The Sikorsky Boeing SB>1 DEFIANT is a technology demonstrator aircraft that was built under the Joint Multi-Role Technology Demonstrator (JMR TD) program to address the next generation performance requirements of the US Army Future Vertical Lift (FVL) initiative. During the development of the SB>1 DEFIANT technology demonstrator aircraft several manufacturing lots of gears were produced with a core hardness that was 10-30% below the minimum engineering requirement. The defect was not detected until a large population of gears was near completion. To prevent significant program cost and schedule impacts, a safe load capacity for the discrepant gears was determined via test. Dynamically loaded ground test articles for SB>1 DEFIANT technology demonstrator aircraft began qualification testing with the low hardness gears. The low hardness issue, root cause, and test method to establish a safe operating load limit are discussed.

Dehennis, Timothy

Tunable Auxiliary Lubrication System for Helicopter Transmissions

F-0081-2025-0243

5/20/2025

The Main Gearbox of a helicopter is a crucial component that delivers the desired performance and ensures the highest possible level of safety of the aircraft; it includes several gears and bearings, which require to be continuously lubricated by a pressurized oil flow. Undesired circumstances may cause the oil to leak from the main circuit, hence reducing its pressure and consequently the oil flow rate targeted towards the rotating components; this modifies their friction coefficient, and subsequently leads to an overheating of the parts with the risk of degenerating in a catastrophic failure. During the design of a helicopter drive system, engineers need to take proper precautions and make sure that the MGB is fully equipped with the proper features to cope with a loss of lubrication event; specifically, the drive system is supposed to be able to run at least 30 minutes after the oil pressure drops to zero. A lot of effort has been put over the years at Leonardo Helicopters to find

Alari, Lorenzo, Sartori, Sergio, Pisani, Paolo, Tamborini, Marco Ernesto, Delvecchio, Gabriele, Scaltritti, Diego

CAE Based Benchmarking of Shaft Deflection for Transmission Gear Rattle Noise

2024-26-02451/16/2024

Vehicle transmission gear rattle is one of the most critical NVH irritants for refined vehicles. It is perceived more dominantly in lower gears of vehicle running. It depends on various design parameters like Input torque amplitude & fluctuations, driveline torsional vibrations, gear micro & macro geometry, shaft flexibility, etc. Establishing exact contribution of each of these parameters to transmission rattle, thru experimental or simulation technique, is very challenging. Current paper explains the NVH CAE benchmark approach deployed to understand difference in rattle behavior of two transmission designs. Subjective and objective evaluation shows that one is better than the other for rattle noise. Paper focuses on simulation and comparison transmission shaft deflection as a measure of transmission rattle. FEA based nonlinear static simulations are carried out by applying torque induced forces at each of the gear contacts for all the gear engaged conditions. Simulated shaft

Bijwe, Vilas B., Kulkarni, Shriram, Vaidya, Rohit, Shah, Bhartendra

Design optimization of Engine Mount bracket to reduce various gear noises in the passenger car cabin

2024-26-02081/16/2024

With the advancement of regulatory norms in the automobile industry, there is challenging to meet performance efficiency targets, especially with a lightweight platform, while providing a superior driving experience to customers. The shift towards weight optimization makes the vehicle structure more susceptible to transfer a diverse range of noise and vibrations through the body. Although most undesirable noises perceived inside the cabin can be reduced by superior technology engine mounts and NVH packaging, all such solutions lead to cost addition. Intelligent considerations in part design can be used to supplement predictable transfer paths to quell unwanted vibrations. One such case is of the gear whine noise in certain rpm bands caused by inherent gear meshing frequency coinciding with the natural frequency of an engine mounting bracket. This paper demonstrates two methodologies to counter such a phenomenon, either through engine mount bracket natural frequency optimization or

Ghosh, Chiranjit, Agrawal, Adheesh, Karmakar, Sudipto, Srivastava, Shubham, Khan, Aamir

Optimization of Magnetic Planetary gear Topology to avoid auto slip during various torque requirements for passenger car application.

