Z-set documentation
Contents
1. tion etc ZCRACKS Conform 3D crack propagation toolbox General Import Export Cracks Insertion SIF Propagation Advanced Environement Datafile zcrack dat Editor gvim CPU for SMP 2 File names without extension Sane name Crack name crack Cracked name cracked Remeshing process parameters Yams options m 500 FEM D Minsize 0 100000 Max size 100 000 Iterations 2 Save Open Quit In order to start using Z cracks simply type Zcracks The Z cracks window will open it is built of many tabs the are linked to the different stages or processes required for crack growth analysis The default General tab contains various field that can be described Z set Non linear material 1 2 amp structure analysis suite Introduction e Datafile is the name of the current directory file name that will store all Z cracks relevant parameters provided in the GUI e Editor is used to set the preferred text editor command line that will be used to edit the various text files for calculation input and output e CPU for SMP is used to set the number of processors that will be used for possibly multi threaded phases of the calculation i e material integration linear solver SIF extraction e Sane name is used to specify the name of the initial finite element mesh that could be eventually imported from an external finite element software note that such file should be in the current working directory as all create files when2. Properties Display Information Slice Direction E Slice Q Annotation C Show cube axes Edit Style Representation Surface With Edges Interpolation Gouraud Material None Point size 200 EJ Line width 100 LI Opacity Subdivision 0 l Volume mapper Pro Edge Style Set Edge cotor fr Volume a fl Z set Non linear material amp structure analysis suite 2 13 ParaView 3 10 0 64 bit Turbine blade failure 2 Se oale A H 2 Displacement x Magnituc CEEL ERRE ELA Pipeline Browser ax E builtin cracked_PROPAG ut o TELE Properties Display Information _ a Apply Reset 9 Delete 2 Vectors Displacement Scale Factor 30 ParaView 3 10 0 64 bit Object Inspector CE Cem KM A4LLAAE Ecec Kd D D Di Tme 7 x E BEBP Oa Ee PER X IN I D D BI D time Le EH 2 Displacement Magnituc 5 90600806s 2 Pipeline Browser ax builtin cracked_PROPAG ut o RTE Object Inspector ex Properties Display Information Apply reset 9 Delete 2 Vectors Displacement l Scale Factor 1 Z set Non linear material amp structure analysis suite Gewn M 3 ABB AAK ECG RD 2 14
3. elements into a surface possibility inserted using the toolbox Type the correct mesh file name and press the Convert button do not press Run that would replace the converted crack mesh by a generated penny shape crack Here are check box functionalities e Ellipse specifies that a plain ellipse must be built instead of a simple disc e Mesh with CZM elements specifies that cohesive elements shall be inserted in the crack surface Min size value is then imposed on the whole surface Buttons are used to e Load load the previously generate crack surface information specified by the id value e Run generate the current surface mesh and include all the lower id crack surfaces e Medit opens medit if available to visualise the generated crack surface meshes added to the sane mesh if Sane name is already set e Zmaster opens Zmaster to visualise the generated crack surface meshes added to the sane mesh if Sane name is already set Z set Non linear material 1 8 amp structure analysis suite Insertion tab Insertion tab ZCRACKS Conform 3D crack propagation toolbox General Import Export Cracks Insertion SIF Propagation Advanced Sets to keep during remeshing Elsets Fasets Lisets Ridges Nsets Remeshing zone Elset radius 2 00000 Quadratic radius 0 00000 Thickness 0 Must extract elset Quadratic mesh Medit Zmaster ParaView Kill This tab is used to drive the mesh refinement an crack insertion pro
4. Non linear material 1 5 amp structure analysis suite Import export tab e Remesh after input is used to call a remeshing process just after the importation Yams options will thus be interpreted e Fuse during remeshing is used to activated a fuse_nset mesher see user manual with a standard tolerance set using the Mesher Meshfusion global parameter e Surface mesh is used to specified that the imported mesh is only a skin mesh and must not be filled using the tetrahedral automatic mesher i e for a 2D problem e Volume meshing only specifies that only the volumetric tetrahedral mesher will be called Buttons functionalities are e Import processes the importation process and generate a Z set mesh file called Name geo e Export exports the crack mesh in the external format using the name specified in the Cracked name global tab e Medit opens the lastly remeshed surface mesh using medit if available such button exist in various tabs and keeps the same functionality e Zmaster opens the imported generated mesh in Zmaster e ParaView opens the imported generated mesh in Paraview if available Z set Non linear material 1 6 amp structure analysis suite a Cracks tab Cracks tab Note that this stage can be skipped if a suitable crack surface was previously generated with another tool see the introduction 1 footnote about the standards that such surface mesh must observe for convenient conversion see the Conve
5. SIF value instead of the default energy release rate value it also has influence on the quantity given to the crack propagation law that must be set in G or K Be aware that the equivalent SIF is computed using the isotropic linear behaviour evaluated on the crack front for any kind of material and only has a meaning for isotropic homogeneous material G is more general Z set Non linear material amp structure analysis suite 1 12 SIF tab e Interaction integral is used to activate the interaction integral branching criterion faster but less general than the vectorial G default one e Out plane propagation is used to specify that a branching direction must be searched useful for mixed mode loading e Smooth opened front is used to set that interpolation of the inside volume values will be used closely to the structure surface for opened front instead of the computed surface one which is hard to get properly this could be a good choice when a very fine crack meshing has been done in order to obtain smoother results during the propagation process e Lips contact is used to take into account lip contact imposing a small deformation non penetration condition in the same way as what is done with CZM If penetration is detected a penalization term will be imposed such a solution is very fast for usual fatigue loadings but requires an updated Newton Raphson p1p2p3 non linear algorithm and usually achieves convergence within about 3 to 5
