A Non-Conventional Technique for Evaluating Welded Joints Based on the Electrical Conductivity

2014 ◽  
Vol 611-612 ◽  
pp. 671-676 ◽  
Author(s):  
Telmo G. Santos ◽  
Gonçalo Sorger ◽  
Pedro Vilaça ◽  
R.M. Miranda
Keyword(s):  
Electrical Conductivity ◽  
Solid State ◽  
Welded Joints ◽  
Conventional Technique ◽  
Carbon Steels ◽  
Fusion Welding ◽  
Friction Stir ◽  
Wide Range ◽  
Welding Processes ◽  
Non Destructive

Recent studies showed that electrical conductivity is a valuable technique to identify the different zones of solid-state welded joints with a good correlation with the microstructure and hardness. This is a relevant result since this technique is expedite and, in some cases, non destructive. The concept was applied to other welding processes as the ones involving fusion and to a wide range of materials. For this, a comprehensive study was performed using friction stir welding, tungsten inert gas (TIG) and gas metal arc (MAG) welding processes in either bead on plate or butt joints in: carbon steel, magnesium and titanium. Eddy current non-destructive testing (NDT) was used to measure the electrical conductivity at different depths in transverse sections of the processed materials. The obtained profiles were compared to the hardness profiles in the same sections. As a result, a good correlation was observed in most materials welded by solid state and by fusion processes. The variation of the electrical conductivity closely follows the one detected in the hardness. Another interesting conclusion is that, even for fusion welding of carbon steels, the technique has potential to complement the hardness measurements and microstructural observations, allowing to identify the distinct zones of welds in materials commonly used in industry.

scholarly journals Welding of magnesium and its alloys: an overview of methods and process parameters and their effects on mechanical behaviour and structural integrity of the welds

2021 ◽  
Vol 8 ◽  
pp. 29
Author(s):  
Desmond Edem Primus Klenam ◽  
Gabriel Seun Ogunwande ◽  
Taiwo Omotosho ◽  
Blessing Ozah ◽  
Nthabiseng Beauty Maledi ◽  
...  
Keyword(s):  
Solid State ◽  
Process Parameters ◽  
Mechanical Behaviour ◽  
Structural Integrity ◽  
Fusion Welding ◽  
Mg Alloys ◽  
Future Research ◽  
Friction Stir ◽  
Weld Joints ◽  
Welding Processes

An overview of welding methods and process parameters and its effects on mechanical behaviour and structural integrity of magnesium and its alloys are discussed. These alloys are less dense and beneficial structural alloys for improved energy efficiency, eco-friendliness and driver of circular economic model for sustainable design and innovative ecosystem. While the application of Mg-alloys is projected to increase, understanding the mechanical behaviour and structural integrity of welded joints are critical. Thus, fusion and solid-state welding processes of these alloys are discussed with emphasis on mechanical characterization. Laser welding is the most effective fusion welding technique for most Mg alloys whereas, the predominant solid-state method is friction stir welding. The importance of process variables such as heat inputs, welding velocity (speed) and post weld treatments on the microstructural evolution, on mechanical and physical properties of the distinct zones of the weld joints are described. The weldment is the most susceptible to failure due to phase transformation, defects such as microporosity and relatively coarse grain sizes after solidification. The implication of the design of quality weld joints of Mg alloys are explored with areas for future research directions briefly discussed.

Effect of Process Parameters on the Joint Integrity in Friction Stir Welding of Ti-6Al-4V Lap Joints

2013 ◽  
Vol 554-557 ◽  
pp. 1083-1090 ◽  
Author(s):  
Gianluca Buffa ◽  
Livan Fratini ◽  
Matthias Schneider ◽  
Marion Merklein
Keyword(s):  
Friction Stir Welding ◽  
Titanium Alloys ◽  
Process Parameters ◽  
Lap Joints ◽  
Fusion Welding ◽  
Main Process ◽  
Filling Material ◽  
Friction Stir ◽  
Wide Range ◽  
Welding Processes

Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. The wide diffusion the process is having is due to the possibility to weld materials traditionally considered difficult to be welded or “unweldable” by traditional fusion welding processes due to peculiar thermal and chemical material properties. Additionally, the process allows welding a wide range of sheet thickness (up to 50mm) avoiding typical fusion welding processes defects, like cavities and porosities, with no shielding gas, filling material or joint preparation. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry due to the extremely high strength-weight ratio together with good corrosion resistance properties. Welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity resulting in bonding with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW can represent a cost effective and high quality solution. A few studies have been developed on the FSW of titanium alloys butt joints, while there is a complete lack of knowledge as far as different joint morphologies are regarded (lap joints, T joints, etc.). In the paper the results of an experimental campaign on lap joints made out of thin Ti-6Al-4V sheets are presented. The effect of the main process parameters on the micro and macro mechanical properties has been investigated and related to the microstructural transformations occurring during the process because of the thermo-mechanical action of the tool.

