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حرية الوصول المقاله
1 - Evaluation of Mixed-Mode Center Crack SIF in a Curved Plate Repaired by Stop Holes, Composite Patch, and Hybrid Methods
Sirvan Mohammadi sadegh daryaeiIn this research, using the 3D finite element method and considering different materials for a composite patch, the effect of separate and simultaneous use of stop holes and composite patch (one-sided and two-sided) on reduction of SIF in a curved plate including mixed- أکثرIn this research, using the 3D finite element method and considering different materials for a composite patch, the effect of separate and simultaneous use of stop holes and composite patch (one-sided and two-sided) on reduction of SIF in a curved plate including mixed-mode crack is investigated. Glass-epoxy, graphite-epoxy, carbon-epoxy, and boron-epoxy are used for repair patches. For the one-sided patch, the effects of different geometric parameters on the efficiency of the repair are investigated. For all four composite patches, as the thickness of the patches increases, KI and KII decrease, but with increasing the patch length, KI and KII increase. The research results also show that with increasing the width of the glass-epoxy patch, KI and KII almost do not change, but for other patches, as the patch width increases, the SIF increases. The effect of the radius of curvature of the plate on the efficiency of various repair methods is also investigated. In all repair methods studied, SIF decreases with increasing radius of curvature of the curved plate. Different repair methods are compared and the best method with the highest efficiency is introduced. The best repair mode is the hybrid repair method (stop-holes and two-sided boron-epoxy patch), which reduces KI and KII by 84.50 and 86.6%, respectively. Finally, the effect of adhesive thickness used for patch bonding on hybrid repair method efficiency and durability is investigated. for all four materials of patches understudy, KI and KII increase with increasing the thickness of the adhesive, but on the other hand, as the thickness of the adhesive increases, the maximum Von Mises stress in the adhesive decreases. تفاصيل المقالة -
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2 - Fracture Parameters for Cracked Cylincal Shells
M Kadri A Sahli S SahliIn this paper, 2D boundary element stress analysis is carried out to obtain the T-stress for multiple internal edge cracks in thick-walled cylinders for a wide range of cylinder radius ratios and relative crack depth. The T-stress, together with the stress intensity fac أکثرIn this paper, 2D boundary element stress analysis is carried out to obtain the T-stress for multiple internal edge cracks in thick-walled cylinders for a wide range of cylinder radius ratios and relative crack depth. The T-stress, together with the stress intensity factor K, provides amore reliable two-parameter prediction of fracture in linear elastic fracture mechanics. T-stress weight functions are then derived from the T-stress solutions for two reference load conditions corresponding to the cases when the cracked cylinder is subject to a uniform and to a linear applied stress variation on the crack faces. The derived weight functions are then verified for several non-linear load conditions. Using the BEM results as reference T-stress solutions; the T-stress weight functions for thick-walled cylinder have also been derived. Excellent agreements between the BEM results and weight function predictions are obtained. The weight functions derived are suitable for obtaining T-stress solutions for the corresponding cracked thick-walled cylinder under any complex stress fields. Results of the study show that the two dimensional BEM analysis, together with weight function method, can be used to provide a quick and accurate estimate of T-stress for 2-D crack problems. تفاصيل المقالة -
حرية الوصول المقاله
3 - Evaluation of Stress Intensity Factor in a Center Cracked Curved Plate Repaired with Stop Holes, Composite Patch, and Hybrid Methods
S Mohammadi S DaryaeiStop holes and composite patches are the most important methods used to repair cracked plates. In this research, using a 3D finite element method and considering different materials for a composite patch, the effect of separate and simultaneous use of stop holes and com أکثرStop holes and composite patches are the most important methods used to repair cracked plates. In this research, using a 3D finite element method and considering different materials for a composite patch, the effect of separate and simultaneous use of stop holes and composite patch (one-sided and two-sided) on the reduction of SIF in a cracked curve plate is investigated. The best position and arrangement of crack stop holes and the best dimensions and material used for the composite patch are determined. Then, the effect of the radius of curvature of the plate on the efficiency of various repair methods is investigated. The results show that with increasing the radius of curvature of the plate, the SIF value decreases in all repair methods and the efficiency of the patch improves in the cases of using the patch or the hybrid method. Besides, from the radius of curvature of approximately 5 meters onwards, a further increase in the radius of curvature does not affect the efficiency of various repair methods. Simultaneous use of the graphite-epoxy double-sided patch and stop holes reduces SIF by 79.9% compared to unrepaired condition. تفاصيل المقالة -
