MPa Tension Research Articles

Born suckers: the cibarial pump of Philaenus spumarius scales across ontogeny to ensure functional equivalence.

A select group of hemipterans within the suborder Auchenorrhyncha are the only animals that feed exclusively on xylem sap - a nutritionally poor liquid that exists under negative pressure within a plant's xylem vessels. To consume it, xylem-feeding bugs have evolved enlarged cibarial pumps capable of generating enormous negative pressures. A previous study examining the allometry of this feeding model suggested that small xylem feeders pay relatively higher energetic costs while feeding, favouring the evolution of larger-bodied species. However, this interspecific analysis only considered adult xylem-feeding insects and neglected the considerable intraspecific change in size that occurs across the insect's development. Here, we examine the changes in cibarial pump morphology and function that occur during the development of Philaenus spumarius, the common meadow spittlebug. We show that the cibarial pump scales largely as expected from isometry and that the maximum negative pressure is mass independent, indicating that size has no effect on the xylem-feeding capacity of juvenile spittlebugs. We conclude that a first instar nymph with a body mass 2% of the adult can still feed at the >1 MPa tension present in a plant's xylem vessels without a substantial energetic disadvantage.

Influence of Biosynthesized Nanoparticles Addition and Fibre Content on the Mechanical and Moisture Absorption Behaviour of Natural Fibre Composite

This study looks at how incorporating nanofiller into sisal/flax-fibre-reinforced epoxy-based hybrid composites affects their mechanical and water absorption properties. The green Al2O3 NPs are generated from neem leaves in a proportion of leaf extract to an acceptable aluminium nitrate combination. Both natural fibres were treated with different proportions of NaOH to eliminate moisture absorption. The following parameters were chosen as essential to achieving the objectives mentioned above: (i) 0, 5, 10, and 15% natural fibre concentrations; (ii) 0, 2, 4, and 6% aluminium powder concentrations; and (iii) 0, 1, 3, and 5% NaOH concentrations. Compression moulding was used to create the hybrid nanocomposites and ASTM standards were used for mechanical testing such as tension, bending, and impact. The findings reveal that combining sisal/flax fibre composites with nanofiller improved the mechanical features of the nanocomposite. The sisal and flax fibre hybridised successfully, with 10% fibres and 4% aluminium filler. The water absorption of the hybrids rose as the fibre weight % increased, and during the next 60 h, all of the specimens achieved equilibrium. The failed samples were examined using scanning electron Microscopic (SEM) images better to understand the composite’s failure in the mechanical experimentations. Al2O3 NPs were confirmed through XRD, UV spectroscope and HPLC analysis. According to the HPLC results, the leaf’s overall concentrations of flavonoids (gallocatechin, carnosic acid, and camellia) are determined to be 0.250 mg/g, 0.264 mg/g, and 0.552 mg/g, respectively. The catechin concentration is higher than the phenolic and caffeic acid levels, which could have resulted in a faster rate of reduction among many of the varying configurations, 4 wt.% nano Al2O3 particle, 10 wt.% flax and sisal fibres, as well as 4 h of NaOH with a 5 wt.% concentration, producing the maximum mechanical properties (59.94 MPa tension, 149.52 Mpa bending, and 37.9 KJ/m2 impact resistance). According to the results, it can be concluded that botanical nutrients may be used effectively in the manufacturing of nanomaterials, which might be used in various therapeutic and nanoscale applications.

Residual stresses in additively manufactured parts: predictive simulation and experimental verification

