A New Rational-based Optimal Design Strategy of Ship Structure Based on Multi-level Analysis and Super-element Modeling Method

A new multi-level analysis method of introducing the super-element modeling method, derived from the multi-level analysis method first proposed by O. F. Hughes, has been proposed in this paper to solve the problem of high time cost in adopting a rational-based optimal design method for ship structural design. Furthermore,the method was verified by its effective application in optimization of the mid-ship section of a container ship. A full 3-D FEM model of a ship,suffering static and quasi-static loads, was used as the analyzing object for evaluating the structural performance of the mid-ship module, including static strength and buckling performance. Research results reveal that this new method could substantially reduce the computational cost of the rational-based optimization problem without decreasing its accuracy, which increases the feasibility and economic efficiency of using a rational-based optimal design method in ship structural design.

SUPER-ELASTIC CONSTITUTIVE MODEL CONSIDERING PLASTICITY AND ITS FINITE ELEMENT IMPLEMENTATION

Based on the experimental results of super-elastic NiTi alloy, a three-dimensional super-elastic constitutive model including both of stress-induced martensite transformation and plasticity is constructed in a framework of general inelasticity. In the proposed model, transformation hardening, reverse transformation of stress-induced martensite, elastic mismatch between the austenite and martensite phases, and temperature-dependence of transformation stress and elastic modulus of each phase are considered. The plastic yielding of martensite occurred under high stress is addressed by a bilinear isotropic hardening rule. Drucker-Prager-typed transformation surfaces are employed to describe the asymmetric behavior of NiTi alloy in tension and compression. The prediction capability of the proposed model is verified by comparing the simulated results with the correspondent experimental ones. Based on backward Euler＇s integration, a new expression of consistent tangent modulus is derived. The proposed model is then implemented into a finite element package ABAQUS by user-subroutine UMAT. Finally, the validity of such implementation was verified by some numerical samples.

COMPUTATION OF SUPER-CONVERGENT NODAL STRESSES OF TIMOSHENKO BEAM ELEMENTS BY EEP METHOD

The newly proposed element energy projection(EEP) method has been applied to the computation of super_convergent nodal stresses of Timoshenko beam elements.General formulas based on element projection theorem were derived and illustrative numerical examples using two typical elements were given.Both the analysis and examples show that EEP method also works very well for the problems with vector function solutions.The EEP method gives super_convergent nodal stresses,which are well comparable to the nodal displacements in terms of both convergence rate and error magnitude.And in addition,it can overcome the “shear locking” difficulty for stresses even when the displacements are badly affected.This research paves the way for application of the EEP method to general one_dimensional systems of ordinary differential equations.

Self-adaptive strategy for one-dimensional finite element method based on EEP method with optimal super-convergence order

Based on the newly-developed element energy projection （EEP） method with optimal super-convergence order for computation of super-convergent results, an improved self-adaptive strategy for one-dimensional finite element method （FEM） is proposed. In the strategy, a posteriori errors are estimated by comparing FEM solutions to EEP super-convergent solutions with optimal order of super-convergence, meshes are refined by using the error-averaging method. Quasi-FEM solutions are used to replace the true FEM solutions in the adaptive process. This strategy has been found to be simple, clear, efficient and reliable. For most problems, only one adaptive step is needed to produce the required FEM solutions which pointwise satisfy the user specified error tolerances in the max-norm. Taking the elliptical ordinary differential equation of the second order as the model problem, this paper describes the fundamental idea, implementation strategy and computational algorithm and representative numerical examples are given to show the effectiveness and reliability of the proposed approach.

Super-Enrichment of Dispersed Elements and Associated Ore Deposits

Dispersed elements do not always occur as associated elements in the ore deposits of other elements. Instead, they can constitute independent ore deposits. The focus of this paper is placed on the mechanism of super-enrichment of the four dispersed elements Tl, Ge, Se, and Te under favorable geological conditions, where their enrichment coefficients are so high that their abundances can reach n×10+3-n×10+4, sometimes even up to n×10+6 times (e.g. Te) those of the crust. As a result, they can form their independent ore deposits. Studies have shown that such independent ore deposits are mostly distributed in the southwestern part of China, most of which belong to low-temperature ore deposits, ranging in age from Yanshanian to Himalayan (Cretaceous to Cenozoic), with a significant time gap with the host strata. Moreover, this paper also deals with the existing forms (as independent minerals, occurring isomorphously and being adsorbed) of the dispersed elements in those independent ore deposits. The discovery of independent ore deposits of dispersed elements is a great breakthrough in the study of dispersed element metallogenesis.

