ASM Metals HandBook Vol. 8 - Mechanical Testing and Evaluation
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Fig. 13 Localized shear deformation band in tungsten alloy W90
The susceptibility to adiabatic shear failure under pure shear loads can be examined by dynamic torsion tests on
tube specimens (Ref 39, 40, 41, 42) and shear tests using hat-shaped specimens (Ref 19, 21, 22, 23, 24, 25, 26,
27, 28, 31, 32, 33, 34, 35, 36, 43, 44, and 45). The torsion test allows the determination of stresses, shear
strains, and strain rate conditions in a thin cross section at the initiation of adiabatic shear failure. The hat-
shaped specimen method, as previously described in this article, has the advantage of applying very high strains
and very high strain rates and, by geometry, can produce narrow shear bands, even in materials not susceptible
to shear band formation. The disadvantage of the hat-shaped specimen method is that the stress concentration at
both sides of the shear plane prevents a local stress determination.
It is also known that adiabatic shear failure occurs in uniaxial compression tests (Ref 46, 47, 48). This is
observed mostly in high-strength materials like thermomechanically treated steels, titanium alloys, or ultrahigh-
strength steels. Additionally, in most impact applications, pure shear or compression stress states are few. This
leads to a necessity for biaxial dynamic loading systems that allow reproducible experiments under defined
stress conditions of solid specimens instead of thin tubes (Ref 49, 50, and 51). This approach has been
developed based on drop-weight testing with high strain rates as a way to evaluate the materials sensitivity or
susceptibility for adiabatic shear failures. The advantage of the drop-weight testing (in contrast to typical
Hopkinson setups) is that large amounts of stored energy can be applied, so that the strain-rate history is not
influenced by the strain hardening of the test material under compressive and compression/shear loading. The
drop-weight method also allows high strain testing of in. (20 mm) cross sections, even of high-strength
materials. This may be of interest if there are geometry-dependent gradients in the hardness or stress-strain
behavior.
References cited in this section
19. K.-H. Hartmann, H.D. Kunze, and L.W. Meyer, Metallurgical Effects on Impact Loaded Materials,
Shock Wave and High-Strain-Rate Phenomena in Metals, M.A. Meyers and L.E. Murr, Ed., Plenum
Press, 1981, p 325–337
21. J.A. Hines and K.S. Veccio, Dynamic Recrystallization in Adiabatic Shear Bands in Shock-Loaded
Copper, Metallurgical and Materials Application of Shock Wave and High-Strain-Rate Phenomena,
L.E. Murr, K.P. Staudhammer, and M.A. Meyers, Ed., Elsevier Science B.V., 1995, p 421–428
22. F.D.S. Marquis, M.A. Meyers, Y.J. Chen, and D.S. Kim, High-Strain, High-Strain-Rate Of Tantalum,
Metall. Mater. Trans. A, Physical Metallurgy and Materials Science, Vol 26 (No. 10), 1995, p 2493–
2501
23. S. Nemat-Nasser, Y.-F. Li, and J.B. Isaacs, Experimental/Computational Evaluation of Flow Stress at
High Strain Rates with Application to Adiabatic Shear Banding, Mech. Mater., Vol 17 (No. 2–3), 1994,
p 111–134
24. R.W. Chen and K.S. Vecchio, Microstructural Characterization of Shear Band Formation in Al-Li
Alloys, J. Physique IV (France), tome 4, Coll. C8, 1994, p 459–463
25. U. Andrade, “High-Strain, High-Strain-Rate Deformation of Copper,” Ph.D. thesis, University of
California, San Diego, 1993
26. M.A. Meyers, L.W. Meyer, J. Beatty, U. Andrade, K.S. Vecchio, and A.H. Chokshi, High Strain, High-
Strain Rate Deformation of Copper, Shock Wave and High-Strain-Rate Phenomena in Materials, M.A.
