Brass Fibers Research Articles

Experimental Investigation on Flexural Behaviour of Sustainable Reinforced Concrete Beam with a Smart Mortar Layer

This paper deals with an experimental study of the flexural behavior of sustainable reinforced cement concrete (RCC) beams with a smart mortar layer attached to the concrete mixture. In total, nine RCC beams were cast and tested. Two types of reinforced concrete beams were cast, and three different beams of sizes 1000 × 150 × 200 mm and six different beams of sizes 1500 × 100 × 250 mm were considered. The flexural behavior of these RCC beams was studied in detail. The electrical resistivity of these beams was also calculated, which was derived from the smart mortar layer. Research on the application of smart mortars within structural members is limited. The experimental results showed that the smart mortar layer could sense the damage in the RCC beams and infer the damage through the electrical measurement values, making the beam more sustainable. It was also observed that the relationship between the load and the fractional change in electrical resistance was linear. The fractional change in electrical resistivity was found to steadily increase with the increase in initial loading. A significant decrease in the fractional change in electrical resistivity was seen as the load approached failure. When a layer of mortar with brass fiber was added to the mortar paste, the ultimate load at failure was observed and compared with the reference beam specimen using Araldite paste. Compared to the hybrid brass-carbon fiber-added mortar layer, the brass fiber-added mortar layer increased the fractional change in the electrical resistivity values by 14–18%. Similarly, the ultimate load at failure was increased by 3–8% in the brass fiber-added mortar layer when compared to the hybrid brass-carbon fiber-added mortar layer. Failure of the beam was indicated by a sudden drop in the fractional change in electrical resistivity values.

외해가두리용 황동망과 섬유망에서의 참돔(Pagrus major) 생산성 비교연구

This study aimed to investigate the productivity of red seabream (Pagrus major) raised in brass net cages and fiber net cages installed in the offshore sea with a depth of more than 35 meters. The weight gain (WG), daily growth rate (SGR), feed coefficient ratio (FCR), and survival rate (SR) of red seabream were calculated to compare the productivity of a brass net cage and a fiber net cage. The productivity of red seabream was calculated by giving weight gain (WG), feed efficienct ratio, and survival rate of 50%, 30%, and 20% weights, respectively. The growth rate, feed efficienct ratio, and survival rate of red seabream were higher in the brass net cage than in the fiber net cage, and the productivity was improved by 34.7% (P<0.05).

Cross tension and compression loading and large-scale testing of strain and damage sensing smart concrete

Multifunctional self-sensing smart concrete can provide a structural health monitoring (SHM) solution that is robust, reliable, and low-cost. Smart concrete, which includes coarse aggregates with 15 mm size, brass fibers, silica fume, superplasticizer and water, has been developed as a promising multifunctional material. The normal and cross compression and split tensile tests were conducted on 75 mm cube samples; large scale compression test was conducted on 15 × 15 × 30 cm prism; large scale bending tests were applied to prisms with sizes 15 × 15 × 75 cm and 15 × 30 × 150 cm. The normal and cross compressive strain gage factors were 54 and 59 while linearities were 6.6% and 7%, respectively. Normal and cross tensile strain gage factors were 3.0 and 2.9 while corresponding linearities were 6.6% and 13%. As the sample size increased, the electrical resistivity increased and strain sensitivity decreased due to obstruction of electrons by aggregates that revealed a “size effect” for piezoresistivity of smart concrete. Large scale bending test results verified the piezoresistivity of smart concrete while crack formation and propagation increased the electrical resistance dramatically. Smart concrete can be utilized to monitor both strain and damage.

Thermomechanical Simulation of Ferritic Rolling of Titanium-Niobium Interstitial-Free Steel

Abstract Austenitic or two-phase rolling of ultra-low carbon steels face temperature control issues and generate shape defects. Ferritic rolling has been developed as a solution, and ferritic hot-rolled sheets are used as final products, replacing hot-rolled followed by cold-rolled sheets. However, it is not in regular industrial production because of mill limitations. Hence, ferritic hot rolling must be optimized for developing a ferritic cold-rolled and close-annealed sheet through subsequent processing. In this work, industrial ferritic rolling process was simulated for a titanium-niobium interstitial-free steel using a thermomechanical simulator. Multi-hit plane strain compression tests were carried out at three different regimes below the lower transformation temperature (Ar1). Steels were processed under high strain and strain rates as experienced during industrial hot rolling operation, and the results were compared with the conventional austenitic rolling. The flow stress of the material in the ferritic regime decreased with decreasing deformation temperatures but increased at temperatures below 700°C. Nonuniformity in grains and texture also increased with decreasing temperatures. High-temperature rolling in ferritic condition close to Ar1 temperature does not differ significantly from the austenitic condition, whereas the low-temperature ferritic rolled material had through-thickness microstructural nonuniformity and unwanted goss and brass fibers. The intensity of gamma-fiber {111} || normal direction (ND) required for formability was highest in the intermediate temperature zone. Deformation between temperatures of 850°C and 800°C was found to be ideal. Based on simulation studies, full-scale plant rolling was carried out under the optimized ferritic regime. The microstructure and texture matched closely with the simulation results. This work provides a working window for ferrite rolling in an industrial hot strip mill for developing ferritic cold-rolled close-annealed products.

