Position Of Maximum Stress Research Articles

Numerical Analysis of a Novel Shaft Lining Structure in Coal Mines Consisting of Hybrid-Fiber-Reinforced Concrete

To address the temperature cracking of concrete in frozen shaft linings in extra-thick alluvial layers in coal mines, a novel shaft lining structure of coal mines consisting of hybrid-fiber-reinforced concrete (HFRC) was developed. Using the Finite Element Method (FEM), a numerical simulation test of the HFRC shaft lining structure with four factors and three levels was carried out, and the mechanical characteristics of the shaft lining structure were obtained. The results show that under a uniform surface load, the maximum hoop stress position of the HFRC shaft lining presents a transition trend from the inside surface to the outside surface; the hoop strain of shaft lining concrete is always a compressive strain, and the inside surface is greater than the outside surface. The empirical formula for the ultimate capacity of this new type of shaft lining structure was obtained by fitting. Compared with the model test results, the maximum relative error of the calculated value is only 6.69%, which provides a certain reference value for designing this kind of shaft lining structure.

Interfacial interaction and roughness parameters effects on the residual stresses in DCL-TBC system with different thickness distributions

Compared with the traditional Single-Ceramic-Layer Thermal Barrier Coating system (SCL-TBCs), the application of the Double-Ceramic-Layers Thermal Barrier Coating system (DCL-TBCs) can strengthen the thermal insulation performance and ameliorate the interfacial oxidation behavior. The residual stresses due to the mismatch of thermal expansion, are so important that they can lead to the spallation and delamination failure of the entire system. In present work, considering the evolution of failure positions in the DCL-TBCs, the effects of interfacial interaction and roughness parameters on the residual stresses were investigated under two different thickness distributions of the ceramic layer. Therein, the numerical models with the general periodic boundary have been developed. Results show that the morphology of the yttria partially stabilized zirconia (YSZ)/thermally grown oxide (TGO) interface can affect the stress distribution along the lanthanum zirconate (LZ)/YSZ interface in the TBCs with low thickness of YSZ, but this influence can be negligible if the YSZ is thick enough. The qualitative distribution of the residual stress along the LZ/YSZ interface is similar for various interfacial roughness parameters, and the maximum tensile stress is always presented at the peak of the LZ/YSZ interface. But for the YSZ/TGO interface, the increase in the roughness parameters can lead to the change of the maximum tensile stress position and even the transition of the stress state in the local region. Also, as the reference for judging the maximum tensile stress location, the critical wavelength was obtained based on the parametric calculation procedure, and the relationship between the critical wavelength and the YSZ/TGO interface amplitude has also been revealed. Moreover, the analysis results can also help to understand the failure mechanisms of the DCL-TBCs and provide a reference for further process optimization.

Damage Assessment and Progressive Collapse Resistance of a Long-Span Prestressed Double-Layer Composite Torsional Reticulated Shell

Long-span prestressed double-layer composite torsional reticulated shells have beautiful shapes, which make them a solution widely applied in public buildings requiring long-span structures, such as airports and stadiums. However, once the progressive collapse occurs, this will cause serious issues. There are few studies on the damage assessment of long-span spatial structures under accidental loads. This paper proposes a new dynamic damage evaluation index that takes into account the displacement and the cumulative plastic energy dissipation to evaluate the damage of the long-span prestressed double-layer composite torsional reticulated shell. Sleeve structures were applied to the long-span space structures to study their control effect on structural damage. The equivalent load transient unloading method was used to analyze the dynamic time history of the structure. Results show that the structure suffered severe damage and progressive collapse failure after removing four nodes at different positions near the supports. In the position where the plastic hinges first appear and the position with the maximum displacement, the sleeve structures have a poor damage control effect on the structure. Arranging the two sleeve structures in the position of maximum stress, the damage of the structure can be controlled, thus reducing the severe damage and progressive collapse failure to basic intact damage.

Effect of notch root angle on fatigue behavior of aluminum to steel resistance spot welds

Aluminum was resistance spot welded to steel with varying electrode polarity on the aluminum sheet to produce different notch root angles but maintain the same weld nugget diameter and intermetallic layer thickness. Fatigue life was longer in negative polarity welds having larger notch root angle owing to the reduced maximum principal strain at the notch root. In fatigue, pull-out fracture was observed in negative polarity welds while interfacial fracture occurred in the positive polarity welds because of reduced tensile and shear stress at the notch root and the position of maximum tensile stress moving away from the notch root tip.

