US2822897A - Welded structure - Google Patents

Description

Feb. 11, 1958 w. 1-1. PETERSON WELDED STRUCTURE 3 Sheets-Sheet 1 Filed Dec. 9, 1954 I nven for illiamliPferJon Feb. 11, 1958 P w. H. PETERSON ,897

WELDED STRUCTURE Filed Dec. 9, 1954 3 Sheets-Sheep 2 will I fnvenior William HPeierson .Aiiorney Feb. 11, 1958 w. H. PEQTERSON 9 WELDED STRUCTURE Filed Dec. 9, 1954 s Sheets-Sheet a .lnv enfor Willi amH Pe i''l'SOn United States Patent ice WELDED STRUCTURE William H. Peterson, Homewood, Ill., assignor to Pullman-Standard Car Manufacturing Company, Chicago, 11]., a corporation of Delaware Application December 9, 1954, Serial No. 474,109

18 Claims. (Cl. 189-36) This invention relates to the prevention of early brittle fracture in welded structures, particularly in mild steel welded structures.

While the phenomenon of brittle fracture of steel has been recognized almost since the introduction of Bessemer steel in 1875, and some studies were made at different times in various countries, very little was known regarding it. Largely as the result of numerous structural failures due to brittle fracture, in welded merchant ships early in World War II, extensive studies have been made during the past fifteen years which have shed somewhat more light on the problem, largely in the description of phenomena associated with this type of fracture. It may fairly be said, however, that so far such studies have revealed mainly the extreme difficulty not only of solving the problem of brittle fracture but of even determining the basic causes thereof and the concepts involved.

Brittle fracture is not limited to welded structures, and as it relates to welded steel structures is not confined to ships, presenting problems in practically all types of such structures, and particularly though not necessarily those subjected to relatively low temperatures. Only a few of the practically innumerable welded structures subject to brittle fracture and to which the present invention is applicable to prevent such failure are specifically disclosed herein. As one example, freight car underframes have unavoidable points of stress concentration at which brittle fracture sometimes occurs under cold weather conditions, one such point, for instance, being found in the body bolster. The body bolster is formed with at least one vertical web or diaphragm welded to horizontal top and bottom cover plates and terminating closely adjacent to the center sill, in many cases contacting and being welded to the center sill. At the inner corners defined by the web and cover plates, points of high stress concentration exist, due to residual stresses resulting from shrinkage of the welds connecting the web and plates, or to triaxial combinations of tensile stresses resulting from applied load, or to the vector sum of both types of stresses.

Thus, a particular combination and magnitude of stresses exist at each such point in a welded structure, as in the bolster, which will cause extensive fracture of the structure at loads frequently experienced in service at low temperatures. The occurrence of brittle fracture in. mild steel welded structures is characterized by virtually no flow of the material, and little energy is required to, propagate extensive fractures as compared to ductile fracture. Generally, highly local yields with beneficial redistribution of stresses can be effected by plastic flow of the steel due to its normal properties, leaving the structure perfectly useful. In cases where low temperature so changes the properties of the material as to prevent such plastic deformation, brittle fracture is very apt to occur when the yield point is reached. Obviously, the structure retains its serviceability after undergoing small local deformations, whereas if it is fractured its serviceability is lost, as in the case of the railway car bolster,

2,822,897 atented Feb. 11, 1953 for example. It has been found that by the introduction of a rounded hole closely adjacent the point of stress concentration, considerable plastic flow can desirably be attained in the structure at such location, so as to prevent brittle fracture at low temperatures, without appreciably affecting the structure adversely under normal conditions, it being the aim to provide plasticity in a structure where otherwise plastic yielding of the material could not occur, thereby increasing in great degree the work required to cause failure of the structure. This is of great importance in resisting dynamic loads. Such an opening at the same time directs applied stresses away from the point of concentration.

It is therefore a principal object of the invention to provide for plastic flow in welded steel structures at locations where brittle fracture might otherwise occur due to lack of plasticity.

