Welded Connections MCQ Quiz in मल्याळम - Objective Question with Answer for Welded Connections - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Butt Weld: In this joint, the parts lie in the same plane and are joined at their edges. This joint is designed if members are to be subjected to direct tension or compression.

Fillet Weld: A fillet weld is used to fill in the edges of the plates created by corner, lap and tee joints. It is adopted when two members are to be welded at 90° to each other.

Slot Weld: It is used for attaching flat plates using one or more holes or slots in the top part and then filling with filler metal to fuse the two parts together.

Seam Weld: In seam welding, overlapping sheets are gripped between two wheels or roller disc electrodes and current is passed to obtain either the continuous seam. Hence pressure is continuously applied for welding the two members.

The effective length of groove weld:

As per IS: 800-2007, Clause 10.5.4.2 

The effective length of butt weld or groove weld shall be taken as the length of the continuous full-size butt weld, but not less than four times the size of the weld or minimum of 40 mm.

Maximum clear spacing between the effective length of the weld:

• For the welds in compression zone = Minimum of 12 × Thickness of the weld or 200 mm
• For the welds in tension zone = Minimum of 16 × Thickness of the weld or 200 mm

Ends of the longitudinal fillet welds shall not be less than the width of the member.

Explanation

As per IS 800: 2007, Table 21, the minimum size of a fillet weld is based on the thickness of the thicker plate which is given below in the

tabulated form:

Further, it is also specified in the code that when the minimum size of the fillet weld given in the table is greater than the thickness of the thinner part, the minimum size of the weld should be equal to the thickness of the thinner.

Therefore, it is clear from above that size of the fillet weld should not be less than 3mm or not more than the thickness of the thinner part.

The Value of Effective throat thickness either depends upon K values which depend on the angle between fusion faces or depends upon the size of the weld.

Throat Thickness (T_t) = K × Size of the weld

The K values vary as mentioned in the table below

Concept:

The strength of the fillet weld is found with the help of the formula given below;

Strength of weld (P) = σ × Lw × tt

Where σ = working stress in weld, L_w = total length of weld, and t_t = throat thickness of weld.

Calculation:

Given

Size of fillet weld (s) = 6 mm

Working stress (σ) = 100 MPa

Length of weld (L_w) = 100 + 100 + 100 = 300 mm

Throat thickness of fillet weld (t_t) = 0.7s = 0.7 × 6 = 4.2 mm

Strength of weld (P) = σ × L_w × t_t

Strength of weld (P) = 100 × 300 × 4.2 = 126000 N

Strength of weld (P) = 126 kN

Hence option (4) is correct.

Concept:

The Value of Effective throat thickness either depends upon K values which depend on the angle between fusion faces or depend upon the size of the weld.

Throat Thickness (Tt) = K × Size of the weld

The K values vary as mentioned in the table below

Hence, A fillet weld is not recommended if the angle between the fusion faces is less than 60°.

Reduction for the welded joint is considered only if,

\({\rm{length\;of\;joint\;}}\left( {{{\rm{l}}_{\rm{j}}}} \right) > 150 \times {t_t},\;where\;{t_t} \to throat\;thickness\;\)

\(Reduction\;factor\;\left( {{\beta _{lj}}} \right) = 1.2 - 0.2 \times \frac{{{l_j}}}{{150 \times {t_t}}}\)

\({t_t} = 0.7 \times s\;\left( {size\;of\;weld} \right),\)

if the angle of fusion is 60°to 90° or if the angle of fusion is not given.

\(\therefore {{\rm{t}}_{\rm{t}}} = 0.7 \times 6 = 4.2mm\)

Length of joint is 700 mm > 630 mm (150 × 4.2)

\(\therefore {\beta _{lj}} = 1.2 - 0.2 \times \frac{{700}}{{150 \times 4.2}} = 1.2 - 0.2222 = 0.97777\; \approx 0.98\)

Explanation:

Transverse fillet welds are preferred due to uniform stress distribution.

More load at ends in longitudinal fillet welds leading to non – uniform distribution.

Transverse fillet weld loaded uniformly leads to more uniform stress distribution.

Note:

Fillet welds closer to the minimum size of the weld are economical for the same strength. It is because the volume of material required for large size weld for the same strength will be several times that required by a smaller size weld.

Concave shape fillet welds are avoided. There are two reasons for this:

1. The concave fillet weld on cooling shrinks and there will be tensile stress on its surface. This leads to the development of cracks. However, when these are desired, it should be made in two passes – the first slightly convex, and the other passes are built – up to form a concave surface.
2. The cost of forming a concave weld will be high as this involves expertise, chipping and cleaning in all the operations involved.

Explanation:

Fillet weld: 

It is done whenever two plate overlapped and welding is to be done. This type of weld is called fillet weld and when force is applied on such type of weld shear strength is going to develop in plate. But fillet weld is not giving the proper strength and it may be fail in shear. Hence Plug or slot weld is done is plate to prevent the shear failure of plates and it experience the same shear stress as fillet weld.

Plug weld: 

In plug weld small holes are made in one plate and is kept over another plate to be connected and then entire hole is filled with filler.

Slot weld: 

In it welding is done along the periphery of hole.

Below in image all type of weld has been shown

Concept:

The Value of Effective throat thickness either depends upon K values which depend on the angle between fusion faces or depend upon the size of the weld.

Throat Thickness (Tt) = K × Size of the weld

The K values vary as mentioned in the table below

Explanation:

If the angle between fusion faces of a fillet weld is 60° - 90°, the effective throat thickness as per Indian standard is equal to \(\frac{1}{{\sqrt 2 }}\) size of weld.