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A ailable online a www.sciencedi ec .com
P ocedia S uc u al In eg i y 43 (2023) 148–153
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©
2023 The Au ho s. Published by ELSEVIER B.V.
This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
10.1016/j.p os .2022.12.250
10.1016/j.p os .2022.12.250 2452-3216
© 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (
h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0
)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
A ailable online a www.sciencedi ec .com
ScienceDi ec
S uc u al In eg i y P ocedia 00 (2022) 000–000
www.else ie .com/loca e/p ocedia
2452-3216 © 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
10 h In e na ional Con e ence on Ma e ials S uc u e and Mic omechanics o F ac u e
Compa ison o a igue pe o mance o polye hylene pipe g ades in
he o m o ex uded and comp ession molded specimens
Lukáš T á níčeka,b*, Jan Poduškab, Ja osla Kuče ac, Luboš Náhlíkb and Pa el Hu ařb
aCEITEC BUT, Pu kyňo a 123, 621 00 B no, Czech Republic
bIns i u e o Physics o Ma e ials AS CR, Žižko a 22, 616 00 B no, Czech Republic
cPolyme Ins i u e B no, Tkalco ská 36/2, 602 00 B no, Czech Republic
Abs ac
Due o he e y long ope a ional li e imes (up o 100 yea s) o polye hylene pipes, he e is a s ong demand o accele a ed es ing
o pipe ma e ials o expe imen ally p o e he abili y o a ce ain ma e ial o achie e such li e ime. Among he accele a ed es s o
pe o mance, he c acked ound ba (CRB) es is he mos con enien . The CRB es akes ad an age o cyclic loading ha is
applied on cylind ical specimens wi h a ci cum e en ial no ch in he middle. The specimens a e usually manu ac u ed om pla es
p oduced by comp ession molding om he in es iga ed ma e ial. Howe e , o polye hylene pipe p oduce s, he possibili y o
making he specimens by ex usion would sa e ime and lowe he cos s. This s udy is dealing wi h he compa ison o CRB es ,
and a new es ca ied ou on no ched pipe samples p oduced by ex usion. The goal is o in es iga e he possibili y o measu ing
he pe o mance di ec ly on ex uded pipe specimens. The compa ison is illus a ed on expe imen al esul s o se e al polye hylene
pipe g ades o PE80, PE100 and PE100RC o en used o pipe manu ac u e.
© 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
Keywo ds: ex uded pipe specimens; SCG esis ance; polye hylene pipe li e ime; accele a ed es ing
1. In oduc ion
Polyme pipes ha e been used o mo e han 70 yea s o wa e and gas anspo a ion as well as o sewage sys ems.
Fo high-quali y pipes made o mode n ma e ials, such as high-densi y polye hylene (HDPE), li e imes be ween 50 o
* Co esponding au ho . Tel.: +420 532 290 347.
E-mail add ess: a [email protected]
A ailable online a www.sciencedi ec .com
ScienceDi ec
S uc u al In eg i y P ocedia 00 (2022) 000–000
www.else ie .com/loca e/p ocedia
2452-3216 © 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
10 h In e na ional Con e ence on Ma e ials S uc u e and Mic omechanics o F ac u e
Compa ison o a igue pe o mance o polye hylene pipe g ades in
he o m o ex uded and comp ession molded specimens
Lukáš T á níčeka,b*, Jan Poduškab, Ja osla Kuče ac, Luboš Náhlíkb and Pa el Hu ařb
aCEITEC BUT, Pu kyňo a 123, 621 00 B no, Czech Republic
bIns i u e o Physics o Ma e ials AS CR, Žižko a 22, 616 00 B no, Czech Republic
cPolyme Ins i u e B no, Tkalco ská 36/2, 602 00 B no, Czech Republic
Abs ac
Due o he e y long ope a ional li e imes (up o 100 yea s) o polye hylene pipes, he e is a s ong demand o accele a ed es ing
o pipe ma e ials o expe imen ally p o e he abili y o a ce ain ma e ial o achie e such li e ime. Among he accele a ed es s o
pe o mance, he c acked ound ba (CRB) es is he mos con enien . The CRB es akes ad an age o cyclic loading ha is
applied on cylind ical specimens wi h a ci cum e en ial no ch in he middle. The specimens a e usually manu ac u ed om pla es
p oduced by comp ession molding om he in es iga ed ma e ial. Howe e , o polye hylene pipe p oduce s, he possibili y o
making he specimens by ex usion would sa e ime and lowe he cos s. This s udy is dealing wi h he compa ison o CRB es ,
and a new es ca ied ou on no ched pipe samples p oduced by ex usion. The goal is o in es iga e he possibili y o measu ing
he pe o mance di ec ly on ex uded pipe specimens. The compa ison is illus a ed on expe imen al esul s o se e al polye hylene
pipe g ades o PE80, PE100 and PE100RC o en used o pipe manu ac u e.
© 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
Keywo ds: ex uded pipe specimens; SCG esis ance; polye hylene pipe li e ime; accele a ed es ing
1. In oduc ion
Polyme pipes ha e been used o mo e han 70 yea s o wa e and gas anspo a ion as well as o sewage sys ems.
Fo high-quali y pipes made o mode n ma e ials, such as high-densi y polye hylene (HDPE), li e imes be ween 50 o
* Co esponding au ho . Tel.: +420 532 290 347.
