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1
Cai, Peng, Zhongfan Luo, Xuhua Duan, and Xinshao Qin. "Effect of reciprocating and unidirectional sliding motion on the friction and wear of phenolic resin based composite." Industrial Lubrication and Tribology 71, no. 4 (May 7, 2019): 573–77. http://dx.doi.org/10.1108/ilt-07-2018-0277.
Анотація:
Purpose The purpose of this paper is to investigate the effect of reciprocating and unidirectional sliding motions on friction and wear of phenolic resin-based composite. Design/methodology/approach The phenolic resin-based composite was fabricated by hot press molding, and then the tribological properties were tested on a CSM tribometer with two types of friction motion modes – reciprocating friction and unidirectional friction. Findings The results showed that the composite exhibited low friction coefficient in unidirectional test. However, the wear factor recorded under unidirectional sliding condition was 12-16 times higher than the reciprocating friction results. The SEM and optical microscopy test results showed that changing the relative motion mode resulted in different topography of transfer film, which is responsible for the different friction and wear characteristics of the composite under reciprocating and unidirectional friction conditions. Originality/value Effect of different friction modes, reciprocating friction and unidirectional friction, on friction characteristics of the composite is sought. Different topography of transfer film formed under reciprocating and unidirectional friction conditions contributed to the different friction characteristics.
2
Pasco, Corentin, Muhammad Khan, Jaipal Gupta, and Kenneth Kendall. "Experimental investigation on interply friction properties of thermoset prepreg systems." Journal of Composite Materials 53, no. 2 (June 9, 2018): 227–43. http://dx.doi.org/10.1177/0021998318781706.
Анотація:
A comprehensive novel investigation into the characterisation of interply friction behaviour of thermoset prepregs for high-volume manufacturing was conducted. High interply slipping rate and normal pressure typically used for high-volume manufacturing present challenges when preforming carbon fibre reinforced plastics. The study involved multiple reinforcement architectures (woven and unidirectional with the same rapid-cure resin system) which were characterised using a bespoke interply friction test rig used to simulate processing conditions representative to press forming and double diaphragm forming. Under prescribed conditions, woven and unidirectional prepregs exhibit significantly different frictional behaviour. Results demonstrated the unidirectional material obeys a hydrodynamic lubrication mode. For the woven material, a rate-dependent friction behaviour was found at low normal pressure. At higher normal pressure however, the woven material exhibited a friction behaviour similar to that of a dry reinforcement and significant tow displacement was observed. Post-characterisation analysis of test-specimens showed significant resin migration towards the outer edges of the plies, leaving a relatively resin-starved contact interface. The findings generate new knowledge on interply friction properties of thermoset prepreg for high-volume manufacturing applications, yet reveal a lack of understanding of the influence of tow tensions as well as the pre-impregnation level for a range of processing conditions.
3
Talib, Anis Adilah Abu, Aidah Jumahat, Mohammad Jawaid, Napisah Sapiai, and Alcides Lopes Leao. "Effect of Wear Conditions, Parameters and Sliding Motions on Tribological Characteristics of Basalt and Glass Fibre Reinforced Epoxy Composites." Materials 14, no. 3 (February 2, 2021): 701. http://dx.doi.org/10.3390/ma14030701.
Анотація:
Basalt fibre is a promising mineral fibre that has high potential to replace synthetic based glass fibre in today’s stringent environmental concern. In this study, friction and wear characteristics of glass and basalt fibres reinforced epoxy composites were studied and comparatively evaluated at two test stages. The first stage was conducted at fixed load, speed and distance under three different conditions; adhesive, abrasive and erosive wear, wherein each composite specimens slide against steel, silicon carbide, and sand mixtures, respectively. The second stage was conducted involving different types of adhesive sliding motions against steel counterpart; unidirectional and reciprocating motion, with the former varied at pressure—velocity (PV) factor; 0.23 MPa·m/s and 0.93 MPa·m/s, while the latter varied at counterpart’s configuration; ball-on-flat (B-O-F) and cylinder-on-flat (C-O-F). It was found that friction and wear properties of composites are highly dependent on test conditions. Under 10 km test run, Basalt fibre reinforced polymer (BFRP) composite has better wear resistance against erosive sand compared to Glass fibre reinforced polymer (GFRP) composite. In second stage, BFRP composite showed better wear performance than GFRP composite under high PV of unidirectional sliding test and under B-O-F configuration of reciprocating sliding test. BFRP composite also exhibited better friction properties than GFRP composite under C-O-F configuration, although its specific wear rate was lower. In scanning electron microscopy examination, different types of wear mechanisms were revealed in each of the test conducted.
4
Caliman, Radu. "Tribological Study in Case of Polymeric Composite Materials Reinforced with Unidirectional Carbon Fibers Having Stratified Structure." Applied Mechanics and Materials 657 (October 2014): 422–26. http://dx.doi.org/10.4028/www.scientific.net/amm.657.422.
Анотація:
This paper presents a study of the tribological properties of polymeric composite materials reinforced with unidirectional carbon fibers having stratified structure. Unidirectional reinforces carbon fiber materials are more effective if refer to specific properties per unit volume compared to conventional isotropic materials [. Potential benefits of carbon fibers composite materials are: high resistance to breakage and high value ratios strength/density; resistance to high temperatures; low density and high resistance to wear; low or high friction coefficient. The composites are complex and versatile materials but their behaviour in practice is not fully studied. For instance, polymeric composite materials reinforced with carbon fibers after being investigated in terms of wear, did not elucidate the effect of fiber orientation on wear properties [. Is therefore necessary to investigate the effect of carbon fibers orientation on the friction wear properties of the reinforced composite materials tested to adhesive and abrasive wear. Research work has been done with unidirectional composite materials having overlap 16 successive layers made from a polymeric resin and 60% of carbon fibers. The stratified structure was obtained by compressing multiple pre-impregnated strips, positioned manually. During this experimental work, three types of test samples were investigated: normal, parallel and anti-parallel, taking in consideration the carbon fibre orientation with respect to the sliding direction. The specific wear rate was calculated according to: the mass loss, density, the normal contact surface, the sliding distance and load rating. The friction coefficient is computed function to the friction load and loading value.
5
Liu, Bin, Zu Hua Yang, and Jian Song Zhou. "Tribological Behavior of Polyimide/Zinc Oxide Hybrid Films." Advanced Materials Research 105-106 (April 2010): 438–40. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.438.
Анотація:
A series of polyimide/ZnO films were successfully prepared via a solution process. The friction and wear behavior of the hybrid polyimide films in dry sliding against Si3N4 ball was examined on a DF-PM ball-on-block unidirectional friction and wear test rig. The worn surface morphologies of the films were observed with a scanning electron microscope. It was found that the introduction of zinc oxide led to improving the tribological characteristics and thermal stability of the polyimide films. The polyimide/zinc oxide hybrid films had much better friction-reducing ability and wear-resistance than the neat PI film.
6
Cheng, B., and M. Kortschot. "An energy-based model for the wear of unidirectional carbon fiber reinforced epoxy." Journal of Composite Materials 54, no. 28 (June 24, 2020): 4535–44. http://dx.doi.org/10.1177/0021998320935486.
