Impact Performance of Advanced High Strength Steel Thin-Walled Columns
The crashworthiness performance of spot-welded columns fabricated with advanced high strength steels is evaluated using finite element (FE) analysis. A failure criterion for the spot-welds is implemented into the FE model to predict accurately the progressive axial collapse of the columns. The behavior of two Dual Phase (DP) steels and a High Strength Low Alloy (HSLA) steel are compared by examining the mean crushing force, peak load and crushed column length for single-hat and double-hat configurations, both experimentally and numerically. Numerical results of the developed FE model correlate favorably available experimental data for different impact conditions.
Nonlinear finite element modeling of dynamic localizations in high strength steel columns under impact
Abstract This paper presents a consistent methodology for the assessment of nonlinear behavior of structural steel column under severe loading conditions. Nonlinear finite element analysis is conducted to study localization failure in axially pre-loaded columns made of high strength steel HY-100 and subjected to transverse impact. The thermo-viscoplastic response of high strength steel at low and high strain rates and temperatures is also investigated using a physically based constitutive model. The constitutive model which exhibits dominant performance in describing the thermo-mechanical behavior of metals is then implemented into the commercial finite element code ABAQUS/Explicit via user material subroutine coded as VUMAT. The effect of impact velocity, impactor mass, impact location and pre-loading condition on the localization behavior of the steel columns is also investigated. The outcomes of this study could be utilized to provide some guidelines to design codes to come up with simplified method of analysis for steel structures subjected to impact loading.
Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems
Abstract Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.