Papers by Keyword: Analytical Model

Abstract: In this paper, the effects of seawater exposure on the bending and damping properties of fibre-reinforced sandwich structures were investigated experimentally and analytically using the residual property model (RPM). Glass fiber reinforced plastics facesheets with PVC foam core, exposed to seawater exposure until saturation was subjected to flexural and dynamic mechanical analysis tests. Key mechanical properties were used to develop an analytical residual property model. Results indicated that after exposure, while the flexural strength and modulus reduced by 20% and 19% respectively, the storage, loss moduli and tan delta increased by 7%, 20% and 12% respectively. Furthermore, the accuracy of property degradation was demonstrated for the predicted properties, thereby establishing the suitability of RPM as a cost-effective means for material property determination.

Abstract: Anti-submarine (ASM) ring nets are fundamental components for various passive solutions to mitigate rockfall hazard. While numerical models could accurately assess their performance for all the applications, the modelling of a whole system comprising the net is time-consuming. An analytical model of wire ring nets currently on the market, applicable to the different configurations, can thus represent a profitable tool to investigate the performance of nets used in retaining systems. Currently, for flexible rockfall barriers the whole system structural behaviour is evaluated with real tests impact tests performed in the centre of the system, only, possibly overestimating the system capacity and consequently underestimating the residual risk at installation sites. An analytical model is proposed in this paper with the aim to evaluate the mechanical behaviour of wire ring nets for eccentric impacts too. The model validation is performed using quasi-static experimental punching tests results related to both rigid and flexible boundaries conditions for the centred impact case, while numerical models, realized applying well-established approaches, strengthen the model validation for eccentric impacts. Analyses performed during the barrier design phase and its service life enable to assess the real efficiency of retaining systems.

Abstract: Digitalisation of the construction sector is one of the priorities in the European Union and one of the main technologies used for this purpose is Building Information Modelling (BIM). An important advantage of BIM is that it enables management of information about the built environment through all phases of the asset lifecycle: procurement, design, construction, operation and maintenance. Major promotion for the use of BIM in construction projects in EU member countries comes from the EU directive on Public Procurement and many public investments are related to infrastructure projects, including bridges. Indeed, in some countries, for certain public projects it is now mandatory to use BIM. This paper focuses on the implementation of BIM for bridges, which was overall much slower than for buildings. Some of the differences between BIM for bridges and BIM for buildings are pointed out, as well as what is identified as major barriers for implementation of BIM in bridge projects. At the same time, there are significant advancements with respect to openness and standardization on the international level, which are essential for widespread and effective use. Several software developers have taken on the challenge to provide bridge BIM solutions, some with the intention of using a single model for both physical representation of a bridge in blueprints and analytical calculations to design and verify mechanical resistance of the structure. This paper uses one such example to discuss current possibilities, some of the great advantages this technology offers, but also potential problems in the bridge BIM modelling procedure, when BIM model is used for structural analysis.

Abstract: In this work, an analytical model describing the quasi-static operation of a monolithically integrated SiC solid-state circuit breaker (SSCB) device is rederived and refined. This SSCB is based on a 4H-SiC JFET technology offering a self-sensed blocking mechanism. The proposed model is solely based on physical parameters including the SSCB design parameters. With respect to the refinement, the proposed model is not limited to one-sided pn-junctions, considers incomplete ionization of dopants, and is able to represent breakdown characteristics. In this regard, the JFET gate breakdown characteristics are derived taking thermionic emission, space-charge-limited current and impact ionization into account. To calculate the SSCB output characteristics, a bisection-based optimization algorithm is applied carefully considering individual JFET operating states.

Abstract: Corrosion has severe consequences for the integrity of pipelines used in the petroleum industry. Modelling and optimising the parameters of a circulating fluid are two of the numerous methods for combating corrosion. The objective of this study was to develop a multiphase flow simulation model for estimating the corrosion rate of oil and gas pipelines, considering the erosional effect. In addition to carbon dioxide (CO₂) and hydrogen sulphide (H₂S) corrosion, the present model also takes into account the impacts of chloride concentrations. The current model evaluates and reflects a comprehensive understanding of corrosion in a saline environment, making it readily applicable for estimating corrosion rates for industrial applications. The model's results indicate a prediction accuracy of about 85%. Field data gathered under a broad range of environmental conditions confirms the model's prediction accuracy. The predictions from the present model are in good agreement with the field data. In addition, the present model was found to be more effective than the model created by Dewaard and Milliam. This research is likely to have widespread applications in the oil and gas industry for predicting more accurate corrosion rates.

