Surface Roughness Research Articles

Characterization of Wear Patterns in Gun Barrel’s Throat Region Using Forensic Microscope: Insights Into Long-Term Effects of High-Pressure Gas Exposure

Objectives: This research aims to explore the damage sustained by the gun barrel's throat region over a long period of use, shedding light on the wear characteristics, and providing valuable insights into the long-term effects of high-pressure gas exposure during firing. Methods: To achieve this objective, the appearance of the gun barrel's throat region was characterized using forensic microscopy techniques. Visual and microscopic examinations were conducted on five (5) gun barrels with ten years or less of service usage and five (5) gun barrels with over ten years of service usage from the Philippine National Police to assess the degree of wear in the barrel’s throat region. Findings: The findings revealed varying degrees of wear in the barrel throat regions. Firearms with 10 years or less of service usage exhibited moderate corrosion, narrow cracks, and minimal soot particle presence while firearms with over 10 years of service usage showed severe corrosion, deep cracks, scattered potholes, superficial scraped surfaces, and heavy soot particle presence. Novelty: This research contributes to the understanding of barrel performance, maintenance, and potential hazards associated with aging firearms, thus providing novel insights into the long-term effects of high-pressure gas exposure during firing. By examining the changes in material properties and surface roughness of the gun barrel’s throat region, this study seeks to improve the understanding of how repeated firing impacts gun barrel performance and longevity. This, in turn, may aid in developing future maintenance practices to enhance firearm durability and safety. Keywords: Gun Barrels, Wear Characteristics, Gun Barrel Throat Region, High-Pressure Gas Exposure, Wear Patterns

Niobium Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon ratio was adjusted from 0 to 0.32 while maintaining a constant growth time of 30 min. For the second and third series, the oxygen to argon ratios were fixed at 0.40 and 0.56, respectively, with deposition times ranging from 15 to 60 min. A structural transition from crystalline to amorphous was observed at an oxygen to argon flow rate ratio of 0.32. This transition coincided with a change in appearance, from non-transparent with metallic-like electrical conductivity to transparent with dielectric behavior. The transparent niobium oxide films exhibited thicknesses between 51 nm and 198 nm, with a compact, dense, and featureless morphology, as evidenced by both top-view and cross-sectional images. Films deposited on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates displayed a maximum surface roughness (Sq) of 9 nm and a maximum optical transmission of 83% in the visible range. The electrochromic response of niobium oxide thin films on ITO-coated PET substrates demonstrated a maximum coloration efficiency of 30 cm2 C−1 and a reversibility of 96%. Mechanical performance was assessed through bending tests. The ITO-coated PET substrate exhibited a critical bending radius of 6.5 mm. Upon the addition of the niobium oxide layer, this decreased to 5 mm. Electrical resistance measurements indicated that the niobium oxide film mitigated rapid mechanical degradation of the underlying ITO electrode beyond the critical bending radius.

Effect of process variables on microhardness and surface roughness in SPIF of beryllium copper

Beryllium copper is gaining the popularity among material research community owing to its excellent properties like high strength-to-weight ratio, corrosion resistance, and high electrical conductivity. This work aims to enhance the performance of ‘Single Point Incremental Forming (SPIF)’ of Beryllium copper using desirability function analysis (DFA). Feed rate (FEED), Step size (SS), wall angle (WA), and tool rotation speed (TRPM) are the four vital input parameters that have been chosen. This research investigates the effects of variations in these four factors on the truncated cone’s surface roughness and microhardness. After testing different levels of these parameters, the optimal setting using desirability function analysis was 0.4 mm step size, 200 mm min−1 feed rate, 47° wall angle, and a tool rotation speed of 1500 rpm with desirability of 70.7%. Further, measured data was subjected to Analysis of Variance (ANOVA) tests to determine the significance of all parameters on the responses. Results of the ANOVA analysis showed that the step size and tool rotation speed had the most profound impact on surface roughness and micro-hardness respectively. Feed rate and wall angle were the least significant parameters in affecting the surface roughness and micro-hardness respectively. The confirmation experiments validated fine-tuning with predicted and experimental values.

