Earticle

디스크 커버는 브레이크 디스크 및 캘리퍼를 보호하기 위해 설치하고, 고객에게 인도되기 직전에 제거된다. 본 연구에서 디스크 커버의 온도는 주행 시험 차량(2000cc, 디젤)을 대상으로 측정되었다. 주행 시험(120km/h-제동(0.3G)-정지-120km/h-제동(0.5G)-정지)에서 측정된 최고 온도는 디스크 커버 상부에서 260~270℃ 이었고, 디스크 커버 주위에 상당한 변화를 보였다. 이는 고온 디스크로부터 커버로의 주요 열전달이 대류를 통해서임을 커버 주위의 온도 분포로부터 추론 할 수 있다. 즉, 마찰 제동에 의해 발생된 고온의 공기가 디스크 커버 상부까지 올라간 것이다. 그리고 주행 시험 중에 디스크 커버의 상부 영역만이 용융되었다. 디스크 커버의 두께를 0.7mm부터 1.0mm로 증가시키고, 마스킹 테이프 1장을 디스크 커버 상부 영역에 부착하였다. 그 후에 디스크 커버는 주행 시험 시 마찰 제동에 의해 형성된 고온의 공기에도 변형되지 않았다.

The disk cover is installed to protect brake disk and calliper and it’s removed right before delivering to customers. The temperature of disk cover was measured driving test vehicles(2000cc, diesel) in this study. The highest temperature measured for the driving test(120km/h-braking(0.3G)-stop-120km/h-braking(0.5G)-stop) was 260~270℃ in the upper part of the disk cover and the temperature varied considerably around the disk cover. It can be inferred from this temperature distribution around the cover that the major heat transfer from hot disk to cover was through convection. In other words, the hot air generated by braking friction moved up to the upper part of the disk cover. And only the upper area of the disk cover was melted down during this driving test. The thickness of disk cover was increased to 1.0mm from 0.7mm and 1 paper of masking tape was pasted in the upper region of the disk cover. Then the cover endured the heated air formed by braking friction during the driving test.

본 연구에서는 경주용 자동차에서 기존에 사용 중인 형상을 가진 모델 A와 경량화를 한 모델 B를 설계하고 열 변형과 열응력을 동반한 구조해석을 하였다. Model A가 Model B에 비하여 최고온도가 낮음을 보인다. 다른 냉각 조건이 주어지지 않고 디스크의 형상에 따른 냉각성능은 Model A가 더 뛰어남을 알 수 있다. Model A가 Model B에 비하여 거의 2배 이상으로 그 열응력이 낮아져 내구성면에서도 우수함을 알 수 있었다. 응력이 가장 크게 나타나는 부분 은 형상에 관계없이 허브와 접합되는 구멍으로 나타났다. 본 연구에서의 해석결과는 실제 자동차 브레이크 디스크의 형상을 설계하는데 있어서 유용하다고 보인다. 본 연구에서 얻은 해석 결과는 실제적으로 경주용 자동차 브레이크 디스 크의 강도를 파악하는 데에 적용될 수 있다. 경주용 자동차 브레이크 디스크의 해석 결과를 이용함으로서, 본 연구가 미적인 설계 및 해석이 적용된 융합 연구라고 보여진다.

In this study, the model A with the existing shape used at racing car and the model B with light weight were designed. The structural analysis with thermal deformation and stress were carried out. Model A shows that the maximum temperature is lower than model B. The cooling performance due to the shape of the disk without any other cooling conditions can be shown to be better for model A. Model A was seen to be superior in durability as the thermal stress reduced by almost twice as much as model B. The part where the greatest stress occurred appeared to be the hole jointed with the hub regardless of its shape. The analysis results at this study are seen to be useful at designing the shape of the actual vehicle brake disc. The analysis results obtained in this study can be applied at grasping the strength of the brake disk for racing car practically. By utilizing the analysis result of the brake disk for racing car, this study is seen as the convergence study that the aesthetic design and analysis are applied.

