خزش در فلزات آمورف (شیشه فلزات) Creep in amorphous metals

Creep in amorphous metals

خزش در فلزات آمورف (شیشه فلزات)

ABSTRACT

This paper reviews the work on creep behavior of amorphous metals. There have been, overthe past several years, a few reviews of the mechanical behavior of amorphous metals. Ofthese, the review of the creep properties of amorphous metals by Schuh et al. though oldestof the three, is particularly noteworthy and the reader is referred to this article publishedin 2007. The current review of creep of amorphous metals particularly focuses on thoseworks since that review and places the work prior to 2007 in a different context where newdevelopments warrant.

 

اثر سرعت جوشکاری بر تنش پسماند در طول جوشکاری قوس با الکترود تنگستن تحت پوشش گاز

Influence of welding speed and power on residual stress during gas tungsten arc welding (GTAW) of thin sections

with constant heat input: A study using numerical simulation and experimental validation

اثر سرعت جوشکاری و توان بر تنش پسماند

در طول جوشکاری قوسی الکترود تنگستن (GTAW) مقاطع نازک با ورودی گرمای ثابت

مطالعه ای با استفاده از شبیه سازی و اعتبارسنجی تجربی

ABSTRACT

The temperature distribution and residual stresses for a GTAW circumferential butt joint of AISI 304 stainless steel using numerical simulation have been evaluated. For evaluation of weld induced residual stresses, the analysis of heat source fitting was carried out with heat inputs ranging from 200 to 500 J/mm to arrive at optimal heat input for obtaining proper weld penetration and heat affected zone (HAZ). For this chosen heat input, the influence of different weld speeds and powers on the temperature distribution and the residual stresses is studied. The heat source analysis revealed the best choice of heat input as 300 J/mm. The residual stresses on the inner and outer surfaces, and along the radial direction were computed. Increase in temperature distribution as well as longitudinal and circumferential residual stresses was observed with the increase in weld speed and power. The validity of the results obtained from numerical simulation is demonstrated with full scale shop floor welding experiments.

 

انتقال حرارت و رفتارانجماد پوسته‎ای در قالب ریخته‎گری پیوسته

Heat Transfer and Deformation Behavior of Shell Solidification

in Wide and Thick Slab Continuous Casting Mold

انتقال حرارت و رفتار تغییرشکل انجماد پوسته‎ای در ورق بزرگ و ضخیم قالب ریخته‎گری پیوسته

ABSTRACT

The shell solidification in continuous casting mold is a rather complex process that is coupled with thermal and mechanical behaviors, which are related to numerous of defects occurring in slabs surface and subsurface during practical continuous casting. Intending to increase the understanding of shell thermal and mechanical behaviors in continuous casting molds to improve the casting process, numerous studies[1-13] have been conducted over the past few decades by numerical simulation. However, among these previous studies, most of the mathematical models neglected the effects of mold flux film on shell heat transfer[1-6,11] or assumed that the mold flux film distribution in shell/mold gap was uniform or changed linearly with the mold height[7-10,12,13]. It is obvious that the assumptions did not conform to the actual case of practical continuous casting that the mold flux film in mold distributes dynamically both along mold height and circumference with the evolutions of shell/mold gap and shell temperature, and affects the shell thermal and mechanical behaviors greatly.

رفتار استحاله سرد شدن پیوسته فولاد خط لوله‎ی X70

Continuous cooling transformation behavior of X70 pipeline steel

رفتار استحاله سرد شدن پیوسته فولاد خط لوله‎ی X70 

ABSTRACT

The comprehensive mechanical properties of steel depended on the final microstructure and grain refinement. In order to obtain high performance pipeline steel, composition design and the application of controlled rolling and controlled cooling technology had become a key, especially the latter which had decisive influence on the product’s final texture and comprehensive performance in modern iron and steel material production. Along with the development of the modern rolling equipment as well as the in-depth study of controlled rolling and controlled cooling technology, the application of controlled rolling and controlled cooling technology had become an important means of fully excavating the potential of the material properties based on the existing material chemical compositions and it had got the extensive attention from modern iron and steel materials research field.

غرق شدن تایتانیک بعلت مشکل متالورژیکی

RMS Titanic: A Metallurgical Problem

آر ام اس تایتانیک : یک مشکل متالورژیکی

ABSTRACT

On 14 April 1912, at 11:40 p.m., Greenland Time, the Royal Mail Ship Titanic on its maiden voyage was proceeding westward at 21.5 knots (40 km/h) when the lookouts on the foremast sighted a massive iceberg estimated to have weighed between 150,000 to 300,000 tons at a distance of 500 m ahead. Immediately, the ship’s engines were reversed and the ship was turned to port (left) in an attempt to avoid the iceberg. In about 40 seconds, the ship struck the iceberg below the waterline on its starboard (right) side near the bow. The iceberg raked the hull of the ship for 100 m, destroying the integrity of the six forward watertight compartments. Within 2 h 40 min the RMS Titanic sank.

Metallurgical examination and chemical analysis of the steel taken from the Titanic revealed important clues that allow an understanding of the severity of the damage inflicted on the hull. Although the steel was probably as good as was available at the time the ship was constructed, it was very inferior when compared with modern steel. The notch toughness showed a very low value (4 joules) for the steel at the water temperature (−2 °C) in the North Atlantic at the time of the accident.

 

تاثیر فرایند تمپر بر ساختار و خواص مکانیکی فولاد HSLA-100

Influence of tempering on the microstructure and

mechanical properties of HSLA-100 steel plates

تاثیر فرایند تمپر بر ریزساختار و خواص مکانیکی صفحات فولادی HSLA-100

ABSTRACT

The influence of tempering on the microstructure and mechanical properties of HSLA-100 steel (with C-0.04, Mn-0.87, Cu-1.77, Cr-0.58, Mo-0.57, Ni-3.54, and Nb-.038 pct) has been studied. The plate samples were tempered from 300 °C to 700 °C for 1 hour after austenitizing and water quenching. The transmission electron microscopy (TEM) studies of the as-quenched steel revealed a predominantly lath martensite structure along with fine precipitates of Cu and Nb(C, N). A very small amount of retained austenite could be seen in the lath boundaries in the quenched condition. Profuse precipitation of Cu could be noticed on tempering at 450 °C, which enhanced the strength of the steel significantly (yield strength (YS)—1168 MPa, and ultimate tensile strength (UTS)—1219 MPa), though at the cost of its notch toughness, which dropped to 37 and 14 J at 25 °C and −85 °C, respectively. The precipitates became considerably coarsened and elongated on tempering at 650 °C, resulting in a phenomenal rise in impact toughness (Charpy V-notch (CVN) of 196 and 149 J, respectively, at 25 °C and −85 °C) at the expense of YS and UTS. The best combination of strength and toughness has been obtained on tempering at 600 °C for 1 hour (YS-1015 MPa and UTS-1068 MPa, with 88 J at −85 °C)

 

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.

 

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