Influence of Fine Shot Peening on Mechanical Properties of Orthopedic Plate and Screw

Abstract

As the bone fracture is now considered the second most serious disease in the world, a huge number of orthopedic devices for bone healing is being developed. However, there happened to be a number of incidents in which the orthopedic plates were broken inside the body due to inadequate strength. The present study aims to investigate the effects of Fine Shot Peening (FSP) conditions on performances of orthopedic plates and screws. In this research, there are 3 types of medical alloys to be studied namely SUS316 alloy, Ti6Al4V alloy and Ti6Al7Nb. In FSP process, 40 and 80 μm diameter of silica media was selected and utilized. FSP was carried out under the pressure of 0.5 MPa in Nitrogen atmosphere. The study shown that Ti6Al4V alloy with FSP media diameter of 80 μm resulted in 11% increment of bending strength and 40% increment of surface hardness. Regarding the orthopedic screw, the result shown that after applying FSP, the pull out strength from bone could be increased above 76%.

Investigation of surface hardness and roughness on formability of aluminum alloy sheet AA2024-T3 subjected to the shot peening process by silica shots

“…In addition, the shot peening parameters of pressure, distance between nozzle and material, nozzle angle, media type, and media size all contribute to the enhanced hardness and residual stress. [19][20][21]24]. This study investigated the influence of 100 µm silica media on AA2024-T3 sheet specimens with a thickness of 1.2 mm.…”

“…Therefore, the higher hardness could be interpreted by plastic deformation generated from dimples on the surface after shot peening [22,23]. The hardness is also increased with the impact energy from the collision of silica media on the surface specimen due to generating more dumpers on the surface [18][19][20]24]. The plastic deformation generated by silica media collisions could be successfully accumulated if the quantity of media was increased.…”

“…This is because every parameter plays a part in the change in material properties after testing. Several researchers have dedicated their work to investigating the effects of the shot peening process on the mechanical properties and modified surface treatment as described in [4,[14][15][16][17][18][19][20].…”

“…Shot peening can be induced to improve the surface properties because the process is powered by a collision and the energy generated by the impact between the particle media and the workpiece surface creates a very small dent [19,20], a plastic transformation. For the above reasons, residual stress is created on the surface by shot peening particles.…”

“…The effect of the dimple on the modified surface: the plastic deformation is generated by the impact energy, which the particle size produces the small dimple after shot peening treatment. Apparently, Ongtrakulkij and Khantachawana [19] studied the fine shot peening process (FSP) and found that it enhances mechanical and surface properties using various media sizes. The experimental results demonstrate that the surface hardness and bending strength are strongly and slightly affected by media size, respectively.…”