Vincenzo Nigrelli

Integrated Computer-Aided Innovation: The PROSIT approach

Abstract The 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 designers 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 moto-scooters 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].

Optimal positioning of the humeral component in the reverse shoulder prosthesis

IntroductionTotal reverse shoulder arthroplasty is becoming more and more the standard therapeutic practice for glenohumeral arthropathy with massive lesions of the rotator cuff. The biomechanical principle of this prosthesis is represented by the reversion of the normal anatomy of the shoulder joint. This non-anatomical prosthesis leads to a medialization of the rotation centre of the glenohumeral joint and also to a distalization of the humeral head. All that causes a deltoid tension increasing so allowing a larger abduction of the arm. Main complications of the reverse shoulder prosthesis are due to the joint instability, the scapular notching and the wear of the polyethylene insert.PurposeThe main goal of the present work is to study the effect of the positioning of the humeral component on the intrinsic stability of the reverse shoulder prosthesis. In particular, through finite element method simulations, the variation of the stability ratio of the shoulder joint has been calculated for both vertical and horizontal dislocating loads depending on the humeral stem version angle. Moreover, in order to estimate the wear of the polyethylene cup, some analyses have been developed to calculate the pressures on the polyethylene insert.Results The obtained results demonstrate the dislocation of a shoulder prosthesis and the wear of the polyethylene insert can be prevented or limited by conveniently varying the version angle of the humeral component.

A comparison of simplex and simulated annealing for optimization of a new rear underrun protective device

In this paper, two optimization approaches to improve the product design process have been analysed. Through the analysis of a case study, concerning the designing of a new High Energy Absorption Rear Underrun Protective Device (HEARUPD), two different optimization approaches (simplex and simulated annealing) have been compared. In the implemented optimization processes, the crash between an economy car and the rear part of a truck has been simulated by dynamic numerical (FEM) analyses. Moreover, authors have proposed the use of a suitable linear function of four variables with the purpose of reducing the multi-objective optimization processes to mono-objective ones. That has been made to simplify the analysis procedures without affecting the quality and the completeness of the optimization processes. The obtained results, as well as showing the high effectiveness of the integrated use of numerical crash analyses and optimization methods, demonstrate that simplex method is more effective than simulated annealing one for optimization problems where the single analysis loop requires much time. Even if the solutions are quite similar in terms of calculated values of the objective function, design and state variables, simplex method needs shorter computational time than simulated annealing to obtain an optimized solution.

Methodical Redesign Of A Semitrailer

Redesign of a product becomes necessary as a consequence of the evolution of the market requirements, of the man creativity, of the influence of the environmental factors, of the technological development etc. The redesign activity, especially in a context of exasperated economic competition, has become a crucial point in order to try to increase the competitiveness, if not even the life, of a product and/or a company. The redesign must allow the resumption of the increasing process of the performances. This aim requires a methodical and structured approach, which can also cause the modification of the standard conception of the product. In this paper the possibility to reduce the mass of a semitrailer is analysed, modifying its structure. Various solutions have been considered, characterized also by new topology and/or materials, and between all of them the one constituted from a structural floor in composite material has been chosen.

A new design approach to the use of composite materials for heavy transport vehicles

In order to keep or to reach a high level of competitiveness and performance of a product, it is necessary to explore all the possible solutions that allow the best compromise between costs and project requirements. By this point of view the study of alternative designs and/or materials to use, is an important aspect that can identify a new concept or way of thinking about a product. This paper presents how to make use of composite materials in the field of heavy vehicles transportation. A new semitrailer in composite material has been designed, using a methodical redesign approach and an optimisation process. The main innovation in this project is, besides the use of the Glass Fibre Reinforced Plastics (GFRPs), also a new topology of the vehicle frame; the designed semitrailer, in fact, has a monocoque structure.

Braking procedure analysis of a pegs-wing ventilated disk brake rotor

Fade test results of a ventilated disk brake rotor with pegs-wing performed by means of an inertia dynamometer, consisting of 14 repeated brake applications from an initial brake speed of 160 km/h down to 0 km/h, with constant deceleration are shown. The first brake application test results are compared to the FEM numerical predictions with MSC Visual Nastran on the entire disk. These conform well to the experimental data, although numerical thermal field is slightly higher than the experimental one. Besides, ventilated disk brake rotor shows great dimensional stability and the ability to dissipate a great amount of thermal flow.

