Bimaterial Structure Research Articles

The impact of seepage effect on repaired interface failure in steel bridge deck pavement: A case of pothole distress

The repeated failure of repaired interface in steel bridge deck pavement (SBDP) under complex service environment makes SBDP maintenance challenging. The primary objective of this paper was to figure out the impact of seepage on repaired interface failure, addressing the secondary damage on SBDP after distresses maintenance. A uni-body bi-material structure (UBS) specimen was fabricated to simulate the repaired interface. Besides, a simulation experimental device of hydrodynamic scouring action was put forward to evaluate the effect of cycle numbers on failure behavior of repaired interface during an indirect tensile test. In addition, numerical simulation analysis was conducted to determine the tensile stress characteristics of repaired interface under load-seepage coupling effect. Findings revealed that the failure state of repaired interface may change from brittle fracture to large deformation damage under seepage effect. The longer the duration of hydrodynamic scouring action, the more serious damage of the repaired interface, with 540 cycles resulting in an approximately 25 % reduction in interface strength. Furthermore, the stress condition of repaired interface is significantly worse when consider the coupling effect of load and seepage, approximately 40 % greater than that of a single load action. And it is closely related to its relative position with the orthotropic steel bridge deck and the actual stress conditions. The research findings presented in this paper can serve as a theoretical foundation for SBDP maintenance.

Experimental, analytical, and numerical studies of the energy absorption capacity of bi-material lattice structures based on quadrilateral bipyramid unit cell

The present study investigates the mechanical performance and energy absorption capacity of bi-material 3D lattice structures via experimental, analytical, and numerical approaches. The analytical model has been developed to obtain the effective parameters in energy absorption, such as equivalent elastic modulus and yield stress. Analytical relations based on hyperbolic shear deformation beam theory were extended to calculate the mechanical properties of an extracted unit cell from the lattice structure subjected to applied loads and appropriate boundary conditions. Then, experimental and nonlinear numerical studies have been conducted to analyze the energy absorption properties of the bi-material lattice structure. Quasi-static compression tests were conducted to analyze this lattice structure's mechanical properties and energy absorption capacity. As the numerical study, the elastic-plastic damage behavior was implemented in finite element analyses to examine the nonlinear response of considered structures. The obtained results reveal that the numerical models exhibit an acceptable prediction. According to the results, not only does the use of hybrid structures provide more energy absorption and improve mechanical properties, but also, in comparison to the usual lattice structures fabricated with a single material, the rational combination of two materials makes the bi-material three-dimensional lattice structure to inherit the optimum energy absorption and stiffness.

Dynamic Response of Paper-Based Bi-Material Cantilever Actuator

This work presents a dynamic modeling approach for analyzing the behavior of a bi-material cantilever actuator structure, consisting of a strip of filter paper bonded to a strip of tape. The actuator’s response is induced by a mismatch strain generated upon wetting, leading to the bending of the cantilever. The study delves into a comprehensive exploration of the dynamic deflection characteristics of the bilayer structure. It untangles the intricate connections among the saturation, modulus, hygro-expansion strain, and deflection, while uniquely addressing the challenges stemming from fluid–structure coupling. To solve the coupled fluid–solid differential equations, a combined numerical method is employed. This involves the application of the Highly Simplified Marker and Cell (HSMAC) technique for fluid flow analysis and the Finite Difference Method (FDM) for response deflection computation. In terms of the capillary flow model, the Computational Fluid Dynamics (CFD) simulations closely align with the classical Washburn relationship, depicting the wetted front’s evolution over time. Furthermore, the numerical findings demonstrate that heightened saturation levels trigger an increase in hygro-expansion strain, consequently leading to a rapid rise in response deflection until a static equilibrium is achieved. This phenomenon underscores the pivotal interplay among saturation, hygro-expansion strain, and deflection within the system. Additionally, the actuator’s response sensitivity to material characteristics is highlighted. As the mismatch strain evolving from paper hygro-expansion diminishes, a corresponding reduction in the axial strain causes a decrease in response deflection. The dynamic parameter demonstrates that the deflection response of the bilayer actuator diminishes as dynamic pressure decreases, reaching a minimal level beyond which further changes are negligible. This intricate correlation underscores the device’s responsiveness to specific material traits, offering prospects for precise behavior tuning. The dependence of paper modulus on saturation levels is revealed to significantly influence bilayer actuator deflection. With higher saturation content, the modulus decreases, resulting in amplified deflection. Finally, strong concordance is observed among the present fluidically coupled model, the static model, and empirical data—a testament to the accuracy of the numerical formulation and results presented in this study.