2024-26-00411/16/2024

Authors: Gowtham Raj R, Kiran Rao Mercedes-Benz Research and Development India Private Limited Key Words: Transmission, Magnetic planetary gears (MPG), PM Machine, MATLAB Simulation, Magnetic field Abstract: The automotive industry recently has started implementing magnetic gear in different types as alternative design for transmission system, one such design being Magnetic planetary gear permanent magnet (MPG-PM) machine. The current methodology and the relevant formulas helps to design magnetic planetary gear system, which does not have design considerations for permanent magnet machine and influence of magnetic field. The influence of design characteristics of PM machine, Magnetic field and its material plays a vital role in designing the MPG-PM for electric vehicle applications. A method of optimizing the Gear topology design parameters of a magnetic planetary gear permanent magnet machine (MPG-PM machine) is proposed. The Analytical calculations regarding the design parameters

Ramakrishnan, Gowtham Raj

Lubrication Evaluation of EV transmission

2024-26-03281/16/2024

The advent of EV powertrain has considerable effect on transmission development activities as competed to regular ICE transmission. Conventional ICE transmission and the transmission for an e-powertrain differ on fundamental level. The conventional transmission has number of gear ratios, shift mechanism which enables the transmission to deliver a smooth power output as per demand from the driver. Whereas the e-powertrain transmission is mostly a single gear ratio transmission (reducer) which primarily depends on speed and torque variation from the motor to cater the driver requirement. Hence, the operating speeds of the such e-transmissions can vary from 0 to 20000 in both forward and reverse directions. Such a large speed variation as compared with conventional transmission calls for special attention towards the lubrication of internal components. High speeds and lower oil viscosities tend to disrupt the oil films in between contact surfaces causing metal to metal contact. This

Kushwaha, Rakesh, Bhosale, Vikas, Navale, Pradeep, Patel, Hiral

Experimental Analysis of Multi-Link Rigid Axle Suspension Camber Variation with Vehicle Load

2024-26-00541/16/2024

Jani, Harshil, Rasal, Shraddhesh, Hussain, Inzamam, Asthana, Shivam, ahire, Manoj, Vellandi, Vikraman, Senniappan, Moorthy

Asymmetric Gear Blank Optimization to Reduce Gear Noise for Electric Drive Units

2025-01-00795/5/2023

Gear whine has emerged as a significant challenge for electric vehicles (EVs) in the absence of engine masking noise. The demand from customers for premium EVs with high speed and high torque density introduces additional NVH risks. Conventional gear design strategies to reduce the pitch-line velocity and increase contact ratio may impact EV torque capacitor or its efficiency. Furthermore, microgeometry optimization has limited design space to reduce gear noise over a wide range of torque loads. This paper presents a comprehensive investigation into the optimization of transfer gear blanks in a single-speed two-stage FDW electric drive unit (EDU) with the objective of reducing both mass and noise. A detailed multi-body dynamics (MBD) model is constructed for the entire EDU system using a finite-element-based time-domain solver. This investigation focuses on the analysis and optimization of asymmetric gear blank design features with three-slot patterns. A DOE methodology is employed to

He, Song, Bahk, Cheonjae, Li, Bo, Du, Isaac, Patruni, Pavan Kumar, Baladhandapani, Dhanasekar

A Study on Reduction of Gear Rattle Noise through Clutch Hysteresis Stabilization

2025-01-01005/5/2023

Reducing gear rattle noise within the passenger cabin is a crucial objective in vehicle development due to its direct impact on customer comfort and driving experience. Gear rattle occurs when free gears collide during meshing, primarily driven by high torsional vibrations generated by engine fluctuations. These vibrations are transmitted through the clutch system to the transmission, amplifying noise inside the cabin. To address this issue, this study focuses on optimizing the clutch by stabilizing its hysteresis, which helps in minimizing the torsional vibrations transferred to the transmission input shaft, thereby reducing gear rattle. The investigation centers on a case where significant gear rattle was observed at high vehicle speeds, particularly under high engine torque conditions. A thorough root cause analysis identified that the primary contributor to the noise was a drop in the clutch hysteresis value at elevated engine torques. This drop increased torsional vibrations in

Awasthi, Mradul, Dhankhar, Dinesh Singh, Khare, Devendra Kumar, Rana, Deepak, pandey, Anant

NVH improvement of the BEV transmission by altering bearing mounting arrangement.

