Search results for: elastic fracture toughness

Authors: Shao-Huang Wu, Ai-Yun Wu, Meng-Chen Wu, Chun-Liang Wu, Kai-Ping Shaw, Hsiao-Ting Chen

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Objective: To analyze the forensic autopsy data of known passengers and compare it with the National database of the autopsy report in 2017, and obtain the special patterned injuries, which can be used as the reference for the reconstruction of hit-and-run motor vehicle accidents. Methods: Analyze the items of the Motor Vehicle Accident Report, including Date of accident, Time occurred, Day, Acc. severity, Acc. Location, Acc. Class, Collision with Vehicle, Motorcyclists Codes, Safety equipment use, etc. Analyzed the items of the Autopsy Report included, including General Description, Clothing and Valuables, External Examination, Head and Neck Trauma, Trunk Trauma, Other Injuries, Internal Examination, Associated Items, Autopsy Determinations, etc. Materials: Case 1. The process of injury formation: the car was chased forward and collided with the scooter. The passenger wearing the helmet fell to the ground. The helmet crashed under the bottom of the sedan, and the bottom of the sedan was raised. Additionally, the sedan was hit on the left by the other sedan behind, resulting in the front sedan turning 180 degrees on the spot. The passenger’s head was rotated, and the cervical spine was fractured. Injuries: 1. Fracture of atlantoaxial joint 2. Fracture of the left clavicle, scapula, and proximal humerus 3. Fracture of the 1-10 left ribs and 2-7 right ribs with lung contusion and hemothorax 4. Fracture of the transverse process of 2-5 lumbar vertebras 5. Comminuted fracture of the right femur 6. Suspected subarachnoid space and subdural hemorrhage 7. Laceration of the spleen. Case 2. The process of injury formation: The motorcyclist wearing the helmet fell to the left by himself, and his chest was crushed by the car going straight. Only his upper body was under the car and the helmet finally fell off. Injuries: 1. Dislocation of atlantoaxial joint 2. Laceration on the left posterior occipital 3. Laceration on the left frontal 4. Laceration on the left side of the chin 5. Strip bruising on the anterior neck 6. Open rib fracture of the right chest wall 7. Comminuted fracture of both 1-12 ribs 8. Fracture of the sternum 9. Rupture of the left lung 10. Rupture of the left and right atria, heart tip and several large vessels 11. The aortic root is nearly transected 12. Severe rupture of the liver. Results: The common features of the two cases were the fracture or dislocation of the atlantoaxial joint and both helmets that were crashed. There were no atlantoaxial fractures or dislocations in 27 pedestrians (without wearing a helmet) versus motor vehicle accidents in 2017 the National database of an autopsy report, but there were two atlantoaxial fracture or dislocation cases in the database, both of which were cases of falling from height. Conclusion: The cervical spine fracture injury of the motorcyclist, who was wearing a helmet, is very likely to be a patterned injury caused by his/her fall and rollover under the sedan. It could provide a reference for forensic peers.

Keywords: patterned injuries, atlantoaxial fracture or dislocation, accident reconstruction, motorcycle accident with helmet, forensic autopsy data

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Authors: Jipeng Yan, Xingchen Yang, Xiaowei Zhou, Mengxing Tang, Honghai Liu

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Shear elastic modulus of skeletal muscles can be obtained by shear wave elastography (SWE) and has been linearly related to muscle force. However, SWE is currently implemented using array probes. Price and volumes of these probes and their driving equipment prevent SWE from being used in wearable human-machine interfaces (HMI). Moreover, beamforming processing for array probes reduces the real-time performance. To achieve SWE by wearable HMIs, a customized three-element probe is adopted in this work, with one element for acoustic radiation force generation and the others for shear wave tracking. In-phase quadrature demodulation and 2D autocorrelation are adopted to estimate velocities of tissues on the sound beams of the latter two elements. Shear wave speeds are calculated by phase shift between the tissue velocities. Three agar phantoms with different elasticities were made by changing the weights of agar. Values of the shear elastic modulus of the phantoms were measured as 8.98, 23.06 and 36.74 kPa at a depth of 7.5 mm respectively. This work verifies the feasibility of measuring shear elastic modulus by wearable devices.

Keywords: shear elastic modulus, skeletal muscle, ultrasound, wearable human-machine interface

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Authors: A. H. Yehia, M. M. Rashwan, K. A. Assaf, K. Abd el Samee

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The aim of this work is to use an environmental, cheap; organic non-traditional admixture to improve the structural behavior of sustainable reinforced concrete beams contains different ratios of recycled concrete aggregate. The used admixture prepared by using wastes from vegetable oil industry. Under and over reinforced concrete beams made from natural aggregate and different ratios of recycled concrete aggregate were tested under static load until failure. Eight beams were tested to investigate the performance and mechanism effect of admixture on improving deformation characteristics, modulus of elasticity and toughness of tested beams. Test results show efficiency of organic admixture on improving flexural behavior of beams contains 20% recycled concrete aggregate more over the other ratios.

