Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

Xiao Wei, Hongliang Liu, Lisha Zhang et al.

Compacted clay is widely used in geotechnical projects involving road embankment, subgrades, backfillings, etc. The shearing strength of saturated compacted clay is an important parameter in the analysis of the stability of these structures, and it is affected by states of soil, fabric, stress history, etc., making the characterization of the shearing strength remain difficult. This study investigated the shearing behaviors and shearing strength of a saturated and compacted Qiantang River silty clay using undrained triaxial compression tests. The specimens were compacted to different void ratios and saturated, followed by consolidation to different effective confining pressures for triaxial compression. The shearing behaviors are found to be state-dependent, namely, dependent on the void ratio and effective confining pressure before shearing. Several characteristic states, such as the undrained instability state, quasi-steady state, phase transformations state, and critical state, have been identified for each specimen. The deviatoric stresses at these states were characterized in the framework of critical state soil mechanics. The state parameter can be used to characterize the state-dependent shearing strength, while a modified state pressure index was proposed and found to be a better state variable for characterizing the state-dependent shearing strength of the compacted clay.

Kyrillos Ebrahim, Tarek Zayed, Ridwan Taiwo et al.

Changnü Zeng, Yiyang Zhang, Hu Lu et al.

Abstract The two‐phase flow in porous media is affected by multiple factors. In the present study, a two‐dimensional numerical model of porous media was developed using the actual pore structure of the core sample. The phase field method was utilized to simulate the impact of displacement velocity, the water–gas viscosity ratio, and the density ratio on the flow behavior of two‐phase fluids in porous media. The effectiveness of displacement was evaluated by analyzing CO2 saturation levels. The results indicate that the saturation of CO2 in porous media increased as the displacement velocity increased. When the displacement velocity exceeded 0.01 m/s, there was a corresponding increase in CO2 saturation. Conversely, when the displacement velocity was below this threshold, the impact on CO2 saturation was minimal. An “inflection point,” M3, was present in the viscosity ratio. When the viscosity of CO2 is less than 8.937 × 10−5 Pa·s (viscosity ratio below M3), variations in the viscosity of CO2 had little impact on its saturation. Conversely, when the viscosity of CO2 exceeded 8.937 × 10−5 Pa·s (viscosity ratio greater than M3), saturation increased with an increase in the viscosity ratio. In terms of the density ratio, the saturation of CO2 increased monotonically with an increase in the density ratio. Similarly, increasing density ratios resulted in a monotonic increase in CO2 saturation, though this trend was less pronounced in numerical simulations. Analysis results of displacement within dead‐end pores using pressure and velocity diagrams reveal eddy currents as contributing factors. Finally, the impact of pore throat structure on the formation of dominant channels was examined.

Lekshmi Murali Rani, Richard Berntsson Svensson, Robert Feldt

The integration of AI for Requirements Engineering (RE) presents significant benefits but also poses real challenges. Although RE is fundamental to software engineering, limited research has examined AI adoption in RE. We surveyed 55 software practitioners to map AI usage across four RE phases: Elicitation, Analysis, Specification, and Validation, and four approaches for decision making: human-only decisions, AI validation, Human AI Collaboration (HAIC), and full AI automation. Participants also shared their perceptions, challenges, and opportunities when applying AI for RE tasks. Our data show that 58.2% of respondents already use AI in RE, and 69.1% view its impact as positive or very positive. HAIC dominates practice, accounting for 54.4% of all RE techniques, while full AI automation remains minimal at 5.4%. Passive AI validation (4.4 to 6.2%) lags even further behind, indicating that practitioners value AI's active support over passive oversight. These findings suggest that AI is most effective when positioned as a collaborative partner rather than a replacement for human expertise. It also highlights the need for RE-specific HAIC frameworks along with robust and responsible AI governance as AI adoption in RE grows.

