Shear Pin Research Articles

Numerical analysis of 3D printed joint of wooden structures regarding mechanical and fatigue behaviour

This paper presents numerical models of a 3D printed plastic joint applicable to the connection of wooden structures. The research presented provides a comparison of two alternative solutions for the geometry of the joint and results from several loading schemes and boundary conditions. Included are analyses evaluating the mechanical behaviour in a simple axial tensile test, a three-point bending test and, finally, a sensitivity analysis of the location susceptible to fatigue damage. The models include a 3D printed polycarbonate joint, wooden elements and steel shear pins. The combined model allows a deeper understanding of the interactions. Finite element method (FEM) software was used to develop the numerical models and suitably defined boundary conditions, and material properties of all parts were adopted. The simulation results show that the 3D joint exhibits a high resistance to tensile loading, while in the case of three-point bending, a higher susceptibility to fracture of the printed joint is observed. The sensitivity fatigue analysis identified critical areas on the 3D printed component that need to be improved before further development. These analyses provide important information for optimizing the design of 3D printed plastic joints intended for wooden structures.

Experimental and theoretical analysis of flexural performance for EPCFA-CSP novel composite structure

The article proposes a novel composite structure, namely the Elastic Polyurethane Coal Fly Ash Corrugated Steel Plate (EPCFA-CSP). One specimen consisting solely of corrugated steel plate and seven composite structure specimens were designed to investigate the bending behavior of the EPCFA-CSP composite structure through four-point bending tests. The results indicate that incorporating mushroom-shaped steel pin shear keys into the combination of EPCFA and CSP yields the most favorable effect. With an increase in structural layer thickness from 30 mm to 50 mm, when the mushroom-shaped steel pin shear key contributes to the stress distribution within the composite structure, both bending stiffness and ultimate load of the composite structure specimen increases by 150.35 % and 63.93 %, respectively. Specimen EPCFA-(50)-CSP-II achieves a flexural stiffness of 89.40 kN/mm, a cracking load of 187.7 kN, and an ultimate load of 205.4 kN. Finally, based on experimental results, a deflection correction formula considering the reduction factor due to combination effects was derived to correct deflections at characteristic points accurately. This formula is applicable at approximately 0.6 times the ultimate load, and calculations using this formula yield ratios between calculated deflections and experimental deflections ranging from 0.88 to 0.97. This demonstrates its effectiveness in correcting deflections and provides valuable insights for designing related composite structures.

Shear performance and failure mechanism of brass pins considering the temperature effect

Premature shear failure of the brass pin often occurs during downhole tool operation, which has a serious impact on subsequent completion operations. Therefore, in order to explore its failure mechanism, the pin shear test considering temperature effect was designed and implemented in this paper to study the shear performance of different numbers of brass pins under different heating temperatures. Experimental data were fitted to obtain the continuous shear load–temperature curves for six, eight, and ten pins. The shear sections and the failure mechanism of the pins at different temperatures were observed by scanning electron microscopy. The results showed that the number of pins and temperature significantly affected the shear load of the brass pin. At room temperature, as the number of pins was increased, the shear load increased by 31.60% (six to eight) and 24.76% (eight to ten). Taking six pins as an example, the increase in the heating temperature from 22°C to 190°C decreased the shear load of the pin by 17.68%. The brass pin exhibited prominent plastic failure characteristics. Moreover, the shear section at room temperature was dominated by the shear band, which has a higher failure energy absorption capacity. As the temperature was increased, the area of fracture zone gradually increased, and consequently, the toughness and plasticity increased. This study provides a reference for the use of brass pins in downhole tools and reduces the possibility of premature shearing and related construction waste.

