本文選題：多胞材料 + 應(yīng)力波　； 參考：《中國科學(xué)技術(shù)大學(xué)》2016年博士論文

【摘要】：多胞材料具有優(yōu)越的抗爆炸抗沖擊性能,常被用作車輛,高鐵,航空航天等領(lǐng)域的能量吸收結(jié)構(gòu)和耐撞裝置。在準(zhǔn)靜態(tài)加載速率下,多胞材料的應(yīng)力應(yīng)變曲線呈現(xiàn)出彈性段、平臺(tái)段和壓實(shí)段,且該應(yīng)力應(yīng)變曲線可以認(rèn)為是多胞材料在準(zhǔn)靜態(tài)下的本構(gòu)行為。在動(dòng)態(tài)沖擊下,多胞材料的力學(xué)行為表現(xiàn)出變形局部化和應(yīng)力增強(qiáng)兩個(gè)特征,但其動(dòng)態(tài)應(yīng)力應(yīng)變曲線到目前為止并不清楚。最近,Zheng等通過細(xì)觀有限元模型結(jié)合局部應(yīng)變場和邊界應(yīng)力得到了多胞材料在高速?zèng)_擊下的應(yīng)力應(yīng)變狀態(tài)點(diǎn),并提出了相應(yīng)的率相關(guān)、剛性-塑性硬化(D-R-PH)沖擊波模型,但該研究也僅僅適用于高速?zèng)_擊下的情形。在中等沖擊速度下,多胞材料的變形模式不再是逐層壓潰的壓縮行為,很難再通過單一的沖擊波理論來進(jìn)行近似表征,故在中等沖擊速度下的多胞材料的力學(xué)行為研究變得極為困難。本文利用波傳播法(該方法不需要依賴于材料本構(gòu)或沖擊波假定)研究多胞材料在動(dòng)態(tài)沖擊下的應(yīng)力應(yīng)變狀態(tài)點(diǎn),揭示了多胞材料在不同沖擊速度下的應(yīng)力應(yīng)變曲線,并得到了一條完整的、唯一的動(dòng)態(tài)應(yīng)力應(yīng)變曲線。除此之外,本文還探究了多胞犧牲層在爆炸載荷下的動(dòng)態(tài)力學(xué)性能,并提出了多胞犧牲層臨界長度的經(jīng)驗(yàn)公式和漸近解。波傳播法是通過材料試樣傳播信息結(jié)合初始/邊界條件來反推材料的應(yīng)力應(yīng)變曲線的一種方法,其最大優(yōu)勢為不需要提前引入材料試樣的本構(gòu)假定。本文基于多胞材料的細(xì)觀有限元模型的Taylor沖擊實(shí)驗(yàn),通過Lagrangian分析法(一種波傳播法)研究了多胞材料的動(dòng)態(tài)力學(xué)行為并得到了多胞材料在不同沖擊速度下的局部應(yīng)力應(yīng)變曲線。局部應(yīng)力應(yīng)變曲線呈現(xiàn)出彈性加載,塑性變形和彈性卸載三個(gè)階段,通過提取局部應(yīng)力應(yīng)變曲線中卸載段前的臨界應(yīng)力應(yīng)變狀態(tài)點(diǎn),本文得到一條動(dòng)態(tài)應(yīng)力應(yīng)變曲線。該動(dòng)態(tài)應(yīng)力應(yīng)變曲線與Taylor沖擊實(shí)驗(yàn)的初速度無關(guān),卻依賴于多胞材料的變形模式(準(zhǔn)靜態(tài),過渡和沖擊模式)。與準(zhǔn)靜態(tài)應(yīng)力應(yīng)變曲線比較,動(dòng)態(tài)應(yīng)力應(yīng)變曲線中的壓實(shí)段表現(xiàn)出更強(qiáng)的塑性硬化效應(yīng),由此可得出多胞材料的率效應(yīng)在動(dòng)態(tài)沖擊研究中并不能被忽略。在沖擊模式下,多胞材料的壓實(shí)應(yīng)變比準(zhǔn)靜態(tài)下的應(yīng)變大很多,該現(xiàn)象表明在動(dòng)態(tài)沖擊下,多胞材料被壓得更加密實(shí)；而在過渡模式下,多胞材料的動(dòng)態(tài)應(yīng)力明顯比準(zhǔn)靜態(tài)應(yīng)力高,表明在過渡模式下的局部慣性效應(yīng)并不能忽略。本文還進(jìn)一步分析了多胞材料的應(yīng)變率敏感性和速率敏感性,結(jié)果表明多胞材料的初始?jí)簼?yīng)力表現(xiàn)出明顯的應(yīng)變率敏感性,而壓實(shí)段呈現(xiàn)出速率敏感性。在高速?zèng)_擊下,多胞材料的動(dòng)態(tài)行為可以通過沖擊波模型近似表征。然而許多沖擊波模型參數(shù)確定均基于多胞材料的準(zhǔn)靜態(tài)應(yīng)力應(yīng)變曲線,并沒有考慮動(dòng)態(tài)下的應(yīng)力應(yīng)變特征。本文通過提取多胞材料在動(dòng)態(tài)沖擊下的特征關(guān)系,如沖擊波速度和沖擊速度之間的關(guān)系,波后應(yīng)變和沖擊速度之間的關(guān)系等,分析各個(gè)沖擊波模型的合理性和可靠性。結(jié)果表明在高速?zèng)_擊下,率相關(guān)、剛性-塑性硬化模型能很好地表征多胞材料的動(dòng)態(tài)行為。根據(jù)跨過沖擊波波陣面的守恒條件,給出了反測多胞材料的D-R-PH沖擊波模型參數(shù)的實(shí)驗(yàn)方法。在應(yīng)用方面,多胞材料具有優(yōu)越的能力吸收和抗爆炸性能。本文采用剛性-塑性硬化模型(R-PH)分析了多胞犧牲層在爆炸載荷下的力學(xué)性能。對多胞犧牲層在三角爆炸載荷作用下的應(yīng)力波傳播建立了一維沖擊波模型,得到了沖擊波在多胞犧牲層中傳播的控制方程,并揭示了沖擊波在多胞犧牲層中的傳播特征。通過參數(shù)分析法揭示了多胞犧牲層中附加質(zhì)量塊質(zhì)量和爆炸載荷強(qiáng)度對犧牲層設(shè)計(jì)結(jié)果的影響。本文還將基于剛性-塑性硬化模型(R-PH)和剛性-理想塑性-鎖定模型(R-PP-L)設(shè)計(jì)的多胞犧牲層的抗爆炸性能進(jìn)行對比,說明基于R-PP-L模型設(shè)計(jì)的多胞犧牲層存在著風(fēng)險(xiǎn)性和不合理性。多胞犧牲層的臨界長度,即犧牲層恰好吸收完爆炸載荷時(shí)的長度,為工程設(shè)計(jì)比較關(guān)心的一個(gè)指標(biāo)。因此,本文通過量綱分析研究了多胞犧牲層臨界長度,分析結(jié)果表明多胞犧牲層臨界長度主要跟三個(gè)無量綱參數(shù)有關(guān)系,并通過控制變量法得到了多胞犧牲層的經(jīng)驗(yàn)公式。本文進(jìn)一步通過正則攝動(dòng)法分析得到了多胞犧牲層臨界長度的漸近解。然而,復(fù)雜的漸近解形式將限制其在工程設(shè)計(jì)中的應(yīng)用,所以本文建議在工程設(shè)計(jì)中應(yīng)當(dāng)選擇形式簡單的經(jīng)驗(yàn)解作為多胞犧牲層的臨界長度設(shè)計(jì)標(biāo)準(zhǔn)。最后,通過基于三維Voronoi技術(shù)的細(xì)觀有限元模型驗(yàn)證了基于R-PH材料模型的多胞犧牲層的設(shè)計(jì)準(zhǔn)則。
