Full Friction Research Articles

A simplified soil-structure interaction model for load-settlement analysis of piles

The full skin friction and full end-bearing of a single pile are not mobilized at the same displacement while the conventional approach often oversimplifies by adding the skin friction to the end-bearing resistance as independent calculation steps. This paper presents a simplified interaction approach for the nonlinear load-settlement analysis of a single pile considering simultaneously the degradation of skin friction resistance and end-bearing resistance hardening under varying loads. The ability to estimate the load-settlement response of piles based on either needed loads or settlement is a special benefit of the proposed approach over existing methods. In addition, the proposed model is able to separate the skin friction resistance, end-bearing resistance and elastic compression at arbitrary settlement. The analytical method shown a satisfactory performance as compared to experimental results for three extensively studied field test situations. The suggested approach shows promise as a suitable solution for the design optimization as well as the preliminary analysis to organize a suitable loading test program. A parametric analysis is conducted to further examine the influence of various significant parameters related to the load-settlement response of piles.

Experimental prediction model for full life friction performance of wet clutch via attention-based LSTM network

Experimental prediction model for full life friction performance of wet clutch via attention-based LSTM network

Modeling and Laboratory Investigation of Tack Coats as Bituminous Pavement Interlayer

The adhesive properties of tack coats between asphalt pavement layers are crucial for the pavement’s structural behavior. This study first involved numerical analyses to compare stress patterns, deformations, and displacements in the pavement structure under various geometric and mechanical conditions. A rational calculation method based on the theory of elastic multilayer systems was used to quantify the impact of layer properties such as thickness, stiffness modulus, and Poisson’s ratio on interlayer bonding. Three bonding conditions—Full Friction, Partial Bonding, and Full Debonding—were analyzed to understand the tack coat’s effect between the top two layers. The second phase involved characterizing the mechanical behavior of the interface through shear strength tests (Leutner shear test) on both laboratory-prepared specimens and samples from a 10-year-old highway. Specimens were prepared using a Roller Compactor and tested under different interface conditions: hot-on-hot (H/H), residual bitumen 200 g/m2 (RB 200), and residual bitumen 400 g/m2 (RB 400). The tests examined the bonding effects in terms of tangential force and shear displacement at failure, as well as the impact of vehicular traffic on rutting and fatigue failure. Finally, this study investigated the long-term aging effects of the binder on interlayer bonding and sought to correlate the results of numerical calculations with those of the laboratory tests.

Brake Wear and Airborne Particle Mass Emissions from Passenger Car Brakes in Dynamometer Experiments Based on the Worldwide Harmonized Light-Duty Vehicle Test Procedure Brake Cycle

Brake wear particles, as the major component of non-exhaust particulate matter, are known to have different emissions, depending on the type of brake assembly and the specifications of the vehicle. In this study, brake wear and wear particle mass emissions were measured under realistic vehicle driving and full friction braking conditions using current commercial genuine brake assemblies. Although there were no significant differences in either PM10 or PM2.5 emissions between the different cooling air flow rates, brake wear decreased and ultrafine particle (PM0.12) emissions increased with the increase in the cooling air flow rate. Particle mass measurements were collected on filter media, allowing chemical composition analysis to identify the source of brake wear particle mass emissions. The iron concentration in the brake wear particles indicated that the main contribution was derived from disc wear. Using a systematic approach that measured brake wear and wear particle emissions, this study was able to characterize correlations with elemental compositions in brake friction materials, adding to our understanding of the mechanical phenomena of brake wear and wear particle emissions.

Concrete Pavement Design Analysis Using AASHTOWare Pavement Mechanistic-Empirical Design Software

Local calibration of pavement performance models embedded in the AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software may be needed to implement this design methodology. A recent survey showed that, despite local calibration, several state highway agencies in the U.S. are using the American Association of State Highway Transportation Officials (AASHTO) Guide for Design of Pavement Structures (1993 version) and the PMED software for comparative design of jointed plain concrete pavement (JPCP). This paper describes the recalibration process of the JPCP distress models in the PMED software and comparative designs obtained by the PMED software and 1993 AASHTO design guide. The results show that the calibration/recalibration process depends on the availability of measured performance data. Not all global coefficients must be changed in the calibration/recalibration process. The 1993 AASHTO design guide yielded higher JPCP slab thickness for projects with high truck traffic than the PMED software when no friction is assumed between the slab and a cementitious base. An assumption of full friction will have a discernible effect on the slab thickness obtained from PMED.

