Deformation Ratio Research Articles

A continuous contact force model for the impact analysis of hard and soft materials

• A new continuous contact model is proposed with high accuracy. • The new model can simulate impacts with remaining surface deformation after impact. • The new model can simulate impacts with zero separation indentation. • The model is verified by two published experimental data and typical contact models. Impacts with remaining surface deformation or zero indentation at the separation time are common in mechanical systems with hard and soft materials, and corresponding contact force models have been established for these two types of collision phenomena, but there is a lack of models that can simulate both types of impacts. A new continuous contact model is proposed that can simulate these two types of collisions with high accuracy. By constructing an approximate equation, the new model is developed based on the typical equation of continuous contact models. Two published experiments related to two types of collisions are used for model validation; in addition, typical continuous models for the impact analysis of two types of collisions are utilized for the comparison. The validation and comparison show that the new model can simulate the impact with remaining surface deformation or zero separation indentation with high accuracy. The influences of the restitution coefficient and remaining surface deformation ratio on the system dynamic behaviors have also been investigated. The new model will be helpful for the dynamic simulation of mechanical systems with contact-impacts phenomena involving hard materials and soft materials.

Investigation on an underwater solar concentrating photovoltaic-membrane distillation (CPV-MD) integrated system

This paper presents an underwater solar concentrating photovoltaic-membrane distillation (CPV-MD) integrated system for regions of coastal cities and islands where land resources are insufficient and suffer from critical shortages in electricity and freshwater. A deformable solar concentrator that works underwater is innovatively designed and matched with the photovoltaic-membrane distillation module. Given its application scenario, the integrated system is designed without metallic components to prevent seawater corrosion. The concentrator's optical characteristics are revealed via optical simulations. The results illustrate that the concentrator bears optimal optical performance when its elastic membrane's deformation ratio α is 0.25 and height ratio γ is 0.35. An experimental setup with a solar cell radius of 50 mm is developed and tested in actual weather to reveal its electricity and freshwater yield performance. It is found that the integrated system exhibits similar performance under the light incident angle of 0°and 10°. Additionally, for the experiment with average solar radiation of 514 W/m2, the integrated system's output power varies between 1.53 W and 1.0 W, with an average electrical efficiency of 3.16 %. The accumulated freshwater yield is 67.8 g, with an average water yield efficiency of 28.5 %. This work may provide a new perspective on underwater solar energy utilization.

Modified block softening model for predicting the compressive stress–strain curve of grouted masonry

An analytical tool called the stability model is proposed based on the experimental phenomena and reasonable assumptions. The predicting results verified the rationality of this method. Then, the block’s softening process is discussed by comparing the stability and block softening models, and the concept of the block element overall softening is proposed. Next, the nominal deformation ratio, calculated by the method established in this study, is used to modify the block softening model. The modified block softening mode obtains accurate prediction results of compressive stress–strain curves and compressive strength, which shows the effectiveness of using the grouted masonry’s nominal deformation ratio to describe the block element softening. Finally, the meaning of the nominal deformation ratio μm′ and deformation ratio μm is clarified. Moreover, the path of using these two parameters to establish a unified theory for predicting the compressive behavior of grouted masonry is analyzed, and the scientific problems that need further study have been discussed.

Modified digital image correlation aided measurement of the transverse to longitudinal deformation ratio for polymeric macro-fibres

Considering the increasing interest of polymeric macro-fibres reinforced concrete, a simple and straightforward method to assess the fibre’s transverse to longitudinal deformation ratio (ηf) becomes a determining aspect in terms of fibre both characterization and fibre–matrix interaction optimization. A noncontact optical measurement procedure to assess this ratio (ηf) - for concrete reinforcement - by a modified 2D Digital Image Correlation method is presented in this paper. This ratio (ηf) has influence on the matrix-fibre interaction and, thus, on the post-cracking tensile response of the concrete composite. Details on the definition, implementation and validation of this measurement procedure are presented. Additionally, an experimental program on 20 selected lab grade and commercial fibres was carried out to analyse the consistency of the measurements and the influence of the fibre’s geometric characteristics (flat, curved, embossed or crimped) on the ηf. The outcomes of this research and the experimental procedure proposed are meant to assist fibre producers on the design process of optimized fibres to be used in structural concrete.

