Experimentální ověření vlivu tepelných a mechanických rázů na stav ostří při nepravidelném přerušovaném řezu

Abstract

The purpose of this PhD thesis is to investigate the effects of experimental influence verification of the thermal and mechanical beats and their subsequent impact on the edge status at regular or irregular interrupted cutting process. The sample was selected from four type of indexable inserts made of ceramic cutting materials supplied by two leading global manufacturers based on nitride or oxide ceramic compositions. The material distinct in their chemical composition was compared. We tested a popular medial carbon steel grade C45, which is in a 14b class at reference material, and grade 14MoV6-3, which is material with a higher toughness and suitability for higher working temperatures.

The theoretical part is an initial attempt to investigate the division of the most common cutting tool material used for modern machining technology for industry, describes the modern ceramic materials, which are classified as advanced ceramic, followed by a description of residual stress created by machining process, method of interrupted cut’s testing and the effect of mechanical and thermal stresses on cutting process.

The practical part focuses on description and experimental design, including subsequent evaluation of individual measurements. Firstly was measured mechanical beats by regular or irregular interrupted cut, which was caused by different number of clamped slats in the interrupted cut simulator and two values of feeds. The following chapter is describing the thermal shock measurement at irregular interrupted cut, a digital measuring module for tool wear insert, monitoring of chip’s character in machining and mechanism of chip formation. The residual stress measuring, for all values of regular or irregular interrupted cutting process and for all feeds, was also extended after gradually deepening knowledge about process.

Finally, the most commonly used roughness parameter, arithmetic average deviation Ra and maximum height of the profile Rz, was compared at the initial engagement of the cutting inserts. The major objective of this study is to verify a resistance of selected cutting tool materials to mechanical and thermal stresses which are created during interrupted cutting, and their impact on regular or irregular interrupted cuts. In order to get a better comparison, we used others testing method as measurement of residual stresses and analysis of compressive and tensile stresses at regular or irregular cutting process. The measurements are also trying to get more detailed information about process while residual stress in order to eliminate volume of internal forces which might lead to changes in the material, mainly changes in the mechanical properties, and get the optimized stresses over its volume.