Basic Problems in the Theory of Bond Strength between the Plies of a Rubber Article

1959 ◽  
Vol 32 (4) ◽  
pp. 1192-1198 ◽  
Author(s):  
G. A. Patrikeev
Keyword(s):  
Bond Strength ◽  
Structural Type ◽  
Vulcanized Rubber ◽  
High Speeds ◽  
Great Hope ◽  
Theoretical Investigations ◽  
Minimum Requirements ◽  
Rubber Article ◽  
Basic Determinant ◽  
Selection Of

Abstract The problem of ensuring adequate bonding strength between uniform and nonuniform layers in composite vulcanized rubber articles is particularly vital in the production of high grade multi-ply articles for heavy duty (high speeds, high dynamic loading and considerable heat build-up) and also in the production of multi-ply articles from dissimilar compounds based on synthetic rubbers of different structural type. In works practice various methods are known for the production of two-ply and multi-ply composite vulcanized rubber articles, based on plying-up in the hot state (sometimes combined with buffing of the unvulcanized parts and the use of special materials to increase the tackiness of the stocks) and also on the use of solvents and the cementing of the stocks by a cement, sometimes of several types applied in sequence. Difficult technological tasks arise in the production of composite articles with dissimilar plies based on rubbers of different chemical composition, for instance of natural and sodium butadiene (or chloroprene) or of natural (or butadiene) and butyl rubber. In spite of considerable practical successes, many of the tasks enumerated above remain unsolved, and there is hardly any great hope of success without a previous examination of a number of basic theoretical questions. A theory of strength has not been worked out even for the most simple case—the stretching of a strip of unloaded vulcanized rubber. There are many questions unstudied, the examination of which must precede the development of a theory of the strength of dissimilar plies in a multi-ply composite rubber article. Before considering the separate questions we regard it as worthwhile to formulate the general tasks of a theory, keeping within the bounds of the problem under discussion, i.e., bond strength. According to the minimum requirements, theoretical investigations ought to enable the selection of correct basic (determinant) scientific lines and to facilitate the development of rational methods of investigation, reflecting the essential aspects of the phenomenon being studied. Of course, major failures and unplanned and wasted labor are often caused by the choice of mistaken lines of investigation or are the outcome of the use of mistaken methods of testing.

Determination of Static and Dynamic Bond Strength between Vulcanizates

1960 ◽  
Vol 33 (2) ◽  
pp. 581-586 ◽  
Author(s):  
M. M. Reznikowskiĭ
Keyword(s):  
Service Life ◽  
Bond Strength ◽  
Dynamic Testing ◽  
Dynamic Pattern ◽  
Static Tests ◽  
Vulcanized Rubber ◽  
Inadequate Knowledge ◽  
Dynamic Methods ◽  
Selection Of

Abstract Methods employed for the determination of bond strength between vulcanizates may be classified as static or dynamic. Each of these groups has its own advantages and shortcomings. One undoubted advantage of the majority of static methods is that the tests are carried out under conditions where the stresses and deformations which determine ply separation may be measured directly. It is at the same time easy to determine the temperature since the specimens undergoing ply separation may be thermostatically conditioned. Nevertheless the practical value of the results obtained in static tests is very limited. In the first place, the character of the stresses governing ply separation in no way reproduces the true picture of the service life of multiply vulcanized rubber articles (in particular, tires), and, secondly, the resistance to ply separation for a single loading, for a number of reasons, may not indicate the endurance of the articles under repeated deformation. In dynamic tests we use the endurance under repeated deformations as a criterion of bond strength, presuming that the dynamic pattern of testing in some way reproduces the pattern of service of the material in the article. Unfortunately, the index of service life of any test specimens depends, in a complex manner which we do not in general understand, not only upon the bond strength between the vulcanizates, but also upon the stresses, deformations and also temperatures developed in the boundary layer. These parameters (stress, deformation and temperature) depend in their turn upon the elastic and relaxation properties of the vulcanizates from which the test specimen is made up. If the testing of the specimens is carried out in a dynamic pattern essentially different from that of service, then the results may be quite contrary to the behavior of the materials in an article. The selection of a rational method of dynamic testing applicable to tire compounds is particularly complicated on account of inadequate knowledge of the dynamic pattern of the operation of the component parts of the tire. Summarizing, we see that in investigations and tests of bond strength between vulcanizates we are obliged to use both static and dynamic methods. The static methods, allowing a quantitative interpretation of the results, must be considered more reliable for investigations in the fields of adhesion and covulcanization, particularly in cases where we are studying the effect of factors which essentially alter the properties (above all, the elastic and hysteresis properties) of pliedup vulcanizates.

