Bulk Strength Research Articles

Energy saving in papermaking by application of hybrid calcium carbonate

Hybrid calcium carbonate (HCC) is prepared by pre-flocculating calcium oxide and ground calcium carbonate (GCC) with ionic polymers, and by injecting carbon dioxide to the pre-flocculated flocs until termination of the reaction at neutral pH. When used in papermaking, HCC gave higher bulk, higher stiffness, and higher tensile strength than GCC did. Furthermore, when higher wet pressing pressure was applied to the paper containing HCC, higher solid content was achieved with still better stiffness, smoothness, and tensile strength in comparison with the paper containing GCC. Actually, very high bulk of the HCC containing paper was compromisingly reduced to obtain high solid content by applying higher wet pressing pressure. Higher solid content achieved by combination of HCC technology and higher wet pressing pressure resulted in paper drying energy savings of more than 10%, while a high quality of all the essential printing paper properties was maintained. Drying energy savings may contribute to greenhouse gas (GHG) reduction and lowering of the paper production cost.

Probing the role of associative polymer on scCO2-Foam strength and rheology enhancement in bulk and porous media for improving oil displacement efficiency

Foam mobility control technique has been extensively applied to encounter unfavorable sweep efficiency during CO2 injection in heterogeneous reservoirs. Harsh reservoir conditions have encouraged a need of effective mobility control agent. In this study, we present a comprehensive experimental investigation utilizing a newly developed water-soluble associative polymer as additive to foam system for stability and rheology enhancement. The performance of polymer enhanced foam on residual oil displacement was also evaluated in porous media. A significant increment in foam longevity and improved foam rheological behavior were obtained with associative polymer presence. Compared to conventional polymer’s performance, the associative polymer enhanced foam could establish the higher flow resistance and better compatibility with reservoir conditions. The addition of associative polymer profoundly increased the foam apparent viscosity and gas mobility reduction factor at optimum foam quality in the absence and presence of oil. A noticeable improvement in oil recovery efficiency was also observed in the case with associative polymer by which 28% incremental oil recovery was achieved, 14% higher than that obtained from polymer-free foam injection. The utilization of associative polymer enhanced foam is considered promising for a deepers foam propagation in the formation to recover substantial amount of residual oil.

Structural Significance of the Mid-level Décollement Within the Western Sichuan Fold-And-Thrust Belt (WSFTB), Insights From Sandbox Modeling

The WSFTB is located outboard of the eastern Tibetan Plateau, western China. It has received great attention due to high earthquake risks and rich resources of oil and gas. For both issues, the detailed structural configuration and deformation mechanism behind it are of great importance, but remain unclear due to the complexity created by the presence of multiple décollements. The effect of regionally distributed shallow Triassic salt décollement (SD) and the basal one (BD) has been well understood. In this paper, we focus on the third décollement situated between them. We conducted three sandbox experiments by varying this mid-level décollement (MD) from absence to presence, and from frictional to viscous, to test the effect on diversity of regional structural configuration. Our experimental results illustrated that 1) Absence of MD facilitated decoupling on SD, forming the greatest contrast between subsurface deformation front and the blind one beneath SD; 2) Frictional MD itself showed little decoupling, while its weakness reduced the bulk strength of deep structural level, lowering decoupling effect on SD and leading to approximating deformation fronts in the shallow and deep; 3) The viscous MD, along with SD relieved the resistance on their interbed layer. Consequently, the fastest deformation propagation rate and farthest deformation front (in all the experiments) occurred in the middle structural level. The modeled fold and thrust structures are comparable with the southern, central and northern WSFTB respectively, suggesting that varied MD may control the along-strike structural variations presented. The results also indicate that MD can alter the deformation partition in depth of any other multiple décollement system.

Determination of the adhesive content of medium density particleboards produced with bio-based polymer

This work contributes to the use of alternative adhesives in the wood-based industry, where pine wood is commonly used. The investigation identifies the influence and the optimal content (8, 12 and 15wt%) of a bio-based polyurethane adhesive in the production of medium density particleboards (MDP). A compaction pressure of 4 MPa at 100oC for 10 minutes is considered in the manufacture of panels based on pine wood residues and bio-based resin. The bulk density, flexural modulus (MOE) and strength (MOR) properties under static three-point bending are obtained according to the Brazilian standard NBR 14810. The results are compared with NBR 14810 and other standards to verify its performance based on the minimum requirements. Bulk density is not significantly affected by the investigated adhesive levels. MOE and MOR reach average values equivalent to 12wt% and 15wt% of the adhesive, and both meet the minimum requirements established in international normative documents. The adhesive level range responsible for maximizing ρ, MOE and MOR is between 12.42wt% and 15.79wt%.

