bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specimen Size and Orientation Effects in Chevron-Notch Fracture Testing of Aluminum Alloy Plate
Authors: Morrison J , KarisAllen KJ 
Published: March 2009

Side grooving of specimens can have a pronounced effect on the fracture behavior of aluminum alloys during plane-strain fracture tests. The first part of this paper describes an investigation of the effect of different amounts of side grooving on KIc determined using compact specimens of varying thicknesses machined from a 6061-T651 plate. The results are also related to KIv measurements made on the same material and are discussed in terms of rising R-curve effects on compact and short-bar fracture specimens.
Chevron-notch fracture tests in accordance with ASTM E 1304-89 were also carried out on nominally 13-mm-thick plates of aluminum alloys 2024-T351, 7075-T651, and 8090-T8771. Various specimen orientations were used, including both in-plane and short-transverse loading. Tension and also, where possible, compact specimen fracture tests have also been carried out on the same plates.
Data are presented showing the variation in load-deflection behavior and measured toughness with alloy type, and also with specimen orientation. Correlations of toughness and strength with plate rolling direction have been made. Problems arising from the E 1304 test method are also highlighted.
Using Chevron-Notch, Short-Bar Specimens for Measuring the Fracture Toughness of a Martensitic Stainless Steel at High Hardness
Authors: Marschall CW , Held PR , Dolan FJ 
Published: March 2009

Fracture toughness tests were conducted at room temperature and at – 196°C on a martensitic stainless steel that had been quenched and tempered to a hardness of Rockwell C 61-63. The fracture toughness specimens were chevron-notch, short-bar specimens for which B was 12.7 mm and W was 25.4 mm. Tests were conducted in accordance with ASTM Test Method for Plane-Strain (Chevron Notch) Fracture Toughness of Metallic Materials (E 1304-89).
Five tests were conducted at each temperature, and each test produced a valid KIv result. Test results were unusually reproducible for plane-strain fracture toughness tests; the standard deviation for room temperature tests was approximately ±5% and for -196°C tests was approximately ±2% of the mean value of KIv.
For comparison with the chevron-notch test results, three standard KIc tests were conducted on fatigue-precracked compact (tension) specimens at room temperature. The tests were conducted in accordance with ASTM Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E 399). As was the case for the KIv tests, the KIc tests produced very reproducible results: the standard deviation for three tests was approximately ±2% of the mean value. However, it was found that the mean KIv values for this high-hardness steel were approximately 18% greater than the mean KIc values. That result confirms the warning included in ASTM E 1304 that KIc values may be larger than KIc values in some materials.
Failure Analysis of Notched Unidirectional Graphite/Epoxy Tubes Under Combined Loading
Authors: Hirschfeld DA , Herakovich CT 
Published: March 2009

Crack growth from notched unidirectional graphite/epoxy tubes subjected to axial, torsional, and combined loading conditions was studied experimentally and theoretically. Tubes with fiber orientations of 2.5, 15, 45, and 87.5° were notched with slots 0.5 cm long, parallel to the tube axis.
The stress state at the notch of the thin tubes was determined using an elasticity analysis of an infinite plate with an elliptical hole. The normal stress ratio theory was used to predict the far-field stresses and the direction of crack growth at crack initiation. The slots in the tubes were modeled as an ellipse having the same notch tip radius as the slot, an ellipse having the same length and width, or as a circular hole depending on the loading regime. The normal stress ratio theory correctly predicted the direction of crack growth parallel to the fibers, but did not provide good correlation with the experimental far-field stress for crack initiation in all cases. It is believed that this lack of correlation for the critical stresses is due to the different notch geometries in the theoretical model and actual tubes.
The fracture surfaces of the failed tubes were examined using a scanning electron microscope. It was found that failure occurred primarily with the cracks growing from the notch either fully within the matrix or along the fiber/matrix interface depending upon the far-field loading.
Effect of Initial Delamination on Mode I and Mode II Interlaminar Fracture Toughness and Fatigue Fracture Threshold
Authors: Murri GB , Martin RH 
Published: March 2009

