Mechanical Strength Values Research Articles

The influence of different heat treatment cycles on the properties of the steels HARDOX® 500 and STRENX® 700

The HARDOX® 500 and STRENX® 700 steels are quenched materials from hot rolling process. The HARDOX® 500 is a low alloy steel with high values of microhardness and mechanical strength, the STRENX® 700 steel is a low alloy steel structural used in applications, where low density is associated with high mechanical strength. In this work, the two steels were submitted to different heat treatments: quenched and tempering, normalization and full annealing. The effects of these heat cycles were analyzed by optical microscopy and Vickers microhardness techniques. It was concluded that in the normalization treatment, the microhardness reduction of HARDOX® was more significant than that one of STRENX®. In the quenched and tempering process, both presented higher microhardness compared to the originally produced and characterized material with higher austenitic grain refining. The HARDOX® presented an effective increase of microhardness. In the heat treatment of full annealing, the HARDOX® 500 and the STRENX® 700 steels had similar microhardness and microstructural morphology values.

ANALISA REKAYASA SIFAT MEKANIK BAJA AISI 4140 DENGAN VARIASI SUHU TEMPERING UNTUK MENINGKATKAN KEULETAN DAN KEKERASAN MATERIAL

Steel is a type of material that is widely used as a main material in the manufacture of various kinds of industrial and automatic machinery spare parts. Some mechanical properties of steel that are often used in design are hardness, ductility and toughness. Often in a design, we have difficulty getting steel with mechanical properties that are appropriate with the design. For this reason, engineering carried out mechanical properties engineering, to obtain steel in accordance with design calculations. AISI 4140 steel is a medium alloy steel. This steel is often used for industrial and automotive machinery parts. This research engineered the mechanical properties of the steel, namely the hardness and ductility of the material. The process is carried out by conducting steel hardening at 850 °C followed by rapid cooling with water media. After that, tempering at temperatures of 300 ᵒC, 400ᵒC and 500ᵒC by cooling together with the furnace. The result is hardness and tensile strength of the material has increased, when compared with untreated material. This method is effectively used to obtain mechanical strength values in accordance with technical planning calculations. . Keywords: Tempering, AISI 4140, Mechanical Properties Engineering

Self-sensing Piezoresistive Composites Based on Cement Incorporating Low Dosage of Carbon Black Used as Multifunctional Construction Materials

HIGHLIGHTS -Carbon black (CB) particles in nanometric domain can be successfully incorporated in cement matrices in order to obtain special concretes/mortars with self-sensing properties. -Piezorezistivity monitoring of mortars is a non-destructive method used to assess the structural characteristics of composite materials. -The presence of CB in studied mortars provides a specific electrical sensitivity which may change when curing time increases. The paper presents the manufacture and characterization of special mortars based on Portland cement (PC) and a nanopowder with electrical properties (carbon black - CB). These materials were characterized from the point of view of mechanical strengths as well as properties specific for self-sensing materials i.e. variation of electrical signal when applying a mechanical strain. The electrical signal and mechanical strength values are strongly dependent on the composition and microstructure of mortars.The values of electrical resistance are strongly correlated with the composition, morphology and curing time of the mortars. In this study significant changes of the electrical behaviour (piezoresistivity) of the mortars vs. curing time (90 or 180 days) were noticed, so this must be considered in practical applications. The best results were obtained for the mortars with 0.5-3 wt.% CB cured for 180 days.

Environmental, mechanical, and biochemical benefits of water hyacinth (Eichhornia crassipes).