2025-01-01045/5/2023

As per metaphor, “The squeaky wheel gets the grease” the transmission of battery electric vehicle (BEVs) gets topmost attention in terms of NVH improvement. While the engine is getting replaced with an almost silent electric motor, the transmission noise appears persistent and demands more silent transmission. This has raised demand for improvement in design as well as manufacturing quality. Various innovations are being done to drive an improvement in the NVH. Following paper will discuss the improvement in NVH achieved through a design innovation in the way bearings are installed and demonstrated a significant amount of improvement. We have used SMT MASTA used as a simulation tool to predict the expected results and a Transmission Dyno test bench in an anechoic chamber to test the NVH performance on physical sample. The innovation was done on a small single speed two stage reduction gearbox coupled with a 100 NM, 14000 RPM battery electric motor. Though the bearings have

Pingale, Abhijeet, Soni, Jaldeep

Virtual Gear Noise Analysis and Case Design Investigation for Concept Parallel Axis Drive Unit

2025-01-01025/5/2023

For electric vehicles, it is critical to develop drive units that produce a minimal amount of noise while meeting efficiency needs for a given application. Modern computational resources and accumulated experience allow for engineers to evaluate gear noise early in the development process and influence the design of the drive unit. This paper documents a high-fidelity virtual engineering approach to evaluate gear noise in a concept parallel axis drive unit and provide learnings to influence design of the external structure to improve NVH performance. By using the latest simulation tools to calculate and visualize the noise and vibration characteristics of the drive unit, designers and developers can implement design changes in optimization iterations to reduce noise and vibration. Gear harmonic response is firstly analyzed through a system model which considers structural deflection and misalignment, then a FE housing model is incorporated which is used for noise radiation evaluation

Lima, Luiz, Shi, Zhenghong, Xu, Hai, REYNOLDS, CRAIG, Miller, John

Study and Application of Gear Micro Modification of Electric Drive System

15-16-01-0001

9/15/2022

Abstract The gear whine in the electric drive system of an electric vehicle is important and remains a challenge in developing novel electric vehicles. A gearbox dynamic model is established, and the effects of modification parameters on the sound pressure level, transmission error, and contact stress of the gear pair are introduced to reduce the gear whine. A multi-objective optimization study of four modification variables under multiple torque conditions is carried out by using transmission error and maximum contact stress as the objective functions. The eclectic programming method is imported to solve the convergence problem of multi-objective optimization. The influence of modification variables on objective functions is studied by establishing an approximate model of the optimal Latin hypercube design. Results show that the application of the multi-objective optimization method combined with the eclectic planning method for the micro modification of the gear can reduce the

Chen, Chen, Zhu, Linpei, Liu, Jing, Wei, Dan, Yu, Hao

Study and Application of Gear Micro Modification of Electric Drive System

15-16-01-0001-TEST-REC9/15/2022

Chen, Chen, Zhu, Linpei, Liu, Jing, Wei, Dan, Yu, Hao

Evaluation of Fretting Phenomenon in Gearbox and Allied Failures

2022-01-07853/29/2022

This paper takes a review of fretting phenomenon on splines of the engaging gears and corresponding splines on shaft of automotive transmission and how it leads to failure of other components in the gearbox. Fretting is a special wear process which occurs at the contact area of two mating metal surfaces when subject to minute relative oscillating motion under vibration. In automotive gearbox, which is subjected to torsional vibrations of the powertrain, the splines of engaging gears and corresponding shaft may experience fretting, especially when the subject gear pair is not engaged. The wear debris formed under fretting process when oxidizes becomes very hard and more abrasive than base metal. These oxidized wear particles when comes in mesh contact with nearby components like bearings, gears etc. may damage these parts during operation and eventually lead to failure. In this paper, a case study is presented wherein fretting has been identified as the root cause of failures of some

Mohire, Sujit, Bhandari, Kiran Kamlakar, Tendulkar, Vishveshvar, Chatterjee, Soumik

Damage-Induced Dynamic Tooth Contact Forces in Spur Gears with Root Cracks

2022-01-07743/29/2022

A finite element/contact mechanics formulation is used to analyze the dynamic tooth forces that arise from damage-induced vibrations in spur gear pairs. Tooth root crack damage of varying sizes are analyzed for a wide range of speeds that include resonant gear speeds. Healthy gears without damage can have contact loss nonlinearity where pairs of teeth normally in contact lose contact due to large amplitude vibration. When spur gear teeth have tooth root crack damage, the added localized compliance from the damage leads to a re-distribution of the forces on the individual gear teeth. These loads cause additional transient dynamic response in the gear pair. For certain speeds and sufficiently large tooth root cracks, the damage-induced dynamic response causes large enough vibration that tooth contact loss nonlinearity occurs. For some speeds near resonance, the damage-induced vibrations cause teeth that normally lose contact to remain in contact due to vibration. Tooth contact loss

