The Synergy Between Energy Efficiency And Property To Drive Life Cycle Energy Assessment Of Laser Additive-subtractive Hybrid Manufactured Parts

Energy conservation and green development are important issues common to the global manufacturing industry.Made in China 2025 has clearly put forward the strategic task and focus of “fully implementing green manufacturing”,and strengthening the application of energy-saving processes and improving the resource/energy utilization efficiency will be an important focus for the green development of manufacturing industry.Laser additive-subtractive hybrid manufacturing(ASHM)is an emerging advanced manufacturing technology with the advantages of high forming accuracy,short manufacturing cycle time and high material utilization efficiency,which facilitates the integrated manufacturing of highly functional,lightweight and personalized multi-structured complex metal parts.However,from the perspective of green and sustainable development,the introduction of high energy-consuming equipment such as laser mahcine and chiller in the manufacturing system,as well as the inefficient heat treatment process when the material absorbs laser energy during processing stage,lead to the situation that the energy consumption and energy efficiency issues are more serious than that of conventional subtractive manufacturing(CSM),especially the correlation and coupling mechanism between the energy efficiency of the manufacturing process and the property of the manufactured parts have not been clarified,which will restrict the green application of the technology in aerospace,defense and military,biomedical and other highly sophisticated fields.Therefore,exploring the synergy mechanism between energy efficiency of the process and the property of the manufactured parts,which in turn drives the development of part life cycle energy consumption assessment and ultimately supports the part pr ocessing process route decision,have become the inevitable requirement of this technology for environment-friendly manufacturing and function-friendly manufacturing.This paper takes the ASHM process of “laser direct metal deposition + milling”as the research object,and explores the linkage relationship of “energy efficiency –performance-energy consumption” from the four dimensions: Laser energy absorption and dissipation,effective utilization of electricity,synergy of energy efficiency and performance,as well as life cycle energy demand assessment of parts,so as to provide theoretical and technological guidance for the green developmen t and application of ASHM.The main research work of this paper is as follows :(1)A multi-level energy efficiency definition and measurement method is proposed.The part manufacturing energy flow is divided into process level,equipment level and life cycle level,and the process-level energy efficiency(PEE)and device-level energy efficiency(DEE)are defined based on the relationship between energy input and output of each l evel,respectively.The predictable characteristics of the PEE and DEE are analyzed,and the influencing factors of energy efficiency are discussed,which provide a theoretical basis for the subsequent energy efficiency parametric modeling.(2)In view of the complex and variable energy conversion and dissipation in laser processing,an energy efficiency modeling method based on material melting enthalpy is proposed.Firstly,the parameterization models of effective energy utilization rate(EUR)and melting volume specific energy(MSE)are constructed,and then the regression identification functions between the two energy efficiency indicators and three basic process parameters,namely,laser power,scanning speed and powder feeding rate,are further established using the response surface design of experiments method.The influence of process parameters on energy efficiency is analyzed,and the mechanism of laser energy absorption and dissipation is revealed.It is found that heat conduction energy loss is the main influence factor on energy efficiency.The analysis provides the process parameter interval for DEE research.(3)In view of the multi-state energy consumption characteristics of the ASHM equipment during processing,an energy consumption modeling method based on the moving state of the cladding head/cutting tool is proposed.Based on the cladding head moving state in the additive manufacturing(AM)stage,the AM energy consumption is divided into deposition energy consumption,rapid moving energy consumption and pause energy consumption.Based on the cutting tool moving state in the subtractive manufacturing(SM)stage,the SM energy consumption is divided into cutting energy consumption and air cutting energy consumption.The power in each moving state is identified by the working statuses of machine sub-systems,and the duration is related to the length of moving path,number of inflection points,as well as the scanning speed.Two DEE indicators: Forming energy utilization rate(FUR)and forming volume specific energy(FSE),are proposed based on the deposition energy consumption and total energy consumption model,and the effects of scanning speed and scanning path on energy efficiency are analyzed.The experiments showed that the energy consumption prediction accuracy of model can reach 97%.By improving the scanning speed of cladding head,the time of AM stage can be shortened,the FSE can be decreased,thus the DEE can be improved.(4)In view of the ambiguous correlation between the energy efficiency and mechanical properties of parts due to the complexity of laser energy dissipation and deposition physical mechanism,a TOPSIS energy efficiency and property co-evaluation method based on criterion-driven weight distribution is proposed.Firstly,the melt pool features are extracted as the intermediate parameter related to energy efficiency and property,and the influence mechanism of energy efficiency on the mechanical properties of parts is revealed.It is found that the distribution of laser energy will affect the three-dimensional size of the melt pool,as well as the gra in size and dislocation density after solidification of the melt pool,and ultimately affecting the defect generation and mechanical properties of the part.Then,a multi-index evaluation framework of TOPSIS based on criterion-driven weight distribution is constructed.Taking the EUR,MSE,FUR,FSE,yield strength and elongation as evaluation indexes,the evaluation scores of different process parameter combination schemes under the four criteria of “average”,“half”,“first two” and “quadratic” are quantitatively compared,Finally,the decision mapping space of multiple process parameter combination schemes is obtained.The collaborative research on energy efficiency and property provides data support for the life cycle energy consumption assessment of parts.(5)In view of the uncertainty in the decision-making of the processing route of parts due to the variability of structure characteristics,use scenarios,as well as the specific energy consumption,a energy consumption evaluation method of parts based on life cycle theory is proposed.The life cycle energy demand evaluation model of ASHM parts is established,which considering the cooperation of multiple parameters such as solid-to-envelope ratio,lightweight coefficient,scenario energy-saving coefficient and process parameters,and the “energy consumption ratio” is proposed as the basis for measuring the decision-making of the part processing route.Taking an aero-engine simplified bearing housing as the case study,the energy requirements of the ASHM process route and the CSM process route for manufacturing the same functional part in the material production stage,manufacturing stage and use stage were quantitatively calculated and compared,and the impact of the multi-parameter synergy effect on the evaluation results was comprehensively analyzed.The results showed that the ASHM process is suitable for manufacturing complex integrated parts with small solid-to-envelope ratio,high degree of lightweight and applied to aerospace scenarios.The research on life cycle energy demand evaluation provides technical support for the decision-making of parts processing route.(6)An energy efficiency prediction and energy consumption evaluation software of ASHM process is developed.The software mainly consists of basic parameter information module,PEE module,DEE module and part energy evaluation module,which can assist processors in predicting the PEE and DEE of ASHM process and evaluating the energy demand of the part in the life cycle stage before manufactur ing.The software provides effective tools to support the research on energy efficiency improvement,energy consumption quota formulation,process parameter scheme optimization and part processing route decision-making of ASHM process.