The Role of Multiscale Strain Localizations in Fatigue of Magnesium Alloys

2014 ◽  
Author(s):  
Jefferson Cuadra ◽  
Kavan Hazeli ◽  
Michael Cabal ◽  
Antonios Kontsos
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloys ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Degradation Process ◽  
Electron Back Scatter Diffraction ◽  
Image Correlation ◽  
Deformation Mechanisms ◽  
Global Strain

The reliable characterization of fatigue behavior and progressive damage of advanced alloys relies on the monitoring and quantification of parameters such as strain localizations as a result of both crystallographic deformation mechanisms and bulk response. To this aim, this article attempts to directly correlate microstructural strain at specific fatigue life to global strain as well as surface roughness in Magnesium alloys. Strain at the grain scale is calculated using Digital Image Correlation (DIC), while surface topography gradients are computed using roughness data at different stages of the fatigue life. The results are further correlated to Electron Back Scatter Diffraction (EBSD) measurements which reveal the profuse and spatially inhomogeneous nature of the crystallographic deformation mechanisms related to yielding and fatigue crack initiation. Emphasis is given on using multimodal NDE data to formulate first a description of the current state of the material subjected to fatigue loading and on identifying conditions that can probabilistically drive the affected by both local and global response, governing degradation process.

Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads

2010 ◽  
Author(s):  
Masao Itatani ◽  
Keisuke Tanaka ◽  
Isao Ohkawa ◽  
Takehisa Yamada ◽  
Toshiyuki Saito
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Static Tension ◽  
Cyclic Torsion ◽  
Cyclic Tension ◽  
Crack Initiation Life

Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.

scholarly journals Modeling of Bimodular Bone Specimen under Four-Point Bending Fatigue Loading

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 474
Author(s):  
Yufan Yan ◽  
Xianjia Meng ◽  
Chuanyong Qu
Keyword(s):  
Compressive Strain ◽  
Fatigue Loading ◽  
Degradation Process ◽  
Neutral Axis ◽  
Image Correlation ◽  
Bending Test ◽  
Correlation Technique ◽  
Fatigue Process ◽  
Four Point Bending ◽  
Bone Properties

The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.

Fatigue Behavior of Impacted Plain-Weave Glass/Epoxy Composites under Tensile Fatigue Loading

2005 ◽  
Vol 297-300 ◽  
pp. 1291-1296 ◽  
Author(s):  
Ki Weon Kang ◽  
Jung Kyu Kim ◽  
Heung Seob Kim
Keyword(s):  
Fatigue Life ◽  
Impact Damage ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Epoxy Composites ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Damage Behavior ◽  
Plain Weave ◽  
The Impact

The goals of this paper are to identify the impact damage behavior of plain-weave E-glass/epoxy composites and predict the fatigue life of the composites with impact-induced damage under constant amplitude loading. To identify these behaviors, the low velocity impact and fatigue after impact tests are performed for glass/epoxy composites having two types of fiber orientations. The impact damage behavior is dependent on the fiber orientation of the composites. The fatigue life of the impacted composites can be identified through the prediction model, which was proposed on the carbon/epoxy laminates by authors regardless of fiber orientations.

Effects of environmental conditions on the axial tension–compression fatigue behavior of carbon/epoxy plain-weave laminates containing flaws

2020 ◽  
Vol 54 (27) ◽  
pp. 4215-4230
Author(s):  
Marc-Claudel Deluy ◽  
Mohamed Khay ◽  
Anh Dung Ngo ◽  
Martine Dubé ◽  
Rajamohan Ganesan
Keyword(s):  
Fatigue Life ◽  
Environmental Conditions ◽  
Cyclic Load ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Real Life ◽  
Compressive Load ◽  
Fatigue Loading ◽  
Plain Weave ◽  
Strain Increase

