钢管弯制弯管壁厚计算

阐述了弯管附加壁厚的计算方法,对于大型锅炉对流受热面设计有一定参考意义。     

关于热轧辊的弯曲与补偿——设计计算与调节补偿

从热轧辊的工作要求及受力状态出发,分析了它的弯曲变形规律及常用补偿方法。主要介绍了"中凸法"及"轴线偏转法"的原理、优点及缺点。介绍了同时采用这两种挠度补偿方法的效果及应有的调整方法。     

90°圆截面弯管内稠油流动特性分析

采用计算流体力学三维层流模型模拟,研究了温度50~75℃、雷诺数Re=300~800、弯管内径D=50.7~131.7 mm、弯径比B=0.75~3.0条件下稠油在90°弯管内的阻力特性,分析了弯管局域阻力系数波动的机理。结果表明,随温度升高、入口雷诺数下降、弯管直径增加,局域阻力系数提高;在弯管0~15°范围内阻力下降,原因是弯管内形成双纵向涡,75°到弯管后0.5D范围内阻力下降,原因是弯管内形成4个纵向涡;弯管的弯径比对局域流动阻力影响很大,B=0.75时相邻截面最大落差达B=3.0时的28.35倍,但管道进出口阻力仅为1.68倍,原因是弯径比B≤1.0时,弯管后1.0D范围内侧形成了局域低压区,对应位置出现流向涡旋,同时弯管后0.5D截面稠油剪切速率达到峰值。     

水煤浆流经局部管件阻力特性的研究

在水煤浆综合输送试验台上研究了水煤浆流经渐缩管、突缩管以及90°水平弯管的局部阻力特性,分析了渐缩角、管径比以及弯径比对上述局部管件阻力损失的影响。结果表明,增加渐缩角使得渐缩管的局部阻力损失减少;较小的管径比变化对突缩管的局部阻力损失没有较大影响;存在一个最佳弯径比,使得水平弯管的局部阻力损失最小。随着雷诺数的增加,渐缩管、突缩管以及水平弯管的阻力系数先迅速下降然后逐渐趋于稳定,而渐缩管当量长度与管径的比值Le/D逐渐下降然后趋于稳定;突缩管的Le/D先下降再增加,对于弯管的Le/D则成线性增加。     

The investigation of the floatation of double oxide film defect in liquid aluminium alloys by a four-point bend test

A mould was designed to produce considerable splashing during filling, resulting in the entrainment of freshly produced double oxide film defects. Two moulds were cast to produce 60 testbars in total, suitable for four-point bend testing, to determine their Weibull moduli. Different faces of the cast test-bars, top and bottom, would have different distributions of double oxide film defects, depending on whether the defects were expected to float or to sink during casting. The faces of the test-bars placed downwards in the four-point bend-tests would experience the maximum tensile load, meaning that the test-bar faces associated with the greatest defect densities (top or bottom) would be associated with the lowest Weibull Modulus. The experiment confirmed that double oxide film defects are positively buoyant, initially, and would float towards the surface of the casting during pouring and solidification.     

Effect of bend angle on plastic loads of pipe bends under internal pressure and in-plane bending

This paper quantifies the effect of a bend angle of a pipe bend on plastic loads, via small strain and large strain finite element (FE) limit analyses using elastic–perfectly plastic materials. To consider the effect of the attached straight pipe, two limiting cases are considered. One case corresponds to the pipe bend without the attached straight pipe, and the other to that with a sufficiently long attached straight pipe. For the former case, the FE results suggest that the limit load is not affected by the bend angle for both in-plane bending and internal pressure. For the latter case, however, the bend angle affects plastic loads. An interesting finding is that the plastic load smoothly changes from the limit load of the straight pipe when the bend angle approaches zero to the plastic load of the 90 pipe bend when the bend angle approaches 90. Based on such observations, closed-form plastic load solutions are proposed for the pipe bend with an arbitrary bend angle under in-plane bending and internal pressure.     

单位阶跃函数在材料力学中的应用

在对梁的弯曲进行研究时，经常要用到弯矩方程。目前常用的弯矩方程表达式通常是一个分段函数表达式，这给理论研究带来了许多冗繁的工作。通过单位阶跃函数，可以把在集中载荷作用下的分段函数的弯矩方程表达式用一个整体方程表示出来，极大的简化了求弯曲变形的计算工作量，同时还具有一定的理论价值。     

Rastrites guizhouensisMuetal.的胞管形态

利用扫描电镜观察Ｒａｓｔｒｉｔｅｓｇｕｉｚｈｏｕｅｎｓｉｓ的超微形态,胞管孤立部分直管状,中部稍膨胀,向末端收缩变小并向腹侧弯曲成小钩状,背部末端弯曲时形成膝弯,腹侧则形成加厚的下口唇和三角形的凹陷唇口窝。Ｒａｓｔｒｉｔｅｓｇｕｉｚｈｏｕｅｎｓｉｓ胞管的形态与一些孤立的：Ｍｏｎｏｇｒａｐｔｕｓｃｏｎｖｏｌｕｔｕｓ,Ｍｏｎｏｇｒａｐｔｕｓｄｅｎｔｉｃｕｌａｔｕｓ．的胞管可以对比。