Main Stress Components Research Articles

Variscan lithotectonic units of the Suchý massif in the Strážovské vrchy Mts., Western Carpathians – products of sedimentary, tectonometamorphic and granite forming processes

The present geological investigation of the Pre-Alpine structure of the western part of Strážovské vrchy Mts (the Suchý massif; Western Carpathians) has distinguished three lithologically distinct Variscan lithotectonic units, which originated (1) in the deeper parts of oceanic basin (prevailingly metapelites with different content of organic matter, metabasalts, metacarbonates?); (2) sediments of the continental slope (flyschoid sediments with a predominance of greiwacke sediments; both VmD0); (3) a unit of continent basement primarily of pre-VmD0 granitic composition (orthogneiss). These rock sequences of differing geotectonic provenances were amalgamated and metamorphosed in the pre-intrusive (Pre-Mississipian) stage; pre-VmD2). Regarding the Variscan polyorogenic evolution, Variscan processes in Tatricum represent the Meso-Variscan evolution (VmD). The maximum P-T conditions of orogenic (regional) metamorphism (up to 610 °C and 7.5–8.5 kbar) were not sufficient for more extensive anatexis. Field observations indicated that the production of a limited volume of granitoid melts occurred mainly at the contacts of amalgamated lithotectonic units. Probably due to the heat, produced by the hot line below the collisional orogen and contributing also to unroofing processes (in orogenic phase VmD2) there started new granitization process. This stage of Mississippian VmD2 granite formation is associated with the emplacement of various types of granitoid magma, encompassing the oldest granodiorites with frequent schliers, representing a poorly differentiated and poorly mobile crystal slurry (present in the SE part of the territory). In the highly evolved collision phase, masses of leucogranites intruded comformably with the deformation plan in the metamorphic complexes, interacting with surrounding metamorphic rocks in shallower crustal conditions and causing their contact metamorphic overprint (up to 590 °C and 3–4 kbar). The syn-deformation character of leucocratic granites is proved by the orientation of biotite flakes parallel to the deformation plane of surrounding metamorphites. Part of leucogranites, especially in the central parts of the bodies, is omnidirectional. The stress field acted not only during the intrusion of the leucogranite magma, but also in the subsolidus stage. The final stage of this process is the formation of large bodies of pegmatites in extensional VmD2 fractures oriented at a large angle to the main stress component. The texture of the grey blocky K-feldspar pegmatites and the lack of H2O-bearing minerals point to pneumatolytic fracturing in a subsequently opened environment in VmD2. The final stage of VmD2 is represented by intrusions of I-type granodiorites with indications of magma mixing, or mingling. The chemical dating of monazites in granitoids allowed to date individual phases of granitization process in the range of 360–345 Ma, which youngest ages correspond with the formation of pegmatites. Dating of monazite in metamorphic rocks points to their thermal overprint during granitization process (360–350 Ma), having already earlier metamorphic overprint (380–370 Ma). The scenario of placement of granitoid intrusions is consistent with the decompression regime (in VmD2) after the end of VmD1c crustal thickening until the fracturing of the crustal block with of I-type magma intrusions of deeper origin. After this period, the exhumation of crystalline blocks, partial diaphtoresis and later surface erosion continue until the Lower Triassic. The re-submergence of the crystalline complexes is associated with a low degree of Alpine metamorphic reworking.

Experimental and Numerical Studies on the Seismic Performance of New Assembled Concrete Frame Beam–Column Joints

