Chapter Four Exam Flashcards by Leah G

Reheating of a flame formed area containing residual stresses is ineffective because?

Reheating is acceptable? Wrong. Maybe subsequent heat stress relieves the first sequence of heating?

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Increasing the included angle of a weld joint preparation will generally?

Increase the amount of distortion because the width of the weld face and weld volume are both increased.

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The purpose of peening the weld metal is to?

Produce compressive residual stresses on the surface.

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For welded fabrications involving butt and fillet weld joints, distortion is influenced by?

Completing the fillet welds before the butt welds? Wrong. Maybe complete butt before fillet.

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Stress is defined as?

Force per unit area. Internal force that strains area.

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Residual stress is best described as?

Strain produced by stresses that exceed yield strength of material? Wrong. Stress after process. Free of external forces. Are internally self balancing??

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Stress relaxation is a method used for

Compensating for the results of shrinkage stresses? Wrong. MaybeUse to measure residual stresses?

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Internal stresses that are locked inside the metal following cutting and welding are?

Residual stresses.

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Mechanical straightening is the most controllable method of correcting distortion. What is a significant limitation of mechanical straightening?

Mechanical straightening can cause cracking.

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What is the modulus of elasticity or Young’s modulus?

Relationship between stress and strain.

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The temperature reached during flame straightening must?

Be high enough to produce upset.

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The best area to produce the first tack weld in butt joints in hollow sections to be welded with the SMAW process is?

Where the root opening is the smallest.

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How can you use Young’s modulus for estimating compressional forces (restricted expansion) during heating a bar that has restricted expansion?

Calculate total compressive forces exerted on the bar.

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Is residual stress readily visible and measurable? Yes or no

No.

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When using heat spots or wedges, it is a good practice to?

Apply heat to bottom of part to allow gravity to straighten it? Wrong. Apply heat to short side of curved object to stretch it? WRONG.

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A method of reducing distortion that involves an external force during welding is called?

Restraint.

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In flame straightening or forming of low alloy steel members, what colour should be watched for?

Dull or Cherry red.

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Fillet welds created in several small passes will cause

More angular distortion.

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Distortion in structural shapes with eccentric weld joints will produce which type of distortion?

Bending.

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Is it recommended to apply stress relief following mechanical straightening? Yes or no.

Yes.

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What is the difference between transverse shrinkage and longitudinal shrinkage in a butt joint?

Longitudinally the weld shrinks longitudinally.

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The net result of thermal cutting using one torch on the long edge of a thin plate is:?

Shrinkage of cut edges due to restricted contraction of cut edge.

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In what application is back-stepping or the skip welding technique normally applied ?

Ship building, large fuel tanks.

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In the application of a V heating technique for flame straightening, the initial flame should be located where?

Wider part of the V heating area first? Wrong. In middle of V area first? Wrong.

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Thermal cutting and welding both result in some degree of distortion due largely to?

formation of residual stresses?

Provided the strength requirements are satisfied, the most appropriate method of reducing distortion in fillet welds is?

Intermittent fillet weld method.

Where is the best place to initiate spot heating in a bulged plate?

At the center of the bulge.

Post weld heat stress relief heat treatment relies on _________ to relieve stresses.

Recovery and recrystallization.

Back stepping is defined as

Applying short weld followed by another which ends at the start of the first.

Why does a hot rolled structural beam shape show compressive residual stresses at the edge of the flange? (Multiple Choice)

Because it cools first.

Flame straightening or forming is performed by quickly heating a localized area. For low alloy steels the maximum temperature of the heat spot should not exceed:

650C.

When welding a double V-butt joint, the distortion can be limited by

Alternating weld passes on either side of the joint.

The longitudinal residual stress in a butt welded joint is?

High tensile.

What is needed in order to produce a permanent upsetting of a part when heated?

Part needs to be free to expand? Wrong. Restricted contraction?

When butt welding hollow sections, distortion can be limited by?

All of above. Proper fit up and alignment, balance heat on neutral axis.

The dimensions and temperature change of the heated area are proportional to:

Resulting expansion and contraction.

When heated, a metal expands how many ways?

3D.

The expansion of metal upon heating is volumetric and results in?

Shape change reversible by removal of the external forces that caused it.

As a result of employing shielded metal arc welding to complete a root pass, the root pass tends to: (Multiple Choice)

Concave as welding progresses? Wrong. Open? Wrong.

Mechanical straightening requires the most _____ of the material?

Ductility.

Recovery is the process of dislocation motion to relieve a buildup of stress and recrystallization is___________. (Multiple Choice)

Process where new grains are formed.

What would be the effect of cambering outside on a windy day?

Wind kink sideways.

Welding two plates together along the long edge can lead to

Transverse shrinkage? Wrong.

When using a thermal cutting process, what happens to the edges of the cut after the metal cools?

Edges are in tension.

A reference point occupying a middle position of symmetrical shape is known as: (Multiple Choice)

Neural axis.

Residual stresses can be measured using?

X-ray diffraction?.

Distortion is caused by?

External force? Wrong.

