Terms Of Surface Integrity Research Articles

Role of the Calcified Cartilage Layer of an Integrated Trilayered Silk Fibroin Scaffold Used to Regenerate Osteochondral Defects in Rabbit Knees.

The repair of osteochondral defects remains challenging, given the complexity of native osteochondral tissue and the limited self-repair capacity of cartilage. Osteochondral tissue engineering is a promising strategy. Here, we fabricated a biomimetic osteochondral scaffold using silk fibroin and hydroxyapatite, including a calcified cartilage layer (CCL). We studied the role played by the CCL in terms of cell viability in vivo. We established osteochondral defects in rabbit knees to investigate the effects of CCL-containing scaffolds with or without adipose tissue-derived stem cells (ADSCs). We evaluated osteochondral tissue regeneration by calculating gross observational scores, via histological and immunohistochemical assessments, by performing quantitative biochemical and biomechanical analyses of new osteochondral tissue, and via microcomputed tomography of new bone at 4, 8, and 12 weeks after surgery. In terms of surface roughness and integrity, the CCL + ADSCs group was better than the CCL and the non-CCL + ADSCs groups at all time points tested; the glycosaminoglycan and collagen type II levels of the CCL + ADSCs group were highest, reflecting the important role played by the CCL in cartilage tissue repair. Subchondral bone smoothness was better in the CCL + ADSCs group than in the non-CCL + ADSCs and CCL groups. The CCL promoted smooth subchondral bone regeneration but did not obviously affect bone strength or quality. In conclusion, a biomimetic osteochondral scaffold with a CCL, combined with autologous ADSCs, satisfactorily regenerated a rabbit osteochondral defect. The CCL enhances cartilage and subchondral bone regeneration.

State of the Art on Laser Assisted Electrochemical Machining

Laser Assisted Electrochemical Machining (LAECM) has proven its advantages and applications over almost all the range of conductive materials. It offers its adroitness to generate simple shapes to complex shapes from macro to micro machining. Laser assisted ECM is a hybrid approach of machining which has been manifested to obtain improved results in terms of surface integrity, thermal damage, geometrical tolerance and material removal rate. Laser assisted Electrochemical Machining (LAECM) is a hybrid machining process in which laser enhances the electrochemical dissolution process by increasing the temperature and hence the current density of the electrolyte. Laser helps to remove material from the particular machining zone and stray machining effect is reduced and thus improves the precision and efficiency of LAECM, also productivity. New route of laser assisted hybrid machining processes has been built in the past decade by few of the researchers to reduce the intrinsic problems of ECM. This paper reviews on the investigation into LAECM process. The article also highlights various possibilities and applications of LAECM process. There are various challenges in LAECM process which have been also discussed in this paper.

Effects of Laser Fluence and Pulse Overlap on Machining of Microchannels in Alumina Ceramics Using an Nd:YAG Laser

The quality of micro-features in various technologies is mostly affected by the choice of the micro-fabrication technique, which in turn results in several limitations with regard to materials, productivity, and cost. Laser beam micro-machining has a distinct edge over other non-traditional methods in terms of material choices, precision, shape complexity, and surface integrity. This study investigates the effect of laser fluence and pulse overlap while developing microchannels in alumina ceramic using an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Microchannels 200 µm wide with different depths were machined using different laser peak fluence and pulse overlap (percentage of overlap between successive laser pulses) values. It was found that high pulse overlaps and fluences should be avoided as they give rise to V-shaped microchannels i.e., 100% bottom width errors. The optimal peak fluence range was found to be around 125–130 J/cm2 corresponding to 3–5 µm depth per scan. In addition, channels fabricated with moderate pulse overlap were found to be of good quality compared to low pulse overlaps.

