Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized SYMPOSIUM ON IMPACT TESTING Presented at the FIFTY-EIGHTH ANNUAL MEETING AMERICAN SOCIETY FOR TESTING MATERIALS Atlantic City, N J., June 27 1955 ASTM Special Technical Publication No 176 Published by the AMERICAN SOCIETY FOR TESTING MATERIALS 1916 Race St., Philadelphia 3, Pa Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized This page intentionally left blank Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized FOREWORD This publication is based on a Symposium on Impact Testing that was held at the Fifty-eighth Annual Meeting of the American Society for Testing Materials in Atlantic City, N J., June 27, 1955 comprising the First and Second sessions The symposium was sponsored by Committee E-l on Methods of Testing with Mr F G Tatnall, Baldwin-Lima-Hamilton Corp., Philadelphia, Pa., serving as Symposium chairman Mr Tatnall also presided at the Second session with H L Fry, Bethlehem Steel Co., Inc., Bethlehem, Pa., as secretary and Mr W W Werring, Bell Telephone Laboratories, Inc., New York, N Y., presided at the.First session with W H Mayo, U S Steel Corp., Pittsburgh, Pa., as secretary In addition to the papers presented as a part of the Symposium, five other papers, being appropriate to the general theme of the Symposium, have been included on "Effects of Manganese and Aluminum Contents on Transition Temperature of Normalized Nickel Steel," by T N Armstrong, and O Miller, International Nickel Co.; "Low-Temperature Transition of Normalized Carbon—Manganese Steel," by T N Armstrong International Nickel Co and W L Warner, Watertown Arsenal; "Effect of Specimen Width on the Notched Bar Impact Properties of Quenched-and-Tempered and Normalized Steels," by R S Zeno, General Electric Co.; "Stress-Strain Relationships in Yarns Subjected to Rapid Impact Loading," by Herbert F Schiefer, Jack C Smith, Frank McCrackin, and W K Stone, National Bureau of Standards; and "Shock Testing with the Rocket-Powered Pendulum," by R W Hager, Sandia Corp Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized NOTE.—The Society is not responsible, as a body, for the statements and opinions advanced in this publication Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized CONTENTS PAGE Introduction Notched-Bar Testing—Theory and Practice—S L Hoyt Discussion Transition Behavior in V-Notch Charpy Slow-Bend Tests—Carl E Hartbower Discussion 10 23 Effects of Manganese and Aluminum Contents on Transition Temperature of Normal25 ized Nickel Steel—T N Armstrong and O O Miller Low-Temperature Transition of Normalized Carbon-Manganese Steels—T N 40 Armstrong and W L Warner Effect of Specimen Width on the Notched Bar Impact Properties of Quenched59 And-Tempered and Normalized Steels—R S Zeno Reproducibility of Charpy Impact Test—David E Driscoll 70 Discussion Automatic Impact Testing S DeSisto 75 From Room Temperature to —236 C—Thomas 76 The Influence of Pendulum Flexibilities on Impact Energy Measurements—Joseph I Bluhm 84 Discussion 93 The Impact Tube: A New Experimental Technique for Applying Impulse Loads— 94 George Gerard Discussion 110 Longitudinal Impact Tests of Long Bars With A Slingshot Machine—W Ramberg and L K Irwin 111 Discussion 125 Stress-Strain Relationships in Yarns Subjected to Rapid Impact Loading—Herbert 126 F Schiefer, Jack C Smith, Frank L McCrackin and W K Stone Shock Tester for Shipping Containers—W H Cross and Max McWhirter 141 Shock Testing with the Rocket-Powered Pendulum—R W Hager 149 Properties of Concrete at High Rates of Loading—D Watstein 156 Discussion Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized 170 This page intentionally left blank Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized STP176-EB/Jan 1956 SYMPOSIUM ON IMPACT TESTING INTRODUCTION Over the years there have been many discussions of the technique and significance of the impact test, including several formal symposia The last Impact Symposium was held in 1938 Much technical development since that time has been attributed to information contained in those symposium papers Now seventeen years later another Im pact Symposium steps into a field that is already brimming with interest and activity Some phases of this field carry the designation "Environmental Testing." Along this line, it was suggested some time ago by members of the Impact Committee, of Committee E-l, that papers on shock tests be included in this symposium which would encompass impact in parts, components, and complete structures, and not confine_the symposium to notched bar testing This broadened scope has been undertaken with what appears to be very beneficial enhancement of the parctical application of the impact test straining rates The end result is an excellent balance between theory and experimental results Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized Copyright© 1956 by ASTM International www.astm.org This page intentionally left blank Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized STP176-EB/Jan 1956 NOTCHED-BAR TESTING—THEORY AND PRACTICE BY S L HoYT1 to fully recognize the rigidity or the stiffening effect, at the notch section, This paper covers a few of the points which is caused by the third dimensional thought to be especially significant in stress This is the stress, amplified by the handling the practical phases of brittle stress concentration, which must exceed fracture the cohesive or brittle strength for brittle When metallurgists and engineers were fracture to result Attention became first confronted with the brittle fracture centered on stress raisers, and the theory of steel, it was thought that impact seems to have been that, since steel is must be the cause But leading experi- ductile, a slight deformation at the root menters soon found this concept to be would