弹体高速侵彻钢筋混凝土靶试验研究

为研究结构弹体对钢筋混凝土靶的高速侵彻破坏效应,利用口径35 mm弹道炮开展了1 030～1 520 m/s速度范围内的高速侵彻试验,获得了弹体的撞击速度、破坏形态、剩余长度、剩余质量和靶体中的侵彻深度及成坑尺寸等试验数据,分析了侵彻深度和侵彻机理随速度的变化关系。结果表明:在1 030～1 390 m/s的速度范围内,弹体头部磨蚀,磨蚀程度随侵彻速度增加而加剧,侵彻深度随撞击速度近似线性增大;撞击速度在1 390～1 480 m/s范围内,弹体头部严重磨蚀,侵彻深度随撞击速度增加而减小;撞击速度大于1 480 m/s后,弹体严重破碎,侵彻深度急剧下降。针对结构弹体高速侵彻过程中的破坏特点,将侵彻速度划分为刚体侵彻区、准刚体侵彻区、侵蚀体侵彻区和破碎体侵彻区,可为钻地弹结构设计提供参考。     

基于物质点法不同头部形状弹体侵彻动靶过程的仿真研究

为分析弹头形状对动靶侵彻性能的影响以及解决有限元法模拟子弹侵彻问题时存在的网格畸变问题,本文采用物质点法建立了弹体侵彻靶板的数值模型。利用编写的程序对卵形弹侵彻静靶过程进行了仿真,并将仿真结果与实验测试结果进行了对比分析。结果表明,利用物质点法仿真子弹侵彻过程是可行和有效的。通过对平头弹、球形弹、卵形弹侵彻动靶过程的模拟仿真,得到了弹体贯穿动靶后弹体的剩余速度、偏转角、扭转角、靶板的毁伤效果。所得结果显示:当靶板速度较低时,卵形弹侵彻动靶时靶板的毁伤面积最小;当靶板速度较高时,卵形弹侵彻动靶时靶板的毁伤面积最大;弹体偏转角和扭转角均随动靶速度的增加而逐渐增大,且卵形弹的偏转角和扭转角均大于平头弹和球形弹;当动靶初速度小于300m/s时,卵形弹的侵彻能力较强;当动靶初速度大于300m/s时,球形弹的侵彻能力较强。本文研究对弹丸侵彻和装甲防护等军工领域有一定的指导作用。     

弹体斜侵彻混凝土靶的实验研究及其数值模拟

以弹体斜侵彻混凝土的弹道特性为研究内容,通过侵彻实验与数值模拟得到了不同速度下的侵彻深度、开坑尺寸、偏转角等参数,实验结果与模拟结果吻合较好。研究结果表明:倾角对开坑深度和开坑形状影响很大;倾角越大,对侵彻深度和偏转角的影响越明显,弹体偏转角随着速度的增大呈现减小的趋势;当倾角增至一定角度后发生跳弹现象,据此得到跳弹极限角与倾角、侵彻速度的关系。     

结构变形对深侵彻弹体偏转的影响

钻地弹是打击地下工事的利器,弹道偏转是降低钻地弹侵彻效率的重要原因之一,弹道偏转的本质原因是弹体偏转,亟需快速且精确地预测多侵彻姿态下弹体的侵深与偏转角度。基于微分面力法,将计及有限大靶所有自由面影响的靶体响应力函数加载在弹体表面,快速模拟了弹体的运动和变形。靶体响应力函数和数值计算模型通过了试验校核。利用刚性弹与可变形弹的运动和变形的对比,剥离并分析了结构变形对弹体偏转的影响。分析显示,结构变形是可变形弹偏转的驱动源之一,其可改变弹体外力矩,并影响弹体瞬时偏转速度。相同条件下,可变形弹偏转角度大于刚性弹。随着弹体长径比减小、着靶速度降低及侵彻斜角增大,刚性弹偏转角度增大;而随着弹体长径比增大、侵彻斜角增大及弹体壁厚减小,可变形弹偏转角度增大。着靶速度对可变形弹偏转角度的影响不单调。当着靶速度不高于800 m/s、侵彻斜角不小于20°时,着靶速度越高、侵彻斜角越大、弹体长径比越大、壁厚越小,则结构变形对弹体偏转的贡献越大。为此,建议选择可变形弹分析非理想侵彻弹体的运动和变形,以提高分析精度与合理性。     

