To be slightly larger, the general selection is more widespread. The "a" or "y" value represents the reduction ratio of the cross-sectional area at the necked fracture to the original cross-sectional area, indicated as a percentage. The larger the "a" or "y" value, the better the ductility of the cast iron drainage pipes. The "y" value can also reflect the plastic deformation ability of the necked part of the steel under three-directional tensile stress conditions, which is relevant to considering the resistance in the thickness direction (3) Cold Bending Function. The cold bending function is tested through cold bending experiments, as shown in Figure-4. During the experiment, the specimen needs to be bent to 180 degrees. If the outer surface of the specimen does not show cracks or delamination, it is considered qualified. The cold bending test not only directly checks the bending deformation ability or plasticity of the steel but also reveals the metallurgical properties within the steel, such as sulfur and phosphorus segregation, and the mixing conditions of sulfides and oxides, which will all reduce the cold bending properties of the steel. Therefore, the cold bending function is an integrated indicator for determining the plasticity and quality of the steel's bending properties. The steel properties demonstrated by the impact toughness and tensile tests, such as strength and plasticity, are static functions, while the toughness test reflects the dynamic properties of the steel.

Steel has two forms of damage: plastic damage and brittle damage. Plastic damage occurs when the section stress of a component reaches the yield point of the material under the effect of external forces, resulting in excessive deformation that exceeds the material or component's strain capacity, ultimately leading to failure at the tensile strength of柔性铸铁排水管. Prior to failure, the component undergoes significant plastic deformation, and the fracture surface after cracking appears fibrous and darkened, with sometimes visible sliding marks. Due to the large plastic deformation and the longer duration of deformation before failure, it is easy to detect and take remedial measures in time, preventing severe consequences. Additionally, under static load conditions, the redistribution of internal forces after plastic deformation in the component makes the stress distribution within the component more uniform, enhancing the structural capacity to withstand static loads. Brittle damage occurs when the component undergoes very little deformation, if any, before failure under the effect of external forces, and the section stress may even be less than the yield strength of the material. The component suddenly fails at the stress concentration point, leading to cracking.

No prior signs of damage were evident; the damage occurred suddenly, characterized by a smooth, lustrous, granular fracture surface, which resulted from metallurgical and mechanical processing, particularly at notches and cracks, which are often the origin of cracking. Cold temperatures, repeated loading fatigue, dynamic loads, and residual stresses often lead to brittle failure. Cellular damage, often occurring at low stresses without明显的屈服变形预兆, is difficult to detect in time and remediate, and the cracking of a single component can lead to the continuous collapse of the entire structure, with severe consequences. When planning, constructing, and utilizing steel structures, it is crucial to prevent the occurrence of brittle failure. The primary functions of steel include its mechanical properties, functional properties, and durability. The mechanical properties of steel include tensile properties, cold bending properties, and impact properties, each determined by corresponding tests in accordance with relevant standards. The mechanical properties of flexible cast iron drainage pipes are expressed through the steel stress-strain relationship curve obtained from a uniaxial tensile test using standard specimens (Figure 1(a)) under normal temperature (10~35℃) and static load (satisfying the loading speed of static force loading).