Sand Cores Research Articles

Effect of Core Box Temperature, Hot-Air Parameters and Micro-Silica Powder on Tensile Strength of Sand Core

A study was conducted on the effects of various influencing factors in the compound hardening process, including core box temperature, such hot-air parameters as temperature, pressure and blowing time, as well as micro-silica powder, on the tensile strength denoted as σ0 of the prepared sand core after cooling to room temperature, on the basis of which the hardening mechanism of the micro-silica powder was revealed. The sand core was bonded using modified water glass. The single factor test was conducted to achieve the optimal compound hardening process for the sand core. According to the research results, the introduction of hot air improved the σ0 of sand core significantly from 1.89 MPa to 2.20 MPa, in comparison with that hardened only by heating the core box. After the addition of micro-silica powder, the σ0 of sand core was further improved to 2.58MPa. According to the results of SEM analysis, the Si atoms in the water glass contributed to improving the modulus of the water glass after the addition of micro-silica powder, thus promoting the water glass to gel when heated. As indicated by FT-IR analysis, the concentration of Si–O–Si bonds was increased as a result of the reaction occurring between micro-silica powder and water glass in the hardening process, implying that micro-silica powder can be effective in enhancing the polymerization of water glass.

Influence of reservoir-scale heterogeneities on the growth, evolution and migration of a CO2 plume at the Sleipner Field, Norwegian North Sea

New analysis of the baseline (pre-injection) seismic data at Sleipner has revealed large-scale, roughly north-trending, channelled ‘fairways’ at a range of stratigraphical levels in the Utsira Sand. The baseline data also reveal localised stratigraphical ‘point discontinuities’ within the reservoir, some of which show evidence of having provided vertical conduits for earlier natural gas flow. The repeat time-lapse seismic datasets, where finer details of reservoir geology are illuminated by the reflective CO2, show smaller-scale, north-trending and sometimes sinuous channels within the larger channel fairways. They also show a number of vertical CO2 pathways within the CO2 plume, corresponding to the point discontinuities seen on the baseline data.Reservoir flow models were set up with flow properties constrained only by the observed levels of CO2 accumulation in the reservoir and the arrival time of CO2 at the reservoir top just prior to the first repeat seismic survey in 1999. The initial model with laterally homogeneous sand units separated by thin semi-permeable mudstones achieved only a moderate match to the observed time-lapse seismic data. Subsequent flow models, progressively incorporating higher permeability vertical CO2 pathways through the mudstones and large-scale channel fairways within the reservoir sands, yielded a progressive and marked improvement in the history-match of key CO2 layers within the plume. Crucially, no layer-specific model calibration was employed to achieve this improvement.New geophysical measurements from Utsira Sand core have recently become available. These measurements provide important constraints on rock physics models of CO2 and brine mixtures in the Utsira Sand. An empirical Brie fluid mixing law for intermediate fluid saturations provides a good fit to the new laboratory data, allowing measurements of CO2 saturation to be converted into seismic velocity. This rock physics model was used to convert CO2 saturation distributions predicted by the most realistic reservoir model into a seismic velocity model of the CO2 plume. Synthetic seismic reflectivity profiles generated using this velocity model show a striking resemblance to the observed time-lapse seismic data, both in terms of plume layer reflectivity and also of time-shifts within and beneath the CO2 plume. This provides confidence in the fidelity of the preferred reservoir model solution.These results represent a significant breakthrough in the understanding and modelling of CO2 plume development at Sleipner. We emphasise that the improvements were brought about not by fine tuning reservoir properties to fit the observed time-lapse data, but simply by incorporating geological permeability features that can reasonably be inferred from the baseline seismic data.

In Planta Localization of Endophytic Cordyceps fumosorosea in Carrizo Citrus.

Entomopathogenic fungi can be a useful resource for controlling insect vectors of citrus plant pathogens, such as the Asian citrus psyllid (Diaphorina citri) associated with huanglongbing or the citrus root weevil (Diaprepes abbreviatus) associated with the spread of Phytophtora spp. In this study, Cordyceps fumosorosea (Cfr) was investigated in planta as a potential endophytic entomopathogenic fungus and various inoculation techniques were used to determine if it would colonize the Carrizo citrange (Citrus × insitorum) seeds and plants. The four inoculation methodologies evaluated were seed soaking, stem injection, foliar spray, and soil drench. Seed immersion trials demonstrated that the roots of the Carrizo citrange plant can be inoculated successfully with Cfr. Stem injection, foliar spray, and soil drench also provided successful inoculation of Cfr. However, this fungus was only endophytic in the plant stem. Sand cores indicated that Cfr moved down through the sand column and was able to inoculate the roots. Given the prevalence of Cfr in the soil during the drench experiment, and that the fungus was able to colonize Carrizo citrange roots through seed immersion, this finding provides evidence of the potential endophytism of this fungus when applied to citrus plant species.

