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Simulation of Dynamic 3D Crack Propagation within the Material Point Method
Get PDFThis paper presents the principles and algorithms for simulation of dynamic crack propagation in elastic bodies by the material point method (MPM), from relatively simple two-dimensional cases to full three-dimensional, mixed-mode crack propagation. The paper is intended to give a summary of the latest achievements on simulation of three-dimensional dynamic crack propagation, which is essentially an unexplored area. Application of the methodology presented in this paper to several dynamic crack propagation problems has shown that the MPM is a reliable and powerful approach for simulating three-dimensional, mixed-mode crack propagation
Uncertainty Analysis Method of Casing Extrusion Load for Ultra-Deep Wells
Get PDFWith the consideration of the randomness of complex geologic parameters for ultra-deep wells, an uncertainty analysis method is presented for the extrusion load on casing in ultra-deep wells through complex formation at a certain confidence level. Based on the extrusion load model for casing in ultra-deep wells and the prerequisite of integrity of formation-cement ring-casing, the probability and statistics theory is introduced and the sensitivity analysis on the uncertainty of extrusion load on casing is conducted. The distribution types of each formation parameters are determined statistically. The distribution type and distribution function of the extrusion load on casing are derived. Then, the uncertainty analysis of the extrusion load on casing is carried out on several ultra-deep wells in Shanqian block as case study. Several conclusions are made regarding to the field trial result. The randomness of formation elasticity modulus and formation Poisson’s ratio are the main influence factors. The equivalent density profile of extrusion load on casing in ultra-deep wells is a confidence interval with a certain confidence level, rather than a single curve; the higher the confidence level is, the larger the bandwidth of the confidence interval of equivalent density profile becomes, and the larger the range of uncertainty interval becomes. Compared with the result of uncertainty analysis, an error exists in the result of traditional single valued calculation method. The error varies with different casing program and can be either positive or negative. The application of uncertainty analysis of extrusion load on casing provides proof for the accurate determination of casing collapse safety factor. Thus, the over engineering design or under engineering design as a result of tradition casing design will be avoided
Karanja Oil Polyol and Rigid Polyurethane Biofoams for Thermal Insulation
Get PDFRigid polyurethane biofoams were prepared from karanja polyol which was derived by ring-opening reaction of epoxidized karanja oil. The polyol, which had a hydroxyl value of 186 mg KOH/g, was thoroughly characterized and the structure confirmed by spectral techniques. The foam formulations were developed to achieve shrinkage-free foams with water used as the blowing agent. The resulting foams were characterized for their mechanical properties like density, compression strength and flexural strength. The densities and mechanical properties, such as compression and flexural strength, varied with the amount of methylene diphenyl diisocyanate (MDI) for a fixed amount of polyol and other additives as a result of side reactions leading to allophanate and urea linkages. Scanning electron microscopy (SEM) results indicated that the cells are spherical and samples are isotropic. However, the cell size distribution varied with MDI content. The thermal conductivity was found to be in the 0.036–0.042 W/m.K range, which is well suited for insulation purposes
Studies on Bone-Derived Calcium Phosphate Materials
Get PDFIn recent years, the development of composite biomaterials has been the subject of very intensive research. The elaboration of technology for manufacturing new biomaterials will allow their practical implementation and adaptation to changing market needs. One of the key components in the developed composite materials will be natural origin hydroxyapatite (HAp) and tricalcium phosphate (TCP) obtained from bone products. In this study, preparation and detailed characterization of bone-derived calcium phosphates as a component of biomaterial composites is proposed. This novel method of obtaining hydroxyapatite for biomedical applications allows the obtainment of a material with expected parameters. In this study, pork bones from meat cutting were subjected to a three-stage treatment: acid hydrolysis, initial calcination and proper calcination. In order to investigate the effect of lactic acid on the properties of the obtained materials, the preparation of a series of hydrolysis reactions with an increasing content of the hydrolysis reagent was assumed. Moreover, the third step of material preparation—proper calcination—was carried out at various temperature and time parameters. Subsequently, several experimental techniques were employed to investigate the expedient physicochemical properties of all calcium phosphate powders
Rapeseed Oil as Feedstock for High Functionality Polyol Synthesis
Get PDFIn this study, polyols with high average functionality were synthesized from a renewable resource, rapeseed oil, as raw material for rigid PU foam production. A well-known method of rapeseed oil fatty acid double bond epoxidation was used to introduce oxirane rings into rapeseed oil structure. The temperature influence on epoxidation reaction conversion rate was studied by volumetric and FTIR spectra analysis. After epoxidation of rapeseed oil, an oxirane ring-opening reaction was carried out to obtain high functionality polyols. Diethylene glycol, a conventional oxirane ring-opening reagent, was compared to amine-based polyfunctional alcohols, diethanolamine and triethanolamine. The introduction of tertiary amine groups into the polyol structure provided catalytical properties for obtained polyols, which will allow a reduction of the amount of catalysts in polyurethane foam formulations. Hydroxyl value, acid value, moisture content, viscosity and density of synthesized polyols were determined, and their structure and average functionality were analyzed by FTIR and MALDI-TOF spectroscopy and GPC analysis. Also, the main characteristics of rigid PU foam obtained from synthesized polyols were determined
