پیشرفت هایی در NDT و مشخصه یابی مواد توسط جریان گردابی

Advances in NDT and materials characterization by eddy currents 

پیشرفت هایی در NDT و مشخصه یابی مواد توسط جریان گردابی

ABSTRACT

Non-Destructive Testing (NDT) plays a vital role to achieve reliability and quality at an acceptable cost. Failures of engineering materials, components and structures are well known and can be disastrous [1]. Avoiding the failures cost effectively ensuring safety of use and reliability on a wide range of industrial components are the major industrial NDT objectives. NDT is facing new challenges for defect detection and quality control of advanced engineering materials such as in multi-material structures [2], non-ferrous alloys for advanced lightweight structures, composites [3] (GLARE), carbon resins composite, Fiber-reinforced Metal Laminates (FML), High Performance Thermoplastic Composites (HPTC) and Metal Matrix Composites (MMC)). In the scope of recent production technologies: Friction Stir Welding (FSW), Friction Surfacing, Friction Stir Processing (FSP) and Single Point Incremental Forming (SPIF), innovative NDT techniques and technologies are required, and must be transfered from research to industry as quickly as possible to solve these challenges.

 

فولادهای میکروآلیاژی وانادیوم-نیوبیوم vanadium-niobium microalloyed steels

As-cast mechanical properties of vanadium/niobium microalloyed steels

خواص مکانیکی فولادهای میکروآلیاژی وانادیوم/نیوبیوم

ABSTRACT

Tensile and room temperature Charpy V-notch impact tests along with microstructural studies were used to evaluate the variations in the as-cast mechanical properties of low-carbon steels with and without vanadium and niobium. Tensile test results indicate that good combinations of strength and ductility can be achieved by microalloying additions. While the yield strength and UTS increase up to respectively 370–380 and 540–580 MPa in the microalloyed heats, their total elongation range from 20 to 25%. TEM studies revealed that random and interphase fine-scale microalloy precipitates play a major role in the strengthening of the microalloyed heats. On the other hand, microalloying additions significantly decreased the impact energy and led to the dominance of cleavage facets on the fracture surfaces. It seems that heterogeneous nucleation of microalloy carbonitrides on dislocations along with coarse ferrite grains and pearlite colonies trigger the brittle fracture in the microalloyed heats.

 

فولادهای زنگ نزن آستنیتی نیکل پایین Low Nickel Austenitic Stainless Steels

Low Nickel Austenitic Stainless Steels 

فولادهای  زنگ نزن آستنیتی نیکل پایین

ABSTRACT

The most common grades of stainless steel are 304 and 316, which are particularly popular because  their austenitic microstructure results in an excellent combination of corrosion resistance, mechanical  and physical properties and ease of fabrication.  The austenitic structure is the result of the addition of approximately 8-10% nickel. Nickel is not alone  in being an austenite former; other elements that are used in this way are manganese, nitrogen,  carbon and copper. 

 

ارزیابی عمق ترک با استفاده از تکنیک های جریان گردابی

Evaluation of crack depth using eddy current techniques

with GMR-based probes

ارزیابی عمق ترک با استفاده از تکنیک های جریان گردابی با پروب ها بر پایه - GMR

ABSTRACT

This paper presents experimental and simulated results obtained using the eddy current nondestructive method to conclude about the depth of linear cracks machined on an aluminum plate. Experimental tests were performed with a sinusoidal excitation field of fixed-amplitude and with a giant magnetoresistance-based sensor to measure the resultant magnetic field on the plate surface. To validate and better insight the experimental results, numerical simulations have been carried out with a commercial program for conditions similar to the experimental case studies. A scheme to infer about crack depth is proposed.

 

خواص مکانیکی جوشکاری اصطکاکی اغتشاشی آلیاژ آلومینیوم در زیر آب

Homogeneity of Mechanical Properties of Underwater

Friction Stir Welded 2219-T6 Aluminum Alloy

یکنواختی خواص مکانیکی جوشکاری آلیاژ آلومینیوم 2219-T6

جوشکاری اصطکاکی اغتشاشی شده درزیر آب

ABSTRACT

Underwater friction stir welding (FSW) has been demonstrated to be available for the improvement in tensile strength of normal FSW joints. In order to illuminate the intrinsic reason for strength improvement through underwater FSW, a 2219 aluminum alloy was underwater friction stir welded and the homogeneity of mechanical properties of the joint was investigated by dividing the joint into three layers. The results indicate that the tensile strength of the three layers of the joint is all improved by underwater FSW, furthermore, the middle and lower layers have larger extent of strength improvement than the upper layer, leading to an increase in the homogeneity of mechanical properties of the joint. The minimum hardness value of each layer, especially the middle and lower layers, is improved under the integral water cooling effect, which is the intrinsic reason for the strength improvement of underwater joint.

