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1.
The aim of this paper is to present a method to identify the dynamics of a structure composed of a milling machine, a tool and a workpiece. The excitation is obtained as a result of the interrupted cutting of a narrow workpiece width and single tooth milling operations. This provides a pulse-like cutting force. The three components of the cutting force and the relative motion between the tool and the workpiece are measured simultaneously. A method was developed to determine the nine terms of the structural transfer matrix under a single cutting operation and without any assumption on the excitation direction. The proposed method is experimentally validated. 相似文献
2.
KatsumiIchitani 《材料热处理学报》2004,25(5):453-456
Heat transfer coefficients of the quench medium are necessary for heat-treatment simulation. Cooling characteristics of quenching oil vary with kinds and usage greatly. Users are selecting oil solutions that come up to their desired hardness and quenching distortion requirements. In particular cooling performance rises by agitation and decompression. Therefore we identified a heat transfer coefficient by usage and kinds of quenching oil. Cooling characteristics are different greatly by a kind of quenching oil. A difference of a cooling characteristic by a kind of oil depends on a temperature range of a boiling stage and the maximum heat transfer coefficient mainly. On the other hand, in a convection stage, there are few changes in a boiling stage. Even if quenching oil temperature is changed, heat transfer coefficients do not change greatly. When quenching oil stirred, heat transfer coefficients of vapor blanket stage and a convection stage rise, but there are a few changes in a boiling stage. When quenching oil is decompressed a temperature range of a high heat transfer coefficient moves to the low temperature side. In addition, a heat transfer coefficient in a vapor blanket stage comes down. For precision improvement of heat-treatment simulation, it is important that the heat transfer coefficient is calculated in conformity to the on-site use reality. 相似文献
3.
A single stable adatom on a {110}-type plane of a tungsten tip is created via field-evaporation in a field-ion microscope
(FIM) operating at room temperature. This single adatom has sufficient surface mobility at room temperature and migrates,
in one-dimension, along a <111>-type direction toward an edge of a {110}-type plane, due to the existence of an electric field
gradient. The plane edge has a higher local electric field than its center, since it has a higher local geometric curvature.
This result implies that the stable position of a single adatom during a scan of a scanning tunneling microscope (STM) tip
on a surface is at the edge and not at the center of a {110}-type plane at room temperature. Therefore, the electron wave
function of a tip is not symmetric and this fact should be taken into account in a careful analysis of STM images. Also a
tip with a dislocation emerging at a {110}-type plane is suggested as an improved STM tip configuration, as the step at the
surface, created by the intersection of the dislocation with it, is a perpetual source of single adatoms. 相似文献
4.
通过对捷联惯性制导与平台惯性制导之间差异的分析,讨论了在进行捷联惯性制导系统的电路设计时所应注意的问题,在此基础上,用C32 DSP和可编程逻辑器件,设计了一个捷联惯性制导系统的电路。 相似文献
5.
6.
This paper addresses problems of a mobile base robot’s part assembly. This process can be broken down into two phases. First, a macro-assembly, bringing a part to an assembly hole or a receptacle (target) for a purpose of a part mating. For the macro-manipulation task, a stability analysis of a mobile base robot subject to disturbances, such as an external impact force and torque as well as a tipping movement, is discussed. The mobile robotic system is stabilized by balancing the system moment through a fuzzy coordinator. Simulations are performed by applying external forces and torque to the system and adding disturbances to the mobile base’s tipping movement. Second, a micro-assembly, mating a part with a target. For the micro-manipulation task, two learning methodologies are presented. First, a learning strategy to minimize the entropy, uncertainty, and eliminate unneeded events in the plan related to avoiding jamming is described. An entropy function, which is a useful measure of the variability and the information in terms of uncertainty, is introduced to measure its overall performance of a task execution related to the part mating. Next, a fuzzy stochastic learning method, based on the probability of a fuzzy set and a modified distance metric, to update the probability of a plan composed of fuzzy events used for the part mating task is introduced. The degree of uncertainty associated with the fuzzy event of plan is used as an optimality criterion, or cost function, e.g. minimum Hamming distance, for a specific task execution. The above techniques are applicable to a wide range of mobile robotic tasks including pick and place operations, maneuvering around workspace, manufacturing, part mating, or complex assembly tasks. 相似文献
7.
