THERMOMECHANICAL RESPONSE OF THE ROTARY FORGED WHA OVER A WIDE RANGE OF STRAIN RATES AND TEMPERATURES

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5431-5437 ◽  
Author(s):  
W. G. GUO ◽  
C. QU ◽  
F. L. LIU
Keyword(s):  
Strain Rate ◽  
Dislocation Motion ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Thermomechanical Response ◽  
Tension Tests ◽  
Wide Range ◽  
Physically Based ◽  
Split Hopkinson ◽  
Modeling Prediction

This paper is to understand and model the thermomechanical response of the rotary forged WHA, uniaxial compression and tension tests are performed on cylindrical samples, using a material testing machines and the split Hopkinson bar technique. True strains exceeding 40% are achieved in these tests over the range of strain rates from 0.001/s to about 7,000/s, and at initial temperatures from 77K to 1,073K. The results show: 1) the WHA displays a pronounced changing orientation due to mechanical processing, that is, the material is inhomogeneous along the section; 2) the dynamic strain aging occurs at temperatures over 700K and in a strain rate of 10-3 1/s; 3) failure strains decrease with increasing strain rate under uniaxial tension, it is about 1.2% at a strain rate of 1,000 1/s; and 4) flow stress of WHA strongly depends on temperatures and strain rates. Finally, based on the mechanism of dislocation motion, the parameters of a physically-based model are estimated by the experimental results. A good agreement between the modeling prediction and experiments was obtained.

Investigation of Dynamic Strain Ageing Effects of Low Alloy Steels 15Kh2MFA and 15Kh2NMFA

2005 ◽  
Vol 482 ◽  
pp. 367-370
Author(s):  
Miroslava Ernestová
Keyword(s):  
Strain Rate ◽  
Tensile Tests ◽  
Dynamic Strain ◽  
Low Alloy Steels ◽  
Strain Rates ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Lower Strain ◽  
Wide Range ◽  
Alloy Steels

The paper summarizes results of tensile tests in low alloy steel (LAS) specimens (steels 15Kh2MFA and 15Kh2NMFA). Slow Strain Rate Tensile tests (SSRT) were performed in air at temperatures from 22 to 325°C over a wide range of strain rates from 2.5×10-6 to 1.67×10-3 s-1. The possible effect of strain rate and temperature to mechanical properties of tested LAS is searched for. The dynamic strain ageing (DSA) was observed within certain temperature ranges at lower strain rates tested and its hardening effect in terms of the maximum strengthening stress decreased linearly with the increase of log strain rate. It has been found that the occurrence of susceptibility to environmentally assisted cracking (EAC) of tested steels in high temperature water (HTW) is corelated to the DSA behavior. The result suggest that DSA reduces ductility of reactor pressure vessel (RPV) steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature. A reasonable coincidence was observed between the susceptibility to DSA exhibited by SSRT in air and with the EAC behavior observed in laboratory experiments.

Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams

2006 ◽  
Vol 306-308 ◽  
pp. 905-910 ◽  
Author(s):  
Zhi Hua Wang ◽  
Hong Wei Ma ◽  
Long Mao Zhao ◽  
Gui Tong Yang
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Aluminum Foams ◽  
Wide Range ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.

A Phenomenological Constitutive Model Constructed for PC/ABS Blends

2006 ◽  
Vol 306-308 ◽  
pp. 989-994 ◽  
Author(s):  
M. Nizar Machmud ◽  
Masaki Omiya ◽  
Hirotsugu Inoue ◽  
Kikuo Kishimoto
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Constitutive Models ◽  
Strain Rates ◽  
Strain Behavior ◽  
Tension Tests ◽  
Proposed Model ◽  
Wide Range ◽  
Different Temperatures ◽  
Prediction Evaluation

Based on previous available constitutive models, a phenomenological constitutive model has been constructed and is proposed to describe the strain, strain rate and temperature dependentdeformation behavior of PC/ABS blends. In this paper, four quasi-static uniaxial tension tests of a specimen tested at different strain rates and temperatures were used to identify the constitutive model constants. By using the proposed constitutive model, predicting the stress-strain behavior of the PC/ABS blend tested at certain strain rate and different temperatures compares well to the behavior exhibited from the tests. From comparison between the DSGZ and the proposed models, proposed model shows a better prediction. Evaluation of the proposed constitutive model was also presented and it has revealed that the proposed model might have a potential to be used for predicting a wide range of temperatures and high strain rates behavior of PC/ABS blends.

Temperature-Dependent Tension Plastic Deformation and Fracture Behavior of Ti-6.6Al-3.3Mo-1.8Zr-0.29Si Alloy at High Strain Rates

2014 ◽  
Vol 626 ◽  
pp. 115-120
Author(s):  
Jun Zhang ◽  
Qi Wei Zhang ◽  
Yang Wang
Keyword(s):  
Strain Rate ◽  
Titanium Alloys ◽  
High Strain ◽  
Impact Resistance ◽  
Strain Rates ◽  
Temperature Dependent ◽  
High Strain Rates ◽  
Tension Tests ◽  
Deformation And Fracture ◽  
Split Hopkinson

Titanium alloys have received great interest in the engineering applications requiring light weight and high impact resistance components. It is necessary to understand the mechanical properties of titanium alloys at high strain rates and various temperatures in the structural design. In the present paper, uniaxial tension tests at strain rates of 190, 500 and 1150s-1 and temperatures of 20, 150, 300°C are carried out using a modified split hopkinson tension bar system to investigate the effects of strain rate and temperature on tension behavior of the Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy. Experimental results indicate that the alloy has the rate and temperature sensitivity and still keeps high strengths and toughness at temperature up to 300°C under high strain rate. SEM observations reveal that ductile fracture is the major fracture mode when the alloy is deformed at high strain rates.

