TECHNOLOGY AREAS: Air Platform, Materials/Processes

OBJECTIVE: Develop physics based gear health models to quantify the benefit of superfinish over conventional gear processing techniques with regard to pitting, spalling and tooth bending fatigue failure modes.

DESCRIPTION: Superfinish processed gears have demonstrated improved performance and durability over conventionally processed gears. However, this improvement has not been quantified. In addition, there is some concern about the uniformity of the process in key areas such as contour surfaces or the root ends of the gear teeth. The Navy needs modeling capability that will quantify the expected performance improvements of superfinish over conventional processing in order to understand lifecycle expectations of this new technology.

The goal of this topic is to develop physics based models which are capable of quantifying the benefits of superfinish processed parts over conventional processing, particularly for key performance metrics including reduced susceptibility to pitting, spalling, and tooth bending fatigue failure modes. The proposed models should also be able to generate accurate virtual test data.

End goals are to use the developed model to:
1. Quantify benefits of super finish over conventional processing
2. Determine the optimum amount of processing for super finish for the H-53K application, to minimize processing time and cost
3. Evaluate alternative super finish processes to quantify the benefit of increased uniformity
4. Potentially enable life credits at some point in the future to capture the benefits of the super finish processing, by modeling and quantifying durability improvements
5. Develop a modeling methodology that enables virtual testing (supplemented by smart selection of limited physical tests as needed), and allows for affordable application to additional material systems and geometries.

Accuracy of proposed models should be demonstrated through validation of virtual test data with actual test data, and deficiencies should be identified and mitigated to the maximum amount practicable. Refine the physics based models based on data collected from component level gear tests. The capability of the developed models to accurately quantify the advantages of superfinish over conventional processes while capturing the risk areas of the process such as the contour surfaces, or the root ends of the gear teeth should be validated via demonstration tests. Pyrowear 53 is the primary alloy of interest for this effort. Other relevant alloys, such as AISI 9310 may be considered during Phase I if availability of technical data for Pyrowear 53 is an issue.

PHASE I: Demonstrate feasibility of physics based gear models to quantify performance advantages of superfinish processing over conventional processing when applied to Pyrowear 53 gears. Alternatively, AISI 9310 steel may be considered during Phase I if Pyrowear 53 technical data is not available to researchers during the limited Phase I timeframe. Demonstrate feasibility of virtual test models to: 1) generate accurate simulated test results; 2) quantify superfinish improvements to the key gear performance metrics described above; and 3) identify the gear features which account for the most uncertainty such as contour surfaces, or the root ends of the gear teeth. Propose a method to address the uncertainty inherent in the models.

PHASE II: Continue to refine and develop the superfinish gear models, with specific application to Pyrowear 53. Develop the modeling methodology in such a way that it allows for reapplication to additional material systems and part geometries. Increase accuracy by accounting for surface finish and machining characteristics, alloy composition and materials characteristics, geometry, case and core hardnesses, case depth, and ratio of case thickness to tooth thickness. Incorporate robust methods of handling uncertainty associated with key features identified in Phase I. Develop and demonstrate the capability to determine optimum amount of superfinish processing to maximize the benefit while minimizing processing time and cost. Evaluate benefits of alternative superfinish processes to quantify the benefits of improved uniformity. Validate via demonstration tests the capability of the developed models to accurately quantify the improved performance of superfinish gears and generate virtual test data. Identify shortcomings of the models as revealed by the demonstration tests, and reduce the shortcomings to the maximum extent practicable.

PHASE III: Finalize the physics based gear models with major Department of Defense end users, airframe, and engine manufacturers and conduct necessary qualification testing for the applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The physics based superfinish gear models developed under this topic would significantly enhance the state of the art for commercial aviation, as well as other areas including ship and ground vehicle applications. The capability would also reduce developmental test costs. The technology is directly transferable to commercial gearbox applications.

REFERENCES:
1. Farahmand, B. (2009). "Virtual Testing and Predictive Modeling," Preface for. Retrieved from http://www.springer.com/cda/content/document/cda_downloaddocument/9780387959238-p1.pdf?SGWID=0-0-45-783503-p173878510

2. Niskanen, P., Manesh, Al, & Morgan, R. (2003). Reducing Wear with Superfinish Technology. "AMPTIAC Quarterly," 7(1). Retrieved from http://ammtiac.alionscience.com/pdf/AMPQ7_1ART01.pdf

3. Carpenter Technology Corporation. (2010). "Pyrowear Alloy 53". Retreived September 9, 2010, from http://www.cartech.com/ssalloysprod.aspx?id=2140

KEYWORDS: Gear; Superfinish; Models; Health; Pitting; Fatigue

Questions may also be submitted through DoD SBIR/STTR SITIS website.