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Träs tryckfasthet vinkelrätt fiberriktningen

Rosengren, Mikael LU (2010) VSM820 20101
Structural Mechanics
Civil Engineering (M.Sc.Eng.)
Abstract
At present there are no concrete guidelines how to calculate the pressure resistance capacity of the timber at the load perpendicular to grain. The test options ASTM, CEN and ICO gives three different results in testing of an equal body. With this knowledge the value for the characteristic compressive strength capacity of the pressure perpendicular to the grain will be reduced to 2.7 MPa. The reduction is chosen for all loading situations. Since no major evaluation has been made how current a reduction is or in which loading situations it should apply for, it will be evaluated in this thesis. In order to make concrete assessments, own tests will be performed and several different models will be analyzed using the finite element method.

The... (More)
At present there are no concrete guidelines how to calculate the pressure resistance capacity of the timber at the load perpendicular to grain. The test options ASTM, CEN and ICO gives three different results in testing of an equal body. With this knowledge the value for the characteristic compressive strength capacity of the pressure perpendicular to the grain will be reduced to 2.7 MPa. The reduction is chosen for all loading situations. Since no major evaluation has been made how current a reduction is or in which loading situations it should apply for, it will be evaluated in this thesis. In order to make concrete assessments, own tests will be performed and several different models will be analyzed using the finite element method.

The finite element method is a numerical calculation with help of boundary worthy differential equations it can solve a problem in an approximate way. To do all stress and strain calculation a finite element program has been used, ABAQUS. ABAQUS is an advanced program that can solve the static and in some cases even dynamic problem for two-dimensional and three-dimensional models. ABAQUS can solve nonlinear problems, which is something that is important in this thesis because the plastic phase for wood is nonlinear. In this thesis all the designed models are made in three dimensions and have been analyzed in static condition for both linearly as non-linear behavior.

A test has been done for two different loading situations. This is to get a better picture how the stress and strain relation works when a load react perpendicular to the grain. Another purpose of the testing is to obtain stress and strain data that can be compared to the material model in ABAQUS.

In order to create a material model in ABAQUS that is comparable to real life, stress and strain data from Suensons testing in 1938 has been used. Material model in ABAQUS was adapted so that it is consistent against all the five tests that were performed by Suenson. When the material model was consistent to Suensons tests, an additional verification of the developed model were made. The samples from the test that was made in this report were modeled in ABAQUS and the results were compared. The results from the comparison were in good agreement because the
structure of the curves was similar.

When the material model in ABAQUS gave correct values for the stress and strain diagrams the ability to analyze other loading situations were possible. Four of the most common load cases were modeled and analyzed. Even though the structure of the diagrams from ABAQUS is correct in correlation to reality, it is very dependent on the quality of the selected timber. Therefore a normalization of the diagrams was made to make them material dependent. The stress is dependent on the pressure
resistance capacity of the chosen material and strains are dependent on both the pressure resistance capacity and the elasticity module for the radial and tangential direction. (Less)
Please use this url to cite or link to this publication:
author
Rosengren, Mikael LU
supervisor
organization
course
VSM820 20101
year
type
H3 - Professional qualifications (4 Years - )
subject
report number
TVSM-5171
ISSN
0281-6679
language
Swedish
id
3566973
date added to LUP
2013-08-02 10:30:54
date last changed
2013-10-07 13:17:10
@misc{3566973,
  abstract     = {At present there are no concrete guidelines how to calculate the pressure resistance capacity of the timber at the load perpendicular to grain. The test options ASTM, CEN and ICO gives three different results in testing of an equal body. With this knowledge the value for the characteristic compressive strength capacity of the pressure perpendicular to the grain will be reduced to 2.7 MPa. The reduction is chosen for all loading situations. Since no major evaluation has been made how current a reduction is or in which loading situations it should apply for, it will be evaluated in this thesis. In order to make concrete assessments, own tests will be performed and several different models will be analyzed using the finite element method.

The finite element method is a numerical calculation with help of boundary worthy differential equations it can solve a problem in an approximate way. To do all stress and strain calculation a finite element program has been used, ABAQUS. ABAQUS is an advanced program that can solve the static and in some cases even dynamic problem for two-dimensional and three-dimensional models. ABAQUS can solve nonlinear problems, which is something that is important in this thesis because the plastic phase for wood is nonlinear. In this thesis all the designed models are made in three dimensions and have been analyzed in static condition for both linearly as non-linear behavior.

A test has been done for two different loading situations. This is to get a better picture how the stress and strain relation works when a load react perpendicular to the grain. Another purpose of the testing is to obtain stress and strain data that can be compared to the material model in ABAQUS.

In order to create a material model in ABAQUS that is comparable to real life, stress and strain data from Suensons testing in 1938 has been used. Material model in ABAQUS was adapted so that it is consistent against all the five tests that were performed by Suenson. When the material model was consistent to Suensons tests, an additional verification of the developed model were made. The samples from the test that was made in this report were modeled in ABAQUS and the results were compared. The results from the comparison were in good agreement because the
structure of the curves was similar.

When the material model in ABAQUS gave correct values for the stress and strain diagrams the ability to analyze other loading situations were possible. Four of the most common load cases were modeled and analyzed. Even though the structure of the diagrams from ABAQUS is correct in correlation to reality, it is very dependent on the quality of the selected timber. Therefore a normalization of the diagrams was made to make them material dependent. The stress is dependent on the pressure
resistance capacity of the chosen material and strains are dependent on both the pressure resistance capacity and the elasticity module for the radial and tangential direction.},
  author       = {Rosengren, Mikael},
  issn         = {0281-6679},
  language     = {swe},
  note         = {Student Paper},
  title        = {Träs tryckfasthet vinkelrätt fiberriktningen},
  year         = {2010},
}