Processing, Analysis, Modelling and Mechanics of Materials and Structures

In order to explore the evolution of physical and mechanical properties and acoustic emission (AE) characteristics of aluminum foam under fatigue and quasi-static compression from a microscopic point of view, the AE monitoring technology was used to analyze the deformation, hardening, and energy absorption characteristics of open-cell aluminum foam under quasi-static compression at different rates (2, 10 and 50 mm/min) and fatigue loading tests with different peak stress ratios k (k = maximum stress/yield stress) by means of MTS fatigue testing machine and CCD camera. The results indicated that under different compression rates, the AE ring down count had the same trend as the engineering stress–strain response of the specimens, the AE ring down count rate at the plastic deformation stage showed the same performance as the work hardening rate, and the AE energy absorption efficiency corresponded well to the experimental results. The specimen entered the densification stage with the stability of AE count and the decrease in energy absorption efficiency. During the fatigue tests of different k values, the change trend of strain was consistent with the response of acoustic emission characteristic parameters, and the fatigue compression damage caused by the deformation process of the specimen can be monitored by the change in AE characteristics. The AE characteristics can dynamically monitor the compression process and provide a new research method and idea for the study of mechanical properties of aluminum foam. Full article

Because of the high hardness, brittleness, and anisotropy of reaction-bonded silicon carbide composites (RB-SiC), it is challenging to process high-quality textures on their surfaces. With the advantages of high processing accuracy and low processing damage, femtosecond laser processing is the preferred technology for the precision processing of difficult-to-process materials. The present work used a femtosecond laser with a linear scanning path and a spot diameter of 18 µm to process microgrooves on RB-SiC. The influence of different processing parameters on the microgroove profile, dimensions, and ablation rate (AR) was investigated. The ablation width W_a and average ablation depth D_a of microgrooves were evaluated, and the various patterns of varying processing parameters were obtained. A model for W_a prediction was developed based on the laser fluence within the finite length (F_L). As a result, the experimental values were distributed near the prediction curve with a maximum error of 20.4%, showing an upward trend of gradually decreasing increments. For a single pass, the AR value was mainly determined by the laser energy, which could reach the scale of 10⁶ μm³/s when the laser energy was greater than 50 μJ. For multiple passes, the AR value decreased as the number of passes increased and it finally stabilized. The above research will provide theoretical and experimental support for the high-quality and efficient processing of RB-SiC surface textures. Full article

In the present work, we take the influences of activated slip systems and the orientation spread into account to predict the cup height using analytical earing models and compare the predicted results with experimental results. The effect of boundary conditions of the various stress states and the work hardening exponents are compared and discussed for profile of single crystals. A stress ratio of −0.3 and a hardening exponent of 0.3 are selected for the prediction of earing profiles. The combination of activation of the single slip systems and orientation spread provides the best prediction of deep-drawing profiles. With further consideration of the orientation spread, an increase in the total orientation leads to peak-broadening, i.e., broad and smooth ears. Furthermore, the difference of the height between the maximum and minimum value of cup profiles is reduced because of the orientation spread. The profile for C is found with single ear at 45°, while the other components individually reveal double ears at 35° and 50° for S, at 15° and 45° for B, at 0° and 90° for Cube, at 5° and 90° for r-Cube, and at 15° and 90° for G. Herein, simple analytical earing models are proposed to understand the effects of slip systems and the orientation spread. The deep-drawing profiles are predicted with six major texture components. Full article

This study aims to develop combined methods with dual and triple use of different non-destructive test (NDT) methods and to examine the effectiveness of these methods. For this purpose, nine different high-strength concrete series were produced, and destructive and NDT methods were applied to these samples on the 3rd and 90th days. Surface hardness, ultrasonic pulse velocity, and penetration resistance were considered from NDT methods. Analyses were made on the response surface method using the NDT measurements and compressive strength values obtained, and four different mathematical models were developed. Models 1, 2, and 3 were designed with dual use of NDT methods, and model 4 was designed with triple use. The absolute relative deviation values for all the developed models’ early and final-age strengths were below 10%. It is of great importance to determine concrete quality with high accuracy and practicality, especially in places like Elazig, where there are thousands of newly constructed buildings since the Sivrice-Elazig earthquake, and rapid production is required. Therefore, it is thought that determining the strength values with high accuracy using the developed combined methods without damaging the building element will provide benefits in terms of time, labor, and cost. Full article

The P-S-N curve is a vital tool for dealing with fatigue life analysis, and its fitting under the condition of small samples is always concerned. In the view that the three parameters of the P-S-N curve equation can better describe the relationship between stress and fatigue life in the middle- and long-life range, this paper proposes an improved maximum likelihood method (IMLM). The backward statistical inference method (BSIM) recently proposed has been proven to be a good solution to the two-parameter P-S-N curve fitting problem under the condition of small samples. Because of the addition of an unknown parameter, the problem exists in the search for the optimal solution to the three-parameter P-S-N curve fitting. Considering that the maximum likelihood estimation is a commonly used P-S-N curve fitting method, and the rationality of its search for the optimal solution is better than that of BSIM, a new method combining BSIM and the maximum likelihood estimation is proposed. In addition to the BSIM advantage of expanding the sample information, the IMLM also has the advantage of more reasonable optimal solution search criteria, which improves the disadvantage of BSIM in parameter search. Finally, through the simulation tests and the fatigue test, the P-S-N curve fitting was carried out by using the traditional group method (GM), BSIM, and IMLM, respectively. The results show that the IMLM has the highest fitting accuracy. A test arrangement method is proposed accordingly. Full article

