The International Journal of Advanced Manufacturing Technology

Junyong, Xia; Youmin, Hu; Bo, Wu; Tielin, Shi

doi: 10.1007/s00170-008-1723-ypmid: N/A

Empirical modeling of machine tools on thermal error has been widely researched, which can compensate for thermal error to some extent but not suitable for thermal dynamic error produced by dynamics heat sources. Ball screw is the main member of feed system of machine tool. On the basis of the theory of heat transfer, thermoelastic phenomenon of unidimensional heat transferring of the ball screw influenced by changeable heat sources is analyzed. A method to establish a dynamics characteristics model of thermal deformation of the ball screw based on least square system identification theory is put forward. Through simulation data, correctness and validity of modeling approach is proven. By this method, modeling of thermal error of X-axis of feed system of DM4600 vertical miller is established which has good identification effect.

Tang, Yinggan; Zhang, Xiumei; Li, Xiaoli; Guan, Xinping

doi: 10.1007/s00170-008-1720-1pmid: N/A

X-ray-based inspection technique is well applied to identification and evaluation of internal defects in castings, such as cracks, porosities, and foreign inclusions. Combining X-ray inspection with digital image processing and automatic image assessment is now the preferred approach for the continuous inspection of castings. However, in practical application, the quality of the X-ray image is poor. Under the circumstances, many classical thresholding methods usually cannot obtain ideal segmentation results. In this paper, we propose an effective segmentation method for the detection of typical internal defects in castings derived for an X-ray inspection system. The proposed method takes advantage of the fuzzy set theory and bound histogram and presents fuzzy exponential entropy for object and background according to the fuzzy sets and gray-level distribution of the image. The ideal threshold is obtained by maximizing the fuzzy exponential entropy associated with the distribution of the object and background classes in the bound histogram. Experimental results indicate that the proposed method is a powerful method to analyze images derived from X-ray inspection for automatically detecting typical internal defects in castings.

Pluta, Zdzislaw; Hryniewicz, Tadeusz

doi: 10.1007/s00170-008-1722-zpmid: N/A

In the paper, the initial cutting conditions by an abrasive grain fixed flexibly have been described. These conditions have been determined by incision angle at the beginning of machining zone as well as the occurring phenomena resulting from a mechanical cooperation of abrasive grain with machined material. It has been revealed that the incision angle may affect the direction of changes of roughness of the smoothed surface, making it possible to forecast this output magnitude. The dependences of this angle on the machining parameters have been derived for the conditions of forward and backward machining. They make it possible to choose these parameters as a rationale for the smoothing effects of finishing. The presented considerations and the conclusions coming out of them have been verified by experiment, and some exemplary proofs of these cognitive actions are described in the paper.

Altunpak, Yahya; Akbulut, Hatem

doi: 10.1007/s00170-008-1724-xpmid: N/A

In this paper, the surface integrity (Ra and Rmax) has been investigated with various aging heat treatment and machinability parameters in an aluminum-silicon based (LM–13) MMCs, produced by infiltration method. The composites have been subjected to heat treatment at different temperatures and times which was discussed in detail in an earlier publication (Altunpak and Akbulut, Teknoloji 8(4):331–339, 2005). In the milling of alumina short fiber reinforced LM–13 aluminum alloys, the surface integrity decreased when feed rate increased. It was found that increasing amount of fiber reinforcement and solutionizing temperature has a significant effect on the surface integrity and sub-surface damage of the materials. Increasing the solutionizing temperature and fiber reinforcement produced higher Ra and Rmax values. Microhardness measurement indicated that the sub-surface damage and the hardness increased by increasing the feed rate and fiber content.

Li-qun, Zhou; Yu-ping, Li; Zhi-gang, Chen

doi: 10.1007/s00170-008-1721-0pmid: N/A

An implicit finite-element code is employed to study the internal grinding process of carbon steel Q235 cirque, and its temperature field and thermal deformation are obtained. The method of thermal load calculation is proposed, a 2D finite element model is developed, and analysis steps are introduced. The diameter of the cirque is 150 mm and that of the inner hole is 56.24 mm. By adopting the clamps of surface locating and three-jaw chuck, it is found that, during the grinding process, the workpiece is in an elastic–plastic state, far from thermal-softening state. The thermal deformation of the ground cirque is basically symmetrical in a diamond shape, but the deformations of the inner circle and the outer circle are not uniform, and the inner circle thermal deformation may be negative or positive. Such different thermal displacements will produce shape error and dimension error in the inner hole. Through comparison of the two clamping modes, it is found that the precision of the surface locating is better than the three-jaw chuck. The symmetrical property of the thermal deformation of the cirque and the comparison of two clamping modes indicate that the computation is valid.

