Download or read book Fatigue Crack Growth Rate Behavior of A36 Steel Using ASTM Load Reduction and Compression Precracking Test Methods written by B. M. Ziegler and published by . This book was released on 2012 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Eccentrically-loaded single-edge crack tension, ESE(T), specimens made of A36 structural steel were tested over a wide range in stress ratios (R = 0.1 and 0.7) in laboratory air. Two test methods were used: (1) ASTM Standard E647 load-reduction method and (2) compression precracking. After compression precracking (CP), three different loading sequences were used: (1) constant amplitude (CPCA), (2) load reduction (CPLR), and (3) constant stress-intensity factor (CPCK). The crack-compliance method was used to determine that the specimens had no residual stresses; and that the effects of tensile residual stresses from compression precracking dissipated in about 2 compressive plastic-zone sizes. Agreement was found between the A36 and TC-128B steel ?K-rate data tested at both low and high stress ratio (R) conditions. At R = 0.1 loading, the CPCA and CPLR tests generated lower thresholds and faster rates than using the standard ASTM load-reduction method. All load-reduction tests exhibited an accumulation of debris at the crack front near threshold conditions. A crack-closure analysis was preformed to calculate the effective stress-intensity factor range (?Keff) against rate using measured 1 % offset (OP1) values for all R = 0.1 tests. The ?Keff-rate data correlated well with the high-R results.

Download or read book Fatigue Crack Growth Rate Behavior of A36 Steel Using ASTM Load Reduction and Compression Precracking Test MethodsEleventh International ASTM ESIS Symposium on Fatigue and Fracture Mechanics 38th ASTM National Symposium on Fatigue and Fracture Mechanics on 18 May 2011 in Anaheim CA written by J. C. Newman and published by . This book was released on 2012 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Methods and Models for Predicting Fatigue Crack Growth Under Random Loading written by J. B. Chang and published by ASTM International. This book was released on 1981 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Growth Measurement and Data Analysis written by S. J Hudak and published by ASTM International. This book was released on 1981 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Growth from Compression Pre Cracks written by Meghan Borz and published by . This book was released on 2014 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The compression pre-crack method can be used to develop near-threshold fatigue crack growth rates much quicker than the ASTM standard load shed method. The compression pre-crack method is faster than the standard method and eliminates load history effects that are of concern when the standard method is used. However, crack growth developed using the compression pre-cracking approach is susceptible to different load history effects. A suite of tests using the compression pre-crack method that were performed on AISI 9310 steel are presented in this paper. An approach for identifying the critical crack growth increments required to develop valid data is presented, and the effects of three potential mechanisms are evaluated. For these tests, the residual stress field resulting from the initial compression field appears to be the more important effect on crack growth behavior. Crack growth increments measured from the notch tip that are 2.5 times larger than the size of the plastic zone resulting from the compression pre-cracking are required in order to develop valid data on the fatigue crack growth rate.

Download or read book Compression Precracking to Generate Near Threshold Fatigue Crack Growth Rates in an Aluminum and Titanium Alloy written by John J. Ruschau and published by . This book was released on 2008 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scope of this paper is to determine the fatigue-crack growth rates in the near-threshold regime for both an aluminum and titanium alloy using the compression precracking constant-amplitude (CPCA) test method on compact specimens. Tests were conducted over a wide range of stress ratios (R=Pmin/Pmax=0.1 to 0.9). Results were compared with threshold and near-threshold data generated on the same materials using the ASTM E647, "Standard Test Method for Measurement of Fatigue Crack Growth Rates," load-shedding test procedure. On the 7075-T651 alloy, very little difference was observed in threshold values between the load-shedding and CPCA test methods. In contrast, the titanium alloy (Ti-6Al-4V) showed very large differences between the CPCA and load-shedding test results in the near-threshold and threshold regimes for the low stress ratios. Results under high R conditions (R>=0.7) agreed well between the two-threshold test methods for both materials. On the titanium alloy, the load-shedding test method also produced a specimen width effect on near-threshold behavior, whereas the CPCA test method produced results that were independent of specimen width and produced "steady-state" constant-amplitude data in the near-threshold regime, after the crack had grown several compressive plastic-zone sizes.

Download or read book Fatigue Crack Growth Thresholds Endurance Limits and Design written by J. C. Newman and published by ASTM International. This book was released on 2000 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Contains 24 papers from the November, 1998 symposium of the same name, sponsored by the ASTM Committee E8 on Fatigue and Fracture, and presented by Newman and Piascik (both of the NASA Langley Research Center). The papers focus on such areas as fatigue-crack growth threshold mechanisms, loading and specimen-type effects, analyses of fatigue-crack-growth-threshold behavior, and applications of threshold concepts and endurance limits to aerospace and structural materials. Annotation copyrighted by Book News, Inc., Portland, OR.

