【阅读】0414起悦读整理（4.28日 14点更新）

八朔酱

整理君 第19篇补牙的那个 好像去年0506库里的一篇《.弹簧的弹力（residual stress）》

The average person is likely to feelmildly alarmed on being told that dental fillings contain locked-in stresses.We all have a somewhat hazy不清楚的 understanding that stress leads tofracture and can vaguely recall dramatic instances of stress-related failures.Thus we are likely to feel that all material stresses are without redeeming挽回的 value and should, if possible, be eliminated.

A truer picture of the behavior ofmaterials is both more complicated and more interesting. It turns out that itis difficult to work a rigid material without introducing permanent internalstresses. Most common manufacturing operations, such as turning, grinding, and peening,can set up internal stresses, and many familiar objects are subject to them,including dental fillings, computer chips, and pipelines.Butthese residual stresses can be beneficial as well as harmful. Indeed,manufacturers sometimes go to great lengths to introduce them. Manystress-related effects and recipes for obtaining them have long been known toartisans. What is new is the ability tomeasure the stress fields directly rather than inferring their nature fromwarpage and breakage. Several trends in engineering design make this analyticalcompetence important.

One of the trends is the proliferationof nontraditional materials. The best way to work a sword or to coil绕成圈 a spring弹簧 may be known, but no comparable body oflore知识 exists for ceramic transducers陶瓷转换器 or semiconductor wafers半导体晶片 or compositeairfoils复合材料机翼. Asecond trend is the trimming of safety margins修正安全边际. Bridges andother load-bearing structures have traditionally been built with large safetyfactors, but the lavish过分给予的,大量生产的 use ofmaterials required by this practice is increasingly uneconomic（原文在这里有改动，给了一些比较具体的数字）; in the case of objects that must belofted高高地升到空中 into space, a large safety factor istotally impractical. A third trend is the reduction in scale of many engineeredsystems. Residual stresses play a much more important role in the microscopicmetal微观金属 interconnects on the surface of a chip缺口 than they do in a thick electrical cable电缆.

Deland_Z

谢谢！thank you！

moonbiya

感谢分享！               

大黄黄

谢谢

杀伐四方

感谢分享！