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This paper presents a triaxial loading device (TLD), which can apply a triaxial force on the spindle of a three-axis machine tool that is executing a 3-degree-of-freedon feeding motion, aiming at simulating cutting forces applied on the spindle in a machining process. A prototype was fabricated and its kinematics and dynamics were analyzed. An explicit force control system was designed based on a fuzzy proportional-integral (PI) controller, integrating a force and a position feedforward. The effectiveness of the control system was evaluated; results illustrate that the fuzzy PI controller reduces the rising time and overshoots, and the force and the position feedforward eliminate the hysteresis and following errors caused by unknown feeding motions, respectively. Loading experiments were conducted to test the dynamic loading capacity of the TLD. The experimental results illustrate that the device is capable to add a triaxial force, which tracks a reference force with acceptable errors, on a spatially-moving spindle with random trajectories in real time. The TLD can simulate the cutting forces that the spindle encounters in real machining process and provides an efficient and economical loading approach that avoids a costly long-term cutting for the reliability tests of three-axis machine tools.

A simple approach to multi-objective optimization of machining parameters is presented. Regression analysis of experimental data is carried out to obtain the correlation between cutting parameters and response variables. Finally, Genetic Algorithm (GA) toolbox ofMATLABis used to carry out multi-objective optimization of two objective functions (surface roughness “Ra” & material removal rate “MRR”). Genetic algorithm is found to be a powerful tool for multi-objective optimization of machining parameters in this study.

This paper presents a novel type of three degree-of-freedom (DOF) redundant parallel tool head (PTH) which is developed by introducing actuation redundancy to an originally designed non-redundant 3-DOF PTH. To diminish the physical constraints imposed by spherical joints, a modified spherical joint with large tilting capacity is introduced. The two types of PTHs, the redundant form and the non-redundant one, are then fully compared with each other in terms of singularity distribution, workspace shape, kinematic performance and stiffness behavior. The comparison results show that the redundant PTH has several notable advantages over the non-redundant one, including enlarged singularity-free workspace, improved dexterity performance and higher stiffness.

The stiffness characteristics of a hexaglide parallel loading machine (HPLM) are investigated in this paper. The architectural model of a HPLM is constructed and analyzed. Then the total stiffness matrix, in which the variations of the Jacobian matrix are considered, is derived based on the analysis of kinematics and statics. The workspace boundary of the HPLM is determined through a boundary searching method (BSM) and the stiffness performance over the workspace is assessed by using the extreme eigenvalues and condition number of the stiffness matrix while the influence of the architectural parameters on the stiffness behavior of the HPLM is also investigated using the same indices. Eigenscrew decomposition method is utilized to illustrate the physical interpretation of the stiffness matrix. Numerical examples follow to prove validity of the methodology.

A six degrees-of-freedom (DOF) parallel material testing machine (PMTM), which is based on Stewart Platform, is first proposed in this paper. Several essential issues including prototyping, compliant axis determination and controller design are investigated with specific methods or technologies. The compliant axis, along which the proposed machine has a better performance, is determined by the eigenscrew decomposition method. The proposed force controller incorporates the simplified inverse dynamic model output as a model-based portion of the controller and its validity is verified by means of simulations. Evaluation tests are performed to examine the practicability of the proposed controller and to determine the loading accuracy of the PMTM. Tensile tests and preliminary multiaxial loading tests are performed to verify the performance of the proposed PMTM. The experimental results illustrate that the proposed PMTM is capable of performing multiaxial loading tests of materials and thus a suitable candidate for multiaxial material testing machine.

A multidimensional loading material testing machine (MLMTM) based on Stewart Platform is proposed in this paper. The kinematic and dynamic characteristics of MLMTM are analyzed, including the influence of universal joint in each limb on dynamic modeling. The dynamic model is established via Kane method, and the control system is founded based on classic PID strategy. Four experiments are performed to examine the validity of proposed dynamic model and control system of the MLMTM, including two uniaxial experiments and two biaxial experiments. Results of these experiments are summarized as well as the capacity of force tracking and load errors are analyzed. The experimental results demonstrate the validity of dynamic model via Kane method and illustrate that the proposed MLMTM is capable of performing multidimensional loading tests.

