Rubber Hardness Research Articles

A study on mechanical and tribological properties of silicone rubber reinforced with white carbon black

This paper analysed the effect of different white carbon black (fumed silica and precipitated silica) on the mechanics and friction property of silicone rubber. The tensile strength, tearing strength, elongation rate and shore hardness of silicone rubber reinforced with different kinds or dosages of white carbon black were investigated in detail. The wear morphology, worn surface analysis and chemical compositions of the rubber sample after the friction test were analysed by means of scanning electron microscopy, three-dimensional profile metre and energy dispersive spectrometer, respectively. Results showed that the mechanics properties of silicone rubber were obviously enhanced with the increase in white carbon black content. Moreover, after the friction test, the vulcanised rubber reinforced with fumed silica has less wear surface protrusions and grinding than that of precipitated silica. The wear rubber filled with fumed silica surface is quite smooth and shows few furrows and grooves, which well corresponds to good anti-wear ability of the reinforcing fillers. In the course of practical application, it is necessary to take into account of the mechanical properties, wear resistance of rubber and the adding amount of filler to achieve the optimum coordination for the best mechanical and friction properties of silicone rubber.

Обоснование выбора упругого элемента для адаптивного режущего долота

Introduction. Problems of the adaptive drilling are currently discussed in a number of works. They are largely devoted to the regulation of standard parameters of the borer tools (depending upon the rock physical and mechanical properties at the mine face), and to implementing drill bit adaptation with complete or partial rearrangement of its structure accomplished through introduction of elastic elements. The paper objective is rationale for choosing an elastic element for an adaptive cutting bit, and its parametrization. Materials and Methods. Experimental research was carried out using a real adaptive cutting bit (dia. 160 mm) with rubber samples having various parameters. For testing, rubber samples with the following varied properties were selected: rubber hardness (Shore scale) 40 to 75 ea; sample height 25 to 60 mm; operating range of pressure load 5 to 30 kN; sample shapes solid parallelepiped, parallelepiped with lateral grooves, perforated parallelepiped, layered parallelepiped with layers ranging from 6 to 15 mm. Based on the experimental results, a comparison was carried out with validation of the most suitable elastic element type and its parameters. Research Results. Findings of the experimental study on elastic elements for adaptive cutting bits are presented. Following the comparison of the most common shapes of shock dampers, it is established that a multi-layered element serves best as an adapting joint. Discussion and Conclusions. Using rubber-based elastomers as elastic elements in adaptive cutting bits appears to be feasible for low diameter cutters. Recommendations are provided regarding rubber hardness, layer thickness, and total height of the elastic element for the specified stroke length values of the adaptive drilling bit blade.

Abrasive Wear Trends of Non-Conforming Contact Surfaces

Abrasive wear is found to decrease the efficiency of any equipment where three body wear takes place. The abrasive wear is found to increase the down time of the equipment, decrease the efficiency of operation, and in extreme condition total failure of the equipment. The abrasive wear is found to depend on operating parameter like hardness of contacting surfaces, abrasive grain size etc. The abrasive wear was found to increase with decrease in hardness and increase with abrasive grain size until grain size reaches a critical value. Once grain size reaches the critical value abrasive wear was found insensitive to the grain size. Different test in laboratory have been designed to simulate the abrasive wear. The one which is very popular is a dry abrasion test rig TR-53. It was found that wear rate increases with increase in rubber hardness of the wheel. The rubber hardness was also found to be dependent on temperature. In the present work a wear model abrasive test is done on cast iron, EN 31 and ceramics. Samples were accompanied at loads of 53.22N and 102.46N. The wear model predicted ploughing mode of wear and was found that the wear characterized in terms of volume loss increased with decrease in hardness. Scanning electron microscope study was carried out on wear scar to identify the wear mechanism which reveal basically cutting and ploughing mode type of wear.

