Mass Loss Of Specimens Research Articles

Tribological and mechanical characterization of glass fiber polyamide composites under hydrothermal aging

Polymer composites are increasingly used in applications where they are subjected to abrasive wear. The bulk of prior research has focused on the performance of polymers under sliding wear conditions and in some cases resulted in a contradiction, particularly when it comes to the effect of reinforcing fibers on the wear performance. Another omission is the absence of pre-conditioning or accelerated aging which is clearly an important factor from an application standpoint. This work aims to highlight the influence of hydrothermal aging on the tribological and mechanical performance of polyamide 6 (PA6) and glass fiber-reinforced polyamide 6 (PA6-GF). The friction and abrasion wear behavior of unconditioned and conditioned PA6 and PA6-GF composites are measured against silicon carbide grinding paper on a pin-on-disk tribometer in a demineralized water medium at 60 °C. Specimens are conditioned in demineralized water at room temperature (RT) 25, 40, and 60 °C to investigate the effects of moisture and temperature. The presence of up to 25 wt.% glass fiber (GF) in PA6-based composites exhibits an increasing trend in abrasion wear mass loss and a reduction in coefficient of friction (COF). Interestingly, the mass loss of specimens conditioned to saturation does not increase compared to that of unconditioned samples. The FTIR spectroscopy is used to study the polymer degradation during hydrothermal aging.

Ultrasonic cavitation erosion of CFRP composites

To date, cavitation erosion of carbon fibre reinforced polymer (CFRP) composites has attracted only limited scientific attention. This paper investigates this knowledge gap through a series of experiments, in which unidirectional and bidirectional (2x2 twill) CFRP composites were exposed to cavitation clouds produced by an ultrasonic transducer in distilled water. Both composites were bonded with epoxy resin. Cavitation erosion tests were conducted according to the ASTM G32-16 standard using a stationary specimen method. The effect of water absorption on monitoring erosion damage was studied using saturated and dry specimens. Specimen mass loss measurements and microscopy observations were done at regular intervals throughout testing. Erosion imprint topographies were studied using X-ray computed microtomography. Three distinct erosion stages were identified from the erosion process observations. Nonuniformities in surface geometry and properties facilitated nucleation and accelerated local erosion. Surface epoxy thickness, fibre diameter and packing, and thickness and layup of fibre bundles influenced the erosion process. The erosion mechanisms included cracking and debonding of epoxy, and tunnelling and trenching in fibre bundles. Research findings indicated that the composite internal structure can potentially be designed for reduced water absorption and increased erosion resistance. Acoustic impedance was most efficient in predicting material response to cavitation erosion.

Bio-Durability and Engineering Characteristics of Heat-Treated Poplar Wood

The aim of this study was to evaluate the effect of brown rot fungus Coniophora puteana activity on physical and mechanical properties as well as biological resistance of heat-treated poplar wood. Two poplar wood species (Populus deltoids and Populus nigra) were heat-treated by thermo-wood (Thermo-D) method. Control and heat-treated specimens were exposed to brown rot fungus C. puteana for 16 weeks. Physical and mechanical characteristics of specimens including density, compression strength parallel to the grain and impact strength were evaluated before and after exposure to fungus. Mass loss of specimens caused by fungal activity (MLF) was also calculated. In addition, the effect of thermal modification on laccase production by C. puteana was assayed. The highest mass loss due to fungal deterioration was observed in control specimens, coinciding with the highest substrate-enzyme interactions and constant decrease in detectable laccase levels. According to the results, thermal modification can be used effectively to protect poplar wood against brown rot fungus attack.

