Zeitschriftenartikel: „DFLUX“

1

Piekarska, W., M. Kubiak, Z. Saternus und K. Rek. „Computer Modelling of Thermomechanical Phenomena in Pipes Welded using a Laser Beam“. Archives of Metallurgy and Materials 58, Nr. 4 (01.12.2013): 1237–42. http://dx.doi.org/10.2478/amm-2013-0156.

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Abstract This study concerns numerical modelling and computer simulation of thermomechanical phenomena accompanying spiral welding of pipes made of stainless steel X5CrNi18-10 using a laser beam. Based on Abaqus FEA software, 3D numerical analysis was performed. Power distribution of spirally moving heat source was implemented into additional DFLUX subroutine, written in Fortran programming language. Thermomechanical properties of steel changing with temperature were taken into account in the analysis. The efficiency of material melting by different welding sources as well as the influence of heat load on the shape of melted zone, deformation of welded pipe and residual stress were examined.

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Zhao, Lei, Lu Sun und Tong Jiang Fan. „Temperature Field Analysis of CRTS-II Ballastless Track Slab Structure on Soil Subgrade“. Applied Mechanics and Materials 587-589 (Juli 2014): 1255–61. http://dx.doi.org/10.4028/www.scientific.net/amm.587-589.1255.

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Temperature changes have a significant impact on the CRTS-II track structure in Beijing-Shanghai high-speed railway which has longitudinally connected type. In this paper temperature fields of ballastless track superstructure are simulated based on heat transfer theory and subroutine of ABAQUS that solar radiation DFLUX and ambient temperature FILM. The results showed that: the maximum temperature difference on the top of track slab is 20°C in summer and 10°C in winter; the maximum temperature difference in CA mortar layer is 4°C in summer and 2°C in winter; the maximum temperature difference in concrete substrate is 2°C in summer and 1°C in winter.

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3

Xie, Wanying, Ji Li, Feiyun Sun und Wenyi Dong. „Antifouling Ability of Hydrophilic PVDF-TiO2 membrane Evaluated by Critical Flux and Threshold Flux“. E3S Web of Conferences 144 (2020): 01015. http://dx.doi.org/10.1051/e3sconf/202014401015.

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The PVDF flat-membrane was modified by hydrophilic nano-TiO2, which blending by ultrasonication and mechanical stirring pretreatment in phase inversion method. To evaluate the permeate productivity and anti-fouling capacity of protein solution, both the critical flux (JCW) and threshold flux (JTH) of PVDF and PVDF-TiO2 membrane were firstly measured by Advanced Constant Pressure-step Method in cross-flow filtration apparatus. Some evaluation indicators were utilized to analyze the results, such as Flux vs. Time and TMP vs. Time Curves, flux decline rate (dFlux/dt) and TMP-Fluxave curve. Two type fluxes were compared, results exhibited that hydrophilic PVDF-TiO2 modified membrane possessed a higher level of both Jcw and JTH and better anti-protein fouling ability after testing by Advanced Constant Pressure-step Method.

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Song, Z. K., Z. Y. Li, J. Xu und Y. C. Sun. „Effects of Heat Source Model and Welding Speed on Welding Temperature Field for a Plan Carbon Steel Plant“. Applied Mechanics and Materials 488-489 (Januar 2014): 83–89. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.83.

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This article studies the effects of heat source shape parameter and welding speed on the evolution of welding temperature field for Q345 plan carbon steel. The heat input and heat source parameters as well as the welding speed are defined by applying DFLUX subroutine in ABAQUS to simulate the transient welding temperature. The effects of heat resource shape parameters and heat input as well as the welding speed on welding temperature field are investigated by means of finite element analysis. It has been found that heat source parameters and welding speed show strong influence on temperature distribution in FZ (fusion zone) and HAZ (heat-affected zone). Meanwhile, it shows a roughly linear relationship between the changes of heat input and the highest temperature.

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Wang, Xiaoying, Kai Li, Yang Zhong und Qian Xu. „Investigation of Thermal Reflective Cracking in Asphalt Pavement Using XFEM Coupled with DFLUX Subroutine and FILM Subroutine“. Arabian Journal for Science and Engineering 44, Nr. 5 (21.09.2018): 4795–805. http://dx.doi.org/10.1007/s13369-018-3554-y.

