1,721,025 research outputs found
A study on the effect of application and resource characteristics on the QoS in service provisioning environments
No full textThis article deals with the problem of quality provisioning in business service-oriented environments, examining the resource selection process as an initial matching of the provided to the demanded QoS. It investigates how the application and resource characteristics affect the provided level of QoS, a relationship that intuitively exists but has not yet being mapped. To do so, it focuses on identifying the application and resource parameters that affect the customer-defined QoS parameters. The article realistically centres upon modeling a data mining application and simple PC nodes in order to study how they affect response times. It moves on, by proving the existence of these specific relations and maps them using simple artificial neural networks so as to be able to wrap them in a single mechanism for resource selection based on customer QoS requirements and real time provider QoS capabilities
Experimental and numerical investigation of the effects of porosity on the in-plane shear properties of CFRPs using the V-notched rail shear test method
No full textVoids occurred after the manufacturing process are a common defect of composite materials. They appear to have a negative impact on the matrix-dominated material properties, the gravity of which depends upon the porosity content, the shape and the volume of pores. In the present work, the effects of porosity on the shear mechanical properties of unidirectional carbon fiber-reinforced plastic composites are evaluated via mechanical testing and numerical simulation. In this framework, the V-Notched Rail Shear test method is applied on carbon fiber reinforced plastic specimens of four porosity levels. Moreover, two finite element methodologies are utilized for simulating this particular mechanical test namely the progressive damage model (PDM) and the Virtual Crack Closing Technique (VCCT). Double cantilever beam (mode I) and end notched flexure tests (mode II) are also conducted for the development of the VCCT model. The results from the shear mechanical tests reveal a considerable drop in both the elastic properties and strength. In addition to that, for larger porosity contents, more cracks are present and crack initiation and propagation occur at a faster pace. Finally, the advantages and disadvantages of the two numerical methods are presented and assessed revealing a satisfying consistency with the results obtained by the mechanical tests
Evaluation of porosity effects on the mechanical properties of carbon fiber-reinforced plastic unidirectional laminates by X-ray computed tomography and mechanical testing
No full textThe effects of porosity on the matrix-dominated mechanical properties of unidirectional carbon fiber-reinforced plastic composites were evaluated using X-ray computed tomography and mechanical testing. Carbon fiber-reinforced plastic plates of four porosity levels were manufactured by implementing different curing cycles. Porosity was detected by X-ray computed tomography tests, conducted on samples taken from the plates, and quantified by analyzing the computed tomography scans using the VGStudio Max software. Four different types of mechanical tests were conducted; namely, transverse tension, V-notched rail shear, three-point bending, and short-beam shear tests. The porosity analysis showed that with increasing the porosity volume fraction, the number of pores decreases, their volume increases while their shape changes from spherical or ellipsoidal to a needle-shape. The results from mechanical tests reveal that the presence of pores reduces all matrix-dominated material properties of the UniDirectional (UD) carbon fiber-reinforced plastic material. The reduction in strength is greater than the reduction in the elastic properties. Moreover, the reduction in the in-plane shear and interlaminar properties is greater than the tensile properties of the UD carbon fiber-reinforced plastic material. Between porosity contents of similar volume fraction, the one with the few large pores proved more severe than the one with the many small pores. The large standard deviation observed for some of the tests is attributed to the non-uniform dispersion of pores
Quality assessment of porous CFRP specimens using X-ray Computed Tomography data and Artificial Neural Networks
No full textDespite their extensive use and the quality amelioration, CFRPs remain susceptible to a variety of manufacturing defects such as the pores. Predictive tools capable of correlating the mechanical properties of CFRP parts with the characteristics of defects as derived from NDT techniques or with the manufacturing parameters could serve as an effective tool for the quality control of CFRP structural parts. The present work contributes towards the development of effective quality control tools for composite materials. Within this context, the characteristics of pores, as evaluated by X-ray Computed Tomography (CT), are correlated with the matrix-dominated mechanical properties of unidirectional porous CFRP specimens using an Artificial Neural Network (ANN). The ANN model has been trained by using a multi-scale numerical model. For the training of the ANN, 30 porosity scenarios have been created and given as input to the numerical model. The predictions of the ANN agree very well with results obtained from mechanical tests. Moving one step forward, a second ANN has been developed to correlate the autoclave pressure directly with the mechanical properties of the CFRP specimens. The validity of this ANN depends on the accuracy of the relation between the autoclave pressure and the characteristics of the pores