본 연구에서는 전동킥보드 브레이크 디스크 열전달을 해석하였다. 브레이크 디스크의 패드 접촉면에 따라 다른 열이 전달된다. 접촉면에서 멀어진 부분에서는 온도가 작아지는 경향이 거의 일정하였으며 Model A가 Model B 보다 는 약간 더 낮은 온도 분포를 보였다. Model A가 Model B에 비하여 그 최대 등가응력이 7% 정도 더 높다. 설계시에 타원형으로 패드와 접촉하는 Model B가 원형인 Model A 보다는 그 응력이 감소됨을 보였다. 접촉면 위쪽으로 열이 더 많이 전달되는 것으로 미루어 볼 때 설계시 브레이크 디스크의 모서리 부분을 고려하여 본다면 Model B가 Model A보다 그 강도가 더 크다고 사료된다. 본 연구 결과를 전동킥 보드의 설계에 활용한다면 더 강도가 좋은 브레이크 디스 크 설계를 할 수 있을 것이라고 생각된다. 본 연구 결과를 전동킥보드 브레이크 디스크에 적용함으로서 열에 대한 브레 이크의 내구성을 평가할 수 있고 그 결과가 강성 있는 브레이크의 설계와 미적인 융합이 될 수 있다고 보인다.

In this study, the thermal analysis on the brake disc of electric kickboard was analyzed. The different heat is transmitted depending on the pad contact surface of brake disc. The trend that the temperature decreases at the part away from the contact surface was almost constant. And model A showed a slightly lower temperature distribution than model B. Model A has a maximum equivalent stress of 7% higher than model B. By being applied with the higher heat transfer above the contact surface, it is thought that model B has a greater strength than model A if the design takes into account the corner of the brake disc. If this study result is utilized to the design of electric kickboard, the design of brake disc with better strength is considered to be established. The durability of brake against the heat can be evaluated by applying this study result to the brake disc of electric kickboard. And it is seen that the result can be the design of brake with strength and the aesthetic convergence.

The brake system drives the vehicle by converting the kinetic energy into thermal energy. The heat energy generated during the braking process increases the temperature of the structure. It causes thermal deformation due to overheating and causes cracks, noise, and vibration that degrade performance. However, it is not possible to fundamentally prevent the temperature rise of the brakes. There is a need for research on improving the heat dissipation performance by improving the shape of the brake. Therefore, this study analyzed the concentrated stress caused by overheating of the brake disc. In order to improve the performance of the disk, shape optimization design was performed. For stress and thermal analysis, the analysis was conducted using the finite element program ANSYS Transient Thermal and Structural tools. PIAnO (Process Integration and Design Optimization) was used to perform optimal design. In the formulation of the optimum design, the stress was minimized by satisfying the constraints. This study intends to present a new brake disc model by performing perforated shape and arrangement.

본 논문은 자동차 제동성능에 대한 운전자의 요구에 따라 브레이크 디스크 튜닝이 많이 이루어지고 있어, 자동 차에 사용되고 있는 순정 디스크와 튜닝제품으로 나오고 있는 디스크의 열적거동을 FEM해석을 통해 분석하였다. 순정 디스크 모델링 및 튜닝 디스크 Model-1, Model-2, Model-3로 모델링을 하고 디스크 회전속도를 1000rpm으로 설정 하여 해석을 실시하였다. 브레이크를 작동하면 디스크와 패드 접촉에 의해 발생하는 작동시 온도와 디스크 정지 후 마찰 면의 온도, 열 변형 등 디스크 표면의 열적거동에 대하여 분석하였다. 브레이크 작동시(0-4.5초) 온도는 순정 디스크보 다 튜닝 디스크가 34℃높게 나타났고, 디스크 정지 후(40.5초) 온도는 튜닝 디스크가 18℃낮게 분석되었으며, 디스크 열에 의한 변형은 튜닝 디스크가 0.3mm정도 많이 변형되었다. 순정 디스크와 튜닝 디스크의 열적거동에 따른 페이드 현상 등을 줄일 수 있는 효과는 있으나, 튜닝 디스크의 홀 가공 및 디스크 면 가공에 따른 열적거동에는 크게 변화가 없음을 관찰할 수 있었다.

