Material Selection for Industrial Projects
Materials and Industrial Processes
Project Development and Material Selection
Before starting any industrial project, thorough project development is essential. A crucial step involves selecting appropriate materials based on various factors and selection criteria.
Material Selection Criteria
Properties
Consider the required properties of the material. For instance, kitchen materials should withstand high temperatures without deformation.
Aesthetic Qualities
Factors like color, texture, and shape contribute to the overall aesthetics. Color is particularly important for safety-related objects requiring quick identification.
Manufacturing Process
Some materials may require specific manufacturing techniques or processes. The chosen material should be compatible with available manufacturing capabilities.
Cost
Product design must balance quality, target users, lifespan, and cost-effectiveness.
Availability
The planned market lifespan influences material choices, varying by product type.
Environmental Impact
Consider the environmental impact of material extraction, processing, the object’s lifespan, and reusability.
Mechanical Properties
Mechanical properties describe a material’s behavior under external forces. These forces oppose internal cohesion forces holding atoms together, responsible for the material’s solid state. If external forces exceed internal cohesion, the material deforms or breaks.
Mechanical Testing
Mechanical properties are assessed through various tests, including:
- Tensile Strength: Ability to withstand stretching forces.
- Compressive Strength: Ability to withstand crushing forces.
- Flexural Strength: Ability to withstand bending forces.
- Torsional Strength: Ability to withstand twisting forces.
- Shear Strength: Ability to withstand cutting forces.
Bending stress can be seen as a combination of tension and compression. Stress intensity varies within the material, increasing further from the neutral line. Slender materials (long compared to their cross-section) can experience buckling under bending stress.
- Tension: High cross-section.
- Compression: High cross-section and short length.
- Flexion: High/low cross-section and long length.
- Torsion: High cross-section.
- Shear: High cross-section.
Elastic and Plastic Deformation
Temporary deformation is called elastic deformation, while permanent deformation is called plastic deformation. Brittle materials (glass, ceramic) break without significant deformation, while ductile materials deform considerably before breaking.
Tensile Test Diagram
- Elastic Zone: Deformations are elastic and disappear when the stress is removed.
- Elastic Limit: Permanent deformation begins.
- Yield Point: Material starts to elongate significantly with little increase in stress.
- Strain Hardening: Material strengthens due to deformation.
- Fracture: Material breaks.
Hardness
Hardness is a material’s resistance to being scratched or indented by another material. The Brinell hardness test uses a steel ball indenter and measures the indentation diameter.
Toughness and Resilience
Toughness is the ability to resist impact. Resilience, also known as impact strength, is the energy needed to break a material with a single blow. The Charpy impact test uses a pendulum to measure resilience.
Fatigue Testing
Fatigue testing assesses a material’s response to repeated cyclic stress (tension, compression, torsion, flexion).
Non-Destructive Testing (NDT)
NDT methods detect internal defects not visible to the naked eye (cracks, pores, inclusions). Examples include:
- Magnetic Particle Testing: Detects surface and near-surface cracks in ferromagnetic materials.
- Radiographic Testing: Uses X-rays or gamma rays to detect internal flaws.
- Ultrasonic Testing: Uses high-frequency sound waves to detect internal flaws.
Thermal Properties
Thermal conductivity measures a material’s ability to conduct heat. Thermal expansion describes the increase in size with increasing temperature, particularly in metals.