Sheet metal part models

Advanced sheet metal part models are represented as soHd. Interference between the sheet metal and the covered parts is checked for automatically by use of covered and covering part volumes and assembly model information. When moving parts are covered, interference is checked for critical positions. 

Three fundamental ways for the construction of sheet metal part models are ... 

Construction of typical sheet metal part model entities in a model space is explained in Figure 8-11. Contours Ci and C2, vectors Vy and V2, and line Li are created in their final place then applied for the creation of walls for the sheet metal part. Walls starting from bend lines BL2 and BL3 are created by extrusion of lines BL2 and Lj, along vectors V] and V2, respectively. 

Sheet metals and the manufacturing processes to form them into sheet metal parts are simple and cheap. Application of sheet metal parts is still very popular. Parts produced by bending and punching processes require special description of the bends and flat patterns in the model. 

Tolerance specifications are applied on wireframe, surface, and solid part model representations. They are also placed in sheet metal part and assembly models. The following modeling functions assist engineers in the systematic creation and placing of correct tolerances in close connection with an existing design and its changes. 

Contours for walls can be associatively extracted from existing solid parts. This allows for sheet metal part design in the context of the surrounding or enclosed assembly. Dimensional associativities between sheet metal and other solid part models allow easy and correct dimension-driven design changes without tedious manual re-dimensioning. 

The unfolded state of a part, or in other words the flat pattern, is fully associative with the part model. This is necessary because the part is cut together with punched features from a sheet metal table. Flattened parts are arranged on a sheet metal... 

The bonded cleats, like the composite parts, are dimensioned according to finite element model (FEM) based on elementary material data sheets checked by elementary characterization tests. The dimensioning of the bonded joint itself is based on previous analogous cases, proprietary Excel calculation sheets and feedback from trials and errors experimentation. Metal parts are dimensioned according to the Von Mises criterion and the HiU criterion is used for composite parts. For manufacturing reasons, a two-part epoxy paste at ambient temperature has been selected for the mechanical and thermal environmental issues on one hand and ease of implementation on the other hand. 

Porphyrin and nonporphyrin metals associated with asphaltenes have not been easy to identify in terms of molecular structure. This is partly due to the fact that the characteristics (i.e., spectra) of all possible model nonporphyrin compounds have not been studied. Nonporphyrin metals are probably small polar molecules that precipitate as asphaltenes (Filby, 1975) or complex at defect sites in large aromatic sheet structures of the type shown in Fig. 10. Porphyrins with increased aromaticity and systems with low aromaticity due to discontinued ring conjugation are both characterized as nonporphyrin species. These compounds do not have the characteristic visible absorption spectra and hence are not readily identified. It is also possible that some of the porphyrin in the residuum may not be extracted and identified due to intermolecular association with the asphaltene-generating molecules. 

Separated metallic or semiconducting islands on top of insulator layers have been widely studied since 1960 s, and the subject received attention even nowadays [9]. The authors agree with the model where the lateral conductivity is determined by a tunneling mechanism between islands (or nanocrystals), while the concentration of carriers taking part in the conduction is thermally activated. The activation energy is reciprocal function of the NC diameter. So, the conductivity (and correspondingly, resistivity) is the exponential function of the NC size. However, in our case, a power function was obtained for the sheet resistance and NC size. The origin of this relation is not clear yet. 

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