INFLUENCE OF STRAIN HARDENING ON THE BEHAVIOR AND DESIGN OF STEEL STRUCTURES

2011 ◽  
Vol 11 (05) ◽  
pp. 855-875 ◽  
Author(s):  
LEROY GARDNER ◽  
FACHENG WANG ◽  
ANDREW LIEW
Keyword(s):  
Structural Steel ◽  
Strain Hardening ◽  
Plastic Material ◽  
Design Method ◽  
Steel Structures ◽  
Material Model ◽  
Rigid Plastic ◽  
Cross Sectional ◽  
Present Generation ◽  
Indeterminate Structures

The present generation of international structural steel design codes treats material nonlinearity through simplified elastic-plastic or rigid-plastic material models. However, the actual stress–strain response of structural steel is more complex than this and features, in particular, strain hardening. Strain hardening refers to the increase in strength beyond yield because of plastic deformation. The influence of strain hardening on the behavior and design of steel structures is examined in this study through both the experimentation and the analysis of existing data, and a method to exploit the additional capacity that arises is outlined. Both determinate and indeterminate structures are considered. The proposed design method, referred to as the continuous strength method (CSM), is a deformation-based design approach employing a continuous relationship between cross-sectional slenderness and cross-sectional deformation capacity, together with a material model that allows for strain hardening. Comparisons are made between test results generated as part of the present study and collected from existing studies, and the predictions from the CSM and Eurocode 3 (EC3). For all cases considered, the CSM, through a rational exploitation of strain hardening, offers a more accurate prediction of observed physical behavior.

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.

An Unexpected Feature of a Class of Damage Evolution Models

2016 ◽  
Vol 713 ◽  
pp. 195-198
Author(s):  
Sergei Alexandrov
Keyword(s):  
Metal Forming ◽  
Damage Evolution ◽  
Plastic Material ◽  
Closed Form Solution ◽  
Material Model ◽  
Form Solution ◽  
Friction Condition ◽  
Rigid Plastic ◽  
Damage Evolution Equation ◽  
Rigid Plastic Material

The main objective of the present paper is to demonstrate, by means of a boundary value problem permitting a closed-form solution, that no solution exists under certain conditions in the case of a rigid/plastic material model including a damage evolution equation. The source of this feature of the solution is the sticking friction condition, which is often adopted in the metal forming literature.

An Adaptive Pressbrake Control for Strain-Hardening Materials

1986 ◽  
Vol 108 (2) ◽  
pp. 127-132 ◽  
Author(s):  
K. A. Stelson
Keyword(s):  
Strain Hardening ◽  
Material Property ◽  
Plastic Material ◽  
Material Model ◽  
Punch Force ◽  
Elastic Plastic ◽  
The Press ◽  
Elastic Plastic Material ◽  
Thickness Variations ◽  
Force Displacement

An improved adaptive pressbrake control algorithm is described. The problem is to control the punch reversal position of the press so that the final unloaded angle of the bend remains unchanged in the presence of material property and thickness variations of the sheets or plates being bent. Pressbrake control algorithms that use punch force-displacement data to identify thickness and material property variations have shown promise. However, since previous controllers have been based on an elastic-plastic material model, the parts have been overbent. In this paper, a controller based on an elastic, power-law strain-hardening model is proposed. Experiments have shown that the model eliminates the tendency to overbend the parts that is present in the elastic-plastic algorithm.

Study on Drilling Force of Pore for Hard-to-Cut Material

2010 ◽  
Vol 455 ◽  
pp. 521-524
Author(s):  
Yong Tang ◽  
Bang Yan Ye ◽  
X.F. Hu ◽  
Qiang Wu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Metal Cutting ◽  
Plastic Material ◽  
Material Model ◽  
Element Model ◽  
Drilling Process ◽  
Drilling Force ◽  
Rigid Plastic ◽  
Key Techniques

This paper studies drilling force of pore for hard-cutting material based on theoretical and experimental investigation during pore drilling process. A coupled thermo-mechanical finite element model of metal pore drilling process was established. Some key techniques such as material model, chip separation and damage criteria and dynamic mesh self-adapting technology in the finite element simulation of metal cutting process were discussed in details. The paper simulated dynamically the chip formation of the twist drilling process in which rigid plastic material model was selected for workpieces and thermal rigid models for tools. The results indicate that the proposed finite element model is not only correct but also feasible in the prediction of the variations of drilling force and torque with amount of feed.

Buckling Behaviour of Stainless Steel Square Hollow Sections

2016 ◽  
Vol 853 ◽  
pp. 301-305
Author(s):  
Shameem Ahmed ◽  
Mahmud Ashraf ◽  
Mohammad Anwar-Us-Saadat
Keyword(s):  
Stainless Steel ◽  
Strain Hardening ◽  
Cross Sections ◽  
Design Method ◽  
Numerical Models ◽  
Slenderness Ratio ◽  
Design Guidelines ◽  
Material Nonlinearity ◽  
Cross Sectional ◽  
Steel Design

Structural stainless steel design guidelines should appropriately recognise its characteristic beneficial properties such as material nonlinearity and significant strain hardening. The Continuous Strength Method (CSM) exploits those through a strain based approach for both stocky and slender cross-sections. In this paper, a new design method is proposed that combines the CSM with Perry type buckling curves. Numerical models were developed to investigate effects of various parameters on column strength and to develop full column curves. It was observed that material nonlinearity significantly influence column strengths, and hence, different column curves were developed for a total of 20 material property combinations by calibrating imperfection factor and limiting slenderness ratio for each set. Proposed method includes the strain hardening benefits for stocky section, and abolished the necessity of calculating effective cross-sectional properties for slender sections. Performance of the proposed technique is compared against those obtained by the Eurocode EN1993-1-4.

