Download or read book The Influence of Plasticity on Crack Length Measurements Using the Potential Drop Technique written by K. M. Tarnowski and published by . This book was released on 2015 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential drop (PD) technique is one of the most common methods for determining crack growth; however, other factors can also change the resistance of the specimen, which may erroneously be interpreted as crack extension. In tough, ductile materials, plastic strain can cause a significant change in PD. This paper presents an experimental investigation which quantifies the apparent crack extension due to strain prior to the onset of physical crack growth and considers ways to mitigate it. Compact tension, C(T), and single edge notch tension, SEN(T), specimen geometries are considered with a range of crack lengths. The influence of probe location is also considered. The results identify apparent crack extensions of up to 1.0 mm in the absence of any physical crack extension. This can be reduced through careful selection of probe locations. Appropriate locations are suggested for the geometries considered. It is also shown that high constraint geometry can significantly reduce the influence of plasticity on PD.

Download or read book The Effect of Large Scale Plastic Deformation on Fatigue Crack Length Measurement with the Potential Drop Method written by P. Ljustell and published by . This book was released on 2011 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: A combined experimental and numerical investigation was conducted on the effects of plastic deformation and material resistance on the relationship between the potential difference and crack size, denoted calibration curve, or equation. The stainless steel 316L was used at room temperature for investigating the limitations of the calibration curve. The nominal calibration equation, obtained from the undeformed geometry, can be used for fatigue crack length measurements at large plastic deformation. However, the reference potential must, for reliable crack length measurements, be measured at the deformed state and later adjusted at every major change of (plastic) deformation. The major part of the change in reference potential was attributed to the geometry change and only a minor part to the resistivity change. The scatter in the potential drop measured crack length, measured on a cycle by cycle basis, was about 30 times smaller here compared to the compliance measured crack length. Also, in situ potential drop sampling was possible, i.e., the test did not need to be stopped for crack length measurements.

Download or read book A DC Potential Drop Procedure for Crack Initiation and R Curve Measurements During Ductile Fracture Tests written by A. Bakker and published by . This book was released on 1985 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the use of a direct current (DC) potential drop technique, a single-specimen technique for the detection of crack growth initiation and subsequent crack growth. From an analysis of the potential drop signal, where the measured signal is divided into parts originating from real physical crack growth and fictitious crack growth caused by deformation of the specimen, a procedure is described to derive both crack initiation and crack growth from the test records of a single specimen. This procedure is then applied to a series of three-point bend (SENB) specimens and the results are compared with the multiple-specimen technique according to the ASTM Test for JIc, a Measure of Fracture Toughness (E 813). The agreement between the results of both methods is satisfactory. Finally, some possible refinements and further improvements of the method are discussed.

Download or read book Measurement of Stable Crack Growth Including Detection of Initiation of Growth Using the DC Potential Drop and the Partial Unloading Methods written by K. H. Schwalbe and published by . This book was released on 1985 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of the Potential Drop Technique for Crack Length Measurement to Fracture Toughness Specimens of the Cts Type written by National Physical Laboratory (Great Britain) and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Mechanics of Solids written by Cesar A. Sciammarella and published by John Wiley & Sons. This book was released on 2012-03-26 with total page 769 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental solid mechanics is the study of materials to determine their physical properties. This study might include performing a stress analysis or measuring the extent of displacement, shape, strain and stress which a material suffers under controlled conditions. In the last few years there have been remarkable developments in experimental techniques that measure shape, displacement and strains and these sorts of experiments are increasingly conducted using computational techniques. Experimental Mechanics of Solids is a comprehensive introduction to the topics, technologies and methods of experimental mechanics of solids. It begins by establishing the fundamentals of continuum mechanics, explaining key areas such as the equations used, stresses and strains, and two and three dimensional problems. Having laid down the foundations of the topic, the book then moves on to look at specific techniques and technologies with emphasis on the most recent developments such as optics and image processing. Most of the current computational methods, as well as practical ones, are included to ensure that the book provides information essential to the reader in practical or research applications. Key features: Presents widely used and accepted methodologies that are based on research and development work of the lead author Systematically works through the topics and theories of experimental mechanics including detailed treatments of the Moire, Speckle and holographic optical methods Includes illustrations and diagrams to illuminate the topic clearly for the reader Provides a comprehensive introduction to the topic, and also acts as a quick reference guide This comprehensive book forms an invaluable resource for graduate students and is also a point of reference for researchers and practitioners in structural and materials engineering.

