Dynamic Tensile Tests of Auto-Body Steel Sheets with the Variation of Temperature

2006 ◽  
Vol 116-117 ◽  
pp. 259-262 ◽  
Author(s):  
Hee Jong Lee ◽  
Jung Han Song ◽  
Hoon Huh
Keyword(s):  
Flow Stress ◽  
Tensile Test ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Speed ◽  
Mechanical Response ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Static State ◽  
Steel Sheets

This paper is concerned with the thermo-mechanical behavior of steel sheet for an autobody including the temperature dependent strain-rate sensitivity. Tensile tests have been carried out with the high strength steel sheets such as SPRC35R, SPRC45E and TRIP60. The tensile tests were performed with the variation of the strain-rates from 0.001/s to 200/s and with the variation of environmental temperatures from -40 to 200. The thermo-mechanical response at the quasi-static state is obtained with the static tensile test and the one at the intermediate strain-rate is obtained with the high speed tensile test. Both the strain-rate and the temperature sensitivity of the flow stress are calculated for the quantitative evaluation of thermo-mechanical behavior of steel sheets. The results demonstrate that as the strain-rate increases, the variation of the flow stress becomes more dependent on the temperature. The results also indicate that the material properties of SPRC35R are more sensitive to the strain-rate and the temperature than those of SPRC45E and TRIP60.

The Effect of Strain-Rate Upon the Tensile Deformation of Materials

1975 ◽  
Vol 97 (2) ◽  
pp. 151-155 ◽  
Author(s):  
R. G. Davies ◽  
C. L. Magee
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
High Speed ◽  
Tensile Deformation ◽  
Rate Sensitivity ◽  
Al Alloys ◽  
Reinforced Plastics ◽  
Strain Behavior ◽  
Static Testing ◽  
Dynamic Factors

The tensile strength of seventeen engineering materials including steels, Al alloys, and fiber-reinforced plastics, has been determined at strain-rates from 10−3 to 103 sec−1. Variable effects on the stress-strain behavior were found in the different materials with the Al alloys showing minimal strain-rate sensitivity and the plastics highest. All results exhibit a logarithmic dependence of flow stress on strain-rate and thus the dynamic factors (ratio of dynamic to low rate or quasi-static strengths) are as dependent upon changes in quasi-static testing speed (∼1 in./min (0.42 mm/s) as they are to changes at high speed (50,000 in./min or 50 mph (22.35 m/s). No significant influence of strain-rate on elongation or reduction in area has been found for any of the materials. Steels, which comprise the majority of the presently investigated materials, exhibit a higher rate sensitivity for yielding than for higher strain deformation. It is shown that the flow stress results for these steels leads to an internally consistent scheme when (1) strength level and (2) strengthening mechanisms are properly accounted for.

Superplastic Deformation Behavior of Spray Formed High Speed Tool Steel at 820°C

2007 ◽  
Vol 561-565 ◽  
pp. 91-94
Author(s):  
Can Dong Zhou ◽  
Jun Fei Fan ◽  
Hai Rong Le ◽  
Jing Guo Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Speed ◽  
Tensile Axis ◽  
Tensile Elongation ◽  
High Speed Steel ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dislocation Creep

Being examined by tensile tests at 820°C with initial strain rates of 2.5×10-4 s-1, 5.0×10-3 s-1and 1.0×10-1 s-1, the hot-rolled spay formed high speed steel (SF-HSS) had superplastic properties. With έ=2.5×10-4 s-1and 5.0×10-3 s-1, the σ-ε curves indicate that there has occurred dynamic recrystallization at the later stage of deformation.The tensile elongation decreases monotonously with strain rate increasing. The strain rate sensitivity m =dlogσ/dlog έ is about 0.23. In the sub-surface of fractured SF-HSS samples with έ=2.5×10-4 s-1,, most of holes on the subsurface are observed to distribute near the carbides and arranged along the tensile axis direction. The interface between coarse carbides and matrix is very weak sites where the holes are easy to nucleate and connect to cracks during deformation. In the necked region, fine carbide particles on the grain boundary have pinned the slip of dislocations and formed dislocation wall inside the grain. Dynamic recrystallization and some climb of dislocations has occurred. The superplastic deformation mechanism with έ=2.5×10-4 s-1 was dislocation creep mechanism controlled by dynamic recrystallization. During deformation, the role of some carbide in the materials was to retard the grain growth and keep SF-HSS having fine equiaxed grain size and remain stable.