Surface integrity of INCONEL 718 turned under cryogenic conditions at high cutting speeds

Nickel alloys such as Inconel 718 have been widely used in the aerospace, oil and gas, and chemical industries, since they have excellent properties that combine high creep resistance and high mechanical strength, fatigue and corrosion. However, these properties make these alloys extremely difficult to machine, due to a high level of heat generation during material removal, causing rapid wear of cutting tools and a detrimental effect on the surface integrity, reducing the fatigue life of the machined component and lowering the productivity. Looking at the literature, it seemed that there is an opportunity to study the surface integrity of Inconel 718, turned under cryogenic conditions at cutting speeds of 250, 275 and 300 m/min. For these reasons, this work aims to evaluate the influence of the cutting parameters on the surface integrity of Inconel 718 turned under cryogenic conditions using liquid nitrogen (LN2) at high cutting speeds. A whisker-reinforced ceramic tool was used in order to provide wear and shock resistance at high cutting speeds; these are factors that are associated with surface integrity in terms of roughness Ra, residual stresses, microhardness and cutting forces. A central composite design was chosen as factorial planning for the independent variables including cutting speed, feed rate and depth of cut when carrying out the experiments. Cryogenic cooling resulted in an average cutting force of 267 N, where the penetration force was higher. The roughness Ra was 0.52 μm and was influenced by the feed rate and depth of cut. The highest tensile residual stresses in the circumferential direction with LN2 and under dry conditions were 1394 MPa and 1237 MPa, respectively and were influenced by the depth of cut. Small changes in microhardness occurred at a depth of 0.3 mm from beneath machine surface and the presence of a white layer was not observed. Although tensile residual stresses were slightly higher when using LN2 compared to dry machining on the surface, the use of LN2 caused higher compressive residual stresses at the subsurface, which can improve the fatigue life of machined components at high cutting speeds. The results showed that lower cutting parameters tend to give the best results in terms of the cutting force and surface integrity.

On briefing the surface modifications of polylactic acid: A scope for betterment of biomedical structures

Polylactic acid (PLA) has been attributed as one of the most significant biodegradable polymers that hold great potential to replace petroleum-based polymers in the near future. This has motivated the chemists, surgeons, industrial engineers as well as research scholars to consider PLA and its copolymers for various biomedical applications including scaffolds, sutures in tissue engineering, and drug carrier vessel for delivery. However, the intrinsic limitations of the PLA in terms of surface integrity, cell adhesion, and degradation are restricting the practical implication at par with the required capabilities. Therefore, in the present review article, an attempt has been made to categorize the various posttreatment processes which can benefit the users to eliminate the existing barriers. Along with, the impacts of the various classes of posttreatment technologies, for PLA and its composites, have been summarized on the basis of outcomes. Overall, the review article will provide technical pathways for the betterment of PLA with practical insights.

New observations on built-up edge structures for improving machining performance during the cutting of superduplex stainless steel

Abstract This work features a comprehensive investigation of built-up edge (BUE) formation during machining of superduplex stainless steel (SDSS), grade UNS S32750. To visually investigate BUE formation during the machining test, a detailed examination of BUE structures obtained at different cutting speeds was performed. The BUE geometries were determined by scanning electron microscope (SEM) and 3D white light interferometry. In addition, various BUE adhesion patterns were analyzed through electron backscatter diffraction (EBSD) and nano-indentation methods. The examined BUE revealed a high level of grain refinement and elongation for both ferrite and austenite structures, as well as a tool protection effect at specific cutting speeds. Finally, the influence of BUE on the machining process in terms of chip formation and surface integrity was studied in detail. Considerable improvements could be made to the frictional conditions and workpiece surface integrity at low cutting speeds.

3D modeling of recrystallized layer depth and residual stress in dry machining of nickel-based alloy