Cybersecurity Standards in the Context of Operating System

2021 ◽  
Vol 54 (3) ◽  
pp. 1-36
Author(s):  
Syed Wasif Abbas Hamdani ◽  
Haider Abbas ◽  
Abdul Rehman Janjua ◽  
Waleed Bin Shahid ◽  
Muhammad Faisal Amjad ◽  
...  
Keyword(s):  
Organizational Context ◽  
Cyber Attacks ◽  
Fine Tuning ◽  
Security Vulnerabilities ◽  
Compliance Testing ◽  
Depth Analysis ◽  
Minimum Requirements ◽  
Security Standards ◽  
High Degree ◽  
Selection Of

Cyber threats have been growing tremendously in recent years. There are significant advancements in the threat space that have led towards an essential need for the strengthening of digital infrastructure security. Better security can be achieved by fine-tuning system parameters to the best and optimized security levels. For the protection of infrastructure and information systems, several guidelines have been provided by well-known organizations in the form of cybersecurity standards. Since security vulnerabilities incur a very high degree of financial, reputational, informational, and organizational security compromise, it is imperative that a baseline for standard compliance be established. The selection of security standards and extracting requirements from those standards in an organizational context is a tedious task. This article presents a detailed literature review, a comprehensive analysis of various cybersecurity standards, and statistics of cyber-attacks related to operating systems (OS). In addition to that, an explicit comparison between the frameworks, tools, and software available for OS compliance testing is provided. An in-depth analysis of the most common software solutions ensuring compliance with certain cybersecurity standards is also presented. Finally, based on the cybersecurity standards under consideration, a comprehensive set of minimum requirements is proposed for OS hardening and a few open research challenges are discussed.

scholarly journals Dilemmas in zirconia bonding: A review

2013 ◽  
Vol 141 (5-6) ◽  
pp. 395-401 ◽  
Author(s):  
Kosovka Obradovic-Djuricic ◽  
Vesna Medic ◽  
Slobodan Dodic ◽  
Dragan Gavrilov ◽  
Djordje Antonijevic ◽  
...  
Keyword(s):  
Bond Strength ◽  
Glass Ceramics ◽  
Ceramic Materials ◽  
The Other ◽  
Zirconia Ceramic ◽  
Bonding Mechanism ◽  
Luting Cements ◽  
Esthetic Dentistry ◽  
Selection Of

This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

scholarly journals Effect of Provisional Cements on Shear Bond Strength of Porcelain Laminate Veneers

2011 ◽  
Vol 05 (04) ◽  
pp. 373-379 ◽  
Author(s):  
Subutay Han Altintas ◽  
Onjen Tak ◽  
Asli Secilmis ◽  
Aslihan Usumez
Keyword(s):  
Bond Strength ◽  
Calcium Hydroxide ◽  
Shear Bond Strength ◽  
Testing Machine ◽  
Acrylic Resin ◽  
Resin Cement ◽  
Control Group ◽  
Molar Teeth ◽  
Laminate Veneers ◽  
Selection Of

ABSTRACTObjectives: The purpose of this study was to evaluate the effect of three provisional cements and two cleaning techniques on the final bond strength of porcelain laminate veneers. Methods: The occlusal third of the crowns of forty molar teeth were sectioned and embedded in autopolymerizing acrylic resin. Dentin surfaces were polished and specimens were randomly divided into four groups (n=10). Provisional restorations were fabricated and two provisional restorations were cemented onto each tooth. Restorations were fixed with one of three different provisional cements: eugenol-free provisional cement (Cavex), calcium hydroxide (Dycal), and light-cured provisional cement (Tempond Clear). Provisional restorations were removed with either a dental explorer and air-water spray, or a cleaning bur (Opticlean). In the control group, provisional restorations were not used on the surfaces of specimens. IPS Empress 2 ceramic discs were luted with a dual-cured resin cement (Panavia F). Shear bond strength was measured using a universal testing machine. Data were statistically analyzed by ANOVA, Tukey’s HSD and Dunnett tests. Surfaces were examined by scanning electronic microscopy. Results: Significant differences were found between the control group and both the light-cured provisional cement groups and the eugenol-free provisional cement-cleaning bur group (P<.05). Groups that had received light-cured provisional cement showed the lowest bond strength values. Conclusions: Selection of the provisional cement is an important factor in the ultimate bond strength of the final restoration. Calcium hydroxide provisional cement and cleaning with a dental explorer are advisable. (Eur J Dent 2011;5:373-379)

