Heavy Grinding Research Articles

Surface morphology and chemical composition analysis of titanium dental implants using SEM and EDX.

The chemical content and surface morphology of titanium implants have a greater impact on the osseointegration characteristic of dental implants. Therefore this study was done to examine the surface morphology and chemical composition of commercially available titanium dental implants. (BioLine Dental Implants Series-single piece (A) and spiral implants (B)). The chemical composition was determined by the Energy Dispersive X-ray Spectroscopy (EDX) method and the surface morphology was performed by Scanning Electron Microscopy (SEM) method. The results for chemical composition of titanium implants using EDX method revealed that titanium (Ti) constitutes the major surface components on the plain and top land area of the single piece compressive implants which is 89.71 weight% and 71.55 weight % respectively. Iron (Fe)-66.60 weight % is considered as major element along with chromium (Cr)-18.34 weight %on the plain area of spiral implants and O (19.90 weight %) and Al (12.43 weight %) on the top land area of spiral implants. The surface morphology and impact of the manufacturing process on the implant surface using SEM method revealed that the similar surface irregularities with diameter ranging from 10 µm to 20 µm on the side view of the top land area and diameter of 10 µm on the side view of plain area for both the samples. Sample A showed some amorphous structures with grainy marks on the apical view whereas Sample B showed heavy grinding and shear marks on the apical view at diameter ranging from 10 µm to 20µm.

Detection methods and bearing failure characteristics analysis related to grinding burns

Grinding burn is one of the bearing failure causes for components. In order to quickly confirm that grinding burn is the cause of bearing failure, detection methods for the grinding burns and characteristics of bearing failure caused by grinding burns have been studied in this paper. The results show that cold acid pickling examination, microhardness test and Barkhausen noise analysis can be used in the detection of heavy grinding burns but have several disadvantages to hinder their application on the detection of slight grinding burns. A grinding burn detection procedure is recommended for the analysis of bearing failure induced by grinding burn. It has been found that the modes of bearing failure induced by grinding burns were contact fatigue spalling developed from the contact fatigue crack, the propagation mechanism of the contact fatigue crack was obtained. And the unique phenomenon of fracture or fragmentation with cracks distributed in the origin or surrounding the spalling pit of the grinding burn layer was also obtained. Based on the above results the future work on detection methods and influence on bearing failure mechanism and life of grinding burn are proposed.

Fabrication of PCD face grinding wheel with positive rake angle by femtosecond laser and its performance evaluation in cemented carbide grinding

Super-hard abrasive grinding is considered to be the main approach to realize precision and ultra-precision machining of difficult-to-machine materials such as cemented carbide, engineering ceramics, titanium alloys and superalloy materials encountered. However, heavy grinding force, high grinding temperature and poor surface integrity are prone to be encountered in conventional negative rake angle grinding of difficult-to-machine materials. In response to these problems, a novel concept of positive rake angle grinding is first proposed and an abrasive grain regularly arranged binder-less polycrystalline diamond face grinding wheel with positive rake angle has been designed and fabricated by femtosecond laser ablation. To evaluate the grinding performance of the face grinding wheel with positive rake angle, grinding experiments of YG8 cemented carbide are conducted and compared with the traditional electroplated diamond grinding tool with equivalent abrasive grain dimension and distribution. The results show that compared with the conventional negative rake angle grinding, the normal and tangential forces in positive rake angle face grinding are reduced by 30.3 % ∼ 36.4 % and 21.1 % ∼ 29.3 %, respectively, and the ratio of normal to tangential force is reduced by 12.6 % ∼ 20.3 %. The surface roughness and average depth of subsurface metamorphic layer are also significantly smaller. The laser fabricated polycrystalline diamond face grinding wheel also has better wear resistance in the grinding of cemented carbide. Therefore, it can be concluded that better ground surface quality is obtained by the novel grinding wheel with positive rake angle. The innovative grinding method can fill the research gap on the grinding mechanism of positive rake angle grinding and further enrich the grinding theory of difficult-to-machine materials.

Highly emissive D-A-π-D type aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE)-active benzothiadiazole derivatives with contrasting mechanofluorochromic features

Mechanochromic luminophors with strong solid-state emission are promising candidates for high-contrast mechanochromic luminescence materials. Meanwhile, mechanically responsive luminogenic molecules with tricolor switching are highly desirable but are seldom reported. In this work, three anthracene-based donor–acceptor-π-donor (D-A-π-D) type benzothiadiazole derivatives were designed and synthesized. These luminogens showed remarkable aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) effect. Furthermore, these luminogens exhibited bright and different solid state fluorescence involving yellow-green, yellow and orange colors, and the fluorescence of their solids could be effectively regulated by mechanical grinding. For luminogen 1, its solid displayed reversible two-color mechanofluorochromic property. As for luminogens 2 and 3, their solids displayed fluorescent colors change from yellow to yellow-green upon slight grinding, and the yellow-green light-emitting solids were converted into orange fluorescent solids after heavy grinding, demonstrating interesting three-color mechanofluorochromism features.

