Search results for: crack investigation

Authors: Won Jung, Wan Emri

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Ferrite magnet is widely used in many automotive components such as motors and alternators. Magnets used inside the components must be in good quality to ensure the high level of performance. The purpose of this study is to design input parameters that optimize the ferrite magnet production process to ensure the quality and reliability of manufactured products. Design of Experiments (DOE) and Statistical Process Control (SPC) are used as mutual supplementations to optimize the process. DOE and SPC are quality tools being used in the industry to monitor and improve the manufacturing process condition. These tools are practically used to maintain the process on target and within the limits of natural variation. A mixed Taguchi method is utilized for optimization purpose as a part of DOE analysis. SPC with proportion data is applied to assess the output parameters to determine the optimal operating conditions. An example of case involving the monitoring and optimization of ferrite magnet process was presented to demonstrate the effectiveness of this approach. Through the utilization of these tools, reliable magnets can be produced by following the step by step procedures of proposed framework. One of the main contributions of this study was producing the crack free magnets by applying the proposed parameter design.

Keywords: ferrite magnet, crack, reliability, process optimization, Taguchi method

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Authors: H. S. S Abou El-Mal, A. S. Sherbini, H. E. M. Sallam

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Mode II fracture toughness (KIIc) of fiber reinforced concrete has been widely investigated under various patterns of testing geometries. The effect of fiber type, concrete matrix properties, and testing mechanisms were extensively studied. The area of hybrid fiber addition shows a lake of reported research data. In this paper an experimental investigation of hybrid fiber embedded in high strength concrete matrix is reported. Three different types of fibers; namely steel (S), glass (G), and polypropylene (PP) fibers were mixed together in four hybridization patterns, (S/G), (S/PP), (G/PP), (S/G/PP) with constant cumulative volume fraction (Vf) of 1.5%. The concrete matrix properties were kept the same for all hybrid fiber reinforced concrete patterns. In an attempt to estimate a fairly accepted value of fracture toughness KIIc, four testing geometries and loading types are employed in this investigation. Four point shear, Brazilian notched disc, double notched cube, and double edge notched specimens are investigated in a trial to avoid the limitations and sensitivity of each test regarding geometry, size effect, constraint condition, and the crack length to specimen width ratio a/w. The addition of all hybridization patterns of fiber reduced the compressive strength and increased mode II fracture toughness in pure mode II tests. Mode II fracture toughness of concrete KIIc decreased with the increment of a/w ratio for all concretes and test geometries. Mode II fracture toughness KIIc is found to be sensitive to the hybridization patterns of fiber. The (S/PP) hybridization pattern showed higher values than all other patterns, while the (S/G/PP) showed insignificant enhancement on mode II fracture toughness (KIIc). Four point shear (4PS) test set up reflects the most reliable values of mode II fracture toughness KIIc of concrete. Mode II fracture toughness KIIc of concrete couldn’t be assumed as a real material property.

Keywords: fiber reinforced concrete, Hybrid fiber, Mode II fracture toughness, testing geometry

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Authors: Hailye Tekleselassie

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Edge computing is a spread computing outline that transports initiative applications closer to data sources such as IoT devices or local edge servers, and possible happenstances would skull the action of new technologies. However, this investigation was attained to investigation the consciousness of technology and communications organization workers and computer users who support the service cloud. Surveys were used to achieve these objectives. Surveys were intended to attain these aims, and it is the functional using survey. Enquiries about confidence are also a key question. Problems like data privacy, integrity, and availability are the factors affecting the company’s acceptance of the service cloud.

Keywords: IoT, data, security, edge computing

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Authors: Ugo Galvanetto, Pirto G. Pavan, Mirco Zaccariotto

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The discipline of Computer-integrated surgery (CIS) will provide equipment able to improve the efficiency of healthcare systems and, which is more important, clinical results. Surgeons and machines will cooperate in new ways that will extend surgeons’ ability to train, plan and carry out surgery. Patient specific CIS of the brain requires several steps: 1 - Fast generation of brain models. Based on image recognition of MR images and equipped with artificial intelligence, image recognition techniques should differentiate among all brain tissues and segment them. After that, automatic mesh generation should create the mathematical model of the brain in which the various tissues (white matter, grey matter, cerebrospinal fluid …) are clearly located in the correct positions. 2 – Reliable and fast simulation of the surgical process. Computational mechanics will be the crucial aspect of the entire procedure. New algorithms will be used to simulate the mechanical behaviour of cutting through cerebral tissues. 3 – Real time provision of visual and haptic feedback A sophisticated human-machine interface based on ergonomics and psychology will provide the feedback to the surgeon. The present work will address in particular point 2. Modelling the cutting of soft tissue in a structure as complex as the human brain is an extremely challenging problem in computational mechanics. The finite element method (FEM), that accurately represents complex geometries and accounts for material and geometrical nonlinearities, is the most used computational tool to simulate the mechanical response of soft tissues. However, the main drawback of FEM lies in the mechanics theory on which it is based, classical continuum Mechanics, which assumes matter is a continuum with no discontinuity. FEM must resort to complex tools such as pre-defined cohesive zones, external phase-field variables, and demanding remeshing techniques to include discontinuities. However, all approaches to equip FEM computational methods with the capability to describe material separation, such as interface elements with cohesive zone models, X-FEM, element erosion, phase-field, have some drawbacks that make them unsuitable for surgery simulation. Interface elements require a-priori knowledge of crack paths. The use of XFEM in 3D is cumbersome. Element erosion does not conserve mass. The Phase Field approach adopts a diffusive crack model instead of describing true tissue separation typical of surgical procedures. Modelling discontinuities, so difficult when using computational approaches based on classical continuum Mechanics, is instead easy for novel computational methods based on Peridynamics (PD). PD is a non-local theory of mechanics formulated with no use of spatial derivatives. Its governing equations are valid at points or surfaces of discontinuity, and it is, therefore especially suited to describe crack propagation and fragmentation problems. Moreover, PD does not require any criterium to decide the direction of crack propagation or the conditions for crack branching or coalescence; in the PD-based computational methods, cracks develop spontaneously in the way which is the most convenient from an energy point of view. Therefore, in PD computational methods, crack propagation in 3D is as easy as it is in 2D, with a remarkable advantage with respect to all other computational techniques.

