scholarly journals Effect of Thermomechanical Treatment on Structure and Functional Fatigue Characteristics of Biodegradable Fe-30Mn-5Si (wt %) Shape Memory Alloy

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3327
Author(s):  
Sergey Prokoshkin ◽  
Yury Pustov ◽  
Yulia Zhukova ◽  
Pulat Kadirov ◽  
Maria Karavaeva ◽  
...  
Keyword(s):  
Body Temperature ◽  
Shape Memory ◽  
Corrosion Fatigue ◽  
Hot Rolling ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Alloy System ◽  
The Body ◽  
Grain Structure ◽  
Air Atmosphere

The Fe-Mn-Si shape memory alloys are considered promising materials for the biodegradable bone implant application since their functional properties can be optimized to combine bioresorbability with biomechanical and biochemical compatibility with bone tissue. The present study focuses on the fatigue and corrosion fatigue behavior of the thermomechanically treated Fe-30Mn-5Si (wt %) alloy compared to the conventionally quenched alloy because this important functionality aspect has not been previously studied. Hot-rolled and water-cooled, cold-rolled and annealed, and conventionally quenched alloy samples were characterized by X-ray diffraction, transmission electron microscopy, tensile fatigue testing in air atmosphere, and bending corrosion fatigue testing in Hanks’ solution. It is shown that hot rolling at 800 °C results in the longest fatigue life of the alloy both in air and in Hanks’ solution. This advantage results from the formation of a dynamically recrystallized γ-phase grain structure with a well-developed dislocation substructure. Another important finding is the experimental verification of Young’s modulus anomalous temperature dependence for the studied alloy system, its minimum at a human body temperature, and corresponding improvement of the biomechanical compatibility. The idea was realized by lowering Ms temperature down to the body temperature after hot rolling at 800 °C.

scholarly journals Highly Tough Hydrogels with the Body Temperature-Responsive Shape Memory Effect

2019 ◽  
Vol 11 (46) ◽  
pp. 43563-43572 ◽  
Author(s):  
Ruixue Liang ◽  
Haojie Yu ◽  
Li Wang ◽  
Long Lin ◽  
Nan Wang ◽  
...  
Keyword(s):  
Body Temperature ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
The Body ◽  
Temperature Responsive

Sour Service Corrosion Fatigue Testing of Flowline Welds

2007 ◽  
Author(s):  
Fraser McMaster ◽  
Hugh Thompson ◽  
Michelle Zhang ◽  
David Walters ◽  
Jonathan Bowman
Keyword(s):  
Corrosion Fatigue ◽  
Wall Thickness ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Production Quality ◽  
Process Selection ◽  
Circumferential Welds ◽  
The Impact ◽  
Sour Service

An examination of the corrosion-fatigue behavior of production quality welds in X65-type pipes was performed. Due to the low cycle operational nature of the production flowline system, the fatigue test frequency was substantially lower (0.01Hz vs. 0.33Hz) than typically utilized during corrosion-fatigue testing. Also the tests were performed at higher stress ranges than previous sour service fatigue tests, which to date have targeted riser fatigue loading regimes. Stress-life (S-N) samples were removed from segments of pipe with outside diameters of 10.75 inch (wall thickness of 1.30 inch) and 9.625 inch (wall thickness of 1.26 inch) containing fully inspected, production-quality circumferential welds. Environments examined included laboratory air conditions as well as deoxygenated brine supplemented by a gas mix of H2S and N2. For all environmental tests performed, the dissolved oxygen levels were maintained at less than 10 ppb during all testing. The measured fatigue life decrease in the curved pipe segments was in the range of 8–110 times due to the combined effect of the material and fluid property variables examined. The results of this work clearly illustrated the impact of sour-service corrosion fatigue, in welded carbon steel pipes, to the multitude of variables involved. Nevertheless, the foregoing experimental work clearly demonstrated the importance of performing environmental relevant testing when considering material and process selection for offshore applications.

