DESAIN LAS

DESAIN LAS
(Welding Design)
Departemen Metalurgi & Material
Fakultas Teknik Universitas Indonesia
Konsep Desain & Fabrikasi Las
1
Sambungan Las (Weld Joint)

Sambungan las merupakan
penerima logam pengisi yang
didepositkan.

Sambungan las dipilih
berdasarkan
 lokasi,
 persiapan yang diperlukan,
 peralatan pengelasan yang
digunakan, dan
 aplikasi sambungan las.

Sambungan las dasar terdiri dari
 butt (tumpul),
 lap (tumpang),
 T,
 edge (sisi) dan
 corner (sudut)
Sambungan Tumpul ( butt joint )
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
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dibentuk bila dua anggota sambungan
yang berada kurang lebih dalam bidang
yang sama didekatkan antara ujung satu
sama lainnya.
dapat digunakan dengan atau tanpa
persiapan terhadap anggota sambungan
yang memiliki ketebalan yang sama
ataupun berbeda.
umumnya digunakan pada subassemblies,
selama fabrikasi dan proses perbaikan.
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Butt Joint
Butt joint- a joint
between two
members aligned
approximately in
the same plane
Different Edge Shapes and
Symbols for some Butt-Joints
3
Application for some Butt-Joints
Sambungan Sudut (corner joint)


Merupakan sambungan las yang dibentuk
bila dua anggota sambungan diposisikan
membentuk sudut kurang lebih 90
dengan sambungan las pada bagian luar
anggota sambungan.
Umumnya digunakan pada konstruksi
bejana tekan dan tangki. Logam pengisi
dapat dibutuhkan dan dapat pula tidak
tergantung pada desain dan fungsi
sambungan.
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Corner Joint
Corner joint - a joint
between two members
located at right angles
to each other
Some Different Edge Shapes
and Symbols for Corner Joints
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Sambungan T ( T-joint )


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Merupakan sambungan las yang dibentuk
bila dua anggota sambungan diposisikan
kurang lebih 90 satu sama lain dalam
bentuk T.
Jika dimungkinkan, dilas pada kedua
sisinya untuk mendapatkan kekuatan
maksimum.
umumnya digunakan dalam fabrikasi
struktur penopang dimana beban
ditransfer ke bidang yang berbeda pada
kurang lebih 90.
T-Joint
T- joint - a joint between
two members located
approximately at right
angles to each other in
the form of a T
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Some Different Edge Shapes
and Symbols for T-Joint
Application for T-Joint
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Sambungan Tumpang (lap joint)
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
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Merupakan sambungan las yang dibentuk
bila dua anggota sambungan diposisikan
saling menumpuk satu sama lain.
Lebih kuat dibandingkan dengan
sambungan tumpul, tetapi
mengakibatkan terjadinya penambahan
berat.
umumnya dilas pada kedua sisinya
umumnya digunakan selama proses
perbaikan dan untuk menambah panjang
material standar ke panjang yang
diperlukan
Lap Joint
Lap Joint- a joint
between two
overlapping
members
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Some Different Edge Shapes
and Symbols for Lap Joints
Sambungan Sisi (edge joint)
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

merupakan sambungan las yang
dibentuk bila sisi dua anggota
sambungan akan disambung.
sisi yang dilas sejajar satu sama
lain.
sering dipakai dalam menyambung
struktur penopang dan struktur baja
yang pendek.
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Edge Joint
Edge joint- a joint
between the edges of
two or more parallel
or nearly parallel
members
Some Different Edge Shapes
and Symbols for Edge Joints
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Proper terminology is needed in
everyday job communication
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
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Joint design identifies, “the shape ,
dimensions, and configuration of
the joint
The individual workpieces of a joint
are called members .
Three types members : nonbutting
member, butting member , and
splice member
A butting member is “a joint member that is prevented, by
the other member from movement in one direction
perpendicular to its thickness dimension”
A non-butting member is “a joint member that is free to move
in any direction perpendicular to its thickness dimension
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A splice member is “ the work piece that
spans the joint in a spliced joint
Single-spliced
butt joint
Double-spliced
butt joint with
joint filler
Types of Welds


Numerous welds can be applied to the various
types of joints
Considerations when choosing joint geometry
and weld types:
accessibility to the joint for welding
 type of welding process being used
 suitability to the structural design
 cost of welding

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Jenis Lasan
(Types of Weld)
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

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groove,
fillet,
plug,
slot,
stud,
spot,
projection,
seam,
back atau backing weld,
surfacing dan
flange.
Types of Welds
Groove Welds


A groove weld is “ a weld made in a groove
between the work pieces”
There are eight types of groove welds
 Square-groove
 Scarf
 V-groove
 Bevel-groove
 U-groove
 J-groove
 Flare-v-groove

Flare-bevel-groove
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Groove Welds
Square and double square-groove welds