Ali Kogani, Behrooz Yousefzadeh

Unilateral transmission refers to the scenario in which the waves transmitted through a system remain in pure tension or pure compression. This transmission phenomenon may occur in systems that exhibit different effective elasticity in compression and tension; i.e. bilinear elasticity. We present a computational investigation of unilateral transmission in the steady-state response of harmonically driven mechanical systems with bilinear coupling. Starting with two bilinearly coupled oscillators, we find that breaking the mirror symmetry of the system, in either elastic or inertial properties, facilitates unilateral transmission by allowing it to occur near a primary resonance. This asymmetry also enables nonreciprocal transmission to occur. We then investigate the nonreciprocal dynamics of the system, including linear stability analysis, with a focus on unilateral transmission. We also extend our discussion to a bilinear periodic structure, for which we investigate the influence of the number of units and energy dissipation on unilateral transmission. We report on the existence of stable nonreciprocal unilateral transmission near primary and internal resonances of the system, as well as other nonreciprocal features such as period-doubled and quasiperiodic response characteristics.

Daniel Mendez, Paris Avgeriou, Marcos Kalinowski et al.

Empirical Software Engineering has received much attention in recent years and became a de-facto standard for scientific practice in Software Engineering. However, while extensive guidelines are nowadays available for designing, conducting, reporting, and reviewing empirical studies, similar attention has not yet been paid to teaching empirical software engineering. Closing this gap is the scope of this edited book. In the following editorial introduction, we, the editors, set the foundation by laying out the larger context of the discipline for a positioning of the remainder of this book.

A.S. Devapriya, T. Thyagaraj

Wenpan CEN, Yinglun QIN, Xiang WANG et al.

Objective Many important discoveries have been made in shale gas exploration in the Lower Carboniferous Luzhai Formation in the central and northern Guizhong Depression, southern margin of the Xuefengshan Uplift, and commercial test production has achieved successful gas ignition. However, the structure and evolution of the depression in this area have not been clearly defined, which restricts an accurate understanding of the formation conditions for organic-rich mud shale, the distribution of favourable sedimentary facies zones, and shale gas enrichment law. Methods Taking the Rongshui area as an example, this paper studies the main structures and their relationships with shale gas preservation through geological investigation and analysis, 2D-3D seismic section structural interpretation, evolutionary equilibrium section interpretation and other technologies. Results It is believed that there are three main faults and four main NE-NNE synclines in the study area. The preexisting NNE-trending Sanjiang-Rong'an fault is the main factor involved in extensional fault depression and compression-strike-slip transformation. In the study area, the extensional fault depression developed in the Late Devonian, strengthened in the Early Carboniferous and stopped in the late Early Carboniferous. The compression-strike-slip effect of the depression reconstruction developed in the Indochinese and Yanshanian stages, and the local tensioning effect developed in the Alpine stage. The main part of the present fold system was formed in the Indosinian period. Influenced by the increasing thrust of the Sanjiang-Rong'an fault from west to east, the structure pattern of broad and slow synclinal-compound synclinal-faulted folds is distributed. Complex synclines are favourable structural units for shale gas preservation, and the favourable structural styles for shale gas preservation are synclines and anticlines. Conclusion This understanding clearly defines the direction of shale gas exploration and deployment in the next step, and provides a beneficial idea for the structure and evolution of the Liucheng slope in the north-central part of the Guizhong Depression.

Weiqi Wang, Xia-Ting Feng, Qihu Wang et al.

