The article concerns the issues of tool wear effect on the quality of a friction stir welding joint quality. The experiment used aluminum alloy 7075 T6 sheet metal, which is used primarily in the aerospace industry. 1.0mm and 0.8mm thick lap joints were tested. Tool wear was determined based on multiple readings on a multisensory machine. The tool wear evaluation was done on the basis of a static tensile strength test and metallographic sections of the joints. The pin of the tool works in more demanding conditions and is more exposed to friction. This results from tooling operations performed at full depth dive in the jointed material. When also considering the small dimensions of the pin such as the diameter and the great forces occurring in this process, it is easy to see why this element is most susceptible to tool wear. The welding process causes the tool to undergo friction wear, which is the cause of reduced tool dive depth in the jointed material. As a result, it is paramount to constantly control the tool extension to achieve the desired quality parameters of the joint. After creating 200m of joints, a decrease in the strength of joints was observed as well as the repeatability of the results connected to a change in the stirring conditions in the material. The change in joint strength and tool wear is also confirmed in the metallographic analysis, which states that the continued degradation of the tool makes it subject to a decrease in size of the characteristic sizes of the thermoplastic zone that is the main determining factor of the joint strength.
The study presents an analysis of wear of tools made of 1.2344 steel and MP159 alloy for the process of obtaining an overlap joint in 1.0 mm and 0.8 mm sheet metal made of 7075 T6 aluminum alloy using friction stir welding (FSW) technology. Tool geometry was designed at the Czestochowa University of Technology. Evaluation of tool wear was conducted based on the measurements of geometry of working area of tools by means of a multisensory meter system and based on the assessment of the working area by means of a stereoscope after individual stages of wear tests. Furthermore, based on the results of a static tensile strength test and metallographic examinations of the specimens sampled from the joints obtained during tool wear tests, the effect of the degree of tool wear on joint quality was also evaluated. Analysis of the results revealed that both the tool made of 1.2344 steel and that made of MP159 alloy were substantially worn, increasing the risk of further use of the tools for the joint material (7075-T6) after obtaining the joint with length of 200m, which suggests their low durability. Furthermore, modification of tool geometry caused by wear led to insignificant improvements in joint strength. Therefore, the results of wear measurement set directions for further modification of tool geometry, also due to the fact that despite a substantial wear, the tools continued to yield high-quality joints without defects. As demonstrated in the study, the type of tool material does not only impact on tool life but also, as it was the case in their geometry, has a significant effect on the quality of obtained joints. Although the tool made of MP159 alloy was worn more than the tool made of 1.2344 steel, it allowed for obtaining the joints with substantially better strength parameters.
The aim of this paper was to present preliminary results of researches conducted in PZL Mielec within the FAST_FSW project (INNOLOT program) on the influence of tool eccentricity on microstructure and mechanical properties of 1.6 mm and 0.8 mm thick Al 7075 T6 sheets joints. Samples were performed using CNC milling machine. The range of tool eccentricity was 0-0.3 mm, rotational speed and feed rate were variable. The influence of the applied welding parameters on microstructure and mechanical properties of joints was assessed on the basis of metallographic inspections and tensile tests. Microstructural observations have shown that the change of FSW tool eccentricity affects the weld geometry: the mixing zone depth, the weld width, or the shape of the contact line.
Purpose This paper aims to experimentally determine the influence of the tool shoulder depth value on the structural and strength properties of the single lap joints made of 7075-T6 aluminium alloy made with friction stir welding (FSW) technology. The aim of the preliminary tests is to optimize the parameters of joining process of thin-walled structures such as the skin-stringer joint or skin-frame joint of the aircraft fuselage. The tests were carried out for materials commonly used in such structures, i.e. 1.6 mm thick sheet 7075–T6 aluminium alloy with cladding on both sides (cladding thickness 4% per each side). The layer of clad protects plates from corrosion. Design/methodology/approach This study shows the results of the investigation for the joining of 7075–T6 ALCLAD aluminium alloy sheets. The welding process was carried out on a computer numerical control milling machine SOLARUCE TA–20A. Linear FSW welding was performed using a commercial tool from RSS SCHILLING with the symbol 10–K–4–Z–M–O, which is fabricated of hot work tool steel. Constant parameters of the technological process were applied. The welding process was executed for different values of the shoulder depth ZS. Findings This paper investigated the dependence between the thinning of the welded material and the depth value of the tool shoulder during the FSW process. The influence of the depth value of tool shoulder on joint strength in the static tensile/shear test was also performed. With the increase of the depth of the tool, the size of flash and structures of the face of the joint changes as well (its annular surface resulting from the tool’s work and the accompanying process of material flow on the run-off side). Such conditions in the process require a proper tool depression to reduce the occurrence of flash and minimize material thinning to achieve high joint strength and maintain the conditions for plasticizing the material. Practical implications Based on the experimental tests carried out, a number of guidelines for the correct conduct of the welding process can be outlined. Originality/value Taking into account the various aspects of the process, the optimal range of the tool depth into the material is a value of approximately 0.06 mm. At this value, the face of the weld is not porous; the flash is easily removed; and the strength of the joint and the deformation of contact line are at an acceptable quality level.
Refill friction stir spot welding (RFSSW) is a new technique of metal structures joining. Within the framework of activities of PZL Mielec in R&D area (program Innolot) researches are realized which aim is to develop the RFSSW technology as a method of joining thin aluminum elements used in aircrafts constructions. The paper presents results of investigations on the RFSSW lap joints welded using rotations in the range from 1500 to 2000 rpm and tool sleeve plunge depth from 1.6 to 1.8 mm. Thin aluminum sheets of thickness 0.8 and 1.6 mm coated with alclad or anodized were welded. Results of the investigations prove that the most common cause of specimens breaking was presence of geometrical defect -the so called hook and weak bonding between parent material and working area of internal sleeve of RFSSW tool. The best tensile strength was reached in case of joint welded at rotational speed 2000 rpm and tool plunge depth 1.6 mm and 1.7 mm (5.37 kN and 5.87 kN adequately). These joints were characterized by very fine and uniform microstructure in the area between sleeve stirred zone and parent material.
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