International Journal of Mechanics and Materials in Design最新文献

The performances of a hydrostatic bearing using the tapered-spool restrictors with appropriate design parameters is superior to other types of pressure compensation, that is the largest stiffness obtained under the lowest power consumption of supplying lubricant. However, the determination of design parameters is difficult, moreover, the simplification of the calculation formula will cause errors. Therefore, this study presents a method for identifying actual design parameters of the single‐action tapered-spool restrictor for actant values. Also, the influences of design parameters on the relationships between flow rate and pressure drop of this type restrictors are studied by both theoretical and experimental analyses. There are three design parameters that affect the characteristics of the tapered-spool restrictor, namely restriction parameter, compliance parameter, and restriction length ratio. Since both compliance parameter and restriction length ratio are functions of supply pressure, design parameters of a restrictor are determined simultaneously by solving a set of identification equations individually for the nominal value of each supply pressure. These identification equations are obtained by minimizing the sum of squared errors between the actual flow rate measured from experimental data and the flow rate calculated from the identification equations. Additionally, the advantages of the tapered-spool restrictors compared with other pressure compensation methods as well as the difficulties and errors in calculating design parameters are further elaborated in this study. Therefore, in order to design the appropriate parameters to match the hydrostatic bearing, the design parameters need to be identified when designing and calibrating such restrictors.

The planar maneuvering mechanism’s motion accuracy and dynamic performance are critical for aero-engine power adjustment and vibration reduction. The uncertain clearance tolerances in the revolute joints lead to uncertainty in the joint contact characteristics and the mechanism’s dynamic performance. The combination of multiple joints’ clearance tolerances can be rationally designed and selected to balance the economy of joint manufacturing and the reliability of mechanism performance. In this paper, the uncertainty relationship between clearance tolerances of the joints and mechanism characteristics is investigated by using fuzzy sets and fuzzy algorithms. A new conformal contact model is established to accurately evaluate the contact forces of the revolute joint containing small clearance, which is demonstrated to have better performance when the joint clearance is small by comparing with two traditional models. The mechanism’s dynamic model is constructed, which introduces the contact forces and dissipation effect of multiple joints. Then, the fuzzy distribution and the fuzzy decomposition theory are applied to represent and grade clearance tolerance, respectively. The uncertain static contact characteristic of the joint is studied at different clearance tolerances by using the fuzzy transformation method, and the corresponding clearance tolerances can be designed and selected according to the specific required elastic contact force. Meanwhile, the uncertainty mapping relationship between the clearance tolerance of multiple joints and mechanism dynamic performance is also established, and the combination of multiple joints’ clearance tolerances can be rationally selected based on the evaluation results of uncertain dynamic performance. The proposed method provides a significant reference to realize the specified mechanism’s performance requirement by designing the joint clearance tolerance.

This study presents an efficient numerical approach for pseudo-lower bound limit analysis of structures. The total stress field is decomposed into two components: an elastic component associated with the safety factor and a self-equilibrating residual component. Subsequently, equilibrium conditions within the optimization problem are satisfied in a weak manner. The application of the adaptive quadtree edge-based smoothed finite element method (ES-FEM), combined with the transformation into the second-order cone programming (SOCP) form, ensures the resulting optimization problem remains minimal in size. Moreover, employing a yield stress-based adaptive strategy in the proposed procedure either accurately provides limit loads with low computational effort or effectively predicts the collapse mechanism through the concentration of elements after mesh refinement progress. The investigation of a series of numerical tests confirms the effectiveness and reliability of the proposed method.

Engineering cementitious composites (ECC) are widely used in concrete structures for resisting impact loads. This paper establishes a peridynamics (PD)-based model for impact crack propagation in ECC, incorporating a failure criterion considering the strain rate effect, to investigate the damage behavior of ECC under impact loading. Firstly, an improved prototype microelastic brittle material (PMB) model considering the strain softening stage is used to model the cementitious matrix of ECC, and the fibers are modeled as one-dimensional rod to establish a PD fully-discrete model of ECC. At the same time, an interface exponential friction attenuation model is introduced. Then, the effectiveness of the model and the PD impact contact algorithm incorporating the strain rate effect was validated through simulations of the four-point bending test on ECC rectangular plates and the drop hammer impact test on plain concrete beams. Finally, the effects of pre-cracks-to-span distance, fiber content, fiber aspect ratio, different strain rate, and impact velocity on the crack propagation and structural deflection of ECC beams under impact loading are investigated.

