Flexible Parts Research Articles

Demand planning strategies for the control of energy flexible components of machine tools

The volatility of the energy market is increasing due to the renewable energies for electricity generation. As a result the adaptation of electricity consumption to electricity generation is gaining importance. Companies can make a significant contribution by controlling their production and thus their energy consumption. Machine tools have various components such as pumps and accumulators for cooling lubricant supply which are suitable to increase the energy flexibility of the machine. In order to be able to evaluate the energy flexibility potential of individual components, strategies from production planning and control (PPC) such as demand planning were examined. Selected strategies were adapted to control the components. With a simulation of the energy consumption of a machine tool, the PPC strategies were compared by determining the energy flexible part of the components energy consumption.

CDPM: Convolutional Deformable Part Models for Semantically Aligned Person Re-identification.

Part-level representations are essential for robust person re-identification. However, common errors that arise during pedestrian detection frequently result in severe misalignment problems for body parts, which degrade the quality of part representations. Accordingly, to deal with this problem, we propose a novel model named Convolutional Deformable Part Models (CDPM). CDPM works by decoupling the complex part alignment procedure into two easier steps: first, a vertical alignment step detects each body part in the vertical direction, with the help of a multi-task learning model; second, a horizontal refinement step based on attention suppresses the background information around each detected body part. Since these two steps are performed orthogonally and sequentially, the difficulty of part alignment is significantly reduced. In the testing stage, CDPM is able to accurately align flexible body parts without any need for outside information. Extensive experimental results demonstrate the effectiveness of the proposed CDPM for part alignment. Most impressively, CDPM achieves state-of-the-art performance on three large-scale datasets: Market-1501, DukeMTMC-ReID, and CUHK03.

Eine psychosomatische Sprechstunde für die regionale betriebsnahe Versorgung

A psychosomatic consultation for regional health care in the workplace – evaluation and recommendations Goal: The study’s goal was the qualitative evaluation of a new variant of the mental health intervention “psychosomatic consultation in the workplace” from the perspective of participating firms and individuals. Methods: The study data encompassed group discussions with workplace actors based on open-ended interview questions about their experiences with the intervention and narrative interviews with individual participants. This material was augmented by problem-oriented expert interviews with psychotherapists and company medical officers and by descriptive statistics of the individuals participating in the consultation. Results: All the firms implemented the consultation in response to perceived high rates of sick leave caused by mental health problems and due to a lack of confidence in how to deal with the employees concerned. The advantages of the consultation are seen to lie in its easily accessible and timely provision of professional assistance (psychoeducation, short interventions, coaching in difficult life situations and referral to other parts of the medical system) and in its flexibility in implementation. The consultation is adaptable to firms’ varying expectations and needs and increases the confidence of workplace actors (especially top management, personnel management, company medical officers and employee representatives) in dealing with mental health problems. Conclusions: The consultation proved to be a flexible, practicable and beneficial part of primary, secondary and tertiary prevention measures in the workplace. It can have positive effects on the preventive behaviour of individual participants. It is recommended that such programmes should be coupled with additional health-promotion services inside and outside the company in the future. Employees should be able to choose between using the consultation either anonymously or non-anonymously in consultation with a trusted colleague or company medical officer. Some form of (anonymous) feedback to company management on the findings of the consultation in relation to systemic sources of psychological distress is also recommended for the purpose of introducing suitable preventive measures. Keywords: psychosomatic consultation in the workplace (PSIB) – mental health – intervention – occupational medicine

Analysis of Influence of a Crane Flexible Supports, Link Flexibility, and Joint Friction on Vibration Associated with Programmed Motion Execution

BackgroundThe paper presents vibration analysis of dynamic models of systems with flexible mechanical components, friction modeled and subjected to position and kinematic programmed constraints, which can be imposed as control goals, work or service task demands.MethodsThe constrained dynamics is derived using an automated computational procedure dedicated to constrained systems. The procedure was successfully implemented to rigid system models. A class of systems composed of flexible parts and subjected to programmed motions is considered in the paper. Their motion analysis has to be accompanied by vibration inspection. The novelty of the presented approach is in the possibility of analyzing system motions and vibrations that can be induced by the presence of programmed constraints.ConclusionsThe constrained motion is examined by the example of a crane model equipped with a flexible link, e.g. a jib, friction modeled in its joints and subjected to programmed constraints. The example delivers a realistic work situation, in which the crane carries loads and moves according to the programmed constraint put on motion.

