英语翻译标题：The Velocity DilemmaAnother aspect of the gating pict

英语翻译
标题：The Velocity Dilemma
Another aspect of the gating picture that needs and is receiving attention is gate velocity.Until the advent of electronic instrumentation,little thought is given to this parameter in most die casting shops.Some students of the process are vaguely aware that there is not complete freedom to roam up and down the gate velocity scale at will.Die casting engineers have often told of grinding the gate to change its direction only to find the casting quality deteriorating*.What was happening was that as they enlarged the gate area they reduced the gate velocity,virtually canceling the possible benefits of their efforts at redirection[1] .
A survey and analysis of hundreds of gating systems in successful production dies showed a peak in the velocity distribution curve in the range of 100-150 ft/sec for aluminum and 80-120 ft/sec for zinc.Researchers who have explored the influence of gate velocity at some length have frequently reported a “no man’s land” in the velocity scale.This slump* in casting quality may occur in one range with one casting and in another range with a different casting.Generally,however,it is seen most often in the 30-50 ft-sec range.
In an effort to understand further the role of gate velocity,the DCRF is currently sponsoring additional work under Wallace at Case Western Reserve University.By means of high speed photography (5 000 frames/sec),the influence of velocity on the nature of the metal stream emerging from the gate orifice is being studied.At this time several things have been learned.
True solid front flow is a myth.Velocities as low as 15 ft/sec were seen to produce a fanlike spray.At higher velocity,the streamers tend to break up into strings of coarse discrete* globules.At still higher velocity,the particles become very fine.This may be the sort of flow referred to by die casters as “fog,” “atomized,” etc.After the nature of the stream with respect to velocity is established and the boundary zones of these modes are determined,these factors will be correlated,with casting quality.Internal and surface quality optima may very possible occur at quite different gate velocity ranges.The reader should keep in mind that we have been referring to the nature of the metal stream immediately after it emerges from the gate orifice and leaps into the open space of the mold cavity.It is clear that in actual practice the stream that starts out as a spray may very well be slowed to a small fraction of its original velocity by impinging* on as few as one or two successive* walls of the die’s convolutions*[2].Thus,those who have observed clearly round nosed,solid stream fronts after the metal has progressed some distance from the gate were not dreaming.In fact,it is probable that as the stream is bounced from one wall to another,it could not possibly retain sufficient velocity to remain a spray of liquid metal particles.
先给15分,

这么长,找专人翻译吧~~~