Synergic effect of metallic fillers as heat dissipaters in the tribological performance of a nonasbestos disk brake pad

Brake friction linings are made of materials with a highly complex formulation that helps in improving the braking performance. The selection of friction materials with good physical, mechanical, and thermal properties is vital, which will decide the braking performance. Apart from giving good physio-mechanical properties, metallic fillers act as heat dissipaters. The objective of this work is to study the synergetic effect of prominent heat dissipaters, namely copper fibers, brass fibers, and zinc powders. Three simplified formulations were developed with 10, 14, and 18 wt.% of these heat dissipaters and named DB1, DB2, and DB3, respectively. It was observed that the addition of heat dissipaters increased the thermal properties. Tribological properties are tested based on SAE J661 standards. It was observed that DB2 had a consistent and higher coefficient of friction of 0.503 with a higher wear rate (7.6%) while DB3 had adequate μ and lower wear rate. The same batches of brake pads were tested in an inertia brake dynamometer following JASO C406 and a wear test was carried out. It was observed that % fade and % recovery were better for DB2 in both cycles. The wear rate in terms of thickness was lesser for DB2 followed by DB1 and DB3. The wear mechanism was analyzed using a scanning electron microscope. The preference selection index method of optimization was used to evaluate the overall performance parameters of the brake friction composites. Heat dissipaters with 14 wt.% have proved to be the better performers, followed by 10 and 18 wt.%.

Characterization of smart brass fiber reinforced concrete under various loading conditions

Self-sensing smart cementitious materials can enable development of load carrying structural systems with an intrinsic condition monitoring system. This paper discusses extensive experimental tests conducted on the brass fiber reinforced concrete composites that incorporates coarse aggregates. First, compressive and split tensile tests were conducted to assess strain sensitivity of the developed smart concrete. In addition, notch bending tests were performed to evaluate ability of the developed concrete in crack or damage sensing. Furthermore, the influence of different parameters such as loading rate, cyclic loading, electrode type, current type, and specimen age on the compressive strain sensitivity of smart concrete was assessed. The governing mechanisms for the self-sensing during the split tensile test and notched bending tests were described. Results indicate that the developed smart concrete with low-cost brass fibers exhibits high compressive strain sensitivity both under monotonic and cyclic loading conditions. The gage factor under compressive loading ranged from 20 to 54 at different loading rates. In addition, a gage factor of 3 was observed under tensile loading. Smart concrete also revealed a very strong correlation between the crack length and change in the electrical resistivity during notched bending tests. These findings suggest that the developed smart concrete can be used as a loading bearing multifunctional material that can sense its own damage and strain.

High-performance Pd/brass-fiber catalyst for selective hydrogenation of acetylene: Effect of calcination-assisted endogenous growth of ZnO-CuOx on brass-fiber

Microfibrous-structured Pd/brass-fiber catalysts are developed for the selective hydrogenation of acetylene in the front-end configuration. The brass fibers are pre-calcined in air to create an endogenously growing ZnO-CuOx composite layer, and 0.25 wt% Pd is loaded on the brass fibers via the impregnation method. The activity and selectivity of our Pd/brass-fiber catalysts are primarily governed by the alloying degree of active sites regarded as Pd-Zn-Cu ensembles with the PdCu(alloy)-PdZnCu(alloy) twin structure, which are strongly sensitive to both the brass-fiber calcination and the catalyst reduction temperatures. For the preferred catalyst obtained using brass fibers calcined at 500 °C and reduced in H2 at 250 °C, over 90% selectivity is achieved at nearly 100% acetylene conversion with promising stability. Additionally, due to the weakened ethylene hydrogenation ability at high reaction temperature over the Pd-Zn-Cu ensembles, the catalysts tend to present higher ethylene selectivity as the reaction temperature increases.