Keywords: computational mechanics, peridynamics, finite element, biomechanics

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Authors: Radhika V., J. M. Chandra Kishen

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The theory of critical distances (TCD), due to its appealing characteristics, has been successfully used in the past to predict the strength of brittle as well as ductile materials, weakened by the presence of stress risers under both static and fatigue loading. By utilising most of the TCD's unique features, this paper summarises an attempt for a reformulation of the point method of the TCD to predict the strength of notched plain concrete beams under mode I quasi-static loading. A zone of micro cracks, which is responsible for the non-linearity of concrete, is taken into account considering the concept of an effective elastic crack. An attempt is also made to correlate the value of the material characteristic length required for the application of TCD with the maximum aggregate size in the concrete mix, eliminating the need for any extensive experimentation prior to the application of TCD. The devised reformulation and the proposed power law based relationship is found to yield satisfactory predictions for static strength of notched plain concrete beams, with geometric dimensions of the beam, tensile strength, and maximum aggregate size of the concrete mix being the only needed input parameters.

Keywords: characteristic length, effective elastic crack, inherent material strength, modeI loading, theory of critical distances

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Authors: M. S. Belashov, A. V. Benin, Lin Hong, Sh. Sh. Nazarova, O. B. Sabirova, A. M. Uzdin, Lin Hong

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The features of calculating structures for the action of weak earthquakes are analyzed. Earthquakes with a recurrence of 30 years and 50 years are considered. In the first case, the structure is to operate normally without damage after the earthquake. In the second case, damages are allowed that do not affect the possibility of the structure operation. Three issues are emphasized: setting elastic and damping characteristics of reinforced concrete, formalization of limit states, and combinations of loads. The dependence of damping on the reinforcement coefficient is estimated. When evaluating limit states, in addition to calculations for crack resistance and strength, a human factor, i.e., the possibility of panic among people, was considered. To avoid it, it is proposed to limit a floor-by-floor speed level in certain octave ranges. Proposals have been developed for estimating the coefficients of the combination of various loads with the seismic one. As an example, coefficients of combinations of seismic and ice loads are estimated. It is shown that for strong actions, the combination coefficients for different regions turn out to be close, while for weak actions, they may differ.

Keywords: weak earthquake, frequent earthquake, damage, limit state, reinforcement, crack resistance, strength resistance, a floor-by-floor velocity, combination coefficients

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Authors: Mezidi Amar

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In this research work, crack propagation at the interface of a composite beam is considered. The behavior of composite beams (CB) depends upon a law based on relationship between tangential or normal efforts with inelastic propagation. Throughout this study, composite beams are classified like composite beams with partial connection or sandwich beams of three layers. These structural systems are controlled by the same nature of differential equations regarding their behavior in the plane, as well as out-of-plane. Multi-layer elements with partial connection are typically met in the field of timber construction where the elements are assembled by joining. The formalism of the behavior in the plane and out-of-plane of these composite beams is obtained and their results concerning the engineering aspect or simple of interpretation are proposed for the case of composite beams made up of rectangular section and simply supported section. An apparent analytical peculiarity or paradox in the bending behavior of elastic–composite beams with interlayer slip, sandwich beam or other similar problems subjected to boundary moments exists. For a fully composite beam subjected to end moments, the partial composite model will render a non-vanishing uniform value for the normal force in the individual subelement. Obtained results are similar to those for the case of vibrations in the plane as well for the composite beams as for the sandwich beams where eigen-frequencies increase with related rigidity.

Keywords: composite beam, behaviour, interface, deflection, propagation

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Authors: Ahmad El Hajjar, Joanna Eid, Salima Bouchemella, Tariq Ouahbi, Benoit Duchemin, Said Taibi

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In our present society, raw earth presents an alternative as an energy-saving building material for dealing with climate and environmental issues. Nevertheless, it has a sensitivity to water, due to the presence of fines, which has a direct effect on its consistency. This can be expressed during desiccation, by shrinkage deformations resulting in cracking that begins once the internal tensile stresses developed, due to suction, exceed the tensile strength of the material. This work deals with the evolution of the strain of clay samples, from the beginning of shrinkage until the initiation of crack, using the DIC (Digital Image Correlation) technique. In order to understand the origin of cracking, desiccation is studied for different boundary conditions and depending on the intrinsic characteristics of the material. On the other hand, a study of restrained shrinkage is carried out on the ring test to investigate the ultimate tensile strength from which the crack begins in the dough of clay. The purpose of this test is to find the type of reinforcement adapted to thwart in the cracking of the material. A microscopic analysis of the damaged area is necessary to link the macroscopic mechanisms of cracking to the various physicochemical phenomena at the microscopic scale in order to understand the different microstructural mechanisms and their impact on the macroscopic shrinkage.

