Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials b...Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteris- tics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.展开更多
It is extremely important to select appropriate feedrates for the stable machining of parts with ruled surface in modern aviation industrial applications.However,the current studies take too much time to achieve this ...It is extremely important to select appropriate feedrates for the stable machining of parts with ruled surface in modern aviation industrial applications.However,the current studies take too much time to achieve this goal.Therefore,this paper presents an efficient feedrate optimization method for constant peak cutting force in five-axis flank milling process.The solution method of the instantaneous undeformed chip thickness(IUCT)is proposed using least squares theory with the cutter entry angle and feedrate as variables.Based on this method,an explicit analytical expression of the peak cutting force for each cutting point is established.Furthermore,a feedrate scheduling method is developed to quickly solve the appropriate feedrate under constant peak cutting force.To verify the proposed IUCT model,the fitting IUCT is compared with the accuracy data at different feedrates.Additionally,some experiments of five-axis flank milling are conducted to demonstrate the effectiveness of the peak force model and the feedrate scheduling method.And the surface roughness before and after feedrate scheduling is detected.The results show that the proposed feedrate scheduling method can quickly adjust the feedrate and ensure constant peak force during machining.At the same time,the surface quality is kept at a high level.展开更多
Aiming at the problems that the simulation accuracy which is reduced due to the simplification of the model,a three-dimensional simulation method based on solid modeling is being proposed.By analyzing the motion relat...Aiming at the problems that the simulation accuracy which is reduced due to the simplification of the model,a three-dimensional simulation method based on solid modeling is being proposed.By analyzing the motion relationship and positional relationship between the caries knife and the workpiece,the coordinate system of the caries machining was established.With the MATLAB software,the cutting edge model and the blade sweeping surface model of the boring cutter are sequentially established.Boolean operation is performed on the blade swept surface formed by the tooth cutter teeth with time t and the workpiece tooth geometry as well as the undeformed three-dimensional chip geometry model and the instantaneous cogging geometry model are obtained at different times.Through the compare between gear end face simulation tooth profile and the theoretical inner arc tooth profile,we verified the accuracy and rationality of the proposed method.展开更多
Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and ...Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of workpiece.However,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational efficiency.In this study,a symbolic difference method is proposed to calculate the UCT.The UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding process.Meanwhile,the UCT distribution characteristics under different machining parameters are analyzed.Then,a surface roughness prediction model is established based on the UCT distribution.Finally,the correctness of the model is verified by experiments.This study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.展开更多
Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottlene...Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottleneck of mechanical stress-induced crack damage. In response to this challenge, the ultrasound-assisted biological bone micro-grinding novel process with a spherical grinding head has been proposed by researchers. Force modeling is a prerequisite for process parameter determination in orthopedic surgery, and the difculty in establishing and accurately predicting bone micro-grinding force prediction models is due to the geometric distribution of abrasive grains and the dynamic changes in geometry and kinematics during the cutting process. In addressing these critical needs and technical problems, the shape and protrusion heights of the wear particle of the spherical grinding head were frst studied, and the gradual rule of the contact arc length under the action of high-speed rotating ultrasonic vibration was proposed. Second, the mathematical model of the maximum thickness of undeformed chips under ultrasonic vibration of the spherical grinding head was established. Results showed that ultrasonic vibration can reduce the maximum thickness of undeformed chips and increase the range of ductile and bone meal removals, revealing the mechanism of reducing grinding force. Further, the dynamic grinding behavior of diferent layers of abrasive particles under diferent instantaneous interaction states was studied. Finally, a prediction model of micro-grinding force was established in accordance with the relationship between grinding force and cutting depth, revealing the mechanism of micro-grinding force transfer under ultrasonic vibration. The theoretical model’s average deviations are 10.37% in x-axis direction, 6.85% in y-axis direction, and 7.81% in z-axis direction compared with the experimental results. This study provides theoretical guidance and technical support for clinical bone micro-grinding.展开更多
