bluuebunny/crossref_metadata_2025 huggingface dataset:
Adam Improved Rider Optimization-Based Deep Recurrent Neural Network for the Intrusion Detection in Cyber Physical Systems
Authors: Kamble Arvind , Malemath Virendra S.
Published: July 2022

This paper designed the intrusion detection systems for determining the intrusions. Here, Adam Improved rider optimization approach (Adam IROA) is newly developed for detecting the intrusion in intrusion detection. Accordingly, the training of DeepRNN is done by proposed Adam IROA, which is designed by combining the Adam optimization algorithm with IROA. Thus, the newly developed Adam IROA is applied for intrusion detection. Overall, two phases are included in the proposed intrusion detection system, which involves feature selection and classification. Here, the features selection is done using proposed WWIROA to select significant features from the input data. The proposed WWIROA is developed by combining WWO and IROA. The obtained features are fed to the classification module for discovering the intrusions present in the network. Here, the classification is progressed using Adam IROA-based DeepRNN. The proposed Adam IROA-based DeepRNN achieves maximal accuracy of 0.937, maximal sensitivity of 0.952, and maximal specificity of 0.908 based on SCADA dataset.
Influence of the Sheet Edge Condition on the Fracture Behavior of Riv-Bonded Aluminum-Magnesium Joints
Authors: Domitner Josef , Silvayeh Zahra , Predan Jožef , Jerenec Filip , Auer Peter , Stippich Jennifer , Ferlič Luka , Štefane Primož , Sommitsch Christof , Gubeljak Nenad
Published: July 2022

This work investigates the influence of the sheet edge condition on the fracture behavior of riv-bonded aluminum-magnesium lap joints under monotonic-static and cyclic-dynamic shear-tensile loads. Therefore, sheets of 1.5 mm-thick EN AW-6016-T4 aluminum alloy were joined with sheets of 2.0 mm-thick AZ91 magnesium alloy using two C5.3×6.0-H4 rivets and epoxy-based adhesive. The side edges of the sheets were either shear-cut or milled after cutting. Before testing, the joints were heat-treated at about 180-200 °C for 20 min in order to cure the adhesive and to peak-age the aluminum alloy. The cyclic load maximum was about 40 % of the monotonic load maximum. The cyclic load minimum was 10 % of the cyclic load maximum, i.e., the load ratio was R = 0.1. The edge condition of the sheets did not have any significant influence in monotonic-static testing; however, in cyclic-dynamic testing the number of cycles to fracture was about four-times higher for samples with milled side edges than for samples with shear-cut side edges. Hence, the potential load capacity of riv-bonded aluminum-magnesium joints cannot be exploited under cyclic loading, if the magnesium sheet has edges with poor quality.
Machining of Additive Manufactured Metal Alloys
Authors: Bruschi Stefania , Bertolini Rachele , Ghiotti Andrea
Published: July 2022

Additive Manufacturing of metal alloys offers unique advantages for producing net-shape components of complex geometries with very little waste of material. Nevertheless, machining operations may be needed on functional surfaces to get the required surface finish and geometrical tolerances. This poses challenging issues since the microstructural features characterizing the AM alloys are drastically different from those of the wrought alloys of the same chemical composition, which, in turn, may affect the mechanical and machining response to a great extent. This paper shows that both the machined surface integrity and tool wear are greatly affected by the microstructural features induced by the previous AM process as well as by the build-up orientation.
Intelligent Iterative Experimental Design to Achieve Maximum Model Quality for Phase Change of 22MnB5
Authors: Hart-Rawung Thawin , Buhl Johannes , Härtel Sebastian , Bambach Markus
Published: July 2022

Conducting experiments for material modeling is very costly and time-consuming when many parameters are involved, resulting in a large number of test conditions. Therefore, it is expedient to develop algorithms for the iterative identification of optimal test conditions. This method should allow the model to learn automatically so that only a small number of test conditions are selected at the beginning of the model calibration. In order to decide whether further experiments should be carried out and which test conditions need to be investigated, meta-models are generated, and the expected gain score is calculated. The next sample is selected based on the highest score, and this procedure continues until the material models meet a termination criteria. The result from the study shows that the implemented method uses 12 test conditions to generate a phase transformation model for 22MnB5 steel. The material models fitted with the proposed method provide acceptable predictions when compared with experimental data.
Numerical Evaluation of Press Forming Parameters and Mould Geometry in Wood Plastic Composite (WPC) Products
Authors: Matthews Sami , Tanninen Panu , Toghyani Amir , Leminen Ville , Varis Juha
Published: July 2022

The purpose of this paper is to investigate factors associated with press-forming of Wood Plastic Composite (WPC) products. The WPC material is a novel, feasible, and economic way to use recycled thermoplastics. Due to the complexity of the fiber-polymer interaction, numerical simulation and thus prediction of WPC behavior in forming have been challenging. Up to now, press moulds have had to be empirically validated. In this paper, we explore the possibility of predicting material behavior using Autodesk Moldflow.
Investigation of the Influence by Size Effects on the Material Characterization of the Uniaxial Compression Stress State
Authors: Hetz Peter , Kraus Martin , Merklein Marion
Published: July 2022

