DIN SPEC 32534-4-2014 Numerical welding simulation - Execution and documentation - Part 4 Example of arc welding process simulation《焊接数值模拟 执行和文档 第4部分 弧焊工艺模拟实例》.pdf

1、March 2014 Translation by DIN-Sprachendienst.English price group 11No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for DIN Specifications.ICS 25.160.01Th

2、ere are various procedures for developing a DIN SPEC: This document has been developed in accordance with the prestandard procedure.!%1AH“2143037www.din.deDDIN SPEC 32534-4Numerical welding simulation Execution and documentation Part 4: Example of arc welding process simulationEnglish translation of

3、 DIN SPEC 32534-4:2014-03Numerische Schweisimulation Durchfhrung und Dokumentation Teil 4: Beispiel Prozesssimulation LichtbogenschweienEnglische bersetzung von DIN SPEC 32534-4:2014-03Simulation numrique de soudage Excution et documentation Partie 4: Exemple de la simulation du procd de soudage lar

4、cTraduction anglaise de DIN SPEC 32534-4:2014-03SupersedesDIN SPEC 32534-4:2013-09www.beuth.deIn case of doubt, the German-language original shall be considered authoritative.Document comprises 16 pages04.14 DIN SPEC 32534-4:2014-03 2 A comma is used as the decimal marker. Contents Page Foreword . 3

5、 1 Scope . 4 2 Normative references . 4 3 Application notes 4 1. Simulation object 6 2. Simulation goals . 7 3. Physical model 7 4. Mathematical model as solution method . 8 5. Implementation . 10 7. Assuring the quality of the simulation results 14 Bibliography . 16 DIN SPEC 32534-4:2014-03 3 Forew

6、ord A DIN SPEC according to the prestandard procedure is a document which cannot yet be given full standard status, either because certain reservations exist as to its content, or because it has been developed according to a procedure deviating from that for a full standard. No draft of this DIN SPE

7、C has been published. This document has been prepared by Working Committee NA 092-00-29 AA Schweisimulation (DVS AG I 2.1) of the Normenausschuss Schweien und verwandte Verfahren (NAS) (Welding and Allied Processes Standards Committee). Further parts are listed in DIN SPEC 32534-1. Attention is draw

8、n to the possibility that some elements of this document may be the subject of patent rights DIN and/or DKE shall not be held responsible for identifying any or all such patent rights. Amendments The following amendments have been made to DIN SPEC 32534:2013-09: a) in Table 3, dimensions and boundar

9、y conditions have been updated; b) in Table 4, boundary conditions have been modified in accordance with Figure 3. Previous editions DIN SPEC 32534: 2013-09 DIN SPEC 32534-4:2014-03 4 1 Scope This DIN SPEC sets out guidelines to determine the effect the composition of the shielding gas mixture has o

10、n the characteristics of the TIG welding arc, and in particular on the arc pressure and the input of heat into the workpiece. Further examples of various documents drawn up on the basis of this template are provided in the respective parts of the DIN SPEC 32534 series. 2 Normative references The fol

11、lowing documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. DIN SPEC 32534

12、-1:2011-03, Numerical welding simulation Execution and documentation Part 1: Overview; text in German and English DIN SPEC 32534-2:2011-09, Numerical welding simulation Execution and documentation Part 2: Documentation template; text in German and English 3 Application notes The example depicted ser

13、ves to document a possible procedure. Depending on the simulation object and goal of the simulation, alternative methods and nomenclature (file names, names of variables and so forth) are also possible and permitted. In particular, the software products used in the cited examples do not represent an

14、 exclusive recommendation in favour of the presented examples or other simulation objects. In view of the ongoing further development of simulation methods and tools it is often possible to use alternative products; it is the responsibility of the user to choose a specific software product. For exam

15、ple, depending on the objective it may be necessary to determine the heat input per unit length with greater precision. DIN SPEC 32534-4:2014-03 5 Company name: Example company Department: Computation Documentation of welding simulation to DIN SPEC 32534-1:2011-03 Processor: Joe Bloggs Version: 1.0:

16、 Date: 2014-02-01 Page 1 of 12 Cover sheet with brief descriptions Simulation object: TIG arc between a tungsten cathode and a cooled copper anode using different shielding gases and amperages. Objective of the simulation: Determine the effect the composition of the shielding gas mixture has on the

17、characteristics of the TIG welding arc, and in particular on the arc pressure and the input of heat into the workpiece. Physical and mathematical model: A magnetohydrodynamic (MHD) arc model is used in combination with a shear-stress-transport (SST) turbulence model, a net emission coefficient (NEC)

