LIBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 c/CIRC/DateDue.p65-p.15 THE STATIC BUMPING MACEIVP AYN ITS NSF IN TUR / . — / NETPRMIVATICH CF TRE FFFRCT OF COUBINFD STRESSES It STEEL,’ A Thesis Subnitted to The Faculty cf The Nichiean Agricultural Collece. by George A. Willoughby Tronas J. Warmington. // Candidates fcr tre jlecree of Sachelor cf Science June, 1916. 4p NA 777" Page 1. The extensive use cf steel in the various lines of industry has made the studv cf its rroperties of great imycrtance, and much has been done in tre making cf machines of varicus tyres for the rurrcosse cf teatine it. There are on the market today several kinds of testins machines for determining the tensile streneth, the hardness, the comrositicn, and ete. of various kinds of this useful material anid most up-tc-date manufacturers have installed in their testins labcratcries some of tnese. One we@l kncwn machine for this kind cf work is the pcwer- driven tension machine which is usei in deterninine the tensile strength cf steel or other materials. The srecimen, which is usually a bar about eichteen inches long, is held vertically by Clanps fastened rigidly in the machine and tension or "pull" is applied by the lowering cf the bettcn clamp thrcugh gears anda screw by a nctor or cther source cf power. The amount of tensicn in pounds is given at any time by the balancins of a large scale Deam on the nachine. This maze is known as the Riele Testing Wachine. Cther examples are thcse rakes known as The Olsen Fydra@Qic Machine, The Torsicn Machine, The Amsler Fydraulic Machine and etc. The American Society fcr Testing Materials appointed a committee to investicate tre features of these machines and the followins report was wade on the speed of testing: "On analvzing and compuring the details of 437 tests, we find sore difference in resulta of the same material tested at the same or nearly the sare speed. This is due, apparently to the difference in testing machines, to the manner of measuring, or to the personal equation cf the operator wrich plays such a PH4ER19 Page <. large part in all testing, and finally to the differnce of the raterial itself, all cf which are factcrs entering into commercial testing at one tine or ancther, sincly or collectively, ari cannct be avcided urder rresent conditions, The results of teneile strength and elongation shew tolerable uniformity in twelve laboratories----Unless one if an exrert in----using ricrormetsrs----there is a liubilityv cf errcers, laree ani srall, and the result is nothine but cuess werk----- There ie a surrris- ince uniformitv in the resu’ts cf elonraticn at all speeds and in all laboratories---Takine all these facta intc consideraticn, your committee----recommends---a maxirum sveed of three inches per mirute fcr steel of the fergine crade, when a two inch section is used, and a maxirum speed cf six intres for steel of the boiler gerade where an eicht inch secticn is used." The two-inck and eicrt-inch secticn means the length of the sreciren between cace marxs. It is a well known fact that the rechanical and heat-treatnents cf steel ani rrobably other metals affect their rhvsical properties. It isa also well kncwn that large members, such as laree columns and I bars are not as strong 48 Snall srecirens of the same kind of material, Therefore it has been advicated, and is now beins carried out, that full sized members shculd be tested to study their behavicr under stress. Machines of enormous capacity have been built, and are not at all uncommen, as large as 6,°°0,000 pounds. A 8,000,090 pound tension machine has been in existance for some tine at the Phoenix Bridce Co. The United States government has recently installed a 10,090,000 pound machine. The accuracy of the weighing echeme is impcrtant. Large Page 3. machines are less sensitive than small ones, as regard the number of pounds required tc naxe them act, but the proporticn is about the same. If inaccuracy is suspected, how can its amount be determined, or in other words, what is the best way to calibrate a machine? It is not usually possible to load a machine with pig iron. In making a syster in loading levers the same inaccuracy is liable to accur as occured in the machine. The American Society for Testins Materials! @crnmittee on "Standard Methods of Testins", recommend the following in the rreceedines of 10°C: "Calibraticn for Testine Machines: (1) Test for accuracy by loading the weighing table with standard weicht3, and comrare tre actual weight at each additicn with the readiness on the bean. If the table is uniformly loadei in this manner with the full ancunt cf weichts that it will accomodate, the proncrticnality of the levers and the weigting bear. can be successfully established. This relaticn, in a rrcrerly designed machine, will remain constart for all lcads, but at a further test for sensitiveness under greater lcais thun can be accommc- datei in this manner, the follcwine rrccegdure is reccomrende!l: (2) Place in the nachine a tensicn bar of such a cross-section that the maximun capacity will not stress it grast the elastic limit. Stress this bar