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INVESTIGATION OF THE RELIABILITY
OF THIN STEEL ROPES d1.0...1.2 мм

Study Objectives: Research objectives are: - Determining the causes of the destruction of an extended rope rope-block system of thin rope, exposed to the atmosphere; - Development of methods to protect cables from damage. work the rope in the block: But the definition of AI Dukelsky in the strands, but the stress tension, with rounding blocks have additional bending stress and xcontact stress in the field xcontact between the outer wires with the rim of the block. These bending and xcontact stresses are pulsating in nature, they disappear by straightening the rope. The result is a metal fatigue, and after a certain number of kinks begin to break down the wire firsxtexternal and then internal, until, finally, does not occur complete destruction of the rope. Design Guidelines CABLE-block system. We give some advice from various sources, concerning the choice of O unit, depending on the O line. Prof. Dukelsky AI "Rope the road ...»: 1) Use wire ropes with gB = 160 ... 180 kg / mm 2 is considered optimal for increasing the longevity of the ropes. We had used rope with gB = 165 kgf / mm 2. 2) The main significance for the longevity of the block have the value O and tensile stress gp. Endurance of the rope in the other equal proportional changes (D / d * 1/Gr) ** 2 3) Recommendations regarding the selection ratio D /d: with a> 20 * D / d> 60 ... 80 where a - angle of wrap block d-diameter rope (We had a D / d = 32, with a = 90 *) «installation and safe operation of cranes»: Heavy duty D / d> 30 The maximum value of D / d> 35 is set for a very heavy modes, in other cases it is much less. And Marhel. And "Crane Ropes": 1) The flexibility of the rope determines its capacity for inflection on the block within the elastic deformation due to internal sliding wires. Flexibility is characterized by the coefficient. Flexibility: By flexible = dc / d, where d - the maximum diameter of wires in the rope, mm. d to - rope diameter, mm. For crane ropes: For flexible> 6.11 (We have to flexible = 1.2/0.45 = 2.7) 2) Rigid cables (with a large O and small wires to the hybrid) is more resistant to wear. (We - Tight ropes). 3} The definition of durability is based on the use of long-term observations of similar cables in operation. MA Bukshteyn "Steel ropes "»: Durability ropes determined by the ratio: K = D / d, where D - diameter of the unit (drum) d - wire diameter. In the recommended designs: K = 450 (We have K = 38 \ 0.4 = 95) If we take K = 450, then the rope d 1,2 requires D = 450 * 0.4 = 180 mm) general recommendation of all the authors: Lining unit elastic material (nylon, rubber ...) is much (1.5 ... 2 times) increases the durability of the ropes (decrease xcontact stress); (We - groove block - steel) features of our unit design: 1) The ratio D / d = 32 for the unit conforms to the recommendations "Rules for the design and safe .... cranes; 2) margin of safety rope np = 60; 3) rope diameter 1.0 ... 1.2 determined by the requirement of minimum the inertia of our tether-block system; 4) The unit is installed on the hinge (3 degrees of freedom) that, according to recommendations of the "Design and operation of the constant network ..." reduces wear on the rope. 5) The rope hard, which guarantees its high durability resistance. 6) Low reliability of our rope is a result of lack of experience in building similar systems such extent and expressed in an underestimation of the influence of operating conditions on the fatigue strength of the ropes. CONDITIONS: 1) The data for weather stations in our area: Average wind speed - 14m / s max - 25 m / s Data on the frequency of wind gusts in there. According to the book "Design and operation of the xcontact Network ...", wind loads in overhead wires can cause a) self-oscillation f = 40 ... 60 1/min - fight with them is the installation of special damping devices; b) vibration f = 100 1 / s - the fight against it is to strengthen the junction of the wires with the supports special springs; NATURE OF FRACTURE ROPES: A survey of damaged kanatav was installed cause breakage of wires ropes - "Typical fatigue fracture with no signs of fraying wires" (See table damage ropes MA Bukshteyn "Steel Ropes"), and 30% of all injuries located at the vanishing point with unit horizontal branch of ropes: INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES WIND LOAD: The impact of wind load on the rope may have the following character: I) vibrations of the rope (without turning blocks): INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES 2) Cranking blocks (due to the lifting and lowering the balances) with increasing length of the branches AB and BC: INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES 3) The rotation balances: INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES We estimate the magnitude of wind effect on the vertical branch of the rope. Methodology "Handbook of cranes": INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES qo = v2/16 n = 1.8 (H suspension = 40 ... 