Surface Quality Characteristics Research Articles

Dimensioning of the Clearance as a Means of Avoiding Burr and Film Formation during the Punching of PC/ABS Cable Ducts

The production of staple articles such as cable ducts offers reductions in resource and production energy consumption if the process is optimized. Side recesses made of polyvinyl chloride (PVC) have already been punched successfully as one of the process steps during the production of cable ducts. However, punching cable ducts made of flame-retardant polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) is challenging because increased burr and film formation occurs. This study introduces the correct dimensioning of the clearance as a means of reducing the burr and film formation and presents the ideal clearance dimensions. This new process design approach comprises the dimensioning of the clearance and its subsequent successful application. Tools with clearances in the relevant size range were purchased and examined by means of punching tests. The punch-outs were evaluated regarding the quality characteristics, such as the burr, film, cut surface quality, shear droop, and plastic flow characteristics. Excerpts from high-speed recordings were used to assess the punch-outs qualitatively. The burr formation is significantly decreased by the use of a correctly dimensioned clearance, allowing for the crack initiated at the punch side and the crack initiated at the die side to meet perfectly. It is assumed that film formation can be avoided via a significant reduction in the friction or heat input during the punching process.

Enhancing the Surface Quality of FDM Processed Flapping Wing Micro Mechanism Assembly through RSM–TOPSIS Hybrid Approach

Improving surface quality attributes is a critical task in the production of micro-sized near-net-shaped components for end-use applications using additive manufacturing techniques. In the present study, we investigated the effect of fused deposition modeling (FDM) process parameters such as layer thickness, part orientation, raster width and raster angle on the surface quality characteristics of as-fabricated test specimens in order to develop the assembly of a flapping wing micro mechanism. Through a Box–Behnken design, a suitable experimental strategy was developed, and test specimens were manufactured. The performance of the experiments was statistically assessed using multi-response analysis of variance (ANOVA). The microstructures of the test specimens produced with various processing parameters were examined using a scanning electron microscope to identify micro surface flaws under various processing conditions. Furthermore, the optimal FDM parameters for improved surface quality attributes such as Ra, Rz and Rq were obtained using a statistical optimization technique known as Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS).

Effect of Heat Treatment on the Resulting Dimensional Characteristics of the C45 Carbon Steel after Turning

The presented article deals with the influence of the heat treatment of C45 steel on the surface quality after turning. Turning is a machining technology used to prepare specific geometrical characteristics of surface and dimensional quality. In the present paper, the same turning conditions were used for the turning treatment of differently heat-treated steels. The soft annealed state, normalized state, hardened state, quenched and tempered at 530 °C state and quenched and tempered at 660 °C state have been analyzed. By using this approach, it has been possible to evaluate the effects of hardening and machining on the resulting parameters after turning (roughness, cylindricity and circularity). The highest hardness was observed in the steel after the hardening process (694 ± 9 HV 10). The hardening has negatively influenced the surface quality. The high hardness was related to martensite formation and caused a damage to the cutting edge of the cut insert used, leading to a significant change in geometrical accuracy. The cylindricity change achieved 0.15 ± 0.03 mm which was significantly higher compared to the theoretical value of the diameter of the machined steel bar. An inaccuracy was also observed in diameter dimension. These inaccuracies were caused by the wear of the cutting edge of the tool used in cutting parameters setting.

