Xuekun Li

Numerical Simulation of the Moving Induction Heating Process with Magnetic Flux Concentrator

The induction heating with ferromagnetic metal powder bonded magnetic flux concentrator (MPB-MFC) demonstrates more advantages in surface heating treatments of metal. However, the moving heating application is mostly applied in the industrial production. Therefore, the analytical understanding of the mechanism, efficiency, and controllability of the moving induction heating process becomes necessary for process design and optimization. This paper studies the mechanism of the moving induction heating with magnetic flux concentrator. The MPB-MFC assisted moving induction heating for Inconel 718 alloy is studied by establishing the finite element simulation model. The temperature field distribution is analyzed, and the factors influencing the temperature are studied. The conclusion demonstrates that the velocity of the workpiece should be controlled properly and the heat transfer coefficient (HTC) has little impact on the temperature development, compared with other input parameters. In addition, the validity of the static numerical model is verified by comparing the finite element simulation with experimental results on AISI 1045 steel. The numerical model established in this work can provide comprehensive understanding for the process control in production.

The Study of the Effect of Magnetic Flux Concentrator to the Induction Heating System Using Coupled Electromagnetic-Thermal Simulation Model

Induction heating is frequently used in the metalworking industry to heat metals for hardening, soldering, brazing, tempering and annealing. Due to its complexity, the using of simulation to analyze induction heating process could become very advantageous both in design and economic aspects. In this paper, an analytical model is established using commercial package Cedrat Flux® 10.3, and the model is verified by the experiments. After the establishment of analytical model, an analysis on the effect of magnetic flux concentrator was conducted.

Modeling and Simulation of Induction Heating with Magnetic Flux Concentrator

Induction heating possesses wide application in surface hardening for steels. In recent years, the emergence of metal powder bonded magnetic flux concentrator (MPB-MFC) enables induction heating better capability, efficiency, and controllability, therefore the analytical understanding through modeling and simulation becomes necessary for process design and optimization. In this paper, the mechanism of the energy transformation in induction heating with magnetic flux concentrator is carried out. The MPB-MFC assisted induction heating for AISI 1045 steel is studied by comparing the finite element simulation with experimental results. The finite element model solves the coupled electro-magnetic-thermal computation problem, which also involves the consideration of the non-linear material magnetic properties in the process. To verify the simulation, middle-frequency induction heating experiments are conducted to compare with the simulated results. The comparison proves the efficacy of the FEM model, and discloses the inner-correlation of the thermal-magnetic-electric fields in the process.

Research on Microscopic Grain-Workpiece Interaction in Grinding through Micro-Cutting Simulation, Part 2: Factorial Study

The grinding process can be considered as micro-cutting processes with irregular abrasive grains on the surface of grinding wheel. Single grain cutting simulation of AISI D2 steel with a wide range of cutting parameters is carried out with AdvantEdgeTM. The effect of cutting parameters on cutting force, chip formation, material removal rate, and derived parameters such as the specific cutting force, critical depth of cut and shear angle is analyzed. The formation of chip, side burr and side flow is observed in the cutting zone. Material removal rate increases with the increase of depth of cut and cutting speed. Specific cutting force decreases with the increase of depth of cut resulting in size effect. The shear angle increases as the depth of cut and cutting speed increase. This factorial analysis of single grain cutting is adopted to facilitate the calculation of force consumption for each single abrasive grain in the grinding zone.

Grain-Workpiece Interaction Study of Grinding Process through Single Grain Cutting Simulation

Grinding process can be considered as micro-cutting processes with the irregular abrasive grains on the surface of grinding wheel. The grain-workpiece interface directly forms the workpiece surface. Therefore, the study of the grain-workpiece interaction through micro-cutting analysis becomes necessary. But the experiments for single grain cutting are difficult to perform. Aimed at this problem, single grain cutting simulations of AISI D2 steel with a wide range of cutting parameters have been carried out with AdvantEdgeTM in this study. The effect of cutting parameters on cutting force, specific cutting force, material removal rate and critical depth of cut has been analyzed.

Experimental study of time-dependent performance in superalloy high-speed grinding with cBN wheels

ABSTRACT The time-dependent performance of grinding is expressed as the change of process output measures as a function of time during grinding. Although the wheel capability will be restored by dressing, the time-dependent performance of grinding during one dressing skip is the determinant on the grinding quality variation in terms of surface integrity and workpiece geometric accuracy. Therefore, understanding of grinding time-dependent performance in relation with the wheel–workpiece microscopic interaction is critical for wheel and process development to achieve stable grinding processes. In this article, the grinding of superalloy with cubic boron nitride (cBN) grinding wheels is performed. The time-dependent performance is recorded to represent the characteristic features, and the microscopic wheel topography is measured under scanning electron microscope (SEM) throughout the grinding process, so as to reveal the root cause for the time-dependent performance and its impact on the workpiece quality variation. The experiment results indicate that during the grinding process, there exist three characteristic stages, namely, initial wheel wear stage, severe wheel wear stage, and wheel resharpening stage. Moreover, the change trend of spindle power consumption, workpiece quality on surface hardness and roughness, wheel wear condition, and G ratio are consistent with the wheel topography evolution reflected by SEM photos, which can be used to present the three grinding stages. The wear and replacement of the efficient grain cutting edges result in the time-dependent performance during superalloy high-speed grinding with cBN wheels.

