Hard Inclusions Research Articles

Easy to fabricate 3D metastructure for low-frequency vibration control

As a burgeoning category of elastic metamaterials, 3D metastructures have garnered significant research attention for manipulating low-frequency acoustic and elastic waves. Bandgap engineering allows for the control of these waves across a subwavelength ultrawide frequency range. However, the manufacturing of these 3D structures poses a challenge, necessitating additional support materials for 3D-printed components, creating difficulties in mass production. In this study, we propose a novel lightweight 3D metastructure design that is easy to fabricate and provides a low-frequency subwavelength bandgap. We replaced conventional struts supporting heavy mass inclusions in typical designs with modified arch beams. This structural modification enables the easy and self-supporting manufacturing of 3D metastructure unit cells without the need for extra support material. Utilizing magnets and steel masses with bolts as hard inclusions, the magnet facilitates the quick assembly of the 3D metastructure, potentially facilitating mass manufacturing in practical applications. The wave dispersion and bandgap properties of the metastructure are investigated numerically, and experimental vibration tests are performed on the 3D-printed and assembled parts. The experimental results and numerical findings demonstrate robust vibration attenuation at low frequencies by the proposed 3D metastructure. The suggested, easy-to-fabricate 3D-metastructure design holds potential applications in low-frequency elastic-wave manipulation, including noise and vibration control.

Effect of hot rolling reduction process on macro-inclusion in high silicon steel plates: A numerical study

Inclusions inevitably exist in steel plate, whose behaviour during rolling severely affects the quality of product. In this article, a finite element method was used to simulate the hot rolling behaviour of hard and soft inclusions in high silicon steel plates at different sizes, positions and shapes (circle and square) when the adhesion to the matrix were weak. The shape, relative position and dimensions around the inclusions after rolling were obtained. When the inclusions are hard, cracks are produced around the inclusions after rolling. When inclusions are soft, there are no cracks around the inclusions. Large hard inclusions are more likely to move to the plate surface. When the inclusions are in the position of 1/16 of the sheet, the relative distance between the inclusions and the surface of the sheets is significantly reduced, from 0.062 at the beginning to less than 0.02. Furthermore, the effect of the size and location of hard inclusions on the microscopic defects produced after rolling is discussed. The microscopic defects around the inclusions increase with increasing size and decreasing distance of the inclusions.

Calculation of loads on cutting picks and moments in gears of shearer drums in cutting hard rock inclusions

Calculation of loads on cutting picks and moments in gears of shearer drums in cutting hard rock inclusions

Multi-scale approach to hydrogen susceptibility based on pipe-forming deformation history

Hydrogen-induced-cracking initiates without external loading due to residual stresses. Pipe manufacturing process composed of crimping, U-ing, O-ing, and expansion has a major impact on local hydrogen concentration, as strain pattern evolves from one forming step to another, causing residual stresses that serve as driving force for hydrogen diffusion. The novelty of the presented work lies in the development of a multi-scale approach that links the residual stresses from the macroscopic pipe-forming process with locally dissolved hydrogen atoms in microstructure under the consideration of microstructural heterogeneities to identify areas susceptible to hydrogen-induced-cracking. First, a 3d-pipe-forming-model was built. Second, representative volume elements with lattice defects were generated to analyze hydrogen trapping in microstructure. Third, representative volume elements were placed in the pipe via sub-modeling, so that local loading history of the pipe was assigned to microstructure models. At the end of the pipe-forming process, representative volume elements were loaded with hydrogen on the surface and final hydrogen concentration was simulated based on residual stresses, considering microstructural effects such as grain size/shape, crystallographic texture and hydrogen traps, e.g. dislocations, voids and inclusions. On meso-/macroscale, a combined isotropic–kinematic hardening material model was implemented, while on microscale, a phenomenological crystal-plasticity-hydrogen-diffusion model was coded. According to the multi-scale simulations under the consideration of microstructural effects the bottom center position in the pipe was detected to be critical to hydrogen-induced-cracking as the maximum local hydrogen concentration was predicted at that location. Based on the loading history hydrogen-induced-cracking susceptibility increases from voids to hard and soft non-metallic inclusions.

