T形管节点落锤动态抗冲击性能试验研究

采用落锤冲击试验机进行了4个T形管节点的抗冲击性能试验研究。通过试验获得了冲击能量E、主管长径比（α=L/D）和主管直径D等参数对管节点破坏模态和变形模式的影响规律,分析了管节点在冲击力作用下整体和局部变形特性,以及冲击力、位移、应变时程曲线与冲击力 变形关系曲线。试验结果表明：主管长径比一定时,冲击能量的大小影响支管受撞T形管节点的破坏模态;破坏模态主要为主管上表面局部屈曲和主管上表面局部屈曲伴随主管整体弯曲变形两种形式;主管上表面局部屈曲产生的塑性变形区域受冲击力的影响不大,但其屈曲凹陷深度随着冲击能量的增大而增大;局部屈曲耗散了大部分冲击能量。基于能量的塑性铰线理论,提出了等效冲击承载力简化评估方法。     

Analytical determination of the ultimate strength of sandwich beams

An analytical determination of the ultimate strength of a typical GRP/PVC sandwich beam has been performed. These beams represent common building practise in marine applications. Equations describing the behaviour of a sandwich panel under beam loading and various failure modes have been developed. The method has been applied to predict the ultimate load for a simple supported sandwich beam. The critical loads have been compared with those from the experimental investigation of a typical bulkhead-to-hull GRP/PVC sandwich T-joint under pull out forces.     

Mode I Fracture Load Predictions of Adhesive T-joints

This paper presents fracture data and a finite element analysis for adhesive T-joints, It is shown that fracture loads of T-joints, bonded with two different structural epoxies and subjected to either tensile loading or three-point bending, can be predicted using a fracture mechanics approach. Fracture loads were predicted by calculating the applied energy release rate, G, using finite element methods, and comparing that with a critical value, G_c, determined experimentally using double-cantilever-beam specimens. By recording the failure sequence of the bondline with a video camera attached to a microscope, it was seen that subcritical crack propagation took place prior to final fracture of the bondline. Accounting for the observed subcritical crack propagation in the finite element analysis gave a good agreement between the actual and the calculated fracture loads.     

高强方钢管轻骨料混凝土桁架加劲T型节点试验

为考察支主管间设置的加劲板构造和支主管截面宽度比对高强方钢管轻骨料混凝土桁架T型节点破坏模式、承载力、连接区应力和应变的分布及演化等受力性能的影响,对加劲节点和常规节点进行了支管轴压静力加载试验.试验结果表明:高强方钢管轻骨料混凝土桁架T型节点的典型破坏模式有连接区主管受压上翼缘凹陷、主管腹板凸曲、主管弯曲、支管侧倾失稳、加劲板屈曲、支主管焊缝开裂和加劲板与支管焊缝开裂等.常规节点的承载力取决于支管根部及其焊缝的承载强度和连接区主管上翼缘的局部承压强度,其荷载-位移曲线形成流塑平台.加劲节点的承载力取决于包括加劲板扩散效应的支管根部及其焊缝的承载强度、连接区主管上翼缘扩散承压强度和加劲板屈曲强度,其荷载-位移曲线呈渐变上升趋势,没有屈服平台.加劲板明显提高了T型节点的承载力,加劲节点的屈服承载力和极限承载力较常规节点分别提高10.0%~40.0％和15.0％~48.3％,加劲节点的承载力随支主管截面宽度比的增加而提高.     

Experimental study on mechanical behavior of an impacted steel tubular T-joint in fire

Blast and fire usually take place together on offshore oil and gas production structures. In order to study the mechanical behavior of the structural members in blast and fire, an experimental investigation has been carried out for a steel tubular T-joint without a fire-proof coating. The specimen was impacted first and then heated up under constant loading. It aims to investigate the failure mode, the critical temperature, and the temperature distribution of the T-joint at elevated temperatures; and furthermore to probe the influence of the impact load on the mechanical behavior of the joint by comparing with the results in a former test without any impact load. The experimental results show that the failure mode of the specimen was caused by the local buckling of the chord wall, which is the same as what are usually observed at ambient temperature. However the critical temperature of the impacted specimen is 690 °C, which is higher than the one without impact loading. The test results are then used to validate the numerical analysis in the future work.     

