Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “TOPOGRAPHY”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Corrosion Behavior of Aqua-Blasted and Laser-Engraved Type 316L Stainless Steel

The effect of aqua blasting and laser engraving on surface microstructure development, residual stress and corrosion resistance of type 316L stainless steel has been investigated. Aqua blasting resulted in a deformed near-surface microstructure containing compressive residual stresses. Subsequent laser engraving produced a surface layer with tensile residual stresses reaching to a depth of 200 microns. Changes of surface roughness topography were accompanied by the development of a thick oxide/hydroxide film after laser engraving. The atmospheric corrosion behavior of all surfaces with MgCl{sub 2}-laden droplets was compared to their electrochemical response in 1M NaCl and 0.7 M HCl aqueous solutions. The measured total volume loss after atmospheric corrosion testing was similar for all investigated surface conditions. Laser-engraved surface exhibited the smallest number of corrosion sites, but the largest mean corrosion depth.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface Modification by Friction Stir Processing of Low-Carbon Steel: Microstructure Investigation and Wear Performance

A low-carbon steel sheet with a thickness of 5 mm was subjected to friction stir processing (FSP) by one to four different passes. The microstructures of different regions were characterized using the optical microscopy and electron backscatter diffraction. The Vickers micro-harness was measured at the distance of 200 μm below the processed surfaces. The influence of pass numbers (PNs) on wear resistance was studied in terms of coefficients of friction (CoFs), weight losses and wear rates. SEM topographies of the worn surfaces were also studied to evaluate the wear mechanisms. Microstructure observations showed that Widmänstatten ferrite plates were formed in stir zones (SZs) and heat affected zones. As PN increased, these grains were widened due to the increment of the carbon diffusivity and lengthened because of the high heat input and microstructure anisotropy. Besides, increasing the PN causes increasing of the hardness and wear resistance, simultaneously. Specifically, the wear rate in the SZ was reduced from 2.8 × 10{sup −2} mm{sup 3} m{sup −1} in base metal to 0.3 × 10{sup −2} mm{sup 3} m{sup −1} in sample which was subjected to 4 FSP passes. However, variation in PN had no considerable effect on CoFs. Oxidative wear mechanism was observed on the worn surface of the steel and the FSPed samples while more debris was formed by increasing the PNs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Residual Stress Distribution and Microstructure of a Multiple Laser-Peened Near-Alpha Titanium Alloy

Laser peening without coating (LPwC) was performed on a Ti-2.5 Cu alloy with multiple passes (1, 3 and 5), using a Nd:YAG laser (1064 nm) at a constant overlap rate of 70% and power density of 6.7 GW cm{sup −2}. Hardness and residual stress profiles indicated thermal softening near the surface (< 100 μm) and bulk softening due to adiabatic heating. Maximum hardness (235 HV at 500 μm) and maximum residual stress (− 890 MPa at 100 μm) were observed for LPwC with 1 pass. Surface roughness and surface 3-D topography imaging showed that the surface roughness increased with the increase in the number of passes. XRD results indicated no significant β phases. However, peak shifts, broadening and asymmetry were observed and interpreted based on dislocation activity. Microstructures indicated no melting or resolidification or refinement of grains at the surface. Twin density was found to increase with the increase in the number of passes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of In Situ Intermetallics on the Microstructural Array and Saline Corrosion Performance of Cast Al/WCp Composites

Al-matrix composites, ex situ reinforced with WC nanoparticles and in situ reinforced with Al{sub 3}(Ti,W), Al{sub 12}W, Al{sub 5}W and Al{sub 4}W, have been fabricated by casting assisted by K{sub 2}TiF{sub 6} wetting agent addition and mechanical stirring. A satisfactory particle incorporation and distribution accompanied by a high reactivity have been attained. The presence, topography, chemical composition of all included phases and their occurrence as clusters or single particles are clarified and justified. Al{sub 12}W is the predominant aluminide phase at WC ≤ 1.5 vol.%. Al{sub 4}W (primarily) and Al{sub 5}W (secondarily) are the predominant aluminide phases at WC ≥ 2.0 vol.%. WC nanoparticles have acted as heterogeneous nucleation sites to Al{sub 3}Ti particles. Reverse polarization tests in 3.5 wt.% NaCl show that the governing form of corrosion is intergranular corrosion of Al around Al{sub 3}FeSi{sub 2} eutectic, fine plates. The corrosion steps/mechanisms are identified. Clusters of aluminides and carbide nanoparticles, as well as intergranular WC nano-dispersoids and their Al-matrix have remained corrosion-free. The role of the aluminides combined with WC remaining nano-cores as inhibitors of the eutectic Al{sub 3}FeSi{sub 2} cathodic activity is highlighted.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface Integrity Analysis of Ti6Al4V After Semi-finishing Turning Under Different Low-Temperature Cooling Strategies

