加筋板结构及焊接顺序对焊接变形的影响

焊接广泛应用于工业中,用于组装不同的产品,如:汽车,船舶,桥梁等。而焊接变形通常是造成尺寸不精确和高制造成本的主要原因。因此,通过有限元模拟预测变形量和通过改善焊接结构的质量来减小焊接变形是至关重要的。本项研究的目的是减少大型船板的变形,有两种方法:首先,采用热弹塑性有限元分析进行变形预测,估算Q345钢焊接接头的固有变形;其次,基于固有应变理论对大型船板的焊接过程进行弹性分析,揭示了板材边缘和内部的变形情况。通过运用有限元模拟,对比不同形状模型的焊接变形,找到最有焊接顺序,可以最大限度降低焊接变形。     

加筋板结构及焊接顺序对焊接变形的影响CSCD

焊接广泛应用于工业中,用于组装不同的产品,如:汽车,船舶,桥梁等。而焊接变形通常是造成尺寸不精确和高制造成本的主要原因。因此,通过有限元模拟预测变形量和通过改善焊接结构的质量来减小焊接变形是至关重要的。本项研究的目的是减少大型船板的变形,有两种方法:首先,采用热弹塑性有限元分析进行变形预测,估算Q345钢焊接接头的固有变形;其次,基于固有应变理论对大型船板的焊接过程进行弹性分析,揭示了板材边缘和内部的变形情况。通过运用有限元模拟,对比不同形状模型的焊接变形,找到最有焊接顺序,可以最大限度降低焊接变形。     

固有应变值施加方式的焊接变形仿真研究

为提高固有应变法在预测焊接变形应用中的准确度,以T型接头为算例,采用SYSWELD仿真软件对多个方案进行数值模拟,研究了固有应变施加方式对焊接变形预测的影响,进而提出了一种新的固有应变施加方式。为了验证此方法的准确性,将三种设计方案的计算结果与热弹塑性有限元方法的计算结果进行分析比较。结果表明:在以焊缝中间线为轴心、焊缝直角边的1/2为半径的范围作为固有应变的施加区域时,其变形预测精度明显提高,变形量更加逼近于热弹塑性有限元分析方法的预测结果。     

焊接接头脆性断裂评定的局部法研究进展

介绍了几种焊接结构断裂行为预测和评定方法的局限性。从理论基础、微观理论基础、评定方法等方面详细论述了焊接接头脆性断裂评定的局部法，并介绍了国内外研究状况及最新进展。指出研究各种塑性损伤模型在焊接接头中的可行性，探讨符合焊接接头特点的塑性损伤模型及控制参量的必要性。分析塑性损伤对Beremin解理断裂模型局部断裂参量的影响，进而利用局部法对焊接接头的脆性断裂行为进行科学预测。     

薄壁箱形梁的焊接变形预测

通过试验和理论的结合，对薄壁箱形梁的焊接变形进行了预测。主要采用热弹塑性有限元法分析焊接时梁的变形情况，结果与实际吻合得非常好，为后面预测大型薄壁结构的焊接变形奠定了基础。     

焊接变形预测的研究进展

焊接变形预测技术对焊接结构的制造和使用有重要意义,数值模拟是近年来研究焊接变形的主要手段和方法,文中综述了预测焊接变形的各种方法及其发展现状,重点介绍了热弹塑性有限元法和固有应变法预测焊接变形的原理、存在的困难和国内外研究者提出的相应解决措施,以及下一步研究有待解决的问题。     

金属塑性成形中裂纹萌生的预测

本文讨论应用有限元法预测塑性成形中裂纹的产生。首先简述金属非线性变形理论，其次介绍有限元方程和算法、应变硬化法则及弹塑性模型，最后应用弹塑性有限元相关的断裂准则来预测塑性成形中裂纹的产生。     

薄壁箱形梁的焊接变形预测研究

本文通过试验和理论的结合,对薄壁箱型梁的焊接变形进行了预测.主要基于ANSYS软件,采用热弹塑性有限元法分析了焊接时梁的变形情况,并进行了试验研究,所得结果吻合很好,为大型薄壁结构的焊接变形预测提供了有价值的数据和方法.     

低应力无变形焊接技术对船舶制造的影响

目前,低应力无变形焊接技术在制造业中被广泛推广,它是一种能够降低焊接残余应力与变形的高质、高效的新型焊接技术。关于如何利用低应力无变形焊接技术控制残余应力与变形,综述近些年国内外学者的研究现状。同时,基于热弹塑性有限元理论,利用低应力无变形焊接技术对船舶制造业中使用最为普遍的钢板对接进行焊接数值模拟仿真,并展望了低应力无变形焊接技术在船舶领域的推广和应用。     

拼焊顺序对大型焊接机壳中分法兰变形的影响

利用热弹塑性有限元方法对大型轴流焊接机壳中分法兰的变形状态进行了数值计算,建立有限元模型,分别计算三种拼焊方案下机壳中分法兰的变形情况。定量地预测了不同拼焊顺序下机壳中分法兰的变形,得到了可获得最优变形状态的拼焊顺序。对比中分法兰计算变形和实际变形测量数据,吻合良好,证明数值优化方法用于大型结构的变形预测是可行的。     

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.     

