scholarly journals Compressive Properties and Constitutive Model of Semicrystalline Polyethylene

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2895
Author(s):  
Kebin Zhang ◽  
Wenbin Li ◽  
Yu Zheng ◽  
Wenjin Yao ◽  
Changfang Zhao
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Yield Stress ◽  
Dynamic Compression ◽  
Molecular Structures ◽  
Strengthening Effect ◽  
Compression Tests ◽  
Compression Process ◽  
Softening Effect ◽  
Constitutive Parameters

The mechanical properties of polyethylene (PE) materials are greatly influenced by their molecular structures, environmental temperature, and strain rate. In this study, static and dynamic compression tests were performed on two semicrystalline PE materials—ultrahigh molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE). The stress–strain curves of HDPE and UHMWPE under uniaxial compression at temperatures of −40–120 °C and strain rates of 0.001–5500 s−1 were obtained. The research findings suggest that both the UHMWPE and HDPE showed significant strain rate-strengthening effect and temperature-softening effect. In particular, HDPE exhibited better compression resistance and high-temperature resistance. The relationships between the yield stress and temperature and between the yield stress and strain rate for both materials were fitted, and the Cowper–Symonds constitutive model was built while considering the temperature effect. The parameters of the constitutive model were obtained and input into LS-DYNA software to simulate the dynamic compression process of HDPE. The simulation result was consistent with the test result, validating the accuracy of the constitutive parameters.

scholarly journals Dynamic Constitutive Model for Reactive Powder Concrete with Standard Curing

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Steel Fiber ◽  
High Strength ◽  
Reactive Powder Concrete ◽  
Strengthening Effect ◽  
Compression Tests ◽  
Softening Effect ◽  
Impact Compression ◽  
Reactive Powder

In view of the disadvantages of steam curing of reactive powder concrete (RPC), RPC with standard curing (SCRPC) is proposed. SC-RPC is an ultra-high strength concrete material prepared with high strength cement, silica fume, and gypsum by standard curing. In this study, quasi-static and impact compression tests were performed to investigate the mechanical properties of SC-RPC. The results show that steel fiber and the strain rate significantly affect the compression performance. Nevertheless, the Holmquist–Johnson–Cook (HJC) constitutive model is mainly used to analyze the dynamic response of brittle materials, such as common concrete, under shock and impact. Therefore, based on the quasi-staticand impact compression tests and the HJC constitutive model for concrete, by analyzing the steel fiber strengthening effect under quasi-static uniaxial compression, strain rate hardening, and the damage softening effect under SHPB impact compression, the steel fiber strengthening factor Kf , dynamic increase factor DIF, and revised damage variable D are introduced, and a modified HJC constitutive model for RPC with standard curing is proposed.

TI-6AL-4V ALLOY FABRICATED BY LASER DIRECT DEPOSITION: DYNAMIC MECHANICAL PROPERTIES, CONSTITUTIVE MODEL, AND NUMERICAL SIMULATION

2020 ◽  
Vol 27 (08) ◽  
pp. 1950191
Author(s):  
TAO WANG ◽  
WEILIN QIAO ◽  
SHENG WANG ◽  
ZHAN LI ◽  
HAO WANG ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Tensile Test ◽  
Strain Rate ◽  
Dynamic Compression ◽  
Dynamic Mechanical Properties ◽  
Strengthening Effect ◽  
Dynamic Mechanical ◽  
Direct Deposition ◽  
Laser Direct Deposition

The dynamic mechanical properties of Ti-6Al-4V alloy prepared by laser direct deposition (LDD) at different strain rates are of great significance for the application of LDD technology in the manufacture and repair of aero-engine parts. The quasi-static tensile test and dynamic compression test of Ti-6Al-4V alloy prepared by LDD (LDD-Ti-6Al-4V) were carried out under the quasi-static and high strain rate using INSTRON-5982 tensile test equipment and Split Hopkinson pressure bar (SHPB) equipment. The true stress–strain curve is obtained, which indicates that the LDD-Ti-6Al-4V has a strain rate strengthening effect. Moreover, the Johnson–Cook (J–C) constitutive model of LDD-Ti-6Al-4V was fitted based on experimental data, and the experimental process of SHPB was numerically simulated. The simulation results are basically the same as the experimental results, which proves the correctness of the J–C constitutive model of LDD-Ti-6Al-4V.

