Clamped Parts Research Articles

Modeling and identification of clamping contact stiffness

The dynamics of thin-walled parts are highly affected by the clamping conditions. Clamping stiffness is a function of c lamping force and surface roughness profiles of the clamp and part. Since the surface profiles cannot be altered, estimating clamping stiffness as a function of the clamping force is essential to simulate vibrations of the machined thin-walled parts. This paper presents the modeling of clamping stiffness as a function of the applied clamping force and material properties. Surface profile parameters are estimated from the identified contact stiffnesses evaluated using the Finite Element (FE) model. The contact stiffnesses are either predicted directly from the proposed mechanics model of the part or estimated from the Fractal surface parameters. It is shown that an average clamping stiffness can be predicted from the Fractal surface parameters, or directly and more accurately from the static model of the clamped part.

A Review on Evaluating the Optimization of Fibre Reinforced Polymer for Compound/Repair Clamp on Leaked Piping System using Computational Simulation

Most industries around world depend on pipelines to transfer millions of gallons of flammable and non-flammable materials. However, this pipeline system has been affected by exposure, which may cause the entire system to fail due to corrosion-based issues. Repair clamps have been used to prevent total failure from happening in a continuous run. However, current design of repair clamp is consisting of metal whereby long usage on corroded pipe could be much more affected. The weight factor will be affecting the fluid flow and the structure of pipe when used in long run. Therefore, in this research, new design for the repair clamp will be done and the material will be change to fibre reinforced polymer (FRP). The new design with FRP will be undergo various stimulation on SolidWorks to compare the properties of clamp and the effect on the affected pipe. Since the FRP material properties has been proven to be more stronger and sustainable compare steel that has been using currently, it will be much more effective to use. As a result, the new design will be much more sustain than the old metal repair clamp. Since the new clamp is lightweight, the weight no longer will affect the corroded pipe internally and externally. Moreover, in this research some of the current repair clamp parts has been reduced and changed to compromise with the usage of the FRP.

Method of accumulation of preload loss of bolted joints due to rotational self-loosening caused by cyclic, transversal excitation

This paper presents a new method to experimentally characterize the rotational self-loosening behavior of bolted joints. Furthermore, a method to calculate the preload loss due to certain relative displacements of the clamped parts was developed. The method obtains all required calculation parameters from the experimental tests performed and neither needs further experimental determination of friction coefficients nor numerical simulations to predict the preload loss. The method accumulates the preload loss of load cycles. Thereby, it can be used to estimate the time a machine can operate until a critical amount of preload is lost. Non-linear dependencies of the preload loss to the displacement amplitude and the remaining preload are considered. The calculation method also applies to load cases with variable load amplitudes. This is validated experimentally.

FEATURES OF VIBRATION DAMPERS APPLICATION IN THE DESIGN OF VIBRATION-RESISTANT METAL CUTTING TOOLS

Dry and viscous friction is used as a damper of oscillation energy in the construction of metal-cutting tools. A mathematical model of a two-mass oscillatory scheme of the insert of an assembled milling cutter was developed and studied, one of the masses of which models the clamped part of the insert - a press connection with dry friction, and the other - the cantilever part, which is subject to self-oscillations that are possible in the process of metal cutting. The influence of dry friction in the press joint of the insert on the amplitude of resonant oscillations of the cutter and the part was analyzed. The possibility of reducing the magnitude of the cutter's self-oscillations is demonstrated by selecting the most suitable parameters for the press connection of inserts with the body of the assembled milling cutter. The influence of internal viscous friction in materials with a high level of energy damping on the amplitude of self-oscillations of the cutter was evaluated and the possibility of their use in the design of a vibration-resistant metal-cutting tool was considered.

