Research

14 pages, 4326 KiB

Open AccessArticle

An Experimental Study on Bushing Formation during Friction Drilling of Titanium Grade 2 for Medical Applications

by Hans Vanhove, Ecem Ozden and Joost R. Duflou

J. Manuf. Mater. Process. 2023, 7(6), 220; https://doi.org/10.3390/jmmp7060220 - 06 Dec 2023

Viewed by 1308

Recent advances towards patient specific titanium sheet based medical implants introduce a new challenge for the fixation of these implants to bones. Mainly, the use of locking screws requires an implant thickness of approximately 2 mm for screw thread formation. Friction drilling is [...] Read more.

Recent advances towards patient specific titanium sheet based medical implants introduce a new challenge for the fixation of these implants to bones. Mainly, the use of locking screws requires an implant thickness of approximately 2 mm for screw thread formation. Friction drilling is a hole-making process that displaces material to create a bushing below the sheet rather than extracting material. This experimental study explores the influence of axial force, rotational speed, and workpiece pre-heating temperature on the bushing height and thickness during friction drilling of titanium grade 2 sheets. The drilling parameters are optimized for both drilling at room temperature and at elevated temperatures for maximum bushing thickness with at least a bushing height of 1 mm. Subsequently, the samples are characterized for their microstructure and hardness, revealing preserved strength with a larger thermomechanical affected zone (TMAZ), a more gradual hardness gradient around the drill zone, and a significant reduction in microdefects in the bushing structure of the pre-heated sheets. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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11 pages, 4552 KiB

Open AccessArticle

Increased Sustainability in Fastener Production with the Example of Self-Piercing Rivets

by Benedikt Uhe, Clara-Maria Kuball, Marion Merklein and Gerson Meschut

J. Manuf. Mater. Process. 2023, 7(6), 193; https://doi.org/10.3390/jmmp7060193 - 31 Oct 2023

Viewed by 1338

Abstract

The sustainability of the manufacturing industry is of special importance to increase the protection of the environment. The production of fasteners like self-piercing rivets, however, is costly, time-consuming and energy-intensive. The heat treatment and the coating, which are mandatory in conventional self-piercing rivets [...] Read more.

The sustainability of the manufacturing industry is of special importance to increase the protection of the environment. The production of fasteners like self-piercing rivets, however, is costly, time-consuming and energy-intensive. The heat treatment and the coating, which are mandatory in conventional self-piercing rivets to achieve adequate strength, ductility and corrosion resistance, are especially crucial in this respect. Within this paper, an approach for an increase in the sustainability in fastener production is presented. The use of alternative, high strain hardening stainless steels as rivet material enables a shortening of the process chain, because post treatment of the rivets after they are formed can be omitted. As the change in rivet material and processing causes some issues along the process chain, the focus of this paper is on the holistic evaluation of the challenges within the forming of high strain hardening steel and the impact of the changed rivet properties on the joining result. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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13 pages, 5594 KiB

Open AccessEditor’s ChoiceArticle

Investigation of Metal Wire Mesh as Support Material for Dieless Forming of Woven Reinforcement Textiles

by Jan-Erik Rath and Thorsten Schüppstuhl

J. Manuf. Mater. Process. 2023, 7(5), 182; https://doi.org/10.3390/jmmp7050182 - 11 Oct 2023

Viewed by 1613

Abstract

Within the rapidly growing market for fiber-reinforced plastics (FRPs), conventional production processes involving molds are not cost-efficient for prototype and small series production. Therefore, new flexible forming techniques are increasingly being researched, many of which have been inspired by incremental sheet metal forming [...] Read more.

Within the rapidly growing market for fiber-reinforced plastics (FRPs), conventional production processes involving molds are not cost-efficient for prototype and small series production. Therefore, new flexible forming techniques are increasingly being researched, many of which have been inspired by incremental sheet metal forming (ISF). Due to the different deformation mechanisms of woven reinforcement fibers and metal sheets, ISF is not directly applicable to FRP. Instead, shear and bending of the fibers need to be realized. Therefore, a new dieless forming process for the production of FRP supported by metal wire mesh as an auxiliary material is proposed. Two standard tools, such as hemispherical punches, are used to locally bend a reversible layup of metal wire mesh and woven reinforcement fiber fabric enclosed in a vacuum bag. Therefore, the mesh aids in introducing shear into the material due to its ability to transmit compressive in-plane forces, and it ensures that the otherwise flexible fabric maintains the intended deformation until the part is cured or solidified. Basic experiments are conducted using thermoset prepreg, woven commingled yarn fabric, and thermoplastic organo sheets, proving the feasibility of the approach. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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15 pages, 6053 KiB

Open AccessArticle

Effect of Process Variables on Interface Friction Characteristics in Strip Drawing of AA 5182 Alloy and Its Formability in Warm Deep Drawing

by Archit Shrivastava and Ravi Kumar Digavalli

J. Manuf. Mater. Process. 2023, 7(5), 175; https://doi.org/10.3390/jmmp7050175 - 29 Sep 2023

Viewed by 1205

Abstract

Warm forming is widely used to enhance the formability of aluminum alloy sheets. In warm deep drawing, the process variables significantly affect frictional characteristics at the tool–blank interface. It has been a conventional approach to use a constant value of friction coefficients in [...] Read more.

