Influence of Cooling Time t8/5 on Impact Toughness of P460NL1 Steel Welded Joints

2020 ◽  
Vol 1157 ◽  
pp. 154-160
Author(s):  
Simon A. Sedmak ◽  
Mihajlo Aranđelović ◽  
Radomir Jovicic ◽  
Dorin Radu ◽  
Ivica Čamagić
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Impact Energy ◽  
Welded Joint ◽  
Welding Process ◽  
Impact Testing ◽  
Cooling Time ◽  
Initiation And Propagation ◽  
Higher Temperature ◽  
Total Impact

The results of impact testing of welded joint specimens taken from a welded plate made of P460NL1 steel are presented in this paper, and analysed with regards to the cooling time t8/5, that was previously calculated. The aim was to determine how the cooling times that were measured, some of which were below the minimum required values, affected the toughness, in terms of total impact energy and its components, crack initiation and crack propagation energy. In addition, this analysis included the effects of temperatures measured at the opposite ends of the plate during the welding process, since this had also affected the cooling times for each welding pass. After observing the differences in total, crack initiation and propagation energy between the tested specimens taken from different parts of the welded plate, it was determined that the specimens from the part where the higher temperatures were measured had shown better, more uniform results, whereas the average total impact energy for specimens from both groups were very similar. It was also noticed that the ratio of crack propagation to crack initiation was more favourable (greater) in the case of specimens from the second group (with higher temperature), as the values of crack initiation energy decreased slightly and the crack propagation energy increased.

On the Topology Update of the Numerical Manifold Method for Multiple Crack Propagation

2021 ◽  
pp. 2150030
Author(s):  
Jun He ◽  
Shuling Huang ◽  
Xiuli Ding ◽  
Yuting Zhang ◽  
Dengxue Liu
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Numerical Method ◽  
Crack Tip ◽  
Search Method ◽  
Numerical Manifold Method ◽  
Crack Initiation And Propagation ◽  
Multiple Crack ◽  
Initiation And Propagation ◽  
Numerical Manifold

Crack initiation and propagation are the two key issues of concern in the geotechnical engineering. In this study, the numerical manifold method (NMM) is applied to simulate crack propagation and the topology update of the NMM for multiple crack propagation is studied. The crack-tip asymptotic interpolation function is incorporated into the NMM to increase the accuracy of the crack-tip stress field. In addition, the Mohr-Coulomb criterion with tensile cut off is adopted to be the crack propagation criterion to judge the direction of crack initiation and propagation. Then a crack tip searching method is developed to automatically update the position of the crack tips. The inapplicability of the original loop search method in the NMM is also illustrated and a novel loop search method based on manifold elements is developed for physical loop updating. Moreover, methods for the manifold element updating and physical cover updating are provided. Based on the above study, the developed numerical method is capable to simulate multiple crack propagation. At last, typical rock rupture problems are numerically simulated to manifest the effectiveness of the developed numerical method.

scholarly journals Elastoplastic Fracture Analysis of the P91 Steel Welded Joint under Repair Welding Thermal Shock Based on XFEM

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1285 ◽  
Author(s):  
Kai Yang ◽  
Yingjie Zhang ◽  
Jianping Zhao
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Thermal Shock ◽  
Power Plants ◽  
Welded Joint ◽  
Welding Process ◽  
Simulation Method ◽  
Fracture Analysis ◽  
P91 Steel ◽  
Repair Welding

P91 steel is a typical steel used in the manufacture of boilers in ultra-supercritical power plants and heat exchangers in nuclear power plants. For the long-term serviced P91 steel pressurized structures, the main failure mode is the welded joint failure, especially the heat affected zone (HAZ) failure. Repair welding technique is an effective method for repairing such local defects. However, the thermal shock composed of high temperature and thermal stress in the repair welding process will pose a critical loading condition for the existing defects near the heat source which cannot be detected by conventional means. So, the evaluation of structural integrity for the welded joint in the thermal-mechanical coupling field is necessary. In this work, the crack propagation law in the HAZ for the P91 steel welded joint was investigated under repair welding thermal loads. The weld repair model of the P91 steel welded joint was established by ABAQUS. The transient temperature field and stress field in repair welding process were calculated by relevant user subroutines and sequential coupling simulation method. The residual stress was determined by the impact indentation strain method to verify the feasibility of the finite element (FE) model and simulation method. In order to obtain the crack propagation path, the elastoplastic fracture analysis of the welded joint with initial crack was performed based on the extended finite element method (XFEM). The influence of different welding linear energy on the crack propagation was analyzed. The results show that the cracks in the HAZ propagate perpendicular to the surface and tend to deflect to the welding seam under repair welding thermal loads. The crack propagation occurs in the early stage of cooling. Higher welding linear energy leads to larger HAZ and higher overall temperature. With the increase of welding linear energy, the length and critical distance of the crack propagation increase. Therefore, low welding linear energy can effectively inhibit the crack propagation in the HAZ. The above calculation and analysis provide a reference for the thermal shock damage analysis of repair welding process, which is of great significance to improving the safety and reliability of weld repaired components.