Temperature and moisture effects on electrical resistance and strain sensitivity of smart concrete

Cement composites, with enhanced electrical properties, have been investigated as multifunctional composites, with application as strain sensors, heating elements or anode in different electrochemical technique. In this work, several aspects regarding the practical application of smart concrete with the addition of brass fibers have been addressed. In general, electrical conductivity of cement composites is dependent on their moisture content and temperature. Therefore, for a real use of this type of sensors the influence of these parameters should be determined. The electrical resistance of the smart concrete decreased linearly with temperature up to 50 °C, therefore this effect can be compensated in strain sensing applications. On the other hand, at higher temperatures, especially after 150 °C, the mismatch strain between brass fibers, cement paste and aggregates resulted in damage, which was detected as an increase of the electrical resistance on the order of 613%. Thus, smart concrete can be used as fire alarm sensor. Also, the relationship between moisture and electrical resistance change was determined. After curing, the samples with moisture content of 5.2% were put in an electric furnace at 90 °C. After 60 min of 90 °C exposure the minimum resistance was measured as 702 Ohm for an average moisture content of 4.8%. At this optimal moisture content, water between fibers was lost and direct contact between fibers was achieved, maximizing the electrical conductivity of the composite. After this point, when the smart concrete was heated for a longer time, the electrical resistance increased almost 300% because water acting as electrolyte was lost. Thus, smart concrete is sensitive to moisture change and can be used as moisture sensor, especially at constructions exposed to harmful water. The effect of moisture content on the strain sensitivity of smart concrete was tested. The mechanism relating piezoresistive properties and moisture content were enlightened. Multifunctional smart concrete can be used as strain, fire and moisture sensor while acting as a load bearing element.

Theoretical and experimental investigation of piezoresistivity of brass fiber reinforced concrete

Structural health monitoring is important for the safety of lives and asset management. In this study, numerical models were developed for the piezoresistive behavior of smart concrete based on finite element (FE) method. Finite element models were calibrated with experimental data collected from compression test. The compression test was performed on smart concrete cube specimens with 75 mm dimensions. Smart concrete was made of cement CEM II 42.5 R, silica fume, fine and coarse crushed limestone aggregates, brass fibers and plasticizer. During the compression test, electrical resistance change and compressive strain measurements were conducted simultaneously. Smart concrete had a strong linear relationship between strain and electrical resistance change due to its piezoresistive function. The piezoresistivity of the smart concrete was modeled by FE method. Twenty-noded solid brick elements were used to model the smart concrete specimens in the finite element platform of Ansys. The numerical results were determined for strain induced resistivity change. The electrical resistivity of simulated smart concrete decreased with applied strain, as found in experimental investigation. The numerical findings are in good agreement with the experimental results.

The strain sensitivity of brass fiber reinforced concrete

The structures are challenged by earthquakes and other environmental factors. Structural health monitoring is crucial to protect the lives. The strain gages used in structural health monitoring have low durability and can get point wise measurements which limit their use. In this study, five different concrete mixtures with different brass fiber volume fractions were designed. Along with the control mixture which does not have brass fiber, six mixtures were designed and three cube samples from each mixture were cast and cured. Compression test was conducted with simultaneous measurement of electrical resistance. The brass fiber reinforced concrete has strong linear relationship between the electrical resistance change and strain. Important progress was achieved in development of “Smart Concrete” which can sense its strain and damage.

Sliding electrical contact behavior of brass fiber brush against coin-silver and Au plating

Sliding electrical contact behavior of the brass fiber brush with 23% packing fraction was investigated as sliding against coin-silver and Au plating under vacuum and air conditions. The friction coefficient, contact resistance and electrical noise of the brushes were analyzed. The microstructure and worn surfaces of the brass fiber brush and counter discs were observed to discover the involved wear mechanisms. The friction coefficients in vacuum are much higher than those in air. The contact resistances and electrical noises of the brush against both discs in vacuum are extremely low. The contact resistance against coin-silver quickly increases as the sliding condition varies from vacuum to air, which is much higher than that against Au plating. Sliding speed has an insignificant effect on the contact resistance and electrical noise of fiber brush. Formation of oxide film and loose oxide particles on the worn surfaces of fibers and the coin-silver disc leads to the increase of contact resistance and electrical noise. The transfer of gold from Au plating to worn surfaces of brass fibers is used to prevent the oxidation of fibers and keep the contact resistance and electrical noise in a relatively low level. The multi-contact mechanism of brass fiber brush has been also discussed.

