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Highlights Sandwich structures have garnered interest as versatile structures for applications in advanced engineering structures. To fabricate sandwich structures, plastics have replaced conventional materials; however, most of these plastics remain in the environment beyond their functional lifespan. This study describes the fabrication of sustainable hybrid sandwich structures with 3D printed poly‐lactic acid (PLA) cores and self‐reinforced polyethylene terephthalate (srPET) face sheets. The mechanical responses of the hybrid sandwich structures with three types of lattice cores, S‐90, S‐45, and S‐V, were compared with those of the parent material sandwich structures after performing bending and impact tests. The face sheet in the hybrid sandwich structure transferred the load to the core without failure. The hybrid sandwich structure containing the S‐90 core exhibited a higher fracture strength (52.4 MPa) and tangent modulus of elasticity (2860 MPa) than those of the other structures. S‐V exhibited the highest fracture strains of 3.3% and 5% for parent material and hybrid sandwich structures, respectively. This study highlights the sandwich structures with excellent mechanical properties for structural applications. Novel sandwich structures with 3D printed PLA cores are fabricated. Three‐point bending and low‐velocity impact tests are performed. Failure occurred in the core, but the Sr‐PET face sheets did not deform. Hybrid sandwich structures significantly improve mechanical performance. [ABSTRACT FROM AUTHOR]

The mechanical properties of sclera play an important role in ocular functions, protection, and disease. Modulating the sclera's properties by exogenous crosslinking offers a way to expand the tissue's range of properties for study of the possible influences on the eye's behavior and diseases such as glaucoma and myopia. The focus of this work was to evaluate the effects of genipin crosslinking targeting the porcine perilimbal sclera (PLS) since the stiffness of this tissue was previously found in a number of studies to influence the eye's intraocular pressure (IOP). The work includes experiments on tensile test specimens and whole globes. The specimen tests showed decreased strain-rate dependence and increased relaxation stress due to the cross-linker. Whole globe perfusion experiments demonstrated that eyes treated with genipin in the perilimbal region had increased IOPs compared to the control globes. Migration of the cross-linker from the target tissue to other tissues is a confounding factor in whole globe, biomechanical measurements, with crosslinking. A novel quantitative genipin assay of the trabecular meshwork (TM) was developed to exclude globes where the TM was inadvertently crosslinked. The perfusion study, therefore, suggests that elevated stiffness of the PLS can significantly increase IOP apart from effects of the TM in the porcine eye. These results demonstrate the importance of PLS biomechanics in aqueous outflow regulation and support additional investigations into the distal outflow pathways as a key source of outflow resistance. [ABSTRACT FROM AUTHOR]

Defects, such as cell wall thickness variations, significantly influence cellular materials' mechanical characteristics. For instance, during a compression test in deformation mode, the crush bands are initiated at cells with a thinner wall thickness. This paper examines the effect of boundary irregularity on the nonlinear elastoplastic mechanical behavior of platelet-reinforced composite materials. Two types of stochastic (random distribution) platelets: with rounded corners and with sharp corners are generated using the Voronoi tessellation method. To better compare the effect of boundary irregularity, the composites are analyzed for three different volume fractions. The microstructure of the composite studied consists of isotropic and linear elastic platelets embedded in a perfectly plastic elastic matrix. Nonlinear numerical simulation of the tensile test was carried out using FE Zebulon software. The results show that the composites exhibit bilinear stress-strain behavior, consisting of two lines representing, respectively, the linear behavior (whose slope is Young's modulus) and the plastic behavior (whose slope is the strain hardening modulus). The effective Young's modulus, yield strength, and tangent modulus of the composites are calculated and compared in terms of the shape and volume fraction of the platelets. In the elastic zone, the results indicate that the curves of the two types of stochastic platelets overlap, giving very close results for Young's modulus. In the plastic zone, the effect of platelet irregularity is noticeable. It has been found that the platelets with rounded corners have a higher tangent modulus than those with sharp corners. This deference can improve the composite's ability to withstand more deformation under high loads, unlike platelets with sharp edges. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Engineered bamboo has been getting recognition as a forerunner in terms of desirable mechanical properties and a sustainable construction material. One of the most widespread variants is bamboo scrimber, also known as Parallel Bamboo Strand Lumber (PBSL). This paper presents a holistic investigation into the uniaxial compressive capacity of short bamboo scrimber columns in terms of failure mode, size effect, aspect ratio and failure strain. The studies in focus have been collated from published articles in literature. Furthermore, intermediately slender to long columns have been investigated with respect to the most common international timber standards and, elastic and inelastic theories. It is shown that the dominant failure mode affects the ultimate strength, especially a failure mode called kinking/local buckling. A size effect was observed and discussed with respect to the failure modes. In addition, a tangent modulus theory was proposed from a constitutive model called the Full-range Ramberg Osgood model that could better predict the critical buckling stress of intermediate-long columns over the conventional theory. Moreover, a modified AS1720 design approach was proposed to accommodate the inherent column behaviour of bamboo scrimber. Finally, a modified Newlin-Gahagan approach was proposed which produced consistent predictions for the experimental buckling stress for columns with varying slenderness across four different studies.

