Ground Surface Integrity Research Articles

Surface generation and material removal mechanism incorporated with the randomness of grain size and distribution in grinding

Grinding process can achieve minimal material removal quantity and multiple material removal mechanisms simultaneously, which makes it extremely popular in industrial applications to meet the requirements of high dimension precision, excellent surface quality and rigorous tolerance. However, due to the randomly-sized and randomly-distributed abrasive grains, an accurate ground surface prediction model remains a significant challenge by considering the actual microstructure of grinding wheel. This research aims to develop a novel surface prediction model to take into account the random nature of the grain size and its distribution in grinding wheel. The generation of ground surface is modeled by calculating the transient trajectory of grain in the whole contact zone. Micro grain-workpiece contact mechanism is revealed in terms of the typical stages of rubbing, plowing and cutting to determine the ground surface morphology. Grinding experiments were performed to compare with the predicted surface morphologies. The proposed model was further validated in the terms of surface topography, roughness and material removal rate. Additionally, material removal mechanism associated with surface generation has been explored by the predicted ground surface and material removal rate under different grain-workpiece interaction states. The provided model is further employed to examine the impact of the randomness of grain size and distribution and grinding parameters on the surface roughness. Thus, the research provides fresh insights into understanding the underlying mechanism in different grain stages as well as revealing the transient contact mechanisms in generating ground surface integrity.

Magnetic non-destructive evaluation of microstructural and mechanical characteristics of hardened AISI H13 die steel upon sustainable grinding

This paper describes the potential of non-destructive techniques such as micro-magnetic Barkhausen noise (MBN) to assess the grinding burn flaws in terms of microstructural and mechanical indices of hardened AISI H13 die steel. To overcome this grinding burn issue, minimum quantity lubrication grinding with eco-friendly machining fluids like paraffin oil (PO) and castor oil (CO) was adopted and compared its performance with well-established conventional grinding like wet and dry. Ground surface integrity with castor oil (CO) was found to be significantly improvement in surface quality including lower surface roughness (Rα: 0.23 μm and Rz: 1.83 μm) with uniform surface topography, absence of oxidization and carbonization film, and negligible change in microhardness and microstructure. The reason is strong and uniform anti-friction and anti-wear tribo-film was produced by castor oil, which minimizes heat penetration through limited ploughing and rubbing action. The MBN outcome i.e., root mean square (RMS) has followed a linear relation with microhardness and temperature of the ground sample with a correlation coefficient of 0.993 and 0.981. Besides, lower amplitude and wide peak envelope get shifted towards a higher magnetic field in the MQL-CO grinding caused by poor thermal softening effect on the ground sample, which restricts magnetic domain wall movement and rotation. These outcomes could guide tooling industries for efficient sustainable grinding with faster thermal damage assessment, which helps to minimize production cycle time and back to clean environment.

Wear evolution of metal bond diamond tool in grinding of sapphire

The wear characteristics of the metal bond diamond tools changes with the grinding process, resulting in affecting the grinding efficiency, tool's life, and surface integrity of the workpiece. In this study, the wear evolution of a metal bond diamond tool, for the case of grinding of sapphire, is investigated by using a novel design of the grinding setup. The wear characteristics of the diamond grits and the metal bond at a fixed zone of the grinding tool were examined. In addition, the evolution of the grinding process, the grinding force, the grinding ratio, and the surface integrity of the sapphire were also evaluated. As the material removal volume increases, the number of participating diamond grits, the proportion of micro-fractured diamond grits, and the average diamond grit protrusion height increase during the grinding process. And the proportion of newly exposed diamond grits decreases and the distribution of protrusion height of diamond grits becomes narrower during the grinding process. Consequently, a higher grinding ratio, stable grinding force, and excellent ground surface integrity are achieved positively when the wear of the metal bond diamond tool transforms from the initial stage to the stable stage with the material removal volume of up to 3600 mm3.

