Drill Diameter Research Articles

Temperature Changes during Implant Osteotomy Preparations in Fresh Human Cadaver Tibiae, Comparing Straight with Tapered Drills.

The success of osseointegration depends on many factors. With temperatures beyond a 47 °C threshold over 1 min, bone survival may be impaired. The purpose of the study was to evaluate, in fresh human cadaver tibiae, the temperature changes during osteotomy preparations using two straight and two tapered implant systems’ drills, external irrigation, and varying revolutions per minute (RPM). The tibiae from a fresh female cadaver were harvested bilaterally. Two tapered and two straight design drills were assessed. Two-hundred and forty osteotomies were prepared at 6 mm depth following the drill sequence of the manufacturers’ protocol for each drilling speed. Difference in temperature (ΔΤ) was calculated by subtracting the baseline from the maximum temperature (ΔT = Tmax − Tbase). Drill design and drill diameter, as independent variables or synergistically, had a significant effect on ΔΤ. Tapered drills: As the drill diameter increased, ΔΤ increased at all RPM. Straight drills: As the drill diameter increased, ΔΤ remained constant or slightly decreased at all RPM. Drill diameter and design had a significant effect on ΔΤ in human tibiae, which never exceeded the critical threshold of 47 °C. Tapered drills caused significantly greater heat production compared to straight drills.

A transfer learning-based digital twin for detecting localised torsional friction in deviated wells

Digital twins seek to replicate a physical structure in a digital domain. For a digital twin to have close correspondence to its physical twin, data are required. However, it is not always possible, or cost-effective, to collect a complete set of data for a structure in all configurations of interest. It is nonetheless useful to repurpose data to help validate predictions for different configurations and scenarios. This statement is true in drilling applications, where, for example, the length of the drill string is altered throughout operation. This paper demonstrates how transfer learning, in the form of three domain-adaptation methods, — transfer component analysis (TCA), maximum independence domain adaptation (MIDA) and geodesic flow kernel (GFK) — can be used to construct a digital twin for localising torsional friction in deviated wells under structural changes (e.g., when the drill column gets longer). The method uses a physics-based torsional model to train a machine-learning classifier that can localise torsional friction for a given drill string length and diameter, where friction localisation labels are known (source). As the length or diameter of the drill string are altered in the field, transfer learning is utilised to map the classifier from the labelled (source) scenario onto these unlabelled (target) scenarios. As a result, transfer learning improves the performance of the classifier when applied to the target data, and increases the domain of validity for the classifier. The performance of the classifier, and therefore its suitability to new drill-string configurations, is estimated by utilising two different distance metrics between the source and a proposed target dataset.

A Coal Bump Risk Assessment and Prediction Model Based on Multiparameter Indices

Coal bump, a common dynamic disaster in mining of deep coal resources, its assessing and predicting is an important component in safety management. This paper presents a model to assess and predict coal bump risk based on multiparameter indices. A new energy accumulation index S was proposed by considering acoustic emission and electromagnetic emission signal characteristics in mine shocks. Combined with indices E (energy of microseisms) and N (frequency of microseisms) of microseismic monitoring, a static and dynamic coal bump risk assessment and prediction model was established. We studied coal bump events that occurred during extraction in 311305 working face of Bayangale coal mine in Inner Mongolia, China. We obtained the acoustic emission and electromagnetic emission signal distribution and change law, using principal component analysis method and density ellipse to establish the index S . A typical precursory of coal bumps is that AE and EME strength has obvious fluctuation period of 3-4 days, index S showing an obvious decreasing trend, while the time-series curve of the microseismic energy is relatively stable, and the vibration frequency curve has a significant upward trend. After predict the potential coal bump risk and its area of occurrence, large diameter drilling (Φ150 mm) on-site was used to relief pressure concertation in coal seam and roof. The results demonstrate that this model based on multiparameter indices is capable of quantitatively prewarning rock burst risk.

