Terms Of Reaction Force Research Articles

An evaluation of cutting head design of current tunnel Boring machines and suggestions to improve machine Performance

ABSTRACT This paper evaluates cutterhead design of current tunnel boring machines (TBMs) in considerations with the actual cutting action of discs observed on the most common cutter heads. The discs on the current TBM cutter heads were found to predominantly perform asymmetrical cutting action, which generates excessive sideway forces impairing steering action of the machine. The effective s/p ratios related to actual cutting action of discs emerge to be significantly higher than those of the laboratory-determined values, and this consequently leads to adverse cyclic deepening effect. The gross lateral loads arising from excessive side forces were stated to be minimised if the adjacent discs are arranged to cut in symmetrical position by adopting appropriate cutterhead design methods suggested in this paper. Furthermore, a dynamic analysis was carried out in terms of reaction forces on cutter heads of different geometries, and it was indicated that flat face cutter heads have better steering abilities than conical or domed types, in mixed face conditions. Similar analysis on disc angular spacing also inferred that scattered type disc arrangements with equal angular spacing are preferable to cutterheads with spoke or star type lacing, in terms of cutterhead balance.

Deep neural operator for learning transient response of interpenetrating phase composites subject to dynamic loading

Additive manufacturing has been recognized as an industrial technological revolution for manufacturing, which allows fabrication of materials with complex three-dimensional (3D) structures directly from computer-aided design models. Using two or more constituent materials with different physical and mechanical properties, it becomes possible to construct interpenetrating phase composites (IPCs) with 3D interconnected structures to provide superior mechanical properties as compared to the conventional reinforced composites with discrete particles or fibers. The mechanical properties of IPCs, especially response to dynamic loading, highly depend on their 3D structures. In general, for each specified structural design, it could take hours or days to perform either finite element analysis (FEA) or experiments to test the mechanical response of IPCs to a given dynamic load. To accelerate the physics-based prediction of mechanical properties of IPCs for various structural designs, we employ a deep neural operator (DNO) to learn the transient response of IPCs under dynamic loading as surrogate of physics-based FEA models. We consider a 3D IPC beam formed by two metals with a ratio of Young’s modulus of 2.7, wherein random blocks of constituent materials are used to demonstrate the generality and robustness of the DNO model. To obtain FEA results of IPC properties, 5000 random time-dependent strain loads generated by a Gaussian process kennel are applied to the 3D IPC beam, and the reaction forces and stress fields inside the IPC beam under various loading are collected. Subsequently, the DNO model is trained using an incremental learning method with sequence-to-sequence training implemented in JAX, leading to a 100X speedup compared to widely used vanilla deep operator network models. After an offline training, the DNO model can act as surrogate of physics-based FEA to predict the transient mechanical response in terms of reaction force and stress distribution of the IPCs to various strain loads in one second at an accuracy of 98%. Also, the learned operator is able to provide extended prediction of the IPC beam subject to longer random strain loads at a reasonably well accuracy. Such superfast and accurate prediction of mechanical properties of IPCs could significantly accelerate the IPC structural design and related composite designs for desired mechanical properties.

Drop Weight Impact Behaviour of Tube Filled Polymeric Syntactic Foam

Accidents are misfortune which could happen to anyone at any place at any time and it affects the vehicle as well as the occupants. Continuous research is being carried out for improving the crashworthiness of the vehicles with different materials. These materials plays important aspect in energy absorption and impact resistant design of the structure, wherein, presence of these materials highly affects the response of structures subjected to impact loading. In the present study, a non-linear finite element code LS-DYNA® is used for numerical simulation of drop weight impact hammer test. The material chosen for simulated testing is polymeric syntactic foam. In this study, effect of density of foam, foam material model, effect of drop height and effect of tube, filled with foam, on energy absorption of foam is studied. Herein, material model chosen for hammer is bilinear material model and crushable foam as well as piecewise linear plasticity model is used to model the foam. Behaviour of foam is compared in terms of reaction force, displacement time history and force-displacement variation. Energy absorption for each model is computed for different velocities considered in the present study and it is observed that tube plays an important role in enhancing the energy absorption of foam.

Modeling and Simulation of Two Wheelchair Accessories for Pushing Doors

ABSTRACTIndependent mobility is vital to individuals of all ages, and wheelchairs have proven to be great personal mobility devices. The tasks of opening and navigating through a door are trivial for healthy people, while the same tasks could be difficult for some wheelchair users. A wide range of intelligent wheelchair controllers and systems, robotic arms, or manipulator attachments integrated with wheelchairs have been developed for various applications, including manipulating door knobs. Unfortunately, the intelligent wheelchairs and robotic attachments are not widely available as commercial products. Therefore, the current manuscript presents the modeling and simulation of a novel but simple technology in the form of a passive wheelchair accessory (straight, arm-like with a single wheel, and arc-shaped with multiple wheels) for pushing doors open from a wheelchair. From the simulations using different wheel shapes and sizes, it was found that the arc-shaped accessory could push open the doors faster and with almost half the required force as compared to the arm-like accessory. Also, smaller spherical wheels were found to be best in terms of reaction forces on the wheels. Prototypes based on the arc-shaped accessory design will be manufactured and evaluated for pushing doors open and dodging or gliding other obstacles.