Ultimate Strength of Aluminum Plates and Stiffened Panels for Marine Applications

2004 ◽  
Vol 41 (03) ◽  
pp. 108-121
Author(s):  
Jeom Kee Paik ◽  
Alexandre Duran
Keyword(s):  
Aluminum Alloys ◽  
Ultimate Strength ◽  
Material Properties ◽  
Plastic Material ◽  
Steel Structures ◽  
Material Model ◽  
Stiffened Panels ◽  
Elastic Plastic ◽  
Steel Panels ◽  
Aluminum Plates

The use of high-strength aluminum alloys in marine construction has certainly obtained many benefits, particularly for building fast ferries and also for military purposes. It is commonly accepted that the collapse characteristics of aluminum structures are similar to those of steel structures until and after the ultimate strength is reached, regardless of the differences between them in terms of material properties. However, it is also recognized that the ultimate strength design formulas available for steel panels cannot be directly applied to aluminum panels even though the corresponding material properties are properly accounted for. This is partly due to the fact that the stress versus strain relationship of aluminum alloys is different from that of structural steel. That is, the elastic-plastic regime of material after the proportional limit and the strain hardening plays a significant role in the collapse behavior of aluminum structures, in contrast to steel structures where the elastic perfectly plastic material model is well adopted. Also, the softening in the heat-affected zone significantly affects the ultimate strength behavior of aluminum structures, whereas it can normally be neglected in steel structures. In this paper, the ultimate strength characteristics of aluminum plates and stiffened panels under axial compressive loads are investigated through ANSYS elastic-plastic large deflection finite element analyses with varying geometric panel properties. An "average" level of welding-induced softening and initial imperfections is assumed for the analyses. Closed-form ultimate compressive strength formulas for aluminum plates and stiffened panels are derived by regression analysis of the computed results.

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.

AXIAL CRUSHING OF TRIANGULAR TUBES

2013 ◽  
Vol 05 (01) ◽  
pp. 1350008 ◽  
Author(s):  
Z. FAN ◽  
G. LU ◽  
T. X. YU ◽  
K. LIU
Keyword(s):  
Plastic Material ◽  
Progressive Collapse ◽  
Material Model ◽  
Acute Angle ◽  
Rigid Plastic ◽  
Element Analysis ◽  
Axial Crushing ◽  
Rigid Plastic Material ◽  
Theoretical Predictions ◽  
New Type

In the present paper, the mechanical behavior of large deformation of a regular equilateral triangular tube under quasi-static axial crushing is reported, which is a polygon with an acute angle and odd number of sides. Based on the results from nonlinear finite element analysis (FEA), a new type of inextensional basic plastic collapse folding element is proposed to describe the plastic progressive collapse. The progressive folding around the stationary horizontal hinges and inclined traveling hinges are involved to develop the new basic folding element. Two types of inextensible deformation modes are discovered, i.e., diamond mode and rotational symmetrical mode. The average crushing load for each mode is predicted from the super-folding element theory, which was proposed from the previous investigation on the axial crushing of square columns. A rigid-plastic material model and a kinematically admissible model are involved in this theory. The results are further validated against experiments. The approximate quasi-static theoretical predictions for the mean crushing loads of triangular tubes provide reasonable agreement with the corresponding experimental results.

Analysis for inversion load and energy absorption of a circular tube

1983 ◽  
Vol 18 (3) ◽  
pp. 177-188 ◽  
Author(s):  
A N Kinkead
Keyword(s):  
Plastic Strain ◽  
Strain Hardening ◽  
Tube Wall ◽  
Plastic Material ◽  
Experimental Results ◽  
Inversion Process ◽  
Rigid Plastic ◽  
Engineering Strain ◽  
Thickness Change ◽  
Set Up

The basic theoretical approach in the mechanics of external or inside-to-outside inversion of circular tubes is examined and extended by the introduction of two additional and previously unperceived sub-structural mechanisms. It is shown that these refinements when applied to published results for ductile aluminium tubing inverted, in a non-frictional process, furnish very encouraging correlations. Since this analysis is made on an ‘engineering plastic strain’ basis a supplementary calculation is made employing ‘pure plastic strain’ or ‘natural strain’ in the predominant sub-structural processes. The resulting comparisons have shown that for rigid/plastic material characteristics the simplification derived in the use of engineering strain does not introduce serious errors in the evaluation of the inversion load. Here it might be mentioned that in many of the cited papers on external inversion, although the initial equations are set up in pure plastic strain terms, frequently the ensuing analysis is simplified by expressing the logarithmic strain as a series and eliminating all but the first term. This reverts the analysis to an engineering strain type. Hence the work described in this connection validates these previously adopted simplifications. In view of the satisfactory correlations achieved by introducing the above theoretical refinements for the external inversion process, the same procedure has also been applied to the case of internal or outside-to-inside tube inversion. Published analysis of the internal inversion process has previously neglected the pronounced thickening effect clearly demonstrated in all experimental results. (Tube-wall thickness change is not at all evident during external inversion and in fact this also assists in simplifying that analysis). In the present approach the effects of friction and work hardening in a compressive die process of internal inversion have been included in the manner already deduced in other research but in addition a further sub-structural process explaining and quantifying the associated thickening of the tube wall has been formulated. Here it should be mentioned that some uncertainty exists in relation to the application of strain hardening based on average plastic strains. However, since the four published experimental results available have been made with materials exhibiting strain hardening characteristics, the total newly developed and previously evolved analyses have been combined to enable some correlation to be made. The predicted internal inversion loads for two separate sets of results in three different materials are in very reasonable agreement with experimental values.

Sign in / Sign up

Export Citation Format

Share Document