 Research
 Open Access
 Published:
Description of fullrange strain hardening behavior of steels
SpringerPlus volume 5, Article number: 1316 (2016)
Abstract
Mathematical expression describing plastic behavior of steels allows the execution of parametric studies for many purposes. Various formulas have been developed to characterize stress strain curves of steels. However, most of those formulas failed to describe accurately the strain hardening behavior of steels in the full range which shows various distinct stages. For this purpose, a new formula is developed based on the wellknown Ramberg–Osgood formula to describe the full range strain hardening behavior of steels. Test results of all the six types of steels show a threestage strain hardening behavior. The proposed formula can describe such behavior accurately in the full range using a single expression. The parameters of the formula can be obtained directly and easily through linear regression analysis. Excellent agreements with the test data are observed for all the steels tested. Furthermore, other formulas such as Ludwigson formula, Gardner formula, UGent formula are also applied for comparison. Finally, the proposed formula is considered to have wide suitability and high accuracy for all the steels tested.
Background
The description of strain hardening behavior of materials using mathematical expression has been the subject of numerous investigations for many years. Strain hardening response of materials is usually characterized indirectly by the true stress–strain curves obtained from tensile tests. Typically, the strain hardening rate can be calculated numerically from the curves and plotted against strain (or stress). It is now well established that the hardening rate of crystals may be divided into various distinct stages (Nabarro et al. 1964; Asgari et al. 1997; Chinh et al. 2004), typically three stages, labeled Stage I, Stage II and Stage III (KuhlmannWilsdorf 1985). The stages of polycrystalline steels are much less evident than those of the single crystal (Reedhill et al. 1973). Therefore, some forms of analysis are normally to describe the strain hardening behavior of steels. For this purpose, the Ramberg–Osgood formula (Ramberg and Osgood 1943) has been used widely for steels in various engineering fields. However, this formula is inherently deficient to describe the strain hardening behavior of steels in the full range.
Distinct stages strain hardening behavior has been observed in various types of steels (Jha et al. 1987; Nie et al. 2012; Umemoto et al. 2000; Tomita and Okabayashi 1985; Atkinson 1979; Kalidindi 1998; Saha et al. 2007). Many formulas were designed to describe the fullrange hardening and some materialspecific formulas have been proposed for stainless steels (Rasmussen 2003; Gardner and Nethercot 2004a, b; Abdella 2006; Quach et al. 2008; Arrayago et al. 2015), TRIP steels (Tomita and Iwamoto 1995), high strength steels (Gardner and Ashraf 2006) and pipeline steels (Hertelé et al. 2012a, b). Although excellent agreement has been provided for specific materials, the formulas have difficulty being adopted for other materials. Additionally, it should be noted that the strain hardening behavior involves a complex interaction among various factors. At the microscale, this aspect of plastic deformation is intrinsically coupled with all other aspects of plastic deformation such as development of preferred lattice orientations, formation of subgrains, and formation of local shear bands (Wilson 1974). For austenitic steels and TRIP steels, the microstructural phase transformation from austenite to martensite also has a great effect on the plastic deformation. (Leblond et al. 1986a, b; Hallberg et al. 2007; Santacreu et al. 2006; Post et al. 2008; Stringfellow et al. 1992; Bhattacharyya and Weng 1994; Diani et al. 1995; Miller and McDowell 1996; Papatriantafillou et al. 2006; Turteltaub and Suiker 2005; Beese and Mohr 2012; Iwamoto and Tsuta 2000). This has been actively studied for decades. Therefore, it is virtually impossible to develop a complete understanding (Chinh et al. 2004) of the behavior, and no unified theory on the physically based functional description has been found (Cleri 2005). Most of these formulas to describe the strain hardening behavior of steel are purely empirical descriptions.
The purpose of this paper is to present a mathematical description of the fullrange strain hardening behavior for steels with smooth, gradual onset of yielding. Note that many mathematical descriptions have already existed, an overview of existing stress–strain formulas and an expression of the new formula are provided in “Formulas characterizing stress strain curves” section. Test data of various types of steels were referred to in “Test data” section. “Validation and comparison” section validated the proposed formula with test data and comparisons with other formulas were also listed. Then, a limitation of the proposed formula is discussed in “Discussion” section. Finally principal conclusions are drawn in “Conclusion” section.
