The Experts below are selected from a list of 93534 Experts worldwide ranked by ideXlab platform
Chunguo Zhang - One of the best experts on this subject based on the ideXlab platform.
-
tensile overload induced plastic deformation and fatigue behavior in weld repaired high strength low alloy Steel
Journal of Materials Processing Technology, 2013Co-Authors: Chunguo Zhang, Gaiping ZhangAbstract:Abstract The effects of tensile over-load (OL) on fatigue crack growth behavior of a weld-repaired High-Strength Low-Alloy (HSLA) Steel were studied by measuring both the fatigue crack growth rate and sample-thickness variation along the fatigue crack growth path. The thickness variation, indicating the degree of plastic deformation (PD), provided an indirect measurement of associated residual compressive stresses at the crack-tip. The applied tensile OL with one-hour holding period in each test generated a damage zone at the crack tip. Microscopic details of the crack-tip damage zone were characterized by scanning electron microscopy. Three groups of expanded compact-tension (E-CT) samples, 10 mm in thickness, were tested: weld-repaired HSLA without soft buffer layer (BL), and weld-repaired HSLA with 4 mm or 10 mm thick BL. The experimental results showed that the OL-induced PD, closely linked to the crack-tip residual compressive stresses, reduced the subsequent fatigue crack growth rate, and that the HSLA with a 10 mm BL had the lowest growth rate, indicating a soft BL with an adequate thickness could further improve the fatigue resistance.
-
residual stress induced deformation and fatigue crack growth in weld repaired high strength low alloy Steel with soft buffer layer
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Chunguo Zhang, Xuding SongAbstract:Abstract Residual stresses (RS) in a bulk weld-repaired Steel structure and thin samples sliced from the welded-section are different due to inevitable variations in the stiffness and boundary conditions. In this study, thin extended compact tension (E-CT) samples for fatigue crack growth measurements were sliced from three extensively weld-repaired High-Strength Low-Alloy (HSLA) blocks with three different welding conditions, i.e. welding with a 4 or 10 mm thick soft buffer layer (BL) and welding without the soft BL. Deformation in the thin E-CT samples with notches due to the partial release of welding-induced RS) was measured, and then the samples were used to measure the fatigue crack growth. In this study, we reported detailed measurements of residual stress-induced (RS-induced) deformation in thin test samples and corresponding fatigue crack growth behavior of an extensively weld-repaired HSLA with or without a thin BL. Three groups of E-CT samples were prepared: weld-repaired HSLA without BL, and weld-repaired HSLA with a 10 mm or 4 mm BL. The RS-induced deformation and corresponding fatigue crack growth were measured, and studied together with the influence of BL. The results showed that the incorporation of a 4 mm BL had a profound influence on reduction of the RS-induced deformation, and the incorporation of a 10 mm BL had a significant influence on the fatigue crack growth behavior in the parent metal, heat-affected-zone and weld metal. Detailed SEM observations show that fatigue characteristics of the weld-repaired HSLA were also influenced by the buffer layer and welding-induced RS.
-
fatigue crack growth behavior in weld repaired high strength low alloy Steel
Engineering Fracture Mechanics, 2011Co-Authors: Chunguo Zhang, Stefan Van Der VyverAbstract:Fatigue crack growth properties and Vickers micro-hardness of a weld-repaired High-Strength Low-Alloy Steel, known for high strength, low carbon, excellent notch toughness and good weldability and formability, have been studied under the following conditions: as-received High-Strength Low-Alloy, weld-repaired High-Strength Low-Alloy without buffer layer, and weld-repaired High-Strength Low-Alloy with various thickness buffer layers. Those conditions are examined to determine the respective fatigue crack growth behaviors and Vickers hardness distribution, and the effects of different weld-repaired conditions on fatigue characterizations and microscopic features of the fracture and fatigue surface. The extended-compact tension specimen geometry is adopted in this study for all tests. Paris fatigue crack growth curves and the hardness distribution across weld metal, buffer layer and parent metal has been measured together with the relevant scanning electron microscope observations along the fatigue crack growth path, with special attention at and around the interfaces between the weld metal, buffer layer and parent metal. The results show the presence of the BL of a moderate thickness has a significant influence on the fatigue crack growth behavior in the heat-affected zone and around the interface between buffer layer and parent metal. The fatigue resistance of the selected High-Strength Low-Alloy + buffer layer + weld metal tri-metal system is higher than that of the High-Strength Low-Alloy + weld metal bi-metal system.
D L Chen - One of the best experts on this subject based on the ideXlab platform.
