bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Intensity Predictions with ANSYS® for Use in Aircraft Engine Component Life Prediction
Authors: Slavik DC , McClain RD , Lewis K
Published: April 2008

Stress intensity (K) predictions are presented using crack opening displacements with¼ points elements at the crack tip to simulate the crack tip singularity. These results are compared to available literature values under remote applied tension for a 2D thru-crack and a 3D semi-elliptical surface crack geometry. Crack-opening displacements with ANSYS were found to calculate K for the 2D thru-crack geometry to within 1 % of an available reference solution and were not strongly influenced by the crack tip mesh parameters evaluated. Predicted stress intensities with crack-opening displacements were then considered for the surface flaw geometry for a range of crack aspect ratios (0.2 ⩽ a/c ⩽ 2.0) and crack depths (0.01 ⩽ a/T ⩽ 0.8). K for the surface flaw geometry was also not significantly influenced by the crack tip mesh refinement and matched literature solutions to within ±5% of predicted K for the crack depth position. Predicted stress intensities at the surface position using crack-opening displacement approaches were: (a) not strictly valid given the nature of the crack tip singularity, (b) dependent on the stress state assumption, and (c) dependent on the degree of mesh refinement. These difficulties were avoided by selecting a 2° angular position below the surface with a plane strain assumption to calculate K from predicted crack-opening displacements. This approach produced a stress intensity that was reasonably assumed to be representative of K at the surface position and was not significantly influenced by the mesh refinement or stress state assumptions. K with this approach was somewhat higher than results using alternative approaches in the literature. The implication of these results compared to other finite element based results with respect to Raju-Newman interpolation equations are discussed with probability plots. Examples with crack opening models in specific aircraft engine components are also provided.
Fracture Parameters of Surface Cracks in Compressor Disks
Authors: Zhuang WZ , Wicks BJ
Published: April 2008

The elastic and elastic-plastic fracture mechanics parameters of surface cracks n compressor disks of aircraft engines are evaluated using both the finite element method and the weight function method. First, a three-dimensional finite element model of a low-pressure compressor disk containing a surface crack at the snap radius is developed. The stress intensity factor distributions along the surface crack front with various crack shapes and sizes in the disk under a typical engine operation condition are calculated. Then, the effect of biaxial stresses on the stress intensity factor of a crack emanating from a tie bolt hole in a representative compressor disk is investigated using the weight function approach. Emphasis is given to determining the effect of the bolt hole plastic zone on the fracture parameters when the compressor disk is highly loaded. Finally, a new theoretical model for the estimation of the fracture parameters of a through-thickness crack in the web region is proposed using a definition of local biaxial stress ratio. The studies show that the developed model can provide better estimation of the plastic zone size and the crack-tip opening displacement than those existing models.
The Effect of Low Cycle Fatigue Cracks and Loading History on High Cycle Fatigue Threshold
Authors: Moshier MA , Nicholas T , Hillberry BM
Published: April 2008

The high cycle fatigue (HCF) resistance of Ti-6Al-4V for gas turbine engine pplications is studied when the material is first subjected to low cycle fatigue (LCF). The high cycle fatigue (HCF) threshold is determined after small LCF surface cracks are formed in notch tension specimens. LCF loading at two stress ratios, R = 0.1 and R -1.0, is used to initiate the LCF cracks, which are detected using direct current potential difference (DCPD). The surface crack sizes are measured under load using a static loading fixture and a scanning electron microscope (SEM). In addition to the SEM surface measurements, heat tinting is used to mark the crack profiles before HCF testing so that fractography can be used after failure to measure the 2D crack geometry. The LCF surface-cracked specimens are tested at room temperature in lab air at 600 Hz using a step-loading procedure at two stress ratios, R = 0.1 and R = 0.5. The LCF loading history is found to affect the HCF threshold compared to what is predicted from long crack threshold values obtained from other crack geometries. Variations in HCF crack growth thresholds obtained on specimens with LCF crack sizes from 25 to 175 μm are attributed to overload and underload effects from the LCF precracking.
Fatigue Crack Growth Threshold Stress Intensity Determination via Surface Flaw (Kb Bar) Specimen Geometry
Authors: Bain KR , Miller DS
Published: April 2008

Many aircraft component failures originate from small-surface flaw cracks in highly stressed locations. It is therefore desirable to measure the threshold stress intensity factor that simulates the key conditions of high-stress and small semicircular surface crack shape. Such a technique has been developed and demonstrated on multiple titanium and nickel-base alloys. This technique is effective at both room and elevated temperatures and at both low and high mean stress.