scholarly journals Investigation on Damage Characteristic and Constitutive Model of Deep Sandstone under Coupled High Temperature and Impact Loads

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhang Rongrong ◽  
Yang Yi ◽  
Ma Dongdong
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Strain Rate ◽  
Test Data ◽  
Impact Load ◽  
High Temperature Treatment ◽  
Strengthening Effect ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Damage Constitutive Model

To investigate the coupling damage characteristics of rock after high-temperature treatment under impact load, dynamic uniaxial compression tests for deep sandstone specimen under laboratory conditions varying with high temperature (i.e., 25°C, 100°C, 300°C, 500°C, 700°C, and 900°C) and strain rate (i.e., 170 s-1, 205 s-1, and 240 s-1) were performed using splitting Hopkinson pressure bar (SHPB) system. Coupling damage variable of deep sandstone was deduced based on the Lemaitre equivalent strain theory. Moreover, the damage parameters of deep sandstone were systematically determined according to the test data, and the effects of high temperature and strain rate on damage growth curves were investigated. Finally, a dynamic compound damage constitutive model, which could consider the coupling damage, was established and verified to describe the dynamic mechanical characteristic of deep sandstone. Theoretical and experimental results indicated that the simulated stress-strain curves matched the test data well and the proposed coupling damage constitutive model could reflect the high temperature-induced weakening and strain rate strengthening effect.

scholarly journals A Yield Stress Model for a Solution-Treated Ni-Based Superalloy during Plastic Deformation

2018 ◽  
Vol 37 (9-10) ◽  
pp. 849-856 ◽  
Author(s):  
Yan-Xing Liu ◽  
Y.C Lin
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Yield Stress ◽  
Deformation Temperature ◽  
Strengthening Effect ◽  
Stress Model ◽  
Compression Tests ◽  
Forming Process ◽  
Yield Behavior ◽  
Solution Treated

AbstractUp to now, there are few reports on the yield behavior of Ni-based superalloy during plastic deformation. However, an accurate yield stress model is significant for simulating the plastic forming process by cellular automaton or finite element methods. Therefore, the yield behavior of a solution-treated Ni-based superalloy is studied by hot compression tests. In order to evaluate yield stresses from the measured flow stress curves, the yield process is analyzed in terms of dislocation theory. Then, yield stresses at different deformation temperatures and strain rates are clearly determined. The experimental results show that the yield stresses are highly sensitive to deformation temperature and strain rate. The determined yield stress almost linearly increases with the increase of the logarithm of strain rate or the reciprocal of deformation temperature. A yield stress model is developed to correlate the yield behavior of the studied solution-treated Ni-based superalloy with deformation temperature, strain rate, and strengthening effect of alloying elements. The developed model can well describe the yield behavior of the studied solution-treated Ni-based superalloy.

scholarly journals Constitutive Behavior of an AA4032 Piston Alloy with Cu and Er Additions upon High-Temperature Compressive Deformation

2019 ◽  
Vol 51 (1) ◽  
pp. 467-481
Author(s):  
Suwaree Chankitmunkong ◽  
Dmitry G. Eskin ◽  
Chaowalit Limmaneevichitr
Keyword(s):  
Activation Energy ◽  
Flow Stress ◽  
Strain Rate ◽  
Hot Deformation ◽  
Base Alloy ◽  
True Strain ◽  
Constitutive Behavior ◽  
Compression Tests ◽  
Primary Si ◽  
Constitutive Parameters

Abstract Aluminum piston alloys of the AA4032 type are produced by direct-chill (DC) casting and subsequent forging; therefore, it is important to understand their thermomechanical behavior. In recent years, it was shown that additions of Cu and Er could improve mechanical properties of these alloys at room and high temperatures. In this work, we studied the constitutive behavior of AA4032-type alloys with and without Cu and Er additions. The experimental true stress–true strain curves were obtained by compression tests under various temperatures [683 K to 723 K (410 °C to 450 °C)] and strain rates (0.01 to 10 s−1) to determine constitutive parameters [strain-rate sensitivity, activation energy, and Zener–Hollomon (Z) parameter] for the hot deformation behavior of AA4032-type piston alloys with and without additions of Cu and Er. The flow stress decreased with increasing deformation temperature and decreasing strain rate. The results also showed that increasing the Cu content increased the flow stress over the applied range of deformation conditions due to solid-solution strengthening and the formation of primary Si particles, which led to an increase in the activation energy during hot deformation. Moreover, the main microstructural damage in the AA4032 alloy with 3.5 pct Cu was predominantly due to the cracking of primary Si particles. Additions of 0.4 pct Er and 3.5 pct Cu lower the activation energy of deformation, Q, as compared to the base alloy and the alloy with 3.5 pct Cu. The microstructures in the deformed specimens consisted of subgrains, recrystallized grains, and fine eutectic phases. The alloys containing Er demonstrated more polygonized grains at a low strain rate than the alloys without Er, indicating that Er hindered recrystallization development. The peak stress of the AA4032 alloy with 3.5 pct Cu alloy was higher than for the base AA4032 alloy and for the AA4032 alloy with 3.5 pct Cu and 0.4 pct Er additions, which was attributed to the prevalence of the work-hardening mechanism over the softening mechanism.

