本文選題：金屬玻璃 + 復(fù)合材料�。� 參考：《北京理工大學(xué)》2016年博士論文

【摘要】：塊體金屬玻璃及其復(fù)合材料具有優(yōu)異的力學(xué)、物理和化學(xué)性能,特別是在玻璃轉(zhuǎn)變溫度以下和高應(yīng)力或高應(yīng)變率條件下變形時(shí),容易發(fā)生局域剪切帶,具有極高的剪切敏感性。因此,該類材料有可能應(yīng)用于新型穿甲彈芯,逐漸成為高速穿甲及裝甲防護(hù)研究領(lǐng)域的前沿?zé)狳c(diǎn)。本文基于有限元模擬開展針對金屬玻璃及其復(fù)合材料剪切帶行為的研究,包括剪切帶的形核、傳播以及剪切帶誘導(dǎo)的斷裂等,深入討論材料的剪切變形和破壞特征以及復(fù)合材料彈體穿甲的“自銳”特性。首先基于熱力耦合模型,考慮自由體積、熱和靜水應(yīng)力對材料變形和破壞的影響,推導(dǎo)了塊體金屬玻璃材料的三維本構(gòu)模型;基于自由體積聚集和結(jié)合的微觀機(jī)理,引入了臨界自由體積濃度的材料破壞準(zhǔn)則。將建立的本構(gòu)模型和破壞準(zhǔn)則寫入LS-DYNA軟件的用戶自定義材料子程序(UMAT)中,對不同受力狀態(tài)和不同溫度條件下金屬玻璃的變形響應(yīng)特性進(jìn)行了有限元模擬研究,具體分析材料內(nèi)部物理參量的演化特性及其所導(dǎo)致的材料宏觀表象。研究發(fā)現(xiàn)初始自由體積濃度、應(yīng)變率、初始溫度和靜水應(yīng)力等內(nèi)外部條件對金屬玻璃的變形和破壞具有重要影響:變形和破壞受材料的微觀結(jié)構(gòu)即自由體積主控,而溫度則起輔助的促進(jìn)作用;應(yīng)變率和初始溫度均產(chǎn)生明顯影響,應(yīng)變率的作用尤為顯著,而靜水應(yīng)力將導(dǎo)致變形的拉壓不對稱特征。進(jìn)一步考慮金屬玻璃材料內(nèi)部結(jié)構(gòu)的不均勻性,建立了包含隨機(jī)分布材料弱區(qū)的有限元幾何模型。針對塊體金屬玻璃在準(zhǔn)靜態(tài)拉伸、壓縮、彎曲以及高速沖擊等不同加載條件下的變形和破壞特性進(jìn)行了分析。結(jié)果表明金屬玻璃在常溫條件下的變形表現(xiàn)為局域化的剪切特征,呈現(xiàn)出顯著的非均勻特性。在準(zhǔn)靜態(tài)加載條件下,剪切帶的生成和擴(kuò)展同時(shí)受應(yīng)力條件和弱區(qū)分布特性的影響;而在沖擊條件下,弱區(qū)的影響減弱。結(jié)合纖維/顆粒增強(qiáng)金屬玻璃復(fù)合材料內(nèi)部結(jié)構(gòu)特征建立相應(yīng)有限元幾何模型,利用修正的熱力耦合本構(gòu)模型來描述金屬玻璃基體的高強(qiáng)度和高剪切敏感性,系統(tǒng)開展了針對復(fù)合材料靜動態(tài)拉壓試驗(yàn)和高速沖擊試驗(yàn)的研究。結(jié)果顯示,復(fù)合材料的壓縮塑性較純金屬玻璃得到明顯提高,而拉伸塑性則相對難以改善。在壓縮變形過程中,纖維增強(qiáng)復(fù)合材料的變形和破壞模式隨纖維體積分?jǐn)?shù)和應(yīng)變率等內(nèi)外部因素的改變而發(fā)生變化,顆粒增強(qiáng)復(fù)合材料則主要表現(xiàn)為剪切特征;在拉伸條件下,材料均主要發(fā)生脆性斷裂,斷面基本垂直于加載方向。相應(yīng)變形和破壞特性同復(fù)合材料內(nèi)部的剪切帶行為密切相關(guān)。最后結(jié)合穿甲試驗(yàn)開展了針對鎢纖維/鎢顆粒增強(qiáng)金屬玻璃復(fù)合材料長桿彈穿甲靶板的有限元模擬研究。具體分析復(fù)合材料彈體的穿甲“自銳”性能,詳細(xì)討論撞擊速度、靶材強(qiáng)度和初始彈頭形狀等因素對彈體的“自銳”行為以及相應(yīng)穿甲性能的影響,同時(shí)對比分析了兩種復(fù)合材料長桿彈之間的異同。
[Abstract]:Bulk metallic glass and its composites have excellent mechanical, physical and chemical properties, especially in the glass transition temperature and high stress or high strain rate deformation, prone to local shear zone with high shear sensitivity. Therefore, this kind of material can be applied in the new type of penetrator. Gradually become the hotspots of high-speed penetration and armor protection research field. This paper based on finite element simulation of metallic glass and its composites on shear behavior, including shear band nucleation, propagation and induction of shear band fracture, in-depth discussion of "self sharpening characteristics of material shear deformation and failure characteristics of composite materials the penetrating". Based on the coupled thermo mechanical model, considering the free volume, heat and hydrostatic stress effects on material deformation and failure. The formulas of three-dimensional bulk metallic glass material Constitutive model; mechanism of free volume aggregation and based on introduction of critical concentration of free volume of material failure criterion. The constitutive model and failure criterion of writing LS-DYNA software subroutine will be established (UMAT), the deformation response characteristics in different stress state and different temperature conditions of metallic glass a finite element simulation of materials macro representation evolution properties of concrete analysis