Another object is the provision in welded steel structures of means for eliminating the effect of high stress concentrations in causing brittle fracture, by providing plasticity at points of such concentrations.

Another object is the provision of means for preventing brittle fracture of welded steel structures due to high stress concentrations.

It is also an important object of the invention to provide in welded steel structures, wherever a weld connection of one plate-like member to another terminates in a region of high tensile stress, means in such region to prevent brittle fracture beginning at the region.

Another object is the provision, in welded steel structures having members connected together by a weld terminating at a region of high tensile stress, of means in such region directing tensile stresses away from the weld termination and providing plasticity in the region to prevent brittle fracture. 7

Still another object is the provision of a method of preventing brittle fracture in welded steel structures by providing for plasticity in such structures.

Other and further objects, advantages, and features of the invention will be apparent from the following description and the accompanying drawings, in which:

Fig. 1 is a perspective view of a railway freight car underframe construction embodying the present invention;

Fig. 2 is an enlarged perspective view of a portion of the underframe shown in Fig. 1, in inverted position, and showing a rounded opening in a horizontal cover plate closely adjacent a weld termination of a vertical web plate;

Fig. 3 is a perspective view of a structure of horizontal and vertical plates Welded together, comparable to the cover plate and web plate construction shown in Fig. 2, and showing the region of brittle fracture due to applied tensile stress and lack of elongation of the structure;

Fig. 4 is a perspective view of a structure similar to that of Fig. 3 but provided with a circular opening in the horizontal plate in line with the vertical plate closely adjacent the toe of the weld connecting the plates;

Fig. 5 is a view of the structure of Fig. 4 after application of tensile stress thereto, showing the plastic deformation thereof without fracture;

Fig. 6 is a fragmentary perspective view of aship deck, partly in section, including a welded hatch corner and a clevis, showing the application of the invention tothis type of structure;

Fig. 7 is a perspective view'of an I-beam with a clevis welded to its lower flange, showing the application of the invention to such a structure;

Fig. 8 is a perspective view of cylindrical'pressure tank to which a support is welded, showing the application of 3 view taken along the line 9--9 of Fig. 8, showing in greater detail the application of the invention.

Referring first to Figs. 1 and 2 of the drawings, there is shown one end :of a railway freight car underframe including a center sill 10 with a body bloster 11 connected thereto, both being of welded mild steel construction. Each end of the center sill is formed with a striker face 12, only one of which is shown. The bolster in this instance comprises a pair of diaphragms, of which only one appears in the drawings, each formed by a pair of vertical web plates 15 in alignment with each other on opposite sides of the center sill and having their inner ends spaced slightly therefrom, the outer ends extending to the sides of the underframe. Top and bottom cover plates 16 and 17, respectively, extend over and under the web plates 15, and the upper and lower edges of the plates 15 are secured to the top and bottom plates each by a fillet Weld 14 extending along both faces of the web plate and around the inner end thereof, the weld toe, or portion of the weld at the inner plate end, being spaced somewhat from the center sill 10. The center sill is subject at both striker faces to heavy impact loads, which occasion both tensile and compressive stresses in the bolster. A point of high concentration of stress is known to exist unavoidably at each weld toe, and under certain applied load and temperature conditions, brittle fracture of a cover plate readily occurs, beginning at such a point and instantly spreading across the entire cover plate, causing failure of the bolster. This invention is directed to preventing brittle fracture beginning at this point or at a similar point in any comparable welded steel structure. In the case of the bolster 11, this is accomplished by providing in each of the top and bottom cover plates a circular opening 22 closely adjacent each weld toe, in alignment with the web plate and of a diameter such as to extend slightly outwardly of the fillet welds on each side of the web plate, or in other words so that the hole extends transversely of the plane of the web plate beyond the edge of the fillet weld on each side of the plate. This is best shown in Fig. 2. Upon application of tensile stresses longitudinally of the cover plate loading the material beyond its yield point, deformation will occur at the portion of the cover plate inwardly of the weld toe without such stressing of the structure adjacent the weld toe as to initiate brittle fracture, even at low temperatures. The provision of the opening 22 thus successfully avoids failure of the bolster due to brittle fracture at this critical point.

