Question 1

Fatigue design: basis of the Soderberg relation  In fatigue/dynamic loading design, the Soderberg line uses which material property on the static-stress axis (unlike other relations that often use ultimate strength)? Choose the correct property.

Accepted Answer

Concept The Soderberg criterion is a linear fatigue design relation that limits mean stress using the yield strength (not the ultimate strength), paired with the fatigue limit for alternating stress. Comparison Goodman and Gerber relations use ultimate tensile strength on the mean-stress intercept; Soderberg is more conservative by using yield strength. Final Answer Yield strength

Question 2

Power screws: condition for an overhauling screw  A screw is said to be ‘‘overhauling’’ when the load tends to lower itself without external effort. Which efficiency range corresponds to this condition?

Accepted Answer

Concept For a square-thread power screw, efficiency is η = tanα / tan(α + φ) where α is the helix angle and φ is the friction angle. Overhauling occurs when the load can drive the screw, i.e., roughly when α > φ, which leads to η > 0.5. Check If α = φ, η = tanα / tan(2α) < 0.5; thus to overrun (overhaul), α must exceed φ, making η > 0.5. Final Answer More than 50%

Question 3

Limits and fits (IS system): interpretation of ‘‘100 H6/g5’’  Under Indian/ISO limits and fits notation, what does ‘‘100 H6/g5’’ indicate about the size reference? Choose the correct interpretation.

Accepted Answer

Concept In the notation 100 H6/g5, the number (100) denotes the basic size in mm. The letters and numbers (H6 for hole, g5 for shaft) specify fundamental deviations and tolerance grades with respect to that basic size. Final Answer Basic size is 100 mm

Question 4

Flange coupling proportions: thickness of flange relative to shaft diameter  Statement to evaluate: In a (cast iron) flange coupling, the flange thickness is taken as one-half of the shaft diameter (t ≈ 0.5d).  Choose the correct option (True/False).

Accepted Answer

Design proportion Standard empirical proportions for an unprotected cast-iron flange coupling include: hub diameter ≈ 2d, hub length ≈ 1.5d, outside flange diameter ≈ 4d, and flange thickness t ≈ 0.5d. Note Exact dimensions are refined by stress checks (keys, bolts, hub), but 0.5d is a widely used starting proportion. Final Answer True

Question 5

Locking devices for nuts: identification by construction detail  Which locking device has a bottom cylindrical portion recessed to receive the tip of a locking set screw? Choose the correct nut type.

Accepted Answer

Identification A ring nut (round nut) can incorporate a recessed cylindrical portion that accepts a locking set screw to secure the nut in place. Why others are wrong Castle nut: uses castellations with a split pin through a drilled bolt, not a set screw recess. Jam nut: a thin nut used against another nut; no set screw. Sawn nut: has a sawn slot tightened by a small screw to clamp, not a recessed seat for a separate locking set screw. Final Answer Ring nut

Question 6

Riveted joint design check: equality of rivets in shear and crushing?  Statement to evaluate: ‘‘In a riveted joint, the number of rivets working in shear must be equal to the number of rivets working in crushing.’’  Choose the correct option (True/F…

Accepted Answer

Concept Design checks for riveted joints independently evaluate shear, bearing/crushing, and tearing. The required number based on shear strength generally differs from that based on bearing strength; the governing (larger) requirement is adopted. Reasoning Nshear = Load / (n·τallow·Ashear)Nbearing = Load / (σb,allow·d·t)Since τallow, σb,allow, and geometry differ, counts seldom match exactly. Final Answer False

Question 7

Belts: belt speed for maximum power transmission  Assume a flat belt with maximum permissible belt tension T and belt mass per unit length m. Find the belt speed condition that maximizes power transmitted. Choose the correct expression.

Accepted Answer

Given/Notation T = maximum permissible belt tension (N) m = mass per unit length of belt (kg/m) v = belt speed (m/s) Approach Power P = (T1 − T2)·v. With centrifugal tension Tc = m v² acting, the available tight-side tension is limited by T = T1 + Tc. Maximizing P with respect to v leads to the classical condition Tc = T/3. Step-by-step outline Let Tc = m v².At optimum, Tc = T/3 ⇒ m v² = T/3.⇒ v = √(T/(3m)). Verification This condition is standard: at maximum power, centrifugal tension equals one-third of the maximum allowable belt tension. Common pitfall Using √(T/m) or √(T/2m); those ignore the power optimum and set centrifugal tension too high. Final Answer v = √(T/3m)

Question 8

Bevel gear classification based on intersecting axes and pitch angle  Two shafts intersect at an angle greater than 90°, and one bevel gear has a pitch angle of 90°. Identify the correct name for this gear pair. Choose the correct option.

Accepted Answer

Concept A bevel gear with a pitch angle of 90° is called a crown gear. When it meshes with another bevel gear and the shaft axes intersect at an angle greater than a right angle, the pair is termed crown bevel gears. Why the other options are wrong • Angular bevel gears: general term for non-90° shaft intersections, not specific to a 90° pitch angle on one gear. • Internal bevel gears: teeth on the inside of a conical surface (different geometry). • Mitre gears: equal bevel gears with axes at 90° and equal tooth counts. Final Answer Crown bevel gears

Question 9

Lubrication regimes in sliding bearings: terminology check  Statement to evaluate: “A sliding bearing in which the working surfaces are completely separated by lubricant is called a zero film bearing.” Decide if the statement is correct or incorrect.

Accepted Answer

Concept When the journal and bearing surfaces are completely separated by a lubricant film, the bearing operates in hydrodynamic (full-film) lubrication. The term zero-film implies the opposite—no separating film (boundary or mixed lubrication). Reasoning Therefore, calling a fully separated condition “zero film bearing” is incorrect; it should be called a full-film (hydrodynamic) bearing. Final Answer Incorrect (False)

Question 10

Fasteners (castle nuts): standard slot count for 25 mm size  For a 25 mm castle (slotted) nut, select the standard number of slots provided for cotter pin locking. Choose the correct option.

Accepted Answer

Concept Castle (slotted) nuts are commonly manufactured with six radial slots, providing several angular positions to align a cotter pin through the nut and drilled bolt shank. This facilitates reliable locking at the required preload. Final Answer 6

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