Science topic

Plasticity - Science topic

In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behavior to plastic behavior is called yield.
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Hi all,
I have a question about the simulation of uniaxial tensile test of sheet metal. When I adopted the GTN Porous fracture model (it was embedded into the ABAQUS software) to simulate the uniaxial tensile test of sheet metal, I found that the simulation results vary with degree of the input material plasticity data. When I input material plasticity data upto 4 (extrapolated by swift law), the simulative displacement obviously exceeded the experimental displacement. And When I input material plasticity data upto 0.123, the simulative displacement Roughly equal to the experimental displacement. I can't think through the reasons behind it, and Can someone explain this?
Thanks in advance for any advice!
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Independent of which material model you take, you need to provide information on the hardening behavior in the post-necking regime in order to be able to simulate this region. Getting this information for a real material from experiments is not trivial. Though, there are established methods to extract true-stress vs. true strain data from the post-necking regime, e.g. using Bridgeman's correction or doing an inverse parameter identification (the latter is necessary definiely in case of complex stress states). A pragmatic approach is that you take the true pre-necking data and extrapolate them to the post-necking regime using an analytical law like a power law or a Voce law. Subsequently, the analytical law can be either rasterized to obtain the tabulated data for the built-in plasticity models of Abaqus or you implement it as a user-defined hardening law using the UHARD routine. Our GTN implementation (open source at https://tu-freiberg.de/nonlocalGTN ) supports power-law hardening by default.
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Hello community,
I'm trying to simulate cracks with cohesive elements (in Abaqus), but I would like to reproduce reality as much as possible. Therefore, I would first like to have elastic behavior after which plasticity comes which brings plastic strain. Then after some accumulated plastic strain, I would like an opening of cohesive elements like a formation of a crack.
I've started examining this case with perfect plasticity or with a slight hardening, I've also tried with proper hardening but can not get a cohesive zone. All dissipation goes in plastic flow.
Do you have any advice on what to do to get first some plastic flow (like in reality) and the formation of the cohesive zone that finally breaks like a genuine crack?
Material is steel:
E: 200000 Poisson: 0.3
Plasticity starts at 250 (perfect plasticity)
Cohesive zone_ Traction separation law
Elastic properties 6000000, 6000000, 6000000
Damage int: ????
Damage evolution0.0001
With Damage Initiation, I was trying different things 250 like where plasticity starts, or with hardening, and then put initiation on 251 or 255 and different combinations. Nothing works.
Thanks a lot in advance,
Domagoj
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Thank you very much Francesco Cervellera, as I'm still building the model and not focusing on a specific material, I'm using parameters of steel.
Therefore, I think it's rather a possible problem in the setup of simulation or some constraint of cohesive elements that I'm facing rather than the material definition that I described in the original post.
Domagoj
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I have seen different visual observation techniques written in a few papers (e.g.: Serrated plastic flow by P. Rodriguez) to identify the type of serration (Type A: sudden plastic flow followed by a drop, Type B: oscillations about general level, Type C: yield drops below the general level of stress-strain curve). However, not all serrations are perfectly shaped. So, identifying serration through visual observation only becomes difficult. Is there any mathematical model or any other way by which the serrations can be characterized?
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I don't think there are techniques, other than visual observation on stress strain curves. This is because serrated yielding is instability of plastic deformation during uniaxial loading, tension or compression.
You may find the following review paper useful, which is more recent than Rodriguez's paper and it explores the empirical/mathematical modelling of the serrated yielding phenomena:
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Hi all,
I am trying to model a joint connecting 1D BEAM elements using ABAQUS connector element with the joint behaviour obtained in a separate 3D analysis. For example, I have a joint modelled in 3D SHELL element and after analysing this joint I obtained a moment-rotation relationship of this 3D joint. This moment-rotation relationship is then assigned to an ABAQUS connector element connecting the 1D BEAM elements in the 1D BEAM model.
My question is how do you correctly define the elastic and plastic range of behaviour in ABAQUS connector element?
1. Is the Elastic behaviour option only for the elastic range of my moment-rotation relationship or do I have to define the full elastic-plastic range in this behaviour option? If the latter is correct, I then need to tell ABAQUS in the Plastic behaviour option from what moment onwards in the full elastic-plastic range defined in the Elastic behaviour option where it should behave plastically?
2. I tried to define negative values in the Plastic behaviour option as my joint can have load reversal, however, it keeps giving me error. Is the Plastic behaviour option only allow positive values? If so is that mean ABAQUS assumed the onset of plasticity occurs at the absolute value of the number I specified for both directions? What if the onset of plasticity of my joint is different in 2 loading directions? Do I need 2 separate Plasticity behaviour options (1 for each direction) for it to work?
I know this is a long question, hopefully, there is someone out there who read through this and could provide me with some direction.
Many thanks,
Heng
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Just found out there was a reply. Thank you very much for your help. I will try to use your method and see if that works for me. Currently, I am using 2 connectors with different plastic rotation behaviours (arranged in parallel) between the 2 connecting points so that they can each handle the loading in the two opposite directions. If I am able to get what you suggest to work it would save 50% of the time for me!
Thanks again,
Heng
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concrete damage plasticity model in ABAQUS of reactive powder concrete containing steel fibers
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If you want to define CDP parameters such as eccentricity and dilation angle in Abaqus, it depends on the concrete used. So you shall calculate the parameters of the used concrete to define it correctly as it differs due to the additives used.
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For thermal contact conductance estimation, selection of plastic or elastic deformation models is based on plasticity index. At lower pressure at the interface, the deformation of surfaces may be elastic even though the plasticity index is greater than 1. Plasticity index will not account for pressure.