Optimizing the drilling process parameters of AZ91 based hybrid composites using TOPSIS and grey relational analysis

AZ91 is a popular magnesium alloy that contains aluminum (Al), zinc (Zn), and small amounts of other elements that offers a good balance of mechanical properties and corrosion resistance, making it suitable for various applications such as automotive, aerospace, sports, and biomedical. The current research works focused on optimizing drilling process parameters such as cutting speed, feed rate, a set of standard tools, and biofriendly coolants against the surface roughness and axial thrust force for AZ91/ nano hBN/ micron TiB2 hybrid composites. Taguchi L18 orthogonal array was used to design the drilling experiments. The axial thrust force and surface roughness of the drilled hole were observed as response of the experiments. Based on the results from TOPSIS and GRA, the optimal conditions were determined to be a spindle speed of 65 m/min, feed rate of 1 mm/rev, using a High-Speed Steel (HSS) tool, and Liquid Nitrogen (LN) coolant for 1 wt% of nano hBN in the hybrid composite. These parameters resulted in the lowest axial thrust force and surface roughness, highlighting their effectiveness in optimizing the drilling performance of AZ91/TiB2/hBN composites.

Influence of different machining methods on the surface roughness of TC4: dry milling, water-based fluid wet milling, and foam spray milling

The surface quality of workpieces is influenced by various factors, including processing parameters, processing techniques, cutting force, and cutting vibration. Many researchers have studied wet cutting to minimize milling forces and vibrations. We explore a high-density water-based foam milling method. By this method the foam is sprayed onto the surface area of tool and workpiece to absorb vibration energy. Firstly, a milling test system was established to conduct tests on TC4 titanium alloy under three different machining conditions (dry milling, water-based fluid wet milling, and foam spray milling), and the three-dimensional (3D) milling forces and milling vibrations were simultaneously recorded during the milling process, and the workpiece’s surface roughness was measured using a contact roughness measuring instrument. Then principal component analysis method was performed on the 3D milling forces and vibrations to obtain dimensionality-reduced feature values. Subsequently, multi-feature combination prediction models of surface roughness corresponding to the three machining conditions were developed using particle swarm optimization and a generalized regression neural network. Finally, the developed prediction models were compared and analyzed. The research results indicate that high-density water-based foam spray milling can effectively reduce the milling force by 70% and the milling vibration by 85% at most. Foam spray milling reduces the average roughness by up to 49%. The roughness prediction accuracy reaches 95.43%, with an error of less than 0.054 µm.

Optimisation of machining parameters in high-speed end milling of hardened AISI H13 die steel by integrating RSM and GA

ABSTRACT This study explores the potential of high-speed hard-end milling as a cost-effective alternative to the time-consuming grinding process for Chromium-molybdenum steel (AISI H13), widely used in cold and hot work tooling. The research aims to optimize machining parameters for achieving desired surface roughness, comparable to grinding and polishing. Cutting depth (0.4 - 0.8 mm), feed rate (1 - 4 μm per tooth), and cutting speed (80 - 140 m/min) were varied, and soybean oil replaced conventional lubricants. Employing Titanium Aluminum Nitride (TiAlN) coated end mills (3 mm diameter, 2 μm coating thickness) and response surface method (RSM) with Design Expert software, the study aimed at reducing tool wear and enhancing surface quality through multi-criteria optimization. Surface roughness analysis led to a streamlined surface by lowering mass flow rate and increasing cutting speed. The optimization approach predicted an optimal surface roughness value of 0.217475 μm at a cutting speed of 110 m/min, a feed rate of 1 μm/tooth, and a cut depth of 0.4 mm using genetic algorithm (GA), closely aligned with RSM’s ideal value of 0.215 μm. Both values converge around the 0.4 mm cut thickness.

