1,721,003 research outputs found
Ottimizzazione del modello geometrico di un Mock-up di paletta per turbina aeronautica
Full text linkScopo di questo lavoro è l’ottimizzazione del modello geometrico di un mock-up per paletta di turbina aeronautica su cui è prevista l’esecuzione di una serie di saldature di prova da realizzare con la tecnologia CDW (Capacity Discharge Welding). Una corretta scelta della geometria del provino è infatti fondamentale per l’attendibilità dei risultati delle prove meccaniche e per validare il processo di saldatura anche su componenti aeronautici. Per la modellazione geometrica è stato eseguito il Reverse Engineering di un prototipo di partenza e successivamente è stato utilizzato un software CAD agendo sulle geometrie 3D. Le simulazioni numeriche FEM sul modello hanno consentito di validare la geometria del mock-up, mediante l’analisi del livello e della distribuzione delle tensioni nelle sezioni più critiche
Automatic error evaluation of axial-symmetric surfaces
No full textThis paper aims at developing a suitable analysis of the point cloud, coming from the optic
scanning of a real object, allowing to evaluate automatically the errors without using a nominal
CAD model or a GPS specification. Really, this possibility is strictly depending on the capability
to recognize in a scanned tessellated model some intrinsic nominal references. This paper is
particularly devoted to the automatic error evaluation of axial – symmetric surfaces; for this kind
of surfaces two types of intrinsic references can be recognized. An original classification of the
error categories is proposed and the related methods for the evaluation of these errors are
presented. The methodology is applied to some real cases and the related results are critically
discussed
Fuzzy sets for geometric shape recognition in triangular meshes
No full textShape recognition of geometric models described by triangular meshes is affected by some problems which made it difficult
to be performed without errors. Some factors, such as the location errors of points due to acquisition process and the coarse
representation of continuous surfaces due to triangular approximation, introduce uncertainty in the recognition process of
the geometric shape. This paper introduces some original fuzzy sets suited to recognize geometric form. The membership
functions of the fuzzy sets are dynamically defined so that they can be adapted to take into account those properties of the
geometric model that affect the uncertainty of the recognition process. The proposed approach is intrinsically very robust
and achieves good results also in recognising form features in geometric models affected by point location errors
Geometric modelling of metallic foams
Full text linkPurpose:
The aim of this work is the development of a procedure able to model the highly irregular
cellular structure of metallic foams on the basis of information obtained by X-ray tomographic
analysis.
Method:
The geometric modelling is based on the feature “pore” characterized by an ellipsoidal shape.
The data for the geometric parameters of the instances are obtained with a methodology
which is driven by the pore volume distribution curve. This curve shows how much the cells,
whose diameter belongs to a given dimensional range, contribute to the reduction of the total
volume.
Result.
The presented methodology has been implemented into a CAD tool consisting of a Matlab
routine identifying the instances of the feature “pore” and a CATIA’s macro modelling the
closed cells foam.
Discussion & Conclusion:
The CAD model developed for two types of closed cells foams approximates by considerable
accuracy both the density and the volume distribution of the real foams
Data exchange problems in the geometrical optimization of turbine-blade mock-up
No full textThe aim of this work is to study IGES data exchange problems found during the transfer from CAD system into FEM software for the “mock-up” that is representative of an aeronautical compressor blade transverse section. Despite the neutral format purpose is to transfer information between different CAD/CAM/CAE systems, frequently several data exchange problems are observed.
In this paper the problems coming out from the data transfer process have been analyzed and some solutions are proposed
Fuzzy sets for geometric shape recognition in triangular meshes
Full text linkShape recognition of geometric models described
by triangular meshes is aected by some problems
which made it dicult to be performed without er-
rors. Some factors, such as the location errors of
points due to acquisition process and the coarse rep-
resentation of continuous surfaces due to triangular
approximation, introduce uncertainty in the recogni-
tion process of the geometric shape. This paper in-
troduces some original fuzzy sets suited to recognize
geometric form. The membership functions of the
fuzzy sets are dynamically dened so that they can
be adapted to take into account those properties of
the geometric model that aect the uncertainty of
the recognition process. The proposed approach is
intrinsically very robust and achieves good results
also in recognising form features in geometric mod-
els aected by point location errors
Automatic evaluation of form errors
No full textAutomating completely the process of geometric
errors verification has some problems. The most criti-cal ones are the preventive shape recognition and the
lack of an agreement about criteria to be used to
associate ideal features to the extracted points from
the real surface.
In this paper an approach for automatic metrologi-cal inspection of manufactured parts is proposed.
Starting from a tessellated model, coming from a
scanned workpiece, the methodology carries out
automatically the partition of the acquired surface by
a shape recognition approach. Then, the ideal featu-res are associated to the corresponding non-ideal fea-tures, based on some criteria that permit to define the
minimum zone solution. The proposed methodology
stands out for the number and the types of the auto-matically recognized features. Finally, the form
errors, related to all the recognized features, are eva-luated.
In this paper the procedure has been used to eva-luate some specific form error typologies for several
simulated case-studies and real objects. The results
deriving from this experimentation are here critically
discussed
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