Fatigue life determination of plasma nitrided medical grade CoCrMo alloy

2010 ◽  
Author(s):  
Ö. BAYRAK ◽  
A. F. YETİM ◽  
A. ALSARAN ◽  
A. ÇELİK
Keyword(s):  
Fatigue Life ◽  
Cocrmo Alloy ◽  
Medical Grade

Energy for crack growth in model rubber components

1972 ◽  
Vol 7 (2) ◽  
pp. 132-140 ◽  
Author(s):  
P B Lindley
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Crack Surface ◽  
Uniform Stress ◽  
Numerical Techniques ◽  
Surface Displacements ◽  
Tearing Energy ◽  
Crack Growth Rates ◽  
Essential Prerequisite

The determination of tearing energy, i.e. the energy available for crack growth, is an essential prerequisite for the estimation of the fatigue life of rubber components. Three methods of determining tearing energy are considered: from changes in total energy, from crack surface displacements, and by comparison with known values for the same crack growth rates. It is shown by applying experimental and numerical techniques to plane-stress testpieces, not necessarily of uniform stress or thickness, that the methods are satisfactory.

Design Formulas of Blind End Closures for High Pressure Vessels

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
R. D. Dixon ◽  
E. H. Perez
Keyword(s):  
High Pressure ◽  
Fatigue Life ◽  
Maximum Stress ◽  
Accurate Determination ◽  
Pressure Vessels ◽  
Stress Distributions ◽  
Fatigue And Fracture ◽  
Asme Code ◽  
Section Viii

The available design formulas for flat heads and blind end closures in the ASME Code, Section VIII, Divisions 1 and 2 are based on bending theory and do not apply to the design of thick flat heads used in the design of high pressure vessels. This paper presents new design formulas for thickness requirements and determination of peak stresses and stress distributions for fatigue and fracture mechanics analyses in thick blind ends. The use of these proposed design formulas provide a more accurate determination of the required thickness and fatigue life of blind ends. The proposed design formulas are given in terms of the yield strength of the material and address the fatigue strength at the location of the maximum stress concentration factor. Introduction of these new formulas in a nonmandatory appendix of Section VIII, Division 3 is recommended after committee approval.

Fatigue Life Assessment of Self-Expandable NiTi Stent

2014 ◽  
Vol 627 ◽  
pp. 45-48
Author(s):  
Cristian Sorin Nes ◽  
Angelica Enkelhardt ◽  
Lucian Bogdan ◽  
Nicolae Faur
Keyword(s):  
Fatigue Life ◽  
Arterial Wall ◽  
Cylindrical Tube ◽  
Life Assessment ◽  
Cyclic Loads ◽  
Fatigue Life Assessment ◽  
A Value ◽  
Vessel Stenosis ◽  
Fatigue Characteristics

Objectives: This paper presents a numerical fatigue life assessment of a self-expandable Nitinol stent. The analysis was performed using the ANSYS 11 software. Methods: Stent durability is an issue which must be addressed during the design of implants. Given the corrosive properties of blood and the cyclic loads that are applied on the stent (the cyclic variation of blood pressure), the determination of fracture parameters and fatigue characteristics of the implant is highly recommended. Breaking of the stent’s wire is particularly dangerous because it can cause the dislocation of a piece of stenotic plaque, which in turn can block a smaller artery, causing a heart attack. On the other hand, any discontinuity in stent structure acts as an accumulating place for stenosis particles, significantly shortening the life of the implant. The stent consists of a cylindrical tube 22.42 mm long, with a diameter of 8.3 millimeters. The wire section is square, 0.2x0.2 millimeters. The stent is only subjected to the pressure generated by the stenoted arterial wall. This evenly distributed pressure is defined at the outer surface of the stent and has a value of 2.5 MPa, corresponding to a 56% blood vessel stenosis. This way, the most severe loading conditions for the stent could be simulated. The stress distribution was then used to asses the fatigue life of the stent. Results and conclusions: The results showed that, in normal conditions (with the maximal internal pressure of 139 mm Hg = 18533 Pa), no damage appears on the stent after 107 cycles.

