physical wear model on wear progress of irregular wear of tires
PHYSICAL WEAR MODEL ON WEAR PROGRESS OF IRREGULAR WEAR OF TIRES (CASE OF RIVER WEAR OF TRUCK & BUS TIRES) *Takeshi 1
Hanzaka1, Yukio Nakajima1 Graduate School of Mechanical of Engineering, Kogakuin University, Japan
Key Words Tire; Irregular wear; Physical wear model; Wear progress; FEM Research and/or Engineering Questions/Objective Wear performance of tires significantly affects the resource conservation, economic efficiency and safety performance. Studies have been rarely conducted on wear progress but just wear of tires. River wear is a kind of irregular wear occurring in truck & bus tires and is progressed by the self-accelerated wear where worn region is rapidly worn more than unworn region. Finally it covers whole rib that is called rib punch. The objective of this study is to clarify the mechanism by developing physical wear model to predict the progress of irregular wear and propose ways for improvement of irregular wear. Methodology In the physical wear model, the description of contact pressure distribution was changed from parabola used in previous studies to generalized parabola to precisely represent the pressure distribution of tires. Furthermore, the function of reduction of mean contact pressure and contact length with respect to step of irregular wear was introduced and it was determined by FEM calculation of simple tire model. The calculation of wear progress consists of five steps; Step 1: Determine the sliding region of tire by considering both longitudinal and lateral shear stress in the contact patch, Step 2; Calculate wear energy, Step 3; Modify tire profile corresponding to wear energy, Step 4; Mean contact pressure and contact length are modified through the introduced function, Step 5; Go to Step 1. Results The physical wear model is qualitatively in agreement with the observation of wear progress where the kernel of irregular wear is initiated due to lateral stress and then the wear is accelerated due to longitudinal stress in tires. Firstly, the change of description of contact pressure distribution hardly affected to results. Secondly, the introduced function of reduction of mean contact pressure and contact length with respect to step of irregular wear affected to one particularly. To improve irregular wear, both of maximum wear energy and step of irregular wear should be decreased. For example, ways for improvement of irregular wear are to increase the Young’s modulus of tread rubber or increase the crown radius to decrease the difference of radius between tire center and shoulder. Although to decrease inflation pressure or decrease groove depth is also effective ways, those ways affect the negative influence on other performances of tires. Limitations of this study This model is based on the brush model where each brush does not possess interaction each other. But the shear force is generated between worn and unworn region in rolling tire, and therefore this model is required to consider the shear spring between brushes for better predictability. The analysis result is well affected by the introduced function of reduction of contact pressure and contact length with step of irregular wear. Therefore, the function is required to be examined using FEM each time if parameters of physical model are changed. What does the paper offer that is new in the field in comparison to other works of the authors? Wear progress has not been conducted in previous studies but just wear of tires. This study offers the first physical model for wear progress of tires. The calculation is qualitatively in agreement with the observation of wear progress in truck/bus tires and ways for improvement are proposed. Conclusions The physical wear model has been developed to clarify the mechanism of wear progress and showed qualitative agreement with the observation. Ways for improvement of irregular wear are to decrease both of maximum wear energy and step of irregular wear.
Hanzaka1, Yukio Nakajima1 Graduate School of Mechanical of Engineering, Kogakuin University, Japan
Key Words Tire; Irregular wear; Physical wear model; Wear progress; FEM Research and/or Engineering Questions/Objective Wear performance of tires significantly affects the resource conservation, economic efficiency and safety performance. Studies have been rarely conducted on wear progress but just wear of tires. River wear is a kind of irregular wear occurring in truck & bus tires and is progressed by the self-accelerated wear where worn region is rapidly worn more than unworn region. Finally it covers whole rib that is called rib punch. The objective of this study is to clarify the mechanism by developing physical wear model to predict the progress of irregular wear and propose ways for improvement of irregular wear. Methodology In the physical wear model, the description of contact pressure distribution was changed from parabola used in previous studies to generalized parabola to precisely represent the pressure distribution of tires. Furthermore, the function of reduction of mean contact pressure and contact length with respect to step of irregular wear was introduced and it was determined by FEM calculation of simple tire model. The calculation of wear progress consists of five steps; Step 1: Determine the sliding region of tire by considering both longitudinal and lateral shear stress in the contact patch, Step 2; Calculate wear energy, Step 3; Modify tire profile corresponding to wear energy, Step 4; Mean contact pressure and contact length are modified through the introduced function, Step 5; Go to Step 1. Results The physical wear model is qualitatively in agreement with the observation of wear progress where the kernel of irregular wear is initiated due to lateral stress and then the wear is accelerated due to longitudinal stress in tires. Firstly, the change of description of contact pressure distribution hardly affected to results. Secondly, the introduced function of reduction of mean contact pressure and contact length with respect to step of irregular wear affected to one particularly. To improve irregular wear, both of maximum wear energy and step of irregular wear should be decreased. For example, ways for improvement of irregular wear are to increase the Young’s modulus of tread rubber or increase the crown radius to decrease the difference of radius between tire center and shoulder. Although to decrease inflation pressure or decrease groove depth is also effective ways, those ways affect the negative influence on other performances of tires. Limitations of this study This model is based on the brush model where each brush does not possess interaction each other. But the shear force is generated between worn and unworn region in rolling tire, and therefore this model is required to consider the shear spring between brushes for better predictability. The analysis result is well affected by the introduced function of reduction of contact pressure and contact length with step of irregular wear. Therefore, the function is required to be examined using FEM each time if parameters of physical model are changed. What does the paper offer that is new in the field in comparison to other works of the authors? Wear progress has not been conducted in previous studies but just wear of tires. This study offers the first physical model for wear progress of tires. The calculation is qualitatively in agreement with the observation of wear progress in truck/bus tires and ways for improvement are proposed. Conclusions The physical wear model has been developed to clarify the mechanism of wear progress and showed qualitative agreement with the observation. Ways for improvement of irregular wear are to decrease both of maximum wear energy and step of irregular wear.