Comparison of self-tapping and self-drilling screws in open reduction of mandible fracture

Objective: The purpose of this study is to assess the early postoperative stability of screw systems with mini plates in the treatment of open reduction mandibular angulus fractures. 
 Material and Method: This study consisted of 3 groups of mini plate or screw fixation: a 1.6 mm diameter drill for Group 1, a 1.2 mm diameter drill for Group 2, and self-drilling screws without drilling in Group 3. We used 9 hemimandibles, 9 plates, and 36 screws in each group. We compared the self-tapping and self-drilling screw systems while maintaining the plate system constant. We generated angulus fractures in 27 hemimandibles taken from 14 sheep mandibles. We separated the samples into 3 groups, each with 9 hemimandibles. All the screws used in the study were 2 mm in diameter and 5 mm in length. We used the servo hydraulic test unit to apply force to the hemimandibles. We applied forces of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, and 150 N to the hemimandibles and recorded the resulting displacements. Data were analyzed with IBM SPSS V23, and conformity to normal distribution was evaluated by the Shapiro-Wilk test.
 Results: There was no difference between the groups in terms of the amount of displacement that occurred as a result of the applied forces. 
 Conclusion: In the treatment of mandibular fractures with open reduction, surgeons should focus on plate-related parameters rather than self-drilling and self-tapping of screws, or drill diameter.

Biomechanical analysis of the drilling parameters for early osteonecrosis of the femoral head

Background and objectiveCore decompression is a surgical procedure commonly used to treat the early osteonecrosis of the femoral head. However, It is not known whether different drilling parameters affect postoperative biomechanical strength. This study aimed to analyze the mechanical stability of different drilling locations and diameters of core decompression using finite element analysis. MethodsFinite element models were established based on computed tomography images obtained from five healthy participants, including the different drilling locations (Lesser trochanter: Above, Parallel, and Below) and diameters. Biomechanical parameters including stiffness and stress were evaluated under slow running loads. ResultsAt the same drilling diameter, the femoral stiffness was highest (p < 0.05) in the Above group and lowest in the Below group, while the maximum equivalent stress of the entry area and the necrotic area was highest (p < 0.05) in the Below group and lowest in the Above group. With the increase of drilling diameters, the stiffness decreased and its decreased percentage comparing the preoperative: Above (1.06–8.82%), Parallel (2.51–13.61%), and Below (3.99–15.06%). The maximum equivalent stress of the entry area and necrotic area increased as the drilling diameter increased, and its increased percentage comparing the preoperative, for the entry area: Above (14.11–219.58%), Parallel (35.91–306.37%), and Below (46.12–240.98%); for the necrotic area: Above (13.64–114.69%), Parallel (29.37–187.76%), and Below (44.76–202.10%). The range of safety drilling parameters (SDP) was obtained (Below<9 mm, Parallel<11 mm, and Above<13 mm) by comparing the maximum equivalent stress of two areas and its yield strength. For patients of different sizes and normal bone mineral density (BMD), the maximum equivalent stress of the two areas did not exceed its yield strength using the range of SDP, except for the patients with abnormal BMD (Osteoporosis) or high body mass index (BMI≥28 kg/m2). ConclusionsThe biomechanical properties of early osteonecrosis of the femoral head deceased with increasing drilling diameters parameters, especially at the location below the lesser trochanter. The SDP (Below<9 mm, Parallel<11 mm, and Above<13 mm) is a suitable reference for most patients to perform slow running postoperatively, while it may be not suitable for patients with osteoporosis or obesity.

Optimization of machining parameters in drilling hybrid sisal-cotton fiber reinforced polyester composites

&lt;abstract&gt; &lt;p&gt;Machining natural fiber reinforced polymer composite materials is one of most challenging tasks due to the material's anisotropic property, non-homogeneous structure and abrasive nature of fibers. Commonly, conventional machining of composites leads to delamination, inter-laminar cracks, fiber pull out, poor surface finish and wear of cutting tool. However, these challenges can be significantly reduced by using proper machining conditions. Thus, this research aims at optimizing machining parameters in drilling hybrid sisal-cotton fibers reinforced polyester composite for better machining performance characteristics namely better hole roundness accuracy and surface finish using Taguchi method. The effect of machining parameters including spindle speed, feed rate and drill diameter on drill hole accuracy (roundness error) and surface-roughness of the hybrid composite are evaluated. Series of experiments based on Taguchi's L&lt;sub&gt;16&lt;/sub&gt; orthogonal array were performed using different ranges of machining parameters namely spindle speed (600,900, 1200, 1600 rpm), feed rate (10, 15, 20, 25 mm/min) and drill diameter (6, 7, 8, 10 mm). Hole roundness error and surface-roughness are determined using ABC digital caliper and Zeta 20 profilometer, respectively. Optimum machining condition for drilling hybrid composite material (speed: 1600 rpm, feed rate: 25 mm/min and drill diameter: 6 mm) is determined, and the results are verified by conducting confirmation test which proves that the results are reliable.&lt;/p&gt; &lt;/abstract&gt;

Optimization of process parameter in drilling of snake grass fiber reinforced composites

