Current Issue : April - June Volume : 2016 Issue Number : 2 Articles : 7 Articles
Ultrasonic metal welding has been the subject of ongoing research and development, most recently concentrating on metal joining in miniature devices, for example to allow solder-free wire bonding. As well as at the small scale, there are also opportunities to research the joining of thicker sheet metals and to widen the range of similar and dissimilar materials that can be successfully joined using this technology. This study presents the design, characterisation and test of a lateral-drive ultrasonic metal spot welding device. The ultrasonic metal spot welding horn is modelled using finite element analysis (FEA) and its vibration behaviour is characterised experimentally to ensure ultrasonic energy is delivered effectively to the weld coupon. The welding stack and fixtures are then designed and mounted on a test machine to allow a series of experiments to be conducted for various welding and ultrasonic parameters. Weld strength is subsequently analysed using tensile-shear tests. The results show how the weld strength is particularly sensitive to the combination of clamping force and ultrasonic vibration amplitude of the welding tip, but there are optimal combinations of these and also limits that must be clearly identified....
The effect of cutting conditions such as\nnumbers of tool teeth, depth of cut and cutting speed on the\ncutting resistance about 12%Cr steel hasn�t been studied\nbefore. So the effect of cutting conditions on the cutting\nresistance will be investigated in this paper. The relationship\nbetween cutting resistance and work damaged layer will be\ntaken into consideration. The results are as follows. (1)The\ncutting resistance becomes larger with the increase of the\ndepth of cut and the numbers of tool teeth. It has no relation\nwith cutting speed. (2)The depth of work damaged layer\nincrease with the increase of the depth of cut and numbers of\ntool teeth. It does not change with the increase of cutting\nspeed. (3)The deformation of cutting surface becomes larger\nwith the increasing depth and numbers of tool teeth. It\nchanges a little with the increase of cutting speed. (4)It was\nfound that the depth of work damaged layer increased with\nthe increase of the cutting resistance. The depth of work\ndamaged layer is thought to have an intimate relation with\nthe cutting resistance. (5)The experimental value for work\ndamaged layer by hardness measuring is thought to be\nreasonable value, because the experimental value is nearly\nequal to the evaluated one obtained from Sokolovs kii�s stress\nequation....
Severe wear is a common damage mechanism in railway turnouts, which strongly affects the dynamic performance of\nrailway vehicles and maintenance costs of tracks. This article explores the effects of profile wear on contact behaviors in\nthe wheelââ?¬â??rail/switch contact and dynamic interaction, and nominal and measured worn turnout rail profiles are used as\nboundary conditions of wheelââ?¬â??rail contact. The calculation of the dynamic loads and the resultant contact stresses and\ninternal stresses makes it possible to rationally design railway turnouts and correctly select the material to be applied\nfor their components. For these reasons, the multi-body system SIMPACK and finite element software ANSYS are used\nto calculate the features of load and subsequently distributions of contact stresses and internal stresses in the regions of\nwheelââ?¬â??turnout components. The results show that profile wear disturbs the distribution of wheelââ?¬â??rail contact point\npairs, changes the positions of wheelââ?¬â??rail contact points along the longitudinal direction, and affects the dynamic interaction\nof vehicle and turnout. For the measured profile in this article, profile wear aggravates vertical dynamic responses\nsignificantly but improves lateral dynamic responses. Profile wear disturbs the normal contact situations between the\nwheel and switch rail and worsens the stress state of the switch rail....
In the present study, finite element dynamic analysis or time history analysis of two-span beams\nsubjected to asynchronous multi-support motions is carried out by using the moving support finite\nelement. The elemental equation of the element is based on total displacements and is derived\nunder the concept of the quasi-static displacement decomposition. The use of moving support\nelement shows that the element is very simple and convenient to represent continuous beam\nmoving, deforming and vibrating simultaneously due to support motions. The comparison between\nthe numerical results and analytical solutions indicates that the FE result agrees with the\nanalytical solution....
Background: The effect of the holding time of the deep cryogenic treatment on the strain hardening of HY-TUF, a\nlow-alloy medium-carbon steel, and a comparison with strain hardening of conventional heat-treated steel were\ninvestigated.\nMethods: For this purpose, a deep cryogenic treatment was done for different holding times of 12, 24, 48, and\n72 h. The metallographic results indicate completion of martensitic transformation; �·-carbide precipitation and\ndecrement of carbon concentration in martensitic matrix happened while carrying out a deep cryogenic process.\nResults: Observations of transmission electron microscopy indicate higher density of dislocations within martensite\nnear the cementite compared to that near the �·-carbides. The tensile flow stress data for this steel was examined in\nterms of Hollomon equation. The results show that strain hardening of conventional heat-treated steel takes place\nin two stages.\nConclusions: This evidence is related to the co-deformation of austenite and martensite. The strain hardening takes\nplace in one stage for the deep cryogenic-treated steels, and their strain hardening exponents increase (from ~0.29 to\n0.47) with an increasing holding time up to 48 h. A further increase in the holding time of the deep cryogenic treatment\nis found not to vary strain hardening exponent. The increase of strain hardening exponent and then observation of\nplateau in this parameter show an optimum value for the holding time of the deep cryogenic treatment (48 h)....
Transportation industries are obliged to address concerns arising from greater emphasis on energy saving and\necologically sustainable products. Engineers, therefore, have a responsibility to deliver innovative solutions that will\nsupport environmental preservation and yet meet industries� requirements for greater productivity and minimised\noperational costs. Aluminium alloys have successfully contributed to meeting the rising demand for lightweight\nstructures. Notable developments in aluminium welding techniques have resolved many welding related problems,\nalthough some issues remain to be addressed. The present study attempts to give an overview of the key factors\nrelated to the formation of defects in welding methods commonly used with aluminium alloys. First, a concise\noverview of defects found in friction-stir welding, laser beam welding and arc welding of aluminium alloys is\npresented. The review is used as a basis for analysis of the relationship between friction-stir welding process\nparameters and weld defects. Next, the formation and prevention of the main weld defects in laser beam welding,\nsuch as porosity and hot cracking, are discussed. Finally, metallurgical aspects influencing weld metal microstructure\nand contributing to defects are tabulated, as are defect prevention methods, for the most common flaws in arc\nwelding of aluminium alloys....
In the industrial fields, many high temperature structures that require a non-destructive inspection\nexist. However, there are currently few sensors that can carry out non-destructive testing in a\nhigh temperature environment. In particular, the ultrasonic sensor is normally not used at over 50\ndegrees Celsius. Also, a special sensor for high temperature is currently available, but there are\nvarious constraints; it has not yet reached a level that is useful in industry. Therefore, we have\nbeen developing a new sensor system using a long waveguide which can transmit an ultrasonic\nwave from a long distance. Especially, this study focuses on applying the developed technique to a\npipe which is used in a nuclear power plant. Therefore, the best rectangular-shaped waveguide\nwas studied and attempted to be wound around a pipe to be driven by an acoustic source of a\nguide wave. Finally, the L (0, 2) and T (0, 1)-mode guide waves were successfully detected by optimizing\nthe shape of the opposite edge of the rectangular-shaped waveguide that could detect the\nreflected signal from an artificial defect machined into a test pipe....
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