Wide Range Of Engineering Materials Research Articles

Identification and optimization of material constitutive equations using genetic algorithms

The modeling and simulation of engineering materials using constitutive equations requires a large set of optimized coefficients that characterize the hardening or softening behavior. Optimizing this large set of coefficients with multiple constraints is very challenging using conventional optimization methods. This research proposes a novel model-agnostic framework based on genetic algorithms to identify and optimize the set of coefficients of the constitutive equations of engineering materials. The proposed framework demonstrates solution convergence, scalability to available data, and high explainability over a wide range of engineering materials, including titanium-based, iron-based, and aluminum-based alloys. The experimental test data for necessary validation of the computational framework was generated using the MTS fatigue testing machine equipped with a highly sensitive extensometer. The Chaboche unified visco-plasticity material model has been implemented as an example in this study which can deal with both cyclic effects, such as combined isotropic and kinematic hardening, and rate-dependent effects associated with visco-plasticity. The experimentally obtained cyclic response of three different classes of materials was compared with their optimized simulated constitutive equations, and the results were in good agreement. Furthermore, the proposed multi-objective optimization using genetic algorithm methodology avoids local optimality and converges to the optimal solution much faster than commercially available software.

State of the art on tool wear characterization in micro-milling

The process of obtaining the required 3D feature by machining a wide range of engineering materials mechanically with the use of small tools is called the micro-milling process. Since the procedure involves the removal of material mechanically, the generation of forces and vibrations is an unavoidable phenomenon. Due to the higher magnitude of forces and vibration, the tool wears at a higher rate. It affects the quality of the part. Moreover, the micro-defects in the workpiece, which are dependent on the type of material and the process in which the workpiece is made also has a significant effect on the tool wear. So, it is imperative to study the tool wear phenomenon during the micro-milling process. In this manuscript, the state of the art on the effect of tool material, workpiece material, surface integrity, and application of cutting fluids on the milling cutter wears is presented. Furthermore, the works carried out by various researchers on the modeling of tool wear is presented.

The Influence of Surface Texturing of Ceramic and Superhard Cutting Tools on the Machining Process-A Review.

Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the machined components. Thus, the modification of the cutting tool surface by application of textures on their surfaces is proposed as a very promising method for improving tool life. Surface texturing is a relatively new surface engineering technology, where microscale or nanoscale surface textures are generated on the cutting tool through a variety of techniques in order to improve tribological properties of cutting tool surfaces by reducing the coefficient of friction and increasing wear resistance. In this paper, the studies carried out to date on the texturing of ceramic and superhard cutting tools have been reviewed. Furthermore, the most common methods for creating textures on the surfaces of different materials have been summarized. Moreover, the parameters that are generally used in surface texturing, which should be indicated in all future studies of textured cutting tools in order to have a better understanding of its effects in the cutting process, are described. In addition, this paper proposes a way in which to classify the texture surfaces used in the cutting tools according to their geometric parameters. This paper highlights the effect of ceramic and superhard textured cutting tools in improving the machining performance of difficult-to-cut materials, such as coefficient of friction, tool wear, cutting forces, cutting temperature, and machined workpiece roughness. Finally, a conclusion of the analyzed papers is given.

Electrical Discharge Coating a Potential Surface Engineering Technique: A State of the Art

Electrical discharge coating (EDC) process is used to deposit material on workpiece surface from sacrificial or green compact tool electrode in an electrical discharge machine. The paper presents the mechanism of EDC using green compact electrode and powder mixed dielectric methods. The tool electrode material, electrode size, process parameters, and type of dielectrics can directly affect the surface integrity of workpiece. Here, a process map of EDC as a function of process parameters, its classification, advantages, and applications for a wide range of engineering materials offers a proper template for the evaluation of coating phenomena. This study shows that EDC is an economic process as compared to other costlier techniques. Additionally, the effect of various EDM and EDC parameters on surface integrity and tribological behavior of deposited coatings is studied with their pros and cons. Finally, the current research trends of EDC and its challenges are elaborated.