Анотація:
The wear resistance of unidirectional carbon fiber reinforced epoxy under severe abrasive sliding conditions was studied. It was found that unidirectional laminates tested with the fibers parallel to the sliding direction (UDp) were more wear resistant than the same laminates tested with fibers transverse to the sliding direction (UDap) under the same set of test conditions. A novel energy-based model was developed to explain the difference in the wear rates. It was found that the difference in wear rates between the two orientations was due to differences in the average volume to surface area ratio of the debris, the energy required to generate new surfaces, and a new k factor that represents the fraction of the total friction energy used for creating wear particles. Furthermore, wear volume per sliding distance was found to be linearly proportional the total frictional energy dissipation for both orientations. These findings can be used to simplify wear predictions for industrial applications.
7
SEGU, DAWIT ZENEBE, PYUNG HWANG, and SEOCK-SAM KIM. "EFFECT OF THE TEMPERATURE ON THE FRICTION AND WEAR PROPERTIES OF BULK AMORPHOUS ALLOY." Surface Review and Letters 21, no. 05 (September 29, 2014): 1450067. http://dx.doi.org/10.1142/s0218625x1450067x.
Анотація:
The present paper report the results of an experimental investigation of the temperature effect on the sliding friction and wear properties of the bulk metallic glass (BMG). To improve the friction and wear properties of the BMG, the disk specimens were developed in the alloy system of Fe 67.6 C 7.1 Si 3.3 B 5.5 P 8.7 Cr 2.3 Mo 2.6 Al 2 Co 1.0 using hot metal and industrial ferro-alloys. The friction and wear test was performed using flat-on-flat contact configuration of unidirectional tribometer and Si 3 N 4 ceramic disk used as a counterpart. The worn surfaces of the BMG were observed by using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The results indicated that the friction and wear properties of the BMG depend on the glass transition and the formation of protective oxide film. The friction coefficient decreased with increasing temperature, while it increased slightly when the temperature passed the glass transition temperature (Tg). The worn specimens were exposed to abrasion, adhesion, oxidation and plastic deformation. In addition, obvious surface flow characteristics was accompany during wear test.
8
Suresh, R., P. Shruthi, R. Sunil Kumar, J. Siva, M. Prem Ananth, and R. Ramesh. "Experimental Investigation of Nano-Composite Coated Stainless Steel (316L) Surfaces under Unidirectional Sliding." Applied Mechanics and Materials 440 (October 2013): 37–41. http://dx.doi.org/10.4028/www.scientific.net/amm.440.37.
Анотація:
This work proposes the investigation of nanosized Titanium Aluminum Nitride (TiAlN) on the Stainless Steel (316L) substrate. A chromium interlayer has been applied over the modified surface which will act as an interlayer between the substrate and hard composite coating. The composite coating was prepared by Magnetron Sputtered-Physical Vapour Deposition (PVD) on chromium coated lapped and textured surfaces of stainless steel substrate. Scratch test was performed to characterize the adherence of the coatings on the substrate. TiAlN surface coating over the textured surface exhibits higher adherence than the lapped surface coating surface. The tribological performance of the wear resistant coatings on lapped and textured surfaces was experimentally investigated by pin on disc tribometer at dry sliding contact conditions under various normal loads. The testing results were compared and the results showed that TiAlN coating on textured surfaces exhibited lower friction coefficient and wear rate than lapped coating surfaces under same testing conditions. Sliding wear characteristics such as coefficient of friction and specific wear rate were investigated.
9
Kobykhno, Ilya, Dmytro Honcharenko, Hong Yu Li, Alexey Leonidovich Steshenkov, Jin Bao Xu, and Vladimir Yadykin. "Friction and Wear Characteristics of UD Thermoplastic Tape Based Nanocomposites with Fullerene Soot." Key Engineering Materials 822 (September 2019): 215–23. http://dx.doi.org/10.4028/www.scientific.net/kem.822.215.
Анотація:
A series of unidirectional thermoplastic tapes (UD tapes) specimens based on carbon fibers and polyamide filled with fullerene soot in a concentration of up to 4 wt. % was made. A study of the tribological properties by the 3 Ball on Plate test and Ring on Plate test and was made. Shown that the introduction of fullerene soot up to 2 wt. % decreases scatter of CoF in both ranges of load and velocity. Also, this concentration decreases wear rate almost 2.5 times compare to unfilled specimen. Mechanism of friction and wear was suggested. The obtained tribological results are well consistent with mechanical properties, and agree with previously suggested theory of the effect of fullerene soot on adhesion between polymer and fibers.
10
Cao, Jialiang, Huan Teng, Wurong Wang, Xicheng Wei, and Hongshan Zhao. "Tribological Properties of the 40Cr/GCr15 Tribo-Pair under Unidirectional Rotary and Reciprocating Dry Sliding." Coatings 12, no. 5 (April 20, 2022): 557. http://dx.doi.org/10.3390/coatings12050557.
Анотація:
The unidirectional rotary and reciprocating sliding experiments of the 40Cr pin/GCr15 disc tribo-pair were carried out on the MFT-5000 Rtec friction and wear tester under the same test conditions with a sliding speed of 0.2 m/s and a load of 150 N. Compared with reciprocating sliding, the tribo-pair in rotary sliding exhibits a stabler friction coefficient and better wear resistance. By analyzing the wear surface morphologies of the two pins, the main wear mechanism was found to be adhesive wear. For the tribo-layer of pin under reciprocating sliding, the surface microstructure plastically converges and forms a ridge from both sides to the middle, while a vortex structure is generated in the tribo-layer of pin under rotating sliding. The metamorphic structure and mircohardness of tribo-layer caused by the sliding forms are the key factors affecting the tribological properties.
11
Gao, Sumei, Quanyong Ju, and Chaowu Jin. "Support characteristics and application of permanent magnet suspension active mass drive system." International Journal of Applied Electromagnetics and Mechanics 67, no. 1 (September 2, 2021): 83–96. http://dx.doi.org/10.3233/jae-201631.
Анотація:
In this paper, a kind of permanent magnet (PM) suspension active mass drive mechanism is proposed, and its structure is designed. It has the advantages of non-contact, almost zero friction, small volume, and so on. Aiming at the active driving mass mechanism of PM suspension, the unidirectional PM suspension system and bi-directional PM suspension system are designed respectively, and their analytical models are established. By analyzing and calculating the magnetic force of the unidirectional and bi-directional PM suspension system, the support coefficient of the suspension system is deduced. After theoretical analysis, the structure is simulated and verified by ANSYS MAXWELL 3D in order to determine the correctness of the analytical calculation of the model. Finally, a test device is made and experiments are carried out in the constant temperature laboratory. The experimental results show that the Nd-Fe-B PMs used in the unidirectional suspension system can provide a maximum force of 260 N, which verify the feasibility of the PM suspension active mass drive system.
12
SUWIŃSKA, Katarzyna, and Jacek ŁUBIŃSKI. "THE IMPACT OF THE SELECTED PARAMETERS OF FDM MANUFACTURING TECHNOLOGY ON TRIBOLOGICAL PERFORMANCE OF ABS–STEEL PAIR UNDER DRY FRICTION." Tribologia 290, no. 2 (June 30, 2020): 85–89. http://dx.doi.org/10.5604/01.3001.0014.3743.
