Effect Of Tilt Angle Research Articles

Fabrication of Micro Dimples Pattern Using Ball End Mill

In this paper, the effect of workpiece tilt angle and feed direction in producing micro dimple pattern using ball end mill tools were studied. Experiments were conducted using carbide ball end mill tools, aluminium Al 6061-T6 workpiece and using CNC machine. Three workpiece tilt angles are selected 0°30° and 45°; and two feed directions z-axis and x-axis. Visual observations using Scanning Electron Microscope (SEM) and geometry measurements using laser scanning confocal microscope were conducted on the fabricated micro dimple patterns. The results show that the workpiece tilt angle produces less burr at the edge of the dimples compared to without tilt (0°). In addition, the workpiece tilt angle can avoid the formation of undercut at the center of the dimple. The workpiece tilt angle of 30° and z-axis feed direction produced better result compared to 0° and 45° tilt angles with the value of ratio diameter/depth closer to the theoretical value.

Friction stir welding of polycarbonate lap joints: Relationship between processing parameters and mechanical properties

Abstract The relation between process parameters and properties of polycarbonate (PC) sheet after friction stir welding (FSW) was investigated. Effects of FSW tool rotation speed (ω), travelling speed (V), tilt angle (α) and plunge depth on material flow, joint tensile strength, flexural strength, impact energy and hardness were investigated. It is shown that at low and high levels of heat input sound joints cannot be attained. At low heat inputs, the local temperature is not high enough to decrease the viscosity of the polymer to fill the interface, and thus voids and large planar cracks are formed in the joint root and stir zone. At high heat inputs, expelling of materials due to high peak temperature occurs. The stir zone is opaque due to changes in carbon chains as well as polymer degradation. Circular rings are appeared at the upper surface of the seam. The size of heat affected zone and stir zone is shown to significantly vary with the processing parameters. A change in the morphology of stir zone with the tilt angle is also shown. A sound joint with the highest strength is attained at ω = 2200 rpm, V = 105 mm/min, α = 2.5° and 1.2 mm tool plunge depth. The highest tensile strength, flexural strength and impact energy were respectively, 82% (~55 MPa), 76% (~61 MPa) and 75% (~19 kJ/m2). Fractographic studies show the presence of divergent lines of the surface, which develop outward from the crack initiation region.

A detailed investigation and performance optimization of a photovoltaic panel integrated with a reflecting mirror

In this paper, the performance of a photovoltaic panel integrated with a reflecting mirror is investigated. In this regard, the effects of panel and mirror tilt angles, and the mirror length on the system performance are modeled. The cell temperature rises have also been considered. Moreover, by a 3D model, the lighting and shading statuses are studied in detail, and all the possible conditions are presented and modeled. The resulting model can calculate the amount of incident solar energy on the panel and the generated electrical power in every moment during a year. This amount is dependent on the system configuration and capacity and its location. A 250-W photovoltaic panel and the city of Tehran have been considered the basics of calculations to assess the model results. By employing the genetic algorithm method, the optimum configuration has been found to have 69.084° and 0° tilt angles for the panel and the mirror, respectively, at the mirror length of 2 m. This configuration can generate 2.38 GJ (613.89 kWh) of electrical energy annually. It was also found that the optimum configuration had 0.024 GJ of annual energy losses due to the effects of cell temperature rise.

Disc angle and tilt angle effects on forces acting on a single-disc type no-till seeder opener

Disc angles which play an important role on horizontal (draft), side and vertical forces are divided into two as the disc and tilt angle. Five disc angles (0, 5, 10, 15 and 20°), five tilt angles (0, 2.5, 5, 7.5 and 10°), three vertical disc loads of 50 kg, 100 kg and 150 kg and no-residue, wheat and corn residue conditions were taken into account in this study which was conducted under soil bin conditions. The angles of the disc opener were easily changed by using a mechanism designed and manufactured for this purpose. According to the obtained results, the increase in disc angle led to an increase of the vertical and draft forces that affect the disc and minimum values at 0° disc angle and maximum values at 20° disc angle were obtained. The vertical forces acting on the disc according to disc angle varied between 321.5 N and 373.4 N while the draft forces were between 92.2 N and 131.3 N. As the tilt angle increased, the draft forces decreased, and these values were measured between 122.7 N and 103.7 N. The vertical forces ranged from 335.1 N to 360.6 N. It has been determined that the 7.5 and 10° tilt angles generally give better results. The increase in the vertical load applied to the disc enabled penetration into the soil, while at the same time an increase incurred in the vertical, draft and side forces acting on the furrow opener. In addition, the vertical, draft and side forces acting on the disc type opener and the data of cross-sectional area of the furrows opened were used to calculate specific vertical, specific draft and specific side forces Results indicate that an increase in disc angle decreased specific draft, side and vertical forces. An increase of the tilt angle caused the specific vertical, draft and side forces to increase.

