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Ballistic impact simulation of composite targets in AUTODYN?

In general we use Johnson-Cook model for bullet, which accounts for strain-rate effects, while for the target (Composites), the we use orthotropic constitutive model. Does it mean that strain-rate effects are not important for composites? The Johnson-Cook model cannot be readily used for composites. How does the AUTODYN considers strain rate effects for composites in ballistic impact simulations? 

UMAT for Kinematic hardening

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I just followed the code that ABAQUS presented (Copied below), but I'm getting very strange results comparing with ABAQUS GUI, what's wrong with that? 

Please help if you have experience 

 

 

      SUBROUTINE UMAT(STRESS, STATEV, DDSDDE, SSE, SPD, SCD, RPL,

     1 DDSDDT, DRPLDE, DRPLDT, STRAN, DSTRAN, TIME, DTIME, TEMP, DTEMP,

     2 PREDEF, DPRED, CMNAME, NDI, NSHR, NTENS, NSTATV, PROPS, NPROPS,

     3 COORDS, DROT, PNEWDT, CELENT, DFGRD0, DFGRD1, NOEL, NPT, LAYER,

     4 KSPT, KSTEP, KINC)

C

saberelarem's picture

On a systematic approach for cracked rotating shaft study: breathing mechanism, dynamics and instability

We present a systematic approach to deal with the modelling and analysis of the cracked rotating shafts behaviour. We begin by revisiting the problem of modelling the breathing mechanism of the crack. Here we consider an original approach based on the form we give to the energy of the system and then identify the mechanism parameters using 3D computations with unilateral contact conditions on the crack lips. A dimensionless flexibility is identified which makes the application of the approach to similar problems straightforward.

Shailendra's picture

Post-doctoral position in Failure of Brittle Materials at National University of Singapore

We anticipate an opening for a post-doctoral fellow position in micromechanics based failure modeling of heterogeneous brittle materials. The focus will be on characterizing the roles of flaw distributions on rate-dependent failure in materials such as concrete. The objective is to develop an understanding of failure processes with the aim of designing high performance brittle materials.

Shailendra's picture

Post-doctoral position in Failure of Brittle Materials at National University of Singapore

We anticipate an opening for a post-doctoral fellow position in micromechanics based failure modeling of heterogeneous brittle materials. The focus will be on characterizing the roles of flaw distributions on rate-dependent failure in materials such as concrete. The objective is to develop an understanding of failure processes with the aim of designing high performance brittle materials.

constitutive model of polymers

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I have been studying constitutive models of polymers for four years, and I have written vumat codes of several constitutive models, such as BPA, Arruda-Boyce, Mulliken-Boyce, Johnson-Cook, DSGZ and G’Sell-Jonas, but I don't understand the theory of anand constitutive model. If anybody share the corresponding the vumat codes of anand constitutive model, I will appreciate his or her help very much, and I am also willing to help him or her by sharing my codes with  him or her. My mailbox is wanghaitao@hust.edu.cn.

ABAQUS: Access stress of integration point of elements during calculation

Hi all,

I'm using ABAQUS and UMAT for structural simulation. I used quadratic element (CPS4) with 4 integration points (IP).

During the calculation (which calling my UMAT), at each time step, for each element, I need to calculate the average stress of these IPs and produce a state variable for these IPs from this average stress. Then, I would need to update this state variable back to these IPs in that element. But as far as I know, the ABAQUS call UMAT for every IP and calculate everything within this current IP.

Prony series with temperature dependent stiffness

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Hello,

I have implemented a viscoelastic model (Simo/Hughes approach: Prony series for small strain)

in Abaqus using Umat and it works fine for dynamic isothermal simulations (I validated with the Prony series implemented in Abaqus).

Now, I want to consider thermal loads (I have temperature dependent stiffnesses from a DMA experiment).

How should I use these temperature dependent stiffnesses in the model?

saberelarem's picture

On a systematic approach for cracked rotating shaft study: breathing mechanism, dynamics and instability

We present a systematic approach to deal with the modelling and analysis of the cracked rotating shafts behaviour. We begin by revisiting

the problem of modelling the breathing mechanism of the crack. Here we consider an original approach based on the form we give to the energy of the system and then identify

the mechanism parameters using 3D computations with unilateral contact conditions on the crack lips. A dimensionless flexibility is identified which makes the application

Drucker Prager Plasticity model

Hi All,

I am trying to code the Drucker prager plasticity model for the 2D plane strain case using consistent tangent modulus. I am using C++, therefore I would appreciate if anyone could share relevant materials which I could use and preferrably for the 2D case so it is not unnecessarily complicated.

