Weihong Zhang

Northwestern Polytechnical University | NWPU · School of Mechanical Engineering

Topology optimization of steady heat conduction problem under both design-independent and design-dependent heat loads is studied by means of a modified bidirectional evolutionary structural optimization (BESO) method. Two types of problems are distinguished by their physical meanings and particularly design-dependent load effect is highlighted in t...

The layout of movable components and the topology of the connecting structure are optimized simultaneously in the integrated optimal design of multi-component system for compliance minimization. In this paper, a Heaviside function based approach is developed for sensitivity analysis with respect to location design variables of components. The mater...

This study presents the integrated layout optimization of multi-component systems using a fixed mesh. The optimization formulation is established under the framework of the extended finite element method (XFEM). The level set method is used to represent components and is combined with the XFEM to describe material discontinuities across elements. S...

Cellular infill structures such as honeycomb have been widely used in the field of light weighting. In recent years, the emergence of additive manufacturing technologies has provided a new solution to fabricate complicated cellular infill structures. This paper presents a continuous printing path planning method for gradient honeycomb structures. G...

For a long period, phyllotaxis (the arrangement of leaves on a plant stem) has been observed as an interesting morphological property of various plants, and the phyllotactic spirals form a distinctive class of patterns in nature. These days, the unique patterns governed by the Fibonacci sequence, or the golden ratio in a deeper sense, have moved be...

Efficient and accurate chatter prediction is essential for selection of chatter-free process parameters in order to improve machining productivity and surface quality of the workpiece. This paper proposes a five-point Gaussian quadrature-based chatter prediction method of milling processes together with a transition matrix reduction scheme to impro...

This paper presents a MATLAB code implementation of the Adaptive Bubble Method (ABM) published by Cai and Zhang (2020) for topology optimization. The ABM has the main feature of inserting deformable holes adaptively into the design domain to reflect the designer’s motto that “The art of structure is where to put the holes.” This method consists of...

This paper is aimed to develop a load allocation topology optimization approach to meet the design requirement of thermo-elastic structures in engineering practice. To formulate the optimization problem, load allocation constraint is proposed by constraining the ratio of considered reaction forces to a proper range. The average displacement at the...

Transformation-induced plasticity (TRIP) in pseudoelastic polycrystalline NiTi shape memory alloys (SMAs) is investigated through tensile tests combined in-situ infrared and digital image correlation (DIC) observations, and a new TRIP concentration phenomenon is revealed. To this end, an instability evolution model for solid–solid phase transformat...

Friction stir welding (FSW) is now widely used in industrial manufacturing fields to join metal materials. Although it avoids solidification cracking, the combination of thermal excursion and plastic deformation introduces significant residual stresses. These residual stresses will combine with the applied stresses in service to cause unexpected fa...

The additive manufacturing technology facilitates the formation of complex lattice structures that are difficult to be fabricated by the traditional manufacturing technologies. In order to investigate the mechanical behaviors and failure modes of Ti6Al4V lattice structures manufactured by laser powder bed fusion (L-PBF), five cell topologies such a...

Carbon fiber reinforced plastic (CFRP) composites have been widely used in the last thirty years. The main issue in using CFRP composite joints is the bond strength between skin and stringer. This paper presents the results of an experimental investigation into the effect of pre-hole z-pinning technique (PHZ) on the impact resistance and post-impac...

In this paper, the length scale control (LSC) methods, including the maximum length scale control (MaxLSC) and the minimum length scale control (MinLSC) for both the solid and void phase, are proposed for density-based multi-material topology optimization. The three-field approach is extended to multi-material topology optimization problems. The lo...

The curing process generates thermal residual stress in z-pinned composites, leading to partial or complete cracking along z-pin/composite interfaces. In this study, we applied a novel multiscale framework to evaluate the delamination behaviours of z-pinned composites considering the effects of z-pin/composite interfacial cracks. Unit cell models w...

Laser powder bed fusion (LPBF) Ti6Al4V has a great potential to be applied in high temperature vehicle structure. The columnar grains of the LPBF components grow along the build derection. Duo to the specific microstructures, the tensile and fatigue properties of LPBF components are anisotropic. So, the study on high temperature mechanical properti...

Al-Li alloy friction stir welded stiffened panels have been widely used in many complex structures of aircraft due to their superior advantages. Static and fatigue shear tests were carried out to study the failure modes of 1.2mm and 1.5mm thick panels. The static failure modes of panels are weld cracking and skin cracking. The failure loads of 1.2m...