The objective of this work is to investigate the effects of environmental conditions on the axial fatigue behavior of a carbon/epoxy plain-weave laminate with an embedded flaw subjected to a partially reversed cyclic load (stress ratio R = −0.1) in tension–compression. This specific material is more commonly used in aerospace engineering for the manufacturing of aircraft structural parts, which are directly exposed to various environmental conditions during service. Specific environmental and loading conditions that are appropriate to simulate real-life conditions are considered to observe and collect information about the material's behavior. For the investigation, dry and wet coupons were submitted to room temperature, 82 and 121 ℃ under loading frequencies of 7 and 15 Hz. A maximum allowable strain increase criterion is used to monitor the flaw growth threshold or delamination onset, during fatigue testing. The ultrasonic imaging (C-scan) technique is used to verify and confirm the delamination onset. Results show that the delamination onset strain increase criterion, along with fatigue life, generally decreased as the operating temperature and humidity were increased and that frequency had little effect on the delamination onset fatigue life. The S– N curves obtained from the tension–compression fatigue data were then compared to those of a previous work carried out in tension–tension fatigue loading. Results show a clear degradation in the delamination onset fatigue life of the coupons tested under tension–tension cyclic loading when the minimum tensile component of the cyclic load was replaced with a compressive load of the same magnitude.

scholarly journals Effect of UV Ageing on the fatigue life of bulk polyethylene

2018 ◽  
Vol 165 ◽  
pp. 08002 ◽  
Author(s):  
Hamza Lamnii ◽  
Moussa Nait-Abdelaziz ◽  
Georges Ayoub ◽  
Jean-Michel Gloaguen ◽  
Ulrich Maschke ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Uv Irradiation ◽  
Chemical Structure ◽  
Fatigue Behavior ◽  
Crystalline Polymer ◽  
Fatigue Loading ◽  
Chain Scission ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Irradiation Effect

Polymers operating in various weathering conditions must be assessed for lifetime performance. Particularly, ultraviolet (UV) radiations alters the chemical structure and therefore affect the mechanical and fatigue properties. The UV irradiation alters the polymer chemical structure, which results into a degradation of the mechanical and fatigue behavior of the polymer. The polymer properties degradation due to UV irradiation is the result of a competitive process of chain scission versus post-crosslinking. Although few studied investigated the effect of UV irradiation on the mechanical behaviour of thermoplastics, fewer examined the UV irradiation effect on the fatigue life of polymers. This study focuses on investigating the effect of UV irradiation on the fatigue properties of bulk semi-crystalline polymer; the low density Polyethylene (LDPE). Tensile specimens were exposed to different dose values of UV irradiation then subjected to fatigue loading. The fatigue tests were achieved under constant stress amplitude at a frequency of 1Hz. The results show an important decrease of the fatigue limit with increasing absorbed UV irradiation dose.

Effect of interface non-flatness on the fatigue behavior of adhesively bonded single lap joints

2017 ◽  
Vol 233 (7) ◽  
pp. 1277-1286 ◽  
Author(s):  
SMJ Razavi ◽  
MR Ayatollahi ◽  
M Samari ◽  
LFM da Silva
Keyword(s):  
Fatigue Life ◽  
Bearing Capacity ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Lap Joints ◽  
Lap Joint ◽  
Adhesively Bonded ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Single Lap Joints

This paper addresses numerical and experimental examination of the role of zigzag interface shapes on the load bearing capacity and fatigue life of adhesively bonded single lap joints. Aluminum adherends with non-flat zigzag interfaces were tested under both quasi-static and fatigue loading conditions. The quasi-static test results revealed that the non-flat adhesive joints have higher load bearing capacity compared to the conventional flat single lap joints. Comparative fatigue tests with different loading levels revealed that the non-flat zigzag single lap joint had considerably higher fatigue life than the conventional lap joint.

scholarly journals The Fatigue Behavior and Mechanism of Large FV520B-I Specimens in a Very High Cycle Regime

2021 ◽  
Author(s):  
Han Zhang ◽  
Ming Zhang ◽  
Li Meng Li ◽  
Bao Hai Xie ◽  
Jun Li Zhang
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Inclusion Size ◽  
Fatigue Properties ◽  
Corrosion Fatigue Crack ◽  
Life Model ◽  
Specimen Test ◽  
Ultrasonic Fatigue ◽  
Very High

Abstract We examined the fatigue properties in very high cycle regime of large FV520B-I specimens in an ultrasonic fatigue test. The fatigue mechanism in very high cycle regime didn’t change and the fatigue properties obviously degraded as the specimen size enlarged. The fatigue life decreased and the S-N curve moved downward due to the increase of inclusion size in large specimens. The maximum inclusion sizes in specimens were predicted by the method of statistics of extreme value. The prediction of fatigue strength using the modified Murakami model was closer to the test result, and the fitting of fatigue life using the corrosion fatigue crack initiation life model was less effective compared with the fitting of small specimen test results

