Compression Resilience Research Articles

A study on the sealing performance of metallic C-rings in reactor pressure vessel

Double metallic C-rings are used in pressure vessel of pressurized water reactor (PWR) to seal the bolt-connected flanges. To evaluate the sealing performance, it is necessary to study both the C-rings’ intrinsic properties and their behavior in reactor pressure vessel (RPV) under various loading conditions. The compression–resilience property and linear load are the basic information to evaluate the performance of a well-designed C-ring's. An equivalent model of C-ring is constructed by means of ANSYS to analyze its intrinsic properties, and is also validated by experiments on scaled samples. This model is applied to develop a 2D-axisymmetric FE model of sealing system including RPV and C-rings with the consideration of nonlinear material, contacting problem and multiple coupled effects. The simulation results of RPV deformation under the hydraulic test condition agree well with the data of factory hydraulic test. With the verified model, an analysis under the designing condition is performed to study C-rings’ behavior in the RPV, and then provides a reliable evaluation on the sealing performance of RPV.

Microstructure of mullite fiber-based hierarchical structures adjusted by Al/Si mole ratio of the raw material powders

Mullite fiber-based hierarchical structures were prepared by mixed slurry filtration and heat-treating method. Mullite fibers׳ framework served as the main structure of the material, and mullite fibers acted as curved substrates for the secondary structures׳ growth. The secondary structures formed on the fibers through fluorine-catalyzed gas phase reaction, and their morphology could be adjusted by tailoring (Al/Si)mol of the raw material powders (mixed AlF3–SiO2 powders). Inter-locked corundum hexagon plates as secondary structures grew on the mullite fibers when (Al/Si)mol of the raw material powders was 3/0. Mullite whiskers became the only secondary structures on the fibers when (Al/Si)mol of the raw material powders was 3/2–3/3. The inserted corundum plates or the intersected mullite whiskers acted as the unfixed lap-jointing points of the mullite fibers in the frameworks. The compression–resilience performance of the frameworks was tested at 1MPa, and the resilience ratio of the frameworks was higher than 90%.

Structure formation process, heat-insulation property and cyclic compression–resilience performance of mullite fibres/whiskers frameworks

Mullite fibres/whiskers frameworks (MF/MW frameworks) were prepared by mixed-slurry-filtration and heat-treating. Hierarchical fibres/whiskers structure formed in the frameworks through fluorine-catalyzed gas-phase reaction. Topaz rods as a transient product first formed in the frameworks, and then gradually transformed into mullite whiskers. Intersected mullite whiskers served as lap-jointing points of the fibres. The volume density, apparent porosity and thermal conductivity of the samples heat-treated at 1100–1500 °C were 0.402–0.541 g cm−3, 81.2–85% and 0.1191–0.1647 W m−1 k−1, respectively. Cyclic compression–resilience performance (maximum stress = 0.4 MPa) of the samples was tested at room temperature. The compression ratio, permanent deformation ratio and resilience ratio of the samples in the first circle compression–resilience test were 2.031–3.833%, 0.125–0.042% and 93.85–98.28%, respectively. The excellent thermal/mechanical properties indicated that the MF/MW frameworks were suitable for being applied as high temperature heat-insulation/sealing materials.

Characterization of a PEG-DE cross-linked tubular silk scaffold

The secondary structure and compliance of a novel small caliber (≤6 mm) silk fibroin (SF) tubular scaffold (SFTS) were investigated. Imitating the structure of natural vascular tissue, the SFTS consisted of a silk knit as the medium and a poly(ethylene glycol) diglycidyl ether (PEG-DE) cross-linked silk fibroin (SF) membrane as the intimal and adventitial layers, integrated to form a porous tissue. FTIR and XRD results showed that PEG-DE could induce SF molecules to form β-sheets during the cross-linking reaction process, resulting in improved crystallinity. As a result of the silk knit medium the SFTS had excellent mechanical properties. The intimal layer, which is in contact with a continuous flow of blood, must have adequate compliance. The results showed that the intimal layer of the SFTS had good stress-strain resistance when combined with the silk knit medium. When the SFTS was prepared with 6% SF, its axial breaking strength was >62 kPa and breaking elongation could reach about 33%; the circumferential breaking strength was >10 MPa and breaking elongation was >18%. The results of compression testing showed that the radial compression resilience of SFTS reached 94%, which was a significant improvement on commercial artificial blood vessels prepared from Dacron.

