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《Planning》2016,(22)
为满足车削大螺距外螺纹刀具后刀面磨损一致性及螺纹面加工表面粗糙度一致性要求,提出轴向分层车削外螺纹的工艺设计方法,设计具有不同切削刃刃口半径和刀尖圆弧半径的外螺纹刀具,分别采用不同进刀次序、加工余量和冷却润滑条件的工艺方案进行车削外螺纹实验;提取刀具后刀面磨损宽度及螺纹面加工表面粗糙度值,揭示出上述工艺变量的改变对刀具后刀面磨损和螺纹面加工表面粗糙度的影响。获得的工艺方案在保证刀具后刀面磨损一致性的前提下,提高了螺纹面加工表面粗糙度一致性,该方法为加工高表面质量大螺距螺纹提供依据。 相似文献
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《Planning》2015,(26)
普通的多头锯齿形螺纹加工程序较为冗杂,因其牙型特殊,编制时工作量大,牙深度和宽度都比普通螺纹大很多,所以检查程序繁琐易出错。根据宏程序的特点,通过对锯齿形螺纹牙型、公差的分析及原理应用,设计出许多简单易行的多头螺纹加工程序。可以通过改变螺纹参数的变量值,加工出不同直径和螺距的锯齿形螺纹,其灵活性较强也较为方便。 相似文献
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高硬度大公称直径内螺纹加工起来非常困难,介绍一种简单实用的机夹式内螺纹车削刀具及具体的切削工艺,提出一种加工高硬度大公称直径内螺纹的加工方法。 相似文献
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梯形螺纹的牙型高度深,精度要求高,牙两侧表面粗糙度值较小,是较难加工的螺纹,文中介绍了在数控车床上利用宏程序粗加工大螺距梯形螺纹的方法,利用低转速精加工梯形螺纹的方法,给出了具体加工程序及其说明,提供的加工程序具有很好的实用价值。 相似文献
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基于太沙基极限平衡理论,对螺纹桩极限承载力进行理论推导,提出螺纹桩两种破坏模式下临界螺距的确定方法和螺纹桩极限承载力计算方法,分析了不同参数对螺纹桩承载力的贡献。研究结果表明:螺纹桩破坏模式由临界螺距Hcr决定,螺距大于临界螺距时为螺牙独立破坏模式,小于临界螺距时为圆柱剪切形破坏模式;螺纹桩螺牙改变了桩体的承载方式,对比同外径圆桩承载力约提高40%,在达到极限荷载时,螺牙提供的承载力约为总承载力的85%;影响螺纹桩螺牙承载力的主要土体指标为黏聚力c、摩擦角φ以及埋深,而滑动区土体自重因素对螺牙承载力的贡献并不明显;当考虑抗剪强度提供的竖向力时,螺纹桩的极限承载力最大提高20%左右。 相似文献
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Wind‐induced fatigue of large HAWT coupled tower–blade structures considering aeroelastic and yaw effects
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Shitang Ke Tongguang Wang Yaojun Ge Hao Wang 《The Structural Design of Tall and Special Buildings》2018,27(9)
An efficient approach for predicting wind‐induced fatigue in large horizontal axis wind turbine coupled tower–blade structures subject to aeroelastic and yaw effects is presented. First, aerodynamic loads under yaw conditions are simulated based on the harmonic superposition method and modified blade element momentum theory, in which wind shear, tower shadow, tower–blade interactions, aeroelastic, and rotational effects are taken into account. Then, a nonlinear time‐history of wind‐induced responses under simulated aerodynamic loads is obtained. Finally, based on these results, wind‐induced fatigue damage and lifespan are predicted according to linear cumulative damage theory. For completeness, the influences of mean wind speed, aeroelasticity, and yaw angle on horizontal axis wind turbine fatigue life are discussed. The results indicate that the aerodynamic loads and residual fatigue life can be estimated accurately by the proposed model, which can be used to simulate the 3D wind fields of wind turbines under given wind conditions. The wind energy of the wind turbine blade is mainly concentrated at its edge and is weaker at the hub. Estimation of wind turbine fatigue life is therefore suggested to be based on the component with the shortest life, being the blade root. Furthermore, yaw conditions significantly shorten fatigue life and should not be ignored. Fatigue life is also rather sensitive to mean wind speed. 相似文献
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ABSTRACTBest pitch position of each blade in the rotation of turbine at different azimuth angle has been calculated at different Tip Speed Ratios (TSRs) by using the aerodynamic analysis. This paper analyses and optimises the various design parameters and its influence on the starting turbine by itself, power coefficient and overall performance of the Vertical Axis Wind Turbine (VAWT). The results indicate that the best pitch position blade method improves the self-starting capacity and power coefficient. The best position blade pitching curve-1 gives maximum power coefficient at 45° pitch angles for TSRs of 0.5 and the best position blade pitching curve-5 with 15° pitch angle gives maximum coefficient of power about 0.49 for TSRs at 2.5. The results indicate that the variation of pitch angle from 45° to 10° with six best position blade pitching curves give the maximum power coefficient for TSRs from 0.5 to 3. 相似文献
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The efficiency of a tunneling project is mainly associated with the abrasivity of the acting soil and the wear resistance of the cutting tools. Heavy wear can dull the cutting tool, which negatively affects the penetration rate and therefore the efficiency of a tunneling process. Completely worn tools with a short service life have to be replaced by newer ones. This circumstance results in unplanned machine shutdowns and higher maintenance costs. It is thus of high economic as well as technical interest to obtain a deeper understanding of soil/cutting tool interactions during tunneling. To meet this challenge, a large number of different testing devices to estimate the abrasivity of soils have been developed within the last two decades. An innovative and promising experimental setup is presented in this work. A horizontal implementation offers the possibility of simulating a tunneling process as well as the tribological system of a TBM tool. The interactions between all system components can be mapped and analyzed in detail. This method offers a unique setup, which allows wear prediction of TBM tools in a homogeneous soil with project-specific parameters (soil composition/condition, soil mechanics, tool material and machine/tunneling data). 相似文献
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液压静力沉桩机夹桩机构研究设计 总被引:4,自引:0,他引:4
本文简述了抱压式液压静力沉桩机的压桩工作原理 ,分析了作业时预制桩的破坏机理 ,设计了一种双层夹桩液压缸、柱面自动调心式的夹桩机构 ,并在ZYB系列桩机上应用 ,经实践检验获得了很好的效果 ,基本上避免了夹坏桩现象的发生。 相似文献