Application of Fractional Derivatives to Modeling the Quasi-Static Response of Polyurethane Foam

2003 ◽  
Author(s):  
Rong Deng ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
System Identification ◽  
Polyurethane Foam ◽  
Elastic Model ◽  
Compression Tests ◽  
Static Compression ◽  
Identification Method ◽  
Dissipative Effects ◽  
Identification Technique ◽  
Nonlinear Elastic ◽  
Quasi Static Compression

A fractional derivative model of dissipative effects is combined with a nonlinear elastic model to model the response of polyurethane foam in quasi-static compression tests. A system identification method is developed based on a separation of the elastic and viscoelastic parts of the response, which is possible because of symmetries in the imposed deformation timehistory. Simulations are used to evaluate the proposed identification method when noise is present in the response. The system identification technique is also applied with some success to experimental data taken from several compression experiments on two types of polyurethane foam blocks.

scholarly journals Relationships of Egg Specific Gravity and Shell Thickness to Quasi-static Compression Tests

1976 ◽  
Vol 55 (4) ◽  
pp. 1282-1289 ◽  
Author(s):  
Malik M. Ahmad ◽  
G.W. Froning ◽  
F.B. Mather ◽  
L.L. Bashford
Keyword(s):  
Specific Gravity ◽  
Shell Thickness ◽  
Compression Tests ◽  
Static Compression ◽  
Quasi Static Compression

Dynamic Compression Behavior of Lotus-Type Porous Iron

2010 ◽  
Vol 658 ◽  
pp. 193-196
Author(s):  
Masakazu Tane ◽  
Tae Kawashima ◽  
Keitaro Horikawa ◽  
Hidetoshi Kobayashi ◽  
Hideo Nakajima
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Testing Machine ◽  
Porous Iron ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Static Compression ◽  
Plateau Stress ◽  
Stress Region ◽  
Quasi Static Compression

Dynamic and quasi-static compression tests were conducted on lotus-type porous iron with porosity of about 50% using the split Hopkinson pressure bar method and universal testing machine, respectively.　In the dynamic compression parallel to the pore direction, a plateau stress region appears where deformation proceeds at nearly constant stress, while the plateau stress region does not appear in the quasi-static compression. The plateau stress region is probably caused by the buckling deformation of matrix iron which occurs only in the dynamic compression. In contrast, the compression perpendicular to the orientation direction of pores exhibits no plateau-stress regions in the both dynamic and quasi-static compression.

Experimental Study on High Damping Rubber Under Combined Action of Compression and Shear

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Tinard Violaine ◽  
Nguyen Quang Tam ◽  
Fond Christophe
Keyword(s):  
Static Load ◽  
Mullins Effect ◽  
Compression Tests ◽  
Static Compression ◽  
Cyclic Shear ◽  
Combined Action ◽  
Loading Tests ◽  
High Damping Rubber ◽  
Quasi Static Compression ◽  
Time Dependance

High damping rubber (HDR) is used in HDR bearings (HDRBs) which are dissipating devices in structural systems. These devices actually have to support permanent static load in compression and potential cyclic shear when earthquakes occur. Mastering the behavior of bearings implies an accurate understanding of HDR response in such configuration. The behavior of HDR is, however, complex due to the nonlinearity and time dependance of stress–strain response and especially Mullins effect. To the authors' knowledge, tests on HDR under combined quasi-static compression and cyclic shear (QC-CS) have not been performed with regard to Mullins effect yet. The purpose of this study is thus to assess experimentally Mullins effect in HDR, especially under QC-CS. In order to achieve this aim, cyclic tensile and compression tests were first carried out to confirm the occurrence of Mullins effect in the considered HDR. Then, an original biaxial setup allowing testing HDR specimen under QC-CS was developed. This setup enables us to identify Mullins effect of the considered HDR under this kind of loading. Tests carried out with this setup were thus widened to the study of the influence of compression stress on shear response under this loading, especially in terms of shear modulus and density of energy dissipation.

