Non-Controllable Risks

From the point of view of a user or designer, non-controllable risks connected with CAD systems application into a construction process are caused by the CAD system itself, that is, the CAD system environment and its programming. This area cannot be modified, since it is set by default by the CAD system manufacturer. 

Modem CAD systems make use of various mathematical cores to calculate parametric functions of curves. ACIS and Parasolid mathematical cores are among the most frequently used. These CAD systems bases have been through a long-term development gradually enhancing their features (issues with drawing, e.g. curved areas and a variety of mathematically common areas, calculating intersections, 3-D bent curves, etc.). 

Regarding the final inaccnracy of geometry calculation, as well as the FEM analysis ontcomes, potential risk sonrces are represented by, for example, the definition of the n calcnlation within mathematical operations. On some occasions, the discrepancies of the calcnlation resnlts are not negligible. 

The principle of calcnlating several continuous mathematical functions in com-pnting programs is based on data discretization followed by interpolation of function valnes. The continnons fnnction interval division into the finite number of points and the final fnnction itself are further interpreted by the interpolar integration of the interval points fnnction values. The type of interpolation may often have an effect on the optimization analysis outcome (e.g. FEM) or on CAD system geometry interpretation. In transformation, the different mathematical interpretations of the basic cnrves definition may cause geometry deformations or data loss, for example, defining a circle cnrve. 

All these potential risk sources can possibly be reduced only partially by means of CAD technique setting options as defined by the software development companies. Feedback from CAD technique users and software development centres is of significant importance. 

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