Surface integrity is one of the important requirements of engineers, and it should be controlled for manufacturing of different components. Among different indications of surface integrity, metallurgical aspects including microstructure changes and residual stresses are remarkably effective on performance and service life of the products. Machining process of Inconel 718 alloy is widely used in advanced industries, and therefore, surface integrity of machined workpieces is essential task. Since experimental investigation in this subject is really difficult and time-consuming, finite element modeling of machining processes is used as beneficial method. In this paper, 3D analysis of machining process of Inconel 718 alloy was carried out to evaluate surface integrity in terms of depth of the recrystallized layer and residual stress. At first section, experimental tests were conducted at different machining process to use them as the benchmark for evaluation of recrystallized layer depth in machining simulation. Using the critical strain criterion, the numerical results of recrystallized layer depth was calculated and successfully verified with corresponding experiments. To improve precision of the numerical results, the user subroutine was implemented in FE code to employ hardness-based flow stress and also cutting tool geometry was precisely measured. At the second section, residual stress distribution in the machined surface was firstly predicted using the elastic–plastic analysis and verified with experimental test. After that, the effect of testing conditions was evaluated and discussed on different indications of residual stress profile. Finally, there is reasonable hope that utilized strategy can be extended efficiently for other manufacturing processes.

Heat Treatment and Lubrication Analysis of the Surface Integrity of Cold Extruded Metals

Cold forming is a process which is largely employed in industry. Thisprocess may have impacts on mechanical properties and surface integrity. This paper presents a study on Surface Integrity (SI) within the context of cold extruded billets with two different materials, steel and aluminium alloys. Different lubricant oils were used in this study, and heat treatment was employed after cold processing. Typical surface alterations such as micro-hardness and roughness were analysed, and a FEM analysis was used to predict the areas with increasing hardness. An analysis of test variance (ANOVA) was conducted, aiming to determine the influence factors of the experiments. Thus, influence factors like oil performance and extrusion load were investigated. The performance and influence of oils on cold extrusion processing for different materials were analysed. Due to the effects of lubricants on surface integrity in terms of hardness and roughness, a comparison was given with projections forsubstituting mineral oils for vegetable oils without losing functional performance.

Experimental and numerical analysis of roller burnishing of Waspaloy

Abstract Nickel based superalloys, such as Waspaloy , are extensively used for applications under heavy environmental conditions due to their superior thermo-mechanical properties. However, manufacturing processes of these materials are challenging since they involve issues related to their poor workability. Thus, huge research work for optimizing the processing parameters is still required. This problem becomes even more pronounced when finishing processes, such as roller burnishing, are considered. In fact, it is crucial to use parameters able to increase the productivity and to improve the quality of the manufactured parts, consequently a huge number of preliminary experimental tests have to be carried out. Hence, numerical simulation can be a valid support for obtaining information about the metallurgical phenomena that affect the materials while large strains occur. However, commercial software are not still able to appropriately predict such modifications. Thus, the main objective of the present work is to study a roller burnishing on Waspaloy in terms of processing parameters and surface integrity by experimental and numerical analysis, in terms of forces, temperatures, roughness, microstructural modification and microhardness. Thus, the customized simulation demonstrated to provide useful information able to drastically reduce the number of needed tests leading also to a deeper knowledge of the microscopic phenomena involved in the process.

Evaluation of surface integrity after high energy machining with EDM, laser beam machining and abrasive water jet machining of alloy 718

Development of future aero engine components based on new design strategies utilising topological optimisation and additive manufacturing has in the past years become a reality. This allows for designs that involve geometries of “free form” surfaces and material combinations that could be difficult to machine using conventional milling. Hence, alternative manufacturing routes using non-conventional high energy methods are interesting to explore. In this investigation, the three high energy machining methods abrasive water jet machining (AWJM), electrical discharge machining (EDM) and laser beam machining (LBM) have been compared in terms of surface integrity to the reference, a ball nosed end milled surface. The results showed great influence on the surface integrity from the different machining methods. It was concluded that AWJM resulted in the highest quality regarding surface integrity properties with compressive residual stresses in the surface region and a low surface roughness with texture from the abrasive erosion. Further, it was shown that EDM resulted in shallow tensile residual stresses in the surface and an isotropic surface texture with higher surface roughness. However, even though both methods could be considered as possible alternatives to conventional milling they require post processing. The reason is that the surfaces need to be cleaned from either abrasive medium from AWJM or recast layer from EDM. It was further concluded that LBM should not be considered as an alternative in this case due to the deep detrimental impact from the machining process.