Анотація:
The paper presents the result of tribological test of ABS and steel samples sliding under dry friction. Polymeric samples were manufactured of ABS material using FDM technology. Testing was carried out in unidirectional sliding in a ring-on-flat contact in a PT-3 tribometer. The scope of tested parameters included volumetric and mass wear, the friction coefficient, and polymeric specimen temperature. Polymeric specimens used in the study were manufactured at various settings of the 3D printing process such as the orientation of the specimen in print with respect to the printer building tray and the thickness of a single layer of the deposited material. Comparisons of the impact of these parameters on tribological performance of the sliding contact were analysed.
13
Madhanagopal, A., and S. Gopalakannan. "Dry Slide Wear Behavior of Graphite and SiC, TiO2 Filled the Unidirectional Glass-Epoxy Composites." Polymers and Polymer Composites 25, no. 3 (March 2017): 193–98. http://dx.doi.org/10.1177/096739111702500302.
Анотація:
This study determines the friction and the wear properties of the unidirectional glass epoxy composite with Gr, SiC TiO2 powder by using pin on disk apparatus. This tribological data is obtained in dry sliding condition for a constant sliding time of 30 minutes. Test specimens are prepared using hand lay-up process and by varying the different (2, 5, 7) percentage each of graphite and SiC, TiO2 particles addition for the combination of fiber and matrix. The tests are performed by varying the operating parameters of contact pressure (p) and velocity (v). The composites (2% 5%, and 7%) are worn by dry sliding at the steel counter face under ambient conditions. The coefficient of friction reaches maximum of 0.78 at 2 kg load, 2 m/s velocity with testing time duration of 24 min. whereas 5%, 7% sample shows the coefficient of friction 0.28, 0.25 respectively. The specific wear rate value drops to 0.79 (mm3/N-m×10−6) at 2 kg load at 2 m/s velocity for the 5% specimen. The maximum reduction in the specific wear rate at 3 kg load, 1m/s velocity is 32.7 percentages, 5.63 percentages for the 5,7 percentage specimen compared to 2% specimen for the graphite and SiC, TiO2 particle filled composite specimen respectively. The SEM images are also taken to support the results.
14
Stehle, T., B. Prof Azarhoushang, D. Becker, and R. Eisseler. "Gleitreibung der tribologischen Paarung CFK – Werkzeugschneidenoberfläche*/Sliding friction of the tribological pair of CFRP / tool cutting surface." wt Werkstattstechnik online 107, no. 01-02 (2017): 81–86. http://dx.doi.org/10.37544/1436-4980-2017-01-02-83.
Анотація:
Die Reibungsbedingungen bei der Zerspanung von verstärkten Faserverbundkunststoffen werden durch die Oberflächengestalt der Werkzeugschneide beeinflusst. In dieser Studie wurde CFK-UD (unidirektional carbonfaserverstärkter Kunststoff) im Streifenziehversuch mit geschliffenen und gestrahlten Testwerkzeugen bei 5 MPa Flächenpressung untersucht. Die Oberflächen der Testwerkzeuge sind durch bestimmte Rauheits- und Funktionsparameter charakterisiert, die sich auf die Gleitreibung der tribologischen Paarung CFK – Werkzeugschneide auswirken. The friction conditions when cutting fiber-reinforced polymers are significantly influenced by the shape of the tool cutting surface. Hence, different strip drawing tests were carried out at a 5 MPa surface pressure to investigate the behavior of unidirectional CFRP with different test tool surface preparations. The tool surfaces were ground and blasted. The created surface topographies are characterized by particular parameters of roughness and function which affect the sliding friction of the CFRP / tool pair.
15
San Andrés, Luis, and Adolfo Delgado. "Identification of Force Coefficients in a Squeeze Film Damper With a Mechanical End Seal—Centered Circular Orbit Tests." Journal of Tribology 129, no. 3 (February 8, 2007): 660–68. http://dx.doi.org/10.1115/1.2736708.
Анотація:
The damping capability of squeeze film dampers (SFDs) relies on adequate end sealing to prevent air ingestion and entrapment. The paper presents the parameter identification procedure and force coefficients of a test SFD featuring a mechanical seal that effectively eliminates lubricant side leakage. The test damper reproduces an aircraft application intended to contain the lubricant in the film lands for extended periods of time. The test damper journal is 2.54cm in length and 12.7cm in diameter, with a nominal clearance of 0.127mm. The SFD feed end is flooded with oil, while the discharge end contains a recirculation groove and four orifice ports. In a companion paper (San Andrés and Delgado, 2006, ASME J. Eng. Gas Turbines Power, 119, to be published) single frequency–unidirectional load excitation tests were conducted, without and with lubricant in the squeeze film lands, to determine the seal dry-friction force and viscous damping force coefficients. Presently, tests with single frequency excitation loads rendering circular centered orbits excitations are conducted to identify the SFD force coefficients. The identified parameters include the overall system damping and the individual contributions from the squeeze film, dry friction and structural damping. The identified system damping coefficients are frequency and motion amplitude dependent due to the dry friction interaction at the mechanical seal interface. Identified squeeze film force coefficients, damping, and added mass, are in good agreement with predictions based on the full film, short length damper model.
16
Andrés, Luis San, and Adolfo Delgado. "Identification of Force Coefficients in a Squeeze Film Damper With a Mechanical End Seal—Part I: Unidirectional Load Tests." Journal of Engineering for Gas Turbines and Power 129, no. 3 (July 25, 2006): 858–64. http://dx.doi.org/10.1115/1.2436571.
Анотація:
Squeeze film dampers (SFDs) with low levels of external pressurization and poor end sealing are prone to air entrapment, thus not generating enough damping capability. Single frequency, unidirectional load tests were conducted on a SFD test rig replicating a commercial jet-engine configuration. The damper journal is 2.54cm in length and 12.7cm in diameter, with nominal clearance of 0.127mm. The SFD feed end is flooded with oil, while the discharge end contains a recirculation groove and four orifice ports, and a mechanical seal ring in contact with the damper journal. A wave spring pushes the ring ensuring tight sealing to prevent gas ingestion. The mechanical seal also serves to contain the lubricant within the squeeze film land for extended periods of time and; while in operation, to prevent contamination of the ball bearing cartridge. The measurements conducted without and with lubricant in the squeeze film lands, along with a frequency domain identification procedure, render the mechanical seal dry-friction force and viscous damping force coefficients as functions of frequency and motion amplitude. The end seal arrangement is quite effective in eliminating side leakage and preventing air entrainment into the film lands. Importantly enough, the dry friction force, arising from the contact forces in relative motion, increases significantly the test element equivalent viscous damping coefficients. The identified system damping coefficients are thus frequency and motion amplitude dependent, albeit decreasing rapidly as the motion parameters increase. Identified squeeze film force coefficients, damping and added mass, agree well with predictions based on the full film, short length damper model.
17
Menezes, Pradeep L., Kishore, and Satish V. Kailas. "Effect of directionality of unidirectional grinding marks on friction and transfer layer formation of Mg on steel using inclined scratch test." Materials Science and Engineering: A 429, no. 1-2 (August 2006): 149–60. http://dx.doi.org/10.1016/j.msea.2006.05.080.
