Toughness Charpy test

The quality known as toughness describes the way a material reacts under sudden impacts. It is defined as the work required to deform one cubic inch of metal until it fractures. Toughness is measured by the Charpy test or the Izod test. 

VI. 12. Examples of the use of the NDTT approach of Method 2 include the British Standards Institution s BS 5500 [VI.3], the ASME Sections III [VI.4] and VIII [VI.5] and the RCC-M Appendix ZG of the Erench Nuclear Construction Code [V1.6]. These methods address, for example, ferritic steels, for which there are substantial databases relating impact energy (Charpy testing) to fracture toughness. In such cases, the Charpy impact energy can be used as an indirect indicator of material... 

Some of the more common mechanical properties are provided in Table 10.1 from IAEA (2009). Relative to various measures of toughness, some tests use a blunt notch, while others use a sharp crack to determine material resistance to crack initiation, crack propagation or both, and are conducted under either quasi-static (slow) loading or dynamic (fast) loading conditions. Of all these tests, the Charpy V-notch (CVN) impact test is the most commonly used. In addition to those mechanical properties, there are common reference fracture toughness indices used for RPV steels and many of those are also shown in IAEA (2009). These indices are important because they are used in various ways to normalize fracture toughness of RPV steels. 

The chip impact test is carried out in a similar way to the Izod test but without a notch. The test specimen is usually 25.4 mm long, 12.7 mm wide, and 1.65 mm thick. The tests are carried out using ASTM D4508 [79]. Because the test involves an un-notched sample, it reflects material toughness rather than the notch sensitivity measured for the Izod and Charpy tests. 

Eight compact tension It test specimens and four l/2t compact tension test specimens each of base metal (transverse) and weld metal material are provided to augment the fracture toughness data determined from the precracked Charpy tests. This guantity of specimens is sufficient to determine fracture toughness properties over the range extending from linear elastic to elastic-plastic fracture behavior. 

Fig. 14. Load-deflection behavior of a number of tough polymers tested in the notched Charpy geometry at low rates (22). To convert N to kgf, multiply by 0.102. Courtesy of the Society of Plastics Engineers.

Fracture Toughness from Flexed-Beam Impact Tests. As stated above, the so-called impact toughness values obtained from Izod and Charpy tests are not material properties because they depend on specimen thickness, notch depth, notch radius, and other factors imrelated to material properties. These... 

Charpy Test. An impact test for fracture resistance. A V-notched specimen, fixed at both ends, is struck behind the notch by a pendulum. The energy lost by the pendulum in fracturing the test-piece gives a measure of the impact strength of the material. See fracture toughness... 

Source T. Ronald, J.A. Hail, eutd C. Pierce, Usefulness of Precracked Charpy Specimens for Fracture Toughness Screening tests of Titanium Alloys, Atefailf. Trans., Vol3,1972,p813... 

The impact performance of unreinforced polymers is very difficult to quantify. The impact strength is usually determined in an Izod or Charpy test. Different impact tests on the same material (Figure 6.2) do not give the same numerical result and the designer has to choose the test and test data most appropriate to that encountered in service. In addition results will depend on the temperature and possibly on the presence or otherwise of a notch and its radius of curvature, the moisture content of the material, the overall dimensions of the specimen, the molecular weight of the polymer, the presence of additives, etc. At room temperature some thermoplastics, e.g. polypropylene, polyamide and polysulphone, are brittle if suitably notched, while wet polyamide is not so and is said to be tough. 

Limitations. The results obtained from the Izod or Charpy test cannot be directly applied to part design because these tests do not measure the true energy required to break the specimen. The notched Izod impact test measures only the notch sensitivity of the different polymers and not the toughness. 

The Izod and Charpy tests are the test methods usually employed for the determination of the toughness of a material and they are especially useful in comparing the toughness of a particular polymer-particle system. Fracture mechanic theories are the conunonly employed routes for the study and characterization of the toughness of, in particular, ductile polymer composites. 

Fracture Toughness from Flexed-Beam Impact Tests. As stated above, the so-called impact toughness values obtained from Izod and Charpy tests are not material properties because they depend on specimen thickness, notch depth, notch radius, and other factors unrelated to material properties. These values are therefore useful only for the comparison of different materials, and are useless for design calculations. By contrast, fracture toughness (ASTM D5045-99), which is a material property, is useful in design calculations. Consequently it is desirable to have fracture toughness values that are taken under impact conditions, and especially if they could be obtained from the Izod or Charpy test machines. 

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