Sophisticated muscle material models are required to perform detailed finite element simulations of soft tissue; however, state-of-the-art muscle models are not among the built-in materials in popular commercial finite element software packages. Implementing user-defined muscle material models is challenging for two reasons: deriving the tangent modulus tensor for a material with a complex strain energy function is tedious and programing the algorithm to compute it is error-prone. These challenges hinder widespread use of such models in software that employs implicit, nonlinear, Newton-type finite element methods. We implement a muscle material model in Ansys using an approximation of the tangent modulus, which simplifies its derivation and implementation. Three test models were constructed by revolving a rectangle (RR), a right trapezoid (RTR), and a generic obtuse trapezoid (RTO) around the muscle's centerline. A displacement was applied to one end of each muscle, holding the other end fixed. The results were validated against analogous simulations in FEBio, which uses the same muscle model but with the exact tangent modulus. Overall, good agreement was found between our Ansys and FEBio simulations, though some noticeable discrepancies were observed. For the elements along the muscle's centerline, the root-mean-square-percentage error in the Von Mises stress was 0.00%, 3.03%, and 6.75% for the RR, RTR, and RTO models, respectively; similar errors in longitudinal strain were observed. We provide our Ansys implementation so that others can reproduce and extend our results. [ABSTRACT FROM AUTHOR]

The tangent modulus method of undisturbed soil is a new method in settlement calculation, which is mainly applied to hard soil with a strong structure, such as silty clay, completely weathered rock, and granite residual soil with an SPT blow count greater than 8. The tangent modulus is mainly obtained from a field plate load test, which can consider the influence of the soil stress level and reflect the nonlinear characteristics of the foundation settlement. In a multi-layer soil foundation, since the deep plate loading test is difficult, a method was proposed to determine the tangent modulus of deep soil. It is assumed that the ratio of the initial tangent modulus to the deformation modulus is equal to the ratio of the unloading–reloading modulus E ur ref to the secant modulus E 50 ref obtained by triaxial unloading–reloading test. Since there are corresponding empirical formulae for SPT counts and the deformation modulus of different types of soils in many regions, the initial tangent modulus can be derived by the above method. In two cases of a composite foundation, the compression modulus and tangent modulus were used to calculate the settlement of the foundation, which is then compared with the measured results. The results show that the proposed method for determining the tangent modulus of deep soil is feasible in theory, and the calculating accuracy of the tangent modulus is significantly higher than that of the traditional compression modulus. [ABSTRACT FROM AUTHOR]