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Dear Researchers,
There are mechanical models for conforming rough surfaces whose contacting asperities deform (i) elastically, (ii) plastically, or (iii) elastoplastically. To know whether the deformation will be plastic or elastic in a given situation of temperature and load, the concept of plasticity index is used. The “plasticity index” indicates the mode of deformation occurring in the contact [8]. The deformation of an asperity is said to be elastic up to some given load for a given hardness of the material above which plastic flow will occur.
Source: DOI:10.1098/rspa.1966.0242
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I am running the tensile experiment (polymer material) in Abaqus explicit with the Ramberg model. But the solution exists with an error. It's showing "The keyword is not existed in explicit".
Then how I give the plasticity parameters explicit.
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Hi
It seems that this unfortunately is only available in Abaqus/Standard, so is not compatible with explicit.
Deformation plasticity can be used with any stress/displacement element in Abaqus/Standard.
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Dear Researcher,
Suppose there is two concentric hollow cylinder and by some metal forming process the inner cylinder is plastically fitted with the outer cylinder in such a way that there is sufficient contact pressure is generated between the two cylinder interface and they are plastically shrink fitted.
Now this assembly place in a high temperature and high pressure environment and due to creep there is decrease in contact pressure.
Can anybody suggest me how to modelled this whole process in COMSOL so that we can find out the decrease in contact pressure with time.
I also have to modelled that if there is a very small hole (gap) at the interface of two cylinder then how the diameter of this hole is changes with time?
If someone using other FEA software or code then please suggest?
Thanks for your valuable suggestions.
Shyam Kishor
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For that thing you may try the following (but again in ANSYS, I hope similar options will be available in COMSOL):
1. Plot the radial deformation of nodes at the interface near the cavity in time history postprocessor it will show at what time point (or load step) diameter of cavity starts increasing.
2. If you are interested in understanding any leak through that cavity, contact pressure zero or contact status open may be used as the indication of the same.
Regards
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Regular polygons of trigonal and hexagonal symmetry are used as yield criteria in theory of plasticity:
References for regular icositetragon (24-gon) as yield criterion are sought for a systematization of yield and strength criteria.
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The regular polygons of trigonal and hexagonal symmetry as yield criteria are summarized in Altenbach, H., Kolupaev, V. A., General Forms of Limit Surface: Application for Isotropic Materials, in Altenbach, H., Beitelschmidt, M., Kästner, M., Naumenko, K., Wallmersperger, Th. (eds.), Material Modeling and Structural Mechanics, Advanced Structured Materials, pp. 1-76, Springer, Cham, 2022. Both 24-gons are called the Rosendahl criteria.
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Only temperature dependence is to be considered but I can't find the way to enter the working temperature or is it defined in the predefined field?
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Hi Saurabh Thakur,
When your model is temperature-dependent and has a high strain rate like impact, you should use the Johnson-Cook theory.
Depending on your simulation, you can define other variables as well. For example, in high-speed manufacturing processes where a large amount of inelastic strain exists, you need to define Inelastic Heat Fraction behavior, which indicates the energy dissipation rate as heat.
I recommend referring to the link below to see some examples and become more familiar with the Johnson-Cook theory.
Best wishes.
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Dear Researcher,
Please help me to find CDP parameters of Ultra High Performance Concrete for ABAQUS input. If you have any excel sheet or previous study, kindly send it to me.
Looking forward to hearing from you.
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Tufail Mabood yup. The data is extracted from Python. Hence, no equations are seen.
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Is it necessary to give Temperature dependency material properties, like Elasticity and plasticity while modeling in ABAQUS? When we are using Subroutine- USDFLD GETVRM (TEMP) to get Nodal point temperature in output.
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I am an M.Tech structural engineering student working on the project ' Numerical analysis of Kath-kuni architecture ( a common masonry typology ) in Himachal Pradesh region of India subjected to earthquake loading in ABAQUS software' . The question of concern is that I am finding it difficult to input plasticity parameters for timber/ wood material that I have used in my model even after searching in various research papers. I have got only elasticity parameters and wood being an orthotropic material requires plasticity parameters and a plasticity damage model to be defined in order to understand the actual material behavior in ABAQUS software. So, kindly help me in finding the plastic properties and a damage model for timber, it would be very helpful to proceed in my current project.
Thanks and regards
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Please check the attached reference.
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Dear all,
I am looking for a research work that implemented an uncertainty or statistical framework to study the impact of the geometric parameters on the fracture response.
I appreciate any help.
Thank you in advance,
Moj Ab
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hello, i am modelling a RC slab in Abaqus, the slab is supposed to fail in punching shear which is a sudden failure. i defined the nonlinear behaviour of concrete using concrete damage plasticity model, but i can't reach the desired results as the failure is not sudden (load-deflection curve shows that the load is decreasing gradually after reaching its max value, an it's supposed to be a rapid degradation not a gradual one). as well as, i know that whenever i there is a localization of cracks somewhere in the model (which is the case in my model), using concrete damage placticity model may make the results mesh-dependant. so what should i do? should i use GFI? or do i need to use concrete smeared crack model to simulate the nonlinear behaviour of concrete instead of using concrete damage placticity model?
thank you in advance.
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That is a good question.
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As stated above. I have a group of trees from two different environments that consists of sets of half-siblings and I'd like to test their plasticity to a climate change variable. Is this a valid approach since they are only expected to share one quarter of their genes? Thank you!
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Es posible.
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For a RCC frame cyclic load analysis in ABAQUS, Materials designed as linear CDP, while submitting the job it shows the warning _
"The strain increment is so large that the program will not attempt the plasticity calculation at 4956 points"
then after 5 unsuccessful attempts shows the error_
"Time increment required is less than the minimum specified"
The simulation was under "General Static"
Incrementations, Error, loading Amplitude, Amplitude plot is attached bellow as .png file.
Please tell me how to overcome the problem that, I can run the simulation smoothly.
