轮式工程机械的行驶平稳性

根据振动理论建立了振动力学模型,并用等效刚度方法分析研究了弹性悬挂轮式工程机械行驶平稳性和振动特性。     

Buckling analysis for delaminated composites using plate bending elements based on higher‐order zig‐zag theory

A finite element based on the efficient higher‐order zig‐zag theory with multiple delaminations is developed. The bending part of the formulation is constructed from the concept of DKQ element. Unlike conventional elements, a developed element has its reference in the bottom surface which simplifies zig‐zag terms on formulation. Exact patch solutions are developed on elements which have the bottom reference system. The present element passes proper bending patch tests in the arbitrary mesh configurations in isotropic materials. Zig‐zag formulation is adopted to model laminated plates with multiple delaminations. To assess the accuracy and efficiency of the present element based on higher‐order zig‐zag theory with multiple delaminations, the linear buckling problem of laminated plates with multiple delaminations has been analysed. The results have been compared with three‐dimensional elasticity solutions. The present element works as an efficient tool for analysing the behaviour of the laminated composites with multiple delaminations. Copyright © 2002 John Wiley & Sons, Ltd.     

高层钢-钢骨混凝土混合结构的设计研究

结合一幢高层钢 钢骨混凝土混合结构的设计 ,着重介绍了在罕遇地震作用下采用层模型和空间模型的弹塑性分析计算结果、钢骨混凝土柱与钢梁的计算、节点设计及相应的构造措施 ,供结构工程师参考。     

Brittle detachment of a stiffener bonded to an elastic plate

The diffusion of contact stresses between an elastic bar, bonded to an elastic half-plane and loaded longitudinally, requires the integration of a singular integral equation. The solution of this equation is not available in closed form, but only by a series expansion of the contact tangential force mutually transmitted between the stiffener and the plate. Since forty years it has been realized that the expansion of the solution in terms of Chebyshev polynomials is its most convenient method of representation. The procedure can also be extended to treat the brittle detachments of the tips of the stiffener when, according to Griffith's criterion of fracture, a balance can be virtually established between the increase of strain energy due to a propagation of cracks and the surface energy created.     

Low Temperature Elastic Constants of Polycrystalline MgB2

We have used a resonant ultrasound spectroscopy technique to measure the bulk and shear modulus of fully dense, polycrystalline MgB₂ between 4 and 300 K. Both moduli show good agreement with published first principle calculations. The internal friction shows a broad maximum around 40 K.     

工字梁的抗剪极限承载力

对工字梁腹板抗剪极限承载力的研究进行总结,对各种公式与文献中的试验结果进行对比,将拉力场理论和转向应力场理论的假定与ANSYS分析揭示的腹板应力发展变化规律进行对比,指出了假定和数值分析结果的不一致。提出了翼缘对腹板转动约束的合理参数,得到精度良好的考虑翼缘约束的腹板剪切屈曲系数。利用得到的屈曲系数,考虑翼缘抗弯承载力的贡献,提出新的工字梁抗剪极限承载力的计算公式。与现有试验数据和ANSYS非线性有限元分析结果的对比,证实建议方法离散性较小,适用范围广,尤其是对于通用高厚比较大的梁,较以往方法有了较大改进。     

Some experimental findings in compression-after-impact (CAI) tests of CF/PEEK (APC-2) and conventional CF/epoxy flat plates

Compression-after-impact (CAI) tests have been conducted for quasi-isotropic thick plates with 48 plies by using the NASA method and on plates with 32 plies by using the SACMA method. Specimens are made of CF/PEEK (APC-2) and conventional CF/epoxy for the NASA plates and CF/epoxy for the SACMA plates. In the NASA CAI tests, the sequence of delamination buckling and its propagation is clearly revealed through various experimental techniques. One major technique is moiré topography, and the other is thermo-mechanical stress analysis with a high-accuracy infrared sensor. The arrest of delamination propagation just before catastrophic failure due to high fracture toughness is clearly captured by the moiré camera. This behavior provides good CAI values of CF/PEEK. The initial buckling properties of the delaminated region by the impact are then extensively discussed. Numerical predictions of initial buckling stress have been obtained by modelled geometry of the delaminated region simplified from its precise structure clarified by ultrasonic C-scanning. They agree fairly well with the experimental results. The in-plane stress distribution in the delaminated region before initial buckling is measured by an infrared stress graphic system. This compared favorably with finite element predictions. Two types of symmetric buckling modes with respect to the central plate surface, twin and single peak ones, are experimentally captured.     

A parametric study of strength reduction factors for elasto-plastic oscillators

Strength reduction factors (SRFs) continue to play a key role in obtaining design forces from elastic design spectra (via response modification factors) in ductility-based earthquake-resistant design. Despite several years of sustained research efforts, it has not been conclusively shown how SRF for a given singledegree-of-freedom structural system depends on various source and site parameters. A parametric study is carried out here for the explicit dependence of SRF spectrum (describing variation of SRF with system period for a given ductility demand) on strong motion duration, earthquake magnitude, geological site conditions, and epicentral distance in case of (non-degrading) elasto-plastic oscillators. For this, scaled response spectra are considered for different combinations of earthquake magnitude, site conditions and epicentral distance, and SRF spectra are generated from 1274 accelerograms recorded in western USA after making those compatible with each of these spectra. It is shown that there is no clear and significant dependence of SRF spectrum on strong motion duration. Further, the parametric dependence on earthquake magnitude, site conditions, and epicentral distance broadly conforms to the trends reported by earlier investigations. In particular, this study confirms that the dependence of SRF spectra on earthquake magnitude should not be ignored. This paper has been contributed in honour of Professor R N Iyengar, Indian Institute of Science, on the occasion of his formal retirement.     

无键联接传动的特点及锥面弹性衬套设计和应用

无键联接在特殊行业和工况中是键联接传递动力和运动的有力补充,介绍了工程上应用的圆弧三边形型面联接、弹性环无键联接、圆柱面过盈联接等几种无键联接传动方式及其工作原理,并分析了各自的性能特点和应用情况。针对无键联接传动的特点、特殊行业和工况的应用实际,设计了锥面弹性衬套无键联接传动结构并介绍了其在工程中的实际应用。     

钻井井架力学性能分析

钻井井架作为钻机系统设备中的关键部分,其力学性能直接关系到整套钻机系统的安全生产。文章推导了常用于分析钻井井架力学性能的理论,即线性屈曲、几何非线性和双重非线性理论。提出同时用这三种理论对钻井井架进行综合比较分析,从而合理地预见井架力学性能的方法。以A形钻井井架为例,进行了详细的分析,得到了井架的失稳形式、极限承载、破坏特征及薄弱部位,为钻井井架的设计、优化与评定提供了参考。