Water hyacinth (WH) has high tolerance in extreme environmental conditions. Here, we examined the potentials of WH (Eichhornia crassipes (Mart) solms) to remove excess nutrients from sewage wastewater. We used four prototypes of water systems: prototypes A (WH + underlay water) and C (WH + sewage water), whereas prototypes B and D were experimental control for A and C, respectively. For prototype A, the percentage removal efficiencies (%Re) for nitrate and phosphate achieved were 75.12 ± 4.22% and 78.90 ± 8.72%, respectively, with a pH increase from 6.29 to 7.69; whereas for prototype C, the values were 54.7 ± 8.11% and 86.10 ± 7.34%, respectively, with a pH decrease from 8.13 to 7.15. For the 3-week retention time, the biomass weight increased in both prototype A (33.26%; [Formula: see text] rate = 15.46g/week) and prototype C (26.43%; [Formula: see text] rate = 12.54g/week). Further, the respective mechanical strength and nutritional values of the WH's fiber and the organic extracts were examined. The air-dried WH stem showed an average tensile stress of 0.04MPa on a load at maximum stress of 137.1N. By comparison, a strand of WH has a tensile strength of 14MPa, inferior to 15, 61, and 400MPa shown by timber, wood, and steel, respectively. However, by knitting, four strands of WH yielded a much-improved tensile strength of 315MPa. Finally, a gas chromatography-mass spectrometer analysis of the plant's extract showed that it contains 35.51% oleic acid, a nutritional extract of high value. Thence, we established a profound economic significance of WH, a macrophyte with latent immense benefits.

Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

AbstractThe aim of this study was to help drive the Tunisian construction industry towards a more sustainable approach given the existence of abundant local raw material deposits that could be exploited for the production of low-CO2binders. Various clay sediments from the Kebili region (southern Tunisia) were characterized by chemical analysis, X-ray diffraction, thermal analysis and geotechnical tests to determine their suitability for the preparation of geopolymer binders. The clays consist of illite and kaolinite with other accessory minerals. To test the possibility of using these materials as precursors for the production of low-CO2and low-cost geopolymers, the raw samples were calcined and activated by addition of solid sodium silicate. Compressive strength tests performed on four alkali-activated clays show that promising mechanical performance may be achieved, with mechanical strength values as high as 25 MPa after 7 days, depending on the clay composition. The mechanical strength is related to the SiO2:Al2O3and Al2O3:(NaO2+ K2O) ratios. Careful selection of the raw materials is, therefore, an essential step in the exploitation of clay deposits to be used for the production of ecological materials such as geopolymers.

Gelatin improves peroxidase-mediated alginate hydrogel characteristics as a potential injectable hydrogel for soft tissue engineering applications.

To develop an efficient injectable alginate-based hydrogel for soft tissue engineering applications, phenol moiety (Ph) was introduced into alginate (Alg-Ph), and the influence of gelatin as cell adhesive molecule was evaluated on the peroxidase-mediated alginate hydrogel properties and cultured chondrocytic cell behavior. Addition of gelatin (1.5% w/v) to Alg-Ph (1.5% w/v) hydrogels (Alg-Ph/gelatin) regulated characteristics of the enzymatically gellable alginate hydrogel with increasing gelation time to 5.1 min (76%). Swelling ratio and degradation rates of the Alg-Ph/gelatin hydrogel also increased 60 and 100%, respectively, while the mechanical strength value was 35% less than the Alg-Ph hydrogel. Scanning electron microscopy images showed that the addition of gelatin could also increase uniformity of pore sizes inside the Alg-Ph/gelatin hydrogels. The chondrocyte cells maintained their original phenotype and revealed statistically more metabolic activities in the Alg-Ph/gelatin hydrogel. Hydrogels subscutaneously implanted in rats could also be identified readily without complete absorption and signs of toxicity or any untoward reactions after 1 month. Viable chondrocyte cells inside globular aggregates were seen as red colored areas in the cell-laden hydrogels. The study demonstrates that enzymatically gellable alginate/gelatin hydrogel has fair potential as a natural-based injectable hydrogel for soft tissue engineering applications.

