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The present paper presents a comprehensive study based on numerical and experimental investigations testing the use of NC lathe machine in SPIF process of a dome part made of AA1060-H14 aluminum alloy. The main idea is to check the viability of NC turning machine in SPIF process of axisymmetric parts usually manufactured using 3-axis milling machines. For this purpose, aluminum thin sheet is firstly characterized and the right material behavior is identified. A VUMAT subroutine is used to implement this material behavior in ABAQUS/explicit FE used to simulate the SPIF-Turning operation. A comparison between experimental and numerical results showed the efficiency of this FE model to simulate a 2-axis SPIF strategy. Results, covering forming effort, thinning, the strain state distribution, fracture occurrence, and surface finish proved that NC turning machines could manufacture rapidly and with more accuracy, revolved components usually formed by a 3-axis NC milling machine.

NiTi wires are considered as the most appropriate wires to be used during the initial phase of orthodontic treatment. This work presents a numerical method to simulate the coupling between the orthodontic appliance and bone remodeling, which are the two mechanisms responsible for the orthodontic tooth movement.The superelastic behavior of a NiTi wire was integrated in a three-dimensional simulation model to reproduce the long-term bone remodeling coupled with tooth alignment using the finite element method. The orthodontic load was derived by deforming the superelastic wire in order to adopt itself to the original position of irregular teeth. Root form was extracted from cone beam tomography imaging files.As a result, the teeth were aligned while the wire was recovering its initial shape. The canine was intruded by 0.53 mm, while the neighboring teeth were extruded by 0.44 and 0.46 mm. When the wire was loaded, it generated a load of 4.6 N on the bracket bonded on the canine. This force was active during the first day of the treatment. Then, the force continued to decline until the end of the correction period. The decreasing load delivered from the wire affected the teeth displacements as observed in real situations.Despite the complexity of the presented numerical simulation, this procedure allowed the analysis of the orthodontic forces that were generated in the clinical experiments and of the biomechanical response of the periodontal support elements when using this kind of wire.ZIELSETZUNG: NiTi-Drähte gelten als die für die Anfangsphase einer kieferorthopädischen Behandlung am besten geeigneten Drähte. In der vorliegenden Arbeit wird eine numerische Methode vorgestellt, um die Verbindung zwischen kieferorthopädischer Apparatur und Knochenumbau zu simulieren – die beiden für die kieferorthopädische Zahnbewegung verantwortlichen Faktoren.Das superelastische Verhalten eines NiTi-Drahtes wurde in ein dreidimensionales Simulationsmodell integriert, um den langfristigen Knochenumbau in Verbindung mit der Zahnausrichtung unter Verwendung der Finite-Elemente-Methode zu reproduzieren. Die kieferorthopädische Belastung wurde abgeleitet, indem der superelastische Draht so verformt wurde, dass er sich an die ursprüngliche Position unregelmäßiger Zähne anpasst. Die Wurzelform wurde aus den DVT(digitale Volumentomographie)-Bilddateien extrahiert.Im Ergebnis wurden die Zähne ausgerichtet, während der Draht wieder seine ursprüngliche Form annahm. Der Eckzahn wurde um 0,53 mm intrudiert, die benachbarten Zähne wurden um 0,44 und 0,46 mm extrudiert. Der aktivierte Draht erreichte eine Kraft von 4,6 N auf das am Eckzahn angebrachte Bracket. Diese Kraft war am ersten Tag der Behandlung wirksam, im Anschluss wurde sie bis zum Ende der Behandlungszeit kontinuierlich geringer. Die nachlassende vom Draht ausgehende Kraft beeinflusste die Zahnverschiebungen, wie dies in der Praxis zu beobachten ist.Trotz der Komplexität der numerischen Simulation ermöglichte das vorgestellte Verfahren die Analyse der in klinischen Experimenten erzeugten kieferorthopädischen Kräfte und der biomechanischen Reaktion des parodontalen Halteapparates bei der Verwendung dieser Art von Draht.

The present paper presents numerical and experimental comparative studies between the conventional bending process (bending using punch and V-die) and bending with a rubber-pad cushion. In fact, a finite-element method is introduced to compare these two procedures used to bend AA1050-H14 Aluminum thin sheet. An elastoplastic constitutive model with quadratic yield criterion of Hill 48 and isotropic hardening behavior has been adopted in FE simulations performed using ABAQUS explicit. To model rubber material, a Mooney–Rivlin theory is used in the finite-element simulation. The purpose of this study is to see the difference between the two methods in terms of effort evolution, springback, stress distribution, thinning. Analyze the effect of the rubber material; in fact, natural rubber, and polyurethane with hardness 50, 70, and 90 shore A are investigated. This numerical study was validated by an experimental investigation that proved the efficiency of the elastic cushion to bend in a better way this thin aluminum sheet.

