Sealed Specimens Research Articles

Fatigue behaviour of double lap riveted joints assembled with and without interfay sealant

Fatigue tests on ‘double shear’ riveted specimens were carried out. Material was aluminium alloy, 7075-T73, thickness 3 mm. Specimen surfaces were protected by chromic acid anodization and epoxy primer. The mating surfaces of some specimens were sealed by a two-component manganese-dioxide cured, polysulfide compound. Specimens were pre-assembled by inserting a temporary spring fastener in a pilot hole. The holes were reamed to the final diameter after sealant curing; then the Hi-Loks were installed. Comparative fatigue tests were carried out on dry assembled specimens. Quite surprisingly, the fatigue resistance of sealed specimens was very low when compared with the results of dry assembled specimens. Hysteresis cycles measured in sealed and un-sealed specimens clearly indicated a lubricant effect of the sealing layer, which justified the results obtained. Additional tests were performed on specimens assembled by applying different clamping force during the sealant curing time. The results obtained indicated an independence of the fatigue resistance on this parameter. Different failure modes were observed in sealed and un-sealed specimens: fatigue cracks nucleated outside the hole at a location in the shadow of the rivet in the un-sealed joints, while fatigue cracks nucleated at both sides of the holes in sealed joints. Finite element calculations carried out under different values of the friction coefficient between the mating surfaces confirmed the different location of the fatigue critical areas in sealed and un-sealed specimens.

Effect of Dust Particle Inflow on the Wear of Rubber Seal Material in Automobile Chassis System

In an automobile chassis system, several environmental factors reduce the durability of automotive components. In particular, dust particles entering through rubber seals increase the friction and wear of sliding surfaces. Increased wear causes noise, fracture, and reduced service life of components. In this study, dust particles were collected on the chassis while driving. The particle sizes and ingredients of the dust were analyzed using microscopy, scanning electron microscopy, and energy-dispersive X-ray. It was found that SiO and AlO were the main ingredients of the dust particles. Based on our analysis of the data, wear tests were performed with the rubber seal specimens using a ball-on-disk type sliding wear tester. When SiO and AlO particles came into contact with the rubber seal specimen, two-body and three-body abrasive wear took place. In tests of SiO particles only, the wear volumes of rubber seal specimens were increased by increasing the particle's injection amount and the size of the dust. In a test of the mixed particles (SiO and AlO), four mixing ratios (8:1, 4:1, 2:1, 1:2 [SiO:AlO]) were used based on the analysis data. When the same size particles of SiO and AlO were used, the wear amounts of the rubber increased with a higher percentage of AlO, which is harder than SiO. When mixed particles with 26.6 μm of SiO and 1 μm of AlO were used, wear increased with increased amounts of SiO.

The calculation and analysis of glass-to-metal sealing stress in solar absorber tube

The failure or degradation of solar absorber tubes is the single largest cost factor for current parabolic trough solar power plant. The main failure reason is that there are residual stresses in the glass-to-metal joint which are generated during the cooling process of sealing. According to the thin shell theory and thermal stress theory, this paper presents the analytic solution for the glass-to-metal sealing residual stress. It also analyses how the thickness of glass tube, thickness of metal ring, and thermal expansion coefficient affect the residual stress distribution. In order to verify the calculation results, the photoelastic technique is used to measure the residual stress and the tensile test is used to obtain the point of the most dangerous stress and the tensile strength for the sealed specimens. It can be concluded that the maximum tensile stress happens at some distance near the sealing interface on the outer surface of glass tube. The seal strength increases when the thickness of the glass tube is increased. The analytic solution is proved feasible to analyze the residual stress of glass-to-metal seals in solar absorber tubes.

An irreversible dipping sealing technique for anodized ZE41 Mg alloy

Anodized coatings are porous and sealing has been considered to be an essential step for anodized magnesium alloys. In this study, a new sealing technique was proposed and validated. Anodized ZE41 was dipped in an E-coating bath solution for a few seconds. After baking, the specimen was found to have considerably improved corrosion resistance. The corrosion rate and polarization current densities were found to be more than 3 orders of magnitude lower and the film breakdown potential over 50 mV higher for the anodized ZE41 after sealing in the E-coating bath solution than for the as-anodized ZE41. An irreversible electroless E-coating deposition model and corrosion mitigation mechanism for a sealed specimen are proposed.