PurposeThe purpose of this paper is to investigate a simulation solution for estimating the residual stresses developed in metal fused filament fabrication (MF3) printed parts. Additionally, to verify these estimates, a coupled experimental–computational approach using the crack-compliance method was investigated in this study.Design/methodology/approachIn this study, a previously validated thermomechanical process simulation was used to estimate the residual stresses developed in the MF3 printing process. Metal-filled polymer filament with a solids loading of 59 Vol.% Ti-6Al-4V was studied. For experimental validation of simulation predictions, the MF3 printed green parts were slitted incrementally and the corresponding strains were measured locally using strain gauges. The developed strain was modeled in finite-element-based structural simulations to estimate a compliance matrix that was combined with strain gauge measurements to calculate the residual stresses. Finally, the simulation results were compared with the experimental findings.FindingsThe simulation predictions were corroborated by the experimental results. Both results showed the same distribution pattern, that is, tensile stresses at the outer zone and compressive stresses in the interior. In the experiments, the residual stresses varied between 1.02 MPa (tension) and −2.28 MPa (compression), whereas the simulations were predicted between 1.37 MPa (tension) and −1.39 MPa (compression). Overall, there was a good quantitative agreement between the process simulation predictions and the experimental measurements, although there were some discrepancies. It was concluded that the thermomechanical process simulation was able to predict the residual stresses developed in MF3 printed parts. This validation enables the printing process simulation to be used for optimizing the part design and printing parameters to minimize the residual stresses.Originality/valueThe applicability of thermomechanical process simulation to predict residual stresses in MF3 printing is demonstrated. Additionally, a coupled experimental–computational approach using the crack-compliance method was used to experimentally determine residual stresses in the three-dimensional printed part to validate the simulation predictions. Moreover, this paper presents a methodology that can be used to predict and measure residual stresses in other additive manufacturing processes, in general, though MF3 was used as demonstrator in this work.

Yield-water relationships of lentil grown under different rice establishments in Lower Gangetic Plain of India

In the Indian subcontinent, lentil (Lens culinaries Medik) is cultivated mainly on carry-over residual soil water and nutrients in rainfed rice (Oryza sativa L.), coincided with increasing temperatures during the reproductive period, thus limiting seed yield. We examined the effect of rice establishment method (REM) viz. direct-seeded rice (DSR) and puddled-transplanted rice (PTR), tillage viz. zero tillage (ZT) and conventional tillage (CT), and nutrient management viz. improved package of practices (IP) including basal (20:40:20::N:P2O5:K2O) and foliar fertilization (2% urea, 0.5% Zn and 0.25% B) and farmers’ practice (FP) with no fertilization on the performance of cool-season lentil concerning soil water retention, crop water stress affecting actual evapotranspiration (ETa), yield and water productivity (WP) on an Aeric Haplaquept, clay loam soil in rainfed rice-fallows of Lower Gangetic Plain (LGP) of India during 2014–15 and 2015–16 cropping seasons. Among the treatments, PTR–ZT had significantly higher profile water storage i.e. 158.84, 141.74, 129.28, and 104.84 mm at sowing, vegetative, flowering, and pod formation periods, respectively. However, at the time of initiation of flowering DSR–CT achieved 0.8 MPa tension as compared to 0.3, 0.2, and 0.1 MPa for PTR–CT, DSR–ZT, and PTR–ZT. Bulk density was increased exponentially with the time that reduced root penetration except for PTR–ZT which maintained the lowest bulk density of 1.43 Mg m−3 at the reproductive stage with minimum soil water stress coefficients (Ks). Treatment combinations of PTR–ZT–IP produced the highest ETa (80 mm) with maximum seed yield (1281 kg ha−1) and WP (1.62 kg m−3), and also exhibited the lowest yield response factor (Ky = 0.87) of lentil which made the plant tolerate to water stress and enhanced the productivity even above the national average. An average of 1% relative yield loss per 1% decline in relative ET suggests the suitability of growing of lentil crop in this post-rice residual water regimes of LGP.

Chitosan and collagen composite for potential application as bone substitute

Biopolymers, such as chitosan and collagen, have excellent biocompatibility and can be used for bone remodeling. Chitosan and collagen can be crosslinked by glutaraldehyde. The aim of this study was to formulate a chitosan, collagen, and calcium phosphate-based device for potential application as bone substitutes. The device was synthesized, molded, dried, and characterized. By FTIR, it was possible to observe a characteristic peak relating to the crosslinking of chitosan and collagen. The images of SEM and BET/BJH results showed the presence of apparent and interconnected pores. TG-DSC have shown two temperature ranges for weight loss. Mechanical tests provided an elastic modulus equal to 239.25 ± 78.37 MPa and maximum tension of 4.33 ± 0.95 MPa, which are comparable to some commercial bone substitutes and other similar synthetic devices. The synthesized device showed interconnected pores and surficial porosity, besides thermal stability at physiological temperature, and mechanical properties comparable to spongy bones.

