A NOVEL SEMI-ANALYTICAL METHOD FOR SOLVING ACOUSTIC RADIATION FROM LONGITUDINALLY STIFFENED INFINITE NON-CIRCULAR CYLINDRICAL SHELLS IN WATER

Based on the extended homogeneous capacity high precision integration method and the spectrum method of virtual boundary with a complex radius vector, a novel semi-analytical method, which has satisfactory computation efectiveness and precision, is presented for solving the acoustic radiation from a submerged infnite non-circular cylindrical shell stifened by longitudinal ribs by means of the Fourier integral transformation and stationary phase method. In this work, besides the normal interacting force, which is commonly adopted by some researchers, the other interacting forces and moments between the longitudinal ribs and the non-circular cylindrical shell are considered at the same time. The efects of the number and the size of the cross-section of longitudinal ribs on the characteristics of acoustic radiation are investigated. Numerical results show that the method proposed is more efcient than the existing mixed FE-BE method.

ELECTRIC FIELD GRADIENT EFFECTS IN ANTI-PLANE PROBLEMS OF A CIRCULAR CYLINDRICAL HOLE IN PIEZOELECTRIC MATERIALS OF 6 mm SYMMETRY

We study electromechanical felds in the anti-plane deformation of an infnite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electro- elastic dielectrics with electric feld gradient in the constitutive relations is used. Special attention is paid to the felds near the surface of the hole.

First demonstration of improving laser propagation inside the spherical hohlraums by using the cylindrical laser entrance hole

The octahedral spherical hohlraums have natural superiority in maintaining high radiation symmetry during the entire capsule implosion process in indirect drive inertial confinement fusion.While,in contrast to the cylindrical hohlraums,the narrow space between the laser beams and the spherical hohlraum wall is usually commented.In this Letter,we address this crucial issue and report our experimental work conducted on the SGIII-prototype laser facility which unambiguously demonstrates that a simple design of cylindrical laser entrance hole(LEH)can dramatically improve the laser propagation inside the spherical hohlraums.In addition,the laser beam deflection in the hohlraum is observed for the first time in the experiments.Our 2-dimensional simulation results also verify qualitatively the advantages of the spherical hohlraums with cylindrical LEHs.Our results imply the prospect of adopting the cylindrical LEHs in future spherical ignition hohlraum design.

Hawking Radiation of Charged Particles via Tunneling from a Cylindrically Symmetric Black Hole in Anti-de Sitter Space-Time

Applying Parikh-Wilzcek＇s semi-classical quantum tunneling model, we study the Hawking radiation of charged particles as tunneling from the event horizon of a cylindrically symmetric black hole in anti-de Sitter space-time. The derived result shows that the tunneling rate of charged particles is related to the change of Bekenstein-Hawking entropy and that the radiation spectrum is not strictly pure thermal after taking the black hole background dynamical and self-gravitation interaction into account, but is consistent with the underlying unitary theory.

The deformation and failure mechanism of cylindrical shell and square plate with pre-formed holes under blast loading

The deformation and failure mechanism of cylindrical shells and square plate with pre-formed holes under blast loading were investigated numerically by employing the Ansys 17.0 and Ls-Dyna 971.To calibrate the numerical model,the experiments of square plates with pre-formed circle holes were modeled and the numerical results have a good agreement with the experiment data.The calibrated numerical model was used to study the deformation and failure mechanism of cylindrical shells with pre-formed circle holes subjected to blast loading.The structure response and stress field changing process has been divided into four specific stages and the deformation mechanism has been discussed systematically.The local and global deformation curves,degree of damage,change of stress status and failure modes of cylindrical shell and square plate with pre-formed circular holes are obtained,compared and analyzed,it can be concluded as:(1)The transition of tensile stress fields is due to the geometrical characteristic of pre-formed holes and cylindrical shell with arch configuration;(2)The existence of preformed holes not only lead to the increasing of stress concentration around the holes,but also release the stress concentration during whole response process;(3)There are three and two kinds of failure modes for square plate and cylindrical shell with pre-formed holes,respectively.and the standoff distance has a key influence on the forming location of the crack initiating point and the locus of crack propagation;(4)The square plate with pre-formed holes has a better performance than cylindrical shell on blast-resistant capability at a smaller standoff distance,while the influence of pre-formed holes on the reduction of blast-resistant capability of square plate is bigger than that of cylindrical shell.

THE GENERAL SOLUTION FOR THE STRESS PROBLEM OF CIRCULAR CYLINDRICAL SHELLS WITH AN ARBITRARY CUTOUT

In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic equation series. The solution can be normal and effective by means of this method. Numerical results for stress concentrations in the shell with a circular, elliptic cutout are graphically presented.

Stability of perfect and imperfect cylindrical shells under axial compression and torsion

Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.