Dynamic analysis for the thresher of a combined harvester subjected to stalk winding

In this paper, the whirl characteristics and instability of the thresher in a combined harvester subjected to stalk winding are investigated. Using the spinning Timoshenko beam assumptions, the governing equations of motion for the thresher-stalk system are obtained via Hamilton’s principle. Considering the elastic end supports, the exact and approximated dimensionless whirl frequency equations are derived. On the basis of the obtained formulas, both whirl characteristics and stability of the thresher-stalk system are investigated numerically, and the validation of the present analysis is conducted by comparing with the results available in the literature. In addition, the effects of mode number, mass ratio, eccentric distance, shear deformation, and slenderness ratio on the critical spinning speed, stability, and instability boundary are deeply discussed. The results show that the whirl characteristics and stability of the thresher-stalk system are strongly dependent on the stalks wound around the thresher.

Experimental study of post-installed anchor embedded in concrete under simulated seismic and wind loads

In this study, experimental protocol to simulate wind-induced vibration of post-installed anchor embedded in concrete was developed. The proposed loading protocol was based on the ratio of deformation due to seismic load and dynamic wind load of anchors in the connection between the sign structure and the concrete building. Then, based on ACI 355.2 and the developed protocol, numerous experimental tests were conducted to evaluate the performance of anchor under simulated seismic and wind loads. In simulated seismic test, crack width of concrete did not affect the performance of anchor. Their maximum force as well as residual capacity showed practically the same value. Moreover, anchor used in this experiment satisfied the condition to be rated as full capacity for seismic performance. In simulated wind test, the crack width did not cause any difference in performance of the anchor in tension test. Though, in simulated wind shear test, there was a major difference for the anchor residual capacity. Additionally, the performance of anchor in simulated wind test did not satisfy the criteria to be rated as full capacity.

Crack-controlled allowable forces for high-strength reinforced concrete columns under cyclic loading using finite element analysis

High-strength reinforced concrete (HSRC) columns have been gradually promoted in use. However, the crack-controlled design method for HSRC columns is still insufficient to ensure serviceability and reparability. Therefore, the main purpose of this work is to provide a simplified method for assessing crack damage to HSRC columns. For this purpose, Finite Element Analysis (FEA) is developed to simulate crack development in selected specimens. Additionally, the FEA results are used to identify the reduction factors that are related to the stiffness and the unloading stiffness and the ratio of shear deformation to total deformation, which are required in the force-crack quantification model. Finally, for practical use in the design, a simplified formula for building the relationship between the shear force and maximum residual crack width for an HSRC column is also proposed. For practical use in the design, this work conducts a case study to build the relationship between the shear force and damage level for an HSRC column. Restated, an engineer can use this relationship to determine the allowable shear forces for ensuring serviceability and reparability.

The immediate and short-term degradation of the wood surface in a cement environment measured by AFM

This study aims to measure the pit torus and border to monitor the immediate and short-term degradation of wood surfaces after the concrete is cast and the cement hydration releases heat. The surface morphology and adhesion force curves were measured by atomic force microscopy during the treatments in saturated calcium hydroxide solutions ranging from 1 h to 27 days. The results showed that the pit torus and pit border showed different degradation processes. The adhesion force was sensitive to the type of the surface chemical components exposed during the degradation, while the surface modulus, deformation and jump-off force ratio were sensitive to the surface structural strength. The surface modulus of the pit torus degraded to 0.61–0.66 of the untreated original (95% CI) after 7-h treatments, and degraded almost completely after 48-h treatments. The surface modulus of the pit border degraded to 0.83–0.95 of the untreated original (CI) after 10 days and to 0.20–0.23 of the untreated original (95% CI) after 27 days of treatments. The treatment temperature 50 °C caused a 10-times faster degradation in the torus modulus compared to the temperature 20 °C.

Rheological Characterization of Cementitious Suspensions with Limestone Calcined Clay for Pumping Applications

Pumping of concrete is an efficient placement technique. When the concrete is pumped in a pipe, the lubrication layer (LL) forms and its rheological properties predominantly dictate the flow and govern the resumption operations. The primary purpose of this study was to investigate the effects of a new admixture, limestone calcined clay (LC2) at variable replacements (0%, 5%, 10%, and 20% by weight) on rheological properties of cementitious suspensions (equivalent to lubricating layer). An increase in yield stress, plastic viscosity, structuration rate, and decreased percolation time were observed with increments in the proportion of LC2 in cementitious suspensions. However, at the optimal dosage of superplasticizer, yield stress and plastic viscosity were decreased by 78% and 82%, respectively, even for the maximum replacement (20%) of LC2. Similarly, the percolation time increased by 15% and the structuration rate decreased by 39%, allowing additional time to deal with any pumping operational delays. From the results, it is also evident that higher deformation ratio of the lubrication layer is beneficial for concretes at rest due to pumping interruption. This study contributes to the fundamental understanding of viscoelastic properties of LC2-based cementitious suspensions, which will improve understanding of lubrication layer behavior for pumping operations.

