• asar paranetrhaye sanaty-taliem-ir

    اثر پارامترهای هندسی بر تغییرات فرکانس طبیعی یک مخزن استوانه ای ترکدار تحت تحریک ضربه در نرم افزارAAbaqus

    1,900 تومان

    هدف این مقاله، بررسی اثر پارامترهای هندسی بر فرکانس طبیعی یک مخزن استوانه ای ترکدار تحت تحریک ضربه و سپس پیدا کردن راهکاری جهت بررسی وجود ترک در مخازن میباشد. روند طی شده در این تحلیل بدین صورت میباشد که در حالت الف) قطر و ضخامت ثابت، تغییرات طول، و در حالت ب)طول و ضخامت ثابت، تغییرات قطر، و در نهایت در حالت ج)طول و قطر ثابت، تغییرات ضخامت بررسی شده است. بدین ترتیب، اثر تغییرات فرکانس طبیعی بر اساس تغییرات پارامترهای هندسی مخزن امکان پذیر خواهد بود. نشان داده شده که در حالت طول و قطر ثابت با افزایش ضخامت مخزن، فرکانس افزایش می یابد. به علاوه، در حالت طول و ضخامت ثابت با کاهش قطر مخزن، و در حالت قطر و ضخامت ثابت با کاهش طول مخزن، فرکانس افزایش می یابد. در آخر به جهت کاهش زمان و هزینه های کارشناسی با بررسی نتایج حاصل شده، برای وجود یا عدم وجود ترک طولی در مخزن رابطه ای تئوری بدست آمده است.

  • baresi asar meydanhaye hararati-taliem-ir

    بررسي اثر ميدان های حرارتي و مغناطيسي روی کربني نانولوله تحت عبور نانو سيال بعنوان نانوسنسور

    1,900 تومان

    در این مقاله اثر میدان های حرارتی و مغناطیسی روی نانولوله کربنی بعنوان نانوسنسور با استفاده از مدل تیر رایلی و بر اساس تیوری غیرموضعی گرادیان کرنشی تحلیل خواهد شد. نانولوله تحت تاثیر میدان های فیزیکی اعم از حرارتی و مغناطیسی می باشد و از آن نانوسیال بعنوان نانوسنسور جهت اندازه گیری فرکانس های شیفت عبور می کند. شرایط تکیه گاهی در مراحل مختلف این تحقیق در نظر گرفته شده است. روابط سینماتیک بر اساس نظریه فن کارمن بکار خواهد رفت. با استفاده از اصل هامیلتون معادلات حرکت استخراج شده اند. برای بیان نیروی سیال از روابط ناویر استوکس استفاده شده است. میدان مغناطیسی بصورت دوبعدی از روابط لورنتز استخراج شده اند. تاثیر پارامترهای مختلف روی ارتعاشات نانولوله بررسی شده است. از نوآوری های مهم و برجسته این تحقیق، تحلیل ارتعاشات و بررسی فرکانس های شیفت نانولوله کربنی تحت حرکت نانوسیال بعنوان نانوسنسور در محیط پاسترناک، اثر میدان های حرارتی و مغناطیسی روی نانولوله کربنی تک لایه و همچنین استفاده از تیوری غیرموضعی-گرادیان کرنشی می باشد. امید است که این مقاله راه روشنی در این مقوله برای آیندگان باشد و به عنوان مرجعی محکم در تحلیل و بررسی نانوسنسورها مورد استفاده قرار بگیرد.

