Remarks on Combined Bending and Twisting of Thin Tubes in the Plastic Range

1953 ◽  
Vol 20 (3) ◽  
pp. 345-348
Author(s):  
E. T. Onat ◽  
R. T. Shield
Keyword(s):  
Approximate Method ◽  
Work Hardening ◽  
Composite Beam ◽  
Plastic Material ◽  
Plastic Range ◽  
Hardening Material ◽  
Incremental Approach ◽  
Perfectly Plastic ◽  
Thin Walled ◽  
Good Agreement

Abstract The influence of the loading program on the agreement between the predictions of the Hencky and the Prandtl-Reuss stress-strain relations for a perfectly plastic material is investigated in the case of the combined bending and twisting of thin-walled tubes. The agreement in the values of the bending and twisting moments is found to vary considerably with the particular loading program chosen. The analysis is extended to tubes composed of a work-hardening material. The bending and twisting moments are obtained numerically using the incremental approach for a square tube which is bent and then twisted. Owing to the large amount of labor involved in this solution, an approximate method using the concept of a “composite” beam is developed, and good agreement in the results is found with those obtained from the incremental solution.

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.

Study on Dynamic Response Characteristics of Composite Thin-Walled Square Beam Subject to Three-Point Bending

2012 ◽  
Vol 201-202 ◽  
pp. 715-720
Author(s):  
Gang Yi Zhou ◽  
Xin Long Dong ◽  
Jun Liu
Keyword(s):  
Composite Beam ◽  
Simulation Analysis ◽  
Impact Load ◽  
Single Beam ◽  
Three Point Bending ◽  
Response Characteristics ◽  
Crushing Force ◽  
Good Energy ◽  
Thin Walled ◽  
Good Agreement

In this paper, the experiment of thin-walled square beam subject to three-point bending by using the self-devised drop-hammer impact was carried out. The mechanical behavior of this thin-walled specimen under impact load was obtained. The process of deformation and the dynamic buckling behaviors of composite square beam were analyzed by mean of simulation technique of finite element using ANSYS/LS-DYNA. The simulation analysis of deformation and crushing force characteristics was in good agreement with the experimental results. Meanwhile, the comparative analysis of percussive force and energy absorbability from composite beam and single beam was performed. It is shown by the investigation that the peak percussive force of such composite beam falls down relative to single beam and it possesses good energy absorbability too. The computed result also shows reducing the thickness of the bottom board of such thin-walled square beam has less of an effect on the energy absorbability.

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.

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.

NONLINEAR STABILITY ANALYSIS OF THIN-WALLED FRAMES USING UL–ESA FORMULATION

2004 ◽  
Vol 04 (01) ◽  
pp. 45-67 ◽  
Author(s):  
GORAN TURKALJ ◽  
JOSIP BRNIĆ
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Displacement Field ◽  
Plastic Material ◽  
Plastic Hinge ◽  
Element Formulation ◽  
Nonlinear Stability Analysis ◽  
Perfectly Plastic ◽  
Straight Beam ◽  
Thin Walled

This work presents a one-dimensional finite element formulation for nonlinear analysis of spaced framed structures with thin-walled cross-sections. Within the framework of updated Lagrangian formulation, the nonlinear displacement field of thin-walled cross-sections, which accounts for restrained warping as well as the second-order displacement terms due to large rotations, the equations of equilibrium are firstly derived for a straight beam element. Due to the nonlinear displacement field, the geometric potential of semitangential moment is obtained for both the torsion and bending moments. In such a way, the joint moment equilibrium conditions of adjacent non-collinear elements are ensured. Force recovering is performed according to the external stiffness approach. Material nonlinearity is introduced for an elastic-perfectly plastic material through the plastic hinge formation at finite element ends and for this a corresponding plastic reduction matrix is determined. The interaction of element forces at the hinge and the possibility of elastic unloading are taken into account. The effectiveness of the numerical algorithm discussed is validated through the test problem.

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.

An efficient procedure for modelling limited plastic flow

1998 ◽  
Vol 212 (8) ◽  
pp. 731-740 ◽  
Author(s):  
P M Blomerus ◽  
D A Hills
Keyword(s):  
Plastic Material ◽  
Notch Root ◽  
Stress Raiser ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Field Boundary ◽  
Efficient Procedure ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Good Agreement

A degree of plasticity is often tolerated at stress raising features in severely loaded, nominally elastic, components. Conventionally, the methods available for analysis are the finite element method (FEM) or an approximate notch root plastic strain method. The method introduced here is based on the idea of distributing dislocations to form a perturbation on an elasticity solution to solve the problem for an elastic—perfectly plastic material in transverse plane strain. Specialized kernels are used to satisfy exactly the far field boundary conditions and those at the stress raiser, so that only the small plastic enclave of material need be discretized. The method is seen to follow the incremental nature of the problem and to take into account the stress redistribution in plasticity. The problem of a circular hole under remote tension is solved and good agreement with an FEM analysis of a similar problem is observed.

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