钛铝异质自冲铆接头疲劳性能及失效机理

对纯钛(TA1)和铝锂合金(AL1420)异质单搭自冲铆接头进行静力学实验和疲劳实验研究,通过三参数经验公式采用S-N曲线拟合法绘制接头的S-N曲线,分析接头的疲劳性能;采用扫描电子显微镜对接头疲劳断口进行观测,研究接头的微观疲劳失效机理.结果表明:接头的静力学性能与疲劳性能不具有一致性,TA1-AL1420(TA)接头静力学性能更优,但其疲劳性能比AL1420-TA1(AT)接头差;TA接头疲劳失效形式为下板断裂,疲劳裂纹萌生于靠近铆钉脚处的板材区域,随后沿着板宽方向扩展,最终导致下板完全断裂.AT接头在短寿命区因铆钉断裂失效,铆钉的断口属于脆性疲劳断裂;在中长寿命区出现铆钉断裂和下板断裂的混合失效形式,疲劳裂纹从下板一端萌生,沿着板宽向另一端方向扩展,导致下板断裂失效.      

铁路弹性道钉扣件研制与应用

钢轨接头系轨道薄弱环节。由于轨道结构条件制约,钢轨接头扣件应用C型弹条受到限制。研用弹性道钉,实现了钢轨接头扣件与C型弹条扣件的相互匹配,共同发挥轨道整体功能,推广前景广阔。     

基于拉力带的系列新型SST-LEJ设计与分析

设计了一种基于大柔度的柔性铰链,命名为SS-LEJ,利用等效法推导了其弯曲等效刚度的理论计算公式,通过设计实例的理论计算和ABAQUS仿真分析,验证理论计算公式的正确性.为了有效提升SS-LEJ的抗拉压性能,设计了4种不同位置和形状的拉力带的SST-LEJ,通过弯曲性能和抗拉压性能的有限元仿真分析,得出SST3-LEJ和SST4-LEJ为4种SST-LEJ当中整体性能较优的两种.将SST3-LEJ和SST4-LEJ与SS-LEJ、Inverted Bending-Orthogonal铰链进行了弯曲性能和抗拉压性能的比较,得出SST3-LEJ和SST4-LEJ的弯曲性能介于SS-LEJ和Inverted Bending-Orthogonal铰链之间,抗拉压性能优于SS-LEJ和Inverted Bending-Orthogonal铰链,说明SST3-LEJ和SST4-LEJ的整体性能较好,达到了预期的设计目的,为大柔度柔性铰链的设计提供了一种思路.      

CFRP Rehabilitation of Concrete Frame Joints with Inadequate Shear and Anchorage Details

The research presented in this study involves full-scale experimental evaluation of carbon fiber-reinforced polymer (CFRP) rehabilitation for existing beam-column joints designed for gravity load with common pre-1970s deficient reinforcement details when subjected to cyclic loading. Numerous studies have demonstrated effectiveness of externally bonded fiber-reinforced polymer (FRP) materials for retrofitting the deteriorating RC structures. Although these materials are widely used in bridges, their applications in buildings have been somewhat limited. In particular, the experimental investigations on external FRP retrofit of deficient beam-column joints have not thoroughly been investigated and they are mainly on scaled-down specimens. The failure of these subassemblies, which possess lack of shear reinforcement within the joint core and shortly embedded positive beam reinforcement, would possibly result in catastrophic collapse of reinforced concrete frame structure during an earthquake event. Recognizing the urgent need to upgrade these structural subassemblies, the current investigation uses CFRP retrofit techniques to enhance the performance of such deficient joints. Experimental variables studied entail the developed CFRP retrofit configurations, and magnitude of the applied column axial load. Comparative analysis of the lateral loads versus drift hysteresis loops, stiffness degradation, and total dissipated energy curves of three as-built and three corresponding CFRP-retrofitted RC joints revealed that significant improvement in the shear capacity of the upgraded joints occurred. More importantly, the slippage of short embedded beam positive reinforcement into the joint was substantially controlled due to the developed CFRP retrofit. The results demonstrate the effectiveness of CFRP retrofit configurations in enhancing the structural performance of actual size connections.     

