Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “friction”

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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Simulation of emergent compaction banding fronts caused by frictional boundaries

This study examines the role of boundary friction in promoting heterogeneous compaction in soft rock specimens loaded at high confining pressure outside the domain of compaction localisation. An elastoplastic constitutive model characterised by tunable hardening/softening behaviour is used to conduct the analyses. Finite-element simulations suggest that material instability is a non-necessary condition for the emergence of compaction fronts. Such fronts propagated as a result of a severe deviation in the local responses induced by frictional constraints. Overall, these findings suggest that boundary effects can bias the assessment of the extent of the compaction localisation domain. Experimental countermeasures and informed model calibration procedures are therefore necessary to minimise such bias and enable more accurate predictions of soft rock compaction.

42 ENGINEERING↗
DOE OSTI2015

Wall-Friction Support of Vertical Loads in Submerged Sand and Gravel Columns

Laboratory studies of the ‘floor-loads’ under submerged vertical columns of sand and/or gravel indicate that such loads can be approximated by a buoyancy-corrected Janssen-silo-theory-like relationship. Similar to conditions in storage silos filled with dry granular solids, most of the weight of the sand or gravel is supported by wall friction forces. Laboratory measurements of the loads on the floor at the base of the water-filled columns (up to 25-diameters tall) indicate that the extra floor-load from the addition of the granular solid never exceeded the load that would exist under an unsupported (wide) bed of submerged sand or gravel that has a total depth corresponding to only two column-diameters. The measured floorloads reached an asymptotic maximum value when the depth of granular material in the columns was only three or four pipe-diameters, and never increased further as the columns were filled to the top (e.g. up to heights of 10 to 25 diameters). The floor-loads were stable and remained the same for days after filling. Aggressive tapping (e.g. hitting the containing pipe on the outside, manually with a wrench up and down the height and around the circumference) could increase (and occasionally decrease) the floor load substantially, but there was no sudden collapse or slumping to a state without significant wall friction effects. Considerable effort was required, repeatedly tapping over almost the entire column wall periphery, in order to produce floor-loads that corresponded to the total buoyancy-corrected weight of granular material added to the columns. Projecting the observed laboratory behavior to field conditions would imply that a stable floor-load condition, with only a slightly higher total floor pressure than the preexisting hydrostatic-head, would exist after a water-filled bore-hole is filled with sand or gravel. Significant seismic vibration (either a large nearby event or many micro-seismic events over an extended period) would likely be necessary before the full (buoyancy-corrected) weight of the sand and/or gravel would be ‘delivered’ to the bottom of the submerged column.

42 ENGINEERING↗
DOE OSTI2018

Complete Status Report Documenting the Development of Friction Stir Welding for Producing a Butt Joint in Thin Wall Tubing of ODS Alloys

A challenging attempt using friction stir welding to produce a butt joint between two 1.0 mm thick plates of 14YWT was nearly successful. The modified tool pin mostly penetrated the thickness of the adjoined thin plate samples resulting in a small blunt notch on the bottom surface of the butt joint. A bend occurred in the thin plate sample due to formation of stresses from clamping the thin plate sample during FSW. The peak displacement of the bend occurred along the center line of the butt joint. The weld zone showed good microstructure mixing with some flashing mostly on the retreating side that suggested excess heat input by friction between the traveling and spinning tool pin and thin plates of 14YWT. Neutron diffraction experiments were performed on the bent sample of 14YWT to measure the residual stresses in the butt joint on the HB-2B beam line at the Neutron Residual Stress Facility at HFIR. However, the neutron scattering to background noise ratio was very low during data acquisition. Measurements of lattice strains were obtained in the rolling (RD) and normal (ND) directions but not in the extrusion direction (ED) of the thin plate sample. Unfortunately, the quality of the data was not sufficient for determining the residual stresses in the butt joint. From the previous neutron scattering experiments conducted on four hot rolled plates (R1, R2, R3 and R4) of 14YWT, the residual stresses were calculated from lattice strain data and plotted in 2-D color contour maps for ED, RD and ND. The results showed variations in the magnitude and spatial position of residual stresses in the microstructure of the four plates. The magnitude in residual stresses in ED and RD increased gradually with increasing rolling deformation for R1 (50%) to R2 (76%), followed by larger increases in R3 (89%) and R4 (95%). The maximum peaks in residual stresses for R4 was ~710-730 MPa in ED and RD. The residual stresses in ND were below ~300 MPa for each of the 4 rolled plates, with a maximum residual stress in R4 (95%) of ~400 MPa. These results indicated that significant residual stresses representing ~57% of the yield stress of 14YWT (SM13) had accumulated in the 14YWT plate after hot rolling to the 1 mm thickness, which was used in the FSW experiments. The microstructure analysis of the 1.0 mm thick plate of 14YWT containing the butt joint produced by FSW revealed significant changes in the grain structure and texture between the unaffected zone (UZ) of the rolled plate and the butt joint weld. In the UZ, the grains were severely elongated after 95% deformation and mainly possessed the {101} texture component in the ED. Two predominant grain misorientation angles were observed: one consisting of small misorientations of <5º between highly elongated grains and the other consisting of large misorientations of >15º in pockets of small grains that might have formed by dynamic recrystallization processes during rolling of the plate at 1000ºC. The morphology and texture of grains in the heat affected zone (HAZ) were similar to those in UZ, except the grains had coarsened due to excess heat input during FSZ. A population of pores formed and the grains both coarsened and changed to isotropic morphology in the microstructure of the butt joint on both the advancing and retreating sides. The texture of grains in both regions were randomly orientated between the 3 poles {001}, {101} and {111}. The main difference in texture of grains between the advancing side and retreating side was with the misorientation angles of neighboring grains. Most of the grains in the advancing side had misorientation angles of >5º indicating that these grains experienced recrystallization. On the retreating side, areas containing larger grains showed high misorientation angles of >15º compared to areas appearing as bands of grains with misorientation angles of <5º and between 5º-15º. Numerous small pockets of grains with low misorientation angles of <5º were distributed in the microstructure among the grains showing high misorientation angles of >15º. It was determined that the grains associated with low misorientation angles contained sub-grain structures, which was consistent with both recrystallization and recovery mechanisms for grains located on the retreating side of the butt joint. These results demonstrate the complex microstructure that evolves in the microstructure of 14YWT resulting from the input of high temperatures and severe deformations during FSW.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Microstructure and Mechanical Performance of the Friction Stir Welds Made on Neutron-Irradiated Steel with Helium

