Abstract: The invention belongs to the field of welding technology and discloses a CMT automatic overlaying method for opening in side wall of bimetallic composite pipes. The method includes: establishing a mathematical model of the opening in a side wall to be welded; Based on the mathematical model, determining the trajectory of the saddle line during overlaying; dividing the trajectory of the saddle line into several welding runs, all of which adopt the downslope welding process; establishing a three-dimensional model of the opening in the side wall to be welded and a CMT overlaying system simulation model; Based on the simulation model, planning the overlaying path of the CMT overlaying, and generating an overlaying offline instruction; Based on the offline instruction, performing CMT overlaying on the opening in the side wall to be welded according to the overlaying sequence, so as to obtain a weld overlay.

Abstract: A method for characterizing propagation of metallic short cracks and long cracks includes: acquiring crack tip opening displacement in a metallic notched sample under cyclic loading; acquiring crack tip opening displacement amount caused by a single monotonic tensile in the notched sample, and crack tip opening displacement caused by monotonic tensile in the notched sample under a maximum far-field stress; and based on an original Shyam model, constructing, according to the crack tip opening displacement amount and the crack tip opening displacement by obtaining yield strength of metals, a Tm?c model for characterizing the propagation of short cracks and long cracks, where the Tm?c model is used for representing the growth rate of short cracks and long cracks.

Abstract: A method for characterizing propagation of metallic short cracks and long cracks includes: acquiring crack tip opening displacement in a metallic notched sample under cyclic loading; acquiring crack tip opening displacement amount caused by a single monotonic tensile in the notched sample, and crack tip opening displacement caused by monotonic tensile in the notched sample under a maximum far-field stress; and based on an original Shyam model, constructing, according to the crack tip opening displacement amount and the crack tip opening displacement by obtaining yield strength of metals, a Tm?c model for characterizing the propagation of short cracks and long cracks, where the Tm?c model is used for representing the growth rate of short cracks and long cracks.

Abstract: The present invention discloses a method and system for predicting a creep-fatigue life of a structural part of a thermal power unit. The method includes: constructing a life prediction model; acquiring a stress relaxation curve in a strain control creep-fatigue test through pure creep data to calculate an initial creep damage; acquiring a cyclic hardening coefficient, an elasticity modulus and other related material constants through the pure fatigue data to calculate an initial fatigue damage; and acquiring a difference between strain energy densities in upper and lower parts of creep-fatigue mean stress, making the difference between strain energy densities less than a set threshold through dichotomy iteration to acquire a final creep damage, a final fatigue damage and an oxidative damage under such a circumstance, and predicting the creep-fatigue life of the high-temperature structural part based on the life prediction model.

Abstract: Disclosed is a deepwater platform welded joint testing system. The testing system comprises a host unit, a hydraulic unit and a control unit, wherein the control unit is connected with the host unit and the hydraulic unit respectively; the host unit comprises a bearing frame placed on a bearing base, biaxial tension/compression loading oil cylinders mounted on the bearing frame, a lateral force resistant mechanism connected to the front ends of the biaxial tension/compression loading oil cylinders, counter-force supports fixed to the top end of the bearing frame and biaxial bending loading oil cylinders mounted on the counter-force supports.

Abstract: A method of predicting low-cycle fatigue crack initiation and propagation behaviors under a multi-scale framework includes the following steps: S1, providing a calculation method for low-cycle fatigue crack initiation and propagation damages under a multi-scale framework; S2, determining a slip system where a maximum damage is located and an accumulated damage of all slip systems by calculation using the calculation method in S1; S3, a crack initiating and propagating in a direction towards the slip system where the maximum damage is located when the accumulated damage reaches a critical value; and S4, conducting calculation repeatedly until a predicted crack length reaches a fracture length of a low-cycle fatigue specimen under test conditions.

Abstract: The present invention discloses a quantitative evaluation method for sensitivity of welding transverse cold cracks in a typical joint of a jacket, including following steps: S1, performing macroscopic analysis, metallographic analysis, fracture analysis and hardness analysis on cracks of a failed component to obtain main causes of cold crack failure; and S2, designing and processing a dedicated sample, and performing rigid restraint crack tests on the dedicated sample at different preheating temperatures to obtain a cracking/non-cracking critical restraint stress ?1cr of the sample.

Abstract: The present invention discloses a quantitative evaluation method for sensitivity of welding transverse cold cracks in a typical joint of a jacket, including following steps: S1, performing macroscopic analysis, metallographic analysis, fracture analysis and hardness analysis on cracks of a failed component to obtain main causes of cold crack failure; and S2, designing and processing a dedicated sample, and performing rigid restraint crack tests on the dedicated sample at different preheating temperatures to obtain a cracking/non-cracking critical restraint stress ?1cr of the sample.

Abstract: The present disclosure relates to a method and system for predicting the critical floating time of a reinforcing phase. According to the method, a particle concentration processing model, a half-life processing model, an agglomeration kinetics model, and a floating time processing model are combined to obtain the critical floating time of a reinforcing phase particle according to an initial particle size of the reinforcing phase particle, a density of the reinforcing phase particle, a mass fraction of the reinforcing phase of a composite soldering material, and a density of the composite soldering material. The method and system can accurately predict the critical floating time of the reinforcing phase particle.

Abstract: This invention discloses a method for preparing a kind of Sn-based silver-graphene lead-free composite solder, including mixing a certain amount of graphene with sodium dodecyl sulfate, then adding a certain amount of dimethylformamide, sonicating for 2 hours, adding a certain amount of silver nitrate to the mixture, continuing the sonication and finally obtaining the homemade. The solders matrix powder is weighed according to different silver-graphene mass fraction required, then poured into a ball-milling tank milling for 5 h. The powder is poured into a stainless steel mold after drying, then placed under hydraulic pressure to 500 Mpa for pressure forming. Later, the cold-pressed cylinder is placed in a high vacuum tube resistance furnace and sintered at 175° C. for 2 hours. After cooling to room temperature, it is formed into a cylinder under the hydraulic press.