Mechanical Behavior of Aluminum and Graphene Nanopowder-Based Composites

Producing items that are of both high quality and long lasting is a difficult task for companies right now. There is a huge need for a wide range of engineering materials in today’s technologically advanced globe. The strength and qualities of the material determine the amount of material that may be used. Due to its excellent mechanical qualities and low density, aluminum-7075 alloy is mostly employed in transportation applications such as aerospace, marine, and vehicle production. This study addresses the fabrication and characterization of Al7075 semisolid metal matrix composite (MMC) reinforced with graphene nanoparticles. Samples are made with and without stirring graphene in aluminum-7075 at various temperatures of 800°, 830°, 860°, 890°, and 920°C. At these temperatures, the material is semisolid, so graphene is introduced and stirred into the molten liquid. The specimens meet the requirements of the American Society for Testing and Material (ASTM). The hardness, tensile strength, impact strength, and compression strength of various materials are evaluated and compared. Temperature lowers tensile strength, hardness, and compression. A scanning electron microscope (SEM) is used to examine the microstructure. The specimen is evaluated using ANSYS. Specimens with stirring have better mechanical characteristics. Graphene has high hardness and strength.

An overview on the microstructure and mechanical properties of sintered aluminum-based composites

Sintered composites have revolutionized as a thermal treatment to consolidate a wide range of engineering materials where the transition of powders takes place thermally in a thermodynamical equilibrium state with a decrease in free surface energy in materials owing to their specific capability. Sintering aids in providing effective bonding between the reinforced powder particles. However, the inadequate understanding of the sintering mechanism may limit the practical application of a few materials such as aluminum metal matrix composites. In addition to the rapid growth of various sintering related technologies, researchers need attention to highlight the structural barriers and forecast the emerging demands while dealing with such composites. A review report is made in this paper regarding the sintering mechanisms and sintering techniques. Common sintering techniques such as traditional, microwave assisted, hot pressing, hot isostatic sintering, and spark plasma sintering are identified and discussed here. As a result, the key challenges in sintering aluminium metal matrix composites that can affect sintering parameters are investigated. From the review, spark plasma is identified to attain densified and pore-free green composites and, microwave sintering is the best technique for achieving uniform microstructure in powder metallurgy samples.

Experimental Investigation of Engineering Materials under Repetitive Impact with Slurry Conditions

In some industrial situations, components are subject to repetitive impact in the presence of a slurry. A novel repetitive impact-with-slurry test rig was developed to evaluate the behaviour of a wide range of engineering materials in such conditions. The test materials could be categorised into five main groups – heat treated steels, stainless steels, chromium cast irons, hardfacing coatings and superalloys. Three-dimensional surface topography was used to quantify the depths and volumes of the produced wear scars. Post-test metallurgical examination was also conducted to further evaluate the wear processes. The wear mechanisms could be split into two main groups of materials; ductile materials were observed to plastically deform and hard/brittle materials demonstrated cracking/spalling mechanisms. Hardened martensitic-type materials exhibited the greatest resistance to repetitive impact wear.

A multi phase-field fracture model for long fiber reinforced composites based on the Puck theory of failure

Phase-Field (PF) methods of fracture have emerged as powerful modeling tools for triggering fracture events in solids. These numerical techniques efficiently alleviate mesh dependent pathologies and are very suitable for characterizing brittle as well as quasi-brittle fracture in a wide range of engineering materials and structures including fiber reinforced composites. In this work, a multi phase-field model relying on the Puck’s failure theory is proposed for triggering intra-laminar cracking in long fiber reinforced composites. The current formulation encompasses the differentiation of fiber and inter-fiber (matrix-dominated) failure phenomena via the consideration of two independent phase-field damage-like variables, and the corresponding evolution equations and length scales. Moreover, for matrix-dominated deformation states, the present formulations endow the incorporation of plastic effects via an invariant-based plasticity model. Special attention is also devoted to its finite element implementation, which is conducted using the user-defined capabilities UMAT and UEL of ABAQUS, in conjunction with the thorough assessment of its thermodynamic consistency. Several representative applications pinpoint the applicability of the proposed computational tool.

