Constant Rate Compression Research Articles

Fabrication and Mechanical Evaluation of Eco-Friendly Geopolymeric Mortars Derived from Ignimbrite and Demolition Waste from the Construction Industry in Peru

Ignimbrite rock is a volcanic material located in the Arequipa region (Peru), and for centuries, it has been used as a construction material, giving a characteristic light pastel, white to pink color to the city of Arequipa, with white being the most common. In the present study, the potential use of three types of Arequipa raw materials (ignimbrite rock powder, calcined clay powder, and demolition mortar powder) as the main source of new binders or the manufacture of environmentally friendly mortars, without the addition of ordinary Portland cement (OPC) is discussed. In this work, an in-depth characterization of the materials used was carried out. The proposed fabrication route for geopolymeric materials was considered for the manufacture of binders and mortars using an alkaline solution of NaOH with values between 12 and 18 molar, as a trigger for the geopolymerization process. Geopolymeric mortars were obtained by adding a controlled amount of fine sand to the previously prepared mixture of binder raw material and an alkaline solution. Conventional OPC and geopolymeric mortars manufactured under the same conditions were mechanically evaluated by uniaxial compression tests at a constant compression rate of 0.05 mm/min and under normal conditions of temperature and atmosphere, where the most optimal values were obtained for 15 molar alkaline solutions of ignimbrite without the addition of aggregates, with values of compressive strength of 42 MPa and a modulus elastic of 30 GPa. The results revealed a significant increase in the maximum strength and modulus of elasticity values when the volumetric fractions of OPC are completely replaced with geopolymeric binders in the study conditions of this work, demonstrating the enormous potential of the ignimbrite rock and construction waste studied, as raw material of alternative mortar binders without the addition of OPC. With this work, the ignimbrite rock, of great value in the region and also found in other areas of the Earth’s geography, was characterized and valued, in addition to the calcined clay and demolition mortar of the region.

Synthesis and thermomechanical behavior of SiC/Si compounds derived from wood waste

The traditional method of manufacturing SiC compounds is associated with a serious environmental problem, mainly due to the need for large amounts of energy (generally derived from oil) to reach processing temperatures (typically above 2500 ºC). In addition, the chemical reaction that gives rise to the formation of SiC has CO and CO2 as by-products. Therefore, in this work an alternative method to manufacture SiC/Si composites using waste from the wood industry as the main raw material was developed. SiC/Si composites were fabricated by infiltration of molten silicon into carbon preforms at 1500 °C. The carbon preforms were obtained by pyrolysis (in an inert Ar atmosphere) of four types of resin-carbon mixtures. The carbon used in the mixtures was obtained by pyrolysis of sawdust powder.The mechanical and thermomechanical behavior in uniaxial compression was studied at a constant compression rate of 0.05 mm/min at different temperatures (ambient, 1100 °C and 1400 °C). The maximum resistance values found were in the range of 58 and 384 MPa, while the Young's modulus values were between 40 and 120 GPa. The porosity found in the materials was between 1 and 4%. Finally, the fabricated compounds presented a homogeneous microstructure of interconnected silicon carbide in gray contrast and dispersed and unconnected whitish phases of uniformly distributed silicon.

Comparative research on tension-compression mechanical properties of the azide propellant

While the azide propellant is a typical particle-reinforced composite material, its mechanical properties are quite different under two different loads of tension and compression. In order to study the possible relationship between the tension and compression mechanical properties of the propellant, so as to further study the loading mechanism of the propellant, this paper carried out constant-rate tension and constant-rate compression tests of the azide propellant and measured the stress-strain curves in different loading case for follow-up comparative study. The mechanical properties of the propellant under different loading rates were analyzed quantitatively, and the differences between the tension and compression stresses of the propellant at different strain rates were quantitatively analyzed, and the change rules of tension-compression mechanical properties of the azide propellant were obtained. The research results can provide the basis for the application analysis of the azide propellant in the engine, and the research method can provide a reference for the tension-compression comparative study of other types of propellants.

