Variation Of Elastic Modulus Research Articles

Relationship between Perceived Leg Length Discrepancy at One Month and Preoperative Hip Abductor Muscle Elasticity in Patients after Total Hip Arthroplasty

Preoperative factors related to perceived leg length discrepancy (PLLD) after total hip arthroplasty (THA) are not well studied. This study aimed to examine the preoperative factors, including hip abductor modulus, related to PLLD one month after THA. The study included 73 patients diagnosed with osteoarthritis secondary to developmental dysplasia of the hip and a posterior approach to surgery. Multiple logistic regression analysis was performed using the presence or absence of PLLD as the dependent variable and preoperative hip abductor's modulus of elasticity, pain, hip abduction range of motion, hip abductor muscle strength and pelvic obliquity as the independent variable. Additionally, receiver operating characteristic curves were used for the extracted variables for calculating the cutoffs, sensitivity, specificity and area under the curve (AUC) to determine the presence or absence of PLLD. The significance level was set at p<0.05. The hip abductor modulus (odds ratio=1.13; 95% confidence interval=1.06-1.21; p<0.001) was selected as a preoperative factor. The cutoff value to determine the presence or absence of a PLLD was 16.32 kPa. The sensitivity and specificity were 81.8% and 72.5%, respectively, and the AUC was 0.8137. The hip abductor muscle elastic modulus affected PLLD one month after THA. If the preoperative hip abductor elastic modulus is higher than the cutoff value, it may affect the appearance of PLLD at one month postoperatively.

Study on Dynamic Mechanical Properties and Failure Mechanism of Sandstones under Real-Time High Temperature

The research on dynamic mechanical properties of rocks under high temperature is the basis for safe and efficient implementation of deep coal mining and underground coal gasification engineering. In this paper, the split Hopkinson bar (SHPB) with real-time high-temperature function was adopted to systematically study dynamic mechanical properties of sandstones. The research showed that under the condition of a fixed temperature, with the increase of strain rate, the dynamic compressive strength and dynamic peak strain of sandstone increased gradually, and the variation of dynamic elastic modulus with strain rate was not obvious. With the increase of temperature, the dynamic compressive strength of sandstone increased first and then decreased, the dynamic peak strain increased gradually, and the dynamic elastic modulus decreased overall. The variation law of macroscopic failure mode and energy dissipation density with temperature was revealed, and the change mechanism was explained considering the influence of high temperature on the internal structure of sandstone. Based on the principle of component combination and the theory of micro-element strength distribution, the dynamic statistical damage constitutive model was established, and its parameters had certain physical significance. Compared with the experimental results, the established model can well describe the dynamic stress-strain relationship of sandstone under real-time high temperature.

Establishment of optimal variable elastic modulus distribution in the design of full-crown restorations by finite element analysis.

To establish optimal elastic modulus distribution throughout the entire all-ceramic crown, aiming at improvement of the mechanical properties of the restoration as well as the adhesive interface, seven 3D models of mandibular first premolars of zirconia monolithic and bilayer crowns and lithium disilicate monolithic and bilayer crowns were constructed. The elastic modulus distribution of 8-layer crown A referred to human enamel, B was calculated by a genetic algorithm (GA) to minimize the principle stresses on the crown, and C minimized the shear stresses at the cementing lines. After applying a static load of 600 N, the maximum principle stresses were calculated and analyzed by finite element analysis (FEA). Group C were found to have the lowest peak shear stress at the cementing line and moderate peak tensile stress in the crown. Introduction of the modified elastic modulus distribution from human enamel into the entire all-ceramic crown reinforces the mechanical properties of the whole restoration as well as the adhesive interface against chipping and debonding.

