Development of a novel synthesis method of a rigid-body four-bar linkage into a compliant mechanism
The four-bar linkage mechanism is widely used in various machinery applications. This study presents a synthesis method to transform a rigid-body four-bar mechanism into a compliant mechanism using four leaf-type hinges based on linear theory and Castigliano's Theorem. The objective is to determine the dimensions and configuration of a flexible four-bar mechanism that replicates the behavior of the initial rigid-body mechanism. The meeting point between the two mechanisms is the flexure hinge of the compliant mechanism, which is determined using the Pseudo-Rigid-Body model (PRBM). To validate the proposed method, a program based on non-linear theory is employed. The results confirm that the dimensional differences between the two are minimal, ranging from 0% to 0.13%. This study demonstrates the feasibility of synthesizing a Rigid-Body Four-Bar Mechanism into a compliant mechanism using the PRBM, as long as the deformations are within the linear domain.
Año de publicación: 2023
The four-bar linkage mechanism is widely used in various machinery applications. This study presents a synthesis method to transform a rigid-body four-bar mechanism into a compliant mechanism using four leaf-type hinges based on linear theory and Castigliano's Theorem. The objective is to determine the dimensions and configuration of a flexible four-bar mechanism that replicates the behavior of the initial rigid-body mechanism. The meeting point between the two mechanisms is the flexure hinge of the compliant mechanism, which is determined using the Pseudo-Rigid-Body model (PRBM). To validate the proposed method, a program based on non-linear theory is employed. The results confirm that the dimensional differences between the two are minimal, ranging from 0% to 0.13%. This study demonstrates the feasibility of synthesizing a Rigid-Body Four-Bar Mechanism into a compliant mechanism using the PRBM, as long as the deformations are within the linear domain.
Año de publicación: 2023
Analytical modelling of a dynamic vibration absorber for Parkinson disease
Parkinson is the most common neurodegenerative disease. It is characterized by the presence of involuntary tremor of human arms. Current treatments as pharmacological and surgery can be invasive for patients due to secondary effects and also high costs are required. In this sense, non-invasives devices have been proposed in order to reduce the tremor amplitude without secondary effects. These devices require a model in order to analyze the dynamic behavior and calculate the optimum parameters. In this article, it is developed an analytical three-dimensional model of a dynamic vibration absorber placed on a human arm. Results show dynamic vibration absorber is effective to reduce the tremor during voluntary motion. However, it is only effective while tremor frequencies are within a narrow range around the tuned frequency used for calculation of absorber parameters.
Año de publicación: 2023
Parkinson is the most common neurodegenerative disease. It is characterized by the presence of involuntary tremor of human arms. Current treatments as pharmacological and surgery can be invasive for patients due to secondary effects and also high costs are required. In this sense, non-invasives devices have been proposed in order to reduce the tremor amplitude without secondary effects. These devices require a model in order to analyze the dynamic behavior and calculate the optimum parameters. In this article, it is developed an analytical three-dimensional model of a dynamic vibration absorber placed on a human arm. Results show dynamic vibration absorber is effective to reduce the tremor during voluntary motion. However, it is only effective while tremor frequencies are within a narrow range around the tuned frequency used for calculation of absorber parameters.
Año de publicación: 2023
Compliant Finger Gripper Based on Topology Optimization
We present the design of a compliant finger based on the topology optimization method through Hill Climber stochastic search. The compliant finger is composed of an arrangement of beams, whose behavior is studied under the formulation of large deformation co-rotational beam elements. The design optimization seeks to maximize deflection of the tip of the compliant finger with the lowest possible input torque and the mechanical advantage via the contact force between the compliant finger and a free-form shaped object. Large tip deformation is sought along a desired path. The actual path traced by the candidate mechanism and the desired path are compared through their Fourier descriptors. Computation of the contact force is performed between the surfaces of Euler-Bernoulli beam and a prescribed free-form shape.
Año de publicación: 2023
We present the design of a compliant finger based on the topology optimization method through Hill Climber stochastic search. The compliant finger is composed of an arrangement of beams, whose behavior is studied under the formulation of large deformation co-rotational beam elements. The design optimization seeks to maximize deflection of the tip of the compliant finger with the lowest possible input torque and the mechanical advantage via the contact force between the compliant finger and a free-form shaped object. Large tip deformation is sought along a desired path. The actual path traced by the candidate mechanism and the desired path are compared through their Fourier descriptors. Computation of the contact force is performed between the surfaces of Euler-Bernoulli beam and a prescribed free-form shape.
Año de publicación: 2023
Lateral Dynamic Simulation of a Bus under Variable Conditions of Camber and Curvature Radius
The objective of this paper is to describe a model for the simulation of the lateral dynamics of a vehicle, specifically buses, under variable trajectory conditions, such as camber and radius...
Año de publicación: 2022
The objective of this paper is to describe a model for the simulation of the lateral dynamics of a vehicle, specifically buses, under variable trajectory conditions, such as camber and radius...
Año de publicación: 2022
Experimental and numerical studies of polyamide 11 and 12 surfaces modified by atmospheric pressure plasma treatment
Polyamide 11 and 12 (PA11 and PA12) have been applicable in various industries, including automotive, oil and gas, and sporting goods, over the past 70 years. Although they have good dyeability, their adhesion to other materials is limited due to relatively poor surface properties, which can be promoted by good wettability and high surface energy. This study aims to improve the surface properties of PA11 and PA12 by employing the advanced method of Atmospheric Pressure Plasma Torch (APPT) treatment. In this regard, the adhesion strengths of four commercially available adhesives were evaluated with the pull-off test on PAs plates before and after APPT treatment. The numerical simulation of this test was carried out in commercial finite element software using a cohesive zone model (CZM) to predict the fracture of adhesively bonded joints. Moreover, the modified PAs were analyzed using XPS, DSC, ATR-FTIR, optical profilometer and surface energy measurement. The results indicated that the surface properties, including wettability, polar surface energy and adhesion bonding, improved by employing the plasma treatment on PAs surfaces. The numerical simulation outcomes showed that the pull-off test might be a viable alternative to determine the CZM laws for fracture mode I.
