Fracture and Fatigue Resistance of Ultrafine Grain CuCrZr Alloy Produced ECAP

2006 ◽  
Vol 503-504 ◽  
pp. 811-816 ◽  
Author(s):  
Alexei Vinogradov ◽  
Kazuo Kitagawa ◽  
V.I. Kopylov
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Stable Crack Growth ◽  
Ultrafine Grain ◽  
J Integral ◽  
Present Communication ◽  
Angular Pressing ◽  
Fatigue And Fracture ◽  
Anisotropy Of Mechanical Properties

Anisotropy of mechanical properties, fatigue and fracture resistance of precipitation hardened CuCrZr alloy ultrafine (UFG) grained by equal-channel angular pressing (ECAP) is in focus of the present communication. Fracture toughness was estimated in terms of J-integral and the fatigue crack growth rate was quantified. It was found that although the estimated JIC-value appeared lower than that reported in the literature for a reference alloy, the ductility, fracture and crack growth resistance remained satisfactory after ECAP while the tensile strength and fatigue limit improved considerably. The stable crack growth rate did not differ very much for ECAP and reference conventional CuCrZr and no remarkable anisotropy in the stable crack growth was noticed.

Influence of process temperature on fatigue crack growth rate of copper in equal channel angular pressing

2021 ◽  
Vol 118 (5) ◽  
pp. 505
Author(s):  
Kaveh Abbasi ◽  
Mojtaba Vakili-Azghandi ◽  
Ali Shirazi
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Tensile Properties ◽  
Crack Growth ◽  
Equal Channel Angular Pressing ◽  
Fatigue Crack Growth Rate ◽  
Final Fracture ◽  
Angular Pressing

The mechanical properties including Vickers hardness, tensile properties and fatigue crack growth rate and also, the microstructure of pure copper severely deformed by the ECAP in different temperatures, were studied in the present work. The equal channel angular pressing (ECAP) is a process applied to make fine grains microstructure. On the other hand, high temperature provides an opportunity for recrystallization of materials and reduces required force for ECAP at the same time. In this paper we have tried to find optimized temperature to perform ECAP effectively and reduce required force. The results indicated that the grains size can reduce from 18.2 to 2.7 µm by ECAP process. This study shows that because of the recrystallization phenomenon and reducing the effect of stress concentration and increasing the number of grain boundaries, the fatigue crack growth rate can decrease significantly. Also, it was found that the major improvement in tensile properties in all the temperature conditions and due to the applied simple shear to the copper, all the ECAPed specimens have demonstrated an enhanced hardness and resistance to fatigue crack growth. Although, these improvements decrease when the temperature increases. Finally, the SEM images of the fatigue fraction sections revealed three areas including, crack initiation, stable crack growth, and final fracture zone. It seems that the final fracture appeared to be a ductile fracture in the ECAP copper sample.

SMALL CRACK GROWTH BEHAVIOR AND EVALUATION OF GROWTH RATE OF COPPER PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING

2012 ◽  
Vol 06 ◽  
pp. 245-250
Author(s):  
KUSNO KAMIL ◽  
MASAHIRO GOTO ◽  
SEUNG-ZEON HAN ◽  
KWANGJUN EUH ◽  
NORIO KAWAGOISHI ◽  
...  
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Plastic Zone Size ◽  
Growth Behavior ◽  
Small Crack ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Angular Pressing ◽  
Average Grain Size

Ultrafine grained copper processed by 4 cycles of equal angular pressing was fatigued to study the growth behavior of a small crack. After the crack initiation, the behavior of a major crack was monitored through plastic replication technique, showing that the crack growth rate is proportional to the crack length regardless of stress amplitudes. The crack growth rate of major cracks was evaluated by a term σanl, not by the stress intensity factor range, ΔK. Analysis on fracture surfaces by scanning electron microscopy showed a planar followed by a striated surface. The formation mechanism of fracture surface morphologies was discussed by considering the average grain size and the reversible plastic zone size at a crack tip.

