Fatigue of NiTi for Dampers and Actuators

2012 ◽  
Vol 83 ◽  
pp. 18-27 ◽  
Author(s):  
Antonio Isalgue ◽  
Vicenç Torra ◽  
Fabio Casciati ◽  
Sara Casciati
Keyword(s):  
Fatigue Life ◽  
Martensitic Transformation ◽  
Size Effects ◽  
Main Parameter ◽  
Testing Machine ◽  
Constant Load ◽  
Thermomechanical Properties ◽  
Niti Wire ◽  
Mechanical Cycling ◽  
Thermal Actuation

The application of Shape Memory Alloy (SMA) devices to practical uses need well established performance. The reliable application in some areas, as dampers in engineering, needs a known, relatively long fatigue life (some million oscillations). The thermomechanical properties of SMA, based on their martensitic transformation, made them attractive to use for damping, taking advantage of the pseudoelastic window and hysteresis on transforming-retransforming. Due to size effects and to the fact that fatigue failure in metallic NiTi usually comes from a defect inducing crack growth, fatigue has to be studied for concrete applications, with the correct samples. The present work points out the possibility to apply NiTi to dampers and actuators. Testing machine experiments indicate that the main parameter controlling fatigue life is the effective stress on the NiTi wire. Long wire life (in the million cycle regime) can be achieved under limited stresses (around or under 200 MPa). Also, experiments have been done on thermal actuation of NiTi wire under traction at constant load. The results demonstrate that long actuator life (larger than 300000 cycles) can be achieved at low stresses (around 100 MPa), coherently with the mechanical cycling. From our results, NiTi is useful to effectively damp vibrations even at relatively low stresses and strains. The experimental results from facilities (cable No. 1 in ELSA-JRC, Ispra, Italy, and IFSTTAR test cable, near Nantes, France) confirm that NiTi wire is able to damp stayed cables.

Thermomechanical Fatigue Behavior of NiTi Wires

2013 ◽  
Vol 738-739 ◽  
pp. 311-315
Author(s):  
Antonio Isalgué ◽  
Javier Fernández ◽  
Nuria Cinca ◽  
I.G. Cano ◽  
Ramón Grau ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Smart Materials ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Constant Load ◽  
Niti Wire ◽  
Structural Fatigue ◽  
Mechanical Cycling ◽  
Thermal Actuation ◽  
Niti Wires

Applications of the functional, smart materials SMA need a careful evaluation of the working conditions and fatigue life. Structural fatigue failure in NiTi usually comes from a surface defect inducing crack growth, and this means that fatigue has to be studied for concrete applications, with the correct samples, as the state of the material presents size effects. Testing machine experiments on Ni-rich pseudoelastic wires indicate that the main parameter controlling the fatigue life in the traction-traction experiments is the effective stress on the NiTi wire. Long wire life (in the million cycle regime) can be achieved under limited stresses (under 170 MPa) in traction-traction tests. Also, experiments have been done on thermal actuation of NiTi wire under traction at constant load. Long actuator life (larger than 400000 cycles) can be achieved at low stresses (around 100 MPa), coherently with the results from the mechanical cycling.

scholarly journals Impacts of Thermal and Mechanical Cycles on Electro-Thermal Anti-Icing System of CFRP Laminates Embedding Sprayable Metal Film

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1589
Author(s):  
Rongjia Li ◽  
Wang Xu ◽  
Dalin Zhang
Keyword(s):  
Fatigue Life ◽  
Metal Film ◽  
Fatigue Testing ◽  
Aerodynamic Force ◽  
Testing Machine ◽  
Laminated Composite ◽  
Heating Element ◽  
Electric Resistance ◽  
Potential Threat ◽  
Mechanical Cycling

The aircraft electro-thermal anti-icing system that can guarantee flight safety may be affected by periodic heating and cyclic aerodynamic force during long-term flight missions, which seems to be a potential threat to ice protection. This paper aims to investigate the impacts of thermal and mechanical cycles on heating elements of the electro-thermal anti-icing system. Specimens were manufactured with CFRP (carbon fiber reinforced polymer) laminated composite, glass fiber prepreg and copper screen, in which sprayable metal film (SMF) was embedded as the heating element. The study focuses on electric resistance variation of SMF and functional fatigue life under the cycling load. Thermal cycling tests were carried out in an insulated chamber where the specimens were heated up to 80 °C and then cooled down to −55 °C for 1000 cycles. Mechanical cycling tests were conducted on a fatigue testing machine where the specimens were imposed on tension-compression loading for 106 cycles. Results showed that the electric resistance of SMF increased with the number of loading cycles. The resistance was increased by 20% and the heating power was decreased by 16.67% after 1000 thermal cycles. During the mechanical cycling tests, it was found that the heating element was destructed before the structural failure, which indicated that the fatigue life of function was lower than that of the structure.

Effect of Slag Composition on Fatigue Life of High Speed Wheel Steel

2013 ◽  
Vol 675 ◽  
pp. 264-269
Author(s):  
Yu Tang
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Oxide Inclusion ◽  
Wheel Steel ◽  
Al2o3 Content ◽  
Confocal Laser ◽  
Composition Analysis ◽  
In Situ Observation

In order to improve fatigue life of wheel steel, secondary-refining process was done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. By morphology observation and composition analysis with FESEM, it is found that during LF-VD process, by slag-steel-inclusion interaction, Al2O3 inclusions could transform to MgO-Al2O3 spinel, and later on to CaO-MgO-Al2O3 inclusions, which are inclined to be eliminated by floatation, lowering T[O] content to 0.0007%, enhancing fatigue life of wheel steel. By In-Situ observation with CONFOCAL laser scanning microscope, it is found that MnS precipitates during solidification process, which would core oxide inclusion to form MnS-oxide complex inclusion, contributing to fatigue life improvement of wheel steel. By INSTRON fatigue testing machine, it is found that by successful inclusion control, tested samples achieve ultra-high cycle of 108 above, realizing experimental purpose of improving fatigue life of wheel steel, boosting domestic production process of CRH high speed wheel steel.

