bluuebunny/crossref_metadata_2025 huggingface dataset:
Epidemiology for Marketing Ski Safety
Authors: Kisser R , Goethals B , Wrobel M
Published: March 2009

During one winter season all downhill skiing injuries occurring in a large Austrian skiing region were recorded. Interviews were carried out with patients as well as with skiers not suffering injury. Several subgroups with a significantly higher risk of injury, which need to be specifically addressed by the safety program, were identified.

To be able to formulate and apply a method of risk analysis for skiing regions as a precondition for the implementation of a comprehensive program to improve skiing safety, a new measure for the risk of injury (injury per vertical kilometer) was employed; it can be used to assess the risk to individuals as well as the risk associated with a given slope or a given day under certain weather conditions.

A skiing safety program along the lines of the World Health Organization “Safe Communities” scheme is proposed, with the main goal being to provide better information to the skiers on correct and safe behavior. It is recommended that the risk analysis employed to evaluate the programme be repeated annually.
Automatic Tracking of Bone Motion Using Ultrasound
Authors: Friedrich MT , Mote CD
Published: March 2009

Severe knee injuries are reaching epidemic proportions in downhill skiing and are a major concern in other sports as well. Several experiments have used external joint motion measurement instruments to investigate the causes and mechanisms of knee injury. However, these measurements do not accurately represent the motion of the underlying bone (except under restricted test conditions) because of soft tissue motion of the transducer relative to the bone.

A new method is described that uses ultrasound imaging to quantify and account for soft tissue motion error by automatically tracking bone motion beneath the skin. The technique tracked in-plane motions of a lamb femur in its surrounding tissue with accuracies of 0.4 mm and 0.7 deg for motions within 10 mm and 6 deg, respectively, of an initial position. Errors in measurement of femur motion of a live test subject with an existing external transducer were computed with the method and were found to be large enough to suggest that these errors must be accounted for during in vivo tests.
Determination of Kinetic Friction and Drag Area in Alpine Skiing
Authors: Kaps P , Nachbauer W , Mössner M
Published: March 2009

The coefficient of friction of skis on snow appears to be influenced by several factors, for example, speed, contact area, snow type, and ski properties. The purpose of this study was to determine simultaneously the coefficient of kinetic friction and the drag area in straight running on a slope with varying inclination and in traversing on an inclined plane. Experimental measurements were taken using photo cells for straight running and by film analysis for traversing. The skier was modeled as a particle that moves on the surface of a slope. The equation of motion with the algebraic constraints of the track of the skier represents a differential-algebraic equation which was solved numerically. The coefficient of friction and the drag area were calculated by minimizing the sum of the square errors between computed and measured time data.

For straight running, the computed coefficient of friction and the drag area were in the same range as obtained by other methods. For traversing, the coefficient of friction could be determined but not the drag area. The skier traversed in an upright position at a speed from 0 to 17 m/s. In this range of velocity the drag area is not constant. It corresponds to critical Reynolds numbers where a sudden drop in the drag coefficient occurs if the body segments are approximated by cylinders.

The results indicate that in both cases the applied method is adequate for determining simultaneously the coefficient of kinetic friction and the drag area if these parameters are independent of the velocity.
Loads Transmitted in the Practice of Snowboarding
Authors: Bally A , Taverney O
Published: March 2009

The sport of snowboarding is increasing in popularity and seems to engender a relatively high risk of injury. The release binding specifically designed for snowboards, which at the moment is at the very beginning of its development, could contribute to a reduction of this risk.

The aim of the present study is to define criteria for the “retention” function of the release binding, and later to establish setting recommendations.

The loads (3 moments and 3 forces) transmitted to each boot via the binding were measured in the normal practice of snowboarding.

The peak loads measured had high scatter and correlated poorly with individual parameters such as weight, height, and snowboarding technique; hence the establishment of setting criteria is problematic at this time.
Patellofemoral Pain in Alpine Skiing
Authors: Aune AK , Madsen JE , Høseth A , Ekeland A
Published: March 2009

Six in a group of 15 elite female skiers, median age 16 (15 to 17) years, suffered patellofemoral pain after altering their giant slalom technique to comply with that of the Norwegian World Cup team. The aim of this study is to describe and compare the new and old techniques and relate them to patellofemoral biomechanics. The new and old techniques were evaluated on the slope by a video camera from different angles and then computerized and analyzed. Any patellofemoral pathology or rotational or torsional abnormalities of the femur and tibia were recorded by computer tomography (CT). An increased degree of vertical movement and knee flexion was observed with the new technique. The CT-scan showed no patellofemoral incongruence or torsional abnormalities in any of the skiers. The patellofemoral pain of these skiers seemed to be due to overloading of the knee rather than to misalignment.
A New Load Application System for In Vitro Study of Ligamentous Injuries to the Human Knee Joint
Authors: Bach JM , Hull ML
Published: March 2009