Strain-Rate Dependence of Compressive Yield Strength of Titanium Grade 4 with Coarse-Grained and Ultrafine-Grained Structures: Experimental Results and Theoretical Calculation

2018 ◽  
Vol 1145 ◽  
pp. 100-105
Author(s):  
Ivan V. Smirnov ◽  
Alexander Y. Konstantinov
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Pure Titanium ◽  
Coarse Grained ◽  
Strain Rates ◽  
Ultrafine Grained ◽  
Titanium Grade

The nanocrystalline (NC) and ultrafine-grained (UFG) structures of metallic materials can lead to their extraordinary high strength. However, most of the papers on this topic consider deformation parameters of NC and UFG materials only for the case of quasi-static tensile tests. Characteristics of dynamic strength and fracture of such materials remain unexplored. This paper presents a study of the mechanical behavior of pure titanium Grade 4 with a coarse-grained (CG) and UFG structure under uniaxial compression with different strain rates. The UFG structure was provided using the method of equal-channel angular pressing. The dynamic compression was carried out on a setup with the Split-Hopkinson pressure bar. It is found that in the observed range of strain rates 10–3-3×103 s–1, the yield stress of the CG titanium increases by 20%, and does not exceed the yield stress of the UFG titanium. However, the yield stress of the UFG titanium remains close to a quasi-static value. It is shown that these strain-rate dependencies of the yield strength can be predicted by the incubation time approach. The calculated curves show that at strain rates above 104 s–1 the yield stress of the CG titanium becomes higher than the yield strength of the UFG titanium.

scholarly journals Mechanical Response and Shear-Induced Initiation Properties of PTFE/Al/MoO3 Reactive Composites

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1200 ◽  
Author(s):  
Junyi Huang ◽  
Xiang Fang ◽  
Shuangzhang Wu ◽  
Li Yang ◽  
Zhongshen Yu ◽  
...  
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Mechanical Response ◽  
Dynamic Compression ◽  
Volume Ratio ◽  
Outer Edge ◽  
Reaction Products ◽  
Initiation Mechanism ◽  
Static Compression ◽  
Drop Weight

Polytetrafluoroethylene/aluminum/molybdenum oxide (PTFE/Al/MoO3) reactive composites of a volume ratio of 60:16:24 were studied in this research. Quasi-static compression, dynamic compression and drop-weight experiments were performed to explore the mechanical response and the shear-induced initiation properties of the composites. Mesoscale images of the specimens after sintering demonstrate that PTFE, Al and MoO3 powders were evenly mixed and no chemical reaction occurred after the materials were stirred, pressed and sintered. The yield stress and compressive strength of PTFE/Al/MoO3 specimens are sensitive to strain rate within the range of 10−3~3 × 103 s−1, and the yield stress shows a bilinear dependence on the logarithm values of strain rate. The established Johnson-Cook constitutive model based on the experimental data can describe the mechanical response of PTFE/Al/MoO3 material well. Drop-weight tests show that the PTFE/Al/MoO3 specimens can react violently when impacted, with the characteristic drop height (H50) calculated as 51.57 cm. The recovered specimens show that the reaction started from the outer edge of the specimen with the largest shear force and the most concentrated shear deformation, indicating a shear-induced initiation mechanism. The reaction products of PTFE/Al/MoO3 specimens were AlF3, Al2O3, Mo and C, demonstrating that redox reaction occurred between PTFE and Al, and between Al and MoO3.

High Temperature Plastic Behaviour of Icosahedral AlCuFe Quasicrystals.

