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Three-dimensional (3D) printing provides more possibilities for composite manufacturing. Composites can no longer just be layered or disorderly mixed as before. This paper aims to introduce a new algorithm for dual-material 3D printing design.

A novel topology design method: solid isotropic material with penalization (SIMP) for hybrid lattice structure is introduced in this paper. This algorithm extends the traditional SIMP topology optimization, transforming the original 0–1 optimization into A–B optimization. It can be used to optimize the spatial distribution of bi-material composite structures.

A novel hybrid structure with high damping and strength efficiency is studied as an example in this work. By using the topology method, a hybrid Kagome structure is designed. The 3D Kagome truss with face sheet was manufactured by selective laser melting technology, and the thermosetting polyurethane was chosen as filling material. The introduced SIMP method for hybrid lattice structures can be considered an effective way to improve lattice structures’ stiffness and vibration characteristics.

The fabricated hybrid lattice has good stiffness and damping characteristics and can be applied to aerospace components.

Notched fatigue life curves of welded joints were established and compared with International Institute of Welding (IIW) standards to verify the metal fatigue performance of welded joints treated with pneumatic impact (PIT).

This paper was based on the notched stress method, and this approach not only allows for the assessment of fatigue failure of welded structures with toes and roots but also for the assessment of fatigue strength of joints with localized post-treatments. The paper summarizes the nominal stress data of weld and pneumatic impact treated (PIT) steel joints of different strengths, fits the nominal stress curves of the joints without the use of strength and obtains the stress concentration factor of the joints through the establishment of the finite element (FE) method. Notched fatigue life curves for welded joints were established and compared with IIW standards.

Notched stress concentration data obtained by the FE method was more reliable. The slope of the fatigue life curve of welded joints treated with pneumatic impact (PIT) increases by at least 2.5%, and the stress concentration factor decreases by 20%.

In the fatigue study of notched systems, there were fewer studies on fatigue life assessment of joints processed by high frequency mechanical impact. The purpose of this paper was to analyze the fatigue test data of typical strength steel welded joints and fit fatigue life curves, and the research content provides an important reference for improving the safety and fatigue failure assessment of heavy steel structures.