50 m) a = 1.2 b = 2.0 g = 1.1 P = qo * n * c * b * g = (142 / 16) * 1.8 * 1.2 * 2.0 * 1.1 = 58.2 kgs/m2 F1 = 40 m * m * 0.0012 58.2 kg / m2 = 2.3 kg INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES f1max = q * l2 / (8 * s) = 2.3 \ 40 kg / m * (40m) 2 / (8 * 2.5 kg) = 4.6 m F2 = PB * 0.5m * 0.1m = 2.9 kg ie fi = 45 ° l2 = f2 = 4m The "geodetic work in the construction of the Serpukhov synchrophasotron »: INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES q = d * v2 / 8 = 1.2 * 142 / 8 = 29.4 kg / m f = q * l1 ** 2 / (8 * H) = 29.4 * 402 / (8 * 25) = 2352mm = 2.3m Let us assume that the curve «a» - a circle. la = SQRT (l1 ** 2 + 16 / 3 * f1 ** 2) = 40.35m delta l = la - l1m = 0.35m n = delta l / (pi * D) = 350mm / (3.14 * 38mm) = 2.94 ie Block provernetsya for «n» turnovers. EVALUATION OF THE INFLUENCE OF TYPE wind effect on the fatigue DESTRUCTION OF ROPE: Number of cycles N loading with the stress that G can withstand the design is determined by the relationship: (G / Go) m = No / N Typically, m = 4 ... 10 No = 10 ** 6 ... 10 ** 7 Go = G-1 - the endurance limit of the sample at No (determined Experimental) as durability of N is inversely proportional to the voltage during loading, then we define the stress arising in the rope with various types of loading. 1). Bending of the rope due to rolling through the block. For straight procrastination (by Dukelsky) we have: G, = E * d / D = 2.1 * 104 kg / mm 2 * 0.4 / 1938 = 221 kg / mm 2 GB wire = 165 kg / mm 2 However, since in the rope has the form of a spiral, so the tension in her significantly less. We take G and = 100 kg / mm 2 2). Bending the rope swing with a counterweight: INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES f = 1m (real value). For a single wire d = 0.4 mm f = P * l ** 3 / (3 * E * Jx), hence P = 3 * E * Jx * f / l ** 3 M = P * l G, = M / W = 3 * E * Jx * f * l / (l3 * Wx) = = 3 * 2.1 * 10 ** 6 * 0.05 * 0.4 ** 4 * 100 * 400 / (400 ** 3 * 0.1 * 0.4 ** 3) = = 787.5 kg / cm2 Gi1> Gi2 and, therefore, bending the rope on the block stand far fewer cycles. CALCULATION OF LIFE ON ROPE Dukelsky "Steel Ropes» Collected papers vol 5 page 225: Number of cycles: I = k * Ao * (D / d) ** 2 * (NH-2) th cycle k = 1, max value Ao = 0.025 steel block Ao = 0.059 polymer lining NH-2 = 60 - 2 = 58 NH-margin. For D / d = 30 I = 1 * 0.025 * 30 ** 2 * 58 = 1,305 thousand loops For D / d = 80 I = 1 * 0.025 * 80 ** 2 * 58 = 9,280 thousand loops 2 months contain 5.1 * 10 ** 6 seconds Thus, if the loading frequency 60 1 / min = 1 1 / sec then 2 months to destroy even a rope with a "good" unit (D / d = 80) and ruggedness NH = 60. Note that all the dependencies and recommendations are made for crane ropes d> 12 mm and have an empirical nature. COMMENT ON QUALITY ROPES: The certificate of quality on the ropes, GOST 3062, we have used in construction, contrary to the requirements of GOST 3241-80 no xinformation The test wires to a cyclic bending loading on GOST 1579-63. BACKGROUND xinfoRMATION ON LIFE ROPE: I. Marhel "Crane ropes" life ropes (Loaded at 60%): 1) Excavator - 1 ... 1.25 months; 2) port valve - 3 ... 4 months, 3) foundry crane - 2mes. 4) truck crane - 6 ... 8 months. Collection of Steel Ropes ": The service life of wire ropes: 6 ... 20 months. CONCLUSIONS: 1) The cause of breakage of the rope, in our case is a fatigue failure section of the rope in the area of ??the block from bending stresses arising from repeated rolling of the rope through the block under the influence of wind loads. Indicated is the result of a wrong choice of operating mode our system. 2) To prevent breakage of ropes for the further operation of the stand necessary in the long intervals between tests (more days) counterweights to lift and put on a platform of service, and in the zone blocks of both branches of each rope to fix the clip. INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES INVESTIGATION OF THE RELIABILITY OF THIN STEEL ROPES REFERENCES: 1) AI Dukelsky "cableways and cable cranes" M. "Engineering" ed. 4 2) I. Marhel "Crane ropes" M. "Engineering" izd.2 3) IA Birger et al, "Calculation of strength ..." M. Mash. izd.Z 4) AI Dukelsky Handbook of cranes "izd.2 5) "Rules of construction and safe operation of cranes" 1983. 6) "Design, construction and operation of the xcontact network and air Line AV Frayfeld ... 7) "Steel ropes" Collection of articles v.5, 6 Kiev "Technique" 8) MA Bukshteyn "steel ropes." 9) GOST 3062-80 GOST 3041-80 GOST 1579-63
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