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Abstract In this paper, a new type of heat exchanger with discontinuous spiral baffles is designed, and its performance on heat transfer is analyzed by numerical simulation. The research results show that the airflow in shell-side flows by a similar helical way, “Flow dead zone” is not found. The high enthalpy airflow’s temperature decreases about 38% of the inlet air temperature by cooling down with a convective heat transfer coefficient of 344.4 W/(m2·K), while the decrease of the airflow pressure is 30%.

Abstract Various research methods are used in the field of scientific research. The most frequently used methods are real experiment and computer modeling. A real experiment requires equipping the laboratory with very expensive equipment. The implementation of experiments in laboratories requires knowledgeable professional personnel to operate the devices. Therefore, when investigating phenomena, the real experiment is gradually being replaced by a numerical experiment using computer technology. Computer modeling with appropriate software provides convenient investigation of technical phenomena in various areas of technological processes. Realization of experiments by computer modeling is more flexible when solving technical processes. The content of the article is a description of the investigation of temperature cycles. The experiment described in this paper focused on measuring the temperature cycles of the butt and fillet welds made of austenitic steel and aluminum. The temperature cycles were investigated via a real experiment and modelling: 1/under laboratory conditions, measured using thermocouples located in the heat-affected zone (HAZ), 2/by numerical experiment performed in the ANSYS program using FEM. Numerical simulation was used to investigate the welding process. When modeling the temperature cycles, we compared the calculated temperatures in the nodes of the model, which corresponded to the places where the thermocouples were placed in the real experiment. Results from both experiments are shown graphically.

Abstract Patient with fully edentulous maxillaries often suffer of several disease as an alteration of facial appearance, difficulties in eating, speech, and chews. Fixed and removable prosthesis can be a solution to rehabilitate this issue. The All-on-Four protocol is one of the possible treatment modalities for implant-supported prosthetics. It consists of placing four implants in an intermorainal position, two perpendicular to the occlusal plane and two tilted distally at a 45° angle. This paper aims to assess the stress distribution on an All-on-Four titanium prosthesis by means of a Thermoelastic Stress Analysis (TSA). This full-field non-contact measurement technique allows, through a thermal imaging camera, to observe how the surface temperature of an object changes under the effect of cyclic load. The principle on which thermoelastic analysis is based is the existence of a relationship between deformation, hence applied stress, and temperature change, called the thermoelastic effect. To perform the tests, the prosthesis was fixed to a resin jaw cast that has similar characteristics to the human bone, so that the same damping that would be present under normal working conditions could be accounted for. The distal artificial molar tooth was kept in contact to a narrow screw, which was attached to a Medium-Force (M-Series) Air-Cooled Shakers made by Santek. This shaker generates a sinusoidal load of 800N with a load cell at 10 Hz frequency, which can maintain the temperature variation of the prosthesis constant. A pre-load was applied before starting the tests. To see the change in temperature a Flir A6751SC thermal camera was used, and videos were acquired with a frame rate of 125 Hz and a resolution of 640x512 pixels. From the experimental TSA tests, the trend of the experimental stress concentration on the titanium specimen was detected. The outcomes of the experimental tests were compared to a 3D prosthesis model by Finite Element Analysis (FEM).

Abstract Many researches devoted to deflagration appearance in hydrogen-air mixes and transition it to detonation. Preference of hydrogen as a fuel is detonation fuel cycle which is more energetic preferable in comparing with ordinary fuel cycle. In connection with this preference problem of hydrogen detonation engine constructing is extreme actual. Essential part of investigations in this field is developing and improving of mathematical methods for numerical simulation of deflagration initiation and transition it to stable detonation. In real physical experiments this deflagration initiation in flows appears via sudden hot spot appearance or near an obstacle on boarding surface. In this paper numerically investigated flows of reactive gas mixes in channels with obstacles with purpose to define regims of deflagration initiation.

Abstract This work develops a software for the probabilistic prediction of rolling contact fatigue in multiple-row ball bearings subject to any loads and rotations. iKonPro®, as it has been named, calculates the failure probability of the raceways and the bearing, taking as input the material fatigue properties, contact-load and -angle distributions for discrete load cases, and the subsurface stress responses to different ball loads. The software is based on the determination of ball kinematics and equilibrium, raceways stress states, and local and global failure probabilities. Here, iKonPro® is applied to a wind-turbine pitch bearing and the results demonstrate that it correctly captures the size effect.