Multiscale finite element prediction of shear and flexural properties of porous CFRP laminates utilizing X-ray CT data
No full textDespite the continuous developments in the manufacturing of CFRP materials, aiming to improve their quality, pores still remain a common defect, which in the form of initial damage, affect severely all matrix-dominated properties, especially the shear and flexural. Thus, the detection and quantification of pores in combination with FE-based predictive tools could potentially be a very efficient tool for the quality control of composite structural parts. In the present paper, a multiscale numerical methodology is used to predict the shear and flexural properties unidirectional (UD) CFRP laminates with different contents of pores utilizing data derived from X-ray Computed Tomography (X-ray CT) scans. The quantification of pores is conducted using the VG Studio Max software. In order to explore the limitations of the X-ray CT method and validate the parameters of pores quantification, the output of the analysis of CT scans is compared against optical microscopy images. A two-scale simulation is performed based on the size difference of the pores using the progressive damage modeling method. In the first scale simulation, the properties of the porous epoxy resin are predicted by means of FE models of representative unit cells (RUCs) constructed using the porosity data obtained from the X-ray CT scans, and in the second scale simulation, the shear and flexural properties of the CFRP specimens are predicted. The predicted values of mechanical properties are compared with results from short-beam shear and three-point bending tests
A numerical methodology for simulating the mechanical behavior of CFRP laminates containing pores using X-ray computed tomography data
No full textPores are the most common defect in carbon fiber reinforced plastics (CFRPs). Numerical predictive tools capable of taking into account the porosity characteristics, as detected by efficient non-destructive testing techniques, could be potentially contribute to the quality control process applied by the industry in manufacturing of CFRP parts. In the present paper, a numerical methodology is developed for simulating the mechanical behavior of porous CFRP unidirectional (UD) laminates by exploiting data extracted from X-ray computed tomography scans. The analysis of detected pores is performed using the VG Studio MAX software. The software parameters are validated by optical microscopy measurements. The progressive damage modeling method is applied in three simulation levels. In the first level, the behavior of the epoxy resin, in the presence of small pores, is simulated by means of a representative unit cell (RUC). In the second level, the behavior of the epoxy resin, in the presence of small and large pores, is simulated by means of a RUC comprising the epoxy resin, in which the behavior simulated from the first level simulation is assigned, and a single pore (MObject) in which all large pores are clustered. The elastic properties and strengths of the porous UD ply, needed in the simulation of the specimen (third level), are computed using analytical micromechanics relations. The proposed methodology was used to simulate the transverse tensile behavior and predict the properties of three different UD CFRP laminates containing pores of different content. The numerical results show a small decrease of transverse stiffness and a significant decrease of transverse tensile strength with increasing the pore content. The methodology was validated through comparison with tension tests
Innovation Potential of the ACCORDION Platform
No full textThe seamless utilization of resources in the cloud-edge spectrum is a key driver for innovation in the ICT sector, as it supports economic growth and strengthens the industry's competitiveness while making next-application services possible with minimal investments and disruption. In this context, the EU project ACCORDION provides an innovative three-layered architecture designed as a comprehensive solution dedicated to latency-aware applications. This paper summarizes the key technological innovations of ACCORDION, highlighting their alignment with the European agenda of the ICT sector
TEACHING Platform for Human-Centric Autonomous Applications: Design and Overview
No full textThe TEACHING project enhances AI applications in pervasive environments via Humanistic Intelligence, fostering synergy between humans and Cyber-Physical Systems of Systems (CPSoS). Here, we present the TEACHING Platform, a microservice-based framework providing the technological advancements to represent humans and CPSoS as containerized software models that interact to mutually empower each other
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