The Iron Age 1942-10-08: Vol 150 Iss 15

—— § 4 : This Hoskins Electric Furnace being used for educational purposes the train- ing aeronautical engineers and licensed aircraft and engine mechanics, the SPARTAN School Aeronautics. The aircraft industry knows the advantages Hoskins electric furnaces for heat-treatment. These furnaces are made box and pot types, the latter for salt and lead. The box furnaces will handle around 750 steel per hour 1500° All Hoskins Furnaces have very durable Chromel heating elements. you need additional heat-treating furnaces, ask for Catalog 58. Hoskins Manufacturing Co., Detroit, Michigan. ELECTRIC TREATING FURNACES HEATING ELEMENT ALLOYS AND LEAD WIRE PYROMETERS WELDING WIRE HEAT RESISTANT CASTINGS ENAMELING THE IRON AGE, published every Thursday the CHILTON CO. (INC.). Entered second class matter November 1932, the Post Office Philadelphia under act March 1879. North America and South America, Foreign $15. Vol. 150, No. 15. Wee A = and ‘ ROMIUM fice OCTOBER 1942 VOL. 150, NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager ° ° ° Managing Editor, LIPPERT News Markets Editor, ROWAN Technical Editor, OLIVER Associate Editors Art Editor, WINTERS Editorial Assistants BENEDETTO Resident District Editors Washington Pittsburgh DONALD BROWNE PHAIR Washington Cleveland OSGOOD MURDOCK San Francisco Editorial Correspondents Buffalo Cincinnati FRAZAR RAYMOND KAY Boston Los Angeles HUGH SHARP JOHN McCUNE Milwaukee Birmingham SANDERSON ROY EDMONDS Toronto, Ontario St. Louis BACON Seattle ° ° ° DIX Manager Reader Service ° ° Advertising Staff Herman, Chilton Bldg., Philadelphia Hottenstein, 1012 Otis Bldg., Chicago Raymond Kay, 2420 Cheremoya Ave., Los Angeles, Cal. Leonard, 100 East 42nd New York Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 100 East 42nd New York Johnson, Market Research Mgr. Hayes, Production Manager. Baur, Typography and Layout. ° ° Member, Audit Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts Index. Pub- lished every Thursday. Price North America, South America and Possessions, $8: Foreign, year. Single copy, $1.00. Cable Address Y." ° ° Owned and Published CHILTON COMPANY (Incorporated) Executive Editorial and Offices Advertising Offices Chestnut and 5éth Sts. 100 East 42nd St. Philadelphia, Pa. New York, N. Y. U.S.A, U.S.A. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH, Vice-President GEORGE GRIFFITHS, Vice-President EVERIT TERHUNE, Vice-President VAN DEVENTER, Vice-President BAUR, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS KANE, HARRY DUFFY CHARLES HEALE This Week Editorial Technical Articles Effect Notching Strained Metals................ The Focke-Wulf 190A3 Welding Design, Specifications and Dry vs. Wet Grinding Carbide Heat Treatment Tool Steel Engineers Discuss Problems New Equipment: Motors and Controllers Features Assembly Line Washington West Coast Fatigue Cracks Dear Editor News and Markets This Industrial Week News Industry Personals and Obituaries Non-Ferrous Metals Machine Tool Activity Scrap Markets Iron and Steel Scrap Prices Comparison Prices Finished Steel Prices Warehouse Prices Index Advertisers Covyright, 1942. by Chilton Company (Inc.) be | ° 167 168 170 172 174 A > Answering and handling customer problems Ryerson. Steel Short- But Ryerson Often Solves the Problem America’s vast production effort, there some man every company who re- sponsible for getting steel—a man who must get things done. some plants he’s called ing agent, expeditor, plant manager, must get results. Ryerson Steel Service built order for his needs! When steel problems become stone wall, Ryerson usually can come thru with some practical solution. suitable alter- nate for steel that’s vitally needed, but isn’t stock; suggestion for heat-treating, ma- chining, welding, some other way adapt the steel hand; rush handling and delivery that will lay the steel down where it’s needed, when it’s needed! It’s nothing new Ryerson cutting corners help customers solve steel prob- lems with speed. Ryerson has been doing that for century—and the experience, the skill and the knowledge steel and its uses, built over that hundred years superlative service, are standing Ryerson and Ryerson customers —in good stead under today’s emergency conditions. While this all the day’s work for Ryerson Steel-Service men—you must keep mind that are entirely out many kinds and sizes that all must sold strict accordance with the WPB program. This help getting things done avail- able your organization. Ryerson Steel- Service men are easy reach; give you prompt consideration. Joseph Ryerson Son, Inc., Chicago, Milwaukee, St. Louis, Cincinnati, Detroit, Cleveland, Philadelphia, Boston, Jersey City. Keep the Open Hearths Burning production: Immediate, from clippings and cuttings made right the steel mill; short term, produced our metalworking plants, and long term resulting from obsolescence. Now, course, with our large ship- ments semi-finished and finished steel our Allies, lose tre- mendous amount potential scrap. Both short term, from borings and turnings, and long term, which these times take long produced. What this should mean those men Washington whose primary AGE function expedite the flow scrap that they have find hitherto halcyon days, there were three kinds scrap available for steel unreached scrap supplies. It’s just the old game hide and seek. And win, you hug the base, nor the basing point. The utilization non-productive, obsolete equipment ought good part the answer the scrap shortage. fact, one our greatest untapped sources. But that equipment happens old broken-down tractor farm North Dakota, according our present basing point system, the scrap fault, and penalized the tune about two dollars ton when shipping the basing point. Now, this two dollars ton extra something scrap consumers would willing pay. means the difference between getting re- OCTOBER 1942 mote, but essential, scrap facing lowered operations this winter. This problem must licked soon. has our fall offensive before the setting-in paralyzing winter, far scrap collecting and ESTABLISHED 1855 processing concerned. The easy way oil the troubled scrap waters would switch basing point basis. That won't make the earth