Measurement and analysis of cold spray residual stress using arbitrary Lagrangian–Eulerian method

Cold spray (CS) residual stress was measured by the X-ray diffraction (XRD) and contour methods. The residual stress components SX and SY, perpendicular to the thickness, have similar distributions and approximately equal magnitudes. Both are compressive on the deposited surface and become tensile inside the structure. An advanced simulation model based on the arbitrary Lagrangian–Eulerian (ALE) method was developed to investigate the residual stress distributions in a single CS microparticle and multi-layer CS microparticles and reveal the formation mechanism. The residual stress components SX and SY predicted by the proposed simulation model have the same distribution as shown by the measurements, i.e., compressive on the surface and tensile inside. As the number of deposition layers increases, the position of maximum tensile stress moves from the substrate to the deposited layers. The residual stress component SZ in the direction of the deposition thickness shows alternate tensile and compressive distributions in the transverse direction, which is quite different from that of the transverse component. The formation of CS residual stress is mainly affected by three aspects: the collisions among microparticles, the interactions between microparticles in the same layer, and interactions between microparticles in different layers. The present work provides a guideline for effectively tailoring the residual stress in CS parts and thereby improving the fatigue lifetime.

Effect of salt solution wet-dry cycling on the bond behavior of FRP-concrete interface

The strengthening of concrete structures with externally bonded fiber reinforced polymer (FRP) was increasingly being used in marine exposure environments. Marine environment exposure may significantly affect the bonding behavior of FRP externally bonded to concrete. This paper is intended for studying the effect of tidal-like condition such as salt solution wet-dry cycling on the behavior of FRP-concrete interface. Exposure tests and analytical approach are carried out on specimens externally bonded with carbon fiber reinforce polymer (CFRP) and basalt fiber-reinforce polymer (BFRP). Test variable include the types of fiber and the environmental exposure periods (0, 90, 180, 270, 360 cycles). From the bending test results, the bilinear bond stress-slip relationships for different exposure periods are derived. Based on these bond stress-slip relationships, the full-range behavior of shear stress along the bond length and debonding load can be obtained through the analytical solution. The test and numerical results show that salt solution wet-dry cycling can greatly affect the bond behavior of CFRP-concrete and BFRP-concrete interface with the increase of exposure periods. With the increase of exposure periods, the position of maximum shear stress tend to move backward, which indicates the behavior of FRP-concrete interface is weakened due to the salt solution wet-dry cycling. Compared with CFRP-concrete interface, salt solution wet-dry cycling exposure has greater influence on the bond behavior of the BFRP-concrete interface.

Effect of Subtropical Natural Exposure on the Bond Behavior of FRP-Concrete Interface.

Subtropical natural exposure may significantly affect the bonding behavior of fiber reinforced polymer (FRP) externally bonded to concrete. To study the effect of subtropical natural climates on the FRP-concrete interface, natural exposure tests and an analytical approach were carried out on specimens externally bonded with carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP). The bilinear bond stress-slip relationships for different exposure periods were derived from the experimental results of the strengthened reinforced concrete (RC) beams. Based on these bond-slip relationships, the full-range behavior of shear stress along the bond length and debonding load can be obtained through the analytical solution. The testing and numerical results showed that subtropical natural exposure can greatly affect the bond behavior of CFRP-concrete and BFRP-concrete interfaces in the early exposure period. In the late exposure period, the bond behavior was basically stable. With the increase of exposure time, the position of maximum shear stress tended to move backward, which indicated that the behavior of the FRP-concrete interface was weakened by natural exposure. Compared to the CFRP-concrete interface, subtropical natural exposure has greater influence on the bond behavior of the BFRP-concrete interface.

