Class Of Deformations Research Articles

Classical Runt Deformity Syndrome Cases in Farmed Penaeus vannamei Along the East Coast of India

ABSTRACT Jagadeesan, V.; Ezhil Praveena, P.; Otta, S.K., and Jithendran, K.P., 2019. Classical runt deformity syndrome cases in farmed Penaeus vannamei along the east coast of India. In: Jithendran...

Prediction of Wrinkling of a Beverage Can Subjected to the Redrawing Process by J2 Deformation Theory

Wrinkling of beverage cans is one of the problems faced by can manufacturers and aluminum suppliers. The bottom of an aluminum can is wrinkled by compression during the forming process. In this study, to predict the occurrence of wrinkles during the redrawing process of AA3104 (t = 0.265 mm), which is the material used to fabricate aluminum cans, the classical plasticity J2 deformation theory (J2D) and flow theory (J2F) were considered. J2F considers only the deformation perpendicular to the yield locus, whereas J2D considers the deformation perpendicular to the yield locus and that tangential to the yield locus. Wrinkles are predicted using finite element (FE) analyses based on J2D and J2F, and the results are compared. J2F could not predict the number and amplitude of wrinkles. By contrast, the wrinkles predicted using J2D exhibited good agreement with sample data obtained for a real can. To find the difference between the results obtained using J2F and J2D, evolutions of stress path in a wrinkled element are compared. It was confirmed that compressive stress is more dominant in the J2D case than in the J2F case. Moreover, the measured effective strain of the element is small, under 0.04. In conclusion, J2D is more suitable for predicting the wrinkling behavior of aluminum cans than J2F. In addition, ANOVA and ANOM analysis are performed to evaluate the influence of the design parameters, namely friction coefficient, thickness, and outer profile angle, and the parameters are optimized to reduce wrinkles by combining the Taguchi method with FE simulation based on the J2D theory.

The effect of multidimensional temperature distribution on the vibrational characteristics of a size-dependent thick bi-directional functionally graded microplate

This article develops the modified couple stress theory to study the free vibration of bi-directional functionally graded microplates subjected to multidimensional temperature distribution. Third-order shear deformation and classical theories of plates are adapted for free vibration analysis of thick and thin microplates, respectively. Employing the third-order shear deformation theory, both normal and shear deformations are considered without the need for shear correction factor. Material of the bi-directional functionally graded microplate is graded smoothly through the length and thickness of the microplate. Gradient of the material is assumed to obey from the power law in terms of the volume fraction of the constituents. Assuming the uniform and nonuniform temperature distributions, the effect of thermal environment on dynamic behavior of the microplate is discussed in detail. Applying the Ritz method, the displacement field is expanded by admissible functions which satisfy the essential boundary conditions, and Hamilton principle is employed to determine the natural frequencies of the microplate. Developed model has been applied to determine the natural frequencies in problems of thin/thick, one-directional/bi-directional functionally graded, and homogeneous/nonhomogeneous microplates. Effects of parameters such as the thermal environment, power law indexes [Formula: see text] and length scale parameter on free vibration of these problems are studied in detail. The results show that higher values of length scale parameter and temperature rise decrease the natural frequency of the bi-directional functionally graded microplate. According to results obtained by classical and third-order shear deformation theories, the third-order shear deformation theory is proposed for vibration analysis of microplates with thickness-to-length ratio less than five.