A Plane Stress Failure Criterion for Inorganically-Bound Core Materials.

Inorganically-bound core materials are used in foundries in high quantities. However, there is no validated mechanical failure criterion, which allows performing finite-element calculations on the core geometries, yet. With finite-element simulations, the cores could be optimised for various production processes from robotic core handling to the decoring process after the casting. To identify a failure criterion, we propose testing methods, that enable us to investigate the fracture behaviour of inorganically-bound core materials. These novel testing methods induce multiple bi-axial stress states into the specimens and are developed for cohesive frictional materials in general and for sand cores in particular. This allows validating failure criteria in principal stress space. We found that a Mohr-Coulomb model describes the fracture of inorganic core materials in a plane stress state quite accurately and adapted it to a failure criterion, which combines the Mohr-Coulomb model with the Weakest-Link theory in one consistent mechanical material model. This novel material model has been successfully utilised to predict the fracture force of a Brazilian test. This prediction is based on the stress fields of a finite element method (FEM) calculation.

Study on the Influence of Sand Core Compactness on Surface Entropy considering Engineering Disturbance

In order to explore the correlation between the compactness of sand core samples and its surface image features and to provide the basis for rapid identification and recognition of core samples in engineering investigation, a typical image data set of sand core samples disturbed by drilling construction in practical engineering has been established, using Python language to compile algorithm to calculate one‐dimensional entropy and two‐dimensional entropy of 60 groups of sand core samples with different densities. The influence of different sand core compactness on surface entropy characteristics was discussed, and the following conclusions were obtained: (1) Affected by drilling construction and disturbance, the looser the sand core surface particles are, the worse the sorting is and the more irregular the shape characteristics are. There is a close relationship between grain texture and compactness. (2) The calculation results of sand image entropy of one‐dimensional entropy and two‐dimensional entropy showed that the entropy value of loose, slightly dense, and medium dense sand images is positively correlated with the compactness of sand. (3) The maximum variance of two‐dimensional entropy of loose, slightly dense, and medium dense sand image in the same borehole is less than 0.09, and the data variance amplification effect of two‐dimensional entropy of image is mainly between different boreholes. (4) The dense feature of core sample structure forms an ordered structure with a gray change boundary, which increases the roughness of the image and leads to the increase of entropy. The two‐dimensional entropy reveals the internal correlation mechanism of the influence of the engineering state on the surface structure of sand more clearly than the one‐dimensional entropy and more effectively characterizes the dense degree of sand particles. (5) Using two‐dimensional entropy to judge the compactness of sand image in the same borehole, the data fluctuation is small, and the algorithm is stable and reliable. The research results have reference values for the detection and analysis of sand sample density in geotechnical engineering investigation.

Inorganic salts and their combinations as binders for core sands

The main factors influencing on the elimination of the disadvantages of inorganic salts used as binder for the production of casting cores, individually and in combination, are established. The hardening and softening mechanisms of core sands based on combinations of inorganic salts are studied.

Modification of lignosulfonates by lithium, sodium and potassium metaborates

The results of the effect of lithium, sodium and potassium metaborates on the binding properties and strength parameters of lignosulfonates are presented. It is found that the introduction of lithium, sodium and potassium metaborates in the composition of lignosulfonates increases the durability and the compressive strength, reduces the friability, and improves the formability of moulding and core sands. New, effective multifunctional modifiers based on lignosulfonate and lithium, sodium and potassium metaborates are developed.

Novel riser designs via 3D sand printing to improve casting performance

3D sand printing (3DSP) has created a new era for sand casting applications by introducing additively manufactured complex 3D sand molds and cores. It has also enabled the design and manufacturing of complex rigging (gating and feeding) systems using non-conventional design rules which were not previously feasible. In this research, two novel riser designs, ellipsoid and spherical risers, along with traditional cylindrical risers are investigated to understand their effects on the solidification time and entrained air volume fraction in Aluminum alloy (A319) castings. Computational simulations are presented to understand the viability of complex riser shapes by comparing critical parameters such as fluid temperature during filling, solidification, and cooling. In addition, solid fraction (SF) and entrained air volume fraction are also studied during filling and solidification. The results for spherical riser performance showed a 7% increase in feeding time during solidification along with a 47.27% reduction in entrained air volume fraction. The ellipsoid riser studied in this research also showed identical solidification time at half the volume of the conventional cylindrical riser. This indicated a 26.5% increase in casting yield. These riser designs will not only facilitate the design optimization of the casting but also improve the casting performance (feeding, solidification) for difficult to cast materials and geometries.

