Near field welding

Near field welding refers to joint V4 in. or less from area of horn contact far field welding to joint more than / from contact area. 

Figure 14.21 Near and far field welding, (a) Near field welding the contact surface of the horn is 6 mm (0.25 in.) or less away from the joint surface, (b) Far field welding the distance between the horn surface and the joint surface is greater than 6 mm (0.25 in.). Vibratory energy is transmitted through the top part to the joint interface.

NOTE With ultrasonic welding (c) denotes contact or near field welding only. 

Material Percent of Weld Strength Spot Weld Staking and Inserting Swaging Weldini Near Field F ... 

PAEK can be both adhesively bonded and welded [40]. PAEK can be welded using standard techniques such as hot plate, friction and near field ultrasonic welding. However, high-energy inputs will be required to melt the polymer. Organisations such as the Welding Institute have published a number of papers in the field. 

Benatar, A., Eswaran, R. V, Near-Field Ultrasonic Welding of Thermoplastics, ANTEC Conf Proc., Soc. Plastics Eng., 1989. 

Two types of ultrasonic seal are possible, ie contact or near field such as with high frequency welding, where the electrode or applicator is applied directly to the material where the weld is to be made, and remote or far field which is suitable for joining rigid mouldings. With the latter, the tip of the work horn is applied to a point of the work which may be some inches away from the faces to be welded, and the vibrations are transmitted through the material. 

Mattrial Gommem Trade Names Near Field Far Field Welding Anplitude 20 kHz Owraad... 

R. John and K. Jata, Residual Stress Effects on Near-Threshold Fatigue Crack Growth in Friction Stir Welds, Friction Stir Welding and Processing, K. Jata, M. Mahoney, R. Mishra, S. Semiatin, and D. Field, Ed., TMS, 2001, p 57-69... 

At certain locations, generally near high-power broadcasting antennas or near high-power RF sealing or welding equipment, fields are Hkely to exceed the exposure guidelines. As NIER power radiates from a source, the spherical surface over which the wave spreads increases as the square of the distance from the source. This leads to the so-called inverse square law by which it is known that, in the far field of an antenna, the power density decreases rapidly. Calculation of RF exposure conditions rehes on this fact from basic physics, and the incorporation of certain conservative assumptions set forth by the FCC in its... 

There are three primary sources of tensile stresses for RPVDs These are (1) fabrication induced stresses, (2) primary stresses, (3) and secondary stresses. Fabrication induced stresses consist of stresses introduced during manufacture and installation (i.e., fit-up and assembly in the shop or field plus those introduced by machining or forming operations and welding). As is the case for weld residual stresses, hard machining, abusive grinding can produce surface residual stresses near or above the yield point of the material. 

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