Science topic

# Finite Element Analysis - Science topic

A computer based method of simulating or analyzing the behavior of structures or components.

Questions related to Finite Element Analysis

Hello everyone

I am new to MATLAB and would appreciate some assistance. I am currently working on an optimization problem that involves finite element analysis. I have two parts A and B that are in contact with each other. Each of these parts is made of a different material and has its own properties. I want to find out how the distribution of relative density in part A affects the distribution of stress and strain energy in part B. I think this is a simple FE problem. But I've never solve such problem through MATLAB before. My question is that “Is it possible to do this through MATLAB? If so, how complex is the coding process for this problem?”

Thank you in advence

Hello to all,

I am modeling a 3d reinforced concrete column in DIANA FEA. On the bottom side, the model is supported by an area support. When the model is meshed and calculated I get 1400 small reaction forces in every mesh node. I would like to create a Force-Displacement diagram and for that, I need one reaction force that is a sum of all small reactions.

I know that I can extract nodal forces in a table and create a sum in Excel, but I want to do a nonlinear analysis with several hundred load steps and that approach is not very efficient.

Any advice on how to get reaction force which represent a sum of nodal forces?

Thanks for any suggestions. It would be much appreciated.

Hello Everone,

I have conducted a multibody simulation of a gearbox casing in Simpack, and I’ve exported the results as a text file. This file contains the

**real and imaginary components of normal velocity**at each node for frequencies ranging from**50 Hz to 200 Hz**.In Abaqus, I’ve created an

**Acoustic Mesh**where the material is**air**. My goal is to apply these nodal velocities (from the Simpack results) to the**nodes at the base of the Acoustic Mesh**and then perform an**acoustic analysis**to calculate the**sound pressure**around the gearbox.Here's what I have so far:

- I've used
**Python (pandas)**to read the text file and convert the velocity data into**NumPy arrays**—one for each frequency, containing the normal velocity at each node. - Now, I need to apply these velocities as boundary conditions in Abaqus for each frequency.

My question is:

- How can I apply these nodal velocities to Abaqus using Python?
- Is there a specific section in the Abaqus manual that covers this?
- Any guidance on how to set this up, would be greatly appreciated.

Thank you in advance for your help!

I am willing to do fluid-structure interaction studies for a 3-D rectangular tank under seismic excitation. For the FE discretization of the tank and fluid domain, can a 2-D element be used in the 3-D space for analysis? If yes, will it reduce accuracy of the results?

I am modelling a hyperelsatic and viscous material in ABAQUS. I have calculated the hyperelasticity parameters using curve fitting. Now, for viscoelasticity, I have stress relaxation results in terms of shear modulus variation with time. While inputting the data into Abaqus, you need two parameters G0 and Ginf along with the experimental results. So i think G0 is the shear modulus at the beginning of relaxation test and Ginf is defined based on hyperelastic parameter(2*C0 for Yeoh Or similar for other models)? Am I correct or else?

Dear community,

I am trying to run a transient structural analysis to simulate the rolling contact between a wheel and a rail. However, in the rolling step, the wheel just keeps going through the rail body without contacting it.

The boundary conditions are a fixed support at the rail bottom face. A displacement boundary condition that only allows displacement of the wheel center in the vertical and longitudinal directions (z and x respectively) as well as rotation about the y axis are applied to a pilot node placed at wheel center. A force condition of 75000 N in the direction vertical direction is applied on the pilot node at wheel center. The contact between the wheel and rail is frictional contact. Please find attached a figure of the problem I obtain and the boundary conditions as they are defined in apdl.

Thank you so much for the help.

Best regards,

Hajar

Hello everyone, I am conducting a simulation task using CEL method in Abaqus related to offshore pipeline. I would like to know how to assign different soil materials for several soil layers of Eulerian part in Abaqus, please help. Thank you so much

Can the CDP (Concrete Damage Plasticity) model or the Hashin Damage model be effectively used for modeling the behavior of engineered cementitious composites (ECC) in finite element analysis (FEA)? Additionally, what are the key factors that should be considered when choosing between these two damage models for accurately capturing the mechanical and damage characteristics of ECC, such as cracking, strain hardening, and failure modes?

ABACUS is a software tool for Finite element analysis .Please explain how to use this tool to analyze experimental problems with example

I have programmed a UEL subroutine for a 3D cohesive element and I have a problem.

When I do the testing using a 3D single element, the subroutine converges if and only if I put initial boundary conditions on all nodes.

For example, imagine the bottom surface is fixed and the upper surface is prescribed a displacement to perform a tensile test. Then, it is necessary to impose the lateral displacements in order to obtain convergence. If this latter constraint is not applied, the subroutine does not work (wrong displacement values obtained, error message). It seems that stiffness matrix becomes ill conditioned in the absence of sufficient boundary conditions. Yet, I observe that the cohesive elements already available in Abaqus cause no problem. For these elements, the convergence is always obtained even if the lateral displacements are not applied.

Why does this work well with Abaqus elements, but not with a user element in UEL? I verified my subroutine and I think that I have strictly implemented the classical formulation for cohesive element.