Elastic tension induced lattice distortions in DD10 single crystal nickel-based superalloy at 500 °C/760 MPa using in situ neutron diffraction

A newly-developed in situ neutron diffraction method has been employed to search elastic tension induced lattice distortions in DD10 single crystal nickel-based superalloy under tensile condition of 500 °C/760 MPa. Multiple lattice reflections, viz., {002}, {003}, {220}, {311} were in situ measured. Two samples which were stretched along [001] direction and 18° deviation of [001] direction, respectively, were measured for comparison. As samples were heated to 500 °C, the lattice stress of both samples gradually relaxes. With 760 MPa tension applied, the response of reflections of γ and γ’ phases were anisotropic. Compared with 0° sample, 18° sample resulted in distinguishable results. Due to the large extra stress, the mismatch along [001] direction is much negative, whereas that perpendicular to [001] get slightly positive. Owing to the different stress states, γ phase is divided into two conditions. The tetragonal distortion with c/a of γ⊥ channel is largest, while that of γ’ phase is small. The distortions at γ/γ’ phase boundary result in broadening the boundary of γ’ phase. In this work, a new elastic-induced lattice distortion model that enhances apprehensions to the constraint effect between γ and γ’ phases is built, which might provide the directly experimental evidence to the origin of rafting.

Primary radiation damage of Fe-10%Cr models under uniaxial, biaxial, and hydrostatic pressure using MD simulation

Reduce activation ferritic/martensitic steels are candidate materials for future nuclear reactors due to their superior mechanical properties and reduced swelling under irradiation. In this research, single−crystal models of Fe-10%Cr have been built with [100][010][001] crystal orientations. The models stressed in both compression and tension by applying seven different pressures between −1000 MPa (tension) to +1000 MPa (compression) in uniaxial, biaxial, and hydrostatic cases. Displacement cascades have been initiated by imparting kinetic energy to an atom in the center of the simulation box. The produced point defects have been identified using the Wigner−Seitz cell method. In all cases, increasing the imparted energy increases the number of point defects. For models under uniaxial pressure, three different regions have been identified and each region has its own unique mechanism that controls the defect production process. For models under biaxial and hydrostatic pressure, the number of produced point defects increases with increasing the pressure in both tension and compression regions; in addition, the number of produced point defects with pressures shows an empirical power relationship. The Cr atoms prefer interstitial positions over creating vacancies in all cases.

KORELASI NILAI KOEFISIEN ARAH SERAT BETON TERHADAP KEKUATAN TARIK LENTUR PADA BETON DENGAN SERUTAN BAJA MAUPUN HAREX SF

Concrete has high compressive strength that is capable of supporting a large and heavy structures. But concrete has a low tension strength and brittle nature (Brittle). The weakness of this concrete properties can be improved by providing treatment such as provide fiber. There are several fibers that can be used to improve the properties of concrete and one of them is the steel fibers. Steel fibers possess the strength and modulus of elasticity which is relatively high. Moreover steel fibers do not change the shape of the influence of alkali in the cement. Imposition in a long period o f time does not affect the mechanical properties of steel fiber. Bond in the composition of the mixture can be increased because fastening mechanically. The study used the steel shavings and fiber materials Harex SF. The aim of this examination was intended to determine the coefficient of concrete fiber orientation at the same time the value of flexural tension strength of concrete produced in the concrete mix wearing Harex SF fiber or steel shavings. Steel fiber used in this study using the percentage of 1 until 4 percent of the weight of the concrete mix and perform quality control for the split tension strength of concrete at 28 days. From this research, the percentage of 3 percent as the optimum value based on the ease of doing the concrete (workability) used for research flexural tension strength of concrete and fiber orientation coefficient of concrete in the concrete with steel shavings and concrete with fibers Harex SF. From the testing that has been done shows: flexural tension strength fiber-reinforced concrete Harex SF 3 percent of 5,037 MPa and flexural tension strength of concrete with steel shavings of 11,035 MPa and the coefficient offiber direction concrete well with fiber Harex SF and shavings o f steel both are between 0 and 1 (0 less than or equal to eta of phi less than or equal to 1) with an average value close to 0, which means both fibers are working properly so that is proven to increase the tension strength offlexural concrete.