Uncertainty quantification for locally resonant coated plates and shells

The effect of uncertainty in design parameters on the acoustic performance of coated plates and coated shells for maritime applications is presented. The locally resonant coatings are designed using a viscoelastic material with an impedance similar to water and embedded with layers of inclusions. Both voids and hard inclusions, which respectively exhibit monopole and dipole resonance scattering, are considered. Effective medium approximation theory is employed to characterise the layers of inclusions as homogenised layers with effective material and geometric properties. The coating is then modelled as a multilayered equivalent fluid composed of alternating layers of the homogeneous viscoelastic material and the homogenised layers of inclusions. The coating is bonded to a rigid backing plate and the acoustic response is calculated using the transfer matrix method. The coating is also externally applied to an elastic cylindrical shell. The acoustic response is calculated by expressing the shell displacements and acoustic pressures in the coating and exterior domain in terms of Fourier series expansions, and applying continuity equations at each interface between the shell surface, coating layers and the surrounding water. Efficient stochastic models based on the non-intrusive polynomial chaos expansion (PCE) method are developed by transforming the analytical models for the coated plates and shells into computationally efficient surrogate models using point collocation. Uncertainty in dominant design parameters associated with the geometry of the inclusions and material properties of the coating is examined. The influence of the design parameters for inclusions tuned to different resonance frequencies and for multiple layers of inclusions is also reported. Strong acoustic performance of coating designs occurs in a broad frequency range around local resonance of the inclusions. For all coating models, uncertainty in parameters which predominantly influence the local resonance of the inclusions were observed to yield the greatest variation in the acoustic responses of the coated plates and shells.

Influence of Oxide Inclusions on the Creep Properties of Electron Beam Welds in Ti-added Reduced Activation Ferritic/Martensitic Steel

In this study, the effects of reducing oxide inclusions on the microstructure, tensile properties at 550 ℃, and creep resistance of electron beam welded (EBW) joints in Ti-added reduced activation ferritic/martensitic (RAFM) steel were investigated. Two RAFM steels, designated as Steel A and Steel B, were prepared by adjusting the Al and Si contents to contain different fractions of oxide inclusions. The microstructures of the base metal and heat-affected zone (HAZ) were analyzed, and the mechanical properties of the welds were evaluated. Reducing the Al and Si content in Steel B resulted in a decrease in both the fraction and size of oxide inclusions compared to Steel A. Both steels exhibited tempered martensitic microstructures with M23C6 and MX precipitates. Hardness tests revealed that the over-tempered HAZ (OTHAZ) was the weakest region. However, both tensile test and creep tests at 550 ℃ showed fractures occurring in the base metal, indicating that the low heat input of EBW effectively minimized the weak HAZ regions. Steel B demonstrated improved tensile properties and creep resistance due to the reduced oxide inclusions. It was found that Steel B had a significantly longer creep life than Steel A at 550 ℃. SEM analysis revealed ductile fracture characterized by dimples, where oxide inclusions containing Al, Si, Ta, and Ti were predominant. The presence of these inclusions reduced the effectiveness of solid solution and precipitation strengthening by consuming Ta and Ti. Additionally, microvoids could easily nucleate at the interface between the hard oxide inclusions and the soft metal matrix during creep. Therefore, the reduction of oxide inclusions improved deformation resistance and high-temperature stability, resulting in better creep resistance in Steel B. In conclusion, the reduction of oxide inclusions in Ti-added RAFM steel enhances the high-temperature mechanical properties and creep resistance of EBW joints, underscoring the importance of oxide control in the development of RAFM steels for fusion reactor applications.

Vibroacoustic response of a locally resonant coated cylindrical shell semi-submerged or fully submerged at a finite depth near a free sea surface

We study the vibroacoustic response of a coated cylindrical shell semi-immersed or fully submerged close to a free sea surface. Different coating designs corresponding to a uniform coating made of a viscoelastic material and locally resonant coatings composed of the viscoelastic material embedded with cavities or hard inclusions are considered. Analytical models that account for fully coupled fluid-structure interaction between the coated shell, the surrounding fluid domain and the free sea surface are developed. The free surface is treated as a pressure release boundary. For a fully submerged coated shell, the image method is employed. For the semi-immersed coated shell, a partial fluid loading condition is imposed on the wetted coating surface. The combined influence of the different coating designs and free surface on the structural and acoustic responses of the semi- and fully immersed shells are described. The influence of variation in dominant coating parameters that primarily impact the local resonances of the inclusions is also reported.

