Visible Cracks Research Articles

Study on the pore structure characteristics and damage constitutive model of sandstone under freeze-thaw conditions

Rocks in Northwest China are often affected by the combined action of freeze-thaw and load erosion. Therefore, in order to better understand the mechanical properties of rocks in seasonal frozen areas and the meso-damage caused by freeze-thaw erosion, uniaxial compression tests, electron microscope scanning tests, X-ray diffraction tests (XRD) and mercury intrusion tests (MIP) were carried out on five sandstone samples with different freeze-thaw times, and the mechanical parameters and meso-damage characteristics of sandstone samples with different freeze-thaw times were obtained. Fractal theory was used to analyze the change in pore volume of sandstone after freeze-thaw cycles. Finally, the damage constitutive equation under the coupling action of freeze-thaw damage and load was established based on Lemaitre’s equivalent effect variation criterion. The results showed that the type of sandstone is a porous coarse-grained sandstone. With the increased freeze-thaw times, the compressive strength and cohesion of sandstone gradually decreased, and the closed pores in sandstone gradually connected, leading to the visible internal macroscopic cracks. Affected by freeze-thaw times, the volume proportion of large pores (100–1,000 µm) in sandstone gradually increased, while the volume proportion of micropores (.05–100 µm) gradually decreased. With the increased freeze-thaw times, the fractal dimension of pore volume decreased from 1.94 to 1.59. The theoretical curve can better fit the characteristic points of the stress-strain curve, which can further reveal the damage mechanism of sandstone under the coupling effects of freeze-thaw and load. The minimum error between the peak point of the experimental curve and the theoretical curve is 3.3%.

Cereal based traditional beverage of tella residue (attela) as a green organic pollutant sorbent for methylene blue dye removal: Equilibrium, kinetics and thermodynamic studies

Dyes are one the foremost hazardous pollutants that affects bio life including the flora and fauna and removing of those pollutants from contaminated environment are remarkable activities within the scientific community. In this respect, the current study is focused on preparation of physiochemical activated cereals based tella residue bio adsorbent for basic blue dye (MB) removal from aqueous environment. Different analytical methods have been utilized to assess the thermal stability, surface area, surface morphology, pore size, pore volume, surface functional group, and a few proximate analyses of the prepared bio adsorbents. The SEM and BET results of the adsorbents reveals physiochemical activation process assists for the formation of visible pores, cracks, irregular shape, and better surface area (51.32 m2/g for RTR and 565m2/g for ATR) respectively. The removal efficiencies of MB by RTR and ATR in an exceedingly batch experiment were 88.4s and 97.2 % at situation of pH (8); adsorbent dosage (0.8 for RTR and 0.6 for ATR), agitation speed (300 rpm), dye concentration (10 mg/L), temperature (298oK) and contact time (100 minute) respectively. The kinetics and equilibrium result of dye adsorption process well described by Pseudo 2nd order kinetic and Langmuir isotherm model respectively. The thermodynamic finding result shows the spontaneous and endothermic nature of the sorption process. The probable adsorption mechanism of MB dye on the prepared bio adsorbents surface may be assigned mainly through chemisorption. The results of this study show, the current adsorbents promise an alternate green rout for treatment dye contaminated wastewaters.

Fabrication of ecofriendly jute fiber reinforced flexible planar composite as a potential alternative of leather

Natural fiber reinforced composites are a lightweight, affordable, and environmentally friendly replacement for many problematic applications. These natural fibers could be constructed into flexible planar materials with the aid of composite phenomena that can be used for a variety of applications where flexibility is important like as artificial leather. In this work, nonwoven matt made from spinning wastes of jute fiber was used to reinforce the biodegradable polyvinyl alcohol (PVA) matrix. The percentage of fibers within the PVA matrix was adjusted to develop the flexible planar composites. The nonwoven matt was immerged into the PVA solution casting mold with the aid of the solution evaporation approach. The flexible planar composite was then obtained through heat-induced pressing. Tensile strength, tearing strength, bending modulus, flexing endurance, abrasion resistance, and moisture management profiles of the developed flexible planar composite were assessed. Additionally, studies were performed for Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric (TGA) analysis. The tensile strength has been found 7.78 N/mm2 with 9.84% elongation for a 1.2 mm thick flexible composite. The flexing endurance has been supported by no visible crack formation against 50,000 flexing cycles. The moisture management profile has been ensured by the hydrophobic surface of the composite. Developed flexible planar composite has been shown to have consistent mechanical performance for use as artificial leather, which could be appealing for the fabrication of leather-alternative bags, belts, and wallets.