Effect of postreatment on the corrosion behaviour of tartaric–sulphuric anodic films

Unclad and clad AA2024 T3 specimens were anodised in a chromium-free tartaric–sulphuric acid bath (TSA) and subsequently postreated by different processes including impregnation in a cold, concentrated chromate solution, Cr-free hot-water sealing, and dichromate hot-water sealing. The purpose of this work is to evaluate the effectiveness of the classical postreatments used in the aircraft industry on the TSA-anodic films and their corrosion resistance behaviour. TSA-anodic films were characterised by scanning electron microscopy (SEM) and their thicknesses were measured by SEM and the eddy current method. Electrochemical impedance spectroscopy (EIS) was used to characterise the barrier and porous layers, and jointly with potentiodynamic polarisation allowed the evaluation of corrosion resistance parameters with immersion time in NaCl solution for anodised and postreated specimens. In all cases the postreatments increased the resistance of the barrier layer against degradation. However, the NaCl electrolyte easily penetrated TSA-anodised porous layers when they were not postreated, while penetration was slightly more difficult in cold-postreated specimens. The effective pore plugging was observed in the sealed TSA specimens resulting in an improved corrosion resistance. On the other hand, unsealed clad AA2024 specimens showed a self-sealing process of the TSA-anodic layer, which was slower for the cold chromate solution-postreated specimens.

Investigation of 3D Moisture Diffusion Coefficients and Damage in a Pultruded E-glass/Polyester Structural Composite

As civil engineers seek to improve buildings and bridges, they are turning to composite materials for some structural components. Thus the long-term life of these materials in damp highly acidic conditions (from concrete pore solutions) is critical. This article presents a study of moisture ingression and damage in a pultruded compression element under exposure to pore solution. The goal was to experimentally find the orthotropic diffusion coefficients for pore solution in the composite material and to evaluate the damage in the composite using SEM. A method for calculating 3D diffusion coefficients based on weight measurements by selectively sealing some surfaces against moisture ingression was successfully employed. This research extends the application of the 3D diffusion solution developed by Pierron et al. [3] to selectively sealed specimens of fixed dimension. The Arrhenius equation was then used to model the diffusion coefficients with respect to temperature. For the first time, sequential SEM images were performed in the same location before and after specimen exposure in an attempt to identify damage development separately from initial damage. These images showed little if any change in specimens exposed at room temperature over the first 19 days: however, characteristically different damage was notable at elevated temperature and for a specimen exposed for 650 days.

Experimental and numerical evaluation of contact pressure in pneumatic seals

An experimental procedure is presented for measuring contact pressure between a pneumatic seal and its counterface. Measurements were performed using pressure-sensitive films, for which a suited calibration procedure was developed, also taking into account humidity influence. Having validated the experimental procedure on a lip seal rectilinear specimen, tests were carried out on commercial piston seals. Results were compared with those coming from numerical simulations performed using a finite-elements analysis.

Imaging of zymogen granules in fully wet cells. Evidence for restricted mechanism of granule growth

The introduction of wet SEM imaging technology permits electron microscopy of wet samples. Samples are placed in sealed specimen capsules and are insulated from the vacuum in the SEM chamber by an impermeable, electron-transparent membrane. The complete insulation of the sample from the vacuum allows direct imaging of fully hydrated, whole-mount tissue. In the current work, we demonstrate direct inspection of thick pancreatic tissue slices (above 400 mum). In the case of scanning of the pancreatic surface, the boundaries of intracellular features are seen directly. Thus no unfolding is required to ascertain the actual particle size distribution based on the sizes of the sections. This method enabled us to investigate the true granule size distribution and confirm early studies of improved conformity to a Poisson-like distribution, suggesting that the homotypic granule growth results from a mechanism, which favors the addition of a single unit granule to mature granules.

Plasma sprayed ceramic coatings without and with epoxy resin sealing treatment and their wear resistance

Plasma sprayed aluminum oxide-based coatings (Al 2O 3) are mainly used as a wear resistant surface covers in mechanical applications. Previous studies have shown that abrasion wear resistance of these coatings can be significantly improved by applying a sealing treatment. It was reported that this improvement is mainly due to microstructural toughening which takes place via the sealing process. Therefore, this study was conducted in order to determine the influence of the microstructural characteristics governed by the spray system settings and epoxy sealing on the wear resistance of these coatings. Unsealed and epoxy resin sealed plasma sprayed specimens prepared from alumina as well as alumina-13% titania were studied. Abrasion wear resistance of these coatings was evaluated employing the standard slurry abrasion response (SAR) and the standard dry sand rubber wheel (DSRW) abrasion tests. The coatings microstructure was characterized by light microscopy and their worn surfaces were analyzed using scanning electron microscopy. Porosity, microhardness and surface roughness of unsealed and sealed coatings were also compared. It was shown that the abrasion wear resistance of the epoxy resin sealed coatings is significantly better than that of the as-sprayed coatings for both types of applied tests.