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6

Hu, Ze Xun, Jian Ping Zhao und Ying Jie Zhang. „Numerical Simulation of Residual Stress in P91 Repair Welding Incorporating Martensitic Transformation“. Key Engineering Materials 795 (März 2019): 416–23. http://dx.doi.org/10.4028/www.scientific.net/kem.795.416.

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The type IV cracking is one of the main reasons for service failure. The repair welding is implemented to solve this problem. The residual stress in P91 repair welding incorporating martensitic transformation (MT) is acquired through finite element simulation. In the simulation, the ABAQUS and the user subroutines FILM, DFLUX, HETVAL, USDFLD, UEXPAN and UHARD are adopted. The effect of MT latent heat on temperature and the effects of the volume expansion, the yield strength change and the transformation plasticity on stress are considered. The results show that there is full MT in the repair welding area and the old welding area. The MT latent heat makes the temperature of the repair welding area increase. The residual stress of the repair welding area decreases because MT relieves the thermal stress. Before repair welding, the residual stress distribution is M-shape, which is consistent with the experimental results. After repair welding, the residual stress of repair welding area decreases and the residual stress of old welding area increases.

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Ahmad, Abdulrahaman Shuaibu, Yunxin Wu, Hai Gong und Lin Nie. „Finite Element Prediction of Residual Stress and Deformation Induced by Double-Pass TIG Welding of Al 2219 Plate“. Materials 12, Nr. 14 (12.07.2019): 2251. http://dx.doi.org/10.3390/ma12142251.

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Finite element (FE) analysis of welding residual stress and deformation is one of the essential stages in the manufacturing process of mechanical structures and parts. It aids in reducing the production cost, minimizing errors, and optimizing the manufactured component. This paper presents a numerical prediction of residual stress and deformation induced by two-pass TIG welding of Al 2219 plates. The FE model was developed using ABAQUS and FORTRAN packages, Goldak’s heat source model was implemented by coding the nonuniform distributed flux (DFLUX) in user subroutine to represent the ellipsoidal moving weld torch, having front and rear power density distribution. Radiation and convection heat losses were taken into account. The mechanical boundary condition was applied to prevent the model from rotation and displacement in all directions while allowing material deformation. The FE model was experimentally validated and the compared results show good agreement with average variations of 18.8% and 17.4% in residual stresses and deformation, respectively.

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Yang, Gaiyan, Liguang Zhu, Wei Chen, Xingwang Yu und Baomin He. „Initiation of Surface Cracks on Beam Blank in the Mold during Continuous Casting“. Metals 8, Nr. 9 (11.09.2018): 712. http://dx.doi.org/10.3390/met8090712.

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Surface cracking seriously affects the quality of beam blanks, a relatively new blank in the continuous casting in China. In order to study the mechanism of the initiation and propagation of surface cracks, this study established a 2D micro-segmented model of the solidification process for a beam blank in the mold, with a user subroutine DFLUX written in Fortran. Using a contact algorithm, the stress in the shell of the beam was analyzed considering the mechanical properties of the material (Q235B), thermal stress, surface friction force and ferrostatic pressure. The results showed that at the center of the web, surface longitudinal cracks were most likely to initiate at a height of 180 mm from the meniscus; at the fillet, surface longitudinal cracks were most likely to initiate at a height of 200 mm from the meniscus. Moreover, the casting speed showed a greater effect on surface crack initiation than the pouring temperature did. This study reveals the cause of longitudinal crack initiation, and the most likely positions of cracks on the strand. Thus, it is instructive for controlling surface cracks in production.

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9

Moghadasi, K., und KF Tamrin. „Multi-pass laser cutting of carbon/Kevlar hybrid composite: Prediction of thermal stress, heat-affected zone, and kerf width by thermo-mechanical modeling“. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 234, Nr. 9 (09.06.2020): 1228–41. http://dx.doi.org/10.1177/1464420720930754.

