Finite Element Method Analysis of Stress Field Considering Thermal Coupled Force During Laser Process

IntroductionLaserphasetransformationhardeningisanewtechnologyduringwhichlaserheatresourceactsdirectlyonsurfaceofmaterialandcompositionscharacteristicofmaterialischanged.Thetechnologyproce8sesacharacterofrapidheatvelocity,highheattempelatureandquickcoolingspeed(l0'col0'aC/s).Thecompositionandcharacteristicofmaterialvariedwithvariousinnertemperaturewillleadtothermalresidualstress.Itiswellknownthattheresidualstressaffectssignificantlyoncharacteristicofmaterial,suchasimProvingstrengthoffatigUere…     

流体自由界面追踪方法对比研究

流体自由界面追踪方法研究是近年来计算流体力学的热门课题,已有多种方法提出.文中对有代表性的VOF方法和Level Set界面追踪方法进行了比较.根据各种算法对旋转和剪切2种虚拟流场中界面演化的追踪结果,探讨了各种方法的准确性.计算结果表明,与VOF方法相比较,Level Set方法,特别是粒子level set方法能够更好地捕捉运动界面.     

悬链线方法在大跨径悬索桥基准索股调整中的应用

研究提出了悬索桥索股调整的精确计算方法,该方法可以计入主塔偏位、索股温度的影响。通过弹性悬链线模型推导了悬索桥基准索股的悬链线简化方法。该法对于中跨主缆调整与精确方法、抛物线简化方法相比精度较高,边跨主缆调整与抛物线法精度接近,误差均较大,但也可满足实际工程需要。     

Computer Prediction on Stress Distribution During Laser Quenching

IntroductionInprocessofindustry,theproblemscoupIedwiththermaIandfOrceareusuaIIymet.LaserqueIlchinginvolvingphasetransformationisoneofthem.HowtosetupafitmatheInatica1modeltosimulatetl1elaserquenchingprocessandhowtocalculateandanalyzenumericallythestresgdistributionarefolIowedwithinterestbymanyresearchersIl'2'3J.Thoseeffol'tsareimportanttooPtilnizethetechnologyparametersandprovideareliablebasisforimprovingthesyntheticallymechanicspropertiesandtheuseagesofmaterials.Alongwithdevelopmentofcomp…     

海底隧道大体积混凝土温度场及温度应力有限元分析

大体积混凝土的温度裂缝与混凝土的温度场和温度应力分布关系密切。重点探讨了应用有限元法求解大体积混凝土温度场和温度应力发展过程的模拟方法。以厦门南港海隧道为例,提出了大体积混凝土温度应力方程,编制了大体积混凝土温度场和温度应力计算程序。研究结果表明,采用有限元可以模拟大体积混凝土在温度场作用下的应力发展过程,计算结果符合混凝土浇筑过程中的温度应力分布规律。     

基于二维激光扫描的煤场储量计算与显示

利用二维激光扫描技术获取煤堆各截面的外表面x,y坐标,通过OLE自动化[1]技术读取和转换自定义格式的三维煤堆数据,并依据Marching Cubes和直接体绘制显示煤场三维形状,并根据数值积分求总体积和经验公式估算出煤的使用量并对煤储量进行合理的调用管理,还对三维数据场的两种体积计算方法进行了计算精度分析。     

刘江至西南绕城段改扩建工程地基处理计算方法研究

根据河南省连霍高速公路刘江至西南绕城段改扩建工程施工图设计经验,对其改扩建过程中双侧加宽路段的地基沉降控制标准及计算方法的选择加以介绍,同时结合工程实际,选取典型断面分别用有限单元法和分层总和法进行计算,其结果表明二者具有良好的相关性,这可用于简化工程计算,且为其他类似工程提供参考。     