The coordination number (CN) is an important structure property of liquid metals. A simple yet extremely precise method for calculating CN is proposed, the classical CN methods are evaluated systematically, and the mathematical forms of the symmetry method are corrected. Using the Gaussian function construct, the first coordination shell of the pair distribution function (PDF), the right-hand side of the first peak of the pair distribution function is extrapolated, and the CN expression is simplified with a Gaussian function to obtain its non-integral form. The first coordination shell is used to explain the Tao coordination number model (Tao CN) and obtain a Modified Tao CN. The Gaussian function is combined with the Tao CN, obtaining the function expression for the peak with peak position. These are important for the structural research of liquid metals. The CN of 27 liquid metals is calculated by these methods. The average relative deviation of the Gaussian function extrapolation method is ±6.46%, of the Modified Tao CN is ± 18.51%; those of the four classical methods range from ±15% to ±42%. The Modified Tao CN and extrapolation methods to calculate CN are more accurate for calculating CN than the classical method; they are more suitable for use in quantitative applications of CN. The equations derived in this work can be applied to the problem of integration of distribution functions to obtain simple mathematical models. Full article

The compression and compressive creep behavior of target shipping containers, which are material properties based on finite element analysis, and the lifetime and load-sharing rate, were analyzed in this study to develop a computer-aided engineering prediction technology for predicting the multi-stage compression behavior of three target packages with different logistics conditions. In the experiment performed in the study, the relative humidity levels were 50%, 70%, and 90%, with creep measurements performed for 12 h for a combination of three levels of applied load and relative humidity. Using the nonlinear model of the stress–strain and creep behavior of the target shipping container, the lifetime was analyzed by estimating the average creep rate of the target shipping container. The load-sharing rate for each logistics situation of the target packages was also analyzed. The reduction rate of the compression strength of the container with respect to the increase in relative humidity was greater in the ‘horizontal long’ container than in the ‘vertical long’ container. As the applied load increased, the rate of increase in the average creep rate increased, i.e., the higher the applied load, the larger the difference in the average creep rate with respect to the relative humidity. The lifetime estimated from the failure strain and average creep rate of the container gradually decreased as the applied load increased at all relative humidity levels. However, as the applied load increased, the difference with respect to the relative humidity tended to decrease. In the target packages used in this study, the ratio of the load-sharing rate between the shipping container and an expanded polystyrene cushioning material was determined to be 2%:98%, with most of the stacking load applied to the product through the cushioning material. Full article

The mechanized resource utilization of domestic waste is the development trend in the field of waste treatment. The difficulty of bag breaking and the easy entanglement of domestic waste are the factors restricting the mechanization of waste separation and recycling. In response to the above problems, an internal blowing anti-tangle bag-breaking device for domestic waste was developed by combining the arc-type cutter and the internal flow field of the rotary. In addition, the motion trajectory of the cutters and the support rods were theoretically analyzed, as well as the force during the bag-breaking process of domestic waste. A three-factor, five-level orthogonal test was carried out to complete the regression ANOVA, and a relationship model was constructed between the test factors such as the cutting–support speed ratio, the center distance, the inlet flow rate and the response indicators such as the bag film length–perimeter ratio and bag film winding specific gravity. The key parameters and their significant interactions with the bag-breaking efficiency were analyzed to obtain the optimal combination of parameters for the device. Under the same conditions, the errors between the physical test and model predictions for the two response indicators were 5.46% and 7.90%, respectively, indicating that the verification test results were basically consistent with the model prediction results. Full article

The large difference in mechanical properties and plastic deformation ability of each layer will have a great impact on the overall performance of a composite sheet prepared by cold-roll bonding. The effect of rolling and material variables on the stress distribution and bonding state in the rolling deformation zone should be studied. In this work, an accurate cold-rolling deformation model considering the anisotropic effect and position-dependent friction model is established using the slab method. Effects of different process and material variables are analyzed. Related experiments were performed on Ti-Al clads and calculation results from the deformation model were compared with the experimental results. This model can well predict the Ti/Al thickness ratio after rolling, and the smaller the initial aluminum strength, the more accurate the predicted value; the minimum error is within 1%. The deformation coordination between the titanium and aluminum layers becomes better with the increase in rolling reduction and initial aluminum strength. At 50% reduction, the deformation ratio of titanium and aluminum increases from 93.8% to 98.1%, which is consistent with the trend of the results calculated using this model. Full article

The article presents a theoretical study of the regimes of high-pressure torsion (HPT) for which slippage of the deforming material on the interfaces with anvils is possible. The approach taken is a generalisation of the currently accepted view of the HPT process. It enables a rational explanation of its salient features and the effects observed experimentally. These include a lag in the rotation angle of the specimen behind that of the anvils, an outflow of the material from the deformation zone, enhancement in gripping the specimen with anvils with increasing axial pressure, etc. A generalised condition for gripping the specimen with anvils, providing a basis for an analytical investigation of the HPT deformation at a qualitative level, is established. The results of the analytical modelling are supported by finite-element calculations. It is shown that for friction stress below the shear stress of the specimen material (i.e., for the friction factor m < 1), plastic deformation is furnished by non-shear flows, which expands the range of possible process regimes. The potential of these flow modes is impressive, which is reflected in the second meaning of the word “gripping” in the title of the article. Non-shear flows manifest themselves in the spreading of the material over the anvil surfaces whose cessation signifies the end of deformation and the beginning of slippage of the specimen as a whole. The model shows that for m < 1 such a finale is inevitable at any axial pressure. It predicts, however, that the highest achievable strain is increased when the axial pressure is raised in the course of the HPT process. Unlimited deformation of the specimen is only possible for m = 1, when slippage of the deforming material relative to the anvils is suppressed. Full article

