bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Mechanical Analysis as a Complementary Damage Characterization Technique for Composite Materials
Authors: Osiroff R , Stinchcomb WW 
Published: March 2009

The applicability of mechanical spectroscopy as a potential complementary technique to characterize damage and fatigue response of fiber-reinforced laminates was investigated. The interaction between damage induced by cyclic mechanical loads and time-dependent behavior was examined [1,2]. The magnitude and nature of the damage and mechanical response were evaluated.
The effects of fatigue damage on the time, temperature, and frequency response of fiber-reinforced laminates were measured by performing dynamic mechanical analysis (DMA) tests on composite coupons which had been subjected to different amounts of fatigue loading and which exhibit varying degrees of fatigue-induced damage. Creep tests at different temperatures were conducted. Frequency multiplexing was accomplished over a temperature range encompassing the glass transition temperature. The effects of frequency on the temperature transitions of the loss and storage moduli were observed.
The DMA test results were interpreted in light of other conventional measures of fatigue response, such as change in dynamic stiffness and residual strength, and compared to nondestructive evaluation data of the different damage modes present in the laminates.
This paper includes a discussion of the applicability of DMA as a potential test methodology to investigate the effects of fatigue-induced damage on the viscoelastic behavior of fiber-reinforced laminates.
Packaging for the 90's: Convenience Versus Shelf Stability or Seal Peelability Versus Seal Durability
Authors: Matty JT , Stevenson JA , Stanton SA 
Published: March 2009

As the popularity of shelf-stable convenience foods increases, there is an emerging need to develop reliable, polymer-based food packages with peelable, heat-sealed lids for foods packaged under hot-fill, aseptic, or retort processes. For these products, seal integrity and package durability are critical to product safety and consumer acceptance. These concerns, in conjunction with the need to provide the convenience of peelable lids, give rise to the challenge of evaluating various aspects of package performance influencing seal integrity, durability, and peelability. Proper evaluation of these parameters requires testing techniques that yield data that are indicative of the attribute under consideration. The results of these tests, along with some fundamental understanding of mechanical and chemical properties of the materials being used, are key factors for measuring the performance of the package “system.” Today, there are a variety of proprietary procedures for evaluating critical aspects of package performance. The plethora of test methods needs to coalesce into a set of standardized procedures that can be used to provide meaningful product performance data communicated in a common language that can be utilized and understood by all of the diverse groups involved in taking a packaging “system” from a concept to the grocery shelf. This need is critical in markets where issues such as consumer safety and liability risks are major factors influencing packaging acceptance.
This presentation provides a detailed review of techniques and equipment developed for easy-to-use, reproducible, standardized procedures to evaluate the performance of polymer-based food packages. It also discusses test results and their relationship to package performance. The discussion will focus on test methods, including equipment and instrumentation, applicable to: 1. Container seal integrity. 2. Lid peelability. 3. Container abuse resistance.
Normalized test data are used to supplement the discussion of the procedures utilized. The impact of fundamental specimen properties, instrument response limitations, and other factors influencing the results will also be reviewed.
Endosteal Osteolysis Around Well-Fixed Porous-Coated Cementless Femoral Components
Authors: Jasty M , Maloney WJ , Harris WH , Galante JO , Callaghan JJ 
Published: March 2009

Seventeen cases of focal endosteal femoral osteolysis around cementless porouscoated femoral components of total hip replacements that were judged not to be loose on the radiographs were identified and analyzed. Fourteen of these cases were from a retrospective review of 474 cementless total hip replacements with a minimum two-year follow-up done by the authors. The incidence of the osteolysis was approximately 3% for femoral components made of both titanium-based alloys and cobalt-chrome-based alloys.
Four of the patients underwent reoperations for osteolysis. All four femoral components were found to be rigidly fixed to the skeleton at surgery. Three of these showed extensive bony ingrowth into the porous coatings on histology. The tissue in the region of osteolysis had a fibrous stroma. However, it contained focal aggregates of macrophages and rare giant cells. On light microscopy, evidence of fine intracellular particulate polyethylene and metallic debris was found in three of the cases. In the fourth, there was a fine fibrous membrane lining a cystic cavity. Although the tissue in the fourth case contained occasional macrophages, foreign material could not be identified on light microscopy. On electron microscopy, however, fine electron-dense particles consistent with metal were noted within the macrophages of this case.
Although these findings represent a small number of cases, they caution against the assumption that femoral osteolysis can be eliminated by using uncemented components. The precise cause for the osteolysis around uncemented porous-coated femoral components is not known. However, it seems that particulate debris from implanted biomaterials, such as metal and or polyethylene, seems to play an important role in the production of osteolysis around prosthetic components. The debris is much smaller and less frequent than that previously observed with cemented components.
Failure Mechanism of a Metal-Backed Patella: An Implant Retrieval Study
Authors: Stulberg BN , Schickendantz M , Merritt K , Bauer TW 
Published: March 2009

