scholarly journals Deformation field heterogeneity in punch indentation

2014 ◽  
Vol 470 (2166) ◽  
pp. 20130807 ◽  
Author(s):  
Tejas G. Murthy ◽  
Christopher Saldana ◽  
Matthew Hudspeth ◽  
Rachid M'Saoubi
Keyword(s):  
Crystallographic Texture ◽  
High Speed ◽  
Plastic Material ◽  
Deformation Field ◽  
Flat Punch ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Shear Type ◽  
Heterogeneous Deformation

Plastic heterogeneity in indentation is fundamental for understanding mechanics of hardness testing and impression-based deformation processing methods. The heterogeneous deformation underlying plane-strain indentation was investigated in plastic loading of copper by a flat punch. Deformation parameters were measured, in situ , by tracking the motion of asperities in high-speed optical imaging. These measurements were coupled with multi-scale analyses of strength, microstructure and crystallographic texture in the vicinity of the indentation. Self-consistency is demonstrated in description of the deformation field using the in situ mechanics-based measurements and post-mortem materials characterization. Salient features of the punch indentation process elucidated include, among others, the presence of a dead-metal zone underneath the indenter, regions of intense strain rate (e.g. slip lines) and extent of the plastic flow field. Perhaps more intriguing are the transitions between shear-type and compression-type deformation modes over the indentation region that were quantified by the high-resolution crystallographic texture measurements. The evolution of the field concomitant to the progress of indentation is discussed and primary differences between the mechanics of indentation for a rigid perfectly plastic material and a strain-hardening material are described.

scholarly journals Ratcheting Assessment of a Fixed Tube Sheet Heat Exchanger Subject to In Phase Pressure and Temperature Cycles

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Khosrow Behseta ◽  
Donald Mackenzie ◽  
Robert Hamilton
Keyword(s):  
Heat Exchanger ◽  
Plastic Material ◽  
Sheet Thickness ◽  
Peak Stress ◽  
Material Model ◽  
Tube Sheet ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Inelastic Analysis ◽  
Plastic Shakedown

An investigation of the cyclic elastic-plastic response of an Olefin plant heat exchanger subject to cyclic thermal and pressure loading is presented. Design by analysis procedures for assessment of shakedown and ratcheting are considered, based on elastic and inelastic analysis methods. The heat exchanger tube sheet thickness is nonstandard as it is considerably less than that required by conventional design by formula rules. Ratcheting assessment performed using elastic stress analysis and stress linearization indicates that shakedown occurs under the specified loading when the nonlinear component of the through thickness stress is categorized as peak stress. In practice, the presence of the peak stress will cause local reverse plasticity or plastic shakedown in the component. In nonlinear analysis with an elastic–perfectly plastic material model the vessel exhibits incremental plastic strain accumulation for 10 full load cycles, with no indication that the configuration will adapt to steady state elastic or plastic action, i.e., elastic shakedown or plastic shakedown. However, the strain increments are small and would not lead to the development of a global plastic collapse or gross plastic deformation during the specified life of the vessel. Cyclic analysis based on a strain hardening material model indicates that the vessel will adapt to plastic shakedown after 6 load cycles. This indicates that the stress categorization and linearization assumptions made in the elastic analysis are valid for this configuration.

Continuous Strength Method for Aluminium Alloy Structures

2013 ◽  
Vol 742 ◽  
pp. 70-75 ◽  
Author(s):  
Mei Ni Su ◽  
Ben Young ◽  
Leroy Gardner
Keyword(s):  
Aluminium Alloy ◽  
Strain Hardening ◽  
Plastic Material ◽  
Design Method ◽  
Material Model ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Base Curve ◽  
Current Design ◽  
Elastic Perfectly Plastic

Aluminium alloys are nonlinear metallic materials with continuous stress-strain curves that are not well represented by the simplified elastic, perfectly plastic material model used in many current design specifications. Departing from current practice, the continuous strength method (CSM) is a recently proposed design approach for non-slender aluminium alloy structures with consideration of strain hardening. The CSM is deformation based and employs a base curve to define a continuous relationship between cross-section slenderness and deformation capacity. This paper explains the background and the two key components - (1) the base curve and (2) the strain hardening material model of the continuous strength method. More than 500 test results are used to verify the continuous strength methodas an accurate and consistent design method for aluminium alloy structures.