An analytical approach of filament bundle swinging dynamics, Part II: identifying equivalent dynamic constitutive parameters of filament bundles

A filament bundle is a type of yarn, which is composed of nearly parallel and highly oriented polymer monofilaments. Due to its nonlinearity both in material constitutive properties and structure, the filament bundle possesses nonlinear viscoelastic properties. It is important to study the dynamic behavior of the filament bundle accurately during its high-speed movement. Therefore, an accurate expression of the constitutive relation of the filament bundle is an essential prerequisite for its dynamic simulation and analysis. Continued the previous study in Part I: modeling filament bundle method, in this paper, an approach was proposed to identify the equivalent dynamic constitutive parameters of the filament bundle considering frequency-dependent characteristics. Firstly, the identification formulas of the dynamic elastic modulus and viscoelastic coefficients were derived based on the Kelvin model. Then, a testing method of the cross-sectional parameters of the filament bundle under a certain tension was proposed, and the testing device was developed to obtain the area of the filament bundle; The dynamic loading test of the bundle filament was conducted in a DMA Q800 dynamic mechanical tester. Thirdly, the equivalent dynamic elastic modulus and viscoelastic coefficients were obtained through the experimental test. Finally, an analytical method was proposed to verify the correctness of experimental results through simulation. The results show that the excitation frequency has a significant influence on the dynamic elastic modulus and viscoelastic coefficient, and the curves of the equivalent dynamic elastic modulus and viscoelastic coefficient present nonlinear variation characteristics.

Extraction of microstructural parameters from sculptured thin films nanoindentation

This work deals with the indentation analysis of nanocolumnar thin films and the difficulties encountered to deduce relevant mechanical parameters by this methodology. SiO 2 thin films prepared by physical vapour oblique angle deposition with different nanocolumnar microstructures have been subjected to indentation analysis. Despite the fact that the films had been made of the same material, deposited on the same substrate and had similar thickness, their indentation responses were different and depended on their particular microstructure. It has been also reali s ed that the measured hardness and elastic modulus variation with the indentation depth were length scale dependent and that there is not a unique analytical thin-film nanoindentation model to extract the mechanical properties from the experimental nanoindentation curves. To overcome these limitations a numerical finite element model (FEM) of the nanocolumnar coatings has been built to figure out the contributions of the different physical phenomena intervening in the indentation process. This FEM simulation relies on a description of the elasto-plastic microstructural units of the coatings and the contact friction interactions between them. Based on this simulation a parametrical representation, incorporating two length scales and the contributions of densification and/or the buckling of nanocolumnar units, has been developed to account for the evolution of the apparent elastic modulus deduced from numerical indentation tests . A Hall-Petch modification of this description considering two length scales instead of the common approximation considering a single length scale has rendered the best agreement with the elastic values determined experimentally. Although, at the present stage, the particular microstructure of the films can not be deduced from the evolution of their elastic moduli with the indentation depth, the obtained results and their interpretation constitute a first though essential step for the elaboration of an inverse analysis methodology capable of correlating microstructure and elastic response of nanocolumnar coatings. • The indentation response of multi-layered PVOAD columnar coatings greatly depends on their microstructure. • Buckling but also densification drive the evolution of indentation elastic modulus and hardness with indentation depth. • FEM of a columnar structure under indentation allow s to reproduce the experimental response of multi-layered PVOAD coatings. • Size dependent model allows to extract length scale parameters from elastic response of PVOAD coatings.

Thermal effect of high temperatures on the physical and mechanical properties of a granite used in UNESCO World Heritage sites in north Portugal

This work discusses the results from a set of physical and mechanical test conducted on 46 cubic samples of a granite from the north of Portugal widely used in local granite-built UNESCO World Heritage sites, heated in a furnace at temperatures ranging from 105 to 700 °C and cooled under different conditions. Then, the obtained results are compared with an extensive database of published case studies, showing that porosity, unit weight, ultrasonic waves velocities, elastic modulus and uniaxial compressive stress variations are mostly related to the induced thermal-stress caused by the anisotropic thermal expansion of the mineral grains. Only mineralogy and specific gravity do not exhibit changes for the studied range of temperatures. For specimens heated to above 500 °C, degradation processes predominate due to alpha-beta phase transition in quartz grains, considerably increasing the linear crack density, length and width and degrading the rock properties. Regarding the influence of the cooling method, thermal effects are amplified when cooling is performed by water immersion because of the inhomogeneous shrinkage and the subsequent tension stress between adjacent particles due to temperature decrease that develop at different pace within the samples. Scanning electron microscopy confirms the increase of damage and the negative effect on the granite properties caused by thermal treatment from 500 °C and by water cooling. For temperatures lower than 500 °C a hardening effect slightly improving elastic modulus and uniaxial compressive strength is observed in slowly and quickly cooled samples. The derived conclusions considerably improve the knowledge about the behaviour against temperature of this type of granite, with the purpose of evaluating the integrity level of granite-built UNESCO cultural heritage sites in northern Portugal.

