液货船惰气电控系统的综合设计

结合某液货船的惰气发生系统,本文介绍了液货船惰气电控系统的设计原则,惰气发生系统的工艺流程及其功能设计,讲述了一套完整的船舶惰气自动控制方案.     

侧围外板的成型仿真分析及工艺优化

以某车型侧围外板为例,介绍了利用CATIA及AUTOFORM软件对侧围外板进行成型仿真分析,并根据成型分析的结果进行工艺优化的方法。最终证明了利用成型仿真分析技术可以很好地模拟冲压成型的实际状态,并以此为依据在虚拟的环境下找到了解决问题的最佳途径,可以指导;中压工艺和冲压模具的设计,较好地控制因设计不当造成模具报废的风险。     

可调螺距螺旋桨水动力性能分析

利用面元法分析可调距螺旋桨的水动力性能.计算过程中,采用较为简捷的关于扰动速度势的基本积分微分方程,并采用双曲面形状的面元以消除面元间的的间隙,Newton-laphson迭代过程被用来在桨叶随边满足压力Kutta条件,使桨叶上下表面的的压力在随边有良好的一致性,同时用模拟物体真实行状的面元法来解决调距桨在螺距变化时的叶剖面畸变的问题.用Morino导出的解析计算公式来计算面元的影响系数,加快了数值计算的速度.以无厚度线性尾涡模拟桨叶泄出涡.调距螺旋桨最佳转轴位置由理论方法求出,使得桨叶的转叶矩为零.计算过程中计入了桨毂的影响,并分析了桨毂对桨叶表面压力分布的影响.最后给出了调矩螺旋桨水动力性能随随螺距的变化规律,并和试验结果作了比较分析.     

白车身侧围焊接机器人焊接作业顺序优化研究

针对轿车白车身焊接机器人作业顺序不合理的问题,采用启发式的节约算法,有效地解决了焊接机器人焊接作业顺序中的最短路径问题,并实现了优化,编写了相应的程序,可以有效地进行焊接作业顺序优化计算。     

汽车车身模具的数字化快速修复技术

针对存在局部物理缺陷或疲劳磨损的汽车车身冲压模具的可重用性,提出了缺陷特征提取和有限元分析耦合技术方案,实现了模具的数字化快速修复。以抽取模具点云中诸如缺陷边界、缺陷原形等特征为基础,并利用特征诱导技术恢复原始模具在缺陷处的基本特征形态。通过冲压过程的动态模拟来矫正基本的特征形态,修复模具在局部缺陷处的CAD模型,为最终以激光焊接技术和高速硬切削技术为基础实现模具的快速物理修复提供可靠的依据。     

汽车覆盖件冲压工艺方案评价的研究

针对汽车覆盖件冲压工艺方案的特点,构建了冲压工艺方案评价指标体系,运用层次分析法建立了权重集,并根据评价指标复杂多样的特点,应用模糊评价法对各种方案进行了评价,优选出了最佳方案。通过实例证明,该评价体系的评价结果客观、合理,可满足汽车覆盖件冲压工艺方案优选的需要。     

Analysis of ultimate uniaxial compressive strength of stiffened panel considering influence of shear load北大核心CSCD

［Objective］This study aims to explore the law of the critical compression stress of stiffened panels under the influence of in-plane shear load, and whether in-plane shear load combined with lateral pressure will introduce a strong coupling effect. ［Method ］ To this end, nonlinear finite element (FE) software ABAQUS is used to perform numerical simulation analysis under combined loads on a group of FE models. A limit state equation/curve is then derived from the dimensionless calculation results based on the minimum square error method. ［Results］The results show that the influence law of in-plane shear load on the critical compression stress of stiffened panels is clarified, and a limit state equation of stiffened panels that considers the effect of shear load is obtained. ［Conclusion］The limit state equation in this paper can provide references for modifying the ultimate strength of stiffened panels under the influence of in-plane shear load. © 2023 Chinese Journal of Ship Research. All rights reserved.     

Load-bearing characteristics of marine complex sandwich composites considering unequal elastic modulus in tension and compression

The panel and core materials of sandwich composite usually have the characteristics of unequal elastic modulus in tension and compression. However, in the numerical calculation of sandwich composite, it is usually considered as the material with the same tensile modulus or compression modulus, which often leads to larger calculation errors. The test results show that when the elastic modulus of tension and compression is about 10 times different, the maximum calculated stress and maximum deflection will be more than twice different. In view of the complexity of sandwich composite structure, based on the bi-modulus model of laminated plates, a simplified theoretical formula and numerical calculation method are proposed for bi-modulus sandwich composite structures in this paper. Furthermore, the accuracy of the proposed numerical calculation method of bi-module is verified by the experimental study of composite single-layer plate structure and sandwich composite cabin structure. The results show that the error between the improved numerical calculation method and the experimental measurement results is basically within 6%. Meanwhile, the numerical method based on field variables has wide application range and high convergence, and can be used to calculate complex marine composite structures.     

Cargo ship aft panel stresses prediction by deconvolution

This article introduces novel extreme value prediction method that can be used for a variety of offshore engineering applications. First, to demonstrate the novel method, fictitious data from a non-linear Duffing oscillator and measured wave heights were used as examples. The second incident included a container ship that experienced significant deck panel strains while traveling across the Atlantic Ocean in bad weather. The main concern for cargo ship transportation is potential loss of container owing to violent movements. It is challenging to model such a situation because waves and ship motions are both non-stationary and complicatedly nonlinear. Extreme motions greatly increase the role of nonlinearities, activating effects of second and higher order.Furthermore, due to the scaling and the choice of sea state, laboratory testing may also be called into doubt. Therefore, data collected from actual ships during difficult weather voyages offers a special perspective on the statistics of ship motions.This paper aims to highlight an alternative method of extrapolation that is based on intrinsic properties of the data set itself and does not assume any extrapolation functional class. Extreme value predictions typically originate from certain statistical distribution functional classes to fit the data and then extrapolate. Engineering design can make use of the unique extrapolation method that has been proposed. The proposed method's forecast accuracy has been verified in comparison to the Averaged Conditional Exceedance Rate (ACER) extrapolation method.