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You can 1) decrease the initial time increment or 2 )go to:
Step>other>gneral solution controls>(choose the step you already defined)>Time incrementation>more>change(IA) from 5 to 10 or more based on your problem.
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Hello everyone,
I am quite new to Abaqus. I am trying to analyze a 3D model of a laterally loaded pile where the pile is modelled as a rigid body with a reference point at a height e from the top of pile and the soil is modelled with Mohr Coulomb plasticity model. In order to obtain the load-displacement plot of the pile a displacement boundary condition is applied at the reference point. As the value of cohesion is very low (0.1kPa), Abaqus explicit solver is used to solve the problem. The energy diagram for the whole model I am getting seems to be incorrect. Also, I am not being able to find a technique to obtain the load required to plot the load-displacement plot. I tried to get the load by collecting all the reaction forces in the direction of loading (x-dir) in all the support.
Is my methodology correct? Also, can anyone please provide any assistance regarding the nature of he energy plot of the model?
Any suggestion will be appreciated.
I have attached the .inp file for anyone's reference.
While analysis I am getting the following warnings;
Integration and section point output variables will not be output for deformable elements that are declared as rigid using the *rigid body option
Output request peeqvavg is not available for element type c3d8r
Output request sequt is not available for the material for element type c3d8r
The option *boundary,type=displacement has been used; check status file between steps for warnings on any jumps prescribed across the steps in displacement values of translational dof. For rotational dof make sure that there are no such jumps. All jumps in displacements across steps are ignored
Step 1, Increment 38: 1 material point(s) failed to converge in the material constitutive routines.
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Thank you for your suggestion. But I don't know LS DYNA and currently also have no access to that software. Is there any method available to perform that analysis in ABAQUS?
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I'm trying to simulate the formation of segmented chips while performing turning of Ti6Al4V, I don't know why my mesh is getting distorted eventhough I'm using a fine one!!!
My wp consists of 3 zones, 1) uncut chip thickness zone where segmented chips are supposed to form, 2) Thin sacrificial layer, 3) Machined zone which results when chips have been formed. For 1 & 3 I've only applied material with JC plasticity no JC damage, for 2 I've assigned JC damge with evolution as well.
Please help.
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Amal Rai Unfortunately, I'm not familiar with Abacus. I saw this approach in many papers. Recently I'm trying to adopt the Discrete Element Method to simulate the FSW process.
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Hello! can someone help me please?
I'm simulating a tensile test with flat specimen in Abaqus explicit using JC plasticity and JC failure criterion. I need the strainxstress curve, a need the total strain not only the plastic strain, but in the "creat xy data --> ODB field output" doesn't appear the E. But I have selected it in the "Field Output Request"
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Hi Juliana, you should settle down Logarithmic Strain (LE) in field output and consider (LE) results after completed running
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During scratch test, the tip applies a force on the thin film surface and tensile stresses are generated behind the tip contact zone. A stress field then subsequently generates inside the film. The film deforms plastically and elastically to respond. Does the substrate deform plastically as well even though the tip doesn't make contact with it directly?
I know that substrate can relieve the stress through plastic deformation during film growth.
But is it similar to the case like scratch or wear test ( apply addition load on the surface)
Does substrate deformation help to relieve the stress generated by scratch tip? If so, plastic deformation or elastic deformation dominates?
Can anyone kindly share your opinion on this please?
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The issue of stress in thin films and functional coatings is a persistent problem in materials science and technology that has congregated many efforts, both from experimental and fundamental points of view, to get a better understanding on how to deal with, how to tailor, and how to manage stress in many areas of applications. With the miniaturization of device components, the quest for increasingly complex film architectures and multiphase systems and the continuous demands for enhanced performance, there is a need toward the reliable assessment of stress on a submicron scale from spatially resolved techniques. Also, the stress evolution during film and coating synthesis using physical vapor deposition (PVD), chemical vapor deposition, plasma enhanced chemical vapor deposition (PECVD), and related processes is the result of many interrelated factors and competing stress sources so that the task to provide a unified picture and a comprehensive model from the vast amount of stress data remains very challenging. This article summarizes the recent advances, challenges, and prospects of both fundamental and applied aspects of stress in thin films and engineering coatings and systems, based on recent achievements presented during the 2016 Stress Workshop entitled “Stress Evolution in Thin Films and Coatings: from Fundamental Understanding to Control.” Evaluation methods, implying wafer curvature, x-ray diffraction, or focused ion beam removal techniques, are reviewed. Selected examples of stress evolution in elemental and alloyed systems, graded layers, and multilayer-stacks as well as amorphous films deposited using a variety of PVD and PECVD techniques are highlighted. Based on mechanisms uncovered by in situ and real-time diagnostics, a kinetic model is outlined that is capable of reproducing the dependence of intrinsic (growth) stress on the grain size, growth rate, and deposited energy. The problems and solutions related to stress in the context of optical coatings, inorganic coatings on plastic substrates, and tribological coatings for aerospace applications are critically examined. This review also suggests strategies to mitigate excessive stress levels from novel coating synthesis perspectives to microstructural design approaches, including the ability to empower crack-based fabrication processes, pathways leading to stress relaxation and compensation, as well as management of the film and coating growth conditions with respect to energetic ion bombardment. Future opportunities and challenges for stress engineering and stress modeling are considered and outlined
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Hi all,
I am culturing primary hippocampal cells from P0 mice and would like to measure whether synaptic plasticity is altered after treatment with different compounds, using whole-cell patch clamp.
What are your favourite techniques/protocols for plasticity measurements in dissociated cell culture using whole-cell patch clamp or other techniques?
We have the options of spike-timing dependent plasticity, chemically-induced LTP, etc.
