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Nikolaos Mavrodontis

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Coupled Thermal-Stress Analysis and Expansion Joints in Abaqus

Posted by Nikolaos Mavrodontis on Mar 6, 2018 9:46:24 AM

In this post we will be showing an exemplary analysis with Abaqus Standard. This analysis will incorporate a coupled thermal-stress problem of  a cylindrical shell (e.g. a pipe enclosing a high temperature fluid used in a factory). This pipe will be connected to a metallic expansion joint that will have the purpose of undertaking the thermal extension of the pipe. The purpose of the coupled analysis will be to demonstrate the mapping of result values via the predefined field option.


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Topics: Abaqus, thermal-stress, expansion

Xflow CFD demonstrating the Magnus effect

Posted by Nikolaos Mavrodontis on Jan 2, 2018 8:46:46 AM

In the current post, we will be focusing on introducing XFlow CFD by demonstrating an aerodynamic effect primarily observable in spheres or cylinders following certain trajectories while spinning at the same time.

This effect is known as the Magnus effect, associated with spinning objects. A sphere for example travelling through mid-air while spinning at the same time , will drag air faster around one of its sides. This will consequently create a pressure gradient between the sides of the sphere, thus creating a lift force that will alter the sphere’s trajectory compared to a case with no spin.  The lift force generated is equivalent to that of an airfoil, only the origin of the necessary air recirculation around the body is by mechanical rotation (the spin)  and not by aerodynamic design ( the airfoil).

XFlow is a next generation CFD software based on the Lattice-boltzmann method designed for a broad range of computational fluid dynamics simulations. XFlow’s  latest release supports coupling with Abaqus for performing fluid structure interaction analyses.

The Magnus effect will be demonstrated with a spinning football analysis in XFlow.

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Topics: XFlow CFD

Modelling hyperelastic behavior using test data in Abaqus

Posted by Nikolaos Mavrodontis on Dec 11, 2017 5:51:49 PM

In this blog, the hyperelastic behaviour modelling in Abaqus will be discussed.  This will be implemented by fitting relevant experimental data with appropriate strain potential energy functions that are built-in in Abaqus and deciding on the function that best models the rubber materials behaviour. Additionally a finite element model will be demonstrated, wherein the designated material behaviour will be show cased.

Last but not least, in the process of explaining relevant aspects  of hyperelastic material modelling with Abaqus, various suggestions and good practices will be shared.

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Topics: Rubber, hyperelastics, test data

How to submit and monitor Abaqus jobs through command window

Posted by Nikolaos Mavrodontis on Oct 30, 2017 12:17:31 PM

This blog focuses on  submitting an Abaqus job through the Command window and monitoring it without the Abaqus CAE interface.

Usually what most Abaqus users will do, in order to submit an analysis, is to create and submit the respectful job file when their preprocessing stage model is complete. This process is done in most cases through Abaqus CAE.
Subsequently the user will track the job monitor (accessible through the Job manager) in order to acquire valuable information regarding model related warnings and convergence performance of the solver.

However, there is quite often the need to submit a job file from the command window. The main reason behind this action, might as well be one of the following: ability to run several jobs simultaneously or sequentially, token re-allocation for extra CPUs in place of the CAE if the total number of tokens are limited, or if there are multiple Abaqus users occupying tokens etc.
The action of submitting a job through the CAE and the available options/outputs for monitoring the job’s progress through the Job monitor are features that can also be realized or accessed simply by the command window.

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Topics: submit monitor abaqus command window

Converting Engineering Stress-Strain to True Stress-Strain in Abaqus

Posted by Nikolaos Mavrodontis on Oct 9, 2017 2:41:42 PM

This blog focuses on the difference between Engineering Stress-Strain and True Stress-Strain. Furthermore we will explain how to convert Engineering Stress-Strain to True Stress Strain from within Abaqus. Abaqus offers many possibilities with respect to material modelling. Apart from including elastic properties, also various options are offered for modelling of plasticity. Usually for accurately modelling materials, relevant testing is conducted.

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Topics: Stress-Strain

Buckling, Post-Buckling & Imperfections modelled with Abaqus FEA

Posted by Nikolaos Mavrodontis on Sep 12, 2017 9:51:48 AM

In this blog, we will describe the possibilities for Buckling and the methodology to take into account imperfections.

Buckling refers to the sudden collapse of a structural member , subjected to high axial compressive loading. This collapse takes the form of a sudden lateral deflection of the structural member. Therefore the structure’s load bearing ability is compromised under buckling. Based on the structure’s characteristics, either a consequent full collapse can occur or the structure’s load bearing capacity is restored in the post-buckled region. When the structure exhibits this sudden lateral deflection under axial compression, it is said that the buckling load has been reached. The importance of considering buckling during structural design is outlined by the fact that the buckling load is lower than the maximum load the structure can withstand under axial compression.

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Topics: Abaqus, Buckling, Imperfections, post-buckling

Bolt pretensioning with use of Abaqus scripting

Posted by Nikolaos Mavrodontis on Jul 11, 2017 1:40:04 PM

For many engineering applications, bolted connections are used extensively for holding various components together and transferring of loads among those components (e.g. bolted connections for connecting trusses, L or T-type flanges).

Usually the bolts used in these types of connections, are under tension (pretension) for providing a slip-resistant connection. Also when a bolted connection is under pretension (e.g. a nut is tightened around the bolt shank) and an external load is applied, the bolt will endure much longer whereas for an un-pretensioned bolted connection the bolt might fail in seconds (different fraction of the external load goes through the bolt shank for each case)

Abaqus CAE offers straightforward methods for manually applying pretension on bolts, as long as the number of bolts within a model is kept to a minimum. However in models incorporating a large number of bolts or bolted connections in general, manually applying bolt pretension can become tedious work and extremely time consuming.

In such a case, applying bolt pretension with the use of a Python script can optimize efficiency, and this shall be demonstrated consequently.

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Topics: Abaqus Bolt Loads

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Simuleon blog topics related to Finite Element Analysis like; Structural Analysis and CFD analysis performed with SIMULIA Abaqus FEA, XFlow CFD, Isight Simulation Automation, Tosca Topology Optimization and Fe-Safe accurate Fatigue.

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