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.

A smart prediction tool for estimating the impact strength of welded joints prepared by vibratory welding process

2016 ◽  
Vol 231 (2) ◽  
pp. 343-346 ◽  
Author(s):  
P Govinda Rao ◽  
P Srinivasa Rao ◽  
A Gopala Krishna
Keyword(s):  
Impact Strength ◽  
Welded Joints ◽  
Welding Process ◽  
Input Voltage ◽  
Grain Structure ◽  
Generalized Regression Neural Network ◽  
Prediction Tool ◽  
Fine Grain ◽  
Vibration Parameters ◽  
The Impact

Previous researches have been devoted to development of vibratory setup for inducing mechanical vibrations into the weld pool during welding process. The designed vibratory setup produces the required frequency with suitable amplitude and acceleration in terms of voltages. This helps in producing uniform and fine grain structure in the welded joints which results in an improvement in the mechanical properties of the weld pieces at heat affected zone. This paper presents the development of a smart prediction tool by implementing generalized regression neural network to establish a relation between vibration parameters such as input voltage to the vibromotor, time of vibration and impact strength of vibratory weld joints. In order to validate the feasibility of the developed prediction tool, a comparison is made with the experimental results.

scholarly journals Impact strength of Friction Stir Welded joints of dissimilar Aluminum alloy

2020 ◽  
Vol 9 (4) ◽  
pp. 2491-2496
Keyword(s):  
Aluminum Alloy ◽  
Impact Toughness ◽  
Impact Strength ◽  
Welded Joints ◽  
Response Surfaces ◽  
Design Matrix ◽  
Friction Stir ◽  
Contour Plots ◽  
Fsw Parameters ◽  
The Impact

Joining processes has been the heart of the manufacturing processes. Welding has played an important part in joining processes since its inception. Friction Stir Welding (FSW) has given promising results especially in the case of aluminum alloys. In the present paper, dissimilar aluminum alloy heat-treatable AA6082 T651and non-heat treatable AA 5083 O were friction stir welded as per design matrix generated according to the rotatable central composite design of response surface methodology. Impact toughness was measured from samples of welded joints. The impact toughness was mapped in terms of FSW parameters and the regression equation is generated. The response surfaces and contour plots are drawn and interpreted. The input parameters are optimized to achieve maximum impact strength. Confirmation runs were performed and found results were found close to the optimized values. The present research is useful for further augmentation of the FSW process of aluminum alloy.

scholarly journals Analysis of Selected Properties of Welded Joints of the HSLA Steels

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1301 ◽  
Author(s):  
Ivan Miletić ◽  
Andreja Ilić ◽  
Ružica R. Nikolić ◽  
Robert Ulewicz ◽  
Lozica Ivanović ◽  
...  
Keyword(s):  
Impact Toughness ◽  
Welded Joints ◽  
Welded Joint ◽  
High Strength ◽  
Hardness Distribution ◽  
Micro Hardness ◽  
Hsla Steels ◽  
Applied Technology ◽  
Welding Procedure ◽  
The Impact

This paper presents research of the impact toughness and hardness distribution in specific zones of a ‘single V’butt multiple-pass welded joints of the high-strength low-alloyed steels. Obtained values of the impact toughness are analyzed in correlation with a microstructure in specific zones of the welded joint, together with the micro hardness distribution found in the related zones. Based on the carried out analysis and results obtained in experiments, the applied technology of welding was evaluated. The original conclusions on influence of the selected welding procedure manual metal arc (MMA) for the root passes and metal active gas (MAG) for the filling and covering passes) on impact toughness of the high-strength low-alloyed steels are drawn. The paper also presents discussion on the valid standards and recommendations related to welding of those steels, from the aspect of applications in design of steel welded constructions.

scholarly journals Asymptotic response of friction stir welded joint under cyclic loading

2021 ◽  
Vol 15 (58) ◽  
pp. 202-210
Author(s):  
Imane Elmeguenni
Keyword(s):  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Welded Joints ◽  
Welded Joint ◽  
Fatigue Behavior ◽  
Welding Process ◽  
Numerical Work ◽  
Promising Alternative ◽  
Friction Stir ◽  
The Impact

Fatigue takes a place more and more important in the design of structures, it remains a key point in the mechanical dimensioning of structures. The Friction Stir Welding (FSW) process is regarded today as the most promising alternative to traditional joining methods. It ranks among the most recent assembly processes and is considered a new technique for the 21st century. Indeed, if the FSW welding process has several advantages, it introduces very strong microstructure heterogeneities in the welded joints. This leads to heterogeneous mechanical behavior in each of the constituent zones. some important efforts have been deployed in industry as well as in research laboratories to understand the behavior of welded joints by the FSW process. There are many questions about the behavior of these areas. This study led to the characterization and understanding of the fatigue behavior of a 2024T351 structure welded by the FSW process. It presente in a numerical work which aims to help determine the asymptotic response of each zone constituting the 2024T351 joint welded by FSW subjected to a cyclic loading and to fully understand the behavior of these zones. To carry out an analysis and a simulation under cyclic loading, our choice fell on the use of the direct cyclic method. Numerical simulation of crack propagation was performed using the extended finite element method XFEM. This research consists in the implementation of the X-FEM in fatigue in a multiscale model X-FEM / direct cyclic. The numerical results consist in highlighting the heterogeneities in the mechanical behavior of the welded joint and in evaluating the impact of the FSW process on the failure of these FSW zones.

