I型金属夹层结构连接构件强度特性研究及灵敏度分析

在国外,激光焊接钢质夹层结构已用于实船,其连接构件的强度特性是尚待解决的关键问题之一.应用有限元分析软件ANSYS,研究2种典型连接构件的面外强度特性及灵敏度.计算中,为降低计算规模,采用MPC壳体连接和子模型分析技术;进行灵敏度分析时,为减少大量方案计算所需的繁琐人工操作,应用Matlab驱动ANSYS,以批处理方式的有限元分析计算各方案的响应值.计算结果显示,在普通焊接接头处存在一定的应力集中.在控制结构重量的条件下,若要降低接头的应力集中系数,对于内嵌方框型连接构件而言,增大连接构件长度和夹层端部面板长度最为有效,增大水平板厚度也有一定的作用;对于外接平板型连接构件而言,最有效的途径是增大连接构件的厚度,并选取合适的连接构件长度.     

体-壳单元组合建模法在圆柱壳开孔结构有限元分析中的应用

研究体-壳单元组合建模法在圆柱壳开孔结构有限元分析中的应用,主要考虑多点约束(MPC)法在处理体单元与壳单元连接时的计算精度和效率。在Ansys中建立相应的模型,并与全壳单元模型及全实体单元模型的计算结果进行对比。结果表明,采用体-壳单元组合建模的模型在孔周壳板应力、结构屈曲模态及极限失稳响应等方面的计算结果与全壳单元模型及全实体模型偏差较小,结果比较可靠。     

激光焊接夹层甲板板格强度计算的子模型方法

提出了基于有限元软件ANSYS的激光焊接钢质夹层甲板板格结构强度计算的子模型方法。分别对考虑激光焊接焊缝缺陷的I型夹层板格结构的壳单元计算模型和体单元子模型进行强度分析,并与全部体单元模型的芯层与上下面板连接处及面板中部处应力分布计算结果进行对比,验证壳单元计算模型和子模型方法用于计算夹层甲板板格强度的正确性。计算结果表明,对强度特征关注区域,可建立多个体单元子模型,确定子模型边界影响区域范围,从而可较为准确地评估夹层甲板板格结构强度特性,包括焊缝处应力分布。壳单元计算模型可获得较为精确的板格变形值,但无法考虑激光焊接焊缝缺陷,获得的焊缝处最大应力值明显偏小。     

夹层板面内连接结构力学性能数值仿真分析

夹层板连接结构始终制约着夹层板在船体结构中的大规模应用。为推进夹层板连接结构的研究设计,以夹层板面内连接结构为研究对象,研究面内连接结构屈服强度、稳定性、极限强度分析的力学模型,然后从建模方式、单元类型、网格尺寸、加载速率、初始缺陷等多个方面研究面内连接结构力学性能数值仿真分析技术。通过研究确定:采用Shell-Shell-Contact建模方式,可以提高计算效率和计算精度;网格尺寸的选取应以计算资源作为主要考虑因素;可采用小尺寸板条模型研究极限强度,加载时间为5~10 T(T为结构固有周期)范围内可提高计算效率和计算精度;施加5%板壳厚度的初始缺陷,可在极限抗压能力分析时引导结构进入一阶屈曲模态。     

舰用钢质夹层结构连接节点研究现状综述

激光焊接钢质夹层结构的连接节点,是钢质夹层结构在舰船应用中的关键问题之一。梳理了钢质夹层结构之间、钢质夹层结构与传统船体结构之间的典型连接节点;阐述了钢质夹层结构连接节点的必要性和重要性,分析了连接节点设计需考虑的多种因素：连接强度、制造工艺和结构重量;汇总了平面对接的连接形式的现有研究成果,并总结了2种高效的有限元分析方法：平面应变模型的分析方法和壳-体连接结合子模型的分析方法。     

含坑点腐蚀的深海耐压球壳有限元分析

对于含坑点腐蚀等局部缺陷的球壳结构,由于结构的不连续性以及缺陷部位应力状态的三维特性,因此很难用传统的连续介质理论及板壳理论进行求解。为了对含坑点腐蚀的球壳的强度、稳定性进行精确分析,文中分别采用坑点腐蚀壳体单元(Pitting Corrosive Shell Element,PCSE)、基于多点约束(Multipoint Constraint,MPC)的壳体单元-实体单元集成以及实体单元三种方法进行对比计算,对比结果表明,采用PCSE方法的计算效率最高,且计算结果的精度满足工程应用要求。最后,基于PCSE方法并通过方差分析,讨论了坑点腐蚀对球壳强度及稳定性的影响。     

