基于MSC.PATRAN的抓斗卸船机的结构疲劳性能研究
摘要
目前,在我国大中型冶金企业中,为了方便地进行物料的起重、搬运和装卸工作,采用了大量的起重机,其中包含众多港口起重机。近年来,随着国民经济的高速发展,钢铁产量不断提高,起重机的工作也日趋繁重。与此同时,冶金企业中的起重机不断出现各种各样的事故,这些事故中,最常见也是最严重的是以疲劳裂纹为特征的起重机金属结构故障。所以,研究裂纹故障的发生原因及其扩展趋势,是当前广大工程技术人员十分关注的问题。起重机金属结构的强度计算及疲劳分析十分复杂,在目前已有的各种分析方法中,基于有限元理论的方法迄今被认为较为合理和有效。
本文以马鞍山钢铁股份有限公司港务原料厂的一台港口抓斗卸船机为研究对象,以MSC. Patran为建模工具,对其整体结构进行了有限元分析,对其中重要构件主梁结构进行了疲劳寿命方面的深入分析研究,对支腿开裂部位进行了疲劳裂纹扩展研究。本文进行了结构的诊断评估,给出了相应的整改方案。
首先,本文论述了开展起重机金属结构研究的重要性,特别是对疲劳的研究,提出了本课题的研究内容,并阐述了研究的意义。接着对本文主要使用的有限元软件MSC.Patran、Nastran以及疲劳有限元分析软件MSC.Fatigue进行了简单介绍。
然后,本文对该抓斗卸船机的整机结构和主梁用MSC.Patran和MSC.Nastran进行了有限元建模和计算,在建立模型的过程中,重点考虑了多点约束的问题。通过计算,得出下列结论:该卸船机的静强度、刚度虽满足要求,但后大梁悬臂根部截面的计算应力已接近许用应力,悬臂端部下挠偏大,并致使后大梁中部上拱偏大,影响小车正常行驶,结构设计存在明显缺陷。经过分析研究,提出了整改方案,并对整改后的结构再次进行了有限元计算,结果表明本文提出的整改措施有效地降低了悬臂根部应力和跨中上拱度,此整改方案是成功的。
本文在介绍了疲劳有限元技术的基础上,针对目前工程当中对于起重机金属结构疲劳研究的现状,利用有限元疲劳分析软件MSC.Fatigue对该卸船机主梁结构进行了指定载荷历程下的疲劳分析。通过分析,得出该卸船机主梁的疲劳寿命分布云图,直观显示出主梁结构各个部分的疲劳寿命,从而为卸船机结构设计的评价和改进以及疲劳研究提供了直观的理论依据。本文对卸船机出现裂纹的支腿建立了子模型,分析了结构的疲劳寿命,找到出现裂纹的原因,并进一步进行了裂纹扩展分析;理论计算结果和实际情况吻合较好,本文的方法具有重要的工程实际意义。
最后,本文还对本课题的理论成果和实践意义进行了总结,提出了今后研究的方向,指出综合运用疲劳分析的有限元方法,对起重机金属结构进行疲劳分析才是全面和完整的,这应该成为未来起重机疲劳研究的发展方向之一。
Currently,in our country’s big and medium-sized metallurgy companies,in order to expediently rise、move and unload the works,we adopt a lot of cranes. Among them includes a lot of port cranes. In recent years, along with the highly developed economy of our country, the production of steel rises increasingly, the load works of cranes have enlarged greatly. At the same time, there appear all kinds of metal problems. Among these problems the most common and also the most serious is the trouble in crane metal structures which mostly are troubles of fatigue crack. Hence, researching the reasons that crack happened and the tendency of the crack’s expanding is the problem that most engineers and technicians are fully concerned with. The crane’s metal structure intensity calculation and fatigue analysis is fully complex, among existing different analysis means, the means based on the FEM is regarded as the comparatively consummate one.
This paper takes one transporter grab ship unloader in MISCO as the research object. Takes a research on the whole structure of the FEM by MSC.Patran, and fatigue longevity of its important component, main beam. Researches of the fatigue crack growth of its support leg. Processes the structures’diagnose valuation and then give repair suggestion.