Abstract The engine cooling system takes away the heat absorbed by high-temperature parts during the operation of the car engine in a timely manner, keeping it working within the normal temperature range. This article applies Flowmaster software to establish a one-dimensional cooling system model for a certain model of National Five diesel engine. Relevant boundary conditions are inputted to complete steady-state simulation calculations of the system under different operating conditions, obtaining the flow rate, pressure distribution, and temperature rise of each component. At the same time, three optimization schemes are designed based on the original cooling system to predict and evaluate the working capacity of the cooling system, Based on the calculation and analysis results, improvement suggestions are proposed to guide the structural design and testing of the cooling system, greatly reducing research and development time and reducing research and development costs. The calculation results show that the flow rate of each component in the rated point, heating test condition, and idle condition of the original plan has decreased compared to the flow rate of a certain four machine on the same platform under the same working condition (the air compressor flow rate is higher than the limit value), and the temperature difference of the radiator and heating flow rate do not meet the specification requirements. Suggest using Plan 3 to increase the water pump speed ratio to 1.25, with a warm air flow rate of 5.33L/min under idle conditions, which is 72% higher than the original plan and meets the vehicle limit requirements. In addition, to ensure the accuracy and reliability of the model and calculations, this project conducted cooling system tests on an engine bench. The comparison between the simulation calculation data and the experimental data showed that the simulation calculation results were consistent with the experimental results.

Abstract The advancement of computational modeling techniques, such as FEM, has allowed to simulate complex machining processes with improved accuracy. Wear prediction is a crucial aspect in understanding and optimizing machining processes, as it directly impacts tool life, surface quality and overall machining efficiency. This work focuses on the FEM simulation, specially utilizing the DEFORM software, in conjunction with the Usui wear model, for wear prediction in machining operations. The Usui wear model, a well-established and widely used wear prediction approach, accounts for multiple wear mechanisms that include adhesion, abrasion, and diffusion. By incorporating the Usui wear model into the FEM simulation framework within the DEFORM software, it is possible to understand wear phenomena in machining processes. The integration of Usui wear model algorithms into DEFORM enables the simulation to accurately predict wear rates, distribution patterns, and progression of tool deterioration. This predictive capability facilitates the identification of critical wear zones and guides proactive measures to improve tool life, reduce production costs, and optimize machining productivity. This work presents research focused on wear prediction in cutting processes, utilizing FEM simulation with DEFORM software and incorporating the Usui wear model. Through a comprehensive analysis of wear phenomena, this research aims to optimize cutting parameters, improve tool life, and contribute to the advancement of machining and manufacturing technologies.

Abstract This paper investigates the results of simulations devoted to the acoustic field variation caused by different boundary conditions applied to the backscattering of the acoustic wave in both low and moderately low frequency ranges. The goal is to analyse the object behaviour and the detection ability of the 2D acoustic field approximations when the simulation data of the scattered sound field is available. The plane waves are backscattered by a dummy human body, positioned in a cabin which has a defined size. The dummy human body is created by using clusters of finite and disjointed but tangent circular cylinders. Each cylinder is a scatterer that emulates various boundary conditions i.e., the scatterers can be sound-soft (Dirichlet boundary condition) and sound-hard scatterers (Neumann boundary condition). The cylinders are filled with biological tissue (i.e., fat). The exterior scattering problem is solved using the preconditioned Krylov subspace iterative solvers (GMRES), as a computationally cheaper alternative. We use the hypothesis that the mass density of the obstacle and wave speed in the obstacle are both constant. During the simulation experiments, we neglected the interactions among scatterers. A frequency range from 100 Hz to 1000 Hz is analysed. Both the Sound Pressure Level (SPL) and Radar Cross Section (RCS) are used to analyse the numerical simulation of the sound field.

Abstract Deep Reinforcement Learning (DRL) algorithms help agents take actions automatically in sophisticated control tasks. However, it is challenged by sparse reward and long training time for exploration in the application of Deep Neural Network (DNN). Evolutionary Algorithms (EAs), a set of black box optimization techniques, are well applied to single agent real-world problems, not troubled by temporal credit assignment. However, both suffer from large sets of sampled data. To facilitate the research on DRL for a pursuit-evasion game, this paper contributes an innovative policy optimization algorithm, which is named as Evolutionary Algorithm Transfer - Deep Deterministic Policy Gradient (EAT-DDPG). The proposed EAT-DDPG takes parameters transfer into consideration, initializing the DNN of DDPG with the parameters driven by EA. Meanwhile, a diverse set of experiences produced by EA are stored into the replay buffer of DDPG before the EA process is ceased. EAT-DDPG is an improved version of DDPG, aiming at maximizing the reward value of the agent trained by DDPG as much as possible within finite episodes. The experimental environment includes a pursuit-evasion scenario where the evader moves with the fixed policy, and the results show that the agent can explore policy more efficiently with the proposed EAT-DDPG during the learning process.