本文選題：沖擊動(dòng)力學(xué) + 多孔材料　； 參考：《中北大學(xué)》2017年碩士論文

【摘要】：多孔金屬有良好的沖擊緩沖功能,在軍用民用兩方面都有重要的應(yīng)用背景,它涉及到?jīng)_擊動(dòng)力力學(xué)等多個(gè)領(lǐng)域,還有許多值得深入研究的問題。本文首先對(duì)多孔金屬在沖擊作用下的本構(gòu)關(guān)系進(jìn)行了研究,重點(diǎn)討論了多孔金屬的沖擊Hugoniot方程與孔隙率的關(guān)系,以及多孔金屬在Hugoniot彈性限及以以下的沖擊行為。詳細(xì)分析了多孔材料沖擊絕熱線的三種不同的計(jì)算方法的算法和精度,并提出了一種三段式多孔金屬?zèng)_擊本構(gòu)關(guān)系的計(jì)算方法。應(yīng)用應(yīng)力波的特征線法對(duì)爆炸加載方式下多孔金屬的沖擊響應(yīng)進(jìn)行了研究。主要分析了沖擊波的初始參數(shù)及沖擊波的衰減過程及衰減程度。結(jié)果表明,在相同的爆炸加載條件下,多孔金屬大大減小初始沖擊波的峰值壓力。多孔金屬的基體材料對(duì)沖擊的衰減程度有所區(qū)別,沖擊阻抗越大的金屬其相應(yīng)的多孔材料對(duì)沖擊波的衰減也越強(qiáng)。炸藥的種類、長度及約束情況對(duì)爆炸加載下多孔金屬的沖擊響應(yīng)也有影響。炸藥性質(zhì)主要影響多孔金屬中初始沖擊波的強(qiáng)度,爆速越大,初始沖擊波強(qiáng)度越大。炸藥長度及約束情況影響多孔金屬中沖擊波的衰減速度,炸藥長度越大,側(cè)向約束越強(qiáng),則多孔金屬中沖擊波的衰減速度越慢。在對(duì)多孔材料均相材料模型和應(yīng)力波特征線法不足的分析基礎(chǔ)上,研究了可將多孔金屬看作均相材料的臨界指標(biāo)。該指標(biāo)可定義為多孔金屬內(nèi)部孔洞的平均直徑,其臨界尺寸與沖擊波的上升沿寬度在同一量級(jí),其范圍大致10~(-3)mm~10~(-1)mm之間�？锥吹倪B通性對(duì)多孔金屬的緩沖吸能性能也有重要影響。影響的機(jī)理主要在于孔內(nèi)氣體的沖擊壓縮性及開孔的閉合。用顯式動(dòng)力學(xué)軟件對(duì)孔洞形狀的影響進(jìn)行了數(shù)值模擬研究。結(jié)果表明,對(duì)于圓形、正方形、六邊形和三角形等簡單形狀的孔洞,六邊形和三角形孔洞的多孔金屬對(duì)沖擊波的誤差效果最好,圓形的稍差,而正方形的最差。對(duì)多孔金屬的沖擊升溫進(jìn)行了分析。升溫能量來源包括基體金屬的絕熱塑性變形,孔洞壁面的摩擦,孔洞閉合氣體絕熱壓縮,以及孔洞閉合引起的表面能釋放。以鎢顆粒為代表的多孔金屬的沖擊過程進(jìn)行了數(shù)值模擬,得到?jīng)_擊過程中孔隙閉合的速度與特征時(shí)間,并依據(jù)模擬結(jié)果對(duì)摩擦表面的升溫進(jìn)行了計(jì)算。計(jì)算結(jié)果與理論分析結(jié)果一致。分析了金屬熔點(diǎn)變化與壓力間的關(guān)系,并對(duì)比了多孔鎢中摩擦表面局部的溫度與其在高壓下的熔點(diǎn)數(shù)據(jù)。結(jié)果表明,在沖擊作用下多孔金屬內(nèi)可發(fā)生局部熔化。對(duì)多孔材料的中沖擊能量的沉積機(jī)理進(jìn)行了簡單討論,主要有塑性功、缺陷生成、相變等方式的能量沉積。由于多孔結(jié)構(gòu)的性質(zhì),這些能量沉積機(jī)理的作用強(qiáng)度高于密實(shí)介質(zhì)。
[Abstract]:Porous metals have good shock buffering function and have important application background in both military and civil fields. They are involved in many fields such as impact dynamic mechanics and so on. In this paper, the constitutive relation of porous metal under impact is studied, and the relation between the Hugoniot equation and porosity, the elastic limit of porous metal under Hugoniot and the impact behavior of porous metal are discussed. The algorithm and accuracy of three different calculation methods for porous material impact hot wire are analyzed in detail. A calculation method for the constitutive relation of three-segment porous metal impact is proposed. The impact response of porous metal under explosive loading was studied by means of the characteristic line method of stress wave. The initial parameters of shock wave, the attenuation process and attenuation degree of shock wave are analyzed. The results show that the peak pressure of initial shock wave is greatly reduced by porous metal under the same explosion loading condition. The attenuation of shock wave is different in the matrix of porous metal, and the higher the impact impedance is, the stronger the attenuation of shock wave is with the corresponding porous material. The type, length and constraint of explosive also affect the shock response of porous metal under explosive loading. The strength of the initial shock wave in porous metal is mainly affected by the explosive properties, and the larger the detonation velocity is, the greater the initial shock wave intensity is. The length and confinement of explosive affect the attenuation rate of shock wave in porous metal. The longer the length of explosive, the stronger the lateral constraint, the slower the attenuation rate of shock wave in porous metal is. Based on the analysis of the shortage of homogeneous material model and stress wave characteristic line method, the critical index of porous metal as homogeneous material is studied. This index can be defined as the average diameter of the pores in the porous metal. The critical size is about the same order of magnitude as the rising edge width of the shock wave, and its range is approximately 10~(-3)mm~10~(-1)mm. The connectivity of pores also has an important effect on the energy absorption performance of porous metals. The mechanism of influence mainly lies in the impact compressibility of gas in the pore and the closure of the opening. The influence of the hole shape was simulated by explicit dynamics software. The results show that for the holes with simple shapes such as circular square hexagon and triangle the error of shock wave of hexagonal and triangular holes is the best the circle is slightly worse and the square is the worst. The impact heating of porous metals was analyzed. The sources of heating energy include adiabatic plastic deformation of the matrix metal, friction on the wall of the cavity, adiabatic compression of the closed gas, and the release of surface energy due to the closure of the hole. The impact process of porous metal represented by tungsten particles was numerically simulated, and the velocity and characteristic time of pore closure during impact process were obtained, and the temperature rise of friction surface was calculated based on the simulation results. The calculated results are in agreement with the theoretical analysis results. The relationship between melting point change and pressure was analyzed, and the local temperature of friction surface in porous tungsten was compared with the melting point data at high pressure. The results show that local melting can occur in the porous metal under impact. The deposition mechanism of impact energy in porous materials is briefly discussed, including plastic work, defect generation, phase transformation and so on. Due to the properties of porous structure, the action intensity of these energy deposition mechanisms is higher than that of dense medium.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG14;TB383.4

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