Prominent Crack Research Articles

Sulfur/carbon cathode material chemistry and morphology optimisation for lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs) are a promising alternative to lithium-ion batteries because sulfur is highly abundant and exhibits a high theoretical capacity (1675 mA h g-1). However, polysulfide shuttle and other challenges have made it difficult for LSBs to be commercialised. Here, a sulfur/carbon (S/C) composite was synthesised and cathodes were fabricated via scalable melt diffusion and slurry casting methods. Carbon nanoparticles (C65) were used as both sulfur host and electrical additive. Various carbon ratios between the melt-diffusion step and cathode slurry formulation step were investigated. An increased amount of C65 in melt-diffusion led to increased structural heterogeneity in the cathodes, more prominent cracks, and a lower mechanical strength. The best performance was exhibited by a cathode where 10.5 wt% C65 (TC10.5) was melt-diffused and 24.5 wt% C65 was externally added to the slurry. An initial discharge capacity of ∼1500 mA h g-1 at 0.05C and 800 mA h g-1 at 0.1C was obtained with a capacity retention of ∼50% after 100 cycles. The improved electrochemical performance is rationalised as an increased number of C-S bonds in the composite material, optimum surface area, pore size and pore volume, and more homogeneous cathode microstructure in the TC10.5 cathode.

Research on directional blasting of multiple slit charge

This study investigated the directional blasting and damage evaluation of multi-slit charge by dynamic caustics experiment system. The results show that directional blasting can be achieved in the three-slit and four-slit charges. The prominent cracks in the slit direction are longer than in other directions. Four-slit charge cracks deviation angle is greater than the three-slit charge, while the length of the crack is excessively less than the three-slit charge. The stress concentration in the y-direction on the lower side of the borehole causes cracks’ deviation. The sum of the peak energy release rate of the four-slit charge is lower than the three-slit charge. The four-slit charge energy is more toward the protected part.

Failure Behavior of Masonry Wall under Bidirectional Forces

The objective of this research is to investigate the failure behavior of masonry walls under bidirectional forces (vertical and lateral loads) for application in the construction of small community buildings with limited load-bearing capacity. To achieve this, three types of bricks, namely clay bricks, lightweight bricks, and block bricks, were subjected to testing in accordance with industrial product standards specific to each brick type. These tests aimed to assess the load-bearing capacity of masonry walls, utilizing full-sheet and half-sheet walls with dimensions of 1.0 meter ×1.0 meter, available in three different styles: 1) walls without gaps, 2) walls with window openings, and 3) walls with door openings, all designed to endure both vertical and lateral forces. The study's findings revealed that the primary mode of failure was attributed to diagonal shear failure, primarily induced by lateral forces rather than vertical ones. Masonry walls subjected to vertical forces displayed no signs of cracking because this was a non-destructive test. In contrast, masonry walls subjected to lateral forces exhibited cracks in diagonal patterns and straight lines as the predominant forms. Notably, both half-sheet and full-sheet brick walls exhibited more prominent cracks compared to block brick walls and lightweight bricks. Cracking was observed in the interfaces between the bricks and the mortar, as well as within the bricks and mortar themselves. Furthermore, it was observed that brick walls with window and door openings had 82 and 76 percent of the brick area compared to walls without gaps, respectively. These walls were able to withstand forces until failure, approximately 48 and 70 percent less on average. Lastly, the study highlighted that the strength of a brick wall is contingent on the tensile strength of the bricks and the shear strength of the mortar.

