Modeling of residual stresses by correlating surface topography in machining of AISI 52100 steel

The residual stresses could affect the ability of components to bear loading conditions and also the performance. The researchers considered workpiece surface as a plane and ignored the effect of surface topography induced by the intermittent cutting process when modeling residual stresses. The aim of this research develops an analytical model to predict workpiece residual stresses during intermittent machining by correlating the effect of surface topography. The relative motions of tool and workpiece are analyzed for modeling thermal-mechanical and surface topography. The influence of dynamic cutting force and thermal on different positions of surface topography is also considered in analytical model. Then the residual stresses model with the surface topography effect can be developed in intermittent cutting. The analytical models of dynamic cutting force, surface topography and residual stresses are verified by the experiments. The variation trend of evaluated values of the residual stress of workpiece is basically consistent with that of measured values. The compressive residual stress of workpiece surface in highest point of the surface topography are higher than that in the lowest point.

Identification method for the dynamic cutting force variation of a high energy efficiency milling cutter

The dynamic cutting force of a high energy efficiency milling cutter is an important indicator for evaluating the stability of the cutting energy efficiency. The existing cutting force analysis focuses on the main characteristics and influencing factors of the cutting force variation in the cutting process, ignoring the influence of the variation of the cutting layer parameters with the cutter tooth error in different cutting stages, and the dynamic cutting force variation is uncertain. In this research, the analytical model of the instantaneous cutting volume of a milling cutter was developed in order to obtain the time-frequency characteristics of the instantaneous cutting volume with the cutter tooth error. According to the sudden changes of the cutting force and the milling vibration, the variations were studied in different cutting stages. The dynamic cutting behavior sequences such as the instantaneous cutting volume, milling vibration, and dynamic cutting force were constructed to characterize the mapping relationship between the dynamic cutting behavior of a milling cutter. Based on these approaches, the identification method for the dynamic cutting force variation of a high energy efficiency milling cutter was proposed. The effectiveness of the method was verified by the results of the milling experiment and the dynamic cutting behavior response analysis. The results showed that the proposed method could effectively identify the variation and its control variables for the dynamic cutting force in the cutting process, and the method could provide a scientific basis for constructing the dynamic cutting force model of a high energy efficiency milling cutter.

Numerical and experimental investigations on cutting force of broaching internal spline holes

Cutting force in broaching process is essential information for quality controlling, troubleshooting and tool life prediction, yet existing technical bottleneck in prediction and acquirement in internal spline holes broaching process. Based on the mechanics of orthogonal metal cutting, a numerical model of the cutting force in internal spline broaching is constructed by Johnson-Cook material constitutive and failure model taking friction on both rake face and flank face into consideration, and is used to numerically estimate the cutting forces. A measurement apparatus is developed and real-time cutting force is monitored, which contains the effects of structural vibration and can be divided into static cutting force and dynamic cutting force. Wavelet transform filtering method is therefore employed to separate the static component from dynamic component. Calculated value of the cutting force by numerical model is in good agreement with the static cutting force by experimental measuring. The model and measurement method are feasible in intelligent manufacturing where internal broaching process is used.

Investigating the Cutting Force Monitoring System in the Boring Process

Due to the closed environment during deep hole boring, it is impossible to observe the working state of the boring bar. Studies show that monitoring the cutting force is the most direct and effective way to reflect the processing status. In this regard, a cutting force monitoring system is designed in the present study for the boring process. The main idea of the designed monitoring system is the piezoelectric effect of the strain gauge. When the tool tip is subjected to the cutting force, the sensor deforms and the strain sensor generates a voltage signal. Accordingly, the cutting force can be obtained by establishing the correlation between the voltage and the applied cutting force. The force of the boring bar and the output of the sensor were analyzed, and an experimental platform for monitoring the boring force was built. This method is applied in a case study and the obtained results demonstrate that the developed cutting force monitoring system has good compatibility, high precision and good dynamic characteristics. It is found that that the measurement error of the designed system in the boring process is less than 9.18%, which meets the accuracy requirements of measurements in the dynamic cutting force under machining conditions.

Experimental investigations of chatter and critical cutting conditions in turning

Vibration can cause problems when it occurs during machining, especially if it cannot be damped and continuous to increase, a phenomenon known as chatter. This thesis project focuses on reviewing the state-of-the-arts work in chatter research, identifying a reliable mechanistic dynamic cutting force model for orthogonal cutting operations when machining slender shafts, carrying out a series of experiments on uniform and stepped workpiece[s], and validating the theoretical predictions of chatter onset conditions against experimental results.

Experimental investigations of chatter and critical cutting conditions in turning

Vibration can cause problems when it occurs during machining, especially if it cannot be damped and continuous to increase, a phenomenon known as chatter. This thesis project focuses on reviewing the state-of-the-arts work in chatter research, identifying a reliable mechanistic dynamic cutting force model for orthogonal cutting operations when machining slender shafts, carrying out a series of experiments on uniform and stepped workpiece[s], and validating the theoretical predictions of chatter onset conditions against experimental results.

Analysis of the effect of tool posture on stability considering the nonlinear dynamic cutting force coefficient

In aviation and navigation, complicated parts are milled with high-speed low-feed-per-tooth milling to decrease tool vibration for high quality. Because the nonlinearity of the cutting force coefficient (CFC) is more evident with the relatively smaller instantaneous uncut chip thickness, the stable critical cutting depth and its distribution against different tool postures are affected. Considering the nonlinearity, a nonlinear dynamic CFC model that reveals the effect of the dynamic instantaneous uncut chip thickness on the dynamic cutting force is derived based on the Taylor expansion. A five-axis bull-nose end milling dynamics model is established with the nonlinear dynamic CFC model. The stable critical cutting depth distribution with respect to tool posture is analyzed. The stability results predicted with the dynamic CFC model are compared with those from the static CFC model and the constant CFC model. The effects of tool posture and feed per tooth on stable critical cutting depth were also analyzed, and the proposed model was validated by cutting experiments. The maximal stable critical cutting depths that can be achieved under different tool postures by feed per tooth adjustment were calculated, and corresponding distribution diagrams are proposed for milling parameter optimization.