Joining Materials Lesson Test (40 Questions)

Answer: C

Correct answer: Arc fusion welding. In fusion welding, an electric arc creates intense heat that melts the edges of the base metals themselves, and the molten metal flows together and solidifies into one continuous piece. Filler may be added, but melting the parent metal is the defining feature. Brazing and soldering are the tempting confusions: both melt only a filler metal while the base metal stays solid. Riveting is purely mechanical and melts nothing.

• A: Blind riveting forms a mechanical lock by deforming a rivet.
• B: Brazing melts filler while suitable base metals remain solid.
• C (correct): The base metal at the joint is melted and resolidified, with or without added filler.
• D: Soft soldering melts a lower-temperature filler rather than the parent metal.

Answer: A

Correct answer: The filler melts but the base pieces stay solid. Brazing heats the joint above about 840 °F, or 450 °C, but below the melting point of the base metals. The molten filler, often a brass or silver alloy, is drawn into the tight joint gap by capillary action and bonds to the surfaces as it cools. Because the base metal never melts, brazing can join dissimilar metals and causes less distortion than welding. The common mistake is treating brazing as welding; brazing melts only the filler.

• A (correct): Brazing uses a molten filler while the base pieces stay below their melting temperatures.
• B: Brazing joins compatible metals, not plastic parts.
• C: Melting the base metal is fusion welding, not the ordinary brazing mechanism.
• D: A brazing filler is essential; joining by heat and pressure alone describes other processes.

Answer: D

Correct answer: Soldering. Soldering uses a filler, typically a tin-based alloy, that melts below about 840 °F, or 450 °C, far below the copper leads and pads being joined. The low temperature protects heat-sensitive electronic parts while giving a joint that conducts electricity well. The distractors use much more heat or force: spot welding fuses sheet metal, oxy-fuel cutting severs steel, and hot riveting deforms heated fasteners. For circuit boards, think low-melting solder.

• A: Cutting separates metal and is unsuitable for normal electronic contacts.
• B: Riveting deforms a fastener and is not the common board-solder connection.
• C: Spot welding produces localized pressure welds between sheet members.
• D (correct): Solder is chosen to bond suitable electrical contacts while avoiding parent-metal melting.

Answer: D

Correct answer: A rivet. A rivet is a pin with a head on one end. It passes through aligned holes in both sheets, and the plain end, the tail, is then hammered or squeezed so it spreads into a second head. With a head on each side, the sheets are clamped and cannot separate. No melting is involved, which separates riveting from soldering or welding. A tungsten electrode and a flux brush are welding and soldering tools, not fasteners.

• A: Solder melts and wets a joint rather than forming a rivet tail.
• B: A brush applies flux but does not retain the sheets by deformation.
• C: A tungsten electrode creates an arc in GTAW and is not set as a rivet.
• D (correct): Setting a rivet enlarges its tail and traps the aligned members.

Answer: C

Correct answer: SMAW (stick welding). Shielded metal arc welding uses a metal rod coated with flux. As the arc melts the rod, the core becomes filler metal while the coating burns to make shielding gas and forms slag, a crust that protects the cooling weld and is chipped off afterward. That slag is the giveaway. TIG is the tempting choice, but it uses a nonconsumable tungsten electrode and a separate shielding gas, so it leaves no flux slag.

• A: Adhesives cure or solidify and do not use coated weld rods.
• B: TIG uses a nonconsumable tungsten electrode with separate shielding.
• C (correct): The consumable coated electrode supplies weld metal and shielding products.
• D: Crimping uses deformation of a terminal instead of an electric arc.

Answer: C

Correct answer: A nonconsumable tungsten electrode. In TIG welding, the tungsten electrode only carries the arc; because tungsten has an extremely high melting point, it does not melt into the weld, and filler is added separately by hand if needed. MIG welding instead feeds a consumable wire that is both the electrode and the filler. That consumable versus nonconsumable difference is the key distinction. The other choices describe riveting and gluing, which are not arc processes at all.

• A: Continuous consumable wire is characteristic of GMAW; TIG instead uses a tungsten electrode that does not supply filler in this way.
• B: The tail of a rivet is set by deformation without creating a tungsten welding arc or using the TIG process.
• C (correct): The TIG electrode is tungsten and ordinarily does not become the filler metal.
• D: Adhesive curing does not produce a tungsten arc.

