Deformation Behavior Of Particles Research Articles

Modeling and analysis of surface integrity transition in cutting of Sip/Al composites based on coordination deformation effect of particle-matrix

With the wide application of Sip/Al composites in key fields, it is critical to understand the material removal behavior and surface integrity evolution mechanism of Sip/Al composites. In this paper, based on the nanoindentation and scratching experiments, the coordination deformation behavior of Si particles and the Al matrix were investigated at the micro-scale, and the mechanism and conditions of surface integrity transition (SIT) of Sip/Al composites were elucidated. Then, taking into account the feature of particle fragmentation and detachment caused by interfacial failure, an analytical model of specific cutting energy for Sip/Al composites cutting under different material removal modes was established. The competitive relationship between ductile deformation and surface defect formation was investigated, and a quantitative prediction model for the critical depth of SIT was proposed. The results show that the evolution of the material removal behavior of Sip/Al composites is a consequence of the coordination deformation the Al matrix and Si particles. The material removal mode of Sip/Al composites transitions from ductile removal to quasi-brittle removal with particle fragmentation and detachment, and there is an obvious SIT characteristic. The prediction results of critical depth are in agreement with the experimental results, with an average error of less than 9.8 %. Moreover, an appropriate increase in cutting speed can effectively enhance the surface integrity of Sip/Al composites. This research contributes to a deeper understanding of the low-damage machining mechanism of Sip/Al composites.

Research Progress on Numerical Simulation of the Deposition and Deformation Behavior of Cold Spray Particles

It is of significant theoretical and practical value to study the deposition process and deformation behavior of cold-sprayed particles to find the deposition mechanism of cold-sprayed coatings, further improve the coating performance, and expand its application scope. However, observing the deposition process and particle behavior through experiments is difficult due to the brief deposition duration of cold spray particles. Numerical simulation offers a means to slow the deposition process and predict the critical velocity, deformation behavior, bonding mechanism, and residual stress of cold-sprayed particles. This paper uses finite element analysis software, including ANSYS LS Dynamic-2022 R1 and ABAQUS-6.14, alongside various prevalent finite element methods for numerically simulating cold spray particle deposition. These methods involve the Lagrange, Euler, arbitrary Lagrange-Euler (ALE), and Smoothed Particle Hydrodynamics (SPH) to investigate the cold spray particle deposition process. The recent literature primarily summarizes the simulation outcomes achieved by applying these methodologies for simulating the deposition process and deformation characteristics of different particles under varying cold spraying conditions. In addition, the reliability of these simulation results is analyzed by comparing the consistency between the simulation results of single-particle and multi-particle and the actual experimental results. On this basis, these methods’ advantages, disadvantages, and applicability are comprehensively analyzed, and the future simulation research work of particle deposition process and deformation behavior of cold spraying prospects is discussed. Future research is expected to provide a more in-depth study of the micro-mechanisms, such as the evolution of the inter-particle and internal organization of the particles, near the actual situation.

Hot deformation behavior and processing map of vanadium particles reinforced AZ31 composite

The vanadium particles reinforced AZ31 matrix composite (VP/AZ31) was prepared using the powder metallurgy method. Subsequently, hot deformation behavior of VP/AZ31 composite was studied through hot compression trials. The experimental parameters were set in a temperature range of 250–400 °C and a strain rate range of 0.001–1 s−1. Based on the experimental results, a strain-compensated Arrhenius constitutive model was developed to accurately forecast the flow behavior of VP/AZ31 composite. Moreover, the thermal activation energy was calculated to be 138.605 kJ/mol and the processing map was delineated according to the dynamic material model theory. The processing map revealed that the optimal processing area existed under 363–400 °C/0.001–0.004 s−1, where the efficiency of power dissipation exceeded 23 %. Notably, the highest efficiency of power dissipation occurred at 400 °C/1 s−1, which exceeded 30 %. Under these conditions, dynamic recrystallization (DRX) was sufficiently developed, indicating the enhancement of workability. It is estimated that the instability region for VP/AZ31 composites occurred within the conditions of 250–325 °C/0.16–1 s−1, characterized by crack formation. The DRX of VP/AZ31 composite is predominantly governed through the mechanism of discontinuous DRX (DDRX).