The design and accuracy evaluation of a new six-degree-of-freedom load application system for in vitro testing of the human knee joint are described. External loads of both polarity in all six degrees of freedom can be applied either individually or in any combination while the knee is permitted to move unconstrained in response to applied loads. The flexion/extension degree of freedom permits the full physiological range of motion. In addition to external loads, forces of the three major muscle groups (quadriceps, hamstrings, gastrocnemius) crossing the joint can be developed. Full automation and rapid convergence of loads to programmed values are achieved through a computer which feeds command signals to servo controller/electro-pneumatic servo valves. The servo valves regulate pressure to pneumatic actuators which develop the various loads. Experiments undertaken to quantify the accuracy of both load and displacement measurements reveal that errors, particularly in load measurement, are effectively controlled through the apparatus design.
Computer Simulation of the Loads on the ACL During Backward Falls Based on an Open Kinematic Chain Model
Authors: Webster JD , Brown CA
Published: March 2009

This study uses computer simulations to examine the influence that specific equipment modifications and skiing variables could have on the loads on the anterior cruciate knee ligament (ACL) during a boot-induced anterior drawer (BIAD) incident. A commercial software package is used to model the skier as an open kinematic chain of pin-jointed links to simulate the forces acting on the knee during a BIAD incident. Several initial velocities of the skier, different snow surface slopes, ski afterbody stiffness, boot stiffness, and binding toepiece stiffness and damping are used and their influence on the simulated loading during a BIAD incident is noted. The higher the speeds, or the stiffer the equipment components are, the higher is the simulated anterior shearing force at the knee, with a supposed greater risk of injury to the ACL.
Occult Fracture Patterns of the Knee Associated with Anterior Cruciate Ligament Tears in Skiing: Assessment with MR Imaging
Authors: Yamagishi T , Yahashi K , Yamato M
Published: March 2009

Thirty-six consecutive magnetic resonance (MR) images of the knee in patients with acute anterior cruciate ligament (ACL) tears from skiing accidents, in whom diagnosis was made by physical examination, was confirmed by arthroscopy and MR imaging in all cases. Twenty-two occult fractures (61%) were identified in the 36 knees. In all cases, initial radiographs showed no evidence of fracture or other osseous abnormality. The most common pattern is an isolated occult fracture of the posterior aspect of the lateral tibial condyle (LTC); the second most common pattern results from a pivot shift phenomenon, which involves a posterior LTC occult fracture associated with an occult fracture of the lateral femoral condyle (LFC). In those patients with large bony injuries and potential articular cartilage damage, an extended period of protected weight-bearing may be needed.
Tibial Plateau Fractures in Downhill Skiing
Authors: Johnson RJ , Ettlinger CF , Ellowitz AS , Shealy JE
Published: March 2009

This study investigates fractures of the tibial plateau resulting from downhill skiing accidents over a 19-year period ending in 1991 at a moderate-sized ski area in northern Vermont. Thirty-nine skiers who suffered tibial plateau fractures were compared with other injured skiers who sustained 11 357 injuries and 2190 noninjured controls over the same time period. Twenty-nine of the 39 tibial plateau fracture cases were used in statistical analysis and most comparisons. Other injury groups included all other injuries, other tibia fractures, and third-degree medial collateral ligament sprains. Compared with the control population, no significant differences were seen in skier height, weight, ability, number of previous skiing injuries, type of trails skied, normal downhill skiing speed, and age of bindings. However, skiers sustaining tibial plateau fractures were more likely to be older, female, fall less often, more experienced, and more likely to have a binding release at some point during their injury event. The mechanism of the lateral fracture pattern seen in 82%of cases in this study appears to be hyperextension and valgus forces.
Release Level for Backward Release
Authors: Bally A
Published: March 2009

Backward release seems to be one of the few remaining improvements still possible to existing mechanical bindings that can reduce the number and the severity of knee injuries, boot-top fractures, and contusions. An adequate choice of the setting is a necessary condition for the effectiveness of this release mode.

In order to evaluate the “softest” setting for backward release that does not cause inadvertent release of the binding (i.e., the “skiable minimum”), several series of field tests were carried out.

In the next step, the skiable minimum setting found by each test skier was correlated with the weight of the skier. For fast and aggressive skiers, the correlation was found to be poor, and a high level of scatter was observed. For other types of skiers the correlation was much better, and scatter was significantly lower.
Water SKi Binding Release Loads: Test Method and Results
Authors: Merala R , Piziali RL
Published: March 2009

The existing technical literature is discussed along with injury data and a method for measuring the loads associated with release from water ski bindings.

Numerous case studies of water skiing-related lower extremity injuries have been published. There do not appear to be any statistically valid epidemiological studies or studies of water ski injury risk factors. An analysis of the 1990 water skiing injury data contained in the U.S. Consumer Product Safety Commission's (CPSC) National Electronic Injury Surveillance System (NEISS) is presented. Nationwide estimates of the number of water skiing related injuries associated with various portions of the body are made. An injury mode breakdown for various structures of the lower extremity is presented. The injury incidence rate is approximately 0.203 injuries per 1000 skier days for all injuries, and 0.041 injuries per 1000 skier days for possibly orthopedic injuries of the lower extremity.