to varicus extents through the full range of the rachine, and at each lcad balance the beam and place upon the weighing table standard weishts cf 100 pounds. A weight 1/250 of the total lcad on the machine should produce a readable movement cf the bean. (3) Where evidence of the accuracy over tre whcle ranre cf the Pace 4, machine is desired, a kncwn load may be arplied by means of an extenscneter ani calibrated bar, whcse mcdulus of elasticity has been determined with exactness, (4) It is reccrmended that a devise be adcpted econfcruing to the follewing reguirerentsa, in which the extensoneter and bar are vervinently attacred te each other. a. This bar shall be annealed cr other-wise treated sc as to deterrine the unequal or internal stress in the material, and to insure ita elastic modulus being uniform for succeszive tests. b. This bar shall be of high elastic lirit material and of Buc cross section that tre lirit shall be well above the total Capacitv of the machine on which it is to be used. ec. The extensoneter shall be rrefsrably cf the indicatine cr direct revdine tyre, ani shall indicate to 1/10,000 of an inch Cr less. d. The extensometer shall be rermiventliv attached tc the bar, and shall meassure the elonsaticn on two cprosite sides. e. The metrcd cf securing the bar to the drav-head of the rach- ine shall ve pesitive and witrcut slip, and shall insure axial lecation. f. The lencth cf the bar meusured by the extensoneter shall be sufficient, but the srallest extensoreter division will correspond to a difference in losdine of 100 pounds cr less. e. The extensometer shall be protected from injurv by a perrminently attached case witn the ccver movable for re:.dine the acile. h. The apnaratus shall be plainly marxei with the maxinum load that can be safely anrlied wéthout injurv. i. The annaratus shall itself be calibrated either by the Pace 5. U.S. Bureau of Standards or in a manner that will insure equally trustworthy results." All of the tests herein refered to are for the determina- ticn of the effect of simple stresses, that is,sirrle tension, compress3icn , torsicn or bendine. What happens when two or more of tres. are actine in a piece at the sare time? Do their relative streneths rerain the sane? Are the various stresses added? These are questicns still unarswered and as the uses of Steel increase thelr imccrtarce increases. Lord Yelvin in the rreraration of his article on Elasticity for the Fnovelopedia Britanica, had « series of tests made uron rianc wire. Ths wire having sufficiert weight to keep it straight wrile susrended "us subijiect2i tc a tcrque at the bettom; when additicnel weioht was added it was fcund that the elastic limit cf the wire in torsicn waa lowerel. Nr. J.J.Guest, in Fneland, carried out a series of tests to obtain tne effect of con.binei etresses on ductile materials, the materials used in the tests beire wreurht iren, mild steel, correr and brasa. The results cf these tests alsc iead tc the sane 18 OM o 07) conclusicn, that th lastic prorearties ar materiale are subjectel to corbined stresses, The alieht kneowledee cf this subject and the entire absence of any infcrraticon available for engineers insrired Mr. Edvard series of investigaticns te pive 6D ]., Fanecek to carry out inforzaticn inzvediately availcble for practical wert. Wig tests included tre fcllcwireg: (a) Test cf steel and iron solid revnds and hollow tubes in torsicn while under tensicn. (b) Test cf steel and ircn solidi rounds and hollow tubes in tension while under torsicn. (co) Test cf steel and iron sclii roun’s and hollew tubes with increasing tension and torsicn. (a) Test of steel ani ircr solid reunds and hollew tubes in commressicn wrile urder tcrsicn. Tre apraratus use was an Clsen Vactine with varicue ccen- trivances of his ovn desion for civine torsicn. The cost was undicubtedly a ereat amount ani tre werk reauired muct time. Fis coneclusicrse «after four vears werk ray be fcund in volure VIII ef the proceedings of The American Society for Testing Materials. It was with the foreecing in mind that the Static Pending Vachine was started and with these thoughts that the writers have labored for nearlv a year with egarnecs to complete the machine and tc test ite value. After several misfortunes,one being the loss of the shors bv fire, the machine has been comrleted tc such an extent that it ean be used for combined eompressicn and bending and it is the aim of the writers to determine the effect of these as much as pessible in the few dave remaining for the work. This Static Bending Machine shown on a following page is easily understcod fron the picture. It is simply a machine for holding a rod as a cantilever loaded at the end with provisicns made for setting the rod at horizontal,at 30 degrees with the horizental, at 45 degrees with tre hcrizental or at 60 degrees Page 7. with the horizcntal, thereby adding compression as well as shear tc the bending. The rod is held in place by a split sleeve drawn up by a nut ard the weigrt holder by another sleeve as shown. There are at rresent three sleeves; Zinch, 1 inct, and 1+ inch diameters. It