E-mail add ess: a [email protected]
2 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
Nomencla u e
aini ini ial c ack leng h
CRB c acked ound ba
D diame e o a CRB specimen
Din inne diame e o a pipe specimen
Dou ou e diame e o a pipe specimen
ΔF o ce loading ange
Δσ s ess loading ange
ΔKI s ess in ensi y ac o ange
Fmin minimum applied o ce
Fmax maximum applied o ce
FNCT ull no ched c eep es
HDPE high densi y polye hylene
l leng h o a CRB specimen
N numbe o cycles o ailu e
NPT no ched pipe es
PENT pennsyl ania edge no ch es
R loading a io in a cyclic es
SCG slow c ack g ow h
hickness o he pipe wall
100 yea s a e gene ally expec ed oday. Du ing hei se ice li e, he s uc u al eliabili y o piping sys ems is essen ial
as p ema u e ailu es may cause se e e ma e ial loss (Nayya 2000).
Fo he long- e m applica ions o polye hylene pipes, he li e ime is connec ed o he esis ance agains c ack
ini ia ion and slow c ack g ow h (SCG). The adi ional expe imen al es ing me hod is based on in e nal p essu e es
s anda dized in ISO 9080 (ISO 2012). Howe e , wi h he de elopmen o polye hylene pipe g ades comes highe SCG
esis ance o he ma e ials, o which he in e nal p essu e es mee s i s ime limi s. This ac led he pipe communi y
o de elop accele a ed es ing me hods o ob ain he ma e ial anking o he SCG esis ance in sho e imes. Among
he mos common me hods a e No ched Pipe Tes (NPT) (Beech 2013), Pennsyl ania Edge No ch Tes (PENT) (Lu
1992) and Full No ch C eep Tes (FNCT) (Fleissne 1998). All hese accele a ed es s a e ca ied ou a ele a ed
empe a u es o T = 80°C and/o unde he in luence o agg essi e chemical en i onmen o accele a e he c ack
ini ia ion and SCG. These es s p o ide a signi ican educ ion in es ing imes in compa ison wi h he hyd os a ic
p essu e es , bu o mode n polye hylene pipe g ades (such as PE100RC) hey s ill equi e imes o se e al mon hs.
The e o e, C acked Round Ba (CRB) es , ha was ecen ly s anda dized as a anking me hod o polye hylene pipes
(ISO 2015), was de eloped (Pin e 2007, F ank 2014, A bei e 2015). The CRB es is ca ied ou on cylind ical
specimens wi h a azo -sha p ci cum e en ial no ch in he middle. The accele a ion o c ack ini ia ion and SCG is
done by cyclic loading ha is much mo e e ec i e han he special agg essi e en i onmen o high empe a u e. The
impo an ac is ha he cyclic loading does no change he mechanism o ailu e (Pin e 2013) and he e o e, i is
sui able o he accele a ion o he SCG (F ank 2019). Mo eo e , he esul s a e ob ained wi hin a ew days e en o
he mos du able ma e ials. I ollows om he abo e ha he CRB es is a quick, obus , and e ec i e ool o quan i y
he esis ance agains SCG o polyme ma e ials.
The specimens o all accele a ed es s a e ypically manu ac u ed om pla es p oduced by comp ession molding,
which is a di e en p ocess ha he one used o polyme pipes p oduc ion – ex usion. Fo polyme pipes p oduce s,
he di ec ex usion o he specimens o accele a ed es ing would lowe he cos and sa e ime. In his espec , he
main aim o he p esen ed wo k is o classi y di e en ypes o polye hylene pipe g ades o PE80, PE100 and PE100RC
using new ex uded pipe specimens in he es s and compa e he esul s wi h classic CRB es s. The expe imen s o
new pipe specimens we e ca ied ou unde he same condi ions as CRB es s, so he accele a ion o he c ack ini ia ion
and SCG was achie ed by cyclic loading. The compa ison as well as he usabili y o he new pipes specimens is
discussed he e, based on he ob ained esul s.
Lukáš T á níček e al. / P ocedia S uc u al In eg i y 43 (2023) 148–153 149
A ailable online a www.sciencedi ec .com
ScienceDi ec
S uc u al In eg i y P ocedia 00 (2022) 000–000
www.else ie .com/loca e/p ocedia
2452-3216 © 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
10 h In e na ional Con e ence on Ma e ials S uc u e and Mic omechanics o F ac u e
Compa ison o a igue pe o mance o polye hylene pipe g ades in
he o m o ex uded and comp ession molded specimens
Lukáš T á níčeka,b*, Jan Poduškab, Ja osla Kuče ac, Luboš Náhlíkb and Pa el Hu ařb
aCEITEC BUT, Pu kyňo a 123, 621 00 B no, Czech Republic
bIns i u e o Physics o Ma e ials AS CR, Žižko a 22, 616 00 B no, Czech Republic
cPolyme Ins i u e B no, Tkalco ská 36/2, 602 00 B no, Czech Republic
Abs ac
Due o he e y long ope a ional li e imes (up o 100 yea s) o polye hylene pipes, he e is a s ong demand o accele a ed es ing
o pipe ma e ials o expe imen ally p o e he abili y o a ce ain ma e ial o achie e such li e ime. Among he accele a ed es s o
pe o mance, he c acked ound ba (CRB) es is he mos con enien . The CRB es akes ad an age o cyclic loading ha is
applied on cylind ical specimens wi h a ci cum e en ial no ch in he middle. The specimens a e usually manu ac u ed om pla es
p oduced by comp ession molding om he in es iga ed ma e ial. Howe e , o polye hylene pipe p oduce s, he possibili y o
making he specimens by ex usion would sa e ime and lowe he cos s. This s udy is dealing wi h he compa ison o CRB es ,
and a new es ca ied ou on no ched pipe samples p oduced by ex usion. The goal is o in es iga e he possibili y o measu ing
he pe o mance di ec ly on ex uded pipe specimens. The compa ison is illus a ed on expe imen al esul s o se e al polye hylene
pipe g ades o PE80, PE100 and PE100RC o en used o pipe manu ac u e.