Answer: D

Correct answer: To help control oxides and improve filler wetting. When metals are heated, oxygen quickly forms oxide films on their surfaces, and molten filler will not bond to oxides; it beads up instead of spreading. Flux cleans away and blocks those oxides during heating so the filler can wet the metal and flow into the joint. Flux is not a substitute for cleaning off grease and dirt beforehand, and some flux residues are corrosive and should be removed after the joint is made.

• A: Flux does not remove every form of dirt, grease or unsuitable coating.
• B: Normal soldering and brazing leave the base metal solid.
• C: Flux does not guarantee corrosion resistance, and its residues can even cause corrosion.
• D (correct): Proper flux assists removal/control of oxide films so filler can wet prepared surfaces.

Answer: A

Correct answer: A properly designed bolted joint. Bolted joints hold parts together by clamping force from a threaded fastener, so removing the nut releases the parts without damaging them. That makes bolts the choice for parts that need inspection, repair or replacement. Welds, structural adhesives and solid rivets are considered permanent: separating them requires cutting, grinding, drilling or breaking the bond. The distinction to remember is temporary fasteners versus permanent joining methods.

• A (correct): Bolts and nuts can generally be unthreaded without intentionally destroying the main members.
• B: Separation normally needs cutting or other damage-producing processing.
• C: Separation may damage the adhesive and bonded surfaces.
• D: A rivet commonly must be drilled or otherwise destroyed for removal.

Answer: D

Correct answer: It forms a retaining head despite limited back-side access. A blind rivet is installed entirely from one side: a setting tool pulls a mandrel through the hollow rivet body, which swells the far end into a second head that clamps the sheets together. That makes it useful on tubing, panels and box sections where you cannot reach behind the work. It is a mechanical process, so any answer involving melting or curing describes soldering, welding or adhesives instead.

• A: Melting solder into a hole is soldering, which plays no part in setting a blind rivet.
• B: Fusing the sheets describes welding; a rivet joins by deformation, not melting.
• C: Curing describes adhesives, not the mechanical setting of a rivet.
• D (correct): Blind riveting provides a means of retaining material when rear access is limited.

Answer: A

Correct answer: Lifting one bonded edge away from the surface. In peel, the load pulls a flexible piece away at an angle, so nearly all the force is carried by a thin line of adhesive where separation is happening instead of being shared across the whole bonded area. That is why adhesive joints are weak in peel and why designers try to load them in shear. The tempting choice, parallel sliding, is shear, which spreads stress over the full overlap. Think of peeling tape off a box.

• A (correct): Peel action concentrates separation near an advancing edge of the bondline.
• B: Bolt engagement is not an adhesive peel test.
• C: That is a simplified description of shear loading.
• D: Uniform compression squeezes the assembly together, whereas peel forces lift one edge away and concentrate opening stress.

Answer: D

Correct answer: One member meeting another at approximately a right angle. Picture the letter T: the edge or end of one piece rests against the face of the other, often near its middle, at about 90 degrees. Welds or fasteners are then placed in the corners where the two pieces meet. Do not confuse it with a corner joint, where the pieces meet at their edges to form an L, or a butt joint, where two pieces lie in the same plane edge to edge.

• A: A butt joint usually places two members edge to edge, not with one piece meeting the middle of another at right angles.
• B: Parallel pieces with a gap do not meet at all, so they cannot form the perpendicular T intersection.
• C: A lap joint places surfaces over one another in an overlap, which is different from the perpendicular T geometry.
• D (correct): The end of one member forms a T-like intersection with another member.

Answer: C

Correct answer: Lap joint. Adhesives perform best when they carry load in shear spread over a wide area, and a lap joint provides exactly that by placing one piece over the other so their faces share a broad bonded region. Within limits, more overlap gives more bonded area to carry the load. A plain butt joint offers only the small edge or end area for glue, so it is much weaker unless reinforced. Memory hook: lap means overlap.

• A: An ordinary butt arrangement lacks an overlap area.
• B: A separation does not create the specified facing overlap.
• C (correct): A lap joint offers facing overlapped surfaces where adhesive can transfer load.
• D: Without an interface or joining method no bonded overlap exists.

Answer: D

Correct answer: Contamination can prevent effective wetting and adhesion. An adhesive must flow out and make intimate contact with the surface, called wetting, before it can grip. Oil, grease, dust, scale or flaking paint sit between the adhesive and the material, so the glue sticks to that weak layer instead and the joint fails there. That is why surfaces are degreased and often lightly abraded first. Cleaning does not change cure time or the properties of the base metal.

