Journal of Computational and Applied Research in Mechanical Engineering
Volume:11 Issue: 1, Summer-Autumn 2021

This work presents a numerical approach to predict the influence of material stiffness in a dental implant using different thread profile shapes, always with a constant number of threads, thread width and thread pitch. Dental implant affects bone tissue, in response to various mechanical stimuli where the biomechanical behavior plays a significant role in the study of stress and strain calculation. In this work, four different thread profile shapes were considered (Model1 - Plateau typeA, Model2 - Plateau typeB, Model3 - Triangular, Model4 - Rectangular) with two different inner diameters equal to 4 and 6 mm, using three different implant materials (titanium, an iso-elastic titanium and zirconium alloys). Two dimensional computational axisymmetric models of a bone-implant were constructed using the finite element method. This study presents the numerical results about the mechanical stimuli on dental implant according to the chosen material and profile shape. The main contribution of this work is giving additional information about the stability and implant loosening with the application on surgical techniques in dental science.

Pressure vessels are used in a variety of applications in many engineering applications. The thin walled cylinders with torispherical heads have been widely used as pressure vessels in engineering applications. In this paper, the free vibration behavior of carbon fiber reinforced composite cylinders ended with torispherical heads with various boundary conditions is investigated. The shape of a torispherical head is consists of a sphere of large radius and a much smaller minor radius at the knuckle. The numerical calculation with finite element method is obtained and the results were compared with the experimental data to confirm the accuracy of the numerical solution. The acceptable accordance between experimental and numerical results leads to use of numerical model instead of expensive experimental tests. In addition, the effects of the thickness of torispherical head and cylindrical section and the lengths of cylinder and torispherical head on vibrational behavior of the structure are studied.

The effects of uniform injection and suction through the surfaces of a perforated square cylinder on the vortex shedding, heat transfer and some aerodynamic parameters have been investigated numerically. The finite-volume method has been used for solving the Navier-Stokes equations for incompressible and turbulent near-wake flow ( ) with the k-ɛ turbulence model equations. To find the optimum conditions, the effects of injection and suction through the front surface (case Ⅰ), the rear surface (case Ⅱ), top-bottom surfaces (case Ⅲ) and all surfaces (case Ⅳ) with various injection/suction coefficient G  are studied. The results reveal that parameters such as pressure and drag coefficients and Nusselt number are influenced drastically in some cases as well as flow field parameters. For instance, the maximum reduction of the drag coefficient occurs at case Ⅳ while the maximum increase and reduction of Nu number occur at  for all cases about 46% and 32%, 61% and 63%, 92% and 60% and 180% and 115% for cases Ⅰ, Ⅱ, Ⅲ and Ⅳ respectively.

The tube flange is typically performed using welding, forging methods, which cost effort and time. In the present work, a metal spinning process to form tube flange was proposed. A flange-forming tool was developed based on the outer tube diameter to form the flange. It consists of three components namely; collet, mandrill, and roller. An experimental work was conducted to investigate the process parameters of the flange process of lead tubes. Different working conditions are considered during conducting of flanged specimens, e.g.  rotating speed, feed rate, and tube wall thickness. The effects of the working conditions on the flanging loads were investigated. The results reveal that the flanging load increases with the increasing rotational speed, tube wall thickness, and with both lower and higher values of feed rate while it decreases with medium values of feed rates. To show the effect of the working conditions on the flange characteristics, a parametric study was conducted. The results show that the surface hardness and surface roughness of the formed flange is improved with increasing all working conditions. A theoretical analysis to model the flange forming loads (axial, radial and tangential) was presented. A comparison between forming loads analytically and experimentally was discussed. The comparison indicates that this percentage of error up to 4% occurs, instead of error percentage up to 28%, in case of neglecting the low feed rate.

