Cracking

The oxygenation process of the top seeded melt-grown (TSMG) single-grain YBa2Cu3O7/Y2BaCuO5 (123/211) bulk superconductors was studied by microstructure observations. It is shown that the c-cracks in these bulks are formed in the oxygenated orthorhombic layer along the a/b-macrocracks. The lattice contraction of the 123 phase in a/b-plane induces tensile stresses in the oxygenated layer, which cannot be relaxed by twin boundary motion. The critical spacing of the c-macrocracks, λcr=14 μm, at oxygenation temperature 380 °C, estimated using Thoules’s model, is in a good agreement with the c-macrocrack spacing measures on standard TSMG 123/211 single-grain samples.

Three-dimensional nonlinear finite element model of reinforced concrete beam has been developed in this study. The general purpose finite element package, ANSYS 8.0, is employed for the numerical analyses. Using SOLID65 solid elements, the compressive crushing of concrete is facilitated using plasticity algorithm while the concrete cracking in tension zone is accommodated by the nonlinear material model. Smeared reinforcement is used and introduced as a percentage of steel embedded in concrete. Comparison with hand calculated results is presented for the concrete beam. Convergence of analytical results is showed. The capability of the model to capture the critical crack regions, loads and deflections for various types of loadings in reinforced concrete beam has been illustrated. Introduction. Concrete structural components require the understanding into the responses of these components to a variety of loadings. There are several methods for modeling the concrete structures through both analytical and numerical approaches [1, 2]. Finite element (FE) analysis is a numerical one widely applied to the concrete structures based on the use of the nonlinear behavior of materials. Finite element analysis (FEA) provides a tool that can simulate and predict the responses of reinforced and prestressed concrete members. A number of commercial FEA codes are available, along with the advanced modules for complex analyses. The use of FEA has increased because of progressing knowledge and capability of computer packages and hardware. Any attempts for engineering analyses can be done conveniently and fast using such versatile FEA packages. Nonlinear material models have been integrated in many of general purpose finite element codes, i.e., ABAQUS, ANSYS, STRAND7, or MSC NASTRAN. Those nonlinear models play a vital role in nonlinear response analyses since each material component tends to possess the complicated stress-strain behavior. Among those packages, ANSYS [3] provides a three-dimensional element (SOLID65) with the nonlinear model of brittle materials similar to the concrete materials. The element features a smeared crack analogy for cracking in tension zones and a plasticity algorithm to take into account the concrete crushing in compression zones. It is eight-node solid isoparametric element with the integration points for the cracking and crushing checks. The linear elastic behavior governs the analyses until exceeding either the specified tensile or compressive strength values. Once the principal stresses at the integration points reach the tensile or compressive strength, the cracking or crushing of concrete elements can be formed. Then, the cracked or crushed regions will form in perpendicular with the locally redistributed residual stresses to the direction of principal stress. These require the nonlinear iterative solution with high performance computer [4, 5].

High-performance concrete (HPC) applies to cement-based material with a strong capacity above 50MPa, has great ductility, and shows excellent performance. This paper reviews the properties of HPC, raw material, and cracking propagation. Reduction in porosity and improvement in microstructure increases the toughness of HPC. Natural materials such as supplementary cementitious material, aggregates, superplasticizers, and micro steel fibers can enhance HPC's mechanical properties and workability. Also, the causes of cracking and relevant test for observing crack propagation are discussed in this paper. Thus, HPC manufacturing tends to improve over the years by using relevant raw materials, common technology such as conventional casting and room temperature curing, and related precautions to reduce cracking in concrete to prolong the service life of concrete structures.

This paper presents the results of a research work aimed to determine the efficiency of using different materials to increase the punching shear strength of slab-column connections. These materials are steel bars, and glass or carbon fiber reinforced polymers as shear reinforcement stirrups. Openings in reinforced concrete (RC) slabs are not commonly prescribed in design codes. Even when they are, they raise concerns regards to the size of the openings and the location of the applied loads. There are many developments in concrete technologies that have major impacts on structural systems. The main conclusions obtained from previous researches are also included in this paper.

This paper describes a new method of analysis and design for steel frames with concrete or masonry infilling walls subjected to in-plane forces. The method is based on data generated from previous experiments as well as results from a series of nonlinear finite-element ( ...