A new type of assembled concrete beam–column joint based on a bolted connection was proposed, aiming to complete the post-earthquake node repair work by replacing precast beams and bolts. To study the seismic performance of the new beam–column joints, two full-scale components of the new joints were fabricated and subjected to low cyclic loading. The whole process from crack generation to component failure was investigated in detail, and seismic performance indicators such as the hysteresis curve, skeleton curve and stiffness degradation curve were compared and analyzed. Based on the experimental results, ABAQUS finite element software was applied to numerically simulate cast-in-place joints and test joints. Based on the failure mechanism of the new assembled beam–column semi-rigid joints, a stress analysis of semi-rigid joints was carried out. The research results show that the two new joints have good seismic performance and energy dissipation performance. Bolts and precast beams are the main stress components, and the repair of new joints can be completed by replacing bolts, which meets the seismic design concepts of “strong columns and weak beams” and “strong joints and weak components”. The larger the diameter of the bolts, the higher the load capacity and the lower the stiffness degradation rate. The finite element simulation results are high-accuracy and can well reflect the seismic performance of the components. It is found that cast-in-place joints are better in energy dissipation capacity than test joints, but the ultimate bearing capacity of test joints is better than that of cast-in-place joints. Based on the experimental stress characteristics of the nodal core zone, a mechanical analysis model of the nodal core zone of the new assembled concrete beam–column joints is proposed, and shear force calculation equations for the core zone of the new assembled concrete beam–column rigid joints and semi-rigid joints are derived.

A study of the fracture mechanisms of hybrid carbon fiber reinforced polymer laminates reinforced by thin‐ply

AbstractThe main stress component which creates delamination in bonded single lap joints with composite adherends is the transverse tensile stress. Therefore, the following study investigates the behavior of composite laminates (reference and hybrid laminates reinforced by thin‐ply) under transverse tensile loading. Texipreg HS 160T700 and NTPT‐TP415 were used as the conventional carbon fiber reinforced polymer (CFRP) and thin‐ply respectively. Hybrid composite laminates were studied using different amounts of thin‐ply, applied through the thickness. The manufactured laminates, of unidirectionally stacked construction, were tested under transverse tensile loading. Digital image correlation was performed to investigate the average peel strain distribution for the composite and to better understand the phenomena associated to the use of hybrid laminates. Experimental results show that the reinforced hybrid composite laminates, created using thin‐plies, present higher failure load compared to the reference conventional CFRP or thin‐ply laminates. This was found to be due to the higher ductility enabled by the presence of thin‐plies. Distributing a constant amount of thin‐ply through the thickness was found to increase the laminate transverse strength, as the thin‐ply laminates act as a barrier against crack propagation. A representative volume element was studied for each configuration since this numerical method brings the opportunity to investigate the studied configurations in microscale.

Micromechanism of Plastic Accumulation and Damage Initiation in Bearing Steels under Cyclic Shear Deformation: A Molecular Dynamics Study

Fatigue failure usually occurs on the subsurface in rolling bearings due to multiaxial and non-proportional fatigue loadings between rolling elements. One of the main stress components is the alternating shear stress. This paper focuses on the micromechanism of plastic accumulation and damage initiation in bearing steels under cyclic shear deformation. The distribution of subsurface shear stress in bearings was firstly investigated by finite element simulation. An atomic model containing bcc-Fe and cementite phases was built by molecular dynamics (MD). Shear stress–strain characteristics were discussed to explore the mechanical properties of the atomic model. Ten alternating shear cycles were designed to explore the mechanism of cyclic plastic accumulation and damage initiation. Shear stress responses and evolutions of dislocaitons, defect meshes and high-strain atoms were discussed. The results show that cyclic softening occurs when the model is in the plastic stage. Severe cyclic shear deformation can accelerate plastic accumulation and result in an earlier shear slip of the cementite phase than that under monotonic shear deformation, which might be the initiation of microscopic damage in bearing steels.

Enhancing the mechanical properties of bismaleimide resin with montmorillonite modified by two intercalators (amino-terminated polyoxypropylene and octadecyl trimethyl ammonium chloride)