To achieve the loading of the stress path of hard rock, the spherical discrete element model (DEM) and the new flexible membrane technology were utilized to realize the transient loading of three principal stresses with arbitrary magnitudes and orientations. Furthermore, based on the deep tunnel of China Jinping Underground Laboratory II (CJPL-II), the deformation and fracture evolution characteristics of deep hard rock induced by excavation stress path were analyzed, and the mechanisms of transient loading-unloading and stress rotation-induced fractures were revealed from a mesoscopic perspective. The results indicated that the stress–strain curve exhibits different trends and degrees of sudden changes when subjected to transient changes in principal stress, accompanied by sudden changes in strain rate. Stress rotation induces spatially directional deformation, resulting in fractures of different degrees and orientations, and increasing the degree of deformation anisotropy. The correlation between the degree of induced fracture and the unloading magnitude of minimum principal stress, as well as its initial level is significant and positive. The process of mechanical response during transient unloading exhibits clear nonlinearity and directivity. After transient unloading, both the minimum principal stress and minimum principal strain rate decrease sharply and then tend to stabilize. This occurs from the edge to the interior and from the direction of the minimum principal stress to the direction of the maximum principal stress on the ε1-ε3 plane. Transient unloading will induce a tensile stress wave. The ability to induce fractures due to changes in principal stress magnitude, orientation and rotation paths gradually increases. The analysis indicates a positive correlation between the abrupt change amplitude of strain rate and the maximum unloading magnitude, which is determined by the magnitude and rotation of principal stress. A high tensile strain rate is more likely to induce fractures under low minimum principal stress.

SHAO Shuai 1, ZHANG Jiaqing 1, SHAO Shengjun 1, 2, 3, SONG Jiayao 1, YAN Guangyi 4, ZHU Xueliang 1

Aiming at the development characteristics of cumulative plastic strain of loess under different stress paths under cyclic loading and unloading conditions, the remolded loess is taken as the research object, and the round-trip loading and unloading tests under different stress paths are conducted using a true triaxial apparatus to explore the influences of different stress paths and amplitudes on the cyclic stress time-history curve, hysteresis curve, backbone curve and cumulative plastic strain curve of loess. The results reveal the effects of the stress paths on the mechanical properties of the remolded loess, describe the correlation among each principal stress, ratio of the intermediate principal stress and the stress amplitude, and the hysteresis curve of the remolded loess is proposed to be approximately elliptical, with the slope of the major axis increasing with the increase of the ratio of the principal stress and decreasing with the increase of the stress amplitude. As the value of the ratio of the principal stress ratio increase, the backbone curve of cyclic stress-strain hardens accordingly, the cumulative plastic strain curve decreases in sequence, and the cumulative plastic strain develops earlier and enters a gentle stage. The research results provide a reference for solving the relevant problems in loess engineering.

Jukka Ruohonen, Kalle Hjerppe

Participatory citizen platforms are innovative solutions to digitally better engage citizens in policy-making and deliberative democracy in general. Although these platforms have been used also in an engineering context, thus far, there is no existing work for connecting the platforms to requirements engineering. The present paper fills this notable gap. In addition to discussing the platforms in conjunction with requirements engineering, the paper elaborates potential advantages and disadvantages, thus paving the way for a future pilot study in a software engineering context. With these engineering tenets, the paper also contributes to the research of large socio-technical software systems in a public sector context, including their implementation and governance.

Mehil B Shah, Mohammad Masudur Rahman, Foutse Khomh

Deep learning (DL) techniques have achieved significant success in various software engineering tasks (e.g., code completion by Copilot). However, DL systems are prone to bugs from many sources, including training data. Existing literature suggests that bugs in training data are highly prevalent, but little research has focused on understanding their impacts on the models used in software engineering tasks. In this paper, we address this research gap through a comprehensive empirical investigation focused on three types of data prevalent in software engineering tasks: code-based, text-based, and metric-based. Using state-of-the-art baselines, we compare the models trained on clean datasets with those trained on datasets with quality issues and without proper preprocessing. By analysing the gradients, weights, and biases from neural networks under training, we identify the symptoms of data quality and preprocessing issues. Our analysis reveals that quality issues in code data cause biased learning and gradient instability, whereas problems in text data lead to overfitting and poor generalisation of models. On the other hand, quality issues in metric data result in exploding gradients and model overfitting, and inadequate preprocessing exacerbates these effects across all three data types. Finally, we demonstrate the validity and generalizability of our findings using six new datasets. Our research provides a better understanding of the impact and symptoms of data bugs in software engineering datasets. Practitioners and researchers can leverage these findings to develop better monitoring systems and data-cleaning methods to help detect and resolve data bugs in deep learning systems.

