Macroscopic and Mesoscopic Large Deformation Measurement Methods for Metal Materials

2010 ◽  
Vol 146-147 ◽  
pp. 1769-1774
Author(s):  
Cai Ping Liu ◽  
Qing Quan Duan
Keyword(s):  
Large Deformation ◽  
Strain Curve ◽  
Grid Method ◽  
Small Deformation ◽  
Deformation Measurement ◽  
Charge Coupled Device ◽  
Initial Stage ◽  
Plastic Deformation Process ◽  
Identification Technique ◽  
Rational Mechanics

The stress-strain curve in the large plastic deformation process is always not available due to the strain gauge deficiencies in large deformation measurement. Considering this problem, digital marker identification technique is used to measure large deformation of Steel Q235 with images taken by with charge-coupled device. Then together with the deformation measured by traditional stain gauge at small deformation stage, the total stress and strain curve is obtained at macroscale. The mesoscopic deformation is measured by a material testing system assembled with scanning electronic microscope. The images from the initial stage to the rupture stage are captured synchronously. What’s more, using the grid method, the strain and rotation in rational mechanics is analyzed.

Mechanical properties of the tadpole tail fin

1998 ◽  
Vol 201 (19) ◽  
pp. 2691-2699 ◽  
Author(s):  
PA Doherty ◽  
RJ Wassersug ◽  
JM Lee
Keyword(s):  
Stress Relaxation ◽  
Large Deformation ◽  
Forced Vibration ◽  
Viscoelastic Properties ◽  
Developmental Plasticity ◽  
Rana Catesbeiana ◽  
Small Deformation ◽  
Collagen Fibres ◽  
Tadpole Tail ◽  
Undulatory Swimming

The tadpole tail fin is a simple double layer of skin overlying loose connective tissue. Collagen fibres in the fin are oriented at approximately +/-45 degrees from the long axis of the tail. Three tests were conducted on samples of the dorsal tail fin from 6-10 Rana catesbeiana tadpoles to establish the fin's viscoelastic properties under (1) large-deformation cyclic loading at 1 and 3 Hz, (2) small-deformation forced vibration at 1 and 3 Hz, and (3) stress relaxation under a 0.1 s loading time. The fin was very fragile, failing easily under tensile loads less than 7 g. It was also strikingly viscoelastic, as demonstrated by 72+/-1 % hysteresis loss (at 3 Hz), 16+/-3 % stress remaining after 100 s of stress relaxation and a phase angle of 18+/-1 degrees in forced vibration. As a consequence of its viscoelastic properties, the fin was three times stiffer in small than in large deformation. This may account for the ability of the fin to stay upright during normal undulatory swimming, despite the absence of any skeletal support. Tadpoles in nature are often found with damaged tails. We suggest that the unusually viscoelastic and fragile nature of the fin helps tadpoles escape the grasp of predators. Because the fin deforms viscoelastically and tears easily, tadpoles can escape predators and survive otherwise lethal attacks with only minor lacerations to the fin. Recent studies have shown that certain tadpoles develop taller fins in the presence of predators. This developmental plasticity is consistent with the tail fin acting as a protective but expendable 'wrap' around the core muscle tissue.

Test of Strain-Time Correspondence Principle with Gel-Containing Elastomers

1986 ◽  
Vol 59 (2) ◽  
pp. 305-314 ◽  
Author(s):  
N. Nakajima ◽  
E. R. Harrell
Keyword(s):  
Large Deformation ◽  
Correspondence Principle ◽  
Small Deformation ◽  
Complex Viscosity ◽  
Shear Stresses ◽  
Growth Data ◽  
Stress Growth ◽  
Linear Viscoelastic ◽  
The Difference ◽  
Linear Viscoelastic Theory

