Influence of roughness on contact interface in fretting under dry and boundary lubricated sliding regimes

This paper presents experimental results of wear process under dry and boundary lubricated metallic (AISI 1034/AISI 52100) contacting bodies with different surfaces morphologies subjected to a wide range of kinematic fretting conditions. Analysis of damage mode observed under such fretting conditions is elucidated in context of surfaces morphologies therefore associated with surface manufacturing processes. Various surface topographies due to specific machining processes (cutting and abrasive modes) have been investigated. Under boundary lubricated (ZDDTP zinc-dialkyl-dithiophosphate) fretting contact paradoxally has a high coefficient of friction at the transition between Partial and Full slip sliding regime. This paper attempts to bridge the gap between the damage mode, sliding conditions and surface roughness to provide an approach to evaluate the surface finishing as a factor in friction and wear damage processes

Konflikt w Mali. Rebelia Tuaregów, islamiści i międzynarodowa interwencja

The paper discusses the origins and course of the current crisis in Mali. The author outlines the reasons for the structural weakness of Mali, resulting from the shape of the borderline drawn at the time of decolonization, the confrontation between the Tuareg and the central government, the impact of the collapse of Gaddafi’s dictatorship in Libya at the onset of a new stage in the confrontation, the role of Islamist groups in northern Mali, and the course of French intervention there. The case of Mali as an almost classic ‘fallen state’ is treated separately.W artykule omówiono genezę i przebieg bieżącego kryzysu politycznego w Mali. Autor nakreślił przyczyny strukturalnej słabości Mali wynikające z dokonanego w czasie dekolonizacji wytyczenia granic, przebieg konfrontacji między Tuaregami a rządem centralnym, wpływ upadku dyktatury Kadafiego w Libii na otwarcie nowej fazy konfrontacji, rolę ugrupowań islamistycznych na północy Mali oraz przebieg francuskiej interwencji w tym państwie. W sposób odrębny potraktowany został przypadek Mali jako klasycznego niemal „państwa upadłego”

Comparison of shot peening and nitriding surface treatments under complex fretting loadings

Considered as a plague for numerous industrial assemblies, fretting associated with small oscillatory displacements is encountered in all quasi-static contacts submitted to vibrations. According to the sliding conditions, fretting cracks and/or fretting wear can be observed in the contact area. On the other hand an important development has been achieved in the domain of surface engineering during the past three decades and numerous new surface treatments and coatings are now available. Therefore there is a critical challenge to evaluate the usefulness of these new treatments and/or coatings against fretting damage. To achieve this objective, a fast fretting methodology has been developed. It consists in quantifying the palliative friction, cracking and wear responses through a very small number of fretting tests. With use of defined quantitative variables, a normalized polar fretting damage chart approach is introduced. Finally, to evaluate the performance of the assemblies after these protective surface treatments under complex fretting loadings, an original sequence of partial slip and gross slip sliding procedure has been applied. It has been demonstrated that performing of a very short sequence of gross slip fretting cycles can critically decrease the resistance of the treated surfaces against cracking failures activated under subsequent partial slip loadings

Identification of Local Lubrication Regimes on Textured Surfaces by 3D Roughness Curvature Radius

This paper proposes a new method of 3D roughness peaks curvature radius calculation and its application to tribological contact analysis as a characteristic signature of tribological contact. This method is introduced through the classical approach of calculation of radius of asperity in 2D. Actually, the proposed approach provides a generalization of Nowicki's method [ ], depending on horizontal lines intercepting the studied profile. Here, the basic idea consists in intercepting the rough surface by a horizontal plane and to calculate the cross section area without including “islands into islands”, i.e. the small peaks enclosed in bigger ones. Then, taking into account the maximal value of the height amplitude of the roughness included into this area, an appropriate algorithm is proposed, without requiring the classical hypothesis of derivability, which may be unstable when applied to engineering surfaces. This methodology is validated on simulated surfaces, and applied to engineering surfaces created experimentally, with a laboratory aluminium strip drawing process. The regions of the textured and lubricated specimens surface are analysed, and the results gives interesting prospects to qualitatively identify the local lubrication regimes: regions with high curvature radii correspond to severe contact (boundary/mixed lubrication regime) while regions with low curvature radii correspond to hydrodynamic lubrication regime

Mozambickie zmagania Portugalczyków w czasie I wojny światowej

The historical literature devoted the Great War in Africa is dominated by the struggle between the German forces, superbly commanded by the initially lieutenant colonel, and finally general Major Paul von Lettow-Vorbeck and units of the British Empire. The main reason of such situation is that in the east of Africa, the Germans continued fighting until the ceasefire in Western Europe in November 1918. In this narrative, there is relatively little room for a broader description of the struggles between the Germans and the Portuguese in Mozambique. The Luzytan military effort was described mainly, and at the same time disapprovingly, by the British. The impression appears that Albion deprecating the Iberian ally tried to dump a significant portion of the responsibility for the South-East Africa failures. The intention of the author of this text is to show Portuguese actions in an objective manner, not burdened with the British imperial narrative. It serves, above all, the use of Portuguese materials. This is - according to the author's knowledge - the first such attempt in the area of Polish historical-military literature. The author discussed the course of armed operations between the Portuguese and German forces and their impact on the findings of international conferences building a new balance of power after the end of the Great War

