Friction Knot Research Articles

EVALUATION OF COATING MATERIAL STRUCTURE OF SCREW TYPE COMPRESSOR ROTOR CONTACT SURFACES

In engineering, as well as in other manufacturing industries, the use of compressed air is an important catch. Compressor production and service company Fonons, Ltd often deals with damage of screw type compressors, sometimes even irreversible. Damages that draw up to 15% are linked to strong wear out of compressor friction knot (rotors). This, in effect, reduces the optimum productivity and work efficiency of the compressor, increases losses between rotors. Compressor service time diminishes. Work foundation is the analysis of methods how to improve screw rotor surfaces. It is necessary as one of the concluding treatment operations in the manufacturing process. It may reduce the influence of the abrasive elements on the contact surface, diminish wear intensity, and increase the service time. Improved contact surface of rotors, which are coated with TiN coating by using physical vapour deposition (PVD) technology, is analysed within the framework. Surface quality control is executed with modern methods, including surface 3D topography analysis and coating quality estimation with the atomic force microscopy (AFM). The main materials are analysed characterizing parameters change according to the recommendation for manufacturing wear proof coatings.

Tensile Strength of Ropes and Friction Hitch Used in Tree Climbing Work

Tree climbing techniques for arboriculture are becoming more and more popular, but like any work activity, there are risks for the operator. The PPE (personal protective equipment) and protective systems studied here include semi-static ropes and friction hitches. The work rope/friction hitch system is a combination that many operators rely on, but unlike current mechanical rope clamps and descenders, they do not have European certifications. For this reason, tensile tests were carried out using a traction bench on rope/knot systems. Two rope models and two types of knots were used to stress the systems and materials as much as possible, so as to observe the resulting ratios. A total of 36 tests were carried out in which measurements were taken, including applied load in traction, knot creep, and rope diameter changes. Several results were obtained, including a maximum load of 18.7 kN, a maximum slip of 9.6 cm and a maximum diameter variation of 3 mm. This work represents a preliminary investigation for verifying the relationship between work ropes and friction knots. Relationships among the variables were observed; differences emerged mainly as a function of the type of knot used rather than the type of rope used. The data obtained is also important for applications towards improving preventative safety measures.

Research of tribotechnical properties of antifriction polymer compositions

The analysis of antifriction polymer compositions on the basis of polyamide, epoxy, phenol-formaldehyde, furan resins, and also on the basis of fluoroplastic with various fillers working in friction knots is made. The influence of fillers on the mechanisms of friction is little studied, so when creating antifriction compositions capable of working in conditions of lubrication in water, the following tasks were set: to justify the number and type of fillers; to investigate the influence of fillers on the process of wear of material and counterbody; determine the optimal composition of the antifriction composition that provides minimal wear of the coating and the counterbody. The object of study were: compositions based on phenol-formaldehyde resin and fluoroplastic, modified with antifriction fillers; details of submersible pumps. The basis of the study was the study of tribotechnical and technological properties of polymer compositions. Based on the analysis of literature data, the target fillers for the creation of antifriction compositions for radial plain bearings and thrust bearings of submersible pumps are selected, their number and composition are substantiated. The criterion for optimization was the mass wear of the polymer coating and the counterbody. The optimal composition of the antifriction composition for radial plain bearings, which contains: a mixture of colloidal graphite Cl and carbon fabric "TGN-2M"; molybdenum disulfide DM-1; powder polyamide 12 APN-B; crushed prepreg comprising a fiberglass filler impregnated with a modified phenol-formaldehyde resin P2M. For thrust bearings, the optimal composition of the fluoroplastic composition is determined, which includes: fluoroplastic F4; molybdenum disulfide; carbon fabric; powdered copper. The physical and mechanical properties of the optimal composition are presented. Technological equipment has been developed for the restoration and manufacture of plain bearings and submersible pump bearings. Molds are made for industrial implementation.

Friction knots – their strength under static load

Friction knots – their strength under static load

In vitro holding security of four friction knots of monofilament or multifilament suture used as a first throw for vascular ligation.