During machining of difficult-to-cut alloys, the rapid tool wear as a consequence of the high values of cutting forces and temperatures significantly affects the surface integrity of the machined surfaces reducing the product in-service performances. The use of conventional cutting fluids limits the tool deterioration, but provides several environmental issues to deal with, such as the exhausted fluid disposal, cleaning of the parts after machining, health hazards for the machines operators. In recent years, several researches have proposed to use environmental-friendly cryogenic coolants, whose very low operating temperatures have demonstrated to be able to inhibit the thermally activated tool wear mechanisms leaving the machined surface almost free from pollutants. In this framework, the aim of this research work is to analyze the surface integrity of the machined surfaces produced in semi-finishing turning of the Ti6Al4V titanium alloy under different low-temperature cooling techniques, namely liquid nitrogen (LN{sub 2}), carbon dioxide (CO{sub 2}) and gaseous nitrogen (N{sub 2}) cooled at different temperatures, using the dry and wet cutting conditions as baseline. The surface integrity was evaluated considering both the surface finish (surface defects, roughness and topography) and the surface microstructural and mechanical alterations (altered layer, nano-hardness and residual stresses). The results showed that the best performances were obtained using N{sub 2} cooled at − 150 °C, which determined both the absence of surface defects, as wrinkles or feed marks irregularities typical of the surface generated under LN{sub 2}, and high compressive residual stresses that made the surface suitable for biomedical and aerospace applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Wear Mechanisms in Contacts Involving Slippers in Axial Piston Pumps: A Multi-Technical Analysis

Axial piston pumps are widely used in actuation as power conversion systems, especially in aeronautics. Even though they combine compactness and efficiency, wear of their parts reduces their lifespan. Studies on these pumps often consist in analytic or numerical analyses of lubricated contact between their components. Piston slippers are in tribological contacts with swashplate, pistons and slipper retainer. This study aims to understand wear mechanisms in the contacts involving this central component. An experimental multi-technical analysis of helicopter pumps parts after several functioning times is presented. To determine wear mechanisms, worn surfaces are observed with SEM. 3D surface roughness measurements provide surface topography. Contact conditions and consequently wear severity and mechanisms differ from one contact to another. Detached coarse carbides from the swashplate surface act as an abrading third-body against slippers and swashplate. Debris generated in this contact is carried by the fluid to the other contacts. Although pistons are made of the same steel as swashplate, there is no carbide detachment and wear comes from debris polluting the fluid. Slipper retainer is almost not worn, and debris causes abrasive wear and craters generation in the slippers.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nonlinear Resonance Response of Porous Beam-Type Implants Corresponding to Various Morphology Shapes for Bone Tissue Engineering Applications

Having excellent biocompatibility and apatite mineralization as well as efficient mechanical properties makes bredigite as one of the most attractive bioceramics. A beam-type porous biological implant in a 3D-printed architecture is designed with micron pore size. The surface properties, morphology, and size of the composed powders are evaluated using Scherrer and Williamson-Hall equation. The effect of MNPs deposition into the bredigite bioceramics and correlation with temperature effect on roughness of the prepared bio-nanocomposite are also investigated for hyperthermia application potential. The composed powders are characterized by x-ray diffraction, and then scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (weight change, TGA), and atomic force microscopy are utilized to evaluate the surface topography. The resonance response is the tendency of a bone scaffold to respond at prominent amplitude while the frequency of its oscillations is equal to the structure’s natural frequency of vibration. Therefore, based on the obtained mechanical properties via the experimental approach for the bio-nanocomposite material, an analytical solution based upon the multiple-timescale method is carried out to analyze the nonlinear primary resonance of a 3D-printed porous beam-type biological implant under uniform-distributed load. According to SEM observations, there are hard agglomerates in the bredigite-magnetite nanoparticles (Br-MNPs) bio-nanocomposite material with low weight fraction of MNPs. However, they are broken down by increasing the amount of MNPs. Also, it is displayed that for lower MNPs weight fraction, the height of jump phenomenon related to the nonlinear resonance response is maximum and minimum for, respectively, irregular and mesoporous shapes of morphology, but their associated forcing amplitudes related to the bifurcation points are minimum and maximum, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Tribological Behavior of Electrochemically Etched AISI 316 Stainless Steel with a Textured Surface