Clinical application of parathyroid autofluorescence imaging in endoscopic thyroid surgery

Objective:To investigate the application value of near-infrared autofluorescence imaging in identifying and protecting parathyroid glands in endoscopic thyroid surgery. Methods:From May 2022 to February 2023, 158 patients who underwent endoscopic thyroid surgery in the Department of Thyroid and Breast Vascular Surgery of Guilin People's Hospital were selected. The endoscopic fluorescence camera system was used to monitor the parathyroid glands under autofluorescence during endoscopic thyroid surgery. A total of 214 pieces were collected, among which the first 15 cases that could not be preserved in situ during the operation needed to be autotransplanted or the tissue clamped parts that could not be clearly identified as parathyroid glands were sent to fast-frozen pathology to determine whether they were parathyroid glands. Results:Among the first 15 patients who could not be preserved in situ during the operation or whose anatomy could not be clearly defined, 23 parathyroid glands were detected by autofluorescence imaging, 21 parathyroid glands were confirmed by pathology, and 2 were adipose tissue, with an accuracy rate of 91.30%; 158 patients underwent surgery Blood calcium decreased 2 hours after operation compared with preoperative blood calcium（P<0.05）, decreased blood calcium 5 days after operation compared with preoperative blood calcium（P<0.01）, and increased slightly 5 days after the operation compared to blood calcium 2 hours after the operation, but the difference was not statistically significant（P>0.05）; while comparing parathyroid hormone（PTH）, PTH at 2 hours after operation decreased significantly compared with PTH before operation（P<0.01）, and PTH at 5 days after operation compared with PTH before operation PTH also decreased（P<0.01）, but increased compared with PTH 2 hours after operation（P=0.001）. Conclusion:In laparoscopic thyroid surgery, the application of near-infrared autofluorescence imaging technology can help surgeons quickly identify and protect parathyroid glands, and reduce the incidence of permanent hypoparathyroidism. Combining autofluorescence imaging, visual anatomy recognition under magnification of laparoscope, and intraoperative frozen pathological examination "trinity" method can improve the success rate of parathyroid gland recognition.

Design, Simulation and Optimization of PZT-5A Cantilever Piezoelectric Pressure Sensor

Aims: The main aim of this research work is:&#x0D; &#x0D; To design a mathematical model of the sensor and validate with the 3D model simulation of the sensor in COMSOL Multiphysics simulator and&#x0D; To optimize the sensor for maximizing its sensitivity.&#x0D; &#x0D; Study Design: In the methodology, we design and utilizePZT-5A piezoelectric in shear mode as the piezoelectric is attached on a cantilever structure. The various factors affecting the sensitivity of the sensor are investigated after validating the mathematical model with the simulated values.&#x0D; Place and Duration of Study: This study is done in the Department of Electronics and Communication Engineering, Rajiv Gandhi University, Arunachal Pradesh at COMSOL Simulation Laboratory during 2022 to 2023.&#x0D; Methodology: In this study, a cantilever structure is considered for the mechanical structure. The stress distribution on the structure is calculated for the applied pressure range from 0 to 1000 Pa. Later, the output voltage of the sensor is calculated. This mathematical model is validated with the COMSOL multiphysics simulator. The optimization of the sensor is done in mathematical tool with maximizing function after providing the conditions. &#x0D; Results: The maximum stress on the sensor structure occurred near the clamped part of the cantilever. The calculated and simulated output sensitivities of the PZT-5A piezoelectric based pressure sensor are-1.6021 mV/kPa and -1.046887 mV/kPa respectively.&#x0D; Conclusion: We conclude that the PZT-5A piezoelectric based pressure sensor has a linear output with negative gradient as the stress induced on the structure is tensile stress. The various parameters that affect the sensitivity of the sensor arefound to depend on the shape and size of the cantilever structure, Poisson’s ratio and Young’s modulus, piezoelectric voltage coefficient and piezoelectric material thickness.&#x0D; Future Scope: In future, this study can be extended by taking different shape and size of the cantilever. The different modes of piezoelectric and different materials may be another future scope of this study.

Structural Design of a Special Machine Tool for Internal Cylindrical Ultrasonic-Assisted Electrochemical Grinding.

