The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, ...The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.展开更多
A medium manganese steel with high wear-resistance,strength and toughness has been produced with addition of a complex modifier (or refining agent) containing Nb,N,RE and Si-Ca. The results showed that the wear resist...A medium manganese steel with high wear-resistance,strength and toughness has been produced with addition of a complex modifier (or refining agent) containing Nb,N,RE and Si-Ca. The results showed that the wear resistance,strength and toughness of the modified medium manganese steel are respectively 1.92 times,1.45 times and 3.63 times as high as that of the referenced unmodified medium manganese steel. The plastic deformation characteristic involved in the wear mechanism of the modified medium manganese steel was investigated by means of plastic-elasticity calculation and TEM electro-microscopy. The relationship between wear resistance and yield strength of the steel was established. Since the wear volume W is proportional to the square of the loading and to the numbers of the abrasives,and inversely proportional to the square of the yield strength of the materials,the wear resistance can be substantially improved by the enhancement of yield strength of the materials. The calculation results generally agreed with the experimental results.展开更多
The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline ...The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.展开更多
目的探讨黄芪桂枝五物汤加味联合中频脉冲电刺激治疗糖尿病合并脑卒中偏瘫的临床疗效。方法选取2019年4月—2022年3月河北北方学院附属第一医院康复科及内分泌科老年糖尿病合并脑卒中偏瘫患者120例,依据随机表分为对照组60例和治疗组60...目的探讨黄芪桂枝五物汤加味联合中频脉冲电刺激治疗糖尿病合并脑卒中偏瘫的临床疗效。方法选取2019年4月—2022年3月河北北方学院附属第一医院康复科及内分泌科老年糖尿病合并脑卒中偏瘫患者120例,依据随机表分为对照组60例和治疗组60例,对照组给予中频脉冲电刺激加常规康复运动疗法,治疗组在对照组基础上给予黄芪桂枝五物汤加味治疗,比较两组患者治疗前后血糖水平、运动神经电生理指标[运动诱发电位潜伏期(motor evoked potentials,MEP)、中枢运动传导时间(central motor conduction time,CMCT)]、运动功能[Fugl-Meyer运动功能评分(Fugl-Meyer Assessment,FMA)]、生活质量及神经功能相关评分[脑卒中专用生活质量量表(Stroke Specific Quality of Life Scale,SS-QOL)、改良Barthel指数(modified Barthel Index,MBI)、美国国立卫生研究所卒中评分量表(National Institutes of Health Stroke Scale,NIHSS)、临床神经功能缺损评分(China Stroke Scale,CSS)量表、抑郁自评量表(Self-Rating Depression Scale,SDS)]。结果(1)血糖水平:治疗12周后,治疗组和对照组空腹血糖和餐后血糖均有所下降,降血糖效果明显;与对照组比较,治疗组血糖水平下降幅度更大(P<0.05)。(2)运动神经电生理指标:两组各项指标(MEP、CMCT)较治疗前均明显降低(P<0.05),且治疗组与对照组比较,治疗组降低幅度更大(P<0.05)。(3)上肢、下肢FMA评分:治疗12周后,对照组和治疗组评分均有明显升高,且治疗组分值提升显著高于对照组(P<0.05)。(4)生活质量评分:治疗后,对照组和治疗组各项评分(SS-QOL、MBI)均明显高于治疗前,且治疗组得分上升幅度显著优于对照组(P<0.05)。(5)神经功能评分:治疗后,两组各项评分(NIHSS、CSS、SDS)均有明显降低(P<0.05),且治疗组比对照组各项评分降低幅度更为显著(P<0.05)。结论黄芪桂枝五物汤加味联合中频脉冲电刺激可有效治疗糖尿病合并脑卒中偏瘫患者的运动功能,有利于改善生活质量,值得临床推广。展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50521503)National Basic Research Program of China (973 Program, Grant No. 2007CB714704)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2006AA04Z406)
文摘The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.
基金This work was supported by the Innovation Fund for Outstanding Scholar of Henan province, No.0621000600.
文摘A medium manganese steel with high wear-resistance,strength and toughness has been produced with addition of a complex modifier (or refining agent) containing Nb,N,RE and Si-Ca. The results showed that the wear resistance,strength and toughness of the modified medium manganese steel are respectively 1.92 times,1.45 times and 3.63 times as high as that of the referenced unmodified medium manganese steel. The plastic deformation characteristic involved in the wear mechanism of the modified medium manganese steel was investigated by means of plastic-elasticity calculation and TEM electro-microscopy. The relationship between wear resistance and yield strength of the steel was established. Since the wear volume W is proportional to the square of the loading and to the numbers of the abrasives,and inversely proportional to the square of the yield strength of the materials,the wear resistance can be substantially improved by the enhancement of yield strength of the materials. The calculation results generally agreed with the experimental results.
文摘The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.
文摘目的探讨黄芪桂枝五物汤加味联合中频脉冲电刺激治疗糖尿病合并脑卒中偏瘫的临床疗效。方法选取2019年4月—2022年3月河北北方学院附属第一医院康复科及内分泌科老年糖尿病合并脑卒中偏瘫患者120例,依据随机表分为对照组60例和治疗组60例,对照组给予中频脉冲电刺激加常规康复运动疗法,治疗组在对照组基础上给予黄芪桂枝五物汤加味治疗,比较两组患者治疗前后血糖水平、运动神经电生理指标[运动诱发电位潜伏期(motor evoked potentials,MEP)、中枢运动传导时间(central motor conduction time,CMCT)]、运动功能[Fugl-Meyer运动功能评分(Fugl-Meyer Assessment,FMA)]、生活质量及神经功能相关评分[脑卒中专用生活质量量表(Stroke Specific Quality of Life Scale,SS-QOL)、改良Barthel指数(modified Barthel Index,MBI)、美国国立卫生研究所卒中评分量表(National Institutes of Health Stroke Scale,NIHSS)、临床神经功能缺损评分(China Stroke Scale,CSS)量表、抑郁自评量表(Self-Rating Depression Scale,SDS)]。结果(1)血糖水平:治疗12周后,治疗组和对照组空腹血糖和餐后血糖均有所下降,降血糖效果明显;与对照组比较,治疗组血糖水平下降幅度更大(P<0.05)。(2)运动神经电生理指标:两组各项指标(MEP、CMCT)较治疗前均明显降低(P<0.05),且治疗组与对照组比较,治疗组降低幅度更大(P<0.05)。(3)上肢、下肢FMA评分:治疗12周后,对照组和治疗组评分均有明显升高,且治疗组分值提升显著高于对照组(P<0.05)。(4)生活质量评分:治疗后,对照组和治疗组各项评分(SS-QOL、MBI)均明显高于治疗前,且治疗组得分上升幅度显著优于对照组(P<0.05)。(5)神经功能评分:治疗后,两组各项评分(NIHSS、CSS、SDS)均有明显降低(P<0.05),且治疗组比对照组各项评分降低幅度更为显著(P<0.05)。结论黄芪桂枝五物汤加味联合中频脉冲电刺激可有效治疗糖尿病合并脑卒中偏瘫患者的运动功能,有利于改善生活质量,值得临床推广。