In this paper, the eigenfunction expansion method combined with local contact models are presented to analyze the repeated impact behaviors between the sphere and the beam. The simulations are verified with the experimental results of a simply-supported beam struck 91 times by a sphere. In order to clarify the validity of the eigenfunction expansion method to solve the repeated transverse impacts on beams, the simulation results of the spring-mass method are also compared with the experiments. It shows that with appropriate contact models, the eigenfunction expansion method can predict agreeable results with the experimental results, especially the impact behaviors (including the accumulated permanent indentation, the coefficient of restitution and the separation velocity of the sphere) representing energy dissipations, due to the consideration of structural vibrations, local impact behaviors, as well as the wave propagations. The comparisons between the eigenfunction expansion method and the spring-mass model show that the wave propagations are important for energy dissipations, which cannot be neglected in flexible structure impacts. The studies are important for the analysis of repeated impact response of beam structures. Full article

The research provides an innovative contribution to the interpretation of three-point and four-point bending tests on mortars by employing a bi-modulus material model, which assumes an asymmetric constitutive law, i.e., different elastic moduli in tension and in compression. To this aim, Euler–Bernoulli and Timoshenko bi-modulus beam models are defined, and the related displacement fields are reported for three-point loading, and provided for the first time for the four-point bending layout. A wide experimental campaign, including uni-axial tensile and compressive tests, three-point and four-point bending tests, and on notched specimens three-point tests for mode-I fracture energy, has been carried out on lime mortar specimens exploiting traditional contact (CE-DT) and contactless (DIC) measurement systems. Experimental results provided the values of tensile and compressive mechanical characteristics, which are employed to validate estimations of the analytical model. The tension-to-compression moduli ratio experimentally observed is on average 0.52. Experimental outcomes of the DIC analysis proved the bi-modulus behaviour during the four-point bending tests showing visible shifting of the neutral axis. The bi-modulus analytical model provides closer results to the experimental ones for the slender specimens subjected to four-point bending. Full article

Air-rib tents are widely used because they are lightweight and site adaptable, but the large deformation of these tents reduces their effective space. It is important to reduce the displacement of the air-rib tent by parameter optimization. The influences of external factors on the tent are studied in this paper. Four parameters of the tent’s wind ropes are the angle of the wind ropes, the number of the wind ropes, and the initial prestress of the wind ropes on the side or end faces. The influence of the angle of the wind ropes and the number of the wind ropes on the displacement is larger than the other two parameters. The closer the wind ropes are to the center of the tarpaulin, the greater the displacement of the tent. Based on an analysis using response surface methodology, the optimal parameters are as follows: the angle of the wind ropes is 41°, the number of the wind ropes on the side is two, the initial prestress of the wind ropes on the end face is 800 Pa, and the initial prestress of the wind ropes on the side is 0 Pa. Under these optimal parameters, the maximum displacement decreases by 10.2%, and the maximum stress barely changes. Full article

The creep strain resistance of expanded polystyrene (EPS) is important; thus, time-dependent creep properties of EPS have been of significant interest. This study is a part of the computer-aided engineering (CAE) prediction-technology development for the inclination of unitized loads of packaged appliances applied to EPS-based cushioning systems. Creep properties are validated to ensure finite element analysis (FEA) reliability regarding the creep behavior of EPS-based cushioning systems. The elastic modulus and Poisson’s ratio (EPS elastic properties) as well as creep properties (plastic properties) were measured. The EPS density range was 16–30 kg/m³, and the temperature range was 0–60 °C. Because the measured mechanical properties were not temperature-dependent, only their density dependence was analyzed. The EPS behavior, measured over 12 h, exhibited a significant creep amount and rate, depending on the applied stress level. FEA was performed on 7-day-long EPS creep, using the measured EPS elastic and plastic properties. The FEA and experimental results were strongly concordant. These EPS creep validation results are expected to improve the reliability of FEA for creep behavior studies of EPS-based cushioning systems. Full article

As giant magnetostrictive material, TbDyFe is regarded as a promising choice for magnetic sensing due to its excellent sensitivity to changes in magnetic fields. To satisfy the requirements of high sensitivity and the stability of magnetic sensors, TbDyFe thin films were successfully deposited on single-crystal diamond (SCD) substrate with a Young’s modulus over 1000 GPa and an ultra-stable performance by radio-frequency magnetron sputtering at room temperature. The sputtering power and deposition time effects of TbDyFe thin films on phase composition, microstructure, and magnetic properties were investigated. Amorphous TbDyFe thin films were achieved under various conditions of sputtering power and deposition time. TbDyFe films appeared as an obvious boundary to SCD substrate as sputtering power exceeded 100 W and deposition time exceeded 2 h, and the thickness of the films was basically linear with the sputtering power and deposition time based on a scanning electron microscope (SEM). The film roughness ranged from 0.15 nm to 0.35 nm, which was measured by an atomic force microscope (AFM). The TbDyFe film prepared under a sputtering power of 100 W and a deposition time of 3 h possessed the coercivity of 48 Oe and a remanence ratio of 0.53, with a giant magnetostriction and Young’s modulus effect, suggesting attractive magnetic sensitivity. The realization of TbDyFe/SCD magnetic material demonstrates a foreseeable potential in the application of high-performance sensors. Full article

Admittedly, the design requirements of compactness, low frequency, and broadband seem to constitute an impossible trinity, hindering the further development of elastic metamaterials (EMMs) in wave shielding engineering. To break through these constraints, we propose theoretical combinations of effective parameters for wave isolation based on the propagation properties of Lamb waves in the EMM layer. Accordingly, we design compact EMMs with a novel ultralow-frequency bandgap, and the role of auxeticity in the dissociation between the dipole mode and the toroidal dipole mode is clearly revealed. Finally, under the guidance of the improved gradient design, we integrate multiple bandgaps to assemble metamaterial barriers (MMBs) for broadband wave isolation. In particular, the original configuration is further optimized and its ultralow-frequency and broadband performance are proven by transmission tests. It is foreseeable that our work will provide a meaningful reference for the application of the new EMMs in disaster prevention and protection engineering. Full article

