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Vibrations is a phenomenon that can cause problems to systems if not dealt with. In heavy duty trucks, vibrations are mainly caused by uneven roads and from the combustion engine. Vibrations can damage components, reduce their service life and cause discomfort for the driver. To manage the problem, vibration isolators can be used to absorb energy and thus reduce the vibrations. Rubber is a commonly used material for vibration isolators thanks to its viscoelastic properties. However, due to the characteristics of rubber, there are difficulties to make accurate simulation models of components such as vibration isolators. To improve the accuracy in simulations, physical testing can be performed to measure the material properties and characteristics such as hysteresis to get a better understanding of how the material and the component will behave. The purpose of the master thesis was to generate and develop concepts of a test rig for a specific vibration isolator from Scania where the force as a function of displacement in the component’s Z-direction should be measured as well as the force in the component’s Y-direction. Further, the component should be compressed in a vertical linear motion. Based on the background information, the following research questions were stated: - How can a hysteresis curve based on frequency input be found by performing physical testing? - How can a test rig be designed to test and measure the material properties of a rubber component in order to parametrize the material? The vibration isolator was investigated and analyzed. From the analysis, seven concepts were generated and were evaluated with a Pugh matrix. From the evaluation, two concepts were chosen to be further developed before a final evaluation using a desirability chart was made. The master thesis resulted in two concepts that were developed named Hinged beam and Guiding plates. Guiding plates was the concept that scored the best in the final evaluation, but the concepts had different strength and weaknesses. Both concepts fulfilled the requirement of compressing the vibration isolator in a vertical linear motion but the measurement of the force in the component’s Y-direction needs to be further investigated. / Vibrationer är ett fenomen som kan orsaka problem för olika typer av system om det inte hanteras. I lastbilar är vibrationer huvudsakligen orsakade av ojämnt underlag samt av förbränningsmotorn. Vibrationerna kan orsaka skada på komponenter, reducera deras livslängd och även orsaka obehag för föraren. Det här problemet kan hanteras genom användning av vibrationsisolatorer som minskar effekten fr.n vibrationerna genom att absorbera dess energi. Gummi är ett material som ofta används för att isolera vibrationer tack vare dess viskoelastiska egenskaper. Egenskaperna gör det dock svårt att skapa noggranna simuleringsmodeller av komponenter så som vibrationsisolatorer. För att öka noggrannheten i simuleringarna kan fysisk testning genomföras och materialegenskaper så som hysteres kan mätas för att få en bättre förståelse för hur både material och komponent beter sig med olika laster. Syftet med det här masterexamensarbetet var att generera och utveckla koncept för testriggar för en specifik vibrationsisolator tillhandahållen av Scania. Kraft som funktion av förskjutning i komponentens Z-riktning samt kraft i dess Y-riktning skulle vara möjligt att mätas. Utöver det var ett krav att komponenten endast ska komprimeras i en vertikal linjär rörelse. Baserat på bakgrundinformationen kunde följande forskningsfrågor formuleras: - Hur kan en frekvensbaserad hystereskurva tas fram genom fysisk testning? - Hur kan en testrigg designas för att kunna testa och mäta materialegenskaper hos en gummikomponent för att kunna parametrisera materialet? Vibrationsisolatorn undersöktes och analyserades. Efter analysen genererades sju koncept som utvärderades med en Pugh matris. Utvärderingen resulterade i att de två bäst presterande koncepten valdes för vidareutveckling innan en sista utvärdering genomfördes med hjälp av ett så kallat desirability chart. Masterexamensarbetet resulterade i två koncept som vidareutvecklades, ett som kallas Hinged beam och ett vid namn Guiding plates. Guiding plates var det konceptet som presterade bäst i den slutgiltiga utvärderingen, men de olika koncepten har dock olika styrkor och svagheter. Båda koncepten uppnådde kraven gällande att kompression av vibrationsisolatorn endast ska ske i en vertikal rätlinjig rörelse men hur krafterna i komponentens Y-riktning ska mätas behöver vidare undersökning.

