Segmented Wheel Research Articles

Enhancing useful flow of cutting fluid and thermal performance in surface grinding via segmented wheel

Cutting temperature is reported to be a serious concern while grinding aerospace materials such as titanium alloy Ti6Al4V, which is having very low thermal conductivity. Segmented wheels designed with active abrasive regions and passive non-cutting slots have been proposed as a potential solution for thermal management in the grinding zone. Reduced accumulation of heat due to intermittency in cutting and enhanced dissipation through passive slots could exhibit improved temperature control even at dry grinding conditions. As the number of segments increased, the grinding force was significantly reduced for Ti6Al4V. Under the wet cutting condition, the segmented wheel could facilitate a more effective flow of cutting fluid into the passive slots, which is referred to as useful flow. However, there was a trade-off set by the number of segments, where an eight-segmented wheel showed superior thermal performance in comparison with the 32-segmented wheel. The reasoning of the same in terms of useful flow patterns and boundary layer thickness has been attempted in this paper.

Formation characteristics of nickel-based diamond abrasive segment by selective laser melting

Selective Laser Melting (SLM) technique provides an alternative to fabricating a metal bond grinding wheel with a high porosity ratio and controllably complex geometries. In this paper, SLM is applied to making nickel-based diamond abrasive segments based on single-tracks SLM tests. The characteristics of the SLMed wheel segments are investigated through analyses on morphology, porosity, cracks, and diamond grains. Balling phenomenon of the Ni-Cr alloys, which leads to the rough surface and porosities, is observed through the surface and cross-sectional observations. The porosity ratio of the as-built abrasive segment ranges from 22.6% to 27.3%. Two types of diamond spatters, entrainment-driven and vapor-driven diamond spatters, are formed in the SLM process based on the observation by a high-speed video camera. Diamond spatters are considered the main cause of the balling phenomenon. Based on microstructure and hardness measurements, the eutectic structure and granular crystallites result in high hardness and increase the cracking susceptibility of the Ni-Cr alloys. This paper reveals the formation characteristics of the SLMed nickel-based wheel segments and the mechanism of porosity formation in the SLM process.

Simulation of intermittent grinding for Ti-6Al-4V with segmented wheel

Abstract Titanium alloy-Ti-6Al-4V, in spite of all its superior mechanical characteristics and functional acceptance, is categorized as a difficult-to-cut super alloy. Major concerns associated with conventional surface grinding of Ti-6Al-4V is its poor thermal conductivity, grinding burn, high tendency of hardening during machining as well as chemical affinity with wheel materials. Higher magnitudes of grinding force and temperature reported during conventional grinding may lead to adverse burning effects and associated concerns such as micro-cracking etc. on the ground surface. Present paper is a simulation study to showcase the capability of intermittent-segmented grinding to eliminate such concerns. A comparison of intermittent segmented cutting with conventional abrasive action in continuous mode is presented through a 3D finite element model in ABAQUS. The effectiveness of intermittent-segmented cutting to control grinding temperature well below the critical limit to avoid burning effects on Ti-6Al-6 V, with a significant reduction in grinding force is illustrated through the present simulation study.

New Adaptive Segmented Wheel for Locomotion Improvement of Field Robots on Soft Terrain

In this paper, a new adjustable segmented wheel is proposed whose platform is composed of a complex closed-loop scissor mechanism wrapped over adjustable spokes. The new platform composed of four proposed wheels is specified to avoid halting, to increase traction force and to adjust body orientation while interacting soft or composite terrains. The soil contact model (SCM), extended from Bekker’s theory is implemented to derive the wheel-soil interaction formulations. Furthermore, the Lagrange approach is used to derive the unmanned ground vehicle (UGV) dynamics including interaction forces. The best configurations of adjustable wheel are tabulated according to the terrain properties and the motion types. Finally, the proposed UGV is compared with a typical ordinary UGV to investigate traction forces and halting avoidance. Based on the simulation results and primary tests of the experimental setup, it can be inferred that this new mechanism can effectively adapt itself to different terrain conditions in order to pass the soft concave regions, climb the soft obstacles and move on the composite terrains.