Formulas characterizing stress strain curves
Overview of existing formulas
The description of the stress–strain curves of metals by mathematical expressions has been a topic of research since the origin of classical mechanics. Numerous formulas have been proposed to describe the stress–strain curves. Osgood (1946) summarized 17 formulas used in the early age of study. Kleemola and Nieminen (1974) discussed the computational method of parameters for some commonly used formulas. Recently, existing common formulas have been reviewed and discussed by Hertelé et al. (2011).
The most wellknown formulas are a series of simple formulas with a power function (Ludwik 1909; Ramberg and Osgood 1943; Hollomon 1945; Swift 1952; Hoffelner 2013). Among them, the Ramberg–Osgood formula (1943) has been widely accepted in the engineering field:
Thus, the true stress–strain relationship can be expressed explicitly:
where σ is the true stress, ε is the true strain, ε _{ p } is the plastic strain, E is the elastic modulus, and K, m are material parameters.
The convenience of this formula is that it can be easily linearized by taking logarithms of the true stress–plastic strain coordinates. Thus, the parameters can be obtained through linear regression analysis.
The deficiency of this formula is that it cannot characterize many materials in the full range exhibiting various distinct strain hardening stages, which have been observed in various types of steels (Quach et al. 2008; Rasmussen 2003; Abdella 2006; Bowen and Partridge 2002; Gardner and Nethercot 2004a, b) and other metals (Monteiro and ReedHill 1973; Markandeya et al. 2006). Therefore, many other types of formulas have been proposed (Ludwigson 1971; Voce 1948; Chinh et al. 2004). Ludwigson (1971) proposed such a formula, which accounts for the deviations at low strains by adding a second term to the Ludwik power law formula (Ludwik 1909):
where K _{1}, m _{1}, K _{2}, m _{2} are material parameters.
Compared to the Ramberg–Osgood formula, there is no single direct expression that shows a straight line in logarithmic or nonlogarithmic coordinates. The formula shows a tendency toward linear behavior for large strains in a doublelogarithmic stress–strain diagram. Therefore K _{1} and m _{1} can be obtained through linear regression of large strains. Thus, ∆ is defined as:
K _{ 2 } , m _{ 2 } can be obtained through linear regression analysis of ln ∆ − ε _{ p }:
The deficiency of this formula is also very clear: it cannot provide an explicit expression of σ − ε and could have difficulties in describing the smooth, gradual onset of yielding observed in many metallic materials (Hertelé et al. 2011).
Therefore, other formulas were proposed to characterize the fullrange strain hardening behavior more accurately with segmented functions (Abdella 2006; Rasmussen 2003; Saab and Nethercot 1991; Hertelé et al. 2011; Real et al. 2014). Most of these formulas are material specific. Recently, Hertelé (2012a, b) proposed such an UGent formula to characterize the plastic behavior of pipeline steels.
where σ _{0.2}, σ _{1}, σ _{2}, n _{1}, n _{2} are fitting parameters.
The UGent stress–strain model was developed to describe the strain hardening behavior of pipeline steels with two distinct stages. As listed in Eq. (7), for small plastic regions σ ≤ σ _{1}, the UGent model respects a Ramberg–Osgood equation with a true 0.2 % proof stress σ _{0.2} and a first strainhardening exponent n _{1}; for large plastic region σ ≥ σ _{ 2 }, the UGent model respects a Ramberg–Osgood equation with the same 0.2 % proof stress σ _{0.2}, but a possibly different strainhardeing exponent n _{2}; Between these two regions, there is a smooth transition where the curve shape gradually changes.
The deficiency of the UGent formula is that it is too complicated to apply in practice and the parameters are difficult to obtain.
Proposed stress–strain formula
In order to deal with the deficiencies mentioned above, a new empirical formula is developed to describe the fullrange strain hardening behavior of steels. The formula is based on the assumption that the real stress–strain curve tends to two different Ramberg–Osgood curves following the relationship of Eq. (8). It tends to the Ramberg–Osgood ε_{p1} − σ curve 1 by Eq. (9) in the small plastic strain region and Ramberg–Osgood ε_{p2}–σ curve 2 by Eq. (10) in the large plastic strain region, respectively.
