Stress Solution of Multiple Elliptic Hole Problem in Plane Elasticity

Using Schwarz’s alternating method and Muskhelishvili’s complex variable function techniques, this paper presents an iterative algorithm method for the effective and accurate calculation of the stresses in an elastic solid of infinite extent containing multiple elliptic holes and subject to external loading at the infinity. The elliptic holes can have different dimensions and locate at any points while their axis orientations must be orthogonal. The proposed iterative algorithm method is based on the approximation of the resultant force vector on each elliptic hole boundary as a series of complex variable. As a result, exact closed-form analytical stress solutions can then be obtained for the solid with a single elliptic hole whose boundary is subject to the reverse resultant force vector in the forms of complex series. The numerical results presented in the paper show that the iterative solution converges quickly and stably. The proposed convergent criterion ensures the satisfaction of the required accuracy of the stress results. The stress concentration at elliptic holes can then be evaluated with high accuracy.     

Stability and Strength of Rigid and Semirigid Plane Frameworks

A computational technique for incorporating stability and strength into the analysis of plane frameworks is presented. The procedure for computing critical and/or collapse loads and for identifying the corresponding failure mode is outlined. The analysis is based on nonlinear kinematic relations and linearly elastic material behavior except at the plastic hinges—concentrated plasticity. The connections can be treated either as rigid or as flexible. The supports, in general, contain rotational restraints. The developed solution methodology is applicable to all multistory‐multibay orthogonal frames. The examples analyzed in the paper include: (1) A single‐story‐two‐bay frame with rigid joint connections; (2) a single‐story‐three‐bay frame with flexible joint connections; (3) a two‐story‐single‐bay frame with both rigid and flexible joint connections; and (4) a three‐story‐two‐bay frame with rigid joint connections. In all cases the loading consists of a symmetric distribution of concentrated loads on the beams, applied at the midspan positions and at or near the beam‐to‐column joints. The effect of several geometric and structural parameters is assessed.     

热源供热发电机组DCS与电气监控系统的应用及特点

介绍金川集团股份有限公司三厂区热源供热发电机组监控系统,论述供热发电机组的控制结构特点和监控内容,阐述热电联产项目的电气控制系统与热工控制系统有机结合的优越性。     

Comparison between Coupled and Uncoupled Consolidation Analysis of a Rigid Sphere in a Porous Elastic Infinite Space

Linear consolidation analyses are usually treated either by means of Terzaghi-Rendulic uncoupled theory or Biot’s consolidation theory. In this note, the problem of consolidation displacements around an axially loaded sphere was considered. It is demonstrated that both the uncoupled analysis and the coupled analysis give the same governing equation for pore fluid pressure dissipation with time. A simplified procedure for deriving transient strain components is illustrated. A general solution for time-dependent displacements is obtained using uncoupled consolidation analysis. Close agreement is evident between the new approximate uncoupled analysis solution and the existing coupled analysis solution with a maximum error of less than 0.5%.     

余热锅炉受热面的积灰及其对策

对余热锅炉受热面积灰的分类、特点及积灰形成的机理进行分析，提出防止积灰的措施及对策。     

加热保温处理对重轨钢中MnS夹杂的影响

 以U75V高速重轨钢为例,研究了加热保温处理对MnS夹杂的影响。采用高温共聚焦激光显微镜分别对铸坯和钢轨中MnS夹杂在连续升温过程中的行为进行了动态原位观察,结果表明MnS夹杂在600~870℃发生球化,在1180℃左右时, MnS夹杂开始发生固溶。根据原位观察结果,在电阻炉中进行了加热保温处理实验。试验结果表明,830℃保温后,MnS夹杂尺寸只是略有减少,长宽比降低。在1180℃保温后,大型MnS夹杂数量明显减少,小尺寸MnS数量增多,且随保温时间的延长,夹杂物数量减少,长宽比进一步降低。通过加热保温处理可以改善重轨钢中长条状大型MnS夹杂。     

椭圆H型翅片管在烟气余热回收中的优化设计

为了利用陶瓷厂的烟气余热,采用有机朗肯循环回收该部分余热。根据有关实验研究结论,对用于烟气和导热油换热的椭圆H型翅片管换热器进行了设计。通过对换热器的优化设计可为烟气余热回收工程应用提供参考。     

空气源泵热水机组在铜箔厂的应用

节约能源、降低成本是现代企业提高效益的重要途径之一.文章介绍了铜箔公司热水制备现状,并分析了根据空气热源泵工作原理,为充分利用设备冷却水余热而对铜箔热水制备系统进行的改造.改造工程在取得经济效益的同时,实现了节能降耗目标.     

