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 Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

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.

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.

Mechanical Stress Measurements in Damascene-Fabricated Aluminum Interconnect Lines

1999 ◽  
Vol 594 ◽  
Author(s):  
Paul R. Besser
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Aspect Ratio ◽  
Tensile Stress ◽  
Mechanical Stress ◽  
Hydrostatic Stress ◽  
Maximum Shear Stress ◽  
Compressive Stresses ◽  
Biaxial Tensile Stress ◽  
Interconnect Lines

AbstractThe mechanical stress state of damascene-fabricated Al interconnect lines was determined on an array of lines on the product die of a logic technology device. Narrow, unpassivated, damascene Al lines have a purely hydrostatic stress (108 MPa). The hydrostatic stress of damascene Al lines (411 MPa) is much larger once the dielectric is deposited. However, the maximum shear stress remains small in magnitude, compared to RIE Al lines of similar thermal history and aspect ratio. The stress of damascene lines was measured as a function of linewidth. Unpassivated, wide lines, have compressive stresses along the length and width and zero along the line height. Passivated wide lines have a biaxial, tensile stress in-plane and zero along the line height.

scholarly journals Deformation rates in combined compression and shear for ice which is initially isotropic and after the development of strong anisotropy

1996 ◽  
Vol 23 ◽  
pp. 247-252 ◽  
Author(s):  
Li Jun ◽  
T.H Jacka ◽  
W.F. Budd
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Stress State ◽  
Strain Rate ◽  
Shear Strain ◽  
Uniaxial Compression ◽  
Simple Shear ◽  
Strain Rates ◽  
Shear Strain Rate ◽  
State Dependent

Laboratory-prepared fine-grained, initially isotropic polycrystalline ice samples were deformed under conditions of simple shear with simultaneous uniaxial compression at a constant temperature of −2.0°C. The aim was to investigate the effects of stress configuration on the flow rate of initially isotropic ice and on ice with subsequent stress and strain-induced anisotropy. Experiments were carried out for various combinations of shear and compression with shear stress ranging from 0 to 0.49 MPa and compressive stress ranging from 0 to 0.98 MPa, but such that for every experiment the octahedral shear stress was 0.4 MPa.The strain curves resulting from the experiments clearly exhibit minimum strain rates while the ice is still isotropic, and steady-state tertiary strain rates along with the development of steady-state anisotropic fabric patterns. With constant octahedral stress (root-mean-square of the principal stress deviators), the minimum octahedral shear-strain rate has no dependence on stress configuration. This result supports the hypothesis that the flow of isotropic ice is dependent only on the second invariant of the stress tensor. This fundamental assumption has been used to provide a general description of ice-flow behaviour independent of the stress configuration (e.g. Nye, 1953; Glen, 1958; Budd, 1969).For the tertiary flow of anisotropic ice, the octahedral strain rate is stress-state dependent as a consequence of the developed crystal-orientation fabric, which is also stress-state dependent, and which develops with strain and rotation. The present tests indicate that the enhancement factor for steady-state tertiary octahedral shear-strain rate depends on the shear or compression fraction and varies from about 10 for simple shear (with zero compression) to about 3 for uniaxial compression (with zero shear).

Full Scale Experimental Analysis of Stress State in Welding Repairs of Drilled Pipelines

2006 ◽  
Author(s):  
Jian Shuai ◽  
Wenping Bu
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Failure Strain ◽  
Maximum Shear Stress ◽  
Full Scale ◽  
Loading Capacity ◽  
Yield Limit ◽  
Strain Gages ◽  
Similar Yield ◽  
Short Tube

Recently, drilling holes in petroleum transmission pipelines is becoming of major concern for pipeline companies. These drilled pipelines must be repaired through welding ways. There are two ways to repair these pipelines in fields. One is welding a short tube with a cap. Another is welding a patch. In this paper, full scale experiments were conducted to assess the stresses state and the loading capability of the repaired pipelines. The φ711×10 pipelines repaired by welding a tube cap or a patch were pressured to burst failure. Strain gages have been used extensively to monitor stress state in full scale pipeline tests. It was showed that welding a tube cap or a patch resulted in the non-uniform stresses distribution and the stress concentration in the extent. These two kinds of the repaired pipeline has almost the similar yield limit pressure which are approximately equal to 85% of that of pipelines that were not damaged. Patching repair has more restriction to the deformation around a hole than tube capping repair, therefore it may have a little better loading capacity than tube capping repair. The burst pressures in these tests are close to that of pipeline which has not been damaged, whereas the location of burst failure is far from where a short tube or a patch is welded. The burst is a ductile fracture by maximum shear stress.