I am currently working with

**recycled aggregate concrete**and using**finite element simulations**to predict its behavior under different conditions. I have faced several challenges in accurately modeling the properties of this material, especially considering its heterogeneous nature and the variability of recycled aggregates.I would like to know what specific challenges others have encountered while modeling recycled aggregate concrete in finite element analysis and what methods or techniques have proven effective in addressing these issues. Any insights into improving the accuracy and reliability of these models would be greatly appreciated.

Dear RG Members,

I’m currently working on extracting data of multiple .rst/.rth files, which are having same mesh and same node numbering, using PyANSYS/PyMAPDL. The end target is to use this data for LCF/Creep/Creep-fatigue/fracture calculations. Currently this data extraction is done manually, we want to automate this process.

The elements I am using is plane77 (with axisymmetric option) for thermal analysis and plane 183 (axisymmetric) for structural analysis (in ANSYS).

Please look at the figure attached.

I want to provide path for all my rth/rst files and respective load/substep numbers for which I want to extract data. On pressing confirm a popup will ask for node number and desired data (temperature/stress/strain/creep strain) for that node number should be there in the output column from all these files (that's the wish). First row data (temperature from a rth file for steady state thermal run) I was able to extract. Got stuck in the second row where I want von Mieses stress from a steady state structural run.

However, when I attempt to parse the result sets using result.parse_step_substep(), I receive only integer indices representing the result sets, rather than a tuple containing the actual load step and substep numbers. For example, my .rst file shows 3 result sets, but the step info returned is simply 0, 1, and 2, without any clear mapping to the original load step and substep numbers from the simulation. Is there a current method within PyMAPDL to directly retrieve data based on specific load step and substep numbers (e.g., Load Step 3, Substep 5), rather than relying on the result set indices?

Thank you for your help and support in advance.

Regards

NC

Let's say we have a standard, regular hexagonal honeycomb with a 3-arm primitive unit cell (something like the figure attached; the figure is only representative and not drawn to scale). The bottommost node is taken as the source of wave input and the ends of the left and right arms are taken as destinations such that Bloch's condition can be applied as q

_{left}= e^{ik1 }q_{bottom}and q_{right}= e^{ik2 }q_{bottom}. I wish to learn how would an iso-frequency contour plot be plotted post performing the dispersion analysis. Thanks in advance.**I am simulating the propagation of cracks on ANSYS APDL using a cohesive zone model. My goal is to effectively illustrate how hydrogen diffusion affects this material.**

To illustrate the influence of hydrogen, I proposed emphasizing its material properties. An experiment involving a tensile test was conducted on a pipeline sample both with and without hydrogen influence. For both the charged and uncharged pipeline samples, a stress-strain graph was created. Using the supplied stress-strain data, I was able to conduct a linear test and determine the young modulus, which allowed me to obtain a reasonable Traction Separation Law result. But when I attempted to apply the nonlinear route, I changed the Material properties by incorporating the stress-strain data into my analysis, and the outcome I got did not resemble any kind of traction separation law graph. I have included the code I used to accomplish this below. Does anyone know how to depict the influence of hydrogen on a metal sample in ANSYS APDL?

**Code for Linear orthotopic material**

/PREP7

ET,1,182 !* 2D 4-NODE STRUCTURAL SOLID ELEMENT

KEYOPT,1,1,2 !* ENHANCE STRAIN FORMULATION

KEYOPT,1,3,2 !* PLANE STRAIN

ET,2,182

KEYOPT,2,1,2

KEYOPT,2,3,2

ET,3,202 !* 2D 4-NODE COHESIVE ZONE ELEMENT

KEYOPT,3,3,2 !* PLANE STRAIN

MP,EX,4,1.353E5 !* E11 = 135.3 GPA

MP,EY,4,9.0E3 !* E22 = 9.0 GPA

MP,EZ,4,9.0E3 !* E33 = 9.0 GPA

MP,GXY,4,5.2E3 !* G12 = 5.2 GPA

!MP,GYZ,4,5.2E3

!MP,GXZ,4,3.08E3

MP,PRXY,4,0.24

MP,PRXZ,4,0.24

MP,PRYZ,4,0.46

GMAX = 0.004

TNMAX = 25 !* TENSILE STRENGTH

TB,CZM,5,,,EXPO !* COHESIVE ZONE MATERIAL

TBDATA,1,TNMAX,GMAX,1000.0

RECTNG,0,100,0,1.5 !* DEFINE AREAS

RECTNG,0,100,0,-1.5

LSEL,S,LINE,,2,8,2 !* DEFINE LINE DIVISION

LESIZE,ALL,0.75

LSEL,INVE

LESIZE,ALL, , ,200

ALLSEL,ALL

TYPE,1 !* MESH AREA 2

MAT,4

LOCAL,11,0,0,0,0

ESYS,11

AMESH,2

CSYS,0

TYPE,2 !* MESH AREA 1

ESYS,11

AMESH,1

CSYS,0

NSEL,S,LOC,X,30,100

NUMMRG,NODES

ESLN

TYPE,3

MAT,5

CZMESH,,,1,Y,0, !* GENERATE INTERFACE ELEMENTS

ALLSEL,ALL

NSEL,S,LOC,X,100 !* APPLY CONSTRAINTS

D,ALL,ALL

NSEL,ALL

FINISH

/SOLU

ESEL,S,TYPE,,2

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,1.5 !* APPLY DISPLACEMENT LOADING ON TOP