For the evaluation of final component properties under consideration of production-induced material characteristics, it is necessary to determine the mechanical parameters of parts and structures. Thus, there is a need of new test methods for the material characterization and quality control of produced goods. The miniaturization of the test specimens offers the potential for the local testing of the material properties at almost any position on the component. However, due to the reduction in size of the test specimens, size effects can occur which may affect the material behavior. For this reason, this contribution analyses the influence of size effects on the derived material parameters in dependence of the specimen size and material by using upsetting tests according to DIN 50106:2016 standard. The materials Cu-OFE (copper), X5CrNi18-10 (stainless steel) and AA7075-T6 (aluminum) are investigated to ensure a broad transferability of the findings. The specimens are cut from a bar stock by using a high precision 3D micro electrical discharge milling machining. Due to the small size, every specimen is measured with an optical 3D coordinate measuring system to determine the exact size. Through these investigations, the reproducibility and scatter in the determination of material properties for scaled cylindrical upsetting specimens are evaluated. Furthermore, limits of geometric dimensions at constant aspect ratios are derived. The results of this investigation enable an estimation of the geometrical influence of the specimen size in regard to the mechanical properties.
FEA Approach for Wear and Damage Prediction of Tools for the Progressive Die Stamping of Steel Washers
Authors: Kaya Ertuğrul , Farioli Daniele , Strano Matteo
Published: July 2022

In progressive die stamping processes, maintenance activities caused by tool damage, and wear represent economic losses for companies. An effective predictive maintenance strategy can only be implemented if maintenance data coming from the operations are correlated to specific process-related information. As a part of a more general data-based predictive maintenance strategy, the main causes of tool damage and wear in a progressive die stamping factory that produces automotive metal washers have been identified by means of FEA simulations. In this study, the progressive die stamping of a dented conical washer is simulated with Transvalor FORGE FEA software by implementing the process parameters used in a real case. In this study, two indicators called FEAwear and FEAdamage are proposed for prediction of die wear and damage for tools with high risk of failure. For validating the accuracy of the FEA simulations, dimension and geometry comparisons are performed between FEA and real washer, and then real and FEA maximum press force comparison is performed. In the end, FEA simulations demonstrated their accuracy in predicting the stamping force of the press and the final part quality, and proposed FEA damage and wear indicators accurately predicted the most critical tools and stations, as confirmed by the real maintenance data. Finally, the simulations also correctly detected potential damage zones of the tools.
Simulation of Wrinkling during Forming of Binder Stabilized UD-NCF Preforms in Wind Turbine Blade Manufacturing
Authors: Broberg Peter Hede , Krogh Christian , Lindgaard Esben , Bak Brian Lau Verndal
Published: July 2022

Binder stabilized preforms are getting increased attention in the wind turbine industry with the aim to increase automation in the production of large blades. In this context a preform is a stack of dry unidirectional glass fiber non-crimp fabrics (UD-NCF), which is consolidated using a polymeric binder. The preform is manufactured in a separate mold, and subsequently placed in the main blade mold. During placement of preforms, fiber wrinkling may occur due to the deformation of the preform. To accommodate this problem, we propose a predictive simulation model that can be used to investigate how different process parameters influence the wrinkle creation. Most forming simulation models in the literature consider frictional laws in the inter-ply interface for multi-layered fabrics. In this work the binder interfaces between the layers are modelled using a cohesive traction-separation law to accurately model binder degradation and wrinkle creation during preform deformation. The model predictions are compared with full thickness preform coupon specimens.
A Model to Construct and Predict Flow Curve of Materials from Compression Test Results with Machine Learning Models Using Python
Authors: Aydın Tolga , Kocatürk Fatih , Zeren Doğuş
Published: July 2022

In order to obtain flow curves from compression test results of a cold forging material and predict flow curves of the material at intermediate temperature and strain rate values, a model was developed using Python programming language in this study. The model consists of two parts: Flow curve determination and flow curve prediction. The compression test data including Force-Stroke values was processed to determine the flow curves in the first part, and the flow curve data constructed for certain temperature and strain rate values of the material was used as input for the machine learning algorithms to predict flow curve at desired intermediate temperature and strain rate values in the second part. Moreover, Ludwik material model parameters were estimated by using curve fitting methods in order to define the material model into the simulation software. Machine learning algorithms and various regression models in Python libraries were tested to predict the flow curves. The performances of different machine learning and regression models were compared with respect to the mean squared error and coefficient of determination performance measures. Support vector regression, k-Nearest Neighbour (kNN) and artificial neural network models were used to predict flow curves of cold forging materials and kNN regression model was able to found predictions with the lowest error rate. As a result, a model that can process the compression test data to predict flow curves at intermediate temperature or strain rate values was developed.
Parameter Identification of Swift Law Using a FEMU-Based Approach and an Innovative Heterogeneous Mechanical Test
Authors: Conde Mariana , Henriques João , Coppieters Sam , Andrade-Campos António
Published: July 2022

