卧式离心式滚磨光整TC4试件表面完整性与抗疲劳性能实验研究

发布时间：2018-06-11 23:41

本文选题：光整加工 + 滚磨　；参考：《太原理工大学》2017年硕士论文

【摘要】：钛合金TC4因其密度小、比强度高、耐腐蚀性能好,在航空航天、石油化工以及医疗等领域得到广泛的应用,但是由于硬度低以及疲劳性能偏差导致在很多方面限制了其进一步的应用。滚磨光整加工作为机械加工的终道加工工序,可以改变零部件表面完整性,提高零部件的抗疲劳性能。为此,本文以航空钛合金材料TC4试件为研究对象,采用仿真与实验结合的方法,对卧式离心滚磨光整TC4试件进行了系统研究,以改善试件表面完整性,进而提高其抗疲劳性能。首先,通过ABAQUS对板材进行静强度分析,基于多元正交回归分析方法与FE-SAFE疲劳寿命仿真对影响板材疲劳性能的显著因素粗糙度、残余应力、外载应力等因素做了定性分析并确定裂纹萌生的初始位置,继而采用ABAQUS6.11集成的裂纹扩展有限元方法对裂纹扩展路径做了仿真模拟并与实验对比,证明了仿真的正确性。其次,采用三因素四水平的正交实验方法对卧式离心滚磨光整加工板材单面及双面进行了实验研究,得到不同工艺参数对表面完整性参数的影响规律;单面加工时,加工时间为60min,磨块直径为10mm,装入量为80%;双面加工时,磨块直径为5mm,加工时间为15min,装入量为80%,材料去除量最大;无论是单面加工还是双面加工,磨块直径为7mm,加工时间为45min,装入量为60%,表面粗糙度下降值最大;磨块直径为10mm,装入量为60%,加工时间为30min时,残余压应力最大。在此基础上,采用综合平衡法得到了表面完整性较优的工艺参数:磨块直径7mm,加工时间45min,装入量60%。最后,进行了单双面光整加工后试件的拉-拉疲劳实验,得出双面加工之后试件的疲劳寿命略大于单面加工之后试件的疲劳寿命;基于阶梯级固定应力水平下单双面加工板材疲劳寿命结果,采用多元线性回归分析的方法,拟合出粗糙度、硬度、残余应力、应力水平对疲劳寿命的影响关系,通过回归分析和方差分析验证了公式的正确性;采用公式计算出了未经滚磨光整加工试件疲劳极限为289MPa,单面滚磨加工之后试件的疲劳极限为450MPa,较加工前疲劳极限提高15.7%;双面加工之后疲劳极限为578MPa,较加工前疲劳极限提高48.5%。进而通过观察断口形貌以及金相组织对抗疲劳机理进行了分析,可以看出加工前后组织细化且裂纹萌生于次表层而非表层;通过XRD衍射实验可以看出衍射峰发生偏移,说明滚磨光整加工引入残余压应力可抑制裂纹萌生以及扩展从而提高疲劳寿命。本文得到了卧式离心滚磨光整加工TC4试件以提高其表面完整性较优的工艺参数,提高了钛合金的疲劳性能;研究成果对于离心式滚磨光整加工钛合金类零部件工艺参数选取提供了依据,为钛合金材料进一步的应用提供了参考。
[Abstract]:Titanium alloy TC4 has been widely used in aerospace, petrochemical and medical fields because of its low density, high specific strength and good corrosion resistance. However, its further application is limited in many respects due to its low hardness and fatigue performance deviation. As the finishing process of mechanical machining, the surface integrity of parts can be changed and the fatigue resistance of parts can be improved. Therefore, in this paper, the TC4 specimen of aviation titanium alloy is taken as the research object, and the horizontal centrifugal rolling finishing TC4 specimen is systematically studied by the method of simulation and experiment, in order to improve the surface integrity of the specimen and improve its fatigue resistance. Firstly, the static strength of plate is analyzed by Abaqus. Based on multivariate orthogonal regression analysis and FE-SAFE fatigue life simulation, the roughness and residual stress are analyzed. The external load stress and other factors are qualitatively analyzed and the initial position of crack initiation is determined. Then the crack propagation path is simulated by using Abaqus 6.11 integrated crack propagation finite element method and compared with the experimental results, which proves the correctness of the simulation. Secondly, the orthogonal experiment method of three factors and four levels is used to study the effect of different process parameters on the surface integrity parameters of horizontal centrifugal rolling finishing plate, and the influence of different process parameters on the surface integrity parameters is obtained. The processing time is 60 minutes, the diameter of the grinding block is 10 mm, the loading is 80 mm, and the diameter of the grinding block is 5 mm, the processing time is 15 minutes, the loading amount is 80 minutes, and the material removal is the largest, whether it is on one side or on both sides, The grinding block diameter is 7 mm, the processing time is 45 minutes, the loading amount is 60 minutes, and the surface roughness decrease value is the largest, while the grinding block diameter is 10 mm, the loading volume is 60 mm, and the processing time is 30min, the residual compressive stress is the largest. On this basis, the optimum surface integrity parameters were obtained by comprehensive balance method: grinding block diameter 7 mm, processing time 45 min, loading volume 60 mm. Finally, the tensile and tensile fatigue tests of single and double-sided finishing specimens are carried out, and it is concluded that the fatigue life of the specimen after double-sided finishing is slightly longer than that of the specimen after single-sided finishing. Based on the results of fatigue life of single and double machined plate under the fixed stress level of step, the influence of roughness, hardness, residual stress and stress level on fatigue life is fitted by the method of multiple linear regression analysis. The correctness of the formula is verified by regression analysis and variance analysis. The fatigue limit of unpolished specimen is 289MPa, the fatigue limit of single surface grinding is 450 MPa, the fatigue limit is 15.7 higher than that of pre-machining, and the fatigue limit of double-sided machining is 578MPa, which is 48.5% higher than that of pre-machining. By observing the fracture morphology and the anti-fatigue mechanism of metallographic structure, it can be seen that the microstructure is fine and the crack originates in the subsurface layer but not the surface layer before and after processing, and the diffraction peak is offset by XRD diffraction experiment. It is shown that the crack initiation and propagation can be inhibited and the fatigue life can be improved by the introduction of residual compressive stress in rolling finishing. In this paper, the process parameters of surface integrity of TC4 specimens processed by horizontal centrifugal rolling finishing are obtained, and the fatigue properties of titanium alloys are improved. The research results provide a basis for the selection of technological parameters for the centrifugal rolling finishing of titanium alloy parts, and provide a reference for the further application of titanium alloy materials.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG580.6;TG146.23

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