Thanks in advance,
Hannah
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Hi Annah,
in order to induce plasticity in neuronal cultures you can pursue 2 different streets. The first one is the chemical induction using a modified external solution supplemented with glycine at saturating concentration for 3 minutes. The second approach could be the dual patch where you will identify 2 connected neurons and after that you stimulate the presynapse in order to potentiate the post. However, the first method is easier than the second one, and it works pretty well.
Good luck for your experiments
Luca
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I want to simulate the plasticity for the Ti and its alloys with two phases (Alpha and Beta) in Abaqus. Now I have already created the microstructure model but unsure what properties I should assign to its two constituent phases, namely alpha and beta, as I only know the bulk material parameters (e.g., Ti-10Mn)?
Alpha and beta are part of Ti-8Mn; the only difference I see is that one will be HCP while the other the BCC structure, so how do I create such a material?
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I assume you are using some kind of crystal plasticity model.
You can find parameters for the alpha phase here:
and see the crystal plasticity implementation here:
In crystal plasticity, you will need to use two different material models for the two phases. Normally in Abaqus you would define two different user materials and assign them to the different grains representing different phases (sections of the geometry).
Best Regards,
Nicolò Grilli
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Elasticity, viscosity damping, horizontal seismic insulation, plasticity, and dynamics are the useful factors that increase the response of the structure to seismic shifts.
how each of these properties of the structure works?
what are the failure limits?
and finally what is the most useful property that the structure must have to react better to the earthquake.?
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Interesting and important query
Following to learn from experts
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I am working on developing a micromechanical FE model for predicting kink-band formation in UD composites. To model matrix plasticity, which model, out of Concrete Damaged Plasticity and Drucker-Prager, is preferred? Any insights particularly on the differences between the two models will be really helpful.
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If you want to calibrate a model with a compression test (epoxy shows different response in tension and compression), just use j2 plasticity, available in ABAQUS. All you need is the evolution of the plastic strain and the yield stress.
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Hey everyone,
Which plasticity model is suitable for modeling 316L selective laser melted steel in miso and micro scale modelling? Is isotropic hardening is good for this type of materials? (I want to model the fracture in melt pools )
Thank you.
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Dear Mojtaba Abdolkhani,
It is preferable to use a modulus of plasticity in the simulation of samples made by selective laser melting of 316L in a vase. This way, the simulation results will be closer to your experimental data. The use of foreign data will lead to deviations, which you will then have to specify with correction parameters. The connections obtained from the laser fusion have a strong influence on the mechanical characteristics and plasticity of the obtained products. Therefore, make standard test specimens by selectively melting the 316L. The obtained data, plasticity model and reinforcement curves are included in the simulation.
Wishing you success in your research.
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Hello all
I intend to obtain orientation changes in the rolling process under the theory of crystalline plasticity. What model can I use to simulate rolling under the theory of crystalline plasticity?
Best
Sina
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Sina Shokuhi This is your decision what you want to obtain. If you are interested just in the overall texture evolution you can use either a mean-field model like VPSC approximating rolling as a plane strain, see e. g. Eq. (7) in
Alternatively you can use finite element method to simulate the rolling process - in such a case you should provide the crystal plasticity model in each integration point. It can be either a single crystal model or a polycrystal (e. g. using Taylor or VPSC). This way you can obtain the spatial resolution of texture evolution but the simulation will be typically more costly.
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I want to simulate the bulging of a circular thin steel plate due to fluid pressure and finally see the rupturing of it.
What is the best criteria to simulate the material properties in plasticity and damage for this type of problem in Abaqus software.
Material is SS316 or something like that which we have the uniaxial tensile test results. And has a 1mm thickness and 100mm diameter.
Loading is a simple progressive uniform pressure.
Thanks
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Hi, This depends on the material response, i.e. the Stress - strain curve. If the material hardened after the yield, Hardening material properties should be considered, i.e. this depend in the slope of the curve after yielding however, elastic-perfectly plastic is most common in analysing to be safer for the design purpose.
Best wishes.
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Including the so-called kinematic hardening in phenomenological material models allows capturing the accumulation of plastic deformation in materials subjected to cyclic loadings. It determines that the size of the "elastic domain" in the deviatoric stress space remains constant and that upon plastic yielding, the domain is simply translated.
In largely deformed materials in tension, the kinematic hardening may result in a translation of the elastic domain to levels where the initial compression yield-limit becomes now a tensile stress value. This implies that upon unloading a plastically-deformed material (returning to zero loads), it may experience plastic deformation as well. My question is, is that physically possible? If yes, how can it be explained?
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Hi!
Kinematic hardening is only a simplified model that is convenient for describing the Bauschinger effect. More realistic is the combined model that combines isotropic and kinematic hardening.
V.N.
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Hello all,
I am confused about the definition of ratcheting for polymers.
For metals, when the material is subjected to cyclic loading, ratcheting is a phenomenon where plastic deformation accumulates progressively with each cycle.
For polymers, plastic deformation certainly causes ratcheting. I found most papers mentioned plasticity or viscoplasticity for polymers' ratcheting. But can the ratcheting occur within the yield surface? Or can the ratcheting be induced by time-dependence or viscous?
Looking forward to anyone's reply to give me some thoughts.
Thanks.
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Dear Yi Chen, no not only polymers, all materials that present accumutated strain under cycling show ratcheting. Please check this free access document. My Regards
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Hey guys,
I am attempting to model the installation of a helical pile into sand using Abaqus CAE (explicit). I am using a CEL model with a rigid pile and Eulerian sand part.
Every time I run the job, the sand part 'explodes' and has very large deformations. I have attempted to rectify this problem via the following trials:
-assigning cohesion to the sand;
-applying a pressure to the sand;
-beginning the installation with the pile already penetrated into the sand part.
