Journal of Mechanical Engineering Research

Analysis of Autogenous Laser Welding in Low Carbon and Large Thickness Steel

Wed, 25 Aug 2021 00:00:00 +0800

With the use of laser welding, it is possible to join different steel, with different thicknesses, with or without the action of protective layers. The quality of laser radiation makes it possible to get certain characteristics that are impossible to get by other processes, such as high welding speeds, less metallurgical effects suffered by the heat-affected zone (ZAC), and this process also does not require filler metal, therefore it is free from possible contamination. Combined with traditional welding methods, laser welding produces narrower weld beads, allowing for better prevention of corrosion and thermal distortions. Although the process already has high industrial knowledge, some random defects, such as porosities and inconsistencies, are still found. This work presents a systematic study to determine the influence of laser welding parameters and how these parameters influence welding defects. For this, the experimental part was carried out in the welding laboratory - LABSOLDA, of the Federal University of Santa Catarina - UFSC, during the laser welding processes, a welding speed of 2.4 m/min was reached. For this experiment, argon was used as a shielding gas and 1020 steel was used as the base material.

Conception the Fluid Flow Behavior within Oil Reservoir Rock by Using Computed Tomography (CT) Scan

Amani J. Majeed, Falah A. Abood, Ahmed K. Alshara — Wed, 25 Aug 2021 00:00:00 +0800

The behavior of fluid flow has been studied during the different flow media over the past decades. In addition, the behavior of the flow of fluid through porous media has garnered much research interest. This paper sheds light on fissured rocks of oil reservoir media (as one of the porous media domain), and the effect of these fissured on fluid flow. In this article, the Finite Volume Method (FVM) has been used to visualize the behavior of single-phase fluid flow in an actual core according to the dualporosity dual permeability model. The study was conducted in two parts, the first was the image processing for one of the real oil reservoir fractured rock images, where the image was processed and simulated by ANSYSCFX software, and the results showed a complete visualizing of the fluid behavior during this domain. As for the other side, a simulation of a real reservoir rock belonging to the Al-Nour field in Iraq / Misan was made. The X-ray Computed Tomography (CT) scan has been used to convert the real fractured core to a dynamic domain. ANSYS-CFX program has been used and the results illustrated the pressure counter, the velocity counter, the velocity streamline, and the velocity vectors for the studied model in three dimensions. A comparison was made between the productivity index for fractured and non-fractured rock and the results explained that the presence of fracture can improve the productivity index to about 5.74%.

Recognition Methods of Geometrical Images of Automata Models of Systems in Control Problem

Anton Epifanov — Mon, 11 Oct 2021 00:00:00 +0800

The laws of functioning of discrete deterministic dynamical systems are investigated, presented in the form of automata models defined by geometric images. Due to the use of the apparatus of geometric images of automata, developed by V.A. Tverdokhlebov, the analysis of automata models is carried out on the basis of the analysis of mathematical structures represented by geometric curves and numerical sequences. The purpose of present research is to further develop the mathematical apparatus of geometric images of automaton models of systems, including the development of new methods for recognizing automata by their geometric images, given both geometric curves and numerical sequences.

Use of the Method of Guidance by a Required Velocity in Control of Spacecraft Attitude

Mikhail Valer’evich Levskii — Wed, 10 Nov 2021 00:00:00 +0800

We apply the method of guidance by a required velocity for solving the optimal control problem over spacecraft’s reorientation from known initial attitude into a required final attitude. We suppose that attitude control is carried out by impulse jet engines. For optimization of fuel consumption, the controlling moments are calculated and formed according to the method of free trajectories together with principle of iterative control using the quaternions for generating commands to actuators. Optimal solution corresponds to the principle “acceleration - free rotation - separate corrections - free rotation - braking”. Rotation along a hitting trajectory is supported by insignificant correction of the uncontrolled motion at discrete instants between segments of acceleration and braking. Various strategies of forming the correction impulses during stage of free motion are suggested. Improving accuracy of achievement of spacecraft's final position is reached by terminal control using information about current attitude and angular velocity measurements for determining an instant of beginning of braking (condition for start of braking based on actual motion parameters is formulated in analytical form). The described method is universal and invariant relative to moments of inertia. Developed laws of attitude control concern the algorithms with prognostic model, the synthesized control modes are invariant with respect to both external perturbations and parametric errors. Results of mathematical modeling are presented that demonstrate practical feasibility and high efficiency of designed algorithms.

Geometrical Dimensional Effect on Natural Frequency of Single Layer Graphene in Armchair Configuration

Harshad Patel — Thu, 18 Nov 2021 00:00:00 +0800

Graphene has remarkable strength, such as yield strength and elastic

constant. The dynamic behaviour of graphene sheet is affected by

geometrical variation in atomic arrangement. This paper introduced

graphene with armchair atomic structure for estimating fundamental natural

frequencies. The presented analysis can be useful for the possible high

frequency nanomechanical resonator systems. The analytical formulation,

based on classical plate theory and continuum solid modelling based finite

element method have been performed for estimation of fundamental natural

frequencies of single layer graphene sheet (SGLS) with different boundary

conditions. The free edge and clamped edge boundary conditions have been

considered. For simplifying analytical formulations, Blevins approach for

dynamic solution has been adopted and for validating analytical results.

The finite element analysis of SLGS has been performed using ANSYS

software. The effect of variation in geometrical parameters in terms of

width and length of SLGS has been analysed for realization of ultra-high

frequency based nanomechanical resonator systems