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The first length standards to use this technique were rectangular section solid bars. A blind hole was bored at each end, to the depth of the neutral plane, and the calibration marks were made at this depth. This was inconvenient, as it was impossible to measure directly between the two marks, but
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To show that every beam must have a neutral plane, the material of the beam can be imagined to be divided into narrow fibers parallel to its length. When the beam is bent, at any given cross-section the region of fibers near the concave side will be under compression, while the region near the
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developed an improved design. By placing the frames partly inside the hull and partly outside, the neutral axis could be rearranged to coincide with the nodal circle once more. This gave no resultant bending moment on the frames and so allowed a lighter and more efficient structure.
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section that was not quite circular, causing the nodal circle to separate from the neutral plane, giving rise to additional stresses. The original design was framed internally: this needed trial-and-error design refinement to produce acceptable dimensions for the rib
95:. If the structure is a membrane supported by strength ribs, then placing the skin along the neutral surface avoids either compression or tension forces upon it. If the skin is already under external pressure, then this reduces the total force to which it is subject.
159:. The neutral plane of the bar is designed to coincide with one surface of the central web connecting the two sides (in this photo the bottom surface). The meter was defined by two fine lines scribed near the ends of the bar on this surface until 1960.
140:. When metal bars were developed as physical standards for length measures, they were calibrated as marks made on a length measured along the neutral plane. This avoided the minuscule changes in length, owing to the bar sagging under its own weight.
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or extension either: when the beam bends, the length of the neutral plane remains constant. Any line within the neutral plane parallel to the axis of the beam is called the
175:. One surface of the centre crossbar of the H was designed to coincide with the neutral plane, and the calibration marks defining the meter were scribed into this surface.
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British bronze yard of 1855. The yard is defined by the distance between two lines scribed on the bottom surface of holes at each ends of the bar, on the neutral plane.
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across any cross section, there must be a boundary between the regions of compression and tension at which the fibers have no stress. This is the neutral plane.
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which served as the definition of the meter from 1889 to 1960. This was made with a splayed H-shaped cross section, called the
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An evenly loaded beam, bending (sagging) under load. The neutral plane is shown by the dotted line.
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In the design of submarines this has been an important, although subtle, issue. The US
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The property of remaining a constant length under load has been made use of in length
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convex side will be under tension. Because the stress in the material must be
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As there is no lengthwise stress force on the neutral plane, there is no
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The Fleet
Submarine in the U.S. Navy: A Design and Construction History
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294:. National Institute of Standards & Technology. Archived from
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The location of the neutral plane can be an important factor in
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252:. London: Arms and Armour Press. pp. 215, 217.
316:L.W. Nickols (1966). "The Measurement of Length".
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320:. Vol. II. London: Heinemann. p. 2.
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272:: CS1 maint: multiple names: authors list (
248:Alden, John D., Commander (USN Ret) (1979).
163:A more convenient approach was used for the
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220:Advanced Engineering Mathematics, 4th Ed
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223:. New York: McGraw-Hill. pp.
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165:international prototype metre
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52:and the outer surface is in
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151:Platinum-iridium standard
117:Portsmouth Naval Shipyard
217:Wylie, C. Ray (1975).
169:platinum-iridium alloy
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102:of World War II had a
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318:Engineering Heritage
288:"Bronze Yard Nº 11"
167:of 1870, a bar of
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185:Airy points
50:compression
332:Categories
302:2013-03-27
234:0070721807
201:References
109:scantlings
77:continuous
46:cantilever
268:cite book
138:metrology
124:Metrology
89:monocoque
40:within a
26:mechanics
179:See also
155:bars of
338:Statics
54:tension
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65:strain
58:stress
28:, the
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38:plane
274:link
254:ISBN
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104:hull
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