D2: Orthopaedic Biomechanics

FLUID STRUCTURE INTERACTION STUDIES OF THERMAL SPRAY COATING ON A TITANIUM ALLOY

Rohit Chaudhari, Vrushabh Sawant, Davidson Jebaseelan, Sreekanth Dondapati

VIT University, Chennai Campus, India

Titanium alloys are used widely as biomaterials in implants and are coated by thermal spraying process because of its several advantages. Thermal Spray coating is carried out at high temperature, which results in generation of residual stresses, the resulting thermal stresses and temperature difference. Literature indicates that coating thickness is an important parameter for thermal stresses and impact stresses also contributes amount of residual stresses. So this study makes an attempt to quantify the relationship between them.

Methodology: Impact analysis and Transient thermal cases are solved simultaneously in this technique,  equivalent stresses are known to be residual stresses. Substrate material is taken as Ti-6Al-4V and coating material are taken as Yttria Stabilized Zirconia (YSZ), Hydroxyapatite and Mixture of both as Hydroxyapatite with 10%, 20% of YSZ. The computation of residual stresses by Fluid Structure Interaction(FSI) in done using LS-DYNA. Simulation is done for by varying the droplet sizes. Residual Stresses are computed for each case and compared among different coating Combinations.

Results: Residual stresses are maximum for YSZ for respective drop size whereas it is minimum for Pure HA. Mixture of HA with 10% YSZ shows residual stresses slightly greater than that of HA. Also, HA and 20% YSZ shows residual stresses than previous combination but less than pure YSZ. So, pure YSZ provides more rigidity than any other combinations and pure HA is quite brittle. Also, stresses generated are maximum at contact surface between substrate and sprayed material.

Conclusion: YSZ coating provides rigidity to substrate whereas HA is brittle. We can use mixture of both by varying quantity of both as per rigidity requirement. Hence quantity of YSZ can be varied as per rigidity requirement of an application.
 

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