Formulation and Characterization of Buccal Patches of Oxaceprol

Background: Oxaceprol is an anti-inflammatory and antirheumatic agent. Buccal route has advantage over conventional mode of drug administration. It avoids hepatic first pass metabolism and improve patient compliance. The main objective of the present study is to formulate and evaluation of buccal patches of Oxaceprol to overcome drawbacks of conventional dosage forms. Buccal patches were prepared by solvent-casting method using HPMC K-15 and PEG as plasticizer. Oxaceprol was initially characterized for its preliminary studies such as organoleptic properties, melting point, solubility, UV Spectroscopy, and FTIR studies. Drug-excipients compatibility was confirmed by FTIR, DSC and assay of drug content. The formulations were prepared and evaluated for parameters like physical appearance, thickness, weight uniformity, % moisture loss, folding endurance, drug content uniformity. All prepared patches of drug were smooth and elegant in appearance. No visible cracks were observed. All formulations were uniform in weight, thickness, and drug content. The folding endurance was increased with an increased in polymer concentration. In vitro drug release of F6 batch was 93.78% at the end 8 hr. Oxaceprol buccal patches showed enhanced the bioavailability. Release exponent n value obtained from Kors Meyer- Peppa’s equation was within 0.5 -1.0 which indicates anomalous release.

Graphene-oxide-reinforced cement composites mechanical and microstructural characteristics at elevated temperatures

Abstract The focus of this research was to investigate the effects of graphene oxide (GO) on the microscopic composition, structure, pore size, and mechanical properties of GO-reinforced cement composites. Furthermore, the research explored the thermal behavior of GO-reinforced cement mortar at different elevated temperatures (250, 500, 750, and 1,000°C). This study considered three sets of GO-reinforced cement composites with 0.1, 0.2, and 0.3 wt% of GO (by weight of cement); the water–cement ratio in all the mixtures was 0.5. To characterize the chemical composition, microstructure, and hydration degree resulting from GO addition, X-ray diffraction, thermogravimetry, derivative thermogravimetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and micro-computed tomography (Micro-CT) were used. The experimental results revealed that GO addition changed the microstructural composition and pore diameter distribution of the cement composite. The optimal amount of GO required for improving the mechanical properties of the cement composite under both unheated and heated conditions was identified to be 0.1 wt%. GO improves the cement matrices’ ability to bind with GO nanosheets, leading to compressive strength retention and decreased micro-cracking (computed by material and defected volume changes by Micro-CT analysis). This is primarily due to the hydration products. However, the optimal amount of GO can result in nanomaterial agglomeration, thus lowering the thermal resistance of the cement composite. Overall, the study identified GO as a nano-additive with the potential to improve the strength and toughness of the cement composites. Moreover, the effect of elastic modulus was also evaluated. As a result, the GO microstructure analysis revealed that it has a porous structure with a visible crack pattern.

Design and test results of different aluminum coating layers on the sCMOS sensors for soft X-ray detection

In recent years, tremendous progress has been made on complementary metal-oxide-semiconductor (CMOS) sensors for applications as X-ray detectors. To shield the visible light in X-ray detection, a blocking filter of aluminum is commonly employed. We designed three types of aluminum coating layers, which are deposited directly on the surface of back-illuminated sCMOS sensors during fabrication. A commercial 2k × 2k sCMOS sensor is used to realize these designs. In this work, we report their performance by comparison with that of an uncoated sCMOS sensor. The optical transmissions at 660 nm and 850 nm are measured, and the results show that the optical transmission reaches a level of about 10-9 for the 200 nm aluminum layer and about 10-4 for the 100 nm aluminum layer. Light leakage is found around the four sides of the sensor. The readout noise, fixed-pattern noise and energy resolution of these Al-coated sCMOS sensors do not show significant changes. The dark currents of these Al-coated sCMOS sensors show a noticeable increase compared with that of the uncoated sCMOS sensor at room temperatures, while no significant difference is found when the sCMOS sensors are cooled down to about -15°C. The aluminum coatings show no visible crack after the thermal cycle and aging tests. Based on these results, an aluminum coating of a larger area on larger sCMOS sensors is proposed for future work.

Raised Floor Systems with Ceramic Tiles

The objective of this study is to evaluate the mechanical strength of raised floor systems with ceramic coatings. The raised floor prototypes are made of three types of ceramic tiles, two of which have a dimension of 60 × 60 cm and one has a dimension of 60 × 120 cm. Instrumentation is performed by attaching the strain gauges to the surface of the ceramic tiles. The raised floor prototypes are subjected to vertical compression loads until visible cracks appear on the surface of the ceramic tiles, and the resistance to system rupture is evaluated by analyzing their deformations. The results indicate that the load application position interferes with the resistive ability of the systems. Systems with plates having low water absorption and high thickness yield high breaking loads, which can be considered as the determining factors for outdoor applications of raised floor systems.

Monitoring the behaviour of seven storeyed RC frame subjected to reversed cyclic loading by nonlinear NDT

Large-scale structures are more prone to risk than small-scale structures due to their increased weight, stiffness and ductility parameters. The main focus of this investigative study is on the structural monitoring of a building using the non-destructive method of non-linear ultrasonic pulse velocity. A single-bay seven-storeyed frame model subjected to reverse cyclic loading of varying amplitudes is monitored by non-linear ultrasonic technique based on third harmonic wave generation. The critical nodes are identified in two different ways: the points of possible plastic hinge formation (PPPHF) through the theoretical background of plastic hinge analysis and the highly sensitive regions in structures (HSR) through numerical analysis. The common nodes of PPPHF and HSR are considered to monitor the structure. The invisible primary structural damage in the initial stage and the visible structural damage up to ultimate load are observed using non-linear ultrasonic waves. The fundamental frequency value and the third harmonic frequency value are observed and processed in MATLAB in the form of a Fast Fourier Transform (FFT) algorithm. The relationship between the condition of the structure and the ratio of third harmonic parameter, load and displacement is compared. In the initial stage of loading, only slight change or no variation in third harmonic ratio is observed at the observation points indicating material disintegration. This varies consistently up to the development of visible cracks and the same varies inconsistently on further loading after the appearance of visual cracks.

Experimental study on the influence of scattered broken wires on the structural performance of prestressed concrete cylinder pipe

Given that the prestressed concrete cylinder pipe (PCCP) derives compressive strength from high-tensile prestressing wires, breaking of steel wires is endangering the safety of PCCP lines. To deeply explore the influence of broken wires on the performance of PCCP, two 3.4 m PCCPs with the same design parameters are tested until failure by separately cutting their steel wires in clustered and scattered manners. And this paper mainly presents the destructive test with scattered broken wires (SBWs) under the water pressure of 1.15 MPa. To collect spatially continuous strain data, four different types of distributed optical fibers are applied on five material layers of the test pipes during the production. The results show that the distribution of breakpoints is highly scattered and each broken wire regains its full tension gradually over about a 60° angle from the breakpoint when the number (ratio) of SBWs does not exceed 120 (39.6 %). As a consequence of the subsequent wire breakage, the scattered breakpoints gradually concentrate, and then mortar cracking and delamination from the wires occurs and increases the length of the wire needed to regain full tension. The numbers (ratios) of SBWs corresponding to the onset of visible cracks in the outer concrete, and mortar, yielding of the steel cylinder, visible cracks in the inner concrete, and final failure are 125 (41.3 %), 145 (47.9 %), 165 (54.5 %), 170 (57.8 %), and 185 (61.1 %), respectively. The measured sizes of breakpoint separation show that the SBWs in one wire-cutting zone has small influence on other zones. And the number of SBWs is greater than three times that of clustered broken wires at the final failure. Both the number and concentration degree of broken wires should consequently be factored into the condition assessment of PCCP. It is worth reminding that the test results obtained are not to be applied indiscriminately to other pipe designs.

Crack-free laser powder bed fusion by substrate design

Additively manufactured components by laser powder bed fusion (LPBF) often suffer from stress-induced cracks (e.g. delamination), especially at the build-substrate interfaces where stiff mechanical constraints and large thermal gradients coexist. To reduce the probability of cracking, this work proposes an innovative strategy to optimize the geometry of the substrate by reducing its mechanical stiffness and, consequently, the stress accumulation during LPBF. To assess the feasibility of the strategy, a coupled thermo-mechanical finite element model, calibrated with the experimental evidence obtained from the LPBF metal deposition of a bridge-type structure, is used to predict the thermo-mechanical behavior of two T-shape AM parts built on (i) a typical solid substrate and (ii) a groove patterned substrate, respectively. The results show that several visible cracks appear at the interface between the build and the typical solid substrate due to stress concentration (up to 1600 MPa), while a crack-free component can be manufactured by adding grooves through the thickness of the substrate, without compromising the resulting microstructure and microhardness of the metallic materials with high crack sensitivity. The difference between the groove patterned substrate design with respect to the use of support structures used for printing cantilever structures is clarified to further justify the novelty of the proposed approach.

