Domain: Engineering — Mechanical Engineering
Target concept: Common Materials for Mechanical Parts

Video generation prompt: The test rig is equipped with two samples of equal dimensions (Q235 carbon structural steel and polytetrafluoroethylene). A hardness tester is used to apply the same pressure to the surfaces of the samples in sequence until indentations appear on both sides. The indenter is then removed after maintaining contact for 3 seconds.

Evaluation guide:
(i) Target concept: Static indentation response as a direct visual proxy for comparative hardness of engineering materials.
Minimum mechanism: Indenter must apply compressive load sufficient to exceed yield stress of softer material (PTFE) but remain below yield/elastic limit of harder material (Q235), producing permanent, non-fracturing, geometrically distinct impressions.
(ii)Storyline: [Frame 0–2] Rig with two identically sized, side-by-side samples in fixed view; [Frame 3–4] Tester approaches Q235 surface; [Frame 5–7] Indenter contacts Q235 and remains motionless (visible stillness); [Frame 8] Indentation appears on Q235 surface; [Frame 9–10] Tester retracts cleanly; [Frame 11–12] Tester approaches PTFE surface; [Frame 13–15] Indenter contacts PTFE and remains motionless; [Frame 16] Deeper indentation appears on PTFE; [Frame 17–18] Tester retracts cleanly; [Frame 19+] Both impressions persist, visibly different in depth, with no secondary effects. Perspective: Fixed frontal close-up, full rig and both samples always fully visible, no occlusion.

Manual:
Experimental Procedure
1. Place Q235 carbon steel and PTFE samples side-by-side on test rig.
2. Position hardness tester indenter over Q235 sample; apply pressure until indentation appears; hold contact for 3 seconds; retract.
3. Repeat step 2 identically on PTFE sample.
Observation of Experimental Phenomena
- Indentation appears on both samples after contact.
- Indentation is shallower on Q235, deeper on PTFE.
- No cracking, melting, or color change occurs.
Summary of Experimental Principles
- Q235 is a ductile, low-carbon structural steel valued for weldability and toughness rather than surface hardness; its hardness is only moderate by steel standards, yet still far greater than PTFE's.
- PTFE is a soft, low-friction polymer with very low hardness and high compressibility.
- Hardness testing measures resistance to permanent indentation under static load — directly reflecting material mechanical property differences.

Prompt Grounding rubric:
level_1: No test rig is visible; or the two samples are not both present; or no hardness tester appears; or neither sample ever shows a tester making contact; none of the three required elements (Q235 sample, PTFE sample, hardness tester) show up in the clip.
level_2: Both samples and the tester are visible, but they are not placed side by side on the same rig; or the tester only ever contacts one of the two samples; or the sequence skips a required step (e.g., pressure is shown applied without the samples first being placed on the rig, or with no hold time visible before the indenter retracts).
level_3: The test rig holds the Q235 sample and the PTFE sample side by side; the tester visibly contacts the first sample's surface, then later contacts the second sample's surface; an indentation appears on each of the two samples; the tester makes contact with one sample, then the other, in that order, with no sample skipped.
level_4: All conditions for score 3 are met, and neither sample shows any indentation mark before the tester touches it; the tester stays in contact with each sample for a clearly visible hold period before lifting away; the two samples keep the same size, shape, and position on the rig throughout the clip.
level_5: All conditions for score 4 are met, and the Q235 sample is visually identifiable as a metallic gray piece and the PTFE sample as an off-white or pale beige piece; the tester's tip lines up over the center of whichever sample it is touching; the rig and both samples stay in the same fixed arrangement, clearly visible, for the entire clip.

Scientific and Causal Correctness rubric:
level_1: The indentation looks equally deep on both the Q235 sample and the PTFE sample; or an indentation appears on the Q235 sample but not on the PTFE sample; or no indentation appears on either sample; or the PTFE sample cracks or chips instead of showing a smooth indentation; or either sample changes color or state for reasons unrelated to the hardness test.
level_2: An indentation appears on both samples, but the mark on the Q235 sample ends up deeper than the mark on the PTFE sample, the reverse of what should happen; or an indentation appears before the tester has actually touched the sample; or the tester lifts away before the 3-second hold is shown completing; or a sample visibly bulges or flows outward rather than showing a simple localized indentation.
level_3: An indentation appears on both samples; the mark on the Q235 sample is shallower than the mark on the PTFE sample; each indentation forms only while the tester is in contact and stays visible after the tester lifts away; neither sample shows melting, discoloration, or fracturing at any point; both samples stay solid and intact throughout the test.
level_4: All conditions for score 3 are met, and each indentation's shape matches what a hardness-tester tip would leave (a simple round or square mark, not a scratch or gouge); once the tester lifts away, neither mark shrinks back or disappears; the surface around each indentation stays smooth and undisturbed.
level_5: All conditions for score 4 are met, and the PTFE indentation has smooth, rounded edges with no small cracks radiating from it; the Q235 indentation has a crisp, well-defined edge with no material pushed up or flowing beyond its boundary; neither sample shows glowing, smoking, or any residue — the whole test looks like simple mechanical indentation, not a thermal or chemical effect.

Spatiotemporal Consistency rubric:
level_1: The rig, either sample, or the tester suddenly jumps position or vanishes and reappears; the room lighting swings from full shadow to full brightness within a single frame; the rig visibly bends or fractures and then looks normal again; the camera view jumps or spins partway through the clip.
level_2: One sample shifts position slightly between the two tester contacts; the tester's tip lines up differently on the two samples (e.g., centered on one, off to the side on the other); the background flickers or the frame edges crop inconsistently; the tester's motion stutters or skips forward suddenly.
level_3: The rig and both samples stay in the same place in the frame the whole time; the tester moves smoothly down to touch a sample, holds still there, then smoothly lifts away; neither sample stretches, warps, or distorts; the lighting stays the same brightness and direction across the whole clip; the tester never appears to pass behind a sample unexpectedly.
level_4: All conditions for score 3 are met, and the tester's path toward and away from each sample is a single smooth motion with no backward jumps or hesitation; the moment of contact and the moment of release both look like clean, continuous transitions rather than sudden cuts; neither sample vibrates or shifts while the tester holds still against it.
level_5: All conditions for score 4 are met, and the camera view never zooms, pans, or tilts for the entire clip; the relative size and overlap of the rig and both samples stay the same from start to finish; the tester's approach, hold, and retraction from each sample look fluid, with no stutter or blur that hides the moment of contact or release.