On machining-induced surface integrity of Inconel 718 fabricated by powder bed fusion

Additive manufacturing (AM) introduces unique grain feature and anisotropy in metals, as well as relatively poor surface quality, so the knowledge about the formation of post-machining-induced surface integrity needs to be extended. This study aims to understand the machining phenomena in orthogonal cutting of Inconel 718 produced via powder bed fusion of metals using a laser beam system (PBF-LB/M), paying particular attention to the cutting energy, chip formation, geometrical defects, and microstructural deformation. Experiments are conducted on both wrought (W 718) and PBF-LB/M (PBF 718) Inconel 718, whereby the cutting speed and the anisotropy of the workpiece in the raw state play an important role. The results indicate that less cutting energy is consumed when cutting PBF 718 in the direction perpendicular to its build direction (BD), followed by cutting in its BD. Denser shearing-induced slip lines and relatively continuous chip morphology are found when cutting PBF 718 in its BD, moreover, the effect of cutting speed on shearing deformation of columnar grains under this condition is analysed. More importantly, this study identifies a significant geometrical defect phenomenon which is unique to PBF 718 and highly depends on the cutting speed and anisotropy of grain feature. A detailed characterisation shows that this behaviour is caused by tearing within the grains in the matrix material and not by the presence of hard inclusions, which has rarely been reported in the literature. The microstructure in the subsurface area exhibits that the density of grain boundaries in the cutting direction plays the key role in plastic deformation, as the machining process mainly causes dragging behaviour in the area below the machined surface. Thus, cutting PBF 718 in the direction perpendicular to its BD shows similar deformation layer to W 718, while cutting PBF 718 in its BD displays much stronger subsurface deformation. The obtained results greatly help to understand the cutting phenomena in post-machining of additively manufactured Ni-based components, especially the integrity for a better functional surface.

Fracture criteria and initiation mechanism of concrete based on material configurational mechanics

AbstractIn this study, the interaction force between an in‐plane elliptical inclusion and a crack is evaluated using the Eshelby equivalent inclusion and material configurational force method. The toughening effect of coarse aggregates on concrete is investigated. The fracture criteria for mixed‐mode cracks based on the characteristics of the crack‐tip plastic zone assessed by the principal configurational stress difference are proposed and verified by experimental results in the literature. The fracture probability is then used to improve the fracture criteria, and the dimensionless factor associated with stress intensity factors is introduced to determine the fracture probability. Additionally, the volume fraction of coarse aggregates, the age and fatigue life of concrete are considered in the present fracture criteria. Theoretical studies show that the interaction between a crack and a hard or soft inclusion exhibits mutual repulsion and attraction. The size and shape of the crack‐tip plastic zones assessed by the Mises stress and the principal configurational stress difference are essentially the same. The fracture load envelopes increase with the increase in the volume fraction of coarse aggregates and the age of concrete and shrink with the increase in the life ratio.

Pinning of crack fronts by hard and soft inclusions: A phase field study.

Through tridimensonal numerical simulations of cracks propagating in material with an elastic moduli heterogeneity, it is shown that the presence of a simple inclusion can dramatically affect the propagation of the crack. Both the presence of soft and hard inclusions can lead to the arrest of a crack front. Here the mechanism leading to the arrest of the crack are described and shown to depend on the nature of the inclusion. This is also the case in regimes where the presence of the inclusion leads to a slowdown of the crack.

Energy attenuation of seismic metamaterials composed of a periodic array of coated elliptical cylinders

Abstract We present a numerical study on energy attenuation of seismic metamaterials consisting of a periodic array of coated elliptical cylinders. The aim is to perceive the effect of aspect ratio for different wave modes so that the metamaterials can interact with the incoming wave causing them to interfere with each other destructively, especially for low-frequency seismic waves with relatively wide bandgap. Previous studies mainly focused on the configuration of coated circular cylinders or spheres, in which the metamaterial is composed of a hard inclusion surrounded by a soft coating layer and dispersed within a hard matrix. Here we utilize numerical simulations based on finite element calculation to analyze the local fields within the unit cell. Effective mass density, mass moment of inertia and shear modulus are analyzed through a homogenization procedure to characterize the macroscopic behavior of the effective medium. The effective behavior will be dependent for different aspect ratios and for different types of wave motions. To verify the effectiveness of energy attenuation, a full-scale model is adopted. Specifically, to identify optimal energy attenuation configurations, we illustrate the attenuation effects of elliptical metamaterials under longitudinal and shear horizontal types of waves. The present study demonstrates that elliptical metamaterials will have more reflexibilities to tune with the aspect ratio of the elliptical geometry as well as the directionality of incidence waves. Based on our simulations, we show the ability of the designed configuration in tuning local resonance frequencies and bandwidths for real implementations and applications of seismic metamaterials.