scholarly journals The impact of microstructural non-conformities on microhardness of EN AW 5754 aluminium alloy welded joints made with the use of the TIG method

2018 ◽  
Vol 48 (1) ◽  
pp. 253-262
Author(s):  
Piotr Woźny ◽  
Józef Błachnio
Keyword(s):  
Aluminium Alloy ◽  
Process Parameters ◽  
Welded Joints ◽  
Welded Joint ◽  
Welding Process ◽  
Strong Link ◽  
Tomographic Method ◽  
The Impact

Abstract The article presents the impact of welding non-conformities on microhardness of EN AW 5754 aluminium alloy welded joints made with the use of the TIG method. The results of microhardness tests of welded samples made with various process parameters. The impact of the welding non-conformities disclosed with the use of a tomographic method on the welded joint microhardness were analysed. The studies showed a strong link between the participation of welding non-conformities, welding process parameters and microhardness of welds.

scholarly journals Impact Tests of UHSS Steel Welded Joints Using the Drop - Tower Impact Drop Method

2019 ◽  
Vol 19 (3) ◽  
pp. 19-31
Author(s):  
J. Dorożyński ◽  
J. Nowacki ◽  
A. Sajek
Keyword(s):  
Impact Strength ◽  
Welded Joints ◽  
Impact Test ◽  
Gma Welding ◽  
High Strength ◽  
Test Method ◽  
Drop Tower ◽  
Current Application ◽  
Impact Tests ◽  
The Impact

AbstractThe article characterizes the impact test method using Drop-Tower Impact Test with the registration of the value of force and energy of breaking. Based on sources, the possibilities and scope of the current application of this method were determined and the current state of knowledge on the results of these tests was reviewed. In order to determine the possibility of using the method in impact tests of high strength steel joints, investigations of hybrid PTA - GMA welding conditions on impact strength of joints of MART S1300QL steel were carried out. In particular, the influence of t8/5 cooling time on the impact strength of welded joints by the Drop - Tower Impact Test method was determined. It has been shown that the use of dropping machine with computer-based registration of breaking force and energy values was possible in the case of impact strength testing of UHSS welded joints and enabled precise analysis of the energy distribution dynamics absorbed by the tested.

Impact of Heat Treatment on the Structure and Properties of the QE22 Alloy Welded Joints

2012 ◽  
Vol 191 ◽  
pp. 183-188
Author(s):  
Agata Kierzek ◽  
Janusz Adamiec
Keyword(s):  
Heat Treatment ◽  
Welded Joints ◽  
Creep Resistance ◽  
Welded Joint ◽  
Casting Process ◽  
Structure And Properties ◽  
Cast Magnesium Alloy ◽  
The One ◽  
Cast Magnesium ◽  
The Impact

The QE22 cast magnesium alloy containing silver, rare earth elements and zirconium is characterized by high mechanical properties and creep resistance of up to 200 ° C. It is cast gravitationally into sand moulds and permanent moulds. After the casting process any possible defects appearing in the cast are repaired with the application of welding techniques. The repaired cast should possess at least the same properties as the one which does not require any repairs. The aim of this thesis was to determine the impact of the heat treatment on the microstructure of the QE22 alloy welded joint. The creep resistance of the welded joints was also analyzed.

scholarly journals The impact of deformation in the zone of welded joints on the force action of the rolling stock on the track

2020 ◽  
Vol 79 (1) ◽  
pp. 9-16
Author(s):  
V. S. Kossov ◽  
O. G. Krasnov ◽  
M. G. Akashev
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Experimental Studies ◽  
Longitudinal Direction ◽  
Local Heat ◽  
Rolling Stock ◽  
Rolling Surface ◽  
Kolmogorov Smirnov ◽  
The Impact

The causes of deformation in the zone of welded joints are considered. Authors experimentally studied changes in hardness on the rolling surface of the rail in the longitudinal and transverse profiles within the thermally affected zone of the welded joint. It is established that the hardness of the rolling surface of the rail in the longitudinal direction in the thermally affected zone of the joint is uneven and is determined by the structures arising from the effects of the thermal cycles of welding and the quality of the local heat treatment. In this case, two "low spots" are clearly traced with a decrease in hardness to 290...300 HB and with a higher hardness up to 350 HB right in the welded joint. Experimentally investigated the change in the depth of the welded joint from the implemented tonnage. At the same time with strain gauge method, using the force method developed by N. N. Kudryavtsev, continuous changes in vertical forces when the wheels move along the welded joint zone were recorded. Average values of vertical forces from loaded cars were established. Experimental distributions of vertical forces were approximated by theoretical laws according to the Kolmogorov — Smirnov matching criterion. Recommendations are given on minimizing the harmful impact of rolling stock on the track in areas of lowering welded joints.The following conclusions were made.1.            Geometry of the joint irregularity is in the form of a W-shaped deformation with an influx of metal on the receiving rail and lowering on the directing rail. The width of the upper part of the deformation varies between 160...200 mm along the axis of the rail.2.            Deformation zone of the welded joint is a source of increased dynamic impact from the wheels of the rolling stock on the elements of the upper track structure. According to the results of experimental studies it was found that the greatest increase in dynamic effects was observed from locomotive wheels up to 45..               . 70 kN, maximum values reached 180...210 kN, from the wheels of loaded freight cars the values of vertical forces increased by 35..     .45 kN, maximum values reached 145...170 kN, from the wheels of empty cars increase dynamic impacts amounted to 14...16 kN, maximum values reached 32...36 kN.

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