bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Tube Expansion Test with Elastomer Using Locally Overaged AA6063 Tubes
Authors: Piccininni Antonio , Silva Maria Beatriz , Palumbo Gianfranco
Published: July 2022

The definitive implementation of Aluminium alloys as the main choice for lighter structural components needs the availability of innovative manufacturing processes capable of overcoming their poor formability at room temperature. The local modifications of the material properties (by means of short-term heat treatments) have shown their effectiveness in such terms. In a previous study from the same authors, it was experimentally investigated that, if a AA6063-T6 tubular component is locally brought to the overaged condition, its strain behavior significantly changes during an expansion test with elastomer. In light of this, the equipment used for the tube expansion tests was simulated by means of a FE model created using Abaqus and properly tuned using data coming from experimental tests carried out on AA6063-T6 tubular specimens. The calibrated model could be thus used to simulate the tube expansion while considering several distributions of the material properties (obtained through different heating strategies). Numerical results confirmed the possibility to change the slope of the strain path, thus suggesting that the strain behavior of a tubular component can be tailored, according to the specific applications, by properly designing the laser heating strategy.
Work Hardening of Metallic Sheets under Tension-Compression and Simple Shear Reverse Loading
Authors: Cruz Daniel J. , Pereira André F.G. , Simões Vasco M. , Amaral Rui , dos Santos Abel , Oliveira Marta C.
Published: July 2022

The hardening models have a significant influence on the accuracy of finite element analysis (FEA). Although, isotropic hardening models are the most widely used, it is known that kinematic hardening models (describing the Bauschinger effect and permanent softening) can significantly improve the accuracy of FEA results. However, when considering sheet metal materials, the parameters of kinematic hardening models are difficult to identify due to the challenges of obtaining experimental results from test with strain path inversions. This work considers an experimental procedure that enables the analysis of the mechanical behaviour of sheet metal materials submitted to reverse loadings. A miniaturized test device was developed to perform tension and compression tests, with reverse loadings, for sheet metal materials. This specimen design has two main advantages: (1) reduces buckling during compression (compared to standard tensile test specimens) and, consequently, (2) enables the characterization of the mechanical behaviour under reverse tension-compression strain paths changes. The small size of the specimens, with 2 x 2 mm gauge area, poses the main challenge of the current methodology, namely the measurement of the strain field distribution using the Digital Image Correlation (DIC) technique. The results obtained from tension-compression tests with mini-specimens are validated by comparison with standard tensile and shear (reverse loading) and tests.
Work-Hardening Behavior of a ZX10 Magnesium Alloy Sheet under Monotonic and Reverse Loadings
Authors: Hama Takayuki , Higuchi Koichi , Yoshida Hikaru , Jono Yuri
Published: July 2022

Magnesium (Mg) alloy sheets are expected to be used as light-weight materials for structural components because of their low density and high specific strength. However, their press formability at room temperature is poor due to the strong crystal anisotropy of the hexagonal structure and the strong basal texture especially observed in AZ series rolled Mg alloy sheets. Recently, ZX series Mg alloy sheets have been developed that weaken the basal texture, thus improving press formability at room temperature. Although the plastic deformation behavior of ZX series Mg alloy sheets should be different notably from that of AZ series Mg alloy sheets, it is not substantially understood yet. In the present study, the work-hardening behavior of a rolled Mg-1.5mass%Zn-0.1mass%Ca (ZX10Mg) alloy sheet under monotonic and reverse loadings was investigated in detail experimentally. The microstructures of prestrained samples were also measured by means of EBSD measurements. Under monotonic tension, the stress in the rolling direction is higher than that in the transverse direction. A plateau region appears only in the transverse direction. Under monotonic compression, plateau regions appear in both the rolling and transverse directions. The in-plane anisotropy is less pronounced than that under tension. Under reverse loading from compression to tension, a sigmoidal curve appears during tension regardless of the loading direction. The sigmoidal trend depends strongly on the loading direction. The mechanisms that induce the abovementioned anisotropic deformation are discussed in terms of the difference in twinning and detwinning activities.
Influence of the Workpiece Material and Cooling Condition on the Texture Obtained through Ultrasonic Vibration-Assisted Machining
Authors: Bertolini Rachele , Castagnotto Ilaria , Ghiotti Andrea , Bruschi Stefania
Published: July 2022

Ultrasonic Vibration-Assisted Machining (UVAM) has been investigated as one of the most suitable methods to imprint patterns on metal surfaces. Actually, UVAM, as a consequence of the superimposition of a high-frequency and small-amplitude vibration to the cutting tool motion, makes possible the generation of micro-textured surfaces. On the basis of the vibration pattern and parameters, cutting process and tool characteristics, micro-dimples of different morphology and dimension can be obtained. However, the literature review has evidenced that none of the available studies considered the influence of the cooling conditions as well as the workpiece material on the obtainable dimples geometry. To this aim an UVAM experimental campaign was carried out at varying cutting speed, workpiece material and cooling conditions. Then, the surface finish was evaluated in terms of dimples size and surface roughness. Experimental results showed that deeper dimples are obtained for materials characterized by higher elastic modulus and machined under cryogenic cooling.
Measurement of Biaxial Deformation Behavior and Material Modeling for HI-PVC Using Multiaxial Tube Expansion Test
Authors: Obuchi Shintaro , Kubo Sohta , Kuwabara Toshihiko
Published: July 2022