Analysis on Micro Complex Shape Via Hole Punching on Low Temperature Co-Fired Ceramics

The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are?changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have?little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.

筒体悬挂结构若干问题分析

以菏泽博物馆新馆项目为背景,从计算方法、构件受力和设计、整体屈服机制等八个方面对筒体悬挂结构体系做了较全面的研究。结果表明:1)计算筒体悬挂结构水平地震作用时无需调整层质量;2)规范底部轴力法、振型分解反应谱法并不适用筒体悬挂结构竖向地震作用计算,考虑最小限值调整后的吊柱设计仍可能偏不安全;3)采用长孔螺栓节点设计能让筒体悬挂结构吊柱在各工况下处于理想轴向拉压受力状态;4)中高烈度区吊柱在大震组合作用下可能受压,有必要复核其受压稳定和承载力;5)吊柱受力在小震阶段为恒、活载控制,大震阶段其恒、活载占比降低,地震逐渐起控制作用;6)合理的吊柱布置除满足建筑条件外,还需兼顾核心筒顶受力,减小筒顶不平衡弯矩;7)核心筒顶上包与否均能实现与屋面悬挂桁架的有效刚性连接;8)合理的筒体悬挂结构屈服机制就是落地核心筒的延性破坏过程,即始于连梁开裂破损,终于筒底墙肢钢筋拉屈、混凝土压溃。

圆柱体方孔配合件钳工加工工艺研究

随着制造业的不断发展,高精度圆柱体方孔配合件的需求日益增加。文章针对圆柱体方孔配合件的钳工加工工艺展开研究,通过优化划线、钻孔、凿方孔和修配等关键工序的加工参数和方法,制备出精度稳定、表面质量高的配合件。实验结果表明,所提出的加工工艺可以将圆度和圆柱度误差控制在0.018 mm以内,使方孔边长偏差小于0.015mm,配合面粗糙度优于0.6μm,能够满足精密机械传动的装配要求。

Analysis and Prediction of Hole Penetrated in Thin Plates under Hypervelocity Impacts of Cylindrical Projectiles

The hole penetrated in thin metallic plates due to hypervelocity impacts of cylindrical projectiles was analyzed by experimental method.The projectile caused a hole-expanding effect when penetrating the target plate because of dynamic shear failure and extrusion.A new empirical model was presented to predict the perforation diameter in thin plates impacted by high-velocity cylindrical projectiles.The fitting coefficients resulted in a root-mean-square of 0.0641 and a correlation coefficient of 0.991.The errors between the predicted and the experimental values were less than 7.251%,and less than 4.705%for 93.333%cases of the dataset.The accuracy of the proposed model is much higher than that of Hill's model.Compared with historical equations,the new model is more accurate and can well describe the variations of different parameters with the normalized penetrated hole.The model takes into account the strength of materials,which contributes to the excellent results.This paper could provide important theoretical support for the analysis of the perforation process and its mechanism.

圆柱孔破损膨胀土强度和变形特性的CT-三轴试验研究

通过8组不同孔径破损膨胀土的CT-三轴试验,研究了圆柱孔破损重塑膨胀土的变形、强度特性以及破损结构的演化规律。试验结果表明:圆柱孔破损对膨胀土的强度有明显的弱化作用,但破损孔径大小的影响不大。吸力一定时,圆柱孔面积变化随着净围压的增加而减小;净围压相同时,吸力大的试样圆柱孔面积减少得越大。净围压在破损重塑膨胀土结构演化中发挥重要作用,随着净围压从50 kPa增加到200 kPa,CT图像的均值(ME值)提高幅度增大,试样内部的平均密度变大;相应地,CT图像的标准差(SD值)降低的幅度也增大,试样结构趋于均匀化。

固体中圆柱形孔脉冲超声波散射的有限元模拟

建立了半无限各向同性弹性固体的具有吸收边界的二维平面应变有限元模型,计算研究了入射平面脉冲超声纵波和横波在固体中横向圆柱形孔上的散射。计算结果以位移场波场快照和位移散度场(纵波)、位移旋度场(横波)波场快照的形式给出,与现有动态光弹实验照片进行了比较,符合得较好。通过对计算数据的处理,清晰地看到了入射纵波沿孔壁的螺旋旋转爬行,证实了理论预计,弥补了光弹实验结果的不足。

气吸滚筒式棉花精量穴播器排种性能试验

针对气吸滚筒式精量穴播器作业过程中能耗大、排种性能不稳定等问题,以主要影响因素:取种盘吸孔线速度和充种负压为研究对象进行正交试验、回归分析,确定各因素对排种性能的影响规律及较优工作参数组合。结果表明:充种相对压力-4.5kPa、取种盘吸孔线速度0.38m/s时为较优作业参数组合,此条件下穴播器的单粒指数为98.67%、综合评价指数为99.00%、重播指数为0.67%、漏播指数为0.67%,满足精量穴播要求。

