دانلود کتاب،مقاله،جزوه و نرم افزار مهندسی مواد
کلیه منابع مورد نیاز دانشجویان و مهندسین مواد (متالورژی ، سرامیک ، جوش ، خوردگی ، نانو و بایومواد)دانلود کتاب،مقاله،جزوه و نرم افزار مهندسی مواد
کلیه منابع مورد نیاز دانشجویان و مهندسین مواد (متالورژی ، سرامیک ، جوش ، خوردگی ، نانو و بایومواد)رفتار خوردگی-خستگی آلیاژ آلومینیوم 7075-T651 تحت بارگذاری های متناوب
Corrosion-fatigue behaviour of 7075-T651 aluminum
alloy subjected to periodic overloads
رفتار خوردگی-خستگی آلیاژ آلومینیوم 7075-T651 تحت بارگذاری های متناوب
ABSTRACT
The corrosion-fatigue behaviour of 7075-T651 aluminum alloy subjected to periodic overloads was examined. This aluminum alloy is typically used in aerospace structural components such as the wing spars of aircraft. Axial fatigue specimens were subjected to a loading spectrum that consisted of a fully reversed periodic overload of near-yield magnitude followed by 200 smaller cycles at high Rratio. The specimens were fatigue tested while they were fully immersed in an aerated and recirculated 3.5 wt% NaCl simulated seawater solution.
مدلهای چند مقیاسی از کامپوزیتهای زمینه سرامیکی بافته شده
Multiscale model of woven ceramic matrix composites
considering manufacturing induced damage
مدلهای چند مقیاسی از کامپوزیتهای زمینه سرامیکی بافته شده
با توجه به آسیبهای ایجاد شدهی تولید
ABSTRACT
Multiscale models play an important role in capturing the nonlinear response of woven carbon fiber reinforced ceramic matrix composites. In plain weave carbon fiber/silicon carbide (C/SiC) composites, for example, when microcracks form in the as-produced parts due to the mismatch in thermal properties between constituents, a multiscale thermoelastic framework can be used to capture the initial damage state of these composites. In this paper, a micromechanics-based multiscale model coupled with a thermoelastic progressive damage model is developed to simulate the elastic and damage behavior of a plain weave C/SiC composite system under thermal and mechanical loading conditions. The multiscale model is able to accurately predict composite behavior and serves as a valuable tool in investigating the physics of damage initiation and progression, in addition to the evolution of effective composite elastic moduli caused by temperature change and damage. The matrix damage initiation and progression is investigated at various length scales and the effects are demonstrated on the global composite behavior.
تفجوشی، شکل دهی، واکنش و رشد بلور توسط سیستم پلاسمای جرقه ای (SPS)
Sintering, consolidation, reaction and crystal growth by
(the spark plasma system (SPS
تفجوشی، شکل دهی، واکنش و رشد بلور توسط سیستم پلاسمای جرقه ای (SPS)
ABSTRACT
The graphite die set in spark plasma system (SPS) is heated by a pulse direct current. Weak plasma, discharge impact, electric field and electric current, which are based on this current, induce good effects on materials in the die. The surface films of aluminum and pure WC powders are ruptured by the spark plasma. Pure AlN powder is sintered without sintering additives in the electric field. The spark plasma leaves discharge patterns on insulators. Organic fibers are etched by the spark plasma. Thermosetting polyimide is consolidated by the spark plasma. Insoluble polymonomethylsilane is rearranged into the soluble one by the spark plasma. A single crystal of CoSb3 is grown from the compound powders in the electric field by slow heating. Coupled crystals of eutectic powder are connected with each other in the electric field.
اثر زیرلایه روی جوانه زنی و رشد نانو ورق های عمودی گرافن
Influence of substrate on nucleation and growth of
verticalgraphene nanosheets
اثر زیرلایه روی جوانه زنی و رشد نانو ورق های عمودی گرافن
ABSTRACT
The present study reports the role of substrate on nucleation and growth of vertical graphene nanosheets (VGNs) under electron cyclotron resonance chemical vapor deposition (ECR-CVD). The VGNs are grown on Pt, Ni, Au, Cu, Si(100), Si(111), SiO2 and quartz substrates simultaneously. The morphology of VGNs is found to vary significantly with substrate. VGNs on Pt have the highest aerial density of vertical sheets while quartz have the lowest. The structural defects in VGNs vary with substrate as evidenced from Raman spectroscopy. The observation of defect related Raman bands such as D'' and D* at 1150 and 1500 cm-1, respectively revealed the existence of pentagon-heptagon rings or carbon onions in VGNs. Formation of such defects at early stage of nucleation dictates the growth mechanism and hence the morphology. A phenomenological four stage model is discussed, to substantiate the nucleation and growth mechanism of VGNs on different substrates, by evoking substrate - plasma interaction during growth.