• A: A clean surface does not bypass adhesive chemistry.
• B: Cleaning has no such guaranteed temperature effect.
• C: Oil often interferes with many adhesive systems.
• D (correct): Oil, loose coatings and dirt can disrupt the intended surface bond.

Answer: C

Correct answer: The base metal. Brazing joins parts with a filler alloy that melts above about 450 °C (840 °F) but below the melting point of the parts being joined. The filler flows into the joint while the base metal only gets hot enough to be wetted. That is the key difference from fusion welding, where the base metal itself melts. Notice that the filler, the added joining metal and the braze alloy are three names for the same molten material.

• A: This refers to the molten filler in brazing.
• B: Filler must melt and wet surfaces in the described process.
• C (correct): Brazing filler is chosen to flow while the base metal remains solid.
• D: The braze alloy is the filler expected to melt.

Answer: B

Correct answer: Resistance spot welding. Two copper electrodes clamp the overlapping sheets and send a large current through them. Electrical resistance at the sheet interface generates intense heat, forming a small molten nugget that solidifies under pressure into a weld spot. No filler rod is needed, which is why the method is common in auto-body and appliance sheet metal. TIG is the tempting distractor, but it uses an open arc rather than clamping electrodes.

• A: A tap forms an internal thread rather than a spot weld.
• B (correct): Current and pressure join the overlapped sheets at localized points.
• C: TIG relies on an arc and is not the specified pressed spot-electrode method.
• D: Wood glue joins by curing at a prepared interface, not electric spots.

Answer: C

Correct answer: Crimping. A crimping tool squeezes the barrel of a terminal or connector so the metal deforms permanently around the wire strands, creating a tight mechanical and electrical connection without heat. It is the standard way to attach lugs and connectors in vehicle and electrical work. Brazing and stick welding both require melting metal, and adhesives rely on a material that cures, so none of them involves simply squeezing a sleeve onto a wire.

• A: Brazing uses molten filler and capillary wetting.
• B: Stick welding forms a weld with a coated electrode.
• C (correct): Crimping plastically deforms a compatible terminal to grip the conductor.
• D: Adhesive bonds depend on a curing or solidifying material.

Answer: A

Correct answer: Base metal next to the weld changed by heat but not melted. During welding, heat spreads from the molten pool into the surrounding metal. The band that never melts but still gets hot enough to change its grain structure, hardness or toughness is the heat-affected zone. It can end up harder and more brittle, or softer, than the original metal, so it is a common place for cracks to start. A frequent mistake is calling the weld bead the HAZ; the bead is the fusion zone.

• A (correct): The heat-affected zone never melts, yet its structure and properties are altered by the welding heat.
• B: Filler in the pool belongs to the fusion zone, not the adjacent base-metal HAZ.
• C: Adhesive cure has nothing to do with a welding heat-affected zone.
• D: A normal weld melts only a small region, not the whole workpiece.

Answer: B

Correct answer: Appearance alone cannot guarantee hidden joint quality. Visual inspection only shows the surface. Porosity, lack of fusion, incomplete penetration and internal cracks can all lie beneath a neat bead, which is why critical welds are checked with methods such as ultrasonic, radiographic or destructive testing. A smooth bead suggests good technique but proves nothing about the inside. Be wary of any answer that turns a single observation into an absolute guarantee.

• A: Fatigue depends on design, materials and actual service.
• B (correct): Inspection may need appropriate methods because some defects are not visible.
• C: Even a visually smooth bead cannot establish compliance with the approved welding procedure, materials, or required hidden-defect inspection.
• D: Subsurface voids may not appear at the surface.

Answer: B

Correct answer: Molten filler being drawn into a close-fitting joint gap. Capillary action is the same effect that pulls water up a narrow glass tube or into a paper towel: a liquid that wets a surface is drawn into a narrow space by surface tension. In brazing, the clean, fluxed joint and small clearance pull molten filler through the joint, even upward against gravity. If the gap is too wide, the capillary pull weakens and the filler will not fill it. The base metal stays solid throughout.

• A: Threading a bolt is mechanical engagement of helical threads, not capillary flow of molten filler.
• B (correct): Wetting and capillary forces help distribute filler within the prepared clearance.
• C: Rivet expansion is mechanical deformation rather than capillary flow of a liquid.
• D: In brazing the base pieces stay solid; only the filler melts.