D,ALL,UY,10

NSEL,ALL

ESEL,ALL

ESEL,S,TYPE,,1

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,-1.5 !* APPLY DISPLACEMENT LOADING ON BOTTOM

D,ALL,UY,-10

NSEL,ALL

ESEL,ALL

NLGEOM,ON

AUTOTS,ON

TIME,1

NSUBST,40,40,40

OUTRES,ALL,ALL

SOLVE !* PERFORM SOLUTION

**Linear Isotropic**

FINISH

/PREP7

ET,1,182 !* 2D 4-NODE STRUCTURAL SOLID ELEMENT

KEYOPT,1,1,2 !* ENHANCE STRAIN FORMULATION

KEYOPT,1,3,2 !* PLANE STRAIN

ET,2,182

KEYOPT,2,1,2

KEYOPT,2,3,2

ET,3,202 !* 2D 4-NODE COHESIVE ZONE ELEMENT

KEYOPT,3,3,2 !* PLANE STRAIN

MP,EX,1,2E5

MP,NUXY,1,0.3

GMAX = 0.004

TNMAX = 25 !* TENSILE STRENGTH

TB,CZM,5,,,EXPO !* COHESIVE ZONE MATERIAL

TBDATA,1,TNMAX,GMAX,1000.0

RECTNG,0,100,0,1.5 !* DEFINE AREAS

RECTNG,0,100,0,-1.5

LSEL,S,LINE,,2,8,2 !* DEFINE LINE DIVISION

LESIZE,ALL,0.75

LSEL,INVE

LESIZE,ALL, , ,200

ALLSEL,ALL

TYPE,1 !* MESH AREA 2

MAT,1

LOCAL,11,0,0,0,0

ESYS,11

AMESH,2

CSYS,0

TYPE,2 !* MESH AREA 1

ESYS,11

AMESH,1

CSYS,0

NSEL,S,LOC,X,30,100

NUMMRG,NODES

ESLN

TYPE,3

MAT,5

CZMESH,,,1,Y,0, !* GENERATE INTERFACE ELEMENTS

ALLSEL,ALL

NSEL,S,LOC,X,100 !* APPLY CONSTRAINTS

D,ALL,ALL

NSEL,ALL

FINISH

/SOLU

ESEL,S,TYPE,,2

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,1.5 !* APPLY DISPLACEMENT LOADING ON TOP

D,ALL,UY,10

NSEL,ALL

ESEL,ALL

ESEL,S,TYPE,,1

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,-1.5 !* APPLY DISPLACEMENT LOADING ON BOTTOM