3D-printable lightweight foamed concrete and comparison with classical foamed concrete in terms of fresh state properties and mechanical strength

This paper presents a novel type of foamed concrete that is termed “3D-printable lightweight foamed concrete” (3DP-LWFC). Unlike classical lightweight foamed concrete (C-LWFC), this novel material is able to keep its shape at the fresh state due to enhanced consistency and viscosity. This peculiarity lends itself to being implemented in automated extrusion production process and 3D printing applications without the use of formwork, which is particularly convenient in the building industry. These unique fresh state properties of 3DP-LWFC are demonstrated through a specific extrusion test conceived and used in this experimental campaign, and highlighted by comparison with results related to C-LWFC. Despite the remarkably different behavior of the novel material at the fresh state, the mechanical strength of 3DP-LWFC is even slightly higher than C-LWFC. This is demonstrated through a wide experimental campaign focused on the compressive and flexural strength of 3DP-LWFC, which includes different dry densities, curing conditions, cement types, water/cement ratios. Additionally, the effect of the mixing conditions on the mechanical strength of 3DP-LWFC, in particular the rotational speed of the mixer during the preparation of the paste, is also analyzed and discussed. It is found that the increase of mixing intensity from 1200 rpm to 3000 rpm resulted in a considerable increase of mechanical strength values of 3DP-LWFC, up to more than 70% for the compressive strength and up to around 100% for the flexural strength.

On the movement of briquetted mass in extruder. Exact solutions

The increased interest in cold agglomeration in recent years has been largely due to the successful experience in operating briquette lines based on stiff vacuum extrusion (SVE). The high performance of SVE extruders and the satisfactory metallurgical properties of extrusion briquettes obtained this way (brex) make it possible to consider this cold agglomeration technology as promising. SVE extruders allow efficient briquetting of the materials with moisture contents values in the range of 12 – 16 % and compacting pressure of 3.5 – 4.5 MPa, leading to the possibility of achieving high values of mechanical strength of raw briquettes and eliminates the need for drying briquetted charge and heat treatment of the green briquettes. The growing scale of practical use of extruders in the steel industry necessitated the development of simple and effective methods for determining their operating parameters. The briquetted mass is a moistened plastic mass, driven by the blades of a rotating auger and squeezed out further through the holes in the extruder die in the form of elongated briquettes, repeating in cross section the shape of the hole. In application to the optimization problems of extrusion briquette technology, the exact solution of the Navier–Stokes equations for a viscous incompressible medium shifted between coaxial cylinders along the common axis of symmetry and twisted around it by longitudinal displacement and axial rotation of the inner cylinder is given, respectively, under sticking conditions and given longitudinal pressure drop. In particular, it was found that the speed of transportation of the mixed mass cannot exceed the speed delivered by the supplied pressure, and the formula of the latter is transferred to the compressible medium as a special viscosity integral for a viscoplastic medium, where it serves as a generalization of known exact solutions. A similar solution for a compressible medium is being sought. The obtained analytical dependencies can be used to calculate the parameters of industrial briquette extruders operating in both the stiff extrusion mode and the semi-stiff and soft extrusion mode, differing in the moisture values of the briquetted mass and the values of the applied pressure.

Single step heat treatment for the development of beta titanium composites with in-situ TiB and TiC reinforcement

Titanium matrix composites have been attracting great interest from aerospace industry due to favorable properties like thermal stability, high specific strength, corrosion, and wear resistance. Optimal relation between mechanical properties demands complex processing routes and, in this context, the effects of a single-step processing route on microstructure and mechanical properties of β titanium matrix composites was placed on focus in this study. The commercial TIMETAL Beta 21S alloy and its modification with the addition of B4C were developed, allowing in-situ formation of TiB and TiC particles in a β matrix. The composites presented highest values of mechanical strength and hardness, and the addition of 3% of B4C provided a significant reduction in grain size, and compressive yield strength and ultimate compressive strength values of 1205 MPa and 1636 MPa, respectively, with a maximum deformation of 20.5%. An orientation relationship investigation provided information about some unconventional relation between the present phases.