A novel system for in-situ observations of early hydration reactions in wet conditions in conventional SEM

A novel system enabling wet microscopy in conventional SEM is described and its performance for in-situ study of hydration reactions is demonstrated. The technology is based on a sealed specimen capsule, which is protected from the microscope vacuum by an electron-transparent partition membrane. Thus, the wet sample can be placed and observed in a “conventional” SEM without the need for drying or employing environmental SEM. Early hydration reactions of gypsum and cement systems were followed during the first 24 h.

A Motor Vehicle Accident Fatality Involving the Inhalation of 1,1-Difluoroethane

A 24-year-old female driver with a history of substance abuse was pronounced dead following a single car motor vehicle accident. A surviving front seat passenger witnessed the decedent inhaling "Dust Off" cleaner just prior to losing control of the vehicle. The propellant compound used in this product is the halogenated hydrocarbon 1,1-difluoroethane (DFE). Sealed autopsy specimens were examined for the presence and subsequent quantitation of DFE utilizing an Agilent 6850 gas chromatograph (GC)-flame-ionization detector. The levels of DFE obtained were as follows: 29.8 mg/L in femoral blood, 40.3 mg/L in pulmonary arterial blood, 85.6 mg/L in aortic blood, 79.9 mg/L in chest cavity blood, 21.2 mg/L in vitreous, 11.7 mg/kg in brain, 27.9 mg/kg in liver, 71.0 mg/L in urine, and 51.8 mg/total gastric contents. The presence of DFE was confirmed in the decedent's urine by injection on an Agilent 6890/5973 GC-mass spectrometer in full scan mode. This case presents a uniquely witnessed observation of the apparent impairing effects and consequences of the acute inhalation of halogenated hydrocarbons such as DFE and the operation of a motor vehicle. The proximity of time of death to inhalant use may also provide insight to postmortem distribution patterns of DFE in relation to normal physiologic blood flow. With further investigations, estimating the time of final use of an inhalant prior to death may be deciphered from such patterns, although a degree of caution should be applied in deaths resulting from severe trauma in which normal tissue structure is compromised because postmortem redistribution may result.

CT Colonography: Effect of Colonic Distension on Polyp Measurement Accuracy and Agreement—In Vitro Study

To investigate the effect of colonic distension on polyp measurement accuracy and reader agreement. Institutional review board permission was obtained. A sealed colectomy specimen from a patient with familial adenomatous polyposis was scanned using a four-detector-row computed tomography (CT) after half and full air distension. A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were used to individually match polyps visible in the CT datasets. Two observers (radiologist, technician) independently estimated the maximum polyp diameter using both two-dimensional (2D) and three-dimensional (3D) surface rendering. Full-distension measurements were repeated 1 week later. Accuracy was analyzed using paired t-test. Observer agreement was assessed using Bland Altman limits of agreement. Twenty-three polyps (4-15 mm) were identified. 2D measurements were significantly smaller than histologic size at both half distension (radiologist first): mean difference [md] -1.1 mm, md -1.7 mm, and full distension md -1.1 mm, md 1.4 mm (all P < .001). 3D measurements were not significantly different from true size other than after half distension for the technician (md -0.7 mm, P = .01). 95% Bland Altman limits for interobserver agreement were narrower after full distension, and better using 2D (half-distension span of agreement approximately 4.7 mm and 6 mm for 2D and 3D, respectively). 2D intraobserver span of agreement between half and full distension was approximately 3.8 mm and 3.2 mm for the radiologist and technician, respectively, compared with 6.2 mm and 5.5 mm using 3D. 3D polyp measurement is more accurate than 2D. However, in the presence of suboptimal distension, inter- and intraobserver agreement is superior using 2D.

CFRPパッチ接着したアルミニウム合金材の塩水浸漬による強度低下に関する研究

CFRP composite patches have been widely used to repair damaged structural components of metallic aircrafts. Though CFRP is well-known as a corrosion-resistant material, once the carbon fibers of CFRP are in direct contact with aluminum alloy, the galvanic interaction between CFRP and aluminum induces the corrosion of aluminum alloy resulting decrease of the joint strength. In this study, tensile specimens made of two pieces of aluminum alloy plates joined with a single-lap cocured patch of unidirectional CFRP prepreg were immersed in salt water for 49 days maximum. For some of the specimens, silicon sealant was applied around the edge of the joint for waterproofing. Every 7 days of immersion, changes in electric potential and in electric resistance were measured followed by the tensile testing. After 49 days of immersion, the joint strength of sealed specimen was found to be more than four times higher than that of unsealed one. The relationship of the joint strength with the change in electric potential and that with the change in electric resistance were obtained. The joint strength was successfully estimated by the change in electric potential and electric resistance.

