安心讀書，踏實做事兒，你必有用，

人大太犬

大俠，我讀交流控制，覺的比直流難多了，先期不理解的東西好多，只好死記硬背了。磁的部分懂的太少了，學(xué)交流機就是硬傷啊。

愛貓人士薛定諤

如果沒有8爺以及社區(qū)各位大俠的指點，我可能早就被周圍的“差不多就行了”，“隨便搞一下”，“湊活”，“百度一下”給帶陰溝里了。接觸的人多了，越發(fā)覺得只有有基礎(chǔ)有數(shù)學(xué)才是真正的硬道理，還在繼續(xù)努力，總會有所收獲

天水藍(lán)

村子里有些人，就是早上出來，蹲在南墻根曬太陽，天南海北啥都懂閑扯， 順便抱怨一下老天如何不公，老板如可刻薄，隔壁那個sb那么賣力氣掙不了幾個錢，有啥用， 等等。 然后回家喝粥吃咸菜， 下午接著出來曬著太陽，擇虱子。

一路一路

大俠的意思是北京是英雄不問出處，你行你就上，而上海就是要先看學(xué)歷看業(yè)績再論其他嗎？
像我這種本科在上海是不是得事倍而功半。

feibiaoshebei

努力，共勉

walyem

昨天翻了下筆記，居然看了那么多書，而筆記上基本都不記得了。碰到急的就抓耳撓腮的，發(fā)現(xiàn)很多東西好理解，用起來就難.

愛貓人士薛定諤

http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/JAI/PAGES/JAI13069.htm
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Influence of Cold Rolling Threads Before or After Heat Treatment on the Fatigue Resistance of High Strength Fine Thread Bolts for Multiple Preload Conditions

Abstract
SI class 12.9 high strength steel bolts were used to investigate the fatigue behavior of bolt threads rolled before/after heat treatment at five different preload values. Bolts used were 3/8 UNRF-24 (fine) and preloads were taken as 1, 50, 75, 90, and 100 % of roll before heat treatment proof stress. Since proof stress was lowered 10 % for roll after heat treatment, these preloads for roll after heat treatment bolts were then actually 1.1, 55, 83, 100, and 110 % of proof stress (to keep load the same). The tests produced a range of R ratios (R=Smin/Smax) between 0.03 and 0.92. Maximum near surface residual compressive stresses, obtained via x-ray diffraction, ranged from −500 to −1000 MPa. Axial loads were applied through the nut and all fatigue failures occurred at the first thread of the nut/bolt interface with crescent shaped cracks dominating in most tests. Multiple ratchet marks (separate crack nucleation sites) occurred for roll before heat treatment bolts, while fewer or no ratchet marks, were evident for the roll after heat treatment. Scanning electron microscopy evaluation indicated all fatigue crack growth regions contained multiple fatigue facets, while final fracture regions contained ductile dimpling. Cyclic creep/ratcheting was monitored and little, or none, was observed for preload tests equal to or less than 75 %. Replication data indicated a log-normal distribution on life was very reasonable. The fatigue resistance for fine threads rolled after heat treatment with preload stresses of 1 % (R ratio less than 0.05) caused very large increases (158 %) in 107 cycles fatigue strength compared to roll before heat treatment. This is in agreement with other roll before/after low R-ratio results. The roll after heat treatment bolts when tested at the higher proof loads had 107 fatigue strengths of 69 to 30 % increase. These increases are much less than the 158 % at 1 % preload, but still significant. Constant life Haigh diagrams at 105 and 107 cycles were in qualitative agreement with VDI 2230 bolt preload guidelines.

* A2 u1 x- W' ?1 b- U因為沒法下載，也不清楚這種12.9級高強螺栓用的什么材料，
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1 Z5 W$ Z( T, U# H- ~) e. S; q如果我要描述我手上現(xiàn)有的某種材料（線材）的這方面性能，但又沒有將其制成成品的條件，是否可以做某種試樣，在上面進(jìn)行您說的冷作，做兩組對比上試驗機

初涉池中

很好的文章

活得精神

默默的給個贊

hai9053

受教了，好好干事