K_{1}, K_{2}, m_{1}, m_{2}, A, B are material fitting parameters.
The optimal parameter values of the proposed formula can be obtained through leastsquares fitting method as depicted in Fig. 1 in following procedure:

In the small scale yielding plastic area, a Ramberg–Osgood formula with m_{1}, k_{1} is assumed to be followed, defined as ε_{p1}σ line in Fig. 1a. The parameters can be easily obtained through a linear regression analysis as Eq. (9) in the log(ε_{p}) − log(σ) coordinate.
$$ m_{1} \cdot \log \varepsilon_{p} + \log K_{1} = \log \sigma $$(11) 
In the large scale yielding plastic area, a Ramberg–Osgood formula with m_{2}, k_{2} should be followed, defined as ε_{p2} − σ line in Fig. 1a. The parameters can also be easily obtained through a linear regression analysis in the same way through Eq. (10):
$$ m_{2} \cdot \log \varepsilon_{p} + \log K_{2} = \log \sigma $$(12) 
In the transition between these two curves mentioned above, the ratio value of ε_{p} − ε_{p1} to ε_{p2} − ε against stress shows a linear relation of Eq. (13), in the coordinate depicted in Fig. 1b. The parameters A, B can be obtained through a linear regression analysis directly.
$$ \ln \frac{{\varepsilon_{p}  \varepsilon_{p1} }}{{\varepsilon_{p2}  \varepsilon_{p} }} = A\sigma + B $$(13)
Test data
To validate the proposed formula, tensile tests at ambient temperature have been performed on three high strength steels. A strain rate of 5 × 10^{−4} s^{−1} was kept in loading to avoid any stress wave effect and to keep in a quasistatic mode. Test data of other steels done by Hertelé et al. (2011) were also selected. The basic tensile characteristics of the steels are summarized in Table 1. PCrNi3MoVA, G4335V, 32CrNi3MoVA are three high strength steels in China used for gun barrels, known as gun steels; API X70 is used for pipeline; TRIP 690 is a high strength Transformation Induced Plasticity steel; DIN 1.4462 is a stainless steel alloy.
Figure 2 depicts the engineering and true stress–strain curves. The parts of the engineering stress–strain curves after necking were ignored and the true stress–strain curves were obtained through the wellknown converting formulas ɛ = ln (1 + ɛ _{ e }) and σ = σ _{ e }(1 + ɛ _{ e }).
Validation and comparison
The proposed formula has been applied to the test data of all the six steels. The optimal parameter values for each steel were obtained through the fitting procedure mentioned above (“Proposed stress–strain formula” section). The general Ramberg–Osgood formula (Ramberg and Osgood 1943), Ludwigson formula (Ludwigson 1971), UGent formula (Hertelé et al. 2011) and a materialspecific Gardner formula (Gardner and Nethercot 2004a, b) have also been applied to the data for comparison.
Additionally, a difference approximation was conducted on the test data to obtain the strain hardening rate:
Parameters of the proposed formula for all steels are summarized in Table 3 and other formulas in Table 2. Furthermore, Fig. 3 depicts the graphical fitting procedures for three gun steels. The strain hardening ratestrain curves and stress–strain curves for three gun steels are shown in Fig. 4. Figures 5, 6 and 7 depict the graphical fitting procedures (a, b), strain hardening ratestress curves (c) and stress–strain curves (d) for pipeline steel, TRIP steel and stainless steel, respectively.
It can be observed from those figures that: First, test data of all the steels show a threestage hardening behavior which can be seen clearly in the strain hardening ratestrain coordinate. Stage I ends at approximately ε = 0.02 for stainless steel and ε = 0.01 for others; Stage II ends at roughly at ε = 0.06 for stainless steel and ε = 0.02 for others.
The difference in the strain hardening rate can be attributed to the operation of different deformation mechanisms (Kocks and Mecking 2003; MontazeriPour and Parsa 2016): Stage I exhibits a distinct decline hardening rate. The sudden drop of hardening rate is associated with crossslip of dislocations bypassing the heads of piled up dislocations (Hockauf and Meyer 2010). After passing the initial Stage I, hardening rate decreases to another region with a constant value defined as Stage II. Stage II exhibits an almost constant hardening rate behavior which is contributed to a steady state for storage and annihilation of dislocations (Zehetbauer and Seumer 1993). After Stage II, the hardening rate decreases continuously into a separate Stage III up to necking point (Kocks and Mecking 2003). Features of Stage III are analogous to Stage I and are considered to be connected with point defect generation and absorption (Zehetbauer and Seumer 1993).