Elastic and plastic chip deformation mechanism in 1D vibration-assisted metal cutting

Both 1D and 2D vibration-assisted machining (VAM) are able to improve the cutting performance in micro cutting in terms of surface integrity, cutting force and tool wear. In 2D VAM, it has already been concluded that a lower nominal cutting speed or a smaller speed ratio will lead to a decreased chip compression ratio (CCR) due to the introduction of more reversed friction. However, in 1D VAM, the effect of speed ratio on the CCR has not been systematically studied yet. In this study, a low-frequency 1D VAM test is firstly conducted to understand the instantaneous chip deformation status and tool-chip contact condition in a vibration cycle, which is then broken into five elastic and plastic categories based on the measured force ratio and relative tool positions. Furthermore, ultrasonic 1D VAM tests are also conducted to evaluate the effect of speed ratio on the chip formation and the variation of CCR.

Influence of surface integrity on the plastic flow in analogous testing of 42CrMo4

Surface modification of workpieces for cold forming processes is common in industrial practice. Specific surface topographies manufactured by means of shot peening form lubricant pockets, which provide a continuous lubricating film throughout the process. Furthermore, hydrostatic as well as hydrodynamic lubrication effects emerge, which further reduce the friction during the process and protect the tool from wear effects. These effects are well researched and applied in order to enable cold forming processes. In dry forming processes, no lubricants are used, and the positive lubrication effects do not appear. Surface modifications by shot peening or knurling change surface integrity in terms of hardness, residual stresses and geometry. The effects of the changed surface integrity on the forming process are not researched. In tribometer tests, a hard and rough surface texture lead to a lower frictional shear stress, whereas a rather smooth and hard surface texture leads to a lower punch force in an extrusion process. The mechanisms between surface textures and the smoothing and forming process are unknown. Furthermore, findings of the tribometer tests cannot be fully transferred to the extrusion process. As in tribometer tests a pin is used as tool and in extrusion a whole die, a discrepancy between the most suitable surface texture for a friction reduction results out of different flow conditions. Still, the tribometer tests give a first reference on a surface pretreament. The paper deals with an investigation of surface textures in order to distinguish characteristics of surface textures respectively a friction reduction. By means of indentation tests of the quenched and tempered steel 42CrMo4 the plastic flow in dependency of different surface integrities are researched. The results show which characteristics help to lower the punch force the most, so for further investigations an optimized surface modification is set up in order to enable a dry metal forming process.

The effects of cutting conditions on cutting temperature and hole quality in drilling of Inconel 718 using solid carbide drills

In this study, the drillability of Inconel 718 has been experimentally investigated under dry, wet, and cryogenic conditions. Drilling tests have been performed at a cutting speed of 15 m/min and a feed of 0.02 mm/rev using TiAlN coated and uncoated solid carbide drills. The effects of cooling/lubrication conditions and coating material on drillability of Inconel 718 are evaluated in terms of thrust force, torque, cutting temperature, hole quality, and tool wear. Experimental results show that cooling/lubrication conditions have significant effects on all performance criteria. Cryogenic cooling significantly reduces the cutting temperatures. Generally, cryogenic drilling exhibits better performance in terms of hole quality and surface integrity. However, it is found that cryogenic conditions increase the thrust force and significantly reduce the tool life due to excessive chippings. Good surface roughness and tool life are achieved under wet conditions. In addition, the use of the coating material also reduces the tool wear dramatically.

Performance of Diamond and Silicon Carbide Wheels on Grinding of Bioceramic Material Under Minimum Quantity Lubrication Condition

