板式初冷器在焦化厂的应用

介绍了板式初冷器在柳钢焦化厂的试运行情况,分析了板式初冷器在实际应用中存在的问题,并提出了适应生产的改进方案,优化板式初冷器的运行效果。

有初挠度简支矩形板的后屈曲特性

船体外壳基本上是由加筋板构成的 ,这种结构可能由于受面内压力作用而屈曲。为充分利用板的承载能力 ,减轻结构重量 ,有时将板设计得比较薄 ,使其工作于后屈曲状态。对大量的加筋板进行非线性有限元计算是一件非常费时的工作 ,在船体的初步设计阶段这样做很不经济。为此需先分析板的后屈曲特性 ,然后把板按某一折减宽度计入到加筋的剖面中去 ,再对加筋板进行整体屈曲分析。这就需要得到对任意边长比和初挠度均适用的应力和应变之间的显式关系 ,而目前尚缺乏这方面的研究。有鉴于此 ,应用von K rm n大挠度薄板方程 ,对承受单向面内压力、四边简支的有初挠度矩形板进行后屈曲特性分析 (其中挠曲函数取为双傅氏级数展开式的前三项 )。首先对边长比小于等于 2的板进行分析 (初挠度根据已有的大量实测结果取为双傅氏级数的一项 )。将有关变量化为无量纲量 ,以无量纲载荷作为小参数 ,用参数摄动法求解非线性代数方程组 ,得到受压边最大应力与平均压应力之间、平均压应力与平均应变之间的显式函数式。分析了不同边长比和初挠度对矩形板后屈曲特性的影响 ,结果表明初挠度的存在会明显降低板的面内刚度。继而将这些结论推广应用到边长比大于 2的情况。

铝板初轧机自动位置控制系统

文章介绍了 1种以 PL C C2 0 0 H为核心的铝板初轧机自动位置控制系统及其模糊控制器的设计方法 ,对传统的比例积分调节器和模糊控制器分别进行了理论分析和仿真研究 ,给出了系统的软、硬件结构 ,PL C配置及现场运行结果。本系统的特点是动态响应快 ,成本低 ,工作可靠 ,操作简单 ,定位精度可达± 0 .0 2 mm。

壳板径向初挠度对内外环肋圆柱壳结构强度的影响分析

用参数化有限元法模拟壳板径向初挠度的分布,通过系列计算和应力系数的对比,研究局部内凹、外凸和整体椭圆度对圆柱壳结构强度的影响。考虑纵向弯曲载荷的贡献,提出了附加弯曲应力的一种估算方法,其结果与有限元接近且偏安全,可用于结构校核及结构加强。跨中壳板局部内凹使弯曲应力急剧上升,而中面应力则变幅较小。局部凹、凸产生的附加弯曲应力方向相反、大小相当,f/t相同时,外凸对应的合成弯曲应力明显小于内凹。局部凹凸度幅值对壳板强度的影响呈非线性,凹陷中心的σ20随f/t提高先缓慢增加而后下降,椭圆度幅值的影响是线性的但很小。

具有初缺陷板弯曲的边界元分析

限于具有初曲率等有缺陷板弯曲问题的控制微分方程的复杂,直接求解原问题基本解推导边界积分方程较为困难,本文通过引入等效荷载,将此问题的控制微分方程,化成与普通板弯曲基本方程形式相同的微分方程,利用一般求解板弯曲问题的边界元法进行迭代求解,建立了分析具有初曲率板弯曲问题的边界元法,算例表明本文方法理论准确,精度良好。

面板局部屈曲的船体双层板架整体屈曲分析

首先应用von K劋ｒｍ劋ｎ大挠度薄板方程 ,对有初挠度的船体板进行后屈曲特性分析。以此为基础 ,导出屈曲后板的减缩有效宽度。进而用减缩有效宽度作为双层板架中受压纵桁的带板宽度。将双层板架模型化为四边弹性转角约束的正交异性板 ,考虑横向剪切变形的影响 ,提出了一种求解双层板架临界应力的方法。

水稻新品种内5优8015示范种植效果初报

内5优8015是中国水稻所选育的水稻新品种。2016年潜山县梅城镇引进试种,结果每穗总粒数157.5粒,实粒数为135.8粒,千粒重称量后为27.0g,10 777.5kg/hm2。该品种株型紧凑,剑叶挺直,抗逆性强,全生育期142d,适合在当地种植。但是,要注意及时烤田、增施穗粒肥和防止倒伏。