The test method is described in detail, but in brief a small EDM flaw is made on the surface of a rectangular specimen. The crack length is monitored via electrical potential drop technique. The crack length and aspect ratio versus the change in electrical potential across the crack tip has been measured and is used to control the load shed during the experiment. Load sheds up to C = - 1181 m-1 have been demonstrated to give comparable thresholds to those measured using single edge notch or compact tension geometries with lower shed rates. Typical experimental results on both Ti-6Al-4V and an advanced nickel-base superalloy (KM4) are shown at both room temperature and elevated temperatures. This technique allows a rapid determination of threshold stress intensity factor for a material in a manner simulating the types of constraint experienced in components.
Modeling Crack Growth in Thin Sheet Aluminum Alloys
Authors: Siegmund T , Brocks W
Published: April 2008

The present study reports on the application of a cohesive zone model to the analyses of crack growth in a thin sheet specimen of a high-strength aluminum alloy. In addition to the elastic-plastic material properties, the parameters cohesive strength and cohesive energy describe material separation. For the sheet specimen under investigation, the cohesive energy is found to be close to the corresponding value of plane strain fracture toughness. The cohesive strength is approximately twice the yield strength. With these two additional material parameters being determined, crack growth experiments in center crack panels are analyzed. Good agreement with experimental records is found. Finally, the applicability of the model to study complex crack configurations as in multi-site damaged specimens is demonstrated.
Residual Strength Analyses of Riveted Lap-Splice Joints
Authors: Seshadri BR , Newman JC
Published: April 2008

Aging aircraft may develop multiple-site damage (MSD) that can reduce the structural integrity of fuselage structures. The existence of small cracks emanating from adjacent rivet holes in a fuselage lap-splice joint is of major concern. The residual strength of a panel with a lead crack is greatly reduced by the presence of smaller collinear cracks compared to that of only a lead crack. Recent studies in predicting the residual strength of flat and curvilinear panels with riveted lap-splice joints gave quite encouraging results, but some difficulties arose in modeling small cracks at rivet-loaded holes. Thus, there was a need to conduct detailed fracture analyses of the crack-linkup phenomenon in lap-splice joints with rivet-loaded fasteners.

The objective of this paper was to analyze the crack-linkup behavior in riveted-stiffened lap-splice joint panels with small MSD cracks at several adjacent rivet holes. Analyses were based on the STAGS (STructural Analysis of General Shells) code with the critical crack-tip-opening angle (CTOA, Ψc) fracture criterion. To account for high constraint around a crack front, the “plane strain” core option in STAGS was used. The importance of modeling rivet flexibility with fastener elements that accurately model load transfer across the joint was discussed. Fastener holes were not modeled, but rivet connectivity was accounted for by attaching rivets to the sheet on one side of the cracks that simulated both the rivet diameter and MSD cracks. Residual strength analyses made on 2024-T3 alloy (1.6-mm thick) riveted-lap-splice joints with a lead crack and various-size MSD cracks were compared with test data from Boeing. Analyses were conducted for both restrained and unrestrained against buckling conditions. Comparison of these analyses with lap-splice-joint test panels, which were partially restrained against buckling, was generally bounded by the restrained and unrestrained failure loads.
SIDD Installation and Direct Design for Reinforced Concrete Low-Head Pressure Pipe
Authors: Heger FJ
Published: April 2008

This paper describes the principal technical provisions in a proposed ASCE Standard Practice for the Direct Design of Buried Reinforced Concrete Low-Head Pressure Pipe using the same new standard installations (SIDD) as recommended in ASCE 15–93, Standard Practice for Direct Design of Buried Precast Concrete Pipe Using Standard Installations (for reinforced concrete gravity flow pipe). The proposed standard practice defines installation requirements and structural analyses for moment, thrust, and shear produced by external loads that are the same as given in ASCE-15. It incorporates design procedures for combined circumferential tension produced by internal pressure and flexure produced by external loads that are essentially in compliance with both ASTM C361 and AWWA C302 and as recommended in AWWA Manual M9. These provisions and the cited referenced standards use load factors that are larger than those used in various standards for direct design of gravity flow pipe and they further limit the maximum combined stress in the reinforcement by inclusion of a limiting maximum design yield strength of 40,000 psi, regardless of the actual yield strength of the reinforcement. There are further limits on the reinforcement stress produced by internal pressure alone as well as on the tensile stress in the uncracked concrete pipe wall that are essentially the same as given in the above standards for low-head pressure pipe.

In addition to providing the requirements and structural effects of SIDD installations, the proposed standard fills a gap in the existing standards for design of low-head concrete pipe by incorporating rational methods for calculating radial tension and shear strengths. Radial tension strength is required to resist the bending moments at the crown and invert produced by external loads. The presence of internal pressure does not increase the required radial tension strength, and the same methods used for gravity flow pipe may be used for determining the radial tension strength of low-head pressure pipe. Shear strength is another matter. The circumferential tension produced by internal pressure produces a significant effect on shear strength. Research by Dr. M. P. Collins and coworkers in Canada is the basis for new more rational procedures for shear strength of flexural members in the AASHTO LRFD Highway Bridge Specification. These are adopted and simplified for use over the range of wall thickness and strain variations applicable to low-head pressure pipe so that for the first time a rational procedure is available in the proposed standard to calculate the shear strength of low-head concrete pipe. Application of the new procedure to pipe designs for the higher fill heights combined with the highest pressure limits in the design tables of ASTM C361 indicates an adequate factor of safety for those designs, including adequate shear strength.
Structural Evaluation of Three-Sided Concrete Culverts
Authors: Frederick GR , Tarhini KM
Published: April 2008

