Back Angle Research Articles

Investigating the effects of PDC cutters geometry on ROP using the Taguchi technique

At times, the polycrystalline diamond compact (PDC) bit’s performance dropped and affects the rate of penetration (ROP). The objective of this project is to investigate the effect of PDC cutter geometry and optimize them. An intensive study in cutter geometry would further enhance the ROP performance. The relatively extended analysis was carried out and four significant geometry factors have been identified that directly improved the ROP. Cutter size, back rake angle, side rake angle and chamfer angle are the stated geometry factors. An appropriate optimization technique that effectively controls all influential geometry factors during cutters manufacturing is introduced and adopted in this project. By adopting L9 Taguchi OA, simulation experiment is conducted by using explicit dynamics finite element analysis. Through a structure Taguchi analysis, ANOVA confirms that the most significant geometry to improve ROP is cutter size (99.16% percentage contribution). The optimized cutter is expected to drill with high ROP that can reduce the rig time, which in its turn, may reduce the total drilling cost.

Implementation of an automatic 3D vision monitor for dairy cow locomotion in a commercial farm

The objective of this study was to evaluate the system performance of a 3D vision system for automatic locomotion monitoring implemented in a commercial dairy farm. Data were gathered during 633 milking sessions on a Belgian commercial dairy farm. After milking, the cows walked in a single-lane alley where the video recording system with a 3D depth camera was installed. The entire monitoring process including video recording, video pre-processing by filtering, cow identification and video analysis was automated. Image processing extracted six feature variables from the recorded videos. Per milking session, 224 ± 10 cows (100%) were identified on average by a radio-frequency identification (RFID) antenna, and 197 ± 16 videos were recorded (88.1 ± 6.6%) by the camera. The cow identification number was merged automatically to a recorded video in 178 ± 14 videos (79.4 ± 5.5%). After video pre-processing and analysis, 110 ± 24 recorded cow-videos (49.3 ± 10.8%) per session resulted in an automatic locomotion score. Daily and cow-individual variations on the merging and analysis rate were due to cow traffic. The minimal cow traffic interval required between consecutive cows was 15 s for optimal merging. System performance was affected by lactation stage, parity of the cows and recording duration. The feature variables curvature angle of back around hip joints (Area Under the Receiver Operating Characteristics Curve (AUC) = 0.719) and back posture measurement (AUC = 0.702) could be considered as fair lameness classifiers. Cow traffic affected the success rate of the video processing. Therefore, automatic monitoring systems need to be adapted to the farm layout.

Effect of geometrical parameters of reentry capsule over flowfield at high speed flow

The main purpose of the paper is to analyze effect of geometrical parameters of the reentry capsules such as radius of the spherical cap, shoulder radius, back shell inclination angle and overall length on the flow field characteristics. The numerical simulation with viscous flow past ARD (Atmospheric Reentry Demonstrator), Soyuz (Russian) and OREX (Orbital Reentry EXperimental) reentry capsules for freestream Mach numbers range of 2.0-5.0 is carried out by solving time-dependent, axisymmetric, compressible laminar Navier-Stokes equations. These reentry capsules appear as bell, head light and saucer in shape. The flow field features around the reentry capsules such as bow shock wave, sonic line, expansion fan and recirculating flow region are well captured by the present numerical simulations. A low pressure is observed immediately downstream of the base region of the capsule which can be attributed to fill-up in the growing space between the shock wave and the reentry module. The back shell angle and the radius of the shoulder over the capsule are having a significant effect on the wall pressure distribution. The effects of geometrical parameters of the reentry capsules will useful input for the calculation of ballistic coefficient of the reentry module.

On the rotation of teleseismic seismograms based on the receiver function technique

The receiver function (RF) technique is a well-established method to investigate the crustal and upper mantle structures based on three-component seismograms of teleseismic events. In the present study, we propose a modified automatic procedure to determine the back azimuth and polarization angles of a teleseismic event based on the RF technique. The method is tested for the recording of 3 permanent and 3 temporary broadband seismic stations located in the vicinity of Poland. Additionally, the analysis of Rayleigh wave polarization is conducted to show that the new procedure is not sensitive to incorrect seismometer orientation. The synthetic modelling of RF by a modified ray-tracing method for 2.5D models beneath each seismic station down to a depth of 60 km is performed to show the effectiveness of the proposed method in the calculation of RF for a complex structure with dipping layers.