material physical parameters and its causes. It is found that initial free volume concentration, strain rate, initial temperature and hydrostatic stress has an important influence on the deformation of the internal and external conditions of metallic glass and destruction: the deformation and destruction of the microstructure by material that is the free volume control, while the temperature plays an auxiliary role; has obvious effects of strain rate and initial temperature, strain rate effect is particularly significant, and hydrostatic stress Will lead to tension compression asymmetry deformation. Further considering the inhomogeneity of the internal structure of metallic glass material, a finite element model with random geometric distribution of the material. In the weak area of bulk metallic glass under quasi-static tensile, compression, bending and high impact deformation and failure characteristics under different loading conditions are analyzed the results showed that the deformation of metallic glass. Under normal temperature conditions for shear localization features, showing a significant nonuniformity. Under the quasi-static loading condition, the shear band formation and expansion also affected by stress conditions and weak characteristic distribution; while under impact conditions, weakening the influence of weak areas. Combined with the characteristics of the internal structure of fiber / particle reinforced metal glass composites established finite element model, constitutive model to describe the high strength metallic glass substrate using the modified thermal coupling The degree of sensitivity and high shear, the system carried out for composite materials of static and dynamic tension compression test and high speed impact test. The results showed that the composite compressive plastic than the pure metallic glass has been significantly improved, while the tensile ductility is relatively difficult to improve. In the compression deformation, deformation and failure mode of fiber reinforced composite materials with the fiber volume fraction and strain rate of internal and external factors change, particle reinforced composites are mainly for shear characteristics; under tensile conditions, materials are mainly brittle fracture section perpendicular to the loading direction. The deformation and failure characteristics of shear with composite materials is closely related with the behavior. Finally, the armour test carried out against the finite element simulation of metallic glass composite long rod projectile penetrating target plate of tungsten fiber / tungsten particle reinforced concrete composite material analysis. The self piercing performance of projectile penetrating armor is discussed. The influence of impact velocity, target strength and initial warhead shape on the self sharpening behavior and the corresponding piercing performance of the projectile are discussed in detail. Meanwhile, the similarities and differences between two kinds of composite long rod projectiles are compared and analyzed.

【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG139.8;TB33

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