D,ALL,UY,-10

NSEL,ALL

ESEL,ALL

NLGEOM,ON

AUTOTS,ON

TIME,1

NSUBST,40,40,40

OUTRES,ALL,ALL

**Non linear : Multilinear isotropic hardening**

/PREP7

ET,1,182 !* 2D 4-NODE STRUCTURAL SOLID ELEMENT

KEYOPT,1,1,2 !* ENHANCE STRAIN FORMULATION

KEYOPT,1,3,2 !* PLANE STRAIN

ET,2,182

KEYOPT,2,1,2

KEYOPT,2,3,2

ET,3,202 !* 2D 4-NODE COHESIVE ZONE ELEMENT

KEYOPT,3,3,2 !* PLANE STRAIN

MP,EX,1,1e7

MP,NUXY,1,0.3

TBDE,MISO,1,,,

TB,MISO,1,1,20,0

TBTEMP,0

TBPT,,0.00300,30000

TBPT,,0.00350,33041

TBPT,,0.00400,34300

TBPT,,0.00450,35267

TBPT,,0.00500,36082

TBPT,,0.00550,36800

TBPT,,0.00600,37449

TBPT,,0.00650,38045

TBPT,,0.00700,38601

TBPT,,0.00750,39123

TBPT,,0.00800,39616

TBPT,,0.00850,40086

TBPT,,0.00875,40312

TBPT,,0.00900,40534

TBPT,,0.00925,40751

TBPT,,0.00950,40964

TBPT,,0.00975,41173

TBPT,,0.02400,49708

TBPT,,0.04000,56160

TBPT,,0.06300,63313

GMAX = 0.004

TNMAX = 25 !* TENSILE STRENGTH

TB,CZM,5,,,EXPO !* COHESIVE ZONE MATERIAL

TBDATA,1,TNMAX,GMAX,1000.0

RECTNG,0,100,0,1.5 !* DEFINE AREAS

RECTNG,0,100,0,-1.5

LSEL,S,LINE,,2,8,2 !* DEFINE LINE DIVISION

LESIZE,ALL,0.75

LSEL,INVE

LESIZE,ALL, , ,200

ALLSEL,ALL

TYPE,1 !* MESH AREA 2

MAT,1

LOCAL,11,0,0,0,0

ESYS,11

AMESH,2

CSYS,0

TYPE,2 !* MESH AREA 1

ESYS,11

AMESH,1

CSYS,0

NSEL,S,LOC,X,30,100

NUMMRG,NODES

ESLN

TYPE,3

MAT,5

CZMESH,,,1,Y,0, !* GENERATE INTERFACE ELEMENTS

ALLSEL,ALL

NSEL,S,LOC,X,100 !* APPLY CONSTRAINTS

D,ALL,ALL

NSEL,ALL

FINISH

/SOLU

ESEL,S,TYPE,,2

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,1.5 !* APPLY DISPLACEMENT LOADING ON TOP

D,ALL,UY,10

NSEL,ALL

ESEL,ALL

ESEL,S,TYPE,,1

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,-1.5 !* APPLY DISPLACEMENT LOADING ON BOTTOM

D,ALL,UY,-10

NSEL,ALL

ESEL,ALL

NLGEOM,ON

AUTOTS,ON

TIME,1

NSUBST,40,40,40

OUTRES,ALL,ALL

**Kinematic isotropic hardening**

/PREP7

ET,1,182 !* 2D 4-NODE STRUCTURAL SOLID ELEMENT

KEYOPT,1,1,2 !* ENHANCE STRAIN FORMULATION

KEYOPT,1,3,2 !* PLANE STRAIN

ET,2,182

KEYOPT,2,1,2

KEYOPT,2,3,2

ET,3,202 !* 2D 4-NODE COHESIVE ZONE ELEMENT

KEYOPT,3,3,2 !* PLANE STRAIN

MP,EX,1,2e5

MP,NUXY,1,0.3

TBDE,KINH,1,,,

TB,KINH,1,1,20,0

TBTEMP,0

TBPT,,0.0297e2,63.37

TBPT,,0.048e2,99.43

TBPT,,0.0877e2,168.39

TBPT,,0.1399e2,242.14

TBPT,,0.1917e2,298.84

TBPT,,0.3498e2,337.76

TBPT,,1.0742e2,344.78

TBPT,,2.3577e2,412.14

TBPT,,3.246e2,444.29

TBPT,,4.1576e2,468.34

TBPT,,4.929e2,484.89

TBPT,,5.893e2,499.91

TBPT,,6.777e2,509.84

TBPT,,7.806e2,518.54

TBPT,,8.6465e2,523.65

TBPT,,11.1e2,532.51

TBPT,,12.269e2,534.09

TBPT,,13.533e2,536.26

TBPT,,15.098e2,536.17

GMAX = 0.004

TNMAX = 25 !* TENSILE STRENGTH

TB,CZM,5,,,EXPO !* COHESIVE ZONE MATERIAL

TBDATA,1,TNMAX,GMAX,1000.0

RECTNG,0,100,0,1.5 !* DEFINE AREAS

RECTNG,0,100,0,-1.5

LSEL,S,LINE,,2,8,2 !* DEFINE LINE DIVISION

LESIZE,ALL,0.75

LSEL,INVE

LESIZE,ALL, , ,200

ALLSEL,ALL

TYPE,1 !* MESH AREA 2

MAT,1

LOCAL,11,0,0,0,0

ESYS,11

AMESH,2

CSYS,0

TYPE,2 !* MESH AREA 1

ESYS,11

AMESH,1

CSYS,0

NSEL,S,LOC,X,30,100

NUMMRG,NODES

ESLN

TYPE,3

MAT,5

CZMESH,,,1,Y,0, !* GENERATE INTERFACE ELEMENTS

ALLSEL,ALL

NSEL,S,LOC,X,100 !* APPLY CONSTRAINTS

D,ALL,ALL

NSEL,ALL

FINISH

/SOLU

ESEL,S,TYPE,,2

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,1.5 !* APPLY DISPLACEMENT LOADING ON TOP

D,ALL,UY,20

NSEL,ALL

ESEL,ALL

ESEL,S,TYPE,,1

NSLE,S

NSEL,R,LOC,X

NSEL,R,LOC,Y,-1.5 !* APPLY DISPLACEMENT LOADING ON BOTTOM

D,ALL,UY,-20

NSEL,ALL

ESEL,ALL

NLGEOM,ON

AUTOTS,ON

TIME,1

NSUBST,40,40,40

OUTRES,ALL,ALL

Hi,

I am trying to model the transient response of a free-free beam (unconstrained) in ABAQUS, where the force is applied through a spring. I am using a two point spring where one end is connected to the beam and the other a reference point, the force is applied to this reference point.

When i visualise the results the spring is showing no results (white) even though I requested the the node set of the reference point.

The beam response is the same as it was without the spring no matter the choice of spring stiffness selected. So i assume the spring is incorrectly modelled.

Have i made a mistake when modelling the spring?

