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A significant increase in roughness of dieless-drawn wires due to the strain-induced roughness phenomenon has been documented. For small-diameter wires, even a slight surface relief creates stress concentrations that may contribute to the wire breakage during cold drawing. This, in turn, significantly limits the achievable diameter of the product and the efficiency of drawing process. The present study, however, demonstrates that reducing the wire roughness is possible by combining the dieless and conventional drawing methods. Thus, it is possible to improve the process workability threefold when compared to dieless drawing alone, and the product quality is simultaneously improved. In addition, the surface defects typical to the dieless-drawn wires have been significantly reduced, resulting in an increase in the wire strength. This new combined technology enables a significant reduction in the wire diameter and facilitates an economical large-scale production of ultra-thin wires. In addition, based on the classic drawing and dieless drawing process, a brass wire with a diameter of 0.017 mm has been manufactured. Six times thinner than a human hair, it is believed to be the thinnest long brass wire currently manufactured in the world.

Clinching technology has been widely applied in automobile assembly industries to join sheet materials of different thicknesses and properties. It does not require any auxiliary parts and only depends on the plastic deformation of materials themselves to form a joint. Furthermore, clinching tools that include the punch and the die are simpler than other thermal joining methods. However, the usability of the clinched joint is restricted by a low joining strength. In order to expand the application range of clinching technologies, researchers have conducted extensive researches on how to improve clinching technologies. In this article, the latest advances of clinching technologies are reviewed on the development of clinching tools and processes. The improved clinching processes including flat clinching, hole clinching, reshaping the clinched joint without a rivet, reshaped joint with a rivet, rivet clinching, rectangular clinching, dieless clinching, roller clinching, laser shock clinching, hydro-clinching, injection clinching, adhesive clinching, resistance spot clinching, friction-assisted clinching, and laser-assisted clinching are introduced. The advantages and disadvantages of different clinching technologies are proposed. In addition, some suggestions for the future development of clinching technology are given in this paper. The clinching technology is developing towards a hybrid joining technology with high strength, high stability, and high efficiency.

This paper examines the surface roughness of a thin brass wire (140–200 microns in diameter) after two dieless drawing (DD) processes, i.e., conventional dieless drawing (CDD) and incremental dieless drawing (IDD). In incremental dieless drawing, small increments in deformation were applied in several passes. It has been proven that the IDD process not only has a greater efficiency but also enables obtaining a wire with significantly lower surface roughness. The explanation for these effects is based on the results of the numerical modeling of both compared processes. The developed numerical model takes into consideration the initial roughness of the wire surface, shape and dimensions of grains, and their diversified mechanical properties. Nanoindentation measurements, microstructure, and plastometric studies allowed us to find the effective flow stress distribution in the grains. The IDD process was found to be much more stable and develop a much more uniform distribution of grain strain than the CDD process. More homogeneous deformation results in surface roughness reduction. Approximately 25–30% reduction in surface roughness of the wire produced by the IDD process was predicted by simulations and confirmed experimentally.

Due to their biodegradable properties, magnesium- and zinc-based alloys are in the focus of interest for numerous medical applications, e.g. in the form of thin wires. To achieve improved processability by using hot forming and to obtain higher diameter reductions per pass, the dieless wire drawing process is presented in this paper. In order to investigate the processability and the resulting mechanical properties, a selection of magnesium- and zinc-alloys as well as process parameters are chosen, and wire manufacturing is carried out using the dieless drawing process. The resulting process windows and mechanical properties for the selected materials are discussed. It is found that the length of the forming zone is an important indicator for the process window and the cross-sectional area reduction accuracy in the dieless wire drawing process. Furthermore, process parameter variations result in a distinct variation of the mechanical properties of the wires, whereas process temperatures close to the wire extrusion temperature result in mechanical properties similar to the as-extruded wires. Good localization of the deformation is found for forming zones of 25–75 mm length at elevated temperatures and cross-sectional area reductions of up to 30% are possible for Z1 and ZX10 in one drawing step. Graphical Abstract

A novel superplastic dieless drawing technique with local heating and tensile deformation has been focused on for fabrication of zirconia ceramic tube. In this study, 3Y-TZP zirconia ceramic tube with outer diameter of 6mm and inner diameter of 4mm as a superplastic material is used experimentally. An apparatus of superplastic dieless drawing with rotary stage for circumferential uniform heating and acetylene burner for high temperature of 1700°C is developed. The superplastiac dieless drawing experiment is carried out to investigate the effect of the ratio of drawing speed to feeding speed on the flexible controllability of diameter after drawing process. As a result, the reduction in area after drawing process can be controlled by the ratio of drawing speed to feeding speed. In addition, a maximum reduction in area of 79.2% can be realized in this process. Consequently, the validity of developed apparatus of superplastic dieless drawing for Zirconia ceramic tube can be demonstrated.

