Carpóforo Vallellano

Bio: Carpóforo Vallellano is an academic researcher from University of Seville. The author has contributed to research in topics: Formability & Necking. The author has an hindex of 17, co-authored 91 publications receiving 979 citations.

Hole-flanging by incremental sheet forming

Abstract: Incremental forming of hole-flanges in sheet metal parts is an emerging process with a high potential economic payoff for rapid prototyping and for small quantity production. However, as with all new sheet metal forming processes, there is need for examining its deformation mechanics and describing the physics behind the occurrence of failure. How metal fails, how pre-cut holes influence strain and stress in single point incremental forming, and how these subjects can be brought together in order to understand the overall formability of hole-flanging by multi-stage incremental forming are still not well understood. However, they are of great importance for improving the performance and industrial applicability of the process. This paper attempts to provide a new level of understanding for the process by combining circle grid analysis and independent characterization of the mechanical properties and formability limits of the material with the fabrication of conical and cylindrical hole-flanges. Experimental observations, measured strain paths and material formability limits by necking and fracture allow concluding that hole-flanging by incremental forming gives rise to a new mode of deformation, not found in conventional incremental forming of sheet metal blanks without pre-cut holes, and to failure by fracture without previous localized necking.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

The Theory of Critical Distances

Abstract: This paper summarises the keynote talk opening the session on ‘Critical Distance Theories of Fracture’; my aim is to describe the methodology used, to demonstrate its applicability in predicting experimental data on fracture and fatigue, to discuss the fundamental basis of the theory and, to suggest areas for future work in this field. The Theory of Critical Distances (TCD) is the name which I have given to a group of theories used for predicting the effects of notches and other stress-concentration features. These theories have a long history, but currently they are being investigated by only a small number of researchers worldwide. This is a pity, because the TCD is capable of accurate predictions in a wide variety of situations. The essential elements are an elastic stress analysis and a material-dependent critical distance, a parameter which we call L. The value of L can be written in terms of other material parameters as: $$ L = \frac{1} {\pi }\left( {\frac{{K_c }} {{\sigma _o }}} \right)^2 $$ (1)

A review of recent advances in tribology

Abstract: The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.