• 한국세라믹학회지
• /
• 제45권1호
• /
• pp.75-81
• /
• 2008

In this study, machining characteristics of AIN-hBN composites were evaluated in end-milling process. As a first step, AIN-hBN composite specimens with various hBN contents were prepared using hot press method. Material properties of the composites, such as relative density, Young's modulus and fracture toughness, were measured and compared. Then, a series of end-milling experinients were performed under various cutting conditions by changing cutting speed, depth-of-cut and feed rate. Cutting force variations were measured using a tool dynamometer during the cutting experiments. Machined surfaces of the specimens were observed using SEM and a surface pro filer to investigate the surface integrity changes. The cutting force decreased with an increases of hBN content. The cutting process was almost impossible for monolithic AIN, owing to severe chipping. In contrast, at high content of hBN, surface damage and chipping decreased, and better surface roughness can be obtained.

• 한국환경과학회지
• /
• 제23권6호
• /
• pp.1075-1083
• /
• 2014

The objective of this study was to evaluate the effect of cutting types on microclimate and growth characteristics of afforested tree in Quercus acutissima stand after different types of cutting. The difference in temperature reaching $5.2^{\circ}C$ was shown in between clear cutting and selective cutting treatments. On July and August days with temperatures more than $35^{\circ}C$ often appeared in clear cutting stand. The values of VPD in July and August were higher than those in other months. Maximum VPD of 3.99 kPa was shown in clear cutting stand on May 23 as a prolonged rainless days appeared. However, VPD in selective cutting stand always stayed under 3.0 kPa throughout growing season. A higher intensity was shown in clear cutting and strip clear cutting stands, reaching to more than $1,600{\mu}mol\;m^{-2}s^{-1}$ at midday on early August, while that in selective cutting stand stayed about 1,500. In relative growth rate selective cutting stand showed a significantly higher relative growth rate in plant height than those in other cutting stands (p<0.05). The number of leaf in current-year branches significantly increased in selective cutting stand, whereas no increase was shown in clear cutting and strip clear cutting stands (p<0.05). In addition, relative elongation rate of current year branch also showed higher values in selective cutting stand compared with that in strip clear cutting stand (p<0.05). However, leaf mass per unit area (LMA) was higher in order of strip clear cutting, clear cutting, and selective cutting stands. From these results it is concluded that environmental conditions in clear cutting and strip clear cutting stands during growing season are more stressful to afforested tree species, resulting in lower relative growth in plant height, elongation of current-year branches, and leaf number per branch compared with those in selective cutting stand. Consequently, more data must be accumulated in the field to find out best cutting type in plantation considering the adaptational characteristic of each tree species varies with species and life span of tree is long.

• 한국공작기계학회논문집
• /
• 제15권1호
• /
• pp.32-38
• /
• 2006

The magnetic fluid polishing technique can polish the tool of complex shape, because the polishing method which polishes as compress the workpiece by the magnetism abrasives to arrange to the linear according to the line of magnetic force. Therefore, we producted the magnetic fluid polishing device in order that mirror like finishing processes the tool surface. In order to a polishing condition selection, polishing characteristic was estimated by polishing conditions which are magnetic flux density, polishing speed, grain size, magnetic fluid. The tool was polished to the selected polishing condition. The result to evaluate the polished tool's performance with the cutting force and tool wear, the polished tool's performance was improved compared with the tool not to polish.

• 한국정밀공학회지
• /
• 제23권10호
• /
• pp.44-51
• /
• 2006

According to global trend of the expanding need of high-quality automobiles, the usage of small precise worm consisting of gearing part for motors to actuate convenience modules has increased rapidly. Precision of those worms has very sensitive characteristic to motor performance and noise. Forming process has been generally used to manufacture worms because of its mass productivity. However, it has problems such as deformation due to residual stress and wear of dies. Planetary milling and side milling are among alternatives using cutting tools. To overcome those problems the two machining methods have some contrast features in the sense of tool numbers and cutting mechanism. In this paper, machinability of both methods was compared in terms of cutting force, precision and cycle time.

• International Journal of Precision Engineering and Manufacturing
• /
• 제8권4호
• /
• pp.10-15
• /
• 2007

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system, Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd:YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi's quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from single quality to multiple quality optimization.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.1064-1067
• /
• 2001

Micro drilling is used in the production of fuel injection nozzle, watch, camera, air bearing and pinted circuit boards(PCB) are demanded for high precision. Recently industries of precision production require more small hole, high aspect ratio and high speed working for micro deep hole drilling. But the undesirable characteristics of micro drilling is the small signal to noise ratios, wandering motion of drill, high aspect ratio and the increase of cutting force as cutting depth increase. So in this paper to obtain the optimization of cutting condition a study on the characteristics of micro deep hole drilling used Tool dynamometer is proposed.

• 한국생산제조학회지
• /
• 제21권5호
• /
• pp.784-789
• /
• 2012

Ultrasonic Cutting which uses a tuned blade resonant in a longitudinal mode, has been used to cut a range of materials from confectionery, baked products and frozen foods, to wood, bone, foams and composites. The Blade design typically uses finite element analysis, and it could be predicted vibration mode, gain and amplitude uniformity of the blade tip at resonant frequency. In this paper, FEA used to predict the vibration characteristic of the blade, and then the results were verified by analysis system of resonant frequency using the processed blade. The crack of the blade which is predicted from FEA was compared with the crack occurred by cutting experiment of rubber materials using the processed blade.

• 한국기계가공학회지
• /
• 제16권4호
• /
• pp.62-68
• /
• 2017

Since the aircraft parts industry is a high-value-added industry, mass production order production, and the hundreds of thousands. Therefore, parts produced However, since these parts require high reliability and stability, a high degree of precision is required. In Korea, there on the roughness of the machined surface in cutting process. However, research on the surface roughness characteristic obtained by which is widely used for aircraft parts is still insufficient in Korea. The purpose of this study is to investigate the effect of turning tool rotation speed and X axis feed rate on the surface roughness of cutting tools in CNC lathes during cutting of aluminum alloy 7075.

• 한국정밀공학회지
• /
• 제15권10호
• /
• pp.128-139
• /
• 1998

In this paper, a finite element method for predicting the temperature and stress distributions in micro-machining is presented. The work material is oxygen-free-high-conductivity copper(OFHC copper) and its flow stress is taken as a function of strain, strain rate and temperature in order to reflect realistic behavior in machining process. From the simulation, a lot of information on the micro-machining process can be obtained; cutting force, cutting temperature, chip shape, distributions of temperature and stress, etc. The calculated cutting force was found to agree with the experiment result with the consideration of friction characteristics on chip-tool contact region. Because of considering the tool edge radius, this cutting model using the finite element method can analyze the micro-machining with the very small depth of cut, almost the same size of tool edge radius, and can observe the 'size effect' characteristic. Also the effects of temperature and friction on micro-machining were investigated.

• 한국기계가공학회지
• /
• 제10권6호
• /
• pp.27-32
• /
• 2011

In recently, it is demanded development of manufacturing techniques for machining of various mechanical parts. Therefore the development of turning is one of the important manufacturing techniques. In this study, an experimental shape in tapered groove turning was suggested, and the turning process was investigated by analyzing cutting speed, feed rate, tapered angle, depth of cut. The surface roughness and cutting force change in the workpiece was measured. From the results, the optimum machining conditions are obtained by design of experiments.