Shear Breakage Research Articles

Retrospective evaluation of perioperative clinical outcomes of diaphyseal femoral fractures repaired with the string-of-pearls locking plate system with adjunctive fixation.

To evaluate outcomes and complication rate of utilizing a string-of-pearls (SOP) plate augmented with adjunctive fixation in the repair of canine femur fractures. Records of canine patients with mid-diaphyseal femoral fractures repaired with the SOP plate and adjunctive fixation were reviewed. Information retrieved from medical records included signalment, patient weight, fracture configuration, repair technique, healing time, and complications based on perioperative radiographic follow-up to clinical union. Forty client-owned dogs met inclusion criteria for this study. Variables analyzed for association with major complications included body weight, fracture configuration, repair technique, and adjunctive fixation. Major complications requiring surgical revision occurred in 8 of 40 fractures. Five cases experienced intramedullary pin migration and were successfully treated with sedated pin removal. The remaining 3 cases involved implant failure via screw shear breakage and required surgical revision of the fixation to achieve a successful outcome. On the basis of a calculated Bonferroni correction, no statistical significance of the tested variables was found in association with major complications; however, significance was limited due to the low statistical power of this study. The use of adjunctive fixation with the SOP locking plate system led to radiographic union without complication in most cases, and no instances of plate breakage were reported. However, implant complications secondary to the adjunctive fixation can occur. Adjunctive fixation used with the SOP plate for repair of canine femur fractures has a high success rate, though pin migration as a complication persists.

A polydisperse model for thixotropic elasto‐viscoplastic suspensions of aggregating particles using population balances

AbstractAn improved population balance‐based rheological constitutive framework for polydisperse aggregating suspensions is derived by incorporating detailed models for orthokinetic and perikinetic aggregation and shear breakage processes. The framework accounts for critical properties such as dynamic arrest, viscoelasticity, kinematic hardening, thixotropy, and yield stress to generate a full range of thixotropic elasto‐viscoplastic (TEVP) response. Additionally, the model is thermodynamically consistent because the dynamics and timescales are completely determined by internal structural and kinetic variables. The model connects the rheological response to the structural descriptors such as the size distribution of agglomerates, mean sizes, fractal dimension, and agglomerate volume fraction. Predictions are compared against a wide range of shear rheology measurements data for model thixotropic suspensions of fumed silica and carbon black, including large amplitude oscillatory shear (LAOS), as well as ultra‐small angle neutron scattering under steady shear (Rheo‐uSANS).

ABAQUS Numerical Simulation Study on the Shear Instability of a Wellbore Induced by a Slip of the Natural Gas Hydrate Layer

To study the shear deformation and failure characteristics of a wellbore and the interaction mechanism with its surrounding rocks induced by a layer slip during natural gas hydrates (NGHs) extraction, this paper conducted a numerical simulation study of wellbore shear induced by a layer slip using ABAQUS software and carried out a laboratory experiment of wellbore shear to verify the accuracy of the numerical model. The results show that the shear force–displacement curves obtained from the laboratory experiments and numerical simulations are consistent with five stages, including the compaction stage, linear stage, plastic stage, strain-softening stage and residual stage. The wellbore shows a “Z”-shaped deformation characteristic after its shear breakage. The shear force of the wellbore is maximum at the shear surface, and it is distributed in an approximate “M” shape along the shear surface. The axial force of the wellbore is small and uniformly distributed in the initial stage of the shear. The wellbore bending moment is minimum at the shear surface, with a value of 0, and it is distributed in a skew–symmetric wave shape along the shear surface. During the shearing, the evolution of the wellbore axial force and shear force can be classified into the distribution pattern along the radial direction on the shear surface and the pattern along the axial direction. The combination of the wellbore axial force and shear force causes the tensile–shear compound failure of the wellbore. During shearing, the wellbore and rock body gradually enter the plastic state with the increase in the shear displacement. When the entire cross-section of the wellbore is in the plastic state, a “necking” phenomenon of the wellbore begins to appear. During the shearing, the frictional dissipation energy and plastic dissipation energy increase constantly. In addition, the elastic strain energy increases to a peak and then decreases to a certain value, which remains unchanged along with the work conducted by the shear force.