Johann RechbergerRoland Dubach 《Surface & coatings technology》1993,60(1-3):584-586
The joint effort of a cutting tool manufacturer and a coating specialist has led to the development of a cutting tool coating based on a soft solid lubricant (patents pending). It is applied by an advanced sputtering technique as a very thin uniform coating with a good adherence to the tools. It has a low coefficient of friction and a low affinity to alloy materials such as aluminium, titanium and precious metals. These factors and others allow machining at high spindle speeds and feed rates with an excellent workpiece surface finish. Values can be maintained which are far superior to even those permitted for cemented carbide tools. In some cases productivity and tool life can be increased by a factor of up to 20. 相似文献
8.
Ismail Lazoglu Fuat Atabey Yusuf Altintas 《International Journal of Machine Tools and Manufacture》2002,42(14)
This article presents a mathematical model and a computational algorithm for the time domain solution of boring process dynamics. The model is developed in a modular form; it includes a workpiece geometry and surface topography module, a kinamatics and tool position module, a dynamic chip load module, a dynamic cutting force prediction module and a structural dynamics module. The time domain model takes cutting process parameters, tool and workpiece geometries and modal parameters of the structure as inputs. It predicts instantanous cutting forces and vibrations along the machining time, and machined workpiece topography as outputs. Some of the simulated and experimental results for various cutting conditions are presented and compared for validation purposes. 相似文献
9.
E. Brinksmeier C. HeinzelN. Bleil 《Journal of Materials Processing Technology》2009,209(20):6117-6123
This paper presents with a new grinding strategy for a surface superfinishing and a grind-strengthening of the surface layer of steels in a single grinding step. To grind-strengthen a surface layer both abrasive material removal and a plastic deformation are needed. This combination together with an appropriate grinding wheel design offers the possibility to ensure high precision surfaces with a consistent quality finish that meets the highest standards. This kind of grinding process could be applied to bearings, for example. During the run-in period, the initial contact surfaces change until they stabilize to a running-in condition and have a new surface topography. Grinding with the new process strategy leads to benefits because a grind-strengthened surface layer eliminates initial wear and abrasion within the system, reduces surface finish roughness, extends fatigue strength, and reduces risk of part failure during operation. 相似文献
10.
11.
The residual stress of a landing gear part of a fighter jet that has a frequent practice of takeoff and landing was evaluated for the safety. The sample was a cylindrical steel bar with a 22.2 mm diameter and 55 mm length used to fix the main landing gear to the aircraft body. For a deep measurement up to 6 mm, we used a neutron beam. From the measurements, the tensile and compressive strain in the axial direction were observed around one side of the pin hole which was across the steel bar vertically with an 8 mm diameter. The strain distribution along the length of the bar presented a similar tendency through the thickness and a larger value on the surface. The maximum value of the residual stress around the pin hole was about 100 MPa. However, there was no strain on the opposite side of the pin hole. From the results, it may be surmised that the steel bar received a steady force in one direction around the pin hole, however the force was weak and affected a small limited area and thus not influence on the steel bar on the whole. 相似文献
12.