Second, linear relationship assumed in the fitting procedure of the proposed formula is verified for all the test data. The proposed formula provides satisfactory representations of the test data for all the six steels in the full range. It can characterize excellently the threestage strain hardening behavior of steels observed in the test. Six parameters of the formula, all of which are easy to understand and interpret in an intuitive way, can be obtained directly and easily through linear regression.
Third, for other formulas, it can be found that: The Ludwigson formula generally seems to provide accurate description of all curves for large plastic strain, e.g. Stage III, but lacks accuracy at a lower strain, below 0.02 for gun steels and stainless steel. This formula also cannot be utilized directly because there is no explicit expression of strain. The Gardner formula, on the other hand, seems to provide an accurate description of the full range curve for stainless steel and the lower strain parts for pipeline steel up to 0.035 and TRIP steel up to 0.07. The UGent formula provides an accurate description of pipeline steel and TRIP steel up to plastic regions near necking but lack accuracy for stainless steel. The fitting procedure of UGent formula is cumbersome and some parameters are arbitrary.
Discussion
Limitations of the proposed formula are discussed in this section. First, obviously the proposed formulas cannot be utilized to describe the strain hardening behavior of steels with a sharp or specific yielding strength, which can be observed in some carbon steels.
Second, as mentioned in “Test data” section, in this paper the strain hardening response of materials is characterized by the stress–strain curves documented in tensile tests. The parts of the engineering stress–strain curves after necking were ignored due to the local necking effect. However, when extremely large deformation was mentioned, this procedure is not quite enough.
Third, to simplify the loading condition, quasistatic loading mode is considered in this paper. However, it is well known that temperature and strain rate have great effect on the plastic deformation behavior. More works are needed on these issues.
Conclusion
In the present paper, a new formula has been proposed to describe the full range strain hardening behavior of steels. The test results demonstrate that the test data of all the six steels observed have a threestage hardening behavior. The proposed formula, based on two different Ramberg–Osgood formulas, can characterize such behavior in the full range using a single expression. The parameters of the formula can be easily and directly obtained through linear regression analysis. The fitting curves and test results were identified to have excellent agreement for all the six steels.
References
Abdella K (2006) Inversion of a fullrange stress–strain relation for stainless steel alloys. Int J Nonlinear Mech 41(3):456–463
Arrayago I, Real E, Gardner L (2015) Description of stress–strain curves for stainless steel alloys. Mater Des 87:540–552. doi:10.1016/j.matdes.2015.08.001
Asgari S, ElDanaf E, Kalidindi SR, Doherty RD (1997) Strain hardening regimes and microstructural evolution during large strain compression of low stacking fault energy fcc alloys that form deformation twins. Metall Mater Trans A 28(9):1781–1795
Atkinson M (1979) Effects of grain size and of carbon content in the strain hardening of polycrystalline iron and lowcarbon steels. Strength Met Alloys 2:789–794
Beese AM, Mohr D (2012) Anisotropic plasticity model coupled with Lode angle dependent straininduced transformation kinetics law. J Mech Phys Solids 60(11):1922–1940
Bhattacharyya A, Weng GJ (1994) An energy criterion for the stressinduced martensitic transformation in a ductile system. J Mech Phys Solids 42(11):1699–1724
Bowen AW, Partridge PG (2002) Limitations of the Hollomon strainhardening equation. J Phys D Appl Phys 7(7):969–978