Indentation cracking in mono and polycrystalline cubic zirconia: Methodology of an apparent fracture toughness evaluation

Indentation-induced cracking with sharp tips is studied on mono- and polycrystalline cubic zirconia. Tests at different applied loads are carried out, ranging below and above a threshold load above which visible surface cracking is noted after testing. This threshold load does not appear to be correlated to any discontinuity in the evolution of either the hardness or the irreversible energy ratio with applied load. The crystal orientation and the presence of grain boundaries clearly affects the shape of the cracks generated around the residual imprint. Polycrystalline samples show significantly shorter indentation induced cracks and therefore a higher apparent toughness than single crystals for the same load. In addition, for single crystals, cracks are deflected towards {110} type planes, appearing to be the most susceptible to cracking, and thus logically presenting the lowest apparent toughness. Tests with a Berkovich tip leads to an average of different crystal orientations, while tests with a Vickers tip can be used to test a specific crystal orientation in the case of a cubic crystal such as zirconia.

A new understanding on titanium coloration-variation of external stimuli and in-depth mechanism analysis

Surface coloring technology plays a very unique role in the diversification of Ti applications. We report our new findings using AC polarization to fabricate chromatic passive films on Ti surface. Compared to passivation films formed using DC anodization, brighter and more uniform colors could be generated in a controlled manner by simply varying the waveform of AC polarization. The colored films fabricated by AC polarization were very dense without visible cracks or defects. DC anodization, AC sine polarization, and AC square polarization exhibited high light reflectivity in the wavelength range of 380–450 nm, 500–650 nm, and 400–500 nm, respectively. The composition distribution and formation process of colored films were analyzed in depth, which enabled our further understanding of the electrochemical coloration mechanism on Ti surface. The thickness of DC anodization, AC sine polarization, and AC square polarization were 161 nm, 203 nm, and 165 nm, which corresponded to the colors of oxford blue, pale yellow, and light blue, respectively. In addition, the corrosion resistance measurements further revealed that the films with lower surface roughness prepared by AC polarization presented great protective effect on the Ti matrix.

Full-Scale Test and Bearing Capacity Evaluation of Large Diameter Prestressed Concrete Cylinder Pipe under Internal Water Pressure

In practical applications, the safe operation of large-diameter prestressed concrete cylinder pipes (PCCPs) depends on the loading performance under internal water pressure. However, there is lack of damage tests for the full-scale large-diameter PCCPs due to economic cost and experimental difficulty. In this paper, a full-scale PCCP with diameter of 3.2 m was tested to verify the bearing capacity for applying to an actual water transfer project. The PCCP was designed by the limit state method and manufactured in a prefabrication plant. During the test, the strains of concrete, prestressed steel wire, and mortar were detected to evaluate the limit state of bearing capacity under internal water pressure. Based on the test results and the strain analysis at the limit state, it was found that when the water pressure reached 1.9 MPa, the concrete outside the steel cylinder was at the serviceability limit state, and the prestressed steel wire was in elastic, while some protective mortar exceeded the serviceability limit state due to the appearance of visible cracks. A good accuracy of the theoretical calculation with the predicted results lower about 9.4% and 8% than tested pressures at decompression and cracking states. Moreover, the cracking pressure of concrete and bursting pressure of pipe were 2.5 and 6 times of the working pressure according to the calculation results. This indicated that the PCCP used in this study had sufficient safety in actual operation. However, it should be noted that the tensile control strain of mortar may be overestimated by the current code.

Evaluation of bond behaviors on functionally graded ultra-high performance concrete (FGUHPC) subjected to elevated temperature

This paper designed a two-layered functionally graded ultra-high performance concrete (FGUHPC) member to meet the bearing and fire-resistant requirements subjected to elevated temperature, where the UHPC layer was used to bear loads and was protected by the lightweight aggregate concrete (LWAC) layer from high temperature. Debonding tests were conducted to evaluate its interfacial behaviors under ambient and high temperatures and the effect of cast-in bolts were investigated. The results showed that all specimens exhibited good fire-resistant behaviors, no visible cracks and spalling were observed for the UHPC layers while the LWAC layers maintained good integrality. Embedded bolts could significantly improve the initial stiffness, bond strength and post-peak ductility of specimens under direct tension at room temperature. The enhancement of bond strength was 40.0 % and 56.5 % when employing bolts with a diameter of 10 mm and 12 mm while that of ultimate displacement was 62.2 % and 58.1 % respectively compared with the specimens without bolts. In the case of high temperature, all specimens showed brittle failure, the bond strength obviously decreased and the effect of bolts on bond behaviors was insignificant due to the deterioration of the LWAC layers. All specimens without bolts showed debonding failure during the tests while the failure mode was converted from breakout to splitting or pullout for the specimens with bolts as the temperature increased.

