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51.
This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a weak point of common free-flying projectile-target testing schemes. 相似文献
52.
53.
《Thin》2014
Approximate finite strip eigen-buckling solutions are introduced for local, distortional, flexural, and flexural-torsional elastic buckling of a thin-walled metal column with perforation patterns. These methods are developed to support a calculation-based strength prediction approach for steel pallet rack columns employing the American Iron and Steel Institute׳s Direct Strength Method, however they are generally posed and could also be useful in structural studies of thin-walled thermal or acoustical members made of steel, aluminum, or other metals. The critical elastic global buckling load including perforations is calculated by reducing the finite strip buckling load of the cross-section without perforations using the weighted average of the net and gross cross-sectional moment of inertia along the length of the member for flexural (Euler) buckling, and for flexural-torsional buckling, using the weighted average of both the torsional warping and St. Venant torsional constants. For local buckling, a Rayleigh–Ritz energy solution leads to a reduced thickness stiffened element equation that simulates the influence of decreased longitudinal and transverse plate bending stiffness caused by perforation patterns. The cross-section with these reduced thicknesses is input into a finite strip analysis program to calculate the critical elastic local buckling load. Local buckling at a perforation is also treated with a net section finite strip analysis. For distortional buckling, a reduced thickness equation is derived for the web of an open cross-section to simulate the reduction in its transverse bending stiffness caused by perforation patterns. The approximate elastic buckling methods are validated with a database of 1282 thin shell finite element eigen-buckling models considering five common pallet rack cross-sections featuring web perforations that include 36 perforation dimension combinations and twelve perforation spacing combinations. 相似文献
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Three different numerical strategies are presented for the estimation of the damping force acting on perforated movable MEMS
dampers. Results from the 2D Perforated Profile Reynolds (PPR) method and the simplified 2D ANSYS method are compared with
accurate full 3D flow simulations. Altogether, 32 different topologies are compared varying, e.g., the dimensions of the square
damper and the square holes, and the number of holes. The case of uniform perforation and perpendicular motion is studied.
Oscillation in the low frequency regime is assumed, that is, the compressibility and inertia of the gas are ignored in the
study. While the PPR method is in good agreement with the 3D simulations, the forces given by the ANSYS method were considerably
smaller. The reasons for this are studied, and a compact expression to explain the small forces is derived. 相似文献
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57.
现代工业中 ,用自动化代替人能更好地、更准确的来完成生产工艺过程。本文根据信江公司的使用情况 ,介绍了SIMATIC S7 以新的系统集成方式兼容的软件来实现生产自动化控制 相似文献
58.
基于FPGA的数字锁相环的研究与实现 总被引:5,自引:1,他引:4
介绍了当前广泛应用的数字锁相环的原理和基于FPGA的设计方法。针对在数字锁相环应用中,当滤波器K值较小时存在的相位抖动问题,提出了一种锁定检测模块的设计,通过仿真验证,该设计能够有效地抑制锁定状态下的相位抖动。 相似文献
59.
杜广滨 《江汉石油职工大学学报》2012,(2):46-47,59
随着地球物理探勘技术的发展,地震勘探仪器应用范围也越来越广泛。在射孔和压裂过程中,应用428XL仪器微地震采集的方法能够降低故障发生率,采集完整的地震资料。值得注意的是如果主机仪器用的是428XL,但地面设备部分或全部使用的是408UL站体,测线数据率必须设置为8Mbit/sec。在施工时,要时刻监视野外排列的情况。当野外排列出现故障时,要记录出现故障的时间以及排列恢复的时间,以便在后期处理时使用。 相似文献
60.
针对滤波补偿装置中要求电容器投切速度快,无冲击电流、电压的问题,设计了一种基于晶闸管移相触发的电路。该电路实现了快速无冲击投切,设计简单,能很好地解决过零触发电路经常遇到的过零检测混乱而导致的误触发,以及触发需等待电容器放电,有一定延迟的问题。通过现场实验测试分析说明,此移相触发电路的良好实用性。 相似文献