This study investigates the biaxial deformation behavior of the High Impact Polyvinyl Chloride (HI-PVC) used as a water pipe material. Multiaxial tube expansion test (MTET) was performed on the HI-PVC circular tube, and the stress-strain curves were measured for nine linear stress paths. The contours of plastic work and the directions of the plastic strain rates were also measurd. The experimental results show that the test sample has a strong anisotropy. Anisotropic hardening behavior was also confirmed from the evolution of the work contours. It was confirmed that the Yld2000-2d yield function had a better agreement with the measued work contour than Hill’s quadratic and the von Mises yield functons. Moreover, it was found that the test sample follows the normality rule with the Yld2000-2d yield function.
Exploring Potentialities of Direct Laser Deposition: Thin-Walled Structures
Authors: Silvestri Alessia Teresa , Perini Matteo , Bosetti Paolo , Squillace Antonino
Published: July 2022

In the context of Industry 4.0, the interest towards the additive manufacturing processes is growing due to their numerous advantages, such as the possibility to prototype, the reduction of waste material, the inferior time to market, ad so on. In particular, a promising technology is the Direct Laser Deposition, which uses a focused laser beam to melt powders as there are deposited. In opposition to the well-established powder-bed fusion technologies, there are still some issues related to this process. This work aims to solve one of them, exploring the potentialities of DLD in printing thin-wall structures. For this purpose, the influence of the adopted deposition strategy and of the layer thickness on the geometrical accuracy and mechanical properties has been investigated. The results have pointed out that the first variable strongly influences the workpiece. It is possible to deposit thin-wall structures with a ZigZag strategy and consider a layer thickness equal to 90% of the height of the single track, printed with the same process parameters.
Thermal Barrier Coatings (TBCs) Produced by Air Plasma Spray: Repair by Grinding and Waterjet (WJ) Processes
Authors: Boccarusso Luca , Durante Massimo , Formisano Antonio , Langella Antonio , Minutolo Fabrizio Memola Capece
Published: July 2022

TBCs (Thermal Barrier Coatings) are multilayer structures usually consisting of a ceramic layer, known as top coat, arranged on a connecting layer, known as bond coat, which, in turn, is arranged above the substrate to protect. These structures are applied in hot section parts of gas turbine engines for providing thermal protection. During the component life, some oxidation end/or wear phenomena can occur, therefore the TBC is generally removed and then reapplied. To simplify the manufacturing process making it more cost effectiveness, the aim of this work is to study the possibility to repair a TBC system by removing the only damaged layer by using non-conventional processes and analyzing in detail the morphological roughness to ensure a good adhesion between the layers.
Frictional and Cohesion Behavior of Natural Tows in Order to Assess the Tow Sliding during Composite Forming
Authors: Salem Mohamed Medhat , De Luycker Emmanuel , Fazzini Marina , Ouagne Pierre
Published: July 2022

The tow sliding defect cause of the apparition of gaps in the reinforcement during woven reinforcement preforming is due to tows failing to accommodate the shape and sliding instead of holding together. The main reason for the defect formation can be attributed to increased pressure or tensions in some tows. Several parameters such as the reinforcement material, weave and tows orientation can significantly impact the sliding of tows and the apparition of the defect. In order to assess the tow sliding, it is important to understand the frictional behavior of the tows as units and the effect of the cohesion of the reinforcement as a whole. In this study, the frictional behavior of the tows was compared to their sliding behavior inside the reinforcement as whole in different conditions using two different methods.
On Considering the Influence of Kinematic Hardening in Finite Element Simulation of Hot Levelling of Structural Steel Heavy Plates
Authors: Baru Naveen Krishna , Laugwitz Marvin , Jochum Martin , Lohmar Johannes
Published: July 2022

Flatness is an important quality parameter of heavy plates and it is generally achieved through cyclic elastoplastic deformation of the plate in a hot roller leveller following the rolling and cooling processes. To investigate and optimize the hot plate levelling (straightening) process, Finite Element (FE) simulations are widely used. Generally, flow curves with isotropic hardening are used for hot plate levelling simulations. However, the plate material might exhibit kinematic hardening, due to the load reversal that is seldom considered due to laborious high temperature cyclic material characterization. The current work aims at understanding the implications of considering kinematic hardening within hot heavy plate levelling simulations. Hot uniaxial and cyclic material characterization of S355 steel at 1000 °C is performed and the corresponding stress-strain curves are extracted. Using an inverse modelling technique, the associated isotropic and kinematic hardening models are calibrated. The cyclic data showed that the S355 steel exhibits kinematic hardening and the Chaboche kinematic hardening model is suitable to model this behaviour. Hot levelling simulations of plates with isotropic and kinematic hardening models showed a noticeable difference in the roll reaction forces and local curvature of the plate during the process while the resulting flatness of the final plate is not very sensitive to the material model for the investigated scenarios.
Offline Robot-Path-Planning and Process Simulation for the Structural Analysis of Coreless Wound Fibre-Polymer Composite Structures
Authors: Hügle Sebastian , Genc Enis , Dittmann Jörg , Middendorf Peter
Published: July 2022

