Nominal Force Research Articles

Object-Oriented Software for Fitness-For-Service Assessment of Cracked Cylinder Based on API RP 579

Fitness-for-service assessment of a cracked component intends to evaluate its remaining strength and remaining life to support the implementation of a maintenance plan. This research aims to develop a fitness-for-service assessment software to facilitate the task. The software development process included identifying the software specifications, designing the software structure, manipulating the information from the standard for programming, the graphical user interface design, and finally verification of the software. The assessment procedure employed in this study was the third edition of the standard API RP 579. The software structure was designed using an object-oriented concept. The software can perform integrity assessment levels 1, 2, and 3 option B, leak-before-break assessment, and remaining life assessment for a cracked cylinder that has a through-thickness crack or semi-elliptical surface crack oriented in an axial or circumferential direction. The applied loads could be a nominal axial force, bending moment, and internal pressure, as well as stress profiles perpendicular to the crack plane due to mechanical, thermal, and residual stresses. Accuracy of the software was demonstrated by applying it to example problems. Some aspects of the software extensibility were conceptually discussed.

FEM modeling of multilayer Canted Cosine Theta (CCT) magnets with orthotropic material properties

CCT magnets are becoming more popular, especially as they provide support for each separate turn of a coils, thus significantly lowering the coil stresses and deformations. A four layer nested CCT dipole was designed at CERN as an R&D effort to study the possibility of using the CCT technology for such a complex magnet. Two pairs of layers produce dipole magnetic fields at 90° angles, allowing a 360° control over the resulting dipole field vector. In order to validate the design in terms of the mechanical strength and the allowed deformations, mechanical FEM models were needed. Three models, having different levels of geometrical details have been developed in the APDL language in the ANSYS software: a 3D model with periodic symmetry and two 2D models, one assuming very simplified geometry of the coils and the formers and the second one with real geometry of the coils and the formers. Realistic coils properties were accounted for via homogenization technique used to obtain average properties of the Nb-Ti strands and the cured resin. Orthotropic behavior of the coil was accounted for via rotations of the element coordinate systems in the 3D periodic model, and via anisotropic material properties for the detailed 2D model.The electromagnetic (EM) analysis was done for the full 3D model of 1.4 m long nested CCT dipole. The EM forces were mapped to the 3D periodic models and the 2D models. The mechanical analysis consisted of the cool-down to 1.9 K in the first step and subsequent application of the nominal Lorentz forces. In addition, behavior at 1.9 K without thermal strains but only EM forces was studied to compute the maximum coil deformations – important to be kept low for good field quality.All three FEM models have been successfully solved providing three estimations of the resulting deformations and stresses. The most loaded part was the interlayer insulation – due to the thermal strains and large torque between the layers, shear stresses above the safe level of 10 MPa were found. Another design was proposed to remove the possibility of the failure of the interlayer insulations via castellations in the formers. Further studies will include the full 3D model and a comparison to the periodic model, in order to find the most suitable boundary conditions for the periodic model. The detailed 2D model requires further developments in terms of electromagnetic force import. As the 2D model requires much less computational power w.r.t. the periodic 3D model, it shows a potential for more realistic geometrical modeling including the Nb-Ti strands and their Kapton insulation, to study the behavior of the interface between the strands, the cured resin, and the formers.

Development of dam inspection robot with negative pressure effect plate

AbstractThis paper describes the development of an underwater robot that performs visual inspection while making mechanical contact with a dam surface by a pulling force generated from thrusters with negative pressure effect plates. In general, small and lightweight remotely operated vehicles (ROVs) have low‐power thrusters. Their positioning performance is inferior with respect to external disturbances. Moreover, it is difficult for untrained operators to control the ROV position to check and inspect dams visually. A negative pressure effect plate attached to a thruster produces negative pressure that maintains mechanical contact between the robot and a dam wall surface and ensures stable robot motion on a dam surface to acquire clear continuous images. As described herein, we theoretically investigate the negative pressure effect plate characteristics and experimentally measure the force generated by the pressure difference. Results show that the force of a thruster with the effect plate is five times greater than the nominal thrust force provided by the thruster alone. Based on those results, we designed and developed the underwater robot with the negative pressure effect plates for dam inspection. Moreover, we conducted an experiment in a water tank and a field test at Shorenji Dam, Mie‐prefecture, Japan. The experimentally obtained results indicated that the negative pressure effective plate is effective at generating sufficient force and at realizing stable robot motion on the dam surface. Results demonstrate that the developed robot acquired clear images of the dam surface continuously with no sophisticated operator or controller.