Keywords: deflection, modulus of elasticity, non-traditional admixture, recycled concrete aggregate, strain, toughness, under and over reinforcement

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Authors: Reda Abdel Azim

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Gas conning phenomenon considered one of the prevalent matter in oil field applications as it significantly affects the amount of produced oil, increase cost of production operation and it has a direct effect on oil reservoirs recovery efficiency as well. Therefore, evaluation of such phenomenon and study the reservoir mechanisms that may strongly affect invading gas to the producing formation is crucial. Gas conning is a result of an imbalance between two major forces controlling the oil production: gravitational and viscous forces especially in naturally fractured reservoirs where the capillary pressure forces are negligible. Once the gas invading the producing formation near the wellbore due to large producing oil rate, the oil gas contact will change and such reservoirs are prone to gas conning. Moreover, the oil volume expected to be produced requires the use of long horizontal perforated well. This work presents a numerical simulation study to predict and propose solutions to gas coning in naturally fractured oil reservoirs. The simulation work is based on discrete fractures and permeability tensors approaches. The governing equations are discretized using finite element approach and Galerkin’s least square technique (GLS) is employed to stabilize the equation solutions. The developed simulator is validated against Eclipse-100 using horizontal fractures. The matrix and fracture properties are modelled. Critical rate, breakthrough time and GOR are determined to be used in investigation of the effect of matrix and fracture properties on gas coning. Results show that fracture distribution in terms of diverse dip and azimuth has a great effect on conning occurring. In addition, fracture porosity, anisotropy ratio, and fracture aperture.

Keywords: gas conning, finite element, fractured reservoirs, multiphase

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Authors: Thiago Viana

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Eventually train accidents occur on railways and for some specific cases it is necessary to use a train rescue with a crane positioned under a platform wagon. These tumbled machines are collected and sent to the machine shop or scrap yard. In one of these cranes that were being used to rescue a wagon, occurred a fall of hoist due to fracture of two large pins. The two pins were collected and sent for failure analysis. This work investigates the main cause and the secondary causes for the initiation of the fatigue crack. All standard failure analysis procedures were applied, with careful evaluation of the characteristics of the material, fractured surfaces and, mainly, metallographic tests using an optical microscope to compare the geometry of the peaks and valleys of the thread of the pins and their respective seats. By metallographic analysis, it was concluded that the fatigue cracks were started from a notch (stress concentration) in the valley of the threads of the pin applied to the right side of the crane (pin 1). In this, it was verified that the peaks of the threads of the pin seat did not have proper geometry, with sharp edges being present that caused such notches. The visual analysis showed that fracture of the pin on the left side of the crane (pin 2) was brittle type, being a consequence of the fracture of the first one. Recommendations for this and other railway cranes have been made, such as nondestructive testing, stress calculation, design review, quality control and suitability of the mechanical forming process of the seat threads and pin threads.

Keywords: crane, fracture, pin, railway

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Authors: Michael McTighe

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Background: The COVID-19 pandemic caused the cancellation of many large-scale in-person sporting events, which led to an increase in the availability of virtual ultra-marathons. This study intended to assess how participation in virtual long distances races relates to levels of physical activity for an extended period of time. Moreover, traditional ultra-marathons are known for being not only physically demanding, but also mentally and emotionally challenging. A second component of this study was to assess how psychological contructs related to emotion regulation and mental toughness predict overall performance in the sport. Method: 83 virtual runners participating in a four-month 1000-kilometer race with the option to exceed 1000 kilometers completed a questionnaire exploring demographics, their performance, and experience in the virtual race. Participants also completed the Difficulties in Emotions Regulation Scale (DERS) and the Sports Mental Toughness Questionnaire (SMTQ). Logistics regressions assessed these constructs’ utility in predicting completion of the 1000-kilometer distance in the time allotted. Multiple regression was employed to predict the total distance traversed during the fourmonth race beyond 1000-kilometers. Result: Neither mental toughness nor emotional regulation was a significant predictor of completing the virtual race’s basic 1000-kilometer finish. However, both variables included together were marginally significant predictors of total miles traversed over the entire event beyond 1000 K (p = .051). Additionally, participation in the event promoted an increase in healthy activity with participants running and walking significantly more in the four months during the event than the four months leading up to it. Discussion: This research intended to explore how psychological constructs relate to performance in a virtual type of endurance event, and how involvement in these types of events related to levels of activity. Higher levels of mental toughness and lower levels in difficulties in emotion regulation were associated with greater performance, and participation in the event promoted an increase in athletic involvement. Future psychological skill training aimed at improving emotion regulation and mental toughness may be used to enhance athletic performance in these sports, and future investigations into these events could explore how general participation may influence these constructs over time. Finally, these results suggest that participation in this logistically accessible, and affordable type of sport can promote greater involvement in healthy activities related to running and walking.

