Mechanical stress, steels

Corrosion also occurs as a result of the conjoint action of physical processes and chemical or electrochemical reactions (1 3). The specific manifestation of corrosion is deterrnined by the physical processes involved. Environmentally induced cracking (EIC) is the failure of a metal in a corrosive environment and under a mechanical stress. The observed cracking and subsequent failure would not occur from either the mechanical stress or the corrosive environment alone. Specific chemical agents cause particular metals to undergo EIC, and mechanical failure occurs below the normal strength (5aeld stress) of the metal. Examples are the failure of brasses in ammonia environments and stainless steels in chloride or caustic environments. 

Lead-silver is primarily used in seawater and strong chloride-containing electrolytes. PbAg anodes are particularly suitable for use on ships and in steel-water constructions, especially as they are relatively insensitive to mechanical stresses. The original alloy developed by Morgan [8,9] consists of 1% Ag and 6% Sb, with the remainder Pb. It is represented as alloy 1 in Table 7-2. A similar alloy developed by Applegate [10] has 2% Ag and the remainder Pb. Another alloy... 

While a metal or alloy may be selected largely on the basis of its mechanical or physical properties, the fact remains that there are very few applications where the effect of the interaction of a metal with its environment can be completely ignored, although the importance of this interaction will be of varying significance according to circumstances for example, the slow uniform wastage of steel of massive cross section (such as railway lines or sleepers) is of far less importance than the rapid perforation of a buried steel pipe or the sudden failure of a vital stressed steel component in sodium hydroxide solution. 

Today boiler vessels are usually fabricated from special boiler plate and firebox steels of varying thickness, while their auxiliaries (supplementary equipment) and appurtenances (boiler accessories and instruments, especially those employed for safety reasons) may be produced from any of several different constructional metals, alloys, and other materials, including cast iron, copper alloys, stainless steels, and so forth. Tubes and tube plates may be variously constructed of carbon steel, low-alloy steels, or special alloy steels, with each design providing for particular required levels of thermal and mechanical stress and corrosion resistance. The overall boiler plant system may have a life expectancy in excess of 50 to 60 years, although individual components may need to be replaced periodically during this period. 

CVD diamond films are not stable on mechanically stressed metals which contain iron, chromium, or nickel and hence steel. In this case films of boron nitride are an alternative. 

At intermediate stress intensity levels (stage 2) the crack propagation rate shows a plateau velocity Vpiateau that is virtually independent of the mechanical stress, but depends on the alloy/environment interface and the the rate-limiting environmental processes such as mass transport of the aggressive species to the crack tip. The plateau in a quenched and tempered low-alloy steel of 1700 MPa yield strength in deaerated water at 100°C... 

The N 300 series is characterized by a wide variety of rubber blacks, covering about 10 different types. As mentioned above, fme-particle active blacks are used for rubber components that need to withstand significant levels of mechanical stress, e.g. tire treads. Semi-active blacks, on the other hand, are used in the tire carcass but also in technical rubber components, from screen and door seals to floor mats. Tires also contain other special carbon blacks, for instance, so-called adhesion blacks for improving radial steel belt adhesion, conductive blacks or inactive blacks for higher filler load rates [4.26]. 

One crucial aspect is the large difference in the thermal expansion coefficients of stainless steel and SiOx (more than 10-fold, Table 5.4.1). As a result, temperature changes create significant stress at the interface between the steel and the SiOx. During operation, mechanical stress is introduced in addition to the thermal stress. To prevent the formation of cracks, the internal stress of the SiOx layer has to be chosen so that the SiOx remains under compressive stress under all operating conditions. Typically, the internal stress needs to be compressive and on the order of 100 MPa. Stability against cracks is favored by a high density of the deposited layer [9],... 

A multipurpose torque sensor was developed by FAST Technology. The specifications of this sensor allows its use in electrically assisted steering systems. FAST Technology developed a method for permanently magnetizing ferromagnetic steel shafts. Fig. 7.12.11 shows the shape of the toroidal magnetic field. The magnetic field beside the shaft varies with the mechanical stress on the shaft. A sensor... 

Pipeline transportation of liquid hydrogen is realized on a small scale and short range. Stainless steel is usually taken for the inner line with low heat conduction spacers as a support in the vacuum jacket. The Kennedy Space Center in Florida uses an LH2 and LOX pipeline of 500 m length with an irmer pipe diameter of 0.15 m. Flow rates achieved are up to 250 LH2 per minute and 100 m LOX per minute, respectively [12]. Transfer is realized by applying pressure, no pumps. Major concerns besides heat leakage is the mechanical stress imposed on the irmer line due to contraction / expansion, pressure oscillations upon cooldown, or two-phase flow. 

This type of attack does not require any specific environment to take place, since it can take place simply in neutral or acidic wet environments. Failure due to hydrogen is named hydrogen embrittlement since it leads to a brittle-Uke fracture surface. Indeed, the ductility of the bulk metal does not change, but the propagation of the crack is due to the mechanical stresses induced in the lattice by hydrogen accumulated near the crack tip. If hydrogen is present in the metal lattice before the application of loads a delayed fracture may occur, i. e. the steel does not fail when the load is applied, but after a certain time. 

Corrosion-resistant and wear-resistant materials (e.g., stainless steel and in special cases suitable plastics) have to be used for the equipment required to produce and apply waterborne paints. This applies to production vessels, storage and transportation vessels, to the feed system used for application (e.g., closed circuit tanks, pipelines, and pumps) all of which must be able to withstand chemical mechanical stress. The use of corrosion-resistant materials for the spraying equipment is also advantageous. 

You can indeed make a super-strong fiber, even stronger than steel, from a polymer, but the polymer must be converted into a special liquid-crystalline state which is really a variety of the viscous state. If you think of a viscous polymer as of some polymeric liquid , then a liquid-crystalline polymer can be regarded as an anisotropic polymeric liquid . The anisotropy occurs spontaneously, with no help from outside (such as orientating fields, mechanical stresses or whatever). 

Since a frequently repeated minimum stress amplitude is needed to initiate corrosion fatigue in stainless steels in passivating solutions, it must be assumed that this load limit is connected with the mechanical stress capacity of passive layers. Only when particularly marked slip starts at one point on the surface will the layer be (racked. At that point, a constantly repetitive process begins, in which a new activation process at the same spot always follows repassivation. Each new passivation process consumes metal, deepens the corrosion, and increases the stress peak until, because of the constantly rising stress, repassivation is no longer possible. The resistance of passive metallic materials under fatigue conditions in electrolytes is therefore largely dependent on three factors ... 

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