Shaft Design Research Articles

Design and construction of a deep shaft for Crossrail

An 8·2m diameter, 40m deep shaft for Crossrail is being constructed below the 10m deep basement of the Moorhouse development near Moorgate in the City of London. The depth of the shaft is such that it will penetrate through stiff London Clay and will be founded at the bottom of the Lambeth Group. The shaft is being constructed after the Moorhouse structure has been completed and the design of the Moorhouse foundations places tight constraints on acceptable ground movements due to construction of the shaft. Furthermore, the shaft needs to be designed to accommodate future ground movements associated with construction of Crossrail. The paper describes the complex relationship between the foundations of Moorhouse, the draught relief shaft and the future Crossrail assets. The optimised design includes extensive slip coating and base grouting of the Moorhouse piles, a complex temporary works dewatering system around the shaft and the option to carry out additional dewatering from within the shaft during construction. Control of ground movements through the Lambeth Group was perceived to be a particular problem in relationship to destressing the ground around the Moorhouse piles. To prevent longterm settlement of these piles, provision was made for radial grouting to “restress” the ground should the need arise.

Design and construction of a deep shaft for Crossrail

Design and construction of a deep shaft for Crossrail

Design of TBM work shaft and TBM launching chamber

The paper is focusing on the considerations in relation to the design and constructions of the large diameter work shaft and the TBM launching chamber for Contract T03 of the Singapore deep tunnel sewerage system (DTSS). This contract includes the design and construction of a 6.0 m finished ID main sewer tunnel, a number of access shafts, lateral connection tunnels as well as structures on the surface. The main sewer tunnel was constructed by means of an earth pressure balanced shield tunnel boring machine (EPB TBM), which was launched from a 7.6 m diameter launching chamber excavated at the bottom of the 12 m diameter, 32 m deep work shaft. The design and selection of construction methods employed for the TBM work shaft were significantly influenced by the proximity of the works to the existing test track of the Bishan MRT depot and a highway interchange with depressed road, which was concurrently under construction at the time of shaft construction. Owing to the presence of the MRT test track in the depot area, stringent performance requirements were established which influenced the selection of construction methods and required groundwater recharging and ground treatment in the vicinity of the shaft. The purpose of the jet grouting treatment was to increase the wall stiffness for reduction of wall displacements and reduction of permeability in the surrounding soil effectively cutting off seepage into the excavated shaft. A total number of 11 groundwater recharging wells were installed around the shaft and along the site boundary to the MRT test track area. In addition, the work shaft in its permanent condition will form the junction of three main sewer tunnels of the DTSS with a de-aeration chamber from an adjacent sewer drop shaft and a temporary back shunt tunnel for TBM operation. Therefore, the lower section of the shaft was designed considering significant amount of shaft lining space consumed by these five tunnel openings. The launch chamber at the bottom of the work shaft was excavated based on the principles of the NATM and supported by sprayed concrete lining. It is one of the main principles of the NATM to tolerate a certain safe level of ground displacements, thereby utilizing the contribution of the ground to the support the excavated cavity. However, given the stringent displacement limits of the MRT test track, minimization of displacements was one of the major objectives for the initial support design. The about 8.5 m diameter excavation was carried out in three separate stages (top heading, bench and invert), which followed each other at closest possible distance in order to minimize ground movements and close the ground support lining as close behind the excavation face as possible. Checking face stability conditions was an integral part of the design of excavation sequence. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Technische Ursache des Bruchs einer Mischerwelle / Technical Background of a Stirrer-Shaft Failure

In a blender for synthetic resins the shaft which carried and activated the stirrers broke after relatively short service. The fracture was identified as having been caused by fatigue and a re-assessment of the design was carried out. The result was, that the shaft design had been rather poor, especially the small radii at the shoulders of the shaft had contributed considerably to crack initiation. This case is a further example for the fact that simple mistakes in design or manufacture still lead to failure with causes which should be well known in fact. The case also shows that even in cases where from the visual inspection alone the failure cause appears to be quite obvious nevertheless substantial calculations of the design have to be performed to prove a poor design.