move, but would certainly make the scrap flow. Such things are not without precedent. This aspirin has been administered foundries, and their cupola cast headache has disappeared. When Washington, for some obscure reason, wanted get silver moving into this country, offered more for that metal than any other buyer. The Metals Reserve Corp. has occasion paid much $200 ton for some scrap. would certainly silly pay $200 ton for scrap one hand, and the other refuse try practical solution the scrap problem. But satisfy those persons who set down principles and then find painful change them, this plan could done experiment. works, and sure will, then will that much more steel. Present standpattism has cost the nation two four million tons steel this year. That ought incentive, indictment, enough institute change pricing policies. With furnaces every steel producing area facing seriously dwindling scrap supply, cannot afford coddle do-nothing attitude the part Washington officials. And the solution simple switching system, should done without delay. 4 we 4 | | | ; 0) N By | Some QUESTIONS ABOUT SCRAP Why scrap used make steel? conserves natural ore resources, lightens the burden upon the nation’s transportation sys- tem, and requires less time convert into molten metal because scrap used steel mills has previously been refined into steel. How scrap used make steel? charged into open hearth furnaces with pig iron and small quantities special ores and limestone. Does scrap make good steel? Yes, the finest steel made from scrap. Electric furnaces, which produce the highest grades steel including some alloy steels, operate al- most entirely upon scrap. What kind scrap needed the mills? Any iron and steel scrap usable, except tin- coated non-ferrous metals which cannot used make steel. How much scrap steel mills require year? 1941 the total was 45,600,000 tons. this amount about half was steel mill scrap and the remainder came from outside sources. What are the causes the scrap shortage? Over 20,000,000 tons scrap were shipped out this country during the 30’s, and never be- fore the history the steel has there been such prolonged period high steel production. All existing accumulations scrap have been taken and now the remote farm, industrial, and household scrap that must sent steel mills. Why not use ore replace scrap? Ore mining operations, transportation facil- ities, ore storage space mills, and blast furnace capacity are based the use scrap and cannot expanded immediately. Are steel mills doing anything help the scrap situation? Yes. They are spending millions dollars publicize the seriousness the scrap shortage. They are building new blast furnaces and ore handling facilities. Inland building one new 1200-ton blast furnace its own plant and two more for the Government. Are the scrap dealers doing their part? Scrap dealers did marvelous job during 1941. the first six months 1942, more scrap was moved the dealers than ever before history. The need now for the general public and general business move their scrap scrap yards, where can properly prepared and rapidly moved consuming centers. Why have mills not accumulated scrap? When war came, mills had normal scrap sup- plies. But, tremendous demand for steel and small scrap offerings quickly lowered mill scrap stocks. How much scrap mills have hand? The supply averages less than two weeks. Many mills are operating less than two days’ supply, which virtually the basis daily receipts. What would happen more scrap reached mills? Within few days steel output would drop least calamity view the desperate need for steel carry the war effort. Why should scrap gathered now use next winter? Cold weather, snow and blizzards reduce collec- tion, preparation and transportation scrap. Mills normally store extra scrap for use winter. This year—a critical can- not accumulate scrap for the winter months because not available them. How can the scrap shortage solved? the segregation and return mills all production scrap; executive authority scrap old buildings, unneeded equipment, obso- lete machinery, dormant and excessive stores, unused dies, tools, fixtures, etc. How can you help? you are executive, use your initiative and authority designate what can scrapped. you are engineer, metallurgist, super- intendent, foreman, storekeeper, master-me- chanic, millwright, workman, call the attention your management anything and everything that you believe can spared and sent the mills scrap. Steel mills must have more scrap that our fighting men will 30—THE IRON AGE, October 1942 have the equipment they deserve and need! | SACHS and LUBAHN Department ing, Case School Applied Science, Cleveland RITTLE failures structural members are frequently as- cribed the presence “notch” the stressed part. This notch may take the form groove, thread, hole, sudden section metal. considerable amount research has therefore been carried out the effect notches the behavior steels and other ma- terials subjected static tension. However, appears that the interpretation the experimental results which are present avail- able rather inconclusive and open argument. Also, the ex- perimental relations quently improperly described and are subject theoretically as- sumed conclusions, the validity which cannot proved dis- proved within the limits error. Notched bars subjected elastic stressed and strained the vicinity the notch than other parts. This stress concentration should re- sult decrease strength. However, such loss strength due notching has definitely been established only the case the endurance limit but smaller for the more ductile metals. the contrary, has been ob- served early stage the scientific testing metals (Kirk- aldy, 1892) that section adjacent larger sec- tions. This has been attributed the restriction the lateral, transverse, flow the sudden section change, notch. The Effects Notching Strained Metals abstract intended clarify the experi- mental evidence notches they affect the behavior metals static tension. The authors show that results date present inconclusive evidence which often im- properly described and related. interest this notch effect ten- sile test bars has been particularly strong since 1923 when Ludwik and