METHOD OF MAKING SHAPE MEMORY ALLOY ARTICLES WITH IMPROVED FATIGUE PERFORMANCE
First Claim
1. A method of making a nitinol implantable medical stent with improved fatigue resistance comprising:
- a) providing an implantable medical stent having an original geometry at body temperature and comprised of shape-set nitinol metal exhibiting superelastic behavior at body temperature; and
b) pre-straining the shape-set nitinol metal by the application of a pre-straining bending force to an extent that selectively induces at least about 8.0% tensile strain at or near only a surface of at least one selected location on the nitinol implantable medical stent while maintaining a significant portion of a transverse cross-section of the at least one selected location within its superelastic material limit;
c) wherein following release of the pre-straining force, the implantable medical stent returns to, or near to, its original geometry at body temperature.
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Accused Products
Abstract
A method of making articles made of shape memory alloys having improved fatigue performance and to methods of treating articles formed from shape memory alloy materials by pre-straining the articles (or desired portions of the articles) in a controlled manner so that the resultant articles exhibit improved fatigue performance. The shape memory articles are preferably medical devices, more preferably implantable medical devices. They are most preferably devices of nitinol shape memory alloy, most particularly that is superelastic at normal body temperature. The pre-straining method of the present invention as performed on such articles includes the controlled introduction of non-recoverable tensile strains greater than about 0.20% at the surface of a desired portion of a shape memory alloy article. Controlled pre-straining operations are performed on the shape-set nitinol metal to achieve non-recoverable tensile strain greater than about 0.20% at or near the surface of selected regions in the nitinol metal article. The pre-straining operations result in a significant increase in fatigue life of the selectively treated regions and an overall improvement in the fatigue performance of the device.
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Citations
42 Claims
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1. A method of making a nitinol implantable medical stent with improved fatigue resistance comprising:
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a) providing an implantable medical stent having an original geometry at body temperature and comprised of shape-set nitinol metal exhibiting superelastic behavior at body temperature; and b) pre-straining the shape-set nitinol metal by the application of a pre-straining bending force to an extent that selectively induces at least about 8.0% tensile strain at or near only a surface of at least one selected location on the nitinol implantable medical stent while maintaining a significant portion of a transverse cross-section of the at least one selected location within its superelastic material limit; c) wherein following release of the pre-straining force, the implantable medical stent returns to, or near to, its original geometry at body temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of making a nitinol implantable medical filter device with improved-fatigue resistance comprising:
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a) providing an implantable medical filter device having an original geometry at body temperature and comprised of shape-set nitinol metal exhibiting superelastic behavior at body temperature; and b) pre-straining the shape-set nitinol metal by the application of a pre-straining bending force to an extent that selectively induces at least about 8.0% tensile strain at or near only a surface of at least one selected location on the nitinol implantable medical filter device while maintaining a significant portion of a transverse cross-section of the at least one selected location within its superelastic material limit; c) wherein following release of the pre-straining force, the implantable medical filter device returns to, or near to, its original geometry at body temperature. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification