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Weft tows in 3D woven composites are commonly approximated as perfectly straight, but their undulations are inevitable in reality, although the extent of undulations in the weft tows is not as pronounced as in the warp tows. Such minor undulations in weft tows have been simulated in this paper. A previously established parametrised modelling and analysis tool for 3D woven composites has been extended to reproduce the varying geometry of the weft tows. Two novel models have been proposed to introduce the undulations, allowing their effects to be simulated. The analysis reveals that, compared to the model with straight weft tows, the effective elastic properties can be affected by the weft tow undulations. In addition, the procedure for defining varying intra-tow fibre orientation was formulated and implemented, addressing lack of consistent and robust functionalities of this kind in modern finite element solvers. [ABSTRACT FROM AUTHOR]

Objective: Electrospun nanofibers exhibit potential as scaffolds for articular cartilage tissue regeneration. This study aimed to fabricate electrospun polycaprolactone (PCL)/silk fibroin (SF) composite nanofiber scaffolds and to explore performance of the scaffolds for articular chondrocyte regeneration. Methods: By altering material composition and preparation methods, three types of nanofiber scaffolds were effectively fabricated, including randomly oriented PCL (RPCL) nanofiber scaffold, randomly oriented PCL/SF (RPCL/SF) nanofiber scaffold, and aligned PCL/SF (APCL/SF) nanofiber scaffold. Physiochemical analyses were performed to determine mechanical properties and surface hydrophilicity of the nanofiber scaffolds. In vitro studies were conducted to investigate performance of the scaffolds on articular chondrocyte proliferation, gene expression and glycosaminoglycan secretion. Cytoskeleton staining was used to observe the arrangement of chondrocytes along the direction of the fibers and their elongation along the fiber arrangement. Results: The physicochemical analysis demonstrated that the APCL/SF nanofiber scaffold exhibited improved mechanical properties and surface hydrophilicity compared to the RPCL and RPCL/SF nanofiber scaffolds. Furthermore, the in vitro cell culture studies confirmed that the APCL/SF nanofibers could significantly promote articular chondrocyte proliferation, type II collagen (COL-II) gene expression, and glycosaminoglycan secretion compared to the RPCL and RPCL/SF nanofiber scaffolds. Additionally, cytoskeletal staining displayed that the APCL/SF nanofiber scaffold promoted the elongation of articular chondrocytes in the direction of parallel fiber alignment. Conclusion: The APCL/SF nanofiber scaffold exhibited promising potential as a composite scaffold for articular cartilage regeneration. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti6Al4V is extensively utilized in biomedical applications due to its excellent biocompatibility, corrosion resistance, and mechanical properties. The design of dental implant surface textures has changed throughout time to address issues with oral rehabilitation in both healthy and damaged bones. The longevity of an implant is significantly impacted by surface roughness. This study examines the use of laser shock peening (LSP) as a surface modification technique to improve the mechanical properties of implants. A numerical model is developed using the commercial finite elements software in ABAQUS/Explicit for simulating dynamic conditions. The aim of the study is to develop surface roughness parameters using computational methods such as studies have not yet been contemplated. The single shot angle, shot repeat, time, material orientation, and laser power are applied for the first time simultaneously to evaluate the impact of material orientation and loading angles on surface roughness parameters. The study showed that the developed computational model’s compressive residual stress was −578.45 MPa, while the experimental samples were −592.18 MPa. Consequently, the difference between the computational and experimental results was 2.32%. Without regard to material orientation or angle, the compressive residual stress of the samples under examination was found to be −578.450 MPa after three repetitions and to decreased to −1.620 MPa after four. These results demonstrate that by varying the material orientation and loading angle, the Ra value may be increased four times.

Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction (RD), and free-end torsion of a tubular specimen machined along the thickness direction (ND) were conducted. The experimental results were used to evaluate an elastic-viscoplastic self-consistent model with the consideration of twinning and detwinning (EVPSC-TDT) on magnesium (Mg) alloys. The EVPSC-TDT model provides stress-strain curves and the hardening rates in close agreement with the experimental results of all the 11 loading cases. The model adequately predicts the textures after fracture of all the 11 loading cases and the evolutions of tension twins with increasing strains for tension in the ND, compression in the RD, and torsion along the ND. The Swift effect was observed in the experiment and was properly simulated by the model.

Objective: Electrospun nanofibers exhibit potential as scaffolds for articular cartilage tissue regeneration. This study aimed to fabricate electrospun polycaprolactone (PCL)/silk fibroin (SF) composite nanofiber scaffolds and to explore performance of the scaffolds for articular chondrocyte regeneration.Methods: By altering material composition and preparation methods, three types of nanofiber scaffolds were effectively fabricated, including randomly oriented PCL (RPCL) nanofiber scaffold, randomly oriented PCL/SF (RPCL/SF) nanofiber scaffold, and aligned PCL/SF (APCL/SF) nanofiber scaffold. Physiochemical analyses were performed to determine mechanical properties and surface hydrophilicity of the nanofiber scaffolds. In vitro studies were conducted to investigate performance of the scaffolds on articular chondrocyte proliferation, gene expression and glycosaminoglycan secretion. Cytoskeleton staining was used to observe the arrangement of chondrocytes along the direction of the fibers and their elongation along the fiber arrangement.Results: The physicochemical analysis demonstrated that the APCL/SF nanofiber scaffold exhibited improved mechanical properties and surface hydrophilicity compared to the RPCL and RPCL/SF nanofiber scaffolds. Furthermore, the in vitro cell culture studies confirmed that the APCL/SF nanofibers could significantly promote articular chondrocyte proliferation, type II collagen (COL-II) gene expression, and glycosaminoglycan secretion compared to the RPCL and RPCL/SF nanofiber scaffolds. Additionally, cytoskeletal staining displayed that the APCL/SF nanofiber scaffold promoted the elongation of articular chondrocytes in the direction of parallel fiber alignment.Conclusion: The APCL/SF nanofiber scaffold exhibited promising potential as a composite scaffold for articular cartilage regeneration.

Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction (RD), and free-end torsion of a tubular specimen machined along the thickness direction (ND) were conducted. The experimental results were used to evaluate an elastic-viscoplastic self-consistent model with the consideration of twinning and detwinning (EVPSC-TDT) on magnesium (Mg) alloys. The EVPSC-TDT model provides stress-strain curves and the hardening rates in close agreement with the experimental results of all the 11 loading cases. The model adequately predicts the textures after fracture of all the 11 loading cases and the evolutions of tension twins with increasing strains for tension in the ND, compression in the RD, and torsion along the ND. The Swift effect was observed in the experiment and was properly simulated by the model. [ABSTRACT FROM AUTHOR]

Multi-scale topology optimization (a.k.a. micro-structural topology optimization, MTO) consists in optimizing macro-scale and micro-scale topology simultaneously. MTO could improve structural performance of products significantly. However, a few issues related to connectivity between micro-structures and high computational cost have to be addressed, without resulting in loss of performance. In this paper, a new efficient multi-scale topology optimization (EMTO) framework has been developed for this purpose. Connectivity is addressed through adaptive transmission zones which limit loss of performance. A pre-computed database of micro-structures is used to speed up the computing. Design variables have also been chosen carefully and include the orientation of the micro-structures to enhance performance. EMTO has been successfully tested on two-dimensional compliance optimization problems. The results show significant improvements compared to mono-scale methods (compliance value lower by up to 20% on a simplistic case or 4% on a more realistic case), and also demonstrate the versatility of EMTO. [ABSTRACT FROM AUTHOR]

In this paper, we present a non-parametric material orientation optimization method for tailoring the vibration eigenvalues of laminated shell structures composed of orthotropic carbon-fiber-reinforced plastic (CFRP) materials. Both of the design problems to maximize an arbitrary vibration eigenvalue and to maximize the gap between arbitrarily specified the vibration eigenvalues are formulated as distribution parameter optimization problems based on the variational method. We introduce KS function to solve the multiple roots problem latent in the vibration eigenvalue optimization problem. The sensitivity functions derived are applied to the H1 gradient method for material orientation to determine the optimal material orientation of each layer. The effectiveness of the proposed method are confirmed by the numerical results of a cantilever plate and a three-layer rectangular shell structure. The proposed method makes it possible to tailor the vibration eigenvalues of laminated shell structures without design parametrization while maintaining the smooth material orientation.