published few experi- ments soft steel tensile test bars provided with notches various types, Fig. Their measurements the stresses and strains during testing resulted stress-strain curves the conventional type, Fig. and also diagrams show- ing the average actual stress, so- true stress, the notched section function the average local strain, “effective strain” (in logarithmic scale), Fig. The conclusion was drawn from these tests that increasing sharpness notching, produced these experi- ments reducing the length the notched section and the angle the notch, causes the following changes the properties the metal: (a) The average ultimate strength and yield strength ductile metal are least per cent greater for very sharp notch, than the respec- specimen. (b) There corre- sponding decrease the ductility, measured the local contraction These changes were correlated with the presence transverse stresses, the magnitude which increases with the sharpness the notch. The transverse stresses restrain the deformation; and the limit- ing condition equal magnitude all three directions, frequently referred triaxial (or hydro- static) tension, any metal should behave brittle manner. Kuntze's Experiments Extensive notched tensile test bars various metals and alloys have been carried fected the experimental technique this Kuntze attempted show that any metal approaches the state hydrostatic tension the notched section the notch sufficiently sharp and deep. Evaluating Ludwik and Scheu’s experiments, according Fig. Kuntze first plotted the various stress values derived from the test, the average ultimate strength* notch strength (Fig. 2), the the maximum load divided the area the notched section. THE IRON AGE, October ° ° ° ° @ & 40 (a) LEFT notched steel ten- (c) (e) Saw cut “actual” stress maximum load, and the actual fracture stress (Fig. 3), against the contraction area, ductility, Fig. 4a. The conclu- sion drawn that all three curves value, the cohesive strength, for ductility zero. Although such extrapolation would appear logical, the data points Fig. not justify it. From the data represented here, seems more likely that the actual maximum load stress curve parallel the notch strength curve rather than shown Fig. 4a, and that inter- sects the fracture stress curve ductility about per cent. The stress-strain curves Fig. clearly relation. which also agrees with the gen- sile test bars inves- tigated Ludwik. RIGHT IG. 2—Conven- strain curves pro- duced the bars shown Fig. Conventional stress,thousand per erally known conditions namely that the fracture stress becomes equal the maxi- mum load stress finite duc- tility. Fig. the notch strength values are plotted against the area removed the notch, notch depth, and extrapolated limit- ing notch strength for depth 100 per cent, using and confirmed Kuntze. However, according own experiments, Figs. such linear extrapolation only valid for very ductile metals and alloys. The effect notch angle this limiting notch strength, Fig. 4c, indicates, according Kuntze, that the limiting notch strength also 140 1G. 3—This chart shows the actual stress-effective strain curves the bars investigated Lud- 100 150 200 250 Effective strain, per cent 32—THE IRON AGE, October 1942 Elongation, per cent reaches the cohesive strength the notch angle becomes equal zero. This conclusion the basis Kuntze’s further work, but at- tempts have been made offer more decisive evidence than that presented Fig. 4c. Regarding the experimental tech- nique, Kuntze chose 60-deg. notches various depths. According Fig. 4c, test bars provided with 60- deg. notches will give limiting notch strength approximately per cent (or perhaps higher) that bars with infinitely sharp deg.) notch. Regarding this relation, not quite clear why, later publications, linear increase limiting notch strength with de- creasing notch angle has been as- leading much higher cohesive strength values than that found from the relations just dis- cussed, Fig. 4c. appears that few quite intricate measurements the elastic strains notched bars" have induced Kuntze intro- duce this questionable linear rela- tion (Fig. 15). The radius the bottom the notch Ludwik’s experiments was 0.008 in. and Kuntze’s approxi- mately 0.005 in. The effect the radius has not yet been investi- gated detail. However, observed that the ductility notched bar decreases with increas- ing diameter. This has been attrib- ing sharpness the notch, de- creasing ratio bottom radius diameter. the other hand, ap- pears that the relative bottom radi- affects the ultimate strength (b) | f ° ° ° evaluation notched tensile tests. Stress, thousand per sq.in. only the ductility very low. investigations have frequently sharp notches. The experiments Kuntze are for the most part, limited the determination the notch strength bars having deg. notch varying depth, Figs. and most cases, the notch strength in- creases linearly with the area re- moved the notch, previously mentioned. Observations the behavior vari- ous metals and alloys, the following general observations were made Kuntze: (a) Most wrought metals and alloys the commercial con- dition, including normalized steels, exhibit the linear relation between notch strength and area removed notch strength (60 deg. notch) usually between 1.7 and 2.2 times the ultimate strength the un- notched bar. This “limiting notch strength ratio,” therefore, appears close for the ductile met- als and alloys. (b) number metals and al- loys with restricted ductility, such Cohesive strength cent steels, duralumin, and brass also followed the linear relation, but this limiting notch strength ratio was small 1.2. few tests duralumin and mag- nesium alloys also yielded notch strength values only slightly higher than the ultimate strength. (c) Cast iron and cast steel, Fig. possess notch strength, the contrary, which differs only slightly from the ultimate strength and shows flat minimum inter- mediate notch depth. (d) Some heat-treated steels having ultimate strength be- tween 100,000 and 140,000 per sq. in. were also found exhibit notch strength which decreased first with increasing notch depth and then increased values consid- erably above the ultimate strength, Fig. (e) metals