Studded tires are widely used in Nordic areas like Sweden for its good road-gripping performance on icy roads. However, the pavement wear and aerosol caused by studded tires become big concerns considering the usage of studded tires. Studies are carried to quantify the wear and aerosol generated during the process. Among the existing test rigs, most of them which includes a full wheel as specimen have relatively large size. This thesis aims on designing a full wheel testrig with small scale which can fit in a common lab room and be easy to operate. / Dubbdäck används i stor utsträckning i nordiska områden som Sverige för sin goda väggreppande prestanda på isiga vägar. Trottoarslitage och aerosol som orsakas av dubbdäck blir dock stora bekymmer med tanke på användning av dubbdäck. Studier genomförs för att kvantifiera slitage och aerosol som genereras under processen. Bland de befintliga testriggarna har de flesta, som innehåller ett helhjul som prov, en relativt stor storlek. Denna avhandling syftar till att designa en fullhjulstestrigg med liten skala som kan passa i ett gemensamt labbrum och vara lätt att använda.

Successful race teams rely heavily on track testing to search for the ideal suspension setup. As more restrictions are placed on the amount of on-track testing by major racing sanctioning bodies, such as NASCAR, teams have increased their attention to alternate testing methods to augment their track data and better understand the dynamics of their racecars. One popular alternate to track testing is 8-post dynamic shaker rig testing. Eight-post rig testing gives the team a better understanding of the vehicle's dynamics before they arrive at the race track, allowing them to use their limited track testing time more efficiently. While 8-post rig testing certainly is an attractive option, an extensive test matrix is often required to find the best suspension setups. To take full advantage of 8-post rig tests, more efficient experimental methods are needed. Since investigating shock absorber selection is often the most time-consuming task, this study focuses on developing more efficient methods to select the best shock absorber setups. This study develops a novel method that applies dynamic substructuring and system identification to generate a mathematical model that predicts the results of future tests as both command inputs and components are changed. This method is used to predict the results of 8-post rig tests as actuator commands and shock absorber forces are varied. The resulting model can then be coupled with shock absorber models to simulate how the vehicle response changes with shock absorber selection. This model can then be applied to experimental design. First, a physically-motivated nonlinear dynamic shock absorber model is developed, suitable for quickly fitting experimental data and implementing in simulation studies. Next, a system identification method to identify a vehicle model using experimental data is developed. The vehicle model is then used to predict response trends as shock absorber selection is varied. Comparison of simulation and experimental results show that this model can be used to predict the response levels for 8-post rig tests and aid in streamlining 8-post rig testing experimental designs. / Ph. D.

This study provides a detailed experimental evaluation of wheel-rail interaction for railroad vehicles, using the Virginia Tech Federal Railroad Administration (VT-FRA) Roller Rig. Various contact dynamics that emulate field application of railroad wheels on tracks are set up on the rig under precise, highly-controlled and repeatable conditions. For each setup, the longitudinal and lateral traction (creep) forces are measured for different percent creepages, wheel loads, and angles of attack. The tests are performed using quarter-scaled wheels with different profiles, one cylindrical and the other AAR-1B with a 1:20 taper. Beyond the contact forces, the wheel wear and the deposition of worn materials are measured and estimated as a function of time using a micron-precision laser optics measurement device. The change in traction versus amount of worn material at the contact surface is analyzed and related to wheel-rail friction. It is determined that the accumulation of the worn material at the contact surface, which appears as a fine gray powder, acts as a friction modifier that increases friction. The friction (traction) increase occurs asymptotically. Initially, it increases rapidly with time (and worn material accumulation) and eventually reaches a plateau that defines the maximum friction (traction) at a stable rate. It is estimated that the maximum is reached when the running surface is saturated with the worn material. Prior to the saturation, the friction increases directly with an increasing amount of deposited material. The material that accumulates naturally at the surface—hence, referred to as "natural third-body layer"—is estimated to be a ferrous oxide. It has an opposite effect from the Top of Rail (ToR) friction modifiers that are deposited onto the rail surface to reduce friction in a controlled manner. Additionally, the results of the study indicate that longitudinal traction decreases nonlinearly with increasing angle of attack (AoA), while lateral traction increases, also nonlinearly. The AoA is varied from -2.0 to 2.0 degrees, representing a right- and left-hand curve. Lateral traction increases at a high rate with increasing AoA between 0.0 – 0.5 degrees, and increases at a slow rate beyond 0.5 degree. Similarly, longitudinal traction reduces at a high rate for smaller AoA and at a slower rate for larger AoA. For the tapered wheel, an offset in lateral forces is observed for a right-hand curve versus a left-hand curve. The wheel taper generates a lateral traction that is present at all times. In one direction, it adds to the lateral traction due to the AoA, while in the opposite direction, it subtracts from it, resulting in unequal lateral traction for the same AoA in a right-hand versus a left-hand curve. The change in traction with changing wheel load is nearly linear under steady state conditions. Increasing the wheel load increases both longitudinal and lateral tractions linearly. This is attributed to the friction-like behavior of longitudinal and lateral tractions. An attempt is made to measure the contact shape with wheel load using pressure-sensitive