 

اثر سرعت جوشکاری اصطکاکی اغتشاشی در زیر آب روی آلیاژ آلومینیوم

Effect of welding speed on microstructures and mechanical properties

of underwater friction stir welded 2219 aluminum alloy

اثر سرعت جوشکاری بر ریز ساختارها و خواص مکانیکی آلیاژ آلومینیوم 2219

جوشکاری اصطکاکی اغتشاشی شده در زیر آب 

ABSTRACT

Underwater friction stir welding (underwater FSW) has been demonstrated to be available for the strength improvement of normal FSW joints. In the present study, a 2219 aluminum alloy was underwater friction stir welded at a fixed rotation speed of 800 rpm and various welding speeds ranging from 50 to 200 mm/min in order to clarify the effect of welding speed on the performance of underwater friction stir welded joint. The results revealed that the precipitate deterioration in the thermal mechanically affected zone and the heat affected zone is weakened with the increase of welding speed, leading to a narrowing of softening region and an increase in lowest hardness value. Tensile strength firstly increases with the welding speed but dramatically decreases at the welding speed of 200 mm/min owing to the occurrence of groove defect. During tensile test, the joint welded at a lower welding speed is fractured in the heat affected zone on the retreating side. While at higher welding speed, the defect-free joint is fractured in the thermal mechanically affected zone on the advancing side.

 

تجهیزات در آزمون جریان گردابی Eddy current testing

Eddy current sensors

سنسورهای جریان گردابی

ABSTRACT

In addition to tavtile ( gauging ) sensors, non contantct metrology is now also used to measure displacement, deformation,, stretching, distances, position and other geometrical shapes and sozes. These sensors often measure faster, more accurately and more reliably than tactile sensors. The measurement data is normally available in real time to automatically regukate and control the production. Quality control is not only carried out on finished products, but metrology can also supervise and optimize production processes. The aim is to improve product quality, reduce rejects to a minimum and to lower total production costs. 

 

حفاظت کاتدی - آزمون دیاگنوستیک Cathodic Protection Procedures

Cathodic Protection  Procedures - Diagnostic Testing

حفاظت کاتدی - آزمون دیاگنوستیک (ملزومات جریان)

ABSTRACT

The purpose of  diagnostic testing (DT)  is to outline a process to test for deficiencies  in a cathodic protection (CP) system, to identify  the cause(s)  of  such deficiencies, and to determine the requirements  to enhance the level of CP  to the structure. In an existing CP system, the DT is to first determine  if  the cause of  low CP levels can be eliminated and, if  not, what additional current is required, in addition  to how and where it can be applied. The CP Technician must have a good understanding of  the criteria as well as  the special conditions and precautionary notes that apply  to  these  criteria.

 

اثرات آنتی باکتریال فلزات Antibacterial effects of metals

Antibacterial effects of metals 

اثرات آنتی باکتریال فلزات

ABSTRACT

In this chapter, the antibacterial effects of metals will be described first, and it will be compared with photocatalytic oxides and organics. Then , anti bacterial coating that have been proposed in practical industries will be introduced. The merits and demerits will be discussed, and the concept of composite materials for antibacterial effect will be proposed followed by a detail discussion. Some possibilities will be mentioned. And finally, the two concrete examples by the authors will be introduced and explained.

 

جوشکاری اصطکاکی نقطه‌ای آلیاژ آلومنیوم-لیتیم aluminium–lithium 2A97 alloy

Microstructure and mechanical properties of

friction spot welding aluminium–lithium 2A97 alloy

ریزساختار و ویژگی‌های مکانیکی جوشکاری اصطکاکی نقطه‌ای آلیاژ آلومنیوم-لیتیم 2A97

ABSTRACT

In this study, we investigated the microstructure and mechanical properties in different regions of the friction spot welded 2A97 aluminium-lithium alloy subjected to different heat treatment processes. The 2.0. mm thick hot-rolled sheet of 2A97 alloy was successfully welded using friction spot welding method with optimised welding parameters. Afterwards, the as-welded 2A97 joints experienced two subsequent heat treatment procedures: solution and ageing; directly ageing. The corresponding microstructure and mechanical properties of the heat-treated specimens were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness test and tensile test. The results show that the mechanical properties of the 2A97 joints before and after heat treatment were significantly modified, which was mainly related to fine-grained microstructure, size and type of precipitates, and dislocation density. Compared to the base material and the material that only experienced direct ageing, the whole friction spot welded 2A97 joint after solution and ageing treatment delivered better mechanical properties.