---
title: "Charpy impact test"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:charpy-impact-test"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/charpy-impact-test
site: BCT Engineering
---

# Charpy impact test

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2066 Shrawan (old course), 4 marks
- Video: [Charpy Impact Test | Laboratory Practical | Strength of Materials](https://www.youtube.com/watch?v=JZMxRgpDzfU) — Lalit Singh Mehta
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/charpy-impact-test
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

Illustrate the Charpy Impact Test with figures.

## Short answer

The Charpy impact test measures notch toughness by striking a V-notched 10×10×55 mm bar with a pendulum hammer. Energy absorbed, E = mg(h1 − h2), is read directly in joules. The test is used to find the ductile-brittle transition temperature; a tough material absorbs high energy while a brittle one absorbs little.

## Answer

The **Charpy impact test** measures the energy a material absorbs when fractured by a sudden blow, and so gives its toughness and notch brittleness.

#### Specimen
A standard bar 10 × 10 × 55 mm with a 2 mm deep V-notch (or U-notch) at the middle.

#### Apparatus
A pendulum hammer of known mass raised to a fixed height, an anvil with two supports 40 mm apart, and a scale to read the energy.

```text
        pivot
          o
          |\
          | \ hammer
   h1 ....|..O
          |
   =======+=====  <- specimen
   |__ ___|__ __|
   supports (anvil), notch faces away from the hammer
```

#### Procedure
1. The specimen is placed simply supported on the anvil with the notch on the side opposite to the striking edge.
2. The pendulum is released from the initial height $h_1$.
3. It strikes the specimen behind the notch, breaks it and swings up to a lower height $h_2$.
4. The energy absorbed is

$$
E = m\,g\,(h_1 - h_2)
$$

It is read directly from the dial in joules.

#### Use
The test is repeated at different temperatures to find the **ductile-brittle transition temperature**. A tough material absorbs high energy; a brittle one absorbs little.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. The Charpy test measures
   A. tensile strength
   B. hardness
   C. the energy absorbed in fracture by a sudden blow
   D. porosity
   Answer: C. Gives toughness and notch brittleness. (Key point: Purpose)

2. The standard Charpy specimen is
   A. a 150 mm cube
   B. a 1 m beam
   C. a 40 mm cylinder
   D. 10 x 10 x 55 mm with a 2 mm V-notch
   Answer: D. Standard size. (Key point: Specimen)

3. The notch faces
   A. away from the hammer, on the side opposite the striking edge
   B. towards the hammer
   C. upwards on the anvil edge
   D. at one end
   Answer: A. Hammer strikes behind the notch. (Key point: Notch position)

4. Energy absorbed is
   A. m g h1 only
   B. m g (h1 - h2)
   C. m (h1 + h2)
   D. g (h1 - h2)/m
   Answer: B. Initial height minus the rise height after fracture. (Key point: Energy)

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