Philippine Mechanical Engineering Licensure Examination (MELE) — Questions and Answers

Question 1: A second-order system with damping ratio ζ = 0.5 is classified as:

Undamped
Overdamped
Underdamped (Correct answer)
Critically damped

Correct answer: Underdamped

An underdamped system has 0 < ζ < 1; with ζ = 0.5 the system exhibits oscillatory step response with overshoot that decays to the final value.

Question 2: What is the primary purpose of a factor of safety in machine design?

To improve aesthetics
To increase cost
To reduce weight
To account for uncertainties in load, material, and geometry (Correct answer)

Correct answer: To account for uncertainties in load, material, and geometry

The factor of safety accounts for uncertainties in applied loads, material properties, and geometric tolerances to prevent failure.

Question 3: Which of the following best describes the shear center of a cross-section?

The point where normal stress is zero
The point through which a transverse load must act to produce no twisting (Correct answer)
The point of maximum shear stress
The centroid of the cross-section

Correct answer: The point through which a transverse load must act to produce no twisting

The shear center is the unique point where a transverse load causes pure bending without twisting of the beam.

Question 4: Which of the following is not a biomaterial?

None of the mentioned (Correct answer)
Ceramics
Metals
Polymers

Correct answer: None of the mentioned

Biomaterials are substances engineered to interact with biological systems for medical applications. Metals (like titanium alloys), polymers (like polyethylene), and ceramics (like alumina) are all extensively used as biomaterials due to their diverse properties, biocompatibility, and suitability for various medical devices and implants. Therefore, none of the listed options are excluded from being biomaterials.

Question 5: Which hydraulic turbine is best suited for high head and low flow rate conditions?

Francis turbine
Pelton wheel (Correct answer)
Kaplan turbine
Propeller turbine

Correct answer: Pelton wheel

The Pelton wheel operates efficiently under very high heads (hundreds to thousands of meters) with relatively low volumetric flow rates.

Question 6: What statement about polymers is accurate?

They have high strength to mass ratio
They have very high molecular mass
All of the mentioned (Correct answer)
They do not have a linear stress-strain curve

Correct answer: All of the mentioned

Polymers are macromolecules characterized by very high molecular masses due to their long, repeating chain structures. Their mechanical behavior often exhibits a non-linear stress-strain curve, reflecting their viscoelastic nature. Additionally, many polymers, especially in composite forms, offer an excellent strength-to-mass ratio, making them ideal for lightweight, high-performance applications. Thus, all the statements accurately describe characteristics of polymers.

Question 7: Which of the following materials exhibits the highest fracture toughness K_Ic?

High-strength steel (4340)
Low-carbon steel (A36) (Correct answer)
Aluminum alloy 7075-T6
Soda-lime glass

Correct answer: Low-carbon steel (A36)

Low-carbon structural steels like A36 have high fracture toughness (≈ 100–200 MPa√m) due to their high ductility, whereas high-strength steels trade toughness for yield strength.

Question 8: Which strengthening mechanism involves introducing solute atoms that distort the crystal lattice and impede dislocation movement?

Precipitation hardening
Solid solution strengthening (Correct answer)
Grain boundary strengthening
Work hardening

Correct answer: Solid solution strengthening

Solid solution strengthening occurs when solute atoms create local stress fields that interact with and pin dislocations.

Question 9: In a laminar boundary layer over a flat plate, the boundary layer thickness δ scales with distance x from the leading edge as:

δ ∝ x^(1/2) (Correct answer)
δ ∝ x
δ ∝ x^(4/5)
δ ∝ x²

Correct answer: δ ∝ x^(1/2)

For laminar (Blasius) boundary layers, δ ∝ x^(1/2) based on the similarity solution.

Question 10: What is the primary practical drawback of applying pure derivative (D-only) control action?

It removes all damping from the response
It makes the system response slower
It amplifies high-frequency measurement noise (Correct answer)
It increases steady-state error to infinity

Correct answer: It amplifies high-frequency measurement noise

Differentiation magnifies rapid signal changes, so a pure derivative controller greatly amplifies high-frequency noise present in measured outputs, making stand-alone D control impractical.

Question 11: In selective laser sintering (SLS), what material property is most critical for achieving dense, high-strength parts?

Particle size distribution (Correct answer)
Electrical conductivity
Surface reflectivity
Melting point

Correct answer: Particle size distribution

Particle size distribution directly affects packing density and energy absorption, determining final part density and strength in SLS.

Question 12: Which statement correctly describes the Joule-Thomson effect for an ideal gas?

Temperature increases during throttling
Temperature decreases during throttling
Enthalpy changes during throttling
Temperature remains unchanged during throttling (Correct answer)

Correct answer: Temperature remains unchanged during throttling

For an ideal gas, the Joule-Thomson coefficient is zero, so throttling causes no temperature change.

Question 13: What exactly is thermodynamics?

study of the conversion of mechanical energy to other forms of energy
study of the relationship between heat and other forms of energy (Correct answer)
study of the conversion of chemical energy to other forms of energy
study of the relationship between mechanical energy to other forms of energy

Correct answer: study of the relationship between heat and other forms of energy

This area of physical science is focused on how heat interacts with many types of energy, including mechanical, electrical, chemical, and others.

