本文選題：圓柱殼 + 局部表面納米化��； 參考：《大連理工大學(xué)》2014年碩士論文

【摘要】：圓柱殼是工程領(lǐng)域中普遍采用的薄壁結(jié)構(gòu)之一。它具有較高的強(qiáng)度、質(zhì)量輕、低成本、吸能效率高等特點(diǎn),因此,常常作為吸能結(jié)構(gòu)被廣泛應(yīng)用在汽車(chē)、航空航天、船舶等領(lǐng)域,起到緩沖吸能、保護(hù)乘員和關(guān)鍵部件的作用。如何提高吸能結(jié)構(gòu)的能量吸收性能已經(jīng)成為研究人員和工程師非常關(guān)注的問(wèn)題,尤其是在汽車(chē)工程領(lǐng)域。 本文借助于局部表面納米化技術(shù),提出一種新的誘導(dǎo)彈塑性圓柱殼屈曲模態(tài)的方法。采用有限元計(jì)算方法對(duì)局部表面納米化圓柱殼在軸向沖擊載荷作用下從屈曲的開(kāi)始到屈曲的演變整個(gè)屈曲過(guò)程和屈曲模態(tài)變化過(guò)程進(jìn)行數(shù)值模擬。通過(guò)分析局部表面納米化后圓柱殼材料性能的改變和表面納米化分布對(duì)圓柱殼屈曲模態(tài)的影響,提出三類典型的局部表面納米化形狀分布。這三類局部表面納米化形狀分布分別為：沿圓柱殼軸向呈均勻間隔、等環(huán)條帶狀分布；沿環(huán)向呈均勻間隔、等長(zhǎng)條帶狀分布；在圓柱殼表面呈等矩形片狀分布等。這些納米化布局可誘導(dǎo)圓柱殼不同的屈曲模態(tài)及發(fā)展路徑。在此基礎(chǔ)上,提出在圓柱殼表面分區(qū)段局部表面納米化布局。所述的區(qū)段采用不同的納米化區(qū)域布局設(shè)計(jì)、不同的納米化程度,并且在區(qū)段間采用特殊的表面納米化過(guò)渡區(qū)等。實(shí)現(xiàn)沖擊載荷小時(shí)可控制圓柱殼在設(shè)定的區(qū)段發(fā)生局部屈曲,而沖擊載荷大時(shí)整體屈曲并分區(qū)段逐段屈曲演變。這種方法為控制結(jié)構(gòu)屈曲模態(tài)提供了一種設(shè)計(jì)方法。 采用數(shù)值模擬的方法研究納米化區(qū)域數(shù)目、納米化區(qū)域形狀及納米化程度等對(duì)圓柱殼屈曲模態(tài)和能量吸收的影響,分析了局部表面納米化圓柱殼屈曲模態(tài)與其吸收能量的關(guān)系,并通過(guò)分析沖擊力位移曲線和利用比吸能等評(píng)價(jià)指標(biāo)對(duì)圓柱殼的能量吸收性能進(jìn)行了評(píng)估。優(yōu)化出圓柱殼達(dá)到最佳吸能效果(如比吸能最大化)時(shí)的各類納米化區(qū)域形狀參數(shù)和布局參數(shù)。同時(shí)討論了圓柱殼長(zhǎng)度、厚度及沖擊速度等對(duì)圓柱殼屈曲變形模式和能量吸收性能的影響。數(shù)值模擬結(jié)果表明,軸向表面納米化條帶、環(huán)向表面納米化條帶和局部片狀表面納米化布局的圓柱殼的屈曲變形模式與能量吸收性能都明顯優(yōu)于原彈塑性圓柱殼。其次,并不是納米化區(qū)域的密集程度越高,變形模式和吸能性能越好。適當(dāng)?shù)募{米化區(qū)域布局可以使圓柱殼屈曲變形模式和吸能性能同時(shí)達(dá)到最優(yōu)。分區(qū)段表面納米化布局能夠?qū)崿F(xiàn)圓柱殼分區(qū)段漸進(jìn)屈曲并多次吸收能量。這種設(shè)計(jì)方法為分層次和分區(qū)段能量吸收結(jié)構(gòu)提供一種新的設(shè)計(jì)思路。
[Abstract]:Cylindrical shell is one of the widely used thin-walled structures in engineering field. It has the characteristics of high strength, light weight, low cost, high energy absorption efficiency and so on. Therefore, it is widely used as energy absorption structure in automobile, aerospace, ship and other fields. It plays the role of cushioning energy absorption, protecting occupants and key components. How to improve the energy absorption performance of energy absorption structures has become a problem that researchers and engineers pay close attention to, especially in the field of automobile engineering. In this paper, a new method for inducing buckling modes of elastic-plastic cylindrical shells is proposed by means of local surface nanocrystalline technique. The finite element method is used to simulate the whole buckling process and the buckling mode change process of the nanocrystalline cylindrical shells subjected to axial impact loading from the beginning of buckling to buckling. By analyzing the change of material properties and the effect of surface nanocrystalline distribution on buckling mode of cylindrical shells after local surface nanocrystallization, three typical local surface nanocrystalline shape distributions are proposed. The nanocrystalline distribution of these three types of local surfaces are as follows: uniform spaced along the axial direction of cylindrical shell, uniform spaced along the circumferential direction, equilong strip distribution, and uniform rectangular flake distribution on the surface of cylindrical shell, etc. These nanostructures can induce different buckling modes and development paths of cylindrical shells. On this basis, the nanocrystalline arrangement of the local surface on the cylindrical shell surface is proposed. The section is designed with different nanocrystalline area layout and different nanocrystalline degree, and special surface nanocrystalline transition zone is used among the sections. The local buckling of cylindrical shells can be controlled when the impact load is small, while the whole buckling evolves step by step when the impact load is large. This method provides a design method for controlling buckling modes of structures. The effects of the number of nanocrystalline region, the shape of nanocrystalline region and the degree of nanocrystalline on the buckling mode and energy absorption of cylindrical shell are studied by numerical simulation. The relationship between the buckling mode of local surface nanocrystalline cylindrical shell and its absorbing energy is analyzed. The energy absorption performance of cylindrical shell was evaluated by analyzing the displacement curve of impact force and using the specific energy absorption index. The shape parameters and layout parameters of nanocrystalline region were optimized when the cylindrical shell achieved the best energy absorption effect (for example, maximum specific energy absorption). The effects of the length, thickness and impact velocity of cylindrical shells on the buckling mode and energy absorption of cylindrical shells are also discussed. The results of numerical simulation show that the buckling mode and energy absorption of cylindrical shells with nanocrystalline axial surface, annular surface nanocrystalline and local sheet surface nanocrystals are better than those of the original elastoplastic cylindrical shells. Secondly, the higher the density of nanocrystalline region, the better the deformation mode and energy absorption performance. The buckling deformation mode and energy absorption performance of cylindrical shells can be optimized by proper nanocrystalline layout. The nanocrystalline layouts of the segmented surfaces can achieve progressive buckling and multiple energy absorption of cylindrical shells. This design method provides a new design idea for hierarchical and segmental energy absorption structures.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB535;TB306

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