Evaluation of Grounding Resistance and Inversion Method to Estimate Soil Electrical Grounding Parameters

Soil resistivity plays a key role in designing grounding systems for highvoltage transmission lines and substations. The objectives of this paper are to determine the best estimated value of the apparent resistivity or electrode grounding resistance of N-layer soil and to use a new inversion method to precisely determine earth parameters. The inversion of electrical sounding data does not yield a unique solution, and a single model to interpret the observations is sought. This paper presents a new inversion method to statistically estimate soil parameters from Schlumberger and Wenner measurements. To validate the method and test the inversion scheme, four soundings were selected: two theoretical and two in the field. The procedure was applied using test data and a satisfactory soil model was obtained

Neural Networks Approach for Characterization of Non-Isothermal Thermoplastic Membrane

Recent developments in computer-aided polymer processing have brought with them the need for an accurate description of the behaviour of industrial thermoplastic membranes under the combined effect of applied stress and temperature. In order to serve this purpose, we consider a non-isothermal approach to characterize the ABS (Acrylonitrile-Butadiene) membrane under biaxial deformation using the bubble inflation technique. Thereafter, Rivlin's theory of hyper-elasticity is employed to define the constitutive model of flat circular membranes. The nonlinear equilibrium equations of the inflation process are solved using finite difference method with deferred corrections. For the final step, a neuronal algorithm (ANN model) is employed to minimize the difference between calculated and measured parameters to determine material constants. The effect of experimental temperature (between -30 and 80 oC) on behaviour is considered in this work

Mechanical properties,wettability and thermal degradation of HDPE/birch fiber composite

Wood-plastic composites have emerged and represent an alternative to conventional composites reinforced with synthetic carbon fiber or glass fiber-polymer. A wide variety of wood fibers are used in WPCs including birch fiber. Birch is a common hardwood tree that grows in cool areas such as the province of Quebec, Canada. The effect of the filler proportion on the mechanical properties, wettability, and thermal degradation of high-density polyethylene/birch fiber composite was studied. High-density polyethylene, birch fiber and maleic anhydride polyethylene as coupling agent were mixed and pressed to obtain test specimens. Tensile and flexural tests, scanning electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetry analysis and surface energy measurement were carried out. The tensile elastic modulus increased by 210% as the fiber content reached 50% by weight while the flexural modulus increased by 236%. The water droplet contact angle always exceeded 90°, meaning that the material remained hydrophobic. The thermal decomposition mass loss increased proportional with the percentage of fiber, which degraded at a lower temperature than the HDPE did. Both the storage modulus and the loss modulus increased with the proportion of fiber. Based on differential scanning calorimetry, neither the fiber proportion nor the coupling agent proportion affected the material melting temperature. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Gear fatigue life and thermomechanical behavior of novel green and bio-composite materials VS high-performance thermoplastics

In many applications, metal gears have been replaced by plastic gears because of their functionality and cost advantages. Despite their many benefits, the intensive use of plastics and composites raises sustainability issues because of the depletion of non-renewable petroleum resources and the pollution that is generated. Thus, alternative ecological solutions for plastic gears are necessary; however, little is known regarding ecologically designed gears. In this study, we propose two types of innovative gear materials. The first is a semi-ecological polyethylene bio-composite gear reinforced with birch fibers, and the second is a fully bio-sourced natural polyethylene gear with birch fibers. This study is the first time such fully ecological composite-plastic gears have been tested. The tests record the evolution of the fatigue and temperature over time under various operating conditions. Furthermore, acoustic emission is used to assess the evolution of fatigue cracks. The results indicate that the fully ecological gears are feasible and offer an alternative to traditional materials, such as engineering plastics, likely at a lower cost. © 2017 Elsevier Lt

Neural Networks Approach for Hyperelastic Behaviour Characterization of ABS under Uniaxial Solicitation