For the deep geological disposal of radioactive waste in France, an Underground Research Laboratory has been constructed in the formation of Callovo-Oxfordian (COx) claystone at a depth of about 490 m. During the excavation, damage of host rock occurred around the openings. To investigate the hydro-mechanical behaviour of damaged COx claystone in the laboratory, it is necessary to propose a method for the preparation of damaged sample because field sampling appears difficult. In this study, such a method was proposed by performing triaxial test loading paths (constant mean stress and constant confining pressure). The anisotropic behaviour of COx claystone was revealed by isotropic loading. The strain–stress curve from triaxial tests exhibited elasto-plastic pattern. Both the shear modulus G and the Young's modulus E decreased slightly with the increase of deviator stress, suggesting the damage behaviour. Interestingly, all results from this study and from the literatures showed that at 90% of the peak deviator stress qmax, the ratio ET,0.9/EI (where ET,0.9 represents the tangent modulus at 90% of qmax and EI represents the initial tangent modulus) is close to 0.22, suggesting that the tangent modulus ET is a good indicator of damage level for the COx claystone sample. Observation using X-ray computed tomography and Mercury intrusion porosimetry showed that the damaged sample is characterised by the creation of significant micro-cracks after the triaxial loading. This finding suggests that ET can be used to control the damage level in triaxial cell for preparing damaged COx claystone samples. Highlights: ET was used to analyse the evolution of damage during shearing. A unique relationship was found between the normalised ET/EI and the normalised q/qmax. A new method was developed to prepare damage claystone. Microstructure observations from CT and MIP tests indicated qualitatively the significant micro-cracks developed inside COx claystone. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a surface-mounted fiber optic conjugate stress sensor (FOCSS) is developed, fabricated, and experimentally demonstrated to accurately evaluate the instantaneous tangent modulus of various metals, thus allowing measurement of the elastic-plastic stressâ€"strain behavior of the host material. The originally proposed embedded version of the conjugate stress (CS) sensor measured the deformations experienced in two fully embedded, ellipsoidal, collocated sensors of significantly different stiffnesses, and related those sensor deformations to host modulus via Eshelby’s equivalent inclusion method. In contrast, the current experimental study focuses on a surface-mounted implementation of the CS sensor. As Eshelby’s analysis is not applicable in this case, a simplified lumped-element spring model is developed to instantaneously relate the deformations in the CS sensor to the local stressâ€"strain state of the host. Therefore, tangent modulus of the host can be estimated from the output of the FOCSS, which can serve as an important damage precursor in structural and prognostic health monitoring for a prominent set of failure mechanisms, including mechanical overstress, fatigue, and corrosion. In this study, the FOCSS data is used in conjunction with the lumped-element spring model to measure the elastic modulus of three different materials of significantly different stiffness: aluminum, copper, and steel. Additionally, as validation of instantaneous tangent modulus tracking, the elastic-plastic stressâ€"strain curves of copper and steel are reconstructed from the FOCSS outputs during uniaxial tensile tests (with a goodness of fit R 2 > 0.98). The results demonstrate the ability of the FOCSS to detect instantaneous modulus as materials experience plastic deformation. [ABSTRACT FROM AUTHOR]

It is still little or no knowledge about the properties of layered wood-based composites and nonwood components in the viscoelastic and plastic region of the force-deflection diagram (FDD). The properties of composites in this area are influenced by several factors such as the composition of the layered composite, the method of modification of the individual layers, the type of adhesive used, etc. This paper focuses on the analysis of the effect of the thickness of individual layers (5 and 9 mm) of beech wood (Fagus sylvatica L.), modification of these layers with different degrees of densification (10, 20, 30, and 40%) and the type of the nonwood component (carbon and high-strength glass fibers) used to reinforce the layered composite on the properties of materials in the plastic region of the FDD. The paper describes the impact of selected factors and those interactions behavior of the tangent modulus in the whole FDD. This is the first study that describes the development of layered wood-based composites and nonwood components in the viscoelastic and plastic region and analyzes the impact of most imported types of modifications on the characteristics in the viscoelastic and plastic regions.

Rockfill materials used for dam construction show obvious stress path dependency during construction process. The constitutive model for rockfill materials are mainly established based on conventional triaxial test. This brings some deviation to the numerical calculation for earth rockfill dam engineering, and it is necessary to develop a constitutive model considering stress paths effect. In the framework of generalized plasticity, plastic modulus can be expressed as the function of dilatancy equation and tangent modulus, hence the influence of stress paths on model can be transfer to the dilatancy equation and tangent modulus. This leads to a new method to describe stress-strain response of rockfill under various loading stress paths. Based on the analysis of large-scale triaxial experiments of rockfill materials with various stress paths, we proposed new dilatancy equation and tangent modulus to better describe stress paths effect and corresponding modified generalized plasticity model is established. Through the prediction and comparison of three groups of rockfill materials triaxial tests, the model established in this paper can simulate behaviors of rockfill materials under various stress paths, using only a set of parameters.

Method of predicting the strength of thin-walled tubes under a complex stress state, taking into account changes in the initial dimensions, is proposed. Uniform plastic deformation of a thin-walled tube under short-term static load by internal pressure and axial tension is considered. The tube material is considered to be homogeneous, isotropic and incompressible. The principle of maximum load is used to derive analytical dependences. The main decisions and conclusions were made using the Considere scheme.

