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The results are presented for impact of defects formed during one-sided friction stir welding plates made of alloy 1901 in the root part on the mechanical properties of resulting butt joints. The defects are represented by the lack of fusion and accumulations of oxide films in the root part of the joint. The defect length is 0.1–0.3 mm and the defects are detected using computer X-ray tomography and analyzing the microstructure of the joints using an optical microscope. The defects present in the root part of the plate joints made of alloy 1901T result in decrease in the welding factor from 0.85 to 0.74. The area of the joint break during a static tensile test shifts from the heat-affected zone to the stir zone. The break of the samples exposed to static tension is initiated by a lack of fusion (the areas occupied by oxide films) in the root part of the joint with a characteristic brittle fracture propagating into the stir zone. The fracture becomes ductile with islands of oxide film entering the weld during the welding process. The presence of the lack of fusion and oxide films in the root part of the joint results in a 2-fold decrease in the joint bending angle. A necessary condition for eliminating the lack of fusion in the root part of the butt joint in plates made of alloy 1901T deals with making the length of the rod (pin) of the working tool equal to the thickness of the workpieces welded, taking into account the degree of immersion of the tool shoulder in the weld metal. [ABSTRACT FROM AUTHOR]

A method for the optimization of the distribution of two materials in a thin symmetric plate is presented. The model for the plate is the Kirchhoff–Love and the optimization method is based on the small amplitude, or low contrast, approximation for homogenization. Numerical results are presented for compliance minimization, i.e., maximizing the global stiffness of the plate, and for minimizing the integral of an even power of the deflection in a subset of the plate. The method arrives at classical designs without the need of penalization, which allows evaluating the exact performance of the proposed shapes and the comparison with some simple intuitive designs. This also gives insight in how small the contrast needs to be for the method to give designs which are better than some intuitive designs. [ABSTRACT FROM AUTHOR]

Currently, bending deformations of lithospheric plates are calculated based on Kirchhoff's theory of bending of thin plates, which was formulated about 170 years ago. This paper examines the possibility of refining these calculations based on the theory of bending of thick plates developed by Timoshenko and Reissner. A new unified derivation is presented of the Timoshenko equations for 2D bending of beams and the Reissner equations for bending of slabs by direct transformation of the general elasticity equations with a simple approximate replacement of power-cubic functions with effective linear ones. This allows a more detailed and clearer understanding of the differences between the equations and the sense of the simplifications made in these theories. By comparing the analytical solutions of the Timoshenko and Reissner equations with the known test analytical solutions of the exact elasticity equations, quantitative estimates of the accuracy of these theories are given. [ABSTRACT FROM AUTHOR]

The production of homogeneous Ti–10Nb–(1–3)Mo (at %) alloys in the form of semifinished products (plates) was studied through multiple remeltings and homogenization annealing. Metallographic studies of the resulting materials in cast, rolled, and annealed states were carried out. The effect of annealing and composition on the structure, phase composition, and mechanical properties of the Ti–10Nb–(1–3)Mo alloy was revealed. Homogeneity after smelting was achieved by annealing at a temperature of 950°C for 12 h. An increase in the Mo content in the Ti–10Nb–(1–3)Mo alloy led to an increase in the strength of the alloys, while the ductility decreased. The achievement of high strength characteristics in selected alloys was associated with the development of annealing parameters after plastic deformation, namely, controlling the size of recrystallized grains and separating the α and β phases. In addition to α-Ti and β-Ti, the samples contained small amounts of ω-Ti, which led to a sharp increase in the hardness of the samples. [ABSTRACT FROM AUTHOR]

Purpose: In comparison to traditional, constant stiffness laminates, variable stiffness composite laminates (VSCL) with curvilinear fibres represent an extra analysis effort. It is the purpose of this work to present and test a relatively simple optimisation procedure, in order to find the maximum fundamental frequency of vibration in bending and in in-plane vibrations. It is also intended to explain why certain fibre paths lead to higher frequencies. Methods: The optimisation is performed using a genetic algorithm (GA), which is described in detail. The bending and the in-plane plate models are based on the p-version Finite Element Method. Each model requires a small number of degrees of freedom, an important feature because applying the GA involves the solution of a large number of eigenvalue problems. In order to support the physical interpretation of the optimal designs, mode shapes and stress fields corresponding to some optimal solutions are illustrated. Results: Single- and multi-layer plates with different boundary conditions and fibre path types are studied. Fibre paths that lead to maximum fundamental frequencies are found and justified. The consequences that maximising the first frequency has on the higher-order modes of vibration are studied. Conclusion: The proposed optimisation and modelling methods are effective. Curvilinear fibres with the characteristics considered led to the maximum first natural frequency of vibration in a few cases, but not all. Particularly in in-plane vibrations, curvilinear fibres can provide major gains in comparison to straight fibres. The increase in the vibration frequency is accompanied by, overall, larger stresses. [ABSTRACT FROM AUTHOR]