Проявления акустической эмиссии в мерзлых грунтах при одновременном влиянии на них переменных механических и термических воздействий

The subject of the research is to establish the fundamental laws of acoustic emission in frozen soils, which allow to create ways to control (monitor) their stability under the influence of variable temperature fields and quasistatic mechanical stress from engineering objects located on these grounds for various purposes. The applied importance of such methods is to increase the speed and reduce the complexity of engineering geological surveys in the northern regions of Russia, carried out with the aim of predicting the loss of stability of the bases of buildings and structures to ensure their safe operation. The study was performed on the original instrumental complex. Its description and characteristics are given. With the use of this complex, thermoacoustic emission effects arising from the repeated alternation of freezing and thawing cycles of the soil during the development of its deformed state, starting from the normal compaction phase and up to the final stage of destruction (the bulging phase), have been studied. It is shown that on the basis of such informative parameters as thermally stimulated activity and duration of acoustic emission pulses, an indicator can be obtained that quantitatively characterizes the stages of the stress-strain state of soils. An experimental dependence of the field of values of this indicator as a function of the mechanical stress and the fractional composition of the test soil is given. The qualitative convergence of this dependence with the classical soil deformation diagram obtained by N.M.Hersevanov is shown, where the stages of compaction, loss of stability (shifts) and destruction are highlighted. Possible physical mechanisms and features of the formation of an acoustic emission response at each of these stages are considered and substantiated. It is noted that the approaches to receiving, processing and interpreting acoustic emission measurement information, which are grounded within the framework of the study, allow to control and monitoring of the carrying capacity and stress-strain state of soils directly in the field.

Clinical correlations of striatal hand deformities in Parkinson's disease

Hand deformities have been recognized since the 19th century as part of the postural abnormalities observed in Parkinson's disease (PD). However, their pathogenesis and clinical correlations are poorly understood. We evaluated 104 hands of 52 consecutive patients with PD by high-resolution photographs taken from the radial aspect of each hand; the degree of flexion of the 2nd metacarpophalangeal (MCP) joint was measured by software. The presence of classical striatal hand deformity (CSHD) was also evaluated, defined as MCP flexion, proximal interphalangeal joint extension, and distal interphalangeal joint flexion. Patients with PD had a mean age of 63.3±12.7years, and 29 (56%) were male. The degree of MCP joint flexion in both hands showed moderate correlation with the MDS-UPDRS-III motor score (r=0.518, P<0.001), mainly related to ipsilateral rigidity and ipsilateral bradykinesia scores, and fair correlation with the Hoehn-Yahr stage. A CSHD only correlated with a younger age at onset of PD (P=0.049). These hand deformities were not markers of dyskinesia, levodopa equivalent dose, or cognitive dysfunction. Metacarpophalangeal joint flexion is the most common hand deformity in PD and correlates with rigidity and bradykinesia. A CSHD was only related to a younger age at onset.

Mode II dominant fracture of layered composite beams and wide-plates: a homogenized structural approach

Brittle delamination fracture under Mode II dominant conditions in unidirectional composite and layered beams and wide-plates is studied using a homogenized structural model based on a zigzag approach. The model captures the unstable propagation of cracks, snap-back and snap-through instabilities, the effects of the interaction of multiple cracks on the macrostructural response and of the layered structure on the energy release rate. The layered structure and the delaminations are described by introducing local enrichments, in the form of zigzag functions and cohesive interfaces, to a classical first-order shear deformation plate theory. The model applies to layers with principal material directions parallel to the geometrical axes, depends on only three displacement variables and the solution of specific problems requires only in-plane discretization, for any numbers of layers and delaminations. Closed form solutions are derived for the energy release rate in bi-material beams and applications are presented to homogeneous, bi-material and layered, simply supported and cantilever, bend-beams, with one and two delaminations.

Static and free vibration analysis of laminated composite and sandwich spherical shells using a generalized higher-order shell theory

In this article, higher-order closed-form solutions are obtained for static bending and free vibration analysis of laminated composite and sandwich spherical shells using a generalized higher-order shell theory. A theory is independent of the choice of shearing stress function (polynomial/non-polynomial) which eventually results in a theoretical unification of most of the classical and higher-order shear deformation theories. The present theory yields an accurate distribution of transverse shear stresses through the shell thickness; therefore, it does not require problem dependent shear correction factor. Governing equations and associated boundary conditions of the theory are derived by employing Hamilton’s principle. Navier type higher-order closed-form solutions are obtained for simply supported boundary conditions. Displacements, stresses and natural frequencies are presented for laminated composite and sandwich plates as well as shallow and deep spherical shells. The results of parabolic, trigonometric, hyperbolic, and exponential models are compared with each other and previously published results to verify the accuracy and efficiency of the present generalized shell theory.