Download or read book Crack Closure Behavior on a Variety of Materials Under High Stress Ratios and Kmax Test Conditions written by Y. Yamada and published by . This book was released on 2012 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue-crack-growth-rate tests on compact specimens have been made on a variety of materials (2024-T3, 2324-T39, 7050-T7451, 4340 steel, and Inconel-718) over a wide range in stress ratios from 0.1 to 0.9 (and 0.95 in some cases) and several Kmax test conditions. Test data has been generated from threshold to near fracture using the compression precracking constant amplitude or compression precracking load reduction test methods in the threshold regime; and constant-amplitude loading at higher rates. A remote back-face strain (BFS) gage was used to monitor crack growth and to measure crack-opening loads. Local strain gages were also placed along and slightly off (about one-half thickness) the anticipated crack path to measure crack-opening loads. Elber's load-against-reduced-strain method was used to determine crack-opening loads by means of visual inspection (equivalent to a 0 % compliance offset). For a particular material, the BFS and local strain gages produced essentially the same crack-opening loads at low stress ratio (R = 0.1) conditions. But at high stress ratios (R >= 0.7) and Kmax test conditions, the local gages produced significantly higher crack-opening loads than the BFS gage in the threshold and near-threshold regimes. Previous research had proposed that high stress ratios (R >= 0.7) and Kmax test conditions produce closure-free conditions based on crack-mouth-opening-displacement or BFS gages, and plasticity-induced crack-closure modeling. However, crack closure under high stress ratios (R >= 0.7) and Kmax test conditions is attributed to residual-plastic deformations, crack-surface roughness, and/or fretting-debris. From local crack-opening load measurements, the effective stress-intensity-factor range (DKeff) appears to be uniquely related to the crack-growth rate in the threshold and near-threshold regimes.

Download or read book The Use of Compression Precracking Constant Amplitude CPCA Test Method to Obtain Near threshold Fatigue Crack Growth Behavior in AA7075 T7351 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditionally, pre-cracking has been performed under tension-tension loading, followed by a load reduction scheme to obtain fatigue crack growth rate data in the near threshold regime. These data have been shown to exhibit load history effects due to remote crack closure. An alternative test method has been developed to minimize these load history effects. This test procedure uses compression pre-cracking to initiate a crack, followed by constant amplitude loading to grow the crack to failure. Compression-compression (C-C) loading as a means of forming a starter crack for fatigue crack growth is a relatively new concept. Cracks grown under C-C loading emanate from the notch tip due to a tensile residual stress field formed during the unloading cycle. The subsequent constant amplitude steady-state crack growth is free of load history effects, after crack growth beyond several compressive plastic zone sizes, and therefore will give a better steady-state representation of the near-threshold regime. A more in-depth examination at this phenomenon is performed herein.

Download or read book The Use of Compression Precracking Constant Amplitude CPCA Test Method to Obtain Near threshold Fatigue Crack Growth Behavior in AA7075 T7351 written by Dustin Henry McKnight and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditionally, pre-cracking has been performed under tension-tension loading, followed by a load reduction scheme to obtain fatigue crack growth rate data in the near threshold regime. These data have been shown to exhibit load history effects due to remote crack closure. An alternative test method has been developed to minimize these load history effects. This test procedure uses compression pre-cracking to initiate a crack, followed by constant amplitude loading to grow the crack to failure. Compression-compression (C-C) loading as a means of forming a starter crack for fatigue crack growth is a relatively new concept. Cracks grown under C-C loading emanate from the notch tip due to a tensile residual stress field formed during the unloading cycle. The subsequent constant amplitude steady-state crack growth is free of load history effects, after crack growth beyond several compressive plastic zone sizes, and therefore will give a better steady-state representation of the near-threshold regime. A more in-depth examination at this phenomenon is performed herein.

Download or read book Fatigue Crack Growth under Spectrum Loads written by and published by ASTM International. This book was released on 1976 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Fatigue Crack Closure Measurement and Analysis written by R. Craig McClung and published by ASTM International. This book was released on 1999 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Growth Rate Testing at High Stress Intensities written by NE. Dowling and published by . This book was released on 1977 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled load fatigue-crack growth rate tests are conducted using compact specimens of various widths between 1 and 10 in. Two engineering metals are tested: A533B pressure vessel steel and A469 alloy rotor steel. In these high-toughness materials, the upper limit of data interpretation based on linear-elastic analysis appears to be controlled by fully plastic limit load behavior. This resulted in the largest specimens yielding data at higher stress intensities than can be investigated in the smaller specimens usually employed in fatigue-crack growth rate testing. Test methods and limitations relative to plasticity are discussed, and it is recommended that deflections be monitored during load controlled testing. Some observations also are made concerning the relevance of static fracture toughness to failure following fatigue-crack growth.