Año de publicación: 2022
Polyamide 11 and 12 (PA11 and PA12) have been applicable in various industries, including automotive, oil and gas, and sporting goods, over the past 70 years. Although they have good dyeability, their adhesion to other materials is limited due to relatively poor surface properties, which can be promoted by good wettability and high surface energy. This study aims to improve the surface properties of PA11 and PA12 by employing the advanced method of Atmospheric Pressure Plasma Torch (APPT) treatment. In this regard, the adhesion strengths of four commercially available adhesives were evaluated with the pull-off test on PAs plates before and after APPT treatment. The numerical simulation of this test was carried out in commercial finite element software using a cohesive zone model (CZM) to predict the fracture of adhesively bonded joints. Moreover, the modified PAs were analyzed using XPS, DSC, ATR-FTIR, optical profilometer and surface energy measurement. The results indicated that the surface properties, including wettability, polar surface energy and adhesion bonding, improved by employing the plasma treatment on PAs surfaces. The numerical simulation outcomes showed that the pull-off test might be a viable alternative to determine the CZM laws for fracture mode I.
Año de publicación: 2022
Theoretical and experimental study of the bending collapse of partially reinforced CFRP–Steel square tubes
Bending collapse of thin-walled steel tubes is a major energy absorption mechanism in lightweight structures, especially for crashworthiness. External composite reinforcements can increase the energy absorption and strength of steel tubes. However, to this date there are still difficulties to determine the maximum load and the collapse behavior of reinforced, multi-material shapes, e.g., steel shapes covered by CFRP. In this work, a theoretical analysis of the collapse of a partially reinforced CFRP–Steel tube is performed, which encompasses the calculation of both the peak bending moment and the bending collapse curve of tubes with either the flanges or webs with reinforcements. The theoretical approach is validated with three-point bending experimental tests and an adequate agreement with experiments is found. The results also show an important increase of up to 57% in the peak load and 45% in the specific energy absorbed for partially reinforced tubes, with a maximum 14% increase in weight, when compared with unreinforced tubes. The developed theoretical model enhances even further the existing bending collapse theories, as it incorporates reinforcements in the model and provides a powerful tool for engineering analyses, and can be implemented in concept models, and optimization algorithms with ease. These findings can be used for enhancing existing and new lightweight structures and improving the crashworthiness of several automotive structures.
Año de publicación: 2022
Bending collapse of thin-walled steel tubes is a major energy absorption mechanism in lightweight structures, especially for crashworthiness. External composite reinforcements can increase the energy absorption and strength of steel tubes. However, to this date there are still difficulties to determine the maximum load and the collapse behavior of reinforced, multi-material shapes, e.g., steel shapes covered by CFRP. In this work, a theoretical analysis of the collapse of a partially reinforced CFRP–Steel tube is performed, which encompasses the calculation of both the peak bending moment and the bending collapse curve of tubes with either the flanges or webs with reinforcements. The theoretical approach is validated with three-point bending experimental tests and an adequate agreement with experiments is found. The results also show an important increase of up to 57% in the peak load and 45% in the specific energy absorbed for partially reinforced tubes, with a maximum 14% increase in weight, when compared with unreinforced tubes. The developed theoretical model enhances even further the existing bending collapse theories, as it incorporates reinforcements in the model and provides a powerful tool for engineering analyses, and can be implemented in concept models, and optimization algorithms with ease. These findings can be used for enhancing existing and new lightweight structures and improving the crashworthiness of several automotive structures.
Año de publicación: 2022
Bending collapse analysis for thin and medium-thin-walled square and rectangular hollow shapes
Thin-walled hollow shapes are of great interest in many industries with weight constraints due to their availability, low price, and strength to weight ratio. However, they are also prone to localized bending collapse, which can be used as an energy absorption mechanism during deformation. Up until now, industrial applications have relied on numerical simulations, non-standardized tests, and a handful of theories to address the bending collapse behavior. In this paper, a modification to the most widely used theory is presented and adapted for hollow shapes with greater thickness that cannot be considered ‘‘thick’’. To verify the accuracy of the proposed modification, a comparison with a detailed FEM model, validated through various threepoint bending collapse experimental tests, has been performed. The results seem to show that the proposed modifications can predict the maximum load and collapse stage behavior of hollow shapes with more accuracy than the original analytical model. Thus, the proposed modification may be used to predict the collapse behavior of commercially available square and rectangular hollow shapes in different fields of application.
Año de publicación: 2021
Thin-walled hollow shapes are of great interest in many industries with weight constraints due to their availability, low price, and strength to weight ratio. However, they are also prone to localized bending collapse, which can be used as an energy absorption mechanism during deformation. Up until now, industrial applications have relied on numerical simulations, non-standardized tests, and a handful of theories to address the bending collapse behavior. In this paper, a modification to the most widely used theory is presented and adapted for hollow shapes with greater thickness that cannot be considered ‘‘thick’’. To verify the accuracy of the proposed modification, a comparison with a detailed FEM model, validated through various threepoint bending collapse experimental tests, has been performed. The results seem to show that the proposed modifications can predict the maximum load and collapse stage behavior of hollow shapes with more accuracy than the original analytical model. Thus, the proposed modification may be used to predict the collapse behavior of commercially available square and rectangular hollow shapes in different fields of application.
Año de publicación: 2021