Sealed Specimens Research Articles

Simulation and Experiment of Elastomer Seal for Pneumatic Servo Cylinder

The rubber seal is a part inserted into servo cylinder to keep the air pressure constant. In order for efficient movements of the servo cylinder, the frictional coefficient of the rubber seal needs to be minimized while the sealing is maintained. In this work the friction characteristics of rubber seal specimen are tested on metal plate at various conditions. The experimental conditions include roughness level, applied pressure, lubrication, and rubbing speed. The design of experiment approach is taken to assess the effect of each parameter. The nonlinear frictional response of the rubber is applied to the FEM model simulating the servo cylinder movement. The result demonstrates that precise optimization of the servo cylinder movement must be preceded by preliminary experiments coupled with the theory and FEM model.

EFFECT OF SURFACE SEALING ON STAIN RESISTANCE OF A NANO-HYBRID RESIN COMPOSITE

This study investigated the influence of sealant application on stain resistance of a nanohybrid resin composite compared to the efficacy of a bonding agent used as a surface sealant on prolonging color stability of the resin composite. 28 disc-shaped materials were prepared from a nano-hybrid resin composite Filtek Z550 and assigned to four groups: G1K: nonsealed; G2:Adper Single Bond; G3: Fortify ; G4: Biscover LV. After 24 h storage in distilled water at 37˚C, all specimens were subjected to thermocycling and immersed into coffee solution. Color measurements were performed using spectrophotometer (VITA Easyshade; Vident) according to CIEL*a*b* system. Color change values were significantly different among the groups in each evaluation period except for after thermocycling (p<0.05). For 7 days evaluation period, the difference between G3 and G4 group was statistically significant while G4 exhibited statistically significant differences (p<0.05 and p<0.0001 respectively) compared to control (G1) in 14 day whereas no significant difference was found between GI and GII in 28-day evaluation period. However, ΔE values of sealed specimens (GIII, GIV) differed significantly from non-sealed (GI) specimens after 28 days of immersion in coffee solution (p<0.05 and p<0.0001 respectively). It may be concluded that using a bonding agent as a surface sealant does not increase stain resistance of resin composites of the sealants evaluated. Biscover LV showed the highest efficacy to prolong color stability of the resin composite.

아스팔트 도로포장 유지보수용 표면처리공법의 공용성 평가

PURPOSES : The objective of this study is to evaluate the performance properties of chip seals and fog seals with polymer-modified emulsions. METHODS : The performance of chip seals and fog seals was evaluated on the basis of common issues in surface treatments. Granite aggregate and four types of asphalt emulsions (one of the unmodified and three of the modified emulsions) were used considering the usage in field. A Vialit test was performed to determine the aggregate retention, and the MMLS3 (Third Scale Model Mobile Load Simulator) test was conducted to determine the aggregate retention, bleeding, and rutting. In addition, the fog seal specimens were tested by the BPT (British Pendulum Test) to evaluate skid resistance. RESULTS AND CONCLUSIONS : Overall, the polymer-modified emulsions (PMEs) showed better aggregate retention and bleeding resistance for both chip seals and fog seals. When comparing the performance of the PMEs, the difference was not considerable. In addition, PMEs present significantly better rutting resistance than unmodified emulsions. For skid resistance, if the recommended mix design is applied, the specimens do not cause issues with skid resistance. Although all of the fog seal specimens were over the criteria for skid resistance, the specimen fabricated by the high emulsion application rate (EAR) of the unmodified emulsion was nearly equivalent to the skid value criteria. Therefore, the use of an unmodified emulsion with a high EAR should be carefully applied in the field.

AN ANALYSIS OF MECHANICAL PROPERTIES OF ANODIZED ALUMINUM FILM AT HIGH STRESS

In this paper, a new environmental-friendly electrolyte containing sulfuric acid and tartaric acid has been used as the substitute of chromic acid for anodization. The work discussed the influence of anodizing voltages on the fatigue life of anodized Al 2024-T3 by performing fatigue tests with 0.1 stress ratio (R) at 320 MPa. Meanwhile the fatigue cycles to failure, yield strength, tensile strength and fracture surface of anodic films at different conditions were investigated. The results showed that the fatigue life of anodized and sealed specimens reduced a lot compared to aluminum alloy, which can be attributed to the crack sites initiated at the oxide layer. The fracture surface analyses also revealed that the number of crack initiation sites enlarged with the increase of anodizing voltage.

