1、Lesson 48 Mechanical VibrationsTerminologyText tour 8/5/20221機械工程專業(yè)英語教程Terminology8/5/20222機械工程專業(yè)英語教程Displacement A vector or the magnitude of a vector from the initial position to a subsequent position assumed by a body位移：物體從起始位置到后來位置的矢量或矢量值Diminish To become smaller or less 變小或減少機械工程專業(yè)英語教程8/5/2022

2、Fourier seriesAn infinite series whose terms are constants multiplied by sine and cosine functions and that can, if uniformly convergent, approximate a wide variety of functions.傅立葉級數(shù)：一個由常數(shù)項與正弦、余弦函數(shù)相乘的無窮級數(shù)，若是一致收斂時，可近似地表示多種函數(shù)。 3To eliminate the adverse effects of most vibration, one of the approaches

3、 is to make a complete study of the equation of motion of the system in question.11. equation of motion 意為“運動方程”。全句可譯為：對于大部分振動而言，避免由其產(chǎn)生的有害影響的一種方式是完整地研究這個系統(tǒng)的運動方程。機械工程專業(yè)英語教程8/5/2022Text tour4Due to the similarities between rectilinear and torsional types of vibration, the discussion and analysis of on

4、e type applyequally well to the other type.22. rectilinear and torsional vibration 意為“直線振動和扭轉(zhuǎn)振動”。全句可譯為：由于直線型振動和扭轉(zhuǎn)型振動存在著相似性，對于一種類型的討論和分析同樣適用于另一種類型。機械工程專業(yè)英語教程8/5/20225In the presence of friction, that portion of motion not sustained by the sinusoidal excitation force will gradually die out.33. sinusoi

5、dal excitation force意為“正弦激振力”。全句可譯為：在有摩擦存在的情況下，不是由正弦激振力支持的那部分振動將逐漸停止。Damping, in its various forms such as air damping, fluid friction, Coulomb dry friction, magnetic damping, internal damping, etc., will always slow down the motion, and cause the eventual dying out of the oscillation.44. magnetic d

6、amping, internal damping意為“磁阻尼，內(nèi)阻尼”。全句可譯為：以諸如空氣阻尼，流體摩擦，庫侖干摩擦，磁阻尼，內(nèi)阻尼等形式存在的阻尼將會使運動減慢，并且最終使振動停止。機械工程專業(yè)英語教程8/5/20226If a resonance is not damped, the displacement of the mass and hence the stretching of the spring element will tend towards infinity.55. displacement of the mass意為“質(zhì)量的位移”。全句可譯為：如果產(chǎn)生共振的系統(tǒng)是

7、無阻尼的，那么質(zhì)量的位移和彈簧的伸長量將趨于無窮大。Thus, if a mechanical component such as a spring is subjected to repetitive or cyclical applications of stress levels much lower than the ultimate strength, it will fracture after a large number of repetitions of this stress.66. repetitive or cyclical applications of stress

8、 意為“重復(fù)或周期性應(yīng)力的作用”。全句可譯為：因為像彈簧這樣的機械零件，在比其極限強度低很多的重復(fù)應(yīng)力或周期性應(yīng)力下，經(jīng)過很多次的重復(fù)作用之后也會發(fā)生斷裂。機械工程專業(yè)英語教程8/5/20227The underlying mechanism in fatigue appears to be the gradual unzipping of intermolecular bonds starting from a defect or weakness in the molecular structure.77. underlying mechanism 意為“基本理論”。全句可譯為：疲勞方面的

9、基本理論認為，分子之間的鍵是被從分子結(jié)構(gòu)有缺陷或薄弱的地方逐漸拉開的。Such noise can be psychologically annoying to human beings working in the environment and can render normal voice communication impossible.88. 全句可譯為：這種噪聲會使處于這個環(huán)境中工作的人們在精神上感到煩躁，并會使人們不能以正常的聲音進行交流。8機械工程專業(yè)英語教程8/5/20229. single-degree-of-freedom 意為“單自由度”。The periodic mo

10、tion of vibration, whether simple or complex, may be considered to be composed of SHM, or a number of SHM of various amplitudes and frequencies bymeans of a Fourier series.1010. Fourier series 意為“傅立葉級數(shù)”。全句可譯為：振動的周期性運動，不管是簡單的還是復(fù)雜的，都可以認為是由簡諧運動組成的，或者是由用傅立葉級數(shù)表示的很多振幅不同和頻率不同簡諧運動來組成的。9機械工程專業(yè)英語教程8/5/2022Man

11、y vibration problems in engineering are nonlinear in nature, i.e. the restoring forces are not proportional to the displacements and the damping forces are not proportional to the first power of the velocity.1111. first power 意為“一次方，一次冪”。全句可譯為：工程上的許多問題在其本質(zhì)上是非線性的，也就是說恢復(fù)力并不與位移成正比，而且阻尼力也不與速度的一次方成正比。An essential difference in the study of nonlinear systems is that a general soluti