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In this article, a nonlinear dynamical investigation of porose functionally graded cylindrical panels using a proposed analytical model is carried out. The material's properties are considered to be porosity-dependent and graded in the thickness direction, corresponding to a power-law distribution. The classical shell theory, with the geometrical shape of nonlinear in von Karman–Donnell, is employed to get the Lagrange motion equations. By applying the Galerkin procedure, the system of nonlinear dynamic vibration equations is found. The natural frequencies and dynamic amplitude vibrations are obtained by using the fourth-order Runge–Kutta approach. In numerical analyses, the effects of porosity factor, power-law index, porous FGM thickness, frequency–amplitude relation, and excitation force on the dynamic response of thin functionally graded porous cylindrical panels are investigated. Through the obtained results, it is discovered that the porosity coefficients have important effects on the natural frequencies and amplitude of the nonlinear dynamic response of the FG structures. It leads to a reduction in natural frequencies by 5.74 % at 10% pores.

In this article, a numerical model based on site theory is developed to study the stability of a pipeline system consisting of a valve, pipe, and surge tank. In the study, four parameters were studied to see how they impact the water hammer phenomenon. They are the pressure in the pipelines, the velocity of the flow, diameter of the conduit carrying liquid, and the liquid’s density. The equations are programmed, analyzed, and graphed using MATLAB. The stability analysis shows that the force of the water hammer is significant at low frequencies and for large diameters. The high frequency of a particular pipe is affected by the type of material the pipe is made from, the method of installation, and the friction coefficient of the inner surface. High frequencies reduce the impact of water hammer forces. Among the main parameters listed, it is found that the oscillations of liquids of low density are higher in the case of water hammers.

This article introduced a three-dimension CAD model of a prosthesis testing platform using SolidWorks software to conduct a kinematic and dynamic analysis of the transfemoral prosthesis of the virtual model. Concurrently, the event-based motion simulation (EBMS) procedure was carried out on the CAD model. The concept of the operational strategy of the test platform was clarified through the machine’s real-life experience before being constructed in vitro. The platform model is capable of reproducing two active movements to simulate the locomotion of the thigh angle and hip vertical displacement for assessing the artificial knee angle motion during the gait cycle. These motions were controlled by two rotary forces (motors) that are utilized to implement control actions in EBMS. The prosthetic knee joint was built with a single axis that performs flexion and extension via the axial force of the spring. The simulation results of the thigh angle motion ranged from 2 0 ° 2{0}^{^\circ } to − 1 5 ° -1{5}^{^\circ } , while the maximum flexion of the prosthetic knee joint was ( 4 6 ° 4{6}^{^\circ } ). The mean absolute error was ( 2.72 7 ° 2.72{7}^{^\circ } ) and ( 8.33 8 ° 8.33{8}^{^\circ } ) for the thigh and knee joints, respectively. In conclusion, the findings can be utilized to facilitate the design and development of prostheses.

The water hammer (WH) phenomenon is one of the most dangerous phenomena in hydraulic systems, especially pipelines, gates, and locks on these lines. There are many analytical solutions to deal with the WH phenomenon, including the treatment of friction losses, but most solutions use linear arithmetic operations, which depart from the actual situation of the WH phenomenon. Also, the methods currently used are most challenging and complex and give imprecise results to treat the mentioned phenomenon. In order to reach a state closer to the situation of losses and stability of the hydraulic system that is close to the actual state, basic partial differential equations were used, taking into account the losses generated in the hydraulic system through mathematical conversion. MATLAB was used to program and solve equations, find mathematical results, draw system diagrams, and simulate a WH wave. Various parameters were investigated to show the stability behavior of the hydraulic system by using state-space Method. So, the effect of the pressure, flow rate, diameter, and fluid type were investigated to calculate the stability of the hydraulic system. The results evaluated showed that the system’s oscillation is less at lower pressure, and the stability period is longer than that at high pressures. In addition, the system needs a longer time to stabilize at the low flow speed due to pressure waves that occur. The stability of the system affected by the WH was examined, and the effect of fluid-specific variables such as velocity, pressure, and type of fluid in addition to the diameter of the pipe and their impact on WH stability was found. The behavior of stability at the WH is nonlinear, and that is why the linear and nonlinear parts of the governing equations of the structure are used to find system through the state-space method through programming and simulation of MATLAB program.

