Stress State and Elements

To assure safe and reliable operation of an LMFBR, design criteria must be established to define the- margin of safety between operating conditions and failure. The designer must demonstrate that the structural analyses, which are performed to confirm the existence of that margin, truly provide a close approximation of real component behavior under typical complex loading conditions. The increase in operating temperature from LWR to LMFBR has created the need for a proven structural design technology that can be applied to components operating in the thermal creep range where material behavior is time dependent. In the period 1963-1970, reactor designers recognized the need for new structural analysis techniques and design criteria to guard against time dependent failure modes not encountered in LWR design. As a result, ASME Code requirements were modified to cover time dependent material behavior and a belated start was made to develop the needed structural design technology. Even at the reduced temperatures currently under consideration for future LMFBR’s, this technology is required since the substitution of ferritic for austenitic stainless steels results in lower creep threshold temperatures.

Facing the escalating demands in both technical competence and financial accountability, practicing structural engineers are being forced into an ever-intensified fast-pace working environment. With more and more structural design codes becoming lengthy and cumbersome and, meanwhile, the time allocated for structural engineering design being drastically reduced, the quality assurance of the structural engineering design has been becoming more critical than ever for practicing structural engineers to succeed. Structural engineering design errors and failures have been observed in a variety of design phases and categories. Among them, there are several typical problems needed to be discussed and a systematical procedure of quality assurance of the structural engineering design shall be studied and developed. As a part of our collective professional effort to assure the quality of the structural engineering design, this paper will discuss following eight typical aspects related to quality control and assurance of structural engineering design and a number of real world practical examples will be presented to assist in illustrating the importance of the quality control and assurance for real world structural engineering design projects.

A study of the thermal buckling behavior of a circular aluminum plate using the digital image correlation technique and finite element analysis

. Production efficiency as well as the reduction of energy consumption and waste are the main drivers for the improvement of large-scale production in chemical industry. In addition, the demand for new processes – these days especially related to the chemical energy conversion as basis for the Energiewende – are additional triggers for innovation. Catalysis, well recognized by the public e.g. in form of the 3-way automobile catalyst, plays an important role for about 90% of all processes in chemical industry. The development of new and improved catalysts is a challenge for chemists – as is the search for new structural materials for mechanical engineers. Due to the often-necessary noble and thus expensive metals (e.g. palladium) in many catalysts, structural and chemical function have been developed separately in the two communities. Recent progress in catalytically active materials allows replacing expensive noble metals in selected catalytic processes by significant cheaper elements [1]. This offers the new perspective to combine structural and chemical functionality by innovative materials. Within this area, intermetallic compounds with their peculiar combination of crystal and electronic structure [2], represent an interesting class of materials to address this vision as will be shown in the contribution.

An experimental-finite element method based on beach marks to determine fatigue crack growth rate in thick plates with varying stress states

Marine soil–structure interfaces are commonly encountered in marine engineering, where they are inevitably subjected to temperature variations and complex stress conditions, including static, dynamic, and creep loads. However, limited studies have addressed the temperature-dependent mechanical behavior of marine soil–structure interfaces under various loading scenarios. This study introduces a self-developed multifunctional large-scale shear apparatus that enables temperature-controlled testing of marine soil interfaces with various structural materials, including concrete, polymer grids, and polymer layers. The apparatus supports static, dynamic, and creep shear testing under precisely controlled thermal conditions. A series of shear tests were conducted on marine soil–concrete, marine soil–polymer grid, and marine soil–polymer layer interfaces to verify the device’s performance. The test results demonstrate that the apparatus can accurately and reliably capture the mechanical responses of marine soil–structure interfaces under different temperatures and loading modes. Furthermore, the results highlight the significant influence of temperature on the shear behavior of these interfaces, emphasizing the necessity of developing such equipment. The findings offer essential insights for the design, evaluation, and long-term stability of marine engineering structures, supporting the development of practical ocean solutions.

Probability density evolution method for seismic displacement-based assessment of earth retaining structures

Civil Engineers are the builders of a nation. They always have played a significant role in providing the infrastructure required for the society. Ever increasing population, rapid urbanization and industrialization, global warming and climate change, increasing incidents of natural and manmade hazards and environmental degradation have become major concerns of the society today and these concerns pose several challenges to the Civil Engineers. There has been a noticeable change in the environment within which civil engineers carry out their work. There is a growing concern on the adverse consequences of the development activities. There is a need for Civil Engineers to rise up to face these challenges and contribute to the development and betterment of the nation in all core areas. A multitude of threats confront us in our effort to achieve the same. Civil engineers have always been looking for innovative tools and techniques for solving the challenging problems that they face during planning, analysis, design and construction of civil engineering structures. It was in this context that the Department of Civil Engineering, National Institute of Technology Calicut, Kerala, India, has come out with the proposal of organizing an International Conference on Materials, Mechanics and Structures 2020 (ICMMS 2020) with major funding from Technical Education Quality Improvement Program-Phase III. This conference was aimed to provide a forum to all Civil Engineers to deliberate on the innovative tools and techniques that are needed to face the challenges in the fields of Materials, Mechanics and Structures.List of Comittees and editors are available in this pdf.