Advanced ceramic materials like sintered and presintered zirconia are frequently used in biomedical applications, where minimum quantity lubrication (MQL) assisted grinding is required to achieve a good surface finish instead of conventional flood coolant. However, insufficient cooling and wheel clogging are the major problems that exist in the MQL grinding process, which depends upon the type of work piece material and the grinding wheel being used. The present study is to determine the performance of the grinding wheels on presintered zirconia under MQL conditions in terms of grinding forces, specific energy, surface integrity, and wheel wear. Experiments are conducted with two different types of grinding wheels as silicon carbide (SiC) and diamond grinding wheels under the same condition. The results indicated that the diamond wheel provided a better surface finish and reduced tangential force under MQL condition, compared to the conventional SIC wheel. This was due to the reduction of wheel loading in the diamond grinding wheel. The specific energy of diamond grinding wheel was reduced with higher material removal rate compared to the conventional SiC wheel. The ground surfaces generated by the diamond grinding wheel showed fine grinding marks with better surface finish. The percentage of G-ratio calculated for the diamond wheel was higher than the SiC wheel by 77%. This was due to the sliding of the grains and less wheel loading in the diamond wheel. The cost difference between the corresponding wheels was discussed to improve the productivity of the grinding process.

Characterization of material removal in ultrasonically assisted grinding of SiCp/Al with high volume fraction

Due to the significant difference between the reinforcement grains and matrix phase, the machining of SiC particle-reinforced aluminum composites (SiCp/Al) is difficult and costly, especially for SiCp/Al with volume fraction higher than 50%. Ultrasonically assisted grinding (UAG), which has unique advantages in the machining of both ductile and brittle materials, is a promising solution of the machining of SiCp/Al. This study conducts both UAG and conventional grinding (CG) process on SiCp/Al with an electroplated diamond wheel. The study explores material removal mechanisms involved in UAG in comparison to that in the CG. It also investigates grinding forces, surface integrity, subsurface damage, and wheel wear. The study finds that material removal in grinding of SiCp/Al is dominated by SiC particle fracture that is induced in the grinding process. The ground workpiece is smeared with an aluminum layer, making it difficult to evaluate surface integrity. Compared with CG, UAG of SiCp/Al results in similar surface integrity in terms of surface roughness and subsurface damage, but a much lower grinding force (35–50% lower).

Performance improvement of eco-friendly MQL technique by using hybrid nanofluid and ultrasonic-assisted grinding

MQL technique has many technological and economic advantages in grinding operation. It can improve grinding performance in terms of surface integrity, grinding forces and G-ratio. On the other hand, MQL is eco-friendly technique because of its small consumption of cutting fluid. Despite these advantages, MQL technique has a serious thermal problem in grinding operations due to a small amount of cooling. Nanofluids can increase heat transfer from workpiece/wheel interface due to its high thermal conductivity. On the other hand, ultrasonic machining can decrease heat generation due to its reciprocating mechanism and reduction of time and length of contact between grain and workpiece. So, it is anticipated that simultaneous utilization of these techniques can reduce thermal damages. In this research MWCNT, Al2O3 and hybrid MWCNT/Al2O3 nanofluid oil mists have been utilized in ultrasonic assisted grinding. MWCNT has high thermal conductivity and Al2O3 has good lubrication effect. Output parameters were maximum temperature, grinding forces and friction coefficient. The results revealed that combination of MQL and UAG decrease of maximum grinding temperature up to 56.3% in comparison to dry grinding (from 254 to 111 °C). Moreover, tangential and normal grinding forces and friction coefficient have been reduced up to 61.5, 47.1, and 27.3%, respectively. Moreover, shiny surface without any thermal damages and burning obtained in comparison to dark and burned surface in dry grinding.

Surface integrity in tangential turning of hybrid MMC A359/B4C/Al2O3 by abrasive waterjet

This paper deals with the abrasive waterjet turning of newly developed hybrid MMC A359/B4C/Al2O3 produced by electromagnetic stir casting. The justification of the fabrication was revealed by microstructural images and x-ray diffraction results. The main aim of the study is to analyse the machining behaviour of produced hybrid MMC under abrasive waterjet turning. The surfaces created at different traverse speed were discussed in terms of surface integrity and surface texture. Optical profilometer was used to generate surface roughness report and 3D visualization of the machined surface. Olympus LEXT OLS 3100 laser confocal microscope was used to collect 2D and 3D surface topographical details of the machined surface. Surface morphology was discussed by FE-SEM images to evaluate surface defects. Residual stresses and microhardness test through the depth profile were also carried out to analyse the machined surface and subsurface. It has been found a perfectly round, slightly undulated surface which shows ploughing nature. The results also reveal the higher rate of material removal with rough cutting.