A method for measuring the release loads of water ski bindings is described. A load cell that measures three orthogonal forces and three orthogonal moments is utilized. Human subjects remove their feet from the bindings in prescribed release modes while data are collected by an automated data acquisition system.

Forward bending and torsional release loads were measured for various types of bindings, including no-wrap, low-wrap and high-wrap bindings. As expected, in those situations where an axial force pushes the foot down against the ski, none of the bindings releases the subject's foot under torsional loading. Torsional release torques for the various bindings vary with the amount of heel liftup. The release loads measured are discussed in the context of release requirements for snow ski bindings. In general, the torques required to release from water ski bindings are smaller than the release torques recommended by snow ski binding release standards.
Electrochemical Noise and Impedance Analysis of Iron in Chloride Media
Authors: Mansfeld F , Xiao H
Published: March 2009

Potential and current noise data have been collected for pure iron foils exposed to 0.5N sodium chloride (NaCl) that was aerated, deaerated, or aerated with sodium nitrite (NaNO2) added as inhibitor. Potential and current noise data were obtained at the beginning of each hour over a 24-h period either sequentially or simultaneously. Statistical and spectral analyses were performed resulting in noise resistance values. For the noise resistance Rn = σV/σI, where σV and σI are the standard deviation values of potential and current, respectively, similar values as for the polarization resistance Rp determined with electrochemical impedance spectroscopy (EIS) at the end of the tests were obtained. The spectral noise resistance Rosn obtained from spectral analysis of simultaneously collected current and potential data agreed satisfactorily with Rp and Rn for aerated and inhibited solutions. Electrochemical noise and impedance data have also been obtained for two polymer coatings on cold-rolled steel during immersion in 0.5N NaCl for five months. The two types of measurements clearly distinguished between the relatively poor performance of the alkyd system and the excellent performance of the epoxy polyamide system. Similar trends with exposure time were observed for the pore resistance Rpo and Rp, on the one hand, and Rn and Rosn on the other hand. However, the numerical values of the parameters obtained with EIS were different from those obtained with electrochemical noise analysis (ENA).
The Effects of Solution Resistance on Electrochemical Noise Resistance Measurements: A Theoretical Analysis
Authors: Cottis RA , Turgoose S , Mendoza-Flores J
Published: March 2009

The theoretical basis of electrochemical noise resistance measurements in the presence of significant solution resistance is examined with a simple linear circuit model. A shot noise model of the noise generation process is assumed to develop the dependence of electrochemical potential and current noise on corrosion rate, although the conclusions in respect to electrochemical noise resistance do not depend on this. It is concluded that the electrochemical noise resistance method measures essentially the same resistance as is measured by a conventional linear polarization resistance measurement, although it is found to be capable of making measurements in higher resistance systems.
Analysis of Electrochemical Noise for Type 410 Stainless Steel in Chloride Solutions
Authors: Kelly RG , Inman ME , Hudson JL
Published: March 2009

The electrochemical noise resulting from the corrosion of Type 410 stainless steel under open circuit conditions in solutions of widely different corrosivity has been examined. Parameters derived from electrochemical noise measurements and conventional electrochemical measurements were correlated with one another and with post-test examination of the specimens. Both the noise resistance and the polarization resistance increased with decreases in solution corrosivity. In all of the solutions studied, the noise resistance was found to be consistently higher than the polarization resistance. In solutions in which pitting occurred, the open circuit potential of the electrode versus a true reference electrode was more sensitive to the transition to stable pitting than was the pitting index.
A Comparison of Spectral and Chaotic Analysis of Electrochemical Noise
Authors: Legat A , Govekar E
Published: March 2009

Potential and current fluctuations spontaneously generated by corrosion reactions are known as electrochemical noise. In certain cases, good correlation can be obtained between the results of the spectral analysis of electrochemical noise and corrosion rate and type. However, because of the chaotic nature of corrosion processes, a special mathematical treatment may be needed. In the present study, the electrochemical noise measured on various metals was treated by methods known from the theory of chaos, and the results were compared with the results of spectral analysis. It has been shown that the chaotic characteristics of electrochemical noise are related to corrosion type, whereas the rate of corrosion has no influence on the fractal dimensions of the noise.
A Review of EPRI Projects Since 1984 that Used Electrochemical Noise Measurement Instrumentation
Authors: Syrett BC , Cox WM
Published: March 2009