High temperature and strain will occur in the cutting area during dry milling of contour bevel gears, which causes plastic deformation of the workpiece, resulting in changes in the physical properties of the machined surface’s metamorphic layer, reducing the quality of the workpiece’s machined surface. Therefore, it is necessary to investigate the properties of the metamorphic layer and the work hardening behavior of the machined surfaces of contour bevel gears. The paper first establishes a single-tooth finite element simulation model for a contour bevel gear and extracts the temperature field, strain field and strain rate at different depths from the machined surface. Then, based on the simulation results, the experiment of milling contour bevel gears is carried out, the microscopic properties of the machined metamorphic layer are studied using XRD diffractometer and ultra-deep field microscopy, and the work hardening behavior of the machined metamorphic layer under different cutting parameters is studied. Finally, the influence of the cutting parameters on the thickness of the metamorphic layer of the machined surface is investigated by scanning electron microscopy. The research results can not only improve the surface quality and machinability of the workpiece, but are also significant for increasing the fatigue strength of the workpiece. Full article

In this study, the effects of Si on the microstructure and tensile properties of weathering bridge steel were elucidated. The thermal mechanical control process (TMCP), containing two stages of controlled rolling and accelerated cooling process, was simulated using a thermo-mechanical simulator for four experimental steels with varying Si contents (0.15–0.77 wt.%). Micro-tensile tests were performed, and the microstructures were observed via optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and electron back-scattered diffraction (EBSD). Furthermore, the tensile properties and microstructures of these steels were analyzed. The results show that a mixed microstructure comprising granular bainitic ferrite (GBF), quasi-polygonal ferrite (QF), and martensite/austenite (M/A) constituent was formed in each sample. With an increase in Si content, the GBF content decreased, QF content increased, mean equivalent diameter (MED) of the QF+GBF matrix increased, and the fraction and average size of the M/A constituent increased. With a rise in Si content from 0.15 to 0.77 wt.%, the contributions of dislocation strengthening, grain boundary strengthening, and precipitation strengthening decreased from 149, 220, and 21 MPa to 126, 179, and 19 MPa, respectively. However, the combined contribution of solution strengthening, lattice strengthening, and M/A strengthening increased from 41 to 175 MPa, which augmented the final yield strength from 431 to 499 MPa. The decreasing yield ratio shows that strain hardening capacity is enhanced due to an increase in the fraction of the M/A constituent as well as in the MED of the QF+GBF matrix. Furthermore, the mechanisms by which Si content controls the microstructure and mechanical properties of weathering bridge steel were also discussed. Full article

The microbiological purity of textiles plays a pivotal role in the use of textiles, especially in hospitals and other medical facilities. Microbiological purity of cotton fabric was achieved by a new disinfection method using tetrabutyloammonium OXONE (TBA-OXONE) before washing. As a result of the disinfection, the cotton fabric became microbiologically pure, despite the markedly decreased washing time with respect to the widely used standard procedure. Shortening of the washing time allowed for significant energy savings. In addition, the effect of the number of disinfection and washing cycles on the tensile properties and tearing force of the fabric was examined. After 120 disinfection and washing cycles the mechanical properties of cotton fabric were only slightly worsened. Full article

The advantageous implications of the microstructure and volume fraction of reversed austenite for the tensile properties of super 13Cr martensitic stainless steel (13Cr SMSS) in an experiment with quenching and double-step tempering treatment in the temperature range of 550–750 °C were investigated. The results show that, with increases in one-step tempering temperature, the content of reversed austenite was enhanced considerably from 0.9% to 13.3%. The reversed austenite distributed in the martensitic lath boundary conformed to the (1$\overline{1}$1)_γ//(011)_α’ and [011]_γ//[$\overline{1}\overline{1}$1]_α’ Kurdjumov–Sachs orientation relationship with the matrix. When tempered at 675 °C for 3 h for the first stage and 600 °C for 2 h for the second stage, the maximum volume fraction of reversed austenite was approximately 13.3%, achieving uniform elongation of 10.4% and total elongation of 27.2%. Moreover, the product of strength and elongation (PSE) was 23.5 GPa·% higher than other samples. The outstanding combination of high strength and commendable plasticity was due to the phase transformation of the reversed austenite into secondary martensite during tensile straining. The reversed austenite consumed the plastic energy at the tip of the microcrack and made the crack tip blunt, which hindered the further propagation of the crack, consequently increasing the total elongation and improving toughness. Full article

Liquid ammonia as a non-aqueous medium has many physical properties close to water, such as small molecular weight and strong permeability. It has been widely used for the ecological processing of cellulosic fibers to improve their luster, softness and dyeing properties. However, there are few reports on the dyeing of wool treated with liquid ammonia, especially at a lower temperature. Herein, a continuous liquid ammonia finishing machine was used to batch process wool followed by dyeing in a commonly-used wool dyeing machine. The results showed that many scale flakes and some cuticle cracking were seen on the fiber surface, and the disulfide bonds of cystine were broken down after liquid ammonia treatment, which promoted the diffusion of dyestuff into the fiber. Moreover, the uptakes and K/S value of wool dyed with Lanaset and Lanasol CE dyes were higher than the untreated wool, and the dyeing temperature could decrease to 85 °C, while the degree of fiber strength reduction merely decreased by 3–5%. Furthermore, for the reactive dyes, the dyeing temperature can reduce to 70 °C with the chemical auxiliaries Miralan LTD, while the degree of strength reduction decrease by 8–10%. Liquid ammonia treatment can be used for dyeing at a lower temperature than boiling temperature (100 °C), reduce energy consumption and reduce the degree of fiber strength reduction of wool. The method shows considerable to great value and is significant in providing a feasible approach for the industrial application of low-temperature dyeing technology. Full article

