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An advanced branch and bound method which reduces the computer resolving time enormously and leads the reliability research of large-scale spatial frame structural systems close to practical use is presented on condition that the same computation accuracy is ensured.

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The effect of tribology factors on bearing vibration is studied experimentally. AR model and WPT are used to processing the normal arid abnormal signals. The results are as follows:1. The vibration of ball bearings is caused by the tribology action of contact pairs of ball and ring races and has the essential of tribo-dynamics. Any factors affecting the tribology characteristics of contact pairs will affect vibration and noise of bearings consequently.2. Vibration characteristics of bearing keep almostly unchanged with the increasing of axial load expecting the increasing of nature frequencies. When radial load increasing with axial load unchanged, nature frequencies keep unchanged but some new vibration peaks appears in the spectrum.3. Vibration amplitudes are damped and nature frequency are enhanced with sufficient lubrication. Vibration and noise of bearings increase obviously and roar can happen and the contact surfaces scratch slightly under insufficient and unclean lubrication state. Bearing will be disabled in a few minutes without any lubrication.4. Bearing vibration is unstable under low speed. With the speed increasing, the vibration become stable and natural frequencies increase slightly but the amplitudes increase apparently.5. Bearing vibration can be excited only by some harmonics ofwaviness without lubrication and by all harmonics with lubrication based on the theoretical analysis.6. The nature frequencies of ball bearings decrease with the increasing sizes. When international clearance increasing, nature frequencies decrease in radial and increase in axial and angular and the amplitudes increase in radial and decrease in axial and angular. When the number of balls increasing, nature frequencies increase and amplitudes decrease. When the pitch diameter increasing, axial nature frequency increase and others nearly keep no change. When outer race groove curvature radius increasing, nature frequencies increase in radial and decrease in axial and angular and amplitudes keep no change in radial and increase in axial and angular. When inner race groove curvature radius increasing, nature frequencies decrease and amplitudes increase.7. The distortion in amplitude and frequency components of bearing vibration signals picked up by the present probe measurement method is founded and right conclusions cannot be achieved by the signals. When accelerometer is rigidly screwed with steel stud onto a flat outer surface of a ball bearing, vibration signal can be got without distortion and the reliability of research on bearing vibration is assured.8. AR model is suitable for large samples of bearing vibration signals, square root of length of samples can be used as the upper limitation of order determination and the FPE order selection criterion is effective. Many advantages of AR spectrum are founded over the classical based on FFT.9. Time-Frequency analysis is necessary for abnormal noise of ball bearings. WPT overcomes the principle shortcomings of STFT and proved to be a best tool to process the abnormal signals.

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Tear-down analysis indicates that for VRLA battery, water loss ,negative plate sulphation and positive active material softening are the main causes of failure.

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Anything which invalidates the input sequence will invalidate the match results.

任何使輸入序列失效的事件都會(huì)使匹配結(jié)果失效。

Causing the omens of boasters to fail, Making fools out of diviners, Causing wise men to draw back And turning their knowledge into foolishness

賽44：25 使說(shuō)假話的兆頭失效三级黄免费视频网站、使占卜的癲狂亚洲熟妇性爱、使智慧人退后、使他的知識(shí)變?yōu)橛拮尽?/p>

Causing the omens of boasters to fail, Making fools out of diviners, Causing wise men to draw back And turning their knowledge into foolishness

賽44：25 使說(shuō)假話的兆頭失效在线国产福利网站、使占卜的癲狂免费看黄色网站在线看、使智慧人退後、使他的知識(shí)變?yōu)橛拮尽?/p>

Combined with the macro-morphology appearance analysis and working conditions of failure casing, the paper reached a conclusion that it is due to the impact and friction which come from the drill tools made the fatigue cracks formation on the casing thread root, and eventually leading to casing rupture failure, the material defects in failure casing accelerated crack initiation and growth.

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It is clarified for the first time that the thermal fatigue failure of solder joint is actually a creep strain low cycle fatigue failure, and a physical model for creep fatigue crack propagation has been proposed. It was pointed out that creep strain increases in the high stress area ahead of the tip of thermal fatigue crack, results on one hand that the slide of crack tip increase, inactivation more serious and crack close length increases, the other hand, that intergranular crack exists, whose direction will affect the fatigue crack propagating.

本文首次闡明了焊點(diǎn)的熱循環(huán)失效本質(zhì)上是以焊點(diǎn)內(nèi)循環(huán)蠕變?yōu)橹饕獞?yīng)變的低周疲勞失效麻豆久久，并在此基礎(chǔ)上提出了蠕變疲勞裂紋擴(kuò)展的物理模型精品亚洲护士av无码番号，指出熱循環(huán)裂紋前端的高應(yīng)力區(qū)內(nèi)，蠕變加劇欧美XXXX做受欧美18，使裂紋前端滑移增加A级毛片高清免费视，裂紋鈍化加劇A级毛片全部免费高清视频人人，導(dǎo)致隨后的裂紋閉合擴(kuò)展長(zhǎng)度增加；同時(shí)蠕變也使裂紋前端的高應(yīng)力區(qū)出現(xiàn)晶間裂紋亚洲色av噜噜狠狠爱，蠕變沿晶裂紋對(duì)主裂紋擴(kuò)展的影響取決于沿晶裂紋的連接方向国产高清在线观看AV片麻豆。

It is shown that the contact interaction enables bottom drillstring to whirl backward, and then an alternate bending stress with higher frequency is produced. So the drillstring fatigue failure could be accelerated. At the same time, a quite strong wallop force of high frequency is produced on the contacting point, and the contacting zone is next to the screw coupling of drill collars. It will easily result in the failure of screw couplings. The research results provide theoretical basis for the prevention of drillstring failure.

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