Assessment of the surface integrity of ground cemented tungsten carbide cutting inserts and its influence on tool wear in turning of ferritic nodular cast iron

In order to improve surface finish, geometric and dimensional tolerances of cemented tungsten carbide cutting tools produced by powder metallurgy, grinding is commonly applied. Due to the high thermal and mechanical loads generated during this process, surface and metallurgical characteristics are directly affected and, as a result, tool performance. Within this context, the influence of grinding wheel characteristics on surface integrity parameters, like surface and edge roughness, hardness and residual stress, was investigated and cutting inserts ground under extreme conditions were applied in rough orthogonal turning of a ferritic nodular cast iron to evaluate their performance regarding tool life. The obtained results showed that higher compressive residual stress values, induced by a vitrified bonded diamond grinding wheel with grain size of 46 µm, contributed to increase tool life, as a protective layer of adhered material was formed on the cutting edge. Flank wear by abrasion was thus avoided and crack formation was the determining factor for the end of the tests. • Finishing process of cutting inserts significantly affects their performance. • Compressive residual stress contributes to increase tool life in rough turning. • Insert surface and edge roughness do not influence tool life in turning cast iron.

Effects of the cooling mode on the integrity and the multi-pass micro-scratching wear resistance of Hardox 500 ground surfaces

In this paper, effects of the cooling mode used in grinding of Hardox 500 on the material grindability, ground surface integrity, and multi-pass micro-scratching wear resistance are investigated. Three modes are experimented: dry grinding, soluble oil, and cryogenic cooling modes. Results showed that the cryogenic cooling achieved high levels of work hardening and compressive residual stresses. Moreover, it was found that the cryogenic cooling improves the multi-pass micro-scratching wear resistance of Hardox 500 comparatively with the polished state and ground surfaces under dry or soluble oil conditions. The improvement rates of the wear volumes generated by the cryogenic cooling represent 46% and 63% of the volumes generated for the polished state when scratch load of 10 N and 20 N were applied respectively. These improvements are discussed based on the integrities of the scratched surfaces and sub-surfaces.

Influence of minimum quantity lubrication on surface integrity of ground hardened H13 hot die steel

In grinding process, cutting fluids play an important role to control high grinding zone temperature. However, their use causes detrimental effect on the operator’s health and environment. On the other hand, dry grinding not only results in thermal damage to ground surface but also deteriorates the surface quality and dimensional accuracy of the ground component. The possible solution is to apply cutting fluids using minimum quantity lubrication (MQL) technique. The objective of present research work is to investigate and compare the effect of different grinding environments: dry, flood, MQL with deionized water (DIW), MQL with liquid paraffin oil (LP), and MQL with castor oil based on vegetable oil (VO) during grinding of hardened H13 hot die steel. Grinding performance was evaluated in terms of specific grinding force, specific grinding energy, grinding force ratio, surface roughness, and microhardness. Ground surface and debris morphology were also analyzed using scanning electron microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy to validate the grinding performance. The results showed that MQL-VO grinding leads to minimum specific grinding force, specific grinding energy, and grinding force ratio. Further, surface roughness was considerably reduced under MQL-VO grinding, where Rɑ and Rz were 0.245 μm and 1.846 μm, respectively. AFM analysis indicated that the surface roughness of MQL-VO grinding was nearly 29.88% less as compared to dry grinding. Smooth ground surface topography, as well as long, thin, and no wear track grinding debris, were observed under MQL-LP and MQL-VO conditions. Moreover, dry grinding resulted in lower microhardness in comparison to other grinding conditions.

Cultural Resources Investigations for the CrownQuest City of Midland Oil and Gas Project, Midland and Glasscock Counties, Texas