Hierarchical mullite structures and their heat-insulation and compression–resilience properties

Near-net-shaped hierarchical structure-adjustable short mullite fibers/mullite whiskers frameworks (MF/MW frameworks) were prepared by slurry-filtration and heat-treating method. The main structure of MF/MW framework was constituted by lap-jointed mullite fibers. Every single fiber in the framework was densely covered by mullite whiskers which formed through fluorine-catalyzed gas-phase reaction, and the fibers actually served as curved substrates for the mullite whiskers' growth. The lap-jointing points of the fibers were served by movable intersected mullite whiskers. Moreover, the microstructure of the frameworks could be adjusted by tailoring the raw materials mass ratio. The volume densities, the apparent porosities and the thermal conductivities of the MF/MW frameworks in different raw materials mass ratios were 0.459–0.487g/cm3, 79.7–82.8% and 0.1356–0.1965W/km, respectively. The compression–resilience property of the samples was tested under 0.4MPa at room temperature. The compression ratio and resilience ratio of the MF/MW frameworks in different raw materials mass ratios were 1.63–2.25% and 92.67–98.16%, respectively. The MF/MW frameworks with advanced thermal and mechanical properties were considered to be promising high-temperature heat-insulation material.

Studies on compression behaviour of polypropylene needle punched nonwoven fabrics under wet condition

The present study deals with the effect of parallel-laid and cross-laid web of polypropylene needle punched nonwoven fabrics on compression properties (initial thickness, percentage compression, percentage thickness loss and percentage compression resilience) under wet condition. These compression properties of polypropylene needle-punched nonwoven under wet condition have also been compared with its dry condition. With the increase in needling density the initial thickness, percentage compression and percentage thickness loss of the fabrics under wet condition decrease to higher extent compared to its dry condition both in case of parallel-laid and cross-laid fabrics. Cross-laid nonwoven fabric presents lower value of initial thickness percentage compression and thickness loss compared to parallel-laid fabric which is very prominent at high needling density (350 punches/cm 2 ). The percentage compression resilience shows increasing trend with the increase in needling density both under dry and wet conditions of parallel-laid web. It also follows similar trend in case of cross-laid nonwoven under wet condition. The optimum needling density for compression resilience of cross-laid nonwoven fabric under dry condition is 250 punches/cm 2 .

Effects of binder fibers and bonding processes on PET hollow fiber nonwovens for automotive cushion materials

In this study, nonwoven fabrics were developed for the replacement of polyurethane foams in car interiors, in particular, cushioning materials for car seats. Polyethylene terephthalate (PET) hollow fibers and two types of bicomponent binder fibers were used to manufacture automotive nonwovens by carding processes and then post-bonding processes, such as needle punching or thermal bonding. The physical and mechanical properties of nonwovens were thoroughly investigated with respect to the effects of binder fibers and bonding processes. The tensile strength and elongation for nonwovens were found to be significantly improved by combined needle punching and thermal bonding processes. In addition, the nonwoven cushioning materials were characterized in terms of hardness, support factors, and compressive and ball rebound resilience. The nonwovens showed greater hardness than the flexible PU foam. However, support factors over 2.8 for the nonwovens indicated improved seating comfort, along with better seating characteristics of greater resilience and air permeability in comparison with the PU foam.

Test Method for Compression Resilience Evaluation of Textiles

A test method was proposed and a measurement system was developed to characterize the compression resilience properties of textiles based on the mechanical device, microelectronics, sensors and control system. Derived from the typical pressure-displacement curve and test data, four indices were defined to characterize the compression performance of textiles. The test principle and the evaluation method for compression resilience of textiles were introduced. Twelve types of textile fabrics with different structural features and made from different textile materials were tested. The one-way ANOVA analysis was carried out to identify the significance of the differences of the evaluation indices among the fabrics. The results show that each index is significantly different among different fabrics. The denim has the maximum compressional resilience and the polar fleece has the minimum compressional resilience. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1992

감즙 염색에 의한 면직물의 역학적 특성과 표면형태

For development of dyeability, the cotton fabric was dyed repeatedly with persimmon juice by padding mangle. We evaluated the mechanical properties and hand value by Kawabata Evaluation System, and observed the change of surface morphology. The results obtained from this study were as follows. With the increase of repeating padding times of dyeing, the linearity of load-extension curve and tensile energy per unit length of the cotton fabric were increased, but the tensile resilience of fabric was decreased. The value of shear stiffness and shear hysteresis were increased. Also compression resilience and linearity of compression thickness curve were increased. The cotton fabric dyed with persimmon juice had shown the thickness and weight increase as the number of padding increase. As repeating times of dyeing with persimmon juice were increased, among the 6 hand values, the item of stiffness, anti-drape stiffness, fullness and softness were increased, while flexibility with soft feeling and crispness were greatly decreased. The amount of coated persimmon juice on the surface of the fabric was gradually increased as the padding times of dyeing. And cotton fabrics were dyed evenly with persimmon juice by padding mangle.