High-speed high-efficient grinding of CMCs with structured grinding wheels

The implantation of ceramic matrix composites (CMCs) is limited due to their high machining costs. To overcome this problem, modified grinding wheels, one macro-structured by segmenting and another laser-structured were used. The grinding tests were carried out at different material removal rates and cutting speeds. The grinding forces, surface roughness, and induced residual stress were compared. The results showed that the wheel structuring resulted in a better performance of the grinding wheel. The grinding forces were respectively 30% and 20% lower in the case of segmented wheel and laser-structured wheel in comparison with the conventional grinding. In addition, the tensile residual stress was reduced as a negative output of the grinding process via structuring. A high-speed high-efficient grinding of CMCs without presence of surface damage was achieved by optimising the process parameters. The material removal rate could be elevated without changing the grinding forces with application of the structured wheel.

High-speed high-efficient grinding of CMCs with structured grinding wheels

The implantation of ceramic matrix composites (CMCs) is limited due to their high machining costs. To overcome this problem, modified grinding wheels, one macro-structured by segmenting and another laser-structured were used. The grinding tests were carried out at different material removal rates and cutting speeds. The grinding forces, surface roughness, and induced residual stress were compared. The results showed that the wheel structuring resulted in a better performance of the grinding wheel. The grinding forces were respectively 30% and 20% lower in the case of segmented wheel and laser-structured wheel in comparison with the conventional grinding. In addition, the tensile residual stress was reduced as a negative output of the grinding process via structuring. A high-speed high-efficient grinding of CMCs without presence of surface damage was achieved by optimising the process parameters. The material removal rate could be elevated without changing the grinding forces with application of the structured wheel.

Porous Silicon Based Rugate Filter Wheel for Multispectral Imaging Applications

Porous silicon based rugate filters are emerging as interesting functionalized optical components in Micro-Opto-Electro-Mechanical Systems due to their specific nanostructures and superior optical properties. In this work, a cost-effective approach to generate a porous silicon based rugate filter wheel containing nine filter segments in the visible wavelength range suitable for multispectral imaging systems is presented. The filter wheel segments are patterned on a silicon wafer using silicon nitride insulating masks and generated using the anodization technique. Specific characteristics of filter segments are adjusted by the current squeezing effect during the anodization through the geometrical size of the filter segments, which results in local current redistributions and consequently porous silicon formation rate and porosity modifications. A finite element model made in COMSOL Multiphysics is also presented to study redistributions of the current density and the current squeezing effect during the anodization for the proposed filter wheel. The proposed filter wheel can be miniaturized and integrated into a portable multispectral imaging system.

Особливості загострювання ножів лущильних і шпоностругальних верстатів

Розглянуто проблему загострювання ножів лущильних та шпоностругальних верстатів, яка є на підприємствах, що спеціалізуються з виготовлення струганого та лущеного шпону. Особливістю загострювання цих ножів є те, що вони мають широку задню поверхню, малі кути загострення та велику довжину. Велика зона контакту абразивного круга з поверхнею ножа призводить до утворення високих температур на поверхні ножа. Внаслідок цього змінюються початкові властивості леза, відбувається його припалювання, виникають великі завусениці, мікротріщини та інші дефекти. Наявні рекомендації щодо раціональних режимів загострення та доводіння дереворізальних інструментів, зокрема лущильних і шпоностругальних ножів, частково вирішують цю проблему, але істотно зменшують продуктивність процесу загострення. Оцінено та проаналізовано конструкції абразивних кругів, які застосовуються для загострення цих ножів. З'ясовано, що для загострення ножів з широкою задньою поверхнею потрібно удосконалювати та розробляти новий спеціальний абразивний інструмент, який повною мірою забезпечить якісне загострювання та високу продуктивність процесу. Цей інструмент не повинен потребувати значних змін у конструкції верстата для загострення дереворізальних ножів, повинен бути дешевим і надійним в експлуатації.