Both the distribution and orientation of anisotropic materials have great effects on the performance of civil and mechanical structures. Taking the maximum structural stiffness as the design objective, a concurrent method for determining the optimal distribution and orientation of orthotropic materials is proposed in this article. The method for determining material orientation theoretically overcomes the 'repeated global minimum' phenomenon, which often occurs in strain-based and stress-based methods, when the material is shear 'strong'. Then, the concurrent optimization methodology for material distribution and orientation is developed by introducing an independent discrete topology variable and continuous material orientation angle. The optimized designs of material distribution and orientation are obtained concurrently by the gradient-based bi-directional evolutionary structural optimization method and the proposed material orientation optimization method. Numerical two- and three-dimensional examples are presented to demonstrate the effectiveness of the proposed concurrent optimization algorithm. [ABSTRACT FROM AUTHOR]

In this study, we propose a distributed-parameter optimization method for the material-orientation design aiming at maximizing the strength of a laminated composite shell structure with anisotropic material, which is homogenized based on a laminate theory. The modified Tsai–Hill criterion is employed as a failure criterion in this study, and its maximum value is minimized with the state equation constraint. The issue of non-differentiability inherent in this min–max problem is avoided by transforming the singular local measure to a smooth differentiable integral functional using the Kreisselmeier–Steinhauser function. The optimum design problem is formulated as a distributed-parameter optimization problem, and the sensitivity function with respect to the material-orientation variation is theoretically derived based on a variational method. The optimal material-orientation variation is determined using the H1 gradient method with Poisson's equation proposed by the authors, where the sensitivity function are applied as Robin condition to vary and optimize the material-orientation distribution. We transfer the sensitivity function to the internal heat generation and determine the material-orientation variation using Poisson's equation to ensure continuous distribution of material orientation. The optimum design examples show that the proposed optimization method can effectively and efficiently obtain the optimum material orientation with the smooth curvilinear distribution and minimize the maximum strength measured by a failure criterion. [ABSTRACT FROM AUTHOR]

In this study, we present a material-orientation optimization method for tailoring the thermal displacements of laminated composite shell structures to required target values. The square displacement error norm between the displacements and the target values is minimized by varying the distributed anisotropic material orientation of each layer. The optimum design problem is formulated as a distributed-parameter, or a design parameterization-free optimization problem, and the sensitivity function with respect to the material orientation variation is theoretically derived based on the variational method. The optimal material orientation variation is determined by the H1 gradient method with Poisson’s equation, where the sensitivity function is applied as the Robin condition to vary and optimize the material orientation distribution. Then, the optimal material orientation variation is determined as the temperature distribution by the Poisson’s equation, which ensures the continuous material distribution. The optimal design examples show that the proposed optimization method can effectively produce the optimum material orientation with a smooth curvilinear distribution for tailoring thermal or static deformation of a laminated composite shell structure.

In this study, we propose a distributed-parametric material orientation optimization method for the optimal design of laminated composite shell structures consisting of anisotropic materials. We consider the compliance as the objective function and minimize it under the state-equation constraint. The material orientation in all the layers is treated as the design variable. The optimal design problem is formulated as a distributed-parameter optimization problem based on the variational method, and the sensitivity function with respect to the material orientation variation is theoretically derived. The optimal orientation variations are determined using the H1 gradient method with Poisson's equation, where the derived sensitivity function is applied as the fictitious internal heat generation under the Robin condition to reduce the objective function while maintaining a smooth material orientation. With the proposed method, we can conventionally obtain the arbitrary optimal distribution of the material orientations of all the layers of complicated large-scale shell structures like aircraft or automotive bodies without design variable parameterization. The optimal results of the design examples show that the proposed optimization method can effectively obtain the optimal distribution of the material orientation in laminated shell structures. [ABSTRACT FROM AUTHOR]

Abstract In this paper, comprehensive experimental and numerical analyses are carried out to compare the fire reaction properties of wool and flax based polypropylene composites under horizontal and vertical orientations. Moreover, extensive numerical analysis results on the fire reaction properties, burn time and surface temperature distribution have been reported. Fire Dynamics Simulator (FDS®) was employed to develop a numerical predictive model for the cone calorimeter. The study revealed that vertical samples ignited later compared to the horizontal ones. In addition, it has been shown that fibre type has a significant effect on the heat release rate in horizontal and vertical tests. The surface temperature distributions showed similar trends for both composites. [ABSTRACT FROM AUTHOR]

