Multi-Dimension Tool Wear State Assessment Criterion on the Spiral Edge of Milling Cutter

In the assessment of the tool wear state for the spiral edge of milling cutter based on machine vision, the traditional assessment criterion is often inaccurate due to the problem of information missing or incomplete especially near the tip area. In order to deal with this problem, different lighting-condition setting and additional non-image information compensation techniques are needed . In view of this, an integration tool wear detection method combined line laser edge detection and machine vision is proposed. Subsequently, the combined data acquirement experimental system is designed and built, which can simultaneously acquires two types of parameters: diameter and images under the same detection condition. Then, based on the above information, a multi-dimension series assessment criterion is proposed consisting of three dimensions index: The one-dimensional assessment index gives the average wear value of the spiral side, which mainly used as data ordination and characterizes the rule of tool wear degradation; the two-dimensional assessment index describes the contour of the wear region and calculates the area value, which can predict the change of the tool wear stage more precisely; the three-dimensional assessment index gives the 3D morphology by adding depth information within the wear region and quantified the volume of the worn-off part, which provides clues for early warning of the deterioration caused by the tool worn. Experiments proved that the multi-dimension series assessment criterion is helpful to reflect the trend of tool life and give a more accurate assessment of the tool wear state for the spiral edge of milling cutter.

Using the Machine Vision Method to Develop an On-machine Insert Condition Monitoring System for Computer Numerical Control Turning Machine Tools

This study uses the machine vision method to develop an on-machine turning tool insert condition monitoring system for tool condition monitoring in the cutting processes of computer numerical control (CNC) machines. The system can identify four external turning tool insert conditions, namely fracture, built-up edge (BUE), chipping, and flank wear. This study also designs a visual inspection system for the tip of an insert using the surrounding light source and fill-light, which can be mounted on the turning machine tool, to overcome the environmental effect on the captured insert image for subsequent image processing. During image capture, the intensity of the light source changes to ensure that the test insert has appropriate surface and tip features. This study implements outer profile construction, insert status region capture, insert wear region judgment, and calculation to monitor and classify insert conditions. The insert image is then trimmed according to the vertical flank, horizontal blade, and vertical blade lines. The image of the insert-wear region is captured to monitor flank or chipping wear using grayscale value histogram. The amount of wear is calculated using the wear region image as the evaluation index to judge normal wear or over-wear conditions. On-machine insert condition monitoring is tested to confirm that the proposed system can judge insert fracture, BUE, chipping, and wear. The results demonstrate that the standard deviation of the chipping and amount of wear accounts for 0.67% and 0.62%, of the average value, respectively, thus confirming the stability of system operation.

Influence of Spheroidizing Heat Treatment on Mechanical Properties of EN47 Steel

The high temperature phase austenite in steel has the property to transform into a variety of room temperature phases like coarse pearlite, bainite & martensite depending upon the cooling cycle. The machinability and toughness depend upon the shape and distribution of pro eutectoid harder phases. The spherical or oval shapes give lesser resistance for machining process. So it is required to design the heat treatment to tailor the property as required by the application. In this view, it is proposed to study the mechanical and micro structural properties of EN47 steel undergoing Spheroidization. The aim of this work is to test the hardness, toughness and wear property of the steel in spheroidised condition. Hardening treatment improves hardness of the material, a marginal decrease in hardness value with improved ductility is observed in tempering. Hardening and longer duration tempering show better wear resistance compared to other heat treatments. Both mild and severe wear regions are observed. Generally mild wear region is observed above five hours of continuous running of the specimen. Micro structural analysis shows the existence of pearlitic structure in as bought & normalized specimen, lath martensitic structure in hardened specimen.