films with various degrees of sensitivity. Additionally, the mathematical modeling of the wheel-roller contact in both pure steel-to-steel contact and in the presence of pressure-sensitive films is presented. The modeling results are in good agreement with the measurements, indicating that the pressure-sensitive films have a measurable effect on the shape and contact patch pressure distribution, as compared with steel-to-steel. / Doctor of Philosophy / This study provides a detailed experimental evaluation of wheel-rail interaction for railroad vehicles, using the Virginia Tech Federal Railroad Administration (VT-FRA) Roller Rig. Better understanding the dynamics and mechanics of wheel-rail interaction would significantly contribute to the development of technologies, materials, and operational methods that can further improve fuel efficiency, and reduce wheel and rail wear. Considering that the railroads are the backbone of cargo and passenger transportation and are critical to economic well-being, the results of this study are expected to contribute to the betterment of society. An attempt is made to emulate the field application of railroad wheels on tracks on the rig under precise, highly-controlled and repeatable conditions. For each set up, the contact forces are measured for different parameters, such as wheel loads. Beyond the contact forces, the wheel profile degradation and the deposition of worn materials are measured and estimated as a function of time using a micron-precision laser optics measurement device. It is determined that the accumulation of the worn material at the contact surface, which appears as a fine gray powder, increases contact forces. The effect of wheel load on contact forces is almost linear. Additionally, the results of the study indicate that the yaw angle between the wheel and the roller (AoA) changes the contact forces direction, which has a higher rate of change for a small AoA such as 0.0 – 0.5 degrees, compared to a larger AoA. An attempt is made to measure the contact shape with wheel load and AoA using pressure-sensitive films with various degrees of sensitivity. Additionally, the mathematical modeling of the wheel-roller contact in both pure steel-steel contact and in the presence of pressure-sensitive films is presented. As expected, both the model and test result indicate that the presence of a film at the contact surface changes both the dimensions and pressure distribution at the contact patch. Quantifying the distortion that occurs as a result of the pressure-sensitive film allows for a better assessment of the pressure distribution measurements that are made with the films in order to potentially discount the resulting distortions.

Yes / An experimental study of wheel movement arising from compliance in the front suspension and steering system of a passenger car during braking is presented. Using a Kinematic and Compliance (K&C) test rig, movement of the front wheels and the suspension sub-frame, together with corresponding changes in suspension / steering geometry under simulated braking conditions, were measured and compared with dynamic measurements of the centre points of the front wheels. The resulting knowledge of front wheel deflections has enabled the causes and effects of steering drift during braking to be better understood in the design of front suspension systems for vehicle stability.

The focus of this study is on the development of a state-of-the-art single-wheel roller rig for studying contact mechanics and dynamics in railroad applications. The use of indoor-based simulation tools has become a mainstay in vehicle testing for the automotive and railroad industries. In contrast to field-testing, roller rigs offer a controlled laboratory environment that can provide a successful path for obtaining data on the mechanics and dynamics of railway systems for a variety of operating conditions. The idea to develop a laboratory test rig started from the observation that there is a need for better-developed testing fixtures capable of accurately explaining the complex physics of wheel-rail contact toward designing faster, safer, and more efficient railway systems. A review of current roller rigs indicated that many desired functional requirements for studying contact mechanics currently are not available. Thus, the Virginia Tech Railway Technologies Laboratory (RTL) has embarked on a mission to develop a state-of-the-art testing facility that will allow experimental testing of contact mechanics in a dynamic, controlled, and consistent manner. VT roller rig will allow for closely replicating the boundary conditions of railroad wheel-rail contact via actively controlling all the wheel-rail interface degrees of freedom: cant angle, angle of attack, and lateral displacement. Two sophisticated independent drivelines are configured to precisely control the rotational speed of the wheels, and therefore their relative slip or creepage. A novel force measurement system, suitable for steel on steel contact, is configured to precisely measure the contact forces and moments at the contact patch. The control architecture is developed based on the SynqNet data acquisition system offered by Kollmorgen, the motors supplier. SynqNet provides a unified communication protocol between actuators, drives, and data acquisition system, hence eliminating data conversion among them. Various design analysis indicates that the rig successfully meets the set requirements: additional accuracy in measurements, and better control on the design of experiments. The test results show that the rig is capable of conducting various contact mechanics studies aimed for advancing the existing art. Beyond developing the experimental testing fixture for studying contact mechanics, this study provides a comprehensive review of the contact models. It discusses the simplifying assumptions for developing the models, compares the models functionality, and highlights the open areas that require further experimental and theoretical research. In addition, a multi-body dynamic model of the entire rig, using software package SIMPACK, is developed for conducting modal analysis of the rig and evaluating the performance of the rig's components. A MATLAB routine is also developed that provides a benchmark for developing creep curves from measurements of the rig and comparing them with existing creep curves. / Ph. D.

