Surface Integrity Parameters Research Articles

Multi-physics field coupling interface lubrication contact analysis for gear transmission under various finishing processes

Surface integrity is crucial for the load-bearing capacity, transmission performance, and service life of gears. Finishing processes can effectively improve surface quality and are widely used in gear manufacturing processes to enhance surface integrity and improve the service performance of gears. Five precision machining tests of form grinding, vibratory finishing, barrel finishing, honing, and abrasive flow machining were conducted on spur gears. High-precision surface integrity characterization methods were used to analyze the surface integrity parameters of the finished gear surfaces, including surface roughness, surface microtopography, residual stress, texture aspect ratio, roughness peak curvature radius. The finishing processes uniformity and effectiveness of the tooth profile surface were also evaluated. By using the finished rough surfaces as inputs and considering the impact of thermal elasto hydrodynamic lubrication on the gear surface, a multi-field coupling contact analysis model encompassing solid, liquid, and thermal fields at the gear meshing interface was established. Lubrication performance parameters such as oil film pressure, oil film thickness, oil film temperature rise, and friction coefficient under various finishing surfaces were compared and analyzed. Experimental results indicate that barrel finishing can simultaneously improve various parameters, such as surface roughness, texture aspect ratio, and compressive residual stress. Finishing processes can effectively reduce surface roughness, improve lubrication performance and reduce the risk of scuffing failure. This approach provided an effective method for the comprehensive evaluation of the effects of various finishing processes. The developed program offers theoretical guidance and data support for the selection and optimization design of gear surface finishing processes.

Gear contact fatigue prediction under mixed elastohydrodynamic lubrication with ellipsoidal asperity rough surface: Experimental and numerical investigation

A three-dimensional(3D) line-contact mixed lubrication model and contact fatigue life prediction model for gears are established, considering the elastoplastic contact of ellipsoidal asperities and their interactions. The localized lubrication states across the actual 3D rough surfaces are visually depicted. The direct asperity contact pressures calculation exhibits greater accuracy and universality. The proposed mixed lubrication model can be applied accurately and efficiently to heavy-load conditions. The synergistic mechanisms of multi-scale surface integrity parameters, such as surface morphology-lubrication coupling, hardness gradient, and residual stress, on gear contact fatigue has been revealed. The results reveal that surface roughness significantly affects the competitive failure mechanism between surface-initiated micropitting and subsurface-initiated macropitting. The increase in surface compressive residual stress is more sensitive to the enhancement of near-surface and subsurface fatigue lives, compared to the increase of peak residual stress and the depth of peak residual stress. The proposed physics-based gear contact fatigue life prediction model has been validated through gear contact fatigue experiments under various operating conditions. The maximum deviation between the predicted and experimental fatigue lives is within 10%. This paper presents theoretical methodologies and data-driven support for optimizing the design and manufacturing processes of gears, specifically focusing on enhancing anti-fatigue properties.

Effect of induction heating composite shot peening on surface integrity parameters of 20CrMnTi gear steel

Effect of induction heating composite shot peening on surface integrity parameters of 20CrMnTi gear steel

The effect of fine particle peening on aviation gear performance, part II: Rolling contact fatigue

AbstractFine particle peening (FPP) technology offers an effective method to achieve outstanding surface integrity and fatigue performance in aviation gears. However, the lack of sufficient research on the correlation between process parameters, surface integrity parameters, and fatigue life undermines the full potential of FPP in strengthening aviation gears. Therefore, we have developed an elastic–plastic contact fatigue life model to predict the fatigue life of AISI 9310 gear steel after different strengthening processes. This model can consider surface integrity parameters such as surface micro‐topography, residual stress gradient, and hardness gradient. To validate the model, we conducted rolling contact fatigue tests and compared the results with the predictions from our model. The influence of process parameters on the rolling contact fatigue of AISI 9310 gear steel was further investigated. A process window for FPP was established, and an optimization method was proposed in order to provide guidance for selecting process parameters for FPP on high‐performance aviation gears.

