Maximum automobile acceleration

Problem. The disadvantage of current dependences for determining the acceleration indicators at engine maximum brake power and driving tire-to-surface friction coefficients is that they are adequate only if the engine and transmission parameters provide power input to the drive wheels rolling without slipping regardless to speed. To eliminate this drawback, it is necessary to take into account that the power input to the drive wheels depends on the engine shaft speed, and therefore on the speed of the vehicle when accelerating. Goal. The purpose of the work is to further develop the theory of the automobile by improving the dependencies that allow determining the automobile acceleration rates and assessing the nature of its acceleration process from the design factors. Methodology. The approaches taken to achieve this goal are based on laws of physics, theoretical mechanics and the theory of automobile. Results. Analytic dependences for determining maximum and limiting automobile acceleration when speeding up depending on its design factors and speed have been improved. Dependences for determining the range of drive wheel slipping on the automobile speed when accelerating and the limiting automobile acceleration under the condition of its pitch stability have been obtained. When studying the automobile acceleration process theoretically it was found that the developed dependences allow determining the nature of automobile movement and assessing the influence of its design factors on the acceleration indicators. Originality. The obtained dependences for determining the maximum and limiting acceleration, the range of driving speeds with wheel slip when automobile accelerating allowed us to clarify the idea of the nature of movement during acceleration and the influence of automobile design factors on the acceleration indicators. Practical value. The obtained dependences can be used in designing new and improving racing cars such as dragsters, and analysing the dynamics of the vehicle when accelerating with full fuel delivery and determining the nature of driving tire-to-surface friction depending on the driving speed.

Defining the rational installation position for the discharging unit of the bucketless rotary imple-ment in the trenching excavator

The increasing volumes of the earthworks performed by trenching excavators during the creation of the lengthy excavations in the soil for the pipelines of different sizes and other purposes create the need to improve the excavators, to create new highly productive machines of the fundamentally new construction. The goal of this work is to increase the performance of trenching excavators equipped with the bucketless rotary implement by improving the process of the soil discharging from the implement. To achieve this goal it is required to reveal the physical essence of the soil excavation by the bucketless rotary implement and based on the performed study to determine the rational installation position for the discharging unit of the bucketless rotor. Methodology. The scientific hypothesis is that discharging of the inner circular cavities of the bucketless rotor during the trench digging and the movement of the excavated soil to the side from the trench is possible by means of rational use of the flow header pressure of the soil that is being transported in the rotor from the excavation. The study is performed with analytical methods using basic principles of the theoretical mechanics, flowing medium statics, force analysis. Results. The study confirms the scientific hypothesis of the possibility to discharge the bucketless rotary implements of the trenching excavators by using the flow header pressure of the excavated soil that is transported by the rotor from the excavation, rational installation position of the discharging unit of the implement is defined. Originality. The scientific novelty of the study lays in the rationale and confirmation of the possi-bility to excavate and transport the soil from the excavation with the implements of the rotary trenching excavators with continuous flow and not with the separate portions. Practical value. Practical value lays in ensuring the 2-5 times performance increase of the excavation using the bucketless rotary implements.

Mathematical models for evaluating the effectiveness of shock-absorbing fasteners of vibro-active mechanisms of marine objects by vibrational power

Для создания виброакустической защиты судового оборудования необходимо учитывать потоки колебательной энергии, распространяющиеся от источников как через опорные и неопорные связи, так и в виде воздушного шума. В работе представлены математические модели оценки эффективности амортизирующих креплений виброактивных механизмов морских объектов по колебательной мощности, учитываемые при обучении разрабатываемой нейросетевой системы классификации морских целей. Теоретические разработки в области виброзащиты и виброизоляции во многом имеют междисциплинарный характер и опираются на методы теории механизмов и машин, теоретической механики, теории колебаний, теории управления, используются методы инфорьт мационные технологии для оценки, поиска и выбора рациональных проектно-конструкторских решений. Создание амортизирующих устройств, способных защитить объекты от вибраций и ударов и, вместе с тем, обладающих ограниченными размерами, является сложной технической проблемой. В связи с этим первостепенное значение приобретают вопросы теории и расчета адаптивных виброзащитных систем. To create vibro-acoustic protection of ship equipment, it is necessary to take into account the flows of vibrational energy propagating from sources both through support and non-support connections, and in the form of air noise. The paper presents mathematical models for evaluating the effectiveness of shock-absorbing fasteners of vibro-active mechanisms of marine objects by vibrational power, which are taken into account when training the developed neural network system for classifying marine targets. Theoretical developments in the field of vibration protection and vibration isolation are largely interdisciplinary in nature and are based on the methods of the theory of mechanisms and machines, theoretical mechanics, vibration theory, control theory, information technology methods are used to evaluate, search and select rational design solutions. The creation of shock-absorbing devices that can protect objects from vibrations and shocks and, at the same time, have limited dimensions is a complex technical problem. In this regard, the issues of the theory and calculation of adaptive vibration protection systems are of paramount importance.

Optimalization of Design Parameters of Experimental Installation Concerning Preparation of Liquid Feed Mixtures

The article describes the initial conditions for the development of universal mechanization means for the process of mixing dry and liquid components. The essence of the method is to study the motion of a particle with different constructive and physical properties of the medium. The mathematical model of particle motion is based on theoretical mechanics and hydraulics. In this case, the main purpose of the study is to find the optimal design parameters for the installation. At the beginning, a theoretical analysis of the installation was carried out using the methods of classical mechanics and hydraulics. Experimental studies were carried out in several stages. At the beginning, one-factor experiments were conducted, followed by allocating the main factors and determining their interaction. Then, using the methods of planning the experiment, we obtained the regression equations and further optimized the parameters to summarize the main findings of the article. Modern installations should have versatility in any technological line; for example, an installation is presented that can not only mix, but further transport the mixture like a conventional pump, while providing a dosing device that is necessary for the feeding of dry components. Theoretical studies have been carried out in which the design of the impeller is substantiated at various speeds. Experimental studies to determine the design parameters of the installation are in continuous operation. The degree of homogeneity was Θ = 74%, with β2 = 80 … 100° and βst = 65 … 102°, while the value of the consumption of electrical energy is equal to Eel = 0.265 … 0.28 kWh/t.

