Glued Structures Research Articles

УЗАГАЛЬНЕННЯ МОДЕЛІ ФОЛЬКЕРСЕНА НА ВИПАДОК ОСЬОВОЇ СИМЕТРІЇ

Thin-walled structures may contain defects as cracks and holes that are leftovers of the material the construction, is made of or they occur during the operation as a result of, for example, mechanical damage. The presence of holes in the plate causes a concentration of stresses at the boundary of the holes and ultimately leads to premature failure of the structural element. Repair of local damage of modern aircraft structures can be made by creating overlays that are glued to the main structure. The overlay takes on part of the load, unloading the damaged area. This method of repair provides tightness and aerodynamic efficiency to the structure. The calculation of the stress state of such glued structures is usually performed by using the finite element method. The classic models of the stress state of overlapped joints are one-dimensional. That is, the change of the stress state along only one coordinate is considered. At the same time, the connections of a rectangular form are also considered. The purpose of this work is to create a mathematical model of the stress state of circular axisymmetric adhesive joints and to build an appropriate analytical solution to the problem. It is assumed that the bending of the plates is absent; the deformation of the plates is even by thickness. The adhesive layer works only on the shift. The main plate and the overlay are considered isotropic. The solution is built on polar coordinates. The stress state of the connection depends only on the radial coordinate, i.e. one-dimensional. The solution is obtained in analytical form. This mathematical model is a generalization of the classical model of the adhesive connection of Volkersen to a circular or annular region and is considered for the first time. Boundary conditions are met exactly. The satisfaction of marginal conditions, as well as boundary conditions, leads to a system of linear equations with respect to the unknown coefficients of the obtained solutions. The model problem is solved and the numerical results are compared with the results of calculations performed by using the finite element method. It is shown that the proposed model has sufficient accuracy for engineering problems and can be used to solve problems of the design of aerospace structures.

Detecting Discontinuities in Polymer Composite Materials and Multilayer Glued Structures

Detecting Discontinuities in Polymer Composite Materials and Multilayer Glued Structures

DETECTION OF ADHESION-FREE AREAS AND EXFOLIATIONS IN MULTILAYER STRUCTURES BY THE ACOUSTIC-TOPOGRAPHIC METHOD

Physical the bases of acoustic-topographic method of defektoskopiya of multilayer structures are briefly covered. Installation for implementation of acoustic-topographic method in two options is developed and mounted: with the magnetostrictive activator and with the electromagnetic (shock) activator. By pilot studies it is established that at control by acoustic-topographic method of brazed and welded structures sensitivity of control significantly (in 2–3 times) is higher, than at control by other methods of defektoskopiya. It is established also that the zone of control of multilayer glued structures is much less, than at control of brazed and welded structures. It is shown that the greatest thickness of the upper leaf of structure at which control by acoustic-topographic method with sufficient sensitivity is still possible, is equal to about 1 mm, at control of structures with thickness of the upper leaf initiation of elastic oscillations it is reasonable to carry out over 1 mm in the shock way. Repeated control with change of point of input of ultrasonic oscillations is in certain cases necessary for specification of picture of distribution of powder near initial point of input of oscillations.

Комплексная защита несущих клееных деревянных конструкций

Комплексная защита несущих клееных деревянных конструкций

RESEARCH AND IMPROVEMENT OF NONCONTACTING TECHNIQUE OF THE ULTRASONIC THROUGH TRANSMISSION METHOD OF NON-DESTRUCTIVE TESTING

Operation capabilities of ultrasonic through transmission method of non-destructive testing of products from polymeric composite materials and multilayer glued structures are considered. It is shown that for detection of defects in products from easily damaged materials, from the hydroscopic materials which are not allowing wetting by liquids, in designs with rough surface, and also for detection of the under surface defects which are not revealed by contact methods, effective use of ultrasonic through transmission noncontacting method. The calculation procedure and designing of ultrasonic through transmission noncontacting probes on the frequency of 200 kHz, allowing to reveal defects in products from polymeric composite materials and in multilayer glued structures with higher sensitivity, than noncontact ultrasonic probes applied now on frequencies 20, 40 and 80 kHz is offered. The constructive scheme of the vibrator with two piezoelectric plates from ceramics TsTS-19, included inphase, with the metal lap playing role of wave guide, and matching layer from foam plastic is provided. It is specified that two piezoelectric plates works in “short circuit” mode therefore sound pressure piezoelectric plates increases by acoustic line twice, and oscillation strength four times.

