Hole Clearance Research Articles

SURVEYING THE EFFECT OF GAS-VENT HOLE DIAMETER AND CLEARANCE BETWEEN PISTON AND CYLINDER ON AUTOMATIC FIRING SYSTEM OF 23mm ЗY23-2

On the basis of analyzing the real model 23mm ЗY23-2, the paper chooses an alternative physics model, building a mathematical modeling dynamics, set up a system of equations and solve to find the cycle of operation on automatic firing system, change some parameters of cylinder and study on its effect to do automatic firing system; besides surveying the effect of gas-vent hole diameter and clearance between piston and cylinder on automatic firing system of 23mm ЗY23-2. The research method is based on the calculation theory to ensure compliance with the manufacturer's gun design and use documents.

Numerical Investigations on Non-Rectangular Anchor Groups under Shear Loads Applied Perpendicular or Parallel to an Edge

Anchorages of non-rectangular configuration, though not covered by current design codes, are often used in practice due to functional or architectural needs. Frequently, such anchor groups are placed close to a concrete edge and are subjected to shear loads. The design of such anchorages requires engineering judgement and no clear rules are given in the codes and standards. In this work, numerical investigations using a nonlinear 3D FE analysis code are carried out on anchor groups with triangular and hexagonal anchor patterns to understand their behavior under shear loads. A microplane model with relaxed kinematic constraint is utilized as the constitutive law for concrete. Two different orientations are considered for both triangular and hexagonal anchor groups while no hole clearance is considered in the analysis. Two loading scenarios are investigated: (i) shear loading applied perpendicular and towards the edge; and (ii) shear loading applied parallel to the edge. The results of the analyses are evaluated in terms of the load-displacement behavior and failure modes. A comparison is made between the results of the numerical simulations and the analytical calculations according to the current approaches. It is found that, similar to the rectangular anchorages, and also for such non-rectangular anchorages without hole clearance, it may be reasonable to calculate the concrete edge breakout capacity by assuming a failure crack from the back anchor row. Furthermore, the failure load of the investigated groups loaded in shear parallel to the edge may be considered as twice the failure load of the corresponding groups loaded in shear perpendicular to the edge.

Analysis of uncertainty relation of pin-shaft fitting in mechanical system with clearance

Pin-shaft fit is one of the most basic assembly structures for mechanical products, and the fit clearance plays a decisive role in the performance, safety and effective operation of the product. Taking the uncertainty of the shaft hole clearance fit in the positioning process as the research objective, based on the analysis of the factors affecting the uncertainty of the shaft hole clearance fit in the positioning process, an information entropy model of the shaft hole machining uncertainty is constructed to quantify describe the uncertainty of the shaft hole clearance fit. The uncertainty index of shaft hole clearance fit is proposed to comprehensively characterize the uncertainty of shaft hole clearance fit accuracy. And analyze the inherent relationship between the uncertainty index and the accuracy of shaft hole clearance fit keeping reliability. The effectiveness and feasibility of the method are verified through examples.

Experimental investigations on the concrete edge failure of shear loaded anchor groups of rectangular and non-rectangular configurations

The failure mode of anchorages placed close to the concrete edge and loaded in shear perpendicular towards the edge is often governed by the concrete edge breakout failure. The design provisions for concrete edge failure given in the current codes are limited in their application for anchor groups with rectangular anchor configurations only. The number of anchors in a row is limited to three for anchorages without, two for anchorages with hole clearance. Furthermore, for anchor groups with multiple anchor rows loaded in shear perpendicular and towards the edge, the failure load may be calculated by assuming the failure crack originating from the front anchor row (EN 1992-4) or from the back anchor row (fib Bulletin 58, ACI 318). The aim of this experimental study was to investigate the behaviour of shear loaded anchor groups of rectangular, triangular and hexagonal configurations undergoing concrete edge failure. A comprehensive experimental program was carried out on single anchors and anchor groups of different configurations to obtain information on (i) the group behaviour, (ii) the crack initiation and propagation, (iii) the influence of the displacement behaviour of single anchors on the behaviour of anchor groups and (iv) the influence of hole clearance pattern. The testing concept, test setup and the detailed evaluation of the test results such as load-displacement curves of the groups, load-displacement curves of single anchors, measurements on the hole clearance pattern and the investigation of the crack pattern and failure mode are discussed in this paper. Based on the evaluation of the test results presented here, a new analytical model is being developed for the concrete edge failure mode of shear loaded anchor groups that will be presented in a future paper.

