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Light Duty Truck Rear Axle Thermal Modeling

FCA-Mohammad Nahid
FCA US LLC-Joydip Saha, Sadek Rahman
  • Technical Paper
  • 2020-01-1388
To be published on 2020-04-14 by SAE International in United States
More stringent Federal emission regulations and fuel economy requirements have driven the automotive industry toward more sophisticated vehicle thermal management systems to best utilize the waste heat and improve driveline efficiency. The final drive unit in light and heavy duty trucks usually consists of geared transmission and differential housed in a lubricated axle. The automotive rear axles is one of the major sources of power loss in the driveline due to gear friction, churning and bearing loss and have a significant effect on overall vehicle fuel economy. These losses vary significantly with the viscosity of the lubricant. Also the temperatures of the lubricant are critical to the overall axle performance in terms of power losses, fatigue life and wear. In this paper, a methodology for modeling thermal behavior of automotive rear axle with heat exchanger is presented to predict the axle lubricant temperature rise and study the effect of coolant temperature on the axle warm-up and efficiency for a typical EPA fuel economy driving cycle. Thermal axle consists of automotive rear axle with a heat…
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Facility for Complete Characterization of Suspension Kinematic and Compliance Properties of Wheeled Military Vehicles

SEA, Ltd.-Dale Andreatta, Gary Heydinger, Anmol Sidhu, Scott Zagorski
  • Technical Paper
  • 2020-01-0175
To be published on 2020-04-14 by SAE International in United States
As part of their ongoing efforts to model and predict vehicle dynamic behavior, the US Army’s Ground Vehicle Systems Center procured a facility in two phases. The facility is called the Suspension Parameter Identification and Evaluation Rig (SPIdER) and has a capacity covering all of the military’s wheeled vehicles, with vehicle weights to 100,000 lbs (45,400 kg), up to 150 inches wide, with any number of axles. The initial phase had the ability to measure bounce and roll kinematic and compliance properties. The SPIdER is the companion machine to the Vehicle Inertia Parameter Measuring Device (VIPER) which measures the inertia properties of vehicles of similar size. In 2015, the final phase of the SPIdER was completed. This phase includes ground plane wheel pad motion so that lateral, longitudinal, and aligning moment compliance and kinematic properties can be measured. These capabilities greatly enhance the SPIdER’s features, giving it the ability for making complete suspension and steering system kinematic and compliance measurements. Horizontal forces and aligning moments can be applied up to the limits of tire slip.…
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Ultralight axle development-fracture mechanics life predictions (40% weight reduction).

Magna Drivetrain of America Inc.-Michael Bujold
  • Technical Paper
  • 2020-01-0179
To be published on 2020-04-14 by SAE International in United States
This paper details the light weight developments with the use of fracture mechanics technology. Forty percent weight reduction was achieved in an automotive axle. Novel pinion cartridge, ring gear , and differential designs were incorporated in this project to achieve weight, efficiency, noise and performance targets. A fracture mechanics (crack growth model) was used to determine steel cleanliness levels required as component size was optimized based on processing variables(steel material properties, initial flaw size, residual stress, duty cycle analysis,...). Prototype hypoid gear samples made from two variations of steel cleanliness were used to qualify the crack growth models with and without the addition of shot peening to vary the residual stress profiles for life requirements. Housing material variations of aluminum and magnesium were used for additional weight reduction in this program.
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Virtual Method for Simulating Driveline Launch Shudder for Solid Axle Suspension Architecture Vehicles

FCA Engineering India Pvt., Ltd.-Dhanasekar Venkatesan
FCA US LLC-Abhishek Paul, Kevin Thomson
  • Technical Paper
  • 2020-01-1271
To be published on 2020-04-14 by SAE International in United States
Driveline launch shudder is a second-order vibration phenomenon excited by the driveline system in vehicles. It is experienced as low frequency tactile vibrations at the vehicle seat track and is further deteriorated by a high torque demand from the engine. These vibrations are unwanted and affect the vehicle ride quality. A virtual method has been developed in ADAMS/Car to simulate the driveline launch shudder event for solid axle suspension architecture vehicles. Detailed modeling of the full vehicle system with appropriate boundary conditions has been presented. The simulated driveline launch shudder event has been quantified in the form of axle windup and accelerations at the driveline pinion, center bearing and seat track locations. A physical test correlation case study has been performed to validate the developed virtual method. This virtual method is also successfully applied to provide a driveline launch shudder mitigation enabler to improve vehicle ride performance.
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Predictive Break-In and Rapid Efficiency Characterization of Beam Axles

FCA US LLC-Timothy Schumaier, Siqin Wei, Jasbir Singh
FEV North America, Inc.-Patrick R. Bias, Thomas D'Anna
  • Technical Paper
  • 2020-01-1413
To be published on 2020-04-14 by SAE International in United States
This report is the result of a project by the USCAR Transmission Working Group Axle Subteam to rethink axle testing and develop a new beam axle break-in and efficiency characterization procedure with several goals in mind: Ensure the axle’s efficiency does not change as it is being characterized, build a detailed map of efficiency at a wide range of operating points, and minimize dyno time. The resulting break-in procedure uses an asymptotic regression approach to predict not only what the fully broken in efficiency of the axle is, but also how much the efficiency of the axle will change during the characterization phase. This allows the break-in cycle to terminate when the efficiency of the particular test article reaches a target stability, rather than after a predetermined duration, minimizing dyno time and ensuring that the completeness of the break-in is consistent across test pieces. The efficiency characterization procedure uses rapid probing of various torque and speed points as axle temperature rises to build a map of efficiency at a wide range of speed, load, and…
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Experimental and Computational Studies of the No-Load Churning Loss of a Truck Axle

