Crane Hook Research Articles

Tailoring material properties in layered manufacturing

This article presents a novel approach for tailoring material properties in parts fabricated using layered manufacturing (LM). Solid model of the part is subdivided into various subparts based on stress analysis. All subdivided solid models are fabricated together by using selective laser sintering (SLS) process with parameters assigned as per their stress values. As mechanical properties are varying with process parameters and hence fabricated part will have customized mechanical properties for different regions. Various issues in implementation have been discussed and a case study of crane hook part is presented to demonstrate implementation procedure. Fabricated crane hook parts have been validated for dimensional accuracy using Reverse Engineering.

Strength Evaluation of Marine Crane Hooks by Static-load and Fatigue Experiments

Strength Evaluation of Marine Crane Hooks by Static-load and Fatigue Experiments

Brittle fracture of a crane hook

The objective of this work is to identify the causes that led to a failure of the crane hook in service. The study of the accident includes: (1) a summary and analysis of the peculiarities inherent to the standards that determine the manufacture and use of this type of device, (2) metallographic, chemical and fractographic analyses, (3) assessment of the steel mechanical behaviour in terms of Vickers hardness profile, its tensile strength and fracture energy, and (4) simulation of the thermal history of the hook. The visual and microstructural inspections reveal some evidences that a weld bed was deposited on the hook surface. Several cracks grew from that area into the material. Fracture surface shows features typical of brittle failures (transgranular cleavage fracture). The unalloyed, low-carbon steel contains a relatively low aluminium (<0.025%) and high non-combined nitrogen (>0.0075%) content. All the gathered evidences are in agreement with a strain-aging process triggering the embrittlement of the material, with the fracture starting from a crack generated at the heat affected zone of an uncontrolled welding of the hook.

Development of Measurement Device of Working Radius of Crane Based on Single CCD Camera and Laser Range Finder

In this paper, what we want to do is to develop an observation device to measure the working radius of a crane truck. The device has a single CCD camera, a laser range finder and two AC servo motors. First, in order to measure the working radius, we need to consider algorithm of a crane hook recognition. Then, we attach the cross mark on the crane hook. Namely, instead of the crane hook, we try to recognize the cross mark. Further, for the observation device, we construct PI control system with an extended Kalman filter to track the moving cross mark. Through experiments, we show the usefulness of our device including new control system of mark tracking.

Visual Feedback Tracking with Laser to Moving Crane Hook

This paper introduces measurement of the working radius of a crane truck based on visual feedback control. In order to realize the measurement, we developed an observation device which is equipped with a CCD camera, a laser range finder, and AC servo motors. Further, we propose a new algorithm for mark recognition and construct a control system with an extended Kalman filter to eliminate a time delay. By performing several experiments, we verify the performance of the observation device, and show the effectiveness of our proposed method.

A Numerical Analysis for a BWR Fuel Assembly Drop Event

A BWR fuel assembly dropped from the crane hook during outage and clashed against the rack bottom plate of spent fuel pool. The area monitoring system indicated no radiation release, however, damage at the top of fuel channel was found in the following inspection. As fuel integrity is essential for further management, a finite element model was established to evaluate the damage condition. Several component elements including fuel rods, tie plates, and channel were set up and integrated into a full assembly. The analysis results provided the impact force on the fuel assembly and the dynamic response of each component element. The event did result in the damage of fuel channel yet fuel rods fracture was not expected. It's consistent with the inspection observations. There is therefore no concern for future operation such as interim dry storage.

An automated gantry crane as a large workspace robot

In the context of further automation of manufacturing processes, automated transportation of heavy weights using cranes becomes more and more important. Applying the skills of robots to crane automation, a wide market of new applications could be developed. The main idea is to interpret the crane as a large workspace-serving robot. The crane hook represents the effector of the robot. As an example for the effector, an automated storage and retrieval unit for rack operations by a crane with three active auxiliary effector axes has been developed and integrated into the control concept. The control has been realized for a reconstructed 5-t-bridge crane with workspace dimensions of 30 m×8.7 m×7 m.

Metal Failures: Mechanisms, Analysis, Prevention

Failure Analysis. Elements of Elastic and Plastic Deformation. Elements of Fracture Mechanics. Alloys and Coatings. Examination and Reporting Procedures. Brittle and Ductile Fractures. Thermal and Residual Stresses. Statistical Distributions. Creep Failure. Fatigue. Defects. Environmental Effects. Flaw Detection. Crane Hooks, Coil Springs, Roller Bearings, Bushings, and Gears. Concluding Remarks. Problems. Index.