Critical Plane Search Method for Biaxial and Multiaxial Fatigue Analysis

2016 ◽  
Author(s):  
Kumarswamy Karpanan
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Strain Amplitude ◽  
Stress Amplitude ◽  
Maximum Shear Stress ◽  
Fatigue Analysis ◽  
Search Method ◽  
Stress Range ◽  
Critical Plane ◽  
Stress Strain

For complex cyclic loadings, stress- or strain-based critical plane search methods are commonly used for fatigue analysis of the structural components. Complex loadings can result in a non-proportional type loading in which it is difficult or impossible to determine the plane with maximum shear stress/strain amplitude. ASME Sec VIII, Div-3 fatigue analysis for non-welded components is a shear stress based fatigue analysis method and, for non-proportional loading, uses the critical plane search method to calculate the plane with maximum shear stress amplitude. For a two-dimensional non-proportional stress state, analytical stress transformation equations can be used to calculate the shear stress or strain amplitude on any plane at a point. The shear stress range on each plane is the difference between the maximum and minimum shear stress. For a three-dimensional stress state, shear stress amplitude calculations are much more complicated because the shear stress is a vector and both magnitude and direction change during the loading cycle. In ASME VIII-3, the maximum shear stress range among all planes, along with the normal stress on the plane, is used to calculate the stress amplitude. This paper presents a method to calculate the shear stress/strain amplitude using 3D transformation equations. This method can be used for any stress- or strain-based critical plane search method. This paper also discusses ASME proportional and non-proportional fatigue analysis methods in detail.

scholarly journals Analysis of Fracture Behaviour of Exploded Metal Cylinders with Varied Charge

2018 ◽  
Vol 183 ◽  
pp. 01036 ◽  
Author(s):  
Xinlong Dong ◽  
Xinlu Yu ◽  
Shunjie Pan
Keyword(s):  
Shock Wave ◽  
Shear Stress ◽  
Shear Fracture ◽  
Maximum Shear Stress ◽  
Equivalent Plastic Strain ◽  
Outer Wall ◽  
Detonation Pressure ◽  
Element Analysis ◽  
Free Expansion ◽  
Metal Cylinder

Explosively driven fragmentation of ductile metals cylinders is a highly complex phenomenon. In this work, the fracture characteristics of exploded TA2 titanium alloy cylinder with varied charge were investigated numerically and experimentally. The results show that the fracture surfaces of fragments lie along planes of maximum shear stress for either a higher or a lower detonation pressure, but their mechanism is different. The finite element analysis demonstrated that the equivalent plastic strain in the middle of the wall is always larger than that of inner and outer wall for metal cylinder during the stage of shock wave driven period. For the high explosive pressures, the micro-cracks originated firstly in middle zone of wall during the stage of shock wave driven, and extend to the inner and outer wall in the direction of maximum shear stress. Explosives which generate lower detonation pressures, the shear fracture of cylinder originated from the inner wall and propagate to the outer wall in an angle of 45° or 135° to radial, the crack begin at the stage of free expansion. The simulated analysis of the process of deformation and fragmentation for exploded metal cylinder agree with the experimental results.

scholarly journals Deformation rates in combined compression and shear for ice which is initially isotropic and after the development of strong anisotropy

1996 ◽  
Vol 23 ◽  
pp. 247-252 ◽  
Author(s):  
Li Jun ◽  
T.H Jacka ◽  
W.F. Budd
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Stress State ◽  
Strain Rate ◽  
Shear Strain ◽  
Uniaxial Compression ◽  
Simple Shear ◽  
Strain Rates ◽  
Shear Strain Rate ◽  
State Dependent

Laboratory-prepared fine-grained, initially isotropic polycrystalline ice samples were deformed under conditions of simple shear with simultaneous uniaxial compression at a constant temperature of −2.0°C. The aim was to investigate the effects of stress configuration on the flow rate of initially isotropic ice and on ice with subsequent stress and strain-induced anisotropy. Experiments were carried out for various combinations of shear and compression with shear stress ranging from 0 to 0.49 MPa and compressive stress ranging from 0 to 0.98 MPa, but such that for every experiment the octahedral shear stress was 0.4 MPa. The strain curves resulting from the experiments clearly exhibit minimum strain rates while the ice is still isotropic, and steady-state tertiary strain rates along with the development of steady-state anisotropic fabric patterns. With constant octahedral stress (root-mean-square of the principal stress deviators), the minimum octahedral shear-strain rate has no dependence on stress configuration. This result supports the hypothesis that the flow of isotropic ice is dependent only on the second invariant of the stress tensor. This fundamental assumption has been used to provide a general description of ice-flow behaviour independent of the stress configuration (e.g. Nye, 1953; Glen, 1958; Budd, 1969). For the tertiary flow of anisotropic ice, the octahedral strain rate is stress-state dependent as a consequence of the developed crystal-orientation fabric, which is also stress-state dependent, and which develops with strain and rotation. The present tests indicate that the enhancement factor for steady-state tertiary octahedral shear-strain rate depends on the shear or compression fraction and varies from about 10 for simple shear (with zero compression) to about 3 for uniaxial compression (with zero shear).

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