07 Disain Las

1DESAIN LAS(Welding Design)

Departemen Metalurgi & MaterialFakultas Teknik Universitas Indonesia

Konsep Desain & Fabrikasi Las

2Sambungan Las (Weld Joint) Sambungan las merupakan

penerima logam pengisi yangdidepositkan.

Sambungan las dipilihberdasarkan 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 )

dibentuk bila dua anggota sambunganyang berada kurang lebih dalam bidangyang sama didekatkan antara ujung satusama lainnya.

dapat digunakan dengan atau tanpapersiapan terhadap anggota sambunganyang memiliki ketebalan yang samaataupun berbeda.

umumnya digunakan pada subassemblies,selama fabrikasi dan proses perbaikan.

3Butt Joint

Butt joint- a jointbetween twomembers alignedapproximately inthe same plane

Different Edge Shapes andSymbols for some Butt-Joints

4Application for some Butt-Joints

Sambungan Sudut (corner joint)

Merupakan sambungan las yang dibentukbila dua anggota sambungan diposisikanmembentuk sudut kurang lebih 90dengan sambungan las pada bagian luaranggota sambungan.

Umumnya digunakan pada konstruksibejana tekan dan tangki. Logam pengisidapat dibutuhkan dan dapat pula tidaktergantung pada desain dan fungsisambungan.

5Corner Joint

Corner joint - a jointbetween two memberslocated at right anglesto each other

Some Different Edge Shapesand Symbols for Corner Joints

6Sambungan T ( T-joint )

Merupakan sambungan las yang dibentukbila dua anggota sambungan diposisikankurang lebih 90 satu sama lain dalambentuk T.

Jika dimungkinkan, dilas pada keduasisinya untuk mendapatkan kekuatanmaksimum.

umumnya digunakan dalam fabrikasistruktur penopang dimana bebanditransfer ke bidang yang berbeda padakurang lebih 90.

T-Joint

T- joint - a joint betweentwo members locatedapproximately at rightangles to each other inthe form of a T

7Some Different Edge Shapesand Symbols for T-Joint

Application for T-Joint

8Sambungan Tumpang (lap joint)

Merupakan sambungan las yang dibentukbila dua anggota sambungan diposisikansaling menumpuk satu sama lain.

Lebih kuat dibandingkan dengansambungan tumpul, tetapimengakibatkan terjadinya penambahanberat.

umumnya dilas pada kedua sisinya umumnya digunakan selama proses

perbaikan dan untuk menambah panjangmaterial standar ke panjang yangdiperlukan

Lap Joint

Lap Joint- a jointbetween twooverlappingmembers

9Some Different Edge Shapesand Symbols for Lap Joints

Sambungan Sisi (edge joint)

merupakan sambungan las yangdibentuk bila sisi dua anggotasambungan akan disambung.

sisi yang dilas sejajar satu samalain.

sering dipakai dalam menyambungstruktur penopang dan struktur bajayang pendek.

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Edge Joint

Edge joint- a jointbetween the edges oftwo or more parallelor nearly parallelmembers

Some Different Edge Shapesand Symbols for Edge Joints

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Proper terminology is needed ineveryday job communication

Joint design identifies, the shape ,dimensions, and configuration ofthe joint

The individual workpieces of a jointare called members .

Three types members : nonbuttingmember, butting member , andsplice member

A non-butting member is a joint member that is free to movein any direction perpendicular to its thickness dimension

A butting member is a joint member that is prevented, bythe other member from movement in one directionperpendicular to its thickness dimension

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A splice member is the work piece thatspans the joint in a spliced joint

Single-splicedbutt joint

Double-splicedbutt joint with

joint filler

Types of Welds

Numerous welds can be applied to the varioustypes of joints

Considerations when choosing joint geometryand 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)

groove, fillet, plug, slot, stud, spot, projection, seam, back atau backing weld, surfacing dan flange.