Determining the Forming Limit Diagram by Experimental Methods

Abstract In general, a large part of the time is devoted to the design and production of reliable parts where extensive knowledge is required for the design engineers to come up with an optimal solution for the tooling and sheet metal forming processes. Most of the time, the principle of trial and error is used to get the desired shapes for the products. This is because the prediction of deformations occurring in sheet metal elements is not available and is highly dependent on the geometry of the part, the tools and the deformation process. Prediction is limited by the proper location of necking, shear breakage, and puckering of the material. Searching for a robust deformation process by trial and error is expensive and inefficient. The use of numerical simulations provides engineers with an alternative efficiency for developing a tool and process to produce quality parts in a more efficient and lower cost. Computer simulation is an extension of theoretical science that is based on mathematical models. Such models attempt to characterize the physical prediction or consequences of scientific theories. The purpose of this work is to present the way of determining the forming limit diagram by various experimental methods.

Single diamond scribing of SiCf/SiC composite: Force and material removal mechanism study

SiC fiber-reinforced SiC ceramic matrix (SiCf/SiC) is an advanced high-temperature material widely used in the heat-resistant componets of the aerospace engine and nuclear reactor, which are generally precisely ground to achieve the designed dimensional and geometrical tolerances. This research investigates the scribing force and material removal mechanism of 2.5D woven SiCf/SiC with the flat and sharp diamond grits, which present the new dressed and worn grinding wheel. The results show that the sharp grit has larger wear on the cutting edge and generates lower force than that of the flat grit at the same scribing depth and groove cross-section area. In both sharp and flat grits, the SiC matrix is mainly removed by the fracture cracks, peeling off, fiber exposure and powdering. In transverse diamond scribing of the SiCf, the fiber debonding and shear breakage are dominant removal feature for the flat grit scribing. Two additional removal patterns, the ductile scratch and fiber cracking, are observed for the sharp grit. In parallel diamond scribing of the SiCf, the shear and bending fractures in the cut-in and cut-out points are two key material removal modes, respectively, especially in the fiber woven structure. This research provides a fundamental understanding of interaction force and the material removal process of SiCf/SiC in grinding.

Numerical investigation of rock sphere breakage upon oblique impact: effect of the contact friction coefficient and impact angle

Discrete element simulations are performed to better understand the breakage of marble spheres upon oblique impact. The influence of the contact friction coefficient and impact angle on the impact-induced breakage is considered. A modelling method for oblique impact is proposed. Detailed parameter calibration and verification of the modelling method were performed. The oblique simulations show that the laboratory breakage behaviour of marble spheres upon normal and oblique impact is well matched through the proposed modelling method. Tensile and shear breakage patterns are observed in laboratory tests and simulations and are significantly influenced by the contact friction coefficient and impact angle. The shear component of the impact velocity determines the breakage at a low impact angle and high contact friction coefficient, while the normal component dominates the breakage at a high impact angle or low contact friction coefficient. The damage ratio, contact force and fragment characteristics are also analysed. Two constants, i.e., the critical shear contact force and critical normal contact force, are obtained. Finally, a comprehensive breakage criterion for brittle particles under oblique impact is proposed. The breakage patterns of brittle particles can easily be determined through the proposed breakage criterion.

