Summary of "Prova di resilienza con il pendolo di Charpy @meccanicando"

Summary of “Prova di resilienza con il pendolo di Charpy @meccanicando”

Main Ideas and Concepts

Resilience Definition: Resilience is the property of materials to resist impacts or sudden forces applied over a very short time. It is essentially the opposite of fragility.

Tough materials have good resilience, elongation, and tensile strength (e.g., steels).
Brittle materials have poor resilience and elongation and are prone to breaking under impact.

Importance of Resilience Testing: Knowing a material’s resilience helps in selecting materials for tools or components subjected to impacts (e.g., anvils, hammers).

Resilience Measurement: Resilience (symbol k) is quantified by the work required to break a standardized test specimen with a single blow, normalized by the specimen’s cross-sectional area.

Unit: kg·m/cm² or joules/cm².

Charpy Pendulum Test Apparatus: - Consists of a heavy hammer (typically 30 kg) swinging like a pendulum. - The hammer breaks a notched test specimen placed in its path. - The energy absorbed by the specimen is calculated from the difference in pendulum height before and after impact. - A dial on the machine directly shows the absorbed energy.

Test Specimens: - Standardized specimens have precise dimensions and a notch to concentrate stress. - The most common is the “manager type”: 55 mm long, 10 mm square cross-section, with a 2 mm deep notch. - Variations exist in notch shape and depth (keyhole, V-notch).

Effect of Temperature: - Impact resistance generally decreases as temperature drops. - Below a critical “transition temperature,” resilience drops sharply, causing brittle fracture risk. - The transition zone is crucial for materials used in varying temperature environments.

Methodology / Step-by-Step Procedure for Charpy Test

Setup:
- Use a Sharpey-type test specimen with a central notch.
- Place the specimen securely in the pendulum machine with the notch facing inward.
No-load Test (Calibration):
- Perform a test without any specimen to check the pendulum’s energy and ensure zero absorbed work.
- Set the pointer to the maximum scale value (e.g., 30 kg·m).
Perform Impact Test:
- Release the pendulum hammer to strike and break the specimen.
- Use the braking device to stop the pendulum after impact.
- Read the absorbed energy value from the dial (e.g., 9.5 kg·m).
Post-Test Observations:
- Collect the broken specimen halves (“stumps”).
- Measure the bending angle of the broken specimen.
  - Approximately 100° indicates tough material.
  - Approximately 180° indicates brittle material.
- In this test, the angle was about 100°, confirming toughness.
Calculate Resilience Index (k):
- Formula: [ k = \frac{L}{S_0} ] where:
  - ( L ) = work absorbed (e.g., 9.5 kg·m)
  - ( S_0 ) = cross-sectional area at notch (e.g., 1 cm × 0.5 cm = 0.5 cm²)
- Example calculation: [ k = \frac{9.5 \times 10}{0.5} = 190 \text{ kg·m/cm}^2 ] or approximately 186 J/cm².
Conclusion:
- The tested material has good resilience and toughness.
- Additional notes:
  - Weight of hammer: 30 kg
  - Notch depth: 5 mm
  - Operating temperature also affects results and should be recorded.

Additional Details

The pendulum hammer has an aerodynamic shape and interchangeable blade.
The manufacturer of the machine used is Galdabini.
Impact speed is approximately 5.5 m/s.

Speakers / Sources Featured

Narrator / Presenter: Explains the theory, procedure, and interpretation of results throughout the video.
Machine Manufacturer: Galdabini (mentioned as the maker of the Charpy pendulum machine).
No other specific speakers or interviewees are identified in the subtitles.