Recent Development of LSDYNA in Stamping Applications. Xinhai Zhu, Li Zhang, Houfu Fan, Yuzhong Xiao LSTC

Transcription

1 Recent Development of LSDYNA in Stamping Applications Xinhai Zhu, Li Zhang, Houfu Fan, Yuzhong Xiao LSTC

2 Enhancement in OneStep Method First introduced back in 2011, all quadrilateral elements in the model were split into two triangular elements internally for calculation. This original formulation (with no option) is now set as option TRIA. A new option QUAD (Revision ) is now available supporting quadrilateral elements with improved algorithm in various areas, which leads to better results. In addition, this option greatly improves calculation speed under multiple CPUs in SMP mode. Another new option QUAD2 is yet one more improvement over the option QUAD with enhanced element formulation, which further improves results in terms of thinning and plastic strain, with slightly longer CPU times. Calculation speed comparisons among the three options can be found in the following table. The option QUAD2 is set as a default as of Revision and is the recommended option.

3 Enhancement in OneStep Method original formulation): QUAD option: QUAD2 option:

4 Enhancement in OneStep Method Damage inclusion in one-step simulation: Damage accumulation D is calculated based on (refer to *MAT_ADD_ EROSION): A load curve can be defined for plastic failure strain vs. stress triaxiality relationship and DMGEXP can be input. The calculated damage accumulation is written into a file called onestepresult as history variable #6, and can be plotted in LS-PrePost.

5 Enhancement in OneStep Method Input load curve ID 500 History variable #6 fringe plot from file onestepresult

6 Traditional FLD Limitations of traditional FLDs It is obtained from flat sheet deformation, will be inaccurate when bending effect is serious Shear stress also make it inaccurate It is obtained from linear strain path When strain path is not linear, large safety margin has to be used Each material has to has its own FLD

7 Equivalent Strain Effective strain-based method (epfld) Formability Index is designed based on epfld FI = Y/Y L 0.1 Y L x Y β = dε 2 / dε

8 FLDs under Non-linear strain path

9 Improvement to contact between guide pin and blank (soft=6) Purpose: to eliminate missing contact between blank edge and gage pins during gravity loading and forming New feature allows definition of blank PID as SSID, doing away with a node set for the expected area of blank edge contact with the pin. Available only for *CONTACT_FORMING_NODES_TO_SURFACE Gage pin is very narrow, smaller than blank element edges Previously a node set must be defined along the blank edge in the area of expected contact with the gage pin. Blank edge mesh is very coarse

10 Improvement to contact between guide pin and blank (soft=6) Problem: without SOFT=6, contact missing between blank edge and gage pins fixed in XZ fixed in Z fixed in XZ Gravity loading (5G) in +Y

11 Blank PID Improvement to contact between guide pin and blank (soft=6) Gage pin PID/PSID *CONTACT_FORMING_NODES_TO_SURFACE $ SSID MSID SSTYP MSTYP SBOXID MBOXID SPR MPR $ FS FD DC V VDC PENCHK BT DT $ SFS SFM SST MST SFST SFMT FSF VSF $ SOFT 6 Gage pin PID20 Sheet blank PID21

12 *INTERFACE_WELDLINE_DEVELOPMENT final desired weldline Predicted initial weldline (weldline.ibo) Welding curve defined by *DEFINE_CURVE_TRIM_3D Output in file weldline.ibo, written in *DEFINE_CURVE_TRIM_3D Welding curve must be on the blank mesh (can be projected onto the formed blank mesh) but does not have to be aligned with meshes.

13 *INTERFACE_WELDLINE_DEVELOPMENT Resimulate with predicted initial blank Simulation verifies final laser weld line being straight

14 Improvement in Springback Compensation Springback compensation has long been in die manufacturing It overcomes user-dependent solution It is more efficient Problems in springback compensations Tangency consistency in the out boundary Large elements of the rigid tool may cause the compensation to be less efficient

15 Improvement in Springback Compensation The tool should be modified to make sure that the blank stay in the middle of the tools However, due to insufficient freedom, the blank cross the tool

16 Improvement in Springback Compensation New feature allows the rigid tool to be split along the trimming curves After split the rigid tool elements along the trimming curve, the tool is compensated nicely

17 Improvement in Springback Compensation Nominal tool surfaces are tangent to binder Compensated tool surfaces are not tangent to binder

18 Improvement in Springback Compensation A new control parameter is added to the keyword: *INTERFACE_COMPENSATION_3D to control the tangency in the out boundary

19 2D and 3D trimming of solids and laminates 2D (along one direction) 3D (element normal) 2D & 3D Double Trim Adaptive mesh Shell Yes Yes Yes Yes Solids Yes Yes Yes* N/A Laminates Yes Yes Yes* One layer of solids only*; Multiple layers of solids okay for nonadaptive mesh*. TSHELL Yes* N/A N/A N/A Note: items designated * are new capabilities.