Tribological behavior of brass fiber brush against copper, brass, coin-silver and steel

The brass fiber brushes with various packing fractions were prepared by the method of filling and dissolving aluminum fibers. The compression tests of brass fiber brushes and brass block were conducted. The tribological behavior of the selected brass fiber brush of 23% packing fraction sliding against the copper, brass, coin-silver and steel discs was investigated. The microstructure, worn surface and wear debris of the brush and counterface materials were observed and analyzed to investigate the involved wear mechanisms. The compressibility of brass fiber brushes increases with the increase of packing fraction, and is much higher than the brass block. The brush against the four discs exhibits significantly high friction coefficient values range from 0.8 to 1.0 but the curves are fairly smooth. The brass fiber brush sliding against copper and brass discs experiences severe adhesive wear and gives a high wear rate compared with that against coin-silver and steel discs. The wear behavior of the brass fiber brush strongly depends on the counterface materials under dry sliding condition. The differences of the friction and wear mechanisms between fiber brushes and solid brushes were also discussed.

Role of different metallic fillers in non-asbestos organic (NAO) friction composites for controlling sensitivity of coefficient of friction to load and speed

Sensitivity of μ (coefficient of friction) of friction composites towards load and speed is composition specific. For an ideal friction material, it should be zero. It was of interest to examine the influence of increasing amount of three commercially popular metallic fillers (steel fiber, brass fiber and copper powder) on the tribological performance of friction composites including sensitivity of μ towards load and speed. Three series of non-asbestos organic (NAO) friction composites comprising of seven composites in the form of brake pads were developed in the laboratory using three metallic fillers as a single variant. All composites were characterized for physical, chemical and mechanical properties. These were further tribo-tested on reduced scale prototype (RSP) for friction, wear and sensitivity of friction coefficient (μ) towards load and speed characteristics. It was concluded that inclusion of metal contents led to enhancement in friction performance of the composites but at the cost of wear resistance, in general. From μ sensitivity point of view, composites with higher metallic contents and hence thermal conductivity (TC) showed better performance. Overall it was observed that copper powder based composite (with 10%) proved as the best performer from both friction and wear point of view.

Optimization of brass contents for best combination of tribo-performance and thermal conductivity of non-asbestos organic (NAO) friction composites

Thermal conductivity (TC) of composites especially friction composites plays a vital role in the performance during braking. Low TC renders the tribo-surface vulnerable for degradation of organic ingredients affecting the braking capability adversely while too high TC on the other hand, results in adverse effect on brake-fluid. Simultaneously it is also required that the composite should exhibit best possible combination of performance properties as a friction material. The optimum combination of various properties hence is to be tailored with right contents of metallic fillers. In this paper the effect of brass fibers in increasing amount on friction and wear performance of non-asbestos organic (NAO) friction composites was studied. Four friction materials based on parent composition and with varying amount of brass (0, 4, 8 and 12 wt%) and barite (35, 31, 27, and 23 wt%) in a complementary manner were developed as brake pads and were characterized for physical, chemical and mechanical properties. These were further tested for their friction and wear behavior in fade and recovery (F & R) mode on a Krauss machine as per ECE R 90 schedule. Moreover, the small specimens (24 mm × 24 mm) of the brake pad were evaluated for studying their friction sensitivity for loads and speeds in simulated braking conditions against a commercial disc on a reduced scale prototype (RSP). Composite with 8% brass fibers (where TC was not highest) proved to exhibit best combination of performance parameters related to friction and wear in both the testing modes. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) were employed to understand wear mechanisms.

Electrical conductivity of a bulk metallic glass composite

The authors report the electrical conductivity of a bulk metallic glass (BMG) based composite fabricated by warm extrusion of a mixture of gas-atomized glassy powders and ductile α-brass powders. The conductivity of the BMG composite can be well modeled by the percolation theory and the critical percolation threshold volume of the high-conductive brass phase was estimated to be about 10%. It was found that the short irregular brass fibers can dramatically reduce the resistivity of the BMG, leading to an improved material with both high strength and good conductivity for functional applications.