© 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
Keywo ds: ex uded pipe specimens; SCG esis ance; polye hylene pipe li e ime; accele a ed es ing
1. In oduc ion
Polyme pipes ha e been used o mo e han 70 yea s o wa e and gas anspo a ion as well as o sewage sys ems.
Fo high-quali y pipes made o mode n ma e ials, such as high-densi y polye hylene (HDPE), li e imes be ween 50 o
* Co esponding au ho . Tel.: +420 532 290 347.
E-mail add ess: a [email protected]
A ailable online a www.sciencedi ec .com
ScienceDi ec
S uc u al In eg i y P ocedia 00 (2022) 000–000
www.else ie .com/loca e/p ocedia
2452-3216 © 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
10 h In e na ional Con e ence on Ma e ials S uc u e and Mic omechanics o F ac u e
Compa ison o a igue pe o mance o polye hylene pipe g ades in
he o m o ex uded and comp ession molded specimens
Lukáš T á níčeka,b*, Jan Poduškab, Ja osla Kuče ac, Luboš Náhlíkb and Pa el Hu ařb
aCEITEC BUT, Pu kyňo a 123, 621 00 B no, Czech Republic
bIns i u e o Physics o Ma e ials AS CR, Žižko a 22, 616 00 B no, Czech Republic
cPolyme Ins i u e B no, Tkalco ská 36/2, 602 00 B no, Czech Republic
Abs ac
Due o he e y long ope a ional li e imes (up o 100 yea s) o polye hylene pipes, he e is a s ong demand o accele a ed es ing
o pipe ma e ials o expe imen ally p o e he abili y o a ce ain ma e ial o achie e such li e ime. Among he accele a ed es s o
pe o mance, he c acked ound ba (CRB) es is he mos con enien . The CRB es akes ad an age o cyclic loading ha is
applied on cylind ical specimens wi h a ci cum e en ial no ch in he middle. The specimens a e usually manu ac u ed om pla es
p oduced by comp ession molding om he in es iga ed ma e ial. Howe e , o polye hylene pipe p oduce s, he possibili y o
making he specimens by ex usion would sa e ime and lowe he cos s. This s udy is dealing wi h he compa ison o CRB es ,
and a new es ca ied ou on no ched pipe samples p oduced by ex usion. The goal is o in es iga e he possibili y o measu ing
he pe o mance di ec ly on ex uded pipe specimens. The compa ison is illus a ed on expe imen al esul s o se e al polye hylene
pipe g ades o PE80, PE100 and PE100RC o en used o pipe manu ac u e.
© 2023 The Au ho s. Published by Else ie B.V.
This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
Pee - e iew unde he esponsibili y o MSMF10 o ganize s.
Keywo ds: ex uded pipe specimens; SCG esis ance; polye hylene pipe li e ime; accele a ed es ing
1. In oduc ion
Polyme pipes ha e been used o mo e han 70 yea s o wa e and gas anspo a ion as well as o sewage sys ems.
Fo high-quali y pipes made o mode n ma e ials, such as high-densi y polye hylene (HDPE), li e imes be ween 50 o
* Co esponding au ho . Tel.: +420 532 290 347.
E-mail add ess: a [email protected]
2 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
Nomencla u e
aini ini ial c ack leng h
CRB c acked ound ba
D diame e o a CRB specimen
Din inne diame e o a pipe specimen
Dou ou e diame e o a pipe specimen
ΔF o ce loading ange
Δσ s ess loading ange
ΔKI s ess in ensi y ac o ange
Fmin minimum applied o ce
Fmax maximum applied o ce
FNCT ull no ched c eep es
HDPE high densi y polye hylene
l leng h o a CRB specimen
N numbe o cycles o ailu e
NPT no ched pipe es
PENT pennsyl ania edge no ch es
R loading a io in a cyclic es
SCG slow c ack g ow h
hickness o he pipe wall
100 yea s a e gene ally expec ed oday. Du ing hei se ice li e, he s uc u al eliabili y o piping sys ems is essen ial
as p ema u e ailu es may cause se e e ma e ial loss (Nayya 2000).
Fo he long- e m applica ions o polye hylene pipes, he li e ime is connec ed o he esis ance agains c ack
ini ia ion and slow c ack g ow h (SCG). The adi ional expe imen al es ing me hod is based on in e nal p essu e es
s anda dized in ISO 9080 (ISO 2012). Howe e , wi h he de elopmen o polye hylene pipe g ades comes highe SCG
esis ance o he ma e ials, o which he in e nal p essu e es mee s i s ime limi s. This ac led he pipe communi y
o de elop accele a ed es ing me hods o ob ain he ma e ial anking o he SCG esis ance in sho e imes. Among
he mos common me hods a e No ched Pipe Tes (NPT) (Beech 2013), Pennsyl ania Edge No ch Tes (PENT) (Lu
1992) and Full No ch C eep Tes (FNCT) (Fleissne 1998). All hese accele a ed es s a e ca ied ou a ele a ed
empe a u es o T = 80°C and/o unde he in luence o agg essi e chemical en i onmen o accele a e he c ack
ini ia ion and SCG. These es s p o ide a signi ican educ ion in es ing imes in compa ison wi h he hyd os a ic
p essu e es , bu o mode n polye hylene pipe g ades (such as PE100RC) hey s ill equi e imes o se e al mon hs.