Keywords: virtual races, emotion regulation, mental toughness, ultra-marathon, predictors in performance

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Authors: Ratnakar Rao, Subair Khan, Hari Haran

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Posterior cruciate ligament (PCL) avulsion fractures is a rare condition and commonly mismanaged.Surgical reattachment has been shown to produce better result compared with conservative management.Only few techniques are reported in arthroscopic fixation of PCL Avulsion Fracture and they are complex.We describe a new technique in fixation of the PCL Avulsion fracture through a posterior trans septal portal using button fixation device (Mini Tight Rope). Eighteen patients with an isolated posterior cruciate ligament avulsion fracture were operated under arthroscopy. Standard Antero Medial Portal and Antero Lateral portals made and additional Postero Medial and Postero Lateral portals made and trans Septal portal established. Avulsion fracture identified, elevated, prepared. Reduction achieved using PCL Tibial guide (Arthrex) and fixation was achieved using Mini Tight Rope,Arthrex (2 buttons with a suture). Reduction confirmed using probe and Image intensifier. Postoperative assessment made clinically and radiologically. 15 patients had good to excellent results with no posterior sag or instability. The range of motion was normal. No complications were recorded per operatively. 2 patients had communition of the fragment while drilling, for one patient it was managed by suturing technique and the second patient PCL Reconstruction was done. One patient had persistent instability with poor outcome. Establishing trans septal portal helps in better visualization of the posterior compartment of the knee. Assessment of the bony fragment, preparation 0f the bone bed andit protects from injury to posterior neurovascular structures. Fixation using the button with suture (Mini Tight Rope) is stable and easily reproducible for PCL Avulsion fracture with single large fragment.

Keywords: PCL avulsion, arthroscopy, transeptal, minitight rope technique

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Authors: S. F. Halim, H. F. Naguib, S. N. Lawandy, R. S. Hegazy, M. N. Baheg

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The main drawbacks of the traditional carbon fabric reinforced epoxy resin (CFRP) are low strain failure, delamination between composites layers, and low impact resistance due to the brittleness of epoxy resin. The aim of this study is to enhance the fracture properties of the CFRP composites laminates via the variation of composite's designs. A series of composites were fabricated in which bidirectional (00/900) carbon fabric (CF) layers were laid inside the resin matrix with orientation codes as F1 [(00, 900)/ (00, 900)], F2 [(900, 00)/ (00, 900)] and F3 [(00,900)/ (900, 00). The mechanical and dynamic properties of the composites were estimated. In addition, the morphology of samples surface was examined by scanning electron microscope (SEM) after impact fracture. The results revealed that the CFRP properties could be tailored fitting specific applications by controlling the fabric orientation inside the CFRP composite design. F2 orientation [(900, 00)/ (00.900)] showed the highest tensile and flexural strength values. On the other hand, the impact strength values of composites were in the order F1 > F2 > F3. The storage modulus, loss modulus, and glass transition temperature Tg values obtained from the dynamic mechanical analysis (DMA) examination was in the order F1 > F2 > F3. The variation in the properties of the composite was clearly explained by the SEM micrographs as the failure of F3 orientation properties was referred to as the complete breakage of the CF layers upon fracture.

Keywords: carbon fiber, CFRP, composites, epoxy resins, flexural strength

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Authors: Xiangfang Xu, Bintao Wu, Yugang Miao, Duanfeng Han

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Experiments were conducted on 5A06 aluminum alloy and Q235 steel using the laser-TIG hybrid heat source welding-brazing method to realize the reliable connection of Al/Fe dissimilar metals and the welding characteristics were analyzed. It was found that the joints with uniform seam and high tensile strength could be obtained using such a method, while the welding process demanded special welding parameters. Spectrum measurements showed that the Al and Fe atoms diffused more thoroughly at the brazing interface and formed a 3μm-thick intermetallic compound layer at the Al/Fe joints brazed connection interface. Shearing tests indicated that the shearing strength of the Al/Fe welding-brazed joint was 165MPa. The fracture occurred near the melting zone of aluminum alloy, which belonged to the mixed mode with the ductile fracture as the base and the brittle fracture as the supplement.

Keywords: Al/Fe dissimilar metals, laser-TIG hybrid heat source, shearing strength, welding-brazing method

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Authors: Hela Krir, Abdelhak Ayadi, Chedly Bradaii

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The influence of both intrinsic factors, elastic energy and memory effect, and radial flow on the appearance and the evolution of the extrudate swelling are investigated in the present work. The experiments have been performed with linear polydimethylsiloxane (PDMS) via a capillary rheometer in which a convergent radial flow was created upstream the contraction. The correspondence between the effects of radial flow, entry elastic stored energy and memory effect is discussed. In particular, as the influence of the considered radial flow, extrudate photographs showed that when the gap ratio is reduced, the extrudate swell is lessened than what it is when radial flow geometry is not installed. Moreover, with a narrower gap, the polymer stores less energy during its passage through the die which implies a lower extrudate swelling at the outlet of the die. Results previously mentioned may be related both to shear and elongational components of radial flow.

