RPI Masters Engineering Project Analysis of Near Net Shape Forged Gears for Helicopter Transmissions Holly Ann Quinn September 28, 2010

2 Problem Statement Is using Near Net Shape (NNS) Forging a better way to manufacture gears for helicopter transmissions? Potential Benefits –Lower Cost –Minimal Waste of Raw Material –Streamlined Process –Decreased Manufacturing Time –Equal Strength, Hardness and Fatigue Properties Potential Detractions –Higher cost of manufacturing tools, i.e. Forging Dies –May need to replace dies more frequently and at greater cost than cutting/grinding wheels Unknowns –Can Hardness and Fatigue properties of gears manufactured with NNS forging match those of “traditionally” manufactured gears?

3 “Traditional” Method of Gear Manufacturing Cutting/Rough Machining Operations –Gear teeth can be generated in multiple ways, such as hobbing or a cutter (horizontal or vertical): Material Processing –Carburization is a process performed at high temperatures during which carbon gas is infused into the coast and drive side of gear teeth to achieve adequate hardness levels. –Tempers are performed to toughen the material and increase ductility. –Heat Treatment often via Quenching is performed to harden the material by rearranging the microstructure to martensite. Finish Machining and Grinding –Gear Teeth are ground to achieve accurate geometry, as well as remove any distorted material acquired during heat treat. –Bearing Journals, Diameters are machined to Blueprint dimensions. Final Material Processing and Plating –Low Temperature Heat Treatment/Stress Relief Bake –Cadmium or Silver Plating to increase strength. –Shot Peening to increase strength. Horizontal Cutter

4 Method of Manufacturing with NNS Forging –The process begins with a billet or piece of forged material stock which is heated to some temperature and flattened into a “pancake” by a press. –Then, the stock is usually “punched” with a die into a mold so that the stock takes the form of the mold: Characteristics of the Part –Close dimensional tolerances –Minimum post-forging machining necessary to achieve the desired geometry –Refined grain structure comprised of an organized orientation of the crystals –Improved the physical properties due to refined microstructure Gear Manufacturing with Near Net Shape Forging

5 Simulations Plan to use DEFORM software to showcase improved microstructure achieved with NNS forging as compared to machined material Improvements in microstructure should correlate with improved fatigue strength of gear.

6 Expectations The main goal of this project is to research the gear manufacturing process that utilizes NNS forging methods and material processing techniques that create a gear with adequate case hardness and strength. The hope is to produce a strong, durable gear at minimal costs and processing time. This would be the most important outcome of this project.

7 Deadlines 9/14/10100 Word Write-up Due 9/21/10Tentative Project Proposal Due 9/28/10Final Engineering Project Proposal and Small Presentation Due 10/5/10Literature Search and Carrying out Work: - Write about processing techniques for case hardness in gears (heat treat/carburization), including discussion about microstructure changes during these processes. 10/12/10Literature Search and Carrying out Work - Start Discussion section, starting with the affect material processing performed on “traditionally” produced gears may have on gears that are produced with NNS forging methods. - Complete Literature Search - Edit and complete sections: Abstract, Introduction, and Methodology. 10/19/10First Progress Report Due Analysis, Computation and Writing - Determine gear geometry and loading conditions - Begin analysis with DEFORM for a NNS forged specimen and compare to machined material. 10/26/10Analysis, Computation and Writing - Continue analysis with DEFORM. Include heat treated/carburized material analysis

8 11/2/10Analysis, Computation and Writing - Write about computational results including the effects of heat treatment on NNS forged gears 11/9/102nd Progress Report w/~6-12 slide Presentation of Progress Due Review, Assessment, Correction and further Analysis, Computation and Writing - Discuss results and comparison of gears resulting from two production methods. - Discuss different processing methods available to manufacture a gear that may better meet design criteria. 11/16/10Review, Assessment, Correction and further Analysis, Computation and Writing - Complete and edit Analysis, Discussion & Results sections of project 11/23/10Review, Assessment, Correction and further Analysis, Computation and Writing - Write Conclusions - Create final project presentation slides 11/30/10 Final Draft of Project Due Final Reviews, Wrap-up and Closure - Complete and Edit Conclusions - Edit presentation slides - Complete References and check citing is correct throughout document 12/7/10Final Reviews, Wrap-up and Closure - Edit and review project documents - Include all reference documents including simulation models and results on RPI website. 12/14/10Final Report Due - Write about design criteria and application for gear, including material properties Deadlines