Critical deformation speeds

At relatively low temperature, i.e. for T < 0.5 Tf, the behavior of materials is mainly elastic and the rapture is brittle in nature. For stresses clearly less than the average breaking stress, the probabihty of destruction is nearly zero. In other words, the growth of flaws is insignificant and the stress intensity factor remains, at any point on the structure, lower than its critical value. If a high deformation speed is imposed (dc/dt > lOs ), we enter into the field of sudden dynamic rapture, which makes it possible, for example in the case of fibers or whiskers, to be free from all enviromnental influences and attain stresses approaching theoretical stress of interatomic decohesion. 

The overspeed test is a form of proof test, in that it looks for a failure. In this case, it is a permanent deformation. Not all permanent deformations are failures. In fact, manufacturers have autofrettaged high tip speed impellers for decades. The fourth edition of API 617 was somewhat misleading as it identified the bore as the only critical area. On... 

The critical state of stress-induced crystallization at high spinning speeds is governed by the viscoelasticity of the polymer in combination with its crystallization behavior. Any kind of coarse particle obviously disturbs the structure and affects the resistance against deformation. The development of stress is controlled by the rheological properties of the polymer. Shimizu et al. [4] found that increasing the molecular weight drastically promotes the crystallinity under stress conditions. 

We have compared results from Fig. 17 with those of several other workers and found good agreement. Bhandari states that a vertical line moving at high speed assumes the shape of a hyperbola [21], Mathews and Lakshmanan criticize the concept of relativistic rotation and introduce the train paradox [22], When a fast-moving train is studied, should one imagine each boxcar to be rotated or the train as a whole rotated What happens to the stationary rails Finally, they conclude that the rotated appearance is not self consistent. We agree with this statement. The train is easily visualized in our Fig. 17b as one of the horizontal rows of deformed squares. From this, it is obvious that the distortion of the total train cannot be explained solely by rotation. 

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