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In the joint replacement surgery, the alumina ceramic are widely used as femoral heads for total hip replacements as an alternative to metal parts. Alumina ceramic materials has good mechanical properties, corrosion resistance, wear resistance, and biocompatible properties. However, the alumina ceramics typically exhibit brittle behavior thus limiting their performance under certain conditions. Due to some machining difficulties, there is almost no direct measurement of dynamic tensile properties of ceramics in the strain rate ranges between 500 s−1 and 5000 s−1. To understand dynamic tensile response of alumina ceramics, Flattened Brazilian Disc method with Split Hokinson Pressure Bar was utilized. In this research, the dynamic fracture process of the alumina ceramic at various tensile loading rates was studied. The effects of sample size were also monitored and analyzed. This paper explores the feasibility of applying the tensile behavior of alumina ceramics to total hip arthroplasty using a Brazilian Disc method.

In this study, the mechanical properties of Caladium (Caladium × hortulanun Birdsey) petiole were investigated. The petiole was considered as a composite beam which consists of rind and core parts. To classify the mechanical properties of rind and core part of petioles, two-phase three-point bending tests were conducted on the specimens cut from petioles. Linear beam theory was used to convert the time-dependent bending forces, during the three-point bending tests, to relaxation moduli. The result shows that the mechanical properties of rind and core parts of Caladium are very different. The relaxation modulus of rind is approximate 40 times higher than relaxation modulus of core at time = 600 s after applying bending load, and the relaxation time distribution of core is wider than the relaxation time distribution of core. The three- and seven-parameter linear viscoelastic constitutive models were used to describe the time-dependent relaxation moduli of rind and core of caladium petiole. The fitted results show that the seven-parameter Wiechert model can describe the viscoelastic behaviour of Caladium petiole very well. The finite element analysis was used to assess the error of this test methodology. The reaction force error because of the tapered diameter of specimens is about 12%.

In order to optimize the design of milling machinery for rice varieties, it is important to understand the mechanical properties such as strength and damage properties of grains of different varieties of rice. The ratio of amylose of rice not only affects the texture of cooked rice but also the mechanical properties of raw rice grain. In this study, the damage properties of different breeds of rice with three different levels of amylose ratios were investigated. The damage properties were investigated by using compression and three point bending tests. The compression tests were conducted on rice specimens with two parallel surfaces made from rice grains and the three point bending tests were conducted on whole rice grains. Although the compression force to break rice kernel under 3 point bending are similar for all types of rice under tests. It can be seen that, among the rice varieties under tests, Chainat 1, the high amylose ratio rice, has the highest compression strength. The understanding of this study can help the developing of methods and devices used for milling processing of rice with different level of amylose to reduce the milling losses.

This work investigated the time dependent mechanical properties of bovine enamel. The cubic specimens of enamel were prepared from bovine incisors and the ramp-hold compression tests were performed to acquire the stress-time and strain-time relation of enamel under compress load. In this study, enamel was considered as linear viscoelatic material. The long-term elastic modulus of enamel was evaluated from the stress and strain relations at the end of ramp-hold tests and the relaxation behaviour of enamel was estimated from the normalized stress-time curves of ramp-hold tests. The relaxation coefficients and characteristic times of linear viscoelastic model were obtained by using iterative inverse finite element method. The results show that a linear viscoelastic model with 3 relaxation time constants can well describe the time dependent behaviour of bovine enamel under uni-axial compression load.

This study examined the time dependent mechanical properties of porcine meniscus under unconfined compression condition. The ramp-hold compression tests with different ramping displacement rates and long-term compression tests with very low displacement rate were performed on porcine meniscus specimens. The time dependent mechanical response of porcine meniscus was described by hyper-viscoelastic constitutive model due to its simplicity and can be easily implemented to finite element models. Inverse iterative finite element analysis procedure was used to obtain the material parameters of hyper-viscoelastic models of meniscus in two stages. In the first stage, the long-term hyperelastic material parameters of meniscus were obtained from the compression test data with very low displacement rate. The long-term hyperelastic material parameters were used as known parameters in the second stage, and the time dependent material parameters were determined from the ramp-hold compression tests with different ramping displacement rates. It can be seen from the force-time curves of ramp-hold experimental data that the mechanical properties of meniscus is highly time-dependent. The instantaneous modulus is more than 50 times higher than the long-term elastic modulus. The third-order reduce polynomial hyper-viscoelastic model established in this study can well describe the mechanical behavior of porcine meniscus under compression load. This model can be used in the finite element study of meniscus biomechanics.

An inverse iterative finite element analysis procedure was developed to investigate mechanical properties of porcine articular cartilage under compression load. Specimen consists of articular cartilage and bone was cut from porcine femur for this study. The specimen was mounted on metal base plate and the compression tests were performed by using material test machine with flat compression plate. The ramp-hold compression tests with different ramping displacement rates and long-term compression test with very low displacement rate were performed on the specimens. The force and compression displacement as function of time were recorded. The profile of specimen was obtained from for generating the geometry model of specimen. The finite element model which consists of bone and cartilage parts was generated from the geometry model of specimen. In this study, bone and cartilage were considered as linear elastic material and hyperviscoelastic material respectively. The generalized pattern search method was used for the optimization process to find the long-term hyperelastic and viscoelastic parameters of cartilage by minimize the experimental loading forces and the reaction forces computed form finite element analysis. The results shows 2nd order reduce polynomial hyperelastic model with two viscoelastic time constants can well describe the mechanical response of articular cartilage and bone specimen under flat plate compression.

Tendril is a threadlike specialized stem, leaf or petiole used by climbing plants for support and attachment. The spiral contraction which occurs after a tendril has caught an object is of great use to the climbing plant. The spiral contraction can drags up the shoot thus there is no waste of growth. Besides, a far more important use rendered by the spiral contraction of the tendrils is that they are thus made highly elastic so that the force is distributed between several adjacent attached tendrils; and this renders the whole far stronger than it otherwise would be, as the tendrils cannot break separately. It is this elasticity that protects the plants from being torn away from their supports during stormy weather or pulled by object. In this study, the mechanical properties of Luffa tendrils were investigated. By using tensile experiments and finite element analyses, the time dependent mechanical properties of attached mature tendrils of Luffa under tensile loads were investigated. The improvement of supporting capability of Luffa tendrils due to spiral contraction was quantified. The results of the finite element analyses showed the maximum tensile force on a tendril can be reduced more than 58% due to distributing force to 4 adjacent attached tendrils when applied concentrated force on the stem.