Calculating wind turbine component loads for improved life prediction

Wind turbines life time is commonly predicted based on statistical methods. However, the success of statistics-based maintenance depends on the amount of variation in the system design, usage and load. Life time prediction based on physical models seeks to overcome this drawback by considering the actual design and evaluating the specific usage, load and operating condition of the considered systems. In this paper, a load-based maintenance approach is proposed to predict wind turbines life time. Physical models are used to evaluate load profiles at wind turbine blade root, rotor hub center and tower head. The effects of surface roughness, side winds, yaw misalignment, rotor tilt and blade cone angle, individual blade pitching and wind turbulences are considered and quantified. It is shown that centrifugal, gravity, Euler and Coriolis accelerations dominate the blade root loads. Tilt and cone angle, as well as individual blade pitching, affect the rotor hub and dynamic tower head loads. Further, the actual wind speed distribution is considered which is also proven to be a critical life time prediction parameter. Finally, a set of parameters is proposed that need to be monitored in a specific wind turbine to enable the practical implementation of a predictive maintenance policy.

Effects on lubrication characteristics of water-lubricated rubber bearings with journal tilting and surface roughness

To study the effect of surface roughness on the lubrication characteristics of water-lubricated rubber bearings (WLRBs) when the stern shaft is tilted, the surface roughness of the bearings was measured by a surface roughness measuring instrument. Considering the tilting stern shaft and surface roughness, a mathematical model was constructed and water film thickness equation was deduced. By adopting the finite difference method, the film thickness and pressure distribution of WLRBs with tilt angle and roughness were analysed. The effects of tilt angle on film thickness and pressure under different surface roughness amplitudes and wavelengths were studied, and the results were then compared with those of smooth surface bearings without tilt angle. Finally, the minimum film thickness and maximum film pressure were analysed. The results showed that when the tilt of rotor and surface roughness of bearing were considered simultaneously, the film thickness exhibited a jagged distribution in the circumferential direction and decreased gradually in the axial direction. The film pressure had slightly irregular fluctuations and a sharp pressure peak. The tilt angle and roughness reduced the minimum film thickness, and the film thickness difference increased. The film pressure increased rapidly and local pressure exhibited slight, sudden changes. The surface roughness amplitude and wavelength had a considerable influence on the water film thickness, and the roughness amplitude had a clear effect on the film pressure. As the roughness amplitude increased, the minimum film thickness gradually declined and film pressure peak fluctuation grew. As the roughness wavelength increased, the film thickness fluctuated irregularly within a certain range of magnitude, and the minimum film thickness was almost constant.

Experimental investigation of natural convection heat transfer of SiO2/water nanofluid inside inclined enclosure

Natural convection heat transfer of SiO2/water nanofluids in a rectangular enclosure was investigated at different concentrations and inclination angles, experimentally. Results indicated that heat transfer has not significantly changed for low concentrations of nanofluids. However, at volume fraction of nanoparticles greater than 0.005, heat transfer coefficient decreased with concentration of nanofluid. The effect of tilt angle on heat transfer was also examined. It was found that at low concentrations of nanofluid, the effect of tilt angle on Nusselt number is more pronounced. Influence of concentration of nanofluid on Nusselt number decreases with increasing inclination angle of the cavity or approaching the heated wall to vertical state. The highest values of Nusselt number were obtained for tilt angles of 0° or horizontal state, and heat transfer rate was decreased with inclination angle.

