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温度对超声波波速及应力测量的影响 总被引:7,自引:0,他引:7
导出了螺栓轴向应力与超声波纵、横波声时及温度的简捷的关系式,讨论了温度引起螺栓轴向应力超声波测量的误差,测出了温度对声速的影响系数,简化了测量过程。实验结果表明应力<250MPa,应力超声测量的绝对误差<10MPa。 相似文献
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通过对螺栓的轴向应力检测模型进行优化处理,直接建立了螺栓轴向应力与纵波、横波渡越时间比的平方的关系。优化后的模型能同时修正温度的影响,模型中各项参数只与螺栓的材料、温度变化有关。利用8.8级M20×130螺栓的各项拟合参数,对其自身、同型号、同材料螺栓在0~300 MPa, 0~40℃的应力检测精度与温度修正进行验证。结果表明其自身应力检测与温度修正误差分别为0~15.1 MPa, 3.31~10.22 MPa;同型号螺栓的应力检测误差为1.1~24.3 MPa;同材料螺栓的两种误差分别为1.9~26.9 MPa, 3.25~19.03 MPa。这说明优化后的模型具有足够的可靠性且适用于同材料螺栓的轴向应力评估与温度影响修正,在工程应用中能有效提高工作效率。 相似文献
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某1000MW机组火电厂汽轮机的C-422材料高温螺栓采取超声波检测发现异常反射信号,然后通过现场渗透检测和磁粉检测,结合光谱分析逐一排除缺陷产生的可能因素,并最终确定了该缺陷为采用镍基焊丝进行冷补焊造成的。通过对该螺栓进行硬度测量,发现其母材、焊缝以及热影响区存在较大硬度梯度,尤其焊缝组织的硬度最低,使之成为该螺栓的最薄弱点。同时,对螺栓进行应力测试分析,发现焊缝中心的轴向应力特别大,且轴向和切向均为拉伸的应力状态,导致螺栓的拉伸屈服极限大大降低,减弱了螺栓的使用性能。 相似文献
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高强度螺栓材料为42CrMoA钢,强度等级为10.9级,在热处理后发现沿轴向开裂。利用光学显微镜、扫描电子显微镜、直读光谱仪、能谱分析仪和显微硬度机等手段,对开裂螺栓进行了宏观、化学成分、硬度、金相、能谱和开裂面电子形貌分析后,得出该螺栓开裂的主要原因是在使用前原材料表面存在锻造折叠,经过拉拔后呈线状分布,形成应力集中,热处理淬火时充当了裂纹源,在强大的淬火应力作用下诱发了热处理轴向开裂。 相似文献
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利用拉伸试验机和超声应力检测仪,对水电机组蜗壳螺栓(35CrMo钢)进行轴向拉伸,测定其在拉伸过程中的应力值及其对应的超声横波和纵波传播时间,获得横波与纵波的声时比,建立弹性应力与超声横波与纵波声时比之间的定量关系,为利用超声波实时测定螺栓弹性应力提供依据。结果表明,在35CrMo钢所承受的轴向弹性应力处于钢的弹性变形范围内时,超声横波与纵波声时比与弹性应力之间呈线性关系。对该模型进行误差分析,结果表明,利用超声横波与纵波测定的应力值与实际应力值之间的误差为0.04%~2.08%,满足工程要求。 相似文献
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A new ultrasonic technique for stress measurement using mode conversion is proposed and applied to the estimation of axial stresses in high-tension bolts. The effect of axial stresses on acoustic wave velocities in axisymmetric cylindrical solids is analyzed, and a linear acousto-elastic equation is formulated. Theoretical ray analysis is performed to compute time of flight (TOF) of mode-converted waves in cylindrical solids. To evaluate the validity of the proposed method, mode-converted longitudinal and shear waves in carbon-steel bolts are generated and captured to measure the TOF of the waves. Simultaneous velocity measurement of two differently polarized acoustic waves are made with enough resolution to estimate axial stresses with values less than 10% of the yield stress of the bolt material. It is observed from experimental results that the TOF ratio of longitudinal and shear waves is linearly proportional to the axial stress in bolts within 5% error, as expected from theory. 相似文献
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Jung-Dae KWON Sunghun LEE Koo-Hyun LEE Jong-Joo RHA Kee-Seok NAN Se-Hun KWON 《中国有色金属学会会刊》2011,(Z1):12-16
As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles. 相似文献
