Impact energy curve

An interesting consequence of the above considerations is the prediction that f-impact energy curves should be greatly flattened in impact machines having small diameter strikers. This prediction is based on the expectation that Pcr does not depend on h or... 

Figu re 8.13 Temperature dependence of the Charpy V-notch impact energy (curve A) and percent shear fracture (curve B) for an A283 steel. 

Anisotropy of these materials may also be shown by V-notch Charpy impact tests. Since size effects are known to be critical in this type test, standard size specimens were used, thereby eliminating the thin core tank plat( . Charpy V impact energy curves obtained with specimens and notches cut from various orientations from commercial plate and from a plate fabricated l)y the developed procedure are showm in Fig. 5-24 [133]. Differences in both the energy values and transition temperatures are apparent for the arious orientations. These differences are reduced by the developed fabrication procedure. 

Fig. 5-24. Impact energy curves for Zircaloy-2 fabricated by two techniques.

Fig. 2. Typical impact energy vs adhesion (10 is high, 0 is no adhesion) curve obtained from the mean break height test carried out at 2I°C with a 2.27 kg ball on 30-cm square laminates. Mean break height dramatically declines when adhesion is at high levels.

Fig. 4. Electron-impact efficiency curves at m/e = 32 and rri/e = 16 for a supersonic beam of O2. Arrows indicate the literature values72 of the ionization energy of O2 and of the appearance energy of 0+.

Fig. 5. Electron-impact efficiency curves at (a) m/e = 41 and m/e = 13, and (b) m/e = 14, recorded at a lab angle of 30° during the CMB study of the reaction 0(3P) + C2H2 at Ec = 12.6kcalmol 1. The thick arrow marks the electron energy (17eV) used for product angular and TOF distribution measurements. In (b) the thin arrow marks the literature value50 of the IE of triplet methylene (see text).

In this chapter we focus attention on the efficiency of ionization, the ionization cross section, and consider some recent experimental measurements and theoretical studies of the ionization process. A sketch of electron impact ionization curves, the variation of the ionization cross section as a function of the electron energy, using CO as an example, are shown in Figure 1. The mass spectrum, collected at the electron energy corresponding to the maximum in the ionization cross section, is also shown, although there will be no further discussion of fragmentation in this... 

Toughness may be defined by impact energy or work of fracture, the area under the load-strain curve, which provides a practical combination of strength and elongation at break. 

On the basis of experimental evidence and theoretical considerations, A B conclude that the frequency curve (f vs impact energy) should be narrowest for h = hcr and still be narrow... 

Mechanical Properties of Cast Resins. The toughness of the cross-linked polymers was determined by the area under the stress-strain curve and by the energy required to fracture. The fracture or impact energy, expressed in inch-pounds, was measured by a simple but reliable test— the Gardner impact—which consists of striking cured specimens with a 2-lb round-nose rod, %-inch in diameter, from various distances the test specimens were discs 0.1 inch thick by 2.0 inches in diameter. 

Fig. 4.29. Angle-resolved positronium formation cross sections, relative to those at 0°, for positron-argon and positron-krypton collisions at impact energies of 75 eV, 90 eV and f20 eV (Falke et al., 1997). The curves are from the theoretical work of McAlinden and Walters (1994). Reprinted from Journal of Physics, B30, Falke et al., Differential Ps-formation and impact-ionization cross sections for positron scattering on Ar and Kr atoms, 3247-3256, copyright 1997, with permission from IOP Publishing.

Ions may also be produced with kinetic energy if there is a maximum in the potential energy curve for the stable excited state, as pointed out by Hippie and Stevenson 23 Xhe last possibility corresponds to an activation energy for the recombination reaction see Section 4.2.1). Measurement of kinetic energy, or proof that the ions are formed at rest, is essential for the reliable deduction of dissociation energies from the electron impact method. 

The electron impact results for carbon monoxide will now be discussed in some detail, as an illustration of the method applied to a diatomic molecule. The ion current against electron energy curves for C " from CO and for O from GO are given in Figure 5.2A.L It will be seen that the initial appearance potential of G + is well defined at 20-9 0 2 eV, and that the appearance potential of 0 is at almost exactly the same voltage, given by Hagstrum... 

In practice one either measures the angular distribution of the scattered electrons and plots f(K) as a function of K, and extrapolates the resulting curve to K = 0 and fits this curve to the known optical oscillator strength /(O), or one carries out the experiment at high impact energy and low (preferably zero) scattering angle and assumes that the optical limit has been achieved. 

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