relieve the stress, and that nothing inadequate and, at the turn of the more was important An example which century, the notch was recognized in its brings out the effect of rigidity is the true light and was introduced into formal failed forging, which while ductile with tests of steel quality At the same time, the single or standard-width test bar was the energy absorbed in breaking the test brittle, with the same notch, when tested bar was universally adopted as the meas- with the double-width bar Another is ure of quality; this led to the simple the Navy Tear Test,3 which gives a much device of breaking the test bar by means higher transition temperature than the of a swinging pendulum Doubtless due Charpy keyhole test bar does with the to the earlier notions, the test thus be- same notch acuity Another misconcepcame commonly known as the "im- tion has been that steels having the same pact test" and so perpetuated the idea tensile properties would all perform that brittle fracture was the result of similarly in the presence of a notch This impact This was in spite of demonstra- was negated at an early date by a formal tions to the contrary, such as the work of and authoritative series of tests conConsidere,2 who found that increasing ducted by the German Society for Testthe strain rate simply raised the tem- ing Materials, the results of which were perature at which brittle fracture oc- published in 1907.4 In more recent times, curred Two other misconceptions impeded R H Frazier, J R Spretnak, and F W understanding of notch brittleness and Boulger, "Reproducibility of Keyhole Charpy delayed the general acceptance of and Tear-Test Data on Laboratory Heats on Steel," Symposium on Metallic Manotched-bar testing First was the failure Semikilled terials at Low Temperatures, Am Soc Testing HISTORICAL BACKGROUND Metallurgical Consultant, Columbus, Ohio Considere, "Contribution a PltJtude de la Fragility dans les Fers et les Aciers," (1904) Mats., p 286 (1953) (Issued as separate publication ASTM STP No 158.) See for example, S L Hoyt, "Principles of Metallography, McGraw-Hill Book Co., Inc., New York, N Y., p 226 (1920) Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized Copyright© 1956 by ASTM International www.astm.org WATSTEIN ON CONCRETE AT HIGH RATES OF LOADING FIG 5.—Displacement of the Anvil During Impact as Determined With a Vacuum Tube Accelerometer 161 capping plate and the rim of the guard having a rubber gasket After failure of the concrete specimen, the capping plate came down on the rim of the guard and prevented the hammer from following through and damaging the dynamometer The device for stopping the hammer on the rebound consisted of a pair of pawls mounted on opposite sides of the cylindrical hammer in such a manner that they permitted free fall of the hammer After the hammer made contact with the surface of the buffer on top of the specimen, the inertia of the cylindrical counterweights, poised alongside the hammer, caused the pawls to trip and to engage the racks as the hammer bounced after the impact In FIG 6.—Block Diagram—Cathode Ray Oscillograph Equipment served to distribute the load and, together with the cylindrical steel guard, served to bring the drop-hammer to a stop after failure of the concrete specimen During the test, the cylindrical steel guard shown on the anvil was placed around the concrete cylinder With the steel guard in place there was about j-in clearance between the bottom of the order to prevent the pawls from "freezing" hi their cocked position following their first or outward swing, it was neces-' sary to use suitable cushioning pads to prevent the return of the pawls to their initial position and to assure stoppage of the hammer at its highest point of rebound The displacement of the anvil during Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized 162 SYMPOSIUM ON IMPACT TESTING the impact was determined indirectly by means of a vacuum tube accelerometer.7 The accelerometer was attached to the steel anvil alongside the dynamometer, and its output was recorded by a cathode ray oscilloscope The accelerometer was calibrated by being subjected to a sinusoidal vibration of known frequency and amplitude The results obtained with the accelerometer are shown by the typical graphs in Fig The acceleration time curve shown at the top of the figure was integrated once to give the velocity-time relationship and again to give the displacementtime relationship As shown in Fig 5, the maximum displacement of the anvil was about 0.01 in at the end of the impact having a duration of 0.009 sec After the anvil attained its maximum acceleration it continued to travel about 0.25 in and was brought to a stop with shock absorbers and rubber buffers The concrete specimens tested in series and were also equipped with type C3 strain gages; the outputs of these gages and of the dynamometer were measured with the equipment described in Fig The equipment consisted essentially of a pair of potentiometers, the outputs of which were fed into two preamplifiers The amplified signals were then fed into a dual beam cathode ray oscilloscope The traces on the tube were photographed with a 35-mm still camera As illustrated hi the block diagram in Fig 6, the strain gages and the dynamometer formed parts of the two potentiometers which were powered with batteries producing a steady current of about 20 ma for normal operation o'f the equipment In several instances, the current in the strain gages was increased up to 30 ma to increase the output of the potentiometer There was no noticeable drift or lack of stability in the Walter Ramberg, "Vacuum-Tube Acceleration Pickup," Journal of Research, Nat Bureau Standards, Vol 37, Dec., 1946, p 391 cathode ray oscilloscope after an initial warm-up period of about hr