Drilling-induced delamination often occurs both at the entrance and the exit of the workpiece during drilling of composite material. Investigators have studied analytically and experimentally that delamination in drilling can be correlated to the thrust force of the drill. With a pre-drilled pilot hole, the delamination can be reduced significantly. Early reference reported models of drilling-i...

Abstract-In this study, the feed rate optimization model based on a Markov Decision Process (MDP) was introduced for spiral drilling process. Firstly, the experimental data on spiral drilling was taken from literature for different axial force parameters and with various feed rate decisions made, having the length of a hole being drilled as a reward. Proposed optimization model was computed usi...

The hole drilling method is based on the measuring of the surface relaxed strains when a small hole is drilled on the examined component. From the relaxed strains, measured generally by using special strain gage rosette, the residual stresses is computed by using proper influence coefficients, provided also by the ASTM E837-08 standard. Such influence coefficients are obtained by numerical simu...

Downhole drilling motors or mud motors are frequently used during the oil and gas well construction, especially for construction of directional and horizontal segments. However, low operation life of the down hole drilling motors and high rate of wear in their working elements may constrain their application due to technical and economical disadvantageousness. In this work, a high-torque modula...

OBJECTIVE Intra-articular screws are used for internal fixation of osteochondral fragments after fracture or osteochondritis dissecans. This causes cartilage injury potentially leading to chondrocyte death. We have visualised/quantified the hole and zone of cell death (ZCD) in cartilage after drilling/insertion of various articular screws. METHOD Using an ex vivo bovine model with transmitted...

The hole drilling method is one of the most used semi-destructive techniques for residual stress analysis of mechanical parts. In the presence of non-uniform residual stresses, the stress field can be determined from the measured relaxed strains using several methods, but the most used is the so called integral method. This method is characterized by some simplifications that lead to approximat...

In directional drilling, the most important thing that leads to pulling out the drill string is end of mud motor working life. Considering the working conditions of down hole mud motors; increasing the mechanical properties of their stator’s elastomer is crucial. Some attempts were done to increase the motor performance through geometrical changes but lack of material improvement is significant...

Managed pressure drilling is a sophisticated pressure control method which is intended to meet increasingly high demands in drilling operations in the oil and gas industry. With this method, the well is pressurized and the drilling mud is released through a control choke which can be used to actively control/reject pressure variations. Such a control system needs to handle several disturbances,...

Analysis of the drilling fluid temperature due to heat transfer of drilling fluid with the formation in under-balanced drilling operation is the main objective of this study. Gas-liquid two-phase flow model considering thermal interaction with the formation is used to numerically simulate a well with real dimensions. In the present study, the continuity, momentum, and energy equations are devel...

The use of blasting cost (BC) prediction to achieve optimal fragmentation is necessary in order to control the adverse consequences of blasting such as fly rock, ground vibration, and air blast in open-pit mines. In this research work, BC is predicted through collecting 146 blasting data from six limestone mines in Iran using the artificial neural networks (ANNs), gene expression programming (G...