Geometric Instabilities in Isotropic Plastic Solids Under Increasing Uniaxial Compression

1972 ◽  
Vol 39 (2) ◽  
pp. 431-437 ◽  
Author(s):  
J. B. Newman
Keyword(s):  
Shear Stress ◽  
Strain Hardening ◽  
Uniaxial Compression ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Rigid Plastic ◽  
Axisymmetric Mode ◽  
Plastic Materials ◽  
Compressive Flow ◽  
Shanley Theory

This analysis seeks three-dimensional instabilities of uniaxial compressive flow in isotropic, strain-hardening, rigid-plastic materials of the Mises and maximum shear stress types. No instabilities are found for Mises materials. Maximum shear materials display axisymmetric, “deflectional”, and “higher-order” buckling. For increasingly slender specimens, the deflectional buckling process merges into that of the Shanley theory. The axisymmetric mode raises the possibility that instabilities contribute to the double axial bulging of ductile compression specimens reported by Na´da´i.

Discussions on Fracture Factors of Brittle Materials under the Shear-Compression Condition

2011 ◽  
Vol 250-253 ◽  
pp. 90-94
Author(s):  
Zhi Hui Li ◽  
Jun Ping Shi ◽  
An Min Tang
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Uniaxial Compression ◽  
Frictional Force ◽  
Shear Fracture ◽  
Maximum Shear Stress ◽  
Brittle Materials ◽  
Fracture Mechanisms ◽  
Initiation Point ◽  
Fracture Angle

Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.

scholarly journals Stress Distribution of CF/EP Laminated Composites under Supercritical Conditions

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Haihong Huang ◽  
Zhenwen Li ◽  
Huanbo Cheng ◽  
Yanzhen Yin
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Transfer Model ◽  
Three Dimensional Model ◽  
Interfacial Layers ◽  
Temperature And Pressure ◽  
Carbon Fiber Epoxy ◽  
Supercritical Temperature

Enormous amounts of wastes have been produced due to extensive use of carbon fiber/epoxy resin (CF/EP) composites. The fact that the supercritical fluid can be used to recycle these composites efficiently has attracted widespread concerns. A three-dimensional model of CF/EP laminates considering the interfacial layers was established. The internal stress distribution of laminates was simulated based on a heat transfer model; and the change of shear stress with supercritical temperature and pressure was investigated. The results show that the shear stress concentration was located in the interfacial layers; the maximum shear stress can be expressed by a curve of convex parabola to the temperature; and the most serious damage occurred in interfacial layers when temperature approached the glass-transition temperature of resin.

Analysis of Three-Dimensional Cutting Process With Thin Shear Plane Model

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Eiji Shamoto ◽  
Masahiro Kato ◽  
Norikazu Suzuki ◽  
Rei Hino
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Minimum Energy ◽  
Three Dimensional ◽  
Shear Plane ◽  
Cutting Edge ◽  
Cutting Process ◽  
Energy Principle ◽  
Chip Flow ◽  
Minimum Energy Principle

A new and basic analytical model of three-dimensional cutting is proposed by assuming multiple thin shear planes with either the maximum shear stress or minimum energy principle. The three-dimensional cutting process with an arbitrarily shaped cutting edge in a flat rake face is formulated with simple vector equations in order to understand and quickly simulate the process. The cutting edge and workpiece profile are discretized and expressed by their position vectors. Two equations among three unknown vectors, which show the directions of shear, chip flow, and resultant cutting force, are derived from the geometric relations of velocities and forces. The last vector equation required to solve the three unknown vectors is obtained by applying either the maximum shear stress or minimum energy principle. It is confirmed that the directions and the cutting forces simulated by solving the proposed vector equations agree with experimentally measured data. Furthermore, the developed model is applied to consider the three-dimensional cutting mechanics, i.e., how the chip is formed in the three-dimensional cutting with compressive stress acting between the discrete chips, as an example.

