Numerical Study on Fragmentation Characteristics of Granite Under a Single Polycrystalline Diamond Compact Cutter in Rotary-Percussive Drilling

2022 ◽  
pp. 1-19
Author(s):  
Huaizhong Shi ◽  
Zhaosheng Ji ◽  
Jinbao Jiang ◽  
Bangmin Li
Keyword(s):  
Coupling Effect ◽  
Numerical Study ◽  
Distinct Element ◽  
Polycrystalline Diamond ◽  
Mechanical Tests ◽  
Sensitivity Analyses ◽  
Impact Frequency ◽  
Percussive Drilling ◽  
Fluctuation Phenomenon ◽  
Polycrystalline Diamond Compact

Abstract Fragmentation characteristics of granite in rotary-percussive drilling are studied using the distinct element method. We developed a model to investigate the interaction between the rock and a Polycrystalline Diamond Compact cutter. The micro contact parameters in the model are calibrated by conducting a series of simulated mechanical tests of the rock. Sensitivity analyses are then conducted according the drilling performances which are quantified as the penetration displacement, the fragmentation volume and the specific energy, as well as the lateral force and the particle size distribution. Results show that the model can well represent the typical fracture system under indentation of the cutter, the torque fluctuation phenomenon in drilling and the formation of lateral chips, which verify the reliability of the model. The cutter with a back rake angle of 55°and impact frequency of 30Hz has the best penetration performance in evaluated parameters. Increasing the frequency has a great effect on the rock breaking speed under the coupling effect of impact and cutting in the low frequency range. Considering crushing efficiency, 50 Hz is the recommended impact frequency. This paper provides a useful tool to represent the fragmentation performance of rotary-percussive drilling and sensitivity analyses shed light on the potential ways to improve the performance.

scholarly journals Adjoint-based parametric sensitivity analysis for swirling M-flames

2018 ◽  
Vol 859 ◽  
pp. 516-542 ◽  
Author(s):  
Calum S. Skene ◽  
Peter J. Schmid
Keyword(s):  
Sensitivity Analysis ◽  
Frequency Response ◽  
Stokes Equations ◽  
Numerical Study ◽  
Computational Cost ◽  
Base Flow ◽  
Sensitivity Analyses ◽  
Perturbation Expansions ◽  
Mean Flow ◽  
Adjoint Solutions

A linear numerical study is conducted to quantify the effect of swirl on the response behaviour of premixed lean flames to general harmonic excitation in the inlet, upstream of combustion. This study considers axisymmetric M-flames and is based on the linearised compressible Navier–Stokes equations augmented by a simple one-step irreversible chemical reaction. Optimal frequency response gains for both axisymmetric and non-axisymmetric perturbations are computed via a direct–adjoint methodology and singular value decompositions. The high-dimensional parameter space, containing perturbation and base-flow parameters, is explored by taking advantage of generic sensitivity information gained from the adjoint solutions. This information is then tailored to specific parametric sensitivities by first-order perturbation expansions of the singular triplets about the respective parameters. Valuable flow information, at a negligible computational cost, is gained by simple weighted scalar products between direct and adjoint solutions. We find that for non-swirling flows, a mode with azimuthal wavenumber $m=2$ is the most efficiently driven structure. The structural mechanism underlying the optimal gains is shown to be the Orr mechanism for $m=0$ and a blend of Orr and other mechanisms, such as lift-up, for other azimuthal wavenumbers. Further to this, velocity and pressure perturbations are shown to make up the optimal input and output showing that the thermoacoustic mechanism is crucial in large energy amplifications. For $m=0$ these velocity perturbations are mainly longitudinal, but for higher wavenumbers azimuthal velocity fluctuations become prominent, especially in the non-swirling case. Sensitivity analyses are carried out with respect to the Mach number, Reynolds number and swirl number, and the accuracy of parametric gradients of the frequency response curve is assessed. The sensitivity analysis reveals that increases in Reynolds and Mach numbers yield higher gains, through a decrease in temperature diffusion. A rise in mean-flow swirl is shown to diminish the gain, with increased damping for higher azimuthal wavenumbers. This leads to a reordering of the most effectively amplified mode, with the axisymmetric ($m=0$) mode becoming the dominant structure at moderate swirl numbers.

scholarly journals ELECTRICALLY CONDUCTIVE POLYCRYSTALLINE SUPER HARD MATERIAL BASED ON DIAMOND AND n-LAYER GRAPHENES

2018 ◽  
Vol 59 (8) ◽  
pp. 69
Author(s):  
Alexandr A. Shul’zhenko ◽  
Lucyna Jaworska ◽  
Alexandr N. Sokolov ◽  
Vladislav G. Gargin ◽  
Ludmila A. Romanko
Keyword(s):  
Physical Properties ◽  
High Pressures ◽  
Polycrystalline Diamond ◽  
Sharp Decrease ◽  
Hard Material ◽  
Electrically Conductive ◽  
High Pressures And Temperatures ◽  
Polycrystalline Diamond Compact

The electrical and physical properties of the electrically conductive super hard material on the basis of polycrystalline diamond and n-layered graphenes obtained at high pressures and temperatures were studied. It was established that the increase in graphene in a polycrystalline diamond compact leads to a sharp decrease in resistance. Wherein the hardness of the samples is slightly inferior to the hardness of diamond poly crystals obtained without the use of graphene.

