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引言 薄壁弯头承受平面弯曲时,在弹性范围内变形与载荷成一定比例增加。当最大应力点的强度折算应力达到屈服应力后,弯头的局部区域进入塑性范围,变形不再与外载成比例,单位外载增量所引起的变形增量越来越大。当弯头某个截面快要全部进入塑性范围时,微小的外载增量就会引起甚大的弯曲变形。而后,当该截面弯矩达到一定数值时,变形猛烈增加而不休止,弯头遭到塑性破坏。这一弯矩称为弯头的塑性破坏极限弯矩,以后简称为极限弯矩。极限弯矩值的大小对管道设计具有一定的参考价值。
Introduction When a thin-walled elbow is subjected to plane bending, the deformation and load increase in a certain proportion in the elastic range. When the stress at the maximum stress point is converted to the yield stress, the local area of the elbow enters the plastic range, the deformation is no longer proportional to the external load, and the increment of deformation caused by the unit external load increment increases. When a section of an elbow is about to enter the plastic range all the time, a small external load increment will cause a very large bending deformation. Then, when the bending moment of the section reached a certain value, the deformation increased violently without stopping, and the elbow was plastically destroyed. This bending moment is called the plastic failure limit bending moment of the elbow, and will be referred to as the ultimate bending moment hereinafter. The value of the ultimate bending moment has certain reference value for the pipeline design.