The deformation behavior of an extruded ZK60 magnesium (Mg) alloy was investigated experimentally under uniaxial loading in the extrusion direction (ED) and the transverse direction (TD). X-Ray diffractometer (XRD) and electron back scattered diffraction (EBSD) were employed to examine the microstructure evolution using companion specimens. The results indicated that the flow stress and strain hardening rate were strongly affected by the loading directions relative to the initial material orientations. Strong tension-compression asymmetry was exhibited when the loading was applied along the ED. Practically identical stress-strain responses were obtained when the tension/compression was applied in the TD. The difference in tension-compression responses between the ED and TD specimens arises from the distinctive twinning activities, which are inherently related to the initial basal texture. When loading was applied in the ED, copious tension twinning can attained only under compression. However, in the TD, either tension or compression can impose similar amounts of grains under c -axis tension, thus activating tension twinning in both directions. Detailed analyses of strain hardening rate responses under different loading paths were made. The deformation mechanisms associated with different stages of strain hardening rate were discussed with a particular emphasis on the roles of deformation twinning. [ABSTRACT FROM AUTHOR]

In this study, we propose a parameter-free optimization method of material orientation for a shell structure consisting of orthotropic materials. We consider the compliance as an objective function and minimize it under the state equation constraint. The material orientation distribution is the design variables to be determined. This optimum design problem is formulated as a distributed-parameter optimization problem, and the sensitivity function with respect to the orientation variation is theoretically derived based on the variational method. The optimum orientation variations are determined by the H1 gradient method with the Poisson's equation, where the sensitivity function is applied as the internal heat generation on the shell surface, a driving force to vary the orientation in order to reduce the objective function while maintaining the smooth material orientation distribution. The optimum and continuously distributed orientation variations are determined as the temperature distribution of this fictitious heat transfer analysis without design parameterization. The optimum design examples show that the optimum the material orientation for the minimum compliance can be effectively obtained with the proposed optimization method.

Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed constant. Through an analysis of the force and torque produced during welding and a simple analytical model, the results indicate that the heat input was reduced when the AA7050 alloy was located in the advancing side (AS) of the joint. The different material positions influenced the material transportation and the interface in the centre of the stir zone (SZ). The microhardness of both materials was lower when they were in the AS of the joint. The differences in the hardness values were reduced at higher welding speeds when the heat input was decreased. The mechanical performance increased when the lower strength alloy was located in the AS. The material orientation exhibited a small influence when the AA7050 alloy was in the AS and in general on the resulting microhardness for all the cases analysed. The tensile strength values were very similar for both orientations, but an increase in the yield strength could be measured when the materials were oriented in the transverse direction.

The effect of material orientation on cyclic deformation and fatigue behavior of rolled AZ80 magnesium (Mg) alloy was experimentally investigated under fully reversed strain-controlled loading in ambient. The testing specimens were taken from a rolled AZ80 Mg plate at four orientations with respect to rolled plane: 0°(ND, normal direction), 30°(ND30), 60°(ND60), and 90°(RD, rolled direction). Fatigue fracture morphologies of specimens along different orientation were analyzed by scanning electron microscopy (SEM). Overall cyclic hardening was observed for the material loaded in different directions. For a given strain amplitude, the ND specimens had the lowest fatigue resistance among the specimens of all material orientations. The fatigue life of an ND30 specimens is similar to that of an ND60 specimen at a given strain amplitude and both are higher than that of an RD specimen when the strain amplitude is higher than 0.4%, whereas an RD specimen exhibits a better fatigue resistance when the strain amplitude is lower than 0.4%. A mixed fracture mode with transgranular and intergranular cracking related to lamellar-like features occurred during stable crack growth, and an intergranular fracture mode related to dimple-like features exhibited in the fast fracture region. A multiaxial fatigue model based on the strain energy density can correlate all the fatigue experiments of the material at different material orientations. [ABSTRACT FROM AUTHOR]

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Abstract: Experimental data is presented relating to surface roughness (2D and 3D) and workpiece integrity when drilling unidirectional CFRP laminates with varying lay-up configurations (Type 1, 2 and 3) at different feed rates (0.2 and 0.4mm/rev) using diamond coated carbide tools. Drill feed rate was ramped down to 0.01mm/rev for the final 0.5mm in all trials. Surface roughness at hole exit was typically lower (up to 4.04μm Ra) compared with the entry section in all tests due to the lower feed rate applied. High resolution SEM micrographs and 3D topographic maps showed that Type 2 ([45/0/135/0/90/0/135/0/45]2S) lay-up gave the lowest roughness of ∼1.16μm Sa after 384 holes at a cutting speed and feed rate of 90m/min and 0.4mm/rev respectively. Cavities, smearing of matrix material and adhered/deposited fibre dust were observed near the exit location at test cessation. [Copyright &y& Elsevier]