Answer: D

Correct answer: It can spread the bearing load over a larger local area. A bolt head or nut touches only a small ring of surface, so clamping force there can crush soft material such as wood, aluminum or plastic, or pull into an oversized hole. A flat washer enlarges that contact area, lowering the pressure for the same clamp force, and gives a smooth surface for the head to turn on. It does not lock the bolt; that job belongs to lock washers, locknuts or thread-locking compound.

• A: A plain flat washer is not a locking device and does not prevent loosening.
• B: Bolt strength depends on its material and size; a washer does not change it.
• C: A washer stays between fastener and surface to distribute bearing load; it does not heat and fuse the adjacent metal parts.
• D (correct): Flat washers provide a bearing surface and often spread contact pressure.

Answer: B

Correct answer: 600 mm². The area of a rectangle is length × width, so multiply the two sides: 30 mm × 20 mm = 600 mm². The units multiply too, giving square millimeters. A common slip is adding the sides (

), which produces a length, not an area. A quick estimate helps: three tens times two tens is six hundreds. In joint design, this overlap area matters because it is the surface that carries the load.

• A: This product is not the multiplication of the given dimensions.
• B (correct): Area equals 30 × 20 = 600 square millimeters in the simple rectangular model.
• C: Adding side lengths does not give rectangular area.
• D: That value doubles the specified overlap area.

Answer: B

Correct answer: 2 N/mm². Stress is force spread over area, so divide the load by the area: 1,200 N ÷ 600 mm² = 2 N/mm². Because 1 MPa equals 1 N/mm², that is also 2 MPa. The usual error is flipping the fraction to area over force, which gives 0.5 and the wrong units. A quick sense check: spreading the same load over a larger area should lower the stress, so area belongs in the denominator.

• A: This reverses the force and area relationship.
• B (correct): Nominal stress is F/A = 1,200/600 = 2 N/mm²; 1 N/mm² is 1 MPa.
• C: This incorrectly uses the area as stress.
• D: Multiplying load by area does not calculate stress.

Answer: C

Correct answer: 5 N·m. Torque measures the turning effect of a force and equals force times the perpendicular distance from the pivot: 20 N × 0.25 m = 5 N·m. A longer wrench handle increases torque for the same push, which is why extra leverage loosens stubborn bolts. Dividing instead of multiplying gives 80 or 0.0125, and units help catch that: torque must come out in newton-meters, a force multiplied by a length.

• A: Dividing force by length gives neither correct magnitude nor units.
• B: Force is not the same physical quantity as torque.
• C (correct): Torque magnitude is perpendicular force times lever arm: 20 × 0.25 = 5 N·m.
• D: Dividing the lever arm by the force (0.25/20) inverts the torque relationship.

Answer: D

Correct answer: 200 N. When identical fasteners share a load equally, each carries the total divided by the number of fasteners: 800

Adding fasteners lowers the load on each, which is why critical joints use several bolts. The trap is multiplying by four, which treats the fasteners as adding load rather than sharing it. Real joints rarely share perfectly because hole fit and stiffness vary, so designers allow a safety margin.

• A: That assigns the entire total load to each fastener.
• B: This does not result from dividing by four.
• C: Multiplication by four increases rather than divides total load.
• D (correct): With the stated ideal equal-share assumption, divide 800 N by four.

Answer: D

Correct answer: Brazing uses a filler that melts at a higher temperature. Soldering and brazing work the same way: a filler metal melts and flows into the joint while the base metal stays solid. The difference is the filler's melting temperature. By the usual convention, fillers melting below about 450 °C (840 °F) mean soldering, and above that mean brazing. Welding is the process that melts the base metal itself, so any choice saying soldering melts the parts confuses it with welding.

• A: Brazing depends on a filler alloy that melts and wets the base materials.
• B: In soldering the parent materials stay solid; only the low-temperature filler melts.
• C: Bolts and nuts are mechanical fasteners; soldering uses a molten filler at the interface.
• D (correct): Brazing fillers melt above roughly 450 °C (840 °F), while solder fillers melt below it.

Answer: A

Correct answer: Continuously fed wire. In gas metal arc welding, often called MIG, a spool of wire is pushed by drive rolls through the gun. The wire is both the electrode that carries the arc and the filler that melts into the weld, so it is consumed continuously while shielding gas protects the pool. The tempting distractor, a fixed tungsten tip, belongs to TIG welding, where the electrode is not meant to melt and filler is added separately.

• A (correct): GMAW commonly feeds a wire electrode through the gun toward the arc.
• B: Adhesives do not provide a wire electrode.
• C: That is riveting and uses no arc electrode.
• D: A tungsten tip is a nonconsumable electrode typical of GTAW/TIG rather than the continuously consumed wire used in ordinary GMAW.

