scholarly journals Numerical and Experimental Investigations of Fracture Behaviour of Welded Joints with Multiple Defects

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4832
Author(s):  
Mihajlo Aranđelović ◽  
Simon Sedmak ◽  
Radomir Jovičić ◽  
Srđa Perković ◽  
Zijah Burzić ◽  
...  
Keyword(s):  
Yield Stress ◽  
Welded Joints ◽  
Welded Joint ◽  
Numerical Models ◽  
Carbon Steels ◽  
The Other ◽  
Experimental Investigations ◽  
Root Penetration ◽  
Strain Diagram ◽  
Multiple Defects

Current standards related to welded joint defects (EN ISO 5817) only consider individual cases (i.e., single defect in a welded joint). The question remains about the behaviour of a welded joint in the simultaneous presence of several different types of defects, so-called multiple defects, which is the topic of this research. The main focus is on defects most commonly encountered in practice, such as linear misalignments, undercuts, incomplete root penetration, and excess weld metal. The welding procedure used in this case was metal active gas welding, a common technique when it comes to welding low-alloy low-carbon steels, including those used for pressure equipment. Different combinations of these defects were deliberately made in welded plates and tested in a standard way on a tensile machine, along with numerical simulations using the finite element method (FEM), based on real geometries. The goal was to predict the behaviour in terms of stress concentrations caused by geometry and affected by multiple defects and material heterogeneity. Numerical and experimental results were in good agreement, but only after some modifications of numerical models. The obtained stress values in the models ranged from noticeably lower than the yield stress of the used materials to slightly higher than it, suggesting that some defect combinations resulted in plastic strain, whereas other models remained in the elastic area. The stress–strain diagram obtained for the first group (misalignment, undercut, and excess root penetration) shows significantly less plasticity. Its yield stress is very close to its ultimate tensile strength, which in turn is noticeably lower compared with the other three groups. This suggests that welded joints with misalignment and incomplete root penetration are indeed the weakest of the four groups either due to the combination of the present defects or perhaps because of an additional unseen internal defect. From the other three diagrams, it can be concluded that the test specimens show very similar behaviour with nearly identical ultimate tensile strengths and considerable plasticity. The diagrams shows the most prominent yielding, with an easily distinguishable difference between the elastic and plastic regions. The diagrams are the most similar, having the same strain of around 9% and with a less obvious yield stress limit.

Influence of post-welding tempering on mechanical behavior of friction welded joints from medium-carbon steels during tensile test

2020 ◽  
pp. 40-49
Author(s):  
A. S. Atamashkin ◽  
E. Yu. Priymak ◽  
N. V. Firsova
Keyword(s):  
Mechanical Behavior ◽  
Welded Joints ◽  
Welded Joint ◽  
Crack Nucleation ◽  
Carbon Steels ◽  
Uniaxial Tensile ◽  
Medium Carbon ◽  
Uniaxial Tensile Testing ◽  
Rotary Friction Welding ◽  
Medium Carbon Steels

The paper presents an analysis of the mechanical behavior of friction samples of welded joints from steels 30G2 (36 Mn 5) and 40 KhN (40Ni Cr 6), made by rotary friction welding (RFW). The influence of various temperature conditions of postweld tempering on the mechanical properties and deformation behavior during uniaxial tensile testing is analyzed. Vulnerabilities where crack nucleation and propagation occurred in specimens with a welded joint were identified. It was found that with this combination of steels, postweld tempering of the welded joint contributes to a decrease in the integral strength characteristics under conditions of static tension along with a significant decrease in the relative longitudinal deformation of the tested samples.

scholarly journals DEVELOPMENT OF PIPE WELDING TECHNOLOGY WITH PULSE ARC FITTINGS BY TUNGSTEN ELECTRODE IN ARGON ENVIRONMENT

