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The article presents the concept of innovative technology for the production of press bodies, especially hydraulic ones. The manufacturing method is distinguished by the use of pre-tensioning of the press body, which guarantees the required rigidity and relatively low production costs. The SolidWorks Simulation application has been successfully used to assess the strength of the press body in conditions of different press temperatures.

In order to solve the problem of unreliable connection between the subframe and the chassis girder under the action of shooting load, which leads to the reduction of the stiffness and strength of the connection between the bodywork part and the chassis girder, and affects the shooting accuracy of the bodywork, combined with the structural characteristics of the rigid connection between the subframe and the chassis girder, the fabric filling and bolt preloading connection method is proposed, the finite element model is established, and the deformation of the connection between the original and the improved scheme is analyzed. The results show that under the action of shooting load, the deformation of the bodywork mounting surface can be effectively reduced and the shooting accuracy of the bodywork can be improved by bolt pretensioning and spinning fabric filling, which provides a certain reference for the optimal design of the lightweight frame.

Bolted connections are indispensable in various engineering structures, and their reliable performance critically depends on maintaining adequate bolt preload. Preload loss due to dynamic loads, fatigue, vibration, and temperature fluctuations can lead to catastrophic structural failures. Existing preload monitoring methods, however, are often complex, invasive, and susceptible to environmental interference, limiting their widespread application. This paper introduces a novel smart nut designed for accurate real-time and continuous monitoring of bolt preload, which integrates a high-precision strain sensing unit within an internal annular groove, enabling non-invasive measurement. Finite element simulations were conducted to validate the structural design and optimal placement of the strain gauges, demonstrating a linear elastic response and symmetrical strain distribution under typical preload conditions. A full-bridge circuit incorporating four strain gauges inside the nut was constructed to correlate output voltage with applied preload. Calibration experiments, including direct pressure testing and bolt pre-tensioning tests, were conducted to achieve practical nut measurement functionality and confirm its accuracy. Experimental results using the calibrated nut to measure bolt preload showed that the nut can accurately measure bolt preload with a maximum error of less than 3.06%. This innovative solution provides a practical, accurate, and easily implementable method for real-time and continuous preload assessment, significantly enhancing structural safety and facilitating timely maintenance in bolted joints.

In underground mining practice, the rock bolt support system is the major support pattern to control the deformation and stability of openings. A rock bolt is generally subjected to complex loads including tension, torsion, bending and shear, which result from the deformation of excavations and exposure to dynamic loads that are generated by rockbursts. An understanding of the response of rock bolt under complex conditions is of great importance for rock bolt support design and practice. New sophisticated equipment has been developed for this purpose. This work involved a comprehensive experimental study on the mechanical behavior of rock bolts under complex loads. The results show that rock bolt pre-tensioning by torque application to the nut can result in decreases in tensile strength and elongation because the rock bolt is subjected to a combination of tension and distortion. When a pre-tensioned rock bolt is subjected to a shear load, the maximum shear force can reach up to 80% of the tensile capacity of the rock bolt. Higher impact energy results in a longer period of dynamic loading and a larger irreversible plastic deformation on the rock bolt, in contrast to a rock bolt that is subjected to low impact energy. The capacity and especially the deformation capacity of a rock bolt may decrease significantly after successive containment of the deformation of the surrounding rock mass from rockbursts.

Optical fibers have revolutionized several technological sectors in recent decades, above all that of communication, and have also found many applications in the medical, lighting engineering, and infrastructural fields. In the aerospace field, many studies investigated the adoption of fiber optics considering the planned transition from fly-by-wire to fly-by-light flight controls. A significant feature of optical fiber is its ability to be used not only as a transmission medium but also as a basis for fiber-embedded sensors; one of the most prominent types is based on Bragg gratings (FBGs). FBGs can replace several traditional sensors, providing measures of temperature, vibrations, and mechanical deformation. Optical sensors provide many advantages over traditional, electrical-based sensors, including EMI insensitivity, ease of multiplexing on a single line, resilience to harsh environments, very compact sizes and global weight saving. Furthermore, punctual knowledge of the temperature field is essential to perform the thermal compensation of the optical sensors used for strain measurements. In this work, the authors analyzed the performance of thermal sensors based on FBGs to verify their stability, accuracy, and sensitivity to operating conditions. Two different methods of FBGs surface application have been considered (gluing with pre-tensioning vs. non-tensioned bonding). The results were then compared to those acquired using typical temperature sensors to determine the relationship between the observed temperature and the Bragg wavelength variation (i.e. the proportionality coefficient Kt). The effects on the proportionality coefficient Kt, arising from fiber pre-tensioning and thermal expansion of the structural support, were then evaluated by comparing the results obtained with the two bonding approaches.