A novel method for enhancing the energy absorption characteristics of circular tubular structures under axial splitting

The present research is an attempt to introduce a novel method for axial splitting of brazen tubes in order to eliminate the dependency of the conventional splitting mechanism on a hardened steel die and improve the energy absorption capability of the presented method. Some circular tubular samples were cut out from commercial brazen tubes and the specimens were then filled with natural rubbers with different shore hardness. For this purpose, the tubes were filled by raw rubbers and placed in an autoclave for a specific time at a controlled temperature to complete the curing process of rubbers. Some slits were created on one side of the rubber-filled tubes and the specimens were compressed during quasi-static axial compression loading between two rigid plates. Based on the experimental results, the effects of diameter and wall-thickness of the tubes, length and number of initial slits, rubber shore hardness and length of initial extra rubber on the energy absorption characteristics of the specimens are investigated. Also, experimental results of the presented splitting method are compared with those of the conventional splitting method (using conical dies for splitting of empty tubes) to find an optimized energy absorber. It was found that in comparison with the conventional splitting method, the presented technique eliminates the restrictions of using almost heavy dies which significantly decrease the overall mass of the system and moreover increases total energy absorption and keeps crush force efficiency in the range of classical splitting.

Effect of replacing carbon black with surfactant-modified silica clay on mechanical properties of natural rubber composites

The effect of replacing carbon black (CB) with surfactant-modified silica clay (SMSC) on hardness and tensile properties of natural rubber (NR) composites was studied using a simplex-lattice design of experiment. SMSC was produced by treating silica clay (SC) with coconut diethanolamine (CDEA) and glycerol monostearate (GMS). Complete replacement of CB with SMSC resulted in the decrease of Shore A hardness and tensile stress at all elongations. At higher CB to SMSC ratio, SMSC modified with CDEA performed better than with GMS. However, at lower CB to SMSC ratio, GMS exhibited larger values in the mechanical properties of NR composites. This can be attributed to the surface morphologies of SMSC and the surface aggregation of surfactant to SC.

Reverse roll coating with a deformable roll operating at negative gaps

Reverse roll coating is probably the most widely used coating operation, yet its full potential has not been exploited as it is shown in this paper which considers operation with a negative gap. We demonstrate through a wide range of experimental data that such operation can yield very thin and stable films with no ribbing or cascade instabilities when low viscosity fluids are used. Typically, stable film thickness less than 5μm can be obtained at speeds up to 150m/min when a rubber roller is used at −100μm gap with fluids of viscosity in the range 10–200mPas. These film thicknesses can be made to decrease further down to 1 or 2µm with a judicious choice of speed ratios (applicator to metering roller) and rubber hardness. Such new findings make this simple coating method an attractive roll to roll technique for application in the newer coating technologies, such as in the production of solar cells and plastic electronics. The data obtained in this study have been underpinned by a model based on the classical lubrication theory, well developed for such flow situations. Essentially it is shown that the film thickness non dimensionalised with respect to the set negative gap is controlled through a single parameter, the elasticity number Ne which combines all the operating parameters. Of course, this flow problem has complexities, particularly at high speed ratios and at zero gap so the data obtained here can serve as a basis for more comprehensive modelling of this classical fluid mechanic problem.

Fabrication of metallic bipolar plates in PEM fuel cell using semi-stamp rubber forming process

Metal is considered to be a good material for a bipolar plate due to its good electrical conductivity, excellent mechanical properties, and low cost. In this study, fabrication of metallic bipolar plates with serpentine flow field microchannels was investigated by a novel rubber pad forming process. Stainless steel 316 with thickness of 0.1 mm was used. Polyurethane rubbers with the hardness of shore A40, A55, A65, and A90 and the thickness of 10, 20, and 30 mm were used in this study to manufacture bipolar plates. At first, convectional rubber pad forming process was used to produce bipolar plates by some experimental tests. In this step, the effect of applied force, rubber hardness, and rubber thickness on filling percentage, thickness distribution, and dimensional accuracy was investigated. The results showed that filling percentage would increase by rising applied force, but channel depth was not equal in different directions. Increases in rubber hardness led to improving uniformity in channel depth. In addition, decreases in rubber hardness and increases in rubber thickness caused higher filling volumes. However, maximum filling percentage, dimensional accuracy, and thickness distribution in convectional rubber forming process were not satisfying. Thus, a novel method was developed in this study in order to improve the quality of fabricated bipolar plates named semi-stamp rubber forming. The results indicated that using semi-stamp rubber forming instead of convectional rubber forming would lead to 11.7, 9, and 1.075% improvement in filling percentage, thinning percentage, and dimensional accuracy, respectively. According to the results, the developed model (semi-stamp rubber forming) could be a feasible technique in fabricating metallic bipolar plates.