THE NEW IMPLEMENTATION METHODS MANAGEMENT MECHANICAL CUTTING AND VIBRO PROCESS

The problem of ensuring the required quality and operation of the properties of machine parts is becoming increasingly important in mechanical engineering. However, to date, no generalized theoretical relationships between surface quality parameters, machining accuracy, performance properties of parts and parameters of machining processes, which allow to solve the problem of technological support of the specified performance properties of parts. The control of the surface formation process with the required properties is carried out mainly by using partial experimental dependences and tables of processing modes. The complexity of the problem is that when machining parts it is necessary to establish such processing conditions that would provide a set of requirements for tool wear, machining accuracy, surface quality characteristics, productivity and more. Working machines of special and general purpose, their separate knots and mechanisms are constantly improved, thus increase of a technical level of machines is carried out by introduction of new technical decisions, use of modern technologies and scientific developments. The experience of development and operation of mechanisms of parallel kinematics confirms their high efficiency and prospects of this direction of mechanical engineering. Due to the design features of the layout, the mechanisms of parallel kinematics have closed kinematic chains that form spatial structures. As a rule, these structures are based on triangular rod systems. They have high rigidity characteristics, provide high speeds and acceleration of working bodies. Accordingly, these capabilities can significantly increase the static and dynamic accuracy of positioning mechanisms. The lack of theoretical foundations for the development of mechanisms, in particular high-precision mechanisms, hinders the widespread introduction of parallel kinematics mechanisms. Improving accuracy requires a comprehensive study of kinematics and work processes, taking place in their main nodes. Therefore, studies aimed at improving the parameters of static and dynamic accuracy of spatial mechanisms of parallel kinematics are relevant.

Performance of grinding nickel-based single crystal superalloy: Effect of crystallographic orientations and cooling-lubrication modes

High-strength and high-temperature resistant nickel-based single crystal (SX) superalloys are employed as a key material system for improving aeroengine component performance. Nevertheless, uncertainties associated with crystallographic anisotropy and the effects of different cooling-lubrication modes introduced during grinding nickel-based SX superalloys complicate the assessment of preformation. Therefore, understanding of performance induced by crystallographic anisotropy and cooling-lubrication modes when grinding nickel-based SX superalloys is a crucial for achieving high component quality. This work assessed the wear characteristics of CBN abrasive tools, surface quality and subsurface morphology when grinding nickel-based SX superalloys in different crystallographic orientations and dry, flood and Minimum Quality Lubrication-palm oil (MQL-PO) modes. The yield strength model with orientation dependence for nickel-based SX superalloy was developed to support for further understanding the anisotropy in grinding forces. Results show that the wear level of CBN abrasive tools is independent on crystallographic orientations. CBN abrasive tools applied different cooling-lubrication modes exhibit specific characteristics in grinding process, such as microchip-deposits – dry grinding; wedge-shaped cracks – flood grinding; oil-film with lubricity – MQL-PO. With crystallographic orientations from the 0° to the 45° orientation and the 45° to the 90° orientation, the trend for predicted values by the yield strength model and for experimental tangential forces both present deceased at first and then increased.

Tolerancing the laser powder bed fusion process based on machine capability measures with the aim of process control

Metal Additive Manufacturing evolves steadily towards industrialization. Laser Powder Bed Fusion (L-PBF) is a commonly used process to manufacture near net-shape metallic parts with high densities. Industrial usability requires high standards of reproducibility, which are defined by capability measures of machines and processes. Meeting the flexibility of Additive Manufacturing (AM) and aiming for mass customization, AM processes have to be under full control and must fulfill all standards.This study discusses a reverse machine capability approach with the goal of calculating achievable tolerance bands by the means of six sigma. Crucial technical part properties such as surface quality characteristics are evaluated in correspondence to the newly developed formalism. After that warning limits and intervention limits are defined and joined into a process control chart with raw data and distribution charts. The presented formalism in conjunction with surface quality characteristics helps designers to identify post-processing requirements, choose post-processing techniques and set oversizes of parts.

Surface quality characterization of thin Nb films for superconducting radiofrequency cavities

Superconducting radiofrequency (SRF) cavities are vital components of particle accelerators nowadays. In order to minimise the energy dissipation, a perfect inner surface of the cavity, hindering the penetration of magnetic field, is required. In this work, we investigated ten planar samples differing in the surface quality of Nb film deposited on Cu substrate, and as a consequence exhibiting various levels of the first entry field, H en, at which the magnetic field starts to enter the film. The observed surface defects are categorised as hills, pits and cracks. For a practical range of dimensions of these features, the factor β, characterising the local magnetic field enhancement, was calculated by the numerical finite-element simulations. It is expected that the local field enhancement causes a premature penetration of the magnetic field, thus lowering H en. Then, for each investigated sample, the range of β values characterising defect type that cause the highest field enhancement, is identified and compared with the H en fields. We have found that the H en of the samples that contain multiple types of the surface features is indeed limited by those defects that cause the highest field enhancement. The H en vs β dependence has shown a good match with linear fit for the set of investigated samples. Thus, the main result is that the local magnetic field enhancement, computed in a straightforward way for the most significant defects, is a strong indicator of the surface quality that is relevant for the superconducting film intended for SRF cavity application.