This report describes new experimental results on the microstructure and mechanical performance of the friction stir welds made on neutron-irradiated steel with helium. The report focuses on helium-related issues, specifically, helium-induced degradation in the welded joint, aiming to repair irradiated components of nuclear power plants (NPPs). The friction stir welds analyzed here were produced at Oak Ridge National Laboratory previously, and limited characterization work was performed, mostly addressing the presence or absence of macroscopic cracks. The present work attempts to perform a more comprehensive study to assess microstructure conditions, grain size, plastic strain gradients, the morphology of the helium-induced damage, and deformation behavior.

42 ENGINEERING↗
DOE OSTI2021

QXF Cold Mass Friction Test

The purpose of this test is to determine the longitudinal force on the stainless steel shell that is required to break the friction between the stainless steel shell and the aluminum shell underneath. This is achieved by suspending the short magnet between two backing plates on the eight grade 8 threaded rods which replace the 8 stainless steel toke tie rods in the magnet assembly. Eight hydraulic cylinders are mounted to each backing plate. Six, 22" sections of the stainless steel shell are welded in place on the magnet, each of which has a slightly different developed length, starting from the baseline design, and becoming progressively looser. A pushing flange is mounted to the stainless steel shells via small tack welds. Four load cells are then attached to the flange at designated points, while additional tooling is attached to each of the cylinders to facilitate the transfer of force from the cylinders to the stainless steel shell During the test, the cylinders will be slowly energized to no more than 7000 psi, with a resultant, longitudinal force on the flange of no more than 125,400 lbf. For each set of shells, the test ends when the load cell monitoring software detects a sharp decrease in force. This will indicate that the friction has broken. The cullenders will then be de-energized and the cycle will repeat for the next test. Welding operations outlined in the procedure (US-HiLumi-doc-4200) are outside the scope of the HA as the work is occurring under a previously-issued burn permit by qualified welders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Comprehensive Characterization of Helium-Induced Degradation of the Friction Stir Weld on Neutron-Irradiated 304L Stainless Steel

The report describes new experimental results on the mechanical performance of the friction stir welds made on neutron-irradiated 304L stainless steel with helium. The report focuses on helium-related issues (e.g., the helium-induced degradation in the welded joint), aiming at the need to repair irradiated components of nuclear power plants. The friction stir welds analyzed here were previously produced at the US Department of Energy’s Oak Ridge National Laboratory, and initial characterization work was performed, mostly addressing the microstructure and if macroscopic cracks and helium bubbles present. The present work attempts to perform a more comprehensive study to assess mechanical performance (i.e., microhardness distribution, tensile properties, tensile deformation behaviors, and fractography analysis).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Subsurface Aggregation of Cationic Friction Reducers: Cause and Prevention

The purpose of this work was to identify the cause of a gelatinous aggregation of friction reducers that was found post-fracturing by RWS operators. RWS sent us samples which we analyzed by scanning electron microscope (SEM). Laboratory experiments were performed to identify the cause of the aggregations and propose a method of preventing them from forming. We concluded that cationic friction reducers were crosslinking with clays, and that this could be prevented by using higher-salinity injection fluid. The results of this study help promote recycling of produced water.