Natural fiber composites are at present more appropriate replacement for synthetic fibers such as carbon, glass and Kevlar fibers in several applications. In the current investigation an attempt is made to fabricate and examine the thrust force and surface roughness of Snake Grass Fibers reinforced composite. Composites were manufactured with Snake Grass Fiber as reinforcement along with epoxy resin as matrix using hand lay-up method. With the sample natural fiber reinforced composites drilling test has been conducted to learn the factor effect on the Thrust force of drilled unidirectional Snake Grass Fibers reinforced composites (SGFRC). L9-Taguchi method was used to perform the drilling experiments. Thrust force estimated with different factors like spindle speed, feed and drill diameter considered for this investigation with the help of smaller the better concept of Taguchi method as objective function. Further regression equation utilized to find Thrust force that with best possible combination with better result compared to experimental values. From the results, it was found that optimum value of thrust force was obtained at 1800 rpm spindle speed, 10 mm/min of feed and 4 mm drill diameter.

E‐Modeling and Evolution of Nanolubricant Coupled Machining Parameters Using Statistical Tool

Optimization is an essential action to select the effective input parameters for the responses obtained from machining. In this work, the combination of six sigma techniques and grey relational optimization are used for the corresponding input parameters, namely, spindle speed, feed rate, and drill diameter. The responses recorded are torque, thrust force, surface roughness, temperature, and ovality. Smaller the better response is preferred for all the output responses. Taguchi design of L27 array is preferred, and based on 27 combinations of input parameters, output responses are recorded. The thrust force and torque values are obtained in the graphical form during drilling process by the vertical machining center. After the drilling process the surface roughness of the hole is measured using profilometer. The probe in the profilometer is moved along the surface of the hole and the corresponding surface roughness values are noted for twenty‐seven holes. The roundness of the hole is measured using a profile projector. The roundness of the hole is expanding due to the heat generated during the machining process. The expanded diameter of the hole is measured along the vertical and horizontal axes using the projector. Six sigma techniques are used to analyze the input parameters such as spindle speed, feed rate, and drill diameter. The optimization technique is used to determine the optimized parameters.

Prediction of Burr Types in Drilling of Al-7075 Using Acoustic Emission and Convolution Neural Networks

The formation of exit burrs during the drilling of ductile metals such as aluminum is critical in precision manufacturing and manufacturing automation. Because drilling burrs are difficult to remove, methods to predict various burr types and/or implement burr minimization schemes that consider the various attributes of burrs must be devised. In this study, not only drilling process conditions, including feed, cutting speed, and drill diameter, but also an artificial neural network is implemented to predict the formation of burrs during the drilling of aluminum-7075, which is widely used in the aerospace and automobile industries. Based on the drilling conditions, the main exit burr characteristics, such as burr size and type, were classified experimentally. Three different types of exit burrs (uniform burrs, uniform burrs with caps, and transient burrs) were observed from the aluminum 7075 workpieces. The classification results were further analyzed using burr control charts and an empirical equation, which enables the understanding of the overall influence of the drilling conditions over the burr types. Moreover, acoustic emission (AE) sensor monitoring scheme was utilized to sample the sensitive time-series signals during drilling burr formation. Subsequently, burr types were predicted using artificial intelligence techniques, namely machining learning and deep learning. First, backpropagation (BP) neural networks were constructed using the drilling conditions and AE signals as input vectors. For a comparative prediction, a convolution neural network (CNN) was implemented to obtain spectrogram image inputs from the sampled AE data. The proposed scheme is useful in predicting drilling burr types by employing a sensitive sensor monitoring setup and advanced artificial intelligence techniques, where both prediction results are well matched with experimental results. In addition, the CNN model shows effectiveness for a commonly practiced manufacturing process as it predicts the burr types with better accuracy than the BP network model (0.9375 over 0.8571).

Thermal Effect of Operatory Room Temperature, Surgical Drill Diameter, and Temperature of Irrigants at Different Depths of Implant Site Preparation - Thermographic Analysis on Goat Mandible.

