Search

The isochromatic strain patterns on the surfaces of mild steel plates containing moving brittle fractures have been determined by using strain birefringent coating and high speed photographic techniques. The major part of these isochromatic patterns may be described by a formula for the isochromatic pattern near a stationary crack in an elastic medium. The variations from this formula are caused by, shock waves in the specimen, inertia effects due to the high velocity of the crack, and yielding near the crack tip. The inertia effects cause a region of biaxial tension ahead of the crack on the plate surface. A. crack model which predicts the extent of the plastic zone near the crack tip has been proposed. The predictions from this model and other theories are compared with experimental estimates of the plastic zone depth. The results of a microstructural examination of fracture surfaces supported Tipper's (1957) explanation of the mechanism for crack propagation.

Where lie the origins of North Korean ideology? When, why, and to what extent did North Korea eventually pursue a path of ideological independence from Soviet Marxism-Leninism? Scholars typically answer these interrelated questions by referencing Korea’s historical legacies, such as Chosŏn period Confucianism, colonial subjugation, and Kim Il Sung’s guerrilla experience. The result is a rather localized understanding of North Korean ideology and its development, according to which North Korean ideology was rooted in native soil and, on the basis of this indigenousness, inevitably developed in contradistinction to Marxism-Leninism. Drawing on Eastern European archival materials and North Korean theoretical journals, the present study challenges our conventional views about North Korean ideology. Throughout the Cold War, North Korea was possessed by a world spirit, a Marxist-Leninist world spirit. Marxism-Leninism was North Korean ideology’s Promethean clay. From adherence to Soviet ideological leadership in the 1940s and 50s, to declarations of ideological independence in the 1960s, to the emergence of chuch’e philosophy in the 1970s and 80s, North Korea never severed its ties with the Marxist-Leninist tradition. On the contrary, this tradition constituted the basic and most fundamental raw material from which North Korean ideology was shaped and developed. The evolution of North Korean ideology was not predetermined by Korea’s historical legacies. Rather, a convergence of historically immediate domestic and international factors led to the emergence of an independent ideology, an ideology that despite its independence from Soviet ideological suzerainty remained situated within a global Marxist-Leninist intellectual space. Though many scholars have argued otherwise, even chuch’e philosophy, the apex of North Korean ideological particularity during the Cold War, was hardly an idealism and instead quite reminiscent of a good old-fashioned Marxist-Leninist materialism.