Question 14: In state-space representation ẋ = Ax + Bu, y = Cx + Du, the matrix A is called the:

Feedforward matrix
Output matrix
Input matrix
System (state) matrix (Correct answer)

Correct answer: System (state) matrix

Matrix A is the system (state) matrix; its eigenvalues are the natural frequencies of the system, and it governs how state variables evolve without external input.

Question 15: Which of the following best describes the role of cutting fluid in high-speed machining?

Increasing tool hardness
Increasing workpiece hardness
Improving surface oxidation
Reducing thermal damage and chip adhesion (Correct answer)

Correct answer: Reducing thermal damage and chip adhesion

Cutting fluids dissipate heat and lubricate the tool-chip interface, preventing built-up edge formation and thermal damage.

Question 16: The degree of reaction in the case of gas turbines and compressors is .

Static temperature drop in stage/ static temperature drop in rotor
Static pressure drop in stage/ static pressure drop in rotor
Isentropic enthalpy drop in rotor/ isentropic enthalpy drop in stage (Correct answer)
Static pressure drop in rotor/ static pressure drop in stage

Correct answer: Isentropic enthalpy drop in rotor/ isentropic enthalpy drop in stage

The degree of reaction in gas turbines and compressors is a dimensionless parameter that quantifies the proportion of the total isentropic enthalpy drop (or static pressure drop) occurring in the rotor blades relative to the entire stage (rotor plus stator). Specifically, it is defined as the ratio of the isentropic enthalpy drop in the rotor to the isentropic enthalpy drop in the stage. This parameter helps characterize the design and performance of turbomachinery.

Question 17: The Nyquist stability criterion determines closed-loop stability based on:

The gain crossover frequency
The number of open-loop zeros in the right half-plane
Net encirclements of the −1 + j0 point by the Nyquist plot (Correct answer)
The roots of the characteristic polynomial

Correct answer: Net encirclements of the −1 + j0 point by the Nyquist plot

Using Cauchy's argument principle, the Nyquist criterion counts net clockwise encirclements of −1 + j0 by the open-loop Nyquist plot to determine the number of unstable closed-loop poles.

Question 18: The Moody diagram relates the Darcy friction factor to:

Strouhal number and frequency
Reynolds number and relative pipe roughness (Correct answer)
Mach number and pipe length
Prandtl number and wall temperature

Correct answer: Reynolds number and relative pipe roughness

The Moody diagram provides friction factor f as a function of Reynolds number Re and relative roughness ε/D.

Question 19: What is the main purpose of normalizing a steel component after forging?

Relieving residual stresses and refining grain structure for uniform properties (Correct answer)
Hardening the surface to resist wear
Increasing carbon content to maximum solubility
Reducing the melting point for subsequent casting

Correct answer: Relieving residual stresses and refining grain structure for uniform properties

Normalizing involves heating above the upper critical temperature and air cooling, which refines the coarse forged grain structure and homogenizes mechanical properties.

Question 20: Surface finish (roughness) on a drawing is indicated by:

A check mark symbol (√) with Ra value (Correct answer)
Wavy lines
Cross-hatching
Dashed boundary lines

Correct answer: A check mark symbol (√) with Ra value

Surface texture is specified using the surface finish symbol (√) with roughness value Ra (arithmetic average) per ASME B46.1 standards.

Question 21: Thermal conductivity of metals generally _______ with increasing temperature.

Increases significantly
First increases then decreases
Remains constant
Decreases slightly (Correct answer)

Correct answer: Decreases slightly

For most pure metals, thermal conductivity decreases slightly with increasing temperature due to increased lattice vibrations scattering electrons.

Question 22: Creep in metals at elevated temperatures is best described as:

Time-dependent permanent deformation under constant stress (Correct answer)
Instantaneous plastic deformation upon loading
Elastic deformation recovered upon unloading
Fatigue damage accumulated over cyclic loading

Correct answer: Time-dependent permanent deformation under constant stress

Creep is the slow, time-dependent plastic deformation that occurs under sustained stress, especially above ~0.4 T_m (homologous temperature).

Question 23: A power screw is primarily designed to:

Guide sliding motion only
Absorb shock loads
Convert rotary motion to linear motion and transmit power (Correct answer)
Fasten two members together

Correct answer: Convert rotary motion to linear motion and transmit power

A power screw converts rotational input torque into translational output force, used in jacks, presses, and lead screws.

Question 24: A datum in GD&T is:

A manufactured surface
A tolerance zone
A theoretically exact point, axis, or plane used as a reference (Correct answer)
A surface finish specification

Correct answer: A theoretically exact point, axis, or plane used as a reference

A GD&T datum is a theoretically perfect geometric reference (point, line, or plane) established from actual part features to measure other geometric tolerances.

Question 25: What does fluid dynamics entail?

Study of fluid behaviour at rest
Study of fluid behaviour at rest and in motion
Study of fluid behaviour in motion
Study of fluid behaviour at rest and in motion (Correct answer)

Correct answer: Study of fluid behaviour at rest and in motion

Fluid mechanics is the branch of physics that studies fluids (liquids, gases, and plasmas) and the forces on them. It is broadly divided into two main areas: fluid statics, which deals with fluids at rest, and fluid dynamics, which deals with fluids in motion. Therefore, the comprehensive study of fluid behavior encompasses both conditions.