6. and specify a radius a value from 1 to 5 would be nice e Set Min size in the General tab to about 1 20 or the circle radius value e Back in the Cracks tab press button Run will generate a plane disc that could be visualised pressing Medit if medit is available else pressing the Zmaster button 3 Generating the cracked mesh In this part the cracked mesh will be generated e Verify that Sane name if set to disc in the General tab e In the Insert tab to preserve fasets Fasets can be set to center pressure top flasque x 0 z 0 e To preserve ridges during the remeshing Ridges can be set to edges1 edges2 e To coarsen the mesh and accelerate computations in the General tab Yams options can be set to m 500 FEM Dridge 70 Dtolerance 3 Dgeomapp 3 Dgradation 10 e Min size value can be kept for now Z set Non linear material 2 6 amp structure analysis suite 2 Turbine disc failure e Back in the Insert tab press button Run refine and visualise the refined mesh pressing Medit if medit is avaliable the mesh should be refined in the neighbour hood of the cracked zone e Press button Run cut and visualise the cut mesh pressing Medit if medit is avail able e You can also verify the cracked mesh pressing the Zmaster button 4 SIF analysis Here a SIF convergence analysis will be done e In the SIF tab check Compute SIF Interaction integral and Outplane propagation e Press the Generate inp button and Edit
7. curves be under your targeted error level If a correct convergence analysis has been performed it can safely be kept for crack propagation as crack front size will increase and produce even better SIF results it is even possible to increase automatically the Min size value accordingly to the crack front extension but this must be done with caution For all gnuplot visualisation the horizontal axis value is the arc length position along the crack front starting form the first node of the associated crack front liset position can be seen using the text editor ascii datafile pressing the G SIF values button Tab fields functionalities are e Front nodes requires an integer value used to specify the number of point where ener getic values will be computed if strictly positive if equals zero a value will be computed for each node of the meshed crack fronts that will produces oscillations in the result due to numerical integration difficulties if negative a value will be computed every value nodes that is used to regularize the obtained values default is 5 it could usually be chosen from 2 up to 16 depending of the mesh refinement e Front requires a integer value used for gnuplot visualisation specifying the front id that is different from the crack surface id expect for single crack front when value must always be 0 Here are check box functionalities e Compute SIF imposes that the quantity of interest be an equivalent
8. inp after e In the text editor complete the input file bc section this way DC kimpose_nodal_dof flasque U1 O flasque U2 0 flasque U3 0 x 0 U1 0 z 0 U3 0 kcentrifugal square ALL ELEMENT 0 0 0 d2 2000 cycle load e Run computation pressing Compute e When finished press Plot SIF to visualise SIF plot along front if gnuplot is avail able e When finished press G SIF values to visualise computed datafile e In the Insert tab check Quadratic mesh and press Run cut e In the SIF tab rerun Compute and compare new values with linear previous ones using plot or new datafile e In the General tab reduce Min size by factor 5 restart cutting process in the Insert tab and SIF analysis in the SIF tab until a suitable convergence is achieved comparing SIF plots e Press the button Zmaster to visualise the converged SIF calculation close it when analysis is finished 5 Crack propagation simulation Here a crack growth analysis will be done e In the Propagation tab set Max advance to the crack radius value for a fast coarse propagation e Set Front ini length to the initial total length of the crack front s could be obtained as the sum of max s value in the generated datafile obtained during the SIF analysis e Check Scale refinement and uncheck Transfer state thus mesh refinement will be automatically adapted to the crack length and no transfer process will be applied Z set Non linear material 2 7 amp str
9. iterations Buttons are used to e Generate inp is used to generate a pre filled Z set input calculation file ready for Z cracks that must be completed to address the user s problem e Edit inp is used to edit the Z set input file using the specified text editor adding boundary conditions materials etc e Compute runs the calculation using the prescribed number of threads e Zmaster opens Zmaster to analyse the calculation results e ParaView opens paraview if available to analyse the calculation results e G SIF values displays the SIF or G values in the created datafile using the specified text editor e Plot G displays the G and optimal G curve along the specified crack front using gnuplot if available e Plot SIF displays the modes I II HI SIF and the equivalent optimal SIF curve along the specified crack front using gnuplot if available e Plot Temperature displays the temperature curve along the specified crack front using gnuplot if available e Plot Branching displays the optimal branching angle curve along the specified crack front using gnuplot if available e Plot Front displays a 3D curve plot of the specified crack front using gnuplot if avail able and Print front value is strictly positive before computation e Kill SIF interrupts the SIF computation task Z set Non linear material amp structure analysis suite 1 13 Propagation tab Propagation tab ZCRACKS Conform 3D crack propagation too
10. using Z cracks and such given name must not contain any extension e Crack name is used to specify a Z set mesh file without extension that describes the geometry of the crack s that will be inserted e Cracked name is used to specify the name of the generated crack mesh and the associated computation files if default value cracked is used the generated initial mesh file will be called cracked geo the associated SIF computation input file cracked_SIF inp and the crack propagation file cracked_PROPAG inp Some parameters are linked to remeshing features and used in every adaptive refinement processes of Z cracks They drive the included Inria remeshing tools that are called in order to clean and refine produced meshes Let detail their functionalities e Min size specifies the absolute minimal size of the meshed elements with a floating point value e Max size specifies the absolute maximal size of the meshed elements with a floating point value e Yams options is used to define a string for surface remeshing options see above note and the Distene Yams manual e Iterations requires an integer value as the number of remeshing iterations depending of the initial mesh characteristic size compared to the crack dimensions and a required Min size value default is 2 can be increased up to 5 10 but it will slow down the remeshing process Let give some information about usual Yams options commands that could be useful see the Distene
