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Brake Colloquium & Exhibition - 36th Annual
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A Study on Safety Intelligent Driving System for Heavy Truck Downhill in Mountainous Area

Beijing Institute of Space Launch Technology-Yanming Zhao
Wuhan Univ. of Technology-Jiakang Quan, Gangfeng Tan, Yongbing Xu, Bo Huang, Tianming He
Published 2018-10-05 by SAE International in United States
Mountainous area makes up more than half of the whole land area of China, the road of which is full of ups and downs. Heavy commercial vehicles as the main means of transport in mountainous areas, braking torque recession, even brake failure, often happens because of the overheating in long downhill journey, which seriously threatens the safety of the driving. Therefore, this paper presents an intelligent assistance system based on Geographic Information System and vehicle dynamics. The main brake duration and heat generation can be effectively reduced through adjusting the speed at the slope top, applying the engine auxiliary brake in the initial stage and choosing braking strategy appropriately, in order to prolong the downhill driving distance and improve the safety during continuous braking. This paper characterizes and analyses the road gradients and their effects on braking heat generation. To analysis the temperature rising characteristics of the main brakes under different initial speeds, the temperature rise model of the brake is established. Furthermore, the effectiveness has been recognized by comparing the main brakes’ temperature variation…
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A Study of the Disc Scoring Generation Principle and Reduction (II)

Hyundai Motor Co.-ByeongUk Jeong, Hyoung Tae Ryu
Myunghwa Ind Co. Ltd.-Chang Jin Kim
Published 2018-10-05 by SAE International in United States
In the latest paper [10], we presented our work based on experiments studying MPU (Metal Pick Up) of the pad and scoring(scratching) of the disc. The main component of MPU was iron “Fe”. If the roughness of the disc was small, the content of iron “Fe” was increased and the segregation of that was decreased especially in initial condition. In this study, we extended our study based on the results by adding some additional factors such as the location of the roughness of the disc, the coefficients brake pad friction, and disc slots. We made various discs of different roughness boundaries and slots, and pads of pad friction coefficients; and conducted two types of tests for whether a slot is present or not with the other same conditions to confirm the impact of the scoring. We find and believe that our experimental data should serve a useful guideline for reducing MPU of the pad and scoring of the disc.
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Correlation of Objective and Subjective Evaluation in Automotive Brake Pedal Feel

Tongji Univ.-Jingyi Zhang, Dejian Meng, Jialin Liu
Published 2018-10-05 by SAE International in United States
In order to establish the correlation between objective and subjective evaluation of brake pedal feel for passenger cars, road tests of brake pedal feel were carried out and an evaluation method was proposed. In the road tests, subjective scores and objective measurements were obtained under the conditions of uniform and emergency braking. The objective measurements include pedal preload, low deceleration pedal force and travel, moderate deceleration pedal force and travel, brake response time and brake linearity. Using the theory of analytic hierarchy process (AHP), the design process of the evaluation method was established. Key setups including the hierarchical structure model, the judgement matrix and the score calculation method of objective measurements were described in detail. Then, the correlation between subjective and objective scores was analyzed. It can be concluded that the evaluation method is effective and it can be applied to brake pedal feel assessment and adjustment.
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A Mathematical Model of the Braking Dynamics of a Car

Kharkov National Auto & Highway Univ.-Olexii Saraiev
Univ. of Houston-Yuliya Gorb
Published 2018-10-05 by SAE International in United States
The braking efficiency of a vehicle is its most important operational property. However, in practice, researchers utilize simplistic physical-mathematical models for the process of vehicle braking that leads to accuracy reduction of these models predictions. The literature data show that the error in assessing braking efficiency can reach 30%. One of the main indicators of the efficiency of a braking system is deceleration. Most accurately, this value can be determined by experimental measurements. However, this is not always possible due to various technical reasons. The existing models typically ignore the impact of the car design and its speed on deceleration. They also either neglect air resistance completely or account only for its horizontal component. This paper presents an improved mathematical model written in the differential form that takes into account the impact of the lifting or downforce components of the aerodynamic forces. The proposed model accounts for the dependence of car wheels adhesion with a road surface on the vehicle’s speed. Model analysis and computation showed that all these factors improve braking performance of the…
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Identification and Resolution of Vehicle Pull and Steering Wobble Using Virtual Simulation and Testing

Mahindra & Mahindra Ltd.-Baskar Anthonysamy, Vishal Barde, Naveen Medithi, Senthil S, Balaramakrishna N
Published 2018-10-05 by SAE International in United States
A vehicle drifts due to several reasons from its intended straight path even in the case of no steering input. Vehicle pull is a condition where the driver must apply a constant correction torque to the steering wheel to maintain a straight-line course of the vehicle. This paper presents an investigation study into the characteristics of a vehicle experiencing steering drift. The aim of the work is to study vehicle stability and the causes of vehicle drift/pull during straight line to minimize vehicle pull level and hence optimize safety measures.A wobble in the steering wheel feels like the steering wheel is shaking to the left and right. This may get worse, if speed increases.This paper focuses on modelling and evaluating effects of suspension parameters, differential friction, brake drag variation, Unbalanced mass in the wheel assembly and C.G. location of the vehicle under multibody dynamic simulation environment.Asymmetry of geometry and compliance between left and right side to be causing the drift. The sensitivities of the suspension parameters are presented for each driving condition. In case of…
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Physical and Virtual Simulation of Lightweight Brake Drum Design for Heavy Duty Commercial Vehicles Using Alternate Material Technologies

