Quality Waterjet Newsletter – 03/2005
Autofrettage and FatigueOn the previous issue we have
talked about fatigue and its impact to high-pressure component life. This
article will introduce a technique that is used widely in this industry to
fight back fatigue and improve component life. This technique is called
Autofrettage. The word Autofrettage was derived from French with a meaning of
“self-hooping”. French people used this technique to pre-stress cannon and
gun barrels to reduce the stresses on the walls from high pressure and
temperature variation during firing. These stresses cause fatigue and
eventually cracking. Autofrettage is done by applying a
pressure that is much higher than normal operating pressure to the subject
high-pressure component, usually in the shape of a tube. This pressure is so
high that it causes the inside wall of the tube to expand and creates a
permanent deformation to a certain depth into the wall thickness. After this
pressure is removed, the outside wall, which was under elastic deformation,
tends to collapse inward. However the inside wall, which has expanded and
deformed permanently, will not allow it. As a result, the inside wall has
residual compression stresses and the outside wall residual tensile stresses.
For a component without Autofrettage, the stress level under normal operating pressure is the highest at the inside wall and decreases gradually towards the outside. With Autofrettage, the stress level is balanced out with the inside wall stresses reduced significantly. This, in turn, extends the fatigue life of the component. The impact can be doubling the component life. More detailed information on this
subject can be found in these two references: (a) F.H. Trieb, J.
Schedelmaier, and M. Poelzl, “Developments on optimized Autofrettage of high
pressure components for waterjet cutting pumps”, Proceedings of 17th
International Conference on Water Jetting, Mainz, Germany, September 7-9,
2004; (b) ASME (American Society of Mechanical Engineering) Code, Boiler and
Vessel Code Section VIII-Division 3, KD 1998 Edition, New York. Beyond High Pressure · What is SUPER-WATER®? SUPER-WATER®
is an additive used in abrasivejets or waterjets in order to focus the
cutting stream, increase cutting speed, and reduce wear of high pressure components.
Traditionally it has been used with great benefit for high-pressure cleaning
and water only cutting applications. Its application has more recently
been expanded to Abrasivejet Machining. For more information, go to www.waterjets.org/super-water.html · Like to learn waterjet cutting
techniques and get hands-on experience? Check out "Hands-On Waterjet
Cutting Techniques Course" offered by RICHEL at www.richel.com. · A book with a working title of
HIGH PRESSURE PUMPS & SYSTEMS is being written by Mike Gracey in Houston,
Texas. If you have some clear photographs showing high pressure pumps,
ultra-high pressure pumps and water jetting project, please contact him at mike.gracey@weatherford.com |
|
QualJet LLC
Quality Waterjet Spare Parts Specialist ·
Quality Waterjet Spare Parts o
Meets/exceeds OEM standards o
Maximize uptime/ revenue ·
Factory Direct Savings ·
Extensive Parts Coverage o
Flow style · On/off
valve · Cutting
head · Swivel o
Ingersoll-Rand style ·
Intensifier ·
On/off valve ·
Cutting head ·
OEM Expert o
20+ year waterjet OEM experience (via OH Precision) o
Accept small OEM order o
Fast turnaround time Q1 Promotion
·
10% discount for any retail purchase by March 31,
2005 ·
25% discount for any stocking order in Q1 Intensifier Pump on Sale Quality intensifier pump (50HP, 55,000psi, 1gpm) is available at 20%
cheaper than equivalent pumps on the market, and an ideal replacement for
worn-out pump or a cost-effective part for new waterjet system. Contact info@qualjet.com for details.
QualJet LLC
12819 SE 38th Street, #240 Bellevue, WA 98006 1-866-QUALJET (782-5538) Fax:
425-378-7776 Email:
info@qualjet.com Website:
www.qualjet.com To unsubscribe the newsletter: unsubscribe@qualjet.com |
|
|
Copyright ©2005, QualJet LLC