On the critical failure mode transition depth for rock cutting with different back rake angles

The failure mode of rock under cutting exhibits a ductile-brittle transition as the depth of cut increases. The critical transition depth, beyond which energy consumed in brittle fracturing surpasses the energy consumed in plastic flow, is the key to differentiating between the ductile and brittle cutting modes and therefore is an important parameter to optimise tool design and operational parameters to meet specific application requirements. This critical failure mode transition depth depends not only on rock properties but also on cutting operational parameters, in particular, the back rake angle. In this work, a series of rock cutting tests were performed to investigate the influence of back rake angle on the critical failure mode transition depth. Size effect law is employed first to identify the critical transition depths, which are then compared with values derived from the analysis of specific cutting energy. It is found that the critical failure mode transition depth increases with the back rake angle. This suggests that the brittle fracture failure induced at large depth of cut can be inhibited by increasing the back rake angle. Cutting at a small back rake angle, on the other hand, is desirable if minimisation of the cutting energy is required in the application.

Fabrication induced spring-back in thermosetting woven composite parts with variable thickness

Rising demand of composite materials for high performance application require a process to manufacture composite parts with accuracy and precision. Residual stress and consequent deformation is one of major limitation in growth of composite industry. Experimental studies reported in literature focused on uniform thickness plates, L shape brackets or rings but depending upon its application, e.g. wind turbine blade, conical structures, etc., real parts do not have always the uniform thickness. In the present study, effect of increasing thickness of a part, variable thickness within a part, angle of bracket, gradient of resin content, and convex and concave tooling on the process induced deformation in angled brackets is studied experimentally. The deformation was divided into two segments: warpage and spring back angle, which were measured using spherometer and microscope along with Scope Image Plus software, respectively. Scanning electron microscopy was used to observe presence of resin content gradient. It is observed that behavior of parts having variation of thickness in them is quite different than the uniform thickness parts. Part having increased thickness at base and flange has up to 10% decrease in distortion. Increased thickness is only effective at larger angles, at sharper angles, there is increase in distortion when thickness is increased. Convex type of tooling induces lower spring-back as compared to concave one.

基于生物力学的驾驶舱坐姿舒适性评价

本文从生物力学角度对飞机驾驶舱坐姿舒适性的评价进行了研究。首先根据飞行员的生理数据进行人体建模，在生物力学仿真软件Anybody中建立“飞行员-座椅”耦合模型，选取肌肉活动、关节扭矩两个评价指标，分别改变座椅高度和椅背倾角，提取仿真数据进行插值处理后得到双变量三维曲面图，从而分析座椅高度和椅背倾角对飞行员主要肌肉活动和关节扭矩的影响。选取肌肉活动的均值、方差和差值平方和这三个参数对坐姿舒适性进行评价，为驾驶舱各设备的总体布局和座椅的几何参数设计提供指导。 In this paper, the sitting comfort evaluation of the cockpit is studied based on biomechanics. Firstly, we establish “pilot seat” model in the biomechanical simulation software Anybody according to the physiological data of pilot and choose two main indexes: the muscle activity and joint torque. We change the seat height and the back angle respectively and the simulation data are obtained after the treatment of double variable 3-D surface chart. We analyze the influence of seat height and back angle changes by the major muscle activity and joint torque of the pilot. The mean value, variance and the square of the muscle activity are selected to evaluate the sitting comfort, providing the guidance for the overall layout of the cockpit and the geometric parameters design for the seat.

Research of annealing mode for high accuracy stamped parts production from titanium alloy 83Ti-5Al-5Cr-5Mo after tooling

The aim of the work is to solve question of accuracy increase in tolled and annealed parts made from forged rod of titanium alloy. Plate pieces were cut from cross-section, annealed at 800°C during 1, 2, 3, 4 and 5 hours. The criterion combining minimum bending radius and spring back angle was found. This criterion shows the maximum values after tooling and annealing for 3 hours.