Download or read book The Influence of Irregularities in the Crack Shape on the Crack Extension Measurement by Means of the Direct Current Potential Drop Method written by FO. Riemelmoser and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The equations used for calculating the crack extension from the change in the potential drop at a fracture mechanics specimen are generally derived for perfectly straight crack fronts. In the practice of fracture mechanics tests the crack, however, usually grows faster in the interior of the specimen than at the exterior, leading to a curved crack front. For such a case we calculate the potential drop by means of a finite difference scheme. It is shown that for curved cracks the usual procedure of the direct-current-potential-drop method underestimates the real crack extension. The same finite difference scheme is then used to account for conductive bars and bridges, which sometimes are left behind the crack front. Finally, the influence of side grooves on the potential drop is investigated.

Download or read book Potential Drop Method for Measuring Fatigue Crack Growth written by A. E. CARDEN and published by . This book was released on 1973 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: IN FATIGUE CRACK GROWTH (FCG) EXPERIMENTS TWO OF THE ESSENTIAL MEASUREMENTS ARE CRACK LENGTH AND CYCLE NUMBER. CRACK LENGTH MEASUREMENT GENERALLY HAS THE LEAST PRECISION AND IS THE MOST EXPENSIVE TO OBTAIN SINCE IT IS USUALLY VISUALLY OBSERVED AND MANUALLY RECORDED. SEVERAL ATTEMPTS HAVE BEEN MADE TO AUTOMATE THE MEASUREMENT AND RECORDING OF THE CRACK LENGTH BUT THE PRECISION WAS LOW WHEN THE CRACK LENGTHS ARE SMALL. A POTENTIAL DROP METHOD DEVELOPED BY MARKOCHEV HAS BEEN APPLIED TO FCG AT ELEVATED TEMPERATURE ON CN SHEET AND CT 2T SPECIMENS WITH GOOD RESULTS. A DIVIDER CIRCUIT GIVES THE RATIO OF THE POTENTIAL DROP NEAR THE CRACK TIP TO THAT IN A SHUNT. OUTPUT IS THEREFORE INSENSITIVE TO CURRENT LEVEL. THE DERIVATIVE OF THE OUTPUT VERSUS CRACK LENGTH IS CONSTANT FROM THE INITIAL CRACK LENGTH TO ABOUT 1/2 A/W. WITH OPERATIONAL AMPLIFIERS AND A MILLIVOLT RECORDER, CRACK LENGTH VERSUS CYCLE NUMBER CAN BE CONTINUOUSLY RECORDED. THE THRESHOLD LEVEL FOR FCG CAN BE MUCH MORE PRECISELY DETERMINED. INCUBATION PERIODS FOR FCG ARE CLEARLY OBSERVED AFTER OVERLOADS. FCG OF 10 TO THE 8TH POWER IN/CYCLE ARE EASILY DEFINED. THE THRESHOLD DELTA K FOR INCOLOY WAS DETERMINED TO BE ABOUT 4 KSI(IN) 1/2 IN LESS THAN 60 HOURS OF TESTING. WITH VISUAL OBSERVATION THE THRESHOLD LEVEL WAS JUDGED TO BE ABOUT 8 KSI(IN) 1/2 IN ABOUT 300 HR OF TEST TIME. THE LOWEST CRACK GROWTH RATE IN THE VISUAL METHOD WAS ABOUT 10 TO THE MINUS 7 IN/CYCLE.

Download or read book Automated Test Methods for Fracture and Fatigue Crack Growth written by W. H. Cullen and published by ASTM International. This book was released on 1985 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of the Electrical Potential Method to Crack Length Measurements Using Johnson s Formula written by Karl-Heinz Schwalbe and published by . This book was released on 1981 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crack Length Measurement During Rapid Crack Growth Using an Alternating Current Potential Difference Method written by JA. Joyce and published by . This book was released on 1988 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The object of this project has been to investigate the applicability of an alternating-current potential difference method of crack length estimation to rapid loading fracture mechanics tests in ferromagnetic materials. The more commonly used direct-current method has been demonstrated to be very sensitive to induced magnetization under rapid loadings. The resulting direct-current output signal is complex and not repeatable, and the component related to crack extension cannot be separated from the total response. The tests reported here show calibrations of a 10 kHz alternating-current system on an A533B material and application of the calibration to a static unloading compliance test and to rapid servohydraulic tests. A d-c component dependent on stress-induced magnetization is still present but can now be separated from the high frequency component using Fourier series methods.

Download or read book An Evaluation of the Plasticity Induced Crack Closure Concept and Measurement Methods written by James C. Newman (Jr.) and published by . This book was released on 1998 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Crack Length Measurement written by C. J. Beevers and published by . This book was released on 1982 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Elastic plastic Fracture Test Methods written by E. T. Wessel and published by ASTM International. This book was released on 1985 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Measurement of Crack Length and Shape During Fracture and Fatigue written by C. J. Beevers and published by . This book was released on 1980 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Automatic Crack Length Measurements by the Electrical Potential Drop Method with Computer Control written by A. Burgers and published by . This book was released on 1980 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystal Plasticity Finite Element Methods written by Franz Roters and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.