In the present work, attention is paid to the nonlinear vibrations and chaotic dynamic behaviors of rotating graphene platelets reinforced metal foams (GPLRMF) blades operating in a thermal environment. Considering three different distribution patterns of graphene platelets (GPL) and foams, the improved Halpin–Tsai model, mixing rules and Maxwell-Eucken model are applied to obtain the physical parameters of rotating GPLRMF plates. The motion equations of GPLRMF rotating plates are established through higher-order shear deformation theory (HSDT), in which the centrifugal force, Coriolis force and heat conduction are included. Under the cantilever and simply supported boundary conditions, the nonlinear ordinary differential equation (ODE) of the system is obtained by Galerkin method. The amplitude-frequency response, bifurcation curve, and chaotic motion of the rotating GPLRMF blades are analyzed with the aid of the methods of multi-scale and Runge–Kutta. Furthermore, comprehensive investigations into the effects of temperature, presetting angle, GPL distribution mode, foam distribution mode, volume fraction, porosity coefficient, rotational speed, damping coefficient, and excitation force on the nonlinear dynamics of rotating plates are performed through numerical analyses. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the results of distal femoral fracture fixation of two different methods, lateral locking plate (LP) or an Intra-medullary nail (IMN), in patients managed in our institution. More specifically, to assess: (a) if there was a difference in functional outcomes between the LP and IMN groups; (b) whether the rate of complications was different between the two groups. Methods: Between January 2009 and December 2018 adult patients with distal femoral fractures managed in our unit with either LP or IMN for extra and intra-articular fractures were eligible to participate. Demographic details, fracture type, procedures performed, time to union, complications and functional scores (Oxford Knee Score) were recorded and analysed. The mean follow up was 4 years (12–120 months). Results: Out of 193 patients who met the inclusion criteria, 93 received an IMN whereas 100 patients were treated with LP. Mean age was 64.2 (18–99) and 70.1 (18–100) for the IMN and LP groups respectively. Overall, the two groups had similar demographics and there was no significant difference in the type of fractures sustained (p > 0.05). The Oxford Knee Score was highest for patients fixed with LP, mean 37.3 (6–48, SD 7.3) versus 28.4 (3–48, SD 14.4), (p = < 0.02) compared to the IMN group. In terms of complications, the rate of non-union was higher in the LP group 8.6% versus 4% in those patients treated with an IMN, p value < 0.01. Conclusion: While the rate of non-union was higher in the LP group and the functional results were superior in the plating group. [ABSTRACT FROM AUTHOR]

In this study, the linear free vibration of intact and cracked functionally graded material plates is investigated numerically and experimentally. The experimental work is limited to the isotropic materials. The numerical work is based on finite element, where a code is developed to obtain the natural frequencies of intact plates based on the first-order shear deformation theory (FSDT) using MATLAB software. Also, a model of through-cracked FGM plate is developed using ANSYS Workbench with the help of APDL coding. The material properties of the plates under study are graded in one, two, and three directions. The novelty of this study emerges through its examination of the synergistic impacts resulting from variations in FGM material properties, crack length, crack orientation, and crack location. These effects are comprehensively discussed in the results section. The result of the present model shows that the use of three-directional FGM reduces the natural frequency compared with the other cases of two-directional and unidirectional FGM. Also, the results show that the effect of FGM gradient on the frequency of intact and cracked plate is high when the gradient index n < 3. The present paper results are useful for the design of FGM plates especially when cracks exist. [ABSTRACT FROM AUTHOR]

An analysis of industrial operation of EGAV 1-19-15-6-2 electrostatic precipitators designed for purifying non-aggressive non-explosive process gases and aspiration air from dust was carried out. The nonuniformity of flow distribution at the inlet to the working volume of electrostatic precipitators was revealed. This non-uniformity can lead to efficiency deterioration, increased energy consumption, and frequent cleaning of precipitation electrodes. The authors proposed constructive improvements of electrostatic precipitators supported with calculations. [ABSTRACT FROM AUTHOR]

The structure, phase composition, and mechanical and corrosion properties of plates made of a structural aluminum Al–Cu–Mg alloy are studied in its various states. The results obtained are compared with the properties of its commercial analog (AK4-1 alloy). The alloy under study is found to surpass its analog in strength properties at room and elevated (up to 175°C) temperatures by 9–12%. The impact toughness KCU of the Al–Cu–Mg alloy is twofold that of the AK4-1 alloy. The increase in the strength and corrosion properties of the alloy after operational heating is shown to be explained by the phase composition and morphology of intermetallic phases, including transition-metal phases, which form in the surface layers of samples in small quantities. [ABSTRACT FROM AUTHOR]

The interaction of a sprocket with the links of a drive gear chain is studied by graphical analysis. In gear chains with rolling hinges, the contact pitch of the chain is increased on chain engagement with the sprocket. The contact pitch is changed when the sprocket turns through two angular increments. Change in the contact pitch is undesirable, because it results in nonuniform chain motion. Recommendations are made for decreasing the dynamic loads in a drive with gear chains. [ABSTRACT FROM AUTHOR]

Objective: Periodic configuration of mechanical and civil structures has shown great potential for noise and vibration reduction. However, the use of Cartesian coordinates in studying periodicity effects in elastic structures overlooks the benefits of radially periodic configurations when dealing with wave propagation in large flexible plates disturbed by a small source area. This paper presents an easy-to-use numerical approach to predicting bandgap characteristics in polar coordinates. Methodology: To demonstrate the vibration-attenuation effect, we consider a circular radially periodic plate model. We use an adapted Wave Finite-Element method in numerical experiments to demonstrate the existence of the attenuation effect. To verify the numerical results, we apply an adapted Floquet theory to polar coordinates. Results and Conclusions: Our findings indicate that theoretical and numerical results are in excellent agreement considering a new parameter that introduces the distance from the origin. The adapted Wave Finite-Element approach and Floquet theory presented here demonstrate their potential to model more complex structures in polar coordinates. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this historical review is to illustrate the progression and evolution of treatment for distal femur fractures. Methods: Scientific literature was searched for descriptions of treatment for distal femur fractures to provide an in-depth overview of the topic, with emphasis on the evolution of surgical constructs used to treat these fractures. Results: Prior to the 1950s, distal femur fractures were treated nonoperatively, resulting in considerable morbidity, limb deformity, and limited function. As principles of surgical intervention for fractures emerged in the 1950s, surgeons developed conventional straight plates to better stabilize distal femur fractures. Angle blade plates and dynamic condylar screws emerged out of this scaffolding to prevent post-treatment varus collapse. Meanwhile, intramedullary nails, and later, in the 1990s, locking screws, were introduced to minimize soft tissue disruption. Treatment failure led to the development of locking compression plates with the advantage of accommodating either locking or nonlocking screws. Despite this advancement, the rare but significant incidence of nonunion has not been eliminated, leading to the recognition of the biomechanical environment as important for prevention and the development of active plating techniques. Conclusion: Emphasis for the surgical treatment of distal femur fractures has incrementally progressed over time, with initial focus on complete stabilization of the fracture while the biological environment surrounding the fracture was ignored. Techniques slowly evolved to minimize soft tissue disruption, allow more ease of implant placement at the fracture site, and attend to the systemic health of the patient, while simultaneously ensuring appropriate fracture fixation. Through this dynamic process, the desired results of complete fracture healing and maximization of functional outcomes have emerged. [ABSTRACT FROM AUTHOR]

