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1
Xu, Tian Han, Yao Rong Feng, Sheng Yin Song, Zhi Hao Jin, and Dang Hui Wang. "Investigation of Fracture Mechanism of Casing-Drilling Steels." Advanced Materials Research 197-198 (February 2011): 1647–50. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.1647.
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The paper reports on an investigation of the fracture mechanism of both tensile and impact fracture in three types of casing-drilling steels. The results show that the tensile fracture surface of N80 steel includes fibrous zone, radiation area and shear lip zone, and those of both K55 and P110 steels include two zones; all the tensile fracture surfaces of three types of casing drilling steels show the ductile fracture mode, the ductile fracture mode indicated with dimples is observed on all zones; the impact fracture surface of the N80 steel possesses a combined quasi-cleavage and ductile fracture modes, a single fracture mode is observed on the fracture surface of both K55 and P110 steels, the K55 steel impact sample is fractured in a cleavage brittle manner, whereas the P110 steel impact sample is fractured in a dimpled ductile manner.
2
Mizuguchi, Takashi, Ryota Oouchi, Rintaro Ueji, Yasuhiro Tanaka, and Kazunari Shinagawa. "Effect of Si Content on Fracture Behaviour Change by Strain Rate in Si Steels." Materials Science Forum 654-656 (June 2010): 1303–6. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1303.
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Fracture behaviour transitions due to change in the strain rate in steels with various Si content ranging from 2% to 5 wt% were studied. Room-temperature tensile tests were conducted over wide range of strain rates ranging from 10-3 s-1 to 103 s-1. Concerning of the steels with low Si content (no more than 3%), the nominal stress - nominal strain curves represented both uniform and local elongations at all strain rates. On the other hand, in 4% Si steel at a strain rate higher than 101 s-1, the tensile sample broke down without local elongation (necking). The stress at breaking was found to be nearly equal to its work hardening rate. The strain rate at which fracture behaviour transition took place in 5% Si steel (10-1s-1) was lower than that in 4% Si steel. TEM observations clarified the existence of deformation twins in the sample that fractured without necking. These results indicated that Si addition is subject to the brittle fractures and that the fracture mechanism transition is closely related with the deformation twinning behaviour.
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Yang, Bang Cheng, Jian Xiong Liu, Rong Xin Guo, and Hai Ting Xia. "Experimental Study on Out-Plane Crack Extension in Rimmed Steel." Advanced Materials Research 690-693 (May 2013): 1767–70. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.1767.
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Study on the fractural mechanism of thin sheet metals focuses on how to efficiently fracture and recycle the scrapped vehicles and electrical equipments. By using the experimental fracture mechanics, the failure mode was studied for 10F rimmed steel sheets to be crushed and recycled. In-plane mode I, out-plane mixed mode I /III and mode III fracture tests were conducted under different loading angles. The effects and contributions of mixed mode crack extensions for 10F rimmed steel sheets were analyzed and some sensitive fractural factors were studied. The experimental results show that pure mode III is most viable to fracture the thin sheet 10F rimmed steels.
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Kremnev, Leonid, Vyacheslav Matyunin, Artem Marchenkov, and Larisa Vinogradova. "On the nature of steel fatigue fracture." International Journal of Computational Physics Series 1, no. 1 (March 1, 2018): 181–83. http://dx.doi.org/10.29167/a1i1p181-183.
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Experimental data confirmed that if steel cyclic stress reduces to less than tensile yield stress values, i.e., in case of high-cycle fatigue, the mechanism of fracture changes from dislocation to vacancy one. The authors based their findings on the fact that steel density determined by the method of liquid displacement is less than that of steel in both initial conditions and after fracture under the cyclic loads exceeding tensile yield stress values. In the latter case steel hardness increases, whereas the specimens fractured under the cyclic stresses less than their tensile yield stress values show no change in hardness. It means that in such a case metal fractures without strain hardening, i.e., undergoes brittle fracturing developing by vacancy mechanism rather than by dislocation one. As a result, such steel obtains the structure and properties similar to those appearing after its exposure to radiation, i.e., friability and brittleness.
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Ambarita, H., M. Daimaruya, and H. Fujiki. "Impact Fracture of Jointed Steel Plates of Bolted Joint of Cars." Applied Mechanics and Materials 566 (June 2014): 232–37. http://dx.doi.org/10.4028/www.scientific.net/amm.566.232.
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The present study is concerned with the development of a fracture criterion for the impact fracture of jointed steel plates of a lap bolted joint used in the suspension parts of a car body. For the accurate prediction of crash characteristics of car bodies by computer-aided engineering (CAE), it is also necessary to examine the behaviour and fracture of the jointed steel plates subjected to impact loads. Although the actual impact fracture of jointed steel plates of a lap bolted joint in cars is complicated, for simplifying it is classified into the shear fracture and the extractive fracture of jointed steel plates. Three kinds of steel plates, i.e., common steel with the tensile strength of 270 MPa and two high tensile strength steels with the tensile strength of 440 and 590 MPa level used for vehicles, are examined. In the impact shear test, the specimens are made of two plates and jointed by a bolt, and in the impact extractive test the specimens are made of a plate and drilled in the centre for a bolt. The impact shear test of jointed steel plates of lap bolted joints is performed using a modified split Hopkinson bar apparatus, while the impact extractive one is performed using one-bar method. Numerical simulations by a FEM code LS-DYNA are also carried out in order to understand the mechanism of shearing and extractive fractures process of jointed steel plates. The obtained results suggest that a stress-based fracture criterion may be developed for the impact shearing and extractive fractures of jointed steel plates of lap bolted joints used in a car body.
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Islam, M. A., and Yo Tomota. "Fatigue Strength and Fracture Mechanisms of IF28 Steels." Advanced Materials Research 15-17 (February 2006): 804–9. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.804.
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Interstitial free (IF) steels are widely used as thin sheet in the automobile industries because of their many favorable properties. Although, fatigue properties of IF steels do not have significant importance to auto body makers, however, they are very concerned about the tensile and fatigue strength of the steels used for structural purposes to ensure safety of passengers. So, fatigue results of this steel might help researchers to understand the behaviors of high strength steels. In this study cyclic and static properties have been studied at room temperature in the air. Initiative has also been taken to observe the fatigue fracture morphology of this steel. Experimental results show that the fatigue limit is corresponding to about 40% of tensile strength and 80% of the yield strength of this steel. Fractographic observations reveal a mixed type of fracture mode (intergranular and transgranular cracking) fractures.
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Yajima, Zenjiro, Yoichi Kishi, and Yukio Hirose. "X-Ray Quantitative Analysis of Transformed Martensite in Austentic Stainless Steel." Advances in X-ray Analysis 39 (1995): 481–89. http://dx.doi.org/10.1154/s0376030800022904.
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Austenitic stainless steel has large toughness and high corrosion resistance compared to other alloy steels. The austenite near the fracture surface will be transformed to the martensite when it is fractured. In the present study, X-ray fractography is applied to a fatigue fracture surface of austenitic stainless steel. The fatigue tests were carried out on compact tension ( CT ) type specimens. The volume fraction of transformed martensite was quantitatively evaluated on fatigue fracture surfaces by the X-ray method. The plastic strain on the fracture surface was estimated by measuring the line broadening of X-ray diffraction profiles. The size of plastic zone left on the fatigue fracture surface was determined from the distribution of the line broadening
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Kantor, Matvey Matveevich, Konstantin Grigorievich Vorkachev, Vyacheslav Aleksandrovich Bozhenov, and Konstantin Aleksandrovich Solntsev. "The Role of Splitting Phenomenon under Fracture of Low-Carbon Microalloyed X80 Pipeline Steels during Multiple Charpy Impact Tests." Applied Mechanics 3, no. 3 (June 24, 2022): 740–56. http://dx.doi.org/10.3390/applmech3030044.