Polyurethane Adhesives for Structural Parts of Means of Transport with Enhanced Processing Properties and Performance

This article presents the characteristics of VILAD-40M polyurethane adhesive used to fabricate glued structures from various laminated materials (sandwich panels) and for structural parts in production of various transport systems. It is shown that VILAD-40M is on par with foreign analogs in terms of processing properties and adhesion strength of adhesion bonds of materials used to fabricate sandwich panels, such as aluminum alloys, steels, fiberglass and ABS resins, and plywood.

ACOUSTIC NON-DESTRUCTIVE TESTING OF MULTILAYERED STRUCTURES FROM PCM DURING THE PRODUCTION AND OPERATION OF AVIATION TECHNIQUE

Considered the use in the production of aviation equipment (airplanes and helicopters), polymer composites differing in enhanced operational and technological properties, such as strength, rigidity, level of working temperatures, etc. Examples are given of using newer gliders in multilayer structures MS-21 aircraft and Mi-38 helicopter of modern composite materials. The review of defects of multilayer structures made of polymer composite materials arising at the stage of manufacturing, storage, transportation and operation of aircraft, and low-frequency methods of their control is presented. It is noted that the main of low-frequency control methods are the impedance method and the method of free oscillations proposed by domestic scientists.The principle of operation of the first portable multifunctional computerized pulsed flaw detector DAMI-C09, combining impedance, impact and eddy current ND methods, is described. It is noted that the flaw detector can be used for manual and automated, as part of a robotic complex, to identify bundles, nonglues and other violations of the integrity of composites, honeycomb structures and glued structures, to determine corrosion centers, surface and internal defects in non-ferromagnetic materials. A feature of the flaw detector is the simplified preparation process for work due to the automated mode of tuning the signal in amplitude or phase using a spectrum analyzer, documenting the monitoring results with the ability to transfer to a computer and subsequent processing with the help of a special APM of the Flaw Detector. Examples of the effective use of the flaw detector in the production and operation of aviation equipment are given.

