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An important input to FEA is material characterization and limit information. In our laboratory we use a Bose 3230 test system for achieving test speeds up to 200Hz. Depending on the project, we may test complete devices, sub-components, coupon samples and/or simple material characterization samples. Many times, we will test more than one [...] For medical devices, rarely does “one size fit all”. The human body is extremely variable and patient populations, especially those with disease present a wide range of differences that the medical device design engineer must consider. Identifying the worst case size for a product family is an important part of the validation process for implantable [...] Finite Element Analysis (FEA) can produce an enormous amount of data as output. Solution variables such as stress and strain are computed throughout an analysis for each increment and at each location within the model. These solution variables are computed at what are called “integration points”. These locations ARE NOT the same as the nodes [...] A typical process for making stents is electropolishing to remove material and processing defects and to impart a smooth finish with rounded corners. It is well known that a polished part will have superior fatigue resistance, but how much does the rounding of edges affect the stress and strain in the stent when loaded? We studied [...] Nitinol is a unique metallic alloy that is ideally suited to use in medical devices. It has excellent biocompatibility and most of all it has the ability to undergo significant recoverable deformations. This allows devices made with Nitinol to be reduced to catheter dimensions and expanded at the implant site. Much work has been done to [...] With the growing use of Nitinol in medical implants, there is a need for improved characterization of the material behavior of Nitinol and methodologies for better product design and engineering. While it is a good starting point, the typical approach of employing the force-deformation response from uniaxial tension tests for input and validation of material [...] Finite Element Analysis (FEA) is routinely used to perform fatigue analyses of cardiovascular stents. For the case of balloon expandable stents, this means modeling the crimping of the stent onto the delivery balloon, the expansion and recoil of the stent as would occur during deployment and finally the simulation of fatigue deformations. Fatigue deformations typically [...] There is no excerpt because this is a protected post. Medical device manufacturers are increasingly required to demonstrate that their products are safe and effective when subjected to complex loading conditions in the human body such as when the device may experience combinations of bending, twisting and compression. Physical test methods are difficult to implement in such cases, can only consider a finite number of [...] You can download my presentation at the 2007 Cleveland Clinic Stent Summit on carotid artery stent fractures from an engineers perspective which discusses combined loading conditions, fatigue, material limits and other factors. |
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