Mechanical Analysis Method Research Articles

Local deformation on damping performance of integral-forming aluminum foam sandwich

Damping performances of porous metals are generally measured by dynamic mechanical analysis (DMA) method which has strictly dimensional requirements on specimens especially on their thickness. In this work, based on sinusoidal excitation and Fourier transform, a new set of test equipment suitable for evaluating damping performances of large-scale porous metals was constructed. On this basis, the influence of local compression deformation on the damping performances of the newly developed integrated-forming aluminum foam sandwich (IFAFS) was investigated by means of single-point excitation method. Damping performances of different regions were obtained through partition measurement and the reasons were discussed which are beneficial to evaluate damping performances of IFAFS after local deformation.

An experimental investigation on the thermal and mechanical characterization of boron/flax/PLA sustainable composite

The current study deals with the effect of boron compounds, zinc borate (ZB), borax: boric acid combines (BxBc), and ulexite which are used to improve fire resistance, on the thermal, microstructural, and mechanical properties of the flax/PLA biocomposites. For this purpose, the mechanical properties of the biocomposites were determined by tensile, impact, and three-point bending tests. Thermogravimetric analysis and the UL-94 burn test were conducted to determine the thermal properties of composites, such as thermal stability and flammability. Thermo-mechanical properties and viscoelastic characteristics of biocomposites were determined by the dynamic mechanical thermal analysis method. Test results showed that ulexite addition could significantly reduce the burning rate by 80%. However, although mechanical properties were adversely affected by the incorporation of boron compounds resulting in a drop of up to 20%, it is believed that boron compound-filled flax/PLA composites have mechanical and thermal properties that can be considered as an alternative material, especially for the automotive industry.

Novel Synthesis Methods of New Imidazole-Containing Coordination Compounds Tc(IV, V, VII)-Reaction Mechanism, Xrd and Hirshfeld Surface Analysis.

In this work, we have proposed two new methods for the synthesis of [TcO2L4]+ (where L = imidazole (Im), methylimidazole (MeIm)) complexes using thiourea (Tu) and Sn(II) as the reducing agents. The main and by-products of the reactions were determined, and possible reaction mechanisms were proposed. We have shown that the reduction of Tc(VII) with thiourea is accompanied by the formation of the Tc(III) intermediate and further oxidation to Tc(V). The reaction conditions’ changing can lead to the formation of Tc(VII) and Tc(IV) salts. Seven new crystal structures are described in this work: Tc(V) complexes, salts with Tc(VII) and Tc(IV) anions. For the halide salts of Tu the cell parameters were determined. In all of the obtained compounds, except for [TcO2(MeIm)4]TcO4, there are π–stacking interactions between the aromatic rings. An increase in the anion size lead to weakening of the intermolecular interactions. The halogen bonds and anion-π interactions were also found in the hexahalide-containing compounds. The Hirshfeld surface analysis showed that the main contribution to the crystal packing is created by the van der Waals interactions of the H···H type (42.5–55.1%), H···C/C···H (17.7–21.3%) and hydrogen bonds, which contribute 15.7–25.3% in total.

Mechanical Behavior Characteristics and Energy Evolution Law of Coal Samples under the Influence of Loading Rate—A Case Study of Deep Mining in Wudong Coal Mine

In order to clarify the mechanical properties and energy changes of coal samples under the influence of mining depth, a mechanical test analysis method to determine that the increase in mining depth increases the loading rate has been developed. Taking the Wudong Coal Mine as an example, a mechanical test analysis of coal samples is carried out. The results show that the surface deformation and failure of coal samples in the loading process presents four stages. That is, the evolution process of ‘complete coal sample’–‘partial failure-failure extension’–‘overall instability’. The maximum temperature of a coal sample when it is destroyed shows an obvious nonlinear increasing trend with the increase in loading rate. With the increase in loading rate, the strength and elastic modulus of coal samples decrease gradually. The cumulative total energy and elastic energy of coal samples are linearly positively correlated with the loading rate. The research results provide ideas for rational control of mining intensity and determination of productivity in steeply inclined thick coal seams for deep mining.