Question 26: A given element's many isotopes all share the same:

Thermodynamic stability
Number of protons (Correct answer)
Number of neutrons
Molar mass

Correct answer: Number of protons

Isotopes are atoms of the same chemical element, meaning they share the identical atomic number. The atomic number is defined by the number of protons in the nucleus, which uniquely determines the element's identity. Isotopes differ only in their number of neutrons, leading to variations in mass number but not in the fundamental elemental identity.

Question 27: A key connecting a gear to a shaft primarily transmits:

Shear force along the axis
Axial force
Bending moment
Torque (Correct answer)

Correct answer: Torque

A key is a machine element that fits into keyways on both the shaft and hub to transmit torque between them.

Question 28: In the k-ε turbulence model, the variable ε represents:

Rate of dissipation of turbulent kinetic energy (Correct answer)
Turbulent Prandtl number
Eddy viscosity ratio
Turbulent kinetic energy

Correct answer: Rate of dissipation of turbulent kinetic energy

In the k-ε model, k is turbulent kinetic energy and ε is the rate at which k is dissipated into heat by viscous action.

Question 29: Which type of stress is induced in a shaft subjected to twisting?

Bending stress
Shear stress (Correct answer)
Compressive stress
Tensile stress

Correct answer: Shear stress

Twisting a shaft induces shear stress, distributed across the cross-section with maximum value at the outer surface.

Question 30: A Kaplan turbine differs from a propeller turbine in that:

It operates under higher heads than propeller turbines
It uses impulse action rather than reaction
Its runner blades are adjustable, allowing efficient part-load operation (Correct answer)
Its runner blades are fixed, while propeller turbine blades are adjustable

Correct answer: Its runner blades are adjustable, allowing efficient part-load operation

Kaplan turbines have adjustable (controllable-pitch) runner blades that, combined with adjustable guide vanes, maintain high efficiency over a wide range of flows and heads.

Question 31: In a Mohr's circle construction, the center of the circle lies at:

((σ_x − σ_y)/2, τ_xy)
(σ_x, τ_xy)
((σ_x + σ_y)/2, τ_xy)
((σ_x + σ_y)/2, 0) (Correct answer)

Correct answer: ((σ_x + σ_y)/2, 0)

The center of Mohr's circle is at the average normal stress ((σ_x + σ_y)/2, 0) on the σ–τ plane.

Question 32: A material has a fracture toughness KIc = 50 MPa√m and a yield strength of 500 MPa. What is the critical crack length for plane strain fracture?

~3.2 mm (Correct answer)
~6.4 mm
~1.0 mm
~10 mm

Correct answer: ~3.2 mm

Using a = (1/π)(KIc/σ)² = (1/π)(50/500)² ≈ 0.0032 m = 3.2 mm for a through crack with Y=1.

Question 33: For a thick-walled cylinder under internal pressure p_i with inner radius a and outer radius b, the hoop stress is maximum at:

The inner surface (r = a) (Correct answer)
The mid-thickness (r = (a+b)/2)
Uniformly throughout the wall
The outer surface (r = b)

Correct answer: The inner surface (r = a)

By the Lamé equations, hoop stress decreases radially outward and is highest at the inner wall r = a.

Question 34: Which of the following is a thermodynamics application?

Gas compressors
All of the mentioned
Refrigerators
Power plants (Correct answer)

Correct answer: Power plants

All refrigerators, deep freezers, commercial refrigeration systems, all types of air conditioning systems, heat pumps, and other devices are subject to the second law of thermodynamics. All types of air and gas compressors, blowers, and fans run on thermodynamic cycles. An essential area of thermodynamics is the investigation of the viability of using various renewable energy sources for residential and commercial applications.

Question 35: Which of the following is best for lubrication when cold and hot rolled steel is formed into rolls?

SAE 120
SAE 20W 40
Micro-emulsion (Correct answer)
Macro-emulsion

Correct answer: Micro-emulsion

The combination of emulsifiers, water-soluble corrosion inhibitors, wetting agents, organic and inorganic salts, and occasionally severe pressure agents gives micro-emulsions some film strength.

Question 36: In a Pelton wheel turbine, the jet of water strikes:

Curved reaction blades submerged in water
Cup-shaped buckets tangentially (Correct answer)
Diffuser vanes at the turbine exit
A spiral casing that increases pressure

Correct answer: Cup-shaped buckets tangentially

A Pelton wheel is an impulse turbine where high-velocity jets strike cup-shaped (double-hemispherical) buckets tangentially, converting kinetic energy to mechanical work.

Question 37: Which dimensionless number is most relevant for determining the onset of cavitation in a hydraulic machine?

Thoma's cavitation number (σ) (Correct answer)
Weber number
Reynolds number
Froude number

Correct answer: Thoma's cavitation number (σ)

Thoma's cavitation coefficient σ = NPSHA / H relates available suction head to the machine head; when σ falls below the critical value σ_c, cavitation begins.

Question 38: Superheating steam in the Rankine cycle primarily serves to:

Decrease boiler pressure
Increase condenser pressure
Increase turbine work output and reduce moisture content (Correct answer)
Reduce pump work

Correct answer: Increase turbine work output and reduce moisture content

Superheating raises steam temperature and enthalpy before the turbine, increasing work output while keeping steam quality high to protect turbine blades.

Question 39: In a Brayton cycle, increasing the compressor pressure ratio (up to the optimal value) generally:

Increases thermal efficiency (Correct answer)
Has no effect on efficiency
Decreases net work output only
Decreases thermal efficiency

Correct answer: Increases thermal efficiency

Higher pressure ratio increases the thermal efficiency of the Brayton cycle because more compression raises the average temperature of heat addition.

