Static Pressing Research Articles

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ВЗРЫВНОЙ ОБРАБОТКИ ПОЛИМЕРА НА ПРОЧНОСТНЫЕ ХАРАКТЕРИСТИКИ ПОЛУЧАЕМЫХ ЖЕЛЕЗОФТОРОПЛАСТОВЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ

The results of studies on the effect of polymer explosion treatment on the physical and mechanical properties of ferrofluoroplast composite materials are presented. It is shown that the compressive strength of materials obtained using blast treatment is higher than that of similar materials compacted by static pressing. Optimal temperature and time parameters of sintering of ferrous-fluoroplastic materials have been established, providing high strength and stability of geometric shapes and sizes of workpieces.

Equipment and Methodology for Studying the Behavior of High-Strength Steels Under Static Pressing of Plate Specimens

Equipment and Methodology for Studying the Behavior of High-Strength Steels Under Static Pressing of Plate Specimens

Properties of Compacts from Mixtures of Calcium Fluoride Micro- and Nanopowders

In this work, compacts from mechanical mixtures of CaF2 micron powder (MCP) with CaF2 nanopowder (NP) additives were produced, with mass ratios of the mixture components ranging from 10:0.125 to 10:1, respectively, using magnetic pulse (MP) and static pressing (SP) methods. The effects of pressure (Pp) and pressing temperature (Tp), concentration and phase composition of the additive on the density and color of compacts were studied, taking into account the properties of the initial components of the mixtures. The evolution of pulsed cathodoluminescence (PCL) spectra and photoluminescence (PL) of compacts from pure powders and their mixtures depending on Pp, Tp and characteristics of initial CaF2 NP was also studied. A new near-infrared (NIR) band associated with fluoride vacancies was discovered with a maximum at ~765 nm in PCL spectra of compacts produced by MP at a temperature of 425 °C. A blue band at 435 nm associated with impurity oxygen vacancies in the CaF2 lattice was found in PL spectra compacts of pure NP and powder mixtures. The density of compacts of pure NP and MCP reached 89% of the theoretical density, and the density of compacts of mixtures did not exceed 78%. The defective structure and phase composition of the CaF2 NP had a decisive effect on the luminescent properties of compacts from mixtures of micro- and nanopowders.

Dynamic pressing as a way of intensification of structural-phase transformations during sintering of ceramic materials

The article presents the studies results of magnetic-pulse pressing in relation to ceramic masses based on non-sintering loam with the addition of coal flotation waste and the possibility of its use as a method for intensifying structural and phase transformations during sintering of masses was shown. A comparative characteristic of the properties of ceramic materials obtained by the usual mode of heat treatment at a temperature of 950 °C by the method of magnetic-pulse pressing with different amplitude of impact force was presented. To determine the operating parameters influence of the magnetic-pulse press on the samples properties, their pressing was carried out with a controlled voltage at a constant capacitance of the capacitor. It was found that an increase in the amplitude of the impact force from 6 kN to 15 kN leads to a decrease in the water absorption of ceramic samples from 21.6 % to 12.1—15.0 %, open porosity from 34.6 % to 21.6—27.0 %, and a threefold increase in mechanical strength. In comparison with samples of static pressing, the cold crushing strength of dynamic pressing samples increases by 34 % (from 8.7 MPa to 13.1 MPa) even with the minimum amplitude of the impact force (6 kN). The macrostructure, phase composition and properties of dynamic pressing ceramic samples obtained at firing temperatures of 920 °C and 950 °C have been studied. It was found that the samples had practically the same level of technical characteristics (water absorption, density, and strength) and they were similar in structure and phase composition (quartz, microcline, ɑ-hematite, X-ray amorphous phase). The possibility of obtaining ceramic materials with a completed process of the structural-phase composition formation and properties at a lower firing temperature has been established.
 On the basis of carried out studies, the possibility of using dynamic pressing as a method for intensifying structural-phase transformations during sintering of ceramic materials has been shown, which can serve as a reserve for energy saving when obtaining ordinary structural building ceramics of increased grade.

STUDY OF THERMOMECHANICAL PROPERTIES OF UHMWPE

The paper presents comparative studies of the thermomechanical properties of ultra-high molecular weight polyethylene (UHMWPE) and its composite containing 0.5% coke-graphite powder (CGP). It was found that explosive pressing with a pressure of 0.25-0.6 GPa provides high heat resistance of UHMWPE and the investigated composite (154-156 ° C). The heat resistance of the composite decreases to 143-145 ° C, but it is higher than that of a similar material after static pressing (128 ° C).