Abstract With four NBR samples and one EPR, oscillatory measurements and stress-growth measurements were performed, the former being at very small deformation and the latter leading to large deformation. The Rheometrics mechanical spectrometer was used with a cone-plate fixture. The temperature was 100°C. The stress-growth data of NBR's, converted to complex viscosity-frequency data through the application of stress-time correspondence principle, were in good agreement with those observed in the oscillatory measurement. Thus, the stress-growth data including the large deformation were “linearized” to form a master curve. With the EPR sample, such a linearization was not necessary. The stress-growth data were adequately treated with the linear viscoelastic theory up to shear stresses approaching the steady state. The difference in behavior between the NBR's and EPR is caused by differences in type and extent of long branching and gel present in the samples.

scholarly journals Equivalent substitution criteria of aluminum for steel and its application in automobile structures

2020 ◽  
Vol 12 (3) ◽  
pp. 168781402091122
Author(s):  
Song Li ◽  
Jiantao Bai ◽  
Xinchen Wang ◽  
Limin Song ◽  
Kai Luo ◽  
...  
Keyword(s):  
Large Deformation ◽  
Small Deformation ◽  
High Strength ◽  
Steel Tube ◽  
Equal Mass ◽  
Body Structure ◽  
Cross Sectional ◽  
Hollow Section ◽  
Automobile Body ◽  
Triple Cell

Lightweight automobile body structure, made of aluminum, can extend the endurance mileage of electric automobile. However, the mechanisms for the application of aluminum in automobile body structure are not clear until now. The main contribution of this work is to propose a method of equivalent substitution criteria of aluminum for steel. This method researches small deformation and large deformation under bending mode. First, formulations of cross-sectional properties, including open, single-cell, double-cell, three-cell, and four-cell sections, are derived, and equivalent substitution criteria in the case of small deformation, which include equal stiffness design and equal strength design, are initially proposed. Second, in the case of large deformation, the steel circular tube and channel tube are substituted by aluminum tube under equivalent stiffness. The bending resistance of five types of tubes, including rectangular hollow section, rectangular hollow section with double-cell, rectangular hollow section with triple-cell, mild steel, and high-strength steel tube, are, respectively, compared considering crashworthiness under equal mass. Third, the side frame and chassis frame examples verify the effectiveness of the proposed method, which is universal and can also be applied in aerospace structures.

Mesoscopic Simulation on the Compression Deformation Process of Powder Particles

2013 ◽  
Vol 753-755 ◽  
pp. 896-901
Author(s):  
Ming Hua Jiao ◽  
Long Sun ◽  
Man Gu ◽  
De Guang Wang ◽  
Yu Cheng Wu
Keyword(s):  
Deformation Process ◽  
Stable State ◽  
Small Deformation ◽  
Mesoscopic Simulation ◽  
Compression Deformation ◽  
Initial Stage ◽  
Strain Process ◽  
Deformation Processes ◽  
Powder Particles ◽  
Compacting Pressure

The compression deformation processes of powder particles were investigated by the way of mesoscopic simulation based on finite element method of discrete body. The strain process of the particles in typical position, the deformation difference of the particles in different positions and the strain status of particles were investigated under various compacting pressure. The results show that the deformation process of the compressed powder particles consisted of three stages, which were the initial stage of small deformation, the major stage of the sharply changes of strain and the ultimate stage of strain tending to stable state. The interface friction has a significant influence on the deformation and pressed density of particles close to die wall. The density can not be increased with the increase of compacting pressure of compaction infinitely.

scholarly journals Centrosymmetric 3D Deformation Measurement using Grid Method with a Single-Camera

2016 ◽  
Vol 57 (4) ◽  
pp. 537-546 ◽  
Author(s):  
H. Wen ◽  
Z. Liu ◽  
C. Li ◽  
X. He ◽  
J. Rong ◽  
...  
Keyword(s):  
Grid Method ◽  
Deformation Measurement ◽  
Single Camera ◽  
3D Deformation

scholarly journals Neural Network Based Pest Identification and Control in Cauliflower Crop using Sounds of Pest

