Instrumented Charpy Test Research Articles

Simple Method for the Determination of Static or Dynamic Modified J-R Curve

Ernst et al proposed a method to calculate the deformation theory J, JD which takes into account the influence of crack growth on J. Furthermore, Ernst introduced a modified version of the J-integral, JM, to allow a large relaxation of restrictions on the amount of crack extension and specimen configuration. In this work, simple formulas for the deformation theory J-integral and the modified J-integral are developed. The methods are applied to the static JIC test and the instrumented Charpy test. The accuracy of the methods in the determination of the J-R curves is discussed, emphasizing the difference between J-R curves for JD and JM.

A study on the Instrumented Charpy test.

The Instrumented Charpy test was conducted on U-, V-, and fine notched specimens and a fatigue precracked specimen of A508 C1.3 steel and the effect of specimen configuration, test temperature and loading speed on the dynamic fracture toughness was investigated. Comparing the load-displacement curves of the U-notched and fatigue cracked specimen, the fracture toughness at the onset of crack extension was determined and proved to coincide with the lowest value of the dynamic fracture toughness. The J-integral and R-curve of the fatigue cracked specimen were corrected for crack extension by a proposed direct calculation procedure in place of ASTM's step-by-step one.

On the accuracy of measurement of dynamic elastic-plastic fracture toughness parameters by the instrumented charpy test

It had been developed in a previous study [ Engng Fracture Mech. 24, 773–782 (1986)] that dynamic elastic-plastic fracture toughness parameters J d and T mat could be evaluated from the instrumented Charpy impact test. However, to popularize this method, strict measuring methods and judging standards on the validity of obtained values must be established. One old and important problem to be clarified is a relationship between an instrumented energy ( E t ) obtained from the area under a load-deflection curve and a dial reading energy ( E r ) calculated from the potential energy of the hammer. The purpose of this study is, therefore, to solve this problem first, and moreover to clarify the dynamic phenomena accompanying the measurement of the load-deflection curve. It is concluded that the energy condition necessary for the test without changing the load-deflection relationship is E 0 (applied energy) ≧ 3 E (total absorbed energy). This is the necessary condition to evaluate meaningful values of J d and the tearing modulus ( T mat ). Moreover, it is shown how the vibrational wave superimposes the load-deflection curve, analyzing the vibrational mode shape of the hammer.

Fracture of Concrete Subjected to Impact Loading

AbstractTo evaluate the response of concrete structures subjected to impact or impulsive loading, it is essential to know how cracks propagate under such dynamic loading conditions. Single-edge notched beams were subjected to varying rates of loading to establish the stress intensity factor K1 versus crack velocity V relationship for mortar and concrete. Impact tests were performed using a modified instrumented Charpy test system. During loading, the rate of crack growth was obtained using special brittle Krak gages.Results indicate the following: (1) For a given strain rate the extent of pre-peak crack growth is larger for concrete than for mortar, and the amount of pre-peak crack growth decreases with increase in strain-rate. (2) Decrease in pre-peak nonlinearity at higher strain rates is probably caused by the decrease in amount of slow (pre-peak) crack growth. Hence, the linear-elastic fracture mechanics (LEFM) approach at high rates may be valid. (3) To obtain realistic size independent value of stress intensity factor, slow crack growth should be included in the calculation for cement composites. (4) The relationship between log K1 and log V is nonlinear especially at the higher rates of loading, for both mortar and concrete.

Analysis of impact properties of 3D-carbon-carbon composite material by the instrumented charpy test

Impact properties of 3D-carbon-carbon composite materials have been studied through fractographic analysis and failure parameters determination using instrumented Charpy testing. Different methods have been used to assess dynamic toughness. Making use of static formulae for homogeneous materials, critical stress intensity factors have been calculated at the maximum of the load-time response of the 3D-C-C notched specimens. Applying a method which takes into account the inertia effect, dynamic stress intensity factors have been determined. Comparison between the related failure parameters K IDy, K IDp and K ISm and their correlation with the corresponding values of the J-integral show the reliability of the results. Gathering fractographic analysis, qualitative examination of load/time curves and dynamic toughness assessment contribute to a better understanding of rupture mechanism in 3D-C-C composite materials.

