Dynamic response of top-down cracked asphalt concrete pavement under a half-sinusoidal impact load

A 3D finite element analysis model of cracked asphalt pavement is established by the FEM software ABAQUS. Based on dynamics mechanics, fracture mechanics and finite element theory, this paper studies the influence of various vehicle speeds, crack location, crack depth, damping ratio etc. on the dynamic response. The results show that the surface deflection, the maximum tensile strain at the bottom of the asphalt layer, and the maximum shear stress of the asphalt layer decreased with the increase in vehicle velocity when there is no crack in the pavement. No matter where the transverse position of the crack is the stress intensity factors increase with the increase in crack depth and decrease exponentially with the increase in longitudinal distance between the vehicle center and the crack. In the case of the crack locating in the center of wheel clearance, the surface deflection increases with the crack depth increasing. But if the crack is at the edge of the wheel track, there will be a critical vehicle velocity where the surface deflection is smaller than the asphalt pavement without crack if the vehicle velocity is above it. The maximum tensile strain at the bottom of the asphalt layer and the maximum shear stress of the asphalt layer are also smaller than the asphalt pavement without crack. The maximum tensile strain and the maximum shear stress decrease with the damping ratio increasing. So the increase in damping ratio can help to alleviate the propagation of cracks.     

Dynamic response of laminated composite shells under various impact loads

Mechanics of Time-Dependent Materials - This paper investigates the dynamic behavior of laminated composite shells (LCS) under the effect of dynamic loads. The governing equations for composite...     

Dynamic response and behavior of reinforced concrete slabs under impact loading

Reinforced concrete slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of their details on their behavior under impact loads are not always appreciated or properly taken into account. This experimental study was aimed at understanding the dynamic behavior of structural concrete slabs under impact loading to improve the state of the art of protective design. This study investigated the effects of different types of slab reinforcements and the applied impact loads on the dynamic response and behavior of reinforced concrete slabs.     

低速冲击激励下嵌入黏弹性阻尼芯层的纤维金属混杂层合板动态响应预测模型

钢筋混凝土(RC)结构在遭受火灾作用时,常会由于楼层坍塌而继发冲击作用,对楼板产生高温与冲击的耦合作用。该文同时考虑高温热力耦合效应和冲击荷载作用下的应变率效应,开展了高温下RC板抗冲击性能研究。通过分别将RC板抗火和抗冲击的试验结果与模拟结果进行对比,验证了该文所建立模型的正确性。分析获得了RC板在不同受火时间和不同能量冲击荷载作用下的动力响应,讨论了板厚和配筋率对高温下RC板抗冲击性能的影响。结果表明：火灾高温作用将显著影响RC板的抗冲击性能。随着受火时间的增加,RC板的冲切破坏损伤更加严重,RC板的跨中峰值位移也更大。板厚的增加能明显改善RC板的高温下的抗冲击性能,而配筋率的增加对RC板在高温下的抗冲击性能的影响有限。     

Dynamic response of aluminum honeycomb sandwich panels under foam projectile impact

The dynamic response of honeycomb sandwich panels under aluminum foam projectile impact was investigated. The different configurations of panels were tested, and deformation/failure modes were obtained. Corresponding numerical simulations were also presented to investigate the energy absorption and deformation mechanism of sandwich panels. Results showed that the deformation/failure modes of sandwich panels were sensitive to the impact velocity and density of aluminum foam. When the panel was impacted by the aluminum foam projectile with the back mass of nylon, the “accelerating impact” stage can be produced and may lead to further compression and damage of the sandwich structures.     

Dynamic response of bimaterial and graded interface cracks under impact loading

The interfacial fracture in bimaterial and functionally graded material (FGM) under impact loading conditions is investigated using experimental and numerical techniques that are valid for both type of interfaces. Experiments are conducted on epoxy based specimens in three point bend configuration and the complex SIF is measured using an electrical strain gage mounted close to the crack-tip. A complementary two-dimensional finite element simulation is performed using tup force and support reactions as input tractions, and the SIF-time history is determined using a displacement extrapolation technique. The experimentally determined SIF-histories match closely with numerical simulation up to the time of fracture initiation. The test results show that the mode-mixity remains nearly constant through out the test in both the materials, and the mixity values correspond to their respective static counterparts. The general dynamic response of the bimaterial and FGM specimens in terms of impact load, support reaction and the magnitude of complex SIF are comparable, and the mode-mixity is the parameter that distinguishes the graded interface from the bimaterial case.     