撞击姿态对构型弹体非正侵彻多层间隔钢靶弹道特性的影响规律

为深入认识构型弹体非正侵彻多层间隔靶板的弹道偏转规律，结合数值模拟和理论分析，研究了构型弹体在不同撞击姿态下侵彻多层间隔钢靶的弹道特性，其中引入弹体侧向接触力和侧向偏转力矩等参量，着重分析撞击着角和攻角对弹道特性的影响规律。结果表明：构型弹体非正侵彻过程中，在纵向发生阶梯式速度衰减，但变化较小；同时，由于穿靶过程中受到侧向接触力及其偏转力矩的作用，在侧向产生显著弹道偏转。撞击着角决定弹体所受外载荷的非对称程度，着角越大，弹体偏转越严重；撞击攻角则主要影响弹肩穿靶时的径向速度和弹尾穿靶时的触靶位置，二者共同影响弹道轨迹，因而存在使弹体偏转程度发生转折的临界攻角。相比于侵彻单层靶，构型弹体非正侵彻多层间隔靶板的显著特点为弹道偏转存在累积效应，且侵彻前一靶板的弹道偏转情况显著影响到侵彻后一靶板时的弹靶作用特征，进而导致弹道偏转与弹靶接触力互相耦合。相关研究对预测构型弹体侵彻多层间隔靶板性能、优化弹体构型和撞击姿态等具有较好的指导价值。     

攻角和入射角对弹体侵彻混凝土薄靶弹道特性影响规律研究

为了研究弹体斜侵彻有限厚混凝土靶板的作用特性,开展了尖卵形弹体斜侵彻间隔混凝土靶实验,获得了弹体侵彻过程中的姿态及弹道特性、靶板破坏参数,分析了攻角与入射角联合作用对弹体侵彻混凝土靶板“二次偏转现象”、靶后偏转角以及弹体侵彻间隔靶板弹道轨迹的影响规律。研究结果表明:入射角越大,“二次偏转现象”越明显,弹体靶后偏转角越大;初始攻角抑制“二次偏转现象”,攻角越大,抑制作用越显著;初始攻角与入射角方向相同时,初始攻角加剧靶后偏转角的增大;当攻角与入射角方向相反时,较小的攻角能够抑制弹体靶后偏转角的增大,而当初始攻角较大时,攻角成为影响弹体偏转的主要因素,攻角越大,弹体靶后偏转角越大。     

椭圆截面弹体斜侵彻金属靶体弹道研究

为研究椭圆截面弹体对半无限金属靶体的侵彻弹道规律,基于14.5 mm弹道枪平台,开展了椭圆截面弹体在0°～20°倾角、850～950 m/s撞击速度下对2A12铝合金的斜侵彻试验。基于空腔膨胀理论及局部相互作用模型,建立了椭圆截面弹体侵彻弹道模型,并结合试验数据验证了模型的准确性。在此基础上,进一步分析了椭圆截面弹体长短轴之比、绕弹轴旋转角度、弹体撞击速度对侵彻弹道的影响规律。弹体长短轴之比为1.0时,弹体退化为尖卵形圆截面弹体,且椭圆截面弹体侵彻弹道稳定性随长短轴之比的增大而变弱,最优长短轴之比为1.0,即尖卵形圆截面弹体。椭圆截面弹体绕弹轴旋转一定角度后,侵彻弹道在平面曲线与空间曲线之间变化,当旋转角度为0°、90°时,侵彻弹道为二维平面弹道,当旋转角度在0°～90°之间时,侵彻弹道为三维空间弹道。当弹体撞击速度由800 m/s提升至1000 m/s时,椭圆截面弹体姿态角增量由18.6°降至17.8°。     

