fract u re, t h is ch aract erist ic m ay be t aken as a p o in t o f referen ce in t h e d et erm in at io n o f fo rm abilit y, fo r exam p le d u rin g a t en sile t est . Ho wev-
er, cases o f failu re in wh ich t h e st abilit y crit erio n bet ween t h e o u t er an d in n er fo rces is in d icat ive o f t h e ach ievable d efo rm at io n , can n o t be u sed
as a basis fo r d et erm in in g fo rm abilit y. Su ch cases in clu d e fo r exam p le t h e u n ifo rm st rain o f a m at erial wit h m arked n eckin g. Th e fo rm abilit y
o f d ifferen t m at erials d iffers even t h o u gh o t h er co n d it io n s are eq u al. Th u s it is t h at so m e m at erials are d escribed as m alleable an d o t h ers as
brit t le. Th ese d escrip t io n s are u su ally based o n t h e ch aract erist ics re- vealed in t en sile t est in g fo r fract u res d u e t o sh rin kage o r elo n gat io n .
Th e fo rm abilit y o f a m at erial is n o t a fixed q u an t it y, h o wever, it d e- p en d s o n t h e m ean h yd ro st at ic p ressu re p
m
exert ed d u rin g t h e fo rm in g o p erat io n :
Th u s, fo r exam p le, a m at erial can h ave a lo w fo rm abilit y fo r o n e t yp e o f fo rm in g o p erat io n wh ere t h e m ean h yd ro st at ic p ressu re is lo w. Ho w-
ever, if a d ifferen t form in g p rocess is em p loyed in wh ich th e m ean h yd rostatic p ressu re is h igh er, th e sam e m aterial can be form ed with ou t
p roblem s. Even m arble can be p lastically d eform ed if th e m ean h yd ro- static p ressu re exerted is su fficien tly great.
2.2.5 Units of measurement
Sin ce t h e im p lem en t at io n o f t h e law go vern in g st an d ard ised u n it s o f m easu rem en t , it is o n ly p erm issible t o u se t h e variables p rescribed by
t h e st at u t o ry in t ern at io n al u n it syst em SI u n it s. Table 2.2.1
p ro vid es a co m p ariso n o f t h e u n it s ap p lied in t h e o ld t ech n ical syst em o f m easu rem en t an d t h e SI u n it s. Th e given vari-
ables can be t ran sferred t o t h e in t ern at io n al m et ric syst em u sin g t h e fact o r 9.81. Fo r ap p ro xim at e calcu lat io n s, it is gen erally su fficien t t o
u se fact o r 10, fo r exam p le:
31
Basic terms
p p
p p
m
= +
+
1 2
3
3
1 10
kp N ≈
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
32
Basic principles of metal forming Table 2.2.1: Conversion of technical to SI units of measurement
Unit system Technical m kp s
SI M KS
Time: t 1 s
1 s Length: l
1 m 1 m
Speed: v 1 ms
1 ms Revolutions no. of strokes:
rpm rpm
Acceleration: a 1 ms
2
1 ms
2
M ass: G 9,81 kg = 1 kp s
2
m 1 kg
1 t = 1000 kg Density:
r
9,81 kgm
3
= 1 kp s
2
m
4
1 kgm
3
Force: F 9,81 kg ms
2
= 1 N New ton = 1 kg ms
2
1 kp 1M P = 1000 kp 1 kN = 1000 N
Pressure: p 9,81 Nm
2
= 1 kpm
2
1 Nm
2
= 1 Pa Pascal = 1 kgm s
2
0,0981 bar = 1 at 10
5
Nm
2
= 1 bar 1,333 mbar = 1 Torr
Tension:
s
9,81 Nmm
2
= 1 kpmm
2
1 Nmm
2
Torque: M 9,81 N m = 1 kp m
1 N m 1 kN m = 1000 N m
M ass moment of inertia: J 9,81 kg m
2
= 1 kp m s
2
1 kgm
2
Performance: P 9,81 W = 1 kp ms
1 N ms = 1 W Watt 0,7355 kW = 1 PS
1kW = 1000 W Work: W
9,81 J = 1 kp m 1 J Joule = 1 N m = 1 W s
1kJ = 1000 J Quantity of heat: Q
4,19 kJ = 1 kcal 1 kJ
Sound pressure level: L 1 dBA
1 dBA
Bibliography
DIN 8580 Entw urf: M anufacturing M ethods, Classification, Beuth Verlag, Berlin. DIN 8582: M anufacturing methods, forming, classification, subdivision, Beuth Verlag, Berlin.
DIN 8583: M anufacturing methods, forming under compressive conditions, Part 1- 6, Beuth Verlag, Berlin.
DIN 8584: M anufacturing methods, forming under combination of tensile and compressive conditions, part 1 - 6, Beuth Verlag, Berlin.
DIN 8585: M anufacturing methods, forming under tensile conditions, part 1- 4, Beuth Verlag, Berlin. DIN 8586: M anufacturing methods, forming by bending, Beuth Verlag, Berlin.
DIN 8587: M anufacturing methods, forming under shearing conditions, Beuth Verlag, Berlin. DIN 8588: M anufacturing methods, terms, dividing, Beuth Verlag, Berlin.
Lange, K: Umformtechnik, Band 1: Grundlagen, Springer-Verlag, Heidelberg 1984.
Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998
3 Fundamentals of press design
3.1 Press types and press construction