Treatability of Melia composita using vacuum pressure impregnation

The performance of treated wood in the field is ultimately affected by retention and penetration of preservative in wood. In the present study, a new preservative system ZiBOC and a commercially used preservative copper-chrome-arsenate (CCA) were used for evaluation of treatability of Melia composita by the vacuum pressure method at different pressure levels in unsealed and end sealed specimens. The retention and penetration levels of both the preservatives were significantly different at (P< 0.05) in sapwood, heartwood and pith zones. Melia composita exhibited treatability class ‘C’ (21 – 42% penetration). The results revealed that longitudinal penetration in Melia composita was the dominant flow as examined by spot test for copper in unsealed and end sealed specimens.

A Prospective Study of In Vivo and Ex Vivo Sealing of the Human Inferior Mesenteric Artery Using an Electrothermal Bipolar Vessel-Sealing Device

Mesenteric vascular ligation is a critical step in minimally invasive colorectal surgery. This study assessed the quality of in vivo and ex vivo sealing of the human inferior mesenteric artery (IMA), as well as the relation of IMA stump and bursting pressure. This was a prospective experimental study in a tertiary-care teaching hospital. In total, 25 patients were included in the study. For the main outcome measures, bursting pressures were measured for each specimen. Ten freshly sealed specimens were histologically assessed for seal quality and lateral thermal damage. We evaluated 54 specimens from 25 patients for bursting pressure, of which 25 were primary sealed vessels (sealed in vivo at surgery) and 29 were secondary sealed vessels (sealed in the laboratory). The mean bursting pressure was 862 mm Hg. The mean diameter was 4 mm (range, 3-5 mm) with a standard deviation of 1 mm. Pearson correlation showed no correlation between diameter and bursting pressure (P=.187) or the length and bursting pressure (P=.247). There was no statistically significant difference in bursting pressures in the four groups of vessels based on length. One calcified vessel had a significantly lower bursting pressure of 89 mm Hg. There was no intraoperative or postoperative bleeding. Ten sealed specimens were sent for histological evaluation, which showed mean lateral thermal damage of 0.57 mm (range, 0-1.75 mm). The bursting pressure in IMAs sealed with a bipolar device is significantly higher than physiological pressures; thus, the device can be safely used in sealing the vessel during colorectal surgery. Additionally, the length of the vessel stump does not correlate with the bursting pressures. Care needs to be taken when the vessel is calcified, which can be a potential cause of a weak seal.

Effect of pre-soaked superabsorbent polymer on shrinkage of high-strength concrete

Pre-soaked super-absorbent polymer (SAP) was incorporated into high-strength concrete (HSC) as an internal curing agent to study its effects on early-age shrinkage and mechanical properties. On the basis of the capillary stress based model for shrinkage prediction of concrete, together with the experimental results of cement hydration kinetics, evolution of internal temperature and humidity, development of pore structure and mechanical properties, the working mechanism of SAP was discussed. Results indicate that the addition of pre-soaked SAP significantly reduces the autogenous shrinkage as well as the early-age shrinkage of HSC under drying condition. In sealed HSC specimens, the drop of internal humidity caused by the self-desiccation effect is notably postponed by addition of pre-soaked SAP. The addition of pre-soaked SAP slightly reduces the compressive strength of HSCs and this effect is more pronounced in early-age concrete. Furthermore, an insightful comparison of the behaviours of the internal curing water introduced by the pre-soaked SAP and the additional free mixing water in concrete was made. Results indicate that the internal curing water behaves differently from the additional mixing water in influencing the cement hydration kinetics, pore structure of hardened cement pastes and the mechanical strength of concrete, due to the different spatial distribution of the two types of water in the concrete bodies. The shrinkage-reducing effect on HSC due to the addition of extra internal curing water incorporated by pre-soaked SAP is much stronger than that of the additional mixing water. Besides, the internal curing water shows much less strength-reducing effect than the additional mixing water. In virtue of the shrinkage prediction model, the working mechanism of pre-soaked SAP in reducing autogenous shrinkage of HSC is proposed on the basis of the following two aspects. The participation of internal curing water in cement hydration process leads to a total volume gain of the hardening cement pastes. Meanwhile, the release of internal curing water from the pre-soaked SAP postpones the drop of internal humidity. The synergistic effect of these two factors effectively reduces the autogenous shrinkage of HSC.