  • tasir badane jeloee-taliem-ir

    تاثیر بدنه جلویی بر رو عملکرد ي آیرودینامیکی چتر نیم کره

    1,900 تومان

    از چترها برای کاهش سرعت محموله های فضایی و هوایی، در فاز نزول و فرود استفاده میشود. عوامل گوناگونی در تغییر ضریب پسای چتر و کاهش عملکرد آن تاثیر دارد. یکی از این عوامل تاثیر هندسه بدنه جلویی و فاصله آن بر روی عملکرد چتر میباشد. در این مقاله، شبیه سازی ایرودینامیکی محموله مقیاس بندی شده یک نمونه رایج در مقابل یک مدل چتر نیمکره متناسب، در فاز فرود انجام گرفته و عملکرد چتر در حالت قرارگرفتن محموله جلویی و بدون آن مورد بررسی قرار میگیرد. همچنین تاثیر فاصله قرارگیری بدنه نسبت به چتر مطالعه میشود. نتایج حاصل از حل عددی نشان میدهد که با قرار گرفتن بدنه جلویی مورد نظر به شکل استوانه ای مخروطی، عملکرد چتر و ضریب پسا به شدت کاهش پیدا میکند به منظور اعتبارسنجی، ضریب پسای بهدست آمده از حل عددی برای چتر نیمکره با ضریب پسای مراجع مربوطه مقایسه شده است.

  • tahlil 3bohdi asar-taliem-ir

    تحلیل سه بعدی اثر شکل هندسی مقطع کانال گاز سمت کاتد بر عملکرد پیل سوختیPEM

    1,900 تومان

    طراحی موثر کانال های جریانگاز در پیل های سوختی پلیمری برای اطمینان از توزیع یکنواخت گازهای واکنشگر بسیار مهم و اساسی است. در این مطالعه، با توسعه یک کد برنامه نویسی سه بعدی به زبان فرترن، تاثیر تغییر ابعاد کانال با ثابت نگه داشتن حجم و طول کانال در حالت دوفازی بر عملکرد پیلسوختی مورد مطالعه قرار میگیرد. نتایج نشان میدهند که با ثابت نگه داشتن حجم کانال و تغییر در ارتفاع و عرض کانال میتوان بر میزان اکسیژن ورودی به لایه نفوذگاز و همچنین بهبود عملکرد پیل اثرگذاری کرد. یافته ها حاکی از آن است که با کاهش ارتفاع کانال و افزایش عرضکانال از میزان اشباعشدگی و همچنین غلظت آب در لایه نفوذگاز کاسته میشود. در نتیجه اکسیژن بیشتری به تخلخل های لایه نفوذگاز و لایه کاتالیست نفوذ میکند و به تبع آن بیشترین چگالی جریان و چگالی توان در مقایسه با سایر طراحی ها تولید میکند.

  • A fuzzy control system of diesel generator speed[taliem.ir]

    A fuzzy control system of diesel generator speed

    تومان

    Diesel generator, in which the generator is driven by the diesel engine to generate alternating current which frequency should keep stable and constant, is broadly used as mobile, urgent or field power sourc. The alternating current frequency is determined by the diesel speed. So the diesel speed should keep stable and constant too. This paper introduces two analogue control systems: rigid feedback and constant-speed feedback control system, and constructs a fuzzy control system of the diesel speed. Comparison of their control performances and practical applications indicate that the fuzzy control method is feasible and better than the others.

  • A REVIEW ON NANOFLUIDS - PART II[taliem.ir]

    A REVIEW ON NANOFLUIDS – PART II: EXPERIMENTS AND APPLICATIONS

    تومان

    Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the  transport properties and heat transfer characteristics of the suspension. This second part of the review covers fluid flow and heat transfer characteristics of nanofluids in forced and free convection flows and potential applications of nanofluids. Opportunities for future research are identified as well.

  • Acoustic emission based drill condition monitoring during drilling of[taliem.ir]

    Acoustic emission based drill condition monitoring during drilling of glass/phenolic polymeric composite using wavelet packet transform

    تومان

    Monitoring of tool condition on the basis of sensor signals requires a selection of suitable signal processing technique and monitoring index, to assess the tool condition. In this paper, wavelet packet transform is used as a tool, to characterise the acoustic emission signals released from glass/phenolic polymeric composite during drilling. The results show that the selected monitoring indices from the wavelet packet coefficients  are capable of detecting the drill condition effectively.