Effect of Hydrogen on the Superplastic Behavior of Ti-6Al-4V Alloy

1990 ◽  
Vol 196 ◽  
Author(s):  
B. Gong ◽  
C. B. Zeang ◽  
Z. H. Lai ◽  
Z. S. Xu
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Superplastic Behaviour

ABSTRACTThe superplastic behaviour of Ti-6Al-4V alloy containing various amounts of hydrogen (0.07 ∼ 0.33wt%) has been investigated by tensile tests at temperatures of 800 ∼ 950°C. Results show that the solution of hydrogen in the alloy helps to reduce the flow stress with strain rate in the range of 1.67 ×10−4 ∼ 1.67×10−2 s−1 and makes the temperature of superplastlc deformation become Lower (810∼870°C). Nevertheless, it also causes a decrease of the strain rate sensitivity exponent and tensileelongation, However, by a suitable alloying with hydrogen (∼ 0.1wt%), the alloy can be made to undergo superplastlc deformation at a rather tow temperature (840°C) with an acceptable loss of superptastic ductility.

Multiscale Material Modeling and Simulation of the Mechanical Behavior of Dual Phase Steels Under Different Strain Rates: Parametric Study and Optimization

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Tarek M. Belgasam ◽  
Hussein M. Zbib
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Volume Fraction ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dual Phase ◽  
Strain Rates ◽  
Microstructure Parameters ◽  
Dp Steels

Recent studies on developing dual phase (DP) steels showed that the combination of strength/ductility could be significantly improved when changing the volume fraction and grain size of phases in the microstructure depending on microstructure properties. Consequently, DP steel manufacturers are interested in predicting microstructure properties as well as optimizing microstructure design at different strain rate conditions. In this work, a microstructure-based approach using a multiscale material and structure model was developed. The approach examined the mechanical behavior of DP steels using virtual tensile tests with a full micro-macro multiscale material model to identify specific mechanical properties. Microstructures with varied ferrite grain sizes, martensite volume fractions, and carbon content in DP steels were also studied. The influence of these microscopic parameters at different strain rates on the mechanical properties of DP steels was examined numerically using a full micro-macro multiscale finite element method. An elasto-viscoplastic constitutive model and a response surface methodology (RSM) were used to determine the optimum microstructure parameters for a required combination of strength/ductility at different strain rates. The results from the numerical simulations were compared with experimental results found in the literature. The developed methodology proved to be a powerful tool for studying the effect and interaction of key strain rate sensitivity and microstructure parameters on mechanical behavior and thus can be used to identify optimum microstructural conditions at different strain rates.

Evaluation of the Failure Elongation of Steel Sheets for an Auto-Body at the Intermediate Strain Rate

2008 ◽  
Vol 385-387 ◽  
pp. 749-752 ◽  
Author(s):  
Seok Bong Kim ◽  
Hoon Huh
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Tensile Elongation ◽  
Testing Machine ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Result ◽  
Tensile Testing Machine ◽  
Static State ◽  
Steel Sheets

This paper deals with the dynamic failure elongation of mild steel, SGACD and advanced high strength steel sheets such as TRIP600, DP600 and TWIP steels. The failure elongation has been obtained from the high speed tensile testing machine with various strain rates ranged from 0.003/s to 200/s. The experimental result demonstrates that the tensile elongation does not simply decrease as the strain rate increases, but it decreases from the quasi-static state to the strain rate of 0.1 or 1/s and increases again up to the strain rate of 100/s. Furthermore, some high strength steels have the tendency that the tensile elongation increases as the strain rate increases. Moreover, the localized strain rate hardening in the necking region induces the increase of elongation.

