See the particles, fix and load a part

Fix a face, load a face

Hold a part where it is clamped and push where the force goes, the way you would set up a bending test. A fixed face holds the material just under it still, so the rest of the part bends from there; a load spreads its force over the face by area. Both follow the face in your model: edit the part in Model and they come along.

The part becomes a free body of its own material, so choose the material in its properties: steel, aluminium, ABS and the other solids in the list.

1. Model a part, for example a long rectangle extruded into a bar, and press Simulate.
2. Press Fix on the bottom bar and click the end face of the bar in the view. It is tinted and hatched; the part is now a free body.
3. Press Load and click the other end face. A 100 N arrow appears on it.
4. In the part's properties, under Loads, set the force, choose Along a direction and enter 0, 0, -1 to push down, and pick how it is applied: At once, Ramped over a time, or At once at a time.
5. Press Go.

Read the result

A scene with a load runs until the part has come to rest and stops there, so the shape you see is the settled one. Results colours the part by how far each point moved, or by von Mises stress, with a legend. A steel bar bends a fraction of a millimetre, so the Deformation buttons draw the bend 10, 100 or 1000 times larger; the numbers stay the computed ones.

The Results panel reads how far each loaded face moved, next to the beam-theory answer in the demo, each support's reaction, the balance between the reactions and the loads with the part's weight, and the largest stress. The ⓘ button explains how each number is computed.

1. Open Demo files, then Cantilever: steel bar under a tip load under Simulation. The first time in a session, press I understand, open Simulation.
2. Press Go. The run stops by itself when the bar has settled, after a few milliseconds of simulated time.
3. In Results, compare Tip with theory, switch between Displacement and von Mises stress, and try Particles at the top of the view to see the particles coloured the same way.

How accurate it is

Simulate computes the part as particles on a grid, and a part only a few grid cells thick comes out softer than it really is. The demo's 20 mm bar is 8 cells thick and bends about 29 % more than beam theory; a 10 mm steel bar in our tests bends about 68 % too far at 4 cells, 25 % at 8, 15 % at 12 and 10 % at 16, closing in on theory as the size gets finer, at a higher computing cost. Results warns when a part is fewer than 4 cells thick. The supports' reactions balance the loads at every size.

Results tells you this for your own part: a chip under its heading reads Rough, Indicative or Closer with the expected error for the number of cells across the thinnest loaded part, estimated from those checks, and a line reminds you that these are early-preview numbers, for comparison only and not for design decisions. The ⓘ button shows where the estimate comes from. Other shapes and loads may differ.

Fixed faces and loads run on the CPU engine for now: a scene that has them runs there even when the GPU is chosen, and says so. A face must be flat. The demo settles in about 40 seconds on a fast desktop.

See exactly what the engine computed

The water and sand you normally see are surfaces drawn around the particles. The Particles view drops that reconstruction and shows the particles themselves, each as a sphere as wide as the particle spacing, so a gap in the material is a gap on screen and a clump is a clump. Both keeps the surface and shows the particles underneath it.

Colour by Speed shows where the material is still moving. Crowding shows where particles have bunched together instead of spreading evenly: at rest neighbours are one particle spacing apart, and red means they sit almost on top of each other. In a solid shows the particles that have gone into a fixed part's walls or floor, with how many there are, so you can judge how well a container holds what you pour into it.

1. Open Demo files, then Open box with a water source under Simulation.
2. Press Go, and while the water pours choose Particles in the Surface | Particles | Both switch under Shaded.
3. Choose Speed to colour the particles by how fast they move; the legend shows the scale in mm/s.
4. Choose Crowding to see where particles bunch together; the legend gives the median distance to the nearest neighbour against the rest spacing.
5. Choose In a solid to see the particles that have gone into the box's walls and floor in red, with their count.
6. Press Pause, then Replay: the switch and the colours work on the recording too. Choose Surface to go back to the usual look.

Has it settled?

Open Details while a run plays or after it ends. Settled? says Still moving with the material's typical speed, Settling while it slows down, or At rest with the time it came to rest. At rest means the typical speed has stayed below one particle cell per second for a tenth of a second of simulated time.

1. Run a scene, for example the open box with its source, and open Details in the run bar.
2. Read Settled? under Steps. To see the water come to rest in the open box, set Duration to 3 s in the scene's settings before pressing Go.

Limits

Particles are drawn at their rest spacing, not at their current size. Speed in Replay is measured between recorded frames, so it is an average over the time between them. In a solid looks only at fixed parts.

Simulation is still experimental. The particle view makes its current limits visible: in the open box demo, the poured water bunches together (Crowding shows it red), so once settled it stands lower than its volume should fill, and some of it sits a couple of millimetres into the walls and floor. These are known engine limits being worked on.