The reliability and predictive accuracy of forming simulation depend on both the material constitutive model and its inherent parameters. As opposed to conventional sheet metal material testing, heterogeneous mechanical tests provide more complex strain and stress states. Heterogeneous mechanical tests can be used to efficiently predict the material behavior in forming processes due to an improvement in the time required and accuracy in the identification of the parameters. The present work aims at identifying the Swift hardening law parameters of a dual-phase steel by means of an optimum-designed interior notched specimen that presents several strain and stress states simultaneously. The finite element model updating (FEMU) technique was used for the identification of parameters, by comparing a DIC-measured virtual material with numerical results iteratively DIC-filtered.
Assessing the Accuracy of Different Remapping Methods in Adaptive Mesh Refinement
Authors: Marques Bruno M. , Neto Diogo M. , Alves José Luis
Published: July 2022

Additive manufacturing of metals has attracted much attention over the last years, promoting the development of several computational models for numerical simulation of the laser powder bed fusion (LPBF) process. Nevertheless, the finite element analysis of the LPBF process requires a large computational time. Thus, adaptive mesh refinement strategies are commonly adopted to reduce computational cost, which require some remapping procedure to transfer the state variables from the old mesh to the new one. The present study analyses two different remapping algorithms, namely the Inverse Isoparametric Mapping (IIM) and the Dual Kriging (DK) method. The IIM method uses the shape functions of the finite elements, while the DK method provides an explicit parametric interpolation. The case study adopted covers both coarsening and refinement procedures, using a mathematical function to define the mapped state variable. The accuracy of the remapping methods was lower in the refinement in comparison with the coarsening procedure. The error in the approximation is lower using the DK method in comparison with the IIM method. However, the IIM method does not suffer from error propagation in successive stages of either refinement/derefinement or coarsening/decoarsening.
Towards a Hybrid Twin Model to Obtain the Formability of a Car Body Part in Real Time
Authors: Peinado-Asensi Ivan , Montes Nicolas , García E. , Falcó Antonio
Published: July 2022

In recent days there are many possibilities in develop solutions for industrial manufacturing process thanks to the emerging technology based in Industry 4.0, where one can measure and manage data from an industrial process in real time been able to know more information than ever before from the process. But still having challenges in complex process where monitoring data and give a solution is less intuitive, mostly due to a complex physical definition of the process and manufacturing car body parts in automotive is a clear example. In deep drawing process is common to have variations in the process parameters and they can carry out bad manufactured parts. The cycle time, the robust process and the complex physics in the process are the main problems to obtain feasible information from the process. In the following it is proposed a new methodology to have full knowledge of the process applying the so-called method Hybrid Twin.
Viscoplastic Self-Consistent (VPSC) Modeling for Predicting the Deformation Behavior of Commercial EN AW-7075-T651 Aluminum Alloy
Authors: Domitner Josef , Buzolin Ricardo H. , Patil Samiksha , Auer Peter , Papenberg Nikolaus , Kabliman Evgeniya , Silvayeh Zahra , Drexler Andreas , Grabner Florian
Published: July 2022

Viscoplastic self-consistent (VPSC) modeling was used for investigating the deformation behavior of commercial EN AW-7075-T651 aluminum alloy at room temperature under quasi-static tension and compression (i) parallel, (ii) diagonal and (iii) transverse to the rolling direction. Textures of the as-received plate and of the samples after tensile and compression testing were determined using electron backscatter diffraction (EBSD). Euler angles and area fractions of the grains were used as input for calculating direction-dependent flow curves and pole figures of the deformed material. The coefficients of the integrated Voce strain hardening law were adjusted in order to fit the calculated flow curves to flow curves obtained from tensile and compression testing. Pole figures calculated with the VPSC modeling method were validated with pole figures obtained from EBSD analysis of deformed samples. VPSC modeling was successfully applied for predicting the general deformation behavior of EN AW-7075-T651 under both tension and compression. However, texture evolution during tensile testing was negligible, whereas notable texture evolution during compression testing occurred beyond a critical strain value.
Method for the Estimation of Wear Resistance Curves in Sheet Metal Forming with Uncoated Tools
Authors: Wu Yu Tian , Li Rui Zhe , Groche Peter
Published: July 2022

