Mircea Gh. Munteanu

University of Udine | UNIUD · Department of Electrical, Management and Mechanical Engineering

The paper proposes a new three-dimensional flexible hinge formed of several serially linked straight- and circular-axis segments that are disposed of in two layers. The novel hinge configuration is capable of large displacements and can be implemented in precision-compliant mechanisms that need to cover large spatial workspaces. Based on simplified...

This research studies the large-displacement response of a fractal-architecture mechanism with circular-axis flexible hinges, which was introduced in [1], by formulating an efficient and accurate nonlinear finite element model. Two three-dimensional line elements are proposed whose nodal degrees of freedom include the three spatial Tait-Bryan angle...

This research proposes the self-similarity design concept of flexible mechanisms by studying the out-of-plane, piston motion of a compliant device. Self-similar compliant mechanisms can be formed by connecting flexible units of scaled-down, identical geometry in series and/or parallel. We study a folded-architecture, compact mechanism class formed...

Films of the electrets material are currently proposed to design compact vibration energy harvesters. They are used to cover the surface of electrodes of some capacitive devices based on a deformable microbeam clamped at both its ends. The performance of those energy harvesters is often predicted in the literature by neglecting the effect of the ge...

This work deals with the practical use of semi-analytical finite elements in the machine design. The case of mechanical shafts is considered. The most usual loading condition characterized by the presence of axial, torsional, bending, and shear loads can be modeled by over imposing an axi-symmetric, an axi-antisymmetric and a harmonic load, corresp...

This work presents a one-dimensional harmonic finite element for the transient elasto-plastic analysis of axisymmetric structures loaded by non-axisymmetric thermal and mechanical loads. The one-dimensional element exploits a semi-analytical approach, based on Fourier series decomposition of the applied loads. The initial stress method is used for...

The design of steelmaking plants makes use of well established methodologies, where the uncertainties related to an approximated simulation of the technological process and the lack of accurate models of the structural behaviour are overcome by simply over sizing the most critical parts. The demand of a strong improvement in term of productivity an...

Work rolls in hot rolling mills are subjected to thermal and mechanical loads that could affect the surface integrity of the roll. To estimate the roll lifetime, the thermomechanical behaviour of the work roll was recently studied adopting a 2D plain strain model. Nevertheless, even this 2D approach requires an extremely long computational time, wh...

Work rolls in hot rolling mills are usually subjected to cyclic thermal loadings, induced by strip heating followed by water jet cooling; it is therefore necessary to perform numerical simulation of several mill rolls up to steady state condition, taking into account the elastoplastic behaviour of the material. This work aims to present a simplifie...

Work rolls in hot rolling mills are usually subjected to cyclic thermal loadings, induced by strip heating followed by water jet cooling. This work aims to present a simplified method for assessing transient temperature and thermal stress distribution in work roll of hot rolling mill. A nonlinear elasto-plastic stress analysis is performed. In the...

This work deals with the thermo-mechanical analysis of a copper mould, which is a component that controls initial solidification in continuous steel casting. Large temperature gradients, caused by a huge thermal flux imposed by steel, are responsible for high stresses and plastic strains. Plant switch-off also induces residual stresses which may in...

This paper presents a numerical approach for the static and dynamic analysis of hydrodynamic radial journal bearings. In the first part, the effect of shaft and housing deformability on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a finite elements (FE) structural model is solved....

A phenomenological approach is proposed to identify some effects occurring within the structure of the microswitch conceived for radio frequency application. This microsystem is operated via a nonlinear electromechanical action imposed by the applied voltage. Unfortunately, it can be affected by residual stress, due to the microfabrication process,...

This paper presents a numerical approach for the analysis of hydrodynamic radial journal bearings. The effect of shaft and housing elastic deformation on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a plane finite elements structural model is solved. Temperature and pressure effec...

This paper presents a numerical approach for the static and dynamic analysis of hydrodynamic radial journal bearings. In the first part, the effect of shaft and housing deformability on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a plane finite elements (FE) structural model is s...

A phenomenological approach is herein followed to describe several superimposed effects occurring within the structure of microswitch for radio frequency application (RF-MEMS). This device is operated via a nonlinear electromechanical action imposed by applied voltage. Unfortunately, it is usually affected by residual stress, after microfabrication...

Measurements of Young's modulus of microstructures are frequently based on dynamic tests on microbeams. The aim of this work is evaluating if the accuracy of these measurements is affected significantly by the anticlastic effect. A nonlinear model of cantilever's dynamic behavior is thus developed and applied to some characteristic cases. The obtai...

