scholarly journals Unified Modelling of Flow Stress and Microstructural Evolution of 300M Steel under Isothermal Tension

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1086
Author(s):  
Rongchuang Chen ◽  
Shiyang Zhang ◽  
Min Wang ◽  
Xianlong Liu ◽  
Fei Feng
Keyword(s):  
Constitutive Model ◽  
Microstructure Evolution ◽  
Constitutive Models ◽  
Strain Curve ◽  
Average Error ◽  
Forming Process ◽  
Stress Strain ◽  
300M Steel ◽  
Average Grain Size ◽  
Lower Temperature

Constitutive models that reflect the microstructure evolution is of great significance to accurately predict the forming process of forging. Through thermal tension of 300M steel under various temperatures (950~1150 °C) and strain rates (0.01~10 s−1), the material flow and microstructure evolutions were investigated. In order to describe both the exponential hardening phenomenon at a higher temperature, and the softening phenomenon due to recrystallization at a lower temperature, a constitutive model considering microstructure evolution was proposed based on the Kocks–Mecking model. It was found that considering the stress-strain curve to be exponential in the work-hardening stage could improve the constitutive model prediction precision. The average error was 2.43% (3.59 MPa), showing that the proposed model was more precise than the modified Arrhenius model and the Kocks–Mecking model. The models to describe recrystallization kinetics and average grain size were also constructed. This work enabled the Kocks–Mecking model to predict stress-strain curves with a higher accuracy, and broadened the applicable range of the Kocks–Mecking model.

scholarly journals A Hybrid Experimental-Computational Approach to Determine Constitutive Models for Hyperelastic Polymers

2019 ◽  
Author(s):  
Atefe Karimzadeh ◽  
Majid R. Ayatollahi ◽  
Bushroa A. Razak ◽  
Seyed S. R. Koloor ◽  
Mohd Y. Yahya ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Hybrid Approach ◽  
Compressive Loading ◽  
Constitutive Models ◽  
Strain Curve ◽  
Polymeric Materials ◽  
Computational Approach ◽  
Compression Tests ◽  
Stress Strain ◽  
Hyperelastic Materials

A study on the selection of hyperelastic constitutive model for polymeric materials is performed using a hybrid experimental-computational approach. Bis-GMA polymer is used as a case study of hyperelastic material to describe the polymer characteristics by determining its Poisson’s ratio and its valid range of the hyperelastic stress-strain curves. These two parameters are then used to determine the hyperelastic constitutive model by using the hybrid approach. Several uniaxial compression tests along with their finite element simulations are implemented in a systematic way, to identify the polymer behavior under the compressive loading conditions. Nano-indentation experiments are conducted to verify the hyperelastic behavior of the polymer. The experimental and computational evidences confirm that the Poisson’s ratio of Bis-GMA is 0.40 and the appropriate hyperelastic constitutive model for this polymer is of a second order polynomial. It is shown that, the results can be used to determine the true stress-strain curve of hyperelastic materials.

scholarly journals Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 529
Author(s):  
Chunzhi Du ◽  
Zhifan Li ◽  
Bingfei Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Shape Memory ◽  
Young’S Modulus ◽  
Residual Strain ◽  
Surface Effect ◽  
Young's Modulus ◽  
Strain Curve ◽  
Stress Strain ◽  
Strength Limit

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

scholarly journals Identification of orthotropic material parameters for acute, necrotic, fibrotic and remodelling myocardial infarcts in the rat

2019 ◽  
Author(s):  
Mazin S. Sirry ◽  
Laura Dubuis ◽  
Neil H. Davies ◽  
Jun Liao ◽  
Thomas Franz
Keyword(s):  
Constitutive Model ◽  
Orthotropic Material ◽  
Constitutive Models ◽  
Biaxial Stress ◽  
Percentage Error ◽  
Fe Model ◽  
Stress Strain ◽  
Material Parameters ◽  
Strain Data ◽  
Tensile Experiment

AbstractFinite element (FE) models have been effectively utilized in studying biomechanical aspects of myocardial infarction (MI). Although the rat is a widely used animal model for MI, there is a lack of material parameters based on anisotropic constitutive models for rat myocardial infarcts in literature. This study aimed at employing inverse methods to identify the parameters of an orthotropic constitutive model for myocardial infarcts in the acute, necrotic, fibrotic and remodelling phases utilizing the biaxial mechanical data developed in a previous study. FE model was developed mimicking the setup of the biaxial tensile experiment. The orthotropic case of the generalized Fung constitutive model was utilized to model the material properties of the infarct. The parameters of Fung model were optimized so that the FE solution best fitted the biaxial experimental stress-strain data. A genetic algorithm was used to minimize the objective function. Fung orthotropic material parameters for different infarct stages were identified. The FE model predictions best approximated the experimental data of the 28 days infarct stage with 3.0% mean absolute percentage error. The worst approximation was for the 7 days stage with 3.6% error. This study demonstrated that the experimental biaxial stress-strain data of healing rat infarcts could be successfully approximated using inverse FE methods and genetic algorithms. The material parameters identified in this study will provide an essential platform for FE investigations of biomechanical aspects of MI and the development of therapies.