Through an exhaustive trial-and-error process, I found that I have solved the exploding sand problem by changing the 'hard' normal contact interaction to a 'linear' contact interaction. However now, the history outputs show no plasticity/plastic deformation! This is kindof important as I am interested in finding the installation disturbance effects of screw-pile installation.
Is anyone aware of what I can do to accurately/realistically model the installation disturbance effects of a screw-pile being installed into sand? I am happy to provide any more information as needed.
Thanks!
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Dear @Harrison stamoudis,
You can assume a cohesion of 0.01kPa for sand as an aparent cohesion.
Feel free to get in touch with me.
Cheers,
Ali Ahmadi
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Dear community,
I would like to derive the formula for the calculation of the deflection of the plate at any point (see attached image).
I am looking into Timoshenko's Theory of Plates and Shells and also on xcalcs and I fail to understand how to derive the formulas. Would anyone be kind enough to help me with this?
For example, how can I use strain energy (V) minimization to get the deflection? How can I derive the strain energy equation and how can I solve it?
Any guidance for dummies is extremely appreciated.
Thank you very much for taking the time to read my post.
Best regards,
George K.
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If you have a look at the beginning of Timoshenko's book, you'll see that your problem is closely related with cylindrical bending of plates. So, deflection can be obtained with grate accuracy as solution of ODE D*w''(x)=-M(x)=-q*(x+a)2/2, x(a)=0, x'(a)=0. The solution is w(x)=-q*(x-a)2*(17*a2 + 6*a*x + x2)/(24*D).
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Please share any Example, Tutorial or any article related to CDPM. For a 3D Pushover analysis.
Thanking in anticipation!
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If you are interested in concrete model for explicit solver (VUMAT), you can use this link to download it
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Frequency determines the number of complete displacements of a body from the initial point of rest within the unit of time 1 sec The amplitude of oscillation is the metric magnitude of a periodic motion of a body that oscillates around its initial equilibrium position. The amplitude of the oscillation and the frequency determine the magnitude of the acceleration. The acceleration of a body falling to the ground is 9.81m / sec = 1g To measure the acceleration of the ground reaching below the base of the structure we use (g) eg constructions can withstand 0.50 g for a short time The magnitude of the earthquake is measured by the acceleration that will eventually reach below the base and not by the magnitude of the Richter scale itself. The acceleration that reaches below the base depends on the magnitude of the earthquake, the focal depth, the distance of the structure from the center of the earthquake and the soil conditions between the earthquake and the structure. Duration is called the event time of the earthquake. Acceleration and duration determine the disaster rate. A structure can withstand high acceleration (1/2 g) for a short time or vice versa low acceleration for a long time. The strength of the construction depends on the magnitude of the acceleration, the duration of the earthquake as well as the seismic damping mechanisms available. Each body has a specific frequency that oscillates and it depends on its height. When the ground frequency coincides to be the same as the construction frequency we have the tuning. During the tuning all the energy of the earthquake is transferred on the construction and if the construction does not have seismic damping mechanisms then the oscillation amplitude gradually increases over time, so the construction receives increasing seismic loads until it is destroyed. In today's seismic design, the inelastic displacement of the structures is considered inevitable and they try to mitigate the damage by using various seismic damping mechanisms. In addition to the above, there are too many unbalanced factors that can cause disaster and in most modern seismic structures. The factors that determine the seismic behavior of structures are numerous, and in part probable. 1) The direction of the earthquake is unknown. 2) the exact content of the seismic excitation frequencies is unknown. 3) duration unknown 4) acceleration unknown Even the maximum possible accelerations given by seismologists, and determine the coefficient of seismic design have a probability of exceeding, greater than 10%. The correlation of quantities such as "inertial stresses - damping forces - elastic forces - dynamic construction characteristics - construction ground interaction - forced ground motion" is non-linear and determines the response of structures to the earthquake. According to modern regulations, the seismic design of buildings is based on the requirements of competent cross-sectional design and plasticity. The inevitable inelastic behavior under strong seismic excitation is directed at selected elements and failure mechanisms. Poor design of the sections around the nodes and the limited plasticity of the elements lead to major failures I mentioned all of the above to understand that when a static study is signed the earthquake can destroy you along with the building its people and its contents. Nothing is certain with an earthquake, and this is because when some of the above factors, such as resonance, long duration and high acceleration, coincide, then the inelastic displacement will not be difficult to pass at a breaking point. Conclusion. Today's seismic design is uninterrupted because it can not control deformation. Seismic damping by different mechanisms may help in the smooth absorption of seismic energy, but there is no guarantee that the structure will stand upright. The quality of constructions and their safety is also a function of the economic situation of the countries, among other factors. Understandably, poor countries cannot be compared to countries with strict modern anti-seismic regulations. Here we see that there is a great need to change the seismic design. We need an anti-seismic design that controls deformations regardless of whether we have coordination, long seismic duration and high acceleration, as well as being accessible in poor countries. I believe that the method I propose (pre-tensioning + anchoring to the ground of all sides of the walls with diaphragm function) will increase the response of the structures and reduce the construction costs, because if the construction is stronger than we need then we remove reinforcing steel and bases and drop the cost.
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Very interesting query but it is away from my field
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I am working with DIANA and I'm going to conduct the analyze under reversed loading by using Menegotto Pinto plasticity model for reinforcement bar.
In the absence of experimental data, how can I find the parameters that are included in Menegotto Pinto plasticity model such as: initial tangent slope ratio, initial curvature parameters and all constant parameters (a1, a2, a3,a4).
Is there any explanation about all these parameters or someone may provide some information about?
All data for reinforcing steel that I have is Poisson ratio=0.3, yield stress=472MPa, and modulus of elasticity=214000
Thanks in advance.
