Local Strain and Stress Calculation Methods of Irregular Honeycombs Under Dynamic Compression

2016 ◽  
Author(s):  
Jilin Yu ◽  
Peng Wang ◽  
Shenfei Liao ◽  
Zhijun Zheng
Keyword(s):  
Shock Wave ◽  
Wave Speed ◽  
Local Strain ◽  
Cellular Materials ◽  
Shock Model ◽  
Cross Sectional ◽  
One Dimensional ◽  
Loading Direction ◽  
Shock Models ◽  
The One

Several continuum-based shock models have been proposed to understand the dynamic compressive behavior of cellular materials, but they are mainly based on the quasi-static stress–strain relation and thus lack sufficient dynamic stress–strain information. A virtual ‘test’ of irregular honeycombs under constant-velocity compression is carried out using the finite element method. A method based on the optimization of local deformation gradient by using the least square method is employed to calculate the one-dimensional strain distribution in the loading direction of the specimen. Meanwhile, a method based on the cross-sectional engineering stress is developed to obtain the one-dimensional stress distribution in the loading direction. The two typical features of cellular materials under dynamic crushing, namely deformation localization and strength enhancement, can be characterized by the strain and stress distributions, respectively. The results also confirm the existence of plastic shock front propagation in cellular structures under high-velocity impact, from which the shock wave speed can be estimated. The shock wave speed obtained from the local strain field method coincides with that from the cross-sectional stress method. The results of shock wave speed are also compared with those predicted by continuum-based shock models. It is shown that the shock wave speed predicted by the R-PP-L (rate-independent, rigid–perfect plastic–locking) shock model or the R-LHP-L (rate-independent, rigid–linearly hardening plastic–locking) shock model is overestimated, but that predicted by the R-PH (rate-independent, rigid–plastic hardening) shock model is close to those obtained from the local strain and cross-sectional stress calculations using the cell-based finite element model.

scholarly journals Shock wave speed and stress-strain relation of aluminium honeycombs under dynamic compression

2018 ◽  
Vol 183 ◽  
pp. 01047
Author(s):  
Peng Wang ◽  
Jun Zhang ◽  
Haiying Huang ◽  
Zhijun Zheng ◽  
Jilin Yu
Keyword(s):  
Shock Wave ◽  
Impact Velocity ◽  
Wave Speed ◽  
Dynamic Compression ◽  
Stress Strain ◽  
One Dimensional ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
The One ◽  
The Impact

The propagation of layer-wise crushing bands in cellular materials under dynamic impact can be described by the plastic shock wave model. A cell-based finite element model of irregular aluminum honeycomb is constructed to carry out several constant-velocity compression tests. The shock wave speed is obtained by the one-dimensional stress distribution in the specimen along the loading direction. The relation between the shock wave speed and impact velocity is obtained and analyzed. It is found that the relation tends to be linear with the increase of the impact velocity. But the shock wave speed tends to be a constant value with the decrease of the impact velocity. A piecewise model is proposed to describe the dynamic stress-strain relation of aluminum honeycombs based on a piecewise hypothesis of the relation between the shock wave speed and the impact velocity together with the one-dimensional shock wave theory. Different stress-strain relations corresponding to different impact velocity regions and different deformation modes are obtained.

Reliability assessment of system under a generalized cumulative shock model

2019 ◽  
Vol 234 (1) ◽  
pp. 129-137 ◽  
Author(s):  
Min Gong ◽  
Serkan Eryilmaz ◽  
Min Xie
Keyword(s):  
Reliability Assessment ◽  
Shock Model ◽  
External Shocks ◽  
Phase Type Distribution ◽  
Internal Factors ◽  
Reliability Characteristics ◽  
Shock Models ◽  
The One ◽  
Random Shocks ◽  
Real Practice

Reliability assessment of system suffering from random shocks is attracting a great deal of attention in recent years. Excluding internal factors such as aging and wear-out, external shocks which lead to sudden changes in the system operation environment are also important causes of system failure. Therefore, efficiently modeling the reliability of such system is an important applied problem. A variety of shock models are developed to model the inter-arrival time between shocks and magnitude of shocks. In a cumulative shock model, the system fails when the cumulative magnitude of damage caused by shocks exceed a threshold. Nevertheless, in the existing literatures, only the magnitude is taken into consideration, while the source of shocks is usually neglected. Using the same distribution to model the magnitude of shocks from different sources is too critical in real practice. To this end, considering a system subject to random shocks from various sources with different probabilities, we develop a generalized cumulative shock model in this article. We use phase-type distribution to model the variables, which is highly versatile to be used for modeling quantitative features of random phenomenon. We will discuss the reliability characteristics of such system in some detail and give some clear expressions under the one-dimensional case. Numerical example for illustration is also provided along with a summary.

