Background: 3D printing technology is an emerging technology based on additive ideas. Desktop-level 3D printers molded by Fused Deposition Modeling (FDM) are widely used. However, their printing accuracy is relatively low accompanied by severe warpage, which limits its application scope and fields. Therefore, analysis of the cause of warpage in the printing process and optimization, has important practical significance for promoting the application of FDM printers. Methods: The goal of this work is to improve the forming precision of 3D prints, through the finite element analysis software ANSYS, utilizing the life and death component innovation and coupling the temperature field and stress field of printing speed, one of the key factors affecting the forming precision. After the calculation and analysis, the following conclusions can be drawn: In testing with other conditions unchanged, when the printing speed is gradually increased, the accuracy of the print is improved first and then decreased. This method provides a new way to analyze the influence of other factors on the forming accuracy and also provides a new way to get the best print parameters under the combined action of many factors. We reviewed several patents related to 3D printing, its optimization, formulations, precision and accuracy in respective field. Results: So, to achieve the best results, layer thickness has great influence on the molding precision. Finally, the results were obtained by finite element analysis, finding the best printing accuracy of the print parameters and verifying them by conducting actual printing. Conclusion: The research shows that the thickness of the layer has the greatest influence on the printing accuracy in the process parameters studied.

Rapid development of the automobile industry has brought the disposal problem of waste rubber tires. Mixing waste rubber tires into concrete can not only solve environmental problems but also improve the mechanical properties of concrete. Rubber aging is one of the main factors to affect the mechanical properties of rubberized concrete. Therefore, an FEM model of rubberized concrete in mesoscale is established in this paper. The influence of rubber aging on the uniaxial compression damage of rubberized concrete is u;studied. The results show that (1) the elastic modulus and compressive strength of rubberized concrete are negatively correlated with the aging level and content of rubber and positively correlated with the particle size of rubber. (2) After uniaxial compression of concrete enters the softening section, the crack resistance of concrete is positively correlated with the aging level and content of rubber and negatively correlated with the particle size of rubber. (3) Compared with the elastic modulus, the compressive strength of rubberized concrete is more sensitive to the change of parameters of rubber, that is, the change range of the compressive strength of rubberized concrete is always greater than the change range of its elastic modulus, when the aging level, content, and particle size of rubber change.

Track bed is the important support structure at the bottom of shield tunnel, during metro operation, the leakage of stray current will lead to corrosion of rebar in the track bed, which will affect the safe operation of metro. In this paper, the corrosion calculation model of track bed rebar under stray current is established, and the effects of stray current input mode and concrete resistivity on the corrosion rate of track bed rebar are studied. The result shows the corrosion rate of track bed rebar decreases nonlinearly with the increase of concrete resistivity, and the reduction gradient of corrosion rate in bilateral input mode is greater than that in unilateral input mode. With the decrease of concrete resistance, the corrosion area will cover the left half in unilateral input mode and cover both ends of track bed rebar in bilateral input mode. When the input point voltage increases by 40%, the corrosion current density in the middle of track bed will increase by about 61%.

It is known that a large amount of vibration mechanical energy will be generated during train operation. If the mechanical energy can be obtained from the track structure, it can greatly optimize the energy configuration of the metro. Currently, most sensors are limited to disk or cymbal structures and are not used in the track bed; different from existing structures, this paper designs a spherical energy harvester based on a rubber bearing floating slab track, wherein the size range of the spherical energy harvesting structure was approximately determined based on the geometric spatial relationships of the actual track bed internal structure. Compared to the traditional disk and cymbal energy harvesters, the mechanical and electrical properties of the spherical energy harvesting structure was studied by a numerical simulation method, and the optimal size of the spherical energy was determined by calculation. The main conclusions are as follows: (1) Compared with the traditional disk harvester and cymbal harvester, the spherical harvester had better mechanical and electrical properties. (2) By calculating the output power of energy harvesters under load matching, we found that the output power of the spherical harvester was two orders of magnitude higher than that of the disk harvester and 53% higher than that of the cymbal harvester. (3) The optimum size of the spherical harvester was when the thickness of piezoelectric layer was 2 mm, the radius was 16 mm, the axial ratio of the spherical shell was 0.4, and the thickness of the spherical shell was 4 mm.