The wear resistance diagram (WRD) is a useful tool for quantitatively estimating the life span of a tribological system in sheet metal forming at different load levels. However, the WRD derived from the authors’ previous research consists merely of scattered points, which make it difficult to reliably estimate the life span and its uncertainties at all load levels. Therefore, a wear resistance curve (WRC) that encompasses the life spans of all load levels is required for a broader scope of application of wear resistance estimation. In this paper, different models for the estimation of the S-N curve describing the fatigue behavior are tested to investigate their applicability in the estimation of wear resistance curves (WRC) in sheet metal forming. WRDs of different tribological systems are investigated and the results of curve fitting are evaluated. Besides the median of the estimated life spans, the WRCs of different confidence levels are also derived quantile calculation to estimate the load dependent uncertainties of tool life spans. Moreover, due to the time-consuming experiments to determine tool life, it is necessary to discuss possibilities for achieving a satisfactory estimation with the smallest possible number of tests. Therefore, the minimal number of tests and the suitable load levels for a satisfactory estimation will be discussed. After the study, several findings have been obtained:Compared to other models, Hwang and Han’s model for estimating fatigue life of composite material shows good applicability and the highest accuracy in estimating the WRC of uncoated tools.In terms of damage development, the fatigue damage of the composite material and the damage caused by wear on uncoated tools have similarities, which explains the applicability of Hwang and Han’s model for the estimation of WRC.Both higher and lower life wear data are the prerequisite for satisfactory wear estimation.
Process Window Definition to Predict Mechanical Properties of Press Hardened Parts of Boron Steel with Tailored Properties
Authors: Palmieri Maria Emanuela , Tricarico Luigi
Published: July 2022

Tailored Tool Tempering (TTT) is an innovative method able to calibrate the strength and ductility characteristics of the components manufacture by means of Press-Hardening process. The process parameters that most influence the final mechanical properties of the soft zone are quenching time and temperature of the heated tools.In this work, with the aim of defining a process window to estimate the soft zone properties of an automotive B-pillar in Usibor®2000 steel using TTT Press-Hardening approach, the strength and ductility of the soft zone are studied varying the quenching time and the temperature of the heated tools. Using a numerical-experimental approach, a Finite Element (FE) model is firstly developed in AutoForm to simulate the TTT Press-Hardening process and to define thermo-mechanical cycles that are characteristics of the soft zone as a function of quenching parameters (quenching time and temperature of the heated tools). FE thermo-mechanical cycles are then physically simulated on Usibor®2000 specimens using Gleeble 3180 system. The treated specimens are subsequently subjected to micro-hardness and tensile tests. Experimental results are adopted to train an artificial neural network used to construct the process window.
Bulging of Isotropic Materials
Authors: Godoy Hernan , Revil-Baudard Benoit , Cazacu Oana
Published: July 2022

There is a large body of literature on both the techniques for bulge testing and experimental results for various metallic materials (see the book of Banabic [1]). Generally, the experimental data for isotropic materials are interpreted using the von Mises yield criterion [2]. In this paper, we investigate the role played by the third invariant of the stress deviator, on the response under bulging of isotropic materials that have the same mechanical response in tension and compression. To this end, we use the yield criterion developed by Cazacu [3] and our implementation of this model in the F.E. code Abaqus [4]. For isotropic materials, this yield criterion involves a unique parameter, denoted ; in the case when it reduces to the von Mises yield criterion while for it involves dependence on . The results of F.E. simulations of bulge tests for isotropic materials characterized by various values of the parameterput into evidence new aspects concerning the stress states experienced by the respective materials under bulging.
Effect of Temperature and Strain Rate on Formability of Titanium Alloy KS1.2ASN
Authors: Sikhamov Ruslan , Ventzke Volker , Dorn Falk , Klusemann Benjamin , Ben Khalifa Noomane , Kashaev Nikolai
Published: July 2022

Titanium alloys are widely used in aerospace and automotive industries due to their excellent mechanical properties, however, the formability is limited, which is an issue during forming. In the present study, the effect of temperature and strain rate on the tensile properties of the titanium α-alloy KS1.2ASN was investigated. It was observed that there is initially no gain in ductility with increase in temperature until 400 °C, however, maximum formability is reached at maximum tested temperature of 600 °C. EBSD analysis revealed that twinning is the main deformation mechanism at room temperature, however, sliding deformation becomes more pronounced with increasing temperature. An increase in strain rate leads to a decrease in elongation, but the influence is less pronounced compared to temperature.
Experimental Investigation of the Effect of EDM Debris Particles Mixed into the Dielectric Fluid on Tool Feed Rate in Drilling-EDM
Authors: Risto Matthias , Wasmuth Uwe , Kotschenreuther Jan
Published: July 2022

In this paper the potential of the recirculation of the EDM debris particles of the workpiece material into the dielectric fluid to increase the tool feed rate vf in drilling Electrical Discharge Machining (drilling-EDM) is experimentally investigated. Two-Channel electrodes made of copper (Cu) and brass (CuZn) in the range from 1.0 mm to 2.5 mm were used. The effect of the EDM debris particles in the dielectric fluid was investigated at a discharge current ie of 25 A, a discharge duration te of 50 μs and a duty cycle of 80 % by comparing the EDM pulse characteristics and the feed rate vf of the EDM process with and without debris particles added to the dielectric fluid (particle concentrations C1 = 2.5 g/l and C0 = 0 g/l, respectively). By the recirculation of EDM debris particles the feed rate could be increased up to 36 % depending on the machining conditions. Furthermore, it was observed that the increase in the feed rate is due to the increase of the percentage of discharge pulses and the decrease of short-circuit pulses as well as a more stable machining process.
Investigations on Combined In Situ CT and Acoustic Analysis during Clinching
Authors: Köhler Daniel , Stephan Richard , Kupfer Robert , Troschitz Juliane , Brosius Alexander , Gude Maik
Published: July 2022

