Effect Of Surface Finish Research Articles

Experimental and numerical study of the slip factor for G350-steel bolted connections

In current practice the shear load-slip behaviour of bolted steel connections is estimated based on the friction coefficient and bolt preload. The friction coefficient is approximated by the slip factor, which is determined experimentally through testing of standard specimens. A linear load-slip (F-d) behaviour is typically assumed, with an arbitrary initial stiffness depending on the slip load and an assumed slip displacement. However, even for the standard slip factor test specimens, the F-d behaviour in the initial stage is not necessarily linear. To enable the development of more accurate models for bolted steel connections, it is essential to understand the F-d behaviour of standard specimens constructed using AS/NZS 3678-350 steel, known as G350, a common Australian steel with limited data in the current literature. An experimental program was performed to investigate the effect of surface finish on the shear behaviour. In addition, numerical simulation was carried out and the results were compared with the experimental results including the F-d behaviour. An empirical formula was proposed for the initial slip behaviour and a good fit was demonstrated. The improved understanding of the shear behaviour could be applied to the design of connections for modular buildings which provide suitable site assembly tolerances while controlling the possible cumulative slip displacement.

Rolling fatigue life of PM steel with different porosity and surface finish

Gears made of PM steel are of interest for the automotive industry because they can be produced to near net shape with only a few processing steps.Automotive gears experience a complex contact situation with rolling as well as combined rolling and sliding. They also have to be able to withstand high loads and fairly high temperature variations.Earlier work show that the main limiting parameter of the contact fatigue life of PM steel is the porosity. A higher porosity/lower density will decrease the fatigue life of the PM component.In the present study, the pure rolling contact fatigue life of PM steel with different density and surface finish has been investigated. A rolling contact fatigue test rig, where rods of the tested material are mounted between two rolling wheels, was used. Two densities of PM steel, 6.8 and 7.15 g/cm3 and a full density reference steel with two different surface finishes, centerless grinded and superfinished, were tested. The tests were run for a given number of load cycles or until failure (fatigue life). SEM was used to study the surfaces and cross-sections to reveal the mechanisms of crack initiation and propagation.The higher density PM steel (7.15 g/cm3) outperformed the lower density steel (6.18 g/cm3) by a factor of around 4 in fatigue life at the same surface pressure, regardless of surface finish. Cracks are initiated at a depth of around 100 µm. These cracks propagate and eventually they reach the surface, causing surface damage and failure. For the low density PM steel, both sub surface crack initiation and failure occurred earlier (at a lower number of load cycles) than for the higher density PM steel.Severe surface damage or wear were not found until failure occurred. Still, some initial alteration of the surfaces was seen already after 0.5 million load cycles, in the form of removal of the highest asperity peaks on the centerless grinded surfaces, and opening of the surface pores on the superfinished surface. No effect of surface finish was found on the fatigue life. The difference in surface roughness could induce a difference in local stress concentrations at the surface, but in this test the cracks causing fatigue failure are initiated at a depth where the stress distribution is not affected by local surface stress concentrations. This means that for fairly smooth surfaces roughness, the surface of PM steel is not important when it comes to pure rolling fatigue life.

Fatigue behaviour of additive manufactured materials: An overview of some recent experimental studies on Ti‐6Al‐4V considering various processing and loading direction effects

AbstractAlthough additive manufacturing (AM) has gained significant attention due to the advantages it offers and is currently a focus of much research, design of critical load carrying components utilizing such processes is still at its infancy. This is due to the fact that most of the load carrying components made by AM processes are subjected to cyclic loads, and fatigue behaviour of AM metals is far less understood as compared with those made by conventional methods, such as wrought and cast metals. To better understand the fatigue behaviour of AM metals, a wide range of issues that affect the behaviour in a synergistic manner must be considered. These include the effects of defects, residual stresses, surface finish, geometry and size, layer orientation, and heat treatment. Additionally, due to the multiaxial nature of the loading and/or complex geometries typically manufactured by AM processes, the stress state is often multiaxial including both normal and shear stresses. In this paper, the aforementioned effects influencing the fatigue resistance of AM parts, including torsion and multiaxial fatigue behaviour, are briefly discussed using some recently generated experimental data on Ti‐6Al‐4V by the authors.

Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings

Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidation behaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

Understanding the effect of surface finish on stress corrosion crack initiation in warm-forged stainless steel 304L in high-temperature water

Surface machining is often assumed to be detrimental to stress corrosion cracking (SCC) in nuclear power plant components because of localized deformation, high associated hardness, roughness and tensile residual stresses. However, in the present work, SCC initiation studies for a warm-forged Type 304L stainless steel in high-temperature water showed that the ~1–2 μm thick ultrafine-grained layer introduced by machining improved SCC initiation resistance. Removing the macroscopic machining ridges via grinding decreased the residual tensile stress but led to more extensive cracking. This paradigm shift demonstrates the dominant effect of the microstructure on the oxidation over the mechanical driving force for SCC.

