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 spaceflight as a result of solar flares, and during cancertreatment therapies where proton beam therapy isprescribed.
Due to cross-linking of the free-radicals in the polymerduring irradiation, mechanical properties such as wearresistance are known to change with gamma irradiation,but the effect of proton irradiation is unknown.
Motivation
To understand the affects of Proton irradiation on HipJoint Replacement UHMWPE.
Ex. Cancer patients, and Radiation Shielding.
To determine if Space radiation doses will affect thematerial properties of the UHMWPE.
Continuation of Last Years Project
Abstract
Following irradiation, uniaxial tensile testing andthermal testing using Differential ScanningCalorimetery (DSC) and Dynamic Mechanical Analysis(DMA) were performed. Results show small butsignificant changes in several material propertiesbetween the Control (0 Gy) and 35 Gy samples,indicating that proton irradiation could have adetrimental effect on the long term performance ofUHMWPE in both medical and space flightapplications.
Objectives
To characterize Proton irradiated UHMWPE for wearresistance using an industry standard pin-on-disk weartesting system.
Program and improve the pin-on-disk wear testingsystem.
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 asurface roughness (Ra value) of 70 nm.
Used a Surface Profilometer to measure the surface roughness Ra valueof the UHMWPE pins and 316 L Stainless steel pucks.
Created a program in SolidWorks to calculate the pair of angles tomake 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 shouldhave a increased wear resistance.
Future Work
To continue working out the problems with the weartesting system.
To figure out a way to grind the pucks without handgrinding.
To work on a vacuum chamber that will not onlysubject the samples to low pressure, but lowtemperatures as well while being irradiated.
Acknowledgements
I would like to give my thanks to the following people:
Casper Wright-Walker
Dr. Kennedy