is intended to make a torsion arm fcr the machine so that ecurbined stresses of all kinds can be rut in the srecimen tc be tested, “BUIMSOLAy TE VIELS Page 8. To Deternine the Effect of Flexure and Compression: When a specimen is stressed in flexure, the fibers on the convex side are in tension and those on the conoave side are in compressicn. Flexure therefcre ruts beth tersion and compression in equal amounts in the stressed member and when the break cccurs the ultimate strength in tension or ecmpression, whichever is lower, has been exceeded. In steel the comrressive and tensile strengths are usually about equal. If, therefore, a specimen of steel be broken in a tensicn machine and another be breken by bending, the unit-stress should be the same in both cases. The same shculd hold also for stresses less than the breaking stress. The unit-etress at tre elastic limit in tension should be equal to the unit-stress at the same point in bending, if the tensile and ccnurressime strengthe are equal. If there is a dif- ference in this value, thre strength in compression at the elastic limit must be less than the tensile strength by the amount equal to the difference between the unit-etress values obtained in the two cases. Now since the elastic limit is that point at which deformaticn geases tc be prororticnal to the load , it may be determined from a stress-strain diagram, or by noting the point at which the load drops as in the case of the machine used( the Static Bending Machine). I. Therefore, test three bars ( more if necessary ) in the tension machine, recording the diameter of the bar in three or more places. The test should be carried on in the follcwing manner: Apparatus: I log board reir of 8 inch dividers Page &. micrcneter calirer 3 elierteen incr srecirers Vark cn the sreciven arn e@ie’t inch sv.ce equidistart from tre enis o* tre bar, ari take the tiareter realires wit)? the ricrereter vetweern the markd. Insert tre sreciren to be tested in the jaws of the mecrire and errly the load et its levest sreed. Keer the bean balerced bv wcevine the reise an? note carefully the behavior of tre scele beur. The elastic linit will be trat rcoint at which tre selile bear drers. fhecerd tee rectin~ on tre hecor. This srculd ce jorewith all three crecirers ani the averace value cf P/A taken ac tre urit stress at ts elestic linit, © beire tre re.dirne cn tre beur anid A the averace cress-secticnal area cf the 4 srecirers. If tre valves cf P/A dc rot cere practically the sare, mere than trree te-ts skevla be run. II, New ravire deternined the tereile atrereth per square incr at tre elastic limit, test trree cr rere bars in the Btatic Beniine Mactire in tre follcwine ranner; Set the hclder in the horizontal rosition and insert a bar (leneth to be deterrined fer abcut a 4004 lcai.) Place tre weiert holier on the end of the sreqinen ard add weicrts carefully until there ie a sudden dror. Recerd tre ienoth required alsc the weiert used. Calculate tre unit stress at tre elastic limit by use cf the fernula §, = KI/o whick fer a circtlar secticn is 301,/na° where M = berdine mcrent in inch rounds and d = diereter cf the esrec- men. Do this with three srecirens if tre values c.f S, are nearly equal. If nct use rcre. Takes tre averaur+ value as tre unit stress in flexure and deterrine wreticr tensicr cr ccnrressicr by cornparing results of test number one. Page 10. III. Test three cr mcre bars with the machine set at 30 decrees eri dc (2 co °F ry CE O decrees co decrees 6S) cr oO J 3 1 +> i ery a "y iV) r) nN p> +» N) ca J) yf» ] ‘we > ~ > cn arn nim ow 4g.c14 50,154 44,000 mosnrce ° - i Te TTA <>? wi ond ” m™ RE ae 7" prerage Tey Fae 16, OOS 46° 53 a are e 3. a ~ ~ ~* ® $ vrer-ve vrit etrernet? as dgeternired bs tre tensicn nuchire fe @ (b c Sa J ct p> o) ey C3 <> ry Cc. 7 3 a G2 ‘ 4) a | @ rd 6) r ® - i) J y 0 az2 19 ~ yo we — cay 3 . ~OETES nin reunis rer squares inst fer the rod at 30 lerrees, 2 i" 1674 Laat 173" 1" 258 4602! O37" Lev zon i. eon 304" 1032 Av. S17" 265" 15¢" Finzl averace = 314° Por the red at 45 derrees. an a4 ft / 4 Lil’ 761" 1102 1" 307" Seg call lie 120" £46" ceo" Av, 1ec* agg" 1¢4lt Pinal averact = 2908 Wer tee redut €% derresa, of 126" 156 qzai 1" 190" 271" la i. _ a _ Av. 132% 714°" azz Finil averarse 210" "rom tre atcve data it is seen treat tre aver re cerrressicn waa rracticszllv tre sare fer all taste in wristh tre rods where at an angle. This beine the cuss the averace urit strereths fcr GO, 453 ant €° decrees stcvld te equ:l. There is tovever, a ‘ir ce two stresses wren udded adc net give 4 t 32 -~-< Sifferearnce ard arrs the tctal etres:. critt the C-decree -- 11" test and tre 2C-decrree- 1" test, beth cf wrich arrear to be inccrrect, we have 451 20574 eo. = . : 3 32 ean r . aa uvernces, aldir- oorpressicn in case cf the areles, F4,315 -~ 50,2418 -- 46,07 .-- 47,030, There valvag seer te Sirirdisr bv abcut 400C# djrresrentive of thea ocrcsiy eenyrre:sicn. % a 2 ~ _—- = - Trato is t*2 enu cf tris? mt 8 : . a £ y+ 3 r as coe a ; 94 os Pais ie 2 wuercticn wrich canrct be ansvere? untii manv tes rave beer curries cut ard carefullv stutied.