Peridynamics study on crack propagation and failure behavior in Ni/Ni3Al bi-material structure

In this paper, the crack propagation and failure behavior of Ni/Ni3Al bi-material structure are investigated under the framework of peridynamics (PD). The effects of the location of the pre-crack, the loading rate, and the interface setting of the bi-material structure on the crack propagation path and propagation rate are discussed. The numerical results show that PD method can effectively simulate the whole process of crack propagation and failure characteristics in Ni/Ni3Al bi-material with an interface, and the accuracy of the results is verified by the finite element method. The crack propagation path and failure characteristics strongly depend on the initial location of the pre-crack. Three different crack propagation paths and failure characteristics are found when pre-crack in the Ni phase, Ni3Al phase, and the Ni/Ni3Al interface, respectively. The numerical results also find the interface setting has a significant impact on the crack propagation, when the interface setting with harmonic mean is more capable of hindering crack propagation and reducing crack propagation rate. The present work provides an important reference for the crack propagation and failure of Ni/Ni3Al idealized superalloy and other composites containing complex interfaces.

Analysis of dynamic anti-plane characteristics of a bi-material structure with an interfacial V-notch

To arrive at the dynamic anti-plane characteristics of bi-material structures with an interfacial V-notch, a virtual domain decomposition technique in conjunction with Graf’s addition theorem is employed. External force systems are then appropriately solved using the Green’s function technique and the “conjunction” method. Thereafter, the displacement amplitude of the interfacial V-notch is analytically derived. In continuing, some parametric studies are conducted and the plotted results are methodically explained and discussed. The obtained results reveal that the dynamic response in the interfacial V-notch structure could become significant for small levels of the shear modulus ratio and the wavenumber ratio.

Dynamic anti-plane response of circular inclusion in bi-material structure with interfacial periodic cracks due to the SH wave

This paper investigates the dynamic anti-plane response of the circular inclusion in the bi-material structure with interfacial periodic cracks due to the SH wave. In our analysis, we use the ‘conjunction’ technology and Green’s function method. The bi-material structure consists of two isotropic elastic right-angle domains consisting of a circular elastic inclusion and a series of periodic cracks at the bi-material interface. The periodic cracks are created to satisfy the free conditions of the stresses by using the interface ‘conjunction’ technology. The Green’s functions are also solved to obtain the displacement solutions of the out-place point source loaded on the vertical boundaries of the right-angle plane. The first Fredholm integral equations with unknown force systems are then established based on the continuity conditions at the bi-material interface. As an example, the distributions of the dynamic stress concentration factor (DSCF) around the circular inclusion are obtained and shown graphically. The numerical results indicate that compared with a single crack having periodic cracks strengthens the situation of the dynamic stress concentration around the inclusion.

Detection of fault zone head waves and the fault interface imaging in the Xianshuihe–Anninghe Fault zone (Eastern Tibetan Plateau)

SUMMARY Fault zone head waves (FZHWs) are an essential diagnostic signal that provides high-resolution imaging of fault interface properties at seismogenic depth. In this study, we validate the existence of a bi-material interface in the Xianshuihe–Anninghe Fault (XAF) zone around their intersection and determine the cross-fault velocity contrast. We employ a semi-automatic workflow to detect and pick FZHWs and direct P waves. In addition, to improve the identification ability of potential FZHWs in the automatic picking process, we adopt a ‘forward-detecting and backward-picking’ strategy combining the short-term average/long-term average (STA/LTA) algorithm with a kurtosis detector. The polarization and characteristic periods of the waveforms are then used to manually refine the picks and evaluate the quality. The results indicate that the average velocity contrast along the southern Xianshuihe Fault is 3–5 per cent, with the northeast side characterizing a faster P-wave velocity, in agreement with tomographic results. A systematic moveout between FZHWs and the direct P waves over a 100 km long fault segment reveals a single continuous interface in the seismogenic zone. The single bi-material fault structure might be conducive to the preparation of large earthquakes and further influences the corresponding dynamic rupture processes.