A recently developed spot joining process namely dieless friction stir riveting is explored for understanding the effect of multi-hole configurations on the joint formation in dissimilar grades of aluminum alloy sheets. These spot joints are strengthened by mechanical interlocking together with metallurgical bonding and possesses the absence of hook defect as well as pin hole defect. This contributes to superior lap shear fracture load than conventional spot joints. The mechanical load performance tests, detailed macro/micro structure analysis, the hardness measurement, external morphological study, and fracture mode analysis are conducted. Single-hole configuration yields appreciable mechanical performance than multi-hole configurations by achieving lap shear fracture load accounting about 7.42 kN and cross-tension fracture load accounting about 2.89 kN. The farther the holes in multi-hole configurations, the more imperfect the mechanical interlocking becomes. The dynamic recrystallization, associated grain growth, and its relation with the extent of plastic deformation in distinct zones of the joint are also identified. The frictional heat flux and severe plastic deformation have significantly affected the hardness of the two sheets. Critical weak zones leading to various fracture modes of the joint are also identified.

In order to meet the requirements of high reliability, long-lifetime and lightweight in a new generation of aerospace, aviation, high-speed train, and energy power equipment, integrated components are urgently needed to replace traditional multi-piece, welded components. The applications of integrated components involve in a series of large-size, complex-shaped, high-performance components made of difficult-to-deform materials, which present a huge challenge for forming ultra-large size integrated components. In this paper, the developments and perspectives of several extreme forming technologies are reviewed, including the sheet hydroforming of ultra-large curved components, dieless hydroforming of ellipsoidal shells, radial-axial ring rolling of rings, in situ manufacturing process of flanges, and local isothermal forging of titanium alloy components. The principle and processes for controlling deformation are briefly illustrated. The forming of typical ultra-large size integrated components and industrial applications are introduced, such as the high strength aluminum alloy, 3 m in diameter, integrated tank dome first formed by using a sheet blank with a thickness the same as the final component, and a 16 m diameter, integrated steel ring rolled by using a single billet. The trends for extreme forming of ultra-large size integrated components are discussed with a goal of providing ideas and fundamental guidance for the further development of new forming processes for extreme-size integrated components in the future.

The product quality of multi-point dieless forming (MDF) is dependent on the process parameters. Moreover, variations in the friction and material properties may substantially worsen the final product quality. In this paper, a technique for compensating for MDF product defects by minimizing the variations in the noise parameters is proposed. This can be attained by a reliability-based robust optimization (RRO) technique to obtain the optimal process settings of the controllable parameters. Initially, two MDF finite-element (FE) simulations of an AA3003-H14 aluminum-alloy saddle shape exhibited a substantial amount of dimpling and wrinkling along with shape errors. FE analyses were consequently carried out using ABAQUS commercial software to obtain the correlation between the control process settings and the variation in the noise with regard to product defects. The best prediction models were chosen from a family of metamodels to swap the computationally expensive FE simulation. Further, a genetic algorithm (GA) was applied to determine the optimal process settings of the control parameters. A Monte Carlo analysis (MCA) was executed to determine how the variation in the noise parameter affects the final product quality. Finally, the RRO FE simulation and experimental results showed that the amendment of the control parameters in the final forming process leads to a considerably better-quality product.

This study is to set a goal to create a model solving the temperature distribution and its evolution for the process of dieless drawing metal wire parts by using slab method and postulating that the wire end suffers a proportional deformation. The results from using a SUS304 stainless wire in 5 mm diameter dielessly drawn show that the highest temperature locates on the symmetry plane at the process beginning, so that the necking takes place there and an end will be formed securely. As a result, the method proposed by this study is feasible. In addition, for a given final shape of the metal wire end, there are many possibilities to get different temperature distribution and its evolution by setting different temperature boundary condition. The higher the boundary temperature set, the higher the temperature distribution, but the lower the drawing force needed.

Recently, dieless forming processes have been introduced to prevent the high costs of dies and tools. Local heating and axial compression process is an innovative method for producing metal bellows. In this research, producing metal bellows using simultaneous local electric arc heating and axial compression has been explained and investigated. SUS304 tubes with an outer diameter of 19 mm and a thickness of 1 mm have been employed to implement the tests. Various parameters could affect the process. Among these parameters, effects of applied displacement and device current, influencing convolution shape, thickness, and required forming force, are studied experimentally. It is found that the height, radius, and angle of the convolution and also the forming force could be controlled by alteration of these parameters. Furthermore, the result of buckling test showed that energy absorption capacity of the manufactured metal bellow has been increased in comparison to a typical tube. This method could be a suitable alternative for induction local heating and can reduce the high equipment costs.