Three-sided concrete culverts can be used to replace short span bridges and multiple sections (barrels) of four-sided concrete box culverts. ASTM Standards do not specify designs for four-sided concrete box culverts with span lengths exceeding 12 ft (3.6 m) nor do they discuss the three-sided concrete culverts. This paper describes the analysis and design of three-sided flat-top precast reinforced concrete culverts with span length ranging between 14 ft (4 m) and 36 ft (11 m). It was shown that the AASHTO distribution width used in performing plane frame analysis gave similar results to the three-dimensional finite element analysis. Therefore, ten shallow structures were selected for analysis and design. The culverts were subjected to live load plus impact, dead load, and lateral earth pressure. The slab and wall thicknesses were selected so that no shear reinforcement is needed. The ultimate strength design was used to determine main reinforcing steel. AASHTO and ASTM recommendations were used to determine the reinforcing steel in transverse direction.
Field Tests of Concrete Pipe Performance During Backfilling
Authors: McGrath TJ , Selig ET , Webb MC
Published: April 2008

Full-scale field tests were conducted on the campus of the University of Massachusetts, Amherst, to evaluate the pipe-soil interactions that take place as pipes are buried and backfilled. The program included concrete, polyethylene, and corrugated steel pipe. This paper focuses on the data from the concrete pipe tests, and assesses it in light of the assumptions of the SIDD design approach adopted by ASCE and AASHTO.

Tests included two types of soil backfill, three compaction levels, three trench widths, varying haunching effort and one test with controlled low strength material. Eleven tests were conducted with 900 mm (36 in.) inside diameter pipe and three installations with 1500 mm (60 in.) inside diameter pipe. Primary measurements on the concrete pipe during backfilling and compaction included pipe-soil interface pressures, soil density, and soil stresses.

Results show significant variations in pipe behavior as a result of installation practices and generally confirm the assumptions of the SIDD design method. Compaction of backfill in the region from the springline to 45 to 60 degrees below the springline has a significant positive effect in mitigating poor bedding and haunching conditions, and the use of soft bedding is effective in reducing invert pressures on the Pipe.
Multiple-Laboratory Round-Robin Study of the Flexural, Shear, and Tensile Behavior of a Two-Dimensionally Woven Nicalon™/Sylramic™ Ceramic Matrix Composite
Authors: Jenkins MG , Lara-Curzio E , Gonczy ST , Zawada LP
Published: April 2008

A round-robin study was conducted on the flexural, shear, and tensile mechanical behavior of a Nicalon™ fiber-reinforced Sylramic™ matrix CFCC continuous fiber ceramic composite (CFCC) to: 1) determine the precision and bias of three ASTM test methods at room temperature for flexure, shear and tension [Test Method for Flexural Properties of Continuous Fiber-Reinforced Advanced Ceramics (C 1341), Test Method for Shear Strength of Continuous Fiber-Reinforced Advanced Ceramics at Ambient Temperatures (C 1292), and Test Method for Monotonic Tensile Strength Testing of Continuous Fiber-Reinforced Ceramic Composites with Solid Rectangular Cross-Sections at Ambient Temperatures (C 1275)]; 2) establish an expansive data base (e.g., Mil-Hdbk-17 CMC effort) for a single CFCC; and 3) evaluate a statistically- significant sample size of a single CFCC for processing and design purposes. The commercial CFCC was comprised of eight plies of ceramic grade Nicalon™ fiber fabric in a symmetric 0/90 lay-up, a proprietary boron-containing interphase, and a silicon nitrocarbide matrix (Sylramic™) derived from polysilazane. Ten each of flexure, in-plane tension, in-plane (Iosipescu) shear, and interlaminar (double notch compression) test specimens were tested by each of seven to ten different laboratories per the applicable ASTM test method for totals of sixty to one hundred replicate tests for each test type. With a few exceptions, coefficients of variation for repeatability and reproducibility ranged from 5 to 10%.
Detailed Study of the Tensile Behavior of a Two-Dimensionally Woven Nicalon™/Sylramic™ Ceramic Matrix Composite
Authors: Jenkins MG , Zawada LP
Published: April 2008

A round-robin study was conducted on the tensile behavior of a Nicalon™ fiber reinforced Sylramic™ ceramic matrix composite (CMC). The goals of the US federal government-funded study were: 1) to determine the precision and bias of ASTM Test Method for Monotonic Tensile Strength Testing of Continuous Fiber-Reinforced Ceramic Composites with Solid Rectangular Cross-Sections at Ambient Temperatures (C 1275), 2) to establish an expansive data base for a single CMC, and 3) to evaluate a statistically-significant sample size of a single CMC for processing and design purposes. The CMC was comprised of eight plies of ceramic grade Nicalon™ fabric in a symmetric 0/90 lay-up, a proprietary boron nitride-containing interphase, and a silicon nitrocarbide matrix derived from polysilazane. Tabbed in-plane, reduced gage-section tensile test specimens (3 × 12 × 150-mm overall, 3 × 8 × 35-mm gage section) were monotonically tested in displacement control (0.02 mm/s) at room temperature in face-loaded grips. Five industrial, two governmental, and two academic laboratories participated, each testing ten tensile test specimens for a total of ninety tests. Results were analyzed for variations in test procedures between laboratories, material density/porosity/panel of origin, elastic constants, and nondestructive evaluation characteristics. Repeatability and reproducibility were assessed from coefficients of variation that ranged from 4 to 10%.
Testing Methodology for Measuring Transthickness Tensile Strength for Ceramic Matrix Composites
Authors: Zawada LP , Goecke KE
Published: April 2008

