Here’s a categorized list of common mechanical design interview questions, covering fundamental knowledge, tools, and practical applications of Mechanical Engineering design.
Mechanical Design engineer Interview Questions -SET-01
What are the main considerations when designing a mechanical component?
- Functional Requirements- purpose and performance.
- Material Selection – Mechanical properties such as strength ,toughness and environmental resistance such as resistance to corrosion.
- Cost.
- Load and Stress Analysis – tatic, dynamic, impact, or cyclic loads the component will face. Also Calculate Factor Of Safety.
- Design for Manufacturability (DFM).
- Assembly and Maintenance.
- Safety and Reliability – Run Failure analysis test and check human safety.
- Space and Weight.
By addressing these considerations, engineers can design mechanical components that meet the required specifications while being efficient, cost-effective, and reliable.
Explain the difference between factor of safety and margin of safety.
The Factor of Safety (FoS) and Margin of Safety (MoS) are both measures used in engineering to ensure that a design or structure can safely withstand expected loads. However, they are calculated and interpreted differently:
Factor of Safety (FoS)
- The Factor of Safety is a ratio that compares the strength or capacity of a system to the actual or expected load. It quantifies how much stronger a system is than the required load it must carry.
- FoS = Strength / Applied Load
- Alternatively, for stress-based analysis:
- FoS = Allowable Stress / Working Stress.
- FoS >1 Ensures safety.
- Describes how much stronger the system is overall
- Commonly used in design standards and codes
Margin of Safety (MoS):
- The Margin of Safety expresses how much the strength exceeds the applied load, relative to the applied load, in percentage or absolute terms. It provides a clear measure of excess strength.
- MoS = (Strength – Applied Load) / Applied Load
- Alternatively, in terms of stresses:
- MoS = (Allowable Stress – Working Stress) / Working Stress.
- MoS > 0 ensures safety.
- A positive MoS indicates the system is safe, while a negative MoS signals that failure is likely under the given conditions.
- Describes the excess strength as a percentage of the applied load
- Often used in failure analysis and testing.
What is the importance of tolerance in design?
Importance of Tolerance:
- Functionality and fit.
- cost control
- Interchangeability.
- Quality control and inspection.
- Safety.
Can you explain the concept of stress concentration and how it can be mitigated in a design?
Stress concentration refers to the phenomenon where stress is significantly higher in a localized region of a material or structure compared to the surrounding areas. This occurs due to abrupt changes in geometry, such as holes, notches, sharp corners, or other discontinuities, which cause the flow of stress to be disrupted and concentrated in those regions.
How to Mitigate Stress Concentration in Design?
- Modify geometry.
- Add fillets and rounding.
- Avoid overloading.
- Even load application.
- Use of Finite Element Analysis concept.
- Reduce cyclic stress.
What are the types of mechanical stresses?
Mechanical stresses refer to the internal forces per unit area that develop within a material when it is subjected to external loads.
Types of Mechanical stress are :
- Tensile stress.
- Compressive stress.
- Shear stress.
- Torsional stress.
- Bending stress.
- Bearing stress.
- Residual stress.
- Thermal stress.
- creep stress.
- Fatigue stress.
Describe the difference between ductile and brittle materials.
| Property | Ductile Materials | Brittle Materials |
|---|
| Definition | Materials that can sustain significant plastic deformation before failure. | Materials that fail with little or no plastic deformation. |
| Deformation | Significant plastic deformation before failure | Little to no plastic deformation before failure |
| Fracture Behavior | Gradual, with necking and stretching | Sudden, with no warning |
| Energy Absorption | High (tough) | Low (brittle) |
| Stress-Strain Curve | Shows yielding and large elongation | Steep and ends abruptly |
| Failure Mode | Shear stress (plastic flow) | Tensile stress (cleavage) |
| Examples | Steel, aluminum, copper | Glass, ceramics, cast iron |
| Fracture Surface | Rough, with dimples | Smooth, flat, and often shiny |
What is modulus of elasticity?
The modulus of elasticity (also called Young’s modulus, denoted as E) is a measure of a material’s stiffness or rigidity. It quantifies the relationship between stress (force per unit area) and strain (proportional deformation) in a material within its elastic region, where the material returns to its original shape after the load is removed.
Formula :
E = σ/ε.
where,
E =modulus of elasticity.
σ = stress.
ε= strain.
What factors determine the machinability of a material?
The machinability of a material refers to how easily it can be cut, shaped, or finished using machining processes like turning, milling, drilling, and grinding. Several factors influence machinability, which determine the ease, quality, and cost of machining operations. These factors include:
- Material properties -Hardness, strength, ductility, brittleness.
- Tool -workpiece interaction.
- Cutting parameters.
- Surface finish and tolerances.
- Heat treatment – Annealing and hardening.
- Microstructure and composition.
- Machine tool capabilities.
- Environmental and safety concerns – chips disposals.
Explain the difference between ferrous and non-ferrous materials
| Property | Ferrous Materials | Non-Ferrous Materials |
|---|
| Defintion | Contain iron as the main component. | Do not contain significant amounts of iron. |
| Iron Content | Contains iron | No significant iron content |
| Magnetic | Usually magnetic | Non-magnetic |
| Corrosion Resistance | Prone to rust (except stainless steel) | Highly corrosion-resistant |
| Weight | Heavier | Lighter |
| Strength | High strength | Moderate strength |
| Conductivity | Poor electrical and thermal conductor | Excellent electrical and thermal conductor |
| Cost | Cheaper | More expensive |
| Examples | Steel, cast iron | Aluminum, copper, brass |
What are the advantages and disadvantages of casting, forging, and machining?
| Process | Defintion | Advantages | Disadvantages |
|---|---|---|---|
| Casting | Casting is a process where a material, usually metal or plastic, is melted until it becomes liquid. This liquid material is then poured into a mold (a hollow shape) and left to cool. Once it cools, it hardens and takes the shape of the mold. | Complex shapes, cost-effective for mass production, minimal waste | Surface finish issues, porosity, weaker properties |
| Forging | Forging is a process where metal is shaped by applying heat and pressure. In simple terms, it involves heating up the metal until it’s soft and then using tools like hammers or presses to shape it into the desired form. | High strength, fatigue resistance, durable | Limited shapes, expensive tooling, post-processing needed |
| Machining | Machining is a process where material is removed from a workpiece to shape it into a desired form. This is typically done using tools like cutters, drills, or lathes. The workpiece is usually made of metal, plastic, or other materials. | High precision, versatile, good for small batches | Wasteful, slow for mass production, tool wear |
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More Interview Questions:
Mechanical Design Interview Questions SET-02.