The improvement of the topological properties in contacts surfaces has been drawn the attention of many commercial firms to reduce energy waste resulting from the influence of friction and wear in combustion engines. These motivations were sufficient for adding nanoparticles upon lubricants to improve their performances. Analysis of nano specimens' experimental tests revealed the enhancement of tribological properties to reduce friction and wear increasing, especially in cutting fluid performance. The operations are elementary and smooth, with the most extended cutting tools life and saving fuel consumption. Nanoparticles additives have been detected by nano techniques to evaluate the Nano tests and determined the morphology properties of nano mixture lubricant to developing or modify the fats. The nanoparticles fill into the cavities of the molecular surface so that forms a nanofilm that insulates, rub parts and slips quickly and softly due to the low value of the coefficient of friction. The nanofilm mechanism has contributed to improving topological characteristics, exceptionally reducing the emission of friction temperatures and preventing gradual deformation of material at solid surfaces, leading to inhibit material failure or loss of functionality. Also, the effect of Bio-lubricant with Nanoparticle additive was investigated.

Purpose: This paper develops a new analytical solution to conduct the free vibration analysis of porous functionally graded (FG) sandwich plates based on classical plate theory (CPT). The sandwich plate made of the FGM core consists of one porous metal that had not previously been taken into account in vibration analysis and two homogenous skins. Design/methodology/approach: The analytical formulations were generated based on the classical plate theory (CPT). According to the power law, the material properties of FG plates are expected to vary along the thickness direction of the constituents. Findings: The results show that the porosity parameter and the power gradient parameter significantly influence vibration characteristics. It is found that there is an acceptable error between the analytical and numerical solutions with a maximum discrepancy of 0.576 % at a slenderness ratio (a/h =100), while the maximum error percentage between the analytical and experimental results was found not exceeding 15%. Research limitations/implications: The accuracy of analytical solutions is verified by the adaptive finite elements method (FEM) with commercial ANSYS 2020 R2 software. Practical implications: Free vibration experiments on 3D-printed FGM plates bonded with two thin solid face sheets at the top and bottom surfaces were conducted. Originality/value: The novel sandwich plate consists of one porous polymer core and two homogenous skins which can be widely applied in various fields of aircraft structures, biomedical engineering, and defense technology. This paper presents an analytical and experimental study to investigate the free vibration problem of a functionally graded simply supported rectangular sandwich plate with porosities. The objective of the current work is to examine the effects of some key parameters, such as porous ratio, power-law index, and slenderness ratio, on the natural frequencies and damping characteristics.

Purpose: In many military applications, composite materials have been used because of their high velocity impact resistance that helps absorption and dispersion energy. It is therefore used in armour and vehicles, aircraft and spacecraft that are subjected to impact of various shapes and velocities. Design/methodology/approach: In the theoretical part, the absorption energy equation for the sample was established by constructing an energy balance equation consisting of five types of energies, it is the compressive energy in the first region (the impact region), the tensile energy in the first region, the tensile energy in the second region, the energy of the shear plugging and the friction energy. Findings: It was found in the experiments that the tensile stress value increased by increasing the volume fraction of fibres to the polyester, and the value of compressive stress decreased. Also manufactured different types of impact samples with dimensions (20*20 cm2 ) and deferent thickness. The results were an increase in the amount of energy absorbed by increasing the ratio of the fibre to the polyester. It is found that the greatest effect in the equation of energy balance is the shear plugging energy, in which the value of the energy absorbed reached 38% of the total energy. And in the second degree friction energy, in which the value of the energy absorbed reached 27% of the total energy. while the other energies are relatively small but with important values, except for the tensile energy in the second region, the Kevlar-Polyester (40-60)%, so that the increase was more than four times the previous case. Research limitations/implications: Three types of reinforcing fibres were used: Kevlar, Carbon and Glass fibres with a matrix material as polyester. Six samples are made for tensile and compression testing, Kevlar-Polyester (30-70)%, Carbon-Polyester (30-70)%, Glass-Polyester (30-70)%, Kevlar-Polyester (40-60)%, Carbon-Polyester (40-60)% and Glass-Polyester (40-60)%. Practical implications: On the experimental part, experimental work tests were carried out to determine the mechanical properties of the samples such as tensile and compression tests as well as conducting the natural frequency test conducting the impact test by bullet to identify the effects and penetration incidence and compare this with the theoretical results. Originality/value: In this research high velocity impact is used with a bullet it diameter 9 mm, mass of 8 g, and a semi-circular projectile head with a specific velocity ranging from 210-365 m/s. The effect of the impact is studied theoretically and experimentally. The elastic deformation is increased for increasing the ratio of the fiber to the polyester and the depth of penetration is decreasing. The hybrid sample is affected in absorption energy and decreasing the penetration. Finally calculated for penetration behaviour theoretically and experimentally for different composite materials and comparison for the results calculated.