In this work, AISI 316 stainless steel (316 SS) was electrochemically etched in four NaCl solutions (10, 15, 20, and 25 wt.%) to form textured surfaces. Surface morphologies, three-dimensional surface topographies, and surface profiles of the textured 316 SS samples were obtained by scanning electron microscopy (SEM) and laser scanning confocal microscope (LSCM). Sliding friction tests of the textured 316 SS samples were conducted in air and under grease lubrication. The results suggested that the variable degrees of microtextured surfaces after electrochemical etching in 10, 15, and 20 wt.% NaCl solutions. The 316 SS samples etched in 15 and 20 wt.% NaCl solutions showed more promising tribological performance than other samples, as reflected by their friction coefficients, mass loss per unit distance traveled (mg/m), and wear morphologies.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Co{sub 3}O{sub 4} Addition on Friction and Dry Sliding Wear Characteristics of 8 mol% Yttria-Stabilized Cubic Zirconia

The aim of the present study was to investigate the influence of Co{sub 3}O{sub 4} additive on the microstructure, wear, and tribological properties of 8 mol% yttria-stabilized cubic zirconia (8YSZ) using a pin-on-disk tribometer, surface profilometer, hardness tester, and a scanning electron microscopy system. Specimens were produced by doping 1-15 wt.% Co{sub 3}O{sub 4} in 8YSZ using a colloidal process, sintering at 1500 °C for 1 h, and subsequent annealing at 1500 °C for 10 and 50 h. Microstructural analysis showed that Co{sub 3}O{sub 4} dissolved partially in 8YSZ, with the undissolved Co{sub 3}O{sub 4} precipitating as a secondary phase at the grain boundaries. Further, the addition of Co{sub 3}O{sub 4} enhanced the grain size. Wear tests were carried out using an Al{sub 2}O{sub 3} ball as the counterface against ceramic disk under dry sliding friction conditions at room temperature (24 °C). The wear volume of 8YSZ decreased from 0.30 to 0.11 mm{sup 3} as a result of the addition of 15 wt.% Co{sub 3}O{sub 4}. Additionally, friction coefficient of the 8YSZ significantly reduced from 0.55 to 0.17 at the beginning stage of the sliding after the addition of 15 wt.% Co{sub 3}O{sub 4}. This was because Co{sub 3}O{sub 4} creates a thin lubricating layer on the friction surface. In addition, the undoped and Co{sub 3}O{sub 4}-doped 8YSZ specimens exhibited abrasive wear under the dry sliding friction conditions, owing to the formation and propagation of microcracks, which resulted in the removal of material from the surface. The specific wear rate of 8YSZ decreased with increasing the Co{sub 3}O{sub 4} content. Thus, the addition of Co{sub 3}O{sub 4} to 8YSZ improves its wear resistance and surface topography.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Preheated Microstructure Vis-à-vis Process Parameters and Characterization of Orange Peel in Incremental Forming of AA1050 Sheets

The present investigation systematically analyzes and compares the influence of microstructure and crystallographic texture of AA1050 sheet to that of the most critical process parameters, namely tool dimension, and incremental step depth, in single-point incremental forming (SPIF) process. The sheet samples were preheated at different temperatures to reform the original, i.e., distorted and misoriented grain distribution. The results from experimental and statistical analyses report higher sensitivity of global spring back, surface topography and forming limits strains to variations in microstructure and texture than tool diameter and incremental step depth. The preheating of the sheets resulted in the formation of preferential texture by grain reformation, which leads to the increase in the fraction of homogeneous orientated grains. Such grains increase the maximum forming limit strains and reduce the global spring back in SPIF. Fractography analysis of the failed components revealed that improvement in formability due to grain homogenization (developed texture) may be attributed to larger average void diameter. Empirical models were also developed, and optimized levels of parameters were identified to maximize the efficiency of the SPIF process. Further, qualitative and quantitative characterization of orange peel roughness was carried out by segregating the external formed surface into surfaces subjected to orange peel roughness and tool-induced texture.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Comparative In Vitro Evaluation Between Zirconia and Veneer Ceramic Materials Using Different Techniques