Hello,

I have a problem in which a steel nail is 'embedded' in a wood piece. The head of the nail is in contact with a steel bracket. As I apply cyclic load on the vertical wood 'wall', the bracket moves up and pulls the nails of the horizontal wood part, which gets pulled out of the wood (see Image). However, as the bracket unloads (and consequently so does the nail) the cohesive interaction that I defined between the nail and the wood simply unload to zero as well. This causes the nails to follow the bracket back into original position. I wanted the nail to retain the maximum displacement imposed by the contact with the bracket before the bracket starts to unload.

Looking at the ABAQUS documentation, it says the when using cohesive behavior, it will always unload to the initial position (see image of the cohesive material model used in ABAQUS). How can I overcome this? It can be either using contact pairs or any other strategy in ABAQUS (except cohesive elements, which I've tried and could not manage to work in my model).

I've already tried to use a custom defined FRIC subroutine in a tangential interaction behavior (doesn't work). I've thought about writing a custom UMAT subroutine, but ABAQUS does not allow a user-defined routine for cohesive response of contact pairs. I've tried to run an analysis with the ABAQUS default cohesive response, then get the nail deformations at peak and try to apply these as boundary conditions at the correct steps of the analysis. I also tried to use the option where ABAQUS maintains the initial position of an object during a step. However, these last two approaches seems to cause numerical instabilities in ABAQUS due to activating and deactivating boundary conditions in between steps.

I am creating a single element model in Abaqus of a composite material. My goal is to match the stress-strain curve of the material which was obtained experimentally. I am using VUMAT for Fabric Reinforced Composites to get a non-linear stress-strain curve. However, every time I run my analysis I get the error "1 elements have missing property definitions". I tried changing the element type, hourglass stiffness, etc., but nothing seems to work. How can I solve this?

Dear Researchers,

Recently, my research group and I have been working on understanding the formulation of axisymmetric elements. We began by studying 4-node and 8-node Axisymmetric-Harmonic elements, which are well described in Cook’s textbooks [1,2] and, e.g., in this paper [3].

We also utilized them in some simple case studies using Ansys APDL software, using PLANE25 Axisymmetric-Harmonic 4-nodes (https://www.mm.bme.hu/~gyebro/files/ans_help_v182/ans_elem/Hlp_E_PLANE25.html) and PLANE83 Axisymmetric-Harmonic 8-nodes (https://www.mm.bme.hu/~gyebro/files/ans_help_v182/ans_elem/Hlp_E_PLANE83.html).

However, these elements (PLANE25, PLANE83) are limited to linear analysis cases.

Therefore, we have moved on to using Solid 272 & 273 - General Axisymmetric Solid Elements with 4 & 8 base nodes, which can also be used for nonlinear analyses.

Unfortunately, to the best of our knowledge, we have not found any articles or references that describe the formulation of these elements in detail (the Ansys reference provides an outline, but it is not sufficient for independent computational implementation).

Specifically, we are seeking information not only on the shape functions but also on handling axisymmetric loads using Fourier decomposition, and most importantly, on how conducting nonlinear analyses.

Does anyone have any papers or books to suggest?

Thank you!

References:

[1] Robert D. Cook , Concepts and Applications of Finite Element Analysis, John Wiley & Sons Inc, 1974, 978-0471169154

[2] David S. Malkus, Michael E. Plesha, Robert J. Witt, Robert D. Cook, Concepts and Applications of Finite Element Analysis, John Wiley & Sons Inc, 2001, 978-0471356059

[3] R.W. Stephenson, K.E. Rouch, R. Arora, Modelling of rotors with axisymmetric solid harmonic elements, Journal of Sound and Vibration 131(3),1989, 431-443, https://doi.org/10.1016/0022-460X(89)91003-1

Hi All,

I am trying to generate the 3D corneal surface from the Zernike Polynomials. I am using the following steps, can anyone please let me know whether they are accurate

Step 1: Converted the cartesian data (x, y, z) to polar data (rho, theta, z)

Step 2: Nomalised the rho values, so that they will be less than one

Step 3: Based on the order, calculated the Zernike polynomials (Zpoly), (for example: if the order is 6, the number of polynomials is 28 )

Step 4: Zfit = C1 * Z1 + C2 * Z2 + C3 * Z3 + ......... + C28 * Z28

Step 5: Using regression analysis, calculated the coefficient (C) values

Step 6: Calculated the error between the predicted value (Zfit) and the actual elevation value (Z)

Step 7: Finally, converted the polar data (rho, theta, Zfit) to Cartesian coordinates to get the approximated corneal surface

Thanks & Regards,

Nithin

Hi

I am trying to model a cutting problem with a blade and comparing the results with and without ultrasonic vibration. From experimental results in our group, the use of ultrasound can significantly reduce the cutting force required, although Im not sure that the current model can show this. Has anyone got any general advice for incorporating such a high-speed boundary condition to the model?