18
Tertuliano, IS, TP Figueiredo, GAA Machado, T. Cousseau, A. Sinatora, and IF Machado. "The effects of surface conditioning and gear oil type on friction and wear behavior under sliding condition." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 1 (November 24, 2017): 73–84. http://dx.doi.org/10.1177/1350650117740012.
Анотація:
Highly additized low viscous lubricants, new coatings, and surface treatments have been employed by original equipment manufacturers in several tribosystems to reduce emission and fuel consumption. In this sense, this work investigates the tribological response of four different advanced fully formulated gear oils and three different materials (coatings and topography) in terms of friction and wear using a ball-on-disc test rig under pure unidirectional sliding condition and boundary lubrication. The tested lubricants had different base oils: mineral, semi-synthetic, and synthetic with different additive packages. The ball's material was AISI 52100 bearing steel and the bulk material of the tested specimens (discs) were SAE 4320 steel with surface as follows: (i) ground; (ii) subjected to ceramic shot peening (CSP) and, (iii) coated with WC/C. Optical and scanning electron microscopy and 3D profilometry were used to evaluate the wear track and tribofilm formation. It was found that the frictional dependence on the surface topography and lubricant type is not significant, whilst the wear mechanisms were highly dependent on material and surface conditioning. The harder and rougher the contact body, the higher the wear produced in the counter body. At the harsher conditions base oil type control wear more effectively than the additive package.
19
Perez Delgado, Yeczain, Koen Bonny, Patrick De Baets, Patric Daniel Neis, Vanessa Rodriguez Fereira, O. Malek, J. Vleugels, and B. Lauwers. "Dry sliding friction and wear response of WC-Co hardmetal pairs in linearly reciprocating and rotating contact." International Journal Sustainable Construction & Design 2, no. 1 (November 6, 2011): 12–18. http://dx.doi.org/10.21825/scad.v2i1.20430.
Анотація:
This paper presents an experimental evaluation of friction and wear properties of WC-Cocemented carbides. A comparison is made between unlubricated rotating and linearly reciprocating pin-onplate sliding pairs. The plate specimens were WC-10wt%Co grades surface finished by polishing orsequential wire-EDM steps, whereas WC-6wt%Co pins were used as counter body. The tests were carriedout at room temperature using a sliding speed of 0.30m/s and mean Hertzain contact pressures of 1.76 and2.08 GPa, i.e., normal contact loads of 15N and 25N, respectively. The worn surfaces on plate sampleswere quantified in terms of 2–D wear profiles obtained by means of surface topography scanningequipment. Wear mechanisms such as polishing and abrasion were identified using optical microscopy.Inferior tribological characteristics for wire-EDM surface finish compared to polishing were found. Higherfriction coefficient and wear levels were measured in unidirectional rotating sliding experiments comparedto linearly reciprocating test conditions.
20
Łubiński, Jacek, and Paweł Śliwiński. "Multi Parameter Sliding Test Result Evaluation for the Selection of Material Pair for Wear Resistant Components of a Hydraulic Motor Dedicated for Use with Environmentally Friendly Working Fluids." Solid State Phenomena 225 (December 2014): 115–22. http://dx.doi.org/10.4028/www.scientific.net/ssp.225.115.
Анотація:
In the paper the method and results are presented of the testing of tribological performance of a number of hard materials available commercially. The tests consisted in unidirectional sliding with liquid lubrication. The load and velocity regime chosen were similar to a standard four-ball lubricity test with constant velocity and load increasing over time. The regime was modified in such a way that over the initial part of the test both the velocity and load were linearly increased until a certain stable level of each input parameter was reached and the test was then continued till the termination due to chosen criteria. The materials used were high alloy tool steels and sintered carbides, normally used in working of metals by cutting. The lubricants environmentally inert or friendly fluids: water, mineral oil-in-water emulsion and vegetable oil. In the tests, typical sliding friction parameters were recorded, later evaluated on the basis of multiple parameters observable within the test such as e.g. maximum load and velocity reached, calculated maximum surface pressure or presence and amplitude of friction induced vibrations. In the group of material/material/lubricant combinations a ranking was created for each parameter in the assessment set by awarding points for performance. Best performance was granted the least amount of points. Overall performance was then judged by the accumulated number of points. The materials, which were evaluated as performing best have been chosen as input materials for the design and manufacture of a prototype motor for later laboratory and field testing.
21
Pieniak, Daniel, Leszek GIL, Albin Michał WIT-RUSIECKI, Aneta KRZYŻAK, Jarosław SELECH, and Dawid ROMEK. "COMPARATIVE STUDIES OF TRIBOLOGICAL PROPERTIES OF CARBON FIBRE REINFORCED POLYMER COMPOSITES (CFRP) IN DRY SLIDING FRICTION CONDITIONS." Tribologia 286, no. 4 (August 31, 2019): 87–94. http://dx.doi.org/10.5604/01.3001.0013.5968.
Анотація:
The aim of the study was to determine the usable and quality features and tribological properties of four Carbon Fibre Reinforced Polymer laminates (CFRP) newly developed by the authors and to indicate the structures with the most advantageous functional properties. The developed material samples were based on two types of prepreg, Kord Carbon (Fiberpreg GmbH) with twill weave and carbon fibres (UD) by the manufacturer (G. Angeloni S.R.L) with a unidirectional system. In the structure of half of the total number of samples, a manufacturer's (NTPT) epoxy adhesive film (AF) layer was used. Tests of indentation hardness (universal) were carried out according to the Oliver-Pharr method. Tests of resistance to abrasive wear were carried out in dry sliding friction conditions, using the ball-disc method. In combination, a ball made of aluminium oxide (Al2O3) was used as a cooperating element. The test results indicate a significant impact of the structure of the tested materials on the increase in contact strength and the improvement of the tribological properties that result from the application of the AF layer.
22
Nasraoui, Mohamed Tahar, Jamel Chakhari, Boubaker Khalfi, and Mustapha Nasri. "Modeling and analysis of a bolted joint under tension and shear loads." Transactions of the Canadian Society for Mechanical Engineering 43, no. 3 (September 1, 2019): 376–86. http://dx.doi.org/10.1139/tcsme-2018-0042.
Анотація:
In this paper, a prismatic bolted joint subjected to tensile and shear loads is studied. The two applied forces are in the same symmetry plane of the connection. A simplified numerical model is developed, which is constructed from unidirectional finite elements and contact elements. The elastic contact layer of connected parts is represented by a succession of springs. An algorithm computing both the free structure stiffness matrix and the contact stiffness matrix is developed. Due to the shear load, static or kinetic friction can occur at contact surfaces between assembled parts. In each iteration, tangential contact forces are calculated and taken into account in problem solving. A program in C language is developed and used to calculate the model unknowns. Three-dimensional finite element simulations are performed using ANSYS software to verify results obtained by the developed model. The model results are also compared with experimental test data.
23
Gebretsadik, Daniel W., Jens Hardell, and Braham Prakash. "Seizure behaviour of Pb-free engine bearing materials under dry condition." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 2 (April 23, 2017): 106–16. http://dx.doi.org/10.1177/1350650117706641.