Application of Eddy Currents in Processed Materials Structural Evaluation

2012 ◽  
Vol 730-732 ◽  
pp. 715-720
Author(s):  
Telmo G. Santos ◽  
João Faria ◽  
Pedro Vilaça ◽  
R.M. Miranda
Keyword(s):  
Electrical Conductivity ◽  
Solid State ◽  
Eddy Currents ◽  
Microstructural Analysis ◽  
Structural Features ◽  
Crystal Defects ◽  
Electrical Currents ◽  
Friction Stir ◽  
Characterization Technique ◽  
Physical Phenomena

Eddy currents are based on electromagnetic induction and analysis of electrical currents on conductive materials. This method is used for thickness measurements, corrosion and defects detection, electrical conductivity and magnetic permeability measurements. Recently, it has been exploited as a materials characterization technique, namely in solid state welding, since, compared to hardness, it is based in distinct physical phenomena. Electrical conductivity is controlled by electronic mobility, while hardness depends on crystal defects and thus a scale factor exists. This paper presents results of this characterization technique applied to multipass solid state friction stir processing (FSP) of AA1100 alloy. These results were compared to microstructural analysis and hardness measurements and show that eddy current is a feasibly, reliable and expedite technique to characterize processed materials. The electrical conductivity measured by eddy currents, maps more precisely structural features, while hardness does not. Measurement of electrical conductivity field suggests having potential to constitute an alternative and/or complement to hardness evaluation with the further advantage of being a non-destructive method.

scholarly journals Non-destructive Evaluation of Friction Stir Welded Joints by X-ray Radiography and Infrared Thermography

2014 ◽  
Vol 86 ◽  
pp. 469-475 ◽  
Author(s):  
T. Saravanan ◽  
B.B. Lahiri ◽  
K. Arunmuthu ◽  
S. Bagavathiappan ◽  
A.S. Sekhar ◽  
...  
Keyword(s):  
Infrared Thermography ◽  
Welded Joints ◽  
X Ray ◽  
Friction Stir ◽  
Non Destructive Evaluation ◽  
Non Destructive

scholarly journals The Effects of In-Process Cooling during Friction Stir Welding of 7475 Aluminium Alloy

2021 ◽  
Vol 50 (9) ◽  
pp. 2743-2754
Author(s):  
Ashish Jacob ◽  
Sachin Maheshwari ◽  
Arshad Noor Siddiquee ◽  
Abdulrahman Al-Ahmari ◽  
Mustufa Haider Abidi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Welded Joints ◽  
Positive Impact ◽  
Welding Process ◽  
Fusion Welding ◽  
Friction Stir ◽  
Cooling Conditions ◽  
Zero Degree ◽  
Welding Technique

Certain age hardenable alloys such as AA7475 cannot be joined with perfection using fusion welding techniques. This requires non-conventional welding technique such as friction stir welding process to join these ‘difficult to weld’ alloys. In this study, three different cooling conditions i.e. cryogenic, sub-zero, and zero-degree Celsius temperature conditions have been analyzed to understand its impact on the welding process. In-process cooling was found to behave effectively and also enhanced the mechanical properties of the welded joints. A stable microstructure was clearly seen in the images observed under the metallurgical microscope. The weld efficiencies were found to be good in each of the samples which are indicative of a strong metallic joint. The effective cooling conditions employed had an overall positive impact on the joint.

scholarly journals Design and Fabrication of Friction Stir Welding End-Effector for an ABB IRB1410 Robot

2016 ◽  
Vol 5 (2) ◽  
pp. 98
Author(s):  
Santosh Vanama
Keyword(s):  
Friction Stir Welding ◽  
High Strength ◽  
Fusion Welding ◽  
Fusion Temperature ◽  
End Effector ◽  
Friction Stir ◽  
Aluminum Sheets ◽  
Operation Pressure ◽  
Welding Processes ◽  
Tool Rotation

<p>The paper propose modelling and fabrication of friction stir welding end-effector for ABB IRB1410 robot. A dynamically developing version of pressure welding processes, join material without reaching the fusion temperature called friction stir welding. As friction stir welding occurs in solid state, no solidification structures are created thereby eliminating the brittle and eutectic phase’s common to fusion welding of high strength aluminium alloys. In this paper, Friction stir welding is applied to aluminum sheets of 2 mm thickness. A prototype setup is developed to monitor the evolution of main forces and tool temperature during the operation. Pressure of a gripper plays a major role for tool rotation and developing torque.  Fabrication of the tool has done. Force calculations are done by placing the sensors on the outer surface of gripper. Methods of evaluating weld quality are surveyed as well.</p>

Establishing the Dependence of Output Parameters Depending on Local Process Conditions for Friction Stir Welding of Pure Copper Plates