Risk assessment and implementation of deformation disaster for operation tunnel based on entropy weight-grey relational analysis

Prevention is of paramount importance in tunnel engineering, especially in operation tunnel. In this study, the deformation data of Suzhou Metro Line 1 are used to evaluate the health of shield tunnel during operation. Firstly, the relationship between effective ratio of bending rigidity and tunnel deformation is analyzed, the results show that the effective ratio of bending rigidity has a negative power relationship with the tunnel deformation, and the conversion from deformation data to effective ratio of bending rigidity is realized and the corresponding risk classification criterion are established. Secondly, Grey Relational Analysis and Entropy Weight Method are used to deal with the deformation data, which overcomes the problem that data selection is not representative. Finally, the optimum effective ratio of bending rigidity is obtained successfully to complete the risk assessment of operation tunnel, and the assessment result is highly consistent with actual project. In addition, the corresponding application named Operation Tunnel Deformation Risk Assessment System is developed by using computer technology, which saves time for assessment and increases flexibility. The risk assessment method passes validation in the case tunnel, which can provide a reference for the disaster prevention in operation tunnel.

A systematic approach to reduce intraocular pressure for the treatment of glaucoma.

Glaucoma is the leading cause of irreversible blindness due to increased intraocular pressure (IOP) in the eye. We have developed a novel treatment option for glaucoma based on a real-time IOP-dependent nitric oxide synthase (NOS) and packed in a therapeutic contact lens to reduce the IOP. First, 1.6 nmole nitric oxide was produced from the genetic chassis, which was optimized for isopropyl β-d-1-thiogalactopyranoside (IPTG) induction in a T7 expression system. For biosafety concerns to human being, the csgAD genes responsible for curli biofilm formation in Escherichia coli were co-expressed with NOS in the designated NOSAD strain to strengthen the adherence of cells to the contact lens, thereby preventing the contamination into the eyes. Moreover, NOSAD is a diaminopimelic acid (DAP) auxotrophic strain, which cannot survive without supplementation of DAP and reached the critical consideration of biosafety to the environment. We also demonstrated that the nitric oxide diffusion was 3.6-times enhanced from penetration into the aqueous humor of porcine eyes. The deformation ratio of the contact lens was correlated to the change of IOP by using a digital image correlation (DIC) system in a porcine eye model. The novel systematic approach provides an alternative treatment for glaucoma patients in the future.

Effect of thermomechanical processing on the mechanical properties of CuZn10 alloy

Abstract The effects of thermomechanical processing on the grain size, tensile strength, and strain rate of a CuZn10 alloy were investigated. Microstructures of thermomechanically treated samples were introduced using a scanning electron microscope. The relationships between the flow stress, reduction ratio, annealing temperatures, and strain rates were detected for determination of activation energies and optimized thermomechanical parameters. The effect of grain size on the mechanical properties was examined by tensile and microhardness tests. The typical fractographs of samples after tensile tests were examined using a scanning electron microscope. It was observed that the annealing temperature and aging time have significant effects on the optimum grain size. Mechanical properties of the thermomechanically treated samples were improved by strain rate, deformation ratio, annealing temperature, and aging time.

Effect of a Perforated Polyethylene Material on Propane-Air Explosion in a Confined Space.

In this study, the effect of polyethylene barriers with different blockage ratios on the explosion behavior of a propane–air premixed gas in a confined space is investigated. The maximum explosion pressure (Pmax), the deflagration index (KG), and the flame propagation process of the propane–air premixed gas with different barrier thicknesses are examined by using a horizontal closed tube with a length of 0.5 m and a diameter of 0.1 m and a high-speed camera. The atmospheric pressure and temperature of the premixed gas were 101.3 kPa and 18 °C, respectively. Based on the Canny operator, the position of the flame front at different times and the shape of the barriers before and after the explosion are determined, and the propagation speed of the premixed flame and the deformation rate of the barriers are obtained. The results indicate that the barriers change the flow field structure of the unburned gas and increase the folding degree of the flame front. With the increase in the blockage ratio, the explosion of a premixed system becomes more rapid and violent. Under the action of Rayleigh–Taylor instability, the variation in the flame propagation speed induces a change in the tube pressure. In addition, the deformation of a barrier causes a change in the maximum explosion pressure. The greater the deformation ratio of the barrier after the explosion, the larger the maximum explosion pressure.