Clinching is a cost efficient method for joining components in series production. To assure the clinch point’s quality, the force displacement curve during clinching or the bottom thickness are monitored. The most significant geometrical characteristics of the clinch point, neck thickness and undercut, are usually tested destructively by microsectioning. However, micrograph preparation goes ahead with a resetting of elastic deformations and crack-closing after unloading. To generate a comprehensive knowledge of the clinch point’s inner geometry under load, in-situ computed tomography (CT) and acoustic testing (TDA) can be combined. While the TDA is highly sensitive to the inner state of the clinch point, it could detect critical events like crack development during loading. If such events are indicated, the loading process is stopped and a stepped in-situ CT of the following crack and deformation development is performed. In this paper, the concept is applied to the process of clinching itself, providing a detailed three-dimensional insight in the development of the joining zone. A test set-up is used which allows a stepwise clinching of two aluminium sheets EN AW 6014. Furthermore, this set-up is positioned within a CT system. In order to minimize X-ray absorption, a beryllium cylinder is used within the set-up frame and clinching tools are made from Si3N4. The actuator and sensor necessary for the TDA are integrated in the set-up. In regular process steps, the clinching process is interrupted in order to perform a TDA and a CT scan. In order to enhance the visibility of the interface, a thin tin layer is positioned between the sheets prior clinching. It is shown, that the test-set up allows a monitoring of the dynamic behaviour of the specimen during clinching while the CT scans visualize the inner geometry and material flow non-destructively.
Possibility of Deformation of Billet with Various Internal Structure in KOBO Extrusion
Authors: Zwolak Marek , Śliwa Romana Ewa , Pawłowska Beata , Wędrychowicz Aleksandra
Published: July 2022

The potential of KOBO unconventional extrusion of metallic materials based on phenomenon of changing the path of plastic deformation with use of cyclic oscillation of the die by given angle and frequency has been presented in this paper. This process is used to change material properties by fragmentation of grains without preheating the billet and press parts with significantly lower extrusion force in comparison to conventional process. Various types of billets (various metallic materials in the form of: solid initial material, condensed chips, layered composite material) were used during the experimental tests to analyze the plastic flow of the material and the possibility of plastic deformation of various metallic materials such as aluminum alloys, magnesium alloys and copper in order to obtain a product with a complex shape in the KOBO process, using dies with different geometries. Mechanical properties, microstructure, scheme of plastic flow and extrusion force were examined during experimental work. KOBO extrusion can be considered as a more cost-effective process than conventional extrusion.
Investigation on Homogeneous Modeling of Gyroid Lattice Structures: Numerical Study in Static and Dynamic Conditions
Authors: Mancini Edoardo , Utzeri Mattia , Sasso Marco
Published: July 2022

The TPMS (triply periodic minimal surface) are receiving great attention for production of open cell scaffold structures, for example in biomedical applications. In this paper stretch-dominated lattice structures have been considered. The Gyroid cell made of epoxy resin by DLP technology was analyzed. The compression test results in quasi-static (10-3 s-1) and dynamic (4x102 s-1) conditions have been used to compute the macroscopic cellular material properties by the homogenization methods. Finally, in order to evaluate the behaviour of the unit cell under multi-axial stress state, combined shear-compression tests have been carried out as well.
Maximizing the Resolution Range of Addictive-Manufactured Miniature-Scale Force-Sensing Devices for Biomedical Applications
Authors: Quagliato Luca , Kim Soo Yean , Ryu Seok Chang
Published: July 2022

This research presents a methodology for the design and manufacturing of miniature-scale force-sensing devices based on an additive manufactured sensor structure, coupled with strain gauge measuring elements, hereafter referred to as measuring device (MD). The proposed MD has been designed and manufactured to maximize the resolution of the steering force measurement in active needles utilized in biomedical applications. The force resolution is defined as the variation of the signal output of the four strain gauges bridge for predetermined increases of the applied force. By means of the proposed approach, the geometry and curing conditions of the sensor structure that allows achieving the maximum allowed deformation for the strain gauges, in the regions where they are installed on the sensor structure, can be defined a-priori, allowing to maximize the resolution of the measured force signal. The proposed methodology has been developed considering a sensor thickness ranging from 1 to 5mm and curing conditions varying from no curing up to 80°C for 120 minutes and showed that, by utilizing the proposed methodology, the measurable force range can be adjusted in the 0.1N~12.8N range with a relevant maximum and minimum resolutions ranging from 712.2 unit/N (force range : 0.1N~5N) to 362.2 unit/N (force range : 0.1N~12.8N), respectively.
Influence of Bioactive and Bio Inert Ceramic Powders on Tribology Properties of PMMA Composite Denture Base
Authors: Hussain Shahad , Al-Sarraf Abdulhameed
Published: July 2022

