Research on theory of machines and mechanismsmechanismandmachineAnd its main components areMechanismAndmechanical kinetics。GenerallymechanismandmachineIt is collectively called machinery, so the research object of mechanical principle is machinery.[1]
Mechanical principle is a discipline that studies the structure and motion of mechanisms in machinery, as well as the structure, force, mass and motion of machines.The main components of this discipline areMechanismandmechanical kinetics。People generally refer to mechanisms and machines as machines.A mechanism is a combination of two or more components that are movably connected to achieve a specified movement.A machine is composed of one or more mechanisms to do useful work or complete the conversion between mechanical energy and other forms of energy.
Different machines are often composed of a limited number of commonly used mechanisms, such as the main mechanisms of internal combustion engines, compressors and presses are crank slider mechanisms.The movement of these mechanisms is different fromGeneral mechanicsThe movement on theGeometric constraintIt has nothing to do with the force, component quality and time.In 1875, F. Lello of Germany separated the above general problems from general mechanics and wrote《Theoretical kinematics》One book, founded the foundation of mechanism.Many concepts, viewpoints and research methods proposed in the book are still in use today.In 1841, R. Willis of Britain published《Principles of Mechanism》。Since the middle of the 19th century,mechanical kineticsAnd gradually formed.In the 20th century, there appeared the mechanical principle of combining mechanism and mechanical dynamics.In 1934, China'sLiu XianzhouHis book "Mechanical Principle" was published.In 1969, the International Organization and Machine Principles Association (IFTOMM) was established in Poland.
The research object of mechanism is various common mechanisms in machines, such asLinkage、Cam mechanism、Gear unit、Screw mechanismandIntermittent motion mechanism(e.gcrank shaft ratchet、Geneva mechanismAnd combination mechanism.Its research content is the composition principle and kinematic certainty of the mechanism structure, as well as the kinematic analysis and synthesis of the mechanism.Mechanism studies the motion of mechanism only from the point of view of geometry, without considering the influence of force on motion.
The research object of mechanical dynamics is machine or combination of machines.The research content is to determine the true motion law of the machine under the action of a known force and its adjustment, friction andMechanical efficiency, balance of inertial force, etc.
According to the traditional research method of mechanical principle, the gap between component contact surfacescomponentThe error caused by elastic or temperature difference deformation, manufacturing and assembly, etc.This is generally feasible for low-speed machinery.However, with the development of machinery towards high-speed and high-precision, we must also study the movement changes caused by the above factors.Therefore, since the 1940s, the problem of mechanism accuracy has been raised.Thanks to space technology andmanipulatorandIndustrial robotWith the rapid development of, the problem of mechanism accuracy has attracted more and more attention, and has become an indispensable part of mechanical principles.[2]
teaching method
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(1) Apply the teaching method of combining multimedia with blackboard writing.Give full play to the hardware advantages of the school's digital classroom.Multimedia software and resources have a good effect on raising questions, revealing contradictions, drawing theoretical problems from the engineering background, and cultivating students' ability to find problems.It has obvious effects on expanding the amount of classroom information, enhancing the awareness of engineering practice, carrying out interactive teaching between teachers and students, and strengthening students' understanding and memory of key and difficult points.At the same time, it is also necessary to use blackboard writing to solve the key and difficult points in teaching, and follow the teaching rules from simple to deep, from simple to complex, and from easy to difficult, so that students can easily understand the knowledge they have learned.
(2) In teaching, attention should be paid to highlighting ideas and methods in the simple mathematical derivation process.Therefore, before mathematical derivation, qualitative analysis should be carried out first, so that students can understand "what is the problem?", "what is the nature of the problem?", "what is the method of solving the problem?" Pay special attention to heuristic teaching, less theory and deduction, more analysis and discussion of the problem.
(3) College education should be "teaching people to fish" rather than "teaching people to fish".Therefore, the key in the teaching process is to teach students the way to learn so that they can benefit for life.Sufficient thinking space should be set aside for students, and some questions should be set aside for students to think, learn by themselves, and study;It is necessary to change the "one voice" of teachers, carry out classroom discussions and activate the academic atmosphere.When choosing exercises after class, students should be refined and few, avoid "imitating others", let students think about the knowledge they have learned and apply it to solving problems.
Through the advanced teaching methods and means of this course, students can master more knowledge in a shorter class.Students should not only know the contents of mechanical principles, ways of thinking and problem-solving methods, but also stimulate their passion for exploration and development of the mechanism major, as well as their persistent pursuit of science.
2. Guidance on learning and research methods
This course is a basic technology course, and its most prominent feature is the combination of basic theory and engineering practice.It is necessary to use the knowledge of physics, mathematics, mechanics, mechanical drawing, engineering materials, machinery manufacturing foundation and other prerequisite courses, especially the knowledge of theoretical mechanics.But it is not a simple repetition of these courses, but to guide students to apply what they have learned to solve problems encountered in engineering practice.Therefore, the learning of this course is different from the learning of theoretical courses and professional courses, and has certain characteristics of theoretical system, logic and strong engineering practice.Therefore, when learning this course, we should pay attention to mastering the basic concepts, principles and methods of mechanism analysis and synthesis.
Focus on integrating theory with practiceThis course does not study a specific machine, but focuses on the common problems of general machines, that is, the basic theories and methods of structural analysis and synthesis of mechanisms.These basic theories and methods closely serve the engineering.Therefore, in the learning process of this course, on the one hand, we should pay attention to the rigor and logic of the theoretical establishment and deduction of these theories and methods, and on the other hand, we should pay more attention to how these theories and methods are applied in engineering practice.In addition, we should pay attention to all kinds of machines in our daily life and production at any time to enrich our perceptual knowledge;And use the learned theories and methods to understand and analyze these machines, so as to deepen understanding and promote theory and practice.
Preliminary establishment of engineering viewpointThis course uses many engineering related terms, conformity, formulas, standards and parameters and some commonly used simplification methods for mechanical research, such as inversion, inversion, conversion, equivalent, equivalence, substitution, etc.In the analysis and synthesis of mechanisms, in addition to analytical methods, there are also some practical methods in engineering, such as experimental methods and trial and error methods.Therefore, when learning, we should correctly understand the meaning of nouns, focus on the application of formulas, and focus on mastering the basic principles and practices of the other side's rules.In addition, the actual engineering problems are all problems involving many factors, which can be solved by many methods, and the solutions are generally not unique.This requires designers to have the ability to analyze, judge and make decisions, and to develop the habit of comprehensive analysis and comprehensive consideration of problems, as well as a scientific, rigorous and meticulous work style.
Take each link of teaching seriously: The completion of all teaching work of this course requires self-study, class listening, exercise class, experimental class, homework after class, question answering, examination and other teaching links.To learn this course well, I hope everyone will pay full attention to each teaching link.[3]