Анотація:
Due to new environmental regulations, Pb-free engine bearing materials are becoming more common and there is a need for studying their tribological performance. Under severe operating conditions, failure due to seizure can occur in engine bearings. In this work, seizure behaviour of different multi-layered engine bearing materials has been studied by using a block-on-ring test setup under dry condition. These materials included Al–Sn-based lining with no overlay, bronze lining with polyamide-imide-based overlay containing MoS2 and graphite, bronze lining with two overlays of Al–Sn-based and polyamide-imide-based material, bronze-based lining with Sn-based overlay and bismuth (Bi)-containing bronze with Sn-based overlay. The tests were performed by gradually increasing the load at a specific time interval and in a stepwise manner and at a constant speed under unidirectional dry sliding conditions. The test materials, counter surfaces and the wear debris were analysed using SEM with a view to understand the seizure mechanisms. Bronze-based lining with a polyamide-imide-based overlay containing MoS2 and graphite does not exhibit seizure up to a load of 475 N. For Al–Sn-based lining without overlay, seizure occurs at a relatively lower load of 125 N. The Al–Sn-based lining with no overlay shows higher friction and the polyamide-imide-based overlay containing MoS2 and graphite shows lower friction during the seizure test. In most cases, there is material transfer onto the test ring counter surface. Material transfer onto the counter surface either due to severe adhesion or wear debris adhered and smeared on it. Al–Sn-based lining and an exposed Al–Sn-based overlay show severe adhesion that causes seizure. On the other hand, exposed Pb containing lining and Bi containing lining seize due to mechanical interlocking caused by the adhered wear debris on both surfaces.
24
Egala, Rajesh, G. V. Jagadeesh, and Srinivasu Gangi Setti. "Experimental investigation and prediction of tribological behavior of unidirectional short castor oil fiber reinforced epoxy composites." Friction 9, no. 2 (July 15, 2020): 250–72. http://dx.doi.org/10.1007/s40544-019-0332-0.
Анотація:
AbstractThe present study aims at introducing a newly developed natural fiber called castor oil fiber, termed ricinus communis, as a possible reinforcement in tribo-composites. Unidirectional short castor oil fiber reinforced epoxy resin composites of different fiber lengths with 40% volume fraction were fabricated using hand layup technique. Dry sliding wear tests were performed on a pin-on-disc tribometer based on full factorial design of experiments (DoE) at four fiber lengths (5, 10, 15, and 20 mm), three normal loads (15, 30, and 45 N), and three sliding distances (1,000, 2,000, and 3,000 m). The effect of individual parameters on the amount of wear, interfacial temperature, and coefficient of friction was studied using analysis of variance (ANOVA). The composite with 5 mm fiber length provided the best tribological properties than 10, 15, and 20 mm fiber length composites. The worn surfaces were analyzed under scanning electron microscope. Also, the tribological behavior of the composites was predicted using regression, artificial neural network (ANN)-single hidden layer, and ANN-multi hidden layer models. The confirmatory test results show the reliability of predicted models. ANN with multi hidden layers are found to predict the tribological performance accurately and then followed by ANN with single hidden layer and regression model.
25
Sarsembayeva, А., A. Zhusshupbekov, and Ph E. F. Collins. "Evaluation of frost heave in clay soils." BULLETIN of L.N. Gumilyov Eurasian National University. Technical Science and Technology Series 135, no. 2 (2021): 14–26. http://dx.doi.org/10.32523/2616-7263-2021-135-2-14-26.
Анотація:
Frost heaving in clayey soils with a low coefficient of permeability raises a lot of questions regarding the cryosuction, surface tension forces, and accompanying phase transfer of water. The freeze-thaw laboratory test results were considered in this work in terms of temperature and volumetric parameters change, dry density, and water mass transfer. The article presents a model for calculating the mass transfer of water (vapour) in the gas state under the influence of cryogenic forces. Findings include the improved understanding of the heat and mass transfer phenomenon during the unidirectional freezing of soils in an open system. Most of the tests for engineering properties registered a slight reduction in relation to strength, cohesion, and angle of internal friction. However, there was a significant increase in the coefficient of permeability after the freeze-thaw cycles with initially dense compacted soil samples, which was due to loosening and moistening of the soil samples during the heave at sub-zero temperatures. The conceptual model for frost heave in soils was developed based on the vapour mass transfer. There was presented algorithm of vapour flow calculation in unsaturated soils using fundamental thermodynamic equations.
26
Ahmed, Rizwan, Christian Maria Firrone, and Stefano Zucca. "Design and Calibration of a Tri-Directional Contact Force Measurement System." Applied Sciences 11, no. 2 (January 19, 2021): 877. http://dx.doi.org/10.3390/app11020877.
Анотація:
In low pressure turbine stages, adjacent blades are coupled to each other at their tip by covers, called shrouds. Three-dimensional periodic contact forces at shrouds strongly affect the blade vibration level as energy is dissipated by friction. To validate contact models developed for the prediction of nonlinear forced response of shrouded blades, direct contact force measurement during dynamic tests is mandatory. In case of shrouded blades, the existing unidirectional and bi-directional contact force measurement methods need to be improved and extended to a tri-directional measurement of shroud contact forces for a comprehensive and more reliable validation of the shroud contact models. This demands an accurate and robust measurement solution that is compatible with the nature and orientation of the contact forces at blade shrouds. This study presents a cost effective and adaptable tri-directional force measurement system to measure static and dynamic contact forces simultaneously in three directions at blade shrouds during forced response tests. The system is based on three orthogonal force transducers connected to a reference block that will eventually be put in contact with the blade shroud in the test rig. A calibration process is outlined to define a decoupling matrix and its subsequent validation is demonstrated in order to evaluate the effectiveness of the measurement system to measure the actual contact forces acting on the contact.
27
Merklein, Marion, and Martin Grüner. "Mechanical Behaviour of Ceramic Beads Used as Medium for Hydroforming at Elevated Temperatures." Key Engineering Materials 410-411 (March 2009): 61–68. http://dx.doi.org/10.4028/www.scientific.net/kem.410-411.61.
Анотація:
The need of light weight construction for high efficient vehicles leads to the use of new materials like aluminium and magnesium alloys or high strength and ultra high strength steels. At elevated temperatures the formability of steel increases as the flow stresses decrease. Forming high complex geometries like chassis components or components of the exhaust system of vehicles can be done by hydroforming. The hydroforming process by oils is limited to temperatures of approximately 300 °C and brings disadvantages of possible leakage and fouling. Using granular material like small ceramic beads as medium could be an approach for hydroforming of ultra high strength steels like MS W1200 and CP W800 at temperatures up to 600 °C. The material properties of granular material are in some points similar to solid bodies, in other points similar to liquids. For understanding and simulation of the behaviour of the medium a basic characterisation of ceramic beads with different ball diameters is necessary. Powder mechanics and soil engineering give ideas for experimental setups. For the conversion of these approaches on the one hand the behaviour of the ceramic beads itself has to be characterized, on the other hand the contact between a blank and the beads have to be investigated. For the tests three different kinds of spheres with a diameter between 63 microns and 850 microns are used. In unidirectional compression test compressibility, pressure distribution in compression direction and transversal compression direction and the effect of bead fracture are investigated. The tests are carried out at different compression velocities and for multiple compressions. For determination of friction coefficients between blank and beads and determination of shear stress in bulk under compression a modified Jenike-Shear-Cell for use in universal testing machines with the possibility of hydraulic compression of the beads is built up. The gained data can be used for material modelling in ABAQUS using Mohr-Coulomb or Drucker-Prager model.