This paper analyzes the thermal behaviors of genuine discs used in automobiles and discs coming out of tuning products through FEM analysis. Modeling with genuine disk modeling and tuning disks Model-1, Model-2, Model-3 and analyzing the disk rotation speed was set to 1000rpm. When the brake is operated, the thermal behavior of the disk surface, such as the operating temperature caused by the disk and pad contact, the friction surface temperature after the disk stop, and the thermal deformation, were analyzed. When the brake was activated (0-4.5 seconds), the tuning disk showed 34℃ higher than the original disk, and after the disk stopped (40.5 seconds), the tuning disk was analyzed 18℃ lowe, deformation due to the disk heat was deformed by 0.3mm for the tuning disk. Although there is an effect to reduce the fading phenomenon due to the thermal behavior of the pure disk and the tuning disk, it can be observed that there is no significant change in the thermal behavior due to the hole processing and the disk surface processing of the tuning disk.

The heat generated in contact type braking system can cause an unacceptable braking performance. Thermal behavior of ventilated disk brake system is presented in this paper. The temperature and velocity fields of 3-D unsteady simulated model are obtained using a software package "FLUENT". The numerical results show that there exits a temperature nonuniformity between the disk faces contacting with pads. The conduction rate through the disk and pad is calculated and the effect of material conductivity is also investigated.

자동차 디스크 브레이크시스템에서는 열유속 및 열변형 등과 같은 이유로 마찰열이 균일하게 분산되지 않는다. 마찰열에 의한 열탄성 변형이 접촉압력 분포에 영향을 미치게 되고, 접촉하중이 디스크 브레이크 표면상의 작은 영역에 집중되어 열탄성 불안정성을 초래 할 수 있다. 본 연구에서는 실험적 계산식과 Kao 제안한 디스크와 패드의 접촉압력에 대한 해석방법을 참고로 하여 3차원 축대칭 모델을 통하여 실제로 제동 시 발생되는 디스크와 패드의 접촉을 고려한 온도 해석 및 열변형 해석을 하였다. ANSYS를 사용하여 디스크와 패드의 접촉면에서 발생하는 열탄성 불안전성 문제를 열하중과 기계적 하중으로 동시에 고려하여 해석하였다. 디스크와 패드가 직접 접촉하는 3차원 축대칭 모델을 구성하여 디스크의 마찰면 온도, 열변형, 접촉 열응력을 관찰함으로써 디스크에서 일어나는 열적 거동을 보다 정확하게 관찰하였다.

In automotive disc brake systems, frictional heat is not uniformly dispersed for reasons such as heat flux and thermal deformation. The thermoelastic deformation due to the frictional heat affects the contact pressure distribution and the contact load may be concentrated on the contact portion on the the disc brake surface, resulting in thermoelastic instability. In this study, thermal analysis and thermal deformation analysis considering the contact between disk and pad occurred during braking through 3D axial symmetry model with reference to the experimental equation and Kao's analysis method of contact pressure of disk and pad. ANSYS is used to analyze the thermal and elastic instability problems occurring at the contact surface between the disk and the pad, considering both the thermal and mechanical loads. A 3D axisymmetric model with direct contact between the disk and the pad was constructed to more accurately observe the thermal behavior of the disk by observing the frictional surface temperature, thermal deformation and contact thermal stress of the disk.