Cooley, Christopher, Wang, Yaosen, Hood, Adrian

Innovative Experimental Approach towards Gear Rattle Investigation

2022-01-07843/29/2022

Today’s customers are very thoughtful towards a new vehicle purchase. Along with the vehicle performance, overall vehicle NVH quality is also one of the most important factor which affects their buying decision. During any new product development, gearbox rattle noise is a fundamental NVH problem which requires to be addressed and solved in the early stages. Gear rattle is an annoying noise phenomenon of the automotive transmission, which is mainly induced by torsional fluctuation of engine. This fluctuation is passed from clutch system to the transmission. The torsional vibration causes the free gears inside the transmission to impact each other, which generates so-called the gear rattle noise. The noise source of the gear rattle in the manual transmission is due to the impact of gears oscillating through their gear backlash and the noise will transfer into the vehicle cabin through the transmission case via shafts, bearings and vehicle structures. This paper describes an experimental

Vaishya, Abhishek Lakhanlal

A Development of Spindle drive power trunk lid system with Optimizing Actuating noise

2022-01-09163/29/2022

The power trunk lid system is a device that automatically opens and closes the trunk lid using a motor, for the purpose to improve user’s convenience. The technology was applied only to high-priced large cars such as Equus and Genesis, but in line with increasing preference for high convenience features, the scope of application is gradually expanding to semi-large and mid-size vehicles. Accordingly, the need to secure profitability through cost reduction emerged, and we developed a power trunk lid system using a spindle drive. Spindle drives can reduce costs by optimizing the required motor specifications compared to conventional swing arm drives, and are lightweight and easy to assemble. However, since a planetary gear with a high gear ratio is used and the rotational speed of the motor is generally high, it has a relatively low characteristic in terms of actuating noise. When we first applied the spindle drive type power trunk lid system to GL3 model (the successor of YG), to reduce

lim, Kyeongjun

Gear fault classification using fuzzy logic in an epicyclic gearbox with statistical features.

2021-28-022010/1/2021

Epicyclic geartrains are often preferred in heavy-duty machinery owing to its ability to transmit large amount of power with minimal loss, good load sharing capacity, huge reduction ratios and compact in size. Machineries employing such complex geartrains need an effective monitoring system to predict gear failure at an early stage which prevents catastrophic failure. In this work vibration signal of the geartrain is acquired using accelerometer under various gear faults conditions such as healthy gear, defect in sun gear, defect in planet gear, defect in ring gear, defect in both sun and planet gears respectively. Then, statistical characteristics or features such as mean, median, mode, variance, skewness, kurtosis, standard error, standard deviation, maximum and minimum, of the time domain vibration signals are extracted. Afterwards, a decision tree algorithm is used to select the most useful statistical features. These selected features form as an input to fuzzy classifier. The

Syed, Shaul Hameed, V, Muralidharan, D, Pradeep Kumar, S PhD, Ravikumar

Gear Whine Noise Reduction by Transmission Error and Contact Pattern Optimization: Simulation and Testing Correlation

2021-01-11038/31/2021

During product development testing, a gear whine issue was identified with a gearbox. The noise was present regardless of the load, observed throughout the operating speed range, and it was especially noticeable at certain points of the operating conditions. A high-fidelity simulation model was built to recreate the issue observed in testing and the objective was to find possible ways to reduce the gear whine. The peak-to-peak transmission error (PPTE or TE), which is the main excitation for gear whine, was evaluated, using the simulation model, throughout the operating conditions, and it showed a peak at the same points as observed in testing. This was attributed to the fact that these gears act as both driving and driven components, which causes fluctuating moment on the gear mesh, and thus the load sharing changes continuously, causing variation in excitation throughout the operating load cycle. This excitation is a function of gear geometry and can be reduced by optimizing the

Lahoti, Soniya, Patil, Pravin, Wagner, Jeremy J.

A Comparative Study of Cradle and Sub Frame Type Powertrain Mounting System on Electric Vehicle

2021-01-10228/31/2021

The growing demand of fuel and cost saving on vehicle, today’s vehicle manufacturer are working on various weight reduction initiative in EV. Lighter weight vehicle have bigger challenges to meet NVH requirement. There are two types of EV called modified and adopted EV’s are commonly in use. The sub frame type of EV system comes under the category of modified EV. In this paper, a mounting system is studied and compared for a cradle type EV as well as sub frame or saddle type EV. MATLAB based optimization tools are used for parameter optimization. The focus is put on the optimization of mounting system location and stiffness for energy optimization, CoG and TRA-EA optimization. The best engine mounting system is compared and adopted based on simulation. 12 DOF studied to address high frequency resonance issues for a sub frame type EV. Finally robustness of the system is checked based on various simulation and optimization.