Even with the state-of-the-art technology of computer-aided design and topology optimization, the present structural design still faces the challenges of high dimensionality, multi-objectivity, and multi-constraints, making it knowledge/experience-demanding, labor-intensive, and difficult to achieve or simply lack of global optimality. Structural designers are still searching for new ways to cost-effectively to achieve a possible global optimality in a given structure design, in particular, we are looking for decreasing design knowledge/experience-requirements and reducing design labor and time. In recent years, Artificial Intelligence (AI) technology, characterized by the large language model (LLM) of Machine Learning (ML), for instance Deep Learning (DL), has developed rapidly, fostering the integration of AI technology in structural engineering design and giving rise to the concept and notion of Artificial Intelligence-Aided Design (AIAD). The emergence of AIAD has greatly alleviated the challenges faced by structural design, showing great promise in extrapolative and innovative design concept generation, enhancing efficiency while simplifying the workflow, reducing the design cycle time and cost, and achieving a truly global optimal design. In this article, we present a state-of-the-art overview of applying AIAD to enhance structural design, summarizing the current applications of AIAD in related fields: marine and naval architecture structures, aerospace structures, automotive structures, civil infrastructure structures, topological optimization structure designs, and composite micro-structure design. In addition to discussing of the AIAD application to structural design, the article discusses its current challenges, current development focus, and future perspectives.

Transformation yield surface of nanocrystalline NiTi shape memory alloy

The verification of the structural components of demonstration fusion power plants requires design criteria developed specifically for those components and the unique conditions at which they are operated. Therefore the creation of a body of structural design criteria appropriate for demonstration fusion power plants is an important activity, with particular attention required for the in-vessel components of the divertor and blanket. For posited failure modes associated with the candidate in-vessel components for the current European Demonstration Power Plant design (EU DEMO), this paper highlights the gaps identified in the leading suites of relevant structural design criteria (ASME BPVC Division III, AFCEN RCC-MRx, ITER SDC-IC). Opportunities for innovative development are then explored for these gaps. Finally, a development path for structural design criteria against the needs of EU DEMO is discussed.

Progress is reported in a program to provide the structural designer with qualified analysis methods, design procedures, design limits and criteria, and the guidance required to assure their proper application. This work is necessary to assure adequate evaluation and assessment of FFTF operational experience; safe and reliable structural design of CRBR, PLBR, and large component test facilities; and development of the structural design technology necessary for successful commercialization of the LMFBR. The program includes the following tasks: design criteria and standards; simplified inelastic analysis methods; computer program validation, implementation, and distribution; and piping integrity.

In the process of long-term service, CFRP structures are often in a complex stress state, the interlaminar resin matrix is sensitive to temperature and humidity in the environment, and different test temperatures after aging also have a significant impact on the interlaminar mechanical properties of CFRPs. A hygrothermal aging environment (80°C/95% RH) was selected to conduct artificial accelerated aging tests for 28 days, and the CFRP was tested at room temperature and high temperature to study the influence of different test temperatures on the failure strength of the CFRP under five complex stress states. The fracture failure morphology, glass transition temperature () and absorbance of some functional groups change after hygrothermal aging. The interlaminar failure strength of the CFRP in five stress states decreases with increasing aging time in a cubic polynomial manner, and the interlaminar failure strength at high temperature is significantly lower than that at room temperature after aging. Finally, the three-dimensional variation surface of the high-temperature quadratic stress criterion with aging time is established, which provides a reference for the durability evaluation of the CFRP high-temperature interlaminar residual strength after hygrothermal aging.

1. In a plane stress state, the time to rupture of alloy EI698VD is described by Eq. (1). Here, an increase in the compressive component σ3 reduces the activation energy of the fracture process. This is confirmed by the results of metallographic study of fractured specimens. 2. Statistical evaluation of the results from analysis of test data using Eqs. (4) and (6)–(8) shows that only criterion (4) adequately describes the rupture strength of the alloy in a plane stress state. 3. The parameter χ depends on the activation parameters of the fracture process. In this case, when the fracture of a material in uniaxial tension and a complex stress state is governed by the same set of mechanisms, the parameter χ is a constant. If these mechanisms are different, then χ changes in relation to the temperature and time to rupture. In this case, it is necessary to use the weighted mean value of χ, which is found from Eq. (10).

In general, the analysis and design of civil engineering structures are based on deterministic approaches where uncertainties in various parameters (soil characteristics, loading, etc.) are not taken into account. In recent decades, the description and analysis of uncertainty in geotechnical engineering, with a focus on the safety of structures, have become increasingly important issues. To fix the level of risk for which geotechnical parameter values must be determined, the Eurocodes have introduced an approach based on the statistical processing of soil data. This paper presents the statistical modeling of geotechnical parameters (cohesion, friction angle, specific weight) of a shallow foundation soil from Daral Peulh area located in Thies in Senegal. Laboratory tests for soil identification were conducted on 26 samples. After outliers, values determined and treated with boxplot method, graphical methods and Kolmogorov and Shapiro-Wilk tests were used to determine the probability distributions associated with geotechnical parameters and the bearing capacity of a shallow foundation. The results conclude after outliers treatment with 5% risk, the probability distributions of the cohesion, the friction angle and the specific weight are normal distributions and can be used for probability design. However, the variability around their means is high for the cohesion, the friction angle and the bearing capacity. For the bearing, the most suitable probability distribution in this case is the lognormal distribution.