This paper discusses experimental methods and test results from a program established to evaluate the transthickness tensile strength of ceramic matrix composites (CMC). Experimental techniques discussed include adhesives, test specimen design, gripping, and fixturing. Testing apparatus and testing protocol are addressed. In addition to addressing experimental techniques, two studies were conducted. The first study investigated the effect of test specimen geometry using circular and square cross section test specimens. The circular button type test specimens were 19 mm in diameter, while the square test specimens were 16.8 mm on a side. Analysis of the test results revealed no statistically significant difference between the two test specimen geometries. The second study involved a mini-round-robin test program undertaken to evaluate a draft test standard and to evaluate the accuracy of the test method. In addition, transthickness tensile strength results from several different CMCs are presented. An attempt is made to correlate between the measured transthickness tensile strength and the varying CMC microstructures investigated.
Stress-Rupture, Overstrerssing, and a New Methodology to Assess the High-Temperature Durability and Reliability of CFCCs
Authors: Lara-Curzio E
Published: April 2008

A testing methodology is proposed to assess the durability and reliability of non-oxide continuous fiber-reinforced ceramic composites for high temperature applications. The strategy is based on determining the reliability of these materials when subjected to random loading schedules consisting of mechanical load and temperature spikes that are superimposed upon otherwise constant stress and temperature values. The frequency and magnitude of the mechanical load and temperature spikes would be representative of the number and characteristics of the transients that are associated with a particular industrial application and that are expected to occur over the life of the component. The effect of overstressing on the stress-rupture behavior of a ceramic grade (CG) Nicalon™ fiber-reinforced silicon carbide (SiC) matrix composite was investigated and results are presented from tests conducted in ambient air at 950°C.
Surface Finish and Notch Effect Model for Strength Predictions of Continuous Fiber Ceramic Composites (CFCCs)
Authors: Ramulu M , Jenkins MG , Kunaporn S
Published: April 2008

Surface texture and process defects resulting from net-shape machining of continuous fiber ceramic composites (CFCCs) are often ignored in the design and analysis of component parts. Recently a mathematical model was proposed which defines the effects of surface texture and notch effects on the strength of engineering components in terms of an effective stress concentration factor (kt). This model was experimentally verified using flexural strength resulting for a graphite/bismaleimide laminate. A further verification of the model applied to CFCC materials is presented in here using tensile test results. It was found that the model successfully predicts the retained strength of CFCCs resulting from net-shape machining over a large range in surface quality.
Notch-Sensitivity of a Woven Oxide/Oxide Ceramic Matrix Composite
Authors: John R , Buchanan DJ , Zawada LP
Published: April 2008

Oxide/oxide ceramic matrix composites (CMC) are currently being demonstrated in high-temperature aerospace applications. An oxide/oxide CMC under consideration by the U.S. Air Force is Nextel720/AS, which consists of an alumina-silica matrix (AS) reinforced with a woven Nextel720 fiber mat. The fracture behavior of notched Nextel720/AS at room and expected service temperatures is discussed in this paper. Specimens with semi-circular and narrow double-edge notches were tested under monotonic loading in laboratory air at 23 to 1200°C, and under sustained (creep) loading at 1100°C. The results show that Nextel720/AS is notch-insensitive at low temperatures (≤ 1000°C) and ≈22% notch-sensitive at higher temperatures (≥ 1100°C) under tensile loading. At 1100°C, the notch-sensitivity increased significantly under sustained loading.
The Effects of Microstructural Damage on the Thermal Diffusivity of Continuous Fiber-Reinforced Ceramic Matrix Composites
Authors: Graham S , McDowell DL , Lara-Curzio E , Dinwiddie RB , Wang H
Published: April 2008

The relationship between microstructural damage and the thermal diffusivity of unidirectional reinforced Nicalon™-LAS II was investigated. Damage in the form of matrix-microcracking and fiber-matrix debonding was induced in the composites through Monotonic and cyclic mechanical loading. The thermal diffusivity of the composites was measured in directions transverse and parallel to the fiber axis by the standard flash diffusivity method. The results showed that damage induced by mechanical loading only affected the thermal diffusivity parallel to the fiber direction. Mechanical loading followed by oxidation of the carbonaceous interface resulted in significant changes in the longitudinal and transverse thermal diffusivity of the mechanically-damaged samples. These experiments showed the important role of the interfacial conductance on both the longitudinal and transverse thermal Diffusivity. The experimental data, along with finite element calculations, were used to assess the use of micromechanics-based models in predicting an effective thermal conductivity of damaged composites.
Effects of Temperature and Environment on the Mechanical Properties of Tyranno-Hex™ Composites
Authors: Drissi-Habti M , Takeda N , Nakano K , Kanno Y , Ishikawa T
Published: April 2008