I have added an image showing the damage model (top two images) and a comparison of reaction force on the blade with and without ultrasound

The results without vibration seem to be sensible, although when I apply the vibration, the cutting tool experiences a high reaction force which I don’t believe represents the true scenario. For the work-piece I have implemented Johnson-Cook plastic and damage criteria. Any general advice foe this type of problem would also be greatly appreciated!

Dear professors and colleagues，

hello！Recently, while studying the CDP model, I have read the manuscripts of various experts and have gained a lot, but I still have some questions.What I particularly want to know is about the parameters of the simulation:Dilatance angle y, Eccentricity e,Form factor Kc.I sincerely want to inquire about how these values should be taken.

Thank you to all experts for reading the questions！

Hello,

Can somebody please give me some reference to a paper or book where it is explained how to condensate:

* from a Q8 serendipity FE to a Q4 FE with drilling DOFs (16 DOFs to 12 DOFs).

* from a H20 serendipity FE to a H8 FE with drilling DOFs (40 DOFs to 24 DOFs).

See the attached figures, taken from the RFEM technical manual.

Regards,

Diego Andrés

I am trying to model a parallel plate compression test for a bioresorbable stent, by using just 1/2 model. With one design everything went perfect, when I uploaded the other one (same BCs, same properties...) it doesn't work. Abaqus says that the strain is too high. I tried to distance the shell plate to 1 mm (as you can see here https://www.transfernow.net/dl/20240519I0ZLE9Ss) to see if there was any change, but nothing. Do you know how can I resolve this?

To be complete, I put as BCs: symmetry on the faces cut in half (loading step) and fixed just one node of the stent along the axial direction (in INITIAL step, not loading). Thanks in advance.

I am simulating a tunnel under blast loading using conwep method in ABAQUS,I would like to know the analysis procedure and steps of analysis?

Hello everyone! I have a query regarding the Torsional constant and the Polar moment of inertia being used in Ansys workbench for a non circular cross-section .

In the Ansys help, i found that for the special case of a circular cross-sections, the torsionnal constant is equal to the polar moment of inertia and calculated by using this formula: Ixx=J=Iyy+Izz. Could any one clarify as to what formulation Ansys follows for the calculation of the Torsional constant and Polar moment of inertia of a non circular cross section.

Thank you!

Hello,

I am new user of DIANA FEA. I am trying to analyse a masonry structure.

But I am getting this error message:

GEOMETRY: NR=1

SEVERITY: ABORT

ERROR CODE: /DIANA/LB/DS30/2236

ERRORMSG.A: Can't normalize null vector.

DIANA-JOB ABORTED.

Can you help me please?

using finite element analysis

Hi all,

I am trying to model a contact problem in DIANA FEA. I went through the DIANA manual and found that DIANA has contact elements which imposes the contact constraint. But there aren't any tutorial or examples available online to do this.

The material property for the contact element has two options target and contactor. When I try to assign the contact element material properties to an existing steel object, the object loses its steel material properties and contains only the contact elements properties which is friction and penetration depth.

Could someone explain how can I assign the contact constraint in DIANA when two steel cubes are touching each other.

I am trying to simulate a rectangular short column (L/D ratio of 2) for cyclic load under axial compression. I am using the concrete damage plasticity model for concrete. The first problem I am facing is

**excess lateral stiffness**in my ABAQUS model as you can see in the force vs displacement curve. I am trying to match the slope of the red curve generated by the cyclic hysteresis response of the column. The dashed line is the result I got. I have only included the elastic property for concrete for this instance. All the pictures related to the analysis are listed below.- The analysis procedure is static/general for
- C3D8R element used for concrete
- T3D2 element used for reinforcement
- Analysis was done in 2 steps axial load and lateral displacement

Can anyone tell me what I am doing wrong?

+6

"How do advanced computational modeling techniques, such as finite element analysis or computational fluid dynamics, aid in the precise characterization and optimization of thermal bridging phenomena within complex building assemblies?"

Hi

I keep getting the following error message when I run any Abaqus job:

**"XML parsing failure for job XXX. Shutting down socket and terminating all further messages. Please check the .log, .dat, .sta, or .msg files for information about the status of the job."**

There are no .lck files to be deleted and everyone else using our academic license seems to be unaffected. Occasionally, I can run a model through writing an input file and running through command prompt. Although even this doesnt work everytime, when I check the dat file I get the following error message:

**in keyword *CONFLICTS, file "Job-1.inp", line 1: Keyword *Conflicts is generated by Abaqus/CAE to highlight changes made via the Keywords Editor that conflict with changes made subsequently via the native GUI.**

*****NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE TO**

**INTERPRET SOME DATA. SUBSEQUENT ERRORS MAY BE CAUSED BY THIS OMISSION**

Any help would be greatly appreciated as my work is getting delayed a bit and I have no idea what to do!

Kind Regards

Alex

I have three modules (in free form .f90 format) which are being called from inside of a UMAT subroutine in ABAQUS, in the following manner:

module module_A

use module_C

use module_B

....

end module_A

module module_B

use module_C

....

end module_B

module module_C

....

end module_C

subroutine UMAT(STRESS,...)

....