18、 model and an interface sheath region model to compute the arc. It is assumed that the plasma arc column is in local thermodynamic equilibrium (LTE). Solution method and software products used: Finite Volume Method (FVM) / ANSYS CFX 12 Summary of results Arc simulation is used to determine the depen

19、dence of arc characteristics on the composition of the shielding gas mixture (argon, helium, hydrogen) and draw conclusions regarding the effect on the arc at the workpiece surface (heat input and arc pressure). It was ascertained that helium has a significant influence on arc pressure and hydrogen

20、a significant influence on heat input. Summary of the measures taken to assure the quality of the simulation results Remarks / Explanatory statements Verified x Yes No Comparison of arc shape as well as the maximum values of plasma temperature and velocity Calibrated x Yes No Modification of interfa

21、ce constants for the sheath regions Validated x Yes No Comparison with space-resolved measurements of the arc pressure and with measurements of the total heat transfer Remarks (optional): Processor: Joe Bloggs, Berta Bloggs DIN SPEC 32534-4:2014-03 6 Company name: Example company Department: Computa

22、tion Documentation of welding simulation to DIN SPEC 32534-1:2011-03 Processor: Joe Bloggs Version: 1.0: Date: 2014-02-01 Page 2 of 12 Description of welding simulation 1. Simulation object see DIN SPEC 32534-1:2011-03, 4.1 A TIG arc is simulated based on the assumption of perfect shielding gas cove

23、rage. The model takes into account the fact that the shielding gas is fed through a nozzle. The workpiece is a non-consumable and water-cooled copper anode. Figure 1 depicts the simulation domain. Figure 1 Computational domain of the simulation (axisymmetric) Legend 1 Cathode 2 Shielding gas nozzle

24、3 Workpiece 4 Flow region As well as the flow region the model also takes account of the solid domains. The properties of the components are listed in Table 1. Table 1 Solid domains Component Material Geometrical data Cathode WLa20 Diameter: 3,2 mm; tip angle: 30; plateau diameter: 0,1 mm Anode Copp

25、er Thickness: 5,0 mm Shielding gas nozzle Copper Internal diameter: 20,0 mm and external diameter: 24,0 mm The distance in the model between the electrode and the workpiece surface is 5 mm, the trailing distance between the gas nozzle and the cathode tip is also 5 mm. The shielding gases studied wer

26、e argon, gas mixtures consisting of argon and helium, and gas mixtures consisting of argon and hydrogen. Arc characteristics were calculated for 100 A and 200 A. DIN SPEC 32534-4:2014-03 7 Company name: Example company Department: Computation Documentation of welding simulation to DIN SPEC 32534-1:2

27、011-03 Processor: Joe Bloggs Version: 1.0: Date: 2014-02-01 Page 3 of 12 2. Simulation goals see DIN SPEC 32534-1:2011-03, 4.2 In addition to the amperage, cathode properties and the distance and angle of the weld torch, the characteristics of arc processes in TIG welding can also be influenced by t

28、he composition of the shielding gas. It is known that by adjusting the gases it is possible to avoid weld seam irregularities in particular and also to considerably increase the maximum possible welding speed. To be able to make use of these advantages in technical applications it is necessary to st

29、udy how the gases act in the arc. The model described in the following is designed to predict the influence of the process gas on the arc and to analyse the influence of individual gas properties. As the shielding gas only affects the weld result indirectly via the arc, the simulation should depict

30、the influence of the shielding gas on the temperature distribution and the flow of plasma in the arc as well as the relevant working load variables between the arc and the workpiece required to form the weld seam (for instance current density, heat flux, moments, and shear and compressive forces). 3

31、. Physical model see DIN SPEC 32534-1:2011-03, 4.3 The arc simulation is based on a magnetohydrodynamic model. A laminar flow character is required in the flow model. It is assumed the plasma is in local thermodynamic equilibrium (LTE). The properties of the fluid are modelled depending on the compo

32、sition of the gas mixtures and as a function of equal local temperatures of electrons and heavy particles (LTE assumption). Ideal shielding gas coverage is assumed, which corresponds to the specified gas mixture. Vapours at the electrodes and effects of thermal segregation are not taken into conside

33、ration. The radiation is modelled by means of the net emission coefficient (NEC) model. Hence, radiation transport is negligible and radiation is taken into account purely in terms of local net emission. The mechanisms of the sheath regions are depicted in a greatly simplified manner by means of an