11. Material amp Structure Analysis Suite Z cracks manual and tutorial Version 8 5 Z set is distributed by Transvalor ENSMP Northwest Numerics Inc Centre des Mat riaux 641 Arnold Road B P 87 91003 EVRY Cedex Coventry RI 02816 France USA http www zset software com support zset software com Neither Northwest Numerics and Modeling Inc the Ecole des Mines de Paris nor ONERA assume responsibility for any errors appearing in this document Information provided in this document is furnished for informational use only is subject to change without notice and should not be construed as a commitment by Northwest Numerics and Modeling Inc Z set ZebFront Z mat and Zebulon are trademarks of Northwest Numerics and Modeling Inc Ecole des Mines de Paris Northwest Numerics and Modeling Inc and ONERA 1998 2013 Proprietary data Unauthorized use distribution or duplication is prohibited All rights reserved Abaqus the 3DS logo SIMULIA CATIA and Unified FEA are trademarks or registered trademarks of Dassault Syst mes or its subsidiaries in the United States and or other countries ANSYS is a registered trademark of Ansys Inc Solaris is a registered trademark of Sun Microsystems Silicon Graphics is a registered trademark of Silicon Graphics Inc Hewlett Packard is a registered trademark of Hewlett Packard Co Windows Windows XP Windows 2000 and Windows NT are registered trademarks of Microsoft Corp Co
12. T T T T T T K_I alpha cracked SIF for FRONTO 4 5 T T T T Z set Non linear material 2 5 amp structure analysis suite g Turbine disc failure Turbine disc failure In the following pages a tutorial example of a crack propagation problem will be studied The aim is to perform a complete crack study from insertion to propagation with SIF analysis 1 Crack import This part is related to the sane mesh importation starting from a mesh file in Salome med format is inside uugiven just put disc in Sane name and set your preferred text editor in the General tab e Go to new directory copy there the file disc med e Launch Z cracks interface using command Zcracks e In the General tab set Sane name to disc preferred text editor and the number of required threads the rest can be skipped it the disc geo file is already present in the current directory e In the Import tab set format to med leave all other field to their default values e Press Import then Zmaster to verify the imported mesh then close the Zmaster window 2 Crack surface definition In this part the initial crack surface will be created e In the Cracks tab set the crack surface center press the Zmaster struct to open the sane disc mesh it is thus possible to pick up a coordinate in the Zmaster mesh window using shift middle click on a mesh node and copy past the given coordinates in the Center field e Set the Normal coordinate
13. Yams manual for an exhaustive description e m XXX is used to set up memory amount in MiB that will be allocated during the remeshing default value is 500MiB such mesh file named crack for instance must contain a shell based 3D mesh better with triangular based elements and an elset named crack containing all surface elements a nset called crack containing its nodes and a liset named crack_front that contains all the cracked surfaces unshared edges its boundary that will generate the crack front Such file can be obtained from a specific mesh that is built elsewhere for complex predefined geometries of using the Z cracks GUI for multiples penny shape or elliptic shape cracks Z set Non linear material 1 3 amp structure analysis suite 2 Introduction FEM indicates that a suitable mesh for finite element computation must be generated Dridge xx is used to specify an angle in degree floating point value that will be used for ridges detection lower values detects more ridges default value is 45 can be deactivated using nr Dgradation xx is used to specify the maximal neighbour edges length ratio defined as gt 1 small values produces surface mesh with a smoother transition between thin and coarse elements default value is 1 3 note that such action doesn t have any influence on the adaptive remeshing volume algorithm thus a high value like 10 is a good choice for 3D meshes as it shows on the surface wh
14. ace Transformation Translate 0 o Scale 1 fa E K KIO ParaView 3 10 0 64 bit D m 4 1427 2 Vincent Chiaruttini xe Be Ssrce M B X MUD ID Di Time EE H Qe e Displacement E Magnitude Surcewitneags i NH 3 AU AALE CCG BACE N Pipeline Browser ax builtin cracked_PROPAG ut o MI injec pacer Ex Properties Display Information Edge Style Set Edge Color r Volume ft AutoAdjustSampleDistances Sample Distance aoan Backface Style Representation Follow Frontface H Transformation 1 Translate 0 IC a Scale 1 fi 7 G KIO To go further other functionalities can be tested e rerun the same problem with the other branching criterion e try to insert a second crack that should intersect with the first one during the propaga tion see the Cracks tab reference manual to set up a new id e consider a problem with a more complex loading and even compression activating contact and non linear solution algorithm Z set Non linear material amp structure analysis suite 2 10 Turbine blade failure Turbine blade failure In the following pages a tutorial example of a crack propagation problem will be studied We will perform a complete crack study from insertion to propagation with SIF analysis This time a predefined temperature
15. agation toolbox General Import Export Cracks Insertion SIF Propagation Advanced Advanced global parameters Debug mode NO Cracked elset NEW Advanced crack parameters Refine factor 0 250000 Element layers 3 Max front 4 Filtering 1 00000e 06 Global fuse 1 00000e 05 Lip fuse 0 00010000 Normal length 0 00000 XFEM radius 0 00000 Extern step 0 0500000 Check ext nodes F Remesh fronts separately This last tab is devoted to advanced Z cracks functionalities It can be used by advanced users for fine tuning for very accurate SIF computations debugging modifying default filtering values Tab fields functionalities are e Debug mode is used to activate and set parameters for the debug mode is set do default No value usual optimized code is run if set to YES value optimized code is run intermediate meshes are generated during the propagation phase finally is GDB is the debugging version is run with intermediate mesh generation but set e Elset defines the name of the elset that will be remeshed is default value NEW is kept the complete mesh will be remeshed or only the given zone during the given distance e Refine radius is a required floating point factor that is used to coarsen the mesh due to its distance from the front default value is 0 35 it can be reduced to 1 for really precise analysis or increased to 1 for fast but coarse calculations e Element layers requires an integer valu
16. at will happen in the volume Dgeomapp xx and Dtolerance xx can be used to coarsen or refine the geometric approximation meshing of surfaces using floating point values value from 001 for fine meshes up to 10 for coarse ones see the Distene manual for more details The Save button is used to write the datafile that stores all field contents and options of the GUI using the name set in the Datafile field In fact for almost every meshing and calculation operations called pressing any of the associated buttons an automatic saving is done The Open button is used to open a previously written Z cracks datafile using the named set in the Datafile field The Quit button is used to exit the Z cracks toolbox The next pages will describe the functionalities provided in each tab following a usual crack propagation study main stages 1 2 3 importing the mesh if required and possibility exporting the cracked one building the initial crack meshes inserting the cracks in the current mesh and processing the adaptive remeshing performing static SIF or energy release rate computation performing crack propagation study using efficiently associated tools Z set Non linear material 1 4 amp structure analysis suite i Import export tab Import export tab Note that this stage can be skipped if a Z set initial sane mesh is available for the analysis ZCRACKS Conform 3D crack propagation toolbox General Import Ex