Although superior material and fabrication procedures may improve the performance :of welded steel structures with respect to brittle fracture, steels of the necessary toughness and ductility are expensive, and special welding techniques and materials are slow and costly, so that in the case of large structures requiring considerable quantities of material, as in railway car construction, the use of such steels and procedures is ordinarily prohibited by economic considerations. On the other hand, the practice of the present invention permits the use of relatively cheap steel and requires no substantial increase in material or labor costs, while effectively eliminating failures occasioned by brittle fracture.

Tests were made on full-size specimens of the bolster and center sill connection portion of car underframes by using a BaldWin-Southwark 300,000-lb. tensile testing machine, at F. to simulate low winter temperatures at which brittle fracture is most likely to occur. The tests were made by applying tension longitudinally of the cover plate portion of the specimens. Referring par ticularly to Figs. 3 through 5, there is shown a schematic representation of welded structure similar to the specimens, comprising a flat plate 18 comparable to the web plate 15 joined to another flat,- somewhat thicker, plate 19 comparable to the top cover plate 16. A fillet weld 20 extending on both sides of the plate 18 secures it to the plate 19 in perpendicular relation, the weld 20 corresponding to the weld 14 and having a weld toe 21 like that of the weld 14. The center sill portion is not indicated, since it had no significant effect on the results of the tests. Welded structures other than bolsters are of course included in the schematic representations of Figs. 3 to 5. Tests on the specimens represented by the structure of Fig. 3 resulted in final brittle fracture of the cover plate portion, originating at the weld toe, and extending across the cover plate portion as shown at A, after a total elongation of only a small fraction of an inch and Well before full load was reached, and with little work. Specimens identical to those which had so failed, except for the provision of a round, smooth-surfaced opening 22 extending through the plate 19 closely adjacent the weld toe 21 and in line with the plate 18, as shown in Fig. 4, were then tested in exactly the same manner. It was found that the structure represented in Fig. 4 underwent extensive elongation, some ten time that of the structure of Fig. 3', and with correspondingly increased work, under considerably greater load, without fracture. The structure finally failed when the applied load exceeded the ultimate strength of the material, as distinguished from the yield strength. The elongation and necking down of the plate 19 :of the structure of Fig. 4 after the yield point was reached is shown in Fig. 5, indicating the plastic deformation possible by reason of provision of the opening 22, as against the lack of plasticity or ductility of the structure of Fig. 3 without the opening. The elongation of the specimens was taken as an index of theductility or plasticity, or in other words the work required to cause failure. Obviously, structures with the plasticity-providing opening give tremendously improved results in this respect. The tests of the bolster and center sill structure specimens were proved valid by subsequent tests of an entire car incorporating the invention in the bolster construction as shown in Figs. 1 and 2. The car tests demonstrated conclusively that under conditions which normally would have resulted in brittle fracture of the cover plate adjacent the inner end of the web plate, there was plastic deformation of the cover plate which prevented failure of the bolster while retaining its serviceability.

