Fracture-mechanics analysis of fatigue-crack propagation in polymethylmethacrylate

1968 ◽  
Vol 3 (3) ◽  
pp. 193-199 ◽  
Author(s):  
H F Borduas ◽  
L E Culver ◽  
D J Burns
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Cracks ◽  
Specimen Thickness ◽  
Loading History ◽  
Tension Tests ◽  
Mechanics Analysis

Repeated tension tests on centre-notched sheet specimens show that the rate of growth of fatigue cracks in polymethylmethacrylate is constant if the range of crack-tip stress-intensity factor is constant. Within the limits considered fatigue-crack growth rate was independent of specimen thickness and loading history.

Fatigue Crack Growth of Alloy 7050-T7451 Plate in L-S Orientation

2012 ◽  
Vol 525-526 ◽  
pp. 221-224
Author(s):  
Rui Bao ◽  
Xiao Chen Zhao ◽  
Ting Zhang ◽  
Jian Yu Zhang
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Characteristics ◽  
Stress Intensity Factor Range ◽  
Constant Amplitude ◽  
Stress Ratios

Experiments have been conducted to investigate the crack growth characteristics of 7050-T7451 aluminium plate in L-S orientation. Two loading conditions are selected, i.e. constant amplitude and constant stress intensity factor range (ΔK). The effects of ΔK-levels and stress ratios (R) on crack splitting are studied. Test data shows that crack splitting could result in the reverse of crack growth rate trend with the increasing R ratio at high ΔK-level. The appearance of crack splitting depends on both ΔK and R.

scholarly journals Corrosion Fatigue Crack Growth Studies on Pressure Vessel and Piping Steels in Water Environment

2017 ◽  
Vol 62 (3) ◽  
pp. 1857-1862 ◽  
Author(s):  
N.M. Mathew ◽  
S. Vishnuvardhan ◽  
G. Raghava ◽  
A.S. Santhi
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Water Environment ◽  
Stress Intensity Factor Range ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth

Abstract Corrosion fatigue crack growth studies were conducted on eccentrically-loaded single edge notch tension specimens made of SA 333 Gr. 6 and SA 516 Gr. 70 carbon steels in water environment. The experiments were conducted using a ±250 kN capacity Universal Testing Machine under constant amplitude sinusoidal loading at a test frequency of 0.50 Hz and stress ratio of 0.1. The fabrication of test specimens and the experiments were carried out based on ASTM E 647 and ASTM E 1820. The crack initiation and growth were monitored and images were captured by using a digital camera at regular intervals of fatigue cycles. By using these images, the length of crack was measured. The tests were terminated when the uncracked portion of the specimens was insufficient to take further load. Crack growth rate and stress intensity factor range values were evaluated at incremental values of loading cycles and crack length. Using the crack growth rate vs. stress intensity factor range plots, best fit curves following power law in the form of Paris’ equation were obtained.

Negative R Fatigue Crack Growth Rate Testing on Austenitic Stainless Steel in Air and Simulated Primary Water Environments

2018 ◽  
Author(s):  
Norman Platts ◽  
Ben Coult ◽  
Wenzhong Zhang ◽  
Peter Gill
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
High Temperature ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Laws

Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst most plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth, and, more importantly, on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies. A test methodology using corner cracked tensile specimens, and based on finite element analysis of the specimens to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading has been previously presented. The current paper further develops this approach, enabling it to be utilized to study a range of positive and negative load ratios from R = −2 to R = 0.5 loading, and provides a greater understanding of the development of stress intensity factor within a loading cycle. Test data has been generated in both air and high temperature water environments over a range of loading ratios. Comparison of these data to material specific crack growth data from conventional compact tension specimens and environmental crack growth laws (such as Code Case N-809) enables the impact of crack closure on the effective stress intensity factor to be assessed in both air and water environments. The significance of indicated differences in the apparent level of closure between air and water environments is discussed in the light of accepted growth laws and material specific data.

Stress Ratio Effect on Fatigue Behavior of Aircraft Aluminum Alloy 2024 T351

2010 ◽  
Vol 1276 ◽  
Author(s):  
M. Benachour ◽  
A. Hadjoui ◽  
M. Benguediab ◽  
N. Benachour
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Stress Ratio ◽  
Ratio Effect ◽  
Aluminum Alloy 2024

AbstractAluminum alloy series 2xxx, 6xxx, 7xxxx and 8xxx enjoy the widest use in aircraft structural applications. Among these materials, aluminum alloy 2024 remains the most commonly used and especially in T351 temper situation. The fatigue crack propagation behaviour of aluminum alloy 2024 T351 has been investigated using V-notch specimen in four bending test. A series of stress ratios from 0.10 to 0.50 was investigated in order to observe the influence of stress ratio on the fatigue life and fatigue crack growth rate (FCGR). The increase in FCGR, which occurs as the stress ratio is increased from 0.10 to 0.50, is generally attributed to an extrinsic crack opening effect. In T-S orientation and at low stress intensity factor, the increasing of stress ratio increase the FCG. Experimental results are presented by Paris law when coefficients C and m are affected by stress ratio. Contrary, at high stress intensity factor, the effect of stress ratio is reversed. We notice a decreasing of fatigue crack growth rate with an increasing of stress ratio. This effect may be explained by microstructure effect in (T-S) crack growth. The analysis of stress ratio effect by Elber model, shown that this model gives bad interpolation in this situation and the parameter characterized the crack closure factor will be adjusted.

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.

A Probabilistic Approach to Fatigue Crack Growth Rate

1980 ◽  
Vol 102 (3) ◽  
pp. 300-302 ◽  
Author(s):  
Akira Tsurui ◽  
Akito Igarashi
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Probabilistic Model ◽  
Probabilistic Approach

A probabilistic model for fatigue crack growth proposed by K. P. Oh is modified in some respects. Under more natural assumptions than Oh’s it is derived that the rate of fatigue crack growth is proportional to some power of the range of the stress intensity factor. It is also shown that the exponent ranges from 2 to 4.

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