Analysis of Timoshenko beam with Koch snowflake cross-section and variable properties in different boundary conditions using finite element method

This study analyzed a Timoshenko beam with Koch snowflake cross-section in different boundary conditions and for variable properties. The equation of motion was solved by the finite element method and verified by Solidworks simulation in a way that the maximum error was about 2.9% for natural frequencies. Displacement and natural frequency for each case presented and compared to other cases. Significant research achievements illustrate that if we change the Koch snowflake cross-section of the beam from the first iteration to the second, the area and moment of inertia will increase, and we have a 5.2% rise in the first natural frequency. Similarly, by changing the cross-section from the second iteration to the third, a 10.2% growth is observed. Also, the hollow cross-section is considered, which can enlarge the natural frequency by about 26.37% compared to a solid one. Moreover, all the clamped-clamped, hinged-hinged, clamped-free, and free-free boundary conditions have the highest natural frequency for the Timoshenko beam with the third iteration of the Koch snowflake cross-section in solid mode. Finally, examining important physical parameters demonstrates that variable density from a minimum value to the standard value along the beam increases the natural frequencies, while variable elastic modulus decreases it.

Role of Fe2Al5 in fracture of novel dissimilar aluminum-steel resistance spot welds using multi-ring domed electrodes

In a comparative study of resistance spot welded (RSW) 1.2 mm AA6022 joined to 2.0 mm high strength low alloy (HSLA) steel and 1.2 mm AA6022 joined to 2.0 mm low carbon steel (LCS) it was found that quasi-static tensile tests and mini shear tests exhibited similar intermetallic compound (IMC) strength but different load capacity, i.e., nominal shear strength in tensile shear tests. This phenomenon was related to the Fe2Al5 structure and properties at the Al-steel interface which were unique for each stack-up. The thicker Fe2Al5 layer in 1.2 mm AA6022-2.0 mm LCS was comprised of fewer but larger grains which contributed to a larger difference between the Young's modulus of FeAl3 and Fe2Al5 than in 1.2 mm AA6022-2.0 mm HSLA. The Fe2Al5 in the AA6022-LCS stack-up was more brittle and rigid with greater nanohardness values and smaller variation in elastic modulus that may have contributed to lower overall joint strength with large variation. In addition, AA6022-LCS welds produced with non-optimized and optimized weld schedules produced different IMC shear strengths which was attributed to the different mismatch in Young modulus values that accentuated the differences in shear stresses at the FeAl3/Fe2Al5 interface.

Experimental Study of Compressive Mechanical Behavior of Red Sandstone after Heating-Cooling Treatment

Investigation of compressive mechanical property of rock materials after heating-cooling treatment is of great significance for deep geothermal energy exploitation. This study conducted a series of uniaxial compressive experiments on red sandstone subjected to different heating-cooling treatments, i.e., heating temperature 25, 200, 400, 600, 800, and 1000°C and cooling temperature of 10°C. The experimental results showed that with an increase in the heating temperature, the peak strength of red sandstone after heating-cooling treatments attained a maximum value under the heating temperature of 400°C. Furthermore, the variations of instantaneous elastic modulus of treated samples are the same as that of primary wave velocity. To futher reveal the failure characteristics of heating-cooling treated red sandstone, related scanning electron microscopy tests were also carried out to analyze the microstructure of red sandstone samples after various heating-cooling treatments, to provide a valuable reference for studying the mechanical properties of rock materials after heating-cooling treatments.

Cyclic compressive behavior of limestone and silicomanganese slag concrete subjected to sulphate attack and wetting-drying action in marine environment

