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Technical Papers

An Improved-Accuracy Method for Fatigue Load Analysis o …

In spite of their increasing popularity, managing the use of wind turbines has been exceptionally challenging. Through computational prognostics, Sentient Science determined that current operating lifetime for a large number of turbines is only between five to thirteen years. Initial estimates indicate that savings of $150,000 per turbine per gearbox replacement can be achieved using physics-based long-term prognostics, leading to a substantial return of investment for wind farm operators. However, long-term prognostics require a precise determination of the loads in all six degrees of freedom occurred on the drive-train.

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Published November 7, 2017

Rolling Element Bearing Steels

Rolling element bearings occupy the sweet spot between cost, size, weight, accuracy, load capacity, friction, durability and accuracy. Modern bearing steels are critically important ultra-high strength structural materials used in a multitude of industrial systems and subject to the highest loading conditions for, in some cases, billions of cycles. They are unique among structural materials because of the localized nature of rolling contact fatigue (RCF) loading, leading to extreme sensitivity of fatigue life to microstructural attributes.

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Published September 8, 2017

Tribological Performance and Coating Characteristics of …

For the first time, the rolling contact performance of Ti-MoS2 films was evaluated using a thrust bearing tribometer and ball­ on-rod tribometers at 1 GPa Hertzian contact stress. Rolling contact measurements performed in humid air indicate that the useful life of Ti-MoS2 as a solid lubricant depends upon the amount of coating material retained in the contacts. Results of the rolling contact experiments performed in a vacuum indicate that Ti-MoS 2 film on balls may function extremely well as a solid lubricant for ball bearings operating in vacuum.

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Published June 12, 2017

Investigation of Microstructural Alterations in Low- an …

Wind turbine drive train system failures have been the major source of down time and costly repairs. One of the main failure modes associated with gearbox failures is the formation of white etching cracks (WECs) in bearings. In this paper, low-speed intermediate shaft (LSIS) and high-speed intermediate shaft (HSIS) bearings are collected from failed gearboxes to examine microstructural alterations and evaluate damage.

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Published June 6, 2017

Gear Health Algorithm Solution For Drive System Design …

The safe, reliable, and efficient operation and maintenance of rotorcraft drive systems is an essential capability of Army Aviation. From a safety and reliability standpoint, this capability ensures that the rotorcraft performs as expected with minimal risk of unforeseen failure and subsequent downtime. From an efficiency standpoint, this capability ensures that failure risks are identified in a timely manner and require minimal resources to mitigate.

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Published July 6, 2016

Overload Evaluation of Rotorcraft Tail Rotor Drive Spir …

This paper details an effort conducted to evaluate the effects of short to moderate duration overloads on the spiral bevel gears of the UH-60 helicopter tail rotor drive train. The focus of the effort was on the UH-60 intermediate gearbox (IGB). An initial analytical assessment of the effect of loads above the endurance limit was conducted using an American Gear Manufacturers Association (AGMA) based approach.

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Published April 24, 2013

Remaining Useful Life Prediction of Helicopter Gearbox …

This paper describes an innovative approach for predicting the remaining useful life (RUL) of a tapered roller bearing in the tail gearbox (TGB) of the UH-60M. The approach integrates vibration-based CIs with two of Sentient Corporation’s software packages, CABPro (Contact Analysis for Bearing Prognostics) and the Prognostic Integration Architecture (PIA). CABPro uses physics-based damage progression modeling to predict the onset and progression of fatigue spalling in rolling bearings based on material properties, bearing geometry, lubrication conditions, and operating conditions.

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Published March 15, 2013

Predicting the Remaining Life of Propulsion System Bear …

Diagnostic technologies for rolling element bearings are relatively well developed, but accurate prediction of remaining life once an incipient fault has been detected is considerably more difficult. This paper describes a comprehensive experimental study of bearing spall progression and a physics-based model being developed for bearing prognostics. The model computes the spall growth trajectory and time to failure based on operating conditions, and uses diagnostic feedback to self-adjust and reduce prediction uncertainty.

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Published March 15, 2013

Correlation of HUMS CIs with a Physics-Based Prognostic …

The purpose of this research is to determine the value of incorporating vibration derived condition indicator (CI) data for UH-60M Black Hawk tail rotor gearbox bearings within a previously developed prognostic architecture. A description of the tail rotor gearbox test facility used to develop ground truth bearing spall information and associated CI data is provided. This is followed by a description of a physics-based spall progression model and the architecture used to provide on-line model updating and uncertainty management. CI data is then used as a source of diagnostic information within the prognostic framework, and the relative performance of each CI with respect to remaining useful life (RUL) prediction quality is presented.

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Published March 15, 2013

Microstructure-Based Fatigue Life Prediction Tool for G …

This paper will summarize the DigitalClone models development, and validation efforts by comparing the simulation results with the Boeing spiral bevel gear physical test data. The CLP technology developed supports Integrated Computational Materials Engineering (ICME) and the Materials Genome Initiative (MGI). This novel technology will enable rapid assessment of the durability of rotorcraft spiral bevel gears.

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Published March 15, 2013