Applied Mechanics and Materials Vol. 394

Abstract: Recently£¬research interests of micro-power generation devices which are based on micro-combustion process have been stimulated by the persistent breakthrough of MEMS techniques. A new type micro-heat recirculating combustor was presented in this paper, and the computation model for premixed methane-air was established which adopting a skeletal reaction mechanism. Combustion characteristics both in heat recirculating combustor and single-channel combustor are analyzed which containing the flame shape, location and temperature at the same simulation conditions. It is found that not only the flame location can be better fixed by heat recirculation measure, but although the flame temperature can be raised for some degrees when compared to the single channel combustor. These results provide some useful information for the design of micro-scale combustors.

Abstract: Throught translation and rotation method of coordinate axis, a problem of the dynamic thermal stress distribution on the two-dimensional section of a flow channel occupied filling medium was studied theoretically. A general analytical solution with related computional process was described in detailed. As an illustration sample, some numberical results are shown in the figure about the dynamical thermal stress distribution on the section of an elliptic flow channel occupied filling medium.

Abstract: To bring a new technological revolution, CNC technology and machines give the birth of a new era of control and production. The rapid development of CNC has considerably advanced the precision and ultra-precision machining technology to improve a new level and great attention. From error prevention and compensation, researches of the CNC machines precision at home and abroad were introduced. Key reasons for error compensation hardly use in the domestic widely were pointed out. Finally, the necessity and main contents of error compensation technology were presented according to the actual situation of enterprises.

Abstract: The main objective of this work was investigate the effect of ball milling on microcrystalline cellulose (MCC) structure. FTIR results shows there are no obvious different in the function groups of between neat and ball milling MCC. Both FTIR and WAXD analysis indicate that the crystalline of MCC samples are change with the ball milling time. The WAXD results also show MCC change from typical cellulose IV to amorphous state when ball milled for 6h, and after 30h the characteristic shape ball milling transformed into cellulose II.

Abstract: Chatter is a self-excited and violent form of vibration which is almost unavoidable in all machining processes. It affects surface roughness, machining accuracy, cutting tool and machine tool life, metal removal rate; and consequently operation cost. This research work focuses on investigation of the influence of the cutting parameters on chatter and implementation of a method based on application of permanent magnet for controlling chatter during turning of stainless steel AISI 304 using coated carbide tool. For this purpose, a powerful permanent bar magnet (of strength 1250-1350 Gauss) was placed inside a specially developed fixture mounted on the lathe machine carriage, to apply magnetic field to the base of the tool holder in the Z direction. The effectiveness of the application of the magnet on chatter suppression was measured in terms of reduction of amplitude of chatter compared to conventional turning. To achieve this, a small central composite design (CCD) of the Response Surface Methodology (RSM) with five levels and an alpha value of 1.4142, was used in the design of the experiments (DoE). Design-Expert 6.0 software was utilized in the model development process. Vibration monitoring was done using an online vibration monitoring system. FFT analysis of the recorded vibration signals was conducted using DASYLab software to evaluate the peak chatter amplitudes and their corresponding excited frequencies. The acceleration amplitude was found to be reduced by a maximum of 73.43% and an average of 31.58% due to the effect of damping on the resonant amplitude offered by the magnetic field created by the permanent magnet.

Abstract: Chatter, the self-excited and violent oscillatory motion between the tool and the work-piece, is detrimental to all machining operations, especially turning. It can lead to poor surface topography, reduced productivity, excessive tool wear, and damaged machine-tool components. Several theories have been introduced to explain chatter, but their predictions have not always been reliable. Therefore, chatter avoidance has relied on inefficient techniques like limiting material removal rates or expensive setups such as actuators and ultrasonic vibration damping systems. However, a deeper investigation into chatter formation reveals that chip morphology and segmentation play a significant role during incidence of machining chatter. The novel Resonance theory of chatter combines the concept of mode coupling of the machining setup and serrated chip formation, to explain the incidence of chatter. To validate the postulates of this theory, models for chip serration frequency are essential. At the same time, a reliable and economical chatter control method is required. To this end, the current research work developed an empirical mathematical model of chip serration frequency in turning of stainless steel AISI 304 using Response Surface Methodology (RSM). Also, it investigated the influence of damping provided by magnetic field from a permanent magnet. The developed chip serration model shows good agreement with experimental data.

Abstract: In this research, respond surface methodology (RSM) model was developed for the investigation and prediction in order to study the effect of cutting parameters and chip serration frequency during machining stainless steel AISI 304. The model can be used for analysis and prediction for complex relationship between cutting parameters and chip serration frequency on metal cutting process. Tin coated carbide insert is used with 120mm tool overhang to investigate the process. Permanent magnet with the 4500 Gauss power is compared in this experiment with the natural frequency to obtain the required data during machining. Chatter is found to appear as a resonance phenomenon when the frequency of chip serration is equal to or integer multiple of the prominent natural frequency/frequencies of the system component (s). Hence, it is important to study the chip serration frequency. At lower cutting speeds the chip is often discontinuous, while it becomes serrated as the cutting speed is increased. It has been identified that the chip formation process at higher speeds also has a discrete nature, associated with the periodic shearing process of the chip. In this paper a statistical technique is proposed to predict the frequency of chip serration as a function of cutting parameters in turning of stainless steel AISI 304 using Response Surface Methodology (RSM). 95% confident level was predicted using analysis of variance (ANOVA).

Abstract: nformation exchange and sharing are difficult in manufacturing process for manufacturing enterprises, especially for aircraft manufacturing enterprises, which have complex product to fabricate and mass information to handle. To solve this problem, a Single Enterprise BOM (SEBOM) based Aircraft Manufacturing Process Management System (AMPMS) is promoted to support the whole process of aircraft manufacturing, based on the analysis of aircraft manufacturing process and the process of data flowing. In AMPMS, in order to satisfy the information requirement, a SEBOM is established by unifying various BOM data. A unified SEBOM management platform is established to managing distributed and heterogeneous SEBOM data. Furthermore, the key technologies including BOM data mapping and BOM data agent management are discussed in detail. The validity and feasibility of AMPMS system are verified by developing a prototype system.

Abstract: The basic hypothesis of this article focuses on the study changes in the tool wear during drilling of stainless steels ELC X04Cr18Ni9Ti. The problem of drilling holes with diameter D=2 to 8 mm resides in the fact that 20 to 30% of these holes do not comply with prescribed requested requirements. This article presents the results of experiments focusing on the study of the damage process in helical drills with diameter d=8.0 mm when drilling into austenitic stainless steel ELC X04Cr18Ni9Ti. This study also includes an analysis of accompanying phenomena in the cutting zone by measuring some selected parameters.

Abstract: We developed an optical module for distinguishing true and fake cracks in LCD and OLED glass board conveyer. We used a pulse modulated infrared laser to improve the functionality of distinguishing true and fake cracks formed at the edges of glass board. The conventional optical detection algorism sensing real cracks modified to reduce any misinformation of fake crack for true crack. We discussed the optimum operational conditions as functions of pulse modulation frequency and wavelength of the laser, transport speed of glass board, spot size and working distance of a focused laser beam.