Clamping Position Research Articles

Software assisted clamping point classification and position optimization for the efficient flexibilization of carbody fixtures using mathematical geometry-based search algorithms

The Fraunhofer IWU has been developed specialized clamping robots for production of different car-models on one fixture. One of the challenges with universal clamping of different components is the contact point between part and clamping device. For the optimization of the clamping contours, a software was developed with which the geometries of the clamping points can be automatically analyzed and classified. With target search criteria, the clamping position on the component can be changed so that the clamping contours are geometrically simplified. Thus, a huge reduction in the complexity of the flexible clamping device is possible.

Animal welfare evaluation at slaughterhouses for pigs at the “Eje Cafetero” region in Colombia

Within the insensitization by electronarcosis and the bleeding processes performed at the pig's slaughterhouses, there are some factors that hinder the achievement of an adequate slaughter of these animals, being this a critical phase in which animal welfare must be guaranteed; the objective of this study was to evaluate and compare the efficiency of insensitization by electronarcosis and two types of bleeding direction (horizontal and vertical). Dependent variables were measured as indicators of animal welfare (absence of the corneal reflex, absence of reflex of sensitivity to painful stimuli, attempts to reinstatement or posture recovery and vocalization), after the stunning and bleeding process, in four slaughterhouses of national category in “Eje Cafetero”, Colombia. The methodological approach included the binomial distribution, descriptive statistics, hypothesis testing and statistical significance. The results show that the efficiency of the insensitization procedures and type of bleeding direction depends on multiple aspects, including the tranquility of the animals during their handling, the correct position of the insensitization clamps, the amperage used and the time between insensitization and bleeding. In this way, the analysis of possible preventive and/or corrective measures includes: Continuous training and supervision of the personnel in charge of carrying out the procedures, the need to immobilize pigs prior to their insensitization process, the continuous monitoring of process variables and the appropriate vascular cutting that ensures animal's death prior to their entrance into the scalding machine.

Extended equipartition in a mechanical system subject to a heat flow: the case of localised dissipation

Statistical physics in equilibrium grants us one of its most powerful tools: the equipartition principle. It states that the degrees of freedom of a mechanical system act as a thermometer: temperature is equal to the mean variance of their oscillations divided by their stiffness. However, when a non-equilibrium state is considered, this principle is no longer valid. In our experiment, we study the fluctuations of a micro-cantilever subject to a strong heat flow, which creates a highly non-uniform local temperature. We measure independently the temperature profile of the object and the temperature yielded from the mechanical thermometers, thus testing the validity of the equipartition principle out of equilibrium. We demonstrate how the fluctuations of the most energetic degrees of freedom are equivalent to the temperature at the base of the cantilever, even when the average temperature is several hundreds of degrees higher. We then present a model based on the localised mechanical dissipation in the system to account for our results, which correspond to mechanical losses localised at the clamping position.

An Intelligent Approach for Contact Pressure Optimization of PEM Fuel Cell Gas Diffusion Layers

The compression of the gas diffusion layer (GDL) greatly affects the electrochemical performance of proton exchange membrane fuel cells (PEMFCs) by means of both the equivalent value and distribution of contact pressure, which depends on the packing manner of the fuel cell. This work develops an intelligent approach for improving the uniformity and equivalent magnitude of contact pressure on GDLs through optimizing the clamping forces and positions on end plates. A finite element (FE) model of a full-size single fuel cell is developed and correlated against a direct measurement of pressure between the GDL and a bipolar plate. Datasets generated by FE simulations based on the optimal Latin hypercube design are used as a driving force for the training of a radial basis function neural network, so-called the agent model. Once the agent model is validated, iterations for optimization of contact pressure on GDLs are carried out without using the complicated physical model anymore. Optimal design of clamping force and position combination is achieved in terms of better contact pressure, with the designed equivalent magnitude and more uniform distribution. Results indicate the proposed agent-based intelligent optimization approach is available for the packing design of fuel cells, stacks in particular, with significantly higher efficiency.

