Comparative experimental study of hot-formed, hot-ﬁnished and cold-formed rectangular hollow sections
|نوع نگارش مقاله||
scopus – master journals – JCR
۴٫۲۷۶ در سال ۲۰۲۰
۲۶ در سال ۲۰۲۱
۰٫۹۰۱ در سال ۲۰۲۰
|شاخص Quartile (چارک)||
Q1 در سال ۲۰۲۰
خرید محصول توسط کلیه کارت های شتاب امکان پذیر است و بلافاصله پس از خرید، لینک دانلود محصول در اختیار شما قرار خواهد گرفت و هر گونه فروش در سایت های دیگر قابل پیگیری خواهد بود.
فهرست مطالب مقاله:
This paper presents a comparative experimental study on the physical, chemical and mechanical properties of indirectly formed hot-formed, hot-ﬁnished and cold-formed structural steel rectangular hollow sections. Characteristic geometrical parameters and chemical compositions are examined to investigate the physical and chemical differences. Tensile test and charpy V-notch impact test are employed to evaluate the difference in strength, ductility and toughness. Further, the residual stress distributions in both transverse and longitudinal directions are measured using the sectioning method and hole- drilling technique. It is found out that although the geometrical parameters and chemical composition of the tested hollow sections are similar, the mechanical properties are signiﬁ- cantly different, especially for strength, ductility and residual stress distribution. While the hot-ﬁnished and hot-formed sections are often treated equally in design, their mechanical properties and residual stresses distribution are actually different.
|بخشی از متن مقاله:|
Structural Hollow Sections (SHS), especially rectangular hollow sections, are widely used in construction due to the recognition of the inherent aesthetic and structural advantages. Currently, SHSs of steels are classiﬁed into two major groups based on the manufacturing methods: cold-formed and hot-ﬁnished, in which hot-ﬁnished hollow sections consist of another two types, i.e. hollow sections formed hot and formed cold with subsequent heat treatment (hot-formed and hot-ﬁnished, respectively) [1,2]. Although these three types of SHSs are manufactured by either direct or indirect forming techniques, the rolling condition/subsequent heat treatment processes lead to signiﬁcant differences in properties . Through decades of study and practice, the importance of physical, chemical and mechanical properties for designing and analyzing steel structures has been well recognized. Based on the preference on these properties, hot-formed sections are widely favored as the ﬁrst choices, while cold-formed hollow sections are often misunderstood and treated unfavorably although they are actually easier to manufacture and more economical . As for hot-ﬁnished sections, they are often treated the same as hot-formed sections in mechanical properties, provided that the sections formed cold are fully annealed in the subsequent heat treatments [5,6].
Among the differences among the three types of SHSs, residual stress is the most frequently concerned, as it is often associated with issues such as brittle fracture, fatigue, stress corrosion, buckling and post-buckling strength reduction [7–۹]. In practice, the SHSs produced by hot-forming techniques are considered to be residual stress free and have no change in mechanical properties from base metal . The concerns for locked-in residual stresses are mainly for cold-formed and hot-ﬁnished SHSs, as they are formed cold by bending in the beginning. For residual stress contained in cold-formed SHSs, numerous work has been done. Detailed studies of through thickness residual stresses in the longitudinal and transverse directions of square and circular cold-formed thin-walled SHSs can date back to 1980s by stripping method . Later, the through thickness residual stress distribution in cold-formed thin-walled SHSs by panel removal method is also reported . Nowadays, it is well recognized that for cold-formed thin-walled SHSs, the longitudinal residual stresses are in tension at outer surface and in compression at inner surface, and the distribution is assumed to be linear through the thickness . However, studies on the cold-formed thick-walled plate subjected to bending [13,14] show that the through thickness residual stress distribution pattern is not linear. Tong et al. measured the longitudinal residual stress distribution of cold- formed thick-walled SHS and found out the through thickness distribution was different from that of the thin-walled and dependent on the geochemical proﬁle . On the other hand, different from the cold-formed SHS, the concern with the hot-ﬁnished SHS is that it is difﬁcult to make sure the sections formed cold are subsequently “properly” heat treated and successfully get rid of the issues associated with cold-forming techniques . Currently, common design standards have taken the effect of residual stresses in consideration implicitly [17–۱۹]. However, there is still few speciﬁc guidelines on designing and evaluating the distribution and amount of the residual stress itself in a given SHS, especially for thick-walled cold-formed and hot-ﬁnished SHSs.
In this study, the inﬂuence of different manufacturing processes on the physical, chemical and mechanical properties of popular thick-walled SHSs including hot-formed and hot-ﬁnished square SHSs manufactured to Grade S355J2H of EN 10210  and cold-formed square SHS complying EN10219  Grade S355J2H is investigated experimentally. The aim is to provide useful data for the EN Standards and engineers as reference. This comparative study is carried out in three phases. Firstly, physical and chemical properties are examined to investigate the difference in the geometry and chemical composition. Secondly, tensile test and chapry V-notch impact test are conducted to analyze the difference in the mechanical properties such as yield stress, tensile stress, ductility and impact toughness. Thirdly, sectioning test and hole-drilling test are employed to evaluate the locked-in residual stress in the SHSs qualitatively and quantitatively. By comparing the performance of the tested SHSs in the above three phases, the differences among the tested SHSs are evaluated.
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