Materials Processes and Industrial Materials: Properties, Testing and Mechanical Behavior

Materials Processes and Industrial Materials

Materials processes industrial: materials and energy, 2 elements: impresc. TT of the processes industrial.

Criteria for Selecting Materials

Properties, qualities, aesthetics, processes, manufacturing cost, availability, and environmental impact.

Mechanical Properties

Describe the behavior of materials when subjected to external forces. Forces such as tensile, compression, shear, and cohesion forces are much less than the internal cohesion of the material. The material resists, but if the internal force is exceeded, the material deforms or breaks.

Mechanical properties of materials are measured through laboratory testing.

Elongation Unit

Relation between the initial and final length.

Mechanical Strength and Tensile Testing

Tensile strength is the ability of a material to withstand a force without deforming or breaking.

• Tension: stretching
• Compression: crushing
• Bending: bending
• Torsion: twisting
• Shear: cutting

Tension and compression are axial stresses.

• Tension: high section
• Compression: high section, low length
• Bending: high section, low length, great depth
• Torsion: high section
• Shear: high section

Models of Deformation: Mechanical Behavior

Temporary deformation: elastic deformation.

Permanent deformation: plastic deformation.

Fragile behavior (glass, ceramics) and ductile behavior (copper, aluminum).

Unitary Stress

Relation between the force applied to the material and its cross-sectional area.

Equivalences: 1 N/mm² = 1 MPa, 1 MPa = 10⁶ Pa.

Tensile Stress-Strain Diagram

The mechanical characteristics of materials are determined from tensile tests (circular specimens). The unitary stress at the maximum point is used to design a part and is known as the maximum working stress. A large safety coefficient ensures the part is safe. A low modulus indicates the presence of pores or serious defects in the material.

Elongation

Tensile deformation to measure elongation is always an elongation. It has a special significance, as it shows how much the material experiences before necking or breaking. The percentage of elongation is used to measure the ductility of metals. Ductile materials have a high value.

Characteristic Mechanical Properties of Materials

The modulus of elasticity indicates rigidity, the elastic limit indicates the stress the material can resist before permanent deformation, and elasticity is the material's ability to recover its shape. Mechanical properties include elongation, plasticity, and tenacity.

Tenacity

Ability to resist shock. Tenacity is the property opposite to fragility: tenacious materials can absorb large amounts of kinetic energy from impact, transforming it into plastic or elastic deformation and preventing fracture.

Resilience Test

The energy required to break a material with a single blow. Resilience is also called impact strength. Its value is obtained indirectly from the tenacity of materials.

Fatigue Test

Materials subjected to repeated or cyclic stresses. Fatigue tests are performed under controlled conditions (S-N curve or Wöhler diagram).

Fatigue Resistance

The stress amplitude that causes material failure after a determined number of cycles.

Fatigue Life

The number of cycles a material can withstand at a given stress amplitude, represented as N. Fatigue cracks always begin on the surface of materials.

Key Formulas

Elongation = E = ΔL / L₀
E (%) = ΔL / L₀ × 100
ΔL = Lf − L₀
Circular area = π r²
Rectangular area = b · h
Unitary stress = F / A = N / mm²
Modulus of elasticity = E = σ / ε
Maximum working stress = σ_max / n (n = safety coefficient)