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Uniaxial compressive strength (UCS) is the most used parameter to measure rock strength. However, restrictions in sampling large volume of material, the need of very large set of results and onsite characterisation of UCS non-destructively are requirements in many scientific and engineering investigations. The estimation of UCS from a single non-destructive or minimally invasive technique (NDT) may result incomplete because each NDT is sensitive to different compositional and textural factors. This paper combines open porosity, P-wave velocity, Leeb hardness and micro-drilling resistance force to estimate USC for a wide range of carbonate sedimentary rock types with different petrographic characteristics. Results reveal that mineralogical composition significatively affects micro-drilling resistance force profiles and P-wave velocity values, especially for quartz-bearing rocks. In addition, texture controls substantially the reproducibility of tests sensible to rock surface properties, such as Leeb hardness and micro-drilling resistance force. Fifteen simple and multiple expressions for UCS are fitted. Linear expressions have shown better coefficients of determination (R2) than non-linear equations because of the linearity shown by individual parameters. Curve fitting improves as the number of petrophysical parameters increase in the multiple linear regression analysis. The best correlation is found when the equation incorporates all the mechanical parameters obtained non-destructively as well as open porosity (R2 = 0.910). Leeb hardness is always the most significant variable of the fitted regressions and its addition into multiple linear equations causes an increase of R2. Open porosity also improves R2 whereas drilling force and P-wave velocity have a lower statistical weight in the expressions. The UCS estimation from all NDT, without considering open porosity, shows a good correlation (R2 = 0.899), which presents the advantage that they can be obtained non-destructively with portable equipment and can provide a numerous set of results at relatively low cost. This work was supported by the Spanish Government [grant number RTI2018-099052-B-I00] and Regional Government of Madrid (Spain) [Top Heritage, grant number S2018/NMT-4372].

WOS: 000535739800008 PubMed: 31736032 AIM: To evaluate the feasibility of an experimentally designed model for training on endoscopic intranasal transsphenoidal hypophysis surgery. MATERIAL and METHODS: In this experimental study, a surgical training model for endoscopic transsphenoidal hypophysis surgery was designed to simulate real life surgical challenges, such as drilling through the sella turcica under endoscopic vision. This laboratory experiment was repeated at 1-week intervals and it was observed that surgeons improved their skills. The compatibility of the training model was evaluated as either poor, acceptable or perfect. RESULTS: The results revealed that according to earlier data, greater success occurred in tests conducted after 1 week. Three new specialist neurosurgeons also expressed that their self-confidence increased during the second procedure. CONCLUSION: This laboratory study will result in improved use of microsurgical instruments and understanding of the three-dimensional surgical field, as well as the development of manual dexterity. We believe that this model will contribute to the practical training of endoscopic hypophysis surgery.

In-line Fabry&ndash, Perot cavities manufactured by a new technique using electric arc fusion of NIR laser microdrilled optical fiber flat tips were studied herein for refractive index sensing. Sensors were produced by creating an initial hole on the tip of a standard single-mode telecommunication optical fiber using a Q-switched Nd:YAG laser. Laser ablation and plasma formation processes created 5 to 10 micron cavities. Then, a standard splicing machine was used to fuse the microdrilled fiber with another one, thus creating cavities with lengths around 100 micrometers. This length has been proven to be necessary to obtain an interferometric signal with good fringe visibility when illuminating it in the C-band. Then, the sensing tip of the fiber, with the resulting air cavity, was submitted to several cleaves to enhance the signal and, therefore, its response as a sensor, with final lengths between tens of centimeters for the longest and hundreds of microns for the shortest. The experimental results were analyzed via two signal analysis techniques, fringe visibility and fast Fourier transform, for comparison purposes. In absolute values, the obtained sensitivities varied between 0.31 nm&minus, 1/RIU and about 8 nm&minus, 1/RIU using the latter method and between about 34 dB/RIU and 54 dB/RIU when analyzing the fringe visibility.

High density and high quality interconnects are necessary for the preparation of miniaturized and lightweight electronic products. Therefore, small-diameter and high-density through-holes in FPCs (Flexible Printed Circuits) are required. However, the current processing methods cannot further decrease the diameters and improve the quality of through-holes. Comparatively, ultrashort pulse laser is a good choice. In this paper, the processing technology for the microdrilling of through-holes in FPCs using a 10 ps pulse laser was systematically studied. The effects of laser parameters, including the wavelength, energy, pulses and polarization, on the drilling of through-holes were investigated. The various processing parameters were optimized and the plausible reasons were discussed. Finally, the desired small-diameter and high-density through-holes in FPCs were obtained. The experimental results showed that, through-holes with diameters of less than 10 µm and inlet interconnection pitches of 0 ~ 2 µm could be successfully drilled in FPCs using ultrashort pulse laser.