again showed the linear relation, but usu- ally had higher limiting notch strength ratio than annealed met- als. Very high ratios, were notch strength Actual load stress Fracture stress Limiting notch strength Area removed notch, per cent Notch angle, deg. found for stretched Davidenkov and con- firmed this effect but also detected that compression duced the ratio. Thus, this ratio directional property and prob- ably related the Bauschinger ef- fect, i.e., increase yield strength the direction but de- crease yield strength the re- verse direction. The notch strength ductile steel does not depend upon the sec- tion size, according Nadai and the specimens are geometrically similar. Tests were made bars having various diam- eters ranging from in. and provided with and semi-circular tional the diameter. Contradic- tory results were obtained which yielded decreasing notch strength and notch ductility values with increasing section size. These results must explained, however, least partly effect in- Quenched Soft IGS. and 6—These charts show the ef- the ultimate strength notches. (After Kuntze.) vo ip | Area removed notch, per cent Area removed notch, per cent THE IRON AGE, October 1942—33 x > ) 2 | 4 | Cast crucible Cast 054% 10% Mn- 1G. 7—The strength and ductility vari- ous steels are affected shown here 60- deg. notches diameter rod. (After +4 Strengt Area removed notch, per cent creasing sharpness the notch, the notches had constant radius the bottom. Temperature Effect the effect heat treatment steel, has been men- tioned already that strength ratio might reduced increasing extent heat-treat- ing successively higher strength levels. Also notch notch depth curves with mini- mum, Fig. might occur. Regard- ing the effect testing tempera- ture, some experiments Floess- SAE 1060 steel having ultimate strength more than 120,000 per sq. in. show that the notch strength, temperatures above room temperature, remains certain fraction higher than the ultimate strength, while gradu- ally decreases values consider- ably below the ultimate strength the temperature reduced below j 0.53% Mn, 0.23 Contraction area, per cent room temperature, Fig. few experiments the effect over- heating, shown the table, have been carried out Davidenkov and Wittmann™. The ultimate strength 0.25 per cent carbon steel was found the same the normal- ized (1750 deg. F.), fine grained condition and the overheated (2000 deg. F.), coarse grained con- dition. The notch strength room temperature (60 deg.—84 per cent notch) also failed reveal differ- ences between the two conditions. However, the notch strength the temperature liquid air was much lower and scattered considerably more for the coarse-grained steel than for the fine-grained steel. Both these notch strength values ap- pear lower than the ultimate strength the steels the tem- perature liquid air (estimated 120,000 lb. per sq. in.) Tests re- ported also show difference the notch strengths ‘Notch strength 150 200 1G. 8—Experiments Floessner show the effect temperature notch strength. The specimens were SAE 1060 steel bars 0.72 in. diameter. RIGHT 9—According Gensamer, the notch strength SAE 1080 Strengt 100 200 Testing temperature, deg.F 34—THE IRON AGE, October 1942 steel heat treated ultimate strength 180,000 Ib. per sq. in. depends, large de- gree, upon the condi- tions tempering. 300 400 Rockwell 48.5. — + Area removed notch, per cent overheated SAE 4140 steel, both steels having ultimate strength approximately 180,000 Ib. per sq. in. (Rockwell hardness 39.5). The notch strength SAE 1080 strength 180,000 per sq. however, depends large degree, according Gensamer, upon the conditions tempering, Fig. Tempering for short time high temperatures produces higher notch strength than temper- ing for long time low tem- perature. Some notched bar tensile tests Gensamer, Pearsall, and SAE 1080 steel aus- tempered various temperatures showed the rather unexpected re- sult, Fig. 10, that the notch strength was quite high for steel having ultimate strength over 200,000 per sq. in. but was al- most low ultimate strength for steel ulti- Ww per a] Notch strength,thousand Oo Tempering tans se at 0 O h a 04" mate strength below 125,000 per sq. in. Additional Bending Rather peculiar results have been tests notched bars which were subjected additional bending strain. Bending various amounts was produced placing shims with various tapers underneath the head the test bar, Fig. 11. The notch strength heat-treated alloy steels having ultimate strength 120,000 lb. per sq. in. was found affected such additional bending strain only the over- heated state (having low impact energy) and even then only slight extent. However, with in- creasing strength and decreasing impact energy the notch strength ratio might reduced from ap- proximately 1.25 (60-deg. notch, per cent area removed) values low 0.3 for sufficiently large bending strains. The authors” claim that the various 0.30 per cent car- bon alloy steels which were investi- gated differ little their behavior these experiments. Their results, Fig. 11, however, indicate that the nickel-chrome-molybdenum steel somewhat superior the chrome- molybdenum vanadium steel, which turn slightly less affected bending than nickel-chrome steel (0.33 per cent C., 0.57 per cent Mn., 3.43 per cent Ni., 0.93 per cent Cr.). These results are difficult ex- plain, and attempt made analyze the stress and 300 ° c 250 = mate strength and the notch strength SAE 1080 steel are affected this manner austem- pering various temperatures. Gensamer, Pearsall ° strain states these tests. The di- rect results, however, are rather significant, namely, that steel having high strength level might fail lower (intentional) ten- sion than steel lower strength level (unintentional) bending also present, and that the magni- tude the impact strength has spect. These results concerning the ef- fect additional bending the notch strength high strength steels also might explain the brittle breaks, which have not been inves- tigated yet, the threaded ends tensile test bars. Test bars tool steel, for instance, should provided with cylindrical section 400 600 100 Austempering temperature, having only per cent the cross-sectional area the