Muhammad Zain-ul-abdein

Numerical investigations of optimum turning parameters—AA2024-T351 aluminum alloy

ABSTRACT Aerospace aluminum alloys have gained the prime significance due to their excellent machining characteristics. Numerous experimental and numerical studies have been conducted to establish the optimum cutting parameters of these alloys. In the numerical cutting models, the authenticity of computational results is suspected particularly because of the complex interaction at tool–chip interface, which involves a high material strain rate and thermal processes. The fidelity of cutting simulation results is appraised by a parametric sensitivity analysis and actual experimentation. In this research, the orthogonal turning of AA2024-T351 aluminum is simulated in Abaqus/Explicit by using a thermoviscoplastic damage model and Coulomb friction model for the contact interfaces. A parametric sensitivity analysis is performed to comprehend the chip morphology, tool–chip interface temperature, reaction force, and strain. Different simulations are performed with varied cutting speeds (200, 400, 600, and 800 m/min), rake angles (5°, 10°, 14.8°, 17.5°), feeds (0.3, 0.4 mm), and friction coefficients (0.1, 0.15). It is observed that an increased rake angle decreases the cutting force and increases tool–chip interface temperature. Similarly, the cutting depth has prominent effect on chip–tool interface temperature as compared to the friction. The computational results are found in close approximation with the published experimental data of AA2024-T351.

Numerical simulation of breast deformation under static conditions

The finite element (FE) simulation of breast biomechanics is essentially a nonlinear analysis, not only due to the nonuniform geometry but also due to the varying material properties. Several researchers (Kruse et al. 2000; Van Houten et al. 2003; Sinkus et al. 2005) have shown a high degree of nonlinearity in elastic modulus of breast tissues. For instance, Van Houten et al. (2003) summarised some of the researchworks for themeasurement ofYoung’smodulus and indicated a large variation due to the difference in types of tissues. Samani et al. (2003), however, developed a technique for an inverse identification of elastic modulus. They obtained the force–displacement curve through indentation over small specimens and then by using FE analysis, they estimated Young’s modulus. In recent years, some authors (Azar et al. 2001; Rajagopal et al. 2006) have kept their focus on FE modelling of breast deformation. Azar et al. (2001), for example, developed a deformable FE model of the breast to predict the deformations under external perturbations. While Rajagopal et al. (2006) compared the FEmodel with silicon gel phantoms to calculate the reference state of the breast. Li et al. (2003) studied a 3D biomechanical model of a female body and performed numerical simulation of the bra and breast interactions. They showed that the FE model can be used as a tool for designing and optimising the bra structure as well as the material. With an aim of optimising the design of a sports bra, the numerical simulation of breast deformation for three different female subjects has been performed in this work. A generalised approach has been used for the first time to develop the FE mesh for the breast in a reference state, and the gravitational loads were applied later so as to capture the deformation behaviour and estimate the material properties.

On the friction stir welding, tool design optimization, and strain rate-dependent mechanical properties of HDPE–ceramic composite joints

Friction stir welding is a recently developed technique for joining low-melting metals and polymers. In the present work, friction stir welded joints of high-density polyethylene (HDPE) sheets were produced using a newly designed tool with a concave shoulder and a grooved conical pin. The joints were produced with and without the additions of ceramic particulates including silicon carbide (SiC), alumina, graphite, and silica. The effect of strain rate on the tensile properties of base material and plain welded joints was examined. In addition to tensile properties of composite joints, hardness profiles across the weld nugget were analyzed. It was observed that the increasing strain rate improved both the tensile strength and the ductility of the plain welded joints. The tool was able to yield a joint efficiency of around 84% in the plain welded samples. Although, in terms of joint efficiency, the composite joints were less efficient than the plain welded HDPE, SiC additions were found to yield better material properties relative to other reinforcements. Finally, it was concluded that an SiC–HDPE composite joint can be of practical importance in high strain rate applications, provided the optimum tool design and stir welding parameters are available.

Finite Element Analysis of Interfacial Debonding in Copper/Diamond Composites for Thermal Management Applications

Copper/diamond (Cu/D) composites are famous in thermal management applications for their high thermal conductivity values. They, however, offer some interface related problems like high thermal boundary resistance and excessive debonding. This paper investigates interfacial debonding in Cu/D composites subjected to steady-state and transient thermal cyclic loading. A micro-scale finite element (FE) model was developed from a SEM image of the Cu/20 vol % D composite sample. Several test cases were assumed with respect to the direction of heat flow and the boundary interactions between Cu/uncoated diamonds and Cu/Cr-coated diamonds. It was observed that the debonding behavior varied as a result of the differences in the coefficients of thermal expansions (CTEs) among Cu, diamond, and Cr. Moreover, the separation of interfaces had a direct influence upon the equivalent stress state of the Cu-matrix, since diamond particles only deformed elastically. It was revealed through a fully coupled thermo-mechanical FE analysis that repeated heating and cooling cycles resulted in an extremely high stress state within the Cu-matrix along the diamond interface. Since these stresses lead to interfacial debonding, their computation through numerical means may help in determining the service life of heat sinks for a given application beforehand.