Determination of the Anand Viscoplasticity Model Constants for SnAgCu

2005 ◽  
Author(s):  
Bryan Rodgers ◽  
Ben Flood ◽  
Jeff Punch ◽  
Finbarr Waldron
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Test Specimen ◽  
Strain Curve ◽  
Temperature Cycling ◽  
Displacement Rate ◽  
Experimental Measurements ◽  
Strain Rates ◽  
Constant Displacement

The major focus of this work was the determination of the nine constants required for Anand’s viscoplastic constitutive model for a lead-free solder alloy, 95.5Sn3.8Ag0.7Cu and to compare them with those for SnPb. The test specimen was a cast dog bone shape based on ASTM E 8M-01, with a diameter of 4mm and a gauge length of 20mm. A series of tensile experiments were carried out: constant displacement tests ranging from 6.5 × 10−5/s to 1.0 × 10−3/s at temperatures of 20°C, 75°C, and 125°C; constant load tests at a range of loads from 10MPa to 65MPa, also at temperatures of 20°C, 75°C, and 125°C. A series of non-linear fitting processes was used to determine the model constants. Comparisons were then made with experimental measurements of the stress-plastic strain curves from constant displacement rate tests: it was found that the model matched the experimental data at low strain rates but did not capture the strain hardening effect, especially at high strain rates. A finite element model of the test was also constructed using ANSYS software. This software includes the Anand model as an option for its range of viscoplastic elements, requiring that the nine constants be input. In this case, an 8-noded axisymmetric element (VISCO108) was used to model the test specimen under constant displacement rate loading. The model was then used to predict the stress-plastic strain curve and this was compared to both the experimental measurements and the fitted Anand model. Reasonable agreement was found between the Anand model and the FE predictions at small strain rates. Finally, a BGA device was simulated under accelerated temperature cycling conditions using ANSYS with the fitted Anand for the SnAgCu solder joints. A Morrow-type fatigue life model was applied using empirical constants from two published sources and good agreement was found between experiment and predicted fatigue life.

The Fictitious Radius as a Tool for Fatigue Life Estimation of Notched Elements

2012 ◽  
Vol 726 ◽  
pp. 27-32 ◽  
Author(s):  
Grzegorz Robak ◽  
Marcel Szymaniec ◽  
Tadeusz Łagoda
Keyword(s):  
Fatigue Life ◽  
Notch Root ◽  
Experimental Tests ◽  
Life Estimation ◽  
Fatigue Life Estimation

In this paper, the fictitious radius - according to Neuber’s method for determination of stresses at the notch root was used. Next, the fatigue lives of elements of the ring notches were calculated, and then compared with results of experimental tests of S235JR steel samples. However, the obtained fatigue lives did not bring satisfactory results. It has been demonstrated that the fictitious radius strongly depends on the expected fatigue life

scholarly journals Determination of the rotary fatigue life of NiTi alloy wires

2016 ◽  
Vol 85 ◽  
pp. 37-44 ◽  
Author(s):  
André Carvalho ◽  
Diogo Montalvão ◽  
Manuel Freitas ◽  
Luis Reis ◽  
Manuel Fonte
Keyword(s):  
Fatigue Life ◽  
Niti Alloy

Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads

2019 ◽  
Vol 105 ◽  
pp. 182-195 ◽  
Author(s):  
Dušan Arsić ◽  
Nebojša Gnjatović ◽  
Simon Sedmak ◽  
Aleksandra Arsić ◽  
Milan Uhričik
Keyword(s):  
Fatigue Life ◽  
Dynamic Loads ◽  
Integrity Assessment ◽  
Residual Fatigue Life ◽  
Residual Fatigue

scholarly journals Heat Input Influence on the Fatigue Life of Welds from Steel S460MC

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1288 ◽  
Author(s):  
Jaromir Moravec ◽  
Jiri Sobotka ◽  
Pavel Solfronk ◽  
Robin Thakral
Keyword(s):  
Fatigue Life ◽  
Heat Input ◽  
Strengthening Mechanism ◽  
Dynamic Loads ◽  
Microalloyed Steels ◽  
Fine Grained ◽  
Weld Fatigue ◽  
Static And Dynamic Loads ◽  
Fine Grained Steels

Fine-grained steels belong to the progressive materials, which are increasingly used in the production of welded structures subjected to both static and dynamic loads. These are unalloyed or microalloyed steels hardened mainly by the grain-boundary strengthening mechanism. Such steels require specific welding procedures, especially in terms of the heat input value. At present, there are studies of the welding influence on the change of thermomechanically processed steels’ mechanical properties, however mainly under static loading. The paper is therefore focused on the assessment of the welding effect under dynamic loading of welded joints. In the experimental part was determined the influence of five different heat input values on the change of weld fatigue life. As a result, there is both determination of five S-N curves for the double-sided fillet welds from the thermomechanically processed fine-grained steel S460MC and the quantification of the main influences reducing the fatigue life of the joint.

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