Study of Destabilization Mechanism of Concrete Component Based on Catastrophe Theory

2011 ◽  
Vol 413 ◽  
pp. 499-506
Author(s):  
Yan Fen Liao ◽  
Yan Xu ◽  
Xiao Qian Ma
Keyword(s):  
Brittle Failure ◽  
Mechanical Model ◽  
Stability Problem ◽  
Load Capacity ◽  
Spring Stiffness ◽  
State Variables ◽  
Temperature Load ◽  
Load Characteristics ◽  
Concrete Component ◽  
Simplified Mechanical Model

A simplified mechanical model in view of concrete component stability problem on fire was established. Assuming the temperature of fire and load as control variables, and material strain (or intensity) as state variables, destabilization mechanism of concrete component under high temperatures was carried out with the application of cusp catastrophic model. And the nonlinear mutation characteristics and failure mechanism of concrete component on fire were investigated. The results indicate that system's catastrophe characteristic is determined by fire duration, temperature, load capacity and load characteristics. When K=-F'(u)/km>1, component destructs in the form of ductility failure, and when K<1, component destructs in the form of brittle failure. As the temperature rises, the caper value increases if the spring stiffness is defined.

scholarly journals Theoretical Study of Synchronous Behavior in a Dual-Pendulum-Rotor System

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Fang Pan ◽  
Hou Yongjun ◽  
Dai Liming ◽  
Du Mingjun
Keyword(s):  
Mechanical Model ◽  
Theoretical Study ◽  
Parallel Robots ◽  
Rotor System ◽  
Spring Stiffness ◽  
Rotation Direction ◽  
Coupling System ◽  
Existence And Stability ◽  
Synchronous Behavior ◽  
Simplified Mechanical Model

A dual-pendulum-rotor system widely appears in aero-power plant, mining screening machines, parallel robots, and the like of the other rotation equipment. Unfortunately, the synchronous behavior related to the dual-pendulum-rotor system is less reported. Based on the special backgrounds, a simplified mechanical model of the dual-pendulum-rotor system is proposed in the paper, and the intrinsic mechanisms of synchronous phenomenon in the system are further revealed with employing the Poincaré method. The research results show that the spring stiffness, the installation angular of the motor, and rotation direction of the rotors have a large influence on the existence and stability of the synchronization state in the coupling system, and the mass ratios of the system are irrelevant to the synchronous state of the system. It should be noted that to ensure the implementation of the synchronization of the system, the values of the parameters of the system should be far away to the two “critical points”.

Progressive failure analysis of scarf-repaired composite laminate based on damage constitutive model

2016 ◽  
Vol 233 (2) ◽  
pp. 180-188 ◽  
Author(s):  
Qiuyi Shen ◽  
Zhenghao Zhu ◽  
Yi Liu
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Composite Laminate ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Load Capacity ◽  
Three Dimensional ◽  
Zone Model ◽  
State Variables ◽  
Element Analysis

A three-dimensional finite element model for scarf-repaired composite laminate was established on continuum damage model to predict the load capacity under tensile loading. The mixed-mode cohesive zone model was adopted to the debonding behavior analysis of adhesive. Damage condition and failure of laminates and adhesive were subsequently addressed. A three-dimensional bilinear constitutive model was developed for composite materials based on damage mechanics and applied to damage evolution and loading capacity analyses by quantifying damage level through damage state variables. The numerical analyses were implemented with ABAQUS finite element analysis by coding the constitutive model into material subroutine VUMAT. Good agreement between the numerical and experimental results shows the accuracy and adaptability of the model.

