In-Vacuo Modal Dynamic Response of the Human Skull

1974 ◽  
Vol 96 (2) ◽  
pp. 490-494 ◽  
Author(s):  
R. E. Nickell ◽  
P. V. Marcal
Keyword(s):  
Shell Element ◽  
Element Model ◽  
General Purpose ◽  
Element Formulation ◽  
Human Skull ◽  
Natural Modes ◽  
Modes Of Vibration ◽  
Doubly Curved ◽  
Insight Into ◽  
Good Agreement

A finite element model of a human skull is analyzed in order to determine the lowest natural modes of vibration. A doubly curved, triangular, thin shell element formulation is used, within the framework of a general-purpose program, to investigate the effect of various support systems on the frequencies and modal shapes. The frequencies are found to be in good agreement with the results of other investigators and the modal shapes offer some insight into a modified theory of craniocerebral damage that includes both skull rotation and cavitation as pathogenic mechanisms.

scholarly journals Dynamic testing of a modern concrete bridge

1979 ◽  
Vol 6 (3) ◽  
pp. 447-455 ◽  
Author(s):  
J. H. Rainer ◽  
G. Pernica
Keyword(s):  
Natural Frequencies ◽  
Dynamic Testing ◽  
Dynamic Properties ◽  
Mode Shapes ◽  
Total Width ◽  
Concrete Bridge ◽  
Reinforced Concrete Bridge ◽  
Natural Modes ◽  
Modes Of Vibration ◽  
Good Agreement

A posttensioned reinforced concrete bridge, slated for demolition, was tested to obtain its dynamic properties. The 10 year old bridge consisted of a continuous flat slab deck of variable thickness having a total width of 103 ft (31.39 m) and spans of 28 ft 6 in. (8.69 m), 71 ft 0 in. (21.64 m), and 42 ft 6 in. (12.95 m). The entire bridge was skewed 10°50′ and the deck was slightly curved in plan.The mode shapes, natural frequencies, and damping ratios for the lowest five natural modes of vibration were determined using sinusoidal forcing functions from an electrohydraulic shaker. These modes, located at 5.7, 6.4, 8.7, 12.0, and 17.4 Hz, were found to be highly dependent on the lateral properties of the bridge deck. Damping ratios were determined from the widths of resonance peaks. The modal properties from the steady state excitation were compared with those obtained from measurements of traffic-induced vibrations and good agreement was found between the two methods.

Implementation and Validation of a 4-Node Shell Finite Element

2014 ◽  
Author(s):  
Marco Morandini ◽  
Pierangelo Masarati
Keyword(s):  
Fluid Dynamics ◽  
Shell Element ◽  
General Purpose ◽  
Flapping Wing ◽  
Element Formulation ◽  
Dynamics Analysis ◽  
Dynamic Problems ◽  
Aerial Vehicles ◽  
Shell Finite Element ◽  
Natural Strains

This paper discusses the formulation and implementation of a 4-node C0 shell element within a general-purpose multibody formulation. A geometrically consistent set of strains and curvatures, defined in a co-rotational framework, is augmented by Enhanced Assumed Strains (EAS) and Assumed Natural Strains (ANS), to alleviate shear and membrane locking. The shell element formulation is validated by solving several static and dynamic problems from the open literature. The proposed element has been successfully used for the coupled structural and fluid-dynamics analysis of flapping wing micro-aerial vehicles.

A Modified Shell Element Model Combined with Yld91 Yield Function in Simulating Aluminum Alloy Applied Hydroforming

2015 ◽  
Vol 639 ◽  
pp. 435-442 ◽  
Author(s):  
Fei Fei Zhang ◽  
Jun Chen ◽  
Jie Shi Chen ◽  
Xin Hai Zhu ◽  
Shi Jian Yuan
Keyword(s):  
Normal Stress ◽  
Fe Simulation ◽  
Applied Pressure ◽  
Shell Element ◽  
Material Model ◽  
Element Model ◽  
Yield Function ◽  
Element Formulation ◽  
Thickness Direction ◽  
Forming Process

Hydroforming has been used widely across many industrial fields. Large applied pressure during hydroforming makes it necessary to consider the influence of normal stress in the thickness direction, while in FE simulation, the use of traditional shell element based upon plane-stress assumption is not appropriate in such cases. Here, the traditional shell element is modified by changing the constitutive relation which took into account the normal stress in the thickness direction, and the modified shell element formula is combined with Yld91 yield function to simulate the forming process of Aluminium alloy. Then the element formulation and material model is implemented into the FE code Ls-Dyna by means of USER interface. Two examples are carried out and good correlations are obtained when compared to the traditional shell element and solid element.

