THE FATIGUE AND FRACTURE BEHAVIOR OF MICRON-RUBBER AND NANO-SILICA PARTICLES MODIFIED EPOXY POLYMER

2012 ◽  
Vol 11 (03) ◽  
pp. 1240002 ◽  
Author(s):  
C. M. MANJUNATHA ◽  
N. JAGANNATHAN ◽  
K. PADMALATHA ◽  
A. C. TAYLOR ◽  
A. J. KINLOCH
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Growth ◽  
Stress Ratio ◽  
Epoxy Polymer ◽  
Fatigue Crack Initiation ◽  
Crack Growth Behavior ◽  
Dog Bone ◽  
Modified Epoxy

A thermosetting epoxy polymer was hybrid-modified by incorporating 9 wt.% of CTBN rubber microparticles and 10 wt.% of silica nanoparticles. The resin was poured into steel mould and cured to produce bulk epoxy polymer sheets from which fatigue test specimens were machined. The total fatigue life of the hybrid-modified epoxy polymer was determined by conducting constant amplitude fatigue tests with dog-bone shaped test specimens, at a stress ratio, R = σ min /σ max = 0.1, using a sinusoidal waveform at a frequency of 3 Hz. Further, the fatigue crack growth behavior of the hybrid-modified epoxy polymer, at a stress ratio, R = 0.1, was determined using a standard 50 mm wide compact tension specimen. The fatigue fracture surfaces were observed using a scanning electron microscope. The cyclic fracture toughness of the hybrid-modified epoxy polymer, estimated from the fracture surface analysis, correlated well with the reported values of the toughness; which was significantly greater than that of the neat epoxy polymer. The energy dissipating micromechanisms of, (i) rubber particle cavitation and plastic deformation of the surrounding material, and (ii) silica nanoparticle debonding followed by plastic void growth, were observed to be operative, resulting in an improved fracture toughness. The fatigue crack initiation and propagation lives were determined from the experimental data. The enhanced capability to withstand longer crack lengths, due to the improved toughness together with the retarded crack growth rate, were observed to enhance the total fatigue life of the hybrid-modified epoxy polymer.

Effect of Processing Layer on Fatigue Strength of Extruded AZ61 Magnesium Alloy

2013 ◽  
Vol 577-578 ◽  
pp. 429-432 ◽  
Author(s):  
Yukio Miyashita ◽  
Kyohei Kushihata ◽  
Toshifumi Kakiuchi ◽  
Mitsuhiro Kiyohara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Magnesium Alloy ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Crack Growth Resistance ◽  
Az61 Magnesium Alloy

Fatigue Property of an Extruded AZ61 Magnesium Alloy with the Processing Layer Introduced by Machining was Investigated. Rotating Bending Fatigue Tests were Carried out with the Specimen with and without the Processing Layer. According to Results of the Fatigue Tests, Fatigue Life Significantly Increased by Introducing the Processing Layer to the Specimen Surface. Fatigue Crack Initiation and Propagation Behaviors were Observed by Replication Technique during the Fatigue Test. Fatigue Crack Initiation Life of the Specimen with the Processing Layer was Slightly Longer than that of the Specimen without the Processing Layer. Higher Fatigue Crack Growth Resistance was also Observed when the Fatigue Crack was Growing in the Processing Layer in the Specimen with the Processing Layer. the Longer Fatigue Life Observed in the Fatigue Test in the Specimen with the Processing Layer could be Mainly due to the Higher Crack Growth Resistance. it is Speculated that the Fatigue Strength can be Controlled by Change in Condition of Machining Process. it could be Effective way in Industry to Improved Fatigue Strength only by the Cutting Process without Additional Surface Treatment Process.

scholarly journals Influence of Pre-Stress Magnitude on Fatigue Crack Growth Behavior of Al-Alloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1267
Author(s):  
Chunguo Zhang ◽  
Weizhen Song ◽  
Qitao Wang ◽  
Wen Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Shot Peening ◽  
Fatigue Property ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Fatigue Crack Growth Behavior

From tensile overload to shot peening, there have been many attempts to extend the fatigue properties of metals. A key challenge with the cold work processes is that it is hard to avoid generation of harmful effects (e.g., the increase of surface roughness caused by shot peening). Pre-stress has a positive effect on improving the fatigue property of metals, and it is expected to strength Al-alloy without introducing adverse factors. Four pre-stresses ranged from 120 to 183 MPa were incorporated in four cracked extended-compact tension specimens by application of different load based on the measured stress–strain curve. Fatigue crack growth behavior and fractured characteristic of the pre-stressed specimens were investigated systematically and were compared with those of an as-received specimen. The results show that the pre-stress ranged from 120 to 183 MPa significantly improved the fatigue resistance of Al-alloy by comparison with that of the as-received specimen. With increasing pre-stress, the fatigue life first increases, then decrease, and the specimen with pre-stress of 158 MPa has the longest fatigue life. For the manner of pre-stress, no adverse factor was observed for increasing fatigue property, and the induced pre-stress reduced gradually till to disappear during subsequent fatigue cycling.