It is not necessary that the opening be round or cir cular, for it may be elliptical, or elongated with round ends and parallel sides, or otherwise of rounded formation; in short, it must not have any sharp angles or corners, since such might themselves tend to initiate cracks. The surface defining the opening must be smooth, and the edges formed thereby at the opposite faces of the plate likewise must be free of irregularities. Surface lines in the hole which follow the outline thereof, that is, which may be considered as lying substantially in planes parallel to the plane of the plate, are not harmful, but edge or surface cracks, grooves, or notches in the other direction, that is, more or less perpendicular to the plane of the plate through which the opening is made, must be avoided completely. For these reasons, it is practically a necessity to drill or machine the opening 22, taking care that no vertical cracks or notches, even very fine ones, are formed and no crystalline disruption occurs. Accordingly, the hole should not be formed by punching. The opening may be formed in any desired manner, however, if a clean, smooth-surfaced hole is provided and no deleterious effect on the surrounding metal results, so that incipient notches or other conditions which might tend to initiate fracture are avoided. A round opening is generally preferred because of the relative ease with which it can be provided in a manner meeting the requirements, and also because the circular shape is best suited to avoid fracture under tensile stresses which might be applied in directions other than longitudinally of the structure, that is, in directions not parallel to the weld. An elongated opening provides for greater plastic flow when the structure is subject to tensile stresses only parallel to the weld. The opening should have, transversely of the center line of thecon nection between the platesor other members, a dimension or width greater than the total width of the connection or bond, and be located in alignment therewith. Thus, as in the cases of the structures of Figs. 1 to inclusive, in which one plate is secured in abutting relation to another plate by fillet welds along each side, the opening should be wider than the distance across the two welds, and should be substantially bisected by the plane of the one plate. Ordinarily, since usually there is a standard relation between the size of fillet welds and the thickness of the members which they secure, the width of the opening is of the order of three or four times the thickness of the plate or other member with which it is aligned. If the abutting plate or member is secured by a fillet weld along only one face, the opening is located in line with the fillet weld instead of the plate, and its width is made somewhat greater than the width of the weld. Again, if the one plate or member is welded, as by some form of resistance welding, only at its abutting edge to the face of another plate or the like, the opening is aligned with the plane of the one plate and has a width slightly greater than the thickness of the one plate. In other words, as already stated, the opening is wider than the bond or connection of the one plate or member to the one which it abuts, and is disposed in alignment with the connection. If the opening is elongated, it must ordinarily be arranged lengthwise relative to the welded connection, that is, parallel to the direction of the tensile stresses. Although the openings are illustrated as extending through the plate adjacent the ends of the weld connections, the invention contemplates also the provision of openings or holes extending only partially through the plate, but of sutficient depth to provide the desired plasticity. Thus, a hole or depression might be formed in the face of the plate on which the weld is made, with its bottom merging smoothly with the sides, or two such holes might be provided, one in each face of the plate, in opposed relation.

No fully provable explanation of the greatly improved structural strength and energy-absorbing capacity or ductility of welded structures having the rounded opening provided therein as described has been found. The reason for the results is almost as conjectural as the present concepts' of brittle fracture itself. It may be that the stresses tend to approach a state of equi-triaxiality at the weld toe as soon as yielding begins, thus substantially preventing plastic flow and causing brittle fracture, and that the provision of the roundedv opening results in the critical point being out of the region of plastic flow. Another possible explanation may be the material is stressed substantially to the yield point by the residual tensile stresses due to welding, so that added tensile stress due to applied load is very apt to result in brittle fracture because the material cannot exhibit plastic flow, the rounded opening permitting plastic deformation so that redistribution of stresses may occur, the critical point then being out of the region of plastic flow. In any case, the question of why brittle fracture occurs most often at low temperatures remains an open one.

The invention is applicable to many other welded steel structures than those of the type illustrated in Figs. 3 to 5 inclusive to prevent brittle fracture, some examples of such other structures being shown in Figs. 6,to 9 inclusrve.

In Fig. 6, there is disclosed the steel deck 23 of a ship provided with a hatch one corner of which is shown, formed by a pair of vertical plates disposed at right angles to each other and joined at their contacting ends by a fillet weld, and also welded to the deck by fillet welds along their outer faces which connect or merge at the corner. Rounded openings 25 are formed in the deck 23, each in line with one of the fillet welds 26 securing the plates 24 to the deck, and close to the end thereof, or

inother words to the junction of the welds. Tensile stresses in the directions indicated by the arrows in Fig. 6, that-is, generally along. or parallel to either of. the hatchdefiningplates 24, willnot result in brittle fracture, since the openings 25 provide for local plastic deformation of the deck and allow the material to yield rather than break, without any appreciable impairment of the service ability of the deck. Thus a potentially very dangerous situation is made safe. A clevis member 27 is also shown in Fig. 6, extending upwardly from the deck 23 and secured thereto by a fillet weld 28 about its lower end. Again, by forming rounded openings 25 in the deck in line with the plane of the clevis 27, brittle fracture at either end or toe of the weld 28 is prevented. The openings 25 provided adjacent the clevis are larger than those adjacent the hatch corner, since the clevis is shown as formed of thicker material than the hatch-forming plates 24 and has fillet welds along both sides. The openings 25 may be closed by rivets 25a and elastic gaskets 25b, as shown in the figure, so as to be'water-tight even if they become elongated or otherwise distorted by plastic flow or the deck 23.