Sevoflurane Analysis in Serum by Headspace Gas Chromatography with Application to Various Biological Matrices

Sevoflurane is a nonflammable general anesthetic administered by inhalation of vaporized liquid that rapidly partitions out of aqueous biological matrices into a gaseous phase because of its volatility and hydrophobicity. We describe a headspace analysis of sevoflurane that can be performed without the use of an expensive automated headspace analyzer. Sevoflurane standards (0-109 mg/L) and quality control specimens (12.2 and 72.9 mg/L) were prepared and quantitated on an intraday and interday basis. Headspace gas was manually injected (150 degrees C) with a 2.5-mL gas-tight syringe into a Perkin-Elmer model 8500 gas chromatograph equipped with a 6-ft x 2-mm i.d. glass column (100 degrees C) containing 0.2% Carbowax 1500 on Carbopak C packing with a flame-ionization detector (200 degrees C), which allowed for elution of the internal standard, 1-propanol (1.56 min), and sevoflurane (2.92 min). Linear regression of the peak-area ratios of sevoflurane to 1-propanol (6.38 g/L), versus the sevoflurane concentrations yielded an average intraday correlation coefficient of 0.989 (S.D. = 0.003, n = 5) and mean quality control specimen values of 14.19 mg/L (C.V. = 5.1%, n = 5) and 66.72 mg/L (C.V. = 3.3%, n = 5). The average interday standard curve correlation coefficient was 0.987 (S.D. = 0.01, n = 5), and the mean quality control specimen values were 12.22 mg/L (C.V. = 13.7%, n = 5) and 74.27 mg/L (C.V. = 8.7%, n = 5). The chromatographic method described produced accurate and reproducible results with a simple on-column headspace gas injection. This method allows for quantitation of sevoflurane in various biological matrices by chromatographic separation of the headspace gas in a sealed specimen container.

Is Superposition of Creep Strains Valid for Concretes Subjected to Drying Creep?

This paper describes an experimental study that examined validity of superposition of creep strains for specimens subjected to drying before loading, loading before drying, and sealed specimens subjected to uniaxial compression. Self-consolidating concrete (SCC) was used for ease of fabrication. Strains were measured using vibrating wire strain gages. In all 3 conditions, (drying before loading, loading before drying, and sealed concrete), creep recovery is only 70-80% of the creep of previously unloaded concrete for loads applied at the same age as the recovery. It can be concluded that superposition is not valid for concrete subjected to drying or sealed concrete in situations that involve unloading. For increasing loads, the validity of the principle of superposition of creep strains depends upon whether the concrete is sealed or subjected to drying. For drying before loading and loading before drying, the measured incremental creeps were 10 and 20% larger, respectively, than the creep of late loaded specimens. For sealed concrete, the creep due to an incremental increase in load was effectively identical to the creep of sealed, late-loaded concrete. The experimental results suggest an alternative hypothesis to calculate the strains recovered on unloading. The rates of development and magnitudes of the recovered creep strains were similar for all test series, suggesting that only basic creep can be recovered.

A Novel Method for “Wet” SEM

Progress in the processing of wet tissues, without the need of fixation and complex preparation procedures, may facilitate the microscopic examination of tissues and cells. Microscopic examination of tissues is a central tool in clinical diagnosis as well as in diverse areas of research. The authors present the application of Wet SEM, a technology for imaging fully hydrated samples at atmospheric pressure in a scanning electron microscope (SEM). The technique is based on 2 principles. First, samples are imaged in sealed specimen capsules and are separated from the evacuated interior of the electron microscope by a thin, electron-transparent partition membrane that is strong enough to sustain a 1-atm pressure difference. Second, imaging is done in a SEM, based on detection of backscattered electrons, which penetrate a few microns into the specimen and thus give information on the cellular level.