An experimental investigations on effects of cooling/lubrication conditions in micro milling of additively manufactured Inconel 718

The demand for additive manufacturing (AM) technology is recently increased in the aerospace, biomedical, and automobile sectors due to the capability of producing complex components with zero tolerance. However, the small or precise part manufactured by AM process needs post-processing such as machining, polishing, etc. because of the poor surface quality characteristics. Therefore, in this paper, the micro-milling was performed on additively manufactured Inconel-718 alloy under different sustainable cooling conditions. The tool wear, surface roughness, and burr generated during micro-milling experiments were investigated under the effect of air, minimum quantity lubrication (MQL), and flood cooling conditions. The results demonstrated that the MQL conditions provide the proper cooling and lubrication effect, and this results in improved tool life (which is almost 45% higher compared to dry conditions. MQL also improved the product quality in terms of surface roughness (almost 65% less surface roughness). Other machining characteristics, such as burr width and cutting forces, were also improved in MQL and flood environments. However, it was noticed that milling with a chilled air environment has not given any significant improvement in terms of machining characteristics.

Investigation of surface quality, microstructure, deformation mechanism, and fatigue performance of additively manufactured 304L stainless steel using grinding

Ground 304L stainless steel (SS) made by laser powder bed fusion (LPBF) process was comprehensively investigated from the aspects of surface integrity, residual stress, microstructure, and mechanical properties. The experimental results indicated that grinding substantially improved the surface quality characteristics and significantly increased the fatigue life by more than two times. The removal of LoF (Lack of fusion) defects and keyholes near the as-built surface plays a critical role in improving fatigue performance due to the enhancement of fatigue crack initiation resistance. In addition, the ground subsurface cracks and newly formed lath-like grains were discovered in ground LPBF 304L SS, and their formation mechanisms were discussed with the aid of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). This work brings new insights into the underlying principles of improving the mechanical properties of LPBF metallic materials through high-efficiency grinding.

A Note on the Change in the Surface Quality Characteristics during Flat Grinding of Titanium Intermetallic with Shape Memory Effect

Ti-based intermetallic compounds are characterized by low machinability, therefore, to obtain accurate dimensions and shape of the surface grinding and Wire EDM are used. The unique properties of NiTi intermetallic alloys are largely influenced by structural phase transformations and variations in microhardness caused by processing accompanied by thermal phenomena. Having an understanding of the physics of the process, it is possible to counteract negative effects, which helps to preserve thermomechanical properties of the final NiTi products. Accumulation of knowledge about the quality of processing with various abrasive tools is part of the larger research presented in this article. Samples of titanium nickelide with a temperature Af=+25 0С were abraded with ordinary and high porosity SiC wheels. The article studied phase transformations using X-ray diffraction analysis and microhardness. The experimental data were processed using mathematical statistics. X-ray diffraction patterns and microhardness analysis showed that a significant effect on the structural transformation and corresponding increase in microhardness is exerted by grinding with green SiC wheels with normal porosity caused by an increased thermal effect on the surface. Simultaneously, the impact of Wire EDM process on microhardness in preparing workpieces for grinding was evaluated. It was established that grinding of Ti-based intermetallic compounds with memory effect should be performed by SiC wheels with an open structure of high porosity.

Three dimensional shape model of TiBw mesh reinforced titanium matrix composites in rotary ultrasonic grinding

TiBw mesh reinforced titanium matrix composites have excellent mechanical properties and high temperature properties, which have a wide application prospect in aerospace and other fields. However, the material processing has the characteristics of poor surface quality and unstable processing. In order to solve these problems, Rotary ultrasonic grinding was carried out on machining titanium matrix composites in this paper. A surface topography model for rotary ultrasonic face grinding of titanium matrix composites was analyzed, in which the effects of the shape of the cut section of the abrasive grain, the plastic deformation of the material, and whiskers were considered to analyze the formation mechanism of the surface of titanium matrix composites machined by rotary ultrasonic machining. The reliability of the model is verified by comparing the simulated topography with the actual topography through grinding experiments.