The ability to predict a grinding force is important to control,monitor,and optimize the grinding process.Few theoretical models were developed to predict grinding forces when a structured wheel was used in a grinding...The ability to predict a grinding force is important to control,monitor,and optimize the grinding process.Few theoretical models were developed to predict grinding forces when a structured wheel was used in a grinding process.This paper aimed to establish a single-grit cutting force model to predict the ploughing,friction and cutting forces in a grinding process.It took into the consideration of actual topography of the grinding wheel,and a theoretical grinding force model for grinding hardened AISI 52100 by the wheel with orderly-micro-grooves was proposed.The model was innovative in the sense that it represented the random thickness of undeformed chips by a probabilistic expression,and it reflected the microstructure characteristics of the structured wheel explicitly.Note that the microstructure depended on the randomness of the protruding heights and distribution density of the grits over the wheel.The proposed force prediction model was validated by surface grinding experiments,and the results showed(1)a good agreement of the predicted and measured forces and(2)a good agreement of the changes of the grinding forces along with the changes of grinding parameters in the prediction model and experiments.This research proposed a theoretical grinding force model of an electroplated grinding wheel with orderly-micro-grooves which is accurate,reliable and effective in predicting grinding forces.展开更多
针对定向凝固镍基高温合金DZ125叶片榫齿，采用电镀成型CBN砂轮对其进行了高效深切磨削（High efficieney deep grinding，HEDG）试验，对磨削比能及工件表面完整性进行了分析。结果显示，在保持速比（Us／‰）不变时，提高磨削速度饥...针对定向凝固镍基高温合金DZ125叶片榫齿，采用电镀成型CBN砂轮对其进行了高效深切磨削（High efficieney deep grinding，HEDG）试验，对磨削比能及工件表面完整性进行了分析。结果显示，在保持速比（Us／‰）不变时，提高磨削速度饥可有效降低磨削比能，提高平均材料去除率。磨削比能表现出“尺寸效应”，其值最终稳定在40～60J／mm^3之间；在相同的平均材料去除率下，磨削比能随着磨削深度的增大而上升；在相同的单颗磨粒切厚下，磨削深度的差异对磨削比能的影响较小。对试验中最大平均材料去除率下获得的工件表面质量进行分析发现，已加工工件表面不同区域磨削纹理均很清晰，无皱叠及犁沟两侧翻起等现象；表层金相显微组织基本无变化，未发现相变、撕裂及晶粒扭曲现象；工件表层加工硬化程度为7．7％～19％，深度为40μm。结果显示了HEDG在高效磨削DZ125叶片榫齿中推广应用的潜力，并为其实际生产中磨削参数的选择提供了参考。展开更多
文摘Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteris- tics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.
基金co-supported by the Major National S&T Program(2017ZX04002001)the Major National S&T Program(2016ZX04004004)。
文摘It is extremely important to select appropriate feedrates for the stable machining of parts with ruled surface in modern aviation industrial applications.However,the current studies take too much time to achieve this goal.Therefore,this paper presents an efficient feedrate optimization method for constant peak cutting force in five-axis flank milling process.The solution method of the instantaneous undeformed chip thickness(IUCT)is proposed using least squares theory with the cutter entry angle and feedrate as variables.Based on this method,an explicit analytical expression of the peak cutting force for each cutting point is established.Furthermore,a feedrate scheduling method is developed to quickly solve the appropriate feedrate under constant peak cutting force.To verify the proposed IUCT model,the fitting IUCT is compared with the accuracy data at different feedrates.Additionally,some experiments of five-axis flank milling are conducted to demonstrate the effectiveness of the peak force model and the feedrate scheduling method.And the surface roughness before and after feedrate scheduling is detected.The results show that the proposed feedrate scheduling method can quickly adjust the feedrate and ensure constant peak force during machining.At the same time,the surface quality is kept at a high level.
基金The National Natural Science Foundation of China (No.52165060,12272189)Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region: (NJYT23022)+2 种基金Science and Technology Projects of Inner Mongolia Autonomous Region: (2021GG0432)Central Guiding Local Science and Technology Development Plan (2022ZY0013)Basic research business fee project for universities directly under Inner Mongolia Autonomous Region (GXKY22046).
文摘Aiming at the problems that the simulation accuracy which is reduced due to the simplification of the model,a three-dimensional simulation method based on solid modeling is being proposed.By analyzing the motion relationship and positional relationship between the caries knife and the workpiece,the coordinate system of the caries machining was established.With the MATLAB software,the cutting edge model and the blade sweeping surface model of the boring cutter are sequentially established.Boolean operation is performed on the blade swept surface formed by the tooth cutter teeth with time t and the workpiece tooth geometry as well as the undeformed three-dimensional chip geometry model and the instantaneous cogging geometry model are obtained at different times.Through the compare between gear end face simulation tooth profile and the theoretical inner arc tooth profile,we verified the accuracy and rationality of the proposed method.
基金supported by the National Key Research and Development Program of China(No.2018YFB2000402)the Open Fund Project of Xinchang Research Institute of Zhejiang University of Technology,and the Fundamental Research Funds for the Universities of Henan Province,China(No.NSFRF200102).