Behavior of FRP-Retrofitted Joints Built with Plain Bars and Low-Strength Concrete

Two series of tests on eight full-scale exterior beam-column joint subassemblages built with plain bars and low-strength concrete were conducted. No transverse reinforcement was present in the joint cores. In the first series of tests, which included three specimens, the behavior of joints before fiber-reinforced polymer (FRP) retrofitting was investigated. In the second series, which included five specimens, the behavior of the FRP-retrofitted joints was investigated. The six specimens consisted of a column, an in-plane beam, a transverse beam, and a slab part, and two specimens were plane members without transverse beams and slabs. The utilized retrofitting scheme is easily applicable for actual exterior beam-column joints, even in the presence of a transverse beam and a slab. Two types of strength limitation were observed for specimens in the first series. The strength of the specimen with beam longitudinal bars sufficiently anchored to the joint core was limited by the shear strength of the joint. The strengths of the other two specimens were limited by the slip of the beams’ longitudinal bars at their anchorages. In the second series of tests, significantly better performance was obtained both in terms of shear strength and ductility, provided that the slip of the beam bars was prevented. Furthermore, by using a simple theoretical algorithm based on truss analogy, the strength and deformability characteristics of the tested reference and FRP-retrofitted joints are predicted with reasonable accuracy. The same algorithm is used for predicting the joint shear strength of specimens tested by other researchers, and satisfactory agreement is obtained between the predictions and test results.     

Performance of Polymer Modified Asphalt Bridge Expansion Joints in Low-Temperature Regions

Conventional asphalt bridge expansion joints used in low-temperature regions generally show cracking within the first 2?years. To improve the low-temperature performance of these joints, the commercial MEIJIA asphalt binder commonly used in bridge expansion joint construction was modified with two polymers: thermoplastic rubber and rubber. The goal is to find an optimum combination of polymers, binders, and aggregates to improve the performance of asphalt expansion joints in low-temperature regions. The polymer modified binders and mixtures were evaluated for their low-temperature properties using ductility, penetration, indirect tension, and bending tests. The study indicates that performance of these joints at low temperature can be enhanced significantly with the right combinations of polymers, binders, and aggregates. Four expansion joints made with the polymer modified asphalt mixtures were installed on two bridges in a cold region. A construction procedure was also developed to install these joints properly to minimize low-temperature cracking along the interface between the joint and bridge deck. After 7?years of service, the four joints show good performance without any visible cracking or rutting.     

Evaluation on Fatigue Performance and Fracture Mechanism of Laser Welded TWIP Steel Joint Based on Evolution of Microstructure and Micromechanical Properties

The fatigue performance and fracture mechanism of laser welded twinning induced plasticity(TWIP)steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.The optical microscopy was used to analyze the evolution of microstructure.The variation of composition and phase structure of fusion zone were detected by energy dispersive X-ray and X-ray diffraction spectrometers.The micromechanical behaviors of the various zones were characterized using nanoindentation.The static tensile test and high cycle fatigue test were performed to evaluate the mechanical properties of welded joint and base metal.The microstructures,tensile properties and fatigue strength of base metal as well as welded metal were analyzed.The fatigue fracture surfaces of base metal and welded joint were observed by means of scanning electron microscopy,in order to identify fatigue crack initiation sites and propagation mechanisms.Moreover,the fatigue fracture characteristics and mechanisms for the laser welded TWIP steel joints were analyzed.     

某型机接头裂纹分析

某型机在进行地面检查时,发现有4个同图号接头的螺纹处存在4～10 mm长度不等的磁痕显示.用化学分析、金相检验、扫描电镜、能谱分析等方法对接头裂纹进行了分析.结果表明:故障接头裂纹性质属过载引起的多源疲劳,裂纹产生的时间应在表面处理之前的机加工过程中,且在表面处理后的使用过程中没有进一步扩展.     

楔横轧梯形螺纹轴成形机理

通过分析螺纹轴齿形成形过程,并结合金属流动特点,获得楔横轧梯形螺纹轴的成形机理.考虑到轧制过程轧件螺旋升角瞬时变化特点和成形段齿形截面变化等因素设计了楔横轧模具,采用有限元分析软件Deform-3D对楔横轧梯形螺纹轴齿形成形过程进行模拟,得到精度较高的梯形螺纹轴轧件.利用有限元点跟踪功能,对轧件多个点进行跟踪,详细分析了轧件螺纹不同位置各点的径向、轴向位移变化情况,从中获得螺纹段各处金属流动规律.采用软件模拟参数进行了相应的楔横轧实验,得到的梯形螺纹轴实验轧件与有限元模拟结果相同.模拟和实验结果表明,模具螺旋升角采用轧件瞬时半径对应螺旋升角时,能够轧制出形状精确的螺纹轴.      