Comparison of the effects of induction heating composite shot peening and conventional shot peening on residual stress, microhardness, and microstructure of 20CrMnTi gear steel

As a commonly used surface strengthening technology, shot peening, which can significantly improve the fatigue strength of mechanical parts, is widely used in the fields of vehicles and aviation. To obtain a larger residual compressive stress and further refine the grain size under normal shot peening intensity and coverage, this study proposes an induction heating composite shot peening (IHCSP) surface strengthening method, aiming to utilize the coupling effect of temperature and stress fields to promote the shot peening strengthening effect. An IHCSP test plan was designed and an IHCSP test bench was created to achieve simultaneous induction heating and shot peening. This study compares the surface integrity parameters and microstructures under three processes: un-peened, conventional shot peening, and IHCSP. The results show that the maximum axial and radial compressive residual stresses increase by 72.41 and 75.4 MPa respectively; the depth of the hardened layer increases by 0.3 mm, the martensitic transformation more complete, the grain size decreases by 483 nm, the dislocation density increases significantly, and nanocrystals are obtained on the surface of the material. These results verify the superiority of IHCSP surface strengthening.

Subtractive processing and surface integrity of additive manufacturing materials

PurposeAs an advanced manufacturing method, additive manufacturing (AM) technology provides new possibilities for efficient production and design of parts. However, with the continuous expansion of the application of AM materials, subtractive processing has become one of the necessary steps to improve the accuracy and performance of parts. In this paper, the processing process of AM materials is discussed in depth, and the surface integrity problem caused by it is discussed.Design/methodology/approachFirstly, we listed and analyzed the characterization parameters of metal surface integrity and its influence on the performance of parts and then introduced the application of integrated processing of metal adding and subtracting materials and the influence of different processing forms on the surface integrity of parts. The surface of the trial-cut material is detected and analyzed, and the surface of the integrated processing of adding and subtracting materials is compared with that of the pure processing of reducing materials, so that the corresponding conclusions are obtained.FindingsIn this process, we also found some surface integrity problems, such as knife marks, residual stress and thermal effects. These problems may have a potential negative impact on the performance of the final parts. In processing, we can try to use other integrated processing technologies of adding and subtracting materials, try to combine various integrated processing technologies of adding and subtracting materials, or consider exploring more efficient AM technology to improve processing efficiency. We can also consider adopting production process optimization measures to reduce the processing cost of adding and subtracting materials.Originality/valueWith the gradual improvement of the requirements for the surface quality of parts in the production process and the in-depth implementation of sustainable manufacturing, the demand for integrated processing of metal addition and subtraction materials is likely to continue to grow in the future. By deeply understanding and studying the problems of material reduction and surface integrity of AM materials, we can better meet the challenges in the manufacturing process and improve the quality and performance of parts. This research is very important for promoting the development of manufacturing technology and achieving success in practical application.

Numerical modeling and experimental investigation on fatigue failure and contact fatigue life forecasting for 8620H gear

Surface integrity parameters exert an enormous function on contact fatigue performance of gears. In this paper, a gear contact fatigue life prediction model that incorporates surface integrity parameters is proposed. The micropitting and pitting damage of failed gears are quantitatively analyzed through micro-characterization techniques. A three-dimensional contact analysis of rough surface is performed to simulate the morphology evolution during gear running-in. And the coupling effect of residual stress and rough morphology on the contact stress field and fatigue life is analyzed. Finally, residual stress optimization design is carried out based on the failed gear. Gears subjected to shot peening are designed and gear contact fatigue tests under various working conditions are performed. The research results indicate that the plastic deformation at the asperities level in the running-in process mainly occurs during the initial loading. The fatigue life significantly increases by improving the residual stress distribution on the tooth surface through shot peening process. The maximum relative error between predicted fatigue life and measured fatigue life is less than 20%, which effectively verifies the accuracy of the proposed model. The technique presented in this study could provide theoretical basis and data support for the anti-fatigue design and manufacturing of gears.

Mechanics and surface characterization of high-speed diamond turning of germanium

Germanium and other brittle single crystal materials can be diamond turned with negative rake angle tools, but to maintain surface integrity parameters are typically chosen conservatively. This work describes experiments performed on (100)Ge crystal samples that support a recent scientific finding: increasing the surface speed in diamond turning of germanium improves surface integrity. Materials are machined on a modern ultraprecision diamond turning machine at constant surface speed and constant feed per revolution keeping both the geometric character and the material flow dynamics constant during machining. Forces are measured in the experiments at cutting speeds ranging from 0.2 m/s to 10 m/s. Surface roughness of the machined surfaces was characterized using coherence scanning interferometry and surface analysis. The key findings of the work are (a) force and specific forces decrease by approximately a factor of 2 over the cutting speed range and (b) surface damage substantively decreases with cutting speed. This is correlated to the behavior of the cutting forces during machining and the chip geometry. The findings indicate that higher material removal rates can be obtained in diamond turning of germanium and that this increase in material remove rates also improves surface integrity.