DEM analysis on the triaxial behaviour of mudstone considering water disintegration

Mudstone is a typical type of soft rocks. It is stable and has high strength in its natural state. However, in presence of water the constituent minerals dissolve and the inter-grain bonds are weakened, which thereby greatly reduces the strength of mudstone. As one of the most prevailing geological formations in the southwestern China, understanding the mechanical behaviour of mudstone at different degrees of disintegration is of great importance to practical engineering. This paper presents a micro-mechanical analysis on the mechanical behaviour of mudstone at different degrees of disintegration using the discrete element method (DEM). The laboratory triaxial tests carried out on mudstone samples that have been merged in water for different time periods are simulated. The dissolution of minerals and weakening of bonds between grains are considered by reducing the selected input parameters of parallel bonds at random locations. Different degrees of disintegration are obtained by multiplying the selected input parameters of parallel bonds with different reducing factors. The stress-strain curves obtained using the proposed approach are in good agreements with the experimental data. The progressive failure mechanism of mudstone at different degrees of disintegration is investigated considering the characteristics of particle motion, contact variation and bond breakage. Micro-scale analysis shows that with the increasing of confining pressure, the fraction of shear breakage of parallel bonds increases but the declining rate of coordination number post peak decreases. These underlie the fundamental mechanism of the change of failure mode of mudstone from brittleness to ductileness. Regardless of its spatial locations, the majority of broken bonds for the disintegrated specimens are those bonds with reduced input parameters. And the fraction of altered bonds within the broken bonds increases with the increasing degree of disintegration. The current research provides insightful understanding of the fundamental behaviour of mudstone in the presence of water.

Experimental Study on the Shear Behavior of the Bonding Interface Between Sandstone and Cement Mortar Under Freeze–Thaw

Shear experiments were conducted on the cement mortar–sandstone bonding interface and the materials themselves to investigate their loss of shear strength and the deterioration mechanism caused by freezing and thawing cycles. The experimental results show that the shear strength of the bonding interface is much lower than that of the original materials themselves under the same normal stress. The shear strength of this interface decreases linearly with increasing number of freeze–thaw cycles, but it linearly increases with increasing normal stress. The cohesion and internal friction angle also decrease as the number of freeze–thaw cycles increases. In addition, obvious freeze–thaw debonding of this interface is observed and it is first caused by the difference in frost-heaving deformation between the cement mortar and the red sandstone, followed by the frost-heaving pressure in the crack formed in the interface. Finally, the shear damage of this interface has been quantified by reconstitution of the interface morphology. As a result, almost all the shear breakage occurs on the red sandstone side, and a concave rough face arises. With the absence of normal stress, the shear abscission area in the red sandstone increases quickly with increasing number of freeze–thaw cycles. However, with increasing normal stress, this shear abscission area decreases, and the layered composite specimens were prone to shear failure straightly along the bonding interface, because the shear dilatancy deformation is constrained. This study provides the shear failure characteristics of cement mortar–rock interfaces under freeze–thaw cycles and contributes to a better understanding of the freeze–thaw debonding mechanism of protective cement mortar layers on rock surfaces.

The numerical analysis of particle-size distribution of clusters in shear flow at one-dimensional closed system and three-dimensional open system

Aimed at optimizing the resin-molding process, a method for numerically analyzing aggregation and dispersion behavior of the filler in resin composite was proposed. The flow of a resin composite during molding was calculated by using computational fluid dynamics (CFD), and particle-size distribution (PSD) of the cluster in each computational domain of the CFD model was estimated by solving the population balance equation (PBE). The proposed numerical-analysis method is based on the thixotropy model of Usui et al. In the thixotropy model, PSD is calculated by taking into account the aggregation and dispersion rate of the cluster by Brownian coagulation, shear coagulation, and shear breakage. Shear-breakage rate of the cluster is evaluated by solving the energy balance of bonding energy of the primary particles cut at the breakage and the drag applied to the cluster by the flow of the fluid. The composite viscosity was calculated using Krieger and Dougherty’s model based on apparent-solid-volume fraction estimated from the calculated PSD. To solve the PBE at low calculation cost, it was discretized using the fixed-pivot technique of Kumar and Ramkrishna. The proposed method was incorporated into the general-purpose CFD software FLOW-3D®, and its accuracy was proved.