An Analysis on the Forming Load of AA 2024 Aluminium Alloy in Combined and Sequence Operation Process

2006 ◽  
Vol 519-521 ◽  
pp. 949-954 ◽  
Author(s):  
Beong Bok Hwang ◽  
J.H. Shim ◽  
Jung Min Seo ◽  
H.S. Koo ◽  
J.H. Ok ◽  
...  
Keyword(s):  
Finite Element ◽  
Load Capacity ◽  
Low Cost ◽  
Forming Load ◽  
Mechanical Press ◽  
Combined Operation ◽  
Aa 2024 ◽  
Load Characteristics ◽  
Simulation Results ◽  
Selection Of

This paper is concerned with the analysis of the forming load characteristics of a forward-backward can extrusion in both combined and sequence operation. A commercially available finite element program, which is coded in the rigid-plastic finite element method, has been employed to investigate the forming load characteristics. AA 2024 aluminum alloy is selected as a model material. The analysis in the present study is extended to the selection of press frame capacity for producing efficiently final product at low cost. The possible extrusion processes to shape a forward-backward can component with different outer diameters are categorized to estimate quantitatively the force requirement for forming forward-backward can part, forming energy, and maximum pressure exerted on the die-material interfaces, respectively. The categorized processes are composed of combined and/or some basic extrusion processes such as sequence operation. Based on the simulation results about forming load characteristics, the frame capacity of a mechanical press of crank-drive type suitable for a selected process could be determined along with securing the load capacity and with considering productivity. In addition, it is suggested that different load capacities be selected for different dimensions of a part such as wall thickness in forward direction and etc. It is concluded quantitatively from the simulation results that the combined operation is superior to sequence operation in terms of relatively low forming load and thus it leads to low cost for forming equipments. However, it is also known from the simulation results that the precise control of dimensional accuracy is not so easy in combined operation. The results in this paper could be a good reference for analysis of forming process for complex parts and selection of proper frame capacity of a mechanical press to achieve low production cost and thus high productivity.

A Meso-Electro-Mechanical Model for PMN-PT-BT Ceramics Behavior

2001 ◽  
Author(s):  
Jinghong Fan
Keyword(s):  
Phase Transition ◽  
Mechanical Model ◽  
Three Dimensional ◽  
Constitutive Behavior ◽  
Rate Equations ◽  
State Variables ◽  
Empirical Relationships ◽  
Nonlinear Hysteresis ◽  
Fully Coupled ◽  
Maximum Permittivity

Abstract A three-dimensional, meso-electro-mechanical model has been formulated for description of PMN-PT-BT ceramics. Unlike the experimentally fit models and phenomenological models which are based on state variables and/or empirical relationships, this fully coupled, computational mesomechanics model for polycrystalline PMN-PT-BT ceramics is developed based on considerations of constitutive behavior of single crystals. Specifically, domain wall nucleation and evolution rate equations are proposed in this work to describe the nonlinear hysteresis behavior of these ceramics near the phase transition temperature with maximum permittivity.

The Prediction of Size Effect on J-R Curve for Eurofer97 Steel by Simplified Mechanical Model

2015 ◽  
Author(s):  
Ludek Stratil ◽  
Filip Siska ◽  
Hynek Hadraba ◽  
Ivo Dlouhy
Keyword(s):  
Fracture Toughness ◽  
Size Effect ◽  
Mechanical Model ◽  
Scale Up ◽  
Test Characteristics ◽  
Toughness Testing ◽  
Point Bend ◽  
Definition Of ◽  
Shelf Region ◽  
Simplified Mechanical Model

The possibilities to derive fracture toughness from small specimens are naturally limited due to constraint requirements which are especially restrictive in toughness testing. The loss of constraint at the crack tip is more likely to occur as specimen size decreases. Application of miniature specimens in fracture toughness testing thus requires a suitable methodology or correction procedure to deal with phenomenon of the constraint loss. Schindler et al. have proposed a simplified mechanical model that can be used to scale-up the key test characteristics from miniature specimen to the larger one. The model is applied to the miniature bending specimens to describe size effect on J-R curve of the Eurofer97 steel. The examined steel exhibits quite high toughness values at upper shelf region of fracture toughness. As a result, experimentally determined J-R curves of three different sizes of pre-cracked bending specimens showed high values of J-integral, which were significantly different each other. Using semi-empirical definition of the exponent of the power law function of J-R curve the performance of the Schindler’s model was quite successful. It was shown that the model is able to handle with size effect of tested pre-cracked three-point-bend specimens.

