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The study delivers a cohesive system that combines structural stress investigation, navigational planning evaluation, and adaptive joint control to optimize hexapod effectiveness on hills, stairs, and uneven surfaces. The robot was developed through the iterative drafting technique and designed by assigning in PLA material. Structural examination with Finite Element Analysis (FEA) under 10 N and 20 N forces demonstrated a positive stress allocation and a safety factor of 2.8, combining compact development with durability. In the ROS/Gazebo exploration investigations utilizing global planners like A*, Dijkstra, RRT, and Artificial Potential Field (APF) in combination with a PID-driven local planner, A* as well as Dijkstra developed nearly the best pathways with 100% accuracy. This cut down on route variation by about 17% in comparison to RRT. RRT established confident that the exploration was always the same, but it established paths that were more lengthy and less smooth. APF, on the contrary, made paths that were smooth but less reliable due to the local minima. Adaptive synchronization for joint control quantitatively provided an improvement in joint angle stability, reducing oscillatory deviations by 12% and displacement errors by 15% relative to baseline controllers. The core novelty within this approach is the integrative methodology that will inherently synergize finite element structural analysis, comparative path planning, and Adaptive joint synchronization: presenting a comprehensive optimization strategy, new to hexapod robotics. Together, these advances allow for robust and efficient real-world deployment of hexapods. Future work will extend to hybrid learning-based planning, and sensor-driven dynamic adaptation.

The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects.  2 and 3 . In Sect.  4 , methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section  5 discusses physical mechanisms of strain rate effects. Section  6 describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section  7 presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.

Roadway instability has always been a major concern in deep underground coal mines where the surrounding rock strata and coal seams are weak and the in situ stresses are high. Under the high overburden and tectonic stresses, roadways could collapse or experience excessive deformation, which not only endangers mining personnel but could also reduce the functionality of the roadway and halt production. This paper describes a case study on the stability of roadways in an underground coal mine in Shanxi Province, China. The mine was using a longwall method to extract coal at a depth of approximately 350 m. Both the coal seam and surrounding rock strata were extremely weak and vulnerable to weathering. Large roadway deformation and severe roadway instabilities had been experienced in the past, hence, an investigation of the roadway failure mechanism and new support designs were needed. This study started with an in situ stress measurement programme to determine the stress orientation and magnitude in the mine. It was found that the major horizontal stress was more than twice the vertical stress in the East–West direction, perpendicular to the gateroads of the longwall panel. The high horizontal stresses and low strength of coal and surrounding rock strata were the main causes of roadway instabilities. Detailed numerical modeling was conducted to evaluate the roadway stability and deformation under different roof support scenarios. Based on the modeling results, a new roadway support design was proposed, which included an optimal cable/bolt arrangement, full length grouting, and high pre-tensioning of bolts and cables. It was expected the new design could reduce the roadway deformation by 50 %. A field experiment using the new support design was carried out by the mine in a 100 m long roadway section. Detailed extensometry and stress monitorings were conducted in the experimental roadway section as well as sections using the old support design. The experimental section produced a much better roadway profile than the previous roadway sections. The monitoring data indicated that the roadway deformation in the experimental section was at least 40–50 % less than the previous sections. This case study demonstrated that through careful investigation and optimal support design, roadway stability in soft rock conditions can be significantly improved.

The development of the Brazilian disc test for determining indirect tensile strength and its applications in rock mechanics are reviewed herein. Based on the history of research on the Brazilian test by analytical, experimental, and numerical approaches, three research stages can be identified. Most of the early studies focused on the tensile stress distribution in Brazilian disc specimens, while ignoring the tensile strain distribution. The observation of different crack initiation positions in the Brazilian disc has drawn a lot of research interest from the rock mechanics community. A simple extension strain criterion was put forward by Stacey (Int J Rock Mech Min Sci Geomech Abstr 18(6):469–474, 1981 ) to account for extension crack initiation and propagation in rocks, although this is not widely used. In the present study, a linear elastic numerical model is constructed to study crack initiation in a 50-mm-diameter Brazilian disc using FLAC 3D . The maximum tensile stress and the maximum tensile strain are both found to occur about 5 mm away from the two loading points along the compressed diameter of the disc, instead of at the center of the disc surface. Therefore, the crack initiation point of the Brazilian test for rocks may be located near the loading point when the tensile strain meets the maximum extension strain criterion, but at the surface center when the tensile stress meets the maximum tensile strength criterion.

