Enabling Automation of Friction Stir Welding: The Modulation of Weld Seam Input Energy by Traverse Speed Force Control

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
William R. Longhurst ◽  
Alvin M. Strauss ◽  
George E. Cook
Keyword(s):  
Standard Deviation ◽  
Axial Force ◽  
Pid Control ◽  
Force Control ◽  
Weld Seam ◽  
Traverse Speed ◽  
Work Piece ◽  
Input Energy ◽  
Plunge Depth ◽  
Friction Stir

Friction stir welding (FSW) joins materials by plunging a rotating tool into the work piece. The tool consists of a shoulder and a pin that plastically deforms the parent materials and then forges them together under the applied pressure. To create the pressure needed for forging, a rather large axial force must be maintained on the tool. Maintaining this axial force is challenging for robots due to their limited load capacity and compliant nature. To address this problem, force control has been used, and historically, the force has been controlled by adjusting the plunge depth of the tool into the work piece. This paper develops the use of tool traverse speed as the controlling variable instead of plunge depth. To perform this investigation, a FSW force controller was designed and implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative (PID) control architecture was tuned using the Ziegler–Nichols method. Results show that the control of axial force via traverse speed is feasible and predictable. The resulting system is more robust and stable when compared with a force controller that uses plunge depth as the controlling variable. A standard deviation of 41.5 N was obtained. This variation is much less when compared with a standard deviation of 129.4 N obtained when using plunge depth. Using various combinations of PID control, the system’s response to step inputs was analyzed. From this analysis, a feed forward transfer function was modeled that describes the machinery and welding environment. From these results, a technique is presented regarding weld seam input energy modulation as a by product of force control via traverse speed. A relative indication of thermal energy in the welding environment is obtained with the feedback of axial force. It is hypothesized that, while under force control, the controller modulates weld seam input energy according to the control signal. The result is constant thermomechanical conditions in the welding environment. It is concluded that the key enablers for force control are the unidirectional behavior and load dynamics of the traverse motor. Larger bandwidths and more stable weld conditions emerge when using traverse speed instead of plunge depth to control the force. Force control of FSW via traverse speed has importance in creating efficient automatic manufacturing operations. The intelligence of the controller naturally selects the most efficient traverse speed.

The Identification of the Key Enablers for Force Control of Robotic Friction Stir Welding

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
William R. Longhurst ◽  
Alvin M. Strauss ◽  
George E. Cook
Keyword(s):  
Friction Stir Welding ◽  
Force Control ◽  
Weld Seam ◽  
Welding Process ◽  
Tool Geometry ◽  
Work Piece ◽  
Successful Implementation ◽  
Plunge Depth ◽  
Friction Stir ◽  
Robotic Friction Stir Welding

Friction stir welding (FSW) is a solid state welding process that uses a rotating tool to plastically deform and then forge together materials. This process requires a large axial force to be maintained on the tool as the tool is plunged into the work piece and traversed along the weld seam. Force control is required if robots are to be used. Force control provides compensation for the compliant nature of robots. Without force control, welding flaws would continuously emerge as the robot repositioned its linkages to traverse the tool along the weld seam. Insufficient plunge depth would result and cause the welding flaws as the robot’s linkages yielded from the resulting force in welding environment. As FSW continues to emerge in manufacturing, robotic applications will be desired to establish flexible automation. The research presented here identifies the key enablers for successful and stable force control of FSW. To this end, a FSW force controller was designed and implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative control architecture was tuned using the Ziegler–Nichols method. Welding experiments were conducted by butt welding 0.25 in. (6.35 mm) × 1.50 in. (38.1 mm) × 8.0 in. (203.2 mm) samples of aluminum 6061 with a 0.25 in. (6.35 mm) threaded tool. The experimental force control system was able to regulate to a desired force with a standard deviation of 129.4 N. From the experiments, it was determined that tool geometry and position are important parameters influencing the performance of the force controller, and four key enablers were identified for stable force control of FSW. The most important enabler is the maintaining of the position of a portion of the tool’s shoulder above the work piece surface. When the shoulder is completely submerged below the surface, an unstable system occurs. The other key enablers are a smooth motion profile, an increased lead angle, and positional constraints for the tool. These last three enablers contribute to the stability of the system by making the tool’s interaction with the nonlinear welding environment less sensitive. It is concluded that successful implementation of force control in the robotic FSW systems can be obtained by establishing and adhering to these key enablers. In addition, force control via plunge depth adjustment reduces weld flash and improves the appearance of the weld.

