چقرمگی شکست یک فولاد ضدزنگ سوپر داپلکس جوشکاری شده

Fracture toughness of a welded super duplex stainless steel

چقرمگی شکست یک فولاد ضدزنگ سوپر داپلکس جوشکاری شده

ABSTRACT

Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture.

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مواد الکتروکرومیک

Electrochromic Materials

مواد الکتروکرومیک

ABSTRACT

 A set of materials exhibit electrochromic activity when constituted as a thin film structure whose coloration can be changed reversibly by electrical charging and discharging . there are two types of such electrochromic materials . The first type is uncolored when unpowered and changes to a colored state when a voltage is applied and returns to its uncolored state when the voltage is removed . In the second type an opposite voltage is required to be applied for bleaching ( or decoloration ) .The degree of coloration is a direct visual indication of the state of charing present in the material .

مواد ابر رسانا

Superconducting Materials

مواد ابر رسانا

ABSTRACT

The phenomenon of superconductivity came to be known in 1911 by observing that a capillary column of mercury immersed in a liquid helium bath woud show an abrupt reduction in resistance and at 4.2 K it became impossible to measure the low resistance exhibited by the column with the then available measurement techniques . It was concluded that below a critical temperature (T_c) the mercury had passed into a new state . Subsequent studies on superconduction were pursued with tin and lead as candidate materials and it was discovered that a critical current density (J_c) is carried by a superconduction sample before it returns to its normal ( metallic ) state .

مقدمه الزامات مهندسی برای مواد کامپوزیتی صنعت هوافضا

Introduction: engineering
requirements for aerospace
composite materials

مقدمه الزامات مهندسی برای مواد کامپوزیتی صنعت هوافضا 

ABSTRACT

Composite materials have gained popularity (despite their generally high cost) in high performance products that need to be lightweight, yet strong enough to take high loads such as aerospace structures (tails, wings and fuselages), boat construction, bicycle frames and racing car bodies. Other uses include storage tanks and fishing rods. Natural composites (wood and fabrics) have found applications in aircraft from the first flight of the Wright Brothers’ Flyer 1, in North Carolina on December 17, 1903, to the plethora of uses now enjoyed by man-made (engineered) composite materials on both military and civil aircraft, in addition to more exotic applications on unmanned aerial vehicles (UAVs), space launchers and satellites. Their adoption as a major contribution to aircraft structures followed on from the discovery of carbon fibre at the Royal Aircraft Establishment at Farnborough, UK, in 1964.

وضعیت صنعت در کنترل آخال ها در طی ریخته گری شمش فولادی

State of the Art in the Control of Inclusions during Steel
Ingot Casting

وضعیت صنعت در کنترل آخال ها در طی ریخته گری شمش فولادی

ABSTRACT

This article extensively reviews published research on inclusions in ingot steel and defects on ingot products, methods to measure and detect inclusions in steel, the causes of exogenous inclusions, and the transport and entrapment of inclusions during fluid flow, segregation, and solidification of steel cast in ingot molds. Exogenous inclusions in ingots originate mainly from reoxidation of the molten steel, slag entrapment, and lining erosion, which are detailed in this article. The measures to prevent the formation of exogenous inclusions and improve their removal are provided, which are very useful for the clean steel production of ingot industries.

مواد نیمه رسانا

Semiconducting Materials

مواد نیمه رسانا

ABSTRACT

Semiconductors are materials which have resistivities between the extremes of metallic conductors and insulators. A typical scale of conductivity of materials is depicted in Figure 10.1 . Semiconductors lie approximately between conductors ( with σ > 10⁵ siemen/meter ) and insulators (with σ < 10^-10 siemen/meter ) . Semiconductors are materials with filled valence bands and have a small forbidden energy gap between the upper-filled band and the overlapping vacant energy band . The electric conduction in Semiconductors is effected by two types of charge carriers namely . electrons ( negative charge carriers ) and holes ( positive charge carriers ) .

مواد فروالکتریک

Ferroelectric Materials

مواد فروالکتریک

ABSTRACT

Ferroelectric materials are typically nonlinear dielectrics with the following characteristics :

• They exhibit distinct dependency of permittivity on the intensity of an applied electric field
• The dielectric displacement versus applied electric field follows hysteresis loop characteristics
• The dielectric constant of these materials are invariably very high , on the order of thousands to tens of thousands .
• The dielectric parameters are pronouncedly dependent on temperature and the ferroelectric properities are observed only within a definite range of temperature
• There is presence of spontaneous dielectric polarization in the absence of external electric field And this polarization can be switched in direction by applying an electric field

مواد فریتی

Ferrites Materials

مواد فریتی

ABSTRACT

Ferrites are mixed crystals of various metallic oxides and may be considered to consist of oxygen ions in a closed-packed structure with cations filling the interstices . They have a general formula : MOFe₂O₃ , xH₂O where M is a divalent metallic ion such as Mn²⁺ , Fe²⁺ , Co²⁺ , Ni²⁺ , Zn²⁺ , Mg²⁺ , and Cd²⁺ . In general , the magnetic satruration intensity to ferrites is lower than that of various metallic magnetic alloys , but the ferrites have very high resistivity and as such are insulator-like . Therefor , the power loss in ferrites is very small especially at high frequencies . Further , ferrites have a narrow hysteresis (BH) loop and can be made with square-loop characteristics .

مواد فرومغناطیسی

Ferromagnetic Materials

مواد فرومغناطیسی

ABSTRACT

Ferromagnetic materials have the ability to carry high magnetic flux . Ferromagnetism refers to the property of increasing the magnetic flux associated with the material when a magnetizing force is applaid , but there exists a saturation point for most of the magnetic materials beyond which the associated magnetic flux does not increase . This condition is referred to as magnetic saturation . Ferromagnetic materials can be distinctly classified into two groups the magnetically soft and magnetically hard . The distinguishing properties are having high permeability and having easy to magnetize for soft materials and hard materials having high coercivity so that once magnetized the materials must be able to resist demagnetizing forces due to any appleid or stary magnetic fiels .

مواد کامپوزیتی پیزوالکتریک

Piezoelectric Composite Materials

مواد کامپوزیتی پیزوالکتریک

ABSTRACT

A piezoelectric Composite is a combination of a piezoelectric ceramic and/or polymer and a nonpiezoelectric polymer constituting a new version of piezoelectric material . In general terms , piezoelectric composite applies to any piezoelectric material resulting from combining a piezoelectric  polymer or ceramic with other nonpiezoelectric materials including air-filled voids . Earlier versions of piezoelectric  composite synthesized include barium titanate embedded polymer matrix and lead zirconate- titanate (PZT) ceramic Powder dispersed in a polymeric receptacle .Subsequent development are : (i)  Flexible piezoelectric composites using PbTiO₃ or PZT plus synthetic rubber ; (ii) PVD-based pyroelectric composites ; (iii) woven PZT ceramic/polymer composites