The e o e, C acked Round Ba (CRB) es , ha was ecen ly s anda dized as a anking me hod o polye hylene pipes
(ISO 2015), was de eloped (Pin e 2007, F ank 2014, A bei e 2015). The CRB es is ca ied ou on cylind ical
specimens wi h a azo -sha p ci cum e en ial no ch in he middle. The accele a ion o c ack ini ia ion and SCG is
done by cyclic loading ha is much mo e e ec i e han he special agg essi e en i onmen o high empe a u e. The
impo an ac is ha he cyclic loading does no change he mechanism o ailu e (Pin e 2013) and he e o e, i is
sui able o he accele a ion o he SCG (F ank 2019). Mo eo e , he esul s a e ob ained wi hin a ew days e en o
he mos du able ma e ials. I ollows om he abo e ha he CRB es is a quick, obus , and e ec i e ool o quan i y
he esis ance agains SCG o polyme ma e ials.
The specimens o all accele a ed es s a e ypically manu ac u ed om pla es p oduced by comp ession molding,
which is a di e en p ocess ha he one used o polyme pipes p oduc ion – ex usion. Fo polyme pipes p oduce s,
he di ec ex usion o he specimens o accele a ed es ing would lowe he cos and sa e ime. In his espec , he
main aim o he p esen ed wo k is o classi y di e en ypes o polye hylene pipe g ades o PE80, PE100 and PE100RC
using new ex uded pipe specimens in he es s and compa e he esul s wi h classic CRB es s. The expe imen s o
new pipe specimens we e ca ied ou unde he same condi ions as CRB es s, so he accele a ion o he c ack ini ia ion
and SCG was achie ed by cyclic loading. The compa ison as well as he usabili y o he new pipes specimens is
discussed he e, based on he ob ained esul s.
150 Lukáš T á níček e al. / P ocedia S uc u al In eg i y 43 (2023) 148–153
Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000 3
2. Expe imen al de ails
CRB specimens wi h he dimensions acco ding o he s anda d (ISO 2015): ou e diame e D = 14 mm, leng h
l = 100 mm and ci cum e en ial azo -sha p no ch aini = 1.5 mm; we e machined om comp ession molded shee s.
Polye hylene pipes wi h ou e diame e Dou = 20 mm and inne diame e Din = 14 mm we e p oduced by ex usion.
The pipe wall hickness = 3 mm was chosen – i was a maximum ha he ex usion die allowed. The pipes we e cu
in o 100 mm long specimens wi h 1 mm deep azo -sha p ci cum e en ial no ch in he middle. Bo h ypes o specimens
we e p epa ed a he Polyme Ins i u e B no.
To ally, 9 di e en polye hylene ma e ials o he pipe g ades PE80, PE100 and PE100RC we e es ed wi h he pipe
specimens and o 5 ou o hese ma e ials CRB es s we e also ca ied ou – see summa y in Table 1.
Table 1. O e iew o es ed polye hylene pipe g ades.
Ma e ial numbe
1
2
3
4
5
6
7
8
9
Pipe g ade
PE80
PE100
PE100RC
Pipe specimen
✓
✓
✓
✓
✓
✓
✓
✓
✓
CRB specimen
✓
✓
✓
✓
✓
The uniaxial a igue es s we e pe o med using he compu e -con olled es ing machine INSTRON E10000. The
specimens we e loaded cyclically wi h equency 10 Hz. The cyclic loading was con olled by o ce, and i had he
sine o m de ined by he maximum o ce Fmax and cyclic load a io R = 0.1 (R = Fmin/Fmax). Acco ding o he ISO
18489, he load ange Δσ is ela ed o he ligamen a ea, hus he o ces Fmin, Fmax and he ange ΔF mus be calcula ed
acco dingly om he chosen Δσ. The le els o Δσ = 11, 12 and 13 MPa we e chosen o PE100 and PE100RC ma e ials,
and 10.5, 11.5, and 12.5 MPa o PE80 ma e ial we e applied. On he o he hand, he pipe specimens we e es ed only
on he le el o Δσ = 10 MPa. The es s we e s opped when he specimens b oke, o he numbe o cycles eached
1×107.
Fig. 1. (a) geome y o he CRB specimen; (b) geome y o he new pipe specimen.
3. Resul s
3.1. F ac u e su ace obse a ion
In he case o CRB es s, i is common o obse e asymme ic ma ks on he ac u e su ace ha esul om he
discon inuous p opaga ion o he c ack, which consis s o epea ed phases o de elopmen and subsequen b eakage
o a p ocess zone (c aze) in on o he c ack ip – see Fig. 2. This is a ypical phenomenon o SCG in polye hylene.
The s anda d o CRB specimens speci ies ha a signi ican pa o he ac u e su ace mus show he SCG
mechanism, o he wise he esul om he specimen is no ep esen a i e because he dominan ailu e mechanism was
duc ile ailu e, which means he load was oo high. The same mechanism o SCG was obse ed on he ac u e su ace
o pipe specimens depic ed in Fig. 3. Howe e , he asymme y was much s onge and he a ea o SCG was much
smalle , which caused a la ge sca e in he da a.
