Date of Graduation

12-2025

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Degree Level

Graduate

Department

Mechanical Engineering

Advisor/Mentor

Zou, Min

Committee Member

Millett, Paul

Second Committee Member

Meng, Xiangbo

Keywords

Friction; Surface Engineering; Tribology

Abstract

Total hip replacement is a highly successful surgical intervention that restores mobility and improves quality of life for patients with severe joint degeneration. However, the long-term durability of artificial hip joints remains limited by tribological challenges, particularly wear-related failures that can lead to osteolysis and revision surgeries. In metal-on-polyethylene bearing systems, reducing friction and wear at the interface between cobalt–chromium–molybdenum (CCM) femoral heads and ultra-high molecular weight polyethylene (UHMWPE) liners is critical to extending implant lifespan. Laser surface texturing has emerged as a promising technique to improve tribological performance by introducing micro-dimples that enhance lubricant retention and reduce asperity contact. While previous research has largely focused on large dimples, small dimples (~5 µm) remain underexplored despite their potential advantages, including higher coverage, improved lubrication, and biomimicry of cartilage microstructures. This thesis investigates the tribological performance of CCM surfaces textured with small, laser-ablated dimples, focusing on how variations in aspect ratio and surface density influence friction and wear behavior. Pin-on-disc tribological testing against UHMWPE under simulated hip joint lubrication conditions revealed that lower aspect ratio and lower density textures significantly reduced friction and wear. In contrast, aggressive textures with higher aspect ratios introduced surface protrusions that negatively affected wear performance. These findings highlight the importance of optimizing texture geometry in biomedical implants. By demonstrating that appropriately designed small dimples can outperform untextured surfaces and larger dimples reported in the literature, this study provides valuable insights into surface texture design strategies aimed at enhancing lubrication, reducing wear, and improving the long-term performance of next-generation artificial hip joints.

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