Concrete in maritime structure is vulnerable to deterioration owing to external sulphate attack, which can be exacerbated by wetting-drying action (WDA), jeopardizing its resistance to cyclic loads such as wind, wave and earthquake actions. This study aims to investigate the compressive fatigue behavior of concrete exposed to sulphate attack and WDA in marine environment. Cyclic compressive loading test was conducted on concrete after 150 days of deterioration. The effects of sulphate attack and WDA, upper stress loading level and loading frequency on fatigue life, residual strain, variation of elastic modulus and post-cyclic compressive strength were investigated. The sulphate penetration profiles, volume change and mass change of concrete during the exposure time were also measured. In addition, the performance of limestone concrete and silicomanganese (SiMn) slag concrete was compared in the study. The sulphate ion was found to penetrate concrete up to a depth of 20 mm, with a maximum content of 1.72%–2.58% near the surface. The cyclic loading test showed that degraded concrete had 38.2% higher residual displacement and 1.4% lower modulus of elasticity than normal concrete. The sulphate attack and WDA weakened the concrete, reducing its fatigue resistance. SiMn slag concrete had a lower fatigue life, larger residual displacement and greater stiffness degradation than limestone concrete.

Generative design of bioinspired wings based on deployable hindwings of Anomala Corpulenta Motschulsky

In view of the application prospect of the hindwing of Anomala Corpulenta Motschulsky in the field of foldable Micro Aerial Vehicles (MAVs), this paper investigated the morphology, macro/microstructure of the hindwing, and the nanomechanical properties of the wing veins and the wing membrane. It revealed the variation of nanohardness and elastic modulus between different veins and different positions of the same wing veins. This paper established a 3D coupling model of the hindwing based on the principle of coupling bionics. This paper presents a simulation analysis of the structural statics (uniform load distribution) and aerodynamics (under different attack angles, flight velocities, and flapping frequencies). Two 3D coupling models (HW-I and HW-II) of the hindwing were discussed the deformation and flight aerodynamic performance of Workbenches and Fluent. On that basis, the bionic wing was generatively designed, and a 3D bionic wing (BioW) model was established using the generative design method. Simulation analyses were performed through structural statics and aerodynamics. The results showed that the stress distribution was relatively uniform and that the overall displacement deformation was minimal for the BioW model. Moreover, the BioW model had better flight efficiency and aerodynamic performance.

Mechanical Deconvolution of Elastic Moduli by Indentation of Mechanically Heterogeneous Materials

Most materials are mechanically heterogeneous on a certain length scale. In many applications, this heterogeneity is crucial for the material’s function, and exploiting mechanical heterogeneity could lead to new materials with interesting features, which require accurate understanding of the local mechanical properties. Generally used techniques to probe local mechanics in mechanically heterogeneous materials include indentation and atomic force microscopy. However, these techniques probe stresses at a region of finite size, so that experiments on a mechanically heterogeneous material lead to blurring or convolution of the measured stress signal. In this study, finite element method simulations are performed to find the length scale over which this mechanical blurring occurs. This length is shown to be a function of the probe size and indentation depth, and independent of the elastic modulus variations in the heterogeneous material, for both 1D and 2D modulus profiles. Making use of these findings, we then propose two deconvolution methods to approximate the actual modulus profile from the apparent, blurred measurements, paving the way for an accurate determination of the local mechanical properties of heterogeneous materials.

Parametric Evaluation of Simultaneous Effects of Damaged Zone Parameters and Rock Strength Properties on GRC

The convergence-confinement method via the ground reaction curve (GRC) is used as the common practice of tunnel design which demands accurate determination of the stress state and material strength behavior in different zones around the tunnel section. Besides, formation of the excavation/blast-induced damaged zone (EDZ/BDZ) adds more complexity to the problem due to variation of elasticity modulus of the rock mass in this zone. As a result, advanced numerical methods via finite element/difference commercial packages or user-coded, semi-numerical techniques are required to develop the GRC, which demands a high degree of proficiency and knowledge of computational plasticity and geomechanics. In this study, a new, simple, and accurate method is proposed for prediction of GRC of circular tunnels constructed in the damaged, elastoplastic rock masses obeying softening in the plastic zone. The effects of deterioration caused by the drilling/blast in the EDZ were taken into account by assuming a reduced and varying Young’s modulus using the disturbance factor, in the form of Hoek–Brown failure criterion and the Geological Strength Index (GSI). Besides, effects of intermediate principal stress and the exponential decaying dilation parameter are taken into account thanks to adoption of the unified strength criterion (USC) as the material strength criteria. To do so, genetic algorithm (GA) via the method of evolutionary polynomial regression (EPR) is used to find a relationship between a number of 19 affecting parameters on the GRC as the input, and the internal support pressure as the target of prediction. Verification analysis was performed to verify the validity of the results using field measurements data as well as other advanced numerical studies found in the literature. Lastly, variation of the support pressure with simultaneous changes in the affecting input parameters was investigated using multivariable parametric study.

