Handy Tools in MSC Apex to Speed-Up FE Modelling

Published 2015-01-08
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The Abderdeen group has found that on average, analysts across industries spend up to 80% of their time on CAD clean-up for analysis purposes. MSC Apex Modeller has proven without a doubt that it brings a new way of editing (and creating) geometry which rapidly improves the created meshes and within a much shorter time frame than analysts are used to.

In a Transnet benchmark it has shown how a job that used to take a week, could be completed in less than half an hour.

Here is the list of tools that makes it possible:
Auto Geometry checking and repair: We would all love to believe that we live and work in a perfect world where at least what you receive from your 3D CAD package is perfect as intended but that is seldom the case. MSC Apex runs an automated geometry repair operation during the translation and importing of geometry which solves problems the analyst normally would have no solution for, other than to try and re-export it into another format from his CAD package or to try and modify the original CAD model until it exports correctly. The auto repair tool is also exposed to the user to get detailed feedback to what and where the problem is as well as to use different clean-up tolerances to repair problems beyond the scope of the default settings.

Mid-surfacing: The ability to auto render the model according to the task you are busy with is very handy. It does not only save you a few clicks every time you need it but gives you the impression that the software is never in your way. With different options to choose from, the constant thickness method is the quickest to create mid-surfaces for all the bodies in the model in one click but for complex parts you could pick a face and it would auto offset it or let you choose a different location for the created surface. The user has literally the best of both worlds, the ability to mid surface everything at once or to manipulate the end result of individual faces where he wants to deviate from the norm.

Stitching: The biggest frustration for an analyst is gaps and overlaps in a model that might be fine for manufacturing but not for performing a structural analysis. In MSC Apex free and connected edges are clearly rendered which informs the user where a resulting mesh will be congruent (equivalenced/connected) and where not. The stitching tool takes care of these in one easy step and does not only sew plates with edges in the same plane but will even shift edges into the same plane (even double curved surfaces) to eliminate small offsets.

Auto Extend: A tool similar to stitching, but specifically developed for surfaces that need to extend until they intersect, is the auto extend tool. With the auto extend tool the mid-surfaces can be extended to connect with other nearby surfaces. They can be extended beyond the half thickness distance to cover larger distances to again cater for modelling errors such as gaps. It even cleans small misalignments where a T-section can cause a small overhang or undercut, all of which the user has control over as to what size overhangs or undercuts should be cleaned and which not. The user can pick all surfaces in the model in one step or again pursue the task in smaller steps and progressively add surfaces to extend to others.

Vertex and Edge drag: This must be singlehandedly the one tool that is responsible for the smile on your face when working with Apex. The ability to grab and snap a vertex or an edge into a new position to clean-up gaps and overlaps is what caused me to play right through the night when I first got my Apex license (see which mouse I found for Apex). Many people has made subsequent comments like “This feels more like playing than work!” purely since it simplifies the process of an otherwise lengthy process of edit and re-create tasks tremendously.

Small feature finder: Small or short geometric entities when meshed enforces short element edges which in turn can cause poorly shaped and distorted elements. With the small feature finder, you can quickly identify and rectify problems that will otherwise cause you a headache downstream when your try to get the geometry meshed or try to convince the solver that it should at least try to produce results. Being able to identify the root cause of such defects, goes a long way to prevent unsuccessful runs and the headaches that go with it.

De-featuring and suppressing features: More often than not the analysis gets more than he needs from the designer and is left with thousands of features he either doesn’t need or need to get rid of to improve his chances of getting a reasonable mesh size and quality. With direct options like pick and its gone or select by type and remove all (or within a size range), the analyst can literally remove thousands of features in seconds while staying in control over what is removed and what is not. Another useful tool is the suppressing feature which does not remove the feature but tells the mesher to ignore it, meaning that elements can then cross internal boundaries of stitched surfaces or ignore vertexes when placing nodes along an edge of a surface or solid. Using these tools the mesh quality can be greatly improved while keeping the node count down to speedup analyses.

Direct Modelling and Meshing: One of the main building blocks in Apex is the ability to directly interact with the geometry and the mesh simultaneously. More often than not a geometric feature that impacts on mesh size or quality is only found after meshing. Direct modelling provides the analyst the ability to fix the problem on the spot on the geometry level which automatically updates the mesh and mesh quality plot. This provides the user instant feedback with regards to the impact of the modification on the mesh quality without the need to redo a few steps before knowing whether or not the mesh was in fact improved.

Improving mesh quality: Feature based meshing makes it possible to setup rules for how certain features should be meshed and again rules can be set up based on feature type and size ranges. These rules are then applied automatically but again the user can control whether or not and where they should be ignored or overruled by specifying a mesh seed or manually moving nodes or simply meshing parts with the rules switched off.

With this arsenal of tools, any analyst can literally shave days of his schedule and produce meshed models ready for analysis within hours, not weeks. A tiresome job now suddenly becomes fun!

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