B. H. Kim, M. K. Larson

This paper was developed as part of an effort by the National Institute for Occupational Safety and Health (NIOSH) to identify risk factors associated with bursts/bumps in the prevention of fatalities and accidents in highly stressed, burst- or bump-prone ground conditions. In this study, we evaluated the effects of different shapes and distribution densities of mineral grains in coal on failure mechanics using the numerical software 3DEC. The main aim of this study was to identify possible failure mechanisms influenced by mineral habit and frequency in coal. Exploring differences in failure mechanics associated with the mineral grains helped to determine the role of mineral character as a possible contributor to characterize burst-prone coals. To achieve the goal of this study, a series of numerical specimens were prepared in the 3DEC model as follows: first, the 3DEC modeling in conjunction with the DFNs (Discrete Fracture Networks) technique was performed to explicitly generate the discontinuities (i.e., cleats and bedding planes) in the numerical specimens based on the results of laboratory analyses. Then, the different realizations of mineral grains were embedded in the 3DEC model to simulate an unconfined compressive strength (UCS) test to assess the influence of the mineralogical characteristics on the UCS. The type of catastrophic failure in coal mines known as dynamic failure—also colloquially referred to as bumps, bounces, bursts, and others—is one of the most challenging and persistent engineering problems associated with coal mining in highly stressed conditions. Coal pillar bursts involve the sudden expulsion of coal and rock into the mine opening. These events occur when stresses in a coal pillar, left for support in underground workings, exceed the pillar's critical capacity, causing the pillar to rupture without warning. These events can be exceptionally violent, ejecting coal and rock with explosive force (Peng 2008; Kim and Larson 2017). Many uncertainties remain in the highly anisotropic characteristics of coal seams associated with geologic structure and spatial redistribution of induced stress in coal pillars due to mining activities (Kim et al. 2018; Kim and Larson 2021). Thus, to prevent fatalities, continuous effort is required to better understand this type of catastrophic failure mechanism in coal mines. This paper is developed as part of an effort by the National Institute for Occupational Safety and Health (NIOSH) to identify risk factors associated with bumps to prevent fatalities and accidents in highly stressed, bump-prone ground conditions.

Y. Huang, Z. Lei, K. Lipnikov et al.

The complex coupling interaction phenomena among rock mechanics, fluid flow, heat transfer and geochemical reactions has become a critical topic in complex subsurface systems including the production of unconventional oil and gas. In this paper, we introduce a fully coupled Thermo-Hydro-Mechanical-Chemical (THMC) framework that is being developed at Los Alamos National Laboratory (LANL). The framework integrates four LANL-developed codes: HOSS, Amanzi, dfnWorks and InyanCC. HOSS simulates deformation of the rock matrix as well as the opening, closing and shear sliding in the discrete fractures (mechanics), while Amanzi solves subsurface multiphase flow and reactive transport, dfnWorks generates meshes with complex discrete fracture networks, and InyanCC links the mechanics and flow solvers while controlling the whole simulation processes. The advantages of this coupling framework are: 1) it is based on hybrid continuum-discontinuum approaches which overcomes the limitations seen with pure continuum assumptions; 2) both mechanics and subsurface flow solvers are fully parallelized for distributed memory systems which allows the users to simulate large scale problems on HPC clusters. Different selected benchmarking problems are simulated using this THMC framework. The results show good agreement with the analytical solutions, which verifies the accuracy of the framework. Current applications of geotechnical engineering and geo-energy in the subsurface rely significantly on complex coupling process among rock mechanics, fluid flow, heat transfer and geochemical reactions, including geothermal production, unconventional oil and gas production and underground nuclear explosions. Hence, Modeling Thermo-Hydro-Mechanical-Chemical (THMC) processes is essential in understanding the coupled processes in subsurface geological media. Fully addressing the computational challenge of coupled THMC process simulation has been exacerbated by the inability to simulate coupled processes in both the rock matrix and discrete fractures. However, modern subsurface simulators taking advantage of the high-performance computation have been proposed to overcome these challenging problems. Cheng, 2016; Rutqvist et al., 2001; and Wang, 2000 proposed different approaches for modeling the evolution of pressure, stress, and temperature fields in porous media, including equations for pressure diffusion, mechanical equilibrium, and energy transport. Rutqvist and Stephansson (2003) introduced a coupled THM model based on sub-grid scale fracture networks. Min and Jing (2003) reported numerical simulations of hydro-mechanical coupling in fracture networks. These models capture the contribution of discrete fracture deformation to permeability anisotropy through the effective properties such as permeability and porosity. However, these methods have limitation in modeling time-evolving large scale THM system when the characteristic length of network structures is much larger than the grid block scale.