Response of Elastomer Seal Materials to Solid Rocket Exhaust Emissions

To explore the effects of solid rocket motor emissions on spacecraft docking seals, a set of elastomer seals and sheet material were placed in the plume during an open-air ground-based test firing of one of NASA’s solid rocket jettison motors. The seal specimens were placed 86 ft (26.2 m) from the nozzle during an approximately 1.5 s firing outdoors. The conditions near the seals were generally hundreds of pounds per square foot of dynamic pressure and temperatures greater than 400°F (204°C) with high plume velocities. Worst-case flight conditions were imposed; however, high-altitude, near-vacuum conditions were not imposed. Thus, the chemistry, temperature, and pressures of the combustion products are expected to be slightly different compared to flight conditions. Because this was a ground-based test done outdoors, the specimens had the opportunity to be soiled by dusty winds, and it is possible contaminants on the seals may have come off after the firing and prior to examination and testing. The goal was to determine if exposure to the plume from the firing would physically damage the seals. Overall, the silicone-base elastomer seals were not measurably damaged by the emissions; leak rates were unaffected.

Effects of Water-Binder Ratio and Coarse Aggregate Content on Interior Humidity, Autogenous Shrinkage, and Drying Shrinkage of Concrete

Experimental studies on shrinkage and interior humidity of three series of concrete with three aggregate contents in each concrete under sealing and drying conditions were carried out. The results show that the development of interior humidity of concrete is influenced strongly by the water-binder ratio and curing status of the specimen. In dry conditions, a fast reduction of the interior humidity is accompanied with a fast increase of shrinkage strain of the unsealed specimen compared with that of the sealed specimen. The effect of coarse aggregate on the interior humidity is insignificant. The difference in interior humidity between exposed and sealed specimens decreases with the reduction of the water-binder ratio. For a given age, the autogenous and drying shrinkages decrease with the increase of coarse aggregate content. The addition of coarse aggregate has a more significant influence on drying shrinkage than autogenous shrinkage.

Solidification–microprestress–microplane (SMM) theory for concrete at early age: Theory, validation and application

This paper presents a new constitutive model describing the mechanical behavior of concrete at early age and beyond. This model, entitled solidification–microprestress–microplane (SMM) model, amalgamates the microplane model and the solidification–microprestress theory and takes into account all the most significant aspects of concrete behavior, such as creep, shrinkage, thermal deformation, and cracking starting from the initial stages of curing up to several years of age. Age-dependent viscoelastic behavior under variable hygro–thermal conditions is described according to the solidification–microprestress theory. Cracking/damage behavior is modeled through an age-dependent microplane model, in which the model parameters are assumed to be dependent on an aging variable evolving with the extent of early-age chemical reactions (hydration, silica-fume reaction, etc.) and temperature. Calibration and validation of the model is performed by the numerical simulations of the age-dependent response of sealed and unsealed specimens subject to a variety of loading conditions and/or drying. Comparison with experimental data shows that the SMM model can reproduce well the interplay of shrinkage, creep, and cracking phenomena during curing and drying.

Treatability evaluation of meranti with ZiBOC and CCA

Low permeability in wood can cause limited retention and penetration of preservative which ultimately affects the wood performance in the field. In the present study, Malaysian red, yellow and white meranti of the Shorea group were selected for evaluation of treatability using commercial copper–chrome–arsenate and ZiBOC – a new preservative system, by the vacuum pressure method at two pressure levels in unsealed and end sealed specimens. A significant difference (P<0·05) in retention levels of both the preservatives was observed in sapwood, heartwood and pith zones. White meranti exhibited treatability class ‘a’ while mottled penetration was observed in red and yellow meranti exhibiting class ‘c’. The spot test for boron, zinc and copper in unsealed and end sealed specimens revealed that longitudinal penetration was not the dominant flow in red and yellow meranti.

Macroholes in stalagmites and the search for lost water

Fluid microinclusions in stalagmites have provided samples of paleowaters present during the growth of the stalagmite, but only in microliter amounts. Genty et al. (2002) discovered much larger water‐filled macroinclusions in some stalagmites. Using computerized tomographic (CT) X‐ray‐scanning and magnetic resonance imaging (MRI) we searched for such macroinclusions in 21 stalagmites from diverse localities in North and Central America and the Caribbean. We show that most stalagmites contained numerous mm to cm‐sized internal cavities (macroholes). These do not penetrate the outer surfaces which in most cases are deceptively unblemished. Some stalagmites have up to 10% average internal porosity. Two types of macroholes are distinguishable: axial holes formed during growth due to slower calcite accumulation at the axial drip site; off‐axis holesformed penecontemporaneously with growth in discrete layers; these cut previous growth laminae showing that they are post‐depositional. Using MRI on uncut, apparently sealed specimens, we find that very few of these cavities contain significant quantities of water although they were clearly formed while the stalagmite was being continuously bathed by drip water. Presumably, the water has escaped post‐depositionally, through micro fissures, extensive connected hole system, crystal boundaries or other defects.