Dynamic Expansion of a Spherical Cavity in an Elastic, Perfectly Plastic Material

1968 ◽  
Vol 35 (2) ◽  
pp. 372-378 ◽  
Author(s):  
Chi-Hung Mok
Keyword(s):  
Spherical Cavity ◽  
High Speed ◽  
Numerical Solutions ◽  
Plastic Material ◽  
Numerical Technique ◽  
Nonlinear Dependence ◽  
Static Approximation ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

It is shown that initial and boundary-value problems involving high-speed elastic-plastic deformation with spherical symmetry can be solved using a finite-difference numerical technique. Numerical solutions for the dynamic expansion of a spherical cavity under a constant pressure are presented to demonstrate the nature and capability of the numerical scheme. While the solution for an elastic material agrees closely with the exact one, the solution for an elastic, perfectly plastic material also receives support from Green’s analytic predictions concerning the motion of the elastic-plastic boundary. At large times, the asymptotic solution of the dynamic elastic-plastic problem is different from the quasi-static solution. This result indicates that the concept of quasi-static approximation may not hold in dynamic plasticity. A nonlinear dependence of the plastic solution on the boundary condition is also observed.

The Application of Limit Analysis to Punch-Indentation Problems

1953 ◽  
Vol 20 (4) ◽  
pp. 453-460
Author(s):  
R. T. Shield ◽  
D. C. Drucker
Keyword(s):  
Limit Analysis ◽  
Plane Surface ◽  
Plastic Material ◽  
Yield Criterion ◽  
Three Dimensional ◽  
Upper And Lower Bounds ◽  
Two Dimensional ◽  
Flat Punch ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

Abstract Limit analysis is applied to obtain upper and lower bounds for the punch pressure in the indentation of the plane surface of an elastic-perfectly plastic material by a flat rigid punch. The two-dimensional flat punch and the three-dimensional flat square and rectangular punch problems are considered. The analysis assumes Tresca’s yield criterion of constant maximum shearing stress k, during plastic deformation. It is shown that the pressure required to produce indentation in the two-dimensional problem lies between 5k and (2 + π)k. The lower bound obtained for any rectangular punch is again 5k while the upper bound for a smooth punch lies between 5.71k for a square and (2 + π)k for a very long rectangle. A value of 5.36k is found for a ratio of length to breadth of 3. The limit pressure for a uniformly loaded area, as distinguished from an area loaded by a punch, is bracketed by 5k and (2 + π)k when the area is convex.

Experiment and FEM Simulation on Residual Stress of Cold Expansion Hole

2007 ◽  
Vol 561-565 ◽  
pp. 1783-1786 ◽  
Author(s):  
Xiao Jun Shao ◽  
Jun Liu ◽  
Yong Shou Liu ◽  
Zhu Feng Yue
Keyword(s):  
Residual Stress ◽  
Plastic Material ◽  
Fem Simulation ◽  
Stress Fields ◽  
Material Models ◽  
Hardening Material ◽  
Cold Expansion ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Cold Expansion Hole

A 2D cylindrical plate model has been established to study the distribution of residual stress of cold expansion hole under different interference values. In addition, the effects of material models on residual stress fields are considered also. Experiments are carried out to measure the residual stress of cold expansion hole and verify simulation results. FEM results show, with interference values increasing, the higher residual radial and circumferential stresses are obtained. At same interference value, the residual stress of Hardening Material( HM ) model is much larger than that of Elastic Perfectly Plastic Material( EPPM ) model.

Plastic Response Estimation in Repeated Elastic Analyses for Strain Hardening Material Model

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
S. L. Mahmood ◽  
R. Adibi-Asl ◽  
C. G. Daley
Keyword(s):  
Strain Hardening ◽  
Strain Energy ◽  
Plastic Material ◽  
Limit Load ◽  
Material Model ◽  
Element Analysis ◽  
Hardening Material ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

Simplified limit analysis techniques have already been employed for limit load estimation on the basis of linear elastic finite element analysis (FEA) assuming elastic-perfectly-plastic material model. Due to strain hardening, a component or a structure can store supplementary strain energy and hence carries additional load. In this paper, an iterative elastic modulus adjustment scheme is developed in context of strain hardening material model utilizing the “strain energy density” theory. The proposed algorithm is then programmed into repeated elastic FEA and results from the numerical examples are compared with inelastic FEA results.