An enzymatic approach to quantify branching on the surface of starch granules by interfacial catalysis

Enzymatically modified starch granules are useful in the food industry by endowing improved thermal properties, resistance to digestion and complexation capacity. However, it is of interest to correlate structural features on the granular surface with functional characteristics relevant to given applications. To meet this requirement, a method was developed to quantify the density of α-1,6 branch points on differently structured starch granules as based on interfacial enzyme catalysis. The branch points are attacked by pullulanase, a debranching enzyme, and the branch point density, as calculated from the kinetic attack site density (kinΓmax), was linked to the chain length distribution (CLD) of the released segments. The procedure involved a combination of conventional and inverse Michaelis–Menten (MM) kinetics for pullulanase degradation of native, branching enzyme- or 4-α-glucanotransferase-modified granular waxy and normal maize starch (WMS and NMS). The treatment by branching enzyme increased the branch point density for WMS from 1.7 to 3.3 nmol/g starch granules. CLD analysis indicated that 4-α-glucanotransferase catalyzed hydrolysis and/or cyclization on the surface of the granules, rather than disproportionation. The CLD data reflected the different spatial organization of amylopectin chains within WMS and NMS granules related to their different amylose contents of 0.7 and 20.7%, respectively. Scanning electron microscopy confirmed that the starch granules retained the morphology without prominent cracks or pores after pullulanase hydrolysis for the analysis of interfacial kinetics. Comparison with the corresponding gelatinized starches gave new insights into the connection between substrate structure and specificity of the two glucotransferases acting on the different starches.

Preparation of CoCrFeMnNi-based high-entropy/aluminide laminated composites: Multielement interdiffusion reactions

CoCrFeMnNi-based high-entropy/aluminide laminate (HAL) composites were produced following the hot pressing diffusion sintering method. The microstructure of the samples was analyzed using the SEM, EDS, and EBSD techniques, and the results revealed that the diffusion reaction phases of the HAL composite consisted of a four-layer aluminide structure based on the Al13(Cr, Mn, Fe, Co, Ni)4 phase. The diffusion behavior of iron dominated the resulting phase, leading to the formation of Fe-Al compounds. Under the influence of the hysteresis diffusion effect of high entropy alloys, Al13(Cr, Mn, Fe, Co, Ni)4 phase layers (ASL I–III) with different grain sizes and growth orientations are formed due to the difference of diffusion rates at different interfaces. At the front end of the diffusion reaction, the aggregation layer of the secondary phase Al9(Fe, Co, Ni)2 appears due to the segregation of Co and Ni elements. The growth kinetics model of HAL composites was explored, and it was observed that a mixture diffusion type controlled the growth of the aluminide layer via ‘grain boundary and lattice diffusion’. The mechanical properties and failure modes of the HAL composites were investigated through quasi-static and dynamic mechanical tests. The fracture toughness reached 25 MPa·m1/2, and the main energy dissipation modes were the deformation of the ductile layer and the fracture of the hard, brittle layer. The dynamic impact failure modes were primarily deformation and 45% adiabatic shear bands, and the impact strength and energy consumption reached up to 1800 MPa and 2260 J/mm3. HAL composites with high alumina content exhibited prominent crack propagation and fragmentation properties under high-speed impact. The stress wave was significantly attenuated in the crushed aluminide layer, which significantly improved the energy absorption effect of aluminide.

Structural Assessment and Long-term Durability Consideration of Concrete on Piers and Galleries of Chandil Dam using Non-destructive Test Method

Interaction of concrete with the persistent prevailing environmental condition will alter its material properties and cause deterioration. There are various causes of distress in the concrete structure, such as improper construction practices, post-construction expansion due to Alkali-Aggregate Reaction (AAR), corrosion of reinforcement, non-homogeneity of concrete, development of cracks due to shrinkage and thermal stresses, aging, etc., Such phenomena are very common in various elements of the dam. The aging of concrete structures and their interactions with persistent prevailing environmental conditions will alter its material properties and cause deterioration. In spite of maintaining the best quality control, concrete may not behave as a homogeneous medium. Conducting any test in a modest way is the key factor for a true assessment of the status of the substratum. Diagnosis of the residual strength of concrete in in-situ conditions using non-destructive tests provides useful information for adopting suitable preventive measures. Deteriorations in the concrete can be broadly imaged using the ultrasonic pulse velocity technique. However, the results of ultrasonic pulse velocity depend on various factors. Such phenomena are very common in various elements of the dam. Since prominent cracks were observed on the pier, hence the structural assessment of piers and drainage galleries of Chandil dam was required to check the quality of concrete. In this regard, Non-Destructive Tests (NDT) were conducted on piers and galleries of Chandil dam, Jharkhand, by using the Ultrasonic Pulse Velocity (UPV) method to assess the in-situ quality of concrete.