scholarly journals Design and Estimation for the Population Prevalence of Infectious Diseases

2021 ◽  
Author(s):  
Eric J. Oh ◽  
Alyssa Mikytuck ◽  
Vicki Lancaster ◽  
Joshua Goldstein ◽  
Sallie Keller
Keyword(s):  
Numerical Study ◽  
Disease Outbreaks ◽  
Sensitivity Analyses ◽  
Multilevel Regression ◽  
Infectious Disease Outbreaks ◽  
Population Prevalence ◽  
Prevalence Estimates ◽  
Relative Robustness ◽  
Biased Estimates ◽  
Limited Testing

AbstractUnderstanding the prevalence of infections in the population of interest is critical for making data-driven public health responses to infectious disease outbreaks. Accurate prevalence estimates, however, can be difficult to calculate due to a combination of low population prevalence, imperfect diagnostic tests, and limited testing resources. In addition, strategies based on convenience samples that target only symptomatic or high-risk individuals will yield biased estimates of the population prevalence. We present Bayesian multilevel regression and poststratification models that incorporate probability sampling designs, the sensitivity and specificity of a diagnostic test, and specimen pooling to obtain unbiased prevalence estimates. These models easily incorporate all available prior information and can yield reasonable inferences even with very low base rates and limited testing resources. We examine the performance of these models with an extensive numerical study that varies the sampling design, sample size, true prevalence, and pool size. We also demonstrate the relative robustness of the models to key prior distribution assumptions via sensitivity analyses.

scholarly journals Seismic Vulnerability of Ancient Colonnade

2016 ◽  
pp. 950-974 ◽  
Author(s):  
Vasilis Sarhosis ◽  
Gian Piero Lignola ◽  
Panagiotis G. Asteris
Keyword(s):  
Seismic Vulnerability ◽  
Numerical Study ◽  
Distinct Element ◽  
Structural Response ◽  
Frictional Resistance ◽  
Sensitivity Study ◽  
Distinct Element Method ◽  
Water Lubrication ◽  
Non Linear ◽  
Element Method

In this chapter, a numerical study to investigate the seismic vulnerability of the two storey colonnade of the Forum in Pompeii has been conducted. Software based on the Distinct Element Method (DEM) of analysis has been used. The colonnade was represented as an assemblage of distinct blocks connected together by zero thickness interfaces which could open and/or close depending on the magnitude and direction of stresses applied to them. Both static and non-linear static analyses have been undertaken. Also, a sensitivity study has been performed to investigate the effect of frictional resistance of the joints on the structural response of the colonnade. This was to simulate potential joint degradation effects and/or possible water lubrication at the joint.

The effect of materials and design on the reliability of through-glass vias for 2.5 D integrated circuits: a numerical study

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Omar Ahmed ◽  
Chukwudi Okoro ◽  
Scott Pollard ◽  
Tengfei Jiang
Keyword(s):  
Integrated Circuits ◽  
Buffer Layer ◽  
Coupling Effect ◽  
Numerical Study ◽  
Numerical Models ◽  
Thermal Strain ◽  
Content Type ◽  
Mismatch Strain ◽  
Pitch Distance ◽  
Stress Buffer

PurposeThis study aims to investigate the factors responsible for substrate cracking reliability problem in through-glass vias (TGVs), which are critical components for glass-based 2.5 D integration.Design/methodology/approachNumerical models were used to examine the driving force for substrate cracking in glass interposers due to stress coupling during heating. An analytical solution was used to demonstrate how the energy release rate (ERR) for the glass substrate cracking is affected by the via design and the mismatch in thermal strain. Then, the numerical models were implemented to investigate the design factors effects, such as the pitch distance, via diameter, via pattern, via design, effect from a stress buffer layer and the interposer materials selection on the susceptibility to substrate cracking.FindingsERR for substrate cracking was found to be directly proportional to the via diameter and the thermal mismatch strain. When a via pattern is implemented for high-density integration, a coupling in the stress fields was identified. This coupling effect was found to depend on the pitch distance, the position of the vias, and the via arrangement, suggesting a via pattern-dependent reliability behavior for glass interposers. Changing the design of the via to an annular shape or a substrate-cored via was found to be a promising approach to reduce the susceptibility to substrate cracking compared to a fully filled solid via. Also, the use of a stress buffer layer, an encouraging design prospect presented for the first time for TGVs in this study, was found to significantly reduce cracking. Finally, alternative via and substrate materials showed lower tendency for substrate cracking, indicating that the reliability of glass interposers can be further enhanced with the implementation of such new materials.Originality/valueThis study signifies the first attempt to comprehensively evaluate the susceptibility to crack formation in glass interposers during heating. Therefore, this study provides new perspectives on how to achieve a significant potential reliability improvement for TGVs.

scholarly journals Examination of Polycrystalline Diamond Compact Cutter used in Drilling Tools in the Oil Industry

2013 ◽  
Vol 19 (S2) ◽  
pp. 1050-1051 ◽  
Author(s):  
J.N. Williard ◽  
D.K. Colbert
Keyword(s):  
Polycrystalline Diamond ◽  
Oil Industry ◽  
Drilling Tools ◽  
Polycrystalline Diamond Compact

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

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