Effect of fine particle peening on surface integrity of flexspline in harmonic drive

High-performance precision gear drives such as harmonic gear have high requirements on tooth profile accuracy, surface quality, fatigue life and other service performance characteristics, which urgently needs an effective surface strengthening method. This work aims to examine the feasibility and effectiveness of fine particle peening (FPP) treatment on surface integrity of flexspline in harmonic drive precision transmission. To this end, FPP process experiments were carried out, and this process was simulated based on a coupling method of discrete element method and finite element method (DEM-FEM) considering the kinematic hardening behavior of the material. The simulation results were in good agreement with the test results. Effects of shot peening pressure, injection velocity, material properties and tooth profile on surface roughness and induced residual stress of the target flexspline were analyzed. The results reveal that after FPP, the amplitude of residual compressive stress of the flexspline can reach 470 MPa, and the surface roughness Sa becomes approximately 0.5 μm. For precision gears with low hardness such as flexspline in harmonic drive, it is suggested to adopt FPP with low air pressure to achieve both saturated residual compressive stress and lower surface roughness, thus benefitting enhanced fatigue life.

Influence of the dynamic disc grinding wheel displacement on surface generation

Different from the general grinding process, the disc grinding quality varies with the part position due to the complicated abrasive removal. Based on the main shaft system dynamic-static characteristic, the work aims to study the disc grinding surface generation mechanism. The element deformation model on dynamic-static characteristic is established. Afterwards, based on the abrasive position and the size information, the three dimensional abrasive trajectory equation is built. The profile search method is applied to analyze the dynamic-static surface generation process of disc grinding material. Combined with the corresponding disc grinding experiment, the influence regulation of the system dynamic-static characteristic on machining surface waviness and surface roughness is investigated. The essence of the uneven machining effect on grinding surface is explained. It shows that the static deformation at the faraway position of the workpiece center is relatively larger than that at the nearby workpiece center. However, the difference of the dynamic vibration is relatively smaller. It can be concluded that the static characteristic is a key factor to influence the disc grinding surface waviness, and disc grinding surface roughness is controlled by the system dynamic-static characteristic. The findings can not only give an in-depth comprehending in disc grinding surface generation mechanism, but also give a parametric controllable measure for improving the machining surface quality characterization.

Influence of different build orientation and laser scan strategies on surface quality, Mechanical and Material Characteristics of 18 Ni-300 maraging steel processed through DMLS

ABSTRACT Direct metal laser sintering (DMLS) is a method used to fabricate metal parts through laser sintering. In this research, experiments are designed to study how scanning patterns and build orientation affect the properties of printed maraging steel (MS1) parts. The mechanical and physical properties of DMLS manufactured parts depend primarily on the building direction and scanning strategies. Three different scanning patterns and build orientations were adopted in this research. Tensile, hardness, the surface roughness of DMLS parts were studied and almost entirely dense under different orientations and strategies and generally higher in horizontal orientation with cross-directional strategy because of thermal history variation. The Uniaxial tensile test findings exhibit that MS has significant anisotropic tensile characteristics, dependent on the specimen orientation and scan strategy. Despite the scanning strategy utilised, the vertical orientation produced the lowest mechanical performances of MS1 parts in terms of strength values recorded compared to all other orientations. Microstructural characterisation is carried out on a sample by using a scanning electron microscope (SEM) and optical microscope (OM) to analyse the fractured surface defects and pores, and X-ray diffraction (XRD) is used to determine the phase transformations. Understanding the impact of various build orientations in tensile, hardness, Surface quality shall enable the manufacturer to use the DMLS process to produce higher-quality MS1 parts.