Engineering high-performance cementitious matrices for improved projectile impact resistance with silane, micro fibrillated cellulose and fine calcined bauxite aggregate

This experimental study evaluated the effectiveness of passive and active strategies in improving the projectile impact resistance of cementitious matrices. The principle of the passive approach is to reinforce the matrix by substituting weak Van de Waal's forces between hydration products with covalent bonds which have the orders of magnitude higher dissociation energy. A silane coupling agent (SCA) and micro fibrillated cellulose (MFC) were selected as the vehicles to engineering the bond scheme at the molecular scale by forming a covalently linked organic-inorganic hybrid. The mechanism of the active strategy is to aggravate damage to the projectile and thus leave less energy available for the penetration process. This is achieved by incorporating exceptionally hard calcined bauxite aggregates (CBA). Impact tests were conducted utilizing 8-mm-diameter conical-nosed steel projectiles at a designed velocity of 650 m/s. Damage was quantified by the depth of penetration (DOP) and equivalent crater diameter (ECD). Results indicated that the SCA and MFC modified matrices resulted in a 30% and 20% reduction in DOP, respectively. The crack intensity was decreased tremendously or even absent for the SCA and MFC modified matrices compared with the prominent cracks of the control radiated from the cratering region. Matrices incorporating fine CBA or siliceous aggregates led to a 55% and 38% smaller DOP, respectively. Crushing of aggregates and appreciable deformation, severe scratches, and significant mass loss of retrieved projectiles were observed. Matrices including fine CBA or siliceous aggregate maintained excellent integrity and drastically less severe cracking on the impact surface as well as the interior region compared with the control.

Characterization of class C and F fly ashes based geopolymers incorporating silica fume

Geopolymers have been proposed as an alternative to ordinary concrete with their appropriate mechanical performances and eco-friendly impacts. In current study investigated the interaction between the class C and F fly ashes on the properties of silica fume incorporated geopolymers. For that purpose, the concentration of the alkali activator were determined according to compressive and flexural strengths. Then, the geopolymers prepared with different fly ash/silica fume ratios at specified alkali activator concentration. Mechanical, physical, chemical and microstructural properties of these geopolymers were evaluated by FT-IR, XRD, TGA, and SEM-EDX. The mechanical properties of geopolymers were enhanced remarkably by NaOH molarity and it was detected that the compressive strength and flexural strength values reached the highest (21.13 ± 1.11 MPa and 6.61 ± 0.56 MPa, respectively) at 10 M. Results were compared according to the fly ash type and the fly ash/silica fume ratios of the geopolymers. Due to the high water demand of silica fume, prominent cracks were seen in the geopolymers including 100% silica fume. Besides, inadequate mechanical properties were obtained when 100% fly ash was used. Consequently, it was clearly revealed that the properties of geopolymers obtained with only fly ash or silica fume were improved by the use of both. Finally, higher mechanical properties (σC: 31.91 ± 1.90 MPa, σF: 8.34 ± 0.23 MPa) and less cracks in the bodies were obtained with class F fly ash (75% wt.).

Effect of Cr Content on Corrosion Resistance of Ni-xCr-Mo Laser-Cladding Coatings under H2S-Induced High-Temperature Corrosion Atmosphere.

