ComputerAided_Design_Engineering_amp_Manufactur.pdf

of a beam is considered for FEA. The geometric information pertaining to the aircraft wing profile is then
transferred from the Concept Modeller system to the I-DEAS package.
The meshing pattern for the FEM model in I-DEAS is automatically generated by using a set of
predefined commands. In the working version of the prototype, we have only considered uniform crosssection
wings, and the entire wing is modeled as a beam. The appropriate design loads and restraints are
also automatically specified at the appropriate locations on the FEM model, which is then sent over to
ANSYS for Analysis. The FEA results are passed on to an intelligent interface unit that extracts the necessary
information that is further used by Proexp, an expert module (built in CLIPS expert system shell), for
verification of initial design analysis results. Depending on the analysis results, Proexp would suggest the
appropriate design modifications (sample suggestion is shown in Figure 1.6). The suggested modifications
are passed over to an intelligent interface unit that automatically records the changes in the FEM model
(either in I-DEAS or ANSYS) or conveys the results of a satisfactory design to the user. After a satisfactory
design of the initial wing configuration has been achieved, the wingbox (the major internal load-bearing
structural component of the wing) is designed. The major structural components of the wingbox are spars,
ribs, and associated components such as rib and spar webs. The structural configuration forms a truss
structure and is covered by the upper and lower covers, which form the external surfaces of the wing. To
start the wingbox design, a separate design program is invoked and a finite element model of the wingbox
is automatically generated. The wingbox design program automatically determines the element types (e.g.,
3-D shell elements, SHELL6313
for upper and lower covers and for spar and rib webs, the element BEAM4
for stiffeners, and spar and rib caps, etc.). As the entire wing model is intended to be loaded with a pressure
distribution along its lower surface to simulate actual flight conditions, appropriate design conditions are
also specified in the wingbox finite element model. The finite element model is then transferred to ANSYS
where the analysis is performed, and the ANSYS output results are interrogated by Wboxexp, another
expert module (CLIPS based) for verification of the stated design conditions. Any changes suggested by
the Wboxexp are sent to the wingbox design program, and this loop continues until a satisfactory design
is achieved. Upon achieving a satisfactory design the system prompts the user, and control is once again
passed to the Concept Modeller system to develop the final product model (Figure 1.7) on the basis of
the design parameters previously obtained. The final product model information can also be used for
other activities such as numerical code (NC) code generation, bill of material (BOM) report and process
planning, and scheduling schemes.
1.4 Application Domain: Process Planning
‘‘Process planning’’ is defined as that task associated with the manufacturing phase of the product
realization process that establishes the manufacturing processes. This includes process parameters,
which are to be used for transforming a product from its initial configuration (i.e., shape and form
of the raw stock) to a predetermined configuration (i.e., shape and form of the finished workpiece)
based on the functional intent of the design as represented in an engineering drawing or solid model. 14
The process plan is also alternatively referred to as an “operation sheet” or a “route sheet” and provides
instructions for sequencing of the manufacturing processes, selection of process parameters, machine
tools, cutting tools, etc.
Automatic (i.e., generative) process planning involves (a) an explicit representation scheme of the
workpiece model, different machining operations, and their effects on the workpiece, (b) reasoning
about the effects of sequences of machining operations and the interaction of operations that may
take place concurrently, and (c) the development of an algorithmic approach for an optimal process
plan that can be adopted with reasonable efficiency for manufacturing the component. The generative
process planning approach for generating process plans is largely dependent on the understanding of
the manufacturing processes and their application in formulating the process knowledge bases of the
planning system. In this research work, 15,16 we have demonstrated the application of ICAD techniques
for automatic generation of process plans by using the blackboard architecture concept10
of problem
© 2001 by CRC Press LLC