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.

 

جوشکاری GTAW آلیاژ آلومینیوم تیتانیوم

Effect of Vibration during GTAW Welding on Microstructure and Mechanical Properties of Ti6Al4V

تاثیر ارتعاش در طی جوشکاری GTAW روی ریزساختار و خواص مکانیکی Ti6Al4V 

ABSTRACT

The drive to improve weld quality and process parameters demands the use of improved welding tech niques and materials [1]. Titanium and its alloys are considered to be the best engineering metals for indus trial applications because of their excellent strengthto weight ratio, high fatigue life, toughness, resistance to corrosion and good fatigue strength [2, 3].

Welding methods such as gas tungsten arc, resis tance, and diffusion welding have been developed in response to the expansion of the titanium industry. 

Titanium alloys easily absorb harmful gases because of their high chemical activity, resulting in poor mechanical properties and unstable structure [4, 5]. Gas tungsten arc welding is the preferred method for avoiding these deficiencies [6]. The weld ing of titanium alloys often increases grain size in the welded metal and heat affected zones [7]. Fusion zones typically exhibit coarse columnar grains in response to prevailing thermal conditions during welded metal solidification [6]. These columnar grains produce inferior mechanical properties in the welds [1]. Methods of weld grain refinement include inocu with heterogeneous nucleants, surface nucleation induced by gas impingement, introduction of physical disturbance through techniques such as elec tromagnetic stirring [4]. Vibratory techniques, and pulsed current welding techniques [8].

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.

 

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.