Ni–xCr–Mo laser-cladding coatings with varying Cr content of 10, 15, 20, 25, and 30 wt.% were fabricated using a self-assembled coaxial laser-cladding device. The H2S-induced high-temperature corrosion tests under reductive atmosphere were conducted at 500, 550, and 600 °C. Subsequently, the influence of Cr content on the microstructural evolution and corrosion resistance of the Ni–xCr–Mo coatings was investigated. The experimental results revealed that 30 wt.% Cr is the limited maximum content that forms the suitable morphology of coatings without large prominent pores and cracks during the fabrication process, and 15 wt.% Cr corresponds to the critical minimum content for excellent corrosion resistance, as implied from the variation tendency of the corrosion weight-gain curves. Moreover, a two-layer structure of the corrosion scales was observed in the Ni–xCr–Mo laser-cladding coatings, which was primarily caused by the selective corrosion between the Ni and S and Cr/Mo and O.

Theoretical modification of the laboratory-determined tensile stress–strain relationship of strain hardening cementitious composites (SHCCs) for large-scale specimens

Strain hardening cementitious composites (SHCCs) are a type of cementitious material reinforced with randomly distributed short fibers that exhibit tensile strain hardening behavior and prominent crack resistance. The tensile behavior of SHCCs could be significantly affected by the distribution of the fiber orientation. In large-scale specimens, the distribution of the fiber orientation is close to ideal three-dimensional uniform random distribution. However, fiber orientation distributions in laboratory SHCC specimens are influenced by the specimen dimensions (width and thickness) and casting process, resulting in neither ideal two-dimensional nor three-dimensional uniform random distribution. Therefore, the performance of large-scale SHCC specimens may be overestimated in analysis when directly using the tensile properties of SHCCs obtained from uniaxial tensile tests of small specimens. Since the uniaxial tensile tests of large-scale SHCC specimens are difficult to be conducted, theoretical evaluation of the tensile properties of mass SHCCs in large-scale specimens were conducted by modifying the uniaxial tensile test results of small specimens. In this paper, closed-form probability distribution models for fiber orientations that consider the influence of the specimen width and thickness were theoretically derived. The effects of the specimen width and thickness on the tensile properties of SHCCs were studied by applying the proposed method to the uniaxial tensile numerical model of SHCCs, while uniaxial tensile specimens with two different geometries and dimensions were tested for verification. Both the analytical and experimental results showed that, within a certain range, the width and thickness of the specimens significantly influenced their ultimate tensile strength and ultimate tensile strain. To relate the uniaxial tensile test results of laboratory-sized specimens to that of mass SHCC in large scale specimens, reduction factors for the stress–strain relationship of SHCCs obtained by traditional tensile test specimens were proposed to account for the specimen size effect based on the model analysis. The reduced tensile stress–strain relationship was applied to a finite element model of SHCC beams under four-point bending tests. It was found that the finite element analysis results obtained by using the reduced tension stress–strain relationship are in better agreement with the test results.

Study on Backfill Acoustic Emission Characteristics and Source Location under Uniaxial Compressive

This study investigates the acoustic emission (AE) characteristic of cemented tailings backfill (CTB) under uniaxial compressive loading. A classified tailings material source from Wushan Copper Mine was used to prepare cylindrical CTB samples. This study used an SLB10 loading machine for the uniaxial compressive test. A PCI‐2 acoustic wave system was attached to the CTB specimen to measure the acoustic emission during loading. Overall, the backfill specimen’s uniaxial compressive strength (UCS) is 3.58 MPa. The failure modes of the CTB sample could be divided into five stages, including the pore microfracture compacting stage (stage‐a), linear elastic deformation stage (stage‐b), yield deformation stage (stage‐c), failure stage (stage‐d), and residual stage (stage‐e). At each stage, the AE characteristic parameters such as the hits per second (HPS), the cumulative number of impacts, energy rate, and total energy vary a lot, which indicates the AE parameter reflects the internal failure evolution of the CTB sample. In stage‐a, no apparent AE behavior was measured. In Stage‐b, there is no evident macroscopic change in the specimen, while the AE parameters steadily and continuously increase. During stage‐c, the number of AE impacts grows sharply, the energy rate increases significantly, and changes suddenly. The cumulative number of AE impacts is 31.3% in stage‐d, and the cumulative energy rate is 49.4%, which is the most active stage of acoustic emission activities. The specimen has prominent crack propagation and bifurcation phenomena. In stage‐d, the CTB sample was destroyed entirely, and the characteristic parameters of acoustic emission were significantly reduced. Finally, multiple regression analysis methods are introduced into the time difference positioning method to locate the AE source. The positioning results show that the technique can better invert the close relationship between the damage and destruction of the CTB and the generation and penetration of the internal cracks and describe it to a certain extent. The failure surface of the filler specimen has an excellent guiding value for the analysis of the interior failure characteristics of the sample.

