bluuebunny/crossref_metadata_2025 huggingface dataset:
The Corrosion of Zircaloy-4 Fuel Cladding in Pressurized Water Reactors
Authors: Van Swam LFP , Shann SH
Published: March 2009

The effects of thermo-mechanical processing of cladding on the corrosion of Zircaloy-4 in commercial PWRs have been investigated. Visual observations and nondestructive measurements at poolside, augmented by observations in the hot cell, indicate that the initial black oxide transforms into a grey or tan and later white oxide layer at a thickness of 10 to 15 μm independent of the thermal processing history of the tubing. At an oxide layer thickness of 60 to 80 μm, the oxide may spall depending somewhat on the particular oxide morphology formed and possibly on the frequency of power and temperature changes of the fuel rods. Because spalling of oxide lowers the metal-to-oxide interface temperature of fuel rods, it reduces the corrosion rate and is beneficial from that point of view.

To determine the effect of thermo-mechanicai processing on in-reactor corrosion of Zircaloy-4, oxide thickness measurements at poolside and in the hot cell have been analyzed with the MATPRO corrosion model. A calibrated corrosion parameter in this model provides a measure of the corrosion susceptibility of the Zircaloy-4 cladding. It was found necessary to modify the MATPRO equations with a burnup dependent term to obtain a near constant value of the corrosion parameter over a burnup range of approximately 10 to 45 MWd/kgU. Different calculational tests were performed to confirm that the modified model accurately predicts the corrosion behavior of fuel rods.

For Zircaloy-4 cladding with a chemical composition near the mid-range of the ASTM specification, it is shown that the in-reactor corrosion performance can be correlated with the thermo-mechanical treatment of the cladding. The evaluation of the in-reactor corrosion data indicates that the corrosion performance of Zircaloy-4 cladding is improved by longer and/or higher temperature anneals in the alpha range after the material has been beta quenched. The best correlation between corrosion performance and thermo-mechanical treatment is obtained with the second order cumulative annealing parameter. This parameter is a measure of the size of intermetallic precipitates of Zr, Fe, and Cr in Zircaloy-4. However, a causal relationship between Zr (Cr, Fe)2 precipitate size and corrosion behavior has not been proven.
Flexible Cementitious Products
Authors: Zoumut HF
Published: March 2009

Cement-based products such as grouts and mortars are being modified with water-based emulsifiable polymers to design products with some of the properties of traditional organic adhesives without sacrificing the properties imparted by the cement. Improved adhesion, strength and flexibility are typical properties of interest for these systems.
The Influence of Various Polymeric Materials on the Physical Properties of a Cementitious Patching Compound
Authors: Bright RP , Mraz TJ , Vassallo JC
Published: March 2009

A series of polymer modified cementitious patches were formulated using a variety of liquid latex and redispersible powder modifiers. Properties evaluated included compressive, flexural and tensile strength, water resistance, abrasion resistance and adhesive strength. Formulations were evaluated at 5%, 10% and 20% polymer loading with the water level adjusted for a constant flow. A second series of experiments were carried out at 10% polymer loading at a constant water level.

The results of the study showed that there was a strong relationship between the water/cement ratio and the overall properties of the formulation. In the experiments with water/cement ratio adjusted to achieve a constant flow, the liquid emulsion that possessed a high degree of water reducing capability achieved the highest strength and water resistance. However, in the experiments with a constant water level, the redispersible powdered emulsions now had at least equivalent properties to the liquid polymers.

These results showed that it is possible to formulate a high performance one component patching and repair mortar using redispersible powder emulsions.
Redispersible Polymer Powders for Tough, Flexible Cement Mortars
Authors: Schneider SI , DeWacker DR , Palmer JG
Published: March 2009

The increasing use of cement mortars over plywood substrates and in high-rise buildings has demanded new performance requirements of these mortars to overcome dimensional movement in these substrates. A -10°C Tg, glass transition temperature EVA redispersible polymer powder is compared to a +10°C Tg" redispersible, EVA polymer powder for flexural, compressive and tensile strength in a standard three to one sand to cement mortar. Both polymers are also compared for plywood adhesion and flexibility in a standard thin-set formulation. It was found that the -10°C Tg polymer gave increased plywood adhesion at higher levels of modification and superior flexibility while still maintaining comparable strength properties to the +10°C Tg polymer. This would indicate that a -10°C Tg EVA redispersible powder will be better able to bridge gaps in a subfloor as well as allow for subfloor movement due to settling or expansion and contraction due to its better flexibility.
Properties of Polymer-Modified Mortars Using Epoxy Resin Without Hardener
Authors: Ohama Y , Demura K , Endo T
Published: March 2009

