US2495782A - Welded reinforcement - Google Patents

Description

Jan 311,

1950 G. L. SMITH 2,495,782

WELDED REINFORCEMENT Filed May 14, 1946 MHLMM 38 i 37 40 37 WELD 36 V y 7 wH|TTEMoRE 4 e 7 s STRAIN GAGE g HOLES *4! I 40' J 24 25 T KIPS KIPS

900 e00 700 e00 500 400 300 200 I00 STRAIN PER INGH IN INCHES X IOOOO AILED AT 974 DUCTILE TEMP. 77 IN. PLATE WITHOUT STRAIN PER INGH IN INCHES X TEMP. 73 F.

5/8 IN. PLATE WiTH WELDS FAILED AT IO72- BRITTLE 2 WELD 46 Gauge Lnnard 5111111111 1N VEN TOR.

ATTORNEY.

stresses and to place ments for the corner areas of view or the overlapping stantially on the Patented Jan. 31, 1950 I 7 2,495,783 woman REINFGRCEMEN 2,495,782 UNITED STATES PATENT oFFicE George L Smith, United States 1 Application May 14, 1946, Serial No. :669,554

(Granted -=underthe act amended April v The invention relates generally to improvements in welded reinforcements and the primary object is to provide a pro-stressed welded reiniorcement for the corners of hatches and similar openings in the plate of welded ships.

Another object of the invention is the provision of an improved method of reinforcing metal plates in which a stress raiser, such as a hatch opening, is present.-

Many of the structural defects which developed in welded ships during. the past few years have taken the-form'of transverse or diagonal cracks starting-at-the-corners of hatchesand other openings in the strength deck; In some cases these cracks havescarried around the structure and. the shiphas broken in two. It is possible thatlow temperatures may have been a contributingcause insomelof these failures, .but.,whatever the cause, the problem has been a grave-one and the necessity for a solution has been most pressing.

Tests have indicated that tensile strains can be introduced into the materialat the. corners of an opening in .a .plateto prevent .acrack, from starting at the corner under overall tensile load or to delay the starting of a cram: at a sharp corner u-ntil theultimate strength of the material has been reached. Byshrinking. or compressing the metal in thecorner areas, the possibility of cracking under tensile load has been reduced.

According to the present invention, heads of weld metal are appliedto the-deck plating at each corne-rof thelhatch orother opening These beads are heavy-enough-to set up largeshrinkage the metal oi the deck-plat ing under-the bead in initial compression. The welded beads are so-sr-nall with respect to the area of the plate under tension that they cannot appreciably affect the ultimate strength of the material, yet tests have indicated that they do in crease the elastic limit of the metal in the areas around the corners 'by approximately 28 percent. Tests have also shown the value of welded beads in increasing the energy absorption capacity of the material and th'e extent to which alternating loads may be increased by the use of these welds. Figure 1 is a fragmentary plan view illustrating the use of overlapping welded bead reinforce- I a rectangular hatch. I Figure 2 is a fragmentary plan viewshowing a test model of a rectangular hatch having the oyerlapplng welded bead reinforcements in its corner areas.

Figure Bis a fragmentary cross sectional detail line 3-3 of Figure 2.

"Figure 4 is=a graph of the load-strain curves of a rectangular hatch model not provided with thewelded bead reinforcements.

Figure 5 is a graph of the load-strain curves welded-beads, taken subof March a 188:, as

tab model illustrated in Figure 6 is a fragmentaryplan view eta-rectangular hatch provided-with a single continuous welded reinforcement, w In the drawings, which forthepurposeof i1..- -lustration show preferredand modified forms of the invention, and wherein similar reference characters denote corresponding parts throughout the views, the letter A generally designates the preferred hatch structure wherein {the strength-deck 9 of the ship is provided with a rectangular opening Ill. The sides-H, I 2 ofopening ill are defined-by strips 43,14 and the ends i5, i6 are'defined by strips ;l-!, 18. The sides-of these strips l l; 18 are welded to the sides of strips it, [4 along lines i9- 22 to form a rigid plate. At the corner portions of the rectangular hatch structure are welded areas 23 each including a plurality of overlapping diagonal welded beads 24+2 8. In the example shown these beads 24- 2 k} are disposed at an angle of '30 degrees to "the major axis 29 of the hatch structure and the nearest edges of the inside beads 24 are spaced from the edges of the hatch opening l ii a distance approximately equal tothe thickness of the deck plate, usually 4; inch or greater. These beads Z t 28 gradually decrease in length from the relatively long inside beads 24 to the shorter outside beadsZB so as to avoid sudden termination of shrinkage strains. Also the end portions 24' of thebeads 24 are preferably tapered in thickness toward their ends. The beads 24-28 may each be of a width approximately twice the plate thickness and of a height approximately half the plate thickness.

