COMPUTATIONAL AND EXPERIMENTAL STUDY OF THE FALLING LOAD TEST OF HIGH-STRENGTH PIPE STEEL X100 (K80)

2021 ◽  
Vol 83 (3) ◽  
pp. 354-368
Author(s):  
A.I. Abakumov ◽  
I.I. Safronov ◽  
A.S. Smirnov ◽  
A.B. Arabey ◽  
T.S. Esiev ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Crack Propagation ◽  
Ductile Fracture ◽  
Pipe Steel ◽  
Load Test ◽  
Resistance Force ◽  
Drop Weight ◽  
Propagation Law ◽  
Movement Distance ◽  
Sample Resistance

The behavior of samples of the promising pipe steel X100 under dynamic three-point bending is studied. This steel is compared with steel X80 currently used in the gas transmission pipeline engineering. Experimental and calculated mechanical characteristics were obtained for pipe steel X100 produced by JSC “VMZ” using data of the standard tests for laboratory samples and drop-weight tests (DWT). Steel X100 demonstrates higher strength indexes in comparison with steel X80, however, it has lower indexes of plasticity and ductile fracture resistance. High-speed video-recording of the crack propagation in a sample of steel X100 was performed in the drop-weight test. In combination with the sample resistance force dependence on the drop-weight movement distance, such testing provided much more information for studying the metal resistance to ductile fracture and allowed revealing the crack propagation law, estimating the specific dissipation energy during the crack propagation, and verifying the computational model used in DWT. Parameters of the X100 steel strain and fracture model were calibrated. The numerical simulation of the behavior of the X100 steel samples in tests at room temperature was performed. Simulation results satisfactorily agree with data of the tests with regard to such parameters as: the sample resistance force dependence as a function of the drop-weight movement distance; the striker work; strained foils, and macrogeometry of fractures in the tested sample. This results may be used for the development of requirements and conditions of using equipped DWT, as well as for the numerical simulation of full-scale tests of pipes made of steel X100 to predict the pipeline resistance to a propagating ductile crack.

scholarly journals NUMERICAL SIMULATION OF A DROP WEIGHT TEST OF DUCTILE PIPE STEEL

2020 ◽  
Vol 82 (4) ◽  
pp. 493-506
Author(s):  
A.I. Abakumov ◽  
I.I. Safronov ◽  
A.S. Smirnov ◽  
A.B. Arabey ◽  
A.G. Glebov ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Ductile Failure ◽  
Crack Tip ◽  
Computer Code ◽  
Tensile Tests ◽  
Steel Sample ◽  
Strength Parameter ◽  
Resistance Force ◽  
Flow Energy ◽  
Drop Weight

The processes in the metal sample of a supply pipeline realized under drop-weight tests (DWT, or DWTT according to ASTM) are studied. DWT is a proof test of the pipeline metal that should ensure high resistance of the pipeline against extensive destruction. Numerical simulation of DWT with the steel sample of full thickness was performed; the steel had К65 strength grade. Parallel finite-element computer code DANCO developed in RFNC-VNIIEF was used for simulations. A detailed description of the rupture formation process required a fine-enough mesh and a supercomputer. To carry out the numerical simulation of the process, the constants of the deformation diagram were used, obtained on the basis of static and dynamic tensile tests of samples at room temperature. A modified Gurson–Tvergaard–Niedelman (GTNm) model for macro-viscous steel destruction (ductile failure) was used to describe the strain and the destruction of the metal. The modification makes it possible to describe direct and oblique cuts and their combinations in case of ductile failure of small-size objects (rods, plates, shells). The calculated dependences of the movement of the crack tip on the movement of the load and the resistance force of the sample on the movement of the crack tip are presented. We have got a good agreement between the computations and experimental data with regard to the “force–displacement” strength parameter, the deformed profiles and macro-geometry of the ruptured sample after the tests. The computation results reveal the mechanics of the crack origination, start and propagation in the sample, describe the plastic-flow energy distribution in the process of dynamic destruction. The results of the work can be used in the development of the requirements and of the implementation conditions of the “tooled” DWT, and for numerical simulation of the extensive destruction at the main pipeline.

