The method of reconstruction of the drive mechanism for lifting floating crane bucket based on an assessment of durability metal floating crane.

A.S. Yablokov

Key words: cycle fatigue experiment, damage, material parameters, the torque converter, impeller, turbine, reactor wheel, grab

The article discusses the problem of assessing the durability of metal structures of the engine room of the floating crane. Examined the effects of the phenomenon of "suction" grab for floating cranes involved in subsea production. The solution of the problem - including in the drive mechanism for lifting the torque converter, as well as the requirements to specifications and design for such a converter.

Contacts: alex-vodnik@mail.ru

Introduction.

When subsea floating cranes as a lifting body uses grapple. Hoist and scoop grab the floating crane is not different from the hoist gantry crane, which when overloaded bulk materials as well as the lifting body uses grapple. However, when operating in the water-saturated material of the grapple under water when scooping and lifting raises additional hydrostatic forces "suction" filtering hydrostatics and viscous flow of the material in the grapple, which depend on the speed of separation and scooping material grapple, which leads to stresses in the hoisting ropes and metal crane. This effect, which occurs in a short period of time, may exceed the 50% allowable load on the crane and a "peak" [1].

Currently 90% of floating cranes have a lifespan of 15 years or more, which makes their use problematic in underwater mining, as their metal worn and are not designed for such loads.

1. Evaluation of the durability of metal floating crane CPL 5-30.

To assess the durability of metal floating crane CPL 5-30, was calculated metal frame floating crane engine room CPL 5-30, Head. №2040, made in 1974 by the "ship" Bor. To date, the floating crane was committed 902,467 cycles and handled 2,256,168 tonnes (according to the organization of the operator). Material metal crane St3kp. Determination of stress-strain state of a floating crane performed depending on the operating conditions of the crane:

1. For the first case, the calculation was chosen nominal mode of operation of the crane, the corresponding maximum permissible load capacity - 5 tons, the marginal wind load working condition - wind speed of 15 m / s, the maximum inertia load and a maximum roll pontoon - 30.

2. For the second case selected peak operation of the crane, this mode occurs when using the grapple in water-saturated material under water, when scooping and lifting raises additional hydrostatic forces, "suction", filtration, hydrostatic and viscous flow of the material, depending on the speed scoop up material and separation of the grapple, which leads to stress the rope hoist and crane metal. This effect occurs in a short period of time and may exceed 30% allowable load on the crane and a "peak".

Lifting speed of cargo: m / s, the maximum weight of the load lifted kN. For a general idea of the nature of deformation of the frame and identify the location of the nodes that are critical in terms of durability, the first stage was carried out by elastic analysis account code [2].

Fig. 1. - The model of the engine room carcass floating crane.

Physical and mechanical characteristics of St3 were adopted as follows: Young's modulus of elasticity mPa, Poisson's ratio ν=0,28, yield point σ_Т = 230 mPa, density ρ=7820 kg/m³. The frame was modeled in full size in compliance with specified characteristics and geometry. Each compound was replaced by a rigid - welded. Modeling supports the frame also been conducted, but in places bearing frame on the turntable imposed boundary conditions precluding movement of nodes in all directions and turn them into these nodes. Based assortments used profiles idealization carcass structure into finite elements was carried out using 8, 10, 20 - the final nodal elements are symmetric in cross section.

The calculation results are shown in Table 1, which shows the maximum values of the stresses and strains in the elements of metal carcass floating crane CPL 5-30.

Table 1 - Results of calculation.

№	Stress	mPa	Strans	m
1	Σ	149	e	0.964x10^-3
2	σX	32,5	eX	0.8x10^-3
3	σY	52,6	eY	0.426x10^-4
4	σZ	65,0	eZ	0.484x10^-3
5	σXY	36,6	eXY	0.227 x10^-3
6	σYZ	46,7	eYZ	0.29 x10^-3
7	σXZ	18,0	eXZ	0.112 x10^-3

Results of calculation of the maximum deformations and stresses in the critical elements of the framework presented in Figure 2. It is seen that the stress state is triaxial (volumetric) character.

a) the equivalent stresses	b) the total deformation
Fig. 2 - The results of the calculation.

From the analysis of solutions of the problem (see Table 1) shows that the stress level does not exceed the yield strength. Figure 3 shows the curve of damage relative to the number of loading cycles , where N_f – number of cycles to macrocrack formation. Analyzing the results of the maximum strain and stress can be concluded that the amount of accumulated damage is in the danger zone (close to the "critical" value ().