During the process of internal cylindrical ultrasonic-assisted electrochemical grinding (ICUAECG), both the workpiece and the conductive grinding wheel are rotating, the machining space is closed and narrow, the electrolyte is difficult to spray into the machining area, and the insulation between the workpiece and the machine bed is challenging. According to the machining characteristics of ICUAECG, the structure of a special machine tool was designed to mitigate these problems. In particular, the rotation, electrolyte supply, electric connection, and insulation modes of the workpiece clamping parts were studied, yielding a novel workpiece clamping- and rotating-device design. This structure can fully use the internal space of the hollow spindle of the machine tool, effectively reduce the external moving parts, and achieve the appropriate liquid injection angle of the electrolyte. The ultrasonic vibration system and its installation mechanism, the dressing device of the conductive grinding wheel, and the electric grinding spindle-mounting and -fixing device were analyzed in detail. Then, a special machine tool for ICUAECG was designed, the operability and feasibility of which were verified by experiments involving conductive grinding wheel dressing and ICUAECG.

An accurate measuring method for the internal jaw stiffness of deformable silicon arms

The internal jaw stiffness of the silicon arm and its uniformity directly determine the geometric position of the clamped part, which in turn affects the geometric accuracy of the fusion target ball. The slight variation of the silicon arm jaw stiffness caused by machining errors is a crucial factor affecting the geometric accuracy of the micro-target. To accurately detect the variation of internal jaw stiffness caused by machining errors, this paper proposes a multi-point stiffness detection method combining micro-feed force application and high-precision image inspection. An experimental measurement device is also built to measure the jaw stiffness of the silicon arm sample. The proposed method, which can obtain the micro-deformation data of the internal jaws under small loads and accurately fit the stiffness, provides a new way to measure tiny, thin-walled, brittle cantilever beam structures.

Research on Developing of a Reconfigurable Gripping Mechanism with Electric Drive

Abstract The paper consists in analyzing some of the researches on specialized literature regarding to gripping systems and proposing a new solution for a gripping mechanism that can fulfill the increasing requirements imposed by the flexible manufacturing systems regarding the orientation and positioning of parts with variable shape and dimensions. Some general consideration on state of the art in the field of gripping mechanism are presented and main development direction are indicated. The second part of the paper contains in the development of new gripper constructive solution. From the literature analysis the main requirement for a gripping system is the multi-tasking ability. The proposed designed solution uses four parallel open-close jaws/fingers controlled by two electric motors. The actuation of the jaws/fingers for clamping the part is accomplished by a primary motor. The main contribution/improvement refers to the introducing of a second/supplementary motor that is used for the movement of the position of the jaws in order to transform the gripper clamping system from a four-jaw construction to a two-jaw gripper construction and vice versa, thus increasing range of clamped parts.

Design and Dynamic Simulation of a Novel Traveling Wave Linear Ultrasonic Motor

To overcome the problem of frequency consistency and simplify the design process of linear ultrasonic motor, a novel traveling wave linear ultrasonic motor with a ring-type stator is proposed in this paper. The combination of two orthogonal bending vibration modes with the same order is selected as the operating mode of the motor. A traveling wave along the side of the stator is utilized to drive the slider to move linearly. The stator adopts a ring symmetrical structure, which can effectively ensure that the resonance frequencies of the two vibration modes are consistent. Thus, we do not need to tune the frequencies of the two vibrations by constantly adjusting the shape of the stator or designing complex clamping parts to fix the stator without making any influence on the vibrations. Meanwhile, a three-dimensional finite element model of the motor is built. Using the model, we obtain the elliptical motion trajectories of the stator driving surface, the output performance of the motor, the sticking-slipping-separation contact characteristic between the stator and the slider and fabricate and measure a prototype of the proposed motor.

