loga

1. 3. Mekanisme Deformasi
➢Deformation is the change in the shape of a
substance/material due to stress applied
➢Deformation is divided into:
1. Elastic Deformation
The change in the shape of a material that returns to its
original size or shape after the load is removed.
2. Deformasi Plastis
The change in shape of a material that remains/permanent
even after the load has been removed
➢ Metal forming process is a process that achieves controlled
plastic deformation of the material until the desired metal
shape is obtained.
There is a need for a basic understanding of deformation
mechanisms
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2. 3. Mekanisme Deformasi
➢Deformasi adalah perubahan bentuk dan ukuran dari suatu
zat/material
➢Deformasi terbagi atas:
1. Deformasi Elastis
merupakan perubahan bentuk dari material yang kembali ke
ukuran atau bentuk semula setelah beban dihilangkan.
2. Deformasi Plastis
merupakan perubahan bentuk dari material yang tetap
meskipun beban telah dihilangkan
➢ Proses Pembentukan logam adalah
proses yang mengusahakan deformasi plastis yang terkontrol
pada material hingga didapatkan bentuk logam yang
diinginkan.
Perlu adanya pemahaman dasar mengenai mekanisme
deformasi
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3. Average Stress, 
C
OC //AA’// BB’
Related to the modulus
of elasticity, E
E=tegangan/regangan
=  
Modulus of
Elasticity
E=  
Strain, 
lo
F=force=gaya
l
Average Stress,
 =F/A
Strain,
 = l / lo
l= l1 – l0
A, Area
Loading and unloading indicating elastic and plastic
deformation.
Total deformation = elastic + plastic deformation
a and c are the plastic deformation after the load is
removed.
b and d are elastic deformations
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Max strain (‘till failure)
Uniform strain
Offset
yield
strength
Ultimate
tensile
strength Fracture
strength
Strain – Stress Diagram

4. T
egangan rata-rata , 
Reganganhinggapatah
Reganganuniform
Kekuatan
tarik Tegangan
Patah
Tegangan
Luluh
Metode
offset
C
OC //AA’// BB’
Berhubungan dengan
modulus elastisitas, E
E=tegangan/regangan
=  
Modulus
Elastisitas
E=  
Regangan, 
Kurvategangan-regangan teknik
lo
F=force=gaya
l
T
egangan rata-rata,
 =Fdibagi A
Regangan,
 = l dibagi lo
l=panjang akhir-panjang awal
A, luaspenampang
Pembebanan danpelepasan beban
yangmenunjukkan deformasi elastis
danplastis.
Deformasi total=jumlah deformasi
elastis dan plastis
a dancadalah deformasi plastis
setelahbeban dilepas.
bdandadalah deformasi elastis
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5.  

  = 0


Displacement of atoms during elastic deformation
atom
Deformation
less than
50%
 = shear stress
 = 0
 
The magnitude of b (atomic shear vector) in Armstrong =10-10
Deformation
more than
50%
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slip/shifted atoms
Displacement of atoms during pastic deformation

6.  

  = 0


Pergeseran atom-atom pada saat deformasi elastis
atom
Deformasi
kurang
dari 0.5%
Mengalami slip
(pergeseran atom)
Ket.
 = tegangan
geser
 = 0
 
Pergeseran atom-atom pada saat deformasi plastis
Besarnya b (vektor geser atom) dalamAmstrong=10-10
Deformasi
lebih
dari 0.5%
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7. Types of Atomic Arrangements or Atomic Crystals
Four kinds of material crystal structures
PC=primitive cubic, BCC=body-centered cubic,
FCC=face-centered cubic, HCP= hexagonal close-packed
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The general unit cell of an atomic crystal

8. Jenis Susunan Atom atau Kristal Atom
Unit sel umumdari suatukristal atom
Empatmacamstruktur kristalmaterial
PC=primitivecubic(kubusprimitif),BCC=body-centeredcubic(kubuspemusatanbadan)
FCC=face-centeredcubic(kubus pemusatansisi),HCP=hexagonal close-packed (heksagonal
tertutup padat)
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9. Examples of metal materials for each structure
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10. Contoh material logam untuk tiap struktur
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11. HWP
Examples of slip directions for each crystal
Some slip planes and directions frequently observed for BBC, FCC, and
HCP crystal structure. Considering symmetry, there are additional
combinations of slip plane and direction similar to each of these, giving a
total of twelve slip systems similar to each (a), (b), and (c), and three for
each of two cases in (d).
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The slip plane is the plane that has the densest atoms, therefore it slips/shifts
the easiest when given a shear force from the outside

12. HWP
Contoh arah slip dari tiap kristal
Beberapabidangslipdanarahpergeseran/slippadakristalBCC,FCCdan
HCP.Mempertimbangkankesimetrian,terdapattambahankombinasi bidang
danarahslip yangmiripdengantiap bidangslip diatas.
Bidang slip adalah bidang yang memiliki atom terpadat oleh
sebab itu paling mudah slip/bergeser bila diberi gaya geser dari
luar
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13. Dislocation defects
Dislocations are line defects in the arrangement of atoms.
The two basic types of dislocations
(a) edge dislocation
(b) screw dislocation
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14. Dislokasi
adalah cacat garis pada susunan atom-atom.
Duamacamdislokasi
(a) dislokasi sisi (edgedislocation)
(b) Dislokasi ulir (screwdislocation)
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15. Plastic Deformation Mechanism
Plastic deformation occurs due to atomic shifts or
dislocations caused by shear stress.
Shear deformation occurring in an
incremental manner due to dislocation motion
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16. Mekanisme deformasi plastis
Deformasi plastis terjadi karena adanya pergeseran
atom atau dislokasi yang disebabkan tegangan geser.
Deformasi geser terjadi secara bertahap akibat gerakan dislokasi
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17. Type 1 plastic deformation mechanism
Slip caused by the motion of an edge dislocation
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18. Mekanisme deformasi plastis tipe 1
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Slip disebabkan oleh gerakan dislokasi tepi

19. Type 2 plastic deformation mechanism
Slip caused by the motion of screw dislocation
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20. Mekanisme deformasi plastis tipe 2
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Slip disebabkan oleh gerakan dislokasi ulir

21. Relationship between dislocations and strength
of cold worked metals
Dislocation
Undeformed
dislocation
Due to cold working Dislocations are increasing
Dislocation movement becomes
increasingly difficult
When a load is applied,
the material becomes
stronger Proses Manufaktur II
Deformed
structural cells 0.1
(10%)
Deformed
structural cells 0.5
(50%)
Deformed
structural cells 2.0
(200%)

22. Hubungan antara dislokasi dan kekuatan logam
yang dikerjakan dingin
Dislokasi
Sel struktur yang
terdeformasi 0.1
Struktur mengecil
yangterdeformasi
Dinding sel menebal
yangterdeformasi
hingga 0.5(50%) hingga 2.0(200%)
Dislokasi yangbelum
terdeformasi
(10%)
Akibat pengerjaan dingin Dislokasi makin bertambah
Pergerakan dislokasi makin sulit
Saat diberi beban dari luar
material makin kuat
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23. Sumber literatur untuk semua bahan di slide ini:
1. Siswosuwarno, Mardjono, “Teknik Pembentukan”, FTI. ITB.
2. ASM International, 2005, ”ASM Handbook Vol.14A:
Metalworking: Bulk Forming”,ASM International
UcapanTerimakasihkepadaParaPenulissumber
literaturuntukslideini
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