Hole Clearance Research Articles

A Technique of Selecting the Optimal Values of the Parameters of the Hydraulic Monitoring Holes of Drilling Bits

It is known that through improvements in the performance of the process of cleaning (from drilling chips) of the well bottom and the drilling bit cutting structure it is possible to increase the mechanical speed and, consequently, drilling effi ciency. Cleaning is performed by feeding washing fl uid into the bottom zone through the hydraulic monitoring holes of the drilling bit. The number and orientation of these holes are determined on the basis of design experience and data on the operation of different modifi cations of a given model of a drilling bit. The structure of the fl ow of the washing fl uid in the well-bore face zone is complicated, with eddies and stagnant zones, which may lead to limitations on the evacuation of drilling chips by means of ascending fl ows and the formation of sediment on elements of the drilling bit cutting structure. Through an analysis of the structure of the fl ow of washing fl uid in the hydraulic monitoring channels and in the bottom zone, it is possible to establish the drawbacks in the construction of the washing system of the drilling bit and estimate the dynamic effect of draining jets on the back of the well bottom and the effi ciency of the nozzles used in the hydraulic monitoring holes [1–4]. The selection of an optimal design of the confi guration and orientation of the hydraulic monitoring holes of a drilling bit on the basis of results of mathematical modeling represents a complex problem. Thus, it is necessary to vary numerous geometric parameters (the diameters of the holes; the angles that govern the direction of drainage of the jets; the coordinates of the holes on the surface of the drilling bit) to fi nd the optimal combination of these parameters, a process that takes much time. Moreover, it is important to determine the optimality criterion of the washing process. For example, an increase in the speed of the ascending fl ow in the hole clearance does not indicate any improvement in the quality of the washing, since the portion of the fl uid refl ected by the walls of the well, the crest of the drilling bit and the elements of the drilling bit cutting structure may be drawn into longitudinal eddies, as a consequence of which the drilling chips will not be completely removed from the bottom zone or will immediately enter the hole clearance. Once the factors that directly infl uence the cleaning of the drilling bit cutting structure and the bottom zone from drilling chips have been determined, it is then necessary to parameterize these factors and determine the extremal values of the parameters. Through the use of the proposed technique, it is possible to formulate an optimization problem, where the result of a solution of the problem are the values of the diameters of the hydraulic monitoring holes and their position and orientation

Numerical Analysis of Influence on Gas Supply Hole Number and Radial Clearance for the Characteristics of Hydroinertia Gas Journal Bearings

Hydroinertia gas journal bearings have been applied to solid state nuclear magnetic resonance spectroscopy. These bearings, which require a larger radial clearance than conventional externally pressurized bearings, achieve stable operation for ultra high-speed rotation of spinner shaft at several million rpm. However, their small diameters, which range within 1-6 mm, have limited experimental verifications of their static characteristics. A computational fluid dynamics analysis was therefore performed to fill this gap. The effects of radial clearance and gas supply hole number on bearing characteristics, such as pressure distribution and load capacity, were investigated. This analysis showed that negative and positive pressures generated some clearance. Pressure distribution also changes in the gas supply hole number. A large load capacity was obtained at this clearance. To verify the phenomenon, measurement of pressure distribution was performed using experimental setup. Negative pressure could be confirmed actually in the large radial clearance condition.

Finite Element Simulation of Process Control for Bolt Tightening in Joints With Nonparallel Contact

In this paper, 3D finite element analysis (FEA) is used to simulate and evaluate different process control methods that are commonly used for automating the assembly of bolted joints in a mass production environment. The finite element (FE) model takes into account the thread helix angle of a fastener along with parallel and nonparallel contact surfaces under the bolt head. Simulation includes the torque-only and the torque-turn process control methods for achieving a desired level of the bolt preload at initial assembly of the joint. The torque-only process control option is simulated by applying the target torque at which the tightening process is automatically stopped. On the other hand, a torque-turn or torque-angle method is simulated by first applying a low level (threshold) torque, to the bolt head, followed by turning the bolt head by a specified angle of turn in order to achieve the desired bolt tension. The effect of variables such as thread and underhead bearing friction coefficients and bolt hole clearance is investigated. The FEA simulation provided in this study would be helpful in developing a reliable tightening strategy for joints with nonparallel bearing surfaces.

