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This research explores how temperature and relative humidity impact the mechanical properties of corrugated cardboard. Samples were treated under a range of controlled climate conditions in a climate chamber to simulate varying environmental exposures. Following this conditioning, we performed a series of mechanical tests: the Edge Crush Test (ECT) to assess compressive strength, four-point Bending Tests (BNTs) in both the Machine (MD) and Cross Directions (CD) to evaluate bending stiffness, Sample Torsion Tests (SSTs) for shear stiffness, and Transverse Shear Tests (TSTs) to measure torsional rigidity. By comparing results across these tests, we aim to determine which mechanical property shows the highest sensitivity to changes in humidity levels. Findings from this study are expected to offer valuable insights into the environmental adaptability of corrugated board, particularly for applications in packaging and storage, where climate variability can affect material performance and durability. Such insights will support the development of more robust and adaptable packaging solutions optimised for specific climate conditions.

Hydrodynamic bearing is becoming an indispensable component of high-accuracy devices such as high-speed machine tools. Recently, the study of textured surface bearing has become one of the highly researched topics. Among the different types of surface texture, partially textured bearing shows outstanding performances on anti-vibration. However, most of the research focuses on the theoretical models of partial texture. In this paper, several bearings with no texture, full texture and partial texture are fabricated for stability and stiffness tests. The result shows that the partially textured bearings with 60% of textured ratio and 4.9% of area ratio exhibit the best properties, which could decrease the maximum amplitude by 45.8% at 9000 rpm. In addition, the textured surface with the optimal textured ratio of 60% can reduce the static stiffness and improve the dynamic stiffness. Therefore, partially textured bearings are particularly significant to the stability enhancement of the bearing system, which can lead to the performance and security improvement of the sliding bearing in high-speed applications.

The stiffness theory of rockburst plays a crucial role in understanding and preventing rockburst events. This theory evaluates the severity of rockbursts through the difference in stiffness. As a fundamental theory, many new theories have emerged from the stiffness theory, and its applications in mines and deep tunnels are diverse. In this paper, we provide a systematic review of the development process, application status, and application field of rockburst stiffness theory from the perspective of theoretical derivation, laboratory testing, and field application. We also identify key and difficult problems in stiffness theory, such as the determination method of stiffness, the influence of post-peak slope, and the study of rockburst criteria. In addition, based on the existing issues related to stiffness determination, exploration of stiffness changes during rockburst development, and low adaptability in predicting rockburst intensity, we propose the influence of the blasting body-surrounding rock stiffness on the spatial-temporal characteristics, intensity, and mechanism of rockburst, dynamic variable stiffness tests, and stiffness theoretical criteria for determining the rockburst intensity as areas for further research on the stiffness theory of rockburst.

The angular contact ball bearings are widely used in various high-speed and precision rotating equipment because of support performance. The contact load of the inner and outer rings is changed because of the centrifugal force of rolling elements caused by high speed in the spindle system of high-speed and precision machine tools. The bearing stiffness changes due to changes in contact load the influence of centrifugal force and gyroscopic moment on the stiffness of angular contact ball bearings under high speed is considered in this paper. Based on the internal load distribution within the bearing and the force analysis of a single rolling element, the relationship between the forces on the bearing and the deformation of each rolling element is analyzed. Then the stiffness model for angular contact ball bearings is established. The stiffness tests were conducted under variable load and speed conditions. The correctness of the stiffness model is preliminarily verified, as the maximum error between experimental and theoretical results was less than 3%.

Applying accurate normal load to a specimen in direct shear tests under constant normal stiffness (CNS) is of importance for the quality of the resulting data, which in turn influences the conclusions. However, deficiencies in the test system give rise to a normal stiffness, here designated as system normal stiffness, which results in deviations between the intended and actual applied normal loads. Aiming to reduce these deviations, this paper presents the effective normal stiffness approach applicable to closed-loop control systems. Validation through direct shear tests indicates a clear influence of the system normal stiffness on the applied normal load (13% for the test system used in this work). The ability of the approach to compensate for this influence is confirmed herein. Moreover, it is demonstrated that the differences between the measured and the nominal normal displacements are established by the normal load increment divided by the system normal stiffness. This further demonstrates the existence of the system normal stiffness. To employ the effective normal stiffness approach, the intended normal stiffness (user defined) and the system normal stiffness must be known. The latter is determined from a calibration curve based on normal loading tests using a stiff test dummy. Finally, a procedure is presented to estimate errors originating from the application of an approximate representation of the system normal stiffness. The approach is shown to effectively reduce the deviations between intended normal loads and the actual applied normal loads.

