Advances in Compact Manufacturing for Shape and Performance Controllability of Large-scale Components-A Review

Research on compact manufacturing technology for shape and performance controllability of metallic components can reanze the simplification and high-reliability of manufacturing process on the premise of satisfying the requirement of macro/micro-structure. It is not only the key paths in improving performance, saving material and energy, and green manufacturing of components used in major equipments, but also the challenging subjects in frontiers of advanced plastic forming. To provide a novel horizon for the manufacturing in the critical components is significant. Focused on the high-performance large-scale components such as bearing rings, flanges, railway wheels, thick-walled pipes, etc, the conventional processes and their developing situations are summarized. The existing problems including multi-pass heating, wasting material and energy, high cost and high-emission are discussed, and the present study unable to meet the manufacturing in high-quality components is also pointed out. Thus, the new techniques related to casting-rolling compound precise forming of rings, compact manufacturing for duplex-metal composite rings, compact manufacturing for railway wheels, and casting-extruding continuous forming of thick-walled pipes are introduced in detail, respectively. The corresponding research contents, such as casting ring blank, hot ring rolling, near solid-state pressure forming, hot extruding, are elaborated. Some findings in through-thickness microstructure evolution and mechanical properties are also presented. The components produced by the new techniques are mainly characterized by fine and homogeneous grains. Moreover, the possible directions for fin＇ther development of those techniques are suggested. Finally, the key scientific problems are first proposed. All of these results and conclusions have reference value and guiding significance for the integrated control of shape and performance in advanced compact manufacturing.

Numerical Simulation and Experimental Research on Microstructural Evolution During Compact Hot Extrusion of Heavy Caliber Thick-Wall Pipe

Compact hot extrusion(CHE) process of heavy caliber thick-wall pipe is a new material-saving production process. In order to reveal the optimum hot extrusion parameters in CHE process, the e ects of the extrusion parameters on the microstructural evolution are investigated systematically. The metadynamic recrystallization(MDRX) kinetic models and grain size models of as-cast P91 steel are established for the first time according to the hot compression tests performed on the Gleeble-3500 thermal-simulation machine. Then a thermal-mechanical and micro-macro coupled hot extrusion finite element(FE) model is established and further developed in DEFORM software. The results indicated that the grain size of the extruded pipe increases with the increasing of initial temperature and extrusion speed, decreases when extrusion ratio increases. Moreover, the grain size is more sensitive to the initial temperature and the extrusion ratio. The optimum hot extrusion parameters are including that, the initial extrusion temperature of 1250 °C, the extrusion ratio of 9 and the extrusion speed of 50 mm/s. Furthermore, in order to verify the simulation precisions, hot extrusion experiment verification on the heavy caliber thick-wall pipe is carried out on the 500 MN vertical hot extrusion equipment. The load–displacement curve of the extrusion process and the grain sizes of the middle part extruded pipe are in good accuracy with the simulation results, which confirms that the hot extrusion FE models of as-cast P91 steel could estimate the hot extrusion behaviors. The proposed hot extrusion FE model can be used to guide the industrial production research of CHE process.

Optimizing Winding Angles of Reinforced Thermoplastic Pipes Based on Progressive Failure Criterion

This paper examines a scheme to optimize the multiple winding angles of reinforced thermoplastic pipes(RTPs)under internal and external pressures.To consider the nonlinear mechanical behavior of the material under changes of winding angle due to deformation,we use three-dimensional(3D)thick-walled cylinder theory with the 3D Hashin failure criterion and theory of the evolution of damage to composite materials,to formulate a model that analyzes the progressive failure of RTPs.The accuracy of the model was verified by experiments.A model to optimize the multiple winding angles of the RTPs was then established using the model for progressive failure analysis and a multi-island genetic algorithm.The optimal scheme for winding angles of RTPs capable of withstanding the maximum internal/external pressure was obtained.The simulation results showed that the ply number of the reinforced layer has a prominent nonlinear effect on the internal and external pressure capacity of the RTPs.Compared with RTPs with a single angle of±55°,the multiple winding angle overlay scheme based on the multi-angle optimization model improved the internal and external pressure capacity of the RTPs,and the improvement in the external pressure capacity was significantly better than the internal pressure carrying capacity.

Prediction of welding residual stress in multipass narrow gap welded pipes with large thickness

The objective of this study is to investigate the influence of post weld heat treatment （PWHT） on the distribution of residual stress in welded pipes with large thickness. The detailed pass-by-pass finite element simulation was developed to study the residual stress in narrow gap multipass welding of pipes with a wall thickness of 150 mm and 89 weld beads. The effect of PWHT on welding residual stress was also investigated by means of numerical analysis. The simulated results show that the hoop stress is tensile stress in the weld region and compressive stress in the parent metal areas adjacent to weld seam. After heat treatment, the residual stresses decrease substantially, and the simulated residual stress is validated by the experimental one. The distribution of the through-wall axial residual stress along the weld center line is a self-equilibrating type.