The trigger, shown in Fig 6, operated by delivering an external synchronizing pulse in response to the closure of a pair of contacts by the drop-hammer The first closure of the contacts provided the triggering pulse, and all subsequent operations of the contacts had no effect on the output of the trigger The triggering switch was mounted on one of the piers of the drop-hammer machine in the path of the sliding brackets that carried the drop-hammer along the guiding rails The elevation of the switch was adjusted with reference to the plane of contact of the hammer, with the buffer placed on the test specimens to initiate the single sweep at a prescribed interval of time before the impact The duration of this interval was determined in accordance with the anticipated duration of impact, the sweep frequency of the oscilloscope, and the velocity of the drop-hammer The duration of impact hi the tests made in the drop-hammer machine ranged from about 0.004 sec in series to 0.0003 sec in series 3, and the corresponding average rates of stressing ranged from about 106 to X 107 psi per sec The duration of impact was controlled by the hardness and thickness of the buffer placed on top of the capping plate The thickness of the buffers ranged from 0.5 to in Dynamometer.—The dynamometer with a capacity of 50,000 Ib consisted of a hollow cylinder made of high-strength aluminum alloy with type C3 bonded wire strain gages attached thereto Four of these gages were arranged around the periphery of the cylinder in a manner calculated to compensate for bending The gages were attached with nitrocellulose cement and were dried in air several hours before being cured in an oven at 60 C Immediately upon removal from the oven, the gages were given a Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized WATSTEIN ON CONCRETE AT HIGH RATES OF LOADING coating of hot cerese wax, which satisfactorily kept atmospheric moisture out of the nitrocellulose cement Calibration of Equipment.—The dynamometer was calibrated statically at intervals during its period of service; these calibrations consisted of loading the dynamometer in a testing machine and observing the corresponding values of loads and the changes in resistance of the bonded wire strain gages The calibrations of the oscillographs shown in Figs and consisted of introducing a known change in the resistance of the strain gage circuits The change in the circuit resistance was made by connecting calibrating resistors in parallel with the gages (Fig 6) This was accomplished by means of a hand operated, single-throw 3-pole switch in tests of series and Two of the knives of the switch served to connect the calibrating resistors across the appropriate strain gages, while the third knife initiated the driven sweep in the oscilloscope The leading edges of the three knives were carefully adjusted by filing to give the desired sequence of contacts In the series tests, calibration of the equipment was made separately for the strain gages and the dynamometer circuits; in the series and tests the calibrations were made simultaneously Two calibrating resistors were used in each of the potentiometer circuits to provide a check on the accuracy of the calibrations and to test the linearity of response of the equipment to the calibrating signals Recording and Reduction of Data.— The data obtained in tests of series were recorded on photosensitized paper by suitable galvanometers (Heiland type C) The records of data in tests of series and were obtained by photographing the 5-in screen of a cathode ray oscilloscope on 35-mm film with a fixed focus camera having an //3.5 lens The time base in the record produced 163 in the recording oscillograph (series 1) was furnished by the transverse time marks which were made every 0.01 sec In the photographic records of the cathode ray oscilloscope (series and 3), the time base was furnished by an audiofrequency oscillator, which modulated the intensity of the beams at frequencies ranging from 5000 to 20,000 cps in such a manner that the traces of the beams became dotted lines In the records of series data, a reference line was furnished by a fixed source of light in the recording oscillograph In the photographic records of series and 3, reference lines were produced by exposing the film to a single sweep of the beams immediately before photographing the test traces The data were reduced directly from the paper record or the 35-mm negative with the aid of a toolmaker's microscope The microscope had a magnification of 15 diameters It was equipped with two micrometer screws with which the stage could be transported in two mutually perpendicular directions Sonic Tests: In addition to determination of the modulus of elasticity in these static and dynamic tests by measuring corresponding values of stress and strain, a dynamic modulus was determined for the by 6-in concrete cylinders by the nondestructive sonic method The values of the sonic modulus of elasticity were those computed from the fundamental longitudinal frequency of the cylinders The apparatus used in the sonic test consisted essentially of a variable frequency audio oscillator, an amplifier, a driving unit and a pickup circuit The amplified power of the oscillator was delivered to the driving unit which was placed in contact with the concrete specimen The specimen was supported on a thick pad of sponge rubber so as to Copyright by ASTM Int'l (all rights reserved); Tue Apr 12 02:07:06 EDT 2016 Downloaded/printed by Petrofac (Petrofac) pursuant to License Agreement No further reproductions authorized TABLE II.—SUMMARY OF RESULTS OF STATIC AND DYNAMIC TESTS Test Series Test Series Test Series Compressive strength, // (6 by 12-in cylinders) : //'c,psi a \c , per cent 2810 2.2 2370 2.2 2400 3.3 Static (fs) and dynamic (/