Fuzhu Han Jun Jiang Dingwen Yu 《International Journal of Machine Tools and Manufacture》2007,47(7-8):1187-1196
In finish machining of wire electrical discharge machining (WEDM), the discharge current has distinct influences on the machined surface. In order to study the differences in surface morphology under various pulse durations, thermo-analysis was carried out to investigate the mechanism of erosion of the workpiece material using the finite element method. Additionally, related single discharge experiments under different pulse energies were performed. Under the same discharge energy, the comparison of analytical and experimental results shows that a discharge current with a short-duration pulse and a high peak value removes the workpiece material mainly by gasifying, while a discharge current with a long-duration pulse and low peak value removes the workpiece material mainly by melting. It was also found that surfaces machined by a discharge current with a short- and long-duration pulses would have similar roughness values when the pulse energies were almost the same and were high enough; however, the surface morphologies would be totally different. A discharge current with a long pulse duration and a low peak value could not produce craters on the workpiece surface when the pulse energy was reduced to a certain value. However, a discharge current with a short pulse duration and a high peak value could produce clear craters on the workpiece surface. This indicates that a discharge current with a short pulse duration and a high peak value can generate better surface roughness, which cannot be achieved with a current with a long pulse duration and a low peak value. 相似文献
13.
Location of steel reinforcement in concrete using ground penetrating radar and neural networks 总被引:2,自引:0,他引:2
M.R. Shaw S.G. Millard T.C.K. Molyneaux M.J. Taylor J.H. Bungey 《NDT & E International》2005,38(3):203
Ground-penetrating radar is becoming increasingly popular for use as a non-destructive assessment method for investigating reinforced concrete structures. The amount of data collected however can be very large and take a significant level of subjective experience to interpret. This study focuses upon the use of a neural network approach to automate and facilitate the post-processing of ground penetrating radar results. The radar data is reduced to a simplified data set by using an edge detection routine. Signal reflections from reinforcing bars displaying a hyperbolic image format are detected using a multi-layer perceptron (MLP) network with a single hidden layer containing 8 nodes to recognise a simplified hyperbolic shape. Training and testing of the network was carried out making use of an emulsion analogue tank, simulating the properties of concrete, and using real concrete specimens. The results showed that the use of a MLP neural network approach could be quite effective in automating the identification and location of embedded steel reinforcing bars from a radar investigation. Accurate estimation of depth, or cover, requires a reliable knowledge of the dielectric properties of the concrete, and recent work using a specially-developed wideband horn antenna for direct determination of in situ properties is also outlined. 相似文献
14.
Eun-Gi Shim In-Jun Park Tae-Heum Nam Jung-Gu Kim Hyun-Soo Kim Seong-In Moon 《Metals and Materials International》2010,16(4):587-594
We studied tris(2-chloroethyl) phosphate (TCEP) as a potential flame-retarding additive and its effect on the electrochemical
cell performance of lithium-ion battery electrolytes. The electrochemical cell performance of additive-containing electrolytes
in combination with a cell comprised of a LiCoO2 cathode and a mesocarbon microbeads anode was tested in coin cells. The cyclic voltammetry results show that the oxidation
potential of TCEP-containing electrolyte is about 5.1 V (vs. Li/Li+). A cell with TCEP has a better electrochemical cell performance than a cell without TCEP in an initial charge and discharge
test. In a cycling test, a cell containing a TCEP-containing electrolyte has a greater discharge capacity and better capacity
retention than a TCEP-free electrolyte after cycling. The results confirm the promising potential of TCEP as a flame-retarding
additive and as a means of improving the electrochemical cell performance of lithium-ion batteries. 相似文献
15.
Adsorption of biomolecules, whether it is a consequence of a material being put into service in a biological medium such as
a biomedical implant device or a heat exchanger tube, are governed by fundamental interactions and surface conditions that
are well characterized (and in some cases not so well). This work reviews those fundamental interactions and also describes
a study of the adsorption of a naturally occurring biological polymer onto a stainless steel alloy. 相似文献
16.
圆筒形件充液拉深成形精度 总被引:1,自引:1,他引:1
本文系统地研究了平底和球面圆筒形件充液拉深成形精度。充液拉深成形中,由于高压液体紧紧将毛坯贴向凸模表面,因而零件具有良好的贴模性并能获得很高的内径精度。同样,由于液压的施加在凸模圆角和压边圈之间产生与凸模运动方向相反的局部胀形,减小了凸模圆角处的弹复,提高了侧壁及球面件底部的形状冻结性。但是,平底零件的底面形状因液压的施加而使形状冻结性不好,平面度降低。 相似文献
17.