Boosting Room Temperature Phosphorescence Performance by Alkyl Modification for Intravital Orthotopic Lung Tumor Imaging.

Pure organic persistent room temperature phosphorescence (RTP) materials have attracted wide attention owing to their great potential in various applications, particularly in bioimaging. However, it is still a challenge to manufacture organic RTP materials possessing quite high efficiency and long lifetime, owing to the high requirements for triplet excitons. In this study, a series of keto derivatives with efficient RTP in crystals are developed through the regulation of molecular aggregation states by simple alkyl groups, resulting in impressive luminescence performance with a longer lifetime and higher efficiency of up to 868ms and 51.59%, respectively. All the alkyl-substituted derivatives exhibit bright RTP intensities after heavy grinding with a pestle, indicating their robust RTP features, which are suitable for many fields. Encouraged by the excellent RTP performance of these luminogens in the crystalline state, successful orthotopic lung tumor imaging with a high signal-to-background ratio (SBR) of 65 is demonstrated in this study to provide the promise of pure organic RTP materials for disease diagnosis, which hold the advantages of low autofluorescence interference and high signal-to-background ratio.

Effects of Different Types of Grinding Fluids on Grinding Force with a Semi-Empirical Based Model

In present paper, a semi-empirical grinding force model is developed combined with the achievements of previous researchers by composing effects of normal and tangential grinding forces in two main parts respectively: cutting force and sliding force. Final equations for the total normal and tangential force components is established. This model is used to predict the total normal and tangential force in the surface grinding. These force components were expressed in terms of the grinding process parameters. There are four unknown coefficients in each equation which can be determined by experiment results at specific conditions with the variations of grinding process parameters. An equation for sliding force is established with the effect of specific sliding energy in terms of the experimental parameters. The average contact pressure and friction coefficient are taken into account. Four different water-based grinding fluids were tested for different specific grinding conditions. Low viscosity grinding fluid can have better performance than the high viscosity one due to the higher useful flow in the grinding contact area. The calculated normal and tangential grinding results are compared with the experimental ones. The verifications show that deviations can be affected by the performance of the fluid at heavy grinding conditions due to the sliding friction inside of rolling friction. To have a better agreement with experiment data. Shallow grinding condition is chosen to obtain the modified model.

Study on Heavy CNC Belt Grinding Technology of High Precision Controllable Pitch Propeller

A high-precision grinding method is presented to the marine controllable pitch propeller. Developed the four-axis simultaneous grinding system based on the abrasive belt grinding principle, and studied the key technologies of the grinder, such as the heavy-duty belt grinding head, the controllable pitch propeller grinding CNC programming software, etc. And on these bases, we have done the four-axis simultaneous heavy belt grinding test verification on the surface of the controllable pitch propeller blade with the grinder, providing a reference to determine the reasonable marine propeller belt grinding process parameters.

Effects of a power-focussed resistance training intervention on backward grinding performance in America's Cup sailing

This study determined whether backward grinding performance in America's Cup sailing could be improved using a training intervention to increase power capability in the upper-body pull movement. Fourteen elite male sailors (34.9 ± 5.9 years; 98.1 ± 14.4 kg; 186.6 ± 7.7 cm) were allocated into experimental (speed-focussed) and control groups. Grinding performance was assessed using a grinding ergometer and an instrumented Smith machine measured force, velocity and power during the bench pull exercise. Conventional training produced significant improvements in bench pull 1 RM (5.2 ± 4.0%; p = 0.016) and maximum force production (5.4 ± 4.0%; p = 0.014). Speed-focussed training improved maximum power (7.8 ± 4.9%; p = 0.009), power at 1RM (10.3 ± 8.9%; p = 0.019) and maximum velocity (8.4 ± 2.6%; p = 0.0002). Backward grinding performance showed greater improvements in the experimental group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding. Changes in maximum power output and power at 1 RM had large correlations (r = 0.56–0.61) with changes in both moderate and heavy load grinding performance. Time to peak force had the strongest relationship, explaining 70% of the change in heavy load grinding performance. Although the performance benefit was not entirely clear the likelihood of a detrimental effect was low ( < 5%) and therefore implementation could be recommended.

Heavy Grinding and High Efficiency Grinding Technology

Heavy Grinding and High Efficiency Grinding Technology

Study on the friction coefficient in grinding

The friction between the abrasive grains and workpiece is a crutial factor determining the main grinding output. Few studies have been carried out investigating the values of the friction coefficient in grinding, due to the difficulty of direct measurement. In this paper, a mathematical model of the friction coefficient in grinding has been established with the aid of a new grinding parameter C ge. Heavy grinding with different wheels and also single-grit grinding tests have been conducted for various work materials. The friction coefficients under different grinding conditions have been obtained using the model and the experimental results. The effects of grinding speed, wheel and work material on the friction coefficient have been discussed.