Multidisciplinary Design Optimization of the Composite Cooling Structure for Nickel-based Alloy Turbine Blade

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Xiaoru Qian ◽  
Peigang Yan ◽  
Wanjin Han
Keyword(s):  
Shear Stress ◽  
Flow Field ◽  
Turbine Blade ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Structure Design ◽  
Von Mises Stress ◽  
Von Mises

Abstract A designed method, multidisciplinary coupling computation and multiobjective optimization, has been established for the composite cooling structure of heavy gas turbine blade manufactured with a directionally solidified Ni-based superalloy. The method combines the one-dimensional fluid network gas-thermal coupling computation, three-dimensional flow field coupled with solid stress field, and anisotropic stress calculation based on finite deformation crystal slip. The temperature, flow field, Von-Mises stress and maximum resolved shear stress of the blade before and after optimization were analyzed. The results show that the optimized blade has lower maximum blade temperature, a more uniform temperature distribution, a lower flow resistance of the coolant channel at the leading edge than that of the original blade. The maximum Von-Mises stress of the optimized blade increases by 10.05 % more than the original blade. The maximum shear stress on the suction side and the pressure surface of the optimized blade are improved and slightly deteriorated compared with that of the original blade, respectively. The corresponding relationship of the maximum shear stress distribution with the local temperature gradient reveals further space for the improvement of the composite cooling structure. This paper has a particular guiding significance for the cooling structure design of the turbine blade.

scholarly journals The Effect of the Specimen–Platen Interface on Internal Cracking and Brittle Fracture of Ice Under Compression: High-Speed Photography

1989 ◽  
Vol 35 (121) ◽  
pp. 378-382 ◽  
Author(s):  
E.M. Schulson ◽  
M.C. Gies ◽  
G.J. Lasonde ◽  
W.A. Nixon
Keyword(s):  
Shear Stress ◽  
Brittle Fracture ◽  
Spatial Variation ◽  
Fresh Water ◽  
Uniaxial Compression ◽  
Fracture Strength ◽  
High Speed ◽  
Maximum Shear Stress ◽  
Crack Density ◽  
High Speed Photography

AbstractUniaxial compression experiments at –10°C at 10−3s−1 on fresh-water, granular ice have established through the use of high-speed photography that internal cracks nucleate preferentially away from the ice/platen (i/p) interface under conditions of i/p contraint, but near the interface under conditions of i/p expansion. Under conditions of little i/p interaction, cracks nucleate more or less randomly throughout the specimen. Correspondingly, the brittle-fracture strength decreases as the i/p interaction changes from compressive to tensile. These effects are explained in terms of the spatial variation of the maximum shear stress and the crack density.

Correlation between surface roughness parameters and contact stress of gear

2020 ◽  
pp. 135065012092866
Author(s):  
Yang Duo ◽  
Tang Jinyuan ◽  
Zhou Wei ◽  
Wen Yuqin
Keyword(s):  
Surface Roughness ◽  
Shear Stress ◽  
Correlation Analysis ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Peak Height ◽  
Tooth Surface ◽  
Curvature Radius ◽  
Roughness Parameters ◽  
Surface Roughness Parameters

To reveal the relationship between rough tooth surface microstructure characteristics and contact performance, contact analysis is carried out based on the measured surface topography of the tooth surface of ultrasonic grinding by utilizing the elastic-plastic contact mechanics and statistical correlation analysis theory. Simple correlation analysis and partial correlation analysis are adopted for the gear three-dimensional surface roughness parameters and the maximum Mises stress and maximum shear stress. Then, the method of stepwise regression analysis and path analysis is used to construct the best fitting linear model of 3D roughness parameters and the maximum Mises stress and maximum shear stress, and the parameters’ decision coefficient is obtained. The research shows: (1) the rank of comprehensive influence factors of the maximum Mises stress is as follows: arithmetical mean height ( Sa), peak material portion ( Smr1), maximum peak height ( Sp), reduced peak height ( Spk), and minimum curvature radius and height ratio ( K), where Smr1, Spk, and K are negatively correlated with the maximum Mises stress; (2) the comprehensive influence variables of the maximum shear stress are in the order of Sa, Spk, and Vmp, among which Spk and Vmp are inversely related to the maximum shear stress.