Effect of particle modification on the shear thickening behaviors of the suspensions of silica nanoparticles in PEG

A series of shear thickening fluids based on the modified silica nanoparticles by silane coupling agent, stearic acid, and titanate suspended in polyethylene glycol (PEG) were prepared, and the effects of particle modification on the shear thickening behaviors of these fluids were investigated. It can be found that the modification obviously decreases the particle agglomeration, improves the particle dispersion property, and increases the maximum particle concentration in fluid but leads to the reduction of the viscosity and shear thickening effect of the fluids due to the decrease of particle interactions. The modified silica fluids exhibit stronger structural recovery ability and shear thickening reversibility even after multiple shear breakage.

Shear thickening effect of the suspensions of silica nanoparticles in PEG with different particle size, concentration, and shear

In this study, a series of shear thickening fluids based on the suspension of silica nanoparticles in polyethylene glycol (PEG) were prepared, and the influences of particle size, concentration, and shear on the shear thickening effect were investigated by rheological measurements. It was observed that with the increase of silica concentration, the viscosity and critical shear rate of the fluid become higher, and the shear thickening phenomenon becomes more obvious. Under the same particle concentration, higher shear thickening effect and lower critical shear thickening concentration appear for smaller nanoparticles but for larger micro particles. As the temperature increases, the enhanced Brownian motion leads to the rising of critical shear rate and the strengthening of shear thickening effect. The rheological properties of these fluids are very sensitive to the shear rate with fast viscosity change for response, and smaller nanoparticles can recover their network structures more easily after shear breakage.

High shear breakage of compact polyelectrolyte-bridged flocs: A method for obtaining model-independent breakage rate function data

A method of obtaining model-independent breakage rate or fragmentation kinetic function (FKF) data in the population balance (PB) equation (PBE) was proposed for the high shear breakage of compact polyelectrolyte-bridged alumina flocs. The continuous particle size distribution function (PSDF) data were obtained as a function of fragmentation time. The PSDF data at zero fragmentation time was and must be used as the input in the PB modelling. Computed temporal PSDF curves were obtained by solving the dimensionless log-form PBE using a FKF based only on the fragmenting particle and a daughter size. Another important requirement is that the experimental time must be used in the scaling. Using appropriate values for the parameters in the FKF, an excellent match between the temporal experimental and computed PSDF data was achieved. Upon meeting all these conditions, the FKF values used in the computation should truly represent the experimental values for all father-daughter size combinations encountered in the fragmentation process. The fragmentation occurred in the rotor-stator device under the conditions where the Kolmogorov microscale and characteristics velocity gradient of 37 μm and 1600 s−1. The ratio of the largest to smallest length scale turbulent eddies was 2047.

Modeling particle-size distribution dynamics in a shear-induced breakage process with an improved breakage kernel: Importance of the internal bonds

An improved aggregate breakage kernel was developed that accounts for the effects of both the internal bonding forces between particles within an aggregate and the fluid shear stress exerted on the aggregate. The ratio of the two opposite forces regulates the probability of aggregate breakage. Using the improved breakage kernel, together with the sectional modeling technique, the dynamics of particle breakage induced by fluid shear was well simulated. The results show that the internal bonding forces determine the strength of the aggregates, and the hydrophobic bonding forces are much stronger than van der Waals' forces for holding the aggregates against shear breakage. The simulations compared fairly well with the experimental results in terms of PSD evolution during the breakage of latex particle aggregates and activated sludge flocs. For the latex particle aggregates, van der Waals' forces apparently are the main internal bonding force between particles. However, for activated sludge flocs, the non-DLVO hydrophobic forces are shown to play an important role in maintaining a stronger structure of the flocs. (C) 2014 Elsevier B.V. All rights reserved.