Tyranno-Hex™ is a newly-developed ceramic matrix composite (CMC) containing a high volume fraction (typically 90%) of fibers. The as-processed material exhibits strong bonding at the fiber-matrix interface; hence the composite behaves as a linear-elastic, brittle material at room temperature. However, at high temperatures (∼1200° C), a composite “toughening” mechanism develops and a large non linear region is apparent on tensile stress-strain curves. This change in behavior is related primarily to the relaxation of the interfacial bonding following the crystallization of the silica matrix into cristobalite. The measured mechanical behavior is discussed based on the microstructural assessment using transmission electron microscopy (TEM). Preliminary studies on coating techniques (sol-gel and powder metallurgy derived) for oxidation protection of the composite are also presented.
Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions
Authors: Halbig MC , Brewer DN , Eckel AJ
Published: April 2008

Ten different ceramic matrix composite (CMC) materials were subjected to a constant load and temperature in an air environment. Tests conducted under these conditions are often referred to as stressed oxidation or creep rupture tests. The stressed oxidation tests were conducted at a temperature of 1454°C at stresses of 69 MPa, 172 MPa and 50% of each material's ultimate tensile strength. The ten materials included such CMCs as C/SiC, SiC/C, SiC/SiC, SiC/SiNC and C/C. The time to failure results of the stressed oxidation tests will be presented. Much of the discussion regarding material degradation under stressed oxidation conditions will focus on C/SiC composites. Thermogravimetric analysis of the oxidation of fully exposed carbon fiber (T300) and of C/SiC coupons will be presented as well as a model that predicts the oxidation patterns and kinetics of carbon fiber tows oxidizing in a nonreactive matrix.
Principles of Ice Hockey Injury Research
Authors: Stuart MJ , Smith AM
Published: April 2008

The goal of sports injury research is to improve understanding of injuries in a specific sport in order to facilitate prevention. Comprehension of epidemiology principles is necessary to design research protocols which are both accurate and pragmatic. Common pitfalls in sports epidemiology include selection bias, detection bias, transfer bias, recall bias, susceptibility bias, and confounding. Calculation of an injury rate requires precise measurement of the number of events (numerator) and the population-at-risk (denominator). Viable strategies for determining the incidence and characteristics of injuries and for observing outcome after an intervention in the sport of ice hockey include prospective cohort observational and interventional analyses.
Injury Report System
Authors: Biasca N , Lorentzon R , Montag D
Published: April 2008

There are a lot of steps to be taken to improve the prevention of certain ice hockey injuries, as well as to develop a network of communication between coaches, managers, referees, equipment manufactures and sports physicians to improve the performance and safety of ice hockey players. Recognizing the potential risk and identifying the causal relationship are the most important directives of all injury data collection systems. For this reason we have just developed an international standardized Injury Report System (IRS) for international comparison. This Injury Report System has been introduced in the Swiss Ice Hockey Association (SIHA) since 1996 and will be soon presented to the Ice Hockey Federations that are members of the IIHF's A and B Pools. The intent of this program is to introduce a systematic, standardized and simple recording system to promote a truly international system for continuously monitoring the risk and pattern of ice hockey related injuries. The main problems of a data collecting system, e.g. Definitions (Injury, Athlete-Exposures, Game Injury Rate and Severity of an Injury), Data Security, Compatibility, are explained in detail. As a consequence of the International Ice Hockey Federation (IIHF) having its legal domicile in Zürich, Switzerland, we have to follow the Swiss Data Protection Law. The data security is only guaranteed if the IRS's data is stored on an anonymous base. In this way it is possible to exchange information internationally and nationally regarding the health of A and B Pools IIHF's registered player with respect to all the paragraphs of the Swiss Data Protection Law. The systematical evaluation and analysis of this data will be the basis of further research to improve equipment, rules and training schedules.
Hockey Headgear and the Adequacy of Current Designs and Standards
Authors: Halstead PD , Alexander CF , Cook EM , Drew RC
Published: April 2008

Technology has surpassed the requirements of hockey headgear standards in use today; however, very few helmets have improved in design/performance. The CSA and ASTM hockey headgear standards are two of the least demanding standards in use and should be updated to account for new materials, a variety of hazards, and use conditions. The design of the helmet should also be investigated to reduce the amount of rotational and possibly cervical injuries. This paper will demonstrate where the current standards need updating and will present theories on how to reduce some of the injuries that plague the sport today.
Comparison of Ice Hockey Helmet Impact Attenuation Tests on Steel and Elastomeric Impact Surfaces
Authors: Sabelli J , Morehouse CA
Published: April 2008

United States ice hockey helmet standards were developed with an elastomeric surface for impact attenuation tests. These tests measure peak acceleration as a function of impact velocity. Recently, other standards have specified a flat steel impact surface, with a lower impact velocity (3.96 m/s as opposed to 4.50 m/s) to compensate for the greater hardness of the surface. It has been proposed that the U.S. standard be revised to use the steel impact surface, with the lower impact velocity.

