Evaluation of technical vs economic decisions in rail grinding
Rail is a significant capital asset for railway companies. It contributes more than half of the capital assets of railway infrastructure. Recent rail inspection data using Ultrasonic rail testing has shown increasing number of rail defects, failures and causing disruptions to rail services. This cost can be further increased when the track quality is poor. In recent years, railroads have been purchasing over 500,000 tons of rails per year at an estimated total cost of US $1.25 billion for replacement of worn out and degraded rails. Rail grinding is considered as viable means in reducing the impacts of rail defects and failures. Rail grinding can result in improved curving performance (wheel/rail interaction) and prevents crack initiation and propagation of surface cracks due to RCF. This paper focuses on analysis of rail degradation process and development of mathematical model considering technical and economic decisions in rail grinding to rail infrastructure owners.
Finite element modelling of the rail gauge corner and underhead radius stresses under heavy axle load conditions
Highly localized stresses generated at the gauge corner of the outer rail cause fatigue cracking. The longitudinal bending stresses in the rail underhead radius position are of special interest, as tension spikes have been identified at this location during in-track measurements under high axle load conditions. The tension spike is a result of vertical and lateral head bending on the web. This effect is highly localized and is additional to the stresses generated due to vertical and lateral bending of the whole rail profile (the so-called global bending). This study examined contact and bending stresses by modelling the rail on a discrete foundation using finite elements and by considering the loading to be a fully slipping elliptical Hertzian contact patch. The analysis revealed that the tensile longitudinal stress was highly dependent on several service conditions: the contact patch offset from the rail centreline, the ratio of lateral (L) to vertical (V) loads, the direction of lateral traction, foundation stiffness and seasonal temperature variations. The tension spike increases, and the depth below the contact surface at which the stresses become tensile reduces, as the contact patch offset and/or the L/V ratio increases. Both these enhance the tendency for rolling contact fatigue cracks to turn downwards and become transverse defects. This is because an increase in tensile bending stresses together with both residual and thermally induced stresses can facilitate cracks to turn perpendicular to the tensile stresses once they reach a critical length. Shear traction towards the gauge corner was found to be the most damaging phenomenon.
Early Missionaries and the Ethnolinguistic Factor During the ‘Invention of Tribalism’ in Zimbabwe
There is evidence from across the disciplines that at least some of the contemporary regional names of African tribes, dialects and languages are fairly recent inventions in historical terms. This article offers some evidence from Zimbabwe to show that missionary linguistic politics were an important factor in this process. The South African linguist Clement Doke was brought in to resolve conflicts about the orthography of Shona. His Report on the Unification of the Shona Dialects (1931) shows how the language politics of the Christian denominations, which were also the factions within the umbrella organization the Southern Rhodesia Missionary Conference, contributed quite significantly to the creation and promotion of Zezuru, Karanga and Manyika as the main groupings of dialects in the central area which Doke later accommodated in a unified orthography of a unified language that was given the name Shona. While vocabulary from Ndau was to be incorporated, words from the Korekore group in the north were to be discouraged, and Kalanga in the West was allowed to be subsumed under Ndebele. Writing about sixty years later, Ranger focusses more closely on the Manyika and takes his discussion to the 1940s, but he also mentions that the Rhodesian Front government of the 1960s and 1970s deliberately incited tribalism between the Shona and the Ndebele, while at the same time magnifying the differences between the regional divisions of the Shona, which were, in turn, played against one another as constituent clans. It would appear then that, for the indigenous Africans, the price of Christianity, Western education and a new perception of language unity was the creation of regional ethnic identities that were at least potentially antagonistic and open to political manipulation. Through many decades of rather unnecessary intellectual justification, and as a result of the collective colonial experience through the churches, the schools and the workplaces, these imposed identities, and the myths and sentiments that are associated with them, have become fixed in the collective mind of Africa, and the modern nation states of the continent now seem to be stuck with them. Missionaries played a very significant role in creating this scenario because they were mainly responsible for fixing the ethnolinguistic maps of the African colonies during the early phase of European occupation. To a significant degree, these maps have remained intact and have continued to influence African research scholarship.