I was e y di icul o ind he op imal load ange o he pipe specimen so ha accep able ep esen a i e esul s
a e ob ained wi h su icien amoun o SCG. This is di ec ly linked o he geome y o he pipe specimens, and i
u ned ou o be he bigges limi a ion o hem. Fo he load ange Δσ = 10 MPa, accep able ep esen a i e esul s can
be ob ained wi h bo h specimens (e en hough he es ing imes end o be e y long o he PE100 and PE100RC
4 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
g ades). Howe e , going highe wi h he load ange causes he pipe specimens o b eak wi h a duc ile ailu e, which
is illus a ed by he ac u e su ace in he Fig. 4, whe e a pipe specimen made o ma e ial 1 (PE 80) loaded by Δσ =
12 MPa ailed a e N =13694 cycles by duc ile ailu e – no SCG occu ed. This happens, e en hough he s ess
in ensi y ac o ange (ΔKI = 0.59 MPa·m1/2, ob ained by FEM) a his load le el is lowe han o CRB specimens
( o Δσ = 10 MPa i is ΔKI = 0.65 MPa·m1/2), which s ill pe o m well and p oduce ep esen a i e esul s a his le el
e en o less SCG- esis an ma e ials. This is caused by he ela i ely hin wall o he pipe – he hin wall makes
cons ain in he icini y o he c ack la ge , which p e en s SCG ini ia ion a a lowe ΔKI, bu when he p opaga ion
s a s, he amoun o SCG is low because i ans e s in o he duc ile ailu e mode e y ea ly o almos ins an ly as he
ligamen becomes hinne , making he esul s no ep esen a i e.
To be able o so he ma e ials acco ding o SCG esis ance, he loading ange o Δσ = 10 MPa was chosen o all
he pipe specimens. The esul s o a igue es ing a e p esen ed in he nex sec ion.
Fig. 2. Pho o o ac u e su ace o a CRB specimen made o PE100RC – ma e ial 8 aken by op ical mic oscope. The a eas o SCG and inal
duc ile ailu e a e depic ed.
Fig. 3. Pho o o ac u e su ace o an ex uded pipe specimen made o PE100RC – ma e ial 8 aken by op ical mic oscope. The a eas o SCG and
inal duc ile ailu e a e shown in he de ail.
3.2. Fa igue pe o mance
Fig. 5 summa izes he ma e ial anking based on he numbe o cycles o ailu e N o ex uded pipe specimens and
CRB specimens, espec i ely. Fo he pipe specimens, he mean alue o N o e e y ma e ial is depic ed by black
do s. Resul s om bo h ypes o specimens di ide he ma e ials in o he polye hylene pipe g ades g oups co ec ly.
Howe e , he esul s o pipe specimens su e by high sca e wi hin e e y es ed pipe g ade, which is caused by he
lack o cons ain and lack o space o he c ack o p opaga e. This makes he c ack p opaga ion mo e suscep ible o
any de ec s and i egula i ies in he geome y as opposed o he CRB specimens, whe e he esul s a e no ably less
Lukáš T á níček e al. / P ocedia S uc u al In eg i y 43 (2023) 148–153 151
Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000 3
2. Expe imen al de ails
CRB specimens wi h he dimensions acco ding o he s anda d (ISO 2015): ou e diame e D = 14 mm, leng h
l = 100 mm and ci cum e en ial azo -sha p no ch aini = 1.5 mm; we e machined om comp ession molded shee s.
Polye hylene pipes wi h ou e diame e Dou = 20 mm and inne diame e Din = 14 mm we e p oduced by ex usion.
The pipe wall hickness = 3 mm was chosen – i was a maximum ha he ex usion die allowed. The pipes we e cu
in o 100 mm long specimens wi h 1 mm deep azo -sha p ci cum e en ial no ch in he middle. Bo h ypes o specimens
we e p epa ed a he Polyme Ins i u e B no.
To ally, 9 di e en polye hylene ma e ials o he pipe g ades PE80, PE100 and PE100RC we e es ed wi h he pipe
specimens and o 5 ou o hese ma e ials CRB es s we e also ca ied ou – see summa y in Table 1.
Table 1. O e iew o es ed polye hylene pipe g ades.
Ma e ial numbe
1
2
3
4
5
6
7
8
9
Pipe g ade
PE80
PE100
PE100RC
Pipe specimen
✓
✓
✓
✓
✓
✓
✓
✓
✓
CRB specimen
✓
✓
✓
✓
✓
The uniaxial a igue es s we e pe o med using he compu e -con olled es ing machine INSTRON E10000. The
specimens we e loaded cyclically wi h equency 10 Hz. The cyclic loading was con olled by o ce, and i had he
sine o m de ined by he maximum o ce Fmax and cyclic load a io R = 0.1 (R = Fmin/Fmax). Acco ding o he ISO
18489, he load ange Δσ is ela ed o he ligamen a ea, hus he o ces Fmin, Fmax and he ange ΔF mus be calcula ed
acco dingly om he chosen Δσ. The le els o Δσ = 11, 12 and 13 MPa we e chosen o PE100 and PE100RC ma e ials,
and 10.5, 11.5, and 12.5 MPa o PE80 ma e ial we e applied. On he o he hand, he pipe specimens we e es ed only
on he le el o Δσ = 10 MPa. The es s we e s opped when he specimens b oke, o he numbe o cycles eached
1×107.
Fig. 1. (a) geome y o he CRB specimen; (b) geome y o he new pipe specimen.