Deshmukh, Sagar, Hazra, Sandip

NVH Analysis and Optimization of Engine Balance Shaft Module

2021-01-10328/31/2021

For any combustion engine, balance has always been important regardless of types of cylinder layout. One of the disadvantages of the inline four engines is the second-order unbalanced forces, which leads to high-frequency excitation of vehicle’s structure and consequent internal noise. Balance shaft modules (BSM) are often used in inline-four engines, to reduce the second-order vibration and mitigate engine imbalance. Balance shafts are often running at light load and high-speed condition which could induce both gear rattle and gear whine from the BSM gear set. Typically, scissor gear set is used between crankshaft and BSM to reduce the gear rattle noise. However, a poor scissor gear design could easily lead to unpleasant gear whine noise. There is an increasing trend to shorten development cycles and reduce cost using simulation models. This paper discusses an analytical method to simulate gear whine and rattle generated by engine BSM. Simulation software MASTA is a robust and fast

Ba, Jing, Sun, Zhaohui, Sandstrom, Alexander, Hu, Kevin, Li, Corey, Shi, Zhenghong

Overall Transmission Error Calculation of Differential Gear

2021-01-11018/31/2021

Overall transmission error (OTE) of gear system has been a main focus of gear dynamics study. The input-output transmission error (TE) depends heavily on mesh phasing conditions. Only reducing loaded transmission error (LTE) of a single gear mesh is not enough to ensure good NVH performance in a multiple gear mesh system. In order to predict OTE during bevel gear design instead of just analyzing single mesh TE, a new bevel gear OTE calculation method will be presented in this study. Based on single mesh parameters including loaded and unloaded TE or mesh stiffness, the OTE of a differential gear set can be calculated without building a complete system model. The effect of phasing on system OTE shows that different tooth combination can have significant effect on dynamic performance which should be considered during design.

Shi, Zhenghong, Chen, Jui, Kolivand, Mohsen, Sun, Zhaohui, Rivett, Eric, Kopp, Gregory, Nantu, Roy, Ba, Jing

Lead Mismatch Calculation of a Helical Gear System Mounted on Balance Shafts

2021-01-06734/6/2021

In powertrain systems, combined deflection of loaded gear tooth as well as that of the shafts on which the gears are mounted is responsible for non-ideal meshing conditions. Uneven load distribution along the teeth between mating gears is one such non-ideal condition that can cause significant NVH issues. Lead mismatch, defined as the amount of mismatch along a pair of gear tooth faces, is a critical parameter to maintain uniform load distribution at the gear contact regions. If each of the adjacent shafts is a balance shaft where a counterweight is mounted at an eccentric location, shaft deflection and the resultant lead mismatch is even more. Also, typically, balance shafts are required to rotate at twice the crankshaft speed. At a high engine speed, Coriolis and centrifugal accelerations acting on the balance shafts can be significant resulting in higher shaft deflection and greater lead mismatch. In the present system, a balance shaft mechanism with helical mating gears are

Chowdhury, Sanjib, Vasu, Anoop, Chung, Jerry, Mehta, Yogesh

Static Transmission Error Analysis of a Hybrid Spur Gear Drivetrain

F-0076-2020-16334

10/5/2020

This study presents static analyses of transmission error in a single gear pair gearbox for six pairs of hybrid composite-steel spur gear designs developed in a previously presented optimization effort. The results were compared to those of the same gearbox featuring a baseline all-steel gear pair. The gearbox models were developed in the commercial software RomaxDESIGNER R17. A tooth stiffness analysis was also conducted to replace the tooth stiffness values calculated in Romax with values that consider the web effects on tooth stiffness. These stiffnesses are used to calculate the mesh stiffness. This analysis showed a 2-5% difference in average tooth stiffness of the hybrid gears compared to the steel gear. The transmission error analysis with the new tooth stiffnesses showed a 1-3% increase in the transverse error in for hybrid gears compared to the baseline steel.

