No abstract

No abstract

This paper introduces a nonlinear finite element analysis on damage propagation behavior of composite sandwich panels under in-plane uniaxial quasi-static compression after a low velocity impact. The major damage modes due to the impact, including the residual indentation on the impacted facesheet, the initially crushed core under the impacted area, and the delamination are incorporated into the model. A consequential core crushing mechanism is incorporated into the analysis by using an element deactivation technique. Damage propagation behavior, which corresponds to those observed in sandwich compression after impact (SCAI) tests, has been successfully captured in the numerical simulation. The critical far field stress corresponding to the onset of damage propagation at specified critical locations near the damage zone are captured successfully. They show a good correlation with experimental data. These values can be used to effectively predict the residual compressive strength of low-velocity impact damaged composite sandwich panels.

Traditional bearing design neglects the influence of elastic deformation of materials on bearing lubrication characteristics, based on a new type of polymer composite water-lubricated bearing materials, the influence of elastic deformation of bearing material is introduced into the simulation. The lubrication performance of the water-lubricated bearings is studied with respect to material parameters and structural parameters. The effects of the elastic deformation on the lubrication characteristics such as the maximum pressure value and the minimum film thickness were compared and analyzed under different bearing clearance structures of a certain type of stern bearings. The results show that, the maximum water film pressure of bearing increases with the clearance ratio, and the maximum water film pressure of elastic bearing is less than that of rigid bearing. With the increase of clearance ratio, the elastic deformation of bearing increases linearly. The increase of bearing elastic deformation results in the difference between minimum water film thickness and maximum water pressure between the elastic bearing and rigid bearing.

A microstructure-based homogenization model is proposed for simulating the cyclic plasticity and predicting the low-cycle fatigue (LCF) crack initiation life of GH4169 superalloy. Classical crystal plastic model (CPM) with a simple softening model is used at the grain level. Then, the transition from grain level to polycrystal level is based on the conservation of virtual work between the two levels. The Eshelby's formulation is applied in the model. Especially, local influences of grain interactions are considered by introducing the external Eshelby's tensor. Relatively precise macroresults and microresults as the finite element method can be provided by the present model with less computational cost. Grain volume averaged fatigue indicator parameters (FIPs) with considering the effect of inclusions are formed to predict the LCF crack initiation life, and a fold-line fitting model is proposed to substitute for the cycle-by-cycle simulation. Predicted lives fit well with the experimental data for both the strain loading and stress loading simulations. Scatter of the life can also be predicted by the model and overwhelming influences of the incubation stage on the variability of LCF initiation life can be captured. It is shown that the inclusions and the inhomogeneous plastic strain are responsible for the scatter of the incubation stage.