双壳船内外壳结构耐撞性试验与仿真研究

结合船舶加筋板结构缩尺模型的耐撞性试验和有限元仿真分析,研究了双壳船舷侧内、外壳结构的碰撞损伤特性,并在此基础上对舷侧内、外壳结构的碰撞损伤性能进行了分析比较.结果表明:虽然双壳船舷侧内、外壳结构在耐碰撞能力方面的差异不是很大,但在渐进破坏过程及其总体破坏模式方面却存在一些明显的区别.而加强筋的侧向挤压变形对加筋板总体碰撞损伤性能并不会产生很明显的影响.影响船体舷侧结构耐撞性能的主要内力要素是加强筋截面内的轴力以及船壳板中面内的膜力.为了提高加筋板结构的耐碰撞能力,就要尽可能地减小结构的局部弯曲变形,较好的设计方案是增加外壳板厚度和减小加强筋尺寸.     

舷侧水对船舶抗碰撞性能的影响

为了评估舷侧液舱在大型撞击物下的抗碰撞特性，采用有限元法和简化理论法对典型球鼻艏在不同撞击速度和液舱水线工况下的舷侧外板和内板的抗破坏性能进行了分析。结果表明:舷侧水效应可以显著提升双舷侧结构的抗破坏性能，但是提升的幅度是有限的，而且水效应对外板的破坏作用力影响较小，对舷侧内板的破坏作用力影响较大；当球鼻艏撞击速度逐渐增高时，舷侧外板和内板的破坏作用力也逐渐增大，但增大速率逐渐降低，其中舷侧外板较舷侧内板的增大速率更快趋于平缓。对不同液舱水线的分析表明:舷侧液舱水线在受撞击的强框架以上时，对抗碰撞性能影响较小；当舷侧液舱水线在受撞击的强框架以下时，对舷侧外板的抗碰撞特性影响较小，但对舷侧内板的抗碰撞特性影响很大，并且随着球鼻艏碰撞速度的增高，不同水线位置对船舶抗碰撞性能的影响也随之增大。     

薄壁管及其泡沫金属填充结构耐撞性的实验研究

对两种AA 6063T6铝合金薄壁空管(方/圆管)结构以及填充泡沫铝的5种不同几何截面的薄壁夹芯管(单方/圆管填充,双方/圆管填充,双方管四角填充结构)分别进行了准静态轴向压缩实验,研究了各种薄壁结构的变形模式和吸能性能,比较了反映不同结构耐撞性的各种参数,如比能量吸收和能量吸收效率因子等。同时,研究了各种填充结构的几何参数对结构耐撞性能的影响,发现填充结构内管的尺寸对结构的耐撞性影响显著。研究结果显示,圆管类型的结构平均压垮载荷、比质量能量吸收、单位行程能量吸收以及能量吸收效率因子都较方管类型结构高。泡沫填充单/双圆管结构由于其较高的压垮力效率和能量吸收效率,能够较平稳高效地吸能,作为耐撞性结构元件具有很大的优势。     

船舶碰撞动力学过程的数值仿真研究

在分析显式非线性有限元基本理论和关键技术的基础上 ,探讨了船舶动力学过程的数值仿真方法 ,并对碰撞过程中船体的力学性能进行了分析 ,获得并讨论了碰撞力、能量吸收和损伤变形的时序结果 ,所得结论具有一般性。碰撞仿真分析中 ,被撞船的舷侧受撞区域和撞击船的首部区域作为可变形结构处理 ,而其余区域则视为刚体。被撞船周围的水划分成Euler有限体积网格 ,船体结构则划分成Lagrange有限元网格 ,并采用耦合技术将它们联系在一起。撞击船周围的水的影响采用附连水质量进行处理。     

