ajp-jp4199707C384

Authors and Publication

  • Authors: A. M. Bragov, A. K. Lomunov

  • Institution: Nizhny Novgorod State University

  • Published in: Journal de Physique IV, August 1997

  • DOI: 10.1051/jp4:1997384

  • Citations: 41, Reads: 418

Abstract

  • This report details dynamic testing of wood properties using the Kolsky method with a Split Hopkinson Pressure Bar (SHPB).

  • Tested Species: Pine, Birch, Lime.

  • Focus: Mechanical properties influenced by cutting direction, nonlinear deformation diagrams, and failure modes (cracking, spallation).

  • Combined with SHPB, plane-wave experiments yielded shock adiabates for wood samples.

Introduction

  • Increased concern for safe transport of nuclear waste and toxic materials necessitates robust container design.

  • Evaluation of wood's damping properties under dynamic loading is under-researched.

  • Objective: Analyze dynamic properties of pine, lime, and birch at pressures up to -500 MPa and strain rates over 10^3 s^-1.

Experimental Apparatus

  • Methods Used:

    • SHPB Method: Applied to measure dynamic compression response at moderate strains.

    • Plane-wave Impact Experiments: Used for high pressure and strain rates.

1.1 Split Hopkinson Pressure Bar Technique

  • Widely used for dynamic testing of materials including metals, polymers, and wood.

  • Equipment includes a pneumatic loading device, pressure bars, and digital recording tools.

  • Capable of generating high strain rates (up to 150 MPa).

1.2 Plane-wave Impact Setup

  • Method for assessing shock compressibility by sending compression waves through wood placed between plates.

  • Utilizes parameters like impact velocity and wave propagation velocity for analysis.

1.3 Specimens

  • Samples cut to measure properties both along and across wood fibers.

  • Tests conducted at ambient temperature; properties recorded include density and mechanical strengths.

Material

Density (g/cm³)

Modulus (MPa) along fibers

Modulus (MPa) across fibers

Tensile Strength (MPa)

Compressive Strength (MPa)

Pine

0.45

16600

1126

100

41.4

Birch

0.56

16660

1124

115.8

46.7

Lime

0.51

-

-

-

39.8

Test Results and Discussion

  • Dynamic Deformation Diagrams:

    • Show non-linear behavior with different characteristics across strain rates.

    • Higher strains lead to visible failure in the material, especially at high strain rates.

  • Results indicate that wood exhibits complex material behaviors influenced by loading direction and strain rates.

Conclusion

  • Dynamic tests reveal glue-like behavior in birch and lime under high strain rates, contrasting with pine's stress reduction upon deformation.

  • Observed commonality across tested species regarding stress decrease post-loading due to decohesion.

  • The data also indicates significant shape recovery post-deformation, emphasizing elastic characteristics despite high levels of strain.

Acknowledgement

  • Sponsored by the Ministry of the Secondary and Professional Education of the Russian Federation, Grant No. 95-0-4.3-21.

References

  1. Kolsky H., Proc. Phys. Soc., B, 62, (1949)

  2. Nicholas T., Impact Dynamics (Willey Interscience, N.Y., 1982)

  3. Kinslow R., High-Velocity Impact Phenomena (Academic Press, New York and London, 1970)[Additional references omitted for brevity.]