Effect of Train Carbody's Parameters on Vertical Bending Stiffness Performance

Finite element analysis（FEA） and modal test are main methods to give the first-order vertical bending vibration frequency of train carbody at present, but they are inefficiency and waste plenty of time. Based on Timoshenko beam theory, the bending deformation, moment of inertia and shear deformation are considered. Carbody is divided into some parts with the same length, and it＇s stiffness is calculated with series principle, it＇s cross section area, moment of inertia and shear shape coefficient is equivalent by segment length, and the fimal corrected first-order vertical bending vibration frequency analytical formula is deduced. There are 6 simple carbodies and 1 real carbody as examples to test the formula, all analysis frequencies are very close to their FEA frequencies, and especially for the real carbody, the error between analysis and experiment frequency is 0.75%. Based on the analytic formula, sensitivity analysis of the real carbody＇s design parameters is done, and some main parameters are found. The series principle of carbody stiffness is introduced into Timoshenko beam theory to deduce a formula, which can estimate the first-order vertical bending vibration frequency of carbody quickly without traditional FEA method and provide a reference to design engineers.

A multi-fidelity prediction model for vertical bending moment and total longitudinal stress of a ship based on composite neural network

In ship engineering,the prediction of vertical bending moment(VBM)and total longitudinal stress(TLS)during ship navigation is of utmost importance.In this work,we propose a new prediction paradigm,the multi-fidelity regression model based on multi-fidelity data and artificial neural network(MF-ANN).Specifically,an ANN is used to learn the fundamental physical laws from low-fidelity data and construct an initial input-output model.The predicted values of this initial model are of low accuracy,and then the high-fidelity data are utilized to establish a correction model that can correct the low-fidelity prediction values.Hence,the overall accuracy of prediction can be improved significantly.The feasibility of the multi-fidelity regression model is demonstrated by predicting the VBM,and the robustness of the model is evaluated at the same time.The prediction of TLS on the deck indicates that just a small amount of high-fidelity data can make the prediction accuracy reach a high level,which further illustrates the validity of the proposed MF-ANN.

考虑不同腐蚀模型的受垂向弯矩作用的FPSO船体梁渐进失效分析

Nowadays,with the increasing operational life of ships,the aging effects on their structural behavior need to be investigated precisely.With the corrosive marine environment taken into consideration,one of the important effects of aging that must be studied is thickness degradation.In this paper,with the use of previously proposed equivalent thickness formulations for corroded plates,the progressive collapse analysis software HULLST is enhanced,and then,the effects of different corrosion models of uniform,random,pitting,and tanker pattern types on the ultimate and residual strengths of a floating production,storage,and offloading vessel hull girder are evaluated for the ages of 0 to 25 years.Results reveal that the uniform corrosion and random corrosion models have close outcomes.The value of relative reduction in the ultimate strength of ship hull girder(compared with the intact condition)ranges roughly from 6%for the age of 5 years to 17%for the age of 25 years in the hogging mode.The relative reduction in the ultimate strength ranges from 4%to 16%in the sagging mode.Pitting corrosion and tanker pattern(random)corrosion models lead to higher relative reductions in ultimate strength.The pitting corrosion model leads to a 16%–32%relative reduction in the ultimate strength for the ages of 5–25 years of the ship in either hogging or sagging.The tanker pattern(random)corrosion model leads to a 6%–37%relative reduction in the ultimate strength in the hogging mode and 3%–31%in the sagging mode at ship ages of 5 to 25 years.

Light weighting opportunities and material choice for commercial vehicle frame structures from a design point of view

This paper focuses on an estimation of light weighting opportunities for the frame structure of com- mercial road vehicles. This estimation is based on simpli- fied static load cases which play a predominant role for the dimensioning of a frame structure and therefore these simplifications are not putting the general validity of the conclusions into question. A comparison of different ma- terials under this scenario shows that light metals do not show any weight reduction advantage in comparison to steel while a material-independent topology optimization has more weight reduction potential for the frame structure than a simple change of materials. Considering the con- straints of part complexity which is directly linked with production and assembly cost, the ladder frame structure has become the current state of the art design. Thus the paper also puts a spotlight on basic rules of node design and vertical load induction in order to keep the weight of such a design as low as possible. Practical examples from manufacturers show that the weight of a commercial vehicle could be reduced by 10%, and main parts of the frame structure could be reduced by 30% using high strength steel in combination with innovative production methods like roll forming.