In the coreless filament winding process (CFW) anchor points are wrapped with pre-impregnated fibre bundles (Towpregs) in a defined chronological order. With this process, fibre-polymer composite structures with a very high lightweight potential and very little material consumption can be created for different applications in the automotive, aeronautical, sports and architectural sector. The winding sequence and the fibre interaction thereby does have an influence on the final fibre architecture and thus on its structural behaviour. To take this into account a process chain for path planning and process simulation out of a design model is presented. To achieve flexible considerations of different design concepts a parameter-based method for the necessary path planning of the final three-dimensional fibre architecture is introduced. The approach is evaluated on different kinds of specimen.
Characteristics of the Combined Rolling and Extrusion Process
Authors: Heinzel Christoph , Müller Sören
Published: July 2022

The combination of the conventional forming processes rolling and extruding enables the continuous production of cross-sectional aluminum long products. Regarding power consumption and resulting material specifications, the combined process offers various advantages in comparison to its conventional alternatives [1, 2]. The combined rolling and extrusion process is in an early stage of maturity. The production of pure aluminum wire is state of the art. The material flow within the process can partially reproduced by the use of numerical simulations [3]. Some process specific characteristics need to be understood and controlled to obtain a better process design and to enable the future production of complex cross-sectional products. This paper describes the results of experimental and numerical investigations regarding the combined rolling and extrusion process. The test specimen of a visioplastic examination on an industrial scale plant [3] was examined by the use of metallography. Those results where compared to a numerical simulation of the industrial experiment. The comparison of these results where then linked to some specific characteristics of the process. The existence of a dead zone with a shape comparable to the conventional indirect extrusion process was proved. The deformation zone of the combined process was divided into four zones which can be differentiated in the experimental as well as the numerical results. General design rules were derived from this differentiation. These design rules were used to optimize the forming geometry of an industrial scale plant. Critical process forces where reduces and resulting scrap material was minimized.
Resistance Heating by Means of Direct Current for Resource-Saving CO2-Neutral Hot Stamping
Authors: Behrens Bernd-Arno , Hübner Sven , Albracht Lorenz , Farahmand Ehsan
Published: July 2022

Hot stamping is a well-established and frequently used manufacturing process in automotive body construction. The number of components manufactured in this way is continuously increasing. Hot stamping is used to produce components with a completely martensitic structure, resulting in high strength and hardness. These components are mainly used in safety-relevant areas of the passenger cell, such as the A-pillar, B-pillar, tunnel and sill. For hot-stamping processes, it is necessary to austenitize the blanks. Heating the sheet metal up to 930 °C in a furnace is very energy-intensive. In large-scale industrial applications, the sheets are generally heated in gas-fired roller hearth furnaces up to 60 m long. Apart from the poor energy balance and the high CO2 emissions of such furnaces, they are associated with high investment and maintenance costs, large space requirements and a long heating time. Rapid heating by means of the Joule effect and direct current instead of alternating current offer an energy-efficient and environmentally friendly alternative for sheet metal heating. Therefore, this technology can make a major contribution to environmental protection and resource saving. Within the scope of this work, parts were rapid-heated and subsequently hot-stamped by means of a novel heating system based on direct current with energy savings of up to 80 %. Using electricity guarantees a good CO2 balance. In addition, resistance heating with a new type of DC-heating system and an adapted process chain is compared with conventional furnace heating. In thermographic images and microstructural examinations of the hot-stamped parts, it can be demonstrated that this direct-current technique is well suited for achieving homogeneous hardness and strength in the whole sheet metal. Thus, this new heating system can enhance the efficiency of the hot-stamping technology.
Reduced FFT-Based Simulation of a Mechanically Loaded Clustered Microstructure Using an Adaptive Set of Fourier Modes
Authors: Waimann Johanna , Gierden Christian , Schmidt Annika , Svendsen Bob , Reese Stefanie
Published: July 2022

Processes, such as deep rolling or induction hardening, have a remarkable influence on the material properties within the surface layer of a work piece. Our overall goal is to develop efficient two-scale methods, which are able to show the microstructural evolution of the machined material. The calculation of a spatially resolved microstructure comes along with a high computational effort. To reduce the computational costs, we combine a clustered description of the structure [1] with a model order reduction technique for the performed fast Fourier transformations (FFT) [2]. We choose a reduced set of Fourier modes, which is adapted to the underlying microstructure and thus based on the occurring strain field [3]. By that, we analyze the influence of a mechanical impact on an elasto-plastically deforming material.
A Hypoelastic Approach for Simulating the Independent Bending Behavior of Textile Composite within the Stress Resultant Shell
Authors: Chen Bo , Boisse Philippe , Colmars Julien , Naouar Naim
Published: July 2022