Background:Drilling of the implant site results in transient rise in temperature of the surrounding bone disrupting the bone healing process and implant stability. Overproduction of heat due to various factors at osteotomy site needs to be controlled as it hampers the final outcome of the procedure.Purpose:The purpose of this study was to evaluate various factors related to implant drills responsible for heat generation and temperature rise during osteotomy.Materials and Methods:A total of 64 bone specimens with dimensions of 15 mm × 15 mm were obtained from goat mandibles and were equally divided into Groups A and B with operating room temperature maintained at 25°C and 30°C, respectively. Osteotomies were performed using drills with diameters (4.2 mm and 5.6 mm) at various drilling depths (10 mm and 13 mm) with external saline irrigation temperatures (4°C and 25°C). Temperature change was recorded by laser thermometer.Results:The surgical drill depths, diameters, and room temperatures made no differences in temperatures at implant drilling sites whereas the temperatures of the irrigants provide sufficient heat control during drilling.Conclusion:Cooled saline provides beneficial effects in controlling the temperatures of osteotomy sites as compared to saline used at room temperature during implant site preparation.

Effect of Various Microstructures Obtained from Heat Treatment on Machinability Behavior of Ti-6Al-4V Alloy

Drilling test on cylindrical work-pieces was carried out to analysis effect of various microstructures resulting from heat treatment on the machinability of the Ti-6Al-4V alloy. Chip morphology plays a predominant role in determining machinability and wearing of a tool during the drilling of titanium alloys. For this purpose, Ti-6Al-4V was heat treated in three variant cycles then drilled by 2mm diameter drill at 18.8 m/s speed and 0.1 mm/rev feed rate. Results show that heat treatment can effect on hardness. The SEM results showed that by changing their phase and morphology obtained from diferent heat treatment cycle, the machining conditions change. Increasing hardness led to increases length of spiral chips that indicate easy drilling. At a lower depth of cutting, ribbon chips are more compacted in comparison with samples which have a lower hardness. Drilling temperature was increased by increasing deep hole. Samples with lower hardness had a higher temperature in drilling.

Dimension-based failure analysis of formed internal threads in AlSi10Mg cast profiles using coupled DT/NDT testing methods

The production of detachable joints in lightweight components using friction drilling and internal thread forming processes could be considered as a lightweight design strategy, which can reduce material and time consumption and enhance the thread strength by imposing a further work-hardening into the subsurface of the formed threads. Pre-study indicated that oversizing the friction drilled bores as a pilot bore can hinder the complete deformation of the thread profiles during the thread forming process. This work investigates the effect of process parameters in the friction drilling process (friction drill speeds and diameter) on the quality of the drilled bores and following formed threads. Computed tomography was chosen to measure the dimension deviation of manufactured bores and threads. Comparing the deviation with the measured static and dynamic strengths declared that increasing the tool diameter by 0.1 mm increased the inner volume of the friction drilled bore, which led to an incomplete deformation of the thread profiles and decreased static and cyclic strength accordingly. Although the friction drilling with an adaptive speed reduced the oversizing of the created bore in comparison to the friction drilled bores with a constant speed, measuring the volume of the formed threads into mentioned bores indicated an opposite trend. While the formed M6-threads into the friction drilled bores with constant speed showed a better strength by subjecting to a quasi-static load, manufactured threads with an adaptive speed indicated a higher dynamic strength. The fatigue tests were monitored through NDT methods by measuring the change in deformation-induced temperature and ACPD potential. The measured results were correlated to plastic strain up to failure corresponding to occurring softening, hardening, or possible crack initiation and propagation in thread profiles.

OPTIMIZATION USING RESPONSE SURFACE METHODOLOGY AND ARTIFICIAL NEURAL NETWORK IN GEARED DRILLING

Drill on different layered composite causes to force the layers ahead of it, creating unacceptable delamination on the leaving side. The current work describes the influence of different process parameters like spindle speed, feed, diameter of drill bit and addition of filler material on delamination damage on carbon and jute hybrid fiber composites during drilling operation. The experimental output for delamination is optimized by RSM-Response Surface Methodology and ANN-Artificial Neural Network Model. The experimental prediction model was established by considering DOE (design of experiments) of three levels performed with drilling operation by varying above said process parameters The optimum values for minimized delamination damage conditions found to be at (J-C-C-J) +5g of filler (fly-ash) composite. This is drilled with 8.5mm diameter drill bit with a feed of 0.08mm/rev at 875rpm speed. From the theoretical results it is recognized that cutting-speed and filler-material have much influencing factors on responses (delamination), and their individual contribution in an order of 47.25% and 47.32% respectively. By using Box-Behnken design RSM model is developed, with a feed-forward back-propagation method to develop the predictive ANN model which consists of 15 neurons in its hidden layer along with ANN Model. Here ANN Results (R2=0.99and RMSE=1.99) showed that the developed model is performing better to predict content of delamination when compare to RSM results (R2=0.97and RMSE=2.24).