Wear mechanism of metal bond diamond wheels trued by wire electrical discharge machining

The stereographic scanning electron microscopy (SEM) imaging was used to investigate the wear mechanism in wire electrical discharge machining (EDM) truing of metal bond diamond wheels for ceramic grinding. A piece of the grinding wheel was removed after truing and grinding to enable the examination of wheel surface and measurement of diamond protrusion heights using a SEM and stereographic imaging software. The stereographic SEM imaging method was calibrated by comparing with the profilometer measurement results. On the wheel surface after wire EDM truing and before grinding, some diamond grain protruding heights were measured in the 32 μm level. Comparing to the 54 μm average size of the diamond grain, this indicated that over half of the diamond was exposed. During the wire EDM process, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruded in the gap between the wire electrode and wheel. These protruding diamond grains with weak bond to the wheel were fractured under a light grinding condition. After heavy grinding, the diamond protrusion heights were estimated in the 5–15 μm range above the wear flat. A cavity created by grinding debris erosion wear of the wheel bond could be identified around the diamond grain.

00/02577 USEC struggles for security

Although the constant-load heavy grinding has wide application in such jobs as steel snagging, foundry deburring, turbine parts machining, etc., the grinding was not fully understood. In this study a heavy grinding test under constant load has been performed to evaluate the effect of working parameters on the grinding performance, using s specially made snag grinding machine of 40KW. The 455mm dia. different resinoid wheels were used, and a 1.0 m long steel plate of different widths was used for workpiece material. Thus, the effects of varying load, traverse speed, wheel width, workpiece width, and wheel type were studied from stand-points of metal removal rate, wheel wear, G-ratio, grinding force and surface roughness. Also, a special attention has been paid to grinding temperature. It is evident that if load is identical the metal removal rate, as well as wheel wear rate, is always the same, regardless of pressure.

Study on the transition process of diamond grain shape in stone grinding

The edge fracture of a diamond grain plays an important role in heavy grinding such as stone grinding, in which the self-dressing action of the diamond grain keep up the edge sharpness and the stock removal. In order to analyze the variation of the edge shape distribution of a diamond grain during grinding, a new analysis method applying the theory of the Marcov Process is proposed. The results are summarized as follows: (i) the diamond grains have large probabilities of transition to a sharp edge and small fracture onset probabilities, hence a high cutting ability is maintained in steady state; (ii) the disappearance onset probabilities of diamond grains don't depend on the edge shape; and (iii) these probabilities made it possible to evaluate transition process of the shapes of diamond grains.

An experimental investigation of the strengths of individual brown corundum abrasive grains

The fracture characteristics of individual abrasive grains such as their strengths and strength distribution are of great importance in grinding process since the shapes of broken abrasive grains which fracture during dressing and grinding heavily influence the surface topography of a grinding wheel. In heavy grinding, the good selfdressing of the grinding wheel makes the cutting edge of abrasive grains sharp to keep the higher stock removal rate this is helpful for lowering the grinding force and the grinding temperature. On the other hand, in precision grinding the tough grains are needed to keep the fine cutting edges generated by very fine dressing. This is because the fracture fragments during grinding will damage the machined surface of the workpiece and lower its surface finish.

ファジィ推論によるベルト研削の形状精度向上

In belt grinding, the amount of heat generated throughout the grinding process is basically less compared with that of the grinding wheel. However, when heavy grinding conditions are selected for obtaining high machining efficiency, the flatness error of the belt machined surface gets considerably larger than under normal conditions because of the high level of heat generation. Therefore, for reducing this flatness error, the depth of cut of the abrasive belt calculated by fuzzy inference was applied to the workpiece surface. In order to do this, the trace curves of abrasive belt on the workpiece surface were calculated by using fuzzy inference, rules of which were decided from simple models based on the basic grinding experiments. As a result, the accuracy of machined surfaces were improved significantly, and the propriety of applying this method for belt grinding was confirmed.

In-Process Measurements of Progressive Variation of Grinding Characteristics in Constant-Load Heavy Grinding

Constant-load heavy grinding was performed on 304 stainless steel with three different alumina wheel types. The variation of grinding characteristics such as removal rate and tangential force with the progress of grinding has been studied using in-process measuring methods. It was obvious that removal rate, wheel rate and tangential force changed remarkably with grinding time, and there are close correlations each other. Wear flat area of abrasive grains were also measured. The variations of grinding characteristics have been explained well with the progressive wear and the generation of self-sharpening.

特集 最近の高能率研削・重研削技術 高硬度鋳鉄ロールの重研削加工

特集 最近の高能率研削・重研削技術 高硬度鋳鉄ロールの重研削加工

特集 最近の高能率研削・重研削技術 高能率研削用ビトリファイドＣＢＮホイールのドレッシング条件と研削性能

特集 最近の高能率研削・重研削技術 高能率研削用ビトリファイドＣＢＮホイールのドレッシング条件と研削性能

特集 最近の高能率研削・重研削技術 高能率研削加工のシミュレーション

特集 最近の高能率研削・重研削技術 高能率研削加工のシミュレーション

特集 最近の高能率研削・重研削技術 最近の立軸平面重研削技術

特集 最近の高能率研削・重研削技術 最近の立軸平面重研削技術