Aging and disease alter the composition and elastic properties of the aortic wall resulting in shape changes in blood pressure waveform (BPW). Here, we propose a new index, harmonic distortion (HD), to characterize BPW and its relationship with other in vitro and in vivo measures. Using a Fourier transform of the BPW, HD is calculated as the ratio of energy above the fundamental frequency to that at the fundamental frequency. Male mice fed either a normal diet (ND) or a high fat, high sucrose (HFHS) diet for 2–10 months were used to study BPWs in diet-induced metabolic syndrome. BPWs were recorded for 20 s hourly for 24 h, using radiotelemetry. Pulse wave velocity (PWV), an in vivo measure of arterial stiffness, was measured in the abdominal aorta via ultrasound sonography. Common carotid arteries were excised from a subset of mice to determine the tangent modulus using biaxial tension-inflation test. Over a 24-h period, both HD and systolic blood pressure (SBP) show a large variability, however HD linearly decreases with increasing SBP. HD is also linearly related to tangent modulus and PWV with slopes significantly different between the two diet groups. Overall, our study suggests that HD is sensitive to changes in blood pressure and arterial stiffness and has a potential to be used as a noninvasive measure of arterial stiffness in aging and disease.

The tangent modulus method of undisturbed soil is a new method in settlement calculation, which is mainly applied to hard soil with a strong structure, such as silty clay, completely weathered rock, and granite residual soil with an SPT blow count greater than 8. The tangent modulus is mainly obtained from a field plate load test, which can consider the influence of the soil stress level and reflect the nonlinear characteristics of the foundation settlement. In a multi-layer soil foundation, since the deep plate loading test is difficult, a method was proposed to determine the tangent modulus of deep soil. It is assumed that the ratio of the initial tangent modulus to the deformation modulus is equal to the ratio of the unloading–reloading modulus Eurref to the secant modulus E50ref obtained by triaxial unloading–reloading test. Since there are corresponding empirical formulae for SPT counts and the deformation modulus of different types of soils in many regions, the initial tangent modulus can be derived by the above method. In two cases of a composite foundation, the compression modulus and tangent modulus were used to calculate the settlement of the foundation, which is then compared with the measured results. The results show that the proposed method for determining the tangent modulus of deep soil is feasible in theory, and the calculating accuracy of the tangent modulus is significantly higher than that of the traditional compression modulus.

The Achilles tendon stores and releases strain energy, influencing running economy. The present study aims to verify the influence of the Achilles tendon tangent modulus, as a material property, on running economy by comparing two groups of elite endurance-performance athletes undergoing different running training volumes. Twelve athletes, six long-distance runners and six pentathletes, were studied. Long-distance runners had a higher weekly running training volume (116.7±13.7 vs. 58.3±20.4 km, p<0.05) and a better running economy (204.3±12.0 vs. 222.0±8.7 O2 mL ∙ kg−1 ∙ km−1 , p<0.05) evaluated in a treadmill at 16 km·h–1 , 1% inclination. Both groups presented similar VO2max (68.5±3.8 vs. 65.7±5.0 mL ∙ min−1 ∙ kg−1 , p>0.05). Achilles tendon tangent modulus was estimated from ultrasound-measured deformations, with the ankle passively mobilized by a dynamometer. True stress was calculated from the measured torque. The long-distance runners had a higher maximum tangent modulus (380.6±92.2 vs. 236.2±82.6 MPa, p<0.05) and maximum true stress than pentathletes (24.2±5.1 vs. 16.0±3.5 MPa, p<0.05). The correlation coefficient between tangent modulus at larger deformations was R=–0.7447 (p<0.05). Quantifying tendon tissue adaptations associated with different running training volumes will support subject and modality-specific workouts prescription of elite endurance athletes. [ABSTRACT FROM AUTHOR]

An implicit integration scheme was developed for simulating the viscoplastic constitutive behavior of Sn3.0Ag0.5Cu solder and programmed into a user material subroutine of the finite element software ANSYS. The numerical procedure first solves the essential state variables by using a three-level iterative procedure, and updates the remaining stress and state variables accordingly. The numerical implementation was applied to consider the responses of solder joints in an electronic assembly under temperature cycling condition. The viscoplastic strain energy density accumulation over one temperature cycle was identified as a feasible parameter for evaluating the thermomechanical reliability of the solder joints. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To ensure the safe and effective application of deep geotechnical engineering, it is necessary to establish a suitable constitutive model of the rocks in thermal environment, including geothermal energy mining, and deep geological treatment of nuclear waste and tunnel fire. A strain-softening damage model of the rocks with defect growth is established based on damage evolution. According to the change in the tangent modulus from the compression phase to the elastic stage, we established a constitutive model reflecting the nonlinearity characteristics of the compression phase. According to the change in the energy conversion, the energy consumption coefficient is introduced to describe the deformation characteristics of the rocks when the residual stress is reached. The specific physical meaning and the calculation method of the energy consumption coefficient are given to correct the shortcomings of the evolution of the damage variable. We then analyzed the relationship between parameters in the constitutive model of the rocks at high temperature and normal temperature. Based on the constitutive model of the rocks at normal temperature, we established a constitutive model reflecting the influence of high temperature. Finally, the established model fit the stress-strain curves of several kinds of the rocks at different temperatures and generated desired results. The established model can be used to describe the stress-strain curve characteristics of the rocks at different temperatures. [ABSTRACT FROM AUTHOR]