Design of variable stiffness composite structures using lamination parameters with fiber steering constraint

In this study, a lamination parameter based optimization algorithm is developed in a finite element framework using classical plate deformation theory. The optimization reveals lamination parameter distribution over the plate which are then converted into fiber directions, stacking sequences and layer thicknesses by means of a material library. The optimum fiber angles in each ply are used to find continuous fiber angle distributions a using weighted residual method for the first time. The method uses finite element based least-squares and continuity constraint (LSC) to find a manufacturable design without making any preliminary assumption such as splines, stream functions, etc., for the fiber angle distributions. Penalty parameter is used to enforce a maximum limiting value for the fiber curvatures. The proposed method is applied to design for the minimum compliance in-plane and out-of-plane problems, and significant improvements are obtained in comparison to the literature findings.

Correction of Poland Syndrome (Chest Hypoplasia) Using Polymethylmethacrylate Implant

Poland anomaly (PA), also known as Poland syndrome, was first described by Alfred Poland as a unilateral underdevelopment or absence of the chest muscle, often associated with deformities such as syndactyly and chest wall deformity [1,2] Poland syndrome is characterized by a variable clinical presentation. The classical deformity consists of unilateral hypoplasia or aplasia of the sternocostal head of pectoralis major muscle and ipsilateral hand malformations. In addition, hypoplasia or aplasia of the breast is observed on the affected side in women.

Fundamental Frequency of Laminated Composite Thick Spherical Shells

In this study, we apply third-order shear deformation thick shell theory to analytically derive the frequency characteristics of the free vibration of thick spherical laminated composite shells. The equations of motion are derived using Hamilton&amp;rsquo;s principle of minimum energy and on the basis of the relationships between forces, moments, and stress displacements in the shell.&#x0D; &#x0D; We confirm the derived equations and analytical results through the finite element technique by using the well-known software packages MATLAB and ANSYS. We consider the fundamental natural frequencies and the mode shapes of simply supported spherical cross-ply (0, 90), (0, 90, 0), and (0, 90, 90, 0) laminated composite shells. Then, to increase accuracy and decrease calculation efforts, we compare the results obtained through classical theory and first-order shear deformation theory.

Second‐order cone programming formulation of discontinuous deformation analysis

SummaryIn classic discontinuous deformation analysis (DDA), artificial springs must be employed to enforce the contact condition through the open‐close iteration. However, improper stiffness parameters might cause numerical problems. The main goal of this paper is to propose a new framework of DDA using second‐order cone programming. The complementarity relationship at contacts can be formulated directly; thus, artificial springs are avoided. Stemming from the equations of momentum conservation of each block, the governing equations of DDA can be cast as convex optimization problems. The basic variables in the formulations can be either block displacements or contact forces. The derived optimization problems can be reformulated into a standard second‐order cone programming program, which can be solved using standard efficient optimization solvers. The proposed approach is validated by a series of numerical examples.

The effect of porosity on free vibration of SPFG circular plates resting on visco-Pasternak elastic foundation based on CPT, FSDT and TSDT

Using the classical, first order and third order shear deformation plates theories the motion equations of an undrained porous FG circular plate which is located on visco-Pasternak elastic foundation have been derived and used for free vibration analysis thereof. Strains are related to displacements by Sanders relationship. Fluid has saturated the pores whose distribution varies through the thickness according to three physically probable given functions. The equations are discretized and numerically solved by the generalized differential quadrature method. The effect of porosity, pores distribution, fluid compressibility, viscoelastic foundation and aspect ratio of the plate on its vibration has been considered.