ПРИМЕНЕНИЕ ВАРИАНТОВ АКУСТИЧЕСКОГО ИМПЕДАНСНОГО МЕТОДА ДЛЯ КОНТРОЛЯ ДЕТАЛЕЙ ИЗ ПКМ И МНОГОСЛОЙНЫХ КЛЕЕНЫХ КОНСТРУКЦИЙ

ПРИМЕНЕНИЕ ВАРИАНТОВ АКУСТИЧЕСКОГО ИМПЕДАНСНОГО МЕТОДА ДЛЯ КОНТРОЛЯ ДЕТАЛЕЙ ИЗ ПКМ И МНОГОСЛОЙНЫХ КЛЕЕНЫХ КОНСТРУКЦИЙ

КОНТРОЛЬ ИЗДЕЛИЙ ИЗ ПКМ И МНОГОСЛОЙНЫХ КЛЕЕНЫХ КОНСТРУКЦИЙ УЛЬТРАЗВУКОВЫМИ МЕТОДАМИ ОТРАЖЕНИЯ

КОНТРОЛЬ ИЗДЕЛИЙ ИЗ ПКМ И МНОГОСЛОЙНЫХ КЛЕЕНЫХ КОНСТРУКЦИЙ УЛЬТРАЗВУКОВЫМИ МЕТОДАМИ ОТРАЖЕНИЯ

Повышение эффективности клееных деревянных конструкций

В статье приведены результаты анализа основных направлений совершенствования технологии клееного бруса, улучшения его эксплуатационных свойств. Одним из возможных путей повышения качества клееных материалов и конструкций является правильный выбор связующего в зависимости от условий эксплуатации продукции. Выбор связующих для изготовления деревянных конструкций зависит не только от их функционального назначения, но и условий изготовления. Обоснование параметров режимов склеивания, основных технологических факторов позволит обеспечивать требуемую прочность клеевых соединений. Анализ предварительных экспериментов показал, что на качество склеивания существенное влияние оказывают ряд факторов, которые условно можно разделить на три группы: свойства древесины, свойства клея, условия склеивания. Однофакторные эксперименты позволили определить минимальные и максимальные значения этих факторов, обосновать их уровни варьирования. В статье представлены результаты реализации многофакторного эксперимента по обоснованию условий и режимов склеивания клееного бруса. Выделены факторы, существенно влияющие на прочность клеевых соединений при скалывании вдоль волокон. Установлено влияние плотности древесины, расхода клея и температуры окружающей среды на прочность клеевых соединений древесины, склеенной поливинилацетатным (ПВА) и эмульсионным полимер-изоцианатным (ЭПИ) связующими, широко применяемыми на предприятиях Северо-Запада России. С увеличением плотности древесины прочность склеивания возрастает. ЭПИ клеи менее чувствительны к изменению условий склеивания. Соединения на этом связующем обладают требуемой прочностью даже при фиксации исследуемых факторов на нижнем уровне. Влияние расхода клея на прочность клеевых соединений на ЭПИ клеях менее существенно по сравнению с ПВА. Установлено, что при закреплении одного из параметров на нижнем уровне при использовании ПВА клеев, с увеличением двух других до максимального уровня прочность клеевых соединений древесины возрастает. Получены математико-статистические модели, описывающие это влияние. The results of the analysis of the basic directions of perfection of glued laminated beam technology, improve its performance properties are presented. One possible way to improve the quality of the glued materials and structures is the correct choice of the glue depends on the operating conditions of production. Selection of glue for the manufacture of wooden structures depends not only on their functionality, but also the conditions of manufacture. Justification gluing mode parameters, the basic technology factors will allow to provide the desired bonding strength. Analysis of preliminary experiments showed that the quality of the gluing are strongly influenced by a number of factors, which can be divided into three groups: wood properties, adhesive properties, the terms of gluing. Univariate experiments allowed to determine the minimum and maximum value of these factors, justify their varying levels. The article presents the results of the multivariate experiment in justification of the conditions and modes of bonding of glued laminated beam. The factors that significantly affect the shear strength of the bond are determined. The effect of the density of the wood, the glue consumption and ambient temperature on the bonding strength of wood, glued with polyvinyl acetate (PVA) and an emulsion polymer isocyanate (EPI) glues, widely used in enterprises of the North-West of Russia. With increase of wood density the adhesion strength grows.EPI adhesives are less sensitive to changes in gluing conditions. The compounds of this glue have the requisite strength even at fixing investigated factors at a lower level. Effect of adhesive consumption on the strength of adhesive joints at EPI adhesives is less significantly as compared to the PVA. Found that by fixing one of the parameters in the lower level when using PVA adhesive, the other two with an increase to the maximum level of adhesive strength increases of wood joints. Obtained mathematical models describing this influence.

Control of glued structures made of dissimilar materials by ultrasound reverberation

This paper considers the physical bases of the ultrasound reverberation method that can detect defects in gluing of double-layer structures made of dissimilar materials, such as metal–plastic and plastic–metal. The advantages and disadvantages of this method are specified. It is shown that the capabilities of the reverberation method significantly expand when using a spectral version of reverberation based on registration of changes in the shape of the envelope of the amplitude spectrum of echo pulses depending on the quality of bonding.

Control of glued structures by the electromagnetic acoustic variant of the impedance method

The functionality of the electromagnetic acoustic variant of the impedance method of controlling multilayer glued structures with metallic casings is studied. It is shown that the main advantage of this variant is the possibility of carrying out control without any direct contact of the working part of the converter with the surface of the examined article.

Evaluation of the humidity state of glued wooden constructions during monitoring

The work presents the research method for determining the humidity of wood in glued structures during their exploitation. The conductometric method serves a basis for the above-mentioned technique, but instead of regular sensors of humidity meter, we suggest the use of special sensors with electrodes of different lengths. It has been shown that the developed method has a number of advantages compared to the gravimetric method for determining wood humidity and can be used to monitor wooden structures during their exploitation with minimal time and labor inputs.