FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1918
1918 - 1408.PDF
DECEMBER 12, 1918 STRESS OPTICAL EXPERIMENTS By MAJOR A. R. LOW, RJV.F. (Continued from page 1381.) .-;••;— - ; SECTION NO. 3 colours is completely shown, and the second order of colours also appears, showing a characteristic salmon pink as distinct from the brick red in the first order. Fig. 16 shows the point of inflection with the 30-lb. dis- tributed load. The point of inflection is Symmetrically placed between the brick red wedges in the top right and bottom left corners. Examples of OpticalJObservations Fig. 13 shows the appearance of the image thrown onthe screen when no external stress is applied. The pale orange colouring indicates a slight amount of stresswhich is either residual or is due to the weight of the girder itself. The two bright edges separated by dark stress bandsfrom the main portion of the surface are caused by a surface effect in the xylonite itself, some physical change taking placein the worked edges of the material. Generally speaking, the dark band represents the neutral axis slightly shiftedupwards by the end pressure. Fig. 17 shows the optical effect of 40 lb. load distributedas before. The neutral axis retains the same position approximately, but the dark grey band which indicatesit is much narrower than before. Three orders of colours appear below the neutral axis, while atopvethe neutral axis thecompleted first order appears and most of the second order. p"*":: IS8'*"1;"' ^.-r, .. .r. .-....-. ...;- :..:.•. . .,- . . • . •-"....--.•..,"....-'. ^•-.--:-.-."•:.i- Fig. 18 shows the optical effect under the same load Fig. 14 shows the optical effect caused by a total after one hour. Marked creeping has taken place, andload of 20 lbs. distributed as before. The neutral axis is shifted up in pretty much the same way as in Fig. 13,and the first order of colours partially appears as a broad band of pale orange in the lower edge, followed by a bandof brick red. FIG. 19. a complete new order of colours has appeared below the neutral axis, namely, the fourth, and likewise above the Fig. 15 shows the effect of a 30 lbs. load distributedas before. The neutral axis remains approximately in the same position as the two preceding photographs, andappears as a broad black band. Below, the first order of FIG. 16. FIG. 20. 1409
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