Methods for Determination of Rubber to Cord Bond Strength

1959 ◽  
Vol 32 (3) ◽  
pp. 898-906
Author(s):  
R. V. Uzina ◽  
L. S. Gromova ◽  
S. A. Vasil'eva
Keyword(s):  
Bond Strength ◽  
Laboratory Method ◽  
Single Thread ◽  
Vulcanized Rubber ◽  
Pull Out ◽  
Cord Fabric ◽  
Fabric Structures

Abstract In selecting methods for determination of rubber to cord bond strength it is necessary to consider the factors which are subject to variation in the system— the type of cord, the composition of the vulcanized rubber, or the composition of the impregnant. The selection (composition) of the methods of assessment of bond strength was carried out in the present study while keeping the type of cord and the rubber compositions constant ; only the composition of the impregnant was varied. Up to the present there has been no single laboratory method for evaluating rubber to cord bond strength for the determination of the service quality of rubber-fabric structures. The bond strength in such a system is assessed in the majority of cases by the use of a series of methods. The existing methods may be systematized according to the nature of the deformation (static or dynamic), the nature of the specimen (with single thread of cord or with cord fabric) and so on. We adopted the following classification of methods: 1). Determination of bond strength of a single thread of cord with the rubber; 2). Determination of bond strength of rubber to fabric model specimens. Determination of bond strength of a single thread of cord with rubber is an exceptionally widely used type of testing in the rubber industry. It is based either on the principle of stripping of a single thread of cord from the rubber under pressure, or on the principle of pull-out of a thread of cord from a rubber specimen.

scholarly journals Idealized walking and running gaits minimize work

2007 ◽  
Vol 463 (2086) ◽  
pp. 2429-2446 ◽  
Author(s):  
Manoj Srinivasan ◽  
Andy Ruina
Keyword(s):  
Numerical Optimization ◽  
Phase Plane ◽  
Step Length ◽  
Metabolic Energy ◽  
One Dimensional ◽  
High Speeds ◽  
Locomotor Patterns ◽  
Positive Work ◽  
Selection Of ◽  
Trajectory Problem

Even though human legs allow a wide repertoire of movements, when people travel by foot they mostly use one of two locomotor patterns, namely, walking and running. The selection of these two gaits from the plethora of options might be because walking and running require less metabolic energy than other more unusual gaits. We addressed this possibility previously using numerical optimization of a minimal mathematical model of a biped. We had found that, for a given step-length, the two classical descriptions of walking and running, ‘inverted pendulum walking’ and ‘impulsive running’, do indeed minimize the amount of positive work required at low and high speeds respectively. Here, for the case of small step-lengths, we establish the previous results analytically. First, we simplify the two-dimensional particle trajectory problem to a one-dimensional ‘elevator’ problem. Then we use elementary geometric arguments on the resulting phase plane to show optimality of the two gaits: walking at low speeds and running at high speeds.

Preliminary Study on Curing of Thick Rubber Article

2015 ◽  
Vol 1134 ◽  
pp. 23-27
Author(s):  
Siti Zulaikha Ibrahim ◽  
Che Mohd Som Said ◽  
Mohamad Asri Ahmad ◽  
Azemi Samsuri
Keyword(s):  
Tensile Strength ◽  
Temperature Region ◽  
The State ◽  
Curing Temperature ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Cure Time ◽  
Zinc Diethyldithiocarbamate ◽  
Preliminary Study ◽  
Rubber Article