Investigation of Interlayer Interface Strength and Print Morphology Effects in Fused Deposition Modeling 3D-Printed PLA.

Fused deposition modeling polymer 3D printing has become a popular versatile additive manufacturing technology. However, there are limitations to the mechanical properties due to the layer-by-layer deposition approach. The relatively low strength of the interface between layers is the cause for potential microstructural weak points in such printed components. The interface strength of 3D-printed Polylactic Acid (PLA) polymer was determined through physical tensile testing in combination with microstructural finite element method (FEM) simulations. A custom tensile specimen was created to isolate the interlayer interfaces for direct testing of interface strength. Tensile tests resulted in an average 2.4 GPa stiffness and an average 22.8 MPa tensile strength for printed specimens, corresponding to a 32.4% and 47.8% reduction from the bulk filament stiffness and strength, respectively. Sectioned tensile specimens were observed under a digital microscope to examine microstructural features such as inter-layer gaps, extrusion cross-section, and voids. These were measured to create accurate FEM microstructural model geometries. The brittle fracture that occurred during the tensile testing was due to debonding of the interfaces. This was represented in Abaqus by using cohesive surfaces. Interface strength was inferred by varying the strength of the cohesive surfaces until the simulation mechanical response matched the physical tests. The resulting interface strength of the PLA polymer was 33.75 MPa on average, corresponding to a 22.5% reduction from bulk properties. Potential improvements to the overall strength of the 3D printed PLA were investigated in simulation by parameterizing improved gap morphologies. As the size of the interlayer gaps decreased, the stiffness and strength of the printed parts improved, whereas completely eliminating gaps resulted in a potential 16.1% improvement in material stiffness and 19.8% improvement in strength. These models show that significant improvements can be made to the overall printed part performance by optimizing the printing process and eliminating inner voids.

Understanding earthquakes using the geological record: an introduction

Understanding earthquakes using the geological record: an introduction

Application of In Situ Calcium Carbonate Process for Producing Papermaking Fillers from Lime Mud.

A portion of the lime mud formed during the causticizing process in the recovery process of kraft pulping should be purged from the calcium cycle as waste before it is fed to the lime kiln; this ensures that the quality of the pulp and pulping chemicals is maintained. The discharged greenish-gray lime mud, which is often disposed as an industrial waste, has been transformed herein into a high-quality papermaking filler via the hybrid calcium carbonate (HCC) and post-HCC (pHCC) technology. Initially, the lime mud was heat-treated and then ground to small-size particles. The ground lime mud was preflocculated with calcium oxide by ionic polymers, and carbon dioxide was injected to the flocs to produce lime mud HCC (LHCC). To produce lime mud pHCC (pLHCC), only the ground lime mud was preflocculated first, calcium oxide was added next, and finally, carbon dioxide was injected to the flocs. The resultant products, LHCC and pLHCC, gave brightness as high as that of the ground calcium carbonate (GCC) in paper while a little higher brightness for pLHCC than for LHCC. They also enabled to increase bulk, stiffness, and tensile strength. Application of the LHCC and pLHCC technology to the lime mud could save waste disposal expenses and produce better-quality paper.

Whole-Field Stress Sensing and Multiscale Mechanics for Developing Cement-Based Composites Containing Recycled Municipal Granular Wastes

Worldwide, there is a growing level of interest to develop sustainable cement-based products and processes in which the usage of natural resources such as sand and limestone are reduced from the current levels. One of the ways to achieve this is by replacing them with suitable inclusions of recycled granular materials from municipal wastes where possible. However, to understand the effects of such inclusions in concrete structures, research advancements are needed to sense and characterise the distribution of stresses (/strains) at the local scale and to establish their links with the fracture and bulk strength characteristics under external loading environments, which is the focus here. In this research, polyethylene (PE)-based granular materials derived from municipal wastes and fly ash obtained from the incineration of municipal solid wastes are used together as secondary raw materials in preparing the concrete mixtures. Photo stress analysis (PSA) is performed here, making non-contact and whole-field digital measurements of maximum shear stress distribution and the directions of the principal stresses at any point of interest on the surface of the samples under external loading. Their links with the fracture toughness and flexural strength of the samples cured at different times are presented. The novel PSA-based stresssensing helps to establish new understandings of the strength characteristics of composites across scales in the applications involving recycling and reusing conventional wastes and possibly in otherengineering applications in the future.