Characterization and mechanical properties of stir-rheo-squeeze cast AA5083/MWCNTs/GNs hybrid nanocomposites developed using a novel preform-billet method

This study explores the development and characterization of Aluminum alloy (AA) 5083 based nanocomposites, reinforced with equal proportion of graphene nanosheets (GNs) and multi-walled carbon nanotubes (MWCNTs) using stir-rheo-squeeze casting. To control the problem of segregation of the nano dispersoids, the study successfully employs a novel approach of making nano-preform billets of the reinforcements by green compacting and then introducing their sections to the alloy melt having compositions 0.5, 1, 1.5, 2, and 2.5% by weight, while stirring. MWCNTs and GNs in 1:1 ratio mixed and milled with ten times the high purity Aluminum (Al) powder volume. HRTEM images and XRD patterns conformed to the size and purity of MWCNT and GNs. SEM images confirmed their sound mixture. The structure was refined by about 60% in 3 wt.% composite, but agglomeration and cracks appeared at this composition. BHN increased consistently as the reinforcement was increased. Tensile and compressive strength increased initially but declined in the composite with 3 wt.% nanofillers due to agglomerations and weak interface bonding. Elongation first decreased and then increased due to counter slip systems introduced by the presence of MWCNTs and GNs. Prominent crack growth was observed in the fractography in 3 wt.% composite. An optimum reinforcement concentration of 1.5–2 wt.% has emerged superior on a combined evaluation of dispersion, refinement of structure, and mechanical properties.

Pyrolysis-catalytic upgrading of brominated high impact polystyrene over Fe and Ni modified catalysts: Influence of HZSM-5 and MCM-41 catalysts

The pyrolysis-catalytic upgrading process of brominated high impact polystyrene (Br-HIPS) was performed using Fe and Ni modified ZSM-5 and MCM-41 catalysts in a two-stage fixed bed reactor. The characterization of catalysts, the product yield and debromination performance in relation to different catalysts were investigated. The results showed that the addition of HZSM-5 and MCM-41 reduced the yield of oil from 69.0 wt % to 64.4 wt % and 62.3 wt %, respectively. The modified catalysts of Fe/ZSM-5 and Ni/ZSM-5 exhibited prominent cracking performance, resulting in the decrease of the oil to 63.2 wt % and 61.2 wt %, respectively, corresponding with an increase of gas products from 7.7 wt % to 16.1 wt % and 20.3 wt %, respectively. However, the mesoporous catalysts of Fe/MCM-41 and Ni/MCM-41 tended to preserve the yield of oil to 65.9 wt % and 65.3 wt %, respectively. In terms of the composition of the oils, a higher yield of single ring aromatics was obtained with Fe modified catalysts, while the addition of ZSM-5 and Ni/ZSM-5 catalysts promoted increased formation of 2 ring aromatics at the expense of single ring aromatics. In addition, the modified catalysts were found to be highly effective at removing bromine from the oils. The Fe modified catalysts exhibited a better debromination performance than Ni modified catalysts, which was in favor of capturing more inorganic bromine and removing bromine from the oils.

