Artículos

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http://hdl.handle.net/20.500.14454/1634

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Examinando Artículos por Autor "Agirre Bikuña, Julen"

Mostrando 1 - 3 de 3
  • Miniatura
    Ítem
    Characterization of friction coefficient at near solidus forming (NSF) conditions using T-shape compression test
    (Elsevier Ltd, 2024-08) Sajjad, Muhammad; Agirre Bikuña, Julen; Plata Redondo, Gorka; Lozares Abasolo, Jokin; Mendiguren Olaeta, Joseba
    Amidst the escalating demand for sustainable manufacturing practices aimed at mitigating global emissions and waste, industries are actively seeking novel forming solutions to address these pressing global challenges. Near Solidus Forming (NSF) processes emerge as a promising alternative to confront such issues, offering the capability to fabricate intricate components reliably while minimizing material waste and energy consumption. This promising manufacturing process is still in its developmental stages for industrial applications, necessitating further exploration and understanding of various factors such as friction, heat transfer, and others. From the literature review, a lack of friction data at these temperatures has been identified. Therefore, this study is dedicated to the advanced characterization of the friction coefficient for Near Solidus Forging (NSF) operations. With that aim, T-shape experimental tests of 42CrMo4 alloy steel have been conducted at high temperatures (up to 1360 °C). Additionally, a lack of consensus on the correct T-shape testing and inverse analysis procedure has been noted. Consequently, apart from the experimental work, an in-depth analysis of the friction coefficient identification procedure has been conducted. As a result, a new geometrical output index is proposed, highly sensitive to the friction coefficient and therefore more reliable compared to state-of-the-art indexes. Furthermore, the influence of the selected geometrical output index and the consideration of sample-to-sample transfer and holding times were studied. Results showed that the increase in workload to consider the sample-to-sample transfer and holding times is not worthwhile, as assuming the average values lead to significantly less work with little impact in the final results (<5 % of error). The study also concludes that a friction coefficient of 0.25, 0.45 and 0.6 has been identified at temperatures of 1250 °C, 1300 °C and 1360 °C, respectively. Additionally, the result of thermal camera showed good agreement with the thermocouple data. Overall, in this study a robust and reliable T-shape testing, and friction coefficient identification procedure is proposed and validated.
  • Miniatura
    Ítem
    Characterization of the heat transfer coefficient at near solidus forming condition using columnar pressing test
    (Springer Science and Business Media Deutschland GmbH, 2024-11) Sajjad, Muhammad; Agirre Bikuña, Julen; Plata Redondo, Gorka; Lozares Abasolo, Jokin; Mendiguren Olaeta, Joseba
    This study addresses the significant gap in the literature regarding the heat transfer coefficient (HTC) under near-solidus forming (NSF) conditions, where materials are shaped close to their solidus state, presenting complex behaviour compared to traditional hot forming processes. Despite the pivotal role of heat transfer in developing a reliable material model for the digital twin (DT), limited data exist particularly regarding HTC characterization at NSF. Additionally, testing methodologies suitable for the high-temperature conditions, crucial for NSF processes, have not been adequately addressed. To fill this gap, this study aims to characterize HTC under NSF conditions using a columnar pressing test. The test was conducted at three different temperatures such as 1250, 1300, and 1360 °C and two different pressures, 2 and 8 MPa. During the test, temperature data was collected at the centre of the sample using a k-type thermocouple. Furthermore, the DT of the pressing test was developed and the three-dimensional finite element model of 42CrMo4 steel was constructed using FORGE NxT® 4.0 FEM software. The simulations were performed with varying HTC values to replicate the experimental test data. Inverse modelling techniques were then applied to compare experimental and simulated data, enabling the characterization and optimization of HTC values under NSF testing conditions. The results demonstrated that HTC in the NSF process is primary impacted by the forming pressure, whereas temperature change showed no variation at the studied ranges. The HTC value of 500 W/m2K and 800 W/m2K was identified at 2 MPa and 8 MPa, respectively. The conclusion of this study aims for a better understanding of heat transfer phenomena in NSF processes, enhancing the reliability of DT for industrial applications.
  • Miniatura
    Ítem
    The influence of the adiabatic heating coefficient on the near solidus forming process
    (Springer-Verlag Italia s.r.l., 2025-03) Sajjad, Muhammad; Agirre Bikuña, Julen; Plata Redondo, Gorka; Lozares Abasolo, Jokin; Mendiguren Olaeta, Joseba
    The Near Solidus Forming (NSF) process represents a critical method for shaping metallic components under extreme temperature conditions. When metals deform plastically, significant amounts of heat can be generated, which is due to the conversion of plastic deformation energy in the material often known is adiabatic heating. In this study, the influence of the adiabatic heating coefficient (AHC) on temperature distribution and plastic strain during NSF process is investigated. For this purpose, three industrial benchmarks previously fabricated using NSF techniques are selected to serve as representative cases for analysis. To conduct the analysis, sensitivity studies is performed at two key temperatures: 1360 °C and 1370 °C. These temperatures are chosen to capture the range of operating conditions typically encountered in industrial NSF applications. The simulation tool FORGE NXT® is utilized to investigate the potential effect of AHC on equivalent plastic strain (EPS). The range of potential AHC values considered is between 85% and 100%, as determined from a comprehensive literature survey. The study suggests that the AHC has a minimal effect on the deformation behaviour of 42CrMo4 steel at NSF condition for the studied benchmarks. The findings of this study provide the inside to the importance of AHC in the developing of a reliable Digital Twin (DT) for industrial NSF application.