Research of the deformation of the shaping unit in an auger extruder caused by the extruding pressure in production of expanded clay

The technological process of forming expanded clay granules in an auger extruder is considered. Based on the analysis of well-known studies, considering the influence of conditions for shaping a ceramic mass on the quality of the produced porous aggregate, the following factor was identified: clogging of the shaping grid leads to an increase in pressure on it, its deformation and the impossibility of further operation. The authors note that there are practically no theoretical studies in the field of determining the most rational modes of functioning of the shaping equipment. The simulation model of an auger extruder shaping unit was developed in the Solid Works software environment, computational experiments on the influence of design parameters on shaping pressure were carried out, and recommendations for further technical application were formulated. The use of the results obtained will improve both the reliability of extruders with a perforated grid, as well as the quality of the final product with the specified quality parameters (bulk density and strength).

Chemical stability of innovative grouts for cast basalt elements

Newly developed tile grouts are intended mainly for environment with strong chemical loading. For this reason, chemical resistance was one of the key parameters observed. The grout for cast basalt tile was polymer based, in particular with epoxide binder and it utilized solidified hazardous wastes as fillers. It is well-known that epoxide binder has high resistance to solutions of inorganic substances. However, it is easily degraded by organic compounds. This was taken into consideration when assessed aggressive environments and their concentrations were selected. Examined substances were 60% solution of sulfuric acid, vapors of this acid (at concentration 96%) and 10% solution of acetic acid. After exposition to action of these aggressive substances, first of all the visual changes were assessed, i.e. change of color, formation of blisters, cracks, flaking or change of sheen. Then influence on microstructure, changes of bulk density and strengths of materials were observed.

Recovering Wood Waste to Produce Briquettes Enriched with Commercial Kraft Lignin

Aiming to use lignocellulosic biomass as energy source, one of the process that may aggregate values is the densification process, which allows the production of bioenergy using solid fuels, mainly for reducing transportation costs. In this research, solid fuel from co-briquetting of wood residues from sawmill using commercial kraft lignin as binder was investigated. The effects of compression pressure (900, 1200 and 1500 PSI) and briquette formulation (varying wood and kraft lignin proportion) on the quality and characteristics of briquettes were evaluated. The main findings were that briquetting of wood residues with kraft lignin resulted in an improvement of bulk density, strength rupture modulus, low heating value (LHV) and high heating value (HHV). The briquettes using 4% and 6% of kraft lignin, and submitted to 1200 to 1500 PSI, presented higher bulk density and strength resistance, respectively. On the other hand, the heating values showed the highest results with the addition of 2% lignin at 900 PSI, being the legal range for additives in briquettes for many countries such as in European Union.

Hyperbranched polymer with dynamic thiol-aldehyde crosslinking and its application as a self-healable bioadhesive.

Bioadhesives crosslinked with dynamic bonds exhibit shear-thinning, self-healing, and on-demand detachment properties, but generally show a weak bonding performance due to their poor bulk strength. Obtaining a strong bioadhesive with reversible crosslinking remains a challenge. To address this issue, herein we engineered a dynamic thiol-aldehyde crosslinked solvent-free adhesive based on hyperbranched polymer. The adhesive was obtained by directly mixing a liquid hyperbranched polymer with thiol end groups (HBPTE) and benzaldehyde-terminated polyethylene glycol (PEGCHO) without any additional catalyst or solvent. The solvent-free strategy yielded a dense crosslinking structure with many aldehyde groups, so this HBPTE-PEGCHO adhesive can strongly bond to tissue and various non-biological substrates. In addition, the HBPTE-PEGCHO adhesive has self-healing and thermo-reversible bonding properties due to the dynamic thiol-aldehyde crosslinking matrix. In vivo wound healing experiments show that this HBPTE-PEGCHO adhesive is tissue-benign, suggesting it can be applied in clinical practice. Combining the hyperbranched polymer-based solvent-free strategy and dynamic thiol-aldehyde crosslinking chemistry provides a simple but effective way to engineer a multifunctional bioadhesive with the desired bonding performance.

