岩石动载损伤模型研究

在分析现有脆性材料爆炸和冲击损伤模型的基础上,根据冲击试验及声波理论,用能量法构造了岩石动载损伤模型．     

岩石冲击损伤特性实验研究

利用一级轻气炮对石灰岩进行冲击损伤实验,并对回收试样进行超声波测试,在此基础上建立了损伤度与碰撞速度、峰值压力及插入损伤的拟合关系。结果表明,插入损伤能很好地反映岩石的损伤程度。     

岩石冲击损伤特性实验研究

利用一级轻气炮对石灰岩进行冲击损伤实验,并对回收试样进行超声波测试,在此基础上建立了损伤度与碰撞速度、峰值压力及插入损伤的拟合关系。结果表明,插入损伤能很好地反映岩石的损伤程度。     

岩石蠕变损伤模型研究

本文基于第三阶段蠕变响应法,建议了一种岩石介质的蠕变损伤模型。在蠕变模型的基础上,进一步讨论了一般材料和一般加载情况下的损伤定义形式。     

动载测试与小波分析在桥梁结构损伤诊断中的联合应用

将结构动载测试与小波分析相结合提出了适用于大跨桥梁结构的两阶段损伤诊断方法。采集桥梁结构在损伤前后各测点的动载测试数据并进行小波包分解得到小波包能量谱，在此基础上计算结构损伤预警指标和损伤定位指标，用以确定损伤的发生及其所在的区域。某三跨连续梁桥的数值模拟研究结果表明了本文所采用的损伤诊断方法的可行性与有效性。     

岩石爆破损伤模型实验研究

岩石中含有以孔隙、气泡、微观裂隙、节理面等形态表现出来的岩石损伤。损伤的存在无疑要对岩石的爆破破碎效果产生影响。本文在相似性分析的基础上,提出了在实验室进行岩石爆破损伤模型实验的新方法,进而对损伤以及介质强度对爆破破碎效果的影响进行了分析研究。     

岩石爆破损伤模型实验研究

岩石中含有以孔隙、气泡、微观裂隙、节理面等形态表现出来的岩石损伤。损伤的存在无疑要对岩石的爆破破碎效果产生影响。本文在相似性分析的基础上,提出了在实验室进行岩石爆破损伤模型实验的新方法,进而对损伤以及介质强度对爆破破碎效果的影响进行了分析研究。     

浅谈国内桥梁检测中的静载和动载试验

本文介绍了在我国桥梁检测中应用广泛的静载试验和动载试验。对静载试验的试验内容及方法进行了较全面的总结;对动载试验的试验内容及方法进行了简要介绍并指出动载试验存在的一些不足。最后本文总结了国内关于静载和动载试验的应用状况及前景。     

岩石冲击损伤试验的数值流形方法模拟

主要根据岩石在冲击载荷作用下的变形与破坏特征,对现有的仅适用于模拟基于线性本构关系和恒定载荷作用下物体变形规律的数值流形程序进行了扩展.程序的扩展主要集中在3个方面:添加了由程序本身决定的程序运行终止条件,把恒定的载荷作用扩展为三角波载荷作用,改变原来的单一线弹性本构关系为由冲击损伤本构关系和线弹性本构关系共同组成的复合本构关系.最后利用扩展后的程序对冲击试验结果进行了模拟,结果与试验符合较好.     

岩石爆破光弹性损伤模型实验研究

通过损伤材料的光弹性分析，提出了利用损伤光弹性材料进行岩石爆破机理研究的新方法。通过实验，摸索出损伤光弹性材料制作的可行措施，得到了可用来进行光弹性试验研究的光弹性材料，并对材料的力学性能以及爆炸作用下损伤对材料中应力波的影响及其相互作用进行了研究。     

存在衰减和真实气体效应的激波管激波速度的计算

用一般理论计算激波管参数,由于激波的衰减不可避免以及一定压力下的气体是非理想气体,故会有不小误差。本分别考虑了衰减和真实气体效应这两种对激波速度有影响的因素,对一种具有良好压力平台的激波管（驱动气体为Ｈ２,被驱动气体为ＣＯ２）中的激波速度进行了计算。首先采用考虑真实气体效应的理论,计算破膜后形成的初始激波速度;在激波沿管运行理论不能准确计算的阶段,采用由实验得出的激波衰减公式进行计算。计算结果与     

水中空气隔层对冲击波传播衰减作用的初步探讨

针对减弱水下爆破作业产生的冲击波的破坏作用,提出了利用空气隔层衰减水中爆炸冲击波的方法,通过理论分析得出了空气隔层可以有效降低水中冲击波峰值超压的结论,并且通过实验证实了空气隔层的冲击波衰减作用。     

爆破振动作用下高层建筑振速变化规律研究

多层介质由压实层、碎石层和混凝土层组成。用量纲分析法导出多层介质中爆破混凝土层破坏效应的函数表达式。通过模拟实验,获得了药包不同药量、不同埋深条件下多层介质破坏效应的试验数据,并通过回归分析,拟合出漏斗的可见深度、实际半径与装药量关系的经验表达式。试验中利用高速录像研究了介质表层鼓包运动的规律。试验结果表明,混凝土层和碎石层在鼓包运动的中期对爆炸破坏效应有较明显的影响。     