Contact stress and bending stress calculation model of spur face gear drive based on orthogonal test

As the stress of gears determines the reliability of transmission, the stress research of face gear drive has great significance from the perspective of both theory and practice. The finite element model of orthogonal spur face gear meshing is attained via root-top section lofting method. The geometry parameters (include modulus, teeth number of face gear, teeth number of pinion and pressure angle) and transmission parameter (nominal contact force) are considered in the stress modeling. This paper, respectively established the empirical equations for contact stress and bending stress of face gear and pinion through stepwise regression by using single factor test and orthogonal test. The empirical equations have been validated by comparing them with results obtained from FEA.

Experimental and numerical studies on pseudo-negative-stiffness control of a base isolated building using magneto-rheological dampers

This article presents a series of experimental and numerical studies on the feasibility and effectiveness of pseudo-negative-stiffness (PNS) control system using magneto-rheological (MR) dampers. First, a MR damper with nominal force capacity of 10 kN was self-developed. A set of experiments was conducted to study the dynamic performance of the MR damper. Then, a PNS control system was established with NI Compact RIO as hardware platform and Labview as software platform. The displacement-based PNS (DPNS) control algorithm was employed to control the MR damper. Dynamic performance tests were performed to investigate the hysteretic behavior of DPNS control force under different excitation conditions and with different control parameters. Next, shaking table tests were conducted on a four-floor steel frame base isolated structure model employing the PNS control system. The seismic responses under uncontrolled case, passive off case, passive on case and DPNS control case were compared. For each control type, the control efficacy was verified for the El Centro, Ji Ji, Kobe_FN and Kobe_FP with increasing peak ground acceleration. The test results show that the DPNS control can further reduce the isolation displacement compared to the passive off case with no accompanying increase of superstructure responses under seismic excitation with different intensities and spectral characteristics. Finally, numerical studies were conducted to compare the effectiveness of DPNS and clipped-optimal control and investigate the effect of time delay of DPNS control. Results indicate that the DPNS control outperforms the clipped-optimal control and the time delay of the DPNS control leads to the adjustment of the DPNS control force at zero displacement, which is beneficial to control efficacy.

An analytical force model for ultra-precision diamond sculpturing of micro-grooves with textured surfaces

The investigation on the cutting force for ultra-precision diamond sculpturing (UPDS) is important to understand its material removal mechanism and tool-workpiece reaction behaviors during cutting. However, few studies have focused on the cutting force model for UPDS of micro-grooves with textured surfaces. The prediction of the cutting force for UPDS is complicated due to its unique kinematics featuring oscillated servo motions, which inevitably leads to the dynamic material removal process featuring time varying plastic deformation directions. In the present study, an analytical cutting force model for UPDS of textured micro-grooves is proposed with the full consideration of the oscillations induced dynamic cutting conditions, round-edged effect as well as the shearing and ploughing mechanisms. Specifically, the nominal shearing force is derived by a dynamic slip-line model involving the time varying shear angle, stress, strain and strain rate in the deformation zone. A two-state model is adopted to describe sticking and sliding states of the chip on the tool rake face, based on which the frictional shearing force is calculated. When the depth of cut is lower than the critical chip thickness, the material is removed by the ploughing force that is of proportional relation to the tool-workpiece interference volume according to the indentation theory. Finally, the whole cutting force is obtained by discretization method, and the model is experimentally validated through sculpturing two types of textured micro-grooves with harmonic structures.