Static and fatigue double-cantilever beam (DCB) and end-notch flexure (ENF) tests were conducted to determine the effect of the simulated initial delamination on interlaminar fracture toughness, Gc, and fatigue fracture threshold, Gth. Unidirectional, 24-ply specimens of S2/SP250 glass/epoxy were tested with Kapton inserts at the midplane at one end to simulate an initial delamination. Four insert thicknesses were used: 13, 25, 75, and 130 μm. Some specimens were also tested with either tension or shear precracks as the initial delamination. To determine Gth, fatigue tests were conducted by cyclically loading specimens until delamination growth was detected. The fatigue fracture threshold was defined to be the maximum cyclic strain energy release rate, Gmax, below which no delamination growth would occur in less than 1 × 106 cycles.
For the DCB specimens, consistent values of Mode I fracture toughness, GIc, were measured for specimens with inserts of thickness 75 μm or thinner, or with shear precracks. The fatigue DCB tests gave similar values of GIth for the 13, 25, and 75-μm specimens. Results for the shear precracked specimens were significantly lower than for specimens without precracks.
Results for both the static and fatigue ENF tests showed that measured GIIc and GIIth values decreased with decreasing insert thickness, so that no limiting thickness could be determined. Results for specimens with inserts of 75 μm or thicker were significantly higher than the results for precracked specimens or specimens with the 13 or 25-μm inserts.
Damage and Failure Mechanisms in Scaled Angle-Ply Laminates
Authors: Kellas S , Morton J , Jackson KE 
Published: March 2009

The effect of specimen size upon the response and strength of ± 45° angle-ply laminates has been investigated for two graphite fiber-reinforced plastic systems and several stacking sequences. The first material system was an epoxy-based system, AS4 fibers in 3502 epoxy, and the second was a thermoplastic-based system, AS4 fibers in PEEK matrix. For the epoxy-based system, two generic ±45° layups were studied; ( + 45°n/-45°n)2s (blocked plies), and ( + 45°/-45°)2nS (distributed plies), where n = 1, 2, 3, and 4. In the case of the thermoplastic system, only the layup with distributed plies was investigated, ( + 45°/-45°)2nS, for n = 1 and 2. The in-plane dimensions of the specimens were varied such that the width/length relationship was 12.7 × n/127 × n mm, for n = 1, 2, 3, or 4.
It is shown that the stress/strain response and the ultimate strength of these angle-ply laminates depends on the laminate thickness and the type of generic layup used. The ultimate strength of the epoxy matrix material was found to be much more sensitive to specimen size when compared to the thermoplastic matrix system. Scaling effects defined with respect to the first ply failure, strain at ultimate failure, and ultimate strength are isolated and discussed. Furthermore, it is shown that first ply failure occurs in the surface plies as a result of normal rather than shear stresses. The implications of the experimental findings upon the validity of the ±45° tension test, which is used to determine the in-plane shear response of unidirectional composites, are discussed.
The Influence of Interleaf Deformation Behavior and Film-Resin Adhesion on the Fracture Toughness of Interleaved Composites
Authors: Armstrong-Carroll E , Iskandarani B , Kamel I , Donnellan TM 
Published: March 2009

Two-dimensional laminated composite materials are susceptible to damage by interlaminar crack growth. Delaminations severely degrade composite load-carrying capability. Interleaved composites are fabricated with thin films inserted between composite prepreg plies. Previous work has shown that interleaved composites have significantly higher delamination and impact resistance than composites without interleaves.
This paper examines interleaving as a technique for the improvement of delamination resistance in composites. In particular, the influence of the deformation behavior of the interleaf film and film adhesion on composite fracture toughness is studied. Teflon and Kapton interleaf film materials are compared. Kapton displays predominantly brittle deformation behavior. Teflon exhibits substantial deformation before failure. Both films are plasma treated to vary film-resin bond strengths. The fracture toughness of composites interleaved with these films is determined. Plasma treatments are shown to increase film-resin adhesion and fracture toughness. The effectiveness of Teflon as an interleaf material may be limited by the toughness of this film. Fracture toughness specimens are found to fail at the film-plasma grafted polymer interface. Additional optimization of the film-grafted polymer bond is necessary for improved performance.
Local Delamination in Laminates with Angle Ply Matrix Cracks, Part II: Delamlnation Fracture Analysis and Fatigue Characterization
Authors: O'Brien TK 
Published: March 2009