3. Resul s
3.1. F ac u e su ace obse a ion
In he case o CRB es s, i is common o obse e asymme ic ma ks on he ac u e su ace ha esul om he
discon inuous p opaga ion o he c ack, which consis s o epea ed phases o de elopmen and subsequen b eakage
o a p ocess zone (c aze) in on o he c ack ip – see Fig. 2. This is a ypical phenomenon o SCG in polye hylene.
The s anda d o CRB specimens speci ies ha a signi ican pa o he ac u e su ace mus show he SCG
mechanism, o he wise he esul om he specimen is no ep esen a i e because he dominan ailu e mechanism was
duc ile ailu e, which means he load was oo high. The same mechanism o SCG was obse ed on he ac u e su ace
o pipe specimens depic ed in Fig. 3. Howe e , he asymme y was much s onge and he a ea o SCG was much
smalle , which caused a la ge sca e in he da a.
I was e y di icul o ind he op imal load ange o he pipe specimen so ha accep able ep esen a i e esul s
a e ob ained wi h su icien amoun o SCG. This is di ec ly linked o he geome y o he pipe specimens, and i
u ned ou o be he bigges limi a ion o hem. Fo he load ange Δσ = 10 MPa, accep able ep esen a i e esul s can
be ob ained wi h bo h specimens (e en hough he es ing imes end o be e y long o he PE100 and PE100RC
4 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
g ades). Howe e , going highe wi h he load ange causes he pipe specimens o b eak wi h a duc ile ailu e, which
is illus a ed by he ac u e su ace in he Fig. 4, whe e a pipe specimen made o ma e ial 1 (PE 80) loaded by Δσ =
12 MPa ailed a e N =13694 cycles by duc ile ailu e – no SCG occu ed. This happens, e en hough he s ess
in ensi y ac o ange (ΔKI = 0.59 MPa·m1/2, ob ained by FEM) a his load le el is lowe han o CRB specimens
( o Δσ = 10 MPa i is ΔKI = 0.65 MPa·m1/2), which s ill pe o m well and p oduce ep esen a i e esul s a his le el
e en o less SCG- esis an ma e ials. This is caused by he ela i ely hin wall o he pipe – he hin wall makes
cons ain in he icini y o he c ack la ge , which p e en s SCG ini ia ion a a lowe ΔKI, bu when he p opaga ion
s a s, he amoun o SCG is low because i ans e s in o he duc ile ailu e mode e y ea ly o almos ins an ly as he
ligamen becomes hinne , making he esul s no ep esen a i e.
To be able o so he ma e ials acco ding o SCG esis ance, he loading ange o Δσ = 10 MPa was chosen o all
he pipe specimens. The esul s o a igue es ing a e p esen ed in he nex sec ion.
Fig. 2. Pho o o ac u e su ace o a CRB specimen made o PE100RC – ma e ial 8 aken by op ical mic oscope. The a eas o SCG and inal
duc ile ailu e a e depic ed.
Fig. 3. Pho o o ac u e su ace o an ex uded pipe specimen made o PE100RC – ma e ial 8 aken by op ical mic oscope. The a eas o SCG and
inal duc ile ailu e a e shown in he de ail.
3.2. Fa igue pe o mance
Fig. 5 summa izes he ma e ial anking based on he numbe o cycles o ailu e N o ex uded pipe specimens and
CRB specimens, espec i ely. Fo he pipe specimens, he mean alue o N o e e y ma e ial is depic ed by black
do s. Resul s om bo h ypes o specimens di ide he ma e ials in o he polye hylene pipe g ades g oups co ec ly.
Howe e , he esul s o pipe specimens su e by high sca e wi hin e e y es ed pipe g ade, which is caused by he
lack o cons ain and lack o space o he c ack o p opaga e. This makes he c ack p opaga ion mo e suscep ible o
any de ec s and i egula i ies in he geome y as opposed o he CRB specimens, whe e he esul s a e no ably less
152 Lukáš T á níček e al. / P ocedia S uc u al In eg i y 43 (2023) 148–153
Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000 5
sca e ed. The e o e, es ing o mo e pipe specimens would be needed o ob ain mo e accu a e esul s. I mus be also
no ed he e ha he es ing imes o he ex uded pipe specimens we e app oxima ely 2 imes longe , which is caused
by he gene ally lowe s ess in ensi y ac o ange a which hese specimens mus be es ed o ob ain ep esen a i e
esul s. Tha is ano he g ea d awback o he pipe specimens.
The compa ison o bo h es s is depic ed in Fig. 6, whe e no malized numbe o cycles is plo ed o i e ma e ials,
o which bo h ypes o specimens we e es ed. The esul s o ma e ial 1 a e aken as he e e ence alues, i.e., he
esul s o N o ma e ials 2, 6, 7 and 8 a e di ided by he N o ma e ial 1. The compa ison shows ha he esis ance
agains SCG o he ma e ials 1 and 2 is he same acco ding o bo h ypes o es s. Howe e , he di e ence in SCG
pe o mance o ma e ials 6, 7 and 8 is no able only in he case o CRB es s. This demons a es he highe sensi i i y
o he CRB es as he new pipe es shows simila pe o mance o hese h ee ma e ials.
Fig. 4. Pho o o ac u e su ace o an ex uded pipe specimen made o PE80 – ma e ial 1 aken by op ical mic oscope. The a ea o duc ile ailu e
is shown in he de ail. No SCG occu ed.
Fig. 5. Expe imen al esul s o SCG esis ance measu ed on (a) ex uded pipe specimens and (b) CRB specimens.