Analysis of Wedge Lock Washer using the Finite Element Method

Washers with a so-called wedge-locking effect are available for the engineering industry. The manufacturer assures, as confirmed by the Junker vibration test, that the tension in the thread increases when the screw is unscrewed. This is due to the appropriate geometry of the washers, which always work together in pairs. On the outside, the washers have serrations which, when tightening the screw, cut into the material of the clamped part, leaving a permanent plastic deformation. On the inside they have wedges, the angle of which is greater than the angle of the helix of the thread. The subject of this work is a study of creating a simulation model that takes into account the discussed effect of wedge lock of the washers. This model will be used in the future for simulation tests of washers with a different geometry than the one proposed by the manufacturer.

Improvement of stiffness during milling thin-walled workpiece based on mechanical/magnetorheological composite clamping

Because of the weak rigidity and complex structure, aerospace thin-walled parts are prone to deformation under the influence of machine tool vibration, cutting force and heat during milling. Based on the previous magnetorheological fluid (MRF) flexible fixture, this paper proposes a mechanical/magnetorheological composite clamping method to suppress vibration and improve machining accuracy. Firstly, the relationship between shear stress, workpiece position and MRF height is experimentally analyzed, and a mathematical model of composite clamping is established. Through the single-factor test, it is found that the experimental and predicted milling force curves tend to be consistent, and the maximum milling force errors in X, Y and Z directions are 19.9%, 13.4% and 16.2% respectively. When the spindle speed, depth of cut and feeding speed change, the errors between experimental and predicted milling force in three directions are controlled within 10%, which can verify the reliability of the prediction model. Then, the frequency response impact experiments are carried out on single mechanical clamping and composite clamping respectively, which proves that the stability of composite clamping is better than single mechanical clamping. Finally, by comparing the test results of milling thin-walled part, it is found that the surface roughness values Ra, Rq and Rz of composite clamping parts decrease by 49.0%, 56.7% and 43.3% respectively. Therefore, the mechanical/magnetorheological composite clamping method proposed in this paper has remarkable effect on suppressing chatter, which can effectively improve the milling surface quality of parts.

Influence of Configuration Error in Bolted Joints on Detection Error of Clamp Force Detection Method

Clamp force errors in bolted joints often cause accidents in various mechanical structures. Therefore, the clamp force must be controlled accurately and maintained for securing the reliability of mechanical structures such as vehicles. However, the clamp force cannot be controlled easily during tightening. Moreover, it is difficult to detect the clamp force after tightening. We previously proposed a method to easily detect the clamp force of a bolted joint that has been tightened. In that method, the bolt thread protruding from the nut is pulled while the nut’s upper surface is supported. The relationship between tensile force and displacement at the pulling point where the tensile force is applied differs before and after the tensile force reaches the clamp force. The method detects the tensile force at the point, where the relationship changes, as the clamp force. In this study, we investigate the influence of squareness error on the bearing surface of the clamped part in a bolted joint on the detection error of the method using experiments and finite element (FE) analysis. The experimental results show that the squareness error has an influence on the detection accuracy. The average detection error in the experiments increases by approximately 10% with an increase in the squareness error. To understand the cause of this phenomenon, we investigate the effects of backlash between mating thread surfaces of bolts and nuts on the detection error. The results show that the error decreased because of the backlash. Consequently, it is assumed that the error is caused by the non-separation of the mating thread surfaces when the tensile force reached the clamp force. Furthermore, the FE analysis results show that the squareness error on the bearing surface of the clamped part has an influence of the squareness error on the detection accuracy. The results indicate that we should control the tolerance of squareness errors on the bearing surface of the clamped part when the clamp force detection method is applied to bolted joints.