STUDY OF THE INFLUENCE OF ALUMINUM DISPERSION ON THERMAL EXPANSION OF HIGHLY FILLED FLUOROPLASTIC COMPOSITE MATERIALS

The effect of dispersion and concentration of aluminum particles and sintering on the thermal expansion of fluoroplastic-aluminum composite materials has been investigated. Composite materials were obtained by static pressing of powder mixtures of fluoroplastic with 50 and 70% aluminum, followed by sintering. It was found that a decrease in the size of aluminum particles increases thermal expansion and decreases the density of CMs, but does not affect heat resistance. It was found that an increase in the aluminum concentration leads to a decrease in the thermal expansion of CM.

STUDY OF THE INFLUENCE OF METAL DISPERSITY ON THERMAL EXPANSION OF FLUOROPLAST-ALUMINUM COMPOSITE MATERIALS

The effect of dispersion and concentration of aluminum particles and sintering on the thermal expansion of fluoroplastic-aluminum composite materials has been investigated. Composite materials were obtained by static pressing of powder mixtures, followed by sintering. It was found that a decrease in the size of aluminum particles does not affect heat resistance, but increases thermal expansion and decreases the density of CM. Found that an increase in the aluminum concentration leads to a decrease in the thermal expansion of CMs before sintering and an increase after sintering.

Analysis of vibro-impact pressing of plant mass with clarification of the mathematical model of the process

Annotation Purpose. Improving the technical level of design of briquette presses through the analysis of the theory of vibro-impact pressing and refinement of the mathematical descriptive model of the process. Methods. The method of dynamic similarity is used to select the mass and stiffness of the model, when the frequencies of the model and the medium are the same. A set of differential equations of motion for solving a dynamic system of vibratory impact briquetting. Mathematical modeling, which assumes the dependence of the degree of compression of the plant mass on the magnitude of the impact load (pulse) and reveals the nonlinear nature of the resistance of the deformation medium. Results. The analysis of studies of dynamic compaction of plant materials for briquettes allowed identifying significant differences in research results. The process of briquetting plant mass under dynamic action is insufficiently studied. The limited scientific basis of vibro-impact briquetting of plant materials has a negative impact on the effectiveness of design developments. According to the results of comparative analysis with the use of certain research methods, a refined mathematical model of the process of vibratory impact briquetting in the form of a system of differential equations is obtained. This model takes into account the most important factors that determine the effectiveness of the vibrating shock press. Solving the equations of the obtained model assumes that the deformation of the material is influenced not only by inertial effects, but also by the rheological properties of the briquetted plant mass. Conclusions 1. Models of static pressing of crushed plant materials are based on the assumption that the processing speed has no significant effect on compaction performance. This assumption is not true in all cases, because the deformation of the material is affected not only by inertial effects, which in the case of static pressing can rightly be neglected, but also the rheological properties of the briquetted raw material. 2. According to the results of the analysis it is established that briquettes with a density of more than 1000 kg/m3 are formed under the pressure of the working body of the press more than 100 MPa. In general, the influence of dynamic (shock and vibration) loads on crushed plant materials at constant values of the parameters characterizing the deformation is considered. A fundamental difference from studies on the static effect on plant mass is the consideration of speeds and accelerations of the working body in the process of briquette formation, as well as caused by its influence of additional dynamic stresses in the plant mass. 3. The analysis of experimental data shows that the coefficient of viscous resistance for plant material is not a constant and varies depending on the density of briquettes. This confirms the need to take into account nonlinear models of briquetted plant material. Keywords: vibro-shock pressing, plant mass, dynamic loading, briquetting, research, analysis, models.

STUDY OF THE STRUCTURE OF HIGHLY FILLED FLUOROPLAST-ALUMINUM COMPOSITES

Structure formation in fluoroplastic-aluminum composites obtained by static and explosive pressing has been investigated. The concentration of dispersed aluminum was 50 and 70% vol. In fluoroplastic-aluminum composites, after static pressing, spalling of metal particles, formed during the preparation of a microsection, was found, which indicates low adhesion of the polymer and metal. The production of fluoroplastic-aluminum composites using explosive pressing leads to the formation of a monolithic material with a high adhesive interaction of the components and the formation of a metal frame.

