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Impact of Mass Cuts on Efficiency

You're welcome to download, read, share, and even reuse it under the CC by-sa license. If it helps you, please consider citing it where you use it – that makes a big difference. If you can afford it, buying the paid pdf or printed edition supports the project and keeps it sustainable. (Right now, about 1 in 400 readers do – thank you if you're one of them ) Enjoy the book – it was a joy to write and share by Olivier Cleynen ISBN: 9781446710067 First edition in English (June 2025), Olivier Cleynen / thermodynamicsbook com Translated from the third edition of the French original [51] Copyright 2015, 2018, 2021, 2025 Olivier Cleynen Engineering Thermodynamics is released under a Creative Commons license: c b a Attribution – Share-Alike 4 0.

Figures (7)

Figure 12.18 When an object is in either tension or compression, the net force on it is zero, but the object deforms by changing its original length L0.L0. (a) Tension: The rod is elongated by ΔL.ΔL. (b) Compression: The rod is contracted by ΔL.ΔL. In both cases, the deforming force acts along the length of the rod and perpendicular to its cross-section. In the linear range of low stress, the cross-sectional area of the rod does not change.
Figure 12.19 Nelson’s Column in Trafalgar Square, London, England. (credit: modification of work by Cristian Bortes)
Figure 12.20 (a) An object bending downward experiences tensile stress (stretching) in the upper section and compressive stress (compressing) in the lower section. (b) Elite weightlifters often bend iron bars temporarily during lifting, as in the 2012 Olympics competition. (credit b: modification of work by Oleksandr Kocherzhenko)
Figure 12.21 Steel I-beams are used in construction to reduce bending strains. (credit: modification of work by “US Army Corps of Engineers Europe District”/Flickr)
Figure 12.22 An object under increasing bulk stress always undergoes a decrease in its volume. Equal forces perpendicular to the surface act from all directions. The effect of these forces is to decrease the volume by the amount ΔVΔV compared to the original volume, V0.V0.
Figure 12.23 In a hydraulic press, when a small piston is displaced downward, the pressure in the oil is transmitted throughout the oil to the large piston, causing the large piston to move upward. A small force applied to a small piston causes a large pressing force, which the large piston exerts on an object that is either lifted or squeezed. The device acts as a mechanical lever.
Figure 12.24 An object under shear stress: Two antiparallel forces of equal magnitude are applied tangentially to opposite parallel surfaces of the object. The dashed-line contour depicts the resulting deformation. There is no change in the direction transverse to the acting forces and the transverse length L0L0 is unaffected. Shear deformation is characterized by a gradual shift ΔxΔx of layers in the direction tangent to the forces.

Key Points

  • View this demonstration to move the box to see how the compression (or tension) in the columns is affected when the box changes its position.
  • The compression is done reversibly (very slowly), but non-adiabatically: the air receives heat through the walls throughout the process.
  • The efficiency of the Carnot engine cycle (7/6) is only reached if the turbine and compressor operate isentropically.
  • A cantilever in a traditionally timber framed building is called a jetty or forebay.
  • Stress is a quantity that describes the magnitude of forces that cause deformation.
  • Strain is given as a fractional change in either length (under tensile stress) or volume (under bulk stress) or geometry (under shear stress).

Terms

Tap a term for a plain-language explanation.

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