‘Beperkte afschrikkingsmacht’ van de Republiek Zuid-Afrika

In the seventies South Africa became a nuclear power. This paper examines the circumstances of and reasons for developing national nuclear capacities. The author presents the political and strategic situation of South Africa and the new threats and challenges which appeared after the collapse of Portuguese colonies in Africa and the arrival of the first Cuban units in Angola. In this context the South African authorities considered the development of nuclear weapons as a fundamental factor in creating a balance of power, and also as an important political tool. It must be emphasised that South Africa saw its own nuclear capacity as an instrument of policy, rather than a classical type weapon to be used on the battlefield. At the end of the apartheid era the South African nuclear bombs were deactivated and dismantled. The country also stopped construction of ballistic missiles. At present the Republic of South Africa is ‘free’ of nuclear weapons

Portugalska Rewolucja Goździków w 1974 roku. Przyczyny-przebieg-następstwa

Streszczenie 25 kwietnia 1974 w Lizbonie rozpoczął się wojskowy zamach stanu wymierzony w autorytarne państwo. Odniósł błyskawiczny sukces. Przejęcie władzy przez wojsko rozpoczęło ciąg niezwykle turbulentnych wydarzeń o kluczowym znaczeniu dla przyszłości państwa. Za zakończenie owego okresu uznać można 25 listopada 1975 roku.  Wtedy to również wojsko udaremniło kolejną próbę zamachu organizowaną przez oficerów o radykalnie lewicowych poglądach. Celem artykułu jest dokonanie rekonstrukcji przyczyn, które doprowadziły do zamachu oraz omówienie przebiegu wydarzeń między kwietniem 1974 roku a listopadem roku następnego. Okres ten określany jest w artykule mianem Rewolucji goździków. Autor posłużył się metodą studium przypadku, w wariancie ukierunkowanym nie tylko na opis, ale również na zaprezentowanie kontekstu badanego zjawiska. Podłużono się opracowaniami w języku portugalskimi angielskim, a także wyborem portugalskich dokumentów i aktów prawnych. AbstractOn April 25 1974 the military coup d'état aimed at the authoritarian state started in Lisboan. The rebels achieved an instant success. The takeover of power by the military started a series of extremely turbulent events of key importance for the future of the state. The end of this period can be considered November 25 1975. It was also then that the military foiled another attempted conducted by officers with radical leftist views. The aim of the article is to reconstruct the causes that led to the coup d'état in April 1974, to discuss the course of events between April 1974 and November of the following year. The period is referred to in this article as the Revolution cloves. The paper presents the consequences of these events for the further history of the Portugal. The author used the case study method in a variant aimed not only at description but also at presenting the context of the phenomenon under study. The studies in Portuguese and English, as well as the selection of Portuguese documents and legal acts, were extended. 

Portugalska Rewolucja Goździków w 1974 roku. Przyczyny-przebieg-następstwa

Streszczenie   25 kwietnia 1974 w Lizbonie rozpoczął się wojskowy zamach stanu wymierzony w autorytarne państwo. Odniósł błyskawiczny sukces. Przejęcie władzy przez wojsko rozpoczęło ciąg niezwykle turbulentnych wydarzeń o kluczowym znaczeniu dla przyszłości państwa. Za zakończenie owego okresu uznać można 25 listopada 1975 roku.  Wtedy to również wojsko udaremniło kolejną próbę zamachu organizowaną przez oficerów o radykalnie lewicowych poglądach. Celem artykułu jest dokonanie rekonstrukcji przyczyn, które doprowadziły do zamachu oraz omówienie przebiegu wydarzeń między kwietniem 1974 roku a listopadem roku następnego. Okres ten określany jest w artykule mianem Rewolucji goździków. Autor posłużył się metodą studium przypadku, w wariancie ukierunkowanym nie tylko na opis, ale również na zaprezentowanie kontekstu badanego zjawiska. Podłużono się opracowaniami w języku portugalskimi angielskim, a także wyborem portugalskich dokumentów i aktów prawnych.   Abstract On April 25 1974 the military coup d'état aimed at the authoritarian state started in Lisboan. The rebels achieved an instant success. The takeover of power by the military started a series of extremely turbulent events of key importance for the future of the state. The end of this period can be considered November 25 1975. It was also then that the military foiled another attempted conducted by officers with radical leftist views. The aim of the article is to reconstruct the causes that led to the coup d'état in April 1974, to discuss the course of events between April 1974 and November of the following year. The period is referred to in this article as the Revolution cloves. The paper presents the consequences of these events for the further history of the Portugal. The author used the case study method in a variant aimed not only at description but also at presenting the context of the phenomenon under study. The studies in Portuguese and English, as well as the selection of Portuguese documents and legal acts, were extended.