Fatigue Fracture of a High-Resistance Structural Steel Component Destined to Sustain Severe Loads Under Service Conditions

A structural steel component that failed under fatigue was examined with the aim to identify the root causes of this failure. Fractographic examination revealed the presence of multiple beach marks; the position and arrangement of those signified the occurrence of fatigue fracture under the presence of combined loading conditions, involving torsion and bending stress components. Crack initiation was observed also at the corners of the steel plate where non-metallic inclusions were located. Stereo-microscopical examination of the fracture surface likely revealed the presence of casting inclusions, probably fluxes or slag particles, near the surface and in the interior of the component. These inclusions could be considered inherent—metallurgical stress raisers, behaving as locations of prominent crack nucleation under cyclic fatigue loading, stimulating subsequent crack propagation and final ultimate rupture.

Fatigue crack behavior in power plant residual heat removal system piping including weld residual stress effects

The piping in some residual heat removal (RHR) systems in nuclear power plants, made of 304L stainless steel, is subjected to a multiaxial cyclic stress state in the cold/hot water mixing zone due to thermal fluctuations. In addition, residual stresses produced by welds and/or surface treatments can be large in magnitude and be tensile or compressive, depending on the proximity to the weld location. Crack networks have been observed to nucleate and grow under these stress states. Prominent cracks originating from micro-cracks on the order of grain size continue to grow to a length of about 2.5mm. The thermal fluctuation is such that crack growth is in the high cycle fatigue regime. In this paper, the plane orientation and growth direction of these cracks with respect to the cyclic and mean stress states and their gradients are analyzed. The roles and interactions of shear, tensile, and compressive stresses with regards to the direction and orientation of the cracks are also discussed. Weld residual stresses (WRS) are decomposed into a local effect in tension near the weld and a structure effect in compression farther away, which also help explain some crack configurations in RHR systems. Moreover, a dependence of WRS field on spatial second derivative of weld temperature field is shown, which can have an important impact for comparison of measured and simulated WRS. Crack growth was also simulated with XFEM in the presence of WRS, with the principal hypothesis that mean stress acts only on crack opening.

Effects of small particles on the mechanical behavior and on the local damage of highly filled elastomers

The mechanical behavior and damage of highly filled elastomers such as propellants are studied experimentally. A model material made of a polyacrylate matrix filled with glass beads and energetic binders filled with ammonium perchlorate and HMX have been formulated. The focus is on materials containing micrometric size particles. The size of fillers was varied from a few microns to hundreds of microns in order to study the impact of the size of particles. The materials stress–strain responses and the volume changes during uniaxial tensile tests have been recorded. Microtomographic slices of strained samples have been obtained in order to look at the type of damage sustained by the acrylate/glass bead materials. It appears that in the presence of large particles, composites showing early prominent crack benefit from the addition of small particles, whereas composites showing well-dispersed matrix/particle decohesion without large cracks show no change of behavior when small particles are added.

The Application of Carbon Composites in the Rehabilitation of Historic Vaults

The on-going renovation and reconstruction of the Premonstrate Monastery in Teplá was the site for the application of the results of research carried out within the NAKI research project [1]. Barrel vaults with lunettes over the arcaded walk of the convent had been damaged at the crown by a continuous tensile crack one to several millimetres in width. The vault was reinforced and stabilised with strips of a carbon composite and epoxy resin. The article describes the design and the stabilisation and reinforcement procedure of the vaults over the arcaded walk on the 1st overground storey of the convent damaged by a continuous, at places prominent tensile crack at the vault crown using the method of non-prestressed strips of a carbon composite.

Biotite controlled chemical alteration of granodioritic–tonalitic saprock: Exploring the use of sieving to enhance compositional linear trends