Bending, free vibration, and buckling of modified couples stress-based functionally graded porous micro-plates

In this study, bending, free vibration, and buckling response of functionally graded porous micro-plates are investigated using the classical and first-order shear deformation plate theories. The Navier solution technique is utilized to obtain analytical solutions to simply supported rectangular plates. A power-law distribution is used to model the variation of two material constituents through the plate thickness. Three different porosity distributions are considered and assumed to take forms of cosine functions. The microstructure-dependent size effects are captured using the modified couple stress theory. Numerical results of bending, free vibration, and buckling are presented to determined the effects of constituent material variation, microstructure-dependent size effects, and porosity distributions on the mechanical response of functionally graded porous micro-plates.

MRI appearance of the anomalous volar radiotriquetral ligament in true Madelung deformity

To characterize the MRI appearance of the anomalous volar radiotriquetral ligament in cases of classic Madelung deformity. With institutional review board approval, a search of the radiology information system was performed to identify cases of potential Madelung deformity using variations of the criteria "Madelung deformity." Cases of classic Madelung deformity were included based on the following criteria: dorsal subluxation of the ulnar head, volar tilt of the distal radius, increased radial inclination of greater than 25°, triangulation of the carpus, and presence of Vickers ligament defined as an anomalous volar radiolunate ligament. Patients with a history of wrist trauma or severe degenerative change distorting anatomy were excluded. The resulting cases were reviewed to characterize the anomalous radiotriquetral ligament. Eight cases of classic Madelung deformity in 6 patients were identified. All 8 cases were characterized by the presence of an anomalous radiotriquetral ligament, which was more conspicuous than Vickers ligament. None of the excluded pseudo-Madelung deformity cases displayed a Vickers ligament or radiotriquetral ligament. The radiotriquetral ligament is an anomalous ligament that is a constant and distinguishing finding in classic Madelung deformity in this study. Awareness of the radiotriquetral ligament and distinguishing it from Vickers ligament on imaging studies and at surgery may have clinical implications that need to be further investigated.

The frequency and diagnostic accuracy of hand deformities in Parkinson's disease.

Hand deformities are well-known abnormalities observed in patients with Parkinson's disease (PD). We determined the frequency and diagnostic accuracy of hand deformities in PD. We studied 44 consecutive patients with PD, 44 age- and gender-matched normal controls and 22 patients with essential tremor (ET). By means of photographs taken in both hands of all participants, the degree of metacarpophalangeal (MCP) joint flexion was quantified by software and by blinded evaluations using a semiquantitative scale from the radial aspect, we grouped hands into four grades. The presence of classical striatal hand deformity (CSHD), defined as MCP joint flexion, proximal interphalangeal joint extension and distal interphalangeal joint flexion was also evaluated. Patients with PD had a higher frequency of MCP joint flexion and CSHD compared to normal controls and patients with ET. Mean MCP joint flexion was higher in both hands in patients with PD: 20.8° vs. normal controls (3.3°-3.9°) and patients with ET (2.8°-6.3°), P = 0.001. Concordance between evaluators for MCP joint flexion was fair: κ = 0.34 (P < 0.001), but poor for CSHD: κ = 0.142-0.235 (P < 0.05). A right hand MCP joint flexion of 12.5° and left hand of 10.5°, showed similar sensitivity (0.70) and specificity (between 0.75 and 0.80) than any degree of MCP joint flexion for the diagnosis of PD. CSHD had a sensitivity (0.60-0.80) and specificity (0.78-0.98) for the diagnosis of PD. Hand deformities are commonly observed in patients with PD, they may aid in the diagnosis of PD when compared to normal controls and patients with ET.

The Nonlinear Properties of a Piezoelectric Cantilevered Plate under Parametric Excitation

In this paper, we investigate the nonlinear dynamics characteristics of the composite piezoelectric cantilevered plate forced under parametric excitation. Based on the Reddy’s classic deformation plate theory and the von Karman nonlinear strain–displacement equations, we deduce the nonlinear partial differential equations by applying the Hamilton’s principle. Then the dimensionless ordinary differential equations of the system with three-degree-of-freedom are derived. We choose a set of parameters of governing equation and employ numerical simulations to investigate the effects of parametric excitation on the nonlinear responses of the system. The results indicate that there exist the periodic and chaotic motions.