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The ambiguity of the splitting effect on X80 low-carbon microalloyed pipeline steels’ tendency towards brittle fracture prompted an experimental study of impact toughness scattering based on multiple Charpy impact tests in a temperature range from 20 °C to −100 °C. A fractographic analysis of a large number of fractured samples was carried out. The relationships between impact toughness, deformability and splitting characteristics were studied. A number of common features of three X80 low-carbon microalloyed pipeline steel fractures were revealed. It was experimentally established that the reason for the scattering of the impact toughness values during completely ductile fracture of specimens, as well as during fracture accompanied by the splitting formation, is the local inhomogeneity of plastic properties. The higher the susceptibility to the formation of splits for a particular steel, the lower the impact toughness. Using the electron backscatter diffraction (EBSD) technique, an uneven distribution of local plasticity in the plastic zone of impact-fractured specimens was established. A comparative analysis of specimens with equal impact toughness values at different test temperatures makes it possible to identify the mechanism of negative splitting influence compensation by the increased plasticity of certain specimen.
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Mizuguchi, Takashi, Rintaro Ueji, Hayato Miyagawa, Yasuhiro Tanaka, and Kazunari Shinagawa. "Fracture Behavior Transition by Change of Strain Rate in Dislocation-Induced Si Steels." Materials Science Forum 706-709 (January 2012): 2187–92. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2187.
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The fracture behavior transition due to the change of strain rate in 5%Si magnetic steel with dislocation microstructures was studied. The Si steel was multi-passed rolled at 800°C to a various reductions up to 50%. The room temperature tensile deformation was conducted at various strain rates from 10-5/s to 100/s. All rolled steels were fractured in ductile manners with local elongation (necking) at slower strain rate. When strain rate was faster, the local elongation disappeared and the fracture manner was turned to brittle. The strain rate at which fracture mechanism changed from ductile to brittle increased with the increasing of the reduction. On the other hand, the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found. The fractured tensile specimen with no local elongations contains deformation twins; whereas these deformation twins were not observed in the fractured specimen with local elongations. This result indicates that dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of toughness in Si steel.
10
Stradomski, Z., S. Stachura, and G. Stradomski. "Fracture Mechanisms in Steel Castings." Archives of Foundry Engineering 13, no. 3 (September 1, 2013): 88–91. http://dx.doi.org/10.2478/afe-2013-0066.
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Abstract The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.
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Timala, Rabindra Bhakta, and Nirmal Panthee. "Sternal Fracture Fixation with a Steel Wire: The New “Timala” Technique." Journal of Trauma and Injury 34, no. 3 (September 30, 2021): 170–76. http://dx.doi.org/10.20408/jti.2021.0014.
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Purpose Traumatic sternal fractures are rare but quite disabling injuries. Timely fixation of sternal fractures reduces pain and prevents respiratory complications. However, the fixation technique should be simple, effective, and readily available in local circumstances. Methods From January 2014 to March 2020, seven patients with sternal fracture/ dislocation underwent steel wire fixation with the new “Timala” technique. In this technique, adjacent ribs are anchored with two steel wires to form an “X” in front of the fractured segment of the sternum. Patients were followed up clinically and radiologically. Results Six of the patients were men and one was a female. Five of them had injuries due to falls and two were injured in road traffic accidents. Their age ranged from 18 years to 76 years, with a median age of 41 years. All seven patients experienced immediate recovery from pain and showed evidence of fracture healing on postoperative chest X-rays and clinical examinations. Conclusions Anchoring ribs to fix the sternum with steel wire is a safe, effective, easily available, and reproducible method to fix sternal fractures or dislocations.
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Nyrkova, L. I., P. E. Lisovy, L. V. Goncharenko, S. O. Osadchuk, V. A. Kostin, and A. V. Klymenko. "Regularities of Stress-Corrosion Cracking of Pipe Steel 09G2S at Cathodic Polarization in a Model Soil Environment." Physics and Chemistry of Solid State 22, no. 4 (December 30, 2021): 828–36. http://dx.doi.org/10.15330/pcss.22.4.828-836.
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Peculiarities of corrosion-mechanical fracture of 09G2S pipe steel samples in the conditions of cathodic protection were investigated. It was established that depending on the level of protective potential, stress-corrosion cracking of pipe steel of a ferrite-pearlite class 09G2S can occur by different mechanisms. The range of protective potentials was determined, at which the anodic dissolution and hydrogen embrittlement occur simultaneously during the fracture of steel, namely from -0.85 V to -1.0 V. The existence of the above mechanisms is confirmed by the change in the strength and viscosity properties of the steel and the morphology of the fractures. For steels of other manufacturing technology and grades, these potential areas may differ.
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Algarni, Mohammed. "Mechanical Properties and Microstructure Characterization of AISI “D2” and “O1” Cold Work Tool Steels." Metals 9, no. 11 (October 30, 2019): 1169. http://dx.doi.org/10.3390/met9111169.
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This research analyzes the mechanical properties and fracture behavior of two cold work tool steels: AISI “D2” and “O1”. Tool steels are an economical and efficient solution for manufacturers due to their superior mechanical properties. Demand for tool steels is increasing yearly due to the growth in transportation production around the world. Nevertheless, AISI “D2” and “O1” (locally made) tool steels behave differently due to the varying content of their alloying elements. There is also a lack of information regarding their mechanical properties and behavior. Therefore, this study aimed to investigate the plasticity and ductile fracture behavior of “D2” and “O1” via several experimental tests. The tool steels’ behavior under monotonic quasi-static tensile and compression tests was analyzed. The results of the experimental work showed different plasticity behavior and ductile fracture among the two tool steels. Before fracture, clear necking appeared on “O1” tool steel, whereas no signs of necking occurred on “D2” tool steel. In addition, the fracture surface of “O1” tool steel showed cup–cone fracture mode, and “D2” tool steel showed a flat surface fracture mode. The dimple-like structures in scanning electron microscope (SEM) images revealed that both tool steels had a ductile fracture mode.
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Niño-Barrera, Javier, José Sánchez-Alemán, Luis Gamboa-Martinez, and Carlos Cortes-Rodriguez. "Resistance to fracture due to cyclic fatigue of stainless steel manual files and its association to surface roughness." Acta Odontológica Latinoamericana 34, no. 1 (April 2021): 18–26. http://dx.doi.org/10.54589/aol.34/1/018.
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The aim of this study was to evaluate the possible association between the roughness of 5 brands of stainless steel endodontic files and their resistance to fracture due to cyclic fatigue. The study included five different brands of stainless steel endodontic files: SybroEndo Triple-Flex Files (Kerr, Glendora, USA), Ready Steel K-Flexofile (Dentsply Sirona, Ballaigues, Switzerland), Mani Flexile Files (Mani, Tochigi- Ken, Japan), FKG K-Files (FKG, La Chaux-de-Fonds, Switzerland) and Zipperer Flexicut Files (VDW, Munich, Germany). Twelve files per brand (total 60 files) were evaluated. File surface roughness over an area (Sa) was quantified using a focus variation microscope. Then the files were subject to a cyclical fatigue test to determine the number cycles to fracture due to fatigue and length of fractured fragment. Finally, fractographic analysis was performed using a scanning electron microscope. The electropolished Ready Steel K-Flexofile® files had the highest roughness according to Sa parameters, though they also had the highest resistance to fracture due to cyclic fatigue and the longest fractured fragment. Moderate positive correlation was found between fractured fragment length and roughness. The fractured surface showed characteristics of ductile fracture with cracks and plastic deformation. The electropolished stainless steel Ready Steel K-Flexofile® files were the most resistant to fracture due to cyclic fatigue even though they had highest surface roughness.