In this paper, a B-spline parameterized density method is proposed to simultaneously optimize the structural topology and the build direction for additive manufacturing (AM). B-spline parameterization is used to represent the structural density field together with Heaviside projection and Boolean operation. Two constraints and a novel filtering sch...

This article presents an analytical method to determine the yield strength and the energy distribution in the milling process of nickel alloy Inconel 718 by incorporating the fracture toughness, the plastic deformation and the friction effect. To study the geometry and mechanics in the oblique cutting process, mathematical analyses are done to deri...

Frame mold is the key tool for autoclave processing of composite structures. Its stiffness and temperature uniformity have important influences on the quality, particularly the synchronization of curing of the processed composite structures. In this paper, a novel topology optimization method is proposed to design the frame mold for improving the s...

On account of the dissipative martensite phase transformation, NiTi shape memory alloy can exhibit large pseudoelastic deformation and high damping capacity, making it a promising candidate in engineering vibration control. The main objectives of this paper are twofold: to investigate the free vibration behavior of the NiTi wires and to design a Ni...

Most of the methods used today for handling local stress constraints in topology optimization, fail to directly address the non-self-adjointness of the stress-constrained topology optimization problem. This in turn could drastically raise the computational cost for an already large-scale problem. These problems involve both the equilibrium equation...

In this article, a joint topology optimization procedure is executed to design phononic crystals (PnCs) with a maximized band gap. First, the band gap of two-dimensional PnCs is calculated using a finite element model under the plane strain assumption for easy and efficient optimization. In the numerical computation of the band gaps, the band struc...

In this paper, a B-spline parameterization based topology optimization method is presented to design 3D self-supporting structures for additive manufacturing (AM). B-spline parameterization being independent of the FE mesh is used to represent the density field characterizing the material layout of the structure. Heaviside projection and Boolean op...

Machined helical springs were designed and fabricated from NiTi shape memory alloy tube stock by cutting helical slots to make the coils, which provided them with high design flexibility and actuation potential. The springs were then subjected to isothermal tensile testing at temperatures of 20°C and 80°C, the experimental data showed that they cou...

This paper presents an experimental investigation of the mode Ⅱ delamination resistance of curved CFRP laminates reinforced with Z-pins. A Pre-Hole Z-pinning (PHZ) process is developed to reduce the in-plane damage of the Z-pinned laminates. The microstructural observation of the Z-pinned laminate specimens indicates that the PHZ process can effect...

Radar cross section (RCS) reduction for cavities is essential in flight vehicle design. As a conventional method to reduce the RCS, coating radar absorbing materials has been widely employed in engineering. Nevertheless, radar absorbing coatings (RAC) will additionally increase the structural weight. In this paper, a topology optimization approach...

The coupling between transformation-induced plasticity (TRIP) and low cycle fatigue of pseudoelastic shape memory alloys (SMAs) is investigated and an upper bound of low cycle fatigue life is found. Through combined in-situ infrared and digital image correlation (DIC) observations on NiTi sheet, we reveal that the low cycle fatigue of SMAs is gover...

This paper proposes a novel micromechanical model to study the curing effects on the in-plane tensile properties and failure mechanisms of carbon/epoxy laminates reinforced with z-pins. The microstructures including fiber distortion and resin-rich pockets caused by z-pins are characterized. The results indicate that cure-induced residual stresses g...

This paper presents a topology optimization approach for the surface flows on variable design domains. Via this approach, the matching between the pattern of a surface flow and the 2-manifold used to define the pattern can be optimized, where the 2-manifold is implicitly defined on another fixed 2-manifold named as the base manifold. The fiber bund...

A high cycle fatigue (HCF) approach based on shakedown, crystal plasticity and cohesive zone theories is developed for metals. To take into account the effect of localized plasticity in grains and grain boundaries, crystal plasticity and elastoplastic cohesive zone models are considered to calculate the mechanical responses of grains and grain boun...

In this paper, the thin-walled structures with lattices and stiffeners manufactured by additive manufacturing are investigated. A design method based on the multi-material topology optimization is proposed for the simultaneous layout optimization of the lattices and stiffeners in thin-walled structures. First, the representative lattice units of th...

Surface flows can represent the motions of the viscous and incompressible fluid at the solid/fluid interfaces. This paper presents a topology optimization approach for surface flows and extends the design space of topology optimization of fluidic structures onto the curved surfaces in the forms of 2-manifolds corresponding to the geometrical config...

