Carbon fiber reinforced polymer (CFRP) is widely used in the aerospace field due to its light weight and high strength. The CFRP milling process is prone to damage such as burrs and tears. The cutting force is closely related to the damage of CFRP and tool wear. In this paper, a back propagation (BP) neural network model of cutting force and edge force coefficients was established. The model considers the effects of instantaneous uncut chip thickness, fiber cutting angle, spindle speed, and axial depth of cut. The unidirectional CFRP laminate instantaneous milling model considering the cutting edge force was further established. The instantaneous milling force prediction model was extended to multi-directional CFRP laminates. And the relationship between the damage mechanism of CFRP and the instantaneous milling force was analyzed. Experiments have proved that the instantaneous milling force prediction model built in this paper has high accuracy.
A long-distance natural gas pipeline system consists of considerable equipment and many pipe segments, but the conventional energy efficiency index of a natural gas pipeline is considered as a whole. Because the specific energy consumption of each unit cannot be determined, the index system is not perfect, and evaluating the energy efficiency of a natural gas pipeline system is difficult. The energy efficiency evaluation model for a natural gas pipeline was established using the analytic hierarchy process. A judgment matrix was constructed based on the energy efficiency index system of a longdistance natural gas pipeline, and the weight coefficient was calculated using the characteristic root method. Then, the consistency of the established judgment matrix was verified. The energy efficiency evaluation model successfully quantified the qualitative factors that affect natural gas pipelines. The comprehensive energy efficiency coefficient G of the natural gas pipeline was obtained from the operational data of the natural gas pipeline; then, the equipment or pipe segments with high energy consumption can be identified. The energy efficiency evaluation program of the natural gas pipeline was developed using Visual Basic for Applications, which significantly reduced the evaluation workload. The natural gas pipeline energy efficiency evaluation model is used to evaluate the energy efficiency of a natural gas pipeline, to identify the high energy consumption equipment or pipe segments, and to propose measures to improve the energy efficiency. The results show that the gas pipeline energy efficiency evaluation model and evaluation procedures can identify high energy consumption equipment or pipe sections in complex natural gas pipelines.
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