On the Orowan stress in intermetallic ODS alloys and its superposition with grain size and solid solution hardening

Abstract The intermetallic trialuminide Al67Ti25Cr8 was strengthened by nano-scaled dispersions of up to 3 vol.% yttrium and aluminum oxide via mechanical milling. Subsequent powder consolidation, heat treatment, and thermo-mechani-cal treatment yielded grain growth to an increasing degree, resulting in grain sizes ranging from sub-μm level to about 0.5 mm. Consequently, the room-temperature yield strength σ 0 as determined by constant compression rate tests, increases due to three different hardening contributions, namely dispersion strengthening σ OR due to Orowan bypassing, fine-grain strengthening σ HP due to Hall-Petch relation, and, finally, as virtually always present, some solid-solution strengthening σ s. The analysis of the particle parameters was done using TEM as well as focused ion beam (FIB) imaging. The latter provides the opportunity to directly determine the mean radius r s of planar intersections with spherical particles and their nearest-neighbour spacing L since it displays a plane section through the 3-dimensional arrangement of dispersoids. The analysis of the strengthening contributions indicates that a Pythagorean superposition permits an appropriate modeling of the measured yield strength σ 0.

Pressure Equilibrium Time of a Cyclic-Olefin Copolymer.

Integrative simulation techniques for predicting component properties, based on the conditions during processing, are becoming increasingly important. The calculation of orientations in injection molding, which, in addition to mechanical and optical properties, also affect the thermal shrinkage behavior, are modeled on the basis of measurements that cannot take into account the pressure driven flow processes, which cause the orientations during the holding pressure phase. Previous investigations with a high-pressure capillary rheometer (HPC) and closed counter pressure chamber (CPC) showed the significant effect of a dynamically applied pressure on the flow behavior, depending on the temperature and the underlying compression rate. At a constant compression rate, an effective pressure difference between the measuring chamber and the CPC was observed, which resulted in a stop of flow through the capillary referred to as dynamic compression induced solidification. In order to extend the material understanding to the moment after dynamic solidification, an equilibrium time, which is needed until the pressure signals equalize, was evaluated and investigated in terms of a pressure, temperature and a possible compression rate dependency in this study. The findings show an exponential increase of the determined equilibrium time as a function of the holding pressure level and a decrease of the equilibrium time with increasing temperature. In case of supercritical compression in the area of a dynamic solidification, a compression rate dependency of the determined equilibrium times is also found. The measurement results show a temperature-invariant behavior, which allows the derivation of a master curve, according to the superposition principle, to calculate the pressure equilibrium time as a function of the holding pressure and the temperature.