This review paper documents the development of a modern approach to online corrosion evaluation: the origins of the approach, configuring multiple techniques to maximize data retrieval, and taking the instrumentation out of the laboratory and into the field. Several Electric Power Research Institute (EPRI) projects conducted over the past decade have used this approach. This paper describes how with the use of modern corrosion surveillance instrumentation the objectives of each of these EPRI projects were achieved and an appropriate corrosion management strategy was developed. The final section includes a discussion of the future of corrosion management systems, and their relation to, and dependence on, electrochemical noise (EN) instrumentation.
Simultaneous Corrosion and Fouling Monitoring Under Heat Transfer in Cooling Water Systems
Authors: Winters MA , Stokes PSN , Nichols HF
Published: March 2009

Corrosion and fouling in cooling water systems can potentially reduce heat-transfer capability, increase maintenance costs, reduce plant availability, and contaminate process lines. Conventional monitoring systems have measured corrosion and fouling separately. Fouling monitors alone are not able to indicate real-time corrosion activity beneath surface deposits. Traditionally, corrosion information has been derived from destructive evaluation of heat exchanger tubes, weight loss coupons, and probes under nonheat flux conditions. To overcome these shortcomings, a monitoring system has been developed that measures corrosion and fouling simultaneously. By using electrochemical noise measurement technology, the system is particularly sensitive to detecting localized corrosion beneath a fouled surface, a major and frequent mode of corrosion failure in heat exchangers. Development of the system has progressed from field trials with a prototype unit to a commercially available system. This paper reports and discusses the most recent evaluation of the system at Amoco's Corporate Research facility in Naperville, Illinois, focusing on the sensitivity of electrochemical noise measurement in detecting localized corrosion (pitting and so forth) on a heat transfer surface in a cooling water environment.
Analysis of Electrochemical Noise from Metastable Pitting in Aluminum, Aged Al-2%Cu, and AA 2024-T3
Authors: Pride ST , Scully JR , Hudson JL
Published: March 2009

We compare methods of analyzing electrochemical current (ECN) and potential (EPN) noise data associated with metastable pitting and the transition from metastable to stable pitting. Various analysis methods were applied to electrochemical noise data associated with metastable pit events on aluminum, aged Al-2%Cu, and AA 2024-T3 ST. Two experimental approaches were used. High-purity Al, roughly simulating copper-depleted grain boundary zones in aged Al-Cu alloys, was potentiostatically polarized so that current spikes associated with individual pitting events could be analyzed. Second, the coupling current between nominally identical galvanically coupled Al, aged Al-2%Cu, and AA 2024-T3 ST electrodes was recorded in conjunction with couple potential using a saturated calomel reference electrode. Pit stabilization occurred when individual pits exceeded a threshold of Ipit/rpit > 10-2 A/cm at all times during pit growth as established from potentiostatic measurements. The magnitude of this ratio is linked directly to the concentration of the aggressive solution within pits. Two related statistical pit stabilization factors (Irms/rpit total from ECN data and the mean of (Ipeak-Iox)/rpit values from each pit current spike) were obtained from galvanic ECN data containing a large number of pit current spikes. These parameters provided a better indication of the transition to stable pitting than the pitting index or noise resistance but also had shortcomings. Spectral analysis using current and potential spectral power density (SPD) data provided qualitative information on pit susceptibility. However, the transition to stable pitting could not be accurately defined because of a lack of information on pit sizes in spectral data.
Effect of Metallurgical Factors on the Electrochemical Noise Measured on AISI Type 430 Stainless Steels in Chloride-Containing Media
Authors: Gorse D , Boulleret C , Baroux B
Published: March 2009

Potentiostatic noise measurements are performed on a series of AISI 430 type ferritic stainless steels containing controlled amounts of sulfur (from 8 up to 47 ppm) and titanium (up to 0.37 wt%), in 0.02M sodium chloride (NaCl) aqueous solution (pH 6.6), in a range of potentials below the pitting potential. We focus on the evolution of the shape of the current transients, going from a titanium (Ti) free and 41-ppm sulfur-containing alloy to different Ti-bearing alloys with comparable amount of sulfur (∼40 ppm). The results are compared to the case of a Ti-free and low sulfur (8-ppm) containing alloy. The shape of the anodic current transients obeys a power law, tn. We distinguish two different situations, with n either less or larger than 1, which can be associated with the Ti and sulfur content in the steel. The influence of the exposure time under polarization is also discussed. It appears that for the manganese sulfide (MnS)-containing alloys, after prolonged polarization, the shape of the metastable pitting events evolves toward that found for MnS-free alloys (Ti-bearing), or low-sulfur-containing alloys. Attention is drawn to the possible relationship between the shape of the current transients and the metallurgical defects acting as pitting initiation sites.
Coupling of Acoustic Emission and Electrochemical Noise Measurement Techniques in Slurry Erosion-Corrosion Studies
Authors: Oltra R , Chapey B , Huet F , Renaud L
Published: March 2009

This study deals with the measurement and the subsequent signal analysis of acoustic emission and current noise recorded during continuous slurry erosion of a metallic target in a corrosive environment. According to a phenomenologic model, the localized corrosion results from the repetitive damage caused by particle impacts. The fluctuations of the acoustic signal and of the electrochemical signal both can be modeled as a shot-noise-like process.