Constant amplitude tension-tension fatigue tests were conducted on AS4/3501-6 graphite epoxy (02/θ2/-θ2)s laminates, where θ was 15, 20, 25, or 30°. Fatigue tests were conducted at a frequency of 5 Hz and an R-ratio of 0.1. Dye penetrant-enhanced X-radiography was used to document the onset of matrix cracking in the central - θ° plies and the subsequent onset of local delaminations in the θ/-θ interface at the intersection of the matrix cracks and the free edge.
Two strain energy release rate (G) solutions for local delamination from angle ply matrix cracks were derived: one for a uniform delamination front across the laminate width, and one for a triangular-shaped delamination area that extended only partially into the laminate width from the free edge. Plots of maximum cyclic G versus the number of cycles to local delamination onset (Gmax versus N) were generated to assess the accuracy of these G solutions. The influence of residual thermal and moisture stresses on G were also quantified.
Effects of Stress Ratio on Edge Delamination Characteristics in Laminated Composites
Authors: Scrivner GC , Chan WS 
Published: March 2009

The effects of stress ratio on delamination onset behavior under cyclic loading was investigated in AS4/3502 [+/-252/90]s graphite/epoxy laminates. For the purpose of this study, delamination onset was defined as a delamination 5% of the laminate width. The resulting data showed definite changes in delamination behavior between stress ratios (R ratio) of 0.1 and 0.5.
For maximum amplitude stresses below about 80% of the static delamination stress, delamination onset occurred later at R = 0.5 than for R = 0.1. Also for the corresponding Gmax, delamination growth rates at delamination onset were slower for R = 0.5 than for R = 0.1. This was reflected in changes of power law exponent from 10.2 for R = 0.1 to 31.6 for R = 0.5 and the constant from 1.10 × 10-2 for R = 0.1 to 254 for R = 0.5.
Fractographic analysis suggested that the failure mode, which appeared to be predominantly Mode I, remained unchanged; however, the density of shallow hackles was greater for R = 0.1 than for R = 0.5. This presumably was due to a more rapid coalescence of microcracks which was consistent with the larger crack opening displacements for R = 0.1.
High-Cycle Fatigue Crack Growth Properties of Aramid-Reinforced Aluminum Laminates
Authors: Stanzl-Tschegg SE , Papakyriacou M , Mayer HR , Schijve J , Tschegg EK 
Published: March 2009

The fatigue crack growth properties of the laminated fiber-reinforced composite material Arall (Arall® 1 and Arall® 2) have been studied at low cyclic stress amplitudes and high numbers of cycles. For the experiments, a high-frequency (21 kHz) ultrasound resonance fatigue machine has been used (R = -1).
In order to determine the threshold stress intensity (for Arall 1), tests were performed by increasing the stress amplitude stepwise. The resulting threshold stress intensity increases with increasing crack length. In addition, tests with constant cyclic stress amplitude were carried out (for Arall 1 and Arall 2). For these, the fatigue crack propagation rates decrease with increasing crack length and become zero at a defined crack length if the applied constant stress amplitude is lower than a defined “critical” stress amplitude. Fiber bridging, causing extensive crack closure, is the reason for this effect. At cyclic stresses higher than this “critical” stress, cracks continue to grow, though with reduced speed.
Damaging effects like delamination owing to failure of the resin in addition influence the fatigue crack growth behavior of Arall at high cyclic stress amplitudes.
Radiation Embrittlement and Annealing Recovery of CrNiMoV Pressure Vessel Steels with Different Copper and Phosphorus Content
Authors: Vacek M , Novosad P , Havel R 
Published: March 2009

The influence of copper and phosphorus content on Charpy-V-notch impact energy, on dynamic fracture toughness, and on radiation hardening recovery of tensile and hardness properties by postirradiation annealing at different temperatures was explored for one commercial heat and six laboratory melts of CrNiMoV pressure vessel steels irradiated to 0.9 to 1.3 × 1023 n/m2 (E &gt; 1 MeV) at 280°C.
Practically linear proportionality between Charpy-V impact energy and dynamic fracture toughness transition curve shifts for all melts was found.
The effect of phosphorus content on radiation embrittlement of laboratory melts considered in this study was very weak in comparison to the significant effect of copper. However, percentage of recovery of radiation-affected hardness was in all laboratory melts permanently slightly lower for melts with higher content of phosphorus with the same copper content.
Copper content had no significant effect on percentage recovery of all laboratory melts as measured by hardness after annealing of irradiated specimens.
The annealing recovery behavior of radiation-affected yield stress (Rp0.2IA) was expressed by an experimental relationship that includes yield stress after irradiation (Rp0.2I), temperature of irradiation (TI), and temperature of annealing (TA).
Influence of Specimen Orientation on the Upper Shelf Energy and Transition Temperature Shift of Reactor Pressure Vessel Steel Base Metal
Authors: Leitz C , Klausnitzer EN , Hofmann G 
Published: March 2009

