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  1. dculp1

    Wire EDM (WEDM) - cutting speed versus conventional milling (titanium)

    For core drills, were you referring to diamond-impregnated drills such as are used on hard materials like ceramic or drills like https://www.hougen.com/cutters/cutters_index.html ? If the latter, I have only been able to find these in 7/16" (11 mm) diameters and larger, with lengths up to 100...
  2. dculp1

    Wire EDM (WEDM) - cutting speed versus conventional milling (titanium)

    I hadn't considered waterjet but it might be reasonable. It would eliminate EDM's two major fatigue problems -- surface pitting and recast surfaces. However, I'm still hoping for info on comparative machining rates for conventional versus wire EDM machining.
  3. dculp1

    Wire EDM (WEDM) - cutting speed versus conventional milling (titanium)

    I'm trying to find any information on comparative machining rates for wire EDM versus conventional milling. This is for machining through-slots in ultrasonic horns - examples in http://krell-engineering.com/fea/industr/industrial_resonators.htm. The supporting web page is...
  4. dculp1

    Slot in plate - best end shape for minimum stress?

    mfgenggear -- I'm not exactly sure what you're asking/suggesting but maybe the following will help. Assume that aluminum has acceptable life at 130 MPa (http://ultrasonic-resonators.org/materials/aluminum/aluminum_properties.html#fatigue). Assume that the current horn has a maximum stress at...
  5. dculp1

    Slot in plate - best end shape for minimum stress?

    mfgenggear -- The aluminum horns are made from either extruded material or plate stock. These are generally soft-chrome plated for wear resistance or nickel plated for appearance. Neither plating is designed to improve fatigue performance. The titanium horns are made from plate stock...
  6. dculp1

    Slot in plate - best end shape for minimum stress?

    Several researchers have found that conventional (low frequency) S-N tests and ultrasonic S-N tests give comparable results for Ti-6Al-4V. See the image from Morrissey ("Ultrasonic Fatigue Testing of Ti-6Al-4V", Journal of ASTM International, May 2005, Vol. 2, No. 5, Paper ID JAI12024)...
  7. dculp1

    Slot in plate - best end shape for minimum stress?

    For a pneumatic press, the maximum air cylinder diameter is ~75mm; the maximum air pressure is ~0.7 MPa. Thus, the maximum possible applied static force is ~3000 N. Assume a horn with face dimensions of 150mm x 13mm. The resulting pressure at the horn's face is ~1.6 MPa. For Ti-6Al-4V with a...
  8. dculp1

    Slot in plate - best end shape for minimum stress?

    Based on the additional application information, do you think that stress intensity factor analysis is relevant. If so, can you provide additional information that may be relevant to my application. (I have minimal knowledge of this and how it can be applied.)
  9. dculp1

    Slot in plate - best end shape for minimum stress?

    LiftDivergence -- 1. Modal analysis doesn't doesn't include contact with the part. This is standard practice in the ultrasonic industry. (This question was raised at a recent Ultrasonic Industry Association symposium.) The reason is that the load is quite variable as the plastic melts. Also...
  10. dculp1

    Slot in plate - best end shape for minimum stress?

    For each loading cycle (e.g., plastic welding a part), the horn contacts the part, then the ultrasonics are activated. The amplitude increases to the fully specified amplitude (a small part of the total cycle) and is maintained constant for a fixed cycle time. At that time the ultrasonics are...
  11. dculp1

    Slot in plate - best end shape for minimum stress?

    The following may clarify the application and goals. For ultrasonic horns, the slot stress is determined by how the horn is designed for the best face amplitude uniformity, the number of slots, the distance of the slot ends from the output face, and the output amplitude relative to the...
  12. dculp1

    Slot in plate - best end shape for minimum stress?

    rb1957 -- The following reference may be helpful -- Wells, Joseph M.; Buck, Otto; Roth, Lewis D.; Tien, John K. (editors), Ultrasonic Fatigue, The Metallurgical Society of AIME, Warrendale, PA, 1982, ISBN 0–89520–397–9 I attended this symposium in 1982. Much else has been written about...
  13. dculp1

    Slot in plate - best end shape for minimum stress?

    For a slot with a 5mm end radius (#1 below), I looked at putting a R1.5mm fillet around the radius (#2 below). Interestingly, this increased the stress by about 5% at the surface for this 13mm thick model. However, since cracks often initiate at corners (especially due to machining...
  14. dculp1

    Slot in plate - best end shape for minimum stress?

    Tmoose -- For fatigue (aluminum, titanium, steel) I always look at von Mises stresses. What additional information would principal stresses provide?
  15. dculp1

    Slot in plate - best end shape for minimum stress?

    SWComposites -- Do you have particular FEA recommendations, considering the objectives of my project and the steep learning curve for most FEA?
  16. dculp1

    Slot in plate - best end shape for minimum stress?

    Tmoose -- See my reply to 3DDave (just above your reply) for the actual application. As noted elsewhere, my static model is a quick ballpark try to see if modifications to the slot geometry can reduce the slot stress in the actual vibration situation. After I have pinned down potential...
  17. dculp1

    Slot in plate - best end shape for minimum stress?

    3DDave -- See the following animations which are for the actual application (not the preliminary static analysis of this post). The horns vibrate in the completely free condition (no constraints). Momentum is conserved across the dark nodal planes (m*v in the positive direction is balanced by...
  18. dculp1

    Slot in plate - best end shape for minimum stress?

    LiftDivergence -- 1. The available materials are limited, particularly by acoustic properties. Steel has good fatigue strength but high acoustic loss. Ti-6Al-4V has relatively low acoustic loss and fairly good fatigue strength (also medically compatible) but is expensive and somewhat difficult...
  19. dculp1

    Slot in plate - best end shape for minimum stress?

    rb1957 -- Once a crack in these resonator-horns is initiated it propagates to to failure almost immediately (typically within a few seconds). Then the frequency drops unacceptably low and the system shuts down. There is no ability to monitor crack growth and make preventive replacement. Having...
  20. dculp1

    Slot in plate - best end shape for minimum stress?

    Jboggs -- I welcome your ideas on how to apply a "real world factor of safety". The only way I know to do this (for this application) is to reduce the vibrational amplitude and the associated vibrational stresses. However, then the resonator-horn would no longer perform it's intended function...

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