Archive of Applied Mechanics最新文献

In computational homogenization approaches, data-driven methods entail advantages due to their ability to capture complex behavior without assuming a specific material model. Within this domain, constitutive model-based and model-free data-driven methods are distinguished. The former employ artificial neural networks as models to approximate a constitutive relation, whereas the latter directly incorporate stress–strain data in the analysis. Neural network-based constitutive descriptions are one of the most widely used data-driven approaches in computational mechanics. In contrast, distance-minimizing data-driven computational mechanics enables substituting the material modeling step entirely by iteratively obtaining a physically consistent solution close to the material behavior represented by the data. The maximum entropy data-driven solver is a generalization of this method, providing increased robustness concerning outliers in the underlying data set. Additionally, a tensor voting enhancement based on incorporating locally linear tangent spaces enables interpolating in regions of sparse sampling. In this contribution, a comparison of neural network-based constitutive models and data-driven computational mechanics is made. General differences between machine learning, distance minimizing, and entropy maximizing data-driven methods are explored. These include the pre-processing of data and the required computational effort for optimization as well as evaluation. Numerical examples with synthetically generated datasets obtained by numerical material tests are employed to demonstrate the capabilities of the investigated methods. An anisotropic nonlinear elastic constitutive law is chosen for the investigation. The resulting constitutive representations are then applied in structural simulations. Thereby, differences in the solution procedure as well as use-case accuracy of the methods are investigated.

This paper aims to present an analysis of the thermo-elastoplastic bending behavior of skew functionally graded (FG) sandwich plates resting on a Winkler/Pasternak foundation, employing a novel three-dimensional (3D) meshless approach. The material properties are assumed to be completely temperature-dependent, and the sandwich plate with FG face sheets and core is exposed to mechanical and thermal loads. The discretized equation systems of nonlinear transient heat conduction and incremental thermo-elastoplasticity are derived using a 3D radial basis reproducing kernel particle approach. The meshless model utilizes a novel high-order kernel that combines Gaussian and cosine functions. The incremental plastic deformation is modeled by the Prandtl–Reuss flow rule along the isotropic hardening von Mises criterion. The results demonstrate excellent agreement when compared with those existing in the literature. The influence of different foundation parameters, skew angles, layer thickness ratios, thickness-to-length ratios, power law exponents, and boundary conditions on the elastoplastic bending behavior of the FG skew sandwich plate is evaluated.

This contribution discusses the influence of different barrier update strategies on the performance and robustness of an interior point algorithm for single-crystal plasticity at small strains. To this end, single-crystal plasticity is first briefly presented in the framework of a primal-dual interior point algorithm to outline the general algorithmic structure. The manner in which the barrier parameter is modified within the interior point method, steering the penalization of constraints, plays a crucial role for the robustness and efficiency of the overall algorithm. In this paper, we compare and analyze different strategies in the framework of crystal plasticity. In a thorough analysis of a numerical example covering a broad range of settings in monocrystals, we investigate robust hyperparameter ranges and identify the most efficient and robust barrier parameter update strategies.

Unlike previous studies that predominantly focused on uni-directional functionally graded materials (FGMs), this work extends the analysis to bi-directional FGM shell panels with various geometries, offering a more comprehensive understanding of their thermal buckling behavior. For the first time, a combination of higher-order shear deformation theory and the p-version finite element method is utilized in this context. Moreover, a novel nonlinear temperature distribution solution derived from the steady-state thermal conduction equation for bi-FGMs is proposed, addressing a significant gap in the existing literature. The investigation explores the effects of curvature, aspect ratio, thickness ratio, and material gradient on the buckling response of shell panels under thermal loading. The study begins with the mathematical formulation of the problem, laying the groundwork for the subsequent analyses. To ensure the accuracy and effectiveness of the custom-made code, a rigorous comparative study is performed. The analysis then extends to examining the impact of material gradient indexes on the shell’s behavior, focusing on variations in buckling temperature rise, mode shapes, and normalized modal stress distribution. Additionally, the investigation includes a comparative analysis of three different types of temperature distributions, considering both temperature-dependent and temperature-independent material scenarios.

A novel lever-type stiffness-based grounded damping dynamic vibration absorber with grounded stiffness is presented in this paper, and the analytical design parameters are derived in detail. At the first, the equations of motion are established and the analytical solution of the primary structure displacement is obtained. It is found that with the introduction of grounded stiffness, the coupled system could be unstable and the stability condition is established. Then, the optimum stiffness ratio, the optimum damping ratio and the optimum grounded stiffness ratio are expressed as the function of mass ratio and lever ratio by minimizing the mean squared displacement response of the primary structure previously established. From the results analysis, the system stability is verified, and it is found that with the change in the lever ratio when the mass ratio is selected, there are three cases for the optimum grounded stiffness ratio, i.e., negative, zero and positive. Thus, for the vibration reduction of primary structure, the proposed dynamic vibration absorber (DVA) with positive grounded stiffness has the best control performance among the three cases. Compared with some typical designed DVAs under harmonic and random excitation, the results show that with the proposed optimum DVA the resonance amplitude and the frequency band of vibration reduction can greatly reduce and broadened, respectively, and the random vibration mitigation can be greatly increased. According to the existing literature, the proposed lever-type stiffness mechanism is justified, which means that the proposed DVA is practical and can be used in many engineering applications.

