The purpose of the Commonality program, initiated by DNA in 1978, was to evaluate e-beam material testing procedures and techniques by comparing material stress and spall data from various US and UK e-beam facilities and experimenters. As part of this joint DNA/SNL/UK Commonality effort, Sandia and Ktech used four different electron-beam machines to investigate various aspects of e-beam energy deposition in three materials. The deposition duration and the deposition profiles were varied, and the resulting stresses were measured. The materials studied were: (1) a low-Z material (A1), (2) a high-Z material (Ta), and (3) a typical porous material, a cermet. Aluminium and tantalum were irradiated using the DNA Blackjack 3 accelerator (60 ns pulse width), the DNA Blackjack 3&#x27; accelerator (30 ns pulse width), and the SNLA REHYD accelerator (100 ns pulse width). Propagating stresses were measured using x-cut quartz gauges, carbon gauges, and laser interferometry techniques. Data to determine the influence of deposition duration were obtained over a wide range of energy loadings. The cermet material was studied using the SNLA REHYD and HERMES II accelerators. The e-beam from REHYD generated propagating stresses which were monitored with quartz gauges as a function of sample thickness and energy loadings. The HERMES II accelerator was used to uniformly heat the cermet to determine the Grueneisen parameter and identify the incipient spall condition. Results of these experiments are presented

Beezhold, W.

Keller, D. V.

Powe, J.

Rice, D. A.

Watts, A. J.