17. cess on the initial sane mesh It constitutes the heart of the crack meshing process Two stages are required in the first one the given sane mesh is remeshed closely to the crack surfaces possibly a zone is extracted in this area and only such part is remeshed insuring a conform interface preserving its exact topology pyramid element can be automatically inserted to link hexahedral elements with tetrahedral ones in the remeshing zone In the second stage the crack is inserted using a robust surface with volume intersection algorithm and an adaptive remeshing process is applied Note that insertion could fail due to badly set remeshing parameters see details about Yams options in the main tab manual Tab fields functionalities are e Elsets specifies the names of all the elsets that must be preserved during the remeshing process separated by a space e Fasets specifies the names of all the fasets that must be preserved during the remeshing process separated by a space e Lisets specifies the names of all the lisets that must be preserved during the remeshing process separated by a space e Ridges specifies the names of all the ridges that must be indicated to the remeshing process separated by a space Z set Non linear material 1 9 amp structure analysis suite Insertion tab e Nsets specifies the names of all the nsets that must be preserved during the remeshing process separated by a space be aware that nset pres
18. dratic interpolation of the generated cracked mesh possibily restrained to the elements close enough to the cracks front using pre scribed distance Quad radius for the entire mesh if such value is set to 0 on the crack front Barsoum s quarter node elements will be applied Buttons are used to e Run refine first stage of the insertion process refines the mesh closely to the crack surface and possibly extracts a sub mesh visualisation of the refined zone can be checked by pressing the button Medit e Run cut second stage and last stage of the insertion process cuts the refined mesh and generate the complete cracked mesh visualisation of the remeshed cut zone can be checked by pressing the button Medit e Medit opens medit if available to visualise the last generated remeshed domain e Zmaster opens the initial sane mesh in Zmaster e ParaView opens the initial sane mesh in Paraview if available e Kill kills the current remeshing process task a too long remeshing process means badly chosen parameters remeshing time is usually about 10s up to 100s for 10000 nodes up to 1000000 nodes generated meshes on a 2011 laptop Z set Non linear material amp structure analysis suite 1 10 SIF tab SIF tab ZCRACKS Conform 3D crack propagation toolbox General Import Export Cracks Insertion SIF Propagation Advanced G theta parameters default branching direction is obtained by a vectorial Gmax Front nodes 8 Gnuplot v
19. e e creating the crack surface mesh e building the crack mesh with a prescribed refinement e solving the mechanical problem and computing stress intensity factors e analysing the results and eventually modify the refinement parameters to converge to the reference SIF values In such case the reference solution is given by the following function 214 Kr a 4 0680 os E cos a 1 where a 0 5 is an angular parameter a and b are the ellipse main axes length 25 and 6 respectively Such curve can be plotted running gnuplot and typing both commands gt set xrange 90 to 0 gt plot 4 0680 sin x 180 pi 2 6 25 2 cos x 180 pi 2 25 Useful values for solution validation are K 0 45 90 1 9929 3 4690 4 0680 2 for both crack extremities and the middle node 1 Initialization In this part global parameters are set in order to correctly model the cracked structure e Go to the Raju directory A mesh file called cube geo must be present e Launch Z cracks using the Zcracks command e In the General tab set Sane name to cube preferred text editor and the number of required threads 2 Crack surface meshing This part is related to the elliptical crack surface meshing process Z set Non linear material 2 9 amp structure analysis suite 3 Elliptical crack in an infinite m e In the Cracks tab set the crack surface center to 0 0 0 e Set the Normal to 0 1 0 thus the ellipse w
20. e meshing operation and join it to all the lower id cracked meshes if present Note that intersecting or very close multiple cracks cannot be inserted directly in a sane mesh as the cutting process will probably fail in such situation it is required to insert separately each crack surface Tab fields functionalities are Z set Non linear material 1 7 amp structure analysis suite A Cracks tab e Surface id is used to set an integer number to identify the current surface it is used for multiple cracks starting from 0 for a single crack up to n for n 1 crack surfaces if but ton Verb is pressed the parameters used to built the specified crack surface imperviously meshed are loaded in the GUI e Center requires 3 floating point numbers for the 3D coordinates of the position of the surface center e Normal requires 3 floating point numbers for the 3D coordinates of the crack surface normal e Radius requires a floating point value of the radius of the disc or the first axis length in the given direction for an ellipse e Direction requires 3 floating point numbers for the 3D coordinates of the first axis direction of an ellipse if selected note that normalisation with the above given surface normal will be applied e Ortho dir radius specifies the radial length in the orthonormal direction for an ellipse with a given floating point value e Surface mesh can be used to convert a user defined crack surface made of Z set shell
21. e used to specify the number of element layers where prescribed minimal size must be imposed values from 2 to 5 can be a good choice 2 is usually nice enough and means that all element located at a distance lower than 2xmin size from the crack front will have their characteristic size fixed at min si note that this value is linked to the volume integration size during the SIF extrac process Z set Non linear material amp structure analysis suite ze tion 1 17 Advanced tab e Max fronts specifies the maximum number of fronts that can be taken into account default is 32 it can be increased if necessary e Face filtering Global fuse Lip fuse are floating point values that should only be changed by advanced users and specific cases with help of the hotline e Print front requires a floating point parameter used to output the front in a suitable gnuplot format it specifies the length of the drawn normal nothing is if the null value is set e Check ext nodes imposes crack front extremities to stay on the structure surface during propagation using the Ext step value else no correction is applied every front point advance following the crack front normal direction eventually corrected by branching criterion e Remesh fronts separately is used to be able to deal with front coalescing correctly default value can be disabled for debugging Z set Non linear material amp structure analysis suite 1 18 External