Random coil chemical shifts for serine, threonine and tyrosine phosphorylation over a broad pH range

Phosphorylation is one of the main regulators of cellular signaling typically occurring in flexible parts of folded proteins and in intrinsically disordered regions. It can have distinct effects on the chemical environment as well as on the structural properties near the modification site. Secondary chemical shift analysis is the main NMR method for detection of transiently formed secondary structure in intrinsically disordered proteins (IDPs) and the reliability of the analysis depends on an appropriate choice of random coil model. Random coil chemical shifts and sequence correction factors were previously determined for an Ac-QQXQQ-NH2-peptide series with X being any of the 20 common amino acids. However, a matching dataset on the phosphorylated states has so far only been incompletely determined or determined only at a single pH value. Here we extend the database by the addition of the random coil chemical shifts of the phosphorylated states of serine, threonine and tyrosine measured over a range of pH values covering the pKas of the phosphates and at several temperatures (www.bio.ku.dk/sbinlab/randomcoil). The combined results allow for accurate random coil chemical shift determination of phosphorylated regions at any pH and temperature, minimizing systematic biases of the secondary chemical shifts. Comparison of chemical shifts using random coil sets with and without inclusion of the phosphoryl group, revealed under/over estimations of helicity of up to 33%. The expanded set of random coil values will improve the reliability in detection and quantification of transient secondary structure in phosphorylation-modified IDPs.

Influence of the Spatial Conformation of Charged Ligands on the Optical Properties of Gold Nanoclusters

Photoluminescent gold nanoclusters (Au NCs) were synthesized in one step in aqueous conditions using a mixture of glutathione and (mono or multivalent) glutathione-modified arginine peptides. By controlling the ratio of coligands, we investigated how the multivalency and the amount of arginines influenced the growth of Au NCs, their surface chemistry, their colloidal stability, and their optical properties. We demonstrated using two-dimensional nuclear magnetic resonance spectroscopy that the organization of the ligand on the Au surface was composed by an inner rigid layer and an outer flexible part via inter- and/or intraligand spatial proximity. This directly impacted the structure of the Au NCs, as confirmed by gel electrophoresis, high-resolution transmission electron microscopy, diffusion-ordered spectroscopy, and mass spectrometry. Increasing arginine content also induced an increase of positive surface charge and an enhancement of the near infrared emission intensity at ∼670 nm with quantum yield u...

Analysis of harmonic gearbox tooth contact pressure

An analysis of a conventional gear wheel shot with MPK methodology has been processed by many authors before. Harmonic gearbox systems are composed of rigid and flexible parts through which the torque is transmitted, thus generating power. The contact pressure is specifically distributed through more teeth whilst against conventional gearbox systems. Firstly, a design description of a dynamic calculation model of a harmonic gearbox system in the planar strain is analysed in this article, as well as the definition of each contact constraint between the rigid and flexible parts of these gear systems in respect of “GLUE” and “TOUCHING” contact types. The last part of this article deals with the force distribution analysis in the teeth with respect to the frictional forces in them. The graphical conclusions of this pressure on each tooth were made. This article mainly focuses on the analysis of the stress in a gear tooth of the harmonic gearbox systems, as well as the research of a special trajectory of the rigid and flexible entity in a solid circular spline of such gear systems.

Dynamic analysis of a simplified flexible manipulator with interval joint clearances and random material properties

Flexible manipulator is an emerging technique in aerospace engineering, especially in the assembly, testing and maintenance of space stations. Dynamic analysis of a flexible manipulator with multiple clearance joints and hybrid uncertainties is a great challenge as compared to traditional flexible manipulator. To solve the problem, a dynamics model for a simplified flexible manipulator with interval clearance joints and random material properties was established. In this model, the Lankarani–Nikravesh contact force model was used to construct the clearance joint, while a combined feedforward–feedback control strategy based on a PID controller was applied to control the flexible manipulator. In addition, the clearance sizes and the Young’s moduli of the flexible parts were described by interval variables and random fields, respectively. To solve the dynamics model, a general methodology, based on the Karhunen–Loeve expansion and Kriging model, was presented. Finally, numerical examples were employed to demonstrate the validity of the proposed approach. The simulation results indicate that the joint clearance, the flexibility of the components and the uncertainties have great impacts on the kinematic accuracy and dynamic behaviors of the flexible manipulator, while hybrid uncertainties result in worse kinematic accuracy and more complex dynamic behaviors.