Mechanical and fatigue properties of graphene oxide concrete subjected to sulfate corrosion

Concrete structures usually have to experience some unfavorable environmental actions during their service life, leading to the mechanical properties degradation, moreover, cyclic loadings such as traffic loads, wind loads may further accelerate structural damage, therefore, improving durability of concrete is of vital for structures servicing in severe environment. Graphene oxide (GO), as a new nano-reinforced material, has ultra-high mechanical properties and large specific surface area as a concrete reinforcing material. This study entailed an examination of the properties of Graphene Oxide Concrete (GOC) with varying levels of GO incorporation (0, 0.02, 0.05, 0.08 wt%). It also encompassed an analysis of the fatigue properties of GOC under different stress levels and varying sulfate wetting and drying cycles. Additionally, the investigation delved into the degradation mechanisms affecting Graphene Oxide Concrete (GOC) when subjected to sulfate erosion conditions. Furthermore, the study assessed the mass loss of specimens and their fatigue life under diverse environmental conditions. The results showed that appropriate GO incorporations could enhance concrete’s mechanical and fatigue properties after sulfate attack. In addition, scanning electron microscope (SEM) analysis showed that GO could adjust the aggregation state of cement hydration products and its own reaction with some cement hydration crystals to form strong covalent bonds, to improve and enhance microstructural denseness.

The resistance of high-strength concrete with ramie fiber using diatomaceous earth to high temperatures

This study was conducted to evaluate the visual appearance, mass change, and compressive strength degradation of high-strength concrete (HSC) with the addition of 0%, 0.15%, 0.30%, and 0.45% ramie fiber. The diatomaceous earth was used to substitute the cement at a 10% replacement level. The HSC specimens were prepared and exposed to different temperatures which were 400 °C, 500 °C, and 600 °C. The exposure time was 5 h. After the exposure, an assessment of visual appearance, measurement of mass, and testing of compressive strength were conducted. Specimens exposed to a temperature of 400 °C only had a color change in visual appearance. At a temperature of 500 °C and 600 °C cracks on the specimen surface began to appear. Specimen mass loss increased with increasing temperature. Moreover, HSC exposed to high temperatures also experienced a decrease in compressive strength in which the compressive strength degradation increased with increasing temperatures. HSC with 10% diatomaceous earth as cement replacement had smaller compressive strength, but better resistance to high temperatures. Meanwhile, the presence of ramie fiber in an HSC mixture improved the compressive strength but lowered the resistance to high temperatures.

Extrusion behavior of bentonite-based materials considering pore size and sand content effects

• An extrusion model was developed and verified considering sidewall friction and sand content effects. • Sidewall friction factor increased with decreasing pore size and increasing sand content. • Sidewall friction or specimen mass loss plays dominant role in the extrusion, depending on pore size. • Diffusion coefficient of montmorillonite increased with increasing sand content. Extrusion of compacted bentonite or bentonite–sand materials into fractures and pores in the host-rock formations improves the buffering ability of the host-rock formations and simultaneously reduces the buffering capacity of the engineering barrier, and ultimately endangering the operation security and stability of the repository. In this work, a model was developed for describing extrusion of bentonite–sand mixture into pores considering pore size and sand content effects. Then, a test apparatus was designed and extrusion tests considering pore size and sand content effects were conducted. Images of the extrusion process were regularly captured and analyzed. Results show that according to the extrusion model, the diffusion coefficient increased with the increasing sand content. Moreover, the sidewall friction factor increased with decreasing pore size and increasing sand content. For samples tested with a sand content of 0, after 15 days test, the extrusion distance increased first and then decreased with increasing pore size. Moreover, the extrusion rate initially decreased with increasing sand content, while after about 42 days test, for tests conducted in a pore radius of 10 mm, the extrusion rate increased first and then decreased with increasing sand content. Finally, considering the influence of pore size on the anisotropy of swelling pressure, the model could well simulate extrusion tests with consideration of pore size and sand content effects.

Fracture propagation and induced strain response during supercritical CO2 jet fracturing

To investigate fracture generation and strain variation during SC-CO2 (supercritical carbon dioxide) jet fracturing, the model of induced strain is established and the experiments are comprehensively studied. The influence factors are comprehensively explored, such as jet pressure, ambient pressure, etc. With the increasing jet pressure, the fracture morphology changes from parallel cracks to oblique cracks. Both the mass loss of specimen and CO2 absorption increase significantly, and the growth rate and minimum value of strain also rise exponentially. Under a high ambient pressure of 8.0 MPa, the main fractures mostly propagated from the surface to the bottom surface of the specimen. The maximum strain and the stable duration under higher ambient pressure are 1.5 times and 10 times, respectively, of the case under the ambient pressure of 5.0 MPa. The comparison shows that the optimal jet distance is 5–7 times the nozzle diameter, resulting in massive mass loss, large CO2 absorption, and peak strain. Moreover, the nonlinear variation of strain curve during jet pressurization is related to the type of rock and ambient pressure. These studies clearly show the relationship between the fracture morphology and induced strain, which are crucial for SC-CO2 fracturing in shale gas reservoirs.