計装化シャルピー試験による動的弾塑性破壊靱性の測定精度上の問題点

計装化シャルピー試験による動的弾塑性破壊靱性の測定精度上の問題点

Irradiation embrittlement of neutron-irradiated ferritic steel

In this study three kinds of Fe-Cr ferritic steels were examined by the instrumented Charpy test and tensile test before and after JMTR irradiation ( 2.2×10 23 f.n./m 2 ). In the unirradiated samples, 100%-martensite 5Cr-2Mo steel showed the highest adsorbed energy and the highest toughness at low temperatures, follewed by the 9Cr-2Mo steel, and the 20%-martensite 5Cr-2Mo steel showed the third highest toughness. In the irradiated samples, however, thoughness was low as a whole, especially in 20%-martensite 5Cr-2Mo steel. It was clarified that 100%-martensite 5Cr-2Mo steel had the lowest Ductile-to-Brittle Transition Temperature (DBTT) and the highest fracture toughness, and that its DBTT and fracture toughness changed a little upon irradiation, showing excellent irradiation characteristics. The general equations were considered for correlation among strength, ductillity, DBTT and fracture toughness ( J value)

計装化シャルピー試験法による動的弾塑性破壊靱性特性値の評価

計装化シャルピー試験法による動的弾塑性破壊靱性特性値の評価

高強度鋼切欠き材の衝撃強度

An instrumented impact charpy test was carried out to evaluate the effects of the notch shape, hardness, and carburized depth on the impact bending strength of notched high strength steels (SCM 440 and SCM 415 steels).The principal results were as follows:(1) The impact bending strength of the notched high strength steel was in near proportion to the tensile strength of the material, having no direct corresponding relationship with the absorbed impact energy.(2) However, the impact bending strength showed an ultimate value which is determined by the notch shape and the tensile strength of the material, and a proportional relationship existed between the impact bending strength and tensile strength below this ultimate value.(3) The impact bending strength of the carburized SCM 415 steel showed a value of about 10% larger than the static bending strength. On the other hand, the impact bending strength of the SCM 440 steel showed a value of about 10% smaller than the static bending strength, and this tendency was contrary to the general trend.(4) The result of fractographic observation by SEM showed that the width of the DIZ (ductile initiation zone between notch root and unstable fracture area) depended largely upon the notch shape and that only the data at such high strength levels as HRC=53 and 55 were in proportion to the impact bending strength.

破壊靱性評価の問題点と計装化シャルピー試験の役割

破壊靱性評価の問題点と計装化シャルピー試験の役割

A modified instrumented charpy test for cement-based composites

A description is given of a modified instrumented Charpy test that is designed to enable impact-testing of cement-based composites. Problems encountered in instrumented impact testing of such composites and solutions to overcome them are discussed. Results of tests on concrete specimens at four different impact velocities are reported and are used to evaluate the performance of the test setup. A simple spring-mass model is used to verify the test results. This model is capable of providing suitable guidelines for the apriori selection of the basic test parameters with a view to minimize parasitic effects of inertial loading.

Analysis of impact properties of A533 steel for nuclear reactor pressure vessel by instrumented Charpy test

Instrumented Charpy impact test can become more useful by connecting the digital memory and microcomputer, where yield load ( P y ), maximum load ( P m ), premaximum load energy ( E i ) and post-maximum load one ( E p ) are automatically and rapidly analyzed. In such analysis, cyclic oscillations in a load signal are corrected and smoothened by using a method of moving averages (the nonrecursive low pass digital filter). Dynamic J 1 c value ( J 1 d ) of A533 steel can be measured in a fatigue precracked type Charpy specimen, provided that a true deflection of specimen and a true crack initiation point in the load-deflection curve are known. For this purpose, elastic compliance values of the testing machine and the specimen are measured dynamically by the elastic low blow test to correct the apparent deflection. Crack initiation point, on the other hand, is detected by the plastic low blow test. It is shown that the crack initiation in the fatigue pre-cracked specimen of this material occurs prior to the maximum load, and that the relation between crack initiation energy ( E Δα ) and pre-maximum load energy ( E i ) is E Δα E i − 0.8 .

Application of instrumented Charpy test in evaluating toughness of heat-affected zones in linepipe welds

Application of instrumented Charpy test in evaluating toughness of heat-affected zones in linepipe welds

Measurement of dynamic fracture toughness JId by instrumented charpy test

Measurement of dynamic fracture toughness JId by instrumented charpy test

The evaluation of tempered martensite embrittlement in 4130 steel by instrumented charpy V-notch testing