Question 40: In CAD, parametric modeling means:

Model geometry is driven by defined parameters and constraints (Correct answer)
Models are created from scanned images
Only 2D drawings are created
Models cannot be modified after creation

Correct answer: Model geometry is driven by defined parameters and constraints

Parametric modeling ties geometry to design parameters (dimensions and constraints), so changing a parameter automatically updates the entire model.

Question 41: The Helmholtz free energy A is defined as:

A = U + PV
A = H + TS
A = U - TS (Correct answer)
A = H - TS

Correct answer: A = U - TS

Helmholtz free energy A = U - TS, and it represents the maximum work obtainable from a closed system at constant temperature and volume.

Question 42: What kind of dislocation inserts an extra plane into the crystal?

Mixed dislocation
Jog dislocation
Edge dislocation (Correct answer)
Screw dislocation

Correct answer: Edge dislocation

An edge dislocation is a linear crystal defect characterized by the termination of a plane of atoms within the crystal lattice. It can be visualized as an extra half-plane of atoms inserted into the crystal structure, causing localized stress and distortion. This specific configuration distinguishes it from other types of dislocations like screw or mixed dislocations.

Question 43: Which machining process is best suited for producing highly accurate flat reference surfaces on cast iron machine tool bases?

Peripheral end milling
Surface grinding (Correct answer)
Plunge EDM
Broaching

Correct answer: Surface grinding

Surface grinding uses a rotating abrasive wheel traversing the workpiece, achieving flatness tolerances and surface finishes unattainable by milling on hardened machine tool components.

Question 44: In stereolithography (SLA) 3D printing, the photopolymer resin is cured by:

Electron beam bombardment
UV laser or projector selectively crosslinking the resin (Correct answer)
Infrared laser heating
Chemical catalyst injection

Correct answer: UV laser or projector selectively crosslinking the resin

SLA uses a UV light source to photopolymerize (crosslink) liquid resin layer by layer, building up the part from a vat of photosensitive material.

Question 45: In CAD, 'extrude' and 'revolve' are examples of:

Rendering techniques
Assembly constraints
Feature-based modeling operations that create 3D geometry from 2D sketches (Correct answer)
Analysis tools

Correct answer: Feature-based modeling operations that create 3D geometry from 2D sketches

Extrude and revolve are sketch-based modeling operations: extrude pushes a 2D profile along an axis, while revolve rotates it around an axis to create 3D solid features.

Question 46: In a counter-flow heat exchanger, the maximum possible temperature change of the cold fluid is limited by:

The cold fluid inlet temperature
The hot fluid inlet temperature (Correct answer)
The wall temperature
The log mean temperature difference

Correct answer: The hot fluid inlet temperature

In counter-flow, the cold fluid can theoretically be heated up to the inlet temperature of the hot fluid, giving the highest thermodynamic efficiency.

Question 47: In a centrifugal pump, the specific speed Ns is used to:

Classify pump geometry and select the optimal impeller type (Correct answer)
Determine pipe friction losses
Calculate NPSH available
Predict cavitation onset

Correct answer: Classify pump geometry and select the optimal impeller type

Specific speed classifies pump geometry: low Ns favors radial-flow (centrifugal) designs, high Ns favors axial-flow designs.

Question 48: Steady-state error in a feedback control system is defined as:

The time for the error to first reach zero
The maximum overshoot during the transient response
The difference between desired and actual output as time approaches infinity (Correct answer)
The error at the moment the step input is applied

Correct answer: The difference between desired and actual output as time approaches infinity

Steady-state error is the residual difference between the reference input and the actual system output after all transients have died out (t → ∞).

Question 49: Which of the following laws of thermodynamics defines enthalpy?

Second law of thermodynamics
First law of thermodynamics
Fourth law of thermodynamics
Third law of thermodynamics (Correct answer)

Correct answer: Third law of thermodynamics

While enthalpy (H = U + PV) is fundamentally defined and derived from the First Law of Thermodynamics, which relates heat, work, and internal energy, the Third Law of Thermodynamics establishes a reference point for entropy at absolute zero. This absolute entropy is crucial for determining absolute values of thermodynamic potentials (like Gibbs free energy, G = H - TS), which incorporate enthalpy, especially in low-temperature contexts. Thus, the Third Law contributes to the complete thermodynamic characterization that includes enthalpy.

Question 50: Which of the following applications also makes use of the hobbing process?

Punching
Metal bending
Sprocket cutting (Correct answer)
Rust removal

Correct answer: Sprocket cutting

Gears, splines, and sprockets are frequently cut using the machining process known as hobbing. The cutting device is referred to as a hob.

Question 51: In Euler-Bernoulli beam theory, which assumption is NOT made?

The beam material is linearly elastic
Shear deformation is negligible
Plane sections remain plane after bending
Large deflections are permitted (Correct answer)

Correct answer: Large deflections are permitted

Euler-Bernoulli beam theory assumes small deflections; large-deflection problems require nonlinear analysis.

Question 52: When loaded, cable that is supporting its own weight has the shape of a .

Spring
Helix
Line (Correct answer)
Complex figure

Correct answer: Line

While a cable supporting its own weight typically forms a catenary curve (or a parabola under a uniformly distributed horizontal load), in many simplified engineering analyses, especially when the sag is very small compared to the span, the cable's shape can be idealized as a straight 'line'. This approximation is often used for initial calculations or in contexts where the curvature is considered negligible for practical purposes.