A design methodology is applied for manufacturing a disk-brake piston component. The design criteria are the limit drawing ratio and the forging load within the available press limit. Also, the final product should not have any geometrical defect. The rigid-plastic FEM has been applied to simulate the conventional four stage manufacturing processes, which include deep drawing and forging process. Simulation of one stage process from a selected stock to the final product shape is performed for generating information on additional requirements for metal flow. Two stage forming processes with different punch corner and nose geometries are also simulated to identify the possible best solutions. Finally, the best manufacturing process is selected, which is using a hemispherical punch int he deep drawing process.

The inter-laboratory comparison test which is demanded on the authorized test of ISO/IEC 17025 is the program to guarantee the confidence of test result. This paper, as a part of the inter-laboratory comparison test between South Korea and China, is refered to the characteristic of friction coefficient of disk brake lining for rolling stock according to disk type. Brake tests were carried out under constant brake force and operating sequence by using dynamo-tester according to disk and disk lining types. To establishing the confidence of test result, we calculated A type uncertainty about friction coefficient and investigated the factors about the variation of friction coefficient.

The Inter-laboratory comparison test which is demanded on the authorized test of ISO 17025 is the program to guarantee the reliability for test results of test organization. In order to apply to the field of railway, brake disk lining as one of the railway components has been selected and the comparison test is executed for the purpose of guaranteeing the reciprocal reliability for the test result of both organizations and enlarging the substantial technique exchange of both nations by the standard establishment with test procedures and test programs from now on.

A SiCp/Al composite disk brake casting for a high-speed application is produced using an adjustable vacuum pressure casting method specially developed for the production of SiCp/Al composite castings with complex structure. Feeding path during the solidification process of the disk brake casting is investigated by solidification simulation with a ProCAST code and checked by measurement of cooling curves. The simulation results match well with the measured cooling curves, which shows that the results of solidification simulation can be well used for a SiCp/Al composite casting production. With the help of solidification simulation, it is easy to establish a suitable feeding path that is the key technology for producing sound castings with the adjustable vacuum pressure casting method. Different casting plans with gating systems and chills are simulated and an improved casting plan for the disk brake casting is proposed based on the research presented in this paper. The casting quality is checked and confirmed by X-ray inspection and destructive inspection, which shows that the casting has few internal defects.

By the increasing amount of vehicles, the increase of car accident served as a major momentum for remind the importance of braking system. The adequate design of a passenger car braking system, which is directly related to the safety of a car, is very important since the safety is an essential design parameter of a car to keep men and car from the damage. The thermal behaviors of the ventilated disk has been investigated based on the air cooling effects during repeat braking operations. In this study, the temperature and velocity fields of 3-D unsteady simulated model are obtained using a software package "FLUENT". The numerical results show that there exits a temperature nonuniformity between the disk faces contacting with pads.

This paper presents the hot spot behaviors on the rubbing surface of ventilated disk brake by using finite element method. The depth of asperities on the rubbing surface is usually $2-3\;{\mu}m$ so the real contact area is microscopically. Non-uniform contacts between the disk and the pads lead to high local temperatures, which may cause the material degradation, and develops hot spots, thermal cracking, and brake system failures at the end. High contact asperity flash temperatures in rubbing systems, which is strongly related to the hot spot. It was generally known that high temperature over about $700^{\circ}C$ may form martensite on the cast iron which is material for automotive disk brakes. In this paper, the contact stress, temperature distribution and strain have been presented for the specific asperities of real contact area microscopically by using coupled thermal-mechanical analysis technique.

This study investigates the effects of operating conditions on the chattering of an automotive disk brake by experimental and computational methods. Design factors, which cause chattering in automobiles, have attracted great attentions for long time; but they are not well understood yet. For this study, we construct a brake dynamometer for measuring the disk surface temperature during chattering, and propose an efficient hybrid algorithm (combining FFT-FEA and traditional FEA program) for analyzing the thermo-elastic behavior of three-dimensional brake system. We successfully measure the judder in a brake system via the dynamometer and efficiently simulate the contact pressure variation by the hybrid algorithm. The three-dimensional simulation of thermo-mechanical interactions on the automotive brake, showing the transient thermo-elastic instability phenomenon, is presented for the first time in this academic community. We also find from the experimental study that the disk bulk temperature strongly influences the brake chattering in the automotive disk brakes.