Effect of Replacing Carbon Black with Surfactant-Modified Natural Feldspar on Mechanical Properties of Natural Rubber Composites

The effect of replacing carbon black (CB) with surfactant-modified natural feldspar (SMNF) on hardness and tensile properties of natural rubber (NR) composites was studied using a simplex-lattice mixture design of experiment. SMNF was produced by treating natural feldspar (NF) with coconut diethanolamine (CDEA) and glycerol monostearate (GMS). Complete replacement of CB with SMNF based from CDEA or GMS decreased Shore A hardness and tensile stress at all elongations. NR composites reinforced with SMNF based from GMS exhibited higher mechanical properties than from CDEA which is attributed to the higher hydrophobicity factor of GMS. CDEA may also have aggregated on the surface of NF, resulting to poor filler dispersion and ineffective stress transfer.

Experimental investigation of Fracture in rubber pad forming of bipolar plate’s micro channels

Abstract Metallic bipolar plates are the most important part of proton exchange membrane fuel cell (PEMFC). In order to manufacturing of these plates, various method such as Hydroforming, electromagnet forming and stamping have been used. In this study rubber pad forming process was selected in order to forming metallic bipolar plates with stainless steel 316. At first effect of punch load, thickness and hardness of rubber on channel depth (before fracture) were investigated in order to determinate the maximum channel depth before fracture. After that, a novel method was developed by machining the rubber pad in order to prevent from fracture and increase in channel depth. According to the result, increase in hardness of rubber lead to decrease in channel depth and increase in applied force and thickness of rubber lead to increase in channel depth. Maximum filling percentage (before fracture) in rubber pad forming process was 76% achieved by Shore A 40 rubber pad with thickness of 30 mm and maximum thinning percentage before fracture is about 30%. Using new method was successful to prevent from fracture and formability has been increased by machining the rubber pad. As a result, the filling percentage for bipolar plate increased to 88%.

油潤滑下におけるＮＢＲの摩擦特性に及ぼすゴム硬さの影響

油潤滑下におけるＮＢＲの摩擦特性に及ぼすゴム硬さの影響

Properties Research of Packer Rubber Materials

According to the use and environmental characteristics of rubber cylinders, a research on the composition and hardness of rubber was carried out. Hydrogenated acrylonitrile-butadiene rubber (HNBR) was used as the main material, which is characterized by high mechanical strength and good wear-resistance. Composition of the rubber cylinder was determined by detailed analysis on each type of raw material, made through experimentation. Through finite element analysis of rubber at different hardness setting force, sealing and tear resistance, it is found out that overall performance is best at shore hardness of 88 degrees.

Physics of failure analysis of power section assembly for positive displacement motor

Power section assembly is the core part of positive displacement motor (PDM), and its mechanical behavior and service life determine the drilling efficiency and cycle. In this paper, fault tree of power section assembly was established, failure reasons were analyzed and improvement measures were put forward. Finite element models of conventional lining and uniform wall thickness lining of 5/6 PDM were established, and the mechanical behaviors were investigated. Working parameters such as drilling fluid pressure, rubber hardness, downhole temperature and pressure difference were discussed. The results show that wear and rust are the main failure modes of the rotor. Failure modes of rubber lining are wear, tear, rupture, peeling off, thermal failure and fatigue failure. Under the action of drilling fluid pressure, the maximum effective stress of rubber lining appears in the bottom of arc, and the minimum stress appears at the top of arc. But deformation distribution is opposite to the effective stress. Deformation of uniform wall thickness lining is more uniform. Effective stress of the lining increases with the increasing of drilling fluid pressure and rubber hardness, but it decreases with the downhole temperature increases. Deformation of the lining increases with the drilling fluid pressure increases, but it decreases with the increasing of rubber hardness and downhole temperature. Effective stress and deformation distribution of rubber lining are more uneven with the pressure difference increases. High stress area lies between the two smallest chambers.

