Expanded titanium meshes based on deformational cutting
Introduction. One of the fields of use of deformational cutting (DC) is the manufacturing of meshes from thin sheet materials. The principle of its production consists in finning of both side of the thin sheet in mutually perpendicular directions with a depth of cut more than half the thickness of the sheet. A significant disadvantage of such meshes is the small effective screening area (the ratio of the total area of holes to the mesh area). One of the promising fields of use of meshes obtained by DC is hernioplasty as titanium implants for the treatment of hernias and reinforcement of bone and soft tissues. Implants require an effective screening area of more than 60 %, high compliance with plastic deformations, and a large specific surface area to hold the tissues sprouting into the implant. In the paper, the DC method is considered as an alternative to the existing titanium woven mesh implants, which have an extremely high cost. Work objective is to study the main relationships of obtaining preforms for meshes by the DC method, the features of mesh stretching, and to analyse the resulting shapes and sizes of mesh cells. In this paper the two-sided finning of thin-sheet blanks of pure titanium VT1-00 with a mismatched direction of finning of opposite sides of the sheet in the range of fins crossing angles of 1.3o-10o with varying the angle of workpiece undercutting and the fin pitch were studied. The analysis of the stretching mechanics for obtaining rhombic, hexagonal, and parallelogram forms of cells was carried out. Results and discussion. The range of fin pitch and crossing angles that ensure the stability of the DC and stretching stability is set. The shape of the cell depends on the length of the fins bonding obtained on opposite sides of the sheet. Increasing the bond length with by a decreasing the crossing angle leads to the transition of the cell shape from rhombic to hexagonal. A cell in the form of a parallelogram is typical for the fins of the opposite sides, which have differences in bending strength. Conclusions: the method of deformational cutting is an alternative of metal punching for through-cutting sheet metal and polymer for its subsequent stretching in order to obtain meshes. The meshes obtained on the basis of DC have a large surface area and an increased ability to plastic deformation. It is justified to obtain the rhombic, hexagonal, and parallelogram forms of mesh cells. The shape of the mesh cell is controlled by selecting the fins crossing angle and the pitch of the fins on opposite sides of the workpiece. The largest cell size and maximum effective screening area of the mesh are provided by meshes with hexagonal cells form at the fins crossing angles on opposite sides of the workpiece less than 3o.