Effect of welding sequence on residual stress in thin-walled octagonal pipe-plate structure

A three-dimensional finite element approach based on ABAQUS code was developed to investigate the effect of welding sequence on welding residual stress distribution in a thin-walled 6061 aluminum alloy structure. To obtain sound numerical results, the therrno-mechanical behaviour was simulated using a direct-coupled formulation. Nine different simulation sequences were carried out by single-pass TIG welding of an octagonal pipe-plate joint, and the distributions of longitudinal and transverse residual stresses both on the outer and inner surfaces of the pipe were analyzed. The results suggest that the final residual stresses in the weld and its vicinity are not affected by the initial residual stresses of the structure. Selecting a suitable welding sequence can reduce the final residual stress in an octagonal pipe-plate joint.

Unanticipated Bond Failure over Supporting Band Beams in Grouted Post-Tensioned Slab Tendons with Little or No Initial Prestress

After grouting the ducts in a large band beam and one-way slab post-tensioned floor system in a large shopping mall （in excess of 1.5 km2 in plan）, doubts arose concerning the level of initial prestress and the strength and serviceability of the slabs was questioned. To assess the strength of the slabs, it was assumed, as a worst case scenario, that some spans may have been constructed with zero initial prestress. Load tests on prototype specimens, with similar dimensions and reinforcement quantities as the floor slabs, were performed to assess the stress development in initially unstressed, but fully grouted, tendons. Unexpected bond failures occurred at the junctions of slab and band beam where the abrupt change in section depth caused a sudden change in tendon stress. The maximum stress that was developed in the initially unstressed tendons at these locations was about 60% of the strength of the tendons.

Plate reinforced square hollow section X-joints subjected to in-plane moment

The static test of 13 square hollow section(SHS) X-joints with different β and different types of plate reinforcement under in-plane moment in brace was carried out. Experimental test schemes, failure modes of specimens, moment-vertical displacement curves, moment-deformation of the chord, and strain strength distribution curves were presented. The effect of β and plate reinforcement types on in-plane flexural property of SHS X-joints was studied. Results show that punching shear of chord face disappears, brace material fracture appears and concave and convex deformation of chord decrease when either collar plates or doubler plates were welded on chord face. Moment-vertical displacement curves of all specimens have obvious elastic, elastic-plastic and plastic stages. As β increases, the in-plane flexural ultimate capacity and initial stiffness of joints of the same plate reinforcement type increase, but ductility of joints decreases. With the same β, the in-plane flexural initial stiffness and ultimate capacity of doubler plate reinforced joints, collar plate reinforced joints, and unreinforced joints decrease progressively. Thickness of reinforcement plate has no obvious effect on in-plane flexural initial stiffness and ultimate capacity of joints. As thickness of reinforcement plate increases, the ductility of reinforced X-joints decreases. The concave and convex deformation of every specimen has good symmetry;as β increases, the yield and ultimate deformation of chord decrease.

Viscoelastic deformation behavior of cement and emulsified asphalt mortar in China railway track system I prefabricated slab track

Under repeated train-induced loads, cement and emulsified asphalt mortar(CA mortar) as a viscoelastic material has a time-dependent deformation, part of which is irreversible. This could lead to debonding between the mortar layer and the track slab. Based on the theory of viscoelasticity and the analytical method of the time hardening law(THL), the viscoelastic deformation behavior of CA mortar was studied. Using ABAQUS, we established a solid model of China railway track system(CRTS) Ⅰ prefabricated slab track, with CA mortar at different initial Young’s moduli under cyclic loading corresponding to the influence of actual train loads. The results reveal that the fitted parameters of the THL for CA mortar are suitable for describing its viscoelastic deformation. As the initial Young’s modulus increases, the strain difference before and after cyclic loading gradually decreases, and the displacement difference increases from 0.2 mm to 0.6 mm. The deformation mainly occurs at the end of a mortar layer with longitudinal distribution of about 2.5 times the fasteners’ spacing. It follows that the viscoelastic performance of CA mortar is one of the most important reasons that cause debonding underneath the track slab. Therefore, we suggest that the adverse effects of viscoelastic behavior of CA mortar should be considered when researching such deformation and damage.