柔度法测量三点弯曲试样弹性模量的影响因素

根据柔度法测量金属材料裂纹长度的原理,讨论了测量三点弯曲SE(B)试样弹性模量的影响因素,并分析了主要因素的影响。在此基础上,用柔度法测量了裂纹尖端张开位移(CTOD)试验用大尺寸SE(B)试样预制疲劳裂纹的长度。经断口测量发现,用柔度法测量的两组母材与焊缝试样的原始裂纹长度具有很好的同一性,为进一步进行CTOD试验提供了保证。     

Classical Approach to Analyzing the Influence of Edge Boundary Conditions on Stresses and Flexibility of Pipe Elastic Bend

A new analytical method is proposed for the analysis of boundary effect in a pipe bend portion loaded by bending moment combined with internal pressure. The proposed method is based on the simplifying hypotheses, which make possible to represent all deformation- and force-related parameters in terms of the tangential displacement assumed in the form of the Fourier series expansion by the circumferential coordinate. A set of quadric differential equations by axial coordinate containing unknown displacement expansion coefficients is derived. We obtained an analytical approximate solution for a pipe bend portion and precise solution for a straight pipe, which are expressed via Krylov functions. We formulate the application procedure for the method of initial parameter, where the values of tangential and longitudinal displacements, axial and tangential forces are used as boundary conditions. We present the equations relating the above-mentioned parameters in the initial and end sections of the pipe bend portion. The results obtained are compared with the available published data. __________ Translated from Problemy Prochnosti, No. 4, pp. 64 – 94, July – August, 2005.     

影响冷弯型槽钢临界弯曲角因素综合分析

计算、分析了带材弹性模量，槽钢腿部长度，腰部宽度，厚度，强度极限和弹性极限对冷弯型槽钢临界弯曲角的影响，其结果对提高产品质量，降低生产成本有参考价值。     

粉体气力输送时弯管的阻力特性及计算方法研究

本文首先综述分析了国内外对不同弯曲曲率半径及角度弯管的阻力特性研究，然后结合作者在多相流动试验台上对４５°、９０°、１１０°、１５０°角度及Ｒ／Ｄ＝２、２．５和３所进行的不同试验结果，采用多变量回归分析法得出适合于计算不同曲率半径和角度的弯管局部阻力系数通用公式，其计算结果与试验值较吻合．     

四点弯疲劳试验尺寸效应及MA760疲劳特性研究

考虑到四点弯疲劳试验在疲劳裂纹启裂及早期扩展行为研究中的优点，本文设计并使用了一个四点湾疲劳加载装置。在不同的内跨距／试样厚度比值（d／H）及外跨距／内跨比值（L／d）下，经有限元计算结果表明：纯弯曲段内的表面应力分布并不是均匀的。计算结果有效地解释了本文及有关文献中的实验结果，文中据此给出了四点弯疲劳试样的推荐尺寸。在室温及高温（750℃）下，对锦基超强合金MA760进行四点弯疲劳试验结果表明：该材料具有很好的抗疲劳裂纹启裂能力，但其抗裂纹扩展能力很差；该材料对内部夹杂物的敏感性与环境温度及试样相对厚度密切相关。     

叠片式吊钩的强度计算

用于铸造起重机的龙门钩除了受到起吊载荷的作用，还受到吊运的液态金属的高温辐射，不仅承受弯曲应力、扭转应力、剪切应力还有高温钢水辐射产生的热变应力等，通过对几个危险截面的强度分析，以最终确定吊钩组的截面尺寸。     

弯道零件的斜孔加工

对于零件弯道的两个3空间斜孔,原通过组合夹具定位后,采用划线加工,加工质量不能满足图纸要求。针对该问题,指出了划线加工的不足,并采用新的加工方法,即在立卧转换加工中心上,开发并运用其潜在的"循环19(即零点跟踪)"功能,从而显著提高了整机的性能。     

山溪坝后式取水及明渠弯道除沙方式研究

随着我国水利水电工程建设的发展,水电站分布越来越集中于偏远山区,供水系统往往需自行建设。为了解决工程建设施工及生活用水问题,通常是将工程附近水源水质较好的山溪作为取水点,并经简单沉沙处理后投入使用。传统的坝前式山溪取水及大型沉沙池除沙普遍面临着汛期取水头部易被泥石流淤积、山溪内施工部位狭窄等问题,根据弯道环流原理,结合杨房沟水电站供水系统取水头部设计及运行使用经验,研究验证了坝后式取水代替传统的坝前式取水,以及明渠除沙代替大型沉沙池除沙方式的实际效果。实践表明,新的取水方式可以满足抗淤能力强、施工占地少,同时除沙能力理想的要求,可为今后类似情况下山溪取水及除沙方式的选择提供参考。     

Numerical study on erosion of a pipe bend with a vortex chamber

Abrasive erosion at bend is a common issue in gas–solid pneumatic system. Vortex chamber design is one of the specialized designs that offers promising prospect at reducing erosion. The performance of design is still relatively unknown in the literature. The aim of this work is to study the effect of basic erosion variables such as the flow Reynolds number, the particle Stokes number, and the vortex chamber size. The results show that the vortex chamber always reduces the erosion in comparison to the common radius bend, and it is more effective at higher Reynolds number. Increasing the chamber size reduces the erosion but the most significant reduction happens when the chamber size to the pipe diameter ratio is increased from 1 to 1.25. The chamber size influences the erosion differently at different Reynolds number. Trends describing these effects were obtained through trial-and-error approach. The particle Stokes number has nonunique effect on erosion. Increasing Stokes number through increasing Re increases the erosion while increasing Stokes number through decreasing Re_p decreases the erosion.     

Spark plasma sintering of B4C and B4C-TiB2 composites: Deformation and failure mechanisms under quasistatic and dynamic loading

Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B₄C and various B₄C-TiB₂ compositions. SPS allowed for consolidation of pure B₄C, B₄C-13 vol.%TiB₂, and B₄C-23 vol.%TiB₂ composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB₂ phase in both small and larger-scaled composites. An optimized B₄C-23 vol.%TiB₂ composite with a targeted low density of ～3.0 g/cm³ exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B₄C matrix in compression and TiB₂ phase in tension, and c) TiB₂ phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB₂ serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor.