Browsing by Author "Garcia-Herrera, Claudio"

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    Biomechanical characterization of the passive response of the thoracic aorta in chronic hypoxic newborn lambs using an evolutionary strategy
    (2021) Rivera, Eugenio; Canales, Claudio; Pacheco, Matias; Garcia-Herrera, Claudio; Macias, Demetrio; Celentano, Diego J.; Herrera, Emilio A.
    The present study involves experiments and modelling aimed at characterizing the passive structural mechanical behavior of the chronic hypoxic lamb thoracic aorta, whose gestation, birth and postnatal period were carried at high altitude (3600 masl). To this end, the mechanical response was studied via tensile and pressurization tests. The tensile and pressurization tests measurements were used simultaneously to calibrate the material parameters of the Gasser-Holzapfel-Ogden (GHO) hyperelasctic anisotropic constitutive model through an analytical-numerical optimization procedure solved with an evolutionary strategy that guarantees a stable response of the model. The model and procedure of calibration adequately adjust to the material behavior in a wide deformation range with an appropriate physical description. The results of this study predict the mechanical response of the lamb thoracic aorta under generalized loading states like those that can occur in physiological conditions and/or in systemic arterial hypertension. Finally, the novel use of the evolutionary strategy, together with the set of experiments and tools used in this study, provide a robust alternative to validate biomechanical characterizations.
  • No Thumbnail Available
    Item
    Computational Shape Design Optimization of Femoral Implants: Towards Efficient Forging Manufacturing
    (2024) Tuninetti, Victor; Fuentes, Geovanni; Onate, Angelo; Narayan, Sunny; Celentano, Diego; Garcia-Herrera, Claudio; Menacer, Brahim; Pincheira, Gonzalo; Garrido, Cesar; Valle, Rodrigo
    Total hip replacement is one of the most successful orthopedic operations in modern times. Osteolysis of the femur bone results in implant loosening and failure due to improper loading. To reduce induced stress, enhance load transfer, and minimize stress, the use of Ti-6Al-4V alloy in bone implants was investigated. The objective of this study was to perform a three-dimensional finite element analysis (FEA) of the femoral stem to optimize its shape and analyze the developed deformations and stresses under operational loads. In addition, the challenges associated with the manufacturing optimization of the femoral stem using large strain-based finite element modeling were addressed. The numerical findings showed that the optimized femoral stem using Ti-6Al-4V alloy under the normal daily activities of a person presented a strains distribution that promote uniform load transfer from the proximal to the distal area, and provided a mass reduction of 26%. The stress distribution was found to range from 700 to 0.2 MPa in the critical neck area of the implant. The developed computational tool allows for improved customized designs that lower the risk of prosthesis loss due to stress shielding.
  • No Thumbnail Available
    Item
    Hybrid numerical-experimental strategy for damage characterization of SAE 1045 steel
    (2023) Aranda, Pedro Miguel; Garcia-Herrera, Claudio; Celentano, Diego; Tuninetti, Victor; Toro, Sebastian Andres; Landeros, Felipe
    In this work, the elastoplastic behavior with continuous mechanical damage in a SAE 1045 steel is characterized using mainly torsional tests and simulations. A numerical-experimental inverse analysis procedure is proposed to fit a von Mises-type elastoplastic model and a Lemaitre-type continuous damage model to the material's mechanical response obtained in torsional tests. A FEM simulation campaign is carried out to calibrate the damage model, considering a two-step linear evolution of the damage variable in terms of the degradation of the elastic torsional stiffness measured in cyclic torsional tests. The procedure is validated with a numerical- experimental comparison in tensile tests to demonstrate the validity of the solution in other loading paths. The numerical model obtained is used to analyze the local effects of the damage and its distribution in torsional and tensile tests.
  • No Thumbnail Available
    Item
    Material and Damage Characterization of the Elastoplastic Response of the EK4 Deep Drawing Steel
    (2022) Barrera, Carlos; Garcia-Herrera, Claudio; Celentano, Diego J.; Signorelli, Javier W.