Four patients with a single-design metal-backed patellar component underwent revision of patellar components of both knees. In each case, a markedly symptomatic side and a mildly symptomatic side were present. Implant retrieval analysis allowed the authors to confirm a mechanism of implant failure we have postulated previously. This type of failure was characterized as a Type II metal-backed patellar failure mechanism, as it is specifically related to failure of the ultrahigh-molecular-weight polyethylene (UHMWPE) and not to fixation of the implant. This failure pattern can result in massive intraarticular wear debris deposition.
The defined mechanism of failure is (1) UHMWPE deformation or wear, leading to (2) UHMWPE split or fracture at the implant periphery, (3) widening/deformation of the capture mechanism with loss of UHMWPE capture, and subsequent (4) metal-to-metal abrasion—the final component of debris generation.
The design parameters resulting in this failure mechanism include (1) UHMWPE that is too thin, (2) a capture mechanism dependent upon UHMWPE integrity, (3) a patellofemoral geometry that allows the possibility of edge loading.
As patellar fixation does not appear to be a clinically significant problem with cemented all-UHMWPE components, the use of metal-backed patellar components, by any technique or with any design, appears unwarranted.
Use of Profile Imaging to Assess Patellofemoral Congruity: Implications for Assessing Patellofemoral Wear in Total Knee Arthroplasty
Authors: Stulberg BN , de Swart RJ , Reger SI , Easley K 
Published: March 2009

Profile imaging can be used to image the articulation of the patellofemoral joint of total knee implants. Using undamaged implants, conformity of the two articulating surfaces could be traced at angles of 50, 70, 90, and 120° of knee flexion. This was applied to five different styles of implants.
Femoral and patellar implants were retrieved from 40 patients undergoing revision total knee arthroplasty (TKA). Only all-polyethylene dome-shaped components were selected. Patellar implants were studied and graded for evidence of wear. Conformity data were then compared with wear data to assess the possible relationships between design parameters and subsequent wear.
Statistically significant differences in wear could be identified as they related to conformity of the articulating surfaces. Sharp patellofemoral edges and carbon-reinforced polyethylene (CRPE) patellar components were a particularly worrisome combination.
Profile imaging is a useful additional tool for assessing design features of implants and their subsequent relationships to implant-generated wear debris.
Advances in One Part Polysulfide Sealant Technology
Authors: Fiorillo AR 
Published: March 2009

One of the major drawbacks of one part polysulfide sealants is their extremely slow cure rates compared to other types of sealants.
Major studies have been conducted in an effort to find ways of accelerating the cure of one part polysulfide sealants. New formulating techniques and new developments in curative technology have shown that one part polysulfide sealants can be formulated that have cure rates similar to other generic types of sealants while maintaining good shelf life stability.
Sealants will be discussed that have been formulated based on these studies. These sealants have been tested and found to meet all the requirements of ASTM C-920.
Quantitative Fracture Surface Analysis of Fatigue Crack Propagation Under Variable Amplitude Loading
Authors: Ranganathan N , Benguediab M , Henaff G , Adiwijayanto F 
Published: March 2009

A method for quantitative analysis of fatigue fracture surfaces has been developed in our laboratory. Firstly, the salient features of the proposed method are presented based on the results obtained under constant amplitude (CA) tests at five R ratios for the 2024 T351 aluminum alloy.
Secondly, the proposed method is applied to fatigue crack growth under variable amplitude loading. Two kinds of tests were studied, simple block loading (BL) consisting of four mean load levels with different number of cycles at the highest R ratio. These tests were also carried out on the 2024 T351 alloy. Finally, variable amplitude loading (VAL) tests using a transport aircraft wing spectrum were carried out on three different aluminum alloys, including an aluminum lithium alloy.
In the case of BL tests the spatial distribution of striations and dimples are quantified with respect to the maximum stress intensity factor. After comparison with CA results, it is shown that the peak to peak load ratio and the highest load ratio in a block are important parameters in determining the fracture surface appearance.
For VAL conditions, the results obtained for the 2024 T351 alloy show that the spatial distribution of the significant fractographic features is quite similar to that obtained at R ≃ O under CA conditions at Kmax levels corresponding to the maximum load in the spectrum. Comparison of fracture aspects under VA conditions for the different aluminum alloys shows that a larger amount of striation like features rather than dimples produces a better crack growth resistance. It is also shown that the presence of secondary cracks may also have a beneficial effect on the crack growth resistance.
In the discussion, a technique for the determination of Kmax and equivalent R ratio for VAL conditions is proposed.
Fractographic Study of Notch Fatigue Crack Closure and Growth Rates
Authors: Sunder R , Prakash RV , Mitchenko EI 
Published: March 2009

