Shock load

Plug dow is apphcable for readily degradable wastewaters subject to filamentous bulking. Upstream controls are required to avoid shock loadings. 

Second, deformation twins were observed in metal grains at the damaged surfaces. Deformation twinning cannot result from corrosion but is the consequence of shock loading of the metal, precisely the effects of microjets of water impacting on the metal surface. 

Graphitic corrosion is a slow corrosion process, typically requiring many years to effect significant damage. Complete penetration of thick cross sections has, however, occurred in as little as 2 years in adverse environments. On the other hand, cast iron components can be found in use in Europe after 160 years of service. Although graphitic corrosion causes a substantial reduction in mechanical strength, it is well known that corroded cast iron, when sufficiently supported, may remain serviceable when internal pressure is low and shock loads are not applied. 

Note also that graphitic corrosion may occur preferentially in poorly accessible areas, such as the bottom of pipelines. Trouble-free service of cast iron components does not necessarily indicate that all is well, since components suffering severe graphitic corrosion may continue to operate until an inadvertent or intentional (e.g., pressuretesting) shock load is applied. At this point massive, catastrophic failures can occur. 

After performing the duty, if the velocity of the flywheel drops to Vj then the energy shared by the flywheel while absorbing the shock load... 

This part deals with the specifications, performance, characteristics and behaviour of motors under different operating conditions, their application and selection. It also covers aspects such as shock loading, motors for hazardous locations and open transient conditions in HT motors during a switching sequence. 

Duty cycles Continuous duty (CMR) (S ) Periodic duties Factor of inertia (FI) Pleating and cooling characteristic curves Drawing the thermal curves Rating of short motors Equivalent output of short time duties Shock loading and use of a flywheel... 

What are the characteristic mechanical responses of solids to shock loading This question is most clearly addressed through the relation between stress-volume relations and wave structures. 

Figure 1.1. A typical stress-volume-distance response of solids to high-pressure shock loading.

The jump conditions must be satisfied by a steady compression wave, but cannot be used by themselves to predict the behavior of a specific material under shock loading. For that, another equation is needed to independently relate pressure (more generally, the normal stress) to the density (or strain). This equation is a property of the material itself, and every material has its own unique description. When the material behind the shock wave is a uniform, equilibrium state, the equation that is used is the material s thermodynamic equation of state. A more general expression, which can include time-dependent and nonequilibrium behavior, is called the constitutive equation. 

The objective in these gauges is to measure the time-resolved material (particle) velocity in a specimen subjected to shock loading. In many cases, especially at lower impact pressures, the impact shock is unstable and breaks up into two or more shocks, or partially or wholly degrades into a longer risetime stress wave as opposed to a single shock wave. Time-resolved particle velocity gauges are one means by which the actual profile of the propagating wave front can be accurately measured. 

The PVFj gauge has been calibrated up to 4 GPa (Bauer, 1984) for both shock loading and release. Graham and Lee (1986) have extended these calibration studies to about 20 GPa, and have measured both a shock loading and release profile in sapphire at 12 GPa, as indicated in Fig. 3.15. 

Bauer, F. (1982), Behavior of Ferroelectric Ceramics and PVF2 Polymers Under Shock Loading, in Shock Waves in Condensed Matter—1981 (edited by W.J. Nellis, L. Seaman, and R.A. Graham) American Institute of Physics, New York, pp. 251-267. 

Chhabildas, L.C. and D.E. Grady (1984), Shock Loading Behavior of Fused Quartz, in Shock Waves in Condensed Matter—1983 (edited by J.R. Asay, R.A. Graham, and G.K. Straub), Elsevier Science, New York, pp. 175-178. 

Rosenberg, Z., and Partom, Y. (1984), Direct Measurement of Temperature in Shock Loaded Polymethlmetacrylate with Very Thin Copper Thermisters, in Shock... 

In this chapter, we will review the effects of shock-wave deform.ation on material response after the completion of the shock cycle. The techniques and design parameters necessary to implement successful shock-recovery experiments in metallic and brittle solids will be discussed. The influence of shock parameters, including peak pressure and pulse duration, loading-rate effects, and the Bauschinger effect (in some shock-loaded materials) on postshock structure/property material behavior will be detailed. 

Shock loading in most metals and alloys produces greater hardening than quasi-static deformation to the same total strain, particularly if the metal undergoes a polymorphic phase transition, such as is observed in pure iron [1]-[10]. Figure 6.1 compares the stress-strain response of an annealed... 

Figure 6.1. Stress-strain behavior of shock-loaded copper compared to the annealed starting condition illustrating an enhanced flow stress following shock-wave deformation compared to quasi-static deformation (based on an equivalent strain basis).

This phenomena has been attributed to the very high strain rates associated with shock loading and the subsonic restriction on dislocation velocity requiring the generation and storage of a larger dislocation density during the shock process than for quasi-static processes [1], [2], [12],... 

---