scholarly journals A fatigue crack initiation and growth life estimation method in single-bolted connections

2019 ◽  
Vol 54 (2) ◽  
pp. 79-94 ◽  
Author(s):  
Arash P Jirandehi ◽  
TN Chakherlou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Estimation Accuracy ◽  
Life Estimation ◽  
Lower Error ◽  
Fatigue Life Estimation

Fatigue life estimation accuracy of mechanical parts and assemblies has always been the source of concern in different industries. The main contribution of this article lies in a study on the accuracy of different multiaxial fatigue criteria, proposing and investigating the accuracy of four optimized fatigue crack initiation life estimation methods—volume, weighted volume, surface and point, thereby improving the multiaxial fatigue life estimation accuracy. In order to achieve the goal, the fatigue lives of bolt clamped specimens, previously tested under defined experimental conditions, were estimated during fatigue crack initiation and fatigue crack growth and then summed together. In the fatigue crack initiation part, a code was written and used in the MATLAB software environment based on critical plane approach and the different multiaxial fatigue criteria. Besides the AFGROW software was utilized to estimate the crack growth share of fatigue life. Experimental and numerical results showed to be in agreement. Furthermore, detailed study and comparison of the results with the available experimental data showed that a combination of Smith–Watson–Topper approach and volume method results in lower error values, while a combination of Fatemi–Socie criterion and surface or point method presents estimated lives with lower error values. In addition, the numerical proposed procedure resulted in a good prediction of the location of fatigue crack initiation.

Effect of Stress Ratio on Fatigue Crack Growth in 95Pb-5Sn Solder

1999 ◽  
Vol 123 (3) ◽  
pp. 311-315 ◽  
Author(s):  
J. Zhao and ◽  
Y. Mutoh ◽  
T. Ogawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio ◽  
High Stress ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Test Conditions

The stress ratio effect on the fatigue crack growth behavior of 95Pb-5Sn solder has been investigated. It is found that both ΔJ and ΔK can correlate fatigue crack growth data well, which means that the crack growth behavior of the 95Pb-5Sn solder under the frequency of 10 Hz was dominantly cyclic dependent. The da/dN-ΔJ relationship can be expressed as: da/dN=1.1×10−11s˙ΔJ1.45. Low level of crack closure was found only in the near-threshold region. Except in this region, no crack closure was observed in the present test conditions. Both transgranular and intergranular fractures were observed on fracture surfaces: the former was dominant in most test conditions and the latter was dominant at the high stress ratio of 0.7. Striations and striation-like features were also found. Many slip bands and cavities along the grain boundary were observed on the crack wake and ahead of the crack tip in the high crack growth rate region.

Fatigue Crack Initiation and Growth of Aluminum Alloy with Stress Ratio Effects

2013 ◽  
Vol 594-595 ◽  
pp. 1105-1111 ◽  
Author(s):  
Haftirman Idrus ◽  
M. Afendi ◽  
Wong Chun Hoe
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Initiation ◽  
Crack Growth ◽  
Stress Ratio ◽  
Fatigue Crack Initiation ◽  
Stress Intensity Factor Range ◽  
Value Range ◽  
Compact Design

Fatigue crack initiation and growth of aluminum alloys with stress ratio were investigated due to it was widely used in aircraft production parts. Various types of aluminium alloy have been selected (6063-T6, 7075-T6, and 2024-T351). Compact design standard based on ASTM standard E647-11 was used for specimen. Cyclic loading experiment was conducted using Instron 8801 Hydraulic Server Machine with da/dN software for setup and parameter setting. Investigations on crack propagation and fracture surface were done by using Scanning Electron Microscope (SEM) to obtain the image of the specimen surface. Further analysis was done on the image to study on the crack initiation and propagation. Various stress ratio effects were set for the compact specimens having thickness 12.7 mm. Relationship between crack growth rate and the stress intensity factor range were further identified with the stress ratio effects. The gradients of crack growth rate increase while the stress ratio, R increase. Higher R-ratio results in higher value range of minimum load applied. Paris law and Modified Forman law were used as comparison with the experimental data for validation purposes and to provide the level of precision.

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