Answer: C

Correct answer: Resin and hardener mixed in the specified proportion. Two-part epoxy cures by a chemical reaction between the resin and the hardener, not by drying. The two components are formulated to react in a set balance, so the ratio printed on the package matters. Extra hardener leaves unreacted material that can make the joint soft, tacky or brittle rather than stronger. Mix thoroughly and respect the working time, since curing begins as soon as the parts are combined.

• A: Improper ratios can impair curing and performance.
• B: Adhesive bonding does not require prior welding.
• C (correct): Correct mixture and cure conditions are essential to the intended material properties.
• D: This is unrelated to two-part adhesive chemistry.

Answer: D

Correct answer: Stop and verify thread size, pitch and alignment. Cross-threading happens when a screw enters at an angle or does not match the threads of the hole, so its threads cut across the mating threads instead of following them. A correctly matched screw usually turns in easily by hand for the first few turns. If it binds immediately, back it out, confirm the size and pitch match, and restart straight. Forcing it with more leverage strips threads and can ruin the part.

• A: Early binding is a warning sign requiring investigation.
• B: Solder is not the proper solution to thread mismatch.
• C: Extra torque can worsen damage and create a false fit.
• D (correct): Forcing mismatched threads can damage both screw and mating material.

Answer: B

Correct answer: Dowel pin. A dowel pin is a precisely sized cylindrical pin fitted into matching holes in two parts so they line up the same way every time they are assembled. Bolts or screws usually supply the clamping force, while the dowels provide accurate location and resist sideways shifting. The other choices are consumables for welding, soldering or gluing and have no precise fit. A useful cue: when a question says align or locate, think pins.

• A: A welding electrode is not intended as a locating pin.
• B (correct): A dowel pin primarily locates components, although details depend on design.
• C: A mixing nozzle dispenses adhesive, not a metal locating dowel.
• D: Solder is not a precision locating pin.

Answer: A

Correct answer: A designed screw-and-nut or threaded-fastener joint. Joints fall into two broad groups: permanent ones such as welds, set rivets and structural adhesives, and removable ones such as screws and bolts. A cover that must come off for maintenance needs a removable method, and threaded fasteners can be loosened and retightened many times without harming the parts. The permanent options would have to be cut, drilled out or pried apart, damaging the cover each time it is opened.

• A (correct): An accessible removable fastener provides a practical maintenance option.
• B: A continuous weld generally obstructs routine removal.
• C: A structural adhesive bonded around a cover is intended to cure into a lasting connection and is difficult to release without damage.
• D: A standard set rivet generally must be drilled out or destroyed to separate members, so it is not the usual choice for periodic service access.

Answer: A

Correct answer: Control the fire hazard under approved hot-work procedures. Welding sparks and spatter can travel many feet, roll through cracks and smolder unnoticed, so combustibles near hot work must be moved away or covered with fire-resistant blankets before the arc is struck. Hot-work procedures often add a permit, an extinguisher at hand and a fire watch during and after the job. Eye protection matters too, but it protects the welder, not the shop, so fire control comes first.

• A (correct): Combustibles, shielding and needed watches are addressed before sparks are produced.
• B: Damp materials may still ignite after heating or drying.
• C: Sunglasses do not replace welding protection or fire precautions.
• D: Sparks and heat can travel or conduct to other locations.

Answer: C

Correct answer: Hazards depend on process, metals, coatings and ventilation. Welding fumes come from everything that gets heated: the base metal, filler, flux, and any paint, plating or oil on the surface. Galvanized steel releases zinc oxide, and stainless steel can release chromium compounds, so the same task can be far more hazardous on a different material. Ventilation, local exhaust and respirators are chosen after assessing these factors. A face shield guards against radiation and spatter but does nothing to clean the air.

• A: A face shield blocks spatter and radiation but provides no ventilation or air filtering.
• B: Coatings, base metals, fluxes and shielding reactions can all contribute fumes and gases.
• C (correct): Exposure assessment and suitable controls are needed for the actual task.
• D: Working outdoors can reduce but does not automatically eliminate fume exposure.

Answer: A

Correct answer: A weld at the junction of surfaces meeting at an angle. A fillet weld fills the inside corner where two surfaces meet, usually at about 90 degrees, and has a roughly triangular cross section. It is the most common weld type and is used on T-joints, lap joints and corner joints. On drawings, the fillet weld symbol is a small right triangle on the reference line. Contrast it with a groove weld, which is placed between edges, such as in a butt joint.