文摘Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of workpiece.However,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational efficiency.In this study,a symbolic difference method is proposed to calculate the UCT.The UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding process.Meanwhile,the UCT distribution characteristics under different machining parameters are analyzed.Then,a surface roughness prediction model is established based on the UCT distribution.Finally,the correctness of the model is verified by experiments.This study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.
基金Supported by National Natural Science Foundation of China(Grant Nos.51975305,52105457,and 52205481)the Special Fund of Taishan Scholars Project(Grant No.tsqn202211179)+1 种基金Shandong Provincial Youth Talent Promotion Project(Grant No.SDAST2021qt12)Shandong Provincial Natural Science Foundation(Grant Nos.ZR2023QE057,ZR2022QE028,ZR2021QE116,and ZR2020KE027).
文摘Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottleneck of mechanical stress-induced crack damage. In response to this challenge, the ultrasound-assisted biological bone micro-grinding novel process with a spherical grinding head has been proposed by researchers. Force modeling is a prerequisite for process parameter determination in orthopedic surgery, and the difculty in establishing and accurately predicting bone micro-grinding force prediction models is due to the geometric distribution of abrasive grains and the dynamic changes in geometry and kinematics during the cutting process. In addressing these critical needs and technical problems, the shape and protrusion heights of the wear particle of the spherical grinding head were frst studied, and the gradual rule of the contact arc length under the action of high-speed rotating ultrasonic vibration was proposed. Second, the mathematical model of the maximum thickness of undeformed chips under ultrasonic vibration of the spherical grinding head was established. Results showed that ultrasonic vibration can reduce the maximum thickness of undeformed chips and increase the range of ductile and bone meal removals, revealing the mechanism of reducing grinding force. Further, the dynamic grinding behavior of diferent layers of abrasive particles under diferent instantaneous interaction states was studied. Finally, a prediction model of micro-grinding force was established in accordance with the relationship between grinding force and cutting depth, revealing the mechanism of micro-grinding force transfer under ultrasonic vibration. The theoretical model’s average deviations are 10.37% in x-axis direction, 6.85% in y-axis direction, and 7.81% in z-axis direction compared with the experimental results. This study provides theoretical guidance and technical support for clinical bone micro-grinding.
基金Supported by National Natural Science Foundation of China(Grant Nos.52275405,52275311,51875050)Hunan Provincial Key Research and Development Program(Grant No.2021GK2021).
文摘The ability to predict a grinding force is important to control,monitor,and optimize the grinding process.Few theoretical models were developed to predict grinding forces when a structured wheel was used in a grinding process.This paper aimed to establish a single-grit cutting force model to predict the ploughing,friction and cutting forces in a grinding process.It took into the consideration of actual topography of the grinding wheel,and a theoretical grinding force model for grinding hardened AISI 52100 by the wheel with orderly-micro-grooves was proposed.The model was innovative in the sense that it represented the random thickness of undeformed chips by a probabilistic expression,and it reflected the microstructure characteristics of the structured wheel explicitly.Note that the microstructure depended on the randomness of the protruding heights and distribution density of the grits over the wheel.The proposed force prediction model was validated by surface grinding experiments,and the results showed(1)a good agreement of the predicted and measured forces and(2)a good agreement of the changes of the grinding forces along with the changes of grinding parameters in the prediction model and experiments.This research proposed a theoretical grinding force model of an electroplated grinding wheel with orderly-micro-grooves which is accurate,reliable and effective in predicting grinding forces.
文摘针对定向凝固镍基高温合金DZ125叶片榫齿，采用电镀成型CBN砂轮对其进行了高效深切磨削（High efficieney deep grinding，HEDG）试验，对磨削比能及工件表面完整性进行了分析。结果显示，在保持速比（Us／‰）不变时，提高磨削速度饥可有效降低磨削比能，提高平均材料去除率。磨削比能表现出“尺寸效应”，其值最终稳定在40～60J／mm^3之间；在相同的平均材料去除率下，磨削比能随着磨削深度的增大而上升；在相同的单颗磨粒切厚下，磨削深度的差异对磨削比能的影响较小。对试验中最大平均材料去除率下获得的工件表面质量进行分析发现，已加工工件表面不同区域磨削纹理均很清晰，无皱叠及犁沟两侧翻起等现象；表层金相显微组织基本无变化，未发现相变、撕裂及晶粒扭曲现象；工件表层加工硬化程度为7．7％～19％，深度为40μm。结果显示了HEDG在高效磨削DZ125叶片榫齿中推广应用的潜力，并为其实际生产中磨削参数的选择提供了参考。
