# Failure Mechanism and Structural Analysis of Chain Slings with Non-Standard Connections
## 4 Structural Analysis
### Analysis Results
According to the analysis, when the tensile elongation reached 32.007 mm, the maximum stress in the chain rose to approximately 1213.3 MPa, and fracture occurred immediately thereafter. The corresponding maximum tensile load was 105,000 N, which is approximately 84.34% of the value observed in Case 3 (124,500 N). This result is very similar to that of Case 4, indicating that in non-standard connection methods, localized stress concentration caused by the manner of attachment has a greater impact on the durability of the chain than factors such as the wrapping direction or the number of load-bearing legs. These findings are also supported by existing literature. For example, international standards such as DIN EN 818-4 and ISO 3056 [37; 38] strongly recommend using auxiliary components such as master links or shackles when assembling chain slings. They explicitly state that the direct wrapping method cannot ensure mechanical reliability. The present analysis results provide structural analysis-based evidence that supports the technical rationale behind these standards. Additionally, this study confirmed that the nonlinearity of the analysis model increases depending on the chain's contact conditions and load distribution, indicating that the failure mechanism of the chain cannot be predicted by tensile behavior alone. Factors such as the contact angle, curvature radius, and coefficient of friction were found to significantly influence the failure point. These findings suggest the need for more detailed parametric analyses in future research. Table 11 summarizes the analysis results from Case 1 to Case 5. In summary, Case 3 effectively demonstrates the structural stability and tensile resistance characteristics of a standard connection method. This is particularly contrasted with the results from Case 4 and Case 5, which represent non-standard connection methods. The use of non-standard  
Figure 22: Analysis results of case 5: (**a**) Total deformation (displacement); (**b**) Equivalent stress; (**c**) Contact location between the chains and the eye bolt (until the failure of chain 1 and 1 occurs). methods was shown to reduce the failure load of the chain sling system by more than 15%, primarily due to altered load transfer paths and stress concentration mechanisms. Consequently, directly attaching the chain to an eyebolt changes the designed load path, induces nonlinear stress distributions and bending deformations, and significantly compromises chain durability. This aligns with the Johnson-Cook damage model, which indicates that damage accumulation progresses more rapidly under bending behavior than under tensile behavior. Even for chains of identical material and specifications, the connection method can cause considerable variation in load distribution characteristics and fracture behavior. This highlights the importance of connection methods in the selection and use of chain slings in industrial applications. Therefore, even new chains must be connected properly by strictly adhering to technical guidelines for use and inspection of chain slings. Regular inspections and timely disposal are essential to prevent accidents. Although direct wrapping of chains around eyebolts still occurs in practice, this study is meaningful in that it quantitatively evaluates the negative impact of such practices on chain durability. For reference, Figures 23-25 provide detailed illustrations of the fracture characteristics of the chain in each respective case.