Friction in the contact between skin and a soft counter material: Effects of hardness and surface finish

The interaction behaviour of skin with a counter surface depends strongly on the surface roughness of the counter surface. For relatively hard surfaces this effect is described in various literature, but for soft, or compliant, materials this is much less studied. Inside the contact, the protuberances on the surface will deform substantially. In order to gain insights into the effect of surface roughness and hardness on the frictional behaviour between skin and a soft counter surface a range of experiments were performed using artificial skin and various silicone compounds which are commonly used in medical devices that interact with the human skin. Using these results, a ‘friction map’ was created that shows the friction behaviour as a function of the elastic modulus and the surface roughness. When the surface roughness is increased the friction coefficient decreases due to the reduction in the real area of contact, which weakens the adhesion between the two surfaces. A minimum coefficient of friction was observed at a surface roughness of approximately 4 µm. For the softest compounds tested there was minimal effect of surface roughness on friction because the roughness protuberances inside the contact will be flattened. Silicone compounds with increased hardness showed a larger sensitivity of the friction to the surface roughness, because these harder surface roughness protuberances are more resistant against deformation. The friction map provides a tool when designing products that require certain frictional properties: for products that are required to adhere to skin a smooth and soft material is recommended, whereas for products that require a low coefficient of friction a harder compound with a surface roughness of approximately 4 µm is recommended.

Discussion of Effect of Disk Grinding Surface Finish on Fatigue Strength of the Nuclear Component Material

Disk grinding is often used to repair the scratches of the surface of the component and also used to weld toe finish to mitigate undesirable stress concentration. This study investigates the effect of disk grinding surface finish on fatigue strength of the nuclear component materials. In order to achieve this objective, fully reversed tension-compression strain-controlled fatigue tests of disk grinding finished austenitic stainless steel SUS316L plate are conducted at RT in air. Two types of disk grinding directions, which are parallel and perpendicular to the cyclic loading direction, are considered in this study, and fatigue test results are compared to S-N curves obtained by emery polishing and lathe machining finished specimens. It is found that the disk grinding surface finish decreases fatigue strength of materials and, in some cases, the fatigue strength of disk grinding finished materials is lower than that of lathe machining finished specimens with maximum height roughness Rz over 100 μm. In order to find out the mechanism of fatigue strength reduction due to the disk grinding, metallographic observations and some measurements such as roughness, hardness and residual stress of the surface are carried out. In addition, the effect of stress concentration and texture of the micro grooves introduced to the surface of the material by disk grinding are discussed.

Effect of surface finishing on flexural strength of translucent y-tzps

Effect of surface finishing on flexural strength of translucent y-tzps

Surface finish effect on dry sliding wear behavior of thermally oxidized commercially pure zirconium

Abstract The effect of surface polishing on the wear behavior of thermally oxidized commercial pure zirconium (CP-Zr) under dry sliding conditions was investigated. Surface ground CP-Zr with a roughness of 0.21 μm (Ra) was thermally oxidized (TO) at 650 °C for 6 h. After TO, some samples were polished to smoothen the surface with a finish of 0.04 μm (Ra). The response of the polished and unpolished TO samples to dry sliding wear was investigated under unidirectional sliding conditions. The results show that surface polishing after TO affects the dry sliding wear behavior of TO CP-Zr in several aspects, including coefficient of friction, wear rate, crack formation and oxide layer breakdown. In particular, it is found that smoothening the TO surface favors the formation of semi-circular cracks in the wear track and accelerates oxide layer breakdown during dry sliding. A slightly rough TO surface helps to reduce the tendency of the oxide layer towards cracking and to increase the wear resistance at high contact loads. The mechanisms involved are discussed in terms of asperity contacts, crack formation, propagation and final fracture.

The Effect of Surface Preparation on Surface Damage and Sigma Formation in Duplex Stainless Steel

Sigma formation in duplex stainless steels is known to be detrimental to the mechanical properties of the material and limits the alloys to low temperature applications. In this paper, the surface damage caused by grinding on different grit sizes or polishing, is assessed using EBSD. The surface finish is then related to the depth of sigma formation in the surface region with a quantification of how the surface finish effects the sigma nucleation and growth. Finally, the effect of surface finish and sigma formation on the oxidation characteristics of the material is considered.

Effect of finishing condition on fracture strength of monolithic zirconia crowns.