We derive stretching and bending energies for isotropic elastic plates and shells. Through the dimensional reduction of a bulk elastic energy quadratic in Biot strains, we obtain two-dimensional bending energies quadratic in bending measures featuring a bilinear coupling of stretches and geometric curvatures. For plates, the bending measure is invariant under spatial dilations and naturally extends primitive bending strains for straight rods. For shells or naturally-curved rods, the measure is not dilation invariant, and contrasts with previous ad hoc postulated forms. The corresponding field equations and boundary conditions feature moments linear in the bending measures, and a decoupling of stretching and bending such that application of a pure moment results in isometric deformation of a unique neutral surface, primitive behaviors in agreement with classical linear response but not displayed by commonly used analytical models. We briefly comment on relations between our energies, those derived from a neo-Hookean bulk energy, and a commonly used discrete model for flat membranes. Although the derivation requires consideration of stretch and rotation fields, the resulting energy and field equations can be expressed entirely in terms of metric and curvature components of deformed and reference surfaces. [ABSTRACT FROM AUTHOR]

We propose bending energies for isotropic elastic plates and shells. For a plate, we define and employ a surface tensor that symmetrically couples stretch and curvature such that any elastic energy density constructed from its invariants is invariant under spatial dilations. This kinematic measure and its corresponding isotropic quadratic energy resolve outstanding issues in thin structure elasticity, including the natural extension of primitive bending strains for straight rods to plates, the assurance of a moment linear in the bending measure, and the avoidance of induced mid-plane strains in response to pure moments as found in some commonly used analytical plate models. Our analysis also reveals that some other commonly used numerical models have the right invariance properties, although they lack full generality at quadratic order in stretch. We further extend our result to naturally-curved rods and shells, for which the pure stretching of a curved rest configuration breaks dilation invariance; the new shell bending measure we provide contrasts with previous ad hoc postulated forms. The concept that unifies these theories is not dilation invariance, but rather through-thickness uniformity of strain as a definition of pure stretching deformations. Our results provide a clean basis for simple models of low-dimensional elastic systems, and should enable more accurate analytical probing of the structure of singularities in sheets and membranes. [ABSTRACT FROM AUTHOR]

During the underwater archaeological survey by Akdeniz University, a shipwreck has been found off the town of Adrasan in the Kumluca district of Antalya. The ship probably sank succumbing to hidden shoals near the coastline. The cargo consists exclusively of Eastern Sigillata A plates and bowls and can be dated between the Late Hellenistic and the Early Roman Imperial period. In this context, it is one of a rare class of shipwrecks of which the cargo consists of a clearly defined ceramic class. This trade ship's wreck lies with its thousands of plates and bowls located both in the rocky and sandy areas and below the seabed at a depth of 38–46 m. [ABSTRACT FROM AUTHOR]

For better protection, good toughness and robust flexibility, all life and plants have skin tissue, and likewise, all books have covers. In this paper, interlayer friction is considered as perturbation, and hardcover book-like laminates with internal friction are studied. For quasi-static problems, the bending response and energy dissipation of the three-point support plate are analyzed in detail. Our numerical studies show that the cover of a hardcover book is more important than the core layer in terms of bending response; for energy dissipation, friction results in a large amount of energy dissipation during each loading and unloading cycle. The core goal of this study is not only to predict the bending deformation of book-like plates, but also to use this representative case to find the common behavior of multilayer structures with internal friction. [ABSTRACT FROM AUTHOR]

In an explicit form, the frequency equations of cutoff frequencies for free vibrations of functionally graded plates whose elastic moduli depend on the transverse coordinate are considered. Plate faces are stress-free, rigidly clamped, or subjected to combined boundary conditions. It is shown that the corresponding left-hand sides of the equations are entire functions, which can be presented as a particular case of Peano series, and their respective mathematical estimates are given. It is also shown that the method suggested is effective and all integration stages can be easily realized by the present-day program packages of numerical and symbolic computations. The new final method is efficient for calculating the cutoff frequencies. They are verified on numerical examples and by comparing with results of the Wentzel–Kramer–Brillouin (WKB) method allowing one to find the asymptotics of high vibrations [ABSTRACT FROM AUTHOR]

An analysis of the operation of EHAH electrostatic precipitators designed for cleaning gases and aspiration air from dust has been carried out. An upgrade of the electrostatic precipitator, which allows eliminating vortex generation, reducing the likelihood of particles slipping (due to their high velocity), improving the collection of purified gas, and reducing stagnant zones in the confuser, has been proposed. A rationally chosen value of the inclination angle of the plates ensures a decrease in the likelihood of a lifting effect, in which particles can slip into the upper electrode-free space. A local decrease in velocity in the outlet gas duct was established to be within 7%. [ABSTRACT FROM AUTHOR]