Quantifying Pore Width Effects on Diffusivity via a Novel 3D Stochastic Approach with Input from Atomistic Molecular Dynamics Simulations.

The increased production of unconventional hydrocarbons emphasizes the need to understand the transport of fluids through narrow pores. Although it is well-known that confinement affects fluids structure and transport, it is not yet possible to quantitatively predict properties such as diffusivity as a function of pore width in the range of 1-50 nm. Such pores are commonly found not only in shale rocks but also in a wide range of engineering materials, including catalysts. We propose here a novel and computationally efficient methodology to obtain accurate diffusion coefficient predictions as a function of pore width for pores carved out of common materials, such as silica, alumina, magnesium oxide, calcite, and muscovite. We implement atomistic molecular dynamics (MD) simulations to quantify fluid structure and transport within 5 nm-wide pores, with particular focus on the diffusion coefficient within different pore regions. We then use these data as input to a bespoke stochastic kinetic Monte Carlo (KMC) model, developed to predict fluid transport in mesopores. The KMC model is used to extrapolate the fluid diffusivity for pores of increasing width. We validate the approach against atomistic MD simulation results obtained for wider pores. When applied to supercritical methane in slit-shaped pores, our methodology yields data within 10% of the atomistic simulation results, with significant savings in computational time. The proposed methodology, which combines the advantages of MD and KMC simulations, is used to generate a digital library for the diffusivity of gases as a function of pore chemistry and pore width and could be relevant for a number of applications, from the prediction of hydrocarbon transport in shale rocks to the optimization of catalysts, when surface-fluid interactions impact transport.

Effect of Progressive Tool Wear on the Evolution of the Dynamic Stability Limits in High-Speed Micromilling of Ti-6Al-4V

Abstract Micromilling can fabricate complex features in a wide range of engineering materials with an excellent finish but the limited flexural stiffness of the micro-end mill can result in catastrophic tool failure. This issue can be overcome by using high rotational speeds. Note that the combination of high rotational speeds and low flexural stiffness can induce process instability which is aggravated by the accelerated wear of the micro-tools at high speeds, specifically, for Ti-alloys. The effect of progressive tool wear on the stability has been investigated in micromilling of Ti-6Al-4V. For incorporating tool wear, the cutting force coefficients are modeled as a function of initial and instantaneous cutting edge radius (CER) and feed per tooth. The initial CER of the micro-tool is considered due to the inherent variability in the tool grinding process. A significant increase (85–114%) in the instantaneous CER is observed with an increase in the length of cut. A 2DOF time-domain model based on semi-discretization method has been used to characterize the evolution of stability limits with an increase in the length of cut. The progressive tool wear affects the stability limits along with the initial CER and the feed per tooth. At higher speeds (90,000–110,000 rpm), the effect of progressive tool wear is pronounced and the stability limits reduce by ∼30% in that range.

An Investigation of Nanomechanical Properties of Materials using Nanoindentation and Artificial Neural Network

Mechanical properties of materials can be derived from the force-displacement relationship through instrumented indentation tests. Complications arise when establishing the full elastic-plastic stress-strain relationship as the accuracy depends on how the material’s and indenter’s parameters are incorporated. For instance, the effect of the material work-hardening phenomenon such as the pile-up and sink-in effect cannot be accounted for with simplified analytical indentation solutions. Due to this limitation, this paper proposes a new inverse analysis approach based on dimensional functions analysis and artificial neural networks (ANNs). A database of the dimensional functions relating stress and strain parameters of materials has been developed. The database covers a wide range of engineering materials that have the yield strength-to-modulus ratio (σy/E) between 0.001 to 0.5, the work-hardening power (n) between 0–0.5, Poisson’s ratio (v) between 0.15–0.45, and the indentation angle (θ) between 65–80 degrees. The proposed algorithm enables determining the nanomechanical stress-strain parameters using the indentation force-displacement relationship, and is applicable to any materials that the properties are within the database range. The obtained results are validated with the conventional test results of steel and aluminum samples. To further demonstrate the application of the proposed algorithm, the nanomechanical stress-strain parameters of ordinary Portland cement phases were determined.