Spinodoid topologies are bicontinuous porous microstructures inspired by the natural spinodal decomposition process. They offer a vast design space and are capable of representing anisotropic topologies, which makes them suitable for use in biomedical applications. This work focuses on some fundamental aspects in spinodoid microstructures. As the first, the extent of anisotropy is computed by a universal index and its correlation with spinodoid design parameters, including relative density and the three cone angles, is investigated. In order to do this, the k-means clustering method is utilized to group the topologies based on their level of anisotropy. Within each cluster, the relationship between the statistical features of the design parameters and the extent of anisotropy is analyzed in detail. As one of the findings, it is revealed that topologies created by larger cone angles will lie in low anisotropy category. Although the sensitivity analysis indicates that all the cone angles are equally important in determining the elasticity tensor elements, our findings demonstrate that there are some discrepancies in the probability density function of cone angles in topologies with high anisotropy. In addition, the results show that lower relative densities tend to lead to higher anisotropy in the structures regardless of cone angle values. In the second stage of this work, a data-driven framework for inverse design is proposed. This approach involves generating high-quality samples and utilizing an efficient data-driven framework capable of handling unequal queries. It can identify multiple spinodoid candidates for a desired elasticity tensor, rather than just one. This approach has great advantages, especially in manufacturing, where different topologies may have varying manufacturing costs. This provides designers with more choices to select from. In the final stage, we estimated the statistical distribution of the elasticity tensor components for the generated spinodoid topologies. By measuring the Mahalanobis distance between a query and the estimated distribution, one can determine whether the query belongs to the property space of spinodoid topologies or not. This approach allows for assessing the similarity or dissimilarity of a query to the distribution of the generated spinodoid topologies.

This paper presents the quasi-static free inversion behavior of a new conical tube absorber. The absorber is composed of a multi-component conical tube with a spherical end cap and varying lengths and diameters. When this structure undergoes an axial load, each tube component freely inverts inside the next component like a telescope. Finite element (FE) models were made using ABAQUS explicit code to simulate the deformation and energy absorption of multi-component conical tubes. To verify the accuracy of the FE models, they were validated with experimental tests. As a general framework for a design optimization study, structural parameters such as wall thickness, cap radius, and edge length of the absorber affect the initial peak load and specific energy absorption. To achieve the optimal design for the multi-component conical tube, mathematical models were developed using the response surface method, and the multi-objective optimization procedure was applied to find the optimal values for the design variables. The results of the multi-objective optimization demonstrated improvements in both objective functions compared to existing designs. Specifically, by increasing the cap radius and decreasing the edge length, the initial peak load was reduced, while increasing the wall thickness the specific energy absorption was enhanced.

Abstract

Vibration characteristics for rotating thin shallow shell blades reinforced with functionally graded graphene platelets (FGGP) under the axial force are conducted. The blade is modeled as four twisted cantilever thin shallow shells, each with a unique shape cylindrical shallow shell panel with a straight or curved boundary as the cantilever side, spherical shallow shell panel and hyperbolic parabolic shallow shell panel. The Halpin–Tsai model, the first-order shear deformation theory and the Rayleigh–Ritz method are used to calculate the frequencies and mode shapes of the blade. The results are validated by comparing them with previous literature and ANSYS. An analysis is conducted on a range of parameters, encompassing graphene properties, rotational velocity, torsional angle, curvature radius, aspect ratio and axial forces, in order to assess their influence on the vibrational properties of the blade. The vibration behaviors of a rotating cylindrical shallow shell panel with a straight cantilever edge are found to be distinctive. The findings indicate that the blade’s stiffness is significantly higher when reinforced with FGGP-X compared to FGGP-U distribution, with FGGP-O distribution exhibiting the lowest stiffness. Furthermore, the study implies that a total layer count exceeding ten has a negligible impact on the degree of graphene distribution. Finally, the study concludes that the curvature and graphene distribution pattern significantly influence the vibration characteristics of the blade.