In this study, several batches of natural rubber (SMR L) were compounded with three different types of accelerators, which were N-cyclohexylbenzothiazole-2-sulphenamide (CBS), diphenylguanidine (DPG) and zinc diethyldithiocarbamate (ZDEC). ZDEC is known as an ultrafast accelerator. The rubber compounds were cured at 140°C, 130°C, 120°C, 110°C and 100°C in accordance with the temperature gradients observed within the thick rubber block. The main aim of this study is to cure the rubber at each temperature region to the same cure time as that of the outermost region (20 minutes at 140°C). The amount of sulfur and accelerator were adjusted accordingly at each curing temperature to match the state of cure at 140°C. The state of cure of of the vulcanized rubbers were measured using hardness and tensile strength. The same state of cure is achieved if the hardness and tensile strength value are within ±2 IRHD and ±3 MPa, respectively with that of the control vulcanized rubber (hardness and tensile strength cured at 140°C). The results shows that the hardness and tensile strength of the vulcanized rubber at each temperature region are within the expected margins. The results clearly indicated that the type and amount of accelerators, and the amount of sulfur were correctly chosen at each temperature.

scholarly journals STUDYING UKRAINIAN IN PRIMARY SCHOOL IN MULTILINGUALISM

2019 ◽  
pp. 105-116
Author(s):  
Valentyna Trunova
Keyword(s):  
Life Experience ◽  
School Students ◽  
Language Of Instruction ◽  
Minimum Requirements ◽  
Speech Training ◽  
Speech Learning ◽  
Working Out ◽  
Preparatory Work ◽  
Speech Situation ◽  
Selection Of

It was established that the level of minimum requirements for the speech training of elementary school students should be the same, regardless of the school in which the students study - with the Ukrainian language of instruction or another (in Russian, Bulgarian, Moldavian, etc.). The study of research on the problem revealed the place of speech situations in the language lessons, literary and extracurricular reading. By a speech situation, the author understands an artificially created situation where the student feels with the hero, or instead of the hero. Types of speech learning situations (real, imaginary, built on the basis of the read text, selected illustrations, drawings) are highlighted. The structural components of the speech situation (the description of the scene, participants in the conversation, the speaker’s life experience, speech patterns, speech task, stimulus, motive, speech reaction) are disclosed and a description of each structural component is given. It is determined that the condition for the effectiveness of the use of speech situations is the selection of speech material that meets certain criteria, principles and approaches, and the preparatory work of the teacher: clarifying the dictionary, working out the pronunciation of words, making phrases, etc.

scholarly journals RECYCLING OF MODIFIED ASPHALT SHEETS FOR AUTOMOTIVE USE

10.6036/10097 ◽  
2021 ◽  
Vol 96 (4) ◽  
pp. 351-354
Author(s):  
MIGUEL FERNANDO ALDAS CARRASCO ◽  
CRISTINA PAOLA PAVON VARGAS ◽  
ANDRES FABRICIO ACEVEDO DAVILA ◽  
HARRISON DE LA ROSA RAMIREZ ◽  
VLADIMIR VALLE ALVAREZ ◽  
...  
Keyword(s):  
Manufacturing Process ◽  
Industrial Scale ◽  
Recycling Process ◽  
Modified Bitumen ◽  
Modified Asphalt ◽  
Asphalt Mastic ◽  
Minimum Requirements ◽  
Rotational Viscosity ◽  
Parameters Of Interest ◽  
Selection Of

In the present study, the recycling of modified bitumen soundproofing membranes, known as automotive-grade asphalt (ART) membranes, was carried out. The ART sheets were incorporated in the mixing stage of the asphalt mastic, which is part of the manufacturing process of new sheets. The selection of the best asphalt mastic formulation was performed at laboratory scale, where the ATR sheet cutting waste was added to the original asphalt mastic at 2.5, 5.0, 7.5, 10.0 and 15.0 % w/w percentages. The formulations were evaluated for six parameters of interest associated with softening point, rotational viscosity, density, weight per area, thickness and creep. It was determined that the properties of all the formulations studied met the minimum requirements stipulated for the commercialization of the product. The recycling process was carried out on an industrial scale using the formulation with 5% w/w of ATR residues, which presented a viscosity close to that of the original mastic. The results at industrial scale were favorable, since the six parameters of interest were within the ranges established in the regulations.

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