Gauntt, Sean, Campbell, Robert, McIntyre, Sean

Providing of Sliding Bearings Reliability of Transmissions Gear Wheels of Transport Cars by Optimization of Assembly Tolerances

2020-01-22399/15/2020

In the design of gearboxes and transfer boxes of heavy-duty vehicle`s transmissions, sliding bearings are often used as supports for gear wheels. Analysis of the results of statistical processing of gearbox parts failures and transfer boxes of wheeled tractors with a pulling force of 30 kN indicates the need to improve the reliability of the sliding bearings of the gear wheels. Such plain bearings ensure free rotation of the gear wheels in case of the torque transmission absence, and when locked by a clutch, the radial load of the gear wheel is sensed, while operating in the slipping rolling mode. Such units are poorly understood and in the technical literature sources there are no recommendations for their engineering, which often leads to errors when selecting operation gaps and press fitted in gear wheels. The manufacturers of the transmissions assemblies replaced the plain bearings, which in this case are made of metal-ceramic bushes, for roller bearings. Also, the application of

Savchuk, Volodymyr, Kuhtov, Valeriy, Gritsuk, Igor V., Podrigalo, Mikhail, Vychuzhanin, Vladimir, Parsadanov, Igor, Bulgakov, Nickolay, Belousov, Evgen, Vrublevskyi, Roman, Samarin, Oleksandr, Kurnosenko, Daria, Verbovskiy, Valeriy

Modeling and Parameter Estimation of Automatic Transmission for Heavy-Duty Vehicle Using Dual Clutch Scheme

2020-01-22429/15/2020

This paper focuses on modeling of the heavy-duty vehicle drivetrain with automatic transmission by using dual clutch scheme. The planetary gear set in the automatic transmission is complicated structure and difficult to understand. The advantage of the dual clutch scheme is that it can be used to represent the complex planetary gear set intuitively, which is a great help to understand the gear shifting process. It is also suitable for being used in the controller due to its low order. Some conditions are required to convert the planetary gear set to the dual clutch model. The heavy-duty vehicle driveline can be converted to the dual clutch model due to its heavy engine and vehicle inertia. This paper also proposes system parameter estimation methods to represent the driveline model. The main parameters are lumped inertia, lumped gear efficiency, output shaft compliance and friction coefficient of clutches. First, a method for estimating lumped inertia and lumped gear efficiency is

Lee, Tae Heon, Choi, Seibum

Cold Idle Gear Rattle in Manual Transmission Passenger Car-Temperature Based Phenomenon

2020-01-22459/15/2020

Gear rattle is due to impact noise of unloaded gears in transmission having freedom to move in backlash region. Engine order vibrations in the presence of backlash in meshing pairs induce the problem. It is a system behavior wherein flywheel torsional vibrations, the pre-damper characteristics and transmission drag torque plays a vital role in an engine idle condition (hot & cold). Idle rattle is a severe issue, which is highly noticeable in cold condition or after 1st engine crank. Gear rattling observed in idle condition is idle gear rattle or neutral gear rattle, specifically in cold condition is a “Cold idle rattle” and this is one of the critical noise parameters considered for entire vehicle NVH. Damper mechanism in the clutch, is used to serve better isolation (by reducing the input excitation to transmission parts) of vibrations between engine and transmission their by reducing gear rattle intensity. Engine firing order, engine downsizing, down speeding (means high peak torque

Kapse, Ravi Ramesh, More, Vivek, Gangane, Swapnil

Quantifying Engine Braking for Various Common Street Motorcycles

2020-01-08804/14/2020

Motorcycle engine braking was measured in each forward gear for a cross-section of typical street motorcycles. Using GPS data acquisition and video, deceleration relative to speed was examined. Motorcycle characteristics included various engine displacements and types of motorcycle. The data acquired will give more insight into the extent which engine braking is a factor for deceleration, a topic which has not been addressed in a peer-reviewed journal article to this date.

Jansen, Henricus, LeBlanc, Beau, Wilhelm, Christopher, Shaw, Tyler, Lowi, Alvin

Continuous Fiber Composite for Use in Gears

TBMG-3569712/1/2019

NASA's Glenn Research Center has developed a breakthrough means of adapting strong but lightweight carbon fiber composite material to fabricate structures of complex shape such as specialized components for drive systems. Conventional methods of using discontinuous fiber composites for forming complex shapes can produce defects including a tendency toward weakness and fatigue at the cut ends of the fibers. Glenn's novel technology instead uses multiple layers of formable continuous fiber composite material, eliminating the cut ends that form a potential site for failure, as well as filler materials between plies.

