Papers by Keyword: Modeling

Abstract: The southern part of Malang Regency, particularly the coastal area, has experienced rapid development in tourism, infrastructure, and new settlements in recent years, which has impacted water availability. Clungup Mangrove Conservation (CMC) in Sendang Biru is one of the ecotourism sites facing water availability constraints, particularly for meeting the needs of public facilities in the CMC area. Various efforts have been made, but they have not been fully effective in providing clean water. This case study uses direct observation and clean water pipeline network modeling using EPANET 2.0 to identify the causes of clean water constraints in the CMC area. Based on observations and modeling, it was found that the flow rate in the distribution pipes is suboptimal due to differences in pipe diameters within the network. Additionally, the water source currently used is surface water from rivers, which contains sediment during the rainy season and affects pump performance. Therefore, the solutions proposed in this case study not only involve replacing pipe diameters but also optimizing the use of the Sendang Biru water source. This research is not purely theoretical but includes the implementation of solutions. Based on evaluations after implementation, the newly designed pipeline network operates effectively and produces the expected water flow.

Abstract: Roll forming pipes for hydrogen infrastructure poses particular challenges for process design, especially with regard to geometric accuracy and the avoidance of forming defects that could compromise the integrity of the pipelines. Geometric accuracy is crucial to ensure uniform pressure distribution within the pipe. Conventional trial-and-error approaches to developing roll flower designs are time-consuming and cost-intensive, especially when working with high-strength steel grades. This work presents an integrated methodology for roll forming of monolithic sheet by incorporating real-world machine stiffness and experimental anisotropy. A finite element model was developed for S235 and S355 steels, validated through three-point bending and Digital Image Correlation (DIC). While database-derived models (JMatPro) underestimated yield stress by up to 30%, the experimental model precisely predicted strain distributions (error < 2%). A central novelty is the integration of in-situ 3D laser scans of the roll forming mill under load, allowing the simulation to account for elastic machine deflection. This enables the prediction of process-induced residual stresses, which are critical for the long-term integrity of pipelines against hydrogen-induced cracking.

Abstract: Sectors such as energy, aerospace, and heavy machinery increasingly rely on the machining of large components, where boring bars can easily exceed 200 mm in diameter and reach length-to-diameter ratios of up to 14. In these operations, chatter remains the dominant limitation due to the inherently low dynamic stiffness of such long tools. While Tuned Mass Dampers (TMDs) are widely applied in small and medium-sized boring bars, but transferring this technology to large-scale tools introduces significant challenges, particularly in the selection and tuning of damper components and the difficulty of evaluating performance prior to manufacturing. Because producing large boring bars is costly, a structured and predictive design strategy is essential to avoid trial-and-error iterations. This work introduces a scaling methodology that adapts TMD-integrated boring bar designs to large dimensions, providing a systematic approach to predict dynamic behavior across different tool sizes. The methodology is demonstrated through a case study involving Ø200 mm boring bar with length of 14 times the diameter. Experimental validation with the manufactured prototype confirms that the proposed scaling strategy enables effective chatter suppression and offers a practical path for extending TMD technology to large-scale boring applications.

Abstract: Medium-Mn steel (MMnS) and quenching and partitioning (QP) steels are two representatives of third-generation advanced high-strength steels (3^rd Gen AHSS), developed to achieve an optimal balance between strength and ductility. In forming applications, global formability reflects a material’s resistance to necking, while local formability indicates its resistance to fracture. Both aspects are essential for assessing mechanical performance. Global formability is often characterized by the forming limit curves at necking and is highly sensitive to work hardening behavior. Similarly, the forming limit curves at fracture determined from different stress states can be applied to evaluate the local formability. In addition, these deformation characteristics can be influenced by anisotropy introduced during sheet processing. Rolling process introduces orientation-dependent variations in both plastic flow and fracture behavior, which significantly affect necking development and fracture initiation. This study investigates and compares the global and local formability of various 3^rd Gen AHSS grades, with a focus on the influence of anisotropy. To investigate the anisotropic effects on plasticity and ductile fracture under different stress states, tensile tests were conducted on specimens with various geometries and orientations cut from sheet materials. Based on the tensile tests, the forming limit framework of Shen et al [1] was broadened to include anisotropic effects.

Abstract: The present paper got the objective to propose and apply a methodology based on plastic behaviour modeling of a magnesium alloy AZ31 and on a Navier-Stokes approach to describe the rib geometry during printing by FDM (Fused deposition modeling). By the plastic modeling the rib section in terms of equivalent radius is obtained by the application of an already proposed constitutive equation under semisolid condition. The same information is obtained by the calculation of dynamic viscosity coefficient of the material under different conditions of nominal extruder nozzles that are 0.3 and 0.1 mm in radius with related extrusion velocity and internal pressure. The rib radius obtained by the plastic model is higher when the big nozzle is used compared with that given by the Navier-Stokes approach while an opposite behaviour is evidenced with the small nozzle where the apparent viscosity is higher. Increasing printing velocity similar rib dimensions are obtained in both the cases.

