Technical application of fracture mechanics to thin-walled structures

This paper reviews recent developments in the application of fracture mechanics to such structures as welded steel tanks, ships, and thin-wall pressure vessels, with particular attention to Japanese work. It describes methods for estimating critical crack size and safe working conditions, taking into account such fabrication variables as angular distortion, welding residual stress, prestrain, plate curvature and stress concentration. Whilst most of the paper is devoted to a consideration of the conditions for crack instability, it also discusses crack arrest and gives experimental results for the effect of thickness on both initiation and arrest.     

Dielectric dispersion in a disordered nitrite compound: AgNo2·NH3

A pronounced dielectric dispersion was observed along the a- and c-axes in a disordered nitrite compound of AgNO₂·NH3. The activation energy of 0.32 eV was found for the dielectric relaxation time both along the a-axis and along the c-axis. Phase transition was not observed down to liquid helium temperature.     

Paramagnetic susceptibility and ultrasonic attenuation of itinerant antiferromagnetism above the Neel temperature

Making use of the two-band model of the itinerant antiferromagnetism, we calculate the wave-vector-dependent paramagnetic susceptibility (i.e., the fluctuation propagator of the order parameter) and the ultrasonic attenuation coefficient above the Neel temperatureT _N .We distinguish two regions depending on the degree of the nesting between the electron and the hole bands. The degree of the nesting is characterized byH, which measures the difference of the Fermi radii of the electron and the hole bands. WhenH is less than the critical nestingH*, the fluctuation is of the diffusion type indicating the transition into the commensurate spin density wave (CSDW) state; the fluctuation propagator diverges atT=T _N forq=0 (the paramagnetic susceptibility diverges forq=G _i /2;G _i are the reciprocal lattice vectors) whereq is the wave number vector. WhenH>H*, on the other hand, the fluctuation propagator diverges atT=T _N ,on the sphere in the wave vector space with the radiusq ₀,signalling the transition into the incommensurate spin wave (ISDW) state; the paramagnetic susceptibility diverges now forq=(G _i /2)+q, where |q|=q ₀.The attenuation coefficient is much enhanced due to the spin fluctuation nearT _N . We find that the attenuation coefficient of the longitudinal sound wave diverges atT=T _N as ^–3/2 forHH* and ^–5/2 forH>H*, where =(T/T _N )–1. The latter prediction is in reasonable agreement with the recent measurement of the attenuation coefficient in pure Cr by Imai and Sawada.     

A note on brittle crack deceleration in a structural steel

The deceleration of a brittle crack in a steel is attributed to plastic deformation developed around the crack. The investigation shows that a ductile fibrous crack stops suddenly, but a brittle cleavage crack does sluggishly.

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Résumé La décélération d'une fissure fragile dans un acier est attribuée à la déformation plastique qui se développe autour de cette fissure.L'étude montre qu'une fissure fibreuse et ductile s'arrête brutalement tandis qu'une fissure fragile et de clivage s'arrête lentement.

     

Homo- and copolymerization of ethylene and propylene with a soluble chromium catalyst

Polymerization of ethylene and propylene was carried out with a soluble $\text{Cr(C}{}_{17}\text{H}{}_{35}\text{COO}\text{)}{}_3\text{AlEt}{}_2\text{Cl}$ catalytic system in toluene. The system was found to be active only for ehtylene polymerization. From e.s.r. measurements of the catalytic system combined with some qualitative experiments, the active species was determined to be Cr²⁺. The reason why it should be incapable of polymerization of propylene was also discussed. The catalytic system showed some activity for ethylene-propylene copolymerization to give a random copolymer with a narrow molecular weight distribution.     

Nonaqueous titrimetric analysis of sulfuric and alkylbenzene sulfonic acids in detergent intermediates

A single differential nonaqueous titration method is presented for the analysis of sulfuric and alkylbenzene sulfonic acids in a detergent intermediate material. The organic and sulfuric acids in the sample were quantitatively titrated potentiometrically with standard cyclohexylamine solution. With certain specified sample compositions, approximate sulfuric acid determinations may be made without sample weighing or the use of standardized titrant. The titration is based upon the ratio of the first and second end points of the differential titration curve. Because of its simplicity, the latter method adaption is especially useful for routine control type analyses.     

Determination of water content of granulated detergents

A quick analytical procedure was described for the determination of water content of granulated detergents. A constant weight loss of sample was obtained within 5 min by microwave drying. The weight loss agrees with the water content by the modified distillation method. The coefficient of variation was 0.7%.