Dent Imperfections in Shell Buckling: The Role of Geometry, Residual Stress, and Plasticity

2020 ◽  
Vol 88 (3) ◽  
Author(s):  
S. Gerasimidis ◽  
J. W. Hutchinson
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Middle Surface ◽  
External Pressure ◽  
Second Step ◽  
Elastic Buckling ◽  
Spherical Shells ◽  
Shell Buckling ◽  
Cylindrical Metal

Abstract Departures of the geometry of the middle surface of a thin shell from the perfect shape have long been regarded as the most deleterious imperfections responsible for reducing a shell’s buckling capacity. Here, systematic simulations are conducted for both spherical and cylindrical metal shells whereby, in the first step, dimple-shaped dents are created by indenting a perfect shell into the plastic range. Then, in the second step, buckling of the dented shell is analyzed, under external pressure for the spherical shells and in axial compression for the cylindrical shells. Three distinct buckling analyses are carried out: (1) elastic buckling accounting only for the geometry of the dent, (2) elastic buckling accounting for both dent geometry and residual stresses, and (3) a full elastic–plastic buckling analysis accounting for both the dent geometry and residual stresses. The analyses reveal the relative importance of the geometry and the residual stress associated with the dent, and they also provide a clear indicator of whether plasticity is important in establishing the buckling load of the dented shells.

Control of Surface Finishing Residual Stresses in Magnetic Recording Head Materials

1988 ◽  
Vol 110 (1) ◽  
pp. 87-92 ◽  
Author(s):  
S. Chandrasekar ◽  
B. Bhushan
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Magnetic Recording ◽  
Surface Finishing ◽  
Recording Head ◽  
Surface Residual Stresses ◽  
Mechanical And Physical Properties ◽  
Magnetic Recording Head ◽  
Processing Techniques

Surface finishing of magnetic recording head materials, such as ferrites, by diamond grinding and lapping results in a residual compressive stress on the surface. Residual stresses alter the magnetic properties of the ferrite causing the recording head performance to deteriorate. Hence, they need to be minimized. This paper considers the role of two processing techniques—annealing and chemical lapping—in controlling residual stress in ferrites. The effect of these processing techniques on various mechanical and physical properties of finished ferrites and the mechanism of residual stress control are discussed.

Instability of Cup-Cylinder Compound Shell Under Uniform External Pressure

1995 ◽  
Vol 39 (02) ◽  
pp. 160-165
Author(s):  
Raisuddin Khan ◽  
Wahhaj Uddin
Keyword(s):  
Critical Pressure ◽  
Nonlinear Differential Equations ◽  
External Pressure ◽  
Shells Of Revolution ◽  
Membrane Stress ◽  
Spherical Shells ◽  
Uniform External Pressure ◽  
Shell Buckling ◽  
Compound Shell ◽  
Method Of Solution

Instability of compound cup-end cylindrical shells under uniform external pressure is studied. Nonlinear differential equations governing the large axisymmetric deformations of shells of revolution which ensure the unique states of lowest potential energy of the shells under a given pressure are solved. The method of solution is multisegment integration, developed by Kalnins and Lestingi, for predicting the mode of buckling and the critical pressure of these compound shells. Results show that, when simple cylindrical and spherical shells which develop the same membrane stress under pressure are used as a compound cup-end cylindrical shell, buckling takes place in the cylinder portion, near the cup-cylinder junction, at loads a few times higher than the buckling load of conventional dome-cylinder shells.

Role of Tool Flank Wear and Machining Speed in Developing of Residual Stress in Machined Surface During High Speed Machining of Titanium Alloys

2015 ◽  
Author(s):  
Xueping Zhang ◽  
Rajiv Shivpuri ◽  
Anil K. Srivastava
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
High Speed ◽  
Flank Wear ◽  
Tool Geometry ◽  
High Speed Machining ◽  
Machined Surface ◽  
Tool Flank Wear ◽  
Machining Speed

Residual stresses generated from finish machining have a significant impact on the fatigue life of mechanical components by controlling crack initiation and propagation processes in their near subsurface. As governing variables, tool geometry, tool wear, machining parameter, work material property, and lubrication conditions have been widely studied to determine their effects on residual stress pattern in machined surface and subsurface. Among those parameters, tool flank wear was seldom fully investigated although tool flank wear, as well as machining speed, has been identified as the most important contributor to residual stress. Especially, tool flank wear becomes more significant due to the poor work thermal property during the high speed machining of titanium Ti-6Al-4V alloy. This study aims to investigate the combined role of tool flank wear and machining speed in developing residual stress in the machining of titanium alloy using finite element method. A microstructure sensitive material model based on Self Consistent Method (SCM) is adopted to incorporate the phase state and its transformations during machining cycle. Critical flank wear land and corresponding machining speeds are identified, beyond which compressive residual stresses are transferred into tensile residual stresses. High machining speeds demonstrate a distinct influence on residual stresses by means of promoting tool flank wear rate. The numerical simulation results are validated by empirical data provided in previous research.

