The tire is one of the most complex subsystems of the vehicle. It is, however, the least understood of all the components of a car. Without a good tire model, the vehicle simulation handling response will not be realistic, especially for maneuvers that require a combination of braking/traction and cornering. Most of the simplified theoretical developments in tire modeling, however, have been limited to on-road tire models. With the availability of powerful computers, it can be noted that majority of the work done in the development of off-road tire models have mostly been focused on creating better Finite Element, Discrete Element, or Boundary Element models. The research conducted in this study deals with the development of a simplified tire brush-based tire model for on-road simulation, together with a simplified off-road wheel/tire model that has the capability to revert back to on-road trend of behavior on firmer soils. The on-road tire model is developed based on observations and insight of empirical data collected by NHSTA throughout the years, while the off-road tire model is developed based on observations of experimental data and photographic evidence collected by various terramechanics researchers within the last few decades. The tire model was developed to be used in vehicle dynamics simulations for engineering mobility analysis. Vehicle-terrain interaction is a complex phenomena governed by soil mechanical behavior and tire deformation. The theoretical analysis involved in the development of the wheel/ tire model relies on application of existing soil mechanics theories based on strip loads to determine the tangential and radial stresses on the soil-wheel interface. Using theoretical analysis and empirical data, the tire deformation geometry is determined to establish the tractive forces in off-road operation. To illustrate the capabilities of the models developed, a rigid wheel and a flexible tire on deformable terrain is implemented and output of the model was computed for different types of soils; a very loose and deformable sandy terrain and a very firm and cohesive Yolo loam terrain. The behavior of the wheel/tire model on the two types of soil is discussed. The outcome of this work shows results that correlate well with the insight from experimental data collected by various terramechanics researchers throughout the years, which is an indication that the model presented can be used as a subsystem in the modeling of vehicle-terrain interaction to acquire more insight into the coupling between the tire and the terrain. / Ph. D.

The primary goal of this work is to design and implement a clutch and brake system on the single tire Terramechanics rig of Advanced Vehicle Dynamics Laboratory (AVDL) at Virginia Tech. This test rig was designed and built to study the performance of tires in off-road conditions on surfaces such as soil, sand, and ice. Understanding the braking performance of tires is crucial, especially for terrains like ice, which has a low coefficient of friction. Also, rolling resistance is one of the important aspects affecting the tractive performance of a vehicle and its fuel consumption. Investigating these experimentally will help improve tire models performance. The current configuration of the test rig does not have braking and free rolling capabilities. This study involves modifications on the rig to enable free rolling testing when the clutch is disengaged and to allow braking when the clutch is engaged and the brake applied. The first part of this work involves the design and fabrication of a clutch system that would not require major changes in the setup of the test rig; this includes selecting the appropriate clutch that would meet the torque requirement, the size that would fit in the space available, and the capability to be remotely operated. The test rig's carriage has to be modified in order to fit a pneumatic clutch, its adapter, a new transmission shaft, and the mounting frame for the clutch system. The components of the actuation system consisting of pneumatic lines, the pressure regulator, valves, etc., have to be installed. Easy operation of the clutch from a remote location is enabled through the installation of a solenoid valve. The second part of this work is to design, fabricate, and install a braking system. The main task is to design a customized braking system that satisfies the various physical and functional constraints of the current configuration of the Terramechanics rig. Some other tasks are the design and fabrication of a customized rotor, selection of a suitable caliper, and design and fabrication of a customized mounting bracket for the caliper. A hydraulic actuation system is selected since it is suitable for this configuration and enables remote operation of the brakes. Finally, the rig is upgraded with the assembly of these two systems onto it. / Master of Science

Tires play an extremely important role in the operation of a vehicle as they transmit forces between the ground and the vehicle. Consistent efforts have been made over the years towards modeling and simulation of tires and more recently, there has been an increasing need to understand the transient response of tires to various high-frequency events such as anti-lock braking and short-wavelength disturbances from the road. Major thrust has been provided by the tire industry to develop simulation models that accurately predict the dynamic response of tires without the use of computationally intensive tools such as FEA. The objective of this research is to explain the development, implementation and validation of a simulation tool based on a dynamic tire model that would assist in the analysis of the effect of tire belt vibrations on the braking performance of a vehicle. A rigid ring tire model, tandem elliptical cam enveloping model and a rule-based ABS model have been developed for this purpose. These were combined together in a quarter vehicle model and implemented in Matlab-Simulink. These models were developed for adaptation with CarSim to provide a simulation tool that can be utilized in both tire and vehicle design processes. In addition to model implementation, a parameterization procedure was developed to estimate the parameters of the rigid ring tire and enveloping model based on experimental data for a given tire. Validation studies have also been performed to ensure the accuracy and validity of the tire model. Following this, the braking performance of ABS under different road surfaces were evaluated. Based on the simulation results, final conclusions were drawn with regards to the analysis and detailed recommendations for future work directed towards the improvement of the tool were provided. / Master of Science