A Study of Sewing Ring Geometry on Wall Shear Stress of Implanting Bi-Leaflet Aortic Valves, Using Computational Fluid Dynamics

2009 ◽  
Vol 25 (3) ◽  
pp. 323-333
Author(s):  
C.-H. Hsu
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Stokes Equations ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Opening Angle ◽  
Analysis Model ◽  
Endothelial Lining ◽  
Ring Geometry ◽  
Wall Shear

AbstractThis paper concentrates on the wall shear stress discussion of implanting bi-leaflet aortic valve and concludes a better valve design. To simulate the haemodynamic characteristics of the blood flow, ANSYS CFX10.0 software was utilized to analyze the three-dimensional Reynolds-averaged Navier-Stokes equations. With a quasi-steady analysis model, we predict values of the blood velocity and the wall shear stress both over the valve leaflets and the endothelial lining. Analysis results highlight that leaflet opening angle and valve geometry affect the shear stress distribution and vortex flow regime. An analysis of haemodynamic study for the St. Jude valve with various openingangles is presented first and the sewing ring geometry change is then recommended. It is found that the wall shear stress decreases significantly after modifying the sewing ring geometry. Maximum shear stress reduces 18.5% compared to that of the original St. Jude model at peak systole. This would ease possible damage of endothelial lining of the aorta.

Stress analysis of some nut-bolt connections with modifications to the external shape of the nut

1987 ◽  
Vol 22 (4) ◽  
pp. 187-193 ◽  
Author(s):  
E A Patterson ◽  
B Kenny
Keyword(s):  
Shear Stress ◽  
Stress Concentration ◽  
Outer Surface ◽  
Maximum Stress ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Fatigue Tests ◽  
Steel Connections ◽  
Circumferential Groove ◽  
Stress Study

The effect on the stress levels in an axially loaded bolt has been investigated for the case where a nut which incorporated a circumferential groove in its outer surface was used. It was found from a three-dimensional photoelastic frozen stress study that the modified nut reduced the maximum stress in the bolt by 5 per cent. The addition of a bevel to the load bearing face of this nut further reduced the maximum stress to 74 per cent of its value in a standard connection. It has been established that these modifications reduce the maximum shear stress in the roots of the nut threads, and that the stress concentration associated with the groove was smaller than the maximum stress concentration in both the nut and bolt thread roots. The increase indicated by photoelastic analyses in the strength of the connection produced by these modifications, has also been substantiated by fatigue tests of steel connections, but these results are not reported in this paper.

Computer Models for the Mechanics of Three-Dimensional Cutting Processes—Part I: Theory and Numerical Method

1988 ◽  
Vol 110 (1) ◽  
pp. 32-37 ◽  
Author(s):  
D. A. Stephenson ◽  
S. M. Wu
Keyword(s):  
Three Dimensional ◽  
Material Behavior ◽  
Gradient Search ◽  
Rigid Plastic ◽  
Simple Material ◽  
Material Models ◽  
Ductile Metals ◽  
Plastic Materials ◽  
Cutting Processes ◽  
Minimum Work

A numerical modeling method for predicting chip form and power requirements in three-dimensional cutting processes is described. The method is based on variational (energy) results from the theory of rigid-plastic materials and is applicable to the steady-state cutting of ductile metals. The analysis involves mainly material behavior assumptions and for simple material models yield results similar to the widely-used minimum work approach. In Part I the theoretical basis of the method and the appropriate numerical algorithm (gradient search or steepest descent) for implementation in specific processes are described. Results for the oblique end turning and drilling processes are compared with experimental data in Part II.

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