Highly Ordered and Dense Thermally Conductive Graphitic Films from a Graphene Oxide/Reduced Graphene Oxide Mixture

Summary We report a new approach to making highly dense, oriented, and crystalline graphite films from heat-treated and pressed graphene oxide (G-O). By introducing small-diameter reduced graphene oxide (rG-O) flakes into the graphene oxide starting material, we found that after heat treatment at 3,000°C, the sample density and atomic order substantially improved over a film composed, at the outset, only of pure G-O flakes. A subsequent mechanical press increased the density but reduced the atomic order. A second 3,000°C heat treatment restored the graphitic structure with graphitization metrics exceeding even those of the first heat treatment. The optimized graphitic film with an original concentration of 15 wt % reduced G-O in G-O gave well-oriented graphitic films with a density of 2.1 g cm−3, cross-plane thermal conductivity of 5.65 W m−1 K−1, and in-plane thermal conductivity of 2,025 ± 25 W m−1 K−1.

Theoretical and experimental studies of the magnetic-pulse press for ceramic powders

Purpose. Investigate the influence of the half-wave and aperiodic inductor excitation pulse on the efficiency and thermal processes of a magnetic-pulse press operating in a cyclic mode. Experimentally establish the influence of the number of operating cycles on the indicators of pulsed pressing of ceramic powders. Methodology. With the help of a mathematical model, the thermal processes of a magnetic-pulse press of cyclic action with aperiodic and half-wave excitation pulses of an inductor winding depending on the number of excitation pulses are investigated. Experimental studies of samples formed of ceramic powders with a different number of power pulses were carried out on a model magnetic pulse press. Results. A mathematical model of a magnetic-pulse press of cyclic action has been developed, which at each working cycle calculates a complex of interconnected electromagnetic, mechanical and thermal processes. It has been established that during cyclic operation the temperature of the armature is higher than that of the inductor winding. With a significant period of pulse repetition during a pause, the temperature rise of the inductor increases slightly, and the anchors decrease markedly. Experimental studies on a model magnetic pulse press at each working cycle provided a force pressure pulse on a ceramic powder with amplitude of 85 MPa and a duration of 1 ms. Originality. It is established that the temperature rise of the inductor in a press with an aperiodic excitation pulse and full discharge of the capacitive drive is higher than when using a half-wave inductor excitation pulse and saving part of the energy in the drive during the entire cyclic process. Temperatures of the armature are almost the same. It is established that pulse pressing allows to obtain samples, the density of which is 12% higher than the density of samples obtained by static pressing. Practical value. It is shown that an increase in the number of power pulses compacts the ceramic powder, increasing the mechanical strength of the sample, reducing its porosity and water absorption

Effect of Explosive Processing on the Structure and Properties of Polyarylate

Polyarylate (PA, polyoxybenzoyl) is a heat-resistant linear aromatic polyester with a high degree of crystallinity, high physicomechanical and tribotechnical properties that is limited in the possibilities of processing into products. The polymer has low deformability and fluidity in the range of softening temperatures, as well as narrow temperature processing intervals, limited by the destruction temperatures. A promising way to obtain compacts from PA is explosive processing, which ensures the simultaneous realization of high pressure (up to 10 GPa) and temperature (up to 1000 °C). Comparative results of morphology, crystalline and chemical structure and thermomechanical properties of polyarylate after static pressing (SP) and explosive processing (EP) are presented. It was found that EP at the pressure of 2.8 GP, which excludes the destruction and decomposition of polymer compacts, does not cause significant changes to its phase composition, crystalline and chemical structure. The monolithic compacts obtained by EP have higher thermostability and heat deflection temperature than statically compressed ones.

Impact of pressure in static and dynamic pressing of ultrafine plasmochemical ZrO2 (Y)-Al2O3 powders on compact density and compaction efficiency during sintering

The effect of different methods of pretreatment and compacting of ultrafine alumina-zirconia powders of composition (in mass%): 20 Al2O3-80 (ZrO2-Y2O3) on densification processes during pressing and subsequent calcination has been studied. Ultrafine powders were prepared by plasma-chemical method. It was found that the initial nanocomposite is a mechanical mixture made up of zirconia nanoparticles and amorphous alumina in a thermodynamically nonequilibrium state. Grinding of powders did not affect their phase state. Powder compacts were produced by means of uniaxial static pressing and magnetic pulse compaction. The impact of mechanical processing of powders on ceramics density was studied. It was shown that dry grinding of powders in a planetary ball mill does not increase the ceramics density. The best and virtually identical results were obtained using preliminary static pressing of powders at increased pressure P = 900 MPa and their subsequent grinding in a ball mill. Dilatometric studies showed that double-action magnetic pulse compaction provides the maximum shrinkage rate at lower temperatures in comparison to that observed under static pressing. The ceramic density achieved is higher than that obtained using other pressing methods.