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thank you for your answer
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I've to model the plastic behavior (Yield Stress vs Plastic Strain) of a polyimide material (Elas_Mod=2500MPa) in Abaqus. The engineering stress vs strain plot is shown as the 3 red curves. I've captured the curve corresponding to 23degC in Matlab, as can be seen in the blue plot. The plot starts from yield point stress = 69MPa. Next I convert this eng. stress and eng. strain to true stress and true strain using:
True_Stress = Eng_Stress*(1 + Eng_Strain)
True_Strain = log(1 + Eng_Strain)
The corresponding plot for True Stress vs True Strain is the green plot. Next I convert the true strain to logarithmic plastic strain using:
Log_Plastic_Strain = True_Strain - (True_Stress/Elas_Mod)
The first value of log plastic strain is changed to zero, representing the yield. The plot of true stress vs log plastic strain is the black plot. Here it can be seen that after a point, the plastic strain decreases with increasing true stress. So when assigning the plastic data in Abaqus, do I use only those points up to which the plastic strain increases and ignore the remaining points? Why does the true stress vs log plastic strain plot have decreasing strain trend which eventually moves towards negative values? Thank you for your time!
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I suspect that you has used strains mesured in percents instead of fractions (for example, it must be 0.4 rather than 40%).
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Greetings,
I'm studying structure changes in a 2D granular sample subjected to shear stress. I have captured the dynamics along time with a video camera and I have obtained particle positions for every frame of my videos through image processing. And my question is:
What kind of statistical or physical-mathematical tools can I employ in order to measure plasticity & elasticity degrees in the bidimensional granular structure?
Thank you in advance for your answer!
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1. What is the difference between hydrostatic and quasi-hydrostatic pressure?
2. Are all SPD techniques providing this pressure?
As Zhilayev et al. mentioned, Multi-directional forging (MDF) not providing quasi-hydrostatic condition in www.scientific.net/DDF.385.302
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Kiarash Mashoufi, thanks, your answer helped me anyway and I found the meaning of Mr zhilyaev comment by myself!
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Want to reduce the Hardness of TPU. As TPU comes in a granular form incorporating plasticizer is difficult. What methods can be used to incorporate plasticizer in TPU?
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Can anybody help me to figure out plasticity values for stainless steel for Dynamic Explicit analysis in Abaqus ?
It doesn't matter about the stainless steel type and please be kind enough to let me know how to get those plasticity values and yield stress values which are coming under material properties...
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Thank you Sir Vincenzo Cucumazzo for your feedback
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Dear researchers
As you know, one of the challenges of using nonlinear procedures is to determine the behavior of plastic hinges of members with deformation controlled action that this behavior is assigned to the plastic hinge by a force-deformation curve and its relations using parameters modeling. various researches has shown that the uncertainties in these modeling parameters significantly affect the structural responses.
Also, the acceptance criteria of different performance levels relating to the mentioned force-deformation curve are needed for performance-based design of structures.
There are two questions now:
1- Are force-deformation curves presented in ASCE 41-13 suitable only for nonlinear static analysis (push over)? or also is applicable for nonlinear dynamic analysis?
2- Given that the acceptance criteria presented in ASCE 41-13 are derived based on the mentioned force-deformation relations in this code (a, b and c modeling parameters), what acceptance criteria can be used to evaluate the structure at the IO, LS and CP performance levels if the other force-deformation relations presented in the technical literature (such as Lignos and Hartloper relations for beams and columns of moment frames, respectively) are utilized for concentrated plasticity modeling?
The mentioned curves (Lignos and Hartloper relations) are mostly used in structural modeling to study the structural collapse, in which the collapse is determined by the criteria mentioned in FEMA p-695 and as a result, acceptance criteria in accordance with these behavior curves have not been researched.
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1. Seismic codes suggest simplified force-deformation models in order to estimate the inelastic behavior both in monotonic and cyclic loading. The monotonic F-δ curve is considered as the envelope and the skeleton curve of F-δ loops under cyclic loading. The real inelastic behavior under cyclic loading depends on the material and the dynamic loading, e.g. reinforced concrete under seismic loading. So, stiffness and strength deterioration should be considered under cyclic loading in the concentrated plasticity modeling technique.
2. Uncertainties about deformation capacity are high beyond the point C of the F-δ curve. Even in the Collapse Prevention performance level (before point C), the ultimate deformations shows significant dispersion in experimental cyclic tests (e.g. reinforced concrete). Consequently, appropriate acceptance criteria for different performance levels and for different materials can be found in seismic codes (ASCE 41-13, FEMA, Eurocode, EN 1998-3, etc) or in other technical literature using model safety factors to scale down the proposed mean values to mean plus standard deviation ones.
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i modeled a simple 15cm*15cm concrete block to check the behavior. and applied a compressive load.
problem is input stress-strain is not matching with output stress(S22) - strain(LE22) as in figure.
my doubt is S22, LE22 are correct components to represent or something else is there 
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Dear Srikanth Kallam In addition to what Ditho Ardiansyah Pulungan underlined, I would like to recommend that you not only check the consistency of the units, but also make sure that the modeling is as realistic as the experiment leads to obtain the stress and strain.
Good luck !!!
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Dear colleagues, I am trying to simulate a strip foundation on a cohesionless soil with a friction angle of 30 degrees. However, I obtain convergence problems. I am using a geostatic step.
The error in the simulation states:
Time increment required is less than the minimum specified
Too many attempts made for this increment
I am new modelling soils in Abaqus, therefore, I'm not sure if I'm ignoring some basic concepts or if there is something I missed when inputting the soil parameters.
Thanks in advance
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This may help to locate the problem:
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From testing data: yield stress, ultimate stress, total strain, ratio of strain at elastic limit by strain at strain hardening and the ratio of elastic yield modulus to the strain hardening modulus.
**The requirement is basically of finding power law parameters. Or any other model parameter capable of representing plasticity.
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To define parameters, the following article will be useful.