Tensile Property of Electrochemically Polished Titanium Alloy

2014 ◽  
Vol 939 ◽  
pp. 146-151
Author(s):  
Takashi Ikushima ◽  
Tetsuhide Shimizu ◽  
Ming Yang
Keyword(s):  
Titanium Alloy ◽  
Tensile Test ◽  
Strain Rate ◽  
Room Temperature ◽  
Quantitative Measurement ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Rates ◽  
Electrochemical Polishing ◽  
Different Thickness

Tensile tests of titanium alloy (Ti-6Al-4V) with different thickness of 0.4 mm and 0.3 mm, were performed to investigate thickness dependency of superplasticity. To keep the same inner microstructure between specimens with different thicknesses, electrochemical polishing method was applied to reduce thickness. By keeping the voltage for the electrochemical polishing as 30 V the thickness decreased as linear with respect to polishing time. Further, tensile tests of 0.4 mm with strain rate 9.310-4 sec-1 were conducted at room temperature and 850 °C. And the superplasticity of 450 % elongation was obtained at 850 °C. For quantitative measurement of superplasticity, strain rate sensitivity (m value) was calculated from the tensile test by changing strain rate. The m values of the unpolished 0.4 mm specimen and the polished 0.3 mm specimen were 0.52 and 0.43, respectively. Strain rates to calculate the m value were 510-4 sec-1 and 110-3 sec-1. Consequently the reduction of thickness resulted in the reduction of m value, which means less superplasticity for thinner sheets of Ti-6Al-4V.

Dynamic Tensile Characteristics of TRIP-Type and DP-Type Sheets for an Auto-Body

2007 ◽  
Vol 340-341 ◽  
pp. 255-262
Author(s):  
Seok Bong Kim ◽  
Hoon Huh ◽  
Sung Ho Park ◽  
Ji Ho Lim
Keyword(s):  
Tensile Strength ◽  
Flow Stress ◽  
Ultimate Tensile Strength ◽  
Strain Rate ◽  
Material Properties ◽  
High Strain ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Effect ◽  
Dynamic Tensile Tests

This paper investigates the dynamic tensile characteristics of TRIP600, TRIP800, DP600 and DP800 at the range of strain rate from 0.003 to 200/s. The tensile test acquires stress−strain curves and the strain rate sensitivity of each material. Experimental results show two important aspects for TRIP-type and DP-type sheets quantitatively: the flow stress increases as the strain rate increases; the elongation is not a monotonic function of the strain rate and increases at the same level of the strain rate even when the strain rate increases. In order to investigate the pre-strain effect for two types of metals at the high strain rate, TRIP600 and DP600 were elongated with the pre-strain of 5 and 10% at the strain rate of 0.003/s. Then, dynamic tensile tests were carried out at the strain rate of 0.003, 1, 10 and 100/s. The results demonstrate that the material properties of TRIP600 and DP600 are noticeably influenced by the pre-strain when the strain rate was over 1/s. The ultimate tensile strength as well as the yield stress increases due to the pre-strain effect.

scholarly journals Compressive Behaviour of Additively Manufactured Periodical Re-Entrant Tetrakaidecahedral Lattices at Low and High Strain-Rates

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1196
Author(s):  
Michaela Neuhäuserová ◽  
Tomáš Fíla ◽  
Petr Koudelka ◽  
Jan Falta ◽  
Václav Rada ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Speed ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Deformation Behaviour ◽  
Rate Sensitivity ◽  
Image Correlation ◽  
Strain Rates ◽  
Static Compression

Compressive deformation behaviour of additively manufactured lattice structures based on re-entrant tetrakaidecahedral unit-cell geometry were experimentally investigated under quasi-static and dynamic loading conditions. Specimens of four different structures formed by three-dimensional periodical assembly of selected unit-cells were produced by a laser powder bed fusion technique from a powdered austenitic stainless steel SS316L. Quasi-static compression as well as dynamic tests using split Hopkinson pressure bar (SHPB) apparatus at two strain-rates were conducted to evaluate the expected strain-rate sensitivity of the fundamental mechanical response of the structures. To evaluate the experiments, particularly the displacement fields of the deforming lattices, optical observation of the specimens using a high-resolution camera (quasi-static loading) and two synchronised high-speed cameras (SHPB experiments) was employed. An in-house digital image correlation algorithm was used in order to evaluate the anticipated auxetic nature of the investigated lattices. It was found that neither of the investigated structures exhibited auxetic behaviour although strain-rate sensitivity of the stress–strain characteristics was clearly identified for the majority of structures.

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