Requirements for oversized holes for reusable steel-concrete composite floor systems

The design of sustainable structures is increasingly gaining attention in the construction sector as a societal and technological challenge. Demountability and reuse of structures contributes to the reduction of the environmental impact of the built environment. Welded headed studs used in traditional steel-concrete composite floor systems need to be replaced by demountable shear connectors to enable the transition of the construction sector to a circular business model. The demountable shear connectors are embedded in large prefabricated concrete floor elements and connected to steel beams by bolts. The holes in the beam flange are oversized to account for geometrical and dimensional deviations of all members and to facilitate rapid execution and easy demounting. The goal of this paper is to present a methodology that quantifies the required nominal hole clearance for reusable composite floor systems. Statistical characteristics of dimensional and geometrical deviations serve as input for Monte-Carlo simulations. The aggregated results of the Monte Carlo simulations are used to determine the required nominal hole clearance for a specified probability of successful installation of the demountable shear connectors. The proposed methodology is applied to the composite floor system of a demountable and reusable car park building. The contradicting requirement of oversized holes and composite interaction is solved by injecting the hole clearance with a (steel-reinforced) epoxy resin. The bearing resistance of the (steel-reinforced) epoxy resin is addressed based on preliminary results of creep experiments on resin-injected bolted connections.

Full-range behaviour of double web angle connections

This paper presents recent experimental and analytical investigations on the full-range flexural behaviour of double web angle connections. Experiments were carried out on bolted double web angle connections with two different configurations featuring three and five bolt rows, respectively. For each connection configuration, five nominally identical specimens were tested to investigate the variability of connection behaviour, including joint stiffness, ultimate resistance and ductility, thereby making a total of ten tests. All tests were conducted well into the post-ultimate range until complete failure of the connection, examining the full-range connection response. The load transferring mechanism of the connection was dynamically changing, partly because the presence of bolt hole clearance caused certain bolts to be initially inactive, only to later become active in transferring load from the beam, and partly because when the beam bottom flange came into contact with the column flange under large connection rotation, the centre of rotation changed causing the compressive load transferred at the bottom bolt rows to unload and reverse. To capture the above complicated changes of load transferring mechanisms and thus capture the full-range behaviour of a bolted web angle connection, an advanced mechanical model was proposed. The model is based on the Component Method, and adopts a decision tree to track the evolution of the load-transferring mechanism of the connection, including the bearing state of each bolt, either under tensile or compressive load, the potential presence of contact between the beam bottom flange and the column flange, and the plastic deformation of the critical connection components. The proposed model was applied to the tested connections with excellent agreement observed between the model predictions and the experimental results. Not only producing full-range force-displacement curves that are very close to the experimental curves, the proposed model also provides useful information about the internal state of the connection, which was not obtainable from the tests.

Experimental and numerical investigations on load-carrying capacity of dowel-type bolted bamboo joints

Bamboo has been widely used for structural and non-structural purpose, for example as scaffolding and cladding for many centuries in South East Asian countries such as China and India, due to its high strength-to-weight ratio, low price and recyclability. In today’s trend of sustainable development, there is a renewed interest in the use of bamboo for modern prefabricated structures. In this paper, dowel-type bamboo joints are introduced for prefabricated bamboo structures. An experimental study has been undertaken to investigate the structural behaviour and the failure mechanisms of the dowelled joints with varying configurations. Test results reveal that the ductile failure mode of the bamboo occurred when large end spacing was applied, and the infilling grout can significantly increase the load-carrying capacity of the dowelled joint. Three-dimensional finite element models were established and validated using available experimental data. Extensive parametric studies were carried out based on the simulation approach to investigate the effects of key influencing variables involved, i.e. hole clearance, friction coefficient, bolt strength, bamboo thickness, grout strength and end spacing. Moreover, analytical models for designing the dowelled joints are proposed and compared with the current codified approach.

A pilot study to assess an in-process inspection method for small diameter holes produced by direct metal laser sintering

Purpose The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed. Design/methodology/approach The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy. Findings The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter. Practical implications Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process. Originality/value The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.