 

Mike Ciavarella's picture

3D Printing Grand Challenge

Abstract Submission Extended to March 1st 2017

More information

Issues with the implementation of Strain gradient plasticity framework of Niordson and Hutchinson (2003) in ABAQUS UEL

I have implemented the rate-independent strain gradient plasticity framework of Niordson and Hutchinson (2003) in UEL. I was able to validate the results of the shear of infinitely wide thin layer between two rigid surfaces (Niordson and Hutchinson, 2003). However, the UEL subroutine fails to converge for the more complex problem of the shear of finite width slab. I suspect the convergence issues are arising out of internal elastic-plastic boundary conditions and the yield criteria. I have few doubts in this regard.

 

sergkuznet's picture

Call for Abstract Submission to the USNCCM14: Modeling Materials with Coupled Physics

Dear Colleagues:

The 14th U.S. National Congress on Computational Mechanics (USNCCM14) will be held at the Palais des Congrès de Montréal, QC, Canada,  July 17-20, 2017 (http://14.usnccm.org/).

Giorgio Carta's picture

“Deflecting elastic prism” and unidirectional localisation for waves in chiral elastic systems

For the first time, a design of a “deflecting elastic prism” is proposed and implemented for waves in a chiral medium. A novel model of an elastic lattice connected to a non-uniform system of gyroscopic spinners is designed to create a unidirectional wave pattern, which can be diverted by modifying the arrangement of the spinners within the medium. This important feature of the gyro-system is exploited to send a wave from a point of the lattice to any other point in the lattice plane, in such a way that the wave amplitude is not significantly reduced along the path.

Cyclic Bidirectional loading in ABAQUS

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I'm modeling a column under Constant Axial load (Y-axis) and Cyclic bidirectional loading (X & Z-axes). Does anyone have experience how to apply Cyclic bidirectional loading in ABAQUS? See the attached picture.

peppezurlo's picture

Catastrophic thinning of dielectric elastomers

Consider a thin dielectric plate with conducting faces: when will it break if a voltage is applied? If it is rigid it will break once its dielectric strength is overcome by the voltage. But what if it is highly stretchable, like the elastomers used for soft actuators, stretchable electronics, or energy harvesters? The precise answer to that question is not known. 

A novel class of highly efficient and accurate time-integrators in nonlinear computational mechanics

A new class of time-integrators is presented for strongly nonlinear dynamical systems. These algorithms are far superior to the currently common time integrators in computational efficiency and accuracy. These three algorithms are based on a local variational iteration method applied over a finite interval of time. By using Chebyshev polynomials as trial functions and Dirac–Delta functions as the test functions over the finite time interval, the three algorithms are developed into three different discrete time-integrators through the collocation method.

Piezoresistivity modeling with Ansys

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Dear Colleagues,  I am working with ANSYS PDL to model a piezoresistive cement-based material; the material is assumed to be isotropic and the piezoresistive strain matrix [m] has to be determined, details are specified in the attachment. I would be pleased if you would provide your expert insight on the following questions.  1. In piezoresistive strain matrix [m], what do components X, Y, XY, YZ and XZ mean physically? How are these quantities determined?

Alejandro Ortiz-Bernardin's picture

Consistent and stable meshfree Galerkin methods using the virtual element decomposition

Paper Accepted for Publication in International Journal for Numerical Methods in Engineering

Consistent and stable meshfree Galerkin methods using the virtual element decomposition

A. Ortiz-Bernardin, A. Russo, N. Sukumar

 

Abstract

Mike Ciavarella's picture

moving singularities (crack analogues) in fretting fatigue

    The stress concentration induced by fretting fatigue was studied with a simple "Crack Analogue" model (CA) by the MIT group of Suresh in the late 1990's, which was then "improved" by the present author to take into account simply both contact loads and bulk stresses loads, and even the case of finite stress concentration in the so-called "Crack Like Notch Analogue" (CLNA) model.

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