A Research on Strength Criteria Based on Material Structure

2014 ◽  
Vol 518 ◽  
pp. 236-243
Author(s):  
Zhen Hai Wei ◽  
Meng Shu Wang ◽  
Ding Li Zhang
Keyword(s):  
Random Distribution ◽  
Strength Criterion ◽  
Tensile Failure ◽  
Material Strength ◽  
Material Structure ◽  
Friction Materials ◽  
Strength Criteria ◽  
Complex Material ◽  
Material Theory ◽  
Strength Models

Strength criteria for materials in the classical elastoplastic theory are formed mostly based on experiments and some assumptions [1, . However, no concensus has been achieved though many strength models were put forward to explore the applicable material strength criteria previously. Even the influence of material structures on strength has not been realized. In this article, the tensile failure strength criterion, shear strength criterion and strength criterion of friction materials are explored on the basis of the model of material with a structure of uniformly random distribution. Through analysis, it can be discovered that the strength criteria in the classical elastoplastic theory can be derived from the complex material theory based on the concept of material structure. However, as the theoretical basis, conditions of derivation and assumptions of concepts are totally different, it is proved that the complex material theory used for studying the material structures can fully cover the contents and conclusions obtained in classical elastoplastic theory.

On New Modifications of Some Strength Criteria for Anisotropic Materials

2016 ◽  
Vol 724 ◽  
pp. 53-57 ◽  
Author(s):  
S.L. Shambina ◽  
F.V. Rekach ◽  
Y.V. Belousov
Keyword(s):  
Limit State ◽  
Strength Criterion ◽  
Material Strength ◽  
Small Element ◽  
Exact Results ◽  
Strength Condition ◽  
Stress Space ◽  
Strength Criteria ◽  
State Of Stress ◽  
The Moment

The strength criterion is the strength condition for a small element of the construction’s material. Strength criterion is analytical interpretation in stress space the allowable boundaries of stress state, within these boundaries the material can work under these conditions without breaking. Since analytical interpretation of the experimental data may be performed in different ways, therefore many different strength criteria exist. Properly chosen strength criterion allows determining the moment when the material is destroyed while it is working under various tense conditions. Also it gives an opportunity to assess the limit state of stress in the most loaded points of the structure. This paper suggests new modifications of some well-known strength criteria which are more comfortable for practical use and can help to achieve more exact results.

Material Strength: A Rational Nonequilibrium Energy Model for Complex Loadings

2020 ◽  
Vol 88 (2) ◽  
Author(s):  
Biao Wang
Keyword(s):  
Failure Process ◽  
Strength Criterion ◽  
Energy Model ◽  
Natural Phenomenon ◽  
Material Strength ◽  
Strength Theory ◽  
Reliable Prediction ◽  
Strength Criteria ◽  
Safety Considerations ◽  
Nonequilibrium Energy

Abstract The failure of materials with some sort of loading is a well-known natural phenomenon, and the reliable prediction of the failure of materials is the most important issue for many different kinds of engineering materials based on safety considerations. Classical strength theories with complex loadings are based on some sort of postulations or assumptions, and they are intrinsically empirical criteria. Due to their simplicity, classical strength theories are still widely used in engineering, and they are very easy to incorporate into any finite element code. Recently, a new methodology was proposed by the author. Instead of establishing empirical models, the material failure process was modeled as a nonequilibrium process. Then, the strength criterion was established with the rational stability analysis for the failure process. In this study, the author tried to use this idea to develop a rational thermodynamic strength theory and to make the theory easy to use in engineering, similar to the classical strength criteria. It was found that the predictions of the rational energy strength theory were very reasonable compared to the experimental data even if no postulation was taken. Through the analysis, it seemed that the strength problem could be efficiently tackled using the rational nonequilibrium energy model instead of using some sort of empirical assumptions or models.

scholarly journals Failure Process Simulation of Interlayered Rocks under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Chi Yao ◽  
Sizhi Zeng ◽  
Jianhua Yang
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Strength Criterion ◽  
Tensile Failure ◽  
Strength Anisotropy ◽  
Rigid Block ◽  
Bedding Planes ◽  
Typical Experiment ◽  
Confining Pressures ◽  
Spring Method

Anisotropy in strength and deformation of rock mass induced by bedding planes and interlayered structures is a vital problem in rock mechanics and rock engineering. The modified rigid block spring method (RBSM), initially proposed for modeling of isotropic rock, is extended to study the failure process of interlayered rocks under compression with different confining pressures. The modified rigid block spring method is used to simulate the initiation and propagation of microcracks. The Mohr–Coulomb criterion is employed to determine shear failure events and the tensile strength criterion for tensile failure events. Rock materials are replaced by an assembly of Voronoi-based polygonal blocks. To explicitly simulate structural planes and for automatic mesh generation, a multistep point insertion procedure is proposed. A typical experiment on interlayered rocks in literature is simulated using the proposed model. Effects of the orientation of bedding planes with regard to the loading direction on the failure mechanism and strength anisotropy are emphasized. Results indicate that the modified RBSM model succeeds in capturing main failure mechanisms and strength anisotropy induced by interlayered structures and different confining pressures.