Contact Fatigue Behavior Evolution of 18CrNiMo7-6 Gear Steel Based on Surface Integrity

In this work, the surface integrity (surface morphology, microstructure, microhardness, residual stress) of contact fatigue (CF) samples with different numbers of running cycles was comprehensively studied. Based on typical working conditions, a fatigue life evaluation method was proposed based on the evolution law of surface integrity. The CF with different numbers of running cycles revealed that the average grain size decreased with the increase in the number of running cycles, and the surface microhardness, residual stress and surface roughness Ra increased first and then decreased. In addition, the relationships between different surface integrity parameters and fatigue life were plotted. Moreover, based on the fatigue life profiles, the running state and remaining life of gear samples can be evaluated.

A novel sandwich structured wheel to achieve mirror finish in grinding of a mould steel

A novel manufacturing tool called sandwich flexible elastic grinding wheel is developed to achieve high material removal rates and machined finish of a mould steel. This tool is made of aluminium matrix, ethylene propylene rubber layer and abrasive layer. Ethylene propylene rubber layer has great elasticity and produces elastic deformation when contacting with the workpiece. With the existence of an abrasive layer, rigidity at small scales allows grinding to occur, which can effectively remove the residual height of the surface and improve the surface quality. In this paper, influences of grinding process parameters of the sandwich elastic grinding wheel on the key characterisation parameters of surface integrity are studied, and the surface roughness and material removal rates under various process parameters are investigated. Then, the process parameters that are suitable for mirror machining are selected by experiments and are demonstrated on an S136 mould steel workpiece. Mirror finish can be achieved by single processing. The surface roughness of the mould steel converges from the original Ra142 nm to Ra7.42 nm, the surface texture is more compact and regular, and the surface integrity is significantly improved.

Enhancing the surface integrity and SCC resistance of 304 austenitic stainless steel by pre-stress grinding

In order to improve the surface integrity and enhance stress corrosion crack (SCC) resistance of stainless steel (SS) materials, this study investigates the application of pre-stress grinding (PG) technique. The impact of PG on various surface integrity parameters, including residual stress, surface topography, surface roughness, and microstructure, is examined. Additionally, the SCC behavior of the ground surface is evaluated and compared under different levels of pre-stress applied during PG. Experimental results demonstrate that the integrity of the PG-treated surface is significantly improved, leading to enhanced SCC resistance. This enhancement can be attributed to the additional compression effect generated by the applied pre-stress, as well as the increased surface rigidity of the material. Furthermore, numerical analyses indicate higher temperatures and lower plastic strain rates during PG, which effectively inhibit the martensitic phase transformation. However, it is important to note that the strengthening effect of pre-stress may have an upper limit, thus higher pre-stress values are not necessarily more advantageous, and it is crucial to ensure that the applied stress does not exceed the yield strength of the material. Additionally, achieving an ultrafine-grained surface requires the implementation of more aggressive grinding parameters.

Design for Manufacturing of Cemented Carbide Coated Components Toward High Wear and Impact Resistance Performance

Abstract Wear- yet impact-resistant demand is a big challenge for coated components under heavy-load service condition. To solve this high-performance manufacturing problem, a new strategy of design for manufacturing (DFM) with integrated design and processing is developed to incorporate processing effect on final performance via the pivot role of surface integrity. An impact performance model and the impact tester are constructed for a component with coated flat block/bulk cylinder mates for potential application in hydraulic machinery. A WC-12Ni/Ni60A two-layer coating on 17-4PH martensitic steel substrate is designed with thermal spray process. Impact crater depth, surface hardening, and residual stresses are identified as major surface integrity parameters determining wear/impact performance by the modeling with testing. The design parameters of geometry, material, and structure are quantitatively linked to the final performance by a process signature (PS) correlative analysis on the identified surface integrity to internal material loading of plastic/elastic strain energies. The PS correlation posts coating thickness as a high-sensitivity parameter for design, facilitating a buffering effect of reduced peak stresses among the coating-substrate system. The DFM optimization is understood by irreversible thermodynamics as reducing energy dissipation of the internal material loading from the external impact loads. The manufacturing inverse problem is thus solved by material-oriented regularization (MOR) on the homologous PS correlations integrating the design and processing phases. The manufactured component, with optimal Ni60A interlayer thickness of 75–100 µm at a top WC-12Ni coating of 200 µm, achieves a desired performance of up to 6000 impacts under a nominal load of 15 kN.