The main purpose of this work is to compare two processing techniques for the fluctuating signals: time analysis (mean value) and spectral analysis (power spectral density [PSD] spectrum) to determine the more suitable signal treatment. Another purpose is also to quantify the balance between the mechanical wear and the corrosive damage of the abraded metallic target. It will be shown that the mean value of the RMS acoustic signal, A(t), and also the PSD of A(t), are related to the mechanical wear of the target and allow real-time measurement of the actual mechanical perturbation in terms of the mass of the ablated material.
Influence of Hydrogen Absorption on the Electrochemical Potential Noise of an Iron Electrode Under Corrosion with Gas Evolution
Authors: Huet F , Jérôme M , Manolatos P , Wenger F
Published: March 2009

Using the electrochemical permeation technique and a model for hydrogen diffusion in a metal, the fluctuations of the concentration, ΔC(t), of hydrogen absorbed in the first atomic layers of an Armco iron membrane, under cathodic polarization and at the corrosion potential in sulfuric acid solution, were measured. The fluctuations of the electrode potential, ΔE(t), and of the electrolyte resistance, ΔRe(t), induced by bubble evolution were also simultaneously recorded. Under cathodic potential, ΔE(t) and ΔC(t) are clearly induced by the evolution of big hydrogen gas bubbles. However, at the corrosion potential, another source of ΔE(t) and ΔC(t) must be proposed. It has been shown that this difference is related to the influence of an intermediate reaction species which partly blocks the hydrogen absorption under cathodic polarization and disappears at the corrosion potential.
Electrochemical Noise Response of Steel Under Hydrodynamic Conditions
Authors: Malo JM , Velazco O
Published: March 2009

Electrochemical potential and current noise (EPN, ECN) signals for a rotating disk electrode (RDE) were measured with regard to the electrochemical and electrical contributions. Particular attention was given to the resistance of the electrical connection to the disk because this is considered a source of electrical noise. Electrical noise measurements were obtained in the absence of an electrolyte using a passive load. The noise levels under static and dynamic conditions did not exceed 10 µV for potential and 0.1 µA for current readings. Electrochemical tests for mild steel in 0.1M sodium sulfate (Na2SO4) show distinct noise patterns for static and hydrodynamic regimes. It is shown that electrical noise contribution is often negligible when compared to electrochemical noise signals obtained for a corrosion process under uniform attack and laminar flow.
Electrochemical Noise Measurements During Exfoliation of Aluminum Alloys
Authors: de Damborenea J , Fernández B
Published: March 2009

Electrochemical noise measurements (ENMs) have been carried out during exfoliation corrosion of an aluminum-lithium alloy (8090) in the EXCO (ASTM Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys [EXCO Test] [G 34]) test solution. By means of the maximum entropy method (MEM), the potential and current fluctuations were converted into power spectral density (PSD) plots to study the specific variables related to electrochemical noise (low frequency amplitude, slopes). Noise resistance obtained from the standard deviation of potential and current was compared with the charge transference resistance (Rct) from electrochemical impedance spectroscopy (EIS) measurements. The results show that ENM can be used to detect early stages in localized corrosion. However, when the solution is very aggressive, indications of localized corrosion can be masked by uniform corrosion.
Characterization of Prerusted Steels in Some Ibero-American Atmospheres by Electrochemical Potential Noise Measurement
Authors: Almeida E , Mariaca L , Rodriguez A , Chavarín JU , Veloz MA
Published: March 2009

The purpose of the MICAT project (Ibero-American Map of Atmospheric Corrosiveness) was to foster collaborative ventures between groups conducting research on atmospheric corrosion. Overall, 14 Ibero-American countries, including Spain and Portugal, are involved with a network of 71 test stations distributed throughout the region and on 4 continents. These test stations represent a broad spectrum of climatological and atmospheric pollution conditions. The objective of the MICAT electrochemical studies was to characterize the protective properties of the corrosion products formed during atmospheric exposure at the different test sites. Prerusted carbon steel specimens at different locations were immersed in a sodium sulfate solution. Some specimens were rust pretreated in phosphoric acid solution with additions of aluminum hydroxide (rust converters) electrochemically evaluated. Electrochemical noise measurements (ENM) and linear polarization resistance (LPR) measurements were performed for different times of immersion. Corrosion rates were related to the presence of the oxides that were initially formed. For specimens rusted in marine atmospheres, the presence of chlorides in the corrosion products promotes localized attack. As to the different rust-converted specimens, ENM revealed the pretreatment evolution and corrosion performance over time. ENM was able to characterize and evaluate the protective properties of oxides and pretreatments according to the nature and environmental conditions to which specimens were exposed.
Characterization of Ductile Fracture Toughness Based on Subsized Charpy and Tensile Test Results
Authors: Schmitt W , Talja H , Böhme W , Oeser S , Stöckl H
Published: March 2009