22. ection produces a second value called Grz The chosen branching angle for the new propagation direction is set to Z set Non linear material amp structure analysis suite 1 11 SIF tab be atan2 Grr Gr value Such an approach is not based on rigorous mechanical con sideration as the usual branching criterion however numerical assessment shows that it predicts efficiently complex mixed mode propagation crack path when a sufficiently small discrete propagation step is imposed even for none isotropic or homogeneous materials Finally for the chosen applied criterion the optimum energy release rate is computed based on a general G 0 approach and a mode I Irwin formula is used to produce an equivalent KI stress intensity value To obtain precise SIF values with an error level lower than 1 some advices can be made e use default values for Front nodes and advanced Refine factor Element layers parameters e always prefer a quadratic mesh to a very fine linear one e obtained values closely to the structure surface for opened front are really hard to get precisely e always proceed a convergence analysis as the remeshing process is very fast Z cracks interface is particularly adapted to this analysis since only the Min size value has to be reduced control the mesh quality with Medit see the tutorial about it and even tually increase the number of remeshing Iterations loop until the distance between two successive plotted
23. edit or Zmaster Let produce the initial cracked mesh This time only the zone close to each front will be remeshed thus check Must extract elset and set a positive large enough value in the Elset radius field for instance 2 and perform the crack insertion For the SIF evaluation process first verify that the following options Compute SIF Interaction integral Outplane propagation and Lips contact are checked Read the inp file and run the computation You can analyse the results which shows that compression occurs alternatively on each crack when the flexion load is imposed e Now proceed to propagation simulation verify that propagation increment is set to a large enough value 4 for instance in order to fasten the process 2 Thermal loading conditions In this part the loading conditions will be modified in order to address a problem with predefined loading conditions Let assume that the thermal map won t be changed due to the crack propagation Thus we only need to update at each time the mesh changes the temperature map performing a nodal transfer process Z set Non linear material amp structure analysis suite 2 11 Turbine blade failure e The first stage consists in generating a fake temperature map This can be done running the thermal inp steady state thermal calculation Type Zrun thermal inp and visualise the solution Zmaster thermal inp 2 tempera ture maps will be generated considered as the low and high te
24. ervation is only guaranteed for corners nodes lines or surface preservation must be insured using liset and fasets Note that if a nset is required during the calculation and is not found among available nsets the nodes from a bsets with the same name will also be searched e Elset radius requires a floating point value if strictly positive it defines a distance that will be used to extract all the elements that contains at least one node that is closer to the crack surface than the prescribed distance only such elements will be remeshed during the process an reintroduced in the final mesh insuring an exact topology preservation of the interface active only if Must extract elset is checked e Quad radius is a floating point parameter related to a maximal distance from the crack fronts under which quadratic interpolation can be used only active if strictly positive and when Quadratic mesh is activated e Thickness is used to treat 2D problem performing an extension if default integer value 0 is specified a 3D problem is considered otherwise the number of layer extensions can be set and then the thickness of each one given i e filled with 3 1 2 5 will produce an extension with 3 layers of thickness 1 2 and 5 Here are check box functionalities e Must extract elset is used to specify that only the given Elset see Advanced tab will be remeshed or the sub part defined by Elset radius e Quadratic mesh is used to impose a qua
25. gation precision usually values from 1 10 up to 10 of Min size are used it can be considerably increased for coarsened faster simulations If a negative value is set ie x it means that advance is proportional to the radius of the integration domain along the crack front with a factor x very useful if front advance is scaled Front ini length is a floating point value that must fit the initial cumulated crack fronts length used if Scale refinement function during propagation is active in order to coarsen or refine the mesh Min size during the propagation to adapt the mesh refinement if the crack front size varies much it usually produces more affordable computation for long crack growth but must be used with caution Initial time is the final time of the pre load that can be applied initially to the studied fatigue problem after this initial fatigue time cyclic loadings will be considered Cycle DeltaT is the constant fatigue cycle interval at the end of which propagation will be applied considering that DN loading cycles have occured C mare floating point values of the Paris law coefficients must be set accordingly to the calculation units depending of mesh size and loading units DeltaN is the explicit increment for the Paris law cyclic integration can be reduced if maximal front advance excesses the Max advance value Here are check box functionalities Scale refinement is used to activate the refinement function adapta
26. ill be built in the x z plane e Set Radius to 25 and direction to 1 0 0 for the grand axis e Check Ellipse and set Ortho dir radius to 6 e Set Min size in the General tab to 1 and Max size to 100 e Back in the Cracks tab press button Run will generate a plane disc that could be visualised pressing the Medit button if medit is available else pressing the Zmaster button 3 Generating the cracked mesh In this part the cracked mesh will be generated e Verify that Sane name if set to cube in the General tab e Inthe Insert tab to preserve fasets Fasets can be set to haut bas gauche droite fond face e To preserve nsets useful for body motion elimination during the remeshing set Nsets to POOO P100 P010 e For accurate geometrical remeshing in the General tab Yams options can be set to m 500 FEM Dridge 50 e Min size value can be kept for now e Back in the Insert tab press button Run refine and visualise the refined mesh pressing the Medit button if medit is avaliable the mesh should be refined in the neighbourhood of the cracked zone e Press button Run cut and visualise the cut mesh pressing the Medit button if medit is available e You can also verify the cracked mesh pressing the Zmaster button 4 SIF analysis Here a SIF convergence analysis will be done e In the SIF tab check Compute SIF Interaction integral and Outplane propagation e Press the Generate inp button and Edit inp after e In the