Assessment of the stability of co-amorphous olanzapine in tablets

Introduction Amorphous and co-amorphous (CAM) materials have recently been used to improve oral bioavailability of drugs, by enhancing water solubility and dissolution rate from solid dosage forms [1,2]. However, stress conditions imposed on amorphous systems during production of such dosage forms (e.g. pressure upon tableting), can revert the drug back into the less soluble crystalline form [3]. This work thus presents a methodology to monitor and quantify the fraction of amorphous olanzapine (OLZ) remaining in immediate release OLZ tablets (Table 1). Table 1. Predicted fraction of amorphous OLZ, by NIR and FTIR spectroscopies, in tablets prepared with the co-amorphous system. ID NIR FTIR CAM physical mixture 100 100 CAM 8 kN 0DT 89 98 CAM 8 kN 20DT 94 94 CAM 25 kN 0DT 95 93 CAM 25 kN 20DT 98 95 Materials and methods Near infra-red (NIR, 9000–4000 cm−1) and Fourier-transform infra-red (FTIR, 4000–500 cm−1) techniques were used to quantify the fraction of co-amorphous OLZ (30%) with saccharin (SAC; 18%) in formulations containing also calcium phosphate (27%), microcrystalline cellulose (20%) and povidone (5%). Tablets (250 mg) were obtained using a universal testing machine fit with circular punches (7.5 mm Ø), at a constant compression rate of 10 mm/min (n = 5); different compression forces (8 and 25 kN) and dwell times (DT; 0 and 20 min) were considered. Evaluation of the impact of the compression conditions on the recrystallization of OLZ from a co-amorphous system was based on a computational model. Results Using a 2nd derivative filter to process both NIR and FTIR spectra, the quantification of amorphous olanzapine was possible with a root mean square error of calibration and prediction above 2% (Figure 1). The method was further applied to evaluate the stability of co-amorphous systems after tableting, revealing that no significant recrystallization occurred, i.e. the co-amorphous were stable under the stress conditions applied. Discussion and conclusions: The use of NIR and FTIR resulted in high correlation between the predicted values and the expected ones, thus enabling these spectroscopic techniques to be used to monitor the conversion of amorphous into crystalline OLZ forms and thus estimate the impact on drug bioavailability. Understanding of the conversion kinetics will ultimately allow anticipation of the time for complete recrystallization. The model developed has also demonstrated that tablets produced were stable, since no recrystallization was observed. Figure 1. NIR calibration curve used to predict the amorphous fraction of OLZ..

Undulating compression and multistage relaxation in a granular column consisting of dust particles or glass beads

For fundamentally characterizing the effect of hierarchical structure in granular matter, a set of compression-relaxation tests for dust particles and glass beads confined in a cylindrical cell was performed. Typical diameter of both grains is approximately 1~mm. However, dust particles are produced by binding tiny ($\sim 5$~{\textmu}m) glass beads. The granular columns were compressed with a piston until reaching a maximum load force of 20~N with a constant compression rate $v$ ($0.17 \leq v \leq 2000$~{\textmu}m~s$^{-1}$). After that, the piston was stopped and the relaxation process was quantified. From the experimental results, we found that the compression force $F$ nonlinearly increases with the increase of compression stroke $z$ depending on particles. Besides, periodic undulation and sudden force drops were observed on $F(z)$ in dust particles and glass beads, respectively. The relaxation process was characterized by an exponential decay of stress followed by a logarithmic dependence one in both kinds of particles. These experimental findings are the main point in this study. To understand the underlying physics governing the compression mechanics, we assumed empirical forms of $F(z)$; $F\propto z^{\alpha}$ for dust particles and $F \propto \exp(z/z_G)$ for glass beads ($\alpha=2.4$ and $z_G=70$~{\textmu}m). Then, we found that the growing manners of periodic undulation and force drops were identical to those of mean compression forces, i.e., power law in dust particles and exponential in glass beads. In addition, the undulation amplitude and wavelength decreased as $v$ increased in dust-particles compression. On the basis of experimental results and the difference between dust particles and glass beads, we also discuss the origin of undulation and the physical meaning of granular-compression models used in engineering fields.

Dynamic Compression Induced Solidification.

This study presents a method for the determination of the dynamic pressure-dependent solidification of polycarbonate (PC) during flow using high pressure capillary rheometer (HPC) measurements. In addition, the pressure-dependent solidification was determined by isothermal pressure-volume-temperature (pvT) measurements under static conditions without shear. Independent of the compression velocity, a linear increase of the solidification pressure with temperature could be determined. Furthermore, the results indicate that the relaxation time at a constant temperature and compression rate can increase to such an extent that the material can no longer follow within the time scale specified by the compression rate. Consequently, the flow through the capillary stops at a specific pressure, with higher compression rates resulting in lower solidification pressures. Consequently, in regard to HPC measurements, it could be shown that the evaluation of the pressure via a pressure hole can lead to measurement errors in the limit range. Since the filling process in injection molding usually takes place under such transient conditions, the results are likely to be relevant for modelling the flow processes of thin-walled and microstructures with high aspect ratios.