Time Zero Value Based on S-Wave Reflection Loss Measurement for Early Age Shrinkage Monitoring of Cementitious Specimens Subjected to Sealed and Unsealed Curing Conditions

Abstract Estimating the time at which to start monitoring early age shrinkage, especially of high performance cementitious materials, can be crucial. Despite numerous studies on early age shrinkage monitoring, there is no general agreement on the time at which early age shrinkage measurements should start (i.e., the “time zero” value [TZV]). The present paper proposes the use of the stiffening time measured via S-wave reflection loss as the TZV for early age shrinkage monitoring of high performance cementitious materials subjected to both sealed and unsealed curing conditions. The results imply that in the case of autogenous or sealed specimens, similar stiffening times occur throughout the specimen depths. In the case of unsealed specimens, however, the results show that the stiffening time might vary with depth depending on the water-to-cementitious ratio used. It is postulated that water redistribution within the specimen, as well as the formation of a “skin layer,” might significantly affect the stiffening time measured in the case of unsealed specimens used for early age drying shrinkage monitoring.

The Effect of Different Types of Separating Medium On Some Physical Properties of Processing Acrylic Denture-base with Two Investment Materials: A comparative Study

Objective(s): In the present study, glycerin is used as a substitute for tin-foil and cold mold seal (Alginate mould seal)in the process of curing heat and cold-cure acrylic resin denture base against stone and plaster.Methodology: 60 specimens were prepared from heat-cure acrylic resin and cold-cure acrylic resin denture base. Thestudy includes 12 groups of specimens depending on the type of processing, investment material and type ofseparating medium that are used in curing process. Each group of them contains 5 specimens for each test.Some of physical properties of the processed acrylic denture base that (water sorption and solubility) have beencompared with those processed using tin-foil and tin-foil substitute.Results: The results have shown that tin-foil is still the best separating medium that is used due to the best propertiesobtained when using tin-foil as a separating medium, while no significant differences have been observed betweenglycerin and cold mold seal specimens in respect to water sorption and solubility of the testing groups.Recommendations: that glycerin can be considered as a satisfactory separating medium for both heat and cold-curedacrylic denture base resins, especially because it is easy to get, easy to use and cheap.

Effects of F-Si sealer on electrochemical characteristics of 15%Al–85%Zn alloy thermal spray coating

Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al–Zn alloy wire material. Thereafter, and sealed specimens with F–Si sealer on Al–Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al–85%Zn seems to be appropriate not only in static environment but also in dynamic environment.

Image Analysis Technique for Monitoring Early Age Shrinkage Strains with Depth from the Top Surface of Monolithic Cementitious Prism Specimens

Abstract This paper describes the use of the image analysis technique for monitoring the variation of early age shrinkage strains with respect to the depth from the top surface of ordinary Portland cement mortar and concrete prism specimens starting as early as 30 min after adding water to the mixture. The applicability of the image analysis technique was demonstrated on both sealed and unsealed cementitious prism specimens. As expected, in situations where the top trowelled surface is protected from moisture loss, the shrinkage strains are similar with depth from the top trowelled surface. On the other hand, magnitudes of shrinkage strains monitored vary with depth when the top trowelled surface is exposed to a dry environment from an early age. The results also showed that the effect of settlements on early age shrinkage strains monitored can be minimized by adopting the current image analysis testing arrangement. Furthermore, when the early age shrinkage strains monitored using the image analysis technique were benchmarked against the results obtained via laser sensors, comparable shrinkage strains values were observed on the sealed prism specimen. On the other hand, the laser sensors were found to provide an “average” value of shrinkage strains that develop across the whole cross section of the unsealed prism specimen.

Prey Size Reconstruction Based on Myctophid Otoliths in Scats of Northern Fur Seals (Callorhinus ursinus)