Keywords: clayey soil, shrinkage, strain, cracking, digital image correlation

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Authors: Mingwei Yi, Liujie Guo, Zongjun Pan, Xiang Lin, Xiaoming Yi

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With the rapid expansion of road construction mileage in China, the scale of road maintenance needs has concurrently escalated. As the service life of roads extends, the design of pavement repair and maintenance emerges as a crucial component in preserving the excellent performance of the pavement. The remaining service life of asphalt pavement structure is a vital parameter in the lifecycle maintenance design of asphalt pavements. Based on an analysis of pavement structural integrity, this study introduces a characterization and assessment of the remaining life of existing asphalt pavement structures. It proposes indicators such as the transverse crack spacing and the length of longitudinal cracks. The transverse crack spacing decreases with an increase in maintenance intervals and with the extended use of semi-rigid base layer structures, although this trend becomes less pronounced after maintenance intervals exceed 4 years. The length of longitudinal cracks increases with longer maintenance intervals, but this trend weakens after five years. This system can support the enhancement of standardization and scientific design in highway maintenance decision-making processes.

Keywords: structural integrity, highways, pavement evaluation, asphalt concrete pavement

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Authors: Tamale Vincent

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Groundwater investigation is the investigation of underground formations to understand the hydrologic cycle, known groundwater occurrences, and identify the nature and types of aquifers. There are different groundwater investigation methods and surface geophysical method is one of the groundwater investigation more especially the Geoelectrical resistivity Schlumberger configuration method which provides valuable information regarding the lateral and vertical successions of subsurface geomaterials in terms of their individual thickness and corresponding resistivity values besides using surface geophysical method, hydrogeological and geological investigation methods are also incorporated to aid in preliminary groundwater investigation. Investigation for groundwater in lwantonde district has been implemented. The area project is located cattle corridor and the dry seasonal troubles the communities in lwantonde district of which 99% of people living there are farmers, thus making agriculture difficult and local government to provide social services to its people. The investigation was done using the Geoelectrical resistivity Schlumberger configuration method. The measurement point is located in the three sub-counties, with a total of 17 measurement points. The study location is at 0025S, 3110E, and covers an area of 160 square kilometers. Based on the results of the Geoelectrical information data, it was found two types of aquifers, which are open aquifers in depth ranging from six meters to twenty-two meters and a confined aquifer in depth ranging from forty-five meters to eighty meters. In addition to the Geoelectrical information data, drilling was done at an accessible point by heavy equipment in the Lwakagura village, Kabura sub-county. At the drilling point, artesian wells were obtained at a depth of eighty meters and can rise to two meters above the soil surface. The discovery of artesian well is then used by residents to meet the needs of clean water and for irrigation considering that in this area most wells contain iron content.

Keywords: artesian well, geoelectrical, lwantonde, Schlumberger

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Authors: Burak M. Gonultas

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Criminal investigation provides a practical contribution to this process while criminology provides a theoretical background in the apprehension of criminals arrest and clarification of crimes. However, studies on criminal investigation, which is a practical aspect of this process, are not sufficient. Every crime involves different dynamics in terms of investigation. But investigations of serious crimes are versatile and contains complex processes because of cases they are conducted. Therefore, professionals who conduct serious crime investigations differ in some aspects from others in the field. The most fundamental element of this differentiation is skills and abilities of these professionals. According to Eurostat data, Turkey is in an important position in terms of homicide rates. Therefore, in Turkey practice of serious crime investigation is specialized. The present study aims to research the skills and abilities expected from professionals in conducting an effective serious criminal investigation in Turkey and so aims to offer a number of suggestions. 25 emerged ability and skills collected from literature were asked to professionals (n=289) with semi-structured form according to 5 provinces with the highest and 2 provinces with the lowest number of serious crime cases. Three data categories were collected during experience: 1- Five most important skills and abilities, 2- The most important skills for knowledge and inquiry management and 3- Ability and skills that stand out for five stages of serious criminal investigation. The most rated skills and abilities are investigative skill (13%, n=134), planning/designing (9,2%, n=95) and interpersonal relations/communication (8,8%, n=91) in 1010 skills and abilities. While the 1st and 2nd suggest elections of these professionals, the 3rd also suggests how and what type of training will be given to these professionals. This practice differs from other studies in the area in terms of separately addressing the skills and abilities expected in stages of investigation and in terms of selected methodology.