Fracture Mechanics Analysis of Aero-Engine Compressor Disc

2013 ◽  
Author(s):  
K. M. Sathish Kumar ◽  
G. V. Naveen Prakash ◽  
K. K. Pavan Kumar ◽  
H. V. Lakshminarayana
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Growth ◽  
Stable Crack Growth

Fracture is a natural reaction of solids to relieve stress and shed excess energy. The design philosophy envisions sufficient strength and structural integrity of the aircraft to sustain major damage and to avoid catastrophic failure. However there are inherent limitations in the methodology, resulting in significant under utilization of component lives and an inability to account for non-representative factors. Ductile materials used in aircraft engine are likely to experience fatigue and stable crack growth before the occurrence of fast fracture and final failure. Fatigue crack propagation can be characterized by a crack growth-rate model that predicts the number of loading cycles required to propagate a fatigue crack to a critical size. Stress Intensity Factors under fatigue loading are below the critical value for quasi-static or unstable crack propagation. Under these circumstances, Linear Elastic Fracture Mechanics helps to characterize the crack growth-rate model. Stable crack growth and final failure generally occur at the very last loading cycle of the life of aircraft. Crack propagation at this stage involves elastic-plastic stable tearing followed by fast-fracture. Since crack growth is no longer under small-scale yielding conditions, Elastic-Plastic Fracture Mechanics is needed to characterize the fracture behavior and to predict the residual strength. The most likely places for crack initiating and development are bolt holes in a compressor disk. Such cracks may grow in time leading to a loss of strength and reduction of the life time of the disc. The objective of this work is to determine Stress Intensity Factor for a crack emanating from a bolt hole in a disk and approaching shaft hole. The objective is achieved by developing a 2D finite element model of a disk with bolt holes subjected to a centrifugal loading. It was observed that stress concentration at the holes has a strong influence on the value of Stress Intensity Factor. Also, fatigue life prediction was carried out using AFGROW software. Different fatigue crack growth laws were compared. This provides necessary information for subsequent studies, especially for fatigue loads, where stress intensity factor is necessary for the crack growth rate determination and prediction of residual strength.

Fatigue Fracture Behavior of ARB Processed Aluminum

2010 ◽  
Vol 654-656 ◽  
pp. 2479-2482 ◽  
Author(s):  
Hiromoto Kitahara ◽  
Takuya Horike ◽  
Masayuki Tsushida ◽  
Shinji Ando ◽  
Nobuhiro Tsuji
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Rolling Direction ◽  
Boundary Structure ◽  
Ultrafine Grain ◽  
Stress Intensity Factor Range

Fatigue crack propagation behaviors of ultrafine grained (UFG) Al sheets fabricated by the accumulative roll bonding (ARB) process were investigated. The ARB process was carried out up to 6 cycles (equivalent strain, eq.=4.8). The ARB processed sheet had lamellar boundary structure elongated to rolling direction of the sheet. The mean spacing of the boundaries was 182 nm. The tensile strength of the starting Al sheet increased after the 6-cycle of the ARB. Fatigue crack growth tests were performed to clarify the crack growth rate and threshold stress intensity factor range for crack growth (Kth). The fatigue crack profile in the ARB processed sheet differs from that in the starting Al sheet. The Kth of the ARB processed sheet was smaller than that of the starting sheet. The Kth of Al would decreased with decreasing the crack closure phenomena after the 6-cycle of the ARB. The fatigue crack growth rate test shows that the critical load for starting to propagate the fatigue crack and the fatigue crack growth rate decreased by ultrafine grain refinement.

Estimation of Crack Growth Rate by J-Integral Range for Type SUS304 Stainless Steel Plate in Creep-Fatigue Tests at High Temperature

2014 ◽  
Author(s):  
Madoka Funai ◽  
Osamu Watanabe ◽  
Akihiro Matsuda
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
J Integral ◽  
Creep Fatigue ◽  
Integral Range ◽  
Crack Growth Rates

In structures having stress concentration under cyclic loading, a small crack initiates and it grows and propagates. Evaluating crack growth is important to estimate the remaining life of cracked components. The present paper shows the estimation of crack growth rate under creep-fatigue loading with some patterns of strain holding times. Creep-fatigue tests of the perforated plate having initial crack were conducted with the different strain holding time under strain-controlled loading at 550°C. The crack growth was observed from the photographs taken at each cycle. The crack growth per one cycle of creep-fatigue loading was evaluated by the creep-fatigue crack propagation law which used increment J-integral range. Comparing the crack growth rates of experimental with those of predicted, the crack growth rates were predicted by using increment J-integral range with the accuracy was factor of 2.

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