FEA technique of hot plate forming process using cell-typed die with cooling device

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG tank.Cell-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed die.Further,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA technique.The analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

Closed-form solutions for free vibration of rectangular FGM thin plates resting on elastic foundation

This article presents closed-form solutions for the frequency analysis of rectangular functionally graded material (FGM) thin plates subjected to initially in-plane loads and with an elastic foundation. Based on classical thin plate theory, the governing differential equations are derived using Hamilton's principle. A neutral surface is used to eliminate stretching-bending coupling in FGM plates on the basis of the assumption of constant Poisson's ratio. The resulting governing equation of FGM thin plates has the same form as homogeneous thin plates. The separation-of-variables method is adopted to obtain solutions for the free vibration problems of rectangular FGM thin plates with separable boundary conditions, including, for example, clamped plates. The obtained normal modes and frequencies are in elegant closed forms, and present formulations and solutions are validated by comparing present results with those in the literature and finite element method results obtained by the authors. A parameter study reveals the effects of the power law index n and aspect ratio a/b on frequencies.

Semisolid metal forming by, novel sloping plate process

Semisolid metal forming by a novel sloping plate process was studied. A sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries with good microstructures and excellent property were prepared by cooling or preheating the sloping plate. During preparing semisolid alloy by the proposed process, the co-action of burst nucleation and dendrite fragmentation causes fine spherical microstructure formation, and casting temperature, cooling strength and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660-690℃for AlMg3 alloy and 660-680℃for AlSi6Mg2 alloy are suggested. A small car hub wheel of AlSi6Mg2 alloy was thixoformed, and its pattern and inner microstructure are fine. The reasonable technological conditions for preparing AlSi6Mg2 slurry are also proposed: the sloping plate preheating temperature is 300℃, and the casting temperature is 680℃.

Closed form solutions for free vibrations of rectangular Mindlin plates

A new two-eigenfunctions theory, using the amplitude deflection and the generalized curvature as two fundamental eigenfunctions, is proposed for the free vibration solutions of a rectangular Mindlin plate. The three classical eigenvalue differential equations of a Mindlin plate are reformulated to arrive at two new eigenvalue differential equations for the proposed theory. The closed form eigensolutions, which are solved from the two differential equations by means of the method of separation of variables are identical with those via Kirchhoff plate theory for thin plate, and can be employed to predict frequencies for any combinations of simply supported and clamped edge conditions. The free edges can also be dealt with if the other pair of opposite edges are simply supported. Some of the solutions were not available before. The frequency parameters agree closely with the available ones through pb-2 Rayleigh-Ritz method for different aspect ratios and relative thickness of plate.

CHARACTERISTIC EQUATIONS AND CLOSED-FORM SOLUTIONS FOR FREE VIBRATIONS OF RECTANGULAR MINDLIN PLATES

The direct separation of variables is used to obtain the closed-form solutions for the free vibrations of rectangular Mindlin plates. Three different characteristic equations are derived by using three different methods. It is found that the deflection can be expressed by means of the four characteristic roots and the two rotations should be expressed by all the six characteristic roots,which is the particularity of Mindlin plate theory. And the closed-form solutions,which satisfy two of the three governing equations and all boundary conditions and are accurate for rectangular plates with moderate thickness,are derived for any combinations of simply supported and clamped edges. The free edges can also be dealt with if the other pair of opposite edges is simply supported. The present results agree well with results published previously by other methods for different aspect ratios and relative thickness.

Edge effects of metal plate in laser forming

To search for the new scanning plan that can reduce the bending angle variation and the bending curvatures of the bending edge, an explanation for the causes of the edge effects was given. Six new scanning strategies were proposed through the change of the scanning length of middle and two ends based on the above analyses. Numerical simulations were carried out to study the edge effects using the six new scanning strategies. The simulation results show that the new scanning strategies can improve effectively the quality of the forming parts.

Layer-block tectonics of Cenozoic basements and formation of intra-plate basins in Nansha micro-plate, southern South China Sea

Layer-block tectonics （LBT） concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea （SCS）. Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei （Rifleman bank）-Andu （Ardasier bank） and Liyue （Reed bank） North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei- Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip detachment of basemental layerblock and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei Andu and Liyue-North Palawan intra-plate basin groups, respectively.