Synthesis and Characterization of Poly(D,L-Lactide)-Based Shape Memory Polymers

2009 ◽  
Vol 79-82 ◽  
pp. 271-274 ◽  
Author(s):  
Yong Gang Li ◽  
Yuan Liang Wang ◽  
Yan Feng Luo
Keyword(s):  
Body Temperature ◽  
Shape Memory ◽  
Recovery Time ◽  
Shape Memory Polymers ◽  
The Body ◽  
Hexamethylene Diisocyanate ◽  
Bending Test ◽  
Polymerization Reaction ◽  
Scanning Calorimetry ◽  
Recovery Temperature

Biodegradable novel poly(D,L-lactide)-based shape memory polymers (SMPs) were prepared from poly(D,L-lactide) (PDLLA) Diols, hexamethylene diisocyanate(HDI) and butanediamine(BDA) via two steps polymerization reaction. Its thermal, mechanical properties and shape-memory behaviors were investigated by means of differential scanning calorimetry, stress-strain measurements and bending test. The glass transition temperature of the SMPs changes with composition from 38 to 45°C which close to body temperature in a predictable manner. These type SMPs can achieve the high modulus and tensile strength, and their elongation at break can be greater than 500% at lower hard segment content. All SMPs display excellent shape-memory properties. When a deformation temperature 20°C above Tg was chosen, the ratio of the shape-memory fixation approximately 100%, and the recovery ratio was 95-100%. Meanwhile, the recovery time is relevant to the recovery temperature, the recovery time decrease with increasing the recovery temperature. By adjusting the composition of SMPs, the recovery temperature could be adjusted to the neighborhood of the body temperature and it can be designed as potential biomaterials for use in biomedical fields.

Fatigue Behavior of Pt-20%Ir Coils Used as Implanted Electrodes in Medical Devices

2013 ◽  
Author(s):  
Haitao Zhang ◽  
Bernard Q. Li
Keyword(s):  
Medical Devices ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Fatigue Curve ◽  
Electrical Signal ◽  
The Body ◽  
Stress And Strain ◽  
Analysis Software ◽  
Element Analysis ◽  
Implanted Electrodes

Pt-20%Ir coils were used in medical devices as conductors for the leads that transfer the electrical signal from an implanted stimulator to the area of the body (e.g., brain or nerves) to be stimulated. In this study, the fatigue behavior and failure mechanism of Pt-20%Ir coils was studied with axial fatigue testing. The stress and strain on the coils was analyzed with the non-linear FEA (finite element analysis) software ABAQUS. A strain vs. fatigue curve was obtained. A SEM (scanning electron microscope) was used to analyze the fatigue fracture surface of the samples.

Shape Memory Alloy Expandable Pedicle Screw to Enhance Fixation in Osteoporotic Bone: Primary Design and Finite Element Simulation

2012 ◽  
Vol 6 (3) ◽  
Author(s):  
Majid Tabesh ◽  
Vijay Goel ◽  
Mohammad H. Elahinia
Keyword(s):  
Finite Element ◽  
Body Temperature ◽  
Shape Memory ◽  
Pedicle Screw ◽  
Stable Solution ◽  
Pedicle Screws ◽  
The Body ◽  
Osteoporotic Bone ◽  
Major Drawback ◽  
Pull Out

The properties of shape memory alloys, specifically the equiatomic intermetallic NiTi, are unique and significant in that they offer simple and effective solutions for some of the biomechanical issues encountered in orthopedics. Pedicle screws, used as an anchoring point for the implantation of spinal instrumentations in the spinal fracture and deformity treatments, entail the major drawback of loosening and backing out in osteoporotic bone. The strength of the screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. The SMArtTM pedicle screw design is developed to address the existing issue in degraded bone. It is based on the interaction of bi-stable shape memory-superelastic elements. The bi-stable assembly acts antagonistically and consists of an external superelastic tube that expands the design protrusions when body temperature is attained; also an internal shape memory wire, inserted into the tube, retracts the assembly while locally heated to above the body temperature. This innovative bi-stable solution augments the pull-out resistance while still allowing for screw removal. The antagonistic wire-tube assembly was evaluated and parametrically analyzed as for the interaction of the superelastic tube and shape memory wire using a finite element model developed in COMSOL Multiphysics®. The outcomes of the simulation suggest that shape memory NiTi inserts on the SMArtTM pedicle screw can achieve the desired antagonistic functionality of expansion and retraction. Consequently, a parametric analysis was conducted over the effect of different sizes of wires and tubes. The dimensions for the first sample of this innovative pedicle screw were determined based on the results of this analysis.

scholarly journals A review study on Corrosion Fatigue and its related testing methodologies