Influence of Mechanical Treatment on Consolidation Processes of Ultradisperse Powders of Stabilized Zirconium Oxide

The effect of preliminary machining of ultradisperse powders of stabilized zirconium dioxide and its composite on consolidation in compacts under uniaxial static pressing and subsequent sintering is studied. The investigations were carried out with powders of compositions (in mol %) 97ZrO2–3Y2O3 and 80Al2O3–20(ZrO2–Y), which were obtained by the sol-gel and the plasma-chemical method, respectively. Mechanical processing of powders was carried out in two ways. The first method consisted in preliminary static pressing of powders at elevated pressure of 900 MPa and their subsequent grinding in a ball mill. The second method consisted in grinding the initial powders in an Activator-2SL planetary mill with drums and grinding balls of zirconia. It is established that mechanical treatment significantly affects the density of compacts. In this case, there is no strict correlation between the density of the sintered ceramic and the density of compacts. With increasing density of compacts, their expansion can be observed at the isothermal holding stage, which leads to a decrease in density of the ceramic. It is shown that, in dry grinding to improve the technological properties of ultradisperse powders obtained by the sol-gel and plasma-chemical methods, the most suitable is the method of mechanical treatment, which consists in pre-pressing the powders at elevated pressure and then grinding them in a ball mill.

Influence of metallic additives on manganese ferrites sintering

Influence of cuprum nanopowder additive received by electric explosion on the process of manganese ferrites MgFe2O4 consolidating at thermal sintering was researched by dilatometry method. Cuprum nanopowder at a rate of 5 mass % was added into the original commercial-grade powder of manganese ferrite MgFe2O4. Powder mixture was numerously blended with screening for better blending before pressing. Powder compacts were formed by cold one-axle static pressing. It was proved that introduction of cuprum additive caused shrinkage increase at final heating stage. There was abnormal compact enlarging at sintering in the air at isothermal stage; the specified process was not observed in vacuum. This difference can be explained by changes in conditions of gaseous discharge from volume of pores.

Impact of pressure in static and dynamic pressing of zirconia ultradisperse powders on compact density and compaction efficiency during sintering

This paper studies the impact of pressure in static and dynamic pressing on densification of stabilized zirconia ultradisperse powder compacts and on compaction kinetics during sintering. Ultradisperse powders of 97 ZrO2 + 3 Y2O3 zirconia were synthesized using the plasma chemical method. Dry uniaxial static pressing and double-action magnetic pulse compaction were employed. It is shown that double-action magnetic pulse compaction provides the maximum density of the product in comparison to that obtained through static pressing. The dilatometric studies showed that the increased density of compacts from stabilized zirconia powders obtained in dynamic pressing does not make ceramics less compact during isothermal aging as it typically occurs during static pressing. This increases the density of ceramics and improves its mechanical characteristics.

Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior.

Advantages of quasi-isostatic pressing for powder materials

The first technology for quasi-isostatic pressing that does not use costly isostatic presses has been developed in Russia. The pressing operation is performed in quasi-isostatic molds on conventional hydraulic or mechanical presses normally used for static pressing. This article examines the advantages that quasi-isostatic pressing has over hydrostatic and static pressing.

Industrial technology for the automated production of grinding balls by quasi-isostatic pressing

An automated high-productivity method of making grinding balls that was first developed in Russia ensures the manufacture of high-quality products and is the most cost-effective method of isostatic pressing. This article examines the advantages of the method over static and hydrostatic pressing.

Green Body Behaviour of High Velocity Pressed Metal Powder

High velocity compaction (HVC) is a production technique with capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts. Several investigations indicate that high-density components can by obtained using HVC. Other characteristics are low ejection force and uniform density. Investigated here are green body data such as density, tensile strength, radial springback, ejection force and surface flatness. Comparisons are performed with conventional compaction using the same pressing conditions. Cylindrical samples of a pre-alloyed water atomized iron powder are used in this experimental investigation. The different behaviour of HVC-pressed green bodies compared to conventional pressed green bodies are analysed and discussed. The HVC process in this study resulted in a better compressibility curve and lower ejection force compared to conventional quasi static pressing. Vertical scanning interferometry (VSI) measurements show that the HVC process gives flatter sample surfaces.