Caracterización numérico-experimental de superficies de fractura dúctil aplicada a planchas de PVC.
Loading...
Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
La predicción precisa de la fractura en materiales poliméricos es un desafío clave en la manufactura avanzada, especialmente en procesos de conformado incremental como el SPIF, donde la evolución del daño es altamente dependiente del estado de tensiones. En este contexto, la incorporación de modelos de fractura basados en variables críticas como la triaxialidad de esfuerzos y el ángulo de Lode permite capturar de manera más realista el comportamiento del material bajo condiciones complejas de carga, superando las limitaciones de los modelos tradicionales. Este estudio busca contribuir al desarrollo de herramientas más precisas para el análisis de fractura en polímeros, proporcionando una base teórica sólida para optimizar el diseño de componentes y mejorar la confiabilidad de los procesos de fabricación.
Este trabajo aborda el estudio del comportamiento mecánico del PVC bajo diferentes condiciones de carga, específicamente de tracción, mixtas y de corte, mediante la implementación del ensayo tipo Arcan y su simulación numérica. Se desarrolla una metodología experimental para caracterizar la respuesta del material en situaciones de carga biaxial y evaluar su fractura. Para ello, se diseñaron y fabricaron probetas tipo mariposa mediante el estudio de la literatura en investigaciones previas, utilizando mecanizado CNC y optimizando los parámetros de corte para obtener tolerancias precisas o adecuadas para el caso.
Las simulaciones se realizaron bajo un modelo FEM en Ansys, empleando modelos de plasticidad conocidos para evaluar la región plástica del material. Sin embargo, los resultados numéricos mostraron un cierto porcentaje de error respecto a los ensayos experimentales, lo que sugiere que la ley de endurecimiento utilizada no representa con total precisión el comportamiento del PVC en la región plástica. Se identificó que factores como la tolerancia en el espesor de las probetas y la distribución de esfuerzos influyen considerablemente en la precisión de los modelos.
Se evaluaron distintos modelos de fractura dúctil para correlacionar los datos obtenidos a partir de las simulaciones de los ensayos con respecto al SPIF, concluyendo que no es posible definir un modelo de daño global sin ajustes adicionales. La superficie de fractura obtenida permite predecir la fractura del material en procesos de conformado incremental monopunto en una geometría de cono para una lámina de PVC de 3 mm de espesor, utilizando ensayos Arcan como referencia para determinar el punto de ruptura. Este resultado valida la aplicabilidad del modelo en procesos de SPIF, proporcionando una base teórica para futuras investigaciones y optimización de la manufactura de materiales poliméricos.
En conclusión, el estudio genera una base de datos robusta sobre el comportamiento del PVC en condiciones biaxiales y propone mejoras en la fabricación de probetas para futuras investigaciones. Se destaca la necesidad de refinar la modelación de la plasticidad del material para mejorar la precisión de las simulaciones, lo que podría lograrse mediante la optimización de los parámetros de corte y el uso de leyes de endurecimiento más representativas.
The precise prediction of fracture in polymeric materials is a key challenge in advanced manufacturing, especially in incremental forming processes such as SPIF, where damage evolution is highly dependent on the stress state. In this context, incorporating fracture models based on critical variables such as stress triaxiality and the Lode angle allows for a more realistic representation of material behavior under complex loading conditions, overcoming the limitations of traditional models. This study aims to contribute to the development of more accurate tools for fracture analysis in polymers, providing a solid theoretical foundation to optimize component design and improve the reliability of manufacturing processes. This work addresses the study of the mechanical behavior of PVC under different loading conditions, specifically tensile, mixed, and shear, through the implementation of the Arcan test and its numerical simulation. An experimental methodology is developed to characterize the material's response under biaxial loading conditions and to evaluate its fracture. To this end, butterfly-type specimens were designed and manufactured based on a literature review of previous research, using CNC machining and optimizing cutting parameters to achieve precise or adequate tolerances for the case. Simulations were carried out using a FEM model in Ansys, employing known plasticity models to evaluate the material's plastic region. However, numerical results showed a certain percentage of error compared to experimental tests, suggesting that the hardening law used does not fully represent the behavior of PVC in the plastic region. It was identified that factors such as specimen thickness tolerance and stress distribution significantly influence the accuracy of the models. Different ductile fracture models were evaluated to correlate the data obtained from the test simulations with respect to SPIF, concluding that it is not possible to define a global damage model without additional adjustments. The obtained fracture surface allows predicting material fracture in single-point incremental forming processes for a conical geometry with a 3 mm thick PVC sheet, using Arcan tests as a reference to determine the rupture point. This result validates the applicability of the model in SPIF processes, providing a theoretical basis for future research and optimization of polymer material manufacturing. In conclusion, this study generates a robust database on PVC behavior under biaxial conditions and proposes improvements in specimen fabrication for future research. It highlights the need to refine the modeling of material plasticity to improve simulation accuracy, which could be achieved by optimizing cutting parameters and using more representative hardening laws.
The precise prediction of fracture in polymeric materials is a key challenge in advanced manufacturing, especially in incremental forming processes such as SPIF, where damage evolution is highly dependent on the stress state. In this context, incorporating fracture models based on critical variables such as stress triaxiality and the Lode angle allows for a more realistic representation of material behavior under complex loading conditions, overcoming the limitations of traditional models. This study aims to contribute to the development of more accurate tools for fracture analysis in polymers, providing a solid theoretical foundation to optimize component design and improve the reliability of manufacturing processes. This work addresses the study of the mechanical behavior of PVC under different loading conditions, specifically tensile, mixed, and shear, through the implementation of the Arcan test and its numerical simulation. An experimental methodology is developed to characterize the material's response under biaxial loading conditions and to evaluate its fracture. To this end, butterfly-type specimens were designed and manufactured based on a literature review of previous research, using CNC machining and optimizing cutting parameters to achieve precise or adequate tolerances for the case. Simulations were carried out using a FEM model in Ansys, employing known plasticity models to evaluate the material's plastic region. However, numerical results showed a certain percentage of error compared to experimental tests, suggesting that the hardening law used does not fully represent the behavior of PVC in the plastic region. It was identified that factors such as specimen thickness tolerance and stress distribution significantly influence the accuracy of the models. Different ductile fracture models were evaluated to correlate the data obtained from the test simulations with respect to SPIF, concluding that it is not possible to define a global damage model without additional adjustments. The obtained fracture surface allows predicting material fracture in single-point incremental forming processes for a conical geometry with a 3 mm thick PVC sheet, using Arcan tests as a reference to determine the rupture point. This result validates the applicability of the model in SPIF processes, providing a theoretical basis for future research and optimization of polymer material manufacturing. In conclusion, this study generates a robust database on PVC behavior under biaxial conditions and proposes improvements in specimen fabrication for future research. It highlights the need to refine the modeling of material plasticity to improve simulation accuracy, which could be achieved by optimizing cutting parameters and using more representative hardening laws.
Description
Tesis presentada para optar al título de Ingeniero Civil Mecánico
Keywords
Polímeros Propiedades mecánicas, Cloruro de polivinilo, Plásticos Análisis