Prager cap model was used to simulate the compaction and predict the residual stress state in green compacts. Constitutive model development for powder compaction and. The text of bonet and wood 2008 provides useful background for elastoplastic constitutive modeling. Material cohesion, d, in the p t plane abaqus standard or in the p q plane abaqus explicit. The problem i am getting is that as more load is applied to the model through the ball, the time increments get smaller and smaller, until the model aborts. A computer modeling procedure of densification of the noncompact titanium feedstock is considered. Effect of process variables on the druckerprager cap model. In ansys they use drucker prager in stead of mohr coulomb for these values. See drucker prager cap model for geological materials, section 4. Data lines to define a linear druckerprager plasticity model shear criterion linearfirst line.
Stiffness matrix is illconditioned and cannot be inverted avoid using the constant option in multistep analysis causes divergence if stabilization is removed in subsequent steps. One is a cohesion mechanism, which operates similarly to the drucker prager creep model described in models for granular or polymer behavior. Modeling of powder compaction with the druckerprager cap. Numerical simulation of residual stress field in green. Uhmwpe the contact surface which is linear elastic, titanium which is linear elastic and bone graft which. The modified drucker prager material model will account for these properties. The concrete damaged plasticity model can be regularized in abaqusstandard using viscoplasticity by permitting stresses to be outside of the yield surface. On the opposite, for a 0, the criterion reduces to. For a while our research group has been using a constitutive model, namely, drucker prager cap implemented in abaqus. This model includes three sections as shown in figure 2. Identification of the modified druckerprager yield. Material model is implemented in abaqus finite element code by user subroutines. These are the user material subroutines umatvumat in abaqus for linear, bilinear and piecewise druckerprager models. A laboratory tests to determine the soil properties have been conducted using the triaxial and consolidation test, the results used to identify the parameters of three constitutive models in abaqus.
Hello i am having a problem with a model that utilises the drucker pragercap model and would be extremely grateful if anyone could help me out. Extended druckerprager models have been proposed where the criterion is expressed in linear i. From other studies, i noticed they modeled the soil using mohr coulomb model, using its shear strength parameters being cohesion and internal friction angle. The druckerprager model has been used to model polymers such as polyoxymethylene and polypropylene citation needed. However, polypropylene shows a quadratic pressuredependence of the yield stress. They are multisurface plasticity models, used most frequently with an associated flow rule. It is shown that, when identifying the accepted model with the accuracy acceptable for engineering calculations, it is reasonable to use the auxiliary curve based on the bernoulli lemniscate. Abaqus builtin features enable a wide range of simulating such problems. Modeling of powder compaction with the druckerprager cap model. The area where i1 is larger than the tension cutoff, tcut, is defined as the tension cutoff region.
Compaction simulated sample was a two level cylindrical component. More recently, druckerprager cap plasticity models have been used for the analysis of compaction of pharmaceutical powders, because they can represent the densi. Numerical simulation of residual stress field in green power. Lamarche publisher elsevier source predictive modeling of pharmaceutical unit operations keywords constitutive models, continuum mechanics model, druckerprager cap model, powder compaction modeling, representative volume element year. A densitydependent modified druckerprager cap model. This paper presents numerical simulation for press compaction of the powdered metal in a sintering process. In section 2 we discuss a modified druckerprager cap model developed by sinka et al. I want to model a tower and its underlying soil in ansys. The other is a consolidation mechanism, which operates similarly to the cap zone plasticity. Druckerpragercap mdpcap model are employed in the abaqus finite element analyses to simulate the stressstrain be havior according to the circumstances created in the laboratory. The creep strain rate produced by the consolidation mechanism is assumed to follow a potential that is similar to that of the plastic strain rate in the cap yield surface. My model is 3d and represents the contact of a ball femur with a cup hip socket. In this model we assume the existence of two separate and independent creep mechanisms. Theoretical description of the 3d druckerprager material.