Polymer matrix composites are suitable materials for medical applications, such as denture base resin polymethyl methacrylate (PMMA). This includes light weight and high strength. This paper describes the effect of selected weight fractions (1, 2, 3, 4 & 5) % wt of nano(Alumina AL2O3, Zirconia ZrO2, Hydroxyapatite HA and Halloysite nanoClay) reinforcements on the biopolymer matrix (PMMA). Some tribology tests were used to evaluate the prepared system (impact strength, hardness surface, and wear rate) tests. The samples were fabricated by (Hand Lay-Up) with different particle reinforcement percentages. All tests were accomplished at room temperature, and samples were developed according to the ASTM standard. The weight fraction of (4% for AL2O3, 4% for ZrO2, 3% for HA and 5% for Clay) nanoparticles are the best results that appeared in the work.
Manufacture of Defined Residual Stress Distributions in the Friction-Spinning Process: Driven Tool and Subsequent Flow-Forming
Authors: Dahms Frederik , Homberg Werner
Published: July 2022

Friction-spinning as an innovative incremental forming process enables large degrees of deformation in the field of tube and sheet metal forming due to a self-induced heat generation in the forming zone. This paper presents a new tool and process design with a driven tool for the targeted adjustment of residual stress distributions in the friction-spinning process. Locally adapted residual stress depth distributions are intended to improve the functionality of the friction-spinning workpieces, e.g. by delaying failure or triggering it in a defined way. The new process designs with the driven tool and a subsequent flow-forming operation are investigated regarding the influence on the residual stress depth distributions compared to those of standard friction-spinning process. Residual stress depth distributions are measured with the incremental hole-drilling method. The workpieces (tubular part with a flange) are manufactured using heat-treatable 3.3206 (EN-AW 6060 T6) tubular profiles. It is shown that the residual stress depth distributions change significantly due to the new process designs, which offers new potentials for the targeted adjustment of residual stresses that serve to improve the workpiece properties.
Cold Spray Metallization of Hybrid Thermoplastic - Thermoset Fiber Reinforced Composite
Authors: Parmar Hetal , Della Gatta Roberta , Viscusi Antonio , Tucci Fausto , Astarita Antonello , Carlone Pierpaolo
Published: July 2022

Surface metallization is amongst the recent trends in the polymer and polymer matrix composites (PMCs) research industries to improve the electrical and thermal properties and exploit the subsequent utilization in the aerospace sector. Specifically, polymer matrix composites have been subjected to the limitations in form of high temperature exposure and substrate deterioration. The present study encompasses a new strategy in the manufacturing and metallization process. The first stage in the manufacturing of hybrid thermoplastic-thermoset composite was the hot compaction which comprised of primary preform preparation enabling the partial impregnation of the thermoplastic resin through the fabric reinforcement layer. The subsequent stage entailed the preform vacuum bagging and conducting catalyzed thermoset resin impregnation. The vacuum resin infusion step included a cocuring cycle to generate a fiber reinforced composite comprising of thermoplastic and impregnated thermoset resin with improved adhesion. Resin flow front movement was analyzed during the resin infusion process. Composite metallization was achieved through cold spray (CS). CS process parameters influence on the coating quality and characterization of laminates through microstructural analysis and results have been reported. The hybrid composite with thermoset resin through thickness and in-plane impregnation was achieved with the intact adherent thermoplastic layer after the curing cycle. In the CS metallization, the effective operative window of stand-off distances (SoD) and temperature has been determined.
Evaluation of the Rheological Behaviour of Magnetorheological Fluids Combining Bulge Tests and Inverse Analysis
Authors: Cusanno Angela , Piccininni Antonio , Guglielmi Pasquale , Palumbo Gianfranco
Published: July 2022

Magnetorheological Fluids (MRFs) are included in the so called “smart materials”: they are suspensions of magnetically responsive particles in a liquid carrier, whose rheological behaviour (e.g., its viscosity) can be changed quickly and reversibly if subjected to a magnetic field. Their application as forming medium in sheet metal forming processes is gaining interests in the recent years since the thickness and the strain distribution on the formed part can be affected by properly changing the properties of the MRF. In order to widely adopt MRFs in such processes, the evaluation of their rheological behaviour according to the applied magnetic field plays a key role. But there are still few works in the literature about the most effective way to characterise the MRFs to be used in sheet metal forming applications.In this work, the rheological behaviour of a MRF is carried out by means of an inverse analysis approach using data from bulge tests performed using an MRF as forming medium. Bulge tests were conducted on sheets having known properties using an equipment with a solenoid to generate the magnetic field, which was specifically designed and manufactured. Pressure rate and magnetic flux density were varied according to a Design of Experiments (DoE) while the strain experienced by the sheet material was acquired by means of a Digital Image Correlation (DIC) system in order to compare it with the numerical one. In particular, the fitting between numerical and experimental data was obtained by changing the MRF’s rheological properties using an inverse analysis technique. The proposed methodology allows to evaluate the MRF behaviour at different levels of both magnetic field and pressure rate, which are determinant for the FE simulation of sheet metal forming processes.
The Effect of the Setting Force on the Fatigue Resistance of a Blind Rivet Nut Set in CFRP
Authors: Van de Velde Arne , Ivens Jan , Maeyens Jan , Coppieters Sam
Published: July 2022