水下结构数值计算中面体单元连接技术及力学试验研究

结合有限元分析软件ANSYS对大潜深、大开口观察窗壳体结构模型的静态力学性能进行了数值分析及试验研究。计算模型考虑了材料非线性、几何非线性的影响。球壳采用面单元建模,观察窗窗座采用体单元建模,减少了计算规模,节省了计算时间。针对这2种不同自由度单元的连接,采用了不同的面体单元耦合技术,讨论了它们对静态力学性能结果的影响,在此基础上进行了试验研究。试验表明,本文所建立的有限元模型和计算策略准确可靠,可供设计时使用。同时也表明了在数值计算中采用MPC接触方法的面体单元耦合技术精度更高。     

子模型方法在舰船设备连接结构强度研究中的应用

对子模型方法进行了详细的介绍，并以某舰用齿轮箱为计算模型，验证了冲击载荷下子模型方法计算舰船大型设备中的连接结构强度问题的有效性，其计算结果与常规计算方法的结果十分吻合．以某舰用齿轮箱为算例进行抗冲击计算，应用子模型方法对该齿轮箱连接构件进行了强度校核．计算结果表明，该齿轮箱的连接构件可以满足相关抗冲击要求，螺栓结构的动态响应特性与螺栓的连接形式有密切关系．研究结果对大型舰载设备连接构件的强度校核提供了新思路，具有一定的参考价值．     

双体船连接桥结构强度的简化计算

双体船的连接桥结构强度是设计时需要重点考虑的问题,采用全船有限元法来分析计算要耗费大量的时间。将连接桥结构简化为一种梁模型,采用简化解析计算方法来分析其扭转强度和横向强度,并与实船的全船有限元法的对比分析结果表明：简化模型和计算方法是可行的,可应用于双体船初步设计阶段,估算连接桥的结构强度,指导结构设计。     

夹层结构玻璃钢游艇整船结构强度有限元分析

目前各大船级社普遍缺乏新颖玻璃钢艇体结构强度的计算规范,因此设计者需要直接计算艇体结构强度。在研究玻璃钢游艇的基础上,用ANSYS软件建立全船有限元模型,采用层合壳单元处理复合材料和复合材料夹层结构并计算分析整船结构强度。分析中所采用的方法对于正确地进行玻璃钢游艇整船直接计算具有指导作用和实用价值。同时所采用的冲击力和水动力加载方法可应用于其他类型的高速艇结构强度的有限元分析。     

Bond-slip behaviour of concrete filled double skin steel tubular (CFDST) columns

This paper provides novel results and key findings for the bond-slip field since there is no single study available in the literature conducted on the bond-slip behaviour of concrete filled double skin steel tubular (CFDST) columns. Likewise, no studies have been focused on the contribution of welded reinforcing bars on the bond behaviour of composite columns. A series of push-out tests on sixteen specimens of CFDST columns are presented to explore the bond-slip behaviour between the cross-sectional elements (the inner steel tube, outer steel tube and the shell concrete). The primary test parameters involve (a) interface type (normal interface, interface with an internal ring, with reinforcing bars, and with shear studs); (b) concrete strength (high strength concrete and normal strength concrete); (c) push-out type (push-out of the shell concrete and push-out of the inner tube). The results demonstrated that greater benefits arose on the bond strength, once the reinforcing bars or internal rings were welded onto the inner steel tube of CFDST columns. Moreover, in addition to remarkably improving the bond strength, the welded reinforcement bars would significantly improve the compressive strength of CFDST columns and eliminate the local buckling of the inner steel tube. On the other hand, the embedded shear studs (bolts) onto inner steel tubes are capable of improving the bond strength with less degree of the shear resistance in comparison with the other interface types. What's more, the current paper is also adapted to explore the influence of concrete grade (normal and high strength) on the bond performance of CFDST columns and it is showed that the bond strength increases considerably as the strength of the shell concrete is increased. Finally, the bond improvement ratio (BIR) is studied which could be a representative index in comparing the performances of the parameters on the bond behaviour.     