Buckling analysis of super-long rock-socketed filling piles in soft soil area by element free Galerkin method

In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditional first type, and a newly invented numerical analysis method, i.e. the element-free Galerkin method (EFGM), was introduced to consider the non-concordant deformation and nonlinearity of the pile-soil interface. Then, based on the nonlinear elastic-ideal plastic pile-soil interface model, a nonlinear iterative algorithm was given to analyze the pile-soil interaction, and a program for buckling analysis of piles by the EFGM (PBAP-EFGM) and arc length method was worked out as well. The application results in an engineering example show that, the shape of pile top load-settlement curve obtained by the program agrees well with the measured one, of which the difference may be caused mainly by those uncertain factors such as possible initial defects of pile shaft and the eccentric loading during the test process. However, the calculated critical load is very close with the measured ultimate load of the test pile, and the corresponding relative error is only 5.6%, far better than the calculated values by linear and nonlinear incremental buckling analysis (with a greater relative error of 37.0% and 15.4% respectively), which also verifies the rationality and feasibility of the present method.

微量元素对超大线能量EH36船板热影响区粗晶区组织和性能的影响

通过焊接热模拟研究了在超大线能量下焊接时Al元素、Mg元素和Ti元素含量对EH36高强船板钢热影响区粗晶区组织、性能的影响规律,采用Thermo-Calc热力学计算与SEM,EDS测试相结合的方法揭示了Al元素、Mg元素和Ti元素含量与母材中氧化物类型、尺寸、数量及粗晶区相变的关系.结果表明,Al_(2)O_(3)无法诱导针状铁素体相变,当Al元素质量分数低于0.005%时,钢中可形成Mg元素、Ti元素或其复合氧化物,可促进粗晶区针状铁素体相变.Mg元素和Ti元素联合添加时,当Mg元素质量分数由0.0042%降低为0.0013%,氧化物类型由MgO转变为Mg_(2)TiO_(4),经统计20个视场内的氧化物数量由408个提高到503个,平均直径由1.37μm减小到1.10μm,显著提高了非均匀形核的比表面积,抑制了晶界铁素体的形成,使t8/5=300 s时粗晶区热模拟试样-20℃冲击吸收能量由43 J提升到127 J.

多跨矮塔斜拉桥超高墩合理形式比选

为研究多跨矮塔斜拉桥超高墩合理形式,以多跨矮塔斜拉桥超高墩为对象,综合对比分析超高墩结构布置形式和受力特点,按截面特性相似的原则提出双薄壁墩、单薄壁墩、组合式墩、叠合式墩四种适用于依托工程的超高墩形式。采用全桥有限元和理论方法,分析不同工况下主梁和桥墩关键截面的内力和墩顶位移、施工和成桥运营阶段的稳定性、E1地震作用下的动力及抗震性能。结果表明:四种方案均满足施工阶段和成桥运营阶段下的稳定性要求,双薄壁墩前三阶均为纵向失稳且稳定安全系数变化较小;在E1地震荷载作用下,双薄壁墩内力响应最小,但位移响应较大,单薄壁墩和叠合式墩与之相反,组合式墩则较均衡。考虑结构整体受力性能,建议多跨矮塔斜拉桥超高墩桥梁选用双薄壁墩或组合式墩。

超大面阵碲镉汞探测器低应力设计及有限元分析

随着碲镉汞材料和器件技术的不断发展,满足大视场、超高分辨率应用需求的超大阵列规模的红外探测器逐步投入工程应用,超大面阵探测器芯片的低温可靠性成为封装技术的重点研究内容。以某超大面阵碲镉汞混成芯片为研究对象,采用有限元仿真分析法研究了冷头材料体系、冷台外径、冷台的结构形式等因素对混成芯片低温应力和芯片光敏面低温变形的影响规律,最终优化设计出一套可满足超大面阵芯片低温可靠性要求的冷头结构和材料体系。仿真结果显示,该冷头体系硅电路低温下最大应力约为70 MPa,碲镉汞光敏区在低温下的变形约为30μm。仿真结果能满足工程应用可靠性要求的经验仿真阈值,有效改进了超大面阵红外探测器的高可靠小型化封装技术。