粘性液体对管道中扭转导波传播特性的影响研究

对带有液体的圆柱/管中的波传播进行了研究。在流动为层流的假设下,研究了有粘性液体管道中扭转导波的位移模式和传播特性。分析了波的频散和衰减曲线,得到了粘性、密度等和第一阶扭转模态衰减的关系,确定了粘性液体对扭转导波的影响,为扭转导波在损伤检测中应用做了一些理论工作。数值计算结果与某文献中实验结果符合较好,一定程度上证明了液体中的层流假设,说明了第一阶扭转模态在损伤探测中的优势。     

Traveling wave solution of heat transfer for small sample moving in the sub-cooled liquid nitrogen

The temperature field of a traveling wave in a system is analyzed. The system consists of a rapidly moving small specimen tube and sub-cooled liquid nitrogen (SLN₂). The temporal and spatial temperature distribution of the subsonic wave is investigated. The relationship between a dimensionless cooling rate and the thermal Mach number (M) is derived. When the quenching speed of sample tube in the sub-cooled liquid nitrogen is equal to or faster than that of the thermal wave propagated, a shock wave is expected.     

Comparability research on impulsive response of double stiffened cylindrical shells subjected to underwater explosion

In order to evaluate the strength and comparability of impulsive environment of model and practical structure in the water when subjected to underwater explosion, a new shock factor based on energy acting on the structure is presented to describe the loading of underwater explosion. To test the validity of this new factor, numerical experiments of double stiffened cylindrical shells are carried out a series of cases designed by the new factor and two other standard shock factors respectively. The results of the cases designed by the new factor indicate that the kinetic energy, potential energy and shock response spectrums of the structures agree well with each other in different cases designed by the equal new shock factor. However, the results of the cases designed by the two other standard shock factors are rather diverse. The analysis considers that the old shock factors do not take the spherical characteristics of shock wave front and relative position between detonation and structure into account, which can hardly reflect the similarity of underwater explosion loadings. The new shock factor can make up for such limitations.     

Re-examination of the shock wave’s peak pressure attenuation in soils

The paper investigates the problem of a charge exploding in soil and focuses on the characteristics of the shock wave’s peak pressure attenuation. Analysis of existing empirical data observes different attenuation factors for apparently similar certain types of soils whereas for other types of soils there is no significant difference. It was also observed that prediction of the shock wave’s peak pressure with existing power law empirical formulas yields a large discrepancy in comparison to test data. The discrepancy is significant even in case where the specific tested soil parameters are used. These observations among others motivated this study. The power law relationship has been investigated through numerical simulations of the shock wave propagation in different soils. The soil is modeled as a bulk irreversible compressible elastic plastic medium, including full bulk locking and dependence of the current deviatoric yield stress on the pressure. The Lagrange approach and the modified variational difference methods are used to simulate the process. The study shows that the shock wave’s peak pressure attenuation for certain types of soils may be well presented by a power law with a constant exponent, whereas other types of soils may be presented by a power law for a limited distance range and their behavior for a wide distance range is poorly described by a linear relationship on a logarithmic scale but is well represented by a bi-linear or a tri-linear realtionship. These findings explain some of the above mentioned observations.     

How do energetic ions damage metallic surfaces?

Surface modification of structural and functional materials under bombardment by energetic ions is observed under different conditions and can be either an unavoidable effect of the irradiation or an intentional modification to enhance materials properties. Understanding the basic mechanisms is necessary for predicting property changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper, we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron induced by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films with (1 0 0) and (1 1 0) surfaces at room temperature. A large number of simulations, ∼400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three scenarios were primarily observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some cases, formation of large 〈1 0 0〉 vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.     

A New Inverse Algorithm for Tomographic Reconstruction of Damage Images Using Lamb Waves

Lamb wave tomography (LWT) is a potential and efficient technique for non-destructive tomographic reconstruction of damage images in structural components or materials. A new two-stage inverse algorithm with a small amount of scanning data for quickly reconstructing damage images in aluminum and CFRP laminated plates was proposed in this paper. Due to its high sensitivity to damages, the amplitude decrease of transmitted Lamb waves after travelling through the inspected region was employed as a key signal parameter related to the attenuation of Lamb waves in propagation routes. A through-thickness circular hole and a through-thickness elliptical hole in two aluminum plates, and an impact-induced invisible internal delamination in a CFRP laminated plate were used to validate the effectiveness and reliability of the proposed method. It was concluded that the present new algorithm was capable of reconstructing the images of the above mentioned various damages successfully with much less experimental data compared with those needed by some traditional techniques.     

近距非接触水下爆炸舰船动态响应的数值模拟

运用通用有限元程序ABAQUS对某型水面舰艇在水下爆炸冲击波作用下的动态响应进行了数值模拟,有效地解决了ABAQUS计算近场水下爆炸时单元破损和单元失效等问题,计算出了某型舰艇水下爆炸的冲击响应结果,获得了船体的应力响应、局部变形、加速度响应和速度响应4个方面的响应规律,并得出以下结论:在全船范围内,加速度和速度总是由下至上逐渐减小,离爆点最近的区域差距最为明显;船体上离爆点最近的区域应力是最大的,不同甲板在相同位置处的应力是不同的。数值模拟所得的舰艇在水下爆炸作用下的响应规律与实际分析规律相符,为舰艇抗爆、抗冲击的结构设计提供了依据。