The wood is a brittle material, so the maximum normal stress theory is best theory of failure.

At the end of the day none of this suggestions can describe wood (which wood???) even in a rough approximation. It's highly anisotropic and nonlinear material behaviour in the elastic as well as the plastic domain are only two main facts, which cannot be challenged by such a kind of question. A possible starting point for literature can be:

Szalai, J., 1994: Anisotrope Elastizitäts- und Festigkeitslehre für Holz und Holzwerkstoffe

- Teil 1. Anisotropie der mechanischen Eigenschaften.

Szalai, J., 2008: Festigkeitstheorien von anisotropen Stoffen mit sprödem Bruchverhalten

Teil 1: Vergleich und Beurteilung der anisotropen Festigkeitskriterien auf Grund von

theoretischen Überlegungen. Acta Silvatica & Lignaria Hungarica 4, 61–79.

Schmidt, J., 2009: Modellierung und numerische Analyse hölzerner Strukturen. Habilitationsschrift,

Technische Universität Dresden.

Schmidt, J.; Kaliske, M., 2006: Zur dreidimensionalen Materialmodellierung von Fichtenholz

mittels eines Mehrflächen-Plastizitätsmodells. Holz als Roh- und Werkstoff 64,

393–402.

Mackenzie-Helnwein, P.; Eberhardsteiner, J.; Mang, H. A., 2005a: Rate independent

mechanical behavior of biaxially stressed wood: Experimental observations

and constitutive modeling as an orthotropic two-surface elasto-plastic material. Holzforschung

59, 311–321.

Eberhardsteiner, J., 2002: Mechanisches Verhalten von Fichtenholz. Springer-Verlag.

Thanks Stefan!

Unfortunately I can´t read in German, but I'll sure try to read Mackenzie-Helnwein et al. 2005. As a matter of fact, I just found the abstract of their book, which refers to the "ductile compression behaviour of wood".

Because I'm just interested now in the compression issue, can I then use the von Mises stress criterion?

So you can better understand my aims, I´m working with the following woods: Yew, willow, hazel, ash, pine, oak, and elm; in order to be able to simulate the function of several ancient objects.

Cheers,

Hello Vera,

the von Mises stress criterion is weighing the different oriented stresses to one "mixed" stress, which is not suitable to be compared to a scalar failure value for wood. I don't know the functionality of the solidworks simulation software but as the name and your description is suggesting I expect there is only an isotropic material failure description included, which is a rough approximation for wood in an one-dimensional calculation even in the principle directions of your chosen wooden material.

You should at least consider three direction dependent strength resp. "yield" values for every wood species. To get an idea for the R-T direction for beech wood:

Hering, S.; Saft, S.; Resch, E.; Niemz, P.; Kaliske, M.; Characterisation of moisture-dependent plasticity of beech wood and its application to a multi-surface plasticity model, Holzforschung,66,3,373-380,2012, http://www.degruyter.com/view/j/hfsg.2012.66.issue-3/hf.2011.162/hf.2011.162.xml

Thanks again Stefan!

As wood is an orthotropic material, I've already conducted real-world tests to obtain several physical and mechanical properties (including yield values) of each of the mentioned wood samples, in all 3 different axis (radial, tangential, and longitudinal; i.e., perpendicular and parallel to the grain).

Since Solidworks has the limitation of only allowing to choose one failure criterion (Maximum von Mises stress, Maximum Shear Stress, Mohr-Coulomb Stress, or Maximum Normal Stress) in each simulation test, in your opinion which one would you use to run the tests on, say, the function of a bow?

Cheers,

The wood is a brittle material, so the maximum normal stress theory is best theory of failure.

Vera, I am interested in doing something very similar, but with cranes instead of bows. What conclusions did you come to? How did you convert the six poisson's ratios shown in Table 4c.5 of your thesis into the three inputs to SolidWorks Simulation for orthotropic materials (XY-XZ-YZ)? regards, Duncan