ARL Penn State Ausform Gear Finishing for Increased Strength and Durability Nagesh Sonti Drivetrain Technology Center ARL Penn State

ARL Penn State Requirements for Aircraft Gearing High profile accuracy and surface finish to minimize vibration and fatigue loading High surface strength and gradient to maximize tooth fracture strength and surface fatigue resistance High toughness of core material to maximize impact strength

ARL Penn State Steps eliminated by Ausform Finishing Blank Machine and Hob Gear Conventional Rotorcraft Gear Manufacture Heat Treat Carburize, harden, Cryogenic treat, temper Grind Gear Nital Etch Inspect HIGH procurement cost Hone Shot Peen

ARL Penn State What is Ausforming? Process Modified steel heat treatment process Plastic deformation of metastable austenite Benefits 30-50% increase in strength Gear finishing time of less than a minute, as compared to over 40 minutes for grinding Over 60% reduction in manufacturing time due to elimination of operations Cost-effective integrated in-line manufacturing operation

ARL Penn State RCF Life of Ausformed Bars

ARL Penn State Endurance of Ausformed Bearings

ARL Penn State BULK AUSFORMING 30 to 50% increase in strength without loss in ductility Over 500% improvement in surface fatigue (L 10 ) life of ausformed balls, rollers and bearings as compared to standard heat treatment Aus-forged spur gears performed significantly better than machined gears Limitations –Requires large forging capability –Requires subsequent finishing operations –Applicable to through hardening steels only AUSFORM FINISHING Penn State technique applies ausforming to localized surface layers for precision finishing –Does not require large forging capability –Applicable to carburizing grade gear steels as well as through hardening steels –Cost-effective integrated inline manufacturing operation Rationale for Surface Ausform Finishing

ARL Penn State Developed double die ausforming machine Demonstrated ausform finishing of V-22 planetary gears Achieve desired accuracy by using high precision roll finishing Demonstrated potential for enhanced gear strength by inducing ausforming effects in surface layers Demonstrated potential for substantial cost reduction by eliminating expensive and labor-intensive operations Prior ONR Mantech Project

ARL Penn State Objective –Increase the power density and reduce the lifecycle cost of rotorcraft gearing by implementing ausform gear finishing Approach –Develop process models to facilitate tooling and process optimization –Qualify ausform finishing process for DoD components –Demonstrate and validate gear performance –Establish commercial suppliers of ausforming equipment ONR/Boeing DUS&T Project

ARL Penn State Objective Qualify ausform finishing process as an acceptable DoD process, as an alternative to hard gear grinding Program Tasks Process modeling to develop tooling, and evaluate variability and sensitivity to tooling/process changes Verify performance enhancement on 9310 and Pyrowear 53 steel test rig gears Develop tooling/process for Apache sun/planet gears, including root/fillet ausform finishing Compare bending fatigue strength of ausform finished and conventionally finished Apache sun/planet gears Conduct transmission tests Deliverables Analytical capability to predict tooling geometry Comparative strength and durability data for test rig gears and Apache sun/planet gears Process specifications for Apache sun/planet gears TeamBoeing Mesa, Honeywell, Purdy, Penn State, Duration January 2000 to July 2003 ONR / Boeing DUS&T Project

ARL Penn State Phase 1:Ausform test rig gears - active profile only –Process modeling –Tooling and test gears manufacture –Optimize tooling and process –Gear performance testing Phase 2:Ausform test rig gears - active profile and root/fillet –Process modeling –Tooling and test gears manufacture –Optimize tooling and process –Gear performance testing Phase 3:Ausform Apache planet/sun gears –Tooling and test gears manufacture –Optimize tooling and process –Process test gears Phase 4:Testing of Apache planet/sun gears –Bending fatigue testing at ARL –Transmission rig testing at Boeing ONR / Boeing DUS&T Project - Phases