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I'm trying to simulate a triplet shear test on Abaqus and I've defined both brick units and mortar joints material behavior by means of the Concrete Damaged Plasticity model available in Abaqus' library. I defined the fracture energy in the tensile stiffening data because I was interested in the aspect of softening regularization.
When performing the analyses on two different (homotetique) mesh discretizations, I would expect to obtain the same response in terms of reaction force and imposed displacement, but it isn't so.
Can anybody help me understand why the regularization doesn't work?
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Different meshes give total different results.
Please refer to this link:
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Hello,
I have been modelling beam and column using concrete damage plasticity material in Abaqus 2019. After the analysis is done, when I checked in visualization, I got the value of DamageT and DamageC more than 1. the max value is nearly 1.4 or 1.7 above. I have been checked the input parameter and believe that the damage parameter is below than 0.9. Have any one face this problem before? it is a bug or there is any other mistake which I probably have done?
I would greatly appreciate it if anybody could help me with this problem.
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Either in the compression damage or tension damage, you have to input the damage parameter column and the corresponding inelastic or cracking strain columns simultaneously.
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I need an explanation from view point of the theories of failure or plasticity theory to explain why the bonding between steel and geopolymer concrete is stronger than with normal concrete.
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I’m sorry Alaa, I work with Geopolymer technology in Italy and Russia. I’m private worker I’m not a professor or a student, I wanted to help you understanding the different hardening technologies but mathematically you have to ask directly to prof. Davidovits . For free this is the best that I can do ;D.
Cordially
Alex Reggiani
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Hello,
I'm simulating a Representative Volume Element (RVE) to estimate it's homogenised properties under pure compression in X direction.
After some attempts I decided to try just an isotropic material model with one-element simulation, but with the similar boundary conditions, which emulate Periodic Boundary Conditions (PBC) in my loading case: symmetry on X on one side, symmetry on Y on both sides and symmetry on Z on both sides as well. One side is subjected to uniform displacement in X direction. I tested the Extended Drucker-Prager model with perfect plasticity after 120 MPa
What I found out in results is that after yield had begun stresses (mises, pressure, principles and S11) kept on rising up to the end of simulation in the same "straight" manner they had benn rising before yield. It doesn't even seem to look like plastic behaviour.
If I change my boundary conditions to simple support on one side perpendicular to X and retain the displacement on the opposite side, the result picture of stresses begins to look more "plastic-like".
Can anyone explain me the performance of material model in first case (PBC)? Thanks in advance
I'm attaching the plots of the both cases. Units for stress are TerraPascals (i.e. my yield strength is 120e-6TPa), horizontal axis is the applied strain in X direction (recalculated from displacement and X size of the element: strain=displacement/x-size)
Thanks in advance
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Hi,
Looking at both the curves it seems if the stress range is kept the same on both the graphs, the variation you will observe will be similar.
In the first graph, the stress is more than 10 times higher than the second case because of which the variation in the lower stress range where elastic to plastic transition is seen is not visible.
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I know that ANSYS uses J2 flow theory (incremental plasticity approach) to solve the elasto-plastic problem. But I want to compare the results of  flow theory of plasticity and deformation plasticity theory. Can I do it using ANSYS or any other commercial software
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Dear Kanishk Sharma,
ANSYS does not possess the ability to perform direct computations with deformation theory of plasticity.
However, in the case of monotonic loading, the Multilinear Elasticity (TB,MELAS) can be used. The material behavior is described in this case by a piece-wise linear stress-strain curve. But the unloading is not linear and there is no hysteresis behavior.
Many years ago, I have implemented the deformation theory of plasticity into the finite element programm PANTOCRATOR (C++ code) developed in the St. Petersburg polytechnic university. Comparison of the finite-element simulation results for the deformation theory with the flow theory has shown their coincidence under proportional loading and strong differences under non-proportional loading.
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This is a tribute to the adaptability and plasticity of viruses which facilitates them to make new races.
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DOI: 10.1186/s12575-020-00127-3
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Hello,
I'm trying to simulate plastic deformation with COMSOL but i don't get any solutions. But if I simulate only linear elstic the simulation converges. What do I have to take into account when I'm using the plasticity module?
Thank you all in advance.
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Helo Kant Hegele
I too have the same issue, I tried everything for Hot rolling problem, did you find the solution finally. if so can you please share the Comsol file here.
TIA
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Hello,
I am modeling an impact as a part of my project and due to the large deformations in this phenomenon, I turned the NLGEOM (GEOMETRIC NON-LINEARITY) on, but in a paper, I came across this point:
"Effects of large scale displacements were not included in the study. Soil plasticity at impact was much more significant, and a solution with time-stepping, plasticity, and geometric
non-linearity was not feasible."
Is the mentioned point correct?
I would be so thankful for your help.
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If you are using plasticity with material non-linearity activated, the geometric non-linearity also shall get considered automatically. In pure elastic simulations involving no plasticity, in general as a rule of thumb, if the displacement exceeds 1/3rd the dimension (In a cantilever, if the selection is more than 1/3rd of the height of cross-section), you need to invoke the geometric non-lineairty and rerun.
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I am building a database of fall-cone test penetration depth vs water content. The database has 120 soils approx. Looking for published and unpublished results to increase the number of entries.
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Dear Marcelo Llano
You can consider the data result shown in the following paper for Quaternary soils. The liquid limit for the soils has been determined using different methods including the fall-cone method.
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I am writing a new plasticity model in Ansys Explicit Dynamics using AUTODYN as solver for Bilinear Isotropic Hardening model but any how unable to add this particular material model code, as I need MATDEF code for above model.
It will be a great help if anyone can help me to write that particular code. So as to define my model and get in continuation with my research.
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Hi Karan,
Aside from the suggested answers, you can also use AceGen in Mathematica.
