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1

Influence of cooling on the performance of the drilling process of glass fibre reinforced epoxy composites

Ramesh B., Elayaperumal A., Satishkumar S., Kumar A., Jayakumar T., Dinakaran D.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 1

135--146

EN

Non-laminated composites find application in construction of bridges, ballistic applications, etc. However, literature on the drilling of non-laminated composite materials and literature on the drilling of thick composite materials under different cooling methods (dry, external and internal) is scarce. Hence the present study is aimed to investigate the influence of different cooling methods on quality characteristics (drill temperature and damage factor) while drilling glass fibre reinforced epoxy (GFRE) non-laminated 20 mm thick pultruded composite rods having 80% fibre weight fraction and 0° fibre orientations with respect to the drill. The drilling experiments using TiN/TiAlN coated tungsten carbide twist drills of diameter 10 mm were conducted using response surface methodology (RSM). The experimental values obtained for quality characteristics are empirically related to process parameters by developing a response surface model using Design-Expert software. The effects of process parameters on quality characteristics were analysed by using response surface graphs. The process parameters (feed, spindle speed and coolant pressure) are also optimized within the selected range. The optimal parameter levels are confirmed by validation test. From this investigation, it is evident that the internal cooling method is significant for obtaining high hole quality.

2

Application of genetic algorithm for damage identification of non-homogenous tapered beam

Panigrahi S. M., Chakrayerty S., Mlshra B. M.

Computer Methods in Materials Science

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2008

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Vol. 8, No. 2

93-102

EN

Non-homogeneous structural members such as beams are very important in various engineering applications and for experimental analysis purposes. A minor damage on any part of the structure reduces the strength of the structure and leads to a major failure. The analysis of non-homogenous beam becomes complicated due to the change of material properties from point to point. However, it becomes much more complicated when there exists a taper on such type of beams. In this paper, a new formulation of an objective function for the genetic search optimization procedure along with the residual force method is presented for the identification of macroscopic structural damage in a non-homogeneous tapered beam. The developed model requires experimentally determined data as input and detects the location and extent of the damage in the beam. Here, numerically simulated data using finite element models of structures are used to identify the damage at a reasonable level of accuracy. Damage parameters given theoretically are compared by the present procedure and are found to be in good agreement.

PL

Niejednorodne elementy strukturalne takie jak belki są istotną częścią konstrukcji inżynierskich i stanowią przedmiot wielu badań doświadczalnych. Nawet niewielkie pęknięcie takiego elementu obniża znacznie jego wytrzymałość i, w konsekwencji, wytrzymałość całej konstrukcji, co może prowadzić do znacznych zniszczeń. Analiza niejednorodnych elementów strukturalnych jest skomplikowana, ponieważ własności materiału zmieniają się w zależności od położenia, a problem staje się nawet bardziej złożony kiedy belka ma kształt stożkowaty. W niniejszej pracy przedstawiono nowe sformułowanie funkcji celu dla optymalizacji takich belek metodą algorytmów genetycznych. Optymalizację połączono z metodą sił residualnych i zastosowano do identyfikacji makroskopowych pęknięć w niejednorodnych belkach o zmiennym przekroju. Opracowany model wymaga danych doświadczalnych jako parametrów wejściowych i pozwala przewidywać lokalizację i rozmiar pęknięcie materiału. Dane wygenerowane numerycznie w oparciu o symulację konstrukcji metodą elementów skończonych zostały wykorzystane do identyfikacji pęknięcia materiału z dobrą dokładnością. Otrzymane teoretycznie parametry zniszczenia zostały porównane z wynikami z opracowanego modelu i otrzymano dobrą zgodność.

3

Application of the fracture-band model to glacier seismic event series

Górski M.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 3

373-379

EN

We present an application of the fracture-band model to the study of icequake series recorded in June 1999 at Hans glacier, Spitsbergen. The determination of seismicity of the glacier is based on two measurement networks. Using the calculated data of seismic moments, stress drops, and seismic radiated energies, we are able to calculate for each event in series the values of seismic efficiency, the total released energy, the ratio of tensile stress to shear stress, the ratio of source thickness to source radius, and the damage factor.

4

Earthquake fracture-band theory

Teisseyre R., Teisseyre K., Górski M.

Acta Geophysica Polonica

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2001

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Vol. 49, nr 4

463-479

EN

We present the theory of general structure of fracturing in an earthquake source; this new model is based on generalization of the shear band model presented in pervious papers. These models of the seismic source zone are based on the thermodynamics of line defects. In the thermodynamics of line defects the dislocation superlattice plays an essential role. The concept of line vacancy (vacant dislocation) enables us to construct a superlattice consisting of dislocations and vacant dislocations. The model introduced applies to plastic deformations; stress load increase may lead to some changes in dislocation density related to the superlattice. Such changes can also be related to a change of the number of vacant dislocations or to a change of the superlattice parameter. An increase of the number of dislocations corresponds in this case to a hardening process and is related to the spatial structure of superlattice. A pronounced plastic deformation is realized through the formation of shear bands; the dislocation number becomes multiplied along the shear planes and in consequence exceeds the number prescribed by the superlattice structure which, however, will be perservered in the direction perpendicular to the shear band planes. Our new generalization takes into account the tensile and shear fracturings forming the concurrent processes; however, some phase shifts between them shall be included. Moreover, in this paper the earthquake structure model may be not only related to the microdefect distribution, but also to an existence of macro-defects bound to a fine structure of focal region. This fine structure can be formed by some elements of the fracture space or by a certain distribution of the grains. Properties of such structures are described by the micromorphic theory. Moreover, we will not split, in a heuristic way, the deformations into the elastic and plastic parts, because the plastic phenomena are to some extent included here by the micromorphic or, as one can say, the granular/block structure properties of the medium. Applications for an analysis of earthquakes, mining tremors, volcanic events and icequakes are presented.