Types of WeldsGroove 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 WeldsSquare and double square-groove welds

Square-groove welds are the most economicalto use, but are limited by thickness of themembers

Welds for one side are normally limited to a1/4 inch or less

Groove WeldsV-and double V-groove welds

With thicker materials joint accessibility must beprovided for welding to ensure weld soundnessand strength

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Groove WeldsBevel- and double-bevel-groove welds

Bevel- and J- groove welds are more difficult to weldthan V- or U-groove welds

Bevel welds are easier in horizontal

Types of WeldsU-groove and Double U-groove

Welds in using J- and U-grooves can beused to minimize weld metal

These welds are very useful in thickersections

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Groove WeldsJ-and double-J-groove welds

J-groove are moredifficult to weldbecause of the onevertical side (exceptin horizontal)

J-and U- are usedwhen economicfactors outweigh thecost of edgepreparation

Groove Weldsflare-bevel and flare-v-groove welds

Flare -bevel andflare-v-groove weldsare used inconnection withflanged or roundedmember

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Groove WeldsScarf

Scarf is used forbrazing

Groove Welds Their names imply what the actual

configurations look like when viewed in across section

Single groove welds are welded fromonly one side

Double groove welds are welded on bothsides

Groove welds in many combinations areused selection is influenced byaccessibility, economy, adaptation tostructural design

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Groove Welds

Fillet Welds

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Ir. Winarto, M.Sc. PhD

Welding Symbols

Understanding Welding SymbolsTerms and Definitions

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Reference Line (Required element)

Arrow

Tail

Reference Line must always be horizontal,

Arrow points to the line or lines on drawing which clearly identify the proposed joint orweld area.

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 informationto be used in making the weld.

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Reference Line (Required element)

Arrow

Tail

Reference Line must always be horizontal,

Arrow points to the line or lines on drawing which clearly identify the proposed joint orweld area.

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 informationto be used in making the weld.

Basic components of a WELDING SYMBOL

Tail omitted when reference not used

Arrow connects reference line to arrow sidemember of joint or arrow side of joint

A circle at the tangent of the arrow and the reference linemeans welding to be all around.

All the way Around

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A flag at the tangent of the reference line andarrow means Field Weld.

Field Weld Symbol

ARROW SIDE

OTHER SIDE

Weld Symbol Terminology

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Break in arrow means arrow side must be sidethat beveling or other preparation required.

Fillet Weld (Arrow Side Only)

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Fillet Weld (Other Side)

1/4

1/4

Size of Fillet Weld Noted

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1/4

1/4

(5/16)

(5/16)

Depth of preparation orgroove

Depth of penetration

Example of Double Bevel Groove weld


Plug or Slot Weld SymbolArrow Side

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5/16

5/16

What does this symbol Represent?

Single-Bevel-Groove and DoubleFillet weld Symbols

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Chain Intermittent Fillet WeldWeld both sides each end and 10inches center to center in between

1/4

1/4

2-10

2-10

10 in


Staggered Intermittent Fillet WeldWeld ends than 10 inch centersstaggered each side

10 in

10 in

2-102-101/4

1/4

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Tabel 1.1 Daftar metode pengujian takmerusak berikut singkatannya

Tabel 1.1 Daftar metode pengujian takmerusak berikut singkatannya

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KEKUATAN SAMBUNGAN LASANDalam 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-laintergantung pada spesifikasi yang diberikan atau dipersyaratkan.

Formula yang dapat digunakan untuk menentukan kekuatan sambunganuntuk lasan dengan alur dan las sudut adalah:

dimana:P = beban yang diberikanSs/c = tegangan tarik atau tekan pada penampang leher (throat)Ss = tegangan geser pada penampang lehera = tebal leherl = panjang logam las efektif a l = luas penampang leher.

laPS

laPS s

cs

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KEKUATANSAMBUNGAN LASAN

Tebal leher diten-ukandengan formula:

SSa 707,02

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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 konstruksilas seperti gambar di sebelah, jikadiketahui kekuatan geser ( ) yangsejajar pembebanan besarnya 20MPa atau N/mm2, sedangkan beban(P) yang ditanggung oleh konstruksitsb adalah 20000 N (2 Ton) denganpanjang las setiap sisi (W) sebesar100 mm.

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07 Disain Las