Furniture Design Ideas

Numerical modelling of soft tissues requires gathering of experimental data of biomechanical properties of these bodies. In conducting studies on the properties of soft tissue, on large samples of research material (pork liver), Hu and Desai (2005) assumed that the tissue is a material that is incompressible, homogenous and isotropic. Assuming the load force of […]

This chapter presents the results of the axial compression of polyurethane foams study (Fig. 8.17), for which a nonlinear model of Mooney-Rivlin was built and a numerical analysis of contact stresses was conducted. By building a mathematical model of elastic foam, it was assumed that this is a model • of isotropic and nonlinear material, […]

Table 8.2 compares the values of material parameters of the foams determined in the course of experimental research through axial compression and calculated on the basis of the equation: with the results of numerical calculations with the use of the finite elements method. On the basis of the compiled values, it can be seen that […]

When considering the homogeneity of the strain, the constant strain gradient can be written in the form: where a0, a(t) sizes of the angle and h0, h(t) heights of the examined sample before and during the strain. If the foam sample is loaded only in the direction of axis 3, then stresses in the direction […]

The optimisation of the construction of mattresses and/or seats is very important in the use of furniture for sleeping and relaxation, motor vehicles, aircrafts or reha­bilitation medical equipment. Descriptions of the mechanics of hard foams are known on the basis of articles of Renz (1977, 1978). Czysz (1986) described the behaviour of soft polyurethane foams […]

This equation has the form: N N і U = £ C00Q1 – 3У+ Y, D J – 1)Ъ; (8.44) i=1 i=1 1 where U potential energy of strains per volume unit, N material parameter and Cj and D1 temperature-dependent material coefficients, /1 = 12 + Ц +12, (8.45) whereby !i = J-3ki, (8.46) where […]

The equation for potential energy of strains according to Marlow has the form: U = Udev(!t) + Uvol (Jel), (8.32) where U is the potential energy of strains per volume unit, with Udev as the deformed part and Uvoi as the volume part—undeformed, 7j = k2 + k2 + k^, (8.33) whereby к = J-hi, […]

This model is very similar to the incompressible material model: w = £ a jei( if+if+ifo – 3+£ «I (yi _ f), ‘ =1 1 1 ’ where the initial shear modulus has the form: and module Ko: N (1 ^ jo = 53 3 + A) . Ogden’s models are mainly used for modelling […]

There are 2-, 3-, 5- and 9-parametric Mooney-Rivlin models known. Mooney-Rivlin model with two parameters: Mooney-Rivlin model with nine parameters, where N =3: 3 _ _ 1 W — ^ Cj(h – 3)Xh – 3)J – (Jel – 1)2. (8.18) t+j=1 – For all forms of the Mooney-Rivlin function, the initial value of the shear […]

Elastomers are a class of polymers having the following characteristics: • They include natural and synthetic rubbers; they are amorphous and consist of long molecular chains (Fig. 8.10); • The molecular chains are strongly twisted, spiral and randomly oriented in undeformed form; and • The molecular chains during stretching get partially straightened; however, when the […]