Question 53: Van der Waals equation of state corrects the ideal gas law by accounting for:

Chemical reactions between molecules
Molecular volume and intermolecular attractive forces (Correct answer)
Quantum effects and radiation
Gravitational effects on gas molecules

Correct answer: Molecular volume and intermolecular attractive forces

Van der Waals equation (P + a/v²)(v - b) = RT corrects for intermolecular attractions (term a/v²) and finite molecular volume (term b).

Question 54: If there are three concurrent forces acting on a body, according to Lami's theorem, what is the connection between each force?

Inversely proportional to the sine of the angle between the other two forces
Directly proportional to the cosine of the angle between the other two forces
Directly proportional to the sine of the angle between the other two forces (Correct answer)
Inversely proportional to the cosine of the angle between the other two forces

Correct answer: Directly proportional to the sine of the angle between the other two forces

Lami's theorem applies to three concurrent forces that are in equilibrium. It states that for such a system, each force is directly proportional to the sine of the angle formed between the other two forces. This theorem provides a convenient way to analyze forces in equilibrium when their directions and one force's magnitude are known.

Question 55: The angle between the workpiece's spindle axis and the hob's spindle axis should equal ___ while making spur gears.

(helix angle of the hob)2
(helix angle of the hob) (Correct answer)
(helix angle of the hob)/2
2*(helix angle of the hob)

Correct answer: (helix angle of the hob)

Since the hob contains helical threads, it must be angled with the workpiece in accordance with the requirements before being put into the workpiece. That angle for spur gears should match the hob's helix angle.

Question 56: A section view in a drawing is used to:

Indicate surface finish
Show the part in an assembled state
Show external features only
Reveal internal features by cutting through the part (Correct answer)

Correct answer: Reveal internal features by cutting through the part

A section view cuts through the object along a cutting plane to reveal internal features that would otherwise be hidden, improving clarity.

Question 57: A significant composite is GFRP. It represents

Gelatin Fibre Reinforced Polymer
Germanium Fibre Reinforced Polymer
Glass Fibre Reinforced Polymer (Correct answer)
Graphite Fibre Reinforced Polymer

Correct answer: Glass Fibre Reinforced Polymer

GFRP is a widely recognized composite material used in various engineering applications. The acronym GFRP stands for Glass Fibre Reinforced Polymer. It consists of high-strength glass fibers embedded within a polymer matrix, combining the benefits of both materials to create a strong, lightweight, and versatile composite.

Question 58: The effectiveness of a heat exchanger is defined as the ratio of:

Overall heat transfer coefficient to surface area
Actual heat transfer to maximum possible heat transfer (Correct answer)
Outlet to inlet temperature difference
Hot fluid heat loss to cold fluid heat gain

Correct answer: Actual heat transfer to maximum possible heat transfer

Effectiveness ε = Q_actual / Q_max, where Q_max is the maximum heat transfer achievable with an infinitely long counterflow exchanger.

Question 59: The triple point of water is approximately:

100°C and 1 atm
0°C and 1 atm
0.01°C and 611.7 Pa (Correct answer)
4°C and 1 atm

Correct answer: 0.01°C and 611.7 Pa

The triple point of water occurs at approximately 0.01°C (273.16 K) and 611.7 Pa, where all three phases coexist.

Question 60: The Routh-Hurwitz criterion determines system stability by:

Examining the signs of elements in the Routh array without computing roots (Correct answer)
Plotting the frequency response of the open-loop transfer function
Finding the gain margin from the Bode plot
Computing the eigenvalues of the system matrix numerically

Correct answer: Examining the signs of elements in the Routh array without computing roots

The Routh-Hurwitz criterion constructs a Routh array from the characteristic equation coefficients and assesses stability by checking for sign changes in the first column, avoiding direct root computation.

Question 61: Which type of welded joint is most efficient under tensile loading?

Lap joint
Butt joint (Correct answer)
T-joint
Corner joint

Correct answer: Butt joint

A butt joint aligns members end-to-end and, when fully penetrated, provides nearly the same strength as the base metal under tensile loads.

Question 62: Which ceramic failure mode is associated with slow crack growth under sustained static loading below the fracture toughness?

Creep rupture
Fatigue fracture
Ductile fracture
Static fatigue (stress corrosion cracking) (Correct answer)

Correct answer: Static fatigue (stress corrosion cracking)

Static fatigue in ceramics involves subcritical crack growth driven by chemical attack at crack tips under sustained stress.

Question 63: In laser beam machining (LBM), the parameter most directly controlling the depth of material removed per pulse is:

Beam diameter at the lens
Assist gas pressure
Peak power density (irradiance) at the workpiece surface (Correct answer)
Wavelength of the laser source

Correct answer: Peak power density (irradiance) at the workpiece surface

Peak power density (W/cm²) determines whether the threshold for ablation, melting, or vaporization is exceeded and how deeply each pulse penetrates the material.

Question 64: The following terms describe species that have various numbers of protons but the same number of neutrons:

Isobars
Isotones (Correct answer)
Isomers
Isotopes

Correct answer: Isotones

Isotones are atoms of different chemical elements that possess the same number of neutrons. This distinguishes them from isotopes (same number of protons, different neutrons) and isobars (same mass number, different protons and neutrons). The term 'isotones' specifically highlights the shared neutron count despite differing atomic numbers.

