Aluminum Windows And Doors,Aluminum Casement Window,Oem Aluminum Casement Windows,Aluminum Sliding Window Frame Guangdong Jihua Aluminium Co., LTD , https://www.jihua-alu.comUseful Tips: Common Terms in Hardware
Understanding the terminology used in hardware and materials science is essential for engineers, technicians, and anyone involved in manufacturing or mechanical systems. Below are some key terms related to material properties and hardness testing.
**a. Yield Strength (Physical Yield Strength):**
Code: σs, Unit: MPa (or N/mm²)
Definition: The stress at which a metal begins to deform plastically under tensile load. At this point, the material undergoes a sudden increase in deformation without an increase in applied force.
**b. Offset Yield Strength (Conditional Yield Strength):**
Code: σr, Unit: MPa (or N/mm²)
Definition: The stress at which a material exhibits a specific amount of plastic deformation after unloading. For example, σr0.2 refers to the stress at which the residual elongation reaches 0.2%.
**c. Proportional Limit Stress:**
Code: σp, Unit: MPa (or N/mm²)
Definition: The maximum stress at which a material behaves elastically. Beyond this point, the relationship between stress and strain becomes nonlinear. For instance, σp0.01 represents the stress when the elongation is 0.01%.
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**Hardness Introduction:**
Hardness is the ability of a material to resist indentation by a harder object. There are several methods to measure hardness:
**Brinell Hardness:**
Code: HBS (for hardened steel ball) or HBW (for hard alloy ball), often written as HB
Unit: No unit; calculated based on the indentation area.
Method: A hardened steel or carbide ball is pressed into the surface under a certain load. After holding the load for a set time, the diameter of the indentation is measured, and the hardness is calculated using a formula.
**Rockwell Hardness:**
Code: HR
Method: A diamond cone or steel ball is pressed into the material under a specific load, and the depth of penetration is measured.
Common scales include:
- **HRC**: Diamond indenter with 150 kgf load, suitable for hardened steels.
- **HRA**: Diamond indenter with 60 kgf load, used for hard materials like carburized steel.
- **HRB**: Steel ball indenter with 100 kgf load, used for softer materials like non-ferrous metals.
**Superficial Rockwell Hardness:**
Used for thin sheets or surface treatments like carburizing or nitriding. Common scales include:
- **HR15N**, **HR30N**, **HR45N** – Diamond indenters with different loads.
- **HR15T**, **HR30T**, **HR45T** – Steel ball indenters with different loads.
**Vickers Hardness:**
Code: HV
Method: A square-based diamond pyramid is pressed into the material under a known load (from 1.961 N to 980.7 N). The diagonals of the indentation are measured, and the hardness is calculated. It is ideal for larger samples and deeper layers.
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**Strength Limit (Ultimate Tensile Strength):**
Code: σ, Unit: MPa (or N/mm²)
Definition: The maximum stress a material can withstand before failure. Different types include:
- **Compressive Strength**: σbc – resistance to crushing forces.
- **Bending Strength**: σbb – resistance to bending.
- **Shear Strength**: σc – resistance to sliding forces.
- **Tensile Strength**: σb – resistance to pulling forces.
**Elastic Limit, Elongation, and Reduction in Area:**
- **Elastic Limit (σe)**: The maximum stress a material can endure without permanent deformation.
- **Elongation (δ)**: The percentage increase in length before fracture. δ5 and δ10 refer to short and long test specimens.
- **Reduction in Area (Ψ)**: The percentage decrease in cross-sectional area at the fracture point.
**Impact Energy and Impact Toughness:**
- **Impact Work (Ak)**: The energy absorbed by a specimen during impact, measured in Joules (J).
- **Impact Toughness (ak)**: Impact work divided by the cross-sectional area at the notch, measured in J/cm².
Common tests include Charpy U-notch (AkU) and Charpy V-notch (AKV).
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If you're interested in learning more about bearings, materials, or mechanical systems, be sure to check out our other articles on bearing maintenance, material properties, and application-specific guidance. Stay updated with the latest insights from China Bearing Network.
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- Analysis of Bearing Steel in Unique Environments
- Centrifugal Pump Bearing Maintenance Techniques
- Bearings in Aviation and Aerospace Applications
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Source: Bearing Network | Time: 2013-03-14
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