Semianalytical method for contact mechanic among shaft and bearing of a submarine vehicle

En el presente trabajo, se estudia y analiza el mejor ajuste del eje del propulsor de un vehículo sumergible a su chumacera, mediante el estudio de la geometría de contacto entre dichos elementos. Para realizar este estudio, se ha aplicado un método semianalítico, basado en las normas de la cuadratura de los principales valores de Cauchy, el método de la secante, y un método numérico para la determinación del mapa tensional de las superficies en contacto entre el eje y la chumacera. Asumiendo que existen imperfecciones de micras en el mecanizado de las superficies en contacto, estas son una causa posible de daños subsuperficiales que favorecen fallos por picaduras (pitting ) o la formación y el crecimiento de las grietas por fatiga. Estos fallos afectan no solo el buen rendimiento propulsivo, sino también las condiciones de estanqueidad, con los consiguientes riesgos que ello supone para la integridad del buque. Los resultados permiten establecer los criterios de diseño en función de los módulos de Young, así como un mecanizado correcto y el ajuste de holguras posterior del sistema eje-chumacera, con lo cual se mejorala fiabilidad de dichos elementos.The present study analyzes the best attachment of the propeller shaft of a submersible to his bearing, studying geometry of contact between those elements. A semi-analytical method based on the rules of the quadrature of the main values of Cauchy, the secant method and a numerical method for determining a tension map have been applied to the study of the contact surfaces between shaft and bearing. It is assumed that there are imperfections in the order of microns when machining the contact surfaces, which can produce subsurface damage that is possible, linked to pitting and the growth of fatigue cracks. Such failures not only will influence on the proper propulsive performance, but also on the watertightness conditions, which is related to the risk of ship integrity loss. The results let us to set design criteria, which account for the Youngs module and the importance of an adequate machining and further adjustment of clearances on the shaft-bearing system, thus improving the reliability of such elements.Peer Reviewe

Experimental Study of Tapping Wear Mechanisms on Nodular Cast Iron

AbstractTapping by cutting is one of the most common operations in manufacturing. This multi-teeth tool, known as a tap, cuts the thread in a hole when the piece has a high added value. The thread quality is ensured when the tap is new or slightly worn, yet when tap wear is high; the quality of profiles exceeds tolerance limits and therefore a defect occurs in the manufacturing line.The aim of this paper is to study the tap wear of titanium nitride coated taps measured on nodular cast iron. The level of tap wear is determined by optical images and the wear mechanics are classified by scanning images and energy dispersion spectroscopy analysis. The results highlight that the critical part in measured taps is between the last chamfer and the first cylinder teeth and, consequently, the thread profile is under-sized. Beside adhesive wear, coating removal and chipping are the main wear aspects during tapping operations

UAS remote sensing products for supporting extraction management and restoration monitoring in open-pit mines

Accurate mapping of open-pit mine areas is a prerequisite for the efficient resource management of extractive companies, but also detailed mapping is a requirement for public administrations, especially regarding the monitoring of restored areas. In previous works, our team has contributed to a better knowledge of the use of Unmanned Aerial Systems (UAS) technologies for soil/vegetation restoration monitoring purposes, and in this work, we present a novel protocol to support combined interests of both private companies and governmental agencies. We introduce a case study in which we show the capability of multispectral sensors onboard of a low-weight multicopter to describe land cover typologies in restored areas (such as grass, scrubs, trees, topsoil and mine spoils) by applying remote sensing and GIS techniques. Moreover, we assess the capability of digital terrain models (Digital Elevation Model, Digital Surface Model, Digital Slope Model) derived from photogrammetric techniques, to provide useful and fast topographic information for the proper management of open-pit mine exploitation and restoration. By applying these techniques, we present a cost-effective workflow adequate to monitor land cover dynamics in restored areas, but also volumetric changes in stockpiles, waste dumps and extraction faces. This combined approach, supporting both environmental and industrial needs, aims to enhance the collaboration between sectors, establishing synergies, reducing costs by sharing knowledge, and adding transparency to their relation

Analysis of self-tapping screw joints in fibre glass reinforced PEI polymer used in the automotive industry

This article presents a study of the joining of polyetherimide (PEI) polymer parts reinforced with fibre glass which has great application in the automotive sector. A simulation model based on the finite element method is proposed. For the modelling of the polymeric material, the three-network viscoplastic (TNV) rheological model was used, with very adequate results and producing a good fit with the experimental data. In addition, a methodology is proposed that allows simplifying a three-dimensional to an axisymmetric model, which implies a notable reduction in computational cost. In addition, the work includes an experimental analysis that evaluates the tightening torque under conditions of assembly repetitiveness, relaxation over time and influence of thermal cycles. These scenarios have a different influence depending on the geometry of the self-tapping screw used. Regarding repetitiveness, it has been verified that PF-30 (CELOspArk (R)) loses 17.16% while in Delta-PT (DELTA PT (R)) it loses up to 41.93% in the tenth repetition. In contrast, in the relaxation over time scenario, the PF-30 loses 13.38% and the Delta-PT loses 17.82%. Finally, regarding the thermal cycles, cooling allows to slightly delay the loss of tightening torque in both screws in a similar way; however, in the heating stage, 36.89% is lost with PF-30 and only 14.66% with Delta-PT. This study represents an improvement in the knowledge of the joining processes of self-tapping screws with polymeric materials of an engineering nature. The simulation model can be easily adapted to other materials and other geometries, and the experimental study offers a vision of the evolution of tightening conditions in realistic operating scenarios

ESDA2006-95528 DNC METHOD FOR FLATNESS REDUCTION BY MACHINE TOOL ERROR COMPENSATION IN PLANING PROCESSES

ABSTRACT Milling is a widely used manufacturing process with the main purpose of generating high precision mechanical components of shapes and sizes given by the numerical control programmed cutting tool trajectory. These mechanical components frequently needs the application of milling operations in order to satisfy the technical specifications that corresponds to their dimensional, geometrical and surface quality requirements. For that reason, the effects of different factors such as cutting tool dynamics, fixturing system design, workpiece material behaviour and applied cutting forces on the desired dimensional precision must be studied, as well as cutting tool and machine tool performance. In this work, the relation between machine tool inaccuracies and geometrical tolerances is analyzed, and a methodology is proposed for improving flatness in planing operations by the correction of imperfections detected in cutting tool displacement according to machine tool axis. These machine tool error correction methodology could be implemented in the current CAD/CAM/CAPP techniques as a means of increasing the milling process performance by identification and correction of CNC milling machine imperfections. The deviations in machine tool displacement during cutting process are identified by metrological analysis, and a modified trajectory for cutting tool is defined by direct numerical control (DNC) from systematic error compensation in machine tool

Semianalytical method for contact mechanic among shaft and bearing of a submarine vehicle

The present study analyzes the best attachment of the propeller shaft of a submersible to his bearing, studying geometry of contact between those elements. A semi-analytical method based on the rules of the quadrature of the main values of Cauchy, the secant method and a numerical method for determining a tension map have been applied to the study of the contact surfaces between shaft and bearing. It is assumed that there are imperfections in the order of microns when machining the contact surfaces, which can produce subsurface damage that is possible, linked to pitting and the growth of fatigue cracks. Such failures not only will influence on the proper propulsive performance, but also on the watertightness conditions, which is related to the risk of ship integrity loss. The results let us to set design criteria, which account for the Youngs module and the importance of an adequate machining and further adjustment of clearances on the shaft-bearing system, thus improving the reliability of such elements