Question 65: A species' atomic number is the sum of its:

Valence electrons
Protons (Correct answer)
Nucleons
Neutrons

Correct answer: Protons

The atomic number of an element is fundamentally defined by the number of protons present in the nucleus of an atom. This number is unique to each element and dictates its chemical identity and position on the periodic table. The number of neutrons can vary (isotopes), and valence electrons are only the outermost electrons, not the defining characteristic of the atomic number.

Question 66: The Nusselt number (Nu) in convective heat transfer is defined as:

VL/ν
hL/k (Correct answer)
gβΔTL³/ν²
ν/α

Correct answer: hL/k

The Nusselt number Nu = hL/k is the dimensionless convective heat transfer coefficient, representing the ratio of convective to conductive heat transfer.

Question 67: What is the primary advantage of using a five-axis CNC machine over a three-axis machine?

Higher spindle speed
Ability to machine complex contoured surfaces in fewer setups (Correct answer)
Faster rapid traverse rates
Lower tooling cost

Correct answer: Ability to machine complex contoured surfaces in fewer setups

Five-axis machines tilt the tool relative to the workpiece, enabling complex curved surfaces to be machined with fewer repositioning setups.

Question 68: The loading in the cable under its own weight has little effect on the cables' Integrity.

Bending moment
Point at which the shear stress is zero
Colour
Geometry (Correct answer)

Correct answer: Geometry

The geometry of a cable, specifically its sag and the overall curve it forms (e.g., catenary or parabolic), is directly and significantly influenced by the distribution of its own weight. This resulting geometric configuration dictates the internal tensile forces and is crucial for understanding the cable's structural behavior and ensuring its integrity under load.

Question 69: In a binary eutectic system, the eutectic point represents:

The composition and temperature where two solid phases and liquid coexist (Correct answer)
A solid-to-solid phase transformation
The solubility limit at room temperature
Maximum melting temperature

Correct answer: The composition and temperature where two solid phases and liquid coexist

At the eutectic point, the liquid phase transforms simultaneously into two distinct solid phases at a fixed composition and temperature.

Question 70: The coefficient of performance (COP) of a heat pump is related to COP of a refrigerator operating between the same temperatures by:

COP_HP = 1/COP_R
COP_HP = COP_R - 1
COP_HP = COP_R + 1 (Correct answer)
COP_HP = COP_R

Correct answer: COP_HP = COP_R + 1

COP_HP = COP_R + 1, because the heat pump delivers both the heat removed from the cold reservoir plus the work input.

Question 71: A hidden line in engineering drawing is represented by:

Chain dotted line
Thin dashed line (Correct answer)
Continuous thick line
Wavy line

Correct answer: Thin dashed line

Hidden lines represent edges or outlines not visible from the current view and are drawn as thin dashed lines per standard drafting conventions.

Question 72: In ASME Y14.5 GD&T, the Maximum Material Condition (MMC) modifier means:

Material cost is maximized
The feature is at nominal size
The feature contains the most material within its tolerances (Correct answer)
The part has the least material

Correct answer: The feature contains the most material within its tolerances

MMC refers to the condition where a feature of size contains the maximum amount of material — largest shaft diameter or smallest hole diameter within tolerance.

Question 73: _____________ is an axial flow reaction turbine if the vanes are fastened to the turbine hub.

Kaplan turbine
Francis turbine
Propeller turbine (Correct answer)
Pelton turbine

Correct answer: Propeller turbine

A propeller turbine is an axial-flow reaction turbine where the runner blades are rigidly fixed to the hub. In this design, water flows axially through the runner, imparting energy to the fixed blades. The simplicity of its fixed-blade design makes it suitable for relatively constant flow and head conditions, distinguishing it from the adjustable-blade Kaplan turbine.

Question 74: What do you name a person's area of study if they research a fluid that is at rest?

Fluid Statics (Correct answer)
Fluid Kinematics
Fluid Dynamics
Fluid Mechanics

Correct answer: Fluid Statics

Fluid statics is the specific branch of fluid mechanics dedicated to the study of fluids at rest. It analyzes the forces exerted by fluids when there is no relative motion between fluid particles or between the fluid and its boundaries. This field focuses on concepts like pressure distribution, buoyancy, and hydrostatic forces in stationary fluids.

Question 75: Axial flow reaction turbines of particular significance are .

Kaplan and Francis turbines
Propeller and Kaplan turbines (Correct answer)
Propeller and Francis turbines
Propeller and Pelton turbines

Correct answer: Propeller and Kaplan turbines

Propeller and Kaplan turbines are both classified as axial-flow reaction turbines, meaning water flows parallel to the axis of rotation through the runner. The Kaplan turbine is an advanced version of the propeller turbine, distinguished by its adjustable runner blades. This adjustability allows Kaplan turbines to maintain high efficiency over a broader range of flow rates and heads, making them particularly significant for variable load conditions.

Question 76: The Carnot COP of a refrigerator operating between TL = 250 K and TH = 300 K is:

1.2
0.83
5.0 (Correct answer)
6.0

Correct answer: 5.0

COP_Carnot = TL / (TH - TL) = 250 / (300 - 250) = 250/50 = 5.0.

