某雷达模块的振动夹具设计

随着电子产品环境适应性要求的提高,特别是振动性能要求的不断提高,振动试验在电子产品环境试验中的作用日益显著。振动试验通过模拟产品在运输、安装及使用过程中所遇到的各种振动环境影响,来确定产品是否能承受各种环境振动,从而判断其能否达到实际使用要求。同时,振动夹具在振动试验中起着重要的作用,其设计的好坏决定着振动试验的成功与否。文中首先对振动夹具的设计进行了理论分析,然后通过某雷达模块振动夹具的设计过程,提出了利用软件仿真并进行逐步优化的设计方法,总结了设计振动夹具的心得,为以后的振动夹具设计提供参考。     

一种支持ARINC600/763标准航电设备进行振动试验的夹具设计与分析

针对航空电子产品需在研制阶段进行工作冲击与坠撞安全、振动等机载设备环境试验,设计了一款专用的振动夹具。根据夹具的基本设计原则,选取合适的铝合金材料,选择适宜的机械加工制造工艺。通过三维设计软件建立了夹具的数字模型,应用ANSYS Workbench仿真分析软件对模型进行了约束模态分析,确定夹具的固有频率及模态振型。分析夹具的前10阶固有频率和模态振型,确认夹具结构设计合理,振动特性满足要求。最后加工夹具实物并按照DO-160G要求进行了正弦扫频测试,结果表明该夹具在振动频率范围内能够满足要求,可用于AIRNC600和ARINC763标准设备振动试验。该夹具结构简单,安装便捷可靠,振动特性传递真实度高,适合推广。     

振动试验夹具动力学设计的综合优化方法

针对夹具设计中容易出现的振动频率低,传递特性差和能量消耗多等问题,提出综合使用拓扑优化和参数优化对夹具进行优化设计的方法.根据振动试验夹具的实际应用和设计原则,利用拓扑优化得到夹具合理的总体布局,用参数优化调整夹具的几何参数,使设计出的夹具能够满足设计要求.以某夹具设计为实例,通过Patran/Nastran有限元分析软件作为仿真分析平台,交替采用拓扑优化和参数优化对夹具进行设计与改进,得出满足要求的振动夹具设计方案,并经过试验证明了设计的有效性.本研究方法对其他结构的动力学设计亦具有一定参考价值.     

振动试验夹具结构动态设计及试验验证

针对传统振动试验夹具结构动态设计主要依靠经验及公式粗略计算的不足,通过构建某夹具的3维有限元模型,利用模态分析对夹具固有频率、低阶振型进行预测,对不满足要求的夹具进行改进。利用随机振动分析从固有频率、振动放大因子、正交运动范围、各固定点间振动量值差别4个方面对改进后的夹具进行仿真计算,并与试验结果对比,验证仿真结果的可靠性,判断夹具设计满足振动试验要求。     

弹载设备振动夹具设计与改进

在弹载设备的研制和交付过程中,振动试验是其环境与可靠性试验最关键的内容之一。振动夹具在振动试验中起着重要的作用,其设计的好坏决定振动试验成功与否。文中全面分析了弹载设备夹具设计的各种要求,设计出了一种符合要求的振动夹具,利用UG NX6软件中高级仿真模块对夹具进行了仿真分析,并对振动夹具进行了测试和结构改进。此文是对弹载设备振动夹具设计的经验总结,可供弹载设备振动夹具设计参考。     

某星载设备的振动夹具设计

为了设计满足某星载设备振动试验需求的振动夹具,文中根据被试件与振动台的接口、试验环境条件、夹具外形与质量静态分析结果以及动强度设计仿真分析结果,设计出了一种合理、易于制备的振动夹具。通过锤击法测定夹具实物的固有频率,验证了本夹具设计的合理性。振动夹具设计需考虑各项约束条件,可通过选择比刚度高的材料减小夹具质量,通过仿真分析可快速完成对夹具的评估,可通过锤击法验证仿真可行度。分析表明本文设计的振动夹具是符合试验要求的,可为以后的振动夹具设计提供参考。     

振动试验夹具设计中需重视的几个参数

讨论了振动试验夹具设计中重点关注的几方面问题,一是掌握它的评价参数,包括特征参数、关联参数及响应参数;另一是夹具成型后需连同试验产品一起在振动条件下进行可靠程度分析。通过对某"L"型夹具的测试,已验证了该夹具设计理论是切实可行的。     

振动试验夹具设计优化及模态分析

振动导致产品及其内部结构动态位移,这些动态位移和相应的速度、加速度可能引起或加剧结构疲劳,以及结构、组件和零件的机械磨损。通过试验室模拟预期振动环境的典型条件和使用方式,可以考察振动对产品的影响,评定产品在预期的运输及使用环境中的适应能力,发现产品的耐环境设计缺陷,验证装备能否承受寿命周期内的振动条件并正常工作。在工程实践中,振动试验使用的夹具从振动台传递的应力往往存在较大的失真,难以再现产品比较真实的使用状态。根据装甲产品振动试验条件及有关试验夹具设计要求,在分析夹具结构的基础上,基于三维软件进行实体建模,并对其进行模态分析,从仿真结果分析夹具可能的不足,并依此对夹具的结构进行优化设计。     