geochemistry↗
DOE OSTI2025

FY25 Cellular Silicone Foam Friction Testing Summary Report

This effort was a collaboration between LANL groups MPA-CINT, E-13, and V-14 to characterize various properties of foam materials for programmatic work. Specifically, MPA-CINT staff members’ contribution to this effort was to perform friction testing of cellular silicone foams of two different porosities with respect to two engineering materials with predefined surface roughnesses. The selected foams (henceforth serving as the sled material interface exposed to motion) had porosities of 67% and 70% with respect to fabricated values. The other materials used in the friction testing measurement couple (static track material) were 304 Stainless Steel (304 SS) and Very High-Temperature Glass-Mica Ceramic, known as Macor®.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation of the Impact of Cross-Polymerization on the Structural and Frictional Properties of Alkylsilane Monolayers Using Molecular Simulation

Cross-linked chemisorbed n-alkylsilane (CH3(CH2)n-1Si(OH)3) monolayers on amorphous silica surfaces have been studied and their structural properties and frictional performance were compared to those of equivalent monolayers without cross-linkages. The simulations isolated for the first time the effects of both siloxane cross-linkages and the fraction of chains chemisorbed to the surface, providing insight into a longstanding fundamental question in the literature regarding molecular-level structure. The results demonstrate that both cross-linkages and the fraction of chemisorbed chains affect monolayer structure in small but measurable ways, particularly for monolayers constructed from short chains; however, these changes do not appear to have a significant impact on frictional performance.

Materials Science molecular dynamics↗
DOE OSTI2017

Analysis of High-Power Diode Laser Heating Effects on HY-80 Steel for Laser Assisted Friction Stir Welding Applications

In this research, several conditions of high power diode laser heated HY-80 steel were characterized to determine the viability of using such lasers as a preheating source before friction stir welding in order to reduce frictional forces thereby reducing tool wear and increasing welding speeds. Differences in microstructures within heat affected zones were identified at specific laser powers and traverse speeds. Vickers hardness values were recorded and analyzed to validate the formation of additional martensite in diode laser heated regions of HY-80 steel. Conditions that produced little to no additional martensite were identified and relationships among high power diode laser power, traverse speed, and martensite formation were determined. The development of heat affected zones, change in grain structure, and creation of additional martensite in HY-80 can be prevented through the optimization of laser amperage and transverse speed.

36 MATERIALS SCIENCE↗
NASA NTRS1956

Friction factors for flow of non-newtonian materials in pipelines

In many industries, non-Newtonian material, such as oils, lubricants, foods, cosmetics, and solid-liquid suspensions, are passed through pipelines during manufacture, application, or transportation. For the proper design of the pipelines, and evaluation of the flow resistance of the materials when flowing in these pipelines is essential. The pressure loss Δ p , due to a material flowing through a straight pipeline can be expressed as a function of a friction factor, φ, so that Δ p = ( pv 2 )/2 L/D φ where φ is a function of the flow properties of the material v is the mean velocity of the material and can be determined from the mas-flow rate, L is the length and D is the diameters of the pipeline, and p is the density of the material. The purpose of this paper is to present a generalized friction diagram, which can be used to determine φ for any material and flow condition, provided the flow properties of the material and the mean flow velocity in the pipeline are known. In composing this diagram generous use is made of the literature and only parts of the diagram and the presentation can claim originality.

Ruth N Weltmann↗
NASA NTRS1966

Friction brake cushions acceleration and vibration loads

Friction brake cushions an object in a vehicle from axially applied vibration and steady-state acceleration forces. The brake incorporates a doubly tapered piston that applies a controlled radial force to friction brake segments bearing against the walls of a cylinder.

Fraser, G. F.↗
NASA NTRS1967

Machine tests slow-speed sliding friction in high vacuum

Testing machine that operates without any lubrication of the machine elements within the vacuum chamber measures static friction and sliding friction at very low speeds. Moving parts are held to a minimum to simplify operation in the vacuum chamber.

Skyrus, J.↗
NASA NTRS1967

Device measures static friction of magnetic tape

Device measures the coefficient of static friction of magnetic tape over a range of temperatures and relative humidities. It uses a strain gage to measure the force of friction between a reference surface and the tape drawn at a constant velocity of approximately 0.0001 inch per second relative to the reference surface.

Cole, P. T.↗
NASA NTRS1969

Prediction of friction coefficients for gases

Empirical relations are used for correlating laminar and turbulent friction coefficients for gases, with large variations in the physical properties, flowing through smooth tubes. These relations have been used to correlate friction coefficients for hydrogen, helium, nitrogen, carbon dioxide and air.

Taylor, M. F.↗