Modeling size effects on fatigue life of a zirconium-based bulk metallic glass under bending

2013 ◽  
Vol 61 (1) ◽  
pp. 273-279 ◽  
Author(s):  
Tao Yuan ◽  
Gongyao Wang ◽  
Qingming Feng ◽  
Peter K. Liaw ◽  
Yoshihiko Yokoyama ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Size Effects

scholarly journals Fatigue behaviour of fibre-reinforced composite T-joints

2018 ◽  
Vol 165 ◽  
pp. 07004
Author(s):  
Ying Wang ◽  
Constantinos Soutis
Keyword(s):  
Fatigue Life ◽  
Testing Machine ◽  
Fatigue Loading ◽  
Maximum Load ◽  
Fatigue Behaviour ◽  
Control Mode ◽  
Static Properties ◽  
T Joints ◽  
Pull Out ◽  
Reinforced Composite

In this paper a study was carried out on the fatigue life of fibre-reinforced composite T-joints subjected to a tensile pull-out loading. The composite T-joints have been made of glass fabric infused with epoxy resin using a vacuum assisted resin transfer moulding technique. Methods such as the use of veil layers, tufting techniques and 3D weave have been employed to improve the interlaminar fracture toughness of the composite T-joints. All the tests were conducted in an Instron testing machine using a specially designed test fixture. Fatigue tests were performed in a load control mode with a stress ratio of R = σmin/σmax = 0.1. The cyclic loading pattern was a sinusoidal wave with a frequency of 6 Hz. The specimens were cycled at a series of constant maximum load values up to failure. Fatigue loads versus life data for each T-joint type were produced at various maximum applied loads. The 3D weave T-joints were found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue life performance; the increasing rate in fatigue life is changed with the number of stress cycles. The location for the through-thickness reinforcement plays an important role in improving fatigue life of the Tjoints. Fatigue life is significantly improved if the web is reinforced in through-thickness direction. A finite element (FE) failure model was also created using ABAQUS to determine the location where delamination is initiated and its subsequent propagation.

Influence of Deformation Speed on Fatigue and Tensile Properties of a Ti-Ni-Cu Shape Memory Alloy

1999 ◽  
Vol 604 ◽  
Author(s):  
Y Kishi ◽  
Z. Yajima ◽  
K Shimizu ◽  
M. Asai
Keyword(s):  
Fatigue Life ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Tensile Properties ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Tensile Fracture ◽  
Scanning Calorimetry ◽  
Sinusoidal Waveform ◽  
Deformation Speed

AbstractThe mechanical fatigue life and tensile property of a Ti-41at.%Ni-8.5at.%Cu alloy, which was solution-treated after some thermo-mechanical treatments, were investigated at 370±1 K as a function of deformation speed. The tensile properties were also investigated at 295±1 K as a function of deformation speed. The B2→B19 martensitic transformation start temperature, Ms, of the alloy was determined to be 338 K by a differential scanning calorimetry, while that of the as-rolled alloy could not be determined. Two types of fatigue tests were carried out by using plate-shaped specimens of 3.5 mm width and 1.5 mm thickness with sinusoidal waveform stresses of 20 Hz and 0.5 Hz frequencies being applied respectively. The fatigue life obtained from the 20 Hz tests was superior to that from the 0.5 Hz tests, the former being about 2 times longer than the latter at the same stress level. Tensile tests were performed at three tensilem speeds of 8.3 × 106, 8.3 × 10−5 and 8.3 × 10−3 m/s. In all the stress - strain curves obtained, an apparent yielding was observed after the liner elastic deformation. The apparent yielding is due to the occurrence of martensitic transformation. The critical stress for inducing martensite and tensile fracture stress increased with increasing tensile speed. Therefore, it is clear that fatigue and tensile properties of Ti-Ni-Cu shape memory alloys are strongly affected by not only test temperature but also deformation speed.

Investigation on the Influence of Fatigue Damage on the Mechanics Property of Anti-Seismic Steel HRB400E Reinforcing Steel Bars

2013 ◽  
Vol 368-370 ◽  
pp. 1678-1682
Author(s):  
Yun Rong Luo ◽  
Tao Zeng ◽  
Lei Fu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Testing Machine ◽  
Cyclic Stress ◽  
Reinforcing Steel ◽  
Strain Behaviour ◽  
Steel Bars ◽  
Cycle Dependent ◽  
Material Testing Machine

Low cycle fatigue (LCF) experiments on anti-seismic steel HRB400E reinforcing steel bars under constant total strain (0.6%) control were conducted on a MTS 809 servo-hydraulic material testing machine. The specimens were then subjected to quasi-static tension until they ruptures on the machine. The mechanical properties such as cyclic stress-strain behaviour, quasi-static strength, and quasi-static ductility of the material at various levels of fatigue damage were investigated .The test results indicate that when compared to its virgin state, in a certain cycles (about 80% fatigue life) the cycle-dependent behaviors of the material can cause a slight change in the strength and ductility, and the ductility of the steel has an opposite trend to the strength. However, a significant decrease occurs to both the strength and the ductility as the cyclic cycles exceeds about 80% fatigue life.

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