Mechanical properties of the electro-active paper (EAPap) actuator were tested to investigate its hygrothermal behavior. Tensile creep behavior was studied with constant load at 30–70% relative humidity ranges and 25–40°C temperature. Creep deformation showed typical trend of abrupt strain increase in a short period followed by steady increase of strain, which resulted from the breakdown of cellulose microfibrils. Dependence on the material orientation of EAPap was observed in the creep tests. As changing the orientation of EAPap samples, the creep resistances were varied. Creep strains and creep strain rates were increased as increasing the relative humidity level at 25°C. However, at the elevated temperature of 40°C, the creep strain rate at secondary creep was not significantly raised under increased relative humidity level from 30% to 50%. The hygrothermal effect by increasing the relative humidity level and temperature on the creep rate was reduced due to the saturated moisture at a higher temperature even with lower humidity level. The activation energy levels for creep were around 607–658 kJ/mol for 30% relative humidity level and 623–671 kJ/mol for 50% relative humidity level depending on the material orientation. Understanding of hygrothermal effect in conjunction with the humidity and temperature provides useful information for the potential nano-bio applications of the EAPap actuator. [ABSTRACT FROM AUTHOR]

• A heterogeneous specimen is designed using a shape optimization algorithm that maximizes a heterogeneity indicator. • Positive correlation between the adopted heterogeneity indicator and the inverse identification quality is found for the Hill 1948 yield criterion. • The orientation of the principal material axis can be considered as a design variable for maximizing identifiability of anisotropic parameters. • The reliability and robustness of different identifiability criteria are scrutinized through virtual experimentation and FEMU. Advanced anisotropic constitutive models involve a large number of model parameters requiring multiple conventional mechanical experiments for accurate calibration. Inverse identification through a single heterogeneous experiment combined with full-field deformation fields enables to reduce the experimental effort. User-dependency in design of such information-rich experiment can be eliminated via shape optimization that is driven by an indicator expressing the degree of strain field heterogeneity. This approach is validated by assessing the identification quality of the heterogeneous experiments through the Finite Element Model Updating (FEMU) technique fed by synthetically generated Digital Image Correlation (DIC) data using a reference material model. Positive correlation between the adopted heterogeneity indicator and the inverse identification quality is found for the identification of the Hill 1948 yield criterion. It is shown that identification metrics can be used to accurately predict the identification quality prior to the FEMU process. Moreover, it is shown that the identifiability of the sought parameters can be significantly improved by considering the orientation of the principal material axis in the specimen. The reliability and robustness of the proposed identifiability metrics are validated using a more advanced anisotropic yield function, namely Yld2000-2D. The identification metrics can therefore be used to enhance the design of information-rich experiments. Finally, it is recommended to treat the material orientation as a design variable. [Display omitted] [ABSTRACT FROM AUTHOR]