Supercritical Carbon Dioxide Treated Kenaf Bast Pulp Fiber Reinforcement in Epoxy Composite
Get PDFDue to environmental concerns, green composites have become a highly researched material. In the present study, kenaf fiber was used as reinforcement in epoxy-based composite with weight fraction ranges from 0, 5, 10, and 15% (w/w of resin). The ratio of epoxy to hardener was 65:32.5. Prior to incorporation, kenaf bast fiber underwent Soda-AQ pulping followed by total chlorine-free bleaching (OAZP sequence). The obtained pulp was then subjected to supercritical carbon dioxide extraction (SCE) treatment. It was observed that epoxy composite with 10% of fiber loading demonstrated the highest mechanical properties with a tensile strength of 64 MPa, tensile modulus of 1.64 GPa, flexural strength of 83 MPa, and flexural modulus of elasticity of 2.94 GPa. The observed improvement was due to the SCE process which enhanced the wetting process of fiber. However, at 15% mechanical properties decreased due to void formation since fiber could not be dispersed properly in epoxy matrix at high concentration
A Finite Element Study of the Influence of Graphite Nodule Characteristics on a Subsurface Crack in a Ductile Cast Iron Matrix under a Contact Load
No full textThis paper describes a study of the effects of graphite nodule characteristics on a subsurface crack in austempered ductile iron (ADI). A representative specimen of ADI, subjected to sliding contact load, is modeled using finite elements aiming to obtain the shear stress intensity factor (KII). The parameters varied were (i) the nodule diameter (two different values were considered), (ii) the distance between the nodule and the tip of the crack and (iii) the position of the load relative to the tip of the crack. The results of the numerical simulations show that the smaller diameter nodule has a larger influence on KII, suggesting a higher contact fatigue crack propagation rate in the material with the smaller nodule. These results are the opposite of those observed in experimental studies and would appear to indicate that other factors should be also considered to ensure realistic estimates of the contact fatigue strength of ADI
A Controlled Conditions of Dynamic Cold Storage Using Nano fluid as PCM
No full textThe dynamic thermal history of storage product system is related to the insulation and also to the inertia. Use a new porous media doped with nanofluid PCM to improve the system efficiency. The analysis of the porous sponge thickness with 8 mm, 16 mm and 20 mm, the integrated nanofluids with 0.1%, 0.15% and 0.2%, the mass of the PCM and the initial temperature of the stored product with -1°C, 4°C, 12°C is achieved in order to underline the advantages of the new saturated porous media (sponges) with the phase change material (PCM) /Al2O3-H2O nanofluid. The carrots are used as the experimental object in the experiments by orthogonal method. And the integral value of average temperature of the air in the box is an index to judge the effect of cool storage. The transportation temperature and duration are mainly affected by the pre-cooling temperature of products, the storage materials, the nanofluids mass fraction, the thickness of porous sponge. Compared with range values, the optimal combination of all the factors for the effect of cool storage is as following: the thickness of porous sponge of 20 mm, the mass fraction of 0.2%, the mass of cold storage materials of 0.4 kg, and vegetables pre-cooling temperature of 4°C . Under constraint of mass (or volume) transportation we demonstrate that the thickness of sponge of 16 mm instead of 20 mm, and nanofluids mass fraction of 0.15% instead of 0.2% could be enough. The equivalent variable is defined basing on theoretical basis to interpret the experiment and analysis
Rotational Motion of Micropolar Fluid Spheroid in Concentric Spheroidal Container
No full textThe slow steady rotation of a micropolar fluid spheroid whose shape deviates slightly from that of a sphere in concentric spheroidal container filled with Newtonian viscous fluid is studied analytically. The boundary conditions used are the continuity of velocity and stress components, and spin vorticity relation. The torque and wall correction factor exerted on the micropolar fluid spheroid is obtained. The dependence of wall correction factor on the micropolarity parameter, spin parameter, viscosity ratio and deformation parameter is studied numerically and its variation is presented graphically. In the limiting cases, the torque acting on solid spheroid in spheroidal container and on the solid spheroid in unbounded medium are obtained from the present analysis
Control of the Convective Flow Instabilities in a Simulated Czochralski Growth System
Get PDFA three-dimensional time-dependent numerical study of the flow instabilities in a simulated Czochralski system is conducted. The comparison with previously published experimental results is reported. The simulations were performed using a refined grid in order to investigate flow instabilities in the crucible. Simulations have been carried out for various crystal rotational speeds, by taking into account the effects of Rayleigh and Marangoni numbers. The temperature fluctuations near the crystal/liquid interface are analyzed. The method used for that purpose is the Fast Fourier Transform with the corresponding spectra. From numerical simulations, it has been observed that for rotational speeds of the crystal less than 10 rpm, the temperature fluctuations are increased until a magnitude of 1.1 K over a period of 6 min. For crystal speeds larger than 10 rpm the fluctuations are extremely reduced to a magnitude less than 0.02 K