Acoustic Performance of a Metamaterial Coating with Uncertainty in Design Parameters

The effect of uncertainty in design parameters on the acoustic performance of a viscoelastic metamaterial coating is investigated. The coating is composed of a layer of hard inclusions embedded in a soft host medium. The layer of inclusions in the soft medium is modelled as a homogenised layer using effective medium approximation theory. Stochastic models based on the polynomial chaos expansion (PCE) method and Monte Carlo (MC) simulations are developed. The effect of uncertainty in geometric and material parameters are quantified by examining the mean and envelopes of the absorption coefficient. Uncertainty in geometric and material parameters produce similar levels of variation in the absorption coefficient of the coating, particularly around the peaks of the absorption coefficient spectrum.

Fracture analysis in 2D plane strain problems for composite materials containing hard inclusions and voids using an extended consecutive-interpolation quadrilateral element

This paper investigates fracture mechanics in particle-reinforced composites by using the extended finite element method enhanced by the consecutive-interpolation quadrilateral element. These composite materials have discontinuous boundaries such as cracks, voids, holes, and soft inclusions. And the extended consecutive-interpolation quadrilateral element (XCQ4) is employed to model these boundaries in two-dimensional linear elastic deformation problems. XCQ4 combines the enrichment functions in the traditional extended finite element method with the consecutive interpolation on a 4-node quadrilateral element. This element uses both nodal values and averaged nodal gradients as interpolated conditions. In fracture analysis, the stress intensity factors (SIFs) are important parameters that must be defined. In this study, the values of SIFs at the crack tips are evaluated with the help of the interaction integrals approach. The obtained numerical results are compared with other reliable results showing high accuracy and convergence rate of the XCQ4 element.

Sound absorption by a soft medium embedded with complex-shaped hard inclusions

Acoustic coatings for marine applications are commonly designed using a soft elastic matrix embedded with an array of resonant inclusions. In this work, a simple analytical approach to predict the acoustic performance of a soft elastic matrix embedded with hard inclusions of complex shape is presented. Utilizing analogies from fluid dynamics and electrostatics, a small number of well-known lumped parameters such as the added mass and capacitance are employed to relate the dominant dipole component of scattering of a complex-shaped hard inclusion to that of an equivalent sphere. Effective acoustic properties are then derived using a homogenization. The absorption coefficient of the coating for a range of complex shapes is compared with numerical simulations.

Inclusion of Deaf and Hard of Hearing Students in Saudi Arabia: A Study of the Perceptions of Teachers.

The researchers investigated how teachers perceive the inclusion of deaf and hard of hearing (D/hh) students in mainstream classrooms in Saudi Arabia. They also examined how teachers' perception of this inclusion is influenced by their position (as a teacher in special or mainstream education). The researchers collected 196 teacher responses using an existing online survey (partly open-ended). They found that, overall, teachers in Saudi Arabia had slightly negative perceptions of teaching D/hh students in mainstream classrooms. But their teaching position did not seem to influence their perceptions. The researchers recommend that efforts be made to reduce negative perceptions of inclusion as a teaching practice in Saudi Arabia. Teachers working with D/hh children in mainstream schools should receive enough training to work successfully with these students. Awareness should be raised of inclusion's benefits and how inclusion differs from mainstream education.

Toward the Optimization of Mining Operations Using an Automatic Unmineable Inclusions Detection System for Bucket Wheel Excavator Collision Prevention: A Synthetic Study

This work introduces a methodology for the automatic unmineable inclusions detection and Bucket Wheel Excavator (BWE) collision prevention, using electromagnetic (EM) inspection and a fuzzy inference system. EM data are collected continuously ahead from the bucket wheel of a BWE and subjected to processing. Two distinct methodologies for data processing were developed and integrated into the MATLAB programming environment. The first approach, named “Simple Mode”, utilizes statistical process control to generate real-time alerts in the event of a potential collision involving the excavator’s bucket and hard rock inclusions. The advanced processing flow (“Advanced Mode”) requires accurate instrument positioning and data from successive EM scans. It incorporates techniques of local resistivity maxima detection (Position Prominence Index) as well as Neural Network-based Pattern Recognition (NNPR). A decision support process based on a Fuzzy Inference System (FIS) has been developed to assist BWE operators in avoiding collision when digging hard rock inclusions. The proposed methodology was extensively tested using synthetic EM data. Limited real data, acquired with a CMD2 (GF Instruments) EM instrument equipped with GPS, were used to control its efficiency. Increased accuracy in the automatic detection of unmineable inclusions was observed using the Advanced Mode. On the other hand, the Simple Mode processing technique offers the advantage of being independent of instrument positioning as well as it provides real-time inspection of the excavated mine slope. This work introduces a methodology for hard rock inclusion detection and can contribute to the optimization of mine operations by improving resource efficiency, safety, cost savings, and environmental sustainability.