Investigations on welding residual stress and distortion in a cylinder assembly by means of a 3D finite element method and experiments

In the present work, both experimental and numerical simulation methods are used to investigate the characteristics of welding distortion and residual stress distribution. A 3D thermo-mechanical Finite Element Analysis (FEA) method is used to predict the welding distortion and residual stress of cylinder-shaped multi-pass layer weldments. Each weld pass is performed using a quarter-circle balanced welding procedure. To investigate the influence of deposition sequence and welding heat input on the welding distortion and residual stress, a continuous welding procedure is also calculated. The corresponding FEA models considered a moving heat source, the deposition sequence, and temperature-dependent thermal and mechanical properties. The results predicted by 3D FEA model are generally in good agreement with the measurements. Finally, the numerical and experimental results suggest that both deposition sequence and heat input affect welding distortion and residual stress distribution. Furthermore, the 3D thermal-mechanical FEA method can predict cylinder-type welding distortion.     

焊接反变形在200EMU车顶组焊过程中的应用研究

铝合金由于具有良好的焊接性能在现代工业中得到大量应用,现有的铝合金焊接性能研究中有限元分析居多,在反变形方面研究较少.通过分析铝合金焊接应力及焊接变形的产生机理,依据尺寸链原理提出以反变形方法建立新的焊接工艺.在控制车顶圆弧尺寸中实际应用该方法,根据经验值不断调整焊接胎位.结果表明该方法可以有效的控制车顶组焊后变形尺寸,解决了200EMU车顶组焊变形尺寸超差的问题,为控制在焊接过程中的变形提供了较好的指导作用.     

基于初始变形的薄板堆焊变形预测技术

针对薄板初始变形对焊接结构件尺寸精度的影响，提出了基于数字图像相关技术的光学检测方法，对薄板堆焊变形预测精度进行全场动态研究。首先采用结构光扫描的方法，获取焊接结构件初始变形轮廓，然后基于初始变形模型进行焊接变形预测，最后通过理想模型和初始变形模型预测数据对比，研究结构初始变形对堆焊变形精度的影响。研究结果表明：基于数字图像相关技术的测量方法是静态、动态获取焊接变形数据的有效手段；相对于理想结构模型，基于初始变形结构的模型，在单点动态和全场静态变形中具有较高的预测精度；两种模型在焊接完成后均呈马鞍形，但初始变形促进了焊接演变过程；初始变形缺陷影响了纵向残余压应力分布，是引起不同焊接变形的根本原因。     

焊接温度场、应力场和应变场相似准则的推导及验证

利用因次分析法和方程分析法推导出焊接条件下模拟件温度场应满足的相似准则,并据此得到实物与模拟件间应力和变形的相似关系,对此相似准则利用数值模拟方法进行平板表面堆焊三维有限元验证,得到了较好对应关系。进一步讨论,得知此相似准则不适用于相变明显的材料。     

薄壁箱形梁的焊接变形预测

通过试验和理论的结合,对薄壁箱形梁的焊接变形进行了预测。主要采用热弹塑性有限元法分析焊接时梁的变形情况,结果与实际吻合得非常好,为后面预测大型薄壁结构的焊接变形奠定了基础。     

齿轮断裂失效机理分析

针对齿轮失效进行机理分析,综合运用有限元仿真、断裂理论计算以及金相分析等方法,从齿轮失效形态、工作应力状态以及其微观金相组织等方面进行了分析,得出了齿轮断裂失效的主要原因是其疲劳强度不足引起,而相关工艺方法及检测手段的缺陷是其失效根本原因,并依据失效机理提出针对性建议。     

Calculation method of radial stress and deformation on conic threaded connections with interference fit

This paper presents a calculation method for radial stress distribution and deformation on conic threaded connections with interference fit. Based on elastic mechanics, a new calculation model is established using the thick-walled-cylindrical theory. A sample calculation for API 88.9 mm conic threaded connection indicates that the method proposed in this paper is reasonable, and the finite element analysis (FEA) method is used to validate the proposed method. The results obtained by the proposed method and FEA method are identical. The model offers a new way of calculating the radial stress and deformation on conic thread connections with interference fit.     

Elastic deformation of a fixture and turbine blades system based on finite element analysis

Finite element analysis (FEA) has been used to recapitulate the interactions between fixtures and components over the last decade. Most of the researches were focussed on the 3-2-1 fixture for components with regular geometry using point-to-point contact elements, where the fixture element is represented by a point-contacting component. Due to predicable behaviour of the fixture–component pair, such a point-to-point contact representation may be sufficient. However, when components with complex geometry, e.g. B-spline surfaces, which are widely used in the automotive and aero-engine industries, are of interest, the point-to-point method can no longer be satisfactory. This paper proposes a method of FEA on a system of a fixture and turbine blades by considering the complex contact geometry and complicated contact status of fixture–component pairs using surface-to-surface contact elements. A complete procedure of FEA modelling including geometry simplification, contact modelling, stiffness of locators, mesh generation, boundary condition and loading sequence is explained in detail. Having verified the FEA prediction of the elastic deformation with the displacement of the workpiece measured by coordinate measurement machines (CMMs), the influential factors of deformation, such as friction and machining directions, are analysed.