In Figure 2 is shown a test hatch B formed of inch plate and having welded areas 35 similar to theareas 23 of the hatch structure A shown in Figure 1. Each welded area 35 was formed by first depositing weld material to 'produce a short bead 35. Then successive overlapping ibea'ds 31-453 of gradually increasing length were formed. Each overlapping bead was thus attached throughout its length to--the plate and 'to the previously applied bead. The inside edge of the longest head 4!! was spaced from the hatch opening a distance equal to the thickof the rectangular ha 'n'ess ofthe plate and the opposite end portions heating andoooling action and appeared to he equallyeifectiyein reinforcing the corners; The rein-iorcedtest hatch -B and another test hatch identical therewith except that it lacked the in a line from corner to corner.

in Figure but welded reinforcement areas 35, were subjected to longitudinal tensile loading and the strains set up in the plates were measured in the following manner. Eight pairs I--8 of holes for a 2- inch base Whittemore strain gage were drilled symmetrically on lines across the plates on each side at the end of the hatch opening 4|. Figures 4 and 5 clearly show the difierences between the strains produced in the reinforced test hatch B and those in the hatch without the welds. Points on the curves were obtained by averaging the gage readings for the two sides of the plate and for the two sides of the hatch and dividing by 8 to get the strains per inch, thus; (1j+1b+8f+8b)/8 gives the average strain in inches per inch for the outer stations I, 8. In the same way points on the curve 4 and 5 were obtained by the equation (4f+4b+5f+5b)/8.= strain in inches per inch.

In Figure 4, which relates to the plate not provided with the welded reinforcements, the curves for stations I and 8, 2 and I, and 3 and 6 are practically identical, whereas the curve for stations 4 and 5 clearly shows the increased strains resulting from stresses at the corners.

- In Figure 5, relating to the test hatch B having the welded reinforcements, the first three curves open out considerably and the one for stations 4 and 5 actually crosses the zero line at a load of about 800 hips. The means stress on the welded test hatch B figured at a load of- 800 kips, corresponding to zero strain at corners, amounts to about 45,000 p. s. i. over the net section. This shows conclusively that the welded reinforcements actually eliminate any intensification of stresses at the corners of the hatch opening until the average stress is well above 45,000 p. s. i. The peculiar shape of curve 4 and 5 of Figure 5 indicates in efiect a pivoting or fulcrum point somewhere in the weld, about which the stretching of the metal outside the welds produces a compressive load on the metal at the corners. This explains the action noted in several previous tests of similar welded reinforced plates where the sides of the hatch opening first deflected inwardly and then outwardly again before failure of the plate.-

Another effect of the welds is that the end of the hatch is bulged up towards the welded side as a result of compressive stresses set up Without the welds, stresses in this line produced by a longitudinal tensile load on the specimen would be tensile and not compressive. This indicates that the weld reverse the cross stresses at a corner which contributes to failure. It is also an indication pointing to the possibility of reducing the angle at which the welds are laid on.

To test this feature, a second specimen identical with the test hatch B shown in Figure 2, except for a change in the angle of the welded beads to 20 degrees, was tested. The curves for this specimen were similar to those shown with the following differences: (a) The curve for stations 4 and 5 did not go so far into the compression side of the diagram.

(b) The curve above that for 4 and model B- (c) The curve for stations 4 and 5 recrossed the zero line at 740,000 instead of 800,000 pounds. It may therefore be assumed that the angle of the welds may be from 20 to 30 degrees withfor stations 3 and 6 crossed 5 much sooner than for the intensification of out endangering their effectiveness in stopping cracks at hatch corners.

Any bulging across corners on board ship would be prevented by the hatch coaming. This would mean an increase in the compressive load, but such an increase would not have any tendency to start a crack at the corners. Furthermore, the bulging action will not take place in the heavier plates used in full scale hatch structures.

In the foregoing tests, the tensile load was released at 750 kips for the unwelded specimen and 950 kips for the welded hatch B; and gage readings were taken to check the resulting recovery action. The curve of the recovery action indicates greater remaining elasticity in the metal at the corners of the welded plate than in the plain one.

In Figure 6 is shown a plate C having a rectangular opening 45 reinforced by an endless welded bead it in the form of an ellipse having its major axis 41 aligning with the central longitudinal axis of the rectangular opening 45. The weld applied was twice the plate thickness in width and one half plate thickness in height. The weld was spaced at plate thickness from the corners of the opening. The gain due to the weld was 8,900 p. s. i. over the net section. This test taken in conjunction with previous ones show that single welds of the size specified, laid alongside stress raisers, such as a right angle corner, add about 8,000 p. s. i. to the strength of the plate. This figure is obtained by scanning all revious tests of plates with single welds on one side only.

Various changes may be made in the forms of welded reinforcements herein shown and described without departing from the spirit of the invention or the scope of the ioilowing claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In a hatch structure for welded ships, a plate provided with a rectangular opening, said plate being normally subjected to tensile loading in the direction of one axis of said opening, whereby the stress in an area of said plate adjacent a corner of said rectangular opening is raised, means for placing the metal in said area under initial compression comprising a head of weld metal welded solely to said area along a line at an angle of between approximately 20 to 30 degrees to said axis and spaced from said corner a distance substantially equal to the thickness of said plate, said bead of weld metal being in longitudinal tension and continuously attached solely to said plate throughout its length.