27. isualization Front 0 Compute SIF Interaction integral Outplane propagation Smooth opened front Lips contact Generate inp Edit inp Compute Zmaster ParaView G SIF values Plot G Plot SIF Plot Temperature Plot Branching Plot Front Kill SIF Using this tab the FE solution of the current cracked structure solution will be computed and post processed to calculate energetic crack parameters It constitutes the crack analysis toolbox Here SIF computation and energy release rates computation can be carried out using a G approach the process is multi threaded using the number of processes specified in the main window Two branching criteria can be used to predict the suitable propagation direction that will be chosen by the advancing crack e the first one is based on the SIF extraction obtained from an integration integral using the Westergaard analytical solutions a maximal opening stress criterion is then used if the extracted stress intensity factor value in mode II K77 is sufficiently high compared to mode I value Kz the branching angle a is computed as a 2 arctan alt VC 5 1 4 This criterion is very fast to get the branching direction but can only be used for homogeneous isotropic materials e the second one is based on two computations of the energy release rate value in two orthogonal directions The first one is along the tangential crack direction is gives a value called G the second one in the orthogonal dir
28. lbox General Import Export Cracks Insertion SIF Propagation Advanced Geometric parameters Max advance 0 500000 Front ini length 0 500000 Fatigue cycles Initialtime 0 00000 Cycle DeltaT 2 00000 Paris relationship parameters Cc 1 00000e 06 m 3 00000 Cycle DeltaN 100 Scale refinement Transfer state Generate inp Edit inp Compute Medit Zmaster ParaView Kill PROPAG Edit plw Using this tab crack propagation simulations can be computed It constitutes the crack growth analysis toolbox Crack propagation currently is restrained to the case of fatigue loading and to an explicit propagation algorithm In this section only the case of a Paris relationship will be considered The time grid is defined in the calculation input file and linked to the crack advance scheme defined after an initial pre load before Fatigue Ti by a cyclic loading of a constant time interval Fatigue DT whereas the law will be written oe C G max Gmin or C Krmar ER K min 2 where Aa is the incremental front advance along the crack front depending on the activation of Compute stress intensity factors Usually a prescribed AN DN value is set but if the Max advance value is reached the fatigue cycle increment will be reduced with possibly floating point AN values The global algorithm can be described as follows for energy release rated based computations if t gt Fatigue Ti 1 set Gmin 0 Gras 0 2 compute current time incremen
29. map will be applied Go to the Blade directory The sane structure mesh is blade geo a steady state thermal model problem is present This time you will be asked to perform by your own a 3D crack propagation simulation Both static SIF and propagation input files are already given A complex but unrealistic loading is been imposed in order to get both traction and compression conditions on each side of the blade The initial mesh is geometrically coarse thus to prevent difficulties during the adaptive remeshing process it is recommended to set the Yams options field to m 500 FEM Dridge 80 Dtolerance 4 Dgeomapp 4 1 Isothermal analysis with multiple cracks In the first part the study of an isothermal problem is considered Default parameters for the refinement can be adapted but you only need to modify what is mentioned in the following directions e Let consider the case of two cracks localized anywhere but one on each side of the blade In the Cracks tab set the Surface id to 0 and press the Zmaster struct button look at the mesh and select a point to pick up its coordinates fill the Center field Set normal accordingly maybe through the vertical direction for a just initiated crack radius can be set to 1 thus set Min size to 1 20 ie 005 Press the Run button Set the Surface id to 1 and select another point on the opposite blade side proceed as previously and finally press the Run Visualise the generated mesh using m
30. mperature maps for a fatigue loading e The next operation is to allow the cracked structure computations to get tempera ture map from the sane structure thermal map Such operation is obtained by the Z set input file transfer inp if a copy of current cracked mesh is done in the file current geo running Zrun transfer inp will transfer temperature nodal values to the current geo mesh nodes Let visualise the transferred map and compare with the original one e Now we need to modify the cracked simulation input file Before starting the computation we will run transfer process on the cracked mesh Add the following lines under the calcul line in the SIF computation file press the Edit inp button in the SIF tab of the Zcracks toolbox kshell cp f cracked geo current geo k xshell Zrun transfer inp this will copy the initial cracked mesh in the current mesh file and run the transfer process e Now we need to apply the thermal loading in the input file in the editor add the following lines kkparameter temperature node rec_size 2 O file current node 1 file current node V V 2 file current node 3 file current node 2 Note that xrec size 2 means that two maps are present in the given current file You can now launch the computation and compare the obtained results with the isothermal case e For the crack propagation input file need to be adapted as well Add the following lines under the xxxxcalcul line i
31. n the SIF computation file press the Edit inp button in the Propagation tab of the Zcracks toolbox xxxshell cp f cracked geo current geo xk xshell Zrun transfer inp followed by parameter temperature node rec_size 2 cycle_conversion 0 1000 4 function 0 4 cycle file current node 1 function 2 4 cycle file current node 2 function 3 4 cycle file current node 2 function 4 4 cycle file current node 2 that will generate the thermal loading condition for all the cycles Z set Non linear material amp structure analysis suite 2 12 Turbine blade failure Update the map file after the remeshing process near the end of the file after the line xxxZcracksxxx add shell cp f REMESHED geo current geo kshell Zrun transfer inp You can now launch the computation and compare the obtained results with the isothermal case 1 8 m FEA Mesh Slice Piot FEA amp a Run 840 870 300 TP map 5 00000 time min3750 000 maxc 1175 91 x x Mesh dimension 3 INodes 3990 ESE Elements 2980 Nsets 4 ETES Bsets 8 oui ta lElsets 0 EE b 12958 faces on the skin for mesh 1 LEJE ParaView 3 10 0 64 bit S amp B Bloc E i Ke D bA times B H Qs 4 Displacement Magnituc Surface with Edges S ii 24 22 Mh 2 zh tg Fe GG BRSOUTSTOSA O Pipeline Browser ax builtin cracked_PROPAG ut o TETE Object Inspector HE
