Quantitative, low cycle, crack initiation fatigue testing of fine wires and CENELEC standard pacing coil

Hildebrand, Laurie B.; Schmidt, John A.; Prentice, John K.; Stotts, Larry J.

doi:10.1002/(sici)1097-4636(1999)48:3<251::aid-jbm8>3.0.co;2-7

Cited by 11 publications

(30 citation statements)

References 6 publications

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“…As these fine wires are an integral part of biomedical devices, their independent reliability is also critical to the overall device reliability. The findings in this work that both elastic modulus and hardness are lower on the edges, as compared to the majority of the wire cross‐section, suggests a possible cause of the observed surface‐initiated fatigue 13. The measured hardness value could be used to screen future material as reported by Shaw 10.…”

Section: Resultsmentioning

confidence: 60%

“…The difference in fine‐wire material properties compared to bulk material properties and the variance in properties across the diameter of fine wires is important, for example, in modeling fatigue life6, 10, 13 and reliability. As these fine wires are an integral part of biomedical devices, their independent reliability is also critical to the overall device reliability.…”

Section: Resultsmentioning

confidence: 99%

“…9,11 Further, because many wire failures were identified as fatigue failures 12 fatigue tests of fine wires have also been successfully performed by numerous researchers. 6,10,13 Last, microindentation hardness tests were conducted on the cross-sections of copper wires (84-m diameter) used in telephone cables. The researchers found that the hardness measurement was effective in screening future materials as harder materials perform more satisfactorily in the field.…”

Section: Introductionmentioning

confidence: 99%

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Measuring mechanical properties of fine‐wire cross‐sections used in medical devices

Polycarpou

Johnson

2004

J Biomed Mater Res

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In this study, it was demonstrated that the nanoindentation technique can be used to measure the elastic modulus and hardness of fine-wire cross-sections with diameters ranging from 100-200 microm. Using miniature optics and a specially developed micrometer positioning system, measurements were successfully performed on the wire cross-sections with an accuracy of 1 microm. Homogeneous wire cross-sections, such as MP35N (high-strength nickel-cobalt alloy), composite wires such as MP35N with a silver core (MP35N/Ag-core), and platinum-clad tantalum (Pt-clad Ta) were studied. From the nanoindentation measurements, the elastic modulus and hardness at different positions and depths were calculated. It was found that both elastic modulus and hardness reached a constant value below the hardened surface, which resulted from mechanical polishing. Material properties obtained from the measurements were compared with the literature values of bulk materials as well as available results on fine wires. The data from the wire cross-sections, especially the uniform material samples, showed that both the elastic modulus and hardness were significantly lower near the outer 10-15 microm of the wire as compared to the rest of the wire, which is due to surface weakening during manufacturing. In addition, both modulus and hardness showed a small but consistent "sawtooth" variation across the diameter of the wires, excluding the outer 10-15 microm, that is postulated to be induced by the distribution of residual stress.

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Measuring mechanical properties of fine‐wire cross‐sections used in medical devices

Polycarpou

Johnson

2004

J Biomed Mater Res

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“…There is also the expectation that increasing specimen diameter decreases the stress gradient across the component and increases the volume of highly stressed material. Hildebrand et al 93 . said their results could have been due to the extremely small diameters of the wires tested, but without discussing mechanisms or microstructural influences.…”

Section: Experimental Characterizationmentioning

confidence: 98%

“…92 Surface defects on wires were observed to initiate fatigue failures. Hildebrand et al 93 tested single wires of cold drawn MP35N, which is commonly used in pacemakers. Wires were tested at R = −1 in a rotating wire loop machine.…”

Section: Fatigue In Wiresmentioning

confidence: 99%

A review of deformation and fatigue of metals at small size scales

Connolley

McHugh

Bruzzi

2005

Fatigue Fract Eng Mat Struct

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A B S T R A C T Mechanical devices are being introduced whose size scale is well below that of conventional mechanical test specimens. The smallest devices have sizes in the nanometer range, though a good proportion of structural devices are of the micrometer scale. Development of these products raises the question of how their mechanical behaviour and reliability may be predicted. Conventional macroscopic test data can be used, but these are obtained using specimens whose size is much larger than the devices themselves. There is a risk that performance predictions will be inaccurate, due to the existence of size effects. This paper covers small size scale testing in metallic specimens and devices, concentrating on freestanding specimens. To begin, some examples of micro-scale devices are given. Fabrication methods for small metallic devices are then briefly described. This is followed by a review of experimental observations of mechanical properties in various metallic materials at the micro-scale, highlighting the differences in results from different research groups and the gaps in our current knowledge. A section on computational and predictive modelling is included, in recognition of the role of modelling in device design and testing. Overall, the findings are that size effects are common, particularly in crystalline samples when the grain size is similar to one or more of the specimen dimensions. However, observations of size effects differ between studies and mechanical properties can vary widely, even for the same type of material. As a consequence, the relationships between specific device processing methods, specimen size and material properties must be adequately understood to ensure successful performance. N O M E N C L A T U R EA = geometric texture factor b = Burgers vector magnitude d = grain diameter D f = fatigue ductility parameter E = elastic modulus h = film, foil or specimen thickness k = 'locking parameter,' representing the relative hardening contribution of grain boundaries K = constant for power law creep k B = Boltzmann constant l = specimen length n = Creep exponent for power law creep N f = number of cycles to failure p = constant in the Basquin and Coffin-Manson relationships

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Mechanical Properties

Zoch

2013

Lecture Notes in Production Engineering

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Quantitative, low cycle, crack initiation fatigue testing of fine wires and CENELEC standard pacing coil

Cited by 11 publications

References 6 publications

Measuring mechanical properties of fine‐wire cross‐sections used in medical devices

Measuring mechanical properties of fine‐wire cross‐sections used in medical devices

A review of deformation and fatigue of metals at small size scales

Mechanical Properties

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