Experiment Study on Interference Amount of Rivet Joining for CFRP/Al Components

CFRP (Carbon Fiber Reinforced Plastic) occupied an important ratio in composite material for its high strength and high modulus. So CFRP/Al laminated construction was applied in airplane industry more and more popular, which was mainly joined by interference-fit connection. In joining process, interference amount is difficult to control. In this article, process parameters such as working voltage and rivet hole clearance was selected to study the relationship between the parameter and interference amount by experimental test method. Besides interference amount is different at CFRP end and metal end, and lays the foundation for theoretical analysis and numerical calculation of interference amount.

Oil and Gas Well Hole Structure and Application in Superdeep Well with Analysis of Material Properties

The designing level of oil and gas well hole structure and application in superdeep well with analysis of material properties play a key role in the expected production target to superdeep oil and gas wells. This paper introduces the hole structure of standard casing size series, main problems in superdeep wells with analysis of material properties, and solving means such as: using liner as production casing, cementing under small clearances of borehole-casing annulus and intermediate casing-production casing annulus, reaming and close clearance hole structure, analysis of material properties and so on. By application, the study above has a good practicality.

원공공차를 가진 볼트 조인트와 핀 조인트의 강도평가에 관한 연구

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, composite joint have become a very important research area because they are often the weakest sites in composite structures. In this paper, the failure strengths of the bolted joint and pin joint which have variable hole clearance were evaluated and compared. From the tests, the first failure loads of the bolted joint and pin joint with 880 ㎛ hole clearance have decreased by 24.2 % and 51.3 % compared to those of joints with 0 ㎛ hole clearance, respectively. Also, the failure index of the joints were calculated by the finite element method and compared with experimental results.

Effects of Assembly Tolerances on Bolted Anchorages in Concrete

AbstractThe performance of concrete anchors located close to a free edge and loaded in shear toward the edge of a concrete member is influenced by several geometric and structural/material parameters. In the case of anchor groups, the behavior of the system is described by highly nonlinear mechanical procedures, due to the interaction with anchors in vicinity. Apart from that, the existence of constructional tolerances (i.e., hole clearance of the bolted connection) leads to randomness in the distribution of the group load to the individual components, thus to uncertainties in the expected resistance of the anchorage. In that context, the structural effects of assembly tolerances have not yet been adequately investigated. As a result, current design guidelines are based on extreme-case concepts, thus often leading to a partial utilization of fastening systems. In the present study, it is attempted to capture the performance of the discussed structural system focusing on the influence of assembly tolerance...

A detailed finite element investigation of composite bolted joints with countersunk fasteners

This paper presents a very detailed FE model of a single lap composite bolted joint, with countersunk fasteners, under static tensile load. The stress states of the CFRP plates and titanium bolts are discussed, the evolution of the contact between the bolts and the holes is analysed, and the numerical results are compared to experimental data. Parametric studies have been performed to study the influence of bolt clamping force, coefficient of friction and bolt–hole clearance on the joint behaviour. It has been found that the model is able to identify correctly the critical locations in the joint (head–shank transition and first thread in bolts and edges of the holes at the faying surface for the plates) and reproduce with accuracy the experimental load–displacement test curves (including an unloading–reloading loop) up to the point where bearing damage occurs. A correlation between the joint stiffness and the contact status between bolts and holes has been found. Five stages have been identified in the joint behaviour: (i) No-Slip, (ii) Slip, (iii) Full Contact, (iv) Damage and (v) Final Failure. The results show that the joint stiffness is higher in the No-Slip stage than in the Full Contact stage, and that this is independent of coefficient of friction and bolt clamping force. The clearance controls the length of the Slip stage and modifies the joint stiffness in the Full Contact stage.

Failure and reliability analysis of pinned-joint composite laminates: Effects of pin–hole clearance

This study deals with the failure and reliability analysis of cross-ply [0/90]2s glass fiber reinforced epoxy composite pinned-joints. A series of ASTM tests were conducted to study the effect of pin–hole clearance (neat-fit, 50, 100, 200, and 300 µm) on the properties of glass fiber reinforced epoxy composite pinned-joints. Failure analysis was examined using load–displacement diagrams and visual and scanning electron microscope examinations of the fractured specimens. The results showed that the first-peak and ultimate strengths were, respectively, reduced by 33.1% and 15.3% with increase in the pin–hole clearance. The corresponding increase in the ultimate displacement was 10.7% and the reduction of the apparent joint stiffness 27%. Weibull function was used to analyze the scatter in the experimental results and estimate the mean and the 50% survival strengths. Safe design strengths at different reliability levels, characteristic strengths, and the lower bound strengths were estimated using time to first failure concept.

