Examples

Each figure below is drawn by the same renderer, from the same data, as the figures in a report exported from Visual Dynamics. Drag to rotate, and scroll to zoom.

The first three come from one modal survey of a rectangular plate: the measured time data, the frequency response functions computed from it, and the finite element model the test was compared with. The rest are finite element models built from scratch in Visual Dynamics: the BARC from planes and again from bricks, and the Frame-Wing from solids.

The measured time data

Time data from the survey, one channel per station, set one behind another on a three-dimensional stage. Six of the 220 accelerometer records are shown; drag to turn the stage.

The measured frequency response functions

The frequency response functions computed from those records, ten of the 22. Drawn on one flat axis they would overlap into a band; spread out in depth, each channel's resonances can be read on their own.

Finite element modes

The first six elastic modes of the plate, from a model of 169 nodes and 144 elements. Choose a mode from the list to animate it, and drag to turn it. The six rigid-body modes of the free-free solution are left out, since they only show the whole plate moving.

A model from planes: the BARC

The BARC (Box Assembly with Removable Component) is a small bolted aluminum structure that the structural dynamics community shares as a common test article. Its solid model, test data and finite element models are shared on the SEM Dynamic Substructuring Focus Group wiki. Here it is built the way a simple plate model is built in Visual Dynamics: each part as the planes it is made of, each given its material and thickness, and each bolt a rigid tie from the elements it clamps to the part below. Four bolts join each channel to the box and four join the beam to each channel. Then Solve Modes.

The first eight elastic modes of the model, drawn from a quarter-inch mesh of 1,445 nodes. Choose a mode from the list to animate it, and drag to turn it. The model was checked against the finite element models shared on the wiki. The whole workflow, from the planes to these modes, is in the documentation, and the project itself, solved, can be downloaded and opened in the app.

The BARC again, from bricks

The same structure built from solid bricks, the higher-fidelity model. Each part is made from as few solids as it can be (the box a block less its inside and its slot, each channel a block less the inside of its C, the beam a block) and meshed into bricks with Mesh Solids, each part on its own nodes where it touches the next. Each bolt is a joint made with Mate Surfaces, which ties the nodes the bolt clamps to the face of the part beneath them: under the washer at each foot, and at the four corners of the brick it passes through at the beam. Each bolt's mass is a point mass at its head. The removable component, the two channels and the beam, is also a model of its own.

The first eight elastic modes of the assembly, drawn from a quarter-inch mesh of 3,170 nodes. Choose a mode from the list to animate it, and drag to turn it. Meshed at an eighth of an inch, the model's first ten elastic modes are within 3.4 percent of the model that was checked against the modes measured on the BARC and shared on the wiki, with the mode shapes in the same order. How it is built is in the documentation, and both models, solved, can be downloaded and opened in the app.

A model from solids: the Frame-Wing

The Frame-Wing is a small aluminum ladder frame and two rectangular wings that screw across it, shared by the structural dynamics community as a test article for substructuring. Its solid models, finite element models and test data are shared on the SEM Dynamic Substructuring Focus Group wiki. A half-inch bar spanning a hundred-millimeter window is neither a beam nor a plate, so this model is built from solids. The frame is a plate with its four windows (their rounded corners leave the fillets) and its 41 holes subtracted, the threaded inserts are cylinders in the tops of the holes, and each wing is a plate less its eighteen holes. Pattern copies the holes in rows, and Mesh Solids meshes the parts into bricks. A wing is bolted on with Mate Surfaces: the wing and the washers under it are meshed apart from the frame, and the washers' undersides are tied to the frame and the screws beneath them, though the two meshes do not match. Then Solve Modes.

The first eight elastic modes of the frame with its thick wing, drawn as the outer surface of the brick mesh. Choose a mode from the list to animate it, and drag to turn it. The frame alone is within a few percent of the frames that were measured. The brick element was checked against the finite element model shared on the wiki: solved here on the same mesh, its first ten elastic modes agree with MSC Nastran's to within 0.1 percent. The whole workflow, from the solids to these modes, is in the documentation, and the projects themselves, solved, can be downloaded and opened in the app.

Three shapes that are not extrusions

Mesh Solids meshes an extrusion into bricks with rings about its holes, and that is the mesh to prefer where the part allows it. Three shapes that do not allow it, a shaft with an oil hole drilled through at 30 degrees, a wye fitting and a V-block with two banks of angled bores, are built from the recipe alone by visualdynamics.demo.shapes and meshed both ways, into bricks on a grid fitted to the shape and into ten-node tetrahedra, with the element quality and the volume against the recipe's recorded for each.

The V-block in 87,798 ten-node tetrahedra at 0.2 in, within 0.02 percent of the recipe's volume. The page on the three shapes has the pictures and the table of numbers for both meshers, as they stand today; it is updated as the meshers change.

About these figures

The figures are drawn by the report renderer, not by code written for this website, so what you turn here is exactly what a report contains.

They do carry less data than a report would: a handful of channels instead of all of them, so that the page loads quickly and turns smoothly. These figures are also limited to 20,000 points each, where a report figure holds up to two million. Any figure that has been thinned, on this page or in a report, says so in a note under its caption, and the thinning keeps every peak. Download the application to see the full data.