Ball-end mill is widely used in workpiece processi ng with free-form surfaces. Such models that can predict processing character istics precisely are very necessary to the aim of cost reducing, quality improvi ng and ...Ball-end mill is widely used in workpiece processi ng with free-form surfaces. Such models that can predict processing character istics precisely are very necessary to the aim of cost reducing, quality improvi ng and productivity progressing, the cutting force prediction is the most import ant among these models. To explore the physical essence of metal cutting, model researchers commonly simplify the geometric conditions in cutting process, and a ssume that the geometric parameters that are needed to solve the physical models have already been predefined, so it results in the separation between model res earch and practical application. In this paper, for the representative cutting f orce models of ball end milling, a new extraction method of geometric parameters is suggested, which makes it possible for physical model to actually serve for the practical manufacturing, and take in the inspection of real production.展开更多
Molecular dynamics （MD） simulations of the consecutive compression-decompression cycles ot hexagonal zinc sulfide （wurtzite） nanoparticles predict an irreversible phase transformation to the cubic polymorph.The ph...Molecular dynamics （MD） simulations of the consecutive compression-decompression cycles ot hexagonal zinc sulfide （wurtzite） nanoparticles predict an irreversible phase transformation to the cubic polymorph.The phase transformation commences at the contact area between the particle and the inden- ter and proceeds with the number of compression cycles. Dislocations are visible for a particle size above 5nm. Results from wet grinding and dry powder compression experiments on a commercial wurtzite pigment agree qualitatively with MD simulation predictions. X-ray diffraction patterns reveal that the amount of cubic polymorph in the compressed samples increases with pressure applied to the powder. In comparison with powder compression, wet milling leads to a more pronounced phase transformation. This occurs because the particles are exposed to a large number of stress events by collision with the grinding media, which leads to the formation of defects and new surface crystallites by particle fracture. According to the MD simulations, phase transformation is expected to occur preferentially in surface crystallites because they experience the highest mechanical load. Because of the phase transformation, the wet ground and compressed samples exhibit a lower photo- luminescence intensity than the feed material. In comparison with powder compression, milling reduces the photoluminescence intensity more substantially. This occurs because a higher defect concentration is formed. The defects contribute to the phase transformation and photoluminescence quenching.展开更多
文摘Ball-end mill is widely used in workpiece processi ng with free-form surfaces. Such models that can predict processing character istics precisely are very necessary to the aim of cost reducing, quality improvi ng and productivity progressing, the cutting force prediction is the most import ant among these models. To explore the physical essence of metal cutting, model researchers commonly simplify the geometric conditions in cutting process, and a ssume that the geometric parameters that are needed to solve the physical models have already been predefined, so it results in the separation between model res earch and practical application. In this paper, for the representative cutting f orce models of ball end milling, a new extraction method of geometric parameters is suggested, which makes it possible for physical model to actually serve for the practical manufacturing, and take in the inspection of real production.
基金supported financially by Arbeitsgemeinschaft industrieller Forschungsvereinigungen(AiF)(Grant No.:IGF333ZN)
文摘Molecular dynamics （MD） simulations of the consecutive compression-decompression cycles ot hexagonal zinc sulfide （wurtzite） nanoparticles predict an irreversible phase transformation to the cubic polymorph.The phase transformation commences at the contact area between the particle and the inden- ter and proceeds with the number of compression cycles. Dislocations are visible for a particle size above 5nm. Results from wet grinding and dry powder compression experiments on a commercial wurtzite pigment agree qualitatively with MD simulation predictions. X-ray diffraction patterns reveal that the amount of cubic polymorph in the compressed samples increases with pressure applied to the powder. In comparison with powder compression, wet milling leads to a more pronounced phase transformation. This occurs because the particles are exposed to a large number of stress events by collision with the grinding media, which leads to the formation of defects and new surface crystallites by particle fracture. According to the MD simulations, phase transformation is expected to occur preferentially in surface crystallites because they experience the highest mechanical load. Because of the phase transformation, the wet ground and compressed samples exhibit a lower photo- luminescence intensity than the feed material. In comparison with powder compression, milling reduces the photoluminescence intensity more substantially. This occurs because a higher defect concentration is formed. The defects contribute to the phase transformation and photoluminescence quenching.
