scholarly journals Characterization of the Mechanical Behavior of a Lead Alloy, from Quasi-Static to Dynamic Loading for a Wide Range of Temperatures

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2357
Author(s):  
Yann Coget ◽  
Yaël Demarty ◽  
Alexis Rusinek
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Digital Simulation ◽  
Armed Forces ◽  
Material Behavior ◽  
Lead Alloy ◽  
Behavioral Models ◽  
Compression Tests ◽  
Wide Range ◽  
The Impact

The current needs in terms of ballistic protection for armed forces require an almost constant improvement in performance to face the constantly evolving threats and scenarios. Ballistic tests are conventionally carried out in order to assess and validate the levels of protection. The challenge is to be able to set up a digital protocol and only carry out final validation tests. Indeed, the advantage of digital simulation lies in the possibility of being able to evaluate a wide variety of configurations. In order to obtain reliable results, it is necessary to use sufficiently precise material behavior models to transcribe the phenomena observed during the impact. Our study focuses on the behavior of a small caliber ammunition with a ductile core impacting personal protection. More particularly on the mechanical behavior of the lead alloy core. Thus, compression tests have been carried out on a wide range of deformation rates, from quasi-static behavior to dynamic regime, at different temperatures. The study in dynamic conditions was carried out using split Hopkinson pressure bars. Due to the material properties, the experimental device had to be adapted in order to optimize the propagation of the waves allowing to measure signals (elastic waves). These tests demonstrate the dependency of the stress with strain rate and temperature. Dynamic restoration and recrystallization phenomena, characteristic of a material deformed in its hot working area, have also been identified. The associated oscillations due to Pochhammer–Chree effect, observable on the stress–strain curves, constitute the major problem for the implementation of behavioral models. Finally, a constitutive model sensitive to strain rate and temperature is investigated for ballistic purposes.

scholarly journals Impact of the Loading Conditions and the Building Directions on the Mechanical Behavior of Biomedical β-Titanium Alloy Produced In Situ by Laser-Based Powder Bed Fusion

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 509
Author(s):  
Housseme Ben Boubaker ◽  
Pascal Laheurte ◽  
Gael Le Coz ◽  
Seyyed-Saeid Biriaie ◽  
Paul Didier ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Electron Backscatter Diffraction ◽  
Material Behavior ◽  
Powder Bed Fusion ◽  
Loading Conditions ◽  
Compression Tests ◽  
Powder Bed ◽  
X Ray ◽  
The Impact

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of β-Ti42Nb alloy. Compression tests are performed under two strain rates (1 s−1 and 10 s−1) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45∘ exhibit higher flow stress than those produced with a building direction of 90∘, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV0.1. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.

A Microstructure-Level Material Model for Simulating the Machining of Carbon Nanotube Reinforced Polymer Composites

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Ashutosh Dikshit ◽  
Johnson Samuel ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Carbon Nanotube ◽  
Weight Fraction ◽  
Material Model ◽  
Material Behavior ◽  
Compression Tests ◽  
Linear Elastic ◽  
Rate Dependent ◽  
Wide Range ◽  
Parametrization Scheme ◽  
Fraction Length

A continuum-based microstructure-level material model for simulation of polycarbonate carbon nanotube (CNT) composite machining has been developed wherein polycarbonate and CNT phases are modeled separately. A parametrization scheme is developed to characterize the microstructure of composites having different loadings of carbon nanotubes. The Mulliken and Boyce constitutive model [2006, “Mechanics of the Rate Dependent Elastic Plastic Deformation of Glassy Polymers from Low to High Strair Rates,” Int. J. Solids Struct., 43(5), pp. 1331–1356] for polycarbonate has been modified and implemented to capture thermal effects. The CNT phase is modeled as a linear elastic material. Dynamic mechanical analyzer tests are conducted on the polycarbonate phase to capture the changes in material behavior with temperature and strain rate. Compression tests are performed over a wide range of strain rates for model validation. The model predictions for yield stress are seen to be within 10% of the experimental results for all the materials tested. The model is used to study the effect of weight fraction, length, and orientation of CNTs on the mechanical behavior of the composites.

