Vibration (vibration) vibration Vibration (known as oscillation) refers to a state change process. That reciprocating motion of objects. In high school physics, quantitative research (you can use formula, mapping method, to determine the values given in the list of law), only the four most simple movement: uniform speed linear motion, uniform circular motion, projectile motion and harmonic vibration . Complex motion, you can rely on these four sports, qualitative research. If you insist on a quantitative study of complex movement, but also rely on these four sports for similar studies. The four most simple movement, uniform speed linear motion and projectile motion is "gone" campaign, the state of motion (position, velocity) versus time is topology (one to one), non- repeated. Uniform circular motion and simple harmonic motion, standing in a long perspective (or "macro-look"), is cyclical, repetitive. Standing within a period of time to see (or "micro-look"), is a topology, unrepeatable. Thus, the latter two sports, than the previous two movements, much more complex. Harmonic vibration can be seen in both directions along the orthogonal uniform circular motion (that is, perpendicular to each other) in the decomposition (is projected), either one direction of motion, are harmonic vibration. It can be seen, much more complex than simple harmonic motion uniform circular motion. Projectile motion can be broken down into: a uniform orthogonal linear motion and another uniform speed linear motion, so the projectile motion than the uniform speed linear motion is much more complicated. In uniform circular motion the process for the orthogonal decomposition of the original size of the same centripetal force, becomes the size and direction changes periodically restoring force. Simple harmonic motion is complicated enough. So simple harmonic vibration on quantitative research to date. Often, however, the situation we encountered micro-vibrations, must be much more complex than simple harmonic motion. Therefore, the study of the transition to the study of simple harmonic vibration, heat and vibration, you need insight, imagination and abstract thinking ability, logical reasoning. Harmonic vibration is characterized by: 1, there is an equilibrium position (after mechanical energy is exhausted, the only position transducer should be stationary). 2, the size and direction of a periodically varying restoring force. 3, a single frequency, constant amplitude. Vibration transducer is an abstract object: Ignore the shape and size of the object, instead of objects with particle research. The vibrating object instead of the particle, called the vibrator. Position of the transducer at a moment in which, by means of displacement x. Displacement x is in equilibrium position as the reference (bps - reference point), get the "position of the transducer in a moment in which" the distance and direction. When we conduct research on uniform speed linear motion and projectile motion, the reference point in the campaign to _select_ a starting point. When we study uniform circular motion and simple harmonic motion, _select_ the reference point in the center or equilibrium position (fixed point). Reference is supposed to be kept stationary during the study (or assumed to be stationary) point, our physical thinking is, "from the amount determined amount of unchanged starting to study." The amount determined by the same amount and are essentially different, even when the speed of the linear motion and projectile motion study, the reference point in the campaign to _select_ a starting point. This amount is determined, it is not necessarily the same amount. In particular, we study the segment, the end of each stage, the next stage is the starting point. We chose the starting point of the movement as a reference point, you can simplify the research process, which is the principle of "simplify" obedience in physics research, therefore, at different stages of research, _select_ a different reference point. In examining the uniform circular motion and simple harmonic motion, because periodic topology on macro and micro, the problem is very complex, so you can not choose the starting point of the movement, as a reference point to study, and to determine and _select_ the same center or equilibrium position, the reference point for research, but also subject to "simplify" the principle of physics. In the harmonic vibration, the amplitude A is the maximum displacement x, which is a constant amount. Vibrator from one state (position and velocity) back to the minimum time required for the state, called a cycle T. Vibrator in a cycle, called a full vibration. Vibrator in a second all-vibration "frequency", called the frequency f. T is the cycle time of a full oscillation frequency f is the frequency of vibration within a second whole, so, Tf = 1 (the equivalent of formula IV Formula 1) Circular frequency ω (pronounced [oumiga]) is a second corresponding central angle. A full vibration corresponding central angle is 2π (ie 360 degrees). This is a concept borrowed uniform circular motion. In uniform circular motion, ω is called the angular velocity. When the uniform circular motion orthogonal decomposition of simple harmonic motion, the angular velocity is transformed into the circular