Modeling and analysis of thin-walled Al/steel explosion welded transition joints for shipbuilding applications

The study presents an analysis of S355J2+N steel and AA5083 aluminum alloy welded structural joints using explosion welded transition joints of reduced thickness. The transition joint thickness reduction significantly hinders the welding of the joints due to the risk of damage to the Al/steel interface as a result of the high temperatures during welding. Numerical modeling of the welding process is performed to determine safe welding parameters for the transition joint. The numerical analysis is supported by measurements of the temperature areas by a thermographic method. Welded structural joints are analyzed to determine the welding influence on the mechanical properties and microstructure of the transition joints. On this basis, a number of tests are carried out, including microhardness distribution measurements, strength tests of joints in two welding configurations and strength tests of the microspecimens of transition joints. Moreover, an experimental and numerical analysis of strain and stress distributions is carried out in combination with the use of the finite element method and digital image correlation, which allow us to identify the critical areas of the joints with regards to their strength. The results of the microstructural and strength tests carried out using macro- and microspecimens show softening of the aluminum alloy layers. However, the AA5083 and AA1050 layer softening as a result of welding did not reduce the load capacity of the transition joints, which could determine the strength of the dissimilar Al/steel welded structural joints.     

Testing and analysis of a 6-m steel truss/composite skin hybrid ship hull model

A hybrid ship hull made of a steel truss and composite sandwich skins was investigated experimentally and numerically. A 6-m model was tested under hogging loads, after having previous been subjected to sagging loads. All loads were introduced as shear through brackets welded to bulkheads. The model was loaded to the design load, at which point there was plastic yielding of the steel truss. However, there was no indication of failure in any of the composite sandwich panels, nor in the adhesive bonds between the panels and the steel truss. The steel truss started to yield at lower strains than expected, a fact which was elucidated by manufacturing and testing subcomponents of the steel truss. Nonlinear elastic-plastic finite element analyses were performed on the complete hull. Results from the numerical analyses were compared with data from both sagging and hogging tests and good correlation was found.     

Study on shell–solid coupling FE analysis for fatigue assessment of ship structure

A simple, robust and high-precision method for shell–solid coupling has been demonstrated. The coupling is achieved by a fictitious shell plane perpendicular to the original shell plane. The guidelines for this coupling technique for ship structural analysis are established by examining the local stress of the stool-like welded joint models. The surface stresses in the vicinity of the weld of a small corner joint model and a large ship structure model calculated by the proposed technique are in good agreement with those obtained from the multipoint constraint-based coupling models and the strain measurements. This demonstrates the effectiveness of the proposed technique in the local approach fatigue assessment of actual ship structures.     

外接平板型金属夹层结构连接构件极限强度分析

激光焊接钢质夹层结构在国外已用于实船,其连接形式是亟待解决的关键问题之一。基于有限元分析软件ANSYS,研究了面内载荷作用下,I型金属夹层结构外接平板型连接构件的失效模式和极限承载能力,以及5种典型初始缺陷的尺寸和连接构件的设计参数对极限载荷的影响规律。结果显示,连接构件较短时,结构失效的主导因素是焊接接头形成了塑性铰;连接构件较长时,主导因素是连接构件失稳。对于各种类型的初始缺陷,随初始缺陷尺寸的增大,极限载荷均降低;连接构件、以及靠近连接构件的夹层面板和夹层腹板的初始缺陷对极限载荷的影响较大。在控制重量的条件下,欲增大极限承载能力,最有效的途径是增大连接构件厚度,并选取合适的连接构件长度。     

Fatigue life prediction of welded ship details

Ship structures are submitted to variable cyclic loading during navigation. The cyclic motion of waves induces variable and complex loadings in the structure, which could generate fatigue damage. Moreover, most of these metallic structures are welded assemblies. This technique generates local stress concentrations at the weld toe, which becomes a critical area regarding fatigue. In previous works, a methodology to predict fatigue life was developed and tested on butt-welded and cruciform joints. The present work focuses on other welded assemblies in order to extend fatigue crack initiation life evaluation to a wider range of ship details. The strategy could be split into two steps. First, a finite element calculation is performed under constant or variable amplitude loadings, in order to analyze the elastic shakedown of the structure. To characterize the material heterogeneity of the welded joint, experimental tests together with micro-hardness measurements, are performed on a simulated heat-affected zone. If there is a shakedown in the structure, a post-treatment is applied to predict the fatigue crack initiation. It is based on a two-scale damage model, initially developed by Lemaitre et al. and again includes the heterogeneity of fatigue properties. To validate this methodology, some experimental tests have been performed on welded assemblies which are typical of shipbuilding applications, using a fatigue machine. These comparisons between experimental and numerical fatigue lives are encouraging.