2019 ◽  
Vol 8 (9) ◽  
pp. 3127-3134
Keyword(s):  
Neural Network ◽  
Back Propagation ◽  
Back Propagation Algorithm ◽  
Initial Stage ◽  
Identification Technique ◽  
Pest Detection ◽  
Maximum Protection ◽  
Acoustic Identification ◽  
Hidden Layer ◽  
And Control

The quantity of pesticides usage in the field increases every year, which in turn affects the nutrients present in the crop. These pesticides also cause water contamination, air pollution, serious health problems in humans and finally making the soil infertile. Necessary action has to be taken to protect the environment and crops from chemicals. A well-established automatic acoustic detection of pest for early pest detection is suggested in this paper. Acoustic identification technique of signal analysis is extensively implemented in agriculture to give maximum protection of crops, ultimately resulting in better production. Successful eradication of pest lies in identification of pest without damaging the nutrients and crops. The proposed technique detects the presence of pests in the initial stage. The sounds of different pests which are dreadfully affecting the agricultural crops are collected. The signals of pests are analyzed in time domain and frequency domain specifications. The features of different pests are extracted using Mat lab programming. The various statistical features of pest are trained and given to the hidden layer of neural network where it automatically classifies the pest indicating the presence of pest. The Back-Propagation algorithm is used for training the samples. When the identification of pest has been done, the pest can be killed by the microwave shock rather than applying highly toxic chemicals. This technique also benefits the farmer by avoiding contact with the pesticides. Direct contact with the pesticides sometimes causes skin cancer to farmers. The technique suggested in this paper is harmless to the farmers and crops, hence increases the production.

Model for predicting the variation of shear stress in unsaturated soils during strain-softening

2020 ◽  
Author(s):  
Xiuhan Yang ◽  
Sai Vanapalli
Keyword(s):  
Shear Stress ◽  
Large Deformation ◽  
Unsaturated Soils ◽  
Strain Softening ◽  
Strain Curve ◽  
Published Data ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
State Stress

Several of the geotechnical structures constructed with unsaturated soils undergo a large deformation prior to reaching failure conditions (e.g. progressive failure of a soil slope). During this process, the shear stress in soils typically increases initially and then reduces with an increase in the shear strain. The prediction of the stress-strain relationship is critical for reasonable interpretation of the mechanical behavior of those geo-structures that undergo large deformation. This paper introduces a model based on the disturbed state concept (DSC) to predict the variation of shear stress in unsaturated soils during strain-softening process under consolidated drained triaxial compression condition. In this model, the apparent stress-strain relationship is formulated as a weighted average of a hyperbolic hardening response extending the pre-peak state stress-strain curve and a linear response extending the critical state stress-strain curve with an assumed disturbance function as the weight. The prediction procedure is described in detail and the proposed model is validated using several sets of published data on unsaturated soils varying from coarse- to fine-grained soils. Finally, a comprehensive error analysis is undertaken based on an index of agreement approach.

Angular Momentum of a Torque-Free Deforming Axisymmetric Gyro

1994 ◽  
Vol 61 (1) ◽  
pp. 117-123
Author(s):  
F. P. J. Rimrott ◽  
F. Janabi-Sharifi
Keyword(s):  
Angular Momentum ◽  
Angular Velocity ◽  
Large Deformation ◽  
Small Deformation ◽  
Matrix Form ◽  
Stability Studies ◽  
Attitude Stability ◽  
Small Deformations

Attitude drift and attitude stability studies of torque-free gyros involve an angular momentum that is constant in magnitude and direction. The problem is to find suitable coordinates to describe the gyro’s behavior, and then to express the (constant) angular momentum in these coordinates. Expressions for small deformation are available. In the present paper the expression, in floating coordinates, for the angular momentum of a torque-free deforming axisymmetric gyro in terms of inertia moments and angular velocity components is extended to beyond small deformations. The angular momentum expression is written first in its general form. Thqn the angular momentum is expressed in matrix form for the calculation of angular momentum components for arbitrarily large deformation. Finally, three models are presented to illustrate the application of the angular momentum expression obtained.

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