基于ANSYS Workbench和HyperWorks的航空沉头螺钉动力学分析与参数化研究

Dynamic analysis and parametric design of aerospacecountersunk screws based on ANSYS Workbenchand HyperWorks

为探究某航天工程应用中沉头螺钉的断裂失效行为,开展了对沉头螺钉的动力学分析与参数化研究。通过SolidWorks建立了沉头螺钉的三维模型,并导入ANSYS Workbench和HyperWorks两类有限元分析软件中,分析并验证了不同网格划分方式、网格大小和约束位置对沉头螺钉最大应力的影响程度。基于有限元分析结果,在ANSYS Workbench中研究了十字槽深度、同轴度、沉头角度和圆角半径对沉头螺钉最大应力的影响规律及各参数的灵敏度。研究结果表明:采用两类有限元分析软件得到的应力结果基本一致,仅相差0.1%。采用ANSYS Workbench时的计算效率更高,沉头螺钉的最大应力位置发生在头杆结合处的过渡圆角处,与实际断裂位置完全一致;相比十字槽深度、沉头角度和圆角半径,同轴度参数对最大应力的影响更明显。该分析结果可为工程技术人员预判沉头断裂影响因素及优化结构提供重要参考。

Summary: High-strength countersunk screws are an important fastener widely utilized in heavyweight machinery industries such as aerospace, automotive and high-speed railway. Due to changes in working environments and working loads, failures occur, such as loosening, pulling out and even fracturing. It has been found that fracturing accounts for 65% of the failure accidents.In this paper, a high-strength countersunk screw utilized in aerospace machines is studied for its fracturing behaviors. This paper focuses on the bolt head fracturing mainly from transient dynamics, parametric analysis and sensitivity analysis. A M4×10 high-strength flat head screw with 30 CrMnSiA material is taken as an example. Firstly, a 3D model is built by SolidWorks and then separately embedded into two types of finite element analysis software, ANSYS Workbench and HyperWorks. The influence of different mesh division methods, mesh size and restraint positions on the maximum stress of countersunk screws is compared and analyzed under the load with a minimum breaking tension of 8 820 N. It is found that, under different element types, the maximum stress is higher than the yield strength, but lower than the ultimate strength;under the same element type, it is higher in HyperWorks with a lower computational efficiency. It is also found that different constraint positions have almost no effect on the maximum stress. Secondly, based on the results of the finite element analysis, the influence of the depth of the cross recess, concentricity, countersunk angle and fillet radius on the maximum stress is studied in the ANSYS Workbench, and the sensitivity analysis is also discussed. For the depth of the cross recess, the maximum stress has almost no change within its tolerance range, but when the depth of the cross recess is greater than 2.8 mm, an increase of the depth of the cross recess significantly affects the maximum stress value. Similarly, for the concentricity, countersunk angle and fillet radius, it is concluded that the given tolerance range specified in the standard is reasonable, but it will have significant change on the maximum stress out of the tolerance range. Lastly, in order to investigate the influence of depth of the cross recess, concentricity and countersunk angle on the maximum stress of countersunk screws, this paper further conducts the sensitivity analysis, obtains the relationship between different parameters and the maximum stress through polynomial curves fitting, and takes the derivative of the curves. Then, residual analysis is used to verify the results.The research results show that the relationship between the depth of the cross recess and the concentricity with the maximum stress exhibits a non-linear relationship, with the influence of the concentricity being more significant. The countersink angle and the fillet radius have a basic linear relationship with the maximum stress. The position of the maximum stress is found in the transition fillet between the head and the stud which exactly occurs at the same position with the actual fracture, and the concentricity has a more obvious influence on the maximum stress. The analysis results provide an important reference for engineers to predict the influencing factors of countersunk head fractures and structure optimization.