Teach lesson
Choosing a material: hardness, toughness, and strength
Students use the Materials remote lab to compare hardness, impact, and tensile evidence and recommend a material combination for a part that may be scratched, struck, or subjected to loading that could cause yielding or failure.
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Learning Outcomes
Distinguish hardness, toughness, and strength as different properties.
Assess the preliminary suitability of a material / alloy / treatment combination using lab-session and reference evidence.
Relate a laboratory test to a design need.
Avoid conclusions such as 'the hardest material is always the best'.
Defend a material choice with evidence and a limitation.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
1. The design problem
8 min
Choose a material for the pull handle of a school workshop drawer. A stuck drawer puts the handle under a pulling load; a falling tool may strike it. First priority: resist permanent deformation or breakage under pulling. Second priority: tolerate accidental impact without brittle fracture. Surface marking matters less than these two requirements. Examine steel 1.4301, as delivered as a preliminary candidate. The laboratory specimens are not finished handles: deciding a safe handle load also requires dimensions, attachment details and appropriate tests.
There is no single property that makes something “a good material.” In this activity, you will compare three different properties:
- Hardness: resistance to marks or scratches on the surface.
- Toughness: the ability to absorb an impact without brittle fracture.
- Mechanical strength: the ability to withstand tensile stress or loading before yielding (permanent deformation) or breaking. This differs from stiffness: stiffness and the part's geometry affect how much it bends elastically under load.
Which test most directly addresses the drawer handle’s first priority, and why? Use the difference between hardness, toughness and strength.
2. Observe material tests
22 min
The lab lets you select a material, alloy, treatment, and test method. Use only the verified route or another route that is visibly available in your session, separately verified by your teacher before class, and then assigned. If the screen shows a number, copy the unit as well. If it only shows an image or video, describe the visible evidence.
Open Materials and gather evidence
Launch Materials from this lesson. Select steel → 1.4301 → as delivered → Hardness measure → HV1.
Run the hardness test and record the material, method, indentation evidence and any value with its full method label. HV1 names the Vickers test condition; it is not a hardness value by itself.
Use the supplied impact photograph and tensile data below for the same alloy and treatment. Enter them as reference evidence in the other two rows.
In a longer session, your teacher may assign an additional available test. Keep its specimen and source separate. Do not use one property to establish another.
Supplied reference evidence — same material: steel / 1.4301 / as delivered.
| Test | Exact source | Evidence you can use | Limit | |---|---|---|---| | Impact | 14301_D_NBI_V1_FS_1 | Inspect the fracture-surface photo below. Describe its texture and the visibly distorted edges. | A photograph alone does not give absorbed energy or prove the handle is impact-safe. | | Tensile | 14301_D_TT_V2_Value.csv | Recorded specimen peak force: 58.528 kN at machine travel 25.334 mm; the final recorded force is 22.6432 kN at 31.4555 mm. | Force and machine travel are not material stress and strain. Without specimen geometry, do not turn these into a handle load rating or tensile strength in MPa. |
Use these two supplied rows with your own hardness observation. They concern the same alloy and treatment, but different specimens and test methods. Label the two rows as supplied reference evidence.
Fracture surface of a notched steel 1.4301 specimen after an impact test, with textured surface and distorted edges.
Evidence of material properties
Complete three rows: your hardness observation and the two supplied references. Identify the source, material/alloy/treatment, property, evidence and confidence with a reason. No numeric impact energy is supplied; leave that optional cell blank.
| Test and evidence source | Exact evidence source | Material / alloy / treatment | Property tested | Observed evidence | Number and unit, if shown | Confidence and reason |
|---|---|---|---|---|---|---|
Which statement makes the best use of the laboratory tests?
3. Make a criteria-based decision
15 min
Choose two properties that represent potentially competing design requirements for the workshop part. Explain why both matter, then assess whether your table contains comparable evidence for the same material / alloy / treatment combination. Do not claim or imply a trade-off or opposing relationship unless both properties were measured comparably for at least two candidate combinations or conditions and show that opposing pattern; otherwise, state what comparison is still needed.
For the workshop part, name the best-supported preliminary material / alloy / treatment candidate, or state explicitly that the available evidence is inconclusive. Use test evidence and identify the exact evidence from the same material / alloy / treatment combination, acceptance threshold, or valid comparison still needed before making a firm decision.
4. Final recommendation
10 min
Write 4–5 sentences to the workshop manager about the drawer handle. Name the tested alloy and treatment. Use two observations, identifying which came from your lab run and which from the supplied references. Explain what they show about the pulling and impact priorities, and what they cannot establish. Finish with a preliminary recommendation or an inconclusive verdict and one specific test or design limit needed before approving the handle.
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