Meyers, L.E. Murr, and K.P. Staudhammer, Ed., Marcel Dekker, 1992, p 529–542
27. M.A. Meyers, G. Subhash, B.K. Kad, and L. Prasad, Evolution of Microstructure and Shear-Band
Formation in α-hcp Titanium, Mech. Mater., Vol 17 (No. 2–3), 1994, p 175–193
28. M.A. Meyers, Y.-J. Chen, F.D.S. Marquis, and D.S. Kim, High-Strain, High-Strain-Rate Behavior of
Tantalum, Metall. Mater. Trans. A, Vol 26, Oct 1995, p 2493–2501
31. S. Nemat-Nasser, J.B. Isaacs, and J. Starrett, Hopkinson Techniques for Dynamic Recovery
Experiments, Proc. R. Soc. (London) A, Vol 435, 1991, p 371–391
32. T. Pintat, Ph.D. thesis, University Bremen, Germany, 1993
33. M.A. Meyers, U.R. Andrade, and A.H. Chokshi, The Effect of Grain Size on the High-Strain, High-
Strain-Rate Behavior of Copper, Metall. Mater. Trans. A, Vol 26, Nov 1995, p 2881–2893
34. T. Pintat, L.W. Meyer, and H. Schrader, Properties of Inhomogeneous Shear Zones in Different
Materials, J. Phys., Coll. C5, 1985
35. T. Pintat, B. Scholz, H.D. Kunze, and O. Vöhringer, The Influence of Carbon Content and Grain Size on
Energy Consumption during Adiabatic Shearing, J. Phys., Coll. C3, 1988, p 237–244
36. M.A. Meyers, L.W. Meyer, K.S. Vecchio, and U. Andrade, High Strain, High-Strain Rate Deformation
of Copper, J. Phys. (France) IV, Coll. C3, 1991, p 11–17
38. L.W. Myer, F.-J. Behler, K. Frank, and L.S. Magness, Interdependencies between the Dynamic
Mechanical Properties and the Ballistic Behaviour of Materials, Proc. of the 12th International
Symposium on Ballistics, Vol 1, p 419–428
39. L.S. Costin, E.E. Crisman, R.H. Hawley, and J. Duffy, On the Localization of Plastic Flow in Mild Steel
Tubes under Dynamic Torsional Loading, Mechanical Properties at High Rate of Strain, Institute of
Physics Conf. Series (No. 47), J. Harding, Ed., 1979, p 90–100
40. J.H. Giovanola, Observation of Adiabatic Shear Banding in Simple Torsion, Impact Loading and
Dynamic Behaviour of Materials, C.Y. Chiem, H.-D. Kunze, and L.W. Meyer, Ed., DGM Informations-
gesellschaft, Oberursel, 1988, p 705–710
41. J. Duffy, Experimental Studies of Shear Band Formation Through Temperature Measurements and High
Speed Photography, Proc. 3rd International Conf. on Mechanical and Physical Behaviour of Materials
under Dynamic Loading, DYMAT Association, Paris, 1991, p 645–652
42. K.T. Ramesh, On the Localization of Shearing Deformations in Tungsten Heavy Alloys, Mech. Mater.,
Vol 17 (No. 2–3), Elsevier, 1994, p 165–173
43. K.-H. Hartmann, H.D. Kunze, and L.W. Meyer, Metallurgical Effects on Impact Loaded Materials,
Shock Wave and High-Strain-Rate Phenomena in Metals, M.A. Meyers and L.E. Murr, Ed., Plenum
Press, 1981, p 325–337
44. L.W. Meyer and S. Manwaring, Critical Adiabatic Shear Strength of Low Alloyed Steel under
Compressive Loading, Metallurgical Applications of Shock Wave and High-Strain-Rate Phenomena,
L.E. Murr, K.P. Staudhammer, and M.A. Meyers, Ed., Marcell Dekker, 1986, p 657–674
45. S. Nemat-Nasser, Y.-F. Li, and J.B. Isaacs, Experimental/Computational Evaluation of Flow Stress at
High Strain Rates with Application to Adiabatic Shear Banding, Mech. Mater., Vol 17 (No. 2–3), 1994,
p 111–134
46. L.W. Myer, Dynamic Behavior of Thermomechanically Treated Ultra High Strength Steel under Tensile
and Compressive Loading, I. Berman and J.W. Schroeder, Ed., High Energy Rate Fabrication, ASME,
1984, p 245–252
47. C.H. Nguyen, Evaluation of the Elastic Response to Impact for High-Strength Steels, Metallurgical and
Materials Applications of Shock-Wave and High-Strain-Rate Phenomena, L.E. Murr, K.P.