To evaluate holding security of 4 friction knots created with various monofilament and multifilament sutures in a vascular ligation model. 280 friction knot constructs. 10 friction knots of 4 types (surgeon's throw, Miller knot, Ashley modification of the Miller knot, and strangle knot) created with 2-0 monofilament (polyglyconate, polydioxanone, poliglecaprone-25, and glycomer-631) and braided multifilament (silk, lactomer, and polyglactin-910) sutures were separately tied on a mock pedicle and pressure tested to the point of leakage. Linear regression analysis was performed to compare leakage pressures among suture materials (within friction knot type) and among knot types (within suture material). Mean leakage pressure of surgeon's throws was significantly lower than that of all other knots tested, regardless of the suture material used. All the other knots had mean leakage pressures considered supraphysiological. Significant differences in mean leakage pressure were detected between various friction knots tied with the same type of suture and various suture types used to create a given knot. Variability in leakage pressure among knots other than the surgeon's throw was greatest for poliglecaprone-25 and lowest for polydioxanone. Most differences in knot security, although statistically significant, may not have been clinically relevant. However, results of these in vitro tests suggested the surgeon's throw should be avoided as a first throw for pedicle ligation and that poliglecaprone-25 may be more prone to friction knot slippage than the other suture materials evaluated.

Retention of basic suturing skills with brief or extended practice in veterinary students

To evaluate the effect of practice duration on accuracy, retention, and confidence when learning how to tie basic surgical knots. Prospective study. Fifteen first-year veterinary students. Students were randomly assigned to a 2-week practice (TWP) or an 8-week practice (EWP) to learn how to tie surgeon's, strangle, and miller's knots. Students' knot-tying accuracy and confidence were evaluated immediately after training, at an intermediate time point (2-6 weeks postpractice), and at 12 weeks postpractice. Students who had been trained during an extended period tied the strangle knot correctly more often at all assessments (P = .025). The ability of students trained for 2 weeks to tie the strangle knot correctly decreased over time (P = .028). These students lost some confidence (P = .03) and repositioned suture more frequently (P = .03) while constructing the strangle knot at the final time point compared with students trained for 8 weeks. Students who completed TWP felt more confident at placing surgeon's knots than friction knots at the final assessment period (P = .0164 miller's knot, P = .0056 strangle knot), whereas confidence did not differ between knot types for students who completed EWP. All students felt less confident with their knot-tying skills at 12 weeks postpractice. Training for 8 weeks rather than for 2 weeks resulted in superior knot tying skills. Students' confidence decreased 12 weeks after training. Prolonged distributed practice is recommended to train students for more complex tasks such as placement of a strangle knot.

Intrascleral sewing-machine technique: A Grooveless/flapless cyclopexy technique for large traumatic Cyclodialysis cleft repairs in pars plana vitrectomy.

To describe a minimally invasive technique for the repair of large traumatic cyclodialysis clefts using intrascleral sewing machine suture and overhand friction knot techniques in pars plana vitrectomy. This prospective, noncomparative, interventional case series included seven eyes of seven patients with a large traumatic cyclodialysis cleft. The sewing machine technique was modified by an intrascleral approach. The procedure was transconjunctival or subconjunctival performed without scleral flaps/grooves. An overhand friction knot was used to lead the cutting ends of the suture buried in the scleral tunnel. The closure of the cyclodialysis cleft was achieved in seven eyes. The mean follow-up duration was 49.1 ± 15.6 weeks (range, 30-70 weeks). The intraocular pressure increased from 7.3 ± 2.1 mm Hg (range, 5-11 mmHg) preoperatively to 13.6 ± 2.4 mm Hg (range, 10-17 mmHg) postoperatively ( P < 0.01). The best-corrected visual acuity improved from a mean of 2.76 ± 2.77 logarithm of the minimum angle of resolution preoperatively to 0.63 ± 0.82 logarithm of the minimum angle of resolution at the final follow-up ( P < 0.01). In conclusion, the present technique is safe and effective in the treatment of large traumatic cyclodialysis clefts with minimal surgical trauma and a decreased surgical duration.

Intraocular Suture Looping and Overhand Friction Knot: A Flapless Technique to Refixate Dislocated Intraocular Lenses.

Intraocular Suture Looping and Overhand Friction Knot: A Flapless Technique to Refixate Dislocated Intraocular Lenses.