Keywords: elastic energy, extrudate swell, memory effect, radial flow

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Authors: S. Levitsky, R. Bergman

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Fluid rheology may have essential impact on sound propagation in a liquid-filled pipe, especially, in a low frequency range. Rheological parameters of liquid are temperature-sensitive, which ultimately results in a temperature dependence of the wave speed and attenuation in the waveguide. The study is devoted to modeling of this effect at sound propagation in an elastic pipe with polymeric liquid, described by generalized Maxwell model with non-zero high-frequency viscosity. It is assumed that relaxation spectrum is distributed according to the Spriggs law; temperature impact on the liquid rheology is described on the basis of the temperature-superposition principle and activation theory. The dispersion equation for the waveguide, considered as a thin-walled tube with polymeric solution, is obtained within a quasi-one-dimensional formulation. Results of the study illustrate the influence of temperature on sound propagation in the system.

Keywords: elastic tube, sound propagation, temperature effect, viscoelastic liquid

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Authors: Manee Hasap, Mongkolchai Hasap, Tasanee Nasae

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The purpose of this study was to evaluate the primary caregivers’ knowledge and capabilities for providing quality care to be hospitalized post-hip fracture surgery elderly patients. The theoretical framework of the study was derived from the concepts of dependent care agency in Orem’s Self-Care theory, and family care provision for the elderly and chronically ill patients. 59 subjects were purposively selected. The subjects were primary caregivers of post-operated hip fracture elderly patients who had been admitted to the Orthopaedic Ward of Songklanagarind Hospital. Demographic data of the caregivers and patients were collected by non-participant observation using the evaluation and recording forms. The reliability of caregivers’ knowledge measurement (0.86) was obtained by KR-20 and that of caregivers’ capabilities for post-operative care evaluation form (0.97) obtained from 2 observers by interrater reliability. The data were analyzed using descriptive statistic, which were frequency, percentage, mean, and standard deviation. The result of this study indicated that elderly patients with post-hip fracture surgery had many pre-discharge self care limitations. Approximately, 75% of the caregivers had knowledge to respond to patient’s essential needs at a high level, while the rest (25%) had this knowledge a moderate level. For observation, 57.63% of the subjects had capabilities in care practice at a moderate level; 28.81% had capabilities in care practice at a high level, while 13.56% had at a low level. The result of this study can be used as basic information for patients and caregivers capabilities developing plan especially, providing patients’ activities, accident surveillance and complications prevention for a good life quality of elderly patients after hip surgery both hospitalization and rehabilitation at home.

Keywords: care givers’ knowledge, care givers’ capabilities, elderly hip fracture patients, patients

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Authors: K. B. Ghazaryan, R. A. Ghazaryan

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Based on the constitutive model and anti-plane equations of anisotropic elastic body of monoclinic symmetry we consider the problem of shear wave propagation in multi-layered disordered composite structure with point defect. Using transfer matrix method the analytic expression is obtained providing solutions of shear Floquet wave propagation in periodic disordered anisotropic structure. The usefulness of the obtained analytical expression was discussed also in reflection and refraction problems from multi-layered reflector as well as in vibration problem of multi-layered waveguides. Numerical results are presented highlighting the effects arising in disordered periodic structure due to defects of multi-layered structure.

Keywords: shear elastic waves, monoclinic anisotropic media, periodic structure, disordered multilayer laminae, multi-layered waveguide

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Authors: C. Benhamideche

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Fluoroaluminate glasses have been reported as the earliest heavy metal fluoride glasses. By comparison with flurozirconate glasses, they offer a set of similar optical features, but also some differences in their elastic and chemical properties. In practice they have been less developed because their stability against devitrification is smaller than that of the most stable fluoroziconates. The purpose of this study was to investigate glass formation in systems AlF3-YF3-PbF2-MgF2-MF2 (M= Li, Na, K). Synthesis was implemented at room atmosphere using the ammonium fluoride processing. After fining, the liquid was into a preheated brass mold, then annealed below the glass transition temperature for several hours. The samples were polished for optical measurements. Glass formation has been investigated in a systematic way, using pseudo ternary systems in order to allow parameters to vary at the same time. We have chosen the most stable glass compositions for the determination of the physical properties. These properties including characteristic temperatures, density and proprieties elastic. Glass stability increases in multicomponent glasses. Bulk samples have been prepared for physical characterization. These glasses have a potential interest for passive optical fibers because they are less sensitive to water attack than ZBLAN glass, mechanically stronger. It is expected they could have a larger damage threshold for laser power transmission.

Keywords: fluoride glass, aluminium fluoride, thermal properties, density, proprieties elastic

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Authors: Nan Tang, Bin Wu, Cunfu He

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The trapezoid rods are widely used in civil engineering as load –carrying members. Ultrasonic guided wave is one of the most popular techniques in analyzing the propagation of elastic guided wave. The goal of this paper is to investigate the propagation of elastic waves in the isotropic bar with trapezoid cross-section. Dispersion curves that describe the relationship between the frequency and velocity provide the fundamental information to describe the propagation of elastic waves through a structure. Based on the SAFE (semi-analytical finite element) a linear algebraic system of equations is obtained. By using numerical methods, dispersion curves solved for the rods with the trapezoid cross-section. These fundamental information plays an important role in applying ultrasonic guided waves to NTD for structures with trapezoid cross section.