In surveillance programs for some older nuclear power plants, the orientation of specimens is longitudinal to the main working direction. According to presently valid codes and standards, the specimen orientation should be transverse. The material toughness is lower in the transverse direction. However, according to former test results, there was common acceptance that the shift as a result of irradiation is independent of orientation. The results of more recent research on trepan material taken from a decommissioned power plant seemed to give reason for doubt in this respect.
Siemens/KWU has simultaneously irradiated Charpy-V specimens made of steel 22 NiMoCr 3 7 (similar to ASTM A 508 cl. 2) with both orientations. Furthermore, transverse specimens were made out of the broken specimen halves from irradiation experiments with only longitudinal specimens using electron beam welding techniques.
The available results of this research and an ample number of relevant data from literature were evaluated. From this it is concluded that independent of a wide variation of parameters the 41-J transition temperature of transverse specimens is on average about 11°C higher than that of longitudinal specimens and the irradiation-induced shift ΔT41 is independent of specimen orientation. The upper shelf energy (USE) shows a wider scatter. As a lower bound, the proposal of the U.S. Nuclear Regulatory Commission (NRC) standard review plan to substitute 65% of longitudinal USE for unavailable transverse values is confirmed by 90% of all data for unirradiated and irradiated material. The deviations, especially of the Gundremmingen trepan results, obviously depend on fabrication inhomogeneity rather than on irradiation effects.
Mechanical and Nondestructive Testing of Irradiated Half Charpy Specimens
Authors: Gillemot F , Oszwald F , Pozsgay G 
Published: March 2009

After the five scheduled surveillance testings of WWER-440-type reactor pressure vessels, 5 × 36 half Charpy and 5 × 36 Charpy size crack-opening displacement (COD) specimen pieces remain. These can be used for further testing to obtain more information on aging or annealing.
Two methods using these specimen remnants are described. The Barkhausen noise measurement is a promising way to get more information on aging by nondestructive testing. On the subsize tensile bars cut from these remnant pieces, tensile properties and absorbed specific energy of fracture (ASFE) can be measured. By comparison of smooth and sharply notched specimens, true toughness value can probably be predicted, and the effect of thermal annealing can be studied.
Radiation Embrittlement of Soviet 1000-MW Pressurized Water Reactor Vessel Steel 15KH2NMFAA
Authors: Vishkarev OM , Zvezdin YuI , Shamardin VK , Tulyakov GA 
Published: March 2009

In the design of the Soviet 1000-MW pressurized water reactor (PWR), developed to replace the former Soviet 440-MW PWR, the irradiation condition is much less severe. This condition permits the use of a new pressure vessel steel (PVS) 15KH2NMFAA containing nickel (Ni) rather than the previously used PVS 15KH2MFAA, thereby achieving better weldability, higher strength (σy350 &gt; 450 MPa at 350°C), and a lower initial transition temperature (Tk = -30°C). PVS 15KH2NMFAA is manufactured from natural, clean, raw materials to increase its radiation stability. Statistical analysis shows that the transition temperature shift after irradiation (ΔTf) at irradiation temperature (Tir) 290°C and fluence (F) of 6 × 1023 n/m23, E &gt; 0.5 MeV is defined by copper (Cu) and phosphorus (P) content: ΔTf=230[(Cu+10P)+20]±25°C
Values under typical practice are: Cu + 10P = 0.10 to 0.15%∙ΔTf. Values calculated using both this equation and the U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.99 (Rev. 2) gave similar results. On the basis of this equation, demands for the permitted impurity level of PVS 15KH2MFAA have been developed as follows: Cu &lt; 0.1 and P &lt; 0.01%.
The well-known Soviet equation ΔTf = Af(F × 10-22)-1/3 for PVS 15KH2NMFAA irradiated at a Tir of 290°C is correct only at F &lt; 1 × 1024 n/m2∙ Af = 23°C (n/m2)-1/3 at the permitted impurity level.
The radiation embrittlement quasi-steady-state model that is presented here provides a sufficient interpretation of the combined effect of both Tir under temperatures ranging from 100 to 350°C and F up to 4 × 1024 n/m2 (E &gt; 0.5 MeV) on the reference PVS 15KH2NMFAA (Cu + 10P = 0.13%). 1ΔTf=1508+22.41Fexp(-5900RT)
The influence of nickel (Ni) on the PVS 15KH2NMFAA RE is decreased by increasing Tir and lowering F.
Irradiation Response of the IAEA CRP-3 Material FFA Measured by Fracture Toughness Specimens
Authors: Valo M , Wallin K , Törrönen K , Ahlstrand R 
Published: March 2009