To reflect the influence of saturation effect, an improved strain-softening damage model is established to link the saturated rocks with the dry rocks. First, the original damage model is improved to describe the characteristics of each stage in the uniaxial compression. According to the change of the tangent modulus from the compression phase to the elastic stage, an improved strain-softening constitutive model reflecting the nonlinear change characteristics of the compression phase is established. According to the change of the energy during the uniaxial compression, the energy consumption coefficient (λ) is introduced to replace the damage ratio coefficient to describe the deformation characteristics of the rocks when the residual stress or failure is reached. The specific physical meaning and calculation method of the energy consumption coefficient are given to correct the shortcomings of the damage evolution in the original model. Then, the relationship between the parameters in the new model for the dry rocks and the saturated rocks is analyzed. Based on the constitutive model of the dry rocks, a new constitutive model which can reflect the influence of the water-weakening is established. Finally, the stress–strain curves of different rocks are fitted by the established model, and good results are obtained. The physical meaning of each parameter in the model is clear, and each parameter can be obtained by the test results. The improved constitutive model can be applicable to both the dry rocks and the saturated rocks. [ABSTRACT FROM AUTHOR]

• We provide a quantitative framework able to reproduce the evolution with strain of the instantaneous stiffness. • We provide a quantitative framework able to reproduce the evolution with strain of the rate of change of the instantaneous stiffness. • We compare the strain stiffening phenomenon in two different nerves and we account for the main features of each specimen through quantitative indexes. The mechanical response of peripheral nerves is crucial to understand their physiological and pathological conditions. However, their response to external mechanical solicitations is still partially unclear, since peripheral nerves could behave in a quite complex way. In particular, nerves react to longitudinal strains increasing their stiffness to keep axons integrity and to preserve endoneural structures from overstretch. In this work, the strain stiffening of peripheral nerves was investigated in vitro through a recently introduced computational framework, which is able to theoretically reproduce the experimental behaviour of excised tibial and sciatic nerves. The evolution and the variation of the tangent modulus of tibial and sciatic nerve specimens were quantitatively investigated and compared to explore how stretched peripheral nerves change their instantaneous stiffness. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurately evaluated the bearing capacity characteristic value of red clay is of great important to make use of high strength. Based on analyzing current specifications methods to determine the bearing capacity eigenvalue of red clay foundation, it is found that deficiencies are the limitation of application, the disturbance of determining indexes such as water content, liquid limit, plastic limit and compression modulus, and even lack of reflecting effects of the stress level, the shape and failure mode of subgrade. To deal with these shortcomings, a method for determining the bearing capacity of red clay foundation in view of the stress level was proposed. This method adopts tangent modulus that can reflect different depth of stress levels instead of compression modulus to calculate the curve of load and settlement under the size of plate, and utilizes the modified Vesic formula to consider the influence of the shape and failure mode of ground to calculate the ultimate bearing capacity as major parameter of different depth of stress level calculation. The indoor shear strength index can be used to calculate the ultimate bearing capacity if there is no plate load test. According to the characteristic of the settlement and load curve, the intrinsic value of subgrade bearing capacity is achieved using the plate load test method. Verified through an engineering cases, the characteristic value of the bearing capacity obtained using this method is more consistent with that obtained by the plate load test, meanwhile more flexible in the actual application. It also can be used for reference to determine the characteristic value of bearing capacity in other red clay area. [ABSTRACT FROM AUTHOR]

The IDEAL IMPLANT® Structured Breast Implant is a dual lumen saline-filled implant with capsular contracture and deflation/rupture rates much lower than single-lumen silicone gel-filled implants. To better understand the implant's mechanical properties and to provide a potential explanation for these eight-year clinical results, a novel approach to compressive load testing was employed. Multi-dimensional strains and tangent moduli, metrics describing the shape stability of the total implant, were derived from the experimental load and platen spacing data. The IDEAL IMPLANT was found to have projection, diametric, and areal strains that were generally less than silicone gel implants, and tangent moduli that were generally greater than silicone gel implants. Despite having a relatively inviscid saline fill, the IDEAL IMPLANT was found to be more shape stable compared to gel implants, which implies potentially less interaction with the capsule wall when the implant is subjected to compressive loads. Under compressive loads, the shape stability of a higher cross-link density, cohesive gel implant was unexpectedly found to be similar to or the same as a gel implant. In localized diametric compression testing, the IDEAL IMPLANT was found to have a palpability similar to a gel implant, but softer than a cohesive gel implant. [ABSTRACT FROM AUTHOR]