Effect of fiber addition on mechanical and tribological properties of a copper/phenolic-based friction material

The purpose of the present work is to compare the effects of addition of different fibers on the mechanical and tribological properties of a copper/phenolic resin-based semi-metallic friction material using the same fiber contents and process conditions. The results indicate that cracks/voids are observed more or less in all post-cured materials. Compared to fiber-free material, materials containing copper and brass fibers have higher compressive strengths, while materials containing cellulose and carbon fibers have lower strengths. After post-curing all materials increase in thickness and decrease in weight and density. Cellulose fiber-added material has the greatest increase in thickness and decrease in density. Except cellulose, all fiber-added materials exhibit higher average COF values than that without fibers. Significant fade occurs to materials containing steel, brass, cellulose and ceramic fibers. Steel fiber-added material has the largest wear, while copper fiber-added material has the smallest wear. A loosely bonded layer of wear debris almost fully covers the worn surfaces of fiber-free as well as brass, cellulose and ceramic fiber-added materials. The debris layer partially covers the surfaces of copper and carbon fiber-added materials, and is substantially absent from the surface of that containing steel fiber. Among all fibers copper fiber appears to be the best candidate due to its relatively high and stable COF as well as low wear.

Friction and Wear Characteristics of Polymer-Matrix Friction Materials Reinforced by Brass Fibers

This study is an investigation of friction materials reinforced by brass fibers, and the influence of the organic adhesion agent, cast-iron debris, brass fiber, and graphite powder on the friction-wear characteristics. Friction and wear testing was performed on a block-on-ring tribometer (MM200). The friction pair consisted of the friction materials and gray cast iron (HT200). The worn surface layers formed by sliding dry friction were examined using scanning electron microscopy (SEM), x-ray energy-dispersive analysis (EDX), and differential thermal analysis-thermogravimetric analysis (DTA-TAG). The experimental results showed that the friction coefficient and the wear loss of the friction materials increased with the increase of cast-iron debris, but decreased with the increase of graphite powder content. The friction coefficient and wear loss also increased slightly when the mass fraction of brass fibers was over 19%. When the mass fraction of organic adhesion agent was about 10–11%, the friction materials had excellent friction-wear performance. Surface heating from friction pyrolyzes the organic ingredient in the worn surface layer of the friction materials, with the pyrolysis depth being about 0.5 mm. The surface layers were rich in iron but poor in copper, and they were formed on the worn surface of the friction material. When the mass fraction of brass fibers was about 16–20%, the friction materials possessed better wear resistance and a copper transfer film formed on the friction surface of counterpart. Fatigue cracks were also found in the worn surface of the gray cast-iron counterpart, with fatigue wear being the prevailing wear mechanism.

Plasticity in Ni59Zr20Ti16Si2Sn3 metallic glass matrix composites containing brass fibers synthesized by warm extrusion of powders

Deformation behavior of centimeter-scale Ni-based metallic glass matrix composites reinforced by brass fibers, synthesized by warm extrusion of gas atomized powders, has been investigated under the uniaxial compression condition at room temperature. Throughout the extrusion process, all blended spherical powders are elongated along the extrusion direction. The brass fibers are well distributed in the metallic glass matrix for the metallic glass matrix composites containing the brass up to 0.4 in volume fraction and no pores are visible. With increasing the brass content, elastic modulus and strength decrease due to the softness of the brass, but enhanced macroscopic plasticity is observed due to the formation of multiple shear bands, initiated from the interface between brass fiber and metallic glass matrix, as well as their confinement between the brass fibers. These behaviors are not observed in the sample synthesized by warm extrusion of only metallic glass powders.

Effects of poly(vinyl alcohol) on fiber cement interfaces. Part I: Bond stress-slip response

Abstract This is the first part of a two-part article describing the effects of adding poly(vinyl alcohol) (PVA) to a cement based matrix to improve the bond at the fiber-matrix interface. Two types of fibers were used, steel and brass fibers (simulating brass-coated steel fibers) in a series of pull-out tests where the load versus global slip up to complete pull-out was recorded. The measured slips was that at the section where the fiber penetrates the matrix. The first article describes the mechanical effects of the addition of PVA, while the second article presents the microscopic observations. Correlation between the two studies is pointed out in the second part and conclusions are drawn. In particular, it is observed that the addition of PVA in the amount of 1.4% by weight of cement matrix leads to a significant improvement in the bond strength as well as in the frictional resistance, thus pull-out work, after the peak load.

特集 プロセスの制御と製品の評価 溶融メッキ薄板コイル材切削金属繊維のブレーズ法による成形

The aim of this research was to form long soldered brass fibers by continuously shaving hot dipped brass sheet and form porous metal fiber compacts by using the brazing method instead of sintering. This brazing method are used for materials that melt at temperatures lower than the sintering temperatures of normal metal fibers and enables contact points to be melted and fixed.