本文選題：軸向靜應(yīng)力 + 波長　； 參考：《江西理工大學(xué)》2015年碩士論文

【摘要】：近年來,針對地震頻繁發(fā)生和爆破拆除建(構(gòu))筑物和開挖各類地下巖土體工程的實(shí)際,為了達(dá)到防災(zāi)減災(zāi)和安全高效施工的目的,應(yīng)力波在各類巖土體或混凝土介質(zhì)中的傳播特性一直是研究的熱點(diǎn)領(lǐng)域之一。爆破應(yīng)力波在地下巖體中傳播時(shí),距震源不同距離的圍巖已具有大小不等的靜應(yīng)力,這主要有以下兩方面引起的:一是原巖應(yīng)力大小本身隨空間的變化而變化;二是地下工程巖體開挖卸荷導(dǎo)致附近圍巖體中的應(yīng)力場發(fā)生較大變化。針對此工程背景,本文提出研究軸向靜應(yīng)力對入射應(yīng)力波的影響,首先分析了軸向均勻靜應(yīng)力對入射半正弦波的振幅、角頻率和波初相的影響規(guī)律;接著分析了軸向均勻靜應(yīng)力對應(yīng)力波畸變的影響;最后將變化的初始應(yīng)力簡化為線性梯度載荷,研究梯度應(yīng)力對彈性桿中應(yīng)力波幅值、波長的影響。主要研究內(nèi)容與結(jié)論如下:(1)通過理論推導(dǎo),研究了彈性桿中軸向均勻靜應(yīng)力的大小與入射半正弦波的振幅、角頻率、初相的關(guān)系。當(dāng)沖頭以相同的速度共軸撞擊具有軸向均勻靜應(yīng)力的彈性桿時(shí),軸向均勻靜應(yīng)力的大小影響入射半正弦波的角頻率,隨著軸向均勻靜應(yīng)力的增大,入射半正弦波的角頻率逐漸的增大;軸向均勻靜應(yīng)力的大小影響入射半正弦波的初相,軸向均勻靜應(yīng)力越大,入射正弦波的初相的絕對值越大,但增量很小,表現(xiàn)為起跳點(diǎn)越滯后。(2)針對在實(shí)驗(yàn)中獲得的入射波在卸載段出現(xiàn)負(fù)值(“翹起”)情況進(jìn)行了簡要分析,研究了軸向均勻靜應(yīng)力對透射波波長、幅值的影響。軸向均勻靜應(yīng)力使得入射波在卸載段時(shí)出現(xiàn)應(yīng)力不平衡,使得入射桿中質(zhì)點(diǎn)反向振動(dòng),從而出現(xiàn)“翹起”現(xiàn)象,且軸向均勻靜應(yīng)力越大,“翹起”值也越大,其值也為軸向均勻靜應(yīng)力的一半;軸向均勻靜應(yīng)力也會(huì)影響透射波的幅值,軸向均勻靜應(yīng)力越大,幅值越小;軸向均勻靜應(yīng)力還會(huì)影響透射波的波長,軸向均勻靜應(yīng)力越大,波長越小。(3)取均質(zhì)圓桿中的單位長度進(jìn)行受力分析,利用牛頓第二定律推導(dǎo)出在具有梯度應(yīng)力細(xì)長桿中應(yīng)力波的波動(dòng)方程,通過行波法求解該波動(dòng)方程的通解,并與無梯度應(yīng)力波動(dòng)方程的通解比較,可得:細(xì)長圓桿中的梯度應(yīng)力影響應(yīng)力波幅值,梯度應(yīng)力越大,應(yīng)力波的幅值衰減的越快,表現(xiàn)在應(yīng)力波的幅值隨著k的增大而減小;細(xì)長圓桿的彈性模量也會(huì)影響應(yīng)力波幅值的衰減速度,在梯度應(yīng)力不變的情況下,彈性模量越大,應(yīng)力波幅值衰減的越慢;細(xì)長圓桿中的梯度應(yīng)力還會(huì)影響應(yīng)力波的波長,梯度應(yīng)力越大,應(yīng)力波的波長越小,表現(xiàn)在應(yīng)力波的波長隨著k的增大而減小。
[Abstract]:In recent years, in order to achieve the purpose of disaster prevention and mitigation and safe and efficient construction, in view of the frequent occurrence of earthquakes and blasting demolition of building (construction) and excavation of various underground rock and soil engineering, The propagation characteristics of stress waves in various rock, soil and concrete media have been one of the hot research fields. When the blasting stress wave propagates in the underground rock mass, the surrounding rock with different distance from the earthquake source already has the different static stress, which is mainly caused by the following two aspects: first, the original rock stress itself changes with the change of the space; Second, the stress field of surrounding rock mass in the surrounding rock is changed greatly by excavation and unloading of underground engineering rock mass. In view of this engineering background, the influence of axial static stress on incident stress wave is studied. Firstly, the influence of axial uniform static stress on the amplitude, angular frequency and initial phase of incident semi-sinusoidal wave is analyzed. Then the influence of axial uniform static stress on the distortion of force wave is analyzed and the change of initial stress is reduced to linear gradient load. The influence of gradient stress on the amplitude and wavelength of stress wave in elastic rod is studied. The main contents and conclusions are as follows: (1) by theoretical derivation, the relationship between the magnitude of axial uniform static stress and the amplitude, angular frequency and initial phase of the incident semi-sinusoidal wave is studied. When the punch impinges the elastic rod with uniform axial static stress at the same velocity, the magnitude of the axial uniform static stress affects the angular frequency of the incident half-sine wave, and increases with the increase of the axial uniform static stress. The angular frequency of the incident half-sine wave increases gradually, the magnitude of axial uniform static stress affects the initial phase of the incident half-sine wave, the greater the axial uniform static stress is, the greater the absolute value of the initial phase of the incident sine wave is, but the increment is very small. The effect of axial uniform static stress on the length and amplitude of transmission wave is studied. The axial uniform static stress makes the incident wave unbalance in the unloading section, which causes the reverse vibration of the particle in the incident rod, thus the phenomenon of "warping" occurs, and the greater the axial uniform static stress, the greater the "warp" value. The axial uniform static stress also affects the amplitude of the transmission wave, the larger the axial uniform static stress, the smaller the amplitude, and the greater the axial uniform static stress will affect the wavelength of the transmission wave, the greater the axial uniform static stress. The smaller the wavelength is, the smaller the unit length of the circular rod is, and the second Newton's law is used to deduce the wave equation of the stress wave in the slender rod with gradient stress. The general solution of the wave equation is solved by the traveling wave method. Compared with the general solution of the non-gradient stress wave equation, it can be concluded that the gradient stress affects the amplitude of the stress wave in the slender circular rod. The larger the gradient stress, the faster the amplitude attenuation of the stress wave, which is shown in that the amplitude of the stress wave decreases with the increase of k; The elastic modulus of slender circular rod will also affect the attenuation speed of stress wave amplitude. The larger the elastic modulus is, the slower the attenuation of stress wave amplitude is, and the gradient stress in slender circular rod will also affect the wavelength of stress wave. The larger the gradient stress, the smaller the wavelength of the stress wave, which is manifested in that the wavelength of the stress wave decreases with the increase of k.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU45

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