Keywords: guided wave, dispersion, finite element method, trapezoid rod

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Authors: Imen Asma Mbarek, Alexis Rusinek, Etienne Petit, Guy Sutter, Gautier List

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Over the past two decades, the automotive, aerospace and army industries have been paying an increasing attention to Finite Elements (FE) numerical simulations of the fracture process of their structures. Thanks to the numerical simulations, it is nowadays possible to analyze several problems involving costly and dangerous extreme loadings safely and at a reduced cost such as blast or ballistic impact problems. The present paper is concerned with ballistic impact and perforation problems involving ductile fracture of thin armor steel targets. The target fracture process depends usually on various parameters: the projectile nose shape, the target thickness and its mechanical properties as well as the impact conditions (friction, oblique/normal impact...). In this work, the investigations are concerned with the normal impact of a conical head-shaped projectile on thin armor steel targets. The main aim is to establish a comparative study of four fracture criteria that are commonly used in the fracture process simulations of structures subjected to extreme loadings such as ballistic impact and perforation. Usually, the damage initiation results from a complex physical process that occurs at the micromechanical scale. On a macro scale and according to the following fracture models, the variables on which the fracture depends are mainly the stress triaxiality ƞ, the strain rate, temperature T, and eventually the Lode angle parameter Ɵ. The four failure criteria are: the critical strain to failure model, the Johnson-Cook model, the Wierzbicki model and the Modified Hosford-Coulomb model MHC. Using the SEM, the observations of the fracture facies of tension specimen and of armor steel targets impacted at low and high incident velocities show that the fracture of the specimens is a ductile fracture. The failure mode of the targets is petalling with crack propagation and the fracture facies are covered with micro-cavities. The parameters of each ductile fracture model have been identified for three armor steels and the applicability of each criterion was evaluated using experimental investigations coupled to numerical simulations. Two loading paths were investigated in this study, under a wide range of strain rates. Namely, quasi-static and intermediate uniaxial tension and quasi-static and dynamic double shear testing allow covering various values of stress triaxiality ƞ and of the Lode angle parameter Ɵ. All experiments were conducted on three different armor steel specimen under quasi-static strain rates ranging from 10-4 to 10-1 1/s and at three different temperatures ranging from 297K to 500K, allowing drawing the influence of temperature on the fracture process. Intermediate tension testing was coupled to dynamic double shear experiments conducted on the Hopkinson tube device, allowing to spot the effect of high strain rate on the damage evolution and the crack propagation. The aforementioned fracture criteria are implemented into the FE code ABAQUS via VUMAT subroutine and they were coupled to suitable constitutive relations allow having reliable results of ballistic impact problems simulation. The calibration of the four damage criteria as well as a concise evaluation of the applicability of each criterion are detailed in this work.

Keywords: armor steels, ballistic impact, damage criteria, ductile fracture, SEM

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Authors: Mohamad Mohsen Yavarizadeh

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Polystyrene (PS) and related homopolymers are brittle materials that typically fail in tensile tests at very low strains. These polymers can be toughened by the addition of rubbery particles which initiate a large number of crazes that produce substantial plastic strain at relatively low stresses. Considerable energy is dissipated in the formation of these crazes, producing a relatively tough material that shows an impact toughness of more than 5 times of pure PS. While cross linking of rubbery phase is necessary in aforementioned mechanism of toughening, another mechanism of toughening was also introduced in which low molecular weight liquid rubbers can also toughen PS when dispersed in the form of small pools in the glassy matrix without any cross linking. However, this new mechanism which is based on local plasticization, fails to act properly at high strain rate deformations, i.e. impact tests. In this work, the idea of combination of these two mechanisms was tried. To do so, Polybutadiene rubbers (PB) with bimodal distribution of molecular weight were prepared in which, comparable fractions of very high and very low molecular weight rubbers were mixed. Incorporation of these materials in PS matrix in a reactive process resulted in more significant increases in toughness of PS. In other words, although low molecular weight PB is ineffective in high strain rate impact test by itself, it showed a significant synergistic effect when combined with high molecular weight PB. Surprisingly, incorporation of just 10% of low molecular weight PB doubled the impact toughness of regular high impact PS (HIPS). It was observed that most of rubbery particles could initiate crazes. The effectiveness of low molecular weight PB in impact test was attributed to low strain rate deformation of each individual craze as a result of producing a large number of crazes in this material. In other words, high molecular weight PB chains make it possible to have an appropriate dispersion of rubbery phase in order to create a large number of crazes in the PS matrix and consequently decrease the velocity of each craze. Low molecular weight PB, in turn, would have enough time to locally plasticize craze fibrils and enhance the energy dissipation.

