Home About us Contact
|
Home About us Contact | ||
|
|
||
Uniaxial Compression Tests (uniaxial + compression_test)
Selected AbstractsTHE ANALYSIS OF STRESS RELAXATION DATA OF SOME VISCOELASTIC FOODS USING A TEXTURE ANALYZER,JOURNAL OF TEXTURE STUDIES, Issue 4 2006H. SINGH ABSTRACT Uniaxial compression test for dough and several commercial products like jello, mozzarella cheese, cheddar cheese, tofu and sausage (cooked and uncooked) was performed using a texture analyzer (TA). Percent stress relaxation (%SR ), k1 (initial rate of relaxation), k2 (extent of relaxation) and relaxation time (RT) were calculated and compared for different products. The TA software was used to convert the raw SR data into a linear form. Constants k1 and k2 were determined from the intercept and slope of the linear data. Higher values of %SR and k2 (90 and 9, respectively) indicated higher elasticity for jello, whereas wheat flour dough samples showed the lowest values (20,30) for %SR and 1 to 2 for k2. The RT and k1 values were not good indicators for differentiating different products based on their viscoelastic behavior. Measurement of RT was limited by the maximum time for which the data were collected, whereas k1, because of its mathematical form, needed careful interpretation. In this study, %SR was found to be a good measure to interpret viscoelasticity of different food samples. [source] VARIATIONS IN FLEXURAL AND COMPRESSIVE FRACTURE BEHAVIOR OF A BRITTLE CELLULAR FOOD (DRIED BREAD) IN RESPONSE TO MOISTURE SORPTIONJOURNAL OF TEXTURE STUDIES, Issue 5 2000Y. P. CHANG Mechanical properties of dried bread (a cellular baked product) equilibrated at different water activities (Aw) were measured using three-point bending and uniaxial compression to compare their responses to moisture sorption. The glass-to-rubber transition was clearly demarcated in all the mechanical property-Aw curves, although there were differences in critical Aw (0.32,0.56) at which the dramatic changes in mechanical properties occurred. The role of water appeared to be strictly that of a plasticizer where flexural mechanical parameters were concerned, leading to reduced modulus and fracture stress but increased fracture strain with increasing Aw. Uniaxial compression tests revealed moisture-induced mechanical antiplasticization effects on the material in the glassy state which resulted in maximum compressive fracture stress but minimum fracture strain over the Aw range from 0,0.56. Compressive modulus apparently was not affected much by moisture sorption up to an Aw of 0.43, above which it decreased sharply. [source] From CT Scan to Ceramic Bone GraftJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Jens Darsell An indirect fused deposition process was used to fabricate controlled-porosity alumina bone grafts using a computer-aided-design file created from computed tomography (CT) scans of a horse's short pastern bone. Structures with both uniform and gradient porosity were fabricated to show the effectiveness of this process for the fabrication of custom orthopedic implants. Cytotoxicity and cell proliferation studies were conducted with different cell lines to show that these bone grafts are biocompatible. Uniaxial compression tests were also conducted to understand the influence of porosity on the mechanical properties of these structures. [source] Brittle-to-Ductile Transition in Uniaxial Compression of Silicon Pillars at Room TemperatureADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Fredrik Östlund Abstract Robust nanostructures for future devices will depend increasingly on their reliability. While great strides have been achieved for precisely evaluating electronic, magnetic, photonic, elasticity and strength properties, the same levels for fracture resistance have been lacking. Additionally, one of the self-limiting features of materials by computational design is the knowledge that the atomistic potential is an appropriate one. A key property in establishing both of these goals is an experimentally-determined effective surface energy or the work per unit fracture area. The difficulty with this property, which depends on extended defects such as dislocations, is measuring it accurately at the sub-micrometer scale. In this Full Paper the discovery of an interesting size effect in compression tests on silicon pillars with sub-micrometer diameters is presented: in uniaxial compression tests, pillars having a diameter exceeding a critical value develop cracks, whereas smaller pillars show ductility comparable to that of metals. The critical diameter is between 310 and 400,nm. To explain this transition a model based on dislocation shielding is proposed. For the first time, a quantitative method for evaluating the fracture toughness of such nanostructures is developed. This leads to the ability to propose plausible mechanisms for dislocation-mediated fracture behavior in such small volumes. [source] Experimental study and constitutive modelling of elasto-plastic damage in heat-treated mortarINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2010Xiao-Ting Chen Abstract This study investigates the effect of a heat-treatment upon the thermo-mechanical behaviour of a model cement-based material, i.e. a normalized mortar, with a (w/c) ratio of 0.5. First, a whole set of varied experimental results is provided, in order to either identify or validate a thermo-mechanical constitutive model, presented in the second paper part. Experimental responses of both hydraulic and mechanical behaviour are given after different heating/cooling cycling levels (105, 200, 300, 400,C). The reference state, used for comparison purposes, is taken after mass stabilization at 60,C. Typical uniaxial compression tests are provided, and original triaxial deviatoric compressive test responses are also given. Hydraulic behaviour is identified simultaneously to triaxial deviatoric compressive loading through gas permeability Kgas assessment. Kgas is well correlated with volumetric strain evolution: gas permeability increases hugely when ,v testifies of a dilatant material behaviour, instead of contractile from the test start. Finally, the thermo-mechanical model, based on a thermodynamics approach, is identified using the experimental results on uniaxial and triaxial deviatoric compression. It is also positively validated at residual state for triaxial deviatoric compression, but also by using a different stress path in lateral extension, which is at the origin of noticeable plasticity. Copyright © 2009 John Wiley & Sons, Ltd. [source] An experimental analogue to model the fibrous tissue layer in cemented hip replacementsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004Victor Waide Abstract Fibrous tissue at the bone,cement interface of cemented joint replacements has been reported frequently in cases of revisions made necessary by aseptic loosening. This work describes the development of in vitro specimens suitable for biomechanical modeling of cemented femoral hip replacements with a fibrous tissue layer at the bone,cement interface. In particular, a series of uniaxial compression tests were performed on silicone elastomer specimens to identify a suitable analogue with similar mechanical characteristics to those reported for the fibrous tissue layer. A method was developed to apply the silicone elastomer at the bone,cement interface. This was examined for two types of cemented hip replacements implanted in composite femurs. The selected thickness of the elastomer layers was in the range of those found in clinical cases of aseptic loosening. Specimens produced by these methods could be used in preclinical biomechanical tests (such as stability or stress shielding tests) to assess the effects of a soft-tissue layer, to model in vitro a long-term-implant scenario, and to provide validation for similar finite element studies. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 232,240, 2004 [source] CHARACTERIZATION OF THE NONLINEAR VISCOELASTIC CONSTITUTIVE PROPERTIES OF MILD CHEDDAR CHEESE FROM INDENTATION TESTSJOURNAL OF TEXTURE STUDIES, Issue 5-6 2005S.M. GOH ABSTRACT A methodology to convert the indentation force,displacement response into the stress,strain properties of nonlinear viscoelastic materials was evaluated. Mild cheddar cheese was used as the test material, and indentation tests were performed using two spherical indenters of different sizes. The indentation tests were performed at different speeds, and the corresponding force,displacement responses were fitted with an analytical solution to obtain the time-dependent constants and the instantaneous force,displacement response. An inverse analysis based on the finite element method was performed to obtain the strain-dependent constants from the instantaneous force,displacement response. The predictions of the viscoelastic stress,strain properties from the indentation tests were compared to independent measurements through uniaxial compression tests, and a reasonable agreement was obtained. [source] | ||||||||||