Applied soil mechanics with abaqus applications 1 properties of soil soil formation, physical parameters of soils, relative density, mechanical properties of soil, sieve analysis, soil consistency, liquid limit, plastic limit, shrinkage limit, plasticity chart, classification systems, compaction. A modified druckerprager cap model for finite element simulation. Prager shear yield surface, providing dominantly shearing flow, is written as eq. The model is implemented in abaqus by writing a user subroutine, and, year 2008.
Sep 19, 2015 i have a simple foundation slab embedded into a layer of soil. Figure 1 shows the yield surface described by the cap model in the pq hydrostatic pressure deviatoric stress plane abaqus, 1998. It can well describe pressuresensitive materials such as rock, soil and concrete. The model for clay and silty subgrades was based on the druckerprager cap model. Concrete damaged plasticity massachusetts institute of. It must be used in conjunction with the cap plasticity option and, if creep material behavior is included in an abaqus standard analysis, with the cap creep option. The purpose of this section is to study an expression that combines the three stress invariants, taken under the form. Hi, i was wondering if someone has a druckerprager cap umat subroutine for abaqus. The druckerprager cap dpc model was selected as the method for modeling the mechanical behavior of pharmaceutical powders.
Effect of process variables on the druckerprager cap. Umatvumat for linear, bilinear and piecewise druckerprager. The model parameters of the investigated powder distaloy ae were determined as functions of relative density through typical mechanical property tests of powder. For polyoxymethylene the yield stress is a linear function of the pressure. The addition of the cap yield surface to the druckerprager model serves two main. Statistical analysis of modified druckerprager cap model. Elasticity and plasticity applied soil mechanics wiley. Highperformance abaqus simulations in soil mechanics. Identification of the modified druckerprager yield condition. Constitutive models, clayey soils, mohrcoulomb, druckerprager, critical state. Jul 16, 2017 a computer modeling procedure of densification of the noncompact titanium feedstock is considered. Numerical simulation based on abaqus and matlab data processing tools, using data from uniaxial extension tests has been carried out to study the accuracy of.
The original druckerprager criterion has been modified to incorporate tension cut off or a cap model e. The modified drucker prager cap plasticity model in abaqus is intended for geological materials that exhibit pressuredependent yield. Jul 18, 2012 the original druckerprager criterion has been modified to incorporate tension cut off or a cap model e. Simulation parameters, such as youngs modulus, poisson rate, internal friction angle, plastic deformation parameters, and initial density of the powder, were measured. Simulation parameters, such as youngs modulus, poisson rate, internal friction angle, plastic deformation parameters, and. The dp model was proposed by drucker and prager 1952.
Numerical simulation of powder metal compaction with. A new numerical simulation model for high pressure. Theoretical description of the 3d druckerprager material model. We use a generalization of the duvautlions regularization, according to which the viscoplastic strain rate tensor. K, the ratio of the flow stress in triaxial tension to the flow stress in triaxial compression. A densitydependent modified druckerprager cap model for. Download package of frictional interface model by stutz et al. Numerical simulation was done in abaqus, utilizing druckerprager cap dpc model. See druckerpragercap model for geological materials, section 4. Compaction process simulation and residual stress prediction of green pm compact were carried out with elastoplastic 3d fea based on the modified druckerprager cap model in abaqus. I have also run a simple 2d model using the drucker pragercap model and i get the same problems as i am getting with the 3d model. More recently, drucker prager cap plasticity models have been used for the analysis of compaction of pharmaceutical powders, because they can represent the densification and hardening of the powder, as well as the interparticle friction cunningham et al. Laboratory tests on crrel silty and clayey soil were performed under several moisture contents and the model parameters were determined. Identification of material parameters for druckerprager.