Question 77: For an ideal gas undergoing a polytropic process PVⁿ = C, if n equals the ratio of specific heats γ, the process is:

Isothermal
Isentropic (Correct answer)
Isobaric
Isochoric

Correct answer: Isentropic

When n = γ (= Cp/Cv), the polytropic process becomes isentropic (reversible adiabatic).

Question 78: A great refractory material is ceramic. A substance is referred to as refractory if it:

resists the flow of electric current
all of the mentioned
retains its strength at high temperatures (Correct answer)
has high refractive index

Correct answer: retains its strength at high temperatures

A refractory material is defined by its exceptional ability to retain its strength, shape, and chemical stability at extremely high temperatures without melting or deforming. Ceramics are excellent refractory materials due to their strong ionic and covalent bonds, which result in high melting points and robust mechanical properties even in severe thermal environments.

Question 79: Which of the following corresponds to the Blake number standard symbol?

Bl (Correct answer)
b
Bi
ba

Correct answer: Bl

The Blake number (Bl) is a dimensionless parameter used in fluid mechanics, particularly in the study of flow through porous media. It characterizes the ratio of inertial forces to viscous forces in such flows. This symbol helps in analyzing pressure drop and flow behavior in packed beds.

Question 80: Which statement correctly describes the difference between Newtonian and non-Newtonian fluids?

Non-Newtonian fluids obey Bernoulli's equation; Newtonian fluids do not
Newtonian fluids have constant viscosity; non-Newtonian fluids have viscosity that depends on shear rate (Correct answer)
Newtonian fluids are always turbulent; non-Newtonian fluids are always laminar
Newtonian fluids have viscosity that varies with shear rate; non-Newtonian fluids do not

Correct answer: Newtonian fluids have constant viscosity; non-Newtonian fluids have viscosity that depends on shear rate

Newtonian fluids have a linear stress–strain rate relationship (constant μ); non-Newtonian fluids (e.g., blood, paint) exhibit shear-dependent viscosity.

Question 81: The compatibility equations in elasticity theory ensure that:

Equilibrium is satisfied at every point
The displacement field is single-valued and continuous (Correct answer)
Boundary conditions are met on all surfaces
Material remains in the elastic regime

Correct answer: The displacement field is single-valued and continuous

Compatibility equations guarantee that the strain field derived from stresses corresponds to a continuous, single-valued displacement field with no gaps or overlaps.

Question 82: Goodman's criterion in fatigue design relates:

Yield strength and ultimate strength only
Mean stress and alternating stress to failure (Correct answer)
Temperature and stress
Strain and displacement

Correct answer: Mean stress and alternating stress to failure

Goodman's criterion provides a linear relationship between mean stress and alternating stress that defines the boundary between safe and unsafe fatigue conditions.

Question 83: In computer-aided process planning (CAPP), the variant approach works by:

Retrieving and modifying an existing plan for a similar part using group technology (Correct answer)
Generating a new process plan from scratch using AI for each new part
Simulating machining operations in a virtual environment before cutting
Automatically programming CNC machines from CAD files

Correct answer: Retrieving and modifying an existing plan for a similar part using group technology

The variant CAPP approach classifies the new part into a family, retrieves the standard plan for that family, then modifies it to suit the specific part's requirements.

Question 84: Which mode of heat transfer does not require a medium?

Radiation (Correct answer)
Diffusion
Conduction
Convection

Correct answer: Radiation

Radiation transfers heat via electromagnetic waves and can occur through a vacuum, unlike conduction and convection which require matter.

Question 85: Which thermodynamic process occurs at constant entropy?

Isentropic (Correct answer)
Isothermal
Isochoric
Isobaric

Correct answer: Isentropic

An isentropic process is reversible and adiabatic, meaning entropy remains constant throughout.

Question 86: Which approach from the list below is only utilized in fluid mechanics?

Lagrangian method
Both Lagrangian and Eulerian methods
Eulerian method (Correct answer)
Neither Lagrangian nor Eulerian method

Correct answer: Eulerian method

The Eulerian method describes fluid properties at fixed points in space as the fluid flows through them, providing a field-based perspective crucial for analyzing continuous fluid motion. While Lagrangian methods track individual fluid particles, the Eulerian approach is uniquely fundamental to the mathematical formulation and practical analysis of fluid flow fields, making it a defining characteristic of fluid mechanics.

Question 87: In a fin, the efficiency is defined as the ratio of actual heat transfer to:

Heat transferred by the base without fin
Maximum possible heat transfer if the entire fin were at base temperature (Correct answer)
Heat transferred by radiation
Heat stored in the fin

Correct answer: Maximum possible heat transfer if the entire fin were at base temperature

Fin efficiency compares actual heat transfer to the ideal case where the whole fin surface is at the base (maximum) temperature.

Question 88: Which of the following materials is most suited for roll forming?

Mild steels and aluminium (Correct answer)
Spring steel
Non-metals
Chromium-molybdenum steel

Correct answer: Mild steels and aluminium

Roll forming can be used to shape both ferrous and non-ferrous metals as well as various non-metallic materials. The two materials utilized in the procedure most frequently are mild steel and aluminum. Roll-formed materials can also be polished, painted, coated, and plated.

Question 89: What purposes does fluid mechanics serve?