-
ultrasonic spot welding of aluminum to high strength low alloy Steel microstructure tensile and fatigue properties
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2014Co-Authors: V K Patel, S D Bhole, D L ChenAbstract:The structural applications of lightweight aluminum alloys inevitably involve dissimilar welding with Steels and the related durability issues. This study was aimed at evaluating the microstructural change, lap shear tensile load, and fatigue resistance of dissimilar ultrasonic spot-welded joints of aluminum-to-galvanized High-Strength Low-Alloy (HSLA) Steel. Two non-uniform layers were identified in between Al and HSLA Steel via SEM/EDS and XRD. One was an Al-Zn eutectic layer and the other was a thin (<2 μm) layer of intermetallic compound (IMC) of Al and Fe in the nugget zone. The lap shear tensile testing gave a maximum load of 3.7 kN and the sample failed initially in between the Al-Zn eutectic film and Al-Fe IMC, and afterward from the region containing Al on both matching fracture surfaces. The fatigue test results showed a fatigue limit of about 0.5 kN (at 1 × 107 cycles). The maximum cyclic stress at which transition of the fatigue fracture from transverse through-thickness crack growth mode to the interfacial failure mode occurs increases with increasing energy input.
-
ultrasonic spot welding of aluminum to high strength low alloy Steel microstructure tensile and fatigue properties
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2014Co-Authors: V K Patel, S D Bhole, D L ChenAbstract:The structural applications of lightweight aluminum alloys inevitably involve dissimilar welding with Steels and the related durability issues. This study was aimed at evaluating the microstructural change, lap shear tensile load, and fatigue resistance of dissimilar ultrasonic spot-welded joints of aluminum-to-galvanized High-Strength Low-Alloy (HSLA) Steel. Two non-uniform layers were identified in between Al and HSLA Steel via SEM/EDS and XRD. One was an Al-Zn eutectic layer and the other was a thin (<2 μm) layer of intermetallic compound (IMC) of Al and Fe in the nugget zone. The lap shear tensile testing gave a maximum load of 3.7 kN and the sample failed initially in between the Al-Zn eutectic film and Al-Fe IMC, and afterward from the region containing Al on both matching fracture surfaces. The fatigue test results showed a fatigue limit of about 0.5 kN (at 1 × 107 cycles). The maximum cyclic stress at which transition of the fatigue fracture from transverse through-thickness crack growth mode to the interfacial failure mode occurs increases with increasing energy input.
-
formation of zinc interlayer texture during dissimilar ultrasonic spot welding of magnesium and high strength low alloy Steel
Materials & Design, 2013Co-Authors: V K Patel, S D Bhole, D L ChenAbstract:Abstract Ultrasonic spot welding (USW) of AZ31B-H24 magnesium alloy sheet to high strength low alloy (HSLA) Steel sheet with a zinc interlayer was successfully achieved. Thin layer of intermetallic compounds (IMCs) of Mg 7 Zn 3 , Mg 2 Zn 11 and MgZn 2 were present at the interface between magnesium and zinc substrate, while at the other interface (iron and zinc), no IMCs were found. A single crystal-like strong basal crystallographic texture in a zinc interlayer was identified. The (0 0 0 2) peak intensity of zinc interlayer after ultrasonic spot welding became ∼30 times higher than that of cold-rolled pure zinc sheet, with basal plane predominantly parallel to the interlayer surface. This was due to the plastic deformation arising from the ultrasonic vibrations, which serve to strengthen the basal texture. The basal plane peak intensity in zinc interlayer was higher when rolling direction (RD) of zinc sheet was aligned perpendicular to the vibration direction than when it was aligned in parallel.
N Arivazhagan - One of the best experts on this subject based on the ideXlab platform.
-
metallurgical and mechanical properties of laser welded high strength low alloy Steel
Journal of Advanced Research, 2016Co-Authors: R Oyyaravelu, P Kuppan, N ArivazhaganAbstract:The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler Steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure.
Abbas Eghlimi - One of the best experts on this subject based on the ideXlab platform.
-
evaluation of microstructure and texture across the welded interface of super duplex stainless Steel and high strength low alloy Steel
Surface & Coatings Technology, 2015Co-Authors: Abbas Eghlimi, Morteza Shamanian, Masoomeh Eskandarian, Azam Zabolian, Majid Nezakat, J A SzpunarAbstract:Abstract The evolution of microstructure and texture across the fusion boundary of a dual-layer super duplex stainless Steel clad metal produced on a high strength low alloy Steel substrate by gas tungsten arc welding process was examined by optical microscopy, X-ray diffraction, electron backscatter diffraction, and energy-dispersive X-ray spectroscopy. It was found that a martensitic band with occasional Type I and Type II boundaries separated the substrate's heat affected zone from the high austenite containing region of the clad metal. Due to the competitive growth, both the ferrite and austenite grains showed almost the same ║ ND orientation near the fusion boundary. While the texture of the austenite was not as strong as that of the ferrite across the cladding layers, the results confirmed that the austenite daughter phase was formed with a close Kurdjumov–Sachs orientation relationship with respect to the parent ferrite phase. It was also found that although both the residual stress and reheating caused some microstructural transformation and texture modification to some parts of the cladding, the major factors affecting the texture were unidirectional solidification, competitive growth, and δ/γ orientation relationship. The only exception was related to the occasional highly deformed mostly austenite area adjacent to the fusion boundary, where partial recrystallization led to formation of some annealing twins. The findings suggested that the reheating which occurred during the deposition of the second layer generated higher ferrite content and produced some secondary austenite with dominant Widmanstatten morphology across the first cladding layer. Moreover, it imposed higher residual strain and also promoted limited recrystallization adjacent to the fusion boundary.
