Abstract
Article investigates the possibilities of reducing drilling forces in brittle material drilling, through high frequency excitation of a work piece. Two excitation con-ditions 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 ana-lysis. With regards to this, either the experimental technique or the simulation model should be tweaked to enable its practical application in further research. DOI: http://dx.doi.org/10.5755/j01.mech.20.6.8785
Highlights
Machining of hard and brittle materials, especially glass is still a major problem because of its lower fracture toughness and higher hardness
It is hypothesized that the main reason for the improvement of critical depth of cut by torsional vibration is the ability of the 3-dimensional compressive stress condition at the vicinity of tool tip to suppress the crack propagation
The aim of this study is to investigate the influence of high frequency work piece excitation, on the drilling forces in drilling of brittle materials, in order to provide guidelines for further investigations of the process
Summary
Machining of hard and brittle materials, especially glass is still a major problem because of its lower fracture toughness and higher hardness. An approach for surface quality improvement is proposed in the paper [2] by taking into account that the quality of machined surface is related to the intensity of the tool tip (cutting edge) vibrations This is based on the excitation of a particular higher vibration mode of a turning tool, which leads to the reduction of deleterious vibrations in the machine–tool–work piece system through intensification of internal energy dissipation in the tool material. The result should demonstrate whether the ultrasonic work piece holder could enhance the quality and efficiency of brittle material drilling. It should provide guidelines for further drilling tests of solid and flexible structures
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