In the Ruhrstahl–Heraeus (RH) vacuum degassing process, we propose a real-time prediction model for the carbon content in molten steel, and show that the decarburization endpoint can be accurately determined using this model. Firstly, we applied a novel off-gas analyzer that can measure the carbon oxide concentration produced in the decarburization reaction faster and more accurately. Next, we generate decarburization curves using the off-gas components measured by the new analyzer. The decarburization curve describes the carbon content profile well during operation, and shows good agreement with the actual carbon content. In order to predict the carbon content during operation in real time, we create an artificial neural network (ANN) using the decarburization curves and operation data. By comparing the endpoint carbon content measured at the end of the operation with the predicted values, we confirmed the excellent predictive performance of the ANN model. Finally, we show that it is possible to accurately determine the decarburization endpoint using the prediction model. We expect that the proposed real-time prediction model can increase the productivity of the RH process. Full article

The production of catalysts such as zeolites is a complex multiscale and multi-step process. Various material properties, such as particle size or moisture content, as well as operating parameters—e.g., temperature or amount and composition of input material flows—significantly affect the outcome of each process step, and hence determine the properties of the final product. Therefore, the design and optimization of such processes is a complex task, which can be greatly facilitated with the help of numerical simulations. This contribution presents a modeling framework for the dynamic flowsheet simulation of a zeolite production sequence consisting of four stages: precipitation in a batch reactor; concentration and washing in a block of centrifuges; formation of droplets and drying in a spray dryer; and burning organic residues in a chain of rotary kilns. Various techniques and methods were used to develop the applied models. For the synthesis in the reactor, a multistage strategy was used, comprising discrete element method simulations, data-driven surrogate modeling, and population balance modeling. The concentration and washing stage consisted of several multicompartment decanter centrifuges alternating with water mixers. The drying is described by a co–current spray dryer model developed by applying a two-dimensional population balance approach. For the rotary kilns, a multi-compartment model was used, which describes the gas–solid reaction in the counter–current solids and gas flows. Full article

For the numerical simulation of components made of short fiber-reinforced composites, the correct prediction of the deformation including the elastic and plastic behavior and its spatial distribution is essential. When using purely deterministic modeling approaches, the information of the probabilistic microstructure is not included in the simulation process. One possible approach for the integration of stochastic information is the use of random fields. In this study, numerical simulations of tensile test specimens were conducted utilizing a finite deformation elastic–ideal plastic material model. A selection of the material parameters covering the elastic and plastic domain are represented by cross-correlated second-order Gaussian random fields to incorporate the probabilistic nature of the material parameters. To validate the modeling approach, tensile tests until failure were carried out experimentally, which confirmed the assumption of the spatially distributed material behavior in both the elastic and plastic domain. Since the correlation lengths of the random fields cannot be determined by pure analytic treatments, additionally numerical simulations were performed for different values of the correlation length. The numerical simulations endorsed the influence of the correlation length on the overall behavior. For a correlation length of 5 $\mathrm{m}$$\mathrm{m}$, a good conformity with the experimental results was obtained. Therefore, it was concluded that the presented modeling approach was suitable to predict the elastic and plastic deformation of a set of tensile test specimens made of short fiber-reinforced composite sufficiently. Full article

Orthotropic steel deck (OSD) bridges are lightweight constructions which are convenient, especially for the achievement of long spans. Conversely, due to the stress concentration in correspondence to the numerous and unavoidable welded construction details, this bridge typology is prone to fatigue cracking under the effect of cyclic loading with high-stress amplitudes. Existing OSD bridges are particularly vulnerable to fatigue damage accumulation because of the dated standards adopted at the time of their design and the fact that heavy lorries have increased in travel frequency and weight. In the present paper, a case study of a northern Italian existing highway viaduct, built in the 1990s, is presented and analyzed. The fatigue damage accumulation was carried out according to the fatigue load models for road bridges reported in Eurocode EN 1991-2 and the assessment criteria indicated in EN 1993-1-9. The stress amplitude, in correspondence to the critical details of the bridge, is assessed by means of detailed finite-element calculations carried out with the software MIDAS GEN^®. The amplitude and frequency of the travelling weights are assessed based on real traffic monitoring from the highway. Moreover, an automatic “rain-flow” algorithm is implemented, which is able to detect each nominal stress variation above the fatigue limit. In general, the bridge is not fully compliant with today’s standards when considering the entire duration of the prescribed life of the design. Countermeasures, like lane number reductions and lane reshaping, are critically analyzed since their effectiveness is questionable as far as the reduction in heavy traffic is concerned. Other interventions, like the replacement of the pavement in order to improve the stress redistribution upon the connection details below the wheel footprint, and continuous bridge inspections or monitoring, look more promising. Full article

The solidification of heavy metal Cr has always been a challenge in the treatment of Cr-containing wastes, due to its high mobility in alkaline environments. In addition, the solidification mechanism of Cr has not been fully investigated. In this study, blast furnace slag (BFS)-based cementitious materials were used as binders for the immobilization of heavy metal Cr to investigate the solidification mechanism of Cr in different hydration products. From XRD, FTIR, XPS, and XANES analyses, it could be seen that SO₄²⁻ in ettringite was replaced by Cr in the form of CrO₄²⁻, making SO₄²⁻ re-dissolve in the liquid phase. The SO₄²⁻ in the solution would compete with CrO₄²⁻ ions, leading to the direct influence of SO₄²⁻ content on the solidification efficiency of Cr. In ettringite, Cr mainly existed in the form of Cr⁶⁺, accounting for more than 84% however, Cr was solidified in Friedel’s salt under two coexisting valence states (Cr⁶⁺ and Cr³⁺). This resulted not only from the slow excitation rate of the BFS in the cementitious system that did not contain sulfate, but also from the existence of a certain amount of reducing substances in the BFS, such as Fe²⁺ and S²⁻, which could reduce some of Cr⁶⁺ to Cr³⁺. In Friedel’s salt, the residual Cr⁶⁺ replaced Cl⁻ in the form of CrO₄²⁻, whereas the Cr³⁺ replaced Al³⁺. The binding energies of Cr 2p3/1 and Cr 2p3/2 decreased with the addition of Cr, indicating that the coordination numbers of Cr³⁺ and Cr⁶⁺ increased, and that the binding energies of Cr³⁺ and Cr⁶⁺ decreased after entering the structure of Friedel’s salt. Full article