Promoting sustainable level of resources and efficiency from traditional manufacturing industry via quantification of carbon benefit: A model considering product feature design and case

The traditional manufacturing industry has low utilization rate of resources, in order to reduce the pressure it brings to environmental sustainable development. To explore the application of carbon benefit in improving resource efficiency level. This paper starts from the perspective of product feature design, and develops a carbon benefit model of feature design scheme from the perspectives of time carbon benefit and economic carbon benefit under the consideration of carbon emission. Taking traditional sand casting as a case, this paper analyzes the function of holes in process design and the carbon benefit of different hole-making schemes. It is better to adopt hole-making scheme of machine under the condition of producing single or a few castings, economic carbon benefit is 0.011 yuan/kgCO2 higher. When produced in large volume, the economic carbon benefit of the sand core hole-making scheme is better, and the impact on environment can be reduced by 0.317 kgCO2/h. In this paper, carbon emission and resource utilization in the subsequent production process are controlled in the product design stage, so as to improve the resource level and efficiency of traditional manufacturing industry. By improving the feature design scheme, enterprises can design feasible energy saving and emission reduction scheme.

A LABORATORY SYSTEM FOR INVESTIGATING OF FLUIDS FLOW CAPACITY THROUGH UNCONSOLIDATED SAND SAMPLES

Practically all studies of reservoir engineering involve detailed knowledge of fluid flow characteristics. The fluid flow performance in porous media is affected by pressure, flow rate, and volume of single fluid phases. Permeability is a measure of how well a porous media allows the flow of fluids through it. Permeability and porosity form the two significant characteristics of reservoir rocks. This research aimed to present the design of laboratory equipment to test the ability of fluid flow through different sandstone samples. Two sand core samples (coarse sand sample and fine sand sample) were tested. The laboratory findings measurements of porosity, saturation, total permeability, effective permeability, and relative permeability were evaluated. The laboratory tests were performed on partially saturated, unconsolidated core sand for two-phase fluid flow. The experimental work was developed for measuring the flow capacity achieved under the steady-state conditions method. Various grain sizes sands were selected as a porous medium to determine petrophysical properties and fluid flow capacity of the rock sample. Nitrogen and air were utilized as gas-phases, and, for liquid-phases, water was chosen as an injection fluid. The steady-state process method was used to determine the permeability and relative permeability of unconsolidated sands to water flow. Different flow rates were measured for different pressure gradients in a viscose flow. As the flow rate increases, the pressure difference also increased. It can be observed that there are a direct correlation and relationship between the flow rate and the pressure difference. The core plug's absolute permeability was measured using Darcy Equation. Absolute permeability does not depend on fluid characteristics but only on media properties. The sample container contains a more significant amount of sand, decrease the permeability, and therefore requires high pressure for fluid flowing within the sample.

Investigation on the Effect of Granulometric Features on the Permeability of No-Bake Resin Bonded Sand Cores

Investigation on the Effect of Granulometric Features on the Permeability of No-Bake Resin Bonded Sand Cores

Preparation of Extracellular and Intracellular Water-Insoluble Monascus Pigments during Submerged Fermentaion

Monascus pigments (MPs) are a group of secondary metabolites produced by the filamentous fungus Monascus. In this study, the dominant MPs in the submerged cultures of Monascus ruber M7, rubropunctatin and monascorubrin, were found to be produced both intracellularly in the cell-bound state and extracellularly in the form of free crystals. To prepare and quantify the extracellular and intracellular water-insoluble MPs (wiMPs), separation of the extracellular crystalline MPs (ecMPs) and mycelia from the fermentation broth was carried out by filtration using filter papers (FPs), nylon mesh filters (NMFs), and sand core funnels (SCFs). Subsequently, the collected ecMPs and mycelia were subjected to microscopic observation and MPs quantitative analysis to evaluate the separation efficiency. Results showed that 200 to 300 mesh/inch NMFs were the optimum filters for separating the ecMPs and the mycelia. This study is the first comparative analysis of different filters for the preparation of extracellular and intracellular wiMPs. It would lead further investigations on the production and secretion of wiMPs by Monascus.