Geoconservação em áreas protegidas

Este trabalho traz informações referentes aos cursos para monitores ambientais realizados em unidades de conservação no litoral norte do estado de São Paulo. A efetivação destes cursos, intitulados “Introdução às Geociências”, foi motivada pela carência de explicações acerca dos aspectos relacionados à formação da paisagem, durante a participação em trabalhos de campo na região. Os cursos têm carga horária de 16 horas e compreendem módulos referentes a Tempo geológico, Ciclo das rochas, Estrutura interna da Terra e Tectônica de placas, bem como de aspectos da história geológica da região. Além dos módulos teóricos, foram realizadas atividades práticas e saídas de campo para as trilhas mais visitadas em cada unidade de conservação. Ao final dos cursos, os alunos responderam a questionários sobre perfil individual e conteúdos apreendidos. Os resultados mostram alto grau de envolvimento dos alunos com o tema, indicando clara disposição dos monitores em transmitir as informações recebidas a futuros visitantes destes parques.

Straightening of Relatively Flexible Cylindrical Parts. Part II. Stress State of the Cylinder Workpiece in Transverse Rolling between Flat Plates

The intended form of relatively flexible cylindrical parts (shafts and axles) may be restored by straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. It is well known that the nonequilibrium stresses are generated in the whole workpiece after straightening by transverse flexure, and the part is eventually deformed again. Therefore, the workpieces should be additionally straightened with surface plastic deformation after straightening by flexure. We use transverse rolling by flat plates for that purpose. The aim in the present work is to determine the capture conditions and the stress state of the workpiece in transverse rolling of cylindrical parts between flat plates. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. A new method is proposed for control of stress state in straightening of cylinderical workpieces. The limiting capture angle α ranging 2–8 degrees and the maximum absolute reduction depending on friction coefficient and on the diameter of workpiece are obtained. The optimum reduction varies ΔH = 0.07–0.15 mm. The calculation data show that the stress state of uniform extension occurs at the center in the workpiece cross section after transverse rolling, and the stress state of reduction is formed at the peripheral areas of the workpiece. The straightening method of transverse rolling between flat plates eliminates crack formation and destruction of the material in the central area of the cylindrical parts.

Experience in application of hybrid contact lenses for astigmatism correction

The review covers the issue of hybrid contact lenses application as one of the modern contact correction methods in patients with ametropias of various genesis. Hybrid contact lenses consist of a rigid central optical part made of highly gas-permeable material and a flexible peripheral part made of hydrophilic material. These lenses combine the optical correction qualities of gas-permeable corneal lenses with the comfort and stable fit usually provided by soft contact lenses. Compared to gas-permeable corneal lenses, hybrid lenses are more comfortable; often have better centration and more stable fit on the eye. Hybrid contact lenses successfully correct both types of astigmatism: regular and irregular. This type of lenses is a good alternative method of contact correction for patients who place heavy demands in terms of the quality of vision.

A methodology for modeling and simulating frictional translational clearance joint in multibody systems including a flexible slider part

The objective of this paper is to present a simple and effective methodology for modeling and simulating frictional translational clearance joint in planar multibody systems including a flexible slider part. By using the finite element method (FEM), the slider is divided into finite elements, and the distributed body forces and boundary stresses (contact forces) on the slider are equivalent to the nodal forces. The normal contact forces are described by a nonlinear viscoelastic contact force model, while the frictional forces are evaluated by the Coulomb dry friction model. By lumping the mass matrix and presenting it in diagonal form, the equations of motion are then inertially decoupled, and the frictional forces are solved independently via trial-and-error algorithm. A penalty method for the revolute joint connecting the slider and other bodies is applied, and equations of motion are integrated numerically. Finally, two numerical examples are given to test the feasibility and effectiveness of the methodology in this paper.