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Váňová, Petra, Jaroslav Sojka, Kateřina Konečná, and Taťána Radkovská. "Comparison of Behaviour of Different Variants of Hydrogenated TRIP Steels at Slow Strain Rate Tests." Key Engineering Materials 810 (July 2019): 70–75. http://dx.doi.org/10.4028/www.scientific.net/kem.810.70.
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The paper describes effect of hydrogen on mechanical properties and fracture characteristics of two types of C-Mn-Si TRIP steel; laboratory prepared steel TRIP 800 and commercially manufactured steel TRIP 780. TRIP steels are very promising materials thanks to their combination of a very good strength and toughness. However, these steels can be embrittled by hydrogen during technological operations related to galvanizing. That is why the knowledge of effects of hydrogen on the properties and fracture characteristics of the TRIP steels is of particular importance. In the presented study, effects of hydrogen were studied by tensile tests after electrolytical hydrogen charging. Electrolytical hydrogen charging was performed in 0.05 M solution of sulfuric acid with addition of potassium thiocyanate to promote hydrogen absorption. Hydrogen provoked embrittlement in both steel variants and changed their fracture micromechanism. Hydrogen embrittlement manifested itself mainly by a loss of plasticity. Index of hydrogen embrittlement, expressed on the basic of a relative drop of elongation to fracture, reached values about 77 % for the steel variant TRIP 800, resp. 83 % for the steel variant TRIP 780. No significant difference was observed between two steel variants studied. Concerning fractographic characteristics, steels containing hydrogen displayed quasi-cleavage fracture mostly on the edges of the sample and around elongated non-metallic inclusions.
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An, Gyubaek, Jeongung Park, Hongkyu Park, and Ilwook Han. "Fracture Toughness Characteristics of High-Manganese Austenitic Steel Plate for Application in a Liquefied Natural Gas Carrier." Metals 11, no. 12 (December 17, 2021): 2047. http://dx.doi.org/10.3390/met11122047.
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High-manganese austenitic steel was developed to improve the fracture toughness and safety of steel under cryogenic temperatures, and its austenite structure was formed by increasing the Mn content. The developed high-manganese austenitic steel was alloyed with austenite-stabilizing elements (e.g., C, Mn, and Ni) to increase cryogenic toughness. It was demonstrated that 30 mm thickness high-manganese austenitic steel, as well as joints welded with this steel, had a sufficiently higher fracture toughness than the required toughness values evaluated under the postulated stress conditions. High-manganese austenitic steel can be applied to large offshore and onshore LNG storage and fuel tanks located in areas experiencing cryogenic conditions. Generally, fracture toughness decreases at lower temperatures; therefore, cryogenic steel requires high fracture toughness to prevent unstable fractures. Brittle fracture initiation and arrest tests were performed using 30 mm thickness high-manganese austenitic steel and SAW joints. The ductile fracture resistance of the weld joints (weld metal, fusion line, fusion line + 2 mm) was investigated using the R-curve because a crack in the weld joint tends to deviate into the weld metal in the case of undermatched joints. The developed high-manganese austenitic steel showed little possibility of brittle fracture and a remarkably unstable ductile fracture toughness.
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Fu, Yu Dong, and Qing Fen Li. "Grain Boundary Fracture Behavior and Segregation of P under Low Tensile Stresses in Steel 2.25Cr1Mo and 12Cr1MoV." Key Engineering Materials 577-578 (September 2013): 193–96. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.193.
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Experimental investigation about the grain boundary fracture behavior and segregation behavior of phosphorus under low tensile stresses in steel 2.25Cr1Mo and 12Cr1MoV was carried out in this paper. AES (Auger electron spectroscopy) experiments and dynamic analyses on the non-equilibrium grain-boundary segregation (NGS) of phosphorus and the SEM photos of grain boundary fracture in Auger specimens of both steels were obtained. The variation of phosphorus segregation level in grain boundary at different aging time was studied. Results show that the non-equilibrium segregation of phosphorus occurred at the grain boundaries in the two steels while subjected to a tensile stress of 30MPa and held at 500°C. The corresponding critical time was about 1 hour for steel 2.25Cr1Mo and 3.5hour for steel 12Cr1MoV respectively. SEM photos of grain boundary fracture in Auger specimens of the test steels show that the grain boundary fracture rate increased with increasing concentration of phosphorus, and that the fracture toughness of steel 12Cr1MoV is much lower than the one of steel 2.25Cr1Mo.
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Feng, Chunjian, Zengli Peng, Xin Li, Shiliu Bao, and Ximin Jiang. "Ductile Fracture Prediction of X80 Pipeline Steel Using Void Growth Model." Metals 12, no. 6 (May 27, 2022): 923. http://dx.doi.org/10.3390/met12060923.
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In this study, the Void Growth Model (VGM) is employed to predict the ductile fracture of X80 pipeline steel. The X80 pipeline tends to be applied in challenging scenarios, such as extremely deep water and long-distance pipelines, which might cause a ductile fracture; however, the study of ductile fractures for pipeline steel is rare, especially for X80 pipeline steel. To understand ductile fractures of X80 pipeline steel, a hybrid numerical–experimental calibration method is used to determine the fracture parameter for the VGM model. The toughness capacity defined by the critical void growth index (VGI) in this study is determined to be 4.304. A shear-tension specimen is applied to verify the calibrated VGM. The results show that the calibrated VGM can predict the fracture initiation of the shear-tension specimen. In addition, the fracture of the shear-tension specimen initiates at the center of the section and propagates to the edge of the groove of the specimen. The initiation of fracture is identical to the testing observation.
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Gervas'ev, Michail A., Valentina A. Sharapova, and Aleksey A. Berdnikov. "Effect of Micro-Alloying with Boron and Niobium on Properties of Cr-Mn-Mo Steels." Materials Science Forum 946 (February 2019): 3–7. http://dx.doi.org/10.4028/www.scientific.net/msf.946.3.
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Economically alloyed steels for critical details of drill pipes have been studied. Effect of microalloying on structure and properties has been investigated. The article shows that boron and niobium additives change the structure and properties of Cr-Mn-Mo steels after quenching and high tempering. Methods of optical and electron microscopy have been used. Basic mechanical properties and impact strength of investigated steels are determined. Optical and electronic fractography has been carried out. The quantitative content of the ductile component is determined in steel fracture. It is shown that steel microalloying leads to a substantial structure refinement. This is due to the influence of niobium on the austenite grain value. An increase in the amount of carbide particles leads to structure refinement with an increased molybdenum content. Boron microadditives allow obtaining the tempered martensite structure throughout the product section. This provides an increase in both the strength and ductile properties. Combined microalloying of chromium-manganese-molybdenum steel with additions of boron up to 0.005 % and niobium up to 0.05 % makes it possible to increase the strength and reduce the tendency to brittle fractures significantly. The nature of the fracture becomes completely ductile. Distinct cleavage fracture surface feature “river patterns” are observed in unmodified steels. Сleavage facetes are large enough, it proves the presence of large grains in the steel. Microalloying changes the destruction mechanism, it becomes a ductile “dimple rupture”. An increase in the molybdenum content to 0.6 % makes it possible to obtain strength above 1100 MPa in microalloyed steel.
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Toribio, Jesús, Beatriz González, Juan Carlos Matos, and F. J. Ayaso. "Anisotropic Fracture Behaviour of Progressively Drawn Pearlitic Steel." Key Engineering Materials 452-453 (November 2010): 1–4. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.1.