Electro Discharge Machining (EDM) is an incredibly recognizable machining for ticklishness profiles in ’difficult to machine ‘materials. In EDM, the material ejection of the cathode is cultivated through exact controlled electric pulse (the flash), which changes the metals of two terminals into dissolve and vaporize, as a result of the breakdown of the dielectric medium. The most commonly used dielectric media are kerosene, paraffin, glycerin, transformer oil, and EDM oil; all are derived from petroleum. These dielectric media undergo pyrolysis and carbon soot formation is deposited on work electrode, and sometimes carbon precipitates into work. To overcome these effects vegetable oils are tried as alternate dielectric media. Pongamia Pinnetta is abundantly available in most countries; and it is cheaper and non-edible. Pongamia Pinnata (PP) oil is extracted from plant seeds, and is blended with EDM oil and several experimentations are done to find its suitability. Operational variables with respect to input and output parameters are identified. Some of these are best EWR, MRR, TWR, and SR with applied current (I), pulse on time (Ton), and pulse off time (Toff) are the ones picked as the input process factors; because for the industrial application many machinists choose these three as the input parameters; and other is constant and picked under specific requirements only. After the successful completion of this experimentations, Pongamia Pinnata oil blends are fit for the industrial application using technique of order preferancing with similar to ideal solution [TOPSIS]. It is observed that no carbon soot formation takes place in the work component with PP oil as the dielectric fluid.

This paper presents an extended cross modal strain energy change method to estimate the severity of damage associated with limited modal data in beam-like structures. This method takes in account the correlation between the analytical modal data and the measured incomplete modal data. A procedure was proposed and the analytical elemental stiffness of the damaged element after it is localized is included in quantification of the measured single damage extent. A three-dimensional numerical beam model with different damage cases is used to simulate the CMSE method application and to getting the bending displacements of the damaged element. An experimental modal analysis (EMA) on a cantilever beam with and without crack was carried out to evaluate the effectiveness of the extended CMSE method. The severity magnitude of the damage was predicted within an acceptable error range through the using validation process. Results reveal that the proposed damage estimation method successfully evaluates single damage severity in beam like structure and can be useful in maintenance technology and structural health monitoring system.

Researchers have worked on many facets of joining of similar/dissimilar aluminum alloys using different joining techniques and came up with their own recommendations. Friction Stir Welding (FSW) is widely preferred for joining aluminum alloys being an economical alternative to produce high-quality welds. However, obtaining high strength welded joints without the detrimental and visible effects still needs attention considering the effect of hybrid FSW techniques, tool material and geometry, process parameters (tool rotation, welding speed, and plunge depth), and post welding treatments. This study presents the state of the art with the authors’ own inferences on the evaluation of FSW performances in terms of joint tensile strength, fatigue strength, corrosion resistance, residual stresses, microstructure, and microhardness. This study also presents attempts made by the researchers on modeling and parametric optimization of FSW to finding scope for application of advanced optimization techniques and development of predictive models for mechanical properties of welded joints. This study emphasizes more studies required on the comparative evaluation of FSW performance with the application of ultrasonic frequency combinedly or individually on advancing and retreating sides of plates.

Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal array. These parameters are;1) transverse speed, 2) type of nano- powders, 3) rotational speed, and 4) groove’s depth friction stir welding T-joints aluminum alloy 6061-T6. This work combines welding T-joint sections and creating MMNCs in welding region simultaneously. The predicted optimum parameters and their percentage of contribution are estimated, utilizing the analysis of variance and signal to noise ratio techniques, depending on tensile test in skin and stringers direction, and hardness test of the joint. Optical microscope and scanning electron microscope (SEM) analysis are used to verify the microstructure and dispersion of nano-powders in welding joint. The best ultimate tensile stress (UTSskin) equal to (177MPa) for the skin welded part was obtained at the optimal conditions of 1550rpm rotational speed, 15mm/min transverse speed, Al2O3 type of powder and 1mm groove’s depth. SEM micrographic for metal matrix nanocomposite of all nine experiments revealed that the nano-particles are irregularly dispersed in nugget zone due to one pass. The rotational speeds of 960rpm, the transverse speed of 15mm/min, type of powder TiO2, and groove’s depth of 1.5mm, give the greatest hardness value of 80HV in nugget zone. The analysis of variance shows that the groove’s depth is the most significant parameter in this investigation.

