Page:Report on the Shrivenham train crash of 15 January 1936 - MoT Shrivenham1936.pdf/18



Macro-etching revealed lack of homogeneity of the material and the presence of wide boundaries containing large slag inclusions between adjacent areas of iron having different grain sizes.

Microscopic Examination.

The microscopic examination of polished and etched sections showed that the metal contained a considerable amount of slag which was present in rather large masses unevenly distributed throughout the material. The shape, mass and distribution of these slag inclusions indicated that the metal had not been subjected to sufficient forging to produce the degree of homogeneity which is desirable. The grain size of the iron varied in different parts of the section, but was generally very large and suggests that the metal was overheated during forging.

Conclusions.

The results of my examination indicate that the wrought iron of which the hook was made was of fair quality chemically, but that it had been insufficiently worked to produce homogeneous material free from coarse slag inclusions.

The hook appeared to have been heated to a high temperature during forging which resulted in the production of a very coarsely crystalline structure to which the poor shock-resisting property of the metal, as shown by the low results of the Izod Test, is chiefly due.

The existence of the small defect in the hook, to which reference is made in the description of the fractured surface, was, in my opinion, a contributory cause of the failure, resulting in the production of "notch brittleness" at the low temperature existing at the time the fracture occurred.

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148.-(b) The Guard of a goods train must keep a good look-out and should he see any reason to apprehend danger, he must make every effort to attract the attention of the Driver.

If there is any Danger to & train on an adjoining line, the Guard must, should his train pass a signal box, exhibit to the Signalman a red hand signal waved slowly from side to side, and the Signalman must, on receiving this signal, act in accordance with Block Regulation 17.

(d) In the case of trains not fitted with the continuous brake, the Guard must, unless special instructions are issued to the contrary, always apply his brake as soon as he becomes a ware that the Driver is applying the engine brake.

126. The Driver and Fireman MUST:

(viii) observe signal boxes when passing them and look back frequently during the journey to see that the whole of the train is following in a safe and proper manner. 124751–54) 3663-2844 860 4/36 P... G.878/ 13