New Formula Relating the Yield Stress-Strain With the Strength Coefficient and the Strain-Hardening Exponent

2004 ◽  
Vol 13 (4) ◽  
pp. 509-512 ◽  
Author(s):  
Zhang Zhongping ◽  
Wu Weihua ◽  
Chen Donglin ◽  
Sun Qiang ◽  
Zhao Wenzhen
Keyword(s):  
Strain Hardening ◽  
Yield Stress ◽  
Strain Hardening Exponent ◽  
Stress Strain ◽  
Strength Coefficient ◽  
New Formula

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.

Determination of Stress-Strain Constitutive Relation of Echelle Grating Al Film by Nanoindentation Test and Simulation

2012 ◽  
Vol 625 ◽  
pp. 312-317 ◽  
Author(s):  
Guang Feng Shi ◽  
Guo Quan Shi ◽  
Lin Sen Song ◽  
Zhi Wei Xu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Hardening ◽  
Yield Stress ◽  
Strain Hardening Exponent ◽  
Stress And Strain ◽  
Stress Strain ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Echelle Grating

For the research on elastic-plastic deformation characteristics of the echelle grating in the mechanical ruling depth range, a series of nanoindentation tests are completed about the deposited Al film of available echelle grating with a Berkovich indenter on a CSM nanoindentation instrument. Then a finite element analysis of the nanoindentation process is studied with an orthogonal experiment method for a series of given parameters containing the yield stress and strain-hardening exponent. The optimum combinations of yield stress and strain-hardening exponent are 200MPa and 0.1, which are got by the objective of the least absolute value of maximum loads deviation between the indentation test and the finite element analysis. Finally the elastic-plastic stress-strain curve of power function of the Al film is represented with the difference analysis from the orthogonal simulations.

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

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.

Investigating the Effect of Miniaturization on the Microtensile Properties of Brass (CuZn30)

2011 ◽  
Author(s):  
Lauren B. Wuertemberger ◽  
Megan N. Chann ◽  
Richard M. Onyancha
Keyword(s):  
Strain Hardening ◽  
Tensile Properties ◽  
Material Properties ◽  
Tensile Tests ◽  
Strain Hardening Exponent ◽  
Manufacturing Processes ◽  
Strength Coefficient ◽  
Grain Sizes ◽  
Heat Treated ◽  
Average Grain Size

As everyday equipment becomes smaller and smaller, it is of increasing importance that the manufacturing processes used for metals are capable of producing parts of appropriate sizes. Currently, manufacturing processes assume macromaterial properties can be applied for microscale production, but is this a valid assumption? This paper investigates the accuracy of applying macroscale tensile properties in microscale applications. In order to test the soundness of this supposition, tensile tests were performed on both macroscale and microscale brass specimens, and the resulting calculated material properties, strain hardening exponent (n) and strength coefficient (K), were compared. Specimens were heat treated to various temperatures before tensile tests were performed, and the strength coefficient and strain hardening exponents of micro and macro tensile specimens were compared. Additionally, it is investigated whether average grain size correlates to material properties. The results showed that in general it is not accurate to apply macroscale tensile properties to microscale applications. However, at mesocale grain sizes, (12–20 microns), the strain hardening exponent values were similar for both macro and microscale specimens.

Effects of Constitutive Parameters on Thickness of Phase Transformed Adiabatic Shear Band for Ductile Metal Based on Johnson-Cook and Gradient Plasticity Models

2006 ◽  
Vol 15-17 ◽  
pp. 609-614 ◽  
Author(s):  
X.B. Wang
Keyword(s):  
Phase Transformation ◽  
Strain Rate ◽  
Strain Hardening ◽  
Yield Stress ◽  
Thermal Softening ◽  
Flow Shear ◽  
Stress Strain ◽  
Static Yield ◽  
Flow Shear Stress ◽  
Static Yield Stress

Gradient-dependent plasticity where a characteristic length is involved to consider the microstructural effect (interactions and interplaying among microstructures due to the heterogeneous texture) is introduced into Johnson-Cook model considering the effects of strain-hardening, thermal softening and strain rate sensitivity. Effects of initial static yield stress, strain-hardening coefficient and exponent, strain-rate and thermal-softening parameters on the occurrence of phase transformation and the thickness of phase transformed adiabatic shear band (ASB) in deformed ASB are numerically investigated. Higher initial static yield stress, strain-hardening coefficient, strain-rate parameter and lower strain-hardening exponent lead to earlier occurrence of phase transformation (lower plastic shear strain). Effect of thermal-softening parameter on plastic shear strain corresponding to the onset of phase transformation is not monotonous. Transformed ASB is located at the center of deformed ASB since the position has higher temperature exceeding the temperature of phase transformation. The thickness of transformed ASB increases with decreasing flow shear stress and the increasing tendency becomes slow. For the same flow shear stress, the thickness of transformed ASB is wider for higher initial static yield stress, strain-hardening coefficient and exponent, strain-rate and thermal-softening parameters. Compared with classical elastoplastic theory applicable to completely homogenous material, gradient-dependent plasticity considering the microstructural effect predicts that phase transformation occurs earlier and that the thickness of transformed ASB changes with flow shear stress.

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.

Cryogenic Material Properties of Polycaprolactone

2019 ◽  
Author(s):  
Amrit Sagar ◽  
Christopher Nehme ◽  
Anil Saigal ◽  
Thomas P. James
Keyword(s):  
Yield Strength ◽  
Strain Hardening ◽  
Liquid Nitrogen ◽  
Material Properties ◽  
Room Temperature ◽  
Strain Hardening Exponent ◽  
Strength Coefficient ◽  
Finite Element Software ◽  
Aspect Ratios ◽  
Deform 3D

Abstract In pursuit of research to create a synthetic tissue scaffold by a micropunching process, material properties of Polycaprolactone (PCL) in liquid nitrogen were determined experimentally. Specimens were prepared using injection molding and tested under compression to determine the stress-strain relationship of PCL below its glass transition temperature. Cryogenic conditions were maintained by keeping the PCL specimens submerged in liquid nitrogen throughout the loading cycle. Specimens of two different aspect ratios were used for testing. Yield Strength, Strength Coefficient, and Strain Hardening Exponent were determined for different specimen aspect ratios and extrapolated for the case with zero diameter to length ratio. Material properties were also determined at room temperature and compared against results available in the literature. Results demonstrate that PCL behaves in a brittle manner at cryogenic temperatures with more than ten times increase in Young’s modulus from its value at room temperature. The results were used to predict punching forces for the design of microscale hole punching dies and for validation of a microscale hole punching model that was created with a commercially available finite element software package, DEFORM 3D. The three parameters Yield Strength, Strength Coefficient, and Strain Hardening Exponent used in Ludwik’s equation to model flow stress of PCL in DEFORM 3D were determined to be 94.8 MPa, 210 MPa, and 0.54, respectively.

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