112,005 research outputs found
Shape optimization of high-energy absorbers
No full textIn this paper, a new approach to simulate and to optimize the performances of a crash-box, in terms of energy absorption or acceleration peak, is presented. As soon as the maximum size of the crash-box (longitudinal and transversal dimensions) has been fixed, the new approach allows optimizing the shape of the transversal section and the thickness of the structure. Thanks to the proposed procedure, engineers can easily identify the best crash-box depending on the particular working conditions. The new method has been tested with different cases study by considering different objective functions. The obtained results show the procedure works well and also demonstrate that the optimal number of edges of the transversal section and the optimal crash-box thickness strongly depend on its main dimensions and on the considered objective function
Behaviour of a speargun with a novel muzzle
Get PDFThe paper presents the results of a numerical and experimental investigation performed on a barrel of a speargun equipped with two kinds of muzzle. In particular, a standard muzzle for speargun (having an elastic propulsion) has been compared with an innovative one called ‘roller’. This new muzzle is equipped with two rollers and special bands. The rubber bands, fixed at the lower side of the barrel, run through the rollers and are engaged in suitable seats of the shaft. These bands are, therefore, longer than the traditional ones and, consequently, with equal force applied by the diver, the roller speargun has a longer range. Thanks to the particular geometry of the new muzzle, one of the front constraints of the elastic bands is moved to the lower part of the barrel or the handle.As a consequence, the scheme of the loads applied on the speargun remarkably changes passing from a standard muzzle to a roller one. All that has a great influence on the level of deformation of the barrel and, consequently, on the accuracy of the shot. Because of the low velocity of the spear (if compared with the firearms), in fact, the accuracy of the shoot if strongly influenced by the barrel bending due to the forces applied by means of the elastic bands. In this paper it is experimentally evaluated the bending of the barrel equipped both with the innovative muzzle and with the traditional one in order to compare their performances. The experimental analysis of the barrel was performed by electrical strain gauges suitably located at the section with the highest values of the strains. In order to find the barrel section with the highest strain values where to locate the strain gauges, a preliminary numerical FEM analysis has been performed. The loads and constraints scheme has been evaluated both for the standard and the new muzzle. In particular, the forces due to the elastic bands, their application points and directions have been experimentally obtained. To speed up the process of numerical simulation, without invalidating the results reliability, simplified FEM models have been used. In particular, a very accurate model of the barrel has been shaped, whereas the models of the muzzles and the handle have been simplified. The forces due to the elastic bands, experimentally obtained, have been applied on the FEM models. The maps of the maximum and minimum principal strains have allowed to find the area with the highest strain values, placed in rear part of the barrel (near the handle). The strain values experimentally measured on the speargun have been very similar to the ones calculated by means of the numerical simulations. That demonstrates the developed FEM models are very reliable and can ben used to predict the performances of the speragun under different loads conditions. The speargun with the new roller muzzle shows very lower strain values if compared with the ones measured in the standard one. Nevertheless, considering the two spearguns have different elastic bands setup, it has been thought the comparison of their performances should be made hypothesizing the same maximum force applied during the speargun charge. This condition, moreover, could be really obtained by changing the kind of the elastic bands in the speargun with the roller muzzle. For this reason, during the results analysis phase, the strain values measured on the roller speargun have been ‘normalized’ by increasing them of a value equal to the ratio of the maximum forces due to the rubber bands. The data post processing has allowed to evaluate the forces and the bending moments on the barrels with the standard muzzle and the roller one. Results show the barrel with the innovative muzzle has, also considering equal forces applied by the diver, a lower bending than the barrel with a traditional muzzle. To evaluate the maximum deflection of both the spearguns, a new numerical simulation has been set up. In particular, in this FEM analysis, the roller speargung has been loaded with a maximum force comparable with the standard one. The obtained results show that the standard speargun has a higher value of the maximum deflection respect to the roller one. Since higher deflection values of the barrel make worse the accuracy of the shot, these results demonstrate the novel speargun can be more precise than the traditional one
