Ultimate strain

At this point it is probable that in time even a more elastic liner will be damaged and allow water or whatever else the pipe is carrying to ooze or weep through the wall. As is the case with the yield point of steel pipe, reaching the weep point is not cataclysmic. The pipe can still continue to withstand quite a bit of additional load before it reaches the point of ultimate strain and failure. Recognize that a more substantial, stronger liner can easily extend the weep point. 

Most structural steels of interest begin to yield at strains of about 0.002 or less. The more ductile steels can undergo fairly large strains beyond this point before the onset of strain hardening. Ultimate strain at rupture of mild steel is typically on the order of 0.20 to 0.25, more than 100 times... 

The maximum in the curve denotes the stress at yield av and the elongation at yield v. The end of the curve denotes the failure of the material, which is characterized by the tensile strength a and the ultimate strain or elon gation to break. These values are determined from a stress-strain curve while the actual experimental values are generally reported as load-deformation curves. Thus (he experimental curves require a transformation of scales to obtain the desired stress-strain curves. This is accomplished by the following definitions. For tensile tests ... 

Ullmann reaction, 10 575 Ulmic coals, 6 703 -ulose suffix, for sugars, 4 696 Ultem, 10 217, 218 Ultimate strain, 11 183 Ultimet... 

For example, the required lower bulk electrical resistance and surface contact resistance are directly related to reducing internal power consumption in fuel cells to achieve maximum power output. The requirements of high flexural strength and flexibility (ultimate strain) are important to assure no distortion of fluid fields and no crack in a plate sustained in the large compressive loading when each unit cell is assembled together as a stack. This is particularly important when the thickness of the plate becomes thinner and thinner (can be close to or less than 1 mm [9]) and the dimension of the fluid field becomes smaller and smaller. Whether it is elastic or plastic, the large... 

Figure 6. Young s modulus (a), ultimate stress (b), and ultimate strain (c) as functions of KL content. The numbers in the figure indicate different molecular weights of PEG.

Ultimate properties, tensile strength, and ultimate strain typically decrease with the addition of HPL however, combinations of molecules with strong interaction between amorphous components may also exhibit enhanced ultimate properties. Injection molding produces superior material properties. 

Fig. 1. Ultimate strains e versus gradient of longitudinal velocity e in extension (explanations are given in the text)...

A convenient wav of measuring Tgn is to determine the ultimate strain(at break and the yield ot a specimen as a function of temperature. The intersection of the two curves defines TBq. 

For many applications the resistance of the material to shock loading is an important property. Here we find ourselves, contrary to the previous section, on the very short side of the time scale. For the impact strength the short-term tensile strength as well as the ultimate strain play a role the impact strength is, in fact, the energy needed for rupture at a high rate of deformation, J impact strength accurately and uniquely. 

FIG. 13.84 Generalised ultimate parameters of an elastomer (after Smith, 1962,1964). (A) Logarithmic plot of stress-at-break (a r27i/T) versus reduced time-to-break (fb/dj) for Viton B vulcanisate. Reference temperature for oT is 313 K (40 °C) (B) logarithmic plot of ultimate strain (gbr) versus reduced time to break (fbr/oj) for Viton B vulcanisate reference temperature for oT is 313 K (40 °C) (C) failure envelope for Viton B vulcanisate. 

When thermoplastics are reinforced with short fibres, both stiffness and strength may be increased, but these improvements are accompanied by a reduction of the ultimate strain for high concentrations of fibres [1-5]. This brittle behaviour is incompatible with growing engineering applications in which tlie parts are subjected to cyclic loadings or impacts, as in automotive under-the-hood applications. Thus, very tough nylon thermoplastics with enhanced creep and impact resistances have been produced by the introduction of a rubbery phase to the... 

In Fig. 4 and Fig. 5, flexural modulus and flexural strength of the cured resin depending on the adipic acid content are shown. It is found that flexural modulus of the cured resin decreased as the adipic acid content in the resin was increased. Introduction of adipic acid instead of maleic anhydride implies decrease of unsaturation of the resin. It seems that the decrease of flexural modulus resulted from decreased crosslink density due to lower unsaturation. It is of interest to note that flexural strength, on the contrary, tends to increase as the adipic acid content is increased. It is speculated that the cured resins of higher adipic acid content have more flexible chain and the flexural modulus are low compared with that of the cured resin of lower adipic acid content relatively. But, ultimate strength of the cured resin of higher adipic acid content is superior to the cured resin of lower adipic acid content due to possibly higher ultimate strain. 

Figure 12.10. Ultimate strain of natural rubber vs. filler content. [Adapted, by permission, fiom Sombatsompop N, Sims G L A, Cell. Polym., 15, No.5, 1996, 317-34.]...

The high-speed ultimate strains of all the composites are larger than the control, up to 90% in the extreme case. 

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