Influence of Strain Rate, Temperature, Plastic Strain, and Microstructure on the Strain Rate Sensitivity of Automotive Sheet Steels

Larour, P.; Bäumer, Annette; Dahmen, Kirsten; Bleck, Wolfgang

doi:10.1002/srin.201200099

Cited by 32 publications

(32 citation statements)

References 28 publications

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“…Generally the influence of strain rate and temperature on the dynamic properties of sheet steel grades in the strain rate range 10 −4 to 1000 s −1 can be well described by the thermal activation theory for automotive sheet steels 1, 18, 28. A strong reciprocity between strain rate and temperature is characteristic for dynamic deformation according to the theory of thermal activated plastic deformation.…”

Section: Discussionmentioning

confidence: 99%

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Strain Rate Sensitivity of Pre‐Strained AISI 301LN2B Metastable Austenitic Stainless Steel

Larour

Verleysen

Dahmen

et al. 2012

steel research int.

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The dynamic behavior of AISI 301LN2B (EN 1.4318) metastable austenitic steel grade has been investigated at 296 K by means of servohydraulic tensile and split Hopkinson bar testing in the strain rate range 0.005–1000 s−1. As delivered, as well as 10% uniaxial, biaxial, and plane strain pre‐strained conditions, without subsequent heat treatment have been tested. A negative strain rate sensitivity is observed in the low strain rate range between 10−4 and 1–10 s−1. Pre‐straining reduces the magnitude of the adiabatic tensile strength softening, especially in the plane strain condition with higher triaxility. The thermal activation related dynamic flow stress increase is not dependent on pre‐straining. The γ → α′ induced additional flow stress increase, however, is highly strain rate and pre‐straining sensitive. The amount of pre‐straining determines the overall ductility at fracture, and therefore the adiabatic temperature increase. The pre‐straining stress state influences the amount of α′‐martensite formed before dynamic testing, and consequently the maximum intensity of the TRIP induced flow stress increase by subsequent dynamic testing.

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Section: Discussionmentioning

confidence: 99%

“…The yield strength R p0.2 can be then modeled as follows:18, 28 where Δ G 0 and σ 0 * are the free activation enthalpy and effective stress at zero thermal activation ( T = 0 K) and m′ is the strain rate exponent.…”

Section: Discussionmentioning

confidence: 99%

Strain Rate Sensitivity of Pre‐Strained AISI 301LN2B Metastable Austenitic Stainless Steel

Larour

Verleysen

Dahmen

et al. 2012

steel research int.

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“…This must be due to the "Dislocation Motion Mechanism", i.e. the high strain rate reduces the time available for movement of existing dislocations in the material [21][22][23]. This behaviour is commonly known as strain rate sensitivity, which is generally more significant in low grade steels than in high grade steels [23][24][25].…”

Section: Static Pull-through Testsmentioning

confidence: 99%

“…the high strain rate reduces the time available for movement of existing dislocations in the material [21][22][23]. This behaviour is commonly known as strain rate sensitivity, which is generally more significant in low grade steels than in high grade steels [23][24][25]. This can also be noted in Table 2, where G300 steel pull-through test results showed increments in the range of 18-20% whilst G550 steel tests showed increments in the range of 13-15%.…”

Section: Static Pull-through Testsmentioning

confidence: 99%

07.23: Effect of loading rate on the pull‐through capacities of cold‐formed steel roof battens

2017

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Localised connection failure is the main shortcoming of cold-formed steel roofing systems subjected to high wind suction loads. Pull-through failure in the vicinity of roof batten to rafter connection is the major connection failure observed during recent high wind events. Both static and fatigue pull-through failures occur based on the type of wind loads (static or cyclic loads). The loading rate to be used in the static and cyclic pull-through failure tests is a moot point as the wind loading frequency can vary during wind events such as storms and cyclones. Therefore, it is necessary to understand the effect of wind loading frequency/rate on the pull-through failures of steel roof battens. This paper investigates the influence of loading rate on both static and fatigue pull-through capacities of steel roof battens by means of a series of static and cyclic tests conducted at various loading rates/frequencies. Initially, tests were conducted on roof battens made of two steel grades (G300 and G550) and two thicknesses (0.8 and 1 mm). The results showed a significant improvement in the pull-through capacities during tests using higher loading rates. They also showed that the current static and cyclic pullthrough design rules/guidelines do not include the effect of loading rate. Secondly, to understand the influence of loading rate on the pull-through capacity of battens, the effect of loading rate on the mechanical properties of steels was investigated using 40 tensile coupon tests. The effect of loading rate on both the tensile strength of steel used and the pull-through capacity of roof batten was then compared. Using the results of comparison, the reasons for the increase in the static pull-through capacity of roof battens with loading rate are discussed and, a recommendation is made in relation to the loading rate to be used with the new Low High Low (LHL) cyclic test. This paper presents the details and results of this study.

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“…5). From a literature survey, the strain rate sensitivity exponent m for mild steel sheets, AZ31Mg alloy sheets, and 5 000 series Al alloy sheets at room temperature would be respectively within the ranges of approximately 0.02 ≤ m ≤ 0.05, [28][29][30] 0.01 ≤ m ≤ 0.04, [31][32][33] and -0.01 ≤ m ≤ 0.005. [34][35][36] Clearly, the strain rate sensitivity exponent is larger in the mild steel and Mg alloy sheets than in the Al alloy sheet, consistent with the decreasing tendency at the beginning of unloading.…”

Section: Relationship Between Nonlinearity and Apparent Elastic Modulusmentioning

confidence: 99%

Non-linear Deformation Behavior during Unloading in Various Metal Sheets

et al. 2015

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The deformation behavior during unloading was examined under uniaxial tension in a mild steel sheet (body-centered cubic metal), an aluminum alloy sheet (face-centered cubic metal), and a magnesium alloy sheet (hexagonal close packed metal). A crystal plasticity finite-element method was also used to investigate the difference in the deformation behavior among on the materials. The nonlinearity during unloading was the largest in the magnesium alloy sheet, and the mild steel sheet showed a larger nonlinearity than the aluminum alloy sheet. On the other hand, the apparent elastic moduli determined from the linear approximation of unloading curves were not always consistent with the characteristics observed in the nonlinearity, and this inconsistency became pronounced as the degree of nonlinearity increased. It was found that the degree of nonlinearity would have a strong correlation with the strain rate sensitivity, suggesting that the apparent elastic modulus was not suitable to model the unloading behavior for materials with high strain rate sensitivity. The crystal plasticity analysis demonstrated that the nonlinearity was much larger in the magnesium alloy sheet than in the other two sheets as observed in the experimental results. The simulation results suggested that one of the reasons that gave rise to the nonlinearity during unloading would be the difference in the critical resolved shear stresses among the slip systems.

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Influence of Strain Rate, Temperature, Plastic Strain, and Microstructure on the Strain Rate Sensitivity of Automotive Sheet Steels

Cited by 32 publications

References 28 publications

Strain Rate Sensitivity of Pre‐Strained AISI 301LN2B Metastable Austenitic Stainless Steel

Strain Rate Sensitivity of Pre‐Strained AISI 301LN2B Metastable Austenitic Stainless Steel

07.23: Effect of loading rate on the pull‐through capacities of cold‐formed steel roof battens

Non-linear Deformation Behavior during Unloading in Various Metal Sheets

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