共查询到19条相似文献,搜索用时 406 毫秒
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利用ABAQUS有限元软件进行了单个圆形高斯光斑的激光冲击强化数值模拟,分析材料表面光斑中心区域形成的"残余应力洞"现象,并通过分析材料的动态力学响应特征揭示了"残余应力洞"的形成机制。结果表明:在冲击波加载时,光斑边界处会产生很强的剪切应力,形成向四周传播的表面稀疏波和向材料内部传播的剪切波。当稀疏波同时传播到光斑中心,发生相遇、汇聚,使材料产生急剧的上下位移过程,造成冲击波加载塑性变形后的二次塑性变形。二次塑性变形中形成了较大的剪切塑性应变,并降低了冲击波加载阶段产生的轴向和径向塑性应变,使残余压应力降低,从而形成"残余应力洞"。 相似文献
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建立三维的铝粉-空气两相爆轰计算模型,采用时-空守恒元解元(CE/SE)方法求解,并开发了悬浮铝粉尘爆轰的三维数值模拟程序.基于消息传递接口(MPI)技术实现了程序的并行化设计.通过对激波管问题以及爆轰管中铝粉-空气两相爆轰实验的模拟验证程序的可靠性.对拐角空间中左侧浓度为368 g·m-3的铝粉-空气混合物两相爆轰及其在拐角空间右侧和下方空气域内形成的冲击波和温压效应开展数值模拟,获得复杂空间内爆轰波或冲击波的传播、反射以及绕射过程.结果表明:两相爆轰在离铝粉尘区域2 m远的空气域内产生的后效冲击波能达到2.66 MPa的固壁反射压力,火球燃烧范围会超出初始铝粉尘区域约0.8 m,并且造成初始铝粉尘区域附近1.5 m范围内空气的温度高达1 600 K.模拟程序可用于铝粉尘爆轰的后效研究,对工业安全及其防护具有指导意义. 相似文献
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介绍并分析了Campbell 等人及其他作者研究非均匀炸药冲击起爆和起爆后行为所获得的实验结果,但不涉及其冲击起爆条件。足够强的冲击波进入非均匀炸药后,爆轰将瞬时(指不经过感应时间)且直接(指不经过其他过程,如爆燃)被引发;非均匀炸药起爆后,其中传播的自始至终是一个不断增长的爆轰波,直至发展为正常爆轰,整个过程都是爆轰的增长(新定义)过程。不存在由反应冲击波不断增长并转变为爆轰波的所谓向爆轰的增长。所谓向爆轰的增长,实际上是爆轰的增长(按新定义)的初期;Craig原定义的爆轰的增长,实际上是爆轰的增长(按新定义)的后期;而所谓反应冲击波,实际上是增长中的初期爆轰波。爆轰的增长(按新定义)是所有猛炸药的特性,炸药反应不充分并逐渐趋于充分是爆轰的增长的化学机制。 相似文献
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针对爆轰波在炸药-金属界面上折射时由实验获得的金属折射冲击波压力与经典爆轰波极曲线理论预测的压力存在显著差异这一问题, 本文展开了进一步的理论和数值模拟分析研究. 首先通过分析指出经典爆轰波极曲线理论的缺陷, 并对爆轰波极曲线理论进行了改进, 改进爆轰波极曲线理论给出了炸药爆轰波折射类型以及折射冲击作用点处的压力值. 然后发展了一个基于次特征理论来数值求解爆轰反应流动控制方程的二阶中心型Lagrange方法, 并数值模拟了一个典型的炸药爆轰波折射实验. 改进爆轰波极曲线理论和数值模拟分析结果表明, 爆轰波折射类型有三种:反射冲击波的正规折射、带Mach反射的非正规折射、无反射波的正规折射, 并且金属折射冲击波压力值随入射角增大而单调减小. 相似文献
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研究了熔石英玻璃元件在纳秒激光等离子体冲击波作用下的表面和横截面损伤形貌,利用有限元法模拟了冲击波在熔石英玻璃内部的传播规律,并基于冲击波在玻璃内部的应力分布规律分析了损伤形成机理.研究发现:在冲击波作用下,石英玻璃会受到沿波面方向的压应力和沿波面切方向的拉应力,在这两种力的作用下,造成以激光辐照中心的弧状层状断裂和沿径向的断裂;冲击波的反射叠加还会使局部拉应力增大,造成靠近后表面的损伤.有限元法能够直观地分析等离子体冲击波对光学元件的作用,并分析光学元件在等离子体冲击波下的损伤机理. 相似文献
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Propagation of shock and detonation waves in channels with U-shaped bends of limiting curvature 总被引:1,自引:0,他引:1
S. M. Frolov V. S. Aksenov I. O. Shamshin 《Russian Journal of Physical Chemistry B, Focus on Physics》2008,2(5):759-774
Systematic experimental and theoretical studies of the propagation of shock and detonation waves in cylindrical tubes and planar channels with two U-shaped bends of limiting curvature were performed. It was demonstrated that U-shaped bends substantially facilitate detonation initiation in gases. The minimum shock wave velocity required to initiate the detonation of a stoichiometric propane-air mixture under normal conditions in a near-critical diameter tube with two U-shaped bends of limiting curvature was found to be ~800 m/s. 相似文献
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The propagation of a small but finite shock disturbance through gas contained within a cylindrical tube is examined theoretically for the case where both the hoop elasticity and radial inertia of the tube are taken into account. Governing equations so derived are found to admit a non-dispersive wave of variable pressure behind the advancing shock front in direct contrast with the situation existing for an initially sharp-fronted infinitesimal disturbance where no steady wave form is possible. Detailed calculations are carried out for the case where the gas filling the tube is air. Results show that increases in either the tube or shock strength are sufficient to make the pressure distribution behind the wave front approach that which would exist in a rigid tube under similar conditions. 相似文献
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Jason R. Burr 《Proceedings of the Combustion Institute》2019,37(3):3471-3478
An experimental study was conducted to characterize fundamental behavior of detonation waves propagating across an array of reactant jets inside a narrow channel, which simulated an unwrapped rotating detonation engine (RDE) configuration. Several key flow features in an ethylene-oxygen combustor were explored by sending detonation waves across reactant jets entering into cold bounding gas as well as hot combustion products. In this setup, ethylene and oxygen were injected separately into each recessed injector tube, while a total of 15 injectors were used to establish a partially premixed reactant jet array. The results revealed various details of transient flowfield, including a complex detonation wave front leading a curved oblique shock wave, the unsteady production of transverse waves at the edge of the reactant jets, and the onset of suppressed reactant jets re-entering the combustor following a detonation wave passage. The visualization images showed a complex, multidimensional, and highly irregular detonation wave front. It appeared non-uniform mixing of reactant jets lead to dynamic transverse wave structure. The refreshed reactant jets evolving in the wake of the detonation wave were severely distorted, indicating the effect of dynamic flowfield and rapid pressure change. The results suggest that the mixing between the fuel and oxidizer, as well as the mixing between the fresh reactants and the background products, should affect the stability of the RDE combustor processes. 相似文献