Combining in-situ observation and interfacial rheology as a tool to investigate the possible mechanism for improved emulsifying performance of gliadin-based colloid particles

Interfacial deformation and interfacial rheology behaviour of prolamin particles are relevant factors affecting their emulsification performance but have not yet been paid considerable attention to. Based on the finding that CMC modification significantly improved the emulsifying property of gliadin colloid particles (GCPs), the present study combined in situ observation and interfacial rheology as a tool to investigate the effect of CMC on the structure characteristics, interfacial deformation and interfacial rheology behaviour of GCPs and their correlation with emulsifying performance. The results demonstrated that gliadin/CMC complex particles (GCCPs) presented looser core-shell structures than GCPs. The interfacial deformation of particles and the formation of smooth interfaces were observed for both GCPs and GCCPs, and GCCPs exhibited faster deformation behaviour, which should correlate to the looser structure. Although GCCPs showed lower surface pressure and viscoelasticity modulus, the existence of CMC promoted the initial adsorption of particles and accelerated the formation of viscoelastic interfacial films, which contributed to the improvement of emulsifying performance. In addition, CMC endowed the interfacial layers with moderate viscosity and fluidity to resist the destabilisation induced by oil droplet deformation. The present study should provide insights for intuitive understanding and fine regulation of the interfacial behaviour of protein particles.

Surface defects formation mechanism of Mg2Si/Al composites by micro cutting

Mg2Si/Al composites have wide application prospects in aerospace and automotive industries. However, many defects often remain on the machined surface after micro cutting. In this paper, the formation mechanism of surface defects of Mg2Si/Al composites by micro cutting was studied by finite element (FE) simulations and machining experiments. Considering the real microstructure characteristics of Mg2Si particles, 2D FE simulations of Mg2Si/Al composites in micro cutting were carried out and then verified by corresponding cutting experiments. The simulation results and experimental data reveal the relationship between damage and deformation behavior of Mg2Si particles and formation mechanism of surface defects. In addition, the effects of cutting parameters such as depth of cutting (DoC), cutting speed and volume fraction of particles on residual defects of machined surfaces were studied. The results show that with lower DoC and higher cutting speed, the residual defects and surface roughness are significantly reduced, especially machining the composites with smaller particle size and lower volume fraction. The research findings provide a theoretical basis for reasonable selection of machining parameters and improving the machinability of Mg2Si/Al.

Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles.

While metal nanoparticles are widely used, their small size makes them mechanically unstable. Extensive prior research has demonstrated that nanoparticles with sizes in the range of 10-50 nm fail by the surface nucleation of dislocations, which is a thermally activated process. Two different contributions have been suggested to cause the weakening of smaller particles: first, geometric effects such as increased surface curvature reduce the barrier for dislocation nucleation; second, surface diffusion happens faster on smaller particles, thus accelerating the formation of surface kinks which nucleate dislocations. These two factors are difficult to disentangle. Here we use in situ compression testing inside a transmission electron microscope to measure the strength and deformation behavior of platinum particles in three groups: 12 nm bare particles, 16 nm bare particles, and 12 nm silica-coated particles. Thermodynamics calculations show that, if surface diffusion were the dominant factor, the last two groups would show equal strengthening. Our experimental results refute this, instead demonstrating a 100% increase in mean yield strength with increased particle size and no statistically significant increase in strength due to the addition of a coating. A separate analysis of stable plastic flow corroborates the findings, showing an order-of-magnitude increase in the rate of dislocation nucleation with a change in particle size and no change with coating. Taken together, these results demonstrate that surface diffusion plays a far smaller role in the failure of nanoparticles by dislocations as compared to geometric factors that reduce the energy barrier for dislocation nucleation.