Keywords: ability, criminal investigation, criminology, homicide, serious crimes, skill, Turkey

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Authors: S. A. Anuar, N. H. Hamid, M. H. Hashim, S. M. D. Salleh

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This paper present the experimental work on the seismic performance of double unit tunnel form building (TFB) subjected to in-plane lateral cyclic loading. A one third scale of 3-storey double unit of TFB is tested at ±0.01%, ±0.1%, ±0.25%, ±0.5%, ±0.75% and ±1.0% drifts until the structure achieves its strength degradation. After that, the TFB is repaired and retrofitted using additional shear wall, steel angle and CFRP sheet. A similar testing approach is applied to the specimen after repair and retrofit. The crack patterns, lateral strength, stiffness, ductility and equivalent viscous damping (EVD) were analyzed and compared before and after repair and retrofit. The result indicates that the lateral strength increases by 22 in pushing direction and 27% in pulling direction. Moreover, the stiffness and ductility obtained before and after retrofit increase tremendously by 87.87% and 39.66%, respectively. Meanwhile, the energy absorption measured by equivalent viscous damping obtained after retrofit increase by 12.34% in pulling direction. It can be concluded that the proposed retrofit method is capable to increase the lateral strength capacity, stiffness and energy absorption of double unit TFB.

Keywords: tunnel form building, in-plane lateral cyclic loading, crack pattern, lateral strength, stiffness, ductility, equivalent viscous damping, repair and retrofit

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Authors: Safitri W. Nur, Prathisto Panuntun L. Unggul, M. Ivan Adi Perdana, R. Dary Wira Mahadika

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On soft soil areas, high embankment as a preloading needed to improve the bearing capacity of the soil. For sustainable development, the construction of embankment must not disturb the area around of them. So, the influence area must be known before the contractor applied their embankment design. For several cases in Indonesia, the area around of embankment construction is housing resident and other building. So that, the influence area must be identified to avoid the differential settlement occurs on the buildings around of them. Differential settlement causes the building crack. Each building has a limited tolerance for the differential settlement. For concrete buildings, the tolerance is 0,002 – 0,003 m and for steel buildings, the tolerance is 0,006 – 0,008 m. If the differential settlement stands on the range of that value, building crack can be avoided. In fact, the settlement around of embankment is assumed as zero. Because of that, so many problems happen when high embankment applied on soft soil area. This research used the superposition method combined with plaxis analysis to know the influences area around of embankment in some location with the differential characteristic of the soft soil. The undisturbed soil samples take on 55 locations with undisturbed soil samples at some soft soils location in Indonesia. Based on this research, it was concluded that the effects of embankment variation are if more gentle the slope, the influence area will be greater and vice versa. The largest of the influence area with h initial embankment equal to 2 - 6 m with slopes 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 is 32 m from the edge of the embankment.

Keywords: differential settlement, embankment, influence area, slope, soft soil

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Authors: Bijit Kalita, K. V. N. Surendra

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The pulley works under both compressive loading due to contacting belt in tension and central torque due to cause rotation. In a power transmission system, the belt pulley assemblies offer a contact problem in the form of two mating cylindrical parts. In this work, we modeled a pulley as a heavy two-dimensional circular disk. Stress analysis due to contact loading in the pulley mechanism is performed. Finite element analysis (FEA) is conducted for a pulley to investigate the stresses experienced on its inner and outer periphery. In most of the heavy-duty applications, most frequently used mechanisms to transmit power in applications such as automotive engines, industrial machines, etc. is Belt Drive. Usually, very heavy circular disks are used as pulleys. A pulley could be entitled as a drum and may have a groove between two flanges around the circumference. A rope, belt, cable or chain can be the driving element of a pulley system that runs over the pulley inside the groove. A pulley is experienced by normal and shear tractions on its contact region in the process of motion transmission. The region may be belt-pulley contact surface or pulley-shaft contact surface. In 1895, Hertz solved the elastic contact problem for point contact and line contact of an ideal smooth object. Afterward, this hypothesis is generally utilized for computing the actual contact zone. Detailed stress analysis in such contact region of such pulleys is quite necessary to prevent early failure. In this paper, the results of the finite element analyses carried out on the compressed disk of a belt pulley arrangement using fracture mechanics concepts are shown. Based on the literature on contact stress problem induced in the wide field of applications, generated stress distribution on the shaft-pulley and belt-pulley interfaces due to the application of high-tension and torque was evaluated in this study using FEA concepts. Finally, the results obtained from ANSYS (APDL) were compared with the Hertzian contact theory. The study is mainly focused on the fatigue life estimation of a rotating part as a component of an engine assembly using the most famous Paris equation. Digital Image Correlation (DIC) analyses have been performed using the open-source software. From the displacement computed using the images acquired at a minimum and maximum force, displacement field amplitude is computed. From these fields, the crack path is defined and stress intensity factors and crack tip position are extracted. A non-linear least-squares projection is used for the purpose of the estimation of fatigue crack growth. Further study will be extended for the various application of rotating machinery such as rotating flywheel disk, jet engine, compressor disk, roller disk cutter etc., where Stress Intensity Factor (SIF) calculation plays a significant role on the accuracy and reliability of a safe design. Additionally, this study will be progressed to predict crack propagation in the pulley using maximum tangential stress (MTS) criteria for mixed mode fracture.