Fig. 7 discloses an I-beam 29 having a clevis 30 secured on the bottom face of the lower flange 31, substantially in the plane. of the web 34 of the beam, by aseparate fillet weld 32 on each side thereof, no extension of the welds about the end faces of the clevis being shown in this, instance. A rounded opening 33 is formed in the lower beam flange 31 adjacent each end faceof the clevis, that is, adjacent the weld terminations, in line with the plane of the clevis and the direction of tensile stresses in the beam, each opening extending sufficiently into the beam web 34 to form an aperture completely through the flange and avoid the possibility of the web affecting the efficacy of the opening. The provision of the openings 33 provides for plastic deformation and prevents brittle fracture at either end of the welds.

In Figs. 8 and 9, a cylindrical pressure tank 35 is shown with an angle bracket 36 for the support thereof welded to the cylindrical or body wall 37. The edge of the bracket extends parallel to the axis of the tank and is secured to the wall 37 by a single fillet weld 38, which thus of course extends in the direction of longitudinal tensile stresses in the wall. A rounded opening 39 is formed through the wall 37 closely adjacent each end of the weld and in alignment therewith, preventing brittle fracture of the wall at either end of the weld. Hoop stresses in the Wall do not materially affect the connection of the tank and bracket so far as brittle fracture is concerned. An arcuate-edged' bracket disposed transversely of the tank and welded to the body wall 37might be used instead of the bracket illustrated, in which case the openings 39 would be located closely adjacent the ends of the bracket and the connecting weld to avoid brittle fracture due to hoop stresses. In such case, also, the weld might be a fillet weld extending along both faces of the bracket, and the openings then would be located in line with the plane of the bracket portion engaging the tank. Any suitable means, such as the bolt, nut, and elastic gasket device 40 illustrated in Fig. 9, may be used for tightly sealing the openings 39.

It will be clear that a pair of plates or like members of different widths may be lapped and joined by a single fillet weld along the edge of the narrower of such members, and openings provided in the wider member at the ends of and in alignment with the weld, substantially as in the case of the tank and bracket construction shown in Fig. 8, for the prevention of brittle fracture.

It should also be clear that the invention is effective whether the tensile stress of magnitude otherwise sufficient to cause brittle fracture is a predominant stress acting in the direction of the weld connection or is a com, ponent in that direction of a predominant stress acting at an angle to the line of the weld connection.

While the invention has so far been described only with respect to the structural aspect, it also provides a method for preventing brittle fracture in welded structures by the imparting to rigid and plastical'ly unyieldingportions,

of such structures a capacity for plastic flow or deformation. The method providing by the invention is apparent from the description of the structural means employed for achieving the desired plasticity and does not require a separate extended explanation. In its broader aspect, the method of the invention comprises the localized removal of material adjacent a point of high stress concentration where plastic deformation cannot otherwise occur, to provide capacity for plastic flow under conditions which in the absence of such provision would cause brittle fracturej Such localized capacity for plastic deformation is provided by the method specifically through the employment of holes or openings in the material adjacent the ends of weld connections between the parts of the structure, as hereinbefore explained.

A rather general statement of the application of the invention to prevent brittle fracture is that whenever in a mild steel welded structure there is a condition of a high concentration of either or both applied and residual tensile stresses and the material adjacent the point of such concentration is not relatively free for plastic how so as to neck or thin down or otherwise deform without fracture, the provision of a rounded hole in the restricted material will provide plasticity to prevent brittle fracture.