In the present work, a geometrically nonlinear finite shell element is first presented to predict nonlinear dynamic behavior of piezolaminated functionally graded carbon nanotube-reinforced composite (FG-CNTRC) shell, to enrich the existing research results on FG-CNTRC structures. The governing equations are developed via an improved first-order shear deformation theory (FSDT), in which a parabolic distribution of the transverse shear strains across the shell thickness is assumed and a zero condition of the transverse shear stresses on the top and bottom surfaces is imposed. Using a micro-mechanical model on the foundation of the developed rule of mixture, the effective material properties of the FG-CNTRC structures, which are strengthened by single-walled carbon nanotubes (SWCNTs), are scrutinized. The effectiveness of the present method is demonstrated by validating the obtained results against those of other studies from literature considering shell structures. Furthermore, some novel numerical results, including the nonlinear transient deflection of smart FG-CNTRC spherical and cylindrical shells, will be presented and can be considered for future structure design.

The purpose of this manuscript is to carry out an experimental and numerical investigation of bulging process of aluminum AA1050-H14 sheet metal in free expansion when using a flexible punch. Three types of rubber with different hardness are used as flexible punch. First, a mechanical characterization and identification of aluminum sheet metal and polyurethane rubber parameters is achieved for validation purpose. Then, an experimental study of flexible bulging process is performed to analyze the effect of rubber type and hardness on forming capability. The obtained results show that the polyurethane with hardness of 70 Shore A is considered as the most suitable punch for the bulging operation when comparing with silicone and natural rubber. Finally, a comparison between bulging with flexible and rigid punches is conducted using the finite element code ABAQUS/Explicit. The developed simulations predict efficiently the realistic thickness distribution along the bulged part.

This paper presents a modified first-order enhanced solid-shell element formulation with an imposed parabolic shear strain distribution through the shell thickness in the compatible strain part. Moreover, zero transverse shear stress on the top and bottom surfaces of the shell is satisfied exactly and the shear correction factors is no longer needed. Furthermore, the developed solid-shell element allows an efficient and accurate analysis of functionally graded material shells under geometric nonlinear static conditions. A simple power-law functionally graded distribution of the shells along the thickness direction is considered. The validity and accuracy of the developed solid-shell element are illustrated through the solution of several known problems taken from the literature. The influences of power-law index on the nonlinear static behavior of the FGM shells are discussed.

This paper focuses on numerical simulation of single point incremental forming (SPIF) process. Via a user-defined material (VUMAT) subroutine is employed to implement a non-associated mixed isotropic–kinematic hardening material model. The accuracy of the proposed non-associated flow rule model to predict the material behavior and the anisotropy in sheet metal forming simulations is examined by comparing numerical results with experimental measurements. The suggested model shows good agreement with experimental results compared to the associated Hill_R and Hill_S models. The proposed non-associated flow rule demonstrates a good efficiency to simulate the springback after sheet metal forming and to predict the thickness variation during incremental sheet metal forming process. The present non-associated model can improve the prediction of both anisotropic and hardening behaviors of material used in numerically controlled sheet metal forming technology.

A geometrically nonlinear analysis of elastoplastic ceramic/metal functionally graded material (FGM) shells is investigated in this paper based on the first-order shear deformation theory. The elastoplastic behavior of the ceramic particle-reinforced metal matrix FGM shell is assumed to follow Ludwik hardening law. The elastoplastic material properties are assumed to vary smoothly through the thickness of the shells. The Mori–Tanaka model and self-consistent formulas of Suquet are employed to locally evaluate effective elastoplastic parameters of the ceramic/metal FGM composite. The homogenization formulation and numerical algorithms are implemented into ABAQUS/Standard via a user material subroutine (UMAT) developed to study the FG shells in large displacements and rotations. With the aim of demonstrating the accuracy of the present method, current numerical results are compared to experimental and numerical ones considering geometrically nonlinear elastoplastic FGMs and show very good agreement. The overall robustness of the new developed solution taking into account both geometric and material nonlinearities is demonstrated through several non-trivial benchmark problems taken from the literature. The effect of the constituent distribution on the deflections is analyzed.

A finite element simulation of flexible bulge forming of aluminum sheet metal is carried out. The effect of rubber pad on forming capability is studied by comparing flexible bulge to hydroforming. Based on the theory of Continuum Damage Mechanics (CDM), a local approach with fully coupling between ductile damage and an anisotropic elasto-plastic model with mixed nonlinear kinematic/isotropic hardening is introduced. The model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. A Mooney-Rivlin theory is adopted for rubber material behavior. Comparisons between both processes in terms of thickness variation, damage occurrence, and sheet formability are conducted for different rubber shores and friction. Numerical findings are in a good correlation with experiments from literature.

This paper is focused on the structural shape optimization of incompressible hyperelastic structures. An analytical sensitivity is devel- oped for the rubber like materials. The whole shape optimization process is carried out by coupling a closed geometric shape in R 2 with boundaries, defined by B-splines curves, exact sensitivity analysis and mathematical programming method (S.Q.P: sequential quadratic programming). Design variables are the control points coordinate. The objective function is to minimize Von-Mises stress, constrained to the total material volume of the structure remains constant. In order to validate the exact Jacobian method, the sensitivity calculation is performed: numerically by an efficient finite difference scheme and by the exact Jacobian method. Numerical optimization examples are presented for elastic and hyperelastic materials using the proposed method.