A differential steered, 13.6 kg robot was developed as an intelligent tire testing system and was used to investigate the potential of using piezoelectric film sensors in small tube-type pneumatic tires to characterize tire-ground interaction.<br />One focus of recent research in the tire industry has been on instrumenting tires with sensors to monitor the tire, vehicle, or external environment. On small robots, tire sensors that measure the forces and deflections in the contact patch could be used to improve energy efficiency and/or mobility during a mission.<br />The robot was assembled from a SuperDroid Robots kit and instrumented with low-cost piezoelectric film sensors from Measurement Specialties between the inner tube and the tire.  An unlaminated and a laminated sensor were placed circumferentially along the tread and an unlaminated sensor was placed along the sidewall.  A slip ring transferred the signals from the tire to the robot. There, the signal conditioning circuit extended the time constant of the sensors and filtered electromagnetic interference.  The robot was tested with a controlled power sequence carried out on polished cement, ice, and sand at three power levels, two payload levels, and with two tire sizes.<br />The results suggest that the sensors were capable of detecting normal pressure, deflection, and/or longitudinal strain.  Added payload increased the amplitude of the signals for all sensors.  On the smaller tires, sensors generally recorded a smaller, wider signal on sand compared to cement, indicating the potential to detect contact patch pressure and length.  The signals recorded by the unlaminated sensor along the tread of the smaller tire were lower on ice compared to cement, indicating possible sensitivity to tractive force.  Results were less consistent for the larger tires, possibly due to the large tread pattern. / Master of Science

The tire–terrain interaction is an essential criterion for assessing tire performance. Understanding the complex characteristics of the dynamic interactions of tires and terrain required a detailed and deep study on the characteristics of the contact patch area of the tire. Most of the studies conducted to determine the properties of the contact patch considered the tire-road interaction in a static condition and there are a limited number of research studies that focused on the dynamic behavior of the tire at the contact area especially when the real-time measurement of the dynamic contact area of the rolling tire with high slip ratio is the matter of interest. In order to completely understand the tire dynamics at the contact patch, a novel optical method based on light refraction and reflection is proposed for the measurement of contact area between the tread of the tire and a rigid transparent surface. To this end, constructing an indoor test rig is required. In this research, a three-dimensional drawing software Autodesk Inventor has been used to analyze a customized testing facility. An indoor test rig has been designed and manufactured to visualize the contact area of a rolling tire. A supporting mechanical system incorporated into this test rig allows providing the tire with variable camber angles and slip ratios. For the rolling tire, a digital camera GoPro has been used under a glass panel to record the tread pattern in detail when the tire passes over it during the test, to represent the footprint for a high slip ratio. From the image obtained with this system, the length, width, ratio, and shape of the patch can be determined, which are related to the effect on tire traction performance. This study specifically proposes a digital image correlation technology that can be used to capture the contact patch of a passenger car tire 205/55R16 and to obtain the geometry features of the contact area. Based on the appropriate image processing techniques in the MATLAB, a precise reconstruction of tire footprint was realized. The results for the footprint properties of the tire with an applied normal load of 4 kN and tire inflation pressures of 21 Psi for free rolling, static state, and the slip ratio of 0%, 2%, 4%, 6%, 8%, 10%, 12%, 15%, 20%, 25%, 30%, and 35% are presented. Presented results in the paper will show that the system is robust enough to obtain a real-time dynamic measurement. The novel method based on digital image processing revealed by the author can be validated as a precision measurement system of footprint characteristics. / Master of Science / The tire–road interaction is an essential criterion for assessing tire performance. Most of the studies conducted to determine the properties of the contact area considered the tire-road interaction in a static condition and there are a limited number of research studies that focused on the dynamic behavior of the tire at the contact area. Thus, a novel optical method based on light refraction and reflection is proposed for the measurement of contact area between the tread of the tire and a rigid transparent surface. To this end, constructing an indoor test rig is required. In this research, a three-dimensional drawing software has been used to analyze a customized testing facility. An indoor test rig has been designed and manufactured to visualize the contact area of a rolling tire. A digital camera has been used under a glass panel to record the tire footprint in detail during the test. The length, width, ratio, and shape of the tire footprint can be determined, which are related to the effect on tire traction performance. Based on the appropriate image processing techniques in the MATLAB, a precise reconstruction of tire footprint was realized. The results for the footprint properties of the tire with an applied normal load of 4 kN and tire inflation pressures of 21 Psi for free rolling, static state, and the different slip ratios are presented. Presented results in the paper will show that the system is robust enough to obtain a real-time dynamic measurement.