Analysis and control of welding deformation for CFETR vacuum vessel PS2

Abstract The large scaled vacuum vessel (VV) of CFETR is designed as a water-cooled, double-walled structure with a D-shaped poloidal cross-section. One sub-sector of VV contains four poloidal segments (PS) assembled by welding. Because of the large size of the VV, the distortion caused by welding will make the assembling difficult. Controlling the deformation during the welding process is a significant technological challenge. This article gives the analysis of the deformation of the component during the welding process, the optimization of the welding process and the design of the welding tooling and clamping positions firstly. Based on the inherent strain theory, the welding deformation analysis of the five different welding sequences of PS2 is performed, and the corresponding welding tooling and clamping positions are designed in accordance with the deformation results. The methods provide highly valuable information for the actual processing, and the welding deformation of PS2 in the actual production has been well controlled, all of which are within the tolerance requirements.

Investigation on the application and retention of intravenous infusion tools in hospitalized children

Objective To investigate the use of different tools of intravenous infusion and the issues associated with intravenous catheter indwelling in hospitalized children and to provide reference for clinical practices. Methods Using the convenient sampling method, from July 24th to 31st, 2018, the intravenous infusion treatment of children inpatients in 49 hospitals within the Beijing Children's Hospital Medical Association was selected for investigation. A self-designed Cross-sectional Questionnaire for Children's Intravenous Infusion and a photo of an intravenous infusion tool were used for data collection. Statistical analysis was performed using SPSS 17.0 software. Results During the data collection period, there were 18 316 hospitalized children in the 49 hospitals, among which there were 14 421 cases of infusions, with the infusions rate of 78.73%. The application rate of indwelling needle was 87.94%. The connector of venous catheter was mainly heparin cap connection (64.23%) . The infusion tools used in 6 398 cases (44.37%) were made by PVC and containing 2-ethyl hexyl phthalate (DEHP) . Aseptic transparent dressing was the main dressing choice. During catheter indwelling, there were some problems such as back-blood in the pipeline or infusion joint, incorrect clamping position of small clips, unclamping, and tube detachment. Indwelling needles had more problems than central venous catheters, including old blood returning in the tube and blood returning in the infusion connector. The difference between the peripheral indwelling needle and the central catheter was statistically significant (P<0.05) . Conclusions The rate of intravenous infusion in hospitalized children is relatively high. Although there are various types of intravenous infusion tools, the choice of infusion tools for children was mainly indwelling needle and heparin cap connection, and there were still room for improvement in catheter maintenance. Key words: Children; Intravenous infusion; Tool; Indwelling; Investigation

Compliant assembly deviation analysis of large-scale thin-walled structures in different clamping schemes via ANCF

PurposeThe structure stiffness is greatly affected by the fixture constraints during assembly due to the flexibility of large-scale thin-walled structures. The compliant deformation of structures is usually not consistent for the non-uniform stiffness in various clamping schemes. The purpose of this paper is to investigate the correlation between the assembly quality and the clamping schemes of structures with various initial deviations and geometrical parameters, which is based on the proposed irregular quadrilateral plate element via absolute nodal coordinate formulation (ANCF).Design/methodology/approachTwo typical clamping schemes are specified for the large-scale thin-walled structures. Two typical deviation modes are defined in both free and clamping states in the corresponding clamping schemes. The new irregular quadrilateral plate element via ANCF is validated to analyze the compliant deformation of assembled structures. The quasi-static force equilibrium equations are extended considering the factors of clamping constraints and geometric deviations.FindingsThe initial deviations and geometrical parameters strongly affect the assembly deviations of structures in two clamping schemes. The variation tendencies of assembly deviations are demonstrated in details with the circumferential clamping position and axial clamping position in two clamping schemes, providing guidance to optimize the fixture configuration. The assembly quality of structures with deviations can be improved by configuration synthesis of the clamping schemes.Originality/valueTypical over-constraint clamping schemes and deviation modes in clamping states are defined for large-scale thin-walled structures. The plate element via ANCF is extended to analyze the assembly deviations of thin-walled structures in various clamping schemes. Based on the proposed theoretical model, the effects of clamping schemes and initial deviations on the deformation and assembly deviation propagation of structures are investigated.