4. Conclusions
This pape p esen s esea ch o SCG esis ance on nine di e en PE ma e ials om he pipe g ades PE80, PE100
and PE100RC. The SCG esis ance was measu ed using wo ypes o specimens: he s anda dized CRB specimens
manu ac u ed om comp ession molded pla es and new ex uded pipe specimens p oposed in his pape .
I can be concluded om he p esen ed esul s ha he new pipe specimens so ed he ma e ials in o pipe g ade
g oups (PE80, PE100 and PE100RC) co ec ly. Howe e , he esul s o all he es ed ma e ials su e by high sca e
and he e o e, mo e specimens would be needed o es ing o ob ain a leas sligh ly mo e accu a e esul s. The eason
o he high sca e o he esul s is gene ally he hin wall o he pipe specimens. I causes ha he slow c ack g ow h
6 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
is subs i u ed by he duc ile ac u e e y ea ly in he c ack g ow h p ocess, o he slow c ack g ow h does no occu
a all. The highe cons ain in he CRB specimens, which is caused by hei shape o a ull cylinde , allows o an
ea ly ini ia ion o he SCG p ocess and p o ides a su icien space o he c ack p opaga ion, which esul s in he
abili y o hese specimens o ca ch ine di e ences be ween he ma e ials. The compa ison o he pipe specimens
wi h he CRB es s con i ms his conclusion.
Fig. 6. Compa ison o esis ance agains SCG o CRB and pipe specimens.
The o iginal mo i a ion o expe imen ing wi h he ex uded pipe specimens was o sa e ime. Howe e , i u ned
ou ha he ime sa ed by he e y as specimen p epa a ion is consumed by he much longe es ing imes o he pipe
specimens. Some modi ica ions o he specimens a e possible o y educing he es ing imes and ob ain mo e
accu a e esul s – inc easing he pipe wall hickness o he specimens and p ecisely de e mining he op imal es ing
load, especially o he mo e SCG- esis an PE g ades. These modi ica ions a e planned o he upcoming wo k in his
ield.
Acknowledgemen s
This esea ch was suppo ed by he p ojec TN01000071 o Na ional Compe ence Cen e o Mecha onics and
Sma Technologies o Mechanical Enginee ing co ounded by he Technology Agency o he Czech Republic.
Re e ences
A bei e , F., Sch i esse , B., F ank, A., Be e , M., Pin e , G., 2015. Cyclic es s on c acked ound ba s as a quick ool o assess he long- e m
beha iou o he moplas ics and elas ome s. Polyme Tes ing 45, 83–92.
Beech, S., Clu on, E., 2013. In e p e a ion o esul s o ull no ch c eep es and compa ison wi h no ched pipe es . Plas ics, Rubbe and Composi es
34(7), 294-300.
Fleissne , M., 1998. Expe ience wi h a ull no ch c eep es in de e mining he s ess c ack pe o mance o polye hylene. Polyme Enginee ing and
Science (2), 330-341.
F ank, A., A bei e , A., Be ge , I., Hu ař, P., Náhlík, L., Pin e , G., 2019. F ac u e Mechanics Li e ime P edic ion o Polye hylene Pipes. Jou nal
o Pipeline Sys ems Enginee ing and P ac ice 10(1).
F ank, A., Pin e , G., 2014. E alua ion o he applicabili y o he c acked ound ba es as s anda dized PE-pipe anking ool. Polyme Tes ing 33,
161-171.
ISO. 2015. Polye hylene (PE) ma e ials o piping sys ems – De e mina ion o esis ance o slow c ack g ow h unde cyclic loading – C acked
Round Ba es me hod. ISO 18489.
ISO. 2012. Plas ics piping and duc ing sys ems: De e mina ion o he long- e m hyd os a ic s eng h o he moplas ics ma e ials in pipe o m
by ex apola ion. ISO 9080.
Lu, X., B own, N., 1992. A es o slow c ack g ow h ailu e in polye hylene unde a cons an load. Polyme Tes ing 11(4), 309-319.
Nayya , M., King, S., 2000. Piping handbook. 7 h edi ion. New Yo k: McG awHill. ISBN 0-07-047106-1.
Pin e , G., Haage , M., Balika, W., Lang, R. W., 2013. Fa igue c ack g ow h in PE-HD pipe g ades. Plas ics, Rubbe and Composi es 34(1), 25-33.
Pin e , G., Haage , M., Balika, W., Lang, R. W., 2007. Cyclic c ack g ow h es s wi h CRB specimens o he e alua ion o he long- e m
pe o mance o PE pipe g ades. Polyme Tes ing 26(2), 180–188.

Lukáš T á níček e al. / P ocedia S uc u al In eg i y 43 (2023) 148–153 153
Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000 5
sca e ed. The e o e, es ing o mo e pipe specimens would be needed o ob ain mo e accu a e esul s. I mus be also
no ed he e ha he es ing imes o he ex uded pipe specimens we e app oxima ely 2 imes longe , which is caused
by he gene ally lowe s ess in ensi y ac o ange a which hese specimens mus be es ed o ob ain ep esen a i e
esul s. Tha is ano he g ea d awback o he pipe specimens.