Plate type surface tension tanks have been widely used in satellites. Capillary phenomena between plates is an important part of liquid behaviour in space. Capillary phenomena between plates with varying width and distance under microgravity are analyzed in detail in this paper. A second-order differential equation for the meniscus height is derived and it can be solved by using the fourth-order Runge–Kutta method. To ensure the model’s accuracy during the entire flow process, the influences of the dynamic angle, the friction force, the convective pressure loss and the liquid meniscus in the reservoir are all considered. For a long time period of flow, the convective pressure loss can be neglected and the equation is simplified. This equation is valid for flows between plates with small varying aspect ratios. Theoretical results are in good agreement with numerical results. Besides, influences of the variation of width or distance of plates are discussed. The flow speed won’t vary monotonically as the distance between plates varies parabolically. The optimized flow channel is possible to be obtained based on this equation. [ABSTRACT FROM AUTHOR]

The aim of this contribution is to provide a brief overview of three-dimensional linear-elastic fracture mechanics (3D LEFM) as well as the latest advances in this area. The primary focus of this review is on the situations where the classical LEFM, which largely relies on plane stress or plane strain simplifications, provides peculiar or misleading results. As no exact analytical solutions are currently available for real cracks, which are inherently three-dimensional (3D), there are many controversial views in the literature and lack of understanding of the effects associated with 3D geometries. Fundamental results and general conclusions in 3D LEFM are largely based on dimensionless and energy considerations as well as on generalisations of outcomes of 3D numerical studies and application of asymptotic techniques. It is believed that 3D considerations alone cannot explain complex and diverse brittle fracture and fatigue phenomena, but these considerations can contribute into the further understanding of these phenomena. [ABSTRACT FROM AUTHOR]

The damage detection process in structures has been an important challenge for the engineering community. The design of structural health monitoring (SHM) systems usually involves selection of actuators and sensors, their positions on the structure and post-processing of output signals. This article presents an approach to determine the optimal frequencies for damage detection in plates considering the perpendicular incidence of longitudinal waves into the damage. At these optimal frequencies are observed the maximum reflected and the minimum transmitted longitudinal wave amplitudes, which are recommended to achieve the damage detection due to their higher differences in wave amplitudes when comparing healthy and damaged conditions. Higher values of two damage detection indexes are obtained at the optimal frequencies. Experimental tests are carried out considering a rectangular aluminum plate with circular piezoelectric transducers. The experimental results demonstrate the proposed approach, and highlight the importance of defining optimal frequencies to detect damage in plates. [ABSTRACT FROM AUTHOR]

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In this work, we study the transversal vibration of thin periodic elastic plates through asymptotic homogenization. In particular, we consider soft inclusions and rigid inclusions with soft coatings embedded in a stiff matrix. The method provides a general expression for the dynamic surface density of the plate, which we compute analytically for circular inclusions or numerically for two-way ribbed plates. Through asymptotic homogenization, we find that band gaps related to in-plane propagating transversal waves occur for frequency intervals in which the effective surface density is negative. The same result is obtained via an asymptotic analysis of the Bloch-Floquet problem on a unit cell, showing the equivalence of the two approaches. Finally, we validate the method by comparing in several examples the predicted band gaps with those obtained from numerical Bloch-Floquet analyses on the real unit cell. [ABSTRACT FROM AUTHOR]

In this paper we consider a severely ill posed problem associated with a two dimensional homogeneous biharmonic equation. By perturbing the original problem and using a two parameters regularization method, we get a stable solution which converges to the solution of the considered problem. Under some priori bound assumptions, different errors estimates for the regularized solution are obtained. These last ones depend on the choice of the space of the exact solution. To show the effectiveness of the proposed regularization method some numerical results are given. [ABSTRACT FROM AUTHOR]

The analysis of industrial operation of EGAV1-22-15-7-4 precipitators, designed for cleaning non-aggressive non-explosive process gases and aspiration air from dust, has been carried out. The non-uniform distribution of flows at the inlet to the working area of the precipitator, which leads to a decrease in the dust collection efficiency, an increase in energy consumption and frequent cleaning of the precipitation electrodes, has been revealed. In the course of the research, the authors of this article have proposed design modifications to improve gas distribution in electrostatic precipitators. [ABSTRACT FROM AUTHOR]

The present work exhibits the analysis of a plate with and without cutout considering the dynamic analysis in a transient zone with its application in the civil, structural, and aerospace industry. For this, first-order shear deformable C0 continuous Finite Element (FE) is implemented to examine transient response of plate. The governing ODE of motion's is integrated using central difference explicit time integration scheme. A lumped mass matrix is obtained by a special diagonlization scheme and the total mass of the element is conserved by inducing effective rotary inertia terms. A FE program is developed based on derived FE formulation to investigate the effect of dynamic loading on such plates. The analysis exhibits the results in terms of displacement, forces, and bending moment of the plate for various aspect ratios and different parameters. The results are shown in terms of tables and graphs for smaller to larger cutout in plates with its different aspect ratio considering transient analysis. The results reveal that transient dynamics analysis shows a considerable difference in the behavior of plates with and without cutout in terms of time period, amplitude, and bending moment than that obtained from static analysis. [ABSTRACT FROM AUTHOR]

