Anomaly of the Work Hardening of Zn-Cu Single Crystals Oriented for Slip in Secondary Systems

2011 ◽  
Vol 56 (4) ◽  
pp. 1021-1027
Author(s):  
K. Pieła
Keyword(s):  
Strain Hardening ◽  
Single Crystals ◽  
Yield Stress ◽  
Work Hardening ◽  
Temperature Anomaly ◽  
Strain Hardening Exponent ◽  
Plastic Behavior ◽  
Thermal Dependence ◽  
Copper Addition ◽  
Secondary Systems

Anomaly of the Work Hardening of Zn-Cu Single Crystals Oriented for Slip in Secondary SystemsThe copper alloyed (up to 1.5%) zinc single crystals oriented for slip in non-basal systems (orientation close to < 1120 >) were subjected to compression test within a range of temperatures of 77-293K. It has been stated, that Zn-Cu crystals exhibit characteristic anomalies of the thermal dependence of yield stress and of the strain hardening exponent. Both of them are related to the change in type and sequence of active non-basal slip systems: pyramidal of the 1storder {1011} < 1123 > (Py-1) and pyramidal of the 2ndorder {1122} < 1123 > (Py-2). The temperature anomaly of the yield stress results from the change of the slip from Py-2 systems to simultaneous slip in the Py-2 and Py-1 (Py-2 + Py-1) systems, occurring in the preyielding stage. On the other hand, sequential activation of pyramidal systems taking place in advanced plastic stage (i.e. the first Py-2 and next Py-2 + Py-1 systems) is responsible for temperature anomaly of strain hardening exponent. Increase in copper addition favors the activity of Py-2 systems at the expense of Py-1 slip, what leads to a drastic differences in plastic behavior of zinc single crystals.

Effect of Modulations on Yield Stress and Strain Hardening Exponent of Solution Treated Cu-Ti Alloys

1998 ◽  
Vol 38 (9) ◽  
pp. 1469-1474 ◽  
Author(s):  
S. Nagarjuna ◽  
M. Srinivas ◽  
K. Balasubramanian ◽  
D.S. Sarma
Keyword(s):  
Strain Hardening ◽  
Yield Stress ◽  
Strain Hardening Exponent ◽  
Stress And Strain ◽  
Ti Alloys ◽  
Solution Treated

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
Y. Q. Sun ◽  
P. B. Hirsch
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

Sensitivity Analysis of Material Parameters on Spring-Back of NC Bending of High-Strength TA18 Tube

2012 ◽  
Vol 472-475 ◽  
pp. 1003-1008 ◽  
Author(s):  
Pei Pei Zhang ◽  
Mei Zhan ◽  
Tao Huang ◽  
He Yang
Keyword(s):  
Elastic Modulus ◽  
Strain Hardening ◽  
Yield Stress ◽  
Strain Hardening Exponent ◽  
Spring Back ◽  
Initial Yield Stress ◽  
Material Parameters ◽  
Strength Coefficient ◽  
Initial Yield ◽  
Nc Bending

Spring-back is one of the key factors affecting the forming quality of the NC bending of high-strength TA18 tubes (TA18-HS tubes). Since material parameters have a direct influence on stress and strain fields during the bending and after unloading, the springback of TA18-HS tubes after NC bending depends on material properties to a great degree. In order to study the effect of material parameters, the sensitivity of material parameters on spring-back of TA18-HS tubes is analyzed in this study, using the numerical simulation and the multi-parameters sensitivity analysis method. The results show the following: (1) The springback angle has a positive correlation with the strength coefficient and initial yield stress, and has a negative correlation with the elastic modulus and strain hardening exponent. Besides, with the increase of elastic modulus, the fluctuation of springback goes gently; with the increase of the strength coefficient and initial yield stress, the fluctuation of springback goes abruptly; but with the variation of the strain hardening exponent, the springback fluctuates slightly; (2) The elastic modulus is the most sensitive material parameter on spring-back, the strength coefficient and initial yield stress rank the second and third, respectively, and the strain hardening exponent is the last. The achievement of the study is valuable to eliminate the non-sensitivity parameters, simplify the optimization project, and improve the spring-back prediction capability.

Inverse scaling functions in nanoindentation with sharp indenters: Determination of material properties

2005 ◽  
Vol 20 (4) ◽  
pp. 987-1001 ◽  
Author(s):  
Lugen Wang ◽  
M. Ganor ◽  
S.I. Rokhlin
Keyword(s):  
Finite Element ◽  
Strain Hardening ◽  
Yield Stress ◽  
Material Properties ◽  
Contact Stiffness ◽  
Experimental Parameter ◽  
Inversion Method ◽  
Strain Hardening Exponent ◽  
Scaling Functions ◽  
Scaling Analysis

This paper, based on extensive finite element simulations and scaling analysis, presents scaling functions for the inverse problem in nanoindentation with sharp indenters to determine material properties from nanoindentation response. All the inverse scaling functions were directly compared with results calculated using the large deformation finite element method and are valid from the elastic to the full plastic regimes. To relate the material properties to measurable indentation parameters a new nondimensional experimental parameter Λ=P/(DS) was introduced, where P is load, D is indentation depth, and S is contact stiffness. This parameter is monotonically related to the ratio of yield stress to modulus. The modulus, hardness and yield stress are presented as explicit functions of Λ and the strain hardening exponent. The error in the inverse modulus, hardness, and yield stress due to uncertainty of the strain hardening exponent was studied and is compared with that of the traditional Oliver–Pharr method. The method of determining the strain hardening exponent from measurement with an additional indenter with a different cone apex angle is described. For this, a scaling function with the strain hardening exponent as the only unknown was obtained. In this way, the modulus, hardness, yield stress and strain hardening exponent may be determined. Experimental results show the inversion method permits the modulus and hardness to be accurately determined irrespective of the effects of pileup or sink-in.