M. Ochmański, D. Mašín, J. Duque

Despite a considerable progress in the analysis and design of monopiles, many methods are based on complex mathematical structures with doubtful or hard assumptions to verify. Therefore, there is still a need for simple and yet accurate methods for the analysis of monopiles under drained and undrained lateral cyclic loading conditions. In this work, a simple yet efficient two-dimensional modelling approach for the analysis of monopiles is proposed. To account for out-of-plane frictional forces, counter-forces derived from virtual frictional forces generated at the out-of-plane pile interface are applied along the pile length together with the scaled pile stiffness. The predictive capabilities of the proposed approach were validated by back-calculating two different experimental sets. The first consists of a small-scale field monopile test on a coarse-grained soil subjected to lateral cyclic loading under drained conditions. The second is a centrifuge test involving a fine-grained soil subjected to lateral cyclic loading under practically undrained conditions. Simulation results with the proposed approach suggest an accurate prediction of pile displacements and bending moments under both drained and undrained lateral cyclic conditions. The method is, however, unable to reproduce pore water pressures generated behind the pile in low permeability materials.

KONG Desen 1, 2, ZHAO Mingkai 1, 2, SHI Jian 1, 2, TENG Sen 1, 2

The relative permeability is an essential mechanical parameter characterizing the two-phase flow of rock media, and how to obtain the relative permeability quickly and effectively has become a critical issue to be solved in the current studies. A fractal analytical model for predicting the relative permeability of two-phase flow is developed using the fractal method to equate the rock pores as the capillaries with varying sizes and establish the equilibrium equation for gas-water phase flow based on the momentum balance. Then, the influences of the pore structure of the rock media on the permeability characteristics of the two-phase flow are studied based on the pore size scale and the tortuosity characteristics of the flow path. The relative permeability curves obtained by the model are in good agreement with the relevant experimental data, which verifies the reasonableness of the model. The results show that the model has better accuracy than other relative permeability models. The permeability characteristics of the rock media are related to fluid properties and pore structure. The smaller the fractal dimension Df and the tortuous fractal dimension DT, the larger the permeability of two-phase flow. In addition, increasing the value of DT decreases the relative permeability of the water phase and increases the relative permeability of the gas phase. The model does not use any empirical constants to calculate the relative permeability, which avoids tedious data processing and can be effectively used in engineering fields such as shale gas extraction.