Design of Machine Elements, Eighth Edition

The eighth edition of Machine Elements provides tools and techniques to facilitate design calculations for the most frequently encountered machine elements. The book opens with a brief overview of the design process relative to general problem solving approaches and specific ANSI design standards. A condensed but informative overview of statics and failure theories is provided, followed by separate chapters for the design of shafts, springs, screws and transmission elements such as belts, clutches, brakes, chains, bearings, and the most common types of gears. Using a phenomenological approach, each type of machine element and its associated variants are described with respect to function, form, and constraints. The provided performance and failure analysis is accessible, with most mathematical derivations given in full detail to increase the usefulness and adaptability of the provided information. Educators and practitioners currently utilizing the 7 edition will appreciate the important changes to the 8 edition. While the organization of the two books is virtually identical through Chapter 14, a structured approach has been applied to all the design examples. This structured approach includes the enumeration of the problem statement, given information, assumptions, solution method, and solution details. While quite standard, this structured approach does facilitate an understanding of the engineering approach and may assist the development of critical thinking skills. The 8 edition also provides 54 improved spreadsheets that are utilized throughout the text. The spreadsheets are well presented and usually include a schematic, relevant equations, an input sec-

축어긋남이 있는 유연복합재 고속구동축의 특성 분석

This research is to investigate the performance of a flexible matrix composite driveshaft with respect to shaft design parameters such as the number of layers, ply orientations, and material properties. A finite element formulation is utilized to estimate the allowable misalignment under given driving torque, the maximum temperature at steady states, and external damping for ensuring whirling stability under supercritical speed. Results indicate that the system performance can be greatly affected by the shaft laminate parameters, especially the ply orientations. Several sets of shaft parameters that will provide satisfactory overall system performance are derived.

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

The effect of technique and shaft configuration in snow shoveling on physiologic, kinematic, kinetic and productivity variables

A repeated measures 2×2 factorial design using a psychophysical experimental methodology was performed to quantify the effect of shaft design (straight and bent shaft) and shoveling technique (forward and backward progression) on heart rate, perceived exertion, productivity, trunk kinematics and load kinetics. Ten male subjects performed four 8-min trials of snow shoveling on a paved asphalt surface. The most notable finding was significantly less trunk flexion with the bent shaft (41.4°) than with the straight shaft design (49.2°). The study results led to a recommendation of a bent-shaft shovel for the purpose of reducing trunk flexion. In the absence of any strong positive evidence and due to poor subjective response to backward progression while shoveling, this technique was not recommended.

A parametric study on rocking vibration of rotating disk/spindle systems with hydrodynamic bearings: rotating-shaft design

The system studied in this paper is a rotating disk/spindle assembly supported by hydrodynamic bearings with a rotating shaft design. Based on an experimentally verified mathematical model [1, 2], this paper presents how various spindle parameters affect critical vibration modes of the system, such as half-speed whirls and (0, 1) unbalanced modes (i.e., rocking modes). The parameters studied include number of disks, hub/shaft interface stiffness, shaft rigidity, thrust bearing location, radial bearing stiffness, radial bearing damping, and radial bearing locations. To simulate operational tests, the numerical study focuses on frequency response functions (FRF) of rotating disk/spindle systems subjected to linear base excitations. Simulation results show that 1-disk configuration has smaller FRF amplitude than the 4-disk configuration. In addition, the amplitude of half-speed whirl is primarily controlled by the radial bearing stiffness. In contrast, the amplitude of (0, 1) unbalanced modes is dominated by hub/shaft interface stiffness. Finally, radial bearing locations significantly affect the amplitude of half-speed whirls and (0, 1) unbalanced modes simultaneously.