Friction Stir Processing: An Operational Method to Improve Ductility in Pure Copper

2013 ◽  
Vol 818 ◽  
pp. 14-19 ◽  
Author(s):  
Vahid Rezazadeh ◽  
Ali Sharbatzadeh ◽  
Ali Hosseinzadeh ◽  
Amir Safari ◽  
Salar Salahi
Keyword(s):  
Friction Stir Processing ◽  
Rotational Speed ◽  
Pure Copper ◽  
Traverse Speed ◽  
Ultrafine Grain ◽  
Work Piece ◽  
Cavity Formation ◽  
Nugget Zone ◽  
Friction Stir ◽  
Lower Heat

mproving ductility in metals using friction stir processing (FSP) is a challenging effort and is made by means of a rotating tool inserted in a work piece providing heat transfer and plastic deformation. In this investigation, improving ductility during FSP was determined as a purpose and the microstructure and mechanical properties of nugget zone were investigated during friction stir processing (FSP) of pure copper. Ductility was measured using tensile elongations at a temperature of 20 °C. By varying the traverse speed from 40 to 100 mm/min at rotation speeds of 300 and 600 rpm, the ultrafine grain microstructure was achieved .Defects were observed in rotational speed of 300 rpm. By increasing traverse speed at constant rotational speed of 600 rpm grain size of the nugget zone decreased and ductility increased. Achievable ductility was limited by cavity formation due to lower heat input and deformation in samples with defects.

Effect of FSP on Strength and Fracture Toughness of Aluminium Alloy 7000

2018 ◽  
Vol 877 ◽  
pp. 20-25
Author(s):  
P.K. Mandal
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Aluminium Alloy ◽  
Axial Force ◽  
Weight Ratio ◽  
High Strength ◽  
Hardness Measurement ◽  
Traverse Speed ◽  
Age Hardening ◽  
Friction Stir

The cast Al-Zn-Mg 7000 alloy has become one of the most potential structural materials in many engineering fields such as aircraft body, automotive casting due to their high strength to weight ratio, strong age hardening ability, competitive weight savings, attractive mechanical properties and improvement of thermal properties. The cast aluminium alloy has been modified of surface layer through a solid-state technique is called friction stir process (FSP). But basic principle has been followed by friction stir welding (FSW). This process can be used to locally refine microstructures and eliminate casting defects in selected locations, where mechanical properties improvements can enhance component performance and service life. However, some specified process parameters have adopted during experimental works. Those parameters are tool rotation speed (720 rpm), plate traverse speed (80 mm/min), axial force (15 kN), and tool design (i.e., pin height 3.5 mm and pin diameter 3.0 mm), respectively. The main mechanism behind this process likely to axial force and frictional force acting between the tool shoulder and workpiece results in intense heat generation and plastically soften the process material. The specified ratio of rotational speed (720 rpm) to traverse speed (80 mm/min) is considered 9 as low heat input during FSP and its entails low Zn vaporization problem results as higher fracture toughness of aluminium alloy. It is well known that the stirred zone (SZ) consists of refine equiaxed grains produced due to dynamic recrystallization. FSP has been proven to innovatively enhancing of various properties such as formability, hardness and fracture toughness (32.60 MPa√m). The hardness and fracture toughness of double passes AC+FSP aluminium alloy had been investigated by performing Vicker’s hardness measurement and fracture toughness (KIC)(ASTM E-399 standard) tests. Detailed observations with optical microscopy, Vicker’s hardness measurement, SEM, TEM, and DTA analysis have conducted to analyse microstructure and fracture surfaces of double passes FSP aluminium alloy.

scholarly journals An Experimental Test and Optimization of Friction Stir Welding Process for AA6082 By using GRA