Examining the Effect of MnS Particles on the Local Deformation Behavior of 8MnCrS4-4-13 Steel by In Situ Tensile Testing and Digital Image Correlation

In this study, the behavior of MnS particles in a steel matrix is investigated through in situ tensile testing and digital image correlation (DIC) analysis. The goal of this research is to understand the mechanical behavior of MnS inclusions based on their position in the steel matrix. To accomplish this, micro-dog bone-shaped samples are prepared, tensile tested, and analyzed. Macro-mechanical results reveal that the material yields at a stress of 350 MPa and has an ultimate tensile strength of 640 MPa, with a total elongation of 17%. For micro-mechanical analysis, scanning electron microscopy (SEM) images are taken at incremental strains and processed using DIC software to visualize the local strain evolution. The DIC analysis quantifiably demonstrates that the local strain is highest in the ferrite matrix, and while lowest in the pearlite matrix, the MnS particles and the interfaces between different materials experienced intermediate strains. The research provides new insights into the micro-mechanical deformation behavior of MnS particles in a steel matrix and has the potential to inform the optimization of the microstructure and properties of materials containing MnS inclusions.

The Effect of Particle Shape on the Compaction of Realistic Non-Spherical Particles—A Multi-Contact DEM Study

The purpose of this study was to investigate the deformation behavior of non-spherical particles during high-load compaction using the multi-contact discrete element method (MC-DEM). To account for non-spherical particles, the bonded multi-sphere method (BMS), which incorporates intragranular bonds between particles, and the conventional multi-sphere (CMS), where overlaps between particles are allowed to form a rigid body, were used. Several test cases were performed to justify the conclusions of this study. The bonded multi-sphere method was first employed to study the compression of a single rubber sphere. This method's ability to naturally handle large elastic deformations is demonstrated by its agreement with experimental data. This result was validated further through detailed finite element simulations (multiple particle finite element method (MPFEM)). Furthermore, the conventional multi-sphere (CMS) approach, in which overlaps between particles are allowed to form a rigid body, was used for the same objective, and revealed the limitations of this method in successfully capturing the compression behavior of a single rubber sphere. Finally, the uniaxial compaction of a microcrystalline cellulose-grade material, Avicel® PH 200 (FMC BioPolymer, Philadelphia, PA, USA), subjected to high confining conditions was studied using the BMS method. A series of simulation results was obtained with realistic non-spherical particles and compared with the experimental data. For a system composed of non-spherical particles, the multi-contact DEM showed very good agreement with experimental data.

Tamping effect during additive manufacturing of copper coating by cold spray: A comprehensive molecular dynamics study

The tamping effect is of great importance for the microstructure evolution, surface roughness, and mechanical performance of additively manufactured coatings by cold spray. A good understanding of the advantages and disadvantages of the tamping effect is therefore crucial for producing high-quality coatings, unfortunately, very few studies along this direction have been conducted. In this study, a multi-particle impact model was proposed to investigate the tamping effect on the deformation behavior and morphology of Cu particles in cold spray. It was found that the tamping effect could induce a traceable change in the flattening ratio of the first coating layer, which served as a reliable indicator for identifying the critical velocity. By continuously flattening the particles, the tamping effect led to a denser microstructure of the under-layer coating, although such a densification effect would become weaker with the increase of coating thickness. At a high impact velocity, the obstruction and extrusion of surrounding particles were not ignorable, as these interactions could significantly affect the thickness and shape of the central coating and thus affect the overview surface quality of additively manufactured copper coatings. In addition, the particles with a higher impact velocity exhibited a stronger tamping effect during cold spray, which resulted in a higher risk to penetrate the coating with potential damage to the substrate.

Microstructure Evolution, Constitutive Modelling, and Superplastic Forming of Experimental 6XXX-Type Alloys Processed with Different Thermomechanical Treatments.