Zirconia surface treatment using different techniques could be employed to overcome the delamination issue reported between veneering ceramic materials and the corresponding zirconia core. The study subjected yttria partially stabilized zirconia core material to grinding and sandblasting as a first surface treatment. An airbrush gun spraying technique was used to coat a uniform thin layer of veneering ceramic (IPS e.max Ceram and Noritake Cerabien ZR) on the core materials followed by performing laser scanning as a second surface treatment. The specimens were investigated for surface topography, interface analysis, elemental compositions, phase transformation, and fracture mode patterns using profilometer, SEM, EDS, XRD, and stereomicroscope. The impact of laser scanning on the shear bond strength before and after storage of specimens in artificial saliva was also studied. Transformable tetragonal phase to monoclinic was predominant in sandblasted specimens followed by laser scanning with observation of micro-cracks at interface. The grinding followed by laser scanning yielded satisfactory outcomes in terms of the presence of coating property. The phase transformation was not detected through the latter technique. The technique greatly enhanced the roughness property and bond strength values which might be considered as a reliable application to improve the longevity of fixed dental crowns in load bearing areas.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Nanoparticle treated stainless steel filters for metal vapor sequestration

The ability to sequester vapor phase radioactive compounds during industrial processes reduces the exposure of workers and the environment to dangerous radioactive materials. Nanomaterials have a lot of potential in this area because they typically demonstrate size- and shape-dependent properties with higher reactivity than bulk. This is due to the increased surface area-to-volume ratio and quantum size effects. In this report, we developed a gold nanomaterial-treated stainless steel filter, namely wools and coupons, that can be efficiently used for zinc vapor sequestration. Without nanoparticle modification, stainless steel coupons do not react or alloy with Zn. Gold nanomaterials were grown onto various stainless steel filters using solution chemistry that is amenable to scaling up. Materials were characterized by electron microscopy, inductively coupled plasma mass spectroscopy and dynamic light scattering before and after exposure to zinc vapors. X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy mapping and ultraviolet-visible spectroscopy confirm the formation of gold-zinc alloys after Zn vapor exposure. Furthermore, the effect of surface topography on nanoparticle morphology, size and loading density were also investigated, and stainless steel surface defects were found to have an impact on the Au NP growth and subsequently Zn sequestration.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface Integrity and Oxidation of a Powder Metallurgy Ni-Based Superalloy Treated by Laser Shock Peening

Laser shock peening is a mechanical surface treatment which can induce large compressive residual stresses and microstructural changes in the material by using repetitive shocks from laser pulses. In this work, the surface integrity (surface microstructure, topography, hardness and residual stress) of a laser shock peening treated powder metallurgy Ni-based superalloy was investigated. Laser shock peening treatment introduces large plastic deformation especially at a depth of about 100 μm from the surface, which increases the local hardness. The residual stress from the surface to the interior of the sample was investigated by synchrotron X-ray diffraction. The maximum compressive stress reaches 400 MPa at the surface, while the depth of the compressive stress is about 0.7 mm. Lastly, the oxidation behavior of the treated and untreated samples was evaluated by thermal exposure at 700°C for 312 h. The LSP treatment decreased the thickness of oxide layer, thereby showing improved oxidation resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Real-Time and Online Monitoring of Glucose Contents by Using Molecular Imprinted Polymer-Based IDEs Sensor

A highly sensitive, selective, reversible, and reusable glucose sensor is developed by using molecularly imprinted polymer-based artificial receptors onto interdigital transducer. Sensor receptors were synthesized through bulk imprinting technology by using styrene as monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, and AIBN as free radical initiator. Topography of the synthesized receptors was investigated by scanning electron microscopy (SEM). Fabricated sensor showed concentration-dependent linear and reversible response with lower limit of detection of 30 ppb and upper limit of detection ~ 500 ppm. Furthermore, newly fabricated sensor is highly selective towards its analyte of interest in the presence of other competing agents, and the regeneration of sensor response has been assessed with the percentage error of less than 2% under the period of 1 year at room temperature and pressure conditions. The reported sensor may have potential technological applications in the field of medical diagnostics, food, and pharmaceutical industry.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Analysis of the Thermal Stability of Very Thin Surface Layers of Corrosion Inhibitors by Time-of-Flight Secondary Ion Mass Spectrometry

