Partition of unity enrichment for bimaterial interface cracks

Partition of unity enrichment techniques are developed for bimaterial interface cracks. A discontinuous function and the two‐dimensional near‐tip asymptotic displacement functions are added to the finite element approximation using the framework of partition of unity. This enables the domain to be modelled by finite elements without explicitly meshing the crack surfaces. The crack‐tip enrichment functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The concept of partition of unity facilitates the incorporation of the oscillatory nature of the singularity within a conforming finite element approximation. The mixed‐mode (complex) stress intensity factors for bimaterial interfacial cracks are numerically evaluated using the domain form of the interaction integral. Good agreement between the numerical results and the reference solutions for benchmark interfacial crack problems is realized. Copyright © 2004 John Wiley & Sons, Ltd.     

船用锚链钢M20Mn冷弯断裂原因分析

通过化学成分测试和金相组织分析，认为M20Mn试样冷弯断裂的主要原因是圆钢存在严重的热轧带状组织和表面增碳。采取选择合适的浇注温度和注速、在浇注过程中避免保护渣污染钢液、控制终轧温度等预防措施，消除了M20Mn冷弯断裂缺陷。     

叠加法作弯矩图再讨论

通过对已知荷载作变换，找出给定区间上的弯矩有无极值的简单判别式，进而计算出极值点处的弯矩。在用叠加法作弯矩图时，可由两个端点处及极值点处的弯矩值而准确地画出弯矩图。     

Improvement on strip flatness of cold temper mills by modifying roll contour shape

A study on roll gap profile (strip profile) control was accomplished in a 1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contour caused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finite element model, the effects of roll contours (ground and wear) on strip profile were investigated. The roll bending effect on strip thickness was also analyzed. It is pointed out that there are some special features of flatness control in the temper mill: during temper rolling, roll deformation is slight due to small rolling load, and the loaded roll gap profile mainly depends on work roll contour, while the backup roll has a little effect on gap crown; the effect of bending force on gauge can not be ignored due to the coupling between flatness control and gauge control. A new roll contour arrangement adaptable to the mill was presented and has been put into practical production. The application of the new set of rolls showed some good results: larger crown control range of work roll bender, higher rolling stability, better strip profile and flatness quality.     

NH_2自由基~2A_1,~2B_1态振转能级的理论计算

采用大振幅弯曲振动哈密顿,同时考虑到Renner-Teller效应,理论上计算了NH2自由基A珟2A1,X珟2B1电子态振转能级,计算值与实验值符合较好。     

集中荷载作用下R.C.双向受弯约束梁斜截面抗剪强度的计算

在13根集中荷载作用下钢筋砼双向受弯约束梁斜截面抗剪试验研究的基础上，采用等效梭形截面法，将双向受弯约束梁转化为单向受弯约束梁，并推出集中荷载作用下钢筋混凝土双向受弯约束梁斜截面抗剪强度的计算方法．     

环扇形板弯曲问题中环向模拟为时间的辛体系

在平面弹性与Kirchhoff板弯曲相似性理论基础上，在辛体系中把环向模拟为时间，研究了环扇形板在内外两侧固支时的弯曲问题。得到零本征解与非零本征解，其结果形式简洁。环扇形板另两侧边界为径向固定时的算例，表明Hamilton体系的有效性与精确性。     

多筋结构件弯曲过程回弹模拟

采用有限元方法分析了多筋结构件成形过程中的回弹现象，研究表明：多筋结构件弹性回复能力相当强，进入塑性变形阶段后塑性变形的比率快速增加；考虑模具加载历史的影响，会进一步提高回弹模拟的精度；塑性变形区主要集中于筋部，筋条的塑性变形既有凸模下压导致的塑性变形，又有蒙皮回弹导致的塑性变形，蒙皮几乎不发生塑性变形．     

车床改装拉床的液压控制系统和主框架的结构稳定性

利用旧车床改装成LJ8510/CGL型键槽拉床,符合绿色制造减小回收成本的要求。采用通用液压元件组成节能型液压控制系统,提高了机床的自动化程度,设计的框架结构承受由主油缸拉动拉刀形成的沿水平轴线方向的拉削力,利用钢结构原理对机床的主框架结构进行整体稳定性计算,针对受力时可能出现单肢先行破坏的情况,分别对弯矩作用于截面的主轴平面内和平面外的稳定性进行计算。改装后的机床液压控制系统拉削工作需要,试车运转正常,连续4h运行,系统油温升高<20℃;整机质量达到国标要求,其设计和分析方法值得推荐。     

Inverse Analysis of Impact Test Data: Experimental Study on Polymeric Materials Displaying Brittle Behaviour

This paper deals with the influence of the testing equipment on impact load measurements. A previously developed method of analysis and processing of the experimental data based on a refined analogical model of the impact event and inverse problem techniques is used. This method makes it possible to obtain the mechanical response of the material, notwithstanding the disturbance of the dynamic effects associated to the test. Results from tests carried out both on falling weight and swing pendulum instrumented testing machines are compared. It is shown that this method can give an accurate estimation of the actual bending force in impact testing independent of the testing equipment.