用正交试验分析电参数对小孔圆柱度的影响

为实现电火花加工小孔圆柱度误差的合理控制,通过工艺试验研究了放电参数与小孔圆柱度间的规律。提出了多截面直角坐标测量方法,用线切割对已加工小孔的工件进行轴向和径向切割,以产生反映小孔特征的母线基准和圆基准;然后,用万能工具显微镜对这两个基准上的特征点进行测量,最终实现小孔圆柱度的定量评定。在此基础上,采用正交试验研究了放电参数(开路电压、电流,脉宽,脉间,抬刀周期)对小孔圆柱度的影响。结果表明,脉宽对圆柱度的影响最为显著,开路电压次之,其余3个参数的影响较弱;实验获得了以圆柱度误差最小为评价目标的一组放电参数:开路电压110V,电流0.6A,脉宽150μs,脉间120μs,抬刀周期1+2s。验证实验得到了平均半径为0.30184mm的小孔,其圆柱度误差为0.021mm,说明用该方法控制电火花加工小孔的圆柱度是有效的。

滑阀内孔圆柱度误差气动测量系统的研究

提出了一种基于压力式气动测量原理的滑阀阀套内孔圆柱度误差测量方法,建立了基于该方法的自动测量系统。在分析滑阀阀套内孔圆柱度误差的气动喷嘴扫描测量原理及测量采集点的特点基础上,研究了基于改进遗传算法的极坐标下最小区域圆柱度误差的评定与计算方法,并进行了实验研究。实验和分析结果表明,该测量方法和系统具有分辨率高和测量精度高的特点,圆柱度误差评定算法的计算效率高、结果稳定可靠,能够满足滑阀阀套内孔圆柱度误差现场自动化测量的要求。

用于异形孔精密加工的超磁致伸缩构件的线性化迟滞建模

根据超磁致伸缩构件精密加工异形孔刀具轨迹的特点,采用纯延时环节串联线性化模型,建立其在高频驱动下驱动电流与输出微位移的迟滞非线性动态模型。通过一定频率下驱动电流与输出位移的相关辨识,获得系统纯延时环节的补偿参数,并建立了驱动电流与无相位差输出位移的线性化模型。当实时控制时,通过迟滞非线性模型的直接逆模型补偿,使位移输出与异形孔的理想刀具轨迹一致。实验验证表明,直接逆模型的最大开环控制误差为2.7μm,最大相对误差为10%。进一步对构件进行微位移反馈闭环控制,实验误差最大值为1.2μm,最大相对误差为7%,提高了系统的控制精度。

穿透裂纹对开口复合材料柱壳屈曲性能的影响

为了解决复合材料柱壳结构成型过程中产生裂纹的问题,为复合材料柱壳类结构设计与质量控制提供参考,文中采用有限元方法分析了含穿透裂纹开口复合材料柱壳的压缩屈曲性能,分析了裂纹长度与方向的影响。结果表明,45°方向的穿透裂纹,其长度小于130mm时,柱壳屈曲强度随裂纹长度的增长略有下降;超过130mm,屈曲强度明显下降。对于定长裂纹,随着裂纹方向角的增加,结构的屈曲强度不断降低。裂纹对柱壳压缩屈曲强度的影响程度本质上取决于裂纹对原有载荷传递路径的影响程度。

不等开口柱形压力容器的渐变角度缠绕规律研究

柱形压力容器缠绕通常要求两端开孔大小相近,在缠绕工艺实施上可以通过平衡缠绕角度的方法实现稳定落纱,当两端开孔相差较大时,常用的螺旋向缠绕将无法实现;针对这一问题,本文提出一种针对不等开口、大长径比的柱形压力容器缠绕线形设计方法,通过筒身段的渐变缠绕角度设计和公式推导,实现了纤维的稳定落纱和筒身螺旋缠绕段的均匀过渡;通过对不等开孔柱形容器样件缠绕工艺实现表明,该设计方法具有良好的实用效果。

内冷通道横流对气膜冷却效率的影响

在吹风比（Br）为0.5～2.0、横流比（Cr）为0～3.0范围内,采用数值模拟方法研究了内部冷却通道横流对单排圆柱形气膜孔气膜冷却特性的影响.相比于基准的无横流进气方式,横流进气诱导冷却气流在气膜孔内形成旋流流动,使得气膜射流与主流的相互作用更为复杂.横流比的影响在不同的吹风比下有较大差异：在较小的吹风比下,横流比小于1.0的气膜绝热冷却效率略高于无横向进气的基准情形,而横流比大于2.0的气膜绝热冷却效率相对基准情形有一定幅度的下降;在较高的吹风比下,横流进气带来气膜绝热冷却效率的增强,横流比为2.0的气膜绝热冷却效率相对较高.在大横流比下,随着吹风比的增加,气膜在展向的覆盖范围明显扩大.