Out-of-plane bending tests are here used to experimentally validate some numerical models of microbeams actuated by the electric field. Out-of-plane bending microcantilevers and clamped–clamped microbeams often suffer the presence of residual strain and stress, respectively, which affect their static and dynamic behaviour and pull-in voltage. In ca...

Among RF-MEMS layouts currently used for designing microswitches, microresonators and varactors, cantilever and double clamped microbeams are widely applied in industrial applications. After a consistent modelling activity which defined suitable numerical approaches to study the static behaviour of such microdevices, authors investigate here the pr...

Electromechanical behavior of microcantilever specimens for in-plane and out-of-plane bending tests, currently designed by industry for Radio-Frequency application, are here analyzed. Main features of these two layouts are discussed. In particular, a comprehensive experimental validation of 2D and 3D numerical models implemented to predict the coup...

Positioning devices based on flexural hinges are often used in microsystems and precision mechanisms. In this work a nonlinear parametric optimization of flexural hinge shapes is performed. Predefined and freeform parametric shapes are compared in terms of compliance, strength, stress concentration factors and parasitic shifts. Transversal and axia...

Von Kármán equations have been used to evaluate the flexural behaviour of rectangular leaf springs with constant thickness. A closed form solution is obtained, showing that flexural stiffness varies continuously from that obtained by considering a beam model to the value given by the linear plate theory. This behaviour depends on section geometry,...

Electrostatic microactuator is a paradigm of MEMS. Cantilever and double clamped microbeams are often used in microswitches, microresonators and varactors. An efficient numerical prediction of their mechanical behaviour is affected by the nonlinearity of the electromechanical coupling. Sometimes an additional nonlinearity is due to the large displa...

In recent years employment of MEMS technology (MicroElectroMechanical-Systems) in designing RF (Radio Frequency) systems is increasingly drawing the attention of the Scientific Community. This is because of the well-known remarkable performances achievable with MEMS implementation of RF components (such as variable capacitors, inductors and switche...

The analysis of a microelectrostatic actuator is presented, formulated by means of the so-called Discrete Geometric Approach applied to the solution of the electrostatic-elastostatic coupled problem. Numerical results computed by means of the proposed approach are compared to those coming from assessed approaches like the finite-element method (FEM...

Experimental validation of numerical models developed by the authors to predict the static behaviour of microelectrostatic actuators is described. Cantilever microbeams, currently used in connection with RF-MEMS and micro-scale material testing were analysed. A set of microcantilevers, bending in the plane of the wafer, i.e. in the same plane as th...

In this paper an experimental validation of numerical approaches aimed to predict the coupled behaviour of microbeams for out-of-plane bending tests is performed. This work completes a previous investigation concerning in plane microbeams bending. Often out-of-plane microcantilevers and clamped-clamped microbeams suffer the presence of residual str...

Microcantilever specimens for in-plane and out-ofplane bending tests are here analyzed. Experimental validation of 2D and 3D numerical models is performed. Main features of in-plane and out-of-plane layouts are then discussed. Effectiveness of plane models to predict pull-in in presence of geometric nonlinearity due to a large tip displacement and...

In this paper an experimental validation of numerical approaches aimed to predict the coupled behaviour of microbeams for out-of-plane bending tests is performed. This work completes a previous investigation concerning in plane microbeams bending. Often out-of-plane microcantilevers and clamped-clamped microbeams suffer the presence of residual str...

This paper concerns the experimental validation of some mathematical models previously developed by the authors, to predict the static behaviour of microelectrostatic actuators, basically free-clampe d microbeams. This layout is currently used in RF-MEMS design operation or even in material testing at mic roscale. The analysis investigates prelimin...

1 this paper presents a stiffness study of two parallel robots from the Isoglide family, which have decoupled motions and are isotropic in translation. Stiffness is an important parameter for robot design and its computation requires often a long calculation time and a high computer capacity. In this paper a new method for stiffness calculation is...

A simple method to study the dynamics of beam-like multi-body systems is presented. The case of large elastic displacements and small strain is considered. Elastic displacements may be so large that the initial configuration of the system is completely changed. This may happen in compliant mechanisms, for instance, which have become widespread in t...

This paper deals with numerical prediction of the nonlinear dynamic behaviour of electromechanical continuous microsystems, in presence of large displacements. Finite Element Method (FEM) is applied, by following so-called “sequential” approach, based on the solution in series of coupled electromechanical problem. In spite of tested approaches avai...