  • bannertaliem-taliem-ir

    Alleviation of rolling contact fatigue on Sweden’s heavy haul railway

    تومان

    A test has been undertaken on Sweden’s Malmbanan, or iron ore railway, to reduce rolling contact fatigue (RCF) damage by developing a preventative maintenance regime involving routine grinding of the rails. In just the first 2 years of the test, the total cost of grinding plus rail replacements was reduced by almost 40%, while both the rail and track quality generally improved immensely. Although it may not be possible to reproduce such savings everywhere that RCF damage occurs, some lessons from the test are of general relevance. In particular, the development of even existing surface-initiated defects can effectively be halted by grinding and thereafter regularly reinstating, a profile which substantially removes loading from those cracks. In this test, the rate of metal removal by grinding was about 0.2 mm per 25 MGT. Methods were also developed for objectively monitoring the transverse and longitudinal profiles of the ground rail, and the depth of metal removed from the rail, i.e. the overall grinding “quality”. It would appear that the desired benefits of grinding can be obtained even if deviations of the transverse profile from a desired reference profile exceed specified limits over a significant fraction of the track.

  • An investigation of microstructureproperty relationships[taliem.ir]

    An investigation of microstructure/property relationships in dissimilar welds between martensitic and austenitic stainless steels

    تومان

    The metallurgical characteristics, tensile, hardness, toughness and corrosion resistance of dissimilar welds  between X5CrNi18-10 grade austenitic and X20CrMo13 grade martensitic stainless steel have been evaluated. Both austenitic and duplex stainless steel electrodes were used to join this combination, using multipass  manual metal arc welding process. Defect free welds were made with each welding consumable. It was found that the tensile strength of weldment, which was produced by duplex electrode (E2209-17), was slightly  lower than that of austenitic electrode (E308L-16). The toughness of the both E2209-17 and E308L-16  deposits was acceptable even at low temperature regardless of heat input. Hardness was increased in both  welds made with E2209-17 duplex and E308L-16 austenitic electrode along the X20CrMo13/weld metal  fusion boundary due to heat annealing and then following high cooling rate. The pitting corrosion resistance of the weld metal made with E308L-16 and E2209-17 filler metal was found acceptable. Although, heat  affected zone in the weldment and X20CrMo13 base metal were affected by electrolytic corrosion. This  investigation has shown that both filler metals can be used to join austenitic stainless steel to the martensitic stainless steel.

  • Corrosion resistance of sintered[taliem.ir]

    Corrosion resistance of sintered duplex stainless steel evaluated by electrochemical method

    تومان

    Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using  electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated. Design/methodology/approach: In presented study  duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been  compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245 °C/min and slow cooling of 5 °C/min in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis of microstructure components. Corrosion  properties have been studied through electrochemical methods in 1M NaCl water solution Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties which depends on  austenite/ferrite ratio in the microstructure and elements partitioning between phases. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion in 1M NaCl solution was achieved for composition with approximate balance of ferrite and austenite in the microstructure. Research  limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a  good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates.

  • Development of Brake System and Regenerative[taliem.ir]

    Development of Brake System and Regenerative Braking Cooperative Control Algorithm for Automatic-Transmission-Based Hybrid Electric Vehicles

    تومان

    In this paper, a brake system for an automatic transmission(AT)-based hybrid electric vehicle (HEV) is developed, and a regenerative braking cooperative control algorithm is proposed, with consideration of the characteristics of the brake system. The brake system does not require a pedal simulator or a fail-safe device, because a hydraulic brake is equipped on the rear wheels, and an electronic wedge brake (EWB) is  equipped on the frontwheels of the vehicle. Dynamic models of the HEV equipped with the brake system developed in this study are obtained, and a performance simulator is developed. Furthermore, a regenerative braking cooperative control algorithm, which can increase the regenerative braking energy recovery, is suggested by considering the characteristics of the proposed hydraulic brake system. A simulation and a vehicle test show that the brake system and the regenerative braking cooperative control algorithm satisfy the demanded braking force by performing cooperative control between regenerative braking and friction braking. The regenerative braking cooperative control algorithm can increase energy recovery of the regenerative braking by increasing the gradient of the demanded braking force against the pedal stroke. The gradient of the demanded braking force needs to be determined withconsideration of the driver’s braking characteristics, regenerative braking energy, and the driving comfort.