The compa ison o bo h es s is depic ed in Fig. 6, whe e no malized numbe o cycles is plo ed o i e ma e ials,
o which bo h ypes o specimens we e es ed. The esul s o ma e ial 1 a e aken as he e e ence alues, i.e., he
esul s o N o ma e ials 2, 6, 7 and 8 a e di ided by he N o ma e ial 1. The compa ison shows ha he esis ance
agains SCG o he ma e ials 1 and 2 is he same acco ding o bo h ypes o es s. Howe e , he di e ence in SCG
pe o mance o ma e ials 6, 7 and 8 is no able only in he case o CRB es s. This demons a es he highe sensi i i y
o he CRB es as he new pipe es shows simila pe o mance o hese h ee ma e ials.
Fig. 4. Pho o o ac u e su ace o an ex uded pipe specimen made o PE80 – ma e ial 1 aken by op ical mic oscope. The a ea o duc ile ailu e
is shown in he de ail. No SCG occu ed.
Fig. 5. Expe imen al esul s o SCG esis ance measu ed on (a) ex uded pipe specimens and (b) CRB specimens.
4. Conclusions
This pape p esen s esea ch o SCG esis ance on nine di e en PE ma e ials om he pipe g ades PE80, PE100
and PE100RC. The SCG esis ance was measu ed using wo ypes o specimens: he s anda dized CRB specimens
manu ac u ed om comp ession molded pla es and new ex uded pipe specimens p oposed in his pape .
I can be concluded om he p esen ed esul s ha he new pipe specimens so ed he ma e ials in o pipe g ade
g oups (PE80, PE100 and PE100RC) co ec ly. Howe e , he esul s o all he es ed ma e ials su e by high sca e
and he e o e, mo e specimens would be needed o es ing o ob ain a leas sligh ly mo e accu a e esul s. The eason
o he high sca e o he esul s is gene ally he hin wall o he pipe specimens. I causes ha he slow c ack g ow h
6 Au ho name / S uc u al In eg i y P ocedia 00 (2022) 000–000
is subs i u ed by he duc ile ac u e e y ea ly in he c ack g ow h p ocess, o he slow c ack g ow h does no occu
a all. The highe cons ain in he CRB specimens, which is caused by hei shape o a ull cylinde , allows o an
ea ly ini ia ion o he SCG p ocess and p o ides a su icien space o he c ack p opaga ion, which esul s in he
abili y o hese specimens o ca ch ine di e ences be ween he ma e ials. The compa ison o he pipe specimens
wi h he CRB es s con i ms his conclusion.
Fig. 6. Compa ison o esis ance agains SCG o CRB and pipe specimens.
The o iginal mo i a ion o expe imen ing wi h he ex uded pipe specimens was o sa e ime. Howe e , i u ned
ou ha he ime sa ed by he e y as specimen p epa a ion is consumed by he much longe es ing imes o he pipe
specimens. Some modi ica ions o he specimens a e possible o y educing he es ing imes and ob ain mo e
accu a e esul s – inc easing he pipe wall hickness o he specimens and p ecisely de e mining he op imal es ing
load, especially o he mo e SCG- esis an PE g ades. These modi ica ions a e planned o he upcoming wo k in his
ield.
Acknowledgemen s
This esea ch was suppo ed by he p ojec TN01000071 o Na ional Compe ence Cen e o Mecha onics and
Sma Technologies o Mechanical Enginee ing co ounded by he Technology Agency o he Czech Republic.
Re e ences
A bei e , F., Sch i esse , B., F ank, A., Be e , M., Pin e , G., 2015. Cyclic es s on c acked ound ba s as a quick ool o assess he long- e m
beha iou o he moplas ics and elas ome s. Polyme Tes ing 45, 83–92.
Beech, S., Clu on, E., 2013. In e p e a ion o esul s o ull no ch c eep es and compa ison wi h no ched pipe es . Plas ics, Rubbe and Composi es
34(7), 294-300.
Fleissne , M., 1998. Expe ience wi h a ull no ch c eep es in de e mining he s ess c ack pe o mance o polye hylene. Polyme Enginee ing and
Science (2), 330-341.
F ank, A., A bei e , A., Be ge , I., Hu ař, P., Náhlík, L., Pin e , G., 2019. F ac u e Mechanics Li e ime P edic ion o Polye hylene Pipes. Jou nal
o Pipeline Sys ems Enginee ing and P ac ice 10(1).
F ank, A., Pin e , G., 2014. E alua ion o he applicabili y o he c acked ound ba es as s anda dized PE-pipe anking ool. Polyme Tes ing 33,
161-171.
ISO. 2015. Polye hylene (PE) ma e ials o piping sys ems – De e mina ion o esis ance o slow c ack g ow h unde cyclic loading – C acked
Round Ba es me hod. ISO 18489.
ISO. 2012. Plas ics piping and duc ing sys ems: De e mina ion o he long- e m hyd os a ic s eng h o he moplas ics ma e ials in pipe o m
by ex apola ion. ISO 9080.
Lu, X., B own, N., 1992. A es o slow c ack g ow h ailu e in polye hylene unde a cons an load. Polyme Tes ing 11(4), 309-319.
Nayya , M., King, S., 2000. Piping handbook. 7 h edi ion. New Yo k: McG awHill. ISBN 0-07-047106-1.
Pin e , G., Haage , M., Balika, W., Lang, R. W., 2013. Fa igue c ack g ow h in PE-HD pipe g ades. Plas ics, Rubbe and Composi es 34(1), 25-33.
Pin e , G., Haage , M., Balika, W., Lang, R. W., 2007. Cyclic c ack g ow h es s wi h CRB specimens o he e alua ion o he long- e m
pe o mance o PE pipe g ades. Polyme Tes ing 26(2), 180–188.