Vibrational excitation of a work piece for drilling force reduction in brittle materials

Article investigates the possibilities of reducing drilling forces in brittle material drilling, through high frequency excitation of a work piece. Two excitation conditions are analyzed - first, when the sample acts as a solid structure and second, when the sample acts as a flexible structure. In order to analyze the effect, work piece excitation has on drilling forces, drilling experiments were conducted, drilling forces were measured and compared between the case when the sample was drilled in a conventional way and when the work piece was excited. Drilling was conducted at different speeds - 145, 290 and 540 rpm. With the increase of speed, average difference between forces of conventional drilling case and drilling of an excited work piece has increased from 24 to 40%. In order to analyze the behaviour of a flexible structure when subjected to excitation, vibration mode simulations of the sample were developed. To test their validity, holographic vibration analysis was conducted - the simulation results do not completely correlate with the experimental ones. Such deviations may be caused by assymetrical clamping of the sample durring the holographic vibration mode analysis. With regards to this, either the experimental technique or the simulation model should be tweaked to enable its practical application in further research.Original Abstract: Straipsnyje tiriama grezimo jegu sumazinimo trapiose medziagose, bandini suzadinant aukstais dazniais, galimybe. Analizuojamos dvi suzadinimo salygos: 1. bandinys suzadinamas kaip standus kunas; 2. bandinys suzadinamas kaip tamprus kunas. Bandinio suzadinimo poveikiui grezimo jegoms tirti buvo atlikti grezimo bandymai. Buvo matuojamos ir lyginamos grezimo jegos suzadinant ir nesuzadinant bandinio. Grezimai buvo atliekami skirtingais greiciais - 145, 290 ir 540 aps./min. Didejant grezimo greiciui, vidutinis grezimo jegu skirtumas tarp suzadinto ir nesuzadinto bandinio grezimo pakilo nuo 24 ik 40%. Antros salygos analizei buvo atliktos bandinio vibraciju rezimu simuliacijos. Simuliaciju adekvatumas buvo patikrintas atliekant holografine vibraciju analize - simuliaciju rezultatai ne visiskai atitinka eksperimentinius. Tai gali salygoti nesimetriskas bandinio prispaudimas holografijos metu, atsizvelgiant i tai turetu buti pakoreguotas arba simuliaciju modelis arba eksperimentine technika, kad butu galimas praktinis modelio pritaikymas tolimesniuose tyrimuose.