Mechanical Strength Characteristics Research Articles

The Effect of a Small Copper Addition on the Electrical Conductivity of Aluminum

Aluminum powder blended with 10, 20, and 30 wt% of copper powder is compacted at 400 °C by four reciprocal extrusion passes. Simultaneous compaction and strengthening result in more than double increase in mechanical strength characteristics for 20 and 30 wt% of copper and a significant increase in electrical conductivity for 30 wt% of copper. This phenomenon is investigated here by the expansion of the “effective media” model for a random binary mixture so that it includes the presence of intermetallic phases and considers the distribution of large copper agglomerates.

Mechanical Strength Characteristics of Ternary Blend Geopolymer Concrete with Steel Fibres under Ambient Curing

As the concrete industry continues to expand, the changes and design of infrastructure is given due insight owing to the current trend. The demand for special concrete is thereby increased. In this present experimental work, production of concrete aims at achieving a strength of 50 N / mm2. Here, cement is replaced by fly ash, GGBS and metakaolin at the nominal proportions integrated with steel fibers in percentages of 0.5, 1 and 1.5 by volume of concrete. Steel fibers used are crimped in shape of aspect ratio 66. Concrete being soft in tension and strong in compression is designed to combat the pressure generated. This will render concrete where tension is resisted by steel fibers. Mix proportion for ternary blend geo polymer used in this study consists of 25% fly ash, 60% GGBS and 15% metakaolin. GGBS and low calcium-based fly ash supplied by the local thermal plant are utilised. At 1.5% of the integration of steel fibers, the highest increase in strength was reported. The introduction of steel fibers showed a good improvement in flexural, compressive and split tensile strength. Out of the three mixes, the one with 1.5% steel fibres, which was the maximum percentage added, showed the best result. Split tensile strength was found to improve by 9% and flexural strength by 73%, which is a commendable result. On the contrary, the Modulus of elasticity showed a decline in its value. A reduction of 13.2% was observed for steel fibre content of 1.5%. It can therefore be concluded that geo polymer concrete with steel fibres has improved ductile properties, besides which, it help in reducing the carbon footprint due to emission of carbon dioxide and carbon monoxide produced by the cement industry.

Direct Osmotic Desalination Technique by Solar Energy

Over the last decade direct (forward) osmosis has attracted much attention in practical applications including artesian water desalination, green power generation, industrial water purification etc. In comparison with the traditional reverse osmosis process the separation is due to natural osmosis, providing lower energy cost for external pressure that is needed for reverse osmosis and lower membrane fouling potential. The main problem for the direct osmosis application efficiency is a selection of appropriate draw solute (otherwise known as a working substance). In the present paper diethyl ether (C₂H₅)₂O has been considered as a working substance having a relatively high osmotic pressure. Heating regeneration has been explored to obtain fresh water and recover the proposed draw solution. The advantage of the diethyl ether over known draw solutes has been discussed. It was noted that for further commercial applications of the diethyl ether as a working substance the membrane should have better characteristics of water permeability, stability, selectivity, and mechanical strength. The pilot device based on the described direct (forward) osmosis technique with the productivity of 1 m³/hr has been manufactured. In the beginning of 2020 the pilot device was successfully installed in a village of Navoiy Region, Uzbekistan to provide its inhabitants with the clean water.

Experimental studies on mechanical properties and impact characteristics of ternary concrete with steel fiber

The paper presents the laboratory investigation on mechanical properties and impact strength characteristics of conventional concrete (CC), ternary concrete (TC) and steel fiber reinforced ternary concrete with w/b = 0.55 at 28, 90, 365 days. Crimped steel fibers of 30 mm length and an aspect ratio of 60, with four volume fractions of 0.5%, 1%, 1.5% and 2% were used as the reinforcing material. In the ternary mixture, pre-determined quantities of micro silica (MS) 10% and ground granulated blast furnace slag (GGBS) 30%, was used to replace the cement. The experimental results shows that the ternary concrete improves the strength characteristics and the addition of steel fiber further enhanced the split tensile and flexural strength. A significant improvement was observed in impact resistance and impact energy of fibrous ternary concretes over conventional and ternary concrete.