Density and permeability of a loess soil: Long-term organic matter effect and the response to compressive stress

Long-term field trials provide an ideal means to assess effects of cultivation practises (e.g., fertilisation, tillage, crop rotation etc.) on soil physical properties and soil fertility. To build upon the knowledge of the role of organic carbon (OC) and other soil properties on soil response to compressive stress, undisturbed soil cores were collected from a long-term fertilisation experiment in Bad Lauchstädt in Germany, including combinations of animal manure and mineral fertilisers. The cores were drained to −100hPa matric potential and exposed to uniaxial confined compression (200kPa). Investigated indicators for compression response included compression index, precompression stress, and resistance and resilience indices based on measured soil physical properties (air permeability, and void ratio). Soil resilience was assessed following exposure of compacted cores to freeze–thaw (FT) and wet–dry (WD) cycles. The OC content increased with increased fertilisation and resulted in decreased initial bulk density, higher air-filled and total porosities, and increased organisation of the pore space. Soil resistance decreased with increasing OC content but the correlation was not significant. However, initial bulk density (ρbi) and initial gravimetric water content (wi) were significantly positively correlated to the indices of soil compression resistance, with the effect of ρbi being significantly stronger. Significant recovery of air-filled void ratio and air permeability was observed following exposure to FT and WD cycles, with the latter cycle showing higher recovery levels. The OC and ρbi significantly influenced the magnitude of recovery following FT cycles, with ρbi showing contrasting trends on void ratio after both WD and FT cycles. It was concluded that the main drivers influencing soil response to compressive stress are ρbi and wi. No direct influence of OC was observed, rather the indirect effect of OC was seen through lower ρbi and greater wi associated with higher OC levels. Further studies are required to differentiate the relative effects of OC, ρbi and wi for variably-textured soils.

Design and Research on the Warm-Mix Rubber-Modified Asphalt Mixture Based on the GTM Method

By using GTM method, with equal volume parameters as the criterion, determined the suitable temperature of Evotherm warm-mix rubber-modified asphalt mixture, and applied Marshall method for repeated experiments, holding that GTM method could increase the cooling rate. Then, it firstly proposed a two-stage design method to conduct design of warm-mix rubber-modified asphalt mixture based on the two-parameter system; on the basis of hot-mix asphalt mixture test, it carried out staged design of asphalt content and temperature to ensure the pavement performance in terms of material composition and volume parameters. Finally, the paper conducted performance test of the designed warm-mix mixture and made comparative analysis of the corresponding hot-mix mixture. The results showed that the low and high temperature performances as well as the water damage resistant performance of Evotherm warm-mix rubber-modified asphalt mixture were superior than that of hot-mix mixture, and its compression resilience modulus was roughly equal to that of the hot-mix mixture, which would not affect the pavement structure design.

Biodegradable nanocomposite hydrogel structures with enhanced mechanical properties prepared by photo-crosslinking solutions of poly(trimethylene carbonate)–poly(ethylene glycol)–poly(trimethylene carbonate) macromonomers and nanoclay particles

Soft hydrogels with elasticity modulus values lower than 100kPa that are tough and biodegradable are of great interest in medicine and in tissue engineering applications. We have developed a series of soft hydrogel structures from different methacrylate-functionalized triblock copolymers of poly(ethylene glycol) (PEG) with poly(trimethylene carbonate) (PTMC) by photo-crosslinking aqueous solutions of the macromonomers in 2.5 and 5wt.% colloidal dispersions of clay nanoparticles (Laponite XLG). The length of the PTMC blocks of the macromonomers and the clay content determined the physicomechanical properties of the obtained hydrogels. While an increase in the PTMC block length in the macromonomers from 0.2 to 5kg/mol resulted in a decrease in the gel content, the addition of 5wt.% Laponite nanoclay to the crosslinking solution lead to very high gel contents of the hydrogels of more than 95%. The effect of PTMC block length on the mechanical properties of the hydrogels was not as pronounced, and soft gels with a compressive modulus of less than 15kPa and toughness values of 25kJm−3 were obtained. However, the addition of 5wt.% Laponite nanoclay to the formulations considerably increased the compressive modulus and resilience of the hydrogels; swollen nanocomposite networks with compressive modulus and toughness values of up to 67kPa and 200kJm−3, respectively, could then be obtained. The prepared hydrogels were shown to be enzymatically degradable by cholesterol esterase and by the action of macrophages. With an increase in PTMC block length in the hydrogels, the rates of mass loss increased, while the incorporated Laponite nanoclay suppressed degradation. Nanocomposite hydrogel structures with a designed gyroid pore network architecture were prepared by stereolithography. Furthermore, in the swollen state the porous gyroid structures were mechanically stable and the pore network remained fully open and interconnected.

