Weld tests for friction welding

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Quality requirements of welded joints depend on the form of application, e.g. in the space or fly industry weld errors are not allowed. [1] Science try to gets good quality welds. There are many scientific articles describing the weld test, e.g. hardness, [2] [3] [4] tensile tests. [3] The weld structure can be examined by optical microscopy [3] [4] [5] and scanning electron microscopy. [6] [4] [5] [3] The computer finite element method (FEM) is used to predict the shape of the flash and interface and others, not only for rotary friction welding (RFW), [7] but also for friction stir welding (FSW), [8] [9] linear friction welding (LFW), [10] FRIEX, [11] and others. Temperature measurements are also carried out for scientific purposes e.g. by use thermocouples [4] [5] or sometimes thermography, [7] [5] mentions about measurements are generally found in research materials and journals.

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Stainless steel Steel alloy resistant to corrosion

Stainless steel, originally called rustless steel, is any one of a group of ferrous alloys that contain a minimum of approximately 11% chromium, a composition that prevents the iron from rusting and also provides heat-resistant properties. Different types of stainless steel include the elements carbon, nitrogen, aluminium, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum. Specific types of stainless steel are often designated by their AISI three-digit number, e.g., 304 stainless. The ISO 15510 standard lists the chemical compositions of stainless steels of the specifications in existing ISO, ASTM, EN, JIS, and GB standards in a useful interchange table.

Friction welding (FRW) is a solid-state welding process that generates heat through mechanical friction between workpieces in relative motion to one another, with the addition of a lateral force called "upset" to plastically displace and fuse the materials. Because no melting occurs, friction welding is not a fusion welding process, but a solid-state welding technique more like forge welding. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications.

Friction stir welding

Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough. It is primarily used on wrought or extruded aluminium and particularly for structures which need very high weld strength. FSW is capable of joining aluminium alloys, copper alloys, titanium alloys, mild steel, stainless steel and magnesium alloys. More recently, it was successfully used in welding of polymers. In addition, joining of dissimilar metals, such as aluminium to magnesium alloys, has been recently achieved by FSW. Application of FSW can be found in modern shipbuilding, trains, and aerospace applications.

Aluminium alloy Alloy in which aluminium is the predominant metal

An Aluminium alloy is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.

Cold spraying

Gas dynamic cold spraying or cold spraying (CS) is a coating deposition method. Solid powders are accelerated in a supersonic gas jet to velocities up to ca. 1200 m/s. During impact with the substrate, particles undergo plastic deformation and adhere to the surface. To achieve a uniform thickness the spraying nozzle is scanned along the substrate. Metals, polymers, ceramics, composite materials and nanocrystalline powders can be deposited using cold spraying. The kinetic energy of the particles, supplied by the expansion of the gas, is converted to plastic deformation energy during bonding. Unlike thermal spraying techniques, e.g., plasma spraying, arc spraying, flame spraying, or high velocity oxygen fuel (HVOF), the powders are not melted during the spraying process.

Nickel aluminide typically refers to the one of the two most widely used compounds, Ni3Al or NiAl, however is generally any aluminide from the Ni-Al system. These alloys are widely used due to their corrosion resistance, low-density and easy production. Ni3Al is of specific interest as the strengthening γ' phase precipitate in nickel-based superalloys allowing for high temperature strength up to 0.7-0.8 of its melting temperature. Meanwhile, NiAl displays excellent properties such as low-density (lower than that of Ni3Al), good thermal conductivity, oxidation resistance and high melting temperature. These properties, make it ideal for special high temperature applications like coatings on blades in gas turbines and jet engines. However, both these alloys do have the disadvantage of being quite brittle at room temperature while Ni3Al remains brittle at high temperatures as well. Although, it has been shown that Ni3Al can be made ductile when manufactured as a single crystal as opposed to polycrystalline. Another application was demonstrated in 2005, when the most abrasion-resistant material was reportedly created by embedding diamonds in a matrix of nickel aluminide.

Magnetic pulse welding

Magnetic pulse welding (MPW) is a solid state welding process that uses magnetic forces to weld two workpieces together. The welding mechanism is most similar to that of explosion welding. Magnetic pulse welding started in the early 1970s, when the automotive industry began to use solid state welding. The biggest advantage using magnetic pulse welding is that the formation of brittle intermetallic phases is avoided. Therefore, dissimilar metals can be welded, which cannot be effectively joined by fusion welding. With magnetic pulse welding high quality welds in similar and dissimilar metals can be made in microseconds without the need for shielding gases or welding consumables.

Clinching

Clinching or press-joining is a bulk-sheet metal-forming process aimed at joining thin metal sheet without additional components, using special tools to plastically form an interlock between two or more sheets. The process is generally performed at room temperature but in some special cases the sheets can be pre-heated to improve the material ductility and thereby avoid the formation of cracks during the process. Clinching is characterized by a series of advantages over competitive technologies:

Incremental sheet forming is a sheet metal forming technique where a sheet is formed into the final workpiece by a series of small incremental deformations. However, studies have shown that it can be applied to polymer and composite sheets too. Generally, the sheet is formed by a round tipped tool, typically 5 to 20mm in diameter. The tool, which can be attached to a CNC machine, a robot arm or similar, indents into the sheet by about 1 mm and follows a contour for the desired part. It then indents further and draws the next contour for the part into the sheet and continues to do this until the full part is formed. ISF can be divided into variants depending on the number of contact points between tool, sheet and die. The term Single Point Incremental Forming (SPIF) is used when the opposite side of the sheet is supported by a faceplate and Two Point Incremental Forming (TPIF) when a full or partial die supports the sheet.