In the preparation of conventional polymer-modified mortars using epoxy resin, the use of any hardener has been considered indispensable for the hardening of the epoxy resin. The authors have noticed that the hardening of epoxy resin occurs in the presence of alkalis in cement mortar. Polymer-modified mortars using epoxy resin without any hardener are prepared with various polymer-cement ratios, and tested for strength, adhesion, water absorption, drying shrinkage, chloride ion penetration and carbonation. From the test results, the polymer-modified mortars using the epoxy resin without any hardener are made successfully, and have some superior properties compared with conventional epoxy-modified mortars. It is concluded that polymercement ratios of 5 to 10% are considered optimum for the preparation of such polymer-modified mortars.
Effects of Latex Modification on the Failure Mechanism and Engineering Properties of Concrete
Authors: Soroushian P , Tlili A
Published: March 2009

Effects of styrene-butadiene latex modification on the failure mechanism, mechanical, physical, and durability characteristics of concrete materials were studied.

Microscopic investigations were performed on concrete cylinders pre-loaded to different compressive stress levels in order to study the process of failure in concrete under increasing stress levels as influenced by latex modification. These results were indicative of the effectiveness of latex in controlling the initiation and growth of microcracks under load.

Test results on the impact resistance and flexural strength and toughness of concrete were used to quantify and statistically confirm the positive effects of latex modification on various aspects of the mechanical properties of concrete.

Durability studies showed that latex modification imparts significant improvements to the scaling resistance and impermeability characteristics of concrete.

Latex modification was also observed to substantially reduce the water absorption capacity of concrete. The effects of latex on free drying shrinkage strains and bulk specific gravity of concrete were not statistically significant.
Evaluation of Latex Modified Concrete Overlays for Cathodic Protection Systems
Authors: Bartholomew JJ
Published: March 2009

Cathodic protection systems employing a mixed precious metal oxide coated titanium mesh anode require a cementitious overlay to encapsulate the anode. Several types of overlays have been used including latex modified concrete for five years. Laboratory and field performance have indicated the overlays using a styrene-butadiene rubber latex modifier do not have any adverse operational or performance affects on the cathodic protection system. Acrylic modifiers have been found to cause the formation of anode reaction products. Data are presented on laboratory tests and on completed field projects.
Using Styrene-Butadiene Latex as a Modifier to Concrete for Bridge Deck and Parking Garage Overlays
Authors: Kuhlmann LA
Published: March 2009

One of the major uses of concrete modified with styrene-butadiene latex is for bonded overlays on bridge and parking garage decks. The application has been in use for over 20 years, demonstrating the viability and long-term performance of this material. The addition of this latex to portland cement concrete improves both the plastic and hardened properties of the concrete, making it well suited for this application. The typical mix design parameters are: cement content of 390 kg/m3; 0.15 polymer solids cement ratio; and maximum water — cement ratio of 0.40. Construction procedures have developed over the years and are now established by many state highway departments. Problems that can occur with selection of materials and during construction have been identified, as well as measures to take to avoid them. Overlays with this material have been in service for over 20 years.
Twenty-Year Performance of Latex-Modified Concrete Overlays
Authors: Sprinkel MM
Published: March 2009

Fourteen bridge decks with latex-modified concrete (LMC) overlays ranging in age from two to twenty years and two overlays without latex were studied. The high quality portland cement concrete overlays without latex showed greater negative increases in half-cell potentials, greater increases in chloride content, and a higher percentage of higher rates of corrosion than the LMC overlays. Also, for these two bridges, higher shear and tensile rupture strengths were obtained at the bond interface with LMC than with concrete without latex. Higher rupture strengths were not obtained on the other bridges because of the low strength of the scarified surface of the base concrete. The permeability, half-cell, chloride, rate-of-corrosion, and bond, strength data indicate that the overlays are performing satisfactorily. Also, LMC overlays placed on decks with less than 2 lb/yd3 (1.2 kg/m3) of chloride ion at the rebar can be expected to have a service life in excess of twenty years.
New Zealand Ski Injury Statistics—1989 and 1990 Ski Seasons
Authors: Lamont MK
Published: March 2009

To many, the sport of skiing is considered risky. The New Zealand ski injury statistics compare favorably with the international figures, except for the beginner tourist type fields. The incidence of upper limb and head injuries is increasing while the incidence of fractures of the tibia are continuing to decline. It is the beginner to intermediate skier, who has skied for fewer than three days that season; who has not had ski lessons; who has not tested his ski bindings, who will be injured before he had skied for more than three hours. It is this group that needs assistance if the incidence of ski injuries is to be reduced.
Alpine Skiing Injuries in Children
Authors: Ekeland A , Nordsletten L , Lystad H , Holtmoen Å
Published: March 2009

The skiing injuries in 59 children under age 15 were recorded in four Norwegian ski resorts during the winter of 1985/1986 and compared with a control population of 63 uninjured children of the same age group.