Optimization study of blasting operations in Roşia Poieni open pit mine, Romania

Purpose. Drilling-blasting technology is one of the simplest and most often used techniques in open pit mining. This allows the excavation of a large volume of rock and useful mineral substance. The operation of blasting using the energy of explosives plays an important role in open pit exploitation, being also the key element of the blasting process through which a corresponding granulometry is obtained. This operation is a part of a series of interdependent operations, in the sense that each operation determines a certain result that will be an important element for the next operation that takes place in the working face. Consequently, the blasting operation with explosives should not be considered as an independent act. A global approach to the entire production technological process including blasting is required. Methods. In the optimization study, the basic method consisted in the analysis of the blasting operations performed at the drilling diameter of 250 mm (blasting technology used in Roşia Poieni open pit mining) and simulation of the excavation of the same rock volume, with the optimization of the explosive charge distribution at two other drilling diameters: 200 and 150 mm. Findings. The main problems when shooting 250 mm dia holes are caused by the length of the tamping in the mineralized rock that leads to the appearance of blocks with dimensions which are maximum allowed in the crusher tank (1.2-1.3 m). That is why discontinuous loads with intermediate tamping are used – the method that successfully limits their number. In order to obtain a granulometry corresponding to the primary crushing operation, which will allow to decrease the crushing costs, it is necessary to use smaller drilling diameters, but with productivity high enough to ensure the optimal development of the extraction process. Originality. Based on the performed study, it is recommended to use the discontinuous load, preserving the total length of the explosive charge. In the zones where the rocks have a Protodiakonov coefficient f &gt; 6.5, it is recommended to apply an appropriate drilling diameter (150-200 mm) and use the intermediate tamping at 2-3 m length to limit the upper stemming area to a maximum of 7 m (to limit or eliminate the occurrence of oversized blocks). Practical implications. The research results will enhance the geometric and safety factors of the operation, limiting the explosion effect on the massif and the environment and reducing the total costs of the cutting operation. The cost of explosives and initiating materials can be reduced by using a smaller quantity of explosive gels in a dry environment (12-18 kg/hole), the difference in the explosive charge length being completed with AM 1.

Image-Based Planning of Minimally Traumatic Inner Ear Access for Robotic Cochlear Implantation.

Objective: During robotic cochlear implantation, an image-guided robotic system provides keyhole access to the scala tympani of the cochlea to allow insertion of the cochlear implant array. To standardize minimally traumatic robotic access to the cochlea, additional hard and soft constraints for inner ear access were proposed during trajectory planning. This extension of the planning strategy aims to provide a trajectory that preserves the anatomical and functional integrity of critical intra-cochlear structures during robotic execution and allows implantation with minimal insertion angles and risk of scala deviation.Methods: The OpenEar dataset consists of a library with eight three-dimensional models of the human temporal bone based on computed tomography and micro-slicing. Soft constraints for inner ear access planning were introduced that aim to minimize the angle of cochlear approach, minimize the risk of scala deviation and maximize the distance to critical intra-cochlear structures such as the osseous spiral lamina. For all cases, a solution space of Pareto-optimal trajectories to the round window was generated. The trajectories satisfy the hard constraints, specifically the anatomical safety margins, and optimize the aforementioned soft constraints. With user-defined priorities, a trajectory was parameterized and analyzed in a virtual surgical procedure.Results: In seven out of eight cases, a solution space was found with the trajectories safely passing through the facial recess. The solution space was Pareto-optimal with respect to the soft constraints of the inner ear access. In one case, the facial recess was too narrow to plan a trajectory that would pass the nerves at a sufficient distance with the intended drill diameter. With the soft constraints introduced, the optimal target region was determined to be in the antero-inferior region of the round window membrane.Conclusion: A trend could be identified that a position between the antero-inferior border and the center of the round window membrane appears to be a favorable target position for cochlear tunnel-based access through the facial recess. The planning concept presented and the results obtained therewith have implications for planning strategies for robotic surgical procedures to the inner ear that aim for minimally traumatic cochlear access and electrode array implantation.