Flash welding Type of resistance welding that does not use any filler metals

Flash welding is a type of resistance welding that does not use any filler metals. The pieces of metal to be welded are set apart at a predetermined distance based on material thickness, material composition, and desired properties of the finished weld. Current is applied to the metal, and the gap between the two pieces creates resistance and produces the arc required to melt the metal. Once the pieces of metal reach the proper temperature, they are pressed together, effectively forge welding them together.

Zirconium diboride Chemical compound

Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.

Friction stir processing

Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding.

Calvin Blignault

Calvin Blignault was a South African mechanical engineer.

Adam H. Koppy was an American mechanical engineer. He was internationally recognised as one of the leading friction stir welding machine designers and builders. He was one of three inventors of a patented adapter for use in friction stir welding that is suitable for use on a milling machine, including a mechanism for adjustment of the weld tool along its longitudinal axis.

Friction extrusion is a thermo-mechanical process that can be used to form fully consolidated wire, rods, tubes, or other non-circular metal shapes directly from a variety of precursor charges including metal powder, flake, machining waste or solid billet. The process imparts unique, and potentially, highly desirable microstructures to the resulting products. Friction extrusion was invented at The Welding Institute in the UK and patented in 1991. It was originally intended primarily as a method for production of homogenous microstructures and particle distributions in metal matrix composite materials.

Ultra-high temperature ceramic matrix composites (UHTCMC) or Ultra-high Temperature Ceramic Composites (UHTCC) are a class of refractory ceramic matrix composites (CMCs), which aspires to overcome the limits associated with currently used CMCs in aerospace field as thermal protection systems (TPS) and rocket nozzles. Carbon fiber reinforced carbon matrix (C/C) can be used up to 3000 °C because carbon is the element with the highest melting point however C/C are ablative materials which dissipate energy consuming themselves. Carbon fiber reinforced silicon carbide matrix composites (C/SiC) and Silicon carbide fiber reinforced silicon carbide matrix composites (SiC/SiC) are considered reusable materials because silicon carbide is a hard material with a low erosion and it forms a silica glass layer during oxidation which prevents further oxidation of inner material. Unfortunately above a certain temperature starts the active oxidation of silicon carbide matrix to gaseous silicon monoxide, consequently loss of protection from further oxidation, which leads the material to an uncontrolled and fast erosion. For this reason C/SiC and SiC/SiC are used in the range of temperature between 1200° - 1400 °C.

Aluminium joining

Aluminium alloys are often chosen due to their high strength-to-weight ratio, corrosion resistance, low cost, high thermal and electrical conductivity. There are a variety of techniques to join aluminium including mechanical fasteners, welding, adhesive bonding, brazing, soldering and friction stir welding (FSW), etc. Various techniques are used based on the cost and strength required for the joint. In addition, process combinations can performed to provide means for difficult to join assemblies and to reduce certain process limitations.

Dissimilar friction stir welding

Dissimilar friction stir welding (DFSW) is the application of friction stir welding (FSW), invented in The Welding Institute (TWI) in 1991, to join different base metals including aluminum, copper, steel, titanium, magnesium and other materials. It is based on solid state welding that means there is no melting. DFSW is based on a frictional heat generated by a simple tool in order to soften the materials and stir them together using both tool rotational and tool traverse movements. In the beginning, it is mainly used for joining of aluminum base metals due to existence of solidification defects in joining them by fusion welding methods such as porosity along with thick Intermetallic compounds. DFSW is taken into account as an efficient method to join dissimilar materials in the last decade. There are many advantages for DFSW in compare with other welding methods including low-cost, user-friendly, and easy operation procedure resulting in enormous usages of friction stir welding for dissimilar joints. Welding tool, base materials, backing plate (fixture), and a milling machine are required materials and equipment for DFSW. On the other hand, other welding methods, such as Shielded Metal Arc Welding (SMAW) typically need highly professional operator as well as quite expensive equipment.

Nanotech metallurgy is an emerging interdisciplinary domain of materials science and engineering, manufacturing, and nanoscience and engineering to study how nanophases can be applied to significantly improve the processing/manufacturing, micro/nano-structures, and physical/chemical/mechanical behaviors of metals and alloys. This definition was first proposed by Xiaochun Li at the University of California, Los Angeles in 2018.

Rotary friction welding (RFW) one of the methods of friction welding, the classic way of which uses the work of friction to create a not separable weld. Typically one welded element is rotated to the other and forge. The heating of the material is caused by friction work and creates a permanent connection. In this method can be welded the same, dissimilar, or composite and non-metallic materials. The friction welding methods of are often considered as solid-state welding.

References

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