Ratchet Boundary Evaluation and Comparison With Ratcheting Experiments Involving Strain Hardening Material Models

2012 ◽  
Author(s):  
H. Indermohan ◽  
W. Reinhardt
Keyword(s):  
Strain Hardening ◽  
Nuclear Power ◽  
Power Plants ◽  
Plastic Material ◽  
Material Model ◽  
Experimental Investigations ◽  
Material Models ◽  
Hardening Material ◽  
Simultaneous Application ◽  
Perfectly Plastic

Pressure components in nuclear power plants are designed to prevent the failure mechanism of incremental deformation or “ratcheting” due to the simultaneous application of mechanical loads such as pressure and cyclic loads. Design criteria using elastic methods that are specified in NB-3200 of ASME Section III Code are derived from a perfectly-plastic material model. The Code allows the use of plastic methods to demonstrate an acceptable response to cyclic loading, but does not provide clear guidance on any specific plasticity model to use. It has been shown in previous studies that some strain hardening plasticity models are unsuitable for establishing the absence of ratcheting. In this paper, the ratchet boundary obtained from the perfectly plastic and the strain hardening Armstrong-Frederick material models are examined based on the published experimental investigations of the classical Bree problem, pipe bends under in-plane bending and tension-torsion tests. Suitable criteria for evaluating the cyclic analysis response are discussed.

Nonlinear Analysis of Axisymmetrically Wrinkled Pipes Under Axial Loads and Internal Pressures

2015 ◽  
Author(s):  
Ashutosh Sutra Dhar ◽  
Abu Hena Muntakim
Keyword(s):  
Residual Stress ◽  
Strain Hardening ◽  
Plastic Material ◽  
Stress History ◽  
Element Analysis ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
History Effects ◽  
Conservative Estimation ◽  
Surrounding Soil

Nonlinear finite element analysis of axi-symmetrically dented/wrinkled pipe has been presented in this paper. The pipe including surrounding soil was modelled using three different approaches to indicate the effects of modelling approaches on the simulation of pipe behavior. In the first approach, pipe was modelled with the geometry of the dented/wrinkled pipe without consideration of any residual stress and stress history. In the second approach, residual stress was applied at the nodal points of the pipe geometry modelled as in the first approach. In the third approach, a dent/wrinkle was created on the pipe wall through applying nodal displacements to include residual stress as well as the stress history effects. The analysis revealed that the first approach provides an un-conservative estimation of the pipe capacity. The second approach provides a reasonable estimation of the pipe capacity for elastic perfectly plastic material. However, the second approach provides a conservative estimation for strain hardening material, since pipe stress history is not considered. For strain hardening materials, both residual stress and the stress history should be considered for the simulation of the pipe behavior. The surrounding soil appears not to contribute to the capacity of the pipes under the loading conditions investigated.

Elastic-plastic stress analysis of a cracked thick-walled cylinder

1983 ◽  
Vol 18 (4) ◽  
pp. 253-260 ◽  
Author(s):  
C L Tan ◽  
K H Lee
Keyword(s):  
Internal Pressure ◽  
Stress Analysis ◽  
Plastic Material ◽  
Boundary Integral ◽  
Hardening Material ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Walled Cylinder ◽  
Plastic Stress

The boundary integral equation (BIE) method for two-dimensional elastic-plastic stress analysis is applied to an internally pressurized thick-walled cylinder containing a radial crack. Two different types of material are considered, namely, an elastic-perfectly plastic material and a work-hardening material. The loading conditions applied include the case when the internal pressure also acts on the crack faces, and the case when it does not. Results are presented showing the plastic zone development in the cylinder and the variations of the fracture mechanics parameter, the J line integral, with increasing internal pressure.

Crystallographic Textures Produced During Sand Blasting

2015 ◽  
Author(s):  
Saurabh Basu ◽  
Zhiyu Wang ◽  
Christopher Saldana
Keyword(s):  
Orientation Imaging Microscopy ◽  
Deformation Field ◽  
Flat Punch ◽  
Sand Blasting ◽  
First Order ◽  
In Situ Techniques ◽  
Orientation Imaging ◽  
Self Consistent

Evolution of crystallographic textures in sand blasted surfaces is studied. Sand blasting is approximated as a series of ideal cylindrical, flat punch and wedge indents. Features of the deformation field produced during indentation with these geometries is studied using in-situ techniques. Subsequently, crystallographic textures produced during indentation with these geometries is delineated using orientation imaging microscopy and simulated using the visco plastic self consistent framework. Finally, using a novel heuristic, the crystallographic textures created during indentation are related to those produced during sand blasting. It was seen that the heuristic is able perform a first order replication of empirically observed crystallographic textures.

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