تحولات مارتنزیتی در آلیاژهای غیرآهنی آلیاژهای حافظهدار
Martensitic transformations in nonferrous shape memory alloys
تحولات مارتنزیتی در آلیاژهای غیرآهنی آلیاژهای حافظهدار
ABSTRACT
In the present paper, the important developments on martensitic transformations in non-ferrous shape memory alloys within nearly 10 years are critically reviewed. Since the alloys include not only noble-metal alloys but also Ti–Ni based alloys, the field is very wide both in contents and in the kind of alloys. We tried to describe items with uniformity, which are common to all alloys, but specific items were also discussed when they are important. Special attention was paid to similarity and dissimilarity among alloys to highlight key points on the issues concerned.
اثر نرخ بارگذاری روی چقرمگی شکست اپوکسی اصلاح شده با لاستیک هیبریدی
Fracture Toughness of a Hybrid Rubber Modified
Epoxy. II. Effect of Loading Rate
چقرمگی شکست اپوکسی اصلاح شده با لاستیک هیبریدی.
II. اثر نرخ بارگذاری
ABSTRACT
خصوصیات ترموالکتریکی بهبود یافته در ساماریم بورید
Enhanced thermoelectric properties of samarium boride
خصوصیات ترموالکتریکی بهبود یافته در ساماریم بورید
ABSTRACT
SmB62 single crystals were successfully grown by the floating zone (FZ) method. The high-temperature thermoelectric properties were investigated, together with magnetic properties and specific heat at low-temperature. The electrical resistivity, ρ, shows variable-range-hopping (VRH) behavior with significantly lower values than other rare-earth RB62 (RB66) compounds. An effective magnetic moment, μeff, of 0.42 μB/Sm was estimated, which if straightforwardly taken indicates a mixed valency for SmB62 with Sm2+:Sm3+ = 1:1, which is the first ever indicated for RB66-type compounds. Localization length of the VRH at the Fermi level, ξ, was estimated to be 3.33 Å indicating that carriers in SmB62 are much less localized than in YB66 which has 0.56 Å. The thermoelectric behavior of SmB62 is striking, with ρ reduced by two orders of magnitude while maintaining large Seebeck coefficients, and as a result the power factor is ∼30 times higher than other rare-earth phases. Overall the figure of merit ZT amounts to ∼0.13 at 1050 K, with an extrapolated value of ∼0.4 at 1500 K, an expected working temperature for topping cycles in thermal power plants; that gives a ∼40 times enhancement for Sm. Since there are few thermoelectric materials applicable for very-high temperature applications, this discovery gives new interest in the samarium higher borides.
اثر افزودن کاربید تیتانیوم روی خواص ترموالکتریک سرامیک ها
Effect of titanium carbide addition on the thermoelectric properties of B4C ceramics
اثر افزودن کاربید تیتانیوم روی خواص ترموالکتریک سرامیک های B4C
ABSTRACT
TiB2/B4C composite ceramics are prepared via hot pressing, in which the TiB2 particles are formed by introducing TiC0.78 and through the reaction between B4C and TiC0.78. The electrical and thermal conductivities and Seebeck coefficient of samples containing 0, 12.5 and 25.4 vol% TiB2 are measured from room temperature up to 1200 K. The results show that the transport properties of the samples vary with the TiB2 content. The transport properties of a 12.5 vol% TiB2/B4C sample are dominated by the B4C matrix as in undoped B4C ceramics, whilst the transport properties of a 25.4 vol% TiB2/B4C sample are dominated by TiB2 particles. The figure of merit of the 25.4 vol% TiB2/B4C sample is higher than that of the undoped B4C ceramic sample between room temperature and about 700 K, which indicates that it is possible to improve the thermoelectric properties by selecting an optimum combination of different materials.
رشد سلولی و دندریتی Cellular and dendritic growth
Cellular and dendritic growth
رشد سلولی و دندریتی
ABSTRACT
Many of the alloys used in practice, such as steel, aluminum-copper alloys, nickel-base and copper-base alloys, are single phase alloys, which means that the final product of solidification is a solid solution. Depending on the thermal and compositional field, cellular or, in most practical cases, dendritic morphology will occur. In other cases, even when the room temperature microstructure is mostly eutectic some primary phases solidify before the eutectic. They can be solid solutions, carbides, intermetallic phases, inclusions, etc. Their morphology affects mechanical properties, and thus, understanding how this morphology can be controlled is a mater of significant practical importance. A detailed discussion of primary phase growth, and in particular of dendrite growth, will be provided in the following sections.
رشد ورقه های گرافن روی نانوسیم های سیلیکا با دانسیته بالا
Catalyst-free approach for growth of graphene sheets on
high-density silica nanowires byCVD
روش بدون کاتالیزور برای رشد ورقه های گرافن روی نانوسیم های سیلیکا
با دانسیته بالا توسط CVD
ABSTRACT
A novel “two-step annealing” method is proposed for the direct synthesis of graphene sheets on high-density dielectric silica nanowires without using metal catalysts. During the first annealing at 1000 °C, the extremely thin SiO2 layer on Si substrate shrinks and forms dense nanoparticles. Using these silica nanoparticles as templates, graphene sheets and silica nanowires are synthesized simultaneously after the second annealing process at 800–850 °C. The experiment results suggest that the graphene sheets grow along the nanowires and its crystalline quality and domain size are determined by the temperature and duration of the second annealing process.