Keywords: molecular weight distribution, polystyrene, toughness, homopolymer

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Authors: H. Hentati, R. Abdelmoula, Li Jia, A. Maalej

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In this work, we present numerical simulations of the quasi-static crack propagation based on the variation approach. We perform numerical simulations of a piece of brittle material without initial crack. An alternate minimization algorithm is used. Based on these numerical results, we determine the influence of numerical parameters on the location of crack. We show the importance of trying to optimize the time of numerical computation and we present the first attempt to develop a simple numerical method to optimize this time.

Keywords: fracture mechanics, optimization, variation approach, mechanic

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Authors: Herng-Sheng Lee, Chi-Yi Chen, Wan-Ting Huang, Li-Jen Chang, Solomon Chih-Cheng Chen, Hsin-Yi Yang

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A variety of gastrointestinal disorders, such as Crohn’s disease, ulcerative colitis, and coeliac disease, are recognized as risk factors for osteoporosis and osteoporotic fractures. One recent study suggests that individuals with irritable bowel syndrome (IBS) might also be at increased risk of osteoporosis and osteoporotic fractures. Up to now, the association between IBS and the risk of fractures at different anatomic sites occurrences is not completely clear. We conducted a population-based cohort analysis to investigate the fracture risk of IBS in comparison with non-IBS group. We identified 29,505 adults aged ≥ 20 years with newly diagnosed IBS using the Taiwan National Health Insurance Research Database in 2000-2012. A comparison group was constructed of patients without IBS who were matched according to gender and age. The occurrence of fracture was monitored until the end of 2013. We analyzed the risk of fracture events to occur in IBS by using Cox proportional hazards regression models. Patients with IBS had a higher incidence of osteoporotic fractures compared with non-IBS group (12.34 versus 9.45 per 1,000 person-years) and an increased risk of osteoporotic fractures (adjusted hazard ratio [aHR] = 1.27, 95 % confidence interval [CI] = 1.20 – 1.35). Site specific analysis showed that the IBS group had a higher risk of fractures for spine, forearm, hip and hand than did the non-IBS group. With further stratification for gender and age, a higher aHR value for osteoporotic fractures in IBS group was seen across all age groups in males, but seen in elderly females. In addition, female, elderly, low income, hypertension, coronary artery disease, cerebrovascular disease, and depressive disorders as independent osteoporotic fracture risk factors in IBS patients. The IBS is considered as a risk factor for osteoporotic fractures, particularly in female individuals and fracture sites located at the spine, forearm, hip and hand.

Keywords: irritable bowel syndrome, fracture, gender difference, longitudinal health insurance database, public health

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Authors: Armin Shirbazo, Hamed Lamei Ramandi, Mohammad Vahab, Jalal Fahimpour

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Hydraulic fracturing, especially multi-stage hydraulic fracturing, is a practical solution for wells with uneconomic production. The wide range of applications is appraised appropriately to have a stable well-production. Production logging tool, which is known as PLT in the oil and gas industry, is counted as one of the most reliable methods to evaluate the efficiency of fractures jobs. This tool has a number of benefits and can be used to prevent subsequent production failure. It also distinguishes different problems that occurred during well-production. In this study, the effectiveness of hydraulic fracturing jobs is examined by using the PLT in various cases and situations. The performance of hydraulically fractured wells is investigated. Then, the PLT is employed to gives more information about the properties of different layers. The PLT is also used to selecting an optimum fracturing design. The results show that one fracture and three-stage fractures behave differently. In general, the one-stage fracture should be created in high-quality areas of the reservoir to have better performance, and conversely, in three-stage fractures, low-quality areas are a better candidate for fracturing

Keywords: multi-stage fracturing, horizontal well, PLT, fracture length, number of stages

Procedia PDF Downloads 176

Authors: Doaa H. Elgohary, Tamer F. Khalifa, Mona M. Salem, M. A. Saad, Ehab Haider Sherazy

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Textiles have conquered new areas over the past three decades, including agriculture, transportation, filtration, military, and medicine. The use of textiles in the medical field has increased significantly in recent years and covers almost everything. Medical textiles represent a huge market as they are widely used not only in hospitals, hygiene, and healthcare but also in hotels and other environments where hygiene is required. However, not all fibers are suitable for the manufacture of medical textile products. Some special properties are required for the manufactured materials, e.g. Strength, elasticity, spinnability, etc. In addition to the usual properties of medical fibers, non-toxicity, sterilizability, biocompatibility, biodegradability, good absorbability, softness, and freedom from additives, etc., desirable properties include impurities. Stitching is one of the most common practices in the medical field. as it is a biomaterial device, either natural or synthetic, used to connect blood vessels and connect tissues. In addition to being very strong, suture material should easily dissolve in bodily fluids and lose strength as the tissue gains strength. In this work, a study to select the most used materials for sutures, it was found that silk, VICRYL and polypropylene were the most used materials in varying numbers. The research involved the analysis of 36 samples from three different materials (mostly commonly used), the tests were carried out on 36 imported samples for four different companies. Each company supplied three different materials (silk, VICRYL and polypropylene) with three different gauges (4, 3.5 and 3 metric). The results of the study were tabulated, presented, and discussed. Practical statistical science serves to support the practical analysis of experimental work products and the various relationships between variables to achieve the best sampling performance with the functional purpose generated for it. Analysis of the imported sutures shows that VICRYL sutures had the highest tensile strength, toughness, knot tensile strength and knot toughness, followed by polypropylene and silk. As yarn counts, weight and diameter increase, its tensile strength and toughness increase while its elongation and knot tension decrease. The multifilament yarn construction (silk and VICRYL) scores higher compared to the monofilament construction (polypropylene), resulting in increases in tenacity, toughness, knot tensile strength and knot toughness.