基于AutoForm的汽车门后背板数值模拟与成形仿真

基于AutoForm软件对某车型的车门后背板进行了数值模拟以及成形仿真研究。针对冲压成形过程中产生的多孔裂纹和边角起皱、表面凹凸不平问题进行了技术研究,并根据数值模拟结果,及时预测了易因变薄造成拉裂等技术问题的区域,并制定了冲压技术措施,从而提高了整套模具的使用率,大大减少了后期修模及操作的时间,使修模变得更为简单。

Closed-form solution of mid-potential between two parallel charged plates with more extensive application

Efficient calculation of the electrostatic interactions including repulsive force between charged molecules in a biomolecule system or charged particles in a colloidal system is necessary for the molecular scale or particle scale mechanical analyses of these systems. The electrostatic repulsive force depends on the mid-plane potential between two charged particles. Previous analytical solutions of the mid-plane potential, including those based on simplified assumptions and modern mathematic methods, are reviewed. It is shown that none of these solutions applies to wide ranges of interparticle distance from 0 to 10 and surface potential from 1 to 10. Three previous analytical solutions are chosen to develop a semi-analytical solution which is proven to have more extensive applications. Furthermore, an empirical closed-form expression of mid-plane potential is proposed based on plenty of numerical solutions. This empirical solution has extensive applications, as well as high computational efficiency.

Formation of the adakite-like granitoid complex and porphyry copper-gold deposit in Shaxi from southern Tancheng-Lujiang fault belt: A clue to the West Pacific plate subduction

On the basis of the geological and geochemical studies, including chemical analysis of bulk rocks, rare-earth and trace element studies, fluid inclusion, and S and O isotopic analyses, the authors described the geological background of the deposit in detail and presented significant proofs for the conditions of formation of the Shaxi porphyry copper-gold deposit. Compared with other large and supper-large porphyry copper deposits in China and the adjacent Cu-Au mineralized areas, the ore-forming processes and conditions were analyzed; and the possibility of forming large porphyry copper deposits in the Shaxi area was discussed. The present study indicated that the ore-forming fluid and material were mainly of magmatic origin, while meteoric water played a certain role in the ore-forming processes. Interactions between subducting and overriding plates provided a major driving force for the formation of igneous rocks and the deposition of metal elements in East China since Jurassic. Based on the geo- chemical data of the Shaxi intrusive, it is found that the copper (gold) mineralization is closely related to the genesis of adakite-like intrusive in the Shaxi area. This adakite-like intrusive was formed in the subduction environment as a result of the subduction of the West Pacific plate toward the East China continent, where there is a great potentiality to form a large porphyry copper deposit.

2205/X65爆炸焊复合板JCO成型过程协同变形行为研究

为了研究JCO成型工艺参数对2205/X65爆炸复合板结合界面附近应变协调性的影响,建立了2205/X65爆炸复合板三点弯曲过程的有限元模型,结合数字图像相关法对模型进行了验证。采用该模型进行仿真研究,结果表明,上模半径越小,界面附近的最大应变差越大,复合板JCO在成型过程中变形不协调区域的宽度越小;跨距越小,复合板在JCO成型过程中变形不协调区域的宽度越大,跨度变化对界面附近最大应变差没有显著影响;下压量增大时,界面附近变形不协调区域的宽度增大,但界面附近最大应变差的变化不显著;下模半径大小和复合板厚度比对加工变形协调性影响不显著。在实际生产中,建议选用较大上模半径和较大跨距,采用小下压量多次成型。

某汽车前副加强板冷冲压成形的优化

为了改善某汽车前副加强板冲压成形中的起皱、开裂和回弹现象,采用有限元软件Dynaform结合正交试验和极差分析获得各评价目标的工艺参数,通过多目标优化软件Design-expert获得零件最优工艺参数,采用节点补偿法获得回弹补偿模型,并对最优工艺参数和回弹补偿模型进行仿真分析。结果表明:最优工艺参数的仿真和回弹补偿效果较好,零件的成形极限状态良好,最小厚度、最大厚度和最大回弹量均符合设计要求。

增材制造中空风冷板工艺设计与试验

为了验证增材制造技术对复杂中空风冷板的可行性,对中空风冷板模型增材制造工艺性、增材制造打印成型工艺性和粉末选择进行了分析对比。文中优选成熟AlSi10Mg铝合金打印参数完成中空风冷板的成型,并对随炉打印的试样力学性能和表面处理防护性能进行了试验验证。试验结果表明,增材中空风冷板性能可以满足产品设计使用要求。