34、interface resistance model. The energy sources of the sheath regions as a result of the flow of current are taken into account. The cathode surface is cooled by thermoemission and heated as a result of ion recombination. Electron recombination causes heating at the anode. DIN SPEC 32534-4:2014-03 8

35、Company name: Example company Department: Computation Documentation of welding simulation to DIN SPEC 32534-1:2011-03 Processor: Joe Bloggs Version: 1.0: Date: 2014-02-01 Page 4 of 12 4. Mathematical model as solution method see DIN SPEC 32534-1:2011-03, 4.4 The magnetohydrodynamic (MHD) equations s

36、ystem (Equations (1) to (7) is used to describe the arc column and the flow range. 0)( =+ut(1) Bjpuutu+=+)()( (2) NEK24)()()(SjTtphuth+=+(3) ( ) 0= (4) jA=0 (5) =j(6) ABrot= (7) In the Equations (1) to (7) denotes density, t time, uvelocity vector, p pressure, stress tensor, j current density vector

37、, B magnetic induction, h specific enthalpy, thermal conductivity, T temperature, electrical conductivity, SNEKthe net emission coefficient, electric potential, 0magnetic permeability and Athe magnetic vector potential. Equations (3) to (7) are calculated in the solid domains. The material variables

38、 are defined according to temperature. The convective term, the pressure term and the radiation term are not included in Equation (3). Instead, the solid domain radiation is taken into account as a boundary condition: )(ASBRadTTq = (8) with the emissions coefficient , the Stefan-Boltzmann constant B

39、and the temperature of the surface TSand the ambient temperature TA. The significant changes of temperature and tension in the sheath regions are approximated by thermal and electrical transfer resistances (Rand R) at the fluid-solid interfaces of the electrodes. These are computed on the basis of t

40、he thermal and electrical conductivity in the LTE and a virtual diffusion length l of the corresponding sheath region (Figure 2). The diffusion length l depends on the composition of the gas and is calibrated by means of measurements (see 7.2). RadqDIN SPEC 32534-4:2014-03 9 Company name: Example co

41、mpany Department: Computation Documentation of welding simulation to DIN SPEC 32534-1:2011-03 Processor: Joe Bloggs Version: 1.0: Date: 2014-02-01 Page 5 of 12 Figure 2 Definition of the transfer resistance at the fluid solid interfaces of the electrodes and the resulting step function based on an e

42、xample of the thermal transfer resistance R and the heat flux ABq between both interface sides A and B The heat input to the electrode surfaces resulting from the flow of current is calculated at the anode qanodeusing Equation (9) and at the cathode qcathode using Equations (10) to (12). qanode Anj

43、(9) qcathodeA+ieVj (A ij) (10) with )0,max(eijnjj =(11) and =TkTAjjBARicheexp2(12) In the Equations (9) to (12) nis the normal vector of the electrode surface, Athe work function of tungsten, iV the first ionization energy of the shielding gas, ij the ion current and jethe electron current at the ca

44、thode, with the latter corresponding to the Richardson thermionic emission current jRich. A in this case is the Richardson constant and kBthe Boltzmann constant for the sheath region. The equation system is solved with the aid of the Finite Volume Method (FVM). The software used is ANSYS CFX, versio

45、n 12.0. =DIN SPEC 32534-4:2014-03 10 Company name: Example company Department: Computation Documentation of welding simulation to DIN SPEC 32534-1:2011-03 Processor: Joe Bloggs Version: 1.0: Date: 2014-02-01 Page 6 of 12 5. Implementation see DIN SPEC 32534-1:2011-03, 4.5 5.1 Mesh and boundary condi

46、tions: Taking advantage of the axis symmetry, the simulation domain is abstracted as a pie chart slice. This is meshed through a layer of volume elements with a beam angle of 6. The geometrical model consists of 20 000 hexahedrons or 42 000 nodes. All volume elements fulfil the following minimum req

47、uirements: Table 2 Mesh properties Angle 40 Volume change 0,4 The size of the volume elements is not uniform. A mesh resolution of 0,1 mm was created perpendicular to the surface at the cathode, a mesh height of 0,4 mm at the anode. Figure 3 depicts the structure of the mesh and the boundaries of th

48、e simulation domain. The boundary conditions for the Equations (1) to (7) are listed in Table 2. Figure 3 Mesh and designation of the boundary condition Table 3 Dimensions of the boundary conditions Width mm Height mm DE 1,6 AB 5 DF 10 BC 5 DH 12 CD 12 AL 30 BG (height difference) 10 DIN SPEC 32534-4:2014-03 11 Company name: Example company Department: Computation Documentation