相同孔径辅助孔与预裂孔在靠界爆破中的应用

采用辅助孔与预裂孔相同孔径(Φ165 mm或Φ200 mm)的爆破技术,提高靠界爆破的半壁孔率,提高减震效果,减少靠界爆破对边坡的冲击力度,从而更有效长久地保护好边坡完整和稳定。     

Ce 对耐热钢 253MA 中板夹杂物和性能的影响

太钢253MA耐热钢(%:0.05～0.10C、20.0～22.0Cr、10.0～12.0Ni、0.14～0.20N、0.03～0.08Ce)中板由电弧炉-AOD精炼氧化期吹N2-钢包喂稀土Ce线-连铸-热轧中板流程生产.结果表明,通过喂Ce线处理,钢中稀土夹杂呈球状,分布在奥氏体晶粒内部,提高了钢的横向冲击性能和持久强度.253MA钢板1 000℃平均氧化速率为0.09 mm/a.     

Taylor展开法在一维、稳态含内热源导热微分方程中的应用

针对一维、稳态且含内热源的导热型微分方程,分别采用区域离散方法A、B划分网格,然后采用Traylor展开法进行数值求解.计算结果表明:导热微分方程中边界节点采用二阶截差展开得到的离散方程,其推导过程比采用一阶截差展开复杂,尤其在计算节点间距不等(区域离散方法B)的情况下更是如此,但其数值求解精度能够得到大幅提高,因此在实际采用Taylor展开法进行数值求解过程中推荐采用区域离散方法B,且边界节点离散方程采用二阶截差展开.     

Fluid Flow,Heat Transfer and Inclusion Motion in a Four‐Strand Billet Continuous Casting Tundish

Inclusions in the steel in a four‐strand continuous casting tundish, billet and wire products are firstly investigated with industrial trials, and the fraction of inclusions removed in terms of total oxygen in the tundish is measured. Then the 3‐dimenional fluid flow, heat transfer and inclusion motion in the tundish are numerically simulated. The κ‐? two‐equation model is used to model turbulence. Inclusion motion and trajectories are calculated by considering drag force and buoyancy force, coupling the effect of turbulent fluctuation (Random Walk Model). The effect of strands‐blocking on the fluid flow, heat transfer and inclusion removal is studied. A new design of tundish is proposed focusing on removing more inclusions from the molten steel.     

Effect of Magnesium on Inclusion Formation in TiKilled Steels and Microstructural Evolution in Welding Induced CoarseGrained Heat Affected Zone

 Effects of Mg on the chemical component and size distribution of Ti bearing inclusions favored grain refinement of the welding induced coarse grained heat affected zone (CGHAZ), with enhanced impact toughness in Ti killed steels, which were examined based on experimental observations and thermodynamic calculations. The results indicated that the chemical constituents of the inclusions gradually varied from the Ti O+Ti Mg O compound oxide to the Ti Mg O+MgO compound oxide and the single phase MgO, as the Mg content increased from 0002 3% to 0006%. A trace addition of Mg (approximately 0002%) led to the refinement of Ti bearing inclusions by creating the Ti Mg O compound oxide and provided favorable size distribution of the inclusions for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ with enhanced impact toughness. Otherwise, a high content of Mg (approximately 0006%) produced a single phase MgO, which was impotent to nucleate an acicular ferrite, and a microstructure comprised of a ferrite side plate and a grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.     

Effect of Magnesium on Inclusion Formation in Ti-Killed Steels and Microstructurai Evolution in Welding Induced Coarse-Grained Heat Affected Zone

Effects of Mg on the chemical component and size distribution of Ti-bearing inclusions favored grain refinement of the welding induced coarse-grained heat affected zone (CGHAZ),with enhanced impact toughness in Ti-killed steels,which were examined based on experimental observations and thermodynamic calculations.The results indicated that the chemical constituents of the inclusions gradually varied from the Ti-O+Ti-Mg-O compound oxide to the Ti-Mg-O+ MgO compound oxide and the single-phase MgO,as the Mg content increased from 0.002 3% to 0.006%.A trace addition of Mg (approximately 0.002 %) led to the refinement of Ti-bearing inclusions by creating the Ti-Mg-O compound oxide and provided favorable size distribution of the inclusions for acicular ferrite transformation with a high nucleation rate in the CGHAZ,and a high volume fraction of acicular ferrite was obtained in the CGHAZ with enhanced impact toughness.Otherwise,a high content of Mg (approximately 0.006%) produced a single-phase MgO,which was impotent to nucleate an acicular ferrite,and a microstructure comprised of a ferrite side plate and a grain boundary ferrite developed in the CGHAZ.The experimental results were confirmed by thermodynamic calculations.     