Contact modeling and input-voltage-region based parametric identification for speed control of a standing wave linear ultrasonic motor

Linear ultrasonic motor is a complicated electromechanical coupling system, precision speed control of which is a challenge for the researchers for difficulties in obtaining its accurate speed prediction model. The stator/slider contact mechanism, which can be described by a stick-slip-separation dynamics, greatly affects the output speed. Considering that practically the full physics of the system is often inaccessible to be modeled accurately for lack of prior knowledge of some physical/structural parameters, this paper presents a novel parametric contact model and the corresponding parametric identification procedure for steady-state speed prediction of a typical standing wave linear ultrasonic motor utilizing longitudinal and bending modes. Compared with the training data-driven general modeling, the approach retains physical insight into some important nonlinear characteristics in the contact process to improve prediction performance. The dynamic equations of the stator are deduced by using Timoshenko beam theory and Hamilton's principle and a new interface friction model including asperity contact based stick friction and normal ultrasonic oscillation related slip friction is developed. Besides, the distinctive feature of position-dependent nonlinearity of linear ultrasonic motor, which can be characterized by variation of the vibration of the stator at interface, is evaluated by introducing a variable named nominal axial force of the stator. In the study, this variable acts as the output of an embedded model in the contact model, parameters and structure of which are to be identified. Further, the effect of the region of input voltage on the contact behavior, is taken into account in the identification. In order to collect the input/output data for the identification procedure, an effective and synchronous data acquisition and transmission hardware/software experimental system is established. By employing off-line maximum likelihood estimation method, the input-voltage-region based parameters can be obtained. It is validated credibility of the speed prediction model under different loads and different input voltages with a prototype of linear ultrasonic motor actuated motion platform.

A Coupled Thermomechanical Modeling Method for Predicting Grinding Residual Stress Based on Randomly Distributed Abrasive Grains

Abstract In this research, we propose a coupled thermomechanical modeling method for predicting grinding residual stress based on randomly distributed grains. In order to deal with the problem that the nominal grinding force is too small to generate the plastic deformation, we hold the opinion that grinding residual stress is totally derived from three factors: thermal stress, the nominal grinding force (pressure) over the entire grinding zone, and the equivalent plowing force just under the bottom of the abrasive wheel. Finite element model (FEM) simulation of the single-grain grinding (SGG) is conducted to obtain the critical plowing depth and the SGG force at an arbitrary cutting depth. Based on the randomly distributed abrasive grains, the equivalent grinding heat source model, the equivalent SGG plowing force model, and the equivalent nominal pressure model are all established. A 2D coupled thermomechanical model is established to simulate the grinding process for temperature fields and grinding residual stress fields. In addition, verification tests are conducted to validate the model. It turns out that the coupled model can accurately predict the multiphysical fields on both temperature and residual stress. Based on the simulation results of the model, the generation mechanism of grinding residual stress is quantitatively studied. This research provides a promising pathway to residual stress control of grinding.

The development of the technical concept of the tractor

The development of the technical concept of an agricultural wheeled tractor is analyzed depending on the continuous growth of its energy saturation, as an indispensable factor in raising the technical level. The technological properties and methods of aggregating tractors of three generations of energy saturation called traction, traction energy and energy concepts, are considered. At present, in the world tractor construction, tractors of the traction concept are almost out of production; tractors of power traction and, to a lesser extent, energy concepts, are mainly produced. Tractors of the second generation differ from tractors of the first generation that they include ballast in a factory complete set. Ballasting has become a necessary way to artificially increase the weight of the tractor and reduce its energy saturation due to the limitation of the speed of technological operations, introduced by the rules of agricultural engineering. It is assumed that in the foreseeable future this restriction will not be removed. Even now, ballasting as a way to compensate for the weight loss of the tractor has almost exhausted its possibilities, because ballast weights reach half of the tractor weight and more. As the tractor continues to increase its energy saturation and maintains limitations on the speed of technological operations, the ballasting will require replacement. The article proposes instead of ballasting the use of a third movable axle and a block-modular aggregation system, as well as the use of electric transmission on the third-generation tractors and an active drive to the motor-wheel of agricultural machinery. It is shown that the second generation tractors have potential technological properties that can be implemented under the condition of competent and easy to operate maneuvering level of ballasting. In general, the use of tractors of the second and third generations of traction energy and energy concepts will significantly reduce: the material intensity of machine tractor unit; fuel consumption; the harmful effects of tractor propellers on the soil, variability (the difference of tractors in terms of the nominal tractive force on the hook) of tractors in the economy.

