410 research outputs found
Crushing Modes of Aluminium Tubes under Axial Compression
A numerical study of the crushing of circular aluminium tubes with and without aluminium foam fillers has been carried out to investigate their buckling behaviours under axial compression. A crushing mode classification chart has been established for empty tubes. The influence of boundary conditions on crushing mode has also been investigated. The effect of foam filler on the crushing mode of tubes filled with foam was then examined. The predicted results would assist the design of crashworthy tube components with the preferred crushing mode with the maximum energy absorption
Contact pressure and wear in sheet metal forming - an FEM analysis
Wear is the principal cause of tool failure in most sheet metal forming processes. It is well known that the contact pressure between the blank and the tool has a large influence on the wear of the tool, and hence the tool life. This investigation utilises the finite element method to analyse the contact pressure distribution over the die radius for a particular deep drawing process. Furthermore, the evolution of the predicted contact pressure distribution throughout the entire stroke of the punch is also examined. It was found that the majority of the process shows a steady state pressure distribution, with two characteristic peaks over the die radius, at the beginning and end of the sheet contact area. Interestingly, the initial transient contact pressure response showed extremely high localised peak pressures; more than twice that of the steady state peaks. Results are compared to wear reported in the literature, during similar experimental deep drawing processes. Finally, the significance and effect of the results on wear and wear-testing techniques are discussed.<br /
Infinitely many solutions for the Schrödinger equations in RN with critical growth
AbstractWe consider the following nonlinear problem in RN(0.1){−Δu+V(|y|)u=uN+2N−2,u>0, in RN;u∈H1(RN), where V(r) is a bounded non-negative function, N⩾5. We show that if r2V(r) has a local maximum point, or local minimum point r0>0 with V(r0)>0, then (0.1) has infinitely many non-radial solutions, whose energy can be made arbitrarily large. As an application, we show that the solution set of the following problem−Δu=λu+uN+2N−2,u>0 on SN has unbounded energy, as long as λ<−N(N−2)4, N⩾5
A new Speech Feature Fusion method with cross gate parallel CNN for Speaker Recognition
In this paper, a new speech feature fusion method is proposed for speaker
recognition on the basis of the cross gate parallel convolutional neural
network (CG-PCNN). The Mel filter bank features (MFBFs) of different frequency
resolutions can be extracted from each speech frame of a speaker's speech by
several Mel filter banks, where the numbers of the triangular filters in the
Mel filter banks are different. Due to the frequency resolutions of these MFBFs
are different, there are some complementaries for these MFBFs. The CG-PCNN is
utilized to extract the deep features from these MFBFs, which applies a cross
gate mechanism to capture the complementaries for improving the performance of
the speaker recognition system. Then, the fusion feature can be obtained by
concatenating these deep features for speaker recognition. The experimental
results show that the speaker recognition system with the proposed speech
feature fusion method is effective, and marginally outperforms the existing
state-of-the-art systems
Implementing a structural continuity constraint and a halting method for the topology optimization of energy absorbers
Crack propagation in non-homogenous materials: Evaluation of mixed-mode SIFs, T-stress and kinking angle using a variant EFG method
Uncertain Dynamic Characteristic Analysis for Structures with Spatially Dependent Random System Parameters
This work presents a robust non-deterministic free vibration analysis for engineering structures with random field parameters in the frame of stochastic finite element method. For this, considering the randomness and spatial correlation of structural physical parameters, a parameter setting model based on random field theory is proposed to represent the random uncertainty of parameters, and the stochastic dynamic characteristics of different structural systems are then analyzed by incorporating the presented parameter setting model with finite element method. First, Gauss random field theory is used to describe the uncertainty of structural material parameters, the random parameters are then characterized as the standard deviation and correlation length of the random field, and the random field parameters are then discretized with the Karhunen–Loeve expansion method. Moreover, based on the discretized random parameters and finite element method, structural dynamic characteristics analysis is addressed, and the probability distribution density function of the random natural frequency is estimated based on multi-dimensional kernel density estimation method. Finally, the random field parameters of the structures are quantified by using the maximum likelihood estimation method to verify the effectiveness of the proposed method and the applicability of the constructed model. The results indicate that (1) for the perspective of maximum likelihood estimation, the parameter setting at the maximum value point is highly similar to the input parameters; (2) the random field considering more parameters reflects a more realistic structure
Investigation of a hydraulic impact: a technology in rock breaking
The finite element method and dimensional analysis have been applied in the
present paper to study a hydraulic impact, which is utilized in a non-explosive
rock breaking technology in mining industry. The impact process of a high speed
piston on liquid water, previously introduced in a borehole drilled in rock, is
numerically simulated. The research is focused on the influences of all the
parameters involved in the technology on the largest principal stress in the
rock, which is considered as one of the key factors to break the rock. Our
detailed parametric investigation reveals that the variation of the isotropic
rock material properties, especially its density, has no significant influence
on the largest principal stress. The influences of the depth of the hole and
the depth of the water column are also very small. On the other hand,
increasing the initial kinetic energy of the piston can dramatically increase
the largest principal stress and the best way to increase the initial kinetic
energy of the piston is to increase its initial velocity. Results from the
current dimensional analysis can be applied to optimize this non-explosive rock
breaking technology
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