• Unit-cell finite element calculations with prescribed Lode parameter and stress triaxiality. • Material yielding defined by the orthotropic Yld2004-18p criterion. • Void growth is affected by material orientation. • The misalignment between loading and orthotropy axes triggers a minimum void growth. In this work, we have brought to light the effect of material orientation on void growth. For that purpose, we have performed finite element calculations using a cubic unit-cell model with a spherical void at its center and subjected to periodic boundary conditions. The behavior of the material is described with an elastic isotropic, plastic orthotropic constitutive model with yielding defined by Yld2004-18p criterion (Barlat et al., 2005). We have used the multi-point constraint subroutine developed by Dakshinamurthy et al. (2021) to enforce constant values of macroscopic stress triaxiality T and Lode parameter L in calculations that have been carried out for different stress states resulting from the combination of T = 0.33 , 1 and 2, with L = − 1 , 0 and 1 (axisymmetric tension, generalized shear and axisymmetric compression, respectively). Firstly, we have performed numerical simulations in which the loading directions are collinear with the orthotropy axes of the material, so that the principal directions of macroscopic stress and strain are parallel. Investigation of the cases for which the minor loading axis coincides either with the rolling, the transverse or the normal direction, has shown that the initially spherical void turns into an ellipsoid whose rate of growth and eccentricity depend on both stress state and material orientation. A key result is that for specific material orientations the anisotropy switches the effect of Lode parameter on void growth, reversing the trends obtained for isotropic von Mises materials. Secondly, we have carried out calculations using a novel strategy which consists of including angular misalignments within the range 0 ∘ ≤ θ ≤ 90 ∘ , so that one loading direction is parallel to one of the symmetry axes of the material, and θ is the angle formed between the other two loading directions and the second and third orthotropy axes. In fact, to the authors' knowledge, these are the first unit-cell calculations ever reported in which the material is modeled using a macroscopic anisotropic yield function with prescribed misalignment between loading and material axes and, at the same time, the macroscopic stress triaxiality and the Lode parameter are controlled to be constant during loading. The finite element calculations have shown that the misalignment between loading and material axes makes the void and the faces of the unit-cell to rotate and twist during loading. Moreover, the main contribution of this work is the identification of an intermediate value of the angle θ for which the growth rate of the void reaches an extreme value (minimum or maximum), so that the numerical results indicate that material orientation and angular misalignment can be strategically exploited to control void growth, and thus promote or delay localization and fracture of anisotropic metal products. The conclusions of this research have been shown to be valid for three different materials (aluminum alloys 2090-T3, 6111-T4 and 6013) and selected comparisons have also been performed using two additional yield criteria (CPB06ex2 and Yld2011-27p). [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on investigating the piezoelectric effects of cellulose-based electro-active paper (EAPap) using quasi-static direct piezoelectricity. Mechanical properties were investigated first and then electro-mechanical behavior was studied by applying electric field during the pulling test. In-plane piezoelectric charge constant (d 31) of EAPap was quantified by the quasi-static relation between induced charge and applied stress. Strong shear electro-mechanical coupling was observed and 45° sample provided the largest in-plane piezoelectric charge constant. The measured piezoelectric charge constant was in the range of 8–28.2pC/N, which are similar to those of piezo polymer. Cellulose EAPap provides promising potential as biodegradable and cheap piezoelectric polymer material. [Copyright &y& Elsevier]

The scientific community has put significant effort into the development and optimization of sensors and actuators manufactured as piezoelectric composites with interdigitated electrodes (IDEs), well known as active fiber composite (AFC) and macro fiber composite (MFC). The advantages of these elements are their higher actuation performance and flexibility as compared to monolithic piezoceramic (PZT) elements. In general, their mechanical properties are calculated based on the classical lamination theory and the uniform field model (UFM). These two theories are well suited for predicting the stiffness and piezoelectric strain constants of the AFC or MFC. Although there are a variety of numerical investigations related to their electromechanical properties, there are no appropriate tools for accessing the stresses within these piezoelectric elements (including the inhomogeneous electric field conditions as well as the change in material properties). Explanations are given for this situation indicating the problems in investigating these types of piezoelectric elements with respect to stress states. In this work a finite element modeling approach is presented, which shows the influence of the IDE on the mechanical properties of PZT fibers. Experimental evidence is presented, which affirms the location of critical stress predicted in this model and explains the reported cracking in AFC in past research. [ABSTRACT FROM AUTHOR]

• Analytical solution is given for optimum orientation of anisotropic microstructure. • An algorithm is developed for concurrent optimization of macro and microstructure. • The method is applicable to compliant mechanism and minimum compliance problems. This paper presents a general formulation and solution method for the problem of two-scale concurrent topology optimization of cellular structure and its anisotropic materials. This formulation seeks simultaneous determination of the macro and micro structural topologies and the orientations of microstructures, such as a unit cell with anisotropic and inhomogeneous material properties. In the present formulation, the microstructure of cellular material is uniform in the entire macrostructure but with spatially-varying orientations. The solution method consists of two new features: (a) a mutual strain energy density-based approach proposed for analytically determining the orientations of fully anisotropic materials in compliant mechanism problems, which can also be modified to address minimum compliance designs and (b) an extended and fully-coupled moving iso -surface threshold (MIST) method and algorithm developed for solving the formulated concurrent optimization problem of cellular structures using two-scale physical response functions. The present formulation and algorithm are validated via studying numerical examples of concurrent optimum design of: (i) macro and micro topologies; (ii) macro topology and orthotropic material orientations; and (iii) macro and micro topologies and material orientations. [ABSTRACT FROM AUTHOR]