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the secondary particle distribution and deformation behavior was studied. The increase in hot rolling degree increased the homogeneity of the particle distribution in the aluminum-based solid solution that improved superplastic properties, providing an elongation of ~470-500% at increased strain rates of (0.5-1) × 10-2 s-1. A constitutive model based on Arrhenius and Beckofen equations was used to describe and predict the superplastic flow behavior of the alloy studied. Model complex-shaped parts were processed by superplastic forming at two strain rates. The proposed strain rate of 1 × 10-2 s-1 provided a low thickness variation and a high quality of the experimental parts. The residual cavitation after superplastic forming was also large at the low strain rate of 2 × 10-3 s-1 and significantly smaller at 1 × 10-2 s-1. Coarse Al9FeNi particles did not stimulate the cavitation process and were effective to provide the superplasticity of alloys studied at high strain rates, whereas cavities were predominately observed near coarse Mg2Si particles, which act as nucleation places for cavities during superplastic deformation and forming.

Interparticle bonding and interfacial nanocrystallization mechanisms in additively manufactured bulk metallic glass fabricated by cold spray

Amorphous Zr-based bulk metallic glass deposit was produced by cold spray additive manufacturing. The bonding mechanism of metallic glass particles was systematically investigated through studying the deformation behavior of individual particles after deposition. We revealed two collective particle bonding mechanisms that contributed to the formation of metallic glass deposits, i.e., high-velocity impact induced localized metallurgical bonding at the fringe of the interface, and high particle temperature induced viscosity reduction and the resultant annular metallurgical bonding band. Moreover, the dynamic evolution mechanism of the amorphous phase into nanocrystal structures at severely deformed interfacial regions during cold spray was carefully investigated. For the first time, we observed different amorphous/nanocrystal structures in cold sprayed metallic glass deposits, which can represent different evolution stages in nanocrystallization process. Based on the observation, it is inferred that the nanocrystallization process can be divided into following three stages: composition segregation, the formation of ordered 1D and 2D transition structures, and 3D nanocrystals. The current study provides new insights into the bonding mechanisms and the mechanistic nanocrystallization origins in cold sprayed bulk metallic glass deposits.

Experimental Study of Internal Erosion in Granular Soil Subject to Cyclic Hydraulic Gradient Reversal

Numerous studies have been conducted to evaluate the influence of internal erosion on the geotechnical properties of soil under unidirectional seepage. Yet cyclic gradients prevail in natural or engineering systems, and the mechanical consequences of soil subjected to cyclic hydraulic gradient reversal have not been addressed in the literature. This paper reported the first batch of internal erosion tests on a modified stress-controlled triaxial apparatus that allows alteration of seepage direction and hydraulic gradient reversals. Three different schemes of hydraulic gradient application, namely monotonic stepwise loading, cyclic reversal after monotonic loading, and direct cyclic loading, were adopted. In each test, the cumulative particle loss, deformation, hydraulic conductivity, and posterosion shearing behavior were evaluated. It was found that the cyclically reversed hydraulic gradient resulted in more severe erosion at the same level of mean hydraulic gradient. Microscopic analysis was also conducted to investigate the mechanism of internal erosion under cyclic hydraulic gradient reversal, in which mitigation of clogging within the soil matrix was observed and found to facilitate the progression of internal erosion.

Microscale deformation behavior of sandstone mineral particles based on XCT scanning

This work aimed to quantify the physical and mechanical behavior of three-dimensional microstructures in rocks under uniaxial compression. A high-precision in situ XCT (X-ray transmission computed tomography) technology was applied to investigating the behavior of mineral grains in sandstone: the movement, the rotation deformation, and the principal strains between fault zone and non-fault zone. The results indicate that after unloading, the shear strain of mineral grains is periodic in the radial direction, the strain of mineral grains in the fracture zone is about 30 times of the macro strain of the specimen, which is about 5 times in the non-fracture zone, and the shear strain near the fault zone is larger than the compressive strain, and there is the shear stress concentration feature.