In the textile composite drape process, the material bending behavior plays a critical role in the onset and development of wrinkles. The bending moment is linked with the membrane forces in the classical shell element which leads to the insufficient for the textile composite draping simulation. Specific to the textile composite, a hypoelastic approach is proposed within the stress resultant shell. A bending stiffness independent of membrane stiffness is introduced to calculate the stress moments in the finite element analysis. This approach is implemented in the commercial software Abaqus, which makes it possible for any user of this software.
Error Estimation of the 3D Reconstruction of a Displacement Field from DIC Measurements
Authors: Oliveira Miguel Guimarães , Lattanzi Attilio , Thuillier Sandrine , Andrade-Campos António , Rossi Marco
Published: July 2022

To enable an accurate simulation of manufacturing processes, it is essential to characterise and model the mechanical behaviour of sheet metals up to large deformations. However, after the onset of necking, deformation becomes highly heterogeneous and the stress is triaxial. By combining full-field measurements and inverse methods, it is possible to calibrate the mechanical behaviour beyond necking. A possibility is to use the virtual fields method, by extending its formulation to a fully three-dimensional approach. However, measuring deformation in the bulk of the material is still a challenge. To address this limitation, a volume reconstruction method able to estimate the deformation inside the specimen was proposed and successfully validated. The aim of this work is to estimate the error of the volume reconstruction method by using a simulated tensile test and the measurement chain associated with a virtual stereo-DIC setup composed of four cameras. A three-dimensional finite element model is used to deform synthetically generated images. The DIC field maps obtained with different setup configurations and DIC settings are used to estimate the error by comparing the reconstructed volume with the reference finite element model. Results show that the impact of conditions and DIC settings on the reconstructed volume is low.
Preliminary Study on the Onset of Necking Detection Using DIT in Tensile Tests
Authors: Palomo David , Martínez-Donaire Andrés J. , Fernández José Andrés López , Borrego Puche Marcos , Vallellano Carpoforo
Published: July 2022

The experimental detection of localized necking is an important issue in sheet metal forming. Today, the most common and extended techniques are strain-based methods using digital image correlation (DIC). The present work discuses a thermal methodology to detect the onset of necking in metals based on the analysis of the temperature gradient using digital infrared thermography (DIT). A series of tensile tests of H240LA-O3 high-strength steel of 1.2mm thickness is analysed using DIC and DIT techniques. It is proposed that necking initiates when the temperature difference at a reference distance from the necking point reaches a critical value, which allows identifying the necking time and estimating the limit strains from the visible images using circle grid analysis.
Impact of a Splined Mandrel Geometry on Die Filling in a Cold Forging Process with Adjustable Deformation Zone
Authors: Weiss Alexander , Arny Mario , Liewald Mathias
Published: July 2022

Manufacturing of hollow components with local functional internal surfaces often requires complex process routes with several individual operations. By using a special hollow cold forging process with an adjustable deformation zone it is possible to manufacture hollow shafts with varying wall thickness over its axial length parts just within a single stroke of the press. Combining this principle with a splined mandrel allows manufacturing of tailored hollow shafts with local internal splines. However, the impact of geometry of mandrel and other process parameters on the shape of the cold forged internal splines have not been investigated yet. Furthermore, an underfilling phenomenon can occur on the outer surface of shaft during specific process states. In this contribution, several mandrel geometries and their impact on the part shape and filling / underfilling phenomenon in the mentioned process are investigated. To determine those effects, a numerical investigation has been conducted. Besides the geometry of the splined mandrel, also other parameters such as die geometry and tool kinematics were considered. The numerically calculated workpiece geometries are compared to the ideal geometries using a deviation analysis.
DIC Strain Monitoring during Fatigue of Cold-Formed High Strength Steel
Authors: Gothivarekar Sanjay , Van Bael Albert , Talemi Reza , Coppieters Sam
Published: July 2022

Owing to the progressive use of cold-formed high strength steel (HSS) for transportation applications, a characterisation of the fatigue behaviour of HSS has become a focal point for material scientists and design engineers. To mimic the behaviour of cold-formed components, a specimen was adopted from previous research that features multiple bent sections. The geometry was obtained by consecutive bending operations at room temperature. When subsequent tensile cyclic loading is applied to the specimen, the localised damage from forming and stress concentrations cause crack initiation on the inside of the bent area. To investigate the effect of cold-forming on the fatigue behaviour experimentally, the evolution of the strain, displacement or stiffness can be monitored during fatigue testing. The current paper presents an experimental framework for investigating the strain fields of a bent specimen during fatigue. The evolution of the strain fields is then linked with characteristic fatigue mechanisms, such as crack initiation and growth.
Role of Viscosity on Optimum Polymer-Fibre Interaction during Rotational Moulding Sintering
Authors: Castellanos David , Martin Peter , McCourt Mark , Kearns Mark , Butterfield Joseph , Cassidy Patrick
Published: July 2022

