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A beam formulation based on reproducing kernel particle method (RKPM) for the dynamic analysis of stiffened shell structures is presented in this paper. The kinematic description of a beam is obtained based on the Timoshenko beam theory. By using the principle of virtual power, the governing equations of a three-dimensional beam are derived. To obtain the numerical model of stiffened shell structures, two schemes are adopted: one is model stiffeners by the RKPM beam formulation, the other one is model the entire stiffened shell by the RKPM shell formulation. In the first scheme, the coupling model of RKPM shell and beam formulation is obtained by adding the corresponding quantities in their governing equations. In the second scheme, by determining the support domain of a stress point according to which component the stress point is located, the full shell simulation is achieved. The reliability and accuracy of those two schemes are verified by several numerical examples. [ABSTRACT FROM AUTHOR]

This paper is devoted to analytical and numerical studies of global buckling of a sandwich circular plate. The mechanical properties of the plate core vary along its thickness, remaining constant in the facings. The middle surface of the plate is its symmetrical plane. The mathematical model of the plate is presented. The field of displacements is formulated using the proposed nonlinear hypothesis that generalizes the classical hypotheses. The equations of equilibrium are formulated based on the principle of stationary total potential energy. The proposed mathematical model of the displacements considers the shear effect. The numerical model of the plate is also formulated with a view to verify the analytical one. Numerical calculations are carried out for the chosen family of plates. The values of the critical load obtained by the analytical and numerical methods are compared. The effects of the material properties of the core and the change of the plate radius on the critical load intensity are presented. [ABSTRACT FROM AUTHOR]

Polymer networks usually have many entanglements as well as a finite extensibility due to the uncrossability and the full stretching of the network chains. In this paper, the nonaffine model proposed by Davidson and Goulbourne is adopted to characterize the influence of entanglements and finite extensibility of the polymer chains on the mechanical behavior of hydrogels. The Davidson-Goulbourne model only contains three material parameters and has a simpler mathematical form than the Edwards-Vilgis slip-link model, which is the only model that has been adopted to characterize the influence of entanglements on the swelling deformation of polymeric gels so far. Some benchmark problems such as free swelling, constrained swelling, uniaxial tension, equibiaxial tension in the immersed state and uniaxial compression in the isolated state are analyzed, respectively, based on the new constitutive equations. The results show that entanglements as well as chain extensibility have important influences on the mechanical response of hydrogels. [ABSTRACT FROM AUTHOR]

Under the load conditions of clamping force and riveting force, the part deformation problems are induced in the assembly process. For the component deformation problems of the thin-wall part assembly, in this paper, from the viewpoint of micro-aspect, the fractal theory model is proposed to analyze the relationship between the part deformation, loads, and contact area for rivet-joint parts; the micro-deformation values for different stages are solved and obtained through theoretical analysis. According to the self-similarity of fractal theory model, the change of the micro-convex body for contact surface will be researched to reflect the macro-deformation properties. Through the measuring experiment for thin-wall parts, the actual three-dimensional coordinate value of each measuring point is obtained before and after riveting assembly, and then, the wavelet neural network method (WNNM) is adopted to predict experiment deformation value based on the obtained deformation value after processing the coordinate value through fitting surface method. Hereby, according to the deformation value for every thin-wall part after processing experiment data, the fractal dimension value will be determined based on the fractal statistic method to analyze the deformation status of different stages. Through analysis and comparison, the results show that the variation regularity of deformation value based on two or three fractal deformation stages is well conformed to and similar to the experimental value and prediction value, which also verify the correctness and effectiveness of the theoretical model, and provide a theoretical basis for further research on thin-wall part assembly deformation from a micro-perspective and improving assembly accuracy quality in future. [ABSTRACT FROM AUTHOR]

During the assembly process of CNC machine tool, the assembly dimensions are varied due to the effect of the component deformation caused by gravity. Hence, a mathematical model predicting assembly errors needs to be constructed considering component deformation before tolerance design process. This paper presents an assembly error model of linear axis of CNC machine tool to analyze the effects of component manufacturing error and deformation on axis based on the 3-2-1 localization theory. Thereafter, axis position and angular deviations are calculated under four different conditions, ideal condition, condition considering manufacturing error only, condition considering the effect of structure, and actual condition. At last, the effect of worktable gravity on Y-axis deformation is taken as an example to verify the model. This model can be used to verify the tolerance at tolerance design or to calculate modification amount in assembly process. [ABSTRACT FROM AUTHOR]

In a free-state condition, deformable bodies (or compliant parts) have a significantly different shape than their nominal geometry (CAD model) due to gravity loads and residual stress. Typically, the dimensional metrology of such parts requires a particular approach where expensive and specialized jigs are needed to constrain and follow the component during inspection. This paper proposes a new method to fixtureless inspect deformable bodies by adapting the coherent point drift (CPD) algorithm. This new approach combines the optimization of the smoothness regularization parameters of the CPD powerful non-rigid registration method alongside the Thompson-Biweight statistical test as an identification method to distinguish profile and localization process manufacturing defects from a part's deformation. In other words, a new 'flexible' registration approach that meets the specifications of compliant parts is proposed. The CAD model is smoothly modified to fit the scanned part by minimizing two criteria that belong to deformable bodies. The first criterion is the conservation of the curvilinear distance (isometric transformation). That is to say, the condition that the stretch difference between the original CAD model and the modified one should be very small. The second criterion is the usual minimization of the Euclidean distance between the modified CAD model and its corresponding scanned part. Many case studies were performed on a typical industrial sheet metal which presented profile and localization defects. The estimated values of the defects, as well as their positions, are much closer to their reference ones in most cases, thus reflecting the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Material constitutive model is one of the basic scientific fundamentals for simulation accuracy of high-speed cutting (HSC). A high-speed orthogonal cutting method (HS-OCM) based on the shear slip distance, aided by split Hopkinson pressure bar (SHPB) experiments, is proposed in this paper to obtain the shear slip deformation characteristics in the HSC of 6061-T6 aluminum alloy. The Johnson-Cook (JC) model was modified in three ways according to the variation tendencies of the effect curves of strain hardening, strain rate strengthening, and thermal softening, and an improved material constitutive model was obtained. The simulation validations of the obtained material constitutive models were executed. It was found that the modified JC model improves simulation accuracy, i.e., the maximum simulation errors of the cutting force and cutting temperature are 18.5 and 12.2 %, respectively. The HS-OCM avoids the cutting speed limitation (<700 m/min) of the quick-stop test usually used in conventional OCM and the difficulty of predicting tendency inflection points of the inverse identification method employing a finite element simulation model, and allows the experimental measurement of the deformation characteristics of 6061-T6 aluminum alloy in high-speed (2000 m/min) cutting. During HSC of 6061-T6 aluminum alloy, the shear stress, shear strain rate, and deformation temperature in the primary deformation zone increase with increasing cutting speed, whereas the shear strain decreases. [ABSTRACT FROM AUTHOR]