2019 ◽  
Vol 2019 (6) ◽  
pp. 65-69
Author(s):  
Александр Комаров ◽  
Aleksandr Komarov ◽  
Александр Вдовин ◽  
Aleksandr Vdovin ◽  
Алексей Забелин ◽  
...  
Keyword(s):  
Welded Joints ◽  
Structural Engineering ◽  
Welded Joint ◽  
Welding Process ◽  
Vertical Surface ◽  
Root Penetration ◽  
Automatic Welding ◽  
Tungsten Electrode ◽  
Wire Feeding ◽  
Joint Quality

The matters of a welded joint efficient structure choice and a technology of automatic welding by a nonconsumable tungsten electrode with pulse arc in argon environment with filler wire feeding and without it to increase quality of the welded joints in hydraulic exploration pipe lines of structural engineering are con-sidered. It is defined that a technological process of welding with flanged pipe feeding ensures quality sta-bility in welded joints, but a welding process with twosided grooving ensuring root joint quality and, accordingly, the whole welded joint is more preferable while using one-sided grooving separate cases of incomplete root penetration, an electrode fault to a side vertical surface of grooving in the course of welding are possible and a more labor-intensive operation of setting a welding torch along a joint axis is also possible. On the basis of the investigation results there were developed welding modes of hydraulic explora-tion elements of an excavator, preproduction models of pipes with fittings were welded. The welded pre-production models were delivered to the plant for an industrial testing fulfillment.

scholarly journals The Effect of Laser Offset Welding on Microstructure and Mechanical Properties of 301L to TA2 with and without Cu Intermediate Layer

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1138 ◽  
Author(s):  
Xiaohui Zhao ◽  
Zhenfu Shi ◽  
Chao Deng ◽  
Yu Liu ◽  
Xin Li
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Brittle Fracture ◽  
Welded Joints ◽  
Intermediate Layer ◽  
Welded Joint ◽  
Eutectic Reaction ◽  
Dissimilar Materials ◽  
Microstructural Characterization ◽  
The Other

Based on dissimilar materials of 301L/TA2, the effect of laser offset and copper intermediate layer on welded joints was investigated. First, the process optimization of laser offsets indicated that the tensile strength of welded joint without intermediate layer was reached to the highest value when the laser was applied on the TA2 side. On the other hand, the tensile strength of welded joint with intermediate layer performed well when laser was applied in the middle position. Then, microstructural characterization and mechanical properties of welded joints were observed and tested. Based on eutectic reaction and peritectic reaction: TiFe and TiFe2 compounds were produced for welded joint without intermediate layer. Cu-Fe solid solutions and Cu-Ti compounds were generated when copper was used as the intermediate layer. The maximum tensile strength of welded joint with and without copper intermediate layer were 396 and 193 MPa, respectively. Finally, fracture mechanism of 301L/TA2 welded joint was studied: Fe-Ti compounds caused brittle fracture of welded joints without intermediate layer; brittle fracture took place in rich copper and Cu-Ti compounds area of welded joints with copper intermediate layer.

Welded Joint Evaluation for Chromium Controlled Carbon Steel Piping to Improve FAC Resistance

2018 ◽  
Author(s):  
Yoshio Uemoto ◽  
Takahiro Kawabe ◽  
Hiroyuki Shibata ◽  
Shoh Tarasawa ◽  
Hiroshi Asano ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Welded Joints ◽  
Chromium Content ◽  
Welded Joint ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Normal Carbon ◽  
Welding Materials ◽  
Steel Piping