2. In a hatch structure for welded ships, a plate provided with a rectangular opening, said plate being normally subjected to tensile loading in the direction of one axis of said opening, whereby the stress in an area of said plate adjacent a corner of said rectangular opening is raised, means for placing the metal in said area under initial compression comprising a plurality of beads of weld metal said plurality of beads being welded solely to said area along lines at an angle of between approximately 20 to 30 degrees to said axis and spaced from said corner a distance substantially equal to the thickness of said plate, each of said beads being in longitudinal tension and each continuously attached to said plate throughout its length.

3. In a hatch structure for welded ships, a

plate provided with an elongate rectangular hatch opening, said plate being normally subjected to tensile loading in the direction of the major axis of said opening, means for prestressing areas of said plate subjected to stress raises so as to increase the elastic limit of the metal in said areas, said means comprising an endless bead of Weld metal Welded solely to said plate, said bead being in tension and of substantially elliptical form with its major axis aligning with the major axis of said opening, said bead being spaced from the corners of said opening a distance substantially equal to the thickness of said plate.

4. In a structure of the character described, a plate provided with a stress raiser and being normally subjected to tensile loading whereby the stress in an area of said plate adjacent said stress raiser is increased, means for placing the metal in said area under initial compression comprising a linear bead of weld metal welded solely to said area and spaced from said stress raiser a distance substantially equal to the thickness of said plate, said bead of weld metal being continuously attached solely to said plate throughout the length of said head.

5. In a structure according to the preceding claim, the opposite end portions of said linear bead being ground oil smooth so as to taper in height toward the ends of the head.

6. In a hatch structure for Welded ships, a plate provided with a hatch opening, said plate being normally subjected to tensile loading whereby the stress in an area of said plate adjacent said opening is raised, means for placing the metal in said area under initial compression comprising a bead of weld metal welded solely to said area and spaced from said opening a distance substantially equal to the thickness of said plate, said bead being in longitudinal tension and continuously attached to said plate throughout the length of the bead, the width of said bead being approximately twice the plate thickness and the height of said bead being approximately half the plate thickness.

'7. In a hatch structure for welded ships, a plate provided with a hatch opening, said plate being normally subjected to tensile loading whereby the stress in an area of said plate adjacent said opening is raised, means for placing the metal in said area under initial compression comprising a head of weld metal welded solely to said area so as to be in longitudinal tens-ion and continuously attached to said plate throughout its length, a second bead of weld metal welded to said area in overlapping relation to the first bead so as to be in longitudinal tension and continuously attached throughout its length, and a plurality of additional beads of weld metal each welded to said area in overlapping relation to a previously attached head, said beads being of graduated lengths so as to avoid sudden termination of shrinkage strains in the area.

8. The method of reinforcing metal plate in an area adjacent a stress raiser which consists in welding electrode metal solely to said area along a margin thereof to form a linear bead that is continuously attached to said plate throughout the length of said bead, then welding additional electrode metal in said area along a side of said linear bead in overlapping relation thereto and beyond the ends thereof to form a second and longer linear bead that is continuously attached to said plate and said first bead, and then in like manner forming successive linear beads in said area each in overlapping relation to and of a greater length than a next previously formed bead and each continuously attached throughout its length.

9. The method of reinforcing a metal plate provided with a rectangular opening and normal- 1y subjected to tensile loading in the direction of one axis of said opening, whereby the stress in an area of said plate adjacent a corner of said rectangular opening is raised, which consists in welding electrode metal solely to said area along a line at an angle of between approximately 20 to 30 degrees to said axis and spaced from said corner a distance substantially equal to the thickness of said plate to form a linear bead that is continuously attached solely to said plate throughout its length.

10. The method of reinforcing a metal plate provided with a rectangular opening and normally subjected to tensile loading in the direction of one axis of said opening, whereby the stress in an area of said plate adjacent a corner of said rectangular opening is raised, which consists in welding electrode metal solely to said area along a margin thereof at an angle of between approximately 20 to 30 degress to said axis to form a linear bead that is continuously attached to said plate throughout its length, then welding additional electrode metal in said area along a side of said linear bead in overlapping relation thereto beyond the ends thereof to form a second and longer linear bead that is continuously attached to said plate and said first bead, and then in like manner forming successive linear beads in said area each in overlapping relation to a next previously formed bead and each continuously attached throughout its length.

11. The method of reinforcing a metal plate provided with a rectangular opening and normally subjected to tensile loading in the direction of one axis of said opening, whereby the stress in areas of said plate adjacent the corners of said rectangular opening is raised, which consists in welding electrode metal solely to said plate in said areas along lines at angles of between approximately 20 to 30 degrees to said axis and spaced from said corners a distance substantially equal to the thickness of said plate to form linear beads that are continuously attached solely to said plate throughout their lengths.

GEORGE L. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 793,958 Richardson July 4, 1905 2,191,469 Hopkins Feb. 27, 1940 2,333,112 Maris et a1. Nov. 2, 1943 2,386,724 Spaulding Oct. 9, 1945 FOREIGN PATENTS Number Country Date I 589,245 Germany 1933 OTHER REFERENCES Proceeding of The Merchant Marine Council, U. S. Coast Guard, June 1944, page 124, 114-79W.

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