Experimental and numerical investigation of fixture time on distortion of welded part

In this paper, the effect of clamping time on welding distortion is studied. The welding process has been done in austenitic stainless steel 304L butt-welded joint by TIG welding method. The numerical thermo-mechanical analysis is performed using commercial finite element software ABAQUS. The welding simulation is performed using the birth and death of elements technique. The heat source model that used in this study is the Goldak double-ellipsoidal model. At last, for verifying numerical results, a set of experimental tests have been carried out and welding distortion has been measured. The experimental measured data are compared with numerical (FEM) results. The results showed that the clamping causes change in direction of bending and angular distortions (opposite of without clamping mode). Any increase in clamping time relatively causes a decrease in angular and bending distortions. A 70% reduction of angular and bending distortions were observed in cold release mode (unclamping after the workpiece has cooled down to room temperature) compared with hot release mode (an immediate unclamping after welding). The position of clamping has a significant effect on distortion reduction as well. If clamping position is moved closer to the weld line, the distortion is decreased. By reducing relative clamping distance of 60 to 20 mm, the angular distortion is reduced to 0.15 mm which is about 25% and bending distortion of 0.6 mm (40%) can be achieved. The angular and bending distortions are increased when the sheet width is reduced during the experiments. It should be noted that the measured results of experiments and numerical method are in a relatively good agreement and the amount of error is within the acceptable limits.

Numerical and experimental investigation of bulk stress distribution in edge under different clamping sequence

PurposeThe edge is a typical aero-structural compliant part, whose length-width ratio is about 60:1 and height-thickness ratio is about 30:1. Distortion of the edge is mainly caused by the bulk stresses which come from the manufacturing process of the plates. This paper aims to investigate the effect of clamping sequence on the bulk stress distribution in the edge.Design/methodology/approachThe paper conducts the numerical and experimental investigations to predict the bulk stress distribution in the edge under different clamping sequences. A finite element model of the plate with residual stress after quenching and stretching is constructed. The edge is milled from the plate numerically and is ready for clamping. The contact model between the clamper and the edge is constructed to simulate the clamping process. Then the edge is virtually clamped in different clamping sequences, and different deformations and bulk stresses are obtained. An experimental edge milled from the plate and a designed clamping platform are used to precisely control clamping force to verify the effect of clamping sequence on the bulk stress distribution in the edge. The experimental edge’s distortions, relative displacements between the edge and the clamper and clamping forces validate the proposed numerical model.FindingsThe primary cause of bulk stress redistribution is the friction between the rigid clamper and the compliant edge. The edge exhibits different deformation under different clamping sequences because of its compliant characteristics.Originality/valueThe proposed numerical model of the edge could predict the bulk stress distribution in the edge under different clamping sequence. The developed clamping platform could be used to conduct clamping experiments, including experiments with different clamping forces, sequences and different clamping positions. It will help to systematically improve the compliant assembling efficiency in civil aircraft industry.

Predicting Path Inaccuracies in Robot-based Machining Operations Using Inverse Kinematics

Machine tools are dominating the machining sector because of their high reliability in process accuracy. On the other hand, industrial robots provide an opportunity for use in applications with fewer process requirements. They offer a high cost-benefit ratio in comparison to conventional machine tools, due to their low investment costs and high flexibility. Low absolute accuracy, low structural stiffness as well as missing consistent process planning tools – designed for industrial robots – prevent an industrial breakthrough. In particular, process planning tools provide a lot of potential for compensating process inaccuracies. This paper presents an approach for predicting path inaccuracies of machining operations using industrial robots. Using the inverse kinematics, rotatory axes’ progressions are calculated for predicting critical switching movements that could lead to high path deviations. On this basis, process parameters like the clamping position or motion strategies will be optimized in order to reduce the number of switching points.