Investigation on the static and dynamic characteristics of 3-DOF aerostatic thrust bearings with orifice restrictor

This paper studies the static and dynamic characteristics of 3-DOF aerostatic thrust bearings with orifice restrictor. The coupled perturbation Reynolds equations are solved simultaneously for the first time to obtain the dynamic stiffness and damping coefficients considering the interaction between these equations. The perturbation mass flow rate is considered in determining the numerical convergence of the solution. The developed model demonstrates the nonlinear relationship between air film thickness and pressure. The effect of air film thickness, tilt angles, rotating speed and perturbation frequency ratio on load capacity, load moments, volume flow rate, dynamic stiffness and damping coefficients are evaluated. The results from the developed model provide guidance for design of aerostatic thrust bearing with required static and dynamic performance.

Stability prediction of five-axis ball-end finishing milling by considering multiple interaction effects between the tool and workpiece

Abstract In five-axis ball-end machining, stability of the milling process is not only determined by the combination of depth of cut and the spindle speed, but also determined by the lead and tilt angles of the milling tool (i.e., the tool orientations). As the degree of freedom increases, five-axis machining machines have more complex dynamic characteristics. Therefore, the influence of the tool-workpiece interactions on the machining performance is more obvious. In this paper, a new five-axis ball-end milling dynamical model which considers the multiple interactions between the tool and workpiece is established for the first time. Based on the established dynamical model, the effects of regenerative effect, structural mode coupling and process damping on the dynamic characteristics of five-axis milling are investigated. In addition, the effects of lead angle and tilt angle on the stability prediction of five-axis milling are investigated. The experimental results show that the proposed five-axis milling dynamical model is more reliable than the traditional one in predicting the stability of five-axis milling.

Numerical study on corrosion profile estimation of a corroded steel plate using eddy current

This article presents corrosion profile estimation as a method to determine the extent of corrosion in steel members having corroded exterior, with or without protective cover, when the only side accessible to the eddy current probe is highly uneven. A high frequency eddy current method is proposed to estimate the corrosion profile of a steel plate directly from the probe lift-offs regardless of varying plate thickness. The three-dimensional, numerical simulations were carried out in the FEM software, COMSOL Multiphysics 5.2a to verify the suitability of this method. A parametric study is conducted to determine the effect of coil height, diameter, their ratio and tilt angle of reflection probe on the estimation accuracy of a triangular notched profile, representative of corrosion, whereby a geometrically optimized probe is obtained. It is then employed to determine the corrosion profile of a corroded steel plate with and without protective cover. The estimated corrosion profiles show good agreement with the actual profile measured by laser displacement meter, confirming the sufficiency of proposed method.

Networked column compartment model for a tilted packed column with structured packing

To successfully implement floating liquefied natural gas technology (FLNG), the separation columns on the topside of FLNG must be optimally designed. To this end, a reliable model that can predict column performance in offshore environments is needed. In this study, a networked column compartment model (NCCM), based on 2D-liquid and gas distribution models (LGDM), was proposed as a reliable offshore column model. A pilot-scale experiment for a column with structured packing was conducted to obtain experimental data regarding the absorption performance of the column in offshore environments. The results of the NCCM were compared with the experimental data. With the aid of the developed model, the effect of tilt angles on absorption performance and packed height was quantified.

Effects of tilt angle between laser nozzle and substrate on bead morphology in multi-axis laser cladding

Laser cladding has been increasingly used for repairing and remanufacturing critical and high-value components due to its unique benefits such as high solidification rates and a small heat-affected zone. In laser cladding, tilt angle between a laser nozzle and a substrate has a significant impact on deposited bead morphology. To ensure the quality of laser cladding, the effects of tilt angle on bead morphology are investigated in this study. An analytical model is introduced to predict bead shapes for three tilting postures. In the first case, a substrate remains horizontal while the nozzle is tilted. All three parameters, including width, height, and peak point offset, will be influenced by the laser beam power distribution. In the second case, a substrate is tilted while the laser nozzle is kept axial to the substrate’s normal, the peak point offset will ascend along with the increasing of the tilt angle (gravity effect). In the third case, the laser nozzle remains vertical while the substrate is tilted, which leads to variations of cladding width, cladding height, and especially peak point shifting value. These parameters will be dependent on the integrated effect of gravity and the laser beam power distribution. A set of experiments is conducted to demonstrate the effectiveness of the proposed model. This study illustrates that the variation of cladding width and height with the tilt angle can be accurately calculated by the predictive model, and that the peak point shifting value is roughly smaller than 5% of cladding width when the tilt angle is less than 30°. These findings show that trajectory planning of multi-axis laser cladding can be optimized using an acceptable range of tilt angle between the laser nozzle and substrate.

