Use of KLST-Type Miniature Charpy Specimens for Measuring Dynamic Fracture Toughness Under Impact Loading Rates PDF Download
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Author: Marc Scibetta
Publisher:
ISBN:
Category : Ductile-to-brittle transition regime
Languages : en
Pages : 10
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Book Description
The knowledge of dynamic mechanical properties is useful in all cases where the strain rate sensitivity of metallic materials is an issue, and whenever the actual loading conditions for a structure (either in normal operation or under accidental circumstances) are different from static. Furthermore, in some investigations, increasing the loading rate in a mechanical test is used to simulate other embrittling mechanisms such as thermal aging or neutron exposure. Precracked Charpy-type (PCVN) specimens, tested under impact loading rates using an instrumented pendulum, have been used for more than 30 years to measure dynamic fracture toughness; the experimental procedure and the analysis methodology are fairly well established, despite the lack of an ASTM or ISO official test standard. This paper addresses the applicability of fatigue precracked miniature Charpy specimens of KLST type (PKLST-B = 3 mm, W = 4 mm and L = 27 mm) for impact toughness measurements in the ductile-to-brittle transition regime and in fully ductile (upper shelf) conditions. In the transition region, tests have been analyzed using the Master Curve approach; the multiple-specimen (low-blow) method has been applied in the upper shelf regime. A well-known and fully characterized reactor pressure vessel steel of the A533B Cl.1 type (JRQ) has been used; the results obtained have been compared with data previously obtained from standard-size precracked Charpy specimens. It has been found that under impact loading conditions PKLST specimens suffer significant loss of constraint when compared to conventional precracked Charpy V-notch samples, in both transition and upper shelf conditions.
Author: Marc Scibetta
Publisher:
ISBN:
Category : Ductile-to-brittle transition regime
Languages : en
Pages : 10
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Book Description
The knowledge of dynamic mechanical properties is useful in all cases where the strain rate sensitivity of metallic materials is an issue, and whenever the actual loading conditions for a structure (either in normal operation or under accidental circumstances) are different from static. Furthermore, in some investigations, increasing the loading rate in a mechanical test is used to simulate other embrittling mechanisms such as thermal aging or neutron exposure. Precracked Charpy-type (PCVN) specimens, tested under impact loading rates using an instrumented pendulum, have been used for more than 30 years to measure dynamic fracture toughness; the experimental procedure and the analysis methodology are fairly well established, despite the lack of an ASTM or ISO official test standard. This paper addresses the applicability of fatigue precracked miniature Charpy specimens of KLST type (PKLST-B = 3 mm, W = 4 mm and L = 27 mm) for impact toughness measurements in the ductile-to-brittle transition regime and in fully ductile (upper shelf) conditions. In the transition region, tests have been analyzed using the Master Curve approach; the multiple-specimen (low-blow) method has been applied in the upper shelf regime. A well-known and fully characterized reactor pressure vessel steel of the A533B Cl.1 type (JRQ) has been used; the results obtained have been compared with data previously obtained from standard-size precracked Charpy specimens. It has been found that under impact loading conditions PKLST specimens suffer significant loss of constraint when compared to conventional precracked Charpy V-notch samples, in both transition and upper shelf conditions.
Author: W. L. Server
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
The use of an instrumented impact hammer on pre-cracked Charpy V specimens has led to an inexpensive method for determining the dynamic fracture toughness, K sub Id. Measurements were made on A-533 steel over a range of temperature ( -125 to + 75F) at a loading rate K clot approximately equal to 1,000,000 ksi (in. to the 1/2 power)/sec. The data were found to be in excellent agreement with those obtained by other workers on much larger specimens. Analysis of the data leads to a new method for estimating the NDT temperature, which may be of practical value in nuclear reactor surveillance programs. (Author).
Author: WN. Sharpe
Publisher:
ISBN:
Category : Charpy tests
Languages : en
Pages : 6
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Book Description
A technique for measuring dynamic fracture toughness on small specimens is described and preliminary data are presented. Dynamic crack tip opening displacements (CTODs) are measured with laser interferometry over times as short as 10 ?s. The measured displacement is converted to stress intensity values via the equations of linear elastic fracture mechanics and the peak value obtained is taken as the dynamic fracture toughness.
Author: GB. Lenkey
Publisher:
ISBN:
Category : Dynamic fracture toughness
Languages : en
Pages : 16
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Book Description
In the engineering practice it is of importance to know the effect of loading rate on the material behaviour, e.g., on the fracture mechanics properties. One of the most widely used testing techniques for determining these properties is the instrumented impact test. Depending on the material behaviour under a given loading condition, different fracture mechanics parameters should be determined. Most of the evaluation procedures of these parameters are still not standardised for higher loading rates. So the aim of the present work was to investigate the applicability of different methods for determining dynamic fracture toughness properties. Instrumented impact experiments combining with magnetic emission measurement have been performed on pre-cracked Charpy-V specimens of E420 C and QStE 690 TM high strength steels. Critical values of stress intensity factor (KId, KJi) related to the initiation of the fracture at different temperatures have been determined Using different methods depending on the type of the fracture.