Mechanical Strength Characteristics of Bio Concrete with Two Different Bacteria

Mechanical Strength Characteristics of Bio Concrete with Two Different Bacteria

Void characteristics and mechanical strength of cementitious mortars containing multi-walled carbon nanotubes

In this paper, the relationship between mechanical strength and void characteristics including porosity, the mean area of voids (MAV), and circularity was determined for the first time by analyzing the petrographic images of some cement mortars containing multi-walled carbon nanotubes (MWCNTs). The results showed that the compressive, tensile, and flexural strength for specimens containing 0.1% MWCNTs (optimum dosage of MWCNT) were 21, 12.5, and 9.5% more than that of the control samples, respectively. Also, it was shown that the application of MWCNTs can change the shape and the amount of voids, thereby imposing a significant impact on the mortar behavior. For the optimum dosage of MWCNTs, the porosity and MAV decreased about 63 and 71%, respectively, while the circularity enhanced 23% in comparison with the ordinary mortar samples. The void shape is one of the reasons for the enhanced properties of the MWCNT mortars. The image processing of the petrographic specimens and probability theorization revealed that the circularity of the voids had a significant impact on the flexural strength of the mortars, while the compressive strength was mostly affected by only the amount of porosity.

Effect of water on the time-frequency characteristics of electromagnetic radiation during sandstone deformation and fracturing

In order to study the effect of water on the electromagnetic radiation (EMR) signals released during rock deformation and fracturing, uniaxial compression experiments were performed on sandstone samples with different water contents. During the experiments, the EMR signals were acquired. Furthermore, the time-frequency characteristics of the signals were analyzed, and their generation mechanism and the effect of water were discussed in depth. The results show that the EMR energy released decreases gradually with the increase of water content, and the EMR energy and water content can be linked by a binomial equation. For sandstone with higher water content, the precursor characteristics of EMR released in the fracturing process are more obvious. With the increase of water content, the proportion of signals in the low frequency band grows gradually, while that of signals in high frequency band falls gradually. Water reduces the macroscopic mechanical strength and fracture mechanical characteristics of sandstone, which weakens the EMR signals produced by piezoelectric effect and charge separation. Besides, with respect to the microscopic fracturing mode, the sandstone with higher water content is more likely to undergo inter-granular fracturing, which may be an important microscopic reason for the weakening of EMR of water-bearing sandstone. An EMR-based damage evolution model of water-bearing sandstone was preliminarily established, and the model helps to calculate the stress state of water-bearing rock.

Physical and Combustion Properties of Binder-Assisted Hydrochar Pellets from Hydrothermal Carbonization of Tobacco Stem

Hydrothermal carbonization (HTC) combined with pelletization is an efficient upgrading process to convert biomass into energy-dense pellets. Binders usually serve an important role in the quality of biofuel pellets. Here, hydrochar was produced from tobacco stem through HTC, and was pelletized in the presence of various binders. The effect of four kinds of binders (K2CO3, CaCO3, xanthan gum and carboxymethyl cellulose) on the basic fuel properties, mechanical strength, moisture adsorption and combustion characteristics was investigated. The results showed that K2CO3 assisted pellet had decreased compressive strength, increased hygroscopicity and high combustion residues. The compressive strength of pellets increased with increasing amount CaCO3 binder probably due to the hardening effect of enhanced adhesion attraction forces between adjacent particles. Meanwhile, the CaCO3 assisted pellet exhibited the lowest moisture uptake behavior. In addition, the introduction of organic binders led to improved mechanical strength, especially for xanthan binder, which could be ascribed to the formation of solid bridges and enhancement of adhesion forces between particles. TGA results suggested that the binder-assisted pellets exhibited desirable combustion characteristics such as decreased ignition temperature and increased comprehensive combustibility index. Kinetic parameters of the combustion process of binder-assisted pellets were also determined by employing the model free isoconversional Kissinger–Akahira–Sunose method. This study demonstrated that HTC of tobacco stem combined with pelletization in the presence of appropriate binders provide an alternative for solid biofuel pellets production. Hydrothermal carbonization (HTC) of tobacco stem combined with pelletization in the presence of appropriate binders provide an alternative for solid biofuel pellets production.