The present work investigated the effect of polymer viscosity properties on the sintering of a fibre-reinforced rotationally moulded composite part. Previous researchers have concluded that polymer characterisation is fundamental to achieving optimum composite materials processing in rotational moulding. Nevertheless, the presence of a disperse phase during sintering directly impacts the current understanding of how sintering works during heating. Lack of pressurisation during rotational moulding implies an absence of driving forces to strongly bond two materials together as necessary in composite structures. It means that sintering and densification are the fundamental phases in which two or more materials can create an interface that can transmit stresses. A novel single-particle interaction test (FPIT) investigated the effect of polymer adhesion during sintering. The test was developed to identify the optimum parameters to achieve the best polymer adhesion to the fibre. The test focused on measuring the polymers' angle of contact (AoC) to the fibre to better understand how to achieve optimum fibre coverage. Combinations of glass fibre (G.F.) with polyethylene (P.E.) of various melt flow indexes (MFI) were tested to identify the role of viscosity on fibre-polymer adhesion. Attempts to automate the contact angle measurement proved challenging, so manual measurement proved to be more effective. Sintering results showed that polymer viscosity has a critical effect on fibre wetting, and the use of Hi-MFI resins or plasticisers can improve adhesion. Finally, results showed that polymer-fibre characterisation plays a crucial role in sintering and densification, and work is ongoing to present conclusions about how sintering and densification affect the full-scale manufacturing process.
Numerical and Experimental Investigations in Orthogonal Milling of 15-5PH Stainless Steel
Authors: Methon Grégory , Courbon Cédric , M'Saoubi Rachid , Girinon Mathieu , Rech Joël
Published: July 2022

The present work presents the development of a numerical model to assess the machining performance in milling of a 15-5PH stainless steel. At first an experimental campaign was conducted using PVD coated TPUN inserts under three levels of cutting speed and feed: 100-170-240 m/min & 0.25-0.35-0.45 mm/rev. Forces were recorded using a Kistler 9257A dynamometer. For each experimental test, chips were mounted and polished to evaluate the chip thicknesses and contact lengths measured on inserts’ rake face. Regarding the numerical simulation, a 2D Arbitrary-Lagrangian-Eulerian (ALE) was then developed in the study. A tool motion was implemented to mimic the chip thickness evolution occurring during the milling process. These simulations allowed to numerically predict the chip thicknesses, contact lengths and cutting forces which were further compared to the experimental data.
Towards 3D Process Simulation for In Situ Hybridization of Fiber-Metal-Laminates (FML)
Authors: Poppe Christian T. , Werner Henrik O. , Kruse Moritz , Chen Hui , Ben Khalifa Noomane , Henning Frank , Kärger Luise
Published: July 2022

Fiber-metal-laminates (FML) provide excellent fatigue behavior, damage tolerant properties, and inherent corrosion resistance.To speed up manufacturing and simultaneously increase the geometrical complexity of the produced FML parts, Mennecart et al. proposed a new single-step process combining deep-drawing with infiltration (HY-LCM). Although the first experimental results are promising, the process involves several challenges, mainly originating from the Fluid-Structure-Interaction (FSI) between deep-drawing and infiltration. This work aims to investigate those challenges to comprehend the underlying mechanisms. A new close-to-process test setup is proposed on the experimental side, combining deep-drawing of a hybrid stack with a linear infiltration. A process simulation model for FMLs is presented on the numerical side, enabling a prediction of the dry molding forces, local Fiber Volume Content (FVC) within the three glass fiber (GF) interlayers, and simultaneous fluid progression. The numerical results show that the local deformation of the hybrid stack and required forces are predictable. Furthermore, lateral sealing of the hybrid stacks leads to deviations from the intended initially one-dimensional fluid progression. Eventually, the numerical results demonstrate that most flow resistance originates from geometrically critical locations. Future experimental and numerical work will combine these insights to focus on the flow evaluation during deformation and a successful part-level application.
Characterization of Yield Surface Evolution of AZ31 from Shear to Equibiaxial Tension
Authors: Lou Yan Shan , Zhang Jia , Zhang Chong , Yoon Jeong Whan
Published: July 2022

This research characterized the strain hardening behavior of AZ31 under different stress states from shear to balanced biaxial tension with a newly proposed yield function. Experiments are conducted for AZ31 magnesium alloy by in-plane shear specimens, dogbone specimens, notched specimens and bulging specimens to characterize the flow behavior under different stress states. The flow behaviors are characterized by a newly proposed yield function in a form of the three stress invariants. The proposed yield function is implemented into ABAQUS/Explicit to predict the plastic response of the alloy under different stress states. It is shown that the proposed yield function can precisely predict the distinct flow behaviors and reaction forces from shear to equibiaxial tension from the initial yielding to fracture.
Extension of a Simulation Model of the Freeform Bending Process as Part of a Soft Sensor for a Property Control
Authors: Stebner Sophie Charlotte , Maier Daniel , Ismail Ahmed , Dölz Michael , Lohman Boris , Volk Wolfram , Münstermann Sebastian
Published: July 2022