Traditional parallel mechanisms (PMs) are usually characterized by small tilting capability. To overcome this problem, a 3-DOF parallel swivel head (PSH) with large tilting capacity is proposed in this paper. The proposed PSH, which is structurally developed from a conventional 3-PRS parallel mechanism (PM), can achieve a large tilting capability by means of structural improvements. Firstly, a modified spherical joint with a maximum tilting angle of ±120o is devised to diminish the physical restrictions on the orientation workspace. Secondly, a UPS typed leg is introduced for the sake of singularity elimination. The superiority of the proposed PSH is theoretically proved by investigations of singularity-free orientation workspace and then is experimentally validated using a prototype fabricated. The theoretical and experimental results illustrate that the proposed PSH has a large tilting capacity and thus can be used as swivel head for a hybrid machine tool which is designed to be capable of realizing both horizontal and vertical machining.

High-speed machine tool working table restrains the machining accuracy and machining efficiency, so lightweight design of the table is an important issue. In nature, leaf has developed a plate structure that maximizes the surface-to-volume ratio. It can be seen as a plate structure stiffened by veins. Compared with a high-speed machine tool working table, leaf veins play a role of supporting part which is similar to that of stiffening ribs, and they can provide some new design ideas for lightweight design of the table. In this paper, distribution rules of leaf veins were investigated, and a structural bionic design for the table was achieved based on regulation of leaf veins. First, statistical analysis on geometric structure of leaf veins was carried out, and four distribution rules were obtained. Then, relevant mechanical models were developed and analyzed in finite element software. Based on the results from mechanical analysis on those relevant models, the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved. Both simulation and experimental verifications were carried out, and results showed that the average displacement of the working table was reduced by about 33.9%.

The performances of different coated carbide drills when drilling cast GH625 nickel-based alloy were evaluated in terms of tool wear and cutting force. Wear pattern observation and cutting force measurement were conducted under different cutting conditions. It was found that the drill coated with TiAlN/TiN showed the best overall performance among all the drill types tested. This drill type gave the longest tool life in terms of number of holes partly due to the excellent wear resistance of TiAlN/TiN multilayer. Besides, the thrust force and torque produced with this drill type were lower, which could be attributed to its good adhesion resistance and chip-ejection ability.

Based on fractal theory, used the index of rockfill compaction characteristics(granularity fractal dimension) which conforms to Talbot curve distribution, combined with blasting schemes and rolling test data of several domestic rockfill dams, the relationship is established between compacted rockfill’s dry density and rock blasting parameters by rockfill granularity fractal dimension and its average diameter, and that provided the basis for rockfill particle grading optimization method. The method is applied by rockfill of JIANGPINGHE dam under construction, and the results show that this method can well reflect the intrinsic relation between rock blasting and rockfill compaction, which can be applied to particle grading design of rockfill dam.

The effects of cutting parameters and tool wear on the surface damage generated in hole making of cast GH625 nickel-based alloy were investigated. The machined surfaces were examined by employing a scanning electron microscopy (SEM). The SEM micrographs of the machined surfaces showed that surface damages induced by boring operation comprised surface cavities, smeared material and ridges parallel to feed marks. Surface cavities were associated with the carbide particles contained in workpiece material and the intrinsic defect of cast GH625 alloy. The cutting conditions had little impact on the extent of surface cavities, but they significantly affected the extent of smearing. Severe smearing of workpiece material could occur at higher cutting speed due to the relatively high cutting temperature generated and the relatively rapid tool wear.

The study focused on surface burn of titanium alloy (TC4) in the grinding process using a novel segmented cup wheel with internal cooling structure. The threshold burn temperature was found in grinding TC4. Plastically deformed coating layers and micro-cracks were observed on ground surface by SEM (Scanning Electronic Microscopy) and depth of microstructure alterations was more than 180 microns in high temperature. Finally, a novel wheel with internal cooling structure was developed for reducing grinding temperature and suppressing surface burn.

The lightweight and high efficiency of natural structures are the inexhaustible sources for engineering improvements. The goal of the study is to find innovative solutions for mechanical lightweight design through the application of structural bionic approaches. Giant waterlily leaf ribs and cactus stem are investigated for their optimal framework and superior performance. Their structural characteristics are extracted and used in the bio-inspired design of Lin MC6000 gantry machining center crossbeam. By mimicking analogous network structure, the bionic model is established, which has better load-carrying capacity than conventional distribution. Finite Element Method (FEM) is used for numerical simulation. Results show better specific stiffness of the bionic model, which is increased by 17.36%. Finally the scaled models are fabricated by precision casting for static and dynamic tests. The physical experiments are compared to numerical simulation. The results show that the maximum static deformation of the bionic model is reduced by about 16.22%, with 3.31% weight reduction. In addition, the first four natural frequencies are improved obviously. The structural bionic design is a valuable reference for updating conventional mechanical structures with better performance and less material consumption.