A preliminary method for the numerical prediction of the behavior of air bubbles in the design of Air Cavity Ships

Air-cavity ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel’s hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship’s bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, considering as parameters the critical mass of air, the rising speed and aspect ratio of the bubble. Then it is evaluated the interaction bubble-flat plate in order to obtain a reliable prediction of the behavior of air bubbles under the hull.

Quantitative subsurface defect detection in composite materials using a non-contact ultrasonic system

The results of an experimental study conducted to detect subsurface defects in a thick Gr/PPS composite test sample using a noncontact ultrasonic system are presented. Surface waves are generated by a pulsed laser and detected by an air-coupled capacitance transducer. By controlling the surface wave wavelength through a shadow mask, it is possible to control surface wave penetration depth in the sample. Surface wave peak-to-peak amplitude is related to the near-surface material condition. Results indicate that signal amplitude decreases as the width of the defect increases and an approximately linear relation can be deduced.

Process parameters influence in additive manufacturing

Additive manufacturing is a rapidly expanding technology. It allows the creation of very complex 3D objects by adding layers of material, in spite of the traditional production systems based on the removal of material. The development of additive technology has produced initially a generation of additive manufacturing techniques restricted to industrial applications, but their extraordinary degree of innovation has allowed the spreading of household systems. Nowadays, the most common domestic systems produce 3D parts through a fused deposition modeling process. Such systems have low productivity and make, usually, objects with no high accuracy and with unreliable mechanical properties. These side effects can depend on the process parameters. Aim of this work is to study the influence of some typical parameters of the additive manufacturing process on the prototypes characteristics. In particular, it has been studied the influence of the layer thickness on the shape and dimensional accuracy. Cylindrical specimens have been created with a 3D printer, the Da Vinci 1.0A by XYZprinting, using ABS filaments. Dimensional and shape inspection of the printed components has been performed following a typical reverse engineering approach. In particular, the point clouds of the surfaces of the different specimens have been acquired through a 3D laser scanner. After, the acquired point clouds have been post-processed, converted into 3D models and analysed to detect any shape or dimensional difference from the initial CAD models. The obtained results may constitute a useful guideline to choose the best set of the process parameters to obtain printed components of good quality in a reasonable time and minimizing the waste of material.

Virtual simulation of an osseointegrated trans-humeral prosthesis: A falling scenario

INTRODUCTION Traditional prosthetic solutions expose the amputee to numerous problems that limit his ability to safely perform the normal activities of daily life. In order to eliminate the problems related to the use of the traditional prosthesis with socket, a new technique was developed for fixing the prosthesis to the amputees based on the principle of osseointegration. The aim of this paper is to study and analyze the stress distribution on the interface between a trans-humeral osseointegrated prosthetic implant and the residual bone, identifying the most stressed areas and thus foreseeing possible failure phenomena of the entire prosthetic system and, after, to compare the stress distribution on three different prosthetic designs that differ from each other for some geometric characteristics. MATERIALS AND METHODS A healthy individual mimics two fall scenarios of which the trans-humeral amputees can most likely be victims: Static fall and Dynamic fall. A force platform (P-6000, BTS Bioengineering) is required for load data acquisition. The CAD model of the trans-humeral osseointegrated implant was created following the guidelines of the OPRA implant. The bone model was created starting from the CAT scan of a left humerus. The FEM simulation was conducted throught a linear analysis. RESULTS Both during static fall and dynamic fall, similar trends have been observed for the reaction force Fz, the torque moment Tz, the bending moments Mx and My. From the analysis of the von Mises stress distribution it was found that the stress distribution is more homogeneous in the case where the thread of the fixture is made by a triangular profile with height of the thread equal to 0.5 mm. However, it can be seen that, when passing from a thread with height of 0.5 mm to a 1 mm, there is a slight decrease in the stress on the whole contact zone between the fixture and the humerus. The same improvement can also be seen in the case of trapezoidal threading. CONCLUSION By modifying the height and/or by varying the thread profile, are obtained slightly better results with respect to the case with a 0.5 mm height triangular thread.