What is claimed:

1. A mild steel welded structure comprising a first plate subject to tensile stresses, a second plate engaging said first plate extending generally parallel to the direction of said tensile stresses, a weld connection securing said plates together and terminating on said first plate at an end of said second plate, and a round smooth-surfaced opening through said first plate located closely adjacent said termination of said weld connection substantially in alignment with the center line of bond provided by the weld connection and having a diameter slightly greater than the lateral extent of said weld connection, whereby under tensile stress the first plate will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

2. A mild steel welded structure comprising a first member subject to tensile stresses,.a second member engaging said first member along a line extending generally parallel to the direction of said tensile stresses, a weld connection along said line securing said members together and terminating on said first member at an end of said second member, and a round smooth-surfaced opening through said first member located closely adjacent said termination of said weld connection and in alignment with the center line of bond provided by the weld connection and having a diameter greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

. 3. A mild steel welded structure comprising a first plate subject to tensile stresses, a second plate engaging said first plate extending generally parallel to the direction of said tensile stresses, a weld connection securing said plates together and terminating on said first plate at an end of said second plate, and a rounded smooth-surfaced opening through said first plate located closely adjacent said termination of said weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line greater than the lateral extent of the weld connection, whereby under tensile stress the first plate will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

4. A mild steel welded structure comprising a first member subject to tensile stresses, a second member engaging said first member along a line extending generally parallel to the direction of said tensile stresses, a weld connection along said line securing said members together and terminating on said first member at an end of said second member, and a rounded smooth-surfaced opening through said first member located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

5. A mild steel welded structure comprising a first plate subject to tensile stresses, a second plate engaging a surface of said first plate extending generally parallel to the direction of said tensile stresses, a weld connection securing said plates together and terminating on said first plate at an end of said second plate, and a rounded smooth-surfaced hole formed in the first plate extending from said surface located closely adjacent said term-in ation of said weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first plate will undergo plastic deformation instead of brittle fracture immediately adjacent'and beyond the termination of the weld.

6. A mild steel welded structure comprising a first member subject to tensile stresses, a second member engaging a surface of said first member along a line extending generally parallel to the direction of said tensile stresses, a weld connection along said line securing said members together and terminating on said first member at an end of said second member, and a rounded smoothsurfaced hole formed in the first member extending from said surface located closely adjacent said termination of said weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

7. In a mild steel welded structure including a first plate-like member subject totensile stresses, a second plate-like member engaging a surface of said first member extending generally parallel to the direction of said tensile stresses, and a weld connection securing said members together and terminating on said first member at an end of said second member, the improvement comprising a rounded smooth-surfaced hole extending through the first member closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

8. In a mild steel welded structure including a first member subject to tensile stresses, a second member engaging a surface of said first member along a lineextending generally parallel to the direction of said tensile stresses, and a weld connection along said line securing said members together and terminating on said first member atan end of said second member, the improvement comprising a rounded smooth-surfaced hole in said first member extending from said surface located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first memberwill undergo plastic deformation instead of .9 brittle fracture immediately adjacent and beyond the termination of the weld. I r

9. A mild steel welded structure comprising a first substantially flat platesubject to tensile stresses, at second substantially flat plate engaging a surface of said first plate disposed substantially perpendicular thereto and extending generally parallel to the direction of said tensile stresses, a weld connection securing said plates-together and terminating on said first plate atan end of the second plate, and a round smooth-surfaced hole extending through said first plate located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a diameter slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first plate will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the Weld.

10. A mild steel welded structure comprising a first member subject to tensile stresses and having a substantially flat surface, a second member having a substantially flat surface and disposed in engagement with said surface of the first member along a line substantially parallel to the direction of said tensile stresses with said surfaces substantially perpendicular, a weld connection along said line securing said members together and terminating on said surface of said first member at an end of the second member, and a round smooth-surfaced hole extending through said first member located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a diameter slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

11. A mild steel welded structure comprising a first substantially flat plate-like member subject to tensile stresses, a second substantially flat plate-like member disposed substantially perpendicular to said first member engaging a surface of said first member and extending generally parallel to the direction of said tensile stresses, a weld connection securing said members together and terminating on said first member at an end of the second member, and a rounded smooth-surfaced hole extending through the first member located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the Weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

12. A mild steel welded structure comprising a first substantially flat plate-like member subject to tensile stresses, a second substantially flat plate-like member disposed substantially perpendicular to said first member engaging a surface of the first member and extending generally parallel to the direction of said tensile stresses, a Weld connection securing said members together and terminating on said first member at an end of the second member, and a rounded smooth-surfaced hole formed in the first member extending from said surface located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line greater than the lateral extent of the weld connection, whereby under tensile stress the first member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the Weld.