The most common injury sites were the lower leg (24%), knee (20%), and head (14%). Only 43% of the bindings for injured children under ten released during the accident, compared with 73% for injured children 10 to 14 years of age. In accordance with this, skiers under ten were more than twice as prone to lower extremity equipment related (LEER) injuries as children in the older age group. Fracture of the lower leg was the most serious of the LEER injuries, and accounted for 21% of the injuries in the youngest children and 10 percent in the age group 10 to 14 years. In contrast 18% of the older children suffered head injuries compared to only 5% in the younger children.

Beginners had an injury risk nine times the average, whereas intermediate skiers were underrepresented among the injured skiers. A skiing experience of three or more seasons reduced the injury risk while skiing. Nine percent of the injuries occurred during powder skiing, whereas 26% of the injured population and 46% of the uninjured population spent some time powder skiing the current day.

In conclusion, being a beginner is the highest injury risk factor in skiing.
Knee Sprains in Alpine Skiing: A Ten-Year Statistical Study
Authors: Allegra F , Fava P , Priano F
Published: March 2009

The authors describe the results of a statistical survey of knee injuries occurring in Alpine skiing. The survey took place at a ski resort in central Italy. A clinical questionnaire that was specifically designed to collect data in a form that would lend itself to computerized processing was used. Several key factors, recorded at the time of the accident, which might have played a role in its occurrences, are taken into consideration. Knee injuries accounted for 29.3% of the total skiing injuries over the ten-year period. In this report only knee sprains (190 cases), representing 27.5% of total skiing injuries, were evaluated.
Translations and Rotations Across the Knee Under Isometric Quadriceps Contraction
Authors: Chiang AL , Mote CD
Published: March 2009

The suggested mechanism of failure of the anterior cruciate ligament (ACL) through quadriceps contraction motivated the research discussed in this paper. The three components of translation and rotation of the tibia relative to the femur, produced under isometric quadriceps contraction in vivo, were measured with a six degree of freedom acoustic transducer. Tests on six subjects were conducted at 30° and 90° knee flexions. The principal component responses across the knee under isometric quadriceps contraction are internal rotation, anterior translation, and proximal translation. The average anterior displacement under a 24 Nm isometric quadriceps contraction was significantly greater (P < 0.001) at knee flexion 30° than at 90° (1.8 mm vs. -0.4 mm). From the data and analyses here, there is no support for the hypothesis that isometric quadriceps contraction alone can produce sufficient anterior displacement of the tibia relative to the femur to rupture the ACL.
Influence of Ski Boot Construction on Knee Load—A Biomechanical Investigation on Safety and Performance Aspects of Ski Boots
Authors: Schaff PS , Hauser W
Published: March 2009

In contrast to the drop in the incidence of fractures of the lower leg that has been observed in recent years, the incidence of knee injuries has not decreased in skiing. There has even been a relative increase of severe knee lesions and isolated ACL ruptures, prompting us to conduct a comprehensive study of this phenomena.

The goal of the study was to develop a new measuring device for alpine skiing research by combining motion analysis, pressure and force measurement, comprehensive examine the forward/backward movement in ski boots in the lab and by means of telemetry on the slope and to come up with a proposal for a new safety concept to reduce the high number of knee injuries in alpine skiing in the future.

The first study was devoted to the forward movement in ski boots. Studying nine beginners and eight experts we found a 20% (sign. 0.05) lower forward lean capability of the beginner group in the same boot.

A randomized study with cross over design conducted on the slope, where we equipped 16 skiers with either soft or stiff boots for the duration of five ski days, revealed the learning behavior and forward position on the slope depending on the boot. The pupils became definitely less adept at learning if they were required to wear stiff ski boots and showed a significant lower forward flex angle. A skiing style in backward lean position was adopted and supported by the fixed backward spoiler.

In order to quantify the influence of the backward spoiler a special ski boot was constructed allowing the rear spoiler to give way at a variable, defined stiffness and register the angular displacement and horizontal force Fh. The results on ten male subjects showed most clearly that even a medium rear spoiler resistance will significantly reduce the peak force values by a factor of 5.5. The deceleration at the knee joint level is significantly higher (factor 1.6) in case of a rigid spoiler. The lab tests could be confirmed on the slope (significant reduction of max. force by factor 8). It also proved that normal skiing can be performed in such a boot without limitations.

In consideration of our results it is concluded that the principle of safety bindings must definitely apply in future in equal measure also to the ski boot. As a proposal for future safety concepts, we developed a safety ski boot, that allowed for the first time the rear part to open and give way after a certain amount of force (adjustable preload). The backward release bindings, which can often produce dangerous malfunctions if a strong force acts on them for a short while, and which were therefore only very reluctantly if all accepted by skiers, could thus be complemented by a safety system in the boots.

