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0.8–2 MPa 120–290 psi Pressure used in boilers of steam locomotives [citation needed] 1.1 MPa 162 psi Pressure of an average human bite [citation needed] 2.8–8.3 MPa 400–1,200 psi Pressure of carbon dioxide propellant in a paintball gun [64] 5 MPa 700 psi Water pressure of the output of a coin-operated car wash spray nozzle [58] 5 MPa ...
If HV is first expressed in N/mm 2 (MPa), or otherwise by converting from kgf/mm 2, then the tensile strength (in MPa) of the material can be approximated as σ u ≈ HV/ c, where c is a constant determined by yield strength, Poisson's ratio, work-hardening exponent and geometrical factors – usually ranging between 2 and 4. [9]
The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m −2 or kg·m −1 ·s −2). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m −2. When indicated, the zero reference is stated in parentheses following the unit, for example 101 kPa (abs).
Some of these derive from a unit of force divided by a unit of area; the SI unit of pressure, the pascal (Pa), for example, is one newton per square metre (N/m 2); similarly, the pound-force per square inch (psi, symbol lbf/in 2) is the traditional unit of pressure in the imperial and US customary systems.
As piston engines usually have their maximum torque at a lower rotating speed than the maximum power output, the BMEP is lower at full power (at higher rotating speed). If the same engine is rated 72 kW at 5400 min −1 = 90 s −1 , and its BMEP is 0.80 MPa, we get the following equation:
The conversion in SI units is 1 ksi = 6.895 MPa, or 1 MPa = 0.145 ksi. The megapound per square inch (Mpsi) is another multiple equal to a million psi. It is used in mechanics for the elastic modulus of materials, especially for metals. [5] The conversion in SI units is 1 Mpsi = 6.895 GPa, or 1 GPa = 0.145 Mpsi.
Ultimate strength is an attribute related to a material, rather than just a specific specimen made of the material, and as such it is quoted as the force per unit of cross section area (N/m 2). The ultimate strength is the maximum stress that a material can withstand before it breaks or weakens. [ 12 ]
Stress has dimension of force per area, with SI units of newtons per square meter (N/m 2) or pascal (Pa). [1] Stress expresses the internal forces that neighbouring particles of a continuous material exert on each other, while strain is the measure of the relative deformation of the material. [3]