Evaluation of road roughness and its influence on operating parameters in open-pit mines

Hauling ore and waste rock is a major cost factor in open-pit mines, encompassing both road maintenance and off-road truck operation. Road maintenance costs are directly influenced by traffic volume and the size of trucks using the roads. Off-road truck operating costs are impacted by various factors, including those affecting their movement, such as the direct interaction between tires and the road surface. Tire-road interaction significantly affects rolling resistance. Rougher surfaces with deeper grooves caused by track sinks lead to higher rolling resistance. This study employed laser profiling to characterize the surface roughness of five mine haul roads in two large Brazilian iron ore mines. This study evaluated the impact of these road irregularities on various operating parameters for 240-ton off-highway trucks, including rolling resistance, average travel speed, travel time, productivity, and unit transport cost. The results indicate that a 10 cm increase in road surface roughness can lead to a significant increase in rolling resistance (up to 5%), a substantial decrease in average speed (25%), a notable increase in travel time (26%), a decrease in productivity (19%), and a corresponding increase in unit transport cost (21%).

The Effect of Cigarettes Smoke on the Color and Properties of a Silicone for Maxillofacial Prostheses.

Although deterioration of silicone maxillofacial prostheses is severely accentuated in smoking patients, the phenomenon has not been systematically studied. To address a gap in the literature concerning the stability of maxillofacial prostheses during service, in this contribution, the effect of cigarette smoke on the aspect and physical properties of M511 silicone elastomer was evaluated. The aspect, surface, and overall properties of the silicone material, pigmented or not, were followed by AFM, color measurements, FTIR, water contact angle measurements, TGA-DTG and DSC, hardness and compression stress-strain measurements. The types of the contaminants adsorbed were assessed by XRF, ESI-MS, MALDI-MS, and NMR spectral analyses. Important modifications in color, contact angle, surface roughness, local mechanical properties, and thermal properties were found in the silicone material for maxillofacial prostheses after exposure to cigarettes smoke. The presence of lead, nicotine, and several other organic compounds adsorbed into the silicone material was emphasized. Slight decrease in hardness and increase in Young's modulus was found. The combined data show important impact of cigarette smoke on the silicone physical properties and could indicate chemical transformations by secondary cross-linking. To our knowledge, this is the first study making use of complementary physical methods to assess the effect of cigarette smoke on the aspect and integrity of silicone materials for maxillofacial prostheses.

Evaluation of chemical mechanical polishing characteristics using mixed abrasive slurry: A study on polishing behavior and material removal mechanism

Chemical mechanical polishing (CMP) is currently the most widely used method for material removal and surface planarization of glass. An environmentally friendly method of improving polishing performance by using a mixed abrasive slurry of ceria and diamond was proposed in this study. The results of polishing experiments showed that compared with single ceria abrasive, the materials removal rate (MRR) of the mixed abrasive slurry increased from 82.7 nm/min to 109.6 nm/min, while the surface roughness (Ra) decreased from 26.4 nm to 0.6 nm after polishing. An amorphous reaction layer formed during the CMP process was observed directly using transmission electron microscopy. Thermodynamic analysis was conducted to investigate the interfacial chemical reactions during the polishing process. A model was proposed to describe the mechanism of the materials removal.

Dynamics of Irregular Hyperelastic Substrate under the Impact of Moving Load

This work delves into the study of stresses induced in a non-homogeneous pre-stressed nearly incompressible elastic substrate with irregularity as a result of a normal load moving on its rough surface. The irregularity on the free surface of the substrate is considered in the form of parabolic irregularity. The solution methodology features the applicability of perturbation method along with substitution method to obtain the displacement components. The expressions of the induced shear and normal stresses have been established in closed form, and their expressions for special cases of the considered problem have also been deduced, which concur well with the existing literature. The influences of affecting parameters viz., non-homogeneity, frictional coefficient, irregularity factor, irregularity depth, hydrostatic stress and depth of the substrate on shear and normal stresses have been depicted graphically by means of numerical computation. The computational results have been manifested for distinct cases of irregularity zone involving parabolic as well as rectangular irregularities present in the considered geometrical model. It has been figured out that the presence of non-homogeneity in the irregular substrate has significant impact on the developed stresses.