Modelling and verification of a novel bi-material mechanical metamaterial cellular structure with tunable coefficient of thermal expansion

The tunable thermal expansion characteristic of metamaterials is beneficial to solve the problems caused by drastic temperature changes. Here, we propose a novel bi-material mechanical metamaterial cellular structure (NBMCS) that can adjust the coefficient of thermal expansion (CTE). Under some parameters restrictions, the structure can realize the regulation of its CTE in a wide range from -115 ppm/℃ to 83.6 ppm/℃ with Al alloy/Low carbon steel combination. A general thermoelasticity equation that builds the relationship among the temperature, the external force, and the displacement is derived, which is then assembled into a theoretical model of NBMCS. Through theoretical analysis and numerical simulations, the underlying mechanism among the CTE of NBMCS, geometric parameters, elastic modulus ratio, and CTE ratio is revealed. Experiments are carried out based on industrial camera and DIC method, which verify the theoretical modelling. Finally, the tunable range of CTE and elastic modulus for three different material combinations are compared. • A novel metamaterial structure with tunable coefficient of thermal expansion. • A general thermoelasticity equation for the structure is established. • Simulation and experiments are carried out to verify the theoretical modeling.

Load-bearing sandwiched metastructure with zero thermal-induced warping and high resonant frequency: Mechanical designs, theoretical predictions, and experimental demonstrations

Current designs of the metastructure can hardly satisfy the demands of the continuous advancement of space exploration. Thus, a new design strategy for the sandwiched metastructure with zero thermal-induced warping, high load-bearing capability, and high resonant frequency is urgently needed and provided here. The metastructure composed of three layers: the top plate and the lattice filled sandwiched layer in material I, and the bottom plate in material II. Theoretical models are derived via the flexibility method and fixed-point deformation assumption, revealing the dependences of out-of-plane thermal-induced warping, mechanical-thermal stability, and load-bearing capability on the dominated geometrical parameters of the metastructure. The remarkable agreements among theoretical predictions, FEA results, and experimental measurements provide the accuracy of the theoretical model in predicting structural thermal-induced warping. Compared with the bi-material structure without the interlayer, the sandwiched metastructure exhibits a negligible out-of-plane thermal-induced warping, reduced by 99.8% (i.e., 0.042μm/°C). Additionally, high load-bearing capability (i.e., 0.17GPa) and high resonant frequency (i.e., 532.3Hz) of the metastructure are validated by FEAs and experiments. In summary, this metastructure design can significantly improve the thermal-mechanical stability of functional components of the spacecraft.

Tunable thermally bistable multi-material structure

The shape memory effect in polymers and alloys enables programming the response of structures via temperature changes; however, the number of materials exhibiting such memory behavior is limited, their response to thermal load is considerably slow, and programming is required to guide the deformation of shape memory materials. The recently revived structural bistability concept offers a potential to design and program reconfigurable structures. In this study, we introduce a thermally bistable structure that displays an abrupt shape memory effect along with snap-through instability behavior. We demonstrate the effect of the wall stiffness of the structure on the bistability of a mechanically bistable element and its nonlinear response. We utilize the thermal softening behavior of two distinct polymers to design a bistable bimaterial structure that restores its original shape when the environment reaches a specific temperature, referred to as triggering temperature. The results reveal that the triggering temperature can change within a range of 300C by changing the width ratio of the stiff material at the wall from 0 to 0.5 for specific material composition. The proposed concept offers new opportunities to utilize tessellated bistable structures as self-sensing actuators and intelligent deployable structures since they can be designed to reconfigure in response to certain changes in temperature.

