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SN弹性砂轮在数控车床磨削和抛光加工中的应用
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作者 李绍鹏 谢海良 《南通职业大学学报》 2006年第2期73-75,95,共4页
SN弹性砂轮是磨具新品种,能够在普通机床上实现对零件的磨削和抛光加工。将数控车床和SN弹性砂轮抛磨技术溶于一体,可进一步拓展数控车床的使用功能。在实际应用中,通过减小数控车床的脉冲当量(即步进位移精度),弥补了数控车床位移精度... SN弹性砂轮是磨具新品种,能够在普通机床上实现对零件的磨削和抛光加工。将数控车床和SN弹性砂轮抛磨技术溶于一体,可进一步拓展数控车床的使用功能。在实际应用中,通过减小数控车床的脉冲当量(即步进位移精度),弥补了数控车床位移精度较低的缺陷;通过特殊的循环程序结构设计,解决了SN弹性砂轮抛磨时不定次数的无进给量或微进给量的补磨磨削,保证了零件的加工精度。 展开更多
关键词 数控加工 弹性砂轮 磨抛工艺 循环程序结构
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Performance of Steel Structures under Fatigue Cyclic Loading
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作者 Nawir Rasidi Agoes Soehardjono MD Sri Murni Dewi 《Journal of Civil Engineering and Architecture》 2011年第3期265-272,共8页
A component or structure, which is designed to carry a single monotonically increasing application of static load, may fracture and fail if the same load or even smaller load is applied cyclically a large number of ti... A component or structure, which is designed to carry a single monotonically increasing application of static load, may fracture and fail if the same load or even smaller load is applied cyclically a large number of times. For example a thin rod bent back and forth beyond yielding fails after a few cycles of such repeated bending. The fatigue failure is due to progressive propagation of flaws in steel under cyclic loading. This is partially enhanced by the stress concentration at the tip of such flaw or crack. The presence of a hole in a plate or simply the presence of a notch in the plate has created stress concentrations at the center points. These stress concentrations may occur in the material due to some discontinuities in the material itself. At the time of static failure, the average stress across the entire cross section would be the yield stress. However when the load is repeatedly applied or the load fluctuates between tension and compression, the center points experience a higher range of stress reversal than the applied average stress. These fluctuations involving higher stress ranges, cause minute cracks at these points, which open up progressively and spread with each application of the cyclic load and ultimately lead to rupture. Fatigue failure can be defined as the number of cycles and hence time taken to reach a pre-defined or a threshold failure criterion. Low cycle fatigue could be classified as the failures occurring in few cycles to a few tens of thousands of cycles, normally under high stress/strain ranges. High cycle fatigue requires about several millions of cycles to initiate a failure. The type of cyclic stresses applied on structural systems and the terminologies used in fatigue resistant design are illustrated in this paper. The common form of presentation of fatigue data is by using the S-N curve, where the total cyclic stress (S) is plotted against the number of cycles to failure (N) in logarithmic scale. The point at which the S-N curve flattens off is called the "endurance limit". To carry out fatigue life predictions, a linear fatigue damage model is used in conjunction with the relevant S-N curve. 展开更多
关键词 FATIGUE cyclic loading S- N curve
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