Diet studies of eared seals (Otariidae) are very important, because they are high-level consumers in marine ecosystems (Bowen 1997). Recently, non-lethal methods such as scat analysis have been applied to diet studies of eared seals (e.g., Zeppelin and Ream 2006; Sigler et al. 2009). In this analysis, diet compositions are estimated from the undigested hard part remains of prey items (fish otoliths, squid beaks, crustacean exoskeletons, etc.; Pierce and Boyle 1991). Fish species are identified based on the morphology of otoliths. Size and weight of fish consumed can also be estimated from the lengths of otoliths in scats (Sinclair et al. 1994). Although scat analysis is a useful method that provides dietary information without animal capture, the resultant information could include biases caused by digestion (Jobling and Breiby 1986; Yonezaki et al. 2003; Gudmundson et al. 2006). Fish otoliths are partially, or even completely, digested during passage through the alimentary system. Feeding experiments of various eared seals have been conducted to investigate the potential biasing effects of digestion on otoliths (e.g., Staniland 2002; Tollit et al. 2003). Numerical loss and length reduction rates of fish otoliths in scat samples were assessed from captive experiments, and correction factors calculated to enable the reconstruction of the original number and body lengths of fishes that were consumed. These correction factors are known to vary with prey species, eared seal species and experimental conditions (e.g., Bowen 2000; Orr and Harvey 2001; Staniland 2002). However, few studies have applied the correction factors to wild samples and tested the validity of the diet reconstruction. The purpose of this study was to use experimentally designed meals and captive northern fur seals (Callorhinus ursinus) to calculate correction factors (CFs) for reconstruction of the myctophid fish size to compensate for the effects of digestion. Moreover, we apply the CFs to otoliths recovered from the large intestine contents of wild fur seal specimens, and estimated the size of the myctophid fish eaten. Myctophid fish used in the experiment are dominant components of micronekton communities in oceanic ecosystems and are important prey items of northern fur seals in the western North Pacific Ocean (Yonezaki et al. 2003; Yonezaki et al. 2008). Therefore, the calculation of CFs of myctophid fish otoliths enables data for use in the reconstruction of the diet of northern fur seals based on scats.

Wear Simulation of a Reciprocating Seal

Modeling of the complex tribological behavior of the elastomer parts is required when designing sliding seal applications. Friction, wear, and lubrication mechanisms of rubber-like materials differ from those in case of metals, ceramics, and rigid polymers; therefore, their modeling also requires other techniques. Tribological behavior of a sliding seal was investigated both experimentally and numerically. In the experimental setup, the counterpart of the seal was pressed and rubbed against the section of the seal in various lubrication conditions. The worn surface of the seal was inspected using white light profilometry. The test configuration was modeled by FEA. A wear algorithm (based on the linear wear theory) with an attached damage analysis was applied to the frictional contact simulation. The nonlinear and time dependent material behavior of the seal was also taken into account. The results of the tribological simulation (in which the internal friction and the effects of damage by rupture of the rubber material were considered) are in good agreement with the results of the surface inspections done on the worn seal specimens. The presented wear simulation technique of deactivating elements is suitable for modeling wear that is larger than the size of the elements in the FE mesh.

Saturated Lightweight Aggregate for Internal Curing in Low w/c Mixtures: Monitoring Water Movement Using X‐ray Absorption

Abstract: The susceptibility for early‐age shrinkage cracking in low w/c concrete has led to the development of new technologies that can reduce the risk of cracking. Internal curing, one of these new technologies, uses saturated lightweight aggregate to supply ‘curing water’ to low w/c pastes as they hydrate. While significant research has been performed to determine the effects of internal curing on shrinkage and stress development, relatively little detailed information exists on movement of water from the LWA to the paste. The details of when water moves and how far it travels has implications on the volume of aggregate and the aggregate gradation that should be used in mixture proportioning with internal curing. This study examines the timing of the release of water from saturated lightweight aggregate (LWA) and the distance that water can travel. X‐ray absorption is used to determine the time at which water is drawn out of the lightweight aggregate and the loss of water is traced over time. Further, it examines the travel distance of the water into the paste. Experimental details associated with the X‐ray technique are provided to describe the importance of specimen alignment. Further, in sealed specimens, the results indicate little water movement prior to set. After set however, the distance of water movement was as much as 2 mm. The importance of water movement is discussed in terms of mixture proportioning and its influence on shrinkage and stress development.

Compressive strength and permeability of high-performance concrete

The compressive strength, chloride penetration resistance and microstructure of two high-performance concretes were examined under three curing conditions. Curing conditions include standard curing (SC), matched curing (MC, which means sealed concrete specimens curing at temperature controlled box) and matched curing of naked concrete (NMC) according to development law of temperature measured in mass concrete on site. Results indicate that concrete under MC and NMC show higher resistance to chloride penetration than the one under SC. Concrete under MC has slightly lower chloride penetration than those under NMC, but the compressive strength of specimens under NMC was higher than the one under MC at 56 d. In addition, concrete under NMC and MC have higher early strength than under SC, especially at early age. However, the order of curing conditions affecting compressive strength of concrete at 248 day is: SC>NMC>MC.