VE Commercial Vehicles Ltd.-Suresh Kumar Kandreegula, Himanshu Deshmukh, Shivdayal Prasad, Sonu Paroche, Ashesh Anil Shah
Published 2018-10-05 by SAE International in United States
Brake drum in commercial vehicles is very important aggregate contributing towards major weight in brake system module. The main function of brake drum is to dissipate kinetic energy of vehicle into thermal energy, as a results in braking operation major load comes on brake drum. Hence this is very critical component for vehicle safety and stability [1].Objective of this paper is to increase the pay load, which is utmost important parameter for commercial vehicle end customers. To achieve the light weighing target, alternate materials such as Spheroidal graphite iron (SGI) has been evaluated for development of brake drum. Many critical parameters in terms of reliability, safety and durability, thickness of hub, wheel loading, heat generation on drum, manufacturing and assembly process are taken into consideration. The sensitivity of these parameters is studied for optimum design, could be chosen complying each other’s values.Digital thermal performance evaluated in house, fine-tuned and verified by correlating with test data available for existing cast iron design and then applied for new design with alternate materials. In two different designs around…
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Study on Brake Disc Dynamics under Asymmetric Thermal Loads

Tongji Univ.-Dejian Meng, Jialin Liu, Jingyi Zhang, Lijun Zhang
Published 2018-10-05 by SAE International in United States
In order to explore the generation mechanism of hot-spots on the automotive brake disc, disc tests under non-frictional thermal loads are carried out on the brake dynamometer test bench. In the tests, the oxy-acetylene flame is used as the heat source, and the distribution characteristics of the disc temperature and displacement are measured and analyzed. To confirm the mechanism of the disc deformation, a disc thermal buckling model using finite element method is established, and the key factors for the disc thermal buckling under thermal loads are further analyzed. It is found that the temperature circumferential gradient is small but the temperature radial gradient is large. The disc presents waviness deformation mode with 5th order in circumferential direction, which is the first thermal buckling mode of the disc. A method using spatial frequency spectrum has been proposed to find the critical time and load of thermal buckling. The heat source power and the rotational speed have no significant influence on the temperature and displacement circumferential and radial distribution of the disc. The temperature radial gradient…
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The Factors Governing Corrosion Stiction of Brake Friction Materials to a Gray Cast Iron Disc

Hyundai Mobis-Wangyu Lee, Dooyeon Kim, Keeyang Lee
Korea Univ.-Jaehyun Gweon, Sanghee Shin, Ho Jang
Published 2018-10-05 by SAE International in United States
Corrosion stiction at the contact interface between a brake friction material and a gray iron disc under the parking brake condition was investigated by evaluating the possible parameters that affect the shear force to detach the corroded interface. Using production brake friction materials, comprising non-steel and low-steel types, corrosion tests were carried out by pressing the brake pad onto the gray iron disc using a clamp at various conditions. Results showed that the shear force to detach the corroded interface tended to increase with applied pressure and corrosion time. On the other hand, porosity, acidity, and hydrophobicity of the friction material did not show a reliable correlation to the stiction force. The poor correlation of the stiction force with the friction material properties indicated that the stiction force was not determined by a single factor but governed by multiple parameters including surface contact areas and inhomogeneity of the ingredients. Microscopic observation of the detached disc surface showed adhered fragments that were removed from the friction material surface, thus shedding light on the possible estimation of…
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Bearing Life Evaluation for Automotive Wheel Bearings Using Design of Experiments

Iljin Global-Seungpyo Lee
Published 2018-10-05 by SAE International in United States
Automotive wheel bearings have primary functions of translating the rotating motion of the wheels into linear vehicle motion while bearing the vehicle weight. Bearing life is affected by many parameters such as bearing geometry, vehicle and bearing technical specifications, driving conditions, lubrication conditions, material properties, and so on. In this paper, both the basic bearing rating life and modified bearing rating life were evaluated using design of experiments. Bearing lives were calculated by the international standard, and the factors affecting bearing life were investigated. Sequential experimental designs were applied. First, screening experiments were performed to analyze the factors affecting bearing life. Next, confirmation experiments were carried out to determine accurate effects of the selected factors from the screening experiments. As a result, contact angle and curvature of inner ring were significant at a 95% of significance level.
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Non-Asbestos Organic (NAO) Disc Pad Wear Behavior: Divergence of Thickness Loss and Weight Loss

Compact International (1994) Co. Ltd.-Meechai Sriwiboon, Nipon Tiempan, Kritsana Kaewlob
SKR Consulting LLC-Seong Rhee
Published 2018-10-05 by SAE International in United States
There is anecdotal evidence that disc pad wear numbers measured in thickness loss and disc pad wear numbers measured in weight loss do not show the same wear trends after wear or performance testing. However, research papers on this topic are difficult to find. Therefore, this investigation was undertaken to study and document this behavior in detail on high-copper, low-copper and no-copper (or copper-free) NAO pads. In all cases, thickness loss measurements are found to be substantially lower than expected from the weight loss data according to the SAE J2522 test schedule. This divergence is caused by pad swelling in the pad layer adjacent to the friction contact surface during brake testing at high temperatures. In addition to formulation changes, disc pad processing conditions such as mixing time and hot molding pressure are found to affect pad swelling. As pad physical properties, especially in the layer adjacent to the friction contact surface, are expected to dynamically change during braking due to the pad swelling, one has to seriously question any attempt to correlate physical properties…
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