This paper presents an experimental investigation into the effect of Z-pin on the low-velocity impact response and flexural properties after impact of the curved CFRP laminates. The Z-pinned specimens are produced using a low-damage pre-hole Z-pinning (PHZ) technique. Unpinned and Z-pinned [0/45/–45/90]4S specimens are both subjected to low-velocit...

Z-pinned composite laminates have been increasingly applied to aircraft and other lightweight products. This paper reviews published multi-scale research into polymer composite laminates reinforced by z-pins. Basic knowledge of multi-scale strategy and z-pin reinforcements has been reviewed at first. Then the methodology and relevant research progr...

The influences of metasurfaces on the propagation of electromagnetic waves generate several important effects, such as asymmetric transmission and polarization conversion, that are highly useful in optical and microwave communication applications. However, easy method for dynamically controlling the asymmetric transmission of linearly polarized wav...

In this work, we develop a topology optimization method for linear elastic contact problems with maximum contact pressure constraint. First, the Kreisselmeier–Steinhauser (KS) function is adopted as an aggregated measure of the maximum contact pressure over specific contact regions. Then, the maximum contact pressure constraint is introduced into t...

To reconcile the contradiction between the improvement of carbon fiber reinforced resin matrix (CFRP) composite performance and the increase of manufacturing cost, this paper proposes a collaborative optimization strategy for the cure process during the composite manufacture to reduce both the process-induced defects and the process time. Consideri...

Since the dynamics of thin‐walled structures instantaneously varies during the milling process, accurate and efficient prediction of the in‐process workpiece (IPW) dynamics is critical for the prediction of chatter stability of milling of thin‐walled structures. This article presents a surrogate model of the IPW dynamics of thin‐walled structures b...

Stiffener layout optimization of complex surfaces is fulfilled within the framework of topology optimization. A combined parameterization method is developed in two aspects. One is to parameterize the material distribution of the stiffener layout by means of B-spline. The other is to build the mapping relationship from the known 3D surface mesh of...

Aiming at the exploration and resource utilization activities on the Moon, in situ resource utilization and in situ manufacturing are proposed to minimize the dependence on the ground transportation supplies. In this paper, a laser-assisted additive manufacturing process is developed to fabricate lunar regolith composites with PA12/SiO2 mixing powd...

This work focuses on the comprehensive modelling of the cure kinetics and the thermochemical coupling to investigate the cure process of CFRP composites. Neural network (NN) is instead of the general cure kinetics model to find the relationships between the cure kinetics parameters where the temperature rate is also involved. Large data sets from n...

Stiffener layout optimization of complex surfaces is fulfilled within the framework of topology optimization. A combined parameterization method is developed in two aspects. One is to parameterize the material distribution of the stiffener layout by means of B-spline. The other is to build the mapping relationship from the known 3D surface mesh of...

With the development of typical additive manufacturing SLM, SLM Ti6Al4V has the potential to be used in high temperature vehicle structure. Mechanical properties after thermal exposure and creep performance of SLM Ti6Al4V and its build direction effects need to be studied in detail. In this paper, tensile and creep samples with 0°, 45° and 90° thre...

The electromagnetic performance of flight vehicles has been attracting considerable interest in recent years. As one of the important indicators of this performance, radar cross section (RCS) has been extensively studied. A significant limitation on the RCS of flight vehicles lies in the fact that tiny gaps will transform into steps during structur...

High-resolution additive manufacturing (AM) facilitates engineering applications of cellular lattices with complex geometries. The unique layer-by-layer process of AM causes the mechanical performance of as-fabricated lattice structures to deviate from the ideal value. In this study, the AM process-induced material anisotropy and geometric inaccura...

Structural stability has attracted increasing attention in topology optimization because of the buckling effect under compression load. In this work, the feature-driven optimization method is developed for structural topology optimization involving buckling constraints. First, the finite cell method is extended to linear buckling analysis. A stress...

In this work, a novel concurrent optimization framework based on multiscale finite element method is proposed to pursue superior-performance hierarchical structures with parameterized lattice. Distinguished with conventional homogenization-based optimization method, this framework gets rid of the assumption of scale separation while optimizing hier...