We consider different models of thermoelastic plates in a bounded reference configuration: with Fourier heat conduction or with the Cattaneo model, and with or without inertial term. Some models exhibit exponential stability, others are not exponential stable. In the cases of exponential stability, we give an explicit estimate for the rate of decay in terms of the essential parameters appearing (delay τ ≥ 0 , inertial constant μ ≥ 0 ). This is first done using multiplier methods directly in L 2 -spaces, then, second, with eigenfunction expansions imitating Fourier transform techniques used for related Cauchy problems; also here essentially energy estimates are used, a spectral analysis is avoided. The explicit estimates allow for a comparison. The singular limits τ → 0 , and μ → 0 are also investigated in order to understand the mutual relevance for the (non-) exponential stability of the models. Numerical simulations underline the results obtained analytically, and exhibit interesting coincidences of analytical and numerical estimates, respectively. [ABSTRACT FROM AUTHOR]

Purpose: To systematically review the outcomes of surgical treatments of chronic acromioclavicular joint dislocation.Methods: Studies were identified by electronic databases (Ovid, PubMed). All studies reporting functional and radiological outcomes of surgical treatments of chronic acromioclavicular joint dislocations were included. Following data were extracted: authors and year, study design, level of evidence, number of patients, age, classification of acromioclavicular joint dislocation, time to surgery, surgical technique, follow-up, clinical and imaging outcomes, complications and failures. Descriptive statistics was used, when a data pooling was not possible. Comparable outcomes were pooled to generate summary outcomes reported as frequency-weighted values. Quality appraisal was assessed through the MINORS checklist.Results: Fourty-four studies were included for a total of 1020 shoulders. Mean age of participants was 38 years. Mean follow-up was 32.9 months. Arthroscopic techniques showed better results than open approach (p < 0.0001). Synthetic reconstructions demonstrated better functional outcomes compared to internal fixation and biologic techniques (p < 0.0001). Among biologic techniques, combined coracoclavicular and acromioclavicular ligaments reconstruction showed better Constant (p = 0.0270) and ASES (p = 0.0113) scores compared to isolated coracoclavicular ligaments reconstruction; anatomic biologic non-augmented graft reconstruction showed better Constant (p < 0.0001), VAS (p < 0.0001) and SSV (p = 0.0177) results compared to augmented techniques. No differences in functional outcomes could be found between anatomic biologic non-augmented graft versus synthetic reconstructions. Overall, methodological quality of the included studies was low.Conclusion: Anatomic reconstructions, both synthetic and biologic, showed the best functional results.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Dynamic stiffness formulation is proposed in this paper for both transverse and in-plane vibration of rectangular plates that account for arbitrary boundary conditions. A generalized superposition method is developed to obtain the homogeneous solutions for the governing equations of both transverse and in-plane vibration. Consequently, the dynamic stiffness matrices are formed in a more straightforward way by projection method, the dimensions of which are greatly reduced in comparison with those from the conventional Gorman's superposition method. The finite element technique is utilized to assemble local stiffness matrix into global coordinates so as to address the dynamics of plate assemblies. Various types of plate-like structures are investigated by the proposed method, through which excellent agreement is found between our results and those from finite element method. The effectiveness, accuracy and convergence of the proposed DSM for both transverse and in-plane vibration are proved in several numerical examples, which demonstrates the proposed DSM is an excellent alternative to the existing DSM. [ABSTRACT FROM AUTHOR]

In this study, local scour occurring downstream from a nozzle with and without plates formed in cohesionless materials was investigated experimentally. The experiments were performed to determine scour geometry, maximum scour depth, and the effect of aeration on scour for water jets impinged obliquely into the downstream pool. Dimensionless variables affecting the scour were determined as densimetric Froude number, dimensionless impingement length, and the ratio of densimetric Froude number to dimensionless impingement length. Experiments were conducted for three nozzle diameters with plates, three nozzle diameters without plates, two different impingement lengths, and three different exit velocities. The results of the experiments showed that the use of the plates in the nozzle, jet impact velocity, jet shape, jet expansion, jet impingement length, and air entrainment rate were critical parameters for scour geometry. As a result, it was found that the jets from a nozzle with plates entrained more air bubbles into the impingement pool than jets from nozzles without plates, thereby decreasing maximum scour depth by spreading the scour over a larger area. This was evident by increasing the impingement length. In addition, scour equations were obtained to determine maximum scour depth, ridge height, and scour hole length from experimental data. [ABSTRACT FROM AUTHOR]

A computer model was developed and a study of the cold rolling modes of 1580 alloy sheets was carried out. The model provided for the achievement of the maximum total degree of reduction in cold rolling of 60% in the minimum number of passes, the rolling force should not exceed 90% of the maximum allowable for the rolling mill, and the Cockcroft-Latham criterion was not reach value 1, so that cracks do not occur along the edges of the rolled products. The simulation results were tested on a billet cut from a large-sized ingot cast at an industrial enterprise by the method of semi-continuous casting. Hot rolling was carried out on a two-roll mill with a roll diameter of 330 mm and a barrel length of 520 mm. For cold rolling a two-roll mill with a roll diameter of 200 mm and a barrel length of 400 mm was used. Based on the simulation results, cold rolling was carried out, as a result of which a 2-mm-thick strip without cracks along the edges was obtained from a hot-rolled billet 5-mm-thick in 8 passes. At the same time in all passes, the rolling force values did not exceed 90% of the allowable for the rolling mill, and the Cockcroft-Latham criterion was less than 1. Thus, it is shown that computer modeling allows to optimize the rolling route of thin sheets of alloy 1580 and to carry out cold rolling with a total reduction rate of 60% for a minimum number of passes to obtain high-quality sheet semi-finished products. [ABSTRACT FROM AUTHOR]