A pure thermal model to evaluate heat-affected zone when milling E-glass fiber-reinforced polyester composites

This paper aims at investigating the resistance-to-vitrification of glass fiber-reinforced plastics when milling. A three-dimensional thermal model using volumetric heat source with Gaussian distributed cylindrical flux was developed as DFLUX subroutine and implemented into Abaqus/Standard code. The wheel feed was simulated by the source motion at 250 mm min−1 with spindle speeds of 11,460, 15,280, and 19,100 rpm. Milling tests using abrasive wheel with 10 mm in diameter were conducted on the composite specimens of dimensions 100 × 25 × 4 mm3 with fibers oriented both parallel and perpendicular to the milling direction. Four equidistant thermocouples were embedded within the medium plane of the specimen in order to measure the temperature histories. Each series of tests was repeated four times under identical conditions. Predictions confronted to measurements demonstrated the validity of the proposed model. Cutting perpendicular to fibers was found favoring in-depth heat dissipation. However, the fibers a...

Numerical simulation of the effects of elastic anisotropy and grain size upon the machining of AA2024

ABSTRACT Turning modeling and simulation of different metallic materials using the commercially available Finite Element (FE) softwares is getting prime importance because of saving of time and money in comparison to the costly experiments. Mostly, the numerical analysis of machining process considers a purely isotropic behavior of metallic materials; however, the literature shows that the elastic crystal anisotropy is present in most of the ‘so-called’ isotropic materials. In the present work, the elastic anisotropy is incorporated in the FE simulations along with the effect of grain size. A modified Johnson-Cook ductile material model based on coupled plasticity and damage evolution has been proposed to model the cutting process. The simulation results were compared with experimental data on the turning process of Aluminum alloy (AA2024). It was found that the elastic anisotropy influences the average cutting force up to 5% as compared to the isotropic models while the effect of grain size was more pronounced up to 20%.

Fatigue Delamination Crack Growth in GFRP Composite Laminates: Mathematical Modelling and FE Simulation

Glass fibre-reinforced plastic (GFRP) composite laminates are used in many industries due to their excellent mechanical and thermal properties. However, these materials are prone to the initiation and propagation of delamination crack growth between different plies forming the laminate. The crack propagation may ultimately result in the failure of GFRP laminates as structural parts. In this research, a comprehensive mathematical model is presented to study the delamination crack growth in GFRP composite laminates under fatigue loading. A classical static damage model proposed by Allix and Ladeveze is modified as a fatigue damage model. Subsequently, the model is implemented in commercial finite element software via UMAT subroutine. The results obtained by the finite element simulations verify the experimental findings of Kenane and Benzeggagh for the fatigue crack growth in GFRP composite laminates.

Sensitivity of GFRP Composite Integrity to Machining-Induced Heat: A Numerical Approach

This paper aims at investigating the temperature effects during abrasive milling of glass fiber reinforced plastic composites (GFRP). A 3D thermal model using volumetric heat source with Gaussian distributed cylindrical flux was developed as DFLUX subroutine and implemented into Abaqus/Standard code. The model employs linear power law for simulating the temperature variation during tool advance. The composite plate is made of glass fibers oriented perpendicular to the tool trajectory. The tool feed was simulated by the source constant motion while speed was taken variable. Four equidistant thermocouples were simulated within the medium plan of the specimen in order to record the temperature evolution. The predictions highlighted the sensitivity of temperature histories to cutting speed. The conductivity and heat capacity played for controlling heating and cooling phases of the curves. The peak temperature exhibited maximum value at TC3 irrespective to speed value. The pure thermal analysis showed sufficient ability to predict the heat affected zone in the GFRP, which is, in turn, a function of tool spindle speed.

Finite Element Analysis of Bend Test of Sandwich Structures Using Strain Energy Based Homogenization Method

The purpose of this article is to present a simplified methodology for analysis of sandwich structures using the homogenization method. This methodology is based upon the strain energy criterion. Normally, sandwich structures are composed of hexagonal core and face sheets and a complete and complex hexagonal core is modeled for finite element (FE) structural analysis. In the present work, the hexagonal core is replaced by a simple equivalent volume for FE analysis. The properties of an equivalent volume were calculated by taking a single representative cell for the entire core structure and the analysis was performed to determine the effective elastic orthotropic modulus of the equivalent volume. Since each elemental cell of the hexagonal core repeats itself within the in-plane direction, periodic boundary conditions were applied to the single cell to obtain the more realistic values of effective modulus. A sandwich beam was then modeled using determined effective properties. 3D FE analysis of Three- and Four-Point Bend Tests (3PBT and 4PBT) for sandwich structures having an equivalent polypropylene honeycomb core and Glass Fiber Reinforced Plastic (GFRP) composite face sheets are performed in the present study. The authenticity of the proposed methodology has been verified by comparing the simulation results with the experimental bend test results on hexagonal core sandwich beams.

Identification of the effective thermal conductivity of a powdered composite using a genetic algorithm

Abstract This work presents a computational method for the identification of the thermal conductivity of a powdered composite. The thermo-physical properties of powdered composites depend not only upon the intrinsic material properties of the filler and the matrix, but also upon several other parameters including the packing density, the particle shape factor and the particle size. In this paper, a genetic algorithm-based model is proposed for the identification of the effective thermal conductivity of a Bakelite–graphite powdered composite. A comparative analysis is also developed between the genetic algorithm and the experimental, theoretical and finite element results. In comparison with the experimental observations, the genetic algorithm model was found to have error values of approximately 5 %, whereas the errors resulting from the theoretical models were up to 12 %.