This work introduces an Abaqus CAE simulation model and its validation for freeform bending with movable die, which is extended in the simulation of a weld seam for the longitudinally welded tube. The superordinate goal is the development of a soft sensor, that can derive mechanical properties of a freeform bent tube as a basis for a closed-loop control. To guarantee a close monitoring of the mechanical properties, the soft sensor needs to be able to extrapolate the mechanical properties spatially. Because the investigated steel tubes are longitudinally welded, the weld depicts a disturbance regarding the rotational symmetry. In developing and validating a numerical simulation of the process, that quantitatively describes the influences the weld has on the mechanical properties, a significant improvement of the qualitative and quantitative prediction of the soft sensor can be achieved. The numerical modelling is done based on tensile tests on material taken from the weld seam, where hardness measurements are then used for the local validation of the model. The validated model now provides a time as well as cost efficient way of a primary investigation of the mechanical properties, especially regarding the local strength of the steel tube for a soft sensor and as input data for a feed forward control in the machine. Therefore, this work represents an important addition to the superordinate goal of developing a closed-loop property-control based on a soft sensor for freeform bending with movable die.
Numerical Modelling of Conventional and Incremental Forming of Thin-Walled Tube
Authors: Suntaxi Carlos , Centeno Báez Gabriel , Rosa-Sainz Ana , Morales-Palma Domingo , Vallellano Carpoforo
Published: July 2022

This study presents a numerical analysis of the tube expansion process by conventional tube-end forming versus single point incremental forming (SPIF) using DEFORM. The work includes the assessment of the strain paths within the principal strain space of these processes with respect to the formability limits as well as their evaluation within the equivalent strain versus stress triaxiality space. The results obtained demonstrated that the mechanics of tube flaring process in conventional and incremental forming are substantially different. This analysis of formability in the light of the accumulated equivalent strain and the average stress triaxiality allowed a better understanding of the differences between both processes in terms of the fracture limit strains.
Assessment of the Optimization Strategy for Nitrogen Cooling Channel Design in Extrusion Dies
Authors: Pelaccia Riccardo , Negozio Marco , Reggiani Barbara , Donati Lorenzo
Published: July 2022

Aluminum extrusion is an efficient industrial process. However, one of the main problems is related to the temperatures developed during the process that can detrimentally affect the achievable productivity, profile quality and/or die life. Cooling of the die with liquid nitrogen represents an efficient solution to overcome this limit but a further issue arises lying in the number of process and design variables that need to be managed in order to set-up of an efficient system. In this context, a 3D FE model of the extrusion process, coupled with a 1D model of the cooling channel, previously proposed by the authors, has been integrated in an optimization platform in order to iteratively and automatically adjusts the channel geometry and the process variables gaining to a final optimal solution in terms of thermal balance, cooling efficiency and nitrogen consumption. The original channel design used during the extrusion of industrial hollow AA6060 profile guaranteed an efficient but unbalanced cooling with a maximum temperature deviation of 60 °C registered by the thermocouple positioned around the bearings. The optimized designs showed temperature deviations below the 16 °C as well as the reduction of 50% in terms of nitrogen consuming.
Simulation of Coarse Grain Evolution during Hot Extrusion of Al-Mg-Si Alloy
Authors: Kronsteiner Johannes , Hovden Sindre , Arnoldt Aurel , Österreicher Johannes
Published: July 2022

Coarse grains at or near the surfaces of extruded aluminum profiles can have a major detri-mental influence on their ductility and surface quality. Thus, the extrusion industry aims to minimizecoarse grains while increasing the productivity of the process. Peripheral Coarse Grains (PCG) de-velop depending on local state variables such as temperature, strain and strain rate. Here we presenta microstructure based material model implemented into HyperXtrude™, capable of predicting thedevelopment of PCG by combining geometric Dynamic Recrystallization (gDRX) and conventionalgraingrowthmodels.Duetoitshistorydependence,themodelisimplementedtorunduringthewholetransient extrusion simulation. The first results of the predicted ram force as well as final grain distri-bution in the profile show reasonable agreement with experimental trials and electron backscattereddiffraction results.
Post-Forming Limits of Carbon Fibre Reinforced Thermoplastic Tubular Structures in a Rotary Draw Bending Process
Authors: Li Meng Yuan , Stokes-Griffin Chris , Sommacal Silvano , Compston Paul
Published: July 2022

This paper presents the post-forming limits of polyamide 6 carbon (CF/PA6) thermoplastic tubes to facilitate design and process optimisation of bent tubular CF/PA6 part manufacturing. Straight CF/PA6 tubes can be post-formed using rotary draw bending at elevated temperature to achieve desired curvatures. Forming limits of the tubes are predicted based on their winding angles, tube geometry, and bending radius, presented as the relation between tube winding angle and bending ratio. Additionally, the corresponding principal shear strain limits are derived from the winding angle limits and tube axial strains. Three sets of CF/PA6 tubes with the configurations of [±30°]4, [±45°]4, and [±60°]4 are heated to 220 °C and post-formed to a bending angle of 90° with a bending ratio of 2. Micro computed tomography imaging is performed to analyse tube geometry after forming to identify forming and failure modes for tubes beyond the forming limits.
On the Influence of Cross-Section Size on Measured Strength of SLM-Produced AlSi10Mg-Alloy
Authors: Vysochinskiy Dmitry , Akhtar Naureen
Published: July 2022

