Microstructure-Based Constitutive Model for Yield Strength and Strain Hardening of 5XXX-Series Aluminum Alloys after Non-Isothermal Fire Exposure

2015 ◽  
pp. 955-962
Author(s):  
P. T. Summers ◽  
S. W. Case ◽  
B. Y. Lattimer
Keyword(s):  
Aluminum Alloys ◽  
Yield Strength ◽  
Constitutive Model ◽  
Strain Hardening ◽  
Fire Exposure

Strain-Rate Sensitivity of Aluminum Alloys AA1200 and AA3103

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
O.-G. Lademo ◽  
O. Engler ◽  
J. Aegerter ◽  
T. Berstad ◽  
A. Benallal ◽  
...  
Keyword(s):  
Aluminum Alloys ◽  
Constitutive Model ◽  
Strain Rate ◽  
Strain Hardening ◽  
Rate Sensitivity ◽  
Structural Parameter ◽  
Model Parameters ◽  
Good Representation ◽  
Nominal Strain Rate ◽  
Instantaneous Rate

Tensile tests are carried out for the aluminum alloys AA1200 and AA3103 at various strain-rates in the range from 10−4 s−1 to 1 s−1. Tests with constant nominal strain-rate and strain-rate jump tests are conducted, and the instantaneous rate sensitivity and the rate sensitivity of strain hardening are investigated. For both materials, the instantaneous rate sensitivity is found to be rather independent of strain, while the rate sensitivity of the strain hardening is important and the saturation stress increases with increasing strain-rate. A phenomenological constitutive model is described that comprises a kinetic equation governing the instantaneous rate sensitivity of the flow stress and a structural parameter that determines the mechanical state of the material. The evolution of the structure parameter is assumed to depend on strain-rate. The model parameters are determined for the two materials using the available experimental information. It is found that the constitutive model provides a good representation of the experimental results.

scholarly journals Constitutive Model for Aluminum Alloys Exposed to Fire Conditions

2008 ◽  
Vol 39 (4) ◽  
pp. 778-789 ◽  
Author(s):  
J. Maljaars ◽  
F. Soetens ◽  
L. Katgerman
Keyword(s):  
Aluminum Alloys ◽  
Constitutive Model ◽  
Fire Conditions

Influencing Factors for Improving Accuracy in Prediction of Stress Corrosion Crack Growth Rate in Boiling Water Reactor Operational Condition: Part 1—Prediction of SCC Growth Rate in Terms of Vickers Hardness

2010 ◽  
Author(s):  
Yoichi Takeda ◽  
Zhanpeng Lu ◽  
Takeshi Adachi ◽  
Qunjia Peng ◽  
Jiro Kuniya ◽  
...  
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Yield Strength ◽  
Strain Hardening ◽  
Crack Growth ◽  
Vickers Hardness ◽  
316L Stainless Steel ◽  
Strain Hardening Exponent ◽  
Theoretical Formulation ◽  
Prediction Curve

It is known that stress corrosion cracking (SCC) found in the operational power plants show complex cracking behaviors and it’s resulted in complex crack shape e.g. crack branching and its uneven crack front. For the cracking near the weldment, this is due to crack penetrated along the complex distribution of residual stress and strain hardened area. In this investigation, in order to advance the accuracy for crack growth prediction with considering such complex fields, theoretical formulation for SCC growth was further modified. Hardness of the materials, which is a measureable parameter even in operational power plant, was focused on to reflect strain hardening of the component like heat affected zone of the weldments. The theoretical formulation for SCC growth has terms with yield strength of the material and strain hardening exponent to describe crack tip strain rate. Strain hardening was simulated by cross rolling with the range of 4 – 32% as thickness reduction. Correlation between yield strength, strain hardening exponent at 288°C and Vickers hardness was obtained by means of tensile tests and hardness tests on 316L stainless steel. It was observed that a monotonic increase in Vickers hardness and yield strength with degree of reduction in thickness worked by cross rolling. Relationship between Vickers hardness and yield strength was found to have linear correlation. Further confirmation was made by plotting the reported mechanical properties data in terms of Vickers hardness. In addition, linear relationship was found between yield strength and strain hardening exponent. These relationships were introduced into SCC theoretical formulation and a SCC growth rate prediction curve in terms of Vickers hardness was proposed. SCC crack growth evaluation tests with selected work hardened 316L stainless steel were performed in oxygenated pure water environment at 288°C to confirm the predictability of the formulation. The prediction curve had a good agreement with available literature data as well as obtained crack growth rates in the hardness range of 140–300HV which was likely expected one in weld HAZ.

scholarly journals Study on Dynamic Mechanical Properties and Constitutive Model Construction of TC18 Titanium Alloy

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 44 ◽  
Author(s):  
Changming Zhang ◽  
Anle Mu ◽  
Yun Wang ◽  
Hui Zhang
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Flow Stress ◽  
Yield Strength ◽  
Constitutive Model ◽  
Testing Machine ◽  
Dynamic Mechanical Properties ◽  
Stress Strain ◽  
Dynamic Mechanical ◽  
Different Temperatures