This study was to evaluate the load bearing capacity of monolithic dental zirconia crowns, and the effect of surface finishing on fracture strength. (1) The zirconia plates were divided into 5 groups and polished by various types of polishing bur, every specimen was analyzed by surface roughness testing, and X-ray diffraction (XRD). (2) The zirconia crowns were classified into 4 groups corresponding to different surface treatments and thickness. All the crowns were cemented and subjected to a load of 7 kg for 5 min. Stored in distilled water at 37°C for 24 h. Observe the typical surface using field emission scanning electron microscopy (FE-SEM). The cycling and fracture tests were carried out. The data was statistically analyzed. The groups had better fracture strength after polishing. This suggests the monoclinic phase can be eliminated by optimizing the polishing process. Moreover, the fracture strength increased with occlusal thickness (p<0.05).

Reflectance determination of optical spectral emissivity of metal surfaces at ambient conditions

Optical pyrometry requires knowledge of both spectral radiance and spectral emissivity to accurately measure temperature. No reliable compendium of spectral emissivity data currently exists for common metals in the optical and near-infrared spectral regions where pyrometry is typically performed. Here, we measure the spectral reflectivity of numerous common metals, with known surface finishes, between 400 and 1100 nm. The measurements are carried out under ambient conditions, near 300 K at an atmospheric pressure of ∼0.78 bar. We then calculate the emissivity as a function of the wavelength for each sample. We define and use the illumination and collection geometries most practical for applying these measurements to radiometric thermometry. We also examine the effect of surface finish upon the relative spectral emissivity of a given material and find qualitative guidelines for predicting the increase in emissivity with increasing surface roughness. These measurements can both improve the accuracy and precision of optical pyrometry and provide the necessary reference value for converting emerging diagnostic measurements of relative spectral emissivity under extreme dynamic conditions into absolute dynamic spectral emissivity.

Effect of Structural State and Surface Finishing on Corrosion Behavior of 1.4970 Austenitic Steel at 400 and 500 °C in Flowing Pb-Bi Eutectic With Dissolved Oxygen

The effect of structural state (solution annealed (SA) and after 40% cold work (CW)) and surface finishing (turning, grinding, and polishing) on the corrosion behavior of austenitic 1.4970 (15-15 Ti) steel in flowing (2 m/s) Pb-Bi eutectic containing 10−7 mass% dissolved oxygen at 400 °C and 10−6 mass% O at 500 °C is investigated. At 400 °C for ∼13,000 h, the corrosion losses are minor for steel in both structural states and for surfaces finished by turning and grinding—a thin Cr-based oxide film is formed. In contrast, the polished surface showed initiation of solution-based corrosion attack with the formation of iron crystallites and preferential propagation along the grain boundaries. The depth of corrosion attack does not exceed 10 μm after ∼13,000 h. At 500 °C for 2000 h, the samples in both structural states showed general slight oxidation. Cold-worked steel underwent a severe groove-type and pit-type solution-based attack of 170 μm in maximum depth, while the SA sample showed only sporadic pit-type corrosion attack to the depth of 45 μm in maximum.

Effects of Corrosion in Supercritical CO2 on the Microstructural Evolution in 800H Alloy

This study investigates corrosion of Fe–Ni-based alloy 800H that were exposed to supercritical CO2 (sCO2), ambient air and argon gas at pressures up to 20 MPa, at 650 and 750 °C for up to 1000 h. This alloy and other comparable metal alloys are expected to be used in sCO2 heat exchanger cycles as proposed in the DOE Advanced Ultra-Supercritical program. Alloy 800H is considered for this application, because it meets the high-temperature strength and creep rupture requirements and is a lower cost alternative to other Ni-based alloys. The oxidation performance and microstructural changes due to exposure in sCO2 have been evaluated and compared with exposures in air and Ar. The 800H alloy showed similar oxide scale thicknesses in sCO2 as in air. A recrystallized zone was observed beneath the oxide formed in air and sCO2. No such zone was observed after exposure to Ar, suggesting this recrystallization was associated with the oxidation process and not simply an effect of surface finishing. A wider recrystallized zone was observed underneath the oxide formed in sCO2 than in air. The effect of air and sCO2 on internal oxidation and carburization was investigated as well, showing that air led to more internal oxidation but less internal carburization than sCO2. It was concluded that the carbon species provided by the sCO2 atmosphere in conjunction with the increased grain boundary density in the recrystallized zone allowed for more ingress of carbon into the base metal, which resulted in a higher densities of carbides beneath the oxide scale.

