Catastrophic shock

The benign shock paradigm is clearly an approximation, but one that has proven very effective. The catastrophic shock paradigm corresponds to the known physical, mechanical, and chemical processes, but its characteristics have proven difficult to quantify. 

A description of shock-compressed solids in terms of the catastrophic shock paradigm was stated many years ago by Kormer [68K02] as ... 

This statement represents an apt, terse description of the elastic-plastic shock-deformation process within the catastrophic shock paradigm. 

We can anticipate that the highly defective lattice and heterogeneities within which the transformations are nucleated and grow will play a dominant role. We expect that nucleation will occur at localized defect sites. If the nucleation site density is high (which we expect) the bulk sample will transform rapidly. Furthermore, as Dremin and Breusov have pointed out [68D01], the relative material motion of lattice defects and nucleation sites provides an environment in which material is mechanically forced to the nucleus at high velocity. Such behavior was termed a roller model and is depicted in Fig. 2.14. In these catastrophic shock situations, the transformation kinetics and perhaps structure must be controlled by the defective solid considerations. In this case perhaps the best published succinct statement... 

These observations were the basis for the proposal that polymers, like ionic crystals, exhibit shock-induced polarization due to mechanically induced defects which are forced into polar configurations with the large acceleration forces within the loading portion of the shock pulse. Such a process was termed a mechanically induced, bond-scission model [79G01] and is somewhat supported by independent observations of the propensity of polymers to be damaged by more conventional mechanical deformation processes. As in the ionic crystals, the mechanically induced, bond-scission model is an example of a catastrophic shock compression model. 

A great deal of experimental work has also been done to identify and quantify the ha2ards of explosive operations (30—40). The vulnerabiUty of stmctures and people to shock waves and fragment impact has been well estabUshed. This effort has also led to the design of protective stmctures superior to the conventional barricades which permit considerable reduction ia allowable safety distances. In addition, a variety of techniques have been developed to mitigate catastrophic detonations of explosives exposed to fire. 

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. 

On initial start-up and shut-down the heat exchanger can be subjected to damaging thermal shock, overpressure or hydraulic hammer. This can lead to leaky tube-to-tubesheet joints, damaged expansion joints or packing glands because of excessive axial thermal, expansion of the tubes or shell. Excessive shell side flowrates during the "shake down can cause tube vibrations and catastrophic failure. 

Employers, at a minimum, must have an emergency action plan that will facilitate the prompt evacuation of employees when there is an unwanted release of a highly hazardous chemical. This means that the employer s plan will be activated by an alarm system to alert employees when to evacuate, and that employees who are physically impaired will have the necessary support and assistance to get them to a safe zone. The intent of these requirements is to alert and move employees quickly to a safe zone. The use of process control centers or buildings as safe areas is discouraged. Recent catastrophes indicate that lives are lost in these structures because of their location and because they are not necessarily designed to withstand over-pressures from shock waves resulting from explosions in the process area. 

In this chapter the scope of the subject the fluidlike deformation of shock-compressed solids modeling the shock as benign or catastrophic the origins of shock-compression science the pressure scale of events the plan of the present work. 

Finally, the phenomenon of shock-induced polarization represents perhaps the most distinctive phenomenon exhibited by shock-compressed matter. The phenomenon has no counterpart under other environments. The delineation of the details of the phenomenon provides an unusual insight into shock-deformation processes in shock-loading fronts. Description of the phenomenon appears to require overt attention to a catastrophic description of shock-compressed matter. In the author s opinion, a study of shock-induced polarization represents perhaps the most intriguing phenomenon observed in the field. In polymers, the author has characterized the effect as an electrical-to-chemical investigation [82G02]. 

At times it is necessary to have a feel for overpressure as it relates to shock front velocity [49]. (See Figure 7-60). Note especially that for a reasonable detonation velocity the peak overpressure could be in the range of 700 to 1000 psi and when referenced to Figure 7-60, the extent of industrial damage would be catastrophic. The use of scaled distance is illustrated in Ref. [41]. 

Anaphylaxis is the most dramatic and potentially catastrophic manifestation of allergic disorders. It can affect virtually any organ including the cardiovascular system. Cardiovascular collapse and hypotensive shock in anaphylaxis have been attributed to peripheral vasodilation, enhanced vascular permeability and plasma leakage, rather than any direct effect on the myocardium. However, there is increasing experimental and clinical evidence that the human heart is a site and target of anaphylaxis. 

Monitoring changes in UOP can help diagnose the cause of ARF. Acute anuria (less than 50 mL urine/day) is secondary to complete urinary obstruction or a catastrophic event (e.g., shock). Oliguria (400 to 500 mL urine/day) suggests prerenal azotemia. Nonoliguric renal failure (more... 

Petroleum and chemical related hazards can arise from the presence of combustible or toxic liquids, gases, mist, or dust in the work environment. Common physical hazards include ambient heat, bums, noise, vibration, sudden pressure changes, radiation, and electric shock. Various external sources, such as chemical, biological, or physical hazards, can cause work related injuries or fatalities. Although all of these hazards are of concern this book primarily concentrates on fire and explosions hazards that can cause catastrophic events. 

One of the big differences in organizing this type of aid from the system of field surgery, is that the deployment and functioning of the mass hospitalization emergency system is unexpected and interferes with normal hospital work routines [11]. More than 20 years ago J.E. Waeckerle wrote Catastrophe at first is scary and shocking, later confuses and creates confusion in all areas, where to start from and what to do [12]. 

Samples are mechanically brittle at sufficiently low temperatures, normally below the T . They also are seen to be brittle at very short times. Thus, a short sharp impact can shatter a material at room temperature if it is naturally below its Tg or if the material has been frozen. Materials that are rubbery at room temperature can be sufficiently brittle at low temperatures to fail catastrophically. In the space shuttle Challenger, an explosion was caused by uncombusted fuel escaping when a rubber O-ring was rendered brittle by low-temperature weather. The key in all of these examples is the speed of molecular motion. For energy to be dissipated, a stress can cause a local increase in molecular motion. If that route is denied by time constraints (e.g., a fast shock) or temperature control (molecular immobility), then a crack is the only way energy can leak out. Cold toffee... 

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