Reinforced Concrete (RC) beam design application for android based on SNI 2847:2013 (CEMA)

In Indonesia RC structures are widely used for high rise, low rise, shop offices, as well as residential buildings. In February 2018, the first author introduced an RC beam design application for Android [12] for two options. Option one is for calculating nominal moment (Mn) and nominal shear force (Vn) of the section when the beam dimensions (b, h) and reinforcements are known; option two is to calculate the number of reinforcements for Mn and Vn when the dimensions (b, h) are known. In this paper, the first author added option three, namely the optimization for the design of RC beams when the internal forces are known and the application calculates the most optimal dimensions (b, h) and reinforcements. The application developed is named Civil Engineering Mobile Application for Concrete Beams (CEMA) and is called C2. In CEMA the user can follow the step by step calculation and the results of the calculation are stored in a database. For option three of CEMA (optimization of RC beam sections), the application was validated by another method called Teaching-Learning-based Optimization (TLBO) method [10]. It is believed that CEMA which is based on SNI 2847:2013 can be useful for Indonesian structural engineers designing and supervising actual construction RC buildings.

ЗАСТОСУВАННЯ КОМП’ЮТЕРНОГО МОДЕЛЮВАННЯ ДЛЯ УТОЧНЕНОЇ ОЦІНКИ ГАЛЬМІВНОЇ ЕФЕКТИВНОСТІ ВАНТАЖНИХ ВАГОНІВ

The new approach to the estimation of experimental studies results of the brake efficiency of freight wagons, based on the implementation of the data model in the form of a differential equation of the train movement during braking and study of braking processes using computer aided simulation methods is described. The mathematical models which take into account the following principal characteristics of the braking system, i.e. the actual functional dependences of the brake cylinder filling time with compressed air during braking, as well as the nominal forces of pressing the brake pads on the wheel pairs; the net specific resistance to movement; the values of normalized descents are given. The implementation of the estimation procedure is illustrated by the experimental open-top wagon, the braking parameters (brake distances, speeds, deceleration, brake coefficients, actual coefficients of friction, etc.) are given.Keywords: brake efficiency, freight wagon, computer-aided simulation, mathematical

Performance of a light timber‐framed compartment in natural fire subjected to lateral load

SummaryA common approach for designing buildings for lateral stability during and post‐fire in New Zealand is to ensure that a fire‐rated structure does not collapse when subjected to a nominal horizontal force. For external walls of residential buildings, which are required to resist a lateral load of 0.5 kPa, it is hypothesised that the adjacent unrated construction could provide sufficient support. A natural fire experiment has been conducted to evaluate the fire performance of a laterally loaded light timber‐framed compartment, with external dimensions of 4.33 m × 3.35 m and a stud height of 2.4 m constructed with a timber truss roof and plasterboard ceiling. During the experiment, the ceiling collapsed at 12 to 13 minutes, and the bottom chord of the roof truss failed in tension after 28 minutes which resulted in the fire‐rated wall losing its lateral stability at 28 minutes. The fire severity experienced in the compartment has been estimated to correspond to an equivalent time of 33‐minute exposure to a standard furnace time‐temperature. It is concluded that there is no need to provide nominal (additional) moment‐resisting fixity at the base of the fire‐rated wall when exposed to the standard fire for no more than 30 minutes.

Modeling a rotator cuff tear: Individualized shoulder muscle forces influence glenohumeral joint contact force predictions

BackgroundRotator cuff tears in older individuals may result in decreased muscle forces and changes to force distribution across the glenohumeral joint. Reduced muscle forces may impact functional task performance, altering glenohumeral joint contact forces, potentially contributing to instability or joint damage risk. Our objective was to evaluate the influence of rotator cuff muscle force distribution on glenohumeral joint contact force during functional pull and axilla wash tasks using individualized computational models. MethodsFourteen older individuals (age 63.4 yrs. (SD 1.8)) were studied; 7 with rotator cuff tear, 7 matched controls. Muscle volume measurements were used to scale a nominal upper limb model's muscle forces to develop individualized models and perform dynamic simulations of movement tracking participant-derived kinematics. Peak resultant glenohumeral joint contact force, and direction and magnitude of force components were compared between groups using ANCOVA. FindingsResults show individualized muscle force distributions for rotator cuff tear participants had reduced peak resultant joint contact force for pull and axilla wash (P ≤ 0.0456), with smaller compressive components of peak resultant force for pull (P = 0.0248). Peak forces for pull were within the glenoid. For axilla wash, peak joint contact was directed near/outside the glenoid rim for three participants; predictions required individualized muscle forces since nominal muscle forces did not affect joint force location. InterpretationOlder adults with rotator cuff tear had smaller peak resultant and compressive forces, possibly indicating increased instability or secondary joint damage risk. Outcomes suggest predicted joint contact force following rotator cuff tear is sensitive to including individualized muscle forces.