28
Ueno, Shunkichi, Satoshi Takata, Yasuhiro Tanabe, Takashi Akatsu, Eiichi Yasuda, and Yoshiharu Waku. "High Temperature Internal Friction Behavior of Unidirectionally Solidified Al2O3/YAG Eutectic." Materials Science Forum 638-642 (January 2010): 2482–86. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2482.
Анотація:
In this paper, the internal friction behaviors of unidirectionally solidified Al2O3/YAG eutectic that are examined by the authors in passed several years are reviewed. The internal friction of this eutectic increased with increasing temperatures above 1200oC. The apparent activation energy of the eutectic sample in the range from 1100 to 1400oC was same to that of Al2O3 single crystal. Above 1200oC, the internal friction of this material drastically increased with increasing temperatures. The magnitude of the internal friction strongly depended on the elevated temperatures and the cycle numbers of the torsional loading. For the 1400oC test, the internal friction gradually increased with the loading cycles and then saturated by 103 times of the loading cycles.
29
Singh, M., R. M. Dickerson, Forrest A. Olmstead, and J. I. Eldridge. "SiC (SCS-6) fiber reinforced–reaction formed SiC matrix composites: Microstructure and interfacial properties." Journal of Materials Research 12, no. 3 (March 1997): 706–13. http://dx.doi.org/10.1557/jmr.1997.0105.
Анотація:
Microstructural and interfacial characterization of unidirectional SiC (SCS-6) fiber reinforced–reaction formed SiC (RFSC) composites has been carried out. Silicon–1.7 at.% molybdenum alloy was used as the melt infiltrant, instead of pure silicon, to reduce the activity of silicon in the melt as well as to reduce the amount of free silicon in the matrix. Electron microprobe analysis was used to evaluate the microstructure and phase distribution in these composites. The matrix is SiC with a bi-modal grain-size distribution and small amounts of MoSi2, silicon, and carbon. Fiber push-outs tests on these composites showed that a desirably low interfacial shear strength was achieved. The average debond shear stress at room temperature varied with specimen thickness from 29 to 64 MPa, with higher values observed for thinner specimens. Initial frictional sliding stresses showed little thickness dependence with values generally close to 30 MPa. Push-out test results showed very little change when the test temperature was increased to 800 °C from room temperature, indicating an absence of significant residual stresses in the composite.
30
Rouby, Dominique, A. Kaflou, Pascal Reynaud, Sylvain Jacques, and O. Rapaud. "Layered Interphases in Ceramic Matrix Composites and Relation with Interfacial Behaviour." Advances in Science and Technology 45 (October 2006): 1475–82. http://dx.doi.org/10.4028/www.scientific.net/ast.45.1475.
Анотація:
Unidirectional SiC/SiC minicomposites were produced by infiltration of a Hi-Nicalon fibre tow by using pulsed chemical vapour deposition (P-CVD). The sequence of precursor gazes inlet steps determines the structure of the Pyrocarbon/TiC layered interphase deposited first on the filaments. The SiC matrix is then deposited with a given thickness. The different interphase structures will be described. The interface behaviour was characterized by indentation method. The load is applied on the fibre-end at a polished cross-section of the composite, and the displacement of that fibre-end is measured. The push-in test on thick specimens shows that the fibre debonds at a given fibre stress and then slides under a certain frictional shear stress. Both parameters increase when the TiC layers become discontinuous, like aligned TiC clusters in a Pyrocarbon matrix. The load-displacement behaviour is in very good agreement with theory when the interfacial shear stress is kept constant, non depending on relative slip displacement. The push-through test on thin composite slices gives directly access to sliding resistance because the fibre is less compressed. The load displacement curves obtained will be described and analysed. For example, sliding velocity jumps revealed a slight increase in sliding resistance with velocity. During push-back, a seating drop was recorded as the fibre returns in its initial position, illustrating a certain effect of roughness.
31
Wang, Jiawei, and Quansheng Sun. "Experimental Study on Improving the Compressive Strength of UHPC Turntable." Advances in Materials Science and Engineering 2020 (July 18, 2020): 1–21. http://dx.doi.org/10.1155/2020/3820756.
Анотація:
Purpose. In the recent years, horizontal rotation methods have been widely used for bridge construction, particularly for constructing overpass bridges on highways, railways, and shipping. However, bridges constructed using the swivel construction method bear several types of loads during the rotation process. Furthermore, the bridge turntable, which is the core force-bearing component of the structure, bears considerably large vertical pressure and horizontal frictional resistance. The present research proposes three strengthening methods when applying ultrahigh performance concrete (UHPC) materials to the turntable of a spherical hinge to improve structural reliability. Furthermore, the mechanical properties of the structure are evaluated using a unidirectional compressive strength test to provide a theoretical and experimental basis for the application of the UHPC material. Design/Methodology/Approach. To evaluate the mechanical performance of the turntable of a spherical hinge, scale models of six sets of UHPC turntables—steel tube-UHPC, stirrup-UHPC, and directional steel fiber UHPC—were constructed in the study. The compressive strengths of the turntable specimens were calculated after theoretical analysis. After obtaining the load-displacement curves of the cube specimens, the force characteristics of the turntable and the failure mechanism of the structure were analyzed by observing the failure mode of the specimens. Findings. The compressive strength of the steel tube-UHPC turntable was 207 MPa, which can completely replace the traditional steel turntable. In addition, the stirrup-UHPC turntable demonstrated a significant loading effect. However, the effect of the restraint radius of the stirrup needs to be considered during the design; otherwise, the loading effect is poor. Furthermore, a directional steel fiber UHPC turntable can improve the compressive strength to a certain extent. We summarize the failure mechanism of the spherical hinge turntable specimens that are expected to play a role in UHPC spherical hinge in engineering applications and construction monitoring. Originality/Value. To the best of our knowledge, this study is the first to employ the UHPC, steel tube-UHPC, stirrup-UHPC, and directional steel fiber spherical hinge turntables in the swivel construction of bridges. The compressive strength and mechanical characteristics of the UHPC structure meet the requirements of the turntable, and more importantly, the manufacturing process (on-site pouring) of the aforementioned UHPC turntable structures is relatively simple. Finally, the manufacturing cost of the turntables is expected to be reduced by more than 50% compared to those of traditional turntables.
32
Zhao, Hongyuan, Ardian Morina, Anne Neville, John Durham, and Richard Vickerman. "Understanding Friction Behavior in Automatic Transmission Fluid LVFA Test: A New Positive Curve Parameter to Friction Coefficient Ratio Index Evaluation." Journal of Tribology 133, no. 2 (March 22, 2011). http://dx.doi.org/10.1115/1.4003480.