• A (correct): Fillet welds commonly occupy T, corner or lap intersections.
• B: A set rivet is a separate mechanical fastener, not a weld.
• C: A cured adhesive layer is a bonded joint, not a weld bead.
• D: A bolted interface is a mechanical connection, not a weld.

Answer: B

Correct answer: Peel. In peel, a flexible piece is pulled away so that almost all the load is concentrated on a narrow line of adhesive at the separation front, much like pulling tape from a roll. Because so little bond area resists at any instant, adhesives are much weaker in peel than in shear. Uniform shear is the tempting distractor, but shear slides the surfaces parallel and loads the entire overlap. Designers limit peel by adding fasteners or stiffening the edges.

• A: A preload exists in a tightened fastener, not the described peel test.
• B (correct): Peel concentrates opening stresses near the edge being separated.
• C: Compression squeezes rather than peels the surfaces.
• D: Pure shear slides surfaces in parallel rather than lifting an edge.

Answer: A

Correct answer: Parts are retained by a pin or fastener without melting filler. Mechanical joining holds parts by shape, friction or clamping: bolts, screws, rivets, pins, crimps and seams. Metallurgical bonding instead creates a bond through molten metal, either by melting the base metal (welding) or by melting a filler that wets it (brazing and soldering). A simple test is to ask whether anything melts. If nothing does, the joint is mechanical; if metal melts and solidifies, it is metallurgical.

• A (correct): Mechanical joints use geometry, clamping or deformation for retention.
• B: Soldering bonds through a melted filler that solidifies, which is metallurgical rather than mechanical.
• C: Brazing employs molten filler metal that wets a prepared joint and does not depend on simply placing a dry pin or bolt through parts.
• D: Fusion welding creates a metallurgical bond through melted and resolidified metal, not a fastener.

Answer: B

Correct answer: Resistance spot welding. The clues are overlapped sheets, electrode pressure, electric current and isolated spots. The electrodes squeeze the sheets while current flows, and resistance at the sheet interface creates heat that melts a small nugget, which solidifies while pressure is held. A typical car body contains thousands of these welds. A continuous arc weld is the likely mix-up, but it produces a running bead along a seam rather than separate circular spots.

• A: Wood adhesives and nails do not employ current through metal sheets.
• B (correct): Spot electrodes heat and press sheet interfaces to create discrete welds.
• C: Threadlocker acts on threaded fasteners, not sheet spot joints.
• D: Continuous arc beads do not describe isolated pressed current spots.

Answer: B

Correct answer: Edge stresses, peel and imperfect bonding may matter. Dividing load by overlap area gives an average stress that assumes every part of the bond works equally. In a real lap joint the pieces stretch and bend under load, so stress piles up at the ends of the overlap, and the offset load adds some peel there. Voids, poor surface preparation or incomplete cure reduce the effective area further. The average can look safe while the edges are already overloaded, which is why designers apply safety factors.

• A: There is no universal failure stress; strength varies widely among adhesive types.
• B (correct): Actual lap joints distribute stress nonuniformly and can contain defects.
• C: Area does affect average stress; it simply is not sufficient on its own.
• D: Structural adhesive lap joints are often permanent, and removability does not affect the area calculation.

Answer: A

Correct answer: Riveting—deforming a fastener; soldering—melting filler. Sort joining methods by what physically happens. Riveting deforms a metal fastener to form a second head, a mechanical process. Soldering melts a low-temperature filler that wets the parts while they stay solid. Brazing is similar but uses a hotter filler, welding melts the base metal itself, and adhesives cure chemically. Each wrong pairing attaches a mechanism to the wrong process, such as describing brazing as melting the base pieces.

• A (correct): These are the distinguishing mechanisms for basic rivets and solder joints.
• B: These processes are unrelated to the listed mechanisms.
• C: The first statement confuses brazing with fusion welding, while the second mistakes welding for chemical adhesive cure; neither pairing is correct.
• D: Neither crimping nor riveting normally works that way.

Answer: C

Correct answer: 2 MPa. Work in two steps. First find the bonded area: 25 mm × 40 mm = 1,000 mm². Then divide load by area: 2,000 N ÷ 1,000 mm² = 2 N/mm². Since 1 N/mm² equals 1 MPa, the answer is 2 MPa. The common mistakes are skipping the area step and reporting the load itself, or slipping a decimal place to get 20 MPa. Checking that the result comes out as force per area catches most of these errors.