Experimental investigations on the drilling parameters to minimize delamination and taperness of hybrid GFRP/Al2O3 composites by using ANOVA approach

PurposeDrilling holes in composite materials is a complex and challenging process because of their intrinsic anisotropic characteristics and unevenness compared to conventional metals. Hybridization of composites enhances the strength and hardness of the material but makes it more difficult to drill a hole in it. The purpose of this study is to optimize the drilling to minimize the delamination and taperness of hybrid glass fiber reinforced plastic (GFRP)/Al2O3 composites.Design/methodology/approachThe present study investigates the impact of drilling parameters on delamination of the drilled hole and the taperness of the hole on hybrid GFRP/Al2O3. Optimum drilling conditions for minimizing delamination and taperness of the hole are determined to enhance the hole quality. Feed (f), speed (N) and drill diameter (D) are the parameters taken into consideration for drilling operation. By applying Taguchi’s signal-to-noise ratio analysis, process parameters have been optimized to reduce the delamination and taperness of holes on Hybrid GFRP/Al2O3 composites. The effect of process parameters was analyzed using the analysis of variance method.FindingsThe investigational results confirmed that the delamination is positively affected by speed, drill diameter and feed rate. Also, the taperness of the hole is positively affected by the drill diameter. Regression-based models were developed to predict the delamination and taperness of the hole matched with the experimental results, which are attained with an order of 95% and 97%.Originality/valueMinimum delamination was found at the optimum condition of drill diameter 10 mm, feed at 0.225 mm/rev and the speed at 151 rpm and minimum taperness were found at the optimum condition of drill diameter 10 mm, feed at level 0.3 mm/rev and speed at 86 rpm for hybrid laminate composite (S-glass+ GFRP/Al2O3) were evaluated.

Sensitivity Analysis of GFRP Composite Drilling Parameters and Genetic Algorithm-Based Optimisation

In this article, a genetic algorithm (GA) is used for optimizing a metamodel of surface roughness (R_a ) in drilling glass-fibre reinforced plastic (GFRP) composites. A response surface methodology (RSM) based three levels (-1, 0, 1) design of experiments is used for developing the metamodel. Analysis of variance (ANOVA) is undertaken to determine the importance of each process parameter in the developed metamodel. Subsequently, after detailed metamodel adequacy checks, the insignificant terms are dropped to make the established metamodel more rigorous and make accurate predictions. A sensitivity analysis of the independent variables on the output response helps in determining the most influential parameters. It is observed that f is the most crucial parameter, followed by the t and D. The optimization results depict that the R_a increases as the f increases and a minor value of drill diameter is the most appropriate to attain minimum surface roughness. Finally, a robustness test of the predicted GA solution is carried out.

Mining-Induced Seismicity during Development Works in Coalbeds in the Context of Forecasts of Geomechanical Conditions

Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.

Experimental investigation on the machinability characteristics in drilling of syntactic foams

Syntactic foams (SFs) finds its application in automobiles, aircrafts and underwater vehicles. Drilling is most frequently used machining operation for assembly of these composite structures. In the present investigation, an effort is made to analyse the effect of cutting speed (Cs ), feed rate (fr ), drill diameter (D) and filler content (F) on machinability characteristics in drilling glass microballoon (GMB) reinforced epoxy SFs. Machinability characteristics analyzed includes thrust force (Tf ) and surface roughness (Sr ). SFs are fabricated by dispersing 25, 35 and 45 vol.% of GMBs in epoxy resin. Experiments are carried out based on full factorial design (FFD) using TiAlN coated carbide drills. Experimental results show that Tf and Sr increases with increasing Cs . As fr increases, Tf increases but decreases the Sr . Increasing GMB content significantly reduces the Tf and Sr of developed SFs.

A Taguchi Approach in Investigating the Effects of Process Parameters in Drilling of Glass Fibre Reinforced Plastic Composite

Glass fibre reinforced plastic (GFRP) composite has found an important place in the industries replacing many metals and alloys. The joints formed are found to be the weakest portions of the assembled GFRP parts. Conventional drilling is the most widely adapted manufacturing process for an efficient assembly. Moreover, drilling of glass fibre reinforced plastics is difficult to carry out due to the anisotropic, non-homogeneous structure and high abrasiveness of the glass fibre and the complex geometry of the drill. For these reasons, the damage gets induced to the hole/workpiece and the cutting tool. In this study, Taguchi approach is employed to analyse the drilling process. An L25 orthogonal array, signal to noise S/N ratio and analysis of variance (ANOVA) are used to identify the effects of process input parameters on the output factors. The process input parameters are drill diameter, cutting speed and feed rate. The output factors/responses are the thrust force, torque, power, temperature, tool life, surface roughness, deviation from dimensional parameters of the holes, peel-up and push-out delaminations. In every set of experiment, an exhaustive work has been carried out till each drill bit reached its tool life. Optimal process parameters are available from the S/N ratio plots whereas ANOVA has identified the significant input factors and their percentage contribution on the responses.