https://hdl.handle.net/10259/6214 2026-04-18T02:39:39Z https://hdl.handle.net/10259/11332 Estimation of ultimate tensile strength of tubular materials using Ring Hoop Tension Test with cylindrical pins Calaf Chica, José; García Tárrago, María José; Preciado Calzada, Mónica; Bravo Díez, Pedro Miguel Mechanical characterization of metallic pipes is essential for assessing their structural integrity in industrial applications. The Ring Hoop Tension Test (RHTT) offers a simpler alternative to traditional methods for determining hoop strength, with two primary variants: the D-shaped pin configuration, which requires custom tooling for each pipe geometry, and the cylindrical pin system, which simplifies testing but introduces bending stresses. While the cylindrical pin method reduces friction-related uncertainties, its applicability for estimating ultimate tensile strength (UTS) had not been explored. This study develops a correlation between the minimum slope of the RHTT load–displacement curve and UTS in the hoop direction, specifically for cylindrical pins. A dual approach combining finite element analysis (FEA) and experimental validation was employed. Numerical simulations examined the influence of pipe slenderness, pin diameter, and strain-hardening behavior, leading to an empirical model. Experimental tests on aluminum 6061-T6 pipes confirmed the method’s accuracy, with deviations below 3 % compared to standard tensile tests. The results highlight the impact of geometric factors, particularly the diameter-to-thickness ratio, and introduce a pin-size correction factor to refine the methodology. This work demonstrates that RHTT with cylindrical pins can effectively estimate UTS, offering a practical and reliable alternative to conventional methods. 2025-12-01T00:00:00Z https://hdl.handle.net/10259/11331 High-frequency mechanical impedance of rubber mounts: Experimental characterization and resonance mechanisms García Tárrago, María José; Calaf Chica, José; Gómez Gil, Francisco Javier The characterization of the dynamic behavior of rubber anti-vibration mounts in electric motor systems is crucial for optimizing the vibro-acoustic performance of electric vehicle interiors. The transition to electric propulsion has revealed new high-frequency vibration sources (up to 3 kHz), including electromagnetic harmonics from motor commutation. Addressing these vibrations is essential to improve passenger comfort and promote the adoption of electric vehicles. This study presents an in-depth investigation into the dynamic response of cylindrical rubber mounts, employing a custom-designed test rig capable of evaluating performance up to 3 kHz. The experimental setup follows the UNE-EN ISO 10846 standard to ensure accurate measurements of vibro-acoustic transfer properties. To minimize high-frequency transmission through the test bench structure, a seismic mass serves as a decoupling element and stable reference. Force sensors are integrated into the seismic mass, ensuring that measured forces correspond solely to those applied to the rubber specimen, thus isolating the results from structural influences. The experimental findings reveal significant deviations in both the mechanical impedance modulus and the offset angle compared to behaviors observed at lower frequencies, which have been the primary focus of previous studies on vehicles with internal combustion engines. At low frequencies, stiffness-dominated behavior prevails; however, at higher frequencies, inertial effects and wave propagation phenomena become significant, altering the stiffness modulus curve and leading to the appearance of a peak characteristic of a resonance frequency. High-frequency responses are further analyzed through implicit harmonic analysis using advanced finite element modeling techniques. The experimental results are validated through this analysis, as the frequency at which the observed peak occurs coincides with a resonance frequency of the component identified in the harmonic analysis. Furthermore, this research demonstrates that these resonances, along with wave propagation effects, contribute to a complex deformation field, potentially accelerating material degradation and failure, addressing the importance of optimizing the design of these components to enhance their durability and performance. 2025-09-01T00:00:00Z https://hdl.handle.net/10259/11298 Design and validation of an in-situ hydrogen embrittlement system in a rotary bending fatigue testing machine Calaf Chica, José; Muñoz Manero, José E.; García Tárrago, María José; Preciado Calzada, Mónica; Bravo Díez, Pedro Miguel Hydrogen is a promising clean energy source, but its integration brings challenges, notably hydrogen embrittlement (HE), which degrades materials used in hydrogen infrastructure. Metals, especially steel, are vulnerable, leading to reduced strength and safety risks. Testing methodologies, including in-situ and ex-situ methods, are crucial to understanding HE. Insitu methods simulate real-time exposure, whereas ex-situ methods focus on post-exposure effects. Rotary bending fatigue tests are particularly interesting as they are cost-effective fatigue machines. This study aims to design and implement an electrochemical cell for in-situ HE testing under cyclic loading in this particular fatigue machine. The study focuses on adapting an electrochemical cell for a rotary bending fatigue machine, testing 42CrMo4 steel. Three key tasks were performed: (i) determining electrochemical parameters for inducing HE through Small Punch Tests (SPTs), (ii) evaluating an electrolyte jet system’s effectiveness, and (iii) designing and validating the electrochemical cell. Electrolytes tested included acid and alkaline solutions, and a novel jetting system was devised to ensure electrolyte coverage during high-speed rotation. The system’s electrical configuration and the cell’s structural adaptations for in-situ hydrogen charging were critical design elements. The tests confirmed the system’s effectiveness in charging the specimen with hydrogen, as evidenced by fatigue life reduction and fracture surface analysis. Specimens precharged with hydrogen, specifically in acidic environments, displayed increased brittleness and premature failure, contrasting with the ductile behavior of non-embrittled specimens. This highlights the system’s potential for future studies on material resistance to hydrogen embrittlement under cyclic loads. 2025-07-01T00:00:00Z https://hdl.handle.net/10259/11296 Estimation of ultimate tensile strength of tubular materials using Ring Hoop Tension Test with cylindrical pins Calaf Chica, José; García Tárrago, María José; Preciado Calzada, Mónica; Bravo Díez, Pedro Miguel Mechanical characterization of metallic pipes is essential for assessing their structural integrity in industrial applications. The Ring Hoop Tension Test (RHTT) offers a simpler alternative to traditional methods for determining hoop strength, with two primary variants: the D-shaped pin configuration, which requires custom tooling for each pipe geometry, and the cylindrical pin system, which simplifies testing but introduces bending stresses. While the cylindrical pin method reduces friction-related uncertainties, its applicability for estimating ultimate tensile strength (UTS) had not been explored. This study develops a correlation between the minimum slope of the RHTT load–displacement curve and UTS in the hoop direction, specifically for cylindrical pins. A dual approach combining finite element analysis (FEA) and experimental validation was employed. Numerical simulations examined the influence of pipe slenderness, pin diameter, and strain-hardening behavior, leading to an empirical model. Experimental tests on aluminum 6061-T6 pipes confirmed the method’s accuracy, with deviations below 3 % compared to standard tensile tests. The results highlight the impact of geometric factors, particularly the diameter-to-thickness ratio, and introduce a pin-size correction factor to refine the methodology. This work demonstrates that RHTT with cylindrical pins can effectively estimate UTS, offering a practical and reliable alternative to conventional methods. 2025-07-01T00:00:00Z