2020 ◽  
Vol 9 (6) ◽  
pp. 740-744
Keyword(s):  
Tensile Strength ◽  
Friction Stir Welding ◽  
Axial Force ◽  
Welding Process ◽  
Traverse Speed ◽  
Test Plate ◽  
Friction Stir ◽  
Fourth Sample ◽  
Grey Relational Grade ◽  
Grey Relational

Friction stir welding (FSW) is a type of joining process, it uses solid state welding method, also it is widely used in same type and different types of welding like Al, Mg, Cu, Ti, and their alloys. In this study, friction stir welding of two aluminum alloys AA6082 is done with many sets of tool rotation speed, feed and axial force. In this experimental work FSW process was carried out for AA 6082 and optimization of that FSW process parameters were find out for maximum tensile strength values. Taguchi’s L4 orthogonal array was utilized for three parameters – tool rotational speed (TRS), traverse speed (TS), and axial force (AXF) with two levels. Several optimization was carried out with Taguchi method of grey relational tests. During the investigation obtained highest tensile strength value fourth sample 60.887 N/mm2 and lowest hardness strength value second sample 31HRB and bead appearance found very best surface occurred fourth test plates at the same time angle distortion observed very fine in the fourth test plate. The result was calculated for both ultimate tensile strength and hardness value. The expected grey relational grade was shifted from 0.704 to 0.792, it was the highest value received throughout this experimental results. It was mentioned that the multi-responses of FSW process was improved with this method.

The Extrinsic Influence of Tool Plunge Depth on Friction Stir Welding of an Aluminum Alloy

2011 ◽  
Vol 410 ◽  
pp. 206-215 ◽  
Author(s):  
K. Kandasamy ◽  
Satish V. Kailas ◽  
Tirumalai S. Srivatsan
Keyword(s):  
Friction Stir Welding ◽  
Aluminium Alloy ◽  
Rotation Speed ◽  
Tool Material ◽  
Traverse Speed ◽  
Test Machine ◽  
Plunge Depth ◽  
Friction Stir ◽  
Scientific Approach ◽  
Tool Rotation

The axial force during friction stir welding is sensitive to plunge depth of the tool and is one of the prime factors, which exercises control over heat generation during welding. Consequently, the plunge depth for a given tool rotation speed, traverse speed, material and test machine needs to be optimized so as to get a defect-free weld. In this paper, we present and briefly discuss the results of an elaborate and enriching investigation aimed at understanding the extrinsic influence of plunge depth of the tool on weld formation in aluminium alloy 7020-T6 for a range of rotation rate and traverse speed and using two different tools. The critical need for use of a scientific approach to optimize plunge depth for a given tool material and test machine in fewer number of steps is emphasized. Key Words: Friction Stir Welding, Tool Plunge, Rotation speed, Traverse speed, Aluminium Alloy 7020

Thermal Analysis of Friction Stir Welding Process Under Different Control and Energy Parameters

2015 ◽  
Author(s):  
Dalong Yi ◽  
Hui Zhang
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Thermal Condition ◽  
Welding Process ◽  
Dissimilar Materials ◽  
Traverse Speed ◽  
Transfer Model ◽  
Welding Condition ◽  
Plunge Depth ◽  
Friction Stir

Friction Sir Welding (FSW) process is a solid state welding technology which is widely used in manufacturing field for joints of many types of same or dissimilar materials such as aluminum alloys, magnesium alloys and steels and so on. In addition, FSW process is also a complex process associated with heat transfer, plastic deformation, grain recrystallization and material property changing phenomenon. It is commonly known that the thermal condition or the temperature distribution of space and time is important to the final welding condition. However, due to the limitation of experiment measurement and the unfinished work of numerical heat transfer model, the relationship between thermal condition and control parameters still remains a question. In this work, a new numerical model based on energy analysis and finite element method is built to calculate the thermal field of FSW process. The energy generation due to plunge depth and the converting coefficient of friction energy to heat are considered in the model. The effects of energy distribution of both sides, energy efficiency of friction, plunge depth, normal force, traverse speed and rotation speed on the temperature distribution of FSW process are investigated.

