Predicting the Effects of Overloads on Fatigue Crack Growth in an Al-SiC MMC Using a Computational Model

2004 ◽  
Vol 126 (2) ◽  
pp. 172-178
Author(s):  
M. S. Bruzzi ◽  
P. E. McHugh
Keyword(s):  
Crack Growth ◽  
Growth Curves ◽  
Cyclic Stress ◽  
Crack Growth Behavior ◽  
Matrix Composites ◽  
Modeling Approach ◽  
Sic Particles ◽  
The Impact ◽  
Modelling Approach ◽  
Fatigue Modeling

A defect tolerant approach to fatigue modeling for constant amplitude loading was developed by Bruzzi and McHugh (2002) and applied to two metal matrix composites: (1) a forged 2124 Al reinforced with 17 percent SiC particles and (2) a cast 359 Al reinforced with 20 percent SiC particles MMC in Bruzzi and McHugh (2003). In reality, however, engineering components are invariably subjected to varying cyclic stress amplitudes. In order to investigate the suitability of extending the fatigue modelling approach developed to variable amplitude loading, the effects of single and periodic peak tensile overloads are investigated in this work for the case of the Al 2124 MMC. The effects of overloads in causing significant changes to the level of closure in the wake of the crack tip, following the overload, in addition to changes in the nominally applied stress amplitude are firstly discussed in an overview. The quantification of the effects of overloads by use of experimental “resistance to crack growth curves” and the extension of the fatigue modeling approach to account for these effects are then described and investigated. Finally the predicted results of the impact of overloads on the short crack growth behavior of the Al 2124 MMC are presented and discussed. The extension of the fatigue modeling approach to account for the effects of overloads provides an additional means of validating the modelling approach developed by Bruzzi and McHugh (2002, 2003).

Evaluation of Fatigue Crack Growth Curves in Existing Codes and a Proposed Modification Based on Experimental Data of Cr-Ni-Mo-V Steel Welded Joints

2016 ◽  
Author(s):  
Yan-Nan Du ◽  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan ◽  
Shan-Tung Tu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Welded Joints ◽  
Growth Curves ◽  
Crack Growth Behavior ◽  
Fatigue Assessment ◽  
Crack Growth Model ◽  
Threshold Regime ◽  
Near Threshold

A comparison of currently available codes for assessment of fatigue crack growth, including ASME (America Society of Mechanical Engineers) SEC. XI, FKM (Forchungskuratorium Maschinenbau) guideline, WES (Japan Welding Engineering Society) 2805, BS7910 and JSME (The Japan Society of Mechanical Engineers), was carried out by paying attention to the suitability of application and the easiness to obtain the parameters, based on fatigue crack growth data of Cr-Ni-Mo-V steel welded joints. Results showed that fatigue crack growth curves provided by the FKM or WES were good choice when few inputs were at hand while the curves in the BS7910, JSME and ASME were recommended for precise estimation. It was indicated that the assessment of welded joints solely by fatigue crack growth behavior at base metal part and the assessment of fatigue crack growth for the aged condition by as-received one both resulted in non-conservativeness, albeit dependent on the range of stress ratios, R. A new bilinear form of fatigue crack growth model independent of R was developed based on transition point occurred in the near-threshold regime. This constituted the bilinear approach to fatigue assessment, and thus contributed to the optimization of fatigue assessment in the near-threshold regime.

Interface Effects on the Tensile and Fatigue Crack Growth Behavior of Fiber-Reinforced Metal Matrix Composites

1996 ◽  
Vol 458 ◽  
Author(s):  
B. S. Majumdar ◽  
S. G. Warrier ◽  
D. B. Miracle
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Single Fiber ◽  
Crack Growth Behavior ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Fatigue Crack Growth Behavior ◽  
Fiber Reinforced

ABSTRACTThe effects of the interface on the tension and fatigue crack growth behavior of fiber-reinforced titanium matrix composites were studied using single-ply and single-fiber SiC/Ti-6Al-4V mini-composites with different SiC fibers and coatings. Attention was focused on fiber failure mechanisms in the absence of a matrix crack (tension loading), and on fatigue crack deceleration mechanisms. In contrast to established models of tensile failure, local load sharing behavior was observed for very weak interfaces, with plasticity playing a major role in enhancing stress concentration effects. The approach included statistical evaluation of fiber breaks, their locations, and comparisons between single-fiber and single-ply composites. Under fatigue loading, crack deflection behavior was found to be consistent with a strength based interface debonding model. Crack shielding through modulus mismatch was found to have a significant effect on crack growth rates, independent of bridging conditions, with a stronger interface performing better under such conditions. The ramifications of the different mechanisms on interface optimization for longitudinal and transverse properties of composites are indicated.