The unvarying condition diesel engines used for commercial applications, transportation and industries lead to the crisis of petroleum fuel diminution and ecological squalor caused due to exhaust gases. Therefore, in this paper optimization of the use of MSB in naturally aspirated, direct injection diesel engines, parameters of pure diesel (D100), 80% diesel + 20% microalgae spirulina (B20), 60% diesel + 40% microalgae spirulina (B40) and pure microalgae spirulina biodiesel (B100) were investigated at various fuel injection pressures (FIP) of 18 to 26 MPa and stationary injection timings (23.5° b TDC). The result shows that optimum effect can be obtained in 22 MPa FIP, with B20 bio-diesel without compromising the performance against diesel. B20 blend presented less NOX and smoke emissions by 13.7% and 22.2% respectively with no significant change in engine performance when compared to diesel at full load operating condition. The simulation and experiment results are verified at the same operating conditions.

In this study, the crushing behavior and energy absorption of various thin-walled structures under quasi-static loading are investigated. Some experimental data from similar work are used for the validation of a simulated model. Some samples are designed and considered with different combined geometries. It was found from simulated model that the most ability of specific energy absorption and crushing force efficiency are related to the circle-square sample. For the circle-square sample, the analytic equations for calculating the mean crushing force are obtained. The mean crushing force result is compared with the result of simulations, showing a good agreement. The multi-objective optimization process for the circle-square structure is performed using non-dominated sorting genetic algorithms for two statuses. The purpose of optimization is to increase the specific energy absorption and to decrease the peak crushing force, which causes the increase of the crushing force efficiency amount. The amount of specific energy absorption in the second status compared to the first status is improved by 17%. The amount of crushing force efficiency is improved by 12% after the optimization process.

This paper proposes a combination of FRANC2D/L (2D crack growth simulation program) and ANSYS mechanical program (3D structural analysis for fracture mechanic analysis). The comparisons between the two software are performed for different case studies for stress intensity factors (SIFs) and crack growth trajectory. Crack growth is numerically simulated by a step-by-step 3D and 2D finite element method. The SIFs are calculated by using the displacement correlation technique. The procedure consists of computing SIFs, the crack growth path, stresses, and strain distributions via an incremental analysis of the crack extension, considering two and three-dimensional analysis. The finite element analysis for fatigue crack growth is performed for both software based on Paris's law, and the crack orientation is determined using maximum circumferential stress theory. The simulation results obtained in this study, using the finite element method, provide a good agreement with experimental results for all the case studies reviewed.

Finding the solutions for heat and mass transfer problems is significant to reveal the main physics of engineering issues. In this work, the Adomian decomposition method is chosen as a robust analytical method for the investigation of temperature and flow features in a viscous fluid that moves between two parallel surfaces. To ensure the validation of results, the outcome of the Adomian decomposition method is compared with that of the Runge-Kutta method, and reasonable agreement is observed. The comparison confirms that the Adomian decomposition method is a robust and reliable approach for solving this problem. Then, diverse parameters such as Prandtl number and squeeze number are studied. Besides, the effect of chemical reaction parameter, Eckert number, and Schmidt number are comprehensively discussed. Findings reveal that the Sherwood number rises when the chemical reaction parameter and Schmidt number increase. Also, it declines with growths of the squeeze number. Likewise, The findings confirm that the Nusselt number enhances with the rising of the Eckert number and Prandtl number, and it declines when the squeeze number increases.

