Elastic rebound

The material known as bouncing putty is also a silicone polymer with the occasional Si—O—B group in the chain, in this case with 1 boron atom to about every 3-100 silicon atoms. The material flows on storage, and on slow extension shows viscous flow. However, small pieces dropped onto a hard surface show a high elastic rebound, whilst on sudden striking they may shatter. The material had some use in electrical equipment, as a children s novelty and as a useful teaching aid, but is now difficult to obtain. 

Higuchi et al. [98] postulated that an additional increase in surface area occurs after this point and that this effect may cause lamination of the tablet due to extensive rebound at decompression. In other words, at the tablet punch powder interface, there may be zones of high density during compression, but upon decompression these zones have elastic rebound and are pulled apart from the rest of the tablet that did not contain this high density. 

A separate group of methods of limited usefulness in regard to brittle materials, making use of impact action with an indenter or steel ball, with registration of elastic rebound of a hammer or beater from the sample, consists of measurements with the Shore scleroscope, the duroscope and several other testers based on this principle, where the results come close to those obtained by the Brinell method. Working on the same principle is also the impact hardness tester, in which the depth of the indent or scratch made by a diamond indenter is measured. 

Prediction of the restitution coefficient has been a challenging research topic for decades. Unfortunately, no reliable and accurate prediction method has been found so far. However, some useful simplified models with certain limits have been developed. One of them is the elastic-plastic impact model in which the compression process is assumed to be plastic with part of the kinetic energy stored for later elastic rebounding, with the rebound process considered to be completely elastic [Johnson, 1985]. In this model, it is postulated that (1) during the plastic compression process, a — r3/2a (2) during the compression process, the averaged contact pressure pm is constant and is equal to 3 Y and (3) the elastic rebound process starts when maximum deformation is reached. Therefore, the compressional force is... 

The production of tablets with the desired characteristics depends on the stresses induced by elastic rebound and the associated deformation processes during decompression and ejection. Ideally, if only elastic deformation occurred, with the sudden removal of axial pressure the particles would return to their original form, breaking any bonds that may have been under pressure. 

A more complex expression has been developed by Chicot and Lesage (1995) that accounts for the interaction effects of substrate and coating such as elastic rebound to yield... 

Direct measurements of permeabilities in unconsolidated marine sediments are difficult, and only few examples are published. They confine to measurements on discrete samples with a specially developed tool (Lovell 1985), to indirect estimations by resistivity measurements (Lovell 1985), and to consolidation tests on ODP cores using a modified medical tool (Olsen et al. 1985). These measurements are necessary to correct for the elastic rebound (MacKillop et al. 1995) and to determine intrinsic permeabilities at the end of each consolidation step (Fisher et al. 1994). In Section 2.4.2 a numerical modeling and inversion scheme is described which estimates permeabilities from P-wave attenuation and dispersion curves (c.f. also section 3.6). 

Bouncing putty is somewhat similar in that the Si-O-B bond occurs occasionally along the chain. It is based on a polydimethylsiloxane polymer modified with boric acid, additives, fillers, and plasticizers to give a material that shows a high elastic rebound when small pieces are dropped on a hard surface but flows like a viscous fluid on storage or slow application of pressure. 

The critical particle velocity that enables elastic rebound is a function of adhesion energy (Pad), particle mass (m), and the coefficient of restitution (e) ... 

In nanometric machining the microstructure of the workpiece material will play an important role in affecting the machining accuracy and machined surface quality. For example, when machining polycrystalline materials the difference in the elastic coefficients at the grain boundary and interior of the grain causes small steps to form on the cut surface, since the respective elastic rebound varies [59]. The study by Lee... 

Common defects encountered with extrusion include effects associated with the viscoelastic nature of plastic melts. As the melt is extruded from the die for example, it may exhibit sharkskin melt fracture and extrudate (die) swell. Diagrams of these defects are shown in Fig. 1.16. Sharkskin melt fracture occurs when the stresses being applied to the plastic melt exceed its tensile strength. Extrudate swell occurs due to the elastic component of the polymer melt s response to stress and is the result of the elastic rebound of the polymer as it leaves the constraints of the die channel prior to cooling. 

Yue, Z.Q. 2013c. On incorrectness in elastic rebound theory for cause of earthquakes. Proceedings of 13th International Conference on Fracture, June 16 1, 2013, Beijing, China. 

Tirupataiah, Y. Venkataraman, B. Sundarajan, G, (1990), The nature of the elastic rebound of a hard ball impacting on ductile, metallic target materials, Materials Science and Engineering A124, 133-140. 

Bouncing putty is prepared by heating a dimethyl silicone with ferric chloride and boric oxide or other boron compounds and adding suitable fillers and softeners to the resultant gum. The material is readily shaped by kneading and may be drawn into threads on application of moderate tension. When dropped on a hard surface, the material shows high elastic rebound it shatters, however, when given a sharp blow. 

Hardness can be measured by many methods, including dynamic loading and static loading. The former applies an elastic rebound method and impact force to press in the steel ball. The latter uses a hard material with a certain shape as the head and presses the head into the sample by gradual loading. 

Earthquakes consist of violent horizontal and vertical movement of Earth s surface resulting from relative movements of tectonic plates. Huge masses of rock in the plates may be locked relative to each other for as long as centuries, then suddenly move along fault lines. This movement and the elastic rebound of rocks that occur as a result cause the earth to shake, often violently and with catastrophic damage. 

When CIIR is blended with butadiene-styrene copolymer (SBR), as the concentrations of CIIR are increased, elastic rebound values are decreased linearly and traction is increased [48]. When CIIR is blended into natural rubber/polybutadiene carbon black-filled compounds, the compound shows a lower hysteresis and equal or better wet traction [49]. 

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