Purpose: In this study, the free vibration analysis of functionally graded materials (FGMs) sandwich beams having different core metals and thicknesses is considered. The variation of material through the thickness of functionally graded beams follows the power-law distribution. The displacement field is based on the classical beam theory. The wide applications of functionally graded materials (FGMs) sandwich structures in automotive, marine construction, transportation, and aerospace industries have attracted much attention, because of its excellent bending rigidity, low specific weight, and distinguished vibration characteristics. Design/methodology/approach: A mathematical formulation for a sandwich beam comprised of FG core with two layers of ceramic and metal, while the face sheets are made of homogenous material has been derived based on the Euler–Bernoulli beam theory. Findings: The main objective of this work is to obtain the natural frequencies of the FG sandwich beam considering different parameters. Research limitations/implications: The important parameters are the gradient index, slenderness ratio, core metal type, and end support conditions. The finite element analysis (FEA), combined with commercial Ansys software 2021 R1, is used to verify the accuracy of the obtained analytical solution results. Practical implications: It was found that the natural frequency parameters, the mode shapes, and the dynamic response are considerably affected by the index of volume fraction, the ratio as well as face FGM core constituents. Finally, the beam thickness was dividing into frequent numbers of layers to examine the impact of many layers' effect on the obtained results. Originality/value: It is concluded, that the increase in the number of layers prompts an increment within the frequency parameter results' accuracy for the selected models. Numerical results are compared to those obtained from the analytical solution. It is found that the dimensionless fundamental frequency decreases as the material gradient index increases, and there is a good agreement between two solutions with a maximum error percentage of no more than 5%.

Modifying buckling behavior of the composite structure has been investigated in the recent few years with different reinforcement fiber and powder materials and nanomaterials. It can be seen from previous studies that the addition of nanomaterials leads to a significant modification in the buckling behavior of structure by using a low mount of nanomaterials. In this work, reinforcement of composite materials using two types of nanomaterials together, SiO2 and Al2O3 nanomaterials, to modify the buckling behavior for plate structure is studied. Therefore, the investigation was done experimentally and numerically. The experimental work is performed by manufacturing composite plates with various weight fractions with the nanoeffect, and then their mechanical properties and buckling characterization were evaluated. The numerical work was done using the finite element method to estimate the plate structure’s buckling behavior with various nanomaterials effects. A comparison between the experimental and the numerical results for plate buckling behavior is expressed, showing that the discrepancy of the results was not more than 12.56%. Finally, the results showed that the buckling behavior for a reinforced plate was improved by 35% when two types of nanomaterials were used together.

Crude oil is one of the most important sources of energy in the world. To extract its multiple components, we need oil refineries. Refineries consist of multiple parts, including heat exchangers, furnaces, and others. It is known that one of the initial operations in the refineries is the process of gradually raising the temperature of crude oil to 370 degrees centigrade or higher. Hence, in this investigation the focus is on the furnaces and the corrosion in their tubes. The investigation was accomplished by reading the thickness of the tubes for the period from 2008 to 2020 with a test in every two year, had passed from their introduction into the work. Where the thickness of more than one point was measured on each tube in the same row and the corrosion rate was extracted for three furnaces, starting from the area of ​​heat transfer by radiation to the heat transfer area of ​​the convection in three different operating units. It was found that the highest percentage corrosion value between the standard tube thickness and the thickness of conduction position was 37% with the conduction zone, and 31% with radiation zone. There, the tubes specification was tested. Five percent Cr-0.5 Moly and the temperature of radiation zone was 578 °C to 613 °C and the stack temperature was 410 °C to 450 °C. So, the results show that the maximum erosion occur at the convection zone.