Mechanism analysis and suppression method of high frequency harmonic resonance in VSC-HVDC

This paper introduces the basic situation of high frequency harmonic resonance in Guangxi on April 10, 2017, which is based on the Luxi back-to-back voltage source converter based high voltage direct current transmission (VSC-HVDC) project in China. Firstly, the harmonic amplification mechanism and its key links in the event are analyzed in detail and verified by simulation. Secondly, the relationship among high frequency harmonic resonance, voltage feedforward control loop and system harmonic impedance is obtained, and the formulas among voltage feedforward control parameters, system harmonic impedance and high frequency harmonic resonance frequency amplitude are deduced. Then, a method to suppress high frequency harmonic resonance by adding a reasonably filter to the voltage feedforward control loop is proposed. Finally, the effectiveness of the proposed method in this paper is verified by simulation and field operation.

Damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders with different thicknesses and preparation directions

PurposeThis study aims to experimentally assess the effect of thickness and preparation direction on the damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders.Design/methodology/approachSn58Bi and Sn3.0Ag0.5Cu solder strips with different thicknesses were prepared from the bulk in longitudinal and horizontal directions, and the ratio of loss modulus and storage modulus of the samples was measured by the dynamic mechanical analysis method as the index of damping properties.FindingsSn58Bi and Sn3.0Ag0.5Cu solders exhibited viscoelastic relaxation, and their damping properties decreased with decreasing thickness. The damping properties of both solders had no obvious difference in longitudinal and horizontal directions. Sn58Bi has a more obvious high-temperature damping background than Sn3.0Ag0.5Cu solder. In addition, compared with Sn58Bi solder, Sn3.0Ag0.5Cu solder had an obvious internal friction peak, which moved toward high temperature with increasing frequency. The activation energies of Sn58Bi solder with a thickness of 0.5 mm at the longitudinal and horizontal directions were 0.84 and 0.67 eV, respectively, which were 0.39 and 0.53 eV, respectively, for the Sn3.0Ag0.5Cu solder.Originality/valueThe damping properties of Sn58Bi and Sn3.0Ag0.5Cu solder decreased with decreasing thickness, while their damping properties changed insignificantly when they were prepared from different directions. The internal friction peak of Sn3.0Ag0.5Cu solder moved to higher temperatures with increasing frequency.

Actuator fault detection for a PEMFC system based on delta operator approach

This paper proposes an actuator fault detection observer design method for a proton exchange membrane fuel cell (PEMFC) system described by delta operator form. In the first, a nonlinear mathematical model for the PEMFC system is proposed by using the mechanism analysis method, which includes the time delay, external disturbance and uncertainty to reduce the conservatism of the design. Then, in order to detect the actuator fault, the functional observer is constructed as the residual generator, and sufficient conditions for the stability of the error system are obtained by using the Lyapunov-krasovsky functional theory in terms of linear matrix inequalities (LMIs), so as to ensure the design of the required functional observer. Finally, simulation results are provided to show the effectiveness of the approach.

The effect of seepage flow on movable solid materials research in debris flow experiments

Debris flows is one of the most common natural disasters in mountainous areas, posing a seriously risk to local people’s life and property. It is fundamental basis to study the criteria for movement of solid materials subjected to seepage flow and surface flow for the purpose of prevent this hazard. Therefore, mechanical analysis methods and laboratory experiments were used to study the effect of seepage flow on movable solid materials in debris flow. First, the definition of movable solid materials was proposed. Then, a geological model of debris flow is established considering saturated seepage flow. Finally, through mechanical analysis, formulas for dynamical force and resistance force are derived. The results show that the dynamical force and resistance force increase linearly with depth when the geologic model is homogenous and the seepage flow saturates the entire debris layer. It also indicated that pore-water pressure is one of the most important factors for causing debris flow, especially when the slope angle exceeds 12°. Through comparing the results of tests and theoretical analysis under saturated seepage flow, the discrepancy is only 1.3%–24.2%, showing that the formulas are fairly reliable. The motion of the solid materials should be described as a mechanical problem rather than a statistic qualitative description. The research contributes to the source volume calculation of small debris-flow watersheds and advances the study of the movable solid materials in complex dynamic conditions.

Research on Mechanical Behavior of the Steel-Concrete-Steel Composite Structures Subjected to High Temperature of Fire.