Sexual assault evidence collection more accurate when completed by sexual assault nurse examiners: Colorado's experience

Introduction The purpose of this study was to determine if sexual assault nurse examiners (SANEs) provide more effective evidence collection compared with non-SANE–trained nurse and physician colleagues. Methods Five hundred fifteen audits were completed by crime laboratory analysts on sexual assault evidence kits submitted to the Colorado Bureau of Investigation from October 1999 to April 2002. Results Of 515 evidence kits audited, 279 were completed by SANEs. Non-SANE physicians and nurses completed 236 kits. Evidence kits collected by SANEs were more likely to have a completed chain of custody (92%) compared with 81% of non-SANE–collected kits. SANEs also were more likely to have properly sealed individual specimen envelopes (91% vs 75%), to have labeled the individual specimen envelopes (95% vs 88%), and to have collected the appropriate amount of pubic hair (88% vs 74%) and head hair (95% vs 80%). SANEs more frequently included the appropriate number of blood tubes (95% vs 80%), collected the appropriate amount of swabs (88% vs 71%), and included a vaginal fluid slide for sperm motility (87% vs 72%). Both groups prepared slides at a high rate for each penetrated orifice (87% vs 90%) and both had a high rate of including the crime laboratory report in the completed kit (97% vs 93%). Discussion Studies such as this provide documentation that evidence collection kits prepared by SANEs are more accurate and complete when compared with evidence collection kits prepared by non-SANE nurses and physicians. Additional studies are needed to further validate the efficacy of SANE-completed evidentiary examinations.

Tissue-dissolution capacity and dentin-disinfecting potential of calcium hydroxide mixed with irrigating solutions

The goal of this study was to compare the tissue-dissolution potential and antibacterial effectiveness of a conventional Ca(OH)(2)/saline paste with equivalent Ca(OH)(2)/NaOCl and Ca(OH)(2)/chlorhexidine digluconate medications. Tissue specimens were obtained from freshly dissected pig palates. Tissue pieces of similar form and weight were incubated in air-tight containers with Ca(OH)(2) pastes or solutions proper for up to 7 days. Antimicrobial testing was performed in dentin blocks infected with Enterococcus faecalis. Medicated, sealed dentin specimens were incubated for 1 and 5 days, and bacterial growth was tested at different dentin depths. Up to day 4, the Ca(OH)(2)/irrigating solution mixtures dissolved tissue more effectively than the conventional Ca(OH)(2)/saline paste. After 7 days, however, no statistically significant differences were found between the saline and hypochlorite mixtures, but the Ca(OH)(2)/chlorhexidine medication was significantly less effective. Dentin block disinfection was quicker and more thorough with the Ca(OH)(2)/chlorhexidine or the Ca(OH)(2)/NaOCl than with the Ca(OH)(2)/saline paste. Ca(OH)(2)/irrigant mixtures under investigation appear more advantageous than the conventional Ca(OH)(2)/saline mixture, and merit further investigation in a clinical study.

SOUND TRANSMISSION THROUGH ELASTOMERIC BULB SEALS

The sound barrier performance of elastomeric vehicle weather seals was investigated. Experiments were performed on a single bulb seal specimen using a reverberation room method. The seal wall velocity was measured using a laser Doppler vibrometer. The sound pressure near the velocity measurement location was measured simultaneously, which allowed the sound intensity on both sides of the seal and the sound transmission loss to be determined. The vibration response and the sound transmission loss of the bulb seal were then computed using finite element analysis. Acoustic–structure interactions were considered for a partially coherent spatially distributed pressure excitation. The experimental data obtained using the reverberation room method allowed the validation of the numerical models. The resonance frequency due to the mass–air–mass mode of vibration was accurately predicted. The model was then used to numerically investigate the influence of various design parameters. It was found that the elastic modulus significantly affects the bulb seal resonance frequency, and that the loss factor of the material has major effects on the sound transmission loss around resonance.

Concentrations and enantiomer fractions of organochlorine compounds in baltic species hit by reproductive impairment

Concentrations and enantiomer fractions (EFs) of organochlorine compounds (OCs) were determined in tissues of gray seal (Halichoerus grypus) and salmon (Salmo salar) originating from the Baltic Sea. The selected seal specimens ranged from starved to unstarved animals, and some of them suffered from a disease complex, while the salmon samples originated from individuals, which were known to produce offspring with and without the M74 syndrome. Significant differences in residue levels and EFs were found between seal groups but not between M74 salmon and non-M74 salmon. The relations between chemical and biological variables of seal samples were investigated with multivariate statistics. Poor health status correlated strongly with age, while bad nutrition condition was associated mainly with high pollution loads and distinctively nonracemic chiral OC compositions. High biotransformation rate (as indicated by fraction of chlordane metabolites in relation to total level of chlordanes) was also associated with large deviations from racemic values and high contaminant levels.