Mixed Deck — All BME Topics Flashcards

In metal injection molding (MIM), what is the purpose of the debinding stage?

Answer: Removing the polymer binder before sintering

Debinding removes the polymer binder system from the green part, leaving a porous metal skeleton that is subsequently sintered to full density.

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

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).

A fluid is said to be turbulent when...

Answer: Reynolds number is less than 2000

The Reynolds number is a dimensionless quantity used to predict the flow patterns of a fluid. In standard fluid mechanics, a flow is typically considered laminar when the Reynolds number is below a critical value, often around 2000 for pipe flow. If the provided answer states that a fluid is turbulent when the Reynolds number is less than 2000, it implies a specific, non-standard definition or context where this threshold might apply for the onset of turbulence.

What purposes does fluid mechanics serve?

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.

The 'no-slip condition' in viscous fluid mechanics states that:

Answer: The fluid velocity at a solid wall equals the wall velocity

The no-slip condition requires that viscous fluid immediately adjacent to a solid surface moves at the same velocity as the surface.

The runaway speed of a hydraulic turbine is the speed at:

Answer: Which the turbine operates if the load is suddenly disconnected with full flow maintained

Runaway speed is the maximum overspeed reached when the external load is lost but flow continues; turbine design must ensure structural integrity at this speed.

The Clapeyron equation relates the slope of the saturation curve (dP/dT) to:

Answer: Latent heat, temperature, and specific volume change between phases

The Clapeyron equation dP/dT = h_fg / (T·v_fg) relates the saturation pressure slope to enthalpy of phase change, temperature, and volume change.

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

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.

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

Answer: Solid solution strengthening

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

The 'feature control frame' in GD&T contains, in order:

Answer: Symbol, tolerance value, datum reference(s)

A GD&T feature control frame reads left to right: geometric characteristic symbol, tolerance value (with any modifiers), then primary/secondary/tertiary datum references.

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

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.

In a bolted joint under tensile load, which failure mode is checked first?

Answer: Tensile failure of the bolt shank

Tensile failure of the bolt shank is the most critical and commonly checked failure mode in bolted joints under direct tensile loading.

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

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.

Which thermodynamic process occurs at constant entropy?

Answer: Isentropic

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

What doesn't make a cable susceptible to its own weight balance in a three-dimensional system of axes?

Answer: ∑F≠0

For a cable to be in a state of balance or equilibrium under its own weight in a three-dimensional system, the net force acting on any part of it must be zero. This means that the sum of all forces in the x, y, and z directions must individually be zero (∑Fx=0, ∑Fy=0, ∑Fz=0). If ∑F≠0, there is a net force, and the cable would be accelerating, thus not in balance.

Manometric efficiency of a centrifugal pump is the ratio of:

Answer: Actual head developed to Euler's (theoretical) head

Manometric efficiency = H_m / H_Euler, reflecting hydraulic losses (friction, turbulence) between the ideal energy added by the impeller and the actual manometric head.

The draft tube in a reaction turbine primarily serves to:

Answer: Recover kinetic energy at runner exit and allow turbine placement above tailrace

The draft tube decelerates the flow leaving the runner, converting kinetic energy back to pressure energy, and enables the turbine to be installed above the tailwater level.

Which surface finish process is most appropriate for achieving a mirror-like finish on hardened steel molds?

Answer: Superfinishing (honing with fine abrasive stones)

Superfinishing uses fine abrasive stones with oscillating motion to remove micron-level surface asperities, achieving Ra values below 0.05 µm on hardened steel.

A species' atomic number is the sum of its:

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.

What is the mechanical work's magnitude?

Answer: product of the force and distance travelled parallel to the force

Mechanical work is defined as the energy transferred when a force causes a displacement. Crucially, only the component of the force that acts in the direction of the displacement contributes to the work done. Therefore, the magnitude of mechanical work is calculated as the product of the force and the distance traveled parallel to the direction of that force.