The influence of washing machine-leg hardness on its dynamics response within component-mode synthesis techniques

In this paper, we investigate a washing machine's dynamic response. Using an experimental modal analysis, the dependence of the first two natural frequencies on the hardness of leg rubber is demonstrated. In order to model this behaviour, a complete washing-machine numerical model is developed, including a detailed model of the leg. A simple linear leg model is proposed, which accounts for the contact conditions and enables an implicit analysis. The model is validated, based on two measurements with different leg configurations. Additionally, the component-mode synthesis methods are proposed. They allow separate treatment of the washing machine's legs and cabinet, as well as reducing the model order. The four model-reduction techniques are compared with the classic finite-element method. It is shown that the component-mode synthesis methods enable fast recalculation times for the modified substructures, while the remaining structure is calculated only once. This leads to a computationally efficient analysis. A comparison of the results shows good agreement between the component-mode synthesis methods and the classic finite-element method.

Numerical prediction of springback and ductile damage in rubber-pad forming process of aluminum sheet metal

Rubber forming is a sheet metal forming process using flexible punch or die. In this paper, finite element method is introduced to analyze rubber-pad forming process of aluminum sheet metal. An elasto-plastic constitutive model with J2 yield criterion and mixed non-linear isotropic/kinematic hardening coupled with Lemaitre's ductile damage has been adopted during flexible forming operation. To model rubber material, a Mooney-Rivlin theory is used in the finite element simulation. A stamping of aluminum sheet metal with soft punch is simulated. A fully coupled elasto-plastic damage model is implemented in ABAQUS/Standard software via UMAT subroutine to study the effect of some key process parameters like hardness of rubber, type of rubber on the variation of the thickness, the springback and damage of aluminum sheet metal.

Preparation and characterization of vulcanized silicone rubber/halloysite nanotube nanocomposites: Effect of matrix hardness and HNT content

Halloysite nanotube (HNT) was successfully surface-treated. The grafted HNT was evaluated by TEM, FTIR and TGA. Modified HNT was used to prepare silicone rubber/HNT vulcanizate nanocomposites. The effects of silicone rubber hardness and HNT loading on the cure characteristics, swelling behavior, dynamic mechanical, thermal and mechanical properties of the resulting rubber compounds were systematically studied by rheometry, DMTA, TGA and tensile testing, respectively. The obtained results were correlated with the microstructure of the samples as investigated by XRD and SEM analyses. Vulcanization curves revealed that the HNT had a positive effect on the cure kinetics of the rubber compounds via steady decrease in scorch time and optimum cure time along with a gradual increase in effective torque with HNT content. The incorporation of HNT into the silicone rubbers enhanced the crosslink density of the nanocomposites. DMTA results showed restricted relaxation processes in HNT-reinforced systems compared with the unfilled silicone rubbers, with more pronounced effect for system with silicone rubber matrix of lowest hardness. The tensile data demonstrated a rise in Young's modulus and tensile strength of the filled rubbers with HNT content. The thermal stability of the rubber compounds gradually improved with HNT loading in the material according to TGA results.

Hardness and compression resistance of natural rubber and synthetic rubber mixtures

This project aims to mechanically characterize through compression resistance and shore hardness tests, the mixture of hevea brasiliensis natural rubber with butadiene synthetic rubber (BR), styrene-butadiene rubber (SBR) and ethylene-propylene-diene monomer rubber (EPDM). For each of the studied mixtures were performed 10 tests, each of which increased by 10% the content of synthetic rubber in the mixture; each test consisted of carrying out five tests of compression resistance and five tests of shore hardness. The specimens were vulcanized on a temperature of 160°C, during an approximate time of 15 minutes, and the equipment used in the performance of the mechanical tests were a Shimadzu universal machine and a digital durometer. The results show that the A shore hardness increases directly proportional, with a linear trend, with the content of synthetic BR, SBR or EPDM rubber present in the mixture, being the EPDM the most influential. With respect to the compression resistance is observed that the content of BR or SBR increase this property directly proportional through a linear trend; while the EPDM content also increases but with a polynomial trend.