PurposeBismaleimide (BMI) is a kind of thermosetting resin and its application is usually limited by low toughness. In this paper, two kinds of reinforcement intercalator amino-terminated polyoxypropylene (POP) and octadecyl trimethyl ammonium chloride (OTAC) were designed and synthesized to toughen BMI resin and the toughening effect was compared and analyzed. The purpose of this paper is to toughen BMI resin and analyze the toughening effect of two reinforcements intercalator amino-terminated polyoxypropylene (POP) and octadecyl trimethyl ammonium chloride (OTAC).Design/methodology/approachSodium-based montmorillonite (Na-MMT) was modified by POP and OTAC, and the ion-exchange reaction obtained organic montmorillonite (POP-MMT and OTAC-MMT). The polymer matrix (MBAE) was synthesized, in which 4,4’-diamino diphenyl methane BMI was used as the monomer and 3,3’-diallyl bisphenol A and bisphenol A diallyl ether were used as active diluents. And then, POP-MMT/MBAE and OTAC-MMT/MBAE composites were prepared using MBAE as matrix and POP-MMT or OTAC-MMT as reinforcement. The Fourier-transform infrared, X-ray diffraction and scanning electron microscope (SEM) of the filler and microstructure and mechanical properties of the composite were characterized to the better reinforcement.FindingsPOP-MMT and OTAC-MMT enhanced BMI-cured products’ toughness by generating microcracks in the polymer to absorb more fracture energy. Meanwhile, POP-MMT and OTAC-MMT were the main stress components and the enhancement of the interface interaction was beneficial to transfer the external force from the matrix to the reinforcement and improved the mechanical properties of the composite. Furthermore, with the intercalation rate increasing, the compatibility of the two phases was increased and the performance of MBAE was also elevated.Research limitations/implicationsBMI is generally used as aerospace structural materials, functional materials, impregnating paint and other fields. However, high crosslinking density leads to moulding material’s brittleness and limits a wider range of applications. Therefore, it has become an urgent priority to explore and improve the mechanical properties of BMI resin.Originality/valuePOP and OTAC have successfully intercalated Na-MMT layers to get POP-MMT and OTAC-MMT, and the interplanar crystal spacing and the intercalation rate were calculated, respectively. The results were corresponding with the SEM images of POP-MMT and OTAC-MMT. After that, the morphology of composites illustrated the compatibility was related to the intercalation rate. According to the mechanism of modified MMT toughening epoxy resin, when they were dispersed uniformly in the matrix, the composite’s mechanical properties had been significantly improved. Additionally, OTAC-MMT with a higher intercalation rate had better compatibility and interfacial force with the matrix, so that the mechanical properties of OTAC-MMT/MBAE were the best.

Influence of Gradient Residual Stress and Tip Shape on Stress Fields Inside Indented TiN Hard Coating

Nanoindentation of treated surfaces, thin films, and coatings is often used as a simple method to measure their hardness and stiffness. These quantities are technologically highly relevant and allow to qualitatively compare different material and surface treatments but fail to capture the entire extent of the highly complex mechanical interaction between indenter tip and the tested surface. Many studies have addressed this question by analytical or numerical modeling, but they must rely on verification by recalculating indentation curves or ex situ microscopy of surface deformation postexperiment. Herein, results from in situ measurements of the multiaxial stress distributions forming beneath an indenter tip while the tested sample is still under load are presented. A 9 μm‐thick TiN hard coating is tested in 1) as‐deposited state and 2) shot‐peened by Al2O3 particles, using two diamond wedges as indenter tips, with 60° and 143° opening angle, respectively. The results reveal a strong influence of the tip shape on the deformation behavior and the main stress component developing inside the sample while under load. In addition, a crack‐closing effect can be attributed to the exponentially declining near‐surface compressive residual stress gradient that is present in the shot‐peened sample.

Seismicity and seismotectonics of the Albstadt Shear Zone in the northern Alpine foreland