MICROCONTROLLER-BASED FOR SYSTEM IDENTIFICATION TOOLS USING LEAST SQUARE METHOD FOR RC CIRCUITS

2015 ◽  
Vol 77 (28) ◽  
Author(s):  
Ang Jia Yi ◽  
M. S. Abdul Majid ◽  
Azuwir M. N. ◽  
S. Yaacob
Keyword(s):  
Mathematical Model ◽  
System Identification ◽  
Least Square Method ◽  
Least Square ◽  
Real Time System ◽  
System Identification Method ◽  
Identification Method ◽  
Verification Methods ◽  
Identification Technique ◽  
Rc Circuit

System identification is one of the method to construct a plant mathematical model from experimental data. This method has been widely applied in the automatic control, aviation, spaceflight medicine, society economics and other fields more. With the rapid growth of the science and technology, the system identification technique has increasingly grown in various applications. Since most of the system identification devices are off-line base, this means that the system identification can only be done after collecting the data and process through a computer devices. This paper will show how to process system identification method with real-time system. This method required a microcontroller as the medium to perform. That’s why the system identification method will be programmed into a microcontroller, based on Least Square Method. Later, the system will be tested on a RC circuit to see the effect of the signal and the mathematical model obtained. The data will undergo the system identification toolbox for process using ARX and ARMAX model. On the other hand, the data will also be collected using the microcontroller created for analysis purpose. To ensure the validity of the model some verification methods are performed. Results show that the Least Square Method using Microcontroller base has the capability to work as a system identification tools.

Effect of Laser Forming on the Energy Absorbing Behavior of Metal Foams

2021 ◽  
pp. 1-29
Author(s):  
Tom Zhang ◽  
Yubin Liu ◽  
Nathan Ashmore ◽  
Wayne Li ◽  
Y. Lawrence Yao
Keyword(s):  
Metal Foam ◽  
Laser Forming ◽  
Compression Tests ◽  
Forming Process ◽  
Static Compression ◽  
Closed Cell ◽  
Similarities And Differences ◽  
Energy Absorbing ◽  
The Impact ◽  
Quasi Static Compression

Abstract Metal foam is light in weight and exhibits an excellent impact absorbing capability. Laser forming has emerged as a promising process in shaping metal foam plates into desired geometry. While the feasibility and shaping mechanism has been studied, the effect of the laser forming process on the mechanical properties and the energy absorbing behavior in particular of the formed foam parts has not been well understood. This study comparatively investigated such effect on as-received and laser formed closed-cell aluminum alloy foam. In quasi-static compression tests, attention paid to the changes in the elastic region. Imperfections near the laser irradiated surface were closely examined and used to help elucidate the similarities and differences in as-received and laser formed specimens. Similarly, from the impact tests, differences in deformation and specific energy absorption were focused on, while relative density distribution and evolution of foam specimens were numerically investigated.

Development of a Multi-Body Model to Predict the Settling Point of a Seat-Occupant System

2014 ◽  
Author(s):  
Yousof Azizi ◽  
Anil K. Bajaj ◽  
Patricia Davies
Keyword(s):  
Polyurethane Foam ◽  
Viscoelastic Model ◽  
Elastic Behavior ◽  
System Response ◽  
Type Model ◽  
Model Parameters ◽  
Static Compression ◽  
Body Model ◽  
Multi Body ◽  
Nonlinear Elastic

The location of the hip-joint (H-Point) of a seat occupant is an important design specification which directly affects the seat comfort. Most car seats are made of polyurethane foam so the location of the H-Point is dependent on the quasi-static behavior of foam. In this study a multi-body seat-occupant model is developed which incorporates a realistic polyurethane foam model. The seat-occupant model consists of two main components: the seat model and the occupant model. In this study the seat is represented by a series of discrete nonlinear viscoelastic elements. The nonlinear elastic behavior of these elements is expressed by a higher order polynomial while their viscoelastic behavior is described by a global hereditary type model with the parameters which are functions of the compression rate. The nonlinear elastic and viscoelastic model parameters were estimated previously using the data obtained from conducting a series of quasi-static compression tests on a car seat foam sample. The occupant behavior is described by a two-dimensional multi-body model with 5 degrees of freedom. A Lagrangian formulation is used to derive the governing equations for the seat occupant model. These differential equations are solved numerically to obtain the H-Point location. These results are then used to calculate the force distribution at the seat and the occupant interfaces. The effects of different system parameters on the system response and the interfacial pressure distribution are also studied.

scholarly journals Effect of addition of HTa to Al/PTFE under quasi-static compression on the properties of the developed energetic composite material

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8540-8545
Author(s):  
Xinxin Ren ◽  
Yuchun Li ◽  
Junyi Huang ◽  
Jiaxiang Wu ◽  
Shuangzhang Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Material ◽  
Compression Tests ◽  
Static Compression ◽  
Reactive Materials ◽  
Reaction Characteristics ◽  
Quasi Static Compression

To study the mechanical properties and reaction characteristics of Al/HTa/PTFE reactive materials under quasi-static compression, five types of Al/HTa/PTFE specimens with different HTa contents were prepared for quasi-static compression tests.

