International Journal of Applied Mechanics

Shape memory alloys (SMAs), known for their unique superelastic effect, exhibit superior mechanical properties compared to traditional materials. In this study, the reproducing kernel particle method (RKPM) is applied to investigate the superelastic effect of the SMAs. A segmented linearization RKPM model is developed to establish the stress–strain relationship for the superelastic effect, and relevant formulas of superelasticity for the SMAs are derived. Finally, the applicability and accuracy of the RKPM in analyzing the superelastic effect of the SMAs are demonstrated through numerical examples.

This paper studied the effects of axially non-uniform material and non-uniform doping on the electro-elastic fields in bent piezoelectric semiconductor beams. The mathematical model is established based on the phenomenological theory of piezoelectric semiconductor and Euler’s beam theory. To solve the governing equations with variable coefficients, the differential quadrature method is adopted. As two representative structures, the pure bending beam and cantilever beam are studied, respectively. From the calculated results, it can be found the varied material properties changed the effective stiffness, as a result, all the field quantities are altered. Meanwhile, the symmetry of all field quantities in a pure bending beam is broken. Considering different Gaussian doping parameters ${\sigma }_n$ and $R_n$, it can be observed that the distribution rule of perturbation carrier density becomes complex. The increment of ${\sigma }_n$ broadens the width of optimum range-producing carriers, however, the increment of $R_n$ describes the moving of the optimum range from left to right. Importantly, the introduction of non-uniform doping breaks the limitation of perturbation carrier density in a cantilever beam with uniform material properties, the maximum value of perturbation carrier density does not appear at the fixed end only. The obtained results could be the guidance in designing high-performance electric devices.

This study investigated the influence of temperature variations on the mechanical and dynamic behaviors of biobased composites incorporating a passive control layer. These composites, which include an external layer made up of Flax/polylactic acid (PLA) and an internal layer of rubber, were manufactured using 3D printing technique. To better understand their mechanical characteristics, bending tests were carried out on samples of Flax/PLA with and without a rubber coating at temperatures ranging from $20^{\circ }$C to $50^{\circ }$C. To evaluate the bending response of the materials under several temperatures settings, three-point bending tests were also conducted on the materials with different viscoelastic layer thicknesses. Additionally, resonance vibration studies were carried out at various temperatures to explore dynamic characteristics like frequencies and damping factors. The analysis of the data revealed the consequences of incorporating a functional rubber layer under diverse circumstances. The results demonstrated that increasing temperatures negatively impacts the mechanical and dynamic characteristics degradation of the composite with the viscoelastic layer. The main objective of this work is that under various thermal settings, passive control layers in biocomposites can display modified mechanical and dynamic behaviors. This understanding of how these biobased composites perform in different environments offers significant context for their possible applications.

A semi-analytical solution is provided to obtain the stress intensity factors (SIFs) of hole-edge cracks with different configurations and the stress fields along the crack propagation direction in an infinite isotropic plane. The complicated solution procedure while using the Muskhelishvili method is improved by expanding an irrational mapping function into an approximate rational function so that singular integral equations could be converted to linear equations. The proposed method used to obtain the SIFs of symmetrical cracks emanating from circular or elliptical holes and a single crack emanating from a circular hole is compared with other methods in the literature. The results show that this method is universal and accurate for hole-edge cracks. In addition, the effects of the lengths of the asymmetrical cracks and the ratio of the semi-axes of the elliptical hole ($a$/$b)$ on the SIFs are studied, which have not been previously reported.