A series of tests was conducted to determine whether tests performed with the proposed lower impact velocity on steel would yield peak acceleration results equivalent to test results with the higher impact velocity on an elastomeric surface. Tests were performed on three different models of ice hockey helmets. Impact tests were conducted at 4.50 m/s on the elastomeric surface, 3.96 m/s on steel, and 4.20 m/s on steel. Results are compared for the three impact schemes.
Spinal and Head Injuries in Ice Hockey - A Three Decade Perspective
Authors: Tator CH , Carson JD , Edmonds VE
Published: April 2008

Over the past three decades ice hockey has changed, particularly the severity of the injuries. Our objectives in this study are to give a historical overview and examine the nature and incidence of major spinal and head injuries sustained while playing ice hockey. Using a retrospective review of questionnaires returned by physicians, we have previously reported 241 cases of fracture or dislocation of the spine, up to the end of 1993. Between 1982 and 1993 an average of 16.8 ice hockey related major spinal injuries were reported each year, from Canada primarily. Most of these injuries occurred to the cervical spine of players 16 to 20 years of age who were playing in supervised games. Our latest study, now nearing completion, will add more cases to our registry, up to the end of 1996. These include a recent dramatic increase in spinal fractures reported by USA Hockey. In addition, we have included concussions in our latest survey because a lack of consistent adherence to hockey rules and to a respectful attitude may impact upon both spinal and head injury and the etiology may be overlapping in some cases.
Serious Spinal Injuries in Swedish Ice Hockey
Authors: Tegner Y
Published: April 2008

Between 1978 and 1996 48 case of spinal injuries in Swedish ice hockey were identified in a retrospectiva survey. This is probably a reliable estimate of the number of spinal injuries in ice hockey players in Sweden. Fifteen of the players had a permanent neurologic damage. The majority of the injuries occurred during organized matches and 55% were in adult ice hockey. Checking from behind was the most common cause of injury.
Effects of an Intervention Strategy on Body Checking, Penalties, and Injuries in Ice Hockey
Authors: Trudel P , Bernard D , Boileau R , Marcotte G
Published: April 2008

Numerous studies and reports have shown that ice hockey at the minor league level is often too violent and that modifications are required in how players behave during games (penalties taken) and in their use of body checking. The purpose of this study was to evaluate the effects of an intervention strategy on three dependent variables: the frequency of legal body checks per game, the type and frequency of penalties, and the number of injuries. The intervention strategy, based on self-supervision, was provided to 28 coaches at the Bantam level (14–15 years old). Although the coaches expressed a high level of satisfaction with the content of the intervention strategy, and stated that they would use it in the future, no significant differences were noticed in any of the dependent variables. This study, however, does provide a template for researchers who wish to validate an intervention strategy for coaches working in a normal coaching environment.
Differences Between Assessments of Penalties in Ice Hockey by Referees, Coaches, Players, and Parents
Authors: Trudel P , Dionne J-P , Bernard D
Published: April 2008

A video montage made up of 40 play sequences, presented on two different occasions, was used to compare referees, coaches, players, and parents on how they assess penalties in ice hockey. The results indicated that the four groups of subjects showed congruency and consistency in their decisions to give penalties. However, the referee group gave more importance to the context of the game and the behaviors of the victim when making decisions. The most interesting result was the large difference between decisions made by subjects in the study and decisions made by officials in the videotaped games. The authors concluded that during games, factors such as pressure from spectators and coaches, relationship established with the players, physical fatigue are factors that can bring the referees to shift from the constituent rules to the normative, unwritten rules.
A Profile of Rule Infractions in Bantam Level Ice Hockey
Authors: Gilbert WD , Trudel P
Published: April 2008

The purpose of the present study was to provide a profile of rule infractions at the Bantam (14–15 years old) level of ice hockey. For each penalty, information is provided on the: (a) category and type, (b) period of the game, (c) number of players penalized, and (d) zone and area on the ice surface where the infraction occurred. Gamesheet reports and videotapes of 55 games from five leagues revealed 850 penalties. There was an average of 15.5 penalties per game with most penalties classified as minor aggression penalties (62.4%). The number of penalties tended to increase from the first period to the third period. Most of the penalties were assessed to one player at a time (74.9%); however, the percentage of multiple player penalties tended to increase from one period to the next. More penalties were assessed to players in their defensive zone, and particularly in the area in front of the net.
Behavior of the High-Temperaturse Titanium Alloy IMI 834 Under Thermo-mechanical and Isothermal Fatigue Conditions
Authors: Pototzky P , Maier HJ , Christ H-J
Published: April 2008