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Numerical modeling offers considerable promise to reduce costs associated with trial-and-error process in the manufacturing industry. In laser cutting of fiber-reinforced composites, the developed thermal stress in the cut region has considerable inﬂuence on the application of the machined composite and the end product quality. Nevertheless, measurement of the thermal stress is quite challenging in practice. Here, an uncoupled thermo-mechanical finite element model is developed to accurately predict formation of heat-affected zone, kerf width, thermal field, and thermal residual stress of an anisotropic carbon/Kevlar fiber reinforced composite during multi-pass laser cutting process. A novel approach of element deletion incorporating temperature-dependent Hashin failure criteria and VUMAT subroutine is proposed. The study is carried out using Abaqus interlinked with Fortran compiler to define laser Gaussian beam (DFLUX subroutine) and material removal (VUMAT subroutine) for determining the temperature gradient and cut characteristics, respectively. The numerical results agree well with the experimental scanning electron micrographs of heat-affected zone and kerf width. In addition, residual temperature after subsequent pass results in greater temperature distribution and heat accumulation. It has also been established that the strength of composite gradually decays with the increase of temperature due to stiffness (elastic moduli) degradation in the area of the cutting zone, accelerating damage initiation in both fibers and matrix.

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10

Assarzadeh, Saeed, und Majid Ghoreishi. „Electro-thermal-based finite element simulation and experimental validation of material removal in static gap single-spark die-sinking electro-discharge machining process“. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 231, Nr. 1 (08.08.2016): 28–47. http://dx.doi.org/10.1177/0954405415572661.

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Existing single spark models are subjected to too simplistic assumptions such as uniform or point heat source, constant plasma radius, invariable materials properties and constant surface temperature during discharge making them far from reality. In this study, more realistic assumptions including Gaussian type distribution of spark heat flux, temperature dependent materials properties, latent heat of melting and expanding plasma channel with pulse current and time have been made to establish a comprehensive modeling platform. The ABAQUS FEM software has been used to simulate the mechanism of crater formation due to a single discharge. The non-uniform thermal flux was programmed through the DFLUX subroutine. The simulation results show that the temperature of work piece decreases as the discharge time increases while the volume of melted and evaporated material increases. A specially designed single spark experimental set-up was developed in laboratory to carry out a few single spark tests for verification purposes. The obtained craters morphologies were examined by optical microscopy and scanning profilometer. It has been shown that the present approach outperforms other previously developed thermal models with respect to cavity outline and size possessing the maximum confirmation errors of 18.1% and 14.1% in predicting crater radius and depth, respectively. Parametric analysis reveals that the melting boundary moves onward by increasing discharge current, whereas it moves back prolonging discharge time. Finally, a closer proximity to experimental material removal rates than those predicted by analytical approach has been recognized which confirms its more precise generalization capabilities towards the real state EDM process.

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11

Cui, Zhaoxing, Xiaodong Hu, Shiyun Dong, Shixing Yan und Xuan Zhao. „Numerical Simulation and Experimental Study on Residual Stress in the Curved Surface Forming of 12CrNi2 Alloy Steel by Laser Melting Deposition“. Materials 13, Nr. 19 (28.09.2020): 4316. http://dx.doi.org/10.3390/ma13194316.

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The performance and service life of the nuclear emergency diesel engine shaft made of 12CrNi2 alloy steel is very important for the safety of nuclear power. Laser melting deposition (LMD) is a challenging camshaft-forming technology due to its high precision, rapid prototyping, and excellent parts performance. However, LMD is an unsteady process under the local action of laser, especially for curved surface forming, which is more likely to generate large residual stress on components, resulting in cracks and other defects. At present, the stress research on LMD curved surface forming is relatively insufficient. In the present paper, material parameter testing, high-temperature mechanical properties analysis, single-track sample preparation, and heat source checks are conducted. At the same time, the ABAQUS software and the DFLUX heat source subroutine are used to compile the curved double-ellipsoidal moving heat source, and the effects of the temperature-dependent thermophysical parameters and phase change latent heat on the temperature field are considered. A three-dimensional finite element model is established to analyze the thermal stress evolution and residual stress distribution of multi-track multi-layer on a curved surface by LMD, and the effect of the scanning method and interlayer cooling time on the residual stress of the formed components is studied. The results show that with the increase in temperature, the strength of the material reduces, and the fracture morphology of the material gradually transitions from ductile fracture to creep fracture. The material parameters provide a guarantee for the simulation, and the errors of the width and depth of the melt pool are 4% and 9.6%, respectively. The simulation and experiment fit well. After cooling, the maximum equivalent stress is 686 MPa, which appears at the junction of the substrate and the deposited layer. The larger residual stress is mainly concentrated in the lower part of the deposited layer, where the maximum circumferential stress and axial stress are the tensile stress. Compared with the axial parallel lap scanning method, the arc copying lap scanning method has a relatively smaller maximum thermal stress and residual stress after cooling. The residual stress in the deposited layer is increased to some extent with the increase in the interlayer cooling time.