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This paper analyses the differences in fracture behaviour of two cold drawn pearlitic steels with different degree of strain hardening: a slightly drawn bar and a heavily drawn wire. The load-displacement curve F-u was analysed in the two cases, with special emphasis in the characteristic points of the plot: the load defining the end of linear behaviour (Fe), the final fracture load (Fmax) and, in the heavily drawn steel, the pop-in load (FY). Results demonstrate that slightly drawn steels exhibit isotropic fracture behaviour with crack propagation along its own plane (mode I propagation). On the other hand, heavily drawn steels exhibit a markedly anisotropic fracture behaviour with crack deflection (mixed mode propagation), and vertical fracture embryos suddenly appear associated with the pop-in instant. This special fracture mode is a consequence of the markedly oriented microstructure of the heavily drawn steel.
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Wang, Deng Wang, Xue Jun Qin, Shi Ying Tang, and Wen Xiang Liu. "Dynamic Fracture of the 20# Cylindrical Steel Shell under Inside-Explosion Loading." Applied Mechanics and Materials 189 (July 2012): 245–49. http://dx.doi.org/10.4028/www.scientific.net/amm.189.245.
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Dynamic fracture of explosion containment vessels subjected to internal blast loads is the foundation for conducting safety assessment and failure analysis of explosion containment vessels. The experiments were carried out to investigate dynamic fracture characteristics of cylindrical steel shells subjected to internal blast loadings at the centers. The elastic-plastic response of cylindrical steel shells was conducted using nonlinear dynamic finite element analysis code LS-DYNA. The fracture mode and fracture mechanism of a cylindrical shell were specially studied through analysis of deformation， macrographs of fracture surface and elastic-plastic response. The results show that dynamical ductility deformations appear and the shear bands form when the cylindrical steel shell expands under internal blast loading. The cylindrical steel shell fractures preferentially along the shear bands due to its softening effect. The fracture mechanism is that the shear bands tear under tensile circumferential stress. The shear bands and the tensile circumferential stress dominate the final fracture mode. The fracture mode is of the ductile fracture.
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Islam, Mohammed Aminul, and Yo Tomota. "Plane bending fatigue behavior of interstitial-free steel at room temperature." International Journal of Materials Research 97, no. 11 (November 1, 2006): 1559–65. http://dx.doi.org/10.1515/ijmr-2006-0243.
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Abstract Interstitial-free steels are widely used as thin sheet for automobile external panels. For this type of application, essential properties of the steel are deep-drawability and stretch-formability. However, low-strength interstitial-free steel is nearly pure iron and work on fatigue fracture behavior of this steel might be adopted as a basic study to understand the behavior of high-strength steels used for structural components. In this study, the fatigue fracture behavior of low-strength interstitial-free steel has been studied at room temperature in air and in an argon atmosphere. Fractographic observations on fatigue fracture surfaces reveal a mixed type of fracture mode (intergranular and transgranular cracking) for all specimens. The major portion of intergranular fracture has been found at the regions of low and medium crack lengths. Further increase in the crack length causes a decrease in the proportion of intergranular cracking and, finally, the fracture mode becomes completely transgranular. At the same test temperature, the proportion of intergranular fracture drastically decreased when the test was carried out in the argon atmosphere.
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Liu, Xiao, and Long Mei Wang. "Effect of Nitrogen on the Mechanical Properties of Heat-Resisting Steel." Advanced Materials Research 535-537 (June 2012): 571–75. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.571.
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In this paper, the effect of N addition on mechanical properties of 21Cr-11Ni austenitic heat-resisting stainless steel was investigated. Scanning electron microscopy was used to study the fracture surfaces in the steels. N in 21Cr–11Ni heat-resisting steel can play a role of stabling austenite and ensuring the structure and mechanical properties in high temperatures. Fracture is changed from cleavage to ductile fracture to 21Cr–11Ni heat-resisting steel, and the strength of test steel are improved at room temperature by adding N, the tensile strength is increased by 8.33%. And the creep rupture strength is improved. The fracture time of the steel containing 0.2% N is 3.2 times higher than the steel containing 0.14% N at 1144K.
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Yang, L., and A. Fatemi. "Impact Resistance and Fracture Toughness of Vanadium-Based Microalloyed Forging Steel in the As-Forged and Q&T Conditions." Journal of Engineering Materials and Technology 118, no. 1 (January 1, 1996): 71–79. http://dx.doi.org/10.1115/1.2805936.
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Microalloyed (MA) steels are a family of steels which are becoming an increasingly important economic alternative to the traditional quenched and tempered (Q&T) steels. Impact resistance and fracture toughness of vanadium-based MA forging steel, which is the most commonly produced MA steel, are investigated in this study. To compare the behavior with the Q&T steel, both the as-forged and the Q&T conditions are evaluated. Experimental results from Charpy V-notch impact and fracture toughness (KR-curve and JIC) tests are presented and discussed. Correlations between fracture resistance properties based on several proposed equations in the literature are also examined.
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Zhang, Peng, Yaniv Brick, and Mukul M. Sharma. "Numerical study of an electrode-based resistivity tool for fracture diagnostics in steel-cased wellbores." GEOPHYSICS 83, no. 2 (March 1, 2018): D41—D48. http://dx.doi.org/10.1190/geo2017-0355.1.
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The efficiency of a hydraulic fracture treatment depends primarily on the dimensions and orientation of propped fractures. We have developed a novel electrode-based resistivity tool concept for mapping proppant distribution in hydraulic fractures in steel-cased wellbores. The proposed tool configuration is shown to overcome the severe limitations of induction tools for the detection and resolution of propped fracture geometries in such wellbores. The concept makes use of an array of electrically insulating gap subsections, which are installed and cemented as permanent parts of the casing string, separating the casing sections. By imposing voltages on the insulating gaps, the conductive casing is excited directly, thus avoiding through-casing signal degradation caused by its high electrical conductivity. This allows us to detect subsurface fractures propped with conductive proppant. The envisioned measurements are performed by running a bottom-hole assembly into the fractured zone on a coiled tubing to impose a voltage across each insulating gap at a time, before and after hydraulic fracture operations. For each excited insulating gap, the voltages across all other insulating gaps are recorded by the electronics embedded in the insulating gaps. To interpret the envisioned measurements, a forward model of the tool, based on a finite volume method, is developed, and the design’s sensitivity to the fracture parameters is demonstrated via case studies. The results indicate that measurements made based on the proposed concept will be highly sensitive to a fracture’s location, size, and angle, and less sensitive to a fracture’s shape. Simulations also indicate that direct contact of the fracture with an excited casing section enables the differentiation of fractures of up to a 100 m radius. Fractures with angles greater than 30° or aspect ratios greater than two can also be distinguished from the ones orthogonal to the well or with an aspect ratio of one.
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Tohgo, Keiichiro, Tomoya Ohguma, Yoshinobu Shimamura, and Yoshifumi Ojima. "Influence of Strength Level of Steels on Fatigue Strength and Fracture Morphology of Spot Welded Joints." Key Engineering Materials 462-463 (January 2011): 94–99. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.94.
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In this paper, fatigue tests and finite element analyses are carried out on spot welded joints of mild steel (270MPa class) and ultra-high strength steel (980MPa class) in order to investigate the influence of strength level of base steels on fatigue strength and fracture morphology of spot welded joints. From the fatigue tests the following results are obtained: (1) Fatigue limit of spot welded joints is almost the same in both steels. (2) Fatigue fracture morphology of spot welded joints depends on the load level in the ultra-high strength steel, but not in the mild steel. From discussion based on the finite element analyses the following results are obtained: (3) The fatigue limit of spot welded joints can be predicted by stress intensity factors for a nugget edge, fracture criterion for a mixed mode crack and threshold value for fatigue crack growth in base steel. (4) Plastic deformation around a nugget in spot welded joints strongly affects the fatigue fracture morphology.