A derivative-free upscaled theory for analysis of defects

Notwithstanding its recent focus on microstructure-driven non-classical aspects, a breakthrough model in continuum mechanics that can evolve the macroscopic deformation of a solid body undergoing fracture whilst systematically incorporating the microstructural information remains elusive. In addressing this issue, we presently obtain, based on the molecular level information, a derivative-free balance law pertaining to a higher scale of interest and useful in a continuum or discrete setting. Derived using a probabilistic projection technique, the law exploits certain microstructural information in a weakly unique manner. The projection generalizes the notion of directional derivative and, depending on the application, may be interpreted as a discrete Cauchy–Born map with the structure of the classical deformation gradient emerging in the infinitesimal limit. As an illustration, we use the Tersoff–Brenner potential and obtain a discrete macroscopic model for studying the deformation of a single-walled carbon nanotube (SWCNT). The macroscopic (or continuum) model shows the effect of chirality – a molecular phenomenon – in its deformation profile. We also demonstrate the deformation of a fractured SWCNT, which is a first-of-its-kind simulation, and predict crack branching phenomena in agreement with molecular dynamics simulations. As another example, we have included simulation results for fractured SWCNT bundle with a view to establishing our claim regarding the efficacy of the proposed method.

Three-dimensional nonlinear bending analysis of FG-CNTs reinforced composite plates using the element-free Galerkin method based on the S-R decomposition theorem

A three-dimensional element-free Galerkin method (EFG) based on the Strain-Rotation (S-R) decomposition theorem, named 3D-SR-EFG, is developed to investigate the nonlinear bending behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) plates. Due to its overcoming the deficiencies of classic finite deformation theories, S-R decomposition theorem can provide a reliable theoretical support for the geometrically nonlinear simulation. The incremental variational formulation based on the S-R decomposition theorem for three-dimensional static large deformation problems is derived from the updated co-moving coordinate formulation and principle of potential energy rate. Global weak-form EFG is adopted to obtain the discrete form of the formulation. Convergence and comparison studies are conducted to validate the numerical stability and accuracy of the proposed 3D-SR-EFG. The influences of volume fraction and distributions of CNTs, plate’s aspect ratio and width-to-thickness ratio, boundary conditions on the nonlinear bending response of the CNTRC plates are numerically analyzed and discussed in parametric studies. Results demonstrate that the 3D-SR-EFG can effectively predict the nonlinear bending behavior of the CNTRC plates. This work also further extends the applications of the S-R decomposition theorem.

Classical deformations of noncompact surfaces and their moduli of instantons

We describe semiuniversal deformation spaces for the noncompact surfaces Zk:=Tot(OP1(−k)) and prove that any nontrivial deformation Zk(τ) of Zk is affine.It is known that the moduli spaces of instantons of charge j on Zk are quasi-projective varieties of dimension 2j−k−2. In contrast, our results imply that the moduli spaces of instantons on any nontrivial deformation Zk(τ) are empty.

A complete set of independent and physically meaningful invariants in the mechanics of solids reinforced by two families of fibres

It has recently been shown [2,3] that only seven of the classical deformation invariants employed in hyperelasticity of solids reinforced by two families of unidirectional fibres are independent. This short communication demonstrates a manner in which such a set of seven invariants is conveniently identified without much deviation from well-known features that characterise their classical counterparts. It also shows that, unlike several of their classical counterparts, these newly identified invariants have all their own physical meaning. This new development is immediate applicable on mass-growth problems of tissue that preserve fibre direction [1] and, notably, on problems involving mass-growth of a circular tube reinforced by two families of helices wound symmetrically around the tube in opposite directions.