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12

Adimurthi, G. D. Veerappa Gowda und Jérôme Jaffré. „The DFLU flux for systems of conservation laws“. Journal of Computational and Applied Mathematics 247 (August 2013): 102–23. http://dx.doi.org/10.1016/j.cam.2012.12.025.

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13

Demers-Kohls, J. F., S. L. Ouderkirk, J. L. Buckle, W. E. Norman, N. S. Cartwright und C. Dagenais. „Evaluation of the Dflex® Device for Fire Debris Analysis“. Canadian Society of Forensic Science Journal 27, Nr. 3 (Januar 1994): 99–123. http://dx.doi.org/10.1080/00085030.1994.10757030.

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14

Roberts, Marion E., Friederike M. S. Barthel, Carolina Lopez, Kate Tchanturia und Janet L. Treasure. „Development and validation of the Detail and Flexibility Questionnaire (DFlex) in eating disorders“. Eating Behaviors 12, Nr. 3 (August 2011): 168–74. http://dx.doi.org/10.1016/j.eatbeh.2011.04.001.

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15

Massey, D., E. Du Pasquier und C. Lennard. „Solvent Desorption of Charcoal Strips (DFLEX®) in the Analysis of Fire Debris Samples: Replacement of Carbon Disulfide“. Canadian Society of Forensic Science Journal 35, Nr. 4 (Januar 2002): 195–207. http://dx.doi.org/10.1080/00085030.2002.10757547.

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16

Marchiol, Fiorenza, Francesca Lionetti, Gian Luigi Luxardi, Corrado Cavallero, Marion Roberts und Barbara Penolazzi. „Cognitive inflexibility and over‐attention to detail: The Italian validation of the DFlex Questionnaire in patients with eating disorders“. European Eating Disorders Review 28, Nr. 6 (16.09.2020): 671–86. http://dx.doi.org/10.1002/erv.2781.

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17

Maria, Anne-Solène, Caroline Barry, Damien Ringuenet, Bruno Falissard, Trecogam Group und Sylvie Berthoz. „Subjective cognitive rigidity and attention to detail: A cross-cultural validation of the Detail and Flexibility Questionnaire (DFlex) in a French clinical sample“. Journal of Clinical and Experimental Neuropsychology 42, Nr. 10 (25.11.2020): 1059–71. http://dx.doi.org/10.1080/13803395.2020.1842333.

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18

Nakhodchi, Soheil, Ali Shokuhfar, Saleh Akbari Iraj und Brian G. Thomas. „Evolution of Temperature Distribution and Microstructure in Multipass Welded AISI 321 Stainless Steel Plates With Different Thicknesses“. Journal of Pressure Vessel Technology 137, Nr. 6 (01.12.2015). http://dx.doi.org/10.1115/1.4030367.

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Prediction of temperature distribution, microstructure, and residual stresses generated during the welding process is crucial for the design and assessment of welded structures. In the multipass welding process of parts with different thicknesses, temperature distribution, microstructure, and residual stresses vary during each weld pass and from one part to another. This complicates the welding process and its analysis. In this paper, the evolution of temperature distribution and the microstructure generated during the multipass welding of AISI 321 stainless steel plates were studied numerically and experimentally. Experimental work involved designing and manufacturing benchmark specimens, performing the welding, measuring the transient temperature history, and finally observing and evaluating the microstructure. Benchmark specimens were made of corrosion-resistant AISI 321 stainless steel plates with different thicknesses of 6 mm and 10 mm. The welding process consisted of three welding passes of two shielded metal arc welding (SMAW) process and one gas tungsten arc welding (GTAW) process. Finite element (FE) models were developed using the DFLUX subroutine to model the moving heat source and two different approaches for thermal boundary conditions were evaluated using FILM subroutines. The DFLUX and FILM subroutines are presented for educational purposes, as well as a procedure for their verification.