刘江至西南绕城段改扩建工程地基处理计算方法研究

根据河南省连霍高速公路刘江至西南绕城段改扩建工程施工图设计经验．对其改扩建过程中双侧加宽路段的地基沉降控制标准及计算方法的选择加以介绍,同时结合工程实际,选取典型断面分别用有限单元法和分层总和法进行计算,其结果表明二者具有良好的相关性,这可用于简化工程计算,且为其他类似工程提供参考。     

寒区隧道气温对隧道温度场的影响分析

根据温度场的控制微分方程及有限元公式,以吐库二线中天山隧道为例,通过理论计算及数值模拟分析,分别得到在同样的时间周期内相同气温变化对隧道调温圈大小的影响,通过对比发现：计算结果基本一致,可作为后期继续深入研究的基础依据.     

Analysis of Key Factors in Cable Force Calculation for Cable-Stayed Bridges

Three methods for calculating cable force (analytic method, fitting method and finite element method) are analyzed and compared. The effects of boundary condition, spectrum resolution, sampling time, and number of sampling points on the precision of cable force identification are discussed, and error analysis is conducted. The results of three methods applied to a practical project are significantly less than the design value. Comparatively, the result of finite element method is the closest to the design value. Moreover, their computational precision and error are compared and analyzed. The precision of frequency identification of cables, long cables in particular, is strongly affected by frequency resolution. If the frequency resolution is included in calculating the cable force, the identification error can be reduced greatly.     

公路施工中特殊结构物放样的计算方法

桥梁锥形护坡、曲线斜桥梁板等结构物的施工放样在公路施工中非常重要。本文结合实际工作介绍了这两种特殊结构物施工放样的计算方法及计算过程。方法简单实用，可提高工作效率并保证施工放样的精度。     

Dynamic modeling and active control of a strap-on launch vehicle

Dynamic modeling and active control of a strap-on launch vehicle are studied in this paper. In the dynamic modeling, the double-compatible free-interface modal synthesis method is used to establish dynamic model of the system, and its model precision is compared with those of finite element method(FEM), fixedinterface modal synthesis method and free-interface modal synthesis method. In the active control, the swing angle of rocket motor is used as design variable, and the control law design based on the model of mass center motion is adopted to validate the system. Simulation results indicate that the double-compatible model synthesis method can properly approximate the FEM which is used as the benchmark solution, and the model precision of the double-compatible modal synthesis method is obviously higher than those of the fixed-interface and freeinterface modal synthesis methods. Based on the control law design, the deflection of mass center of the launch vehicle is very small.     

基于有限单元法的弹性抗滑桩内力计算

以基于有限单元法,提出一种新的基于温克尔弹性地基抗滑桩内力计算模式,在不需要滑动面处的连续性条件且能克服差分法的局限性下,计算出抗滑桩桩身处的最大弯矩.本文通过简化计算公式的推导,即可以缩短计算工时,同时易于掌握,可为类似工程的计算分析提供参考.     

Computer simulation of the continuous annealing recrystallization for cold-rolled strip in galvanizing line

The continuous heating transformation program is developed to investigate the influence of continuous annealing technological parameters on recrystalization for cold-rolled strip in galvanizing line. This program can be used for the calculation of the continuous annealing temperature field of strip steel, determination of the start and end time of recrystallization in continuous heating process, and procurement of the continuous heating transformation diagram. The temperature field for continuous annealing is simulated by means of finite difference method. Based on the Scheil superposition principle, the continuous heating transformation curve is obtained by using time temperature transformation (TTT) curve which is measured experimentally. The developed program has been used in practice, and the strip speed on production line increases by more than 10%.     