Chosen of Strength Criterion for Different Region of Blade

2012 ◽  
Vol 608-609 ◽  
pp. 755-758
Author(s):  
De Tian ◽  
Qi Li ◽  
Jian Mei Zhang ◽  
Xiao Dong Zhang ◽  
Ning Bo Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Strength Criterion ◽  
Fatigue Index ◽  
Element Analysis ◽  
Strength Criteria ◽  
Security And Reliability ◽  
Blade Model ◽  
Dangerous Section

Use software Pro/E to build a blade model based on 1.5MW wind turbine, analyze stress characteristics of different regions including spar cap, webs and trailing edge of the dangerous section of blade at related loads by using different strength criteria to make finite element analysis to check the strength, through comparing the F.I.(fatigue index) and stress bringing about the idea that using different strength criteria to analyze different material of different regions can ensure the security and reliability of the designed blade at large extent.

A Unified Characteristic Theory for Plastic Plane Stress and Strain Problems

2003 ◽  
Vol 70 (5) ◽  
pp. 649-654 ◽  
Author(s):  
Y.-Q. Zhang ◽  
H. Hao ◽  
M.-H. Yu
Keyword(s):  
Plane Stress ◽  
Yield Criterion ◽  
Strength Criterion ◽  
Rigid Plastic ◽  
Strength Criteria ◽  
Special Cases ◽  
Characteristic Theory ◽  
Characteristic Methods ◽  
Von Mises ◽  
Suitable Characteristic

Based on the unified strength criterion, a characteristic theory for solving the plastic plane stress and plane strain problems of an ideal rigid-plastic body is established in this paper, which can be adapted for a wide variety of materials. Through this new theory, a suitable characteristic method for material of interest can be obtained and the relations among different sorts of characteristic methods can be revealed. Those characteristic methods on the basis of different strength criteria, such as Tresca, von Mises, Mohr-Coulomb, twin shear (TS) and generalized twin shear (GTS), are the special cases (Tresca, Mohr-Coulomb, TS, and GTS) or linear approximation (von Mises) of the proposed theory. Moreover, a series of new characteristic methods can be easily derived from it. Using the proposed theory, the influence of yield criterion on the limit analysis is analyzed. Two examples are given to illustrate the application of this theory.

Two-Parameter Parabolic Mohr Strength Criterion and Its Damage Regularity

2006 ◽  
Vol 306-308 ◽  
pp. 327-332 ◽  
Author(s):  
Chun Guang Li ◽  
Xiu Run Ge ◽  
Hong Zheng ◽  
Shui Lin Wang
Keyword(s):  
Uniaxial Tension ◽  
Principal Stress ◽  
Uniaxial Compression ◽  
Strength Criterion ◽  
Friction Angle ◽  
Tensile Failure ◽  
Compression Tests ◽  
Uniaxial Compression Strength ◽  
Griffith Criterion ◽  
Two Parameter

A series of formulas about two-parameter parabolic Mohr strength criterion(2-PP Mohr criterion) are derived. Based on the results of uniaxial tension and uniaxial compression tests, the parameters involved in the criterion can be easily determined, then the criterion in terms of the major principal stress and the minor principal stress is derived, and the damage pattern is also discussed. At last, the formulas about the rupture angle and the friction angle are presented, and their relationship is also given. 2-PP Mohr criterion can describe not only shear but also tensile failure. In this criterion the ratio of the uniaxial compression strength and the uniaxial tension strength is not confined as in Griffith criterion. The formula about the rupture angle provides steady theoretical foundation for determining the direction of crack faces and damage patterns in the computation of macro crack propagation. In fact, Griffith criterion is only a special case of the two-parameter parabolic Mohr strength criterion proposed in this present paper.