Microstructural Refinement of Pure Copper by Friction Stir Processing

2013 ◽  
Vol 787 ◽  
pp. 256-261 ◽  
Author(s):  
Salar Salahi ◽  
Vahid Rezazadeh ◽  
Ali Sharbatzadeh ◽  
Atabak Iranizad ◽  
Hamed Bouzary
Keyword(s):  
Grain Size ◽  
Friction Stir Processing ◽  
Rotational Speed ◽  
Frictional Heating ◽  
Pure Copper ◽  
Traverse Speed ◽  
Work Piece ◽  
Process Conditions ◽  
Nugget Zone ◽  
Friction Stir

Recently friction stir processing (FSP) was developed as a generic implement for microstructural modification based on the principles of FSW using a rotating tool inserted in a monolithic work piece which provides frictional heating and mechanical mixing. In this paper, the microstructural evolution characteristics of nugget zone were investigated during friction stir processing (FSP) of pure copper. Pure copper plates were friction stir processed to the depth of 3.4 mm at different process conditions by varying the traverse speed from 30 to 120 mm/min at rotation speeds of 400 and 600 rpm..Defects were observed in rotational speed of 400 rpm. Grain size of NZ depended significantly on plastic deformation and heat input value. By increasing traverse speed at constant rotational speed of 600 rpm grain size of the nugget zone decreased and the hardness increased. Ultimate tensile strength increased with decrease in grain size. FSP was found as an effective method to develop fine-grained microstructure in copper plates.

Development of a Mechanistic Model for Friction Stir Channeling

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
N. Balasubramanian ◽  
R. S. Mishra ◽  
K. Krishnamurthy
Keyword(s):  
Specific Energy ◽  
Thermal Cycle ◽  
Mechanistic Model ◽  
Traverse Speed ◽  
Processing Parameters ◽  
Processing Conditions ◽  
Ir Camera ◽  
Plunge Depth ◽  
Friction Stir ◽  
Infra Red

A mechanistic model for the process specific energy as a function of the processing parameters during friction stir channeling (FSC) in Al6061-T6 was developed and investigated. The thermal cycle acting on the surface of the workpiece was measured using an infra red (IR) camera and the peak temperatures were studied as a function of the specific energy. The channel area is plotted against the process specific energy and is analyzed. A relationship between the processing conditions (tool rotational rate, traverse speed, and plunge depth) and the channel area is defined.

scholarly journals Modeling and Optimization of Friction Stir Welding Parameters for Joining Dissimilar Aluminum Alloys

2018 ◽  
Vol 4 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Mohamed Mohamed Abd Elnabi ◽  
Tarek Abd Elsadek Osman ◽  
Alaa Eldeen El Mokadem ◽  
Abou Bakr Elshalakany 
Keyword(s):  
Friction Stir Welding ◽  
Base Metal ◽  
Tilt Angle ◽  
Rotational Speed ◽  
Traverse Speed ◽  
Welding Parameters ◽  
Plunge Depth ◽  
Friction Stir ◽  
Confidence Levels ◽  
Tool Tilt Angle

The objectives of this work are to optimize the process parameters on the mechanical properties (ultimate tensile strength (UTS) and ductility) of dissimilar joints between AA5454 and AA7075 produced by friction stir welding and to determine which of them is significant by using Taguchi L16 optimization method. Seven parameters at two levels were selected in this study. The selected parameters are tool rotational speed, traverse speed, pin profile (based on taper angle), D/d ratio, tool tilt angle, plunge depth, and base metal location. Then, mathematical models are built as function of significant parameters/ interactions using Response Surface Methodology. The results of this work showed that the rotational speed, traverse speed, D/d ratio and plunge depth are significant parameters in determining UTS (Mean, Signal to noise ratio (S/N)) at different confidence levels, but pin profile, location of base metal and tool tilt angle are insignificant parameters at any confidence levels. The traverse speed has the highest contribution to the process for UTS about 18.577 % and 16.943 % for S/N ratio and mean, respectively. The accuracy of the models according to the UTS is 97.678 % and 99.56 %for mean and S/N ratio, respectively. The maximum joint efficiency, compared to the strength of the AA5454, is 85.3%.

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