Cellulose-Based Hybrid Structural Material for Radiative Cooling.

Structural materials with excellent mechanical properties are vitally important for architectural application. However, the traditional structural materials with complex manufacturing processes cannot effectively regulate heat flow, causing a large impact on global energy consumption. Here, we processed a high-performance and inexpensive cooling structural material by bottom-up assembling delignified biomass cellulose fiber and inorganic microspheres into a 3D network bulk followed by a hot-pressing process; we constructed a cooling lignocellulosic bulk that exhibits strong mechanical strength more than eight times that of the pure wood fiber bulk and greater specific strength than the majority of structural materials. The cellulose acts as a photonic solar reflector and thermal emitter, enabling a material that can accomplish 24-h continuous cooling with an average dT of 6 and 8 °C during day and night, respectively. Combined with excellent fire-retardant and outdoor antibacterial performance, it will pave the way for the design of high-performance cooling structural materials.

High-strength non-firing ceramics by mechanochemical treatment

Reducing the sintering time/temperature has been long desired. A so-called “non-firing sintering” was previously introduced by authors, without using thermal energy. This method involves the chemical activation of powder surface via ball milling, however, the mechanical strength of solidified bodies by non-firing sintering method is still low. In this study, an optimized non-firing process will be proposed in order to achieve high-strength materials comparable to the high-temperature sintered counterparts. Results showed that by optimizing the process, mechanical strength of 270 MPa and Vickers hardness of 2.1 GPa (214 Hv) were successfully achieved. It is also shown that the particle-particle bridge strength determines the bulk strength.

Bioinspired structure-robust cellulose nanocrystal films with enhanced water resistance, photothermal conversion ability, and fluorescence

Assembling 1D cellulose nanocrystal into robust functional 3D macro-materials can be conducive to the broad application of nanocomposites, but it remains a huge challenge. Inspired by mussel-like adhesion and nacre structures, functionalized sodium alginate was in-situ synthesized with dopamine as a reinforcement agent and an interface jointer for the cellulose nanocrystal (CNC) nanocomposites with excellent mechanical properties. A rhodamine derivative was developed as a structural modifier to extend bulk strength as well as generate outstanding fluorescence. Through facile vacuum-assisted assembly, the resulting nanocomposites showed 210% and 220% increase in strength and Young’s modulus respectively, without losing ductility. Such experiment results were much higher than those of the reported. The thermal stability and water resistance were also improved remarkably, with favorable fluorescent and photothermal conversion functionalities. This study explored a promising approach to prepare biomimetic CNC nanocomposites with favorable properties and extra functionality, showing great potentials for various applications in fluorescent probe field.

Solid solution softening in dislocation-starved Mg–Al alloys

Here, we report molecular dynamics (MD) calculations of spall strength in pure magnesium and magnesium alloys with 1–8 at.% aluminum in solid solution. The Mg–Al solid solution alloys are found to have a weaker spall strength than pure magnesium, e.g. the spall strength of Mg-8 at.% Al is found to be 12% lower than pure magnesium. Moreover, we find that the spall strength of Mg–Al alloys monotonically decreases with increasing concentration of Al content. We term this phenomena solid solution softening (SSS) of spall strength, which is contrary to the conventional solid solution strengthening observed in most alloys (including Mg–Al alloys) deformed at quasi-static loading rates. We argue that this transition from solid solution strengthening at quasi-static rates to SSS at extreme loading rates is due to a transition from dislocation glide dominated failure at low rates to dislocation nucleation dominated failure at extreme rates. The distortion of the host lattice by solute atoms is found to retard dislocation glide, but aids dislocation nucleation. We thus conclude that SSS may manifest in any dislocation-starved system, regardless of loading rate. To this end, we propose a theoretical model for spall strength in dislocation-starved bulk and nanoporous alloys that exhibits remarkable agreement with our molecular dynamics calculations. Our theory bares some resemblance to the double kink nucleation enhancement theory for low-temperature SSS in some body centered cubic metals, e.g. refractory metals alloyed with group IV-VIII elements.

