DEFORM-3D v6 Part 13 pptx

301 formulation, International Journal for Numerical Methods in Engineering, 48, pp. 545-564 [12] Kinkel, S, Gruttmann, F, Wagner, W, 1999, A continuum based three- dimensional shell element for laminated structures, Computers and Structures, 71, pp. 43-62 [13] Gelin, J. C. and Picart, P., 1999, Proceedings of NUMISHEET’99 - The 4 th international conference and workshop on numerical simulation of 3D sheet forming processes, France, September 13-17. 302 Appendix I: Eulerian treatment of the 3D rolling process Note: This facility is encapsulated in the new rolling template that is available. It is recommended to first try to use the template to take advantage of this facility. Requirements:  The work piece mesh should either be a hexahedral, structural mesh or a tetrahedral mesh (no hexahedral, non-structural meshes permitted).  The work piece should be plastic.  The simulation can possess either 1 or 2 rolls.  The inlet of work piece should have a boundary condition code defined as BCCDEF=4. This allows for proper treatment for the eulerian calculation.  The outlet of work piece should have a boundary condition code defined as BCCDEF=5. This allows for proper treatment for the eulerian calculation.  The rolls can be either a rigid object (thermal calculation only) or elasto- plastic object (deformation and thermal calculation).  The roll movement allowed is a rotation about a single axis and a translation.  The sparse solver should be used rather than the CG solver.  In the case where the roll is deformable, the rotational axis needs to be defined. This is done in the rotational symmetry data.  A data file named DEF_ALE.DAT file is used to store simulation specific information. Including this file in the problem directory where the simulation runs will activate the eulerian capability. The format for this file is as follows: # of steady state objects object # object type object # object type where: object type = 1 -> roll object 2 -> sheet object 303 Appendix J: Preventing leakage of nodes in sectioned simulations In many cases, To prevent the leaking of nodes about symmetry planes, requires extra information so that the simulation engine knows the exact definition of the symmetric condition. This is done by two definitions: 1. The deforming body needs a symmetric plane definition on the cut surfaces; 2. The rigid geometry require a symmetric surface definition on their cut surfaces. In the example used for this section, the spike simulation (Figure 176) will be used to demonstrate this capability. Note that the die geometries and the work piece mesh are the same size. What follows is a step-by-step procedure that shows how this simulation is constructed in order to allow the geometry and mesh to coincide in size. Note: If there is a difference in the size of the die versus the work piece in the symmetry surfaces, it is safer to error in making the dies larger. Figure 176: Spike problem being used as the example case. Step 1: Define symmetric surface on work piece cut faces to allow for proper meshing. On the work piece geometry, the cut faces should have symmetric surface defined prior to the meshing step (Figure 177). This option is available from the geometry selection under the symmetric surface tab. This information allows the mesh generator to maintain a tight seam of nodes on the centerline. 305 179) and the bottom die completes the specification that allows the dies and work piece to be the same size. Figure 179: Adding a symmetric surface to the top die prevents any leakage from occurring. 306 Appendix K: The Double Concave Corner Constraint This feature is available under the Simulation Controls -> Advanced menu in the preprocessor. Any given node in an FEM mesh has three degrees of freedom (DOF). In a cartesian coordinate system they can be the X, Y and Z directions. In a cylindrical system, they can be the radial, axial and hoop directions. In any case, no matter what coordinate system one selects, there are no more and no less than three degrees of freedom for any node. In the boundary condition dialog (as seen in Figure 180), the DOF for the nodes are defined through contact, through velocity control and other conditions. The way in which a DOF is defined for a node in contact is to not allow the node to penetrate into the object as well as do not allow separation if the tensile separation criteria is not exceeded (usually a small nominal value). Three contact conditions, completely specify the motion of a given node. Figure 180: The boundary condition dialog. There is a specific case where more than one degree of freedom is required for a given node. Consider the case where a node resides in the corner of a die cavity (as seen in Figure 181). Note that nodes 1,2,3 are in contact with the die surface 308 Figure 182: The two angles that are specified in the double concave corner constraint. 309 Appendix L: Rolling Simulation Overview (In Progress) This appendix will cover a basic three-dimensional rolling case seen in Figure 183. This case consists of three objects: slab, roll and pusher. The slab and the roll are objects used to model rolling and the pusher is used to start the rolling process by allowing the process to begin to bite the slab. Figure 183: Simple 3D rolling case with half-symmetry. 310 Appendix M: Checking the forming loads results of a simulation There are several factors that affect the forming loads and tool stresses of a simulation. This appendix will try to give the reader a cursory introduction into understanding what is required of a simulation in order to give accurate results. It is the presupposition of this document that DEFORM will yield an accurate result given that the inputs properly reflect the actual case being modeled. It has been verified many times that DEFORM is a leader in accurate results for the correct input. The outline of this appendix is to first discuss some guidelines for obtaining proper load results. Since these loads are transmitted as forces onto the dies, it is imperative that these results be accurate in order for the stresses in the dies to be accurate. Guideline 1: Check the flow stress data and make sure that it is representative of your actual stock. This is a very obvious rule that sounds simple at first but tends to be overlooked very frequently. Some people perform testing on their material to make sure that the data they have matches the materials they are using. Often some data is meant for different processes or has had slightly different processing conditions or has a different