Study of Some Physical and Antibacterial Properties of Bio-based (PLA)/(PCL) Blend reinforced with ZrO2 Nanoparticles

The aim of this study was to produce flexible films by combining polylactic acid (PLA) and poly(ε-caprolactone) (PCL), and enhance their strength by reinforcing them with different weight percentages (0.75, 1.5, and 2.25%) of zirconium oxide (ZrO2) nanoparticles (NPs) using a solvent casting process. The physical and antibacterial properties of the films were analysed to determine their suitability for use in food packaging. X-ray diffraction (XRD) patterns of the PLA/PCL films containing 2.25% by weight ZrO2 nanoparticles have a peak at an angle of 2θ = 17.18°, accompanied by smaller peaks. This confirms that these thin films have a semi-crystalline structure and that the molecules in the thin films are well dispersed. Scanning electron microscopy (SEM) analysis of the film surfaces reveals that the pure PLA/PCL films exhibit a smooth surface, while the (PLA/PCL/ZrO2NPs) films have a rough surface. The thermal behaviour of the blends through differential scanning calorimetry (DSC) showed fluctuations due to variations in the reinforcement ratio, resulting in changes in the glass transition and melting temperatures. These oscillations indicate changes in the level of crystallinity. ZnO2 has antibacterial properties that promote growth inhibition, making these films more effective in food packaging.

Effect of relative phase of loose tie rods on nonlinear dynamic behavior of rod-fastening rotor-bearing-seal system

Loosening of multiple tie rods in a circumferential rod-fastening rotor caused by thermal deformation and centrifugal loads is very common in engineering. The relative position of loose tie rods in the circumferential direction will also have an important impact on rotor dynamics. The relevant research has not been done yet. In this paper, a contact model of the rough machined surface is firstly established by combining the probability functions describing rough surfaces and fractal contact theory of asperities, then the contact stiffness model between disks is established based on the contact model. Finally, the dynamic model of the circumferential rod-fastening rotor-bearing-seal system is established and solved. The effect of relative phase of loose tie rods on the nonlinear dynamic characteristics of rod-fastening rotor-bearing-sealing system is studied. It can be concluded that relative phase of the loose tie rod has an important influence on the frequency, bifurcation, and periodic motion of the rotor system. At lower speed, the anisotropy of contact stiffness caused by loose tie rods has little effect on the rotor trajectory, while the generalized bending moment has a greater influence on dynamics of the system. At higher speed, the anisotropy of contact stiffness has a great influence on the axis rail of the rod-fastening rotor.

Development of antifouling antibacterial polylactic acid (PLA) -based packaging and application for chicken meat preservation

Microbial contamination is the leading cause of food spoilage and food-borne disease. Here, we developed a multifunctional surface based on polylactic acid (PLA) bioplastic with antifouling and antibacterial properties via a facile dual-coating approach. The surface was designed with hierarchical micro/nano-scale roughness and low surface energy. Bactericidal agent polyhexamethylene guanidine hydrochloride (PHMG) was incorporated to endow the film with bactericidal activity. The film had good superhydrophobic, antifouling and antibacterial performance, with a water contact angle of 154.3°, antibacterial efficiency against E. coli and S. aureus of 99.9 % and 99.6 % respectively, and biofilm inhibition against E. coli and S. aureus of 63.5 % and 68.9 %, respectively. Synergistic effects of antibacterial adhesion and contact killing of bacteria contributed to the significant antibacterial performance of the film. The biobased biodegradable film was highly effective in preventing microbial growth when applied as antibacterial food packaging for poultry product, extending the shelf life of fresh chicken breast up to 8 days.

INITIATED CHEMICAL VAPOR DEPOSITION (iCVD) OF POLY(ACRYLIC ACID): A COMPARISON BETWEEN CONTINUOUS AND CLOSED-BATCH iCVD APPROACHES

In this study, poly(acrylic acid) (PAA) thin films were deposited on silicon wafer and glass surfaces by initiated chemical vapor deposition (iCVD) method using di-tert-butyl peroxide (TBPO) as the initiator and acrylic acid (AA) as the monomer. During iCVD, two different precursor feeding approaches, namely continuous and closed-batch, were employed. The effects of substrate temperature and the precursor feeding approaches on the deposition rates and surface morphology of the films were investigated. The highest deposition rates for the continuous and closed-batch iCVD approaches were found as 26.1 nm/min and 18.6 nm/min, respectively, at a substrate temperature of 15 °C. FTIR analysis of the films deposited by both approaches indicated high structural retention of the monomer during the polymerization. AFM results indicated that, PAA thin films possessed low RMS roughness values of 2.76 nm and 1.84 nm using continuous and closed-batch iCVD, respectively. Due to the slightly higher surface roughness of the film deposited under continuous iCVD, that film exhibited a lower water contact angle of 16.1° than the film deposited in closed-batch iCVD. In terms of monomer utilization ratio, closed-batch system was found to be more effective, which may help to minimize the carbon footprint of iCVD process.