An Investigation on Dynamic Tensile Properties of TiAl Intermetallic Alloy

1998 ◽  
Vol 552 ◽  
Author(s):  
Yu Wang ◽  
Dongliang Lin ◽  
Yuanxing Zhou ◽  
Yuanming Xia ◽  
Chi C. Law
Keyword(s):  
Strain Rate ◽  
Tensile Properties ◽  
Room Temperature ◽  
Testing Machine ◽  
Rotating Disk ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Intergranular Cracking ◽  
Split Hopkinson Tensile Bar ◽  
Split Hopkinson

ABSTRACTRoom-temperature tensile properties of polycrystalline Ti–;47A1–2Mn–;2Nb alloy with nearly lamellar (NL) microstructures were investigated at the strain rates between 10-;5 and 1000 s-1 using a self-designed Split-Hopkinson tensile bar setup with a rotating disk and conventional testing machine. It was found that tensile ductility varies within a narrow range with the strain rate while dynamic strengths (σd) of the alloy are obviously higher than static strengths (σs). There exists a linear relationship between σs and the logarithm of the strain rate , and between σ d and the strain rate itself (). Fractography analysis indicated that the alloy fractured in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect was excluded from the main cause for the room-temperature brittleness of the investigated alloy.

scholarly journals Effect of strain rate on the hydrogen embrittlement of a DP steel

2018 ◽  
Vol 183 ◽  
pp. 03015
Author(s):  
Tom Depover ◽  
Ahmed Elmahdy ◽  
Florian Vercruysse ◽  
Patricia Verleysen ◽  
Kim Verbeken
Keyword(s):  
Strain Rate ◽  
High Strength Steels ◽  
High Strength ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Dp Steel ◽  
Static Tests ◽  
Split Hopkinson Tensile Bar ◽  
Advanced High Strength Steels ◽  
Split Hopkinson

Advanced high strength steels (HSSs), such as dual phase steels, are widely used in the automotive industry due to their excellent combination of strength and ductility. In certain applications, they might be exposed to hydrogen (H) which is known to be detrimental for the deformation. H embrittlement (HE) is still not fully understood. It might drastically reduce the energy absorbed in a crash event and limits the use of HSSs in car bodies. Although H diffusion is a highly time dependent phenomenon, so far, the combined effect of dynamic strain rates and electrochemical H pre-charging has not been studied. Therefore, a reproducible methodology has been developed. Tensile specimens were electrochemically H pre-charged and immediately tested in a split Hopkinson tensile bar setup. To distinguish between the effect of strain rate and HE, static tests have been conducted using the same procedure. Results show that the HE resistance decreased due to higher H amounts in the sample for all strain rates. The HE increased when slower strain rates were applied due to higher probability of H to diffuse to regions of stress concentration ahead of a crack tip and as such accelerating failure. At the highest strain rate considered (900 s-1), the material still lost about 10% of its ductility.

High Strain-Rate Constitutive Behavior of SAC305 Solder During Operation at High Temperature

2014 ◽  
Author(s):  
Pradeep Lall ◽  
Di Zhang ◽  
Vikas Yadav
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Tensile Tests ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
High Strain Rates ◽  
Wide Range ◽  
Thermal Chamber

Leadfree solders have been used as interconnects in electronic packaging, due to its environmental friendly chemical property. However, those materials may experience high strain rates when subjected to shock and vibration. Consequently, failure will occur to electronics in those situations. Therefore, knowing the material properties of lead-free solders are extremely important, but research on mechanical behaviors of those solder alloys at high strain rates are scarce. Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. However, Anand’s model constants for the transient dynamic strain rates are scarce. In this paper, the nine material parameters to fit the Anand viscoplastic model at high strain rates have been presented. In order to develop the constants for this model, uniaxial tensile tests at several strain rates and temperatures have been completed. A constant strain rate impact hammer which enables attaining strain rates around 1 to 100 per sec has been employed to implement tensile tests and a small thermal chamber is applied to control testing temperature. High speed cameras operating at 70,000 fps have been used to capture images of specimen and then digital image correlation method is used to calculate tensile strain. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε̇ = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125°C). Anand viscoplasticity constants have been calculated by nonlinear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.

Strain-Rate Effect on the Tensile Behaviour of High Strength Alloys

2011 ◽  
Vol 82 ◽  
pp. 124-129 ◽  
Author(s):  
Ezio Cadoni ◽  
Matteo Dotta ◽  
Daniele Forni ◽  
Stefano Bianchi
Keyword(s):  
Strain Rate ◽  
Rate Sensitivity ◽  
High Strength ◽  
Constitutive Law ◽  
Tensile Behaviour ◽  
Strain Rates ◽  
Cross Sectional ◽  
Split Hopkinson Tensile Bar ◽  
Wide Range ◽  
First Results

In this paper the first results of the mechanical characterization in tension of two high strength alloys in a wide range of strain rates are presented. Different experimental techniques were used for different strain rates: a universal machine, a Hydro-Pneumatic Machine and a JRC-Split Hopkinson Tensile Bar. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. An increase of the stress at a given strain increasing the strain-rate from 10-3 to 103 s-1, a moderate strain-rate sensitivity of the uniform and fracture strain, a poor reduction of the cross-sectional area at fracture with increasing the strain-rate were shown. Based on these experimental results the parameters required by the Johnson-Cook constitutive law were determined.

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