https://popups.uliege.be/esaform21/index.php?id=80 Coordinator: Prof. Gianluca Buffa Co-Organisers: Prof. Marion Merklein, Prof. Peter Groche Description: The main topics of the minisymposium are: mechanical fastening operations (clinching, riveting and so on); friction welding; friction stir welding and friction stir spot welding; hybrid joining processes; innovative joining processes (also using adhesives) including forming or pre-forming of the materials to be joined; computational methods for joining simulation of processes; applications of inverse analysis to material characterization in joining conditions; part integrity (prediction of residual stresses, distortions ecc); innovative measurement methods and devices to detect relevant variables in joining by forming (temperatures, pressures, vibrations, wear ….) Mini Symposia fr Wed, 03 Mar 2021 09:34:04 +0100 Wed, 14 Apr 2021 09:54:32 +0200 https://popups.uliege.be/esaform21/index.php?id=80 0 https://popups.uliege.be/esaform21/index.php?id=398 The growing demands of resource-saving processes and products are leading to increasing importance of lightweight construction for the automotive industry. One approach is multi-material design, which uses high-strength steels and aluminium alloys in the production of vehicle bodies. Therefore, reliable processes for joining components with different mechanical properties and geometries are necessary. As conventional joining processes reach their limits, new versatile processes and methods are required which can adapt to different process conditions and disturbance variables. A widely used joining process to join different materials is self-piercing riveting as a joining by forming method, however it is characterised as inflexible to changing process conditions due to a linear process kinematic and rigid dies. An approach to extend the process limits is the application of a tumbling kinematic for the punch. Thus, an adapted tumbling strategy can be used to influence the joining process and to achieve a controlled material flow in order to manufacture tailored joints. For the fundamental investigation of the process, numerical investigations are necessary. In order to achieve high model quality a precise material modelling is crucial. Therefore, a characterisation of the materials HCT590X+Z and EN AW-6014 as typical materials of multi-material mixes and the rivet material 38B2 is performed. Due to the different stress conditions during tumbling self-piercing riveting suitable characterisation methods are selected and carried out. Fri, 19 Mar 2021 18:17:54 +0100 https://popups.uliege.be/esaform21/index.php?id=398 https://popups.uliege.be/esaform21/index.php?id=867 Electrohydraulic forming is a high-speed process, which is based on a force transmission by a working media. In this process, shock waves transmit the punching force in a very short period of time. These shock waves are applied to accelerate the workpiece towards a passive die. Besides forming and embossing of sheets and tubes, joining of sheets with tubes is enabled as a novel application presented in this contribution. Thereby, the tube is embedded temporarily in the die as a functional part. By accelerating the sheet towards the tube end, the joint is formed. This study deals with the question of how this joint is formed in sense of process kinematics and material flow. Therefore, the loading energy, the distance of sheet and tube as well as the sheet thickness was varied and the influence of these parameters and geometric conditions of the tube on the process and resulting joints was observed. Joining of EN AW-1050 aluminum alloy sheets to EN AW-6060 aluminum alloy tubes was performed. These joints were analyzed by microsections and head tension tests. The investigations introduce the new joining process regarding its process behavior and show first joining results. Sun, 21 Mar 2021 22:29:48 +0100 https://popups.uliege.be/esaform21/index.php?id=867 https://popups.uliege.be/esaform21/index.php?id=942 Accumulative roll-bonding (ARB) is a novel plastic straining process aimed at bonding of similar and dissimilar metal combinations. Moreover, it is used recently to produce ultrafine grain materials and metal matrix reinforced composites to enhance mechanical, electrical, and corrosion resistance properties. This work presents an experimental study of roll bonding and accumulative roll bonding of similar AA3105 aluminum alloy at 300°C with a final thickness of 1.2 mm, focusing especially on bond strength evaluation and layers continuities. Tensile tests and three-points bending were performed to mechanical characterize the produced sheets in the various steps and based on the number of the cycles. The maximum strength was reached after 3 ARB cycles. After 4 cycles, the bonding interfaces have a uniform distribution through