低速大质量冲击下伪弹性TiNi合金固支梁响应的数值研究

摘要：本文对低速大质量冲击下伪弹性TiNi合金固支梁的响应和相变演化特性进行了数值研究,目的是了解相变与结构动态响应之间的相互影响。结果表明,落锤冲击载荷作用下,相变固支梁的响应可以分为5个阶段：弹性波动响应,局部相变失稳,驻定相变铰形成,相变铰区扩展和相变铰移动,杆机构。相变铰为弯矩和轴力共同作用下形成的广义铰,同时表现出与塑性铰不同的特征。     

小半径城市高架曲线梁桥地震动响应研究

针对城市高架小半径曲线梁桥弯扭耦合严重、地震危害明显的特点,对武汉新站小半径曲线梁桥的有效的动力计算模型进行了探讨,比较了单根梁模型、板壳模型和脊梁模型在模拟小半径曲线桥时的准确性和精度。在脊梁模型的基础上,基于时程分析方法,采用三向地震波同时输入的方式,分析了小半径曲线桥的动力特性及其地震响应的主要影响因素。分析结果表明：脊梁模型是对小半径曲线桥进行动力分析的有效实用方法;后续结构、桩-土-桥的相互作用、桥墩刚度及支座偏心等敏感因素对小半径曲线桥的地震响应有较大的影响,计算分析时应给予足够重视     

反平面冲击荷载作用下圆柱形洞室的动力响应

对无限弹性土体内圆柱形洞室在反平面冲击荷载的作用下的瞬态响应进行了探讨。用残余变量的方法结合拉普拉斯变换及其逆变换,在频域内的得到土体位移和应力一般表达式,并采用拉普拉斯逆变换的数值方法,给出了问题的数值解。在时域内分析了无限弹性土体内圆柱形孔洞在沿轴向方向的冲击荷载作用下的土体动力响应的变化规律,并将计算结果与静力情况下的作了比较：反平面荷载作用后,波向外发散传播,并沿半径方向衰减,衰减速度较静力情况下的衰减要慢,且距离波源越远二者差别越大;波到达后,该点土体的应力和位移均发生与外荷载相同的三角形变化：先增大,随后减小最后保持为零不变。     

车辆撞击作用下泡沫铝防撞桥墩的动态响应特性

针对车辆撞击桥墩问题,设计了一种采用泡沫铝材料的桥墩防撞装置.采用LS-DYNA软件分别建立有无防撞装置的桥墩三维实体单元模型,分析了车辆撞击作用下各桥墩的动态时程响应.对比了两种情况下车辆对桥墩的撞击力、桥墩位移和应力等特征参量,并从能量传递的角度分析了泡沫铝防撞装置的耗能能力和撞击车辆损伤.结果表明:采用泡沫铝防撞...     

Composite materials response under low-velocity impact

A simple model, based on energy considerations, has been tested to predict the maximum contact force during a low-velocity impact between an impactor and a composite plate. Three different composites, i.e. glass cloth-polyester, carbon cloth-polyester and nylon cloth-polyester, were examined.The results reported here, obtained using an instrumented apparatus, show that the total energy applied during the impact is the governing parameter of the phenomenon, rather than the impactor speed or mass. All the composites under evaluation did not show any variation of elastic modulus with impact velocity. Moreover, the dynamic behaviour of carbon-polyester and nylon-polyester composites can be predicted by simple static tests, because of their insensitivity to rate-dependent phenomena; for these materials a simulation of impact tests by static tests is therefore suggested.Glass-polyester composites did show a rate-dependent behaviour, by an increase in strength of about 70% with respect to the static case; a small number of dynamic tests is, however, sufficient to characterise their behaviour under impact conditions.     

雷击冲击力作用下复合材料层合板动力学响应及损伤特性

采用基于连续介质损伤理论（CDM）的复合材料三维渐进损伤分析模型,以ABAQUS有限元分析软件为平台,结合VUMAT子程序,对雷击冲击力作用下的复合材料层合板进行了三维动力学分析,研究了雷击冲击力作用下层合板的动力学响应及损伤特性。结果表明,在雷击冲击力作用下,层合板做降幅振荡运动,冲击力做功与层合板内能和动能相互转换,同时伴随着黏性耗散能,冲击力做功大小可用雷电流库伦量与作用积分的函数表示;层合板损伤由外力做功大小决定,对于同种材料,基体、纤维及分层损伤分别存在不同的损伤能量临界值,当冲击力做功大于该值,层合板会产生对应的损伤;在相同边界支持条件下,冲击力总功最大值决定了不同损伤类型损伤状态变量的大小,与波形参数和峰值电流无关。     

Dynamic fields near a collinear macrocrack-microcrack configuration under antiplane impact loading

Dynamic interaction between a macrocrack and a collinear, neighboring microcrack is investigated. The mathematical formulation presented here is two-dimensional, and for a state of antiplane strain. A time-domain boundary integral equation method is presented to calculate elastodynamic stress intensity factors generated by the incidence of stress (or displacement) pulses on single cracks and systems of two collinear cracks. As a check of the time-stepping technique presented here, numerical calculations have been carried out for pulse incidence on a single crack, and the results have been compared with those of other authors. For macrocrack-microcrack configurations the variation of the effective stress intensity factors at the tips of the macrocrack with time, with the microcrack location, and with the microcrack size will be displayed and discussed.