SWCA Environmental Consultants (SWCA) was retained by CrownQuest Operating, LLC, to complete an intensive cultural resources investigation for the proposed CrownQuest City of Midland Oil and Gas Project (Project). The Project includes newly proposed oil and gas well pads, crude oil pipeline, and associated access roads on City of Midland property in Midland and Glasscock Counties, Texas. These new components will be constructed within an existing upstream oil and gas system. The 149.9-acre (60.7-hectare) Project area is located approximately 15 miles southeast of Midland, Texas, immediately south of Highway 158, and is situated along and between Johnson and Pemberton Draws. The Project involves a political subdivision within the state of Texas (City of Midland). The Antiquities Code of Texas (ACT) applies because the Project’s activities occur on property owned by the City of Midland and will involve more than 5 acres / 5,000 cubic yards of land disturbance or may potentially affect known archaeological sites. It is SWCA’s understanding that the Project does not currently have a federal nexus, and it is not subject to Section 106 of the National Historic Preservation Act. The purpose of this investigation was to identify and assess any cultural resources, such as historic and prehistoric archaeological sites and historic buildings, structures, objects, and sites (such as cemeteries) that might be located within the boundaries of the proposed Project and evaluate their significance and eligibility for designation as a State Antiquities Landmark. The investigations included a background and historic map review of the Project area and immediately surrounding region followed by pedestrian survey with visual examination and shovel test excavations at proposed Project activity areas. All investigations were conducted in accordance with the ACT and standards and guidelines established by the THC and Council of Texas Archeologists. Following the review and acceptance of the final cultural resources report, all records and photographs will be curated with the Center for Archaeological Research at the University of Texas at San Antonio, per requirements of the ACT in accordance with the CTA guidelines. The cultural resources investigation was conducted under ACT Permit No. 8506. Fieldwork was performed from July 30 to August 4, 2018. The Project setting was mainly eroded and heavily disturbed uplands with occasional exposures of bedrock and caliche. Pedestrian survey was augmented by hand excavating 253 shovel tests and seven auger tests, which were terminated at the maximum reachable depth or at soils likely predating human occupation, typically around 45 cm below surface. The most pervasive land disturbance observed was related to petroleum exploration and extraction activities that have generally impacted ground surface integrity. During the investigation SWCA archaeologists did not observe any prehistoric or historic cultural resources within the Project area. The location near site 41MD4, identified during the background review, could not be visited by SWCA survey staff due to a fire in the facility. The site boundary defined does not extend into a proposed Project activity area and the closest associated Project item is already disturbed. On that basis it is not considered to be a Project concern. Based on the negative findings of the intensive cultural resources survey, SWCA recommends that no further archaeological investigations are warranted within the assessed portions of the CrownQuest City of Midland Oil and Gas Project area.

Effects of Surface Pre-treatment on the Nitrided Layers Properties

In this work the 42CrMo4 steel ground surface integrity was evaluated at different grinding conditions before and after nitriding. An experimental study was carried out to investigate the influence of depth of cut on work piece surface integrity by grinding. Surface integrity was characterized by roughness, micro-hardness, residual stress distribution and ground surface morphology. These properties were compared to nitriding state. These improvements in grindability and in surface integrity are particularly favoured by low depth of cut values. It is also shown that these improvements are essentially due to the reduction of the grinding temperature, which decrease the tensile residual stresses and favours the material removal by shearing and limits the ground surface damage. The roughness of the ground work piece surfaces increases with the depth of cut, which was attributed to plastically deformed coatings on the work piece surface occurring with elevated temperature. The results presented in this study shows that the material history before nitriding does not have any influence on the residual stresses distribution after nitriding. This is due to that during the nitriding treatment, especially in the heating phase; the tensile stresses generated by grinding are cancelled under the temperature effect.

Application of eco-friendly nanofluids during grinding of Inconel 718 through small quantity lubrication

The present work explores the application of nanofluids (NFs) in small quantity lubrication (SQL) mode by suspending eco-friendly Silver and Zinc oxide nanoparticles in deionized water. These nanoparticles have already been established as eco-friendly by several researchers. Hence these NFs may be termed as environmentally sustainable, and the present work is the first attempt to use such NFs in environment-friendly grinding of Inconel 718 (IN718) superalloy. The NFs have been supplied into the grinding zone using an in-house developed SQL setup. The results of the grinding process using NFs have been compared with the outcomes of grinding experiments under dry, wet and SQL with soluble oil. Ground surface integrity, wheel topography, and chip morphology have been investigated with the help of Scanning electron microscopy, Energy-dispersive X-ray spectroscopy, Atomic force microscopy and Stereo Zoom microscopy micrographs. The NFs have been characterized through measurements of zeta potential, hydrodynamic diameter, thermal conductivity, dynamic viscosity, and contact angles in relation to IN718 surface. From the present study, it can be concluded that application of NFs resulted in minimization of grinding forces, coefficient of friction, and improvement in the ground surface integrity. Zinc oxide based NFs have shown better grinding responses mainly because of improved lubrication behavior. It is primarily due to better spreadability that has induced stable lubricious film at the contacting surfaces even at a higher temperature. The findings of this work can be regarded as a first step towards the green and sustainable grinding of high strength superalloys.

Surface Integrity of AlSiC Composites Ground by Monolayer Brazed Diamond Wheels

Monolayer brazed diamond wheel were used to grind AlSiC composite with different volume fraction of SiC. The effects of diamond mesh size of the grinding wheels and the volume fraction of SiC in AlSiC composite on the surface integrity of ground AlSiC composite were investigated. It is found that the surface roughness of ground AlSiC composite with 20% SiC is increased with the reduction of diamond grit’s size because of the clogging of diamond wheel. With the increasing of the volume fraction of SiC, there are more fractured and cracked SiC particles on the ground surface of AlSiC composite. On the other hand, the finer diamond grits (70/80) induce the finer fractured SiC particles on the ground surface of AlSiC with 50% and 70% SiC.

