44 results about "Crack tip opening displacement" patented technology

The invention provides Ni-series low-temperature steel, a manufacture method thereof, a liquefied natural gas storage tank and a ship body for a transportation ship. The Ni-series low-temperature steel includes the following chemical compositions by mass percentage: 0.02-0.10% of C, 0.01-0.20% of Si, 0.50-0.75% of Mn, less than or equal to 0.010% of P, less than or equal to 0.004% of S, 8.50-9.50% of Ni, 0.005-0.40% of Al, 0.005-0.40% of Ti, 0.0005-0.003% of O, 0.0010-0.01% of N, 0.0005-0.004% of Ca, 0.001-1.50% of Cu, 0.001-0.16% of Mo and the balance being Fe. The manufacture method includes steps of: adopting a basic oxygen furnace (BOF)(or an electric arc furnace(EAF)) for smelting+ low frequency (LF)+ VD(or RH) refining technology for refining; adopting a secondary cold area weak cold+ stable low casting process to be matched for steel continuous casting; adopting low-temperature heating+ controlled rolling technology for steel rolling and directly quenching at the temperature above Ar3; and adopting the critical hardening+ tempering process for thermal treatment of steel. Through experiments of low-temperature impacting, non destructive testing (NDT), dark trace (DT), crack tip opening displacement (CTOD), K1a and the like, the Ni-series low-temperature steel is proved to have the advantages of having good obdurability matching and suitable for manufacturing ultra-large type liquefied natural gas (LNG) storage tanks, wherein manufacture volume of the LNG storage tanks exceeds 2*105m<3>, maximum wall thickness exceeds 50mm, and the LNG storage tanks are ultra-high in requirements for safety.

The invention belongs to the field of research of environmental cracking of materials, and provides a sample table for scanning electron microscope (SEM) in-situ observation of stress corrosion cracking, which can realize the SEM in-situ observation of the stress corrosion cracking of a metal material in a liquid medium. The sample table is designed according to a spatial size of an SEM sample room; a micro tension sample can be loaded and kept in a constant displacement state in the aspect of loading the sample; and the sample table is placed in the liquid medium together with a constant displacement sample to produce the stress corrosion cracking, is taken out of the medium and is arranged in the SEM sample room, so that a continuous process of stress corrosion crack propagation can be observed and recorded. Meanwhile, the crack propagation speed and crack tip opening displacement can be accurately calculated according to a stress corrosion cracking SEM image. Through the sample table, the problem that the stress corrosion cracking of the material in the liquid medium cannot be observed by an SEM is solved, and the sample table is an effective tool for researching a stress corrosion cracking micromechanism of the material.

The invention discloses a novel method for measuring compact tension specimen fracture parameters by using double extensometers. The novel method comprises the following steps of: measuring two opening displacements by using the double extensometers; obtaining a crack tip opening displacement (CTOD) of a compact tension test through calculation by using a triangular relation; and calculating a CTOD value under each load and a nominal stress corresponding to the CTOD value, and obtaining a relation between the nominal stress and the CTOD, thereby obtaining a CTOD design curve of the compact tension test. The fracture parameter test method disclosed by the invention has the characteristics of simpleness, easy operation, simpleness for processing data, high precision of a critical CTOD value, comprehensive data, large information quantity, freeness from test precision influences of other parameters, such as strength, Young modulus, rotary factor and load, capabilities of obtaining the CTOD data of the whole test loading process and obtaining the CTOD design curve of the compact tension test under an actual board thickness condition.

The invention relates to a method for predicting the high-low-cycle composite fatigue crack growth life of a turbine joggle structure, and the method comprises the steps: (1), building a crack growth model giving consideration to a crack closure effect; (2), determining a high-cycle load stress intensity factor model; (3), determining a low-cycle load stress intensity factor model; (4), judging whether a current cycle is a high-cycle load or not: executing step (5) if the current cycle is the high-cycle load, or else executing step (6); (5), calculating a composite fatigue lower crack increment, judging whether a next cycle is a low-cycle fatigue load or not: obtaining the maximum crack tip opening displacement of the current cycle if the next cycle is the low-cycle fatigue load, and executing step (7), or else executing step (8); (6), calculating the variance of the low-cycle load lower crack tip opening displacement; (7), calculating the residual crack tip opening displacement and crack increment according to the results inputted at steps (5) and (6); (8), updating the crack length, repeatedly carrying out the steps (4)-(7) if the maximum stress intensity factor is less than the fracture toughness, or else completing the calculation, and obtaining the crack growth life.