20 Double Trim of Laminates and Solids 2D trimming: seed node 3D trimming: seed node

21 Improvement in Lancing MPP enabled Uniform refinement along lancing curve

22 *CONTROL_FORMING_SHELL_TO_TSHELL Change from thin shell to thick shell elements; Create segment sets on both top and bottom sides of the thick shells; Adaptive mesh not supported; Only one layer of thick shell will be generated. PID of the thin shells Thickness of the TSHELL TSHELL mid-plane location (see next page) Segment set ID at the bottom layer of TSHELL Segment set ID at the top layer of TSHELL

23 *DEFINE_CURVE_STRESS Keywords: *DEFINE_CURVE_STRESS Defines material hardening curve based on commonly used hardening laws. Weighted combinations of hardening laws are possible.

24 *CONTROL_ADAPTIVE_CURVE Uniform mesh adaptivity within a curve loop is enabled Define parameters NSEED1, N, and SMIN. Set TCTOL=2. Both TCTYPE 1 and 2 are accepted.

25 Removal of Adaptive Constraints *CONTROL_FORMING_REMOVE_ADAPTIVE_CONSTRAINTS $ PID &blkpid Removes adaptive constraints Fully connect meshes using triangular elements For stoning and accurate springback simulation

26 Clamping Simulation Moving clamp PID *DEFINE_FORMING_CLAMP L.T.0: nodal normal $ $ CLP1 CLP2 VID GAP AT DT $ *DEFINE_FORMING_CONTACT $ IPS IPM FS ONEWAY Corresponding fixed clamp PID Final clamps gap Clamping direction: G.T.0: vector Duration Slave PID Master PID Contact friction Contact way

27 *DEFINE_CURVE_FLD_FROM_TRIAXIAL_LIMIT *MAT_TRANSVERSELY_ANISOTROPIC_ELASTIC_PLASTIC_NLP_Failure $ MID RO E PR SIGY ETAN R HLCID &blk1mid E E $ IDSCALE EA COE ICFLD 909 *DEFINE_CURVE e *DEFINE_CURVE_FLD_FROM_TRIAXIAL_LIMIT , , ,

28 *DEFINE_CURVE_TRIAXIAL_LIMIT_FROM_FLD *MAT_TRANSVERSELY_ANISOTROPIC_ELASTIC_PLASTIC_NLP_Failure $ MID RO E PR SIGY ETAN R HLCID &blk1mid E E $ IDSCALE EA COE ICFLD 909 *DEFINE_CURVE e *DEFINE_CURVE_TRIAXIAL_LIMIT_FROM_FLD , , ,

29 Mesh fusion No mesh fusion With mesh fusion

30 Mesh fusion Springback Analysis No fusion Springback Analysis with fusion Final No. of shell elements = 2476 Final No. of shell elements =

31 Mesh Fusion Effective Plastic Strain Without fusion Effective Plastic Strain With mesh fusion

32 Time Reduction (%) Max. EP Strain Difference (%) Mesh Fusion Angle Difference (%) Min. Shell Thickness Difference (%) Time Reduction No. of CPUs No. of CPUs 12 Springback Angle Difference 10 8 Max. EP Strain Difference 10 Min. Shell Thickness Difference No. of CPUs No. of CPUs Significant reduction in CPU cost No obvious difference in thinning and plastic strain prediction

33 Improvement in Mesh Fusion Significant improvement in CPU time reduction (25%) No obvious effect on thickness and formability prediction Small difference in springback prediction (5%)

34 Adaptivity for Sandwich Structure Background For laminated material, the top and bottom layers are metals and the middle is composite material The top and bottom layers are model with shell element The middle layer is model with solid element Top and bottom shell elements share nodes with solid elements Mesh adapvity was implemented to this structure, but only allow one layer of solid elements Under the request, mesh adaptivity was extended to multi-layer of solid elements

35 Improvement of Sandwich Structure Adaptivity Top and Bottom Shells Middle Solid Sandwich Structure Part consists of Top and bottom are shell parts The middle is the solid structure Initially only one layer of solid can be used for adaptivity. Recent request to use multi-solid element in forming

36 Adaptivity for Sandwich Structure Mesh refinement only happen in the plane, No refinement in the thickness direction One solid element is split into 4 solid elements Works for both SMP and MPP Illustration of mesh refinement for sandwich structure

37 Adaptivity for Sandwich Structure Example of adaptive fission for sandwich structure

38 Improvement of Sandwich Structure Adaptivity One layer of solid element Three layer of solid element

39 New Fission/Fusion for Incremental Forming Characteristics of incremental forming and roller forming Deformation is very local, termination is long, CPU time is HUGE

40 New Fission/Fusion for Incremental Forming

41 The End