بهروز اکبری, حسین خادمی

سابقه و هدف: ذرات معلق در هوا که معمولاً با نام آئروسل شناخته می‌شوند می‌توانند حامل ذرات و عناصر آلاینده و مضر باشند. گرد و غبار خیابانی به ذراتی در اندازه‌های کوچکتر از 70 میکرومتر که بر اثر تعلیق مجدد ذرات حاصل از فعالیت‌های انسانی یا طوفان‌های گرد و غباری وارد محیط‌های شهری می‌شوند، گفته می‌شود. این ذرات میزبان آلاینده‌های مختلف از جمله فلزات سنگین بوده که از منابع مختلف انسان‌زاد و طبیعی تولید می‌شوند. منابع و مقادیر این فلزات در فصل‌ها و شهرهای مختلف می‌تواند بسیار متفاوت باشد. اهداف این تحقیق شامل بررسی تغییرات فصلی غلظت و شدت آلودگی برخی از عناصر سنگین در نمونه‌های گرد و غبار خیابانی و خاک‌های اطراف شهرها در تعدادی از شهرهای استان اصفهان و همچنین مقایسه آن‌ها با تعدادی از شهرهای سایر نقاط ایران و جهان بوده است.مواد و روش‌ها: نمونه‌های گرد و غبار خیابانی در نیمه اول از ماه دوم هر یک از چهار فصل در سال 1398 به تعداد 80 نمونه برای اصفهان و 40 نمونه برای هر یک از شهرهای فلاورجان، نجف‌آباد، شهرضا، خمینی‌شهر و نطنز بوسیله ابزارهای مناسب از سطوح معابر شهری به میزان متوسط 300 گرم برداشت و در ظروف پلاستیکی نگهداری شد. سپس از کلیه نمونه‌ها با روش هضم با اسید نیتریک 6 نرمال عصاره‌گیری شده و مقادیر غلظت کل عناصر سنگین مس، روی، سرب و کبالت در عصاره‌ها بوسیله دستگاه جذب اتمی اندازه‌گیری شد. در نهایت شاخص‌های زمین‌انباشتگی و آلودگی نمرو در نمونه‌ها محاسبه و تغییرات فصلی و مکانی غلظت و شدت آلودگی فلزات سنگین بررسی شد.یافته‌ها: تغییرات مکانی و فصلی غلظت و شدت آلودگی عنصر مس و سرب نشان داد که بیشترین آلودگی این عنصر در شهر اصفهان و همچنین در فصل بهار اتفاق افتاده است. همین بررسی برای عنصر روی حاکی از آن بود که بیشترین آلودگی گرد و غبار خیابانی مربوط به شهر فلاورجان در فصل بهار بوده است. برای عنصر کبالت بیشترین آلودگی برای شهر شهرضا و در فصل زمستان بدست آمد. در تمامی عناصر کمترین مقدار غلظت و شدت آلودگی برای شهر نطنز در فصل تابستان بدست آمده و عنصر سرب در فصل پاییز کمترین غلظت را نشان داد. به غیر از عنصر کبالت، کمترین مقدار غلظت و شدت آلودگی عناصر سنگین این مطالعه در خاک‌های اطراف شهرها اندازه‌گیری شد. مقایسه نتایج بدست آمده با داده‌های گزارش شده برای سایر شهرهای جهان نمایانگر آلودگی بیشتر گرد و غبار خیابانی کلان‌شهر اصفهان نسبت به سایر شهرهای بزرگ دنیا می‌باشد. غلظت عناصر مورد مطالعه در گرد و غبار خیابانی شهر اصفهان برای عنصر مس تقریباً مشابه اهواز و هوانیان (چین) و برای عنصر روی کمتر از آویلیس (اسپانیا) و ژوژو (چین) بوده، برای عنصر سرب کمتر از ژوژو و هولودائو (چین) بوده و برای عنصر کبالت بالاتر از همه شهرهای مورد مطالعه به غیر از بزرگراه رباط-ساله (شمال غربی مراکش) و هوانیان ارزیابی شد.نتیجه‌گیری: از نتایج حاصله و بررسی‌های انجام شده در این مطالعه و مقایسه با سایر مطالعات می‌توان بیان داشت که میانگین غلظت عناصر مس، روی و سرب در گرد و غبار خیابانی بیشترین مقدار را در همه شهرها در مقایسه با نطنز نشان می‌دهد. این امر وجود ترافیک بالاتر، جمعیت بیشتر و به طبع تراکم ماشین‌آلات، وجود ساخت و سازهای بیشتر و عظیم‌تر در شهرهای بزرگ، رفت و آمدهای ترانزیتی وسایل نقلیه، وجود طوفان‌های گرد و غباری اتمسفری شدیدتر در مناطق مرکزی استان اصفهان، خشکسالی و نبود باران کافی نسبت داده می‌شود. کم بودن مقادیر برخی عناصر سنگین در گرد و غبار خیابانی شهر نطنز احتمالاً بدلیل تراکم جمعیت کمتر، جنس مواد مادری متفاوت نسبت به سایر شهرهای مورد مطالعه و فعالیت‌های صنعتی کمترمی‌باشد.