Fatigue of Cold Expanded Open Hole Coupons with Pre-Existing Cracks

2014 ◽  
Vol 891-892 ◽  
pp. 69-74 ◽  
Author(s):  
Pud S. Baburamani ◽  
Rob Ogden ◽  
Qian Chu Liu ◽  
P. Khan Sharp
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Fatigue Crack Initiation ◽  
High Stress ◽  
Cost Effective ◽  
Fatigue Loading ◽  
Experimental Program ◽  
Cold Expansion ◽  
Open Hole ◽  
Life Improvement

Fastener holes have a high stress concentration at the edge of the hole and are primary sources of fatigue crack initiation, resulting in widespread fatigue damage leading to fatigue failures in airframe structures. The split-sleeve cold expansion (SsCx) technology is a simple and cost-effective way to improve the fatigue resistance of fastener holes by the introduction of compressive residual stresses around the holes. An investigation was carried out by DSTO to quantify the effectiveness of this technology, in terms of fatigue life improvement factors on a typical airframe aluminium alloy. Open hole (zero load transfer) coupons were tested to failure in non-cold expanded and cold expanded conditions. Coupons were also pre-cracked to specified crack lengths at the open hole, and cold expanded or left non-cold expanded, and tested to failure. This paper will present the results of the initial phases of the experimental program, involving constant amplitude fatigue loading of open hole coupons with and without cracks. The fatigue life improvement achieved by the use of hole cold expansion technology will be presented.

Effects of Glass-Forming Metallic Film on the Fatigue Behavior of C-2000 Ni-Based Alloy

2005 ◽  
Vol 903 ◽  
Author(s):  
F. X. Liu ◽  
C. L. Chiang ◽  
J. P. Chu ◽  
Y. F. Gao ◽  
P. K. Liaw
Keyword(s):  
Thin Film ◽  
Fatigue Life ◽  
Fatigue Resistance ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Film Coating ◽  
Fatigue Tests ◽  
Glass Forming ◽  
Four Point Bending ◽  
Coated Surface

AbstractGlass-forming Zr47Cu31Al13Ni9 (in atomic percent) films of various thicknesses were deposited on the C-2000 Ni-based alloy substrate by magnetron sputtering. Four-point-bending fatigue tests were conducted on the above system with the coated surface on the tensile side. It has been found that both fatigue life and fatigue-endurance limit can be considerably improved, while the degree of fatigue resistance enhancement depends on the maximum applied stress and the film thickness. Mechanisms of fatigue-resistance enhancements of the coated Ni-based alloy are discussed from the following aspects: reduction of surface roughness by the thin-film coating, good adhesion between thin film and substrate, development of residual compressive stress, and excellent ductility of glass-forming thin film (which would be otherwise brittle in bulk form). Of particular interest, we examine the interaction of substrate slip bands and the thin film ductile property, which would delay fatigue crack initiation process and thus extend the fatigue life.

EFFECT OF CERAMIC COATING THICKNESS ON RESIDUAL STRESS AND FATIGUE CHARACTERISTIC OF 1Cr-1Mo-0.25V STEEL

2002 ◽  
Vol 16 (01n02) ◽  
pp. 181-188 ◽  
Author(s):  
CHANG-MIN SUH ◽  
BYUNG-WON HWANG ◽  
KYUNG-RYUL KIM
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Coating Thickness ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Turbine Rotor ◽  
Fatigue Tests ◽  
Rotor Steel

To evaluate the effect of coatings on the fatigue behaviors of turbine rotor steel, TiN and TiAlN films were deposited on the 1Cr-1Mo-0.25V steels by arc-ion plating (AIP) method with and wihtout screen ion filter. The coating thickness were varied with 2.5 μm, 3.5 μm, and 5.0 μm. A Cu-K α beam source was used as a characteristic X-ray and the crystal plane of (422) was selected to evaluate the residual stresses. In order to clear the relationship between fatigue behavior and residual stress of specimen coated with TiN and TiAlN films, the fatigue tests of specimens with and without coating were carried out at room temperatures respectively. It is shown that the fatigue life of the coated specimen was longer than that of uncoated specimen. The compressive residual stresses on the coatings were higher, and the fatigue crack initiated at an inclusion in the substrate near bond interface. It is known that compressive residual stress caused by hard coating would retard the fatigue crack initiation on the specimen surface, and then led to fatigue strength and fatigue life increasing.

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