Optimization of an integrated electrocoagulation/sedimentation unit for purification of polymer-flooding sewage

This study aims to optimize the electrocoagulation(EC) process of emulsified oil removal from polymer-flooding sewage (PFS), producing in the oil recovery process and characterized by multiple chemical additives, high viscosity, and high stability. Response surface methodology (RSM) and Box-Behnken statistical experimental design (BBD) were applied to investigate the effects of tilt angles of electrodes, flow rate, and current density as well as the interactions on oil removal and energy consumption. All the experiments were performed in a continuous-flow pattern with an integrated unit combined with reaction and subsequent separation zone. The experimental results suggested that EC technology was very efficient in oily wastewater treatment and was able to achieve 97% oil removal after the system enters into the stable stage with a flow rate of 5.5Lh−1 ，applied current density of 18.9mAcm−2 and tilt angle 80°. At this time, the energy consumption is 3.50kWhm−3. Besides, for both of the oil removal and energy consumption, flow rate has the most significant impact, and the current density follows. The results of variance (ANOVA) analysis showed a high correlation coefficient (R2)value of 0.990 and 0.996 for oil removal and energy consumption, respectively, which ensures an adequate fit of the second-order regression.

Experimental study of the natural convection heat transfer performance for finned oval tubes at different tube tilt angles

The natural convection heat transfer of finned oval tubes was studied for different tube tilt angles (0° to 40°), fin spacing (6mm to 16mm) and Rayleigh numbers (11,000 to 130,000). Fin efficiency was determined by temperature measurements along the fin surface and temperature gradient calculations. Nusselt number and volumetric heat flux density were chosen as assessment parameters for the thermal performance. A comparison of the experimental data with correlations from literature was made and good agreement was found. Furthermore, the uncertainty of the measurements was evaluated. In the horizontal tube orientation (0°) the Nusselt number increases with fin spacing. However, the fin efficiency and the volumetric heat flux density reduce. The tilt angle of the longitudinal tube axis was found to have an essential impact on the thermal performance, in particular when the fin spacing is high. For the higher fin spacing values the horizontal orientation gives highest Nusselt number and volumetric heat flux density. At tube tilt angle of 40° the thermal performance becomes lowest for all fin spacing values. When the fin spacing is low, the effect of tube tilt angle is minor. From the experimental results correlations between Nusselt number, Rayleigh number, fin spacing and tube tilt angle are proposed to assist the future design of heat exchanger with tilted finned oval tubes.

Comments on CTOA transferability in “Crack tip opening angle during unstable ductile crack propagation of a high-pressure gas pipeline” [204 (2018) 434–453

When axial fast ductile fracture occurs in high-pressure gas pipes, the plane of the crack opening does not necessarily remain parallel to the pipe axis. There is in general a tilt angle between the opening flanks and the pipe axis. The present discussion shows that taking into account the presence of a tilt angle results in larger estimates of surface CTOA than those reported in a recent paper (Shibanuma et al., 2018). Considering the effect of tilt angle, the data reported in Shibanuma et al. (2018) support the transferability of CTOA from DWTT-type specimens to full-scale pipe.

The influence of wall temperature distribution on the mixed convective losses from a heated cavity

An experimental investigation is presented of the effects of wind speed (0–9 m/s), yaw angle (0° and 90°), and tilt angle (15° and −90°) on the mixed convective heat losses from a cylindrical cavity heated with different internal wall temperature distributions. The internal wall comprised 16 individually controlled heating elements to allow the distribution of the surface temperature to be well controlled, while the air flow was controlled with a wind tunnel. It is found that temperature distribution has a strong influence on the convective heat losses, with a joint dependence on the wind speed and its direction. For the no-wind and side-on wind conditions, the measured range of the heat losses varied by up to 50% with a change in the wall temperature distribution. However, for high head-on wind speeds, this variation reduced down to ∼20%. In addition, the heat losses from downward tilted were ∼3 times larger than the upward facing heated cavity for high wind speeds (typical of tower-mounted and beam-down configurations, respectively). Also, the measured heat losses were found to be only slightly dependent on wind speed and direction in contrast with the downward tilted cases.

