SITIS Topic Details |
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| Proposals Accepted: | |
| Program: | SBIR |
| Topic Number: | A10-169 (Army) |
| Title: | Fatigue Crack Initiation Prediction Tool for Rotorcraft Spiral Bevel Gears | Research & Technical Areas: | Air Platform, Materials/Processes |
| Acquisition Program: | PEO Aviation |
| The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation. | Objective: | This topic seeks to develop a microstructure-sensitive probablistic based analytical technique for predicting the time to crack initiation for high performance spiral bevel gears currently used in rotorcraft drive systems.
| Description: | Spiral bevel gears are used in nearly all modern rotorcraft. Their ability to operate at high speeds with non-parallel input and output shafts enables the power to be transferred from a horizontal plane to the vertically mounted main rotor shaft. These gears are typically manufactured using case carburized alloy steels such as AMS 6265 and AMS 6308. The fatigue strength of the finished gears are a function of the basic geometry, the material micro and macrostructure characteristics, surface finish, lubrication, and the contact pattern achieved between the mating pinion and gear. Current life prediction methods such as the American Gear Manufacturers Association (AGMA) method are empirically based. The AGMA method produces a Stress Index which is difficult to correlate with true stresses that would be obtained via strain gages or the use of modern finite element design methods. This topic seeks to develop a probabilistic based analytical technique for predicting the time to crack initiation for high perfromance spiral bevel gears currently used in rotorcraft drive systems. The method to be developed shall utilize a commercially available finite element method(FEM) based tool to model the spiral bevel gear geometry and the loading and contact pattern of the meshing pinion and gear. The model shall output stresses to be used in a microstructure-sensitive probabilistic based crack initiation prediction tool. AS a minimum, this tool shall include the effects of material cleanliness, grain size, chemical composition, residual stress, hardness, and other factors which are known to influence fatigue strength. The statistical distribution of these characteristics about the mean desired target properties shall be the basis for the probabilistic prediction of load cycles to crack initiation.
| PHASE I: Phase I effort shall consist of a feasabilty analysis assessing the applicability of existing FEM tools to effectively and afforbably create models of meshing spiral bevel gears that will yield accurate stresses for use in the probabilistic life prediction tool. The specific factors effecting fatigue crack initiation in case hardened steel gears fabricated from either AMS 6308 or AMS 6265 shall be identified and the relative influence of each of these factors shall be analized. The potential variation of these factors shall also be identified. An assement of the potential accuracy of the basic approach is a desired outcome of the phase I effort. A Manufacturing Technology Readiness level of 3 is expected at the conclusion of Phase I.
| PHASE II: Phase II shall combine the FEM and probablistic life prediction tools developed in Phase I into a single integrated tool for predicting stress cycles to crack initiation. Effort will be conduct to refine the accuracy stresses generated by the spiral bevel gear FEM model. Effort shall also be conducted to acquire experimental data required to verify the relative influence of factors effecting crack initiation. The use of the FEM tool shall be exercised using a suitable case carburized spiral bevel gear. The participation of a helicopter OEM shall be sought for Phase II effort and a target helicopter spiral bevel gear selected for use in the analysis. The stresses predicted by the FEM tool shall be used as input to the probabilistic life prediction tool. A beta version of the analysis tool shall be developed for assessment by potential commercial users. A Manufacturing Technology Readiness level of 5 is expected at the conclusion of Phase II.
| PHASE III: Phase III shall consist of further refinement of both the FEM tool and the Probabilistic life prediction tool and the interfaces between the two parts of the tool. Further validation to the accuracy of the approach may be perfromed by conducting specifically designed fatigue testing. A market ready version of the spiral bevel life predition tool should also be refined. The commercial availability of this software package is seen as the end vision of this topic. A Manufacturing Technology Readiness level of 7-8 is expected at the conclusion of Phase III.
| References: | 1. Tryon, R. G., Cruse, T. A., (1998) "A Reliability-Based Model to Predict Scatter in Fatigue Crack Nucleation Life", Fat. Frac. Eng. Mat. Str., Vol. 21, pp. 257-267 2. James, M. R., Morris, W. L., (1986) “The Effect of Microplastic Surface Deformation on the Growth of Small Cracks,” Small Fatigue Cracks, Ed., R. O. Ritchie, J. Lankford, TMS, Warrendale, PA, pp. 167-189 3. Simulating Fatigue Crack Growth in Spiral Bevel Pinion,CORNELL UNIV ITHACA NY, Ural, Ani ; Wawrzynek, Paul A. ; Ingraffea, Anthony R., AUG 2003 4.http://www.spiralbevel.com/spiral_bevel_co 5. Bibel, G.D. and Handschuh, R.F. (1997) 'Meshing of a spiral bevel gear set with 3-D finite element analysis', Gear Technology, March/April, pp. 44-47. 6. Huseyin Filiz, I. and Eyercioglu, O. (1995) 'Evaluation of gear tooth stresses by finite element method', ASME Journal of Engineering for Industry, Vol. 117, pp. 232-239. |
| Keywords: | gears, probabilistic design, steels, microstructure, fatigue, manufacturing engineering |
Questions and Answers: |
No questions posed on this topic at this time |
As of midnight September 1, questions for solicitations SBIR 10.3 and STTR 10.B will no longer be accepted.
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