section the threaded ends, order avoid premature breaks outside the gage length (see “A.S.M. Hand- book,” 1940 ed., 666). This can taken indication that thread-breaks might occur ten- sile stresses low per cent the ultimate strength, ap- proximately 75,000 lb. per sq. in. The strength cylindrical ten- sile test bars provided with trans- verse hole was found Matthaes” slightly above the ultimate strength for medium carbon steel and for aluminum but approximate- per cent lower than the ulti- mate strength for duralumin and for magnesium alloys. The contrac- 150 four charts show effects super- quenching tempera- strength ture and strength steels. Speci- 0.040-in. deep. The cross-section view the specimen holders shows the method subject- ing the bars ad- ditional bending strain. Cr-Mo-V Kiessler and Stee/ Taper angle shims, deg. THE IRON AGE, October 1942—35 | oO O strength Oo 100 ® A 4 4 A, SL / tion area the steel was greatly reduced the transverse hole. Apparently tests have been carried out thin flat vided with notches their narrow surfaces. Such tests should par- ticularly informative regarding the theory the notch effects, they approach the two dimensional, biaxial condition. This condition characterized the absence ten- sion the direction perpendicular the wide surfaces the test bars, and consequently crease strength expected notching the narrow surfaces. This verified tests performed investigated and fur- ther discussed The stress which required produce plastic extension 0.002 pe. cent decreases first with increasing notch depth but again, Fig. 12. For larger strains, however, the curve yield strength vs. notch depth becomes more near- straight, and for plastic strain 0.6 per cent the linear relation previously discussed for the notch strength also applies the yield strength. Thus appears that the stress concentration in- troduced the notch decreased small plastic flow insig- | | Fracture 12—The prop- erties 0.2 per cent per cent manganese stre steel are variously affected changes notch depth. (After Kuntze and 100 Area removed notch, per cent flat bars provided with one more holes. These tests yielded average strengths the sections through the holes varying from 106 per cent the ulti- mate strength, depending upon the metal and the dimensions the test bars. The effect notch torsion tests appears much the same nature that tensile tests, according Specimens provided with com- pound notches also be- have practically the same man- ner specimens provided with single notch which equally sharp and The effect notch depth the yield strength values for various amounts plastic strain has been 36—THE IRON AGE, October 1942 nificant factor, judging its effect the strength (or average flow stress required strain the notched section). Also, according the trend the yield strength vs. notch depth curves, the stress concentration should largest for notches intermediate depth. This latter conclusion also ex- plains the effect sharp notches the bending strength ductile metals. observed that the average bending strength notched section smaller for any notch depth than that the un- notched bar, Fig. 13, and the curve shows minimum for compara- tively small notches. Thus, the case the bending ductile metal, the large deformations oc- curring before fracture apparently not completely eliminate the ef- fects the stress concentration induced the notch. Such stress concentrations which are retained after plastic flow has occurred must also made respon- sible for the peculiar effect the notch depth the ductility (con- traction area) observed and further discussed The few observations this respect show that for sharp notches the curve ductility vs. notch depth decreases rapidly first, but with further increasing notch depth, rises slightly again, Figs. and 14. the contrary, gradual decrease ductility with increasing notch depth would have been expected because the cor- responding increase transverse stress, the stress concentration was actually negligible. However, the experiments indicate first all that the stress concentration still exerts considerable influence the break, and second, that this ef- fect maximum intermediate notch depths (30 per cent). The stress failure “fracture stress,” apparently re- duced also first and then some- what raised increasingly deeper notches, Fig. 12. This relation directly correlated with the corre- sponding effects the notch the flow stress and the ductility, al- discussing this effect, points out that the fracture stress deeply notched specimens, according Kuntze, higher than that un- notched specimens. concludes from this that the fracture stress, stress concentration were not present, should increase with in- creasing notch depth, with in- creasing transverse stress. How- ever, this conclusion disregards the complex stress state the instant failure notched specimens. The two principal factors which should sufficient explain the behavior the notched section tensile test bar are thus: The presence average transverse stress; and the local concentration longitudinal stress the vicin- ity the notch bottom. attempt has been made determine the ratio be- tween transverse and longitudinal stress from the transverse strain the notched section measured very low loads means sensitive transverse extensometer, Fig. 15. unnotched, soft steel | 1204 | 100 LEFT 13—Curve show notch depth thc Aluminum alloy RIGHT Notch depth Ratio “Thickness bar contracts approximately fol- lows, per unit stress: 0.264 30,000,000 Poisson’s ratio.) the other hand, deeply notched bar expands the notched section. This expansion for 60- deg. notched bar extrapolates for 100 per cent notch value per unit stress approximately, Fig. 15: 6 x 10-9 = 180,000,000 From this relation, the wrong conclusion was drawn Kuntze that the transverse stress becomes equal the longitudinal stress. Later, adding few experi- ments, corrected this con- clusion the statement that such total triaxiality would attained bar provided with 0-deg., 100 per cent notch, while 60-deg., 100 per cent notch would yield trans- verse stress per cent the longitudinal. The transverse stress resulting from the experiments rep- follows: For given longitudinal stress (s) and transverse stress