Considering the Statistical Distribution of Dynamic Fracture Toughness Data and the Actual Loading Rate at Fracture Initiation When Applying ASTM E1921 at Elevated Loading Rates PDF Download
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Author: U. Mayer Publisher: ISBN: Category : Compact tension specimen Languages : en Pages : 14
Book Description
ASTM E1921-15a describes the determination of the reference temperature T0,X for the loading rate X for ferritic steels in the transition range, where X is the order of magnitude of the average loading rate of the tests evaluated. Because this rate is defined for the linear-elastic part of a test only, the definition of the loading rate, valid for tests showing not only linear-elastic but also plastic behavior, is important. In a research project investigating the correlation of dynamic crack initiation and crack arrest funded by the German government, tests at -20°C on specimens of 22 NiMoCr 3 7 steel (A 508 Cl.2) were performed with different specimen geometry and loading devices in the range from 105 MPa?m s-1 to 3 x 106 MPa?m s-1. Evaluation according to ASTM E1921 shows differences of up to 30 K in T0,X obtained from linear-elastic test series and T0,X obtained from elastic-plastic test series with comparable dK/dt. New results were obtained in the current follow-up joint IWM-MPA project from test series at a loading rate of 5 x 105 MPa?m s-1. Results from tests with 1T C(T)-specimen at various test temperatures in the transition region are presented, analyzed, and reference temperature T0,5 is evaluated. The statistical distribution of the determined dynamic fracture toughness values KId resp., KJc,d and the determination of the characteristic loading rate in the case of elastic-plastic tests is discussed. This analysis shows the need of modifications of the standard evaluation method in ASTM E1921, if used for tests at elevated loading rate. The assumed statistical distribution has to be adapted and the actual loading rate at fracture initiation has to be taken into account. Suggestions for the considerations and requirements for the evaluation of data determined at elevated loading rates are presented.
Author: U. Mayer Publisher: ISBN: Category : Compact tension specimen Languages : en Pages : 14
Book Description
ASTM E1921-15a describes the determination of the reference temperature T0,X for the loading rate X for ferritic steels in the transition range, where X is the order of magnitude of the average loading rate of the tests evaluated. Because this rate is defined for the linear-elastic part of a test only, the definition of the loading rate, valid for tests showing not only linear-elastic but also plastic behavior, is important. In a research project investigating the correlation of dynamic crack initiation and crack arrest funded by the German government, tests at -20°C on specimens of 22 NiMoCr 3 7 steel (A 508 Cl.2) were performed with different specimen geometry and loading devices in the range from 105 MPa?m s-1 to 3 x 106 MPa?m s-1. Evaluation according to ASTM E1921 shows differences of up to 30 K in T0,X obtained from linear-elastic test series and T0,X obtained from elastic-plastic test series with comparable dK/dt. New results were obtained in the current follow-up joint IWM-MPA project from test series at a loading rate of 5 x 105 MPa?m s-1. Results from tests with 1T C(T)-specimen at various test temperatures in the transition region are presented, analyzed, and reference temperature T0,5 is evaluated. The statistical distribution of the determined dynamic fracture toughness values KId resp., KJc,d and the determination of the characteristic loading rate in the case of elastic-plastic tests is discussed. This analysis shows the need of modifications of the standard evaluation method in ASTM E1921, if used for tests at elevated loading rate. The assumed statistical distribution has to be adapted and the actual loading rate at fracture initiation has to be taken into account. Suggestions for the considerations and requirements for the evaluation of data determined at elevated loading rates are presented.
Author: T. Ochiai Publisher: ISBN: Category : Brittle fracture Languages : en Pages : 34
Book Description
Fracture toughness properties of structural steels of 490-MPa strength class and weld metals under dynamic loading are studied in the light of the near crack tip stress fields. The loading rate in toughness tests range from 0.1 to 500 mm/s. The near-tip stress fields are analyzed by 3D-FEM considering the strain rate effect on the flow properties of materials. Temperature rise caused by high-speed plastic deformation is also included in the FE analysis. The critical CTOD at brittle fracture initiation decreases when increasing the loading rate. This is due to the elevation of a local stress near the crack tip. The local approach is applied to the dynamic fracture toughness evaluation. It is shown that the brittle fracture resistance evaluated in terms of the Weibull stress, an integrated stress over a highly stressed region near the crack tip, is a material property independent of the loading rate. Based on the Weibull stress fracture criterion, the dynamic fracture toughness can be predicted from static toughness results. An engineering procedure to estimate the loading rate effect on the fracture toughness is also presented.
