scholarly journals Statistical analysis of mechanical properties of wood

2019 ◽  
Vol 6 (7) ◽  
pp. 64-67
Author(s):  
Agarana et al. ◽  
Author(s):  
Fathima Banu Raza ◽  
Anand Kumar

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.


2021 ◽  
Vol 113 ◽  
pp. 36-42
Author(s):  
Barbara Białowąs ◽  
Karol Szymanowski

Effect of thermomechanical densification of pine wood (Pinus sylvestris L.) on cutting forces and roughness during milling. The paper presents the results of research concerning the assessment of machinability of pine wood thermomechanically compacted. The assessment was made on the basis of the cutting forces and surface roughness after the milling process. Selected properties of native and modified wood were examined. Based on the research, it was found that compacted wood is characterized by higher cutting forces during milling. The surface quality after milling was examined and the roughness index Ra values were determined. The research shows that the modified wood is characterized by a lower Ra value both along and across the grain. Statistical analysis showed that the modification had a statistically significant effect on the values of cutting forces and the physical and mechanical properties of the tested wood.


2019 ◽  
Vol 25 ◽  
pp. 89-92
Author(s):  
Adrian Wit ◽  
Sebastian Wronski ◽  
Jacek Tarasiuk

Bone trabecular structure can be characterized as a connected network of mineral bars and plates with unique mechanical properties. Standard methods of producing bone-like structures based on periodic structures or foams have same limitations. The organization of the trabecular bone (meso scale) is adapted to the values of stresses and strains affecting the skeletal system. To simulate bone-like structure, the methodology of generating stochastic structure based on hyperuniform spatial points distribution is proposed. Statistical analysis of generated structure shows the possibility to generate clouds of points in wide range of random close packing density, up to 59.52%. Points connected by Voronoi tessellation produce to unique porous topology with no closed-cells and with wide range of connectivity. Manufacturing of a generated structure is only limited by used technique. The proposed algorithm was developed regardless of the manufacturing technique, however, same examples of the structure were printed using 3D addictive technology. The mechanical properties of developed structure are strongly dependent on the material from which they are made, but the modification of the structure allows to change the strength in specific and controlled way.


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