scholarly journals Crack Growth Tests in Air Plasma-Sprayed Yttria Coatings for Alumina Ceramic Matrix Composites

Ceramics ◽  
2019 ◽  
Vol 2 (3) ◽  
pp. 514-524
Author(s):  
Stefan Hackemann ◽  
Marion Bartsch
Keyword(s):  
Crack Growth ◽  
Bending Strength ◽  
Ceramic Matrix Composites ◽  
Atmospheric Plasma ◽  
Crack Growth Behavior ◽  
Matrix Composites ◽  
Air Plasma ◽  
Spray Process ◽  
Aging Conditions ◽  
Plasma Sprayed

Yttria coatings for all-oxide combustor walls were tested for their crack-growth behavior. These environmental and thermal barrier Y2O3-coatings were processed by atmospheric plasma spraying (APS). The stiffness and strength were measured for as-received and aged samples that were heat treated at 1000 °C, 1100 °C and 1200 °C for a 10 h dwell time. The results show a clear development with respect to the aging conditions. The changes of the modulus and the bending strength indicate that the microstructural changes are not completed, even after aging at 1200 °C for 10 h. The fracture toughness was tested for different orientations on samples aged at 1200 °C. Bending tests as well as indentation experiments were conducted. Furthermore, a bending device was designed to observe the crack-growth in situ. The device had to be rigid and is driven by a piezo stack. The crack growth resistance shows differences in the rise of the R-curves for different orientations of the crack propagation. This is in agreement with the microstructure that results from the plasma spray process.

Experimental and Numerical Investigation of Plasticity-Induced Fatigue Crack Closure in Overmatched Welds

2013 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Claudio Ruggieri
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Compact Tension ◽  
Cyclic Stress ◽  
Growth Behavior ◽  
Weld Strength ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior

This work provides a numerical and experimental investigation of fatigue crack growth behavior in steel weldments including crack closure effects and their coupled interaction with weld strength mismatch. A central objective of this study is to extend previously developed frameworks for evaluation of crack closure effects on fatigue crack growth rates (FCGR) to steel weldments while, at the same time, gaining additional understanding of commonly adopted criteria for crack closure loads. Very detailed non-linear finite element analyses using 3-D models of compact tension C(T) fracture specimens with square groove, weld centerline cracked welds provide the evolution of crack growth with cyclic stress intensity factor which is required for the estimation of the closure loads. Fatigue crack growth tests conducted on plane-sided, shallow-cracked C(T) specimens provide the necessary data against which crack closure effects on fatigue crack growth behavior can be assessed. Overall, the present investigation provides additional support for estimation procedures of plasticity-induced crack closure loads in fatigue analyses of structural steels and their weldments.

scholarly journals Crack Growth Behavior through Wall Pipes under Impact Load and Hygrothremal Environment

2018 ◽  
Vol 14 (4) ◽  
pp. 9-15
Author(s):  
Ali Jamal Khaled ◽  
Ahmed Abdul Hussain
Keyword(s):  
Crack Growth ◽  
Impact Load ◽  
Low Carbon Steel ◽  
High Accuracy ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Bending Stress ◽  
Low Carbon ◽  
Number Of Cycles ◽  
The Impact

This research concerns study the crack growth in the wall of pipes made of low carbon steel under the impact load and using the effect of hygrothermal (rate of moisture 50% and 50℃ temperature). The environmental conditions were controlled using high accuracy digital control with sensors. The pipe have a crack already. The test was performed and on two type of specimens, one have length of 100cm and other have length 50cm. The results were, when the humidity was applied to the pipe, the crack would enhance to growth (i.e. the number of cycles needed to growth the crack will reduce). In addition, when the temperature was increase the number of cycles needed to growth the crack are reduced because the effect of heat on the mechanical properties of the material. In addition, when the test performed on the specimens of length 50cm the number of cycles needed to growth the crack is increase because the effect of bending stress on the pipes.