13. A mild steel welded structure comprising a first substantially flat plate subject to tensile stresses acting in different directions, a pair of plates engaging said first plate arranged at an angle to each other with adjacent ends in engagement and each' extending generally parallel to one of said tensile stress directions and substantially perpendicular to said first plate, a weldconnection securing each of said pair of plates to said first plate and terminating on said first plate at said ends of the pair of plates, and a pairof rounded holes extending through said first plate each located closely adjacent the termination of the weld connection between one of said pair of plates and said first plate and in alignment with the center line of bond provided by that weld connection and each having a dimension transverse of the respective weld connection slightly greater than the lateral extentof said weld connection, whereby under tensile stress the first plate will undergo plastic deformation instead ofbrittle fracture immediately adjacent and beyond the termination of the Weld.

14. A mild steel welded structure comprising a substantially flat plate subject to tensile stresses, a generally plate-like member disposed substantially perpendicular to said plate in engagement with a surface thereof and extending generally parallel to the direction of said tensile stresses, a weld connection securing said member to said plate and terminating on said plate at opposite ends of said member, and a pair of rounded smooth-surfaced holes extending through the plate each located closely adjacent one termination of the weld connection substan tially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the Weld connection, whereby under tensile stress the plate will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

15. A mild steel welded structure comprising an I-bearn subject to longitudinal tensile stresses, an apertured platelike clevis substantially perpendicular to a flange of the I-beam extending generally parallel to the direction of said tensile stresses and substantially centered relative to the plane of the web of the I-beam, a weld connection securing the clevis to said flange terminating on the flange at opposite ends of the clevis, and a pair of rounded smooth-surfaced holes extending through said flange and into said web each located closely adjacent one termination of the Weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the flange will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

16. A mild steel welded structure comprising a flanged member subject to tensile stresses, a generally plate-like member disposed substantially perpendicular to a flange of said flanged member in engagement with a surface thereof and extending generally parallel to the direction of said tensile stresses, at weld connection securing said plate-like member to said flange and terminating on said flange at opposite ends of said plate-like member, and a pair of rounded smooth-surfaced holes extending through the flange each located closely adjacent one termination of the weld connection in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the flange will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

17. A mild steel welded structure comprising a curved plate subject to tensile stresses, a substantially flat plate engaging said curved plate extending generally parallel to the direction of said tensile stresses, a weld connection securing the plates together and terminating on said curved plate at an end of said fiat plate, and a rounded 11 g smooth-surfaced opening extending through said curved plate located closely adjacent said termination of the weld connection substantially in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the curved plate will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

18. A mild steel welded structure comprising a curved member subject to tensile stresses, a member engaging said curved member having a substantially fiat surface extending generally parallel to the direction of said tensile stresses, a weld connection securing the members together and terminating on said curved member at an end of said flat-surfaced member, and a rounded smooth-surfaced hole formed in said curved member extending from the surface thereof engaged by said fiat-surfaced member located closely adjacent said termination of the weld connection and in alignment with the center line of bond provided by the weld connection and having a dimension transverse of said center line slightly greater than the lateral extent of the weld connection, whereby under tensile stress the curved member will undergo plastic deformation instead of brittle fracture immediately adjacent and beyond the termination of the weld.

References Cited in the file of this patent *UNITED STATES PATENTS 2,382,584 Scheyer Aug. 14, 1945 FOREIGN PATENTS 102,367 Australia Oct. 27, 1937

Images