Study on stress distribution in microregion close to the shell of core-shell particle reinforced metal matrix composites

The stress distribution in microregion close to the shell of core-shell particle reinforced metal matrix composites is studied by the finite element analysis in this work. It is found that the stress distribution of the composites is dependent on the elastic modulus of both shell and core phases as well as the difference between them. If the elastic modulus of the formed shell is larger than that of the core, the load borne by the shell will be increased, otherwise, the load borne by the matrix and the core will be increased. The formation of shell and its nature can also significantly change the position of the maximum stress on the reinforced particles but have little influence on that in the matrix. When the elastic modulus of the shell is smaller than that of the core, the maximum stress position in the core-shell particle will be at the core and close to the interface between core and shell, otherwise, it is shift to the shell and also close to the interface between core and shell. The degree of the stress concentration in Al matrix becomes more serious after the formation of the shell in the reinforced particles, while that in shell of core-shell particles mainly depends on the modulus difference of core and shell.

Design and physical model experiment of an attitude adjustment device for a crawler tractor in hilly and mountainous regions

To address the problems of difficult leveling and poor stability of hill crawler tractors, an attitude adjustment device based on a parallel four-bar mechanism was designed, and the mechanical reasons for the sideslip instability of hill crawler tractors were analyzed. On this basis, a posture adjustment mechanism based on a parallel four-bar mechanism was proposed, and the structure of the complete attitude adjustment device was designed. To ensure that this device meets the strength requirements during operation, a mechanical analysis of the key components (active rocker and slave rocker) was carried out to accommodate the load during leveling. Based on ANSYS software, a finite element simulation analysis was used to determine the maximum stress position of the active and slave rockers. Finally, to verify the accuracy of the above simulation analysis results and determine the influence rules of the lateral slope angle, longitudinal slope angle and loading quality on the abovementioned maximum stress, a physical model test bench of the attitude adjustment device was built. An orthogonal regression experiment was carried out with the maximum stresses of the active and slave rockers as the test indices. The experimental data were analyzed by Design-Expert 10 software, and the results show that the order of the primary and secondary factors influencing the maximum stress of the active rocker was the loading mass, lateral slope angle and longitudinal slope angle. The order of the factors influencing the maximum stress of the slave rocker was the longitudinal slope angle, lateral slope angle and loading mass. The active and slave rockers meet the strength requirements. This work provides technical support for the production of hill crawler tractor physical prototypes.

Stress Analysis and Strength Test of 2500 Fracturing Truck Frame

For the fracturing trucks, which is an important member of oil and gas fracturing, the stress and strength of fracturing truck’s frame have a very significant influence on the continuous fracturing operation. This paper takes the frame of 2500 fracturing truck as the research object, analyses its stress condition, and conducts the static strength test and dynamic strength test of the whole frame of fracturing truck, respectively tests the strain of 15 measuring points of the frame under the fully loaded static condition and the right front wheel lifting condition, and finds out the distribution rule of the stress and strain of the frame. The results show that the maximum stress position of the frame under migration condition is at the root of the rear support of the tank, the total stress is 146.76 MPa, the minimum safety factor reaches 2.35, and the strength of measuring point meets the requirements.

Numerical Study on Subsurface Stress in Hertzian Contacts under Pure Sliding Conditions

In this study, the two-dimensional numerical simulation on the subsurface stress field in Hertzian contact under the pure sliding condition for different speeds and coefficients of friction is presented. The Hertzian contacts are represented by a dry contact between a rigid flat surface and an elastic cylinder with radius R=12.5 mm. Simulation is carried out through two steps, the first one is for applying normal load and the second one is for applying angular speed for the cylinder. The results of subsurface stress filed for pure sliding are compared to non-moving Hertzian contact. The results show that pure sliding speed has a major effect on the value of maximum von Mises stress in the subsurface of contact. The effect of sliding speed is attributed to tangential forces and elastic deformation in the contact. On the other hand, the coefficient of friction has a primary effect on the position of maximum stress and the shift of the contact region. Indeed, when pure sliding motion is introduced with a low value of friction coefficient, the shift of the contact region is negligible compared to non-moving Hertzian contact. The study is extended to investigate the effect of contact geometry on subsurface stress for Hertzian contact in the cam-follower interface. The shape of the follower has a significant effect on the value and distribution of Hertzian stress, thus, the fatigue life of rubbing surfaces of the cam-follower interface.

