Advances in Manufacturing

Characteristics of force chains in frictional interface during abrasive flow machining based on discrete element method

Tian-Xun Xiu, Wei Wang, Kun Liu, Zhi-Yong Wang, Dao-Zhu Wei

2018, 6(4): 355-375. doi:10.1007/s40436-018-0236-7

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Abrading is a very important sub-technology of the surface treatment technology with vast applications in the industry. This study aims at analyzing the inherent laws of friction systems during abrading. In particle flow code modeling, the abrading process can be simplified to the movement of particles in a parallel-plate shear friction system. In this study, the PFC2D software is used to construct the particle flow friction system with the set of parallel plates and the model parameters according to the abrading processing equipment and processing materials, control the simulation of a single variable, and compare the output data to estimate the impact of change of parameters on the force chain. The simulation results show that the shear dilatancy can be divided into three stages:plastic strain, macroscopic failure, and granular recombination stages. The distribution and load rates of the weak force chains depend on the load, velocity, friction coefficient between granules, granular diameter, and number of granular layers. The number of granular layers and the load increase cause the direction of the force chain to be oriented with the vertical direction, and the force chains move toward the horizontal direction as the velocity increases. The increase in load does not cause the shear dilatancy stage to occur; the velocity, friction coefficient between granules, and granular diameter increase cause the shear dilatancy to occur gradually.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0236-7

Investigation into the room temperature creep-deformation of potassium dihydrogen phosphate crystals using nanoindentation

Yong Zhang, Ning Hou, Liang-Chi Zhang

2018, 6(4): 376-383. doi:10.1007/s40436-018-0234-9

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It has been a tremendous challenge to manufacture damage-free and smooth surfaces of potassium dihydrogen phosphate (KDP) crystals to meet the requirements of high-energy laser systems. The intrinsic issue is whether a KDP crystal can be plastically deformed so that the material can be removed in a ductile mode during the machining of KDP. This study investigates the room temperature creep-deformation of KDP crystals with the aid of nanoindentation. A stress analysis was carried out to identify the creep mechanism. The results showed that KDP crystals could be plastically deformed at the nanoscale. Dislocation motion is responsible for creep-deformation. Both creep rate and creep depth decrease with decrease in peak force and loading rate. Dislocation nucleation and propagation bring about pop-ins in the loaddisplacement curves during nanoindentation.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0234-9

Improved thermal resistance network model of motorized spindle system considering temperature variation of cooling system

Yang Liu, Ya-Xin Ma, Qing-Yu Meng, Xi-Cheng Xin, Shuai-Shuai Ming

2018, 6(4): 384-400. doi:10.1007/s40436-018-0239-4

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In the motorized spindle system of a computer numerical control (CNC) machine tool, internal heat sources are formed during high-speed rotation; these cause thermal errors and affect the machining accuracy. To address this problem, in this study, a thermal resistance network model of the motorized spindle system is established based on the heat transfer theory. The heat balance equations of the critical thermal nodes are established according to this model with Kirchhoff's law. Then, they are solved using the Newmark-β method to obtain the temperature of each main component, and steady thermal analysis and transient thermal analysis of the motorized spindle system are performed. In order to obtain accurate thermal characteristics of the spindle system, the thermalconduction resistance of each component and the thermalconvection resistance between the cooling system and the components of the spindle system are accurately obtained considering the effect of the heat exchanger on the temperature of the coolant in the cooling system. Simultaneously, high-precision magnetic temperature sensors are used to detect the temperature variation of the spindle in the CNC machining center at different rotational speeds. The experimental results demonstrate that the thermal resistance network model can predict the temperature field distribution in the spindle system with reasonable accuracy. In addition, the influences of the rotational speed and cooling conditions on the temperature increase of the main components of the spindle system are analyzed. Finally, a few recommendations are provided to improve the thermal performance of the spindle system under different operational conditions.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0239-4

Modeling of laser adjustment for large diameter tubes using robotic kinematic theories