[Abstract]:Multi cell materials have excellent anti blast resistance and are often used as energy absorption structures and crashworthiness devices in vehicles, high speed iron, aerospace and other fields. Under quasi static loading rate, the stress-strain curves of multi cell materials show elastic segments, platform segments and compaction sections, and the stress strain curves can be considered as quasi static multi cell materials. Under dynamic impact, the mechanical behavior of multi cell materials shows two characteristics of deformation localization and stress enhancement, but the dynamic stress-strain curve is not clear so far. Recently, Zheng and so on through the mesoscopic finite element model combined with the local strain field and boundary stress to get the multi cell material under high speed impact. In the stress strain state point, the corresponding rate correlation, the rigid plastic hardening (D-R-PH) shock wave model is proposed, but the study is only applicable to the case under high velocity impact. Under the medium impact velocity, the deformation mode of the multi cell material is no longer the compression behavior of the laminating pressure, and it is difficult to use the single shock wave theory to make the approximate table. It is very difficult to study the mechanical behavior of multi cell materials at medium impact velocity. In this paper, the stress strain state of multi cell materials under dynamic impact is studied by wave propagation method (this method does not depend on material constitutive or shock wave hypothesis), and the stress-strain curves of multi cell materials under different shock velocities are revealed. A complete, unique dynamic stress-strain curve is obtained. In addition, the dynamic mechanical properties of the multi cell sacrificial layer under the explosive load are also explored, and the empirical formula and asymptotic solution of the critical length of the multi cell sacrificial layer are proposed. The wave propagation method is used to reverse the material through the material sample propagation information combined with the initial / boundary conditions. A method for the stress-strain curve of the material is the greatest advantage of the constitutive assumption that the material specimen is not needed in advance. Based on the Taylor impact test of the meso finite element model of the multi cell materials, the dynamic mechanical behavior of the multi cell materials is studied by Lagrangian analysis (a wave propagation method) and the multi cell materials are obtained in different types. The local stress-strain curve under the impact velocity. The local stress-strain curve shows three stages of elastic loading, plastic deformation and elastic unloading. By extracting the critical stress and strain state point before the unloading section of the local stress strain curve, a dynamic stress-strain curve is obtained. The dynamic stress-strain curve and the Taylor impact compaction curve are obtained. The initial velocity is independent of the initial velocity, but depends on the deformation mode of multi cell materials (quasi-static, transition and impact modes). Compared with the quasi-static stress-strain curve, the compaction section in the dynamic stress-strain curve shows a stronger plastic hardening effect. Thus, the rate effect of multi cell materials can not be ignored in the dynamic impact study. Under the model, the compacted strain of multi cell material is much larger than that under quasi-static strain. This phenomenon indicates that under dynamic impact, the multi cell material is compacted more densely, and the dynamic stress of multi cell material is obviously higher than that of quasi-static stress in the transition mode, which indicates that the local inertia effect in the transition mode can not be ignored. The strain rate sensitivity and rate sensitivity of multi cell materials are analyzed. The results show that the initial crushing stress of multi cell materials