金属双极板冲压成形数值分析及回弹补偿

针对小型风冷电堆金属阳极板冲压成形的质量缺陷问题,运用Autoform软件对双极板冲压成形工艺进行了仿真分析,研究了压边力、冲压速度、模具间隙和摩擦因数对成形质量的影响。以最大减薄率和回弹量为优化目标开展了正交试验,得出了对成形质量影响最大的因素为压边力,而冲压速度对成形质量的影响最小。在此基础上,确定了最优工艺参数组合:压边力为80 kN,冲压速度为400 mm·s^(-1),模具间隙为0.15 mm,摩擦因数为0.15。结果表明,优化后的最大回弹量为1.487 mm,相较优化前减小了1.416 mm。最后,基于Autoform软件,对双极板进行了模面回弹补偿,发现回弹补偿后最大回弹量减小了41.2%。通过试验验证了仿真的可靠性。

汽车激光雷达盖板的双色注塑模具设计

根据某车型激光雷达盖板的双色结构及形状,采用动模型芯旋转式结构的模具方案,设计了一套一出二的热流道双色注塑模具。利用Moldflow软件进行了双色成型分析,双色注塑第一次注射成型透明的PMMA材料的产品,第二次注射成型黑色ASA材料的产品。为实现该双色产品的结构成型,在定模处设计了2组不同结构的型腔,在动模处设计了2组左右对称的型芯,并且,在型芯侧设计了双斜导柱抽芯机构,冷却系统设计为“直通式+隔水片”的随形循环水路;顶出系统设计为2组独立的液压油缸,在产品顶出取件中,第一次注射成型的PMMA产品不顶出,第二次注射成型的ASA材料的产品采用“直顶+斜顶”的组合机构将双色产品推出,最终通过机械手完成产品的取件。实践生产证明了该双色模具结构合理、运行稳定、成型的双色塑件表面无缺陷。

某厂房项目大跨度预制双T板滑模安装及吊装施工分析

某工程局部区域有夹层结构,双T板无法一次性吊装到位。经对各施工方案的研究、比较和优化,决定采用滑模施工工艺。论文主要研究了大跨度预制双T板安装过程中使用滑模桁架的施工工艺和流程,并对吊装施工的验算复核进行了分析。

考虑回弹的水平上调式三辊卷板机卷圆精度研究

为提高卷圆成形精度,建立了不考虑回弹与考虑回弹时水平位移量与卷圆半径之间的理论模型。采用ABAQUS软件建立了卷圆成形有限元模型,并通过实验验证了理论模型及有限元模型的可靠性。基于可靠的有限元模型,研究了材料、摩擦力和板厚对卷圆成形精度的影响规律。研究结果表明,不考虑回弹时实验和仿真的成形半径与目标半径之间的误差分别为31.3%和20.7%。考虑回弹后的误差分别降低至2.2%和1.2%;在相同水平位移量下,材料的屈服强度越高,成形半径越大;摩擦力对成形半径的影响较小;板料越厚,成形半径越小。针对不同材料与不同厚度的板料卷圆成形,考虑回弹时的理论模型能够获得更精确的水平位移量,从而提升卷圆精度。

大型厚板曲面件的多点成形仿真

传统的厚板曲面件制造方法存在着成本高、效率低等问题,多点成形技术为这一问题提供了解决方法。但多点成形技术又因为回弹导致工艺参数难以确定使实验操作次数增加,降低成形效率。为了提高成形效率,采用ABAQUS有限元软件模拟与实验相结合的方法进行板料成形的研究与分析。首先,利用有限元软件进行三维建模并模拟板料的成形过程;然后,通过对模拟结果的分析进行模具型面的补偿修正;最后,利用修正后的模具型面进行实验操作,获得了符合要求的零件。对修正后的型面进行成形实验可以减少操作次数,提高实验的成形效率,为后续的研究提供参考。

质子交换膜燃料电池金属双极板流道结构及制造工艺

金属双极板因具有强度高、导电性和传热能力好、能量损失小、密封性好等优势,且加工方便、加工成本低、可制造超薄厚度及高体积比功率等特性,逐渐成为双极板材料的首选,而流道结构设计和制造工艺是影响金属双极板成形质量和工作性能的关键。对比了金属双极板常用传统流道结构与新型流道结构,分析了结构变化对燃料电池性能的影响;梳理了金属双极板的冲压成形、液压成形、软膜成形、辊轧成形、电磁成形、特种成形等塑性成形工艺技术及成形装备;最后对金属双极板的流道结构设计与制造工艺进行了展望。