A bladed thin-walled rotor with magnetic bearings in gas turbines has minimal wear to improve the service life. Especially, the rotor system can actively suppress vibrations. Yet, thermal–elastic–magnetic coupling-induced rubbing features of a bladed thin-walled rotor with magnetic bearings are not clear, and blade rubbing behaviors induced by high temperatures always occur in this kind of rotor. This paper establishes a new bladed thin-walled rotor model with distributed electromagnetic actuators to reduce thermoelastic vibrations and develops a solution approach for obtaining the thermal–elastic–magnetic coupling-induced rubbing characteristics of the rotor. The solution approach is verified, and the effectiveness of the distributed electromagnetic actuator model is demonstrated. The magnetic supports require two differential-control actuators at each position to generate the electromagnetic force, due to irregular concave–convex deformations of the rotor. Thereafter blade rub behaviors for the thin-walled rotor system are revealed. Uniform and smaller thermal deformations of the rotor system with the present actuator model avoid tip rub due to preventing thermal energy concentration. With the proper bearing capacity of a single actuator, an adequate number of actuators are required to ensure stability. The proposed theoretical prototype of the bladed thin-walled rotor with distributed electromagnetic actuators prevents blade rubbing caused by high temperatures. The provided solution approach can evaluate the vibration characteristics of a rotating thin-walled rotor with magnetic supports in the high-temperature environment.

Multilayer materials have found extensive application within the aerospace industry due to their notable mechanical attributes. The operational longevity and dependability of such materials are substantially influenced by the performance characteristics of individual layers. In this study, an indentation method was established for employing a weighting function to simultaneously characterize the elastic modulus, hardness and film thickness of tri-layer materials. The results of numerical simulations indicate that incorporating the substrate effect in such an approach allows for precise assessment of the mechanical properties of tri-layer materials with diverse thicknesses. To validate the method, nanoindentation tests were performed using two tri-layer materials (i.e., Al/Cu/304SS and Cu/Al/304SS). Further, according to numerical and experimental data, the proposed model could be reduced to evaluate the mechanical properties of a bilayer material. The present findings demonstrate the effectiveness and applicability of the proposed indentation method in characterizing multilayer materials, facilitating reliable assessment in practical applications.

Nested ring energy absorbers absorb most of the kinetic energy of an impact in an irreversible manner, reducing the damage to the human body or cargo inside the carrier in a collision. Compared to conventional single ring, nested ring can greatly increase the specific energy absorption (SEA) without significantly increasing the cost. This paper proposes a new design idea for the nested ring structure, which forms a new design by rotating the traditional configuration. Since the symmetry is broken, the deformation mode is asymmetric. Both experimental tests and finite element simulations are performed. The experimental results match the simulation results with less than 5% deviation, demonstrating the new design improves energy absorption capacity by 7% compared to previous nested ring designs.

The traditional damping structure usually transfers the vibration energy into heat, dissipated and without harvesting. But for harsh environments, such as military activities and lunar probe patrols, the vibration energy can be extracted, and realize the purpose of self-power condition monitoring. In this paper, a bionic suspension with energy-harvesting property is proposed based on bionic configurations. The bionic suspension adopts a symmetrical three-link arrangement to simulate the arrangement of bones, and a horizontal spring to simulate muscles. The micro-generator embedded in the knee joint provides the main damping force for the overall structure and also plays a role in harvesting energy. The dynamic equation and virtual prototype model are established, and the effects of parameter changes on the performance of vibration reduction and energy harvesting are analyzed, and the relationship between the two is revealed. The results show that the parameters to achieve their respective optimal performance are not consistent in the trend, though it is difficult to obtain the best performance of both, it can be designed according to the specific functions to be satisfied. This structure can be utilized as a general model for vibration reduction and energy harvesting scenarios, providing new ideas for self-powered sensing and condition monitoring configurations.

This work examines an oblique water wave scattering by a rigid floating structure with the consideration of uniform current and no current, in the presence of two porous barriers with distinct height and porous properties placed in front of the structure. The objective is to study the associated reflection and to find means to mitigate the waveload on the floating structure. These barriers are considered at some distance apart from each other. It is assumed that the train of water waves interacts with the porous barriers and the floating structure due to which it undergoes partial reflection. The fluid domain is considered in terms of five distinct sub-regions in each of which the solution of the relevant boundary value problem in terms of the velocity potential is obtained through the employment of the techniques of separation of variables and eigenfunction expansion. The resulting system of equations is obtained by utilizing the matching conditions corresponding to the continuity of mass flux and pressure across each virtual vertical boundary. The roots of the dispersion relation are evaluated and utilized while solving the system of linear equations through a standard matrix technique which gives the unknown coefficients. For understanding the role of the porous barriers, the reflection coefficient and the hydrodynamic forces are evaluated and analyzed. In this context, the impact of the space between these two porous barriers, their height, and the values of the porous-effect parameters are thoroughly examined. It is observed that placing of these barriers at an appropriate distance from each other can substantially mitigate both horizontal force and vertical force acting on the floating structure. This study reveals a periodic nature of the reflection coefficient corresponding to an increase in the distance between the barriers. Further, another important observation is that the reflection coefficient results in an increment as the height of these porous barriers is increased. It, as a result, produces a reduction of the wave forces acting on the floating structure. The study of the oblique wave scattering by the floating structure is extended to the case of the presence of a uniform current. In this case, an enhancement in the reflection coefficient is observed, and subsequently, horizontal and vertical forces on the floating structure decrease. The impact of some other parameters on the reflection coefficient and the forces is also studied, and some observations are recorded. The results are validated against two established results which shows a very close match.