Raman needle arthroscopy for in vivo molecular assessment of cartilage.

The development of treatments for osteoarthritis (OA) is burdened by the lack of standardized biomarkers of cartilage health that can be applied in clinical trials. We present a novel arthroscopic Raman probe that can “optically biopsy” cartilage and quantify key extracellular matrix (ECM) biomarkers for determining cartilage composition, structure, and material properties in health and disease. Technological and analytical innovations to optimize Raman analysis include (1) multivariate decomposition of cartilage Raman spectra into ECM‐constituent‐specific biomarkers (glycosaminoglycan [GAG], collagen [COL], water [H2O] scores), and (2) multiplexed polarized Raman spectroscopy to quantify superficial zone (SZ) COL anisotropy via a partial least squares–discriminant analysis‐derived Raman collagen alignment factor (RCAF). Raman measurements were performed on a series of ex vivo cartilage models: (1) chemically GAG‐depleted bovine cartilage explants (n = 40), (2) mechanically abraded bovine cartilage explants (n = 30), (3) aging human cartilage explants (n = 14), and (4) anatomical‐site‐varied ovine osteochondral explants (n = 6). Derived Raman GAG score biomarkers predicted 95%, 66%, and 96% of the variation in GAG content of GAG‐depleted bovine explants, human explants, and ovine explants, respectively (p < 0.001). RCAF values were significantly different for explants with abrasion‐induced SZ COL loss (p < 0.001). The multivariate linear regression of Raman‐derived ECM biomarkers (GAG and H2O scores) predicted 94% of the variation in elastic modulus of ovine explants (p < 0.001). Finally, we demonstrated the first in vivo Raman arthroscopy assessment of an ovine femoral condyle through intraarticular entry into the synovial capsule. This study advances Raman arthroscopy toward a transformative low‐cost, minimally invasive diagnostic platform for objective monitoring of treatment outcomes from emerging OA therapies.

Quickly analyze the limit load of thinning defect elbows with elastic modulus adjustment method

In the process of production and service of pressure pipeline, local thinning defects may occur due to dielectric corrosion, manufacturing defects and other reasons. These defects reduce the carrying capacity of the pipeline and lead to leakage and rupture of the pipeline. Therefore, the integrity assessment of components and structures is required. Traditionally, the inelastic finite element method (FEM) is highly dependent on the specification of adequate mesh density and an assurance of numerically stable solutions. However, in engineering design, independent validation methods, such as Elastic Modulus Adjustment Procedures (EMAP), provide fast and stable solutions at relatively low cost. On the basis of elastic finite element analysis (FEA), the upper and lower bounds of limit load can be obtained by specifying the variations of elastic modulus in EMAP method. In this paper, an elastic modulus adjustment parameter k, which can improve the convergence of EMAP, is used to achieve stable convergence in the application of elbow with double defects. The EMAP method is also proved to be more efficient than the inelastic finite element analysis (FEA). Furthermore, the effect of defect size and distribution on the limit load of the elbow is studied.

Effect of yield criterion and variable elastic modulus on springback prediction of Ti-6Al-4V sheet V-shaped bending

Effect of yield criterion and variable elastic modulus on springback prediction of Ti-6Al-4V sheet V-shaped bending

Stress-dependent elasticity and wave propagation — New insights and connections

To establish a consistent framework for seismic wave propagation that accommodates the effects of stress changes, it is critical to take into account the different definitions of stress and their corresponding effects on seismic quantities (e.g., wave speeds) as dictated by continuum mechanics. Revisiting this fundamental theoretical foundation, we first emphasize the role of stress within various forms of the wave equation resulting from different choices of stress definitions. Subsequently, using this basis, we investigate connections among existing theories that describe the variation of elastic moduli as a function of changes in stress. We find that there is a direct connection between predicting stress-induced elastic changes with the well-known third-order elasticity tensor and the recently proposed adiabatic pressure derivatives of elastic moduli. However, each of these approaches has different merits and drawbacks in terms of experimental validation as well as in their use. In addition, we investigate the connection with another general approach that relies on micromechanical structures (e.g., cracks and pores). Although this can be done algebraically, it remains unclear as to which definition of stress and which corresponding constitutive relationship should be considered in practical scenarios. We support our analysis with validations using previously published benchmark experimental data.