Didactic Software for the Design of Rotative Shafts

The present work proposes the development of a program in Visual Basic to the didactics improvement in teaching machine components design, focusing the calculation procedures adopted in the design of rotative shafts, considering its dynamic behaviour as the fundamental influence in the vibrational response of a rotative machine. The design and diameters evaluation of the component, previous to its integration as a part of the rotative machine group, is done in a software developed in Visual Basic, with an interactive interface with the user, that models a presented shaft with loads, geometry and bearing position through singularity functions. This model, when analysing either the static or the dynamic condition, supplies answers to the user with respect to the shaft deflections, supports reactions, stress state and the final geometry. Viewing that the objective of that software is being used in disciplines of Mechanical Design, the same not only should be capable of calculating the shaft dimensions, obeying fatigue failure approaches and for multiaxial stress state, but also to present a didactic and simplified interface to the user.

An Integrated Computer-Aided System and Parts Component Repository for Shaft Design Automation

This research proposes an Object-Oriented Database (OODB) system that integrates computer-aided systems and parts component repository to automate a traditional propulsion shaft design for a shipyard. The software system is based on three concepts: an object-oriented graphic user interface, a parametric design, and a shared component database. Calculations of strength, alignment, vibrations, and sag & gap for the shaft design can therefore be completely integrated. All of the data produced in the CAD processes can be managed, integrated and applied in the OODB system. Furthermore, to easily integrate the systems developed at different periods of time, a Common Object Request Broker Architecture (CORBA) infrastructure is introduced to facilitates an object-oriented data flow bus exchanging data during the design stage. In the estimation or design process, all of the design and drawing output can be completed in a considerable short time. By integration of the shaft design process, precise estimation of design cost can be determined. A highly efficient production can be made due to the fact that working hours, costs and construction span times are reduced.

소형 선박용 복합재료 축 설계를 위한 음력해석에 관한 연구

소형 선박용 복합재료 축 설계를 위한 음력해석에 관한 연구

Composite Shaft Optimization Using Simulated Annealing, Part I: Natural Frequency

In this study a fiber-reinforced composite shaft design is optimized. The optimization procedure is carried out in two stages. First, the shaft natural frequency is maximized with the constraint imposed on the shaft buckling torque and torsional strength. In the second stage of optimization, shaft weight is minimized with the constraint imposed on the natural frequency obtained from the first stage, shaft buckling torque and torsional strength. Shafts of uniform layup and uniform wall thickness (UU), uniform fiber layup and variable wall thickness (UV), variable fiber layup and uniform wall thickness (VU) and variable fiber layup and variable wall thickness (VV) have been considered. The shaft is modelled as a simply supported Timoshenko beam in which shear deformation, rotary inertia and gyroscopic effects are included. Rayleigh-Ritz displacement are used for deriving the solution equation. A Simulated Annealing (SA) global optimization routine is used. Although this routine requires large number of function evaluations to find the optimum solution, it finds the global optimum with high probability even for ill conditioning functions with numerous local minima.

Calibration of Load and Resistance Factor Design: Resistance Factors for Drilled Shaft Design

The AASHTO load and resistance factor design specification was approved for use in 1994 with phi factors determined from fitting allowable stress design (ASD). Unfortunately, the latter did not provide resistance factors for shafts founded in sand, gravel, and rock or identify the influence of construction (dry, wet, and cased). Using a database of 273 shafts, of which 185 failed (settlement equal to 5% of the diameter) and have sufficient soil information, the resistance factors were determined for a number of different AASHTO design methods based on probability of failure. Effects of skin friction, combined skin and end bearing, and method of construction were investigated for different soils/rock. It was found that all the methods had resistance factors between 0.3 and 0.6, which correspond to a factor of safety of 2.5 to 4.5 in ASD. Current FHWA design methods gave the highest resistance factors in soils with the cased method of construction. In the case of rock, the dry hole method of construction and the intermediate geomaterials design method gave the highest resistance factors.