The long-term stability of tunnel structures is significantly influenced by the time-dependent behavior of the surrounding rock. Existing constitutive models often deviated from surrounding deformation due to the anisotropic nature of rock mass. In response, this study introduces a novel reinforced learning fusion constitutive model to accurately capture the time-dependent behaviors of soft rock. The framework and methodologies are first outlined, followed by the instantiation of the constitutive model of Burgers and creep parameters using laboratory testing data. To enhance accuracy, an XGBoost model is trained to reinforce the results of the constitutive model. The reliability of the proposed model is then validated against the original constitutive model and other representative machine learning models. Experimental findings demonstrate the superior characterization ability and stability of the presented reinforced model, where the calculation error reduces by 7.2E−06 at least, and $R^2$ score is improved by at least 1% to others. Consequently, the proposed model is reliable, offering a promising approach to capturing the actual time-dependent behaviors of tunnel surroundings in practical field applications.

In this research, energy absorption characteristics of nested thin-walled aluminum structures with square cross-section have been investigated, and the effect of the three parameters: eccentricity, rotation, and tube aspect ratio on the energy absorption characteristics of the structure has been studied. The properties investigated were the specific energy absorption and crush force efficiency. An aluminum 1050 sheet was used to build the tubes. After making the samples and determining how the tubes were placed with each other, the structures were subjected to quasi-static axial loading. Also, for parametric investigations, the behavior of the structures was simulated using LS-Dyna software. The results showed that the simultaneous effect of the three desired parameters has increased the specific absorbed energy and the crushing force efficiency. When the tubes were at maximum eccentricity, the specific energy absorption and crushing force efficiency increased by reducing the aspect ratio and rotation angle. On average, the best sample’s specific energy absorption and crush force efficiency increased by 41.9% and 22.2%, respectively, compared to the single tube.

In this paper, the equation for computing the maximum Stress Intensity Factor (SIF) of cross-crack under hydraulic-mechanical coupling was derived by the dislocation method and the integral equation, and the influence of cross-crack geometric parameters (branch-crack length, pinch angle, inclination angle) on the interacting SIF was analyzed, and its influence law was obtained. Using the maximum shear and tensile SIF ratio criterion as a basis, the fracture criterion of hydraulic-mechanical coupling cross-crack was established, and the initiation process of hydraulic-mechanical coupled red sandstone cross-crack was predicted (including the cross-crack initiation angle, initiation load, and initiation mechanism). Results showed that for cross-crack with the inclination angle fixed ($\alpha =45^{\circ }$), $K_{\mathrm{\text{I}},k\mathrm{\text{max}}}(𝜃)/K_{\mathrm{\text{Imax}}}^0(𝜃)$ of crack tip C decreases slowly. For cross-crack with change of $a_1/a_2$. $K_{\mathrm{\text{I}},k\mathrm{\text{max}}}(𝜃)/K_{\mathrm{\text{Imax}}}^0(𝜃)$ of crack tip A increases, and crack tip C decreases with $a_1/a_2$. For the cross-crack hydraulic-mechanical coupling test, as the cross-crack angle $\alpha$ grows, the fracture initiation stress first reduces before increasing. Initiation mechanisms are Mode I fracture and initiation angles are usually negative. The hydraulic-mechanical coupling cross-crack initiation criterion is validated by the experimental findings, which align with the expected outcomes.