Virtual Labs

1. Which Rockwell hardness scale commonly uses a 120° diamond cone (Brale) indenter and a major load of 150 kgf?

a: HRA Explanation

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b: HRB Explanation

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c: HRC Explanation

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d: HRF Explanation

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2. Why is the major load removed while the minor load is retained before taking the Rockwell hardness reading?

a: To measure the permanent indentation depth Explanation

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b: To cool the specimen Explanation

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c: To increase the indentation diameter Explanation

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d: To reduce machine vibration Explanation

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3. A higher Rockwell hardness number indicates:

a: Greater permanent deformation Explanation

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b: Lower resistance to indentation Explanation

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c: Greater resistance to indentation Explanation

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d: Higher ductility Explanation

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4. Which of the following is an advantage of the Rockwell hardness test over optical indentation tests?

a: No indentation is produced Explanation

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b: The hardness value is read directly without measuring the indentation Explanation

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c: It measures tensile strength directly Explanation

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d: It requires microscopic examination after every test Explanation

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5. Which indenter is generally used for the Rockwell B scale?

a: Diamond pyramid Explanation

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b: Diamond cone Explanation

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c: Steel ball Explanation

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d: Flat punch Explanation

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6. Why should successive Rockwell indentations be made at different locations on the specimen?

a: To avoid interaction between adjacent indentations Explanation

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b: To reduce specimen thickness Explanation

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c: To increase the applied load Explanation

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d: To improve machine calibration Explanation

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7. A material produces a very shallow permanent indentation during a Rockwell test. This indicates that the material is:

a: Very soft Explanation

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b: Highly ductile Explanation

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c: Very hard Explanation

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d: Brittle Explanation

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8. Which testing parameter should remain constant for all trials performed using the same Rockwell scale?

a: Specimen colour Explanation

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b: Selected indenter and applied loads Explanation

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c: Operator experience Explanation

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d: Ambient lighting Explanation

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9. Why is it recommended to report the average Rockwell hardness from multiple trials?

a: To increase the applied load Explanation

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b: To eliminate the need for calibration Explanation

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c: To obtain a more reliable estimate of the specimen hardness Explanation

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d: To increase indentation depth Explanation

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Rockwell Hardness Experiment