Tribological properties of winding hoisting rope between two layers with different sliding parameters

The friction and wear behavior exists in ultra-deep coal mine between multi-layer winding hoisting ropes, and it decreases the rope’s service life directly, which threatens the safety coal mine hoist. In order to obtain the tribological properties of winding hoisting rope, the effects of sliding velocity, displacement amplitude, and their combination on the tribological behavior of winding hoisting rope in ultra-deep coal mine were investigated on a self-made test rig. The results show that the effect of velocity on the coefficient of friction and temperature rise is more obvious than the stroke. Additionally, the mean value of the coefficient of friction in steady stage decreases from 0.721 to 0.524 with an increase in velocity and stroke at the same time. Furthermore, the temperature rise increases from about 3.43°C to 13.73°C with the velocity at stable stage, and the stroke has little influence on the temperature rise. Moreover, with the increase in velocity and stroke simultaneously, the damage in the wear region does not become more severe. In addition, the wear mechanisms include abrasive wear and adhesive wear, and its wear characteristics in the wear region are plastic deformation, pits, furrows, broken wires, cracking, and spalling.

Tribological property of the cobalt—chromium femoral head with different regions of wear in total hip arthroplasty

The tribological properties of engineering and biological materials have been investigated at microscale levels through the calculation of the surface roughness and frictional coefficient using atomic force microscopy (AFM). Although a number of previous studies have reported the frictional coefficients of diverse bearing materials in total hip arthroplasty (THA), the relationship between the surface roughness and frictional coefficient of bearing materials of THA have not been reported, and furthermore, the tribological properties for different wear regions of a cobalt-chromium (Co—Cr) femoral head have not been well identified. Therefore, the objective of this study is to investigate the relationships between the surface roughness, frictional coefficient, and hardness for both the main-wear and the least-wear regions of a Co—Cr femoral head 10 years after THA. The average Vickers hardness of the Co—Cr femoral head was 380.7 ± 11.3 HV. With the scanned area of 25 μm×25 μm through AFM, the frictional coefficients of the main-wear and the least-wear regions were 0.229 ± 0.054 and 0.243 ± 0.059, respectively, and showed no statistical differences between these two regions ( p = 0.449). However, differences in the surface roughness ( Rq) between the main-wear region ( Rq = 96.5 ± 26.2 nm) and the least-wear region ( Rq = 17.7 ± 4.2 nm) were statistically significant ( p<0.0001). The results of the current study suggest that the frictional property of the Co—Cr femoral head is not significantly correlated with its surface roughness, and also provide guidelines for improving the surface characteristics of metallic implant materials.

High Pressure Wear Characteristics of Alloyed Ductile Cast Iron - Effect of Cu, Mn, Si and Mo

Under a high-pressure condition, the wear characteristics of alloyed and unalloyed ductile cast iron were investigated. Mn, Cu, Si and Mo were chosen as alloying elements, and their effects on mechanical properties of hardness and toughness were correlated with wear properties. In most cases, high-pressure wear of alloyed and unalloyed DCI were sequentially developed by mild wear region followed by severe wear. The transition of wear mode was indicated by the drastic increase of friction coefficient and wear rate. The observation of worn surface at mild-wear region suggested that wear had been concentrated at graphite phases, whereas severe wear mode damaged both of graphite and matrix. It was found that DCI alloyed with Si-Mo exhibited the most prominent resistance to the beginning of severe wear while the toughness of DCI was also a crucial factor.

Sliding Wear Calculation in Spur Gears

In gear applications where precipitous tooth failure mode such as scoring or scuffing has been avoided, “normal” wear becomes a life-determining factor. In this paper, sliding wear in spur gears, including the considerations of gear dynamics and rough-elastohydrodynamic lubrication, is analyzed. Formulas for equivalent wear rate and tooth wear profile along the line of action are derived. Results show that most materials are removed from both the addendum and dedendum tooth surfaces, and that the highest wear occurs at the beginning of an engagement. This high wear region corresponds to the root of the driving (pinion) teeth and the tip of the driven (gear) teeth. These analytical results correlate well with the practical evidences in AGMA documentation.