Choose a slightly larger size; the general selection is more prevalent. "a" or the reduction ratio of the cross-sectional area at the necked fracture to the original cross-sectional area is indicated as a percentage. A larger "a" or value indicates better plasticity in cast iron drainage pipes. The "y" value can also reflect the plastic deformation ability of the necked part of the steel under tri-axial tensile stress conditions, which is relevant to considering the thickness direction resistance to layered failure. The cold bending property is tested through cold bending experiments, as shown in Figure-4. During the experiment, the specimen needs to be bent to 180 degrees, and if the outer surface of the specimen does not exhibit cracks or delamination, it is considered qualified. The cold bending test can not only directly check the bending deformation ability or plasticity of the steel but can also reveal the internal metallurgy of the steel, such as sulfur, phosphorus segregation, and the mixing status of sulfides and oxides, all of which will reduce the cold bending property of the steel. Therefore, the cold bending property is an integrated target for determining the plasticity and quality of the steel's bending properties. The steel properties, such as strength and plasticity, reflected in the impact toughness and tensile tests are static properties, while the toughness test reflects the dynamic properties of the steel.

Steel can be damaged in two forms: 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 beyond 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. Plastic damage is easily detectable before failure due to the large plastic deformation and the extended duration of deformation, allowing for timely remedial measures to prevent severe consequences. Additionally, under static load conditions, the plastic deformation of the component leads to a redistribution of internal forces, resulting in a more uniform stress distribution within the component, enhancing the structure's ability to withstand static loads. Brittle damage, on the other hand, occurs when the component undergoes minimal 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. Failure occurs suddenly at points of stress concentration, where the component cracks.

Damage occurred without any prior indication, emerging suddenly. The fracture surface is smooth and lustrous, granular in nature, resulting from metallurgical and mechanical processing, particularly at notches and cracks, which are often the origins of cracking. Cold temperatures, cyclic loading fatigue, dynamic loads, and residual stresses often lead to brittle failure. Because cellular damage is typically low-stress failure, without obvious yield deformation precursors, it is difficult to detect and take timely corrective measures. Moreover, the cracking of a single component can often lead to the continuous collapse of the entire structure, with severe consequences. When planning, constructing, and utilizing steel structures, it is crucial to pay special attention to preventing the occurrence of brittle failure. The main 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, all determined by corresponding tests as specified by relevant standards. The mechanical properties of柔性铸铁排水管 are expressed through the steel stress-strain relationship curve obtained from a uniaxial tensile test conducted under ambient temperature (10~35℃) and static load (with a loading speed satisfying static loading requirements) using standard specimens (Figure 1(a)).