Fluid mechanics enables to comprehend the behaviour of fluids under a variety of forces & atmospheric conditions
Fluid mechanics enables to comprehend the behaviour of solid fluids under pressure
Fluid mechanics enables to comprehend the behaviour of fluids under various temperatures only (Correct answer)
None of the mentioned

Correct answer: Fluid mechanics enables to comprehend the behaviour of fluids under various temperatures only

Fluid mechanics is a branch of mechanics concerned with the forces and flow of fluids. While it encompasses many aspects like pressure, velocity, and forces, temperature is a critical parameter that significantly influences fluid properties such as viscosity and density. Therefore, comprehending fluid behavior under various temperatures is indeed a key purpose, as temperature changes directly affect how fluids move and interact.

Question 90: Which type of polarization in dielectrics has the slowest response to an alternating electric field?

Electronic polarization
Orientational (dipolar) polarization
Space charge polarization (Correct answer)
Ionic polarization

Correct answer: Space charge polarization

Space charge polarization involves migration of free charges to interfaces and has the lowest frequency response, occurring only at very low frequencies.

Question 91: In calculations for cable exposed to its own weight, the magnitude of the resultant of the two vectors is always:

Greater than one of the vector’s magnitude
Smaller than one of the vector’s magnitude
Axis we choose to calculate the magnitude
Depends on the angle between them (Correct answer)

Correct answer: Depends on the angle between them

When combining two vector forces, such as tensions in a cable, the magnitude of their resultant vector is not simply the sum of their magnitudes. Instead, it depends on both the magnitudes of the individual vectors and the angle between them. This relationship is precisely described by the law of cosines for vector addition, where the angle significantly influences the final resultant magnitude.

Question 92: Critical speed of a rotating shaft is the speed at which:

Fatigue failure begins
Torque capacity is exceeded
Shaft speed equals natural frequency of lateral vibration (Correct answer)
Bearing temperature reaches maximum

Correct answer: Shaft speed equals natural frequency of lateral vibration

Critical speed occurs when the rotational speed equals the natural frequency of the shaft's lateral (bending) vibration, causing resonance and large deflections.

Question 93: Which line type represents the axis of symmetry in engineering drawings?

Thin dashed line
Zigzag line
Thick continuous line
Long chain (dash-dot) line (Correct answer)

Correct answer: Long chain (dash-dot) line

A centerline (long chain or dash-dot-dash line) indicates axes of symmetry, center points, and paths of motion in engineering drawings.

Question 94: Which polymer chain configuration results in the highest degree of crystallinity?

Atactic
Isotactic (Correct answer)
Random copolymer
Branched chains

Correct answer: Isotactic

Isotactic polymers have all substituents on the same side of the backbone, allowing chains to pack regularly into crystalline regions.

Question 95: Fourier's law of heat conduction states that heat flux is proportional to:

Specific heat
Thermal diffusivity
Temperature gradient (Correct answer)
Temperature

Correct answer: Temperature gradient

Fourier's law states q = -k(dT/dx), meaning heat flux is directly proportional to the negative temperature gradient.

Question 96: The Euler turbine equation relates the torque produced by a turbomachine to:

Change in fluid temperature across the rotor
Pressure drop across the impeller only
Change in the tangential component of fluid velocity between inlet and outlet (Correct answer)
Change in fluid density through the machine

Correct answer: Change in the tangential component of fluid velocity between inlet and outlet

Euler's equation T = ρQ(r₂Vθ₂ − r₁Vθ₁) shows torque depends on the change in angular momentum (tangential velocity × radius).

Question 97: For compressible flow in a converging-diverging nozzle, a normal shock wave can appear in the:

Diverging section at supersonic conditions (Correct answer)
Inlet plenum
Converging section only
Throat only

Correct answer: Diverging section at supersonic conditions

Normal shocks form in the diverging section when back pressure is between the design (fully supersonic) and subsonic exit conditions.

Question 98: In a refrigeration system using the vapor-compression cycle, the throttling device (expansion valve) reduces pressure by:

An irreversible isenthalpic process (Correct answer)
An isentropic expansion
Absorbing heat from surroundings
Doing work on the refrigerant

Correct answer: An irreversible isenthalpic process

The expansion valve is an isenthalpic (constant enthalpy) throttling device where pressure drops irreversibly without work or heat transfer.

Question 99: The Pilling-Bedworth ratio (PBR) predicts oxidation resistance. A PBR value between 1 and 2 indicates:

The oxide layer is porous and non-protective
The metal undergoes catastrophic oxidation
The oxide layer is protective and adherent (Correct answer)
No oxidation occurs

Correct answer: The oxide layer is protective and adherent

A PBR between 1 and 2 means the oxide volume slightly exceeds the metal volume consumed, creating a continuous, protective barrier.

Question 100: Superelastic behavior in shape memory alloys (e.g., Nitinol) is driven by:

Grain boundary sliding at elevated temperature
Twinning deformation with no recovery
Dislocation glide and permanent plastic strain
Stress-induced martensitic phase transformation that is fully reversible (Correct answer)

Correct answer: Stress-induced martensitic phase transformation that is fully reversible

In superelastic alloys, applied stress induces a martensitic transformation; upon unloading, the martensite reverts to austenite, recovering all strain.

Philippine Mechanical Engineering Licensure Examination (MELE)

The Philippine Mechanical Engineering Licensure Examination (MELE) is administered by the Professional Regulation Commission (PRC) and tests BME graduates across Mathematics/Engineering Sciences, Power/Industrial Plant Engineering, and Machine Design to earn the Registered Mechanical Engineer (RME) license.

100

Questions

150 min

Time Limit

70%

To Pass

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