弹体高速侵彻效率的实验和量纲分析

为了研究高速侵彻时弹体撞击速度、材料强度等对质量侵蚀特性和侵彻效率的影响规律,开展了不同材料强度和长径比的弹体高速侵彻半无限厚素混凝土靶实验,弹体撞击速度为880~1 900 m/s,弹头形状为尖卵型(半径口径比为3),口径为30 mm。由实验发现:弹体撞击速度对侵彻效率的影响呈抛物线分布,最大侵彻效率时的弹体特征撞击速度约1 400 m/s;高速侵彻时弹体的质量侵蚀主要发生在卵形头部,弹身及尾部损伤极少;速度超过特征撞击速度时,弹体侵蚀严重,甚至弯曲变形或解体;弹体强度提高至约2倍时,质量侵蚀率降低约80%。基于实验,利用量纲分析原则建立了量纲一侵彻效率和量纲一弹体撞击速度的函数关系式,可估算出最大侵彻效率对应的弹体撞靶速度,为高速侵彻效应模拟实验提供理论指导。     

80%钨纤维增强锆(Zr)基块体金属玻璃复合材料长杆弹侵彻钢靶实验研究

本文在765~1766m/s速度范围内,对钨纤维体积分数为80%的增强锆(Zr)基块体金属玻璃复合材料长杆弹进行侵彻Q235钢靶的穿甲试验,对残余弹体进行宏、细观观测,研究弹体材料的失效破坏模式。穿甲试验表明,在大于1000m/s速度侵彻时,钨纤维非晶弹拥有头形自锐能力,表现出优秀的侵彻能力。弹材变形和破坏主要发生于弹体头部边缘层,呈局域化和尖锐化特点,而且边缘层厚度在整个高速穿甲过程中保持动态平衡。由于非晶基体作用,弹体材料易发生剪切断裂等破坏,通过流动形成质量侵蚀并导致弹体头部边缘层形成自锐。     

钨合金弹体对混凝土靶的超高速侵彻机理

为研究钨合金弹体超高速侵彻混凝土靶的相关机理,构建了适用于超高速撞击的金属强度模型、失效模型和混凝土的本构模型,对93钨合金弹体超高速撞击混凝土靶问题进行了数值模拟。开展了钨合金弹体超高速撞击混凝土靶实验,分析了靶板成坑特性,研究了侵彻总深度和残余弹体长度随撞击速度的变化规律,理论分析了长杆钨弹超高速撞击混凝土的侵彻模型和混凝土靶内的应力波传播。得到以下主要结论:（1）利用金属及混凝土的新本构模型获得的超高速撞击混凝土靶的破坏形貌数值模拟结果与实验结果一致;（2）超高速撞击条件下混凝土靶成坑为“弹坑＋弹洞”形,成坑体积与弹体动能近似成正比;（3）超高速撞击条件下,侵彻深度随弹速提高呈现先增大后减小的现象,高速段侵深降低是弹体经历销蚀侵彻后“刚体侵彻阶段”减少造成的;（4）建立的钨合金超高速撞击混凝土侵彻分析模型,可用来预估侵彻深度、残余弹长、蘑菇头直径等参数;（5）采用建立的超高速撞击混凝土靶内应力波传播理论模型得到的计算结果与实验结果吻合较好。     

Zur einfachen Berechnung von Dephlegmatoren binärer Dampfgemische

Zusammenfassung Die Dephlegmation ist eine nicht-adiabate Rektifikation ohne Rücklauf am Apparatekopf, die durch die Ackermann/Colburn-Drew-Gleichungen beschrieben werden. In diesem Beitrag wird eine vergleichende Analyse von stationären makroskopischen Modellen mit unterschiedlicher Reduktion gegeben.

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On simple calculation procedures of binary mixed vapour dephlegmation

The dephlegmation is a non-adiabatic rectification without reflux at the top of the column, which for calculation can be described by the Ackermann/Colburn-Drew-equations. In this paper a comparing analysis of steady macroscopic models with different degree of model reduction is given.