Square-groove welds are the most economical
to use, but are limited by thickness of the
members
Welds for one side are normally limited to a
1/4 inch or less
Groove Welds
V-and double V-groove welds
With thicker materials joint accessibility must be
provided for welding to ensure weld soundness
and strength
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Groove Welds
Bevel- and double-bevel-groove welds

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Bevel- and J- groove welds are more difficult to weld
than V- or U-groove welds
Bevel welds are easier in horizontal
Types of Welds
U-groove and Double U-groove


Welds in using J- and U-grooves can be
used to minimize weld metal
These welds are very useful in thicker
sections
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Groove Welds
J-and double-J-groove welds
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J-groove are more
difficult to weld
because of the one
vertical side (except
in horizontal)
J-and U- are used
when economic
factors outweigh the
cost of edge
preparation
Groove Welds
flare-bevel and flare-v-groove welds

Flare -bevel and
flare-v-groove welds
are used in
connection with
flanged or rounded
member
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Groove Welds
Scarf

Scarf is used for
brazing
Groove Welds
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Their names imply what the actual
configurations look like when viewed in a
cross section
Single groove welds are welded from
only one side
Double groove welds are welded on both
sides
Groove welds in many combinations are
used selection is influenced by
accessibility, economy, adaptation to
structural design
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Groove Welds
Fillet Welds
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Welding Symbols
Understanding Welding Symbols
Terms and Definitions
Ir. Winarto, M.Sc. PhD
19
20
Reference Line must always be horizontal,
Arrow points to the line or lines on drawing which clearly identify the proposed joint or
weld area.
Reference Line (Required element)
Arrow
Tail
The tail of the welding symbol is used to indicate the welding or cutting processes,
as well as the welding specification, procedures, or the supplementary information
to be used in making the weld.
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Reference Line must always be horizontal,
Arrow points to the line or lines on drawing which clearly identify the proposed joint or
weld area.
Basic components of a WELDING SYMBOL
Arrow connects reference line to arrow side
Reference Line (Required element) member of joint or arrow side of joint
Arrow
Tail omitted when reference not used
Tail
The tail of the welding symbol is used to indicate the welding or cutting processes,
as well as the welding specification, procedures, or the supplementary information
to be used in making the weld.
A circle at the tangent of the arrow and the reference line
means welding to be all around.
All the way Around
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Field Weld Symbol
A flag at the tangent of the reference line and
arrow means Field Weld.
Weld Symbol Terminology
OTHER SIDE
ARROW SIDE
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Break in arrow means arrow side must be side
that beveling or other preparation required.
Fillet Weld (Arrow Side Only)
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Fillet Weld (Other Side)
Size of Fillet Weld Noted
1/4
1/4
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Example of Double Bevel Groove weld
Depth of preparation or
groove
1/4 (5/16)
1/4 (5/16)
Depth of penetration
Plug or Slot Weld Symbol
Arrow Side
Ir. Winarto, M.Sc. PhD
26
What does this symbol Represent?
5/16
5/16
Single-Bevel-Groove and Double
Fillet weld Symbols
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Chain Intermittent Fillet Weld
Weld both sides each end and 10
inches center to center in between
1/4
2-10
1/4
2-10
10 in
Ir. Winarto, M.Sc. PhD
Staggered Intermittent Fillet Weld
Weld ends than 10 inch centers
staggered each side
1/4
2-10
1/4
2-10
10 in
10 in
Ir. Winarto, M.Sc. PhD
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Tabel 1.1 Daftar metode pengujian tak
merusak berikut singkatannya
Tabel 1.1 Daftar metode pengujian tak
merusak berikut singkatannya
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KEKUATAN SAMBUNGAN LASAN
Dalam mendesain suatu struktur yang difabrikasi dengan pengelasan,
berbagai jenis kukuatan sambungan las harus menjadi pertimbangan,
seperti kuat tarik, energi terserap (impact), kuat fatik dan lain-lain
tergantung pada spesifikasi yang diberikan atau dipersyaratkan.
Formula yang dapat digunakan untuk menentukan kekuatan sambungan
untuk lasan dengan alur dan las sudut adalah:
Ss 
c
dimana:
P
a l
Ss 
P
a l
P = beban yang diberikan
Ss/c = tegangan tarik atau tekan pada penampang leher (throat)
Ss = tegangan geser pada penampang leher
a = tebal leher
l = panjang logam las efektif
 a l = luas penampang leher.
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KEKUATAN
SAMBUNGAN LASAN

Tebal leher diten-ukan
dengan formula:
a
S
 0,707 S
2
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T Fillet Welds
Weld subject to longitudinal shear only
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Latihan Soal Kekeuatan Las

Hitunglah ukuran minimum fillet
(fillet weld size) suatu konstruksi
las seperti gambar di sebelah, jika
diketahui kekuatan geser ( ) yang
sejajar pembebanan besarnya 20
MPa atau N/mm2, sedangkan beban
(P) yang ditanggung oleh konstruksi
tsb adalah 20000 N (2 Ton) dengan
panjang las setiap sisi (W) sebesar
100 mm.
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