For condensate and feed water piping in nuclear power plants, it is desired to mitigate the pipe wall thinning risk due to Flow-Accelerated Corrosion (FAC). In aspect of material selection, low alloy steels are generally applied to improve FAC resistance. However, low alloy steels are inferior to carbon steels from the point of material cost and construction efficiency due to requirement of post weld heat treatment (PWHT). On the other hand, chromium is known as the most effective element to improve FAC resistance, and it is reported that a certain improvement of FAC resistance is also expected for carbon steels by increasing chromium content to over 0.10 wt%. Such chromium controlled carbon steels are manufactured within the chemical composition range specified by material code of carbon steels, such as ASME B&PV Code Sec.II. Therefore, the amount of alloy content is lower than those for low alloy steels. The authors expect that PWHT can also be exempted for a certain thickness range of chromium controlled carbon steels, according to the exemption condition for normal carbon steels by ASME B&PV Code Sec.III. Furthermore, the chromium controlled carbon steels are generally cheaper than low alloy steels for base materials such as pipe and plate. However, since chromium content of normal welding materials for carbon steels is generally lower than 0.05 wt%, chromium controlled carbon steel welding materials are specially-produced material. It makes the procurability worse compared to normal carbon steel welding materials. Additionally it should be confirmed if the increased chromium content affects the soundness of welded joint. From the above reasons, it is necessary to decide the appropriate welding materials and methods for the chromium controlled carbon steel piping, considering the procurability of welding materials and the soundness of welded joint. In this study, the authors prepared the test pieces which simulate the assumed circumferential butt welded joints, then conducted the mechanical test such as tensile, impact, bend and hardness test to evaluate the soundness of welded joints. Furthermore, the authors evaluated the chromium content distribution of welded joints by using the Electro Probe Micro Analyzer (EPMA), in order to confirm if the chromium content is maintained over 0.10 wt% within the whole expected area.

Расчетные методы оценки ударной вязкости сварных элементов с трещинами

2020 ◽  
Vol 44 (3) ◽  
pp. 22-36
Author(s):  
Keyword(s):  
Stress Intensity ◽  
Impact Strength ◽  
Welded Joints ◽  
Development Process ◽  
Welded Joint ◽  
Operating Temperature ◽  
Crack Development ◽  
Heterogeneous Structure ◽  
Critical Crack Length ◽  
The Impact

Практика показывает, что для сварных конструкций, эксплуатируемых в условиях Крайнего Севера необходимо уделять внимание работоспособности сварных соединений при низких температурах. Металл сварных соединений в процессе воздействия обработки изменяет свои свойства, снижается ударная вязкость, образуется гетерогенная структура с большой степенью разнозернистости. Чтобы оценивать и иметь возможность правильно контролировать термическое воздействие и последствия сварочного процесса, требуется решить задачу аналитического определения ударной вязкости для всех зон сварного соединения. В настоящей статье представлен инженерный метод оценки ударной вязкости, применимый для любой зоны сварного соединения, в которой имеется острый или особый концентратор напряжений – трещина. Разработанный аналитический метод расчета ударной вязкости отражает качественную и количественную картину взаимосвязи структурно-механических характеристик и работы развития трещины в диапазоне температур 77…300 К. Предложенная схематизация зависимости критического коэффициента интенсивности напряжений от температуры позволила найти коэффициенты, характеризующие свойства материала, и выполнить расчеты изменения предела текучести и предела прочности от температуры эксплуатации. Построены графики зависимости работы развития трещины от температуры эксплуатации для сталей 15ГС и 17ГС, сравнение которых с экспериментальными данными показывает удовлетворительное согласование. Найдено, что при напряжениях предела выносливости отношение работы развития трещины к критической длине трещины постоянно, не зависит от температуры и для сталей 15ГС и 17ГС равно около 10. Ключевые слова: ударная вязкость, работа разрушения, коэффициент интенсивности напряжений, трещина, феррито-перлитная сталь, зона термического влияния. For welded structures under operation in the Far North, attention must be paid to the performance of welded joints at low temperatures. The properties of metal of welded joints are changed in the process of treatment, its toughness decreases, and a heterogeneous structure with a large range of different grain sizes is formed. In order to evaluate and be able to correctly control the thermal effect and the consequences of the welding process, it is necessary to solve the problem of analytical determination of impact strength for all zones of the welded joint. The paper presents an engineering method for evaluation of the impact strength applicable to any area of the welded joint in which there is a sharp or super sharp stress concentrator – a crack. The developed analytical method for calculating the impact strength reflects a qualitative and quantitative codependency of structural and mechanical characteristics and the process of crack development in the temperature range of 77–300 K. The proposed schematization of dependence of the critical coefficient of stress intensity on the temperature made it possible to find coefficients characterizing the properties of the material and to perform calculations of changes in yield strength and tensile strength on operating temperature. Graphs of the crack development process dependency on the operating temperature for 15ГС and 17ГС steels were constructed, and their comparison with experimental data displays satisfactory agreement. It was found that at endurance limit stresses, the ratio of the crack development process to the critical crack length is constant, non-dependent on temperature, and is equal to 10 for 15ГС and 17ГС steels. Keywords: impact strength, fracture work, stress intensity factor, crack, ferrite-pearlite steel, heat affected zone, steel tempering.

