A method of fracture toughness testing using a fracture toughness testing device for compact tensile specimens in a low temperature environment

Abstract

The invention provides a device and a method for testing breaking tenacity of a compact tension specimen in a low-temperature environment. The device comprises an insulated container for containing low-temperature liquid medium, upper and lower clamps and a displacement transmitting mechanism, wherein a specimen is soaked in low-temperature liquid medium and comprises a crack mouth in a horizontal orientation; the upper and lower clamps are connected with the specimen, respectively arranged at two sides of the crack mouth, and respectively connected with upper and lower pistons of a tensile testing machine; the displacement transmitting mechanism comprises two vertical guide rails which are parallel and slide oppositely; upper and lower blades are respectively arranged at two ends of the each vertical lead rail; the upper blades of the two vertical guide rails are oppositely arranged to form an upper tool edge connected with an extensometer; the lower blades of the two vertical guide rails are arranged oppositely to form a lower tool edge connected with the crack mouth, so that a loaded line displacement of the specimen is transferred to the extensometer above the liquid level of the low-temperature liquid medium, so as to accurately measure the loaded line displacement. Meanwhile, the extensometer is prevented from directly contacting the low-temperature liquid medium to be easily damaged, and the device and the method are simple and reliable in structure, and convenient to install and operate.

Description

technical field [0001] The invention belongs to the technical field of performance testing of materials, and in particular relates to a fracture toughness testing device and method of a compact tensile sample in a low-temperature environment. Background technique [0002] Body-centered cubic metal materials show obvious ductile-brittle transition phenomenon with the decrease of service temperature, that is, there is a specific temperature range called the ductile-brittle transition temperature region of the material, and in the ductile-brittle transition temperature region, the fracture toughness increases with Small temperature changes may also lead to great changes in the fracture toughness of the material. Even at the same temperature, the fracture toughness obtained by the test is very scattered. [0003] Ferritic steel for pressure vessels has obvious ductile-brittle transition phenomenon, which becomes a potential threat to the structural integrity and safety of pressu...

AI Technical Summary

Problems solved by technology

However, when the C(T) sample is used for the fracture toughness test, limited by the geometric shape and clamping method of the sample, the C(T) sample is immersed in the low-temperature liquid medium as a whole in the way that the crack mouth is horizontally oriented. The extensometer used to measure the load line displacement (LLD) of the sample also needs to be completely immersed in the low temperature liquid medium, which makes the extensometer easy to be damaged

Therefore, it is difficult to measure the LLD of the C(T) sample when the fracture toughness test of the C(T) sample is carried out by the low-temperature liquid medium immersion method.

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