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Ünal, Halil Ibrahim, Hakan Atapek, Baran Gürkan Beleli, Seyda Polat, Serap Gümüs, and Ersoy Erisir. "Characterization of the fracture behaviour of X42 microalloyed pipeline steel." International Journal of Structural Integrity 6, no. 5 (October 5, 2015): 567–77. http://dx.doi.org/10.1108/ijsi-09-2013-0020.
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Purpose – The purpose of this paper is to investigate the fracture of grade X42 microalloyed steel used as pipe material after tensile test at room temperature and impact tests at 0, −20 and −40°C, respectively. Design/methodology/approach – In the first stage of the study, X42 steels in the form of sheet and pipe materials were selected and etched samples were characterized using light microscope. In the second stage, mechanical properties of steels were obtained by microhardness measurements, static tensile and impact tests and all the broken surfaces were examined by scanning electron microscope to determine the fracture type as a function of both microstructure and loading. Findings – The examinations revealed that: first, the sheet material had a typical ferritic-pearlitic matrix, second, the transverse section of the sheet steel exhibited a matrix consisting of polygonal ferrite-aligned pearlite colonies and the longitudinal one had elongated ferrite phase and pearlite colonies in the direction of rolling, third, ferrite and pearlite distribution was different from the sheet material due to multiaxial deformation in the pipe material, fourth, tensile fracture surfaces of the steels had typical dimple fracture induced by microvoid coalescence, fifth, impact fracture surfaces of the steels changed as a function of the test temperature and cleavage fracture mode of ferritic-pearlitic matrix became more dominant as the temperature decreased, and sixth, grain morphology had an effect on the fracture behavior of the steels. Originality/value – The paper explains the fracture behaviour of X42 microalloyed pipeline steel and its fractographical analysis.
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Li, Xiangyu, Fugang Li, Minzu Liang, Kefan Zhang, and Zhandong Tian. "Research on Dynamic Constitutive Model and Fracture Characteristics of Two High Strength Steels." Journal of Physics: Conference Series 2168, no. 1 (January 1, 2022): 012016. http://dx.doi.org/10.1088/1742-6596/2168/1/012016.
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Abstract 58SiMn and 50SiMnVB are commonly used shell materials in bombs, and their dynamic constitutive model and fracture properties directly determine the mass distribution of the bomb. Tensile tests were carried out on two high-strength steels, and the parameters of the yield point, tensile strength and plastic failure strain as well as the John-Cook model were determined. The fracture morphologies of the two steels in the quasi-static tension and in the dynamic tension were analyzed. The research results show that the yield strength of 58SiMn steel remains unchanged with increasing strain rate. The yield strength and tensile strength of 50SiMnVB increase as the rate of elongation increases, and the ability to plastically deform decreases, which shows the properties of embrittlement under high speed loading. With the same elongation rate, 50SiMnVB steel has higher strength and toughness. 58SiMn steel is a tensile brittle fracture from a macroscopic point of view and a quasi-split fracture from a microscopic point of view; 50SiMnVB steel is a mixed lap shear fracture under axial tensile load. With increasing loading rate, the tensile fracture tends to pure shear fracture.
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Deng, Chu Han. "Fracture Feature and Failure Cause Analysis of Cable Wire on Bridges." Applied Mechanics and Materials 178-181 (May 2012): 2472–78. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.2472.
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Cable wire is characterized by light weight and high strength and is widely applied in long span bridges. However, steel cable wire is vulnerable to fatigue and corrosion, which has been proved to be true through collapses of several bridges because of cable failure. This paper will the following 4 types of the fractures of steel wire: cone-shaped fracture, serrated fracture, cup-shaped fracture and step-like fracture to explore failure cause of cable wire. This paper also illustrates the fracture feature respectively and failure causes considering environmental and loading condition of cable.
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Liu, Hong Bo, Long Jun Xu, Shuang Li, and Yong Song Shao. "A Model of Steel Frame for Simulating Connection Fractures." Key Engineering Materials 452-453 (November 2010): 469–72. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.469.
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Following the 1994 Northridge earthquake, widespread damages were discovered in welded steel moment frame buildings. In order to accurately simulate the typical seismic damage of welded steel moment frame structures, a new simplified model is proposed for performing seismic evaluation of welded steel moment frame structures. In this model, the slabs effect is considered, as well as the effects of the slip between slabs and steel beams, deformation of panel zone and connection fractures. Fracture toughness demands were evaluated in terms of the mode I stress intensity factor. The model was employed in simulation of seismic damage of Blue Cross Building which experienced fractured connections in the Northridge earthquake. It indicates that the model can accurately predict the earthquake response of welded steel moment frame structures and estimate the level of damage. The approach proposed in this paper has important meaning to the research on seismic damage of steel frame which may experience fractured connections.
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Atrens, Andrej, Qian Liu, Clotario Tapia-Bastidas, Evan Gray, Bartolomeus Irwanto, Jeff Venezuela, and Qinglong Liu. "Influence of Hydrogen on Steel Components for Clean Energy." Corrosion and Materials Degradation 1, no. 1 (June 13, 2018): 3–26. http://dx.doi.org/10.3390/cmd1010002.
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The influence of hydrogen on the mechanical properties of four, medium-strength, commercial, quenched-and-temped steels has been studied using the linearly increasing stress test (LIST) combined with cathodic hydrogen charging. The relationship was established between the equivalent hydrogen pressure and the hydrogen charging overpotential during cathodic hydrogen charging, though the use of electrochemical permeation experiments and thermal desorption spectroscopy. The cathodic hydrogen charging conditions were equivalent to testing in gaseous hydrogen at hydrogen fugacities of over a thousand bar. Under these hydrogen-charging conditions, there was no effect of hydrogen up to the yield stress. There was an influence of hydrogen on the final fracture, which occurred at the same stress as for the steels tested in air. The influence of hydrogen was on the details of the final fracture. In some cases, brittle fractures initiated by hydrogen, or DHF: Decohesive hydrogen fracture, initiated the final fracture of the specimen, which was largely by ductile micro-void coalescence (MVC), but did include some brittle fisheye fractures. Each fisheye was surrounded by MVC. This corresponds to MF: Mixed fracture, wherein a hydrogen microfracture mechanism (i.e., that producing the fisheyes) competed with the ductile MVC fracture. The fisheyes were associated with alumina oxide inclusion, which indicated that these features would be less for a cleaner steel. There was no subcritical crack growth. There was essentially no influence of hydrogen on ductility for the hydrogen conditions studied. At applied stress amplitudes above the threshold stress, fatigue initiation, for low cycle fatigue, occurred at a lower number of cycles with increasing hydrogen fugacity and increasing stress amplitude. This was caused by a decrease in the fatigue initiation period, and by an increase in the crack growth rate. In the presence of hydrogen, there was flat transgranular fracture with vague striations with some intergranular fracture at lower stresses. Mechanical overload occurred when the fatigue crack reached the critical length. There was no significant influence of hydrogen on the final fracture.
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Wang, Tie Bao, Chun Xiang Cui, Lin Fang, and Shao Jing Bu. "Fracture Behavior and Microstructure of 60Si2MnA Spring Steels Modified by V-Nb Inoculants." Advanced Materials Research 415-417 (December 2011): 1085–89. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1085.