When welding heavy plates it is a good idea to have a small root opening rather than butting the parts tightly together because: (Multiple Choice)

The small root opening will allow the plates to move together as the weld shrinks and help to prevent cracking.

Distortion in hollow section manifolds can be reduced by using:

Strong backs.

What does the strain gauge measure in the stress-relaxation method?

Stress? Wrong.

Shrinkage forces along the length of the weld line are known as?

Maybe longitudinal forces?

Thermal and mechanical processes used during manufacturing can cause a condition in the metal known as: (Multiple Choice)

Manufacturing stresses? Wrong.

Part of a good welding procedure should include:

Welding technique, voltage and distortion.

To become reduced in size, to pull together, shrink, or wrinkle is known as?

Contraction.

Why is the use of a carbon steel fixture not allowed to contact stainless steel directly? (Multiple Choice)

May cause corrosion.

An increase in plate thickness will

Decrease longitudinal shrinkage.

When a component is welded on one side only, the unbalanced shrinkage forces will:

Cause the welded side to shorten.

How does the travel speed in welding affect the resulting distortion?

High travel speeds tend to uniformly heat the plate? Wrong. Maybe the incorrect speed will create temperature gradients? Wrong....

Ductility is a property of a material that:

Allows it to be moulded or shaped.

A plate was heated uniformly throughout and was left on the top of a table to cool down. The plate would: (Multiple Choice)

Be the same as before heated.

Is there is any correlation between the neutral axis and the centre of gravity of the cross-section of a shape? Yes or no. (Multiple Choice)

Yes.

The unit of measurement for the coefficient of thermal expansion is

micrometers per metre per degree celsius.

In flame straightening, if the temperature is too low the member will not be straightened. Why? (Multiple Choice)

There is insufficient heat to produce an upset.

Cambering a beam will allow a curvature predominantly in which of the following directions? (Multiple Choice)

Flange curl up or down and web stays flat.

Which of the following will produce the least angular distortion in a fillet joint?

Single pass welding.

For the same plate thickness and heat input, in plate A the travel speed is equal to 5 m/sec and plate B is equal to 10 m/sec. Which plate would distort more? (Multiple

Plate B has less distortion.

The result of uneven heating can be used to our benefit when a change in shape is desired; one example of this is called: (Multiple Choice)

Cambering.

Patterns used to form channels vary with the direction in which the movement takes place. If cambering is required, heat should be applied: (Multiple Choice)

To the flange in form of V heating and block heating the web? Wrong. In the form of equal block heating flange and web?? Wrong.

One of the best methods to limit distortion in a stainless steel manifold is to:

Apply local preheat to joints.

Which alloys expand more after heating, mild steel or austenitic stainless steel?

Austenitic SS.

X-ray diffraction is used to measure residual stresses and compare changes in: (Multiple Choice)

Atomic spacing.

The final camber should not be checked until the member has cooled completely.(True/False)

True.

Increasing the included angle of a weld joint preparation will generally: (

Increase amount of distortion because the width of the weld face and weld volume are both increased.

In order to control distortion, complex parts are built in fixtures. A fixture:

Must always be used to prevent distortion? Wrong.

Preheating reduces distortion by:

Providing more uniform expansion and contraction?

Distortion is the result of?

Permanent shape change created by free expansion and contraction in one or more directions? Wrong.

Cracking will most likely occur when

Free expansion and contraction are prevent.

A reference point occupying a middle position of symmetrical shape is known as:

The neutral axis.

The formulae "e = a × ΔT" is used to calculate?

Thermal strain.

Is there any thermal expansion on mild steel after 800 °C?

Steel expands exponentially? Wrong.

What are the forces exerted by the surrounding material at the spot heated zone?

Expansion? Wrong.

A physical property of a metal that governs its change in shape on heating is:

coefficient of thermal expansion.

On flame heating, a safety consideration is:

Not to heat over 650C? Wrong.

A shape change produced by stress is:

Strain.

When automatic oxy-fuel gas cutting a strip from one edge of a plate distortion will occur. Why? (Multiple Choice)

Uneven heating by automatic travel shortens the edge of the next cut.

An area that is upset during spot heating will produce _________ during cooling.

Radial compressive stresses? Wrong.

To produce sweep in a channel with the web on the outside of the curvature then:

Only flange needs to be shortened by using vee heat.

Line heating, strip heating, and "V" heating are techniques used in:

Distortion prevention? Wrong. Maybe Pre heating?

The welding of seams should be?

Should be stopped 300-400 mm short of unwelded butt joint.

The kerf area of an oxy-fuel cut edge represents an area of _________ stress?

Compressive? Wrong.

Restricted contraction may set up internal tensile stresses enough to cause failure if the metal is not ductile enough to accommodate the deformation. (True/False)

True.

The sequence in which welds are carried out should be studied from the viewpoint of avoiding:

Excessive welding? Wrong.

What is the type of heat pattern typically used to remove a bulge in a plate?

Spot welding.

What is the difference between transverse shrinkage and angular distortion in a butt joint? (Multiple Choice)

Width in the transverse direction is less and in angular distortion both plates contract forming a pronounced angle? If not then it is width of transverse direction is more and in angular distortion both plates contract forming prounouced angle.