Core Overview Bending and Torsion Testing Snehal Shetye
Core Overview, Bending and Torsion Testing Snehal Shetye, Rob Mauck
Biomechanics Core – How we operate w Key players: • Rob Mauck (Director) – Snehal Shetye (Technical Director) – Ashley Rodriguez (Research Specialist) w https: //www. med. upenn. edu/pcmd/biomechanics. html w Submit project request form • In reality most PIs just directly contact Rob w Rob and Snehal sit down with client group to review proposed project, feasibility, approach. w Core user has a choice: • Self-service (you get trained and then test yourself) • Fee for service (Snehal and Ashley do the project for you) w After getting trained, you get access to Google Calendar for the particular equipment w Remember to cite us in your manuscript: • Grant number is P 30 AR 069619
Available Equipment w Instron 5542 (x 2) w Instron 5543 w Instron 5848 (x 2) w Instron Electro. Puls w Instron 8874 w Compression Micro. Tester w Freezing Stage Microtome w Polarizing Scope w Dynamic Cross-Polarized Light Imaging Setup w Gis. MO (cross-sectional area measurement device) w 3 D Printer w Software • MATLAB, Graph. Pad, SPSS, Abaqus, Trellis, Rhino 3 D, QCapture Pro w Milling Machine, Mini-Lathe, Vertical and Horizontal Bandsaws, Soldering and Electrical Equipment
Signing up and Etiquette w Signup on Google Calendar: • PCMD: <PI Last Name>: <your pennkey> – Note: Mc. Kay does get first dibs on equipment usage – Generally, you can only access equipment between the hours of 9 -5 pm ○ We can bend the rules for special circumstances – All hardware is shared among all users, including Mc. Kay, so usually allocate extra time for find your fixtures! w Format is important • We summarize quarterly usage and send invoices to PIs • Current PCMD Biomechanics core discount: 90% w If there is a scheduling conflict • Talk to Snehal or email the other person (pennkey is on calendar signup) and ask nicely w Accessing Snehal • Don’t hesitate to contact me anytime (I am at Mc. Kay from 6: 30 am to 4 pm) • Do remember I have two jobs: Soslowsky Lab and PCMD Biomechanics Core
3 -point Bending Load (F) 3 -point test
Shear and Moment Diagram Maximum moment at center point of beam
4 -point Bending Load 4 -point test
Shear and Moment Diagram Maximum moment spans distance between top actuators
Parameters Compression w Tension
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Stuff to Consider w w w Measure length of all your samples to determine proper support spacing 3 -point bending not recommended for fractured bone 4 -point bending is generally always recommended over 3 -point unless tissue is too small Torsion tests work well for fractured specimens Most ideal to test all samples on same day (day-to-day variation in test setup can influence results) Keep orientation constant for all samples! • Find a stable orientation such that bone does not rotate while being loaded
Example 4 -point bend setup
Failure modes in bone
When to use torsion tests? w 3 -pt or 4 -pt bend tests work well for intact specimens w Fractured samples • 3 -pt test will cause significant stress concentrations at the contact point – Usually that is where the fracture/callus is – Definitely not recommended • 4 -pt test loading points should span the healing site – Difficult to achieve on mouse femora/tibiae – Cannot control size and location of fracture callus • Torsion – Usually have unobstructed access to epiphysis – Only test that evaluates the entire free length of the bone – Does need 6 -dof fixation at the termini – Takes longer for prep and setup Load (F) Load
Torsion testing
Torsion Parameters w
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Torsion Testing
Questions?
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