A new type of steel–concrete–steel composite structure was adopted and widely used in the immersed tunnel of the Shenzhen–Zhongshan access. The research on the mechanical behavior of the new composite structure under a high temperature of fire is of great engineering significance to the fire protection design of the structure. Both the model test and a numerical simulation were adopted to study the mechanical behavior and damage characteristics of the new composite structure under fire. The RABT standard temperature rise curve was used to simulate the temperature rising law under fire (it reflects the characteristics of temperature rise in case of fire in an enclosed environment: rapidly raised to 1200 °C within 5 min, maintained at 1200 °C for 120 min, then it is cooled to normal temperature after 110 min). The temperature distribution law inside the structure, the deformation development law of the roof and the crack distribution were analyzed based on the thermal–mechanical coupling analysis method. The results showed that the internal part of the composite structure close to the fire surface was directly affected by the high temperature, and the temperature presented a step distribution law, while the part far from the fire surface was affected by the lag effect of the temperature transfer, and the temperature presented a continuous growth law. The roof deformation presented a three-stage model of “rapid growth-deformation stability-deformation recovery” with time. The overall cracks of the composite structure showed a symmetrical distribution under fire. The composite structure presented a shear failure mode as a whole. The results could provide a reference for the study of fire resistance for the new composite structure and support the structural fire protection design of the immersed tunnel of the Shenzhen–Zhongshan access.

Study on Multisize Effect of Mining Influence of Advance Speed in Steeply Inclined Extrathick Coal Seam

Abstract Aiming at the multisize effect of mining in steeply inclined extrathick coal seam, taking the fully mechanized top-coal caving mining in B3+6 coal seam +425 level in the south of Wudong coal mine as the background, this paper studies the mining stress evolution law under the influence of advancing speed, analyzes the mechanical characteristics of coal samples under the mining action of steeply inclined extrathick coal seam, and completes the multisize effect study of mining in steeply inclined extrathick coal seam. The results show that the stress change theory of fully mechanized top-coal caving mining in steeply inclined seam is deduced, and the loading and unloading stress of fully mechanized top-coal caving mining is positively correlated with the advancing speed of the working face. The numerical simulation experiment shows that the ideal advancing condition increases with the advancing speed of the working face, and the cyclic loading and unloading amplitude under the mining stress path increases, the cyclic times decrease, the main influence area increases, and the acting time decreases. The peak value of mining stress, the width of the plastic zone, and its elastic energy under high-speed propulsion are obviously larger. A method of mechanical behavior analysis of coal samples is proposed, which takes the mining stress path of the numerical simulation experiment as the indoor scale loading and unloading stress path of coal samples. The average compressive strength of coal samples under the mining stress path increases with the advancing speed of the working face, and the damage degree of coal samples increases with the advancing speed of different stress paths. The input strain energy of coal cyclic loading and unloading increases with the increase in the advancing speed of the stress path. The input strain energy of the coal sample has obvious linear relationship with the advancing speed of different paths. The research results can be used for reference in the study of multisize effect of mining impact of advancing speed.

Mechanism analysis and control method of electric spring off-limit failure based on two-port impedance model

Mechanism analysis and control method of electric spring off-limit failure based on two-port impedance model

Construction Technology and Engineering Application of Post Installation of Concrete Decorative Lines on Building Facades

For the consideration of beautiful appearance of building facades, many building facades are designed with reinforced concrete lines. The traditional building facade concrete decorative line needs secondary pouring construction, which has the problems of complex construction process, low construction precision, high construction cost and poor construction quality. This paper presents a construction method of post installation of concrete decorative lines on building facades. Firstly, the principle of post installation of concrete decorative lines on building facades is clarified by theoretical analysis method, then the design and calculation method of decorative lines is clarified by mechanical analysis method, and then the specific construction process of decorative lines is clarified in combination with the on-site construction process. Finally, the post installation construction technology of concrete decorative lines on building facades is applied to a project example, and the economic analysis is carried out. The results show that the post installation of concrete decorative lines on the building facade is mainly based on the construction principle of prefabricated installation; The stress analysis of decorative lines needs to focus on the strength of the connectors between the lines and the building structure; Compared with the traditional secondary pouring construction method of decorative lines, the post installation construction method can save about 30% of the cost, and the construction process is more safe and efficient, with higher construction precision and quality. It is suggested that it can be popularized and applied in similar projects.