Fatigue Crack Growth of β-21S Titanium Alloy Under Constant Amplitude and miniTWIST Flight Spectra at 25°C and 175°C

1997 ◽  
Vol 119 (4) ◽  
pp. 387-392
Author(s):  
R. R. Stephens ◽  
R. I. Stephens ◽  
A. L. Veit ◽  
T. P. Albertson
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Curves ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Constant Amplitude ◽  
Near Threshold

β-21S titanium alloy sheet fatigue crack growth behavior was investigated at 25°C and 175°C under constant amplitude (R = 0.1 and 0.5) and miniTWIST flight spectra. Based upon nominal ΔK values, constant amplitude fatigue crack growth behavior at 175°C was either similar to (R = 0.1), or slightly better than (R = 0.5) 25°C. With crack closure taken into account, the fatigue crack growth curves at 175°C, plotted as a function of Keff, were shifted to the left of the fatigue crack growth curves at 25°C at near threshold values. Under flight spectra conditions, fatigue crack growth life at 175°C was 40 to 90 percent longer than at 25°C. Flight spectra life calculations using NASA/FLAGRO based upon constant amplitude fatigue crack growth data, were primarily conservative but in good agreement with experimental data. Fatigue crack growth was transgranular with crystalline facets and striations that were evident at higher constant amplitude fatigue crack growth rates and with the miniTWIST spectra. Striations were observed to a limited extent at threshold and near threshold conditions at 25°C, but not at 175°C. Based upon desirable constant and variable amplitude fatigue crack growth and fatigue/fracture crack morphology, this β-21S sheet alloy appears to be an acceptable material for damage tolerant aerospace situations between 25°C and 175°C.

High-Temperature Fatigue Crack Propagation in P/M Ni3Al-B Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
K.-M. Chang ◽  
S.C. Huang ◽  
A.I. Taub
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Time Dependence ◽  
Crack Growth ◽  
Elevated Temperatures ◽  
Cyclic Stress ◽  
Propagation Mechanism ◽  
Crack Growth Behavior

AbstractDuctile Ni3Al-B type intermetallic alloys show a unique fatigue crack growth behavior at elevated temperatures. A crack propagation mechanism has been investigated in an experimental P/M alloy by testing the alloys with different fatigue frequencies at 400°C. The Ni3Al-B intermetallic alloy shows a substantial time-dependence of fatigue cracl growth rate when tested in air. Under a given cyclic stress intensity, an order of magnitude difference of crack growth rate was observed by decreasing the fatigue frequency. However, such a time-dependence did not occur when the alloy was tested in vacuum. It is concluded that “dynamic” embrittlement in an oxidation environment is the major factor controlling the fatigue crack growth in ordered Ni3Al-B alloys at elevated temperatures.

scholarly journals Damage Tolerant Design of Turbine Engine Disks

1982 ◽  
Author(s):  
C. H. Cook ◽  
C. E. Spaeth ◽  
D. T. Hunter ◽  
R. J. Hill
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Damage Tolerance ◽  
Fatigue Cracks ◽  
Design System ◽  
Crack Growth Behavior ◽  
Analytical Prediction ◽  
Turbine Engine ◽  
Damage Tolerant ◽  
The Impact

This paper describes a USAF sponsored effort to develop, apply, test, and evaluate Pratt & Whitney’s Damage Tolerant Design System for cold-section gas turbine engine disks. The design system includes a Damage Tolerance Specification proposed for new USAF engine programs, material characterization for crack-growth behavior, design procedures, and analytical life prediction methodology for consideration of large flaws. To evaluate and refine the design system, a current engine fan disk was redesigned to operate safely for a specified time after the occurrence of 0.030-inch (0.76 mm) surface length fatigue cracks. The redesigned disk was tested to failure while monitoring crack growth and correlating observed measurements with analytical prediction. Test results were used to refine the design system. Current work involves extending Damage Tolerant Design capability to hot-section powder-metallurgy disks. The impact of these efforts is twofold; current designs will benefit from improved life prediction capability in applying Retirement-for-Cause philosophy, and future designs can take advantage of the Life-Cycle-Cost benefit of designing for damage tolerance.

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