Results of a strength-based optimisation of flexural hinge shapes are given. Both pre-defined and freeform parametric shapes are considered. By employing non-linear parametric optimisation algorithms, shapes that are best suited for the desired applications are determined.

Stiffness performance is a very important aspect to be considered in the design of parallel machines. This article presents a comparative stiffness analysis based on numerical simulation for a reconfigurable parallel machine to 3 or 4 degrees of mobility (D.O.M.). The two configurations have decoupled motions and are isotropic in translation. This...

Electrostatic actuated flexible structure are frequently encountered in microsystems. The behaviour of these devices is characterized by electromechanical coupling, due to the mutual interaction between the electrostatic field and the deflection of the structure. A common case, frequently analyzed in the literature, is that of cantilever beam loade...

In this work a procedure for the optimal design of flexural hinges to be microfabricated by a lithographic process is proposed. The structural optimization problem is approached by coupling a parametric finite element model to an optimization algorithm. A computer code was developed to generate the mesh at each optimization step accordingly to the...

Dynamic analysis of highly elastically deformed bodies subjected to rotational movement is very important from a practical point of view: the centrifugal forces may considerably modify the body configuration. The classical large displacement theory is complicated and it leads to very time-consuming computer codes. In this work, a simple numerical m...

Here, an approach to describe the dynamics of 2D and 3D mechanisms that leads to a simpleand fast analysis is presented. Any position of an elastic mechanism may be defined usingonly rotations. Because in space the finite angles are not vectors, the Euler–Rodriguesparameters were adopted to describe the 3D rotations. The assembling process of the l...

The paper deals with the numerical analysis of the static and electromechanical behaviour of microbeams under effect of large deflections. The presence of such coupling effect requires taking into account of the interaction between the electric field and the structure, by following a coupled field analysis. The latter is made difficult by the intri...

In this work, a way to solve very accurately, in a acceptable computer time, a large scale of non-linear elastodynamic problems is presented. Elastic beam systems under large motion are studied and Timoshenko beam model was adopted. The exact differential equations written for the actual, deformed configuration of the system are solved. These equat...

In this work the 3D dynamics of mechanical systems, structures and mechanisms, are studied. These systems are divided into so-called macro-elements. Because of large rotations involved by the motion of each macro-element the Euler-Rodrigues parameters are used to describe the global motion of the system. The paper presents in details the study of o...

In the first part of the paper the theory of the 3D dynamics of mechanical systems composed by elastic beams, structures and mechanisms, was studied. These systems are divided into so-called macro-elements and the movement equations of one macro-element were established. Only the Euler-Rodrigues parameters are used to describe the global motion of...

In this work a procedure for the optimal design of flexural hinges to be microfabricated with a lithographic process is proposed. The structural optimization problem is approached by coupling a parametric finite element model to an optimization algorithm. A computer code was developed to generate the mesh at each optimization step accordingly to th...

Bending is a local conformational micropolymorphism of DNA in which the original B-DNA structure is only distorted but not extensively modified. Bending can be predicted by simple static geometry models as well as by a recently developed elastic model that incorporate sequence dependent anisotropic bendability (SDAB). The SDAB model qualitatively e...

Local bending phenomena can be predicted by elastic models that incorporate sequence-dependent anisotropic-bendability (SDAB). SDAB models consider DNA to be an initially straight, segmented, elastic rod, in which the flexibility of each segment is greater towards the major groove than it is in other directions. While local bending can be predicted...

Binding energy of DNA-Cro protein complexes is analyzed in terms of DNA elasticity, using a sequence-dependent anisotropic bendability (SDAB) model of DNA, developed recently [M.M. Gromiha, M.G. Munteanu, A. Gabrielian and S. Pongor, J. Biol. Phys. 22(1996) 227-243.]. The protein is considered to bind aspecifically to DNA that reduces the freedom o...

Simplified elastic rod models of DNA were developed in which the rigidity of DNA is sequence dependent and asymmetrical, i.e. the bending is facilitated towards the major groove. By subjecting the models to bending load in various directions perpendicular to the longitudinal axis of DNA, the bending deformation and the average conformation of the m...

The first-order calculations do not suit in all practical cases, second-order calculations being often necessary. A plane tension state, which can operate as a result of centrifugal forces, or a non-uniform distribution of the temperature on the radius, can have a notable influence on the bending behavior of thin plates as well on the natural frequ...