A novel cooling system for a hot elastic plate is considered by combined utilization of magnetic field, wavy channels and ternary nanofluid. Some applications can be found in electronic cooling, material processing and convective heat transfer control. The elastic object is placed between sinusoidal wavy channels where magnetic field of different strengths is imposed. Ternary nanofluid is used as cooling medium in both channels. Cooling performance assessment is made by various values of Reynolds number (Re, between 250 and 1000), Hartmann number of different channels (Ha, between 0 and 15), amplitude (A, between 0.05 and 0.3) and wave number (N, between 1 and 4) of corrugation, and nanoparticle loading (svf between 0 and 0.03). Entropy generation analysis is also considered. Thermal performance enhancement factor for the maximum and lowest Re configurations in the rigid and elastic object cases are 1.70 and 1.65, respectively. The amount of cooling performance improvement generated by imposing magnetic field at the highest strength is 58.5% and 80% with rigid and elastic objects, respectively. The cooling performance is improved by the wavy form amplitude; however, the wave number relation is non-monotonic. When comparing the wavy channel with the flat one, the increments of thermal performance for stiff and elastic plates are 52% and 57%. Using elastic and stiff objects with nanofluid results in increases in cooling performance of 47.2% and 55.5% when compared to the use of base fluid alone. The best thermal performance is always provided by a rigid item with wavy channels. The least amount of cooling is achieved by using an elastic plate and flat channel. The best options are to increase the magnetic field strength and amplitude of the wavy channel as thermal performance improves and entropy generation drops.

This paper investigates the effects on the behavior of a saturated porous material of an evolving microstructure induced by the mass exchange between the solid and the fluid phases saturating the porous network, using two-scale asymptotic expansions. A thermodynamically consistent model of the fluid physics flowing through the porous network is proposed first, describing microstructure variations to be captured implicitly via the level set method. The two-scale asymptotic expansions method is then applied to obtain an upscaled model capable to account for mass transfer. This last is proven to depend not only on the gradient of the macroscopic forces, such as the fluid pressure and the chemical potential, but also on the average velocity of the solid–fluid interface. Numerical simulations are carried out using the finite element method in order to evaluate the relative weight of the new terms introduced.

In this article, the importance of studying the behavior of small-scale rotating materials and structures is highlighted for its valuable contribution to many scientific and engineering fields. As a result, these types of microbeams have been studied using nonlocal elasticity theory (NET) and modified couple stress (MCST) models, as well as Euler–Bernoulli assumptions for thin beams. The temperature-dependent heat conduction model and the Moore–Gibson–Thompson (MGT) model of heat transfer are also integrated. The effects of nonlocal properties, length scale, thermal conductivity factor fluctuation, the angular velocity of rotation, and thermal parameters on the behavior of the studied variables were investigated. The results were validated and applicable, and the data were systematically compared with previous literature and other investigators. The results show that the materials behave differently at the nanoscale than the results of the usual continuum mechanics approach due to taking into account nonlocal and length-scale effects.

A vehicle’s dynamic load is the force exerted on the tire by the road when the vehicle is in motion. The road is damaged not just by the vehicle’s horizontal and vertical forces, but also by the vertical forces generated by the vehicle’s movement. However, road surface impacts also increase dynamic load and shorten tire life, both of which reduce dynamic safety. This research aims to determine the impact of road condition and vehicle speed on the dynamic load acting on the multi-purpose forest firefighting vehicle. The author created a model using differential equations to describe vehicle vibrations by separating a multi-body system. Using MATLAB software to survey and determine the dynamic load coefficient on the multi-purpose forest firefighting vehicle as it travels over ISO 8608:2016 roads at different speeds. Within the parameters of the standard working speed range, According to ISO standards, the maximum dynamic load factor at the front and the rear left wheel on each of the four types of roads rise in direct proportion to the speed at which the vehicle is moving and the height of the road surface. When a vehicle is traveling at a speed of 25 km per hour on the worst type of road that the author assessed, which was a class E road, the dynamic load coefficient’s maximum value has the following values: maxk_d11 = 2.71, maxk_d31 = 2.75. The rate of travel and the elevation of the roadway both affect the dynamic load coefficient that the vehicle experiences. The findings from the research are going to be used as the foundation for finishing the building of the multi-purpose forest firefighting vehicle.