Abstract. The region around the town Albstadt, SW Germany, was struck by four damaging earthquakes with magnitudes greater than 5 during the last century. These earthquakes occurred along the Albstadt Shear Zone (ASZ), which is characterized by more or less continuous microseismicity. As there are no visible surface ruptures that may be connected to the fault zone, we study its characteristics by its seismicity distribution and faulting pattern. We use the earthquake data of the state earthquake service of Baden-Württemberg from 2011 to 2018 and complement it with additional phase picks beginning in 2016 at the AlpArray and StressTransfer seismic networks in the vicinity of the ASZ. This extended data set is used to determine new minimum 1-D seismic vp and vs velocity models and corresponding station delay times for earthquake relocation. Fault plane solutions are determined for selected events, and the principal stress directions are derived. The minimum 1-D seismic velocity models have a simple and stable layering with increasing velocity with depth in the upper crust. The corresponding station delay times can be explained well by the lateral depth variation of the crystalline basement. The relocated events align about north–south with most of the seismic activity between the towns of Tübingen and Albstadt, east of the 9∘ E meridian. The events can be separated into several subclusters that indicate a segmentation of the ASZ. The majority of the 25 determined fault plane solutions feature an NNE–SSW strike but NNW–SSE-striking fault planes are also observed. The main fault plane associated with the ASZ dips steeply, and the rake indicates mainly sinistral strike-slip, but we also find minor components of normal and reverse faulting. The determined direction of the maximum horizontal stress of 140–149∘ is in good agreement with prior studies. Down to ca. 7–8 km depth SHmax is bigger than SV; below this depth, SV is the main stress component. The direction of SHmax indicates that the stress field in the area of the ASZ is mainly generated by the regional plate driving forces and the Alpine topography.

Understanding and eliminating thermo-mechanically induced radial cracks in fully metallized through-glass via (TGV) substrates

This work aims to understand and eliminate the formation of thermo-mechanically induced radial cracks in copper (Cu) metallized through-glass via (TGV) substrates made of Corning® high purity fused silica (HPFS® fused silica), after subjection to 420 °C annealing treatment. Radial cracks were found to be formed in Cu TGV substrate during the heating step of annealing treatment process, caused by high stress buildup resulting from the large mismatch in the coefficient of thermal expansion (CTE) between the HPFS® fused silica substrate and the Cu metallization. From analytical studies, high tensile circumferential stresses were found to be the main stress component that is responsible for the formation of radial cracks during heating. From experimental studies, it was found that radial crack formation was exponentially dependent on the applied heating rate, and that faster heating rate increased the probability for their formation. However, a crack-free metallized TGV substrate was achieved when heating rates ≤6.5 °C/min was applied, thus, eliminating radial crack formation. Radial crack elimination was attributed to the significant activation of stress relaxation mechanisms in the Cu. This was confirmed by the measurement of an inverse dependence of Cu protrusion with the applied heating rate. Additionally, the Cu protrusion data confirms that the leading stress relaxation mechanisms in the Cu TGV were grain boundary sliding (GBS), plastic deformation and Coble diffusional creep.

Design of a kind of Steel Cable Bridge for Belt Conveyor

Steel cable bridge is a kind of flexible suspension bridge with steel wire rope as the main stress components. It has the advantages of low construction cost, short engineering period, reliable structure, simple construction, etc., and has been widely used in driving and walking passages. In this paper, a 110m steel cable bridge supporting the belt conveyor is as an example, the finite element software Midas/civil is used to establish a spatial calculation model, and the cable force and displacement are calculated and analyzed. The results and calculation process can provide theoretical basis and practical experience for the design of steel cable bridge for belt conveyor.

Structural Design and Elastic–Plastic Analysis of Zhangzhou Theater

Zhangzhou Theater is a complex composed of an opera house, a cinema, businesses and underground supporting facilities. It adopts a frame shear wall structural system and is 48 m tall. Owing to the multiple ultralimits of torsional irregularity, large local holes, multiple inclined columns and large space of the structure, a performance-based seismic design method is needed. In this study, response spectrum analyses of the structure were carried out using two types of software and compared. Moreover, elastic time-history analysis, yield and elastic analysis under intermediate earthquakes, and elastic–plastic time-history analysis under rare earthquakes were implemented. Relevant reinforcement measures were applied to weak positions according to the analysis results. The failure mode and failure region of main stress components in the structure under the rare earthquakes were analyzed to ensure that weak positions and important positions of the structure would meet elastic–plastic deformation requirements under rare earthquakes.