Analysis of Adaptive Clamping Force of Fixture Based on Finite Element Method

The deformation of the workpiece under the action of clamping force is an important factor that affects the machining accuracy in the machining process. In order to deal with the deformation of such workpiece, the research of machining deformation under the adaptive clamping force of intelligent fixture was carried out based on genetic algorithm and finite element analysis method, and the synchronization and optimization of fixture layout and clamping force were realized. The optimum clamping force of each key clamping position of the fixture is calculated by MATLAB, and the adaptive clamping force optimization design model is established to solve the clamping force curve. Under the same fixture layout, the constant clamping force and the adaptive clamping force are used respectively as the simulation boundary conditions, and the simulation model of the workpiece milling is established. The stress values and deformation after the workpiece are processed under the two clamping forces. The results show that the stress value and the processing deformation under the adaptive clamping force are both smaller, which verifies the validity of the research method.

The C.L.A.M.P. Nephrometry score: A system for preoperative assessment of laparoscopic partial nephrectomy with Segmental Renal Artery Clamping

Laparoscopic partial nephrectomy with segmental renal artery clamping is associated with a less warm ischemic injury and better postoperative affected renal function compared with main renal artery clamping. However, its indication remains unclear. We established a standardized nephrometry scoring system (The C.L.A.M.P. Nephrometry Score) to evaluate its flexibility in preoperative assessment. This scoring system based on 5 components. The ranking (C)oefficient of each score and the (L)ocation of the clamping position of the target artery and areas of the target artery entering the renal sinus: (A)nterior boundary, (M)ulti-boundary and (P)osterior boundary. We applied this system to analyze data from 106 consecutive patients who underwent SRAC during LPN and divided these patients into 3 groups based on their C.L.A.M.P. scores. The rate of conversion to main renal artery clamping and clamping success rate and the affected side GFR reduction showed significant differences among the groups (P < 0.001). However, parameters such as blood loss, Warm ischemia time and postoperative hospitalization were not significantly different. The C.L.A.M.P. nephrometry score shows strong ability in distinguishing different complexities of artery characteristics and plays a promising role in identifying patients who are suitable for the SRAC technique.

Oxidation and erosion resistance of multi-layer SiC nanowires reinforced SiC coating prepared by CVD on C/C composites in static and aerodynamic oxidation environments

A multi-layer SiC nanowires reinforced SiC (SiCnws-SiC) coating was prepared in-situ on carbon/carbon (C/C) composites by three chemical vapor deposition (CVD) processes. The microstructure and phase composition of the nanowires fabricated on the first-layer SiCnws-SiC coating and the coatings were examined by SEM, TEM, and XRD. The bamboo-like SiC nanowires with a 50 nm diameter and a length of several tens of micrometers are straight, randomly orientated and distributed like a net on the first-layer SiCnws-SiC coating. The growth direction is [111], and the growth mechanism is VS. The multi-layer SiCnws-SiC coating has three layers: the thickness of the first-layer is roughly 400 µm, and the outer two layers are about 200 µm. Each layer has a sandwich structure. The isothermal oxidation and erosion resistance of the multi-layer SiCnws-SiC coating were investigated in an electrical furnace and a high temperature wind tunnel. The results indicated that the weight loss of the multi-layer SiCnws-SiC coated C/C composites was only 1.8% after oxidation in static air at 1773 K for 361 h. Further, the coated sample failed due to fracture of the coating at the clamping position (i.e. 80 mm) after erosion at 1873 K for 130 h in the wind tunnel. The weight loss of the coated C/C composites occurred due to the formation of penetrating cracks in the coating during the oxidation thermal shock. The maximum bending moment and the larger clamping force caused the coating fracture and resulted in intense oxidation of the substrate and the failure of the specimen.

A Novel Method for Modeling the Electromagnetic Characteristics of Switched Reluctance Motors

