Performance characterization of high-strength steel and quenched and tempered steels and their joints for structural applications

Abstract

Although in the last decades the applicable regulations for the design of steel structures have been deeply improved accounting for modern design approaches and technologies, in a few industrial fields, concepts and formulations derived from centuries-old experience are even nowadays the governing rule. This very often limits the potential offered by the technological innovations in high-performance material, such as quenched and tempered (QT) steels. After having verified in the scientific literature, in the commercial one and in several open material databases that some main data necessary to the comprehensive characterization of QT steel used in building large metal structures are lacking, an extensive experimental campaign was undertaken to achieve an updated and specific fatigue strength characterization for certain types of materials. The aim is to overcome the strict requirements of current regulations on the application of both parent QT materials and welded homogeneous and heterogeneous joints between different steel strength. The experimental campaign allowed filling the knowledge gap as well as providing further understanding whether the use of high-strength steel is effective in the improvement of performances of large steel structures, whose fabrication procedures are typical of building sites rather than workshops. Their extensive application in current building practice is expected to be highly beneficial in terms of weight and costs.

Statistical Analysis of the Mechanical Behavior of High-Performance Polymers: Weibull’s or Gaussian Distributions?

“…In this strain range, the onset of the local fracture processes (chain scission, interfibrillar slipping) is expected. Hence, this mechanical property ‘approaches’ the fracture properties such as σ and ε b for which the Weibull’s model works properly [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. On the other hand, the E 1 value characterizes the very beginning of the sample deformation.…”

“…The advantage of such materials with respect to high-performance inorganic materials lies in their extremely high specific characteristics (related to the material density ρ ). For instance, for a high-strength steel characterizing with very high values of σ = 1–2 GPa [ 4 ], the σ -to- ρ ratio, at a steel density of ρ ≈ 8 × 10 3 kg/m 3 , is σ / ρ = 0.13–0.25 × 10 −3 GPa·m 3 /kg while that for the ultra-oriented ultra-high-molecular-weight polyethylene (UHMWPE) gel fibers with σ = 6 GPa [ 2 ] and ρ ≈ 1 × 10 3 kg/m 3 attains σ / ρ = 6 × 10 −3 GPa·m 3 /kg, i.e., it is 25–50 times greater than that for steel.…”

“…Actually, if the distribution of a measured dataset can be represented with a bell curve that is characteristic of the Gaussian (or normal) distribution, it implies that the data scatter is caused by the sum of many independent and equally weighted factors [ 23 ]. By contrast, if it obeys the Weibull’s statistics, it should have the shape of a linear plot in specific coordinates “lnln[1/(1 − P j )] − ln σ ”, where P j is the cumulative probability of failure, suggesting the dominant role of the surface cracks and their propagation across the sample cross-section in the sample fracture [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ].…”

Специфика Статистики Упругих И Деформационно-Прочностных Свойств Высокопрочных Волокон Полипропилена

“…д. ), поскольку для них удается достигнуть высоких значений прочности (σ = 2−6 GPa) [1][2][3][4][5] и модуля упругости (E = 230 GPa) [6], сопоставимых с характеристиками неорганических материалов [7][8][9][10][11][12][13][14][15][16]. Отличительной особенностью некоторых полимерных материалов (как правило, высокоориентированных) является то, что удельные характеристики их механических свойств, нормированные по плотности материала (ρ), являются рекордными по сравнению со всеми другими материалами.…”

“…Отличительной особенностью некоторых полимерных материалов (как правило, высокоориентированных) является то, что удельные характеристики их механических свойств, нормированные по плотности материала (ρ), являются рекордными по сравнению со всеми другими материалами. Например, для высокопрочной стали с достигнутыми в настоящее время наибольшими значениями σ = 1−2 GPa [14][15][16] при плотности ρ ≈ 8000 kg/m 3 отношение σ к ρ составляет σ/ρ = (0.13−0.25) • 10 −3 GPa • m 3 /kg в то время как для ультраориентированных гель-волокон сверхвысокомолекулярного полиэтилена (СВМПЭ) с σ = 6 GPa [1][2][3] и ρ ≈ 1000 kg/m 3 величина σ/ρ может достигать 6 • 10 −3 GPa • m 3 /kg, т. е. быть в ∼ 25−50 раз больше, чем для стали. Величина этой удельной характеристики для СВМПЭ может уменьшаться по сравнению с другими типами высокопрочных материалов неорганической природы, например, кварцевыми волокнами с σ = 6 GPa [9].…”