Impact and Bandgap Characteristics of Periodic Rods With Viscoelastic Inserts and Local Resonators

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Y. Alsaffar ◽  
O. Aldraihem ◽  
A. Baz
Keyword(s):  
Finite Element ◽  
Impact Loading ◽  
Complex Modulus ◽  
Structural Response ◽  
Element Model ◽  
One Dimensional ◽  
Theoretical Predictions ◽  
Finite Element Package ◽  
Viscoelastic Composites ◽  
First Time

Abstract A comprehensive theoretical and experimental study is presented of the bandgap behavior of periodic viscoelastic material (VEM) composites subjected to impact loading. The composites under consideration consist of an assembly of aluminum sections integrated with periodic inserts which are arranged in one-dimensional configurations. The investigated inserts are manufactured either from VEM only or VEM with local resonators (LR). A finite element model (FEM) is developed to predict the dynamics of this class of VEM composites by integrating the dynamics of the solid aluminum sections with those of VEM using the Golla-Hughes-Mctavish (GHM) mini-oscillator approach. The integrated model enables, for the first time, the accurate predictions of the bandgap characteristics of periodic viscoelastic composites unlike previous studies where the viscoelastic damping is modeled using the complex modulus approach with storage modulus and loss factor are assumed constants and independent of the frequency or the unrealistic and physically inaccurate Kelvin–Voigt viscous-damping models. The predictions of the developed FEM are validated against the predictions of the commercial finite element package ansys. Furthermore, the FEM predictions are checked experimentally using prototypes of the VEM composites with VEM and VEM/LR inserts. Comparisons are also established against the behavior of plain aluminum rods in an attempt to demonstrate the effectiveness of the proposed class of composites in mitigation of the structural response under impact loading. Close agreements are demonstrated between the theoretical predictions and the obtained experimental results.

Perforation mechanics of UHMWPE soft ballistic sub-laminate and soft ballistic armor pack: A finite element study

2021 ◽  
pp. 089270572110420
Author(s):  
Bazle Z (Gama) Haque ◽  
John W Gillespie
Keyword(s):  
Finite Element ◽  
Single Layer ◽  
Areal Density ◽  
Element Model ◽  
Transverse Impact ◽  
Free Standing ◽  
Uhmwpe Fibers ◽  
Ballistic Limit Velocity ◽  
Definition Of ◽  
First Time

Soft-ballistic sub-laminate (SBSL) made from ultra-high molecular weight polyethylene (UHMWPE) fibers in [0/90] stacking sequence are the building block of a multi-layer soft-ballistic armor pack (SBAP, aka Soft Armor). A systematic study of the perforation dynamics of a single layer SBSL and several multi-layer SBAPs (2, 3, 4, 8, 16, 24, 32 layers) is presented for the first time in the literature. A previously validated finite element model of transverse impact on a single layer is used to study the perforation mechanics of multi-layer SBAPs with friction between individual layers. Following the classical definition of ballistic limit velocity, a minimum perforation velocity has been determined for free-standing single layer SBSL and multi-layer SBAPs. For the multi-layer SBAPs, complete perforations have been identified as progressive perforation of individual layers through the thickness. The minimum perforation velocities of multi-layer SBAPS is linear with the areal density for the eight (8) layer target and thicker. Large deformation behavior and perforation mechanics of the SBAPs is discussed in detail.

Dynamic Impact Measurements on Crossings, in Free Floating and In-Situ Conditions

2014 ◽  
Author(s):  
M. A. Boogaard ◽  
A. L. Schwab ◽  
Z. Li
Keyword(s):  
Finite Element ◽  
Condition Monitoring ◽  
Impact Loading ◽  
Dynamic Behaviour ◽  
Element Model ◽  
Mode Shapes ◽  
Dynamic Impact ◽  
In Situ Test ◽  
In Situ Conditions

As vibration based condition monitoring requires a good understanding of the dynamic behaviour of the structure, a good model is needed. At the TU Delft a train borne monitoring system is being developed which currently focusses on crossings. Crossings are prone to very fast degradation due to impact loading. In this paper a finite element model of a free floating frog is presented and validated up to a 100 Hz using dynamic impact measurements. The mode shapes of the free floating frog are then also compared to some preliminary results from an in-situ test. This comparison shows that the in-situ frequencies can be up to twice the free floating frequency.

Finite Element Modeling and Advanced Imaging by Instrumented Tap Testing

1999 ◽  
Author(s):  
V. Dayal ◽  
Tanveer A. Choudhary ◽  
D. K. Hsu ◽  
J. J. Peters ◽  
D. J. Barnard
Keyword(s):  
Finite Element ◽  
Structural Response ◽  
Element Model ◽  
Force Response ◽  
Honeycomb Core ◽  
Advanced Imaging ◽  
Tap Test ◽  
Main Emphasis ◽  
Non Destructive ◽  
Composite Face

Abstract Tap test is a very trusted and well used technique for the non-destructive evaluation of composite materials. Conventionally, a coin has been used for the tapping and the inspector listens to the resulting sound. The more advanced force response provides a number which can be correlated to the damage. A finite element model of the test has been developed with full honeycomb features and a dynamic tap is applied. The goal is to measure the reduction in stiffness of the structure due to simulated defects. This could be useful to both the manufacturer, as well as the user, to know the change in the structural response of the structure for a possible pass/fail criteria. We will also present results of an instrumented tap test with scanner. The main emphasis is on the testing of honeycomb core with composite face sheet panels. The results presented show the sensitivity of the tap test on simulated defects in honeycomb panels.