Lightweight structural alloys have broad application prospects in aerospace, energy, and transportation fields, and it is crucial to understand the hot deformation behavior of novel alloys for subsequent applications. The deformation behavior and microstructure evolution of a new Al-Zn-Mg-Li-Cu alloy was studied by hot compression experiments at temperatures ranging from 300 °C to 420 °C and strain rates ranging from 0.01 s⁻¹ to 10 s⁻¹. The as-cast Al-Zn-Mg-Li-Cu alloy is composed of an α-Al phase, an Al₂Cu phase, a T phase, an η phase, and an η′ phase. The constitutive relationship between flow stress, temperature, and strain rate, represented by Zener–Hollomon parameters including Arrhenius terms, was established. Microstructure observations show that the grain size and the fraction of DRX increases with increasing deformation temperature. The grain size of DRX decreases with increasing strain rates, while the fraction of DRX first increases and then decreases. A certain amount of medium-angle grain boundaries (MAGBs) was present at both lower and higher deformation temperatures, suggesting the existence of continuous dynamic recrystallization (CDRX). The cumulative misorientation from intragranular to grain boundary proves that the CDRX mechanism of the alloy occurs through progressive subgrain rotation. This paper provides a basis for the deformation process of a new Al-Zn-Mg-Li-Cu alloy. Full article

Ti alloys contemplating the simultaneous addition of Fe and Nb are available in the literature as Fe enhances the strength and Nb improves the biological behaviour of Ti. Nevertheless, casting has been the main manufacturing process, the Nb content is normally ≥10 wt.%, and no tensile properties are available. In this study, Ti-5Fe-xNb alloys (x = 2, 6, and 9 wt.%) were produced via powder metallurgy, which is more energy efficient than casting, with the aim of understanding the relationship between the mechanical behaviour and the microstructural changes brought about by the progressive addition of a greater amount of Nb. This study shows that the increment of the Nb content reduces the densification of the alloys, as the relative density decreases from 98.2% to 95.0%, but remarkably increases the volume fraction of the stabilised β phase (14→36%). Accordingly, the Ti-5Fe-xNb alloys are characterised by Widmanstätten microstructures, which become finer for higher Nb contents, and progressively higher mechanical properties including yield stress (725–949 MPa), ultimate tensile strength (828–995 MPa), and hardness (66.5–67.6 HRA), but lower elongation to fracture (4.0–5.1%). It is found that the ductility is much more influenced by the presence of the residual pores, whereas the strength greatly depends on the microstructural changes brought about by the addition of the alloying elements. Full article

Studies have been steadily conducted on the forming process of the bending pipe that enables the transport of underground resources. Recently, it has been suggested that bent pipes for transport withstand high pressure during the forming process, but it is judged that the research on methods able to overcome the limitations of non-uniform dimensional distribution due to the difference in the mechanical properties and thickness of the outer and inner pipes is insufficient. This study proposes a new precision forging method called the cut-forged-joint process (CFJP) for the manufacture of bent pipe containing bi-metal. The initial billet and mandrel were designed considering the standard dimensions of bent pipes, and pre-simulation was performed applied to the designed models. The results of dimensional accuracy obtained by forging experiments and the computational forming simulation were compared with each other to verify the reliability. As a final outcome, it was confirmed that it is possible to secure the dimensional accuracy of bi-metal bent pipes by applying the newly proposed CFJP. Full article

The failure of a 101.6 mm drill pipe was studied by combining experimental testing and finite element simulation. The macro analysis, metallographic structure and energy spectrum, chemical composition and a mechanical property test of the failed drill pipe sample were firstly carried out. Then, a three-dimensional finite element model of drill pipe failure was established based on the experimental results. Finally, the failure mechanism of drill pipe was analyzed and the mitigation measures were put forward. The results showed that solids settling sticking was the direct cause of fracture failure of the drill pipe joint. Due to the violent friction and wear between the drill pipe joint and the settled sand, the large amount of heat generated caused the microstructure of the joint material to undergo phase transformation and the bearing capacity to be reduced. Finally, fracture occurs under tensile and torsional loads. Full article

Laser polishing (LP) is a process that allows a significant reduction of the surface roughness of a metal workpiece via re-melting a shallow layer of material. However, the practical use of LP is limited due to the difficulty of satisfying the high surface polishing quality for industries such as jewelry. Hence, this study presents a thermal model based on the Chernoff formula for fixed and moving LP processes. The model was validated via a sensitivity analysis of the coefficient of absorption of the solid and liquid phase and through comparing the results with the corresponding experimental observations of the melt pools produced. In this investigation, a continuous wave, high power diode laser (980 nm wavelength, Ø 0.9 mm spot size with a flat top distribution) was coupled to a fixed focusing head. The material was a hardened tool steel (X38CrMVo5-1 steel-1.2343) with an initial surface state obtained by electrical discharge machining (EDM) of CH30 on the Charmilles scale for EDM, which corresponds to a roughness Ra of 3.15 µm. The results show that the model is able to represent the thermal behavior of the tool steel during LP. The best results are obtained with two constant coefficients, one for the solid based on the measurement at room temperature (a_s = 35%) and one for the liquid fixed so that the model fits the experiment data (a_l = 25%). Full article