超单元技术在整车NVH开发中的应用

超单元技术是一种基于有限元方法的模拟分析技术,可以将车辆的噪声、振动与声振粗糙度(NVH)问题进行精细化分析和优化设计。文章首先介绍超单元技术的基本原理和主要优点;其次,用超单元技术对整车进行NVH分析,并验证其在整车路面噪声仿真及衬套灵敏度分析中的应用;最后,总结了超单元技术在整车NVH开发中的应用效果,并对该技术未来的发展方向进行了展望。结果表明,超单元技术是一种高效、精确、可靠的整车NVH开发工具,将在未来的汽车制造和NVH优化中发挥越来越重要的作用。

超级微波消解-ICP-AES法测定铑粉中16种杂质元素

在高温高压条件下用盐酸-双氧水消解铑粉样品,采用电感耦合等离子体发射光谱仪(ICP-AES)测定其中16种杂质元素[1]。进行了光谱干扰研究、谱线选择、加标回收、精密度以及基体匹配比对试验。该方法简便、快速、准确,其测定范围为0.0005%~0.10%,RSD在1.88%~12.15%之间,加标回收率在92.0%~114.6%之间,不同方法结果对照数据吻合良好。该方法可满足铑粉中16种杂质元素的测定要求。

微波消解-电感耦合等离子体质谱法测定肥料中9种污染元素

采用电感耦合等离子体质谱法(ICP-MS)测定,超级微波消解并优化不同类型肥料的消解条件,建立了超级微波-ICP-MS测定多种类型肥料中V、Cr、Co、Ni、As、Cd、Hg、Tl、Pb 9种污染元素含量的方法。本方法的线性相关系数均大于0.9999,方法检出限范围为0.000500~0.0293 mg/kg,各元素加标回收率为85.0%~110%,该方法灵敏度高、准确度较好,可实现不同类型肥料样品中多元素的准确测定。

沿海地区超强台风作用下核电塔机抗风性能分析

基于GB/T 13752—2017《塔式起重机设计规范》确定了超强台风作用下QTP300(7526B)型核电塔机的风荷载及其荷载组合方式,并考虑风荷载的不同加载方式(立面加载和平面加载),对核电塔机非工作状态下的抗风性能进行了有限元静力分析。结果表明:与将风荷载分配到有限元模型的所有节点上相比,选取指定节点施加风荷载所得到的结果更大,表明在风荷载应加载到所有立面节点上;迎风面构件对背风面构件的挡风作用对塔机结构的应力分布及最大应力均无显著影响,而塔机结构的最大位移则随挡风作用的增强而增大,表明风荷载加载应考虑迎风面构件的挡风作用;塔机整机结构最大应力出现在底部主肢构件上,其大小均小于钢材的允许应力,该型号核电塔机可以承受17级超强台风作用。

特高混凝土面板堆石坝的结构分区研究

面板堆石坝变形控制的前提是保证坝体各分区的施工质量,而这与坝体分区结构设计关系密切。在坝体分区结构设计环节中,差异过大的主次堆石分区会导致面板出现过大的挠度变形,同时也容易产生开裂、脱空等问题。通过三维非线性有限元分析计算,着重从结构设计理论的角度分析了特高面板堆石坝应力变形特性的影响因素。结合某特高混凝土面板堆石坝,设计了坝体的不同分区方案,从计算结果的对比分析中得出了特高坝的建议分区原则:若次堆石区填料材料特性较差,应尽可能保证次堆石区靠近下游,同时主堆石区和次堆石区分界线应靠近下游;尽量避免次堆石区设置在坝顶范围,以免在次堆石区产生较大的竖向位移对坝顶及上游坝面的影响;全断面采用主堆石区或减小主次堆石区变形模量的差异性,有利于坝体的变形协调。

井筒对特大跨越输电塔风致响应的影响

采用数值模拟方法研究井筒对特大跨越输电塔风致响应的影响,提出钢管混凝土杆采用钢管杆等代的等效建模方法,采用时域法和频域法研究有无井筒输电塔在顺线路和横线路方向的风致响应,最后将风振系数结果与规范规定值进行比较。研究表明:利用截面刚度等效原则进行钢管混凝土杆等效为钢管杆的方法是可行的;考虑井筒后输电塔的前两阶自振频率降低明显,输电塔的位移和加速度均增大;时域法和频域法的计算结果接近;有井筒输电塔的整体风振系数比无井筒输电塔大11%~15%;风振系数计算结果与《架空输电线路荷载规范》(DL/T 5551—2018)的规定值比较接近。