Accurate measurement and determination of the electromagnetic characteristics of the switched reluctance motor (SRM) are indispensable to their advanced control and performance analysis. This paper proposes a novel method for modeling the flux-linkage characteristics of SRM. This strategy without rotor locking, includes three steps, namely measuring, estimating and calculating steps. In the first step, flux linkage curves with current at four equilibrium positions are obtained by an indirect measurement method. In the second step, the flux-linkage characteristic of SRM in the middle position is estimated by its two adjacent flux-linkage curves. In the third step, a decoupled analytical model based on the five-order Fourier series is developed to construct the entire flux-linkage characteristics. The proposed method can not only eliminate the requirements on rotor clamping devices or position sensors, but also achieve fast and accurate modeling for the electromagnetic characteristics of SRM. Comparative studies are carried out between the proposed method and the conventional rotor clamping method, and the results demonstrate that the proposed method has a good agreement with the conventional rotor clamping method. Moreover, the simulation model is established in MATLAB/Simulink software based on the entire electromagnetic characteristics calculated by the proposed method. The accuracy of the proposed method is further verified by comparing the simulation and experimental results under different operating modes of the SRM.

Parametric Analysis of Friction Stir Welding Process

In this paper a thermo- mechanical model is created for friction stir welding process using ANSYS APDL commands using FEA techniques is presented. Several characteristics of FSW are studied, including tool-work piece surface interaction, heat generation because of friction during the operating conditions of the FSW process, plastic deformation and plastic heat generation due to the non-linear nature of the materials used in finite element analysis. A nonlinear direct coupled-field analysis is performed, as thermal and mechanical behaviours during the friction stir welding process are mutually dependent and coupled together. ANSYS APDL macro is created in such a way that it can be used for multiple design variants and load parameters in order to perform the FSW study for multiple design variants. The proposed model is then utilised to carry out parametric studies to know the effect of various process parameters like welding speed, total rate of heat input and location of the clamping on the temperature distribution and residual stress in the work piece. With the data obtained from the simulated models, various observations are made by changing the input process parameters. A transient thermo mechanical analysis is performed using coupled field elements for different tool diameters and different sizes of the base plates that are to be welded using FSW.In this project FSW process is studied in various stages DWELL, PLUNGE and TRAVERSE by solving the finite element model in separate load cases. To avail the plastic heat bi-linear isotropic material properties are used. From the results obtained from this study, it is observed that the heat input, for making good welds, is mainly restricted and controlled by the lower bound of the temperature. Also it is found that keeping the clamping position closer to the weld is better in order to keep the peak residual stresses at a lower limit. Further, it is found that adopting nonlinear models resulted in a more realistic solution than the usage of linear models as a wide temperature range is used in the simulation process which is in general highly non-linear and wherein convergence becomes an important problem to be dealt with.

The clamping position optimization and deformation analysis for an antenna thin wall parts assembly with ASA, MIGA and PSO algorithm

In order to reduce the deformation and assembly error in an antenna thin wall parts assembly process, the assembly location or clamping positions need to be optimized. In this paper, the effect of clamping positions and clamping force on the thin wall parts deformation is analyzed considering the gravity by finite element simulation under different clamping force. The clamping positions are optimized with the Adaptive Simulated Annealing (ASA), Multi-Island Genetic Algorithm (MIGA) and Particle Swarm Optimization (PSO) algorithm by Isight software to reduce the deformation. Comparing with MIGA and PSO method, the results show that the clamping position optimization based on ASA exhibits the better results and superior than the MIGA and PSO no matter whether it has the effect of gravity. Simultaneously, through establishing the contact force model and contact deformation model, the nonlinear relationship between contact force, contact deformation and contact area is qualitatively analyzed, and the node deformation is calculated by theoretical formula. Comparing with those results, it is shown that the theoretical value matches well with the simulation results. Finally, some clamping scheme principles are proposed so that it provides a basis for reducing the deformation and assembly error of thin wall parts in future.

Effect of the cutter path and the workpiece clamping position on the stability of the robotic milling system

The milling robots have many advantages compared with the traditional numerical control machine, but the chatter phenomenon in the robotic milling obstructs its popularization. Therefore, the chatter problem in the planar milling by robot is discussed in the way of cutter path and clamping position to give directions for chatter suppression and quality improvement. Firstly, the dynamic behaviour of the robotic milling system is studied by the models of the chatter stability domain analysis, which include robot stiffness model and dynamic milling force model. The mode coupling effect is considered in chatter stability lobe diagram of robotic milling, which is different with the machine tool. Then, the robotic milling experiments are conducted at six different clamping positions relative to robot by two ways of cutter path. Based on the obtained modal parameters under the different milling conditions, the corresponding chatter stability lobe diagrams are plotted. By the comparative analysis about the experiment results, it is found that the surface quality of workpiece with the feed motion of milling tool along the Y-axis direction of robot world coordinate system is better than the X-axis direction and the chatter is more likely to occur in the down milling than in the up milling. Furthermore, a proper workpiece clamping position can availably prevent the chatter in the robotic milling. These conclusions can be references for designing a suitable machining scheme in the robotic milling to ensure the application of robot in the metal cutting.

