Papers by Keyword: Brittle

Abstract: Steel has been one of the most widely used materials in land and sea construction due to its advantageous properties, especially carbon steel. This study focuses on molecular dynamics simulation to demonstrate carbon steel’s mechanical behavior. A uniaxial tensile test was conducted for body-centered cubic (bcc) structured carbon steel and pure iron to learn the effect of carbon presence. Both simulation cells were simulated under temperature variation to reveal its effects. It was found that carbon steel is stronger than pure iron based on their value on yield and tensile strength, namely up to 2.434 GPa and 1.368 GPa respectively, which are stronger at room temperature. This study also revealed that carbon steel exhibits better elastic properties with a Young’s modulus of 285.749 GPa, compared to that of pure iron 230.117 GPa. Additionally, this molecular dynamic study also identified another phenomenon, such as brittle-to-ductile temperature of carbon steel at 340 K. Structural explanation is provided in the form of bcc structure fraction during the strain progression and under temperature variation. These findings provide a comprehensive molecular perspective to unveil mechanical properties of carbon steel.

Abstract: This paper presents a constitutive relationship to describe the uniaxial response in statics of brick and mortar samples of Adobe, a traditional masonry whose components are made of sundried soil mixture reinforced with fibres. Only recently Adobe has been attracting scientific attention, primarily as a consequence of the dramatic failures these structures have suffered in regions prone to earthquakes. Furthermore, it possesses eco-friendly material properties which are attractive features for western countries forced to reduce the environmental impact of modern building industry. Nevertheless, the mechanical properties of Adobe are still largely neglected, especially with regards to the influence of soil mixture components. The study of the structural performance of masonry starts from the assessment of the material performance of its components. Thus, an extensive characterization campaign was performed by Delft University of Technology and the Military Engineering Laboratory of the Netherlands. Three types of bricks and one type of mortar with different mixture components proportions, were subjected to granulometry, moisture content, density tests and uniaxial compressive and three point bending tests. Predictive formulations for compressive and tensile strength and deformation values have been proposed by the authors. These relations include the dependency of mixture components and moisture content. In this paper, constitutive laws are developed for Adobe in pure compression and tension validated by experimental results. In compression, the force-displacement curves were interpolated according to several existing constitutive laws and the model originally developed by Priestley for concrete masonry elements was finally selected as best fitting. Despite the differences in terms of mechanical parameters, the analytical assessment revealed that the experimental force-displacement graphs of all the different types of bricks could be interpolated using the same model with the same calibrating values. Furthermore, the uniaxial response in tension was derived according to an inverse approach. A numerical model recently developed by the authors and calibrated with respect to the compressive and bending tests was used to simulate uniaxial tensile tests. Also in tension, a common trend among types was observed. The results of the constitutive modelling frames components of Adobe within the class of quasi brittle (geo) materials, with particular reference to concrete. This paper presents the experimental results of the tested samples and the related analytical and numerical modelling.

Abstract: The aim of this study is to evaluate the mechanical properties and study the failure of laminated glass reinforced composite coated with gelcoat of different thickness. Firstly, the gelcoat was applied to the mould using brush and subsequently, glass fiber reinforced composite laminates were fabricated on it using vacuum bagging technique. The mechanical properties of the composites various were tested by using tensile and three-point flexural tests. The fracture behaviour of different gelcoat thickness was observed using scanning electron microscope (SEM) to determine the failure behaviour that occurred. The flexural test was performed in two ways, i.e., gelcoat layer facing top and facing down. For both flexural tests, composite coated with 0.30 mm thick of gelcoat shows the highest mechanical strength. Tensile test is useful to investigate the interfacial bonding in between gelcoat and laminate composite. The composite coated with 0.40 mm of gelcoat showed the highest tensile strength, an increase of 38 % compared to the uncoated composite. It was observed that an increase in gelcoat thickness increased the brittleness of the laminated composite. From the failure analysis, failures were caused by the delamination of matrix between the plies, while the gelcoat was still strongly bonded with composite laminate.

Abstract: Wood flute back combination design [, experimental study to verify the practicality of wood back shocked. Development and application of wood back shocked, and replace the current wooden building construction template for the realization of environmental protection, energy conservation plays an important.

Abstract: Observations and analysis of samples from scanning electron microscopic (SEM) micrographs has been concerned in this work. The samples originate from fractured mechanical mode I tensile testing of a thin polymer film made of polypropylene used in the packaging industry. Three different shapes of the crack; elliptical, circular and flat, were used to investigate the decrease in load carrying capacity. The fracture surfaces looked similar in all studied cases. Brittle-like material fracture process was observed both by SEM micrographs and the experimental mechanical results. A finite element model was created in Abaqus as a complementary tool to increase the understanding of the mechanical behaviour of the material. The numerical material models were calibrated and the results from the simulations were comparable to the experimental results.

Abstract: A shaft of electric motor fin-fan cooler failed after two years operation. The inspection revealed that the v-belt attached on the electric motor loosed before the failure occurred. Visual investigation results showed the brittle fracture with less plastic deformation. Multiple crack origins observed on the edge of the shaft indicates that the more than one stress concentration generated within the shaft. Microstructure observation revealed fine grain on the edge and become coarse into the center of the shaft. The hardness test results were in good agreement to the microstructure observation where the edge are is harder than the center. Fractography using SEM revealed inclusions located within the shaft and some inclusions are clustered on the area where the cracks initiate to propagate. The presence of intermetallic inclusions was identified by microanalysis using EDS. Inclusions that are brittle in nature become stress concentrations for the operating load since its properties is close to ceramic. The presence of fine grain and inclusions on the edge of the shaft become detrimental to the shaft properties and the presence of fine grain aggravate the failure for its effect according to Hall-Petch theory.

Abstract: Bolted steel-wood-steel connection is an important fashion of connections in timber structure, the manners of failure loaded parallel-to-grain include bearing, row shear-out, group tear-out and splitting, and the brittle failure modes are predominant in some tested results of bolted connections specimens. End distance, bolt spacing, row spacing and the thickness of wood have important influence on the failure modes, and meanwhile, the bolt diameter can not be neglected. Based on the different failure fashion, the equations of strength were given.

Abstract: The slicing technology with active braze coating diamond wire has been studied to lower the manufacturing cost and to increase the efficiency of wire sawing. The study shows that the grains have strong retention on the resin matrix as well as longer tool life.

Abstract: Optical Microscope and SEM(Scanning Electron Microscope) are used to observe the crack evolution of rock under compression. Two kinds of rock (marble and granite) are investigated. The evolution of crack pattern shows that localization is a key factor inducing brittle failure. Crack of granite readily tends to localize and show more brittle. Contrarily, randomly distributed cracks induced by compression load results into the low brittle of marble. The mechanism underline this phenomenon is that marble has higher heterogeneous than granite. So, the key point to describe the brittle failure mechanism of rock is to determine the micro-mechanical and the damage evolution properties.

Abstract: Most existing models for abrasive jet machining (AJM) are based on erosion models for either ductile or brittle materials. This classification imposes some limitations, because most materials are neither absolutely ductile nor absolutely brittle, but lay within the continuous spectrum between those two idealizations. This work reports recent progress in the modeling of erosion processes for real materials, and discusses the implications of a new model in estimating the performance of AJM. The new model is more capable in explaining the effects of jet velocity, abrasive particle size, and various material properties on the efficiency of the cutting process.