The effect of that the tire has on the overall aerodynamic drag in a car-tire assembly has been studied and deemed considerable from past studies. It has been shown that to know how tire parameters affect the drag on the car-tire assembly, it is important to understand how the vehicle body and the tires influence the flow structures. Previous studies have focused on the tire attributes that have some impact on the aerodynamic performance of the vehicle. These tire attributes, however, haven't been studied to the extent where one can get a better understanding of the impact of each of these attributes. This paper studies the impact that specific tire attributes have on the overall aerodynamic drag on the vehicle based on a thorough and systematic sensitivity study. The effect of tire attributes in a vehicle assembly as well as the sensitivity study of a rim protector on a standalone tire is conducted. This helps in better understanding the flow structures around the car body and around the tire for the improvement in the aerodynamic performance of the vehicle. This is a two-part study. One component of this study is a parametric sensitivity analysis of a tire in a tire – vehicle assembly. The other component is a parametric sensitivity analysis of the rim protector design on a standalone tire. / Master of Science / The drag performance is one of the most important factors that contributes to the overall efficiency of a vehicle. There has always been a huge demand in the automotive industry for such studies. Over the years, experimental studies conducted have shown to be invaluable to the industry. But a big downside to experimental studies is that they are extremely expensive. Experimental studies on Vehicle bodies require a wind tunnel and expensive measurement equipment. This has led to a high demand for more computational studies in this field. Various authors over the past few years have studied and challenged various solution procedures used in computational studies. The trade-off for these studies is always cost vs. accuracy. This thesis attempts to simulate both for a vehicle assembly as well as a standalone tire model to come up with a robust solution method for the computational analysis of flow over a vehicle body. The goal of this thesis is to conduct a parametric sensitivity study for the cross-section profile of the tire in vehicle assembly as well as a parametric sensitivity study for the rim protector profile of the tire in a standalone tire. At the end of the study, we will get a better understanding of the impact that each of the parameters have on the drag performance of the vehicle and the standalone tire.

by Leung Koon-keung Jack. / Bibliography: leaf 54 / Thesis (M.B.A.)--Chinese University of Hong Kong, 1982

Tire bales are a suitable construction material for conditions which require a lightweight material with high permeability and strength. Although several tire bale case histories have been reported in the literature, only limited material properties of the bales are available. Determining the mechanical and physical properties of the tire bales is necessary for the proper design and construction of future tire bale structures. The development and results from a series of large scale laboratory and field test procedures, used to determine the mechanical and physical characteristics of a tire bale structure, are provided in this dissertation. A tire bale structure, as compared to the individual tire bale, is defined as two or more tire bales stacked upon each other resulting in an interface contact between layers of the tire bales. Results from the test programs indicate that the interface between the tire bales controls the strength and compressibility of the bale structure. The strength of the interface was characterized utilizing a large scale direct shear test, which was modified to include the effects of moisture, soil infill and stress orientation on the interface strength. Interface shear stresses were used to define shear strength parameters for the different tire bale interfaces. The compressibility of the tire bale structure was characterized utilizing a large scale vertical compression test. The influence of the individual tire bale geometry on strength and compressibility was determined by conducting the large scale tests on two bale types, the standard block bale and the standard cylinder bale. A tire ridge interface model was developed to represent the physical characteristics of the tire bales that control the strength and deformations along the interface. Tensions within the baling wires were measured during the direct shear and compression tests using strain gauges attached to the baling wires. A tension meter was also developed so that the baling wire tensions could be determined without damaging the tire bale and baling wires. A destructive expansion pressure test was used at the conclusion of the research program to determine the pressures the tire bale exerts on the surrounding structure after wire breakage. / text

About half of the building stock in Turkey is masonry type and one fourth of the building stock is one-storey brick type masonry buildings. Especially the rural masonry houses are commonly constructed by their own residents without any engineering knowledge. Traditional masonry houses usually have heavy roofs which generate large lateral forces on walls during earthquakes. Readily available retrofitting techniques are mostly complicated and costly making it not feasible for uneducated poor residents to strengthen their own houses. The aim of this thesis is to develop a new alternative strengthening technique using scrap tires that is economic and easy to apply on the walls of one-story masonry houses. In order to investigate the usage of scrap tires for masonry wall post-tensioning, forty three scrap tire rings (STRs) from nine different brands and nine rim-rings direct tension experiments were conducted. The average tensile load capacities of STRs and rim-rings were found as 132.6 kN and 53 kN, respectively. Six strip walls (i.e., four brick- and two briquette-walls) strengthened by applying post-tensioning loads with STCs and hybrid system were tested in out-of-plane bending direction. The out-of-plane capacity of the brick and briquette walls increased up to about 9 times and 5 times with respect to their nominal capacities, respectively. Finally, two-full scale traditional masonries were tested by the tilting table. The capacity of strengthened house increased 75% with respect to the unstrengthened one. The results obtained form the conducted tests are highly promising and suggest that the method can be used as a low-cost and simple strengthening technique for seismically deficient single storey, masonry type houses.

Thesis (M.A.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 113-117). Also available via the World Wide Web in PDF format.