shows obvious strain rate sensitivity, while the compaction section shows the rate sensitivity. Under the high velocity impact, the dynamic behavior of multi cell materials can be approximated by the shock wave model. However, many parameters of the shock wave model are parameters. The quasi static stress-strain curve based on multi cell materials is determined, and the dynamic stress-strain characteristics are not taken into account. In this paper, the relationship between the dynamic impact of multi cell materials, such as the relationship between the velocity of shock wave and the velocity of shock, the relationship between the post wave strain and the impact velocity, is extracted, and the rationality of the shock wave model is analyzed. The results show that the rigid plastic hardening model can characterize the dynamic behavior of multi cell material well under the high velocity impact, and the rigid plastic hardening model can well characterize the dynamic behavior of the multi cell materials. According to the conservation conditions of the cross impact wave front, the experimental method of the D-R-PH shock wave model parameters of the multi cell material is given. The mechanical properties of the multi cell sacrificial layer under the explosive load are analyzed by the rigid plastic hardening model (R-PH). The one-dimensional shock wave model is established for the propagation of the stress wave of the multi cell sacrificial layer under the triangle explosion load, and the control equation of the shock wave propagating in the multi cell sacrificial layer is obtained, and the impact is revealed. The influence of the mass of mass and the strength of the explosive load on the design results of the sacrificial layer in the multi cell sacrificial layer is revealed by the parameter analysis method. The anti explosion properties of the multi cell sacrificial layer based on the rigid plastic hardening model (R-PH) and the rigid ideal plastic locking model (R-PP-L) are also designed in this paper. The comparison shows that the multi cell sacrificial layer based on the R-PP-L model has the risk and unreasonableness. The critical length of the multi cell sacrificial layer, that is, the length of the sacrificial layer exactly absorbs the length of the explosion load, is a more concerned indicator for the engineering design. Therefore, the critical length of the multi cell sacrificial layer is studied by the dimensional analysis, and the analysis of the critical length of the multi cell sacrificial layer is analyzed. The results show that the critical length of the multi cell sacrificial layer is mainly related to the three dimensionless parameters, and the empirical formula of the multi cell sacrificial layer is obtained by the control variable method. In this paper, the asymptotic solution of the critical length of the multi cell sacrificial layer is obtained by the canonical perturbation method. However, the complex asymptotic form will limit its engineering design. Therefore, this paper suggests that in engineering design, a simple form of empirical solution should be chosen as the critical length design standard for the multi cell sacrificial layer. Finally, the design criteria of the multi cell sacrificial layer based on the R-PH material model are verified by the mesoscopic finite element model based on the three-dimensional Voronoi technology.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TB301

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