Browsing by Author "Shenvi, Mohit Nitin"

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    Compacted Snow Testing Methodology and Instrumentation
    Shenvi, Mohit Nitin (Virginia Tech, 2024-03-05)
    Snow is a complex material that is difficult to characterize especially due to its high compressibility and temperature-sensitive nonlinear viscoelasticity. Snow mechanics has been intensively investigated by avalanche and army researchers for decades. However, fewer research studies have been published for compacted snow, commonly defined as snow with a density in the range of 370-560 kg/m3. From a mobility perspective, the tires are the primary point of force and motion generation and their interaction with the terrain causes an increased reliance on the skill of the driver for safer mobility. Thus, standards like ASTM F1805 are implemented for the evaluation of winter tires which can be used in harsh conditions like ice and snow. This work focuses on evaluating the prior efforts performed for the measurement of snow properties. In addition, analysis using regression models and principal component analysis is performed to understand the extent to which specific measurements related to snow affect the traction of the tire. It was found that the compressive and shear properties of snow contribute more than 90% to the variation in the traction coefficient of a tire when evaluated on a compacted snow domain per ASTM F1805. Identification of this phenomenon allowed the enhancement of an existing device that can be used for measuring the compaction and shear properties of snow. The device hence conceptualized was manufactured in-house and tested at the Smithers Winter Test Center to benchmark against existing devices available commercially. Further, a more analytical method for evaluating the resistive pressure for the penetration of the device was formulated. Based on this, a possible framework for the determination of the bevameter parameters using measurements of the new device has been proposed which needs to be validated experimentally and computationally.
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    Comparative Study of the Effect of Tread Rubber Compound on Tire Performance on Ice
    Shenvi, Mohit Nitin (Virginia Tech, 2020-08-20)
    The tire-terrain interaction is complex and tremendously important; it impacts the performance and safety of the vehicle and its occupants. Icy roads further enhance these complexities and adversely affect the handling of the vehicle. The analysis of the tire-ice contact focusing on individual aspects of tire construction and operation is imperative for tire industry's future. This study investigates the effects of the tread rubber compound on the drawbar pull performance of tires in contact with an ice layer near its melting point. A set of sixteen tires of eight different rubber compounds were considered. The tires were identical in design and tread patterns but have different tread rubber compounds. To study the effect of the tread rubber compound, all operational parameters were kept constant during the testing conducted on the Terramechanics Rig at the Terramechanics, Multibody, and Vehicle Systems laboratory. The tests led to conclusive evidence of the effect of the tread rubber compound on the drawbar performance (found to be most prominent in the linear region of the drawbar-slip curve) and on the resistive forces of free-rolling tires. Modeling of the tire-ice contact for estimation of temperature rise and water film height was performed using ATIIM 2.0. The performance of this in-house model was compared against three classical tire-ice friction models. A parametrization of the Magic Formula tire model was performed using experimental data and a Genetic Algorithm. The dependence of individual factors of the Magic Formula on the ambient temperature, tire age, and tread rubber compounds was investigated.
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    Correlating tire traction performance on snow with measured parameters of ASTM F1805 using regression analysis
    Shenvi, Mohit Nitin; Sandu, Corina; Untaroiu, Costin D.; Pierce, Eric (Elsevier, 2023-09)
    Winter tires sold in North America are often tested using the ASTM F1805 testing process to determine if they can be labeled with the ‘mountain snowflake’ symbol which indicates better performance for snow usage. The standard dictates the requirements for testing and necessary track preparation methodologies. In addition, the requirements of the standard dictate the range of three major conditions for tests to be carried out, namely the CTI penetration measurement, the snow temperature, and the ambient temperature. However, these parameters cannot be directly used in the simulation stage of snow modeling for better evaluation of prototypes. It is well-known that snow properties depend on a wide variety of parameters, making the creation of an accurate and robust snow material model, and, consequently, applying a simulation-based approach for tire design, difficult. This work focuses on the analysis of a dataset of five winter seasons of a 14-in. Standard Reference Test Tire on snow used to benchmark the performance of a potential winter tire. The blinded data measured at Smithers Winter Test Center were used in the analysis to train regression models for predicting the traction coefficient and evaluating the extent to which the measured parameters affect the variation in the traction coefficient. This study utilized twenty-six different modeling approaches and implementation of principal component analysis. The findings of this study highlight the relative importance of the compression and shear characteristics of the snow on the traction of the tire. It was found that regression methods based on Gaussian processes were better at predicting the traction coefficient. The study also highlights the importance of utilizing a single physical tire as the reference tire for benchmarking according to the ASTM F1805.