Here the subroutines from module_A and module_B are being called

...

end subroutine UMAT

Now, what is the appropriate format for writing these modules with UMAT subroutine? How to merge different module files into a single *.for file (free format)?

Greetings to all.

I am trying to make a composite ply sheet made up of 3 material, after assigning properties and visualizing ply stack layer it is NOT stacked along the thickness(which is needed) but in fact for some reason stacked along lateral direction.

I am attaching view-port image for reference , please guide me where I am going wrong.

Please assist me.

I have created a FE model including:

1. Bead (Green),

2.Cell (Red)

3.Components inside the Cell, beams, truss, and nucleus.

Constraint:

Embedmentt, all components embed in cell.

Boundary condition:

1. Bottom of cell are fixed

2. Bead compress along the Z direction with 500nm

I have finish the calculation through Implicit Dynamic, however, actually i don't have densities of each material (those used in Implicit Dynamic are assumptions).

So, can i solve this question just with E and v with Abaqus/standard?

Most of the researchers concerned with analytical study or numerical study use ANSYS for the FE Modeling. The awareness about NASTRAN is low. What may be the reason and Why?

I am looking for a code (open source preferably) for finite element analysis that allows the user to specify

*some*of the node coordinates of the mesh. The code should be able to generate and adjust the rest of the mesh nodes.I would appreciate it very much if I could have some suggestions for such a code. Thanks!

Hello,

I am doing reduced order modelling for nonlinear analysis and I have to use the POD and Galerkin projection to reduce my matrices size. The problem is that since it's a nonlinear analysis, the matrices have to be updated for each increment. And for commercial FEA softwares, I do not have access to the stiffness matrices for each step time.

Does someone have any suggestions (using abaqus subroutines for example).

Thank you in advance.

While Modelling infillwall, why does after failure the line drops in a straight pattern rather than moving along the displacement as seen from experimental results?

I am simulating the machining of Ti6Al4V on ABAQUS using dynamic explicit procedure. I have taken the data for johnson cook damage from research papers but none of them mentioned displacement at failure. I am not getting the chips as expected because the displacement at failure is wrong. How to calculate this?

How to apply a prescribed reversed cyclic loading in Midas Fea? (Links for tutorials or snapshots of the steps will be a great help)

I am a final year Masters's Student from Heriot-Watt University currently working on my dissertation project titled "A THEORETICAL ASSESSMENT OF THE STRUCTURE OF A LIQUID STORAGE TANK UNDER SEISMIC FORCES" with the following objectives:

1. Verification of Current Theories (Housner, Preethi, and Malhotra) of liquid Structure Behavior (sloshing wave height) under seismic forces for petroleum-filled storage tanks using Finite Element Modelling and Finite Element Analysis.

2. Assessment of the possible failure mechanism of the superstructure of the various liquid storage vessels under exposure to seismic forces using Finite Element Modelling and Finite Element Analysis based on the API 650 Design Standard.

3. Proposal and initial assessment of the effectiveness of a Bass Isolation System on the sloshing wave height using Finite Element Modelling and Finite Element Analysis.

Can the

**Ansys modal analysis module**be used to model a fluid-filled storage tank and determine the sloshing wave height along with the impulsive and convective mass components of the fluid based on the application of specific Acceleration, Velocity, and displacement values?Can I subsequently transfer the model to the

**Ansys Static Structural Module**to determine the various resulting stresses that will develop within the tank structure due to the seismic forces and the fluid-structure interactions?If not, can you guys offer any advice on what methodology I should take?

Dear sir or ma'am,

I am solving a 3D heat conduction equation involving a moving heat source (a laser). The goal is to get the thermal behaviour of the domain with time.

I am using structured grid and using the element size less than the dia of laser spot, which is way too small. It is computationally very heavy for my small laptop.

There is a method which uses adaptive moving mesh. A finer mesh surrounds the laser spot as it moves. But I do not have any idea how to implement that in my code.

Could you please recommed any thing where I can start? or how should I proceed?

Thank you and regards,

Ravi Varma

what are the benefits of finite element analysis in road construction?

Can someone guide during numercial modelling using FEA software DIANA FEA, in cyclic loading i dont see the pinching effcet. what is the reason that might be

I'm working on p-norm topology optimization in plane stress using a MATLAB code adapted from the article An efficient 146-line 3D sensitivity analysis code of stress-based topology optimization" by Hao Deng, Praveen S. Vulimiri and Albert C.To. I've noticed small sensitivity values (e.g., 4.54e-05, -7.30e-09) with a stress norm parameter (p) of 5. Are such values typical in this context, and should negative sensitivity values be expected? The relevant codes are attached.

Your experiences and recommendations would be greatly appreciated.

Thanks!

Hello everyone,

I save my FEM results as VTK files, these files include data such as Points, Variables values, mesh type etc.

I have been trying to get a vector graphic (like SVG) to display smooth and nice results.

I tried ParaView, but I think they do not support vector graphics in recent versions.

I also tried to write a Python code for this purpose using vtk and matplotlib libraries. It works almost fine, but when I want to plot the mesh too, there are problems.