Parameters of Dislocation Structure and Work Hardening of Ni3Ge

2004 ◽  
Vol 842 ◽  
Author(s):  
N. A. Koneva ◽  
Yu.V. Solov'eva ◽  
V. A. Starenchenko ◽  
E. V. Kozlov
Keyword(s):  
Single Crystals ◽  
Yield Stress ◽  
Dislocation Structure ◽  
Temperature Anomaly ◽  
Friction Stress ◽  
Orientation Dependence ◽  
Compression Tests ◽  
Quantitative Measurements ◽  
Different Temperatures ◽  
Scalar Dislocation Density

ABSTRACTOrientation dependence of the yield stress temperature anomaly in Ni3Ge single crystals with the L12 structure was investigated during compression tests. The measurements were carried out in the 4.2 K-1000 K temperature interval for two orientations of single crystals, [001] and [234]. The dislocation structure was studied by TEM. Quantitative measurements of different parameters of dislocation structure were carried out. The values of the scalar dislocation density, ρ, were determined for different temperatures in the deformation interval from the yield stress up to fracture. Temperature dependence of the friction stress τF (T) and the interdislocation interaction parameter α(T) were also obtained. The change in the fraction of straight dislocations as a function of temperature was analyzed.

On determination of material parameters from loading and unloading responses in nanoindentation with a single sharp indenter

2006 ◽  
Vol 21 (4) ◽  
pp. 995-1011 ◽  
Author(s):  
Lugen Wang ◽  
S.I. Rokhlin
Keyword(s):  
Finite Element ◽  
Strain Hardening ◽  
Yield Stress ◽  
Finite Element Simulations ◽  
Strain Hardening Exponent ◽  
Scaling Functions ◽  
Stress And Strain ◽  
Wide Range ◽  
Loading And Unloading

This paper quantitatively describes the loading-unloading response in nanoindentation with sharp indenters using scaling analyses and finite element simulations. Explicit forward and inverse scaling functions for an indentation unloading have been obtained and related to those functions for the loading response [L. Wang et al., J. Material Res.20(4), 987–1001 (2005)]. The scaling functions have been obtained by fitting the large deformation finite element simulations and are valid from the elastic to the full plastic indentation regimes. Using the explicit forward functions for loading and unloading, full indentation responses for a wide range of materials can be obtained without use of finite element calculations. The corresponding inverse scaling functions allow one to obtain material properties from the indentation measurements. The relation between the work of indentation and the ratio between hardness and modulus has also been studied. Using these scaling functions, the issue of nonuniqueness of the determination of material modulus, yield stress, and strain-hardening exponent from nanoindentation measurements with a single sharp indenter has been further investigated. It is shown that a limited material parameter range in the elastoplastic regime can be defined where the material modulus, yield stress, and strain-hardening exponent may be determined from only one full indentation response. The error of such property determination from scattering in experimental measurements is determined.

Micro-asperity Contact Area considering Strain Hardening for Metallic Materials

2021 ◽  
pp. 1-31
Author(s):  
Jinli Xu ◽  
Jiwei Zhu ◽  
Wei Xia ◽  
Baolei Liu
Keyword(s):  
Strain Hardening ◽  
Contact Area ◽  
Work Hardening ◽  
Present Model ◽  
Strain Hardening Exponent ◽  
Asperity Contact ◽  
Metallic Materials ◽  
Area Index ◽  
Area Model ◽  
Plastic Regime

Abstract A novel micro-asperity contact area model, which considers influences of strain hardening, is proposed to describe contact area between a deformable sphere and a rigid flat for metallic materials. Firstly a generalized formula considering work-hardening behaviors (Pilling-up or Sinking-in) between contact area and interference is proposed for fully plastic regime based on the definition of plastic contact area index. Then a relationship to calculate the critical interference at the inception of fully plastic deformation is derived. In order to incorporate the transition from elastic regime to fully plastic regime, a quadratic rational form formula is proposed based volume conservation model for mixed elastoplastic regime. Therewith a modification is conducted to ensure continuity of contact area model at critical interference for fully plastic regime. Ultimately several representative models and experiment results are exhibited to analyze the availability of present model. It is noted considering work-hardening fully plastic contact area index is not a constant value of 2 for any metallic materials, which is a function of strain hardening exponent. Demonstration testifies that smoothness constraint is not necessary at the critical interferences. The prediction data of present model is consistent with experiment results contrasting that of other models. Current generalized contact area model considering influence of work-hardening results in a better understanding of the contact area between a deformable sphere and a rigid flat and indicates a probability to analyze contact characteristics of two mating rough surfaces accurately.

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