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    Review of compressed snow mechanics: Testing methods
    Shenvi, Mohit Nitin; Sandu, Corina; Untaroiu, Costin D. (Elsevier, 2022-04)
    Snow is a complex material that is difficult to characterize especially due to its high compressibility and temperature-sensitive nonlinear viscoelasticity. Snow mechanics has been intensively investigated by avalanche and army researchers for decades. However, fewer research studies were published for the compacted snow, defined as snow with a density in a range of 370–560 kg/m3. This review focuses on the various testing methods that are used especially to characterize the behavior of compacted snow under compressive and shear loading. The working principles, inherent assumptions, and advantages/disadvantages of the devices are summarized. In addition, some of the important material properties of snow like density, elastic modulus, etc., and their measurement is highlighted. Lastly, a correlation of the testing methods to commonly used approaches in modeling snow is presented. Overall, we believe that this study can help to better understand the existing test data related to compacted snow and guide future testing in this field.
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    Tread rubber compound effect in winter tires: An experimental study
    Shenvi, Mohit Nitin; Verulkar, Adwait; Sandu, Corina; Mousavi, Hoda (Elsevier, 2022-02)
    This paper presents an indoor experimental study focused on analyzing the effect of various tread rubber compounds on the tire performance on ice. A set of sixteen tires (two per rubber compound) with identical dimensions, construction, and tread pattern, but of different tread rubber compounds, was investigated using the Terramechanics Rig which measures all forces and moments acting on a tire that is rolling (free or with slip) on ice. All operational parameters (normal load, inflation pressure, ice static coefficient of friction, ice temperature) were kept constant. Testing the tires under free rolling provided insights into the effect of the tread rubber compound on the resistive forces. The investigation led to conclusive evidence that the tread rubber compound affects drawbar pull coefficient significantly (double for best than for the worst tire). It was found that the effect of the tread rubber compound in the lower slip region is most prominent, which is also where vehicles operate most of the time. The decrease in the stiffness is generally considered a positive sign for improvement in available friction but this cannot be a generalized conclusion when analyzing the tire as a whole, which is one of the major findings of this study.
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    Tread rubber compound effect in winter tires: Benchmarking ATIIM 2.0 with classical models
    Shenvi, Mohit Nitin; Mousavi, Hoda; Sandu, Corina (Elsevier, 2022-06)
    Tire-terrain interaction is complex and affects the performance of the vehicle; more so when the terrain is ice which affects the handling of the vehicle. Analysis of the contact between the tire and ice, especially in the countries like United States, Canada, etc. is imperative but a trial-and-error approach consisting of the design and manufacture of novel tires for testing and analysis seems a foregone conclusion. Thus, it is important to have accurate methods of simulation of tire performance on ice in order to design better tires without inputting much cost in the manufacturing process. This study chose to simulate the performance of sixteen tires which were identical in all aspects of design and construction except for the tread rubber compound which varied resulting in two tires having the same tread rubber compound. These simulations were performed using the in-house developed ATIIM, ATIIM 2.0, and modified versions of three simplified classical models namely the model by Hayhoe and Shapley and two models by Peng et al. A qualitative comparison of the performance of the models was performed in order to highlight their advantages and disadvantages.