In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested ...In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig.The joint was analyzed statically by t e finite element analysis(F3A),and metallographic analysis of fatigue fracture was done by the electron scanning microscope.Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated.Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue facture.The initial welding defects and constructional detail constitute the main factor of fatigue failure.The S-N curves for the joints were developed through a linear regession analysis of fatigue data.A formula for calculating constant amplitude fatigue,base on the concept of the hot spot stress amplitude,is proposed.展开更多
In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to ...In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.展开更多
This paper introduces the cold-rolled DP590 high strength automotive steel sheets produced by Sougang Steel,which involve two different composition systems,one with high Al content and the other with C-Si-Mn.These two...This paper introduces the cold-rolled DP590 high strength automotive steel sheets produced by Sougang Steel,which involve two different composition systems,one with high Al content and the other with C-Si-Mn.These two materials are pot-welded and the optimized welding current range and the best welding current are obtained.Both the two kinds of materials welding current's scope is 1 800 A,but the current of C-Si-Mn system DP590 is 1 400 A higher then the high Al content one' s;when these two kind of materials are welded with the optimal current,the nugget can be get by no defect.There have some difference in these two base materials.High Al DP590 has a bandy metallurgical structure compose with ferrite and martensite,the volume fraction of martensite is 8%,the grain size is 10.5.C-Si-Mn system DP590 compose with ferrite and martensite also while the volume fraction of martensite is 9%,the grain size is 9.5.Weld structure of high Al DP590 are bainite and lath martensite when C-Si-Mn system DP590's is lath martensite only.The variation of HV is same for these two materials nugget,the length of the are both 10 mm,there have no soft zone in the weld scope.The HV of the both materials are the same of 210 -220.The HV of high Al DP590 weld scope is 280,when C-Si-Mn system DP590 is much more then it with 425.After test these two welded sample get the same failure modes,the maximum shearing resistance and maximum positive tension of high Al DP590 are both less than the C-Si-Mn system DP590.展开更多
基金The National Natural Science Foundation of China(No.51578357)the Natural Science Foundation of Shanxi Province(No.2015011062)Talent Training Program in the Postgraduate Joint Training Base of Shanxi Province(No.2016JD11)
文摘In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig.The joint was analyzed statically by t e finite element analysis(F3A),and metallographic analysis of fatigue fracture was done by the electron scanning microscope.Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated.Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue facture.The initial welding defects and constructional detail constitute the main factor of fatigue failure.The S-N curves for the joints were developed through a linear regession analysis of fatigue data.A formula for calculating constant amplitude fatigue,base on the concept of the hot spot stress amplitude,is proposed.
文摘In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.
文摘This paper introduces the cold-rolled DP590 high strength automotive steel sheets produced by Sougang Steel,which involve two different composition systems,one with high Al content and the other with C-Si-Mn.These two materials are pot-welded and the optimized welding current range and the best welding current are obtained.Both the two kinds of materials welding current's scope is 1 800 A,but the current of C-Si-Mn system DP590 is 1 400 A higher then the high Al content one' s;when these two kind of materials are welded with the optimal current,the nugget can be get by no defect.There have some difference in these two base materials.High Al DP590 has a bandy metallurgical structure compose with ferrite and martensite,the volume fraction of martensite is 8%,the grain size is 10.5.C-Si-Mn system DP590 compose with ferrite and martensite also while the volume fraction of martensite is 9%,the grain size is 9.5.Weld structure of high Al DP590 are bainite and lath martensite when C-Si-Mn system DP590's is lath martensite only.The variation of HV is same for these two materials nugget,the length of the are both 10 mm,there have no soft zone in the weld scope.The HV of the both materials are the same of 210 -220.The HV of high Al DP590 weld scope is 280,when C-Si-Mn system DP590 is much more then it with 425.After test these two welded sample get the same failure modes,the maximum shearing resistance and maximum positive tension of high Al DP590 are both less than the C-Si-Mn system DP590.