Research on full balance friction hoist shiplifts

Research on full balance friction hoist shiplifts

A novel bi-directional rail variable friction pendulum-tuned mass damper (BRVFP-TMD)

The shape of hysteretic loops for a friction pendulum system transforms when excited by bi-directional motion, which exhibits unexpected dynamic behavior compared with unidirectional motion. Therefore, a novel bidirectional rail variable friction pendulum-tuned mass damper (BRVFP-TMD) with two independent rails that satisfied the purpose of bidirectional structural response control and provided a full bidirectional friction force was proposed. The variable friction arrangement was applied to the rails so that the BRVFP-TMD could be accomplished with a linear hysteretic damping property that is contributed by the displacement-dependent variable friction force. Using unidirectional harmonic excitations with attack angle as bi-directional loading, illustrations were created to investigate the control effect of traditional pendulum friction TMDs with a spherical sliding surface. This demonstrated the collapse of hysteretic loops of traditional pendulum friction TMDs and superiority of BRVFP-TMD in terms of mechanism. For the BRVFP-TMD with a lightly damped structure, the optimizations of the fixed-point theory were accessed to obtain the closed-form solutions of the optimal parameters of the BRVFP-TMD. Numerical verifications based on bidirectional motions were conducted to evaluate the performance of the BRVFP-TMD. The bidirectional earthquake results indicated stable and excellent performance of the BRVFP-TMD in terms of either frequency response reduction or friction energy dissipation efficiency. Meanwhile, bidirectional wind-induced vibrations confirmed the correctness of the optimization and the stable robustness of the optimized BRVFP-TMD.

Approach to Estimate Time to Friction Loss in Pavement Mechanistic-Empirical for the Florida Concrete Test Road

Local calibration of the fatigue cracking model used in the AASHTO Pavement Mechanistic-Empirical (ME) software is critical to accurately prediction of the performance of jointed plain concrete pavement (JPCP). Although calibration involves optimizing coefficients used in the model, other design inputs such as time to friction loss can have a significant impact on pavement performance. The degradation of friction between the concrete and supporting layers is a critical input since it indicates deterioration of the JPCP system before fatigue cracking is observed on the surface. This paper proposes an approach for estimating the time to friction loss for JPCP based on the relationship between effective thickness and pavement age determined with falling weight deflectometer (FWD) data. This study shows that using the estimated time to full friction loss rather than the default time causes a significant impact on pavement performance compared with only optimizing calibration coefficients. Ten sections with a similar climatic zone and JPCP structures to Florida’s concrete test road were considered in the development of a relationship between the time to full friction loss and pavement structure thickness. The relationship was used to estimate the expected time to friction loss for the Florida concrete test road as approximately 55 months for sections with a concrete thickness of 7 in. and 164 months for concrete sections of 10 in.

Efficient tribocatalysis of magnetically recyclable cobalt ferrite nanoparticles through harvesting friction energy

Friction, a common phenomenon in ordinary life, can be converted into positive and negative charges via triboelectrification and can further react with the OH- and dissolved O2 in the solution to generate some active species with strong redox ability in theory, which can be named as tribocatalysis. In this work, the efficient tribocatalysis is obtained in the magnetically recyclable CoFe2O4 nanoparticles synthesized via a hydrothermal method for Rhodamine B (RhB) dye decomposition, in which the mechanical stirring is adopted to generate the friction between the stirring rod and the nanocatalysts surface. After being stirred for 5 h, the CoFe2O4 nanoparticles can tribocatalytically decompose 91.9% RhB dye solution with a concentration of 5 mg·L−1. Due to the continuous full contact and friction between the stirring rod and the CoFe2O4 nanoparticle, the negative and positive charges are respectively retained over the contact area of the CoFe2O4 nanoparticle and the stirring rod, so as to react with hydroxide ions and dissolved oxygen to generate active species achieving the RhB dye decomposition. Subsequently, the different shapes of stirring rod experiments prove that the full contact between the CoFe2O4 nanoparticle and the stirring rod is essential for the efficient tribocatalysis. The electron spin resonance experiments confirm that both ·OH and ·O2- are the main active species. On basis of the recycling utilization experiments’ results, after being magnetically-recycled for 3 cycles, the CoFe2O4 nanoparticles can still decompose 86.5% RhB dye. With these advantages of the efficient tribocatalysis and the magnetically recycle ability, CoFe2O4 nanoparticles are hopeful in dealing with dye wastewater through harvesting the ordinary friction energy in environment.

Characterization, wear and emission properties of MnS containing laser cladded brake disc

In this study, the laser cladding of gray cast iron brake discs using a Fe-based coating material was investigated. A 5 wt% MnS was added as a solid lubricant to the coating formulation to track the improvement of wear and emissions. Microstructural and tribological characteristics of the coated discs (with and without MnS) were studied comparatively. Three different friction materials, that are typically used for commercial brake pads, were adopted to evaluate the performance of the coatings. The pin on disc results indicated that, with the addition of MnS, both friction coefficient and wear rate have been reduced to levels comparable with those obtained in case of uncoated gray cast iron discs. The tribological behavior of MnS containing coating showed the best results when sliding against a Cu full friction material.