Abstract The plasticity of thermally modified European oak (Quercus robur L.) and f thermally modified Norway spruce (Picea abies Karst. (L.)) timber was evaluated in bending, and the plastic properties were related to the changes in chemical composition of the wood after modification. The objective was to gain new knowledge about the properties of materials in the plastic region of the force-deformation diagram in bending. A new software was developed (MATESS) and used to identify important characteristics of the material. This software eliminates shortcomings in current standards, such as simplifications in the evaluation of data when sufficiently sensitive measuring equipment is not available. The characteristics studied were: modulus of rupture (MOR), plastic potential (P P) chord modulus (CH M), the moduli of plasticity (E E), and the moduli of plasticity (E MV , E P). Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed chemically to reveal the patterns that occur during the loading of the specimens. Thermal modification has different effects on the mechanical properties of oak and spruce, especially on CH M , E MV and E P , due to their different contents and structures of their chemical components. A strong correlation (r > 0.90) between hemicellulose content and MOR and Pp values was found for both species. The coefficients of determination indicated a very low dependence (r2 < 0.1) of MOR, P P , CH M , E E , E MV and E P , on the average density. Highlights • Impact different temperatures be the termal modifications on the selected properties in plastic area. • On basic the results we can modified technology of thermally modifications in wooden constructions. • The methods of modification (thermal treatment) can be modified in order to achieve the required material parameters. • Thermal modification has a different effect on the mechanical properties of oak and spruce (especially CHM, EMV and EP). • However, there were strong correlations (r > 0.90) between changes in hemicelluloses and MOR and Pp values in both species. • In the correlation between the MOR, PP, CHM, EE, EMV EP and the average density, the coefficients of determination were very low (r2 < 10%). [ABSTRACT FROM AUTHOR]

Purpose: To assess the effects of prostaglandin F2α analogues travoprost on the biomechanical behavior of ex-vivo rabbit cornea. Materials and Methods: 18 Japanese white rabbits were included in the study. The left eye (treated group, Tr) of each rabbit was preserved for 10 days in storage medium Eusol-C solution with 1:10 travoprost diluent, while the contralateral eye (control group, Co) was preserved in a similar but travoprost-free medium. Strips of corneal tissue were dissected and tested under cyclic load conditions with up to 0.1 N uniaxial tension force. The resulting load-elongation data were used to derive the stress-strain behavior and the tangent modulus (Et) of the tissue. Differences in Et between the treated (Et-Tr) and control group (Et-Co) were assessed statistically to determine the biomechanical effects of travoprost on the cornea. Results: Central corneal thickness (CCT) in the two groups was similar before (P = 0.073) and remained similar after storage (P = 0.303) although it became significantly thicker in both groups after preservation (P < 0.01). Compared with the control group, the travoprost treated corneas exhibited lower Et values but the differences reduced and became insignificant with rises in stress to which the tissue was subjected (1 - Et-Tr/Et-Co = −11.7 ± 41.8%, P < 0.05 at 10 kPa stress; −9.2 ± 36.1%, P > 0.05 at 20 kPa; −7.3 ± 35.4%, P > 0.05 at 30 kPa). Conclusions: Significant reductions in corneal stiffness, that are associated with the use of travoprost, were observed experimentally under low applied stresses. This stiffness-reduction effect should be considered in clinical management, especially in primary open angle glaucoma treatment. [ABSTRACT FROM AUTHOR]

Both the tangent modulus theory and the double modulus theory are classical theories which can be applied to the elastic-plastic stability analysis of columns. In the traditional tangent modulus theory, numerous iterations are required to calculate the critical buckling stress and this makes the method very time-consuming. In this paper, an explicit formula for establishing a direct correlation between the critical stress and the Euler stress has been proposed to reduce trial calculations. This formula can be applied to spherical shells by simplifying their stiffened plates to the form of beams on elastic foundations. The explicit expressions of both modulus theories can be used to calculate the ultimate strength of a spherical shell under pressure. The results from the proposed expression are compared with experimental results and other numerical results. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3) and national (JUS) standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.