Pin Li, Jun-Tong Xi

2018, 6(4): 401-408. doi:10.1007/s40436-018-0235-8

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Laser adjustment is a new technique that employs laser forming processes to align components along specific directions. To develop a laser adjustment solution with a minimal number of bends, herein, a new modeling and calculation method that uses robotic kinematic theories is introduced. A numerical example and the corresponding laser adjustment solution are presented. The simulation results suggest that a straight tube with a flange connector can be adjusted to match the corresponding connector with three bends. Finally, the simulation results were verified using experiments. The maximum deviation was approximately 0.4 mm and the deviation of the flange connector was smaller, showing that a good adjustment quality could be achieved using the specific adjustment solution.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0235-8

Hidden feature extraction for unstructured agricultural environment based on supervised kernel locally linear embedding modeling

Zhong-Hua Miao, Chen-Hui Ma, Zhi-Yuan Gao, Ming-Jun Wang, Cheng-Liang Liu

2018, 6(4): 409-418. doi:10.1007/s40436-018-0227-8

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An online hidden feature extraction algorithm is proposed for unknown and unstructured agricultural environments based on a supervised kernel locally linear embedding (SKLLE) algorithm. Firstly, an online obtaining method for scene training samples is given to obtain original feature data. Secondly, Bayesian estimation of the a posteriori probability of a cluster center is performed. Thirdly, nonlinear kernel mapping function construction is employed to map the original feature data to hyper-highdimensional kernel space. Fourthly, the automatic determination of hidden feature dimensions is performed using a local manifold learning algorithm. Then, a low-level manifold computation in hidden space is completed. Finally, long-range scene perception is realized using a 1-NN classifier. Experiments are conducted to show the effectiveness and the influence of parameter selection for the proposed algorithm. The kernel principal component analysis (KPCA), locally linear embedding (LLE), and supervised locally linear embedding (SLLE) methods are compared under the same experimental unstructured agricultural environment scene. Test results show that the proposed algorithm is more suitable for unstructured agricultural environments than other existing methods, and that the computational load is significantly reduced.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0227-8

Application of grey relational analysis based on Taguchi method for optimizing machining parameters in hard turning of high chrome cast iron

Ali Kalyon, Mustafa Günay, Dursun Özyürek

2018, 6(4): 419-429. doi:10.1007/s40436-018-0231-z

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High chrome white cast iron is particularly preferred in the production of machine parts requiring high wear resistance. Although the amount of chrome in these materials provides high wear and corrosion resistances, it makes their machinability difficult. This study presents an application of the grey relational analysis based on the Taguchi method in order to optimize chrome ratio, cutting speed, feed rate, and cutting depth for the resultant cutting force (F_R) and surface roughness (R_a) when hard turning high chrome cast iron with a cubic boron nitride (CBN) insert. The effect levels of machining parameters on F_R and R_a were examined by an analysis of variance (ANOVA). A grey relational grade (GRG) was calculated to simultaneously minimize F_R and R_a. The ANOVA results based on GRG indicated that the feed rate, followed by the cutting depth, was the main parameter and contributed to responses. Optimal levels of parameters were found when the chrome ratio, cutting speed, feed rate, and cutting depth were 12%, 100 m/min, 0.05 mm/r, and 0.1 mm, respectively, based on the multiresponse optimization results obtained by considering the maximum signal to noise (S/N) ratio of GRG. Confirmation results were verified by calculating the confidence level within the interval width.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0231-z

Flexural strength of fused filament fabricated (FFF) PLA parts on an open-source 3D printer

Shilpesh R. Rajpurohit, Harshit K. Dave

2018, 6(4): 430-441. doi:10.1007/s40436-018-0237-6

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Fused filament fabrication (FFF) has been widely used to develop prototypes as well as functional parts owing to its capability for creating parts with complex geometries in a short time without the specific requirement of tooling. The mechanical properties of parts produced by FFF exhibit 70%-80% of the mechanical properties of parts produced by injection molding. The mechanical properties of FFF-produced parts are primarily dependent on the selection of various process variables. The mechanical properties of the part can be enhanced through the proper selection of process variables. In the present experimental investigation, the effects of the process variables, viz. raster angle, layer height, and raster width on the flexural properties of FFF-printed polylactic acid (PLA) is studied. The result shows that flexural strength is primarily influenced by layer height followed by raster angle. The sample printed with 100-μm layer height and 0° raster angle exhibits a higher tensile strength. Further, the microscopic examination of the deformed specimen is performed to understand the mode of failure. Specimens printed at different raster angles show different modes of failure.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0237-6