This study discusses the design of a force control strategy for reducing force disturbances in the Virginia Tech – Federal Railroad Administration (VT-FRA) Roller Rig. The VT-FRA Roller Rig is a state-of-the-art roller Rig for studying contact mechanics. It consists of a 0.2m diameter wheel and a 1m diameter roller in vertical configuration, which replicates the wheel-rail contact in a 1/4th scale. The Rig has two 19.4 kW servo motors for powering the rotational bodies and six heavy-duty servo linear actuators that control other boundary conditions. The Rig was operationalized successfully with all degrees of freedom working in the default position feedback control. During the Rig's commissioning, this approach was found to result in vertical force fluctuations that are larger than desired. Since the vertical force affects the longitudinal and lateral traction between the wheel and roller, keeping the fluctuations to a minimum provides a better test condition. Testing and data analysis revealed the issue to be in the control method. The relative position of the wheel and roller was being controlled instead of controlling the forces between them. The latter is a far more challenging control setup because it requires a faster dynamic response and full knowledge of forces at the interface. Additionally, force control could result in dynamic instability more readily than position control. Multiple methods for force control are explored and documented. The most satisfactory solution is found in a cascaded loop force/position controller. The closed loop system is tested for stability and performance at various load, speed, and creepage conditions. The results indicate that the controller is able to reduce the standard deviation of vertical force fluctuations at the wheel-rail contact by a factor of four. In terms of power of the vertical force fluctuations, this corresponds to a 12 dB reduction with the force control when compared with the previous control method. This study also explores the possibility of automating the tests in order to enable running a larger number of tests in a shorter period of time. A multi-thread software is developed in C++ for executing a user-defined position, velocity, or force vs. time trajectory, and for recording the data automatically. The software also provides continuous monitoring, and performs a safe shutdown if a fault is detected. An intuitive GUI is provided for constant data polling and ease of user operation. The code is modular in order to accommodate future modifications and additions for various testing needs. The engineering upgrades included in this study, together with the baseline testing, complete the commissioning of the VT-FRA Roller Rig. With unparalleled parameter control and testing repeatability, the VT-FRA Roller Rig holds the promise of being used successfully for various contact mechanics needs that may arise in the railroad industry. / MS / Roller Rigs have seen widespread use around the world for research and development of railway vehicles. These test rigs are specialized machinery that provide the means to test a particular aspect of railroading in a controlled environment, allowing for thorough parametric analyses which aid in the design and development of railroad vehicles. One such test rig is the Virginia Tech – Federal Railroad Administration (VT-FRA) Roller Rig, located at the Railway Technologies Laboratory in Blacksburg, Virginia. It is a state-of-the-art test rig which is developed with the objective of providing a controlled test environment for studying railway contact mechanics. A good understanding of the wheel/rail contact is critical to railroad engineering, and this problem has been the subject of research for about a century now. Several compelling mathematical models have been proposed, but the experimental verification of those theories has proven to be difficult. Traditionally, field testing data has been utilized for comparison with prediction from the models. However, field tests are plagued by a low level of noise control and the inability to carry out sophisticated parametric analyses. VT-FRA Roller Rig holds the promise to fill this gap with its sophisticated electro-mechanical design and high precision instrumentation. The VT-FRA Roller Rig replicates the wheel-rail contact in a 1 /4 th scale by utilizing the INRETS scaling strategy. The locomotive wheel is replicated by a 0.2m diameter wheel and the tangent track is replicated by a 1m diameter roller. The relative size difference ensures that the contact distortion effects from the use of roller are kept to a minimum. The wheel and the roller are arranged in a vertical configuration, and are independently powered by two 19.4 kW servo motors. This enables the VT-FRA Roller Rig to achieve a precise creepage control of up to 0.1%. VT-FRA Roller Rig also has six heavy-duty servo linear actuators which are responsible for controlling four boundary conditions: cant angle, angle of attack, lateral displacement and vertical load. A sophisticated six-axis contact force-moment measurement system allows for precise measurements with a high dynamic bandwidth. The Rig was operationalized successfully with all degrees of freedom working in the default position feedback control. During the Rig’s commissioning, this approach was found to result