Ekkard Brinksmeier Frank Vollertsen Oltmann Riemer Michael Koerdt Axel Meier Simon Kibben Jan Möller 《Production Engineering》2013,7(6):619-627
A lithography method by means of a diamond turned hologram (DTH) is presented, that allows patterning of sloped surfaces. The DTH is manufactured by a modified diamond turning process, using a piezoelectric actuator, the nano fast tool servo, which modulates the depth of cut within submicrometer range at a frequency up to 10 kHz. In order to machine a DTH to be applied as phase masks for ultraviolet lithography, workpiece materials have to feature a sufficient reflectivity and excellent machinability. Ultra-fine grained aluminium was identified as most suitable workpiece material, since its reflectivity measures around 80 % and a homogenous structure can be machined. The employed DTH is used in a lithography setup in conjunction with a helium cadmium laser emitting at a wavelength of λ = 325 nm. Patterns up to a linewidth of 30 μm were successfully and consistently transferred on a photoresist coated planar substrate with a tilt angle of 30° with respect to the optical axis. 相似文献
18.
Correlation between laboratory and weathering tests with a low carbon steel in maritime atmosphere The work presented here shows a possible correlation of the corrosion behaviour of a low carbon steel in maritime atmosphere and in a salt spray chamber. The corrosion tests in maritime atmosphere have been conducted in the open air and in a covered cabin at the coast of the Black Sea over two years. The laboratory corrosion tests have been conducted in a salt spray chamber and had a duration of 70 days. The correlation between laboratory and weathering tests is represented graphically. The chemical composition of the corrosion products is given. 相似文献
19.
Expedient modeling of ball screw feed drives 总被引:3,自引:0,他引:3
Ball screw feed drives are the most commonly used mechanism to provide linear motion in high speed machine tools. Position
accuracy and the achievable closed loop bandwidth of such drive systems are usually limited by the structural vibration modes
of the mechanical components. Higher order plant models allow for a better understanding of the system dynamics, improve the
design process of feed drives and are essential for the development of sophisticated control strategies. The ball screw shaft,
describing a complex flexible structure, is probably the most significant component concerning structural vibration modes
of a feed drive. In this paper, the behavior of the shaft and its dominant influence at different operating and coupling conditions
is particularly addressed. Using a hybrid modeling technique, the main characteristics of the shaft are derived and projected
onto a clearly arranged and versatile lumped mass model. Simulative and experimental examinations are conducted and a parameter
analysis is performed. The presented model proofs to be accurate for a great range of parameters and in addition allows for
a physical interpretation of the dominant structural vibration modes of a feed drive. 相似文献
20.
《Journal of Materials Processing Technology》2014,214(2):217-228
Force-fit integration of piezoceramic fibers in micro-formed structures is a new approach for function integration in structural sheet metal parts. In a first step, a micro-structured surface is formed in a planar semi-finished sheet metal part by micro-impact extrusion. Piezoceramic fibers are then assembled into this micro-structured surface with a small assembly clearance. The fibers and the structured surface of the sheet metal are joined by a forming process. In the next step, the sheet metal with piezoceramic fibres within a locally micro-formed substructure is shaped by deep drawing into a 3D-geometry. In this paper, results of the micro-impact extrusion and the joining by forming experiments are presented. Furthermore, the design constraints for assembly and joining due to the dimensional and form deviations of the piezoceramic fibers are discussed. Results of a numerical study of micro-forming, joining by forming and the global loading during a deep drawing process step were in good agreement with the experimental investigations. The direct comparison between experiment and numerical simulation increases the process knowledge and shows further improvement potential. 相似文献