• A: The nominal shear stress must be load divided by bond area; reporting the whole load as stress ignores the 1,000 mm² overlap.
• B: This exceeds the correct nominal value by a factor of ten.
• C (correct): Area 25 × 40 = 1,000 mm²; stress 2,000/1,000 = 2 N/mm² = 2 MPa.
• D: This value follows an incorrect force-area calculation.

Answer: B

Correct answer: A removable mechanical fastener compatible with the joint. Start with the requirement that rules options out: the sheets must come apart repeatedly without damage. Welds, set rivets and structural adhesives are permanent, so removing them means cutting, drilling or prying, which damages the parts. Screws, bolts or quick-release fasteners can be removed and reinstalled many times. Epoxy is tempting because the stem mentions bonding, but bond strength does not help if the joint cannot be separated for service.

• A: A structural epoxy bond is not intended for easy nondestructive removal.
• B (correct): Service access is a strong reason to consider screws or bolts with suitable design.
• C: Separating a welded seam would normally require cutting and repairs.
• D: A set blind rivet usually must be drilled out, destroying it, to separate the sheets.

Answer: B

Correct answer: About 1,148 °F, so brazing. Convert:

A filler that melts above about 840 °F (450 °C), but below the base metal, is a brazing filler.

• A: The conversion is right, but soldering fillers melt at or below about 840 °F.
• B (correct): (9/5)(620) + 32 = 1,148 °F, which is above 840 °F, the brazing range.
• C: This multiplies by 9/5 but forgets to add 32.
• D: This applies the Fahrenheit-to-Celsius formula to a value that is already in Celsius.

Answer: C

Correct answer: Oxygen makes oily material burn violently. Oxygen is an oxidizer, not ordinary shop air. In oxygen-rich conditions, oil or grease can ignite and burn violently, so oxygen equipment must be kept clean.

• A: Corrosion is not the main reason; the danger is rapid, intense fire.
• B: Grease does not usefully change flame temperature; it is a fire hazard in oxygen.
• C (correct): Oxygen-rich conditions can greatly intensify combustion, so oil or grease can ignite with dangerous force.
• D: Gauge accuracy is not the issue; oil and oxygen together create a serious ignition hazard.

Answer: D

Correct answer: 125 N. Torque = force x perpendicular arm, so force = torque / arm. Convert the arm first: 32 cm = 0.32 m.

• A: This divides by 32 without converting centimeters to meters.
• B: This multiplies torque by arm length; force is torque divided by arm length.
• C: This multiplies 40 by 32; torque must be divided by the arm, in meters.
• D (correct): Convert 32 cm to 0.32 m, then force = torque / arm = 40 / 0.32 = 125 N.

Answer: B

Correct answer: Butt joint. Joint names describe geometry: edge to edge in one plane is a butt joint, overlapped pieces form a lap joint, and a right-angle meeting forms a T-joint.

• A: A lap joint overlaps one piece on top of the other.
• B (correct): A butt joint places pieces edge to edge without overlapping.
• C: A T-joint has one piece meeting another at roughly a right angle.
• D: A corner joint brings two pieces together at an angle to form a corner.

Answer: D

Correct answer: 4 MPa. Find the bonded area first: 50 mm x 15 mm = 750 mm². Then stress = force / area =

N/mm², or 4 MPa.

This is only a nominal average; real joints have edge and peel stresses.

• A: This divides the load by the 15 mm length alone instead of by the overlap area.
• B: This divides the load by the 50 mm width alone instead of by the overlap area.
• C: This divides area by load (750 / 3,000); stress is load divided by area.
• D (correct): Area = 50 x 15 = 750 mm², and 3,000 N / 750 mm² = 4 N/mm², which is 4 MPa.

Answer: A

Correct answer: Tack welds. Tack welds are short welds placed at intervals along a joint to hold the parts in alignment and keep the gap even while the full weld is made. They help resist distortion as heat from welding causes the metal to expand. Tacks are usually blended into the final weld, so they must be clean and sound. Fillet and groove welds describe the shape of the joint being welded, and spot welds are made with resistance welding on overlapping sheet metal.

• A (correct): Tack welds are small temporary welds that hold parts in alignment before the final weld.
• B: A groove weld fills a prepared opening between members; it is a full joint weld.
• C: Spot welds are discrete resistance welds made with electrode pressure and current on overlapped sheets.
• D: A fillet weld fills the corner where surfaces meet at an angle; it is not defined by holding parts temporarily.