Shear strength and breakage of disturbed snail fossils adjacent to the preservation zone in the Mae Moh coal mine

The preserved area of snail fossils, with layers of up to 10 m deep, in the lignite coal mining area of Mae Moh in northern Thailand has been set aside; however, there is concern about the impact of weathering and erosion in the long term due to the breakage and low strength of snail fossils. Therefore, the present study aims to investigate the strength properties of the snail fossils in association with the effect of particle breakage using a direct simple shear test. Disturbed snail fossil samples were collected from the subsurface of the Mae Moh coal mine outside the preservation area. The results indicate that snail fossils are highly compressible due to the angular and delicate snail particles. In addition, the internal friction angle of snail fossils is close to 31°, which is much lower than that of other carbonate sands, but comparable to those of hard particle sands or commonly encountered sands.

Breakage and ultimate states for a carbonate sand

This paper presents data from ring-shear and one-dimensional compression tests, which have been used to cause breakage under large shear strains and large compressive stresses respectively. A comparison of the behaviour of carbonate sand in monotonic shear and compression is reported, focusing on void collapse, grading properties and particle shape evolution. Trends in breakage behaviour under compression and under shear were similar; however, ultimate steady-state properties differed significantly. The higher effect of shear breakage was evident, in that the steady-state gradings for sheared material had higher fractal dimensions, indicating that the gradings were finer, and morphological changes in particle shape were more significant. Steady-state gradings tended to be multi-fractal in nature rather than mono-fractal, and showed that a unique monotonic steady-state grading does not exist. Two types of ring-shear device were compared, and the differences between the results highlighted a dependence of steady-state properties on test apparatus configuration.

Design of High-Efficient Bits for Igneous Rock in Xushen Gasfield

The igneous rocks in deep formations of the Xushen gasfield have the following characters: high abrasive property, high hardness, and high drillability, which lead to many drill bit accidents, few footage per bit , low efficiency of drilling, long drilling cycle, these severely restrict the exploration and development process of gas field. According to the features of deep formation, a hybird cutters bit is designed. It has three cones, with the overhang cone , duplicate taper and offset cone characters. The tungsten carbide cutters and the polycrystalline diamond compacts cutters are alternative collocation in the same tooth row in the bit. The exposed height of the tungsten carbide cutters is higher than polycrystalline diamond compacts cutters. The back rake angle of polycrystalline diamond compacts cutters is 10 ~ 40 °, the side rake angle is 10 ~ 30 °. The normal direction of working face stay the same with the composite slip direction, and the side rake pointed at adjacent gullet. Through the design method, it is integrated that the advantages of roller bit and PDC bit, the way of impact breakage and rotational shear breakage and the prominent performance of tungsten carbide cutters and polycrystalline diamond compacts cutters. It can improveROP and bit life.

Dispersion of water into oil in a rotor–stator mixer. Part 1: Drop breakup in dilute systems

Most previous studies of liquid–liquid dispersion in complex geometry are limited to turbulent flow at low continuous phase viscosity. In this study, a viscous continuous phase was employed over a range of flow conditions including both the laminar and turbulent regimes. Equilibrium drop size was measured for water dispersed into viscous food grade mineral oils in a batch Silverson L4R rotor–stator mixer. The influence of fluid viscosities and interfacial tension (by adding an oil-soluble surfactant) were examined. In order to isolate the effect of drop breakage from coalescence, Part 1 is limited to dilute conditions (water phase fraction, ϕ=0.001). In the laminar regime, drop breakup was more likely due to a simple shear breakage mechanism than one for extension. Following Grace (1982), a semi-empirical drop size correlation was developed. For turbulent flow, the validity of the sub-Kolmogorov inertial stress model for correlating equilibrium mean drop size was verified. Surfactants were found to mostly decrease drop size by lowering interfacial tension. Except for laminar systems near the critical micelle concentration, where Marangoni stresses appear to play some role, the effect of surfactants on the drop size could be correlated using the equilibrium or static interfacial tension. The influence of water phase fraction and coalescence is considered in Part 2 (Rueger and Calabrese, 2013) of this paper.

