Mechanical Surface Characteristics Research Articles

Advancement of constant and progressive load multi‐cycle indentation method on surface properties characterization of polymers

AbstractIn recent years, polymers have been popular in industrial applications due to their lightweight, corrosion‐resistant, improved surface polish, ease of manufacturing, cost‐effectiveness, and so forth. Similarly, micro/nano‐indentation has gained popularity as a technique for assessing the surface mechanical characteristics of polymers. The present study conducted comprehensive experiments using cyclic micro‐indentation on engineering polymers, specifically poly‐ether‐ether‐ketone (PEEK), poly(methyl methacrylate) (PMMA), and poly(tetra‐fluoroethylene) (PTFE). An appropriate and optimal indentation method has been proposed after analyzing the behavior and significance of all the input parameters in evaluating the properties. Both constant load multi‐cycle (CLMC) and progressive load multi‐cycle (PLMC) were considered for this investigation. A comparative evaluation has been conducted to assess two multi‐cycle tests on these materials. From the analysis of the input parameters, including maximum loads, loading and unloading rates, and the number of cycles, the unloading rate and indentation cycle are crucial factors in determining hardness (H) and elastic modulus (E). Increasing the loading rates leads to an increase in H and a reduction in E for all three materials. This effect arises from the thermal effect, which is characterized by the creep modulus and a closed hysteresis loop. Employing the holding duration and multiple cycle data in constant load multi‐cycle can significantly influence the creep behavior and use of the hysteresis loop for fatigue behavior. Similarly, a progressive load multi‐cycle indentation with a force greater than 0.5 N and a minimum of five cycles is the most accurate approach for evaluating surface mechanical parameters.

Experimental investigation of sandy soil stabilization using chitosan biopolymer

The performance of an environmentally friendly biopolymer synthesised from secondary resources to overcome the wind erosion of sandy soil was investigated in this study. The study employed a multi-scale approach to investigate the mechanical, erosional, and hydraulic properties of sandy soil. At the macroscale, experimental techniques such as unconfined and triaxial compression tests, permeability measurements, contact angle assessments, and wind tunnel experiments were utilized to characterize the bulk behavior of the soil. Concurrently, molecular dynamics (MD) simulations were conducted at the nanoscale to predict surface mechanical characteristics and elucidate chemical interactions at the molecular level. Results show that when the outer surface of the sandy particles is coated with a sparse concentration of biopolymer, the sandy aerosol inhibitory performance is significant even under extreme storm conditions reaching speeds of 140 km/h of storms. The study on the impact of biopolymer content, curing time, and curing conditions revealed that the addition of chitosan biopolymer has the ability to enhance the bonding between particles and significantly enhance the mechanical properties of sandy soil. The atomic insight from molecular dynamics reveals huge entanglement between sandy particles and biopolymer by Van der Waals interaction. The results of the Unconfined Compressive Strength test indicate that chitosan enhances the compressive strength of sand by up to 320 kPa. Additionally, the triaxial test demonstrated that the application of chitosan led to a 34.2 kPa improvement in the cohesion of sand. Furthermore, analysis of the permeability test results revealed a decrease in the hydraulic conductivity coefficient from 1.6 × 10^-6 m/s to 5.7 × 10^-7 m/s, representing a reduction of approximately 35 %.

Surface modification of AZ61 Magnesium Alloy with Stelcar Alloy Powder Using Laser Cladding Technique

Objective: To examine the tribological and mechanical characteristics of the AZ61 alloy reinforced with Stelcar alloy powder by surface modification through laser cladding. Methods: Surface modification was done by using a laser cladding machine, where the input parameters including Scanning Speed (SS), Laser Power (LP) and Powder Feed Rate (PFR) were adjusted. Experimental design followed a L9 Taguchi approach, and optimization of input parameters for the surface modified AZ61 alloy reinforced with Stelcar alloy particles was achieved using Grey Relational Analysis (GRA). Output responses, namely wear volume and micro hardness were measured to assess the effectiveness of the optimization process. Findings: From the results obtained through the experiments, powder feed rate contributes to 82.81% of the variability in wear volume, whereas the laser power mostly impacts micro hardness; influencing it by 89.46% confirmed with ANOVA. In order to determine the optimal processing parameters among various objectives, this research applies the grey relational method. The results showed that the wear volume and micro hardness of the composite were significantly affected by the Stelcar reinforcement. Employing Grey relational analysis combined with several optimization objectives into a transparent method, resulting in a clad material with the lower wear volume and higher micro hardness. The optimized processing parameters predicted grey relational grades with an error rate of 1.39% and a significant contribution of 63.60% from laser power. This study confirmed that multi-objective optimization could enhance laser-cladded surface mechanical characteristics and laid out the theoretical foundation for this approach. Novelty: This study introduces an innovative approach to surface modification by employing the laser cladding technique to reinforce Stelcar alloy particles, thereby creating a dense coating on the substrate. Keywords: Laser Cladding, AZ61 magnesium alloy, Stelcar alloy, Coating, Optimization