考虑车辆高速和低速耐撞性的多目标优化设计

<正>面高速耐撞性设计,需确保车内乘员的人身安全,使车内乘员的人身伤害降到最低;正面低速耐撞性设计,要求尽量减少车辆在碰撞中的损伤,使车辆具有良好的碰撞损伤修复经济性。本文根据上述特点,将车辆的正面高速耐撞性与正面低速耐撞性相结合,并且考虑车身部件的轻量化,提出了一种优化设计方法。该方法将保险杠、吸能盒内外板以及前纵梁内外板五个部件厚度作为优化设计变量,在正面低速碰撞中,以前纵梁吸收的碰撞总能量作为其是否发生较大变形的依据,利用代理模型和遗传算法进行了优化计算。最后,将该方法应用在某一车型的耐撞性设计中。     

新型多边形锥管的准静态压缩与耐撞性分析

在车辆的耐撞性研究中，锥形薄壁管因其具有稳定的力-位移曲线和变形过程，被认为是轴向加载下的一种理想的能量吸收器。设计了两种类型的新型多边形锥管，通过在传统的多边形锥管上引入特殊的折纸图案，诱导结构按预制的折纸图案发生变形，从而提高其在准静态轴向压缩条件下的耐撞性；并通过准静态压缩实验研究了截面边数和壁厚对其变形模式和耐撞性的影响。结果表明：截面边数的增加使结构更容易发生局部屈曲和塑性失稳；增加壁厚会使局部屈曲和塑性失稳相对减弱，但结构会产生更多的裂缝。截面边数N对耐撞性的影响主要体现在初始峰值力上，初始峰值力随N的增加而增加，平均压缩力、比吸能和压缩力效率随N变化无明显规律；壁厚t对耐撞性有较大的影响，初始峰值力、平均压缩力和比吸能都随t的增加而增加，压缩力效率随t增加无明显规律。同时，通过传统六边形锥管(CH6)与两类新型六边形锥管(N6M1和N6M2)对比发现，折纸图案的引入在降低初始峰值力、提高平均压缩力和压缩力效率方面有显著优势。     

仿生多胞薄壁管耐撞性分析及优化

为提高薄壁管结构耐撞性，以雀尾螳螂虾螯为仿生原型，结合仿生学设计方法，设计一种含正弦胞元的多胞薄壁管结构。以初始峰值载荷、比吸能和碰撞力效率为耐撞性指标，通过有限元数值模拟分析了不同碰撞角度（0o、10o、20o和30o）条件下，仿生胞元数对薄壁管耐撞性的影响，通过多目标的复杂比例评估法获取仿生薄壁管的最优胞元数。基于不同碰撞角度权重因子组合，设置了4种单一角度工况和3种多角度工况，采用多目标粒子群优化方法获取了不同工况下薄壁管结构最优胞元高宽比和壁厚。复杂比例评估结果表明，胞元数为4的薄壁管为最优晶胞数仿生薄壁管。优化结果表明，单一角度工况下，最优结构参数高宽比的范围为0.88～1.50，壁厚的范围为0.36～0.60 mm，碰撞角度为0o和10o的最优高宽比明显小于碰撞角度为20o和30o的；多角度工况下，最优高宽比范围为1.01～1.10，壁厚范围为0.49～0.57 mm。     

高速动车组被动安全性和耐撞性研究

随着列车高速和重载的发展,对列车被动安全性的研究日益重要.本文以CRH3动车组为载体,应用碰撞仿真软件PAM-CRASH和多学科协同优化软件iSIGHT进行碰撞数值模拟分析和吸能结构优化,得到CRH3动车组在大变形碰撞时的变形模式及各碰撞参数,并对动车组的吸能结构进行评估及最优设计,实现车辆的被动安全保护和耐撞性优化设...     