Micromechanical material models have been established as a powerful tool for the prediction of the ductile fracture resistance. Suitable damage parameters of the Gurson model can be obtained from small volume specimens like tensile, Charpy or subsized Charpy specimens and then applied to predict transferable J-resistance curves as obtained from standard fracture mechanics specimens. In this paper dynamic tests on subsized Charpy and precracked bend specimens, SE(B), as well as static and dynamic experiments on tensile specimens for the ferritic steel A533B (HSST 03), are presented and analyzed. Two- and three-dimensional finite element models are used to determine the stress-strain behaviour and strain rate sensitivity and to find a set of damage parameters which explains the results. These parameters are then used to predict a J-resistance curve representative for a compact specimen C(T)25.
Effects of Ligament Size and Tensile Properties on the Fracture of Pressure Vessel Materials Under Impact Loading
Authors: Sidener SE , Kumar AS , Hamilton ML
Published: March 2009

Dynamic finite element modeling of the fracture behavior of pressure vessel materials under impact loading was conducted to study the effects of ligament size and tensile properties on the crack extension (USEe) and propagation (USEpr) energies. The sum of USEe and USEpr is the total energy absorbed, USEp, in complete fracture of the specimen. ASTM standard (full size) and subsize precracked Charpy specimens with varying ligament sizes (b) were investigated for five materials with a wide range of ductility. It was found that for all materials studied the dependence of USEp on ligament size for half and third size specimens was similar, but quite different from that for full size specimens. USEp varied as b2 for half and third size specimens. For full size specimens, it varied as b2.5 for low ductility and as b3.5 for high ductility materials. It was further found that the ratio, r, of crack extension and propagation energies decreased sharply with b for both low and high ductility materials if the ligament sizes were less than half the width. For larger ligament sizes, the value of r was close to 1 for all materials and specimen sizes. The crack extension energy did not show any systematic pattern in its variation as a function of material ductility or specimen constraint. USEpr, however, did show a systematic variation with ligament size. For the highest ductility material, the full size USEpr. behaved as b3.5 whereas USEpr,. for the half and third size specimens behaved approximately as b2.5. For the lowest ductility material, USEpr for all three sizes behaved approximately as b2.
Analysis of Procedures for the Determination of the Yield Force (Fgy) for Instrumented Sub-Sized Charpy-V Specimens
Authors: Taylor H
Published: March 2009

A method for the determination of the yield force (Fgy) is defined in Annex D of the Draft Standard for impact Testing of Sub-Sized Charpy Specimens [1]. The procedure describes an iterative method for finding the straight line (Hooke's line) in the initial part of the force-displacement curve. Fgy is then taken as the point of intersection of this line with a fitted line through the fully plastic range of the data. This method is applied to force-time data collected during Phase 1 of a Round-Robin [2] to validate the Proposed Standard. Analysis of the results shows that a modification to the procedure improves the reliability of the method for finding the Fgy values.
The Actual Properties of WWER-440 Reactor Pressure Vessel Materials Obtained by Impact Tests of Subsize Specimens Fabricated out of Samples Taken from the RPV
Authors: Korolev YN , Kryukov AM , Nikolaev YA , Platonov PA , Shtrombakh YI , Langer R , Leitz C , Rieg C-Y
Published: March 2009

This paper presents the results of a study on degradation due to irradiation occurring in WWER-440 reactor pressure vessel (RPV) steel, using subsize Charpy specimens (5×5×27.5 mm3). An application of subsize specimens for estimation of irradiation embrittlement of RPV steel has been substantiated. Comparison between ductile-to-brittle transition temperatures (DBTT) for full-size and subsize Charpy specimens has been carried out. The relation between these two values has been clarified. The results of testing trepans and templates cut out from WWER-440 reactor pressure vessels are considered. The main results of the program TACIS-91/1.1. are discussed.
Fracture Toughness Test on Precracked Charpy Specimens in The Transition Range for Linde 80 Weld Metals
Authors: Hour KY , Yoon KK
Published: March 2009

The emphasis of this paper is to summarize the experience gained from an on-going B&W Owners Group test program on precracked Charpy specimens in accordance with the proposed ASTM Standard “Test Method For the Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range”. Both unirradiated and irradiated precracked Charpy specimens were tested in three-point bending, reconstituted, and retested to establish the reference temperature, T0, for various Linde 80 weld metals. Tests results were compared to those generated from an ORNL test program on Linde 80 weld metals and B&W Owners Group compact tension specimens tested in the transition range to determine the validity of using precracked Charpy specimens. Master curves were constructed for Linde 80 weld metals and then compared to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code KIc reference fracture toughness curve. The ASME lower-bound KIc curve is positioned relatively conservatively. The results indicate that the current practice of Code fracture toughness for low upper-shelf weldments is conservative. Experience gained on preparation of specimens, precracking technique, selection of test temperature, test technique, and data analysis is summarized in this paper.
Fracture Toughness Measurements in the Transition Regime Using Small Size Samples
Authors: Chaouadi R
Published: March 2009