Improvements of Fatigue Life in Drilling Structures by Both Cold Expansion and Indentation
No full textB-Scan image analysis for position and shape defect definition in plates
No full textDefinition of size, shape and location of defects into a mechanical component is of extreme importance in the manufacturing industry in general and particularly in high-tech applications, and in applications that can become dangerous due to the structural failure of mechanical components. In this paper, a laser-UT system has been used to define position and shape of internal defects in aluminum plates. An infrared pulsed laser is used to generate ultrasonic waves in a point of the plate and a CW laser interferometer is used as receiver to acquire the out-of-plane displacements due to the ultrasonic waves in another point of the plate. The method consists of acquiring a B-Scan map on which some information on the defects in the mechanical component are visible. Storing the characteristics of the wave reflected by the defect and acquired in the B-Scan, the detection and the drawing of the defect is possible. The acquisition of the times of arrival of the waves reflected by the defect from the B-scan allows defining large parts of the shape of the defect. The times of arrival are acquired from the B-scan by analyzing the colour variations due to the wave reflected by the defect. The experiments operated from both sides of the plate allow drawing the defect in a virtual image of the plate section, from which the definition of defect shape and position can be determined
Finite-element simulation of residual stress induced by split-sleeve cold-expansion process of holes
Get PDFA three-dimensional finite-element simulation was conducted for a split-sleeve cold-expansion process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3DTM, a Lagrangian implicit code designed for metal forming processes, was used to model the cold-expansion process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved
Integrated Computer-Aided Innovation: The PROSIT approach
Get PDFThe paper presents a methodology aimed at the improvement of the product development cycle through
the integration of Computer-Aided Innovation (CAI) with Optimization and PLM systems. The
interoperability of these tools is obtained through the adoption of Optimization systems as a bridging
element between CAI and PLM systems. This methodology was developed within the PROSIT project
(http://www.kaemart.it/prosit).
The paper describes the main issues related to the integration of these complementary instruments
and the solutions proposed by the authors. More specifically, the main idea of the PROSIT project to link
CAI and Optimization systems is the adoption of the latter tools not just to generate optimized solutions,
but also as a design analysis tool, capable to outline critical aspects of a mechanical component in terms
of conflicting design requirements or parameters. CAI systems are then applied to overcome the
contradictory requirements. The second step, i.e. the integration between Optimization and PLM
systems, has been obtained through the development of Knowledge-Based (KB) tools to support
designer’s activities. More in details, they provide means to analyze and extrapolate useful geometrical
information from the results provided by the optimizer, as well as semi-automatic modelling features for
some specific geometries. A detailed example related to the design of a plastic wheel for light motoscooters
clarifies the whole procedure. The paper integrates, extends and updates topics presented in
Cugini et al., Barbieri et al. and Cascini et al. [U. Cugini, G. Cascini, M. Ugolotti, Enhancing interoperability
in the design process—the PROSIT approach, in: Proceedings of the 2nd IFIP Working Conference on
Computer-Aided Innovation, Brighton (MI), USA, October 8–9, 2007, published on Trends in Computer-
Aided Innovation, Springer, ISBN 978-0-387-75455-0, pp. 189–200; L. Barbieri, F. Bruno, M.
Muzzupappa, U. Cugini, Design automation tools as a support for knowledge management in topology
optimization, in: Proceedings of the ASME 2008 International Design Engineering Technical Conferences
& Computers and Information in Engineering Conference (IDETC/CIE 2008), Brooklyn, New York, USA,
August 3–6, 2008; L. Barbieri, F. Bruno, M. Muzzupappa, U. Cugini, Guidelines for an efficient integration
of topological optimization tools in the product development process, in: Third International Conference
on Design Computing and Cognition, Atlanta, USA, June 23–25, 2008; G. Cascini, P. Rissone, F. Rotini,
From design optimization systems to geometrical contradictions, in: Proceedings of the 7th ETRIA TRIZ
Future Conference, Frankfurt, Germany, November 6–8, 2007]
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