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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 1 6

Fig. 6 — Testing of LRM full guidewire 0.014-in. diameter in 2D plate model. Hypotube joint (a) and LRM solid-state weld joint (b).

Adv. Manuf. Technol. , Vol 61, p 205-212, 2012. 2. P. Vondrous, L. Kolarik ,and M. Kolarikova, Plasma Arc Welding of NiTi and 304 Steel, Annals of & Proceedings of DAAAM Intl. , Vol 23:1, p 2304-1382, 2012. 3. H.M. Li, et al., Laser Welding of TiNi Shape Memory Alloy and Stainless Steel Using Ni Interlayer, Materials & Design, Vol 39, p 285-293, 2012. 4. S.D. Meshram, T. Mohandas, and G.M. Reddy, Friction Welding of Dissimilar Pure Metals, J. Mat. Proc. Tech, Vol 184, p 330-337, 2007. 5. N. Kahraman, B. Gulenc, and F. Find- ik, Joining of Titanium/Stainless Steel by Explosive Welding and Effect on Interface, J. Mat. Processing Technol., Vol 169, p 127-133, 2005. 6. J. Tsujino, et al., Ultrasonic Butt Welding of Aluminum, Aluminum Alloy and Stainless Steel Plate Specimens, Ultrasonics, Vol 40, p 371-374, 2002. 7. A. Rajasekhar, Effect of Welding Pro- cess and Post Weld Heat Treatments on Microstructure and Mechanical Prop- erties of AISI 431 Martensitic Stainless Steel, Int. J. Tech. Research and Appl., Vol 3, p 280-285, 2015.

TABLE 1—TENSILE DATA SUMMARY FOR 0.014-IN. DIAMETER SOLID-STATE WELDED GUIDEWIRES

% of NiTi break load*

Break load (Std. dev.), lb

Sample ID Sample quantity

Failure location

LRM seamless joint

5

28.6 (0.72)

89

Joint interface

NiTi wire attached to NiTi hypotube

Hypotube joint

5

5.1 (0.35)

16

*NiTi wire tensile strength for 0.014-in. NiTi wire was roughly 32 lb.

on the Nitinol wire, typical of a ductile fracture mode, Fig. 5(d). Figure 6 shows the two wires in simulated performance testing using a 2D plate model, which features several channels simulating tortuous vessels. The wire is inserted through a guide catheter (Vistabrite tip JL4 Fr manu- factured by Cordis) into a predeter- mined pathway to assess wire tracking and torque response. The guidewire with the LRM solid-state weld tracked much further into the pathway than the guidewire hypotube joint. Red arrows indicate the distal-most position that Nitinol wire was joined to stainless steel wire via a proprietary solid-state process without the use of filler materi- al. This process proves to be a superior method to create joints between dis- similar metals such as stainless steel and Nitinol. It offers significant perfor- mance enhancements for guidewire each wire navigated. CONCLUSIONS

applications by merging a high-stiffness stainless steel body for pushability with a softer, more kink resistant Nitinol for the distal section. The solid-state weld process yields a fine-grained HAZ and defect-free interface, resulting in excel- lent bend and tensile properties at the joint. Initial performance testing using a 2D plate model simulating vascula- ture indicates that the LRM solid-state weld offers superior performance in clinical application compared to one of the leading bimetal guidewires on the market. ~AM&P For more information: Arne Rim- mereide is manager of R&D, Lake Re- gion Medical, 340 Lake Hazeltine Dr., Chaska, MN 55318, 952.641.8383, arne. rimmereide@lakeregionmedical.com, www.lakeregionmedical.com. References 1. J. Pouquet, et al., Dissimilar Laser Welding of NiTi to Stainless Steel, Int. J.