Keywords: crack-tip deformations, contact stress, stress concentration, stress intensity factor

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Authors: Alae Lamtai, Said Elkoun, Hniya Kharmoudi, Mathieu Robert, Carl Diez

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This study applies Taguchi's design of experiment methodology and grey relational analysis (GRA) for multi objective optimization of an industrial recycling line. This last is composed mainly of a mono and twin-screw extruder and a filtration system. Experiments were performed according to L_16 standard orthogonal array based on five process parameters namely: mono screw design, screw speed of the mono and twin-screw extruder, melt pump pressure and filter mesh size. The objective of this optimization is to decrease the loss of Stress Crack resistance (SCR) using Notched Crack Ligament Stress (NCLS) test and increase the gain of the elongation at break, flexural modulus, and Izod impact strength of the Polyethylene (PE) blend before and after recycling. Based on Grey Relational Analysis (GRA), the optimal setting of process parameters was identified, and the analysis of variance (ANOVA) indicated that mono-screw design and screw speed of the mono and twin-screw extruder impact significantly the mechanical properties of recycled Polyethylene (PE) blend.

Keywords: mechanical recycling, stress cracking resistance (SCR), anova, taguchi, grey relational analysis

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Authors: Faraj A. E. Alhegagi, Bassam F. A. Alhajaji

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Ductile and brittle fractures are the two main modes for the failure of engineering components. Fractures are classified with respect to several characteristics, such as strain to fracture, ductile or brittle crystallographic mode, shear or cleavage, and the appearance of fracture, granular or transgranular. Cleavage is a brittle fracture involves transcrystalline fracture along specific crystallographic planes and in certain directions. Fracture of duplex stainless steels takes place transgranularly by cleavage of the ferrite phase. On the other hand, ductile fracture occurs after considerable plastic deformation prior to failure and takes place by void nucleation, growth, and coalescence to provide an easy fracture path. Twinning causes depassivation more readily than slip and appears at stress lower than the theoretical yield stress. Consequently, damage due to twinning can occur well before that due to slip. Stainless steels are clean materials with the low efficiency of second particles phases on the fracture mechanism. The ferrite cleavage and austenite tear off are the main mode by which duplex stainless steels fails. In this study, the cracking mode and path of specimens of duplex stainless steels were investigated. Zeron 100 specimens were heat treated to different times cooled down and pulled to failure. The fracture surface was investigated by scanning electron microscopy (SEM) concentrating on the cracking mechanism, path, and origin. Cracking mechanisms were studied for those grains either as ferrite or austenite grains identified according to fracture surface features. Cracks propagated through the ferrite and the austenite two phases were investigated. Cracks arrested at the grain boundary were studied as well. For specimens aged for 100h, the ferrite phase was noted to crack by cleavage along well-defined planes while austenite ridges were clearly observed within the ferrite grains. Some grains were observed to fail with topographic features that were not clearly identifiable as ferrite cleavage or austenite tearing. Transgranular cracking was observed taking place in the ferrite phase on well-defined planes. No intergranular cracks were observed for the tested material. The austenite phase was observed to serve as a crack bridge and crack arrester.

Keywords: austenite ductile tear off, cracking mode, ferrite cleavage, stainless steels failure

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Authors: Naik Nithesh, Andre Rozek

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The heat transfer and friction loss performances of a single rib-roughened rectangular cooling channel having four novel rib shapes were evaluated through numerical investigation using Ansys CFX. The investigation was conducted on a rectangular channel of aspect ratio (AR) = 4:1 with rib height to hydraulic diameter ratio (e/Dh) of 0.1 and rib pitch to height ratio (e/P) of 10 at Re = 30,000. The computations were performed by solving the RANS equation using k-ε turbulence model. Fluid flow simulation results of stationery case for different configuration are presented in terms of thermal performance parameter, Nusselt number and friction factor. These parameters indicate that a particular configuration of novel shaped ribs provides better heat transfer characteristics over the conventional 45° ribs. The numerical investigation undertaken in this study indicates an increase in overall efficiency of gas turbine due to increased thermal performance parameter, heat transfer co-efficient and less pumping pressure.

Keywords: gas turbine, rib shapes, nusselt number, thermal performance parameter

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Authors: C. E. Sutton, A. Varvani-Farahani

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Fatigue damage and life prediction of particle metal matrix composites (PMMCs) under uniaxial and multiaxial loading conditions were investigated. Three PMM composite materials of Al6061/Al2O3/20p-T6, Al6061/Al2O3/22p-T6 and Al6061/SiC/17w-T6 tested under tensile, torsion, and combined tension-torsion fatigue cycling were evaluated with various fatigue damage models. The fatigue damage models of Smith-Watson-Topper (S. W. T.), Ellyin, Brown-Miller, Fatemi-Socie, and Varvani were compared for their capability to assess the fatigue damage of materials undergoing various loading conditions. Fatigue life predication results were then evaluated by implementing material-dependent coefficients that factored in the effects of the particle reinforcement in the earlier developed Varvani model. The critical plane-energy approach incorporated the critical plane as the plane of crack initiation and early stage of crack growth. The strain energy density was calculated on the critical plane incorporating stress and strain components acting on the plane. This approach successfully evaluated fatigue damage values versus fatigue lives within a narrower band for both uniaxial and multiaxial loading conditions as compared with other damage approaches studied in this paper.

