Search results for "STIFFNESS"
showing 10 items of 524 documents
Design and optimization of bonded patch repairs of laminated composite structures
2015
International audience; The present study proposes a method for design optimization of external patched repairs. The tensile behavior of notched specimens with patched repair was studied using finite element analysis and compared with experimental results. It was found that high stress concentrations along the transverse edges of circular patches and/or at the longitudinal edges of the hole leads to early damage initiation in the parent plate. The damage initiation site and its propagation depend on the patch in-plane stiffness. The optimal patch design can be characterized by a strength ratio R*. The overall design of the patch repair can be considered using a dimensionless design paramete…
Identification of a static tool force model for robotic face milling
2014
In this paper two different process models which can predict the mean value components of the tool forces when milling aluminium, bronze and steel with an industrial robot have been estimated. The parameters in the process models were depth and width of cut, while feedrate and cutting speed were found from the tool manufacturer's datasheets. The models were estimated from a large set of machining experiments. Different measurement sets were used for parameter estimation and for model verification. The estimated models were found to be accurate. For the experiments in aluminium and the model using only the depth of cut as parameter, the average error was about 18N. For the model using both d…
Evaluation of infilled frames: an updated in-plane-stiffness macro-model considering the effects of vertical loads
2015
The influence of masonry infills on the in-plane behaviour of RC framed structures is a central topic in the seismic evaluation and retrofitting of existing buildings. Many models in the literature use an equivalent strut member in order to represent the infill but, among the parameters influencing the equivalent strut behaviour, the effect of vertical loads acting on the frames is recognized but not quantified. Nevertheless a vertical load causes a non-negligible variation in the in-plane behaviour of infilled frames by influencing the effective volume of the infill. This results in a change in the stiffness and strength of the system. This paper presents an equivalent diagonal pin-jointed…
Unified formulation for a family of advanced finite elements for smart multilayered plates
2016
AbstractFamilies of layer-wise and equivalent single-layer advanced finite elements for the analysis of smart multilayered plates are formulated in a unified framework. The proposed modeling strategy reduces the multifield problem to an effective mechanical plate by the condensation of the electromechanical state into the plate kinematics, which is assumed as a variable order expansion along the plate thickness. Carrera Unified Formulation is invoked to derive the elemental stiffness and mass matrices and the mechanical and magneto-electric equivalent forces. The obtained smart plate finite element equations involves kinematical variables only and this extends the tools developed for multil…
Fundamental period of infilled reinforced concrete frame structures
2016
AbstractThe fundamental period of vibration appears to be one of the most critical parameters for the seismic design and assessment of structures. In the present paper, the results of a large-scale analytical investigation on the parameters that affect the fundamental period of reinforced concrete structures are presented. The influence of the number of storeys, the number of spans, the span length, the infill wall panel stiffness and the percentage of openings within the infill panel on the fundamental period of infilled RC frames was investigated. Based on these results, a regression analysis is applied in order to propose a new empirical equation for the estimation of the fundamental per…
Multi-Objective Design of Optimisation of a Class of PKMs - The 3-DOF Gantry-Tau
2010
The main contribution of this paper is the use of the evolutionary multi-objective methodology based on the com plex search algorithm and geometric approaches to optimise a parallel kinematic structure. The design optimisation scheme includes the kinematic (collisions free workspace), elastostatic (Cartesian stiffness in the Y direction) and elastodynamic (first resonance frequency) properties of the PKM as the objectives. The optimisation constraints are the support frame lengths, actuator positions, end-effector’s kinematic parameters and the robot’s arm lengths. The optimisation results are presented in this paper.
Off-line path correction of robotic face milling using static tool force and robot stiffness
2015
In this paper the developed method for off-line compensation of tool deflections when milling aluminum with an industrial robot is presented. The efficiency of this approach is verified with high precision measurements of deflections using a laser tracker. The compensation method includes both the static milling process model which can predict the mean value components of the tool forces and a new combined local/global approach for estimating the combined stiffnesses of joints. With a process model such as the one presented in this paper and estimates of the robot's joint stiffness values, the tool path can be adjusted to counteract deflections of the tool during milling operations. The mod…
Structural behavior of the old masonry bridge in the Gulf of Castellammare
2016
Abstract Masonry arch bridges represent a very significant part of the heritage of road and railway artworks all over the word and especially in the Mediterranean area, both in terms of: numbers; reduced environmental impact; and static efficiency. In these cases, the cost of maintenance is often limited to the content and channeling of surface water and control of vegetation, which can eventually take root on the joints of the masonry at the shoulders. In masonry bridges, there are no expansion joints or hinges with support equipment or trolleys, as in metal bridges and reinforced concrete ones, or paint, or resin surface protection, all items that affect the cost of maintenance. The perma…
Low stiffness variation in structural systems: identification and localization
2008
When a very low damage occurs, the undamaged structural response totally overlaps the damaged one either in time domain or in frequency domain; on the other hand, by considering some characteristics of the analytical signal, such as the phase, it has been possible to develop a damage identification procedure that allows the identification and localization of damage even if the structure experiences multiple damages at the same time. This procedure is also robust with respect to the presence of measuring noise. In order to assess the validity of the proposed damage identification procedure, numerical applications on single degree of freedom and 2 DOF and 4 DOF are presented using data record…
Dynamic identification of a reinforced concrete frame in progressive states of damage
2006
Two, full size, reinforced concrete frames were put on a shaking table and underwent seismic excitations with increasing intensities. The aim of the reported experiment was to study changes in their dynamic, modal parameters due to development of cracks in concrete. Dynamic identification of these frames was carried out through diagnostic tests interlaced with the damaging excitations. This paper presents the results of their identification in various states of damage, using low level non-destructive damage estimation methods. A characteristic decrease of natural frequencies and an increase of structural damping was observed. The drop of the natural frequency was fastest for the 1st mode an…