The freedom in choice of geometries in additive manufacturing (AM) favors the use of structures with large surface and small cross-section such as lattice structures and thin-walled hollow profiles. On the other hand, the practices of strength testing of metals require a certain bulk of the material to be printed to be able to produce a sample and test material properties. The size of the sample cross section might influence the strength and up to 30% decrease in strength for small struts was reported in the literature. Understanding the influence of the cross-section size on the strength of SLM-produced metal is crucial to be able to relate the strength determined through tensile testing and the strength of an SLM-produced component with complex geometry. This article deals with effect of cross-section size on the measured strength of the SLM-produced AlSi10Mg-alloy. It is demonstrated how the decrease in strength can be explained by the difference between measured and actual cross-section area induced by surface roughness rather than by the difference in microstructure between the samples of different sizes.
Copper Wire Multi-Pass Drawing: Process Modeling and Optimization
Authors: Di Donato Sara , Donati Lorenzo , Negozio Marco
Published: July 2022

During cold wire drawing process, the drawing stress applied to the wire at the exit of the die must be lower than the material yield stress (including strain-hardening) to avoid wire necking and fracture. Several studies have been developed to investigate and model the stress acting on the wire in the single pass drawing and its dependence on the main process parameters. The aim of this work is to apply an analytical model for the calculation of the drawing stresses during the whole complex multi-pass manufacturing process in industrial environment, considering not only the forces acting in the die but also the driving forces of the rotating capstans (drawing tension and back tension). The drawing of ETP Pure Copper (99.9% in weight), using two industrial multi-pass machines with different reduction ratio sequences, is analysed and then discussed in order to understand the different failure rates. Finally, the study compared step by step, the evolution of the drawing stresses respect to material yield stress when different processing conditions (i.e. change of capstan windings, change of friction conditions in the die and in the capstan) are applied.
The Analysis of Small-Scale Notches on the Fatigue Performance of SLM Ti-6Al-4V; A Theory of Critical Distances Approach
Authors: Gillham Bobby , Yankin Andrei , Shipley Harry , McNamara Fionnan , Tomonto Charles , O'Donnell Garret , Trimble Daniel , Yin Shuo , Taylor David , Lupoi Rocco
Published: July 2022

Selective Laser Melting is an additive manufacturing practice that permits the production of metal alloy-based parts. While facilitating the design of complex geometry, SLM leads to the fabrication of a unique material structure that showcases distinct behavioural characteristics relative to their traditional methods of material manufacture. Defects that are innate to SLM inspire the presence of a compositional outlook that is inhomogeneous in nature and only serves to hinder part efficiency. Thus, the Theory of Critical Distances offers a refreshed proposal to evaluating notched Ti-6Al-4V material produced by additive manufacturing processes. Key principles of the theory’s working mechanisms are outlined. Subsequently, symmetrical notches of contrasting size are assessed. Findings reveal that the Theory of Critical Distances is adequately compatible with accurate fatigue prediction of SLM Ti-6Al-4V in its as-built state. Additionally, fracture surface analysis reveals that crack initiation is predominantly a surface-based phenomenon. Hereby, increased focus must be given to the quality of processed material that is located at the externalities of additively manufactured components, in order to enhance their service life capabilities. This will induce an increasingly uniform material structure that will allow for more predictable behavioural characteristics.
A Model for Roll-Drawing of Full Sections with Experimental Verification
Authors: Braun Rolf , Ananta Ilham Zuhdi , Buono Gilar Bagaskoro , Overhagen Christian , Uddin Mayeen
Published: July 2022

Roll-drawing of full sections is an alternate process for wire drawing through a closed die, as it conserves less hard tool materials. It therefore enhances the resource efficiency of thin wire production. As the tools are rotating, the relative velocity is lower and friction is reduced. Apart from this, there is only little knowledge about the process mechanics inside the deformation region. According to the relative motion mentioned above, a neutral point should exist within the deformation region, but this hypothesis is unconfirmed until today. In the present work, a combination of an improved empirical model for the lateral spread in roll-drawing and a mechanical model for roll drawing based on the slab method is proposed. The mechanical model deviates from the well-known rolling theory by the fact that a zero deformation torque should exist on the rolls, it predicts the neutral angle, the forward-slip, the external drawing force and the roll separating force. The hypothesis of existence of a neutral point in the deformation region is supported by experimental measurements of the nonzero forward slip in the roll-drawing process. Measurement is done on copper wire, where 200 passes with initial round section sizes ranging from 2 mm to 1.3 mm with an increment of 0.1 mm are evaluated.
Analysis of Side-Wall Wrinkling in Deep Drawing Processes
Authors: Dal Saniye Rabia , Darendeliler Haluk
Published: July 2022