Failure Evaluation of Hybrid Joints using Taguchi Method

The structural joints for various applications like automobile, aero planes, ships etc. used mechanical fasteners or adhesives for joining purpose. The mechanical fastener increases the weight of the joints and the adhesives have a catastrophic failure nature. So to reduce the overall weight of the joint and avoid the catastrophic failure of the joint, Hybrid Joint, which is the combination of the two methods (Bolts and adhesives) is used. The Analytical Hierarchal process (AHP) is used to select the parameters that affect the performance of the joint. The selected parameters were bolt size, tightening torque, bolt hole clearance, adhesive type, adhesive thickness, overlap length and joint material and the response variables were failure load and displacement The optimum parameters were selected by using Taguchi analysis with L27 orthogonal array experimental design. The significant parameters were found to be Adhesive type, Adhesive thickness and Joint Material.

Experimental and numerical investigations on the concrete edge failure of anchor groups of arbitrary configurations

Concrete edge failure often governs the failure of anchorages, which are installed close to the concrete edge and are loaded in shear perpendicular towards the edge. The design provisions for concrete edge failure given in the current codes are rather limited in applicability. Only anchorages arranged in a rectangular pattern are allowed. For anchorages without hole clearance, the maximum permissible anchor pattern is with three anchors in a row, and for anchorages with hole clearance, a maximum of only two anchors in a row is allowed. Furthermore, for anchor groups with multiple anchor rows loaded in shear perpendicular to the edge, the failure load may be calculated by assuming the failure crack initiating from the front anchor row (EN1992-4) or by assuming the failure crack initiating from the back anchor row (fib Bulletin 58, ACI 318). No design guidelines exist for non-rectangular anchor configurations. In such cases, the design is based on engineering judgement. In this study, experimental and numerical investigations were performed on anchor groups of triangular and hexagonal configurations to study the concrete edge failure. It was observed that the failure crack always initiates from the back anchor row, even in case of anchor groups, where the first cracking is associated with the first anchor row. The first cracking may have an influence on the displacement behaviour of the group, which might limit the design in SLS. However, this is dependent on the displacement behaviour of individual anchors within the group, edge distance, spacing and hole clearance.

Finite element analysis and mathematical characterization of contact pressure distribution in bolted joints

Quantitative characterization of contact pressure distribution in bolted joints directly influences the calculation accuracy of connection stiffness. In this paper, a three-dimensional finite element model of the bolted joints is established using the software ANSYS, and pretension force and contact between the joint components are accommodated in the model. Then, parametric studies are carried out to investigate the effects of the material properties, preloads, bolt sizes, grip lengths and hole clearances on the contact pressure distribution. According to the finite element analysis results, a polynomial equation system is derived for mathematical representation of contact pressure distribution in bolted joints. Furthermore, the conical envelope angle used in the mathematical characterization is identified for the bolted joints with different bolt sizes and grip lengths. Finally, an experimental platform is constructed for the measurement of contact pressure distribution, and then the applicability of mathematical characterization is validated by comparison with a series of experiment results.

Proof of concept of a demountable steel‐concrete composite flooring system

ABSTRACTEnvironmental concerns steer the construction industry towards more sustainable developments such as demountable and reusable structures. Composite structures are a frequent solution for multi‐story buildings and bridges, however the use of welded shear connectors requires labour and energy intensive disassembly. Two bays of a demountable flooring system for a multi‐storey car park building were erected in the laboratory. The flooring system consists of large prefabricated concrete decks connected to tapered steel beams. The feasibility of assembly and disassembly of the flooring system was tested under laboratory condition. Shear interaction was achieved by an embedded bolt and coupler which are connected to the top flange of the steel beam by an external injection bolt. Oversized holes are used in the top flange of the steel beam to accommodate fabrication and execution deviations and the deformations occurring during construction. Extensive imperfection measurements and finite element models were used to design the oversized hole diameter to 32 mm. The hole clearance must be compensated either by pretensioning or injecting the bolt‐to‐hole clearance with an epoxy resin to enable instantaneous composite action under live loads. Experimental injection of 150 injection bolts confirms that epoxy resin can reliably fill the hole clearance, and that the injection process takes 30 seconds per bolt. Various non‐uniform shear connector arrangements were considered to minimize construction costs and maximize the speed of execution. The mechanical behaviour of the demountable composite beam was tested experimentally and numerically.