Effects of mechanically alloying Al2O3 and Y2O3 additives on the liquid phase sintering behavior and properties of SiC

In order to improve the sintering of SiC, mixtures of Al2O3 and Y2O3 powders are commonly included as sintering additives. The aim of this work was to use mechanically alloyed Al2O3–Y2O3 mixtures as sintering additives to promote liquid phase sintering of SiC using spark plasma sintering. The results showed that milling reduced the particle size of the powders and led to the formation of complex oxide phases (YAP, YAM, and YAG) at low temperatures. As the ball milling time increased, the mass loss of specimens sintered with mechanically alloyed Al2O3–Y2O3 mixtures decreased, and accordingly the relative density increased. However, the hardness and flexural strength of sintered SiC specimens first increased and then decreased. Because the specimens prepared with oxides milled for a long time contained too much YAG/YAP and accordingly too much liquid at sintering temperature. This negatively affected the mechanical properties of the SiC specimens because of the increased volume of the complex oxide phases, which have inferior mechanical properties to SiC, in the sintered specimens. When the ball milling time was 6 h, the hardness (24.02 GPa) and flexural strength (655.61 MPa) of the SiC specimens reached maximum values.

Decay Resistance and Color Change of Pine and Beech Wood Impregnated with R. Luteum and R. Ponticum Plant Extracts

In this study, the effect of impregnation with natural extracts on decay resistance and color change of pine and beech wood was analyzed. Flowers of Rhododendron luteum and Rhododendron ponticum plants were extracted according to the decoction method and aqueous solutions were prepared at different concentration levels (2 %, 4 % and 7 %). In addition, ferrous sulfate, copper sulfate and aluminum sulfate mordants were added to the solution to improve the properties of the extracts. Then the wood specimens were impregnated with the prepared solutions. The results indicated that the effect of plant species on the mass loss of specimens exposed to T. versicolor (white-rot fungus) was insignificant. Non-mordant extracts had a slight effect on the mass loss of the specimens. However, in pine and beech specimens impregnated with mordant-added (especially ferrous sulfate-added) extracts, mass loss was significantly reduced and resistance to fungal rot was almost completely achieved. The concentration level did not have a significant effect on the mass loss of specimens treated with mordant-added extracts. After impregnation, the L* value of all specimens (especially those treated with ferrous sulfate-added extracts) decreased and the specimens darkened. The a* and b* values increased in specimens treated with non-mordant and aluminum sulfate-added extracts and these specimens tend to have a red-yellow color. The a* value decreased and the b* value increased in wood specimens treated with copper sulfate-added extracts. The green-yellow color trend of these specimens increased. Both the a* and b* values of the specimens treated with ferrous sulfate-added extracts decreased and the green-blue color tendency increased in these specimens. The increase in the concentration level positively affected the determined color changes. The total color change (ΔE*) was higher in wood specimens (especially pine) treated with ferrous sulfate-added R. ponticum extracts.

Effect of curing conditions on freeze-thaw resistance of geopolymer mortars containing various calcium resources