the sheet thickness, it is possible to distinguish only the interface formed in the last pass in the fracture surface, and no significant enhancement in strength was observed. Starting from 2 ARB cycles, micro-cracks were observed at the outer surface for bending angles greater than 90 deg, and at 180 deg all ARBed samples except A1 were failed. Mon, 22 Mar 2021 10:27:45 +0100 https://popups.uliege.be/esaform21/index.php?id=942 https://popups.uliege.be/esaform21/index.php?id=1613 The increased use of polymer-based material in the manufacturing of vehicles structures makes critical the management of multi-material interfaces, and hence the issue of polymer-metal joining. It has been demonstrated in the literature that for large-scale manufacturing, self-piercing riveting (SPR) represents a reliable alternative technique to conventional resistance spot welding (RSW). However, the riveting operation induces, by nature, damages to the joint composite layer due to the steel rivet crossing it. In this study, the damage of the SMC thermoset material during SPR process has been experimentally investigated. Moreover, the influence of the riveting velocity as a major SPR process parameter on the composite layer damage has been identified. Eventually, the failure mechanisms of the polymer-metal joint resulting from failure under lap-shear and pure tension loadings were studied with the support of the numerical simulation tool. Mon, 22 Mar 2021 20:17:44 +0100 https://popups.uliege.be/esaform21/index.php?id=1613 https://popups.uliege.be/esaform21/index.php?id=1911 The use of high-strength steel and aluminium is rising due to the intensified efforts being made in lightweight design, and self-piercing riveting is becoming increasingly important. Conventional rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and the coating. To shorten the manufacturing process, the use of stainless steel with high strain hardening as the rivet material represents a promising approach. This allows the coating of the rivets to be omitted due to the corrosion resistance of the material and, since the strength of the stainless steel is achieved by cold forming, heat treatment is no longer required. In addition, it is possible to adjust the local strength within the rivet. Because of that, the authors have elaborated a concept for using high nitrogen steel 1.3815 as the rivet material. The present investigation focusses on the joint strength in order to evaluate the capability of rivets in high nitrogen steel by comparison to conventional rivets made of treatable steel. Due to certain challenges in the forming process of the high nitrogen steel rivets, deviations result from the targeted rivet geometry. Mainly these deviations cause a lower joint strength with these rivets, which is, however, adequate. All in all, the capability of the new rivet is proven by the results of this investigation. Tue, 23 Mar 2021 10:35:05 +0100 https://popups.uliege.be/esaform21/index.php?id=1911 https://popups.uliege.be/esaform21/index.php?id=1948 Three-dimensional modelling enables to determine the in-plane material flow in asymmetrical situation. Thus, the distortion of the sheets to be joined can be characterized more exactly. This study shows a method for building up a three-dimensional shear-clinching framework without damage criteria. In fact, the die-sided sheet in shear-clinching was designed as a pre-punched sheet and slugs. The material separation in the die-sided joining partner, which in two-dimensional simulation is often described by macro- and micromechanical fracture criteria, was realised in this study based on a defined contact condition. By means of a shear-cutting simulation, a correlation between the break angle and the separation stress was determined, which was used as a separation criterion in the shear-clinching simulation. The separation line was confirmed using post-particles. To validate this model, the results of the simulation using a quadratic single-point specimen were compared to the experiments with respect to the distortion of the joining partner. In general, the built three-dimensional framework provides for further tool developments with regard to the reduction of distortion in shear-clinching. Tue, 23 Mar 2021 11:13:32 +0100 https://popups.uliege.be/esaform21/index.php?id=1948 https://popups.uliege.be/esaform21/index.php?id=2611 The present paper offers a FE modeling strategy to predict the stress state in carbon fiber reinforced plastic (CFRP) plate material after installing a Blind Rivet Nut (BRN). In industry, a BRN is a permanent mechanical fastener used to equip plate material with a threaded part. Analogue to the installing process of the more common blind rivet, the BRN deforms plastically in such a way a counter head is formed on the underside of the plate. Simultaneously, the