Inconel 718, a nickel, chrome and iron alloy, has special advantages, such as high-temperature strength, thermal resistance and corrosion resistance, which facilitate wide usage in the aerospace industry, especially in the hot sections of gas turbine engines. However, machining this alloy is correlated closely with the material’s inherent propertie...

In this paper, we propose a B-Spline Offset Feature (BSOF) for feature-driven topology optimization. The feature is inspired from the geometric morphology of worms characterized by an elongated cylindrical, bilaterally symmetric, and well-segmented body along a highly deformable directrix. B-spline is used to define the directrix with its outward a...

In this work, a topology optimization approach is developed for additive manufacturing (AM) of 2D and 3D self-supporting structures. Three important issues, i.e., overhang angle control, avoidance of the so-called V-shaped areas and minimum length scale control are addressed. 2D solid polygon and 3D polyhedron features are introduced as basic desig...

High-resolution laser additive manufacturing (LAM) significantly releases design freedom, promoting the development of topology optimization (TO) and advancing structural design methods. In order to fully take advantage of voxelated forming methods and establish the quantitative relationship between the mechanical properties of printing components...

Most of the methods used today for handling local stress constraints in topology optimization, fail to directly address the non-self-adjointness of the stress-constrained topology optimization problem. This in turn could drastically raise the computational cost for an already large-scale problem. These problems involve both the equilibrium equation...

This paper develops a multi-objective optimization method for the cure of thick composite laminates. The purpose is to minimize the cure time and maximum temperature overshoot in the cure process by designing the cure temperature profile. This method combines the finite element–based thermo-chemical coupled cure simulation with the non-dominated so...

There are renewed interests in grid-stiffened composite structures due to the high structural stability and damage tolerance enabled by multiple intersected stiffeners. The limited design space of repeated straight grid patterns has been remarkably expanded by introducing non-uniform curved grid-stiffened composite structures (NCGCs). In this work,...

A crystal plasticity-based constitutive model is developed to describe the thermomechanical behavior of pseudoelastic NiTi single crystal. The model includes, for the first time in the literature, all inelastic mechanisms influencing the fatigue behavior of NiTi SMAs in a finite strain framework: martensite transformation, deformation slip in auste...

The purpose of this paper is to present a shape preserving topology optimization method to prevent the adverse effects of the mechanical deformation on the Radar Cross Section (RCS). The optimization will suppress the variation of RCS on the perfect conductor surface by structural design. On the one hand, the physical optics method is utilized to c...

A novel micro-mechanical modeling approach is developed to predict the partially debonding of a Z-pin reinforced composite laminates after the cure process. Cohesive zone model (CZM) is employed to represent the interphase between Z-pin and resin. The quadratic stress criterion and the Benzeggagh-Kenane propagation criterion are coupled to determin...

The results obtained in traditional topology optimization with a single density design variable assigned to each element, are typically improved through h-refinement where the resolution of the FE mesh is scaled up along with the number of density elements/voxels, without increasing the order of the finite element interpolation. Higher order elemen...

Multiple-laser and matrix-heat source exposures are emerging systems for powder bed fusion (PBF) to improve productivity. However, the newly available process planning such as scanning patterns may induce different transient thermal distribution and distortion in selective laser sintering or melting process. This work proposes novel scanning strate...

Laser powder bed fusion (LPBF) of Ti6Al4V, one of additive manufactured titanium alloy, has a great potential to be applied in aviation structural components. At present, the fracture behaviours of Ti6Al4V manufactured by LPBF under different loading conditions, especially under torque, bending and shear loading, is still insufficient. To meet this...

In order to study buckling fatigue behavior and failure modes of 2A97 Al-Li alloy stiffened panels under shear loading, 1.2 mm and 1.5 mm thick 2A97 Al-Li alloy stiffened panels were designed and manufactured. The static and fatigue tests were performed under shear loading. The results indicate that the shear failure modes of stiffened panels are g...

Multidisciplinary topology optimization (TO) for additive manufacturing (AM) exhibits unprecedented design and manufacturing freedom as an effective lightweight methodology. In order to fully utilize the AM advantages of materialized arrangement in spatial and voxel-by-voxel digitalized printing, multidisciplinary TO for AM requires a full understa...

Polymer nanocomposites with high thermal conductivity have been increasingly sought after in the electronic industry. Based on molecular dynamics simulations, this work assesses the thermal transport in polyethylene (PE) nanocomposites with the presence of a new one-dimensional nanofiller-a carbon nanothread (NTH). It is found that the axial therma...