Research on the High Temperature Constitutive Model of 300M Ultrahigh Strength Steel

2016 ◽  
Vol 836-837 ◽  
pp. 484-492
Author(s):  
Hui Ping Zhang ◽  
Na Zhao ◽  
Xu Shi ◽  
Xiao Lei Zhang ◽  
Yi Ren
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Strain Rate ◽  
Thermal Deformation ◽  
Strain Curve ◽  
Peak Stress ◽  
Stress Strain Curve ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steel ◽  
300M Steel

300M ultrahigh strength steel has good mechanical properties. It has been widely used in the force bearing components of aircraft. In this paper, By using Gleeble1-500D thermal simulator, we studied the change regularity of stress-strain curve of 300M steel using hot compression deformation when temperature is from 800°C to1100°C, strain rate is from 0.001 S-1to 1 S-1 and the strain is 0.7.The experimental results showed that when the strain rate is constant, the flow stress and the peak stress decrease with the increase of deformation temperature. When the deformation temperature is constant, the flow stress and peak stress increase with the increase of strain rate. From the test, we got the true stress-strain curve, calculated the thermal deformation constants such as the deformation activation energy of 300M ultrahigh strength steel. Eventually, we built the thermal deformation constitutive model in hyperbolic sine form of 300M steel.

Development of a Flow Evolution Network Model for the Stress–Strain Behavior of Poly(L-lactide)

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Maureen L. Dreher ◽  
Srinidhi Nagaraja ◽  
Jorgen Bergstrom ◽  
Danika Hayman
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Computational Modeling ◽  
Medical Devices ◽  
Constitutive Models ◽  
Constitutive Relationship ◽  
Displacement Curve ◽  
Stress Strain ◽  
Strain Behavior ◽  
Flow Evolution

Computational modeling is critical to medical device development and has grown in its utility for predicting device performance. Additionally, there is an increasing trend to use absorbable polymers for the manufacturing of medical devices. However, computational modeling of absorbable devices is hampered by a lack of appropriate constitutive models that capture their viscoelasticity and postyield behavior. The objective of this study was to develop a constitutive model that incorporated viscoplasticity for a common medical absorbable polymer. Microtensile bars of poly(L-lactide) (PLLA) were studied experimentally to evaluate their monotonic, cyclic, unloading, and relaxation behavior as well as rate dependencies under physiological conditions. The data were then fit to a viscoplastic flow evolution network (FEN) constitutive model. PLLA exhibited rate-dependent stress–strain behavior with significant postyield softening and stress relaxation. The FEN model was able to capture these relevant mechanical behaviors well with high accuracy. In addition, the suitability of the FEN model for predicting the stress–strain behavior of PLLA medical devices was investigated using finite element (FE) simulations of nonstandard geometries. The nonstandard geometries chosen were representative of generic PLLA cardiovascular stent subunits. These finite element simulations demonstrated that modeling PLLA using the FEN constitutive relationship accurately reproduced the specimen’s force–displacement curve, and therefore, is a suitable relationship to use when simulating stress distribution in PLLA medical devices. This study demonstrates the utility of an advanced constitutive model that incorporates viscoplasticity for simulating PLLA mechanical behavior.

Anisotropy of the Stress-Strain Curves for Line Pipe Steels

2010 ◽  
Author(s):  
Kensuke Nagai ◽  
Yasuhiro Shinohara ◽  
Shinya Sakamoto ◽  
Eiji Tsuru ◽  
Hitoshi Asahi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Strain Curve ◽  
Longitudinal Direction ◽  
Stress Strain Curve ◽  
Forming Process ◽  
Stress Strain ◽  
Line Pipe ◽  
Lower Aging Temperature ◽  
House Type ◽  
The Difference

To suppress the appearance of Lu¨ders strain and to decrease yield to tensile strength ratio in the L-direction (longitudinal direction), as well as the C-direction (circumferential direction), have been more important for strain-based design. In this study, conventional UOE and ERW pipes were examined in terms of tensile properties in both directions. In the case of UOE pipes, yield point was clearly observed on the stress-strain curve in the C-direction. However, stress-strain curves in the L-direction showed the round-house type. This difference became prominent after heat treatment for the anti-corrosion. Namely, clear Lu¨ders strain appeared in the C-direction at a lower aging temperature compared with that in the L-direction. On the other hand, contrasting results were obtained in the case for ERW pipes. Thus far, it’s been thought that the difference between UOE and ERW pipe was caused by the direction of final strain during the pipe forming process. There are also differences in the occurrence of Lu¨ders strain between each grade. A stress-strain curve maintained the round-house type in X100 grade pipe after the heat treatment at 240°C for five minutes; however, X70 grade pipe showed the stress-strain curve in the L-direction with Lu¨ders strain after the heat treatment at the same temperature.