Vibration attenuation and dynamic control of the piezolaminated plate actuated with coupled electromechanical loading are aimed and achieved in the present work. Efficient finite element methodology with higher-order shear deformation theory is assisted to blend the effects of shear strains in the computational model. An isoperimetric eight-noded rectangular element is implemented through linear electric potential distribution along the thickness to set up the relations. Coupled electromechanical loading is considered in the formulation to consider the piezoelectric sensing and actuation mechanism. Piezolaminated plates with both cross-ply and angle-ply orientation of bonded substrate lamina are considered in the analysis. Vibration responses of multilayered composite plates with surface-mounted piezolaminates are evaluated for open-circuit and closed-circuit boundary conditions of the electric field. Results obtained from the analysis are well revealed for frequencies of various modes of simply supported piezolaminated plates. Dynamic vibrational response and effect of the control gain (Gv) in terms of velocity feedback on the dynamic characteristics of a piezoelectric laminated plate are examined. Another aim of proposing this FE model is to demonstrate the effect of placement of fibers in a different orientation for the PVDF layer to achieve active damping, and attenuation of vibrations of the laminated composite plate is also achieved and demonstrated. [ABSTRACT FROM AUTHOR]

Navier's closed-form solution for the higher order theory of micropolar plates based on the CUF approach has been developed here. Obtained using a principle of virtual displacements the 2D system of the differential equations for the higher order theory of micropolar elastic plates is solved here for the case of simply supported plates using Navier's method of the variables separation. For the higher order theory of micropolar plates developed here, which is based on CUF, some numerical examples have been done and the influence the rotation field on the stress–strain fields has been analyzed. Methods of determination of the classical and micropolar elastic moduli of different materials have been analyzed, and available experimental data have been presented in Nowacki's notations. The obtained equations can be used for calculating the stress–strain and for modeling thin walled structures in macro-, micro- and nanoscale when taking into account micropolar couple stress and rotation effects. [ABSTRACT FROM AUTHOR]

Abstract—Based on the time step algorithm, we have developed a mathematical model of the viscoelastoplastic deformation of flexible plates cross-reinforced in planes parallel to the middle plane. The strains of the plate composite components are assumed to be small and are decomposed into elastic and plastic components. The viscoelastic behavior of the composite materials is described by the Maxwell–Boltzmann body relations. The inelastic deformation is represented by the equations of the theory of a plastic flow with isotropic hardening. The normal stresses in the transverse direction are approximated linearly over the plate thickness. For this reason, the linear strains in the transverse direction and their rates are excluded from the governing equations for the composite components. The weakened resistance of fibrous plates to transverse shear is taken into account within the nonclassical Reddy bending theory. The geometric nonlinearity of the problem is considered in the Karman approximation. The formulated initial-boundary value problems are solved numerically with the application of an explicit cross-type scheme. A workaround is used to obtain a stable numerical scheme: the stresses in the Maxwell–Boltzmann viscoelastic relations at the current discrete time are expressed via the stress rate by the trapezoid formula with a backward step. We have investigated the elastoplastic and viscoelastoplastic bending dynamic behavior of relatively thick, orthogonally reinforced fiberglass rectangular plates subjected to blast loads. A change in the reinforcement structure is shown to lead to a change in the residual deflection of the structure. We demonstrate that the amplitude of reinforced-plate oscillations in the vicinity of the initial time exceeds significantly the residual deflection. [ABSTRACT FROM AUTHOR]

For efficient separation of liquid heterogeneous systems in oil and gas industry, various types of sedimentation tanks, separators, hydrocyclones, etc. are used, the principle of which is based on gravitational and centrifugal separation of heterogeneous masses of different densities. In order to ensure the best hydrodynamic conditions for the process of suspensions separation in a hydrocyclone and to prevent clogging of the discharge hole, an apparatus that contains only the cylindrical part of the housing is proposed. The presence of a taper displacer ensures the maintenance of optimal hydrodynamic conditions along the entire length of the apparatus, from the inlet to the discharge hole. The taper of the displacer affects the distribution profile of the tangential velocities of the fluid in the near-wall region, ensuring the constancy of the velocity profile along the radius and the specific flow rate over the cross section of the apparatus. Basing on the results of studies carried out on a real product (a mixture of PVCR with water) at a pressure and flow rate corresponding to the production ones, an industrial prototype of the apparatus has been designed and produced. [ABSTRACT FROM AUTHOR]

It is proved in the article that the recently revealed cracks of a new type, which have a different mechanism of destruction of the medium than the Griffith cracks, cannot be obtained as a result of the convergence of the sides of the wedge-shaped cavity in the plate. Thus, cracks of a new type are obtained as a result of the virtual convergence of the lateral sides of a rectangular cavity in the plate. The block element method is used for proof. The same method is used to simulate some types of nanoparticles, materials of mosaic structure and to study the formation of new cracks in such materials. [ABSTRACT FROM AUTHOR]

The article provides a brief overview of studies on crystalline materials with negative Poisson's ratio (crystalline auxetics) with cubic anisotropy. It has been demonstrated that 1/4 part of all cubic crystals has auxetic properties. Even more auxetics are found among chiral nano/microtubes with cubic cylindrical anisotropy. It has been established that chiral nano/microtubes made of cubic crystals exhibit linear Poynting's effect under torsion, in contrast to the known nonlinear effect for isotropic materials. In the case of longitudinal tension of two-layered composites, it is shown that Voigt's rule of mixtures is violated in the presence of a layer of auxetic materials. [ABSTRACT FROM AUTHOR]

