scholarly journals Mechanical Behaviors of Flax Fiber-Reinforced Composites at Different Strain Rates and Rate-Dependent Constitutive Model

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 854 ◽  
Author(s):  
Dayong Hu ◽  
Linwei Dang ◽  
Chong Zhang ◽  
Zhiqiang Zhang
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Flax Fiber ◽  
Fiber Reinforced Composites ◽  
Strain Rates ◽  
Reinforced Composites ◽  
Dynamic Mechanical ◽  
Rate Dependent ◽  
Dynamic Mechanical Behavior

Flax fiber-reinforced composites (FFRCs) exhibit excellent environmentally friendly qualities, such as light weight, low cost, recyclability, and excellent mechanical properties. Understanding the dynamic mechanical behavior of FFRCs could broaden their potential applications in lightweight, crashworthy, and impact-critical structures. This study presents a study on the fabrication of FFRCs by vacuum-assisted resin infusion. The dynamic stress–strain responses of the fabricated specimens at strain rates ranging from 0.006 s-1 to 2200 s-1 were evaluated using quasi-static tests and the Split–Hopkinson pressure bar (SHPB). The results indicated that the FFRC exhibited superior strain rate sensitivity. Final deformation photographs and scanning electron micrographs clearly revealed the damage evolution of the FFRC specimens, as well as various failure mechanisms, including fiber–matrix debonding, fiber pull-out, and fiber fracture at different strain rates. On the basis of the experimental results, a simplified Johnson–Cook model was established to describe the strain-rate dependent constitutive model of FFRC. The validation of the suggested constitutive model was embedded in the finite element simulations and could well repeat the strain wave observed from the experiment results. Finally, the quasi-static compression and drop-hammer impact of pyramidal lattice structures with FFRC cores were investigated both numerically and experimentally, proving the effectiveness of the simplified Johnson–Cook model. This study could potentially contribute to a deeper understanding of the dynamic mechanical behavior of FFRCs and provide fundamental experimental data for future engineering applications.

scholarly journals Extension of Flow Behaviour and Damage Models for Cast Iron Alloys with Strain Rate Effect

2020 ◽  
Author(s):  
Chuang Liu ◽  
Dongzhi Sun ◽  
Xianfeng Zhang ◽  
Florence Andrieux ◽  
Tobias Gerster
Keyword(s):  
Cast Iron ◽  
Constitutive Model ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Damage Model ◽  
Iron Alloys ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Damage Models ◽  
Rate Dependent

Abstract Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry. To study the mechanical behavior of a typical ductile cast iron (GJS-450) with nodular graphite, uni-axial quasi-static and dynamic tensile tests at strain rates of 10− 4, 1, 10, 100, and 250 s− 1 were carried out. In order to investigate the effects of stress state, specimens with various geometries were used in the experiments. Stress–strain curves and fracture strains of the GJS-450 alloy in the strain-rate range of 10− 4 to 250 s− 1 were obtained. A strain rate-dependent plastic flow law based on the Voce model is proposed to describe the mechanical behavior in the corresponding strain-rate range. The deformation behavior at various strain rates is observed and analyzed through simulations with the proposed strain rate-dependent constitutive model. The available damage model from Bai and Wierzbicki is extended to take the strain rate into account and calibrated based on the analysis of local fracture strains. The validity of the proposed constitutive model including the damage model was verified by the corresponding experimental results. The results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 alloys. The predictions with the proposed constitutive model and damage models at various strain rates agree well with the experimental results, which illustrates that the rate-dependent flow rule and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain rates.