Staudhammer, and M.A. Meyers, Ed., Elsevier, 1995, p 699–706
48. M. Stelly and R. Dormeval, Adiabatic Shearing, Metallurgical Applications of Shock-Wave and High-
Strain-Rate Phenomena, L.E. Murr, K. Staudhammer, and M.A. Meyers, Ed., Marcel Dekker, 1986, p
607–632
49. L.W. Meyer, E. Staskewitsch, and A. Burblies, Adiabatic Shear Failure under Biaxial Dynamic
Compression/Shear Loading, Mech. Mater., Vol 17 (No. 2–3), 1994, p 203–214
50. L.W. Meyer, L. Krueger, W. Gooch, and M. Burkins, Analysis of Shear Band Effects in Titanium
Relative to High Strain-Rate Laboratory/Ballistic Impact Tests, J. Phys. (France) IV, Vol 7, 1997, p
415–422
51. L.W. Meyer, L. Krüger, and S. Abdel-Malek, Adiabatic Shearing Banding: Strength and Deformation
Behaviour as well as Damage Process, Materialprüfung, Vol 41, Hanserverlag, 1999, p 31–34 (in
German)
High Strain Rate Shear Testing
Test Setup and Operation
A drop-weight tower consists essentially of a heavy weight that drops on a specimen placed on an anvil (Fig.
14). The frame (A) and all other parts of the test setup are of high stiffness, and the weight is guided in a special
ball-bearing system in order to ensure a precise alignment of the hammer. Below the weight, a small tup is
fixed to give a precise loading condition. To measure the load time history, calibrated strain gages are glued on
the tup. The displacement can be measured with both a high-speed electro-optical camera and a light gate
system from which the strain rate can be calculated. All measured data are amplified and stored in a fast
oscilloscope. Special stopping devices and high-speed brakes allow evaluation of test results including recovery
tests at any stage in the deformation history. The strain-rate limit is about 200 s
-1
, compared to strain rates of
about 2 × 10
3
s
-1
for Hopkinson-bar methods (Ref 51).
Fig. 14 Tower and specimen for drop-weight compression-shear testing, A, frame; B, falling weight; C,
tup with force measurement; D, anvil; E, specimen; F, stopping device; α, angle of inclination
Reference cited in this section
51. L.W. Meyer, L. Krüger, and S. Abdel-Malek, Adiabatic Shearing Banding: Strength and Deformation
Behaviour as well as Damage Process, Materialprüfung, Vol 41, Hanserverlag, 1999, p 31–34 (in
German)
High Strain Rate Shear Testing
Application and Analysis of Results
Drop-weight testing is a method for high strain rate compression testing that can produce combined
compression-shear loading by using cylindrical specimens with a relatively small inclination angle along the
loading axis of up to 10° (Fig. 14). This type of specimen configuration leads to nearly the same compressive
stress distribution but applies additional shear stress. For example, an inclination of 3° to the loading axis gives
an additional shear loading of 5.2% of the axial compression load (Fig. 15). Compared to the hat-shaped
specimen with its shear forcing geometry, the inclined cylindrical specimen geometry just “offers” a dynamic
biaxial stress state, and the material responds with its own specific behavior of sensitivity to adiabatic shear
failure. Therefore, with this testing procedure, the tendency of failure under adiabatic shearing can be
successfully evaluated under high-rate biaxial compression-shear loading. With the aid of stopping devices
(Fig. 14), the history of the shear band development also can be explored thoroughly.
Fig. 15 Ratio of shear load to compressive load as a function of specimen inclination to the loading axis
The general effect of shear-band formation on uniaxial compression behavior is shown in Fig. 16 and 17. At
low strains, the compressive stress-strain behavior is nearly the same for uniaxial and biaxial conditions. At
high strains, however, biaxial loading leads to a turning point (point A in Fig. 17) and a stress maximum (B in
Fig. 17). This behavior is explained by the development of shear bands (Ref 49). Depending on the material
behavior, the subsequent adiabatic shear failure follows immediately or after few percent of strain (point C in
Fig. 17). For example, Fig. 16 plots the dynamic compressive stress-strain behavior of a sintered and swaged
tungsten alloy. Under (pure) compressive loading, the material can be compressed to high amounts of
deformation without any shear bands or cracks. With the increase of an additional stress component in shear,
the compressive strength and deformation behavior is changed beyond τ/σ = 7%. At a loading state of τ/σ =
10.5%, the adiabatic shear failure leads to a sharp reduction in axial deformation of about 30%. A further
increase of additional shear stress causes a failure at 20% axial deformation.