Determining Deformation Behavior of AISI 9310 Steel Varying Temperature and Strain Rate for Aerospace Applications

2021 ◽  
Author(s):  
Adanma Akoma ◽  
Kevin Sala ◽  
Chase Sheeley ◽  
Lesley D. Frame
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
Test Sample ◽  
Material Behavior ◽  
Image Correlation ◽  
Sample Length ◽  
Stress Behavior ◽  
Flow Stress Behavior ◽  
The Impact

Abstract Determination of flow stress behavior of materials is a critical aspect of understanding and predicting behavior of materials during manufacturing and use. However, accurately capturing the flow stress behavior of a material at different strain rates and temperatures can be challenging. Non-uniform deformation and thermal gradients within the test sample make it difficult to match test results directly to constitutive equations that describe the material behavior. In this study, we have tested AISI 9310 steel using a Gleeble 3500 physical simulator and Digital Image Correlation system to capture transient mechanical properties at elevated temperatures (300°C – 600°C) while controlling strain rate (0.01 s-1 to 0.1 s-1). The data presented here illustrate the benefit of capturing non-uniform plastic strain of the test specimens along the sample length, and we characterize the differences between different test modes and the impact of the resulting data that describe the flow stress behavior.

Refined Modeling of Projectile Impact Onto Submerged Structure

2008 ◽  
Author(s):  
Justin Onisoru ◽  
Ovidiu Coman ◽  
Paul Wilson ◽  
George Thomas
Keyword(s):  
Strain Rate ◽  
Structural Integrity ◽  
Initial Conditions ◽  
Safety Issue ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Material Behavior ◽  
Spent Fuel ◽  
The Impact

Structural integrity of spent fuel racks is a critical safety issue in nuclear power stations. The standard approach of evaluating the effects of an impact projectile on a submerged structure, which constitute the start point of the current study, involves three main steps: determination of the conditions just prior to the impact (that are considered as initial conditions for the analysis), setting the mechanism of transferring energy from the projectile to the target structure, and determining how that energy is absorbed by the impacted structure. Usually, the dynamics of the projectile are ideally considered, the influence of the fluid presence is restricted to the determination of the impact velocity and strain rate dependency is limited to choosing a true stress vs. strain curve corresponding to some constant strain rate. Starting from the standard engineering approach, the authors have refined the model considering more realistic dynamics of the projectile, extending the influence of the fluid to the entire analysis and using a more accurate strain rate dependant material behavior. Explicit Finite Element analyses are used in order to incorporate the desired effects.

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.

A Modified Double Multiple Nonlinear Regression Constitutive Equation for Modeling and Prediction of High Temperature Flow Behavior of BFe10-1-2 Alloy

2018 ◽  
Vol 37 (1) ◽  
pp. 75-87
Author(s):  
Jun Cai ◽  
Kuaishe Wang ◽  
Jiamin Shi ◽  
Wen Wang ◽  
Yingying Liu
Keyword(s):  
Flow Stress ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Nonlinear Regression ◽  
Flow Behavior ◽  
Strain Rate Range ◽  
Compression Tests ◽  
Constitutive Analysis ◽  
Average Absolute Relative Error ◽  
Wide Range

AbstractConstitutive analysis for hot working of BFe10-1-2 alloy was carried out by using experimental stress–strain data from isothermal hot compression tests, in a wide range of temperature of 1,023~1,273 K, and strain rate range of 0.001~10 s–1. A constitutive equation based on modified double multiple nonlinear regression was proposed considering the independent effects of strain, strain rate, temperature and their interrelation. The predicted flow stress data calculated from the developed equation was compared with the experimental data. Correlation coefficient (R), average absolute relative error (AARE) and relative errors were introduced to verify the validity of the developed constitutive equation. Subsequently, a comparative study was made on the capability of strain-compensated Arrhenius-type constitutive model. The results showed that the developed constitutive equation based on modified double multiple nonlinear regression could predict flow stress of BFe10-1-2 alloy with good correlation and generalization.

scholarly journals Machine Learning Enhanced Dynamic Response Modelling of Superelastic Shape Memory Alloy Wires

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 304
Author(s):  
Niklas Lenzen ◽  
Okyay Altay
Keyword(s):  
Machine Learning ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Thermodynamic Parameters ◽  
Expert Knowledge ◽  
Material Behavior ◽  
Model Parameters ◽  
Engineering Structures ◽  
Wide Range

Superelastic shape memory alloy (SMA) wires exhibit superb hysteretic energy dissipation and deformation capabilities. Therefore, they are increasingly used for the vibration control of civil engineering structures. The efficient design of SMA-based control devices requires accurate material models. However, the thermodynamically coupled SMA behavior is highly sensitive to strain rate. For an accurate modelling of the material behavior, a wide range of parameters needs to be determined by experiments, where the identification of thermodynamic parameters is particularly challenging due to required technical instruments and expert knowledge. For an efficient identification of thermodynamic parameters, this study proposes a machine-learning-based approach, which was specifically designed considering the dynamic SMA behavior. For this purpose, a feedforward artificial neural network (ANN) architecture was developed. For the generation of training data, a macroscopic constitutive SMA model was adapted considering strain rate effects. After training, the ANN can identify the searched model parameters from cyclic tensile stress–strain tests. The proposed approach is applied on superelastic SMA wires and validated by experiments.