The model is implemented in abaqus by writing a user subroutine, and a calibration process on microcrystalline cellulose mcc avicel ph101 powders is. Druckerpragercap theory in the present model, the plasticity of pebble beds is described by the druckerpragercap model, which is a commonly used in geomechanics. In section 2 we discuss a modified drucker prager cap model developed by sinka et al. Plasticity drucker prager model the yield criterion can be defined as. The modified druckerprager cap model is used to describe the rheological flow of the deformed mass. Druckerpragercap is a typical soil mechanical theory model and it was used to simulate the squeezing process in this study, while abaqus software is used to simulate dynamic stressstrain evolution during the process. The modified druckerprager material model will account for these properties. White paper 10 ways to improve wiring harness manufacturing. Both models were implemented into the abaqus finite element software and their performance. Download now white paper 10 ways to improve wiring harness manufacturing wiring harness manufacturing is a sophisticated and challenging business where quality, accuracy, and speed are essential to success. Mohrcoulomb plasticity, extended druckerprager models and modified druckerpragercap model.
Modeling of powder compaction with the druckerprager cap model authors a. Study of a druckerprager criterion several criteria are named after drucker and prager. Drucker prager cap mdp cap model are employed in the abaqus finite element analyses to simulate the stressstrain be havior according to the circumstances created in the laboratory. The procedure of determining the parameters of druckerprager dp cap model was simplified. Constitutive models, clayey soils, mohrcoulomb, drucker prager, critical state. How to model soil in ansys workbench using drucker prager. It is shown that, when identifying the accepted model with the accuracy acceptable for engineering calculations, it is reasonable to use the auxiliary curve. Similar to other plasticity models, there are three criteria controlling the framework of a dp type model, and hence accuracy of predictions by the model.
The capability allows for the specification of one or more damage initiation criteria, including ductile, shear, forming limit diagram. Drucker prager cap is a typical soil mechanical theory model and it was used to simulate the squeezing process in this study, while abaqus software is used to simulate dynamic stressstrain evolution during the process. The model 10 is derived by addition of a cap yield surface to the drucker. The cap may harden or soften, and is coupled to the drucker. In this paper we focus on constitutive model development and implementation into abaqus and present examples to illustrate how the density distribution is influenced by all factors listed above. Data lines to define drucker prager cap plasticity yield surface parameters first line.
Efforts will be made to implement this model with abaqus software since abaqus. Stress integration for the druckerprager material model. The model is implemented in abaqus by writing a user subroutine, and. Cap plasticity massachusetts institute of technology. The region where i1 is less than the cap yielding function defined as the cap hardening area. The results indicate that the mcc model can fit the stressstrain. Nafems fe model using three constitutive soil models to. For a while our research group has been using a constitutive model, namely, druckerpragercap implemented in abaqus.
A constitutive model relating the state to the stress is needed. Abaqus users druckerpragercap model shear failure problem. I know this routine is already available in the abaqus library, but id like to make some slight modifications to the subroutine. Cap hardening massachusetts institute of technology. It is a plasticity model with multiple yield surfaces. The creep strain rate produced by the consolidation mechanism is assumed to follow a potential that is similar to that of the plastic strain rate in the cap yield surface figure 11.
Specify the extended drucker prager plasticity model. However, as soon as try to incorporate the internal friction an. Hi, i was wondering if someone has a drucker prager cap umat subroutine for abaqus. A new numerical simulation model for high pressure squeezing. In abaqus, modified druckerprager cap model is widely used for the compaction problems of different metals in many research papers. In abaqusexplicit the linear druckerprager model can be used in conjunction with the models of progressive damage and failure discussed in damage and failure for ductile metals. This option is used to define yield surface and flow potential parameters for elasticplastic materials that use one of the extended drucker prager plasticity models. I have no trouble converging to a solution by defining the soil only using its density, elasticity and poisson factor. Prager cap and similar models for the constitutive behavior of geotechnical materials are widely used in finite element stress analysis. The model is implemented in abaqus by writing a user subroutine, and by l. Influences of powder compaction constitutive models on the. More recently, druckerprager cap plasticity models have been. The addition of the cap yield surface to the drucker prager model serves two main purposes.
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