A mechanical model has been presented for analysis of plates resting on extensible geosynthetic reinforced granular fill lying on soft soil improved by stone columns. Foundation has been idealised as a plate and geosynthetic layer as rough elastic membrane. Granular fill, soft soil and stone columns has been idealised respectively as Pasternak shear layer, Kelvin–Voigt elements and Winkler springs and their nonlinear behaviour has been considered. Deformation compatibility condition at interface of geosynthetic and granular fill has been considered. An iterative finite difference scheme with proper boundary conditions has been used to solve governing differential equations and the system of simultaneous equations so obtained, have been solved using LU decomposition method. Response of plate in terms of deflection and bending moment and tension mobilized in geosynthetic has been presented in non-dimensional form. Influence of type of geosynthetic (extensible and inextensible) in reducing the settlements in conjunction with stone columns has been presented and the significance of each parameter influencing the plate response has been studied by means of detailed parametric study. [ABSTRACT FROM AUTHOR]

The article considers two problems, one of which is related to the engineering direction, devoted to the study of the resources of bearings with coatings that have received a certain defect. The second relates to the mechanics of natural phenomena and is associated with the phenomenon of subduction. Subduction is the process of moving oceanic lithospheric plates under the continental in the coastal zone. It is the phenomena of subduction that lead to earthquakes that generate tsunamis. It is estimated that the length of the coastal zones where the subduction process takes place is 45 thousand kilometers. Subduction zones are zones of intense coastal marine and oceanic earthquakes that are characterized by faults in lithospheric plates. The authors managed to notice that both of these problems are mathematically described by the same boundary-value problems. To study and solve them, the block element method is used, which allows one to precisely solve these problems. The study showed that in the zones of defects and faults, high stress concentrations occur, leading to destruction of the coatings. The consequences of such destruction are investigated. [ABSTRACT FROM AUTHOR]

A mathematical model of viscoelastic-plastic bending deformation of spatially reinforced plates is developed based on the time step method. The viscoelastic behavior of the components of the composition is described by the Maxwell-Boltzmann equations, and plastic behavior by flow theory with isotropic hardening. The low resistance of composite plates to transverse shear is taken into account within the framework of Reddy's theory, and the geometric nonlinearity of the problem is considered in the von Kármán approximation. The corresponding initial-boundary-value problem is solved using a leapfrog numerical scheme. The dynamic viscoelastic-plastic bending of spatially reinforced fiberglass rectangular plates subjected to air blast wave loading is investigated. It is shown that for relatively thick plates, replacing a flat reinforcement structure by a spatial reinforcement structure leads to a significant decrease in the maximum and residual deflections and strain intensity of the binder material, and for relatively thin plates, this replacement is ineffective. It is found that in the initial stage of deformation, the amplitude of oscillation of the composite plate far exceeds the residual deflection. [ABSTRACT FROM AUTHOR]

To identify the strength properties of a block structure including a bearing pair cage and the lubricated bearing itself, a model of a bearing with a defect is considered. The cage is a deformable base with a thin coating having defects. The coating is under the influence of a lubricant, which under operating conditions loses viscosity and can be modeled by a thin layer of an ideal incompressible fluid, on which the vertical external pressure from the bearing is applied. To study the local properties of the bearing in the vicinity of the defect, the base of the cage is considered as deformable layer with a defective coating containing on top a layer of ideal incompressible fluid. It is assumed that the coating has the most complex latent defect described by a crack, the plane of which is perpendicular to the boundary of the coating. The described block structure is investigated by the block element method, and the features of bearing behavior are revealed. [ABSTRACT FROM AUTHOR]

Experiments show a strong increase in damping with the vibration amplitude during nonlinear vibrations of beams, plates and shells. This is observed for large size structures but also for micro- and nanodevices. The present study derives nonlinear damping from viscoelasticity by using a single-degree-of-freedom model obtained from standard linear solid material where geometric nonlinearity is inserted in. The solution of the problem is initially reached by a third-order harmonic balance method. Then, the equation of motion is obtained in differential form, which is extremely useful in applications. The damping model developed is nonlinear and the parameters are identified from experiments. Experimental and numerical results are compared for forced vibration responses measured for two different continuous structural elements: a free-edge plate and a shallow shell. The free-edge plate is interesting since it represents a case with no energy escape through the boundary. [ABSTRACT FROM AUTHOR]

This paper evaluates the longitudinal wave speed through a plate in which its two opposing sides are elastically restrained in the width direction, taking into consideration the material auxeticity and strain as well as changes to the density and cross-sectional area. Apart from the known role of Young's modulus and density, the present results reveal that the wave speed can be enhanced by increasing the width elastic restraint. In the case of high elastic restraint, the speed of both tensile and compressive waves can be minimized by selecting plate materials with Poisson's ratio of low magnitude. In the case of low elastic restraint, the speed of tensile and compressive waves can be greatly reduced by selecting plate materials with large positive and large negative Poisson's ratio, respectively. For the special case of negligible strain, the longitudinal wave speed reduces to the elementary wave speed in prismatic rods and in plates of infinite width when the width elastic restraint stiffness approaches zero and infinity, respectively. The obtained results not only avail more parameters for adjusting the longitudinal waves in plates, but also identify the differing methods of effectively controlling the wave speed between tensile and compressive waves when the strain magnitude is non-negligible. [ABSTRACT FROM AUTHOR]

This study involves an analytical approach to investigate the dynamic responses of plates subjected to blast and impulsive loads. Navier's approach was employed in order to obtain the equations for displacements and moments. The method validity was evaluated by making comparisons between the analytical and the numerical predictions of the plate time histories and the maximum displacement. A small discrepancy among the results proved the validity of the proposed analytical formulae. The effects of the plate aspect ratio, the thickness, and the charge weight on the plate deflection due to the blast loads were investigated by employing analytical and numerical approaches. The plate displacement changed linearly with respect to the charge weight, whereas it had a nonlinear variation for the plate thickness. [ABSTRACT FROM AUTHOR]