Keywords: fatigue damage, life prediction, critical plane approach, energy approach, PMM composites

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Authors: Farshad Amini, Kejun Wen

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The formation of reflective cracking of pavement overlays has confronted highway engineers for many years. Stress-relieving interlayers, such as paving fabrics, have been used in an attempt to reduce or delay reflective cracking. The effectiveness of paving fabrics in reducing reflection cracking is related to joint or crack movement in the underlying pavement, crack width, overlay thickness, subgrade conditions, climate, and traffic volume. The nonwoven geotextiles are installed between the old and new asphalt layers. Paving fabrics enhance performance through two mechanisms: stress relief and waterproofing. Several factors including proper installation, remedial work performed before overlay, overlay thickness, variability of pavement strength, existing pavement condition, base/subgrade support condition, and traffic volume affect the performance. The primary objective of this study was to conduct a long-term monitoring of the paving fabric interlayer systems to evaluate its effectiveness and performance. A comprehensive testing, monitoring, and analysis program were undertaken, where twelve 500-ft pavement sections of a four-lane highway were rehabilitated, and then monitored for seven years. A comparison between the performance of paving fabric treatment systems and control sections is reported. Lessons learned, and the various factors are discussed.

Keywords: monitoring, paving fabrics, performance, reflective cracking

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Authors: Med. A. Djeridane, M. Ferhat, H. A. Benhorma, O. Bouledroua

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This research is dedicated to exploring the failure of a turbine blade within a gas transportation plant, with a primary focus on conducting a comprehensive examination through advanced metallurgical and mechanical analyses of the identified failed blade. Crafted from the nickel superalloy Inconel IN738LC, the turbine engine had accumulated approximately 61,000 operational hours before the blades failed, causing severe damage to the transportation plant and necessitating a prolonged shutdown. The investigative procedure commenced with an in-depth visual inspection of the blade surfaces, succeeded by fractography analysis of the fracture surfaces, microstructural investigations, chemical analysis, and hardness measurements. The findings unveiled distinctive fatigue marks on the fracture surface. Critical microstructural changes were identified as a consequence of the blade's operation at high temperatures. The investigation determined that the crack initiation resulted from coating damage at the leading edge, subsequently propagating through fatigue. Ultimately, due to a reduction in cross-sectional area, the fracture was completed. This comprehensive analysis sheds light on the intricate factors contributing to turbine blade failure and offers valuable insights for enhancing operational reliability in similar environments.

Keywords: gas turbine, blade failure, TCP phases, fatigue, quantitative analysis

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Authors: Emilio A. Berny-Brandt, Sonia E. Ruiz

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Steel tubular towers serving as support structures for large wind turbines are subject to several hundred million stress cycles arising from the turbulent nature of the wind. This causes high-cycle fatigue which can govern tower design. The practice of maintaining the support structure after wind turbines reach its typical 20-year design life have become common, but without quantifying the changes in the reliability on the tower. There are several studies on this topic, but most of them are based on the S-N curve approach using the Miner’s rule damage summation method, the de-facto standard in the wind industry. However, the qualitative nature of Miner’s method makes desirable the use of fracture mechanics to measure the effects of fatigue in the capacity curve of the structure, which is important in order to evaluate the integrity and reliability of these towers. Temporal and spatially varying wind speed time histories are simulated based on power spectral density and coherence functions. Simulations are then applied to a SAP2000 finite element model and step-by-step analysis is used to obtain the stress time histories for a range of representative wind speeds expected during service conditions of the wind turbine. Rainflow method is then used to obtain cycle and stress range information of each of these time histories and a statistical analysis is performed to obtain the distribution parameters of each variable. Monte Carlo simulation is used here to evaluate crack growth over time in the tower base using the Paris-Erdogan equation. A nonlinear static pushover analysis to assess the capacity curve of the structure after a number of years is performed. The capacity curves are then used to evaluate the changes in reliability of a steel tower located in Oaxaca, Mexico, where wind energy facilities are expected to grow in the near future. Results show that fatigue on the tower base can have significant effects on the structural capacity of the wind turbine, especially after the 20-year design life when the crack growth curve starts behaving exponentially.

Keywords: crack growth, fatigue, Monte Carlo simulation, structural reliability, wind turbines

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Authors: Ravande Kishore

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The paper present the results of experimental investigation carried out to understand the mechanical properties of concrete containing marble dust. Two grades of concrete viz. M25 and M35 have been considered for investigation. For each grade of concrete five replacement percentages of sand viz. 5%, 10%, 15%, 20% and 25% by marble dust have been considered. In all, 12 concrete mix cases including two control concrete mixtures have been studied to understand the key properties such as Compressive strength, Modulus of elasticity, Modulus of rupture and Split tensile strength. Development of Compressive strength is also investigated. In general, the results of investigation indicated improved performance of concrete mixture containing marble dust. About 21% increase in Compressive strength is noticed for concrete mixtures containing 20% marble dust and 80% river sand. An overall assessment of investigation results pointed towards high potential for marble dust as alternative construction material coming from waste generated in marble industry.