2018 ◽  
Vol 1146 ◽  
pp. 32-37 ◽  
Author(s):  
Marius Adrian Constantin ◽  
Ana Boşneag ◽  
Eduard Niţu ◽  
Lia Nicoleta Boţilă
Keyword(s):  
Friction Stir Welding ◽  
Process Parameters ◽  
Welding Speed ◽  
Frictional Heating ◽  
Pure Copper ◽  
Fusion Welding ◽  
Process Conditions ◽  
Friction Stir ◽  
Local Process ◽  
Welding Processes

Welding copper and its alloys is usually difficult to achieve by conventional fusion welding processes because of high thermal diffusivity of the copper, which is at least 10 times higher than most steel alloys, in addition to this, there are the well-known disadvantages of conventional fusion welding represented by necessity of using alloying elements, a shielding gas and a clean surface. To overcome these inconveniences, Friction Stir Welding (FSW), a solid state joining process that relies on frictional heating and plastic deformation, is being explored as a feasible welding process. In order to achieve an increased welding speed and a reduction in tool wear, this process is assisted by another one (TIG) which generates and adds heat to the process. The research includes two experiments for the FSW process and one experiment for tungsten inert gas assisted FSW process. The process parameters that varied were the rotational speed of the tool [rpm] and the welding speed [mm/min] while the compressive force remained constant. The purpose of this paper is to correlate the evolution of temperature, tensile strength, elongation and microscopic aspect with the linear position on the joint (local process parameters) for each experimental case and then make comparisons between them, and to identify and present the set of process parameters that has the best mechanical properties for this material.

scholarly journals Additive Friction Stir-Enabled Solid-State Additive Manufacturing for the Repair of 7075 Aluminum Alloy

2019 ◽  
Vol 9 (17) ◽  
pp. 3486 ◽  
Author(s):  
R. Joey Griffiths ◽  
Dylan T. Petersen ◽  
David Garcia ◽  
Hang Z. Yu
Keyword(s):  
Aluminum Alloy ◽  
Additive Manufacturing ◽  
Solid State ◽  
Side Wall ◽  
Fusion Welding ◽  
7075 Aluminum Alloy ◽  
Hole Filling ◽  
Friction Stir ◽  
Advantages And Disadvantages ◽  
Through Hole

The repair of high strength, high performance 7075 aluminum alloy is essential for a broad range of aerospace and defense applications. However, it is challenging to implement it using traditional fusion welding-based approaches, owing to hot cracking and void formation during solidification. Here, the use of an emerging solid-state additive manufacturing technology, additive friction stir deposition, is explored for the repair of volume damages such as through -holes and grooves in 7075 aluminum alloy. Three repair experiments have been conducted: double through-hole filling, single through-hole filling, and long, wide-groove filling. In all experiments, additive friction stir deposition proves to be effective at filling the entire volume. Additionally, sufficient mixing between the deposited material and the side wall of the feature is always observed in the upper portions of the repair. Poor mixing and inadequate repair quality have been observed in deeper portions of the filling in some scenarios. Based on these observations, the advantages and disadvantages of using additive friction stir deposition for repairing volume damages are discussed. High quality and highly flexible repairs are expected with systematic optimization work on process control and repair strategy development in the future.

Phenomenological Modeling of Fusion Welding Processes

MRS Bulletin ◽  
1994 ◽  
Vol 19 (1) ◽  
pp. 29-35 ◽  
Author(s):  
S.A. David ◽  
T. DebRoy ◽  
J.M. Vitek
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Base Metal ◽  
Weld Pool ◽  
Welding Process ◽  
Poor Performance ◽  
Consumer Products ◽  
Phase Changes ◽  
Fusion Welding ◽  
Welding Processes

Welding is utilized in 50% of the industrial, commercial, and consumer products that make up the U.S. gross national product. In the construction of buildings, bridges, ships, and submarines, and in the aerospace, automotive, and electronic industries, welding is an essential activity. In the last few decades, welding has evolved from an empirical art to a more scientifically based activity requiring synthesis of knowledge from various disciplines. Defects in welds, or poor performance of welds, can lead to catastrophic failures with costly consequences, including loss of property and life.Figure 1 is a schematic diagram of the welding process showing the interaction between the heat source and the base metal. During the interaction of the heat source with the material, several critical events occur: melting, vaporization, solidification, and solid-state transformations. The weldment is divided into three distinct regions: the fusion zone (FZ), which undergoes melting and solidification; the heat-affected zone (HAZ) adjacent to the FZ, that may experience solid-state phase changes but no melting; and the unaffected base metal (BM).Creating the extensive experimental data base required to adequately characterize the highly complex fusion welding process is expensive and time consuming, if not impractical. One recourse is to simulate welding processes either mathematically or physically in order to develop a phenomenological understanding of the process. In mathematical modeling, a set of algebraic or differential equations are solved to obtain detailed insight of the process. In physical modeling, understanding of a component of the welding process is achieved through experiments designed to avoid complexities that are unrelated to the component investigated.In recent years, process modeling has grown to be a powerful tool for understanding the welding process. Using computational modeling, significant progress has been made in evaluating how the physical processes in the weld pool influence the development of the weld pool and the macrostructures and microstructures of the weld.

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