Due to their position in various industrial applications, convective fluid flow structure is intricate and enticing to investigate. Here the flow has been made by considering multitudinous apropos parameters like induced magnetic factor, heat source and viscous dissipation effects for the mixed convective chemically radiative fluid from a vertical surface. The frame work of mathematical pattern is conferred with in the circumstances of a system of ordinary differential equations under felicitous legislation.The governed mathematical statement is handled analytically by perturbation strategy. Diagrams and numerical values of the profiles are delineated with apropos parameters. Our sketches illustrate that the induced magnetic field is perceived to be downward with intensification in magnetic parameter. Temperature profile is accelerated by rising thermal radiation and concentration distribution is decelerated by enhancing the chemical reaction and Schmidt number.

A numerical simulation of laminar fluid flow and heat transfer over built-in cylinders in a channel is presented. Effects of cylinders that located in a rectangular channel with constant wall temperature on flow and heat transfer have been investigated by the drag coefficient on cylinders wall, skin-friction factor on channel wall, Strouhal number, pumping factor, Nusselt number, and Performance Index (PI) factor, which denote the heat transfer in terms of the pressure drop. Results are validated by the most reliable published works in the literature. Effects of Reynolds number and blockage ratio (β) for the equilateral triangular cylinder for 120≤Re≤180 and 0.15≤β≤0.55 on flow and heat transfer are investigated with more details. Results indicated that by increasing Re for constant blockage ratio, the drag coefficient, Strouhal number, and Nusselt number increase; but the skin-friction coefficient, pumping factor, and PI factor decrease subsequently. Additionally, with an increase in blockage ratio at constant Re, the drag coefficient, skin-friction coefficient, pumping factor, and Strouhal number grow up; but Nusselt number diminishes and PI factor has an optimum range. Furthermore, results reveal that variation in blockage ratio has more significant effects on the flow and heat transfer than variation in Reynolds number.

Information about the dynamic loading of a steel structure is important for its static design as well as for an assessment of its fatigue life. In the case of a hydraulic static-pile-pressing machine, these loads are mainly caused by vibrations and load sway, which occurs as a result of the slewing motion of the boom around the vertical axis and from the radial movement of the load’s suspension point. This paper presents the study of the dynamics of a hydraulic static-pile-pressing machine during the process of lifting and slewing a pile using a mounted crane. A six-degree-of-freedom non-linear spatial-dynamic model is employed and a non-linear mathematical model of the machine is formulated. To confirm the mathematical model, the comparison between the measured results and simulation results using the mathematical model shows that the mathematical model is reliable. These results can be used to optimize the machine design based on calculations of its dynamics, fatigue, life expectancy and stability from a dynamic point of view.

The present research attempts to analyze the surface topography of WEDMed Inconel 825 concerning surface crack density (SCDi) and recast layer thickness (RCLt). Formation of cracks, recast layer, and heat-affected zone are the major issues in determining the final performance of the WEDM machined sample. In this study, WEDM characteristics viz. pulse on time (Ton), pulse off time (Toff), gap voltage (SV), peak current (IP), wire tension (WT), and wire feed (WF) are optimized for the response SCDi and RCLt by response surface methodology. The outcome manifests that the topography of the machined surface becomes more rougher at the increased value of Ton, IP, and SV. RSM emerges as a great tool in the development of a predicted model based on the desirability approach and finding optimal parametric combinationm which results in reduced SCDi and RCLt. At the optimum combination of process parameters, i.e., 109 machine unit Ton, 36 machine unit Toff, 54 V SV, 120A IP, 9 machine unit WT and 7 m/min WF, the values obtained for SCDi and RCLt are 0.00160 μm/μm2 and 20.991μm, respectively with an error of less than 5%.