Umbrella Wheel: A Stair-Climbing and Obstacle-Handling Wheel Design Concept

This paper proposes a new design for stair-climbing using a wheel that can split into segments and walk up stairs or surmount other obstacles often found where humans traverse, while still being able to retain a perfectly round shape for traveling on smooth ground. Using this change of configuration, staircases with a wide range of dimensions can be covered efficiently and safely. The design, named Umbrella Wheel, can consist of as many wheel segments as desired, and as few as two. A smaller or higher number of wheel segments has advantages and disadvantages depending on the specific situation. Modeling the trajectory of the wheel when as it ascends or descends stairs is given and the results are analyzed.

The quality of workpiece surface in rough machining of materials with different hardness values by using segmented grinding wheels produced in Vietnam

Segmented grinding wheels have been developed to increase the grinding ability of abrasive grains in discontinuous machining. The cutting ability of the segmented grinding wheels is evaluated. The discontinuity coefficient η of the working surface of a segmented grinding wheel is defined as a ratio of the total length of spacings between the segments to the total circumference of the wheel. Five newly developed segmented grinding wheels with η = 10.91, 16.37, 18.19, 20.01, and 21.83% and one conventional wheel (η = 0%) were used for grinding unhardened and hardened steels as well as aluminum alloy. The results have shown that a smoother workpiece surface was obtained using segmented grinding wheels with η = 18.19% in machining the unhardened steel and with η = 20.01% in machining the aluminum alloy.

Synthesis of action variable for motor controllers of a mobile system with special wheels for movement on stairs

Summary The article presents a procedure of obtaining waveform of angular velocities for special segmented wheels required for smooth movement of a stair-climbing chassis on stairs. The waveform was determined for a specified velocity of the chassis using a dynamic contact analysis in the CAD system SolidWorks. The main part of the work was to verify whether real motors on a testing chassis are capable of producing the required angular velocity with its significant step changes. The values of angular velocities were sent to drive control units from a software control system of the chassis. The chassis was recorded during the movement on stairs on a video camera and the resulting video was then analyzed by a special single-purpose image processing algorithm, which detected key points in individual frames. Outcome of the algorithm are tables with positions and velocities of individual key points during time. Tests proved that with lower velocities it is possible to achieve very good results with the chassis moving almost steadily.

Wear of non-segmented and segmented diamond wheels in high-speed deep grinding of carbon fibre-reinforced ceramics

Carbon fibre-reinforced ceramics (CFRCs) are relatively new and promising materials for various high-tech. industrial applications due to their superior properties. However, the employment of these materials has been impeded by their high machining costs. A specially designed metal-bonded segmented diamond wheel has been developed in order to reduce the cutting forces and temperatures and enhance the MRR. Studying the wear behaviour and wear mechanisms of the segmented wheel, compared to a non-segmented wheel with the same specification, was necessary for economic assessment of the process. The investigation was conducted for a surface grinding process. The selected cutting conditions assure an acceptable range of the surface roughness and a high material removal rate. The radial wear, the G-ratio and the wear behaviour of the wheels were examined at the specified specific material removals up to 4,704 mm3/mm. Compared to the non-segmented wheel, the segmented wheel has experienced higher radial wear. However, the G-ratio can be increased considerably by the intermittent grinding process. The main wear mechanisms of the segmented wheel are the inter-crystalline grain fracture and grain pull-out, while in the case of non-segmented wheel, the grain flattening is the main wear mechanism. Furthermore, grinding forces and temperatures, which influence the wear behaviour of a wheel considerably, are significantly reduced by the intermittent grinding process. The residual stress analysis showed that the utilized grinding processes have induced just a negligible residual stress into the CFRC workpieces.

Analysis of temperature distributions in surface grinding with intermittent wheels

An analytical model was established to calculate the curve of temperature distributions in surface grinding with intermittent wheels. In order to predict the numbers of the pulses imposed on the fluctuating temperature profile, a new quantity, the dynamic number of wheel segments in the grinding zone, was defined. The temperatures at the grinding zone were measured by using a foil thermocouple. It is found that the new quantity, the dynamic number of wheel segments, can be used to accurately predict the pulses on the measured temperature curves in the grinding zone. Through matching the calculated temperature curves with the measured results, it is found that the temperature profile is greatly dependent on the wheel segment-engaging states even at identical grinding parameters. However, the wheel segment-engaging states have little influence on the values of peak and valley temperatures.