Chemical characteristics of surface and phreatic water and their effects on the growth of Populus euphartica Oliv. in desert areas of Tarim National Nature Reserve, China

Chemical characteristics of surface water and phreatic water and their relationship with the growth of Populus euphratica Oliv. were explored. In the study area, hydrochemical types of the surface water were mainly SCaⅢ or ClNaⅢ (Based on the O. A. Arliekin's classification) and PH value of the surface water was below 8.0. The surface water from various sampling sites has a higher total hardness belonging to hard water and extremely hard water. The contents of sulfates and chlorides in the surface water in the protection zone ranged from 204.1 to 486.3 mg/l and from 70.9 to 239.9 mg/l, respectively. Phreatic water is mainly recharged by the surface water infiltration. In terms of water quality, TDS, total hardness and total alkalinity of phreatic water at W2 sampling point were 17.3, 9.3 and 4.7 times of surface water, respectively. Populus euphratica was able to grow normally in the environment of brackish water, where total hardness, total alkalinity, and TDS of overflowing river were in the range of 325.3~769.5, 142.6~290.3 and 782.2~1037.5 mg/l, respectively. The Populus euphratica in juvenile phase was a few, and its rejuvenation was confronted with difficulty. The present study can provide a reference for exploring the water quality characteristics of surface and phreatic water and their relationship with the growth of Populus euphratica. Bangladesh J. Bot. 50(3): 831-836, 2021 (September) Special

Sources and fate of excessive ammonium in the Quaternary sediments on the Dongting Plain, China

Excessive ammonia-nitrogen (N) in aquifers has caused groundwater pollution on the Dongting Plain (DTP), which seriously threatens the safety of drinking water. It is urgent and necessary to determine the sources and enrichment mechanisms of ammonia-N in groundwater. Carrying out water and soil collaborative research on a three-dimensional scale can more comprehensively analyze the sources of N, including natural and anthropogenic sources. In this study, surface and groundwater quality characteristics were examined from a total of 77 sites on the DTP. Two subsequent boreholes were drilled in the high ammonia concentration area and normal groundwater area, respectively, to compare the effects of anthropogenic activities. Indicators from hydrogeochemical and pedogeochemical analyses, as well as various isotopes, including δ15N-NH4+, δ15N-TON, δ15N-NO3−, δ18O-NO3−, δ18O-H2O, δD-H2O, and δ13C-TOC were used to identify ammonium sources and transformation mechanisms in the strata. We found that the sediments were contaminated by manure and sewage in the aquifers, and part of the shallow groundwater was additionally contaminated by nitrogen fertilizers. Excessive ammonium-N was also detected in the deep aquitards and sediments, which were mainly dominated by mineralization. Ammonia oxidation (with weak hydroxylamine oxidation) is an important biogeochemical process in which ammonia and nitrate do not accumulate in oxidizing groundwater environments. However, heterotrophic nitrification (HN) and anaerobic ammonium oxidation (ANAMMOX) are the release mechanisms for excessive ammonium-N under reducing conditions. In addition, organic matter (OM) on the DTP had a wide range of biogeochemical proxies generated by phytoplankton within a lake, and the comparatively resilient terrestrial organic residues washed in from the surrounding terrestrial area. This study breaks through the conventional mechanisms for the release of excessive ammonium from sediments to aquifers, which provides new ideas for research on ammonium in sediments and ammonia in groundwater.

Investigations on the influence of particle reinforcement and wire materials on the surface quality and machining characteristics of AA6061-TiB2 alloy in WEDM

In this research, the significance of particle reinforcement and the effect of wire materials on machining of AA6061-TiB2 composite by Wire Electrical Discharge Machining (WEDM) was investigated. Stir cast AA6061–TiB2 (varying 5, 10, and 15 wt.%) was used as the work material for this present study owing to its superior mechanical properties and profound applications. WEDM is the most viable cutting process to produce intricate shapes and sharp corners with good surface texture. Taguchi methodology was used to conduct the experiments. Phase constituents of the work material were observed using XRD analysis. The results revealed that aluminium and titanium diboride are the major phase constituents without any reaction phases. Metallographic analysis was conducted to figure out the erosion mechanism and crater formation during spark discharge. The experimentation reveals that the percentage of particle reinforcement was the dominating factor in surface quality (62.04%) and machinability (34.2%). The TiB2 (5 wt.%) reinforced composite exhibits excellent machinability and surface quality. Furthermore, in terms of machining rate, zinc-coated brass wire performs better than plain brass wire. Contrastingly, plain brass wire exhibits superior surface quality. In addition to that multi-objective optimization was performed using desirability analysis to achieve higher material removal rate and lower surface roughness. After the confirmation test, it is seen that the experimental values are in close agreement with the estimated values.