The irradiation response of the French forging material FFA offered by International Atomic Energy Agency (IAEA) has been measured. Charpy-V and precracked specimens of three-point bending (3-PB) geometry for J-Δa curve measurement have been irradiated in the surveillance position of the Loviisa nuclear power plant (NPP) in a flux of 2 × 1011 n/cm2s to a fluence of approximately 2.0 × 1019 n/cm2 E &gt; 1 MeV, at a temperature of 265°C.
The irradiation-induced transition temperature shifts measured with Charpy-V and fracture toughness specimens are correlated by using indexed temperature values.
The shapes of the brittle fracture transition curves, measured with 3-PB specimen geometry, for irradiated and reference material states are compared using a statistical brittle fracture model. Both the shape of the average curve and the scatter of the measured points are considered.
The effect of irradiation on the ductile fracture behavior based on the measured fracture resistance curves (J-Δa) is presented. The 3-PB specimen geometry is used also for measuring the fracture resistance curves.
Influence of Phosphorus on Thermal and Neutron Embrittlement of Pressure Vessel Steels
Authors: Soulat PE , Miannay D , Horowitz H 
Published: March 2009

In conjunction with an international study coordinated by the International Atomic Energy Agency (IAEA), a review was made of three Japanese model steels with different phosphorus and copper contents irradiated at 5.1019 n ∙ cm-2 (E &gt; 1 MeV) to explain the influence of phosphorus on the thermal and neutron embrittlement of steels.
The results obtained show an important phosphorus effect on radiation hardening and embrittlement in the low-copper steels, an appreciable embrittlement after thermal segregation of phosphorus due to a change in fracture mode from cleavage to intergranular, and a radiation hardening and embrittlement of the same order of magnitude on the segregated steel for irradiation effect.
Irradiation and Annealing Behavior of 15Kh2MFA Reactor Pressure Vessel Steel
Authors: Popp K , Bergmann U , Bergner F , Hampe E , Leonhardt W-D , Schützler H-P , Viehrig H-W 
Published: March 2009

This work deals with the mechanical properties of reactor pressure vessel (RPV) steels used in the pressurized water reactors (PWR) of former Soviet type WWER-440. The materials under investigation were a forging (base metal 15Kh2MFA) and the corresponding weld. Charpy V-notch specimens and tensile test specimens were irradiated in the PWR WWER-2 Rheinsberg at about 270°C up to the two neutron fluence levels of 4 × 1018 and 5 × 1019 n/cm2 (E &gt; 1 MeV). Post irradiation annealing heat treatments were performed, among others a 475°C/152 h treatment of technical interest.
A set of experimental data is given regarding the influence of sampling depth (through thickness position within the forging), neutron irradiation, and annealing on the properties derived from instrumented Charpy impact testing, tensile and hardness tests. The ferrite content varies through the thickness of the forging. The variation of the mechanical properties can be explained qualitatively with the varying ferrite content. The surface layer of the forging is more sensitive to neutron irradiation than material from the 1/4-T position.
To evaluate the effect of annealing heat treatment, the kinetics of the recovery process for the hardness has been investigated. The recovery coefficients for different mechanical properties and parameters have been compared. The annealing behavior is too complex to predict the effect of a large-scale annealing of an RPV on the basis of single hardness measurements.