In all probability this would be a contributing factor to reducing the high incidence of knee injuries in skiing.
Strains Within the Anterior Cruciate and Medial Collateral Ligaments of the Knee at Loads Causing Failure
Authors: Berns GS , Hull ML , Patterson HA
Published: March 2009

The contributions of this paper are twofold. One is measurement of loads and corresponding strains at failure in both the anterior cruciate (ACL) and medial collateral (MCL) ligaments of the knee, the two ligaments most commonly injured. To make these measurements, a five degree-of-freedom automated system was used to apply either a single load or a combination of two loads at flexion angles ranging from 0° to 45°. Approximately half of the specimens were loaded to fail the ACL and half the MCL. An anterior force consistently failed the ACL while a valgus moment and/or an external axial moment failed the MCL. Despite this consistency, there was wide variation in failure loads between specimens with more than a twofold difference in load levels. Also, there was a large variation in ligament strain at failure with a mean value of 6.7% and a coefficient of variation of 0.64.

The second contribution of this paper is the development and testing of empirical models to predict ligament failure. To provide data for these models, prior to the load-to-failure tests of the knee specimens, the load application system was used to apply sub-injury level loads corresponding to varus/valgus moments, axial moments, medial/lateral forces, anterior/posterior forces, and compressive force at flexion angles of 0°, 15°, and 30° for single loads and 0° and 30° for combination loads. Regression analysis was performed to determine empirical equations relating strain to both load and flexion angle. The ability to extrapolate these models to predict strain measured in the load-to-failure tests was evaluated. In general, the empirical models did not accurately predict strain at injurious load levels. The inability to make an accurate prediction was traced to the conservative sub-injury load levels used to develop the empirical models.
Skiing Forces and Moments at the Knee and Boot Top: Boot Stiffness Effects and Modeling
Authors: Yee AG , Mote CD
Published: March 2009

The goals of this study are (1) to quantify the contribution of boot stiffness to the maximum forces and moments predicted at the boot top and knee, (2) to identify generalized regression models predicting the moment components at the boot top and knee for a skiing population, and (3) to quantify the contribution of inertial forces to the forces and moments predicted at the boot top and knee. Six subjects skiing a slalom course alternated test ski runs with lowest boot stiffness and highest boot stiffness settings in a boot with adjustable stiffness. Average (over all subjects and test runs) maximum ankle flexion is significantly greater (P = 0.005) by 11.5 degrees for the soft boot compared to the stiff boot. Average maximum compression force along the tibia is significantly smaller (P = 0.024) by 178N for the soft boot runs compared to the stiff boot runs. No other maximum force or moment component at the boot top and knee is significantly different between soft and stiff boot ski runs. Bending moments at boot top and knee are not clearly related to ankle flexion near neutral boot flexion (20 deg). Maximum bending moments at the boot top do not necessarily occur at maximum ankle flexion.

Generalized regression models predicting moments at the boot top and knee are developed for the subject population, using regression coefficients from individual ski runs normalized by subject height and weight. For the soft boot setting, average regression model correlation coefficients for A-P bending at the boot top, varus-valgus moment at the knee, and torsional moment along the tibia are 0.980, 0.916, and 0.867, respectively. Corresponding values for the stiff boot setting are 0.979, 0.889, and 0.882.
Prediction of the Loading Along the Leg During Snow Skiing
Authors: Quinn TP , Mote CD
Published: March 2009

The complete force and moment on each cross section of the leg between the ski boot top and the knee during normal skiing were predicted from measurements of the force and moment under the toe and heel of the boot and the flexion of the ankle. The force and moment components predicted at the base of the boot were significantly different from those predicted at sites of potential injury at the boot top and the knee. The extreme torsional and extreme varus-valgus moments predicted at the knee over all subjects tested were 70 Nm and 149 Nm, which are within the estimated range of the ultimate strength of the knee without support from contracted muscles crossing the knee.

Regression analyses were used to find the force components at the base of the boot that best predict the bending and torsional moments at the boot top and knee. The torsional moments at the boot top and knee are better predicted by the medial-lateral force at the toe than by the medial-lateral force at the heel. The varus-valgus moment at the boot top and knee are better predicted by the resultant medial-lateral force component at the base of the boot than by the medial-lateral force at the toe or by the medial-lateral force at the heel. The set of forces that includes the force normal to the ski at the toe, the force normal to the ski at the heel and the component of the total force normal to the ski directed perpendicular to the leg was better at predicting the anterior-posterior bending moments at the boot top and knee than the force normal to the ski at the heel or the force normal to the ski at the toe or a linear combination of those two forces.
Injury Mechanisms of the Ankle Joint in High Ski Boots: Photoelastic and Mechanical Investigations on the Human Bone Specimen
Authors: Plitz W , Kuhn V , Maier A , Carl C , Hagena F-W
Published: March 2009

A special testing device was developed to simulate the different kinds of injuries and to determine the necessary or originating forces and moments. By means of this testing device it was possible to adjust the following parameters referring to the ankle joint in accordance with the possible positioning in the various kinds of high ski boots—dorsal flexion, pronation or supination, and load, dependent on the skier's weight.

