UNCLASSIFIED New Technologies for Military Track Bushing Accelerated Testing and Evaluation Scott Gruenberg, Scott Bradley – Keweenaw Research Center, Michigan Technological University Stephen Gentner, David Ostberg - TARDEC 25 August 2014 UNCLASSIFIED: Distribution Statement A. Approved for public release UNCLASSIFIED Outline • Introduction • Background • Track Bushing Architecture – Single Pin – Double Pin • • • • • • MIL-DTL-11891G Appendix A Double Pin Field Test Full Pitch Bushing Test Machine Hall Effect Transducer Technology Path Forward Conclusions 25 August 2014 UNCLASSIFIED 2 UNCLASSIFIED Introduction • The life expectance of most track systems is governed by the life of the elastomeric components • Ground Pads normally fail first – However they are replaceable on most US track system (exc. T107/M88 Hercules) • Bushings are the usual cause of failure for most track systems - only replaceable at a depot level through rebuild • Backing Rubber has become a close second • On Vehicle testing is very expensive compared to lab tests 25 August 2014 UNCLASSIFIED 3 UNCLASSIFIED Background • Laboratory bushing testing developed by TARDEC decades ago • Part of MIL-DTL-11891(G) Appendix A • All Bushing compounds for all track systems (except the M1) need to be tested per this Specification • Originally developed to weed out sub-standard compounds, adhesives, manufacturing process, etc • Current test is for a single-pin track bushing and is not representative of the double-pin track used by current fleet of tracked vehicles 25 August 2014 UNCLASSIFIED 4 UNCLASSIFIED MIL-DTL-11891 Appendix A • T130 Long Bushings • Test simultaneously applies: – Radial Load of 0-5200 lbs at 64 ± 1 cpm – Torsional deflection of +15° to -15° at 256 ± 4 cpm • 75°F Ambient Temperature • 9 total bushings tested ‒ 8 lowest tests must average > 130,000 radial cycles ‒ None of the 9 can have less than 110,000 radial cycles ‒ .145 inch deflection defined as failure 25 August 2014 UNCLASSIFIED 5 UNCLASSIFIED MIL-DTL-11891 Appendix A • T130 Long Bushings 25 August 2014 • Test Machine UNCLASSIFIED 6 UNCLASSIFIED MIL-DTL-11891 Appendix A • T130 Long Bushings • Test Machine “Tensile” Side This side looks like it is brand new “Compressive” Side This side experiences the failure characterized by a crush zone. No torsional mode is seen. 25 August 2014 UNCLASSIFIED 7 UNCLASSIFIED Track Bushing Architecture • Single Pin Shoe Architecture 3/2 Lattice Backing Rubber Center Guide Octagonal Pin Grouser Ground Pad T 130 25 August 2014 UNCLASSIFIED 8 UNCLASSIFIED Track Bushing Architecture • Double Pin Shoe Architecture Backing Rubber Pin Ground Pad Grouser Center Guide T 150 T 161 End Connector 25 August 2014 UNCLASSIFIED 9 UNCLASSIFIED Double Pin Field Test • T158LL Bushings • YPG Test 0 miles ‒ Top new bushings 1000 miles ‒ Bottom worn bushings ‒ 250 mile increments between samples 2000 miles 25 August 2014 UNCLASSIFIED 10 UNCLASSIFIED Double Pin Field Test • T158LL Bushings • YPG Test ‒ Complete bushing failure in one track shoe. ‒ Radial Crush zone exists ‒ Torsional failure around pin circumference also seen in field test failure mode 25 August 2014 UNCLASSIFIED 11 UNCLASSIFIED Full Pitch Bushing Test Machine • Servo-hydraulic • Capable of testing small T130 test bores up full size T107 track shoes • Programmable • 30,000 lbs radial • ± 20° torsional 25 August 2014 UNCLASSIFIED 12 UNCLASSIFIED Full Pitch Bushing Test Machine • Measure and Records – – – – – – Radial Load Radial Displacement Torsional Angle Torsional Load Ambient Temp Right and Left Shoe Temp • Records – Radial and Torsional Cycle Count 25 August 2014 UNCLASSIFIED 13 UNCLASSIFIED Full Pitch Bushing Test Machine • Comparison of Edge Effect Crack Initiation T158LL Outside Doughnut (End Connector Side) Field Test Sample 25 August 2014 Lab Test Sample UNCLASSIFIED 14 UNCLASSIFIED Full Pitch Bushing Test Machine • Comparison of Failure Mode Field Test Sample Lab Test Sample 25 August 2014 UNCLASSIFIED 15 UNCLASSIFIED Full Pitch Bushing Test Machine • Comparison of Failure Mode Abraded Material Found Between Interior Bushings Field Test Sample 25 August 2014 Lab Test Sample UNCLASSIFIED 16 UNCLASSIFIED Hall Effect Transducer Technology Track Pitch Showing the Location of the Hall Effect Sensors 25 August 2014 UNCLASSIFIED 17 UNCLASSIFIED Hall Effect Transducer Technology Schematic of Pin and Track Pitch Showing the Location of the Magnets and Hall Effect Sensors Bushing 2 Bushing 6 Bushing 9 Bushing 13 HE1 HE3 HE3 HE1 7 5 3 1 8 HE2 6 HE4 4 HE4 2 HE2 Shoe2 Shoe1 HE1-Top HE2-Bot Inboard Side HE3-Top HE4-Bot HE1-Top HE2-Bot HE3-Top HE4-Bot Slave Master Outboard Side Top View 25 August 2014 UNCLASSIFIED 18 UNCLASSIFIED Hall Effect Transducer Technology Schematic of Pin and Track Pitch Showing the Location of the Magnets and Hall Effect Sensors Binocular Tube Track Block Track Pin HE 1 & 3 12 deg 7 Deg 7 Deg HE 2 & 4 Sensors Locations Wedge Bolt Locking Feature Orientation Magnets End View 25 August 2014 UNCLASSIFIED 19 UNCLASSIFIED Hall Effect Transducer Technology • T161 Instrumentation Transducer Location Computer 25 August 2014 Data Acquisition Boards UNCLASSIFIED 20 UNCLASSIFIED Hall Effect Transducer Technology • T161 Data From YPG – Southbound Laguna Paved Disp (inch) Sprocket Road Wheels Idler Sprocket Rollers Angle (deg) 25 August 2014 UNCLASSIFIED 21 UNCLASSIFIED Hall Effect Transducer Technology • T161 Data From YPG – Southbound Laguna Paved – Processed Data From Shoe in Sprocket – Shows Bending of Pin Length 25 August 2014 UNCLASSIFIED 22 UNCLASSIFIED Conclusions • Failure Mode of the Elastomer Bushing between the Single Pin MIL-DTL-11891 Test and the T158LL Field Failures do not Match • Full Pitch Test Machine Failure Mode does closely match the Field Failure Mode, however cycle count to mileage relationship has not been established • With the addition of the bushing displacement history from the Hall Effect Shoe incorporated into the Servohydraulic machine, closer correlation should be acheived 25 August 2014 UNCLASSIFIED 23 UNCLASSIFIED Path Forward • Characterize TRADOC OpMode Courses at YPG with T158LL Hall Effect Shoe • Process Data from Courses and Determine “Damaging Content” of the Load Case • Develop Load Profile Data File of “Damaging Content” to be Run on the New Full Pitch Bushing Test Machine • Correlate Failure Modes, Cycle to Mileage Relationship, Etc. 25 August 2014 UNCLASSIFIED 24 UNCLASSIFIED Questions ??? 25 August 2014 UNCLASSIFIED 25
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