Answer: D

Correct answer: Porosity. Trapped gas pockets are porosity. Contamination such as oil, moisture or rust and poor shielding are typical contributors, and adding more heat does not reliably cure it.

• A: Undercut is a groove melted into the base metal along the weld toe, not internal gas holes.
• B: Incomplete fusion means weld and base metal failed to bond in some region; it is not described by gas bubbles.
• C: The heat-affected zone is base metal changed by heat; it is a region, not a gas-void defect.
• D (correct): Porosity is the term for trapped gas voids in a weld.

Answer: A

Correct answer: Dissimilar metals, an electrolyte and an electrical path. Galvanic corrosion needs dissimilar metals, an electrolyte and an electrical path between the metals. Isolation, coatings and drainage can reduce the risk.

• A (correct): Galvanic corrosion needs unlike metals in electrical contact with an electrolyte such as salt water present.
• B: Unequal expansion can stress a joint, but it is a separate issue from galvanic corrosion.
• C: Overtightening can damage threads or stretch bolts, but it does not create galvanic action.
• D: Same metals without an electrolyte lack the conditions galvanic corrosion requires.

Answer: A

Correct answer: Each carries 350 N, but strength still needs checking. With equal sharing, load per rivet = 1,750

That number is only the arithmetic share; real capacity depends on rivet material, bearing, net-section tearing, edge distance and fatigue.

• A (correct): 1,750 / 5 = 350 N, yet bearing, tearing, edge distance and fatigue can still control the joint.
• B: The load share is right, but equal division alone does not prove any rivet or plate is strong enough.
• C: This divides by 4 instead of the 5 rivets that share the load.
• D: This multiplies the load by the rivet count instead of dividing it.

Answer: C

Correct answer: Hold the pieces in close contact while the glue cures. The adhesive forms the bond. Clamps simply hold the pieces aligned and in contact during the curing interval, after which they are removed.

• A: Clamps are removed after curing; the glue, not the clamps, forms the permanent bond.
• B: Ordinary clamps apply pressure only; they do not supply heat to speed curing.
• C (correct): Clamps keep the joint aligned and tight while the adhesive sets; the glue does the bonding.
• D: Clamping should hold the surfaces together, not force out the adhesive needed for the bond.

Answer: B

Correct answer: Bolts with insulating washers or coatings. Two requirements decide this: the guard must be removable, which points to threaded fasteners, and dissimilar metals in damp conditions call for a corrosion strategy such as insulating washers or coatings.

• A: Welding makes the guard permanent and aluminum is not routinely fusion welded to a steel frame.
• B (correct): Bolts allow regular removal, and isolation reduces galvanic corrosion between aluminum and steel in damp conditions.
• C: A cured adhesive is not designed for monthly nondestructive removal.
• D: Rivets must be drilled out to remove the guard, and bare steel in aluminum invites corrosion.

Answer: C

Correct answer: Brazing. Ask what melts. Only the filler melts, so it is soldering or brazing; the filler melts at about 1,300 °F, above the 840 °F boundary, so the process is brazing.

• A: Soldering also uses capillary flow, but its filler melts at or below about 840 °F, not 1,300 °F.
• B: Fusion welding melts the base metal, and here the tubes never melt.
• C (correct): The base stays solid and the filler melts above 840 °F but below copper's melting point, which defines brazing.
• D: Friction welding uses rubbing heat and pressure between the parts with no filler drawn into a gap.

Answer: C

Correct answer: A self-locking nut. Locking features such as self-locking nuts or suitable thread-locking compounds address loosening. A plain flat washer distributes load but does not lock the nut.

• A: A flat washer mainly spreads bearing load; it is not a positive locking device.
• B: A dowel pin locates and aligns parts; it does not keep a nut from turning.
• C (correct): A self-locking nut has a built-in feature, such as an insert or deformed thread, that resists loosening.
• D: Extra length does not add a locking feature or stop the nut from backing off.

Answer: A

Correct answer: A welding helmet with a suitable filter shade. An exposed welding arc can injure the eyes and skin. Use a welding helmet or screen with a filter shade suited to the operation; ordinary safety glasses do not provide that filtering.

• A (correct): Arc radiation requires a proper filter lens; a helmet with the right shade provides it.
• B: Side shields stop flying particles from the side but do not filter intense arc radiation.
• C: Polarized sunglasses reduce glare but are not rated filters for welding arc radiation.
• D: A dust mask addresses breathing, not eye exposure to arc light.