Afterward, the injury mechanism was induced by means of a continuous outer or inner rotation of the fixed lower leg. Starting from the Genetic Classification of ankle joint injuries according to Lauge-Hansen, which describes their origin and pattern, the following problem arose: Is this Genetic Classification of fractures in the ankle joint area also wholly valid in the case of an “arthrodesian” effect in the high ski boot? In order to answer this question, tests were performed on human bone specimen. The load characteristics and the directions of the application of force were determined in preliminary tests in ordef to obtain well-aimed clinical patterns of injuries in fracture tests. For this purpose, photoelastic examinations were carried out by means of photoelastic bone coating and polarized light.

The results of our tests so far are: Torsion of the lower leg relative to the tarsus may occur in the high ski boot even if the boot is optimally fastened; considering the special situation of the high ski boot, the cases of simple eversion and inversion should be added to the classification based on Lauge-Hansen; injuries induced with fixed positions of pronation and supination have proved to be just like those of free movement.
Activated Muscle Contribution to Leg-Loading Capacity in Rats
Authors: Nordsletten L , Ekeland A
Published: March 2009

The binding release values for alpine skiers recommended by the International Association for Safety in Skiing (IAS) are based on the lower leg strength, partly derived from testing of tibia cadaver specimens. Telemetric studies on the slope have disclosed that the musculature may increase the lower leg-loading capacity. The magnitude of this muscle contribution to the leg-loading capacity is, however, difficult to determine in humans. The results of three-point bending tests of the lower leg of rats during tetanic muscle contraction induced by electrical stimulation of the ischiatic nerve is presented. The contralateral tibia without soft tissues served as a control. The increase in average ultimate bending moment was 76%. The mean ultimate bending stiffness decreased to 96%, whereas ultimate deflection angle increased by 94% and ultimate (absorbed) energy by 230%.
3-D Video Motion Analysis on the Slope—A Practical Way to Analyze Motion Patterns in Alpine Skiing
Authors: Schaff P , Hauser W
Published: March 2009

A detailed knowledge of motion patterns in sport is the basis for injury prevention, as well as performance enhancement. During the last two decades, enormous progress has been made in the field of video technology (U-matic, VHS, SVHS), that is now an alternative to 16 mm film. The goal of this study is to use a new SVHS video analysis system (Peak Performance System) on the slope for analyzing three different skiing techniques and revealing the practicality, accuracy and reliability of such a technique under extreme field conditions. Demonstrating each of the techniques, three different skiers were measured ten times, by using a 3-D camera setup with three synchronized video cameras. Sampling rate was set to 50 Hz. The calibration was done by using a theodolite and a calibration frame (cube) for smaller fields of view. The total time to set up the whole field was found to be one hour. In order to have a large enough picture to digitize, we chose only one turn to be in the field of view.

We found significant differences between the techniques in vertical acceleration, upper body rotation and angular displacement of the knee joint. By means of a computer animated stick figure, we could optically demonstrate the differences after rotating the figure into the proper position. Splitting the screen in up to four quadrants allowed comparison of the different techniques on screen.

The results lead to the conclusion that such a technique is a reliable, practical tool to establish a risk discrimination for the knee between different techniques. In addition there is valuable information that can be used to enhance the performance of the skier as well as lead to injury prevention.
A New Mechanical Ski Binding with Heel Release Activated by the Bending Moment at the Boot Sole
Authors: Caldwell B , Landry D , Hull ML
Published: March 2009

This article describes a design concept for a new mechanical ski binding where heel release is activated exclusively by the anterior/posterior bending moment at the boot sole rather than the upwards force at the boot heel. This moment possibly correlates more strongly to the bending moment at the site of boot-top fractures than the upwards heel force. To gain this performance, the boot is forced to pivot about an axis transverse to the ski and directly beneath the ankle joint. A motion transformer converts vertical motion of the AFD into horizontal motion resisted by compression springs. Inasmuch as heel release is controlled by the degree of motion, adjusting the spring compression adjusts the release level. To activate release of the heelpiece, a Marker M40 binding, which rotates with the boot about the pivot, was modified by replacing the “Sensomatic” mechanism. The modification consists of a specially designed multi-link trigger mechanism that enables the binding to be unlatched without forcibly overcoming the spring force. This mechanism enables a force of 0.5N to activate release when the upwards force on the heel cup is 1000N (forward lean bending moment ∼270 Nm). Despite the incorporation of this trigger mechanism, the vertical elasticity, longitudinal compliance, and adjustability to different boot sole lengths are preserved. To demonstrate the workability of the concept, a prototype was constructed and tested successfully. With the workability of the concept proven, the development of a skiable prototype appears to be a worthwhile next step.
An Alpine Ski Binding with Electrically Modulated Twist Release
Authors: Eseltine K , Hull ML
Published: March 2009

