Santanu Kumar Karmakar

Morphological and Kinematic Aspects of Human Spine â As Design Inputs for Developing Spinal Implants

In present time, pain and stiffness in the cervical region of spine has become quite a common phenomena owing to the urbanized lifestyle of people which involves watching television or working on desktop computer for long hours without changing sitting postures. This pain and stiffness most often results from degeneration which takes place in the spinal discs which are located in between the vertebrae. However, the concept of establishing spinal pain as being caused by Degenerative Disc Disease is still problematic and unclear. Result of analysis on an anatomically accurate and validated intact finite element model of the spine indicated that the strain energy density and stress (internal responses) in the bony vertebra adjacent to the degenerated disc increased. During last few decades, biomedical engineers have been closely working with physicians for developing effective biomechanical techniques for relieving such pain. With conventional methods of spinal arthrodesis, the adjacent-segment ROM was significantly increased but with cervical disc arthroplasty, it has been reported to be preserved at the preoperative level. Artificial inter-vertebral disc has been in use for almost two decades in mainly European and some Asian countries. However, insertion of artificial cervical disc also has many technical issues and is not without risk. Complications, including the need for resurgery, device migration and physiological bodily response to the wear debris of the implant have been reported. An in-depth knowledge about the morphological and kinematic aspects of the spine is very much essential for designing and developing any such instrumentation. These include: - (a) shape and dimensions of bone vertebrae, (b) type and estimated values of loads to which the implants will be subjected, (c) motion patterns of vertebrae at the location where degeneration has taken place. Lastly, the choice of available materials that can be safely used for developing such implants is to be finalized. After these design inputs are obtained, computational stress analysis for bone and implants and also tribological characterization is to be done for investigating the wear rate of different combinations of materials in contact – that are planned for use as implants.

Temperature rise and wear of sliding contact of alloy steels

The tribo-failure of machine elements under relative sliding velocities is greatly affected by frictional heating and resultant contact temperature rise. Nevertheless, the tribo-failure of automotive components is a combined effect of mechanical, thermal and chemical phenomena. Over the decades, there have been developed a number of different mathematical models for predicting surface temperature rise at sliding contact under different geometries of asperity contacts and operating conditions. The experimental investigation is still relevant today to find out the surface temperature rise at sliding contact along with the outcomes of friction and wear under various operating conditions for real time applications. The present work aims at finding average surface temperature rise at different sliding velocities, normal loads with different surface roughness experimentally. It also involves to prepare two different rough surfaces of alloy steels and to study their influences in the process of generating contac...