Shear behavior of cylindrical pin-sleeve connectors of neighboring segments of immersed tunnels

A pin-sleeve system was used as a shear connector at the joints between the segments of the Dalian Bay immersed tunnel. To investigate the structural behavior of the pin-sleeve connectors, eight push tests were performed, and an analytical model was developed. Each specimen consisted of three reinforced concrete blocks representing the tunnel segments and two parallel joints between the three blocks connected by pin-sleeve connectors. The design of the specimens was aimed at studying the influences of the assembly error of the tunnel segments, corrosion of the shear pins, and group effect of the pin-sleeve connectors on their structural behavior. The specimens differed in the initial opening of the joints, diameter of the shear pins, and number and spacing of the connectors in one of the two parallel joints. The main conclusions drawn from the experimental investigations are as follows: (i) The joints mainly fail because of the failure of the shear pins. (ii) The effect of the initial joint opening on the ultimate bearing capacity was insignificant. (iii) A reduction in the cross-sectional area of the shear pins by 36% resulted in a reduction in their bearing capacity by 51%, indicating a non-proportional relationship between them. In addition, the derived formulae allow for a more reliable computation of the ultimate shear forces of the pin-sleeve connectors compared to those obtained from those taken from codes of practice. Finally, a simple formula was obtained using polynomial regression, which can be easily applied by engineers.

Numerical simulation of actuation processes and decoupling pyroshock of a pressure cartridge-type pin puller

In this study, a finite element model of a pressure cartridge-type pin puller is used to simulate the actuation process and predict the actuation shock using the deflagration equation of state and the fluid-structure coupling algorithm of the MSC/Dytran. The established model is validated by comparing the simulation results with the experimental results for pressure and actuation shocks. Based on the established finite element model, the contribution of the four shock sources to the actuation shock is quantitatively decoupled by changing the state of the pin puller. The results demonstrate that the maximum shock caused by the piston impact was 7454.33 G in the analysis frequency range of 500 Hz–10 kHz. The piston impact was the primary contributor to the actuation shock, accounting for approximately 80.80%. The contribution of the shock caused by payload release was approximately 18.56%. However, the total contributions of the shock generated by the pyrotechnic charge combustion and piston cutting off the shear pin were less than 1%. The conclusions of this study can provide a reference for the structural and shock-reduction design of pressure cartridge-type pyrotechnic separation devices.

Failure Analysis of Tubing Collapse in a Gas Well

The tubing used in a gas well rarely collapses and fails during applying annulus pressure. In this study, the failure causes of tubing collapse were analyzed by means of data verification, macroscopic observation, magnetic particle inspection, physical and chemical inspection, optical microscopy, and tubing collapse test. Mechanical analysis of the string and full‐scale physical simulation test simulating downhole working conditions. Finally, the verification analysis of the collapse test is carried out by the finite element analysis (FEA). The results showed that (1) the physical dimension, physical and chemical properties, and collapse resistance of this batch of tubing met the requirements of the tubing ordering technical standard. (2) Assuming that the well packer slip was unsealed and could slide freely, the mechanical theoretical analysis of collapsed tubing string and collapse test under simulated working condition load was carried out, which reproduced the load when the tubing collapsed. It can be seen from this that the packer did fail. (3) The FEA calculation results showed that when the external pressure was greater than 30.75 MPa, it would inevitably lead to collapse failure in case of packer unsealed. In conclusion, the root cause for the collapse failure of the 105th underground tubing string was that the packer lost its sealing function, resulting in an abnormal axial load. While under the action of external pressure, the tubing was overloaded and collapsed. It is recommended to carry out verification tests on the material performance of packer slip, the dimensional changes of packer tool outer diameter and inner diameter under actual well conditions, the creep behavior of packer seal, and the performance of shear pin under actual working conditions, especially in the well containing H2S, so as to prevent the pressure leakage of gas well annulus caused by packer unsealing and the reoccurrence of such downhole string collapse accidents. The first collapse test under simulated working condition load is conducted in this paper. Analyzing the collapse failure work and putting forward suggestions to effectively prevent similar failures from happening again are of great significance to the oilfield.

Design methodology and modified shear constitutive model of the shear pin connection

Currently, the shear pin connection (SPC) is a structural measure in the double spherical seismic isolation bearing (DSSIB). However, there is no unified design methodology for the SPC. In addition, the existing shear constitutive model is the linear elastic model (LEM). Its drawback is the inability to capture the gap in the bearing and the plasticity, damage, as well as fracture behavior of the SPC. Therefore, based on the performance requirements for two-level seismic fortification, a detailed design methodology for the SPC is proposed. With the SPC in the Fuzhou Daoqingzhou Bridge as a prototype, the finite element model of the SPC is developed in order to discuss the applicability of the LEM for predicating the shear behavior of SPC. The results showed that the fracture displacement and absorbed energy obtained by the finite element analysis were significantly larger than those predicted by the LEM. Then, to compensate the drawback of the LEM, a tri-linear model (TLM) is proposed as the modified shear constitutive model of the SPC. Finally, the effects of TLM and LEM of the SPC on seismic performance of the isolated bridge were investigated. Obviously, the maximum displacement of the bearing calculated by the TLM is up to 1.38 times that calculated by the LEM. This suggests that the TLM has accurate predictions of mechanical property of the SPC.