Keywords: biodegradable yarns, braided sutures, irritation, knot tying, medical textiles, surgical sutures, wound healing

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Authors: Reza Hedayati, Meysam Jahanbakhshi

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In this work, Fracture Mechanics is used to predict crack propagation in the adhesive joining aluminum and composite plates. Three types of loadings and two types of glass-epoxy composite sequences: [0/90]2s and [0/45/-45/90]s are considered for the composite plate. Therefore, 2*3=6 cases are considered and their results are compared. The debonding initiation load, complete debonding load, crack face profile and load-displacement diagram have been compared for the six cases.

Keywords: adhesive joint, debonding, fracture, LEFM, APDL

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Authors: M. Karami Khorramabadi, A. R. Nezamabadi

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This paper studies free vibration of functionally graded beams Subjected to Axial Load that is simply supported at both ends lies on a continuous elastic foundation. The displacement field of beam is assumed based on Engesser-Timoshenko beam theory. The Young's modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton's principle, the governing equation is established. Resulting equation is solved using the Euler's Equation. The effects of the constituent volume fractions and foundation coefficient on the vibration frequency are presented. To investigate the accuracy of the present analysis, a compression study is carried out with a known data.

Keywords: functionally graded beam, free vibration, elastic foundation, Engesser-Timoshenko beam theory

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Authors: M. Zemouli, K. Amara, M. Elkeurti, Y. Benallou

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We present a theoretical study of the structural, elastic and thermodynamic properties of the zinc-blende AlBi for a wide temperature range. The simulation calculation is performed in the framework of the molecular dynamics method using the three-body Tersoff potential which reproduces provide, with reasonable accuracy, the lattice constants and elastic constants. Our results for the lattice constant, the bulk modulus and cohesive energy are in good agreement with other theoretical available works. Other thermodynamic properties such as the specific heat and the lattice thermal expansion can also be predicted. In addition, this method allows us to check its ability to predict the phase transition of this compound. In particular, the transition pressure to the rock-salt phase is calculated and the results are compared with other available works.

Keywords: aluminium compounds, molecular dynamics simulations, interatomic potential, thermodynamic properties, structural phase transition

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Authors: J. Milton, C. Uzoigwe, O. Ayeko, B. Offorha, K. Anderson, R. G. Middleton

Abstract:

Background: We used the UK National Hip Fracture database to determine the effect of institution hip fracture case volume on hip fracture healthcare outcomes in 2019. Using logistic regression for each healthcare outcome, we compared the best performing 50 units with the poorest performing 50 units in order to determine if the unit volume was associated with performance for each particular outcome. Method: We analysed 175 institutions treating a total of 67,673 patients over the course of a year. Results: The number of hip fractures seen per unit ranged between 86 and 952. Larger units tendered to perform health assessments more consistently and mobilise patients more expeditiously post-operatively. Patients treated at large institutions had shorter lengths of stay. With regard to most other outcomes, there was no association between unit case volume and performance, notably compliance with the Best Practice Tariff, time to surgery, proportion of eligible patients undergoing total hip arthroplasty, length of stay, delirium risk, and pressure sore risk assessments. Conclusion: There is no relationship between unit volume and the majority of health care outcomes. It would seem that larger institutions tend to perform better at parameters that are dependent upon personnel numbers. However, where the outcome is contingent, even partially, on physical infrastructure capacity, there was no difference between larger and smaller units.

Keywords: institution volume, mortality, neck of femur fractures, osteoporosis

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Authors: D. Kari Basavaraja, M. G. Skanda, C. Soumya, V. Ramesh

Abstract:

This paper discusses the effects of sodium hypophosphite concentration, pH, and temperature on deposition rate. This paper also discusses the evaluation of coating strength, surface, and subsurface by varying the bath parameters, percentage of phosphate, plating temperature, and pH of the plating solution. Taguchi technique has been used for the analysis. In the experiment, nickel chloride which is a source of nickel when mixed with sodium hypophosphite has been used as the reducing agent and the source of phosphate and sodium hydroxide has been used to vary the pH of the coating bath. The coated samples are tested for impact energy by conducting impact test. Finally, the effects of coating bath parameters on the impact energy absorbed have been plotted, and analysis has been carried out. Further, percentage contribution of coating bath parameters using Design of Experiments approach (DOE) has been analysed. Finally, it can be concluded that the bath parameters of the Ni-P coating will certainly influence on the strength of the specimen.

