Numerical and Experimental Analysis of Titanium Sheet Forming for Medical Instrument Parts

Abstract

The paper analyses the forming of the surgical instrument handles made of Grade 2 titanium sheets. Sheet metal forming is a technology ensuring high strength and light weight of products. Replacing stainless steels with titanium further reduces instrument weight and additionally provides the required resistance to corrosive environments typical for surgeries. The low instrument weight is important to prevent fatigue of surgeons and allow them to maintain high operational accuracy during long term surgeries. The numerical analysis of the technological process was performed in order to adapt it to forming tool handles using titanium sheets instead of steel sheets. The numerical calculations were experimentally verified. It was found that, in the case of titanium handles, it is necessary to use a blank holder in the first forming operation to eliminate sheet wrinkling in the flange area. The shape and dimensional accuracy of the drawn part after trimming were high enough and the 4th forming operation became unnecessary. Moreover, the process modification included lubrication using rapeseed oil with the addition of boric acid, which effectively prevents the galling of titanium on the working surfaces of the steel tools and ensures a more uniform distribution of plastic strains in the drawn part.

Theory, Method and Practice of Metal Deformation Instability: A Review

“…Huang et al [ 171 ] analyzed the influence of geometric parameters on flange wrinkling based on the theoretical model of the flange forming limit of spinning thin-walled plates by numerical simulation and experimental research. Through comparative analysis, the FE model can predict wrinkling well and the simulation calculation results are basically consistent with experiments, as shown in Figure 15 a. Więckowski et al [ 184 ] optimized the forming process of flange edge wrinkling based on the stamping results of a two-stage mechanical handle of titanium sheet by FE simulation. In stamping processes, the use of an edge holder is imperative to prevent the flange edge from wrinkling.…”

“… Research results of deformation instability by finite element simulation and experimental methods: ( a ) flange forming of the spinning thin-walled plate [ 171 ]; ( b ) stamping forming of a titanium alloy mechanical handle [ 184 ]; ( c ) deep drawing of the AA1100 aluminum alloy [ 185 ]; ( d ) 304 steel plate shear wrinkling test [ 187 ]; ( e ) various buckling modes of tube compression instability [ 140 ]. …”

Tribological Aspects of Sheet Titanium Forming

“…What is more, they are resistant to most corrosive environments. Therefore, titanium sheets are of great interest in the biomedical and aerospace industries [ 9 , 10 , 11 , 12 ].…”

“…This wear mechanism occurs in the event of insufficient lubrication or when the lubricant film is broken due to high surface pressures of up to 100 MPa [ 27 ]. The buildup of the formed material on the tools is a technological problem associated with titanium sheet forming that is difficult to control [ 12 , 28 ].…”

Analysis of the Effectiveness of Technological Lubricants with the Addition of Boric Acid in Sheet Metal Forming

“…Until recently, steel products made of drawing or deep-drawing sheets dominated; however, with the growing tendency to reduce the weight of the structure and increase its corrosion resistance, other materials, such as stainless steel, aluminum, and titanium, as well as their alloys, were introduced. Forming these sheets requires intensive lubrication to facilitate the material flow and eliminate the phenomenon of sticking of the formed material to the tool’s working surfaces [ 5 , 6 , 7 , 8 , 9 ]. Lubricants based on mineral and synthetic oils, as well as water-based lubricants are mostly used.…”