Effect of Spin-Torque Oscillator Tilt Angle in Microwave-Assisted Magnetic Recording

Microwave-assisted magnetic recording with a tilted spin-torque oscillator (STO) was examined. Tilting the STO toward the trailing shield of a write head makes it easier to achieve stable oscillation. The signal-to-noise ratio (SNR) of written tracks was examined using an analytical head field distribution based on a finite-element model of a write head. The maximum SNR was similar for a range of STO tilt angles, but the optimum position of the STO in the write head gap depended on the STO tilt angle.

Investigation of optimal tilt angles and effects of soiling on PV energy production in Pakistan

Tilt angle of photovoltaic (PV) panel strongly contributes to the amount of solar radiation harvested by the PV panel. In this paper, we model the optimal PV tilt angle for Lahore and some of the other major cities in Pakistan using the available solar radiation data from NREL and ESMAP. The model is used to propose an optimal schedule for PV tilt in Lahore involving four adjustments in a year that can provide ∼6.6% increase in the yearly energy generation relative to a fixed tilt. The model is validated with PV tilt experiments. Moreover, a simple model is developed to estimate the upper/lower bounds of soiling losses in Lahore using the reported distributions for aerosol particulates. We show that the power loss due to soiling could be up to 10% for a lightly soiled panel and could go up to 40% for a heavily soiled panel. We further explore the tilt angle effect on the soiling losses in Lahore by doing soiling experiments. For a period of 100 days, dust deposition on a horizontal panel results in 26.2% energy loss as compared to a clean panel. For the same period, the corresponding loss for a vertical tilt was 13.5%. The variability of soiling effects with respect to tilt is used to predict an optimal tilt angle when the soiling losses are significant. These findings provide important insights into the protocols of tilt adjustments in presence of environmental dust for PV systems in Pakistan and further highlight the significance of soiling losses for the typical aerosol conditions in Lahore.

Mechanical and microstructural behaviour of Al-Mg4.2 alloy friction stir butt welds

The purpose of the current work is to analyse the effect of tilt angle and tool hardness on mechanical and microstructural characteristics of FSWed Al-Mg4.2 joints. The joints were fabricated varying the tilt angle and tool hardness at six different levels each, keeping other FSW parameters constant. Microstructure, macrostructure, strength and hardness characteristic of the welds has been sifted in order to understand the sensitivity of studied input variables on the joints quality. The outcome of the present investigation clearly indicates that the tilt angle and tool hardness notably affects the performance parameters of the FSWed joints. The paper suggests that 1°−3° tilt angle and 40–50 HRC tool hardness produces sound quality joints. The present work dredges a novel look on FSWed Al-Mg4.2 joints by dint of relating the macrostructure, microstructure and fractographs with the plasticized material movement in the process.

Enhancing UAV–SfM 3D Model Accuracy in High-Relief Landscapes by Incorporating Oblique Images

Complex landscapes with high topographic relief and intricate geometry present challenges for complete and accurate mapping of both lateral (x, y) and vertical (z) detail without deformation. Although small uninhabited/unmanned aerial vehicles (UAVs) paired with structure-from-motion (SfM) image processing has recently emerged as a popular solution for a range of mapping applications, common image acquisition and processing strategies can result in surface deformation along steep slopes within complex terrain. Incorporation of oblique (off-nadir) images into the UAV–SfM workflow has been shown to reduce systematic errors within resulting models, but there has been no consensus or documentation substantiating use of particular imaging angles. To address these limitations, we examined UAV–SfM models produced from image sets collected with various imaging angles (0–35°) within a high-relief ‘badland’ landscape and compared resulting surfaces with a reference dataset from a terrestrial laser scanner (TLS). More than 150 UAV–SfM scenarios were quantitatively evaluated to assess the effects of camera tilt angle, overlap, and imaging configuration on the precision and accuracy of the reconstructed terrain. Results indicate that imaging angle has a profound impact on accuracy and precision for data acquisition with a single camera angle in topographically complex scenes. Results also confirm previous findings that supplementing nadir image blocks with oblique images in the UAV–SfM workflow consistently improves spatial accuracy and precision and reduces data gaps and systematic errors in the final point cloud. Subtle differences among various oblique camera angles and imaging patterns suggest that higher overlap and higher oblique camera angles (20–35°) increased precision and accuracy by nearly 50% relative to nadir-only image blocks. We conclude by presenting four recommendations for incorporating oblique images and adapting flight parameters to enhance 3D mapping applications with UAV–SfM in high-relief terrain.