frequency. (It was also called the circular frequency angular frequency) Obviously, ω = 2πf (four is equivalent to Equation 3), (corresponding to the number of vibrations per second full angle) ωT = 2π (Medley equivalent Equation 2) (each full vibration corresponding angles) Finally, the definition of full-vibrations per minute to "speed n", apparently, n = 60f (Medley equivalent to Equation 4) T, f, ω, n amount of four, that one, the other three are known, the four equations into each other, is called "four equivalent type." As long as the object periodically reciprocating motion is vibration. For example, shoot the ball, its v-t figure corresponds to the sawtooth electrical engineering, it is also the vibration. Someone said: "shoot the ball no equilibrium position, or center of symmetry equilibrium position is not moving, it can not be considered vibration." People say, certainly did not learn electrical engineering. There is a branch of mathematics called Fourier integral, it can put any vibration, broken down into a number of simple harmonic motion. These harmonic vibration frequency is an integer multiple of the original vibration, the vibration of the original main frequency (pitch), is the smallest of these harmonic vibration frequency. Other multiplier (overtone), the amplitude is much smaller than the pitch. Therefore, this constitutes a "timbre" of the concept of non-harmonic oscillation. Sounding body of the human ear to distinguish the process is spontaneous, automated, instinctively using the Fourier integral process, very clever. Since the frequency of the sound determined by the sound source, so that, regardless of the wave propagation to our ears, we still accurate way recognizable characteristics of sounding bodies. Broadly speaking the vibration state of the system is the description of the parameters (such as displacement, voltage) at its upper and lower reference values alternating process. Narrowly refers to mechanical vibration, namely mechanical system vibration. Electromagnetic vibration commonly called oscillation. Mechanical vibration system can be maintained, must be flexible and inertia. Since the elastic system from its equilibrium position, a restoring force is generated, the system returns to the original position to procure; due to inertia, the system returns to the equilibrium position of the kinetic energy accumulated during, so that the system beyond the equilibrium position to the other side of the movement. It is because of the elastic and inertial interaction that has caused the vibration system. According to the system of freedom of movement, a single degree of freedom system vibration (such as the pendulum vibration) and multi-freedom vibration systems. Multi-degree of freedom system with finite discrete system corresponding to the vibration described by ordinary differential equations; infinite number of degrees of freedom systems and continuous systems (such as rods, beams, plates, shells, etc.) corresponds to the vibration by partial differential equations. Equation does not include time system called autonomous systems; said non-autonomous systems with significant time. By the forces of the system, there is freedom of vibration, vibration and forced vibration attenuation. By elastic and damping forces of nature, there is a linear vibration and nonlinear vibration. Vibration can be divided into deterministic and random vibration, which is non-deterministic rules, such as vehicles traveling in the bumps. Vibration is a common phenomenon in nature and engineering. Vibration negative aspects are: the impact of equipment function, reduce working precision machinery and equipment, increased component wear, fatigue and even cause structural damage; positive aspects of vibration is: There are many require the use of vibration equipment and processes (such as vibration transmission, vibration grinding vibrating pile, etc.). The basic task is to discuss the analysis of vibration excitation of the system (i.e., input means external system disturbances, also known as interference), the response (i.e., the output means that the reaction system after activation), and the dynamic characteristics (or physical parameters) of the three Relations between. After the 1960s, significant advances in computer technology and vibration testing for utilization analysis, experimental and computational methods to solve vibration problems has opened up broad prospects. Mechanical vibration is an object (or a portion of the object) for reciprocating movement in the vicinity of the balanced position (position of the object at rest). Can be divided into free vibration, forced vibration. Can be divided into no damping vibration and vibration damping. Common harmonic oscillator model sports a spring pendulum model. Vibrations in the machinery industry applications: Application of the mechanical vibration is very common in the vibrating screen industry, for example the basic principles of the system, by mounting the lower end of the motor shaft, a weight (weight uneven Heng), the rotary motion of the motor into a horizontal, vertical, inclined three dollar campaign, then the campaign to convey to the screen surface. If the weight change of the phase angle of the vertical portion of the direction of travel of the raw material can be changed.
