Evaluation of Friction and Wear Properties of Polymeric Materials
for Use in Total Joint Prostheses using Micro-Tribometer mod. UMT-2
ASTM F732-82 (reapproved
1991)
Summary of Test Method:
This
test method is used to evaluate the friction and wear properties of
combinations of materials that are being considered for use as the bearing
surfaces of human total joint replacement prostheses. The test method utilizes
a flat-ended polymer cylinder upper specimen and a flat stainless steel lower counterface that is immersed in bovine blood serum. The
load is applied downward onto the cylinder specimen. The flat lower specimen
slides linearly, back and forth under the cylinder specimen. The test
parameters are listed below.
Test Parameters
|
Lubricant |
Temperature |
Applied Load |
Stroke Length |
Osc.
Frequency |
Duration |
|
Bovine blood serum |
37º C |
225 N |
1 inch |
1.0 Hz |
70 hrs. |
Polymer
Specimen: length 13 mm, diameter 9 mm.
Counterface surface
finish: 0.026 to 0.05 µm.
Wear
is reported as volume loss of the polymeric specimen as a function of sliding
distance. Volume loss is determined by dividing the measured weight loss by the
density of the polymer.
The UMT allows for monitoring during the
test the actual dynamic normal load, friction force and friction coefficient, and
depth of wear. Optionally, it can measure additional parameters of contact
acoustic emission and temperature.
UMT
Hardware Configuration:
·
4”
Mounting Block – PN M30C116
·
Model
DFH-50 Dual Friction/Load Sensor
-
range
5 N to 500 N
·
Suspension
– PN AM30C110F-4
·
Pin
Holder
-
for sensors mod. DFH
·
Polymer
Specimen Pin
·
Counterface Material
·
Plastic
Slurry Tray
·
Bovine
Blood Serum
·
Lower
linear
Manually adjust for 1”
travel
-
mod. RHH
·
Temperature
Chamber - PN AM30D81B
·
Optional
Additional Sensors
- mod. TMR-150
Temperature Measurement & Recording
-
mod. RTD Temperature Sensor
UMT Software Test
Setup:
UMT Options File:
Load the options file which contains settings
for the Linear Reciprocating Motion drive and the 500 N force/load sensor.
Test Sequence:
The Test Sequence should consist of 2 sheets.
Sheet 1 is for settling time for the carriage to
establish the initial normal load.
Carriage - applies a 225 N Constant Force for a Duration of 10 sec.
Spindle – Velocity is 0 revs/min.
Slider
–
is idle.
Sheet 2 is for the actual sliding test.
Carriage - applies a 225 N Constant Force for a Duration
of 70 hours.
Spindle
– Velocity is 60 revs/min, Move-Continuous, and Direction-
Clockwise
Slider
–
is idle.
Data Collection:
The following should be checked under DataFile:
Fx – Friction Force
Fz –
Normal Force
T – Time
Z1 –
Carriage Position (Used to determine Wear Depth)
Te
input – Temperature (optional)
Report:
Use
the Viewer program to plot test results.
Select
the parameters to be displayed by checking
the appropriate box under Parameters on the
Viewer screen.
For
viewing COF plots of reciprocating tests check the Fz
box, click on the Symmetry button, click on the Peak Detect button, and then
check the COF box.
Multiple
test results can be viewed at the same time as in the example below.
