The formation and development of serrated chip morphology and adiabatic shear bands (ASBs) and the microstructure of fracture surfaces in the serrated chips during hard machining of hardened alloy steel are observed, the mechanism of adiabatic shear fracture is analyzed. The observation and analysis indicate that the cutting speed has significant influence on the transformation of chip morphology and microscopic morphology of ASBs, the material properties can significantly influence on microstructural pattern of fracture surfaces and fracture mechanism during serrated chip formation. The ductile damage fracture induced by adiabatic shear has decisive effect on serrated chip formation, a microcosmic model of adiabatic shear ductile fracture during hard machining including nucleation, growth, coalescence and fracture of microvoids within ASB is proposed.
The frictional modelling literature is reviewed, and it is demonstrated that unrealistic drift results when the shape coefficient is 1.0 for the LuGre and the integral friction models. Drift will not occur but other dynamic friction characteristics can't be represented when the shape coefficient is 0. Based on the above, the LuGre friction model and the Integral friction model are improved. The velocity-friction characteristic, the stick-slip and the cycling caused by friction and the drift are compared in simulation. The results show that the improved friction model well reflects realistic friction dynamic characteristics and avoids drift. Finally, the improved friction model is used in a nonlinear mathematic model of a valve controlled hydraulic cylinder system. The cylinder's motion at low velocity is simulated and the related experimental results are presented. The results show that the improved friction model gives realistic low velocity motion of the cylinder.
In demand-synchronized production, when constructing flexible production systems to produce a variety of products while maintaining high efficiency, a preparation lead time is required because of such physical constraints as making setup changes and supplying facilities. Preparation lead time must also include time to arrange suitable software conditions. If forecasting required production volumes several days in advance with a certain degree of precision is possible, making systematic preparations for constructing the production system is also possible. The objectives of this research are to precisely forecast demand fluctuation within several days of delivery and thus have the ability to forecast production volume. We propose a method for forecasting production volumes, based on an analysis of past order data and the determination of their similarity by Fourier analysis. We confirm the efficiency of our proposed method by conducting experiments and forecasting production volumes using actual orders.
This paper presents a new class of discrete orthogonal moments, W-moments, based on a hybrid orthogonal function system, W-system of degree one. The W-moments have two main advantages, one is computationally simple due to the piecewise linear structure of the basis functions, and the other is the reproducibility, namely shapes and even shape groups can be precisely reconstructed by finite number of the W-moments, due to the orthogonality of the basis functions on a discrete data set. These properties make the W-moments preferable to the conventional moments when used for describing complex shapes consisting of multiple disjointed curves. To evaluate the proposed moments, image retrieval experiments are conducted on MPEG-7 CE2 and a self-constructed trademark data set. In the experiments, the W-moments are first derived from the trademark images, similarity between query image and each trademark in the database is then evaluated using the Euclidean distance between their W-moments feature vectors, and the trademark retrieval is finally accomplished by comparing their similarities. The experimental results show that the moments proposed in this paper give preferable retrieval results in comparison to other five conventional moments, and the W-moments should be feasible and efficient in practical application.
Smart devices have been developed and widely used recently, so they have been applied in the industrial field. If mobile technology is applied to the CAD field, users will be able to obtain many advantages such as high mobility and ease of collaboration. To develop a feature-based CAD system that can be made available on smart devices, we suggested a system using multi-touch inputs in 2012; this was a stand-alone system available without a network. However, the system could not create complex shapes by itself because of the absence of a modeling kernel for the mobile platform and the low computing power of smart devices. To solve this problem of shape creation, this study proposes a client-server system for CAD systems on smart devices. When modeling commands are created from drag-type buttons, at each step, the analyzed modeling commands are sent to the server, the server creates the model and sends it to the smart device, and the smart device visualizes the modeling result. This system can make more complex models than those possible with the existing system. This study compares the developed system with the existing system in order to verify the usability of the new CAD system on smart devices; further, this study suggests how to extend this system to collaborative systems. This CAD system for smart devices can increase the mobility and cooperative nature of CAD systems.
High efficiency and high precision machining technologies have been recently required in a variety of industries. In general, aerostatic spindle systems can realize such machining, while at high speed rotation it generates a large amount of heat that causes thermal deformation of the spindle. However, few research papers on thermal deformation-minimized spindle systems have been published so far. This paper presents a newly developed aerostatic spindle system driven by a built-in air turbine. The developed spindle system has a self-cooling function of the air turbine with internal air flow. In addition, the spindle system has a compact and simple structure compared with the conventional spindle cooling systems. The built-in air turbine is designed so as to improve the cooling and torque performances. Actual spindle rotational experiments are performed in order to evaluate rotational accuracy and thermal characteristics of the spindle system during high speed rotating. Experimental results confirmed that the spindle system can minimize thermal deformation of the spindle by the self-cooling function.
This study proposes a novel inner and outer spiral micro in-pipe robot. The inner and outer spiral robot structure is designed. The fluid flow field in the turbulent pipe is solved through computational fluid dynamics method, and the accuracy of the adopted numerical method is verified. The influences of environmental (liquid density, liquid viscosity, pipe diameter, and eccentricity) and operating (inner spiral rotational speed, outer spiral rotational speed, and robotic running speed) parameters on the robot performance are numerically analyzed. Inner and outer spiral driving devices are designed and fabricated according to the working principle of the inner and outer spiral robot. In addition, the feasibility of the proposed robot is verified by performing an experiment in a pipe filled with 201 methyl silicone oil.
A simulation of the rolling contact fatigue strength of a traction drive element was developed. This simulation accounts for both the distribution of sizes of inclusions in the element material and the influence of traction forces at the element surface. The shear strength of the matrix structure surrounding an inclusion was estimated with an equation. The hardness distribution and the Weibull distribution of inclusion dimensions, which are necessary parameters to calculate the rolling contact fatigue strength, were determined by observation of an actual test specimen. The purpose of this report is simulations to evaluate the effect of the crowning radius on the rolling contact fatigue strength and the torque capacity. The simulations were carried out by varying the crowning radius of the virtual roller. To consider the effect of the crowning radius, a simulated two-dimensional virtual roller, which has actual material properties, was modified to a roller multilayered toward the axial direction. The simulation assuming the actual roller led to a difference of 1.0% from the experimental rolling contact fatigue strength. This difference was 2.4 points smaller than the result for the two-dimensional virtual roller. The rolling contact fatigue strength decreased with increasing crowning radius for two reasons. One was the increase in the number of inclusions under the high stress due to the increasing crowning radius. The other was the expansion of the portion of the roller subject to high stresses down to a depth having small hardness. However, the torque capacity calculated from the contact force resulting in failure increased with the increasing crowning radius.