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Nomenklatur A Austauschfläche pro Apparate- m²/m länge - C Korrekturfunktion - D Diffusionskoeffizient m²/h - Enthalpiestrom J/h - Impulsstrom kmol m/h - N Zahl der theoretischen Trennstufen - N Molstrom kmol/h - T Temperatur °C - Molmasse kg/kmol - L Apparatelänge m - c_p molare Wärmekapazität J/kmol grd - d Durchmesser m - Enthalpiestromdichte J/h m² - g Erdbeschleunigung m/h² - h molare Enthalpie J/kmol - j Impulsstromdichte kmol/h m - n Molstromdichte kmol/h m² - 1 Länge m - u axiale Geschwindigkeit m/h - x Molkonzentration im Fluid kmol/kmol - y Molkonzentration im Dampf kmol/kmol - z Molkonzentration (S. G1.2) kmol/kmol - Differenz - t Kontaktzeit h - Austauschkoeffizient für die J/h m² grd Enthalpie - ß Austauschkoeffizient für die kmol/h m² Komponente - Austauschkoeffizient für den kmol/h m Impuls - Massendichte kg/m² - Zähigkeit kg/m h - _f Rieselfilmdicke m - ^f Wärmedurchgangskoeffizient J/h m² grd Kennzahlen Re u·d·/ - Sc /·D - Sh ··d/·D Indizes a außen - d dampfseitig - f flüssigkeitsseitig - g Phasengrenze - h hydraulisch - i innen - k Kühlmedium - m mittel - o oberes Apparateende - t total - u unteres Apparateende - w Wand - x Komponente an LS im Fluid - y Komponente an LS im Dampf - gültig für große übergehende Molströme     

Spin-up in a saturated porous medium

It is shown that, on the Brinkman model, spin-up is confined to boundary layers whose thickness is of order k ^1/2, and the spin-up is established in a time of order k/, where k, , and denote permeability, density, porosity and dynamic viscosity, respectively.     

Second Order Multiple Scales for Oscillators with Large Delay

We use the method of multiple scales (MMS) to study small perturbations, governed by a parameter , of a harmonic oscillator by a small term with a large delay. These systems differ significantly from others where small terms have delays; or an term has delay in a system near a Hopf bifurcation. Here, the slow flow in time t depends strongly on even at lowest order, and itself has an delay. The MMS has already been applied elsewhere for such systems, but only to first order and with attention restricted to periodic and quasiperiodic solutions. Here, we address transients as well as proceed to second order. The second order analysis holds unless a special resonance occurs (we assume it does not). Several numerical examples are presented. In each case, the slow flows are infinite-dimensional, show strong -dependence, require significantly less computation time than the full solutions, yet agree well with the same.     

Averaging of a Layered Elastic Medium with Low Dynamic Dissipation at the Interlayer Boundary

Averaged relations for a layered medium with dynamic dissipation at the interlayer boundary are constructed for dynamic problems of longitudinal shear and twodimensional theory of elasticity. For low dissipation, the averaged boundaryvalue problem is shown to be singularly perturbed. The degeneration of the boundaryvalue problem is studied qualitatively.     

Anwendung der Methode der finiten Elemente zur Berechnung eines instationären Wärmeleitvorganges,dargestellt am Beispiel: Kühlung einer Springform bei der Keilriemenvulkanisierung

Zusammenfassung Ausgehend von einem praxisnahen Beispiel wird allgemein aufgezeigt, wie sich die Methode der finiten Elemente, die in der Kontinuumsmechanik bereits weit verbreitet ist, auch zur numerischen Lösung instationärer dreidimensionaler Wärmeleitvorgänge in inhomogenen Körpern mit beliebigen Randbedingungen heranziehen läßt. Es werden zwei Wege zur Auswertung des Variationsintegrals gewiesen, deren einer eine Verallgemeinerung des sogenannten digitalen Beukenmodells darstellt. Im Anhang wird eine physikalische Interpretation des Variationsintegrales gegeben.