Effects of Composition on the Physical Properties of Water-Soluble Salt Cores

The demand for producing essential cast parts and the design requirements for superior engineering performance have increased in recent years. Sand cores used in conventional aluminum cast parts are harmful to the environment, which limits their application. Utilizing water-soluble cores in the aluminum casting industry is expected to be an environmentally friendly approach due to recyclability of the salt cores. In this study, water-soluble salt cores were made from chloride- and/or carbonate-containing salts in various amounts. The salts were melted and cast into steel molds to obtain salt cores. The salt cores were subjected to three-point bending tests to determine their mechanical strength, the melting points were determined with thermal analyses, and the water solubility was measured at room temperature and 50 °C. A maximum bending strength of 17.19 MPa, a maximum melting point of 776 °C and a maximum water solubility of 89 g salt/100 ml water were obtained for the samples with compositions of 75% KCl–25% K2CO3 and 25% Na2CO3–75% K2CO3, respectively. Fractographs of the samples used in bending tests were taken by a still camera in macro mode, and from these fractured surfaces, scanning electron microscopy studies were performed. The X-ray diffraction pattern of the sample exhibiting optimal properties (28.3% Na2CO3 and 71.7% K2CO3) also showed that K2CO3, NaKCO3 and KNaCO3 phases were present in the structure, as expected. An actual casting process with aluminum die casting of an automotive part was also performed. The diecast aluminum part was subjected to a leak-proof test, and X-ray images were used to check for porosity in the part.

Modification of inorganic binder used for sand core-making in foundry practice

With modified water glass as binder and the introduction of micro silicon powders into the core-making process, an improvement was made to the tensile strength and collapsibility of the sand core. The potassium hydroxide, sodium hexametaphosphate and white sugar were applied as the modifiers of water glass. The optimum proportion of the modifiers was determined through the combination of single factor test and orthogonal test. The optimum proportion of water glass, potassium hydroxide, sodium hexametaphosphate and white sugar is 1000: 40: 5: 5 (wt.). In terms of weight, modified binder and micro silicon powders accounted for 2% and 0.6% of sand, respectively. The sand core was hardened by going through a warm core box process, in which the temperature of core box was 150 °C, and the compressed hot air was blown at 120 °C for 40 s under a pressure of 0.2 MPa. As for the sand core bonded with modified water glass, the tensile strength is 2.46 MPa at room temperature (σ0) and 2.49 MPa at 25 °C and 40% RH for 24 h (σ24), which are 2 times more than that with unmodified binder. The bonded strengths of sand core are increased as a result of the reaction between −OH groups from addition of potassium hydroxide and SiO2 particles widely distributed in the sand core. Comparing with the sand core bonded with unmodified water glass, the high temperature residual tensile strength (σr) of sand core bonded with modified water glass under 600 °C for 5 min, is sharply reduced from 0.20 MPa to 0.01 MPa. By the comparison with unmodified water glass, the dynamic viscosity of the modified water glass and the flowability of molding sand using modified water glass are increased from 74 mPa·s and 2.15 g to 80 mPa·s and 2.21 g, respectively. As revealed by FT-IR analysis, new groups including PO3− , PO43− , and Si-O-C appear in the molecular structure of modified water glass, which are beneficial to the collapsibility of sand core.

The effect of different grain sizes and heat input on the gas pressure inside artificial resin-bonded sand cores

Sand cores are used to form the cavities of the castings. The quality of castings is directly affected by the quantity of the gases released from the cores. During our research, the effect of different grain sizes and heat input on the pressure of the gases evolved from the cores was investigated. The granulometric properties of the sand used for making the cores have a significant impact on the pressure of the gases. Because of the uneven particle size distribution of multi fraction sands, the gas flow conditions in the cores can be different. The gas pressure in the cores made from sieved sands can be changed between 6 and 9 mbar. According to the recorded cooling curve of the melt, it can be established, that in the case of the presented pouring conditions, a solid metal layer with adequate strength could not be developed before the gas could pass through the core/casting interface. This phenomenon may result in gas blowhole defects on the casting surface.

Examination of correlation between the granulometric properties of molding and core sand mixtures and their production parameters

Foundry technology uses a lot of several natural materials. The chemically bonded sand mixtures main component is the foundry sand approx. 90-98%. Sand properties depend on it has chemical and mineralogical composition; mainly particle-size distribution and shape of grains and its size and sand surface texture. A comparative measurement of 3 foundry sand with different surface quality was carried out. Chemically bonded sand mixtures were prepared to measure their gas permeability and 3-point bending strength. A new qualifier number, CQi was used to compare our investigations.

The impact of ice on the tensile strength of unconsolidated sand - A model for gas hydrate-bearing sands?

