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This paper aims to determine the rational operating regime of a rotary percussive drilling machine under optimal conditions.

An orthogonal array of Taguchi, signal-to-noise (S/N) ratio, ANOVA Pareto analysis and regression analysis are used to investigate the effect of drilling operational factors on the penetration rate. A series of experiments based on orthogonal arrays L₂₇ was carried out, and the results were collected and analyzed using the statistical software Minitab.

The statistical analysis (ANOVA Pareto) of the results showed that among all setting parameters, air pressure is the most essential element that affects the penetration rate. The rational operating regime of the rotary percussive drilling machine was determined with optimum air pressure values of 17 bar (Level 3), rotation speed of 60 rpm (Level 3) and a thrust of 825 kgf (Level 2), which maximize the penetration rate. A quadratic regression model was developed for the penetration rate. The predicted values are compared with the experimental data and are considered to be in good agreement.

The study uses the orthogonal array of Taguchi, S/N ratio, ANOVA Pareto analysis and regression analysis to investigate the effect of drilling operational factors on the penetration rate.

The drill string vibrations can create harmful effects on drilling performance because they generate the stick-slip phenomenon which reduces the quality of drilling and decreases the penetration rate and may affect the robustness of the designed controller. For this reason, it is necessary to carefully test the different rock-bit contact models and analyze their influences on system stability in order to mitigate the vibrations. The purpose of this paper is to investigate the effects of rock-bit interaction on high-frequency stick-slip vibration severity in rotary drilling systems.

The main objective of this study is an overview of the influence of the rock-bit interaction models on the bit dynamics. A total of three models have been considered, and the drilling parameters have been varied in order to study the reliability of the models. Moreover, a comparison between these models has allowed the determination of the most reliable function for stick-slip phenomenon.

The torsional model with three degrees of freedom has been considered in order to highlight the effectiveness of the comparative study. Based on the obtained results, it has been concluded that the rock-bit interaction model has big influences on the response of the rotary drilling system. Therefore, it is recommended to consider the results of this study in order to design and implement a robust control system to mitigate harmful vibrations; the practical implementation of this model can be advantageous in designing a smart rotary drilling system.

Many rock-bit functions have been proposed in the literature, but no study has been dedicated to compare them; this is the main contribution of this study. Moreover, a case study of harmonic torsional vibrations analysis has been carried out in well-A, which is located in an Algerian hydrocarbons field, the indices of vibrations detection are given with their preventions.

Introduction The concept of a firm foundation to any stable structure, be it political, financial or physical, is one of the most commonly accepted metaphors in use today. Since every building has to be supported by the ground and to interact with it in a manner which is acceptable to the user, it is surprising that often so little attention is paid to the determination of the ground's characteristics.

The Control of Vibration at Work Regulations (CVWR), quantify workplace vibration exposure using exposure action, and exposure limit values (EAV and ELV respectively). Hand‐arm vibration (HAV) risk can be objectively assessed using hand‐tool vibration magnitude data, for comparison to the EAV and ELV. When considering risk controls, one disadvantage of this ‘focus’ on vibration magnitude, is that it might deflect appreciation of the economic implications of such controls, resulting from for example: restrictions on tool usage time; the need for operator rotas where continuous tool use is required; and complications in estimating labour costs because of these types of condition. Based on a sample of hand‐tools’ performance data, this research developed ‘hybrid’ (performance/vibration) dimensions for quantifying tools’ efficacy; representing (interalia) units of work achievable to reach the EAV and ELV. These hybrid dimensions characterize an alternative performance‐based (and therefore financially related) way of considering a tool’s ‘suitability’ within CVWR parameters; over and above the (selection) criterion of tool vibration magnitude. Analyses are then presented that investigate the time and cost ramifications of using multiple operators, to sustain continuous tool usage while keeping exposure levels within CVWR limits.

Reliability plays an important role in the execution of the maintenance improvement and the understanding of its concepts is essential to predict the type of maintenance according to the equipment state. Thereby, a computational tool was developed and programming with VBA in Excel® for reliability and failure analysis in a mining context. The paper aims to discuss these issues.

The developed approach use the modeling of stochastic processes, such as the renewal process, the non-homogeneous Poisson process and less conventional method as the Bayesian approach, by considering Jeffreys non-informative prior. The resolution gives the best associated model, the parameters estimation, the mean time between failure and the reliability estimate. This approach is validated with the reliability analysis of inter-failure times from underground rock bolters subsystems, over a two-year period.

Results show that Weibull and lognormal probability distribution fit to the most subsystems inter-failure times. The study revealed that the bolting head, the rock drill, the screen handler, the electric/electronic system, the hydraulic system, the drilling feeder and the structural consume the most repair frequency. The hydraulic and electric/electronic subsystems represent the lowest reliability after 50 operation hours.