Sensitivity of Shoulder Musculoskeletal Model Predictions to Muscle-Tendon Properties.

While the sensitivity of estimated muscle forces to muscle-tendon properties is well documented for the lower limbs, little is known about the shoulder and upper limbs. The purpose of this study was to assess the sensitivity of estimated shoulder muscle forces and scapulohumeral joint force to muscle-tendon properties. One healthy male participant performed arm flexions and simulated throwing maneuvers. Kinematics were recorded using intra-cortical pins. Muscle forces were estimated using static optimization with the generic delft shoulder and elbow in OpenSim, and scapulohumeral joint forces were calculated from the estimated forces. Then, variations from -25% to +25% of the nominal values of the tendon slack length, the optimal fiber length, the maximal isometric force, and the pennation angle were applied to the musculoskeletal model to compute affected muscle forces and scapulohumeral joint force. The variations in muscle-tendon properties led to changes up to 9.6N or 174% in the muscle nominal forces. The more sensitive muscles were those that produced the greatest force: the rotator cuff muscles and the prime movers specific to the task. Among the four muscle-tendon properties, the maximal isometric force and the optimal fiber length had the greatest influence on the muscle force variability. Glenohumeral force was slightly influenced by muscle-tendon properties (<8%). Generic models (i.e., those without personalization of muscle-tendon properties) can lead to misinterpretations of muscle force. Efforts should focus on the maximal isometric force and the optimal fiber length of the rotator cuff muscles and prime movers.

Dynamic Mesh Forces in Accounting of the Time Variable Mesh Stiffness of a Gear Train

The paper considers the problems connected with the periodic variation of the tooth stiffness during the engagement in a spur gear train that arise due to the different number of teeth involved in torque transmission. Thus, the process of engagement is accompanied by a redistribution of the dynamic forces between the teeth at the boundaries of the engagement phases from the one-pair contact to the double-pair contact. As a result, it can cause forced and parametric vibrations. The dynamic mesh forces caused by kinematic error and time variable mesh stiffness are associated with the periodic mesh of the teeth. It is further shown that the load on the meshing pairs of teeth can be several times higher than the nominal forces. As a result, the operation of a machine is accompanied by high level of noise and vibration.

RESEARCH RESULTS OF THE EFFICIENCY OF THE MOTOR GRADER SIDE WORKING EQUIPMENT

Introduction. Nowadays there is sufficient number of the working bodies’ parameters, which allow performing technological operations in different conditions with minimal labor and energy resources. It is necessary to produce significant excavation during roads’ construction. Therefore, to perform such technological procedure excavation and road machinery are used. The motor grader is an earth-moving machine and is necessary for surface profiling, moving and construction materials’ level.The motor grader efficiency is determined by the performance criterion. World producers of earthmoving and road machinery associate the growth of quality and speed of work with the improvement of the executive working bodies. Moreover, new design variants of dumps are being developed, including design variants for motor graders. Such solution would allow to reduce the necessary number of passages along the construction site and to shorten the time for mounting the working body. The article presents the variant of the motor grader working equipment improving by installing the side working dump.Materials and methods. The calculated dependences of the main parameters of the motor grader are obtained, such as the coupling weight, the nominal traction force, the resistances arising in the operating mode when cutting and moving the ground, and the total engine power for the operating mode at 4 km per hour speed. Strength characteristics of the side working equipment of the motor grader are investigated. The analysis is carried out by using the Solid Software.Results. The results of the theoretical studies are presented graphically and reflected the stresses, displacements and deformations in proposed lateral working equipment of the motor grader. Using the Solid Works software product it is possible to determine the safety margin of the proposed design. The conducted research allows confirming the working capacity of the proposed technical solution.Discussion and conclusion. The proposed technical solution allows increasing the productivity of the machine while performing the planning works, while maintaining the specified accuracy of their implementation. In addition, such design allows profiling not only the horizontal surface, but also the embankment construction when the side blade is located at an angle of up to 20 degrees.