chemistry. If testing is not an option, often one can try to correlate load results over several simulated processes and try to determine the suitability of material data. Guideline 2: Make sure that the material data covers the process condition range. The required material data for a simulation can be only flow stress data for a rigid-plastic material at isothermal conditions. In the case of a non-isothermal elasto-plastic simulation, elastic, plastic and thermal data should be specified. All the required data should be specified for the range of temperature, strain and strain rate that the process exists at. If any extrapolation occurs, the results can become inaccurate. Guideline 3: Check that the mesh resolution of work piece is reasonable to capture the shape of the dies. The number of required elements in a simulation can vary depending on the process and the desired results. In the case of a simple upset of a round bar, the deformation gradient is not large and the only region that can require a fine mesh is at the contact areas if a hot work piece is contacting a cold tool. However, in 311 the case of a forging of a complex shape such as a crankshaft, many elements are required to capture the many details of the final shape. Guideline 4: Make sure that if the process is hot or warm that correct die speed is considered as well as time for the part to be transferred In the case of hot forming and some warm forming cases, the materials tend to be sensitive to forming rate. In this case, the speed of the moving tool can impact the results greatly. The impact of the forming rate can be seen directly in the flow stress data. By checking how much the flow stress data changes at a given temperature based on the forming rate can show very large changes in the stress of the material (thus the forming load of the part) versus the forming rate. Also, in cases where a part is very hot, small periods of time between transfers can add up to a non-negligible amount of heat loss. This is important to consider since many materials can have their properties changes very quickly at hot temperatures. Guideline 5: Check at the end of the simulation that the flash thickness is correct (or that the tool travel distance is correct) This should be of no surprise to anyone who designs tools are works in the metal forming industry. As a part fills all the crevices of a die, the load will tend to increase rather quickly. If the simulation is overstroked or understroked, the results will behave just like real life. The results will tend to over or underestimate loads respectively. Guideline 6: Make sure that the friction value is consistent with the actual process In many processes such as a forward extrusion, the friction can contribute to the forming load of the process. DEFORM provides some recommended values within the interface but it is important that the user should take care to check whether these values are applicable to the process at hand. 312 Appendix N: Model set up for Steady state machining process from the DEFORM Pre-Processor. ( ( K K e e y y w w o o r r d d f f i i l l e e a a v v a a i i l l a a b b l l e e t t o o t t h h e e u u s s e e r r : : s s t t e e a a d d y y _ _ s s t t a a t t e e _ _ m m a a c c h h i i n n i i n n g g . . K K E E Y Y , , P P r r o o c c e e s s s s t t y y p p e e : : T T u u r r n n i i n n g g ) ) O O b b j j e e c c t t i i v v e e : : • • T T o o p p r r e e d d i i c c t t s s t t e e a a d d y y s s t t a a t t e e c c h h i i p p g g e e o o m m e e t t r r y y • • T T o o p p r r e e d d i i c c t t s s t t e e a a d d y y s s t t a a t t e e t t h h e e r r m m a a l l b b e e h h a a v v i i o o r r P P r r o o c c e e d d u u r r e e : : H H e e r r e e i i s s a a s s t t e e p p - - b b y y - - s s t t e e p p i i n n s s t t r r u u c c t t i i o o n n o o n n h h o o w w t t o o p p e e r r f f o o r r m m t t h h i i s s a a n n a a l l y y s s i i s s Figure 184: Result of lagrangian simulation of chip forming S S t t e e p p 1 1 L L o o a a d d t t h h e e m m a a c c h h i i n n i i n n g g d d a a t t a a b b a a s s e e i i n n P P r r e e a a f f t t e e r r s s u u f f f f i i c c i i e e n n t t c c h h i i p p h h a a s s f f o o r r m m e e d d i i n n t t h h e e t t r r a a n n s s i i e e n n t t ( ( L L a a g g r r a a n n g g i i a a n n ) ) m m o o d d e e [...]... be present at the interface to give adequate temperature distribution through the thickness of the parts As friction welding can be a rather fast process, the temperature gradient through the thickness of the part can be rather steep, thus it is highly recommended to make a fine mesh in the depth of the part as well There are several ways in which to run such an operation A few are as follows:  Single... database is located Note that there are a few extra options that can be run for different options In particular are the options for END.DAT and TRW2.DAT The first allows the user to consider the fact that the ends will not heat as much as the rest 322 of the part since it will be exposed to the air for part of the oscillation The second option allows the pressure distribution to be non-uniform at the... 185: Setting the simulation type to steady state S te p 2 Set the analysis type to the Steady-State Machining mode in the simulation controls menu Figure 186: Set the number of steady state iterations 313 S te p 3 Set the number of steady state iterations (Number of simulation steps) Figure 187: Entering the BCC menu S te p 4 Enter the BCC menu to define the free surface nodes on the chip Figure 188:... accordance with I26 I3 – total number of data pair defining half amplitude A41, A42 – time, half amplitude A51, A52 ditto …… Example: 2 3 8 0 0.3 0.5 1.3 2.6 4 5 0.05 30 5 1 0 0.01 0.012 0.016 0.017 0. 013 0.014 0.015 323 10 0.02 Notes: 1 The oscillator should have the direction defined (“Speed” type movement) 2 Coulomb friction should be used together with an appropriate coefficient 3 Heat transfer mode . changes in the stress of the material (thus the forming load of the part) versus the forming rate. Also, in cases where a part is very hot, small periods of time between transfers can add up. distribution through the thickness of the parts. As friction welding can be a rather fast process, the temperature gradient through the thickness of the part can be rather steep, thus it is highly. that if the process is hot or warm that correct die speed is considered as well as time for the part to be transferred In the case of hot forming and some warm forming cases, the materials