Data-Reconstruction-Based Modeling of SRM With Few Flux-Linkage Samples From Torque-Balanced Measurement

This paper proposes a combined modeling method for switched reluctance machine (SRM) with few samples of flux linkage characteristics measured without rotor clamping devices and position sensors. The proposed method mainly consists of two steps, namely data reconstruction and characteristic description. In data reconstruction, the entire flux linkage characteristics are obtained by training support vector machine (SVM) with the measured few samples. The characteristics from the trained SVM are consistent well with those from the rotor-clamping measurement. In characteristic description, back-propagation neural network (BPNN) is adopted to describe the reconstructed flux linkage characteristics and calculated static torque characteristics. On this basis, the simulation model of the SRM prototype is built in MATLAB. The results from simulation under both motoring and generating mode are compared with those from experiments, and good agreements can be found, which prove the effectiveness of the proposed modeling method. To further demonstrate the accuracy and application of the entire flux linkage characteristics obtained from data reconstruction, BPNN is used again to build the mapping from flux linkage and phase current to rotor position for rotor position estimation, and some results are presented. The applicability of the proposed method to different SRM topologies is discussed as well.

Error analysis and assessment of unsteady forces acting on a flapping wing micro air vehicle: free flight versus wind-tunnel experimental methods

An accurate knowledge of the unsteady aerodynamic forces acting on a bio-inspired, flapping-wing micro air vehicle (FWMAV) is crucial in the design development and optimization cycle. Two different types of experimental approaches are often used: determination of forces from position data obtained from external optical tracking during free flight, or direct measurements of forces by attaching the FWMAV to a force transducer in a wind-tunnel. This study compares the quality of the forces obtained from both methods as applied to a 17.4 gram FWMAV capable of controlled flight. A comprehensive analysis of various error sources is performed. The effects of different factors, e.g., measurement errors, error propagation, numerical differentiation, filtering frequency selection, and structural eigenmode interference, are assessed. For the forces obtained from free flight experiments it is shown that a data acquisition frequency below 200 Hz and an accuracy in the position measurements lower than ± 0.2 mm may considerably hinder determination of the unsteady forces. In general, the force component parallel to the fuselage determined by the two methods compares well for identical flight conditions; however, a significant difference was observed for the forces along the stroke plane of the wings. This was found to originate from the restrictions applied by the clamp to the dynamic oscillations observed in free flight and from the structural resonance of the clamped FWMAV structure, which generates loads that cannot be distinguished from the external forces. Furthermore, the clamping position was found to have a pronounced influence on the eigenmodes of the structure, and this effect should be taken into account for accurate force measurements.

An integrated approach for optimal fixture layout design

Fixture layout optimization is a procedure to optimize position of locators and clamps in order to minimize specified objectives. Deformation of workpiece is a serious problem of concern while designing a fixture. Proper positioning of fixture elements is indispensable to achieve desired machining accuracy, better surface finish and high productivity. In this work, a novel methodology is proposed that incorporates full factorial design of experiments and statistical analysis. Furthermore, the stability of the workpiece is ensured prior to the prediction of objective function. The result of the proposed technique is compared with the results of the genetic algorithm–based optimization technique. A case study has been considered to evaluate the proposed methodology. The objective function determines maximum elastic deformation of the workpiece during the entire machining process. Finite element method is used to formulate the objective functions. The constraints are natural frequency of the workpiece–fixture system and reaction forces. Besides, artificial neural network–based model is developed to predict the elastic deformation of the workpiece–fixture system within the range of design parameters.