Extrinsic calibration and kinematic modelling of a laser line triangulation sensor integrated in an intelligent fixture with 3 degrees of freedom

This article presents the kinematic modelling for the extrinsic calibration of a laser line profile sensor integrated in an intelligent fixture. It aims to characterize the real 3D shape of flexible parts when they are clamped to ensure suitable stiffness for machining processes, aiding to define the machining path to improve the precision of the process. This tool consists of two linear axes and a rotary axis (3 DOF) which enables scanning the area of the part to be processed automatically. In order to carry out the accuracy evaluation of the intelligent fixture, some methods present in the state of the art have been considered and compared. Moreover, in order to design and identify the most suitable calibration procedure a previous simulation process is carried out based on sensitivity analysis. To complete the study, a test piece has been scanned with the intelligent fixture and compared with an external metrological frame employed as a ground truth. In addition, a characterization of the geometric performance of the fixture's linear actuators is carried out to check the geometric performance and its influence on the extrinsic calibration process accuracy. The results of this article show the importance of performing simulation processes in order to define the best measurement scenario for extrinsic calibration. Besides, it demonstrates the influence of the method used to perform extrinsic calibration in order to obtain good precision in the measures, where the geometric performance of the drives have a decisive influence.

Assembly variation analysis of the aircraft panel in multi-stage assembly process with N-2-1 locating scheme

The flexible aircraft panel parts are easy to deform during the assembly process, the deformation can directly affect the assembly accuracy of the aircraft panel, and further affect the assembly quality of the aircraft fuselage. In order to evaluate the assembly accuracy of the aircraft panel in multi-stage assembly process with N-2-1 locating scheme, this paper proposes an assembly variation analyzing approach, considering the effect of the contact force between the panel skin and the fixture components on the deformation of the panel in the assembly process. The mathematical models are established to conclude the contact force between the panel skin and the fixture components in multi-stage assembly process of the panel with N-2-1 locating scheme, and the effect of the contact force between the skin and the fixture components on the deformation of the panel in assembly is investigated. An assembly variation model is built for the aircraft panel considering the variation sources including the manufacturing error of the flexible panel parts, fixture error, and the deformation of the panel in multi-stage assembly process considering the effect of the contact force. Finally, the proposed assembly variation analyzing approach for the aircraft panel is tested with a case study.

Dynamic modeling and chatter analysis of a spindle-workpiece-tailstock system for the turning of flexible parts

Chatter happens frequently in turning of flexible parts, jeopardizing the dynamic stability of the operation. The chatter stability prediction is dependent on the accurate estimation of the structural parameters of the cutting system. This paper aims to quantify the influence of the support conditions on dynamics of the flexible parts in straight turning. Given the time-varying cutting tool position during machining, first, the chatter stability of the cutting system along the cutting path is analyzed, and the critical stiffness expression for chatter onset prediction is deduced. Then, two models of the spindle-workpiece-tailstock system using analytical and numerical methods are constructed and compared. The simulation results showed that increasing the spindle bearing or tailstock support stiffness cannot effectively improve the stiffness distribution and the eigenfrequency of the machined rod, whereas the frequency of the system tends to be increased evidently with the chuck size decreased. In comparison with the experimental results, it has been shown that the model involving the effect of spindle bearing and center support enables to produce more accurate modal parameters estimation and chatter onset location prediction than the simplified model. Besides, the measured displacement signals demonstrate a good mapping relation with the theoretical analysis results. The present study could provide an in-depth understanding of the dynamic behavior of flexible workpieces in turning operations.

Seismic Retrofit of an Industrial Building Using Damping Devices

The prefabricated industrial buildings, similar to the one presented in this paper, featured a high seismic vulnerability during the 2012 Emilia earthquake (Italy). The main structural deficiencies were a consequence of the lack of connection between columns, beams and roof elements. The case study presented in this paper is an industrial building composed of two structural units with different initial stiffness. The strengthening approach was different for the two parts. The stiffer part was equipped with Buckling Restrained Braced Frames (BRBF), thus adding stiffness and energy dissipation. The more flexible part was decoupled from the rest of the building and fluid viscous dampers were installed in the joint between the two structural units. The relative movement between the two parts can activate the damping devices, which dissipate part of the input seismic energy, hence a structural weakness is turned into a positive resource for energy dissipation.