حرية الوصول المقاله
4 - Crack Interaction Studies Using XFEM Technique
K SharmaIn this paper, edge crack problems under mechanical loads have been analysed using extended finite element method (XFEM) as it has proved to be a competent method for handling problems with discontinuities. The XFEM provides a versatile technique to model discontinuitie أکثرIn this paper, edge crack problems under mechanical loads have been analysed using extended finite element method (XFEM) as it has proved to be a competent method for handling problems with discontinuities. The XFEM provides a versatile technique to model discontinuities in the solution domain without re-meshing or conformal mesh. The stress intensity factors (SIF) have been calculated by domain based interaction integral method. The effect of crack orientation and interaction under mechanical loading has been studied. Analytical solutions, which are available for two dimensional displacement fields in linear elastic fracture mechanics, have been used for crack tip enrichment. From the present analysis, it has been observed that there is monotonous decrease in the SIF-1 value with the increase in inclination, while SIF-II values first increases then it also decreases. Next study was performed for first edge crack in the presence of second crack on opposite edge. The results were obtained by changing the distance between the crack tips as well as by changing the orientation of second crack. SIFs values decrease with increase in distances between the crack tips for collinear cracks. In next study, for the first crack in presence of inclined second edge crack and it was found that SIFs increase initially with the increase in inclination and decrease after that. It emphasizes the fact that cracks at larger distances act more or less independently. In next study, with the use of level set method crack growth path is evaluated without remeshing for plate with hole, soft inclusion & hard inclusion under mode-I loading and compare with available published results. تفاصيل المقالة -
حرية الوصول المقاله
5 - Cracks Analysis in Zavin Concrete Dam Using Fracture Mechanics Approach
Hossein Rezaee Azariani Mohammad Reza Esfahani keivan bina Soheil GharehMost of the existing concrete dams are subjected to cracking. These cracks are caused by various factors such as construction practices, curing, loads and volume change of mass concrete which reduce the efficiency, failure or instability of concrete dams. Using fracture أکثرMost of the existing concrete dams are subjected to cracking. These cracks are caused by various factors such as construction practices, curing, loads and volume change of mass concrete which reduce the efficiency, failure or instability of concrete dams. Using fracture mechanics as a new method to estimate stability and durability of concrete dams is recommended in scientific publications in worldwide. This study aimed to apply the principles and criteria of linear elastic fracture mechanics to evaluate the propagation of cracks in body and foundation of Kalat concrete gravity dam -that is located in the northern province of Khorasan Razavi, Iran- subjected to the worst-case loading, including the extraordinary loading case due to earthquake with full reservoir. For this purpose, ZENCRACK-v 7.7 and ABAQUS-v 6.10.1 software were utilized and nonlinear analysis of finite element are performed. Subsequently, linear elastic fracture mechanics criteria including stress intensity factor and maximum circumferential stress were calculated for existing cracks in various parts of dam body and foundation and stability of initial cracks, kinking angle and extension of them were determined. Based on the obtained results, crack propagation in areas near to both dam abutments is investigated. To do so, a plain strain condition is assumed that only expanded in longitudinal and transverse axes, but with being away from abutments toward dam center, crack growth logged from plain strain condition and expanded in the vertical direction. Also, under earthquake load with 10 second duration, maximum tension and compression stress were occurred between 2.32 to 4.26 seconds. تفاصيل المقالة -
حرية الوصول المقاله
6 - بررسی تاثیرچسبندگی-لغزش برترک خوردگی صفحه ی بتن آرمه با استفاده ازمدل شبکه ای