A novel evaluation of train running safety on the HSR bridges under earthquakes based on the observed track deformation rate

Safe operation of the trains on the high-speed railway bridge requires the railway line to have a high level of track regularity. High-speed railway bridges can deform unevenly under horizontal earthquakes, and the solid instantaneous deformation of the track can cause the train to derail. This paper develops a refined nonlinear model of the train-track-bridge coupling vibration subjected to seismic shaking to capture as comprehensively as possible the impact of the transient deformation of the track on the train operation at each moment and position. In addition, the risk factors and derailment characteristics are investigated in depth. The findings showed that the earthquake caused the bridge's girder ends to undergo severe dislocation and rotation, which facilitates the derailment of a train. Moreover, the vibration coupling between the train and the bridge becomes strong after bearing shear pin failure. Based on the statistical results of derailment causes, a novel index for evaluating the train running safety on the high-speed railway bridge is proposed. Besides, the engineering applications of this index are also introduced. Indeed, this new index can be used as the lower limit for evaluating train derailment on HSR bridges during earthquakes.

Modelling and simulation of lightweight hollow pins as a substitution for solid shear pins used for assembly joints in aerospace applications

Shear pins are generally used as a mechanical safeguard in assembly operations. They are considered sacrificial members which undergo early fracture to safeguard the other components in the assembly. Currently, solid shear pins are used and technically such pins add to the total weight of an assembly. Weight savings is one of the best contributions that can help the design of components to reduce weight and cost wise. In this regard, hollow shear pins can be a suitable alternative. However, there exists a minimum literature on the use of hollow shear pins in assemblies. The current work presents the theoretical and computational analysis of an industrially used solid shear pin that is modified as a hollow pin. Extensive modeling and simulation of the hollow pins are carried out to check the feasibility of replacing the solid shear pins with hollow shear pins. Due to the profound effect of the notch which changes stress concentration, it appears that weight savings using hollow notched pins possibly are not feasible while the hollow un-notched pins are beneficial. The industrial applicability of the hollow pins can be considered as beneficial components primarily towards functionality. In addition to the weight saving, they can also act as channels for passing wires and other similar entities of an assembly.

Simulation and Test of a MEMS Arming Device for a Fuze.

To solve the structural strength problem of a MEMS arming device for a fuze, a kind of arming device applied to a certain type of 40 mm grenade is designed. This paper introduces the working principle of the arming device; simulates the shear pin, rotary pin and locking mechanism in the device; designs a variety of different test tools for test verification; and further increases the explosion reliability and arming safety tests. The results show that the arming device improves the structural strength and can meet the action requirements of a certain type of 40 mm grenade for safety release, as well as the application requirements of explosion reliability and arming safety.

Improving vehicle’s seismic safety by equipping railway bridges with FPB and misalignment control device

Running safety of the railway vehicles on the bridge during earthquakes is a major concern for railway engineering. To reduce the derailment risk of railway vehicles on bridges, friction pendulum bearings (FPB) are proposed to be equipped on simply supported bridges in this study. The full nonlinear behavior of the FPB is introduced into the vehicle-bridge interaction model. The effect of FPB’s manufacturing variations, including the shear pin’s strength and friction coefficient, on the misalignment was investigated. The manufacturing variations of the FPB were found to produce large lateral misalignment, which further contributes to large wheel-rail forces when the vehicle passes over the girder ends. It diminishes the improvement in the vehicle’s seismic safety provided by FPBs. Thus, a misalignment control device is proposed to limit the misalignment of the railway bridges equipped with FPBs. The vehicle-bridge interaction analysis results show that no wheel uplift occurred on the bridge equipped with FPBs and misalignment control devices during an earthquake. It indicates that the FPB significantly reduces the vehicle’s derailment risk on bridges compared with the non-isolated bearings.