Анотація:
The frictional characteristics of some basic additive systems used in automatic transmission fluids (ATFs) were assessed using a variable speed friction test machine. The test evaluates the coefficient of friction in unidirectional sliding contact over a range of speeds, loads, and temperatures. Tests were performed on a steel-versus-clutch friction material tribocouple, mainly to establish the link between the lubricant/surface interactions and additive system performance. A new parameter that measures the positive μ-v curve slope speed range was applied, together with friction coefficient ratio index, to show the antishudder property. It is suggested that this is a good complimentary method to the friction coefficient ratio index evaluation. Lubricant formulation is important to the overall friction performance. Both friction modifiers and detergents are shown to be important to the ATF antishudder performance. Oil absorption ability of the post-test friction material surface is proposed to be an important parameter to indicate the antishudder durability in the test. The detergent and antiwear agents are also suggested to be responsible for the decreased oil absorption and pore plugging of the friction material surface.
33
John, Premkumar, Rajeev Vamadevan Rajam, Rajkumar Mattacaud Ramachandralal, and Krishnakumar Komalangan. "Dry wear behavior of A356-SiCp functionally graded composite in unidirectional and reciprocating contacts." Industrial Lubrication and Tribology ahead-of-print, ahead-of-print (September 23, 2021). http://dx.doi.org/10.1108/ilt-04-2021-0139.
Анотація:
Purpose The purpose of this study is to distinguish the difference in tribological behavior of functionally graded composites in two sliding modes, namely, unidirectional and reciprocating. Design/methodology/approach A356-(10 Wt.%)SiCp functionally graded composite material (FGM) was prepared by vertical centrifugal casting and then a comparison was made between the tribological characteristics using pin-on-disk and pin-on-reciprocating plate configurations under identical operating conditions (sliding distance (s): 350 m; load (W): 30 = W = 120 N, in steps of 30 N; and velocity (v): 0.2 = v = 1.2 m/s, in steps of 0.2 m/s). Two types of test pins were considered, namely, a test pin taken from the outer zone of the FGM with maximum particle concentration and a test pin taken from the inner zone of the FGM in a matrix-rich region. Findings The study revealed that, for the test pin taken from the outer zone of the FGM in the low-velocity range (0.2–0.4 m/s), the reciprocating wear of the friction pair was dominant, while unidirectional wear was dominant in the velocity range of 0.6–0.8 m/s for the entire load range investigated. However, when the velocity was increased from 1.0 to 1.2 m/s, conflicting nature of dominancy in the wear characteristics of the friction pair was observed, depending on the loading condition. In addition, the inner zone FGM pin underwent seizure in the reciprocating mode, whereas this phenomenon was not seen in the unidirectional mode. Originality/value Differences in wear and friction characteristics of FGM friction pairs in two different sliding modes were investigated over a wide range of operating parameters.
34
Wos, Slawomir, Waldemar Koszela, Andrzej Dzierwa, and Pawel Pawlus. "Effect of triangular oil pockets on friction reduction." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, September 17, 2021, 135065012110446. http://dx.doi.org/10.1177/13506501211044623.
Анотація:
The effect of the apex angle of triangular oil pockets created on a disc surface on friction was studied. Experiments were carried out using an Optimol SRV5 tribotester equipped with a pin-on-disc module under unidirectional lubricated sliding. Both the sample and counter sample was made of steel of 45 Hardness Rockwell C (HRC) hardness. Only 1 ml of oil was put to the inlet side of the contact area at the beginning of each test. All textured surfaces had the same pit-area ratio and an average depth of dimples. Oil pockets were positioned in the spiral array. It was found that the effect of the apex angle of triangular dimples on friction reduction was important. When the normal load was lower, the smallest coefficient of friction was achieved for the sliding pair with a disc apex angle of 60°. Under a larger normal load, a higher apex angle corresponded to a higher coefficient of friction.
35
Morón, R. C., G. A. Rodríguez-Castro, M. A. García Maldonado, A. Salazar-Gaona, D. Bravo-Bárcenas, I. Campos-Silva, and A. Palacios-Méndez. "Friction and Damage Evolution of the Borided CoCrMo Alloy." Journal of Tribology 141, no. 8 (June 6, 2019). http://dx.doi.org/10.1115/1.4043851.
Анотація:
Abstract In this study, friction and evolution of cohesive failures (cracks and spallations) in CoB/Co2B layers were analyzed. Thermochemical treatment was carried out at 950, 975, and 1000 °C during 6, 8, and 10 h of exposure time, respectively. The characterization techniques include scanning electron microscopy (SEM) for morphology inspection of layers and thickness measurement, X-ray diffraction for the investigation of phases formed, and instrumented indention to obtain hardness, Young’s modulus, and residual stresses. The practical adhesion of the boride layers was evaluated by a progressive load scratch test (PLST), and the critical loads of cracking, chipping, and spallation were calculated. Later, unidirectional multipass scratch tests (MPSTs) were performed by applying subcritical loads selected from the lower spallation load (54 N); these tests were conducted for a different number of scratch passes. The results show that the coefficient of friction (COF) and coating damage depend on the applied load, the number of passes, and coating thickness. In multipass scratch, the mechanical properties, residual stress state, and thickness play a significant role in the evolution of the coating damage that manifests in the form of cracks and cohesive spallations. Considering the scratch and multipass scratch results, it was found that the sample with 10 h of exposure time presents a better performance among the samples.
36
Bouquerel, Laure, Nicolas Moulin, and Sylvain Drapier. "A Contribution to the Study of the Forming of Dry Unidirectional HiTape® Reinforcements for Primary Aircraft Structures." Frontiers in Materials 7 (January 27, 2021). http://dx.doi.org/10.3389/fmats.2020.571779.
Анотація:
In the context of developing competitive liquid composites molding processes for primary aircraft structures, modeling the forming stage of automatically-placed initially flat stacks of dry reinforcements is of great interest. In the case of HiTape®, a dry unidirectional carbon fiber reinforcement designed to achieve performances comparable to state-of-the-art pre-impregnated materials, the presence of a thermoplastic veil on each side of the material for both processing and mechanical purposes should also be considered when modeling forming in hot conditions. As a dry unidirectional reinforcement, HiTape® is expected to exhibit a transversely isotropic behavior. Computation cost and strong characterization challenges led us to model its behavior at the forming process temperature (above the thermoplastic veil melting temperature) through a homogeneous equivalent continuous medium exhibiting four ‘classical’ deformation modes and a specific structural mode, namely out-of-plane bending. The response of both single plies and stacks of HiTape® to this latter structural mode was characterized at the forming process temperature using a modified Peirce flexometer. Results on single plies showed a non-linear softening moment-curvature behavior and a corresponding flexural stiffness much lower than what can be inferred from continuum mechanics. Moreover, testing stacks revealed that the veil acts as a thin load transfer layer between the plies undergoing relative in-plane displacement, i.e. inter-ply sliding. This inter-ply response was then characterized separately at the forming process temperature thanks to a specific method relying on a pull-through test. Experiments performed at pressures and speeds representative of the forming stage revealed that a hydrodynamic lubricated friction regime predominates, i.e. a linearly increasing relationship between the friction coefficient and the modified Hersey number. From an industrial point of view, high forming pressures and low speeds are therefore recommended to promote inter-ply slip to limit the occurrence of defects such as wrinkles.