Keywords: construction material, partial replacement, marble dust, compressive strength

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Authors: R. A. Shahmiri, O. Standard, J. Hart, C. C. Sorrell

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Yttrium stabilized tetragonal zirconium polycrystalline (Y-TZP) has been used as a dental biomaterial. The strength and toughness of zirconia can be accounted for by its toughening mechanisms, such as crack deflection, zone shielding, contact shielding, and crack bridging. Prevention of crack propagation is of critical importance in high-fatigue situations, such as those encountered in mastication and para-function. However, the poor translucency of Y-TZP means that it may not meet the aesthetic requirements due to its white/grey appearance in polycrystalline form. To improve optical property of the Zirconia, precise evaluation of its refractive index is of significance. Zirconia`s optical properties need to be studied more in depth. Number of studies assumed, scattered light is isotropically distributed over all angles from biological media when defining optical parameters. Nevertheless, optical behaviour of real biological material depends on angular scattering of light by anisotropy material. Therefore, the average cosine of the scattering angle (which represent recovery phase function in the scattering angular distribution) usually characterized by anisotropy material. It has been identified that yttrium anti-sites present in the space charge layer have no significant role in the absorption of light in the visible range. Addition of cation dopant to polycrystalline zirconia results in segregate to grain boundaries and grain growth. Intrinsic and extrinsic properties of ZrO2 and their effect on optical properties need to be investigated. Intrinsic properties such as chemical composition, defect structure (oxygen vacancy), phase configuration (porosity, second phase) and distribution of phase need to be studied to comprehend their effect on refraction index, absorption/reflection and scattering. Extrinsic properties such as surface structure, thickness, underlying tooth structure, cement layer (type, thickness), and light source (natural, curing, artificial) of ZrO2 need to be studied to understand their effect on colour and translucency of material. This research reviewed effect of stabilization of tetragonal zirconia on optical property of zirconia for dental application.

Keywords: optical properties, zirconia dental biomaterial, chemical composition, phase composition

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Authors: Daniel P. Clayton, Edward A. Ball

Abstract:

This paper describes an investigation into the isolation characteristics and bandwidth performance of RF combiners that are used as part of Chireix PA architectures, designed for use in the X-Band range of frequencies. Combiner designs investigated are the typical Chireix and Wilkinson configurations which also include simulation of the Wilkinson using manufacturer’s data for the isolation resistor. Another simulation was the less common approach of using a Branchline coupler to form the combiner, as well as simulation results from adding an additional stage. This paper presents the findings of this investigation and compares the bandwidth performance and isolation characteristics to determine suitability.

Keywords: bandwidth, Chireix, couplers, outphasing, power amplifiers, Wilkinson, X-Band

Procedia PDF Downloads 223

Authors: Ashwini Shripatwar, Mayur Biyani, Nikhil Rao, Rajendra Bodake, Sachin Sane

Abstract:

This paper documents the correlation of valve cover sealing, cracking, and warpage Finite Element Modelling with observations on engine test development. The valve cover is a component mounted on engine head with a gasket which provides sealing against oil which flows around camshaft, valves, rockers, and other overhead components. Material nonlinearity and contact nonlinearity characteristics are taken into consideration because the valve cover is made of a composite material having temperature dependent elastic-plastic properties and because the gasket load-deformation curve is also nonlinear. The leakage is observed between the valve cover and the engine head due to the insufficient contact pressure. The crack is observed on the valve cover due to force application at a region with insufficient stiffness and with elevated temperature. The valve cover shrinkage is observed during the disassembly process on hot exhaust side bolt holes after the engine has been running. In this paper, an analytical approach is developed to correlate a Finite Element Model with the observed failures and to address the design issues associated with the failure modes in question by making design changes in the model.

Keywords: cracking issue, gasket sealing analysis, nonlinearity of contact and material, valve cover

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Authors: Benzerara Mohammed, Redjel Bachir, Kebaili Bachir

Abstract:

The cracking of the concrete is a more crucial problem with the development of the complex structures related to technological progress. The projections in the knowledge of the breaking process make it possible today for better prevention of the risk of the fracture. The breaking strength brutal of a quasi-fragile material like the concrete called Toughness, is measured by a breaking value of the factor of intensity of the constraints K1C for which the crack is propagated, it is an intrinsic property of material. Many studies reported in the literature treating of the concrete were carried out on specimens which are in fact inadequate compared to the intrinsic characteristic to identify. We started from this established fact, in order to compare the evolution of the parameter of toughness K1C measured by calling upon ordinary concrete specimens of three prismatics geometries different (10*10*84) cm³ and (5*20*120) cm³ &(12*20*120) cm³ containing from the side notches various depths simulating of the cracks was set up. The notches are carried out using triangular pyramidal plates into manufactured out of sheet coated placed at the centre of the specimens at the time of the casting, then withdrawn to leave the trace of a crack. The tests are carried out in 3 points bending test in mode 1 of fracture, by using the techniques of mechanical fracture. The evolution of the parameter of toughness K1C measured with the three geometries specimens gives almost the same results. They are acceptable and return in the beach of the results determined by various researchers (toughness of the ordinary concrete turns to the turn of the 1 MPa √m). These results inform us about the presence of an economy on the level of the geometrie specimen (5*20*120) cm³, therefore to use plates specimens later if one wants to master the toughness of this material complexes, astonishing but always essential that is the concrete.