Warm forming is widely used to enhance the formability of aluminum alloy sheets. In warm deep drawing, the process variables significantly affect frictional characteristics at the tool–blank interface. It has been a conventional approach to use a constant value of friction coefficients in the finite element (FE) simulations. However, this can occasionally result in suboptimal accuracy of the predictions. In the present work, strip drawing tests were carried out on AA5182 aluminum alloy sheets to investigate the effect of important process variables, namely, temperature, contact pressure, and drawing speed, on the friction coefficient in the warm forming temperature range (100–250 °C) under lubricated condition. The results obtained from the strip drawing tests were used for defining the friction conditions in the simulation of warm deep drawing of cylindrical cups incorporating the variation of the friction coefficient with contact pressure and speed at different temperatures. The Barlat89 yield criterion was used to define the effect of anisotropy in the material. The Voce hardening law and Cowper–Symonds model were used to incorporate the effect of strain hardening and strain rate, respectively, in the simulation. Drawability and peak force were compared with the predictions when a constant friction coefficient was assumed. Warm deep drawing experiments were conducted to validate the predicted drawability and load–displacement curves. It is clearly observed that the accuracy of prediction of the limiting drawing ratio and peak load through simulations is improved by incorporating the effect of pressure and speed on friction coefficient as it captures the local variations of friction during warm deep drawing precisely, rather than assuming a constant average friction coefficient at all the tool–blank contact areas. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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13 pages, 5601 KiB

Open AccessArticle

Design, Numerical and Experimental Testing of a Flexible Test Bench for High-Speed Impact Shear-Cutting with Linear Motors

by Pascal Krutz, André Leonhardt, Alexander Graf, Sven Winter, Elmar Galiev, Matthias Rehm, Verena Kräusel and Martin Dix

J. Manuf. Mater. Process. 2023, 7(5), 173; https://doi.org/10.3390/jmmp7050173 - 26 Sep 2023

Cited by 1 | Viewed by 1342

Abstract

Given the use of high-strength steels to achieve lightweight construction goals, conventional shear-cutting processes are reaching their limits. Therefore, so-called high-speed impact cutting (HSIC) is used to achieve the required cut surface qualities. A new machine concept consisting of linear motors and an [...] Read more.

Given the use of high-strength steels to achieve lightweight construction goals, conventional shear-cutting processes are reaching their limits. Therefore, so-called high-speed impact cutting (HSIC) is used to achieve the required cut surface qualities. A new machine concept consisting of linear motors and an impact mass is presented to investigate HSIC. It allows all relevant parameters to be flexibly adjusted and measured. The design and construction of the test bench, as well as the mechanism for coupling the impact mass, are described. To validate the theoretically determined process speeds, the cutting process was recorded with high-speed cameras, and HSIC with a mild deep-drawing steel sheet was performed. It was discovered that very good cutting edges could be produced, which showed a significantly lower hardening depth than slowly cut reference samples. In addition, HSIC was numerically modelled in LS-DYNA, and the calculated cutting edges were compared with the real ones. With the help of adaptive meshing, a very good agreement for the cutting edges could be achieved. The results show the great potential of using a linear motor in HSIC. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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15 pages, 5743 KiB

Open AccessArticle

Thermomechanical Joining of Hypoeutectic Aluminium Cast Plates

by Thomas Borgert, Moritz Neuser, Kay-Peter Hoyer, Werner Homberg and Mirko Schaper

J. Manuf. Mater. Process. 2023, 7(5), 169; https://doi.org/10.3390/jmmp7050169 - 15 Sep 2023

Cited by 1 | Viewed by 1037

Abstract

Consistent lightweight construction in the area of vehicle manufacturing requires the increased use of multi-material combinations. This, in turn, requires an adaptation of standard joining techniques. In multi-material combinations, the importance of integral cast components, in particular, is increasing and poses additional technical [...] Read more.

