Domain: Engineering — Materials Science & Engineering
Target concept: Comparison of steel ball indentation in aluminum and steel under the same load

Video generation prompt: On a workbench, an aluminum plate is placed on the left side and a steel plate on the right side. Two identical steel balls, one positioned above each plate, are pressed onto the plates simultaneously under the same load and then lifted.

Evaluation guide:
(i) Target concept: Plastic deformation under uniaxial compressive loading of dissimilar metals with identical indenter geometry and load.
Minimum mechanism: Aluminum must exhibit greater permanent plastic strain than steel under the same contact stress; indentation must result from localized yielding, not elastic rebound or fracture; the load and plate thickness shown must be large enough that the resulting dents are clearly visible to the eye without magnification.
(ii)Storyline: [Frame 0–2] Static wide shot: workbench with aluminum plate (left) and steel plate (right) in fixed, adjacent positions; two identical steel balls suspended, one centered above each plate. [Frame 3–5] Both balls descend vertically together, each contacting its own plate in the same frame (synchronous onset). [Frame 6–7] Balls held stationary; indentations form and stabilize (no recovery, no creep). [Frame 8–10] Balls lift vertically together; plates remain fixed; final indentations are fully visible and differentially deep. Perspective: fixed frontal view, full side-by-side framing maintained; no occlusion of either plate or ball at any point.

Manual:
Experimental Procedure
1. Place an aluminum plate on the left side and a steel plate on the right side of a flat workbench.
2. Position two identical steel balls directly above the two plates, one ball centered over each plate, at equal height.
3. Using a load large enough to leave a dent visible to the naked eye, press both steel balls down simultaneously, one onto each plate, until contact is established.
4. Hold briefly, then lift both steel balls vertically away from the plates.
Observation of Experimental Phenomena
After lifting, the aluminum plate shows a deeper, wider indentation with more prominent rim uplift that persists unchanged; the steel plate shows a shallower, narrower indentation with sharper rim definition that likewise persists unchanged.
Summary of Experimental Principles
Under identical load, aluminum (lower yield strength, higher ductility) deforms more plastically than steel (higher yield strength, lower ductility), resulting in a permanent indentation that is deeper and wider in the aluminum plate than in the steel plate.

Prompt Grounding rubric:
level_1: The workbench, the aluminum plate, the steel plate, or at least one of the two steel balls is missing from the frame, the two plates are never placed together on the workbench at all, or no pressing action of any kind occurs.
level_2: The workbench and both plates are visible, but the aluminum plate is not on the left and the steel plate is not on the right as described, or only one steel ball is ever shown pressing down (the other plate is never touched), or the two balls press down at clearly separate moments rather than together.
level_3: The workbench is shown with the aluminum plate on the left and the steel plate on the right; two steel balls are visible, one positioned above each plate; both balls are shown pressing down onto their respective plates and are then lifted away afterward.
level_4: Beyond level 3, the two balls make contact with their plates in the same frame or in immediately consecutive frames with no implied waiting period between the two presses, and the sequence moves directly from pressing to lifting without any unrelated action inserted (no repositioning the plates, no pause for tool handling, no swapping of balls).
level_5: Further still, both steel balls keep the same size, shape, color, and surface texture before, during, and after contact; the two plates stay fixed in place with no sliding, tilting, or shifting during the pressing or lifting; and the camera holds one stable, front-facing framing that keeps both plates and both balls fully visible throughout, without zooming, panning, or cropping either side out of frame.

Scientific and Causal Correctness rubric:
level_1: The indentations on the two plates look identical in depth and width, the steel plate shows a deeper indentation than the aluminum plate, no indentation is visible on either plate at all, or what appears on either plate is a hole, crack, or tear rather than a smooth depression consistent with plastic indentation.
level_2: An indentation is visible on only one of the two plates, or both show indentations but at the same depth and rim shape with no visible difference between them, or the aluminum indentation appears shallower than the steel one.
level_3: Both plates show a clear indentation left by their ball; the depression in the aluminum plate is visibly deeper and larger, with more pronounced rim uplift, than the depression in the steel plate; neither plate shows an unrelated phenomenon such as cracking, spalling, or melting.
level_4: Beyond level 3, each indentation appears essentially as soon as its ball makes contact and neither spreads, fades, nor shrinks while the ball is held in place, and once both balls are lifted away the two indentations remain exactly as deep and wide as they were during contact, with the aluminum dent still visibly deeper and wider than the steel dent.
level_5: Further, both indentations show a rim consistent with a spherical indenter (round rather than lopsided or torn), and the aluminum dent additionally shows a wider, more gradually sloped depressed zone while the steel dent shows a narrower, sharper-edged rim, so the two final indentations stay clearly distinguishable by shape as well as by depth.

Spatiotemporal Consistency rubric:
level_1: One of the two plates or either steel ball disappears from view or reappears in a different spot with no visible path connecting the two positions, a ball jumps toward its plate with no downward motion shown beforehand, the scene's lighting swings between much darker and much brighter with no visible cause between the pressing and lifting phases, or a plate's surface shows a seam, tear, or clipping artifact during contact.
level_2: The workbench or a plate visibly warps, bends, or flexes in a way unrelated to the indentation itself, one of the steel balls rotates or slides sideways with no applied force shown, or the background or framing shifts or zooms partway through the sequence.
level_3: The workbench, both plates, and both balls keep consistent position, scale, and orientation for the whole sequence; the lighting stays even without sudden brightness changes; each ball's motion is a smooth, continuous path downward, a brief pause, then upward; and neither plate nor ball shows any structural break or gap.
level_4: Beyond level 3, the contact and lift-off of each ball happen smoothly with no frame-skipping, freezing, or instant jump between not-touching and touching, and each indentation grows in a continuous, gradual way rather than snapping from a flat surface to a fully formed dent within a single frame.
level_5: Further, the motion throughout stays fluid with no strobing, ghosting, or blur heavy enough to obscure the edges of the plates or balls, and both plate surfaces keep a consistent texture and reflectivity before, during, and after contact, with no artificial gloss or smearing appearing at any point.