Keywords: elementary representative volume, concrete, fissure, toughness

Procedia PDF Downloads 187

Authors: Stephen J Futter, Michael I Okereke

Abstract:

This paper presents an investigation of the premature in-service failure of the engine mounting towers that form part of the bedframe commonly used for industrial power generation applications. The client during a routine in-service assessment of the generator set observed that the engine mounting towers had cracked. Thus, this study has investigated in detail the origin of the crack and proffered solutions to prevent a re-occurrence. Seven step problem solving methodology was followed during this paper. The study used both experimental and numerical approaches to understand, monitor and evaluate the cause and evolution of the premature failure. Findings from this study indicated that the failure resulted from a combination of varied processes from procurement of material parts, material selection, welding processes and inaptly designed load-bearing mechanics of the generating set and its mounting arrangement. These in-field observations and experimental simulations provided insights to design and validate a numerical finite element sub-model of the cracked bedframe considering thermal cycling: designed as part of these investigations. Resulting findings led to a recommendation of several procedural changes that should be adopted by the manufacturer, in order to prevent the re-occurrence of such pre-mature failure in future industrial applications.

Keywords: Engine, Premature Failure, Failure Analysis, Finite Element Model

Procedia PDF Downloads 258

Authors: T. A. Sakr, Hanaa E. Abd-El-Mottaleb

Abstract:

Outrigger-braced wall systems are commonly used to provide high rise buildings with the required lateral stiffness for wind and earthquake resistance. The existence of outriggers adds to the stiffness and strength of walls as reported by several studies. The effects of different parameters on the elasto-plastic dynamic behavior of outrigger-braced wall systems to earthquakes are investigated in this study. Parameters investigated include outrigger stiffness, concrete strength, and reinforcement arrangement as the main design parameters in wall design. In addition to being significant to the wall behavior, such parameters may lead to the change of failure mode and the delay of crack propagation and consequently failure as the wall is excited by earthquakes. Bi-linear stress-strain relation for concrete with limited tensile strength and truss members with bi-linear stress-strain relation for reinforcement were used in the finite element analysis of the problem. The famous earthquake record, El-Centro, 1940 is used in the study. Emphasis was given to the lateral drift, normal stresses and crack pattern as behavior controlling determinants. Results indicated significant effect of the studied parameters such that stiffer outrigger, higher grade concrete and concentrating the reinforcement at wall edges enhance the behavior of the system. Concrete stresses and cracking behavior are sigbificantly enhanced while lesser drift improvements are observed.

Keywords: outrigger, shear wall, earthquake, nonlinear

Procedia PDF Downloads 256

Authors: Suk Woo Hong, Chang Sung Seok, Jae Mean Koo

Abstract:

Recently, the welding is widely used in modern industry for joining the structures. However, the waterworks pipes are exposed to the fatigue load by cars, earthquake and etc because of being buried underground. Moreover, the residual stress exists in weld zone by welding process and it is well known that the fatigue life of welded structures is degraded by residual stress. Due to such reasons, the crack can occur in the weld zone of pipeline. In this case, The ground subsidence or sinkhole can occur, if the soil and sand are washed down by fluid leaked from the crack of water pipe. These problems can lead to property damage and endangering lives. For these reasons, the estimation of fatigue characteristics for water pipeline weld zone is needed. Therefore, in this study, for fatigue characteristics estimation of spiral welded waterworks pipe, ASTM standard specimens and Curved Plate specimens were collected from the spiral welded waterworks pipe and the fatigue tests were performed. The S-N curves of each specimen were estimated, and then the fatigue life of weldment Curved Plate specimen was predicted by theoretical and analytical methods. After that, the weldment Curved Plate specimens were collected from the pipe and verification fatigue tests were performed. Finally, it was verified that the predicted S-N curve of weldment Curved Plate specimen was good agreement with fatigue test data.

Keywords: spiral welded pipe, prediction fatigue life, endurance limit modifying factors, residual stress

Procedia PDF Downloads 265

Authors: Vidit Mohan, Ashwin P. Ramesh, Anirudh Toshniwal

Abstract:

Alkali-Surfactant-Alternate-Gas(ASAG) injection, a novel EOR process has the potential to improve displacement efficiency over Surfactant-Alternate-Gas(SAG) by addressing the problem of surfactant adsorption by clay minerals in rock matrix. A detailed laboratory investigation on ASAG injection process was carried out with encouraging results. To further enhance recovery over WAG injection process, SAG injection was investigated at laboratory scale. SAG injection yielded marginal incremental displacement efficiency over WAG process. On investigation, it was found that, clay minerals in rock matrix adsorbed the surfactants and were detrimental for SAG process. Hence, ASAG injection was conceptualized using alkali as a clay stabilizer. The experiment of ASAG injection with surfactant concentration of 5000 ppm and alkali concentration of 0.5 weight% yields incremental displacement efficiency of 5.42% over WAG process. The ASAG injection is a new process and has potential to enhance efficiency of WAG/SAG injection process.

Keywords: alkali surfactant alternate gas (ASAG), surfactant alternate gas (SAG), laboratory investigation, EOR process

Procedia PDF Downloads 440