Structural Hybrid Supercapacitor

Supercapacitors (SCs) have attracted tremendous attention due to their high specific power and long cycle life. The two major issues with SCs are low specific energy and self-discharge. The benefits of doping mediators or redox species in electrolytes include: 1) providing extra pseudocapacitance out of bulk of electrode materials, 2) increasing the electronic and ionic conductivities of electrolyte in the composite electrodes; and 3) releasing the ions into electrolyte to promote the capacity of electrolyte. Redox species or mediators as dopants in electrolytes are reported to realize the specific capacitance up to 400-500 F/g and the specific energy up to 30-50 Wh/kg. For the issue of self-discharge, adding primary cell materials into the mediator SC is proposed because the materials can provide a micro-current to compensate the self-discharge current. In this research, Cu powder/CuSO4 and Zn powder/ZnSO4 were added into the positive and negative electrodes respectively. The positive electrode also contained PVDF/LiTFS polymer electrolyte doped with K4Fe(CN)6 as mediator whereas the negative electrode contained PVDF/LiTFS doped with (VO)SO4 as mediator. A mixture of epoxy/PVDF/LiTFS thin film was used as the separator between the electrodes also to provide adhesion. Figure 1 shows the galvanostatic charge/discharge (GCD) curves of a structural hybrid SC. A cyclic voltammetry (CV) curve obtained at a scan rate of 10 mV/s of this hybrid SC is illustrated in Figure 2. The broad peak from 0.4V to 0.8V is an indication of pseudocapacitance behavior related to the redox reactions of the mediators. The asymmetric shape of CV curve is related to the electrochemical reactions of Cu and Zn during charging/discharging. It was found that the voltage of the SC can be withheld at 1V for more than 3 months. The mechanical strength of the SC was tested using a MTS machine. It was found that the elastic constant as 20 MPa and ultimate tension strength was 2 MPa. Figure 1

Preparation of a new animal glue binder for foundry use

A new casting binder was prepared based on an animal bone glue. In order to overcome the disadvantages of the animal glue agglomeration at room temperature, an alkaline decomposition process was used, with acrylic acid, ammonium persulfate, and glucose as modifiers of the animal glue to obtain a high strength of binding. In the process of alkaline decomposition, NaOH was used as the catalyst with the addition of 3, 4, 5, 6, 7, 8wt.%, respectively, into 100 g of animal glue and the alkaline decomposition temperature was set for 30, 40, 50, 60, and 70 oC, with an identical decomposition time of 30 min, in order to reduce viscosity of the animal glue and maintain a liquid state at room temperature. The added acrylic acid, ammonium persulfate and glucose were determined through an orthogonal experiment. The experimental results are as follows: the optimal amount of NaOH addition is 5wt.%; alkaline decomposition temperature is 50 oC; the optimal weight ratio of three kinds of modifiers to animal glue is acrylic acid: ammonium persulfate: glucose: animal glue = 30:3:15:100; the modification reaction should be performed at 75 oC with a reaction time of 90 min. With the addition of 3% binder to sand, a final tensile strength of about 3.36 MPa and surface tension value of about 25.387 mN∙m-1 are achieved; the gas evolution at 850 oC is 19 ml∙g-1 and the residual strength after high temperature (700 oC × 10 min) is 0 MPa. Finally, the new binder was characterized and analyzed by means of element analysis and an IR infrared spectrum.

Physical and geospatial attributes of inceptisols and ultisols under native vegetation in Humaitá, AM, Brazil

Natural grasslands with savannah-like characteristics associated to forest mosaics are found within Southern and Eastern Amazonas, Western Rondonia and Northern Roraima, being conditioned to local edaphic factors. The aim of this study was to assess both physical and geospatial attributes of an Cambisol under natural grasslands and an Ultisol under a forest fragment in Humaita - AM, Brazil. In each area, we established a sampling grid in the dimensions of 70 × 70 m, with regular sampling spacing of 10 m and three collection depths: 0.0-0.05, 0.05-0.10 and 0.10-0.20 m, totaling 192 sampling points. Macroporosity (MaP), microporosity (MiP), bulk density (Ds) and total porosity (TP) were determined by soil samples with preserved structure, using a volumetric ring. Soil resistance to penetration (SRP) was measured by an automatic penetrometer after being subjected to a 0.006 MPa tension. Data were submitted to descriptive statistics and geostatistics analysis. The soil under natural grasslands showed values considered critical of Ds, SRP, MaP at all evaluated depths, with significant values at 0.10-0.20 m layer of 1.54 kg dm -3 ; 2.08 MPa and 0.05 m 3 m -3 , respectively. Ultisol under the forest fragments showed higher range values and consequently greater geospatial continuity due to the assessed physical attributes, since this soil has a greater stability of its physical structure. Based on the physical properties of the soil, structural function ineffectiveness of the Ultisol is a key factor for the occurrence of grassland in this region.