SAE 1039

Alloy Digest ◽  
1977 ◽  
Vol 26 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Cost ◽  
Manganese Content ◽  
Heat Treating ◽  
General Purpose ◽  
Carbon Steels ◽  
The Other ◽  
Steel Mills ◽  
Medium Strength ◽  
Hot Rolled

Abstract SAF 1039 steel can be used in the hot-rolled, normalized, oil-quenched-and-tempered or water-quenched-and-tempered condition for general-purpose construction and engineering. Its manganese content is a little higher than some of the other standard carbon steels with comparable carbon levels; this gives it slightly higher hardenability and hardness. It provides medium strength and toughness at low cost. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CS-66. Producer or source: Carbon steel mills.

scholarly journals Improving the Properties of Laser-Welded Al–Zn–Mg–Cu Alloy Joints by Aging and Double-Sided Ultrasonic Impact Compound Treatment

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2742
Author(s):  
Furong Chen ◽  
Chenghao Liu
Keyword(s):  
Plastic Deformation ◽  
Tensile Strength ◽  
Tensile Properties ◽  
Welded Joints ◽  
Welded Joint ◽  
Weld Zone ◽  
Aging Treatment ◽  
Residual Tensile Stress ◽  
Impact Surface ◽  
Deformation Layer

To improve the loose structure and serious porosity of (Al–Zn–Mg–Cu) 7075 aluminum alloy laser-welded joints, aging treatment, double-sided ultrasonic impact treatment (DSUIT), and a combination of aging and DSUIT (A–DSUIT) were used to treat joints. In this experiment, the mechanism of A–DSUIT on the microstructure and properties of welded joints was analyzed. The microstructure of the welded joints was observed using optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD). The hardness and tensile properties of the welded components under the different processes were examined via Vickers hardness test and a universal tensile testing machine. The results showed that, after the aging treatment, the dendritic structure of the welded joints transformed into an equiaxed crystal structure. Moreover, the residual tensile stress generated in the welding process was weakened, and the hardness and tensile strength were significantly improved. After DSUIT, a plastic deformation layer of a certain thickness was generated from the surface downward, and the residual compressive stress was introduced to a certain depth of the joint. However, the weld zone unaffected by DSUIT still exhibited residual tensile stress. The inner microhardness of the joint surface improved; the impact surface hardness was the largest and gradually decreased inward to the weld zone base metal hardness, with a small improvement in the tensile strength. Compared with the single treatment process, the microstructural and mechanical properties of the welded joint after A–DSUIT were comprehensively improved. The microhardness and tensile strength of the welded joint reached 200 HV and 615 MPa, respectively, for an increase of 45.8% and 61.8%, respectively. Observation of the fractures of the tensile specimens under the different treatment processes showed that the fractures before the aging treatment were mainly ductile fractures while those after were mainly brittle fractures. After DSUIT of the welded joints, a clear and dense plastic deformation layer was observed in the fracture of the tensile specimens and effectively improved the tensile properties of the welded joints. Under the EBSD characterization, the larger the residual compressive stress near the ultrasonic impact surface, the smaller the grain diameter and misorientation angle, and the lower the texture strength. Finally, after A–DSUIT, the hardness and tensile properties improved the most.

scholarly journals Influence of Shielding Gas on Microstructure and Properties of GMAW DSS2205 Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2671
Author(s):  
Xin-Yu Zhang ◽  
Xiao-Qin Zha ◽  
Ling-Qing Gao ◽  
Peng-Hui Hei ◽  
Yong-Feng Ren
Keyword(s):  
Corrosion Resistance ◽  
Welded Joints ◽  
Welded Joint ◽  
Crystal Defects ◽  
Shielding Gas ◽  
Electrochemical Tests ◽  
Corrosion Resistance Property ◽  
Mechanical Properties And Corrosion ◽  
Ar Gas ◽  
Welded Seam

