Numerical Studies on Size Effect Behaviors of Glassy Polymers Based on Strain Gradient Elastoviscoplastic Model

2018 ◽  
Vol 86 (2) ◽  
Author(s):  
Yujun Deng ◽  
Jin Wang ◽  
Peiyun Yi ◽  
Linfa Peng ◽  
Xinmin Lai ◽  
...  
Keyword(s):  
Finite Element ◽  
Size Effect ◽  
Strain Gradient ◽  
Simulation Models ◽  
Theoretical Models ◽  
Deformation Energy ◽  
Glassy Polymers ◽  
Traditional Theory ◽  
Fe Model ◽  
Processing Load

The improvement of the accuracy and efficiency of microforming process of polymers is of great significance to meet the miniaturization of polymeric components. When the nonuniform deformation is reduced to the microscopic scale, however, the mechanics of polymers shows a strong reinforcement behavior. Traditional theoretical models of polymers which have not considered material feature lengths are difficult to describe the size effect in micron scale, and the process simulation models based on the traditional theory could not provide effective and precise guidance for polymer microfabrication techniques. The work reported here proposed strategies to simulate size effect behaviors of glassy polymers in microforming process. First, the strain gradient elastoviscoplastic model was derived to describe the size affected behaviors of glassy polymers. Based on the proposed constitutive model, an eight-node finite element with the consideration of nodes' rotation was developed. Then, the proposed finite element method was verified by comparisons between experiments and simulations for both uniaxial compression and microbending. Finally, based on the FE model, under the consideration of the effect of rotation gradient, the strain distribution, the deformation energy, and the processing load were discussed. These strategies are immediately applicable to other wide-ranging classes of microforming process of glassy polymers, thereby foreshadowing their use in process optimizations of microfabrication of polymer components.

On the Axisymmetric Response of a Damaged Flexible Pipe

2014 ◽  
Author(s):  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman ◽  
George C. Campello
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Load Capacity ◽  
High Stress ◽  
Experimental Tests ◽  
Theoretical Models ◽  
Experimental Measurements ◽  
Fe Model ◽  
Flexible Pipe ◽  
High Stress Concentration

This work focuses on the structural analysis of a damaged 9.13″ flexible pipe to pure and combined axisymmetric loads. A set of experimental tests was carried out considering one up to ten broken wires in the outer tensile armor of the pipe and the results obtained are compared to those provided by a previously presented finite element (FE) model and a traditional analytical model. In the experimental tests, the pipe was firstly subjected to pure tension and, then, the responses to clockwise and anti-clockwise torsion superimposed with tension were investigated. In these tests, the induced strains in the outer armor were measured. Moreover, the axial elongation of the pipe was monitored when the pipe is subjected to tension, whilst the twist of the pipe was measured when torsion is imposed. The experimental results pointed to a slight decrease in the stiffness of the pipe with the increasing number of broken wires and, furthermore, a redistribution of forces among the intact wires of the damaged layer with high stress concentration in the wires close to the damaged ones. Both theoretical models captured these features, but, while the results obtained with the FE model agreed well with the experimental measurements, the traditional analytical model presented non-conservative results. Finally, the results obtained are employed to estimate the load capacity of the pipe.

Experimental Evaluation and Modeling Analysis of Micromilling of Hardened H13 Tool Steels

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Hongtao Ding ◽  
Ninggang Shen ◽  
Yung C. Shin
Keyword(s):  
Tool Wear ◽  
Size Effect ◽  
Strain Gradient ◽  
Chip Formation ◽  
Experimental Evaluation ◽  
Strain Gradient Plasticity ◽  
Fe Model ◽  
Tool Steels ◽  
Gradient Plasticity ◽  
Continuous Chip

This study is focused on experimental evaluation and numerical modeling of micromilling of hardened H13 tool steels. Multiple tool wear tests are performed in a microside cutting condition with 100 μm diameter endmills. The machined surface integrity, part dimension control, size effect, and tool wear progression in micromachining of hardened tool steels are experimentally investigated. A strain gradient plasticity model is developed for micromachining of hardened H13 tool steel. Novel 2D finite element (FE) models are developed in software ABAQUS to simulate the continuous chip formation with varying chip thickness in complete micromilling cycles under two configurations: microslotting and microside cutting. The steady-state cutting temperature is investigated by a heat transfer analysis of multi micromilling cycles. The FE model with the material strain gradient plasticity is validated by comparing the model predictions of the specific cutting forces with the measured data. The FE model results are discussed in chip formation, stress, temperature, and velocity fields to great details. It is shown that the developed FE model is capable of modeling a continuous chip formation in a complete micromilling cycle, including the size effect. It is also shown that the built-up edge in micromachining can be predicted with the FE model.

