Brittleness

Brittleness identifies material easily broken, damaged, disrupted, cracked, and/or snapped. Brittleness can result from different conditions such as from drying, plasticizer migration, etc. Brittle materials exhibit tensile S-S behaviors different from the usual S-S curves. Specimens of such materials fracture without appreciable material yielding. They lack toughness. Their brittle point is the highest temperature at which a plastic or elastomer fractures in a prescribed impact test procedure. 

Plastics that are brittle frequently have lower impact strength and higher stiffness properties. A major exception is reinforced plastics. The tensile S-S curves of brittle materials often show relatively little deviation from the initial linearity, relatively low strain at failure, and no point of zero slope. Different materials may exhibit significantly different tensile S-S behavior when exposed to different factors such as the same temperature and strain rate or at different temperatures. 

A brittleness temperature value is used. It is the temperature statistically calculated where 50% of the specimens would probably fail 95% of the time when a stated minimum number are tested. The 50% failure temperature may be determined by statistical calculations. 

Temperature influences the S-S curve. With a decrease in temperature the yield stress and strain usually decreases or the strain rate decreases. Point D corresponds to specimen fracture/failure. It represents the maximum elongation of the material specimen its coordinates are called the ultimate, or failure strain and stress. As temperature decreases the ultimate elongation usually decreases or the strain rate increases. 

Crazing is also called hairline craze. They can be fine, thin, tiny type cracks that may extend in an unreinforced or reinforced plastic network 

Alkyds cure through a reaction of the unsaturated fatty acid component with oxygen in the atmosphere. Once the coating has dried, the reaction does not stop but continues to crosslink. Eventually, this leads to undesirable brittleness as the coating ages, leaving the coating more vulnerable to, for example, freeze-thaw stresses. 

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CH2=CHC = CCH = CH2. a colourless liquid which turns yellow on exposure to the air it has a distinct garlic-like odour b.p. 83-5°C. Manufactured by the controlled, low-temperature polymerization of acetylene in the presence of an aqueous solution of copper(I) and ammonium chlorides. It is very dangerous to handle, as it absorbs oxygen from the air to give an explosive peroxide. When heated in an inert atmosphere, it polymerizes to form first a drying oil and finally a hard, brittle insoluble resin. Reacts with chlorine to give a mixture of chlorinated products used as drying oils and plastics. 

C, b.p. 907"C, d 713. Transition element occurring as zinc blende, sphalerite (Zn,Fe)S calamine or smithsonite (ZnCO j), willemite (Zo2Si04), franklinite (ZnFe204). Extracted by roasting to ZnO and reduction with carbon. The metal is bluish-white (deformed hep) fairly hard and brittle. Burns... 

The mechanical properties of waxes and solid paraffins are of considerable importance for most applications and numerous tests have been developed for characterizing the hardness, the brittleness, and resistance to rupture. 

This test attempts to characterize the brittleness of bitumen at low temperatures. It consists of measuring the temperature at which fissures appear on a bitumen film spread on a blade as it is repeatedly flexed. This test is delicate and of questionable reliability, but it is currently the only one that allows the elastic behavior of bitumen on decreasing temperature to be characterized. It is standardized in France (T 66-026). 

Fault traps which are the result of brittle crustal deformations... 

As discussed in Section 2.0 (Exploration), the earth s crust is part of a dynamic system and movements within the crust are accommodated partly by rock deformation. Like any other material, rocks may react to stress with an elastic, ductile or brittle response, as described in the stress-strain diagram in Figure 5.5. 

If a rock is sufficiently stressed, the yield point will eventually be reached. If a brittle failure is initiated a plane of failure will develop which we describe as a fault. Figure 5.6 shows the terminology used to describe normal, reverse and wrench faults. 

Whereas faults displace formerly connected lithologic units, fractures do not show appreciable displacement. They also represent planes of brittle failure and affect hard... 

These lab tests were done to gain a specific data base for such a brittle material compared to the normal steels used for the manufacturing of pressure equipments. In any case the application of AE was only possible due to the rapid development of the data processing and the new state-of-the-art equipment where this technique is built in.(3)... 

As it was determined by the test, the stretch diagram at the uniaxial load carrying ability of the carbon plastic UKN-5000 is almost linear until the destruction point. The samples are breaking brittle, and the relative deformation is small (E < 2%). 

Modelling for Fatigue and Fracture Prediction of Brittle and Elasto-Plastic Materials Using Acoustic Emission Technics. 

It is very important, from one hand, to accept a hypothesis about the material fracture properties before physical model building because general view of TF is going to change depending on mechanical model (brittle, elasto-plastic, visco-elasto-plastic, ete.) of the material. From the other hand, it is necessary to keep in mind that the material response to loads or actions is different depending on the accepted mechanical model because rheological properties of the material determine type of response in time. The most remarkable difference can be observed between brittle materials and materials with explicit plastic properties. 