Objective: Objective of the present work is to theoretically estimate the strains generated in a plate by a reverberant acoustic excitation, in SEA frame work. New expression: An expression for determining the strains due to the trace wave generated in the plate is derived, which is an essential component of vibration caused due to the acoustic excitation. Results: Strains developed in a plate when subjected to reverberant acoustic field are obtained experimentally and the results are compared with the theoretically estimated results and they are in good agreement. [ABSTRACT FROM AUTHOR]

General nonlinear ultrasonic techniques (NUTs) use tone-burst ultrasonic waves with a narrow bandwidth so that the fundamental frequency component and the second-order harmonic component can be clearly separated in the frequency domain. Meanwhile, when using a longitudinal wave propagating in the thickness direction, the number of cycles of tone-burst signals can be limited by the object thickness. In some cases, only a pulsed signal or a single-cycle signal, which has broad bandwidth, may be applicable to avoid superposition of the first transmitted wave and the multi-reflected waves. Such cases complicate the use of general NUTs, and it is necessary to apply a method to precisely extract the second-order harmonic component even in broadband signals to the NUT. In this study, the pulse inversion (PI) method, which can extract only even harmonics or odd harmonics by superposing or subtracting two wave signals obtained from 180° out-of-phase inputs, is applied to an NUT using broadband ultrasound. The performance of the PI-based NUT with respect to material degradation is verified using a series of heat-treated aluminum alloy specimens with various levels of precipitates. The experimental results show that the nonlinearity parameters measured with single-cycle signals agree well with the previous well-validated experimental results obtained using narrowband signals. Next, the PI-based NUT is used to assess the localized material degradation of a stainless steel plate subjected to high-cycle fatigue. The experimental results show that the profile of the measured nonlinearity parameters as a function of scan position is consistent with the intended distribution of localized fatigue damage, which demonstrates the potential feasibility of the proposed technique for evaluation of localized material degradation in plates. [ABSTRACT FROM AUTHOR]

The reinforced concrete structures of hydroelectric power plants and nuclear power plants differ from civil structures by their massive nature, including high cross-sections, low reinforcement percentage, and the presence of block seams. A decrease in the safety of these structures results when these features are not taken into account. Methods of calculation that take these features into account are proposed. [ABSTRACT FROM AUTHOR]

The effect of the non-homogeneity of material properties has been considered the important variation mechanism in the static responses of quasicrystal structures, but the existing theoretical model for it is unable to simulate the material change format beyond the exponential function. In this paper, we create a new model of functionally graded multilayered 1D piezoelectric quasicrystal plates using the state vector approach, in which varying functionally graded electro-elastic properties can be extended from exponential to linear and higher order in the thickness direction. Based on the state equations, an analytical solution for a single plate has been derived, and the result for the corresponding multilayered case is obtained utilizing the propagator matrix method. The present study shows, in particular, that coefficient orders of two varying functions (the power function and the exponential function) of the material gradient provide the ability to tailor the mechanical behaviors in the system's phonon, phason, and electric fields. Moreover, the insensitive points of phonon stress and electric potential under functionally graded effects in the quasicrystal layer are observed. In addition, the influences of stacking sequences and discontinuity of horizontal stress are explored in the simulation by the new model. The results are very useful for the design and understanding of the characterization of functionally graded piezoelectric quasicrystal materials in their applications to multilayered systems. [ABSTRACT FROM AUTHOR]

Background: Screw-plates disassembly incidence after pertrochanteric fracture (PF) amounts to 1 and 16% among the elderly population. The main occurrence is early cervical screw cut-out. The population at highest risk of disassembly remains difficult to identify. The correlation between femoral offset loss and disassembly occurrence has never been surveyed.Objectives: A radiological prognosis score for screw plate disassembly was defined to reflect trochanteric impaction (TI); it was based on a femoral offset ratio.Study design and methods: Our single-centre retrospective case-control study surveyed patients suffering from Dynamic Hip Screw (DHS, Synthes®) disassembly following osteosynthesis of non-pathological osteoporotic PF between 2004 and 2014. All cases were categorised by age and gender and paired to three patients in the control group. The primary endpoint was TI measurement, corresponding to offset loss on the operated hip compared to healthy hip offset and expressed as a percentage. The measurement was done on an immediate postoperative X-ray. The secondary endpoints were tip apex distance (TAD) measurement, Ender and AO classifications, as well as postoperative weight-bearing prescription.Results: Twenty-three cases and 69 controls were surveyed. The case group’s average age was 87; 70% of the cases were women. The main disassembly occurrence delay was after 27 days. Average TI was 26% within the patients global group and 12% within the control group (p < 10−5). Over a 21% impaction percentage, disassembly occurrence represents a greater risk: OR = 21.95% CI [5.4-104.3], p < 10−5. Ender 3 type fractures were the most frequent indication for surgery within the case group. Average TAD was 20 mm within the case group, and 17 mm within the control group (p = 0.03). The weight-bearing prescription rate was 52% within the control group and 21% within the case group (p = 0.014). 14.5% of the control group had a TI > 21%.Conclusions: Using the offset ratio tool, TI measurement was associated with a greater risk of DHS disassembly when it was higher than 21%. The exclusive use of a DHS device does not seem optimal for a TI > 21%. Weight-bearing may be prescribed for all the patients with a TI < 21%, provided good implant positioning is secured. [ABSTRACT FROM AUTHOR]