Implementation of fatigue model for unidirectional laminate based on finite element analysis : theory and practice

The aim of this study is to deal with the simulation of intra-laminar fatigue damage in unidirectional composite under multi-axial and variable amplitude loadings. The variable amplitude and multi-axial loading is accounted for by using the damage hysteresis operator based on Brokate method [6]. The proposed damage model for fatigue is based on stiffness degradation laws from Van Paepegem combined with the 'damage' cycle jump approach extended to deal with unidirectional carbon fibres. The parameter identification method is here presented and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the LadevSze damage model and the permanent shear strain accumulation based on Van Paepegem's formulation. This approach is implemented into commercial software (Siemens PLM). The validation case is run on a bending test coupon (with arbitrary stacking sequence and load level) in order to minimise the risk of inter-laminar damages. This intra-laminar fatigue damage model combined efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level. This work concludes on the next challenges to be addressed (validation tests, multiple-loadings validation, failure criteria, inter-laminar damages...)

Intercomparison of the northern hemisphere winter mid-latitude atmospheric variability of the IPCC models

We compare, for the overlapping time frame 1962-2000, the estimate of the northern hemisphere (NH) mid-latitude winter atmospheric variability within the XX century simulations of 17 global climate models (GCMs) included in the IPCC-4AR with the NCEP and ECMWF reanalyses. We compute the Hayashi spectra of the 500hPa geopotential height fields and introduce an integral measure of the variability observed in the NH on different spectral sub-domains. Only two high-resolution GCMs have a good agreement with reanalyses. Large biases, in most cases larger than 20%, are found between the wave climatologies of most GCMs and the reanalyses, with a relative span of around 50%. The travelling baroclinic waves are usually overestimated, while the planetary waves are usually underestimated, in agreement with previous studies performed on global weather forecasting models. When comparing the results of various versions of similar GCMs, it is clear that in some cases the vertical resolution of the atmosphere and, somewhat unexpectedly, of the adopted ocean model seem to be critical in determining the agreement with the reanalyses. The GCMs ensemble is biased with respect to the reanalyses but is comparable to the best 5 GCMs. This study suggests serious caveats with respect to the ability of most of the presently available GCMs in representing the statistics of the global scale atmospheric dynamics of the present climate and, a fortiori, in the perspective of modelling climate change.Comment: 39 pages, 8 figures, 2 table

Author Correction: Development of a sensitive, quantitative assay with broad subtype specificity for detection of total HIV-1 nucleic acids in plasma and PBMC

Correction to: Scientific Reports https://doi.org/10.1038/s41598-021-03016-1, published online 28 January 202

Development and validation of verbal emotion vignettes in Portuguese, English, and German

Everyday human social interaction involves sharing experiences verbally and these experiences often include emotional content. Providing this context generally leads to the experience of emotions in the conversation partner. However, most emotion elicitation stimulus sets are based on images or film-sequences providing visual and/or auditory emotion cues. To assimilate what occurs within social interactions, the current study aimed at creating and validating verbal emotion vignettes as stimulus set to elicit emotions (anger, disgust, fear, sadness, happiness, gratitude, guilt, and neutral). Participants had to mentally immerse themselves in 40 vignettes and state which emotion they experienced next to the intensity of this emotion. The vignettes were validated on a large sample of native Portuguese-speakers (N = 229), but also on native English-speaking (N = 59), and native German-speaking (N = 50) samples to maximise applicability of the vignettes. Hierarchical cluster analyses showed that the vignettes mapped clearly on their target emotion categories in all three languages. The final stimulus sets each include 4 vignettes per emotion category plus 1 additional vignette per emotion category which can be used for task familiarisation procedures within research. The high agreement rates on the experienced emotion in combination with the medium to large intensity ratings in all three languages suggest that the stimulus sets are suitable for application in emotion research (e.g., emotion recognition or emotion elicitation)

Effect of cell compression on the water dynamics of a polymer electrolyte fuel cell using in-plane and through-plane in-operando neutron radiography

Water dynamics in the membrane electrode assembly (MEA) and flow channels of polymer electrolyte fuel cells (PEFCs) is governed by the complex interplay of many physical and operational factors. The chemical nature and structure of the gas diffusion layer (GDL) plays a large part in this and is affected by the extent to which is mechanically compressed. Here, X-ray computed tomography shows the effect of cell compression on the MEA, and how it differs under the land and channel regions. Multi-orientation neutron radiography reveals the effect of compression on the way in which water accumulates and is transported between land and channel and between cathode and anode. By performing neutron imaging in both the in-plane and through-plane directions, it is possible to determine what constitutes a given ‘thickness’ of water mapped across the extent of an MEA. Changing MEA compression from 25% to 35% has a significant effect on water distribution and dynamics in operational cells. The effect of compression on performance is most marked in the mass transport region, and there are consequences for liquid accumulation in channels and back-diffusion of water from the cathode to the anode