7-5/8in超高强度直连型石油套管的开发

根据超深复杂井身结构设计的需要,开发了7-5/8 in超高强度直连型石油套管。通过合理钢种设计及工艺控制,使得套管在超高强度下具有良好的韧性;良好的材料性能及螺纹密封面的设计,解决了直连型套管连接强度和密封性能的问题。试验结果表明,7-5/8 in超高强度直连型石油套管不仅具有超高的抗挤毁能力,还具有良好的连接强度及密封性能,适用于特殊井身结构的盐层段。     

Comparison of microstructure and properties between joints of FSW and TIG 316L austenitic stainless steel

FSW and TIG were conducted on 316L stainless steel.Variation during microstructure and properties in joints obtained by different welding methods was studied.The results show that the effect of severe mechanical stirring and intense plastic deformation creat a fine recrystallized grain in the welding joint during FSW.As for TIG,the temperature of welding joint exceeds the melting point of welded material itself.The entire welding process belongs to the solidification of a small molten pool;and the microstructure of the joint takes on a typical casting structure.When the welding parameters were selected appropriately,the average ultimate tensile strength of FSW joints can reach 493 MPa,which is 83.6%of base metal;the average elongation is 52.1%of base metal.The average ultimate tensile strength of TIG joints is 475 MPa, which is 80.5%of base metal;the average elongation is 40.8%of base metal.The tensile test of FSW joints is superior to the TIG joints.The microhardness of FSW joint compared to base metal and TIG joint having a significant improvement,which arel95.5 HV,159.7 HV and 160.7 HV,respectively;grain refinement strengthening plays an important role in enhancing the microhardness.The electrochemical corrosion tests show that the joint of FSW 316L austenitic stainless steel has a good corrosion resistance.     

N型组合节理类岩体单轴压缩破坏试验

针对实际工程中平行与交叉裂隙组合呈N字形裂隙岩体的稳定性问题,以N型组合节理为研究对象,开展了N型节理类岩体试件超声波检测试验和单轴静载试验,结合断裂力学理论,分析其强度特征、破坏特征和超声波波速衰减规律。结果表明：（1）N型组合节理类岩体的裂纹类型依次有翼型裂纹和次生倾斜裂纹,其扩展路径最终均趋向于主应力方向,不同于单节理下的裂纹发展规律;（2）当主节理倾角一定时,主次节理夹角和节理条数对试件的物理性能有一定的影响。各组合节理试件的波速衰减率范围在0.9%～9.6%之间,且15°和90°夹角节理试件的波速衰减最快,而60°夹角节理试件的衰减最慢;（3）组合节理类岩体的本构关系、峰值强度和破坏特征均表现出非线性特征。峰值强度分布规律基本服从M型分布,不同于单节理下的U型分布,其中15°、30°、45°、75°和90°夹角试件,以及完整试件呈准脆性破坏,其他夹角试件呈脆性破坏。     

Q235/5083异种材料自冲铆接头力学性能的研究

通过异种材料Q235钢板和5083铝板进行自冲铆接,分别研究了组合方式、板厚、接头热处理（模拟车身烘烤过程）等工艺因素对接头力学性能的影响,结果表明:5083铝板作为下板时接头的性能更优,并且Q235上板板厚对接头的性能有一定的优化作用.在该实验中,接头b#的组合方式是较优的工艺参数,即1.5 mm Q235-2.0 mm5083;经过烘烤后接头的失效载荷和失效位移都有不同程度的增加,其中性能较优的接头b#经烘烤后失效载荷提升了5.80 %,失效位移提升了8.26 %;汽车车身涂装过程中进行烘烤作业对接头的性能不会造成强度损失,相反还会对接头力学性能和稳定性有一定程度的优化作用.      

Seismic Rehabilitation of Reinforced Concrete Frame Interior Beam-Column Joints with FRP Composites

An experimental research program is described regarding the use of externally applied carbon fiber-reinforced plastic (CFRP) jackets for seismic rehabilitation of reinforced concrete interior beam-column joints, which were designed for gravity loads. The joints had steel reinforcement details that are known to be inadequate by current seismic codes in terms of joint shear capacity due to the absence of transverse steel hoops and bond capacity of beam bottom steel reinforcing bars at the joint. Lap splicing of beam bottom steel reinforcement at the joint using externally applied longitudinal CFRP composite laminates is investigated. Improvement of joint shear capacity using diagonal CFRP composite laminates is another strengthening scheme employed. Concrete crack widths for the as-built specimens and the extent of CFRP delamination for the rehabilitated specimens at various drift ratios are reported. The test results indicate that CFRP jackets are an effective rehabilitation measure for improving the seismic performance of existing beam-column joints with inadequate seismic details in terms of increased joint shear strength and inelastic rotation capacity. In addition, CFRP laminates are effective rehabilitation measures for overcoming problems associated with beam bottom steel bars that have inadequate embedment into the beam-column joints.     