Download or read book Prediction of Fatigue crack Growth Under Variableamplitude and Spectrum Loading Using a Closure Model written by and published by . This book was released on 1981 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Anomalous Fatigue Crack Growth Data Generated Using the ASTM Standards written by J. C. Newman and published by . This book was released on 2006 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ASTM standard for fatigue crack growth, E 647, was co-developed by industry and government in the late 1970s to define a standard procedure for generating material crack growth behavior under a variety of loading conditions. The standard specifies tolerances on laboratory procedures, specimen configurations to generate material characterization information of a high integrity. Recent research developing fatigue crack growth rate data has uncovered significant issues with the standard test method and specimen configurations. The data generated has been largely dependent on specimen configuration, i.e., M(T) and C(T) specimens produce very different crack growth rate curves; C(T) specimens of different sizes do not generate the same material response; and finally, the development of steady-state, as defined using constant ?K testing, does not agree with the data generated with the standard ASTM test method. Therefore, in this paper the authors present data that does not lend confidence in the integrity of the standard C(T) specimen tested using the ASTM standard method and investigate causes for the observed anomalous crack growth rate behavior.

Download or read book Fatigue Crack Growth Under Variable Amplitude Loading in ASTM A514 B Steel written by J. M. Barsom and published by . This book was released on 1973 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the fatigure-crack-growth behavior of ASTM A514-B steel under variable-amplitude random-sequence stress spectra such as occur in actual bridges. The fatigue-crack growth-rate data were obtained by using wedge-opening-loading specimens tested under variable-amplitude load spectra that are represented by a Rayleigh distribution function. The data show that the average fatigue-crack-growth rates under variable-amplitude random-sequence load fluctuation are approximately equal to the rate of fatigue-crack growth under constant-amplitude cyclic-load fluctuation equal to the root-mean-square value of the variable-amplitude fluctuation. The average fatigue-crack-growth rates, da/dN, under variable-amplitude random-load fluctuation and under constant-amplitude load fluctuation were found to agree closely when da/dN was plotted as a function of the root-mean-square stress-intensity-factor range, ?Krms. To verify the preceding observation, tests were conducted under the following variable-amplitude load fluctuations represented by the same Rayleigh distribution function: random sequence, ascending sequence, descending sequence, and ascending-descending sequence. All tests were conducted at a constant minimum load equal to 200 lb. The fatigue-crack growth-rate data obtained under these various loading sequences were close and were approximately equal to the average rate of fatigue-crack growth under constant-amplitude load fluctuations having a magnitude equal to the root-mean-square value of the distribution function. Thus, within the limits of the present investigation, the average fatigue-crack-growth rates, da/dN, under variable amplitude (random-sequence or ordered-sequence) load fluctuations and under constant-amplitude load fluctuations can be represented by the equation da/dN=A(?Krms)n where ?Krms is the root-mean-square stress-intensity-factor fluctuation (in ksi n.), and A and n are constants. Further work is needed to establish the applicability of the foregoing observations to various metals and to various continuous distribution functions.

Download or read book Load History Effects Resulting from Compression Precracking written by JA. Newman and published by . This book was released on 2005 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compression precracking (CPC) has seen renewed interest as a possible alternative procedure for generating fatigue crack growth threshold data with minimal load history effects, but recent testing confirms results from the literature that compression precracking does induce load history effects through residual stresses that influence subsequent fatigue crack growth test data. Using the CPC method, specimens are precracked with both maximum and minimum compressive loads. Compressive yielding occurs at the crack-starter notch, resulting in a local tensile residual stress field through which the fatigue crack must propagate. Although the tensile residual stress field contributes to the driving force for precracking, it also introduces the possibility of history effects that may affect subsequent fatigue crack growth. The tensile residual stress field elevates the local driving force at the crack tip, promoting higher crack growth rates than would be expected from the applied loading. This paper presents three-dimensional finite element results and experimental data for compact tension specimens that characterize the load history effects induced by compression precracking. The analysis results indicate that for low tensile loading levels near the threshold region, the residual stresses cause the calculated crack tip driving force to increase from the applied driving force by 25% or more. In addition, significant crack growth of about two times the estimated plastic zone size is needed to grow away from the residual stress field and reduce the calculated crack tip driving force to within 5% of the applied driving force. Experimental results show that growth of about two to three times the estimated plastic zone size is necessary to establish steady growth rates under constant ?K loading for the materials and loading levels evaluated. Constant ?K testing following compression precracking will demonstrate when residual stress effects are no longer significant and will ensure consistent growth rates.