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ابر برجسب

Pulsed Eddy Current Inspection of Support Structures

in Steam Generators

بازرسی جریان گردابی پالسی برای سازه های نگهدارنده در ژنراتورهای بخار 

ABSTRACT

Degradation and fouling of support structures in nuclear steam generators (SGs) can lead to SG tube damage and loss of SG efficiency. Inspection and monitoring of support structures combined with preventative maintenance programs can alleviate these effects and extend SG life. Conventional eddy current inspection technologies are extensively used for detecting and sizing indications from wall loss, frets at supports, cracks and other degradation modes in the tubes, as well as assessing the condition of support structures. However, these methods have limited capabilities when more than one degradation mode is present simultaneously, or when combined with fouling. Pulsed eddy current combined with principal components analysis (PCA) was examined for inspection of 15.9 mm (5/8") Alloy-800 tubes and surrounding stainless steel (SS410) support structures. Clear separation of PCA scores associated with tubes from those associated with ferromagnetic SS410 supports permitted measurement of tube-to-support gaps, in either the presence of tube fretting or variation of relative position of the tube within SS410 supports. For concentric tubes, frets could be sized independently of SS410 hole diameter variations, which in other materials could represent support corrosion. Capability to clearly separate scores was attributed to large differences in relaxation times for diffusion of transient fields through the tube compared with diffusion into the ferromagnetic support structure. 

  



ادامه مطلب ...




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.

 

ادامه مطلب ...






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.

  

ادامه مطلب ...






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.

 

ادامه مطلب ...






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. 

  

ادامه مطلب ...






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.

  

ادامه مطلب ...






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.

 

ادامه مطلب ...






Solidification crack susceptibility of aluminum alloy weld metals 

حساسیت به ترک انجمادی در فلزهای جوش آلیاژهای آلومینیوم

ABSTRACT

The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C. Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

 

ادامه مطلب ...




Investigation on Corrosion Behaviour of Copper Brazed Joints 

تحقیق روی رفتار خوردگی اتصالات لحیم کاری مس

ABSTRACT

DHP (Deoxidized High Phosphorus(copper is widely used in various heat transfer units such as, air conditioners, refrigerators, evaporators and condensers. Copper sheets and tubes (ISODHP) were brazed with two different brazing alloys. Corrosion resistances of the joints were examined by polarization test. The selected fillers consisted of a silver-based brazing alloys (hard solder); AWS-BCu5, and a copper-based filler AWS BCuP2. All the joints were brazed utilizing two different brazing processes including furnace brazing under argon and air atmosphere. All of the fillers were used with and without flux. The microstructure of the brazed sheets was examined using both optical and scanning electron microscope (SEM). Hardness and leak tests were carried out on all the brazed tubes. In all brazing alloys selective and galvanic corrosion were observed in filler metals, but in copper phosphor alloys the copper adjacent to the joints were noticeably corroded by pitting method. It was found that the samples brazed with BAg5 filler metal using argon furnace show a higher resistance to corrosion. They also have a good ductility in the brazed zone.

 

ادامه مطلب ...






Joining of Si3N4 Ceramic Using PdCo(NiSiB)-V System

Brazing Filler Alloy and Interfacial Reactions

اتصال سرامیک Si3N4 با استفاده از آلیاژ پرکننده لحیم

در سیستم PdCo(NiSiB)-V و واکنش های مرزی

ABSTRACT

The wettability of V-active PdCo-based alloys on Si3N4 ceramic was studied with the sessile drop method. And the alloy of Pd50.0–Co33.7–Ni4.0–Si2.0–B0.7–V9.6 (wt%), was developed for Si3N4 ceramic joining in the present investigation. The rapidly-solidified brazing foils were fabricated by the alloy Pd50.0–Co33.7–Ni4.0–Si2.0–B0.7–V9.6. The average room-temperature three-point bend strength of the Si3N4/Si3N4 joints brazed at 1453 K for 10 min was 205.6 MPa, and the newly developed braze gives joint strengths of 210.9 MPa, 206.6 MPa and 80.2 MPa at high temperatures of 973 K, 1073 K and 1173 K respectively. The interfacial reaction products in the Si3N4/Si3N4 joint brazed at 1453 K for 10 min were identified to be VN and Pd2Si by XRD analysis. Based on the XEDS analysis result, the residual brazing alloy existing at the central part of the joint was verified as Co-rich phases, in which the concentration of element Pd was high up to 18.0–19.1 at%. The mechanism of the interfacial reactions was discussed. Pd should be a good choice as useful alloying element in newer high-temperature braze candidates for the joining of Si-based ceramics.

 

ادامه مطلب ...






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