Small and medium-sized enterprises in the digital business sector

The chapter is a systematic literature review of fundamental theories about small and medium business (SME) success. The chapter examines how they specifically impact digital SMEs. The chapter examined six theories: dynamic capability view (DCV), composition-based view of firm growth (CBV), resourcebased view (RBV), resource dependence theory (RDT), upper echelon theory (UET), strategic contingency theory (SCT). The results showed that RBV, DCV, and UET become relevant in articulating the value inherent to the internal resources in SMEs (which render their capabilities dynamic). In contrast, the SCT framework and the RDT model show more significance in relation to uncertainty and contingency. CBV was found to be a more pertinent framework to predict the success of SMEs. The results support CBV’s hypothesis that SMEs (including digital SMEs) are able to be competitive without extensive resource advantage, too complicated technologies, or market power. The increased deployment of CBV can be advocated as a critical determinant of digital SME success

A progessive damage fatigue model for unidirectional laminated composites based on finite element analysis: theory and practice

The simulation of the fatigue damage of laminated composites under multi-axial and variable amplitude loadings has to deal with several new challenges and several methods of damage modelling. In this paper we present how to account for the complex loading by using the damage hysteresis operator approach for fatigue. It is applied to a fatigue model for intra-laminar damage based on stiffness degradation laws from Van Paepegem and has been extended to deal with unidirectional carbon fibres. The parameter identification method is presented here and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the Ladevèze damage model and the permanent shear strain accumulation based on Van Paepegem’s formulation. This approach has been implemented into commercial software. The intra-laminar fatigue damage model combines efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level

Bodemschematisatie; opschaling door aggregatie van bodeminformatie voor modelsimulaties op nationale en regionale schaal

Dit rapport beschrijft de ontwikkeling van geautomatiseerde methoden voor opschaling van bodeminformatie door ruimtelijke en gegevensaggregatie voor modeltoepassingen, bodemschematisatie genoemd. Ze bestaan uit de selectie van bodemgegevens, ruimtelijke aggregatie van kaarteenheden van de bodemkaart, gegevensaggregatie door definiëring van rekenprofielen met procesparameters en het genereren van bodemkundige modelinvoer. Met statistische analyse van twaalf verschillende modeluitvoervariabelen is nagegaan welke van de ontwikkelde methoden voor bodemschematisatie het geringste informatieverlies gaf uitgaand van de ruimtelijke structuur op de Bodemkaart van Nederland, schaal 1: 50 000. De voorspelfout binnen kaarteenheden bedroeg minimaal 45. Het algoritme voor de ruimtelijke aggregatiemethode waarbij het studiegebied Beerse-Reuzel van 203 naar 23 ruimtelijke eenheden werd teruggebracht, gaf het meest representatieve beeld van de variabiliteit tussen de oorspronkelijke kaarteenheden. De toename vande voorspelfout door gegevensaggregatie werd door twee van de vier hiervoor ontwikkelde methoden het kleinst gehouden

A progessive damage fatigue model for unidirectional laminated composites based on finite element analysis: theory and practice

The simulation of the fatigue damage of laminated composites under multi-axial and variable amplitude loadings has to deal with several new challenges and several methods of damage modelling. In this paper we present how to account for the complex loading by using the damage hysteresis operator approach for fatigue. It is applied to a fatigue model for intra-laminar damage based on stiffness degradation laws from Van Paepegem and has been extended to deal with unidirectional carbon fibres. The parameter identification method is presented here and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the Ladevèze damage model and the permanent shear strain accumulation based on Van Paepegem’s formulation. This approach has been implemented into commercial software. The intra-laminar fatigue damage model combines efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level

CH Cygni I: Observational Evidence for a Disk-Jet Connection

We investigate the role of accretion in the production of jets in the symbiotic star CH Cygni. Assuming that the rapid stochastic optical variations in CH Cygni come from the accretion disk, as in cataclysmic variables, we use changes in this flickering to diagnose the state of the disk in 1997. At that time, CH Cyg dropped to a very low optical state, and Karovska et al. report that a radio jet was produced. For approximately one year after the jet production, the amplitude of the fastest (time scales of minutes) variations was significantly reduced, although smooth, hour-time-scale variations were still present. This light curve evolution indicates that the inner disk may have been disrupted, or emission from this region suppressed, in association with the mass-ejection event. We describe optical spectra which support this interpretation of the flickering changes. The simultaneous state change, jet ejection, and disk disruption suggests a comparison between CH Cygni and some black-hole-candidate X-ray binaries that show changes in the inner disk radius in conjunction with discrete ejection events on a wide range of time scales (e.g., the microquasar GRS 1915+105 and XTE J1550-564).Comment: 7 pages, 4 figures, to appear in the Ap