Search Results (3)

The overall temperature in high latitude regions has been rapidly increasing in recent years, creating a demand for infrastructure to support increasing human activities. Recent advances in material science have resulted in the development of advanced high-strength steels (AHSS), which are new grades of cold-formed steel (CFS) with unprecedented strength. To design safe infrastructure, the material properties of AHSS under subzero temperatures must be quantified. An experimental investigation following the steady-state test protocol was carried out to quantify the subzero temperature effects on the material properties of AHSS and conventional CFS sheets with yield strengths ranging from 395 MPa to 1200 MPa. Two types of AHSS (dual phase and martensitic) and two types of conventional CFS (mild and high-strength low-alloy) were investigated at temperatures down to −60 ${}^{\circ }$C. The stress–strain relationship, elastic modulus, and key stresses and strains were reported from the experiments. The results show that AHSS’s material properties do not degrade but are mildly strengthened at subzero temperatures than at ambient, which indicates that AHSS is a suitable construction material for structural members in high-latitude regions. Furthermore, modeling on stress–strain relationships of AHSS and conventional CFS at subzero temperatures was developed, demonstrating excellent fits with the experiment data. Full article

Studies involving the mechanical properties of high-strength steel (HSS) at elevated temperatures have received considerable attention in recent years. However, current research on HSS at high temperatures is lacking. As a result, the design of fire-protective steel structures with high standards is not sufficiently conservative or safe. This study investigates the effect that elevated temperatures have on the mechanical properties of ASTM A572 Gr. 50 and 60 steels. Reduction factors for the yield strength, tensile strength, and elastic modulus were derived and compared with the standard (AISC, EN1993-1-2) and previous studies (NIST). This study also provides extensive data on the reduction factors for the yield strength, tensile strength, and elastic modulus of mild steel (MS), HSS, and very-high-strength steel (VHSS). The reduction factor for the yield strength was analyzed by expanding the strain level up to 20%. Equations for the yield strength, tensile strength, and elastic modulus were proposed. In future studies, various strains should be analyzed according to the grade of the steel, with the derivation of a reduction factor that considers the plastic strain of the steel. Hence, the findings reported in this study generated a database that can be applied to fire safety design or performance-based fire-resistant design. Full article

Design and manufacturing are the key steps in the sustainable manufacturing of any product to be produced. Within the perspective of injection molds production, increased competitiveness and repeated changes in the design require a complete optimized manufacturing process. Local and minor improvements in the milling process do not generally lead to an optimized manufacturing process. The goal of the new geometry and parametric analysis of the mould is to reduce the quality issues in mild steel grade 60. In this explicit research, the surface roughness (smoothness) of indigenously produced injection moulds in the local market in Pakistan is investigated. The CNC milling machine (five-axis) is used for the manufacturing of an injection mould, and the Taguchi method of the design of the experiment is applied for parameters optimization. Hence, the overall process is assisted in balancing the milling machine parameters to trim down the surface roughness issue in mild steel moulds and increase their sustainability. The spindle speed (rpm), the depth of cut (mm), and the feed rate (mm/rev) are considered as input variables for process optimization, and the experiments are performed on mild steel grade 60. It is deduced that the combination of a spindle speed of 800 rpm, feed rate of 10 mm/rev and depth of cut of 0.5 mm is the best case in case of minimum surface roughness, which leads to sustainable products. It is also deduced from ANOVA, that the spindle speed is a factor that affects the surface roughness of mild steel products, while the feed rate turns out to be insignificant. Full article