This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution ...This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.展开更多
A blasting-like lubricating process(combination of shot blasting and lubricating processes)is proposed.In this process,the specimens to be treated,alloy shots,and solid lubricating powder are rotated together in a rol...A blasting-like lubricating process(combination of shot blasting and lubricating processes)is proposed.In this process,the specimens to be treated,alloy shots,and solid lubricating powder are rotated together in a roller.The surface pockets formed due to the impact by the shots can store lubricants,and the lubricant can also adhere to the specimen surface by hitting.The effects of process parameters,including rolling time,rotational speed,mass of alloy shots,and the diameter of shots,on the surface topography of the steel specimen are investigated using 13 experimental schemes.The distribution ratio and average depth of surface pockets on the defined areas of the specimen are quantitatively analyzed.Four selected schemes with the MoS_(2) solid lubricating powder are further carried out to lubricate the cylindrical billets,and the lubricating effect is evaluated using the steady combined forward and backward extrusion test.The indicated friction factor of the novel blasting-like process is smaller than that of the conventional phosphate-soap coating process.展开更多
An experimental setup for cold extrusion process with electric-hydraulic chattering was developed and its working principle was introduced. The finite element （FE） model for a kind of cup part （material： 20Cr） wa...An experimental setup for cold extrusion process with electric-hydraulic chattering was developed and its working principle was introduced. The finite element （FE） model for a kind of cup part （material： 20Cr） was built by using the software Deform-3D. FE simulation experiments with and without electric-hydraulic chattering were carried out to analyze the velocity fields and the metal grid flow lines. The extrusion ex- periments of the cup part were also performed under different conditions. The difference of metal flow lines with and without electric-hydraulic chattering was discussed via a scanning electron microscope （SEM） and the Keyence super-depth three-dimensional microscopic system. The results showed that with the electric-hydraulic chattering, the velocity of material flow increases, whereas deformation resistance decreases. Electric hydraulic chattering results in easy metal flow, small bending degree of metal flow lines, slender and dense metal grains, and thereby an improved quality of the deformed parts.展开更多
large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion proces...large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.展开更多
文摘This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.
基金the National Natural Science Foundation of China(No.51475294)。
文摘A blasting-like lubricating process(combination of shot blasting and lubricating processes)is proposed.In this process,the specimens to be treated,alloy shots,and solid lubricating powder are rotated together in a roller.The surface pockets formed due to the impact by the shots can store lubricants,and the lubricant can also adhere to the specimen surface by hitting.The effects of process parameters,including rolling time,rotational speed,mass of alloy shots,and the diameter of shots,on the surface topography of the steel specimen are investigated using 13 experimental schemes.The distribution ratio and average depth of surface pockets on the defined areas of the specimen are quantitatively analyzed.Four selected schemes with the MoS_(2) solid lubricating powder are further carried out to lubricate the cylindrical billets,and the lubricating effect is evaluated using the steady combined forward and backward extrusion test.The indicated friction factor of the novel blasting-like process is smaller than that of the conventional phosphate-soap coating process.
文摘An experimental setup for cold extrusion process with electric-hydraulic chattering was developed and its working principle was introduced. The finite element （FE） model for a kind of cup part （material： 20Cr） was built by using the software Deform-3D. FE simulation experiments with and without electric-hydraulic chattering were carried out to analyze the velocity fields and the metal grid flow lines. The extrusion ex- periments of the cup part were also performed under different conditions. The difference of metal flow lines with and without electric-hydraulic chattering was discussed via a scanning electron microscope （SEM） and the Keyence super-depth three-dimensional microscopic system. The results showed that with the electric-hydraulic chattering, the velocity of material flow increases, whereas deformation resistance decreases. Electric hydraulic chattering results in easy metal flow, small bending degree of metal flow lines, slender and dense metal grains, and thereby an improved quality of the deformed parts.
基金Supported by National Natural Science Foundation of China(Grant No.51372216)Jiangsu Science and Technology Plan Project of China(Grant No.BE2015113)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.BKJB460016)
文摘large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.