Background and Objective: Repetitive practicing of microneurosurgical techniques in experimental laboratory using real surgical instruments on training models is extremely important before starting the real surgical interventions. The modeling of the surgical steps with creating of suitable laboratory models is also another important issue in the successfully gaining of microneurosurgical practice. Materials and Methods: In this experimental study, it was created a laboratory training model for microneurosurgical drilling of cranial bones including the close location with the neural and vascular structures. All steps of this study were performed under the operating microscope. Twenty-five fresh chicken wings obtained from supermarket were used for this study. The difficulty and suitability of the model was evaluated in terms of the usability in the training of microneruosurgical microdrilling. Difficulty of the procedure was divided as three degree (very easy, easy, and difficult). The objective criterion for the evaluation of the difficulty of the procedure was the protection of the neurovascular and muscular structures during the procedure. Results: The suitability of the procedure was also evaluated within three groups as bad, good, and perfect. In four (16%) chicken wing's bone, the difficulty of the microdirilling was evaluated as difficult. Fifteen (60%) of the chicken wing's bones were microsurgically drilled with easy procedure. The remaining six (24%) of the wing's bone microdrilling was evaluated as very easy procedure. The suitability of the model was evaluated as bad in three (12%) of the chicken wing's bone. The suitability was found as good in 16 (64%) of the bones. In the remaining three (24%) of the chicken wing's bone microdrilling, the suitability of the model was evaluated as perfect. Conclusion: Microsurgical drilling of the chicken wing's bone without any vascular and muscular injury is accepted as the indication of the successfully surgical microdrilling process. Consolidation of the surgical practice in a laboratory setting, grasping and using of microsurgical instruments, can be repeated in several times in this model. We believe that this model will contribute to the practical training of microneurosurgery.

The combination of multiple physical, chemical and biological factors causes the weathering of limestone used in the field of cultural heritage. To overcome the limitations of traditional consolidating products and to meet the requirements of the historical building substrates, during the European collaborative project NANOMATCH, alkaline earth alkoxides were developed and studied as consolidating agents for limestone. Among these new products, calcium ethoxide, with the formula Ca(OEt)2, was chosen for this study and investigated in depth as an alternative consolidating treatment. It was first characterized through a study of the carbonation process: its kinetics, reaction pathway and the evaluation of formed mineralogical phases. Subsequently, it was applied on limestones with different total open porosity to test its performance as a consolidating agent. The compatibility and the efficiency of the treatment were investigated with a multi-technique approach and compared with results obtained with a reference product, based on nanolime. This study indicates that calcium ethoxide shows better results with respect to the reference product, both in terms of compatibility and consolidation effect.

Pulsed fiber lasers are innovative laser sources which promise to be suitable tools for micromachining operations due to their high beam quality, strong focusability, and high productivity. In this work, percussion laser microdrilling on 0.5-mm-thick commercially pure titanium sheets making use of a nanosecond pulsed fiber laser is investigated. The work is aimed at studying the effects of the main process parameters (pulse energy and pulse frequency) on the quality features of the machined through holes, i.e., diameters, taper, circularity, and area of top spatter. Adequate regressive models are developed to define the functional relationship between the hole quality and the main process parameters. The effects of laser microdrilling on material microstructure of the regions in close proximity to the machined holes are also investigated by means of nanohardness measurements and microstructural analyses.

Microholes for the production of high precision devices were obtained by ultrashort pulsed laser machining of martensitic stainless steels. A micro-drilling cycle based on the sequence of a drilling through phase, an enlargement and finishing phase is proposed in order to solve the trade-off between process time and quality of the ablated surfaces without making use of complex design of experiments. The three phases were studied taking into account the evolution of the microhole shape as a function of the main process parameters (number of passes per phase, incidence angle and radius of the beam trajectory respect to the hole׳s axis). Experiments testified that the drilling strategy was able to produce cylindrical holes with diameter of 180±2 μm on a 350 μm thick plate in total absence of burrs and debris within a drilling time of 3.75 s. Repeatability tests showed a process capability of nearly 99%. SEM inspection of the inner surface of the microholes showed the presence of elongated and periodic ripples whose size and inclination can be controlled adjusting the incidence angle of the beam over the tapered surface before the ultimate finishing phase.