Effect of Separation on Ductile Crack Propagation Behavior During Drop Weight Tear Test

2010 ◽  
Author(s):  
Takuya Hara ◽  
Taishi Fujishiro
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Fracture Resistance ◽  
High Strength ◽  
Opening Angle ◽  
Ductile Crack ◽  
Line Pipe ◽  
Propagation Behavior ◽  
Drop Weight ◽  
Drop Weight Tear Test

The demand for natural gas using LNG and pipelines to supply the world gas markets is increasing. The use of high-strength line pipe provides a reduction in the cost of gas transmission pipelines by enabling high-pressure transmission of large volumes of gas. Under the large demand of high-strength line pipe, crack arrestability of running ductile fracture behavior is one of the most important properties. The CVN (Charpy V-notched) test and the DWTT (Drop Weight Tear Test) are major test methods to evaluate the crack arrestability of running ductile fractures. Separation, which is defined as a fracture parallel to the rolling plane, can be characteristic of the fracture in both full-scale burst tests and DWTTs. It is reported that separations deteriorate the crack arrestability of running ductile fracture, and also that small amounts of separation do not affect the running ductile fracture resistance. This paper describes the effect of separation on ductile propagation behavior. We utilized a high-speed camera to investigate the CTOA (Crack Tip Opening Angle) during the DWTT. We show that some separations deteriorate ductile crack propagation resistance and that some separations do not affect the running ductile fracture resistance.

scholarly journals Study on Compound Mode Crack Propagation Law of Semi Circular Arch Roadway Under Impact Load

2021 ◽  
Author(s):  
Chengxiao Li ◽  
Renshu Yang ◽  
Yuantong Zhang ◽  
Chen An
Keyword(s):  
Numerical Simulation ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Impact Load ◽  
Central Axis ◽  
Mode I ◽  
Finite Element Software ◽  
Circular Arch ◽  
Propagation Law ◽  
The Impact

Abstract Various kinds of defects are usually contained in the underground roadway. When the roadway is impacted by external load, the location of defects will influence the roadway with different degrees. In order to study the effect of the location of defects on crack propagation in roadway, in this paper, the stress wave produced by the bullet impacting the incident rod was used as the impact load. Meanwhile, the variations of speed, displacement and dynamic stress intensity factor (DSIF) of cracks, during crack propagation, were obtained by using the experimental system of digital laser dynamic caustics (DLDC). And the extended finite element software ABAQUS is used for numerical simulation. Based on the method of experimental-numerical simulation, the crack propagation path is verified and the impact fracture behavior of semi-circular arch roadway with different defect positions is presented. It can be concluded that when the prefabricated crack is located at the central axis of sample, the crack propagation belongs to pure mode I; when the prefabricated crack is 5mm away from the central axis, the crack propagation appears between mode I and I-II mixed mode alternately; when the prefabricated crack is at the edge of semi-circular arch roadway, the crack propagation follows I-II mixed mode

Probabilistic Crack Propagation Behavior of Railway B Grade Steel

2010 ◽  
Vol 97-101 ◽  
pp. 484-487
Author(s):  
Wei Li ◽  
Qiang Li ◽  
Ping Wang
Keyword(s):  
Crack Propagation ◽  
Reliability Assessment ◽  
Threshold Value ◽  
Threshold Region ◽  
Propagation Behavior ◽  
Propagation Law ◽  
Confidence Degree ◽  
State Region ◽  
Crack Propagation Behavior ◽  
Grade Steel

Fatigue crack growth rate (FCGR) test of B grade steel was performed to clarify the probabilistic behavior of crack propagation in near-threshold region and steady-state region. As a result, a crack propagation law considering influence of threshold value and average stress can be well proposed to estimate crack propagation behavior of B grade steel. The estimated value of threshold value ΔKth is 293.65MPamm1/2, approaching the experimental value of ΔKth, about 280.39MPamm1/2. Furthermore, the probabilistic FCGR curves of B grade steel are established from the viewpoint of survival probability and confidence degree, which reflects the influence of scatter regularity of data and sample size on reliability assessment.

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