In general, the lower prosthesis consists of socket, leg, ankle, and foot. The socket is the crucial part for connecting the remaining part of the limb and the prosthesis, as it is essential to distribute the load to the amputation patient to provide comfort and add to the proper appearance of the amputation patient. A research that was included methods of manufacturing it, choosing the composite materials necessary for the design, higher durability, lighter weight, and less cost. Previous research used polymer composites reinforced with fibers as glass fibers, carbon fiber, and Kevlar. Other researchers have studied natural fibers' use as reinforcement fiber by mixing resin materials or adding nanomaterials to modify the mechanical properties and reduce costs. After calculating performing the required mechanical tests such as tensile, fatigue, and impact testing, the required properties of the composite material are found, where the prosthesis socket is manufactured below the knee with the application of different loads of the socket. A review of socket models used in developing countries was performed with regard to design, modeling, and finite element analysis (FEA). This review aims to study the material's behavior and mechanical properties by using natural fibers for manufacturing prosthetic sockets. The review discusses the socket manufacture methods proposed to develop the socket industry based on natural fibers to reduce the hot and humid environment using Kenaf and other natural fibers.

This study investigates the effect of Nano-zinc oxide on tensile properties of natural rubber composites by replacing the conventional zinc oxide by Nano-zinc oxide as an activator. It has a small particle size and large surface area in comparison with conventional zinc oxide. In this paper, one compound has a conventional zinc oxide as an activator with concentration 8phr (part per hundred rubber) and eight compounds have Nano-zinc oxide as an activator with concentrations (0.2, 0.6, 1, 1.4, 1.8, 2.2, 2.6, 4) phr. The tensile test sample carried out by using the Monsanto T10 Tensometer. Results show that maximum values of tensile strength and elastic modulus at 300% are found with Nano-zinc oxide at 1.8 phr. Replacing the conventional zinc oxide by Nano-zinc oxide decreases the price of the compounds due to reducing the amount of zinc oxide inside the compounds by 77.5%. It also reduces the contamination of the environment and improves the tensile strength by 38.31%. http://dx.doi.org/10.30572/2018/kje/090105

Climate is one of the main parameters that can influence building designs in Iraq. Analysis and assessment of microclimatological data can aid urban architects and engineers to optimize human comfort through environmentally sustainable practices. The results indicated that the long-term measurements of total solar insolation and ambient temperatures have increased by 2.9% and 6.5% respectively. Albedo resulted in good correlation with heating coefficients and temperature of R2 = 0.89 and 0.63 respectively. Annual cooling degree days and heating degree days have reduced, while annual mean ambient temperatures and annual solar radiation have increased.

This study presents the optimum operating parameters and geometrical of the functionally graded sandwich plate with porous materials (FGPMs), widely used in aircraft structures subjected to uniaxial critical buckling load. This process is developed design optimisation parameters by employing Multi-Objective Genetic Algorithm (MOGA) techniques. According to a simple power law, the assumption of varying material characteristics of the porous FG core through the plate thickness is considered. In addition, to evaluate the linear buckling behaviour, a new mathematical model based on the classical plate theory (CPT) is proposed. The impact of different design parameters on the performance of the functionally graded structure is studied. Then, finite element modelling is used to validate the results of the analytical solution. Finally, the optimisation method includes both design of experiments (DOE) and response surface methodology (RSM), which are used to find out the critical buckling load of the FG sandwich plate with porous metal core bonded with two homogenous skins using suitable adhesion. The mandatory constraints are the maximum critical buckling and maximum total deformation. In this work, 100 design points are considered to determine the total deformation load multiplier, maximum deformation, and equivalent stress of sandwich plate with graded materials and even distribution of porosities. The buckling analyses of the FGPM sandwich plate subjected to the compression loading are presented by conducting an experimental program. The results show good convergence between suggested analytical and FEA simulation with an average error percentage of no more than 2 %. References ISSN 0128-7702 e-ISSN 2231-8534 Article ID JST-2794-2021 Download Full Article PDF Share this article FacebookTwitterLinkedInMore Make a Submission Related Articles Latest Women in Leadership: Insights from Female Principals of Rural Secondary Schools in Vhembe District of South Africa Malaysian State Sports Schools Football Coaching Process Key Themes Development: Constant Comparison Method in Data Analysi