Numerical modeling of interfacial cracking with soft and hard inclusions

In this work, we use pseudo-spring-augmented smoothed particle hydrodynamics (SPH) framework to understand how the crack paths differ in edge-cracked plates with inclusions when they are made of functionally graded material (FGM) versus homogeneous plates. Modeling crack propagation in such multi-component structural systems is necessary to uncover the underlying failure mechanisms. While traditionally researchers have used mesh-based techniques like the finite element method to understand crack propagation, these methods have limitations. Consequently, mesh-less techniques such as SPH are gaining popularity. After verifying our framework on a plate made of two materials, we compare and contrast the crack path propagation between FGM plates and homogeneous plates, both having soft and hard inclusions. The crack paths get influenced significantly due to the presence of inclusions. Regardless of the type, in presence of soft inclusions, plates fail due to the failure of the inclusion. On the other hand, cracks tend to deflect away from hard inclusions in both plates. The amount of deflection is governed by the relative stiffness of the plate material. Consequently, the deflection is different in FGM plates compared with homogeneous ones.

Research on residual stress and hydrogen diffusion of X80 pipeline welded joint

Hydrogen enrichment induced by pipeline welding residual stress is a key issue affecting the safe service of hydrogen pipelines. In order to explore the influence of welding residual stress on hydrogen diffusion and the effect of heat treatment, an X80 pipeline model with a six-layer girth weld was established using ABAQUS software, and coupling analysis of temperature field, stress field, and hydrogen diffusion was carried out. The distribution of residual stress in the welding area and local inclusion area was analyzed, the relationship between the hydrostatic stress and hydrogen diffusion of the pipeline, and the influence of the direction and shape of the inclusion on hydrogen diffusion were explored, and the effect of post-weld heat treatment on the residual stress and hydrogen diffusion in the welding area and local inclusion area was studied. The hydrostatic stress curve is similar to the hydrogen concentration distribution curve, and hydrostatic stress can be considered the main driving force for hydrogen diffusion in the pipeline. As the angle between the inclusions and the hydrogen diffusion direction increases, the hydrogen diffusion flux will gradually decrease. The more slender the inclusions, the stronger the diffusion ability of parallel or 45° inclusions, and the weaker the diffusion ability of perpendicular inclusions. Hydrogen enrichment occurs in inclusions or inclusion boundaries before and after post-weld heat treatment of the pipeline, and the internal hydrogen concentration of hard inclusions is higher than that of soft inclusions. Post-weld heat treatment can significantly reduce welding residual stress and hydrostatic stress, thereby reducing hydrogen enrichment concentration.

Refinement and Modification of Al2O3 Inclusions in High-Carbon Hard Wire Steel via Rare Earth Lanthanum.

In this paper, an experimental protocol of adding rare earth lanthanum (La) was used to refine and modify inclusions (Al2O3) in aluminum-deoxidized steel. An optical microscope (OM), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS) were used to study the impact of size distribution, number density, distribution uniformity, interfacial distance, area density, and so on of rare earth La on high-carbon hard wire steel inclusions. As indicated by the findings when the addition amount of La is 0.063%, the refining and homogenizing effect of Al2O3 inclusions in steel is the best. The average diameter of the inclusions is 1.75 μm, the uniformity is 0.84, the proportion of the interfacial spacing greater than 10 μm is 48.4%, and the area density of inclusions is set at 0.014. Based on classical thermodynamics and Factsage software, the effect of La activity on inclusion formation was computed. As indicated by the findings, the addition of rare earth La mainly combines with O and S in the liquid steel, and the La-containing inclusions wrap around the Al2O3 inclusions, hindering the Al2O3 inclusions. Through the evolution of inclusions during solidification, the modification of Al2O3 inclusions via rare earth La and the types of inclusions are discussed. The experimental results and theoretical calculations verify that the optimal treatment plan is to add 0.063% La.

Scaling relations for sound scattering by a lattice of hard inclusions in a soft medium

Soft elastic materials embedded with resonant inclusions are widely used as acoustic coatings for maritime applications. A versatile analytical framework for resonance scattering of sound waves in a soft material by a lattice of hard inclusions of complex shape is presented. Analogies from hydrodynamics and electrostatics are employed to derive universal scaling relations for a small number of well-known lumped parameters that map resonant scattering of a complex-shaped hard inclusion to that of a sphere. Multiple scattering of waves between inclusions in proximity is also considered. The problem is then treated using an effective medium theory, viz, a layer of hard inclusions is modeled as a homogenized layer with some effective properties. The acoustic performance of hard inclusions for a range of shapes with spheres of the same volume are compared. Results obtained using this approach are in good agreement with finite element simulations.