非均匀变温场中主缆初始位形的迭代计算

利用解析法推导了变温度场中悬索桥空缆线形的悬链线线形公式;建立了两种已知设计条件时悬索桥空缆线形的迭代方法;根据主缆的温度变化方程导出了温度变化时无应力索长计算公式。计算结果表明:在非设计温度下,主缆的位形及其内力值均与设计理论值有较大误差,因此在悬索桥的结构分析中必须考虑温度变化的影响。     

边跨非常规合龙对连续刚构桥主梁线形的影响分析

连续刚构桥边跨常用的合龙方式是先完成边跨现浇段浇筑成型、最后进行边跨合龙段浇筑成型。某高速公路上一座主桥为5跨预应力连续刚构桥,采用边跨现浇段、边跨合龙段同时浇筑一次成型这一比较特殊的合龙方式。建立反映其边跨非常规合龙方式的有限元数值模型,并对其进行计算。通过对边跨非常规合龙方式和边跨常规合龙方式的有限元对比分析发现,边跨采用非常规合龙方式,进行及时有效的施工控制,采用合理的预抛值,并在次边跨合龙时采取合理的施工措施,可以得到比较良好的主梁线形和比较协调的墩顶位移,并且能保证施工过程和使用过程的安全性。     

Calculation of Transient Stress Field During Laser Transformation Hardening Process

IntroductionHighpowerCOzlaserssdsetransformationhardeningtechniquehasbeensuccessfullyusedinindusnyforWYears.BecausethetemPeratUrefleldislocalizedinmaterialdurllglasertransfonnationhMngProcess,highthermstrCsswillgenerateinmatgrialduringlasertfansformationhardeningProcess.Therisalsohighresidualstressinmaterial,bothintCnsionandcomPression['-'].ComPressresidualstressishelptoincreasethefatigueldrimeofthelasertreatedmaterial,butthetensilestresswillshortenthefatiguelifetmeofthelasertreatedmator…     

船舶开口结构应力无网格分析技术研究

文章提出了船舶结构开口处应力分析的无网格分析技术.将船体结构通过简化为板格结构,再将结构离散为独立的离散点,由移动最小二乘法建立离散点的位移场,然后在整个系统内建立起系统控制方程.本文提出的方法由于不涉及到网格划分,避免了有限元法在结构应力高梯度区域分析计算时出现的精度降低等问题.文章最后通过实例计算,并与有限元方法计算的结构进行了比较,得出了本文提出方法的有效性和准确性.     

Robust adaptive horizontal vibration isolation of towed seismic streamers

The horizontal vibration of towed seismic streamers is a main reason for efficiency reduction of the seismic survey and tail tangling. A vibration suppression scheme of towed seismic streamers is investigated in this paper. The towed seismic streamer is divided into two spans, a controlled span, i.e., the low tension span, and an uncontrolled span, i.e., the high tension span, by a bird. The system model includes a hyperbolic partial differential equation with variable coefficient describing the towed seismic streamers, and an ordinary differential equation describing the dynamic of bird. Robust based-model knowledge and adaptive controllers, based on the Lyapunov method, are designed to isolate the vibration of towed seismic streamers caused by the course deviations of towing vessel, the variations of towing vessel velocity and the variations of towed seismic streamer density. The robust based-model knowledge and adaptive controllers exponentially and asymptotically drive the span-towed seismic streamer displacement to zero, respectively. A finite difference scheme is used to validate the efficiency of the control law. The proposed controller can isolate effectively the disturbance originated from the towed vessel, and can provide the improved damping but not sacrifice the isolation performance. The adaptive scheme can tolerate the lack of knowledge of some uncertain parameters and can directly execute the online adjustment of the parameters. Meanwhile, the proposed control law is robust and can resist the model uncertainty due to parameter incertitude, model error and unknown disturbance and so on. The control law only includes velocity and slope, while it does not need the displacement which is difficult to measure in the practical operations. Thus it is easy to implement.     

A Precise Integration Method for Linear Viscoelastic Solid

This paper presented a new convenient method for viscoelastic problems which are generally solved through complex Laplace transform. State space equation is derived from the differential form of constitutive equation of linear viscoelastic solid that can be solved by a precise integration method which is used in many fields with the advantages of high precision and convenience. For linear viscoelastic solids and crack, the finite elements program of the precise integration method is developed, which appears to be efficient and precise.