Soil microbial and physical properties and their relations along a steep copper gradient

Copper (Cu) is accumulating in agricultural soils because it is an essential component of mineral fertilizers and pesticides. This could lead to toxic effects on soil macro- and micro-organisms and impact soil structure development. We investigated the effect of historical Cu contamination (>80years; from background concentrations up to 3837mg Cukg−1) on soil microbial enzyme activity, physical properties and resilience to compression. Soil samples and cores were taken from a fallow sandy loam field in Denmark. Microbial activity was quantified using fluorescein diacetate (FDA) and dehydrogenase (DHA) assays. Water dispersible clay was measured on field moist and air dried samples. For the resilience assay, soil cores (drained to −100hPa) were subjected to uniaxial confined compression (200kPa) followed by wet–dry or freeze–thaw cycles. Microbial enzyme activity significantly decreased with Cu concentration ≳500mgkg−1 with the two microbial assays linearly correlated with each other as well as with the water dispersible clay. An effect concentration causing a 50% reduction (EC50) in enzyme activity was observed at 521mgkg−1 for FDA and 542mgkg−1 for DHA. Significant increases in water dispersible clay, bulk density and decreases in air-filled porosity and air permeability were observed from Cu≳900mgkg−1. The increased density of the contaminated soils led to greater compression resistance and resilience relative to the uncontaminated soil. The results suggest that a threshold level for Cu exists (∼500mgkg−1 for this soil type) beyond which microbial activity decreases and soil structure becomes more compact with reduced permeability to air.

Compression behaviour of jute–polypropylene blended needle-punched nonwoven under wet conditions

The subject of this paper is the compression behaviour of jute–polypropylene blended needle-punched nonwoven under wet conditions. It is essential to know the compression behaviour of the needle-punched fabrics under wet conditions because of its various applications like geotextiles and carpets. Needle-punched fabric samples were prepared based on the three-factor three-level Box–Behnken design of experiment to study the individual as well as interaction effects of process parameters of fabric weight, needling density and blend proportion of jute and polypropylene fibre blend on compression properties under wet conditions. Initial thickness, percentage compression, percentage thickness loss and percentage compression resilience are the compression properties considered. The compression properties under wet conditions were compared with their respective dry conditions. This study reveals that most of the wet samples show a slightly higher value of initial thickness, percentage compression and thickness loss than dry samples, irrespective of processing variables, though for compression resilience value it is vice versa. The effect of blend does not have much influence on percentage compression in wet conditions. There is optimum level of needling density (around 250 punches/cm2) and blend proportions (around 75% polypropylene) for minimum percentage thickness loss of wet fabric under higher fabric weight. The compression resilience increases with increase in the content of polypropylene in the blend of polypropylene and jute. Optimum compression properties (highest percentage compression and compression resilience with minimum percentage thickness loss) can be achieved at fabric weight of 450 g/m2 with the combination of around 250 punches/cm2 needling density and around 75% polypropylene content.

Impacts of Gradation on the Property of Lime-Fly Ash Bound Macadam

This paper studied the lime-fly ash bound macadam mixed with different proportions of lime fly-ash and aggregates which is often used in construction projects, analyzed the impacts of the aggregate content to the unconfined compressive strength, modulus of compressive resilience property with various lime content and is showed that dense skeleton lime-fly ash bound macadam reached the desirable strength property and had good effect on pavement performance Therefore, it is concluded that lime-fly ash bound macadam with desirable property, replacing fine aggregates is achievable, Test results show that coarse aggregate of lime fly-ash stabilized aggregate can form skeleton structure and has the advantage of high strength and other better material properties which can meet the requirements pavement.