A new aspect of post-depositional alterations of lithic artefacts: the case of Medzhibozh Lower Palaeolithic assemblages

Flint artefacts have been identified in the materials of the Lower Palaeolithic sites of Medzhibozh, which have experienced the effects of post-depositional alterations (PDA). We suggest a particular combination of anthropogenic and natural effects on lithic artefacts. In the vicinity of Medzhibozh in the Khmelnytskyi region in the West of Ukraine, several multilayered stratified Lower Palaeolithic sites are currently known. Artefacts and accompanying fauna have been identified in subaerial buried soils, initial hydromorphic soils, and alluvial deposits. The ages of the artefact-bearing sediments are preliminarily estimated to be between 1.2 and 0.4 Ma. The lithic assemblages of all horizons contain technologically and typologically archaic artefacts, the industry being referred to as Mode 1. Various types of rock were used as raw materials, including locally occurring flints in the form of pebbles and flattened nodules. Flint products from many assemblages are characterized by rounding and sheen due to their extended exposure to water-permeable horizons. Most of the flint artefacts belonging to a particular assemblage are of a similar type of preservation. The assemblages also contain artefacts with surfaces of different states of preservation, suggesting that they are of different ages. These could either be products of reutilisation or natural alterations. However, more recent surfaces tend to be isolated and do not form a removals system. Moreover, most of the individual PDA pieces show a technological and morphological consistency of differently preserved surfaces, indicating that a force initiating detachment was applied simultaneously. We, therefore, consider artefacts showing a variate state of scar preservation to be PDA products. We assume we are dealing with a new aspect of post-depositional alterations of lithic artefacts. Natural alteration had subjected artefacts, which received internal damage to the structure earlier when processed by man. The bipolar-on-anvil technique was actively used at Medzhibozh. Many artefacts show signs of multiple attempts of knapping, accompanied by a change in the position of the segmenting item. Such signs are impact pits, visible cracks, and Herzian cones disturbing the rock's texture. We believe that the internal cracks that appeared in the area of the not detached spall contribute to the accelerated natural alteration of the item in this area and, ultimately, to the detachment of the flake. The probability of spalling depends on the intensity of the internal distress, the structure of the rock, the climatic conditions, and the post-depositional environment. The most responsible factor for the effect of the “time-delayed spalling” seems to be repeated cycles of temperature changes. A comprehensive study of post-depositional modifications of lithic artefacts is essential in studies of Lower Palaeolithic sites, particularly the technological Mode 1 (Oldowan). This is due to the highly heterogeneous raw materials used, the bipolar-on-anvil knapping technique, and a long period of post-discard behaviour of artefacts. Key words: Lower Palaeolithic, Medzhibozh, stone artefacts, post-depositional alterations, time-delayed spalling, taphonomy.

Experimental Investigation of Cracking and Impact Resistance of Polymer- and Fiber-Enhanced Concrete for Ultra-Thin Whitetopping.

In order to investigate the effectiveness of polymer modification and fiber reinforcement on the cracking and impact resistance of concrete materials prepared for ultra-thin whitetopping (UTW), carboxyl butyl benzene latex and polyformaldehyde fibers were added to the conventional cement concrete mix. In addition, test methods that used an asphalt mixture performance tester (AMPT) and mechanical rammer were developed to evaluate concrete cracking and impact resistance, respectively. Results from the AMPT test revealed that the cracking resistance can be enhanced with polymer and fiber, especially the initial tensile load peak, which can be improved by more than 40% when fiber and polymer compound modification is applied. Meanwhile, the impact loading test revealed that the inclusion of both fiber and polymer results in a two-fold increase in the number of impacts before visible cracking occurs, and the number of blows to failure increased by 21.4%. Moreover, microstructures were investigated by scanning electron microscopy (SEM) to confirm the reinforcing mechanism of both polymer modification and fiber reinforcement.