The design of a new binding for Alpine skiing where the release level of the toepiece in twist is modulated based on the level of neural stimulation of one of the vastii muscles in the quadriceps group is described. A conventional binding toepiece was modified to offer two levels of release by placing two springs in series with a spacer between them. A special solenoid-activated mechanism was designed that could either hold the spacer fixed or release it depending on the electrical signal indicating the degree of muscle activation. If the spacer is held fixed, then the active spring has fewer coils and is stiffer (high release level). The design of this special mechanism is described and the computations necessary to ensure reliable activation with a low force solenoid summarized. The special circuitry that was designed to actuate the solenoid is also described. The results of testing a prototype binding system are described as well.
Ski Jumping Injuries
Authors: Yamamura T , Sugawara M , Ishii S
Published: March 2009

This article is a retrospective report on the injuries of competition ski jumps in Sapporo, Japan during the period between 1985 and 1990. In these five seasons, 56 official ski jumping games, including the world cup games, were held in Sapporo. The total number of jumps amounted to 7831 with 71 jumps with falls for a fall rate of 9.07 per 1000 jumps. By hill size, the fall rate was 8.29 per 1000 jumps on the large hill and 10.16 per 1000 jumps on the small hill. Weather conditions directly affected the fall rate, which increased in windy weather with varied wind velocity. The most common location of injuries were the face, neck, shoulders, and upper extremities.
Tobogganing Injuries in Australia
Authors: Sherry E , Biankin AV
Published: March 2009

People come to the snow fields either to ski or to enjoy the snow-covered environment. The latter group includes people who toboggan.

In Australia, many people have either never seen snow or are at the beginner's stage of skiing. However, this is changing as cheap package bus tours to ski resorts now put snowrelated sports within the economic grasp of more people. Many of these newcomers view tobogganing as a safer introduction to snow sports. Although it is easier and cheaper, it may not be safer.

We collected detailed data on 77 tobogganing injuries from the 1985 season. This data included basic epidemiological information on the Australian tobogganist including determination of the mechanism of injury. The average age of the injured tobogganist was 18.2 (range 4 to 62), 49% were male, 50% were injured within 1 h of this activity, most (84%) had never snow skied, and 65% were unaware of the hazards of tobogganing.

Of the 77 injuries, 24 (31.2%) were to the lower spine and pelvis and, except for one, were only soft tissue injuries with no neurological signs. One was an acetabular fracture of the pelvis; 21 (27%) injured their lower limbs; 9 were contusions, 1 was a tibial plateau fracture, 7 were fractured ankles, 3 were ankle sprains and 1 minor fracture; 20 (26%) suffered head and face injuries; and 4 suffered a fractured nose and 16 had lacerations/contusions. Ten (13%) injured their upper limb, two (3%) were fractures, and two (3%) had soft tissue injuries of their cervical spine. No serious head or spinal injuries were seen (that is, no neurological signs).

Adverse snow and weather conditions appeared to play a minimal role in the causation of injuries (5%); 65% of injuries were due to loss of control, while 19.5% were due to natural hazards such as rocks or ditches. Of injuries, 10.5% were tobogganists hit by tobogganists as they walked back up the slope dragging their toboggan.

Tobogganing in Australia is not the sophisticated Northern hemispheric equivalent seen at the Winter Olympics. The vehicle available here is a cheap, plastic shell, square and shallow (measuring 80 by 38 by 63 cm) with an attached rope to pull it up the slope but with no steering or braking controls. Tobogganists mostly sit with their spine flexed and their feet either within or extending outside the toboggan. On contested slopes, collisions may occur with the ground, rocks, flora, other tobogganists, and pedestrians. The operator uses his legs to brake, curls his hands out over the side of the vehicle to secure himself, and his pelvis rests flat against the hard toboggan surface.

We conclude that tobogganing is a perilous introduction to snow-related sports, and it is not as safe as skiing. There is a need to provide a more controllable vehicle and tobogganist education with regard to the possible dangers.
A Historical Introduction to Fretting Fatigue
Authors: Waterhouse RB
Published: March 2009

Fretting was first reported by Eden et al. in 1911 [1] who found that brown oxide debris was formed in the steel grips of their fatigue machine in contact with a steel specimen. It was not until 1927 that Tomlinson [2] conducted the first investigation of the process and designed two machines to produce small-amplitude rotational movement between two annuli in the first case, and an annulus and a flat in the second. The movement was controlled by a long lever system. Since the resultant debris on his steel specimens was the red iron oxide αFe2O3, which had arisen from chemical reaction with oxygen in the air, he coined the phrase “fretting corrosion.” He also established that the damage could be caused by movements with amplitudes as small as a few millionths of an inch (∼125 nm) and the important fact that relative movement had to occur, which he termed “slip.”
The Problems of Fretting Fatigue Testing
Authors: Waterhouse RB
Published: March 2009