Tempered martensite embrittlement (TME) was studied in vacuum-melted 4130 steel with either 0.002 or 0.02 wt pct P. TME was observed as a severe decrease in Charpy V-notch impact energy, from 46 ft-lb. at 200 °C to 35 ft-lb. at 300 °C in the low P alloy. The impact energy of the high P alloy was consistently lower than that of the low P alloy in all tempered conditions. Fracture was transgranular for all specimens; therefore, segregation of P to the prior austenitic grain boundaries was not a factor in the occurrence of TME. Analysis of load-time curves obtained by instrumented Charpy testing revealed that the embrittlement is associated with a drop in the pre-maximum-load and post-unstable-fracture energies. In specimens tempered at 400 °C the deleterious effect of phosphorus on impact energy became pronounced, a result more consistent with classical temper embrittlement rather than TME. A constant decrease in pre-maximum-load energy due to phosphorus content was observed. The pre-maximum-load energy decreases with increasing tempering temperature in the range of 200 °C to 400 °C, a result explained by the change in work hardening rate. Carbon extraction replicas of polished and etched as-quenched specimens revealed the presence of Fe2MoC and/or Fe3C carbides retained after austenitizing. Ductile crack extension close to the notch root was related to the formation of fine microvoids at the retained carbides.

シャルピー衝撃試験による溶接部切欠きじん性評価に対する一考察 ＩＩ 遷移曲線におよぼす材質的不連続の影響

The present study was carried out to clarify the effect of neighboring mechanical heterogeneity on the ductile-to-brittle transition behavior of steel in the Charpy impact test. Specimens were manufactured from a high tension structural steel with bead welding by electron beam weld. Instrumented Charpy test was carried out in the transition temperature range. The resuts of the Charpy test were shown to be dependent not only on the toughness of weld metal but also the mechanical properties of base metal in the vicinity of weld metal. The mechanical heterogeneity existing in the neighborhood of the notch root decreased the upper shelf energy and raised the transition temperature in the Charpy test of specimens with weld bead.In addition, the elasto-plastic analyses on stress and strain in the Charpy specimen with weld bead were conducted by using finite element method. The analyses showed why the upper shelf energy and the transition temperature were affected not only by the toughness of weld metal under the the notch root but also the mechanical properties of base metal in the vicinity of weld metal.

Application of Computer Techniques to Charpy Impact Testing of Irradiated Pressure Vessel Steels

Abstract A Rockwell AIM 65 microcomputer has been modified to control a remote Charpy V-notch impact test machine. The computer controls not only handling and testing of the specimen but also transference and storage of instrumented Charpy test data. A system of electrical solenoid activated pneumatic cylinders and switches provides the interface between the computer and the test apparatus. A command language has been designated that allows the operator to command checkout, test procedure, and data storage via the computer. Automatic compliance with ASTM test procedures is built into the program.

計装化シャルピー試験による動的破壊靱性J<SUB>Id</SUB>の測定法

計装化シャルピー試験による動的破壊靱性J<SUB>Id</SUB>の測定法

ガラスマット強化プラスチックの動的破壊じん性

The dynamic fracture toughness values of glass mat reinforced polyester laminates were compared with the analytical values of dynamic stress intensity factor, and their temperature dependence was discussed using instrumented Charpy test results. The results obtained are as follows:(1) The ratio of dynamic fracture toughness KId to the static one KIS, which was obtained by the finite element method, decreased with time by oscillating around one, when the load increased at a constant rate. The ratio of KId/KIS was between 0.99 and 1.1, when the loading speed was about 0.55kgf/μs and KIS was greater than 30kgf/mm3/2 for EW test specimens, and when the speed was about 0.35kgf/μs and KIS was greater than 20kgf/mm3/2 for FW test specimens. The difference between the dynamic fracture toughness values obtained by the static K-calibration using the maximum load and by the dynamic K-calibration was smaller than the variation of measured values.(2) The dynamic fracture toughness values of EW specimens decreased slowly as the temperature became higher, while those of FW specimens were about constant at temperatures below 60°C. The toughness values of both specimens decreased rapidly as the temperature became higher than the thermal deformation temperature of resin (about 90°C). This temperature dependence of toughness was different from that of specific absorbed energy.

Sharp crack and blunt notch toughness behavior of quenched and tempered AISI 4340 steel

Precracked and blunt notch Charpy tests of AISI 4340 steel were carried out by instrumented Charpy tests for a variety of heat treatments. Scanning electron microscopy, transmission electron microscopy and optical microscopy were carried out to characterize microstructure and fracture surfaces. Results show that in precracked conditions high temperature austenitization at 1200 °C produces a twofold increase in the dynamic fracture toughness in the as-quenched condition compared with conventional austenitization at 870 °C, whereas in blunt notch testing conventional austenitization produces a better dynamic fracture toughness. High temperature austenitization, together with a large austenitic grain size, also results in substantial amounts of autotempered ϵ carbide in the as-quenched structure. These structural features are employed to seek an explanation for the anomalous toughness behavior in sharp crack and blunt notch testing of quenched and tempered AISI 4340 steel.