Engineering Applications and Devices: Session 3
Program Organizers: Alan Pelton, G.RAU Inc.
Thursday 9:00 AM
July 13, 2017
Room: Gold Coast
Location: Hyatt Regency Chicago
Session Chair: Huilong Hou, University of Maryland, College Park
Features Cavitation Resistance of Multifunctional Coatings from Materials with a Shape Memory Effect: Dmitriy Dmitrenko1; Blednova Zhesfina1; Balaev Etibar1; 1Kuban state technological University
It is established on the basis of the analysis of structural components of criterion of cavitation resistance of multifunctional coatings from materials with a shape memory effect (SME) that the major factors influencing the cavitation resistant coatings are: tendency to straining hardening, reversible deformation, the adhesion strength, microhardness, uniformity of structure and roughness’s of a surface. Weights coefficients for assessment of influence of each of the specified components are defined. The mechanism of enhancing of cavitation resistance of coatings from materials with SME based on structural and phase transformations in the coating material, subject to local cavitation effects. Tests on cavitation resistance of multilayer coatings of materials with SME performed according to standard methods of analysis of structural-phase state and functional-mechanical properties that they are allowed to recommend as a cavitation-resistant. Architecture layered surface composition is proposed, which provides increase of durability of products in the conditions of cavitation-abrasive environment.
Role of Precipitates on the Formation of Recovery Stresses in FeMnSi based Shape Memory Alloys for Pre-stressing Applications: Ariyan Arabi-Hashemi1; Christian Leinenbach1; 1Empa - Swiss Federal Laboratories for Materials Science and Technology
In the recent years, FeMnSi based shape memory alloys (SMA) have attracted significant interest due to their potential for engineering applications such as seismic damping or element reinforcing. The present contribution investigates the role of precipitates, here exemplarily VC, on the recovery stress formation in restrained samples of the Fe–17Mn–5Si–10Cr–4Ni–1(V,C) (ma.-%) SMA. We show that the recoverable strain and the recovery stress are affected in different ways by the precipitate size and that the latter one has to be chosen carefully in order to optimize the recovery stress. By tuning the shape memory effect and matrix strength through changing the precipitate size in different heat treatments we achieved a recovery stress of more than 550 MPa using a comparably low heating temperature of 160°C which allows using the alloy for pre-stressing elements in concrete structures.
The Use of Generation III Nitinol for Fatigue-Critical Medical Devices: Alan Pelton1; S.M. Pelton1; A. Sorg1; T. Jörn1; J. Ulmer2; D. Niedermaier2; M.R. Mitchell3; P. Saffari4; 1G.RAU Inc.; 2EuroFlex GmbH Kaiser-Friedrich-Straße; 3Mechanics and Materials Consulting, LLC; 4Engage Medical Device Services, Inc.
During the past decade, manufacturers have accelerated the pace to provide "ultra-clean" Nitinol to the medical device industry. The goal of these metallurgical and processing improvements is to improve in vivo device fatigue behavior. Robertson, et al. (2015) showed that the fatigue strain limit of Generation II Nitinol (40µm inclusion length, area fraction <0.5%) is significantly greater than Generation I Nitinol (100µm inclusion length, area fraction >1.5%). These results afford great insight into the performance of even higher purity microstructures required for fatigue-critical neurovascular and structural heart implants. Generation III Nitinol is manufactured from a unique VAR/EBR process with a resultant <7µm inclusion length and <0.5% area fraction. Comparative fatigue testing with "diamond" coupons demonstrates a 100% improvement in the fatigue strain limit of Generation III compared with Generation II Nitinol. These results will be discussed in terms of finite element models, metallography and fracture analysis.
10:00 AM Break