Fig. 16 Engineering compression stress-strain behavior of a swaged tungsten (W-Ni-Co-Fe) alloy
cylindrical specimen with inclination to the loading axis varying between 0 and 10°
Fig. 17 Typical behavior of engineering compression stress and axial deformation under a biaxial
compression-shear load
In order to evaluate the influence of the biaxial compression-shear loading, data were developed for tungsten
alloys and a high-strength, α-β titanium alloy, Ti-62222Si (Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si). The titanium
alloy was tested at room temperature under a wide range of strain rates. Under quasi-static loading, the material
failed at about 32% compressive deformation with a nearly homogeneous distributed deformation around the
45° shear plane (Fig. 18). With increasing strain rates to 10
2
s
-1
and 10
3
s
-1
, the deformability is limited by
adiabatic shear failure. The compressive deformation is reduced to about half of that under quasi-static loading.
With increasing inclination of the specimen at = 200 s
-1
, the increase in the ratio of shear to compression stress
leads additionally to both a strong reduction of the deformability and compressive strength (Fig. 19).
Fig. 18 Deformability behavior under pure compressive loading as function of strain rate for titanium
alloy Ti-62222Si. Open circles, failure under stable plastic flow; solid circles, failure with adiabatic shear
bands
Fig. 19 Effect of shear-compression stress ratio on the compressive strength and deformability of
titanium alloy Ti-62222Si with initial strain rate of about 2 × 10
2
s
-1
Figure 20 shows a comparison of the deformability of different materials as a function of induced stress state
under dynamic loading of about 200 s
-1
for titanium alloy Ti-6Al-4V and four tungsten-heavy alloys in different
heat treatment and swaging conditions. The state of deformation just prior to failure is indicated by the symbols
in the figure. The open symbols represent a nearly uniform broad strain distribution in the specimen without
any additional cracks or strain concentrations. The diamonds with a cross inside represent the first occurrence
of a crack in the specimen, such as small tensile or shear cracks or shear failure over a broad shear zone. Solid
symbols indicate sharp and concentrated, nonuniform strain distribution where failure occurs by adiabatic
shear. The size was 6 mm in diameter and 6 mm in height.
Fig. 20 Compressive deformation versus the biaxial shear-compression load ratio for titanium alloy Ti-
6Al-4V and several tungsten alloys (see text). Open symbols: uniform deformation, no cracks, no
failures; symbols with a cross inside: first tensile or shear cracks, (normal) shear failure (not
concentrated); solid symbols: adiabatic shear failure
Tungsten alloy A (diamond symbol) is used in a sintered condition and reaches the highest deformation. Under
uniaxial compression, this material can be compressed beyond 70% deformation without shear failure. First
shear cracks appear at 45° to the loading axis. Under a combined compression/shear loading with 15 °
inclination to the loading axis, only 23% axial strain is required for a broad (but not concentrated) shear failure.
At 10° inclination and 34% axial strain, the test was stopped. Investigation of the deformed microstructure in
the sample revealed that no cracks had appeared. The width of the shear band was about 0.5 mm in thickness.
Response of tungsten alloy B (in the sintered and swaged condition and plotted with square symbols) shows a
different failure behavior. Under pure uniaxial dynamic compression, the evolution of small cracks was
detected on the surface. With the influence of combined shear stress, the compressive deformation to failure is
reduced. At a loading of τ/σ = 5.2% (3° inclination to the loading axis), one adiabatic shear failure at 34% axial
deformation was measured in a group of three tests. At τ/σ = 10.5% or 6 ° inclination, all three specimens failed
by adiabatic shear at around 20% deformation. With further increase in additional amount of shear stress, the
compressive deformation to failure decreases continuously without any change in failure mode. This diagram
demonstrates that the method employed can distinguish between different materials as well as between
materials within the same group.