Prediction of Board Level Pad Cratering Strength With the Predefined Failure Criteria From Joint Level Testing

Abstract Conventional reliability tests for the evaluation of pad cratering resistance are mainly classified into two categories: the board level test and the joint level test. The board-level test is to imitate the loading conditions during normal operation. However, this type of test is expensive and not flexible. The joint level test is used extensively in the industry because it has the advantages of lower cost, higher throughput, and more quantitative results. It also allows the elimination of confounding factors such as PCB and component stiffness. Therefore, it is always desirable to predict the board level performance by a joint level test. In order to achieve this objective, the correlation between the joint level and the board-level tests must be fully understood. Nevertheless, a precise correlation between the two types of tests for pad cratering evaluation is yet to be defined. This study investigates the pad cratering failure mode for the correlation of critical failure factors between joint and board level tests. An intermediate critical failure factor could be taken as a failure criterion in board-level testing for failure detection. For verifying the validity of such a failure criterion, an experimental study should be performed. The 4-point bending test is chosen as the board-level test for critical failure factor validation. In addition, an innovative pin shear test method is developed as the joint level test for failure factor detection. Both test methods are assessed by a series of parametric studies with an optimized process to ensure the accuracy of the results. From the results of the experimental study and simulation, the critical failure factor correlation is established between the board level 4-point bending and the joint level pin shear test. Using finite element analysis (FEA), the critical failure strain is identified from the pin shear test model and will be employed as the board level failure criterion. Subsequently, the obtained failure criterion is verified by a 4-point bending model. As a result, this indirect correlation method can predict the board level failure with various geometric parameters.

Concept Design and Analysis of the Magnet System of the Sustained High Power Density Tokamak Facility

A recent National Academy study recommended a next-step sustained high power density (SHPD) facility for the United States that can be a bridge to a compact fusion pilot plant. A design has been initiated to investigate a possible SHPD non-deuterium-tritium device that builds upon recent low aspect ratio tokamak studies. A 1.2-m device with a 2.4 aspect ratio has been chosen to evaluate physics performance goals within a double-null plasma machine arrangement centered on three component features: high current density toroidal field (TF) and central ohmic heating/poloidal field (PF) coils, liquid metal divertor/first wall systems, and the integration of a limited set of outboard dual-coolant lead lithium test blankets that can be maintained within a vertical maintenance approach. The underlying initiative of the U.S. program is to promote research and technology advancements that lead to the construction of a compact pilot plant that produces electricity from fusion at the lowest possible capital cost. High-field, higher power density will bring down the size of a fusion device and can lower the cost, but this can only occur with the development of high-current density TF and PF windings, a support system to handle the higher magnetic loads, and a cost structure that is economically viable. High-temperature superconductors (HTSs) offer the potential to meet high-field/high-current requirements and is under development by a number of institutions. Fabrication process improvement would continue to bring down the price if a market for fusion devices were to develop and the production level of HTS cable were to increase; however, this is not happening with any expedience especially related to fusion applications. At present, HTS conductors are an order of magnitude more expensive than low-temperature superconductors (LTSs), making an early application for a near-term SHPD experimental device problematic, especially for a low aspect ratio design that has minimum component space within the device inboard region. In lieu of an HTS-based, high-current density TF winding design, a moderately high-current density winding design (>80 MA/m2) based on cable-in-conduit LTS conductors in a multiwinding pack arrangement sized for low and high field was defined. This paper focuses on the design of the magnet system, with attention given to the analysis performed on the SHPD TF casing structure. The analysis is carried out for various sections: (1) Emag analysis of the SHPD structure, (2) TF casing winding pack evaluation for TF-TF self-load only with slit model and three-dimensional geometry, (3) effect of the shear pin in the TF casing structure, and (4) compression ring effect on the SHPD structure.