Numerical Assessment of Tribological Performance of Different Low Viscosity Engine Oils in a 4-Stroke CI Light-Duty ICE

<div class="section abstract"><div class="htmlview paragraph">Decreasing fuel consumption in Internal Combustion Engines (ICE) is a key target for engine developers in order to achieve the CO<sub>2</sub> emissions limits during a standard cycle. In this context, reduction of engine friction could help meet those targets. The use of Low Viscosity Engine Oils (LVEOs), which is currently one of the avenues to achieve such reductions, was studied in this manuscript through a validated numerical simulation model that predicts the friction of the engine’s piston-cylinder unit, journal bearings and camshaft. These frictional power losses were obtained for four different lubricant formulations which differ in their viscosity grades and design. Results showed a maximum friction variation of up to 6% depending on the engine operating condition, where the major reductions came from hydrodynamic-dominated components such as journal bearings, despite an increase in friction in boundary-dominated components such as the piston-ring assembly. Also, an evaluation of the potential fuel reduction that can be obtained by low viscosity oils during a WLTC approval cycle was performed. Overall, a fuel saving of 1% was obtained. In general terms, the majority of the engine map showed potential for mechanical loss reduction through LVEOs, that is, a better engine efficiency and consequently a decrease in the fuel consumption and CO<sub>2</sub> emitted to the atmosphere. The present work also exemplifies the trade-offs encountered when reducing the engine friction through LVEOs and highlights the need to co-engineer the hardware and lubricant in order to utilize the full friction reduction potential of LVEOs.</div></div>

Study on Friction in Automotive Shock Absorbers Part 2: Validation of Friction Simulations via Novel Single Friction Point Test Rigs

The most important change in the transition from partial to high automation is that the vehicle can drive autonomously, without active human involvement. This fact increases the current requirements regarding ride comfort and dictates new challenges for automotive shock absorbers. There exist two common types of automotive shock absorbers with two friction types. The intended viscous friction dissipates the chassis’ vibrations, while the unwanted solid body friction is generated by the rubbing of the damper’s seals and guides during actuation. The latter so-called static friction impairs ride comfort and demands appropriate friction modeling for the control of adaptive or active suspension systems. In the current article, the simulation approach introduced in part 1 of this study is validated against a single friction point and full damper friction measurements. To achieve that, a friction measurement method with novel test rigs has been developed, which allows for reliable determination of the friction behavior of each single friction point, while appropriately resembling the operating conditions of the real damper. The subsequent presentation of a friction simulation using friction model parameters from different geometry shows the general applicability of the overall friction investigation methodology. Accordingly, the presented simulation and measurement approaches enable the investigation of dynamic friction in automotive shock absorbers with significantly increased development efficiency.

Nature of Non-Adiabatic Electron-Ion Forces in Liquid Metals.

An accurate description of electron-ion interactions in materials is crucial for our understanding of their equilibrium and nonequilibrium properties. Here we assess the properties of frictional forces experienced by ions in noncrystalline metallic systems, including liquid metals and warm dense plasmas, that arise from electronic excitations driven by the nuclear motion due to the presence of a continuum of low-lying electronic states. To this end, we perform detailed ab initio calculations of the full friction tensor that characterizes the set of friction forces. The non-adiabatic electron-ion interactions introduce hydrodynamic couplings between the ionic degrees of freedom, which are sizable between nearest neighbors. The friction tensor is generally inhomogeneous, anisotropic, and nondiagonal, especially at lower densities.

A computational modeling of fully friction contact-interaction in linear friction welding of Ni-based superalloys

A three-dimensional coupled thermo-mechanical model was developed to simulate the linear friction welding (LFW) of same or dissimilar Ni-based superalloys. Full friction contact-interaction for two deformable workpieces rubbing against each other was considered using plastic/plastic friction pair model. Numerical simulated results have been well validated by experimental measured data. Owing to the inherent motion mechanism of LFW, interfacial heat flow varied with time periodically, resulting in the periodic evolution of interface temperature. The distribution of stress field at stationary side alternated dynamically with respect to that at oscillatory side. During LFW of GH4169 to FGH96 superalloys, more heat flowed into the GH4169 superalloy, which resulted in greater temperature gradient than that at side of FGH96 superalloy. More softened materials were extruded out from interface at GH4169 side owing to their better flow property. Peak stress near the interface of GH4169 superalloy side was higher than that at FGH96 side. Additionally, the characteristics of modeling of LFW based on plastic/plastic friction pair model were investigated by performing numerical simulations for LFW experimental phenomena.

