Contribution to the analysis of grinder vibrations using condition monitoring procedures based on vibration measurements

The article deals with the vibration of the workpiece on the grinder using a cBN grinding wheel. The workpieces were made of hardened steel with a hardness of 62 HRC and ceramics: Al2O3, SiC, Si3N4, and ZrO2/Y2O3. Grinding was performed at different infeed rates during 5 consecutive passes. Up and down grinding were also evaluated. Measured realizations of the acceleration of the workpiece during grinding were processed in the time and frequency domain and compared with each other. We consider acceleration patterns to be diagnostic signals that will help to understand the process of chip formation during grinding as well as the process of damaging parts made of the tested materials.

Experimental Research on Material Removal Mechanism and Grinding Force of FeCoNiCrMo0.1 High Entropy Alloy (HEA)

High entropy alloy (HEA) is an advanced alloy material, which has a wide application prospect due to its excellent properties. However, the material removal mechanism and change rule of grinding force of HEA in the grinding process have seldom been studied. The main work of this paper is that the material removal mechanism of the FeCoNiCrMo0.1 HEA is obtained by analyzing grinding debris and subsurface microstructure after grinding, the theoretical grinding force model of HEAs in plane grinding process is established on the basis of the force of a single abrasive grain, and the experimental verification is performed. According to the experimental results, the influences of different grinding parameters on grinding force are discussed, the influences of different types of grinding wheels on grinding force are analyzed, and the grinding forces generated by grinding different FeCoNiCr HEAs are compared. The results indicate that the material removal mechanism of FeCoNiCrMo0.1 HEA is the plastic removal. With the increase of grinding speed and the decrease of grinding depth and feed speed, both normal and tangential grinding forces decrease. Under the same grinding parameters, the grinding force produced by electroplated CBN grinding wheel is greater, followed by resin-bonded CBN grinding wheel and vitrified CBN grinding wheel. The grinding force produced by grinding FeCoNiCrAl0.1 HEA is lower than that produced by grinding FeCoNiCrMo0.1 HEA under the same grinding conditions. The calculated value of grinding force model is consistent with the experimental value, which can scientifically reflect the variation law of HEA grinding force.

Numerical and Experimental Study on the Grinding Performance of Ti-Based Super-Alloy

The experiments of the surface grinding of Ti-6Al-4V grade 5 alloy (Ti-64) with a resin-bonded cubic Boron Nitride (cBN) grinding wheel are performed in this research to estimate the influence of cutting parameters named workpiece infeed speed, Depth of Cut (DOC), cooling condition on the grinding force, force ratio, and specific energy. A finite element simulation model of single-grain grinding of Ti-64 is also implemented in order to predict the values of grinding forces and temperature. The experimental results show that an increase of workpiece infeed speed creates higher intensified cutting forces than the DOC. The grinding experiments under wet conditions present slightly lower tangential forces, force ratio, and specific energy than those in dry grinding. The simulation outcomes exhibit that the relative deviation of simulated and experimental forces is in the range of 1-15%. The increase in feed rate considerably reduces grinding temperature, while enhancement of DOC elevates the heat generation in the cutting zone.

Investigation of the Wear Behavior of Abrasive Grits in a Dry Machining Inconel 718 Narrow-Deep-Groove with a Single-Layer Cubic Boron Nitride Grinding Wheel

The wear behavior of a single-layer electroplated cubic boron nitride (cBN) grinding wheel was investigated in creep feed profile grinding Inconel 718 narrow-deep-groove with a width of 2 mm. In this paper, the protrusion height of cBN grits on the side edge of the grinding wheel was measured by three-dimensional optical profiler, and a scanning electron microscope was used to detect the topography of worn cBN grit and the nickel bonding layer. The investigation results indicated that the steady wear stage of the grinding wheel shared more than 84.6% of the wheel lifespan, and the machining precision of the grinding wheel was kept at a high level. The fracture mode of the cBN grit was proven to be cleavage. The source of the cleavage cracks was observed on the surface of wear flat or the side surface of the cBN grit. The holding strength of cBN grit could be weakened due to the joint surface breakage, the displacement of grit, or the cracks of the nickel bonding layer. The transition layer was contributed to the decrease of the bonding strength. Severe macro fractures and the concentration of pulled out grits were observed on the transition edge and the inner area of the side edge, separately. This study provides a deep understanding of the wear mechanism of a single-layer electroplated cBN grinding wheel.