Automation of existing tower cranes: economic and technological feasibility

Tower cranes enjoy a long useful working life. Therefore, a vast population of cranes are still in use today that do not feature the advanced automation and sensor technologies such as those with which some of the new models are equipped. This paper examines the technological and economic feasibility of retrofitting existing tower cranes with semi-automatic devices for motion control. The proposed improvements are intended to enhance the cranes' efficiency and their capacity to meet the challenges of today's tightly scheduled construction projects. Based on work studies and analyses of craning cycles, the concept offered by the proposed improvements distinguishes between the long-distance navigation of the crane's hook and the fine maneuvering in the loading and unloading zones. The expected economic benefits resulting from the enhancement of the crane's performance, with regard to both types of motion, far exceed the cost of installing the various devices.

Structural Configuration Examples of an Integrated Optimal Design Process

Structural optimization procedures usually start from a given design topology and vary proportions or boundary shapes of the design to achieve optimality of an objective under various constraints. This article presents examples of the application of a novel approach for initiating formal structural optimization at an earlier stage, where the design topology is rigorously generated. A three-phase design process is used. In Phase I, an optimal initial topology is created by a homogenization method as a gray-scale image. In Phase II, the image is transformed to a realizable design using computer vision techniques. In Phase III, the design is parameterized and treated in detail by conventional size and shape optimization techniques. Fully-automated procedures for optimization of two-dimensional solid structures are outlined, and several practical design problems for this type of structures are solved using the proposed procedure, including a crane hook and a bicycle frame.

Design Method of Active Attenuator for Prevention of Electric Shock in a Large Crane Near a Radio Broadcasting Antenna.

We have already announced the design method of the passive attenuator to prevent a high voltage which induced at a crane hook of a large crane used near a medium wave radio broadcasting antenna. But it is very difficult fundamentally to microminiaturize this passive attenuator.In this time, we developed an active attenuator that possible to miniaturize where a negative resistor or a fourterminal amplifier is included. From the result analyzing this crane equipped with an active attenuator theoretically, we show the design method of the active attenuator. In this paper, first the equivalent circuit of the crane equipped with the active attenuator as a receiving antenna is induced. And we show that the attenuated characteristics of the active attenuator by the model experiment accords with the theoretical attenuated characteristics which employ an equivalent circuit under the same condition.

Swing-free transport of suspended objects: a general treatment

It is shown that there is a family of control strategies that result in swing-free movement of objects suspended from a movable point (e.g. a bridge crane). While it is possible to control the swing with acceleration periods of arbitrary length, it is necessary in that case to know the period of the suspended object, which requires knowledge of the location of the object's center of mass. In a practical application of this result, the best strategy is to build a sensing system into the bridge and crane hook that allows the crane to recognize when the hook is directly below its support point. The control strategy is then to accelerate for one full period, which is recognized when the hook returns to the point directly below its support point. If the bridge continues to move at this velocity, the suspended object will not swing. To stop in a swing-free state, the crane begins to decelerate at the same rate as it accelerated, starting at a distance from its goal equal to the distance traveled while accelerating.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

フラクトグラフィによる破損した機械部品のか動応力振幅の推定

Fracture morphologies are often formed as a result of plastic deformation at the crack tip. Therefore, it has been found that sizes of fracture morphologies (striation spacings, stretched zone width etc.) are correlated with fracture mechanics parameters. Such relationship makes possible the quantitative analysis of service failures of machines or structures.In this paper, striation spacings were measured by transmission microscope fractography on the replica obtained from fatigue failed machine parts (gears, shaft and crane hook), and the values of applied stress amplitude or cycles given to propagate the crack until failure occurred were estimated using the relation between the striation spacing and stress intensity factor, ΔK. Fatigue tests or fatigue crack growth tests were carried out with the specimens taken from actually failed machine parts to know the fatigue properties for the parts. The combined fractographic fracture mechanics method was found very valuable in the quantitative analysis of fatigue failures of machine parts.

Finite Deflections of Curved Beams

A theory was developed to predict load-deflection curves for curved beams under loading conditions that produce finite strains. The theory assumed that the curved beam could be approximated by a number of truncated pie-shaped segments with circular arcs for the inner and outer boundaries. The cross section of each segment was assumed to have a plane of symmetry; the centroidal normal force and bending moment acting on the segment were assumed to lie in the plane of symmetry and to remain constant over the included angle of the segment. Using known tension and compression engineering stress-strain diagrams, internal values of centroidal normal force and moment could be calculated for assumed deformations of the segment. An iterative procedure was used to obtain the deformations which would make the internal values of centroidal normal force and moment equal to the applied values. The deformed shapes of the pie-shaped segments were reassembled to give the deformed shape of the curved beam. Good agreement was found between theory and experiment for nine mild steel curved beams and two commercially available crane hooks.

