共查询到20条相似文献,搜索用时 15 毫秒
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本文提出了一种研究均布外压下复合材料球壳内表面薄层脱层屈曲特性的理论方法,基于弹性相似性原理建立了复合材料球壳受压内表面脱层跳跃屈曲的模型,采用非线性大挠度理论建立了脱层屈曲的控制方程,分别研究了初始状态含脱层和不含脱层的复合材料球壳的脱层屈曲特性,得到了两种情况下脱层屈曲临界载荷的表达式,讨论了脱层厚度、脱层位置、脱层大小对脱层临界屈曲载荷的影响。结果表明:对于初始状态靠近内表面存在脱层的复合材料球壳,如果脱层厚度很薄,在压力达到一定值时,内表面的脱层区域将发生跳跃屈曲,其屈曲的挠度远远大于脱层的厚度,屈曲的临界载荷随脱层大小的增大而增大,且与脱层厚度几乎成正比;对于初始状态不含脱层的受压复合材料球壳,在靠近其内表面区域存在一个位置,其对应的脱层屈曲临界载荷为最小,最有可能脱离球壳整体,发生跳跃屈曲;如果层间强度不足,该脱层还有可能进一步地扩展,从而导致薄层大面积地脱离整体,降低结构刚度。 相似文献
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Elastic critical buckling load of a column depends on various parameters, such as boundary conditions, material, and crosssection geometry. The main purpose of this work is to present a new method for investigating the buckling load of tapered columns subjected to axial force. The proposed method is based on modified buckling mode shape of tapered structure and perturbation theory. The mode shape of the damaged structure can be expressed as a linear combination of mode shapes of the intact structure. Variations in length in piecewise form can be positive or negative. The method can be used for single-span and continuous columns. Comparison of results with those of finite element and Timoshenko methods shows the high accuracy and efficiency of the proposed method for detecting buckling load. 相似文献
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《船舶与海洋工程学报》2018,(4)
Experimental studies are carried out with slender bodies vertically exiting out of the water using a high-speed camera. The mechanisms for the formation, development, and collapse of the cavity around the slender body are explored. The dynamic characteristics of the shoulder cavity and the trail cavity during the water-exit of low-speed bodies are analyzed for various water depths and initial velocities. The results show that the initial velocity has a great influence on the formation, development, and collapse of the cavity. The length and the thickness of the shoulder cavity vary non-linearly with the depth. 相似文献
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《舰船科学技术》2017,(15)
The vibration isolation performances of typical hull structure with viscoelastic interlayer are analyzed according to wave theory,and the influences of interlayer Young’s modulus and length on the vibration reduction are discussed.The theoretical analysis shows that combination of polyurethane interlayer with blocking mass can enhance the vibration isolation performance and expand isolation frequency band.In order to verify the effectiveness of polyurethane interlayer,the model test of power cabin’s vibration is carried out.The test data shows that the reduction of 20–1 000 Hz variation acoustic level at hull shell is more than 5 dB. 相似文献
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To overcome the current difficulties of high-precision machining and the high manufacturing and maintenance costs of spherical seals for deep-water drilling ball joints, a new spherical seal technique is proposed in this paper. The spherical seal is mainly composed of silicone rubber and polytetrafluoroethylene(PTFE). Rational structural design makes the seal independent from the ball and other components, making it easy to replace if leakage occurs at its surface. PTFE can elastically deform over a certain deformation range, which guarantees that two sealing surfaces fit tightly together. O-Ring and PTFE elasticity makes up for any lack of accuracy during spherical machining and decreases the machining precision requirements for spherical surfaces. Using a finite element technique and nonlinear theory, the performance of the spherical seal under the influence of various factors is determined. The results show that the spherical seal designed in this paper exhibits excellent sealing performance under lowtemperature and high-pressure conditions. The spherical seal, a combination of an O-ring and PTFE, has the advantages of cheap manufacturing and maintenance costs and excellent sealing performance. 相似文献
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《船舶力学》2021,(6)
本文基于CFD方法对圆盘撞水弹跳过程的运动特性进行了研究,对三种典型撞水运动状态进行了模拟,数值结果与文献中的试验结果吻合良好。基于计算结果,获得了圆盘可以成功弹跳的初始参数组合范围。圆盘弹跳过程中,前方会产生一股射流,其脱离圆盘的射出速度可以达到入水速度的两倍左右。随着圆盘自旋速度的增加,圆盘受到的流体动力逐渐增加,但速度衰减也随之逐渐增加。相对较小的初始倾角和入水角总是有利于圆盘撞水后的弹跳,但过小的初始倾角可能会不利于连续多次弹跳过程。对圆盘连续弹跳过程的数值模拟结果表明,圆盘运动路线并非一直向前,而是受自旋影响运动方向有一定程度的偏转,圆盘第一次撞水弹跳的高度和距离远大于后面几次的弹跳过程。 相似文献
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Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be configured as either a mono- or bi-stable isolator. This paper focuses on investigating the relative performance of these two classes under the same excitations. Force transmissibility is used to measure the isolation performance, which is defined in terms of the RMS of the ratio of the transmitted force to the excitation force. When the system is subjected to harmonic excitation, it is found that the maximum reduction of the force transmissibility in the isolation range using Quasi-Zero stiffness is achieved. When the system is subjected to random excitation, it has the same effect of Quasi-Zero stiffness. Further, optimum damping can be changed with stiffness and has minimum value. 相似文献