Chemical–mechanical polishing (CMP) is widely adopted as a key bridge between fine rotation grinding and ion beam figuring in super-smooth monocrystalline silicon mirror manufacturing. However, controlling mid- to short-spatial-period errors during CMP is a challenge owing to the complex chemical–mechanical material removal process during surface morphology formation. In this study, the nature of chemical and mechanical material removal during CMP is theoretically studied based on a three-system elastic–plastic model and wet chemical etching behavior. The effect of the applied load, material properties, abrasive size distribution, and chemical reaction rate on the polishing surface morphology is evaluated. A microscale material removal model is established to numerically predict the silicon surface morphology and to explain the surface roughness evolution and the source of nanoscale intrinsic polishing scratches. The simulated surface morphology is consistent with the experimental results obtained by using the same polishing parameters tested by employing profilometry and atomic force microscopy. The PSD curve for both simulated surface and experimental results by profilometry and atomic force microscopy follows linear relation with double-logarithmic coordinates. This model can be used to adjust the polishing parameters for surface quality optimization, which facilitates CMP manufacturing. Full article

Brittleness is an essential parameter to determine the deformation and failure behavior of rocks, and it is useful to quantify the brittleness of rocks in numerus engineering practices. A novel energy-based brittleness evaluation index is proposed in this study, which redefines the dissipated proportion of ultimate elastic strain energy relative to post-peak failure energy and residual elastic strain energy. A series of conventional triaxial compression (CTC) tests were performed on shale rock to verify the reliability and accuracy of the brittleness index. The results show that the proposed index can precisely reflect the deformation and failure characteristic of rocks under different confining pressures. Based on the testing data from six types of rocks in previous studies, the universality of the novel index was verified. According to comparison with existing brittleness indices, the new brittleness index can more precisely characterize the brittleness of rock. Full article

With the need of developing new materials, exploring new phenomenon, and discovering new mechanisms under extreme conditions, the response of materials to high-pressure compression attract more attention. However, the high-pressure state deviating from the Hugoniot line is difficult to realize by conventional experiments. Gas gun launching graded materials could reach the state. In our work, the corresponding Al-Cu composites and graded materials are prepared by tape casting and hot-pressing sintering. The microstructure and the acoustic impedance of the corresponding Al-Cu composites are analyzed to explain the impact behavior of Al-Cu graded materials. Computed tomographic testing and three-dimension surface profilometry machine results demonstrated well-graded structure and parallelism of the graded material. Al-Cu GMs with good parallelism are used to impact the Al-LiF target at 2.3 km/s using a two-stage light-gas gun, with an initial shock impact of 20.6 GPa and ramping until 27.2 GPa, deviating from the Hugoniot line. Full article

Existing concrete random aggregate modeling methods (CRAMMs) have deficiencies in in the parameterization of the mesoscale pore structure. A novel CRAMM is proposed, whose pore structure is determined by the pore gradation, total porosity, sub-porosity, and pore size of each pore gradation segment. To study the influence of pore structure on the mechanical properties of concrete, 25 mesoscopic concrete specimens with the same aggregate structure but different meso-scale pore structures are constructed and subjected to uniaxial compression tests. For the first time, the influence of sub-porosity of each pore gradation segment, average pore radius (APR), pore specific surface area (PSSA), and total porosity on concrete failure process, compressive strength, peak strain, and elastic modulus were quantitatively and qualitatively analyzed. Results indicate that the pore structure makes the germination and propagation of the damage in cement mortar show obvious locality and affects the formation and expansion of macroscopic cracks. However, it does not accelerate the propagation of the damage in cement mortar from the periphery to the center of the specimen, nor does it change the phenomenon that the ITZ is more damaged than other meso-components of concrete before peak stress. Macroscopic cracks occur in the descending section of the stress–strain curve, and the sudden drops in the descending section of the stress–strain curve are often accompanied by the generation and expansion of macroscopic cracks. The quadratic polynomial, exponential, and power functions can well fit the relationship between total porosity and compressive strength and the relationship between PSSA and compressive strength. The linear, exponential, and power functions can well reflect the relationship between total porosity and compressive modulus and the relationship between compressive modulus and PSSA. For concrete specimens with the same total porosity, the elastic modulus and strength show randomness with the increase in the sub-porosity of macropores and are basically not affected by the APR. Based on the grey relational analysis, the effects of pore structure parameters on the elastic modulus and compressive strength are in the same order: total porosity > T [k₁,k₂] > T [k₂,k₃] > T [k₃,k₄] > T [k₄,k₅] > AVR > PSSA. The order of influence of the pore structure parameters on the peak strain is: T [k₂,k₃] > T [k₁,k₂] > T [k₃,k₄] > T [k₄,k₅] > APR > PSSA > total porosity. Full article

The machined-surface integrity plays a critical role in corrosion resistance and fatigue properties of ultra-high-strength steels. This work develops a multiphysics model for predicting the microstructure changes and microhardness of machined AerMet100 steel. The variations of stress, strain and temperature of the machined workpiece are evaluated by constructing a finite-element model of the orthogonal cutting process. Based on the multiphysics fields, the analytical models of phase transformation and dislocation density evolution are built up. The white layer is modeled according to the phase-transformation mechanism and the effects of stress and plastic strain on real phase-transformation temperature are taken into consideration. The microhardness changes are predicted by a model that accounts for both dislocation density and phase-transformation evolution processes. Experimental tests are carried out for model validation. The predicted results of cutting force, white-layer thickness and microhardness are in good agreement with the measured data. Additionally, from the proposed model, the correlation between the machined-surface characteristics and processing parameters is established. Full article