upper side of the deformation chamber expands in the radial direction creating an interference fit. The interference fit together with the counter head units the nut to the plate. However, the high contact forces between the BRN and the plate often cause damage in the CFRP material compromising the integrity of the joint. The latter observation implies that while setting a BRN in CFRP, the detrimental contact forces must be controlled to guarantee a qualitative joint. The necessary understanding of the stress distribution in the plate material is numerically investigated in two steps. In the first step, a computational efficient axisymmetric model is used to reveal the contract pressure between the BRN and the plate during the setting process. In the second step, the contact pressures are transferred to a 3D model of the plate. In this stage, the orthotropic properties of the composite are assigned to the plate material and an adequate failure criterion is adopted. The result is compared to a full 3D model using the Tsai – Wu failure criterion. Wed, 24 Mar 2021 18:30:23 +0100 https://popups.uliege.be/esaform21/index.php?id=2611 https://popups.uliege.be/esaform21/index.php?id=2781 In lightweight design, clinching is a cost-efficient solution as the joint is created through localized cold-forming of the joining parts. A clinch point’s quality is usually assessed using ex-situ destructive testing methods. These, however, are unable to detect phenomena immediately during the joining process. For instance, elastic deformations reverse and cracks close after unloading. In-situ methods such as the force-displacement evaluation are used to control a clinching process, though deviations in the clinch point geometry cannot be derived with this method. To overcome these limitations, the clinching process can be investigated using in-situ computed tomography (in-situ CT). However, a clinching tool made of steel would cause strong artefacts and a high attenuation in the CT measurement, reducing the significance of this method. Additionally, when joining parts of the same material, the sheet-sheet interface is hardly detectable. This work aims at identifying, firstly, tool materials that allow artefact-reduced CT measurements during clinching, and, secondly, radiopaque materials that can be applied between the joining parts to enhance the detectability of the sheet-sheet interface. Therefore, both CT-suitable tool materials and radiopaque materials are selected and experimentally investigated. In the clinching process, two aluminium sheets with radiopaque material in between are clinched in a single-step (rotationally symmetric joint without cut section). It is shown that e.g. silicon nitride is suited as tool material and a tin layer is suitable to enhance the detectability of the sheet-sheet interface. Wed, 24 Mar 2021 18:59:21 +0100 https://popups.uliege.be/esaform21/index.php?id=2781 https://popups.uliege.be/esaform21/index.php?id=3649 The determination of ideal process parameters for mechanical joining processes such as self-pierce riveting currently requires a comprehensive understanding of the process, the availability of the materials to be joined and the corresponding system technology. General process models can simplify the use of these joining technologies, accelerate development cycles and thereby reduce the effort for implementation into production. In this paper, the development of general data-based process models for the mechanical joining method self-pierce riveting with semi-tubular rivet is described. Extensive experimental and numerical investigations with more than 2300 joint combinations for steel and aluminum sheets with tensile strengths between 240 - 1020 MPa were generated for the building of the models. Based on these results, different meta-models are fused into general data-based process models for the self-pierce riveting process in order to show the general relationships between material properties, process parameters and joining results. The paper discusses the acquisition of the experimental and numerical data, the statistical methods for evaluation and the application of the data-based process models. Mon, 29 Mar 2021 13:55:44 +0200 https://popups.uliege.be/esaform21/index.php?id=3649 https://popups.uliege.be/esaform21/index.php?id=3665 Tailored blanks, especially semi-finished parts formed by welding steel and aluminum alloys, are being employed in the automobile industry to reduce the weight of automobiles. However, when dissimilar metals are welded, galvanic corrosion due to differences in ionization tendency occurs, decreasing the reliability of such welded products. In addition, the heat input when aluminum alloys are welded causes an aging problem. In this study, combined-cycle corrosion testing was performed for S45C/6000 series steel/aluminum alloys