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Fig. 9—Stress distribution resulting from an unwelded internal boundary on brittle weld metal (left) and ductile weld metal (right). The ripping action starts from the inside and reduces the apparent strength of the joint materially Fig. 7 represents stress distribution usually found in welds made from one side of a plate. Such welds fre- quently introduce ragged contours, since the form of penetration of the weld metal cannot be controlled com- pletely from one side. Where the de- sign of the structure is such that welding from both sides is imprac- tical, the use of backing-up strips per- mits the production of a compromise contour which is at least predictable. Fig. 8 illustrates the stress distri- bution around another common type of defect, overlap, which often occurs at the hands of an inexperienced weld- er. It is caused by running over of the molten weld metal on to the sur- face of the plate, where it merely solidifies instead of fusing with the parent metal. Weld Contour Important Fig. 6 emphasizes another of the many forms of vicious stress distribu- tion that may creep into a structure. It contrasts the stress conditions around a fillet weld having a concave contour with that around a fillet weld having a triangular cross-section. The triangular throat weld, while having a lower average stress due to its greater throat dimension, has higher Maximum stresses because of the abrupt change in contour that it rep- resents. The concave throat weld has a smaller throat area and therefore possesses a higher average stress, but its points of maximum stress are con- siderably lower than those in the tri- angular throat weld. There are many instances permeat- ing the entire machine design picture in which the proper procedure to rec- tify a succession of fatigue failures is to remove metal rather than make addition to the existing section. The effect of removing metal properly is to raise the average stress a few per 18 cent, while making a reduction of sey- eral hundred per cent in the values of the maximum stress. The concave throated weld fillet is a case in point. The concave throat contour provides the most uniform distribution of stress and is the closest approach to the ideal that can be obtained in practice. The conventional term, throat dimen- sion, has no meaning in this case since the technique involved in removing the internal boundary consisted of welding completely through the joint. Fig. 1 shows a failure resulting from a slovenly job of welding. The fatigue crack centered about the stress concentration produced by an extraneous bit of weld metal care- lessly left by the welder to project from an important boundary of the structure. It should be noted that the doubly aggravated condition which exists when a point of high stress coincides specifically with a zone of badly damaged parent material is the rule rather than the exception in all of the joints illustrated. Ductility Gives Higher Strength Fig. 9 contrasts the action of the poisonous stress distribution result- ing from an unwelded internal bound- ary on a ductile and on a brittle weld metal. The ripping action which starts from the inside reduces the ap- parent strength of this joint mate- rially. The brittle weld metal shows a fracture without an _ attendent change of shape while the ductile ma- terial, through a plastic deformation at the points of high stress, enables the structure to change its shape to a degree which materially raises the actual strength of the joint. Fig. 10 illustrates the same com- bination of effects occurring in a fillet welded joint. Compare the actual be- havior of the joint under a tensile load with the stress distribution as shown in the photoelastic study. The ductility of the weld metal in this case allowed a _ sufficient correction of contour at the points of maximum stress so that the failure actually oc- curred some distance away from the joint. It should be emphasized that the mechanism of ductility is not available for the correction of struc- tural discrepancies in cases where the load is of a repeated nature. (To be concluded) Effective Dec. 1, the Standard Oil Co. of New Jersey advanced the price of bunker oil by 10 cents a barrel. The new prices are $1.20 on the At- lantic coast; $1.05 at Gulf and West Indies ports, and $1.25 at Panama canal ports. No information was re- ceived concerning diesel fuel oil prices though recent quotations show an advance. Fig. 10—An improperly made fillet welded joint. in tension is shown at the right. to occur at some distance from the joint. is shown at the right MARINE REVIEw—January, 1934 Actual behavior of the joint Ductility of the weld metal caused the failure Photoelastic study of such a joint