ARL Penn State Process Modeling

ARL Penn State Die development requires process modeling to account for the effects of thermal history, metallurgical transformations, and deformation gradients Ausform Finishing Process Induction Heat Pre-form Gear Final Quench Finished Gear Roll Finish Rolling Die Marquench Finished gear Accuracy of ± ” (4 µm) for precision rotorcraft gears

ARL Penn State Conventional Tooling Development Start Ausform Finish Gears Meet Specs Finish Modify Die Tooth Form Grind Dies Guess Die Tooth Form Heat Treat Dies Hob Gears Heat Treat Gears Hob Dies Inspect Gears Does not Meet Specs Die development can take many regrind iterations

ARL Penn State Process Modeling to Develop Tooling Start Ausform Finish Gears Meet Specs Finish Modify Die Tooth Form Grind Dies Predict Die Tooth Form Guess Die Tooth Form Heat Treat Dies Hob Gears Heat Treat Gears Hob Dies Inspect Gears Does not Meet Specs Model Ausform Process Goal is to reduce hardware regrind iterations to 2-3

ARL Penn State Induction Heating and Marquenching Process Model Integrated Model of Multi-tooth Ausforming Process Roll Finishing Process Model Ausform Finishing Process Models

ARL Penn State Ausforming model methodology development completed and validated Achieved program objective by significantly reducing number of hardware iterations Ausforming models successfully applied to development of various test gears Ausforming models extended to analyze flank and root/fillet finishing Model method has been applied to develop die design for Boeing planet gear Process Models - Summary

ARL Penn State Process Results Ausforming Process

ARL Penn State Microhardness Comparison

ARL Penn State Induction Heating Pattern on Planet Gear

ARL Penn State Hobbed and shaved24-30 µin Ra Ground12-16 µin Ra Honed8-10 µin Ra Ausform finished4-6 µin Ra Surface Finish Comparison

ARL Penn State Ausformed Gear Tooth Profile Charts Before AusformingAfter Ausforming

ARL Penn State Ausformed Gear Lead Charts Before AusformingAfter Ausforming

ARL Penn State Ausformed Gear Index Charts Before Ausforming Total Index Variation Left Flank: ” Right Flank: ” After Ausforming Total Index Variation Left Flank: ” Right Flank: ”

ARL Penn State Root Ausform Finishing of Gears Goal Apply ausforming to root/fillet region to enhance bending strength Status Root ausforming of spur and helical gears developed

ARL Penn State Established ausforming tooling and processing conditions for processing the test gears including Boeing planet gears Achieved required metallurgical design specifications for Pyrowear 53 and AISI 9310 steel test gears Achieved required surface finish and gear accuracy specifications for the test gears and Boeing planet gears Gear Processing Summary

ARL Penn State Gear Bending and Surface Durability Testing Performance Testing

ARL Penn State Performance Testing Status Baseline Gear Testing Status Single tooth bending fatigue testing of ground TR-1 gears completed Rotating Surface fatigue testing of ground TR-2 gears completed Rotating Surface fatigue testing of ground TR-1 gears - 75% complete Rotating bending fatigue testing of ground TR-1 gears - 25% complete Scoring resistance testing of ground TR-2 gears completed Ausformed Gear Testing Status Single tooth bending fatigue testing of ground TR-1 gears - 10% complete Rotating Surface fatigue testing of ground TR-2 gears - initiated Rotating Surface fatigue testing of ground TR-1 gears - initiated

ARL Penn State Phase 1:Ausform test rig gears - active profile only –Process modeling –Tooling and test gears manufacture –Optimize tooling and process –Gear performance testing Phase 2:Ausform test rig gears - active profile and root/fillet –Process modeling –Tooling and test gears manufacture –Optimize tooling and process –Gear performance testing Phase 3:Ausform Apache planet/sun gears –Tooling and test gears manufacture –Optimize tooling and process –Process test gears Phase 4:Testing of Apache planet/sun gears –Bending fatigue testing at ARL Program Status Summary Tasks CompletedTasks yet to be completed