Laser-induced surface reconstruction to enhance interfacial bonding reliability of CFRP/titanium hybrid joints

Adhesive bonding is widely used in aeronautical carbon fiber-reinforced polymer (CFRP)/titanium (Ti) alloy hybrid structures to satisfy the demands of high-strength and lightweight. The physicochemical properties of adherend surfaces significantly impact the bonding performance. In this study, laser-induced surface reconstruction (LISR) was designed for the reliable joining of Ti alloy and CFRP. A three-level-three-factor central composite design (CCD) approach-based response surface methodology (RSM) analysis was applied to statistically specify parameter optimization of the laser energy output. Surface morphology and wettability of CFRP ablated were studied. Chemical compositions were determined by X-ray photoelectron spectroscopy (XPS). Tensile-shear tests were performed, and fractured surfaces were analyzed. The tensile shear strength with LISR process has been improved by 19.1%, in comparison with that of mechanical grinding treatment. The cross-like texture based on designed geometric configuration was fabricated without damaging the underlying fibers, thus increasing the surface roughness and contact area at interface. The wettability transition mechanism was investigated, demonstrating that the hydrophilicity of reconstructed surfaces primarily attributes to the more polar groups (C−O, C=O, etc.) on CF surfaces. This study provides a reliable surface treatment method for fabricating high-performance composite structures by adhesive bonding.

Influence of laser treatment on the adhesion force of metallized carbon fiber reinforced polymer (CFRP) composite

Carbon fiber reinforced polymer (CFRP) is an engineering composite material with excellent performance. After metallization, the CFRP composite exhibits unique properties such as electromagnetic shielding and high electrical conductivity. In this study, we utilized laser treatment process to enhance the adhesion strength of the copper layer electrolessed on CFRP composite. The surface microstructure of CFRP and the copper layer was determined using an optical microscope, and the adhesion force of the copper layer on CFRP composite was measured through 3M tape and pull-out tests. The results indicate that with an increase in the number of laser treatment cycles, the trenches depth on the surface of CFRP composite also increases, leading to high surface roughness and thus enhancing the adhesion strength between the copper layer and the composite. The adhesion state of the copper layer on laser-treated CFRP composite can be qualitatively classified as grade 5B. Additionally, both mechanical cutting and laser treatment can improve the adhesion strength of the samples. The samples treated by mechanical cutting and the laser scan with ±45° exhibit the highest adhesion strength of 5.48 MPa. This is 415 % higher than that of the untreated sample, with a minimum damage area after pull-out testing, approximately 10 %. Compared to the sandblasting pretreatment process, the adhesion strength of the sample by laser treatment increased by 119 %.

Effect of heat treatment on the anisotropic machinability of additive manufactured titanium alloys in micro-milling

For titanium alloy parts prepared by selective laser melting (SLM), post-treatment operation is usually utilized to meet the needed surface accuracy and dimensional tolerances. However, the heat treatment process and anisotropy of different surfaces of SLMed titanium alloy can directly affect its machinability. In this study, the anisotropic machinability of SLMed TC4 before and after heat treatment was comprehensively compared by the milling force, surface quality, top-burr and work hardening. The results indicate that the milling force and work hardening degree of top surface of SLMed TC4 material are larger than those of side surface, and top surface the presents the better surface quality and smaller top-burr. It exhibits obvious anisotropic machinability in micro-milling. After heat treatment, the anisotropic machinability between different surfaces of SLMed TC4 materials were significantly reduced. The average surface roughness difference rate of top and side surfaces decreased from 10.08% to 2.79%, and the total average top-burr size difference rate decreased from 19.53% to 9.99%. The difference rate of milling force and work hardening degree of the top and side surfaces both showed a decreasing trend. This work demonstrates that the anisotropic machinability of SLMed TC4 material in micro-milling can be effectively mitigated by the heat treatment process.