Development of q-L-EIV interactive curves for comparison of the environmental performance of composite slabs and RC slabs from the perspective of mechanical features

A building slab, as a main stress component, plays an important structural role. To better understand the environmental performance of various slabs and assist design decision-making considering both environmental protection and structural requirements, this paper evaluated and compared the EIs of two commonly used slabs (RC slabs and composite slabs) with various sectional forms from the perspective of mechanical features. The functional unit was defined as the cross-sectional area of a slab satisfying certain structural span and load requirements. Based on the LCA-based BEPAS model, the EI of slabs were divided into two safeguard areas (resource depletion and ecological damage) and then expressed by the EIV index in units of “yuan” using the willingness to pay (WTP) weighting method. Combining EIV and permitted load-span (q-L) curve, q-L-EIV interactive curves were developed to holistically illustrate the structural and environmental performance of slabs in a single diagram. A series of comparisons were conducted to demonstrate how the developed q-L-EIV interactive curve work to facilitate analysis and selection of slabs. Additionally, sensitivity analyses were performed to evaluate the effects of main parameters (i.e. steel ratio, steel strength, concrete strength and recycling rate) on EIA results of slabs. The research results indicated that there are large differences between the EIs of various slabs, and composite slabs were widely recommended in engineering applications from the view of environmental sustainability. Moreover, the proposed curve can serve as a reference tool of slab design to provide structure-environmental oriented implications in construction industry practice.

Residual stress measurements on AISI 316L samples manufactured by selective laser melting

This paper aims to understand the formation and the effect of residual stress on selective laser melting (SLM) parts. SLM is a powder bed based additive manufacturing (AM) process and can be compared to a laser welding process. Due to the high temperature gradients and the densification ratio, which are characteristic of this process, residual stresses occur. The investigation of residual stress is performed using X-ray diffraction (XRD) for samples made of austenitic stainless steel AISI 316L (EN 1.4404). This research examines residual stress at different depths and at two outer surfaces. For the measurement of stresses at different depths, the samples’ surface layers were removed by electropolishing. At sufficiently large distances from the top surface, the stresses in the area of the edge layer initially increase strongly and then decline again. The value and orientation of the resulting main stress components are dependent on the examined layer. At the top surface, the residual stresses are higher in scan direction than in perpendicular direction. In contrast, at the lateral surface the maximum main stress is perpendicular to the scan and parallel to the building direction. These two cases can be described very well by the two mechanisms in SLM, namely the temperature gradient mechanism (TGM) and the cool-down phase. It is also shown that at samples with a relative structural density of >99%, the residual stress values are independent of the applied energy density.

A fast procedure of stress state evaluation in magnetically anisotropic steels with the help of a probe with adjustable magnetizing field direction

The paper presents a novel approach to the stress state evaluation issue. It deals with a strongly (magnetically) anisotropic materials for which a direct interpretation of the Barkhausen effect (BE) intensity would lead to erroneous results. In such a case one has to take into account both the measured BE intensity and the orientation of the magnetisation direction relative to the magnetic easy axis. For the in plane stress distribution evaluation one has to perform at least three measurements in the non-collinear directions. The application of an apparatus with automatically changing magnetizing field direction allows to obtain the angular distribution of the BE intensity in about 30 s (with the angular step of 10°). Thanks to the dedicated post-processing software the procedure of the measurement data processing, resulting in the full information on the stress distribution (main stress components and their orientation in all the investigated points) is almost instantaneous. Apart from the measurement results the stress determination procedure requires two additional pieces of information. The first one is the calibration data obtained for at least two applied strain directions (along easy and hard magnetisation axes)— the data for the intermediate orientations are usually interpolated. The second one is the ‘reference level’ of the BE intensity angular distribution. In the case of welded plates it is obtained by averaging the results obtained at the analysed points before welding. The way of results presentation proposed in that paper is very illustrative and shows an interesting feature of the stress distribution in welded plates—namely the appearance of a ‘vortex’ structure of main stress.

