1,721,012 research outputs found
Crushing performances of axially compressed Woven Kenaf fiber reinforced cylindrical composites
No full textThis paper presents experimental investigations on the crushing performances of axially compressed woven kenaf fiber reinforced cylindrical composites. Based on the literature survey, there are tremendous amount of work are available on the crushing performances regardless whether the composite contained synthetic or natural fibers. However, lack number of work found in discussing the crushing capability for the composite tubes fabricated using woven kenaf mat reinforced composites. Kenaf fiber in the form of yarn is weaved into a woven mat before it is submerged into a resin bath prior the mats are shaped to form a cylindrical tube. There are two important parameters are used such as number of layers and fiber orientations. The composite tubes are then quasistatically compressed to obtain the force-displacement curves. Energy absorption capability and other crashworthiness parameters are calculated and discussed in term of number of layers and fiber orientations. According to the results, it is found that both number of layer and fiber orientations played an important role in an elastic region or the first region. On the other hand, in the second stage, it is insignificantly affected the plateau stage where the curves seemed not much different
Mode I stress intensity factors of sickle-shaped surface cracks in round solid bars under bending moment
No full textSickle-shaped crack may occur on the surface of solid round cylinder under some
specific reasons such as design discontinuities or material defects. This type of crack is
capable to grow circumferentially around the bar and it is called a sickle-shaped surface
cracks. The complete solution of stress intensity factors (SIF) of sickle-shaped surface
cracks is hard to find and therefore the objective of this paper is to present the behaviour
of these cracks under remotely applied bending moment. In order to understand the role
of these cracks, there are seven crack aspect ratios, a/b considered, ranging from 0.0 to
1.2. For each crack aspect ratio, there are six relative crack depths, a/D used ranging
from 0.1 to 0.6. ANSYS finite element program is used to model the crack. Stress
intensity factor (SIF) which is based on the J-integral is used to characterize the cracks.
For relatively shallow cracks (a/D ? 0.3), the role of SIFs along the crack front is
insignificant regardless of a/b. However, for the deeper cracks (a/D > 0.3), the effect of
a/b is tremendous on the SIFs. If a/b is increased from 0.0 to 1.2, higher SIFs are
obtained around the central compared with the outer regions of the crack fronts. This is
due to the fact that the circumferential cracks at both sides of the bar experience lack of
mode I opening mechanism compared with the crack faces at the upper side cracks. It is
suggested that the phenomena of crack closure are not only caused by the plastic
deformation, surface roughness and other related factors but the shape of crack also
plays an important role
An overview of fracture mechanics with ANSYS
No full textThis paper reviewed the use of ANSYS finite element program in analyzing the engineering structures containing defects or cracks. It is provided a fracture mechanics module which is capable to model the crack tip efficiently. In studying the cracks in elastic medium, linear elastic fracture mechanics (LEFM) is used where the crack-driving force called stress intensity factor, J-integral, energy release rate is provided as indicators of failure. There are three approaches can be used to calculate the stress intensity factors (SIF) such as Displacement Extrapolation Method (DEM) and Interaction Integral Method (IIM). Energy Release Rate (ERR) is calculated using Virtual Crack Closure Technique (VCCT) then it is converted to SIF. Based on the comparison, it is found that DEM, VCCT and J-integral techniques produced the SIFs are almost closed to the results obtained from open literature. However, IIM method lead to under estimate the SIFs
Crushing mechanisms of cylindrical winding kenaf fiber reinforced composites
No full textThis paper presents the crushing behavior of cylindrical kenaf fiber reinforced
composites subjected to axial compressive loading. Lack of information available
on the study of cylindrical composites fabricated using kenaf yarn fibers where it is
wound around the cylindrical mold. There are two important parameters are used
during the composite fabrications namely fiber orientations (00, 50 and 100) and
number of layers (1, 2 and 3 layers). These composite tubes are crushed axially
and forces versus displacement curves are recorded. Then, the specific energy
absorptions and force ratios are determined. As expected, increasing the number
of layers increased the specific energy absorptions but it is not significantly
affected the force ratio even different fiber orientations are used. During
progressive collapses, most of the failures mechanisms observe are localized
buckling with large wall fragmentations
Effect of silane treatments and fiber loadings on tensile properties of coir fiber reinforced composites
No full textNowadays, increasing awareness of replacing synthetic fiber by glass fiber has emerged due to environmental problems and pollution. Automotive manufacturers also seek new material especially biodegradable material to be used as non-load bearing application parts. This present work discusses the effect of silane treatments and fiber loadings on tensile properties of coir fiber reinforced polyester composites. From the experimental results, both silane treatments and fiber loadings increased the tensile properties. The presence of silane coupling agent on the fiber surfaces enhanced the compatibility between fiber and polymeric matrix. This compatibility promoted the capability of composites to sustain higher tensile loadings. From SEM observation pictured that longer fiber pull-out is a dominant factor for 5% fiber loading composites result lower tensile strength. Interfacial debonding also occurred for untreated fiber with silane coupling agent while silane treated fiber reinforced composites. Shorter pull-out fibers are observed and fibers are well gripped within the matrix showing betterinterfacial bonding and good tensile properties are achieved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Crushing behavior of foam filled steel extrusion / Al Emran Ismail
No full textThe concern of vehicle structural integrity and safety is given highly considerable amount of research and development by engineers and scientist world wide. Weight reduction of structures without compromising the structural durability is the important aspect because weight is strongly related to fuel consumption. In this work, rigid polyurethane foam is used to fill into steel extrusions. Different foam density is used to reinforce the steel tubes and at the same time different steel wall thickness also adopted to study the crushing behavior under quasi-static compression loading loaded at different angles. Force versus displacement of each column condition is recorded automatically, compared and analyzed. The area under the curve represent the energy absorbed by the column and the column length is properly designed to prevent buckling which will be resulted catastrophic failure leading to low energy absorption capability. Then, the final crushed columns are analyzed to study the correlation with the crushing characteristics. It is found that the energy absorption increased when increasing the foam density but when the tube wall reached a maximum thickness, the foam density no longer affected to increase the energy absorption
EXPERIMENTAL STUDIES ON THE QUASI-STATIC AXIAL CRUSHING BEHAVIOR OF FOAM-FILLED STEEL EXTRUSION TUBES
No full textThe concerns of automotive safety have been given special attention in order to reduce human fatalities or injuries. One of the techniques to reduce collision impact or compression energy is by filling polymeric foam into metallic tubes. In this work, polyurethane foam was introduced into the steel extrusion tubes and quasi-statically compressed at constant cross-head displacement. Different tube thicknesses and foam densities were used and these parameters were related to the crashworthiness aspect of the foam-filled structures. It is found that both tube thickness and foam density played an important role in increasing the crashworthiness behaviours of the structures but when the tube thickness reached certain value, foam density unable to properly work in increasing the energy absorption of the structures
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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