A Calculation Method for the Deformation Behavior of Warp-Knitted Fabric

Abstract In this paper, a new method to simulate the structure and loop deformation behavior of double-bar reflex-lapping warp-knitted fabrics based on the structural characteristics is proposed. A simplified mass-spring model was built in which loops knitted by filaments were considered as particles with the uniform mass distribution connected by structure springs for overlaps and shear springs for underlaps. Deformation forces and direction on particles were analyzed to describe the displacement and deformation behavior of particles. A loop model with eight control points was established, and the relationship between control points and particles was studied combining the quadratic Bezier curves. The deformation simulation was implemented by a simulator program with C# and JavaScript via web technology on Visual Studio 2015. The stereoscopic sense of filaments was realized by changing the direction and intensity of the light. The results show that the fabric deformation and the loop shape can be accurately achieve using the simplified mass-spring model compared with the real sample.

Analyzing the Effect of Particle Shape on Deformation Mechanism during Cutting Simulation of SiC P/Al Composites.

To analyze the effect of particle shape on deformational behavior in the cutting simulation process for metal matrix composites (MMCs), two 2D mesoscopic-based finite element (FE) models reinforced with randomly distributed circular and irregular polygonal particles were developed. Different material properties (metal matrix phase, particle reinforced phase) and the properties of the particle–matrix interface were comprehensively considered in the proposed FE model. Systematic cutting experiments were conducted to compare the differences between two modeling approaches with respect to particle fracture, chip formation, cutting force and surface integrity. The results show that the irregular polygonal particle model is closer to the microstructure of MMCs, and is better able to reflect the deformation behavior of particles. The simulation model with irregular polygonal particles is even able to capture more details of the impact caused by particles, reflecting variations in the cutting force in the actual cutting process. The initiation and propagation of microcracks is mainly determined on the basis of particle geometry and further affects chip formation. Both models are able to correctly reflect surface defects, but the irregular polygonal particle model provides a more comprehensive prediction for the subsurface damage of MMCs.

How can single particle compression and nanoindentation contribute to the understanding of pharmaceutical powder compression?

The deformation behaviour of a powder and, thus, of the individual particles is a crucial parameter in powder compaction and affects powder compressibility and compactibility. The classical approach for the characterization of the deformation behaviour is the performance of powder compression experiments combined with the application of mathematical models, such as the Heckel-Model, for the derivation of characteristic compression parameters. However, the correlation of these parameters with the deformation behaviour is physically often not well understood. Single particle compression and nanoindentation enables the in-depth investigation of the deformation behaviour of particulate materials.In this study, single particle compression experiments were performed for the characterization of the deformation behaviour of common pharmaceutical excipients and active pharmaceutical ingredients (APIs) with various, irregular particle morphologies of industrial relevance and the findings are compared with the results from powder compression. The technique was found useful for the characterization and clarification of the qualitative deformation behaviour. However, the derivation of a quantitative functional relationship between single particle deformation behavior and powder compression is limited. Nanoindentation was performed as complementary technique for the characterization of the micromechanical behavior of the APIs. A linear relationship between median indentation hardness and material densification strength as characteristic parameter derived by in-die powder compression analysis is found.

HVAF deposition mechanism of γ-TiAl-based coating containing β phase

The Ti-45Al-7Nb-4V, Ti-45Al-7Nb-4Cr, Ti-45Al-7Nb-2V-2Cr alloy coatings were prepared on the surface of the aluminum alloy by high-velocity-air-fuel (HVAF). The surface and cross-section of three kinds of titanium aluminum alloy coatings and the micromorphology of the bonding interface between the coating and substrate were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The deformation behavior of titanium aluminum alloy particles and the phase composition of the titanium aluminum alloy coating were analyzed by X-Ray Diffraction (XRD) and energy dispersive x-ray analysis (EDAX). The results show that the coordinated deformation between TiAl particles and Al alloy matrix is a necessary condition for the deposition of the first layer of titanium‑aluminum alloy particles. The bonding mechanism of the TiAl coating and the matrix is mechanical bonding, and there are both mechanical bonding and metallurgical bonding between spraying particles. In the process of coating deposition and formation, the β phase grains undergo coordinated deformation to form typical structures such as striped grains and circular columnar crystals. The deformation mechanism of the titanium aluminum alloy particles is the slip and kink mechanism in the grains, and the sliding and rotation mechanism of the grain boundary and the phase boundary. Adiabatic shear instability and dynamic recrystallization occurred during the formation of titanium aluminum alloy coating.