joined by friction welding. First, S45C steel pipes were joined to A6061-T6 and A6063-T6 aluminum alloy pipes by friction welding. Then, after combined-cycle testing, changes in appearance and joint strength were investigated as the number of cycles increased. In the natural aging test, test pieces were placed in a desiccator whose temperature was adjusted to about 20 °C with a humidity from 0 to 10 %. One piece was removed at predetermined time intervals and used in tensile testing. After tensile testing, fracture surfaces were observed with an optical microscope. For the S45C/A6061 friction- welded material, a decrease in tensile strength was found at the 36th cycle. It was confirmed that the strength of the S45C/A6063 friction-welded material decreased clearly at the 27th cycle. Any obvious changes in strength were not seen in specimens after 540 hours of natural aging. Mon, 29 Mar 2021 14:00:28 +0200 https://popups.uliege.be/esaform21/index.php?id=3665 https://popups.uliege.be/esaform21/index.php?id=3801 Mon, 29 Mar 2021 14:41:07 +0200 https://popups.uliege.be/esaform21/index.php?id=3801 https://popups.uliege.be/esaform21/index.php?id=4008 In recent years, the development of innovative joining methods has increased significantly due to the demands of several industries, such as the naval one, for lightweight structures. In fact, the safeguarding of the sea takes place through the reduction of climate-altering gas emissions, which is induced by energy savings. The latter can be achieved by the adoption of innovative technological solutions inherent to both the manufacturing processes and the increase in the use of light alloys. These solutions can reduce the environmental impact of vessels both in refitting operations and in new buildings. Although its potential in producing effective joints of different materials, the Friction Stir Welding process is still poorly used in the naval field due to difficulties in welding dissimilar joints of thick plates. In this paper, Friction Stir Welding was used to produce joints, in lap configuration, out of two very different, yet widely used in the naval sector, materials. This research work focuses on the engineering of the process, in terms of identification of welding parameters aimed at welding AA5083 H321 aluminum alloy and naval steel grade DH 36 plates with a thickness of 6mm. The results obtained indicate that sound joints can be obtained with a reasonably wide process parameters window when the aluminum plate is placed on top of the steel one. Tue, 30 Mar 2021 09:58:47 +0200 https://popups.uliege.be/esaform21/index.php?id=4008 https://popups.uliege.be/esaform21/index.php?id=4257 Ceramic adhesives are an interesting alternative to traditional methods to join metal to ceramics such as fastening, vacuum brazing and gluing. Ceramic adhesives are made of an inorganic matrix with a filler (alumina, zirconia, silica, etc.), and they require a thermal cure cycle in order to establish adhesion. In this work, the adhesion between two different adhesive and Ti6Al4V is studied in details and the influence of the curing cycle is analyzed. Two different adhesives have been used, the first made of a phosphate matrix with an alumina filler, the second made of a silicate matrix wit an alumina filler. The results indicates that in the case of the first adhesive a high temperature cure it is necessary in order to establish a strong adhesion with the metal; on the contrary the second adhesive is capable to create a strong bonding already at low temperature. Thu, 01 Apr 2021 17:34:23 +0200 https://popups.uliege.be/esaform21/index.php?id=4257 https://popups.uliege.be/esaform21/index.php?id=4277 Driven by the CO2-emission law by the European government and the increasing costs for raw materials as well as energy, the automotive industry is increasingly using multi-material constructions. This leads to a continuous increase in the use of mechanical joining techniques and especially the self-piercing riveting is of particular importance. The reason for this is the wide range of joining possibilities as well as the high load-bearing capacities of the joints. To be able to react to changing boundary conditions, like material thickness or strength variation of the sheets, research work is crucial with regard to the increase of versatility. In this paper, a numerical study of the influences on the selfpiercing riveting process is presented. For this purpose, the influence of different process parameters such as rivet length and die depth on various quality-relevant characteristics were investigated. With the help of the design of experiment, significant influences were determined and interactions between the individual parameters are shown. Thu, 01 Apr 2021 17:46:14 +0200 https://popups.uliege.be/esaform21/index.php?id=4277 