Modeling of torsion fatigue in shape memory alloys

2019 ◽  
Vol 30 (20) ◽  
pp. 3146-3162 ◽  
Author(s):  
Mohammad Reza Mohammadzadeh ◽  
Mahmoud Kadkhodaei ◽  
Mahmoud Barati ◽  
Shabnam Arbab Chirani ◽  
Luc Saint-Sulpice
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Current Knowledge ◽  
Low Cycle Fatigue ◽  
Dissipated Energy ◽  
Loading Frequency ◽  
Thermomechanical Model ◽  
Number Of Cycles ◽  
Fatigue Criterion

Fatigue in shape memory alloys is one of the crucial aspects of their behavior; however, the current knowledge is mainly focused on uniaxial fatigue and is inadequate for engineering purposes. In this article, a fatigue criterion based on the stabilized dissipated energy has been presented to investigate the torsional low-cycle fatigue of superelastic shape memory alloys. To this aim, a one-dimensional torsional constitutive model in addition to a modified fully coupled thermomechanical model has been utilized so that the torsional cyclic responses especially in relatively high loading frequencies, which contribute to remarkable temperature variations and consequent response changes, could be taken into account. The calculated stabilized dissipated energy, then, has been used in an energy approach fatigue criterion in order to predict the fatigue life; hence, an explicit relation, which is capable of determining the number of cycles to failure for different loading conditions at a given loading frequency, has been obtained. The numerical results have been appraised for NiTi specimens, and they have been shown to be in a good agreement with the experimental data. Finally, using the proposed approach, the effect of fatigue test parameters on the fatigue life has been studied.

scholarly journals Rotary bending fatigue analysis of shape memory alloys

2017 ◽  
Vol 29 (6) ◽  
pp. 1183-1195 ◽  
Author(s):  
Maede Hesami ◽  
Laurent Pino ◽  
Luc Saint-Sulpice ◽  
Vincent Legrand ◽  
Mahmoud Kadkhodaei ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Dissipated Energy ◽  
Uniaxial Tensile ◽  
Temperature Phase ◽  
Stress Plateau ◽  
Bending Fatigue ◽  
Numerical Predictions

In this work, a one-dimensional constitutive model is used to study rotary bending fatigue in shape memory alloy beams. The stress and strain distributions in a beam section are driven numerically for both pure bending and rotary bending to show the basic differences between these two loading types. In order to verify the numerical results, experiments are performed on NiTi specimens with an imposed bending angle using a bending apparatus. Since the specimens show significant stress plateau for forward and backward transformation in their stress–strain response, an enhanced stress–temperature phase diagram is proposed in which different slopes are considered for the start and finish of each transformation strip. In order to study low cycle fatigue of shape memory alloys during rotary bending, the stabilized dissipated energy is calculated from numerical solution. A power law for variations of the fatigue life with the stabilized dissipated energy is obtained for the studied specimens to predict their fatigue life. The numerical predictions of the present approach are shown to be in a good agreement with the experimental findings for rotary bending fatigue. Uniaxial tensile fatigue tests are further performed on the studied specimens to investigate effect of loading type on the fatigue lifetime.

scholarly journals Cyclic behavior and energy approach of the fatigue of shape memory alloys

2009 ◽  
Vol 31 (3-4) ◽  
Author(s):  
Ziad Moumni ◽  
Wael Zaki ◽  
Habibou Maitournam
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Behavior ◽  
Dissipated Energy ◽  
Relevant Parameter ◽  
Generalized Standard Materials ◽  
Number Of Cycles ◽  
Plastic Shakedown

This paper presents an energy-based low-cycle fatigue criterion that can be used in analyzing and designing structures made from shape memory alloys (SMAs) subjected to cyclic loading. Experimentally, a response similar to plastic shakedown is observed: during the first cycles the stress-strain curve shows a hysteresis loop which evolves during the first few cycles before stabilizing. By adopting an analogy with plastic fatigue, it is shown that the dissipated energy of the stabilized cycle is a relevant parameter for estimating the number of cycles to failure of such materials. Following these observations, we provide an application of the cyclic model, previously developed by the authors within the framework of generalized standard materials with internal constraints [16], in order to evaluate such parameter. Numerical simulations are presented along with a validation against experimental data in case of cyclic superelasticity.

Modeling of Internal Damage Evolution During Actuation Fatigue in Shape Memory Alloys

2018 ◽  
Author(s):  
Francis R. Phillips ◽  
Daniel Martin ◽  
Dimitris C. Lagoudas ◽  
Robert W. Wheeler
Keyword(s):  
Phase Transformation ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Damage Evolution ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Internal Damage ◽  
Functional Fatigue ◽  
Non Linear

Shape memory alloys (SMAs) are unique materials capable of undergoing a thermo-mechanically induced, reversible, crystallographic phase transformation. As SMAs are utilized across a variety of applications, it is necessary to understand the internal changes that occur throughout the lifetime of SMA components. One of the key limitations to the lifetime of a SMA component is the response of SMAs to fatigue. SMAs are subject to two kinds of fatigue, namely structural fatigue due to cyclic mechanical loading which is similar to high cycle fatigue, and functional fatigue due to cyclic phase transformation which typical is limited to the low cycle fatigue regime. In cases where functional fatigue is due to thermally induced phase transformation in contrast to being mechanically induced, this form of fatigue can be further defined as actuation fatigue. Utilizing X-ray computed microtomography, it is shown that during actuation fatigue, internal damage such as cracks or voids, evolves in a non-linear manner. A function is generated to capture this non-linear internal damage evolution and introduced into a SMA constitutive model. Finally, it is shown how the modified SMA constitutive model responds and the ability of the model to predict actuation fatigue lifetime is demonstrated.