Rate-Dependent Behavior and Constitutive Model of Polycarbonate at Strain Rate from 10-5 to 103 S-1

2011 ◽  
Vol 117-119 ◽  
pp. 434-437
Author(s):  
Wen Jun Hu ◽  
Xi Cheng Huang ◽  
Fang Ju Zhang ◽  
Cheng Jun Chen
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Temperature Dependent ◽  
Static Tests ◽  
Rate Range ◽  
Rate Dependent ◽  
Dependent Behavior

Uni-axial quasi-static tests at strain rates 10-5, 10-4, 10-3,10-2 and 10-1 s-1 and dynamic compressive tests at strain rates 1679, 2769,5000 and 8200 s-1 have been carried out to study the mechanical behavior for polycarbonate used in the avigation industry. The stress–strain curves of polycarbonate in the strain-rate range from 10-5 to 8200 s-1 have been obtained. The effects of the strain rate on yield phenomenon and rate-dependent mechanical behavior are discussed. A plastic flow law based on the DSGZ rate-temperature-dependent constitutive model was used to describe the mechanical behavior of polycarbonate in the strain-rate range from 10-5 to 103 s-1. The results at the six strain rates are in excellent agreement with the experimental data, which illustrates that the constitutive model can describe the mechanical behavior for polycarbonate at low and high strain rates perfectly.

The Effect of Materials Testing Mode on Mechanical Behavior Under Temperature Influence in Complex Deformation Processes

2007 ◽  
Author(s):  
S. Anurag ◽  
Y. B. Guo
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Material Testing ◽  
Materials Testing ◽  
Plasticity Model ◽  
Complex Deformation ◽  
Material Constants ◽  
Dynamic Mechanical ◽  
Dynamic Mechanical Behavior ◽  
Deformation Processes

Complex deformation processes such as forming and machining involve large strain, high strain rate, high temperatures, strain rate/temperature coupling, and potential loading history effects. The conventional empirical and semi-empirical plasticity models are not adequate for characterizing dynamic mechanical behavior of work materials at the complex loading scenarios. The accuracy of characterizing the dynamic mechanical behavior in deformation processes using any constitutive models is strongly affected by materials testing data in which a constitutive model is fitted. Tension or compression tests have been widely used to approximate material properties in various manufacturing processes. However, it has been a critical question whether tension or compression test should be utilized for capturing the true nature of complex material deformations. In this study, the influences of two material testing modes on mechanical behavior of AISI52100 steel (62 HRc) were investigated using the internal state variable (ISV) plasticity model. Twenty material constants have been found by nonlinear fitting the ISV plasticity model to the base line test data obtained from each deformation mode. It has shown that the material testing modes have profound effects on some materials constants of the ISV model. The stress sensitivity study to ISV model parameters has identified the critical material constants for reflecting the nature of material deformation. The different testing modes have significant influence on the material constants associated with isotropic hardening rather than kinematic hardening.

scholarly journals Dynamic Mechanical Characteristics and Constitutive Modeling of Rail Steel over a Wide Range of Temperatures and Strain Rates

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Peijie Liu ◽  
Yanming Quan ◽  
Guo Ding
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Split Hopkinson Pressure Bar ◽  
Rail Steel ◽  
Strain Rates ◽  
Dynamic Mechanical ◽  
Flow Response ◽  
Strain And Strain Rate ◽  
Average Absolute Relative Error ◽  
Wide Range

Rail steel plays an indispensable role in the safety and stability of the railway system. Therefore, a suitable constitutive model is quite significant to understand the mechanical behavior of this material. Here, the compressive mechanical behavior of heat-treated U71Mn rail steel over a wide range of strain rates (0.001 s−1–10000 s−1) and temperatures (20°C–800°C) was systematically investigated via uniaxial quasistatic and dynamic tests. The split Hopkinson pressure bar (SHPB) apparatus was utilized to perform dynamic mechanical tests. The effects of temperature, strain, and strain rate on the dynamic compressive characteristics of U71Mn were discussed, respectively. The results indicate that the flow response of U71Mn is both temperature-sensitive and strain rate-sensitive. However, the influence of temperature on the flow response is more remarkable than that of strain rate. On the basis of the experimental data, the original and modified Johnson-Cook (JC) models of the studied material were established, respectively. Using correlation coefficient and average absolute relative error parameters, it is revealed that better agreement between the experimental and predicted stress is reached by the modified JC model, which demonstrates that the modified one can characterize the mechanical behavior of the studied material preferably.

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