空气源热泵热水系统性能及应用分析

阐述了空气源热泵热水系统的基本组成和工作原理,结合该系统在企业生活热水系统中的应用情况,分析了其运行效果及经济效益。     

烧结环冷机热工测试及余热源参数确定

冷却机热废气温度和流量是烧结余热电站设计中两个首要的基础参数。通过对唐钢炼铁厂北区1号、2号两台190 m2环冷机正常生产工况下的热工测试,采用直接测试和热平衡两种方法进行数据计算及对比分析。计算分析表明,2号环冷机存在严重的漏风问题,废气温度偏高,1号环冷机测试数据与热平衡计算结果基本吻合。最后以1号环冷机测试分析结果为依据,分别确定了单进口和双进口两种余热锅炉热废气参数。     

Transient Behavior of Inclusion Chemistry,Shape, and Structure in Fe-Al-Ti-O Melts: Effect of Titanium Source and Laboratory Deoxidation Simulation

During ladle processing of interstitial-free (IF) steel melts, it is possible for transient titanium-containing oxides to be formed if the local titanium/aluminum (Ti/Al) ratio is locally and temporarily increased after aluminum killing. The phase stability diagrams suggest that if the Ti/Al ratio is increased, then Al₂TiO₅ and/or a liquid Al-Ti-O region can become stable, and eventually at even higher Ti/Al ratios, Ti₃O₅ becomes stable. In this study, the Ti/Al ratio was successively altered to investigate (1) how the inclusions evolved after titanium addition to aluminum-killed iron melts and (2) whether the inclusions present after sufficient time were those predicted by thermodynamics. When the Ti/Al ratio was maintained at 1/4, such that Al₂O₃ is the only thermodynamically stable oxide, the results show that transient titanium-containing oxides exist temporarily after titanium addition, but with time, the predominant inclusion was Al₂O₃, which would generate little shape change and produce transient stage inclusions with less titanium contents. When the Ti/Al ratio was increased to 1/1 (Al₂O₃ still being the only thermodynamically stable oxide), the results show a more distinct increase in the titanium content of the transient inclusions. The transient reaction was, in this case, accompanied by an irreversible shape change from spherical to irregular inclusions. When the Ti/Al ratio in the melt was increased to 15/1 within the Al₂TiO₅ stable phase region, the inclusion population evolved from spherical-dominant ones to irregular ones. It was found that the final inclusion chemistry has more titanium but less aluminum content compared with the expected from the Al₂TiO₅ chemistry. Besides, the transmission electron microscopy (TEM) results showed the existence of Ti₂O. When the Ti/Al ratio in the melt was increased such that Ti₃O₅ is the thermodynamically stable inclusion (Ti/Al ratio of 75/1 or ∞), the inclusions evolved after titanium addition toward TiO_x inclusions, which is accompanied by a shape change from spherical to irregular. The TEM results revealed and confirmed the existence of metastable Ti₂O besides the thermodynamically stable Ti₃O₅, and it was consistent with the results based on oxidation studies of thin layers of titanium with Al₂O₃ substrate. It was discovered that Ti₂O has the tendency of transforming into the thermodynamically stable phase Ti₃O₅ under certain conditions.     

半钢炼钢加块状含碳材料补充供热试验

本文介绍马钢二炼钢厂20t转炉添加块状含碳材料补充供热的试验情况,解决了半钢炼钢热源不足问题,从而使钢质量提高,废钢比增加及显著的经济效益。     

Flow through Trapezoidal and Rectangular Channels with Rigid Cylinders

A physical model study was performed in which wood dowels were used to model rigid vegetation. The dowel configurations used in the flume were intended to simulate the effects of willow post systems (i.e., collections of rigid cylinders placed along a streambank to reduce streambank erosion). In addition, an analytical model is presented for predicting depth-averaged velocity distributions in straight trapezoidal or rectangular channels with newly constructed willow post systems. The analytical model is founded on wake theory and is applicable to channels with submerged and unsubmerged rigid cylinders. Data from three independent physical model studies were used to validate the analytical model. Depth-averaged velocities predicted using the analytical model, Upred, were compared to velocities observed in the physical models, Uobsd, and yielded discrepancy ratios, Upred/Uobsd, that were typically between 0.80 and 1.20. Results from this study are that significant variables for reducing local velocities are cylinder height, diameter, and density (number of cylinders per unit area); and the arrangement of the cylinders (i.e., rectangular versus staggered grid) is inconsequential.