Influence of the Test Configuration and Temperature on the Mechanical Behaviour of WC-Co

In this work, the effect of the test configuration and temperature on the mechanical behaviour of cemented carbides (WC-Co) with different carbide grain sizes (dWC) and cobalt volume fractions (VCo), implying different binder mean free paths (λCo), was studied. The mechanical strength was measured at 600 °C with bar-shaped specimens subjected to uniaxial four-point bending (4PB) tests and with disc specimens subjected to biaxial ball-on-three-balls (B3B) tests. The results were analysed within the frame of the Weibull theory and compared with strength measurements performed at room temperature under the same loading conditions. A mechanical degradation greater than 30% was observed when the samples were tested at 600 °C due to oxidation phenomena, but higher Weibull moduli were obtained as a result of narrower defect size distributions. A fractographic analysis was conducted with broken specimens from each test configuration. The number of fragments (Nf) and the macroscopic fracture surface were related to the flexural strength and fracture toughness of WC-Co. For a given number of fragments, higher mechanical strength values were always obtained for WC-Co grades with higher KIc. The observed differences were discussed based on a linear elastic fracture mechanics (LEFM) model, taking into account the effect of the temperature and microstructure of the cemented carbides on the mechanical strength.

Evaluation of thermoplastic polyolefin materials for the hard shed of composite insulators

AbstractThis article explores the possibility of using polyolefin materials for composite insulator sheds. The transfer component (silicone oil or erucamide) is added into a polyolefin material to improve its hydrophobic properties. Results show that the silicone oil‐modified polyolefin material (polyolefin‐S) exhibited an obvious hydrophobicity transfer property. When the equivalent salt deposit density and nonsoluble deposit density are 0.1 and 0.5 mg/cm2, respectively, the static contact angle increases from 75° to 87° as the silicone oil transfer time increases from 24 to 96 hr. Meanwhile, polyolefin‐S exhibits high mechanical strength, hardness, volume resistivity, and surface resistivity values of 21.4 MPa, 62.6 HD, 1.7 × 1015 Ω m and 1.2 × 1016 Ω, respectively. Moreover, polyolefin‐S shows excellent tracking and erosion resistance of 4.5 kV level in the inclined plane test. The results verify that the polyolefin material is a promising candidate material for the hard shed of composite insulators.

Influence of dispersed fillers on properties and processability of polyvinyl chloride compositions

In this reaserch, the results of filling PVC compositions are presented on the example of only two types of dispersed fillers from among industrial wastes, presented in the form of fine particles and highly porous grains:beghouse dust and expanded perlite sand. The influence of the type of filler on the value of mechanical strength was also studied by the method of measuring it under one-side pressure. It was established that when filling with ultrafine filler BP, an increase in the elastic modulus and complete “degeneration” of the forced high elasticity are observed. It seems interesting the change of the melt flow index of PVC compositions with the introduction of both fillers.

On the Movement of Briquetted Mass in Extruder. Exact Solutions. 1

The increased interest in cold agglomeration in recent years has been largely due to the successful experience in operating briquette lines based on stiff vacuum extrusion (SVE). The high performance of SVE extruders and the satisfactory metallurgical properties of extrusion briquettes obtained in this way (brex) make it possible to consider this cold agglomeration technology as promising. SVE Extruders allow efficient briquetting of the materials with moisture contents values in the range of 12–16% and compacting pressure of 3.5–4.5 MPa, leading to the possibility of achieving high values of mechanical strength of raw briquettes and eliminates the need for drying briquetted charge and heat treatment of the green briquettes. The growing scale of practical use of extruders in the steel industry necessitated the development of simple and effective methods for determining their operating parameters. The briquetted mass is a moistened plastic mass, driven by the blades of a rotating auger and squeezed out further through the holes in the extruder die in the form of elongated briquettes, repeating in cross section the shape of the hole. In application to the optimization problems of extrusion briquette technology, the exact solution of the Navier–Stokes equations for a viscous incompressible medium shifted between coaxial cylinders along the common axis of symmetry and twisted around it by longitudinal displacement and axial rotation of the inner cylinder is given, respectively, under sticking conditions and given longitudinal pressure drop. In particular, it was found that the speed of transportation of the mixed mass cannot exceed the speed delivered by the supplied pressure, and the formula of the latter is transferred to the compressible medium as a special viscosity integral for a viscoplastic medium, where it serves as a generalization of known exact solutions. A similar solution for a compressible medium is being sought. The obtained analytical dependencies can be used to calculate the parameters of industrial briquette extruders operating in both the stiff extrusion mode and the semi-stiff and soft extrusion mode, differing in the moisture values of the briquetted mass and the values of the applied pressure.