  • Drilling of carbon composites using a one shot drill bit. Part I Five stage[taliem.ir]

    Drilling of carbon composites using a one shot drill bit. Part I: Five stage representation of drilling and factors affecting maximum force and torque

    تومان

    The thrust force and torque produced during drilling contain important information related to the quality of the hole and the wear of thedrill  bit  . In this paper, the force and torque produced during drilling of carbon fibre using a ‘one shot’ drill bit is investigated. The signals in the time domain were divided into stages and common problems and defects associated with each stage discussed. It is also shown how tool wear and thickness of the workpiece affect the thrust force and torque throughout the drilling process. The findings of this paper are used to develop a mathematical model of the maximum thrust force and torque as described on Part II of this paper and are a valuable reference for future  optimisation of drilling carbon composites with a ‘oneshot’ drill bit.

  • Effect of PWHT cycles on fatigue crack growth and toughness of[taliem.ir]

    Effect of PWHT cycles on fatigue crack growth and toughness of quenched and tempered pressure vessel steels

    تومان

    Transportable pressure vessels, commonly manufactured from quenched and tempered (QT) steels, require mandatory postweld heat treatment (PWHT) regardless of plate thickness. During their life, transportable pressure vessels may have up to 4 PWHT cycles at  temperatures between 540 and 590 ◦C, and concerns have emerged about possible effects on the mechanical properties of the base (parent) plate. This paper reports work on the resistance to fatigue crack growth, impact toughness and CTOD fracture toughness of two types of QT steels. The parent metal region was examined for both steels, and then exposed to temperatures and times in the PWHT range. Although there was a marginal decrease in the resistance to fatigue crack growth for up to four postweld heat treatment cycles, there was a significant decrease in impact toughness and CTOD fracture toughness.

  • Electrical discharge machining of ceramiccarbon nanostructure[taliem.ir]

    Electrical discharge machining of ceramic/carbon nanostructure composites

    تومان

    The miniaturization of mechanical components with complex shapes is a great challenge in emerging  applications. Silicon nitride (Si3N4) ceramics are excellent candidates for such applications due to their  outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using normal mechanical machining methods. If the material were electrically conductive, electrical discharge  machining (EDM) could be applied to produce precise and complex shapes. In this paper, in order to  investigate the effects of electrical conductivity on the EDM characteristics, several carbon nanostructure  composite materials are fabricated and EDMed using the assisting electrode method proposed by the current authors. The performance of the process is evaluated as a function of the carbon nanostructure content and type. The former is separately selected to be close to the electrical percolation threshold (0.9 vol.% and 5.3 vol.% for carbon nanotube (CNT) and graphene Nano platelet (GNP) composites, respectively), and well above that limit (5.3 vol.% and 20.6 vol.%), where electrical conductivities on the order of 10 and 100  S·m-1 are attained for CNTs and GNPs-based nanocomposites, respectively. In addition, bare Si3Nspecimens are also tested. Material removal rate, electrode wear ratio, and surface roughness of the  machined pieces are analyzed for all testing conditions.

  • Exploring the Mechanical Properties of[taliem.ir]

    Exploring the Mechanical Properties of Spot Welded Dissimilar Joints for Stainless and Galvanized Steels

    تومان

    Spot weldability of dissimilar metal joints between stainless steels and nonstainless steels was investigated. The aim was to determine the spot welding parameters for the dissimilar metal joints and to characterize the mechanical properties of the joints. Metallographical investigations, microhardness measurements, peel tests, lap shear tests, cross-tension tests, corrosion fatigue tests, and stress corrosion cracking tests were  performed. It was found that in the dissimilar metal joints between stainless steel and nonstainless steel, the failure load of the cross-tension specimens was around 72–78% of that of the lap shear specimens. The weld nugget of the dissimilar metal joints was fully martensitic, but it was ductile enough so that the failure type was plug failure in both lap shear and cross-tension tests. In the case of the corrosion fatigue testing of the spot welded joints, different strength levels of the base materials did not have an effect on the corrosion fatigue strength, but the sheet thickness had a significant effect. The fatigue strength of a spot welded specimen increased with the increasing sheet thickness. Electro-coating of the test specimens did not have an effect on the corrosion fatigue properties of the spot welded joints.