The fixtureless inspection of flexible parts based on semi-geodesic distance

Some types of manufactured parts like sheet metals and skins often have a significantly different shape in a free-state position compared to their state-of-use position (as defined by their nominal CAD models) due to a combination of gravity and/or the residual effects of stress. Traditionally known as flexible (nonrigid compliant) parts, these dedicated fixtures are used for inspection operations in order to maintain flexible parts from a free-state position to a state-of-use position. This paper introduces a new automatic defect identification method primarily intended for two less-investigated manufacturing defect types: contour profile errors and hole localization. By combining simple techniques such as mesh boundary detection, fast boundary-based correspondence searches and accurate fast marching on triangulated meshes, the semi-geodesic distances from each boundary vertex on the acquired SCAN mesh to all the other boundary vertices is calculated, stored in a table and then compared to the corresponding values on the part's nominal CAD mesh. The comparisons found in the tables result in an estimation of the location and amplitude of the two aforementioned defect types. Compared to other work in this field, the overall approach does not rely on any mesh registration or finite-element analysis with tedious boundary conditions setup. It is also relatively fast. A fast algorithm/app based on this method was named the AFDA (Automatic Free-state Defect Approximation) and was validated against case studies in the aerospace sector. The results reflect the utility and effectiveness of the proposed approach.

Volume-aware design of composite molds

We propose a novel technique for the automatic design of molds to cast highly complex shapes. The technique generates composite, two-piece molds. Each mold piece is made up of a hard plastic shell and a flexible silicone part. Thanks to the thin, soft, and smartly shaped silicone part, which is kept in place by a hard plastic shell, we can cast objects of unprecedented complexity. An innovative algorithm based on a volumetric analysis defines the layout of the internal cuts in the silicone mold part. Our approach can robustly handle thin protruding features and intertwined topologies that have caused previous methods to fail. We compare our results with state of the art techniques, and we demonstrate the casting of shapes with extremely complex geometry.

Straightening of Relatively Flexible Cylindrical Parts. Part I. Establishing the Loading Conditions in Transverse Straightening

Relatively flexible cylindrical parts (shafts and axles) may be straightened by loads produced by different stresses in different distributions. A promising method is straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. The goal in the present work is to determine the stress state of the workpiece in transverse straightening so as to select the best type of load and treatment conditions. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. Effective methods of loading in the transverse straightening of cylindrical parts are determined. Analytical calculations yield the residual stress corresponding to straightening of the cylindrical parts. The residual stress required for straightening depends on the initial flexure, the material in the workpiece, and its size. The stress state of cylindrical parts is determined for different types of transverse loading. The flexural stress for straightening of a shaft under a distributed load is less than the stress due to a transverse force. To straighten a rod (diameter 10 mm, length 200 mm) with initial flexure 0.5 mm, flexural stress of about 370 MPa must be created. In the transverse straightening of cylindrical parts, flexure under the action of a distributed load is an effective loading method. Limiting flexural coefficients of 5.3–5.5 are obtained for all values of the shaft rigidity in straightening by transverse flexure under a distributed load when l/L = 0.8. The proposed mathematical model correctly determines the residual stress corresponding to straightening of the cylindrical parts. The formula derived for calculating the total flexure and determining the effective load may be recommended for practical use in production conditions so as a ensure precise straightening of relatively flexible parts such as shafts.

Bi-objective Optimization Model for Integrated Preventive Maintenance and Flexible Job-shop Scheduling Problem

This paper develops an integrated model for flexible job-shop scheduling problem with the maintenance activities. Reliability models are used to perform the maintenance activities. This model involves two objectives: minimization of the maximum completion time for flexible job-shop production part and minimization of system unavailability for the PM (preventive maintenance) part. To aim the objectives, two decisions must be taken at the same time: assigning n jobs on m machines in order to minimize the maximum completion time and finding the appropriate times to perform PM activities to minimize the system unavailability. These objectives are obtained with considering dependent machine setup times for operations and release times for jobs. In advance, the maintenance activity numbers and PM intervals are not fixed. Two multi objective optimization methods are compared to find the pareto-optimal front in the flexible job-shop problem case. Promising the obtained results, a benchmark with a large number of test instances is employed.