two directions), the expansion (e,) the transverse direction is, ac- cording the laws elasticity: ms; [se (1 — m) — ms}, 30,000,000 Ib. per sq. in. for steel; and Poisson’s constant 0.264. effect notch and notch angle the ductility rolled and an- nealed For 60-deg. notch, the unknown transverse stress given the equation: = - = 30,000,000 180,000,000 0.264) 0.264 0.264 0.227 0.359 0.586 Therefore, the transverse stress 60-deg., 100 per cent notched bar would be, according these tests, approximately per cent the longitudinal. This method ap- plies only very small, purely elas- tic loads. Thus, according the elastic measurements, represented Fig. 15, average transverse stress per cent the average longitudinal stress would pres- ent 60-deg. notched section under elastic strain. The transverse stress present when there are much larger, plas- tic strains, can estimated from the observation that the limiting ROOM TEMPERATURE Condition Steel Ultimate Strength, Lb. Per In. Fine-grained Coarse-grained 49,000 Effect Temperature Notch Strength Area removed notch, per cent notch strength (s,) approximate- twice the ultimate strength (s,) the unnotched specimen for 60-deg. Using the condition that the shear stress, the differ- ence between the principal stresses, should constant during the plas- tic flow specific metal’ and the point maximum load should equal the ultimate strength, the following relation results: where s,, the transverse stress the point maximum load for the limiting condition (100 per cent notch). Therefore, this point the average transverse stress amounts approximately per cent the longitudinal stress. These values, and per cent respectively, in- dicate triaxiality for 60-deg. notch considerably below total tri- axiality “hydrostatic tension” where the transverse stress would the same magnitude the longitudinal. This would indicate LIQUID AIR TEMPERATURE 300 deg. Notch Strength, Notch Strength, Lb. Per Sq. In. Lb. Per Sq. In. 75,000 81,000 88,000 133,000 (78,000 average) (108,000 average) 75,000 78,000 53,000 103,000 (76,000 average) average THE IRON AGE, October 1942—37 | | a Stn l q a ig that for 60-deg. notch condition hydrostatic tension would not exist, and consequently ductile met- als would not fail brittle man- ner. This supposition confirmed the fact that the ductility vs. notch depth curves, determined far, not approach zero ductility for 100 per cent notch, but the ductility apparently again increases for very deep notches after having passed through minimum. (Figs. and 14.) Editor’s Note: Next week the authors conclude this two-part data stress distribution notched tensile specimens and discussion some fundamental conceptions hesive strength. Bibliography Sachs; “Stress THE IRON AGE, vol. 146 (1940), Aug. pp. 31-34; Aug. pp. 34-37. Ludwik and Scheu, “Effect Notches Soft Iron,” Eisen, vol. (1923), pp. 999-1001. Ludwik, “Yield Point, Cold and Hot Shortness,” Zeit. D., Ing., vol. (1926), pp. 379-386. Kuntze, “Cohesive Strength,” Berlin, 1932. Notched Tensile Test Archiv. vol. (1928-29), pp. 109-117. Kuntze, “Impact Strength and Conventional ties,” Archiv. Eisenhuettenwesen, vol. (1928-29), pp. 583-590. Kuntze, “The Strength Threads,” Zeit. Ing., vol. (1929), pp. 469-471. Kuntze, “The Practical Proce- dure for Notched Bar Tensile Metallwirtschaft, vol. (1932), pp. 179-184. Kuntze, “The Procedure De- termining Cohesive vol. (1932), pp. 343-347. $q.in 109 Inverse modulus elasticity Area removed cent notched sections steel bars af- fected this manner variations notch depth. Notches are follows: 135 deg.; deg.; deg.; cor- rected. (After Kuntze.) ° ° Kuntze, “The Problems Cohe- sion,” Zeit. Metallkunde, vol. (1930), pp. 264-268. Kuntze, Strain and Triaxial Stress States Notched Specimens,” Zeit. Physik, vol. (1931), pp. 785-792. Kuntze, “Ductility and Strength Notched Specimens,” Zeit. Physik, vol. pp. 45-65. Kuntze, “The Safety Against Rupture Welded Constructions,” Wiss. Abb. Materialpruefungsan- stalten, No. (1939), pp. 11-18. (1901), pp. 805-812. (1902), pp. 374-380. McAdam, “The Technical Co- hesive Strength Metals,” Journal Applied Mechanics, vol. (1941), pp. 155-165. McAdam, “The Technical Co- hesive Strength and Yield Strength Metals Technology (1942), Jan., Tech. Publ. No. 1414. Matthaes, “Notch Effects under Static Stress,” Luftfahrtforschung, vol. pp. 28-40; Metal Treatment, vol. (1938), Spring Is- sue, pp. 15-23. andin, “The Cohesive Strength Previously Stretched and Com- pressed Tensile Test Zeit. Metallkunde, vol. (1930), pp. 264-268. Nadai and McGregor, “Concerning the Effect Notches and Laws Similitude Material Testing,” Proceedings, vol. 34, (1934), pp. 216-228. Floessner, “The Mechanical Prop- erties Notched Bars,” Dr. Thesis, Dresden, 1927. Davidenkov and Wittmann, “Mechanical Analysis Impact Techn. Physics USSR, vol. (1937), No. pp. 1-17. “Static Crack Strength Metals, Its Determination and Metal Progress, vol. (1940), pp. 58-64. Smith, “The Mechanical Prop- erties the Isothermal Decomposi- tion Products Austenite,” Trans- actions, A.S.M., vol. (1940), pp. 380-398. Pellini and Low, “The Tensile Properties Pearlite, Bain- ite, and Spheroidite,” A.S.M., Convention 1941, Preprint No. 19. Kiessler and Connert, Bar Tensile Tests with posed Bending Strain,” Arch. huettenwesen, vol. (1940-41), pp. 555-560. Matthaes, “The Notched Bar Im- pact Test and Its Accompany Phenomena,” Dr. Thesis, Dresden, 1927. Sachs, “Stress THE IRON AGE, vol. 146 (1940), Aug. pp. 31-34; Aug. pp. 34-37. Machine Lettering Speeds ITHIN the year, method lettering engineer- ing drawings, bills material and specifications has been developed the Ralph Coxhead Vari-Typer Corp., New York. The method, which employs special Vari-Typer built handle large sheet sizes and number type faces, credited with shortening the finishing time drawings about 500 per cent. number instances cited users indicate that drawings which 38—THE IRON AGE, October 1942 normally require five days for hand lettering can lettered easily the machine one day. The machine, basically stand- ard office composing machine, equipped with instantly changeable types and spaces, operates like typewriter but can take sheet ft. long. super-carriage with ex- tending bars each