Vibration of segmented grinding wheels under an external load

Vibration of segmented grinding wheels under an external load

Surface Burn and Suppression in Grinding TC4 with Segmented CBN Cup Wheel

The study focused on surface burn of titanium alloy (TC4) in the grinding process using a novel segmented cup wheel with internal cooling structure. The threshold burn temperature was found in grinding TC4. Plastically deformed coating layers and micro-cracks were observed on ground surface by SEM (Scanning Electronic Microscopy) and depth of microstructure alterations was more than 180 microns in high temperature. Finally, a novel wheel with internal cooling structure was developed for reducing grinding temperature and suppressing surface burn.

A Note on Two Cooling Methods in Surface Grinding

This paper reviews two cooling methods for surface grinding. These include i) replacing the toxic coolant by a mixture of cold air and vegetable oil mist, and ii) minimising the use of coolant using a segmented grinding wheel system. The discussion concludes that the cold air-oil mist provides an environmentally conscious mean for surface grinding. However, due to the limit of its cooling capacity, it is more applicable for fine grinding. Using the segmented wheel system can minimise coolant consumption and can improve grindability.

Fracture Morphology of Composite CBN Wheel Segments Based on Graphite Self-Lubricating Effects

Multilayer brazed CBN wheel segments based on graphite self-lubricating has been fabricated. The bending strength of wheel segments was measured and the fracture morphology of tested segments was detected. The results show that the bending strength of segments with CBN grains decrease to a small extent from 116MPa to 97MPa with the linear increase of graphite content from 5 wt.% to 15 wt.%. Due to the poor strength and certain stress concentration by the added graphite, the fracture interface transfers from the whole CBN grains to the bonding matrix with the increasing of the graphite. In addition, the pore sizes are decreased obviously.

Suppression of Surface Burn in Grinding of Titanium Alloy TC4 Using a Self-inhaling Internal Cooling Wheel

Based on analysis of surface average temperature and burn degree, this article obtains the threshold temperature of surface burn in grinding titanium alloy with cup wheels. Meanwhile, the impact of the burn degree on the metallographic structure of workpiece surface and metallurgical phase transformations is investigated. In order to reduce the grinding temperature and improve the grinding efficiency, a self-inhaling structure cup segmented wheel is developed to generate internal cooling effect. The internal cooling technology is compared with traditional cooling conditions in the grinding experiments on TC4 (Ti-6Al-4V). The results indicate that the self-inhaling internal cooling wheel can reduce the grinding surface temperature by 30% or more, and the grinding efficiency doubles. Utilizing water-based semi-synthetic coolant, the segmented wheel with the self-inhaling structure can further reduce the grinding temperature by about 50%.

2A2-L09 雪用翼車輪4輪ビークルの開発 : サスペンションとステアリング(特殊移動ロボット)

Variably Configured Segmented Wheels (VCSW) for driving on snow can be available for snow rescue robot. However, because of many irregularities on the snow road, it is necessary to improve the performance of ground contact. Free joint mechanism is equipped with four-wheel vehicles as the suspension. In addition, another free joint is also applied to improve steering performance. All four wheels of the vehicle are controlled by speed servo systems. Effectiveness of the speed servos are tested successfully. Step climbing experiment, the vehicle surmounted high step which is 93% of wheel radius. Turning experiments to improve the steering performance show the necessity of yaw control.

Theoretical and experimental investigation of intermittent grinding of SiC with a segmented grinding wheel

The widespread replacement of metals by the advanced ceramics has been limited by the high manufacturing costs of these materials and the difficulties involved. To meet the increasing demand of advanced ceramics, the current technological constraints should be overcome. One of the main targets in grinding of these materials is increasing the machining efficiency. Utilisation of a segmented grinding wheel can reduce the grinding forces and temperatures and increase the material removal rate. Hence, an especially designed segmented wheel (T-Tool) has been developed in this study. Both theoretical and experimental results illustrate the high performance of the developed grinding wheel. The obtained results show that the application of the T-Tool wheel can increase the G-ratio and decrease the grinding forces considerably. A decrease of up to 35% of grinding forces has been achieved.