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As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles. 相似文献
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以DN300阀门法兰与class2500盲板螺栓联接为研究对象,基于ANSYS有限元软件,建立法兰-盲板螺栓联接有限元模型。仿真计算在螺栓预紧力和流体压力耦合作用下,通过螺栓联接处的径向线与相邻两螺栓中间部位径向线在轴向位移的变化。基于GB150算法对法兰-盲板螺栓施加预紧力,通过有限元仿真分析密封区域接触应力、轴向形变,分析阀体密封腔在法兰圆周方向的气密性,并通过试验进行密封性验证。结果表明:采用螺栓预紧联接法兰周向具有良好的密封性,仿真与试验结果一致;研究并确定了螺栓预紧力的范围下限;密封区域密封垫外侧接触应力远大于内侧,密封垫外侧起主要密封作用。 相似文献
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螺栓组载荷分布不均是齿轮齿条钻机产生振动甚至损坏的重要原因之一。工程中,螺栓连接点常常会受到复杂的时变低速重载,螺栓组容易因载荷分布不均而发生断裂,从而影响钻机的稳定性。为研究不同螺栓分布情况下螺栓组所受应力情况,通过建立多螺栓连接的力学模型对螺栓载荷分布情况进行分析,并在此基础上考虑结构复杂的连接件提出一种多螺栓连接载荷计算方法。设计并进行了试验研究和有限元分析,通过对比其结果,验证了计算方法的准确性。基于提出的理论计算方法,给出载荷作用下螺栓剪切应力的分布规律,对比了螺栓均匀分布模型和非均匀分布模型的剪切应力分布特点,结果发现非均匀螺栓分布的承载分布均匀性要优于均匀分布的螺栓。 相似文献
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Hyun-Chul LeeYoung-Gwan Jin Sun-Kwang HwangKi-Ho Jung Yong-Taek Im 《Journal of Materials Processing Technology》2011,211(6):1044-1050
Using a wedge tension test for service and safety reasons, this study determines the fracture location of a previously developed high-strength M8 bolt with a tensile strength of 1600 MPa. The strength distributions of the manufactured bolt are examined in compression and microhardness tests to ensure a better understanding of the experimental results of the wedge tension test. The strength variations of the manufactured bolt were confirmed through scanning electron microscope measurements of the interlamellar spacing of the pearlite. Because of the strength condition in the neck of the bolt and the geometry-induced stress concentration, the head of the manufactured bolt can be separated from the neck during the wedge tension test. In this study, stress analyses were therefore conduced to prevent the head separation. That is, the stress concentration on the neck of the bolt was checked by varying the fillet radius for a given pitch size of the bolt. The numerical findings were subsequently validated by the wedge tension test. The findings are the basis of practical industrial design guidelines on the fillet radius to prevent the head of the manufactured bolt from being separated. 相似文献
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运用ANSYS Workbench对球面磨床的专用夹具部件进行多工况的非线性接触分析,研究夹具各个零件之间的接触状态,分析夹具整体结构和球体的变形量、极限应力、扭转角度以及结合面之间滑移量,确定夹紧螺栓预紧力,校核夹紧机构的可靠性。此方法为球面磨床专用夹具的设计与校核提供参考。 相似文献
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船用作业吊篮在距地面20m岛处作业时发生坠落事故。通过断口宏微观观察、化学成分分析、力学性能检测及金相组织检查等,对事故中的断裂螺栓进行检验和分析。对吊篮系统在役情况下的应力分布和安全性进行计算和分析,计算结果表明:事故中M36mm螺栓在正常服役、违章作业、存在微裂纹缺陷等条件下是安令的。对吊篮坠落事故的发生过程进行分析与计算,结果表明:当吊篮系统受到外力作用而失去平衡的瞬间,巨大的剪切载荷造成梁端部M10mm连接螺栓首先剪切断裂,梁坠落过程中M36mm螺栓在冲击、扭转和弯曲应方下发牛断裂,最终整个吊篮系统发生高空坠落。 相似文献