Tensile behaviour of S690QL and S960QL under high strain rate

Abstract

Despite offering significant strength-to-weight advantages, high-strength structural steels, such as S690QL and S960QL, are used only in limited offshore applications. This is due to the lack of material characterisation in regard to their tensile behaviour, with little data available on loading rates other than those typically experienced offshore. The concern is that high strength structural steels with high yield-to-tensile ratio >0.90 are obtained at the expense of ductility and strain-hardening capacity. In this paper the tensile properties from two high strength structural steels were studied and characterised over a range of strain rates and, the results are compared against the performance of mild steel. High strength structural steels with yield-to-tensile ratios in excess of 0.90 were significantly less sensitive to the effect of strain rate than mild steel with yield-to-tensile < 0.85 at ambient temperature. The yield stress of S690QL and S960QL moderately increase to about 9% and 6% respectively from quasi-static to 100 s-1 strain rate, which is within typical strain rates encountered in primary offshore structural applications.

Effect of Material Anisotropy on the Mechanical Response of Automotive Steel under High Strain Rates

“…Figure 5 shows the characteristic of fluctuation, of which the stress-strain curve can be approximately fitted as a sine attenuation function (σ = A 0 e −ξε sin(ωε + φ) + C 0 ), where C 0 is the constant, and the distance between the first two crests and the distance between the first crest and the trough is taken as the cycle (T) and the amplitude (A 0 ), as shown in Figure 5a. In the high speed dynamic tensile test, the stress signal oscillation will inevitably occur owing to the increase of loading rate, and Alabi believed that it was the stress wave generated by the imbalance between internal friction and external force at high strains that caused the loading signal to be noisy [5][6][7]14,[26][27][28][29]. Anyway, we assign the first appeared maximum stress σ U as upper yield stress to consider the strain-rate response of all specimens.…”

“…The C-S model has been employed to simulate the dynamic response of different steels, as listed in Table 3 [12][13][14]17,30]. There exists significant difference in the characteristic parameters D and p, in particular, a vast gap can be found between the D values of different steels.…”

“…Since steel structure is very sensitive to the change of strain rate, diverse models have been established to predict the dynamic deformation behavior of structural steels [11][12][13][14][15]. The Johnson-Cook (J-C) model defines the constitutive relation of the effective yield stress with strain, strain rate and temperature [11].…”

“…Compared with the J-C models, a modified Hollomon-Voce model is proposed to predict the ratedependent response. According to the dynamic response of S235, S690QL and S960QL, Alabi et al [14,15] proposed the strain hardening exponent and strain sensitivity to explain the mechanical performance of these materials even in the presence of flaws. Nevertheless, the classical Cowper-Symonds (C-S) constitutive model has been widely applied to describe the performance of materials under dynamic deformation situations with good reliability [16,17].…”

Tensile Behaviour of TMCP Q690d High-Strength Structural Steel at Strain Rates From 0.00025 to 760 S-1

“…The strain rate-dependent behaviours of structural steel of different grades with the yield strength ranging from 321 to 906 MPa have been investigated [15][16][17][18][19][20][21][22][23]. The existing references show that structural steel is sensitive to strain rate and its yield stress is more sensitive to strain rate than the ultimate tensile strength.…”