This study focused on the effects of curing conditions (standard and steam curing) on the freeze–thaw resistance of geopolymer mortars containing Class C fly ash, Class F fly ash, slag, and Ca(OH)2. Geopolymer mortar specimens were prepared with water-to-Class C fly ash ratios of 0.35 and 0.40, and CaO contents of 45% and 100% with different compositions. The specimens were subjected to freeze–thaw cycles until the mass loss exceeded 5% or the relative dynamic elastic modulus was below 60%. The reaction hydrates and pore structures were analyzed using scanning electron microscopy with energy-dispersive spectrometry and mercury intrusion porosimetry, respectively. In terms of mechanical performance, steam curing condition was better than standard curing condition for the early-age strength of geopolymer mortars. The compressive strength of the geopolymer mortars at 2 d and 28 d was increased 2.2–5.1 times and 0%-40%, respectively, under steam curing condition compared with standard curing condition. The experimental results indicated that Class C fly ash geopolymer mortar (CF35) under steam curing condition and Class F fly ash-slag geopolymer mortar with 100% CaO content (SF35C100) under standard curing condition exhibited remarkable freeze–thaw resistance with a freeze–thaw resistance grade of F300 at the lowest. Moreover, the water-to-ash ratio was critical for the freeze–thaw resistance under both standard and steam-curing conditions. The mass loss of specimens with water-to-ash ratios of 0.35 and 0.40 under standard curing condition were 4.67% and 8.79%, respectively, at 25 freeze–thaw cycles, whereas that of specimens with water-to-ash of 0.35 under steam curing condition was 3.03% at 300 freeze–thaw cycles. In addition, the freeze–thaw resistance of geopolymer specimens with different compositions had a direct relationship with the microstructure of the geopolymer mortars. Furthermore, the experimental results verified that a higher compressive strength did not necessarily indicate a better freeze–thaw resistance.

Influence of Rubber Powder Modification Methods on the Mechanical and Durability Properties of Rubberized Magnesium Oxychloride Cement

In the present study, three modification methods, including water washing, sodium hydroxide (NaOH), and styrene–acrylic emulsion, were used to modify waste rubber powders. The influence of rubber powders on the mechanical properties and frost resistance of magnesium oxychloride cement was examined, and the different modification mechanisms were also analyzed. Based on the analysis of hydrophilic properties after modification, styrene–acrylic emulsion achieved the best modification effect, while water washing produced the least modification effect; regarding mechanical properties, magnesium oxychloride cement mixed with NaOH modified rubber powders achieved the best modification effect, in which the 28 d flexural strength and compressive strength increased by 41.2% and 59.6%, respectively. During the freeze-thaw cycles, the mass loss of specimens was reduced with an increase in the content of rubber powders. In addition, after 300 cycles, the relative dynamic modulus of elasticity of the blank sample was about 28.12%, while that of the magnesium oxychloride cement mixed with NaOH modified rubber powders was approximately 42.38%. In general, the properties of the modified rubber powder–magnesium oxychloride cement composite material can meet the requirements for engineering materials, which provides a theoretical basis and technical support for the application of rubberized magnesium oxychloride cement.

Compatibility of FeCrAlMo in Flowing Pb-Li at 600°C to 700°C

A series of monometallic thermal convection loops (TCLs) has been conducted to determine the maximum temperature where FeCrAl alloys have compatibility with eutectic lead lithium (Pb-Li) for a dual-coolant fusion blanket. Pre-oxidizing commercial alloy APMT (Fe-21Cr-5Al-3Mo) for 2 h at 1000°C to form a surface α-Al2O3 layer was very effective in reducing the mass loss of specimens in the hot and cold legs of the most recent TCL that was operated for 1000 h with a peak temperature of 700°C. However, unlike previous experiments, the postexposure room temperature ductility of many of the APMT specimens was degraded to <10% total elongation, and many of the specimens at the highest temperature (>680°C) were severely damaged or were not recovered. Wide-angle X-ray scattering found that the pre-formed α-Al2O3 scale transformed to a mixture of trigonal and tetragonal LiAlO2. The overall results suggest that the maximum temperature for FeCrAl is limited to <700°C.

Long-Term Marine Environment Exposure Effect on Butt-Welded Shipbuilding Steel

Extreme environments, such as marine environments, have negative impacts on welded steel structures, causing corrosion, reduced structural integrity and, consequently, failures. That is why it is necessary to perform an experimental research sea exposure effect on such structures and materials. Research presented in this paper deals with the mechanical behavior of butt-welded specimens made of AH36 shipbuilding steel when they are exposed to a natural marine environment (water, seawater, sea splash) for prolonged periods (3, 6, 12, 24, and 36 months). The usual approach to such research is to perform accelerated tests in a simulated laboratory environment. Here, relative mass change due to corrosion over time is given along with calculated corrosion rates. Corroded surfaces of specimens were inspected using optical and scanning electron microscopy and comparison, based on the numbers and dimensions of the corrosion pits (diameter and depth) in the observed area. As a result, it can be concluded that exposure between 3 and 6 months shows significant influence on mass loss of specimens. Further, sea splash generally has the most negative impact on corrosion rate due to the combined chemical and mechanical degradation of material. Pit density is the highest at the base metal area of the specimen. The diameters of the corrosion pits grow over the time of exposure as the pits coalesce and join. Pit depths are generally greatest in the heat affected zone area of the specimen.