scholarly journals Experimental and Theoretical Determination of the Frost-Heave Cracking Law and the Crack Propagation Criterion of Slab Track with Water in the Crack

2019 ◽  
Vol 9 (21) ◽  
pp. 4592 ◽  
Author(s):  
Fengzhuang Tong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Yanglong Zhong ◽  
Wenqiang Zhao ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Opening ◽  
Evaluation Criteria ◽  
Image Correlation ◽  
Frost Heave ◽  
External Temperature ◽  
Slab Track ◽  
Initiation And Propagation ◽  
Evolution Laws

Crack propagation produced by frost heave affects the durability of slab-track structures in high-humidity and cold regions in China. This work is intended to reveal the evolution laws of frost-heave crack propagation, establish evaluation criteria for crack propagation, and investigate factors involved in frost-heave crack propagation. Firstly, by preparing slab-track specimens with initial cracks, an experiment of frost-heave crack propagation was designed. The process of frost-heave crack propagation was carried out by means of digital image correlation (DIC) technology and acoustic emission (AE) technology, respectively. These experiments revealed the evolution laws of generalized strain and AE events’ location during crack initiation and propagation, respectively, and the key parameters of micro-crack initiation strain and unstable propagation strain were obtained. By using theoretical and experimental analysis, a double-strain criterion for frost-heave crack propagation was proposed. Finally, factors involved in frost-heave crack propagation were investigated. The results show that crack initiation can be reflected by the crack-tip strain. The average micro-crack initiation strain and unstable propagation strain were found to be 224 με and 243 με, respectively. Moreover, it was found that the frost-heave crack propagation was caused by an ice plug which formed at the crack opening. When the crack width is larger than 2.7 mm and the external temperature is lower than −6.6 °C, cracks propagate easily under the frost-heave force.

scholarly journals Fretting fatigue crack initiation and propagation in Ti6Al4V sheets under tribocorrosive conditions of artificial seawater and physiological solutions

2020 ◽  
Vol 234 (12) ◽  
pp. 1526-1534 ◽  
Author(s):  
Zeeshan Anjum ◽  
Masood Shah ◽  
Hassan Elahi ◽  
Mushtaq Khan ◽  
Mohammad Mujahid ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Testing Machine ◽  
Fatigue Crack Initiation ◽  
Physiological Solution ◽  
Fretting Corrosion ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Dry Conditions ◽  
Phosphate Buffered Saline

The interaction of mechanical components experiencing relative movements and cyclic loads in a corrosive environment is known as fretting corrosion or tribocorrosion. In the current work, the mechanism of crack initiation and propagation in dovetail slots of Ti6Al4V samples (in contact with carbide rods) under fretting corrosion conditions was investigated. A newly developed test rig installed on a universal testing machine was used to conduct tests at 20 Hz frequency under 5 and 7.5 kN fretting loads. Tests were conducted at room temperature in 3.5% NaCl and phosphate-buffered saline solutions. Crack propagation in all samples was examined by a metallurgical microscope, and the detailed analysis of fractured samples was carried out by a scanning electron microscope. In comparison to dry conditions, early crack initiation and faster crack propagation were observed in salt and physiological solution environments. Colored spots and large amounts of chlorine, sodium, and oxygen were found around cracks, and plastically deformed regions in the 3.5% NaCl environment provided the evidence of a corrosive attack. Large amounts of oxygen, phosphorous, chlorine, potassium, and sodium were detected in the phosphate-buffered saline environment.