The combination of the Internet and emerging technologies such as nearfield communications, real-time localization, and embedded sensors lets us transform everyday objects into smart objects that can understand and react to their environment. Such objects are building blocks for the Internet of Things and enable novel computing applications. As a step toward design and architectural principles for smart objects, the authors introduce a hierarchy of architectures with increasing levels of real-world awareness and interactivity. In particular, they describe activity-, policy-, and process-aware smart objects and demonstrate how the respective architectural abstractions support increasingly complex application.

Experiments on man-made flawed rock-like materials are applied extensively to study the mechanical behaviour of rock masses as well as crack initiation modes and crack coalescence types. A large number of experiments on specimens containing two or three pre-existing flaws were previously conducted. In the present work, experiments on rock-like materials (formed from a mixture of sand, plaster, limestone and water at mass ratio of 126:9:9:16) containing multiple flaws subjected to uniaxial compression were conducted to further research the effects of the layout of pre-existing flaws on mechanical properties, crack initiation modes and crack coalescence types. Compared with previous experiments in which only three types of cracks were found, the present experiments on specimens containing multiple flaws under uniaxial compression revealed five types of cracks, including wing cracks, quasi-coplanar secondary cracks, oblique secondary cracks, out-of-plane tensile cracks and out-of-plane shear cracks. Ten types of crack coalescence occurred through linkage among wing cracks, quasi-coplanar secondary cracks, oblique secondary cracks, out-of-plane shear cracks and out-of-plane tensile cracks. Moreover, the effects of the non-overlapping length and flaw angle on the complete stress–strain curves, the stress of crack initiation, the peak strength, the peak strain and the elastic modulus were also investigated in detail.

This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component.

Floating offshore wind turbines (FOWTs) are subject to nonlinear hydrostatic and hydrodynamic loads due to their intricate platform geometry. However, most fully coupled simulation tools for FOWTs rely on linearized hydrostatics and frequency-domain potential flow models transformed into the time domain, which assume a stationary waterline and wetted surface. To overcome these limitations, this study develops an innovative coupled simulation tool named FAST2WASIM (F2W), which incorporates nonlinear hydrostatic and hydrodynamic effects while preserving computational efficiency for engineering applications. This paper first describes the overall framework of the F2W methodology, outlines its underlying hydrodynamic theory, and presents the numerical model of the OC4 DeepCwind semi-submersible FOWT. Response predictions under a range of test conditions are then compared between FAST and F2W, demonstrating the validity of the proposed tool and revealing the inadequacies of conventional linear methods in predicting the hydrodynamic behavior of semi-submersible FOWTs. Finally, a novel structural analysis workflow for semi-submersible FOWTs based on F2W is introduced, and its differences from the traditional approach are examined in terms of computational time and structural stress outputs. This work offers an efficient and high-fidelity approach for simulating nonlinear hydrodynamics of semi-submersible FOWTs and provides valuable insights for practical engineering design.

The liquid oxygen subcooler is a key unit for the deep cooling, storage, and transportation of liquid oxygen. Its frequent start–stop operation under liquid nitrogen bath conditions introduces potential risks to service reliability. This study employs a thermo-structural sequential coupling approach to evaluate the stress behavior of ABS components in a flat plate-fin heat exchanger during the pre-cooling, heat-exchange, and recovery stages. Based on the maximum shear stress (Tresca) criterion, the evolution of principal stresses in the brazed layer under liquid nitrogen bath conditions was analyzed, and a conservative assessment of the material’s fatigue behavior was conducted. The results indicate that the equivalent stress is governed by the third principal stress, originating from the thermal compression effect induced by low-temperature constraint shrinkage. During the heat exchange phase (2700 s), the inlet equivalent stress reached 93.49 MPa, which is below the 258 MPa limit, falling within Region 1. Local stress concentration is primarily driven by thermal loading, with brazing layer thickness, curvature radius, and liquid oxygen pressure serving as key control variables. Under a safety factor of 1.15 (107 MPa), fatigue testing exceeding 1.5 million cycles has confirmed the static safety and operational reliability of the ABS.

This paper deals with the impact of corrosion on the mechanical properties of steel in reinforced concrete. Steel bars were extracted from a 27-year-old corroded reinforced concrete beam that had been exposed to a chloride environment. Bars with different degrees of corrosion and with different corrosion pit depths were tested in tension. A comparison was made between nominal and true stress for corroded and control steel specimens. It was noted that the degree of corrosion strongly affected the mechanical properties of the steel, particularly the ultimate stress and strain. Interestingly, the true yield strength of all the corroded steel bars remained almost constant while their true ultimate strength was considerably increased. A reduction of the ultimate elongation appeared to be the major effect of corrosion and affected the compliance with standards.