Mechanical Properties Research Based on Snowplow Operation Device

In this paper, combining with the domestic design and application of the snowplow in quality and quantity two aspects, basing on engineering application software ADAMS and CATIA, dynamics for 10t snowplow working device was researched, and the strength of the main stress components was analyzed by finite element method. On the basis of lightweight, strength and structure reasonable design, the snowplow device structure was verified feasibility through the research results. The paper studies could have a certain theoretical reference for the theoretical design and practical application of similar products.

Durability Analysis and Carbonation Life Prediction of River Bridge

The shajiang river bridge on the appearance test, concrete rebound detection, concrete cover depth detection, concrete carbonation depth detection, concrete chlorine ion content detection, and the detection results in statistics and analysis. Based on the bridge of the service the atmospheric environment parameters and testing data, the paper calculates and analyzes the main stress components the carbonation bridge reliability index and remaining life of carbide, assessing the bridge for the service life and reinforcement maintenance and offer the scientific basis.

Strength Analysis and Optimal Design on Flip Axis of Steel Roll Clamp

Turn coil clamp is an important auxiliary equipment of steel rolling production in iron and steel enterprise. At present, although the clamp has been put into production use which can satisfy the basic needs of enterprise. Its production efficiency and security still need to be improved. Based on the above case, this time a new steel coil clamp that is researched can greatly improve efficiency and safety. To make the structure more reasonable, the double shaft which is one of the main stress components is needed analysis and optimal design.

Study on the New Energy-Saving Structure System with Seismic Performance

As one of the main stress components of energy-saving structure system, grid frame shear wall was chosen as the main research object. The low cyclic loading tests were applied to test the mechanical properties of three kinds of grid framework with aspect ratios 0.69, 1.1 and 2.75. Based on the analysis of failure mode, bearing capacity, ductility, and energy dissipation capacity and so on, the factors affecting on the seismic performance of the grid frame shear wall were discussed.

Based on the Grey Relation Analysis of Ecological Composite Wall Seismic Performance Research

Ecological composite wall as ecological composite wall structure of the main stress components, the seismic performance is ecological composite wall structure seismic performance evaluation system of the main content. Based on the grey system theory, the grey correlation analysis to the key parameters (the mouth of the cave, frame structure, height to width ratio) change ecological composite wall test results are analyzed, the key parameters on the ecological composite wall the influence law of seismic performance, for choosing wall structure design method to provide basis.

Salivary cortisol, heart rate, electrodermal activity and subjective stress responses to the Mannheim Multicomponent Stress Test (MMST)

The availability of effective laboratory paradigms for inducing psychological stress is an important requirement for experimental stress research. Reliable protocols are scarce, usually laborious and manpower-intensive. In order to develop an economical, easily applicable standardized stress protocol, we have recently tailored the Mannheim Multicomponent Stress Test (MMST). This test has been shown to induce relatively high stress responses without focusing on social-evaluative components. In this study we evaluated changes in electrodermal activity and salivary cortisol in response to the MMST. The MMST simultaneously combines cognitive (mental arithmetic), emotional (affective pictures), acoustic (white noise) and motivational stressors (loss of money). This study comprised two independent experiments. For experiment 1, 80 female subjects were recruited; 30 subjects (15 females) participated in experiment 2. Significant changes in electrodermal activity and salivary cortisol levels in response to MMST exposure were found. Subjective stress and heart rate responses were significantly increased in both experiments. These results indicate that the MMST is an economical stress paradigm which is also applicable in larger cohorts or multicenter studies for investigating stress reactions. As social-evaluative threat is not the main stress component of the MMST, this procedure represents a useful and complementary alternative to other established stress protocols.

The Structure Design and Finite Element Analysis of the Self-Moving Silent Piler Based on the Pile Reaction Force

The self-moving Silent Piler based on the pile reaction force is a new kind of construction equipment by static pressure hydraulic pressure, which utilizes reaction force derived from fully installed cement column to support the silent piler body. The construction characteristics and working principle of the silent piler have been discussed in this paper. The structure of the device has been designed. The FEA to the main stress components and force has been analyzed.