Optimization of Veneer Drying Temperature for the Best Mechanical Properties of Plywood via Artificial Neural Network

The drying of veneer is an essential part of the veneer-producing process to aid the gluing during the manufacture of the plywood and laminated veneer lumber. Determining the optimum veneer drying temperature without decreasing of mechanical properties is also very important from industrial viewpoint. Due to the high drying costs, increased temperatures are being used commonly in plywood industry to reduce the overall drying time and increase capacity. However, high drying temperatures can alter some physical, mechanical and chemical characteristics of wood and cause some drying-related defects. In this study, it was aimed to predict the optimum drying temperature for alder and scots pine veneers via artificial neural network modelling for optimum mechanical properties. Therefore, mechanical strength values of plywood panels manufactured from alder and scots pine veneers were dried at temperatures of 110, 130, 150, 170, 190 and 210°C. Shear strength, bending strength and modulus of elasticity of the plywood panels were experimentally determined according to EN 314-1 and EN 310 standards. Then, the mechanical strength values based on veneer drying temperatures are subjected to prediction by artificial neural network modelling. As a results of this study, the optimum drying temperature values were obtained as 165, 162 and 161°C in Scots pine plywood and 190, 195 and 196°C in alder plywood, for best shear strength, bending strength and modulus of elasticity values, respectively.

Low cost pyrrhotite ash/clay-based inorganic membrane for industrial wastewaters treatment

The elaboration and optimization of a low-cost microfiltration membrane based on natural clay and pyrrhotite ash solid waste were performed leading to a change in the membrane surface morphology and improved its hydrophobicity. The impact of pyrrhotite ash fraction and sintering temperature on mineralogy, morphology, porosity, permeability, mechanical strength and corrosion resistance was evaluated. The highest values of permeability and mechanical strength were 22.88 10−7 m3/h m².kPa and 27.42 MPa respectively, for the membrane prepared with 50 % of pyrrhotite ash and sintered at 1000 °C. Two different tannery and dairy industrial wastewaters were tested. The filtration efficiency at different transmembrane pressures was evaluated by the rejection rate of turbidity, conductivity, pH, oil and fat. The performance of conventional treatment such as sedimentation compared to MF confirmed that the elaborated membrane consists the best alternative, with a removal rate of organic oil and fat about 94 %, and practically a total reduction of water turbidity up to 100 %, compared to sedimentation with only 15 % and 72 % respectively, the conductivity of permeate was not much different from the conductivity of the raw wastewater, and only a few percent for chrome. Additionally, the four models of Hermia were adopted to study the membrane fouling phenomena where the cake formation model fits best to the flow decline experimental data during the filtration of both effluents. The process developed in this investigation can be considered an eco-friendly one since it tends to valorize the pyrrhotite ash solid waste and preserve natural clay, moreover, it staves off energy waste by avoiding dry step during the thermal treatment of ceramics.

Diagnostics of the ice on the strike protection wire

The relevance of the research problem is chose of effective technology of strike protection wire monitoring in span with use of technical system of analysis of technical condition of strike protection wire of 110 kV voltage power line for complex assessment of the impact of both external climatic factors from wind and ice loads and the magnitude of the thermal elongation of the strike protection wire with influence of current during de-icing process. Analysis of the strike protection wire mode and their limiting values of mechanical strength allow evaluation of the effectiveness of events of prevent of accidents and reduce the undersupply of electricity to the end consumers. Visualization of the operative parameters of the strike protection wire in the span of the overhead power line will allow reduce the time to make decisions on the prevention of accidents of lines. Algorithm of monitoring of operative parameters of wires of overhead power lines base on information of longitudinal and transverse angles received from sensors installed directly on the strike protection wire.