Thermally Induced Seizure in Journal Bearings During Startup and Transient Flow Disturbance

2003 ◽  
Vol 125 (4) ◽  
pp. 833-841 ◽  
Author(s):  
Rajesh Krithivasan ◽  
M. M. Khonsari
Keyword(s):  
Finite Element ◽  
Transient Flow ◽  
Empirical Relationship ◽  
Element Model ◽  
Flow Disturbance ◽  
Thermally Induced ◽  
Modeling And Analysis ◽  
Start Up ◽  
Insight Into ◽  
Good Agreement

This paper presents a finite element model that describes the thermomechanical interactions of a journal bearing undergoing thermally induced seizure (TIS). Two Categories of TIS are studied; the first part deals with occurrence of seizure during the start-up period followed by an investigation of TIS due to a transient flow-disturbance. The paper outlines the finite element modeling and analysis procedure involved in simulating TIS. An extensive set of parametric simulations covering load, speed, shaft radius, operating clearance, bearing length, friction coefficient and thermal expansion coefficient are performed to gain insight into the phenomenon of TIS. A statistical procedure is applied to the simulated results and an empirical relationship is derived. Good agreement between the empirical and published results attests to the capability of the model and its potential for predicting thermally induced seizure during system start up and during flow disturbance.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

Improved Bilinear Degenerated Shell Element

2015 ◽  
Vol 12 (02) ◽  
pp. 1550004 ◽  
Author(s):  
N. V. Swamy Naidu ◽  
B. Sateesh
Keyword(s):  
Shell Element ◽  
Shell Structures ◽  
Thin Plates ◽  
Element Formulation ◽  
Rigid Body Modes ◽  
Test Requirements ◽  
Degenerated Shell Element ◽  
Deformation Modes ◽  
Torsional Rotation ◽  
Transverse Shear Strains

The development of a new four node 24 degree of freedom bilinear degenerated shell element is presented for the analysis of shell structures. The present finite element formulation considers the assumed covariant transverse shear strains to avoid the shear locking problem and the assumed covariant membrane strains, which are separated from covariant in-plane strains, to overcome the membrane locking problem. The formulation also includes the deviation of the normal torsional rotation of the mid surface in the governing equation. This element is free from serious shear and membrane locking problems and undesirable spurious kinematic deformation modes. The element is tested for rigid body modes and distorted edges to meet the patch test requirements. The versatility and accuracy of this new degenerated shell element is demonstrated by solving several numerical examples for thick and thin plates.

scholarly journals Numerical aspects for efficient welding computational mechanics

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 139-148
Author(s):  
Tarek Aburuga ◽  
Aleksandar Sedmak ◽  
Zoran Radakovic
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Mechanical Analysis ◽  
Tensile Test Specimen ◽  
Integrity Assessment ◽  
Mass Scaling ◽  
Three Dimensional Models ◽  
Thermal Mechanical Analysis

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

Contrastive Study on Finite Element Models of High-Strength Pipelines Crossing Active Faults

2016 ◽  
Vol 850 ◽  
pp. 957-964
Author(s):  
Wei Zheng ◽  
Hong Zhang ◽  
Xiao Ben Liu ◽  
Le Cai Liang ◽  
Yin Shan Han
Keyword(s):  
Finite Element ◽  
Design Method ◽  
Active Faults ◽  
Shell Element ◽  
High Strength ◽  
Element Model ◽  
Beam Element ◽  
Finite Element Models ◽  
Fixed Boundary ◽  
Equivalent Boundary

There is a potential for major damage to the pipelines crossing faults, therefore the strain-based design method is essential for the design of buried pipelines. Finite element models based on soil springs which are able to accurately predict pipelines’ responses to such faulting are recommended by some international guidelines. In this paper, a comparative analysis was carried out among four widely used models (beam element model; shell element model with fixed boundary; shell element model with beam coupled; shell element model with equivalent boundary) in two aspects: differences of results and the efficiency of calculation. The results show that the maximum and minimum strains of models coincided with each other under allowable strain and the calculation efficiency of beam element model was the highest. Besides, the shell element model with beam coupled or equivalent boundary provided the reasonable results and the calculation efficiency of them were higher than the one with fixed boundary. In addition, shell element model with beam coupled had a broader applicability.

Numerical Simulation of Thermoplastic Composite Material by ANSYS

2011 ◽  
Vol 279 ◽  
pp. 181-185 ◽  
Author(s):  
Guo Hua Zhao ◽  
Qing Lian Shu ◽  
Bo Sheng Huang
Keyword(s):  
Numerical Simulation ◽  
Composite Material ◽  
Composite Structures ◽  
Material Model ◽  
General Purpose ◽  
Thermoplastic Composite ◽  
Finite Element Code ◽  
Peek Composite ◽  
Test Result ◽  
Good Agreement

This paper proposes a material model of AS4/PEEK, a typical thermoplastic composite material, for the general purpose finite element code—ANSYS, which can be used to predict the mechanical behavior of AS4/PEEK composite structures. The computational result using this model has a good agreement with the test result. This investigation can lay the foundation for the numerical simulation of thermoplastic composite structures.

Sign in / Sign up

Export Citation Format

Share Document