Stopping devices also make it possible to arrest the dynamic test at any point of deformation. This possibility
allows the recovery and subsequent analysis of the evolution of shear-band formation and shear-failure
development by means of optical or transmission electron microscopy. For example, metallographic
examination of Ti-6Al-4V (Ref 49) revealed that the beginning of the adiabatic shear formation leads to a
decrease of the slope of the stress-strain curve. With the use of stopping devices, an intermediate stage of the
developing shear band is shown (Fig. 13).
Reference cited in this section
49. L.W. Meyer, E. Staskewitsch, and A. Burblies, Adiabatic Shear Failure under Biaxial Dynamic
Compression/Shear Loading, Mech. Mater., Vol 17 (No. 2–3), 1994, p 203–214
High Strain Rate Shear Testing
Thick-Walled Cylinder Testing
Vitali F. Nesterenko, Department of Mechanical and Aerospace Engineering, University of California, San
Diego
The thick-walled cylinder (TWC) method is used for high strain rate testing of solid materials (Ref 52, 53, 54,
55, 56) and porous mixtures (Ref 57, 58). Figure 21 shows the basic experimental configuration used to
produce the radial collapse of the metallic specimens. The system uses the controlled detonation of an explosive
to generate the pressures required for the collapse of metallic samples. The specimens are placed within a
copper jacket (copper-driver tube); the system extremities are composed of steel plugs. Annealed
polycrystalline oxygen-free high-conductivity copper with grain size 100 μm or less was chosen as a driver
because of the high resistance of this material to shear localization. Stopper tubes of copper can be used inside
the hollow specimen to decrease strain. Driver and stopper tubes can also be constructed from tantalum, which
can dissipate more energy during collapse.
Fig. 21 The basic experimental setup for explosion-driven collapse of a metallic sample
The TWC method is a valuable technique because it allows testing under conditions more complex than
uniaxial conditions. Practically all applications under high strain rates involve either two-dimensional or three-
dimensional deformation. With the exception of the before-mentioned shear-compression test, the Taylor
impact test, the tensile/torsion tests of Stiebler (Ref 2, 3), other shear and torsional tests, and cavity expansion
experiments by Klopp and Shockey et al. (Ref 59), most high strain rate testing is uniaxial.
Multiaxial testing is useful in the evaluation of localized regions of high deformation such as shear bands (Ref
60, 61, 62). The observations of shear bands under controlled strain conditions is very important for comparison
of material behavior. The role of pressure is very important for localization in solid materials, and the strain-
controlled TWC method is well suited for this application. An important feature of this method is that a
relatively large amount of material is in the state of pure shear before the start of instability. This provides
conditions for spontaneous shear localization, which is different, for example, than “forced” localization in the
hat-shaped specimens method (Ref 63) discussed previously in this article.
Plastic flow of single crystals at high strains, and high strain rates is another example where the symmetry
breakdown due to crystal structure can result in complex three-dimensional flow, which has been analyzed
through numerical modeling and experiments (Ref 64). High strain rate flow of damaged ceramics also requires
three-dimensional tests, because it involves localization of deformation on early stages of flow (Ref 65, 66)
and, as a result, a broken symmetry of any initially symmetric one-dimensional or even two-dimensional
configuration. The development of computational models for the flow of fragmented ceramics under armor
penetration conditions, like the FRAGBED model by Curran, Seaman, Cooper and Shockey (Ref 67, 68) needs
adequate support by three-dimensional experiments. Especially important are experiments that may allow
separation of the volume distributed and the deformation localized inside shear bands (Ref 69, 70). The
experimental validation of this type of modeling needs tests that subject prefractured ceramics to high strain,
high strain rate compressive flow with controlled conditions and with the ability to recover the heavily damaged
ceramics with very small postevent deformation. The last condition is very important because it allows the test
to reveal the brittle fracture details of contacting ceramic particles and microstructural features of localized
flow—such as shear-induced dynamic sintering of SiC within shear bands for fine particle size/granular
material (Ref 71).
