In a free state, flexible parts may have different shapes compared to their computer-aided design (CAD) model. Such parts may likewise undergo large deformations depending on their space orientation. These conditions severely restrict the feasibility of inspecting flexible parts without restricting the deformations of the part and therefore require dedicated and expensive tools such as a conformation jig or a fixture to maintain the integrity of the part. To address these challenges, this paper propo.ies a new in.spection method, the iterative displacement inspection (¡DI) algorithm, that evaluates profile variations without the need for specialized fi.xtures. This study e.xamines 32 models of simulated manufactured parts to show that the IDI algorithm can iteratively deform the meshed CAD model until it resembles the scanned manufactured part, which enables their comparison. The method deforms the mesh in such a manner so as to ensure its smoothness. This way, neither surface defects nor the measurement noise of the scanned parts are concealed during the matching process. As a result, the case studies illustrate that the method's error essentially only represents the scanned part's measurement noise. The inspection results, therefore, .solely reflect the effect of variations from the manufacturing process itself and not the deformation of the part.
Please cite this article as: Abenhaim GN, Desrochers A, Tahan AS, Bigeon J. A virtual fixture using a FE-based transformation model embedded into a constrained optimization for the dimensional inspection of nonrigid parts. Computer-Aided Design (2015), http://dx.doi.org/10. 1016/j.cad.2014.12.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. conditions setting methods available in FE software. In addition to these limits, these approaches do not take into account the forces used to restrain the part during the inspection, as commonly mandated for aerospace panels.To address these shortcomings, this paper presents a virtual fixture method that predicts the fixed shape of the part without the aforementioned drawbacks of current approaches. This is achieved by embedding information two case studies on physical parts are performed using the proposed virtual fixture method to evaluate the profile and assembly force specifications of each part.
The improvement of the simulation process requires an integration of the design and analysis models. There are two essential tasks in the design analysis process: (i) Computer Aided Design (CAD) which provides the geometric description of the model and (ii) the Finite Element Method (FEM) used for mechanical behaviour simulations. The interoperability between these two tasks reduces costs and improves product quality through the acceleration of design analysis loops. Our activity fits into this research orientation by providing a method to link the FE analysis and the CAD model. This is done by reconstructing the CAD model from the FE analysis results (deformed mesh). This paper proposes a method to update the CAD geometry from the deformed mesh. This approach allows for rebuilding the CAD model after analysis by extracting geometric information from the deformed mesh. An illustration of the developed method is discussed at the end of this paper.
Aerospace panels are commonly restrained on complex inspection fixture jigs during the measurement process. Forces used to restrain the parts are also monitored as mandated by thier functional requirements. Given the difficulties in measuring these types of parts, this paper reviews the available fixtureless inspection methods with a focus on the challenges of their implementation, and their aptitude to be used to estimate the profile and the necessary restraining forces of an aerospace panel. To perform this investigation, finite element analysis is used to predict the constrained shape of four (4) simulated free-state aerospace panels, with two different type of boundary conditions, in five scenarios. From those analyses, the importance and limits of current finite element boundary setting methods embedded in fixtureless inspection methods for nonrigid parts are highlighted.
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