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Encyclopedia
zhendong Vibration vibration Object through its equilibrium position by a reciprocating movement or physical change in the vicinity of the back and forth the average (or balance). Overview Vibration is one of nature's most common phenomenon. Large as the universe, small subatomic particles, all exist vibration. Various forms of physical phenomena, including sound, light, heat, vibration and so contained. People's lives can not be separated Vibration: vibration of the heart beat, the eardrum and the vocal cords are the indispensable function of the human body; human visual stimulation by light, and the light is essentially also an electromagnetic vibration; life can not be without sound and music, and sound generation, transmission and reception are inseparable from vibration. In the field of engineering technology, vibration phenomena abound. For example, bridges and buildings in gusts vibration or seismic excitation, aircraft and ship during the voyage vibration, machine tools and machining tool vibration, vibration, power machinery, the control system of self-excited vibration, etc. . In many cases, the vibration is considered to be negative. For example, the vibration will affect the function of precision instruments and equipment, reducing precision and smoothness, another drama fatigue and wear components, thereby shortening the life of machines and structures. Vibration may also cause damage to the structure of large deformation, vibration and collapse but had some bridges destroyed; buffeting flutter of an aircraft wing, wheels often cause accidents; travel and cabin vibration load conditions will deteriorate multiply; intense vibrations Noise will form a serious hazard. However, the vibration has its positive side. For example, the vibration is the basis of communication, radio, television, radar and other work. Since the 1950s, there were many in succession using vibration production equipment and processes. For example, the transmission of vibration, vibration screening, vibration grinding, polishing vibration, vibration pile driving, vibration to eliminate stress, and so on. They greatly improved the working conditions, a ten, a hundred times to improve labor productivity. It is expected that with the continuous progress of production practice and scientific research, the use of vibration will increase. Different areas of vibration phenomena although distinctive, but often have similar mechanics mathematical description. It is on the basis of this commonality, it is possible to establish some sort of unified theory to deal with all kinds of vibration problems. Vibration is such a basic discipline, which by means of mathematics, physics, experimental and computational techniques to explore the mechanism of various vibration phenomena, to clarify the basic law of vibration, the vibration in order to overcome the negative factors, the use of the positive factors for the reasonable solution various vibration problems encountered in practice provide a theoretical basis. Classification of mechanical vibration system is the mechanical vibration system (ie, mechanical system) vibration. Any mechanical system, as long as it has elasticity and inertia, vibration may occur. This mechanical system is called vibration system. Vibration system can be divided into two categories, discrete system and continuous system. Continuous systems with parametric continuous distribution, but can be turned into a discrete system by focusing on parametric method. Divided by the degree of freedom vibration system can be classified as a multi-degree of freedom system with limited and unlimited multi-DOF system. The former corresponds to discrete systems, which corresponds with the continuous system. Discrete system parameters from the centralized components. Mechanical system has three components concentrated parameters: quality, springs and dampers. They are idealized mechanical model. Quality (including inertia) is only the inertia of the mechanical model. Meter itself is the quality of the spring, only the resilient "model"; force and the elastic deformation is proportional to a spring, called linear springs. Inertia damper model has neither nor flexible. It is the energy component, resulting in the resistance movement; resistance is proportional to the velocity of a damper, called linear dampers. Discrete systems in engineering have broad representation. For example, fixed on the concrete foundation of precision machine tools, but also laid the foundation under flexible liner (Figure 1 paved with concrete foundations elastic pad machine). When isolation analysis, machine tools and basic need to look at the overall vibration. In this case, taking into account the basic machine and much less flexible than the pad, it can be omitted its elasticity and put them as a lumped mass; the other hand, the quality of the liner mass is much smaller than the machine tools and basic , may be omitted, and the spring pad considered; friction and friction pad itself bound between the foundation and acts as a surrounding damping, they can be taken together as a damper. Thus, the analysis in isolation, this system can be simplified to a discrete system (Figure 2 simplified into discrete systems). Of course, in the analysis of machine vibration or machine itself, the workpiece, tool systems