A fractographic study was carried out on fatigue crack closure and crack growth rates in an Al-Cu alloy under conditions of monotonic and cyclic yield at the notch root. Comparative tests were also conducted on smooth specimens subject to elastic loading conditions. A notch root fatigue crack can see substantial difference between crack closure and opening stress. This difference is considered responsible for local mean stress effects observed in notch fatigue response to complex load sequences. The difference between closure and opening stresses diminishes to negligible proportions as stress excursions reduce to elastic interval and is therefore hardly observed in long cracks.
To support validation effort on predictions, notch root crack growth rates were determined from optical fractography under a programmed load adaptation of the FALSTAFF load sequence. The results of these measurements suggest that scatter in short crack growth data is similar to that in long cracks at comparable growth rates. Life to initiation of (naturally initiating) multiple notch root cracks is dissimilar. The crack having been in existence longest appears to assume the role of the dominant crack and accelerates others (smaller) cracks.
Measures of Fuel Thermal Stability — Which Answer is Correct?
Authors: Clark RH , Bishop GJ 
Published: March 2009

It is highly desirable to be able to predict the degree of fuel thermal degradation within a jet engine fuel system from simple chemical parameters or rapid small-scale testers. However, given the complexity of the problem, which includes such variables as system components, fuel heat history, fuel flow regimes and residence times, it is likely that no one single measurement can hope to provide the answer.
Shell Research's approach to investigating jet fuel thermal stability is proceeding along three parallel fronts:- • Large-scale rigs realistically simulating engine components, so enabling predictions of fuel performance in the real environment. • Critical examination of the JFTOT specification test, assessing its ability to predict service fuel performance unequivocally. • Fundamental mechanistic studies to provide the necessary chemical background for the studies. These include analyses of fuel composition and kinetic measurements of fuel oxidation.
This paper describes each method, the advantages, disadvantages and nature of the measurement. The differences between the various types of measurement are explained. Finally, the results from each test are drawn together to yield a simple mechanism for fuel thermal degradation.
Use of Mechanistic Life Prediction Methods for the Design of Damage-Tolerant Composite Material Systems
Authors: Reifsnider KL 
Published: March 2009

An increasing number of engineering applications depend on the use of material systems such as fiber-reinforced composites. For the most part, the manner in which these systems are “designed” is presently heuristic. Although much analysis and understanding of “how such materials are made” is available, there is comparatively less systematic rigor that addresses “how such materials should be made”. This is a serious inhibition to the exploitation of these materials and material systems.
During the last few years, a variety of approaches has been developed for the analysis of composite materials, especially fiber-reinforced systems. The body of literature is especially replete in the technical area of “effective stiffness” models, many of which are sophisticated and well founded—and reasonably well validated. A comparable body of work which addresses “effective strength” is not available. However, the author and his colleagues have developed a mechanistic approach of this type, that is generally referred to as the “critical element concept,” whereby careful laboratory work is used to define representative volumes of material that enclose a “typical” failure mode. This representative volume is divided into a “critical element” that controls the final failure event, and “subcritical elements” that alter the local stress state around the critical element.
The present paper extends this concept to the fiber/matrix level by introducing micromechanical strength models to be used in the critical elements. The result of this advance is that mechanistic models that include explicit representations of the parameters that describe the manner in which the material systems are made can be used to estimate remaining strength when those parameters change during the lifetime of the material. Moreover, the model can then be used to “design” or tailor a material system for specific long-term performance. This last topic is the focus of the present paper. The approach will be demonstrated, and the influence of several parameters will be discussed. This discussion will then be used to advance several concepts for the rigorous design of material systems for damage tolerance.
Exact Determination of ΔKeff and Crack Propagation Prediction for Selected Loading Sequences
Authors: Zhang SJ , Döker H , Nowack H , Schulte K , Trautmann K-H 
Published: March 2009

In the present study the correlation between the crack opening and crack propagation behavior under selected loading histories was systematically investigated on center cracked Al 7475-T7351 specimens. The development of the crack opening stress intensity Kop as the lower limit of the effective stress intensity factor range ΔKeff, has been determined using the near threshold crack growth (NTCG) method as proposed by Döker and Bachmann. Significant crack closure (i.e., ΔKeff &lt; ΔK) was found for all sequences, and also for those at very high R-ratios (R &gt; 0.83). The crack growth behavior was determined by the DC-potential drop method and by striation measurements and showed significant retardation. The Kop values correlated with the da/dN measurements.
The experimentally determined Kop and da/dN behavior was compared to predictions as performed by J. C. Newman, Jr. applying his advanced FASTRAN II model. The predictions of the development of the Kop and of the da/dN values compare quite well except in one case, where the model predicted complete crack arrest. The affected cycle numbers for the retardation periods were also satisfactorily predicted (except in that one case). From the investigations performed in the present study it is concluded that exact measurements of the trends in Kop as caused by load sequence effects form an important basis for further improvements of crack propagation calculations.
FEM Analysis of Cyclic Deformation Around the Fatigue Crack Tip After a Single Overload
Authors: Oliva V , Kuneš I 
Published: March 2009