In the present study, the microstructures and properties of DSS 2205 solid wire MIG welded samples prepared in different shielding gases (pure Ar gas, 98%Ar + 2%O2 and 98%Ar + 2%N2) were investigated for improving the weldability of DSS 2205 welded joint. The work was conducted by mechanical property tests (hardness and tensile test) and corrosion resistance property tests (immersion and electrochemical tests). The results show that adding 2%O2 into pure Ar gas as the shielding gas decreases crystal defects (faults) and improves the mechanical properties and corrosion resistance of the welded joints. Phase equilibrium and microstructural homogeneity in welded seam (WS) and heat-affected zone (HAZ) can be adjusted and the strength and corrosion resistance of welded joints increased obviously by adding 2%N2 to pure Ar gas as the shielding gas. Compared with DSS 2205 solid wire MIG welding in 98%Ar + 2%O2 mixed atmosphere, the strength and corrosion resistance of welded joints are improved more obviously in 98%Ar + 2%N2 mixed atmosphere.

PROBING AWAY SIDE JET MODIFICATION WITH THREE PARTICLE CORRELATIONS

2007 ◽  
Vol 16 (07n08) ◽  
pp. 1982-1987
Author(s):  
◽  
N. N. AJITANAND
Keyword(s):  
Spatial Distribution ◽  
Correlation Functions ◽  
Theoretical Models ◽  
The Other ◽  
Experimental Investigations ◽  
Powerful Method ◽  
Particle Correlation ◽  
Low Viscosity ◽  
Jet Modification ◽  
Rhic Data

Recent experimental investigations have focussed on the abnormal spatial distribution of away side jet fragments as signals of significant medium induced effects. A variety of theoretical models including recent string-theory based efforts have supported the notion of Mach Cone like effects in the low viscosity QGP fluid. However, the presence of significant flow fields may deflect the fragmentation direction producing a significantly differing type of jet topology from that of the Mach cone. Three particle correlation functions constitute a powerful method whereby the predominance of one or the other type of mechanism can be differentiated. In this work the use of such an approach will be demonstrated via simulations and the results of its application to RHIC data will be presented.

Electric Current Pulse Welding of Titanium with 18-10 Stainless Steel

2009 ◽  
Vol 83-86 ◽  
pp. 1251-1253 ◽  
Author(s):  
E.G. Grigoryev ◽  
V.N. Bazanov
Keyword(s):  
Stainless Steel ◽  
Electric Current ◽  
Current Pulse ◽  
Contact Zone ◽  
Welded Joints ◽  
High Speed ◽  
Welded Joint ◽  
Electric Current Pulse ◽  
Pulse Effect ◽  
Different Thickness

The purpose of the work was to determine the capabilities of the pulse effect of electric current and pressure to produce welded joints of various component parts of different thickness from 18-10 stainless steel and titanium. Application of electric current pulses on the surfaces of contacting metallic conductors leads to considerable changes in the surface structure. Depending on the initial state of the surfaces and parameters of the pulse effect this can result in melting without formation of joints, formation of a strong welded joint with characteristics no worse than those of welded metals, and in destruction of the contact zone. A combination of a short electric pulse with simultaneous application of mechanical pressure in the weld zone causes high-speed deformation of the contact zone. The process of joint formation itself does not cause any appreciable diffusion during welding. The greatest energy emission and the maximal heating occur on the contacting surfaces being welded with the passage of an electric current pulse through the welding zone. Simultaneously with intensive heating, and due to applied pressure, high-speed deformation of materials takes place and a strong welded joint is formed. Optimal parameters for the welding of titanium and 18-10 stainless steel have been determined on the basis of the tests conducted. Investigations into the welding of titanium and 18-10 stainless steel have shown that application of a short electric current pulse and pressure produces stronger welded joints composed of both similar and different metals of considerably different thickness.

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