37
"New theoretical model of stress transfer between fibre and matrix in a uniaxially fibre-reinforced composite." Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences 425, no. 1868 (September 8, 1989): 215–44. http://dx.doi.org/10.1098/rspa.1989.0104.
Анотація:
A new analytical method has been developed that can predict the stress transfer between fibre and matrix in a uniaxially fibre-reinforced composite associated with either a single matrix crack or a fibre break. Account is taken of thermal residual stresses arising from a mismatch in thermal expansion coefficients between the fibre and matrix. In addition Poisson ratio mismatches are also taken into account. The theoretical approach retains all relevant stress and displacement components, and satisfies exactly the equilibrium equations, the interface conditions and other boundary conditions involving stresses. Two of the four stress-strain-temperature relations are satisfied exactly, whereas the remaining two are satisfied in an average sense. The required non-interface displacement boundary conditions are also satisfied in an average sense. The general representation is used to solve three types of stress transfer problem. A matrix crack and a broken fibre are analysed for the case when there is perfect bonding between fibre and matrix. The third type of problem takes account of frictional slip at the interface governed by the Coulomb friction law. The approximate analytic approach described in this paper, and the preliminary numerical predictions presented, indicate that the stress transfer between fibres and matrix in a unidirectional fibre-reinforced composite, loaded in tension, can now be investigated theoretically in more detail than before. The paper includes some discussion of singularities in the stress fields, which are smoothed by the averaging techniques employed in the analysis. The analytical approach has enabled the development of a micro-mechanical model of frictional slip at the fibre-matrix interface based on the Coulomb friction law, which is more realistic than assuming that the interfacial shear stress is a constant. Predictions are presented of the stress distributions along the fibre-matrix interface and, in particular, it is shown how the length of the frictional slip zone is related to applied strain, friction coefficient, fibre volume fraction and the difference between the test and ‘manufacturing’ temperatures. An indication is given of many other areas of composite modelling where the new theory will be applied.
38
Subramaniyan, Anand Kumar, Sudarshan Reddy Anigani, Snehith Mathias, Akshay Pathania, Prasad Raghupatruni, and Shubhendra S. Yadav. "Influence of post-heat treatment on microstructure, mechanical, and wear properties of maraging steel fabricated using direct metal laser sintering technique." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, September 13, 2021, 146442072110373. http://dx.doi.org/10.1177/14644207211037342.
Анотація:
The post-heat treatment of direct metal laser sintered parts is expected to have superior mechanical properties. Therefore, the purpose of the present study is to investigate the post-heat treatment effect on the microstructure, mechanical and wear properties of direct metal laser sintering processed maraging steel. Hence, a systematic methodology for microstructural characterization, mechanical properties, and tribological performance evaluation was performed. The microstructural examinations were performed using optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction technique. The micro-hardness and tensile properties were determined. The unidirectional sliding wear test was performed using a pin on disc wear testing machine for three different sliding velocities (0.8, 1.2, and 1.6 m/s) and three different normal loads (5, 10, and 15 N). The present study’s findings establish that the post-heat treatment techniques significantly altered the microstructural morphology and features. The results showed that the heat-treated sample had finer and non-continuous microstructure and more complex intermetallic precipitate phases, leading to higher hardness (∼64%) and higher tensile strength properties (70–80%) compared to the as-printed sample. The unidirectional sliding wear test results showed that the sliding velocity significantly affected frictional and wear characteristics of direct metal laser sintering processed maraging steel. The wear resistance of the heat-treated sample was three times higher than the as-printed sample, particularly at higher sliding velocities. In addition, the lower coefficient of friction values (∼24%) was observed for heat-treated sample compared to as-printed sample at higher sliding velocities. The post-heat treatment aids as an effective method to enhance mechanical properties of direct metal laser sintered parts and qualify them for tribological applications. The results endorse the suitability of the heat-treated direct metal laser sintered maraging steel in practical tool and die applications involving extreme tribological operating conditions such as higher sliding velocities and contact stresses.
39
Danchaivijit, Sawai, L.-Y. Chao, and D. K. Shetfty. "Matrix Cracking In Brittle-Matrix Composites with Tailored Interfaces." MRS Proceedings 365 (1994). http://dx.doi.org/10.1557/proc-365-251.
Анотація:
ABSTRACTMatrix cracking from controlled through cracks with bridging filaments was studied in a model unidirectional composite of SiC filaments in an epoxy-bonded alumina matrix. An unbonded, frictional interface was produced by moderating the curing shrinkage of the epoxy with the alumina filler and coating the filaments with a releasing agent. Uniaxial tension test specimens (2.5 × 25 × 125 mm) with filament-bridged through cracks were fabricated by a novel two-step casting technique involving casting, precracking and joining of cracked and uncracked sections. Distinct matrix-cracking stresses, corresponding to the extension of the filamentbridged cracks, were measured in uniaxial tension tests using a high-sensitivity extensometer. The crack-length dependence of the matrix-cracking stress was found to be in good agreement with the prediction of a fracture-mechanics analysis that employed a new crack-closure force - crack-opening displacement relation in the calculation of the stress intensity for fiber-bridged cracks. The prediction was based on independent experimental measurements of the matrix fracture toughness (Kcm), the interfacial sliding friction stress (τ) and the residual stress in the matrix (σmI). The matrix-cracking stress for crack lengths (2a) greater than 3 mm was independent of the crack length and agreed with the prediction of the steady-state theory of Budiansky, Hutchinson and Evans[2]. Tests on specimens without the deliberately introduced cracks indicated a matrix-cracking stress significantly higher than the steady-state stress.
40
Fu, Tao, Jianpu Hou, Zhixin Zhu, Lingxiao Meng, Zhonghua Sun, Kai Wang, and Xiaoqian Ren. "Experimental Study on UHPC-Based Grouting Materials and Mechanical Performance of Grouted Splice Sleeve Joints." Frontiers in Materials 9 (June 23, 2022). http://dx.doi.org/10.3389/fmats.2022.912509.
Анотація:
The prefabricated concrete structure is regarded as the main body of the green construction technology, while the joint connection of the prefabricated components is the weak link of force. In addition, the grouting sleeve connection is a widely used connection method in the prefabricated component joints. The effective anchorage of reinforcement is realized by the implementation of a mechanical bite force, friction force and bonding force between reinforcement, grouting material and sleeve inner wall, respectively. Along these lines, in this work, a UHPC-based grouting material was prepared, and its main technical performance was tested. The influence of the grouting mix proportion and anchorage length on the stress performance was thoroughly investigated by carrying out a unidirectional tension test of eight grout-filled splice sleeves. The acquired results show that UHPC grouting containing micro and particles possess high mechanical strength and durability. The incorporation of UHPC grouting containing steel fibers can further improve the compressive and flexural strength. However, its fluidity will be reduced and grouting difficulties will be induced. For that reason, the utilization of UHPC-based grouting material without steel fibers is recommended. The grout-filled splice sleeve joints with UHPC meet also the strength requirements, and the sleeve can be found in the elastic stage in the test, indicating that sleeve joints possess a higher safety margin.