(TiB+La2O3)/Ti-V-Al lightweight high temperature shape memory composites with high strength fabricated by reaction hot pressing and hot rolling

In the present study, lightweight high-strength Ti-V-Al based high temperature shape memory composites were fabricated to broaden the application of shape memory alloys. In-situ TiB whiskers and La2O3 particles were introduced and the distribution of reinforcements was optimized by the combination of low-energy milling, hot-press sintering and subsequent hot rolling. The in-situ reinforcements formed a network structure, which evolved from an equiaxed shape to an ellipsoidal shape. Furthermore, the direction of the reinforcement was inclined to the rolling direction. In the reinforcement-lean area, the phase constitution evolved from the β parent phase to the α″ martensite phase, and the width of the α″ martensite gradually widened with increasing distance to the in-situ reinforcements. The composites maintained high martensitic transformation temperature characteristics. Excellent mechanical properties with a high tensile strength of 885 MPa and a large elongation of 13.1% are obtained in the composite with a 1.0 wt% LaB6 addition and 70% deformation ratio. Meanwhile, the composite realized 3.49% recoverable strain under 6% pre-strain conditions.

The Characterization of Running-In Coatings on the Surface of Tin Bronze by Electro-Spark Deposition

Antifriction materials, such as silver, copper, Babbitt B83, and graphene oxide (GO), were used to prepare running-in coatings on the surface of bronze QSn10-1 by electro-spark deposition (ESD). The analyses of mass transfer, roughness, thickness, morphology, composition, nanoindentation, and tribological properties of the coatings were investigated. The results showed that the running-in coatings were dense with refined grains that were uniformly distributed and in a metallurgical bond state with the tin bronze substrate. At optimum process parameters, the mass transfer was 244.2 mg, the surface roughness was 15.9 μm, and the thickness of the layers was 160 μm. The diffraction peaks clearly indicated the phases corresponding to α-Sn, SbSn, Cu6Sn5, and Cu, and a phase of Ag3Sn appeared. The modulus and the hardness of the running-in coatings were 24.9% and 14.2% of the substrate, and the deformation ratio of the coatings was 10.2% higher than that of the substrate. The friction coefficient of the running-in coatings was about 0.210 after the running-in stage, which was 64.8% of that of the substrate (0.324). The main wear mechanism of the running-in coatings under optimal process parameters is plastic deformation, scratching, and slight polishing. The running-in coating deformation under the action of high specific loads provides the automatic adjustment of parts and compensation for manufacturing errors.

A new potential interface tension model for MPS method avoiding unphysical particle cohesion

Improvement of the capability to accurately track the interface between immiscible phases/components is of great importance to the numerical analysis with complex multi-component and multi-phase flow dynamics, which might be involved in severe accidents of light water reactors, such as Molten Core-Concrete Interaction (MCCI). In order to model the interface tension between immiscible phases/components, Zhu et, al., precedingly developed a potential interface tension model in MPS method based on Kondo et al.‘s earlier model for surface tension and succeeded to stably model the interface tension qualitatively by introducing different attractive forces for different pairs of particle types. However, it has been known that pressure is overestimated in Zhu et, al.‘s potential interface tension model. Moreover, this study has shown that the fluid flow can be numerically hindered with Zhu et al.‘s potential interface tension model. These issues of Zhu et al.‘s potential interface tension model is caused by unphysical particle cohesion due to the inter-particle attractive forces determined by the surface tension coefficients, which are required even when the free surface is not considered. Meanwhile, in the framework of SPH method, Zhou et, al., proposed to model interface tension by introducing the repulsive force between different phases. Hence, this study aimed to develop a new potential interface tension model for MPS method which can overcome the conventional drawbacks of pressure overestimation or unphysical flow hindrance, by incorporating the repulsive force between immiscible fluid phases referring to Zhou et, al.‘s idea within SPH method.The interface tension in the present method is modeled as the repulsive force derived from the “repulsive potential” and is considered only near the interface to avoid the unphysical particle cohesion due to the inter-particle attractive forces. The amplitude coefficient in the repulsive potential is determined by the methodology similar to that proposed by Kondo, et, al.With the newly developed interface tension model, the common issue of numerical flow hindrance that occurred in the previous interface tension models in MPS method has been resolved. The validation of the newly developed interface tension model shows good agreement with theoretical evaluations of Laplace pressure and the droplet deformation ratio in a shear flow. Moreover, the new interface tension model has been validated against a 3-dimensional immiscible fluid stratification test, in which the new interface tension model shows good agreement with the test results and improvement of the pressure profile evaluations compared to that by Zhu et al.‘s model. Further extension of the present model so as to incorporate surface tension and wall wetting is one of the most important issues which require future development.