end makes this large sheet handling capacity pos- sible. The carriage movable that the operator can work any part the drawing and ingeni- ously devised feed roll lever permits the extension the tracing roll be- yond the carriage ‘the machine. Interchangeable cylindrical type fonts permit use variety sizes and styles alphabets. adjustable spacing arrangement provided allow for the different widths type required the vari- ous alphabets. | | 1 ' | | | 20 + + - - 5 | | | | I | The Focke-Wulf 190A3 superiority which surrounded the Messerschmitt 109 the early days the war has grown around the new German Focke-Wulf 190 fighter during the past few months. Its record combat since first appeared September, 1941, has proved its quality. But now last the En- glish are position judge its true merits real foundation fact, according Aeroplane. It’s good—it’s even very good. But there’s nothing mystical about and it’s far from unbeatable. there was any German air- plane the English could have chosen have captured intact for inspec- tion and flying trials would have been the 190. dentially, one was forced land intact England some time ago. Immediately, the English were able examine closely and watch The conclusions are these. This Focke-Wulf 190A remark- ably compact and efficient fighter, heavily armed, well armored and fighter—it cannot fly high the 109F—and, because its high landing speed not particu- larly easy machine fly. shows room for further development, but there fighting feature about which cannot done better. things stand present the Focke- very formidable fighter between about 16,000 ft. and 24,000 ft.—as good anything else the world present. Above and below those heights, less dangerous. Technically, the most interesting feature the design the use air-cooled engine, magnificently cowled and efficiently cooled. Aero- dynamically, the machine poor; structurally excellent; electri- cally first class; produc- tion job should easy, re- sult much painstaking care and thought; from flying viewpoint delightful the controls, but its finish bad, its range limited, the engine rough and its boost low. detail, the top normal boost 375 miles per hr. 18,000 ft. emergency the throttle can put “through the gate,” and with override boost and high r.p.m. the absolute maximum for one minute 390 miles per hr. 20,- 000 ft. The speed falls off rapidly above and below this height—at 4500 ft. the top speed 326 miles per hr. The machine has brought 125 miles per hr. and touches down 110 miles per hr. The undercarriage well forward that severe braking possible. Armament Armament four cannon and two machine-guns. The two 7.92 mm. (0.314-in.) Rheinmetall-Bor- sig machine-guns are mounted top the fuselage front the pilot. They fire through the pro- peller rate 600 rounds per min. each and have 1000 rounds ammunition each. The combined weight their fire only per min.—equal only one the English wing-mounted Brownings. Two mm. (0.7874-in.) Mauser cannon are mounted the wing roots and fire through the propeller. This the first time cannon have been used with interrupter gear. These Mauser cannon are very fine weapons with high rate fire and high muzzle velocity. Without interrupter gear they fire the rate 950 rounds per min. With allowance for the very wide blades the three-blade propeller their rate fire the 190 prob- ably not more than 700 rounds per min.—despite other quotations higher figures. But 700 rounds per min. quite useful and gives combined rate fire 350 per min.—10 times that the machine guns. Each Mauser has 200 rounds ammunition—enough for sec. firing. The two outer cannon mounted the wings outboard the propeller are, comparison, poor weapons. They are mm. Oérlikons with rate fire, uninterrupted, only 450 rounds per min. Their muzzle velocity low. Each gun has 60- round drum which appears filled with rounds, normally, giv- ing duration fire sec. The weight fire from the two Oérlikons 225 lb. per min. Thus the total weight fire about 610 per min.—which THE IRON AGE, October 1942—39 | 7 * 3 a § a 5 very great indeed. made less effective the short range the machine guns and the poor hitting power the Oérlikons and thus does not compare favorably with the English four-cannon machines appears first. Layout small, compact airplane and shows everywhere much evidence care- ful thought and excellent team work between the designers the air- frame, engine accessories. Every service worked electrically except the wheel brakes and the constant-speed gear the VDM propeller, which are hydraulic. The 24-volt electrical system good and works well. The Germans are past masters this sort detail. Aerodynamically, the 190 low-wing monoplane with equal taper leading and trailing edges and square-cut wing tips. The single fin and rudder unbraced, the cantilever tailplane adjust- able, the wide track undercarriage retracts inwards and the tailwheel backwards. The BMW 14- cylinder two-row air cooled radial motor projects very little front the wing. Its close fitting long cooling, but not controllable for air entry exit any way. Main- tenance obviously easy except for the 10-hr. inspection the engine; the back most inaccessible only few accessories have been grouped there. For any major work the engine can removed from the five-point suspension. Curiously enough, the aerody- namic design seems poor. The aero- foil section bad with very blunt entry and maximum thickness rela- tively far forward. certainly nothing like the American low-drag sections. The finish, too, bad and the joints where the doors fit over the gun trays are poor. Com- pared with standard British finish production machines the finish most inferior. The 190 very widely subcontracted. Detail design seems good. The wing built one main and one auxiliary spar and one piece. This makes repair difficult, but saves something like 300 weight. The same true the fuselage which also one piece. trimming tabs are provided anywhere—only small, perforated plates ailerons, elevators and rudder, adjustable the ground. Change trim looked after the adjustable tailplane which 40—THE IRON AGE, October 1942 cause this difficulty trimming the undercarriage must not lowered any speed less than 120 miles per hr. The split flaps are