Dynamic changes of gravity fields before and after the 2008 Wenchuan earthquake (Ms8.0)

Abstract: The pattern evolution and dynamic mechanism of the dynamic changes of regional gravity fields occurring before and after the Wenchuan M s8.0 earthquake are analyzed, based on five epochs of 1998–2007 mobile gravity data from the middle-south section of the north–south seismic belt, and two epochs of field research data collected after the 2008 Wenchuan earthquake in combination with GPS data, leveling observations, and geotectonic environment data. The regional dynamic gravity changes demonstrate the effects of the eastward flow of solid matter in the Qinghai-Tibetan plateau and the preparation of the 2008 Wenchuan earthquake (2–10 yr). The two most meaningful gravity indicators of the Wenchuan earthquake preparation are the positive (increasing) gravity changes occurring over many years in the southwest epicenter and the large-scale gradient zone of gravity variation, with the cumulative difference between the two sides of the gradient zone of gravity exceeding 200 μGal. The positive gravity changes may facilitate a constant energy accumulation and the gradient belt may support seismic shear breakage. Overall, the gravity changes associated with the earthquake preparation indicate a pattern of accelerating increase-decelerating increase-earthquake occurrence. The Songpan-Ganzi block generally displays a negative gravity change, providing evidence for a local upwarping of the deep crust-mantle and an interior expansion of the deep crust attributable to high temperatures. The viewpoint is consistent with the dilatant mechanism for earthquake preparation.

Reinforced direct bonding of optical materials by femtosecond laser welding

A process for reinforcing a direct bond between optical materials using femtosecond laser welding is presented. As a side benefit, the optical transmission properties of the joined components are shown not to be altered by the joining process. The joints exhibits higher shear breakage loads, yielding a maximum measured joint strength of 5.25 MPa for an applied load of 75 kg in fused silica. The laser sealing of direct bonds between dissimilar materials improves their resistance to thermal shocks. Direct bonds sealed by a circular weld seam can withstand thermal shocks at temperatures at least twice as great as nonreinforced direct bonds. The combination of ultrashort laser welding and direct bonding provides an innovative joining method that benefits from the advantages of both contributing physical processes.

PIV characterisation of flocculation dynamics and floc structure in water treatment

Particle flocculation with chemical flocculant addition is an essential step in water treatment. The performance of flocculation and the property of the flocs formed affect the overall results of the treatment process. In addition to particulate impurities, the presence of organic matter in water, such as natural organic materials (NOM), also influence the effectiveness of chemical flocculation. In this paper, the PIV system was employed to investigate the flocculation dynamics for different flocculants in different model waters. With the PIV and image analysis, the change in particle size distribution could be well recorded. Using the sequence of flocculation, shear breakage and re-flocculation on a jar-test device together with the PIV system, the rate of floc formation, the strength of the flocs, the recovery of broken flocs, and the morphological and structural features of the flocs were characterized. The results indicated that the adsorption of HA on the particle will stabilized the particles, hence hindered the flocculation process. Sweep flocculation using a higher chemical coagulant dosage was an effective means of process enhancement for the removal of particulates and associated organic matter. The dynamics of A–B–R process was characterized by particle size distribution (PSD) measurement with PIV setup. The particle strength and reversibility capability were examined. Strength index showed the HA flocs have comparable strength, while recovery index indicated a less recovery capability with the increasing of HA concentration after exposure to a higher shear, especially for ferric HA flocs. It appears that the bonds holding HA flocs together are not purely physical bonds given the limited regrowth seen. Finally, evolution of floc structure during A–B–R process was analysed by investigated the fractal dimension D b . The results were generally consistent with previous PSD measurements. It suggested that the structure of flocs in breakage became more compact with little permeability. An increase in floc compaction provides a further explanation for the limited regrowth for most of flocs. According to the performances of alum and ferric, it can be noticed that HA flocs have different properties dependent on which chemical coagulant is used. Alum produced larger HA flocs which endured a higher recovery capability after exploring higher shear, hence, compared to ferric, it could be preferred to using in the practical enhanced coagulation unit.