Weight reduction is often a key factor in modern mechanical design, therefore materials such as carbon fibre reinforced plastics (CFRP) are increasingly used and integrated within multi-material structures using adhesive technologies, which require high effort and are difficult to disassemble. The capability of a blind rivet nut (BRN) to join different materials without these disadvantages has created a growing industrial interest in the fastener. However, installing a BRN in CFRP laminate induces a significant stress concentration in the plate, which potentially causes damage. Given that ‘damage free’ joints are demanded by the industry, the BRN is often not considered as a suitable joining technique. In the present research, an experimental campaign is performed to investigate the fatigue resistance of a BRN joint in CFRP. It is demonstrated that the resulting compressive stress after installing a BRN can enhance the fatigue resistance of the specimen. The results increase the potential of the BRN as a fastener for CFRP.
Experimental and Numerical Investigation on Manufacturing-Induced Pre-Strain on the Load-Bearing Capacity of Clinched Joints
Authors: Bielak Christian Roman , Böhnke Max , Bobbert Mathias , Meschut Gerson
Published: July 2022

Background. Clinching is a conventional cold forming process in which two or more sheets can be joined without auxiliary parts. A pre-forming of the parts to be joined, which is introduced by previous manufacturing steps, has an influence on the joining result. When considering the suitability for joining with regard to the formability of the materials, the influence of the preforming steps must be taken into account. The influences of strain hardening and sheet thickness on the joining properties must be investigated. In this context, a Finite Element Method (FEM) based metamodel analysis of the clinching process was carried out in [1] to investigate the robustness of the clinching process with respect to the different material pre-strains. In [2], the method was extended to the load bearing simulation.Procedure. The metamodel from preliminary work based on various FE models, which predicts the load-bearing capacity of a clinched joint influenced by pre-straining, is compared here with experimental data and the accuracy of the metamodel prediction is discussed. For this purpose an experimental procedure was further develop which allows the preforming of metal sheets from which joining specimens can be separated with a certain degree of unidirectional deformation. In the study, the procedure for preparing the joint specimens and the results of the loading tests are presented. Different possible relevant pre-strain combinations are investigated and compared with the simulation results, to validate the FE models and choose suitable metamodel.
Realtime Prediction of Self-Pierce Riveting Joints - Prognosis and Visualization Based on Simulation and Machine Learning
Authors: Falk Tobias , Schwarz Christian , Drossel Welf Guntram
Published: July 2022

Machine learning is used in many fields nowadays to predict events, be it a pure classification or the prediction of certain values. Thus, these methods are also increasingly used in mechanical joining technology, for example for the prediction of joint strengths, in the classification of defects and rivet head positions or in the prediction of discrete result values such as interlock. This paper further shows how the complete joint contour including the output of stresses, strains and damage can be predicted and visualized in real time for self-piercing riveting with semi-tubular rivet. First, classical sampling is carried out in experiments with steel and aluminum sheets of different types and thicknesses. These are used as a basis for the qualification of the numerical simulations. For this validation experiments and simulations are compared via joint contour and force curves. For the simulations validated in such way several tool variants are carried out in variation calculations for each material-thickness combination. The simulation meshes of the thus generated database are standardized with respect to comparability (same number of nodes) and a data reduction is performed. After testing different approximation approaches, the best possible results are predicted and can be visualized in the developed software demonstrator.
Load-Adapted Surface Modifications to Increase Lifetime of Forging Dies
Authors: Paschke Hanno , Weber Martin , Brunotte Kai , Rothgänger Marcel , Petersen Tom , Siegmund Martin , Peddinghaus Julius
Published: July 2022

Diffusion treatments offer possibilities to enhance the performance and the service lifetime of hot forging tools. In combination with coating after nitriding, the surface layer hardness can be further increased. Within the scope of this study, a surface layer hardness above 2,000 HV0.005 was determined for borided or DLC (diamond-like carbon) coated surface layers. An increased surface layer hardness improves the abrasive wear resistance of forging dies. Furthermore, the plastic deformation of thermally softened forging die areas can be reduced. Beside these desirable effects, the ductility of diffusion treated or coated near surface layers is reduced and thermomechanical cracks are promoted. Therefore, additional approaches were developed to improve the thermomechanical crack behaviour of forging dies. Patterned plasmanitriding by the use of coverages to prevent areas from nitrogen diffusion, new combination processes of plasmanitrocarburizing (PNC) followed by plasmanitriding (PN) and the innovative boriding were investigated on different abstraction levels. A system of several testing rigs was set up to enable the abstraction of the thermal shock conditions in different stages. The patterned nitriding, boriding and combination plasma process (PN + PNC) were evaluated in a series of industrial field tests to derive recommendations for suitable tool treatments.
Periodic Homogenization in Crystal Plasticity: A Comparative Study between 3D and 2D
Authors: Mirhosseini Shahrzad , Perdahcioglu Emin Semih , Soyarslan Celal , van den Boogaard Ton
Published: July 2022