The main reason that affects the discomfort in a driving vehicle is the vibration response. The human body vibration leads to many malfunctions in both comfort and performance in human health. As a result, the human body’s simulation in sitting posture in the driving vehicle has a strategic relationship for all Tires and vehicles manufacturers. The digital process simulation of the human body seat vehicle vibration shows two significant advantages. The first advantage is the prevention of the high-cost modifications in the construction stage of the vehicle, while the second one describes the stability test during the undesirable vibrations. This study modelled the human body’s dynamic characterisations, natural frequency, and mechanical response when seated in the driving vehicle with vibration transmissibility in the vertical direction have been using the biomechanical vibration model. The vertical vibrations and the transmissibility of the human body dynamic response are presented in detail. Exciting results have been obtained, and they are significant for human health, which relates to sitting posture in the driving vehicle. It can assist in understanding the influences of low-frequency vibration on human health, comfort, and performance, and therefore it could be applied for ride comfort evaluation. An analytical solution to derive the general equations of motion for the human system was developed. Then, using the vibration analysis technique and the corresponding equations, the accurate dynamic response of the selected mode is identified. Furthermore, the mathematical modelling for free vibration using the finite element analysis has been performed to determine the appropriate values and set its description. Then, the comparison results of the two techniques have been carried out.

The current work presents a free vibration analysis of a simply supported rectangular functionally graded sandwich plate using a new analytical model. The core of the sandwich plate is made up of porous metal, and the top and bottom faces are made up of homogenous materials. The core metal properties are assumed to be porosity dependent and graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The contribution of this paper is to evaluate the performance of functionally graded porous materials (FGPMs) as it is used for many biomedical applications, particularly in tissue engineering. Theoretical formulations are based on the classical plate theory to find the free vibration characteristics of the imperfect FGM sandwich plate and include different parameters. Parameters included are graded distributions of porosity, power-law index, core metal type, and aspect ratios. A numerical investigation using finite element analysis (FEA) and the modal analysis was conducted with the assistance of the commercial ANSYS-2020-R2 software to validate the analytical solution. To detect the various parameters influencing the fundamental frequencies of sandwich plate comprehensive numerical results are presented in dimensionless tabular and graphical forms. The results reveal that the frequency parameter of the sandwich plate increases with the increase of the porosity parameter and number of the constraints in the boundary conditions. Furthermore, the increase in the number of layers leads to an increase in the accuracy of the results for the same FGM core thickness. An accepted agreement can be observed between the proposed analytical solution and numerical results with a maximum error discrepancy of 8%.

Creep loading is a significant engineering challenge because it could increase materials failure, especially material subjected to mechanical and thermal loading. The prostheses and orthoses composites have not been resistant to high temperatures and can be subjected to shrinking effects, and the improvement of the creep behaviour of prostheses and these materials has to be investigated. One way to improve this is by consolidating Nano additives' percentage (from 0 to 3.5%). Thus, the study covered these additives' effect on the creep characterization for prosthetic and orthotic composites using various volume fraction carbon Nano particular materials. The investigation was achieved using experimental and artificial neural network techniques to calculate the strain–time relation for prosthetic and orthotics composite materials with various volume fraction of carbon Nanoparticle materials. So, the experimental technique was achieved, firstly, manufacturing the Nanocomposite samples and then calculating the mechanical properties and creep behaviour. Besides, a numerical calculation of the creep behaviour for composite material using artificial neural network techniques and then comparing them was presented. Comparing the experimental and artificial neural network techniques results has shown a good agreement with a maximum discrepancy (2.58%). Also, the results showed that the obtained mechanical properties and creep reach five times for composite materials without Nanoparticle, with reinforcement by Nanoparticles.

In this study, a new mathematical model is presented for a simply supported rectangular sandwich plate made of functionally graded materials (FGMs) with porosities to evaluate the buckling stresses with different design parameters. The rectangular imperfect FGM plate is assumed to have various porosity distributions through the plate thickness, while the upper and lower skins are made of homogenous materials. Mathematical models were derived based on the classical plate theory (CPT) principles, and the effect of changing porous index, elastic parameters, porosity ratio, and length to thickness ratios on the buckling stresses of the functionally graded sandwich plate was investigated. A numerical investigation with the assist of finite element analysis (FEA) was conducted using commercial software ANSYS 2020 R2. Eight-node SOLID186 elements are modeled and analyzed to validate the obtained results of the analytical solution. Also, systematic numerical analyses for the selected models to evaluate the buckling stresses in a sandwich structure with different boundary conditions and frequent FG plate layers are carried out. The results show that the critical buckling load of the FG sandwich plate is decreasing when the power-law index (k) and porosity percentage increase and increasing with higher aspect and slenderness ratios, and the increasing the number of layers leads to an increase in the accuracy of the results for the same FGM sandwich beam thickness. There is an acceptable convergence between analytical and numerical techniques with a percentage discrepancy no exceed 6%.