Glass Bead Shot Peening

7/29/2019 Glass Bead Shot Peening

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M = 4 /3 .rr R" x 2.5 or the specific gravity in gm/cc3.The variance between the weight of the individualparticles or each nominal range serves to show the ef-TYPICAL PEENING INTEN SITIESDRY PEENING WITH BALLOTIN1I M P K T CLh5.S BEADS

m 4 0 c o . 0 1 0 o n a w*l a m s s u a r (PSI)

TYPICAL PffNING INTENSITIES TYPICAL PEIWIYG INTENSITIESDRY PEENING WITH BA LLO TINI DRY PEENING WITH IALLO TI I IIMPACT GLASS BEADS

fect of the exponents to the 3rd power o n the m ass ofparticles and thereby on the peening intensity which isobtained.Once again, it should be emphasized that the purposeof these tests were to generalize the peening intensitiesthat could be obtained with glass beads to provideguidelines for testing of specific machines o r applica-tions. It should be noted that similar nozzle and air jetsizes would be necessary to duplicate these intensities.CLASS BEAD PEENING RESULTS

Noble7 reports a series of tests show ing the results ofglass bead peening at various intensities on surfaces ofvarious hardnesses.Figure 5 demonstrates the depth of residual compres-sive stress after peening with glass beads nominally.015 ins. (38 0 microns) in diameter. This was done bydetermining arc and stress characteristics of samplesafter the removal of gradients from the surface by etch-ing. The hardnesses shown are RC 40 and 60. The archeights are .022N and .018N. These curves are knownas "typical stress gradients."Figure 6 is a stress gradient on a Aockw ell C 40 sur -

F i g u r e 4C O M P A R I S O N O F NOMINAL S l Z E R A N G E S OF G L A S S B E

CB eW E I G H T

S l Z E U S . S i e v e I N C H E S M I C R O N S m i c r o g ra m s m

face . Thi s indicates the depth of stress achieved indicated intensities.ECONOMICSOFGLASS BEAD PEENING

Becaus e of the ma terial characte ristics of glass, iconsumption is a consideration in the use of glassD E P T H I N C H E S,001 .W2 .Wl ,004 .W5 .w

E?! B L A S T I N G M E D I U M - G L A S S MADS ,015"ii N P l U L STRESS C U D I W T CUWS O n A l Y E DON 0.2 in . THICK SPECIMENSAFTERB U S T I Y O 10 SEC.peening. We conducted tests from our own protodetermin e the nat ure of this impact consumption measure it as accurately as possible. In preparinprotocol it was necessary to consider the varwhich, in this case, are three dimensional. Firsspecific almen peening intensity; second, the sglass bead material being used (i.e. diameter or mthird, the hardness of surface. A fourth variable in the nozzle angle which we have studied in istests. Indications are that impact consumption mreduced by use of a reflecting nozzle angle whicredu ce th e possibility of glass impacting on glass th

TYPICAL HEIGHT VERSUS DEPTHor m u T L4o(IKADS) . i

reflection of glass particles back into the nozzle sIn order to reduce the complexity of the testiadopted the 90 degree angle as being the oneacceptable in shot peening processes.


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establish a universal qua ntity of im pact con-tion we adopted the term "percent per cycle"is a figure that can be multiplied by any Bedto create an estimated consumption. To illustratewe arrive at the "percent per cycle" take a flow100 Ibs. per hour through a nozzle with a per-3 percent, the consump-"od d be 3 Ibs. per hour. If the flow rate is 500in multi-nozzle machine the "percent per cycle"would then account for a use of 15 Ibs.hour.

with carefully controlled cycles. Consumption was

al hat was smaller than the smallest screen open-f the nominal size range.Samp les were carefully slit with Tyler 1 6or 1 to 1 sample reducers according to the methods

the test all material was withdrawn from the gen-

in material was recorded and calculated into theFigure 7 shows a summary of impact con-

nts an average of fo ur cycles. Consumption mayduring individual cycles.7 A shows the impact consumption data weobserved at a 6 0 degree angle, For some of the7 are lower. Incase blastin g pre ssu re was increased to reach th earc height with the nozzle 60 degrees to the al-strip surface. A 10 in. distance was used at b oth

y we recommend individual tests of specific

surface the higher the consumption of glass beadsbe at a given intensity. It is also evident

erally th e actua l consum ption norm ally is less thantheoretical 90 degree consumptions given here be-

the active charge, this reduces the flow of active. Of course, the total economics of any processe judged by the cost of subsequent operationse total savings or total value that can be realizeduse of glass. In general, the consumption cost ofshould be compared against the cost of passiva-or subsequent treatment that might be necessaryother media. Any value that might be ascribed tomore attractive surface which results from glassd blasting should also be con sidered.requirements for low intensities; for particularfinishes; to avoid metal removal; or to avoidbo cutting edges would indicate the use of glass

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GENERAL

AlmenIntensity.W7 N:!

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SireKl170-230)

H f 100-140)

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B(30-401

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DATAFigure 7

O N CONSUMPTION OF GLASS BEADI N SHOT PEENING90. Angle Nozzle

50 C75 B

30 C

30 C50 C

Figure 7ACOMPARISON OF 60. AN D 90. BLAST ANGLESFOR IMPACT CONSUMPTION(nozzle distance in 10")90' Angle 60' Angl

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U U.- "'a 2 : i t u ' y 2: -z 0 $Y g c.: ' . = c .=" i0 3 s4 a. "7 dP'* 2" $42: 2:i U

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Glass Bead Shot Peening