Chinh NQ, Horváth G, Horita Z, Langdon TG (2004) A new constitutive relationship for the homogeneous deformation of metals over a wide range of strain. Acta Mater 52(12):3555–3563. doi:10.1016/j.actamat.2004.04.009
Cleri F (2005) Evolution of dislocation cell structures in plastically deformed metals. Comput Phys Commun 169(1–3):44–49
Diani JM, Sabar H, Berveiller M (1995) Micromechanical modelling of the transformation induced plasticity (TRIP) phenomenon in steels. Int J Eng Sci 33(13):1921–1934
Gardner L, Ashraf M (2006) Structural design for nonlinear metallic materials. Eng Struct 28(6):926–934. doi:10.1016/j.engstruct.2005.11.001
Gardner L, Nethercot DA (2004a) Experiments on stainless steel hollow sections—part 1: material and crosssectional behaviour. J Constr Steel Res 60(9):1291–1318
Gardner L, Nethercot DA (2004b) Experiments on stainless steel hollow sections—part 2: member behaviour of columns and beams. J Constr Steel Res 60(9):1319–1332
Hallberg H, Håkansson P, Ristinmaa M (2007) A constitutive model for the formation of martensite in austenitic steels under large strain plasticity. Int J Plasticity 23(7):1213–1239
Hertelé S, De Waele W, Denys R (2011) A generic stress–strain model for metallic materials with twostage strain hardening behaviour. Int J Nonlinear Mech 46(3):519–531
Hertelé S, De Waele W, Denys R, Verstraete M (2012a) Fullrange stress–strain behaviour of contemporary pipeline steels: part I. Model description. Int J Pres Ves Pip 92:34–40
Hertelé S, De Waele W, Denys R, Verstraete M (2012b) Fullrange stress–strain behaviour of contemporary pipeline steels: part II. Estimation of model parameters. Int J Pres Ves Pip 92:27–33
Hockauf M, Meyer LW (2010) Workhardening stages of AA1070 and AA6060 after severe plastic deformation. J Mater Sci 45(17):4778–4789
Hoffelner W (2013) STPPT056: Extend stress–strain curve parameters and cyclic stress–strain curves to all materials listed for section VIII, Divisions 1 and 2 Construction (62). ASME Standards Technology, LLC (reprinted)
Hollomon JH (1945) Tensile deformation. Trans AIME 162:268–290
Iwamoto T, Tsuta T (2000) Computational simulation of the dependence of the austenitic grain size on the deformation behavior of TRIP steels. Int J Plasticity 16(7):791–804
Jha BK, Avtar R, Dwivedi VS, Ramaswamy V (1987) Applicability of modified Crussard–Jaoul analysis on the deformation behaviour of dualphase steels. J Mater Sci Lett 6(8):891–893
Kalidindi SR (1998) Modeling the strain hardening response of low SFE FCC alloys. Int J Plasticity 14(12):1265–1277. doi:10.1016/S07496419(98)000540
Kleemola HJ, Nieminen MA (1974) On the strainhardening parameters of metals. Metall Trans 5(8):1863–1866
Kocks UF, Mecking H (2003) Physics and phenomenology of strain hardening: the FCC case. Prog Mater Sci 48(3):171–273
KuhlmannWilsdorf D (1985) Theory of workhardening 1934–1984. Metall Trans A 16(12):2091–2108
Leblond JB, Mottet G, Devaux JC (1986a) A theoretical and numerical approach to the plastic behaviour of steels during phase transformations—I. Derivation of general relations. J Mech Phys Solids 34(4):395–409
Leblond JB, Mottet G, Devaux JC (1986b) A theoretical and numerical approach to the plastic behaviour of steels during phase transformations—II. Study of classical plasticity for idealplastic phases. J Mech Phys Solids 34(4):411–432
Ludwigson DC (1971) Modified stress–strain relation for FCC metals and alloys. Metall Trans 2(10):2825–2828
Ludwik P (1909) Elemente der technologischen Mechanik. Springer, Berlin
Markandeya R, Satyanarayana DVV, Nagarjuna S, Sarma DS (2006) Correlation of structure and flow behaviour of Cu–Ti–Cd alloys. Mater Sci Eng A 428(1):233–243
Miller MP, McDowell DL (1996) Modeling large strain multiaxial effects in FCC polycrystals. Int J Plasticity 12(7):875–902
MontazeriPour M, Parsa MH (2016) Constitutive analysis of tensile deformation behavior for AA1100 aluminum subjected to multiaxial incremental forging and shearing. Mech Mater 94:117–131
Monteiro SN, ReedHill RE (1973) An empirical analysis of titanium stress–strain curves. Metall Trans 4(4):1011–1015
