Flexural Strength

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1 - Comparison of flexural strength and surface roughness of temporary crowns made by conventional and digital methods
Mansureh sadat Abtahi Mehrdad Barekatain Mehrdad kazemian Fereshteh Shahri

Background: Assessment of dental materials do by different methods. The aim of this study was to compare the flexural strength and surface roughness of temporary crowns manufactured through conventional and digital methods. Materials and method: An experimental laborat چکیده کامل

Background: Assessment of dental materials do by different methods. The aim of this study was to compare the flexural strength and surface roughness of temporary crowns manufactured through conventional and digital methods. Materials and method: An experimental laboratory study was conducted on 60 rod-shaped samples made from three different materials. These materials were ENA high filler flowable composite, CENTRIX self-curing acrylic base composite and 3D printer resin. To create the 3D printer group samples, the original metal model was scanned and the design file was printed using a 3D printer. For the composite samples and acrylic bases, a silicone index was used, which was composed of the original metal model. Ten samples of each material were stored in artificial saliva for 30 days. The samples were then tested for flexural strength and surface roughness. The data collected was analyzed using a one-way analysis of variance, Bonferroni’s post hoc (α =0.05). Results: The average flexural strength varied significantly among the three materials after being immersed in artificial saliva for a month (p<0.001). The ENA flow material's average flexural strength was significantly higher than the CENTRIX material and printed resin (p<0.001), and the CENTRIX material's average flexural strength was significantly higher than printed resin (p<0.001). The CENTRIX material also had a significantly higher initial roughness mean (Ra) value compared to the ENA flow material (p=0.010) and printed resin (p=0.009), while there was no significant difference between the ENA flow material and printed resin (p=1.00). One month after immersion in artificial saliva, the CENTRIX material's mean surface roughness (Ra) was significantly higher than the ENA flow material (p=0.005) and printed resin (p=0.040). Conclusion: Flowable composite resin presents better mechanical properties when compared to acrylic base resin and printed resin. The surface roughness of flowable composite and printed resin is lower than acrylic base composite, but the surface roughness of all materials increases when exposed to saliva. پرونده مقاله

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2 - Effect of Quartz Particle Size on Sintering Behavior and Flexural Strength of Porcelain Tiles Made from Raw Materials in Uganda
Ochen William Florence D&#039;ujanga Bosco Oruru

The presence of quartz particle size (> 45 µm) has a deleterious effect on the properties of porcelain tiles. The effect is caused by many factors including microstructure (pore) evolution after sintering. This study aims at investigating the effect of quartz p چکیده کامل

The presence of quartz particle size (> 45 µm) has a deleterious effect on the properties of porcelain tiles. The effect is caused by many factors including microstructure (pore) evolution after sintering. This study aims at investigating the effect of quartz particle size (QPS) on sintering behavior and flexural strength of porcelain tiles made from raw materials in Uganda. The samples were pressed at 40 MPa, fired from 1150-1350 0C at a firing rate of 60 0C/min, and soaked for 1 hour. The sintering behavior was analyzed based on linear shrinkage, water absorption and Scanning Electron Microscope (SEM) micrographs. Phase identification was carried out using X-ray diffraction method. The optimal sintering temperature of 1300 0C was established, and firing to 1350 0C resulted in bloating as observed by SEM. Samples containing fine and medium QPS had a value of 0.47 % and 0.90 % water absorption respectively at optimum temperature. Pressed tiles with and those > water absorption are classified as Group BIa and BIb respectively (ISO 13006), suitable for use as floor or wall tiles. Also, the average flexural strength of 33, 18 and 8 MPa was exhibited by samples with fine, medium and coarse QPS respectively. The results indicate that only samples with fine and medium QPS satisfy the requirement MPa and > 12 MPa for floor and wall tiles respectively (ISO 13006). پرونده مقاله

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3 - Investigation of Mechanical Properties of Lithium-Based Geopolymer Composites Reinforced with Basalt Fibers
R. DavoudianDehkordi A. A Nourbakhsh H MonajatiZadeha

Recently, geopolymer binders have been considered because of low cost, simple processes for synthesis and many raw materials in nature. Geopolymer with brittle nature does not have high strength and cannot be used alone for structural materials. Therefore, to use in dif چکیده کامل

Recently, geopolymer binders have been considered because of low cost, simple processes for synthesis and many raw materials in nature. Geopolymer with brittle nature does not have high strength and cannot be used alone for structural materials. Therefore, to use in different structures, the composite which is reinforced with fibers such as carbon, glass, basalt, etchasbeen used. In this research, influence of different parameters such as firing temperature and weight fraction of continuous basalt fiber on strength of lithium-based geopolmer composites reinforced by basalt fibers was studied. Firstly, raw materials for geopolymer preparation were calcined. Then, geopolymer matrix with specific molar ratio was made with three different weight percent of basalt fiber. The Molds were put in an oven and after that the composites were taken out of the molds. Then the samples were cured at three different temperatures. After heat treatment, C-MOR of composites was tested and flexural strength and fracture energy for different samples were calculated. The results showed that basalt fiber composites at 200˚C had high strength, but by increasing temperature the strength decreased. Also, Fracture energy of composites at 200˚C was higher than other temperatures. پرونده مقاله

