Vortex-induced waves along cables

International audienceA low-order model for transverse vortex-induced vibrations of cables in stationary uniform flow is analyzed. The near wake vortex street is modeled by a continuous distribution of non-linear van der Pol oscillators, arranged along the spanwise extent of the structure and interacting by diffusion and stiffness. The structure, described as a classical tensioned cable, is forced by the fluid via a linear fluctuating lift model and reacts on the fluid through different linear actions. The model dynamics is investigated analytically and discussed with respect to the choice of the coupling terms, then verified by numerical simulations, in comparison with literature data. Discussion follows on the effectiveness of the linear inertial action of the structure on the fluid in describing, qualitatively and quantitatively, the main features of vortex-induced vibrations phenomenology, and standing versus traveling wave behavior

Coupling of forming process and fatigue design computations: a local approach

WOSInternational audienceThe fatigue design of stamped parts is supposed to take into account for the forming process. In this paper, stamping of steel sheets is addressed by basic rules coming from elementary solid mechanics and plasticity. As an effective alternative to complex FE computations, such a pragmatic approach highlights how the forming process affects fatigue design and allows direct application in an industrial framework

Seam weld shell element model for thin walled structure FE fatigue design

In automotive industry, the FE fatigue analysis of mechanical structures made of steel thin walled parts and seam welded assemblies uses a dedicated technique based on shell element modelling for components and on 1D rigid elements for welds. This method has been validated with several intensive fatigue test campaigns using gas metal arc welded samples with different assemblies, for both bending and torsional loads. The fatigue results are relative to crack initiation at the weld toe with bending normal stress or with longitudinal shear stress for several load ratios. The purpose of the current work is the transposition of the initial method to another FE welded model. In a recent IIW guideline for the assessment of weld root fatigue, a shell element weld model has been proposed for seam weld fatigue assessment in case of weld root crack initiation. The idea is to analyse the possible extension of this FEA weld element model for weld toe fatigue analysis and several comparisons of stress results are detailed and discussed. Different fatigue criteria are used to verify the correlation with the fatigue test results. First, the approach is based on maximum shear stress, then structural stress is calculated and results are compared to IIW S/N curves

Chemotactic effect of prorenin on human aortic smooth muscle cells: a novel function of the prorenin receptor

The discovery of a specific prorenin receptor has opened to a possible biological function of prorenin independently from angiotensin I production. In the present study we show that prorenin receptor is expressed in normal human vessels (mammary arteries and saphenous veins) and in cultured human aortic smooth muscle cells, by western blotting, quantitative real time PCR and immunocytochemistry analysis. Prorenin (10 nmol/L) exerted a 3 fold induction of smooth muscle cell migration assessed by Boyden chamber chemotaxis assay after 6h stimulation and a 30% increase of smooth muscle cell random motility determined by video microscopy. The prorenin decoy peptide (10 \uf06dmol/L) almost completely inhibited smooth muscle cell migration in response to prorenin, while no effect was observed with a scrambled peptide. Knock down of prorenin receptor by small interfering RNA completely affected the migratory response of smooth muscle cells to prorenin. Prorenin increased focal adhesion size (+42.8\ub123.0%) and RhoA activation (+15.0\ub15.0%) after 10 minutes stimulation associated with cleavage of the focal adhesion kinase (pp125FAK) at 60 minutes. The generation of a 50kDa fragment of pp125FAK was suppressed by the calpain inhibitor ALLN (100 \uf06dmol/L), which also inhibited smooth muscle cell migration in response to prorenin. Thus, in the present report we show that prorenin is expressed in human vessels and in cultured smooth muscle cells where it exerts a chemotactic action. This effect is associated with a profound cytoskeleton and focal adhesion re-organization, RhoA activation and calpain-mediated pp125FAK cleavage

Carotid artery stenting: influence of experience and cerebrovascular risk factors on outcome

Aim: To evaluate technical success, complications and the influence of the learning curve on outcome in carotid artery stenting (CAS) performed in patients not suitable for surgery. Patients and methods: One hundred and nine procedures of protected carotid stenting in 103 high risk patients were performed. All patients presented at least one factor that potentially increased the surgical risk of carotid endoarterectomy (CEA), according to SAPPHIRE criteria. Neurologic complications were quantified by the National Institutes of Health Stroke Scale (NIHSS) and were evaluated by median Rankin Scale (mRS). To evaluate the influence of experience of the operator to perform CAS, we retrospectively analyzed periprocedural and neurological complications of the first 50 procedures compared with that of the following 59 interventions. Results: Technical success rate was 98%. Neurological periprocedural complications were revealed in 4.5% of patients. In-hospital and 30-days neurological complications rate was 7.6 and 2.6% respectively. Periprocedural neurological complications rate was lower in the last procedures performed, according to a higher confidence of the operators. Conclusions: CAS may be performed as an alternative of CEA for the treatment of severe carotid obstructive disease in patients not suitable for surgery. The learning curve positively influence complications rat