A novel comprehensive framework for surface roughness prediction of integrated robotic belt grinding and burnishing of Inconel 718

Surface roughness serves as a critical metric for assessing surface integrity, directly influencing the service performance of components. Hardening burnishing is a regularly used post-grinding procedure for Inconel 718 that can simultaneously reduce surface roughness and improve surface mechanical characteristics. A novel comprehensive framework is proposed to predict the surface roughness of Inconel 718 processed by the integrated robotic belt grinding and burnishing system developed in this study. Accounting for abrasive grain conditions and material removal rate during grinding, the L-BFGS-B optimization algorithm and image processing are utilized to predict the ground surface roughness first. Building upon this foundation, theoretical models are applied to ascertain the critical burnishing force needed to enter the hardening burnishing stage. Following this, the Expansion Cavity Model and Hertz theory are used to predict the roughness of the hardening burnished surface, which is only applicable when the step-over value exceeds a critical value. The proposed framework not only enhances our comprehension of the mechanisms underlying material surface deformation but also offers a novel avenue for predicting surface roughness during integrated robotic belt grinding and burnishing with high accuracy.

Investigation of the surface mechanical properties of functionalized single-walled carbon nanotube (SWCNT) reinforced PDMS nanocomposites using nanoindentation analysis.

Functionalizing single-walled carbon nanotubes (SWCNT) with different chemical functional groups directly enhances their chemical adhesion and dispersion in viscous polymeric resins such as polydimethylsiloxane (PDMS). Nevertheless, the ideal surface polarity (hydrophilic or hydrophobic) for SWCNT to foster stronger chemical bonding with PDMS remains uncertain. This investigation delves into the impact of enhanced SWCNT dispersion within PDMS on the surface mechanical characteristics of this flexible composite system. We use carboxylic acid-functionalized SWCNT (COOH-SWCNT) and silane-functionalized SWCNT (sily-SWCNT), recognized for their hydrophilic and hydrophobic surface polarities, respectively, as reinforcing agents at ultra-low weight percentage loadings: 0.05 wt%, 0.5 wt%, and 1 wt%. We perform quasi-static nanoindentation analysis employing a Berkovich tip to probe the localized mechanical behavior of PDMS-SWCNT films at an indentation depth of 1 μm. Plastic deformation within the samples, denoted as plastic work (Wp), as well as the elastic modulus (E), hardness (H), and contact stiffness (Sc) of the composites are examined from the force-displacement curves to elucidate the enhancement in the surface mechanical attributes of the composite films.

Effect of TiO2 on Thermal, Mechanical, and Gas Separation Performances of Polyetherimide-Polyvinyl Acetate Blend Membranes.

Blend membranes consisting of two polymer pairs improve gas separation, but compromise mechanical and thermal properties. To address this, incorporating titanium dioxide (TiO2) nanoparticles has been suggested, to enhance interactions between polymer phases. Therefore, the objective of this study was to investigate the impact of TiO2 as a filler on the thermal, surface mechanical, as well as gas separation properties of blend membranes. Blend polymeric membranes consisting of polyetherimide (PEI) and polyvinyl acetate (PVAc) with blend ratios of (99:1) and (98:2) were developed via a wet-phase inversion technique. In the latter, TiO2 was incorporated in ratios of 1 and 2 wt.% while maintaining a blend ratio of (98:2). TGA and DSC analyses were used to examine thermal properties, and nano-indentation tests were carried out to ascertain surface mechanical characteristics. On the other hand, a gas permeation set-up was used to determine gas separation performance. TGA tests showed that blend membranes containing TiO2 had better thermal characteristics. Indentation tests showed that TiO2-containing membranes exhibited greater surface hardness compared to other membranes. The results of gas permeation experiments showed that TiO2-containing membranes had better separation characteristics. PEI-PVAc blend membranes with 2 wt.% TiO2 as filler displayed superior separation performance for both gas pairs (CO2/CH4 and CO2/N2). The compatibility between the rubbery and glassy phases of blend membranes was improved as a result of the inclusion of TiO2, which further benefited their thermal, surface mechanical, and gas separation performances.