Wrinkling, developed due to compressive instability, is one of the main failure modes in deep drawing processes. Depending on the die geometry and blank holder force, it can be observed as flange wrinkling and/or side-wall wrinkling. In this study, side-wall wrinkling in cylindrical cup drawing process is investigated by using different constitutive models that are formed by using CPB06ex2, Hill’48, BBC2008-8p and BBC2008-16p yield criteria with isotropic hardening, and von Mises yield criterion with isotropic, kinematic and combined hardening. Numerical simulations are performed by implementing CPB06ex2, BBC2008-8p and BBC2008-16p models to a commercial finite element code through user subroutines. AA5042-H2 aluminium alloy is selected as a sheet material with 0.2083 mm thickness. In order to verify the developed models, the experimental results of the previous works for wrinkling profile and punch force evolution are employed. The results are compared and presented for the considered yield criteria.
A Method for Benchmarking of FEM Packages for Multi-Stage Sheet Metal Forming Simulations
Authors: Strano Matteo , Semeraro Quirico , Panzeri Matteo
Published: July 2022

Computer simulation plays a crucial role in the designing of sheet metal stamping processes for the prediction of process output, before try-out die sets are manufactured. Different commercial software packages are available on the market for sheet forming simulation, but their accuracy can vary, depending on the selection of the pre-processing parameters and on their formulation. Software benchmarking can be used to select the most appropriate package for a given application. Calibration, i.e. the inverse determination of the correct set of pre-processing parameters, can be used for improving the prediction accuracy. The scientific literature on numerical simulations of sheet metal forming processes presents some examples of software calibration and very few examples of benchmarking. The literature generally neglects a critical and important issue: the inherent variability of real forming processes. In this work, the experimental results of two similar multi-stage deep drawing processes are presented and compared to the simulation output of two popular software packages used in the industry. Statistical methods for benchmarking and calibration are proposed. The paper demonstrates how benchmarking can be misleading if process variability is not considered.
Distinct Antimicrobial Analysis to Evaluate Multi-Component Wound Dressing Performance
Authors: Padrão Jorge , Pinheiro Inês , Silva Carla , Ribeiro Alice , Bouça Verónica , Melro Liliana , Fernandes Rui Daniel Vilaça , Ribeiro Ana Isabel , Felgueiras Helena , Zille Andrea
Published: July 2022

Wound infection hinders adequate healing, being particularly grievous and prevalent in burn wounds and chronic wounds. Wound infection extends inflammation, preventing epithelialization and angiogenesis. Therefore, infection prolongs healing time, steeply increases treatment costs and degrades patients wellbeing. One successful strategy to control wound infection is to apply an active wound dressing, able to eliminate or significantly reduce the microbial population present at the infection site. Silver nanoparticles (AgNPs) are a multipurpose antimicrobial agent with a wide scope of applications which include wound dressings. Nevertheless, several studies denote AgNPs dose-dependent cytotoxicity, and their capability to bypass the blood-brain barrier and induce a neurotoxic effect. Hence, we propose to adopt two different strategies to attempt the simultaneously immobilize and increase the load of AgNPs within the wound dressing fabric. Thus, the envisaged objective is to prevent potential systemic cytotoxicity /through immobilization and to improve its antimicrobial capability due to the higher concentration of AgNPs. Two different approaches were used: i. AgNPs were suspended in an alginate (ALG) solution, ii. AgNPs were embedded in Mordenite (MOR) zeolite, followed by addition of an ALG solution. Both suspensions were incorporated into polyester fabric assisted by its surface activation by dielectric barrier discharge (DBD) plasma treatment. The bactericidal and virucidal effectiveness of each composite was tested against bacteria species known to induce nosocomial infections and a bacteriophage that is a potential surrogate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Two distinct antimicrobial analysis were used to provide insights on the antimicrobial effectiveness of the obtained composites and to indirectly assess the release of AgNPs.
Modeling of Deep Rolling as a Distortion Compensation Strategy during Profile Grinding
Authors: Schieber Christian , Hettig Matthias , Zaeh Michael F. , Heinzel Carsten
Published: July 2022

This paper analyzes the possibility to induce residual compressive stresses utilizing deep rolling in a long, slim steel workpiece that is profile ground and that resembles a linear guide rail. These intentionally caused residual compressive stresses at the side surfaces of the workpiece are intended to counteract the distortion due to residual stresses in the V-groove of the guide rail induced by grinding. A finite element model was prepared based on the initial state of the workpiece. The amount of respective stresses depended on the load intensity and duration of the process. The experimental data regarding the residual stress profiles due to the deep rolling process and the resulting workpiece distortion were used to validate the simulation, so that an adjustment or a calibration of the thermometallurgical and thermomechanical material data was possible. The key findings are the numerical design of appropriate strategies for the distortion potential induction, the experimental distortion results, knowledge on the mechanical treatment by deep rolling, and the successful modeling of the mechanical treatment and the process strategy.