Digital Image Finite Element Analysis of Geotechnical Engineering Materials

Geotechnical heterogeneous materials contain a large number of defects, such as granular structures of different types and spatial geometric distribution, cracks, and voids, and have a complex internal meso-structure. Moreover, the mechanical properties and defect structures of various meso-media have an important influence on the fracture mechanism, which makes the analysis of the fracture process of geotechnical materials a nonequilibrium and nonlinear three-dimensional mechanical problem in space. However, due to the complexity of mathematical theory, the limitation of laboratory test and field observation, test conditions, and technology, it is very difficult to study the three-dimensional fracture process of geotechnical materials, and numerical simulation has become one of the powerful tools to solve these problems. This paper first introduces the concept of digital image and the development of geotechnical engineering, and then analyses the types of engineering materials used in geotechnical engineering construction. A finite element method for mechanical analysis based on digital images is proposed. The method can be used to study the influence of the internal microstructure of geotechnical engineering materials on the mechanical response of materials. By analyzing the images, it can be concluded that the aggregate content is 36.1%, the matrix content is 48.9%, and the rest is the proportion of interface elements. The digital image numerical analysis method in this paper is based on two-dimensional space, but according to the principle of stereological logic transformation, it can be applied to three-dimensional finite element analysis.

In-situ reaction compatibilization modification of poly(butylene succinate-co-terephthalate)/polylactide acid blend films by multifunctional epoxy compound

Poly(butylene succinate-co-terephthalate) (PBST) copolyester, is a new type of biodegradable synthetic polymer material that has emerged in recent years, but it cannot meet the market requirements, because of its low strength. The high-strength and high-modulus polylactic acid (PLA) was blended with PBST to increase its strength, and the chain extender ADR-4370 was used to modify PBST/PLA films by reaction and compatibilization. Compared with the 80/20 wt% PBST/PLA films, the tensile strength after modification with 0.3 wt% ADR was increased by 21.8 % and 44.3 % in the machine direction (MD) and in the transverse direction (TD), respectively. The Water Vapor Permeability (WVP) was decreased from 10.0 × 10−14 to 3.09 × 10−14 g·cm/cm2·s·Pa. The compatibilization mechanism was studied by gel permeation chromatography, infrared spectroscopy, dynamic mechanical analysis, rheological analysis, and other characterization methods. The formation of the copolymer PLA-g-PBST is the most important factor to improve the compatibility of the system and the mechanical properties of the films.

Initial sintering mechanism and additive effect in zirconia ceramics

AbstractY2O3‐stabilized ZrO2 (YSZ) ceramics have been used for various engineering applications because of their excellent mechanical properties or oxide‐ion conductivity applicable to solid‐electrolyte. The performance of YSZ depends on the sintered texture that is directly determined by sinterability of raw powders. A new kinetic analysis method of diffusion mechanism based on an initial sintering theory (grain‐boundary or volume diffusion) is theoretically derived, the initial sintering mechanism of hydrolytic YSZ powder is experimentally determined, and the effects of powder characteristics on sinterability are discussed. Furthermore, the additive‐enhanced sintering is proposed. A small amount of Al2O3 significantly enhances the densification. Using the additive effect, the low‐temperature degradation that is the fault of zirconia ceramics can be improved by decreasing the sintering temperature.

Evaluation of the High- and Low-Temperature Performance of Asphalt Mortar Based on the DMA Method

Asphalt mortar is a typical temperature-sensitive material that plays a crucial role in the performance of asphalt mixture. This study evaluates the high- and low-temperature performance of asphalt mortar based on the dynamic mechanical analysis (DMA) method. Temperature-sweep tests of asphalt mortars were conducted using the DMA method under fixed strain level, frequency, and heating rate conditions. The dynamic mechanical response curves, characteristic temperature, and other indices were obtained and used to investigate the high- and low-temperature performance of asphalt mortar. The results showed that the phase transition temperatures T1, T0, and Tg can be used to evaluate the low-temperature performance of asphalt mortar. Additionally, they had a good linear relationship, and the evaluation results were consistent. Meanwhile, T2, E60, and tan(δ)max indicators can effectively evaluate the high-temperature performance of asphalt mortar. Asphalt plays a key role in the performance of asphalt mortar. Mortars with neat asphalt A70 and modified asphalt AR had the worst and best high- and low-temperature performances, respectively. Furthermore, the finer gradation improved the low-temperature performance of asphalt mortar, while the coarser gradation improved the high-temperature properties of modified asphalt mortars but had the opposite effect on neat asphalt A70.

The Effect of Agglomeration on the Electrical and Mechanical Properties of Polymer Matrix Nanocomposites Reinforced with Carbon Nanotubes.

