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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.

kourousis's picture

Is the study of Low Cycle Fatigue (LCF) and cyclic plasticity useful for biomedical metals?

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I would like to open a discussion in relation to the following question:

"Is the study of Low Cycle Fatigue (LCF) and cyclic plasticity useful for biomedical metals?"

It appears that there is some level of misunderstanding around this issue. Thus, I would be very interested to find out the views of iMechanica community engineers and researchers working on biomedical metals and applications (i.e. implants) on this.

Mike Ciavarella's picture

A very simple estimate of adhesion of hard solids with rough surfaces based on a bearing area model

"A very simple estimate of adhesion of hard solids with rough surfaces based on a bearing area model" is in press in Meccanica, can be viewed at Abstract In the present note, we suggest a single-line equation estimate for adhesion between elastic(hard) rough solids with Gaussian multiple scales of roughness.

Hamid Souri's picture

A theoretical study on the piezoresistive response of carbon nanotubes embedded in polymer nanocomposites in an elastic region

Herein, we report a theoretical study of polymeric nanocomposites to provide physical insight into complex material systems in elastic regions. A self-consistent scheme is adopted to predict piezoresistive characteristics, and the effects of the interface and of tunneling on the effective piezoresistive and electrical properties of the nanocomposites are simulated. The overall piezoresistive sensitivity is predicted to be reduced when the lower interfacial resistivity of multi-walled carbon nanotubes (MWCNTs) and the higher effective stiffness of nanocomposites are considered.

Measuring the relative density of open cell metal foams


I would like to know how to measure the density of open cell porous iron foam. I am studying the mechanical behavior of pure iron foams for which I need to compare the relative densities of different foam samples. Could the density of the foams be simply calculated by the mass over the bulk volume (volume of the struts + volume of the pores) of the foam? Can I use Archimedes principle to calculate the foam density given that I have open cells? What is the best method to calculate the foam density? 

Best Regards,


gaurp's picture

Characterization of Human Diaphragm at high strain rate loading.

In this paper, we studied the strain rate dependent failure properties of human diaphragm tissue using uniaxial tensile testing at four strain rates, i.e. 0.0015/s, 65/s, 130/s and 190/s. The custom made quasi-satatic and drop tower based dynamic test setups was used to conduct the tests uptill 200/s strain rate.

Ali Ramazani's picture

Modeling the Hydrophobicity of Nanoparticles and Their Interaction with Lipids and Proteins

We present a method of modeling nanoparticle (NP) hydrophobicity using coarse-grained molecular dynamics (CG MD) simulations, and apply this to the interaction of lipids with nanoparticles. To model at a coarse-grained level the wettability or hydrophobicity of a given material, we choose the MARTINI coarse-grained force field, and determine through simulation the contact angles of MARTINI water droplets residing on flat regular surfaces composed of various MARTINI bead types (C1, C2, etc.).

What kind of tensile testing grips is right for your samples and application?

Choosing the most appropriate tensile grips to effectively secure your samples is critical in getting accurate measurements of tensile properties such as tensile strength, peak load, elongation, tensile modulus, and yield.

Xiangbiao Liao's picture

Recent work "Self-Assembly of Islands on Spherical Substrates by Surface Instability"

Through strain-induced morphological instability, protruding patterns of roughly commensurate nanostructures are self-assembled on the surface of spherical core/shell systems. A three-dimensional (3D) phase field model is established for a closed substrate. We investigate both numerically and analytically the kinetics of the morphological evolution, from grooves to separated islands, which are sensitive to substrate curvature, misfit strain, and modulus ratio between the core and shell.

Bin Liu's picture

The surface-forming energy release rate versus the local energy release rate

In our just published paper, we identify two ways to extract the energy (or power) flowing into a crack tip during propagation based on the power balance of areas enclosed by a stationary contour and a comoving contour. It is very interesting to find a contradiction that two corresponding energy release rates (ERRs), a surface-forming ERR and a local ERR, are different when stress singularity exists at a crack tip. Besides a rigorous mathematical interpretation, we deduce that the stress singularity leads to an accompanying kinetic energy at the crack tip.

Meisam. Asgari's picture

In vitro fibrillogenesis of tropocollagen type III in collagen type I affects its relative fibrillar topology and mechanics

Tropocollagen types I and III were simultaneously fibrilized in vitro, and the differences between the geometric and mechanical properties of the heterotypic fibrils with different mixing ratios of tropocollagen III to I were investigated. Transmission electron microscopy was used to confirm the simultaneous presence of both tropocollagen types within the heterotypic fibrils. The incorporation of collagen III in I caused the fibrils to be thinner with a shorter D-banding than pure collagen I.

How to measure hydroxyl radical concentration (airborne)?

Dear engineers and scientists,


Measuring and artificially producing hydroxyl radicals is relatively new research with great challenges due to short half life. I have asked this question on many forums to gather as much information as I can and my question is:


How can we measure hydroxyl radical concentration? I am only interested in airborne concentration, hydroxyls in water and cells are not relevant to my research.


Also there are few articles mentioned every time in these type of discussions and they are:

Tear strength, porosity, hole size

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Have any one here worked on the effect of porosity and holes size on the mechanical properties, inclduing tear stregth of a film? I have a porous polyethylene film and I need to know what is the effect of holes size on the non-linear properties, such as tear strength, for a fixed porosuty of 40%. The filmthickness is about 10-20um. The hole size varies from 100 nm to 1 um to 10 um to 100um and higher.



Rouzbeh1's picture

Post-Doctoral Associate/Research Scientist Position in Advanced Materials at Rice University


Position Description: 

A postdoctoral associate/research scientist position in the area of advanced synthesis and characterization of materials and nanocomposites is available at Rice University. The successful candidates will work in a highly inter-disciplinary and stimulating environment.


Job Duties and Responsibilities: 

Building a Digital Wind Farm

We've recently published an extensive review of the state-of-the-art in modelling and simulation for wind energy. The paper is open access for a limited time and can be found online at the link below.

Hewitt, S; Margetts L and Revell A, "Building a digital wind farm", Archives in Computational Methods in Engineering, 2017.

Frank Richter's picture

reflection and transmission coefficients in long elastic bars


Dear iMechanica Community,

I'd like to ask for advice on modelling reflection and transmission coefficients when two bars with different cross-sectional areas contact each other and are exposed to pulse loading.

I have modelled this process in Abaqus/Explicit as a two-dimensional simulation. The investigation was conveniently done as a parametric study, defining the lateral dimension as parameter. Both bars are slim (length 2 m, diameter 2 cm) and elastic.


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