Effect of addition of OPC on Performance characteristics of Self-compacting Alkali activated slag concrete mixes

An attempt has been made in the present research to develop construction friendly, self-compacting, alkali-activated slag concrete mixes with ground granulated blast furnace slag (GGBFS) as the major source of binder material. In an effort to make the concrete mixes more eco-friendly and sustainable, by-products from Iron and Steel Industry such as steel slag sand and Electric Arc Furnace (EAF) slag aggregates, were used as the fine and coarse aggregates respectively. While the total binder content has been varied in the range of 700 – 800 kg/m3 (in increments of 50 kg/m3), all the trial mixes had a constant w/b ratio of 0.40. Different amounts of sodium silicate solutions, with specified amounts of sodium hydroxide flakes dissolved in them, are used as alkaline solutions, with the combined Na2O percentage in them varying between 6% - 8%. Test specimens were cast with mixes which showed enhanced flow-properties as per relevant EFNARC guidelines and were tested for their mechanical strength and durability characteristics. Effect of admixing of ordinary Portland cement (OPC) in smaller percentages (2.5% - 10 %, in increments of 2.5%), on the performance characteristics of this novel class of AAC mixes is evaluated. Increased cement contents are found to lead to better flow ability properties and higher strengths values with lower sorptivity values in all the Cement-Admixed, Self-compacting, Alkali-Activated Slag Concrete mixes (CASAASC mixes) tested herein. Studies with a scanning electron microscope have shown more densified morphologies developed, accounting for better performances of these mixes.

Effect of Molybdenum Content on Structure and Properties of a Co-Cr Biomedical Alloy

The present study aimed to develop several Co-Cr biomedical alloys with different amounts of molybdenum. The weight percentages of molybdenum were in the range of 0-4 wt.% in the base alloy (Co-30Cr). The microstructures, phases, density, mechanical strength, wear behavior and corrosion characteristics of these alloys were evaluated. The results showed that density, hardness and compressive strength increased by increase in Mo content in the alloy. In contrast, corrosion rate decreased when the Mo weight percentage was increased. Furthermore, addition of Mo up to 3 wt.% caused the volumetric wear loss to increase. However, 4 wt.% Mo in the alloy led to a reduction in the volumetric wear loss, even lower than that of Co-30Cr alloy without molybdenum. The variations of friction coefficient, however, were different under different operating conditions. Since no single alloy could merely satisfy all the desired characteristics, the entropy–analytic hierarchy process (AHP)–gray relational analysis (GRA) technique was utilized to select the best alloy among the examined materials. From the ranking order gained, it was indicated that M-4 (having 4 wt.% Mo) biomedical alloy possesses the best combination of all the properties.

Influence of cyclic wetting‐drying on the mechanical strength characteristics of coal samples: A laboratory‐scale study

