کامپوزیت‎های تقویت شده با الیاف سه بعدی فیبر شیشه-پلی پروپیلن

Polypropylene/glass fibre 3D-textile reinforced composites

for automotive applications

کامپوزیت‎های تقویت شده با الیاف سه بعدی فیبر شیشه/پلی پروپیلن

برای کاربردهای خودرو

ABSTRACT

Textile-reinforced thermoplastic composites offer huge application potentials for a rapid manufacturing of components with versatile possibilities of integrating functions. However, an application of these new materials requires the knowledge of the directional dependent material properties. In this study, results are presented concerning selected relevant load cases for industrial applications. For the new group of multi-layered flat bed weft-knitted glass fibre/polypropylene composites (MKF-GF/PP), tensile tests under different temperatures and test velocities have been carried out as well as Charpy impact tests, open hole tension tests and dynamic-mechanical analysis. The mechanical properties of MKF-GF/PP and unidirectional GF/PP composites with tailored fibre surface and interphase, respectively, have been compared to those of woven GF/PP composites and GF/PP composites made of non-crimp fabrics (NCF) as a benchmark.

 

مواد کامپوزیت نساجی : کامپوزیت های زمینه پلیمری

Textile Composite Materials: Polymer Matrix Composites

مواد کامپوزیت نساجی : کامپوزیت های زمینه پلیمری

ABSTRACT

Textile composites are fiber-reinforced composite materials, the reinforcement being in the form of a textile fabric (woven, knitted, braided). In the production of composite parts, the use of textile reinforcements brings benefits in handability of the fabrics (hence in automation possibilities and in cost) and in easier applicability of closed-mold processes. In performance, due to interlacing of yarns in textile, the interlaminar/ through-the-thickness/ impact properties of composite are improved; matrix cracks, originated inside the yarns, do not propagate through the material but are stopped when the yarn changes its direction. The latter mechanism leads to higher-energy absorption capabilities in crash-resistant applications

 

مزایای اقتصادی و فنی استفاده از آهن خام در شارژ کوره های کوپولا یا برقی

Technical and economic advantages of pig iron in

the charges of cupolas or electric furnaces

مزایای اقتصادی و فنی استفاده از آهن خام در شارژ کوره های کوپولا یا برقی

ABSTRACT

The study has the following general objective: to determine the technical and economic advantages of the use of pig iron in charges remelted either in the cupola or in the electric furnace. It has been found that the consumption of pig iron per tonne of castings produced by iron foundries has dropped significantly in all Community member countries in the last few years. This decline seems to result primarily from the price difference between pig iron and scrap, which is encouraging foundries to accommodate to the latter, which is of course not as close to the iron to be produced, with the help of new melting and metallurgical testing techniques

 

خواص، رفتار و روش های تولید نانوکامپوزیت Al-Al2O3

A Review on Properties, Behaviour and Processing Methods

for Al- Nano Al-Al2O3Composites

مروری بر خواص، رفتار و روش های تولید نانوکامپوزیت های Al-Al2O3

ABSTRACT

Nanotechnology is spreading vastly in the various demanding fields of engineering and medicines like aerospace, defence, automobiles, electronics, materials, chemistry, energy, environment, information & communication, consumer goods and bio- technology. It created a high impact on development of new generation nano materials with advanced features and wide range of their applications. Reinforcement of submicron or nano-sized particles with aluminium matrix yields superior mechanical and physical properties and changes morphology and interfacial characteristics of nano-composites. A wide range of research has been done on the processing methods and material properties of Al-Al2O3 nano-composites. Recently, ultrasonic assisted casting, nano-sintering, powder metallurgy, high energy ball milling, friction stir process are being applied for the production of Al-Al2O3 nano-composites in which agglomeration of the reinforcing particles causes grain growth resulting changes in the microstructure. Control of the grain size by minimizing agglomeration of nano particles and retaining the enhanced microstructure during these processes has become a challenging task. This area is further looked-for research work to control the microstructures under various processing conditions.

 

عملیات حرارتی قطعات ریخته‎گری‎ بزرگ از فولاد 15Kh3M1FTsL

Heat Treatment of Large Castings from Steel 15Kh3M1FTsL

عملیات حرارتی قطعات ریخته‎گری‎ بزرگ از فولاد 15Kh3M1FTsL

ABSTRACT

The effect of heat treatment on mechanical properties, impact toughness, and cold-shortness threshold of cast steel 15Kh3M1FL is investigated. A heat treatment mode including homogenizing, air hardening, and high-temperature tempering of castings is suggested for commercial use.