-
effect of current type on microstructure and corrosion resistance of super duplex stainless Steel claddings produced by the gas tungsten arc welding process
Surface & Coatings Technology, 2014Co-Authors: Abbas Eghlimi, Morteza Shamanian, Keyvan RaeissiAbstract:Abstract In this research, super duplex stainless Steel filler metals were clad on high strength low alloy Steel substrates by the tungsten arc welding process using pulsed and constant currents. To characterize the pulsed current effect, the phase composition and microstructure of the claddings were compared, and the corrosion behavior of the claddings was evaluated using cyclic polarization, electrochemical impedance spectroscopy and critical pitting temperature measurements. The results showed that the slower cooling rate of the constant current cladding led to a higher total reformed austenite content and better corrosion resistance. It was also found that the formation of thermally-activated secondary austenite did not influence the corrosion behavior significantly. The electrochemical impedance spectroscopy indicated that the passive film formed on the pulsed current cladding was more defective. The constant current cladding also showed ten degree higher critical pitting temperature than the one which was produced by pulsed current.
Jwo Pan - One of the best experts on this subject based on the ideXlab platform.
-
fatigue behavior of laser welds in lap shear specimens of high strength low alloy Steel sheets
International Journal of Fatigue, 2014Co-Authors: Kamran Asim, Kulthida Sripichai, Jwo PanAbstract:Abstract In this paper, the fatigue behavior of laser welds in lap-shear specimens of non-galvanized SAE J2340 300Y high strength low alloy (HSLA) Steel sheets is investigated based on experimental observations and a fatigue life estimation model. Optical micrographs of the laser welds before and after failure under quasi-static and cyclic loading conditions are examined. The micrographs show that the failure modes of laser welds under quasi-static and cyclic loading conditions are quite different. Under quasi-static loading conditions, the weld failure appears to be initiated from the base metal near the boundary of the base metal and the heat affected zone at a distance to the pre-existing crack tip, and the specimens fail due to the necking/shear of the lower left load carrying sheets. Under low-cycle loading conditions, the weld failure appears to be initiated from the pre-existing crack tips and the specimens finally fail from the ductile fracture through the lower left load carrying sheets. Under high-cycle loading conditions, the weld failure appears to be initiated from the pre-existing crack tips and the specimens finally fail from the kinked fatigue crack propagating through the upper right load carrying sheets. Finite element analyses of the laser welded lap-shear specimens with consideration of the weld bead protrusion were carried out to obtain the global and local stress intensity factor solutions for the main cracks and kinked cracks, respectively. The stress intensity factor solutions can be used to explain the kinked fatigue crack growth patterns under high-cycle loading conditions. The kinked fatigue crack growth model based on the global and local stress intensity factor solutions for finite kinked cracks obtained from the finite element analyses is adopted to estimate the fatigue lives of the laser welds. The fatigue life estimations based on the kinked fatigue crack growth model agree well with the experimental results.
-
failure mechanism of laser welds in lap shear specimens of a high strength low alloy Steel
ASME 2010 Pressure Vessels and Piping Conference: Volume 6 Parts A and B, 2010Co-Authors: Kamran Asim, Jaewon Lee, Jwo PanAbstract:In this study, the failure mechanism of laser welds in lap-shear specimens of a high strength low alloy (HSLA) Steel under quasi-static loading conditions is examined based on the experimental results. Optical micrographs of the welds in specimens before tests were examined to understand the microstructure near the weld. A micrographic analysis of the failed welds in lap-shear specimens indicates a ductile necking/shear failure mechanism near the heat affected zone. Micro-hardness tests were conducted to provide an assessment of the mechanical properties of the joint area which has varying microstructure due to the welding process. A finite element analysis was also carried out to identify the effects of the weld geometry and different mechanical properties of the weld and heat affected zones on the failure mechanism. The computational results of the finite element analysis indicate that the material inhomogeneity and geometry of the weld bead play an important role in the ductile necking/shear failure mechanism. The computational results match well with the experimental observations of the necking/shear failure and its location. A finite element analysis with consideration of void nucleation and growth based on the Gurson yield function was also carried out. The results of the finite element analysis based on the Gurson yield function are in good agreement with the experimental observations of the initiation of ductile fracture and its location.Copyright © 2010 by ASME