Recent developments in computer-aided polymer processing have brought along the need for accurate description of the behavior of materials under the conjugated effect of applied stress and temperature. In order to serve this purpose, in this study, experimental data provided by uniaxial tensile technique tests for thermoplastic halter (CTPH) comprised of hyperelastic materials when subjected to combined effects of applied stress and temperature are coupled with numerical simulations to obtain the required parameters for the characterization of such materials. First, stresses and displacements the thermoplastic halter are recorded during experiment. Thereafter, Mooney-Rivlin's and Ogden theory of hyperelastic is employed to define the constitutive model of thermoplastic halter (CTPH) and nonlinear equilibrium equations of the process are solved using finite element method with Abaqus software. As a last step, a neuronal algorithm (ANN model) is employed to minimize the difference between calculated and measured parameters to determine material constants for Mooney-Rivlin and Ogden models. Although the developed procedure can be applied to several polymeric materials, in this paper, this technique is successfully implemented for acrylonitrile–butadiene– styrene (ABS). Using these coefficients, the material behavior of ABS with Mooney-Rivlin and Ogden constitutive laws is reproduced. The material model obtained in this study for ABS can be implemented into industrial and academic softwares for applications and design purposes

Evaluation of mechanical properties and durability performance of HDPE-wood composites

The objective of this work is to evaluate the mechanical properties and durability performance of bio-composite materials made from sawdust and thermoplastic polymer (HDPE). For the preparation of the composites, sawdust in different proportions with Maleic Anhydride grafted Polyethylene (MAPE) as the coupling agent was used. The thermal and mechanical properties were successively characterized. The results indicate that adding wood fillers to a polymer matrix increases the degree of crystallinity and improves the tensile strength and ductility of composites. On the contrary, resistance to water absorption decreases as a function of the wood fillers. Scanning electron microscopy (SEM) was used to analyze morphological structure alteration when exposed to intense weathering. The biodegradability of bio-composites up to 97 days was also investigated; the results indicate that, by increasing the filler content, the amount of weight loss increased as well. In other words, even though the addition of sawdust to thermoplastic polymer improves the mechanical performance of a composite material, it also accelerates the biodegradation rate of the composite. An optimum amount of filler content might compromise the effect of biodegradation and mechanical properties of composite materials

Effect of Wood Fillers on the Viscoelastic and Thermophysical Properties of HDPE-Wood Composite

Wood polymer composites (WPC) have well proven their applicability in several fields of the plasturgy sector, due to their aesthetics and low maintenance costs. However, for plasturgy applications, the characterization of viscoelastic behavior and thermomechanical and thermophysical properties of WPC with the temperature and wood filler contents is essential. Therefore, the processability of polymer composites made up with different percentage of wood particles needs a better understanding of materials behaviors in accordance with temperature and wood particles contents. To this end, a numerical analysis of the viscoelastic, mechanical, and thermophysical properties of composite composed of high density polyethylene (HDPE) reinforced with soft wood particles is evaluated

Evaluation of Grounding Resistance and Inversion Method to Estimate Soil Electrical Grounding Parameters

Soil resistivity plays a key role in designing grounding systems for high-voltage transmission lines and substations. The objectives of this paper are to determine the best estimated value of the apparent resistivity or electrode grounding resistance of N-layer soil and to use a new inversion method to precisely determine earth parameters. The inversion of electrical sounding data does not yield a unique solution, and a single model to interpret the observations is sought. This paper presents a new inversion method to statistically estimate soil parameters from Schlumberger and Wenner measurements. To validate the method and test the inversion scheme, four soundings were selected: two theoretical and two in the field. The procedure was applied using test data and a satisfactory soil model was obtained

Pulsed thermography in the evaluation of an aircraft composite using 3D thermal quadrupoles and mathematical perturbations

Abstract This paper is devoted to the characterization of a subsurface flaw within an anisotropic medium during a nondestructive evaluation test using stimulated infrared thermography. A typical illustration is a delamination within a stratified composite material. The originality of the current study consists of providing simple analytical solutions to evaluate the depth and the volume of the flaw in a three-dimensional heat transfer configuration. The volume of the flaw is defined as the product of its lateral extent by its thickness. If the thermal contact resistance of the flaw is known, its lateral extent can be derived from the volume expression. The method proposed here consists of applying first a Laplace transform on the time variable t, then a Fourier transform on the space variables, x and y. The numerical or semi-analytical true solution of integral equations generated by this problem may be very time-consuming, especially in a three-dimensional configuration. We therefore suggest a modelling reduction using the analytical perturbation method written only at its first order. It is however assumed that flaw thermal resistance is small compared to the whole thermal resistance of the material under investigation. The perturbation formalism leads to the construction of approximate analytical solutions that are very convenient for quantitative inversion. The validity of this method has been analysed through a real nondestructive test performed on a calibrated carbon-epoxy laminate of known characteristics