Okamura T.,KIRIU Corporation |
Yumoto H.,KIRIU Corporation
SAE Technical Papers | Year: 2010
Regarding the vibrational characteristics of a brake disc causing brake squeal, there are two factors: eigenmode alignment (or natural frequencies) and damping capacity. Focusing on the effects of dimensions on damping capacity of a brake disc, intensive CAE experiments for analyzing the effects were conducted. It was found that disc damping capacity can be increased independently of natural frequency by modifying disc dimensions. It was also found that peak accelerance obtained from a frequency-response function of a brake disc is an effective parameter for evaluating damping capacity of a brake disc. Copyright © 2010 SAE International.
Okamura T.,KIRIU Corporation
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2014
There are various processes for finishing the friction surfaces of a brake disc, which affect the braking effectiveness of a vehicle in the early stages of use in some cases. To examine the interaction between the disc surface texture, rotational direction, and friction material, a series of experiments on a tribotester using small-scale specimens was conducted.In a previous paper (2013-01-2056), the results from the first series of experiments, which involved of thirty disc surface textures and a less aggressive non-asbestos organic (NAO) friction material in on-brake-drag conditions combining constant speed and normal-load, was reported. Disc surfaces were finished by the following finishing processes in two rotational directions: turning under four cutting conditions, roller burnishing after turning, turning with a wiper insert, and grinding with two stones. Contact-pressure dependency of friction and wear was confirmed. Roller-burnished and wiper-turned discs exhibited different friction and wear at a certain contact pressure between rotational directions in the turning process.In the present study, four discs finished by grinding in a different cross-hatch pattern from that in the previous study and two friction materials (aggressive NAO and low-steel friction materials) were additionally tested. The findings from the test results on friction, wear, and transfer-layer build-up are presented. The directional difference in friction and wear was confirmed to depend on the combinations of disc surface texture, friction material, contact pressure, and test period. Even a grinding-finished disc and low-steel friction material exhibited a directional effect in some cases. © 2014 SAE International.
Okamura T.,KIRIU CORPORATION
SAE Technical Papers | Year: 2013
The surface texture of a brake disc in some cases affects the braking effectiveness of a vehicle in the early stages of use. Brake discs usually turn in one rotational direction during their finishing process but are turn in two directions on a vehicle. This causes a difference in friction or wear between two wheels. Directional surface textures of brake discs finished by turning or roller burnishing may cause this interaction to become more severe than those finished by grinding. Full-scale tests using actual friction pairs are effective for estimating the total braking performance of a full vehicle or its corners. However, they are exposed to various factors and different brake-disc locations creating different friction and wear histories. The author, therefore, concluded that fundamental experiments using small-scale specimens are necessary to examine the details of the interaction between the disc surface texture, rotational direction, and friction material. In this paper, the author reports the results of the first series of experiments, which consisted of thirty disc surface textures and a friction material under an on-brake-drag condition. Disc surfaces were finished by turning with normal and wiper inserts, roller burnishing, and grinding. Contact-pressure dependency of friction and wear was confirmed in preliminary tests and the pressure, which caused the largest difference among the tests, was selected for the main tests. The findings from the test results on friction, wear, and transfer-layer buildup are presented and the effects of disc surface textures on friction and wear are discussed. Copyright © 2013 SAE International.
Okamura T.,KIRIU CORPORATION |
Yumoto H.,KIRIU CORPORATION |
Imasaki M.,KIRIU CORPORATION
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2012
The propensity of brake squeal depends significantly on the vibrational characteristics of disc rotors. In this study, we focused on the differential effects of disc dimensions on the natural frequencies of various vibration modes. We analyzed the results of the CAE factorial experiments presented in our previous paper, which were conducted on four disc rotors with different designs such as front-and back-vented and solid discs. As a result, the effects of disc dimensions on natural frequencies were confirmed to depend on vibration modes, their orders (or the number of nodal diameters), and the basic design of disc rotors. The dimensions that change the stiffness of the friction ring such as ventilation-path width and fin thickness had larger effects on the out-of-plane circumferential modes of high orders than those of low orders. The dimensions around the necking, on the other hand, had a large effect on the low-order modes. The significance of these effects depends on the basic design of disc rotors as well. The effects of some typical dimensions on natural frequencies obtained from CAE experiments were further verified by comparing them with physical test results. © 2012 SAE International.