In recent decades, the industrial applications of refined grained pure copper and its alloys have been expanded. The properties such as high strength, high density, and low deformability make these alloys more attractive. Hence, investigating the fracture mechanism of refined grained copper is of great significance. In this study, the fracture analysis of copper is investigated using the equal channel angular pressing process. Experimental results on metal alloys demonstrate that stress states should be incorporated in the constitutive equations. Therefore, the fracture process is analyzed by focusing on its relationship with the Lode angle variable. To prepare the equal channel angular processed specimens, a die set is manufactured, and tensile strength tests are carried out on dog-bone and notched flat plate specimens up to fracture. In addition, the mean value of grain sizes of the copper specimens is evaluated. The results demonstrate that the grain refining process profoundly enhances the load-carrying capacity of copper specimens. Moreover, the dog-bone tensile tests clearly show that the peak value of the strain hardening in refined grained copper occurs up to two passes, and after two passes the strain hardening drops. Furthermore, the results reveal that the Lode anglel variable has a significant influence on the failure of the refined grained copper specimens.

Engineering materials and structures have crack-like defects leading to premature failures. The usage of fracture mechanics to assess the structural integrity requires knowledge on the type, location, shape, size, and orientation of the flaws. Tomographic reconstruction is one of the commonly used nondestructive testing methods for flaw characterization. The cross sectional image of the object being tested is obtained through the application of various reconstruction methods that are categorized as either analytical methods or iterative methods. In this work, an iterative algorithm that works on the principles of genetic algorithms is developed and used for the reconstruction. The results of simulation studies on the tomographic reconstructions using genetic algorithms for the identification of defects in isotropic materials are discussed in the paper. The solution methodology based on the use of genetic algorithms is applied to reconstruct the cross sections of test specimens with different flaw characteristics. Simulated time-of-flight data of ultrasound rays transmitted through the specimen under investigation is used as input to the algorithm. The time-of-flight data is simulated neglecting the bending of ultrasound rays and assuming straight ray paths. Numerical studies performed on several specimens with flaws of known materials but unknown location, size and shape are presented. The number of ultrasonic transmitters and receivers needed for complete scanning of the specimen’s cross section is analyzed and presented. The findings of the parametric analysis and sensitivity analysis in order to choose appropriate range of algorithm parameters for performance quality and robustness of the algorithm are presented. The performance of the present algorithm with noisy projection data is also discussed.

The centrifugal slurry pump is the most common slurry flow pump used in mining industries. The pump head and efficiency are affected by the size, concentration, and density of solid particle when these pumps are applied for the control of slurries. Because the suspended solids in the liquid could not well absorb, store, and transmit pressure energy, they cause quite different changes in efficiency and performance curve shape. This study was conducted to investigate the variations of the mentioned factors at different flow rates using a numerical simulation of the centrifugal slurry pump. For this purpose, the 3D turbulent flow was solved by applying Reynolds-Averaged Navier-Stokes (RANS) equations using the Shear Stress Transfer (SST) turbulence model based on Eulerian-Eulerian for 45% to 120% flow rates in CFX (Ver. 17) software. The accuracy of the numerical solution was investigated by comparing the characteristic curves resulting from the numerical solution with experimental data‏. The obtained results show a satisfactory fitting among the calculated values from the numerical analysis and experimental data to predict pressure and velocity distribution and global performance. Moreover, by simulating the effect of different parameters of the slurry flow, their effect on the characteristic curves of the slurry pump was compared. These results reveal that the numerical solution can efficiently predict the variation trend of the slurry flow parameters.

The present paper considers the devise and development of a novel theory to examine the flexure analysis of exponentially graded plates exposed to thermal and mechanical loads. The properties such as elastic modulus and thermal modulus are assumed to vary exponentially along the thickness by keeping the poisson’s ratio constant.  This theory fulfills the nullity conditions on the upper and lower sides of the exponentially graded plates for transverse shear stress. Hamilton’s principle is used to derive the equation of motion. The present theory’s numerical results are assessed with three-dimensional elasticity solutions and the results of other authors available in the literature. The influence of thermomechanical loads, thickness ratios, and aspect ratios on the bending response of exponentially graded plates are studied in detail. The analytical formulations and solutions presented herein could provide engineers with the potential for the design and development of exponentially graded plates for advanced engineering applications.