Finite Element Simulations of Dynamic Shear Fracture of Hollow Shear Pins

The shear pin structure is widely used in aeronautics and astronautics structures to deal with emergency structure separation problems. The shear pin design has a strict restriction on the precise failure load and definite failure mode. Previous research has conducted shear fracture tests and simulations of solid shear pins while there is a lack of detailed research on the shear fracture of hollow shear pins with large diameters. In this research, a 3-dimensional finite element model was built based on the actual shear pin installed on the aircraft engine pylon and the model was validated by the experiment. The influences of the inner diameter of hollow shear pins on the shear fracture process were investigated by conducting finite element simulations. The structural deformation, energy dissipation in the fracture process, and failure load of shear pins were evaluated. It is found that as the inner diameter increases, the failure mode of shear pins changed and would result in difficulties on the structure separation. To solve this problem, a new configuration of hollow shear pin was proposed for the purpose of obtaining both desired failure load and failure mode. The new configuration was verified by the fracture simulation and it is found that the new configuration is effective and can be used to improve the shear fracture performance.

Torque characteristics of guide vanes protection device of Francis turbine in hydropower plant

Water turbines are widely used in water conservancy project and failure of it will have a great impact on the project safety and social benefits. Consequently, it is necessary to take protective measures and equip protective devices for turbines. This study investigates the torque characteristics of guide vane protection devices in a hydropower plant through controlled variable experiment. The investigation includes the operation mechanism and torque distribution mode of the guide vane protection devices working independently and collaboratively. The results show that the torque distribution ratio of the friction device continuously reduces with the increase of load, on the contrary, the distribution ratio of the shear pin increases. With the increase of load, the torque borne by the friction device and shear pin increases continuously, when the friction device reaches the limit state, friction failure occurs. Therefore, in the combination condition, the load can be set at the torque distribution intersection point as far as possible to effectively extend the working time of the protection device in case of accidents. Moreover, it can also extend the overall life of the protection devices.

Is the biological adaptiveness of delusions doomed?

Delusions are usually considered as harmful and dysfunctional beliefs, one of the primary symptoms of a psychiatric illness and the mark of madness in popular culture. However, in recent times a much more positive role has been advocated for delusions. More specifically, it has been argued that delusions might be an (imperfect) answer to a problem rather than problems in themselves. By delivering psychological and epistemic benefits, delusions would allow people who face severe biological or psychological difficulties to survive in their environment - although this has obvious epistemic costs, as the delusion is fixed and irresponsive to compelling counterevidence. In other words, it has been argued that delusions are biologically adaptive. The adaptiveness of delusions has been compared by Ryan McKay and Daniel Dennett to a shear pin, a mechanism installed in the drive engine of some machines which is designed to shear whenever the machine is about to break down. By breaking, shear pins prevent the machine from collapsing and allow it to keep functioning, although in an impaired manner. Similarly, when delusions form, they would allow a cognitive or psychological system which is about to collapse to continue its functioning, although in an impaired manner. However, this optimistic picture of delusions risks being undermined by both theoretical and empirical considerations. Using Sarah Fineberg and Philip Corlett’s recent predictive coding account as a paradigmatic model of the biological adaptiveness of delusions, I develop two objections to it: (1) principles of parsimony and simplicity suggest that maladaptive models of delusions have an upper hand over adaptive models; and (2) the available empirical evidence suggests that at least some delusions stand good chances of being psychologically adaptive, but it is unlikely that they also qualify as biologically adaptive.

Investigation of Frequent Failure of Francis Hydraulic Turbine Guide-Vane Shear Pin of Shiroro Hydro-Electric Power Station

Francis Hydraulic Turbine Guide-vane shear pin is a mechanical sacrificial component designed to break when the mechanical overload arises to prevent severe damage of guide-vane, which is an expensive component in the turbine assembly of hydro-power station. The pin is expected to serve for a minimum period of 10 years under normal working condition before failure occurs as obtained in most hydro-electric power stations globally. The shear pins in Shiroro hydro-electric power generation station located in Niger state of Nigeria were found to be frequently failing within a year of operation before reaching its predetermined load. This research investigated the possible causes of the frequent failure of the shear pins with a view to proffer solution. Analyses of the existing shear pin with respect to material specifications, micro-structural analysis using spectrophotometer where both visual and scanning electrode microscopy (SEM) was done in addition to mechanical tests to ascertain conformity with standards. The results showed that the shear pin material conforms to the ASTM 420, which is the standard for production of the shear pin. The SEM results shows that the failure of the shear pins was due to low cyclic fatigue growth attributed to the effect of intermittent and unsteady operations of the turbine. The visual examination revealed no defect on the phases of the material indicating that the fractured failure was not due to any form of inconsistency resulting from segregation or related effects. The mechanical test revealed yield strength of 600 N/mm2, ultimate tensile strength of 750 N/mm2 and hardness of 29 HRC which agreed with standard specifications for the shear pin. The results indicated that the frequent failure of shear pins could be as a result of other sources other than material specifications.