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The microstructure of V-Nb inoculants after melt spinning was investigated by performing TEM examination and to the sample steels, the prior austenite grain sizes and fracture morphology were investigated by SEM observation. The results show that the V-Nb inoculants obtained is amorphous and the sample steel modified by V-Nb inoculants which make it possible to be a large amount of nucleation centers existing in the form of (V, Nb)C and achieve the effect of grain refinement in the solidification stages of liquid steel has been found to have the finest prior austenite grain sizes and the average prior austenite grain sizes of steel without addition of V and Nb(Steel A), steel microalloyed with V and Nb(Steel B) and steel modified by V-Nb inoculants(Steel C) are respectively 30μm, 20μm and 10μm. Tensile behavior of samples was studied under tempering at 400°C for 30 min after quenching, tensile results show that the fracture of steel modified by V-Nb inoculants appears dimples which represent ductile fracture. However the tensile fracture of V-Nb microalloyed steel is mixture of quasi-cleavages and dimples. Under tempering at 550°C for 30 min, Steel B and Steel C both show a fractograph with cleavage fracture.
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Shi, Gang, and Yufeng Chen. "Investigation of ductile fracture behavior of lap-welded joints with 460 MPa steel." Advances in Structural Engineering 21, no. 9 (December 18, 2017): 1376–87. http://dx.doi.org/10.1177/1369433217746342.
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Fractures in welded connections usually occurred at Earthquake. The lap-welded joints are an important type of welded connections in high strength steel structures. In this article, the ductile fracture behavior of lap-welded joints has been studied experimentally and numerically with 460 MPa steel. A series of coupon tests were used to determine two corresponding weld materials (ER55-D2 and ER55-G) mechanical properties. Two micromechanics models (void growth model and stress-modified critical strain models) had been calibrated by circumferentially notched tension specimens and calculated the fracture parameters numerically, which had been applied in predicting in five lap-welded joints. The experimental study showed that the fracture mode of 460 MPa lap-welded joints exhibited plastic damage under the tension tests. Numerical analysis of the fracture parameters also showed that the ductile fracture behavior of lap-welded joint with ER55-G was better. The study establishes an accurate numerical model for analyzing the ductile fracture behavior of Q460 high strength steel lap-welded joints that is applicable in predicting the fracture failure of welded steel structures.
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Kononov, Dmitry, Svetlana Gubenko, Igor Ivanov, and Sergey Urushev. "Using fractal characteristics to analyze the development of whole-rolled wheel destruction." MATEC Web of Conferences 329 (2020): 02009. http://dx.doi.org/10.1051/matecconf/202032902009.
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Purpose: Determination of mechanical characteristics of wheel steel by analyzing the development of destruction of solid-rolled wheels. Methods: Determination of the crack resistance of all-rolled wheels by testing samples from wheel steel for off-center tension with an edge crack, fractal parametrization of the fracture relief by processing the fracture photo using the R/S analysis method for fracture sections, which allows determining both the total fractal dimension of the fracture (the average for all sections), and in a specific area where there are changes in the fracture morphology. Construction of the dependence of the crack resistance parameter on the fractal dimension. Results: The possibility of analyzing wheel steel fractures by studying their fractal dimension is determined. A method of fractal parametrization of the wheel steel fracture relief is developed, which allows to obtain the value of the fractal dimension in different directions of crack growth. The fractal dimension of wheel steel is determined for different hardness values (after annealing and after thermal improvement). The dependence of the fractal dimension on the ductility characteristics of wheel steel is revealed: the lower the ductility characteristics (elongation, relative contraction) and, accordingly, the higher the hardness, the lower the value of the fractal dimension. The dependence of the fractal dimension on the coefficient of crack resistance of wheel steel KIC is determined, which makes it possible to predict the crack resistance of wheel steel depending on the fractal dimension of the fracture, as well as to judge the nature of the fracture – brittle, viscous or fatigue. Practical significance: The use of fractal fracture parameterization avoids time-consuming tests when determining the mechanical characteristics of wheel steel, as well as to determine the mechanical properties in the case when other methods are no longer applicable (small sample sizes).
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Qu, Shi Yao, Zeng Da Zou, and Xin Hong Wang. "Shear Strength and Fracture Behavior of SiCw/Al2O3 Composite-Carbon Steel Brazed Joints." Key Engineering Materials 297-300 (November 2005): 2441–46. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2441.
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Shear strength and fracture behavior of Al2O3 matrix ceramic composite brazed joints to carbon steel with Ag-Cu-Ti brazing alloy in flow argon have been studied by means of SEM, EDX and all-purpose testing machine. Results have shown that there is a close relationship between the shear strength and the fracture form of brazed joints. The fracture occurring completely in the composite near the composite/filler metal interface corresponds to the low strength of a joint, and the strength of the joint fractured partially in the composite usually increases with decreasing the proportion of the composite on the fracture surface in the steel side. When the fracture occurs in the reaction layer between the composite and the filler metal, the closer the fractured position comes to the composite/reaction layer interface, the higher the joint strength. The maximum shear strength is obtained when the fracture occurs fully at the interface.
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Tan, Zhaoqiang, Yong Liu, Xiaolin Huang, and Songlin Li. "Fatigue Behavior of Alloy Steels Sintered from Pre-Alloyed and Diffusion-Bonding Alloyed Powders." Metals 12, no. 4 (April 12, 2022): 659. http://dx.doi.org/10.3390/met12040659.
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Porosity and phases are considered to be two key factors for the fatigue performance of powder metallurgy steels. In this paper, the fatigue strengths of the alloy steels sintered from two typical types of powders, pre-alloyed Fe-Cr-Mo (Astaloy CrM), and diffusion-bonding alloyed Fe-Cu-Mo-Ni (Distaloy AE), were comparatively analyzed in view of the geometry of porosity, the phases constitution, and fractography of fracture. Different modes of fatigue fracture were distinguished between the two materials. Namely, a trans-particle fracture is predominant in the Disitaloy AE steel due to the heterogeneous phases which consist of soft phases in powder interior and hard phases along powder borders. In contrast, the fatigue fracture of the Astaloy CrM steel with a homogeneous mono-phase of martensite is characterized by an inter-particle fracture at the sintering necks. Moreover, the fatigue endurance limit of the Distaloy AE steel was not pronouncedly improved by increasing sintering temperature in comparison with the Astaloy CrM steel. This was attributed to the softening of the network constructed by martensite at sintering necks. A modified Murakami model which considers micro-scale defect and micro-hardness is effective to predict the fatigue performance of the alloy steels sintered from pre-alloyed and diffusion-bonding alloyed powders, respectively.
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An, Gyubaek, Jeongung Park, Mituru Ohata, and Fumiyoshi Minami. "Fracture Assessment of Weld Joints of High-Strength Steel in Pre-Strained Condition." Applied Sciences 9, no. 7 (March 28, 2019): 1306. http://dx.doi.org/10.3390/app9071306.
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Unstable fractures tend to occur after ductile crack initiation or propagation. In most collapsed steel structures, a maximum 15% pre-strain was recorded, at the steel structural connections, during the great earthquake of 1995, in Japan. Almost-unstable fractures were observed in the beam-to-column connections, where geometrical discontinuities existed. Structural collapse and unstable failure occurred after large-scale plastic deformations. Ship structures can also suffer from unstable fractures in the welded joints. The fracture resistance of butt-welded joints subjected to tension in the pre-strained condition was estimated by considering the toughness deterioration, due to pre-strain and toughness correction for constraint loss in a tension specimen. The target specimen for this fracture assessment was a double-edged, through-thickness crack panel, with a crack in the weld joint (heat-affected zone (HAZ)). The critical fracture toughness value (crack tip opening displacement (CTOD)) of a large structure with pre-strain, which was applied to the HAZ region, was estimated from a small-scale, pre-stained, three-point bend specimen. Fracture toughness values, evaluated by a CTOD test, were recently mandated for shipbuilding steel plates. The critical fracture toughness value is a very useful parameter to evaluate the safety of huge ship structures.