The Effect of Laser Irradiation on The Properties of Micro to Nanolayer Titanium Alloy

In this work, a new technique for Laser irradiation of Ti6Al4VELI was developed, this alloy is an alpha-beta structure, the irradiation was done at room temperature in the normal atmosphere without any external media, the effects of laser irradiation on the Ti6Al4VELI such as the chemical composition of the alloy before and after laser irradiation were recorded by Energy dispersive X-ray “EDX” technique. the affected zone (thickness) of the laser irradiation technique was limited to the surface in micro to the nanoscale. The variation in mechanical properties due to laser irradiation at different wavelengths was measured by the determination of the variation of modulus and hardness at maximum load with a number of pulses. The wear rate was measured for the Ti6Al4VELI before and after laser irradiation at 5000 pulses where the maximum improvement in the hardness occurs at all wavelengths, in the current study, it improves surface mechanical characteristics. The effect of laser irradiation on the structures was studied by SEM, the quantitative analysis was done at all irradiation conditions. Laser treatment is suitable for both field works and industry. The improvement in mechanical properties occurs due to microstructure changes without significant changes in chemical composition. the efficiency and lifetime of the alloys were increased, the work is registered as patent number 24014 in the Egyptian patent office.

Effect of annealing temperature on the magnetic domain structure and surface mechanical properties of Ni-C composite thin films: Magnetic and lateral force microscopy, and force-distance spectroscopy

Present study demonstrates the effect of annealing temperature on magnetic domain structure and surface mechanical properties of Ni-C composite thin films. The thin films with constant nickel and carbon concentration were synthesized by electrodeposition method at low voltage and at room temperature. The electrodeposited thin films were annealed at 80 °C, 100 °C, 120 °C and 140 °C for twenty minutes. Magnetic domain structures of varying width and contrast were observed in the films with change in annealing temperature by magnetic force microscopy (MFM). A qualitative study of the effect of annealing temperature on surface friction of the thin films were investigated by Lateral force microscopy (LFM). A decreasing trend is observed in the surface friction of the films with increase in annealing temperature. The Force-Distance spectroscopy was performed on the thin films annealed at different temperatures to explore the chemical and surface mechanical characteristics of the samples. Pull-off force or adhesive force of the thin films is decreased with increase in annealing temperature of the films.

Impact of laser parameters on additively manufactured cobalt-chromium restorations

Statement of problemThe selective laser melting (SLM) process has become popular for the fabrication of frameworks for metal-ceramic restorations, although their surface roughness is greater than with cast or milled frameworks. Limited information is available regarding the surface mechanical characteristics of cobalt-chromium (Co-Cr) SLM-manufactured restorations. PurposeThe purpose of this in vitro study was to adapt the laser parameters for a remelting strategy, scanning the outer boundary of Co-Cr specimens, to reduce surface roughness and solidification defects, to determine microhardness, to investigate surface morphology and microstructure, and to establish surface mechanical characteristics. Material and methodsCo-Cr specimens were SLM manufactured by using a typical melting (TM) strategy and an adaptive remelting (AR) strategy. The AR strategy involves rescanning 50% of the contour, varying the laser parameters. The roughness parameters considered were Ra and Rz. Vickers hardness was measured by microindentation with a 9.81-N force (ASTM E384-17). The surface morphology was investigated by scanning electron microscopy, the chemical composition by energy-dispersive X-ray spectroscopy, and the phase identification by using X-ray diffraction. The mechanical surface properties measured were the nanohardness, elastic modulus, and dissipation energy. One-way ANOVA with the Tukey procedure was used to compare the groups (α=.05). ResultsThe innovative AR strategy reduced the surface roughness by 45% compared with TM, comparable with their cast counterpart. The smoothest AR surface was obtained by using 75 W and 350 mm/s for the first scanning of the contour, followed by a second remelting with 80 W and 700 mm/s. The microstructure of AR specimens had limited solidification defects, a chemical composition similar to that of raw powder, and a surface microhardness over 600 HV1. A fine grain structure in a single matrix phase was detected both on TM and AR specimens. The mechanical characteristics of the smoothest Co-Cr surface were 218 GPa elastic modulus, 746 HVIT Vickers nanohardness, 21 243 pJ plastic energy, and 26% nanoindentation work ratio. Significant differences were observed between the melting strategies (P<.05) both for surface roughness and microhardness. ConclusionsThe laser scanning strategy affects both the surface roughness and the hardness of SLM-manufactured specimens. The results show that using the AR strategy and proper laser parameters can reduce the roughness and increase the surface hardness of Co-Cr specimens made of conventional powder feedstock.