Experimental and Modeling Analysis of Micro-Milling of Hardened H13 Tool Steel

2011 ◽  
Author(s):  
Hongtao Ding ◽  
Ninggang Shen ◽  
Yung C. Shin
Keyword(s):  
Tool Wear ◽  
Size Effect ◽  
Strain Gradient ◽  
Chip Formation ◽  
Micro Milling ◽  
Fe Model ◽  
Tool Steels ◽  
Gradient Plasticity ◽  
H13 Tool Steel ◽  
Continuous Chip

This study is focused on experimental evaluation and numerical modeling of micro-milling of hardened H13 tool steels. Multiple tool wear tests are performed in a micro side cutting condition with 100 μm diameter endmills. The machined surface integrity, part dimension control, size effect and tool wear progression in micromachining of hardened tool steels are experimentally investigated. A strain gradient plasticity model is developed for micromachining of hardened H13 tool steel. Novel 2D FE models are developed in software ABAQUS to simulate the continuous chip formation with varying chip thickness in complete micro-milling cycles under two configurations: micro slotting and micro side cutting. The steady-state cutting temperature is investigated by a heat transfer analysis of multi micro-milling cycles. The FE model with the material strain gradient plasticity is validated by comparing the model predictions of the specific cutting forces with the measured data. The FE model results are discussed in chip formation, stress, temperature, and velocity fields to great details. It is shown that the developed FE model is capable of modeling a continuous chip formation in a complete micro-milling cycle, including the size effect. It is also shown that built-up edge in micromachining can be predicted with the FE model.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

scholarly journals Influence of finite element mesh size on the carrying capacity analysis of single-row ball slewing bearing

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110090
Author(s):  
Peiyu He ◽  
Qinrong Qian ◽  
Yun Wang ◽  
Hong Liu ◽  
Erkuo Guo ◽  
...  
Keyword(s):  
Finite Element ◽  
Carrying Capacity ◽  
Mesh Size ◽  
Finite Element Mesh ◽  
Fe Model ◽  
Element Mesh ◽  
Heavy Load ◽  
Slewing Bearing ◽  
Maximum Contact ◽  
Slewing Bearings

Slewing bearings are widely used in industry to provide rotary support and carry heavy load. The load-carrying capacity is one of the most important features of a slewing bearing, and needs to be calculated cautiously. This paper investigates the effect of mesh size on the finite element (FE) analysis of the carrying capacity of slewing bearings. A local finite element contact model of the slewing bearing is firstly established, and verified using Hertz contact theory. The optimal mesh size of finite element model under specified loads is determined by analyzing the maximum contact stress and the contact area. The overall FE model of the slewing bearing is established and strain tests were performed to verify the FE results. The effect of mesh size on the carrying capacity of the slewing bearing is investigated by analyzing the maximum contact load, deformation, and load distribution. This study of finite element mesh size verification provides an important guidance for the accuracy and efficiency of carrying capacity of slewing bearings.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Finite element modelling of microstructural changes during equal channel angular drawing of pure aluminium

2021 ◽  
Author(s):  
Serafino Caruso ◽  
Stano Imbrogno
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Finite Element ◽  
Size Variation ◽  
Fe Model ◽  
Pure Aluminium ◽  
Continuous Dynamic Recrystallization ◽  
Research Activities ◽  
Hardness Change ◽  
Continuous Dynamic

AbstractGrain refinement by severe plastic deformation (SPD) techniques, as a mechanism to control microstructure (recrystallization, grain size changes,…) and mechanical properties (yield strength, ultimate tensile strength, strain, hardness variation…) of pure aluminium conductor wires, is a topic of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model able to describe the microstructural evolution and the continuous dynamic recrystallization (CDRX) that occur during equal channel angular drawing (ECAD) of commercial 1370 pure aluminium (99.7% Al). A user subroutine has been developed based on the continuum mechanical model and the Hall-Petch (H-P) equations to predict grain size variation and hardness change. The model is validated by comparison with the experimental results and a predictive analysis is conducted varying the channel die angles. The study provides an accurate prediction of both the thermo-mechanical and the microstructural phenomena that occur during the process characterized by large plastic deformation.

Sign in / Sign up

Export Citation Format

Share Document