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Farshad Abbasi
Keyword(s):  
Fatigue Test ◽  
Corrosion Fatigue ◽  
Crack Detection ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
International Standards ◽  
Mechanical Degradation ◽  
Damage Mechanisms ◽  
Corrosion Fatigue Crack ◽  
Set Up

Corrosion Fatigue is the mechanical degradation of a material under the joint action of damage mechanisms corrosion and fatigue. Corrosive nature of the seawater puts severe durability requirements on materials of which are often exposed to corrosion fatigue and abrasive conditions simultaneously. Therefore, identification of the combined effects of both corrosion and fatigue damage mechanisms is necessary to improve predictive models for the corrosion fatigue phenomenon. Present article is the result of a desktop study (scientific literature and standards) with the aim of study the feasibility of designing and manufacturing of a corrosion fatigue testing set-up that would allow the designer to compare the performance of different materials exposed to corrosion fatigue, permitting also the comparison with results from dry fatigue testing. The corrosion fatigue mechanism is described in more detail and a short presentation of some typical lab-scale corrosion fatigue test setups is given. This is followed by illustration of international standards and guidelines which will be used to design a new corrosion fatigue test set-up for evaluating the fatigue behavior of material in seawater environment. Finally the experimental techniques for corrosion fatigue crack detection and propagation along with the fundamental basic of corrosion fatigue modeling are illustrated.

Fatigue Behavior and Microstructure of Pt-20Ir Wire as Lead Conductor in Implantable Medical Device

2012 ◽  
Author(s):  
Bernard Q. Li ◽  
Kailynn Cho ◽  
Haitao Zhang
Keyword(s):  
Medical Device ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Surface Region ◽  
Electrical Signal ◽  
The Body ◽  
Implantable Medical Device ◽  
Near Surface ◽  
Cold Draw ◽  
The Wire

Pt-20Ir cold draw wire has been used as lead conductor in implantable medical devices. The lead is a medical device to transfer the electrical signal from a implanted stimulator to the body area for stimulating such as brain and neurological nerves. In this study, fatigue behavior and failure mechanism of Pt-20Ir wire was studied with rotary bending fatigue testing. The relations between the cyclic strain amplitude (ε) and the cycles to failure (N) were obtained and compared with MP35N wire which is the most commonly used metal wire as lead conductors. The results show Pt-20Ir cold drawn wire (0.102 mm) has a fatigue endurance strain limit of 0.18% which is significant lower than that of MP35N wire. Microstructure of Pt-20Ir cold draw wire was also analyzed. Results show that the grain size of in wire is elongated like bundled fiber structure. The texture of wire is strongly fiber textured and with a strong gradient from outside layer to center of the wire. Near surface region has <111> textured grain and around center region of the wire has <100> textured grain. The center of grain also has larger size than near surface.

Fatigue of Unidirectional Cord-Rubber Composites

1999 ◽  
Vol 27 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Y. Liu ◽  
Z. Wan ◽  
Z. Tian ◽  
X. Du ◽  
J. Jiang ◽  
...  
Keyword(s):  
Damage Accumulation ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Testing System ◽  
Rubber Composites ◽  
Cycle Frequency ◽  
Periodic Loading ◽  
Fatigue Damage Accumulation ◽  
Rubber Composite

Abstract A fatigue testing system is established with which the real-time recording of stress, strain, temperature, and hysteresis loss of rubbers or cord-rubber composite specimens subjected to periodic loading or extension can be successfully carried out. Several problems are connected with the experimental study of the fatigue of rubber composites. In constant extension cycling, the specimen becomes relaxed because of the viscoelasticity of rubber composites, and the imposed tension-tension deformation becomes complex. In this method, the specimen is unlikely to fail unless the imposed extensions are very large. Constant load cycling can avoid the shortcomings of constant extension cycling. The specially designed clamps ensure that the specimen does not slip when the load retains a constant value. The Deformation and fatigue damage accumulation processes of rubber composites under periodic loading are also examined. Obviously, the effect of cycle frequency on the fatigue life of rubber composites can not be ignored because of the viscoelasticity of constituent materials. The increase of specimen surface temperature is relatively small in the case of 1 Hz, but the temperature can easily reach 100°C at the 8 Hz frequency. A method for evaluating the fatigue behavior of tires is proposed.

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