Shear behaviors and failure mechanisms of 2D C/SiC pins prepared by chemical vapor infiltration

Connecting and fastening large-scale all-C/SiC airfoils to the fuselage of hypersonic vehicle requires C/SiC fasteners of high-performances under the re-entry environment. In this paper, 2D C/SiC pins prepared by chemical vapor infiltration (CVI) were sheared off to demonstrate their strength sensitivity to the nonuniform microstructures, such as porosity and ply orientation. Results showed that their average shear strengths increase linearly from 85.8 to 134.8 MPa as their average total porosity decreases from 23.2% to 14.5%. The shear strengths of 2D C/SiC pins are almost the same as the in-plane shear strengths of 2D C/SiC composites, under the condition that both have identical total porosity. In contrast, the variances of the pin shear strength are much higher than the in-plane shear strength, which is mainly ascribe to the effects of the loading angle between the shear plane and the ply orientation. The porosity of the 2D C/SiC pin is the main microstructural factor influencing the pin shear strength. Matrix shear cracking, debonding between matrix and fibers, crack deflection along fibers and interlayer sliding are the main shear failure mechanisms. Due to the secondary bending deformation, the interlayer sliding and the corresponding fiber pull-out mechanisms dominate the final ductile fracture behavior.

The shear pin strength of friction pendulum bearings (FPB) in simply supported railway bridges

The friction pendulum bearings (FPB) begin to be used in railway bridges in China. In one earthquake region in China, the shear pins of FPB are required to be well to provide the enough shear force and stiffness under service loads (such as the vehicle forces being less than 170 kN in the longitudinal direction and 40 kN in the transverse direction) or small earthquake loads with a peak ground acceleration (PGA) being less than 0.1 g, however, are cut off to isolate seismic energy under large earthquake loads with a PGA being larger than 0.2 g. It is necessary to identify the appropriate strength of FPB shear pin to satisfy the above requirements. This paper selected the simply supported bridges on a single-line railway in the above earthquake region as the study object, which had a span length of 32 m and two height types of piers (8 m and 25 m). A prototype finite element model (FEM) and a scaled FEM were numerically analyzed, and a scaled experimental model was tested on shake table for each bridge. The results of them were compared with each other to validate the rationality of all models and to achieve the appropriate strength of FPB shear pin. The results show that the appropriate strengths of FPB shear pins are 540 kN in the longitudinal direction and 300 kN in the transverse direction for the bridge with the pier height of 8 m. Likewise, 350 kN and 270 kN are determined as the appropriate strengths of FPB shear pins for the bridge with the pier height of 25 m in the longitudinal and transverse directions, respectively. The numerical method of FEM is correct based on the experimental validation, and can be used to identify the appropriate strengths of FPB shear pins for other railway bridges.

Effect of pinless tool shoulder diameter on dieless friction stir extrusion joining of AA 5052-H32 and AA 6061-T6 aluminum alloy sheets

A new spot joining process called dieless friction stir extrusion is proposed, in which simultaneous mechanical interlocking (collar formation) and metallurgical bonding is the key aspect of joint formation. The pinless flat stir tool eliminates pinhole and hook formation, the common defects of friction stir spot welding. Aluminum alloy sheets such as AA 5052-H32 and AA 6061-T6 are spot joined and the effect of change in tool shoulder diameter (10–18 mm) on joint strength and joint formation is evaluated. Lap shear fracture load of 6.22 kN obtained at optimum tool shoulder diameter of 14 mm is higher than that of conventional spot joining techniques. Macrostructure analysis revealed that increase in tool shoulder diameter results in poor mechanical interlocking. Consequently, pin shear failure is common at highest tool shoulder diameter. Critical weak zones of failure are identified. The change in tool shoulder diameter has significant impact on the external joint morphology.