Surface Integrity of AlSiC Composites Ground by Monolayer Brazed Diamond Wheels

Monolayer brazed diamond wheel were used to grind AlSiC composite with different volume fraction of SiC. The effects of diamond mesh size of the grinding wheels and the volume fraction of SiC in AlSiC composite on the surface integrity of ground AlSiC composite were investigated. It is found that the surface roughness of ground AlSiC composite with 20% SiC is increased with the reduction of diamond grit’s size because of the clogging of diamond wheel. With the increasing of the volume fraction of SiC, there are more fractured and cracked SiC particles on the ground surface of AlSiC composite. On the other hand, the finer diamond grits (70/80) induce the finer fractured SiC particles on the ground surface of AlSiC with 50% and 70% SiC.

The Characteristics of High-Speed Cylindrical Grinding of Silicon Carbide and its Influence on the Surface Layer

There has been increased interest in the use of advanced ceramic materials such as silicon carbide in the recent past, due to its unique physical and mechanical properties. However, the increase of the machining rate relies on the understanding of material removal mechanism on the microstructural scale and the relationship between the grinding characteristics and formation of surface/subsurface machining-induced damage. In this paper, grinding characteristics and surface integrity of SiC ground with diamond wheel on cylindrical grinding machine have been investigated. The grinding chip and the ground surface damage have been studied with scanning electron microscope (SEM). In particular the residual stress distribution has been analyzed by a single exposure technique d - sin2 (Ψ) method with the aid of powder X-ray diffractometer.

Analysis of Microstructure of Grinding Strengthening Layer in Point Grinding under Small Depth of Cut Conditions

Grinding strengthening and hardening can change and improve the ground surface integrity directly by the composite process of thermal load and mechanical force during process. The thickness and distribution of strengthening layer in ground surface makes the key role to measure the surface integrity of workpiece. The hardness and size of strengthening layer can influence the fatigue strength working life of the workpiece significantly. Based on the grinding strengthening test of 45 steel specimens, the strengthened layer microstructure, thickness and surface hardness were analyzed. This study illustrates the mechanism of grinding strengthened layer formation and also provides the theoretical basis for grinding strengthening and hardening layer quality control and grinding strengthening process making properly under small depth of cut conditions.

Study of surface integrity of ground bearing steel using Barkhausen noise technique

An experimental study was undertaken to compare the role of process parameters on the grindability of bearing steel (unhardened and hardened) in conventional grinding domain with particular emphasis on surface integrity. Surface residual stress on the ground specimens has been assessed using X-ray diffraction technique and Barkhausen noise analysis. The aim of this article was to compare the applicability of Barkhausen noise analysis technique to assess the state of residual stress with simultaneous change in microstructure along with the formation of white layer, microhardness, the incorporation of plastic deformation, etc. The results indicate a significant effect of downfeed and work speed on surface integrity parameters like residual stress, microstructure, and microhardness. Residual stress varied in the present work over a domain of 50–700 MPa. Despite simultaneous variation in the microhardness, microstructure, and residual stress during grinding, a linear correlation could be established between Barkhausen noise parameters and residual stress.

Novel processing of Barkhausen noise signal for assessment of residual stress in surface ground components exhibiting poor magnetic response

The Barkhausen Noise Analysis (BNA) technique has been utilised to assess surface integrity of steels. But the BNA technique is not very successful in evaluating surface integrity of ground steels that exhibit poor micro-magnetic response. A new approach has been proposed for the processing of BN signal and two newly proposed parameters, namely ‘count’ and ‘event’, have been shown to correlate linearly with the residual stress upon grinding, with judicious choice of user defined ‘threshold’, even when the micro-magnetic response of the work material is poor. In the present study, residual stress induced upon conventional plunge surface grinding of hardened bearing steel has been investigated along with unhardened bearing steel for benchmarking. Moreover, similar correlation has been established, when primarily compressive stress is induced upon high speed grinding using cBN wheel with moderately deep cut suppressing the micro-magnetic response from the ground medium carbon steel as the work material.