Influence of Retained Austenite on Fatigue Performance of Carburized Gears

2019-28-010210/11/2019

SAE 8620 and 20CrMo materials were subjected to carburizing process to obtain the identical hardened layer of HRC 61-64. The carburized surface and core properties of the materials were examined and characterized through optical microstructure to measure the presence of cementite carbides and Retained Austenite (RA). From the results, it was found that the SAE 8620 and 20CrMo materials have 10 % and 14% of RA respectively. Whereas, the core and case structure were free from network carbides. The fatigue test was conducted to correlate the RA and fatigue strength of the materials. It was revealed that material with lower RA has higher fatigue strength than material with higher RA. Higher amount of retained austenite leads to reduction in amount of martensitic and compressive residual stress attributed to lower the contact fatigue strength. Untransformed austenite is metastable and is transformed to untempered martensite, which causes brittleness to the component and leads to premature

Ramasamy, Rajeshkumar, Sivathanu, Seenuvas, Neelakandan, Varatharaj, Ganesan, Thulasirajan, Chakrapani Rao, Praveen

Experimental Investigation on Gear Rattle Noise Reduction in Passenger Car

2019-01-15616/5/2019

Gear rattle noise reduction inside the passenger cabin is one of the major challenges for customer comfort enhancement. Therefore, it becomes a prime target during transmission design and development. Gear rattle is generated due to meshing teeth collision of free gears, which is caused due to torsional vibration of engine transferred through clutch. Vibrations are generated due to free gears teeth impact and are transferred to shaft, bearings and transmission housing. The sound absorption and structural vibration of transmission housing was optimized by changing the geometrical features of the transmission housing that affects radiated noise. Experimental approach for gear rattle noise reduction through transmission housing modification is described in this paper. Moreover, CAE method is also incorporated with the experiments for optimization of future vehicle transmission system designs.

Khare, Devendra Kumar, Vaishya, Abhishek Lakhanlal, Pujara, Archan Sunibhai, Krishna, Radhe, Satpathy, Kingshuk, Choudhary, Ved Prakash, Pandey, Anant

Design Optimization of Differential Bevel Gear for NVH Improvement

2019-01-15526/5/2019

With fast pacing development of automobile industry and growing needs for better driving experience, NVH performance has become an important aspect of analysis in new driveline product development especially in hybrid and electric powered vehicles. Differential bevel gear has significant role in the final drive. Unlike parallel axis gears such as spur or helical gear, bevel gear mesh shows more complicated characteristics and its mesh parameters are mostly time-varying which calls for more extensive design and analysis. The purpose of this paper is to conduct design study on a differential bevel gear unit under light torque condition and evaluate its NVH characteristics. Unloaded tooth contact analysis (UTCA) of those designs are conducted and compared for several design cases with different micro geometry to investigate their pattern position and size variation effects on NVH response. Loaded tooth contact analysis (LTCA) that is based on semi-analytical and semi-FE method is used to

Shi, Zhenghong, Chen, Jui, Kolivand, Mohsen, Sun, Zhaohui, Kopp, Gregory, Peng, Ying

The Utilization of Onboard Sensor Measurements for Estimating Driveline Damping

2019-01-15296/5/2019

The proliferation of small silicon micro-chips has led to a large assortment of low-cost transducers for data acquisition. Production vehicles on average exploit more than 60 on board sensors, and that number is projected to increase beyond 200 per vehicle by 2020. Such a large increase in sensors is leading the fourth industrial revolution of connectivity and autonomy. One major downfall to installing many sensors is compromises in their accuracy and processing power due to cost limitations for high volume production. The same common errors in data acquisition such as sampling, quantization, and multiplexing on the CAN bus must be accounted for when utilizing an entire array of vehicle sensors. A huge advantage of onboard sensors is the ability to calculate vehicle parameters during a daily drive cycle to update ECU calibration factors in real time. One such parameter is driveline damping, which changes with gear state and drive mode. A damping value is desired for every gear state

Furlich, Jon, Blough, Jason, Robinette, Darrell

Improvement of Hypoid Gears Dynamics Performance Based on Tooth Contact Optimization

2019-01-15636/5/2019

The meshing noise of hypoid gear has a significant influence on driving axle system. It should be strictly controlled in order to reduce the whole vehicle noise. Meshing internal excitation of hypoid gear is a main source of vibration noise, closely connected with geometrical shape and meshing status. There is no comprehensive analysis on the impact of various contact patterns on vibration noise in previous studies. Therefore, the method for controlling contact characteristics of hypoid gears is studied in this paper, which includes adjusting the position and length of contact pattern, direction of contact trace and the theoretical transmission error. Also, a non-linear dynamic model with multi-freedom for the hypoid gear pair of the driving axle is established to evaluate the dynamic response of the gear pair. Then an example was carried out to improve the dynamic characteristic of hypoid gears by tooth profile modification. It is proved that the dynamic transmission error and mesh

