Fracture of steel

Fracture of Steel.

04

[Jour. Frank. Inst.,

Modulus of rupture -~ 4,586 lbs. per square inch. Mean deflection for 402 lbs. ---- "1128. Modulus of elasticity = 1,259,224 lbs. per square inch. Maximum intensity of shear at neutral axis ~ 129 lbs. per square inch. NO. 31.--SPRUCE JOIST, 3~ in. by 12 in. centre.

Span 18 feet. Loaded at

Tested by Messrs. Davis and Morse. Load in lbs.

Defleetion in inches,

Differenees.

I

"1486

"1486

1,289

887 I

• 3030

• 1544

1,691

•4514

•1484

2, 093

• 6129

",615

2, 495

• 7615

• 1486

3, 701

..............................

7, 721 l

Cracking commenced• B r e a k i n g l o a d . B r o k e s u d d e n l y b y c o m p r e s m o n o t top ilb r e s a n d s h e a r i n g a l o n g t h e n e u t r a l a x i s . S p l i t showed s e v e r a l s m a l l p i n k n o t s , r u n n i n g v e r t i c a l l y i n t h e beam, a n t i a p p a r e l l t l y p i n n i n g t h e s i d e s o f t h e l r a c t u r e together..

Modulus of rupture ~ 5,559 lbs. per square inch. Mean deflection for 402 lbs. ---~ "1523. Modulus of elasticity -~ 1,231,498 lbs. per square inch. Maximum intensity of shear at neutral axis ---- 154 lbs. per square inch.

Fracture of S t e e l . w R u p t u r e s often occur in steel, which are very difficult to explain. They are generally attributed to inequality in cooling or to imperfect annealing, but some experiments, which have been reported to the institution of naval architects, seem to show that the fractures are always attributable to a defect in the quality of the :steel before rolling, and not to the inequality of the strains to which it is finally subject. When a piece of sound steel plate was heated t¢ redness, and then cooled unequally by scattering water on variou~ parts of the heated surface, it was hammered in various ways and submitted to a series of experiments of the most trying character, with• out giving any indication of fracture.--Chron. Industr., No. 39. C.