Dana Incorporated-Steven Wesolowski
Lubrizol-Farrukh Qureshi
  • Technical Paper
  • 2020-01-1415
To be published on 2020-04-14 by SAE International in United States
This paper summarizes the work performed in predicting and measuring the contribution of oil churning to the no-load losses of a commercial truck axle at typical running speeds. A computational fluid dynamics (CFD) analysis of the churning losses was performed. The CFD modeling accounted for design geometry, operating speed, temperature, and lubricant properties. The model computed the torque loss due to oil churning due to the viscous and inertia effects of the fluid. It also displayed the flow pattern generated and computes the oil volume fraction at any location within the volume. CFD predictions of power losses were then compared with no load measurements made on a specially developed dynamometer driven test stand. The same axle that was used in the CFD model was tested in three different configurations: with axle shafts, with axle shafts removed, and with ring gear and carrier removed. This approach to testing was performed to determine the contribution of each source of loss (bearings, seals, and churning) to the total loss. After bearing and seal loss measurements and predictions were…
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Fast Conception (FastCon) – A tool for concept design and optimization of twist beam axles

University of Siegen - FLB-Jens Olschewski, Xiangfan Fang, Kanlun Tan
  • Technical Paper
  • 2020-01-0920
To be published on 2020-04-14 by SAE International in United States
The common development phase of a TBA usually starts with several concepts, based on benchmarking or empirical values. Based on these concepts the first CAD Models are designed and then converted into FE- and MKS models, so that the stiffness and kinematic characteristics can be evaluated. From these first results, it can be estimated which concept is suitable to fulfill all the requirements. The selected concept will be further optimized via numerous CAD and CAE iterations until it meets all concept targets. Due to this process, the quality and the development time of the final development strongly depends on the chosen concept. The presented algorithm FastCon-TBA (FastConcept Twistbeamaxle) is a development tool, which simplifies the process described above and makes it more efficient. Based on the concept variables FastCon analytically evaluates all relevant kinematic and elastokinematic characteristics. To calculate the properties each part of the TBA is idealized as a beam. Each beam element can have a specific orientation and crossection, which allows to approximate the deformation behavior of the TBA. Considering the boundary conditions…
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Development of Active Rear Axles Steering Controller For 8X8 Combat Vehicle

OntarioTech University-Moataz Ahmed, Moustafa El-Gindy, Haoxiang Lang, Mohamed Omar
  • Technical Paper
  • 2020-01-0174
To be published on 2020-04-14 by SAE International in United States
Lateral dynamic control considered to be crucial to enhance the handling characteristics and stabilization of a vehicle as a safety demand. In this paper, an active rear axles steering control system will be developed using optimal quadratic regulator (LQR) control methodology. The controller aims to minimize the vehicle sideslip and consequently increase its handling stability and transient state performance. The controller design has been utilized the independent steering of the vehicle`s 3rd and 4th axles as control inputs. Furthermore, the developed controller will be combined with feedforward zero sideslip (ZSS) controller based on the steady state model of the vehicle and satisfying the Ackermann steering condition. In addition, the steady state handling performance will be evaluated using Skid Pad test. The transient state performance will be assessed at low coefficient of friction (COF) surface using FMVSS 126 Electronic Stability Control (ESC) system test speed, while Open Loop Step Slalom Test will be used for assessing the controller at high COF. The controllers will be implemented using MATLAB Simulink and will be simulated in a co-software…
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Longitudinal Vehicle Dynamics Modeling for AWD/4WD Vehicles to study torque split between front and rear axles.

FCA US LLC-Prashant Sondkar, Swapneel Gharpure, Vince Schrand, Pradeep Attibele
  • Technical Paper
  • 2020-01-1410
To be published on 2020-04-14 by SAE International in United States
All-wheel Drive (AWD) is a mature technology and most automobile manufacturers offer this feature on their vehicles. Improved traction, enhanced vehicle stability, and better handling are some of the key characteristics of AWD vehicles which are achieved by distributing appropriate level of torque to the front and rear axles. Accurately capturing the torque split between the two axles is essential for sizing of driveline components like gears, bearings, and shafts. Traditionally, the torque split is considered to be either 50-50%, or solely proportional to the static weight distribution between the two axles. Design decisions are made based on historical test data. In this paper longitudinal vehicle dynamics model for AWD systems is proposed to understand the influence of various key factors such as dynamic weight transfer, compliance of driveline components, changing tire radius, and tire pressure on the torque split. Comparison with the test data is performed to understand the significance and limitations of the model. While more detailed models have been built and used for various purposes, to the authors' knowledge, this is the…
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An extended structural stress method for predicting fatigue life of non-welded axle components

American Axle & Manufacturing, Inc.-Anoop Vasu, Shizhu Xing, Jifa Mei, William Webster, Scott Jacob, Jerry Chung, Ravi Desai
  • Technical Paper
  • 2020-01-0606
To be published on 2020-04-14 by SAE International in United States
Leaking in a cover-pan of an axle assembly can result in severe durability issues. Preliminary tests of axle assembly for a fore-aft beaming test (replicating the load on the axle while accelerating or decelerating the vehicle) exhibited MPI indications of crack/leak adjacent to multiple bolt holes on the cover-pan. FEA results were able to capture the critical locations accurately. However, the crack initiation predictions were extremely conservative in nature due to the stress riser next to the bolted joints. Testing also indicated that a surface crack due to the bolt-edge-contact could withstand significant load cycles before a leak is formed (through thickness crack in the cover-pan). A unique simulation framework is implemented to perform the crack propagation life of the axle component. Traction structural stress method, build to predict the propagation life of welded components, was extended to predict the life of non-welded components. Unlike the welded components, mean-stress effect needs to be considered for predicting the propagation life. The test results from multiple axle designs indicate that the suggested method could predict the cover-pan…