In this paper, tool life, tool wear criteria, initial wear and cutting length at initial wear are picked out from 295 milling tool wear curves to calculate initial wear rate K0, final wear rate K1 and the ratio K between the two. By statistic analysis of K0, K1 and K, a statistical regularity between K0 and K1 is found, which indicates that the faster the initial wear, the shorter the tool life would be. Based on the statistical regularity, a milling tool rapid selection method is proposed, and an experiment on selecting the best tools for machining TC4 is carried out to verify the method. The results show that the method can reduce the consumption of material and time significantly, which confirm the efficiency of the method.

The paper presents a new multi-dimensional loading structure based on parallel mechanism used for testing the materials and components. The mechanics of structure is introduced, kinematics and control model is analyzed, and loadings are simulated. It shows that because various actual forces can be supplied and controlled, static and dynamic performances of components can be evaluated by this structure, with which the capacity of the load-bearing can be ensured accurately. The data obtained by this structure is very important for the design of the materials and the components.

To satisfy the requirement in blisk machining, a barrel-ball milling (BBM) cutter suitable for machining both blade and hub is presented in this paper. The selection of cutter parameter and calculation of cutter location were put forward. The new efficient machining cutter location via the advanced optimization on cutter machining strip width was gained. By the numerical simulation of blisk blade machining, the feasibility of the BBM cutter and cutter location strategy were verified. The result showed that the efficiency of this method was increased to more than three times compared to the machining with a ball cutter.

A flank milling tool positioning method using a barrel cutter is proposed. An offset point is used as the first anchor point. Two rotary angles of the barrel cutter are adjusted to find the optimized tool position with the largest machining strip width. The result tool position calculated using the proposed method is gouge-free because the local interference avoidance method is integrated inside the tool positioning procedure. Error distribution beneath the barrel cutter is well estimated by virtual of the instant envelope curve of the cutter. The envelope curve is discretized into points. The distances between these points and the model surface are the machining errors beneath the cutter. The employment of the envelope curve also largely reduces the computational load of the algorithm. Finally, numerical implementation and simulation are performed to validate the feasibility of the method.

Based on the configuration principles of biological skeletons and sandwich stems, a machine tool column with stiffening ribs inside was designed using structural bionic method. After the lightening effect was verified by finite element simulation, scale-down models of a conventional column and a bionic column were fabricated and tested. Results indicate that the bionic column can reduce the maximum static displacement by 45.9% with 6.13% mass reduction and its dynamic performances is also better with increases in the first two natural frequencies. The structural bionic design is effective in improving the static and dynamic structural performances of high speed machine tools.

A new strategy for 5-axis NC machining called Rotate-For-Intersect Machining (RFIM) was presented in this paper. The cutter was settled by two cutter contact points and in order to obtain optimized tool position and orientation, grid point method and bi-section method ware utilized in searching cutter’s rotate angle and tilt angle. Finally the algorithm was implemented on UG platform following further development and the effectiveness of the method was validated.

The development of a virtual axis cutter grinder was introduced. The main contents of this paper include layout design, parameters design method, control system and program system. The purpose of the development of the parallel machine tools is for cutter grinding. The dimension of the cutter and the translation workspace for cutter grinding usually is small and is therefore suitable for the parallel machine tool application. The new machine tool has high rigidity and good precision.

In order to reduce the weight of airplane and increase its mechanical behaviors, more and more large integrated parts are applied in modern aviation industry. When machining thin-walled aeroplane parts, more than 90% of the materials would be removed, resulting in severe distortion of the parts due to the weakened rigidity and the release of residual stress. This might also lead to stress concentration and damage of the parts. The effect of material removal from residually stressed billet is simulated using FEA software M SC. Marc and the causations of distortion is analyzed. To verify the finite element simulation, a high speed milling test on aluminum alloy 7050T7351 is carried out. The results show that the simulation result is consistent with the experimental one. It is concluded that the release of residual stress is the main cause of machining distortion.