    Although EK4 drawing steel is nowadays widely used to manufacture a great variety of parts, it exhibits a marked normal and planar anisotropy that can make it difficult to control the process during its forming. In order to achieve an accurate description of the elastoplastic material response in sheet forming operations, this work presents a detailed material and damage characterization of EK4 deep drawing steel through a two-step methodology involving both experiments and finite element simulations. Firstly, tensile tests on sheet samples cut along the rolling, diagonal and transverse directions were carried out. The corresponding measurements were used to calibrate the material parameters related to the following modeling approaches adopted in the present study: the Hollomon hardening law, the non-associated Hill-48 phenomenological constitutive model and the anisotropic Hosford-Coulomb ductile fracture criterion. Secondly, this characterization was assessed and validated in the numerical simulation of the technological Erichsen test in which the material is mainly subjected to a biaxial stress state. The obtained predictions show a good agreement when compared with the corresponding experimental measurements of the punch load-displacement curve and thickness radial profile at the final fracture stage of the sample.
  • No Thumbnail Available
    Item
    Polycaprolactone and poly-β-cyclodextrin polymer blend: a Biopolymers composite film for drug release
    (2022) Antonella Sepulveda, Francesca; Sanchez, Julio; Oyarzun, Diego P.; Rodriguez-Gonzalez, Fidel E.; Tundidor-Camba, Alain; Garcia-Herrera, Claudio; Zapata, Paula A.; Pizarro, Guadalupe del C.; Martin-Trasanco, Rudy
    Nowadays, biomedical films containing drug carriers are preferred over conventional ones, since the protection of the injury and the therapy is joined within a single device. In the current work, we prepared polycaprolactone (PCL) composite films with beta-cyclodextrin (beta CD) or its epichlorohydrin crosslinked polymer (beta CDP) as ibuprofen (Ibu) drug carrier. The composite films were prepared at different PCL/additive ratios (2, 5, 10 and 20 wt%). ATR-FTIR spectroscopy and water contact angle (WCA) measurements indicated a scarce presence of the additives on the surface. Cross-section scanning electron micrographs showed the presence of aggregates corresponding to beta CD and beta CDP in the inner regions of the films. The incorporation of beta CD and beta CDP into the PCL films did not affect their thermal properties as was determined from differential scanning calorimetry (DSC). PCL-films with 10 wt% of the inclusion complexes Ibu@beta CD and Ibu@beta CDP were prepared and the release studies were performed. At pH = 7.2, PCL-Ibu@beta CDP composite film released 55% of Ibu within the first six hours; eight times the amount released by PCL-Ibu@beta CD within the same time interval. A plausible mechanism for ibuprofen release is discussed based on the cross-section SEM micrographs of composite films.
  • No Thumbnail Available
    Item
    Wrinkling on Stimuli-Responsive Functional Polymer Surfaces as a Promising Strategy for the Preparation of Effective Antibacterial/Antibiofouling Surfaces
    (2021) Gonzalez-Henriquez, Carmen M.; Rodriguez-Umanzor, Fernando E.; Alegria-Gomez, Matias N.; Terraza-Inostroza, Claudio A.; Martinez-Campos, Enrique; Cue-Lopez, Raquel; Sarabia-Vallejos, Mauricio A.; Garcia-Herrera, Claudio; Rodriguez-Hernandez, Juan
    Biocompatible smart interfaces play a crucial role in biomedical or tissue engineering applications, where their ability to actively change their conformation or physico-chemical properties permits finely tuning their surface attributes. Polyelectrolytes, such as acrylic acid, are a particular type of smart polymers that present pH responsiveness. This work aims to fabricate stable hydrogel films with reversible pH responsiveness that could spontaneously form wrinkled surface patterns. For this purpose, the photosensitive reaction mixtures were deposited via spin-coating over functionalized glasses. Following vacuum, UV, or either plasma treatments, it is possible to spontaneously form wrinkles, which could increase cell adherence. The pH responsiveness of the material was evaluated, observing an abrupt variation in the film thickness as a function of the environmental pH. Moreover, the presence of the carboxylic acid functional groups at the interface was evidenced by analyzing the adsorption/desorption capacity using methylene blue as a cationic dye model. The results demonstrated that increasing the acrylic acid in the microwrinkled hydrogel effectively improved the adsorption and release capacity and the ability of the carboxylic groups to establish ionic interactions with methylene blue. Finally, the role of the acrylic acid groups and the surface topography (smooth or wrinkled) on the final antibacterial properties were investigated, demonstrating their efficacy against both gram-positive and gram-negative bacteria model strains (E. coli and S. Aureus). According to our findings, microwrinkled hydrogels presented excellent antibacterial properties improving the results obtained for planar (smooth) hydrogels.