Steam oxidation of ytterbium disilicate environmental barrier coatings with and without a silicon bond coat

AbstractThe current generation of multilayer Si/Yb2Si2O7 environmental barrier coatings (EBCs) are temperature limited by the melting point of Si, 1414°C. To investigate higher temperature EBCs, the cyclic steam oxidation of EBCs comprised of a single layer of ytterbium disilicate (YbDS) was compared to multilayered Si/YbDS EBCs, both deposited on SiC substrates using atmospheric plasma spray. After 500 1‐h cycles at 1300°C in 90 vol%H2O‐10 vol%air with a gas velocity of 1.5 cm/s, both multilayer Si/YbDS and single layer YbDS grew thinner silica scales than bare SiC, with the single layer YbDS forming the thinnest scale. Both coatings remained fully adherent and showed no signs of delamination. Silica scales formed on the single layer coating were significantly more homogeneous and possessed a markedly lower degree of cracking compared to the multilayered EBC. The single layer EBC also was exposed at 1425°C in steam with a gas velocity of 14 cm/s in an alumina reaction tube. The EBC reduced specimen mass loss compared to bare SiC but formed an extensive 2nd phase aluminosilicate reaction product. A similar reaction product was observed to form on some regions of the bare SiC specimen and appeared to partially inhibit silica volatilization. The 1425°C steam exposures were repeated with a SiC reaction tube and no 2nd phase reaction product was observed to form on the single layer EBC or bare SiC.

Effects of load and rotational speed on the friction and wear properties of PTFE composites

PTFE composites has a lower hardness and shear strength than steel. Therefore, wear mainly occurs in PTFE composites itself when rubs with steel. For studying the friction and wear properties of PTFE composites, a series of experimental tests were conducted under different sliding velocities and load pressures using block-on-ring testing machine. Through weighting PTFE composites specimens before and after the experiment, we can get the wear mass losses of specimens, then the wear rate of PTFE composites is obtained by combining material density, loading pressure and wear length. At the same time, the friction coefficient is recorded in real time by the monitoring system of the testing machine The analysis results are as follows: at constant sliding velocities, the wear rate of PTFE composites gradually decreases with the increase of loading pressure; at constant loading pressure, the wear rate of PFTE composites decreases gradually with the increase of sliding speed. This leads to further conclusions that motor should not run in low speed range for a long time when PTFE composites is used as motor bearing material.

Heat Treatment of Pine Wood: Possible Effect of Impregnation with Silver Nanosuspension

The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat treatment. Impregnation of wood with a 400-ppm silver nanosuspension was carried out under an initial vacuum pressure of 0.07 MPa, followed by a pressure of 0.25 MPa for thirty minutes, before heat treatment. Heat treatment was carried out under hot air at three relatively mild temperatures, 145, 165, and 185 °C. Results showed improvement of some properties in heat-treated wood at 145 °C. This was indicative of the improving impact caused by hornification and irreversible hydrogen bonding in the course of water movements due to heat treatment; significant fluctuations in the intensities of FTIR spectra bands at 1750–1500 cm−1 were corroborating evidence of chemical alterations in hemicellulose polymer. The high mass loss at temperature 185 °C, and the extreme thermal degradation thereof, overcame the improving effects of hornification and formation of irreversible hydrogen bonds, consequently mechanical properties decreased significantly. Interaction of different elements involved made it hard to predict properties in specimens modified at 165 °C. Impregnation of specimens with nanosilver suspension resulted in significant increase of mass loss in specimens heat-treated at 185 °C, and significant fluctuations in properties of specimens heat-treated at 145 °C.