Effect of edge distance on shear friction capacity of steel plates anchored with reinforcing bars in comparison with headed bolts

The shear friction capacity calculated using clauses 11.6.4 to 11.6.10 in ACI 318-14 or clauses 11.5.1 to 11.5.6 in CSA-A23.3-14 do not take into consideration the effect of edge distance on the shear friction capacity. The main objectives of this research are to study the effect of edge distance on the shear friction capacity by means of a specifically designed experimental program, to determine the minimum edge distance to develop the shear friction capacity, and to derive an expression for reduction of shear friction capacity for edge distances less than the minimum edge distance. The study involved testing eight specimens. In four specimens, a steel plate was anchored using welded reinforcing steel bars, and in the other four specimens the steel plate was anchored using headed concrete anchors (bolts) (HCA). The steel plates were tested under shear load at edge distances of 75, 150, 225, and 300 mm (3.0, 6.0, 9.0, and 12.0 in), for the two types of anchorage. The results were compared to design values according to ACI 318-14 and CAN/CSA-A23.3-14 standards. An equation is derived to compute the minimum edge distance after which the full shear friction capacity is developed. Another equation is derived to compute the proposed shear capacity for reinforcing bar anchors for edge distances less than the minimum edge distance.

Experimental research on marine oil-lubricated stern tube bearing

Bearings of propeller shafts are very crucial elements of the propulsion system of each of the ships. The safety of shipping depends on their durability and reliability. The new legal restrictions mean that today we are looking for environmentally friendly solutions. That is why water-lubricated bearings are becoming more and more popular. So, will oil-lubricated shaft bearings belong to the past? The bearing with a white metal bushing lubricated with mineral oil, which was subjected to experimental tests, has a number of advantages. First of all, it works in the area of full fluid friction, and in typical shipbuilding conditions it has a significant excess of hydrodynamic load capacity. Therefore, replacing mineral oil with an environmentally friendly lubricant with a similar viscosity seems to be a promising solution. Motion resistance larger than that in water-lubricated bearings compensates for the reliability and durability of this solution.

Friction stir welding of thick section reduced activation ferritic–martensitic steel

Full penetration friction stir welding was conducted on 12 mm thick reduced activation ferritic–martensitic steel at tool rotational speeds of 500 and 900 rev min−1. Comparator welds at 500 rev min−1 were also produced in 6 mm thick reduced activation ferritic–martensitic steel plate to evaluate section thickness effects. Increase in section thickness led to an increase in heat input, which strongly influenced the microstructure evolution in stir zone (SZ), thermo-mechanical affected zone and the overall hardness in the SZ of this steel. In the as-welded condition, the base metal microstructure was significantly altered and resulted in carbide-free grain boundaries. The desirable microstructure and mechanical properties were achieved by subjecting the as-welded joints to appropriate post-weld heat treatments.

Probing the Viscosity Dependence of Rate: Internal Friction or the Lack of Friction?

Deviation from the Kramers' inverse viscosity dependence of rate, k ∝ 1/η, is often attributed to the presence of internal friction in proteins after Ansari et al. in 1992 showed that the folding rate could fit k ∝ 1/(η + σ) where σ is considered the internal friction. Several experimental and computational studies thereafter used fits to Ansari's equation or extrapolated the rate to η = 0 to estimate the internal friction in proteins and attributed its origin to various internal interactions such as ruggedness, dihedral rotation, and salt bridges. Here, we show that the above method to calculate the internal friction is incorrect since the rate in a simple model system without any internal friction yields a nonzero σ. Further investigation reveals that σ correlates with the relative deviation from Kramers' rate at different viscosities, where the deviation itself is caused due to the absence of full solvent friction rather than the presence of internal friction.

Simulation of movement dynamics at collision of vehicles

Abstract A method for calculating the number of rotations of vehicle after side collision made by the vehicle in its translational-rotational motion after a road traffic accident is proposed. This method allows taking into account the full friction work of tires on the road, which is a prerequisite for calculating the speed of the hitting vehicle at the moment of side collision with the vehicle being hit. In this case, the full friction work of tireson the road is determined by summing up the work of translational motion and turn relative to the centre of mass of the vehicle being hit. Correct calculation of the number of rotations ensures significant increase of reliability of the reconstructed event and obtaining materials for a non-biased investigation of the road traffic accident.

Conserving algorithms for frictionless and full stick friction dynamic contact problems using the direct elimination method

SummaryIn this paper, conserving time‐stepping algorithms for frictionless and full stick friction dynamic contact problems are presented. Time integration algorithms for frictionless and full stick friction dynamic contact problems have been designed to preserve the conservation of key discrete properties satisfied at the continuum level. Energy and energy‐momentum–preserving algorithms for frictionless and full stick friction dynamic contact problems, respectively, have been designed and implemented within the framework of the direct elimination method, avoiding the drawbacks linked to the use of penalty‐based or Lagrange multipliers methods. An assessment of the performance of the resulting formulation is shown in a number of selected and representative numerical examples, under full stick friction and slip frictionless contact conditions. Conservation of key discrete properties exhibited by the time‐stepping algorithm is shown.