AbstractWater‐coal interactions have gained much recent attention, although few studies focus on the strength of coal under wetting‐drying cycles. This study investigates changes in the microstructure and mechanical strength of coal that are induced by water‐coal interactions, at the macroscale and microscale. Fourteen specimens after continuous wetting and fourteen specimens after wetting‐drying cycles were tested, indicating that peak stress and elastic modulus decrease with increasing continuous wetting time and number of wetting‐drying cycles, while peak strain increases. We analyzed changes in the coal microstructure using a scanning electron microscope (SEM) and the Image Pro Plus 6.0 (IPP 6.0) software. The regression model for cyclic wetting‐drying reveals that porosity and pore circularity are the main correlation indicators associated with uniaxial compressive strength. Therefore, different numbers of wetting‐drying cycles could induce different degrees of damage to coal, which increases progressively through gradual changes to its microstructure. These findings indicate that wetting‐drying cycles have a more significant impact on the stability of coal mass than continuous wetting. Our results are of use in determining the size of coal pillars, and expanding the knowledge base related to the mechanical properties of coal mass, water bursting, water recharge channels, and the stress‐crack‐permeability evolution law in mines.

A Study on the Fatigue Fracture for Out-Plane Shear According to TDCB Slope Angle by Using UD CFRP

Weight lightening in transport machines satisfies both internal combustion engines’ performance and efficiency and emission reduction technologies. Weight lightening is a part of ongoing research to increase the range of electric power sources. Carbon fiber reinforced plastics (CFRP) is a lightweight material with the highest specific strength. However, CFRP is used as a metal and dissimilar material in the part because it is vulnerable to the manufacturing process due to by the cracks in internal fiber structures. In this study, the design dimensioning, mechanical strength characteristics, and durability characteristics of tapered double cantilever beam (TDCB) with mode III (Out-plane shear) load according to slope angle using UD CFRP were determined through the adhesive peeling static and fatigue test. Mode III (Out-plane Shear) adhesive peeling static and fatigue tests showed that TDCB specimen has excellent strength and durability of 8° as a result of the mode III adhesive peeling static and fatigue test. The standards and methods used in this study were conducted in accordance with the British industrial standards (BS 7991) and ISO international standards (ISO 11343).

Experimental study on the mechanical strength and dynamic strain aging of Inconel 617 using small punch test

In the present work, the mechanical strength and deformation characteristics of Inconel 617 were studied using small punch test at different temperatures and deformation rates. As temperature increases, small punch characteristic parameters decreases and three temperature intervals are defined. An important conclusion here is that dynamic strain aging phenomenon can be found at a high-temperature small punch deformation of Inconel 617 in a multi-axial stress state. Due to serration plastic flow, small punch characteristic parameters of Inconel 617 appear no significant changes in the temperature range from 300 °C to 700 °C. To describe dynamic strain aging behaviour, serration type, critical displacement, and maximum load drop are discussed. As the temperature increases or deformation rate decreases, the serration type of the load–displacement curve gradually changes from Type A to Type C, and maximum load drop increases. Meanwhile, critical displacement displays normal and inverse behaviour at different temperature ranges. Based on the deformation characteristics analysis, the mechanical strength of Inconel 617 in different aging states was analysed. Finally, the relationship between the mechanical strength, small punch characteristic parameters and hardness was established. The results show that small punch test is an effective method for reasonably estimating the mechanical strength and dynamic-strain aging behaviour of Inconel 617.

Design and manufacture of a 100 kA coaxial pulsed power cable for plasma generator and PPS in ETC guns

Based on our previous pulsed current and internal overvoltage test data and the experience of common commercial high power cables, a 100 kA coaxial pulsed power cable is designed and manufactured to adapt the coaxial electric energy breech transmission between the plasma generator and the pulsed power supply (PPS) in electrothermal-chemical (ETC) guns. The index parameters are analyzed and determined. Semi-conductor layers and a shield stiffener are introduced to prevent the deformation and burst of the pulsed power cable structurally. The semi-conductor layer can eliminate the air gap and balance the electric field in the cable. The shield stiffener can multiply the mechanical strength to restrain the strong electrodynamic force produced by the core dislocation of the outer conductor. The multi-coupling of electromagnetic field, stress field and thermal field analysis are established to assist in aided design of electrical strength, mechanical strength and temperature rise characteristics. Both a DC voltage withstand test and pulsed discharge tests are introduced to verify and inspect the performance and dynamic response of the pulsed power cable. The 25 kV/5min DC voltage withstand test result shows that the sample leakage current is nearly 3 μA and no abnormal phenomena of the pulsed power cable sample occurred. The pulsed discharge tests show that the sample can sustain the 100 kA peak current. Furthermore, this 100 kA coaxial pulsed power cable can satisfy the ETC test requirements.