星形混合多胞管的耐撞性数值与理论研究

为研发轻质高效的能量吸收装置，提出了基于多边形截面与星形截面混合设计的星形混合多胞管。采用数值模拟方法研究了星形混合多胞管在轴向加载条件下的吸能特性和变形模式，并结合简化超折单元理论推导了该管的平均碰撞力理论公式。研究结果表明，星形混合多胞管的多边形截面与星形截面之间产生了协同效应，额外吸收了更多的冲击动能：当多边形边数N=6时，混合截面的协同性最好；当N=8时，该管的能量吸收效率最高。在此基础上，进一步开展了几何参数分析，发现壁厚对于星形混合多胞管的耐撞性有显著的影响，碰撞力水平随着壁厚的增加而线性增长。此外，星形角度的变化对耐撞性的影响相对较小，碰撞荷载效率和比吸能随着星形角度的增加表现出先增大后减小；当星形角度α=120°时，该管拥有最佳的耐撞性。     

复合材料夹层结构在舰艇碰撞防护中的研究进展

为了提高舰艇的碰撞防护能力,已发展了各种舰艇碰撞防护方法。传统的碰撞防护手段会使舰艇重量大幅增加,影响舰艇总体性能。复合材料夹层结构的出现给舰艇碰撞防护结构设计提供了另外一条途径,成为近期国内外相关研究的热点。本文以舰艇碰撞防护为背景,从复合材料夹层结构的低速冲击实验方法、变形损伤机理、冲击吸能影响因素、分析研究方法等几方面进行回顾、总结和归纳,并对今后的研究方向进行展望。     

Existence of solutions of systems of partial differential equations of fractional order

We obtain sufficient conditions for the existence and uniqueness of a solution of a system of partial differential equations of fractional order in spaces of integrable functions.Translated from Neliniini Kolyvannya, Vol. 7, No. 3, pp. 328–335, July–September, 2004.     

Diagonalization of a three-dimensional system of equations in terms of displacements of the linear theory of elasticity of transversely isotropic media

A dynamic three-dimensional system of linear equations in terms of displacements of the theory of elasticity of transversely isotropic media is given explicit expressions for phase velocities and polarization vectors of plane waves. All the longitudinal normals are found. For some values of the elasticity moduli, the system of equations is reduced to a diagonal shape. For static equations, all the conditions of the system ellipticity are determined. Two new representations of displacements through potential functions that satisfy three independent quasi-harmonic equations are given. Constraints on elasticity moludi, at which the corresponding coefficients in these representations are real, different, equal, or complex, are determined. It is shown that these representations are general and complete. Each representation corresponds to a recursion (symmetry) operator, i.e., a formula of production of new solutions.     

Calculation of aerodynamic characteristics of arrays of profiles of arbitrary shape

It is well known that the problem on nonseparating potential flow of an incompressible fluid about an array of profiles reduces to an integral equation for a certain real function, determined on the contours of the profiles of the array. As such a function one can take, as was done, for instance, in [1–5], the relative velocity of the fluid on the profiles of the array. For arrays of profiles of arbitrary shape it is necessary to solve the corresponding integral equation numerically. In the particular examples of the calculation of aerodynamic arrays that are available [1–3] the numerical methods used were based on the approximate evaluation of contour integrals by rectangle formulas. As investigations showed, sizeable errors arose thereby in the approximate solution obtained, these being especially significant in the case of curved profiles of relatively small bulk. In the present paper a method for the numerical solution of the integral equation obtained in [5] is proposed. The method is based on the replacement of a profile of the array with an inscribed N polygon, the length of whose sides is of the order N^–1 and whose internal angles are close to . Convergence with increasing N of the numerical solution to an exact solution of the integral equations at the reference points is demonstrated. Examples of the calculation are given.Novosibirsk. Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 105–112, March–April, 1972.     

Doubling of the period of oscillation of a pendulum of variable length

Kiev Institute of Construction Engineering. Translated from Prikladnaya Mekhanika, Vol. 26, No. 6, pp. 74–80, June, 1990.     