Figure 3. Brittle material AE responses as count velocity N and logarithm spectrum log (S) characteristics of the process...

Figure 5. Amplitude-phase characteristics of the model for visco-elasto-plastic (left column) and brittle (right column) materials 1- spectrum responses 2- TF models.

Figure 6. Location of poles and zeros for visco-elasto-plastic material (left) and brittle material (right) under loading close to fiacture.

The material is brittle. There are relatively large radii to be obeyed to enable the vacuum envelope to withstand atmospheric pressure, and tubes must be handled carefully. 

Due to the absorbed photon energy in the moment of the beam admission the particles and the substrate surface warm up very fast. As a consquence of the thermal induced stresses between the relative brittle hard particles, some particles brake apart and, because of the released impulse energy, they are ejected out of the effective beam zone, transmission... 

The tensile strength in the joint part shown Fig.ll has less than the maetrial strength. As for this, joint strength is thought to be a decrease more than the strength of Ti because of an increase in the intermetallic compound of TiC that a little brittle. 

Substances in this category include Krypton, sodium chloride, and diamond, as examples, and it is not surprising that differences in detail as to frictional behavior do occur. The softer solids tend to obey Amontons law with /i values in the normal range of 0.5-1.0, provided they are not too near their melting points. Ionic crystals, such as sodium chloride, tend to show irreversible surface damage, in the form of cracks, owing to their brittleness, but still tend to obey Amontons law. This suggests that the area of contact is mainly determined by plastic flow rather than by elastic deformation. 

Under compression or shear most polymers show qualitatively similar behaviour. However, under the application of tensile stress, two different defonnation processes after the yield point are known. Ductile polymers elongate in an irreversible process similar to flow, while brittle systems whiten due the fonnation of microvoids. These voids rapidly grow and lead to sample failure [50, 51]- The reason for these conspicuously different defonnation mechanisms are thought to be related to the local dynamics of the polymer chains and to the entanglement network density. 

The deposition of organic films by plasma polymerization is an important application of non-thennal plasmas 1301. Plasma polymers are fonned at the electrodes and the walls of electrical discharges containing organic vapours. Oily products, soft soluble films as well as hard brittle deposits and powders are fonned. The properties of plasma... 

Arsenic and antimony resemble phosphorus in having several allotropic modifications. Both have an unstable yellow allotrope. These allotropes can be obtained by rapid condensation of the vapours which presumably, like phosphorus vapour, contain AS4 and Sb4 molecules respectively. No such yellow allotrope is known for bismuth. The ordinary form of arsenic, stable at room temperature, is a grey metallic-looking brittle solid which has some power to conduct. Under ordinary conditions antimony and bismuth are silvery white and reddish white metallic elements respectively. 

The precautions stated are to avoid uptake of oxygen, nitrogen and other impurities which render the metal brittle the excess magnesium and magnesium chloride can be removed by volatilisation above 1300 K. 

The metal looks like iron it exists in four allotropic modifications, stable over various temperature ranges. Although not easily attacked by air. it is slowly attacked by water and dissolves readily in dilute acids to give manganese(II) salts. The stable form of the metal at ordinary temperatures is hard and brittle—hence man ganese is only of value in alloys, for example in steels (ferroalloys) and with aluminium, copper and nickel. 

Pig-iron or cast iron contains impurities, chiefly carbon (up to 5 ). free or combined as iron carbides. These impurities, some of which form interstitial compounds (p. I I3i with the iron, make it hard and brittle, and it melts fairly sharply at temperatures between 1400 and 1500 K pure iron becomes soft before it melts (at 1812 K). Hence cast iron cannot be forged or welded. 

Dichloramine-T. Dilute 80 ml, of freshly prepared 2N sodium hypochlorite soluticMi (preparation, p. 525) with 80 ml. of w ter, and then add with stirring 5 g. of finely powdered toluene-p-sulphonamide, a clear solution being rapidly obtained. Cool in ice-water, and then add about 50 ml. of a mixture of equal volumes of glacial acetic acid and water slowly with stirring until precipitation is complete the dichloro-amide separates at first as a fine emulsion, which rapidly forms brittle colourless crystals. Filter off the latter at the pump, wash well with... 

These are relatively infusible, brittle materials that are insoluble in most solvents. 

Raise the temperature gradually to 200-250° until the mass finally forms large bubbles and puffs up into a voluminous mass. At this point allow the beaker to cool. Remove the brittle mass from the beaker as completely as possible and powder it in a mortar. 

Sulfur is pale yellow, odorless, brittle solid, which is insoluble in water but soluble in carbon disulfide. In every state, whether gas, liquid or solid, elemental sulfur occurs in more than one allotropic form or modification these present a confusing multitude of forms whose relations are not yet fully understood. 

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