Finite-Element Model of Impact Loading and Deformation of a Flexible Steel Ring-Net Debris-Flow Barrier

2020 ◽  
Vol 21 (3) ◽  
pp. 04020026
Author(s):  
Aliena M. Debelak ◽  
Christopher A. Bareither ◽  
Hussam Mahmoud
Keyword(s):  
Finite Element ◽  
Debris Flow ◽  
Finite Element Model ◽  
Impact Loading ◽  
Element Model ◽  
Ring Net

Evaluation of the CSR-H Sloshing Criterion Using Direct Fluid Structure Calculation

2015 ◽  
Author(s):  
Po-Wen Wang ◽  
Chi-Fang Lee ◽  
Yann Quéméner ◽  
Chien-Hua Huang
Keyword(s):  
Finite Element ◽  
Fluid Dynamic ◽  
Plate Thickness ◽  
Structural Response ◽  
Element Model ◽  
Dynamic Responses ◽  
Interaction Technique ◽  
Time Step ◽  
Fluid Structure ◽  
Structural Rules

The objective of this study was to clarify the theoretical basis of sloshing loads and required plate thickness formulations in the harmonized common structural rules. This study used computational fluid dynamic (CFD) to calculate sloshing loads and used finite element analyses (FEA) to evaluate structural response. The sensitivity of the CFD predictions to the time step and grid size was also investigated. Cargo oil tanks were then selected in a handy size oil tanker and a very large crude carrier to evaluate the longitudinal and transverse sloshing loads on the tank boundaries. The results showed that the sloshing pressures computed at four filling levels were mostly consistent with CSR-H. Afterward, the sloshing pressure produced by CFD was applied to the finite element model by using a fluid-structure interaction technique to obtain the dynamic response of the structure. The dynamic responses were investigated to validate the quasistatic approach for sloshing assessment.

BIOMECHANICAL BEHAVIOUR OF BOVINE SKIN: AN EXPERIMENT-THEORY INTEGRATION AND FINITE ELEMENT SIMULATION

2015 ◽  
Vol 76 (10) ◽  
Author(s):  
Nor Fazli Adull Manan ◽  
Jamaluddin Mahmud ◽  
Aidah Jumahat
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Deformation Behaviour ◽  
Element Model ◽  
Tensile Tests ◽  
Theory Integration ◽  
Element Simulation ◽  
Knowledge Enhancement ◽  
First Time

This paper for the first time attempts to establish the biomechanical characteristics of bovine skin via experiment-theory integration and finite element simulation. 30 specimens prepared from fresh slaughtered bovine were uniaxially stretched in-vitro using tensile tests machine. The experimental raw data are then input into a Matlab programme, which quantified the hyperelastic parameters based on Ogden constitutive equation. It is found that the Ogden coefficient and exponent for bovine skin are μ = 0.017 MPa and α = 11.049 respectively. For comparison of results, the quantified Ogden parameters are then input into a simple but robust finite element model, which is developed to replicate the experimental setup and simulate the deformation of the bovine skin. Results from experiment-theory integration and finite element simulation are compared. It is found that the stress-stretch curves are close to one another. The results and finding prove that the current study is significant and has contributed to knowledge enhancement about the deformation behaviour of bovine skin.

The Calculation of the Rotor Critical Speed of Turbopump

2012 ◽  
Vol 529 ◽  
pp. 220-223 ◽  
Author(s):  
Jun Feng Wang ◽  
Kang Sun
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Critical Speed ◽  
Element Model ◽  
Rotor Dynamics ◽  
Gyroscopic Effect ◽  
One Dimensional ◽  
Dimensional Finite Element ◽  
Shearing Deformation ◽  
Rotor Structure

With the rotor structure ofturbopump, using a one-dimensional finite element method, considering the mass of shaft, gyroscopic effect and influence of shearing deformation,establishedtheone-dimensional rotor dynamics finite element model, calculated its six rank of the critical speed, and compared the gyroscopic effect and mass of shaft to the influence of the critical speed turbopump, and the results show that, considering the mass of shaft there is a slight decrease of critical speed value, and gyroscopic effect on critical speed calculation has a significant effect, therefore, gyroscopic effect must be considered in the design of turbopumps.

Finite element simulation of folding carton erection failure

2007 ◽  
Vol 221 (7) ◽  
pp. 753-767 ◽  
Author(s):  
D M Sirkett ◽  
B J Hicks ◽  
C Berry ◽  
G Mullineux ◽  
A J Medland
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
High Speed ◽  
Element Model ◽  
Machine Material ◽  
Linear Elastic ◽  
Element Simulation ◽  
Packaging Industry ◽  
First Time ◽  
The Eu

In response to recent European Union (EU) regulations on packaging waste, the packaging industry requires greater fundamental understanding of the machine-material interactions that take place during packaging operations. Such an understanding is necessary to handle thinner lighter-weight materials, specify the material properties required for successful processing and design right-first-time machinery. The folding carton industry, in particular, has been affected by the new legislation and needs to realize the potential of computational tools for simulating the behaviour of packaging materials and generating the necessary understanding. This paper describes the creation and validation of a detailed finite element model of a carton during a common packaging operation. The model is applied here to address the problem of carton buckling. The carton was modelled using a linear elastic material definition with non-linear crease behaviour. Air inrush suction, which is believed to cause buckling, was quantified experimentally and incorporated using contact damping interactions. The results of the simulation are validated against high-speed video of carton production. The model successfully predicts the pattern of deformation of the carton during buckling and its increasing magnitude with production rate. The model can be applied to study the effects of variation in material properties, pack properties and machine settings. Such studies will improve responsiveness to change and will ultimately allow end-users to use thinner, lighter-weight materials in accordance with the EU regulations.

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