First, this paper discusses the importance of preceding the research on the grab ship unloader’s metal structures and especially the research on the fatigue longevity. It also puts the main content of the problem and elaborates its significance in theory and practice. Then this paper introduces the theory: the fracture mechanics and software such as Patran、Nastran and fatigue research software: MSC.Fatigue.
Second, this paper gives the finite modeling and calculation to the grab ship unloader’s structure by MSC.Patran and MSC.Nastran. In the processes of making modeling, we take more attention to the multi-point constraint. By the calculation, we make such conclusion that the quiet intensity and rigidity meet the demands; calculating stress of the back cantilever root of beam approaches the allowing stress. There is big deflection which causes big camber at the middle of beam .This has influenced the car’s normal movement. Apparently, it’s a design bug. After study, we put forward some schemes of the modification. Then we use the FEA software to analyze the structure again, result proves that the modification schemes presented in this paper can effectively cut down the stress and deflection of the cantilever root. Prevent the incidence of structure’s rupture accident. This scheme of modification is successful.
On the bases of introducing the technology on fatigue FEA, in view of the present conditions in the centre of the project as to the unloader metal structure’s fatigue research, this paper makes use of the software MSC.Fatigue to proceed the fatigue analysis on this main beam structure under certain loads, by the analysis,we can get the cloudy pictures of the fatigue life distribution, and can clearly see every parts fatigue life. Therefore this analysis can supply theory basis for grab ship unloader’s design and improvement and fatigue research. Build a sub-model of the grab ship unloader’s leg where a crack at the weld appears, analyse the structure’s fatigue life and find the reasons for the occurrence of cracks and for the further analysis of crack growth .The calculation result is basically consistent with actual situation. This paper has important engineering practical value.
At the end of this paper, some conclusions on this subject’s practical and academic signficance are presented, this paper also submits the research directions in the future, point out that utilizing the fatigue analysis’s FEM and the fracture mechanics synthetically to the crane’s metal structure fatigue analysis is complete and integrated ,this should become one of the fatigue research orientation for the future cranes.
本文以马鞍山钢铁股份有限公司港务原料厂的一台港口抓斗卸船机为研究对象,以MSC. Patran为建模工具,对其整体结构进行了有限元分析,对其中重要构件主梁结构进行了疲劳寿命方面的深入分析研究,对支腿开裂部位进行了疲劳裂纹扩展研究。本文进行了结构的诊断评估,给出了相应的整改方案。
首先,本文论述了开展起重机金属结构研究的重要性,特别是对疲劳的研究,提出了本课题的研究内容,并阐述了研究的意义。接着对本文主要使用的有限元软件MSC.Patran、Nastran以及疲劳有限元分析软件MSC.Fatigue进行了简单介绍。
然后,本文对该抓斗卸船机的整机结构和主梁用MSC.Patran和MSC.Nastran进行了有限元建模和计算,在建立模型的过程中,重点考虑了多点约束的问题。通过计算,得出下列结论:该卸船机的静强度、刚度虽满足要求,但后大梁悬臂根部截面的计算应力已接近许用应力,悬臂端部下挠偏大,并致使后大梁中部上拱偏大,影响小车正常行驶,结构设计存在明显缺陷。经过分析研究,提出了整改方案,并对整改后的结构再次进行了有限元计算,结果表明本文提出的整改措施有效地降低了悬臂根部应力和跨中上拱度,此整改方案是成功的。
本文在介绍了疲劳有限元技术的基础上,针对目前工程当中对于起重机金属结构疲劳研究的现状,利用有限元疲劳分析软件MSC.Fatigue对该卸船机主梁结构进行了指定载荷历程下的疲劳分析。通过分析,得出该卸船机主梁的疲劳寿命分布云图,直观显示出主梁结构各个部分的疲劳寿命,从而为卸船机结构设计的评价和改进以及疲劳研究提供了直观的理论依据。本文对卸船机出现裂纹的支腿建立了子模型,分析了结构的疲劳寿命,找到出现裂纹的原因,并进一步进行了裂纹扩展分析;理论计算结果和实际情况吻合较好,本文的方法具有重要的工程实际意义。
最后,本文还对本课题的理论成果和实践意义进行了总结,提出了今后研究的方向,指出综合运用疲劳分析的有限元方法,对起重机金属结构进行疲劳分析才是全面和完整的,这应该成为未来起重机疲劳研究的发展方向之一。
Currently,in our country’s big and medium-sized metallurgy companies,in order to expediently rise、move and unload the works,we adopt a lot of cranes. Among them includes a lot of port cranes. In recent years, along with the highly developed economy of our country, the production of steel rises increasingly, the load works of cranes have enlarged greatly. At the same time, there appear all kinds of metal problems. Among these problems the most common and also the most serious is the trouble in crane metal structures which mostly are troubles of fatigue crack. Hence, researching the reasons that crack happened and the tendency of the crack’s expanding is the problem that most engineers and technicians are fully concerned with. The crane’s metal structure intensity calculation and fatigue analysis is fully complex, among existing different analysis means, the means based on the FEM is regarded as the comparatively consummate one.