Current capabilities of the residual stress diffractometer at the high flux isotope reactor.

The engineering diffractometer 2nd Generation Neutron Residual Stress Facility (NRSF2) at the Oak Ridge National Laboratory's High Flux Isotope Reactor was built specifically for the mapping of residual strains. NRSF2 is optimized to investigate a wide range of engineering materials by providing the user a selection of monochromatic neutron wavelengths to maintain the selected Bragg reflection near 2θ = 90°, which is the optimal scattering geometry for strain mapping. Details of the instrument configuration and operation are presented, and considerations for experimental planning are also discussed. Selected examples of recent residual stress work completed with NRSF2 are presented to highlight capabilities.

Aspect ratio evolution associated with surface cracks in sheets subjected to fatigue

This paper presents a fracture mechanics approach to the phenomenon of fatigue crack propagation in geometries such as plates and sheets. The aim is to analyze the crack path (aspect ratio evolution) in a wide range of engineering materials (characterized by different values of the m-parameter of the Paris law) and subjected to two kinds of cyclic loading (tension and bending). To this end, a numerical procedure was designed and implemented starting from a discretization of the crack front (defined as an ellipse) and considering a sort of crack advance on the basis of the Paris law, governed by the stress intensity factor (SIF) obtained by Newman and Raju. Numerical results suggest that surface cracks in sheets tend to grow following a preferential cracking path associated with a very shallow initial flaw with quasi-circular front shape. The rise of the Paris coefficient m leads to a faster convergence between the different crack paths (i.e. quicker approach of the diverse curves) during fatigue propagation starting from the distinct initial crack aspect ratios. In addition, better convergence is also achieved for bending loading (when compare with the case of tension).

Modeling and fabrication of micro tools by pulsed electrochemical machining

Accurate and precise micro tools are essential for the micromachining of complex micro features in a wide range of engineering materials including metals and ceramics. Existing micro tool fabrication processes suffer from drawbacks such as surface cracks, residual stress and deformations. Electrochemical machining of micro tools is proposed in this work to overcome these limitations. In this research, a mathematical model has been developed to predict the diameter of the micro tool fabricated. Experimental verification of the model using an in-house built micro electrochemical machining system reveals good correlation with theoretical predictions. Using the procedure described in this paper, very high aspect ratio (280–450) tungsten micro tools have been produced.

Built of Cermet Layer Using Thermal Plasma Spraying (APS)

The technology of thermal plasma spray take an advanced position among different coating technologies, because of it`s allowing to use a wide range of engineering materials depending on it`s melting point, to get a super mechanical, electrical, and thermal properties in comparing with other thermal spray methods. So it is improves the properties of metals, ceramics, and plastics parts which are used in industry at all.

Analysis of spherical indentation of materials with plastically graded surface layer

In the present work, a comprehensive parametric study for establishing contact mechanics of instrumented normal spherical indentation on homogeneous materials and materials with plastically graded surface layer (PGSL) was undertaken by dimensional analysis and finite element modeling. The spherical indentation response for homogeneous materials can be described only by two dimensionless parameters: strain hardening exponent and a unified parameter that can describe effects of both the normalized yield strength and the normalized indentation depth. The influences of these two parameters were investigated for a wide range of engineering materials, and the results may be used as an estimate of loading response and pile-up/sink-in behavior when the material properties are known. In the materials with PGSL, a linear gradient in yield strength, and no variation in elastic modulus and strain hardening exponent were explored. The indentation response of the materials with PGSL can be described only by three dimensionless parameters: the normalized indentation depth, the dimensionless strength gradient parameter, and the normalized PGSL thickness. The effects of these three parameters were studied systematically. The normalized pile-up/sink-in parameter is found to be an increasing function of the strength gradient parameter. The normalized pile-up/sink-in parameter increases (decreases) with increasing PGSL thickness for a fixed positive (negative) gradient case at large indentation depth. The results also indicate that the materials with positive PGSL can bear more loads and have significantly more resistance to contact crack formation.