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Zhang, X., Lina Zhang, Jun Jie Qi, and Yue Ma. "Study of Bonding of Grain Boundaries in Steels Using EELS." Materials Science Forum 475-479 (January 2005): 4063–66. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.4063.
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A novel EELS technique was developed to study bonding of grain boundary in many kinds of steels. We measured the normalized intensities of Fe white lines and calculated the occupancies of 3d states of iron, and then analyzed the relationship of the occupancies of 3d states of iron and the fracture property of the steels. We found that if the grain boundary has a different occupancy of 3d state of iron from that of the bulk, the steel tends to have an intergranular fracture, whereas if the grain boundary has almost the same occupancy of 3d state as the bulk, the steel tends to have a transgranular fracture. Our result shows that the difference in the occupancy of 3d state between bulk and grain boundary can be used to study the fracture mode at grain boundary in steel.
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Zhao, Chuan, Shushan Wang, Cean Guo, Yuhui Sun, Xuncheng Guo, and Feng Ma. "Mechanism of Microscopic Fracture of Typical Shell Steel under Impact Loading." Shock and Vibration 2022 (February 23, 2022): 1–12. http://dx.doi.org/10.1155/2022/1508114.
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The aim of the current study was to investigate the effects of strain rate and metallographic structure on the fracture mode and fracture pattern of a typical shell steel material under impact loading. A ballistic gun was used to launch a spherical tungsten alloy projectile to impact target 50SiMnVB and 60Si2Mn steel plates. The morphological characteristics of the cracks on different target plates were observed under a metallurgical microscope, and the effects of the strain rate and metallographic structure on the fracture mode and fracture pattern were analyzed. The results showed that when the strain rate was relatively low, the material mainly produced ductile fracture and brittle trans-granular fracture under impact loading; when the strain rate was relatively high, intergranular fracture and cleavage fracture were the main modes of fracture under impact loading. In addition, at higher strain rates, the metallurgical form mainly influenced the pattern of fracture of the material, with tempered troostite being more likely to produce a mixture of shear and tensile fractures than tempered sorbite. The results obtained provide an experimental basis for the mechanism of microscopic fracture of shell steel materials and, to a certain extent, reveal the correlations between fragmentation and the strain rate and microstructure of the material.
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Tyson, W. R. "Experimental Techniques in Fracture Characterization." Materials Science Forum 567-568 (December 2007): 39–44. http://dx.doi.org/10.4028/www.scientific.net/msf.567-568.39.
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Characterization of fracture toughness is discussed in relation to specification of steels for northern pipelines. The state of the art and research trends in measurement of CTOD for girth welds and CTOA for linepipe steel are described.
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Hashemi, S. H., I. C. Howard, J. R. Yates, and R. M. Andrews. "Measurement and Analysis of Impact Test Data for X100 Pipeline Steel." Applied Mechanics and Materials 3-4 (August 2006): 369–76. http://dx.doi.org/10.4028/www.scientific.net/amm.3-4.369.
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Charpy upper shelf energy is widely used as a fracture controlling parameter to estimate the crack arrest/propagation performance of gas transportation pipeline steels. The measurement of this fracture criterion particularly for modern steels and its apportion into different components, i.e. fracture and non-related fracture energy, are of great importance for pipeline engineers. This paper presents the results of instrumented Charpy impact experiments on high-grade pipeline steel of grade X100. First, the instrumentation technique including the design and implementation of a strain gauge load-cell and the details of the data-recording scheme are reviewed. Next, the experimental data obtained from the Charpy impact machine so instrumented are presented and discussed. These include the test data from full and sub-sized Charpy V-notched specimens. The instrumented Charpy machine was able to capture the load history in full during the fracture process of the test specimens resulting in a smooth load-time response. This eliminated the need for filtering used in similar test techniques. From the recorded test data the hammer displacement, impact velocity and fracture energy were numerically calculated. The results showed that there was a significant drop in hammer velocity during the impact event. This resulted in a change in the fracture mode from dynamic to quasi-static which was more appreciable for full-size Charpy test samples. As a result, sub-sized specimens might be preferable for impact testing of this steel in order to guarantee the conditions of dynamic crack propagation in the specimen ligament. Accurate analysis of the instrumented impact test data showed that the ratio of crack initiation energy to propagation energy was around 30% for the X100 steel. It can be concluded that in impact testing of high-grade pipeline steel a significant portion of overall fracture energy is consumed in non-related fracture processes. This high fracture initiation energy should be accounted for if the current failure models are going to be used for toughness assessment of highstrength low-alloy gas pipeline steels.
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Beskardes, G. Didem, W. Anderson McAliley, Mohsen Ahmadian, David T. Chapman, Chester J. Weiss, and Jason E. Heath. "Power Density Distribution in Subsurface Fractures Due to an Energized Steel Well-casing Source." Journal of Environmental and Engineering Geophysics 24, no. 2 (June 2019): 285–97. http://dx.doi.org/10.2113/jeeg24.2.285.
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Robust in situ power harvesting underlies the realization of embedded wireless sensors for monitoring the physicochemical state of subsurface engineered structures and environments. The use of electromagnetic (EM) contrast agents in hydraulically fractured reservoirs, in coordination with completion design of wells, offers a way to transmit energy to remotely charge distributed sensors and interrogate fracture width, extent, and fracture-stage cross-communication. The quantification of available power in fracture networks due to energized steel-cased wells is crucial for such sensor designs; however, this has not been clarified via numerical modeling in the limit of Direct Current (DC). This paper presents a numerical modeling study to determine the EM characteristics of a subsurface system that is based on a highly instrumented field observatory. We use those realistic field scenarios incorporating geometry and material properties of contrast agents, the wellbore, and the surrounding geologic environment to estimate volumetric power density near the wellbore and within hydraulic fractures. The numerical modeling results indicate that the highest power densities are mainly focused around the wellbore excited by a point current source and the fracture boundary. Using DC excitation, the highest power density in the fracture is at the fracture tip. The relatively high-power density on the order of tens of mW/m 3 at the vicinity of the wellbore and at fracture tips suggests that remote charging of sensor devices may be readily possible. Simulation results also show that the region of the highest power density can be significantly increased when the EM source is located inside a conductive fracture, which may lead to a promising deployment strategy for embedded micro-sensors in geologic formations.
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Das, Sreekanta, J. J. Roger Cheng, and David W. Murray. "Behavior of wrinkled steel pipelines subjected to cyclic axial loadings." Canadian Journal of Civil Engineering 34, no. 5 (May 1, 2007): 598–607. http://dx.doi.org/10.1139/l06-165.
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Full-scale laboratory tests were carried out at the University of Alberta to investigate the post-wrinkling ultimate behavior of steel pipelines. The pipe specimens exhibited extreme ductile behavior and did not fail in fracture under monotonically increasing axisymmetric compressive axial loads and displacements. Fractures developed at the wrinkled region, however, when a wrinkled pipe specimen was subjected to cyclic strain reversals due to unloading and loading of primary loads. This paper presents test procedures, complete post-wrinkling behavior, fracture limit strain values, and fracture configurations obtained from full-scale tests on wrinkled pipe specimens under cyclic and monotonic axial loadings. Key words: steel pipeline, laboratory testing, cyclic axial loading, wrinkling, post-wrinkling behavior, accordion failure, strain reversals, fracture.