Abstract: Open-die forging is an incremental bulk metal forming process for producing large, safety-relevant components such as turbine and generator shafts. Besides achieving the target geometry, the process improves mechanical properties through grain refinement and the elimination of casting-related defects. With the increasing use of high-alloy steels, precise process control is required to prevent surface and internal cracking caused by material damage. However, predictive models for damage evolution under the thermo-mechanical conditions of open-die forging remain limited, particularly with respect to high-temperature recrystallization and the incremental process character with inherent pause times. In this work, a recrystallization-sensitive damage model was developed and validated for open-die forging. The parameters of the Lemaitre damage formulation were determined for the cold work tool steel D2 (1.2379, X155CrVMo12-1) using hot tensile tests over the relevant forging temperature range. Dynamic recrystallization kinetics were characterized by hot compression tests and described using an Avrami-type JMAK formulation, while static recrystallization behavior was analyzed by stress relaxation experiments and also modeled with JMAK kinetics. These results enabled the quantification of recrystallized fractions as functions of strain, temperature, strain rate, and dwell time. To link microstructural evolution with damage development, tailored recrystallization states were generated in dilatometer experiments and examined metallographically with respect to void formation and healing. The extended model was implemented in a finite element framework and validated through open-die forging experiments on demonstrator geometries, showing its capability to predict damage initiation under industrially relevant conditions.

Abstract: The article examines the development features of the studied gas field and analyzes the efficiency of different hydraulic fracturing (HF) technologies. An integrated analysis of the field’s production history was carried out, covering the evaluation of applied HF methods, results of diagnostic injection tests, regression calculations, and characterization of fracture parameters. Historical production and reservoir pressure data were used to calibrate a material balance model in MBAL, ensuring consistency between observed and simulated results. HF operations using both crosslinked gel and slickwater were analyzed. Results of DFIT and mini-frac tests allowed the determination of key fracture parameters – length, height, conductivity (FCD), net pressure, and fluid efficiency. Based on the integrated dataset, a five-year forecast of field performance was developed. Wells treated with slickwater demonstrated higher and more stable flow rates compared with conventional crosslinked gel treatments, especially under lower reservoir pressures and timely well clean-up. The study emphasizes the importance of combining historical production analysis, fracture diagnostics, and regression methods with material balance modeling for reliable long-term productivity forecasting. The findings provide practical implications for optimizing HF parameters, selecting fluid systems, and planning reservoir development strategies aimed at maximizing gas recovery under depletion conditions.

Abstract: Noting that there is very little literature on the topic, a first analytical approach is proposed in this work for estimating the viscosity-like parameter of three-phase viscoplastic materials. In a first part, the conditions of application and the consequences of the three classical averaging equations involving the strain rates, the stresses and the power are reviewed for 2-phase mixtures and extended to three phases. The classical static and Taylor bounds as well as the heuristic Iso-strain rate assumption are analyzed. An extension of the Mori-Tanaka estimation to the three-phase case is then proposed for viscoplastic linear constituents. If the volume fraction of one of the phases (inclusions) is very low, in particular when its viscosity tends towards zero or infinity, fully analytical results are presented, which provides an extension of the classical dilute model.

Abstract: In this study, the electromagnetic heating of a steel sample in dilatometer was modeled with finite element method. The model was developed to simulate electromagnetic heating process of Linseis DIL L78 DQT/RITA Quenching & Deformation dilatometer, using the dimensions, current and frequency measured from the dilatometer for model validation. Thermophysical and electromagnetic behaviour of a steel is highly temperature-dependent, necessitating the temperature dependent material properties of the test material. The goal of this study was to replicate the behaviour of the electromagnetic heating in the dilatometer as accurately as possible. In electromagnetic heating the material properties have a significant impact on the efficiency of the heating process. The material must be electrically conductive to allow generating the electric current caused of a changing magnetic field which forms the electric field on the surface of the heated material. Material properties, which vary with temperature, were defined in the model as a function of temperature to ensure realistic thermophysical behaviour of the simulated part. Two different analysis solvers were used for electromagnetic and heat transfer analysis. The model was validated using measured data from the dilatometer.

Abstract: This study focused on the valorization of swelling clay from Damniadio. This swelling clay is extracted during construction and dumped in the wild. The aim of this study was to valorize this clay in construction in order to produce bricks strong enough to be used in construction. The physical properties of this clay were evaluated, as well as the mechanical performance of the bricks produced. Finally, a model of a building component was produced using Autocad and Graitec OMD software. Compressive strength and tensile strength values ranged from 1.82 MPa to 30.24 MPa and from 0.14 MPa to 1.83 MPa respectively for raw earth bricks, and from 2.31 MPa to 40.6 MPa and from 0.15 MPa to 2.29 MPa respectively for kiln-dried earth bricks. The modelling of these bricks has thus shown their potential for use as load-bearing structures, making them both more environmentally friendly and more economical in a context where the purchase of concrete will be more expensive than the extraction and processing of clay.