【作者】 孙涛；

【导师】 王续跃； 王一奇；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2022， 硕士

【摘要】 纤维金属层板（FMLs）是一种金属薄板和纤维增强复合材料交替铺层的层间混杂复合材料,兼备二者的优点,广泛应用于航空航天领域。然而FMLs成形难度高是无法大范围工业应用的原因之一。激光弯曲成形无需模具,柔性大,在成形FMLs结构件中的优势在于不会对材料结构造成损伤。由于FMLs材料各向异性,存在激光成形精度和质量问题。因此,深入研究激光束与FMLs相互作用具有重要的理论意义和实用价值。本文以玻璃纤维增强铝合金层板（GLARE）为研究对象,通过实验探究了激光工艺参数与板材参数对弯曲成形的影响;基于有限元方法对弯曲过程进行了数值模拟;对GLARE层板激光多路径扫描产生的应力释放现象进行分析与抑制,主要工作如下:（1）GLARE层板激光弯曲试验研究。确定了GLARE层板无损伤激光弯曲工艺参数窗口;弯曲角度随激光功率、扫描次数增大而增大,随离焦量、扫描速度增大而减小,随90°铺设角度的单层占比增加而减小,随自由端距离的增大先增大后减小;并通过正交实验确定了最优加工参数组合。（2）GLARE层板激光弯曲数值模拟。基于ABAQUS建立了考虑脉冲激光特点和GLARE层板的结构特性的激光弯曲成形模型,对成形过程中温度场、应力应变场、位移场进行讨论分析以解释GLARE层板激光弯曲成形机理;模拟结果与实验结果一致性好,温度与位移最大误差在±5%以内。（3）GLARE层板多路径扫描应力释放现象规律研究与抑制。GLARE层板成形后在自然时效下残余应力状态较为稳定;应力释放导致的角度回弹变形随单道弯曲角度α、扫描道数N_L、90°单层占比的增加而增大,随扫描间距P的减小而增大;提出上下层交替扫描激光弯曲成形方法进行抑制,当θ_Expected=20°,累积弯曲角度保留系数K提高了45.31%,减小了角度回弹变形,提高了GLARE层板单曲面的激光弯曲成形精度。（4）采用上下层交替扫描方法试制GLARE层板圆弧面样件。以曲率半径150 mm圆弧面为目标曲面,采用等扫描间距、等单道弯曲角度的方式进行路径规划,对应力释放现象产生的角度回弹变形进行补偿,试制圆弧面样件实际曲率半径为151.576 mm,弯折区无明显分层等缺陷;上、下层铝合金硬度较基板均有提高,表面粗糙度略有增大。本文用数值模拟的方法解释了GLARE层板激光弯曲成形机理,提出了上下层交替扫描激光弯曲成形方法抑制激光多路径扫描中应力释现象放导致的角度回弹变形,在指导GLARE层板单曲率零件高精度成形方面具有重要意义。更多还原

【Abstract】 Fiber metal laminates（FMLs）are interlaminated hybrid composites in which metal sheets and fiber reinforced composites are alternately layered.It has the advantages of both metal and fiber-reinforced composite materials,and is widely used in the aerospace field.However,the reason why FMLs cannot be widely used in industry is the difficulty of forming Laser bending is a flexible forming technique that requires no molds.Its advantage in fabrication FML structure is its ability to achieve the damage free element for the structural application.Since FMLs are anisotropic materials,there are problems with laser forming accuracy and quality.Therefore,it is of great theoretical significance and practical value to study the interaction between laser beams and FMLs.In this paper,glass fiber reinforced aluminum alloy laminate（GLARE）is the research object.The effects of laser process parameters and sheet parameters on bending forming were studied.A numerical model for laser bending of GLARE was established.The stress release phenomenon in GLARE laminate laser multi-path scanning is analyzed and suppressed.The main work of this paper is as follows:（1）Experimental study on laser bending of GLARE laminates.The GLARE laminate non-damage laser bending process window is determined.Bending angle increases with the increase of laser power and scanning times,decreases with the increase of defocus Z and scanning speed V;decreases with the increase of the proportion of 90°fiber GFRP monolayer,and increases at first and then decreases with the increase of the distance between the scan line and the free end.The optimal combination of processing parameters is determined by orthogonal experiment.（2）Numerical Simulation of GLARE during Laser Bending Process.Based on ABAQUS software,a numerical simulation model considering the characteristics of pulsed laser and the structural characteristics of GLARE laminates is established.The laser bending mechanism of GLARE laminates is explained by the analysis of temperature field,stress-strain field and displacement field.The laser bending mechanism of GLARE laminates is explained by the analysis of temperature field,stress field,strain field and displacement field.The simulation results are in good agreement with the experimental results,and the maximum error between temperature and displacement is less than±5%.（3）The study and suppression of stress release in multi-path scanning of GLARE laminates.After laser bending of GLARE laminates,the residual stress is stable under natural aging.In the laser multipath scanning process,the springback deformation caused by stress release increases with the addition of the composite layer and the lower aluminum alloy layer,the increase of the bending angleα,the decrease of the distance between the scanning lines P and the increase of the scanning channel number N_L.The method of alternating scanning the upper and lower layers is proposed to restrain the stress release and reduce the angular springback deformation caused by the stress release.Whenθ_Expected=20°,the cumulative bending angle retention coefficient K is increased by 45.31%,the angle springback deformation is reduced,and the laser bending accuracy of single curved surface of GLARE laminate is improved.（4）The arc face sample of GLARE laminate is manufactured by alternating scanning of upper and lower layers.Taking the curvature radius 150mm arc-face as the target surface,the path planning is carried out by the way of equal scanning spacing and equal single-channel bending angle,and the springback deformation caused by stress release is compensated according to the experiment.The actual radius of curvature of the trial-produced arc face sample is 151.576mm,and there is no obvious delamination in the bending zone.The hardness of the upper and lower aluminum alloy in the bending zone is higher than that of the substrate,and its surface roughness increases.In this paper,the laser bending mechanism of GLARE laminates is explained by numerical simulation,and the alternating scanning method of upper and lower layers is proposed to restrain the springback deformation caused by stress release in laser multi-path scanning,which is of great significance in guiding the high precision forming of Glare parts and structures with single curvature.更多还原