https://popups.uliege.be/esaform21/index.php?id=4298 In many branches of production, components using large number of joints are combined together to make complex structures. The use of mechanical joining techniques offers the possibility to join structures with a wide range of material/geometry configurations. Due to changing in material properties during the production of formed parts, the robustness of the joint must be guaranteed. In this regard, a numerical method has been developed to predict the geometrical properties of the joint as a function of pre-straining of the metal sheets. In this way, the material combination and the joining tools are to be considered. The resulting metamodels were used to estimate the robustness of the joining process. In this study, the method is extended by a numerical load capacity model, which is generated from the joining process model using an automatic algorithm. The simulation model used for predicting the load capacity is validated by experiments. It is shown that the resulting automatic method is able to completely map a process chain and to predict the load capacity of the mechanical joints under consideration of the pre-strain. Furthermore, the correlation between the pre-strain and the load capacity is presented. Thu, 01 Apr 2021 17:54:38 +0200 https://popups.uliege.be/esaform21/index.php?id=4298 https://popups.uliege.be/esaform21/index.php?id=4327 This work evaluates the viability of applying Friction Riveting as an alternative for the assembly of components on printed circuit boards (PCBs). The popular press-fit technology for assembling components on PCBs consists of a pin inserted tightly into a relatively smaller hole, resulting in good electrical and mechanical properties. However, some limitations are highlighted, such as numerous processing steps and the need for predrilled holes. Friction Riveting is based on mechanical fastening and friction welding principles, where polymeric components are joined with metallic rivets through frictional heating and pressure. The main benefits of using Friction Riveting in PCBs compared with fit-press are (i) a reduced number of processing steps and (ii) shorter joining cycles, because there is no pre-drilling involved with fasteners anchored within the PCB in a single step. The joints were manufactured using 5 mm diameter AA-2024-T3 rivets and 1.5 mm thick glass-fiber-reinforced epoxy laminates (FR4-PCB). It is shown for the first time that it is possible to deform metallic rivets within thin composite plates at a reduced diameterto-thickness ratio. The feasibility study followed a one-factor-a-time approach for parameter screening and optical microscopy assessed joint formation of the deformed rivets inside the laminates through volumetric ratio (VR). The joints present significant deformation (VR=0.5) at the tip of the rivet inserted into overlapped PCBs plates, with thicknesses below 3.0 mm, which is considered the lowest achieved so far with Friction Riveting. Thu, 01 Apr 2021 18:09:34 +0200 https://popups.uliege.be/esaform21/index.php?id=4327 https://popups.uliege.be/esaform21/index.php?id=4682 Joints are an essential part of modern (lightweight) structures in a broad variety of applications. The reason for this is the rapidly increasing number of different material combinations needing to be joined in application areas like the automotive industry. It is currently common to use numerous auxiliary or standardized elements instead of individually adapted joining elements. This leads to a large number of different joining elements per product and thus to high costs. An innovative approach to overcoming this issue is the design, manufacture and setting of joint-specific joining elements. A good candidate for the manufacture of adapted joining elements of this type is the so-called friction spinning process. The joining elements formed in this way can be specifically adapted to the application in question in terms of both shape and mechanical properties. The part geometry required for the properties of a given joint is formed using a universal forming tool. This makes it possible to form a wide variety of sub geometries for the auxiliary joining part as a function of the prevailing joint condition, using a single forming tool and starting from the same semi-finished bar material. By applying different process strategies for the rotational speed and feed rate during the forming operation, the same part geometry can even be given different local mechanical properties. The following contribution presents the results of ongoing research work and includes the process concept, process properties, tooling and the results of experimental investigations into the joining of two sheet metal parts with help of this new joining process. Thu, 08 Apr 2021 18:56:17 +0200 https://popups.uliege.be/esaform21/index.php?id=4682