支撑轴向受压下穿墙螺栓抗腹板屈曲的矩形中空钢截面T型节点的加固

在支撑承受轴向荷载作用下,通过控制弦腹板的面外屈曲,对穿墙螺栓加固矩形中空钢截面T型节点的效果进行验证。本研究验证了螺栓数量和排列方式及腹板高度与墙厚比(h/t)对加固效果的影响。对203mm×76mm×(3.09,4.5,5.92)mm的矩形弦杆进行试验,直径为8mm的钢螺栓的数量从1～15变化,且各自不同分布。首先在弦杆的竖向墙面上钻孔,然后通过一面墙插入螺栓并与另一面墙锚固。研究表明:高厚比(h/t)为65的弦杆节点强度增加了29%;当h/t减小到45和35时,节点强度增加值分别为6.2%和3.1%;螺栓数量和分布对其加固效果影响很小。     

电站锅炉过热器和再热器T型三通对集箱静压分布影响的试验研究

为了获得过热器和再热器T型三通对集箱静压分布及三通两侧分流比对涡流区和集箱静压分布的影响规律,以空气为工质对纯三通模型进行流动特性试验.研究结果表明:带三通集箱静压分布受一次涡流和二次涡流的共同影响,一次涡流影响范围为-2.5D~2.5D(D为等径三通内径),二次涡流影响范围为-1.5D~1.5D;三通两侧分流比对涡流区范围影响较小;随着三通某侧流量增大,该侧静压降低,但静压分布规律无明显变化.在一次涡流影响范围内,正母线和右下40°线的静压差异受分流比的变化影响较小;侧母线的静压差异随分流比的增大而有所增大.     

新型焊割技术在锅炉行业的应用

为了解决目前锅炉焊接操作中存在效率较低、手法和技术较难掌握这一问题,采用STT（surface tension transfer,表面张力熔滴过渡）焊机完成了产品的初步焊接试验。试验结果表明,STT焊机的焊接速度是TIG焊的数倍,且基本不产生熔渣和飞溅,焊接时和焊接后的清理容易、费用低,对焊工技术和经验要求较低,技法容易掌握。另外,为了提高锅炉不锈钢曲面上开孔的工作效率并保证表面质量,采用精细等离子技术进行了产品封头的曲面开孔,在实际操作中解决了精确度控制和挂渣问题,为后续焊接工序减少打磨时间提供了质量保证。     

Low speed impact behaviour of adhesively bonded foam-core sandwich T-joints

This paper investigates the effects of foam core density and aluminum skin plates on the low speed impact behaviour of adhesively bonded sandwich T-joints having a PVC foam core and aluminum face-sheets. The dynamic response of adhesively bonded sandwich T-joints was analyzed by the explicit finite element method. Two different material models were implemented to the foam core material: a hyperelastic model and a crushable foam material with ductile damage whereas the aluminum face-sheets were modelled as an elasto-plastic material. The cohesive response of adhesive interfaces was included using three dimensional cohesive element based on cohesive zone model. Adhesively bonded sandwich T-joint specimens were manufactured and tested to validate the numerical model. A very good agreement between the experimental and FE results were achieved. The density of the foam core material of adhesively bonded sandwich T-joint played important role on the joint failure mechanism. The joint having a stiffer foam core experienced more damage in both stiffener panel and adhesive layers.     

A study on the influence of clamping on welding distortion

This paper presents numerical case studies on the influence of clamping on welding distortion. For the case studies a 1 mm DP600 overlap joint and a 6 mm S355 T-joint have been selected, and reference simulations have been performed. The results have been compared to experiments in a previous paper and show a good agreement. The influence of the clamping time, the release time and the influence of clamp preheating has been investigated for both geometries. Here, the effect of the clamping on buckling distortion as well as bending and angular distortion has been studied. It is shown that the final residual stresses and distortions depend strongly on the clamping conditions. Adaptive clamping may be helpful as an in-line technique for welding distortion mitigation by forcing the material to deform plastically.