Atomistic Insights into the Phase Transformation of Single-Crystal Silicon during Nanoindentation.

The influence of the indenter angle on the deformation mechanisms of single-crystal Si was analyzed via molecular dynamics simulations of the nanoindentation process. Three different types of diamond conical indenters with semi-angles of 45°, 60°, and 70° were used. The load–indentation depth curves were obtained by varying the indenter angles, and the structural phase transformations of single-crystal Si were observed from an atomistic view. In addition, the hardness and elastic modulus with varying indenter angles were evaluated based on the Oliver–Pharr method and Sneddon’s solution. The simulation results showed that the indenter angle had a significant effect on the load–indentation depth curves, which resulted from the strong dependence of the elastic and plastic deformation ratios on the indenter angle during indentations.

Multiresponsive, Self-Healing, and Hierarchical Materials Constructed from Anion Recognition-Based Supramolecular Polymer Networks

3A type supramolecular monomers in which three calix[4]pyrrole units connected to a central benzene unit with varying linker lengths were synthesized through azide–alkyne click reactions between two different azide cores and an alkyne-functionalized calix[4]pyrrole. These compounds were then complexed with a BB-type monomer tetrabutylammonium suberate in chloroform and acetonitrile via hydrogen bonding between calix[4]pyrrole units of 3A monomers and carboxylate units of suberate anions, leading to the formation of anion recognition-based supramolecular polymer networks. Owing to the dynamic noncovalent interactions, the resulting systems were found to be responsive against temperature, competing anions, and pH. Rheological analyses of the supramolecular polymer networks revealed that the system with a longer distance between the benzene core and calix[4]pyrrole units exhibits transient network behavior and viscoelastic self-healing ability below 20% deformation ratio. These systems were also used for the fabrication of hierarchical materials ranging from zero-dimensional (0D) to three-dimensional (3D) by utilizing various methods. This work demonstrates for the first time the preparation of anion recognition-based supramolecular polymer networks based on calix[4]pyrroles and their utilization in the formation of multiresponsive, self-healing materials for the fabrication of hierarchical materials.

In situ micromechanical analysis of a nano-crystalline W-Cu composite

W-Cu composites are commonly used as heat-sinks or high-performance switches in power electronics. To enhance their mechanical properties and mutually their usability, grain refinement of the initially coarse-grained microstructure was realized using high–pressure torsion. This leads to different microstructural conditions, exhibiting fine-, ultrafine-grained or nanocrystalline microstructures. Scanning as well as transmission electron microscopy was performed to analyze the respective grain size and microstructures. The hardness and Young’s modulus of the deformed specimens were quantified by nanoindentation testing. Furthermore, X–ray diffraction indicated a decreased grain size and changed lattice spacings upon increasing the deformation ratio. The deformed specimens were tested for their fracture behaviour by continuous stiffness measurements during in-situ microcantilever bending experiments. Here, mean J–integral values of 288 ± 38 J/m2 and 402 ± 89 J/m2 were determined for the 5 and 50 times turned specimens, respectively. The combination of different characterization methods applied on a W–Cu composite allows to identify both, beneficial and unfavourable microstructural components regarding the fracture properties.

Research on Tensile Properties of Carbon Fiber Composite Laminates

In order to study the thread tensile performance of carbon fiber composite laminates, the connection between the test piece, connecting bolts, bushings, and the composite matrix, was leveraged for loading, and combined with an ultra-sound scanning imaging system, experiments were carried out on the dynamic response to record the failure behavior of the laminate structure of equal thickness. The effects of different pull-off loading strengths on the dynamic failure process, deformation profile, midpoint deformation, failure mode, and energy dissipation ratio of the thread were studied. The results show that (1) with the increase in pull-off strength, the response speed of mid-point deformation increases, the thread deformation mode changes from overall deformation to partial deformation, and the localized effect increases, accompanied by severe matrix and fiber fracture failure; (2) the thread energy dissipation ratio ascends with increasing pull-off strength and exhibits three distinct stages, i.e., elastic deformation, central fracture, and complete failure, which are directly related to the structural failure mode; (3) the failure load increases with the increment of the thickness of the laminate, and the maximum failure surface of the specimen will move from the upper layer of the laminate to the lower layer along the thickness direction; (4) the deformation velocity of the midpoint augments with the increase in the tensile rate, which can be included as a factor to assess the tensile properties of carbon fiber composites.