PHYSICAL PROPERTIES OF EGGSHELLS: A COMPARISON OF THE PUNCTURE AND COMPRESSION TESTS FOR ESTIMATING SHELL STRENGTH

1977 ◽  
Vol 57 (2) ◽  
pp. 329-338 ◽  
Author(s):  
J. R. HUNT ◽  
PETER W. VOISEY ◽  
B. K. THOMPSON
Keyword(s):  
Shell Thickness ◽  
Shear Fracture ◽  
Compression Fracture ◽  
Compression Tests ◽  
Fracture Force ◽  
Static Compression ◽  
Fracture Properties ◽  
Puncture Force ◽  
Increase In Accuracy ◽  
Quasi Static Compression

Quasi-static compression and puncture methods of measuring eggshell strength were compared by testing consecutive eggs from each of 89 birds alternately until eight eggs per bird were tested by each method. Results indicated that the tensile and shear fracture properties of the shell material were linearly related to each other, and to shell thickness and specific gravity. Both puncture force and compression fracture force were significantly different on a between-hen basis even when adjusted for shell thickness. Puncture force was more closely related to shell thickness on a between-egg basis than was compression fracture force. Puncture force was not related to shell thickness on a within-egg basis. The increase in accuracy gained from repeated puncture measurements on a within-egg basis was discussed.

Mechanical Resistance Improvement of Oxidized Metallic Hollow Spheres Stacking

2011 ◽  
Vol 62 ◽  
pp. 117-123
Author(s):  
Cecile Davoine ◽  
Sebastien Mercier ◽  
F. Popoff ◽  
A. Götzfried
Keyword(s):  
Hollow Spheres ◽  
Relative Weight ◽  
Small Samples ◽  
Mechanical Resistance ◽  
Compression Tests ◽  
Mechanical Stiffness ◽  
Significant Deterioration ◽  
Static Compression ◽  
Oxidation Mechanisms ◽  
Quasi Static Compression

The oxidation of stainless steel hollow spheres stacking has been studied at 800, 900 and 1,000°C in laboratory air in the range of 200h. The experimental results based on the relative weight gain of oxidized samples revealed an effect of the sphere’s size over the kinetic of oxidation: the quicker oxidation of the material constitued by smallest spheres suggests that the ratio of exposed surface is preponderant in the oxidation mechanisms. A quasi total transformation of the metal into oxides has been observed after 100h at 1000°C. Some simple quasi-static compression tests highlighted a significant deterioration in mechanical resistance for samples oxidized for 100h at 900 and 1,000°C. The global collapse of the oxidized samples could be imputed to the presence of oxides into the shells porosities by implying a decrease of their ductility. In order to improve the mechanical resistance of oxidized hollow spheres stacking, the adding of a dense metallic undercoat is proposed. The concept is tested by producing small samples of nickel-based hollow spheres stacking. The observation of oxidized samples shows that the shell of hollow spheres are not totally oxidized, providing a continuous metallic squeletton beneficial for mechanical stiffness at high temperatures.

Optimization of constitutive model parameters for simulation of polystyrene concrete subjected to impact

2017 ◽  
Vol 9 (2) ◽  
pp. 121-140 ◽  
Author(s):  
Tae Kwang Yoo ◽  
Tong Qiu
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Material Model ◽  
Drop Impact ◽  
Model Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Impact Tests ◽  
Quasi Static Compression

This article presents the results of a series of experimental testing and numerical modeling studies to optimize the parameters of a constitutive material model to accurately simulate the behavior of polystyrene crushable concrete during impact loading using LS-DYNA. Quasi-static compression tests and confined drop impact tests were conducted. To model the quasi-static compression tests, the response surface methodology was used to optimize Poisson’s ratio and friction angle in the pseudo-tensor model in LS-DYNA. Using the optimized model parameters, the simulated compression stress versus strain relationship showed an excellent agreement with those from the compression tests. To model the confined drop impact tests, the strain rate sensitivity parameter in LS-DYNA was optimized by comparing the drop impact simulations at different strain rate sensitivity values with the drop impact tests. This study suggests that the pseudo-tensor material model is potentially suitable for modeling crushable concrete. Although the optimized constitutive model parameters are specific for the polystyrene concrete mix used in this study, similar approach can be used to optimize model parameters for other polystyrene concrete mixes.

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