References cited in this section
2. K. Stiebler, Beitragzum Flieβverhalten der Stähle Ck35 und X2CoNiMnMoNNb211653 unter
zweiachsiger dynamisher Belastung, Ph.D. thesis, RWTH Aachen, Germany, 1989
3. K. Stiebler, H.-D. Kunze, and E. El-Magd, Description of the Flow Behaviour of a High Strength
Austenitic Steel under Biaxial Loading by a Constitutive Equation, Nuclear Engineering and Design,
Vol 127, 1991
52. V.F. Nesterenko, A.N. Lazaridi, and S.A. Pershin, Localization of Deformation in Copper by Explosive
Compression of Hollow Cylinders, Fiz. Goren. Vzryva, Vol 25 (No. 4), 1989, p 154–155 (in Russian)
53. M.P. Bondar and V.F. Nesterenko, Strain Correlation at Different Structural Levels for Dynamically
Loaded Hollow Copper Cylinders, J. Phys. (France) IV Coll. C3, Vol 1, supplement to J. Phys.
(France) III, p 163–170
54. V.F. Nesterenko, M.P. Bondar, and I.V. Ershov, Instability of Plastic Flow at Dynamic Pore Collapse,
High-Pressure Science and Technology 1993 (Joint International Association for Research and
Advancement of High Pressure Science and Technology and American Physical Society Topical Group
on Shock Compression of Condensed Matter Conf.), (Colorado Springs), 28 June to 2 July 1993, AIP
Conf. Proceedings, Part 2 (No. 309), p 1173–1176
55. V.F. Nesterenko and M.P. Bondar, Localization of Deformation in Collapse of a Thick Walled Cylinder,
Fiz. Goren. Vzryva, Vol 30 (No. 4), 1994, p 99–111 (in Russian)
56. V.F. Nesterenko and M.P. Bondar, Investigation of Deformation Localization by the “Thick-Walled
Cylinder” Method, DYMAT J., Vol 1 (No. 3), 1994, p 245–251
57. V.F. Nesterenko, M.A. Myers, C.H. Chen, and J.C. LaSalvia, Controlled High-Rate Localized Shear in
Porous Reactive Media, Appl. Phys. Lett., Vol 65 (No. 24), 1994, p 3069–3071
58. V.F. Nesterenko, M.A. Myers, C.H. Chen, and J. LaSalvia, The Structure of Controlled Shear Bands in
Dynamically Deformed Reactive Mixtures, Metall. Mater. Trans. A, Vol 26, 1995, p 2511–2519
59. R.W. Klopp, D.A. Shockey, L. Seaman, D.R. Curran, J.T. McGinn, and T. Resseguier, A Spherical
Cavity Expansion Experiment for Characterizing Penetration Resistance of Armor Ceramics, Mech.
Test. Ceram. Ceram. Comp., AMD, Vol 197, ASME, 1996, p 41–55
60. D.E. Grady and M.E. Kipp, The Growth of Unstable Thermoplastic Shear with Application to Steady-
Wave Shock Compression in Solids, J. Mech. Phys. Solids, Vol 35, 1987, p 95–119
61. T.W. Wright and H. Ockendon, Research Note: a Scaling Law for the Effect of Inertia on the Formation
of Adiabatic Shear Bands, Int. J. Plast., Vol 12 (No. 7), 1996, p 927–934
62. A. Molinari, Collective Behavior and Spacing of Adiabatic Shear Bands, J. Mech. Phys. Solids, Vol 45
(No. 9), 1997, p 1551–1575
63. Y.-J. Chen, M.A. Myers, and V.F. Nesterenko, Spontaneous and Forced Shear Localization in High-
Strain-Rate Deformation of Tantalum, Mater. Sci. Eng., A, Vol 268, 1999, p 70–82
64. S. Nemat-Nasser, T. Okinaka, and V.F. Nesterenko, Experimental Observation and Computational
Simulation of Dynamic Void Collapse in Single Crystal Copper, Mater. Sci. Eng. A, Vol 249 (No. 1–2),
1998, p 22–29
65. W. Chen and G. Ravichandran, Static and Dynamic Compressive Behavior of Aluminum Nitride under
Moderate Confinement, J. Am. Ceram. Soc., Vol 79, 1996, p 579–584