Energetic Investigation of Aging Effect on Mechanical Behavior in Wood by Means of XRD Measurement

ABSTRACT In this study, it is aimed to consider whether the strain energy could evaluate the mechanical durability of wood. To investigate the aging effects on the mechanical properties of bulk wood and cellulose microfibrils in the cell walls of wood, XRD measurements were taken under tensile loading. Specimens were recent wood and wood used for 250 years (aged wood). Thermal modifications were further applied for additionally aging treatment of both specimens. The standardized strain energy of the bulk wood and cellulose microfibrils was exponentially reduced with increasing mass loss of specimens. The reduction degree of aged wood was smaller than that of recent wood. Using this phenomenon, it was proposed that the aging effect can be quantitatively evaluated.

Velocity estimation of micro-particles driven by cavitation bubble collapses through controlled erosion experiments

The high-energy phenomenon of particle acceleration driven by cavitation bubble collapses has garnered research interests over the past few decades. Potential applications range from cavitation-induced drug delivery, chemical synthesis, sonochemistry to micro-machining operations. However, the acceleration mechanisms and the velocities attained by particles remain in huge contention. A novel particle velocity estimation model based on experimental mass loss input is put forward in this paper. Micro-abrasive particles, of 5 µm to 50 µm average diameter, were exposed to intense ultrasonic irradiation of 20 kHz in a deionized water medium for 10 min. The accelerated particles were captured by target specimens placed at 0.5 mm from the ultrasonic horn surface in a controlled experiment. Through the quantification of specimen mass loss, the average particle impact velocity could be estimated by a reverse solid particle erosion model. Results show that the magnitude of particle velocity is in the range of 8–40 m/s and is dependent on both particle size and ultrasonic amplitude. The results also suggest that micro-jet is the likely particle acceleration mechanism in the presence of a solid wall boundary from a microscopic perspective.

Effect of Particle Flow Rates on Erosion Ratio in Particle Impingement Experiments

Erosion caused by solid particles could not be neglected in oil and gas transportation industry, especially in gathering gas pipelines. Particles with small size may also erode the inner wall of pipelines after cumulative impacting and even lead to the leakage. Normally, a lot of solid particles are carried in the gathering gas before filtrating. Additionally, corrosion productions may fall off the wall as the gas flowing. Researches on erosion of pipeline caused by solid particles are important for predicting the remaining wall thickness, which can be a guide for pipeline inspection and safety protection. However, effect of particle flow rates on erosion ratio is normally omitted in studies on erosion ratio calculations. It was observed that particle flow rates have a great influence on the mass loss of specimens in the impingement experiments of this work. According to groups of Particle Tracking Velocimetry (PTV) results obtained under various conditions, the particle velocity decreased when the particle flow rate was larger under the same experimental condition and the mass loss of the specimen became lower. Relations between particle velocity and particle flow rate under different experimental conditions were calculated according to the PTV results. Further, relations between erosion ratio and particle flow rate were purposed in this work. It is better to consider effect of particle flow rate while calculating solid particle erosion of pipelines in industry.

Physico-mechanical properties of thermally modified Eucalyptus nitens wood for decking applications

Eucalyptus nitens is a fast growing plantation species that has a good acclimation in Spain and Chile. At the moment it is mainly used for pulp and paper production, but there is a growing market for solid wood products made from this species. Thermal modification offers a good alternative to produce high quality material to manufacture products with high added value. This study used unmodified and thermally modified E. nitens wood from Spanish and Chilean plantations to elaborate external decking and examine if it complies with the necessary properties to be a competitive product. A process similar to ThermoWood® was applied at the following temperatures: 185 °C, 200 °C and 215 °C. For each modification and for an unmodified specimen mass loss, volumetric swelling, anti-swelling efficiency (ASE) and equilibrium moisture content (EMC) were determined. Brinell hardness, dynamic hardness, screw and nail withdrawal resistance, and abrasion resistance according to the Shaker method and the Taber Abraser method were also determined. According to this study, thermally modified E. nitens from both countries showed high potential to be used as decking material, particularly when modified at 200 °C.