Fretting fatigue testing usually arises as the result of some failure which it is imperative to overcome either by a modified design or application of some surface treatment. In such cases the test rig is usually designed to replicate the actual situation as closely as possible (e.g., a press fit or riveted joint) with environmental conditions as near to those occurring in practice (e.g., high temperature or a marine atmosphere). In laboratory testing the purpose is much wider, and usually entails, for instance, the assessment of different materials for their susceptibility to fretting damage, or the effect of variables such as clamping load, amplitude of slip and frequency, in particular environmental conditions. The type of fatigue test is very relevant (i.e., whether the response is the same in rotating-bending, push-pull or torsion, and whether in the latter two cases, a mean stress is applied). The nature of the contact is also material (i.e., whether it is flat-on-flat or cylinder-on-flat, or even crossed cylinder). How is the clamping stress to be applied? If by a proving ring, then the pressure can change according to whether the debris is trapped or can escape; a dead weight method might be preferable. Surface finish and residual stress are factors which must be taken into account. All these matters must be considered in devising a recommended testing procedure.
Testing Methods in Fretting Fatigue: A Critical Appraisal
Authors: Vincent L , Berthier Y , Godet M
Published: March 2009

Fatigue damage in fretting after crack formation is only initiated under very specific conditions of both amplitude and load. Experience shows, that for a given load the velocity difference between the core of the rubbing specimen and the friction pads is accommodated as amplitude increases through the three following mechanisms: 1. Elastic displacements in homogeneous rubbing solids (or first bodies) is a non-destructive process which will not alter specimen life. 2. Elastic displacements in cracked rubbing solids (or first bodies) can lead to fatigue failure. This mechanism is dangerous as it can lead to failure and thus to life reduction. 3. Shear in debris beds (third-bodies), formed by particles detached from first-bodies. In most instances, these beds protect the rubbing surfaces and prevent or at least retard crack formation and thus fatigue.

The significant drop in life observed experimentally in modified fatigue machines is noted only because the conditions which lead to Mechanism 2 above are often favored in this type of device. An original static fretting fatigue approach is proposed.
Variables of Fretting Process: Are There 50 of Them?
Authors: Dobromirski JM
Published: March 2009

It has been reported that up to 50 variables might influence the magnitude and rate of the fretting process.

Predictions of the fatigue strength under fretting conditions were reported to be successful when based on “stress models” (e.g., the fracture mechanics approach). These predictions use only a few variables of the fretting process such as external load, contact pressure, coefficient of friction, and the amplitude of relative slip.

A concept of “primary” and “secondary” sets of fretting variables has been proposed. The “primary” set of variables includes the coefficient of friction, magnitude of slip and contact pressure acting at the fretting interface. The “secondary” set of variables affects the fretting process through changes these variables cause in the “primary” set of variables.

The coefficient of friction has been identified as the main variable of the fretting process. Analysis of the literature shows that the effect which many other variables have on the fretting process can be explained by the changes these variables cause in the value of the coefficient of friction.
The Development of a Fretting Fatigue Experiment with Well-Defined Characteristics
Authors: Hills DA , Nowell D
Published: March 2009

It is shown that many of the unknowns present in a rotating-bending fretting fatigue experiment, fitted with a clamped bridge arrangement, may be avoided by moving to an entirely different geometry, based on a standard uniaxial tensile test specimen. A pair of cylinders is pressed against this specimen, producing a Hertzian contact, and a shear force is developed by impeding axial displacement. The apparatus is run in the partial-slip regime so that the relative displacement within the contact may be calculated.

The well-defined geometry permits a rigorous analysis of contact pressure, shear traction distribution, interior stress fields, and crack tip stress intensity factors for any cracks present. Explicit equations for these quantities are developed which enable the physical parameters responsible for crack initiation, development, and early propagation to be readily obtained. Refinements to the classical contact calculations include analysis of the effects of using elastically dissimilar contacting elements, the influence of the thickness of the specimen, and the effect of surface roughness on the contact pressure and the interior stress field. A size effect discovered using this apparatus described is also reported.
Fretting Fatigue Analysis of Strength Improvement Models with Grooving or Knurling on a Contact Surface
Authors: Hattori T , Nakamura M , Ishizuka T
Published: March 2009

Previously the authors introduced a fretting fatigue evaluation method using stress analysis and fracture mechanics analysis of the contacting structures. Using this method the fretting fatigue limit can be estimated by comparing the calculated stress intensity factor of the crack which originates at the contact edge with the material's threshold stress intensity factor range.