Remaining useful life prediction framework for crack propagation with a case study of railway heavy duty coupler condition monitoring

A general Remaining useful life (RUL) framework for predicting crack propagation of mechanical system structures based on limited condition monitoring data was proposed. For states of invisible cracks, a method that considers the common characteristics of the object was proposed by using the crack propagation stage as the delay time, combining statistical distribution and hypothesis testing. Then, for the states of visible cracks, methods based on a hypothetical distribution and support vector regression with the Kalman filter considering the current state and individual degradation characteristics were proposed. Finally, taking the condition monitoring data of the coupler body crack state as a case, the RUL prediction from the whole to the individual differences is achieved. The research results indicate that the framework achieves a competitive effect in RUL of internal crack propagation structures of railway wagons, which have important theoretical and practical value for integrity assessment and reliability life prediction.

Experimental Study on External Loading Performance of Large Diameter Prestressed Concrete Cylinder Pipe

A prestressed concrete cylinder pipe (PCCP) is created with a complex composition of concrete core, welded steel cylinder, prestressed steel wire, protective mortar and anti-corrosion coating. Due to the economy and complexity of structural prototype tests, the ultimate loading test on PCCP is rarely conducted. In this paper, the three-edge bearing test was carried out on a 3.2 m diameter PCCP with embedded steel cylinder. The strains of concrete core, prestressed steel wire and protective mortar were monitored, and the distribution and width of the concrete cracks were recorded. The test results show that the cracking on the inside concrete at the crown zone occurred before those on the invert zone of the pipe. The prestressed steel wire postponed the tensile stress of out-side concrete at the springing line until subjected to the calculated cracking load (Pc). Due to the moment redistribution caused by the cracking on the inside of the concrete at the crown/invert, the protective mortar at the springing line was cracked at 1.2 Pc and exhibited visible cracking after 1.4 Pc. The prestressed steel wire reached the elastic and strength limit states of 1.4 Pc and 1.6 Pc, respectively. The PCCP designed by the limit state design method can resist the increased external loads after reaching the serviceability limit state. The final failure load of the test pipe is greater than 1.6 Pc, and there is sufficient safety in actual operation. Due to the fact that the damage to the concrete at the crown/invert zone may become a fuse of PCCP failure, the tensile stress of the inside concrete at the crown/invert zone of the PCCP should be accurately verified in the design process.

Macro/mesofracture and instability behaviors of jointed rocks containing a cavity under uniaxial compression using AE and DIC techniques

To better understand the macro/mesofracture and instability behaviors of the jointed surrounding rock of a cavity, a series of uniaxial compression tests on jointed granite samples with openings were conducted using acoustic emission (AE) and digital image correlation (DIC) techniques. The experiments indicated that with increasing joint angle, the peak strength and elastic modulus first decreases and subsequently increases, reaching a minimum as the joint angle approaches 45°. The linear transition point of the AE cumulative count before the peak stress is related to crack initiation or interpenetration, while each instantaneous increase in the AE count after the peak stress is associated with the stress drop caused by the localization of high strain or the formation or further development of visible cracks. The accelerated release of AE energy probably has a better early warning ability for the prediction and forecast of rock instability and failure. Moreover, the prominent strain localization bands indicate crack initiation, and the crack extension behavior signifies the gradual evolution of the strain localization bands. The existence of joints changes the stress distribution patterns in the samples, and the high stress concentration areas formed at the joint tips and around the cavities interact and jointly dominate the fracturing process, eventually leading to complex failure modes. The unstable failure of the specimens is mainly induced by tensile cracks around the caverns and the joint tips, accompanied by local shear failure.

Application of sericin‐based edible coating material for postharvest shelf‐life extension and preservation of tomatoes

AbstractThis paper studied the effects of sericin‐based edible coating material on the quality and shelf‐life of tomatoes over 40 days of storage at 25°C and relative humidity of 70%. The key constituents of the coating material are sericin (1.5%), chitosan (1.0%), Aloe vera (1.0%), and glycerol (1.5%) in an aqueous solution and applied onto tomatoes in a simple dip‐coating technique. Weight loss, firmness titratable acidity (TA), total soluble solids (TSS), pH, and lycopene content were investigated and scanning electron microscopy was used to observe the semipermeable nature and the thickness of the coating layer. The results stated that the developed coating material reduced weight and firmness losses in tomatoes. With increased storage time, fruit TA content was increased and the values of pH, TSS, lycopene content, total phenolic content, and total antioxidant concentration stood low in comparison with uncoated tomatoes. With no evidence of wrinkles (up to 21 days), visible cracks, or deterioration on coated fruits during the study period, the application of sericin‐based coating might be useful commercially for maintaining the postharvest quality control of tomatoes and even other fruits as well.