Повышение долговечности строительно-дорожных машин на основе совершенствования ремонта узлов трения

Повышение долговечности строительно-дорожных машин на основе совершенствования ремонта узлов трения

ASSESSMENT OF THE DETERMINATION DETAILS OF CONNECTED TRIBOSYSTEMS CONNECTED

In the course of their work, rotary feeders were studied, which continuously submitted the cod in the boiler of alkaline solution at a temperature of 160°C and a pressure of 1.2 MPa. At the same time, under pressure of the hydro-abrasive stream of alkali, wear and increase of the gap in the feeder occurs, which makes it impossible to operate the automated transport system. To reduce the gap in the feeder, the mechanism of the add-on of the rotor is used, which allows to continuously compensate for the gaps formed during wear during the year. The total amount of wear of the rotor and the body, which is used to compensate for wear in the nodes of friction, depends on the initial conicity and the magnitude of the axial displacement of one of the parts.During operation, under the action of an alkaline hydroabrasive medium, an increase in the clearance between the rotating rotor and the body occurs, which is accompanied by an increased alkali flow through the feeder and the cessation of the loading of the boiler's chip. To compensate for the gap, a special mechanism of the additive is provided, with the help of which the movement of the rotor in the axial direction to the depth of the conical body by 1-2 mmreduces the gap by 25-50 microns.Mathematical dependences are obtained for determining: the total wear of the connecting parts, the values of the angles of the taper and the biases of the joints. For automation of technological processes it is expedient to use in friction knots connecting conic surfaces which provide for a long time the cyclic compensation of the gap formed as a result of wear. The angles of the taper and the slopes on the interconnected surfaces are kept constant on both the rotating part and the non-rotating part. The angles of the taper and the slopes on the interconnected surfaces that came out of the connection vary from the original values. The total amount of wear of the rotor and the body that goes on to compensate for wear in the nodes of friction depends on the initial conicity and the magnitude of the axial displacement of one of the parts. Mathematical dependences are obtained for determining: the total wear of the connecting parts, the values of the angles of the taper and the biases of the joints. сопрягаемых деталей, величины углов конусности и уклонов сопряжений.

INCREASE EXPLOITATIVE INDICATORS OF FRICTION WEDGES BY FORMING COATINGS WITH SPECIAL FEATURES

The article is devoted to the development of innovative coatings, to increase the wear resistance of friction wedges of the dummies of the vibration of the trucks carriages. Increasing the inter-repair mileage of trucks will provide significant reduction of the cost of operation of the trolley and the car as a whole for the life cycle. In order to achieve this, it is necessary to reduce wear in the friction nodes of the trolley by choosing the optimal combination of materials for the manufacture of parts of the fader of oscillations, namely the friction wedge, as well as the application of a recovery technology with the formation of wear-resistant microstructures of the coating, which will provide the necessary friction coefficient in the conditions of long-term operation.In this work, metallographic, laboratory studies were conducted on the wear of coatings, which are applied from aqueous solutions of salts to iron-and-carbon alloys operating under friction conditions; the dependencies between technological parameters of the process and the operational properties of the formed coating are established.The material with optimal properties in terms of the working conditions of the friction wedges was selected and proposed. The technology of avoiding the formation of a bleached layer at restoration of the sizes of friction wedges by means of surfacing or spraying is offered. It is proposed to use an oxylated solution in aqueous copper salts solution to form a protective coating before restoration of the size by surfacing. The dependences between the parameters of drawing and wear indexes were revealed and on the basis of the conducted researches the optimum parameters of formation of coverings were determined.The proposed improvement of the technology of restoration of friction wedges will provide reduction of wear in the friction knots of the vibration of truck carriages in 1,5-2 times, which will lead to an increase in inter-repair runs while maintaining the technical parameters of the trolley and will provide significant reduction of the cost of operation of the trolley and the car as a whole for all life cycle.

This issue of ACTA

This issue of ACTA

Outcomes of intraocular lens scleral fixation with the friction knot technique.

To examine the clinical outcomes of intraocular lens (IOL) scleral fixation with the friction knot technique. Retrospective case series of 152 eyes of 152 patients with inadequate capsular bag support operated with the friction knot IOL scleral fixation technique by a single surgeon. The fixated IOLs were one-piece or three-piece models all with open loop haptics. Main outcome measures were change in corrected distance visual acuity (CDVA) and postoperative complications. The mean follow-up time was 11.7months (median 4.9, range 0.7-64.8). The mean logarithm of the minimum angle of resolution CDVA improved from preoperative 0.77±0.73 (Snellen 20/118±7.3 lines) to 0.44±0.56 (Snellen 20/55±5.6 lines) at the final visit (p<0.001). The main postoperative complications were ocular hypertension (30.3%), uveitis-glaucoma-hyphaema syndrome (12.5%; UGHS), vitreous haemorrhage (11.2%) and retinal detachment (8.6%). Two (1.3%) cases of suture breakage were seen. In multivariate Cox regression analysis, age under 60years [hazard ratio (HR)=5.41; 95% confidence interval (CI) 1.95-15.01] and scleral fixated one-piece IOL (HR=4.23; 95% CI 1.44-12.44) were found as significant independent risk factors for developing new UGHS. The friction knot technique provides a firm scleral fixation. Scleral fixation may successfully be utilized in dislocated three-piece IOLs with loop haptics. We recommend avoiding scleral fixation of one-piece IOLs in young patients due to a high risk of UGHS.