Author: Enrico Lucon Publisher: ISBN: Category : Ductile iron Languages : en Pages : 12
Book Description
For fracture toughness tests in the ductile-to-brittle transition region, ASTM E1921-05 requires specimens to be loaded using a loading rate dK/dt between 0.1 and 2 MPa?m/s during the initial elastic portion. It has been proposed that the standard allow testing at higher loading rates, including precracked Charpy specimens tested on an instrumented pendulum machine (impact toughness tests). The revised standard would require test results (KJc or To) to be reported along with the relevant loading rate, and should therefore provide guidance on how to assess the value of dK/dt in a relatively simple but reliable manner. Various options for measuring the loading rate have been investigated in this paper for several fracture toughness tests performed at different loading rates (quasi-static, dynamic, and impact). For each loading rate, three different toughness levels have been considered: low, medium, and high. Three considerably different materials have been selected: two RPV steels (JRQ, JSPS) and a ferritic/martensitic 9 % chromium steel (EUROFER97). It is found that the preferable option is given by the ratio between KJc and time at the onset of cleavage, whereas the elastic value Kel/tel or the average dK/dt can be used when partial unloadings are performed.
Author: Hans-Jakob Schindler Publisher: ISBN: Category : Ferritic steel Languages : en Pages : 10
Book Description
An increased loading rate causes not only a shift of the ductile-to-brittle transition curve, but also a slight change of the shape of this curve. The latter tends to become steeper as the loading rate increases. This effect was observed even at loading rates that are considered to be quasi-static according to ASTM E1921-13: Standard Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2013. Actually, the coefficient 0.019 in the exponent of the MC turned out to be substantially higher at elevated loading rates. This means that a basic assumption of the evaluation procedure of ASTM E1921 is not met, which leads to an increased uncertainty of T0 or T0,x, respectively. This effect of is most pronounced in testing at elevated loading rates using the single-temperature option. An improved method to determine the reference temperature is proposed, where the exponent in the median transition curve in ASTM E1921 is considered to be an open parameter. The resulting reference temperatures, denoted as T100 andT100,x, respectively, are expected to be more accurate than standard T0, which is confirmed by comparison with experimental data. Furthermore, the validity requirements for T100 are less restrictive and more suitable than those in ASTM E1921, since they do not depend on the outcome of the tests. Based on the improved data, an improved estimation formula for the rate-induced shift of T0 is derived. Suggestions are made for improvement of ASTM E1921.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The dynamic fracture toughness of an ASTM A533, Grade B steel plate was determined at several temperatures in the ductile-brittle transition region. Crack-tip loading rates ranged from approximately 10(sup3) to 10(sup5) MPa m/s. The fracture toughness was shown to decrease with increased loading rate. The dynamic fracture toughness was compared with results from previous investigations, and it was shown that the decrease in toughness due to increased loading rate at the highest test temperature was not as severe as reported in previous investigations. It was also shown that the reference temperature. T(sub0) was better index of the fracture toughness vs. temperature relationship than the nil-ductility temperature, RT(subNDT), for this material.
Author: SM. Graham Publisher: ISBN: Category : Bruchmechanik Languages : en Pages : 23
Book Description
The dynamic fracture toughness of an ASTM A533, Grade B steel plate was determined at several temperatures in the ductile-brittle transition region. Crack-tip loading rates ranged from approximately 103 to 105 MPa?m/s. The fracture toughness was shown to decrease with increased loading rate. The dynamic fracture toughness was compared with results from previous investigations and it was shown that the decrease in toughness due to increased loading rate at the highest test temperature was not as severe as reported in previous investigations. It was also shown that the reference temperature, T0, was a better index of the fracture toughness vs. temperature relationship than the nil-ductility temperature, RTNDT for this material.
Author: GB. Lenkey Publisher: ISBN: Category : Dynamic fracture toughness Languages : en Pages : 16
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: National Research Council (U.S.). Committee on Rapid Inexpensive Tests for Determining Fracture Toughness Publisher: National Academies ISBN: Category : Technology & Engineering Languages : en Pages : 266
Author: U. Mayer
Author: U. Mayer
Author: T. Ochiai
Author: Enrico Lucon
Author: Hans-Jakob Schindler
Author: 
Author: Welding Institute
Author: 
Author: SM. Graham
Author: GB. Lenkey
Author: National Research Council (U.S.). Committee on Rapid Inexpensive Tests for Determining Fracture Toughness