Influence of Residual Stresses on the Damage of Composite Laminates under Tensile Loading

2015 ◽  
Vol 784 ◽  
pp. 361-368
Author(s):  
Zhong Meng Wen ◽  
Xiao Lu Gong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Composite Laminates ◽  
Tensile Loading ◽  
Hole Drilling ◽  
Acoustic Emission Technique ◽  
Hole Drilling Method ◽  
Incremental Hole Drilling ◽  
Drilling Method

This work investigates the effect of residual stresses on the damage of composite laminate. The incremental hole-drilling method is applied to determine residual stresses in composite laminates [02/θ2]s and then acoustic emission technique is used for the identification of damage appearance during the tensile testing. The samples with different residual stress distribution are prepared through curing and post curing in order to study the role of residual stress on the damage of composite laminates. Besides the experimental method, the theoretical approach is applied to illustrate the role of residual stress on the damage of composite laminates.

scholarly journals Buckling of spherical shells revisited

2016 ◽  
Vol 472 (2195) ◽  
pp. 20160577 ◽  
Author(s):  
John W. Hutchinson
Keyword(s):  
Middle Surface ◽  
External Pressure ◽  
Maximum Pressure ◽  
Imperfection Sensitivity ◽  
Spherical Shells ◽  
Mode Localization ◽  
Axisymmetric State ◽  
New Findings ◽  
Post Buckling ◽  
The 1960S

A study is presented of the post-buckling behaviour and imperfection sensitivity of complete spherical shells subject to uniform external pressure. The study builds on and extends the major contribution to spherical shell buckling by Koiter in the 1960s. Numerical results are presented for the axisymmetric large deflection behaviour of perfect spheres followed by an extensive analysis of the role axisymmetric imperfections play in reducing the buckling pressure. Several types of middle surface imperfections are considered including dimple-shaped undulations and sinusoidal-shaped equatorial undulations. Buckling occurs either as the attainment of a maximum pressure in the axisymmetric state or as a non-axisymmetric bifurcation from the axisymmetric state. Several new findings emerge: the abrupt mode localization that occurs immediately after the onset of buckling, the existence of an apparent lower limit to the buckling pressure for realistically large imperfections, and comparable reductions of the buckling pressure for dimple and sinusoidal equatorial imperfections.

scholarly journals Imperfection Sensitivity of Externally Pressurized Spherical Shells

1967 ◽  
Vol 34 (1) ◽  
pp. 49-55 ◽  
Author(s):  
J. W. Hutchinson
Keyword(s):  
General Theory ◽  
Shell Thickness ◽  
Middle Surface ◽  
External Pressure ◽  
Postbuckling Behavior ◽  
Imperfection Sensitivity ◽  
Spherical Shells ◽  
Small Deviations ◽  
Severe Effect ◽  
Shell Geometry

The initial postbuckling behavior of a shallow section of a spherical shell subject to external pressure is studied within the context of Koiter’s general theory of postbuckling behavior. Imperfections in the shell geometry are shown to have the same severe effect on the buckling strengths of spherical shells as has been demonstrated for axially compressed cylindrical shells. Large reductions in the buckling pressure result from small deviations, relative to the shell thickness, of the shell middle surface from the perfect configuration.

scholarly journals Role of Crack-Tip Residual Stresses in Stress Corrosion Behavior of Pre-stressing AA7020

2019 ◽  
Vol 9 (03) ◽  
Author(s):  
Ashish Thakur
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Corrosion Behavior ◽  
Stress Corrosion Cracking ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
Compressive Residual Stresses

This paper analyzes stress corrosion cracking (SCC) of pre-cracked samples in the presence of compressive residual stresses generated in the vicinity of the crack tip during fatigue pre-cracking. Research focuses on the role of cracktip residual stresses of compressive nature, generated by fatigue loading, in stress corrosion cracking of pre-cracked samples of medium high strength aluminum alloy 7020 subjected to localized anodic dissolution and hydrogen assisted cracking. Fatigue pre-cracking load on the samples generates compressive residual stresses in the vicinity of the crack tip which improve the stress corrosion behavior of the aluminum alloy by delaying either the metal dissolution or the hydrogen entry, thus increasing the fracture load in an aggressive environment. The rice model of the residual stress distribution in the vicinity of a crack tip may be usedto explain these retardation effects by estimating the stress level and plastic zone size. Microscopically, compressive residual stress produce a transition topography between the fatigue pre-crack and the cleavage-like (unstable) fracture mode.

The Influence of Residual Stress on Micromachine Stiction

2004 ◽  
Author(s):  
Kai-Tak Wan ◽  
Lior Kogut
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Microelectromechanical Systems ◽  
Adhesive Contact ◽  
Adhesion Forces ◽  
Adhesion Contact ◽  
Interfacial Contact ◽  
Cylindrical Punch ◽  
Punch Displacement

Adhesion plays an important role in microelectromechanical systems (MEMS). It is a major concern in MEMS reliability and oftentimes excessive adhesion forces lead to permanent adherence of MEMS surfaces resulting in microdevice failure. The role of residual stresses in the adhesive contact between a pre-stressed membrane and a rigid flat-ended cylindrical punch is studied. Breaking the contact can be achieved under either fixed-load or fixed-grips configuration. The influence of the residual stress on the pull-off force, punch displacement, and contact area at pull-off is studied. It is shown that residual stresses have significant influence on interfacial contact behavior in MEMS and, hence, should be taken into consideration in formulating the adhesion contact mechanics.

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