In this paper, macroscopic behavior obtained from crystal plasticity finite element simulations of irregularly shaped 3D and 2D volume elements (VEs) are compared. These morphologically periodic VEs are generated using the open-source software library Voro++. Periodic boundaryconditions are utilized to homogenize the material response employing a prescribed macroscopic deformation gradient tensor. To accelerate the assignment of periodic boundary conditions, a conformalmesh is employed by which periodic couples of faces on the hull of the volume element have identicalmesh patterns. In the simulations, plane strain conditions are assumed, which means that the averagethickness strain in 3D VEs is set to zero. However, grains are allowed to strain in the thickness direction. In the case of 2D VEs, plane strain elements are used. The principal goal of this comparison isto evaluate the accuracy of 2D VEs simulations. In the current study, two kinds of 2D VEs are generated: 1) Slicing 3D VEs normal to the thickness direction, 2) Separately generating 2D VEs. The firstmethod corresponds to sectioning 3D microstructures using EBSD. This approach is generally usedas an assumed more accurate alternative to 2D VEs. Based on the results, there is a large gap betweenthe flow curves of 2D and 3D VEs. Additionally, 2D sectioning of 3D VEs does not necessarily endup in higher precision in material behavior predictions.
Investigating the Melt-Pool Temperature Evolution in Laser-Powder Bed Fusion by Means of Infra-Red Light: A Review
Authors: Obeidi Muhannad Ahmed , Ul Ahad Inam , Brabazon Dermot
Published: July 2022

Recent decades seen the success of Additive Manufacturing (AM) in many industrial applications including aerospace, biomedical, automotive, and tooling. In the manufacturing of metallic parts, AM technology has the ability to produce parts with complex geometries which are difficult or impossible to produce using the conventional fabrication methods, such as machining and casting. Another benefit of AM is the employment of metal and metal alloys which are difficult to machine. Alloys such as titanium, nickel-titanium, and stainless steel have a wide range of applications particularly in the aerospace and biomedical industry. Selective Laser Melting (SLM), also known as Laser Powder Bed Fusion (L-PBF) is a type of AM technology used for the 3D printing of metal and alloy parts. The major drawback in L-PBF technology is the anisotropic properties of the produced parts. From L-PBF, these anisotropies exist due to instant melting and re-solidification of the metal powder, the ultra-high cooling rates and the variant temperature levels across the build layers and within the single layer itself. This article explores the essential role of the melt-pool temperature and temperature gradients that occur during the L-PBF process and their effects on the additively manufactured part’s properties.
On the Design of a Heterogeneous Mechanical Test Using a Nonlinear Topology Optimization Approach
Authors: Gonçalves Mafalda , Andrade-Campos António , Thuillier Sandrine
Published: July 2022

Numerical simulation is nowadays increasingly used to avoid the costs and time associated with the development and optimization of metal forming processes. However, the accuracy of the numerical results is still an issue. Material behavior and characteristics are required by simulation software, and these are usually obtained by performing a considerable number of classical mechanical tests. To improve this procedure, heterogeneous tests have been used instead. More and richer information can be obtained with a single test due to the heterogeneous displacement and strain fields that are induced. This work aims at designing a heterogeneous mechanical test using a topology-based optimization methodology. Highly heterogeneous displacement fields are induced on the sheet specimen by applying an extended version of the theory of compliant mechanisms. To account for large deformations, a geometrically nonlinear finite element analysis is proposed together with a consistent topology optimization approach. The material behavior is considered linear elastic. The performance of the obtained solutions is evaluated considering the heterogeneity of stress states using a mechanical indicator. Validation of the developed methodology is performed and an optimal mechanical test is obtained presenting a high diversity of stress states.
Combined Probabilistic Approach and Stress State Dependency on the Failure Modeling of HPDC Aural-2 Alloy
Authors: Zhang Yong Fa , Shen Fu Hui , Zheng Jiang , Münstermann Sebastian , Han Wei Jian
Published: July 2022

Both experimental method and numerical method are used to analyze the large variation in the material ductility of high pressure die casting (HPDC) Aural-2 alloy in the present work. The X-ray tomography (XRT) technique is used to characterize and reveal the significant variation of the internal porosity for the investigated material. The Mises plasticity model in conjunction with a mixed Swift-Voce hardening law, and a stress state dependent fracture initiation criterion are used to accurately describe the deformation response of the material. Very good agreement with the experimental results is obtained in the predicted average force-displacement responses for the calibrated stress states. A probabilistic damage mechanics model is put forward to depict the apparent stochastic ductile fracture behavior over a wide range of stress states. The 5th and 95th percentiles of the fracture initiation locus are recalibrated based on the proposed probabilistic ductile fracture model, which could provide an almost perfect prediction of the maximum and minimum bounds of force-displacement curves.