in force fluctuations that were larger than desired. Since the vertical force affects the longitudinal and lateral traction between the wheel and roller, keeping the fluctuations to a minimum provides a better test condition. Testing and data analysis revealed the issue to be in the control method. The relative position of the wheel and roller was being controlled instead of controlling the forces between them. This study documents the development process of a reliable force control methodology for the VTFRA Roller Rig. Force control is a far more challenging control problem when compared to position control because it requires a faster dynamic response and full knowledge of forces at the interface. Additionally, force control could result in dynamic instability more readily than position control. Multiple methods for force control were implemented on the VT-FRA Roller Rig. Satisfactory solution is achieved with the complicated cascaded loop force/position controller, and the stability and performance of the control system is ensured by a slew of tests at various operating conditions. This study also explores the possibility of automating the tests in order to enable running a larger number of tests in a shorter period of time. A multi-thread software is developed in C++ for executing a user-defined position, velocity, or force vs. time trajectory, and for recording the data automatically. The software also provides continuous monitoring, and performs a safe shutdown if a fault is detected. An intuitive GUI is provided for constant data polling and ease of user operation. The code is modular in order to accommodate future modifications and additions for various testing needs. The engineering upgrades included in this study, together with the baseline testing, complete the commissioning of the VT-FRA Roller Rig. With unparalleled parameter control and testing repeatability, the VT-FRA Roller Rig holds the promise of being used successfully for various contact mechanics needs that may arise in the railroad industry.

The purpose of this study has two parts directed toward a common goal. First, a state-ofthe-art quarter-car test platform has been designed and constructed to offer increased testing flexibility at a reasonable cost not found commercially. With this new test rig completed, the second objective is a proof-of-concept evaluation of a well known adaptive control algorithm applied to this new quarter-car test rig for the purpose of replicating the dynamic suspension response, such as a response that was recorded during a road test. A successful application of this control algorithm on the quarter-car rig is the necessary first step toward its application on an 8-post test rig for a direct comparison to current practices. Before developing a new test rig, the current state-of-the-art in quarter-car rigs was first evaluated as well as indoor vehicle testing in general. Based on these findings, a list of desired functional requirements was defined for this new design to achieve. The new test rig was built and evaluated to determine how these goals were met and what the next steps would be to improve the rig. The study then focused on evaluating control policies used for reproducing dynamic responses on vehicle road simulators such as 4- post and 7-post shaker rigs. A least-mean squares (LMS) adaptive algorithm is introduced and applied first in software using a linear two-mass quarter-car model, and then to the actual hardware-in-the-loop quarter-car rig. The results of the study show that the resulting quarter-car test rig design is quite flexible in its ability to test a multitude of suspension designs and also its ability to accommodate new hardware in the future such as a body loaders. The study confirms that this particular implementation of the LMS algorithm is a viable option for replicating test vehicle response on an indoor quarter-car test rig. Thus, a future study to compare the use of this algorithm to the current industry standard batch processing method is possible. / Master of Science

This thesis regards the design process of a test rig for a new type of clutch. To save excessive fuel losses in heavy vehicles, a dog clutch has been designed with elastic engagement to lower peak torque. Currently, there is no way of testing this clutch. The purpose of this thesis is therefore to design a test rig that allows physical testing of this newly developed clutch. The thesis describes how suitable tests/measurements are found to indicate clutch functionality. By following a design process, these tests/measurements are incorporated in a test rig design. Initially, requirements were set. With these requirements, concepts have been generated. After some reviewing and improving, one final concept has been chosen. This concept has been designed using separate subsystems. When integrating these subsystems, a final design is realised. The final design measures the axial positions of components inside the clutch. It also measures torque and speed of the input and output. This all while having a variable input speed, engagement force, output braking torque, and output rotational inertia. The test rig is suitable for long-term testing to test wear of the different clutch components. Advice on future works has been given to the company based on the achieved results.