The Peninsular Ranges, southern California, USA, commonly contains eroded sections of regolith composed of (1) saprock enclosing corestone or (2) alluvial deposits overlying plutonic/metamorphic basement. In this paper, we present a study focused on evaluating the chemical weathering patterns exemplified by type 1 regolith. In an attempt to enhance the coverage of altered samples about calculated compositional linear trends, the <45μm fractions were separated from saprock samples and were chemically analyzed.Though Alfisol is common within the study area, due to erosional exhumation, such soil is absent at the specific site sampled during this investigation, and colluvium directly overlies saprock and corestones. Mean annual precipitation ranges from 25cm–51cm with a mean annual air temperature of 13°C–18°C.In centered p(A), p(CN), and p(K) ternary space, A, CN, and K are compositions representing molar percentages of Al2O3, CaO*+Na2O, and K2O, respectively, in the sum of A, CN, and K. CaO* is the molar percent of CaO following correction for CaO in apatite. Centering preserves the geometrical relationships between plotted samples, but moves them to the center of the ternary diagram.Saprock samples plot about a linear compositional trend directed away from the p(K) apex. Using orthogonal projection, the average weathering intensity value, t, of the bulk saprock samples is 0.09 (±0.04). When the sieved <45μm fractions are considered along with the bulk saprock samples, a similar linear compositional trend is calculated, but sieved fractions plot closer to the A–CN join, and have an average t-value of 0.89 (±0.04). Hence, inclusion of the sieved fraction extended the coverage of altered samples about the weathering trend.Using Na as a reference frame, a statistically significant loss of 10% (+9/−8%) and 14% (+6/−5%) K and P mass, respectively, occurred during the development of saprock. The loss of K mass is attributed to the alteration of biotite to hydroxy-interlayered vermiculite and mixed-layer biotite/vermiculite, while the loss of P mass is due to the dissolution of apatite. In addition, statistically significant increases in Si (6%±4%) and LOI (56% (+37/−30%)) mass occurred. The increase in Si mass reflects either, or both, illuviation of small amounts of kaolinite into the prominent crack system observed at the study site, or the addition of pedogenic silica. Such increases are apparently the result of processes that were operative in the now erosionally removed section of Alfisol. The results of the above elemental mass changes produced a statistically significant increase in bulk mass of 5%±3%.The results of our work suggests that the inclusion of <45μm fraction chemical data can significantly enhance the coverage of calculated linear compositional trends, and could be a useful investigative tool for future studies.

Investigation into the Cracking of SAILMA 350 HI During Forming

Vanadium microalloyed hot rolled steel of 13.8 mm thickness, when hot formed at 900 °C into axle housings were rejected because of a prominent crack running along the length of the component. A detailed metallurgical investigation revealed that the cracking during forming was the result of the opening up of pre-existing fine crack along the length of the hot rolled coils. These cracks were barely visible on the hot rolled coils that were formed into the axle housings. Metallographic and hardness tests indicated that these cracks might have been generated as a result of decarburization of the slab during soaking that led to a softer surface layer of the slab. During subsequent hot rolling mechanical defect might have been caused on the decarburized surface that is much softer than a material with a usual carbon content. It was concluded that soaking in the reheating furnace with low carbon potential might have led to extensive decarburization of the slabs. Soaking in a furnace atmosphere with adequate carbon potential was recommended as a remedial measure to prevent decarburization of the surface layers of the slabs.

Evidence of a hidden landslide slip surface beneath a mountain hamlet

Earthquake-triggered landslides are some of the most destructive natural disasters. Although remote detection of landslides is economic and efficient, it may miss the more subtle signs of hidden landslides. The Kizawa Tunnel and facilities in its vicinity were severely damaged in the 2004 mid-Niigata Prefecture earthquake. After investigation of the most prominent cracks, the damage was attributed to the slip along a hidden weakness plane. Evidence supporting this argument is summarized in this paper. However, the extent of the shear plane is not limited to the interior of the northern part of the tunnel. The dislocation observed in the two wells to the south of the Kizawa Tunnel together with other findings from previous studies indicates that Kizawa hamlet lies on the southern extension of the same shear plane. Taking account of the presence of flat sedimentary structures, the shear plane may extend in all directions. The authors also surveyed other signs of damage along the perimeter where the shear plane intersects the ground surface. The geological and geomorphological features of the hidden landslide are discussed. Reactivation of interlayer sliding is a threat to the local residents, and thus more attention should be paid to monitoring the movement of the slope to avoid devastating damages.