In this paper the authors apply this fretting fatigue strength evaluation method to fretting fatigue strength improvement models with grooving or knurling on a contact surface. These estimated results are compared with the experimental results of a fretting fatigue test using grooving or knurling pad type specimens. The strength improvement of these two models can be confirmed analytically and experimentally. Finally, the optimization of groove shapes such as the radius and depth of a groove are discussed using the above evaluation method.
Fretting Fatigue in the Power Generation Industry: Experiments, Analysis, and Integrity Assessment
Authors: Lindley TC , Nix KJ
Published: March 2009

Experimental procedures for carrying out fretting fatigue tests using either the proving ring method or a specifically developed servo-hydraulic biaxial rig are described. S-N curves are generated with and without fretting in order to establish the important variables that can affect fretting fatigue and to rank material fretting combinations that should be avoided. The S-N tests and associated metallography indicate that small cracks, typically 0.25–0.5 mm deep, initiate rapidly at only a small fraction of fatigue life. Fracture mechanics and near-threshold fatigue concepts can be used to predict the conditions for continued growth or arrest of the small fretting defects.
The Influence of Fretting Corrosion on Fatigue Strength of Nodular Cast Iron and Steel under Constant Amplitude and Load Spectrum Tests
Authors: Fischer G , Grubisic V , Buxbaum O
Published: March 2009

The fatigue life reduction caused by fretting corrosion was determined in comparative fatigue life tests for axially loaded flat specimens made of GGG 40 (cast nodular iron, ASTM A 536-80: 60-40-12) and of St 34-2 (hot rolled structural steel, ASTM A 283-78: Grade C). A special test rig was constructed for superimposing fretting corrosion onto constant amplitude and spectrum loading of the specimen. Various surface conditions and two levels of surface pressure were investigated. Using the results of these tests and the parameters derived, comparative damage calculations were performed aiming at predicting fatigue life in the presence of fretting corrosion. Means to avoid fretting corrosion were also explained.
The Application of Electrochemical Techniques to Evaluate the Role of Corrosion in Fretting Fatigue of a High Strength Low Alloy Steel
Authors: Price S , Taylor DE
Published: March 2009

An experimental assembly has been developed to enable aqueous fretting fatigue tests to be performed with an orthogonally crossed cylinder arrangement of fatigue specimen and fretting pad. The equipment has been employed in a study of the fretting fatigue behavior of the high strength, low alloy steel, Corten A, in both air and synthetic seawater environments.

The use of impressed cathodic protection has identified electrochemical dissolution processes as having a significant influence on fatigue life. Normal corrosion fatigue in seawater produces a 60% reduction in fatigue life compared to that in air, while the imposition of fretting causes a further 24% reduction in fatigue life.

The initiation sites of fretting fatigue cracks occur at the boundary between slip and non-slip regions in both air and aqueous environments. Cracks propagate at an oblique angle to the surface of the fatigue specimen. On leaving the zone of influence set up by the alternating shear stress, the cracks propagate perpendicular to the applied cyclic stress.
Fretting Fatigue Testing: Current Practice and Future Prospects for Standardization
Authors: Attia MH
Published: March 2009

A literature review has been carried out to identify the interactive role of the variables governing the fretting fatigue process and to examine the wide spectrum of the present testing practice. It has been shown that the present practice does not ensure an acceptable degree of uniformity and results repeatability. The issues and areas that should be addressed for future development of standardized test methods and equipment are also identified. A special emphasis is placed on the conceptual development needed for modeling the thermal mechanical aspects, of the contact problem under fretting.
The NIH Recombinant DNA Advisory Committee: An Example of the Self-Regulatory Process
Authors: McGarrity GJ
Published: March 2009

The National Institutes of Health (NIH) first developed guidelines for the safe laboratory use of recombinant DNA in 1976. The NIH organized the Recombinant DNA Advisory Committee (RAC) to advise and guide work in this area. The RAC consists of biomedical researchers and members from the general public.

The NIH guidelines have been modified several times since 1976 as new data have become available. This flexibility has enabled the RAC to keep pace with the rapid developments occurring in research and development in this area. The scope, content, and methods of revision of the NIH guidelines are described. The scope and objectives of the RAC are also described. Available data suggest that the RAC has made significant contributions to the field and has created a high degree of confidence among scientists and the public.
Safety in Bioprocessing: An Industrial Perspective
Authors: Foglesong MA
Published: March 2009

The experience of Eli Lilly and Co. has demonstrated that large-scale bioprocessing can be conducted under conditions that provide safety for the fermentation operator as well as the environment. Thirty years of medical surveillance of workers associated with large-scale bioprocessing has shown no increased incidence of morbidity or mortality associated with these processes. Over 100 000 h of experience with large-scale recombinant DNA fermentations has demonstrated that, with proper design and validation criteria, genetically engineered microorganisms can be developed and the operation scaled to efficient and economical processes with excellent protection to the environment and the operating personnel. Large-scale mammalian cell culture processes, which possess their own unique set of bio-safety issues, are being developed with safeguards that ensure the use of well-characterized cell lines, the inactivation of process streams, and the elimination of risk to the bioprocess operators.