selected for position press but- tons the cockpit. From take-off they are drooped deg.; deg. droop used for landing. The cockpit small, but the lay- out excellent. The controls are re- markably frictionless and this has been achieved without recourse balances any sort. interest- ing feature that the last couple inches travel the pulling back the stick land locks the tail- wheel centrally. Strangely enough, the view from the cockpit good, except for taxiing. The cockpit cover slides backwards complete with all the fairmg, but cannot opened the air even when the motor being run up. Cockpit ventilation good; there are draughts and fumes. bale out, the whole hood can jetti- soned pressing button, when cartridge fires and breaks the sup- porting tube, allowing the hood blow clear. The cockpit well appointed and has very complete instrument equipment. The instruments have conveniently small dials which good feature. The armor has been carefully fitted. panel mm. (0.55 in.) thick placed the sliding cover behind the pilot’s head. head mm. (0.35 in.) thick be- hind his seat. The windshield— which sloped acute angle— has bullet-proof glass in. thick. The reflector gun sight inside the windshield small, neat and ap- parently efficient. The nosering the cowling armored with 5-mm. plate and the second portion the cowling covered with 3-mm. armor. result this well disposed armor the 190 must very difficult destroy machine gun fire, although naturally vulner- able cannon. fuel carried the wing. There are two tanks all with total capacity 115 tank gal. under the pilot’s seat and tank gal. behind that. Both are self-sealing the normal way. Naturally, the engine the heart the machine. The BMW remarkably compact proportions. Exact performance details have not yet been ascertained, but the nor- mal maximum appears about 1600 h.p. only 4.5 lb. boost— which remarkably small. The ab- solute maximum—according Ger- man sources—with the override boost operation—is about 1760 h.p. and that gives the maximum speed 390 miles per hr. 20,000 ft. Unlike the BMW the 190 has controllable entry exit. The oil cooler the nose the cowling with fixed area, re- verse flow, through it. The main cooling air exhausted through louvres the side the cowling. Six exhaust manifolds eject under the cowling and there are four ad- ditional manifolds each side. The very wide blades the VDM airscrew are small diameter and this fact must seriously handicap the performance height. Bigger diameters are restricted the length the undercarriage which has track about ft. and already stalky. electrically re- tracted inwards and, goes up, doors, partly closing the wells, open admit the wheels and then close round them, completely sealing the undercarriage. one the best undercarriages any known plane, the only better being that the North American Mustang. The tailwheel retracted ingeniously simple cable which pulled the motion the main while retracting. Provision made for bomb slung under the fuse- lage just behind the undercarriage. electrically released. From flying point view the 190A3 handles well. The aile- rons particular are finger light and remain down the stall. virtue the fighting speed and its diving speed out fight very high. How- ever, the high wing loading makes necessary wide radius turn and British fighters can turn inside it. built win air superiority. was probably designed dog-fighter rather than bomber-destroyer and the fact that the enemy are using 109F the West tends confirm this view. The small span and the limited fuel capacity and short du- ration fire suggest the same thing. The very heavy armament has been added since the design was originally conceived 1938 and probably since the first flying trials the end 1940. The whole the design, particularly the sence trimming tabs, suggests (CONCLUDED PAGE 163) . ° c Consulting Engineer, Lincoln Electric Co. been directed towards certain types specifications and in- spection limits. Some this has been just general objections, some fault-finding, and some definitely constructive. the last named, there has been too little attention directed towards defining the ulti- mate performance the part be- ing manufactured. The perform- ance required, the method manu- facture and the control and that method must studied and co-ordinated. Failure recognize the ease and simplicity control the fabri- cation welded parts, for example, and failure put these controls into operation has resulted con- fusion, time lost and considerable argument. good deal this de- lay could have been avoided the manufacturing requirements and limits were matched with the performance necessary. Wide lim- its where and close limits where required are illustrated the following general examples. The variation great consequence where the struc- ture is, let say, single mem- ber, such small portable bridge like this, the requirements hold inch would costly time, and produce results justifying that cost time. Getting down somewhat closer limits, the fit bolts and the holes parts joined can much more sloppy than the fit shaft Died Sept. 19, 1942. Welding Design, Specifications and Inspection this discussion policy, the author points out that the ultimate performance the product con- stantly kept mind designers, engineers, fabricat- ors and inspectors, unnecessary expense reach close tolerances will avoided, yet all the performance required will attained. bearing. Some these conditions are illustrated the photographs. Inspection and study these, keep- ing mind the above statements, indicate the scope the problem. This general problem may considered under five divisions: De- sign, specification, fabrication, in- spection and performance. Design Design not just matter figuring out strengths and sizes involved. There must kept mind all times the ultimate per- formance required, and the speed signer also must familiar with usual types machines and not call for unusual types equipment. Assembly must such that easily done. regards such mat- ters fit-up, how much variation can allowed? How easy put the parts together? How ac- cessible the weld? Can the oper- ator see what doing, and are the welds easily inspected? The designer will find neces- sary select certain materials. P