• A new concurrent optimization method for structures and materials proposed. • An analytical approach for determining local material orientation is derived. • The volume fractions of macro- and micro-structures are determined by a weight constraint. • The optimization greatly improves the natural frequency of the structure. In this paper, an efficient concurrent optimization method of macrostructures, and material microstructures and orientations is proposed for maximizing natural frequency. It is assumed that the macrostructure is composed of uniform material with the same microstructure but with various orientation. The bi-directional evolutionary structural optimization (BESO) method is applied to optimize the macrostructure and its material microstructure under a given weight constraint. Meanwhile, the optimality condition with respect to local material orientation is derived and embedded in the two-scale design of macrostructures and material microstructures. Numerical examples are presented to demonstrate the capability and effectiveness of the proposed optimization algorithm. The results show that the current design of macrostructures, material microstructures, and local material orientation greatly improves structural dynamic performance. [ABSTRACT FROM AUTHOR]

Material orientation effects on cyclic deformation and fatigue of a rolled AZ31B magnesium (Mg) alloy were experimentally studied. Monotonic tension, monotonic compression, and fully reversed strain-controlled tension-compression experiments were conducted using testing specimens taken from a rolled plate along five different directions with respect to the rolled direction (RD): 0 ° (RD), 22. 5 ° , 45 ° , 67. 5 ° , and 90 ° (ND). Fatigue lives range from few loading cycles to over 10 6 cycles. Significant anisotropy was observed in the monotonic and cyclic deformation behavior. Cyclic hardening was observed for all five orientations at a high strain amplitude. The strain-life curves of all the material orientations form a relatively narrow band. The strain-life curve obtained from each material orientation is characterized with two distinct kink points which are closely associated with the dominating plastic deformation mechanisms, fatigue properties, and fatigue cracking behavior. The RD specimens show the highest fatigue strength while the 45 ° specimens display the lowest fatigue strength among the five material orientations. A discussion is made on the unique deformation behavior of the 45 ° specimens. Image 1 • Comprehensive experimental results of cyclic deformation and fatigue of a rolled Mg alloy. • Material orientation effect on static properties of a rolled Mg alloy. • Material orientation effect on fatigue properties of a rolled Mg alloy. • Characteristic deformation associated with the kink points in the strain-life fatigue curve. • Unique deformation characteristics of the 45-degree material orientation. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed constant. Through an analysis of the force and torque produced during welding and a simple analytical model, the results indicate that the heat input was reduced when the AA7050 alloy was located in the advancing side (AS) of the joint. The different material positions influenced the material transportation and the interface in the centre of the stir zone (SZ). The microhardness of both materials was lower when they were in the AS of the joint. The differences in the hardness values were reduced at higher welding speeds when the heat input was decreased. The mechanical performance increased when the lower strength alloy was located in the AS. The material orientation exhibited a small influence when the AA7050 alloy was in the AS and in general on the resulting microhardness for all the cases analysed. The tensile strength values were very similar for both orientations, but an increase in the yield strength could be measured when the materials were oriented in the transverse direction. [ABSTRACT FROM AUTHOR]

Objective:Due to the rolling manufacturing process, most advanced high-strength steels (AHSS) demonstrate in-plane anisotropic material behavior. This study investigates the effects of material orientation on the axial crush behavior and fracture of AHSS with axial crush tests and computer simulations. Methods:Crush simulation models considering material anisotropy and damage evolution were developed in LS-DYNA based on the drop-tower crush test results and coupon characterization test data for DP780 steel. The modified Mohr-Coulomb (MMC) isotropic fracture model was employed in the crush simulation models for fracture prediction. Results:The 12-sided components fabricated in the transverse (T) direction of the sheet exhibited slightly higher crush loads and reduced crush distances compared to those in the longitudinal (L) direction. The crush behavior in each direction was generally proportional to ultimate tensile strength. All of the materials investigated in this study showed some cracking in the crush tests for both component orientations, but only DP780 showed significant anisotropy in fracture behavior with more cracking for the T direction compared to the L direction. Overall, the amount of cracking observed in the tests had little or no significant effect on the axial crush performance. The MMC fracture loci in both the L and T directions were determined using a reverse engineering approach, and the stress–strain curves beyond the uniform elongation point were extended using an optimization method. Both material models MAT103 and MAT224 predicted the crush and fracture behavior with reasonably good accuracy. Conclusions:The predicted fracture mode and force–displacement curves agreed well with the test data for both the L and T directions in axial crush tests of the 12-sided components. The simple isotropic material model MAT224 is adequate for crush simulations to predict material orientation effects on AHSS component crush performance and fracture behavior. [ABSTRACT FROM AUTHOR]