The high-temperature titanium alloy IMI 834 was studied with regard to the stress-strain response under thermo-mechanical fatigue conditions, the evolution of the microstructure, the relevant damage mechanisms and their implications for fatigue life. For this purpose isothermal and thermo-mechanical fatigue tests were performed in the temperature range from 350°C to 650°C in vacuum and air, respectively, and changes in the microstructure were determined by means of transmission electron microscopy. It was found that planar dislocation slip prevails in all tests in which the temperature does not exceed 600°C. Hence, in this temperature range the stress-strain response under thermo-mechanical conditions can be predicted solely based on the isothermal behavior. By contrast, a transition to wavy slip takes place at higher temperatures, affecting significantly the stresses in the low-temperature part of the corresponding thermo-mechanical fatigue tests. Fatigue life was generally observed to be lower in out-of-phase tests as compared to in-phase loading. Furthermore, the tests performed in high vacuum demonstrated that oxidation strongly affects fatigue life, but does not basically change the influence of testing mode on cyclic life. This can mainly be attributed to the additional effect of the acting mean stress.
Thermo-mechanical Deformation of Al319 - T7B with Small Secondary Dendrite Arm Spacing
Authors: Sehitoglu H , Smith TJ , Maier HJ
Published: April 2008

Thermomechanical fatigue and isothermal deformation experiments were conducted on cast Al 319 alloys with small secondary arm spacings (SDAS) in the range of 25 to 35μm. The alloy was studied in the overaged state designated as T7B. In the case of the T7B treatment the material possesses dimensional stability, but incurs considerable loss of strength with time and cyclic deformation at temperatures exceeding 250°C. A two-state variable unified constitutive model was developed to characterize the stress-strain response for the material. The model handles temperature and strain rate effects and captures the microstructurally induced changes on the stress-strain response. The thermomechanical fatigue response under in-phase (TMF IP) and out-of-phase (TMF OP) conditions was simulated and the material exhibited a decrease in the stress range by as much as 50% with continued cycling. The decrease in strength was attributed to the significant coarsening of the precipitates at high temperatures and was confirmed by transmission electron microscopy.
The Role of Temperature Rate Terms in Viscoplastic Modelling: Theory and Experiments
Authors: Kühner R , Aktaa J , Angarita L , Lang K-H
Published: April 2008

To describe inelastic material behaviour under nonisothermal loading conditions on the base of a viscoplastic model it is not sufficient to use only temperature-dependent model parameters. Also the temperature rate in the evolution equations of the internal variables must be considered. To investigate the influence of the temperature rate, experiments should be defined in which the model response shows a remarkable dependence on the temperature rate. Such experiments could be performed on a coupled “two-bar system” under thermal and complex thermomechanical loading, respectively. Using a recently developed testing facility experiments with a coupled “two-bar system” are realized. This allows different temperature paths to be applied to the two bars which can be coupled to produce the same total strain throughout the experiment. At the same time, the sum of the forces of the two bars is controlled as a function of time. In addition it is possible to perform suitable thermomechanical experiments on an “one-bar system.” Here experiments with loading conditions similar to those observed at the “two-bar system” can be performed. The results show that temperature rate terms are necessary to model ratchetting effects correctly. Therefore, approaches taken from the literature were investigated and modified to achieve best agreement between modelling and experiment.
Thermo-mechanical Out-of-Phase Fatigue Life of Overlay Coated IN-738LC Gas Turbine Material
Authors: Zamrik SY , Renauld ML
Published: April 2008

Thermomechanical fatigue (TMF) is a unique type of fatigue process in which a component is simultaneously subjected to fluctuating loads and temperature. Isothermal life prediction techniques are often not applicable to TMF conditions since mechanical properties are temperature dependent with different damage mechanisms. There are two major cycles in TMF: the in-phase (IP) cycle where the maximum strain peak coincides with the maximum temperature and the out-of-phase (OP) cycle where the maximum strain and the lowest temperature coincide.

Experimental and analytical methods are developed to address the effect of thermomechanical strain cycling on coated nickel base superalloy IN-738LC material which is a γ' (Ni3Al) strengthened material used primarily for land based gas turbine blades. The coating system was a NiCoCrAlY overlay type. Tubular specimens in the two conditions, coated and uncoated, were primarily tested in out-of-phase (OP) TMF loading with a temperature range of 482–871°C. Using a viscoplastic concept which accounts for strain/temperature cycling response of substrate and coatings in terms of hysteresis loops which characterize the evolution of stress/strain/cycle up to mid-life cycle, a life prediction model was developed incorporating the effect of creep (strain hold-period), environment, and temperature. Test results show the OP TMF type cycle is the most damaging cycle for the coated IN-738LC material when compared to both in-phase and isothermal cycles. All experiments were strain-controlled with a triangular waveform and a strain-ratio A = εamp/εmean = ∞.
Effect of SiC-Reinforcement on Thermo-mechanical Fatigue of a Dispersion-Strengthened High-Temperature Aluminum Alloy
Authors: Jung A , Maier HJ , Christ H-J
Published: April 2008