A two-dimensional elastoplastic finite element method (FEM) program was developed for analysis of cyclic deformation around the fatigue crack tip under variable amplitude loading. Edge fatigue crack growth in a thin rectangular AlCu4MglMnl plate under repeated tensile loading with a single 50% overload cycle was modeled. The computations show in detail the specific effects of an overload leading to the delayed retardation of the crack.
Results of the analysis were used for a direct estimation of crack growth rate according to Sih's energetic theory. A concept of “dead cycles” without crack advance was introduced to eliminate the influence of an unrealistically large crack jump in a model cycle. The crack growth rate was computed from the strain energy density change in the dead cycle and from the critical strain energy density resulting from low-cycle fatigue tests. For constant amplitude loading, the theoretical crack rate approximately agrees both with the experiments and with the crack rate determined from the crack opening stress by the ΔKeff method.
Problems with Current Methodology in Using the Arrhenius Equation to Predict the Long-Term Behavior of Polymeric Materials in Geotechnical Environments
Authors: Bright DG 
Published: March 2009

Polymeric materials used in earth structures and waste containment sites have minimum performance requirements to be maintained over a service life ranging from 1 to 100 years. The ability to predict the material performance in these applications with time has great appeal. However, it is necessary to know the mode, mechanism, and profile of behavior of these materials over an anticipated lifetime. Today, there is a proliferation in the use of rate expressions supposedly representing a material's response with time to a specific environmental condition. The objective is to review the impact of current protocol and simplifying assumptions on the prediction of long-term behavior of polymeric materials.
The problems with the current methodology are multiple. For a specific environmental condition associated and polymeric material, literature shows that the rate expression and its order vary with the experimenter and his or her parameters of choice in measuring the material's behavior. Thus, the integrated expressions predict different behaviors with time. Elevated temperatures are commonly used to accelerate a deteriorative mode sufficiently to collect data within a reasonable time frame. Typical range of elevated temperatures commonly traverse at least one polymeric phase transition. Deteriorative mechanisms change with physical state thus affecting the development of rate parameters representative of another physical state. Within the Arrhenius equation, the rate constant (k) is to be a function solely of temperature, and the activation energy (E) is to remain constant over the temperature range of evaluation and extrapolation and with time in long-term predictions. Literature has established that a ±1.0 kcal/mol (4.186 kJ/mol) error in E will cause an error of ±100% at a 95% confidence level in the extrapolation of kinetic rate predictions from 225 to 25°C.
The engineer and designer will see the dangers and the consequences associated with using rate expressions supposedly representing a deteriorative mode, and the impact of methodology and simplifying assumptions commonly employed to predict long-term behavior.
Mono-Energetic Mono-Directional Resonance Neutron Activation of Natural Indium Metal Target
Authors: Ertek C , Oigawa H 
Published: March 2009

The mono-energetic neutrons of 1.456eV energy are obtained from 1 MWth TR-I SWIMMING POOL TYPE RESEARCH REACTOR using double collimated beams and BRAGG reflection of pure Beryllium mono-crystal with extremely fine energy resolution.
Foil thickness for 3 foils were 26.,28. and 44.10-4 cm and they were perpendicular to the beam of mono-energetic neutrons and were irradiated in sandwich form. After irradiation, the saturation activities were obtained using Phillips two-pie special “beta-ray” detector in a well controlled and shielded geometry. Counting reproducibility was excellent(better than 0.1%). SPECIAL ATTENTION was paid to the irradiated(side A) and non-irradiated(sideB) sides of the foils. Usual irradiation and decay corrections were applied to obtain the saturation activities.
In this work, the preliminary calculations of reaction rates using Nakazawa M. et al.,JENDL Dosimetry file, JAERI 1325,(1992) were performed. Considerable differences are found between the calculations and experiment and possible reasons are still under investigation. The preliminary calculations of reaction rates using ENDFB/VI are in agreement with JENDL-3 estimates. Absolute reaction rate estimates are not yet ready.
Considerable numbers of research centers are interested in the experiment and very constructive inputs are expressed and obtained from Hiroyuki Oigawa, Shigeaki Okajima and T. Mukaiyama, JAERI, Japan; N.P. Baumann and K.O. Ott, USA; E. Zsolnay and E. Szondy, Hungary; M.C. Lopes and J. Molina,Portugal; F. Bensch, H. Böck Austria; and M. Turgut and A.Ìsyar,Turkey, Investigations using collision theory,multiple scattering and monte-carlo techniques have been undertaken.