Evaluation on relationship between accelerated carbonation and deterioration of concrete subjected to a high-concentrated sewage environment

Performance of concrete with different carbonation degrees subjected to a high-concentrated domestic sewage environment was studied to explore the relationship between concrete carbonation and concrete degradation. An accelerated carbonation method was adopted to obtain concrete specimens with various degrees of carbonation. The properties of the corroded concrete, including surface appearance, mass loss, mechanical strength and pH value as well as microstructure, were evaluated. It was found that the pH value of the carbonated concrete had an exponential function along with the carbonation depth, which can be considered as an index to present the change in the carbonation degree. Although concrete carbonation played a role to increase its compressive strength, the decrease in surface alkalinity of concrete accelerated the concrete deterioration when exposed to the sewage environment. With the increase of the carbonation degree, the strength loss of the corroded concrete increased gradually due to the seriously deteriorated microstructure. The sharp decrease in the content of element Ca on the surface layer of the carbonated concrete also indicated that the carbonation promoted the decalcification of hydration products and the generation of bio-acids. Furthermore, both the corrosion depth and the mass loss of concrete increased with the decrease of their surface pH values after exposure to the sewage, and there was a power function between the surface pH value and sewage attack extent of concrete.

Engineering applications of chemically-bonded phosphate ceramics

Phosphate cements originated more than a century ago for specific applications to the field of dentistry. These cements have other applications including: biomaterials with bone applications, stabilization of hazardous waste, and structural cements. However, the applications in civil infrastructure are recent and not widely known. Therefore, this review discusses and analyzes phosphate cements, presenting the most significant findings of the research to address their mechanical behavior of these cements. It also describes the impact and application of phosphate cements as a structural product (pastes, mortars and concretes), in addition to typical values of mechanical strength, workability, commercial applications, etc. As a result, the review allows to elucidate advantages and disadvantages in comparison with existing technologies and the mechanical possibilities of these cements as biomaterials and for the immobilization of radioactive waste.

Effect of several parameters on non-autoclaved aerated concrete: use of recycling waste perlite

This article presents the results of an experimental study on a new protocol to create a non-autoclaved cellular concrete containing a partial substitution of sand by an equivalent volume of pure perlite and perlite waste. The development of the experimental protocol was performed based on a series of steps to control each parameter that influences this swelling procedure (temperature, water content, duration, containment, restricted swelling and filling height). Each parameter has been the subject of feasibility test, process and thermal validation analysis. The perlite pure or waste used for volume substitution (30%/30%) of sand was characterised by a lower density, which allowed the concrete to swell under non-autoclaved conditions. Each element were tested to evaluate their influence on thermal insulation properties. Presence of recycled product decreased the mechanical strength but promoted thermal insulation properties. An optimisation of the formulation is needed to keep a high porosity but obtained a better mechanical strength. With an increase of 2% of cement we can increase the mechanical strength value of 21%. Based on the investigated formulations, 100% expanded material with a thermal conductivity of 0.176 W/m.K was achieved. As such, the non-autoclaved swelling protocol facilitated the development of insulation material based on recycled products.

Analysis of the Mechanical Strength of Polymeric Composites Reinforced with Sisal Fibers

ABSTRACT This work focused on the evaluation of the mechanical strength of sisal fiber reinforced composites panels in view of using vacuum infusion processing method. The most recent market requirements are green material, which is sustainable and eco-friendly. The polymer used in the composite matrix is a polyurethane derived from castor oil and therefore, fits in the concept of green material, for its renewable source and solvent-free production method. The vacuum infusion of the polymer within a sealed bag is a production method that avoids/reduces the formation of bubbles within the mold, which in turn can produce composite panels with higher values of mechanical strength. For the evaluations in this work, several panels were produced with the different architecture of fabrics. The variations consisted of the production of aligned fibers; one-layer of plain weave fabric and three-layers of plain weave fabric. Mechanical strength was evaluated by means of tensile test and flexural three point bending tests; the morphology of the fracture surface was evaluated by SEM images. The tensile strength of the panels resulted in values of 146.34 MPa, 9.19 MPa and 15.87 MPa for aligned, one-layer, three-layers panels, respectively. The flexural strength resulted in values of 23.23 MPa for three-layers panels.