Tensile strength is an important parameter when it comes to predictions of potential fracturing of sediments by natural processes such as the emplacement of ice or gas hydrate lenses, as well as anthropogenic fracturing or else the stability of engineering constructions such as boreholes. Yet, tensile strength (στ) measurements of unconsolidated ice-bearing or gas hydrate-bearing sands are scarce and affected by a large variability.In the course of the SUGAR project we successfully used ice as a model for pore-filling and “load-bearing” gas hydrate in sand to determine compressional wave velocity. We were thus able to verify comparable formation characteristics and morphologies of ice and gas hydrate within the pore space. As these are important values for the tensile strength of ice/hydrate-bearing sands, ice was also used as a model for hydrate-bearing sands, despite differences in the mechanical behavior and strength of pure ice and gas hydrate. Water-saturated sand cores with ice saturations (Sice) between 0 and 100% were tested at −6.8 °C. The varying Sice were a result of the freezing point depression caused by saline solutions of different concentrations. The στ was directly determined using a sleeve-fracturing test with an internal pressure that was created within the frozen samples. The setup was also adapted to fit a pressure vessel for tests using confining pressure.The correlation of Sice – στ shows an exponential increase of στ with Sice. Whereas at Sice < 60% the increase is small, it is large at Sice > 80%. In conjunction with the change in strength, the viscoelastic behavior changes. A clear peak strength occurs at Sice > 80%. We conclude that given 60% < Sice < 80% the pore-filling morphology of the ice converts into a frame-building habitus and at Sice > 80% the frame gains strength while the amount of residual water decreases. Tensile failure and cracking now exceed grain boundary sliding as the prevailing failure mode. The ice morphology in the sand is non-cementing and comparable to a gas hydrate-sand mixture.

Effect of water saturation on the role of polymer elasticity during heavy oil recovery

During enhanced oil recovery, polymers are used to improve the sweep efficiency during chemical injection process. Polymers are mainly characterized based on their viscoelasticity response; however, the role of polymer elasticity on heavy oil considering the effect of water saturation in porous media has not been well explored. In this work, four blends of polyacrylamide polymer solutions with similar molecular weight and shear viscosity but different bulk elasticity (due to different molecular weight distribution) were used. A series of flooding experiments were performed using a cylindrical core sand pack saturated with heavy oil designed to simulate linear flow. The flow rate was selected based on the shear rate range present in field applications. Effect of elasticity during the injection of these polymer solutions were compared during tertiary recovery experiments in terms of oil recovery and residual resistance factor at different initial water-flood volumes. The results indicate that the effect of polymer elasticity was more profound in tertiary mode with higher water saturation. An additional pressure drop was required to push a higher elastic solution. The required pressure drop to push the polymer solutions increased with water saturation.

Ophiomorpha irregulaire and associated trace fossils from the Upper Cretaceous of Patagonia, Argentina: Palaeogeographical and ethological significance

There are two contrasting opinions on the stratigraphic and palaeogeographic distribution of the relatively rare trace fossil Ophiomorpha irregulaire: 1) the trace is mostly restricted to the Upper Cretaceous of the Western Interior Seaway, or 2) it has a post-Palaeozoic record and a worldwide geographic distribution. In this study we document the finding of O. irregulaire in Upper Cretaceous turbidites of the Alta Vista Formation, southern Patagonia, providing additional evidence on the morphology and composition of its pelletal masses, the ethology of its producer and the palaeogeographical and palaeoenvironmental distribution of the trace fossil. The burrow walls are lined with dark mud and their elongate, spiky pellets are formed by a sand core that is also lined with mud. The association with typical fodinichnia, such as Halopoa, Spirophyton, and Zoophycos and the common presence of O. irregulaire in sediments with abundant plant detritus, suggest that the producer was a deposit feeder. Crosscutting relationships and occurrences at several levels within thick-bedded turbidites, suggest a relatively deep tier emplacement of the trace. The finding of the trace in the Southern Hemisphere supports its envisaged worldwide palaeogeographic distribution

Acoustical and Optical Determination of Mechanical Properties of Inorganically-Bound Foundry Core Materials.

Inorganically-bound sand cores are used in many light-metal foundries to form cavities in the cast part, which cannot be realised by the mould itself. To enable FEM simulations with core materials, their mechanical properties have to be measured. In this article, we adapt methods to determine the Young’s and shear modulus, the Poisson ratio and the fracture strain of sand cores. This allows us to fully parametrise an ideal brittle FEM model. We found that the Young’s and shear modulus can be obtained acoustically via the impulse excitation technique. The fracture strain was measured with a high-speed camera and a digital image correlation algorithm.