Elastic and pseudoviscous properties of coal under quasi-static and impact loadings

1984 ◽  
Vol 21 (2) ◽  
pp. 203-212 ◽  
Author(s):  
J. R. Klepaczko ◽  
T. R. Hsu ◽  
M. N. Bassim
Keyword(s):  
Strain Rate ◽  
Elastic Properties ◽  
Viscoelastic Properties ◽  
Viscoelastic Model ◽  
Rate Sensitivity ◽  
Bedding Plane ◽  
Strain Rates ◽  
Compression Tests ◽  
Wide Range ◽  
Coefficient Of Viscosity

An investigation of the elastic and viscoelastic properties of Nova Scotia coal was carried out over a wide range of strain rates (quasi-static to impact). High resolution stress–strain diagrams for the coal were obtained from compression tests for the lower and medium strain rates up to [Formula: see text] and with the split Hopkinson bar technique for the high strain rate region up to [Formula: see text].The elastic properties of the coal showed a moderate rate sensitivity at low and moderate strain rates.Above the strain rate [Formula: see text] both Young's modulus and the stress level of microcracking initiation σf0isplayed extreme rate sensitivity and was found to be a linear function of strain rate. The associated coefficient of viscosity perpendicular to the bedding plane was η* = 3.08 × 104 Pa∙s.The viscoelastic model so determined can be used to assess the elastic properties of coal at even higher strain rates, a situation that is similar to an explosive loading. Keywords: coal, strain rates, dynamic, viscoelastic properties.

EFFECTS OF STRAIN RATE DEPENDENCY OF MATERIAL PROPERTIES IN LOW VELOCITY IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1165-1170 ◽  
Author(s):  
HIROFUMI MINAMOTO ◽  
ROBERT SEIFRIED ◽  
PETER EBERHARD ◽  
SHOZO KAWAMURA
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Yield Stress ◽  
Coefficient Of Restitution ◽  
Finite Element Simulations ◽  
Material Behavior ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Strain Rate Dependency ◽  
The Impact

Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of strain rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. Finite Element simulations using strain-rate dependent material behavior are carried out. In addition, Finite Element simulations with elastic-plastic material behavior, which ignore the strain rate dependency, are carried out as well as elastic material behavior. Comparisons between the experiments and the simulations using strain-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the strain rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.

scholarly journals Analytical Descriptions of Dynamic Softening Mechanisms for Ti-13Nb-13Zr Biomedical Alloy in Single Phase and Two Phase Regions

2017 ◽  
Vol 62 (4) ◽  
pp. 2029-2043
Author(s):  
G.-Z. Quan ◽  
X. Wang ◽  
Y.-L. Li ◽  
L. Zhang
Keyword(s):  
Flow Stress ◽  
Kinetic Model ◽  
Strain Rate ◽  
Single Phase ◽  
Dual Phase ◽  
Compression Tests ◽  
Two Phase ◽  
Softening Mechanism ◽  
Wide Range ◽  
Dynamic Softening

AbstractDynamic softening behaviors of a promising biomedical Ti-13Nb-13Zr alloy under hot deformation conditions across dual phaseα+βand single phaseβregions were quantitatively characterized by establishing corresponding dynamic recovery (DRV) and dynamic recrystallization (DRX) kinetic models. A series of wide range hot compression tests on a Gleeble-3500 thermo-mechanical physical simulator were implemented under the strain rate range of 0.01-10 s−1and the temperature range of 923-1173 K. The apparent differences of flow stress curves obtained in dual phaseα+βand single phaseβregions were analyzed in term of different dependence of flow stress to temperature and strain rate and different microstructural evolutions. Two typical softening mechanisms about DRV and DRX were identified through the variations of a series of stress-strain curves acquired from these compression tests. DRX is the dominant softening mechanism in dual phaseα+βrange, while DRV is the main softening mechanism in single phaseβrange. The DRV kinetic model for single phaseβregion and the DRX kinetic model for dual phaseα+βregion were established respectively. In addition, the microstructures of the compressed specimens were observed validating the softening mechanisms accordingly.

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