Self-adaptive one-dimensional nonlinear finite element method based on element energy projection method

The element energy projection （EEP） method for computation of super- convergent resulting in a one-dimensional finite element method （FEM） is successfully used to self-adaptive FEM analysis of various linear problems, based on which this paper presents a substantial extension of the whole set of technology to nonlinear problems. The main idea behind the technology transfer from linear analysis to nonlinear analysis is to use Newton＇s method to linearize nonlinear problems into a series of linear problems so that the EEP formulation and the corresponding adaptive strategy can be directly used without the need for specific super-convergence formulation for nonlinear FEM. As a re- sult, a unified and general self-adaptive algorithm for nonlinear FEM analysis is formed. The proposed algorithm is found to be able to produce satisfactory finite element results with accuracy satisfying the user-preset error tolerances by maximum norm anywhere on the mesh. Taking the nonlinear ordinary differential equation （ODE） of second-order as the model problem, this paper describes the related fundamental idea, the imple- mentation strategy, and the computational algorithm. Representative numerical exam- ples are given to show the efficiency, stability, versatility, and reliability of the proposed approach.

Finite element modeling for analysis of cracked cylindrical pipes

The characteristic properties of shell element with similar shapes are used to generate a so-called super element for the analysis of the crack problems for cylindrical pressure vessels. The formulation is processed by matrix condensation without the involvement of special treatment. This method can deal with various singularity problems and it also presents excellent results to crack problems for cylindrical shell. Especially,the knowledge of the kind of singular order is not necessary in super element generation; it is very economical in terms of computer memory and programming. This method also exhibits versatility to solve the problem of kinked crack at cylindrical shell.

超级微波消解-电感耦合等离子体原子发射光谱法测定硼铁中铬、锰、镍、铜、铝、钛元素的含量

提出了超级微波消解-电感耦合等离子体原子发射光谱法测定硼铁中铬、锰、镍、铜、铝、钛元素含量的方法。以3 mL硝酸、1 mL盐酸、2 mL氢氟酸、1 mL硫酸、1 mL高氯酸为消解酸体系,采用超级微波消解仪对0.1 g硼铁样品进行处理。在升温压力4 MPa条件下,于最高消解温度270℃保持40 min,样品可以完全消解。结果表明:以基质匹配法定量,6种待测元素工作曲线的线性范围均为0.1~2.0 mg·L^(-1),检出限为8.5×10^(-5)%~2.22×10^(-4)%;按照标准加入法对实际样品进行回收试验,回收率为90.0%~110%,测定值的相对标准偏差(n=11)均小于3.0%;方法用于硼铁标准样品分析,测定值与标准值具有较好的一致性。

某外形收进超高层结构斜柱钢环梁节点有限元分析

针对某外形收进的超高层钢管混凝土斜柱节点,基于对斜柱区域内力传递路径的分析,按照钢环梁节点构造的方式对斜柱底部节点进行了设计。通过ABAQUS建立节点的有限元模型,根据结构整体计算结果施加荷载,对相贯节点的应力、破坏模式进行研究。分析结果表明:本工程斜柱钢环梁节点在设计荷载作用下基本处于弹性状态,满足抗震性能设计要求。斜柱节点在相贯处混凝土出现了应力集中,同类工程中若出现更大的设计荷载可考虑对此处采取加厚钢板等构造加强措施。

SELF-ADAPTIVE STRATEGY FOR ONE-DIMENSIONAL FINITE ELEMENT METHOD BASED ON ELEMENT ENERGY PROJECTION METHOD

Based on the newly-developed element energy projection （EEP） method for computation of super-convergent results in one-dimensional finite element method （FEM）, the task of self-adaptive FEM analysis was converted into the task of adaptive piecewise polynomial interpolation. As a result, a satisfactory FEM mesh can be obtained, and further FEM analysis on this mesh would immediately produce an FEM solution which usually satisfies the user specified error tolerance. Even though the error tolerance was not completely satisfied, one or two steps of further local refinements would be sufficient. This strategy was found to be very simple, rapid, cheap and efficient. Taking the elliptical ordinary differential equation of second order as the model problem, the fundamental idea, implementation strategy and detailed algorithm are described. Representative numerical examples are given to show the effectiveness and reliability of the proposed approach.