Investigation of the Micro Hardness at the Cut Surface of Fine Blanked Parts with Variation of Sheet Material and Cutting Temperature

Fine blanking is a production technology of high importance especially for the automotive industry. As a procedure of sheet metal separation, it is possible to produce complex parts in a single stroke. As a difference to conventional punching, the cutting surface of fine blanked parts can often be used as a functional surface without further process steps. However, fine blanking as a forming process changes the microstructure of the metal sheet to a higher extend than cutting or machining processes. Due to this, it is of utmost importance to investigate the cause-effect-relations between the fine blanking process parameters and the resulting properties of the fine blanked part. Especially the condition of the cut surface as an important quality criterion has to be investigated. The quality characteristics of the cut surface of fine blanked parts are often subject of investigations. In addition, it would be of importance to investigate how the material properties in the shear zone are changed by the fine blanking process. This on one hand in turn can enable conclusions to be drawn about possible punch wear. If, on the other hand, hardening of the cut surface takes place as a result of fine blanking, then this could have a positive influence on the application properties of fine blanked components. Thus, an experimental fine blanking investigation of the micro hardness of the cutting surface has been made with variation of steel material and cutting temperature. It could be demonstrated that the micro hardness increases in direction towards the burr. This is independent on material and cutting temperature.

Multi-objective optimization of steel AISI 1040 dry turning using genetic algorithm

This study investigated the AISI 1040 steel turning in dry environment with four cutting inserts of different corner radii coated by CVD method. Experimental investigations were performed for different levels of cutting speeds, feeds and depths of cut using a randomized full factorial design. Quality characteristics of the workpiece machined surface were measured (arithmetical mean roughness) as well as the cutting inserts tool life characteristics (average width of flank wear). Machining times and chip volume were calculated, and based on this, chip quantity in time (material removal rate). The response surface approach and analysis of variance were used to determine the effects of input process parameters on the response variables. Based on the derived regression models, multi-objective optimization of output process parameters was performed using genetic algorithm. The objective function was simultaneous minimization of flank wear, minimization of surface roughness and maximization of material removal rate. The parameters of the genetic algorithm (crossover ratio, crossover fraction, mutation rate, Pareto front population fraction) were varied to obtain the optimal values of the objective function. Additionally, a sensitivity analysis was performed, which showed that the selected values of genetic algorithm parameters gave the best (minimum) value of objective function. Instead of the usual approach of obtaining only one combination of optimal parameters as a final solution, the basic idea was to obtain multiple combinations of optimal input process parameters depending on the importance of each output process parameter, i.e. requirements of production. Accordingly, the results of multi-objective optimization showed that there are a large number of Pareto optimal solutions. To validate the optimal input and output process values, confirmation experiments were conducted for selected trials of Pareto optimal results obtained from multi-objective optimization. A mean error percentage of 1.478% and 1.146% for flank wear and arithmetical mean roughness, respectively, proves that the predicted optimum values are confirmed by experimental results.

An investigation of surface quality characteristics of 3D printed PLA plates cut by CO2 laser using experimental design

ABSTRACT In this work, two typical surface characteristics, i.e., mean surface roughness and angle of the kerf during laser processing of 3D-printed Polylactic Acid (PLA) plates with 4.00 mm in thickness, are investigated. A carbon dioxide laser was utilized to separate 27 work pieces of rectangular shape. The governing laser parameters, speed of cutting and laser power, were varied according to full factorial experimental methodology. An orthogonal array (OA) having nine combinations was implemented, and nine specimens were cut with the same set-up and the same parameters three times (27 replicates in total). The experimental results were analyzed using descriptive statistical analysis, i.e., histograms, box plots, interaction charts and optimized using analysis of means (ANOM) plots as well as ANOVA analysis. The data analysis indicated that laser speed is the dominant parameter for the kerf angle, whilst both the laser velocity and power are important for mean surface roughness of the cut surface for PLA 3D-printed parts. The spread of the data is smaller in Y direction, which indicates that the weaving phenomenon affects the laser cut performance.