In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead ...In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead force is one of the most important pa- rameters in sheet metal forming process control. This paper derives the model of loop drawbead restraining force (DBRF) using plastic forming theory, and gives the min imum blankholding force. Experiments are carried out to verify the proposed DBRF model. The good agreement between the calculated values and experiments data justi- fies the proposed loop drawbead restraining force model.展开更多
Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and...Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.展开更多
At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank ho...At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.展开更多
The force feed lubrication method is used for drawing aluminum clad steel wire. It is studied how deformation of wire and aspect of the lubricant film are influenced by the die angle, the reduction, the drawing spee...The force feed lubrication method is used for drawing aluminum clad steel wire. It is studied how deformation of wire and aspect of the lubricant film are influenced by the die angle, the reduction, the drawing speed and the gap between pressure die and wire. It has been concluded that when the factors above mentioned promote to thicken lubricant film, the drawing force is reduced and this favors the homogenous deformation of aluminum coating and steel core.展开更多
On the basis of the criterion of no-wrinkle, the principle and method of prediction and determination of both friction coefficient and forming force on sheet metal deep-drawing are put forward, and proved it's exp...On the basis of the criterion of no-wrinkle, the principle and method of prediction and determination of both friction coefficient and forming force on sheet metal deep-drawing are put forward, and proved it's expedience and practicability. They are suitable for assessment of lubricant properties. Friction coefficient and forming force are a function of material parameter, design parameter and process parameter, especially relative prevent wrinkle blank-holder force. Product of both friction coefficient and prevent wrinkle blank-holder force is only function of process parameter after determining material parameter and design parameter.展开更多
Forming technology of Mg alloy (AZ31B) sheets can be investigated by thermal deep drawing experiments. In the experiments, the blank holder and die contacting with the blank were heated to the same temperature as the ...Forming technology of Mg alloy (AZ31B) sheets can be investigated by thermal deep drawing experiments. In the experiments, the blank holder and die contacting with the blank were heated to the same temperature as the blank by using the heating facility. The circular blank heated in an oven is formed at a temperature range of 100~400 ℃ to obtain the optimum forming temperature range and the effects of major technical parameters on the workpiece quality. It is found that the blank is brittle at temperatures lower than 200℃. Temperatures higher than 400℃ are not suitable for forming of the sheets because of severe oxidation and wrinkling. AZ31B shows an excellent formability at temperatures from 300 to 350℃ and can be formed into a workpiece with good quality. When the blank holder force is 9 kN, extruded sheets with a thickness of 1 mm can be formed into cups without wrinkling. Workpieces show strong anisotropic deformation behavior on the flanges.展开更多
The previous experiments of wire drawing with ultrasonic vibration were mostly carried out on self-made machine or drawing test machine and the drawing speed didn＇t conform to practical production. In order to promot...The previous experiments of wire drawing with ultrasonic vibration were mostly carried out on self-made machine or drawing test machine and the drawing speed didn＇t conform to practical production. In order to promote the practical application of the technology, the ultrasonic vibration system was designed and manufactured by using the classical dynamics method. The dynamic characteristic of the ultrasonic vibration system was analyzed. The performance parameters of the system were measured on the resistance analyzer. The oxygen-free brass wire drawing with ultrasonic vibration at the approximate speed of practice was carried out on the LH-200/17 drawing machine. By comparing the wire drawing through ultrasonic vibration and the conventional wire drawing, the experimental results show that the drawing process with ultrasound was steady at the high drawing speed of 1 126 mm/s, while the broken wire often occurs at the speed of 980 mm/s during the conventional wire drawing; the ultrasonic vibration reduced the drawing force by 7 %; and the ultrasound also reduced the uneven deformation of the wire and greatly improved the surface quality of the wire. The research results provide theoretical and experimental support for the practice and application of the wire drawing by ultrasonic vibration.展开更多
Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force...Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force is put forward by experimental method in cup-shaped drawing process. The experimental results were compared with numerical results and proved agreement. It shows the method is effective.展开更多
Regarding the sizing surface zone as a quasi-plasticity one and using yielding criterion,a new drawing force calculating formula in which the sizing surface friction was taken into account is deducted.The calculated a...Regarding the sizing surface zone as a quasi-plasticity one and using yielding criterion,a new drawing force calculating formula in which the sizing surface friction was taken into account is deducted.The calculated and experimental results show that for rod drawing and tube sinking,it is permissible to neglect the effect of the friction at the sizing surface,but for tube drawing with a stationary mandrel,especially for thin-wall tube drawing this friction should not be neglected.展开更多
Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces w...Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.展开更多
文摘In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead force is one of the most important pa- rameters in sheet metal forming process control. This paper derives the model of loop drawbead restraining force (DBRF) using plastic forming theory, and gives the min imum blankholding force. Experiments are carried out to verify the proposed DBRF model. The good agreement between the calculated values and experiments data justi- fies the proposed loop drawbead restraining force model.
