EFFECT OF BODY SHAPE ON THE AERODYNAMICS OF PROJECTILES AT SUPERSONIC SPEEDS

An investigation has been made to predict the effects of forebody and afterbody shapes on the aerodynamic characteristics of several projectile bodies at supersonic speeds using analytical methods combined with semi-empirical design curves. The considered projectile bodies had a length-to-diameter ratio of 6.67 and included three variations of forebody shape and three variations of afterbody shape. The results, which are verified by comparison with available experimental data, indicated that the lowest drag was achieved with a cone-cylinder at the considered Mach number range. It is also shown that the drag can be reduced by boattailing the afterbody. The centre-of-pressure assumed a slightly rearward location for the ogive-cylinder configuration when compared to the configuration with boattailed afterbody where it was the most forward. With the exception of the boattailed afterbody, all the bodies indicated inherent static stability above Mach number 2 for a centre-of-gravity location at about 40% from the body nose

Theoretical and experimental analysis of the physical behavior of gaskets in shock absorber

The current study examines the theoretical and experimental behaviour of gaskets when using different cases of disc samples (free-free, free-fix and fix-fix). The samples are made of rubber. The deformation of the gasket as a function of loading depends significantly on how it is fixed to the rigid supports. Physical properties have been explained. In experimental analysis of the sample disc "Free-Free", the loading velocity does not have a significant influence on the range of values of the mentioned velocity. All the curves in the "Free-Fix" disc load illustrate that at the same deformation, the average pressure is higher than in the case of the "free-free" disc. At the deformation of 1.49 mm, the average pressure is 33% higher than all other graphs. In the case of the "Fix-Fix" disc, it is observed that the load, evaluated by the average pressure, is clearly higher than in the case "Free-Fix" disc. At a deformation of 1.49 mm, the average pressure was found to be 15 times higher

Destructive and Nondestructive Tests for Concrete Containing a Various Types of Fibers

Fibers have been considered an effective material that was used to improve the concrete's weak properties, namely its tensile strength, ductility, and crack resistance. Thus, the current study highlights two major objective, the former is the fibers shapes and types on the mechanical properties of the fresh and hardened concrete while the latter explores the impact of the fiber contents on the concrete mechanical properties developments. To achieve these targets six types of fibers (five of them made of steel and the last was polyolefin fibers) with various shapes are utilized. The tests were carried out to investigate the fibers shape and material contribution in the concrete mix properties improvement. The samples were subjected to destructive and non-destructive tests such as workability, compression, bending, and splitting. The non-destructive tests include ultrasonic pulse velocities and the Schmidt Hammer test. Three kinds of fibers (two of steel and one of polyolefin fiber) are used with variable content ratios of 0.5, 0.75, 1.0, and 1.5% to study the fiber content effect. Generally, the workability of fresh concrete has a reverse relationship with fiber presence and fiber content ratios. The compressive capacity, splitting and flexural strength has a direct proportion with fibers contents. The hooked steel fibers appeared the best results in terms of shape comparison. Doi: 10.28991/CEJ-2022-08-11-07 Full Text: PD

The response of a high voltage transformer with various geometries of core joint design

The core losses in a three phase transformer can be significantly reduced by improving the core joint geometry. The researchers were applied numerous types of T-joint designs in order to reach the optimum design that can be used in three phase transformer to reduction the losses. Two types of T-joint design are presented in this paper; T-joint with 90° butt-lap design and T-joint with 45° mitered design. A 3-phase distribution transformer was simulated in 3D using Ansys Maxwell software. The core loss for a three-leg three phase transformer rated 1000 KVA and the flux density distribution are investigated. The simulation results show the core losses were increased up to 3% and the flux density was increased to reach more than 22% flux density become higher when using T-joint with 90° butt-lap design as compared with T-joint with 45° mitered design

Analysis on magnetic flux density and core loss for hexagonal and butt-lap core joint transformers

This paper presents the results of new hexagonal configuration at the T-joint of three-phase transformer core. The proposed model is compared with previous T-joint design, Butt-lap, which is widely used at present by many transformer manufacturers. The magnetic flux density distribution and core loss of a transformer rated 1000kVA are analyzed for the two types of T-joint design. The 3D simulation are carried out by using the ANSYS-Maxwell software. The results show that the magnetic flux density of the hexagonal shape T-joint is well distributed compared to that in the Butt-lap T-joint design. The core loss for the proposed model (hexagon) T-joint indicates a reduction of more than 11 % compared to the Butt-lap T-joint design

New optimization technique to design the core of three-phase transformer

Reduction losses in three-phase transformers have drawn the attention of researchers, in the recent years. In this study, an intelligent algorithm employing particle swarm optimization (PSO) has been used to get the optimum T-joint design of a core in a three-phase transformer. This technique was employed to design a new geometry of a joint to obtain the minimum loss in a three-phase transformer. In achieving this target, a 3D finite element method had been used to simulate the proposed transformer model. Power losses in the core and winding losses had been considered as the heat sources, and the results were validated based on the test data obtained from transformer factory. The results presented that the total losses have been decreased up to 10% compared to the corresponding values from common designs. Moreover, the core losses have been reduced in the range of 11% compared to similar parameters in the conventional design

EXPLAINABLE MODELS FOR MULTIVARIATE TIME-SERIES DEFECT CLASSIFICATION OF ARC STUD WELDING

Arc Stud Welding (ASW) is widely used in many industries such as automotive and shipbuilding and is employed in building and jointing large-scale structures. While defective or imperfect welds rarely occur in production, even a single low-quality stud weld is the reason for scrapping the entire structure, financial loss and wasting time. Preventive machine learning-based solutions can be leveraged to minimize the loss. However, these approaches only provide predictions rather than demonstrating insights for characterizing defects and root cause analysis. In this work, an investigation on defect detection and classification to diagnose the possible leading causes of low-quality defects is proposed. Moreover, an explainable model to describe network predictions is explored. Initially, a dataset of multi-variate time-series of ASW utilizing measurement sensors in an experimental environment is generated. Next, a set of pre-possessing techniques are assessed. Finally, classification models are optimized by Bayesian black-box optimization methods to maximize their performance. Our best approach reaches an F1-score of 0.84 on the test set. Furthermore, an explainable model is employed to provide interpretations on per class feature attention of the model to extract sensor measurement contribution in detecting defects as well as its time attention

DEVELOPMENT OF THE CROSS-COUPLING PHENOMENA OF MIMO FLIGHT SYSTEM USING FUZZY LOGIC CONTROLLER

This paper describes the performance of a simplified dynamic controller with fuzzy logic controllers. The six degree-of-freedom simulation study focuses on the results with and without fuzzy logic controller. One area of interest is the performance of a simulated the cross coupling effect. The controller uses explicit models to produce the desired commands. In this paper the effect of the cross-coupling between channels on the overall performance of the flight system has been considered. Two fuzzy controllers have been added to the system to improve its performance. This paper presents the development and simulation of a modified system is presented using MatLab Simulink. Also it focuses on the use of fuzzy logic controller in model-based control of multiple-input, multiple-output systems. Here, we address the question of how the overall performance of the system is affected when both fuzzy logic controllers are applied at the same time. Simulation and experimental results of a flight system , as an illustrative example, are presented