Nabarro FRN, Basinski ZS, Holt DB (1964) The plasticity of pure single crystals. Adv Phys 13(50):193–323
Nie WJ, Wang XM, Shengjie WU (2012) Stress–strain behavior of multiphase high performance structural steel. Sci China Technol Sci 55(7):1791–1796
Osgood WR (1946) Stress–strain formulas. J Aeronaut Sci 13(1):45–48
Papatriantafillou I, Agoras M, Aravas N, Haidemenopoulos G (2006) Constitutive modeling and finite element methods for TRIP steels. Comput Method Appl Mech Eng 195(37):5094–5114
Post J, Datta K, Beyer J (2008) A macroscopic constitutive model for a metastable austenitic stainless steel. Mater Sci Eng A 485(1):290–298
Quach WM, Teng JG, Chung KF (2008) Threestage fullrange stress–strain model for stainless steels. J Struct Eng 134(9):1518–1527
Ramberg W, Osgood WR (1943) Description of stress–strain curves by three parameters. National advisory committee for aeronautics (reprinted
Rasmussen KJR (2003) Fullrange stress–strain curves for stainless steel alloys. J Constr Steel Res 59(1):47–61
Real E, Arrayago I, Mirambell E, Westeel R (2014) Comparative study of analytical expressions for the modelling of stainless steel behaviour. Thin Wall Struct 83:2–11. doi:10.1016/j.tws.2014.01.026
Reedhill RE, Cribb WR, Monteiro SN (1973) Concerning the analysis of tensile stress–strain data using log dσ/dεp versus log σ diagrams. Metall Mater Trans B 4(4):2665–2667
Saab HA, Nethercot DA (1991) Modelling steel frame behaviour under fire conditions. Eng Struct 13(4):371–382
Saha PA, Bhattacharjee D, Ray RK (2007) Effect of martensite on the mechanical behavior of ferritebainite dual phase steels. ISIJ Int 47:1058–1064
Santacreu P, Glez J, Chinouilh G, Froehlich T (2006) Behaviour model of austenitic stainless steels for automotive structural parts. Steel Res Int 77(9–10):686–691
Stringfellow RG, Parks DM, Olson GB (1992) A constitutive model for transformation plasticity accompanying straininduced martensitic transformations in metastable austenitic steels. Acta Metall Mater 40(7):1703–1716
Swift HW (1952) Plastic instability under plane stress. J Mech Phys Solids 1(1):1–18
Tomita Y, Iwamoto T (1995) Constitutive modeling of TRIP steel and its application to the improvement of mechanical properties. Int J Mech Sci 37(12):1295–1305
Tomita Y, Okabayashi K (1985) Tensile stress–strain analysis of cold worked metals and steels and dualphase steels. Metall Mater Trans A 16(5):865–872
Turteltaub S, Suiker A (2005) Transformationinduced plasticity in ferrous alloys. J Mech Phys Solids 53(8):1747–1788
Umemoto M, Tsuchiya K, Liu ZG, Sugimoto S (2000) Tensile stress–strain analysis of singlestructure steels. Metall Mater Trans A 31(7):1785–1794
Voce E (1948) The relationship between stress and strain for homogeneous deformation. J Inst Met 74:537–562
Wilson DV (1974) Relationships between microstructure and behaviour in the uniaxial tensile test. J Phys D Appl Phys 7(7):954–968
Zehetbauer M, Seumer V (1993) Cold work hardening in stages IV and V of FCC metals—I. Experiments and interpretation. Acta Metall Mater 41(2):577–588
Authors’ contributions
JZ designed the research. TL performed the analysis and wrote the paper. ZC gave some good suggestions. All authors read and approved the final manuscript.
Acknowledgements
This research was supported by the Special funds for Quality Supervision Research in the Public Interest (“Research on Key Technologies for the Design Standard of UltraHigh Pressure Vessels”, Grant No. 201210242).
Competing interests
The authors declare that they have no competing interests.
Author information
Affiliations
Corresponding author
Additional information
An erratum to this article is available at http://dx.doi.org/10.1186/s400640163785x.
Rights and permissions
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
About this article
Cite this article
Li, T., Zheng, J. & Chen, Z. Description of fullrange strain hardening behavior of steels. SpringerPlus 5, 1316 (2016). https://doi.org/10.1186/s4006401629983
Received:
Accepted:
Published:
Keywords
 Strain hardening behavior
 Stress strain curve
 Plastic deformation