Generation of Artificial Road Profile for Automobile Spring Durability Analysis

This paper presents the use of a generated artificial road profile in the simulation of a quarter car model for spring durability based-force extraction. In situ measurement of the road loading profile for automotive spring durability analysis, requires considerable cost and effort due to the complex experimental setup. Hence, an artificial road profile was generated for the quarter car model simulation to obtain the spring force signals. Initially, according to the ISO 8608 standard, a class “A” artificial road profile was generated using a designated waviness value, unevenness index and random phase angle. The generated road profile was used as the input to a constructed quarter car model to obtain the spring force signals. Subsequently, the generated nominal force signal was used to predict the fatigue life of the spring. Moreover, to obtain the localise fatigue behaviour of the spring, a finite element spring model together with the force signal was used for fatigue prediction. Under this class “A” road excitation, the spring possessed very high fatigue life of 1.87 × 106 blocks to failure. Further, a series of spring variant was analysed for fatigue life through this road class excitation. The relationship between spring stiffness and fatigue lives established using power regression and the coefficient of determination (R2) as high as 0.9815 was obtained. Therefore, this analysis will assist in automobile spring design regarding fatigue when road load data is not available.

Use of grooved clamping plate to increase strength of bolted moment connection on cold formed steel structures

The purpose of this study was to look at an alternative way of enlarging the strength of the moment connection on cold formed steel structures using the grooved clamping plate. To support the research we use the experimental method of testing the moment connection on the cold formed steel with the addition of grooved clamping plate. Experimental results show that the cold formed steel moment connection using the grooved clamping plate can be significantly increased compared to a cold formed steel moment connection that only increases the diameter of the bolt and the distance between the bolts. From these results, it is known that the addition of the grooved clamping plate at moment connection can give a nominal moment force increase of almost 200%, whereas the addition of bolt spacing and diameter gives only a nominal moment force increase of almost 50%. Of course, this experimental result will be an alternative innovation in terms of enlarging the strength of the moment connection on cold formed steel.

An investigation on the active control strategy for a high-speed pantograph using co-simulations

The article presents simulation results on the active control strategy for a railway pantograph to improve contact quality in pantograph–catenary interface. Three different approaches were investigated: nominal torque tuning, torque active control and combination of them—combined control approach. The first control scenario minimizes the pantograph nominal uplift force exerted on the catenary. The second approach is based on active pantograph toque control, employing the proportional–integral–derivative controller, to compensate actual contact force error. The last control scenario links the above-mentioned approaches. Promising results are obtained employing the co-simulation environment recently presented by the authors.

Comparison of WF &amp; Tubular Links on the Eccentrically Brace Frame System due to Cyclic Loads

Eccentrically Brace Frame system develops its ductility using link inelasticity. Therefore, the strength of the structure in resisting the lateral force is highly dependent on the link and some types of link that are commonly used. Furthermore, it needs to compare the behavior of two section frames that most commonly used as a link in EBF system building; they are WF section and tubular section. In addition to the cross-sectional factors, deformation of the link is also highly dependent on the length of the link, hence the test will also be done on three different type of link lengths, they are short links, intermediate links, and long links, that are according to the classification of link lengths defined in AISC Seismic Provision. Before starting the analysis, a literature study has been reviewed to learn more about the behavior of a link under cyclic load. The numerical analysis has been done to find the strength of the link and modeling with the Finite Element Analysis (FEA) using ABAQUS. After all analysis and the calculation are completed, the results will appear in three-dimensional modeling form, Displacement versus Force diagrams and the stress-strain curves to show the ductility of all specimens. The result of the study showed that in short links, both WF link and tubular link achieve nominal shear force is equal to V p plastic shear force with values 390 kN for tubular section and 437 kN for WF section, and the value of shear force to the classification of the short link is very dependent on the body cross-sectional area. Tubular link’s body with an area of 89% of the WF link total weight generates shear forces 89% of the shear force from WF link because the formulation of the plastic shear force V p is highly dependent on factors of body cross-sectional area ( A w ). According to the research result, it shows that for both WF and tubular link cannot reach nominal shear force when the length of the link over the requirement of the shear link.