梁柱问题和压杆第二类稳定问题的共性

采用一种简化的强度利用率函数,求出了具有初始挠度,初偏心和横向载荷作用的轴心压杆的轴向载荷的解析算式。并用附加弯矩的概念论述了区分压杆的强度和稳定问题的标志,说明压杆的第二类稳定问题和梁柱问题具有共性——均属于强度问题。25个压杆模型实验的数据给于了验证。     

一个新的簿板大挠度广义势能原理

在薄板大挠度问题最小势能原理的一种新提法(势能密度中同时含有应变与应力函数的形式)的基础上,用线性Lagrange乘子法,解除包括薄膜和弯曲广义应力-广义应变关系在内的全部变分约束条件,建立了一个新的薄板大挠度问题三类变量广义势能原理。     

基于系统识别的梁类构件故障诊断

建筑结构的损伤诊断分析是结构性能评估的基础 .采用静态检测方法对梁类构件的损伤诊断问题进行了理论分析 .根据梁截面等效抗弯刚度的变化建立了梁的力学模型 ,利用在集中荷载作用下梁的挠度变化 ,并基于系统识别原理 ,建立了梁类构件的损伤诊断分析方法 .通过实例计算 ,表明该方法具有较好的收敛性和稳定性     

预应力钢箱梁的非线性分析

为提高预应力钢筋梁的计算精度，对预应力钢箱梁的两个受力阶段作了全过程非线性分析，建立了预应力钢箱梁的非线性分析模型，采用平衡原理和能量原理分别推导出预应力钢箱梁在预加力阶段和荷载阶段的控制微分方程，用上述方程进行理论计算所获得的数据，如钢梁的跨国挠度、底板应变均与预应力钢箱梁模型的实验结果符合良好，表明了建立的模型和所推导的控制微分方程的有效性和正确性，对影响钢箱梁刚度的因素诸如预加力的大小，预应力钢索的跨中垂度等进行了详细讨论，讨论结果表明，当外荷载较小时，预加力对钢箱梁刚度影响较小，当外荷载较大时，预加力对钢箱梁刚度影响较大，钢索在跨中的垂度越大对钢箱梁刚度的提高越大。     

不等宽T型方管节点静力工作性能的研究

直接焊接方管节点是复杂的三维空间薄壁结构，对其理论分析必须考虑几何非线性和材料非线性的影响。采用能处理几何非线性和材料 非线性影响的有限元方法分析不等宽T型方管节点的受力全过程，对材料应变硬化、大挠度效应及弘杆所受荷载对节点承载力的影响进行了研究。研究结果表明，材料应变硬化对节点影响不大，大挠度效应显著提高了节点的承载力，弘杆所受轴压荷载降低了节点承载力。     

甲醇装置转化炉出口甲烷偏高原因分析

分析100kt/a焦炉气制甲醇装置二段炉出口甲烷偏高的原因,认为是金属烧嘴偏流而引起的,并提出相应的措施。     

The effects of processing variables on stress development in ultraviolet-cured coatings

A cantilever deflection technique was used to monitor stress development during ultraviolet photo-cure of acrylate coatings to the glassy state. Two coating systems were studied: a trifunctional monomer (trimethylol propane triacrylate, TMPTA) and a tetrafunctional monomer (pentaerythritol tetraacrylate, PETA). Both were photoinitiated with 2,2-dimethoxy-2-phenylacetophenone (DMPA). Average in-plane stresses of up to 30 MPa were measured upon curing at room temperature. The rate and magnitude of stress development rose with the photoinitiator concentration and with light intensity. Curing with more strongly absorbed light had similar effects. Light absorption caused decreased stress magnitudes in thicker coatings. Somewhat unexpectedly, the rate and magnitude of stress development increased with monomer functionality even though the conversion fell. Moreover, curing thick coatings with high radical concentrations (strongly absorbing light and large photoinitiator concentrations) caused ripple defects to form. With the appearance of these defects, stress ceased to rise with the photoinitiator concentration. Fourier transform infrared spectroscopy was employed to monitor conversion and to help understand these stress development trends. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1267–1277, 1997     

Investigation of production parameters in fracture behavior of hot-pressed Al2O3–SiC/graphite fibrous monolithic ceramics: Fibers orientation and cell boundary fraction

Fibrous monoliths (FMs) exhibit graceful failure in flexure and have higher toughness values. In this research, a mixture of Al₂O₃ and SiC as the core and graphite as the shell material of fibers were produced by extrusion-molding technique and after aligning along intended directions (0°, 90°, and 0°/90°) were sintered using the hot-pressing method at the temperature of 1500°C under pressure of 35 MPa for 1 hour. The significance of fibers orientation angle and the cell to cell boundary volume ratio in defining the fracture behavior of the FMs was detected. Because of the extensive crack interactions with graphite cell boundary such as crack deflection and delamination, with increasing cell boundary content from 25 to 30 vol%, the fracture toughness was enhanced. The highest flexural strength (184.8 ± 0.61 MPa) obtained from samples with 0° fibers orientation compared to 0°/90°. Since in the transverse plies (layers with 90° aligning), the properties of matrix phase are dominant, hence the strength in specimens with 0°/90° fibers orientation decreased considerably due to weak graphite matrix phase. In addition, the fracture toughness value increased up to 8.35 ± 0.74 MPa·m^1/2 for the unidirectional architecture of (0°) in comparison with cross-ply (0°/90°) architecture.     

关于风压不均匀系数的研究

通过比较、分析我国与俄罗斯、日本、德国的输电线路设计规程对于风压不均匀系数取值的规定及差异, 提出我国输电线路设计规程的风压不均匀系数取值的修正方案。同时对在输电线路工程设计中执行该修正方案的可操作性以及对线路杆塔指标的影响进行了研究和评估。在以后新设计的输电线路工程中, 对于杆塔规划、塔头尺寸的确定和杆塔定位后导线与绝缘子串的风偏校核等各环节,可按照该修正方案开展工作。     

求变截面梁位移方法的研究

实际工程中比较常见的变截面梁,其抗弯刚度是一个变量,在进行其刚度计算时,用各种方法求出其挠曲线方程,然后根据方程再求出梁的最大位移,从而对该变截面梁进行刚度校核并使其安全可靠.本文针对变截面梁,提出了求位移的单位力法、积分法、最小势能原理法,通过实例验证了所提方法的正确性,这无论对于实际工程应用还是理论研究都具有重要的...