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Bakhracheva, Yulia. "Fractographic Study of the Mechanism of Destruction of the Nitrocarburized Layer." NBI Technologies, no. 2 (December 2020): 26–31. http://dx.doi.org/10.15688/nbit.jvolsu.2020.2.5.
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In this paper we investigate the nature of the impact fracture of steels 20 and 20Cr specimens in the nitrocarburized layer and in the core. The object of the study were the samples after thermocycling and isothermal nitrocarburizing. As the results showed, the greatest increase in impact ductility is achieved in five cycles of nitrocarburizing. It is shown that the destruction of the hardened layer and the steel core after the isothermal process is quasirectangular in nature. The presence of the diffusion layer treated by modes of thermocycling nitrocarburizing, areas of ductile fracture and quasi-cleavage in the fracture indicates greater intensity of the process of destruction in comparison with the isothermal process, in which areas of intergranular fracture are present and ductile fracture elements are not present in the fracture. Thus, the fractographic study revealed some features of the mechanism of steel destruction after chemical-thermal nitrocarburizing in comparison with the isothermal process. During thermal cycling of steels, a large amount of the ductile component is observed in the fracture. As the results showed, the greatest increase in impact ductility is achieved in five cycles. In steel 20Cr, the impact ductility increases by 2 times, and in steel 20 by 2.6 times. Increasing the number of cycles to 9 leads to a significant reduction in impact ductility. So in steel 20Cr after chemical-thermal nitrocarburizing, the impact ductility values become less than after classical processing. A further increase in the number of cycles leads to an even greater decrease in the impact ductility values.
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Liu, Xiao, and Jing Long Liang. "Effect of Ce on Microstructure and Mechanical Properties of 21Cr-11Ni Austenitic Stainless Steel." Advanced Materials Research 711 (June 2013): 95–98. http://dx.doi.org/10.4028/www.scientific.net/amr.711.95.
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The effect of Ce on structure and mechanical properties of 21Cr11Ni austenitic stainless steels were studied by metallographic examination, scanning electron microscope (SEM), tensile test. The results show that the proper amount of Ce can refine microstructure of austenitic stainless steel. Fracture is changed from cleavage to ductile fracture by adding Ce to austenitic stainless steel. 21Cr11Ni stainless steel containing 0.05% Ce can improve its high temerature strength, and the strength is increased 21.81% at 1073K respectively comparing with that of 21Cr11Ni stainless steel without Ce.
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Scarpini Cândido, Verônica, and Sergio Neves Monteiro. "The Effect of Phase Transformation on the Tensile Fracture of Austenitic Stainless Steel." Materials Science Forum 869 (August 2016): 508–13. http://dx.doi.org/10.4028/www.scientific.net/msf.869.508.
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The tensile fracture of two austenitic stainless steels with different degrees of stability for low temperature strain induced martensitic transformation was investigated. A stable AISI type 310 stainless steel displayed typical tensile stress-strain curves with decreasing work hardening rate at temperatures in the interval of 25 to-196°C, in which no martensitic transformation occurred. By contrast, a metastable type 302 stainless steel with martensitic transformation from 25 to-196°C showed a range of plastic deformation with increasing work hardening rate. The fracture of the stable 310 steel presented the characteristic cup and cone ductile aspect with micro dimples and sparse evidence of intergranular cracks. On the contrary, the martensitic transformation in the metastable 302 steel causes a neckless fracture with generally brittle appearance, despite the relatively high strain attained at fracture. At-80 and-196°C, associated with higher amount of transformed martensite, the fracture surface was covered with micro-craters formed around inclusions enveloped by thin strain induced martensite lamellae.
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Zrilić, Misa, Marko Rakin, Aleksandar Sedmak, R. Aleksić, Z. Cvijović, and Miodrag Arsić. "Ductile Fracture Prediction of Steam Pipeline Steel." Materials Science Forum 518 (July 2006): 537–42. http://dx.doi.org/10.4028/www.scientific.net/msf.518.537.
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Considering the conditions to which steels used for the manufacture of steam pipelines are exposed, the micromechanism of their destruction in exploitation is exclusively the ductile one. In order to make an estimation of the level of the damage that occurs in exploitation, in this paper a combined experimental and numerical procedure has been developed based on micromechanical or local approach to the fracture mechanics of metallic materials. After the analysis of the results obtained for micromechanical criterion of failure for virgin steel and that used in the steam pipeline, a proposal for prolongation of the working life of tested steel for steam pipelines until the next overhaul is given.
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An, Gyubaek, Seunglae Hong, Jeongung Park, and Ilwook Han. "Investigation of Correlation Between Fracture Toughness and Charpy Impact Energy of Cryogenic Steel Welds." Journal of Nanoscience and Nanotechnology 21, no. 9 (September 1, 2021): 4921–25. http://dx.doi.org/10.1166/jnn.2021.19251.
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The high manganese steel was developed to improve the fracture toughness and safety at cryogenic temperatures, the austenite structure was formed by increasing the manganese (Mn) content. The developed weld high manganese steel was alloyed with austenite stabilizing elements (e.g., C, Mn, and Ni) for cryogenic toughness and fluxes contained less than 10% of acidic slag formers such as rutile (TiO2) and silica (SiO2). This paper describes the work carried out to enhance the fracture toughness of Mn contents in an economical way by means of increase of manganese up to 23% instead of using nickel (Ni) which has unique element to improve fracture toughness especially at cryogenic steel. The new cryogenic steels should be carefully evaluated in terms of safety for application in real structures including LNG ships. In this study, the fracture toughness performance was evaluated for recently developed cryogenic steels (high-Mn steels), especially the crack tip opening displacement (CTOD) parameter was evaluated using the prediction formula proposed by conventional equation. The CTOD value was investigated the effect of microstructure and mechanical properties of Fe–C–Mn and Fe–C–Mn–Ni high manganese steel, it was revealed that the e-martesnsite phase formed in high manganese steel of 0.2C–20Mn and 0.4C–20Mn as a result of a low stability of austenite upon strain-induced phase transformation.
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H Nazht, Humam. "Radiological Evaluation of Fractures Healing Processing Fixed by Food Grate Stainless Steel Rods in Rabbits." Open Access Journal of Veterinary Science & Research 4, no. 3 (2019): 1–8. http://dx.doi.org/10.23880/oajvsr-16000189.
Full textAbstract:
This study was designed to follow up the radiological changes of the fracture healing process of the induced transverse femoral mid shift fracture in rabbits that fixed by food grate stainless steel rods (FGSR). Eight adult local breed rabbits were employed to induce complete transverse mid shift fracture in the femoral bone, under general anesthesia with highly aseptic technique. The fracture fragments fixed with FGSR, the study followed for more than two months by weekly radiographic examination, which revealed, the fracture healing occurs by secondary or indirect bone union, in which the new bone formation can be visible radiographically at the end of 2 nd week Post operati on (p. o.) around the fractures line which still visible, the callus formation increase in volume and density at the end of 3 rd week, at the end of 4 th weeks bony bridge formation and disappear of fracture line, at the end of the 6 th weeks radiological unio n occurs and the FGSR removed and remodeling phase started and continuous next week the conclusion the fracture healing processing of the induced fracture in the femoral bones in rabbits which fixed FGSR as internal fixation methods can be determined radio graphically.
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Mishin, V. M. "MICROMECHANISMS DELAYED FRACTURE STEEL." Tambov University Reports. Series: Natural and Technical Sciences 21, no. 3 (2016): 1166–69. http://dx.doi.org/10.20310/1810-0198-2016-21-3-1166-1169.
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