Thermomechanical evaluation of new geopolymer binder from demolition waste and ignimbrite slits for application in the construction industry

ABSTRACTGeopolymeric mortars with volumetric fractions of 0.6:1:0.3 for a binder powder, fine sand and sodium hydroxide solution (12M), respectively; have been fabricated by mixing the solid materials and the subsequent addition of sodium hydroxide solution 12M to form a workable paste, to later be cured for 28 days at room temperature. The microstructures of the fabricated materials reveal the existence of two phases with notable difference, one continuous to the geopolymer binder phase and another discontinuous of fine sand particles agglutinated by the binder phase. Mechanical compression tests are performed at a constant compression rate of 0.05 mm/min and at temperatures ranged from room temperature to 500°C. The mechanical results are ranged from 19 and 69 MPa for all the materials studied. On the other hand, there was an increase in mechanical resistance up to test temperatures of 200°C and the progressive reduction of resistance at temperatures above 200°C, with a fragile-ductile transition zone between 400 and 500°C and completely ductile behavior from test temperatures of 500°C.

Fabrication of New Geopolymer Binder from Demolition Waste and Ignimbrite Slits for Application in the Construction Industry

Geopolymeric mortars with volumetric fractions of 0.6:1:0.3 for a binder powder, fine sand and sodium hydroxide solution (12M), respectively; have been fabricated by mixing the solid materials and the subsequent addition of sodium hydroxide solution 12M to form a workable paste, to later be cured for 28 days at room temperature. The microstructures of the fabricated materials reveal the existence of two phases with notable difference, one continuous to the geopolymer binder phase and another discontinuous of fine sand particles agglutinated by the binder phase. Mechanical compression tests are performed at a constant compression rate of 0.05 mm/min and at temperatures ranged from room temperature to 500°C. The mechanical results are ranged from 19 and 69 MPa for all the materials studied. On the other hand, there was an increase in mechanical resistance up to test temperatures of 200°C and the progressive reduction of resistance at temperatures above 200°C, with a fragile-ductile transition zone between 400 and 500°C and completely ductile behavior from test temperatures of 500°C.

Fabrication and Properties of High Temperature Proton Conducting Perovskites

High temperature protonic conductors (HTPC) were fabricated by solid-state sintering and by melt processing by laser-heated floating zone method. Several families of compositions were selected: SrCe1-xMxO3-δ (with M: Zr and Y; x = 0.1, 0.2), BaCe1-xMxO3-δ (with Yb, Ca and Y; x = 0.05, 0.2), Sr3Ca1.18Nb1.82O9-δ, SrZr0.8Y0.2O3-δ and SrTi0.95Sc0.05O3-δ. Their mechanical properties have been studied by compression test at constant load and constant compression rate. As produced directionally solidified materials presented a unique microstructure consisting of strongly textured cells with an intercellular phase. The cells have a crystalline Pnma structure. The relation between the processing, dopants, microstructure and mechanical properties is discussed. Understanding of plasticity is important to determine the ultimate component performance, and because its direct relationship to processing and transport. The high temperature mechanical properties of melt grown crystals are superior to the mechanical properties of polycrystals.

P-55: Tiny Codec for Decreasing Frame Memories in Display Driver ICs — Smart Pixel-Data Codec (SPC)

We propose a tiny compression and decompression codec, Smart Pixel-data Codec (SPC), for display pixel data. This codec can greatly reduce frame memories with a constant data compression rate and, therefore can reduce chip area of display driver ICs. Since random accessibility to the frame memory is kept for the SPC circuit, it is very suitable for the circuit implementation on display driver ICs. Comparable image quality with original images has practically been achieved even for the compression rate of 72%.