Low Cycle Fatigue Properties of FGH720Li Superalloy

2021 ◽  
Vol 1035 ◽  
pp. 292-296
Author(s):  
Zi Chao Peng ◽  
Jun Ying Sheng ◽  
Xu Qing Wang ◽  
Yue Tang
Keyword(s):  
Fatigue Life ◽  
Powder Metallurgy ◽  
Applied Stress ◽  
Low Cycle Fatigue ◽  
Influencing Factor ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Nickel Base Superalloy ◽  
Loading Frequency ◽  
Cycle Fatigue

Low cycle fatigue (LCF) properties of a powder metallurgy(PM) nickel base superalloy FGH720Li were systematically studied in this work, including smooth LCF and notched LCF tested at various temperatures and different stress. The relationship between the fatigue life and applied stress was analyzed both for smooth fatigue and notch fatigue tests. The effects of loading frequency and stress ratio on LCF behavior were also studied. As an important influencing factor of the fatigue life in powder metallurgy superalloy, the effect of inclusions on LCF life was also investigated. The results showed that the fatigue properties of FGH720Li alloy was excellent, when tested at the temperature of 450°C and applied stress of 1230MPa, the fatigue life could exceed 5×104 cycles. When tested at 650°C and 1150MPa, the average fatigue life was still beyond 2×105 cycles.

A Macromechanical Constitutive Model of Shape Memory Alloys Under Uniaxial Cyclic Loading

2012 ◽  
Vol 28 (3) ◽  
pp. 469-477 ◽  
Author(s):  
H. Lei ◽  
B. Zhou ◽  
Z. Wang ◽  
Y. Wang
Keyword(s):  
Cyclic Loading ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Hysteretic Behavior ◽  
Test Results ◽  
Model Match ◽  
Number Of Cycles ◽  
The Relationship

AbstractIn this paper, the thermomechanical behavior of shape memory alloys (SMAs) subjected to uniaxial cyclic loading is investigated. To obtain experimental data, the strain-controlled cyclic loading-unloading tests are conducted at various strain-rates and temperatures. Dislocations slip and deformation twins are considered to be the main reason that causes the unique cyclic mechanical behavior of SMAs. A new variable of shape memory residual factor was introduced, which will tend to zero with the increasing of the number of cycles. Exponential form equations are established to describe the evolution of shape memory residual factor, elastic modulus and critical stress, in which the influence of strain-rate, number of cycles and temperature are taken into account. The relationship between critical stresses and temperature is modified by considering the cycling effect. A macromechanical constitutive model was constructed to predict the cyclic mechanical behavior at constant temperature. Based on the material parameters obtained from test results, the hysteretic behavior of SMAs subjected to isothermal uniaxial cyclic loading is simulated. It is shown that the numerical results of the modified model match well with the test results.

Low-Cycle Fatigue of TiNi Shape Memory Alloy and Formulation of Fatigue Life.

1998 ◽  
Vol 64 (626) ◽  
pp. 2548-2554
Author(s):  
Takahiro HASHIMOTO ◽  
Hisaaki TOBUSHI ◽  
Takafumi NAKAHARA ◽  
Yoshirou SHIMENO
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue

Mechanical Properties of Cast Shape Memory Alloy for Brain Spatula

2011 ◽  
Vol 674 ◽  
pp. 213-218 ◽  
Author(s):  
Hisaaki Tobushi ◽  
K. Kitamura ◽  
Yukiharu Yoshimi ◽  
K. Miyamoto ◽  
K. Mitsui
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Power Function ◽  
Tensile Deformation ◽  
Low Cycle Fatigue ◽  
Fatigue Properties ◽  
Bending Fatigue ◽  
Deformation Properties ◽  
Plane Bending

In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed based on the tensile deformation properties of the existing copper and the TiNi rolled-SMA. The fatigue properties of both materials were also investigated by the plane-bending fatigue test. The results obtained can be summarized as follows. (1) The modulus of elasticity and the yield stress for the cast and rolled SMAs are lower than those for the copper. Therefore, the conventional rolled-SMA spatula and the new cast-SMA spatula can be bent easily compared to the existing copper-brain spatula. (2) With respect to the alternating- and pulsating-plane bending fatigue, the fatigue life of both the copper and the SMAs in the region of low-cycle fatigue is expressed by a power function of the maximum bending strain. The fatigue life of the conventional rolled SMA and the new cast SMA is longer than that of the existing copper. The fatigue life of the new cast and rolled SMAs in the pulsating-plane bending is longer than that in the alternating-plane bending. (3) The fatigue life of the rolled-SMA and the cast SMA for alternating- and pulsating-plane bendings can be expressed by the unified relationship with a power function of the dissipated work.

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