Precracked Charpy V-notch Research Articles

A comparison of various dynamic elastoplastic fracture toughness evaluating procedure by instrumented impact test

Instrumented impact test was carried out by using the pre-cracked Charpy V-notch (PCVN) specimen. The J ld values in the upper shelf of API X-52 pipeline steel were determined by several methods: 1. (1) pre-maximum load energy method; 2. (2) compliance changing rate method; 3. (3) low blow test; 4. (4) Kobayashi's COD relation; 5. (5) stretch zone size measurements; 6. (6) J-R curve; and 7. (7) equivalent energy method. Based on comparative study of the various J ld estimation procedures, it was indicated that the low blow test may be the best method for obtaining an effective J ld value, and the compliance changing rate method was a rapid and inexpensive way for the engineering practice.

Fracture toughness of maraging steel from Charpy ?V? notch specimens

Compact tension (CT) and Charpy “V” notch (CVN) (impact and three-point bend) specimens of 18 Ni 1800 MPa maraging steel (parent metal and weldment) were used to determine plane strain fracture toughness (K IC) and CVN impact energy (CVNIE), respectively. Using an empirical equation,K IC-CVNIE correlation is attempted which could be advantageously utilized for routine quality control of inward material to effect savings in cost and time. Investigations reveal betterK IC-CVNIE correlation for tests using the precracked CVN specimens. Scanning electron microscopic (SEM) observations reveal good correlation between fractographic features and fracture toughness.

Studies on the temperature dependence of charpy V-notch initiation energies for a pipeline steel and its welds

Instrumented impact tests were carried out on an API X-52 steel and its weldment by using Charpy V-notch (CVN) specimens and pre-cracked Charpy V-notch (PCVN) specimens. The physical meaning of the energy absorbed up to the maximum load in the load-deflection curve, E i, and several factors affecting the E i value were studied. It was found that for the CVN specimen the E i value expressed the crack initiation energy, and for the PCVN specimen the E i value was the sum of the crack initiation energy and part of energy of crack propagation. The E i value decreased with decreasing test temperature no matter whether the material was homogeneous or heterogeneous. For the CVN specimen, there were three characteristic temperatures in the E i- T°C relation curve: (1) T b—the temperature below which cleavage crack initiation would occur; (2) T d—the temperature above which a ductile crack initiated; (3) T r—the higher limit of temperature of the middle shelf in the E i- T°C relation curve. However, there were only two characteristic temperatures, T b and T d, for the PCVN specimen. The E i value was affected by specimen orientation, chemical composition of weld metal, and constraint. For ductile fracture, E i E t and E p E t values ( E t = E i + E p, E p—post-maximum load energy in the load-deflection curve) were insensitive to microstructure and material state, such as rolling or casting, over a certain range of material strength. The E i E t value decreased with increasing constraint at the same time as the E E p E t value increased. A peak of the E i E t values appeared at the T d temperature in the E i- T°C relation curve, whilst, on the other hand, a valley point of the E p E t values then occurred.

Brittle-ductile transition curve determined by charpy impact testing on CVN, precracked CVN and side-grooved precracked CVN specimens

Brittle-ductile transition curve determined by charpy impact testing on CVN, precracked CVN and side-grooved precracked CVN specimens

A Comparative Study of the Effect of Low Temperature on the Fracture Toughness and Cyclic Properties of Two Candidate High-Strength Low-Alloy Steels for Arctic Pipeline Applications

Abstract Because of the need for a better understanding of the effect of Arctic low temperature environments on the mechanical behavior of high-strength low-alloy (HSLA) steels, a comparative study has been undertaken to evaluate the effect of low temperature on the mechanical properties of two candidate steels, columbium-molybdenum “acicular ferrite” HSLA steel and high-columbium HSLA steel. The paper presents the data relating to the effect of low temperature on the mechanical properties, namely, dynamic fracture toughness KId properties, through instrumented impact testing of precracked Charpy V-notch samples and cyclic properties of the two steels. It also discusses the results in terms of their significance to material specification, selection, and performance criteria for safe and economical transportation of petroleum resources from the Canadian Arctic.

Reference Fracture Toughness Curves for Irradiated Pressure Vessel Steels

Recently developed statistically-based fracture toughness reference curve procedures (Charpy V-notch and precracked Charpy methods) have been applied to unirradiated and irradiated plate and weld material from the HSST program and the Maine Yankee reactor surveillance program. The results have been compared to the reference procedure based upon the ASME Code and NRC regulations (KIR curve) and to actual measurements of fracture toughness. It was found that the fracture toughness measurements were closely grouped around the mean property curve predicted by the Charpy V-notch method. The bounds for each method were similar for HSST Plate 02, but differed considerably for the Maine Yankee material. It was found that the KIR approach overstated the shift in the temperature of the property transition for the Maine Yankee reactor material. However, the low temperature fracture toughness was predicted to be lower than predicted by the KIR approach. These conclusions are subject to some reservations because of the poor quality of some of the referencing data, and because the precracked Charpy and Charpy V-notch reference curve procedures are still being developed and tested. Reasons for the differences between the current KIR method as compared to the proposed new methods have been traced to shortcomings in current procedures.

Determination of the Fracture-Energy Criterion JIc of Two Steels by Static and Dynamic Testing

Abstract The fracture energy criterion JIc was determined on two carbon-manganese steels, SA-516-70 and SA-105-B, from a single specimen. A graphic method is proposed for verifying the validity of measured values of JIc. Static JIc and dynamic JIcD experiments on precracked Charpy V-notch specimens at ambient temperature enabled the observation of the effect of loading rate on the value of JIc. For these two steels, the effect of side grooves was detected only in dynamic testing. For SA-516-70 steel, JIcD > JIc, while JIcD > JIc for SA-105-B steel, because of transition temperature fracture behavior. For SA-516-70, static testing was performed on three-point bend specimens of different dimensions to determine the effect of geometrical parameters on the value of JIc. A ligament 1-cm long is the lower limit for the determination of JIc.

The Determination of the J-Integral on Precracked Charpy Specimens by Instrumented Impact Testing and Slow-Bend Testing

The fracture criterion JIC is determined on SA-516-70 steel using precracked CVN specimens. The addition of an appropriate side-groove results in a better plane-strain condition at the crack tip and removes a major part of the absorbed energy due to lateral deformation. The value of JIC static is calculated from a single three-point-bend experiment. The displacement of the cracked front is followed by the measurement of the electrical resistance. We have shown that a single specimen is sufficient for determining JIC. Experiments on an instrumented Charpy machine were used for the calculation of the value of JICD. We assumed, for elasto-plastic behavior, that the maximum point of the load-displacement curve corresponds to the instability threshold of the crack. The values of JIC and JICD obtained by these two methods are compared and discussed.