Efficient compression of borehole resistivity and acoustic imaging data using wavelets

This paper presents a new approach to borehole resistivity and acoustic imaging data compression. The method is based on the discrete wavelet transform (DWT) combined with the set partitioning in the hierarchical trees (SPIHT) coding method. The primary advantages of the DWT + SPIHT method are its superior compression performance, simple implementation, and constant compression and transmission rate control. This new approach generally performs better than the traditional discrete cosine transform (DCT) followed by Huffman coding methods such as JPEG, particularly for target compression ratios greater than 50:1. Image block size plays a key role in using this method. To achieve the best compression performance, the image block size needs to be selected appropriately. In general, large image block sizes and more DWT decomposition levels result in higher compression ratios and/or fewer reconstruction errors. Whenever possible, image block sizes that allow the maximum levels of dyadic DWT decomposition should be used. When insufficient data samples are available in either depth or azimuthal direction, a small number of extra data samples can be added without sacrificing the overall compression performance. The DWT + SPIHT method also shows good fidelity in representing major features in borehole images such as fractures and sinusoids.

On the Orowan stress in intermetallic ODS alloys and its superposition with grain size and solid solution hardening

Abstract The intermetallic trialuminide Al67Ti25Cr8 was strengthened by nano-scaled dispersions of up to 3 vol.% yttrium and aluminum oxide via mechanical milling. Subsequent powder consolidation, heat treatment, and thermo-mechanical treatment yielded grain growth to an increasing degree, resulting in grain sizes ranging from sub-µm level to about 0.5 mm. Consequently, the room-temperature yield strength σ0, as determined by constant compression rate tests, increases due to three different hardening contributions, namely dispersion strengthening σOR due to Orowan bypassing, fine-grain strengthening σHP due to Hall – Petch relation, and, finally, as virtually always present, some solid-solution strengthening σs. The analysis of the particle parameters was done using TEM as well as focused ion beam (FIB) imaging. The latter provides the opportunity to directly determine the mean radius rs of planar intersections with spherical particles and their nearest-neighbour spacing L since it displays a plane sectio...

Deformation characteristics of Mg 60Cu 30Y 10 alloy at temperatures near Tg

The mechanical behaviour of nanocrystallized samples with a crystalline volume fraction of 15%, 50%, 75% and 100% was investigated by constant compression rate tests at different strain rates at 430 K and shows an increase in yield or flow stress provided that their crystalline volume fraction were less than 50%.

Al-Mn-Ce quasicrystalline composites: Phase formation and mechanical properties

Aluminium-based composites with quasicrystalline particles as reinforcements were synthesized via the powder metallurgy processing route. In order to obtain bulk samples with a nanoscale microstructure most equivalent to that resulting from rapid solidification, powders of Al-Mn-Ce alloys were prepared by pulverization of melt-spun ribbons using a planetary ball mill. Significant differences in the phase formation upon quenching, composite microstructure and thermal stability of the microstructure were found for different alloy compositions. Severe grain growth during the subsequent consolidation by hot extrusion caused the formation of a micrometre-scale composite instead of the nanoscale phase mixture initially existing after rapid solidification. After hot extrusion, the specimens were deformed by compression at a constant compression rate at room temperature. With an ultimate strength of up to 975 MPa and a ductility of more than 4% the material yields excellent properties compared with conventionally produced aluminium-based alloys.

Synthesis and mechanical properties of mechanically alloyed Al-Cu-Fe quasicrystalline composites

Al-Cu-Fe alloys were prepared by mechanical alloying starting from elemental powders in a high-energy planetary ball mill. Three different alloy compositions with the same c Cu : c Fe ratio of 2:1 but different aluminium contents, that is Al55Cu30Fe15, Al63Cu25Fe12 and Al70Cu20Fe10, were investigated. A sequence of solid-state reactions resulting in quasicrystalline phase formation in Al63Cu25Fe12 proceeds during milling and during annealing of the as-milled powder. These reactions were studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. In order to form an aluminium-matrix composite, Al63Cu25Fe12 single-phase quasicrystalline powders were blended with different amounts of aluminium. In an intermediate milling step the powder blend was homogenized. The powders were consolidated by hot extrusion. The bulk samples revealed a homogeneous dispersion of the particles in the matrix but a rather heterogeneous size distribution. The mechanical properties at room temperature were tested by constant-rate compression tests. A rule-of-mixtures dependence of the ultimate strength and the yield strength on the volume fraction of the quasicrystalline particles was found.