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《Proceedings of the Combustion Institute》2023,39(3):3001-3010
Inward-propagating cylindrical flames are studied numerically by high-resolution simulations using a one-step Arrhenius kinetics. Emphasis is placed on the effect of shock waves on the flame propagation by setting initial ignition conditions with and without shock wave. It is found that without initial shock wave, the inward-propagating flame propagates initially at a constant speed, while in the later stage of the propagation, it shows a small-amplitude oscillatory motion. When the shock wave initially introduced is medium, a large-amplitude oscillatory motion is caused by the interaction of shock waves with the inward-propagating flame. Moreover, autoignition occurs at the center and develops outwardly into a cellular flame. However, as the introduced shock wave is strong, autoignition created at the center evolves outwardly a cellular detonation. 相似文献
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This paper discusses the mathematical formulation of Detonation Shock Dynamics (DSD) regarding a detonation shock wave passing over a series of inert spherical particles embedded in a high-explosive material. DSD provides an efficient method for studying detonation front propagation in such materials without the necessity of simulating the combustion equations for the entire system. We derive a series of partial differential equations in a cylindrical coordinate system and a moving shock-attached coordinate system which describes the propagation of detonation about a single particle, where the detonation obeys a linear shock normal velocity-curvature (Dn–κ) DSD relation. We solve these equations numerically and observe the short-term and long-term behaviour of the detonation shock wave as it passes over the particles. We discuss the shape of the perturbed shock wave and demonstrate the periodic and convergent behaviour obtained when detonation passes over a regular, periodic array of inert spherical particles. 相似文献
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Deok-Rae Cho Su-Hee Won Jae-Ryul Shin Jeong-Yeol Choi 《Proceedings of the Combustion Institute》2013,34(2):1929-1937
The three-dimensional structures of a detonation wave propagating in a circular tube were investigated using a one-step irreversible Arrhenius kinetics model. A series of parametric studies were carried out to investigate the different modes of cell structure formation by changing the pre-exponential factor. Maximum pressure trace was recorded along the tube wall to investigate the detonation cell structures. The unsteady results obtained in three dimensions revealed the generation mechanism of the wave front structures of two-, three- and four-cell mode detonations. A six-cell mode detonation could be obtained using a finer grid. With the increase in pre-exponential factor, it was found that the number of detonation cells is increased while the cell size is reduced accordingly. In all the multi-cell modes, the detonation wave structures and smoked-foil records on the wall are formed by the propagation of transverse waves along the wall in clockwise and counter-clockwise directions, while the slapping wave moves in the radial direction. The presence of the slapping wave further strengthens the wave interactions in three-dimensional simulation. Comparison with two-dimensional simulation confirms the effect of the slapping wave in the radial direction. As a result, the detonation wave front structures changes from the polygonal shape to the multi-bladed fan shape, periodically. 相似文献
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The initiation and propagation of detonation waves in combustible high speed flows were studied experimentally. A planar detonation wave traveling in an initiation tube was transmitted into a test section where a combustible high speed flow was induced by an incident shock wave generated in a shock tube. In this study, the flow Mach numbers were obtained as 0.9 and 1.2. The experimental results show that depending on the flow velocity, the apparent propagation velocity of a detonation wave is higher in the upstream and lower in the downstream direction than the CJ velocity. Smoked plate records reveal cellular patterns deformed in the flow direction, and the calculated aspect ratios of the cell were found to agree well with the experimental ones on the basis of the assumption that the velocity of the transverse wave is not affected by the flowing mixture. By analyzing the shock-wave diffraction at the position where there is an abrupt change in the area, on the basis of Whitham’s theory, it was deduced that in the present experimental set-up, the detonation was initiated by the reflection of the diffracted shock waves on the sidewalls of the test section. The agreement between the experimental and calculated results regarding the position of the cellular patterns on the smoked plate record indicated that the position of detonation initiation in high speed flows is shifted downstream due to the flow velocity. 相似文献