Validity and reliability of wheelchair sitting posture measures using Coach’s Eye in abled subjects

ABSTRACTPeople in wheelchairs spend a long time in the sitting position and often incur alignment problems resulting in neck and back pain. This study: (1) assessed the validity/reliability of Coach’s Eye (CE) smart device application, (2) examined the effect of seat to back support angle adjustments on head, neck, and shoulder posture in the sitting position, and (3) compared changes in cervical rotation at each back support angle. Abled subjects sat in a wheelchair with back support angles positioned at 90°, 100°, and 110°. CE, as well as ImageJ software, was used to analyze three angles: sagittal head angle (SHA), cervical angle (CVA), and shoulder angle (SA). There were highly significant differences for CVA and SA (p < 0.001) among the three seat to back support angles. Validity of CE was examined by correlating CE with ImageJ scores. CE had high validity for all angles (r = 0.99, 0.98, 0.99 respectively, p < 0.001). Inter-rater reliability for SHA, CVA, and SA was high (intraclass correlation coefficient [ICC] ranged from 0.95 to 0.99). Head (CVA) and shoulder (SA) alignment was closest to neutral posture with back support angles set at 110° and 90°, respectively.

The effects of chamfer and back rake angle on PDC cutters friction

Single PDC cutter tests at a high pressure cell were conducted and analyzed to gain an understanding of the effect of cutter geometry on its frictional response. First, sets of tests conducted with sharp non-chamfered cutters are analyzed. A decreasing trend between the friction angle and back rake angle is consistently observed. The reason can be attributed to a change in flow direction of the rock in front and near the cutting face. A linear relationship between the friction angle and cutter back rake angle is proposed. The coefficient of this relationship can be calculated using the rock internal friction angle and at least one drilling data for the given drilling fluid and contacting surfaces.Four sets of tests with cutters of different diameters (13 and 16 mm) and chamfer lengths (0.010 and 0.016 inch) were conducted. The test results are presented and analyzed using the abovementioned semi empirical model. The method is to associate a chamfered cutter's action to an equivalent non-chamfered cutter back rake angle. It is observed that applying the test data to this analysis produces results that make physical sense with the geometric shape of a chamfered cutter.Finally, contact stress data, for the range of back rake angles tested, confirm a strong increasing trend with back rake angle. The observations indicate that, for the conditions of these tests, that the frictional response of a cutter with developed wear flat is dominated by the wear flat friction itself.

Relative Significance of Multiple Parameters on the Mechanical Specific Energy and Frictional Responses of Polycrystalline Diamond Compact Cutters

A high pressure single polycrystalline diamond compact (PDC) cutter testing facility was used to investigate the effect of five factors on PDC cutter performance on Alabama marble. The factors include: depth of cut (DOC), rotary speed, back rake angle, side rake angle, and confining (wellbore) pressure. The performance is quantified by two parameters: mechanical specific energy (MSE) and friction angle. Fractional factorial design of experiments methodology was used to design the experiments, enabling detection of potential interactions between factors. Results show that, in the range tested, the only statistically significant factor affecting the MSE is DOC. In other words, DOC's influence is predominant and it can mask the effect of all the other factors. These results could have applications in real time pore pressure detection. Further, the results show that back rake angle is the most statistically significant factor in friction angle. Side rake angle and depth of cut also affect the friction angle, but in a relatively unimportant manner. The MSE–DOC behavior is explained and modeled by cutter edge–groove friction and the circular cutter shape. It is speculated that high cutter edge friction overwhelms the actual cutting process. A comparison of five currently present models in the literature with these results is presented and the conclusion is that the future PDC cutter models should digress from the traditional shear failure plane models.

Analytical and experimental investigation of hydrodynamic performance and chamber optimization of oscillating water column system

Among the numerous types of renewable energy technologies, wave energy technologies have been considered by many experts as one of the most promising for Taiwan. However, the amount of energy presently provided by wave energy technologies constitutes a minor percentage of Taiwan's total energy production. This paper presents experimental results using a laboratory water chamber, wherein the fundamental parameters of an oscillating water column (OWC) system's geometrical design are individually investigated and optimized for maximum amplification factor of wave energy to mechanically useful energy. The effects of back plate angle, fence plate and open wide parameters of chamber in a view of wave energy catching capability are analyzed. Three experimental models are evaluated to include a discussion of the back plate, fence plate, and open wide. The OWC's operation qualitatively differs from that predicted by linear theory, identify to critical flow characteristic; front wall down-wash in the water column. The surveys were then expanded to offer general arrangement or a planning material for the geometry optimization of the chamber that could potentially achieve the largest amplification factor of an oscillating water column (OWC) system. The amplification factor of the change in back angle of the OWC is significant.