Best,
Romik
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I want to determine liquid limit and plastic limit for irbid soil, the soil samples are very stiff and have a large size. I want to know if grinding the samples affects of plasticity or not affect.
Thanks in advance
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According to ASTM, the material like the soil under consideration should be prepared before testing. The preparation procedure includes placing the specimen in a pan and adding sufficient water to cover the material. Then, it should be allowed to soak until all lumps have softened and the fines no longer adhere to the surfaces of the coarse particles.
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Hello,
As the question suggest, I am curious to know if there are good papers/textbooks on understanding the reloading between yielded and unyielded surfaces.
Say I have a yielded surface due to the elastoplastic contact between two metallic spheres. I unload them and reload them slightly offset from their previous contact positions such that the contact area overlaps previously contacted ( and yielded regions) and virgin non-contacted material.
How would contact during this loading work?
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Hi Devanjith,
a simple approach would be, to study the new contact problem the same way as always, with the gap between the surfaces changed due to yielding. However, this problem will be asymmetric, so you probably won't find textbook solutions. FEM or BEM simulations should work just fine, though.
Bigger problem with that idea is, that
"once the sphere is completely unloaded, a complex state of residual stresses remains in the body of the sphere due to the sustained plastic deformation." [1]
Multiple elasto-plastic loading on the same spot has been studied in detail in [2].
Best reagrds,
Emanuel
[1] Ghaednia, H.; Wang, X.; Saha, S.; Xu, Y.; Sharma, A.; Jackson, R.L.: A Review of Elastic–Plastic Contact Mechanics. Applied Mechanics Review, 69(6), 060804 (30 pages) (2017)
[2] Y. Kadin, Y. Kligerman, I. Etsion: Multiple loading–unloading of an elastic–plastic spherical contact. International Journal of Solids and Structures, 43(22-23), 7119-7127 (2006)
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Hi, I would like to use concrete damaged plasticity models for rigid PU foam. i would like to know how to find the parameters for the same 
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Hi Vicky Varghese , Did you get solution for this ? Could you please share? I am working on similar PU foam ...
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I am trying to simulate the cutting of concrete (without any reinforcement) using a tool with a nose radius of 0.02 mm. I have modeled concrete in 2d using the damaged plasticity model with the values shown in the pictures attached. My tool is a deformable 2d body with an elastic modulus of 200 GPa.
I have modeled the region of concrete that needs to be cut using a mesh size of 0.05 mm. The concrete part is 10 mm in length and 4 mm in height. Tool is 4mm x 4mm. The mesh is set to be linear, explicit and for plane strain conditions with element deletion option set to true.
I have defined cutting speed using the velocity boundary condition and it is 833 mm/s. The stress units are in MPa. Length units in mm. Am also using ALE domain (standard values) for mesh refinement (thinking it might help). Friction coefficient is set to 0.2.
The problem I am having can be seen in the picture named Problem. It is that the concrete is getting pressed in by the tool (feed force) and the region is buckling under compression and eventually leads to excessive distortion error or a zero mass element error.
In my opinion the problem is in the material model itself that it is not getting crushed under compression. Could someone kindly help me out with this? Thanks a lot in advance.
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Let try it.
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Errors are as follow:
*cap plasticity requires the use of *cap hardening
The material options *cap plasticity, *cast iron plasticity, *clay plasticity, *concrete, *concrete damaged plasticity, *drucker prager, *foam, *crushable foam, *mohr coulomb, *jointed material and *plastic are mutually exclusive
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Let use an accurate input data for CDPM.
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Which diagram for the confined concrete by a steel tube should I use in concrete damaged plasticity model in ABAQUS: uniaxial compressive diagram or confined concrete diagram?
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model unconfined concrete as the test set up, forget the term of "confined concrete"
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I have made a concrete damage plasticity model of M30 grade concrete. But it is showing higher stress values than specified in concrete property. I am attaching the paper which I took as a reference. Can anyone tell me what may be the reason?
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In my idea, you plotted integration points. Re-plotting the nodes, problem will be solved.
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Hi everyone,
I have simple one bay reinforced concerete. I am trying to analysis it with Concrete Damage Plasticity model and I want to get the hysteretic curves to compare with the experimental results. Although I can get good results about max and min capacities of the structure, I can not get the pinching effect and rigidity degredation. Can anyone give me an idea how to get pinching in cyclic loading?
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Up to my experience, pinching may not be modeled by abaqus unless using certain programmings. In most of the papers about pinching study of concrete, OpenSees was utilized.
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Drucker-Prager Properties used in SAP2000 for concrete only refer to friction angle and dilatation angle while the hysteresis curves also are limited.
Purpose: To calibrate SAP 2000 model with Abaqus model.
P.s: Attached the nonlinear properties of concrete in SAP2000
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Hi, up to my knowledge, SAP2000 is unable to consider CDP model.
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Hello everyone,
May I know how to model masonry wall using simplified micro modelling in ABAQUS?
Any particular parameters that I should include in my model? (i.e. Concrete Damage Plasticity)
I can't seem to find any tutorial on masonry structure online. Would be great if I could get some advice from you. Thank you.
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One point that I can add to previous answers that be careful when you define stiffness and damage parameters of the contact between masonry units.
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Hello,
According to the power law, Stress=K*strain^n. Could someone please explain why an increase in strain hardening exponent n results in less material necking from this equation?
Please see the attached plot, here I used K=1 to ignore it's effect and I have varied n for n different values.
It seems that for the same stress put into the material, the curve at n=0.1 produces the smallest strain, where as the curve at n=0.5 produces the largest strain, up to strain=1. If the stiffest material is desired, is n=0.1 not more favourable here?
This behaviour changes at strains greater than 1, this has also left me confused.
Any clarification on this will be very much appreciated.
Thank you!