Numerical Analysis of Fastener Delamination/Disbond Arrest Mechanism in Aircraft Composite Structures

The effectiveness of using a fastener as a fail-safe delamination/disbond arrest mechanism in aircraft composite structures is investigated. This is accomplished by simulating the crack propagation behavior of a split-plate model with a fastener in the commercial finite element software Abaqus. In mode I, the fastener is capable of completely stopping the crack propagation; in mode II, the fastener provides resistance to propagation via three main mechanisms: 1) the fastener joint stiffness, 2) fracture mode transition, and 3) crack-face friction generated by fastener preload. The fastener hole clearance significantly reduces the effectiveness of the arrest mechanism by delaying the engagement of the fastener joint. Thisworkprovides the basis for the development of analyticalmethods for the design and optimization of crack-arrest features in composite aircraft.

Experimental investigation of built-up double-Z members in bending and compression

Using the conventional cold-formed shapes in built-up assemblies (composed members, trusses, etc.) has allowed designers of light-steel framing to widen the applications of cold-formed steel (CFS) to structures of larger scale. Built-up elements, fastened by bolts, screws or welds are usually symmetrical, more stable and of higher capacity. However, they are not addressed in the various design codes for CFS structures. Additional flexibility is caused by slippage between the constituents of a composed member, especially if bolts are used as interconnectors and hole clearances are provided to ensure the ease of assembly. The paper presents experimental studies on the behaviour of double-Z built-up members (bolted). First, twelve members are tested in weak-axis bending, to evaluate the stiffness of the member for the axis of symmetry. Second, the overall behaviour is analysed in eight compression tests on slender members. The goal is to determine the actual failure mode and overall buckling capacity of these members.

Precision grid and hand motion for accurate needle insertion in brachytherapy

In prostate brachytherapy, a grid is used to guide a needle tip toward a preplanned location within the tissue. During insertion, the needle deflects en route resulting in target misplacement. In this paper, 18-gauge needle insertion experiments into phantom were performed to test effects of three parameters, which include the clearance between the grid hole and needle, the thickness of the grid, and the needle insertion speed. Measurement apparatus that consisted of two datum surfaces and digital depth gauge was developed to quantify needle deflections. The gauge repeatability and reproducibility (GR&R) test was performed on the measurement apparatus, and it proved to be capable of measuring a 2 mm tolerance from the target. Replicated experiments were performed on a 2(3) factorial design (three parameters at two levels) and analysis included averages and standard deviation along with an analysis of variance (ANOVA) to find significant single and two-way interaction factors. Results showed that grid with tight clearance hole and slow needle speed increased precision and accuracy of needle insertion. The tight grid was vital to enhance precision and accuracy of needle insertion for both slow and fast insertion speed; additionally, at slow speed the tight, thick grid improved needle precision and accuracy. In summary, the tight grid is important, regardless of speed. The grid design, which shows the capability to reduce the needle deflection in brachytherapy procedures, can potentially be implemented in the brachytherapy procedure.

Numerical Simulation of Riveting Process

In order to fully understanding the distribution of residual stress after riveting and the relationship between residual stress and riveting process parameters during riveting, Finite Element Method was used to establish a riveting model. Quasi-static method to solve the convergence difficulties was adopted in riveting process. The riveting process was divided into six stages according to the stress versus time curves. The relationship of residual stress with rivet length and rivet hole clearance were established. The results show numerical simulation is effective for riveting process and can make a construction for the practical riveting.

Experimental evaluation of the effect of clamping force and hole clearance on carbon composites subjected to bearing versus bypass loading

Abstract A series of carbon fibre laminate bearing versus bypass load tests were carried out investigating the effect of hole clearance, laminate lay-up, washer contact size and clamping force value. Explanations of the underlying effects that influence the results are discussed. The results compare well with literature but hole clearance was shown to increase joint strength when bypass loads are dominant, which seems counter intuitive, and has not been reported in literature.