Isothermal and thermo-mechanical fatigue (TMF) behavior of a dispersion-strengthened aluminum alloy has been studied between room temperature and 350°C. Cyclic stress-strain (CSS) response was found to be dominated by dispersoid-dislocation interactions, and thus, the effect of an additional SiC reinforcement on CSS behavior was only minor. As the dispersoids are thermally very stable, identical microstructures were observed to form independent of the actual loading conditions. Consequently, CSS response under TMF conditions could be accurately predicted from isothermal tests only. Damage evolution, by contrast, was found to depend drastically on the type of test. A microcrack propagation model could be successfully used to correlate all tests performed on the unreinforced alloy. In the SiC-reinforced material, however, both creep damage and oxidation damage were more severe under TMF conditions than predicted from isothermal tests, and life prediction is nonconservative, if only based on isothermal tests.
Thermal Strain Fatigue Modeling of a Matrix Alloy for a Metal Matrix Composite
Authors: Halford GR , Lerch BA , Arya VK
Published: April 2008

The Total Strain Version of the method of Strainrange Partitioning was used as the basis for modeling the thermomechanical fatigue resistance of the matrix material of the metal matrix composite, SCS-6/Ti-15-3. As prescribed by the model, the resistance was assessed through the use of bithermal creep-fatigue experiments. Bithermal temperatures of 205 and 427°C were imposed. A minimal number of strain limit-controlled, in-phase PP (pure fatigue, no creep) and CP (tensile creep) as well as out-of-phase PP (pure fatigue, no creep) and PC (compressive creep) experiments were conducted on conventional, axially-loaded, cylindrical-bar specimens. Inelastic strain range versus cyclic life curves for each of the Strainrange Partitioning bithermal cycles were evaluated and found to be nominally coincident. Cyclic elastic strain range versus inelastic strain range curves as well as elastic strain range versus life curves were documented for pure-fatigue and creep-fatigue conditions. The time-dependencies of these relationships were calibrated with the available data. These results enable the construction of total strain range versus fatigue life curves for thermomechanical fatigue for in- and out-of-phasing and for any arbitrary creep-time per cycle. Results are pplicable to the cyclic life prediction of metal matrix composites using the Ti-15-3 matrix material.
The Role of Oxidation on the Thermo-mechanical Fatigue of Timetal 21S Matrix Composites
Authors: Jin O , Johnson WS
Published: April 2008

Isothermal fatigue tests were performed on unnotched quasi-isotropic SCS-6/Timetal 21S (Ti-15Mo-2.6Nb-3Al-0.2Si) composites at room temperature, 400°C and 500°C with various hold times (0, 1 and 10 seconds). The specimen tested at 500°C showed significant oxidation, especially along the grain boundaries. In addition, there were changes in various physical properties of the composites at elevated temperatures: oxidation, phase transformation, viscoplastic flow of matrix, and interface reaction. The measurement of oxide thickness of both with and without load indicated that the oxidation of the matrix material was more severe with applied load than without load for the same amount of exposure time. Simple spectrum loading tests were conducted to examine the effect of test temperature on the formation of oxidation and its influence on the damage accumulation in the composites. Different numbers of applied cycles per block were used: n1 and n2 = 10, 100, and 1000 cycles. The change in temperature along with stress acted as thermal cycle that further introduced damages into the composites and reduced their life. As the number of applied cycles increased, the failure life of the composites was increased. The small number of cycles per block showed a shorter life due to more frequent changes in temperature level.
Multiaxial Thermo-mechanical Deformation Behavior of IN 738 LC and SC 16
Authors: Ziebs J , Meersmann JFC , Kühn HJ , Klinglehöffer H
Published: April 2008

A study was undertaken to develop an understanding of the fatigue life on IN 738 LC under simple and simulated in-service operating thermomechanical cycling (TMF) in air. The experiments were conducted in the temperature ranges 450 – 950 °C, 450 – 760 °C and 600 – 850 °C. Results indicate that the lives differ with strain-temperature phasing. Diamond cycles gave the longest lives. A life prediction assessment is proposed based on the inelastic work ∑ MF σij Δεinij at Nf. It is, shown that the J2 theory is applicable to TMF loadings. Initial experiments on single crystal superalloy SC 16 prove that there is a non-uniform strain distribution in the plastic region along the circumference of [001] oriented specimens. These findings must be weighed when performing TMF tests.
Development and Industry Acceptance of Nuclear Gauges
Authors: Troxler WF
Published: April 2008

Mr. William F. Troxler delivered the keynote speech at the ASTM SYMPOSIUM ON CONSTRUCTION AND CONTROLLING COMPACTION OF EARTH FILLS, presented on July 1, 1999 in Seattle, Washington. As an original contributor to in-situ moisture and density measurement, Mr. Troxler detailed the history of how these devices were developed and accepted in the construction industry.

Beginning with his early work for the US Department of Agriculture and NC State University School of Agriculture to develop a device to measure the water content, Mr. Troxler describes how this device was combined with a similar device that measures the density of soils to create the surface moisture/density gauges used in the highway construction industry. The first models of this device were unacceptable because of the errors created by the chemical composition and other factors. Mr. Troxler explains how the development of calibration blocks with permanent density and moisture content values improved the gauge precision to the extent that the devices were more precise than current methods employed in the industry. Additional points of interest are included to explain how the nuclear moisture/density gauge became a standard test method in the industry.