Push-out tests on demountable shear connectors of steel-concrete composite structures

Circular Economy refers to a move from linear business models, in which products are manufactured from raw materials, used and then discarded, to circular business models where products or parts are re-used, remanufactured or recycled. Structural steel is highly compatible with this concept; however, when steel-concrete composite structures are used, recycling becomes difficult and the potential for reuse is lost. In order to make steel-concrete composite structures reusable, bolted connections should replace the commonly used welded headed studs. Furthermore, the reusable parts should be designed to withstand repeated use.This paper presents a desktop study and the corresponding laboratory experiments on demountable shear connectors that facilitate recyclability and even provide the potential for reusing complete structural elements. In the Laboratory of Steel and Composite Structures of the University of Luxembourg 15 push-out tests have been carried out using different bolted connection systems suitable for multiple use. The shear connectors have been evaluated based on their shear strength, stiffness, slip capacity, ductility and ability of demounting. The investigated systems included pre-stressed and epoxy resin injection bolts, solid slabs and solid slabs in combination with profiled steel sheeting. The results showed that the tested demountable shear connections could provide higher shear resistance than conventional shear connections. The critical failure mode was the shear failure of the bolts, which is a brittle failure. There was no visible damage observed on the connected members. The application of epoxy resin in the hole clearance resulted in lower slip capacity. The outcome provides an important basis for the justification of the forthcoming enhancement and validation of numerical models of the demountable shear connections. The failure behaviour, the observed damages and the resulting ability of the elements for re-use are discussed in detail.

ANALISIS METODE CASING WHILE DRILLING UNTUK SETTING CASING 16” PADA SUMUR C2

C2 well is an exploration well located in south sumatera area managed by PT. MEPI in planned CSS field will be drilled to a depth of 12.000 ftTVD vertically. Planning the use of casing while drilling is done by using 16" protective casing on the trajectory 17-1/2" from a depth of 1.500 ft to 4.600 ft. The use of casing while drilling (CWD), is expected by using the casing as drillstring, then the clearance between the boreholes wall with the OD casing becomes small which will cause the event "Plastering Effect". This phenomenon is expected to isolate the wall of the drill hole which is easy to happen lost circulation. On vertical wells only need a casing method while drilling level-2 (non-retrievable) because at level-2 only casing with bits (drillshoe) only, where drillshoe will be left in the shoe casing. From the analysis results can be said on well C2 can be applied casing method while drilling because in terms of hydraulics drilling which the drill hole clearance with horsepower square inch method (HSI) and cutting lift based on cutting carrying index (CCI) is good, but for mechanics drilling needs to be considered torque, drag, and buckling loads. In terms of torque loads MLT Rings should be installed for 16” protective casing, from drag loads where the 2.000 HP rig can withstand maximum load of hookload, and 16" protective casing might not occur buckling as the maximum weight on bit (WOB) is still under critical buckling load.

Design of composite flooring systems for reuse

Composite floor systems are frequently used for high-rise buildings and multi-storey car park buildings, mainly because of the competitive combination of the steel beam and the concrete deck. Traditionally, composite beams are cast in-situ and shear interaction between the concrete and steel beam is provided by welded headed studs. The application of welded headed studs prevents the non-destructive separation of the composite beam, which leads to a very low scoring in the sustainable assessment in terms of the reuse of structural components. An alternative to welded headed studs are bolted shear connectors, which allow for demountability and reusability of a (prefabricated) composite floor system. A key challenge for demountable and reusable composite beams consisting of prefabricated elements is to provide sufficient tolerances to allow for easy execution and demounting, but also to achieve a stiff and strong shear connection under live loads. The required tolerances can, for instance, be obtained by using large bolt-to-hole clearances. The, at first glance, contradictory requirement of a large hole clearance in the execution phase and high stiffness under live loading conditions was solved by using injection bolts. The goal of this paper is to demonstrate how the demountable and composite structures fit in the circular economy framework, and to show that such a demountable and reusable structure was successfully erected and demounted under laboratory conditions. In addition, a cost assessment will be addressed using a simple methodology based on estimated service life (ESL) factors to estimate the annual environmental costs of a composite floor system.