Consistent lightweight construction in the area of vehicle manufacturing requires the increased use of multi-material combinations. This, in turn, requires an adaptation of standard joining techniques. In multi-material combinations, the importance of integral cast components, in particular, is increasing and poses additional technical challenges for the industry. One approach to solve these challenges is adaptable joining elements manufactured by a thermomechanical forming process. By applying an incremental and thermomechanical joining process, it is possible to react immediately and adapt the joining process inline to reduce the number of different joining elements. In the investigation described in this publication, cast plates made of the cast aluminium alloy EN AC-AlSi9 serve as joining partners, which are processed by sand casting. The joining process of hypoeutectic AlSi alloys is challenging as their brittle character leads to cracks in the joint during conventional mechanical joining. To solve this, the frictional heat of the novel joining process applied can provide a finer microstructure in the hypoeutectic AlSi9 cast alloy. In detail, its Si is finer-grained, resulting in higher ductility of the joint. This study reveals the thermomechanical joining suitability of a hypoeutectic cast aluminium alloy in combination with adaptively manufactured auxiliary joining elements. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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19 pages, 9370 KiB

Open AccessEditor’s ChoiceArticle

Fracture Characterisation and Modelling of AHSS Using Acoustic Emission Analysis for Deep Drawing

by Eugen Stockburger, Hendrik Wester and Bernd-Arno Behrens

J. Manuf. Mater. Process. 2023, 7(4), 127; https://doi.org/10.3390/jmmp7040127 - 05 Jul 2023

Viewed by 982

Abstract

Driven by high energy prices, AHSS are still gaining importance in the automotive industry regarding electric vehicles and their battery range. Simulation-based design of forming processes can contribute to exploiting their potential for lightweight design. Fracture models are frequently used to predict the [...] Read more.

Driven by high energy prices, AHSS are still gaining importance in the automotive industry regarding electric vehicles and their battery range. Simulation-based design of forming processes can contribute to exploiting their potential for lightweight design. Fracture models are frequently used to predict the material’s failure and are often parametrised using different tensile tests with optical measurements. Hereby, the fracture is determined by a surface crack. However, for many steels, the fracture initiation already occurs inside the specimen prior to a crack on the surface. This leads to inaccuracies and more imprecise fracture models. Using a method that detects the fracture initiation within the specimen, such as acoustic emission analysis, has a high potential to improve the modelling accuracy. In the presented paper, tests for fracture characterisation with two AHSS were performed for a wide range of stress states and measured with a conventional optical as well as a new acoustical measurement system. The tests were analysed regarding the fracture initiation using both measurement systems. Numerical models of the tests were created, and the EMC fracture model was parametrised based on the two evaluation areas: a surface crack as usual and a fracture from the inside as a novelty. The two fracture models were used in a deep drawing simulation for analysis, comparison and validation with deep drawing experiments. It was shown that the evaluation area for the fracture initiation had a significant impact on the fracture model. Hence, the failure prediction of the EMC fracture model from the acoustic evaluation method showed a higher agreement in the numerical simulations with the experiments than the model from the optical evaluation. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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17 pages, 10348 KiB

Open AccessEditor’s ChoiceArticle

Characterization of the Fracture Forming Limits by Radial Extrusion

by Rui F. V. Sampaio, João P. M. Pragana, Ivo M. F. Bragança, Carlos M. A. Silva, Chris V. Nielsen and Paulo A. F. Martins

J. Manuf. Mater. Process. 2023, 7(3), 107; https://doi.org/10.3390/jmmp7030107 - 01 Jun 2023

Cited by 2 | Viewed by 1482

Abstract

This paper introduces a new formability test based on double-action radial extrusion to characterize material formability in the three-dimensional to plane-stress material flow transitions that are found in bulk metal-formed parts. The presentation draws from a multidirectional tool, which was designed to convert [...] Read more.

This paper introduces a new formability test based on double-action radial extrusion to characterize material formability in the three-dimensional to plane-stress material flow transitions that are found in bulk metal-formed parts. The presentation draws from a multidirectional tool, which was designed to convert the vertical press stroke into horizontal movement of the compression punches towards each other, aspects of experimental strain determination, fractography, and finite element analysis. Results show that three-dimensional to plane-stress material flow transitions at the radially extruded flanges lead to different modes of fracture (by tension and by shear) that may or may not be preceded by necking, such as in sheet metal forming. The new formability test also reveals adequate characteristics to characterize the failure limits of very ductile wrought and additively manufactured metallic materials, which cannot be easily determined by conventional upset compression tests, and to facilitate the identification of the instant of cracking and of the corresponding fracture strains by combination of the force vs. time evolutions with the in-plane strains obtained from digital image correlation. Full article

(This article belongs to the Special Issue Selected Papers from the 20th International Conference on Sheet Metal (SHEMET 2023))

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