Charpy vs. Izod: An Impact Testing Comparison

Both Charpy and Izod impact testing are popular methods of determining impact strength, or toughness, of a material. In other words, these tests measure the total amount of energy that a material is able to absorb. This energy absorption is directly related to the brittleness of the material. Brittle materials, such as ceramics or glass, tend to have lower absorption rates than ductile materials like copper or aluminum.

Understanding a material’s energy absorption properties is critical, as it predicts how much plastic deformation the material will be able to withstand before catastrophic failure. It is also important to understand the similarities and differences between these two common impact test methods.

Charpy Impact Testing

The Charpy impact test was developed by S.B. Russell and Georges Charpy at the turn of the 20th century. It remains to this day one of the most popular impact testing methods due to the relative ease of creating samples and obtaining results. The test apparatus consists of a weighted pendulum, which is dropped from a specified height to make contact with the specimen. The energy transferred to the material can be inferred by comparing the difference in the height of the pendulum before and after the fracture.

A Charpy test specimen, which is placed horizontally into the machine, is typically a 55 x 10 x 10mm (2.165" x 0.394" x 0.394") bar with a notch machined into one of the faces. This notch, which can be either V-shaped or U-shaped, is placed facing away from the pendulum and helps to concentrate the stress and encourage fracture. Testing can be performed at both ambient and reduced temperatures, sometimes as low as -425F.

Charpy impact testing is most commonly performed to ASTM E23, ASTM A370, ISO 148, or EN 10045-1. While the test is most commonly performed on metals, there are also a number of standards that exist for plastics and polymers, including ASTM D6110 and ISO 179.

Izod Impact Testing

伊佐德冲击试验是以英国工程师埃德温·吉尔伯特·伊佐德的名字命名的，他在1903年首次描述了这种试验方法。试验装置和试样设计与夏比冲击非常相似，但存在一些显著差异，包括试样的方向，试样垂直夹在装置中，缺口朝向摆锤。然后，摆锤在缺口上方的指定区域撞击样品。

与夏比冲击的主要区别之一是，可以在塑料或金属试样上进行伊佐德冲击试验。塑料样品通常是一根64 x 12.7 x 3.2 mm的棒材，带有加工过的V形缺口。金属样品通常为圆形127 x 11.43 mm棒材，带有1或3个加工V形缺口。

Common Izod impact test methods include ASTM D256, ASTM E23, and ISO 180.

I have metallic samples. Which method should I perform?

虽然Izod法和Charpy法测量的性能相似，但试样设计和试验配置却有很大的不同，因此在选择使用何种方法进行试验时应格外小心。您的测试提供商应该能够根据您的最终目标和特定材料提供方法建议。

Should you decide to perform Izod impact, you will need to decide on which specimen configuration to use. There are varying configurations of round specimens versus square specimens and single notched specimens versus those with up to three notches. Since it is often required to average 3 results for impact testing, the 3 notch specimen could be more economical, as it will take less material to get three impact results. Another possible advantage of the 3 notch sample is that the final result can be an average of directions depending on the specimen configuration. This could help eliminate bias caused by directional properties if this is a concern for your material.

小结：夏比冲击试验和伊氏冲击试验的主要区别是什么？

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