Self-adaptive near-field radiative thermal modulation using a thermally sensitive bimaterial structure

The active control of the near-field radiative heat transfer has recently aroused significant attention. The common methods include utilizing phase-change materials, applying external electric or magnetic field and regulating the chemical potential. Herein, we propose a self-adaptive near-field radiative thermal modulation using a thermally sensitive bimaterial structure composed of gold and silicon nitride. Due to the huge differences between their Young's moduli and thermal expansion coefficients, the bimaterial structure has a bending tendency upon a sudden temperature change. The curved surface has a significant influence on the near-field radiative thermal transport, which largely depends on the separation gap between the two spaced objects. Two different bending scenarios are discussed, and the bimaterial structure can both spontaneously recover to its original planar state through self-adaptive thermal regulation. 24-fold and 4.4-fold variations in small-scale radiative heat transfer are demonstrated, respectively, for a 5 °C rise and 1 °C drop of the bimaterial. This work opens avenues for a dynamic and self-adaptive near-field radiative thermal modulation, and a large tuning range is worthy of expectation.

Elastic cloaking for a periodic distribution of parallel finite cracks

We achieve elastic cloaking for a periodic distribution of an infinite number of parallel finite mode III cracks by means of the complex variable method and the theory of Cauchy singular integral equations. The cloaking bimaterial structure is composed of an undisturbed uniformly stressed left half-plane perfectly bonded via a wavy interface to the right half-plane which contains periodic cracks. The original design of the wavy interface and the positions of the periodic cracks are ultimately reduced to the solution of a Cauchy singular integral equation which can be solved numerically.

Determination of stress intensity factors for elements with sharp corner located on the interface of a bi-material structure or homogeneous material

This paper presents a new universal analytical and numerical method allowing for determination of stress intensity factors (SIFs) for notches and cracks located in both a homogeneous and a heterogeneous material. An advantage of the proposed method is that it does not require knowledge of an analytical description of singular stress/displacement fields or connection of SIFs to energy parameters such as energy release factor. In this method, a universal analytical function has been used, which in combination with data obtained using finite element method (FEM) allows for a direct determination of stress intensity factors. One parameter that is necessary to know when using the proposed method is the eigenvalue lambda . The characteristic equation allowing for determination of the eigenvalues for any corner has been given herein. What is more, also a criterion clearly defining the nodes is determined, from which FEM numerical results are implemented to the developed analytical function. In order to verify the proposed method, for a selected group of geometrical and material structures with sharp corner, values of stress intensity factors were determined and compared to data available in the literature. Satisfactory compliance of obtained results with literature ones was found.

Enhanced transmission through a Si-InSb-Si bimaterial subwavelength grating with slits at the terahertz range.

Two groups of grating structures with subwavelength slits, composed of different materials are investigated to realize an extraordinary optical transmission (EOT) phenomenon. We find that the transmittance of a InSb grating at the frequencies corresponding to surface plasmon (SP) excitation is almost zero, which verifies the negative role of SPPs in transmission anomalies. And optical characteristics of these bimaterial grating structures are thoroughly analyzed by the transmittance spectrum and optical field intensity. In addition, the greatly enhanced transmission was achieved by changing the temperature, doping concentration, and the geometrical parameters of the InSb-Si-InSb bimaterial grating structure, and the optimized transmission can reach almost 94%. Besides, it is verified that the position of the peaks is strongly dependent on the depth of the slits. Last, we demonstrate the transmission of the InSb-Si-InSb bimaterial grating is higher than its counterparts, and the collimated beaming effect is also realized through it. These features make this structure an excellent candidate for plasmonic components in all optical and optoelectronic fields.

Temperature sensing performance and calibration of bi-material layer structure: role of material property variation

With the increasing demand of adopting advanced soft materials in MEMS and sensing applications, the material property variation of the soft materials with respect to the varying environmental conditions becomes an important factor to alter the device/sensor performance. In this study, a temperature sensor based on a bi-material layer structure has been adopted to investigate the role of material properties to the temperature sensing performance. Analytical formulations are derived under three different assumptions of the coefficient of thermal expansion (CTE) and Young's modulus of the actuate layer material: (1) a constant, (2) a linear function of temperature, and (3) a nonlinear function of temperature. It is found that the both the magnitude and the linearity of the curvature and deflection with respect to temperature variation have been greatly impacted by the non-constant CTE of the actuate layer material, especially at the low temperature region. However, the curvature and deflection alternation caused by non-constant Young's modulus is negligible at the low temperature region and becomes slightly noticeable when approaching the high temperature limit. Meanwhile, the accuracy of the linear calibration has been evaluated to present the impact of the material properties variation to the sensing performance of the bi-material layer structure. This study brings attention to the MEMS community that correct material assumptions in strength of mechanics theory need to be adopted to accurately predict the nonlinear performance of temperature sensor due to the material property variation. The accuracy of linear calibration needs to be evaluated.

