DESAIN LAS (Welding Design)
Departemen Metalurgi & Material Fakultas Teknik Universitas Indonesia
Konsep Desain & Fabrikasi Las
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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 )
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
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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 )
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)
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)
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
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)
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
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
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
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
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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.
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
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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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