Strength reliability and in vitro degradation of three-dimensional powder printed strontium-substituted magnesium phosphate scaffolds

Strontium ions (Sr2+) are known to prevent osteoporosis and also encourage bone formation. Such twin requirements have motivated researchers to develop Sr-substituted biomaterials for orthopaedic applications. The present study demonstrates a new concept of developing Sr-substituted Mg3(PO4)2 – based biodegradable scaffolds. In particular, this work reports the fabrication, mechanical properties with an emphasis on strength reliability as well as in vitro degradation of highly biodegradable strontium-incorporated magnesium phosphate cements. These implantable scaffolds were fabricated using three-dimensional powder printing, followed by high temperature sintering and/or chemical conversion, a technique adaptable to develop patient-specific implants. A moderate combination of strength properties of 36.7MPa (compression), 24.2MPa (bending) and 10.7MPa (tension) were measured. A reasonably modest Weibull modulus of up to 8.8 was recorded after uniaxial compression or diametral tensile tests on 3D printed scaffolds. A comparison among scaffolds with varying compositions or among sintered or chemically hardened scaffolds reveals that the strength reliability is not compromised in Sr-substituted scaffolds compared to baseline Mg3(PO4)2. The micro-computed tomography analysis reveals the presence of highly interconnected porous architecture in three-dimension with lognormal pore size distribution having median in the range of 17.74–26.29μm for the investigated scaffolds. The results of extensive in vitro ion release study revealed passive degradation with a reduced Mg2+ release and slow but sustained release of Sr2+ from strontium-substituted magnesium phosphate scaffolds. Taken together, the present study unequivocally illustrates that the newly designed Sr-substituted magnesium phosphate scaffolds with good strength reliability could be used for biomedical applications requiring consistent Sr2+- release, while the scaffold degrades in physiological medium. Statement of significanceThe study investigates the additive manufacturing of scaffolds based on different strontium-substituted magnesium phosphate bone cements by means of three-dimensional powder printing technique (3DPP). Magnesium phosphates were chosen due to their higher biodegradability compared to calcium phosphates, which is due to both a higher solubility as well as the absence of phase changes (to low soluble hydroxyapatite) in vivo. Since strontium ions are known to promote bone formation by stimulating osteoblast growth, we aimed to establish such a highly degradable magnesium phosphate ceramic with an enhanced bioactivity for new bone ingrowth. After post-processing, mechanical strengths of up to 36.7MPa (compression), 24.2MPa (bending) and 10.7MPa (tension) could be achieved. Simultaneously, the failure reliability of those bioceramic implant materials, measured by Weibull modulus calculations, were in the range of 4.3–8.8. Passive dissolution studies in vitro proved an ion release of Mg2+ and PO43- as well as Sr2+, which is fundamental for in vivo degradation and a bone growth promoting effect.In our opinion, this work broadens the range of bioceramic bone replacement materials suitable for additive manufacturing processing. The high biodegradability of MPC ceramics together with the anticipated promoting effect on osseointegration opens up the way for a patient-specific treatment with the prospect of a fast and complete healing of bone fractures.

Origin of parameter degeneracy and molecular shape relationships in geometric-flow calculations of solvation free energies

Implicit solvent models are important tools for calculating solvation free energies for chemical and biophysical studies since they require fewer computational resources but can achieve accuracy comparable to that of explicit-solvent models. In past papers, geometric flow-based solvation models have been established for solvation analysis of small and large compounds. In the present work, the use of realistic experiment-based parameter choices for the geometric flow models is studied. We find that the experimental parameters of solvent internal pressure p = 172 MPa and surface tension γ = 72 mN/m produce solvation free energies within 1 RT of the global minimum root-mean-squared deviation from experimental data over the expanded set. Our results demonstrate that experimental values can be used for geometric flow solvent model parameters, thus eliminating the need for additional parameterization. We also examine the correlations between optimal values of p and γ which are strongly anti-correlated. Geometric analysis of the small molecule test set shows that these results are inter-connected with an approximately linear relationship between area and volume in the range of molecular sizes spanned by the data set. In spite of this considerable degeneracy between the surface tension and pressure terms in the model, both terms are important for the broader applicability of the model.