Keywords: bath parameters, coatings, design of experiment, fracture toughness, impact strength

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Authors: Jithin S. Kumar, Ramesh Kannan Kandasami

Abstract:

Geomaterials are generally porous in nature due to the presence of discrete particles and interconnected voids. The porosity present in these geomaterials play a critical role in many engineering applications such as CO2 sequestration, well bore strengthening, enhanced oil and hydrocarbon recovery, hydraulic fracturing, and subsurface waste storage. These applications involves solid-fluid interactions, which govern the changes in the porosity which in turn affect the permeability and stiffness of the medium. Injecting fluid into the geomaterials results in permeation which exhibits small or negligible deformation of the soil skeleton followed by cavity expansion/ fingering/ fracturing (different forms of instabilities) due to the large deformation especially when the flow rate is greater than the ability of the medium to permeate the fluid. The complexity of this problem increases as the geomaterial behaves like a solid and fluid under certain conditions. Thus it is important to understand this multiphysics problem where in addition to the permeation, the elastic-plastic deformation of the soil skeleton plays a vital role during fluid injection. The phenomenon of permeation and cavity expansion in porous medium has been studied independently through extensive experimental and analytical/ numerical models. The analytical models generally use Darcy's/ diffusion equations to capture the fluid flow during permeation while elastic-plastic (Mohr-Coulomb and Modified Cam-Clay) models were used to predict the solid deformations. Hitherto, the research generally focused on modelling cavity expansion without considering the effect of injected fluid coming into the medium. Very few studies have considered the effect of injected fluid on the deformation of soil skeleton. However, the porosity changes during the fluid injection and coupled elastic-plastic deformation are not clearly understood. In this study, the phenomenon of permeation and instabilities such as cavity and finger/ fracture formation will be quantified extensively by performing experiments using a novel experimental setup in addition to utilizing image processing techniques. This experimental study will describe the fluid flow and soil deformation characteristics under different boundary conditions. Further, a well refined coupled semi-analytical model will be developed to capture the physics involved in quantifying the deformation behaviour of geomaterial during fluid injection.

Keywords: solid-fluid interaction, permeation, poroelasticity, plasticity, continuum model

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Authors: Hossein Kheirollahi, Yunhua Luo

Abstract:

Studying stress and strain trends in the femur and recognizing femur failure mechanism is very important for preventing hip fracture in the elderly. The aim of this study was to identify high stress and strain regions in the femur during normal walking and falling to find the mechanical behavior and failure mechanism of the femur. We developed a finite element model of the femur from the subject’s quantitative computed tomography (QCT) image and used it to identify potentially high stress and strain regions during the single-leg stance and the sideways fall. It was found that fracture may initiate from the superior region of femoral neck and propagate to the inferior region during a high impact force such as sideways fall. The results of this study showed that the femur bone is more sensitive to strain than stress which indicates the effect of strain, in addition to effect of stress, should be considered for failure analysis.

Keywords: finite element analysis, hip fracture, strain, stress

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Authors: Navid Zarif Karimi, Hossein Heidary, Giangiacomo Minak, Mehdi Ahmadi

Abstract:

In this paper analytical model based on the mechanics of oblique cutting, linear elastic fracture mechanics (LEFM) and bending plate theory has been presented to determine the critical feed rate causing delamination in drilling of composite materials. Most of the models in this area used LEFM and bending plate theory; hence, they can only determine the critical thrust force which is an incorporable parameter. In this model by adding cutting oblique mechanics to previous models, critical feed rate has been determined. Also instead of simplification in loading condition, actual thrust force induced by chisel edge and cutting lips on composite plate is modeled.

Keywords: composite material, delamination, drilling, thrust force

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Authors: T. Zergoug, S. E. H. Abaidia, A. Nedjar, M. Y. Mokeddem

Abstract:

Physical properties of uranium di-nitride (UN2) were investigated in detail using first principles calculations based on density functional theory. To treat the strong correlation effects caused by 5f Uranium valence electrons, on-site Coulomb interaction correction via the Hubbard-like term, U (DFT+U) was employed. The UN2 structural, mechanical and thermodynamic properties were calculated within DFT and Various U of DFT+U approach. The Perdew–Burke–Ernzerhof (PBE.5.2) version of the generalized gradient approximation (GGA) is used to describe the exchange-correlation with the projector-augmented wave (PAW) pseudo potentials. A comparative study shows that results are improved by using the Hubbard formalism for a certain U value correction like the structural parameter. For some physical properties the variation versus Hubbard U is strong like Young modulus but for others it is weakly noticeable such as the density of state (DOS) or bulk modulus. We noticed also that up from U=7.5 eV, elastic results become not conform to the cubic cell elastic criteria since the C44 values turn out to be negative.

Keywords: uranium diNitride, UN2, DFT+U, elastic properties

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