Design of carbon fiber composite shafts for high speed air spindles

For the stable operation of high speed air spindles, the low rotational inertia and high damping ratio of spindle shafts as well as high fundamental natural frequency are indispensable. Conventional steel spindles are not appropriate for high speed operation because of their high rotational inertia and low damping ratio. In this study, a high-speed air spindle composed of a carbon fiber epoxy composite shaft and two steel flanges was designed for maximum critical speed considering both the deflection due to bending load and the radial expansion due to centrifugal force and temperature rise during high-speed rotation. The stacking angle and thickness of the composite shaft and the adherend dimensions of the steel flanges were selected through vibrational analysis as well as considering the bending stiffness and centrifugal characteristics.

Computer-aided Shaft Design and Selection of Rolling-contact Bearings Using an Expert System

In this study, a computer program was developed using Q-Basic programming language to analyze the strength and deformation of a rotating circular stepped shaft. These shafts have a variety of power- transmitting mechanical elements (components), such as pairs of gears, and pulleys that are modeled in 3-D. In addition, force and moment analyses of these elements running on the shafts are examined. Notch sensitivity and stress concentration factors given graphically were formulated using the finite difference method. Furthermore, to select the best rolling-contact bearings, an expert system requiring the knowledge-based technique was employed. The knowledge of the expert system and data of the roll ing bearing catalogue were input into the program. To perform the expert system, the LEONARDO software technique was used.

Influence of Axial Force in The Intermediate Shaft on the Load Capacity of the Paired Cardan Mechanism

The design of intermediate shaft with axially movablesplined joint must be adapted to the variable position of theshaft axis, i.e. to the change of the joint angle during operation.This design is also used for the reduction of axial forces whichare caused by inaccuracy in the production and assembling ofC(ll·dan mechanisms. The axial force which is generated by frictionof contact swfaces in the splined joint is the function of themagnitude of the transfeJTed torsion moments, splined dimensions,lubrication conditions, and materials used for contactswfaces. It will cause additional bearing loads at cross journalsand in the shaft supports, as well as unallowed vibrations andnoise during operation, thus affecting the safety and lifetime ofthe Cardan mechanism. The theoretical and empirical analysisof Cm·dan mechanisms, which have been studied with andwithout axial forces in the splinedjoint and its effect on durabilityof mechanism elements have been presented.

Optimum Shape Design of Rotor Shafts Using Genetic Algorithm

In general, the dynamic design of a rotor system is to optimize the system in stability at the operating speed, unbalance response in the vicinity of the rotor critical speeds, and minimize the system weight considering economics. This paper deals with the optimum shape design of the rotor shaft to change the critical speeds under the constraints of the constant mass. As to the design procedures, the genetic algorithm was applied to find the optimum diameters of a rotor shaft so that the optimized rotor system can yield the critical speeds as far from the operating speed as possible. Genetic algorithm is a search algorithm based on the natural world, which states that the individual with the superior character creates the superior descendant because of having excellent adaptability, high survivability, and more crossing chance, and the natural genetics that repeatedly perform the process of reproduction, crossover, and mutation. The results show that the critical speeds of the rotor-bearing systems can be significantly improved by slight modification of the shaft diameters, even without increasing the total mass of a rotor system.

Shape factors and material indices for dimensionally constrained structures Part 1: Beams

Shape factors and material indices have been recently developed for the optimal design of load-bearing beams and shafts. These shape factors and material indices are generally only applicable where there are no dimensional constraints. However, dimensional constraints are very common in mechanical design because of the integrated nature of modern machinery and equipment. This paper extends the methodology of a previous paper by Ashby by developing the shape factors and material indices for the case of constrained height in beams. The paper also shows that dimensional constraints can have a very significant effect on the optimal selection of material and shape.

Shape factors and material indices for dimensionally constrained structures Part 2: Shafts

Shape factors and material indices have been recently developed for the optimal design of load-bearing beams and shafts. These shape factors and material indices are generally only applicable where there are no dimensional constraints. However, dimensional constraints are very common in mechanical design because of the integrated nature of modern machinery and equipment. This paper extends the methodology of a previous paper by Ashby by developing the shape factors and material indices for the case of constrained diameter in shafts. The paper also shows that dimensional constraints can have a very significant effect on the optimal selection of material and shape.