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Application of finite element solution technique in transient heat conduction calculation: illustrated by cooling of a locked form in v-belt-vulcanization

Starting from a problem of technical interest the universal application of finite element solution technique, broadly used in continuum-mechanics, for a numerical calculation of three-dimensional instationary heat-conduction through inhomogeneous bodies with real boundary-conditions is demonstrated. Two different ways in treating the variation-integral are shown, one of which is a generalization of so-called digital Beuken-model. In the appendix a physical interpretation of the variation-integral is given.

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Formelzeichen [ ] quadratische Koeffizientenmatrix - {_: ^:} Spaltenvektor - a, ¯a Wärmeübergangszahl - Variationssymbol - Wärmeleitzahl - Gewichtsfaktoren bei der Gaußschen Quadratur - spezifische Dichte - Temperaturfunktion - Dissipationspotential - , t, T, t Zeit, Zeitintervall - , _w, Temperatur, Kühlwassertemperatur, Übertemperatur - ₀,¯ Anfangstemperatur, transformierte Temperatur - c spezifische Wärme - r, z Zylinderkoordinaten im rotationssymmetrischen Fall - s Transformationsparameter der Laplace-Transformation - m, n, M, N natürliche Zahl - L Koeffizient - I generalisierter Fluß - O Oberfläche - V, V_g, ¯V Volumen, Grenzschichtvolumen, Gesamtvolumen - R Restglied - S Schwerpunkt - X generalisierte Kraft - g, i, j, k, o, p, q, r Indizierung von Knotenpunkten und Referenzpunkten usw - [L], [C], [O], [A], [E] Leit-, Kapazitäts-, Oberflächen-, Quotienten- und Einheitsmatrix     

Heat transfer in laminar flow in a uniformly porous channel with an applied transverse magnetic field

Summary The steady laminar flow of an incompressible, viscous, and electrically conducting fluid between two parallel porous plates with equal permeability has been discussed by Terrill and Shrestha [6]. In this paper, using the solution of [6] for the velocity field, the heat transfer problems of (i) uniform wall temperature and (ii) uniform heat flux at wall are solved.For small suction Reynolds numbers we find that the Nusselt number, with increasing Reynolds number, increases for case (i) and decreases for (ii).Nomenclature stream function - 2h channel width - x, y distances measured parallel, perpendicular to the channel walls - U velocity of fluid in the x direction at x=0 - V constant velocity of suction at the wall - nondimensional distance, y/h - nondimensional distance, x/h - f() function defined in (1) - density - coefficient of kinematic viscosity - R suction Reynolds number, V h/ - Re channel Reynolds number, 4U h/ - B ₀ magnetic induction - electrical conductivity - M Hartmann number, B ₀ h(/)^1/2 - K constant defined in (3) - A constant defined in (5) - 4R/Re - q local heat flux per unit area at the wall - k thermal conductivity - T temperature of the fluid - X –1/ ln(1–) - C _p specific heat at constant pressure - j current density - Pr Prandtl number, C _p/k - P mass transfer Péclet number, R Pr - Pe mass transfer Péclet number, P/ - T ₀ temperature at x=0 - T _H() temperature in the fully developed region - T _h(X, ) temperature in the entrance region - Y _n () eigenfunctions, uniform wall temperature - _n eigenvalues - e() function defined by (24) - B _n 2/3 _n ² - A _n constants defined by (28) - a _2m constants defined by (30) - F _n () eigenfunctions, uniform wall heat flux - a _n , b _n , c _n , d _n , e _n constants defined by (45) and (48) - S a parameter, U ²/q - h ₁ heat transfer coefficient - T _m mean temperature - Nu Nusselt number - Nu _T Nusselt number, uniform wall temperature - Nu _q Nusselt number, uniform wall heat flux     

Bifurcation sequences of a Coulomb friction oscillator

In some parameter ranges, the dynamics of a forced oscillator with Coulomb friction dependent on both displacement and velocity is reducible to the dynamics of a one-dimensional map. In numerical simulations, period-doubling bifurcations are observed for the oscillator. In this bifurcation procedure, the map arising from the Coulomb model may not have standard form. The bifurcation sequence of the Coulomb model is compared to that of the standard one-dimensional maps to see if it exhibits universal behavior. All observed components of the bifurcation sequence fit the universal sequence, although some universal events are not witnessed.     

