. In the coming weeks, I will report on many other engineering groups who are creating virtual 3D models and realistic simulations of the human body to develop innovative products and medical treatments that are significantly enhancing the quality and longevity of our lives.

Enjoy,

Tim

p.s.

Have you had knee surgery, a knee replacement, or other type of implant? Feel free to leave a comment about your experience or your view of using realistic simulation for bioengineering research.



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