 

سختی مارتنزیت تمپرشده در فولادهای کربنی و کم آلیاژی

Hardness of Tempered Martensite in Carbon

and Low-Alloy Steels

سختی مارتنزیت تمپرشده در فولادهای کربنی و کم آلیاژی

ABSTRACT

This paper presents the results of a systematic study of the effect of carbon, manganese, phosphorus, silicon, nickel, chromium, molybdenum, and vanadium on the hardness of martensite in low to medium carbon steels tempered for one hour at 100~ (56~ intervals in the range 400 to 1300~ (204 to 704~ Results show that the as-quenched hardness depends solely on carbon content. On tempering, the effect of carbon on hardness decreases markedly with increasing tempering temperature. Studies of carbon-0.5 manganese steels showed that the incremental increase in hardness from 0.5 pct manganese after a given tempering treatment was independent of carbon content. Based on this result, studies of the effects of the other alloying elements were made using a 0.2 or 0.3 pct carbon, 0.3 to 0.5 pct manganese steel base composition. The hardness of the resulting tempered martensite was assumed to be due to a given alloy addition, and when two or more alloying elements were added, their effects were assumed to be additive.

 

اتصال آلیاژهای آلومینیوم 5083 و 6061 به روش جوشکاری اصطکاکی تلاطمی

Joining of 5083 and 6061 aluminum alloys by friction stir welding

اتصال آلیاژهای آلومینیوم 5083 و 6061 به روش جوشکاری اصطکاکی تلاطمی

ABSTRACT

Friction stir welding (FSW) has emerged as a new solid state joining technique [1], especially for aluminum alloys [2–6]. In this process, a rotating tool travels down the length of contacting metal plates, and produces a highly plastically deformed zone through the associated stirring action. The localized heating zone is produced by friction between the tool shoulder and the plate top surface, as well as plastic deformation of the material in contact with the tool [1].

At the present time, FSW is used mainly for joining similar materials. For dissimilar welding, there have been few systematic studies aimed at clarifying the effect of material combination and welding conditions on weld properties [7, 8].

 

بافت‌های مقاوم در برابر شکست پلی پروپیلن تقویت‌شده با الیاف بلند

An integral design and manufacturing concept for crash resistant

textile and long-fibre reinforced polypropylene structural components

یک طراحی انتگرالی و ایده‌ی تولید برای بافت‌های مقاوم در برابر شکست

و ترکیبات ساختاری پلی پروپیلن تقویت‌شده با الیاف بلند

ABSTRACT

For the design of crash resistant structures for automotive applications, mainly metallic materials are currently considered. However, the advanced specific energy absorption capacity and a high lightweight potential qualifies fiber and textile reinforced thermoplastic composites for such components. With a load adapted material design as well as an efficient manufacturing concept these properties can be exploited to a full extend. A seat pan is chosen as an exemplary structure to illustrate the four main aspects of the investigations: evaluation of glass fiber polypropylene composite configurations; development of a manufacturing and process chain; crash and impact experiments on structural level and numerical modelling strategy. Hybrid yarn based textiles, such as a commercially available 2/2-twill fabric and novel multi-layered flat bed weft-knitted fabrics have been considered to be combined with a long-fibre reinforced thermoplastic material (LFT, cutting length of 25 mm) for complexly loaded sections like ribbings. A special emphasis is set on a similar to mass-production manufacturing process. A fully automated integral hot pressing process has been developed, where an automated handling system places the conglomerate of extruded LFT-material and preheated hybrid yarn textile in a fast-stroke press, achieving process cycles of 45 s. Finally, the structural evaluation under crash loading conditions is compared against numerical results

 

تئوری جدید تأثیر مدیوم بر شبیه سازی انتقال حرارت مواد متخلخل

A novel effective medium theory for modelling

the thermal conductivity of porous materials

تئوری جدید تأثیر متوسط بر شبیه سازی انتقال حرارت مواد متخلخل

ABSTRACT

A novel effective medium theory was proposed to model the thermal conductivity of porous materials. In this theory, phases (or components) are treated as small spheres dispersing into an assumed uniform medium with the thermal conductivity km. A simple algebraic expression for the thermal conductivity based on this theory was derived, in which each has a distinct physical basis. The expression can unify five basic structural models (Series, Parallel, two forms of Maxwell–Eucken, effective medium theory) through variations of km. Furthermore, the feasibility of the model was evaluated using the experimental data from previous literatures and those calculated by this model.

 

اثر فشار اکسیژن بر خواص فیلم های ZnO دوپ شده با Nb

Influence of oxygen pressure on the structural, electrical and optical

properties of Nb-doped ZnO thin films prepared

by pulsed laser deposition

اثر فشار اکسیژن بر خواص ساختاری، الکتریکی و نوری فیلم های ZnO

دوپ شده با Nb آماده شده توسط لایه نشانی لیزری پالسی

ABSTRACT

Nb-doped zinc oxide (NZO) transparent conductive thin films with highly (0 0 2)-preferred orientation were deposited on glass substrates by pulsed laser deposition method in oxygen ambience under different oxygen pressures. The as-deposited films were characterized by X-ray diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), electrical and optical characterization techniques. It was found that a desirable amount of oxygen can reduce the related defect scattering and enhance the carrier mobility. The resistivity and average optical transmittance of the NZO thin films are of 10−4 Ω cm and over 88%, respectively. The lowest electrical resistivity of the film is found to be about 4.37 × 10−4 Ω cm. In addition, the influence of oxygen pressure on optical properties in NZO thin films was systematically studied as well.