Conceptual Design for Upper Beam of Hydraulic Press

2011 ◽  
Vol 697-698 ◽  
pp. 414-419
Author(s):  
H.B. Yu ◽  
Y.C. Li ◽  
Chun Zhang
Keyword(s):  
Conceptual Design ◽  
Mechanical Model ◽  
Design Method ◽  
Hydraulic Cylinder ◽  
Hydraulic Press ◽  
Structural Scheme ◽  
Technical Parameters ◽  
The Press ◽  
Prototype Design ◽  
Simplified Mechanical Model

Conceptual design method for the upper beam of the press is proposed. Based on the technical parameters (nominal load and tablesize) and press structural scheme (number and layout of the hydraulic cylinder), simplified mechanical model of upper beam is established and then the conceptual design model is derived. According to the model, conceptual prototype with equivalent moment of inertia of the cross section is achieved. The structure prototype of upper beam is then obtained based on the conceptual prototype by introducing the design rules and experience and solving an optimization model. The method is applied to the structure prototype design of upper beam of a 100MN hydraulic press.

scholarly journals Study of the Interfacial Bond Behavior between CFRP Grid–PCM Reinforcing Layer and Concrete via a Simplified Mechanical Model

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7053
Author(s):  
Huijuan Dai ◽  
Bo Wang ◽  
Jiawei Zhang ◽  
Junlei Zhang ◽  
Kimitaka Uji
Keyword(s):  
Mechanical Model ◽  
Test Results ◽  
Interfacial Bond ◽  
Bond Behavior ◽  
Pull Out ◽  
Interface Bond ◽  
Reinforcing Layer ◽  
Bond Mechanism ◽  
Grid Interval ◽  
Simplified Mechanical Model

This paper presents the results of pull-out tests conducted to investigate the interfacial bond behavior between a carbon-fiber-reinforced polymer (CFRP) grid–polymer cement mortar (PCM) reinforcing layer and existing concrete, and proposes a simplified mechanical model to further study the interface bond mechanism. Four specimens composed of a CFRP grid, PCM, and concrete were tested. The influence of the type of CFRP grid and the grid interval on the interface bond behavior was discussed. The failure patterns, maximum tensile loads, and CFRP grid strains were obtained. The change process of interface bond stress was investigated based on the grid strain analysis. In addition, the simplified mechanical model and finite element model (FEM) were emphatically established, and the adaptability of the simplified mechanical model was validated through the comparative analysis between the FEM results and the test results. The research results indicate that a CFRP grid with a larger cross-sectional area and smaller grid interval could effectively improve the interface bond behavior. The tensile stress was gradually transferred from the loaded edge to the free edge in the CFRP grid. The interface bond behavior was mainly dependent on the anchorage action of the CFRP grid in the PCM, and the bond action between the PCM and the concrete. The FEM results were consistent with the test results, and the simplified mechanical model with nonlinear springs could well describe the interface bond mechanism between the CFRP grid–PCM reinforcing layer and concrete.

DEVELOPMENT OF A METHOD FOR SELECTING THE SHAPE OF THE LOAD CHARACTERISTIC THE ADAPTIVE FRICTION CLUTCH WITH A SEPARATE POWER CIRCUIT

2020 ◽  
Author(s):  
D.A. Ramazanov ◽  
Keyword(s):  
Total Mass ◽  
Load Capacity ◽  
Power Circuit ◽  
Load Characteristic ◽  
Design Version ◽  
Friction Clutch ◽  
Load Characteristics ◽  
Nominal Load

The main provisions of the method for selecting the form of the load characteristic of the AFM with a separate power circuit are formulated. The method involves taking into account the nominal load, the total mass of the drive, the value of the gain of the adaptive friction clutch with a separate power circuit and the accuracy of its operation, as well as recommendations for the choice of the second design version of the clutch. The choice of the type of adaptive friction clutch, taking into account the load characteristics, is based on the different load capacity and accuracy of operation, which correspond to these forms.

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