Charpy V-notch impact test

All pressure retaining steels applied at a specified minimum design metal temperature (2.11.4.5) below -30°C (-20°F) require a Charpy V-notch impact test of the base metal and the weld joint unless they are exempt in accordance with the requirements of paragraph UHA-51 in Section Vlll, Division 1 of the ASME Code. Impact test results shall meet the requirements of paragraph UG-84 of the Code. 

The cost of using other steels was calculated in a similar manner, using additional quality, pressure vessel, fine grain practice, heat treatment and Charpy V notch impact test extras appropriate for each grade. An additional extra of 0.30 per cwt was included for the non standard thicknesses calculated for steels other than SA-36. 

Within FP-5 project FRAME work will be done to improve the assessment of the most important parameter used to measure the embrittlement conditions of the RPV. Currently this is done through indirect measurements in a rather conservative way (the so-called reference temperature methodology, which makes use of Charpy-V notch impact testing). It is difficult to estimate in a quantitative way the conservatism of this methodology. Therefore the work proposed will focus on the development of a method which allows to measure directly the fracture toughness. This should result in a better and more accurate estimation of the embrittlement conditions of the RPV material. 

The investigations of the wrapper showed the material behavior after non-destructive tests, tensile, creep and charpy-V-notched impact tests. All these tests were performed with base material as well as with welds, at room temperature and at the different reactor temperatures. 

Tko is determined from values of Charpy V-notch impact test results in which only two criteria are applied notch toughness, which depends on the room temperature yield strength of a tested material, and 50% ductile appearance in fracture surfaces. Thus, there is no direct correlation between this T o and the f 7ViDT value that is used according to the AS ME for PWR vessels. Nevertheless, experimental tests give the following correlation ... 

In addition to the typical mechanical-property testing of materials and weldments, impact testing is required to ensure that the product is properly designed for the anticipated operating temperatures. Standards from ASTM, ASME, and others address these design requirements and generally specify materials that have Charpy V-notch impact test requirements added to the normal mechanical property tests. 

In the case of weldments, Charpy V-notch impact testing of the base metal, the heat-affected zone, and the weld metal is also required to ensure that the weldment will function satisfactorily at the design temperature. Welding must be performed with care to ensure that the completed weldment is produced in accordance with standard procedures. 

These results confirmed suspicions that failure was due to excessive amounts of nitrogen, carbon, and oxygen. To characterize the condition of the vessel further, Charpy V-notch impact tests were run on the unaffected base metal, the HAZ, and the uncorroded (sound) weld metal. These tests gave the data in Table 12.7 for ductile-to-brittle transition temperatures. 

V-notch impact tests, such as the Charpy test, are used to test the susceptibility of materials to brittle failure see Wells (1968) and BS 131. 

Some specifications require a minimum Charpy v notch impact requirement of 15 ft lb energy absorbed at the minimum expected service temperature. However, this does not mean that a test specimen exhibiting 60 ft lb is four times tougher than the minimum. The main value of notched bar impact testing is as a criterion for acceptance of materials where reliable correlation with service behavior has been obtained. 

The report of the inquiry [111] criticised the design and fabrication of the alterations made to the original pontoon. The actual cause of the accident was the failure of some tie bars in the detail around the jacking points. The failure was due to brittle fracture which initiated from severe notches such as a small radius curve at the fillet between the spade end and the shank of the tie bar. Weld defects and fatigue cracks were also present in tie bars subsequently recovered from the sea bed. The tie bars had been flame cut to shape and had weld repairs visible to the eye. There had been no post welding heat treatment of the steel. The steel complied with the original specification but tests showed low Charpy V notch impact values. Photo elastic tests indicated a stress concentration factor of 7 at the fillet between the spade end and the shank. The fracture was initiated in the opinion of the inquiry tribunal by the low ambient temperature of around 3°C. 

Tito - critical temperature of brittleness in initial, unirradiated condition. This temperature is determined from Charpy V-notch impact toughness test values where criteria values of notch toughness depend on room temperature yield strength value (thus, criteria values are different for unirradiated and for irradiated conditions). For details - see Chapter 10. 

Test Tensile yield strength atRT Charpy V-notch impact toughness at- 2 C(-80 F) Drop weight tear energy atO C(32 F) ... 

K-, 76°K and 20°K. Tests were also conducted on Charpy V-notch impact specimens at the same temperatures. 

Note 4 Each plate shall be impact tested and meet the Charpy V notch (ASTM A 370, Type) requirements of Par. 2.2.3 of API Specification 620. 

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. 

Notch Impact toughness Energy Lateral expansion % shear fracture Dynamic T41J/ Vk, Tq3j, use To,89 mm 7 50% Blunt Charpy V-notch (CVN) impact test e.g., ASTM E 23, EN ISO 148. Obtain curve fit to data vs test temperature, determine various transition temperature indices, e.g., T41J, and upper shelf energy (USE). Initiation and propagation test ... 

ASTM (2013g), Standard Test Method for Impact Testing of Miniaturized Charpy V-notch Specimens, E2248, Annual Book of ASTM Standards, Vol. 03.01, ASTM. International, West Conshohocken, PA. 

Sokolov M A and Nanstad R K (1995), On impact testing of subsize Charpy V notch type specimens, pp. 384-414 in Effects of Radiation on Materials, 17th International Symposium, ASTM STP1270, D S GeUes, R K Nanstad, A S Kumar and E A Little, eds, American Society for Testing and Materials, Philadelphia, PA. 

In accordance with 10 CFR 50 Appendix G, Paragraph IV A, the reactor vessel beltline materials have minimum upper-shelf energy, as determined from Charpy V-notch tests on unirradiated specimens in accordance with Paragraphs NB-2322.2(a) of the ASME Code, of 75 ft-lbs. Charpy impact tests will be performed on... 

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