This paper takes one transporter grab ship unloader in MISCO as the research object. Takes a research on the whole structure of the FEM by MSC.Patran, and fatigue longevity of its important component, main beam. Researches of the fatigue crack growth of its support leg. Processes the structures’diagnose valuation and then give repair suggestion.
First, this paper discusses the importance of preceding the research on the grab ship unloader’s metal structures and especially the research on the fatigue longevity. It also puts the main content of the problem and elaborates its significance in theory and practice. Then this paper introduces the theory: the fracture mechanics and software such as Patran、Nastran and fatigue research software: MSC.Fatigue.
Second, this paper gives the finite modeling and calculation to the grab ship unloader’s structure by MSC.Patran and MSC.Nastran. In the processes of making modeling, we take more attention to the multi-point constraint. By the calculation, we make such conclusion that the quiet intensity and rigidity meet the demands; calculating stress of the back cantilever root of beam approaches the allowing stress. There is big deflection which causes big camber at the middle of beam .This has influenced the car’s normal movement. Apparently, it’s a design bug. After study, we put forward some schemes of the modification. Then we use the FEA software to analyze the structure again, result proves that the modification schemes presented in this paper can effectively cut down the stress and deflection of the cantilever root. Prevent the incidence of structure’s rupture accident. This scheme of modification is successful.
On the bases of introducing the technology on fatigue FEA, in view of the present conditions in the centre of the project as to the unloader metal structure’s fatigue research, this paper makes use of the software MSC.Fatigue to proceed the fatigue analysis on this main beam structure under certain loads, by the analysis,we can get the cloudy pictures of the fatigue life distribution, and can clearly see every parts fatigue life. Therefore this analysis can supply theory basis for grab ship unloader’s design and improvement and fatigue research. Build a sub-model of the grab ship unloader’s leg where a crack at the weld appears, analyse the structure’s fatigue life and find the reasons for the occurrence of cracks and for the further analysis of crack growth .The calculation result is basically consistent with actual situation. This paper has important engineering practical value.
At the end of this paper, some conclusions on this subject’s practical and academic signficance are presented, this paper also submits the research directions in the future, point out that utilizing the fatigue analysis’s FEM and the fracture mechanics synthetically to the crane’s metal structure fatigue analysis is complete and integrated ,this should become one of the fatigue research orientation for the future cranes.
引文
[1] 王启义主编.中国机械设计大典第2卷.机械设计基础[M].南昌:江西科学技术出版社 2002
[2] Maddox S J . Proceedings of International Conference on Fatigue of Welded Structures. Cambridge : The Welding Institute , 1987.