Behaviour and strength of bolted connections failing in shear

This paper investigates the behaviour and strength of structural steel bolted connections whose failure modes involve shear yielding and/or fracture. Such failure modes include the shear-out (or tearout) and the block shear failure modes. The use of shear failure planes corresponding to the bolt diameter is shown to result in significant overestimations of the ultimate capacities for bolted connections with reduced or no hole clearance. In contrast, the use of the effective (or active) shear planes are consistently accurate for the specimens with standard, oversize or no clearance bolt holes. The paper points out that the location of fracture initiation can be easily misidentified by a superficial inspection of the deformed and fractured state of the bolt hole. The paper also explains that the ultimate shear-out capacity of a steel bolted connection can be reached without fracture due to geometric changes downstream of the bolt, provided the reduction in resistance is not offset by strain hardening. The explanation is demonstrated through a finite element analysis that does not simulate fracture, but is able to accurately determine the ultimate shear-out capacity of a high-strength steel specimen tested by independent researchers.

Numerical Evaluation of Pin-Bearing Strength for the Design of Bolted Connections of Pultruded FRP Material

This paper presents finite-element predictions for the strength of a pultruded fiber-reinforced polymer (FRP) material subjected to pin-bearing loading with hole clearance. One of the distinct modes of failure in steel bolted connections is bearing. It is caused by the compression action from the shaft pressing into the laminate, and when there is no lateral restraint the mechanism observed at maximum load shows brooming for delamination failure. Each lamina in the glass fiber polyester matrix material is modeled as a homogeneous, anisotropic continuum and a relatively very thin resin layer is assumed to contain any delamination cracking between stacked layers. A cohesive zone model is implemented to predict the size and location of the initial delamination, as well as the load-carrying capacity in a pin-bearing specimen. Finite-element simulations (as virtual tests) are performed at the mesoscale level to validate the modeling methodology against experimental strength test results with delamination failure, and to show how pin-bearing strength varies with parameter changes. For an example of the knowledge to be gained for the design of bolted connections, the parameteric study in which the mat reinforcement is either continuous strand or triaxial (+45°/90°/−45°/chopped+45°/90°/−45°/chopped strand) shows the latter does not provide an increase in pin-bearing strength.

An improved spring method for calculating the load distribution in multi-bolt composite joints

Abstract Fast and reliable prediction of the load distribution is necessary in the initial design of the composite bolted joint structures. Traditional spring method is time consuming in the modelling of a composite bolted joint structure. In this paper, an improved spring method considering the hole clearance and friction effects is developed for efficient modelling of the composite bolted joint structures. This method is based on spring method and finite element theory. A seven-bolt double-lap joint model is built as an example to study the effects of plate width, plate thickness, bolt pitch and clearances on the load distribution. The improved spring method is also adopted in the Monte Caro simulation with clearances considered as uncertain-but-bounded parameters. The results show that the proposed method is time efficient for the load distribution prediction of the bolted joint composite structures.

Influence of cage clearance on the heating characteristics of high-speed ball bearings

This paper presents a five degree-of-freedom (5-DOF) quasi-dynamic model to analyse the relationship between the cage clearance and heating characteristics. First, a mathematical model is constructed for analysing the various heating rates associated with different working conditions, the elasto-hydro-dynamics of the cage is considered. Then, numerical studies are used to validate the precision and efficiency of this method. Second, an experimental system is developed to evaluate the theoretical method. Finally, the various of heating characteristics associated with the guide and pocket hole clearances, are analysed quantitatively. The results show that there is a critical value for both the guide and pocket hole clearance and that the heating is obviously decreased and gradually stabilizes when the clearance exceeds this value.

Improving the performance of bolted joints in composite structures using metal inserts

As the use of fibre reinforced polymer materials in bridge construction is becoming more popular, appropriate joining techniques, particularly for field joints, are necessary. Bolted joints are a common method for joining fibre reinforced polymer structures. The main advantage of bolted joints is their detachability, but they have a number of shortcomings. On the one hand, hole clearances, which are needed to facilitate on-site assembly, reduce the stiffness and joint efficiency. On the other hand, it is not possible to rely on the beneficial effects of bolt pre-defined tension loads, i.e. load transfer in friction, due to the considerable losses of bolt tension caused by the creep deformation in the composite material. To tackle these problems, a solution utilising metallic inserts in the hole is proposed in this paper. A series of experimental tests have been conducted to investigate the effect of inserts on the bolt-tension relaxation, the stiffness and the load-bearing behaviour of joints. Finite element analyses were also employed. The study demonstrates several benefits of the inserts: the bolt tension relaxation is minimised, the load transfer by friction may be feasible to be utilised in the bridge service state and the joint efficiency is increased in terms of stiffness and strength.