UNT (University of North Texas) Digital Library

~ ~· cy ' •. DNA/SNLA CO/>l HONALITY PROGRAM ( (J) D. V. Ke ller, A. J. Wa tts, D. A. Rice, J. Powe Kt 2ch Co r poration W. Beezhold , Sandia National Laboratorie s* Albuquerque, New Mexico SUM~1ARY The purpose of the "Commo nality" program, initiated by DNA in 1 978, was to eval uate e- beam ~aterial testing proc e du re s and tech~igues by co~par ing material s t r ess and spall data fro m va rious U.S. and U.K . e-beam ~acilities and experimenters. As part of this joint DNA /SN L/UK Conoonality effor t , Sandia and Kte c h us ed four diffe~ent electron-beam·- machi~es to i nve stigate various aspects of e -be am energy deposition in t h r ee ma teri a ls. We varied the d eposition duration and the deposition profiles , and mea sured the resulting stresses produced. The mater ials studied were: 1) a low-Z material ·(Al), 2) a high-Z material (Ta), and 3) a typical porous illaterial, a cer met. We irradiated aluminum and t antalum using the D~A 3lackjack 3 accelerator (60 ns pulse width ) , the D~A Bl ackjac k 3 ' accelerator (30 ns pulse width ), and the SNLA RE~1YD accele r ator (1 00 ns pulse h' idth). Propagat ing stresses were Qeasured using X-cut quar tz gauges, carbo n gauges, and laser interferonetr y tec hni que ~. Data to d ete rmine the influence of deposition duration were obtained over a wide range o f energy loadings. The cermet material was studied usi ng the SNLA REHYD and HER~ES II accelerators. The e-beam from REHYD generated propagating stresses which were monitored with quartz gauge s as a function of sample thickness and energy loading s. The HER1·1ES II accelerator was used to uniformly heat the cermet to determine the Gruneisen parameter and identify the incipient spall condi-tion. Result s of the se experiments wi ll be_ p rese n ted. ASTER ' r--------DISCLAIMER -----------, This book was prepared as an account of work sponsored by an agency of the United States Govl!fnment. Neither the United States Govl!fnment nor any agenCy thereof. nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy. completeness. or usefulness of any information, apparatus, product, or process disclosed. or represents that its use v.ould not infringe privately owned rights. Reference herein tO any specific commercial product, process. or service by trade name. trademark, manufacturer. or otherwise. does not necessarily conSlitute or imply its endorsement, recommendation. or favoring by the United Stall!$ Government or any agency thereof. The views and opinions of authors expressed herein do not nuauaril't' 9tt'!""" Mf!ArT 1hrl"oll nf ThP. I lnitPrt S!i\11!5 G~nrnE!f11 or any agency thereof. *This work was supported by th e U.S. De partment of Energy and by t he Defense Nucl e~ r Agericy. tP 1JUMITE!l DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. INTRODUCTION The objectives of this joint DNA/SNLA program were to obtain valid and reproducible data on material responses to·· electron irtadiation from differing electron beam facilities. The "Commonality" program, of which this work is a part, was initiated in 1978 by DNA to provide a common database so that co~parisons between facilities -would be ind~pendent of the particular testing and dosimetry techniques utilized. Each experimental group used its preferred diagnostic techniques. Commoh-supply materials were used to eliminate test result variations due to material differences. The work repotted h~rejn was_perform~d by a group of Ktech and SNLA experimenters and utilized four electron beam. machines: Blackjack 3 and 3 prime (BJ3, BJ3') at Maxwell Laboratories, Inc., San Diego, and Rehyd and Hermes II at SNLA. Table 1 suffimarizes the pertinent machine chaiact~ristic~ along with ·those of u. s. machines used by the other "c6mmonslity" experimenters. / For the tests at Sandia and-Maxwell, Ktech Corporation performed the beam characterization and materials irradiation experiments and SNLA provided the data acquisition techniques and {hstrumentation.* The materials, aluminum (Type 1100), tantalum, and a 50VJ2 cermet, were supplied by SRI. Menlo Park, and SNLA. The Al and Ta samples were prepared; respectively, from one original .material piece by D. Schallhorn at Harry Diamond ~Data acquisition~ork WQS performed by J. Romine~ M. Ruebush; and G. Hansen of Division 1126. -2-Laboratories (lDL). Ktech procured its own supply of aluminum (Type 6061-T6) and -tantalum for· some of the in1ti~l-experiments. Phase I of this program involved the study of aluminum using the BJ3, BJ3' and Rehyd machines. Al was chosen as a standard material for technique checkout because its equation-of-state is best known. Also, because of Al's low density, there was little stress relief during the deposition time. The three machines yielded similar deposition profiles ~n Al (range 0.5 gm/cm 2 , ~ 0.2 em) but differed in deposition times (be~ween 30 nsecs and 120 nsecs FWHM). The parameter~ studied were the deposition profiles, the resulting stresses and their propagation characteristics. For Phase I the aluminum samples were 0.110" thick, greater than the deposition range. Energy loadings of 50-900 cal/gm and deposition times of 30-120 nsecs \·:ere used. This dose· range covered behavior through melt and just beyond incipient vaporization ( ~ 718 cal/gm). Phase II was the study of the tantalum, again using BJ3, BJ3' and Rehyd. The deposition range of about 0.5 gm/cm 2 for this high density material involves a very shallow depth (0.03 em), ahd. with these machines the peak induced stresses depend significantly on depo~ition ti~e and the consequent stres~ release effects. The tantalum samples were 0.030" or 0.050" thick, greater than the deposition range. The Ta was ·subjected to energy loadings of 50-900 cal/gm and deposition times of 30-120 nsecs. The higher loadings induced significant partial vaporization (~ 260 cal/gm). -3-Phase III was the study of a porous shielding_material, 50VJ2 cermet. For this material only Rehyd and Hermes II were used to ·investig~te the sample behavior as a function of thickness and energy loading. The cermet has an effective intermediate z (5 22) and a density of 3 .. 26 gm/cm 3 . The intent of the Rehyd tests was to keep constant the. deposition profile and timing while investigating the stress dependerice as a function of the sample thickness (0.050", o.oso••, 0.110") and energy loading~ All three sample thicknesses were ·gre~ter th~n.th~ Rehyd deposition range. The 0 .. 050" sample was marginal. The stress relief depth was 0.05 em for the Rehyd 120 nsecs deposition time; this depth was comparable to the electron range, so some stress relief. 6ccurred during deposition. The stress profiles were ~xpected to displaY a ~trong attenuation.with distance that is usual for porous materials. The propagated stress waves were measured \~ith quartz gauges, using fused silica buffers for the thinnest samples to avoid electron deposition diiectly into the gauge. Direct measurements of the Gr~neisen parameter and the spall strength were also made for this cermet using the Hermes II machine. Hermes II at 8-10 MeV yields a large deposition ·, 2 . range (~ 5.0 gm/cm ) and, consequently, produces uniform deposition profiles 1n the samples used. This report ·summarizes briefly the experimental techniques used and the types and quality of data obtained. Although some specific numerical results ar~ presented, all results -4-are preliminary at this time. Complete data reduction and analysis of the results have not yet been completed. Detailed hydrocode calc~lations .of predicted stress histories for compari-sons with these data, and with the data by other commonality experimenters, are in process at SRI. These commonality correla-tions and conclusions will be reported separately .. EXPERIMENTAL TECH~IQUES Figures 1 and 2 illustrate typical calorimetry arrays for both spatial dosimetry (using ~otal stopping carbon calorimeters) and dose-depth measurements (using thin carbon foils). Also indicated is the manner of mounting samples ~rid gauges. For the mate~ial irradiations by the e-beams, the dose-depth stack was replaced by the appropriate sample/gauge configuration. For all shots the diode characteristics were recorded using the Sandia 7912-PDPll data recording and reduction sy~tem. This system recorded v and I (voltage and current) and computed the diode impedance, the diode power, the pulse duration, ana the time-integiated electron energy spectrum. This information allriws deposition calculations to be performed using the Monte Carlo transport codes ELTRAN and TIGER. Figure 3 ill~strates a typical dose-depth analysis using BJ3 1 • ' The material response monitoring techniques used by Kt~ch included quartz and carbon gauges, and laser velocity and displacement interferometry (LVI and LDl). The quartz gauges were usually placed directly on the specimen, whereas the carbon gauges and LVI qenerally in~lll~ed the use of a PMMA (Plexiglas) or fused silica material in which the gauge or mirror was r -5-embedded. For a thin specimen, a fused silica buffer was also used to prot~ct quartz gauges f~om direct electron depositi?n· EXPERIMENTAL RESULTS Figures 4, 5, and 6 illustrate typical Al stress measurements taken with the three monitoring techni~ues of quartz and carbon gauges, and LVI. For the carbon gauges and LVI condi.tions the influence of the buffers of PMMA and fused silica, respec~ive-ly, must be taken into account. The P~MA "shocks-up" the stress wave profile giving the steep observed rise. The long-lived tail on the carbon gauge record resulted from the impedance mismatch between Al and PMMA, and repiesehted the "ring down" of the stress reflect~ng back and forth in the thinner Al piece. The fused silica buffers mostly smooth th~ str~ss profiles, lessening the steepness of the front of the original material wave. To allow evaluation