http://nopr.niscair.res.in/handle/123456789/82 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/227 Title: Fracto–mechanoluminescence produced during slow deformation of solids <br/> <br/>Authors: Chandra, B P; Mahobia, S K; Kuraria, R K; Chaudhary, Vibha <br/> <br/>Abstract: The present paper reports the mechanoluminescence (ML) induced by the movement of cracks produced during slow deformation of solids. The ML may be induced by fracture of crystals due to several processes involved in charging of newly-created surfaces. In fracto-ML, the number of ML pulses emitted indicates the number of cracks moved in a crystal. Thus, there is one-to-one correspondence between the number of cracks formed and the number of ML flashes emitted during the deformation of a crystal. An expression derived for the dependence of the number of ML flashes, Nք on the strain ε of crystals may be expressed as, Nք= [{exp ⍺(ε–ε f )}–1], where εf is the fracture strain and ⍺ is a constant. The total ML intensity indicates the total area of the newly-created surfaces created during the deformation of a crystal. As the decay time of ML is constant and of the order of microseconds, in the case of slow deformation, the peak of ML intensity induced by a single crack indicates the area of newly-created surfaces. The studies on fracto-ML give important information that the number of cracks increases exponentially with the deformation of crystals and the area of newly created surfaces increases linearly with the deformation of crystals. The ML may be useful in the study of crack dynamics in microsecond and nanosecond ranges, whereby important information related to the initiation, propagation and interaction of cracks in solids may be obtained. The rapid photographic methods and CCD cameras can be used effectively to map the ML emission from fracture of solids. A good agreement is found between the theoretical and experimental results. <br/> <br/>Page(s): 443-446 Wed, 28 Nov 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/226 Title: LiSIPA doped polyaniline-colloidal graphite composites : Synthesis and characterizatio <br/> <br/>Authors: Saini, Parveen; Choudhary, Veena; Dhawan, S K <br/> <br/>Abstract: Aniline has been polymerized in the presence of colloidal graphite using lithium sulphoisophthalic acid (LiSIPA) as dopant, via the chemical oxidative polymerization route. The thermal stability and electrical conductivity have been improved significantly as compared to polyaniline doped with conventional inorganic dopants like HCl or H₂SO₄. The XRD and FTIR show a systematic shifting of the characteristic bands/peaks with the increase in the graphite content, which indicates sufficient interaction between graphite and polyaniline. The UV-visible spectra also show the characteristic bands of polyaniline which shows the hypsochromic shift with the increase in the graphite content. Apart from their doped counterparts, these composites also show sufficient conductivities, even in the undoped forms. <br/> <br/>Page(s): 436-442 Wed, 28 Nov 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/225 Title: Effect of using ground waste tire rubber as fine aggregate on the behaviour of concrete mixes <br/> <br/>Authors: Balaha, M M; Badawy, A A M; Hashish, M <br/> <br/>Abstract: The development of environmentally accepted methods of used tire disposal is one of the greatest challenges that waste management experts face today. Using of wastes and by-products as concrete aggregate has attained great potential in the last few years. The aim of this work is to investigate the possibility of the usage of ground waste tire rubber (GWTR) in the civil construction as a partial replacement for fine aggregates and the influence of these wastes on the properties of ordinary concrete. The cement content for concrete mixes is 300, 400, and 500 kg/m³. The total fine aggregate (TFA) in all mixes is sand, which is partially replaced by GWTR particles. The percentages by volume of GWTR/TFA are 5%, 10%, 15% and 20%. The physical and mechanical properties of rubberized concrete are compared with those of ordinary concrete mixes. Also, three treated materials, polyvinyl acetate, silica fume and sodium hydroxide (PVA, SF and NaOH) are used for treatment the ground waste tire rubber to improve the interface friction between rubber particles and cement matrix. The results show that the mass density (bulk density) of hardened rubberized concrete decreases with increasing rubber content, this is an advantage for that concrete application. Also concrete specimens containing rubber particles are much tougher than those without rubber particles. The damping ratio of the rubberized concrete containing 20% rubber is much higher than those of normal concrete by about 63.2%. Rubberized concrete incorporating treated rubber particles gives better results than concrete incorporating normal rubber. <br/> <br/>Page(s): 427-435 Wed, 28 Nov 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/224 Title: Experimental investigation of reinforced concrete beams with and without steel fiber under explosive loading <br/> <br/>Authors: Altun, Fatih; Köse, M. Metin; Yilmaz, Canan; Ari, Kamuran; Durmuş, Adem <br/> <br/>Abstract: The aim of this study is to determine the energy absorption capacities of the reinforced concrete (RC) beams of the same concrete class and to obtain the performances of the steel-fiber added beams according to the damage characteristics obtained by the explosive loading. In this paper, effects of blast load on the RC beams samples with and without steel fiber have been investigated. First, the compressive strength of concrete made with and without steel fiber have been measured. Second, the load carrying capasities of the RC beams produced with and without steel fiber are determined by two point loading test. Lust, the damage levels under explosive loading applied on the RC beams produced with and without steel fiber have been observed. The results show that RC beams made with steel fiber is damaged less in blast loading than that of conventional RC beams. The results also show that the expression used in calculating the amount of the explosive material needs to be revised. <br/> <br/>Page(s): 419-426 Wed, 28 Nov 2007 22:58:59 GMT