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

 

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].