Search results for "Paris"
showing 10 items of 1097 documents
Two years performance comparison of Elkem Solar multicrystalline silicon with polysilicon in a PV grid-connected system
2014
This abstract summarizes two years performance of an Elkem Solar and polysilicon photovoltaic (PV) system installed in the Sunbelt Region, which has been fully operational since 2011. The PV system consists of 28 multicrystalline silicon PV modules made from the standard Siemens process and from material produced by a metallurgical route - the Elkem Solar Silicon (ESS®) process. The present study suggests that after two years of field operation, both types of modules show similar degradation of power at STC. The ESS® PV modules have better performance than standard polysilicon modules as a function of solar irradiation, and thereby the total kWh generated has been slightly higher for the ES…
Efficiency comparison between SiC- and Si-based active neutral-point clamped converters
2015
This paper presents an efficiency comparison between silicon-carbide technology and silicon technology. In order to achieve this, the efficiency of an active neutral-point clamped converter built up with silicon carbide power-devices is compared with the efficiency of an active neutral-point clamped converter built up with silicon power-devices, under a particular operating mode and a particular selection of devices. Firstly, overall losses of both converters are estimated. Then, experimental tests are carried out to measure their overall losses and efficiency. Finally, experimental results are compared with the estimations to support the analysis. The efficiency of the SiC converter is hig…
A model for predicting the mixed-mode fatigue crack growth in a bonded joint
2013
Bonded joints are highly sensitive to the presence of defects and to the degradation phenomena, and this aspect represents the primary obstacle to their use in different structural engineering applications. Delamination in a bonded joint represents, in fact, one of the primary, most common and insidious causes of damage. In this paper, a numerical–experimental study on the crack propagation along the adhesive layer of a bonded joint specimen is carried out. Experimental study is focused on the evaluation of the damage modalities of a bonded joint when the specimens are subject to fatigue load. Experimental tests are compared with the results of several numerical analysis performed in ANSYS …
Elastic-plastic fatigue crack growth in 18G2A steel under proportional bending with torsion loading
2006
The paper presents the results of fatigue crack growth on low-alloy 18G2A steel under proportional bending with torsion loading. Specimens with square sections and a stress concentration in the form of external one-sided sharp notch were used. The tests were performed under the stress ratios R = -1, -0.5 and 0. The test results were described by the ΔJ-integral range and compared with the ΔK stress intensity factor range. It has been found that there is a good agreement between the test results and the model of crack growth rate, which includes the ΔJ-integral range.
Residual stresses in friction stir welded parts of complex geometry
2011
Residual stresses play a key role on the mechanics underlying the fatigue crack growth propagation of welded joints. Indeed, compressive residual stresses may induce a beneficial enhancement of the fatigue life under loading condition whereas tensile residual stresses may act to increase the stress distribution at crack tip, resulting in a life-threatening condition of the welded structure. In-process distortion and final geometry of welded joints are also affected by residual stresses. In this paper, the longitudinal residual stress distributions in friction stir welding (FSW) joints were investigated for butt and skin–stringer geometries, including lap and T configurations. To measure res…
ΔJ-integral range estimation for fatigue crack growth rate description
2004
Abstract The paper presents an equation for fatigue crack growth rate description taking into account the ΔJ-integral range, which was verified experimentally for variable bending. Plane, notched specimens were tested under unilaterally restrained bending for different values of stress ratio R. The results of tests and numerical calculations were presented as characteristics of fatigue crack growth rate. It has been shown that in the case of a change of stress ratio from R=−1.0 to R=0.0, the crack rate increases twice for 10HNAP steel and five times for 18G2A steel. The empirical formula presented in the paper describes well the test results of fatigue crack rate in the steels.
Fatigue crack growth of new FML composites for light ship buildings under predominant mode II loading condition
2019
The use of light but strong materials is largely studied in various area of the shipbuilding, this because the need of reducing the weight, and especially the weight of all the structures above the main deck assume primary importance for the stability. Traditionally in fast boats like fast ferries, hydrofoils, patrol boats, the typical materials are Aluminum alloy or composites, both those materials have advantages and disadvantages, but the new development of technologies made possible to combine them, in order to have a new material, combining the advantages of both, in terms of fatigue resistance, firefighting characteristics. In this paper, predominant mode II fatigue delamination tests…
Rapid evaluation of notch stress intensity factors using the peak stress method: Comparison of commercial finite element codes for a range of mesh pa…
2018
The peak stress method (PSM) is an engineering, finite element (FE)-oriented method to rapidly estimate the notch stress intensity factors by using the singular linear elastic peak stresses calculated from coarse FE analyses. The average element size adopted to generate the mesh pattern can be chosen arbitrarily within a given range. Originally, the PSM has been calibrated under pure mode I and pure mode II loadings by means of Ansys FE software. In the present contribution, a round robin between 10 Italian universities has been carried out to calibrate the PSM with 7 different commercial FE codes. To this aim, several two-dimensional mode I and mode II problems have been analysed independe…
Complementary Judgment Matrix Method with Imprecise Information for Multicriteria Decision-Making
2018
The complementary judgment matrix (CJM) method is an MCDA (multicriteria decision aiding) method based on pairwise comparisons. As in AHP, the decision-maker (DM) can specify his/her preferences using pairwise comparisons, both between different criteria and between different alternatives with respect to each criterion. The DM specifies his/her preferences by allocating two nonnegative comparison values so that their sum is 1. We measure and pinpoint possible inconsistency by inconsistency errors. We also compare the consistency of CJM and AHP trough simulation. Because preference judgments are always more or less imprecise or uncertain, we introduce a way to represent the uncertainty throu…
GRASP for the uncapacitated r-allocation p-hub median problem
2014
In this paper we propose a heuristic for the Uncapacitated r-Allocation p-Hub Median Problem. In the classical p-hub location problem, given a set of nodes with pairwise traffic demands, we must select p of them as hub locations and route all traffics through them at a minimum cost. We target here an extension, called the r-allocation p-hub median problem, recently proposed by Yaman [19], in which every node is assigned to r of the p selected hubs (r@?p) and we are restricted to route the traffic of the nodes through their associated r hubs. As it is usual in this type of problems, our method has three phases: location, assignment and routing. Specifically, we propose a heuristic based on t…