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Résumé On étudie l'interaction dynamique entre une macrofissure et une microfissure colinéaire voisine. La formulation mathématique présentée est à deux dimensions et relative à un état de déformations antiplanaires. On présente une méthode à intégrales permettant de calculer les facteurs d'intensité de contraintes élastodynamiques dus à l'effet de pics de contraintes ou de déplacements sur des fissures simples ou sur des systèmes de deux fissures colinéaires. Pour contrôler la technique présentée, des calculs numériques sont effectués pour l'effet d'une impulsion sur une fissure simple, et les résultats sont comparés avec ceux d'autres auteurs. Pour des configurations macro-microfissure, on établit et on discute la variation des facteurs d'intensité de contraintes aux extrémités de la macrofissure en fonction du temps, de la position de la microfissure et de sa dimension.

     

SWATH船在砰击载荷作用下动态响应研究

针对SWATH在波浪中航行时,其湿甲板底部易遭受砰击从而引起船体振动的现象,对SWATH的砰击动态响应和强度进行了研究。利用SWATH在规则波中船波相对运动推导了随空间和时间变化的砰击载荷,采用有限元数值仿真,计算了SWATH湿甲板受砰击载荷作用的动态响应,分析了其位移和应力分布规律;并与静强度法砰击响应进行了比较,对湿甲板强度设计方法进行了探讨,为船舶结构设计提供参考     

Dynamic delamination fracture toughness of a graphite/epoxy laminate under impact

Dynamic delamination fracture toughness in a [90/0]_5s T300/934 graphite/epoxy laminate was investigated using impact loading. Delamination cracks of three different sizes were embedded at the mid-plane of the composite specimen. The threshold impact velocity that causes propagation of the delamination crack was used in the dynamic analysis with the finite element method. From the finite element solution, the time-history of the strain energy release rate was calculated. The critical strain energy release rate was taken to equal the maximum value of the response history.     

大空间柱面网壳结构在爆炸荷载下的动力响应

摘 要：通过应用LS-DYNA程序对柱面网壳结构室内爆炸的数值模拟实验,建立了大空间结构在爆炸作用下进行动力响应计算的合适模型。数值模拟计算结果与J.亨利奇公式结果吻合。通过提取结构表面有限测点的冲击波超压并将其POD分解,解决了冲击波荷载的时空差异性及结构表面压力场分布问题。采用Ritz-POD法对大空间单层柱面网壳结构在爆炸荷载下的动力响应进行了数值模拟计算,研究了结构矢跨比、结构高度、炸药TNT当量及爆炸点位置等参数变化对结构动力响应的影响。结果表明,计算模型适用于大空间结构的爆炸动力响应分析。大空间结构的最大位移和应力响应随炸药TNT当量的增加成非线性增大,应力响应成倍增大,位移响应成数倍增加。偏心爆炸冲击波比中心爆炸对大空间结构构件的损害大,对结构的边跨构件最为不利。对于应力控制设计的结构,应更注重支座附近和边跨结构的防爆能力。矢跨比大的结构防（抗）爆炸冲击波的能力较强。     

Estimation of the plastic structural response under impact

By means of effective load, P_e, and effective impulse, I_e, a characteristic curve for the response of structures subjected to general pulse loading is obtained. The structural response to an arbitrary impact can be estimated from this curve. Alternatively, a characteristic curve by means of total effective load, P′_e, and total impulse, I, is also deduced so as to simplify the computation, while its validity is discussed.     

Multimodal nonlinear spectral response of a beam with impact under random input

A linearization procedure for estimating the spectral response of a randomly excited beam—stop system is proposed. The elastic stop is replaced by a spring with a stiffness depending on the amplitude of the deflection at the impact location. The probability density function of the amplitude is obtained using the stochastic averaging principle. Next, an estimate of the nonlinear response spectrum is derived providing the expectation of the spectral density function of the random spring linear system with respect to the probability density function of the amplitude response (assumed to be a random variable). The efficiency of the method is checked by comparing results with those of numerical simulations.