Billets have oxidized layers and defects on their surface due to the production process, so they must be surface?regulated by grinding. There is no special equipment for surface regrinding of large square steel billets; a square steel regrinding equipment was designed. Kinematic simulation verification was completed using ADAMS software. The results show that the regrinding equipment can simultaneously and smoothly complete the grinding operation on two adjacent surfaces. Using finite element software ANSYS to carry out stress analysis and modal analysis of the regrinding machine under load, and improve the structure; according to the simplified kinematic model, static analysis was carried out to get the required input driving torque, and the selection of the critical components of the spring was completed. Theoretical calculations and simulation results show that this regrinding machine can efficiently grind the surface of large square billets.

The data acquisition and modeling of the depressed pipe were carried out using a 3D scanner, and the residual strength at the depressed pipe was evaluated; based on the modeling, the finite element analysis of the 3D modeled pipe containing the depression was carried out using ABAQUS software, and the stress?strain analysis was carried out using numerical simulation; the geometric deformation detection method was used to detect the depressed pipe, and the stress?strain at the depressed pipe was calculated and analyzed. The load?bearing capacity of the recessed pipe was evaluated; a comparative analysis was conducted for both cases of the pipe with/without internal pressure. The results show that the maximum Von Mises stress at the depression differs greatly between the two cases with/without internal pressure; in the case with internal pressure, the maximum Von Mises stress is located at the perimeter of the pipe depression rather than at the depression; in the case with internal pressure, the maximum equivalent force in the area near the depression is 22.6 MPa, while the maximum equivalent force in the case without internal pressure is 14.8 MPa. The maximum Von Mises stress applied to the pipe is distributed in the deepest part of the depression with a value of 710.3 MPa, and the maximum equivalent force becomes 8.99%, which is distributed in the inner part of the depressed pipe when the downward displacement constraint of 50 mm is set in the indenter. In engineering applications, the 3D scanning technology can be used to obtain the contour of the pipe depression more quickly, and the output data can be used to provide technical support for subsequent stress?strain analysis, pipe evaluation, and rehabilitation.