Investigation of different abrasive jet machining methods applied to milling tool coatings for post-treatment

Post-processing of tool coatings is an essential way to remove defects, enhance coating properties, and improve tool performance, where abrasive jet machining plays an important role. This paper introduces a novel application of self-developed elastic abrasives to the post-treatment of coated tools, with a comparison against hard abrasive (Al2O3) jet machining (HAJM). The results demonstrate that EAJM significantly reduces the surface roughness of the coating and enhances the wear resistance of milling tools across a wide range of jetting parameters without damaging the coating. Conversely, HAJM yields more pronounced improvements in physical properties such as coating hardness, elastic modulus, and residual stress, and also significantly enhances tool performance, albeit with a need for precise process parameters. Overly aggressive HAJM parameters can lead to diminished coating performance and reduced tool life. Additionally, the study reveals that the improvement in tool life is closely linked to the physical properties of the coating, which contributes to the enhanced performance observed with HAJM-treated tools. To further investigate this, a mathematical model was established to analyze the coupling effect of jet pressure and time on tool life. The proposed model identifies the optimal ranges of the jetting coefficient for HAJM and EAJM as 326–4870 kPa·s and 1061–17,780 kPa·s, respectively, offering a novel approach to optimizing tool performance and life.

Influence of electrophysical characteristics of plasma electrolytic treatment of 16MnCr5 structural alloy steel on structural and phase changes in the surface and its tribological properties

The possibility of using plasma electrolytic technologies for surface treatment of 16MnCr5 steel in order to increase its wear resistance is shown. The influence of electrophysical characteristics of plasma electrolytic treatment on structural-phase changes of the surface and its tribological properties is studied. A comparison of anodic and cathodic variants of diffusion saturation, as well as subsequent polishing on the results of surface modification is carried out. The complex effect of surface layers strengthened above 1100 HV, including iron carbide and nitride, martensite and retained austenite, to a depth of up to 250 μm with the preservation of a viscous core and the formation of a relatively homogeneous surface with reduced roughness on increasing wear resistance has been revealed. The features of tribological behavior of surfaces formed under different electrophysical parameters of processing, mainly related to the difference in surface microrelief, are shown. The correlation of the Kragelsky-Kambolov criterion as a complex assessment of surface roughness with its wear resistance is shown. The influence of changes in sliding speed and friction load on the occurrence and development of leading processes that determine the intensity and nature of destruction of friction surfaces is established.

MECHANICAL CHARACTERIZATION OF RUBBER-BONDED ELASTIC GRINDING WHEELS BY BENDING TESTS

The elastic modulus of a grinding wheel is one of the most representative properties when it comes to the study of its in process behavior, which makes it a parameter of great interest for both researchers and manufacturers of grinding wheels. Rubber-bonded grinding wheels are characterized by their high elasticity, which makes them stand out in superfinishing applications, achieving surface roughness of Rz < 1 µm and mitigating the risk of burning the ground parts. Despite the good performance of this type of grinding wheel, they are not as popular as conventional rigid wheels, and their mechanical characteristics are still unknown. Moreover, while a few investigations have focused on determining the mechanical properties and their relationship with the in-process performance of vitrified or resinoid bonded grinding wheels, there are not investigations that have studied the mechanical properties of elastic grinding wheels. In this work, the elastic modulus, flexural strength and deformation of rubber-bonded elastic grinding wheels have been studied by means of three-point bending tests. Different compositions of the different materials that make up this type of grinding wheel have been analyzed, as well as the strength of the bond between the abrasive compound and the grinding wheel core. This study is intended to help to better understand the behavior of elastic grinding wheels and to develop more efficient grinding processes. In addition, it allows manufacturers to increase their knowledge of the properties of this type of grinding wheel and offers an effective method for its mechanical characterization. Keywords: Grinding, elastic grinding wheels, rubber bond, wheel characterization, elastic modulus, flexural strength, bending