Prediction of the depth of dynamically recrystallized microstructure during hard turning of AISI 4140

Metallurgical and mechanical surface characteristics are among the key properties of the material and determine the performance as well as the lifetime of a machined part. These characteristics can be defined as surface roughness, residual stress states, hardness distributions, ductility and chemical stability and can be summarized under the term ‘surface integrity’. Due to hard turning, an altered microstructure and surface topography is created. This altered microstructure is called White Layer and characterized by a dynamically recrystallized (DRX) microstructure. To predict the depth of the DRX layer, the Zener-Hollomon (ZH) model is implemented in different finite element softwares (Abaqus/Explicit and MSC Marc/Implicit) and the results are compared.

Severe Shot Peening to Get a Nano-Structured Surface Layer in Low-Alloy Steel

Shot peening is a cold work treatment that consists in impacting a metallic surface with a flux of spherical shots with the aim to introduce compressive residual stresses field and work hardening on the surface layer. Both aforementioned parameters are responsible for improved fatigue behaviour of treated components. Recent studies have shown that if applied using severe parameters (severe shot peening), this treatment can be categorized as a severe plastic deformation surface treatment. Severe shot peening is able to strongly modify the microstructure of the surface layer of material by increasing the dislocation density that define new grain boundaries and progressively form ultrafine structure. In this work, conventional shot peening and severe shot peening treatments were applied to 39NiCrMo3 steel samples with the aim to study the microstructural changes. The samples were also characterized in terms of surface roughness, micro hardness, residual stresses, and surface work-hardening. Particular attention was focused on the microstructural analysis as a function of the coverage level, with the aim to assess the evolution of grain size from the surface to the inner material and induced gradient microstructure. The results indicated that severe shot peening causes a more remarkable improvement of the general surface mechanical characteristics with respect to conventional shot peening, and revealed a notable microstructural alteration induced by the treatment.

Experimental Research on Mechanical Properties of Cement Based Composites PVA Fiber Reinforced

Airport pavement surface mechanical characteristics and PVA fiber content, through experiments on PVA fiber reinforced cement matrix composites flexural strength, compressive strength and other mechanical properties are analyzed experimentally.

The Effect of Chemical Compositions of Tool Steel on the Level of White Layers Homogeneity and the Surface Hardness

The process of nitriding is commonly used in electronic hardware besides the automotive components. So far, there are still gains no optimum result. The atom diffusivity homogeneity effects on the material surface mechanical characteristics are yet to be done. The effecting factors like the composition of the chemicals elements in the materials are needed to be observed. In this paper the nitriding process on three types of tool steel materials with a different chemical composition was observed. The nitriding temperature and time is 550 0C and 4 hours, respectively. The white layer formed on the surface was indentified connected to their mechanical properties. The result showed that the hardness of materials is strongly affected by the stability or the homogeneity of the white layer in the surface. The homogeneity is strongly influenced by the chemical elements composition in materials. The highest hardness level, 975.5 HV occurs at the AISI P20 which shows the most homogeneous thickness surface due to Chrom composition of 2%. The next hardness level, 751.2 HV takes place in the AISI 4340 steel with 1.4 % Cr composition, and the lowest hardness, 720.8 HV occurs at the AISI 4140 with 1.07% Chrom.

Effects of Chemical Additives of CMP Slurry on Surface Mechanical Characteristics and Material Removal of Copper

Investigations were performed to study the effects of H2O2 as oxidant, glycine as complexing agent, and benzotriazole (BTA) as inhibitor on surface mechanical characteristics and material removal of copper. Etch rates and surface roughness of Cu samples were measured in the presence of these chemicals at pH 4 or pH 10 under static conditions. Scanning electron microscopy images revealed that the surface of etched copper samples became layered and porous. Scratching experiments were carried out on the etched surface to investigate effects of these chemicals on mechanical removal of copper using atomic force microscopy. It was observed that the scratched depth of these etched Cu samples was higher than that of Cu metal. The addition of glycine enhanced chemical dissolution and mechanical removal greatly. However, the further addition of BTA made both of them decreased, suggesting BTA not only inhibitor of chemical dissolution, but also inhibitor of mechanical removal. In most cases, the measured hardness values of etched copper surface were slightly higher than that of Cu metal. These results indicated that changes of surface structure were the primary reason for increase of mechanical removal of copper, but not changes of copper surface nanohardness.