Abstract: The aim of the present investigation is to determine the ideal values for several parameters, such as the external diameter of the polyethylene liner, the Young's modulus of the cup, and the friction coefficients between the polyethylene liner's contact area and the acetabular shell and prosthetic head of the dual-mobility cup. Reduced stresses at the bone/cement interface are crucial for ensuring a well-fixed dual-mobility cup (DMC) with the acetabulum because orthopedic cement (PMMA) is the weakest component of total hip arthroplasty (THA). Four factors, such as the PE liner size, the rigidity of the cup, and the friction coefficients, are optimized using the three-dimensional finite element method (FEM) and experimental design approach (EDA). The numerical results show that the hemispherical-liner size, mechanical characteristics of the cup, surface state of the femoral head, liner PE, and shell components all influence the mechanical strength of the bone cement. To prevent fracturing the bone cement, which would render the total hip arthroplasty ineffective. The optimal values of the maximum von Mises stress in bone cement will be determined using this methodology. The numerical outcome shows that when the Young's modulus of the cup rises, the maximum stress in bone cement falls until it reaches a minimal value. The maximum stress in bone cement, however, increases as the PE liner's exterior diameter increases. Because the maximum stress is still below the yield stress of bone cement, the artificial hip joint is still considered safe despite the increased stress value.

Abstract: The properties of piezoelectric materials due to the effect of electrical, mechanical, thermal, radiation, and chemical parameters are systematized. On the basis of Maxwell's relations (obtained from expressions for thermodynamic functions) and the application of the system analysis methodology, it made it possible to develop an analytical model of the relationship between the parameters and properties of piezoelectrics in the form of a system of equations. The results of the metrological analysis of an analytical model, which made it possible to identify the sources of additional errors in the measurement of parameters, to derive formulas for their calculation, which in turn contributes to an increase in the accuracy of measurements of the piezoelectrics parameters and products based on them, are presented.

Abstract: The choice of a machine for an application and a given specification remains a complex problem. This will involve, for example, bringing together criteria such as: performance, space saving, economical, reliable, little acoustic noise and others. The best machine selection to fulfill all constraints is an important step for the project to be realized. This work focus on Stirling Engine based Generator and study all types of rotating machines that can be employed for maximum electric power production. Analytical electromagnetic models where developed for all types of rotating machines that satisfied minimum requirement for the project by solving Maxwell equations. The purpose is to develop the design model and combine electromagnetic and thermal study of the machines. Finite Element Method is used to compare the performances of the generators for the best choice. Results show that for applications not requiring bigger output power, the major criteria for the selection is the optimal magnetic induction created by the inducer in the stationary part of the machine. For application such as Stirling generators, permanent magnet (PM) machine satisfy many comparison criteria such as maximum power at low speed, torque density, high efficiency. Beyond exposing a selection method for a project, this work lay down a step-by-step method for engineers and scientists for the crucial stage of design and conception work

Abstract: The development of weight-efficient reusable launch systems has increased the urgency of problems associated with ultra-low-cycle fatigue. In this paper, one-sided three-point bending cyclic tests of GFRP specimens were performed. Parallel to the cyclic tests, registration of acoustic emission signals has been performed to identify the main damage mechanisms underlying ultra-low-cycle fatigue of fabric-reinforced composites. The obtained displacement-time diagrams showed a noticeable effect of creep on the deformation process. It was found that fiber fracture is the main mechanism of microdamage accumulation. A phenomenological three-element model based on the Norton-Bailey law and the Masing structural model was proposed. The model allowed describing both the deformation process of the specimens in time and their durability at different load levels. An optimization algorithm based on the deformable polyhedron method was used to find the optimal set of the model parameters.

Abstract: This paper presents an analytical model of various electrical parameters for an ultra thin symmetric double gate (SDG) junctionless field effect nanowire transistor (JLFENT). The model works for all the regions of operation of the nanowire transistor without using any fitting parameter. The surface potential is derived based on the solutions of Poisson’s and current continuity equations by using appropriate boundary conditions. The Pao–Sah double integral was used to obtain the drain current, transconductance and drain conductance. The results obtained from analytical model are validated by comparing with GENIUS 3D TCAD simulations. The simplicity of the model makes it appropriate to be a SPICE compatible model.