The evaluation of durability of the floating crane CPL 5-30 Head. №2040 concluded that the development of the resource metal frame of the engine room (residual life is within the error calculation) and is necessary to overhaul with replacement metal bearing loaded elements, or the reconstruction of the crane.

Fig. - 3 - Curve damage.

2. A method for increasing the reliability of steel structures and the drive mechanism for lifting floating crane clamshell.

The torque converter allows you to automatically adjust the speed of lifting and closing the grab by creating a feedback between the load on the ropes and speed scooping and lifting the grab. They allow you to smoothly change the gear ratio from the motor to the gearbox by 3.5 times in the direction of increasing and correspondingly increasing the torque on the shaft of the gearbox, which will overcome the effect of "peak" loads. Additionally, a means, which prevents the actuator from any overload, since the torque transmission therein through the liquid, rather than through a rigid kinematic linkage.

Analysis of the properties and characteristics of the existing torque converters [3, 4] allows us to formulate requirements for them to be installed in the mechanism of lifting floating crane:

1.Torque converter possessing high speed, must have the appropriate damping properties to avoid the effect of his work on the high-frequency oscillations in the hoisting ropes.

2. Torque converter must ensure operation of the motor drive in optimal conditions, will not enter when all the input power is spent on "myatie" fluid. Such requirements are met completely "opaque" torque converters [3, 5, 6], but the creation of torque converters of this type is problematic [6, 8], so it is advisable to apply torque converters with a low degree of "transparency" in the range of 1.0 ... 1.1 in the main working area.

Transparency - property impeller change the amount of torque when changing the gear ratio torque converter. If the change gear ratio of torque on the pump wheel remains constant, the torque converter is called the "opaque."

3. Torque converter must convert the torque in the drive to the full range of workloads. Floating crane for maximum transformation ratio must be between 1.4 ... 1.6 [1]. Within the specified value ratio and maximum accepted level of transparency appropriate to use a single-stage torque converter having its greatest simplicity of design [4, 6, 7].

4. Torque converter should have a locking device in order to provide the drive with a constant low speed, i.e. have a freewheel.

5. For creating a drive mechanism for lifting torque converter is necessary to combine original characteristics of the induction motor and the torque converter, which is carried out by combining the rated torque of the motor with the zone of maximum efficiency torque converter. In this case, the converter convert properties used in all operating modes of the drive with the implementation of positive qualities, in relation to underwater mining.

On the basis of the formulated requirements necessary to select the following parameters converter mechanism for lifting floating crane.

Optimum is a single-stage torque converter with a comparatively simple design and the cheapest to produce.

The main requirement to the torque converter - high efficiency in the working area. This requirement may be more fully realized in integrated torque convertors (s centripetal turbine and the symmetrical arrangement of the pump and turbine wheel . Moreover, in a centripetal turbine torque converter when installed in the reactor wheels clutches realized efficient operation of the fluid coupling mode. The observed property is due to the fact that the output torque converters of this type of hydraulic fluid from the pump wheel is located on a larger diameter circle its circulation.

This analysis of the performance requirements and the design of the drive torque converters for floating cranes lifting mechanism, the relevant conditions and loads, suggests that they correspond to the most complex type torque converter with a centripetal turbine.

At the hoist drive, developed by the authors at the Department of handling machines Volga State Academy of Water Transport, received a patent for utility model №91999, and work is underway to further development and implementation of the actuator.

References.

1 Nikitaev, IV Ship power grab installations for the extraction of ore materials on the continental shelf / IV Nikitaev - Nizhniy Novgorod: VSAWT, 2000. - 26 p.

2 CAD / CAE system APM WinMachine

3 Anokhin, VI The use of high-speed torque converters on crawler tractors / VI Anokhin - M .: Mechanical Engineering, 1972. - 304 p.

4 Anokhin, VI On the choice of the basic parameters of the converter for hydromechanical transmission speed tracked agricultural tractor / VI Anokhin, [et al.]. // Tractors and agricultural machinery. - 1985. - №10. - S. 11 - 15.

5 Kochkarev, AJ Hydrodynamic transmission / AY Kochkarev - L .: Mechanical Engineering, 1971. - 336 p.

6 Narbut, AN Torque converter / AN Narbut - M .: Mechanical Engineering, 1966. - 218 p.

7 Anisimov, VB Torque converters for building and road machines / VB Anisimov - M .: Stroyizdat, 1967. - 42 p.

8 panties, SM Automotive torque converters / SM Pants - M .: Mechanical Engineering, 1977. - 211 p.