1,228 research outputs found
Analysis and modelling of a rotary forming process for cast aluminum alloy A356
Spinning of a common aluminum automotive casting alloy A356 (Al-7Si-0.3 Mg)
at elevated temperatures has been investigated experimentally with a novel
industrial-scale apparatus. This has permitted the implementation of a fully
coupled thermomechanical finite element model aimed at quantifying the
processing history (stress, strain, strain-rate and temperature) and predicting
the final geometry. The geometric predictions of this model have been compared
directly to the geometry of the workpieces obtained experimentally. This study
is novel in regards to both the size and shape of the component as well as the
constitutive material representation employed. The model predictions are in
reasonable agreement with experimental results for small deformations, but
errors increase for large deformation conditions. The model has also enabled
the characterization of the mechanical state which leads to a common spinning
defect. Suggestions for improving the accuracy and robustness of the model to
provide a predictive tool for industry are discussed
Tilted guides with friction in web conveyance systems
One challenge in designing web conveyance systems is controlling the displacement and vibration of the webs by guides without introducing instabilities or higher frequency disturbances from flange impacts. A solution to this problem is to use an actively or passively tilted guide or roller to steer the web. In this paper, a model of tilted guides with friction is developed, and it is shown that tilted guides produce a change in the webâs displacement, slope, bending moment, and shear force. When the web is conceptually unwrapped from its path, the normal force between the web and a tilted guide has a component that acts in the direction of the webâs lateral displacement, resulting in an equivalent force and bending moment acting on the web. The model is validated by measurements, and is compared to a previously existing model of guide tilt. In the configurations studied, the displacement of the web near the guide is linearly dependent on the tilt angle and tension and it increases exponentially with the webâs span length. When the guideâs tilt is oriented towards the center of the webâs wrap around the guide, the equivalent bending moment is zero in the absence of friction, and there is good agreement between the model developed in this paper and the previously existing model. However, when the center of the webâs wrap is oriented 90° away from the guideâs tilt orientation, the equivalent force is zero in the absence of friction, and measurements demonstrate the necessity of the equivalent bending moment
Enhancing vibration control in cable-tip-mass systems using asymmetric peak detector boundary control
In this study, a boundary controller based on a peak detector system has been designed to reduce vibrations in the cableâtipâmass system. The control procedure is built upon a recent modification of the controller, incorporating a non-symmetric peak detector mechanism to enhance the robustness of the control design. The crucial element lies in the identification of peaks within the boundary input signal, which are then utilized to formulate the control law. Its mathematical representation relies on just two tunable parameters. Numerical experiments have been conducted to assess the performance of this novel approach, demonstrating superior efficacy compared to the boundary damper control, which has been included for comparative purposes"This work has been funded by the Generalitat de Catalunya through the research projects 2021-SGR-01044."Peer ReviewedPostprint (published version
Adaptive boundary control of an axially moving system with large acceleration/deceleration under the input saturation
We present the dynamical equation model of the axially moving system, which is expressed through one partial differential equation (PDE) and two ordinary differential equations (ODEs) obtained using the extended Hamilton's principle. In the case of large acceleration/deceleration axially moving system with system parameters uncertainty and input saturation limitation, the combination of Lyapunov theory, S-curve acceleration and deceleration (Sc A/D) and adaptive control techniques adopts auxiliary systems to overcome the saturation limitations of the actuator, thus achieving the purpose of vibration suppression and improving the quality of vibration control. Sc A/D has better flexibility than that of constant speed to ensure the operator performance and diminish the force of impact by tempering the initial acceleration. The designed adaptive control law can avoid the control spillover effect and compensate the system parameters uncertainty. In practice, time-varying boundary interference and distributed disturbance exist in the system. The interference observer is used to track and eliminate the unknown disturbance of the system. The control strategy guarantees the stability of the closed-loop system and the uniform boundedness of all closed-loop states. The numerical simulation results test the effectiveness of the proposed control strategy
Condition monitoring of belt based motion transmission systems
A key asset of Royal Mail Group consists of a nationwide network of sorting offices
that forms a constituent component of the means through which the organisation
provides an efficient nationwide postal service within the United Kingdom. It may be
argued that the efficiency currently possessed by modem sorting offices is due to the
utilisation of machines that automate the process of sorting items of mail. The modem
letter-sorting machine possessed by Royal Mail can sort up to 30,000 letters per hour;
such machines serve as an example of an achievement of the application of
Mechatronics. The maintenance of letter sorting machines constitutes a large overhead for the
organisation. In the face of competition from pervasive electronic media within the
personal communications market and the prospect of deregulation, Royal Mail seeks
to streamline its operation in part by the reduction of the overheads incurred through
maintenance of letter sorting machinery. The adoption of condition based
maintenance techniques and predictive maintenance, for letter sorting machine
components such as belts and bearings, forms part of the strategy through which
Royal Mail seeks to reduce this overhead. Utilisation of flat belts and timing belts for
the implementation of key functions in letter sorting machinery, such as the transportation of items of mail within the mail sorting process, results in the use of
many such components within letter sorting machinery. A direct link exists between
the maintenance of peak performance of a sorting machine and the maintenance of belt drives; as such the maintenance of belt drives forms a substantial component of
the maintenance overhead.
The focus of this thesis consists of the condition monitoring of belt based motion
transmission systems and in particular, flat belts. The research that forms the basis of
this thesis consists of three elements. Firstly, consideration of current knowledge of
belt based power transmission such as knowledge of the mechanics of the belt based
power transmission process within the context of condition monitoring... [cont'd
Nonlinear Dynamics
This volume covers a diverse collection of topics dealing with some of the fundamental concepts and applications embodied in the study of nonlinear dynamics. Each of the 15 chapters contained in this compendium generally fit into one of five topical areas: physics applications, nonlinear oscillators, electrical and mechanical systems, biological and behavioral applications or random processes. The authors of these chapters have contributed a stimulating cross section of new results, which provide a fertile spectrum of ideas that will inspire both seasoned researches and students
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