32. ntents Reference manual Introduction 244 5 HARAS eee Sa SB Be RER aus has Import export tab Cracks tab Insertion tab SIF tab Propagation tab Advanced tab External tools Tutorial Elliptical crack in an infinite medium Turbine disc failure Turbine blade failure 1 1 1 2 1 5 LT 1 9 ili 1 14 i al bg 1 19 2 1 2 2 2 6 2 11 Chapter 1 Reference manual 1 1 Introduction Introduction A new module called Z cracks has been released in Z set version 8 5 This tool provides a generic and efficient framework for 3D cracks studies with both static crack configuration stress intensity factor SIF computation and mixed mode propagation under assumption of linear elastic fracture mechanics LEFM and small deformations Associated to a specific graphical user interface GUI this module is built on a robust 3D adaptive remeshing technique and an efficient multi threaded SIF extraction post processing The present manual provides a review of the abilities of such tool describing different aspects related to e sane mesh import export features crack surface description and multiple cracks inser tion e static crack calculation with SIF and energy release rate outputs e propagation calculation with simple or user defined propagation laws for fatigue loading e advanced aspects complex multiple cracks contact 2D problems cohesize zone inser
33. on linear material 28 amp structure analysis suite g Turbine disc failure Zmaster GQ m 3 4 1420 2 Vincent Chiaruttini xe set D Results Map 95 Time 9 50000000e 01 Magnification 20 Results factor 1 0 7 Rendered S N E 74 es q Contour Gauss point data 00 max 10299 6 Mesh outline form Error at zMaster Results_contour c 865 Enere Please select one and only one component Initial mesh Number of nodal components selected 0 Home Number of integ components selected 0 j Draw Previous Next Loading mesh from binary file cracked_PROPAG zres fea 48 zres mesh 1 geo eee Done Anim Close 9544 faces on the skin for mesh 1 Doing a post sigmises ii Doinga post sigmises a Doing a post sigmises N Doing a post sigmises Z set Non linear material 2 9 amp structure analysis suite Turbine disc failure ParaView 3 10 0 64 bit emma i N e K lt 4 gt D DI amp Time Fr EH H Displacement Ir fru Surfacewthedges KS AB HAAE LGG E 0600806520 k Pipeline Browser ax D m 3 4 1429 2 Vincent Chiaruttini xe a E builtin cracked_PROPAG ut o TELE Object Inspector ax Properties Display information Edge Style set Edge Color H Volume BE AutoAdjustSampleDistances Sample Distance Specular White Backface Style Representation Follow Frontf
34. port Cracks Insertion SIF Propagation Advanced Import format med Scale Factor 1 00000 Get surfaces 0 00000 Quadratic input mesh Remesh after input Fuse nodes during remeshing Surface input mesh Volume remeshing only Import Export Medit Zmaster ParaView This tab concerns the way to import any mesh that comes from Abaqus inp Salome med or Inria mesh formats It also allows to perform surface detection mesh coarsening or refinement scaling and insures exportation feature of any cracked mesh generated by the tool Tab fields functionalities are e Import format is used to set the import export format must be among abaqus for Abaqus inp file med for Salome mesh files and mesh for Inria mesh files import only e Scale factor gives a floating point parameter as a scale factor applied during import and reverted during export useful as Z cracks parameters are always linked to absolute values e Get surfaces gives a floating point angular criterion in degree that will be used to call extract_surface see user manual mesher after mesh importation only if not null to extract the input mesh ridges and continuous surfaces separated by detected ridges Here are check box functionalities e Quadratic mesh is used to set that the imported mesh is quadratic it will be converted to linear native quadratic meshes cannot be kept during crack processing but quadratic computation is always possible Z set
35. rt functionality in this tab Conform 3D crack propagation toolbox General Import Export Cracks Insertion SIF Propagation Advanced Surface id 0 Load Zmaster struct Penny shape crack Center 0 00000 0 000 Normal 0 00000 0 00000 Radius 1 00000 Ellipse shape crack Direction 0 00000 0 000 Ortho dir radius 3 00000 Ellipse Run Medit Mesh with CZM elements Surface mesh Convert Zmaster In this tab simple shaped crack surfaces can be generated single or multiple cracks geometries can be meshed in order to be inserted into a numerical model Currently crack geometry can be disc or plain ellipse that will create discontinuities when intersected with the sane structure mesh For multiple cracks it is needed to process incrementally defining the first surface with id 0 pressing the Run button then setting id 1 giving information and pressing Run once again until all required crack geometries are defined In order to modify a previously defined surface it is needed to specify its id in Surface id and then to press button Load in order to restore its related parameters in the GUI When modified press button Run to perform mesh generation and save the crack surface parameters When finished it is necessary to set Surface id to the final crack surface id press Load and Run to build the final mesh with all the updated crack surfaces In fact with a value set in surface id pressing Run button process the current id surfac
36. t and keeps extremal G values 3 if mod t Fatigue Ti Fatigue DT 40 go back to 2 4 compute propagation length with AN DN Z set Non linear material amp structure analysis suite 1 14 5 6 7 Propagation tab maximal computed front advance is greater than Max advance reduce AN accordingly update N value with AN and process remeshing with advanced new crack position go back to 1 Such an algorithm should be applied carefully as no geometrical update and stress state is considered during fatigue cycle step DN Thus for highly reliable crack studies Max advance should be set to the same order as Min size note that for complex mixed mode only the branching direction associated to the maximal obtained G value during the loading cycle will be used Note that SIF values computed at any required time step are stored in text files saved in the zres directory that keep to simulation results Tab fields functionalities are Max advance specifies the floating point absolute value of the upper bond of the crack advance length that can be applied during the remeshing process for a Paris law it can reduce linearly the AN increment to satisfy such length for incremental or more complex propagation laws such length is used to define when the propagation must be operated front advance is accumulated in the propagation law and when it becomes larger than Max advance remeshing process if operated having thus a great influence on crack propa
