Hello everyone, I'm doing a simulation consisting of 3 steps: welding treatment, cooling, creep treatment. So my idea was that to “split” the whole simulation in two independent ones: welding+cooling (first sim); creep (2nd sim). I was having issues with the creep simulation, but I solved them changing BCs; I don't have issues with the welding+simulation, but I get problems when I try to put them together to for a larger simulation where welding, cooling and creep are simply steps and not simulations by themselves.
first, I'llexplain the creep sim: I have performed a creep analysis on a dogbone specimen made of ss 304. In property module I've created the material, specifying Young's modulus (1.5e11) and Poisson's ratio (0.33) on sheet "Elastic" and specifying Power Law Multiplier (8e-58), eq stress order (6.69) and time order (0) in sheet "Creep". Then I create Visco step in Step module, specifying a time period of 4000 s (Nlgeom: on); in the sheet "Incrementation" I've choosen the max number of increment (10000), Initial increment size (.1), minimum (1e-5) and max (10), then I've choosen creep/swlling...tolerance (5e-6). After that I've created a coupling constraint in Interaction module, then a reference point for the upper surface of the specimen (where I applied load), I've created a simmetry BC for the bottom section (half specimen for the test), then I've defined a load (pressure) of 60 Mpa of Magnitude (traction) with an amplitude defined in tabular way (linear, from 0 to 1 of the amplitude in 100 s). I've done the mesh, i've created and started the job, but I've got an Aborted job, the error was: "time increment required is less than the minimum specified". For other details: first I've made a dogbone specimen (half of it) (pic at this link, you can see also the mesh: https://imgur.com/a/Y3gssE3). Then in the Property module, "edit material", I've used the Norton's Law (https://imgur.com/NGtOD5Q) with these value: https://imgur.com/Ev1HJ9d. I've found them in table 3 at the link " https://www.mdpi.com/2075-4701/13/2/197 " (A is power law mult, n is eq stress order for the temperature of 700°C). Always in Property module, "elastic", I've choosen Young's modulus (1.5e11 Pa) and 0.33 for Poisson's (still at 700°C). I've created a Solid Homogeneus section and assigned that to the specimen. In Step module, I've create a procedure type "Visco" from the list, then I've put 4000 s in basic sheet (Nlgeom on), then in incrementation I've put the values you can see here: https://imgur.com/y0dIfFo. I've create a constraint coupling in Interaction Module (https://imgur.com/pD62OzZ) to make all the surface moving with the reference point. In Load, I've created a symmetry BC for lower surface (https://imgur.com/CeRzN7Q), then I've create a load on the upper surface (https://imgur.com/g5eGsfC) and I've defined a linear and then a constant pressure load (https://imgur.com/qUwwQ42). The load appears like that: https://imgur.com/JCWs5Og. Then I've made the mesh (regular one, 1 mm the size up to 1.5 cm the bigger squares) (https://imgur.com/m3eoGCU). Then I've created job.
Now I'll explain the other simulation, the welding+cooling: it consists in the same geometry, the same material (SS 304), but I’ve defined the following material behaviors: density: I’ve used temperature-dependent data, uniform distribution (https://imgur.com/w2g9zBZ) elastic: I’ve used temperature-dependent data (https://imgur.com/jJZXXTH) Expansion, plastic, conductivity, specific heat: same, list of values temperature-dependent. Latent heat (https://imgur.com/Ap9Kq2P) After defined material properties/behaviour, I’ve assigned a solid homogeneus to the section. In Step module, I’ve defined 2 steps: welding, coupled temp-displacement type (https://imgur.com/013wHKc), 3.33 s of time period, Nlgeom on; then a cooling step, always coupled temp-displacement type (https://imgur.com/bEMZkVh) , 1000 s of time duration. In the module “Interaction”, I’ve created for the step welding a Surface film condition (for thermal convection) with a film coefficient of 15, ambient temp of 25°C, selecting the surfaces you see in pic (https://imgur.com/1xJaee6). I’ve also created another interaction, Surface radiation, using an emissivity coefficient of 0.7 (using the same surfaces of the previous pic). In the menu “Model”, “Edit attributes”, I’ve defined Absolute zero temp (to be able to use Celsius degrees in my sim) and I’ve defined Stefan-Boltzmann constant (https://imgur.com/7SIBe83). In module “Load”, for the initial step, I’ve choosen symmetry/antisymmetry/encastre condition, XSymm for the little surface parallel to yz plane (https://imgur.com/NfX83fh), and for the same step I’ve choosen encastre for the larger section parallel to yz (https://imgur.com/FEUa0F5). Then, I’ve assigned a predefined field of temperature of 25°C to the whole part in the step “initial”, then I’ve create a load, type “Body head flux”, magnitude 1, “user-def” distribution (I’ve used the DFLUX subroutine). I deactivated the load for the cooling step, then I’ve meshed the part (regular mesh, using edge seeds). I’ve selected subroutine for my job, and I’ve started it.
Now my problem, as I said before, consists to join this first steps to the creep one in order to create one whole simulation with all the 3 steps together. As you can see, the differences are the following: 1) in the Material Property, I’ve a temperature-dependent data list for welding-cooling, and only 1 row of data for creep; same speech for density. 2) BCs vary for welding-cooling and for creep (and also the load) I’ve tried to put all together using Material properties for welding-cooling also for creep (I don’t know if it’s possible to define a new material but I think it’s a wrong procedure), I deactivated the propagated BCs of welding-cooling for the welding and I’ve created a new one (encastre, see the creep sim showed before). I got a specimen that changes position inside the viewport and, when the creep sim starts, it bends doing a circular motion around the little surface parallel to yz plane (https://imgur.com/ljhy2Ph).
Could you help me to get what am I doing wrong? Thanks so much.
Abaqus