Elaboration and Investigation of Metallic Coating with Inclusion of Potassium Polytitanate

The possibility of receiving of compositional Ni-P coating modified by potassium polytitanate was analyzed. An aqueous solution to obtain the composite coatings on the basis of nickel-phosphorus alloy modified by K2О·nTiO2 onto steel details of the friction knots was developed. The complex oxide K2О·nTiO2 represents a layered material from the scaly form nanocrystals with 20-80 nm thick and "diameter" 280 nm. The velocity forming of the modified compositional Ni-P coating was investigated, and the optimal quantity of the introduced potassium polytitanate (8 g/l), as a modified compound into solution, was determined, too. The tribological characteristics and micro-hardness of the resulting coatings depending on the chemical composition of solution and surface state of the rider were investigated.

Determination of parts tolerances in friction knots of grey and nodular cast iron with thermal diffusion platings vanadium and chrome

In the study, experiments with a vanadium coating of samples were conducted, to establish the limits of the increase in the landing dimensions and the designation of limiting deviations in dimensions and the designation of limiting deviations in the dimensions of the manufactured parts. The maximum deviations relative to dimensions of cast iron parts with thermal diffusion platings vanadium and chrome in friction knots of machines and mechanisms were explored. The plate thickness and the linear sizes increment of gray and nodular cast iron hardened products were determined. Were obtained uniform in thickness carbid platings as a result of the experiments on producing of thermal diffusion vanadium and chrome plating.

Tribological Properties of AlSi17Cu5Mg Alloy Modified with CuP Master Alloy with Various Speeds of Friction

Abstract The paper presents the influence of modification with phosphorus (CuP10) on the tribological properties of the alloy AlSi17Cu5Mg coupled abrasively with cast-iron EN GJL-350. Tests of coefficient of friction and wear of mass were conducted on tribological tester T-01. An important aspect in the assessment of the tribological properties is the analysis of initial material microstructure in reference to silumin which underwent modification with phosphorus. It was found that the difference in structure of tested materials, mainly sizes of primary silicon crystals significantly influences the tribological properties whereas the speed change of the friction knot does not have such big influence.

Ecological aspects of recycling the polyethylene terephthalate waste materials

The advantages and defects of modern technology treatment of polyethylene terephthalate (PETF) wastes, and amounts of the accumulation PETF-tares are analyses in article. Has been established that exploitative properties of experimental samples from secondary PETF, development by method compressed pressing, allowing their use in non-loading friction knots of the machines and mechanisms.

Material machining for friction knots of moving parts for agricultural machines

The study deals with the effect of the cutting parameters such as the cutting speed, feed and cooling on the quality of machined surfaces in the process of hole drilling for the sliding bearings used in agricultural technique. This effect has been studied on various metals such as copper, brass, dural and leaded bronze, which are commonly used for their friction knots of the moving parts for agricultural machinery. The results suggest the use in the design of collection parts, scything strips, as well as lifting equipment of agricultural technique, where particular linear and rotary movements of the friction parts are slow, as well as for the design of appropriate drilling procedures.

Simulations of the untying of molecular friction knots between individual polymer strands

The dynamics of molecular knots is implicated in a broad range of phenomena, from DNA replication to relaxation of polymer melts. Motivated by the recent experiments, in which biopolymer knots have been observed and manipulated at a single-molecule level, we have used computer simulations to study the dynamics of "friction knots" joining individual polymer strands. A friction knot splicing two ropes becomes jammed when the ropes are pulled apart. In contrast, molecular friction knots eventually become undone by thermal motion. We show that depending on the knot type and on the polymer structure, a microscopic friction knot can be strong (the time tau the knot stays tied increases with the force F applied to separate the strands) or weak (tau decreases with increasing F). The strong knot behavior is a microscopic analog of macroscopic knot jamming. We further describe a simple model explaining these behaviors.

A useful knot in ptosis surgery

Skin closure in ptosis surgery requires deeply placed stitches which encompass the edges of the skin and the levator aponeurosis. In the authors' modification, a friction knot is tied with stiff monofilament suture material. This technique substantially simplifies subsequent removal of the suture.