Effect of Cryogenic Grinding on Fatigue Life of Additively Manufactured Maraging Steel

Additive manufacturing (AM) is replacing conventional manufacturing techniques due to its ability to manufacture complex structures with near-net shape and reduced material wastage. However, the poor surface integrity of the AM parts deteriorates the service life of the components. The AM parts should be subjected to post-processing treatment for improving surface integrity and fatigue life. In this research, maraging steel is printed using direct metal laser sintering (DMLS) process and the influence of grinding on the fatigue life of this additively manufactured material was investigated. For this purpose, the grinding experiments were performed under two different grinding environments such as dry and cryogenic conditions using a cubic boron nitride (CBN) grinding wheel. The results revealed that surface roughness could be reduced by about 87% under cryogenic condition over dry grinding. The fatigue tests carried out on the additive manufactured materials exposed a substantial increase of about 170% in their fatigue life when subjected to cryogenic grinding.

Effect of laser-assisted ultrasonic vibration dressing parameters of a cubic boron nitride grinding wheel on grinding force, surface quality, and particle morphology

In this article, the laser-assisted ultrasonic vibration dressing technique was applied to the cubic boron nitride (CBN) grinding wheel to study the effect of various process parameters (namely, laser power, dressing depth, feed rate, and grinding wheel speed) on the grinding force, surface quality, and morphological evolution of CBN abrasive particles. The results showed that abrasive particles’ morphology mainly undergoes micro-crushing, local crushing, large-area crushing, macro-crushing, and other morphological changes. The dressing force can be effectively reduced by controlling the dressing process parameters. Besides, grinding tests are performed on the grinding wheel after dressing to reveal specimens’ surface quality. Excellent grinding characteristics and grinding quality of the grinding wheel were obtained by the proposed technique with the optimized process parameters.

Variation of Grain Height Characteristics of Electroplated cBN Grinding-Wheel Active Surfaces Associated with Their Wear

During the operation of a single-layer grinding wheel (SLGW), irreversible changes occur on its active surface due to wear. The study of grinding-wheel microgeometry changes can be based on the measurement of the surface texture as well as the determination and analysis of its parameters. The article deals with the selection of suitable texture parameters and an appropriate mathematical model carrying information about the SLGW condition. In the study, samples of Pyrowear 53 steel were ground using electroplated cBN single-layer grinding wheels until they were completely worn out or removed assumed volume of the workpiece material. Each SLGW worked with constant process parameters. Among the 144 parameters tested, the highest sensitivity to changes in wheel active surfaces caused by wear was shown by the mean value of the mean island heights Zmean_m. In-depth research was conducted for Zmean_m and reduced peak height Spk. Compared to Spk, Zmean_m has proven to be a better measure of wear, especially when large areas of sticking occur. Moreover, the second-degree models linking Zmean_m and Spk to the process parameters and the specific material loss were better suited to the empirical data than the exponential models.

The study on surface grinding process of TI–6AL–4V alloy with resinoid cBN grinding wheel

The grinding process of Titanium (Ti) alloys is extremely difficult as the cutting temperature is much higher than other machining processes due to the low thermal conductivity, high chemical reactivity, and rapid work hardening during machining of Ti alloys. This research investigates the effect of technology parameters on the surface roughness in the surface grinding of Ti–6Al–4V (Ti64) alloy with resinoid cBN grinding wheel. The experimental results show that the surface roughness is significantly affected by the feed rate, depth of cut (DOC) and cooling condition. Increasing feed rate or DOC all provides the higher surface roughness. The surface roughness obtained in the wet grinding is higher than those of the dry cutting. The scanning electron microscopy (SEM) images of Ti64 surfaces show that the machining surface with fewer defects can be produced with wet grinding process.