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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.

Amit Acharya's picture

Fracture and singularities of the mass-density gradient field

A continuum mechanical theory of fracture without singular fields is proposed. The primary
contribution is the rationalization of the structure of a `law of motion' for crack-tips, essentially
as a kinematical consequence and involving topological characteristics. Questions of compatibility
arising from the kinematics of the model are explored. The thermodynamic driving force
for crack-tip motion in solids of arbitrary constitution is a natural consequence of the model.
The governing equations represent a new class of pattern-forming equations.

mohsenzaeem's picture

Effects of SiC, SiO2and CNTs nanoadditives on the properties of porous alumina-zirconia ceramics produced by a hybrid freeze casting-space holder method

Highly porous alumina-zirconia ceramics were produced by adding space-holder materials during freeze casting. To increase the strength of porous ceramics, different amounts of nanoadditives (silicon carbide-SiC, silica-SiO2, and multi-wall carbon nanotubes-CNTs) were added. Space-holder materials were removed by preheating, and solid samples were produced by sintering. Up to 68% porosity was achieved when 40% space-holder was added to the solid load of slurry. Wall thicknesses between pores were more uniform and thinner when nanoadditives were added.

FastBEM Fracture 2-D available for download

The fast boundary element program used in the recent paper:

Y. J. Liu, Y. X. Li, and W. Xie, "Modeling of multiple crack propagation in 2-D elastic solids by the fast multipole boundary element method,"  Engineering Fracture Mechanics, 172, 1-16 (2017)

Faxin Li's picture

A breakthrough in Guided Wave – Excitation of shear-horizontal (SH) wave is not a problem any longer

Excitation of non-dispersive shear-horizontal (SH) waves in plates is always a challenge. Recently, we successfully excited single-mode SH0 wave in plates using a face-shear (d24) mode piezoelectric transducer. Meanwhile, the d24 mode transducer can selectively receive SH0 wave and filter Lamb waves. This work was published as a Letter in the IOP journal Smart Materials and Structures (http://dx.doi.org/10.1088/0964-1726/25/11/11LT01).

Fatemeh Ahmadpoor's picture

A perspective on the statistical mechanics of 2D materials

2D materials are fascinating for numerous reasons. Their geometrical and mechanical characteristics along with other associated physical properties have opened up fascinating new application avenues ranging from electronics, energy harvesting, biological systems among others. Due to the 2D nature of these materials, they are known for their unusual flexibility and the ability to sustain large curvature deformations. Further, they undergo noticeable thermal fluctuations at room temperature.

bardia's picture

PhD/masters position in Mechanical Department at University of Hawaii at Manoa

A PhD/masters position is available in AMMI Lab at University of Hawaii at Manoa in the field of surgical robotics. Interested and outstanding candidates should visit my website at http://uhatmanoa.wixsite.com/ammi. Information about general admission process could be found on http://uhatmanoa.wixsite.com/ammi/prospective-students.

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