Experimental Study on Mechanical Behaviors of Lime-Stabilized Soils with Small Lime Content

In order to investigate the mechanical behaviors of lime-stabilized soils with small lime content, the specimens with 4%~8% lime content and 90%~95% degree of compaction are prepared, and then in use for the unconfined compression strength test, the diametral compression test and the compression resilience modulus test after they have cured in a standard curing room for 7 to 180 days respectively. These test results show that all of the unconfined compression strength, the splitting strength and the compression modulus of resilience increase with the degree of compaction and the curing time. Thereinto, the compression modulus of resilience does rapidly between 28 and 90 curing days, and the unconfined compression strength of the soil with 4% lime content does little after 28 curing days while the compression strengths and the splitting strengths of the other soils do quickly until 90 curing days. In addition, for a given degree of compaction, these strengths of the soils with the less lime content are potentially greater at the early curing time.

Studies on compression properties of polyester needle-punched nonwoven fabrics under dry and wet conditions

In this article, the effects of fabric weight, fiber cross-sectional shapes (round, hollow, and trilobal), and presence of reinforcing material on the compression properties (initial thickness, percentage compression, percentage thickness loss, and percentage compression resilience) under dry and wet conditions of polyester needle-punched industrial nonwoven fabrics are presented. It has been found that initial thickness of the fabric decreases under wet condition for both with and without reinforcing materials. The percentage thickness loss values are higher under wet condition in case of samples with reinforcing material compared to samples without reinforcing material. In the presence of reinforcing material, the trilobal cross-sectional fabric samples show the highest increase in thickness loss under wet condition followed by round and hollow cross-sectional polyester needle-punched nonwoven samples. Compression resilience is the highest in case of round cross-sectional fabric without reinforcing material under wet condition than fabric with reinforcing material. The initial thickness increases, and percentage compression and thickness loss decrease with the increase in fabric weight irrespective of fiber cross-sectional shapes both in dry and wet conditions. The initial thickness, percentage compression, and percentage compression resilience of the fabric decrease but percentage thickness loss increases under wet condition compared to the dry condition irrespective of the fiber cross-sectional shape. Compared to other cross-sectioned polyester samples, the hollow cross-section samples undergo very less consolidation under wet condition due to their consolidated structure. There is a drastic drop in compression resilience and increase in thickness loss under wet condition than in dry state irrespective of the fiber cross-sectional shape.

Study on Confined Consolidation Test of Natural Loess

The main object of study is the natural loess. The confined compression test and confined compression resilience test of nature loess and remolded loess under nature water content condition was done separately by using unsaturated high pressure consolidation apparatus. Through comparisons of test data, we investigated the effects of overconsolidated and structural factors on the loess compressibility under specific moisture conditions and analyzed the natural laws of compressive deformation properties of loess.

Tuning the compressive mechanical properties of carbon nanotube foam

A post-growth chemical vapor deposition (CVD) treatment was used to tune the compressive mechanical properties of carbon nanotube (CNT) arrays. Millimeter tall CNT arrays with low compressive resilience were changed to a foam-like material with high compressive strength and almost complete recovery upon unloading. The foam was tuned to provide a range of compressive properties for various applications. The treated arrays demonstrated compressive strength up to 35× greater than the as-grown CNT array. Unlike polymeric foams, the CNT foam did not decompose after exposure to high temperatures. Investigation of the foam structure revealed that the CVD treatment increased CNT diameter through radial growth, while increasing the CNT surface roughness. The morphological changes help to explain the increase in CNT array compressive strength and the transition from permanent array deformation to foam-like recovery after compressive loading.

Study on the Compression Properties of Epoxy Matrix Composites Reinforced by PES Warp-Knitted Spacer Fabric

This research paper presents an experimental investigation on the compression and compressive resilience properties of warp-knitted spacer fabric composites with different resin content and different kinds of resin. By means of hand roller coating technology, four kinds of warp-knitted spacer fabric composites were made. The experiments were tested according to GB/T1453-2005 and ISO3386/2:1984. It is shown that the resin content and resin type seriously affect the compression and compressive resilience properties of warp-knitted spacer fabric composite. The data indicated that when the warp-knitted spacer fabric composite coated with the same kind of resin, with increasing resin content the elastic modulus added and the compressive resilience decreased. Having the same resin content, the compression properties of pacer fabric composite increase with the increase of flexural strength of resin; while the compressive resilience decrease.