This paper takes a four-point contact ball bearing of a wind turbine as the research object, analyzes the force and deformation relationship under the combined action of axial load and radial load, obtains the load distribution of rolling elements, and establishes a time-varying stiffness model of four-point contact ball bearings without clearance. The stiffness variation law of the case bearing in one rolling period is analyzed, and the time-varying characteristics of stiffness are characterized by the average stiffness and stiffness amplitude variation rate. The influence laws of the number of rolling elements, initial contact angle, axial load, and radial load on the time-varying characteristics of bearing stiffness are analyzed. The results show that within one rolling period, the average value of axial stiffness is about 2.21 times that of radial stiffness, and the amplitude variation rates of radial stiffness and axial stiffness are 0.0047% and 0.002%, respectively. The time-varying characteristics of both are not obvious. The influence of the number of rolling elements on the two stiffnesses is almost linear, while the influence of axial load on stiffness is small; the initial contact angle is positively correlated with axial stiffness and negatively correlated with radial stiffness. With the increase in radial load, the two stiffnesses also increase. Finally, the stiffness test of four-point contact ball bearings was carried out, and the error between the test value and the theoretical value was less than 15%, which preliminarily verified the correctness of the stiffness model.

Purpose The purpose of this study is to describe the proposed alpha solar rotary mechanism (ASRM) and how it is used to accurately modify the solar array of the China Space Station (CSS) in orbit to maintain continuous tracking of the sun to provide power. It also highlights the need to evaluate the performance of the ASRM and predict potential failure modes in various extreme scenarios. Design/methodology/approach To evaluate the performance of the ASRM, a dynamic model was created and tested under normal and faulty conditions. In addition, a multidirectional stiffness test was conducted on the prototype to verify the accuracy of the ASRM's dynamic model. The high-precision ASRM model was then used to predict potential failure modes and damaged parts in various extreme scenarios. Findings The simulation results were in good agreement with the test results, with a maximum error of less than 8.85%. The high-precision ASRM's model was able to accurately predict potential failure modes and damaged parts in extreme scenarios, demonstrating the effectiveness of the proposed model and simulation evaluation test. Originality/value The proposed high-precision ASRM model and simulation evaluation test provide an effective way to evaluate the structural safety and optimize the design of the spacecraft. This information can be used to improve the performance and reliability of the CSS's solar array and ensure continuous power supply to the station.

The effect of delamination on the stiffness reduction of composite pipes is studied in this research. The stiffness test of filament wound composite pipes is simulated using cohesive zone method. The modeling is accomplished to study the effect of the geometrical parameters including delamination size and its position with respect to loading direction on stiffness of the composite pipes. At first, finite element results for stiffness test of a perfect pipe without delamination are validated with the experimental results according to ASTM D2412. It is seen that the finite element results agree well with experimental results. Then the finite element model is developed for composite pips with delaminated areas with different primary shapes. Thus, the effect of the size of delaminated region on longitudinal and tangential directions and also its orientation with respect to loading direction on delamination propagation and stiffness reduction of the pipes is assessed.

A new type of suspension bridge is proposed based on the gravity stiffness principle. Compared with a conventional suspension bridge, the proposed bridge adds rigid webs and cross braces. The rigid webs connect the main cable and main girder to form a truss that can improve the bending stiffness of the bridge. The cross braces connect the main cables to form a closed space truss structure that can improve the torsional stiffness of the bridge. The rigid webs and cross braces are installed after the construction of a conventional suspension bridge is completed to resist different loads with different structural forms. A new type of railway suspension bridge with a span of 340 m and a highway suspension bridge with a span of 1020 m were designed and analysed using the finite element method. The stress, deflection of the girders, unbalanced forces of the main towers, and natural frequencies were compared with those of conventional suspension bridges. A stiffness test was carried out on the new type of suspension bridge with a small span, and the results were compared with those for a conventional bridge. The results showed that the new suspension bridge had a better performance than the conventional suspension bridge.

When producing packaging from corrugated board, material weakening often occurs both during the die-cutting process and during printing. While the analog lamination and/or printing processes that degrade material can be easily replaced with a digital approach, the die-cutting process remains overwhelmingly analog. Recently, new innovative technologies have emerged that have begun to replace or at least supplement old techniques. This paper presents the results of laboratory tests on corrugated board and packaging made using both analog and digital technologies. Cardboard samples with digital and analog creases are subject to various mechanical tests, which allows for an assessment of the impact of creases on the mechanical properties of the cardboard itself, as well as on the behavior of the packaging. It is proven that digital technology is not only more repeatable, but also weakens the structure of corrugated board to a much lesser extent than analog. An updated numerical model of boxes in compression tests is also discussed. The effect of the crushing of the material in the vicinity of the crease lines in the packaging arising during the analog and digital finishing processes is taken into account. The obtained enhanced computer simulation results closely reflect the experimental observations, which prove that the correct numerical analysis of corrugated cardboard packaging should be performed with the model taking into account the crushing.