The Role of the Non-Collagenous Extracellular Matrix in Tendon and Ligament Mechanical Behavior: A Review

Tendon is a connective tissue that transmits loads from muscle to bone, while ligament is a similar tissue that stabilizes joint articulation by connecting bone to bone. 70-90% of tendon and ligament's extracellular matrix (ECM) is composed of a hierarchical collagen structure that provides resistance to deformation primarily in the fiber direction, and the remaining fraction consists of a variety of non-collagenous proteins, proteoglycans, and glycosaminoglycans (GAGs) whose mechanical roles are not well characterized. ECM elements such as elastin, the proteoglycans decorin, biglycan, lumican, fibromodulin, lubricin, and aggrecan and their associated GAGs, and Cartilage Oligomeric Matrix Protein (COMP) have been suggested to contribute to tendon and ligament's characteristic quasi-static and viscoelastic mechanical behavior in tension, shear, and compression. The purpose of this review is to summarize existing literature regarding the contribution of the non-collagenous ECM to tendon and ligament mechanics, and to highlight key gaps in knowledge that future studies may address. Using insights from theoretical mechanics and biology, we discuss the role of the non-collagenous ECM in quasi-static and viscoelastic tensile, compressive, and shear behavior in the fiber direction and orthogonal to the fiber direction. We also address the efficacy of tools that are commonly used to assess these relationships, including enzymatic degradation, mouse knockout models, and computational models. Further work in this field will foster a better understanding of tendon and ligament damage and healing as well as inform strategies for tissue repair and regeneration.

On properties of h-differentiable functions

Research in the theory of functions of an h-complex variable is of interest in connection with existing applications in non-Euclidean geometry, theoretical mechanics, etc. This article is devoted to the study of the properties of h-differentiable functions. Criteria for h-differentiability and h-holomorphy are found, formulated and proved a theorem on finite increments for an h-holomorphic function. Sufficient conditions for h-analyticity are given, formulated and proved a uniqueness theorem for h-analytic functions.

Student-Centered Online Teaching Practices in Theoretical Mechanics

The COVID-19 pandemic has had a serious impact on education at all levels and types, and the education system, including colleges and universities, has been forced to respond by a sudden shift to online teaching. Successful online teaching requires careful thinking, planning, and technical and human support from teachers. Based on the reflection on the offline classroom teaching of theoretical mechanics for many years and the online teaching practice of first half of 2020, the author summarizes effective strategies for implementing online teaching of theoretical mechanics. We prepared the theoretical mechanical lessons through a “student-centered” approach, such as preparing teaching materials, students and teaching methods. These teaching strategies include (i) Adopting live-stream teaching as the main teaching method, (ii) Applying electronic blackboard to online deductions, (iii) Linking theory to practice for better understanding of knowledge, (iv) Integrating curriculum content in ideological and moral education, (v) Conducting formative assessment to supervise and motivate online learning. The implementation of these online teaching strategies has effectively promoted the development of students' independent learning ability.

Innovative Approaches and Methods in Teaching Technical Subjects

: Relevance. In the learning process, it is necessary to pay attention, first of all, to those methods in which listeners identify themselves with the educational material, are included in the studied situation, are encouraged to take active actions, experience a state of success and accordingly motivate their behavior. Aim. The purpose of our experimental study was to determine the possibility and effectiveness of using active and interactive forms in teaching technical disciplines. Methods. Scientific methods were applied such as working with documents, comparative analysis, literature review, questionnaires, statistics, etc. Results. In the results of experimental work, the indicators of students are given for three years in three subjects: theoretical mechanics, practical mechanics and modelling. Conclusion. In the conclusion, conclusions are given on this topic.

Sources of Harmonic Force and Speed in Mechatronic Automatic Systems

To study resonance and near-resonance phenomena, a symbolic (complex) method was used, which makes it possible to significantly increase productivity, simplify and formalize mathematical transformations. Parallel and sequential connections of elements of a mechanical system with a source of harmonic force or a source of harmonic speed as a source of external mechanical harmonic action are considered. The analytical descriptions of resonance in theoretical mechanics courses correspond to parallel connection. There are devices, in a satisfactory approximation, capable of performing the functions of sources of force and sources of speed. The source of harmonic speed can be a crank-yoke drive and a flywheel with a large moment of inertia. The source of the harmonic force can be the rod of the pneumatic cylinder, the cavity of which communicates with the cavity of another pneumatic cylinder, the diameter of which is immeasurably higher than that of the first, and the piston performs harmonic oscillations. The mechanical harmonic influences described in the courses of theoretical mechanics correspond to the source of the force. Four modes are described — resonances and antiresonances of forces and velocities. The use of the symbolic (complex) method has significantly simplified the study of resonance and near-resonance phenomena, in particular, it has made it possible to deeply unify and formalize the consideration of various mechanical systems. The cumbersome and time-consuming operations associated with the preparation and solution of differential equations have been replaced by simple algebraic transformations. Resonance and antiresonance of forces, resonance and antiresonance of velocities are determined.