Knock damage

R.J. Nates and A.D.B. Yates, Knock Damage Mechanisms in Spark-Ignition Engines, SAE Technical Paper 942064 (1994). 

In any case, I eventually recovered (and so did Jerry), but my immune system must have suffered serious damage, which manifested itself three years later, when I collapsed in my office one day and was found to be bleeding internally from a form of rare stomach cancer, which necessitated major surgery but was fortunately localized. I again recovered and have had no further difficulties since. Whether weakening and knocking out my immune system to overcome the previous problems had any effect is not clear, but it could have been a factor. Despite my health problems I was able to continue my work without much interruption, and the scientific productivity of my group has not... 

Radiation Damage. It has been known for many years that bombardment of a crystal with energetic (keV to MeV) heavy ions produces regions of lattice disorder. An implanted ion entering a soHd with an initial kinetic energy of 100 keV comes to rest in the time scale of about 10 due to both electronic and nuclear coUisions. As an ion slows down and comes to rest in a crystal, it makes a number of coUisions with the lattice atoms. In these coUisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms which are displaced by an incident ion are caUed primary knock-on atoms (PKA). A PKA can in turn displace other atoms, secondary knock-ons, etc. This process creates a cascade of atomic coUisions and is coUectively referred to as the coUision, or displacement, cascade. The disorder can be directiy observed by techniques sensitive to lattice stmcture, such as electron-transmission microscopy, MeV-particle channeling, and electron diffraction. 

Brick buildings severely damaged, 75% external wall collapse. Fired heaters badly damaged. Storage tanks leak from base. Threshold for eardrum damage to people. Domino or knock-on radius. Pipe bridges may move. 

Always provide a suitable knockout pot ahead of the jets. Water droplets can quickly damage a jet. The steam should enter the pot tangentially. Any condensate leaves through a steam trap at the bottom. It is a good idea to provide a donut baffle near the top to knock back any water creeping up the vessel walls. 

SIMS is inherently damaging to the sample since ion bombardment removes some material from the surface. However, other forms of damage may also occur. These include surface roughening, knock-on effects, preferential sputtering, decomposition, and implantation of source ions [49]. 

Figure 10-11. Condensate in the steam—the result of too few steam traps-knocked off the impingement plate and damaged the calandria tubes.

Metals are immune to radiation damage by ionization. This is also a consequence of the free electron structure. Fast charged particles and ionizing rays can knock off electrons from the atoms they encounter. In metals, the positive vacancies so formed are immediately filled up by the electron gas, leaving no sign of damage apart from a small amount of heat. 

The potential for knock-on effects resulting from equipment damage should be considered. 

Its effects on the body are widespread. Inhalation of the vapor is the most common mode of entry, and when the chemical is inhaled in sufficient concentration, it has an immediate effect on the brain (hence the high that Harry was partial to) and ultimately, over longer periods, it causes damage to the liver and kidneys. Now it so happened, that although Harry had been working for five years with concentrations of carbon tetrachloride above the recommended limit, any obvious damage to his brain, liver, and kidneys at that time was no more than he would have derived from knocking back a six pack of beer several times a week. So what was the trouble ... 

Gasoline with too low an octane number can cause knocking in the engine of a car, when the fuel ignites too easily and burns in an uncontrolled manner. Knocking lowers fuel efficiency, and it can damage the engine. 

The damage continued to the top of the furnace, but screen and superheater tubes were not damaged. One soot blower was blown onto the roof of an adjoining building and another knocked loose. 

If a surface reaction is to involve more than monolayer-chemisorption, then the species adsorbed on the surface must be able to migrate into the second and deeper layers forming new chemical bonds and often new molecular species. This is step 3, product formation, and it often requires an activation mechanism to proceed, i.e., a monolayer is formed and the reaction stops unless the substrate is held at elevated temperature or there is ion or electron bombardment. Damage-enhanced diffsusion, knock-on collisions, and bond breaking may promote the reaction in the presence of ion bombardment. Although the precise mechanisms are unclear, it is certain that electron and ion bombardment cause step 3 to occur in some instances where the chemical reaction does not proceed in the absence of radiation. 

Various fuel grades are designed to guarantee knock-free operation. Knocking combustion can damage the engine and can result in serious power loss if allowed to persist. 

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