Performance analysis of a thick copper-electroplated FDM ABS plastic rapid tool EDM electrode

Saroj Kumar Padhi, S. S. Mahapatra, Rosalin Padhi, Harish Chandra Das

2018, 6(4): 442-456. doi:10.1007/s40436-018-0238-5

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The importance of rapid tooling (RT) and additive manufacturing (AM) appears to be indispensable for boosting the process of manufacturing and expanding the horizon of production technology worldwide. This concept draws the attention of numerous scholars to arrive at a conclusive theory for the widespread utilization of RT. This study attempts to determine the viability and performance of an RT electrode in the field of electro discharge machining (EDM). The electrode prototype is made using an acrylonitrile butadiene styrene (ABS) plastic by fused deposition modeling (FDM), an AM technique, electroplated with copper of desired thickness, and used in die sinking EDM of D2 steel. The scanning electron microscope analysis of the electroplated samples confirms that it is possible to obtain the desired thickness of the metal by electroplating on any electrically conductive surface. In the present work, an experimental study is performed for examining the electroplated copper thickness of the plastic EDM electrode and its performances. It is found that the electroplated ABS plastic EDM RT electrode successfully performs the machining operation of D2 steel, and the results are comparable with a solid electrode. The study reveals that the RT electrode can be regarded as a viable tool for rough cutting or semi-finishing cut EDM functions. The experimental results are thoroughly discussed, examined, analyzed, and evaluated for the purpose of developing the appropriate form of the concept.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0238-5

Electric discharge phenomenon in dielectric and electrolyte medium

Mukesh Kumar Sindhu, Debasish Nandi, Indrajit Basak

2018, 6(4): 457-464. doi:10.1007/s40436-018-0221-1

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Electric discharge is a common tool nowadays for machining of materials. It may be through a liquid medium or through air. Any metals, hard alloys, and nonmetals can be machined using the energy of electric discharge. In electric discharge machining (EDM), the discharge occurs between two electrodes through a liquid medium and it is applicable only for electrically conducting materials and alloys. In electrochemical discharge machining (ECDM), the medium is an aqueous electrolyte and it is of two types. In the first type, the discharge occurs between two electrodes. One of the electrodes is the workpiece, and the other is the tool. In the second type, the discharge occurs between one electrode and an electrolyte. It is used for electrically nonconducting materials and the discharge energy is utilized maintaining the nonconducting workpiece in proximity of the discharge. All these electrical discharges are transient phenomena and do not result in a stable discharge in the form of arc. The output parameters depend on the discharge energy that requires precise control to maintain the accuracy of the machining. For micromachining, the control of the discharge is paramount both in terms of energy and pattern. Using various shaped tools, machining media with additives, different types of applied potentials, and supporting mechanical motions are some of the attempts made to improve the machining output. Optimization of these parameters for machining particular materials (or alloys) is a popular field of research. The present work is directed toward the investigation of discharge initiation and development by analyzing the cell current and discharge voltage relationship for both EDM and ECDM. The rectangular direct current (DC) pulse with different frequencies and the duty factor (on-off time ratio) are used for investigation. Observations on the voltage-current relationship are made for the external potential prior to discharge at discharge and above the discharge potential. Though the external potential above the discharge voltage is useful for machining, these observations elucidate the mechanism regarding the initiation of the electric discharge under different conditions. The manner of discharge development in dielectrics and electrolytes is observed to be different. This understanding will aid in deciding the design of the discharge circuit including the external potential and its pattern for certain desired outputs in machining.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0221-1

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