Deformation Behavior of Single Particle Cold Spray Ti-6Al-4V Splats

The rapid development of cold spray technology has made it a viable option to repair and remanufacture damaged components as well as to create novel materials for biomedical applications. One of the most influential parameters of this distinctive process is the deposition velocity, which ultimately controls the degree of material deformation and material adhesion. Although the majority of materials can be successfully deposited at relative low deposition velocity (<700m/s), this is not representative of Ti alloys which have high yield strength. The amount of deformation and resultant properties of the coating are related to the velocity, temperature, and tensile strength of the particles. The ability to predict the deformation and resultant properties helps in developing process parameters and tailoring coatings to get the desired properties. In the current study, the particle deformation behavior and bonding with the substrate was investigated over a range of impact conditions. The effects of deposition velocity, gas temperature, gas pressure and nozzle stand-off distance were studied using cold sprayed splats of spherical Ti-6Al-4V powder deposited on to 316 SS substrate utilizing helium as a carrier gas. Finite element modeling of the impacted particles was conducted using Johnson-Cook high-strain-rate properties in a Lagrangian analysis to predict the overall deformation and estimated stress state of the impacted particles. Particle temperature due to impact was also predicted. Overall predictions were in good agreement with experimental results. Optical microscopy, scanning electron microscopy (SEM) and focused ion beam (FIB) were used to identify three distinct regions within the impact morphologies; these include the initial impact region, the jetting region, and the upper splat region.

Different Deformation Behaviour Between Zirconia and Yttria Particles in Dispersion Strengthened Platinum-20% Rhodium Alloys

Platinum-20% rhodium strengthened by oxides of zirconium and yttrium were prepared by solidification of platinum-rhodium-(zirconium)-yttrium powder which had been internally oxidised. After forging, rolling and annealing, 1 mm plates were obtained. Then the plates were mechanically ground to 50–70 μm from rolling-normal direction, followed by argon ion milling until a hole appeared on the centre of the foil to obtain samples which were characterised by transmission electron microscopy (TEM), combined with thermodynamic analysis. The existence of spherical ZrO2 and Y2O3 particles was verified with platinum and rhodium present as pure metals at the same time. It was found that the deformation behaviour of ZrO2 and Y2O3 particles was quite different during processing, where the former basically maintain their spherical shape and were bonded tightly to matrix, while the latter were compressed along normal direction and form two cracks on both sides of Y2O3 particles along the rolling direction. The differences in hardness and interface bonding properties of these two types of particles are supposed to be the main causes of different deformation behaviour during hot forging and cold rolling.

Effect of particle size and deformation behaviour on water ingress into tablets.

Drug release performance of tablets is often highly dependent on disintegration, and water ingress is typically the rate-limiting step of the disintegration process. Water ingress into tablets is known to be highly influenced by the microstructure of the tablet, particularly tablet porosity. Initial particle size distribution of the formulation and the predominant powder deformation behaviour during compression are expected to impact such microstructure, making both factors important to investigate in relation to water ingress into tablets. Two size fractions (<125 and 355-500µm) of plastically deforming microcrystalline cellulose (MCC) and fragmenting di-calcium phosphate (DCP) were compressed into tablets with porosities ranging from 5 to 30% (with 5% increments). The total porosity of the tablets was measured using terahertz time-domain spectroscopy and liquid transport into these tablets was quantified using a flow cell coupled to terahertz pulsed imaging. It was found that tablets compressed from large MCC particles resulted in slower water ingress compared to tablets prepared from small MCC particles. In contrast, no difference in liquid transport kinetics was observed for tablets prepared across both size fractions of DCP particles. These results highlight the complex interplay between material characteristics, the process induced microstructure, and the liquid transport process that ultimately determines the drug release performance of the tablets.