Computer-controlled pneumatic pressure algometry—a new technique for quantitative sensory testing

Hand-held pressure algometry usually assesses pressure-pain detection thresholds and provides little information on pressure–pain stimulus–response function. In this article, a cuff pressure algometry for advanced pressure-pain function evaluation is proposed.The experimental set-up consisted of a pneumatic tourniquet cuff, a computer-controlled air compressor and an electronic visual analogue scale (VAS) for constant pain intensity rating. Twelve healthy volunteers were included in the study. In the first part, hand-held algometry and cuff algometry were performed over the gastrocnemius muscle with constant compression rate. In the second part, the cuff algometry was performed with different compression rates to evaluate the influence of the compression rate on pain thresholds and other psychophysical data. Pressure-pain detection threshold (PDT), pain tolerance threshold (PTT), pain intensity, PDT–PTT time and other psychophysical variables were evaluated.Pressure-pain detection thresholds recorded over the gastrocnemius muscle with a hand-held and with a cuff algometer, were 482±19kPa and 26±1.6kPa, respectively. Pressure and pain intensities were correlated during cuff algometry. During increasing cuff compression, the subjective pain tolerance limit on VAS was 5.6±0.95cm. There was a direct correlation between the number of compressions, the compression rate and pain thresholds.The cuff algometry technique is appropriate for pressure-pain stimulus–response studies. Cuff algometry allowed quantification of psychophysical response to the change of stimulus configuration.

Synthesis and mechanical properties of cast quasicrystal-reinforced Al-alloys

We report on the preparation and mechanical properties of Al-based-composites with quasicrystalline particles as reinforcement. Al–Mn–Ce/Fe and Al–Mn–Pd bulk samples were synthesized by die casting into a copper mould at moderate cooling rate. Thin ribbons were prepared by melt-spinning as a reference state for the phase formation under most rapid quenching conditions. Microstructural analysis was done using X-ray diffraction, scanning and transmission electron microscopy as well as calorimetric methods. Significant differences in the phase formation, the composite microstructure and the thermal stability of the microstructure were found for different alloy compositions. The deformation behaviour was characterized by constant-rate compression tests at room temperature for a number of alloy variations yielding excellent properties compared to conventionally produced Al-alloys. The mechanical properties vary within a wide range of strength and ductility as a function of the quasicrystal volume fraction and their morphology. Also first tests at elevated temperatures were carried out, revealing a promising high temperature stability of the composite.

Nanostructured materials in multicomponent alloy systems

Production of bulk nanostructured composites with amorphous matrix revealing a significant supercooled liquid region was carried out by die casting and mechanical alloying (MA) and subsequent consolidation at elevated temperatures. Multiphase materials with different volume fractions of nanocrystalline precipitates were prepared from as-cast fully amorphous samples by isothermal annealing. In contrast, MA powders were blended with insoluble metallic and oxide particles upon milling. The different samples were analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and transmission electron microscopy (TEM), and viscosity measurements. The mechanical behavior of cast samples was investigated using constant (true) compression rate tests at strain rates ranging from 1×10 −5 to 3×10 −3 s −1. The Newtonian viscous flow behavior of the composites at temperatures around T g is mainly triggered by the homogeneous flow of the supercooled liquid. The easy flow behavior above T g was used to consolidate bulk dense specimens from mechanically alloyed composite powders. Microhardness measurements at room temperature reveal a substantial increase of the hardness of the composites due to the uniform distribution of nanoscale particles.