Characteristic properties of ceramic membrane derived from fly ash with different loadings and sintering temperature

Nowadays, ceramic membrane developed from wastes has gained attention, especially towards water separation applications. With abundant and high silica content of fly ash, low cost ceramic membrane was successfully prepared via phase inversion and sintering technique. Prior to both phase inversion and sintering process, ceramic suspension was prepared at different loadings, ranging from 40wt% to 50 wt% fly ash and subsequently sintered at temperature ranging from 1150°C to 1350°C. By varying fly ash content and sintering temperature, the morphology, mechanical strength and phase transformation characteristics of the prepared membrane were affected. The characterisation of prepared membrane were investigated by using scanning electron microscopy, three-point bending test, and X-ray diffraction (XRD). The mechanical strength of the membrane increased with increasing fly ash loading (up to 45 %), however too much fly ash loading resulted in decrease of its mechanical strength probably due the presence of unburnt at higher fly ash contents. This unburnt carbon contributed to the vacant space during sintering process and had the tendency to increase formation of pores, simultaneously reduced its mechanical strength. In addition, the SEM results also illustrated a cross-sectional image of the membrane which had become more elastic with increasing fly ash loading and denser as sintering temperature gradually increased. In addition, increasing the fly ash loading likely discouraged the formation of desired finger-like structure. The XRD results however showed continuous presence of mullite with the increasing sintering temperature which contributed higher mechanical strength. The preliminary performance tests indicated that the optimum conditions to produce hollow fibre ceramic membrane from fly ash were at 45 wt % fly ash loading sintered at 1350°C and has a pure water flux of 131 L/m2h.

Multi-scale investigation on the phase miscibility of polylactic acid/o-carboxymethyl chitosan blends

Absract Polylactic acid (PLA), due to its high mechanical strength, biocompatibility, excellent biodegradability and good processing characteristics, can be used to print the bone scaffold with complex structures, but the poor cell affinity and inflammation resulted by the acidity of intermediate produce still pose a challenge. To address these issues, o-carboxymethyl chitosan (CMC) was used to modify PLA, and the phase miscibility of PLA/CMC blends with different component ratios was investigated by a multi-scale method. Here, molecular simulation and experimental methods were applied to predict the miscibility of polylactic acid and o-carboxymethyl chitosan blends. Results indicated that PLA and CMC are miscible when the concentration of CMC in blends below 20 wt%, and partially miscible at 30 wt% concentration of CMC, but completely immiscible at higher CMC content (>30 wt%). Conclusions from this work can be used to forecast the miscibility of PLA/CMC composites at different compositions and can provide a scientific basis for formula designs of PLA/CMC polymer composites for 3D printing artificial bone scaffolds.

Investigation of fused deposition modeling processing parameters of 3D PLA specimens by an experimental design methodology

Abstract The main objective of this study is to analyze the tensile strength of PLA parts manufactured through fused filament fabrication (FFF) using a commercially available 3D printer. This study is primarily focused on the effects of the tensile strength of specimens subjected to the influence of four factors; layer thickness, fill density, raster orientation and sample structure type. A 2331 mixed-level factorial design approach was used, and the individual effects of the four main factors and their interactions determined. This experimental design had been implemented for two different infills: rectilinear and honeycomb. Specimens were printed at raster orientation angles of 30 °, 60 ° and 90 ° at a fill density of 50 % and 100 %. A layer thickness of 0.15 mm and 0.05 mm was chosen for printing the specimens. The samples were tested using a standard tensile testing machine with an extensometer to determine mechanical strength characteristics such as ultimate tensile strength, maximum force and maximum elongation. The data obtained was then analyzed using Minitab 13.20 software. The results showed that 30 ° raster orientation yields the highest mechanical properties at each individual layer when compared to 60 ° and 90 °. The fill density proves to be the most influential parameter on tensile strength, followed by the sample structure type. The results also found tensile strength to directly proporionate to layer thickness. By improving the material properties through the addition of layers as observed in the results, it will be possible to provide support for software developers, mechanical designers and engineers to reduce manufacturing time, material use and costs.