Author: RE. Link
Publisher:
ISBN:
Category : Constraint
Languages : en
Pages : 21
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Book Description
The dynamic fracture toughness of a reactor pressure vessel steel was investigated using small specimens. Precracked Charpy-size SE(B) specimens and circumferentially cracked round bars (CRB) loaded in tension were used to investigate the dynamic fracture toughness of an A533, Gr. B steel plate within the ductile-brittle transition region. The specimens used in this investigation were removed from the broken halves of conventional 4T C(T) specimens that had been utilized in a previous investigation of the dynamic fracture toughness of this material. Crack-tip loading rates in excess of 104 MPa-m1/2/s were achieved in the current tests. Multiple specimens were tested at each temperature in order to permit the determination of the reference temperature, T0. A fracture toughness scaling model for the circumferentially cracked round bar developed by Sciabetta was used to account for the loss of constraint in this specimen. A master curve approach was used to characterize the dynamic toughness in the ductile-brittle region. The shift in transition temperature was compared to a model for the strain rate dependence of T0 developed by Wallin. The shift in transition temperature of the CRB specimen was accurately predicted by the model. The CRB specimen and the dynamic SE(B) specimens gave good results considering the material inhomogeneity typical of the plate tested.
Author: Ravinder Chona
Publisher: ASTM International
ISBN: 080311429X
Category : Metals
Languages : en
Pages : 187
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Book Description
![Standard Charpy V-notch and Fatigue Precracked Charpy Specimens in Impact Loading for Determination of Dynamic Fracture Toughness, [K Sub Id] PDF](https://books.google.com/books/content/images/frontcover/slG4NwAACAAJ?fife=w80-h100)
Author: Douglas Allen Parker
Publisher:
ISBN:
Category : Metals
Languages : en
Pages : 150
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Book Description
Author: DF. Cannon
Publisher:
ISBN:
Category : Dynamic fracture toughness
Languages : en
Pages : 19
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Book Description
A simple, reliable, and repeatable method has been developed for determining dynamic plane-strain fracture toughness using an on-specimen strain gage. This extends the range of the British Standard Method for Determination of the Dynamic Fracture Toughness of Metallic Materials (BS 6729) to include measurement at impact testing rates. Dynamic finite element computing was used to optimize the position of the gage on the specimen. In tests at low loading rates on Charpy specimens, good agreement was found between toughness values calculated from the applied load and the calibrated gage, and with those measured by the shadow optic caustic technique. At higher rates, several gage types and two adhesives were compared. A satisfactory method was developed for performing tests at high and low temperatures. The technique was applied to larger bend specimens of two steels, and a test program was conducted at seven laboratories to assess the influence of testing machine and instrumentation variables. From the results, a standard calibration and test procedure has been developed.
Author: H. Conque
Publisher:
ISBN:
Category : Crack arrest
Languages : en
Pages : 13
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Book Description
The use of coupled pressure bars (CPB) to induce dynamic fracture in tough materials using small specimens is investigated. CPB experiments were performed with a nuclear pressure vessel steel, A533 Grade B Class 1, over the temperature range 37 to 100°C. The dynamic fracture initiation toughness at a stress intensity loading rate, KI, of 2 x 106 MPa•m1⁄2 s-1 was deduced from the simulation of the fracture experiment with a dynamic viscoplastic finite-element fracture code. At 100°C, no cleavage fracture was observed for either dynamic crack initiation or subsequent propagation and arrest. A procedure to measure initiation, propagation, and arrest toughnesses of nuclear pressure vessel steels up to service temperature with CPB specimens is introduced.
Author: TJ. Koppenaal
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 26
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Book Description
The dynamic fracture toughness, KId, was measured in a number of ferrous alloys using precracked Charpy specimens and an instrumented impact machine. The alloys investigated included quenched and tempered steels (H-11, D6AC, and 4340), 18Ni maraging steels (grades 200, 250, and 300) and a high-temperature, stainless maraging steel (Pyromet X-15). Standard Charpy specimens were precracked in fatigue and tested at either 72°F (22°C) or -65°F (-54°C). Values of KId, were determined as a function of yield strength and microstructure, and correlations were established between KId and both the energy to initiate fracture, Wm/A, and the total energy of fracture, W/A. The instrumented, precracked Charpy test is shown to be a convenient method of determining relative fracture toughness; under proper conditions this test procedure can be used to determine the dynamic planestrain fracture toughness.