[3] Gurney T R. Fatigue of welded structures. Cambridge :Cambridge University Press , 1979
[4] A.A.Griffith.“The Phenomena of Rupture and Flow in Solids”.Trans, R.Soc.(Lond),Vol.A221,1920,P163
[5] B.P.Haigh,“The Relative Safety of Mild and High-Tensile Alloy Steels under Alternating and Pulsating Stresses,”Proc.Inst.Automob.Eng.,Vol.24,1929/ 1930,P.320
[6] P.C.Paris and F.Erdogan . A Critical Analysis of Crack Propagation Law, Trans, ASME, J.Basic Eng., Vol.85, No.4, 1963, P528
[7] Janson J , Hult J. Fracture mechanics and damage mechanics , a combined approach[J]. deMech.Appl.1977
[8] 翟甲昌,何庆生.桥式起重机钢结构可靠性分析[J].起重运输机械,1992,(4):3-9
[9] 沈海军,郭万林等.基于结构疲劳寿命可视化技术的虚拟疲劳设计[J].中国机械工程,2003,14(11):930-931
[10] 须雷.起重机的现代设计方法[J].起重运输机械,1996,(8):3-7
[11] 李之中,卢薇.起重机钢结构疲劳试验及疲劳设计研究[J].山西科技,2001(4):42-43
[12] 商伟军.泛谈起重机金属结构疲劳问题[J].港口科技动态,1994,(3):23-27
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[21] 连晋华.冶金起重机疲劳寿命的可靠性评估[J].机械工程与自动化.2004,123(2),14-16
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[2] Maddox S J . Proceedings of International Conference on Fatigue of Welded Structures. Cambridge : The Welding Institute , 1987.
[3] Gurney T R. Fatigue of welded structures. Cambridge :Cambridge University Press , 1979
[4] A.A.Griffith.“The Phenomena of Rupture and Flow in Solids”.Trans, R.Soc.(Lond),Vol.A221,1920,P163
[5] B.P.Haigh,“The Relative Safety of Mild and High-Tensile Alloy Steels under Alternating and Pulsating Stresses,”Proc.Inst.Automob.Eng.,Vol.24,1929/ 1930,P.320
[6] P.C.Paris and F.Erdogan . A Critical Analysis of Crack Propagation Law, Trans, ASME, J.Basic Eng., Vol.85, No.4, 1963, P528
[7] Janson J , Hult J. Fracture mechanics and damage mechanics , a combined approach[J]. deMech.Appl.1977
[8] 翟甲昌,何庆生.桥式起重机钢结构可靠性分析[J].起重运输机械,1992,(4):3-9
[9] 沈海军,郭万林等.基于结构疲劳寿命可视化技术的虚拟疲劳设计[J].中国机械工程,2003,14(11):930-931
[10] 须雷.起重机的现代设计方法[J].起重运输机械,1996,(8):3-7
[11] 李之中,卢薇.起重机钢结构疲劳试验及疲劳设计研究[J].山西科技,2001(4):42-43
[12] 商伟军.泛谈起重机金属结构疲劳问题[J].港口科技动态,1994,(3):23-27
[13] Janosch J J, Debiez S; Influence of the shape of undercut on the fatigue strength of fillet welded assemblies-application of the local approach [M];Welding in the World; 1998
[14] Taylor D; Geometrical effects in fatigue: a unifying theoretical model [M];International Journal of Fatigue; 1999
[15] 龙靖宇.桥式类型起重机的随机疲劳强度及载荷谱编制.[硕士学位论文].武汉:武汉钢铁学院,1981
[16] 翟甲昌.王生等.桥式起重机焊接箱形梁的疲劳试验[J].起重运输机械,1994,(2):3-8
[17] 王生,翟甲昌.桥式类型起重机箱形梁变幅疲劳试验研究[D].太原重型机械学院学报,1996,17(2):139-144
[18] 李亿祥.起重机焊接箱形梁的疲劳试验[J].山西机械,2000,(2):55-58
[19] 平克楠.大型冶金铸造起重视金属结构程序疲劳试验研究[J].太重技术导报,1995,(2):4-7
[20] 周承恩,谢季佳,洪友士.超高周疲劳研究现状及展望[J].机械强度,2004,26(5),526-533
[21] 连晋华.冶金起重机疲劳寿命的可靠性评估[J].机械工程与自动化.2004,123(2),14-16
[22] 马爱军,周传月,王旭. Patran 和Nastran 有限元分析专业教程[M].北京:清华大学出版社,2005
[23] 陈火红,祁鹏. MSC.Patran/Marc 培训教程和实例[M].北京:科学出版社,2004
[24] Arul M Britto. PATRAN Beginner's Guide, 2005
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