At present, there is a problem of too much prestress loss in the construction of multi-layer logistics warehouses in China. To meet the quality requirements of the project, this paper puts forward the research on the construction technology of pretension prestressed reinforced concrete structure of multi-layer logistics warehouse. The loss of prestress in the construction process can be effectively controlled by incorporating pre-tensioning technology into the construction process, placing prestressed tendons, and tensioning operations. Taking a logistics warehouse construction project as the construction object, using the construction technology designed in this paper to construct, the experiment proves that the construction technology of the pretension prestressed reinforced concrete structure of the multi-layer logistics warehouse proposed in this paper can effectively reduce the prestress loss caused by the instability of the construction structure, and can effectively improve the construction quality of the multi-layer logistics warehouse. This shows that the application and practice of pretension prestressing technology in the construction process of reinforced concrete structures has a positive reference significance, which can meet the needs of green engineering such as energy saving and emission reduction, and also provide a positive reference value for the construction technology of multi-layer logistics warehouse.

As a critical component of natural gas vehicles (NGVs), the safety of hydrogen cylinders should be the foremost consideration in research. Therefore, this study focuses on the design and fatigue performance evaluation of a Type III 35 MPa onboard hydrogen storage cylinder. During the research process, static structural analysis was conducted on the cylinder using ANSYS simulation software. First, a precise finite element model (FEM) of the cylinder was established, and the aluminum liner was wound using the ACP (ANSYS Composite PrepPost) module, with a reinforced thickness design applied to the dome region to enhance its load-bearing capacity. In the pre-processing stage, a 74 MPa pre-tensioning (autofrettage) treatment was applied to the cylinder to improve its stability and safety under high-pressure conditions. Subsequently, under both working pressure (35 MPa) and burst pressure conditions, the stress distribution, strain characteristics, and fatigue life of the cylinder were thoroughly calculated and analyzed. Through these analyses, mechanical performance data of key regions of the cylinder were obtained, providing a solid theoretical foundation for subsequent structural optimization. Furthermore, the research results offer valuable insights for design improvements and performance enhancement of hydrogen storage cylinders, demonstrating significant engineering application value.

In rotor blade fatigue tests used for the certification process, load frames are used to introduce the loads to the blade. These load frames have a constraining effect on the cross-sectional deformation. This work investigates these constraining effects using a finite element contact analysis on a current-generation commercial rotor blade. Two different load frame variants are considered: a conventional load frame covering most of the cross-section and a reduced load frame covering only the main spar caps. The interaction between blade and load frame is implemented via contact formulations, which allows pretensioning in combination with a flap and a lead-lag load case. Strains on the outer surface of the blade are evaluated and compared to an artificial reference loading. The area of influence of the load application through the load frame, in which the strains deviate significantly due to clamping effects, mostly corresponds to the 0.75 times the chord length assumed for the certification [1]. The strains in the trailing edge are significantly less affected by the reduced load frame variant than by the conventional one, thus potentially making it possible to consider the trailing edge at the position of the load frame as being properly tested for certification purposes.

The article proposes a method for calculating the static position of the machine body. The mathematical model of the running gear is given. The dependence of the position of the center of mass in height relative to the ground on the pre-tension forces, as well as the angular deviation of the longitudinal axis of the hull from the horizontal position, is shown. A control calculation was performed, the results of which are presented in the form of graphical dependencies. The numerical experiment was carried out on the example of a tracked vehicle of a light category with a rear drive wheel.

The cohesive/overlapping crack model represents an effective tool in the study of failure transition phenomena occurring in plain or reinforced concrete structures. In the present paper, this non-linear fracture mechanics model is applied to study the global structural behavior of prestressed concrete beams casted by means of pre-tensioning technique or, more generally, having a straight steel strand layout. In this context, a thorough analysis of scale effects is presented to investigate local mechanical instabilities such as snap-back and snap-through phenomena due to concrete cracking or crushing, highlighting the crucial role of the ductile-to-brittle transition in the design of prestressed concrete structural elements. Keywords: concrete cracking; concrete crushing; ductile-to-brittle transition; non-linear fracture mechanics; prestressed concrete; scale effects.