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Several number of ball joints are used in the suspension system. For these ball joints, rubber dust covers are used in order to maintain sufficient lubrication and protect the ball joint from contaminants such as water and dusts. In recent years, the number of breakage or grease leakage of the dust cover used under ultralow temperature is increasing with the growth of automobile selling in developing countries. In this research, we have studied the mechanism of dust cover breakage under ultralow temperature by focusing on the low temperature behavior of a rubber material.

Buckling at low temperature of a constant velocity joint (CVJ) boot was studied. In order to meet demands for reduction of boot size and weight, insight into the buckling mechanism is essential for optimized design of the boot. Since the buckling mechanism was not understood, it was hitherto impossible to simulate it. In this paper, the mechanism was clarified from both analytical and experimental investigation, and a simulation method was developed by using ABAQUS/Explicit. This method is effective in evaluating buckling resistance of new boot designs.

Propeller shaft boot is used under high temperature and high speed spinning operating conditions. Centrifugal force is an essential factor to be taken into consideration for designing such a boot which undergoes the said operating conditions. There is a failure mode related to the said operating conditions where the boot bellows get to balloon in a certain amount of operating time and rupture eventually. This is related to creep property, which is one of the material characteristics of rubber boot. In order to predict the boot deformation under high temperature and high speed spin conditions, we carried out static large deformation and nonlinear analysis with centrifugal force taken into consideration, using viscoelastic model for materializing the said creep property under high temperature conditions.

This paper addresses the temperature dependence of friction properties in seals (O-rings and D-rings) for use in reciprocating motions. The narrower focus here is on several factors: the effects of a lubrication state, the change in dimension and the physical properties of a rubber material. It can be assumed that they influence the temperature dependence of a frictional force. As shown in this study, A frictional force has a profile characterized by temperatures. It is revealed that the profile of a frictional force is mainly attributable to the deformation of a rubber material in motion-the physical properties (elastic modulus) of a rubber materials-and the rate of recovery in elasticity of a rubber material. In addition, a temperature showing the maximum frictional force is largely attributable to the low-temperature properties of a rubber material. It is revealed that the temperature dependence of a frictional force is mainly influenced by the material properties of rubber.

Lubricants such as wax and grease are used to improve adhesion, frictional properties, and sliding noise of thermoplastic elastomer (hereafter referred to as TPE) products used for automotive parts. These lubricants help improve the lubrication of products when added to TPE products or applied directly to the surface. Long-term effectiveness can be expected from the former method due to the gradual movement of the lubricant from the inside to the surface. Clarifying this transfer phenomenon should therefore be very important for predicting and controlling product characteristics. This paper reports on an analysis method applying infrared spectroscopy developed by the authors, and investigations conducted on the surface transfer of lubricants such as wax and grease for polyester TPE used for CVJ boots.

This paper presents a new concept of thermoplastic polyester elastomer boot (here in after referred to as TPEE boot) fitted for inboard, constant velocity universal joint (here in after referred to as CVJ). The CVJ has an irregularly shaped, tri-lobed housing for the purpose of weight and noise reduction. In this investigation, we carried out a series of analysis using FEM to develop the boot design. Our successful TPEE boot comprises two distinct features: (1) a boot with its inner surface sealing portion shaped to fit the outer surface of tri-lobe CVJ housing, and (2) a grommet to be fitted onto the boot and fastened by a clamp from the outside. Conventional boots for CVJ with tri-lobe shaped housing usually have a sealing portion of cylindrical profile, and a bushing is applied therein to fill the clearance between the CVJ housing and the boot sealing portion. The novel concept described herein is a particular method of applying a grommet outside of the boot.

This paper reports on a new concept for static seal designs taking into consideration the surface roughness of sealing surfaces. The concept focuses on fluid penetration from the interstices between the seal and counterface caused by surface roughness. In the study, we investigated the relation between the leakage and surface roughness of the sealing surface of the elastomer seal. At the same time, we also analyzed the contact state of the elastomer seal based on the equations of Ishiwata et al. on deformation of elastomer surface into rough surfaces [1]. The micro-leakage testing machine (SMLA) developed by the authors was used to measure micro-leakage at high precision and in a short time [2]. The results showed that the sealing phenomena were related to the ratio of seal surface contact pressure Ps / elastic modulus of seal E, determined by the compression ratio of seals, and does not depend on the chemical structure and hardness of the elastomer used.

The correlation between the micro surface roughness and sealability of O-rings was experimentally analyzed. We developed a SMLA (Seal Micro Leakage Analyzer) for observing the contact of micro asperities using a micro-prism glass plate, and a micro-leakage measurement device for O-rings. Using the SMLA, the contact of micro asperities of O-rings surfaces ranging from 1.6 microns to 16.3 microns was clearly visualized. We also measured the contact area and leakage amount at the same time, and studied the sealing mechanism. The visualized images of the contact area were analyzed by image processing. The results showed that the micro asperites on the O-ring surfaces were squashed elastically to form a band which sealed in the fluid.

The flow behavior of rubber compounds inside a mold is very complicated including various phenomena such as heat transfer from the mold, wall slip and swell at the divergent cavity. A slit rheometer which can measure the flow behavior inside a mold during curing was developed. The rheometer has a window which enables the observation of the flow behavior directly under 50 MPa. The pressure loss gradient along the flow direction and shear viscosity were found to be independent on the degree of cure but wall slip was observed. The wall slip phenomena could not be explained by slip analysis, because plug flow occurred due to little effects of the poiseuille flow. The pressure behavior inside the slit could be well predicted by using the equation obtained by assuming stress relaxation of visoelastic fluid occurs without share along the wall. The stress relaxation phenomena were predicted by taking into account the short and log relaxation time.

In order to clarify the sealing mechanism of radial lip seals, a new test apparatus with a hollow glass shaft was developed, and the fluid behavior under sealing condition was observed by using the Laser Induced Fluorescent (LIF) method. In this paper, the description of the test apparatus and first measurement results are shown. A laser dye dissolved in synthetic oil below the seal lip was excited at a wavelength of 427nm by a SHG solid state blue light laser. The fluorescence was detected by a CCD camera through an optical filter. The fluid paths of the oil beneath the seal lip appeared ahead of each rib as soon as a shaft started to rotate. Furthermore, the intensity of the fluorescence, which is related to the fluid film thickness, increased with shaft speed increasing. First measurement results obtained with the LIF method were in good agreement with other measurement results.