Experimental and numerical studies on the formability of TB5 titanium sheet in rubber cold forming

Titanium alloys are often used in aircraft manufacturing. Titanium sheet exhibits low formability and high springback at room temperature, and this causes significant challenges with conventional forming methods. In this study, the phenomena and mechanisms of the formability of TB5 titanium alloys in rubber forming were investigated. It was found that rubber forming was effective for TB5 titanium sheets. Wrinkling in rubber forming was controlled by the side blankholder. The effects of the design parameters of the side blankholder on wrinkling were studied. A typical part was used to investigate the rubber cold forming of TB5. The largest height of the wrinkle became smaller with the increase of the forming pressure, while the hardness of rubber had little effect on the wrinkling. In order to eliminate the wrinkles completely, a wedge was introduced to increase the forming pressure on the shrink flange. Using the wedge, the forming pressure was increased a lot, and the wrinkles were flattened. Springback was controlled by die compensation. Aging treatment was used to increase the strength and part accuracy. After the aging treatment, the internal stress in the cold forming was released. The springback of the flange was corrected.

Static and Dynamic Sealing Performance Analysis of Rubber D-Ring Based on FEM

In order to study the performance of the dynamic seal and static seal of D-ring, the FEM models of D-ring and O-ring were built, and the process of reciprocating seal of the D-ring was simulated. In addition, the effects of pre-compression, medium pressure, friction coefficient, and rubber hardness on sealing performance were discussed. The friction coefficients between rubber sealing ring and steel part, under different lubrication conditions, were measured through the experiment. The results show that, in static seal, the maximum contact stress of the D-ring increases with the increasing of pre-compression, friction coefficient, medium pressure, and rubber hardness. Besides, O-ring can be well replaced by D-ring in static seal. Since it can avoid distortion and twisting effectively in reciprocating dynamic seal and prolong its working life, D-ring has a better sealing performance in reciprocating seal than O-ring. As the friction coefficient grows, the amplitude of the maximum contact stress fluctuation increases as well as the fluctuation of the cross-section deformation which has a bad influence on sealing performance and fatigue life of the D-ring.

A 3D-printed functioning anatomical human middle ear model

The middle ear is a sophisticated and complex structure with a variety of functions, yet a delicate organ prone to injuries due to various reasons. Both, understanding and reconstructing its functions has always been an important topic for researchers from medical and technical background. Currently, human temporal bones are generally used as model for tests, experiments and validation of the numerical results. However, fresh human preparations are not always easily accessible and their mechanical properties vary with time and between individuals. Therefore we have built an anatomically based and functional middle ear model to serve as a reproducible test environment.Our middle ear model was manufactured with the aid of 3D-printing technology. We have segmented the essential functional elements from micro computed tomography data (μCT) of a single temporal bone. The ossicles were 3D-printed by selective laser melting (SLM) and the soft tissues were casted with silicone rubber into 3D-printed molds. The ear canal, the tympanic cavity and the inner ear were artificially designed, but their design ensured the anatomically correct position of the tympanic membrane, ossicular ligaments and the oval window.For the determination of their auditory properties we have conducted two kinds of tests: measurement of the stapes footplate response to sound and tympanometry of the model. Our experiments regarding the sound transmission showed that the model has a similar behavior to a human middle ear. The transfer function has a resonance frequency at around 1 kHz, the stapes' response is almost constant for frequencies below the resonance and a roll-off is observed above the resonance. The tympanometry results show that the compliance of the middle ear model is similar to the compliance of a healthy human middle ear.We also present that we were able to manipulate the transmission behavior, so that healthy or pathological scenarios can be created. For this purpose we have built models with different mechanical properties by varying the hardness of the silicone rubber used for different structures, such as tympanic membrane, oval window and ossicle attachments in the range of Shore 10–40 A. This allowed us to set the transmission amplitudes in the plateau region higher, lower or within the tolerances of normal middle ears (Rosowski et al., 2007).Our results showed that it is possible to build an artificial model of the human middle ear by using 3D-printing technology in combination with silicone rubber molding. We were able to reproduce the anatomical shape of the middle ear's essential elements with high accuracy and also assemble them into a functioning middle ear model. The acoustic behavior of the model can be reproduced and manipulated by the choice of material. If the issues such as resonance of the casing and steep roll-off slope in higher frequencies can be solved, this model creates a reproducible environment for experiments and can be useful for the evaluation of prosthetic devices.

430 触力覚センサを用いたスポンジやゴムの硬さ比較装置の試作(GS4-4 センシング・欠陥検出)

430 触力覚センサを用いたスポンジやゴムの硬さ比較装置の試作(GS4-4 センシング・欠陥検出)