By: Kirk Norasak C0-Authors: Jonathan Ball Eric Lucas Dr. John DesJardins University of Kentucky-Home Clemson University-REU Program

What do these pictures have in common?

Introduction The proton irradiation of materials can occur during space flight as a result of solar flares, and during cancer treatment therapies where proton beam therapy is prescribed. Due to cross-linking of the free-radicals in the polymer during irradiation, mechanical properties such as wear resistance are known to change with gamma irradiation, but the effect of proton irradiation is unknown.

Motivation To understand the affects of Proton irradiation on Hip Joint Replacement UHMWPE. Ex. Cancer patients, and Radiation Shielding. To determine if Space radiation doses will affect the material properties of the UHMWPE.

Continuation of Last Years Project Abstract Following irradiation, uniaxial tensile testing and thermal testing using Differential Scanning Calorimetery (DSC) and Dynamic Mechanical Analysis (DMA) were performed. Results show small but significant changes in several material properties between the Control (0 Gy) and 35 Gy samples, indicating that proton irradiation could have a detrimental effect on the long term performance of UHMWPE in both medical and space flight applications.

Objectives To characterize Proton irradiated UHMWPE for wear resistance using an industry standard pin-on-disk wear testing system. Program and improve the pin-on-disk wear testing system.

Experimental Irradiated the UHMWPE at doses from 0 Gy to 35 Gy. Machined the UHMWPE into pin test samples. Used the ASTM standard to clean the samples. Used a grinding wheel to polish the 316 L Stainless Steel pucks to a surface roughness (Ra value) of 70 nm. Used a Surface Profilometer to measure the surface roughness Ra value of the UHMWPE pins and 316 L Stainless steel pucks. Created a program in SolidWorks to calculate the pair of angles to make a circle on the Orthopod. Wear test UHMWPE using the Orhopod pin-on-disk system.

Machined Pins

ASTM Cleaning Pins

Grinding the Pucks

Surface Profilometer

Solidworks Circle Program

Orthopod Wear Testing

Orthopod Wear testing cont.

Orthopod Wear Testing Cont.

Results of Wear testing …..Pending Based on Gamma irradiation, the UHMWPE should have a increased wear resistance.

Future Work To continue working out the problems with the wear testing system. To figure out a way to grind the pucks without hand grinding. To work on a vacuum chamber that will not only subject the samples to low pressure, but low temperatures as well while being irradiated.

Acknowledgements I would like to give my thanks to the following people: Casper Wright-Walker Dr. Kennedy