Yumin He

The Analysis of Curved Beam Using B-Spline Wavelet on Interval Finite Element Method

A B-spline wavelet on interval (BSWI) finite element is developed for curved beams, and the static and free vibration behaviors of curved beam (arch) are investigated in this paper. Instead of the traditional polynomial interpolation, scaling functions at a certain scale have been adopted to form the shape functions and construct wavelet-based elements. Different from the process of the direct wavelet addition in the other wavelet numerical methods, the element displacement field represented by the coefficients of wavelets expansions is transformed from wavelet space to physical space by aid of the corresponding transformation matrix. Furthermore, compared with the commonly used Daubechies wavelet, BSWI has explicit expressions and excellent approximation properties, which guarantee satisfactory results. Numerical examples are performed to demonstrate the accuracy and efficiency with respect to previously published formulations for curved beams.

A Study of Failure Strength for Fiber-Reinforced Composite Laminates with Consideration of Interface

Composite laminates can exhibit the nonlinear properties due to the fiber/matrix interface debonding and matrix plastic deformation. In this paper, by incorporating the interface stress-displacement relations between fibers and matrix, as well as the viscoplastic constitutive model for describing plastic behaviors of matrix materials, a micromechanical model is used to investigate the failure strength of the composites with imperfect interface bonding. Meanwhile, the classic laminate theory, which provides the relation between micro- and macroscale responses for composite laminates, is employed. Theory results show good consistency with the experimental data under unidirectional tensile conditions at both 23°C and 650°C. On this basis, the interface debonding influences on the failure strength of the [0/90]s and [0/±45/90]s composite laminates are studied. The numerical results show that all of the unidirectional (UD) laminates with imperfect interface bonding provide a sharp decrease in failure strength in the plane at 23°C. However, the decreasing is restricted in some specific region. In addition, for [0/90]s and [0/±45/90]s composite laminates, the debonding interface influences on the failure envelope can be ignored when the working temperature is increased to 650°C.

Studying the nonlinear properties and strain-rate sensitivity of SiC short fiber-reinforced Al matrix composites

Abstract Stress-strain analysis has been an interesting issue for the mechanical design of composite structures. In this paper, a three-dimensional mechanical model based on generalized method of cells is presented to study the thermal residual stress and loading rates influence on the mechanical responses of short fiber-reinforced (SFR) composites. The effects of the fiber shape on the elastic constant of the SFR were investigated. To verify the prediction method, the calculated elastic modulus was compared with the results of finite element method. On this basis, a unified constitutive model is used to acquire the nonlinear properties of matrix materials. For comparison, SFR composites with and without consideration of thermal residual stress influences on the nonlinear responses are both considered. The results show that the distinct difference for SFR composites can be found at an early stage of loading. Meanwhile, the thermal residual stress influences on the mechanical behaviors present two characteristic stages.

Crack fault quantitative diagnosis based on finite element of B-spline wavelet on the interval

The model-based forward and inverse problems in the diagnosis of structural crack faults were studied. The forward problem is to solve the natural frequencies through a cracked structural model and the inverse problem is to quantitatively determine the crack parameters using the experimental testing frequencies. Then, the one-dimensional crack element of B-spline wavelet on the interval (BSWI) was built to solve the forward problem. Contour plots of normalized crack location versus normalized crack size were plotted by using the first three natural frequencies as the inputs. The intersection of the three curves predicted the normalized crack location and size. The experimental study verified the validity of the wavelet-based crack element in solving crack singular problems to overcome the disadvantages of the traditional finite element method (FEM), such as low efficiency, insufficient accuracy, slow convergence to correct solutions, etc. At the same time, it had adequate identification precision. The new method can be applied to prognosis and quantitative diagnosis of incipient crack.