ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Call number: ZSP-201-83/14
    In: CRREL Report, 83-14
    Description / Table of Contents: An analysis of ice fracture that incorporates dislocation mechanics and linear elastic fracture mechanics is discussed. The derived relationships predict a brittle to ductile transition in polycrystalline ice under tension with a Hall-Petch type dependence of brittle fracture strength on grain size. A uniaxial tensile testing technique, including specimen preparation and loading system design was developed and employed to verify the model. The tensile strength of ice in purely brittle fracture was found to vary with the square root of the reciprocal of grain size, supporting the relationship that the theory suggests. The inherent strength of the ice lattice and the Hall-Petch slope are evaluated and findings discussed in relation to previous results. Monitoring of acoustic emissions was incorporated in the tests, providing insights into the process of microfracture during ice deformation.
    Type of Medium: Series available for loan
    Pages: 43 Seiten , Illustrationen
    Series Statement: CRREL Report 83-14
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Development of testing technique Test specimens Tensile testing Compression testing Experimental results Tensile tests Compression tests Discussion Conclusions Suggestions for further work Literature cited Appendix A: Additional information on seed grains Appendix B: Thin-sectioning procedure Appendix C: Displacement transducer calibration
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 1984-01-01
    Description: A procedure is described for testing ice in tension. It incorporates a one-piece lucite mold, two carpeted “Synthane” end-caps and a pair of yokes anti ball joints. Use of the procedure has resulted in a successful test rate greater than 80%.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 1984-01-01
    Description: A procedure is described for testing ice in tension. It incorporates a one-piece lucite mold, two carpeted “Synthane” end-caps and a pair of yokes anti ball joints. Use of the procedure has resulted in a successful test rate greater than 80%.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 1983-01-01
    Description: Structure/property relationships, while well-researched in metallic and in some ceramic materials, have been essentially ignored 1n studies on the mechanical properties of ice. To rectify this situation, experiments have been designed and have been underway for the past two years to investigate one mechanical property, i.e. tensile strength, and the effect of one structural feature, i.e. grain size, on this property. A clear relationship has been established, and is reported here. Other work is in progress and will also be reported in due course.Equiaxed and randomly oriented aggregates of freshwater ice, of grain size (as seen in two-dimensional sections) varying from 1.0 to 7.3 mm, were prepared in the form of large cylinders (91 mm diameter × 231 mm length). The aggregates were deformed to fracture under uniaxial tension, using a specially designed ball-joint and yoke assembly to ensure axial loading. Data were obtained at -10 ±0.2°C (i.e. at 96% of the melting point) at a strain-rate of 10−6 s−1.Figure 1 shows that the tensile strength decreases with increasing grain size, from 1.25 MPa for d = 1 mm to 0.80 MPa for d = 7 mm. Moreover, this figure illustrates that the data are highly reproducible; i.e. that strength is reproducible to within ±5% for a given grain size over the complete range. Fig. 1.Graph showing the decrease in the tensile strength of ice with increasing grain size.Concerning the functional relationship between tensile strength of and grain size, analysis shows that the following equation is well obeyed:Where σj is 0.6 MPa and k is 0.02 MPa m½ at -10°C and 10−6 s−1. This point is illustrated in Figure 2. Fig. 2.Hall-Petch plot showing the relationship between the tensile strength and the grain size of the ice.The d−½ character of this relationship, which is of the classical Hall-Petch form observed frequently in metallic materials, indicates that the tensile strength of ice is controlled by some process involving stress concentration, possibly the propagation of microcracks nucleated by the interactions of dislocations or the propagation of pre-existing defects. Of these, the former is the more probable. The reason is that processes involving dislocation motion, when expressed by the difference of σf – σi, are expected to increase linearly with increasing d−½, whereas processes involving the propagation of pre-existing defects predict a linear relationship between σf and d−½ which extrapolates through the origin. The former behavior is the one observed.It is thus concluded: (i) that the tensile strength of equiaxed and randomly oriented freshwater ice, when deformed slowly at -10°C, decreases with increasing grain size, (ii) that the functional relationship between tensile strength σf and grain size d is σf = σj + kd−½, where σj and k are materials parameters, and (iii) that the tensile strength of polycrystalline ice is controlled by the propagation in a brittle manner of microcracks nucleated by dislocation interactions.AcknowledgementThis work was funded by the US Army Research Office, Contract No. DAA G-29-80-C-0064.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 1983-01-01
    Description: Structure/property relationships, while well-researched in metallic and in some ceramic materials, have been essentially ignored 1n studies on the mechanical properties of ice. To rectify this situation, experiments have been designed and have been underway for the past two years to investigate one mechanical property, i.e. tensile strength, and the effect of one structural feature, i.e. grain size, on this property. A clear relationship has been established, and is reported here. Other work is in progress and will also be reported in due course. Equiaxed and randomly oriented aggregates of freshwater ice, of grain size (as seen in two-dimensional sections) varying from 1.0 to 7.3 mm, were prepared in the form of large cylinders (91 mm diameter × 231 mm length). The aggregates were deformed to fracture under uniaxial tension, using a specially designed ball-joint and yoke assembly to ensure axial loading. Data were obtained at -10 ±0.2°C (i.e. at 96% of the melting point) at a strain-rate of 10−6 s−1. Figure 1 shows that the tensile strength decreases with increasing grain size, from 1.25 MPa for d = 1 mm to 0.80 MPa for d = 7 mm. Moreover, this figure illustrates that the data are highly reproducible; i.e. that strength is reproducible to within ±5% for a given grain size over the complete range. Fig. 1. Graph showing the decrease in the tensile strength of ice with increasing grain size. Concerning the functional relationship between tensile strength of and grain size, analysis shows that the following equation is well obeyed: Where σj is 0.6 MPa and k is 0.02 MPa m½ at -10°C and 10−6 s−1. This point is illustrated in Figure 2. Fig. 2. Hall-Petch plot showing the relationship between the tensile strength and the grain size of the ice. The d−½ character of this relationship, which is of the classical Hall-Petch form observed frequently in metallic materials, indicates that the tensile strength of ice is controlled by some process involving stress concentration, possibly the propagation of microcracks nucleated by the interactions of dislocations or the propagation of pre-existing defects. Of these, the former is the more probable. The reason is that processes involving dislocation motion, when expressed by the difference of σf – σi, are expected to increase linearly with increasing d−½, whereas processes involving the propagation of pre-existing defects predict a linear relationship between σf and d−½ which extrapolates through the origin. The former behavior is the one observed. It is thus concluded: (i) that the tensile strength of equiaxed and randomly oriented freshwater ice, when deformed slowly at -10°C, decreases with increasing grain size, (ii) that the functional relationship between tensile strength σf and grain size d is σf = σj + kd−½, where σj and k are materials parameters, and (iii) that the tensile strength of polycrystalline ice is controlled by the propagation in a brittle manner of microcracks nucleated by dislocation interactions. Acknowledgement This work was funded by the US Army Research Office, Contract No. DAA G-29-80-C-0064.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...