Dynamic stress control of bi-material structure subjected to sawtooth shock pulse based on interface characteristics

This paper focuses on dynamic stress control of bi-material structure under the action of sawtooth shock pulse. The factors that are likely to influence the dynamic stress are studied based on the analytical method. Then two bi-material models and a homogenous material model are investigated through the finite element method. The supplement of tungsten carbide layer could reduce the stress of aluminum alloy significantly are proposed here, while the supplement of polyamides layer, to some extent, enlarge the stress of aluminum alloy. It also suggests that the stress control is related to several key factors - the acoustic impedance, the Poisson's ratio, the ratio of thickness to width of material, the deformation and the wave frequency.

A novel 3D printable multimaterial auxetic metamaterial with reinforced structure: Improved stiffness and retained auxetic behavior

A multimaterial strategy is adopted in combination with the structure innovation to achieve enhanced structural stiffness, and meanwhile, to retain the auxetic behavior for auxetic metamaterials. A bimaterial reentrant structure with additional soft arch-like beams and hinges is proposed, and then investigated using both experimental and simulation approaches. The results indicate that the buckling issue of the beam/wall can be significantly reduced if the strength of the hinge is kept small, and the reduction of auxetic behavior due to increased stiffness can also be minimized. Therefore, the strategy to enhance the design flexibility for auxetic metamaterials is verified.

Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load

The use of fused deposition modeling (FDM) process in the making of the multi-material 3D printed part is adding a new dimension in the area of additive manufacturing technology. This paper highlights the procedures to print bi-material laminate parts with different raster orientation by applying FDM technique and describe its mechanical behaviour using classical laminate theory (CLT). For excellent thermal diffusion and substantial functionalities, polylactic acid (PLA) and polylactic acid carbon black (PLA CB) were selected as feedstock materials for printing bi-material structure. The theoretical in-plane stiffness of 3D printed bi-material laminate parts was calculated by using the philosophy of CLT, and the result was validated against experimental value. Fourier-transform infrared spectroscopy (FTIR) study on feedstock filament materials and 3D printed samples ascertained the cause for molecular degradation in printed parts. Furthermore, at different raster orientation, the average tensile properties like tensile stiffness, ultimate tensile strength(UTS) and breaking strain of 3D printed bi-material laminate parts were investigated and compared with mono-material laminate models. Fractography analysis of failure surfaces of bi-material laminates was done by scanning electron microscope(SEM) to explore the nature of failure under tensile loading.

Scattering of harmonic antiplane shear waves by an arc-shaped interfacial crack in functionally graded annular bi-material guide rail

The dynamic behavior of an arc-shaped interfacial crack in an orthotropic functionally graded annular bi-material structure is investigated. In order for the analysis to be executable, the material properties are assumed to vary with the power function of the radial coordinates. By applying the separation variable method, the boundary value problem of the partial differential equation describing the fracture problem of this article can be transformed into a Cauchy kernel singular integral equation with the unknown jump of displacements across the crack surfaces. The obtained integral equation is solved numerically by Lobatto–Chebyshev collocation method to show the effects of the geometric and physical parameters upon the dynamic stress field near the crack tips.Communicated by Kuang-Hua Chang.

Research on Multiple Griffith Cracks at the Interface of Fine-Grained Piezoelectric Coating/Substrate

The behavior of a fine-grained piezoelectric coating/substrate with multiple Griffith interface cracks under electromechanical loads is investigated. In this work, double coupled singular integral equations are proposed to solve the fracture problems. Both the singular integral equation and single-valued conditions are simplified into an algebraic equation and solved by numerical calculation. Thereby, the intensity factors of electric displacement and stress obtained are used to obtain the expression of the energy release rate. Furthermore, numerical results of the energy release rate with material parameters are demonstrated. Based on the obtained results, it could be concluded that the energy release rate is closely related to the size of the interface cracks and the mechanical-electrical loading. For a bimaterial structure, the fine-grained piezoelectric structure exhibited better material performance compared to the large one.