Evaluation of Mechanical Strength Characteristics of Double Ducted Unmanned Amphibious Aerial Vehicle using Finite Element Analysis

Unmanned Aerial Vehicles are extensively exploited for diverse applications importantly surveillance, defence and military, photography. Development of unmanned amphibious vehicle with integrating features of hovercraft principles and multirotor to navigate along and above the water surface, land surface and flying in the air is challenging demand. This article presents conceptual design of amphibious vehicle for the payload capacity of 7 kg with an endurance of 20 minutes and provision for mounting water sampler to collect water samples in remote water bodies. Structural strength characteristics of each part of the amphibious vehicle and integrity of same are analysed by Finite Element Analysis. FEA results indicated that the designed amphibious vehicle structure is well within the stress limit and minimal displacement is obtained. Based on structural analysis materials for various parts of the amphibious vehicle are determined and integrated structure is analysed.

Leather solid waste: An eco-benign raw material for leather chemical preparation – A circular economy example

One of the long lasting problems associated with leather industry is to meet environmental standards for both liquid and solid wastes. Statistics show that one tonne of wet-salted hides/skins yields around 650 kg of solid waste. Among various wastes generated, trimmings for the most part have been underutilized. Collagen presents in trimmings waste are effectively used but hair goes unutilized or at the most as feed for boilers during gelatin manufacturing. Hence, newer technology is needed for complete and effective utilization of raw trimmings. In leather manufacture, formaldehyde condensates polymers are used as re-tanning agent to enhance the compaction of leather. However, these products are hard for biodegradation and also cause the release of free formaldehyde in leather, which is a known carcinogen. Here, there is a need for development of formaldehyde free re-tanning agent for eco-benign leather processing. In this work an attempt had been made to develop formaldehyde free biodegradable eco-benign re-tanning agent from raw trimming of tannery solid waste as a circular economy model. Alkaline (7.5%w/w NaOH) – hydrogen peroxide (10%w/w) pre-treatment followed by thermal hydrolysis at 100 °C for 5 h was an optimized method for effective hydrolysis of trimmings and the process of preparation of product results in the holistic utilization of raw trimmings. The developed product was characterized using Dynamic light scattering and FTIR techniques. The product prepared was further used in leather manufacture as a re-tanning agent and was found to impart multifunctional properties to leathers such as fullness, grain tightness and shade of dye brilliance. Product improves the mechanical strength characteristics of leather and also the exhaustion of post-tanning chemicals. SEM analysis shows that the experimental leather is more compact and flat than control. This novel strategy had not only solved the issue of solid waste but also resulted in a greener leather auxiliary leading to greener environment.

Facile fabrication and performance comparison of aramid‐nanofiber membrane formed by water or ethanol

Favorable mechanical strength, thermal stability and transparency are important to polymeric composite membranes. Addressed herein is a facile fabrication and performance comparison of aramid nanofiber (ANF) membrane formed by water or ethanol. FTIR and XRD showed that no structural damage occurred in ANFs despite reduction in diameter. Both the two kinds of membrane demonstrated extraordinary thermal stability with a decomposition at above 500°C. High mechanical strength and different hydrophilic characteristics pave a way for expanding composites membranes with considerable attractive functionality. POLYM. COMPOS., 40:2534–2538, 2019. © 2019 Society of Plastics Engineers