Effect of N2 Gas Flow Ratio in Plasma-Enhanced Chemical Vapor Deposition with SiH4–NH3–N2–He Gas Mixture on Stress Relaxation of Silicon Nitride

The effects of N2 gas flow ratios in silicon nitride deposition with SiH4–NH3–N2–He gas mixtures at a temperature of 275 °C on stress relaxation have been investigated. We have demonstrated that film stress can be controlled in the range from -692 MPa (compression) to 170 MPa (tension) by increasing N2 gas flow ratio. From the evaluation of the composition ratio of N/Si, film density, and bonding structure, the relationships between film stress and these properties are investigated. The amount of nitrogen incorporated into the film as N–H bonds increased with increasing N2 flow ratio, resulting in a higher composition ratio of N/Si. At a higher N2 gas flow ratio, excess N2 gas in the plasma may disturb the ion bombardment of ionized species on the film surface, resulting in a decrease in the film density. The higher N2 gas flow ratio leads to the generation of a Si–N bonding structure with a larger bond angle at the nitrogen atom site due to bond-strain relaxation, leading to a higher frequency of Si–N stretching vibration. Therefore, a nitrogen-richer SiN film with many N–H bonds and a lower film density exhibits bonding structures with a lower bond strain, leading to the relief of film stress.

Fracture penetration in planetary ice shells

The proposed past eruption of liquid water on Europa and ongoing eruption of water vapor and ice on Enceladus have led to discussion about the feasibility of cracking a planetary ice shell. We use a boundary element method to model crack penetration in an ice shell subjected to tension and hydrostatic compression. We consider the presence of a region at the base of the ice shell in which the far-field extensional stresses vanish due to viscoelastic relaxation, impeding the penetration of fractures towards a subsurface ocean. The maximum extent of fracture penetration can be limited by hydrostatic pressure or by the presence of the unstressed basal layer, depending on its thickness. Our results indicate that Europa's ice shell is likely to be cracked under 1–3 MPa tension only if it is ⩽2.5 km thick. Enceladus' ice shell may be completely cracked if it is capable of supporting ∼1–3 MPa tension and is less than 25 km thick.

Conceptual and numerical models of ring-fault formation

Most ring faults of collapse calderas are primarily shear fractures the initiation and development of which depends on the state of stress in the host rock. The state of stress in a volcano is controlled by the loading conditions, such as magma-chamber geometry and pressure, but also by the mechanical properties of its rock units and structures (such as existing contacts, faults, and joints). Ring-fault formation is thus essentially a problem in rock physics. Field observations show that some ring faults are dip–slip, whereas others are partly faults (shear fractures) and partly ring dykes (extension fractures). Although slip on existing ring faults is much more common in basaltic edifices (shield volcanoes) than in true composite volcanoes, in both types of volcanoes most caldera unrest periods do not result in ring-fault slip. Here I present new conceptual and numerical models of caldera formation in volcanoes with shallow spherical (circular) or oblate ellipsoidal (sill-like) magma chambers. In the layered models, the host rock above the chamber is composed of 30 comparatively thin layers with stiffnesses (Young's moduli) alternating between 1 GPa and 100 GPa. The chamber itself is located in a single, thick layer. The crustal segment hosting the chamber is either 20 km or 40 km wide but has a constant thickness of 20 km. The loading conditions considered are: (1) a crustal segment subject to 5 MPa tension; (2) crustal segment subject to excess magmatic pressure of 10 MPa at the bottom (doming of the volcanic field containing the chamber); (3) a combination of tension and doming; and (4) chamber subject to underpressure (negative excess pressure) of 5 MPa. The main results are as follows: (1) Excess pressure and underpressure in a chamber normally favour dyke injection rather than ring-fault formation. (2) For doming or tension, a spherical magma chamber favours dyke injection except when the layer hosting the chamber is very soft (10 GPa) or one with recent dyke injections, in which case the surface stress field favours ring-fault formation. (3) For a sill-like chamber in a 20-km wide crustal segment, a ring-fault can be generated by either tension or tension and doming; for a 40-km wide segment, doming alone is sufficient to generate a ring fault. (4) Since individual layers in a volcano may develop different local stresses, stress-field homogenisation through all the layers between the chamber and the surface is a necessary condition for ring-fault formation. (5) Because the mechanical properties of the layers that constitute basaltic edifices are more uniform than those that constitute true composite volcanoes, it follows that stress-field homogenisation, and thus ring-fault formation or slip, is more commonly reached in basaltic edifices than in composite volcanoes. (6) Both for basaltic edifices and composite volcanoes, the stress fields most likely to initiate ring faults are those generated around sill-like chambers subject to tension, doming, or both.