37. t mouse middle button allows to pick up a node and copy information in the ter minal number position reference color Z set Non linear material amp structure analysis suite 1 19 External tools e key V defines the new view center using the last picked up element e key r R removes allows all last selected object faces sharing the same reference very useful to visualise inside the mesh e key scales objects useful to visualise inside the mesh due to the openGL clipping distance e key F1 F2 can be use activate edit a user defined planar clipping e key i reinitializes the view to its original position Z set Non linear material amp structure analysis suite 1 20 Chapter 2 Tutorial 2 1 Elliptical crack in an infinite m Elliptical crack in an infinite medium This simple tutorial is aimed to get used to the Z cracks toolbox in order to perform a SIF convergence analysis on a reference problem This example is built from the Code_Aster documentation see http www code aster org manual v3 04 110 The initial structure geometry is given by the cube geo mesh it is 1 8 of a parallelepiped block of 2500 x 1450 x 240 dimensions where an elliptical crack with a b 25 6 are the ellipse main axes length is inserted in the middle all length units are millimetres A vertical traction is imposed and a 1 MPa pressure is applied on both vertical sides The main stages that are related to this study ar
38. text editor complete the input file bc section this way DC kimpose_nodal_dof POOO U1 0 POOO U2 POOO U3 P100 U2 P100 U3 PO10 U3 gauche U1 0 face U3 0 kpressure haut 1 time kpressure bas 1 time Z set Non linear material 2 3 amp structure analysis suite i Elliptical crack in an infinite m e Run computation pressing Compute e When finished press the Plot SIF button to visualise SIF plot along front if gnuplot is available e When finished press G SIF values to visualise computed datafile e In the Insert tab check Quadratic mesh and press Run cut In the SIF tab rerun Compute and compare new values with linear previous ones using plot or new datafile In the General tab reduce Min size by factor 5 restart cutting process in the Insert tab and SIF analysis in the SIF tab until a suitable convergence is achieved comparing SIF plots Press the button Zmaster to visualise the converged SIF calculation close it when the analysis is finished Now restart such example with a simple penny shaped crack with a radius 25mm the theoretical Kz 20 a 7 value is 5 6419 Z set Non linear material 24 amp structure analysis suite A Elliptical crack in an infinite m Zmaster Nsets 29 x ax Bsets saz Elsets 6 aan 9420 faces on the skin for mesh 1 EJE Done with open a a Doing a post sigmises b b Doing a post sigmises Gann ame sue 4 5 T
39. tion during the crack growth see Lip size Transfer state is used to activate the unknowns transfer process after remeshing be tween the old and the new mesh Deactivating such option can accelerate the simulation process for LEFM computations but a the incremental loading is applied must be defined accordingly Z set Non linear material amp structure analysis suite 1 15 Propagation tab Buttons are used to e Generate inp is used to generate a pre filled Z set input calculation file ready for Z cracks that must be completed to address the user s problem adding boundary con ditions materials etc e Edit inp is used to edit the Z set input file using the specified text editor specified e Compute runs the calculation using the prescribed number of threads e Medit opens medit if available to visualize the latest generated surface mesh very useful to follow the crack propagation during the calculation e Zmaster opens Zmaster to analyse the calculation results e ParaView opens paraview if available to analyse the calculation results e Kill PROPAG interrupts crack propagation computation task e Edit plw can be used to replace the usual Paris propagation by a more complex propagation law editing an associated plw text file for instance kbehavior fatoxflu cofe 3 1e 4 N 100 Z set Non linear material amp structure analysis suite 1 16 Advanced tab Advanced tab ZCRACKS Conform 3D crack prop
40. tools External tools Efficient use of the Z cracks requires a minimal knowledge of the associated external tools gnuplot paraview and medit The gnuplot interface is quite intuitive to zoom rescale or pick coordinate and an official documentation can be found online see http www gnuplot info documentation htm1 paraview is more complex and requires to refer to the online documentation see http www paraview org paraview help documentation html Advanced paraview users will be able to generate nice crack propagation movies see http www youtube com user OneraMNU videos for instance medit is far less intuitive but can be really useful for efficient complex re meshing validation When medit is launched pressing key h will display the software help in the launched terminal Let herein describe the most useful commands e key c colors the mesh faces e key e assigns a specific color to each referenced faset e key g colors each nset liset and ridges in red color this is very useful to identify degenerated surface elements as they usually contain over constrained ridges e key z Z are used to zoom unzoom the view e key b to toggle between dark and light background e pushing mouse left button allows to rotate the view e pushing mouse middle button down allows to displace the view e shift mouse left button allows to pick up a face and copy information in the terminal number position nodes reference color e shif
41. ucture analysis suite Turbine disc failure e Press the Generate inp button and Edit inp e In the text editor complete the input file this way x resolution kcycles dtime 1 1 increment 1 ratio automatic 1 e 5 KDC kimpose_nodal_dof flasque U1 0 flasque U2 0 flasque U3 0 x 0 U1 0 z 0 U3 0 kcentrifugal square ALL ELEMENT 0 0 0 d2 1 e6 cycle load xxxtable xxcycle cycle load 0 1000 xtime 0 1 2 xvalue 0 1 0 e Use default parameters for everything else the propagation will be cracked front advance controlled with an maximal advance corresponding to the initial crack radius during each remeshing and the corresponding N number of cycles will be adapted e Press Compute to launch the propagation calculation it will be run until complete collapse of the disc when no more crack front exists or computation fails unable to converge e During the calculation pressing buttons Zmaster ParaView Medit let follow the crack propagation advance as well as pressing buttons related to SIF analysis in the associated tab shows evolution of energetic crack parameters for the last computed time step e Closing Z cracks window will not interrupt the calculation Zcracks can be re opened to follow the launched propagation calculation To stop the calculation press button Kill in the Propagation tab Following figures present various obtained results for a particular case of this tutorial Z set N
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