Charpy impact testing

Example 2.23 A series of Charpy impact tests on uPVC specimens with a range of crack depths gave the following results... 

Table GR-2.1.3(d) Charpy Impact Test Temperature Reduction...

The Izod and Charpy impact tests are mostly used. A defined pendulum strikes the specimen sample, notched or un-notched, clamped with a defined device. The absorbed energy is calculated and expressed ... 

Figure 8.15 Schematic illustration of Charpy impact test. Reprinted, by permission, from P. K. Mallick, Fiber-Reinforced Composites, p. 249. Copyright 1988 by Marcel Dekker, Inc.

Charpy impact test—a destructive test of impact resistance, consisting of placing the specimen in a horizontal position between two supports then striking the specimen with a pendulum striker swung from a fixed height. The magnitude of the blow is increased until specimen breaks. The result is expressed in in-lb or ft-lb of energy-... 

For fracture-critical tension members, Charpy impact test may be required,... 

A set of three Charpy Impact test specimens shall be taken from a pipe representing each heat of steel furnished on the order. The samples shall be tested in accordance with Appendix SR-5 of API 5L... 

Many applications of ceramic composites will expose the material to impact damage. Here again, the amount of work which has been done in this arena is limited, and needs to be increased. Impact tests can be performed using drop towers or Charpy impact testing apparatus. Such measurements have been done at room temperature30 and the apparatus can be adapted for use at elevated temperatures. 

NUMERICAL DETERMINATION OF THE ENERGY CALIBRATION FUNCTION go FOR HIGH RATE CHARPY IMPACT TESTS... 

Instrumented Charpy impact tests on unnotched samples are conducted to determine the energy absorbing capability and dynamic fracture behaviour of the C/SiC composites. The dynamic fracture toughness (ak) is calculated using the following equation ... 

Figure 5.15. Impact fracture surface of C/SiC composites [24] (a) after Charpy impact test and (b) after the nails penetrated test...

Low-temperature embrittlement occurs in carbon and low-alloy steels at temperatures below their brittle-ductile transition temperature range. The effect is reversible when the alloy is heated above the transition range, ductility is restored. This embrittlement is avoided by following the Charpy impact test requirements of the relevant engineering codes. The need to test depends primarily on the material, its thickness and the minimum design temperature. 

Impact test, Charpy Impact test, Izod... 

The ability of a material to resist deformation and fracture in the presence of a notch. The most common toughness test is the Charpy impact test which, because of its high speed of straining, is normally unable to detect the presence of hydrogen embrittlement in ferritic steels. 

For polymer sheets, the notched Izod impact strength is often reported (ASTM D256). In this test, as well as the Charpy impact test in the same ASTM standard, the polymer sample is subjected to an impact from a falling hammer, and the... 

FIGURE 3.36 Impact test, (a) Schematic diagram of Charpy impact testing machine, (b) Arrangement of Charpy impact specimen, (c) Mounting of Izod impact specimen. 

Elastic stress concentrations cannot explain most product failures, since yielding nearly always occurs before crack initiation. However, they indicate locations where yielding is likely to occur first. Therefore, the failure stress in Charpy impact tests (Section 9.5.1) should not be calculated using the notch q value. Craze formation is another form of (localised) yielding, which also modifies the stress distribution in the product. Section 9.4.4 shows that craze breakdown may occur at a critical opening displacement, rather than at a critical stress. Hence, elastic-plastic analyses must be used for most polymer product failures. 

Variation of the energy absorbed in a Charpy impact test with the radius of the notch tip in 3 mm thick bars (from Ogorkiewicz, R. M., Ed, Thermoplastics—Properties and Design, Wiley, 1974). 

The 5 ms failure time in a Charpy impact test is 2000 times smaller than the 10 s failure time in a slow bend test. This increases the value of the yield stress, without necessarily increasing the stress for crazing. For some polymer/temperature combinations there may be a changeover from yielding to crazing and plane strain fracture. 

This MDMT procedure is used to determine the lowest permissible temperature for which charpy impact testing is or is not required. The ASME Code requires this be determined for every pressure vessel and the MDMT be stamped on the nameplate. While eveiy pressure vessel has its own unique MDMT, this may or may not be the MDMT that is stamped on the nameplate. Not only does ever) pressure vessel have its own unique MDMT, but every component of that pressure vessel has an MDMT. Tlie vessel MDMT is the higliest temperature of all the component MDMT s. On occasion, the MDMT is specified by the end user as an arbitrary value. The vessel fabricator is then responsible to verily that the actual MDMT of every component used in that pressure vessel is lower than the arbitrary value requested for the nameplate stamping. Considering this, there are various definitions for MDMT depending on how it is used. The definitions follow ... 

Test MDMT The temperature at which the vessel is charpy impact tested. 

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