The present paper reports the treatment of fracture toughness data in the ductile-to-brittle transition regime by using Charpy size specimens. Size effect and statistical variation are taken into account according to a statistical model associated to the weakest link model. The methodology is first calibrated on a reference reactor pressure vessel material, for which fracture toughness data obtained on large samples are available. This methodology is successfully applied to a number of RPV steels to determine the fracture toughness behaviour in the transition regime. Monte Carlo simulations are performed to determine the confidence interval of the reference temperature as derived from a small number of tests.
Use of Precracked Charpy and Smaller Specimens to Establish the Master Curve
Authors: Sokolov MA , McCabe DE , Davidov YA , Nanstad RK
Published: March 2009

The current provisions used in the U.S. Code of Federal Regulations for the determination of the fracture toughness of reactor pressure vessel steels employs an assumption that there is a direct correlation between KIc lower-bound toughness and the Charpy V-notch transition curve. Such correlations are subject to scatter from both approaches which weakens the reliability of fracture mechanics-based analyses. In this study, precracked Charpy and smaller size specimens are used in three-point static bend testing to develop fracture mechanics based KJc values. The testing is performed under carefully controlled conditions such that the values can be used to predict the fracture toughness performance of large specimens. The concept of a universal transition curve (master curve) is applied. Data scatter that is characteristic of commercial grade steels and their weldments is handled by Weibull statistical modeling. The master curve is developed to describe the median KJc, fracture toughness for 1T size compact specimens. Size effects are modeled using weakest-link theory and are studied for different specimen geometries. It is shown that precracked Charpy specimens when tested within their confined validity limits follow the weakest-link size-adjustment trend and predict the fracture toughness of larger specimens. Specimens of smaller than Charpy sizes (5 mm thick) exhibit some disparities in results relative to weakest-link size adjustment prediction suggesting that application of such adjustment to very small specimens may have some limitations.
On the Utilization of High Rate Pre-Cracked Charpy Test Results and the Master Curve to Obtain Accurate Lower Bound Toughness Predictions in the Ductile-to-Brittle Transition
Authors: Joyce JA
Published: March 2009

Much recent work in the field of elastic-plastic fracture mechanics has been directed to developing a mechanics-based relationship between the onset of cleavage fracture in structural components and that of Charpy specimens. In the case of a commercial nuclear power plant the surveillance specimens are expected to have undergone an irradiation history equivalent to that of the pressure vessel, and hence to have the correct fracture toughness properties. The small size of these specimens, however, makes it difficult to obtain fracture toughness measurements that are transferrable to the much larger and higher constraint pressure vessel.

Application of proposed specimen size requirements[1] to this problem shows that for the typical fracture toughness and strength levels in nuclear pressure vessels, the pre-cracked Charpy specimen could lose constraint well before the onset of cleavage and the results obtained will then provide a very non-conservative estimate of the conditions required for the onset of cleavage in the vessel. Recent computational work by Koppenhoefer and Dodds[2] has strongly suggested, however, that if the specimen is loaded rapidly, additional constraint might be present which would allow the Charpy results to predict correctly the onset of cleavage in the nuclear pressure vessel. These authors predict that the presence of modest viscoplasticity will increase the deformation level at which constraint is lost and this in turn will allow Charpy size specimens to be adequate predictors of the onset of cleavage fracture in structural size elements.

In this paper pre-cracked Charpy specimens of A515 steel are tested at four different loading rates and five different temperatures in the lower ductile-to-brittle transition. The reference temperature, T0, is developed and shown to be very dependent on the loading rate and very independent of the temperature at which the data set was measured.
Characterization by Notched and Precracked Charpy Tests of the in-Service Degradation of Reactor Pressure Vessel Steel Fracture Toughness
Authors: Fabry A
Published: March 2009

The current engineering and regulatory practice to estimate fracture toughness safety margins for nuclear reactor pressure vessels (RPV's) relies heavily on the Charpy V-Notch (CVN) impact test. The uncertainties of this correlation ("indexing") approach are known. Techniques to more directly estimate in-service toughness degradation using a variety of precracked specimens are under active development worldwide, with emphasis on their miniaturization. In the nuclear context, it is essential to address many concerns, such as: representativeness of the surveillance programs with respect to the vessel in terms of materials and environment, transferability of test results to the structure (constraint and size effects), conservatism of lower bound toughness estimation procedure, credibility relative to trends of existing data bases, etc.

