technical atmospheres (at) to kilopound per square inch (ksi) conversion

What is the technical atmosphere?

The technical atmosphere (at) is a non-SI unit of pressure equal to one kilogram-force per square centimeter. It was widely used in engineering, especially in Europe, before the pascal became standard.

Definition

The technical atmosphere is defined as the pressure of one kilogram-force acting on one square centimeter:

$$1\ \text{at} = 98066.5\ \text{Pa}$$

This equals exactly 1 kgf/cm² (98,066.5 Pa), because standard gravity is 9.80665 m/s². It is close to, but distinct from, the standard atmosphere (atm = 101,325 Pa) and the bar (100,000 Pa).

Origin and History

The technical atmosphere arose from the gravitational metric system of units, which used the kilogram-force rather than the newton. Expressing pressure as kilogram-force per square centimeter was intuitive for engineers weighing loads, and the unit became common in mechanical and hydraulic engineering, boilers, and pneumatics through much of the 20th century.

Law and Notable Facts

The technical atmosphere is not part of the SI and its use is discouraged in favor of the pascal or bar. It is easily confused with the standard atmosphere; the two differ by about 3.3%. Gauge and absolute variants were often written "atü" (gauge) and "ata" (absolute) in German-language engineering.

Real-World Examples and Conversions

• 1 at = 1 kgf/cm² = 98.0665 kPa ≈ 0.9678 atm.
• 1 at ≈ 14.223 psi, close to but slightly below the 14.696 psi of one standard atmosphere.
• A pressure of 10 at (about 981 kPa) is a common rating benchmark for industrial hydraulic components.
• 1 at ≈ 0.980665 bar, so the bar and technical atmosphere differ by under 2%.

What is the kilopound per square inch?

Kilopound per square inch (ksi) is a unit of pressure commonly used in engineering, especially in North America. It represents a high amount of pressure, making it suitable for measuring the strength of materials.

Definition of Kilopound per Square Inch (ksi)

Ksi stands for "kilopound per square inch." It's a unit of pressure defined as 1,000 pounds of force applied per square inch of area.

$$1 \, \text{ksi} = 1000 \, \frac{\text{lbf}}{\text{in}^2}$$

Formation of Kilopound per Square Inch

The unit is derived from the combination of two units:

• Kilopound (kip): A unit of force equal to 1,000 pounds-force (lbf).

• Square Inch (in²): A unit of area equal to the area of a square with sides of 1 inch.

Relationship to Other Pressure Units

Kilopound per square inch can be converted to other common units of pressure:

• Pascal (Pa): The SI unit of pressure. $1 \, \text{ksi} \approx 6.895 \times 10⁶ \, \text{Pa}$ or $6.895 \, \text{MPa}$
• Pound per Square Inch (psi): $1 \, \text{ksi} = 1000 \, \text{psi}$

Applications and Examples

Ksi is frequently used in material science and structural engineering to express the yield strength and tensile strength of materials like steel, concrete, and aluminum.

• Steel Strength: The yield strength of high-strength steel might be around 50 ksi to 100 ksi or even higher.
• Concrete Strength: Concrete compressive strength is often specified in psi or ksi. For example, high-performance concrete may have a compressive strength of 10 ksi or more.
• Hydraulic Systems: High-pressure hydraulic systems, such as those used in heavy machinery, can operate at pressures measured in ksi.

Historical Context and Notable Figures

While there isn't a specific law or person directly associated with the invention of ksi, its usage is deeply rooted in engineering practices developed throughout the 20th century. The adoption of ksi reflects a practical approach to dealing with large pressure values in material testing and structural design. Figures like Stephen Timoshenko, a pioneer in engineering mechanics, indirectly influenced the widespread use of such units through their work on material strength and structural analysis.