Efficient drilling of holes in Al 2O 3 armor ceramic using impregnated diamond bits

This study aims at achieving a high efficient mode of hole-drilling in Al 2O 3 armor ceramic by using impregnated diamond bits. First, the most suitable diamond segment for the armor ceramic is selected by using higher quality diamonds and varying the composition of the metal matrix, as well as combining to the drilling test and SEM examination. Bit structure parameters such as grain size, diamond concentration, number of slots and wall thickness are optimized then by an orthogonal test. Experiments for analyzing the influence of the axial force and spindle speed to the efficiency are also carried out. Then hole quality is discussed. Finally, the ground surface integrity of Al 2O 3 armor ceramic is analyzed under SEM examination. The results show: (1) the bit with diamond type of SMD40 and metal matrix of Cu50Co25Sn18Ti7 (wt%) presents the best self-dressing capability among the four kind of different matrix bits; (2) the bit with wall thickness of 2.5 mm, grain size of 35/40 US mesh, diamond concentration of 100% and number of slots of 2 achieves a higher efficient mode; (3) the increased axial force and spindle speed could increase the drilling efficiency but overlarge axial force and too high spindle speed also lower the efficiency; (4) hole quality can be improved by using an prepress exerted device; (5) the ground surface of Al 2O 3 armor ceramic is composed of fractured area and ductile streak area which indicate that the material removal mode is contributed by both brittle fracture and ductile cutting, and the brittle fracture removal is dominant.

Surface integrity of precision ground fused silica for high power laser applications

Surface integrity of optics used in high power laser systems is vital to their successful application. Reduction of subsurface damage is demanded during their processing. Rapid grinding of large and complex shape optics can be performed using the BoX® ultra precision grinding machine. Importantly, the depth of subsurface damage induced, even at high material removal rates, has been shown to be very small in comparison to previous studies. In this paper, grinding experiments have been conducted to verify the amount of defects beneath ground fused silica surfaces produced under selected processing conditions. The subsurface damage levels were revealed using a sub-aperture polishing process in combination with an etching technique. Observed subsurface damage can be separated in two distinct depth zones characterised as ‘process’ and ‘machine dynamics’ related.

A new technology on enhancing heat transfer during grinding of titanium alloy

Purpose – Grinding may generate high temperature along the arc of grinding zone, especially during the grinding process of difficult‐to‐machine materials. It can cause thermal damage to the ground surface and poor surface integrity. Conventional cooling methods based on large amounts of water‐oil emulsions can be both ineffective and environmentally unacceptable. The purpose of this paper is to offer a new high efficiency cooling method – cryogenic pneumatic mist jet cooling (CPMJ) to enhance heat transfer in the grinding zone during grinding of difficult‐to‐machine materials.Design/methodology/approach – CPMJ equipment is a set up, which can produce water mist of −5°C with jet velocity above 150 m/s and mean particle size below 20 μm at the impingement distance of 10‐40 mm on the symmetry axis. To validate the cooling efficiency of CPMJ equipment, heat transfer experiments were carrying out on it. Finally, CPMJ was applied to the grinding of titanium alloy to verify its cooling effects.Findings – With hi...

Study on MQL in Point Grinding Process for Green Manufacturing

In point grinding process, the contact area of point grinding is much smaller than that of conventional cylindrical grinding under same conditions, so the grinding power and heat to measure is lower and the cooling condition is improved obviously. For green manufacturing, the point grinding process has the significance to reduce the consumption of grinding fluid and improve ground surface integrity and greenness. This study analyzes the geometric configuration of the contact area between wheel and workpiece in point grinding process, establishes the geometric and mathematic models of the contact area, and investigates the relations between the grinding parameters and the grinding power by the simulations. The MQL and semi-dry point grinding experiments are performed on the ground surface integrity. These investigations show that the MQL and semi-dry grinding can be achieved in point grinding process under less contact area and higher jet pressure condition for the high greenness demand.

Experimental Investigation on Dry Point Grinding Process Based on Green Manufacturing

Due to point contact cause, the point grinding process have the lower grinding power and heat to measure and the better cooling conditions. For green manufacturing, the point grinding process has the significance to reduce the consumption of grinding fluid and improve the ground surface integrity and the process greenness. This study analyzes the geometric configuration of the contact area between the wheel and the workpiece in point grinding process, establishes the geometric and mathematic models of the contact area, and investigates the relations between the grinding parameters. The dry point grinding experiments are performed on the ground surface integrity. These investigations show that the dry grinding can be achieved in point grinding process under less depth of cut and the higher grinding speed for the high machining greenness demand.