文摘Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.
文摘At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.
文摘The force feed lubrication method is used for drawing aluminum clad steel wire. It is studied how deformation of wire and aspect of the lubricant film are influenced by the die angle, the reduction, the drawing speed and the gap between pressure die and wire. It has been concluded that when the factors above mentioned promote to thicken lubricant film, the drawing force is reduced and this favors the homogenous deformation of aluminum coating and steel core.
文摘On the basis of the criterion of no-wrinkle, the principle and method of prediction and determination of both friction coefficient and forming force on sheet metal deep-drawing are put forward, and proved it's expedience and practicability. They are suitable for assessment of lubricant properties. Friction coefficient and forming force are a function of material parameter, design parameter and process parameter, especially relative prevent wrinkle blank-holder force. Product of both friction coefficient and prevent wrinkle blank-holder force is only function of process parameter after determining material parameter and design parameter.
基金The authors express their thanks to the supports of One-hundred-person Project of CAS and project 863 the High Technology Research Foundation of China(grant No.2003AA331120)
文摘Forming technology of Mg alloy (AZ31B) sheets can be investigated by thermal deep drawing experiments. In the experiments, the blank holder and die contacting with the blank were heated to the same temperature as the blank by using the heating facility. The circular blank heated in an oven is formed at a temperature range of 100~400 ℃ to obtain the optimum forming temperature range and the effects of major technical parameters on the workpiece quality. It is found that the blank is brittle at temperatures lower than 200℃. Temperatures higher than 400℃ are not suitable for forming of the sheets because of severe oxidation and wrinkling. AZ31B shows an excellent formability at temperatures from 300 to 350℃ and can be formed into a workpiece with good quality. When the blank holder force is 9 kN, extruded sheets with a thickness of 1 mm can be formed into cups without wrinkling. Workpieces show strong anisotropic deformation behavior on the flanges.
基金supported by Heilongjiang Provincial Natural Science Foundation of China (Grant No. E200614)
文摘The previous experiments of wire drawing with ultrasonic vibration were mostly carried out on self-made machine or drawing test machine and the drawing speed didn＇t conform to practical production. In order to promote the practical application of the technology, the ultrasonic vibration system was designed and manufactured by using the classical dynamics method. The dynamic characteristic of the ultrasonic vibration system was analyzed. The performance parameters of the system were measured on the resistance analyzer. The oxygen-free brass wire drawing with ultrasonic vibration at the approximate speed of practice was carried out on the LH-200/17 drawing machine. By comparing the wire drawing through ultrasonic vibration and the conventional wire drawing, the experimental results show that the drawing process with ultrasound was steady at the high drawing speed of 1 126 mm/s, while the broken wire often occurs at the speed of 980 mm/s during the conventional wire drawing; the ultrasonic vibration reduced the drawing force by 7 %; and the ultrasound also reduced the uneven deformation of the wire and greatly improved the surface quality of the wire. The research results provide theoretical and experimental support for the practice and application of the wire drawing by ultrasonic vibration.
基金Supported by Science and Technology Development Foundation of Shanghai (015211009).
文摘Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force is put forward by experimental method in cup-shaped drawing process. The experimental results were compared with numerical results and proved agreement. It shows the method is effective.
文摘Regarding the sizing surface zone as a quasi-plasticity one and using yielding criterion,a new drawing force calculating formula in which the sizing surface friction was taken into account is deducted.The calculated and experimental results show that for rod drawing and tube sinking,it is permissible to neglect the effect of the friction at the sizing surface,but for tube drawing with a stationary mandrel,especially for thin-wall tube drawing this friction should not be neglected.
文摘Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.