Assessment of ease of excavation of surface mines

An empirical ground classification system for surface mines is presented. It is designed to provide a means for determining the ease of excavation, diggability, by mechanical excavators. The background and the methodology for determining this excavation index is introduced. This index, which is suitable for rock characterization relies on the point load index of the rock, its block size as defined by the presence of discontinuities. The system is also flexible to account for the influence of weathering as well as the relative ground structure which may assist or hinder the excavation process. The economic consequences of selecting mining excavation equipment are also addressed. The Excavation Index was applied with success to 49 case studies (Hadjigergiou, J. Studies of machine ground interaction in surface mines. Ph.D. thesis, McGill University, 1993, p. 214).     

Development and design of new methods of measurement of state of strain of structures

The present paper deals with development and design of new methods utilizing Wiedemann's effect for determination of state of strain in building structures. Wiedemann's effect and some features of torsional strain of magnetic field are the basis of new experimental method. Especially the point electromagnetic strain gages using the effect of pure torsion of electromagnetic field to enable universal examination. For strain-gage measurements, almost all physical quantities are used which can be related to the variation in length of the structures. From the electric strain measurements, the most commonly used methods are the measurements by resonance-wire strain gages or by electric-resistance strain gages. In this paper, electromagnetic strain gages are discussed using the Wiedemann effect, and the author describes some new measuring equipment and his own suggestions and methods based on an application of this effect.     

Method of calculation of interaction of wall flows

A flow of viscous compressible fluid in the neighborhood of the line of interaction of wall flows is considered. A method of calculating the line of interaction and the direction of the self-induced secondary flow is developed. Papers [1–3] are devoted to the simulation of a separation flow with singularities in the neighborhood of singular lines and points, where boundary-layer equations are invalid. However, the theories of local separation used at present have mainly been developed only for two-dimensional problems, while the models of viscous-inviscid interaction have restrictions in application for turbulent flows with developed separation. The interaction of three-dimensional wall turbulent flows is considered below. It is assumed that the thickness of the boundary layers and the scales of the interaction zones are small in comparison with the characteristic dimension of the system, while the line of discontinuity of the solutions of the three-dimensional boundary layer equations is the same as the line of interaction of the wall flows.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 53–59, March–April, 1987.The author is grateful to G. Yu. Stepanov and V. N. Ershov for their interest in my work and their valuable remarks.     

Equations of oscillations of rods of variable composition

We obtain differential equations for the general case of longitudinal, torsional, and transverse oscillations of rods to some parts of which masses are being added or detached. We solve certain special problems concerning the oscillations of such rods of variable composition. In deriving generalized equations of oscillations of rods of variable composition we employ the assumption of planar sections, the assumption of small deformations, and other customary simplifications. We also employ the simplifying assumption of close action; i.e., we assume that the masses being detached and added interact with the rod only at the instant of direct contact. Forces of internal nonelastic resistance are not taken into account. We assume also that in the undeformed state the elastic axis is rectilinear and that the centers of gravity of cross sections are not displaced from their initial positions relative to the cross sections. There may be a change of mass per unit length of the rod both on account of a change in density as well as on account of a change in area of a cross section, the latter being understood to be the union of the initial area of the cross section and the areas of the parts being added and detached. In addition, with the rod there may be associated particles of variable mass distributed continuously or discretely along the length of the rod. We assume that these particles do not interact among themselves but only with the rod.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 103–108, January–February, 1972.     

Stabilization of solutions of the nonlinear equation of filtration of a two-phase liquid

The asymptotic behavior (with unlimited increase in time) of solutions of boundary-value problems for the filtration equation for a two-phase liquid that describe the displacement of immiscible incompressible liquids from a bed is studied. Convergence of these solutions to the unique solution of the steady problem (stabilization) is established, and, under additional assumptions, the rate of convergence is evaluated. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 3, pp. 30–36, May–JJune, 1999.     

Stability of shells of revolution made of heat-sensitive composites

Institute of Mechanics, Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 28, No. 10, pp. 52–57, October, 1992.