Influence of the welding sequence on residual stress and distortion of fillet welded structures

T-joints are one of the most common welded joints used in the construction of offshore structures, including ships and platforms. In the present study, a sequentially coupled thermo-mechanical finite element model that considers temperature-dependent material properties, high temperature effects and a moving volumetric heat source was used to investigate the effect of welding sequence on the residual stresses and distortions in T-joint welds. The parameters of Goldak's double ellipsoidal heat source model were predicted using a neural network. The numerical models were successfully validated by the experimental tests. The results show that the welding sequences have significant effects on the residual stresses and distortions, both in the magnitude and distribution mode. The optimization of the welding sequences should be investigated numerically or experimentally before the construction welded structure.     

Vehicle classification from low-frequency GPS data with recurrent neural networks

The categorization of the type of vehicles on a road network is typically achieved using external sensors, like weight sensors, or from images captured by surveillance cameras. In this paper, we leverage the nowadays widespread adoption of Global Positioning System (GPS) trackers and investigate the use of sequences of GPS points to recognize the type of vehicle producing them (namely, small-duty, medium-duty and heavy-duty vehicles). The few works which already exploited GPS data for vehicle classification rely on hand-crafted features and traditional machine learning algorithms like Support Vector Machines. In this work, we study how performance can be improved by deploying deep learning methods, which are recently achieving state of the art results in the classification of signals from various domains. In particular, we propose an approach based on Long Short-Term Memory (LSTM) recurrent neural networks that are able to learn effective hierarchical and stateful representations for temporal sequences. We provide several insights on what the network learns when trained with GPS data and contextual information, and report experiments on a very large dataset of GPS tracks, where we show how the proposed model significantly improves upon state-of-the-art results.     

焊接速度对AH36船用高强钢焊接残余应力及其释放的影响

焊接件由于焊接速度不同,焊接残余应力分布存在很大差异,焊接残余应力在循环载荷作用下会产生释放现象,焊接残余应力存在对于结构安全性和稳定性有很大影响,有必要开展焊接速度对于焊接残余应力及其释放影响研究。基于ABAQUS软件二次开发建立平板对接焊试件焊接残余应力以及释放有限元模型,利用顺序耦合热力学数值仿真计算三种焊接速度下的焊接残余应力分布,并开展三种焊接速度下初始焊接残余应力在三种拉伸循环载荷作用下的释放情况研究。     

EQ1170KA客车底盘焊接接头疲劳裂纹扩展速率的研究

本文研究了EQ1170KA客车底盘焊接接头疲劳裂纹扩展速率的规律,结果表明:焊接接头不同部位的疲劳裂纹扩展速率各不相同,焊接残余应力和金相组织对疲劳裂纹扩展速率都有一定的影响。     

意大利玛连尼沥青拌和设备雾化燃烧器的正确使用和调整

简述了雾化燃烧器的工作原理及对不同燃料油的使用要求，并详述了系统启动运转前的检查调整要点和燃烧器的点火程序及故障检查和部件维修。     

吹吸式通风装置在棚车棚板焊接烟尘控制中的应用

吹吸式通风装置是一种能有效控制污染源扩散的通风装置。在棚板焊接上单纯采用吸气罩来排除大面积焊接烟尘，存在着效果不理想以及方式不够合理等问题。因而提出了将吹吸式通风装置用于棚板焊接烟尘控制上。对其烟尘控制的有效性和合理性作了具体分析，同时介绍了吹吸式通风装置送、排风量的计算方法。     

盲孔法测量921A钢焊接残余应力的应变释放系数研究

根据盲孔法测量残余应力的基本原理和孔边塑性变形修正方法，分别对盲孔法测量921A钢焊接残余应力时的应变释放系数A、B进行实验标定，通过试验得出了921A钢盲孔孔边塑性变形对测量精度的影响和盲孔法测量921A钢焊接残余应力的塑性修正公式；并对实验标定应变释放系数与通孔应变释放系数理论解进行比较，表明试验结果与通孔应变释放系数理论值有较好的一致性，测量结果经塑性修正，最大误差减小到2．5％以下，试验结果可以直接在盲孔法测量921A钢焊接残余应力工程实际中应用。     

关于900t铁路架桥机钢结构焊接工艺采用标准的探讨

900t铁路架桥机是高速铁路及客运专线桥梁建设中使用的关键设备。目前,国内在铁路架桥机钢结构的制造及焊接工艺方面,还没有专门的规范或规程。通过对几种国家和行业规范或规程焊接工艺标准的对比、分析,对900t铁路架桥机钢结构的焊接工艺提出一些参考性意见。     

浅谈发动机缸体的焊修

我国北方地区的车辆受气候环境的影响,汽车在运营过程中易产生发动机缸体裂损现象,本文详细地分折了产生裂损的原因及焊修作业的特点,并根据以上特点提出了合理可行的焊修工艺方案。     

钢材层状撕裂及抗层状撕裂焊接接头的设计

钢材层状撕裂是焊接钢桥中一种非常危险的缺陷,通常发生在角焊接头处。钢材中夹杂物的数量、分布和形态以及基体金属的塑性和韧性是影响层状撕裂的钢材因素。钢材中含硫量越多,夹杂物以片状形态大量密集于同一平面,发生层状撕裂的倾向就越大。钢材的刚度越大、板越厚,越容易产生层状撕裂。相同板厚、相同焊接方法条件下,焊缝断面越大,越易产生层状撕裂。角焊缝接头中选择贯通板,T型或十字型焊接接头中选择不熔透或部分熔透角焊缝,热加工时避开蓝脆温度和红脆温度,冷加工时确保一定的曲率半径(大于15倍板厚),改善隅角焊的坡口形式,用小线能量焊接取代大能量焊接,采用低强度焊道打底、焊前预热等,均可抑制层状撕裂的发生。同时,给出日本和Eurocode3的层状撕裂评定方法和Z向钢的选材标准,以便设计和制造人士准确把握。