In this work, we investigated the effect of carbon nanotubes addition and agglomeration formation on the mechanical and electrical properties of CNT–polymer-based nanocomposites. Six specimens with carbon nanotubes (CNTs) fractions of 0%, 0.5%, 1%, 2%, 4% and 5% were manufactured and characterized by dynamic mechanical analysis (DMA) and four-probe method. The stress–strain curves and electrical conductivity properties were obtained. Scanning electron microscopy (SEM) was used to characterize both agglomeration and porosity formation. By employing micromechanics, through representative volume element (RVE), finite element analysis (FEA) and resistor network model (RNM), the Young’s modulus and electrical conductivity values were calculated. The samples’ elastic moduli showed an increment, reaching the maximum value at a CNTs fraction of 2%, thereafter an adverse effect was caused in the high CNT percentage samples. The final electrical conductivity seemed greatly altered with the addition of CNTs, reaching the percolation threshold at 2%. The unavoidable formation of CNT agglomerates appeared to influence the final physical properties. The CNT agglomerates adversely affect the mechanical performance of high-CNT-percentage samples. Conversely, an exponential increment in the electrical conductivity was presented as the agglomerates formed networks allowing the transport of electrons through the tunnelling effect. These phenomena were experimentally and numerically confirmed, showing a good correlation.

Numerical analysis on torsional behavior of rectangular and square CFDST members

This paper numerically investigated the behavior of rectangular and square concrete-filled double skin steel tubular (CFDST) members under torsion. The finite element model of rectangular and square CFDST members was established and verified against the test results for the members under cyclic torque. The comparison of the finite element analysis results and experiment results show that the comprehensive finite element model can accurately predict the torsional behavior of rectangular and square concrete-filled double skin steel tubular members. Parametric analyses by using the calibrated finite element model were conducted to investigate the influence of various parameters, such as hollow ratio, concrete strength, yield strength and cross-sectional steel consumption of steel tubes on the torsional behavior of rectangular and square CFDST members. Based on the mechanical analysis and regression analysis methods, the design formula was proposed to predict the torsional capacity of rectangular and square CFDST members. The comparison results show that the proposed formula for predicting the torsional capacity of rectangular and square CFDST members has good accuracy.

Structure–property relationships and constitutive viscoelastic behaviors of polyether‐block‐amide elastomers in melt and solid states

AbstractIn this study, effects of copolymer composition on the structural, thermal, and viscoelastic properties of segmented multi‐block polyamide elastomers (PEBAX® 3533, 5533, and 6333) and polyamide‐12 (PA12) were quantified by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and dynamic mechanical analysis (DMA) methods and rheological measurements. Soft segment, poly(tetramethylene oxide) (PTMO), contents of copolymers were proved by FTIR analysis. It was found that the increase in PTMO content dramatically reduced the crystallization and melting temperatures and degree of crystallinity values of copolymers. Different rheological test protocols performed in melt state revealed that zero shear rate viscosity values of polyamide elastomers increased with the increasing amount of hard segment. On the other hand, increase in hard segment content yielded lower flow activation energy value. In this study, we mainly focused on understanding quantitative relationships between block copolymer structure and their rheological behaviors and found that the soft segment content of ~40 (mole %) is the critical point for changing the rheological behaviors of block copolymer PAEs, dramatically. DMA measurements implied that the solid‐state viscoelastic behaviors of samples were governed by the hard content of copolymers. Higher hard content decreased long‐term creep strain and creep rate.

The Effect of Starch and Magnetite on the Physicochemical Properties of Polyurethane Composites for Hyperthermia Treatment

In this study, modified polyurethanes (PUs) with starch and magnetite were synthesized in the form of scaffolds for potential applications in orthopedics. Polyurethanes were synthesized using a one-step method. PU synthesis was carried out using poly(ε-caprolactone) 2000 as soft segments and 4,4 ′ -methylenediphenyl diisocyanate (MDI). Various molar ratios of starch and 1,5-pentanediol (PDO) as crosslinker/chain extender were applied, and the effects of incorporating different amounts of magnetite, as well as the role of PDO to starch ratio, were studied. The use of the additive in the form of magnetic particles was to feature the polyurethane materials for use in hyperthermia. The prepared polyurethanes were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA) methods. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) analysis and preliminary bioactivity assessment were also performed. The addition of magnetic particles did not cause significant changes in the properties of the obtained materials compared to starch. The tested materials have the potential to be used to fill or replace bone defects in orthopedics, where they can undergo hyperthermia treatment.