For the first time, this case study defines practical failures and reliability information for rock bolter subsystems based on real operation data. This paper is useful to the comparative evaluation of rock bolter by detecting the weakest elements and understanding failure patterns in the individual observation subsystems on the overall machine performance.

The Control of Vibration at Work Regulations (CVWR) became law in 2005. They are of particular relevance to construction – which by nature of its activities – presents abundant whole‐body, and hand‐arm, vibration hazards. The principal aim of this research was to assess perceptions among a sample of UK construction professionals; regarding workplace vibration hazards generally and the CVWR specifically.

A structured questionnaire survey was carried out among a small but carefully targeted sample of professionals drawn from construction. These included health and safety managers, production managers and designers. A total of 88 useable responses were received. Data were analysed principally using the mean index technique.

Generally, a realistic view of hazards was observed; although some significant misperceptions were noted. Self‐confessed levels of knowledge regarding the subject were typically “low”. This appeared something of a paradox, in that “training workers” was cited as the most commonly used risk control method for both whole‐body, and hand‐arm vibration risks, respectively.

Disparity was observed between what respondents knew about the subject and the purported (extensive) use of training as a risk control method. This indicates that a degree of introspection may be beneficial on the part of employers, regarding their training design and delivery mechanisms. Differences in perceived degrees of vibration risk, exist between health and safety professionals and construction managers; implying that there is a need for improved communication between those responsible for planning vibration management controls, and those charged with implementing them at the workplace.

The paper presents research that assess perceptions among a sample of UK construction professionals; regarding workplace vibration hazards generally and the CVWR specifically.

A series of articles dealing, in as simple a way as possible, with the basic facts of lubrication, lubricants, their selection and prescription, specification, application, and testing. This series is primarily intended for students, engineering personnel who may be unfamiliar with certain aspects and others who, one way or another, are interested in this important subject.

Reports on the exhibits and exhibitors at Manufacturing Week, which took place at the NEC, 10‐12 November 1998. It reveals that machine vision is the major attraction at the show with over a quarter of the exhibitors exhibiting activity in this area. A number of the companies who offer turnkey systems are highlighted; some include vision as an element in their systems while others are totally dedicated to application of the technology. The emphasis in the article is on applications with the predominance being for inspection. Brief case studies are given of inspecting automotive switches, a contact lens line, robot grinding of propellers and a seat belt retractor assembly system. Some new products are also described including a “control free” junction for Bosch twin belt pallet conveyors and compact fast camera with integral image acquisition and processing electronics.

This paper aims to present a technique that has been developed to study the wear in the camshaft and tappet. The engine manufacturers use the most suitable materials, lubrication additives and surface coatings to minimize friction in all the components of the engine. Reduced friction results in less wear of critical engine components. The researchers are constantly trying to find an improved lubrication formula which reduces the wear and friction coefficient at a considerably low price. In this regard, the cam follower interface is of much importance because most of the wear occurs in this interface.

The tappets and the cam lobes are analyzed to determine wear. A two-dimensional optical surface profilometer is used to measure the tappet wear, and a high-resolution linear variable differential transformer is used for the measurement of cam lobes. Tests are conducted on Mercedes Benz engine OM 646 under constant camshaft speed, constant inlet lubricant temperature and constant lubricant pressure to study the oil rheology on cam tappet wear.

The results show that the wear occurs on the cam tappet interface, which is almost a linear phenomenon, and it increases with use.

Customized jigs were made to measure wear of camshaft and tappet.

The purpose of this paper is to show how the time frame for the execution of a construction project in Algeria is rarely respected because of organizational problems and uncertainties encountered while the execution is underway.

A case study on the construction of a metro station is used as a pilot project to show the effectiveness of replacing traditional construction processes by more innovative procedures. Concurrent engineering (CE) is applied to optimize the execution time of the underground structure. A numerical simulation is integrated into the construction process in order to update design parameters with real site conditions observed during the construction process.

The results show that the implementation of CE is efficient in reducing the completion time, with an 18 per cent reduction observed in this case study. A cost reduction of 20 per cent on the steel frame support and a total cost reduction of 3 per cent were obtained.

The study demonstrates that the application of CE methods can be quite valuable in large, complex construction projects. Vulgarizing it as “the solution” to adjust time frame delay, control quality and cost, might be an issue for local construction enterprises in Algeria.

Using the concept of CE by overlapping different activities involved in a construction project and making use of simulation tools in the process at different stages of the execution have resulted in modifying the excavation method and hence reducing the completion times.