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19

Han, You Sung, Kyehyung Lee, Myoung-Soo Han, Hyunchil Chang, Kanghyouk Choi und Seyoung Im. „Finite Element Analysis of Welding Processes by Way of Hypoelasticity-Based Formulation“. Journal of Engineering Materials and Technology 133, Nr. 2 (03.03.2011). http://dx.doi.org/10.1115/1.4003099.

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Welding is one of the most important joining processes, and the effect of welding residual stresses in a structure has a great deal of influence on its quality. In spite of such a key interest, the analysis of a welding process has not been successful as in a structural analysis. This is partially because welding involves complex phenomena that are manifested by the phase evolution and by thermomechanical processes as well. In the present study, a hypoelasticity-based formulation is applied to welding processes to determine residual deformation and stresses. Algorithmic consistent moduli for elastoplastic deformations including transformation plasticity are also obtained. Leblond’s phase evolution equation, coupled with the energy equation, is employed to calculate the phase volume fraction; this plays an important role as a constitutive parameter reflecting phase fraction effects in a mechanical constitutive equation. Furthermore, transformation plasticity is taken into account for an accurate evaluation of stress. The influence of the phase transformation and the transformation plasticity on residual stress is investigated by means of numerical analyses using metallurgical parameters in Leblond’s phase evolution equation that are adjusted with respect to various cooling rates in a CCT-diagram. Coding implementation is conducted by way of the ABAQUS user subroutines, DFLUX, UEXPAN, and UMAT. The numerical examples demonstrated that the phase transformation and the transformation plasticity have a significant effect on the residual stress of a welded structure.

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20

Feli, S., M. E. Aalami Aaleagha, M. Foroutan und E. Borzabadi Farahani. „Finite Element Simulation of Welding Sequences Effect on Residual Stresses in Multipass Butt-Welded Stainless Steel Pipes“. Journal of Pressure Vessel Technology 134, Nr. 1 (07.12.2011). http://dx.doi.org/10.1115/1.4004571.

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In this paper, a finite element simulation, based on abaqus software is presented for analyzing the temperature history and the residual stress states in multipass welds in stainless steel pipe. The uncoupled thermal–mechanical a three-dimensional (3D) model and a two-dimensional (2D) model are developed. The volumetric heat source with double ellipsoidal distribution for front and rear heat source, proposed by Goldak and Akhlaghi, has also been used. Furthermore, a moving heat source has been modeled by abaqus subroutine DFLUX. A user subroutine FILM has also been used to simulate the combined thermal boundary conditions. The results of both a 3D model and a 2D axisymmetric model which are compared with the available experimental measurements show good agreements. Predictions show that the axial and hoop residual stresses in a 3D model and a 2D axisymmetric model have the same distributions in all locations except the starting point of welding. The effects of welding sequences on the thermal and structural analysis are also investigated. Four types of welding sequences for circular welds of pipe have been used and thermal history and axial and hoop residual stresses are compared. Predictions show that for other locations (except the starting point of welding) there are no important differences of axial and hoop residual stresses for welding sequences and they have the same distribution along axial direction.

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21

Wang, Huili, Sifeng Qin, Ben Wang und Shaobo Zhou. „Welding-induced Residual Stresses in U-Ribs of a Steel Bridge Deck“. Periodica Polytechnica Civil Engineering, 18.08.2021. http://dx.doi.org/10.3311/ppci.18112.

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To calculate the welding-induced residual stresses in U-ribs of the steel deck plate and conduct quantitative analysis of influential factors, the U-ribs of steel deck plate of Xinghai Bay Bridge was taken as the research object. In the ABAQUS finite element software, the local models of U-ribs of steel deck plate were established. Nodal body force loads, i.e., heat generation rate, of the double ellipsoidal heat source models were applied via the compiled subsidiary Dflux program. The welding process of the v-groove welds was simulated, to obtain the residual stresses distribution in the top plate and U-rib plates. The influence of thickness of top plate and angle of welding groove on the residual stresses in the U-ribs were studied. The results show that the welding-induced residual stresses calculated by the numerical method proposed in this paper agree well with the experimental data. The maximum residual stresses in the top plates and the U-rib plates all occur near the welds, which exceeds the yielding limitation of the material. As the thickness of top plate increases, the maximum values of residual stresses in the top plates and U-ribs increase. However, with the increase of groove angle, the maximum values of residual stresses in the top plates and U-rib plates decrease.

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