of the stress records it is essential to ensure one-di~ensional conditions for as long as possible. Great care was taken with the choice of irradiation area, sample thickness, and buffer/moni~or geometry to guarantee one-dimena1onal situations. Typi~ally the beam fluence varied by less than 20% across a sample irradi~tion diameter (about 0.7"). Figur~ 7 . ·~ illustrates the consideration involved in this one-dimensional determination. Indic~ted· on Figs. 4, 5, and 6 are the calculated limits to one-dimensionality times for these experimental conditions. Due to the non-flat deposition profiles coupled with stress propagation during energy deposition, the peak induced stresses are less than the direct Gruneisen stresses for instantaneous -6-energy deposition. The magn.itude of this stress relief effect depends on the deposition profile width, the deposition time and the material sound speed. Figure 8 gives the generalized effects for Al and Ta as a function of deposition timing using these e-beam machines. It is seen that where Al exhibits only a relatively small dependence on time, Ta is very dependent. Figure 9 gives a direct comparison of Al stress profiles normalized to gauge stress per unit material specific energy loading. Despite the wide range of energy loadings and d~posi­tion times, very .little varia~ion in the normalized peaks is observed, as expected. Figure 10 gives a direct 'com~arison of Ta stress profiles normalized to gauge stress per unit material specific energy loading. A dramatic dependence in peak stress is observed as· a function of deposition time, as e~pected, while the influence of deposition profile widths, due to differing mean el~ctron energies, can also be seen. Figure 11 illustrates th~ observed gauge· stresses for ih~ 'three cermet thicknesses exposed at Rehyd. It is seen that ~t constant energy loading the thinner sample gives the higher peak stress, as expected for a porous material. To directly study the Gruneisen r and spall strength of the cermet, Hermes II was chosen for the electron irradiation since it gav~ a reasonably uniform deposition within the samples (0.080" thick) and had a short enough deposition tim~ (70 nsecs) to give only minor through-the-thickness stress relief. Energy loadings of up to 85 cal/gm were achieved. ; . ( -7-The Grlineisen r was determined using LDI and employing the stress matching technique with fused silica as the reference material having a free surface mirror. Figure 12 illustrates the position-time (x:t) and stress-particle velocity (P:u) · analy~is appropriate to the experimental arrangement. Figure 13 gives a typical LDI interpretation showing clearly the first three velocity state~ which allow extrapolation to the initial cermet thermal stress, and hence determination of the Grilneisen parameter (i.e., via P = fpE}. Also evident is the influence of the finite deposition time and the jump incurred due to the thin epoxy bond between the porous sample and fused silic~ reference. Figure 14 .summarizes the stress inferred versus energy loading and indicates a mean v~lue of r ~ 0.05 over the range of 0-60 cal/gm. To determine the spall strength of the cermet, a triple stack of free-surface samples (0.080" thick) were irradiated in a common ~hot. Figur~ 15 illustrates the ar~angement, gives mean energy loadings, and shows the observed modes of damage. A variation from complete spall to no damage was obtained, and incipient spall loading of about· 70 cal/gm was identified. Figu0e 14 suggests a corresponding tensile strength of about 0.55 kbars, assuming a simple release path inversion of initial thermal stress into tension, appropriate for approximate·uniform energy loading. The small non-uniformity in the deposition profile is the reason why the spall plane is towards the rear of the samples .. ( -B-SUMMAhY AND Cb~CLUStONS The ability to load, monitor, and understand the response· o~ three tlas~es of materials exposed to electron beam irradia- · tioh~ from fo~r differ~nt electron beam machines has been d~~bh~tt~ted. Alumihum, tantalum and a cermet were successfully itradi~ted over the loa~ing range 50-900 cal/gm and with deposi-tibh time~ ttom ~O~l20 nset. Th~ aluminum exhibited only slight .~epehd~hce bh aepbsition duration, as expected; the tantalum §tre~~ ~~hiblte~ the ahtic1pated strong dependence on deposition ti~e. ~bt the cet~et, the ~tUneisen parameter was determined to be abb~t 0.05. ~he spall strength for uniform heating ~as. to~hd to be bhe-h~lf kilobar, and stress generation, propagati6h, · ah~ attenuatibh ~ere tetotded ~s a functioh of thickn~ss and lo~~ih~. bet~iled eotrelation between merisurements and calcula-tlbhs ate ih ptogte~s. 

DNA/SNLA commonality program

https://digital.library.unt.edu/ark:/67531/metadc1191547/m2/1/high_res_d/7010963.pdf

DNA/SNLA commonality program

Abstract

Similar works

Full text

Available Versions

UNT (University of North Texas) Digital Library