Cracks are typical line structures that are of interest in many computer-vision applications. In practice, many cracks, e.g., pavement cracks, show poor continuity and low contrast, which brings great challenges to image-based crack detection by using low-level features. In this paper, we propose DeepCrack-an end-to-end trainable deep convolutional neural network for automatic crack detection by learning high-level features for crack representation. In this method, multi-scale deep con-volutional features learned at hierarchical convolutional stages are fused together to capture the line structures. More detailed representations are made in larger-scale feature maps and more holistic representations are made in smaller-scale feature maps. We build DeepCrack net on the encoder-decoder architecture of SegNet, and pairwisely fuse the convolutional features generated in the encoder network and in the decoder network at the same scale. We train DeepCrack net on one crack dataset and evaluate it on three others. The experimental results demonstrate that DeepCrack achieves F-Measure over 0.87 on the three challenging datasets in average and outperforms the current state-of-the-art methods.

Hydrogen embrittlement of a precipitation-hardened Fe-26Mn-11Al-1.2C (wt.%) austenitic steel was examined by tensile testing under hydrogen charging and thermal desorption analysis. While the high strength of the alloy (>1 GPa) was not affected, hydrogen charging reduced the engineering tensile elongation from 44 to only 5%. Hydrogen-assisted cracking mechanisms were studied via the joint use of electron backscatter diffraction analysis and orientation-optimized electron channeling contrast imaging. The observed embrittlement was mainly due to two mechanisms, namely, grain boundary triple junction cracking and slip-localization-induced intergranular cracking along micro-voids formed on grain boundaries. Grain boundary triple junction cracking occurs preferentially, while the microscopically ductile slip-localization-induced intergranular cracking assists crack growth during plastic deformation resulting in macroscopic brittle fracture appearance.

State-of-the-Art of the RILEM TC 241-MCD:
- Represents new state of the art in MCD, twenty years after earlier publication
- Provides an indispensable resource for the future
- Published under the auspices of the prestigious RILEM society
Premature cracking in asphalt pavements and overlays continues to shorten pavement lifecycles and creates significant economic and environmental burden. In response, RILEM Technical Committee TC 241-MCD on Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements has conducted a State-of-the-Art Review (STAR), as detailed in this comprehensive book. Cutting-edge research performed by RILEM members and their international partners is presented, along with summaries of open research questions and
recommendations for future research. This book is organized according to the theme areas of TC 241-MCD - i.e., fracture in the asphalt bulk material, interface debonding behaviour, and advanced measurement systems. This STAR is expected to serve as a long term reference for
researchers and practitioners, as it contributes to a deeper fundamental understanding of the mechanisms behind cracking and debonding in asphalt concrete and composite pavement systems.

Tujuan teknologi perengkahan katalitik ditingkatkan untuk medapatkan hidrokarbon berisi berbagai campuran fraksi gasoline, kerosene dan diesel. Didalam penelitian ini untuk perengkahan katalitik digunakanlah katalis Cr/Mo/HZA dan Ni/Mo/HZA. Katalis Cr/Mo/HZA yang didapatkan kemudian dikalsinasi pada suhu 500℃. Katalis Ni/Mo/HZA diperoleh dengan cara yang sama yaitu mengganti dengan NiCl2.6H2O. Perengkahan ini dilakukan dengan merefluks sejumlah metil ester yang diperoleh dari minyak limbah cair pabrik minyak kelapa sawit dengan 1,5 g katalis Cr/Mo/HZA dan katalis Ni/Mo/HZA pada suhu 350-380℃. Hasil refluks akan dianalisis dengan GC-MS. Pemanfaatan katalis Cr/Mo/HZA menghasilkan fraksi kerosene 31,35%, dan fraksi diesel 10,16%, sementara itu katalis Ni/Mo/HZA menghasilkan fraksi gas sebesar 0,33%, fraksi gasoline 10,63%, dan fraksi kerosene sebesar 11,02%. Parameter hasil perengkahan katalitik diantaranya yaitu densitas, mendekati densitas bensin dan kerosene, viskositas menuju viskositas kerosene, nilai bilangan asam berkisar dua kali bilangan asam bensin maupun kerosene, sedangkan kadar air masih tinggi jika dibanding kadar air bensin kerosene.

This paper discusses an in-depth analysis and a solution guide for the OPCDE Challenge. The crackme is rather straightforward and simple for the experienced reverser. However, for a beginner it could be problematic due to the nature of the protection and calculation method. I am going to show a couple of ways to explore how to attack it. Ranging from a pure abstract static analysis, dynamic analysis using a debugger, Concolic and Symbolic execution to Constraint solvers.