Answer the following questions.
Notch sensitivity factor.
The Notch Sensitivity Factor is a crucial concept in materials engineering and fatigue design. It quantifies how sensitive a material is to the presence of a stress concentrator (like a notch, hole, fillet, crack, or sudden change in cross-section). In simpler terms: It tells you how much a real-world "notch" reduces a material's fatigue strength compared to its ideal, smooth condition.
Spigot and socket joint for pipes.
A spigot and socket joint (also commonly called a bell and spigot joint) is a type of pipe connection used in plumbing and pipeline systems. One end of a pipe is formed into a plain, narrower spigot (male end), while the opposite end of the adjoining pipe has an enlarged socket (or bell, the female end). The spigot is inserted into the socket to create a continuous pipeline.
State two important reasons for adopting involute curves for a gear tooth profile.
- Constant velocity ratio during meshing: The involute profile ensures that the angular velocity ratio (speed ratio) between meshing gears remains constant throughout the contact period, providing smooth and uniform power transmission without fluctuations.
- Insensitivity to variations in center distance: Small changes in the distance between gear centers (due to manufacturing tolerances, wear, or assembly) do not affect the velocity ratio or proper meshing, making involute gears more forgiving and easier to install/maintain compared to other profiles like cycloidal.
What factors should be considered to design springs for fatigue resistance?
- Material selection: Use high-quality, high-strength steels (e.g., music wire or valve-grade) with good endurance limits and resistance to corrosion.
- Stress management: Keep operating stresses low; use Goodman diagrams or S-N curves to ensure mean and alternating stresses stay within safe limits.
- Surface treatments: Apply shot peening to induce compressive residual stresses and improve surface finish to prevent crack initiation.
- Geometry optimization: Minimize stress concentrations (e.g., smooth radii in hooks for extension springs) and balance wire/coil dimensions.
What are the key criteria for selecting bearings in different applications?
- Load Magnitude and Direction
- Rotational Speed
- Expected Service Life and Reliability
- Available Space and Mounting
- Misalignment Tolerance
- Lubrication and Maintenance
- Cost and Availability
What are the key design considerat ions for pipe joints, gaskets, seals, and packing?
Key design considerat ions for pipe joints
- Fluid Service & Internal Pressure
- Material Compatibility & Selection
- Joint Type & Method of Connection
- Mechanical Strength & Structural Loads
- Leak Tightness & Sealing
- Thermal Considerations
- Codes, Standards & Regulations
Key design considerat ions for pipe gaskets
- Gasket Type & Construction
- Pressure-Temperature Rating
- Fluid/Media Compatibility (Chemical Resistance)
- Flange Conditions & Sealing Mechanism
- Gasket Properties (Critical Performance Parameters)
Key design considerat ions for pipe seals
- Seal selection
- Operating Conditions
- Material Selection
- Seal Type and Geometry
- Compression and Load
Differentiate between single and multiple plate clutches in terms of design and operation.
What is the significance of the stress concentration factor in mechanical design?
The stress concentration factor (SCF) is a dimensionless factor that quantifies how much stress is amplified in a structural component due to the presence of geometric discontinuities such as notches, holes, grooves, or sudden changes in cross-section.
Significance of Stress Concentration Factor:
- Engineers use SCF to identify critical points where failure might initiate.
- Components must be designed to withstand the maximum stress (including concentration effects) rather than just nominal stress.
- Stress concentrations significantly reduce the fatigue life of components because cracks often initiate at these points.
- Knowing the SCF helps in choosing materials with suitable strength or in modifying geometries (e.g., adding fillets, smoothing notches) to reduce stress concentrations.
Discuss the maximum normal stress theory, maximum shear stress theory.
Maximum Shear Stress Theory:
Applied satisfactorily to ductile materials.This theory states that failure can be assumed to occur when the maximum shear stress in the complex stress system is equal to the value of maximum shear stress in simple tension.
Maximum normal stress theory
It states that when the maximum normal stress in any direction of a brittle material reaches the strength of the material - the material fails. Thus, finding the principal stresses at critical locations is important.
How is a design data handbook useful in the mechanical design process?
A design data handbook is crucial in mechanical design as
a comprehensive reference for standard data, formulas, material properties, and design procedures, streamlining calculations, ensuring adherence to industry standards (like BIS/ISO), and enabling quick, reliable selection and sizing of machine elements like shafts, gears, springs, and fasteners, ultimately reducing errors, saving time, and improving consistency in design .
a comprehensive reference for standard data, formulas, material properties, and design procedures, streamlining calculations, ensuring adherence to industry standards (like BIS/ISO), and enabling quick, reliable selection and sizing of machine elements like shafts, gears, springs, and fasteners, ultimately reducing errors, saving time, and improving consistency in design .
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