An official website of the United States government
Abstract Fuel efficiency becomes very important for new vehicles. Therefore, improving the aerodynamics of tires has started to receive increasing interest. While the experimental approaches are time-consuming and costly, numerical methods have been employed to investigate the air flow around tires. Rotating boundary and contact patch are important challenges in the modeling of tire aerodynamics. Therefore, majority of the current modeling approaches are simplified by neglecting the tire deformation and contact patch. In this study, a baseline computational fluid dynamics (CFD) model is created for a tire with contact patch. To generate mesh efficiently, a hybrid mesh, which combines hex elements and polyhedral elements, is used. Then, three modeling approaches (rotating wall, multiple reference frame, and sliding mesh) are compared for the modeling of tire rotation. Additionally, three different tire designs are investigated, including smooth tire, grooved tire, and grooved tire with open rim. The predicted results of the baseline model agree well with the measured data. Additionally, the hybrid mesh shows to be efficient and to generate accurate results. The CFD model tends to overpredict the drag of a rotating tire with contact patch. Sliding mesh approach generated more accurate predictions than the rotating wall and multiple reference frame approaches. For different tire designs, tire with open rim has the highest drag. It is believed that the methodology presented in this study will help in designing new tires with high aerodynamic performance.
more »
« less
Experimental Investigation of the Tractive Performance of Pneumatic Tires on Ice
ABSTRACT This investigation was motivated by the need for performance improvement of pneumatic tires in icy conditions. Under normal operation, the pneumatic tire is the only force-transmitting component between the terrain and the vehicle. Therefore, it is critical to grasp the understanding of the contact mechanics at the contact patch under various surfaces and operating conditions. This article aims to enhance the understanding of the tire-ice contact interaction through experimental studies of pneumatic tires traversing over smooth ice. An experimental design has been formulated that provides insight into the effect of operational parameters, specifically general tire tread type, slip ratio, normal load, inflation pressure, ice surface temperature, and traction performance. The temperature distribution in the contact patch is recorded using a novel method based on thermocouples embedded in the contact patch. The drawbar pull is also measured at different conditions of normal load, inflation pressure, and ice temperatures. The measurements were conducted using the Terramechanics Rig at the Advanced Vehicle Dynamics Laboratory. This indoor single-wheel equipment allows repeatable testing under well-controlled conditions. The data measured indicates that, with the appropriate tread design, the wheel is able to provide a higher drawbar pull on smooth ice. With an increase in ice surface temperature, a wet film is observed, which ultimately leads to a significant decrease in traction performance.
more »
« less
- Award ID(s):
- 1650423
- PAR ID:
- 10216180
- Date Published:
- Journal Name:
- Tire Science and Technology
- Volume:
- 48
- Issue:
- 1
- ISSN:
- 0090-8657
- Page Range / eLocation ID:
- 22 to 45
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)ABSTRACT Tire-pavement interaction noise (TPIN) is one of the main sources of exterior noise produced by vehicles traveling at greater than 50 kph. The dominant frequency content is typically within 500–1500 Hz. Structural tire vibrations are among the principal TPIN mechanisms. In this work, the structure of the tire is modeled and a new wave propagation solution to find its response is proposed. Multiple physical effects are accounted for in the formulation. In an effort to analyze the effects of curvature, a flat plate and a cylindrical shell model are presented. Orthotropic and nonuniform structural properties along the tire's transversal direction are included to account for differences between its sidewalls and belt. Finally, the effects of rotation and inflation pressure are also included in the formulation. Modeled frequency response functions are analyzed and validated. In addition, a new frequency-domain formulation is presented for the computation of input tread pattern contact forces. Finally, the rolling tire's normal surface velocity response is coupled with a boundary element model to demonstrate the radiated noise at the leading and trailing edge locations. These results are then compared with experimental data measured with an on-board sound intensity system.more » « less
-
Utility trucks with boom equipment function on environmentally sensitive areas and severe terrains where off-road conditions may cause significant damage to the trucks’ mobility and their safe operation. Indeed, considerable variations of landscape elevation and dynamic changes of terrain properties lead to extensive differences in the wheel normal reactions, drastic fluctuations of the rolling resistance at each tire, and finally, substantial changes in the total resistance to motion, which includes both the tire rolling resistance and the resistance due to the truck gravity component. Additionally, lateral forces caused by truck inclinations can lead to instability in motion, too. As a result, a utility truck can become immobilized in either longitudinal or lateral direction of movement because of one or the combination of the following events – loss of longitudinal mobility due to extensive tire slippage at some/all wheels, loss of lateral mobility due to tire side skid or rollover of the truck. To eliminate the above-listed causes that can lead to the utility truck immobilization, this study suggests a novel approach to managing the input/output factors that influence both longitudinal and lateral forces of the utility truck. In fact, the 3D morphing of the boom equipment is proposed as the input factor for managing the wheel normal reactions as the outputs. Ultimately, a changeable positioning of the boom equipment relative to the truck frame results in variable wheel normal reactions, which are the main contributors to the normal tire deformation and soil compaction, and thus, to the rolling resistance of each and all tires. This paper presents and discusses the method and results of computational simulations of the F450-based utility truck with boom equipment on medium mineral soil. The normal reaction at each wheel is evaluated under which the boom equipment morphs safely without causing roll over of the truck and, consequently, the total resistance to the motion force is determined. Modeling and simulation of the truck were conducted with the use of terramechanics-based tire-terrain models. This research study of the rolling resistance contributes to a research project on morphing utility truck, dynamics in severe terrain conditions. Keywords: Utility Truck, Morphing, Terrain Mobilitymore » « less
-
This paper presents mobility modes and control methods for the SnoWorm, a passively-articulated multi-segment autonomous wheeled vehicle concept for use in Earth’s polar regions. SnoWorm is based on FrostyBoy, a four-wheeled GPS guided rover built for autonomous surveys across ice sheets. Data collected from FrostyBoy were used to ground-truth a ROS/Gazebo model of vehicle-terrain interaction for simulations on snow surfaces. The first mobility mode, inchworm movement, uses active prismatic joints that link the SnoWorm’s segments, and allow them to push and pull one another. This pushing and pulling of individual segments can be coordinated to allow forward motion through terrain that would immobilize a single-segment vehicle. The second mobility mode utilizes fixed links between SnoWorm’s segments and uses the tension or compression measured in these links as a variable to control wheel speeds and achieve a targeted force distributions within the multi-segment vehicle. This ability to control force distribution can be used to distribute a towed load evenly across the entire SnoWorm. Alternatively, the proportion of the load carried by individual segments can be increased or decreased as needed based on each segment’s available drawbar pull or wheel slip.more » « less
-
Ambient energy harvesting using piezoelectric transducers is becoming popular to provide power for small microelectronics devices. The deflection of tires during rotation is an example of the source of energy for electric power generation. This generated power can be used to feed tire selfpowering sensors for bicycles, cars, trucks, and airplanes. The aim of this study is to optimize the energy efficiency of a rainbow shape piezoelectric transducer mounted on the inner layer of a pneumatic tire for providing enough power for microelectronics devices required to monitor tires. For this aim a rainbow shape piezoelectric transducer is adjusted with the tire dimensions and excited based on the car speed and strain. The geometry and load resistance effects of the piezoelectric transducer is optimized using Multiphysics modeling and finitemore » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2346/tire.18.460409