In order to effectively prevent and control the rutting problem of asphalt pavement in the deep loess area of Eastern Gansu and reduce road diseases, diatomite was added into the asphalt mixture for laboratory tests. Through Marshall test and rutting test, the optimum mix proportion of the diatomite asphalt mixture, and the optimal mix amount of the diatomite in this area were determined. The pavement performance of activated diatomite asphalt pavement and SBS asphalt pavement in this area is compared and analyzed through laboratory tests and on-site road paving. The test results show that under the same ambient temperature, the activated diatomite asphalt pavement has the advantages of lower surface temperature, high stability, and low-water permeability coefficient than SBS modified asphalt pavement. In addition, by fitting the fatigue test data of these two asphalt pavements, it is found that the fatigue life of diatomite asphalt mixture is more sensitive to the change in stress level and has better fatigue resistance. Therefore, it is concluded that the use of diatomite modified asphalt pavement in the loess area can improve the temperature stability of the pavement, prolong the service life, and reduce the cost of construction, which can be popularized. Full article

Based on the nonlinear piezomagnetic equation, the piezomagnetic effect of prismatic iron-cobalt alloy is analyzed by using the ANSYS finite element simulation platform. The variation of the dynamic piezomagnetic coefficient of the iron-cobalt alloy under different bias magnetic fields and different stress was studied through simulation. Referring to the working condition of the tractor force sensor and according to the principle of magnetic circuit superposition, a piezomagnetic force sensor was designed and manufactured using iron-cobalt alloy. According to the electromagnetic theory and piezomagnetic effect, the three-dimensional model and magnetic circuit mathematical model of the sensor are established, and the system simulation model of the piezomagnetic sensor was established based on the MATLAB/Simulink module. The experimental platform of the magnetostrictive force sensor was built to verify the correctness of the simulation model, and the effects of bias magnetic field and force on the output characteristics are studied. The simulation and experimental results show that the maximum piezomagnetic coefficient was 9.2 T/GPA when the bias magnetic field intensity was 14.74 kA/m. The force measuring range of the sensor is 0–120 kN, and the sensor has high sensitivity within 0–80 kN. The sensor has a simple structure, is suitable for the force measurement and control of an electro-hydraulic lifter under heavy load, and can better adapt to the harsh working environment. Full article

Collisions between ships and offshore platforms frequently occur, with severe consequences. Predicting the collision depth under different conditions is very important to evaluate the severity of the consequences. Considering the time-consuming numerical simulation problem and the accuracy problems of existing approximation algorithms, this paper proposes a comprehensive approach to estimating penetration depths by obtaining two collision coefficients for specific collision structures based on the partial results of numerical simulations and simplified theoretical analysis. In this study, the collision process between a supply ship with a transverse framing stern and an offshore semi-platform was first numerically simulated based on the explicit dynamic method. The changes in ship velocity, impact force, and energy conversion before and after the collision processes were obtained through numerical simulations of the collisions with different speeds and angles. Then, by combining the external dynamics and numerical results, the analytical results of dissipated energy under other collision conditions were obtained using a simulated restitution coefficient. For the following internal dynamics analysis, according to the failure modes of specific structural components in different regions, an appropriate structural energy absorption formula was combined to obtain the relationship between the penetrations and energy absorption in a particular collision area. According to the friction energy ratio derived by the simulation, the penetration depths in the offshore platform were calculated. The results showed that the deviations between the proposed method and direct simulation results were less than 15% in the cases of a medium- to high-energy collision. It can be concluded that the restitution coefficient and friction energy ratio in different collision conditions can be approximately determined for a specific collision system by typical numerical simulations, thus quickly calculating the penetration depths of other conditions. Full article

In this study, a functional relationship between the solid particle density $({\rho }_s)$, void ratio $\left(e\right)$, and dry density $({\rho }_d)$ of mechanically and biologically treated (MBT) municipal solid waste (MSW) was examined. In total, 60 waste specimens were tested with an air pycnometer device and corresponding triplets $(e, {\rho }_d,\mathrm{and}{\rho }_s)$ of values were obtained. In addition, a long-term oedometer test with an allowed decomposition process was also conducted. Based on the obtained results, the variability in the solid particle density caused by heterogeneity and decomposition, as well as its influence on the corresponding void ratio and dry density values, were critically evaluated. The obtained results showed that the variability in the solid particle density caused by waste heterogeneity had a significant influence on the initial void ratio value. Furthermore, the obtained results also showed that the change in the solid particle density, caused by the degradation process, had a significant impact on the final void ratio and dry density values. In addition, an empirical relationship, ${\rho }_d=f\left(e\right),$ was proposed. The proposed function allows a landfill operator to establish the corresponding dry density at an arbitrary chosen void ratio, and vice versa, without having the exact knowledge of the corresponding solid particle density value. Full article

The ammonothermal method is considered the most promising method of fabricating bulk gallium nitride (GaN) crystals. This paper improves the ammonothermal growth model by replacing the heater-long fixed temperature boundary with two resistance heaters and considering the real thermal boundary outside the shell. The relationship between power values and temperatures of dissolution and crystallization is expressed by the backpropagation (BP) neural network, and the optimal power values for specific systems are found using the non-dominated sorting genetic algorithm (NSGAII). Simulation results show that there are several discrepancies between updated and simplified models. It is necessary to build an ammonothermal system model with resistance heaters as a heat source. Then large-sized GaN crystal growth is analyzed based on the well-developed numerical model. According to the simulation results, both the increasing rate and maximum stable values of the metastable GaN concentration gradient are reduced for a larger-sized system, which is caused by the inhomogeneity of heat transfer in the autoclave. Full article

Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%. Full article