Zhang, Weiqing, Wang, Yawen, Lin, Chia-Ching, Lim, Teik, Guo, Xiaodong, Wang, Kan, Zheng, Yong

Target Setting Process for Hybrid Electric Drives Using TPA, Jury Study, and Torque Management

2019-01-14536/5/2019

The idea of improved efficiency without compromising the “fun to drive” aspect has renewed the auto industry’s interest toward electrification and hybridization. Electric drives gain from having multiple gear ratios which can use advantageous operating set points thus increasing range. Furthermore, they benefit significantly from frequent decelerations and stopping as is experienced in city driving conditions. To recuperate as much energy as possible, deceleration is done at high torque. This presents an interesting but serious sound quality issue in the form of highly tonal whine harmonics of rapidly changing gears that do not track with vehicle speed thus being objectionable to the vehicle occupants. This paper presents an NVH target setting process for a hybrid electric transmission being integrated into two existing vehicles, one belonging to the premium segment and another aimed at enthusiasts with off-road applications. The demand for power has shifted from mechanical domain into

Singh, Vinod, Parbat, Aniket, Charan, Anil

Gear System Parameters and Its Influence on Gearbox Noise

2019-01-15626/5/2019

Tonal noise due to gears is one of the fundamental noise problems in a gearbox. Gear tooth deflections generate dynamic forces that lead to unwanted load fluctuations, thus noise. Different factors that are considered to control this noise, some to mention like proper gear macro design, microgeometry corrections, and housing compliance. However, identifying the appropriate variable as a measure of contribution to the overall response helps in getting more accurate remedial solutions. Some outputs to track are different harmonic components of TE, temperature effects, components of forces, rim compliance and friction. For evaluation, usually, the amplitudes of individual harmonics of transmission error are related to the respective orders of the noise levels assuming it as one of the primary excitation parameters of gear noise. In this paper, a brief overview of TE and its harmonic distribution is discussed with the example of an ideal gear mesh model and then quantifying TE with the

Dewangan, Yogesh Kumar, Nair, Pranoy Sureshbabu, Nair, Dipin

Gear Bearings

TBMG-345786/1/2019

NASA Goddard Space Flight Center developed gear bearing technology that combines gear and bearing functions into a single unit that significantly improves gear drives for electrical, internal combustion, and turbine motors. The gear bearing design incorporates rifle-true anti-backlash, improved thrust bearing performance, and phase-tuning techniques for superior low-speed reduction. Because it combines gear and bearing functions, it reduces weight, number of parts, size, and cost, while also increasing load capacity and performance.

Design Optimization of a Hybrid Spur Gear

F-0075-2019-14674

5/13/2019

This study develops an optimization technique for a sinusoidal interlock design of a hybrid spur gear consisting of a metallic outer ring to support high contact stress bonded to a composite inner web for weight reduction. Two objectives (mass and shear traction on the metal-composite interface under static loading conditions) were minimized for four design variables subject to two constraints. Borg MOEA, a multi-objective evolutionary algorithm developed at The Pennsylvania State University, and an in-house finite element solver were used to generate Pareto-optimal solutions to this design problem. Two of the designs were then analyzed in greater detail to determine stress distributions throughout the gear. In the future, this technique will be refined and applied to optimization of more representative rotorcraft gears, with the aim of reducing drive train weight and meeting performance requirements.

Gauntt, Sean, Campbell, Robert, McIntyre, Sean

Swept Volume Approach for the Characterization of Pumping Loss of Shrouded Meshed Cylindrical Gears

F-0075-2019-14681

5/13/2019

High speed rotorcraft transmissions are subject to load-independent power losses consisting of drag and pumping loss. Tightly conforming shrouds enclosing the transmission gears are often incorporated to reduce the drag component of the total load independent losses. However, tightly conforming axial shrouding can result in an increase in the pumping loss component. Quantifying the pumping loss of shrouded gear transmissions has been the subject of many studies. This study presents a new approach for estimating pumping loss based on the concept of swept volume borrowed from the positive displacement pump and compressor industry. In this study, pumping loss of shrouded gear transmissions is considered to be related to the swept volume of the gear sets and the downstream flow resistance created by the shroud clearances. The drag loss and pumping loss of a spur gear pair have been determined through testing using the NASA Glenn Research Center Gear Windage Test Facility. The results from

Hurrell, Michael, Delgado, Irebert