A global bolted joint model for finite element analysis of load distributions in multi-bolt composite joints

This paper presents the development and validation of a global bolted joint model (GBJM), a highly efficient modelling strategy for bolted composite joints. Shell elements are used to model the composite laminates and the bolt is represented by a combination of beam elements coupled to rigid contact surfaces. The GBJM can capture effects such as bolt–hole clearance, bolt-torque, friction between laminates, secondary and tertiary bending in the laminates as well as the load distribution in multi-bolt joints. The GBJM is validated using both three-dimensional finite element models and experiments on both single- and multi-bolt joints. The GBJM was found to be robust, accurate and highly efficient, with time savings of up to 97% realised over full three-dimensional finite element models.

An Improved Stiffness Model for Bolted Joints

Abstract An improved stiffness model is proposed for bolted joints made of similar and dissimilar plates. A novel approach is used to obtain an expression for the effective area used for determining the joint stiffness. More accurate estimate of the joint stiffness provides a more reliable prediction of the joint behavior both during its initial assembly, as well as under subsequently applied tensile loads in service. The effect of the grip length-to-diameter ratio, joint sizes, underhead contact radii ratio, hole clearance, and plate material/thickness ratio are investigated. Experimental data are used for determining the envelope angle α in the proposed analytical model. Finite element modeling is used for evaluating the accuracy of the proposed stiffness model.

Design of Anchors Close to an Edge under Shear Loading. Engineering approach for consideration of load direction

An universally valid proposal is made for the design of anchors close to an edge under shear loads for concrete edge failure. The angle of the shear load is taken into account during determination of the load distribution on each anchor of a group. Thus the model may be used for applications without and with hole clearance and for shear loads as well as for torsion moments.

An FE analysis of the stresses in pultruded GRP single-bolt tension joints and their implications for joint design

FE (Finite Element) analysis is used to determine stresses on critical planes and around the hole edge in a two-dimensional model of a single-bolt tension joint in pultruded GRP (Glass Reinforced Plastic) plate material. The analysis takes account of bolt–hole clearance and friction at the contact surfaces between the bolt shank and the hole. It is shown that even when the hole clearance is nominally zero (∼0.2 mm) critical stress distributions, normalized with respect to the far field stress, are not invariant but change as the tension increases. Friction between the bolt shank and the hole and the small hole clearance (∼0.2 mm) are the principal factors which cause the zone of contact (defined by the angle it subtends at the centre of the bolt) to increase with increasing tension, and produce significant changes in the stress distributions at critical locations. These observations cast doubt on the validity of the simplified method for joint design given in the EUROCOMP code [In: Clarke JL, editor. Structural design of polymer composites – EUROCOMP design code and handbook. London: E.&F.N. Spon; 1996], because the method relies on normalized critical stress distributions remaining unchanged as the tension applied to the joint increases.

Study of the Effect of Hole Clearance and Thread Fit on the Self-Loosening of Threaded Fasteners

This study provides an experimental and theoretical investigation of the effect of hole clearance and thread fit on the self-loosening of tightened threaded fasteners that are subjected to a cyclic transverse service load. An experimental procedure and test setup are developed in order to collect real-time data on the rate of clamp load loss per cycle as well as the loosening rotation of the bolt head. Three levels of hole clearance are investigated; namely, 3%, 6%, and 10% of the bolt nominal diameter. For the commonly used 2A thread fit for a selected bolt size, three classes of the nut thread fit are considered; namely, 1B, 2B, and 3B. A simplified mathematical model is used for the analytical investigation of the effect of the hole clearance and thread fit on threaded fasteners self-loosening. The experimental and theoretical results are presented and discussed.

3D FEA Simulations to Assess Residual Stresses in Riveting Processes

Abstract Multiple site damage (MSD) in aircraft structures can be defined by the presence of numerous minute cracks arising at different locations such as rivet holes in lap joints. One source of initiation can be due to residual stresses induced in the lap joints during the riveting process. This paper describes a finite element methodology of a quasistatic, displacement controlled riveting process to capture the local geometry features representative of service hole quality for accurate simulation of residual stresses in riveted lap joints. A three-dimensional finite element (FE) model that takes into account material, geometric, and contact non-linearities is developed using ABAQUS/Standard 6.4-1 to simulate the joining process. The interest of FE simulations is to conduct parametric studies to observe effects of varying hole clearance, misaligned holes, friction, and presence of debris on the residual stress state in the skin. Based on studies conducted, comments are made regarding any observed variation in tensile hoop stress, which is the primary source of fatigue cracks in riveted lap joints. A relation between the rivet-head deformation ratio and rivet-head height with applied displacement is developed using the finite element model, as a means of controlling the rivet-head deformation.