# Lightweight Research in Engineering: A Review
## 4 Lightweight Pathways and Research Progress
### Structure Lightweight
#### 4.2.1 Size Lightweight
The W-type stiffeners were selected to optimize the layout andsize of the column, and the lightweight design of the column structure was realized. [PERSON] et al. [33] used the correlation analysis method to analyze the influence of design variables such as 90 position shapes and thicknesses on the structural rigidity of the SUV body-in-white, and selected the design variables with lightweight potential. Then, the multiperformance optimization design of the 30 design variables was carried out and finally achieved a good lightweight effect in 2016. In 2017, [PERSON] et al. [34] established the optimization mathematical model for the cross-section size of the frame longitudinal beam, and the finite element analysis software programs were used to carry out modal analysis of the optimized frame solid model in order to verify its dynamic characteristics meet the dynamic requirements, which indicated that the lightweight optimization design is reasonable and effective. For the lightweight design of satellite structures, [PERSON] et al. [35] considered the manufacturing process constraints of augmented materials comprehensively, applied the topological optimization method to find the optimal path of force transmission in the feasible design space of structures, abstracted the corresponding truss structure on the basis of this method, and then applied the dimension optimization method to design the optimal truss member cross-section size. Finally, considering the optimal rod size and structural processing constraints, geometric reconstruction is carried out in order to obtain a structural design scheme for additive manufacturing. In 2018, [PERSON] et al. [36] studied the lightweight design of the Chinese University Student Formula Race Car frame through size optimization under the premise of satisfying the frequency, strength, and stiffness constraints. Finally, the nonlinear optimization model was approximated by sequential linear programming, and a good lightweight effect was achieved. [PERSON] et al. [37] established a mathematical model with the minimum span beam as the objective function, the allowable stress of the beam as the constraint, and the unit thickness as the variables in the optimization of the spar size. By taking the volume of spar as objective function, the allowable stress of the spar as constraint, and web thickness as design variable, size optimization is conducted for the main spar and the rear spar. Subsequently, [PERSON] et al. [6] took a midsize off-road vehicle frame as the optimization object, used the experimental design method to carry out the sensitivity analysis of design variables, and established the structural optimization model based on the necessary trade-offs of design variables. Simultaneously, the multi-island genetic optimization algorithm was used to calculate the natural frequencies of the frame under the three conditions of maximum stress, displacement and free mode, so as to optimize the discrete sizes of the frame plates under the constraints of natural frequencies, geometric sizes, and strength. [PERSON] et al. [38] took the folding electric vehicle and main folding frame for the object and used SolidWorks to establish a simplified three-dimensional model of the main folding frame, which was imported into the ANSYS Workbench for static analysis. Lightweight design of the main folding frame connecting rod by topology optimization and size optimization under the static-load, sudden-braking, sharp-turn conditions. [PERSON] et al. [39] used a horizontal machining center bed as the research object, and used the wall thickness of the bed and the longitudinal thickness, the lateral thickness of the rib as the design parameters, and carried out an orthogonal test on the test data by least-squares method. The response surface model of the bed mass, maximum deformation, maximum stress, and the first four natural frequencies are obtained.