Influence of the heat treatment on the microstructure and machinability of titanium aluminides produced by electron beam melting

Additive manufacturing (AM) has been emerging as a promising fabrication technology for polymers and metal products. This technology is able to fabricate complex shape components with high geometrical freedom and allows to reduce the overall waste material, as the powder can be recycled several times, and time from drawing to production can be consistently reduced. In the case of materials for aerospace applications, like TiAl alloys, conventional machining is needed to obtain the required surface finish. The machinability is strongly dependent on the specific alloys and on the production technology used, leading to different microstructures, that can be tuned undergoing the alloys to several treatments after the AM process. The paper focus on the effect of post processing treatment on hardness, structural properties and machinability of Ti48Al2Nb2Cr obtained by electron beam melting process. Untreated and heat treated alloys were considered. Turning tests were carried out under dry conditions by using cemented carbides cutting tools coated with TiCN-Al2O3-TiN. The structure, microstructure and hardness of the material were studied and related to machinability, that was evaluated in terms of tool life and surface integrity, focusing on both surface and sub-surface alterations. Tool wear, cutting forces, chip morphology and surface roughness were also analyzed. Adhesion prevailed on abrasion as main wear phenomenon, leading to cutting edge breaking. Results indicated a higher machinability of the alloys that underwent post processing treatment because of the different microstructure and crystalline phases induced. Indeed, α2 and β phases present in heat treated material enhanced the formation of built up edge, acting as protective layer and then slowing down the degradation phenomena. Also the lower porosity leaded to a lower diffusion phenomenon, positively affecting the tool life.

Novel design and characterisation of surface modification in wire electrical discharge machining using assisting electrodes

Electrode and dielectric materials have been extensively studied for surface modification using traditional electrical discharge machining and wire electrical discharge machining (WEDM). This paper develops a new WEDM surface modification process with assisting electrodes arranged in a stack order and target workpiece material which transfers the preferred alloy elements to the target surface. The process involves material migration from the upper and lower stack electrode materials to the sandwiched workpiece material when the wire reciprocally moves in the vertical direction at a proper feed rate. The designs of the machine tool and of the function of the discharge circuit are reported in detail. Experiments using statistical methods in fractional factorial (Taguchi L9) and full factorial (4×3×3) are performed to identify the dominant factors for the developed surface alloying process. The effectiveness of the element transfer was verified with optimal parameters, such as the hardness of the workpiece material, the thickness of the sandwiched electrode materials, gap voltage, peak current, pulse on-time, pressure, and the flow rate of the dielectrics and flushing strategies. The surface integrity in terms of roughness, micro-hardness and the associated microstructure is also investigated to advance understanding of the underlying mechanism of the WEDM surface alloying.

A novel approach of high-performance grinding using developed diamond wheels

A novel approach of high-performance grinding is proposed using developed diamond wheels, to obtain minimally damaged surface layer in silicon wafers. For this reason, resin bond diamond wheels are specifically developed with lanthanum oxide (La2O3), magnesium oxide (MgO), and ceria (CeO2) as additives, respectively. The wheels contain grains with a mesh number of 20,000 and a volume fraction of diamond grains of 37.5%. The diamond wheel with ceria additives demonstrates the best grinding performance in terms of surface integrity and roughness. It allows to generate an amorphous surface layer of 43 nm in thickness, without grinding damage beneath in a silicon wafer. This is different from previous reports, in which an amorphous layer is at the top, followed by a damaged crystalline layer underneath induced by a diamond wheel. Below the amorphous layer is the pristine crystalline lattice, which is confirmed using the high-resolution transmission electron microscopy (HRTEM). The ceria wheel results in a surface roughness R a of 0.88 nm and a peak-to-valley (PV) value of 8.3 nm over an area of 70 × 50 μm2 on a Si wafer at a feed rate of 15 μm/min.