Nanoscale Material Heterogeneity of Glowworm Capture Threads Revealed by AFM.

Adhesive materials used by many arthropods for biological functions incorporate sticky substances and a supporting material that operate synergistically by exploiting substrate attachment and energy dissipation. While there has been much focus on the composition and properties of the sticky glues of these bio-composites, less attention has been given to the materials that support them. In particular, as these materials are primarily responsible for dissipation during adhesive pull-off, little is known of the structures that give rise to functionality, especially at the nano-scale. In this study we used tapping mode atomic force microscopy (TM-AFM) to analyze unstretched and stretched glowworm (Arachnocampa tasmaniensis) capture threads and revealed nano-scale features corresponding to variation in surface structure and elastic modulus near the surface of the silk. Phase images demonstrated a high resolution of viscoelastic variation and revealed mostly globular and elongated features in the material. Increased vertical orientation of 11–15 nm wide fibrillar features was observed in stretched threads. Fast Fourier transform analysis of phase images confirmed these results. Relative viscoelastic properties were also highly variable at inter- and intra-individual levels. Results of this study demonstrate the practical usefulness of TM-AFM, especially phase angle imaging, in investigating the nano-scale structures that give rise to macro-scale function of soft and highly heterogeneous materials of both natural and synthetic origins.

Prediction of bending springback of the medium-Mn steel considering elastic modulus attenuation

The improvement of lightweight and safety is the development requirement of automobile parts. Therefore, the demand of thin-walled parts with ultra-high strength is more urgent. However, with the increase of strength, the springback phenomenon of parts is particularly serious, which greatly affects the forming quality of parts. Generally, the springback of automobile parts should be controlled within 5%. Thus, the accurate simulation and prediction of springback can provide important support for the manufacture of ultra-high strength automobile thin-walled parts. In this paper, the bending springback of the medium-Mn steel, as one of the third-generation automobile steels, was studied based on experiment and simulation under different conditions. Tensile tests were carried out to evaluate comprehensive mechanical properties with high strength and high plasticity. Cyclic loading-unloading tests were conducted to analyze the changing rules of unloading elastic modulus and inelastic recovery with strain. The correlation model between unloading elastic modulus and true plastic strain was further established and the model parameters were obtained. Furthermore, V-shaped bending tests were carried out under different conditions to analyze the effects of rolling direction, bending angle, and punch fillet radius on springback. The effect of rolling direction on springback angle is negligible. The bending angle has a positive effect on springback angle, while the punch fillet radius has a negative effect. Finally, the material model with constant and variable elastic moduli were developed by using user-defined material subroutines for the medium-Mn steel. V-shaped bending tests under constant and variable elastic moduli were simulated and compared with the experimental result. The simulated result with variable elastic modulus was closer to the experimental one, which proves the importance of considering the change of unloading elastic modulus in the numerical simulation of medium-Mn steel. The research result of this paper is helpful to enhance the simulation accuracy of springback of medium-Mn steel part and promote its industrial application.

Elastic and attenuation behavior of the Bi1-x Re x FeO3 (x = 0 & 0.1; Re = La, Pr, Nd & Sm) multiferroic system

ABSTRACT A series of single-phase rare earth-doped bismuth ferrites were prepared by the solid state reaction method. After characterizing the samples with XRD, the bulk density measurements were carried out by the immersion method. The ultrasonic longitudinal (Vl ) and shear (Vs ) wave velocities were measured using 1 MHz quartz transducers with the help of the pulse transmission technique. Using the ultrasonic velocity values, Young’s and rigidity moduli along with Poisson’s ratio and Debye temperatures were calculated. As the materials are porous, the zero porous moduli have also been calculated using the Hasselman and Fulrath model. The observed variation of elastic moduli with different dopants has been explained qualitatively. The low-temperature behavior of ultrasonic longitudinal (Vl ) wave velocities was also measured. A small change of slope was observed at 208 K in BFO, BLFO and BSFO samples. Finally, the ultrasonic attenuation coefficient values of all the samples were also measured.