حمید شجاعی فر مسعود فرزامچکیده: دراین مقاله سه مدل چسبندگی-لغزش(Farra,Harajli,CEB-FIP) که برمبنای نتایج مطالعات تجربی قبلی بدست آمده اند، مطالعه می شوند تا اثر چسبندگی-لغزش در فاصله ی ترک و نحوه ی انتشار ترک صفحه ی بتن آرمه بررسی شود. برای این منظور، یک صفحه ی بتن آرمه با استفاده از مدل عددی أکثرچکیده: دراین مقاله سه مدل چسبندگی-لغزش(Farra,Harajli,CEB-FIP) که برمبنای نتایج مطالعات تجربی قبلی بدست آمده اند، مطالعه می شوند تا اثر چسبندگی-لغزش در فاصله ی ترک و نحوه ی انتشار ترک صفحه ی بتن آرمه بررسی شود. برای این منظور، یک صفحه ی بتن آرمه با استفاده از مدل عددی شبکه ای توسط نرم افزار ABAQUS مدل سازی شده است و روند ترک خوردگی توسط خرابی عضوهای میله ای بتن نشان داده شده است. مدل های شبکه ای بر اساس معیار ترک خوردگی توسعه یافته و با بکارگیری اصول مکانیک شکست در ارزیابی ترک خوردگی اعضا بتن آرمه بکار رفته اند. بتن وفولاد با یک مدل برهم کنش دهنده (Bond-Link) و با در نظر گرفتن اثر چسبندگی-لغزش با یکدیگر ترکیب شده اند تا رفتار مصالح ترکیبی بتن آرمه را توصیف کنند. نتایج تحلیل ها نشان دادهاند که مدل های چسبندگی-لغزش تاثیر مهمی در فاصله ی ترک، عرض ترک، نحوه ی انتشار ترک و موضع شدگی خرابی دارند. تفاصيل المقالة -
حرية الوصول المقاله
7 - Stress Field Analysis of V-Notches with Tip Cracks in a Polymer Material Using Digital Image Correlation
ن. سلطانی م.ر. یادگاری ا. اشراقیIn this study, displacement field around v-notches of a poly methyl metha crylate (PMMA) specimen with tip cracks will be analyzed using digital image correlation technique. First intensity factor in combination with in-plane rigid body translations and rotation compone أکثرIn this study, displacement field around v-notches of a poly methyl metha crylate (PMMA) specimen with tip cracks will be analyzed using digital image correlation technique. First intensity factor in combination with in-plane rigid body translations and rotation components will be determined by linear least squares fitting of the displacement field data to the corresponding relations among stress intensity factor and displacement field. The effect of v-notch angle on the results would be investigated. Experimental results will be compared with those obtained from finite element analysis. Good consistency is shown to exist between the results of two methods. The existence and a measure of a small region (corresponding to the plastic deformation zone in front of the crack tip) is demonstrated which should be excluded in data extraction for digital image correlation post-processing using linear elastic fracture mechanics relations. تفاصيل المقالة -
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8 - Modeling and Crack-growth and Calculate First Intensity Factor with Ansys Software
S.M. Hossein MirgilaniStudy about Fracture Mechanics and the root cause of fracture in order to estimates lifetime for Mechanical parts in designing process and manufacturing have tremendous role in this realm. Stress intensity factor comes into design which not only is dependent to geometry أکثرStudy about Fracture Mechanics and the root cause of fracture in order to estimates lifetime for Mechanical parts in designing process and manufacturing have tremendous role in this realm. Stress intensity factor comes into design which not only is dependent to geometry also extremely to load condition; for instance, it is important in failure processes (brittle and ductile Materials) or to predict rest life for a mechanical part under fluctuating stress. Stress intensity factor is separated from stress concentration factors. This dimensionless factor, is used to quantify how "concentrated" the stress is. Stress concentration factors are due to geometrical changes of cross sections and regardless of the load condition. At this article, concentrate on modeling and growing a crack during Tension Stress and calculate first stress intensity factor with Ansys software and compare the result with Westgard function تفاصيل المقالة -
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9 - Experimental study of fracture mechanics in the aluminum matrix composites containing Fifteen percent silicon carbide particles
محمد رنجبران محمد تقی نجفی مهدی اعطائی رسول امینیIn this investigation ‚the fracture toughness of A356 containing15%SiC composite was studied. Al/SiC composites have been considered because of their mechanical and erosion properties .Low fracture toughness in Al/SiC as compared with Aluminium alloys is one of it أکثرIn this investigation ‚the fracture toughness of A356 containing15%SiC composite was studied. Al/SiC composites have been considered because of their mechanical and erosion properties .Low fracture toughness in Al/SiC as compared with Aluminium alloys is one of its disadvantage. In this study at first A356 alloy was melted in a smelting electrical furnace then poured into the mould. A356-15% SiC were composed by melting method and mixing continuously (in order not to precipitate SiC to the bottom) in the presence of a nature gas. The melt was poured in a metallic mould, then specimens were cut from the products bars in order to calculate fracture toughness according to ASTM. Obtained results for different specimens compared together. In this study Crack Opening Displacement (COD) is used to determine fracture toughness rate. KIcwas calculated in composites and compared with that of base alloy. As a result KIcin composite samples were decreased significantly, debris, cracks, gas cavity. تفاصيل المقالة
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