Evaluation of the Seat Index Point Tool for Military Seats

Abstract : This study evaluated the ISO 5353 Seat Index Point Tool (SIPT) as an alternative to the SAE J826 H-point manikin for measuring military seats. A tool was fabricated based on the ISO specification and a custom backangle measurement probe was designed and fitted to the SIPT. Comparisons between the two tools in a wide range of seating conditions showed that the mean SIP location was 5 mm aft of the H-point, with a standard deviation of 7.8 mm. Vertical location was not significantly different between the two tools (mean -0.7 mm, sd 4.0 mm). A high correlation (r=0.9) was observed between the back angle measurements from the two tools. The SIPT was slightly more repeatable across installations and installers than the J826 manikin, with most of the discrepancy arising from situations with flat seat cushion angles and either unusually upright or reclined back angles that caused the J826 manikin to be unstable. The investigators who performed the measurements indicated that the SIPT was easier to use. The data show that the SIPT is a reasonable substitute for the SAE J826 manikin when ease-of-use considerations favor the SIPT, such as restricted space around the seat, low seat heights, or low cushion angles. Human posture measurements in seats with large discrepancies between the tools will be needed to determine which provides a better prediction of sitter position.

Sit-to-Stand and Stand-to-Sit Control Mechanisms of Two-Wheeled Wheelchair.

This paper presents a mechanism for standing and sitting transformation of a wheelchair using a two-wheeled inverted pendulum concept with reduced torque requirement, in simulation studies. The motivation of this work is to design a compact standing mechanism to help an elderly/disabled person with functional limitation in lower extremities to maneuver in small and confined spaces and enable them to perform standard daily life routines independently. The wheelchair system at the upright standing position is tested with different travel distances, and the challenge is to control both sit-to-stand and stand-to-sit operations in a stable manner using flexible-joint humanoid. An additional spring/damping element is incorporated at each wheel to provide a comfortable ride for the user especially during stand-to-sit transformation task. A PD-fuzzy control with modular structure is implemented, and the performance of the system is observed through visual nastran 4d (vn4d) visualization software and simulation in matlab. The stand-to-sit performance tests have shown more than 38% reduction in tilt and back seat angles fluctuation in linear travel motion using a suspension system, while the initial tilt torque needed is 50% less than the amount required in previous designs.

Analysis of resistance factors for LFRD of soil nail walls against external stability failures

This paper presents reliability analyses of soil nail walls against two external ultimate limit states, global and sliding stabilities, which are related to the external stability failures of soil nail walls. Reliability analyses are conducted using Monte Carlo simulation technique. Soil nailing is a popular retaining system in highway construction and slope stabilization, and its current design practice is still based on the working stress design. There remains a need to establish a more rational design framework—load and resistance factor design—based on the concept of limit state design and reliability analysis for soil nail walls. The development of load and resistance factor design approach must consider multiple ultimate limit states, associated with external, internal, and facing failures. The analyses of resistance factors against two external failures are conducted in this study considering various influencing factors, including statistical parameters of soil friction angle, ultimate bond strength between soil and nails, soil type, wall geometry (wall height, back slope angle, and face batter angle), and nail configurations (nail inclination angle, drillhole diameter, and nail spacing). In the end, a series of resistance factors are proposed for potential application of load and resistance factor design approach against external failures for soil nail walls according to different design codes.

Viscoelastic Response of the Human Lower Back to Passive Flexion: The Effects of Age.