Modeling of minimum uncut chip thickness in micro machining of aluminum

Micro mechanical machining operations can fabricate miniaturized components from a wide range of engineering materials; however, there are several challenges during the operations that can cause dimensional inaccuracies and low productivity. In order to select optimal machining parameters, the material removal behavior during micro machining operations needs to be understood and implemented in models. The presence of the tool edge radius in micro machining, which is comparable in size to the uncut chip thickness, introduces a minimum uncut chip thickness (MUCT) under which the material is not removed but ploughed, resulting in increased machining forces that affect the surface integrity of the workpiece. This paper investigates the MUCT of rounded-edge tools. Analytical models based on identifying the stagnant point of the workpiece material during the machining have been proposed. Based on the models, the MUCT is found to be functions of the edge radius and friction coefficient, which is dependent on the tool geometry and properties of the workpiece material. The necessary parameters for the model are obtained experimentally from orthogonal cutting tests using a rounded-edge tool. The minimum uncut chip thickness (MUCT) is then verified with experimental tests using an aluminum workpiece.

Wettability versus roughness of engineering surfaces

Wetting of real engineering surfaces occurs in many industrial applications (liquid coating, lubrication, printing, painting, …). Forced and natural wetting can be beneficial in many cases, providing lubrication and therefore reducing friction and wear. However the wettability of surfaces can be strongly affected by surface roughness. This influence can be very significant for static and dynamic wetting [1]. In this paper authors experimentally investigate the roughness influence on contact angle measurements and propose a simple model combining Wenzel and Cassie–Baxter theories with simple 2D roughness profile analysis. The modelling approach is applied to real homogeneous anisotropic surfaces, manufactured on a wide range of engineering materials including aluminium alloy, iron alloy, copper, ceramic, plastic (poly-methylmethacrylate: PMMA) and titanium alloy.

Damage Tolerance of a Sandwich Panel Containing a Cracked Square Lattice Core

The fracture response of a sandwich panel, with a center-cracked core made from an elastic-brittle square lattice, is explored by finite element simulations and simple analytical models. First, predictions are given for the unnotched strength of the sandwiched core and for the fracture toughness of the lattice under remote tension, remote compression, or remote shear. It is assumed that the lattice fails when the local stress in the cell wall attains the tensile or compressive strength of the solid, or when local buckling occurs. Failure maps are then constructed for a cracked sandwich panel, with axes given by a dimensionless crack length and dimensionless height of the sandwich core. The shear strength of the cracked sandwich panel is examined in detail. The precise form of the failure map for shear loading depends upon the tensile failure strain of the solid and upon the relative density of the lattice. The relevance of the shear failure map to lattices made from a wide range of engineering materials is illustrated through material-property charts. An extension of the method to cyclic loading is discussed.

Measurement of flow stress at high temperature in solid torsion tests

This document outlines good measurement practice to be adopted for the determination of flow stress at high temperature in torsion tests on solid metallic materials. The recommendations are applicable to hot (isothermal) tests at medium to high rates of strain (10–3–102 s–1) at temperatures relevant to metal working practice.Guidance is provided on appropriate testpiece geometries and methods of verifying the temperature distribution along the length of the testpiece. Flow diagrams are given showing all the steps that are necessary, including the correction factors that need to be applied for deformational heating and for the determination of true stress. Details are given of the calibration procedures that should be followed to provide traceability to the National Measurement System.Technical input to the document has been provided by the steering group of a European SMT funded project on High Temperature Testing, TESTIFY, that contained representatives of industrial users and producers of a wide range of engineering materials as well as academic modellers.An experimental programme was conducted during the preparation of this document to underpin the procedures in this guide.