Effect of characteristic parameters of pitting on strength and stress concentration factor of cable steel wire

In order to investigate the influence of characteristic parameters of pits on the strength and stress concentration factor of cable steel wire, 198 cable steel wires with pits were manually prepared. The variation law of stress distribution of steel wire was analyzed, and its relationships with strength and stress concentration factor were studied through tensile test and finite element analysis. On this basis, the calculation model of yield strength and stress concentration factor of steel wire with pits was established. The influences of secondary pits on stress distribution and stress concentration factor of steel wire were also analyzed. The results showed that the strength of steel wire decreased gradually and the stress concentration factor increased with the increase of pit depth and the decrease of pit width. The change of pit clearance on the same side had no obvious effect on the strength and stress concentration factor of steel wire, but it had significant effect when located on the opposite side. The strength and stress concentration factor of steel wire with adjacent pits usually depended on the depth of the larger pits. The pits with depth to width ratio of 1 to 2 had the most significant effect on the stress concentration factor. Moreover, secondary pit would change the stress distribution, and the position of maximum stress changed from near the mouth to the bottom of the pit. The stress concentration factor of secondary pit was obviously higher than that of steel wire with only the primary pit.

Design and Optimization of a Joint Torque Sensor for Robot Collision Detection

It is important to maintain safety and reliability during human–robot cooperations with a service robot. Collision should be monitored and detected in real time to avoid possible damages. In this paper, we propose the design and optimization of a novel strain-gauge-type joint torque sensor for robot collision detection. It features a thin structure, quick response, and high sensitivity. A holed spoke structure is proposed to transfer maximum stress position and improve stress distribution. To achieve the best sensitivity and stress evenness of the sensor, a mathematical optimization with two objective functions is formulated to topologically optimize the flexure spoke structure. Optimal structure parameters are thus obtained. Sensor signal processing is proposed based on the Wheatstone full bridge. Its corresponding hardware is designed and implemented to be integrated into the sensor. Calibration and evaluation are carried out to validate the sensor performance.

Application of Rock Kaiser Effect in Deep In-situ Stress Test

In order to solve the serious roadway failure in Yaoqiao coal mine, Kaiser effect was used to measure the in-situ stress in level-800m roadway. Through making samples 6 special directions on the beamed rock cores and doing acoustic experiment, the unilateral plus stress values on each direction are obtained. Through coordinate transformation, the magnitude and direction of the primary stress of the original rock were calculated. The result shows that level - 800m belongs to high stress area, and there exists certain tectonic stress. The relative position of horizontal maximum and minimum ground stress is determined, which provides reference for the roadway layout and support in Yaoqiao mine.

Dynamic Analysis of Shaft Structure Based on ANSYS/LS-DYNA

In this study, a part of the shafting structure of the accessory transmission system consisting of shaft-gear-bearing is studied. ANSYS/LS-DYNA explicit dynamics simulation software is used to simulate the dynamics of the shaft structure. It compares and analyzes the overall shaft structure, gears and bearings. The simulation results show that: The place where the equivalent stress of the shaft structure is relatively large is mainly concentrated at the tooth root and the tooth surface, where the stress is mainly in the vicinity of two or three teeth. With the change of time, the maximum equivalent stress value and position of the rolling elements are also correspondingly changed, it provides a reference for the design and optimization of gear and bearing in the actual assembly process for transmission system.

The Finite Element Analysis and Calculation of Small Underframe of D15 Type 250 t Depressed Center Flat Car

In order to verify the force of depressed center flat car in use process, this article USES the finite element analysis software for small underframe of D15 Type 250 t Depressed Center Flat Car has carried on the static strength and stiffness analysis and calculation. Finally it is concluded that under different load cases the maximum stress position and Von. Mises stress nephogram of the small underframe of Depressed Center Flat Car, the test results show that the dynamics of small underframe performance meet the requirements of relevant standards and technical conditions.

Force and Strength Analysis of the Reel with Jaw of Torsion-bar Spring

Structure characteristics and working principle of the reel with jaw of torsion-bar spring are introduced. The reel can not only eliminate the leakage risks of hydraulic jaw, but also reduce the investment cost of enterprises and improve the surface quality of the products. The static analysis of mandrel, sector plate and oblique wedge were conducted, and the main data of stress distribution and deformation were obtained, which provide a reliable theoretical basis for the design and optimization of the reel. The research results show that the external support has a great effect on the stress and deformation of the mandrel. With the increase of the weight of steel stress increases, the drum deformation increases, but the analysis of the position of maximum stress, can be obtained to drum stress and deformation is the main reason of excessive bending moment caused by heavy steel rolls. The bending moment and deformation can be reduced significantly at the end of the steel coil, which can effectively improve the service life of the drum.