The Establishment of Coupled Electromagnetic-Thermal Analytical Model of Induction Heating System With Magnetic Flux Concentrator and the Study on the Effect of Magnetic Permeability to the Modeling

Induction heating is frequently used in the metalworking industry to heat metals for hardening, soldering, brazing, tempering and annealing. Due to its complexity, the using of simulation to analyze the induction heating process could become very advantageous both in design and economic aspects. In this paper, an analytical model is established using commercial package Cedrat Flux® 10.3, and the model is verified by the experiments. After the establishment of analytical model, an analysis on the effect of workpiece magnetic permeability to the modeling was conducted.© 2013 ASME

The Study of Wear Flat Effect on the Single Grain Micro-Cutting Performance in Superabrasive Grinding from a Simulation Perspective

Grain-workpiece interface, which resembles a micro-cutting process, directly modifies the workpiece surface and dominates all the output measures of a grinding process. The abrasive grains always become worn or dulled during grinding, which alters the grain-workpiece interface output and turns to be the primary factor that causes the transient or time dependent behavior in monolayer superabrasive grinding. Therefore, the study on how the grain wear influences the grain-workpiece interaction through micro-cutting analysis becomes necessary. As the emergence of the packaged FEM software for micro-cutting simulation, apart from single grit cutting test, it enables another qualitative and quantitative investigation method on grain-workpiece interface mechanism in an efficiency and effective manner. Based on previous efficacy verification of Third Wave AdvantEdgeTM, the FEM simulation is carried out to investigate the effect of grain wear on its micro-cutting performance. The simulation results provide an illustrative manner to interpret the phenomenon and mechanism, and the results can be used in the grinding process modeling in the future as well.

An improved segmentation method for defects inspection on steel roller surface

In the field of metal rolling, the quality of the steel roller’s surface is significant for the final rolling products, e.g. metal sheets or foils. Besides the dimensional accuracy and surface roughness, the optical uniformity of the roller surface is also required for high quality rolling application. The typical optical defects of rollers after finish grinding include speckles, chatter marks, feed traces, and combination of all above. Unlike surface roughness, the optical defects can hardly be characterized by the topography or scanning electrical microscope measurement. Only the inspection by bared eyes of experienced engineers appears to be the effective manner for surface optical defects examination for large steel rollers. In this paper, an on-site machine vision system is designed to add on to the roller grinding machine to capture the surface image, and then an improved optical defects segmentation algorithm is developed based on the active contour model. Finally, experiments are carried out to verify the efficacy of the improved model.In the field of metal rolling, the quality of the steel roller’s surface is significant for the final rolling products, e.g. metal sheets or foils. Besides the dimensional accuracy and surface roughness, the optical uniformity of the roller surface is also required for high quality rolling application. The typical optical defects of rollers after finish grinding include speckles, chatter marks, feed traces, and combination of all above. Unlike surface roughness, the optical defects can hardly be characterized by the topography or scanning electrical microscope measurement. Only the inspection by bared eyes of experienced engineers appears to be the effective manner for surface optical defects examination for large steel rollers. In this paper, an on-site machine vision system is designed to add on to the roller grinding machine to capture the surface image, and then an improved optical defects segmentation algorithm is developed based on the active contour model. Finally, experiments are carried out to ve...

IM (Indentation Method) Based Impact Fracture Characteristics of cBN Crystal and Their Influence on High Speed Wheel Performance

Cubic Boron Nitride (cBN) is considered a superabrasive due to its excellent material behavior, and is commonly used in the manufacturing of high end grinding tools, in particular for machining hard-to-machine materials, in order to achieve high productivity in combination with high precision. During the actual grinding process, the performance of grinding tools is significantly affected by the fracture response of employed cBN crystals to the external impact load related to the grinding speed. Therefore, two types of cBN crystals are selected in this paper and their fracture resisting behaviors are measured under various impact loading rates through the Indentation Method (IM). In order to establish the fracture behavior of cBN crystals and the overall grinding performance of cBN wheels, high speed surface grinding experiments are conducted and grinding performances are evaluated regarding the evolution of grinding force and power consumption, wheel wear and grinding efficiency, as well as the chemical stability of cBN materials on affinity. The experimental results show a good agreement of cBN crystal’s impact fracture properties on the cBN grinding wheel performance, which helps to understand cBN crystal’s high speed grinding characteristics.