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4 - بررسی روش NSM برای تقویت تیرهای بتنی دوسر گیردار با میله‌های کامپوزیتCFRP
محمدکاظم شربتدار محمدرضا محمدیان

ککاشت سطحی میلگرد(NSM) یکی از روش های جدید مقاوم سازی بر اساس خاصیت چسبندگی پلیمر های CFRP به صورت میلگرد درون شیار هایی در قسمت پوشش بتن می باشد. خوردگی و یا کمبود آرماتورها در المان های بتنی، موجب ضعف آن ها تحت بارهای سرویس و زلزله خواهد شد. این شرایط مستلزم مقاوم ساز چکیده کامل

ککاشت سطحی میلگرد(NSM) یکی از روش های جدید مقاوم سازی بر اساس خاصیت چسبندگی پلیمر های CFRP به صورت میلگرد درون شیار هایی در قسمت پوشش بتن می باشد. خوردگی و یا کمبود آرماتورها در المان های بتنی، موجب ضعف آن ها تحت بارهای سرویس و زلزله خواهد شد. این شرایط مستلزم مقاوم سازی سازه ها برای افزایش ظرفیت می باشد. استفاده از روشNSM CFRP Bar می‌تواند موجب افزایش ظرفیت خمشی و برشی المان های بتنی شود. این مقاله شامل جزئیات و نتایج کار آزمایشگاهی و عددی می باشد. در قسمت کار آزمایشگاهی دو نمونه تیر بتنی طراحی و ساخته شد و سپس تحت بار متمرکز در وسط دهانه تست گردید. هر دو نمونه به صورت دوسرگیردار و با مشخصات یکسان بودند. یکی از نمونه ها به عنوان نمونه مرجع و دیگری به روش NSM مقاوم سازی شد. در این مقاله از میله های دست ساز CFRP استفاده شده است که ساخت آن سریع و آسان بوده و در صورت عدم دسترسی به میله های استاندارد FRP، با هزینه بسیار کم و با استفاده از نیروهای کم تجربه قابل تولید در محل می باشد. از نتایج تست آزمایشگاهی جهت کالیبراسیون نمونه های عددی در برنامه ABAQUS استفاده شده است. نتایج حاصل نشان داد که روش NSM یک روش راحت و اقتصادی جهت مقاوم سازی بوده و استفاده از آن در تقویت تیرها، موجب افزایش در ظرفیت باربری، توزیع مناسب ترک ها و کنترل تغییر شکل اعضای تقویت شده می گردد. پرونده مقاله

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5 - Evaluation of the Mechanical Strength of Gerbera Flower Stem in Response to Silicon and Salicylic Acid Application
Mesbah Babalar Behzad Edrisi Roohangiz Naderi

Stem and peduncle bending by the weight of the flower is one of the main postharvest problems in gerbera (Gerbera jamesonii Bolus.) and sometimes caused stem crushing or water loss. In this research, silicon and salicylic acid were applied to enhance the mechanical stre چکیده کامل

Stem and peduncle bending by the weight of the flower is one of the main postharvest problems in gerbera (Gerbera jamesonii Bolus.) and sometimes caused stem crushing or water loss. In this research, silicon and salicylic acid were applied to enhance the mechanical strength of inflorescence stem, and the results revealed that stem curving was decreased by silicon and salicylic acid treatments. Shear strength and lignin content were increased by SA treatments at both upper and lower parts of the stem. It seems that lignin content was associated with shear strength at upper part of stem. Additionally, silicon content of flower stem was significantly increased under silicon application and mechanical strength of the lower part of stem has correlation with silicon content in stem tissue. These results suggested that silicon and salicylic acid application could enhance the mechanical strength of inflorescence stem and improve the cut flower quality in gerbera. پرونده مقاله

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6 - Design and optimization of poly lactic acid/bioglass composite screw for orthopedic applications
عماد حسینی انوشه زرگر خرازی

However, problems such as osteoporosis due to high elasticity of metals relative to bones, and local infections and systemic problems caused by releasing metallic ions have motivated research on replacing metallic screws with non metallic ones. In this study, the compos چکیده کامل

However, problems such as osteoporosis due to high elasticity of metals relative to bones, and local infections and systemic problems caused by releasing metallic ions have motivated research on replacing metallic screws with non metallic ones. In this study, the composite containing poly-l-lactic acid and bioactive glass fibers were considered for the design of the screw using ABAQUS software (V6.11). The elastic constants were first estimated in micro analysis then transferred to macro analysis for modeling in two-layer situations composed of unidirectional fibers and random fibers (UD/R) and also for modeling in three-layer situations composed of unidirectional fibers, fibers with an angle of ±20 degree in relation to force vector, and random fibers (UD /±20/R) with various percentages of layer thickness. Results show that in the analysis with %65 layers of unidirectional fibers, %10 layers by fibers with an angle of ±20 degree, and %25 of layers with random fibers, flexural modulus, flexural strength, and longitudinal elasticity coefficient were estimated about 22.7 GPa, 347 MPa, and 24.8 GPa respectively, the last one being slightly higher than that of cortical bone. Considering similar results for cortical bones, our designed composite screws are robust enough to replace metal screws for repairing orthopedic fractures پرونده مقاله

فهرست مقالات Flexural Strength

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