Evaluation of thermal management strategy based on zoning of stress states of a gas turbine disk

Considering that either passive thermal management from thermal protection or active thermal management from thermal loading reorganization is determined by thermal management strategy, this paper proposes an evaluation method based on the zoning of the stress states of a disk for different thermal management strategies to assess the advantages and disadvantages of different thermal loading combinations or distributions at the initial design stage. The theoretical model for thermal management strategies is first established by abstracting the combination of thermal loading parameters (Qe, Qin and h¯). Subsequently, the zoning principles are defined based on the stress state characteristics. The sensitivity factors Sσ,in and Sσ,e are introduced to quantify the variation degrees of the thermal loading parameters Qin and Qe for stress state. A rotating turbine disk with a nearly real geometry is used as evaluation object to investigate the effects of different thermal management strategies from three aspects: the position of maximum stress, the iso-surface of the maximum stress level and the variation profile of the disk. Results show that the stress states for each thermal management strategy can be divided into four zones based on the position of the maximum von-Mises stress and the direction of the circumferential stress. A three-dimensional space region partition is generated for each stress state, which shows that the appropriate thermal loading combinations in the design are limited and have an application scope. Generally, the thermal loading combinations in the Domain 1(I) zone represent the most appropriate objects in the design process, whereas the other zones should be avoided because of the enormous negative temperature gradient they produce in the disk. Moreover, the values of sensitivity factors Sσ,in and Sσ,e in the considered disk profiles are similar, and the effects of the variations in the thermal loading parameters Qin and Qe on the maximum stress are not influenced by the disk profile.

Combined effects of different temperature and pressure loads on the “L”-type large-diameter buried pipeline

Large-diameter buried pipeline was widely used because of its energy-saving advantage and high efficiency. In this paper, “L”-type heat pipe network was taken as the research object, which was studied using the flow-heat-solid coupling method. The ANSYS Workbench platform was used to simulate heat transfer and the flow of the medium in the pipe network. The pressure and temperature of the flow field and the temperature, equivalent stress, and total deformation of the solid structure under different conditions were calculated, and the effects of different mediums on the variables of the temperature were compared. According to the theory of stress classification, stability analysis method was used to check the strength of the pipe network structure. Results show the stress and deformation of the anchorage section of the pipe network were mainly affected by the temperature of the fluid. When the pressure and temperature loads worked individually or simultaneously, maximum deformation occurred in the lateral region of the long arm near the elbow, and the maximum equivalent stress position changed according to the load change. When the medium temperatures were 60°C and 80°C, the strength of the pipe network structure satisfied the requirements according to the structural strength check analysis.

Effect of Curved Surface Shape and Feed Velocity on Microstructure and Mechanical Performance of Gray Cast Iron After Spot Continual Induction Hardening

Spot continual induction hardening (SCIH) is a surface heat treatment process, which can strengthen more than one small area or relative large area on complicated component surface. In order to investigate the microstructure and mechanical properties of gray cast iron with curved surface after SCIH, the microstructure, microhardness and residual stresses were analyzed under different process conditions. The results showed that the martensite grain in hardened region of concave surface was larger than that of convex surface. The domain sizes of concave and convex surfaces were smaller than that of matrix region due to the high heating rate in SCIH process. The phase transformation depth increased with the increasing of convex surface radius but decreased with the increasing of concave surface radius. The maximum values of residual tensile and compressive stresses increased with the increasing of feed velocity for convex and concave surfaces, respectively. The appearance positions of maximum tensile and compressive stresses were closer to center for convex and concave surfaces, respectively, when feed velocity increased from 1 to 5 mm/s. The achieved results indicated that the SCIH with relatively low feed velocity was more suitable for improving the mechanical properties of gray cast iron. Compared with convex surface, the concave surface of workpiece can obtain better mechanical properties under the same feed velocity of inductor.