Craters on Charon: Impactors from a Collisional Cascade Among Trans-Neptunian Objects

Abstract We consider whether equilibrium size distributions from collisional cascades match the frequency of impactors derived from New Horizons crater counts on Charon. Using an analytic model and a suite of numerical simulations, we demonstrate that collisional cascades generate wavy size distributions; the morphology of the waves depends on the binding energy of solids and the collision velocity v c . For an adopted minimum size of solids, = 1 μm, and collision velocity v c = 1–3 km s−1, the waves are rather insensitive to the gravitational component of . If the bulk strength component of is for particles with radius r, size distributions with small Q s are much wavier than those with large Q s ; systems with e s ≈ −0.4 have stronger waves than systems with e s ≈ 0. Detailed comparisons with the New Horizons data suggest that a collisional cascade among solids with a bulk strength intermediate between weak ice and normal ice produces size distributions fairly similar to that of impactors on Charon. If the surface density Σ of the protosolar nebula varies with semimajor axis a as Σ ≈ 30 g cm−2 (a/1 au)−3/2, the timescale for a cascade to generate an approximate equilibrium is 100–300 Myr at 45 au and 10–30 Myr at 25 au. Although it is necessary to perform more complete evolutionary calculations of the Kuiper Belt, collisional cascades are a viable model for producing the size distribution of solids that impacted Charon throughout its history.

Structure-dependent strength and toughness in dodecahedral silica nanocage

Nanocages are structurally complex hollow low-dimensional materials that offer unique properties and functions that are inaccessible in bulk materials. They have tremendous potential in revolutionizing a number of fields including drug delivery and nanotechnology, but their applications remain limited primarily due to inadequate understanding of their extreme mechanical properties. Here, using reactive force field-based classical molecular dynamics simulations, we explore the bulk modulus, strength, and toughness modulus for a number of dodecahedral silica nanocages. The results show that, both under hydrostatic tension and compression, the mechanical properties vary nonlinearly with the structural parameters. Also, unlike bulk silica—which shows softening under tension in the nonlinear regime of mechanical deformation—silica nanocage exhibits stiffening at higher deformation that originates from the structural resistance of the nanocage. We show that the surface-area to volume ratio accurately describes the softening and stiffening behavior of the cage. Likewise, under compression, the nanocage shows three distinctive regimes: (i) linear decrease in stress with increasing strain, (ii) constant stress states with increasing strain representing shrinkage of the empty space, and (iii) exponential decrease in stress with increasing strain dominated by strong repulsion. These findings highlight the possibility of attaining a diverse set of mechanical properties from a nanocage by tailoring its structural parameters.

Room temperature bonding of aluminum nitride ceramic and semiconductor substrate

AlN and Si substrates were bonded at room temperature after sputtering the surfaces under ultra-high vacuum conditions. The bonding strength was insignificant when they were directly bonded. However, the strong bonding equivalent to the Si bulk strength (2.5 J/m2) was achieved by a process modification to form a 1.5-nm-thick Si adhesion layer on the AlN substrate. When the Au/Ti bonding layers were deposited on the surfaces before bonding, such strong bonding was also obtained. As the bonding layers were atomically thin, we expect that the thermal resistance between the substrates is limited compared with other integration techniques.

Contact Yield Initiation and Its Influence on Rolling Contact Fatigue of Case-Hardened Steels

AbstractStress distributions and plastic deformation zones are factors directly influencing the fatigue life of components under cyclic contact. An effective approach to improving the resistance of a steel to contact fatigue failure is surface hardening, which builds gradient yield strength from the surface of the steel to the bulk. When using the distortion energy theory as the criterion to identify failure initiation for a case-hardened steel, contact yield starts in the subsurface wherever the von Mises stress reaches the local material strength, rather than at the point of the maximum von Mises stress in the subsurface. If the yield strength changes from the surface to the bulk following a straight line, the location of yield initiation should occur at the tangency of the strength line and the von Mises stress curve. Analyses on circular, rectangular, and elliptical contacts are presented to reveal the locations of contact yield initiation for such case-hardened steels subjected to rolling contact stresses, for which the influence of friction can be ignored. A group of formulas relating contact yield initiation, in terms of the critical pressure, location of the first yield, and plasticity index (transition to plasticity) to case-hardening parameters, such as the case slope, the minimum case depth, and surface and bulk strengths, are derived to facilitate contact element designs using case-hardened materials. The results are applied to examine the rolling contact behaviors of several case-hardened steels, and the data correlation suggests that their rolling contact fatigue lives are related to a nondimensional case-hardening slope besides external loading.