An enhanced RPV surveillance strategy is being developed in Belgium. It combines state-of-the-art micromechanical and damage modeling to the evaluation of CVN load-deflection signals, tensile stress-strain curves and slow-bend tests of reconstituted, precracked Charpy specimens. A probabilistic micromechanical model has been established for static and dynamic transgranular cleavage initiation fracture toughness in the ductile-brittle transition temperature range; this model allows one to project toughness bounds for any steel embrittlement condition from the corresponding CVN and static tensile properties, using a single scaling factor defined by imposing agreement with toughness tests in a single condition. The outstanding finding incorporated by this “toughness transfer model” is that the microcleavage fracture stress is affected by temperature in the ductile-brittle transition and that this influence is strongly correlated to the flow stress: this does phenomenologically explain the shape of the KIc, KId-temperature curves as well as the actual magnitude of the strain rate and irradiation effects. Furthermore, CVN crack arrest loads and fracture appearance are also taken advantage of in order to estimate KIa degradation. Last, but not least, the CVN-tensile load-temperature diagram provides substantial information used for the modeling of in-service steel strengthening, of intergranular fracture susceptibility and other irradiation-induced and ageing effects.

Systematic application of this enhanced surveillance approach is expected to contribute to the improvement of the engineering and regulatory predictive capability, while making optimal use of the limited inventory of available surveillance material.
Using Small Cracked Round Bars to Measure the Fracture Toughness of a Pressure Vessel Steel Weldment: A Feasibility Study
Authors: Giovanola JH , Klopp RW , Crocker JE , Alexander DJ , Corwin WR , Nanstad RK
Published: March 2009

The research objectives were to demonstrate the feasibility of using small fatigue precracked round bars to measure the initiation fracture toughness of ductile nuclear pressure vessel steels and weldments and to refine and validate experiment and analysis procedures. Initiation fracture toughness values were measured for a duplicate of HSSI Weld 72W, unirradiated, in the temperature range -150° to 50°C, using small cracked round bar (CRB) specimens. The results were compared with the values obtained with 1T-CT specimens. The good agreement between the toughness values measured with CRB and 1T-CT specimens indicates that using small CRB specimens (possibly cut from Charpy bars) to measure fracture toughness is feasible. A relationship between J and the displacement due to the crack δcr, where δcr is obtained from extensometer measurements, was established experimentally. Fracture initiation in CRBs of the size investigated here occurred at or near maximum load, with the crack growth prior to maximum load being less than 200 εm. This observation, together with the unique relationship between J and δcr, open the possibility of greatly simplified testing and data reduction procedures for fracture experiments with CRB.
Fracture Toughness Derived from Small Circumferentially Cracked Bars
Authors: Scibetta M , Chaouadi R
Published: March 2009

Small circumferentially Cracked Round Bars (CRB) are used to derive the fracture toughness of reactor pressure vessel steels. This cylindrical geometry is of practical interest for the nuclear industry as it only requires a small amount of irradiated material and as it is easy to test on a tensile machine.

This paper describes an experimental procedure to obtain fracture toughness measurements from CRB with a diameter of 10 mm. Emphasis is put on crack growth monitoring during rotating bending fatigue precracking, on the formulae used to analyse the load displacement trace of a fracture toughness test and on the correction to be applied to take the loss of constraint into account.

Experiments show that the method has the potential to derive fracture toughness valuesfrom the lower shelf to the lower transition region. Finite element analysis shows that the constraint of this geometry is generally lower than for bend specimens but is higher at higher load levels, allowing comparison to toughness data valid according to prevailing standards.
The Effects of the Configuration of a Weld-reconstituted Compact Tension Specimen on Fracture Toughness Determination
Authors: De Backer F , Gutiérnez-Solana F
Published: March 2009

For integrity assessment of reactor vessels it is desirable to obtain elastic-plastic fracture mechanics properties of the vessel material and evaluate how such properties evolve during operation. The J-R curve provides a direct evaluation of these properties. As surveillance capsules normally do not contain specimens for that purpose, the possibility exists of using reconstituted compact tension specimens (CT). These specimens have inserts of the material concerned taken from the undeformed part of Charpy specimens, whether tested or not, and are reconstituted with electron-beam welding.

In order to evaluate the validity of the fracture toughness characterization with CT specimens reconstituted in this way, a comparison is made between the J-R curves obtained from CT specimens with and without insert. To analyze the influence of the specimen configuration on fracture toughness characterization, reconstituted CT specimens of different thicknesses and weld configurations are tested.

To help the analysis, plastic zone size estimations of reconstituted specimens are made to verify if the plastic zone interferes with the reconstitution weld. A clear qualitative relationship has been found between the interference of the plastic zone with the weld and the validity of the J-R curves obtained with reconstituted specimens.
Reconstitution of Sub Charpy-size V-notched and Pre-Cracked Specimens
Authors: Valo MJ
Published: March 2009

Specimen reconstitution is a technique which allows limited amounts of material to be used effectively for mechanical testing. In this respect the technique can partly act as an alternative for specimen miniaturization. As welding is the commonly used fusion method there is an inherent risk of annealing of irradiated material, which could lead to non-conservative test results in irradiation embrittlement studies. The objective of this study was to characterize in detail temperature transients in welding and the load carrying capacity of the weld seams. The technique was also verified with Charpy-V and fracture toughness tests using irradiated material.