Mechanical Properties and Fracture Toughness of Aluminum Vessels by Friction Stir Welding

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda ◽  
Masayuki Inuzuka ◽  
Hidehito Nishida
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Crack Initiation ◽  
Base Metal ◽  
Welded Joint ◽  
Stir Zone ◽  
Crack Initiation And Propagation ◽  
Friction Stir ◽  
Fine Grained ◽  
Initiation And Propagation

Mechanical properties and fracture toughness in friction stir welded joint of vessels of structural aluminum alloy type A5083-O are investigated. Welded joint from 25 mm-thick plate is fabricated by one-side one-pass friction stir. Charpy impact energy and critical crack-tip opening displacement (CTOD) in friction stir weld are much higher than those of base metal or heat-affected zone, whereas mechanical properties such as stress-strain curve and Vickers hardness do not have a conspicuous difference. Effects of microstructure on crack initiation and propagation are studied in order to clarify the difference of fracture toughness between stir zone and base metal. Both tensile test and bending test show that the fine-grained microstructure in stir zone induces to increase ductile crack initiation and propagation resistance by analyzing fracture resistance curves and diameter of dimples in fracture surface. It is found that high fracture toughness value in stir zone is affected fine-grained microstructure by friction stirring.

scholarly journals Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears

2007 ◽  
Author(s):  
Robert F. Handschuh ◽  
Timothy L. Krantz ◽  
Bradley A. Lerch ◽  
Christopher S. Burke
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Test Machine ◽  
Spur Gears ◽  
Crack Initiation And Propagation ◽  
Bending Fatigue ◽  
Initiation And Propagation ◽  
Single Tooth ◽  
Relationship Of ◽  
The Relationship

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semi-logarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

scholarly journals Investigation on the Fracturing Permeability Characteristics of Cracked Specimens and the Formation Mechanism of Inrush Channel from Floor

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jianning Wang ◽  
Weitao Liu ◽  
Jianjun Shen
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Formation Mechanism ◽  
Water Pressure ◽  
Water Inrush ◽  
Confining Pressure ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Final Failure ◽  
Cracked Specimens

To study the fracture characteristics and the permeability change law of the cracked specimens during the complete stress-strain process, a mechanical model was constructed, from which different types of crack initiation angles were obtained. The crack inclination angles under uniaxial compression, confining compression, and confining tension, and the influence of confining pressure and pore water pressure on the crack propagation and permeability of rock mass were investigated and simulated with RFPA-Flow software using prefabricated crack models with crack initiation angles of 30°, 45°, and 60°. Furthermore, the formation mechanism of inrush channel from floor was qualitatively analyzed. The results indicated that the theoretical initiation angles of wing cracks, secondary coplanar cracks, and secondary inclined antiwing cracks were found to be 70.53°, 0°, and 123.8°, which were consistent with the simulation results. The crack propagation was mainly concentrated at the postpeak stage of the complete stress-strain curve, causing the peak of seepage velocity to lag behind the stress peak. For the case with a constant confining pressure, the rate of crack initiation and propagation to final failure was positively correlated with the internal pore pressure. For the case with a constant water pressure, the speed of crack initiation and propagation to final failure decreased first and then increased as the confining pressure increased. In addition, the longitudinal propagation of wing cracks and the increase in permeability were prone to occur in the low confining pressure zone, which induced the formation of water inrush channels. The research result provides an improved understanding for predicting and preventing water inrush disasters.

Experimental Study on Crack Propagation by AE Location under Uniaxial Compression Condition

2007 ◽  
Vol 353-358 ◽  
pp. 2329-2332
Author(s):  
Xing Dong Zhao ◽  
Yuan Hui Li ◽  
Rui Fu Yuan
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Crack Initiation And Propagation ◽  
Stress Strain ◽  
Initiation And Propagation ◽  
Ae Location ◽  
Granite Samples ◽  
Compression Condition

AE technique is proved a efficient tool for real-time monitoring of the crack initiation and propagation during rock failure process under uniaxial compression condition. In this paper, An AE system was employed to investigate the crack propagation and failure modes of three groups of granite specimens (80mm×100mm×170mm) with the same pre-existing crack. The AE sensors can be surface mounted. By using a Geiger location algorithm, AE event location can be determined by time-of-arrival times. The propagation velocities of p-wave or s-wave of granite samples were measured. Experiments on pre-existing crack propagation of granite samples were carried out on the press machine. From the testing result, failure mode of three kinds of granite samples was mainly shear failure, while the secondary crack propagated slowly and could not influence the failure mode of granite sample. By surveying the relation of accumulative AE events and stress-strain curve, AE activity represents different characters with stress-strain changing during the total loading process, microcracking contributing to fracture propagation with strain corrosion. AE location result reflected crack initiation and propagation, which is of great importance in studying rock instability and predicting rock failure mode.

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