Studies on Stress Transference Mechanism of Steel Fibre Reinforced Concrete

ＩｎｔｒｏｄｕｃｔｉｏｎＨｏｗｔｈｅｉｎｔｅｎｓｉｏｎａｎｄｍｏｄｕｌｅｏｆｓｔｅｅｌｆｉｂｒｅｒｅｉｎｆｏｒｃｅｄｃｏｎｃｒｅｔｅ (ＳＦＲＣ)ｄｅｐｅｎｄｓｏｎｉｔｓｃｏｎｓｔｉｔｕｅｎｔｐｒｏｐｅｒｔｉｅｓａｎｄｃｏｎｔｅｎｔｉｓａｐｒｉｎｃｉｐａｌｐｒｏｂｌｅｍｔｏｐｒｅｄｉｃｔｍａｃｒｏ＿ｍｅｃｈａｎｉｃｓｐｒｏｐｅｒｔｉｅｓｏｆＳＦＲＣ,ｔｈｅｋｅｙｃｏｎｓｉｓｔｓｉｎｔｈｅｃｏｎｆｉｒｍａｔｉｏｎｏｆｓｔｒｅｓｓｄｉｓｔｒｉｂｕｔｉｏｎ .Ｉｎｔｅｒｆａｃｉａｌｓｔｒｅｓｓｔｒａｎｓｆｅ…     

Hydrodynamic models as applied to the investigation of magnetic plasma stability

In the present paper magnetohydrodynamic models are employed to investigate the stability of an inhomogeneous magnetic plasma with respect to perturbations in which the electric field may be regarded as a potential field (rot E 0). A hydrodynamic model, actually an extension of the well-known Chew-Goldberg er-Low model [1], is used to investigate motions transverse to a strong magnetic field in a collisionless plasma. The total viscous stress tensor is given; this includes, together with magnetic viscosity, the so-called inertial viscosity.Ordinary two-fluid hydrodynamics is used in the case of strong collisions=. It is shown that the collisional viscosity leads to flute-type instability in the case when, collisions being neglected, the flute mode is stabilized by a finite Larmor radius. A treatment is also given of the case when epithermal high-frequency oscillations (not leading immediately to anomalous diffusion) cause instability in the low-frequency (drift) oscillations in a manner similar to the collisional electron viscosity, leading to anomalous diffusion.Notation f particle distribution function - E electric field component - H₀ magnetic field - density - V particle velocity - e charge - m, M electron and ion mass - _i, _e ion and electron cyclotron frequencies - viscous stress tensor - P pressure - r_i Larmor radius - P pressure tensor - t time - frequency - T temperature - collision frequency - collision time - j current density - _i, _e ion and electron drift frequencies - k_x, k_y, k_z wave-vector components - n₀ particle density - g acceleration due to gravity. The authors are grateful to A. A. Galeev for valuable discussion.     

Unsteady effects in a thin viscous shock layer near a three-dimensional stagnation point of a body moving with given acceleration and deceleration

An unsteady viscous shock layer near a stagnation point is studied. The Navier-Stokes equations are analyzed in the limit 1, Re₀ , df/dt = ^n-mF(t/^m). The Reynolds number Re₀ is defined in the paper by Eq. (1.3) (df/dt is the velocity of the body with respect to an inertial frame of reference moving with the original steady velocity –V'_t8, ₂ = ( – 1)/( + 1)). Various flow regimes in the case 1, l, n max(2m, m + 1), m 0, where ² = 1/Re₀ are analyzed. Equations are derived that generalize the asymptotic analysis to the case of a viscous unsteady flow of gas in a thin three-dimensional shock layer. The problem of a thin unsteady viscous shock layer near the stagnation point of a body with two curvatures is formulated. Examples of numerical solution are given for different ratios of the principal curvatures of the body, the wall temperature, the parameters of the original steady flow, and the acceleration and deceleration regimes.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 100–111, March–April, 1981.I thank Yu. D. Shevelev for a fruitful discussion of the work.