Yanyan, Yan; Bo, Zhao; Junli, Liu

doi: 10.1007/s00170-008-1732-xpmid: N/A

Based on the model of a grain cutting trace in workpiece during two-dimensional ultrasonic assisted grinding, microscopic cutting trace of the grain is analyzed, and the grain cutting trace of spiral line is defined, the motion model of the contact between single abrasive particle and workpiece in a vibration period is established during two-dimensional ultrasonic assisted grinding, and the results show that the grain motion mode of two-dimensional ultrasonic assisted grinding is similar to the rotary cutting mode. Grinding experiments on surface quality of nano-ZrO2 ceramic are carried out using diamond grinding in different condition, both with and without ultrasonic vibration. Experimental results show that the surface quality after two-dimensional ultrasonic assisted grinding is superior to that after diamond grinding, and it is easier for two-dimensional ultrasonic assisted grinding as material removal mechanism employs ductile grinding mode.

Sakthivel, T.; Sengar, G.; Mukhopadhyay, J.

doi: 10.1007/s00170-008-1727-7pmid: N/A

The weld properties remain an area of uncertainty with respect to the effect of different speeds of friction stir welding (FSW). For this purpose, hardened steel tool of FSW was used, which consists of the shoulder and pin. The shoulder of the tool not only provides additional heat generated by friction but also prevents plasticized material to escape. In the present investigation, aluminum welds were made at various welding speed using the FSW technique. The welds were characterized for mechanical properties and microstructural investigation. It is observed that good correlation exists between the mechanical properties and welding speeds. The best mechanical properties were obtained at lower welding speed.

Demir, Eralp

doi: 10.1007/s00170-008-1738-4pmid: N/A

The purpose of this study is to explain the experimentally observed differences in the machined surface quality and cutting forces of single crystals with the change in cutting direction and/or cutting plane with respect to the crystal orientation. Taylor-based perfectly plastic model is used to relate the crystallographic orientation to the cutting forces and the specific energy considering friction between the chip and the rake face of the tool. The model is valid for the depths of cuts that are greater than the limit below which size scale effects are observed (∼ 1μm). The periodic force and shear angle variations in the microtome experiments of Black et al. (Von Turkovich and Black, Trans Am Soc Mech Eng 92:130–134, 1970; Black, J Eng Ind 101:403–415, 1979; Cohen and Black, 1984) and the change in force and surface quality with a change in turning axis of a single crystal copper and aluminum in diamond turning experiments of To, Lee, and Chan (To et al., J Mater Process Technol 63:157–162, 1997) can be explained with the results of the model.

Seo, P.; Kang, C.; Lee, S.

doi: 10.1007/s00170-008-1730-zpmid: N/A

In this paper, the reheating process and mechanical properties of thixo die cast A356 alloy, using electromagnetic stirring (EMS) and extrusion before thixo die casting, were discussed. The EMS is used mainly to manufacture raw materials with a globular microstructure. If relevant reheating is carried out, products with excellent mechanical properties can be manufactured by EMS. Contrarily, extruded material has a fine dendrite microstructure and has rarely been assumed to be suitable for the thixo die casting process. This study demonstrated that the microstructure of extruded material could be globularized and applied to the thixo die casting process only with the relevant reheating parameters. This applicability was estimated through image analysis obtaining the solid fraction, the mean equivalent diameter, and roundness under various reheating conditions. After thixo die casting experiments using three materials, which were EMS, low-extrusion material (LER), and high-extrusion ratio materials (HER), mechanical properties were comparatively analyzed. EMS and HER materials show better mechanical properties than LER.

Tsai, Feng-Che; Yan, Biing-Hwa; Kuan, Chun-Yu; Hsu, Rong-Tzong; Hung, Jung-Chou

doi: 10.1007/s00170-008-1734-8pmid: N/A

This study performs experimental investigation into the application of abrasive jet polishing (AJP) to the surface finishing of electrical-discharge-machined SKD61 mold steel workpieces. The results indicate that the AJP processing conditions which optimize the surface quality of the SKD61 workpiece when polishing using #2000SiC abrasives are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm2 (0.4 MPa), a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Under these processing conditions, a polishing time of 20 min is sufficient to reduce the surface roughness from an initial value of Ra = 1.7 μm to a final value of Ra = 0.27 μm, corresponding to an improvement of 84.12%. The experimental results demonstrate that the maximum attainable improvement in the surface quality of the polished workpiece is limited by a surface-hardening effect caused by the ball-impact phenomenon and the embedment of #2000SiC fragments in the workpiece surface.