Aims: The modeling of the surgical steps with creating a suitable laboratory models is critically important issue in the successful gaining of microneurosurgical practice. In this experimental study, a laboratory-training model was created for microneurosurgical drilling of delicate and thin cranial base bones using walnut shell in the repetitive repeating of experimental microsurgical training technique. Materials and Methods: All steps of this study were performed under the operating microscope. Twenty-five walnut shells were used for this experimental feasibility study. The difficulty and suitability of the model were evaluated in terms of the usability in the training of microneurosurgical microdrilling. Difficulty of the procedure was divided into three degrees (very easy, easy, and difficult). The objective criterion for the evaluation of the difficulty of the procedure was the protection of the interior organic material during the procedure. The suitability of the procedure was also evaluated within three groups, bad, good, and perfect. Results: In three (12%) walnut shells, the microdrilling was evaluated as difficult. The microdrilling procedures of the twelve (48%) walnut shells were evaluated as easy procedure. Microdrilling procedure of the remaining ten (40%) of the walnut shells was evaluated as very easy. The suitability of the model was evaluated as bad in two (8%) of the walnut shells. The suitability was found as good in 17 (68%) of the walnut shells. In microdrilling of the remaining six (24%) of the walnut shells, the suitability of the model was evaluated as perfect. Conclusion: Microsurgical drilling of the walnut shells without any interior organic injury is accepted as the indication of the successful surgical microdrilling process. Consolidation of the surgical practice in a laboratory setting, grasping, and using of microsurgical instruments can be repeated several times in this model. We believe that this model will contribute to the practical training of microneurosurgery. [Arch Clin Exp Surg 2018; 7(1.000): 24-28]

Run out is one of the major problems in microdrilling processes, causing unexpectedly short tool life, sudden breakage, and dimensional inaccuracy. In this study, a two-step monitoring system for run out detection is proposed. The first step uses the fast Fourier transform for extracting features from the online measured force signals. In the second step, a neural network-based model predicts the process condition from the previously obtained features. The model was trained and tested by using force signals obtained from tungsten and titanium alloys, which are widely applied in electronic and aerospace industries. A 0.1-mm-diameter microdrill was used in the experimental study, and three different feed rates were applied for each material. The trained model was validated with data that was not used in the training process. In this validation, the system was able to detect more than 70 % of the run out conditions with less than 10 % of false detections. For microdrills, detecting and reducing run out can yield considerable gains in tool life and productivity. © 2014, Springer-Verlag London., This work was supported by the Spanish Ministerio de Economía y Competitividad [Ministry of Economy and Competitiveness] through its DPI2012-35504 CONMICRO research project. The authors wish to thank the reviewers for their invaluable comments and suggestions.

Holes quality errors are an undesired but unavoidable consequence in drilling operations. Due to the small dimensions involved in the microdrilling processes, quality measurement and control must be carried out offline, by using microscopy or other high precision measurement devices. This paper presents a study about the correlation between the holes quality and the force signals in the microdilling process of 0.1 mm and 0.5 mm-diameter holes in a sintered tungsten-copper alloy. The surface of the obtained holes was scanned by means of an interferometry microscope and the error of the holes was computed from the scanned data. The three components of the forces were measured during all the drilling process. The behavior of these signals, in three different intervals (tool entrance, forward motion and backward motion) was described by wavelet package analysis. The features having higher correlation with the holes quality error were the average power of the axial component of the forces in the frequency bands of 0~391 Hz and 3906~4297 Hz, during the backward motion. With these features, a statistical regression model was fitted. The main outcomes of this study are the basement for obtaining reliable models for monitoring systems in microdrilling operations., This work was supported by the Spanish Ministerio de Economia y Competitividad [Ministry of Economy and Competitiveness] through its DPI2012-35504 CONMICRO research project.

Laser microdrilling is the process of material removal by ablation using focused laser pulses. With brief preamble on laser system, how a micro-orifice is created successfully on 50mu;m thick copper foil using modified Nd:YAG ophthalmic laser is elucidated. The micro-orifice is required to control the flow of lubricant from the centrifugal lubricator used in spacecraft moving mechanisms. The orifices are characterized using scanning electron microscope (SEM), and the process parameters are optimized. Orifices from 1.5mu;m to 2.7mu;m diameter are produced. The work is further extended to drill microholes in 60mu;m copper wire. It is observed that the bead formed at melt zone near the hole can be conveniently used for microjoining. Copyright � Taylor & Francis Group, LLC.