2000 ◽  
Vol 643 ◽  
Author(s):  
Jan Fikar ◽  
Joël Bonneville ◽  
Nadine Baluc ◽  
Pierre Guyot
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Friction Stress ◽  
Dislocation Model ◽  
Compression Tests ◽  
Creep Tests ◽  
Flow Strength ◽  
Stress Strain ◽  
Softening Effect ◽  
Dislocation Interaction

AbstractIcosahedral AlCuFe poly-quasicrystalline specimens were deformed in constant strain rate compression tests at temperatures ranging between 300K - 1020K. Below nearly 0.7 Tm (Tm is the melting temperature) the specimens were brittle. Above the brittle-to-ductile transition temperature, after the elastic stage the stress-strain curves exhibit a marked yield-point followed by a stage of strain softening only. Transient creep tests were performed at different given stress/strain levels after interrupting the constant strain-rate deformation tests. After the transient tests, the flow strength of the specimens was investigated anew at constant strain rate. The results are interpreted in the framework of a dislocation model, where two effects opposing dislocation movement are considered: firstly, the usual elastic dislocation interaction, yielding a work-hardening contribution, and, secondly, a friction stress specific to the quasiperiodic lattice, leading to a softening effect.

scholarly journals Strain Compensation Constitutive Model and Parameter Optimization for Nb-Contained 316LN

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 212 ◽  
Author(s):  
Jingdan Li ◽  
Jiansheng Liu
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Compression Tests ◽  
Continuous Dynamic Recrystallization ◽  
Transmission Electron ◽  
Strain Compensation ◽  
Temperature Ranges ◽  
Continuous Dynamic

Hot deformation behavior of Nb-contained 316LN was investigated using a series of compression tests performed on a Gleeble-1500D simulator at temperature of 950–1200 °C and strain rate of 0.01~1 s−1. Based on the strain compensation method, a modified Arrhenius constitutive model considering the comprehensive effects of temperature, strain rate, and strain on flow stress was established, and the accuracy of the proposed model was evaluated by introducing correlation coefficient (R) and average relative error (AARE). The values of R and AARE were calculated as 0.995 and 4.48%, respectively, proving that the modified model has a high accuracy in predicting the flow stress of Nb-contained 316LN. The microstructure evolution and the dynamic recrystallization (DRX) mechanism of the experimental material were explicated by optical microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM). It was found that continuous dynamic recrystallization (CDRX) characterized by subgrain evolution and discontinuous dynamic recrystallization (DDRX) featured by grain boundary nuclei are two main dynamic recrystallization (DRX) mechanisms of Nb-contained 316LN. Furthermore, based on the results of microstructure analyses, optimum parameters were obtained as temperature ranges of 1100~1200 °C and strain rate ranges of 0.01~1 s−1.

Temperature and Strain-Rate Effect to Mechanical Behavior of Mo-Cr Alloy Cast Iron

2011 ◽  
Vol 704-705 ◽  
pp. 918-922
Author(s):  
Jing Kui Ruan ◽  
Ming Mao Hu
Keyword(s):  
Cast Iron ◽  
Strain Rate ◽  
High Speed ◽  
Tensile Yield Strength ◽  
Strengthening Effect ◽  
Softening Effect ◽  
Auto Panel ◽  
Alloy Cast Iron ◽  
Alloy Cast ◽  
Alloy Iron

Mo-Cr alloy cast iron is the most important material often used to make auto panel dies. To study high-speed machining process of auto panel dies, the material’s elastic modulus and fracture critical values of Mo-Cr alloy iron at 20°C-800°C were studied based on the high temperature elongation test. The material’s stress-strain relation curves at various temperatures (20°C-500°C) and various strain-rates (500/s-5000/s) were studied and the dynamic tensile yield strength values were obtained by dynamic SHPB(Split Hopkinson Pressure Bar) high-speed compression test. The test observation showed that Mo-Cr alloy iron has heat resistance and its behavior is between toughness and brittleness materials. Its toughness is enhanced with temperature increasing. At 20°C-500°C and strain-rates (500/s-5000/s) the dynamic tensile yield strength is decreased about 17％-24％ by temperature softening effect and is increased about 56％-70％ by strain-rate strengthening effect. The strain-rate strengthening effect prevails over temperature softening effect. Keywords: Auto panel die; Mo-Cr alloy cast iron; SHPB; Temperature softening effect; Strain-rate strengthening effect

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