I used Triangulation from matplotlib.tri, but it only supports triangles mesh, while my mesh type is 9-node quadrilaterals.

So, the question is, what is the best way to get SVG image of a VTK file?

Thanks,

Masoud

In 1D cases Hermite shape functions can be easily implemented. However, in 2D cases, if we want to use cubic Hermite triangle element (10 DOFs), then it is pointed out that the transformation between the physical triangle and the reference triangle is not affine-equivalent (or it is nonconforming). In this case, if calculating the gradient matrix directly then it will lead to wrong results.

The nonconforming nature of cubic Hermite triangle element is mentioned in Reddy's "An introduction to nonlinear finite element analysis" (see the attached figure), however, further discussion and examples of applying cubic Hermite triangle element are not presented in this book.

I am wondering if there are any available books/references that cover the details of the information related to this question.

Hi,

I am doing 2D FEA analysis of nanoindentation. It has been peformed on displacement control where the indenter moves 300nm vertically. Unfortunately, I am getting a kind of zigzag curve in the load and displacement plot. I have tried to refine the mesh but am still having the same issues. is there any suggestion to solve this problem? I have attached the plot

I use Abaqus for dynamic analysis of composite structures. In Abaqus, the damping can be defined at a material/element level and global level in the analysis. I am confused about the structural damping part in Abaqus and the damping at the material level as described below.

In the global level, the Rayleigh damping is Del = alpha x M + beta x K and the Structural Damping will modify the global stiffness matrix by a factor 's' where the stiffness matrix will be Ks=sK. 's' is the structural damping factor.

According to many textbooks, they take into account the effect of the structural damping by assuming an equivalent viscous damping ratio which could be added to the one from material damping when calculating the alpha and beta values in the Rayleigh Damping model.

In the material level, the number of elements, volume, and density of the elements alongside the alpha and beta values determine the damping matrix. I wonder if the alpha and beta values are the same as the global ones. I suspect they will be different because in the global level, the natural frequency and damping ratio of the entire model are used to calculate the alpha and beta values.

Your advice on these issues is highly appreciated.

I have Force-Displacement values of a tensile test that undergoes uniaxial loading. Please find attached the stress strain curve of the loading.

Sigma1 denotes the Equivalent stress of the element at current time increment and Sigma0 denotes Peak equivalent stress of the element reached at the end of the loading stage. I need to calculate a stress ratio Sigma1/Sigma0 at each time increment.

In order to calculate the stress ratio, the time increment of the peak stress has to be reached after which the field variables (of USDFLD) in the previous time increments has to be modified to calculate the stress ratio. This stress ratio has to be applied to the material model of the same simulation.

Is it possible/recommended to achieve this using USDFLD? Or is there a better alternative in ABAQUS?

I have geometry file of pelvis and sacrum bone. I need to create cortical bone shell over this model with 2mm thickness. Then I will manipulate the geometry by making holes into the the two bones to insert a screw and conduct finite element analysis. How can I make the shell over the bones for my purpose? I have attached the geometry file with here.

Hi,

I am doing 2D FEA analysis of nanoindentation. It has been peformed on displacement control where the indenter moves 300nm vertically. Unfortunately, I am getting a kind of zigzag curve in the load and displacement plot. I have tried to refine the mesh but am still having the same issues. is there any suggestion to solve this problem? I have attached the plot

Hello dear colleagues

Hope you're fine.

I'm trying to model a threaded connection with a 2D axisymmetric model.

I need to make several models with slight changes and differences.

In some models, once the job is submitted, before the analysis gets started, it gets aborted due to "some nodes have Negative coordinate values" error.

When I check the error node set, they are all placed on the axis of symmetry.

I tried several ideas to work this out but none of them was successful like:

>changing element type,

>constraining the part in the direction prependicular to the axis of symmetry

>Using another datumn coordinate system

I appreciate it if you have any ideas to fix this error.

PS: some other models get solved without this error while these models are copied from one another and I couldn't see any difference seem to be related to this error between them

Anyone working with Abaqus additive manufacturing plugin. I need your guidance regarding error in AM simulation.

"Error in job Job-1: Toolpath-mesh intersection module: ERROR: Torch direction cannot be parallel to a segment.Event series-2_UMD_1"

How to resolve the problem?

Hi all! I am trying to understand the stress vs strain plot for my model. I am using Abaqus/Explicit so 'LE' is the strain that I selected for output. I am trying to understand the trend of stress vs LE plot. Why am I getting opposite that expected? Can anyone please help me to understand this? The loading and unloading branch are mirror image of what I am expecting. Also, why I am getting positive strain?

Hi all! There is an optional feature in Abaqus to define a concrete failure point by going to 'edit keywords' and adding '*concrete failure' for concrete damage plasticity model. Can anyone please explain it to me what will happen if this concrete failure point is added and what if it's not added? I know it is also essential to trigger element deletion but looks like it's inclusion is changing the output results not only the visualization.

I am new to Gmsh and I have a problem on how to find the boundary nodes from mesh file.My mesh file and model are given below.