Bending of an Eccentric Cicular Ring with a Cut-Out Portion by Concentrated Forces at Its Inner Edge

To investigate stress distributions in crane hooks, we consider an eccentric circular ring with a cut-out portion undergoing equal and opposite concentrated loads at the ends of its inner diameter. Applying the theory of two-dimensional elasticity and using bipolar coordinates, we solve the problem by method of superposition of a closed ring subjected to the same loads and a ring with a cut-out portion loaded by forces and bending couples at both ends. As the result, we can obtain exact solutions for stress distributions along the inner and outer circumferences in the form of infinite series and computing residues, derive simplified formulas, from which it is verified that the outside parts of the ring bordered by the loading points are free from stresses. Further, using the solutions, we calculate stress distributions for several examples and compare them with results on curved bars in the elementary theory.

Bending of an Eccentric Circular Ring with a Cut-Out Portion Undergoing Forces and Bending Couples at Both Ends

To solve the problem of bending action of piston rings or crane hooks, we considered an eccentric circular ring with a cut-out portion undergoing forces and bending couples at both ends. Using the theory of elasticity for plane stress and applying bipolar coordinates, we obtained correct solutions for the above problem and compared the solutions with those by the usual elementary theory. From the results of calculations, we reach the conclusion that the solution by the usual elementary theory is reliable, only when the eccentricity between the centers and the difference between the radii of two circles of the boundaries are small.

Bending of an Eccentric Circular Ring with a Cut Out Portion Undergoing Forces and Bending Couples at the Both Ends

To solve the problem of bending action of piston rings or crane hooks, we considered an eccentric circular ring with a cut out portion undergoing forces and bending couples at the both ends. Using the theory of elasticity for plane stress and applying bipolar coordinates, we obtained correct solutions for the above problem and compared the solutions with those by the usual elementary theory for curved bars. From the results of calculations, we have a conclusion that the solution by the usual elementary theory is very reliable, only when the eccentricity between the centers and the difference between the radii of two circles of the boundaries are small.

Electrical aspects of overhead travelling cranes

The paper is intended to serve as a guide to engineers who desire to install electrically operated lifting equipment over an area of factory, warehouse, stockyard or power plant. Emphasis is laid on performance rather than design, and mention of many of the smaller items of crane equipment has purposely been omitted. The paper discusses the information required from the purchaser by the manufacturer, and indicates the results that the purchaser may expect to get at the crane hook. A brief survey of regulations affecting the installation of cranes is given, together with some remarks on maintenance and running costs.

Calculation of Stress in Crane Hooks

Abstract Two methods for calculating stress in crane hooks which have given good results in practice are described. One method, based on a numerical integration of the curved-bar equations, involves only slide-rule accuracy and may be used for irregular shapes of cross section. The second or analytical method is based on an analysis of an equivalent trapezoidal section, and is applicable to hooks having sections which do not deviate too much from the trapezoidal form. Comparison of the results of the two methods when applied to actual crane hooks indicates that the more rapid analytical method is sufficiently accurate for most practical purposes.

Design of Crane Hooks and Other Components of Lifting Gear

Most lifting gear components consist essentially of curved beams of very ductile material, the radius of curvature often being small in comparison with the dimensions of the beam. In addition, in rings, chain links, etc., the distribution of bending moment is not directly calculable from the values of the applied loads, but is influenced also by the condition that the centre line of the section of the component must remain continuous when under load. The design of lifting gear components requires, therefore, the determination of the bending moments, etc., set up, the calculation of the stresses due to these bending moments, etc., and the consideration of the modification to the stress system consequent upon yielding in parts of the components. The effect of the curvature of the centre line of the component on the distribution of stress is first discussed, the method of calculation for different forms of beam section being indicated, and the best form of section investigated. The effect of yielding is next considered. It is shown that, if any portion of the component yields under load, the removal of the load will leave this portion in a state of stress of opposite sign to that under which it yielded, and it is concluded that calculated stresses even as high as the sum of the yield stresses in tension and compression may be actually set up in the material as ranges of stress without causing continuous plastic deformation. The general method of calculating the bending moments in rings and links, etc., is demonstrated and comparison is made between exact and approximate methods. General formulæ for egg links (including rings and chain links), studded links, and eyebolts are obtained and typical examples, drawn from recent British Standard Specifications, are worked out. The results of tests on components designed according to the general principles of the paper are described and the use of fatigue testing both in determining the true factor of safety and as an experimental check on the calculations is demonstrated.