Verification of a Finite Element Method for Solving One-Dimensional Equations of Blood Flow Incorporating a Viscoelastic Wall Model

2009 ◽  
Author(s):  
Rashmi Raghu ◽  
Charles A. Taylor
Keyword(s):  
Blood Flow ◽  
Surgical Planning ◽  
Computational Cost ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Cross Sectional ◽  
One Dimensional ◽  
The One ◽  
Modeling Flow ◽  
Three Dimensional Simulations

The one-dimensional (1-D) equations of blood flow consist of the conservation of mass equation, balance of momentum equation and a wall constitutive equation with arterial flow rate, cross-sectional area and pressure as the variables. 1-D models of blood flow enable the solution of large networks of blood vessels including wall deformability. Their level of detail is appropriate for applications such as modeling flow and pressure waves in surgical planning and their computational cost is low compared to three-dimensional simulations.

scholarly journals Shock Initiation of a Satellite Tank under Debris Hypervelocity Impact

2019 ◽  
Vol 9 (19) ◽  
pp. 3957
Author(s):  
Zhao ◽  
Zhao ◽  
Cui ◽  
Wang
Keyword(s):  
Shock Wave ◽  
Power Density ◽  
Wave Theory ◽  
Hypervelocity Impact ◽  
Shock Initiation ◽  
One Dimensional ◽  
Minimum Power ◽  
Shock Wave Pressure ◽  
The One ◽  
Debris Impact

For the risk assessment of a satellite to determine whether the satellite tank explodes under the hypervelocity impact, the Walker–Wasley criterion is selected to predict the shock initiation of the satellite tank. Then, the minimum power density of liquid hydrazine is determined based on the tests, the expressions of shock wave pressure and pressure duration are constructed based on the one-dimensional wave theory, and the initiation criterion for the liquid hydrazine tank is established. Finally, numerical simulation and the initiation criterion are adopted to calculate the power density in the satellite tank under the debris impact at the velocity of 10 km/s. The calculated power density agrees well with the simulated power density, they are both larger than the minimum power density, demonstrating that the shock wave generated by the hypervelocity impact is sufficient to trigger an explosion in the satellite tank.

scholarly journals Inverse scattering for the one-dimensional Helmholtz equation with piecewise constant wave speed

2020 ◽  
Vol 36 (7) ◽  
pp. 075008 ◽  
Author(s):  
Sophia Bugarija ◽  
Peter C Gibson ◽  
Guanghui Hu ◽  
Peijun Li ◽  
Yue Zhao
Keyword(s):  
Helmholtz Equation ◽  
Inverse Scattering ◽  
Wave Speed ◽  
Piecewise Constant ◽  
One Dimensional ◽  
The One

One-Dimensional Density Distributions of Powder Media in Dies Subjected to Multishock Compactions

1988 ◽  
Vol 110 (4) ◽  
pp. 355-360 ◽  
Author(s):  
Y. Sano
Keyword(s):  
Shock Wave ◽  
Density Distribution ◽  
Friction Force ◽  
The Other ◽  
Wall Friction ◽  
Uniform Density ◽  
Simple Type ◽  
One Dimensional ◽  
Density Distributions ◽  
The One

A theoretical attempt to clarify the reason why the compacts of powder media have uniform density distributions as the density of the compacts becomes high, is made for the compaction of the copper powder medium of a simple type by punch impaction. Based on the one-dimensional equation of motion including the effect of die wall friction force, there are two main factors which influence the density distribution of the medium during the compaction process; one is the propagation of the shock wave passing through the medium, while the other is the friction force between the circumferential surface of the medium and the die wall. The equation reveals that the effect of the force increases little as the density becomes high as a result of the repetitive traveling of the shock wave between the punch and plug. The propagation or more definitely the repetitive traveling, on the other hand, increasingly unformalizes the density distribution during the process as the number of the traveling increases. Owing to the aforementioned effects of the two factors on the density distribution during the process, the high density compacts become uniform.

Theoretical and experimental investigations of the reflexion of normal shock waves with vibrational relaxation

1967 ◽  
Vol 30 (1) ◽  
pp. 51-64 ◽  
Author(s):  
N. H. Johannesen ◽  
G. A. Bird ◽  
H. K. Zienkiewicz
Keyword(s):  
Shock Wave ◽  
Vibrational Relaxation ◽  
Experimental Investigations ◽  
Rayleigh Line ◽  
Dimensional Problem ◽  
Density Measurements ◽  
Wave Characteristic ◽  
One Dimensional ◽  
The One ◽  
Theoretical Results

The one-dimensional problem of shock-wave reflexion with relaxation is treated numerically by combining the shock-wave, characteristic, and Rayleigh-line equations. The theoretical results are compared with pressure and density measurements in CO2, and the agreement is found to be excellent.

A Finite-Element Simulation of Pulsatile Flow in Flexible Obstructed Tubes

1982 ◽  
Vol 104 (2) ◽  
pp. 119-124 ◽  
Author(s):  
E. Rooz ◽  
D. F. Young ◽  
T. R. Rogge
Keyword(s):  
Finite Element ◽  
Pulsatile Flow ◽  
Continuity Equation ◽  
Element Model ◽  
Momentum Equation ◽  
Cross Sectional ◽  
One Dimensional ◽  
Element Simulation ◽  
The One

A finite-element model for pulsatile flow in a straight flexible partially obstructed tube is developed. In the unobstructed sections of the tube the model considers the continuity equation, the one-dimensional momentum equation, and an equation of state relating tube cross-sectional area to pressure. For the obstructed region, a nonlinear relationship between the flow and the pressure drop across the stenosis is considered. The applicability of a model is checked by comparing predicted flow and pressure waveforms with corresponding in-vitro experimental measurements obtained on a mechanical system. These comparisons indicate that the model satisfactorily predicts pressures and flows under variety of frequencies of oscillation and stenosis severities.

Sign in / Sign up

Export Citation Format

Share Document