The casting properties of a SiCP/Al composite are analyzed in this paper and the methods for producing complex castings of SiCP/Al composite disk brake together with their difficulty are discussed. An adjustable vacuum pressure casting method is established on the basis of a normal adjustable pressure casting method. The SiCP/Al composite disk brake casting is made with the established method. The results show that the adjustable vacuum pressure casting is a successful casting method for producing SiCP/Al composite castings of large dimensions and complex structures, which gives few defects as confirmed by Xray real- time image system.

The change in the critical speed due to surface temperature of automotive disk brakes may be analyzed both theoretically as well as experimentally. Juddering of disk brakes is closely related to its critical speed. In analyzing the critical speed, if $\sigma$ is positive, Disk develops TEI(Thermo-Elastic Instability) resulting in juddering in disk brakes. And $\sigma$ is affected not only by the critical speed but also by the initial temperature of disk surface. As the initial temperature of the disk surface rises, the critical speed decreases and juddering is developed more easily. Also, when hot spots are developed by TEI, they show large temperature difference in small local range.

In the disk braking of the railway trains, kinetic energy of the vehicles is converted into thermal energy by friction between a brake disk and the pad materials. This can be cause of the iterative thermal shock and generates thermal cracks on the brake disk surface. In this study, we show the comparative thermal fatigue test procedures and thermal crack analysis process to evaluate the thermal fatigue characteristics of candidate materials designed for development of heat-resistant brake disk material. We carried out tests on the conventional brake disk materials used for Saemaul and Mugunghwa trains, then we comparatively analyzed the thermal crack initiation and propagation on the surface of a specimen. A thermal fatigue test procedure and a crack analysis process were suggested to evaluate the heat resistance of the developed materials at later studies.

Low alloy heat resistant brake disk and sintered brake pad are applied to mechanical brake system for the speed-up of urban rapid transit. In this research, we analyzed how the frictional characteristics between brake disk and pad are influenced by the disk mass. At a high disk mass, the friction stability was the lower value as a result of the lack of tribofilm formation at the disk surface. Wear rates of friction materials showed the higher value at a low disk mass and wear rates of 10 mm and 15 mm showed the similar level. Average friction coefficient was the lower value at the 10 mm disk thickness and range of variation of average friction coefficient was also the smaller value at the 10 mm disk thickness. However, there were no significant changes in the friction coefficients under any of test conditions. Surface roughness of a disk showed the highest value at the 5 mm disk and surface roughnesses of 10 mm and 15 mm showed the similar level. As a result, friction characteristics of disk mass influenced the friction stability, as well as the wear rate of friction pad and disk, but not the friction coefficient.

Low alloy heat resistant brake disk and sintered brake pad are applied to mechanical brake systemfor the speed-up of urban rapid transit. In this research, we analyzed how the frictional characteristics betweenbrake disk and pad are influenced by the disk mass. At a high disk mass, the friction stability was the lower valueas a result of the lack of tribofilm formation at the disk surface. Wear rates of friction materials showed the highervalue at a low disk mass and wear rates of 10 mm and 15 mm showed the similar level. Average friction coefficientwas the lower value at the 10 mm disk thickness and range of variation of average friction coefficient was also thesmaller value at the 10 mm disk thickness. However, there were no significant changes in the friction coefficientsunder any of test conditions. Surface roughness of a disk showed the highest value at the 5 mm disk and surfaceroughnesses of 10 mm and 15 mm showed the similar level. As a result, friction characteristics of disk mass influencedthe friction stability, as well as the wear rate of friction pad and disk, but not the friction coefficient.