Effect of surface finishing on the colour stability and translucency of dental ceramics

BackgroundThe purpose of this study was to investigate the effects of staining solutions and surface finishing on the colour stability and translucency of hybrid ceramic (HC) and resin nanoceramic (RNC) materials.MethodsTwenty four groups consisting of 10 specimens (240 specimens in total) were created out of HC and RNC, including six groups to be stored in distilled water served as the controls groups. The Vita Enamic technical set, Shofu polishers, medium and fine rubber wheels and Sof-Lex polishing discs were used as polishing instruments. Cola, tea, and coffee were used as staining solutions. The colour differences (∆E*) and translucency parameter (TP) were evaluated by a spectrophotometer. Data were analysed by a One-way Analysis of Variance (ANOVA) and Mann-Whitney U test.ResultsThere was a statistically significant difference between the ∆E* values of the HC specimens in the coffee groups and the ∆E* values of the other HC groups (p < 0.05). The ∆E* values of the RNC specimens in the coffee and tea groups were not different from the specimens in the cola groups (p > 0.05). The TP values of the polished groups were higher than the Sof-Lex groups and the Shofu groups on both HC and RNC materials (p < 0.05).ConclusionsIncreased ∆E* values were observed in HC specimens stored in a coffee solution compared to the specimens stored in a tea or cola solution. Both of the RNC specimens stored in coffee and tea had higher ∆E* values than the RNC specimens stored in the cola. The TP values of both HC and RNC specimens stored in the coffee solution decreased.

Surface Finish Effects Using Coating Method on 3D Printing (FDM) Parts

One of three-dimensional (3-D) printing economical processes is by using Fused Deposition Modelling (FDM). The 3-D printed object was built using layer-by-layer approach which caused “stair stepping” effects. This situation leads to uneven surface finish which mostly affect the objects appearance for product designers in presenting their models or prototypes. The objective of this paper is to examine the surface finish effects from the application of XTC-3D coating developed by Smooth-On, USA on the 3D printed parts. From the experimental works, this study shows the application of XTC-3D coating to the 3-D printed parts has improve the surface finish by reducing the gap between the layer

Wear and friction performance under lubricated reciprocating tests of steel powder mixtures sintered by Spark Plasma Sintering

Abstract Literature indicates that porosity in sintered materials decreases mechanical properties and fatigue resistance. However, given porosity shape and distribution on a surface, it is possible that these small cavities could improve surface lubrication conditions. This work aims to evaluate the effects of porosity, surface finishing, oil viscosity and heat treatment on wear and friction of two sintered carbon steels during lubricated high contact pressure tests. Samples were characterized prior and after tests by SEM, optical profilometry and hardness measurements. Main results showed that surface hardness and porosity controlled wear behavior of sintered material in high load conditions. Rougher material seemed to activate anti-wear additives contained on the lubricant, promoting less worn volume than polished samples.

Effect of surface finish on stain affinity of a lithium disilicate esthetic ceramic material

Effect of surface finish on stain affinity of a lithium disilicate esthetic ceramic material

Fatigue Design with Additive Manufactured Metals: Issues to Consider and Perspective for Future Research

Additive manufacturing (AM) is a state of the art technology enabling fabrication of complex geometries, in addition to providing other advantages as compared to the traditional subtractive manufacturing methods. However, a wide variety of factors significantly influence fatigue behavior and structural performance of components made of AM metals. In addition to the fabrication process parameters, these include the effects of build direction, surface roughness, residual stresses, and heat treatment, and multiaxial stress states. At the microstructural level, defects such as pores and lack of fusion particles, as well as other microstructural features affect the behavior. In this paper, first a brief review of the aforementioned factors affecting the fatigue behavior will be presented. Then some experimental multiaxial fatigue data for selective laser melting (SLM), which is a powder bed fusion (PBF) metal AM process, of a common Ti alloy (Ti-6Al-4V) with applications in many industries are presented and discussed. The effects of surface finish, heat treatment, and stress state will be evaluated, as well as failure mechanisms in different life regimes and the role of defects. Finally, some additional factors that must be considered before wide acceptance of the AM technology in critical load bearing applications will be addressed.

Characteristics of Volatile Organic Compounds Released from Various Types of Decorative Particleboards

Abstract Surface finishes change the characteristics of volatile organic compounds (VOCs) released from wood-based panels. This research studied the effects of different finishes on the VOCs released from particleboard (18 mm thick). Various materials, such as polyvinyl chloride (PVC), melamine paper, and water-based paint, were compared with unfinished particleboard. A 1-m3 climate chamber and gas chromatography–mass spectroscopy were used to examine the types and rates of release and the percentages of various VOCs released by decorative particleboard over 28 days. By comparing the characteristics of VOCs released from unfinished particleboard, the effects of different surface finishes were determined. The VOC substances of concern released from particleboards were analyzed by their type and concentration until they reached a state of equilibrium on day 28. Results showed that none of the surface finishes changed the variety of total VOC (TVOC) released from particleboard, but they had a prominent influence on the rate of TVOC released, especially in the early stages. Acrylic water-based paint increased the TVOC release rate from the particleboard, whereas the PVC and melamine finishes decreased the rate. Surface finishing greatly influences the concentration of various VOCs. Although the same types of VOCs were released by the various finished particleboards, they each had different release rates and different variations in their release-rate tendencies. Surface finishing can change the percentages of various VOC components, so that the amounts were different depending on the finish, and different types of VOCs were controlled better by certain types of finishes.