汽车前大灯振动试验夹具设计

振动试验夹具在振动试验中起到连接试件与振动台的作用,能否平稳地将振动台的载荷传递到试件上,对试验结果的准确性起决定性作用。针对某汽车前大灯,根据振动试验规范要求,通过对材料、结构和制造方式的选择,设计了用于在试验中固汽车前定大灯的夹具。在设计过程中运用Hyperworks软件对设计的夹具进行拓扑优化以及模态仿真分析来优化设计结果,最终通过试验,验证了所设计的夹具满足试验要求,保证了试验过程的稳定性和试验结果的可靠性。     

电子设备机柜振动试验夹具设计

电子设备在振动试验中需要夹具转接,夹具的性能直接影响到设备的可靠性,夹具设计是振动试验中的一个重要环节.文中介绍了一种振动试验夹具的设计,并采用有限单元法对其进行了模态分析.结果表明该夹具动态特性可满足设计要求,可用于多种型号的机柜振动试验,并可节省试验费用.     

Wavelike gas dispersion in a liquid in a compressor-free environment

An experimental investigation has been performed regarding the operation of a new type of wave-generating gas disperser in a liquid in entrainment mode in a compressor-free environment. The wave-generating disperser and ejector-caused gas flow relationship with the water pressure at the disperser inlet under different design factors has been obtained. The gas bubbles’ average size has been measured in a biphase stream leaving the disperser. Recommendations for the selection of the disperser parameters have been submitted. The goal of this work is the simplification of plants intended for dispersing gas in a liquid, diminishing the gas bubbles’ size, and reducing the dispersion energy flow. This is a pressing problem for many chemical technology targets, for wastewater biological treatment systems, and for chlorinating or ozonizing tap water.     

An electric arc in a helium flow in a high-current plasmatron

Experimental studies of an electric arc in a helium flow are described. A generalized dependence of the electric field on the determining criteria has been obtained on the basis of the experimental data, and a plasmatron has been designed on the basis of the technique developed. Its thermal efficiency is 0.68–0.74, and the mass-averaged temperature of the helium flow is T = 3700–4200 K. The plasmatron can be used in various technological processes involving energy conversion.     

Analysis of a mitered joint in a cylindrical shell in bending

The problem of in-plane bending of a single unreinforced mitered joint between two cylindrical shells of equal diameter is analyzed according to thin shell theory. The solution is constructed by the method of matched asymptotic expansions. Formulas for the stress amplification factor and flexibility factor are derived and comparisons are made with available test results.     

Operation of a Dilution Refrigerator in a Micromode

Two design versions of a ³He-in-⁴He dilution refrigerator with ³He pumping out through its condensation on a cold wall are described: a classical refrigerator with a heat exchanger and a refrigerator with a collector that allows for operation in a quasi-single mode. The refrigerator operated stably in both cases when a power of 30 W was fed to the still, i.e., at a circulation rate of ³He of a few micromoles per second. In this case, the mixing chamber was cooled down to a temperature below 0.05 K.     

Diagnostics of a cavity in a prismatic beam

A beam with a cross section in the form of a hollow rectangular box is considered. A method for calculation of the dimensions of a cavity in a beam by two natural bending frequencies that are taken from different spectra is proposed. These are the spectra of vibrations in two mutually perpendicular planes that are chosen in such a way that the neutral axis of the cross section is parallel to the sides in both cases. The dependence of the natural frequency on the cavity’s parameters is studied. It is proven that the frequency values of the beam under investigation and of an identical beam with a solid cross section do not coincide at any size of the cavity and the natural frequency values of the former beam are always higher than those of the latter one.     

PIV measurements in a turbulent wall jet over a backward-facing step in a three-dimensional,non-confined channel

A study of a turbulent wall jet over a backward-facing step is especially of interest because it shows a rich phenomenon flow and a mechanism to alter the flow characteristics downstream of the step. However, studies on this flow configuration are rare. In this paper, we considered this flow configuration in a non-confined channel as the specific engineering applications of electrical rotating machines and alternator that can be found in modern wind generators of the power production industry and automobile engines. The turbulent wall jet over a backward-facing step in a non-confined wind tunnel had the jet Reynolds number of 24,100 and the step Reynolds number of 11,900. Particle image velocity (PIV) and stereoscopic PIV measurements were performed along the central plane and several cross-stream planes. Numerical simulation of the test configuration was conducted by solving the three-dimensional Reynolds Averaged Navier–Stokes (RANS) equations with the second-order closure Reynolds stress model (RSM). The mean flow fields and second-order statistical moments from the RSM simulation were compared to results that were obtained through the PIV and stereo-PIV experiments. The mean reattachment length obtained from the current configuration was much shorter than those from the backward-facing step in the plane channel. The stereo-PIV measurements in the cross-stream planes revealed a high three-dimensionality of the flow, a high population of streamwise vortice in the upper region, near the side walls and the corners formed by the side walls and the bottom wall. The obtained results also confirmed the presence of the wall-jet formation on the bottom wall.     

Synthesis of a precision coupling in a piston transmission

A design for a precision coupling in a piston transmission is proposed. A method is outlined for the geometric synthesis of the mechanism when the piston’s working part has a circular profile.