Inversion Principle and Application of Ultrasonic Detecting Surface or Interface Integrity Parameters of Aviation Functional Coatings

Inversion Principle and Application of Ultrasonic Detecting Surface or Interface Integrity Parameters of Aviation Functional Coatings

Evaluation of fretting corrosion fatigue in burnishing of Ti6Al4V component for artificial hip joint

Modular hip replacements provide a flexible way to reconstruct the joint with optimized biomechanics, but one of the most common causes of modular hip prostheses failure is the fretting corrosion at the neck-head interface combined with their related micro-motion. In this context, the present study aims to improve the neck surface strength by means of burnishing process. An experimental campaign on Ti6Al4V hip joint neck was carried out at varying burnishing parameters: force and speed. The main surface integrity parameters affecting the neck performance have been evaluated, namely mean surface roughness, micro hardness, affected layer and microstructure. Afterwards, fretting corrosion fatigue tests on necks and alumina ceramic heads were performed under standard conditions simulating human walking. The relative motions at the neck-head interface were analyzed by an innovative technique able to detect changes during the test with high accuracy.

Fatigue analysis of electro discharge machined Nitinol 60

Nitinol 60 (NiTi60) is a shape memory alloy (SMA) where the atomic percentage of nickel is slightly higher than titanium. It advantages the material to have higher hardness and better sensitivity to phase transformation. One of the machining techniques that is preferred to cut hard material is electrical discharge machining (EDM). This study aims to examine the fatigue characteristics of a NiTi60 alloy that has undergone electro-discharge machining and examine the impact of machining parameters on microstructural changes. In this investigation first, the influence of EDM process parameters such as pulse current, voltage, pulse on time, and pulse off time on surface integrity aspects was investigated. Second, the impact of these process variables on fatigue strength was examined. The surface integrity parameters of EDM-machined specimens, such as microcracks, surface crack density (SCD), white layer thickness (WLT), and residual stress formation have been examined by various characterization techniques. The obtained results show that pulse current and voltage are dominating factors affecting SCD. The thickness of the white layer seems to be increased with the rise in the pulse current and pulse on time, and tensile kinds of residual stresses are present in the WLT region, whose magnitude is dependent on process parameters. The fatigue tests were performed using a servo hydraulic testing machine at a frequency of 20[Formula: see text]Hz for 106 number of cycles. The fatigue crack initiation, propagation, and effects of process parameters have been examined. It has been found that an increase in pulse current and voltage leads to the generation of microvoids in the WLT region and thereby causes fatigue cracks to take birth. Later on, a correlation between WLT and SCD was observed by implementing an artificial neural network (ANN) model. The accuracy of ANN model prediction is reported to be high, where WLT and SCD have a 0.98 observed correlation coefficient.

The processing parameters optimization of UVAM-processed CuNiAl alloy based on surface integrity parameters

The surface integrity of a material has a significant impact on fretting wear performance. Based on the analysis of the material surface integrity, the machining parameters were optimized to obtain the best fretting wear performance of CuNiAl alloy. First, the effects of ultrasonic vibration-assisted milling (UVAM) processing parameters on the surface integrity of CuNiAl alloy were studied. Consequently, the relationship between UVAM processing parameters and CuNiAl alloy surface integrity parameters was established through the optimized support vector machine (PSO-SVM) model. The relationship between the surface integrity parameters, processing parameters, and fretting wear performance was established. The best fretting wear performance was obtained at a spindle speed of 147.4 m/min, feed rate of 76 mm/min, and vibration current of 199.5 mA.

Ultrasonic inverse identification of surface integrity of aviation functional coatings through material-oriented regularization

Accurately controlling surface integrity of aviation functional coatings including defect, geometry, structure, and property is important to balance the comprehensive performance of aviation parts. In this paper, a new ultrasonic inverse method of surface integrity of aviation functional coatings is presented through a developed material-oriented regularization scheme, which combines model regularization, data regularization, and sensitivity matrix analysis. A sensitivity-matrix-based inversion method of ultrasonic detecting multiple surface integrity parameters is developed using the optimized high-sensitivity characteristic detection signal. Taking ultrasonic inverse detection of elastic constants of plasma-sprayed Al2O3 coating and inverse prediction of porosity of ZrO2 coating as examples, the validity of proposed ultrasonic inversion method is illustrated. Results show that the inverted elastic constants C11, C13, C33, and C44 of Al2O3 coating are 123.81 GPa, 34.38 GPa, 190.20 GPa, and 24.63 GPa, respectively. The relative error between inverted and experimental C33 and C44 are all less than 4.0%. The inverted elastic constants show obvious “inverse” elastic anisotropy, which is due to the preferred orientation of micro-cracks in Al2O3 coating. Compared with actual porosity of ZrO2 coating, the predicted porosity using sensitivity matrix optimized Gaussian process regression algorithm has a relative error of less than 5.3%. The proposed ultrasonic inverse method provides a new path for solving the complex ultrasonic non-destructive detecting problems, which are difficult for traditional “trial-and-error” ultrasonic methods.