Qiang Liu, Xiao-dong Guo, Chang-qi Wang et al.

<p>The Songnen Plain is a crucial agricultural area in China, and in the past 20 years, a large number of dry fields have been developed into paddy fields in order to improve land output efficiency. As a result, the effective irrigation area of agriculture has increased annually, and the conversion mode and quantity between surface water and groundwater have changed considerably. It is essential to identify the changes in groundwater resources and their influencing factors for the sustainable development of economy and society. This study evaluates groundwater resources in the Songnen Plain using the water balance method based on meteorological, hydrological and groundwater monitoring data from 2000 to 2020. The results show that the groundwater resources in the region amount to 15.945 billion m³ with precipitation infiltration being the most important component, accounting for 73.09%, which is followed surface water irrigation infiltration and river and ditch infiltration, constituting 14.55% and 10.32%, respectively. Different factors influence groundwater resources in different periods. Compared to 1985, the increase of surface water irrigation infiltration is the primary factor responsible for the increase of groundwater resources, while other recharge sources have decreased during the same period. Compared to 2005, all groundwater resources have increased, with the increase of surface water irrigation infiltration and river channel infiltration being the primary factors.</p>

Matthew Frenkel, Hebah Emara

The launch of ChatGPT at the end of 2022 generated large interest into possible applications of artificial intelligence in STEM education and among STEM professions. As a result many questions surrounding the capabilities of generative AI tools inside and outside of the classroom have been raised and are starting to be explored. This study examines the capabilities of ChatGPT within the discipline of mechanical engineering. It aims to examine use cases and pitfalls of such a technology in the classroom and professional settings. ChatGPT was presented with a set of questions from junior and senior level mechanical engineering exams provided at a large private university, as well as a set of practice questions for the Fundamentals of Engineering Exam (FE) in Mechanical Engineering. The responses of two ChatGPT models, one free to use and one paid subscription, were analyzed. The paper found that the subscription model (GPT-4) greatly outperformed the free version (GPT-3.5), achieving 76% correct vs 51% correct, but the limitation of text only input on both models makes neither likely to pass the FE exam. The results confirm findings in the literature with regards to types of errors and pitfalls made by ChatGPT. It was found that due to its inconsistency and a tendency to confidently produce incorrect answers the tool is best suited for users with expert knowledge.

Markus Sudmanns, Athanasios P. Iliopoulos, Andrew J. Birnbaum et al.

Mesoscale simulations of discrete defects in metals provide an ideal framework to investigate the micro-scale mechanisms governing the plastic deformation under high thermal and mechanical loading conditions. To bridge size and time-scale while limiting computational effort, typically the concept of representative volume elements (RVEs) is employed. This approach considers the microstructure evolution in a volume that is representative of the overall material behavior. However, in settings with complex thermal and mechanical loading histories careful consideration of the impact of modeling constraints in terms of time scale and simulation domain on predicted results is required. We address the representation of heterogeneous dislocation structure formation in simulation volumes using the example of residual stress formation during cool-down of laser powder-bed fusion (LPBF) of AISI 316L stainless steel. This is achieved by a series of large-scale three-dimensional discrete dislocation dynamics (DDD) simulations assisted by thermo-mechanical finite element modeling of the LPBF process. Our results show that insufficient size of periodic simulation domains can result in dislocation patterns that reflect the boundaries of the primary cell. More pronounced dislocation interaction observed for larger domains highlight the significance of simulation domain constraints for predicting mechanical properties. We formulate criteria that characterize representative volume elements by capturing the conformity of the dislocation structure to the bulk material. This work provides a basis for future investigations of heterogeneous microstructure formation in mesoscale simulations of bulk material behavior.