Soil resistance to penetration and least limiting water range for soybean yield in a haplustox from Brazil

The objective of this study was determine the resistance to penetration (PR), least limiting water range (LLWR) and critical bulk density (Db-crit) for soybean yield in a medium-textured oxisol (Haplustox). The treatments represented the soil compaction by passing a tractor over the site 0, 1, 2, 4, and 6 times, with 4 replications in a randomized experimental design. Samples were collected from 0.02-0.05, 0.07-0.10 and 0.15-0.18 m depths. Soybean (Glycine max cv. Embrapa 48) was sowed in December 2002. Plant height, number of pods, aerial dry matter, weight of 100 seeds, and the yield in 3.6 m² plots were recorded. Soybean yield started reduction at the PR of 0.85 MPa and Db of 1.48 Mg m-3. The LLWR was limited in highest part by water content at field capacity (0.01 MPa tension) and in lowest part by water content at PRcrit, achieved the Db-crit to yield at 1.48 Mg m-3.

Residual Stresses in Bulk Metallic Glasses due to Thermal Tempering

Bulk metallic glasses (BMGs) are attractive structural materials that develop residual stresses during processing due to thermal tempering. In this process, compressive surface stresses are generated within thin layers balanced with tension in the interior. In the present study, stress generation was analyzed experimentally and theoretically in a BMG plate and a cylinder. The residual stresses were measured using the crack compliance method. It was shown that high stresses can be attained in metallic glasses due to thermal tempering: over −300 MPa compression on the surface balanced by +150 MPa tension in the middle. The experimental data were then compared to the predictions of a viscoelastic model that took into account the equilibrium viscosity of BMG as a function of temperature. The model was shown to be accurate within 5 to 25% of the experimental stress data. It is therefore a powerful tool for estimating processing-induced residual stresses in bulk metallic glasses.

Neutron diffraction measurements of residual stress in a powder metallurgy component

Residual stresses in a typical industrial green component were determined using neutron diffraction. The measured residual stresses were found to correlate with cross-sectional variations. Residual stress at the edge of the compact in contact with the die wall during compaction reached up to +80 MPa (tension) and −100 MPa (compression).

Near-infrared spectroscopy for soil water determination in small soil volumes

Critical soil water levels for soil microscale processes are difficult to determine because of variability in large soil volumes and lack of techniques for logging soil water contents in small soil volumes. This study tested nearinfrared (NIR) spectroscopy for soil water content determination. Five soil horizons with a range in soil texture, soil organic carbon, carbonates, pH and horizon depth, were tested at air-dry, field capacity and 0.1 MPa tension water content. Volumetric soil water content, determined using the standard method of oven-drying and soil bulk density, was compared to NIR absorbance in various combinations and wavelengths. The NIR spectra obtained with the probe in direct contact with the soil gave better results than when the probe was separated from the soil with a glass slide. The most reliable validation results were obtained using a multivariate partial least squares regression of the full spectrum with an r2 of 0.95 and RMSE of prediction of 6.4%. Smoothing and derivatives of the spectra did not improve the validation results. The relationships for absorbance at single wavelength segments, ratios, differences and area under the curve around the 1940 nm peak were good (r2 values near 0.85 ) but poorer than the results using the full spectra. The high correlation coefficients obtained with the wide variety of soils utilized in this study suggest that NIR absorbance is a practical method for determining volumetric soil water content for small soil volumes. Key words: Near-infrared spectroscopy, soil water, Near-infrared absorbance