| Tool life reliability is one of the most important evaluation indicators of cutting tool performance. Reliability of cutting tool life of hardened steel45and hardened steel40Cr is studied in this paper based on the former research on tool life reliability. Tool life equation is extended and the relationship between tool life and tool geometry parameters is established. Cutting test is carried out and the results are analyzed. Both tool wear model and tool life reliability prediction model based on Gamma process are established. Tool life reliability is predicted under the condition of small sample without failure data, and sensitivity of tool life reliability prediction model is analyzed. Tool life reliability evaluation model is established, and is used to estimate tool life reliability under the condition of large sample with complete failure data.Tool life influence factors are classified, and the approach to analyze the factors is proposed. The Taylor tool life basic equation is extended and generalized equation of tool life extension equation is proposed. The tool life extension equation is applied in a narrow range to facilitate the experimental study. The relationship between tool wear and tool geometry parameters is established. This provides the theoretical basis for the analysis of influence factors of tool life and the evaluation of reliability in this paper.Statistical analysis and non-parametric test of tool geometry parameters of are carried out, and the distribution of tool geometry parameters is identified. The structure of the work piece is designed for ease of the test carrying out and the cutting time controlling, which can improve the efficiency of the reliability test. The milling experiment is carried out and the tool wear form is observed. Tool wear appears two forms:uniform wear and non-uniform wear for both kind of work piece materials, and the generation mechanism is explained.Tool wear process is modeled by a Gamma process and the parameters of the Gamma process is estimated through square estimation. Under the condition of small sample without failure data, the tool life reliability prediction models of cutting tools under two cases are established. For the first case, the cutting tool manufacturing error is considered and for the second case the cutting tool manufacturing error is not considered. Based on Gamma process of tool uniform wear, the milling tool life reliability is predicted. The sensitivity analysis of tool life reliability is carried out, and the sensitivity of each parameter of the reliability model is obtained. The influence to tool life reliability of manufacturing error of cutting tools and the maximum permissible machining error of the machine tool are mainly studied.The relationship between tool life and tool geometry parameters is solved by multiple linear regression (MLR). The influence to tool wear/life of cutting edge radius, the width of chip breaker groove margin and the height of cutting edge is established. The dispersibility of tool wear in various stages of cutting is studied. Tool life calculated by uniform wear width obeys normal distribution and tool life calculated by non-uniform wear width obeys logarithmic normal distribution. Reliability evaluation models for both wear forms are established based on tool life extension equation, and the influence factors of reliability are analyzed.This paper can provide guidance for the prediction and evaluation of tool life reliability. |
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