The Studies of Rock Damage Softening Statistical Constitutive Model under True Triaxial Stress State

2014 ◽  
Vol 580-583 ◽  
pp. 312-315
Author(s):  
Hui Mei Zhang ◽  
Xiang Miao Xie ◽  
Geng She Yang
Keyword(s):  
Constitutive Model ◽  
Strain Curve ◽  
Stress Path ◽  
Complex Stress ◽  
Model Parameters ◽  
Stress Strain ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Complex Stress Path ◽  
The Impact

From the feature of rock micro-unit failure obeys Poisson random distribution, the damage softening statistical constitutive of was established under true triaxial confinement based on D-P criterion, so the impact of the intermediate principal stress on rock deformation and failure was considered in theory, and the actual engineering rock complex stress path evolution was reflected more realistically. Furthermore, according to the geometrical conditions of stress-strain relationship, the theoretical relationship between constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming, which enhance the adaptability of the model. Finally, the rationality of the model verified by the measured data.

Experimental Research on the Stress - Strain Curve of Regional Confined Concrete under Single Axial Press

2014 ◽  
Vol 584-586 ◽  
pp. 1289-1292
Author(s):  
Guo Liang Zhu
Keyword(s):  
Mechanical Properties ◽  
Theoretical Analysis ◽  
Constitutive Model ◽  
Theoretical Basis ◽  
Strain Curve ◽  
Confined Concrete ◽  
Constitutive Relationship ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Relationship Of

Regional confined concrete is base on confined concrete. It is the theory and application of a new attempt and development on confined concrete. To apply it to the actual project, we need to research mechanical properties and establish constitutive relationship of regional confined concrete. According to the research, we had carried on a series of tests, founded the stress-strain constitutive model of regional confined concrete under single axial press. The accuracy of theoretical analysis were more fully verified , and a theoretical basis for the application was provided.

scholarly journals A Damage Constitutive Model of Rock Subjected to Freeze-Thaw Cycles Based on Lognormal Distribution

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Hang Lin ◽  
Linyuan Liang ◽  
Yifan Chen ◽  
Rihong Cao
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Lognormal Distribution ◽  
Constitutive Models ◽  
Strain Curve ◽  
Statistical Distribution ◽  
Freeze Thaw ◽  
Accurate Quantitative Analysis ◽  
Distribution Parameters ◽  
Damage Constitutive Model

The constitutive model of rock is closely connected with the mechanical properties of rock. To achieve a more accurate quantitative analysis of the mechanical properties of rock after the action of freeze-thaw cycles, it is necessary to establish the constitutive models of rock subjected to freeze-thaw cycles from the view of rock damage. Based on the assumption of rock couple damage, this study established a statistical damage constitutive model of rock subjected to freeze-thaw cycles by combining the lognormal distribution, which is commonly used in engineering reliability analysis, and the strain strength theory. Then, the coordinates and derivative at the peak of the stress-strain curve of the rock after the action of freeze-thaw cycles were obtained through experiments to solve the statistical distribution parameters με and S of the model, whereafter, the theoretical curves by the established model were compared with the experimental curves to verify the validity of it, which shows a great agreement. Finally, the sensitivity analysis of the statistical distribution parameters was implemented. The results indicate that με reflects the strength of the rock, which shows a positive relation, and S stands for the brittleness of the rock, which shows a negative relation.

A constitutive model of concrete confined by steel reinforcements and steel jackets

2005 ◽  
Vol 32 (1) ◽  
pp. 279-288 ◽  
Author(s):  
Y-F Li ◽  
S-H Chen ◽  
K-C Chang ◽  
K-Y Liu
Keyword(s):  
Constitutive Model ◽  
Concrete Strength ◽  
Strain Curve ◽  
Steel Reinforcement ◽  
Confined Concrete ◽  
Stress Strain ◽  
Steel Jacket ◽  
Proposed Model ◽  
Concrete Cylinders ◽  
Different Types

In this paper, a total of 60 concrete cylinders 30 cm in diameter and 60 cm in length confined by steel jackets of different thicknesses and different types of lateral steel reinforcements are tested to obtain the stress–strain curves of the cylinders. A constitutive model is proposed to describe the behavior of concrete confined by steel reinforcement, steel jackets, and both steel reinforcement and steel jackets used to retrofit and strengthen reinforced concrete structures. The confined concrete stress–strain curve of the proposed model is divided into two regions: the curve in the first region is approximated using a second-order polynomial equation, and that in the second region using an nth-order power-law equation, where n is a function of the unconfined concrete strength and the lateral confining stress. The results of the experiments show that different types of lateral steel reinforcement contribute greatly to the compressive strength of concrete cylinders confined by the reinforcement. Comparing the stress–strain curves of the uniaxial test with that from the proposed model, we conclude that the proposed model for concrete confined by a steel jacket and lateral steel reinforcement can predict the experimental results very well.Key words: constitutive model, steel jacket, confined concrete.

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