The powerful nature of the secondary ion mass spectrometry (SIMS) technique was explored in order to analyse very thin surface layers that were self-assembled on steel material from acidic solution. These surface layers are adsorbed corrosion inhibitors. The SIMS technique proved useful to characterise the molecular structure and homogeneity of thin surface layers in the nanometre range of specific analytes on the metallic substrate. Using SIMS, the thermal stability of these layers was further investigated and the desorption energy at a certain temperature was determined, where special attention was devoted to the method’s static limit. In order to compare, and for certain cases emphasise, the benefits gained by using SIMS in such surface analysis compared with the X-ray photoelectron spectroscopy (XPS) method, the same samples were also analysed by means of the latter. XPS is usually considered to be the most powerful analytical tool in surface analysis studies, but, as shown herein, it has certain limitations compared to SIMS. Finally, the surface topography was investigated by employing atomic force microscopy (AFM) in order to carry out a comprehensive surface analysis. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Well-Balanced Second-Order Convex Limiting Technique for Solving the Serre–Green–Naghdi Equations

In this article, we introduce a numerical method for approximating the dispersive Serre–Green–Naghdi equations with topography using continuous finite elements. The method is an extension of the hyperbolic relaxation technique introduced in Guermond et al. (J Comput Phys 450:110809, 2022). It is explicit, second-order accurate in space, third-order accurate in time, and is invariant-domain preserving. It is also well balanced and parameter free. Special attention is given to the convex limiting technique when physical source terms are added in the equations. The method is verified with academic benchmarks and validated by comparison with laboratory experimental data.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Assessment of surface and bulk-dominated methodologies to measure critical resolved shear stresses in hexagonal materials

We present that crystallographic slip in hexagonal metals involves a number of geometrically distinct slip families characterized by their slip direction and slip plane (basal, prismatic, and pyramidal). Owing to the low symmetry of hexagonal lattices, each of these slip families only have a few symmetrically equivalent slip systems (family members). Furthermore, different slip families become active at different resolved shear stress, i.e., they have different critical resolved shear stress values (CRSS). The plastic anisotropy of hexagonal materials makes the numerical prediction of their plastic behavior challenging and depends critically on the knowledge of CRSS values. The present contribution assesses the reliability of three proposed methods (with additional variations) to quantify CRSS values of the different hexagonal slip families. Those methods (a to c) rely on: (a) the statistics of observed surface slip traces in a (slightly) deformed polycrystal; (b) an iterative adjustment of CRSS values until a simulated single crystal indentation matches the corresponding experiment in terms of load–displacement response and residual surface topography of the indent; (c) in-situ high-energy X-ray diffraction to measure the evolution of resolved stress (from lattice strains) in grains for which single-family slip is probable based upon specific lattice reorientation conditions. Virtual experiments are performed on synthetic microstructures such that the (extracted) CRSS values resulting from simulating the different methodologies can be rigorously compared against the (target) CRSS values that are installed in the phenomenological constitutive material description used in the simulations. The resulting CRSS values of methods (a) exhibit a strong dependence on, and deterioration with, decreasing level of slip trace observability, which is an uncertain quantity in experimental measurements. For the inverse indentation method (b), the predicted CRSS values are within 8 % of their reference CRSS values for the two investigated cases. Lastly, the high-energy X-ray diffraction method (c) most reliably determines CRSS values for basal and prism slip, but lacks a strict grain selection criterion to assess pyramidal slip.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Unveiling the origins of work-hardening enhancement and mechanical instability in laser shock peened titanium

Laser shock-peening (LSP) produces complex gradients in microstructures and residual stresses, which enables fabrication of metallic engineering components with superior mechanical properties. In this work, we use non-destructive and spatially resolved high-energy X-ray diffraction (HE-XRD) to investigate the influences of LSP on microstructure, surface topography, and residual stress for high purity titanium plates. LSP is found to produce large compressive in-plane residual stresses near the peened surface which monotonically decay to zero about 2.5 mm below the surface. These properties were also tracked during in-situ tensile loading, allowing stress partitioning and work-hardening rates to be measured as a function of depth. The surface region is found to have the highest work-hardening rate and remain mechanically stable up to sample failure. In addition, a crystal rigid rotation along a transversal axis of about 27 & nbsp; was observed at large applied strain near the surface region, which is attributed to the formation of denser dispersed shear bands. Furthermore, a sudden drop in tensile stress was observed at a depth of similar to 160 mu m from the LSP surface, indicating the formation of a localized mechanical instability zone (LMIZ). The origin of this LMIZ could be attributed to the increase in shear stress induced by a load transfer from LSP surface due to the formation of denser dispersed shear bands. These observations indicate a localized transition in deformation behavior has occurred from dispersed shear banding to LMIZ and homogeneous deformation.

36 MATERIALS SCIENCE↗