Low back pain is a leading cause of disability in the elderly. The potential role of spinal instability in increasing risk of low back pain with aging was indirectly investigated via assessment of age-related differences in viscoelastic response of lower back to passive deformation. The passive deformation tests were conducted in upright standing posture to account for the effects of gravity load and corresponding internal tissues responses on the lower back viscoelastic response. Average bending stiffness, viscoelastic relaxation, and dissipated energy were quantified to characterize viscoelastic response of the lower back. Larger average bending stiffness, viscoelastic relaxation and dissipated energy were observed among older vs. younger participants. Furthermore, average bending stiffness of the lower back was found to be the highest around the neutral standing posture and to decrease with increasing the lower back flexion angle. Larger bending stiffness of the lower back at flexion angles where passive contribution of lower back tissues to its bending stiffness was minimal (i.e., around neutral standing posture) highlighted the important role of active vs. passive contribution of tissues to lower back bending stiffness and spinal stability. As a whole our results suggested that a diminishing contribution of passive and volitional active subsystems to spinal stability may not be a reason for higher severity of low back pain in older population. The role of other contributing elements to spinal stability (e.g., active reflexive) as well as equilibrium-based parameters (e.g., compression and shear forces under various activities) in increasing severity of low back pain with aging should be investigated in future.

Investigation of Effects of Tool Geometry Parameters on Cutting Forces, Temperature and Tool Wear in Turning Using Finite Element Method and Taguchi’s Technique

Turning is one of the most widely metal cutting methods. Machines, tool geometry and machining parameters are the main factors influencing machining quality and efficiency. So there is a lot of research on it. This paper studies on the influence of the geometrical parameters of the tool including: back rake angle (BR), side rake angle (SR) and side cutting-edge angle (SCEA) on cutting forces, temperature and tool wear in turning using FEM (by Deform 3D finite element simulation software) and Taguchi’s technique (by Minitab16 statistical software) is used to design the experiment and to analyze output quality characteristics from simulation results. And the optimum tool geometry parameters are given.

Understanding the effect of channel coupling on fusion of6Li+64Ni

The effect of inelastic excitation and single particle transfer reactions on fusion have been investigated for the system 6 Li+ 64 Ni at near barrier energies. The calculations show that a simultaneous coupling to the inelastic excitation of projectile and target along with positive Q-value 1n- and 1p-stripping channels, describes the experimental CF cross sections reasonably well in the below barrier region. Exploring the interplay of different reaction channels in the collision of weakly bound systems is a subject of interest, both experimentally and theoretically, over the past several years [1–4]. In a recent work [5], the effect of coupling to inelastic excitations and single particle transfer channels on the back angle quasi-elastic excitation function had been reported for the system 6 Li+ 64 Ni. To investigate the effect of these couplings on fusion excitation function, a complementary experimental observable, for 6 Li+ 64 Ni is the primary motivation of the present work. Unlike the heavy targets, for the lower medium mass targets like 64 Ni the measured fusion cross sections with weakly bound projectiles provide total fusion (TF) cross sections instead of the cross sections for complete fusion (CF) of the whole projectile. The TF cross section for 6 Li+ 64 Ni system includes along with CF cross section the contributions from incomplete

Planform Dependency on Airfoil Design Results for Supersonic Wing in Supersonic and Transonic

In this study, the wing design problem for different planforms for supersonic transport (SST) under supersonic and transonic cruise conditions is discussed to obtain knowledge of the supersonic air-foil from the viewpoint of wing planform dependency. Two types of planforms were considered—a cranked arrow wing with a high sweep-back angle and a tapered wing with a low sweep- back angle. The optimum airfoils of these planforms were designed by efficient global optimization, which combined the evolutionary algorithm with the Kriging surrogate model. To acquire design knowledge, the functional analysis of variance was applied to the solution space and the design space. The design results show that the optimum airfoil and the contribution ratios of design variables for the airfoils of the two planform are different.

Numerical simulation of rock cutting using 2D AUTODYN

In a drilling process for oil and gas exploration, understanding of the interaction between the cutting tool and the rock is important for optimization of the drilling process using polycrystalline diamond compact (PDC) cutters. In this study the finite element method in ANSYS AUTODYN-2D is used to simulate the dynamics of cutter rock interaction, rock failure, and fragmentation. A two-dimensional single PDC cutter and rock model were used to simulate the orthogonal cutting process and to investigate the effect of different parameters such as depth of cut, and back rake angle on two types of rocks (sandstone and limestone). In the simulation, the cutting tool was dragged against stationary rock at predetermined linear velocity and the depth of cut (1,2, and 3 mm) and the back rake angles(-10°, 0°, and +10°) were varied. The simulation result shows that the +10° back rake angle results in higher rate of penetration (ROP). Increasing depth of cut leads to higher ROP at the cost of higher cutting force.