The effect of anterolateral ligament integrity on the tibia displacement and reaction forces of anterior cruciate ligament

Objective:Recent studies focused on rotational instability and remained positive pivot test in patients with anterior cruciate ligament (ACL) reconstruction. Clinical, radiological and biomechanical studies showed the importance of the anterolateral ligament (ALL) integrity. ALL is one of the stabilization structures against the internal rotation of the tibia under forces which was associated with Segond fracture previously. Even some authors claimed that ACL failure and risk of re-rupture increased if only ACL reconstruction performed in patients with simultaneous ALL injury. The aim of the study is to evaluate the importance of ALL on knee biomechanics during anterior drawer test and internal rotation forces with different flexion angles in terms of reaction forces on ACL and the amount of tibia displacement via finite element analysis.Methods:Three dimensional (3D) solid model of knee joint and ALL injured models were constructed based on DICOM formatted computed tomography (CT) images. 0°, 15°,30°,45°,60°,75° and 90° flexion angles were applied respectively to reference models. Then varied anterior drawer and internal rotational forces were used to investigate the effect of ALL. ANSYS ®Version 17 was used in analyses and same boundary conditions were used in all models.Results:In critical analyzing the all results; medial displacement and the amount of anterior drawer distance were increased in all ALL injured models when compared with references. Therewithal the rotational displacements were increased by increasing the knee flexion angle and rotational torque. But, it was not a significant change in the amount of displacement between the models with respect to anteroposterior displacement when the anterior drawer force was increased.Conclusion:ALL particular has an important role in the stability of the internal rotation occurs against the force and with increased contribution rate to the knee joint stability by increasing the knee flexion angle. But the reaction forces were not affected by ALL integrity. So this study do not support the previous studies which suggest simultaneously reconstruction of both ligaments to avoid re rupture of ACL in cases with ALL injured.

Spent nuclear fuel system dynamic stability under normal conditions of transportation

In a horizontal layout of a spent nuclear fuel (SNF) assembly under normal conditions of transportation (NCT), the fuel assembly’s skeleton formed by guide tubes and spacer grids is the primary load bearing structure for carrying and transferring the vibration loads within an SNF assembly. Therefore, the integrity of guide tubes and spacer grids will dictate the vibration amplitude/intensity of the fuel assembly during transport, and must be considered when designing multipurpose purpose canister (MPC) for safe SNF transport. This paper investigates the SNF assembly deformation dynamics during normal vibration mode, as well as the transient shock mode inside the cask during NCT. Dynamic analyses were performed in the frequency domain to study frequency characteristic of the fuel assembly system and in the time domain to simulate the transient dynamic response of the fuel assembly.To further evaluate the intensity of contact interaction induced by the local contacts’ impact loading at the spacer grid, detailed models of the actual spring and dimples of the spacer grids were created. The impacts between the fuel rod and springs and dimples were simulated with a 20g transient shock load. The associated contact interaction intensities, in terms of reaction forces, were estimated from the finite element analyses (FEA) results. The bending moment estimated from the resultant stress on the clad under 20g transient shock can be used to define the loading in cyclic integrated reversible-bending fatigue tester (CIRFT) vibration testing for the equivalent condition. To estimate the damage potential of the transient shock to the SNF vibration lifetime, drop tests were performed on the CIRFT specimens. FEA was used to investigate the contact reaction at CIRFT test samples during impact loading induced by drop tests, and the result was compared with that from a 20g acceleration transient shock load.

Rib fractures under anterior–posterior dynamic loads: Experimental and finite-element study

The purpose of this study was to investigate whether using a finite-element (FE) mesh composed entirely of hexahedral elements to model cortical and trabecular bone (all-hex model) would provide more accurate simulations than those with variable thickness shell elements for cortical bone and hexahedral elements for trabecular bone (hex–shell model) in the modeling human ribs. First, quasi-static non-injurious and dynamic injurious experiments were performed using the second, fourth, and tenth human thoracic ribs to record the structural behavior and fracture tolerance of individual ribs under anterior–posterior bending loads. Then, all-hex and hex–shell FE models for the three ribs were developed using an octree-based and multi-block hex meshing approach, respectively. Material properties of cortical bone were optimized using dynamic experimental data and the hex–shell model of the fourth rib and trabecular bone properties were taken from the literature. Overall, the reaction force–displacement relationship predicted by both all-hex and hex–shell models with nodes in the offset middle-cortical surfaces compared well with those measured experimentally for all the three ribs. With the exception of fracture locations, the predictions from all-hex and offset hex–shell models of the second and fourth ribs agreed better with experimental data than those from the tenth rib models in terms of reaction force at fracture (difference <15.4%), ultimate failure displacement and time (difference <7.3%), and cortical bone strains. The hex–shell models with shell nodes in outer cortical surfaces increased static reaction forces up to 16.6%, compared to offset hex–shell models. These results indicated that both all-hex and hex–shell modeling strategies were applicable for simulating rib responses and bone fractures for the loading conditions considered, but coarse hex–shell models with constant or variable shell thickness were more computationally efficient and therefore preferred.

The mechanism of the interstellar isomerization reaction HOC+→HCO+ catalyzed by H2: New Insights from the reaction electronic flux

A theoretical study of the mechanism of the isomerization reaction HOC(+) --> HCO(+) is presented. The mechanism was studied in terms of reaction force, chemical potential, reaction electronic flux (REF), and bond orders. It has been found that the evolution of changes in REF along the intrinsic reaction coordinate can be explained in terms of bond orders. The energetic lowering of the hydrogen assisted (catalyzed) reaction has been identified as being due to the stabilization of the H(3)(+) transition state complex and the stepwise bond dissociation and formation of the H-O and H-C bonds, respectively.