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《船舶与海洋工程学报》2015,(3)
In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method(FEM) by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. 相似文献
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《船舶力学》2017,(6)
为了获得连续水下爆炸声源,文章设计了金属导爆索网栅结构,并开展了水下爆炸压力测试和气泡脉动实验,研究了金属导爆索网栅结构水下爆炸的声压级特性,水下爆炸的声持续时间,对应的混响效应,利用Hilbert-Huang变换对水下爆炸信号的频谱特性进行了分析。研究结果表明:金属导爆索网栅结构水下爆炸可根据设计连续产生多个脉冲冲击波信号,形成近似平稳的连续波,随后产生的气泡脉动和混响效应能够明显提高水下爆炸声的持续时间;金属导爆索网栅结构具有很强的声功率,水下爆炸声压级最高能够达到249 d B,爆炸60 ms后金属导爆索的爆炸声压级仍在200 d B以上;金属导爆索网栅结构水下爆炸声频率范围广,在100 kHz以下低频段能量最高。金属导爆索网栅结构水下爆炸脉冲信号频率成分丰富,具有低频和瞬时的特点,且大部分集中在100 kHz以下,尤以50 kHz以下的最为明显;脉冲信号具有多个能量峰值,能量值较集中,波动能量基本上都集中在频率为100 kHz范围以内,尤以50 kHz以下的低频能量最大,高于100 kHz以上频段的能量的分量很小。脉冲冲击波的个数和声持续时间可由金属导爆索网栅的排列方式和长度控制,脉冲冲击波间的时间间隔可调,发生装置稳定易控。 相似文献
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《船舶力学》2015,(6)
张力腿涡激振动易引起系泊系统的疲劳损伤,危害张力腿平台的安全性和可靠性。该文借鉴细长立管涡激振动的相关研究,同时考虑张力腿与立管在截面尺度、预张力大小以及边界条件存在的巨大差距,采用切片理论结合CFD数值模拟方法,对平台运动影响下张力腿涡激振动开展了研究。考虑定常张力与时变张力对涡激振动的影响,采用GAMBIT软件分区建立了多切片计算网格,将编制求解涡激振动的UDF程序嵌入Fluent软件中,采用动网格技术实现流场的更新并计算作用于张力腿上的瞬时升力和拖曳力。文中还比较了仅考虑流和考虑浪、流联合作用张力腿的时变张力影响,研究了两种典型波高共计六种工况,计算结果表明:随着流速的增加,各模态权重比例将发生跳转现象;尽管由于平台运动导致张力腿受力的随机性,但平台运动对张力腿涡激振动影响较小。 相似文献
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《船舶与海洋工程学报》2021,(3)
This study investigates the interaction and influence of surface cracks on the spherical pressure hull of a deep-sea manned submersible.The finite element model of the spherical hull is established,and a semi-elliptical surface crack is inserted in the welding toe of the spherical hull as the main crack.Considering the combined effect of external uniform pressure and welding residual stress at the weld toe,the stress intensity factor(SIF) is obtained based on the M-integral method.Inserting disturbing cracks at different positions on the spherical hull surface,the interaction and influence between multi-cracks are revealed by numerical calculation.The results show that the existence of the disturbing crack has a great influence on the stress intensity factor of the main crack,and the influence is different with the different location of disturbing crack.The study of the interaction of multiple cracks under different interference factors and the influence of disturbing cracks on the main crack can provide some reference for future engineering applications. 相似文献
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In this study, we investigated the hydrodynamic and energy conversion performance of a double-float wave energy converter(WEC) based on the linear theory of water waves. The generator power take-off(PTO) system is modeled as a combination of a linear viscous damping and a linear spring. Using the frequency domain method, the optimal damping coefficient of the generator PTO system is derived to achieve the optimal conversion efficiency(capture width ratio).Based on the potential flow theory and the higher-order boundary element method(HOBEM), we constructed a threedimensional model of double-float WEC to study its hydrodynamic performance and response in the time domain. Only the heave motion of the two-body system is considered and a virtual function is introduced to decouple the motions of the floats. The energy conversion character of the double-float WEC is also evaluated. The investigation is carried out over a wide range of incident wave frequency. By analyzing the effects of the incident wave frequency, we derive the PTO's damping coefficient for the double-float WEC's capture width ratio and the relationships between the capture width ratio and the natural frequencies of the lower and upper floats. In addition, it is capable to modify the natural frequencies of the two floats by changing the stiffness coefficients of the PTO and mooring systems. We found that the natural frequencies of the device can directly influence the peak frequency of the capture width, which may provide an important reference for the design of WECs. 相似文献
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In this paper, the spray and combustion characteristics of diesel/butanol-blended fuels were studied within a high-temperature and high-pressure constant volume chamber equipped with a single-hole injector. Two blends with 80% diesel/20% butanol and 60% diesel/40% butanol mixed by volume were tested in this study. The pure diesel B0 was also tested here as a reference. The spray penetration, flame lift-off length, and soot optical thickness were obtained through high-speed schlieren imaging, OH<... 相似文献