宝钢T92钢管焊接性能试验及焊接接头运行评价

检验及分析评价了宝钢产SA-213 T92钢高压锅炉管的焊接工艺性能及焊接接头性能,对T92钢焊接接头挂管电厂锅炉实炉运行考验,并对服役1年的T92钢焊接接头进行了高温持久强度试验及评价。结果表明,宝钢T92高压锅炉管焊接工艺性能及接头性能各项技术指标均符合DL/T 868—2004标准要求,实炉运行业绩良好,服役1年的T92管焊接接头高温持久强度总体仍达到或超过GB 5310—2008、EN10216—2007标准要求。     

Biomechanical evaluation of operative procedures to treat Kienb?ck's disease

Operative procedures used to treat Kienb?ck's disease have been biomechanically evaluated experimentally. We have shown that joint leveling procedures, such as radial shortening and ulnar lengthening, experimentally unload the ulna and the radial lunate fossa. For wrists with neutral ulnar variance, a lateral opening or medial closing radial wedge procedure unloads the radial lunate fossa. Scapho-trapezio-trapezoidal fusion and scapho-capitate fusion also unload the radial lunate fossa but at the expense of loading the adjacent joints. Neither a capitate-hamate fusion nor a carpal tunnel release alter the radial ulnar carpal joint loading.     

Seismic Rehabilitation of Deficient Exterior Concrete Frame Joints

The performance of rehabilitated reinforced concrete beam-column joints was compared with the response of existing joints designed to preseismic codes to assess proposed rehabilitation techniques. Six beam-column subassemblies with nonductile reinforcement detailing were tested. The joints were subjected to quasi-static load that simulates seismic forces. The first three specimens had inadequate anchorage length of the bottom beam bars. Two of them were strengthened by using carbon-fiber-reinforced polymer sheets attached to the bottom beam face and then tested. The other three specimens had no steel ties installed in the joint zone, in addition to inadequate anchorage length of the beam bars. Two of the beam-column joints were strengthened by glass-fiber-reinforced polymer jackets of the joint zone and steel rods or plates. The rehabilitation techniques were found effective in eliminating the brittle joint shear and steel bar bond-slip failure modes, and ductile beam hinging instead occurred.     

Improved Longitudinal Joint Details in Decked Bulb Tees for Accelerated Bridge Construction: Fatigue Evaluation

This companion paper focuses on an investigation of improved continuous longitudinal joint details for decked precast prestressed concrete girder bridge systems. Precast concrete girders with an integral deck, which are cast and prestressed with the girder, provide benefits of rapid construction along with improved structural performance and durability. Despite these advantages, the use of this type of construction has been limited to isolated regions of the United States. One of the issues limiting more widespread use is the perceived problem with durability of longitudinal joints used to connect adjacent girders. Four full-scale slabs connected by No. 16 (#5) headed reinforcement detail using a 152 mm (6 in.) lap length were fabricated and tested. An analytical parametric study was conducted to provide a database of maximum forces in the longitudinal joint. These maximum forces are then used to determine the loading demand necessary in the slab testing due to the service live load. Static and fatigue tests under four-point pure-flexural loading, as well as three-point flexural-shear loading, were conducted. Test results were evaluated based on flexural capacity, curvature behavior, cracking, deflection, and steel strain. Based on these test results, the improved longitudinal joint detail is a viable connection system that transfers the forces between the adjacent decked bulb tee girders.     

钛合金榫头微动疲劳试验研究现状与发展

综述了涡轮发动机钛合金叶片榫头微动疲劳失效的两种试验方法(轴向微动疲劳试验和榫型微动疲劳试验)的研究现状。轴向微动疲劳试验技术适用于微动疲劳失效机理的研究,应用于抗微动疲劳防护层试验验证的研究也较多;而榫型微动疲劳试验技术则多用于力学分析和模型建立等方面。榫头微动疲劳问题的研究还远未完善,应综合运用微动磨损、轴向微动疲劳和榫型微动疲劳等技术,并配合有限元分析手段,开展微动疲劳机理、多因素影响及防护层作用等方面的系统研究。     

铰接式卡车铰接头螺纹磨损修复方案探讨

The key of articulated truck is to connect the front and rear parts of the hinged joint, which connects the power part of the vehicle with the load part. As the connector of the front frame and the rear frame, the hinged joint plays an important role in the hinged joint. After a long time running, the hinge joint is affected by the impact, bending moment and other composite loads, and its thread will appear wear, break and other failure forms. Based on the analysis of the structure and current situation of the hinge joint, the advantages and disadvantages of the hardfacing process and the inlay process are compared, and a better scheme for repairing the thread wear of the hinge joint is proposed.