Cylindrical liner Z-pinch experiments for fusion research and high-energy-density physics

2015 ◽  
Vol 81 (3) ◽  
Author(s):  
G. C. Burdiak ◽  
S. V. Lebedev ◽  
F. Suzuki-Vidal ◽  
G. F. Swadling ◽  
S. N. Bland ◽  
...  
Keyword(s):  
Shock Waves ◽  
Radiation Transport ◽  
Axial Magnetic Field ◽  
Wave Structure ◽  
High Energy ◽  
High Energy Density ◽  
Material Strength ◽  
Bulk Motion ◽  
Strength Models ◽  
Z Pinch

A gas-filled cylindrical liner z-pinch configuration has been used to drive convergent radiative shock waves into different gases at velocities of 20–50 km s−1. On application of the 1.4 MA, 240 ns rise-time current pulse produced by the Magpie generator at Imperial College London, a series of cylindrically convergent shock waves are sequentially launched into the gas-fill from the inner wall of the liner. This occurs without any bulk motion of the liner wall itself. The timing and trajectories of the shocks are used as a diagnostic tool for understanding the response of the liner z-pinch wall to a large pulsed current. This analysis provides useful data on the liner resistivity, and a means to test equation of state (EOS) and material strength models within MHD simulation codes. In addition to providing information on liner response, the convergent shocks are interesting to study in their own right. The shocks are strong enough for radiation transport to influence the shock wave structure. In particular, we see evidence for both radiative preheating of material ahead of the shockwaves and radiative cooling instabilities in the shocked gas. Some preliminary results from initial gas-filled liner experiments with an applied axial magnetic field are also discussed.

New strength formulae for rock surrounding a circular opening

2013 ◽  
Vol 50 (7) ◽  
pp. 735-743 ◽  
Author(s):  
Wen Fan ◽  
Mao-hong Yu ◽  
Long-sheng Deng ◽  
Xianglin Peng ◽  
Li-wei Chen
Keyword(s):  
Plastic Material ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Special Cases ◽  
Elastic Plastic Material ◽  
Strength Models ◽  
Strength Formula ◽  
Strain Model

In this paper, the unified strength theory proposed by Yu Mao-hong in 1991 is used to develop new strength formulae for rock surrounding a tunnel. The new formulae can be applied to an elastic–plastic material. The formulae have a series of expressions with the unified parameter, especially variations such as the well-known Kastner and Airy formulae, which are widely used in rock mechanics and engineering. These formulae are derived on the basis of the Mohr–Coulomb strength criterion. For the strength-weakening (plastic-softening) of geomaterials, the analytical solutions for the radius of the plastic residual zones, radius of the plastic-softening zones, and displacement around the opening are presented according to the elastoplastic-softening – residual plastic, tri-linear stress–strain model. In addition, the derivation for the stress state in the surrounding rock is given. The Kastner formula, Airy formula, and available solutions can be considered as special cases in the new strength formula. The influence of softening, shear dilatancy, and different strength models on the results is analyzed. The results presented in this paper are useful for analyzing surrounding rock with various stress conditions and reinforcement of caves.

Laser-Assisted Bending

2007 ◽  
Vol 344 ◽  
pp. 235-241 ◽  
Author(s):  
Kari Mäntyjärvi ◽  
Markku Keskitalo ◽  
Jussi A. Karjalainen ◽  
Anu Leiviskä ◽  
Jouko Heikkala ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Strain Hardening ◽  
Process Parameters ◽  
Laser Power ◽  
High Strength ◽  
Material Strength ◽  
Material Structure ◽  
Original Material ◽  
Heat Sources ◽  
Conventional Procedure

When sheets of high-strength (HS) and ultra-high-strength (UHS) steels are bent by a press brake the process suffers from large bending forces, considerable springback, and eventual cracks. Additionally, some unpredictable effects, such as lost contact to the punch, caused by strain hardening may occur producing a bend with erroneous radii. The strain hardening of the bending line may make further processes, such as forming or welding, more complex. One solution to these problems is to anneal the bending line with a laser in advance. Of course, it is also possible to utilise other types of heat sources, but the laser can offer the most precisely controlled heat treatment. The proper process parameters depend on the material, and it has been noticed that inadequate process parameters may harden the material instead of annealing. In this work some experiments on bending sheet metal samples of HS or UHS steel with previously laser-annealed bending lines have been carried out and the outcome analysed. The results show that the annealing produces better bending results compared to the conventional procedure. This includes lower springback, less hardening in the bending line and more precise geometry of the bend. It can be even suggested that proper annealing with strain hardening in bending will produce the original material structure. Obviously, more theoretical and experimental work is required to optimise the process parameters including the laser power and speed for each pair of material strength and thickness.

Sign in / Sign up

Export Citation Format

Share Document