Surface Mechanical Characteristics and Fatigue Life Experiments of Premixed Water Jet Peening Strengthening

In order to obtain the premixed water jet peening strengthening amplification effect,research the effects of premixed water jet peening on surface micro hardness,surface residual stress and fatigue life of 2A11 aluminum alloy and 45 steel.The micro hardness tester and X-ray stress analyzer are used to respectively determine peened surface micro hardness and surface residual stress.The scanning electron microscope is used to observe the fatigue fracture morphology,then the change rules of peened surface micro hardness and surface residual press stress with the change of peening pressure,scanning velocity and target distance.It is indicated that the premixed water jet peening can greatly improve the fatigue life of 2A11 aluminum alloy and 45 steel,the fatigue life of peened specimens can respectively improve 25.31 and 18.56 times in comparison to unpeened specimens when the stress amplitude of 2A11 aluminum alloy and 45 steel is respectively 155.7 MPa and 282 MPa.The fatigue cracks of unpeened specimens initiate from the surface of specimens;but for peened specimens,some fatigue cracks initiate from the surface of specimens,others from inside of specimens,when the fatigue source is inside the specimen,cracks initiate at the inclusion.Therefore,the premixed water jet peening is an effective method to improve the fatigue life of metallic componens.

Combined Influence of Substrate Stiffness and Surface Topography on the Antiadhesive Properties of Acr-sP(EO-stat-PO) Hydrogels

Biomaterials that prevent nonspecific protein adsorption and cell adhesion are of high relevance for diverse applications in tissue engineering and diagnostics. One of the most widely applied materials for this purpose is Poly(ethylene glycol) (PEG). We have investigated how micrometer line topography and substrate elasticity act upon the antiadhesive properties of PEG-based hydrogels. In our studies we apply bulk hydrogel cross-linked from star-shaped poly(ethylene oxide-stat-propylene oxide) macromonomers. Substrate surfaces were topographically patterned via replica molding. Additionally, the mechanical properties were altered by variations in the cross-linking density. Surface patterns with dimensions in the range of the cells' own size, namely 10 μm wide grooves, induced significant cell adhesion and spreading on the Acr-sP(EO-stat-PO) hydrogels. In contrast, there was only little adhesion to smaller and larger pattern sizes and no adhesion at all on the smooth substrates, regardless the rigidity of the gel. The effect of varied substrate stiffness on cell behavior was only manifest in combination with topography. Softer substrates with line patterns lead to significantly higher cell adhesion and spreading than stiff substrates. We conclude that the physical and mechanical surface characteristics can eliminate the nonadhesive properties of PEG-based hydrogels to a large extent. This has to be taken into account when designing surfaces for biomedical application such as scaffolds for tissue engineering which rely on the inertness of PEG.

Final stages of sintering of ceramic materials: Effect of residual porosity and microstructure on mechanical characteristics of surface

The final stage of sintering determines the mechanical characteristics of material. Usually the final stages of sintering are optimized via residual porosity and grain size and shape (that are believed to control mechanical characteristics) with the help of temperature and time of sintering. Elimination of residual porosity at final stage of sintering may be accompanied by excessive grain growth. Grain growth may take place as a result of secondary recrystallisation during solid state sintering. During sintering in the presence of a liquid phase, grain growth may be a result of “dissolution-precipitation” mechanism, as well as a result of direct coalescence owing to migration of solid-solid boundaries. A study of the load dependence of hardness and deviations of values of microhardness from the average value can be an instrument of optimization of the final stages of sintering.

Mechanical properties of ion implanted glasses

It is well known that heavy ion implantation causes modifications of the surface mechanical characteristics of glasses. At first a compaction is induced with increasing ion fluence, then a relief is observed after a maximum tension stress. In this paper we report the results of a study on the mechanical resistance of Ar implanted soda-lime glasses. Vickers microindentation tests have been performed by measuring both the percentage of cracks, which develop after application of a loaded square pyramidal indenter on the glass, with respect to the number of tests and the length of cracks. In order to clarify the mechanisms responsible for the ion induced mechanical modifications, the influence of the implantation parameters and the thermal stability of the modified surface layers have been investigated.