In order to investigate the static and dynamic mechanical properties of TC18 titanium alloy, the quasi-static stress–strain curve of TC18 titanium alloy under room temperature was obtained by DNS 100 electronic universal testing machine (Changchun Institute of Mechanical Science Co., Ltd., Changchun, China). Meanwhile, the flow stress–strain curves under different temperatures and strain rates are analyzed by split Hopkinson pressure bar (SHPB) device with synchronous assembly system. On the basis of the two experimental data, the JC constitutive model under the combined action of high temperature and impact load is established using the linear least squares method. The results show the following: the yield strength and flow stress of TC18 titanium alloy increase slowly with the increase of the strain rate, and the strain value corresponding to the yield strength is reduced. With the increase of strain, the flow stress increases at first and then decreases at different temperatures. The strain value corresponding to the transition point rises with the temperature increase, and the corresponding stress value remains basically unchanged. With the increase of experimental temperature, the flow stress shows a downward trend, and the JC constitutive model can predict the plastic flow stress well.

scholarly journals Monitoring of Thermal Aging of Aluminum Alloy via Nonlinear Propagation of Acoustic Pulses Generated and Detected by Lasers

2019 ◽  
Vol 9 (6) ◽  
pp. 1191 ◽  
Author(s):  
Mengmeng Li ◽  
Alexey Lomonosov ◽  
Zhonghua Shen ◽  
Hogeon Seo ◽  
Kyung-Young Jhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Yield Strength ◽  
Thermal Aging ◽  
Finite Amplitude ◽  
Quadratic Nonlinearity ◽  
Laser Ultrasonic ◽  
Ultrasonic Techniques ◽  
Non Destructive

Nonlinear acoustic techniques are established tools for the characterization of micro-inhomogeneous materials with higher sensitivity, compared to linear ultrasonic techniques. In particular, the evaluation of material elastic quadratic nonlinearity via the detection of the second harmonic generation by acoustic waves is known to provide an assessment of the state variation of heat treated micro-structured materials. We report on the first application for non-destructive diagnostics of material thermal aging of finite-amplitude longitudinal acoustic pulses generated and detected by lasers. Finite-amplitude longitudinal pulses were launched in aluminum alloy samples by deposited liquid-suspended carbon particles layer irradiated by a nanosecond laser source. An out-of-plane displacement at the epicenter of the opposite sample surface was measured by an interferometer. This laser ultrasonic technique provided an opportunity to study the propagation in aluminum alloys of finite-amplitude acoustic pulses with a strain up to 5 × 10−3. The experiments revealed a signature of the hysteretic quadratic nonlinearity of micro-structured material manifested in an increase of the duration of detected acoustic pulses with an increase of their amplitude. The parameter of the hysteretic quadratic nonlinearity of the aluminum alloy (Al6061) was found to be of the order of 100 and to exhibit more than 50% variations in the process of the alloy thermal aging. By comparing the measured parameter of the hysteretic quadratic nonlinearity in aluminum alloys that were subjected to heat-treatment at 220 °C for different times (0 min, 20 min, 40 min, 1 h, 2 h, 10 h, 100 h, and 1000 h), with measurements of yield strength in same samples, it was established that the extrema in the dependence of the hysteretic nonlinearity and of the yield strength of this alloy on heat treatment time are correlated. This experimental observation provides the background for future research with the application goal of suggested nonlinear laser ultrasonic techniques for non-destructive evaluation of alloys’ strength and rigidity in the process of their heat treatment.

Coupled Interfacial Energy and Temperature Effects on Size-Dependent Yield Strength and Strain Hardening of Small Metallic Volumes

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
Abu N. M. Faruk
Keyword(s):  
Yield Strength ◽  
Size Effect ◽  
Strain Hardening ◽  
Interfacial Energy ◽  
Thermal Loading ◽  
Temperature Sensitive ◽  
Gradient Plasticity ◽  
Energy Effect ◽  
Size Dependent ◽  
Film Substrate

Plasticity in heterogeneous metallic materials with small volumes is governed by the interactions of dislocations at interfaces. In particular, interfaces of a material confined in a small volume can strongly affect the mechanical properties of micro and nanosystems. In this paper, the framework of higher-order strain gradient plasticity theory with interfacial energy effect is used to investigate the coupling of interfacial energy with temperature and how it affects the initial yield strength (i.e., onset of plasticity) and the strain hardening rates of confined small metallic volumes. It is postulated that the interfacial energy decreases as temperature increases such that size effect decreases as temperature increases. As an application, the size effect of thermal loading of a film-substrate system is investigated. It is shown that the temperature at which the film starts to yield plastically is size-dependent, which is attributed to the size-dependent yield strength. Furthermore, the flow stress is more temperature sensitive as the size decreases.

A Characteristic and a Precisely Constitutive Model for Undrained Clay

2020 ◽  
Vol 975 ◽  
pp. 203-207
Author(s):  
Shih Tsung Hsu ◽  
Wen Chi Hu ◽  
Yu Heng Lin ◽  
Zhuo Ling
Keyword(s):  
Shear Strength ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Strain Hardening ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Proposed Model ◽  
Taipei Basin ◽  
Undrained Shear

Constitutive models for soils are usually adopted in numerical method to analyze the behavior of geotechnical structures. This study performs a series of consolidated-undrained triaxial tests to establish the stress-strain curve of clay. A constitutive model that considers continuous strain hardening-softening is proposed based on the results of triaxial tests. Triaxial test results reveal that undrained shear strength linearly increases with an increase in consolidated pressure , the normalized undrained shear strength is about 0.52 not only for this study but also for the other two cases around Taipei Basin. Due to undrained condition, an associated flow rule between plastic strain increment and stress tensor is adopted. As accumulative plastic strain or/and consolidated pressure change, the mobilized undrained shear strength also changes. All parameters needed for the proposed model can be expressed as a function of undrained shear strength Su, The mobilized undrained shear strength for the proposed model during strain hardening-softening can be in term of accumulative plastic strain. This model can calculate the stress-strain curves of clayed soils accurately.

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