Influence of heat treatment on the tool life while machining SLM Inconel 718 with reference to C&W Inconel 718

In this study tool life experiments were performed on Inconel 718 (IN718) alloy. The Inconel 718 samples were produced by conventional Cast and Wrought (C&W) and by Laser Powder Bed Fusion (L-PBF) techniques like Selective Laser Melting (SLM). The as-built SLM samples which were subjected to only Hot Isostatic Pressing (HIP) are labeled as SLM HIP and both Hot Isostatic Pressing and Aeronautic Heat Treatment are labeled as SLM HIP-AHT. The tool life machining tests were performed using PVD coated carbide insert under emulsion conditions. The surface integrity parameters such as surface roughness, residual stresses, and microhardness were evaluated. The wear mechanisms on the rake and flank faces of the PVD insert were characterized. It's deduced that notch and flank wear near the depth of the cutting zone were the predominant failure mode affecting the tool life. The age-hardened microstructural features of C&W and HIP heat-treated SLM samples have a negative impact on the tool life. Whereas the microstructure obtained by the SLM HIP-AHT sample indeed played an important role by exhibiting 26 % more tool life than SLM HIP samples and 79 % more tool life than the C&W sample.

Surface integrity and transmission performance of spiral bevel gears subjected to shot peening: A comparison between concave and convex surfaces

As a typical surface strengthening method, shot peening can effectively enhance the bending fatigue resistance of spiral bevel gears by improving the surface integrity parameters. Due to the complex geometry of spiral bevel gears, one group of shot-peening parameters can hardly satisfy the performance requirements of concave and convex surfaces. Thus, the effect mechanism of shot peening on both surfaces needs a thorough understanding. Meanwhile, the effect of shot peening on the transmission performance of gears is still somewhat cloudy and controversial, which confuses the optimization of shot-peening parameters. To address this issue, the effect of shot peening on the surface integrity and transmission performance of spiral bevel gears is systematically investigated by experiments. The results show that due to the smaller curvature radius, the surface integrity of the concave surface is better than that of the convex surface before and after shot peening. Specifically, for the shot-peened gears, the dislocation density at the concave surface is 9.1 % higher than that at the convex surface; the intergranular oxidation (IGO) layer for the concave surface is 2.1 % shallower than that for the convex surface; the maximum compressive residual stress for the concave surface in the profile direction is 6.9 % higher than that for the convex surface; the peak value of hardness for the concave surface is 3.5 % higher than that for the convex surface. Furthermore, smoother tooth flanks can lead to better transmission performance of gears, and shot peening has side effects on it. The transmission performance in the drive condition is better than that in the coast condition before and after shot peening.

Low plasticity burnishing surface treatment: impact on surface integrity parameters of turned cylindrical Ti- 6Al-4V specimen

ABSTRACT Surface integrity parameters are the major aspect in the extension of the fatigue life of aero- engine components. In this study, a modified burnishing surface treatment (low plasticity burnishing) with reduced cold work was proposed to improve surface integrity characteristics such as surface finish and hardness, and to induce stable, advantageous compressive residual stress in a cylindrical Ti-6Al-4 V specimen (as-received). In this process, a rolling rigid spherical tungsten carbide ball is pressed across a Ti-6Al-4 V specimen at an appropriate fluid pressure generated by the hydraulic unit. The low plasticity ball burnishing tooling system supported by a hydraulic unit of capacity 30 MPa is designed and developed in this study. By using a suitable specimen holding fixture, the ball burnishing with a small amount of plastic strain was carried out on the Ti-6Al-4 V cylindrical specimen. This research examined the effect of burnishing process variables namely tool pass and burnishing fluid pressure on compressive residual stresses, surface roughness, and hardness in Ti-6Al-4 V. The explicit dynamic analysis was carried out by using FE-Analysis software ABAQUS 6.17 as a part of numerical simulation. Hydraulic burnishing pressure and burnishing passes are the most influential parameters in generating favourable compressive residual stress, qualitative surface finish with less cold work in Ti-6Al-4 V turned specimen.