ANALYSIS OF THE CONDITION OF A PIPE FIXED IN A CLAMPING DEVICE

Due to the fact that clamping devices are widely used in various industries, the requirements for the operation of such devices are constantly increasing. This is due to an increase in the general requirements for processing accuracy, as well as an increase in the forces acting on the clamped part. The reliability of these devices when working with thin-walled cylindrical parts is of great importance.&#x0D; Thin-walled cylinders used in mechanical engineering are subject to significant loads. With prolonged exposure to loads from clamping forces, as well as from axial tensile forces, plastic deformations of cylindrical parts occur. In the oil and gas industry, when clamping drill and casing pipes in some areas in the capture zone, stresses exceed the yield strength. Multiple clamping of the pipe will reduce the pipe wall in the gripping area, which causes premature pipe failure. Therefore, increasing the holding capacity of clamping mechanisms is relevant.&#x0D; Analysis of broken drill pipes, which have been operating in wedge grips for a long time, showed that in most cases the pipes undergo plastic deformation caused by damage to the pipe surface by the teeth of the ram. To clarify the actual conditions of loading the pipe and the possibilities of increasing the capacity of the clamping devices, studies of the contact pressures in the clamping zone were carried out.&#x0D; A new pipe clamping chuck is also presented, which provides a sufficiently high reliability of fastening of cylindrical parts.

Distributed transfer function-based unified static solutions for piezoelectric short/open-circuit sensing and voltage/charge actuation of beam cantilevers

Closed-form unified solutions using the distributed transfer functions (DTFs) method are presented for the first time for the static short/open-circuit sensing and voltage/charge actuation of moderately thick beam cantilevers with co-localized surface-bonded piezoelectric patches. For this purpose, the smart beam is divided into three segments, of which the clamp and free sides parts are elastic, while the middle one is made of an elastic core sandwiched between two electroded piezoelectric patches. The latter can be different in material properties and thickness but should have the same length, and their widths can be different from the host elastic beam. The theoretical formulation is based on Timoshenko’s first-order shear deformation theory for the kinematics and piezoelectric constitutive equations and the principle of virtual works for the variational equations. The latter integrate explicitly the physical equipotential constraints on the patches electrodes. The balance equations and boundary conditions are derived for the three segments independently and then connected at their interfaces by the equilibrium equations and continuity conditions. The unified static solutions for the resulting four problems are derived analytically in closed form using the DTF approach. These are validated against only open literature benchmarks having tabulated results or analytical formulas in order to avoid curves induced inherent additional deviations. Very good correlations were obtained in comparison with the found reference two-dimensional (2D) plane strain/stress analytical and 2D plane strain/stress and three-dimensional finite element results.

Analytical modeling of axial stiffness of tensile bolted joints under concentric external load

Stiffness of bolted joints is a critical parameter for determining deformations and natural frequencies of assemblies. In this study, the effect of external load on axial stiffness of bolted joints is clarified theoretically for the first time. The stiffness of stress zones between and beyond load planes is derived on the basis of the strain energy method and used to formulate the stiffness of bolted joints. The influence of the distance between the load planes of the external load, axial positions of the external load, and difference in the material of the clamped parts on the stiffness of the bolted joints are investigated by applying the proposed formulations and finite element method. Comparisons with finite element results indicate that the proposed formulation can accurately predict the stiffness of the bolted joints.

Dynamic behaviour of a bolted joint subjected to torsional excitation

Abstract This paper presents results of experimental and theoretical studies on the dynamics of a bolted joint under torsional excitation. Hysteresis curves of the resultant torque versus the applied angle of twist are obtained from the experimental results. These experiments have shown relative slippages between the clamped parts and between the contact threads. Based on the experimental results, the coefficients of friction between the contact surfaces are obtained using a theoretical method. An effective modelling method is presented to exactly construct helical thread profiles. Using the finite element model thus obtained, the hysteresis curves are reproduced from the finite element analysis. Finally the hysteresis curves are recreated by a modified Jenkins element model which agrees with the detailed finite element model.

A Simple, Reusable and Low-Cost LVDT-Based in Situ Bolt Preload Monitoring System during Fastening for a Truck Wheel Assembly

The aim of this study is to design and test a new, simple, and reusable linear variable differential transformer (LVDT)-based in situ bolt preload monitoring system (L-PMS) during fastening of a truck wheel assembly. Instead of measuring the elongation of a bolt, the distance between the end surfaces of both the bolt and nut was monitored via the L-PMS. The distance obtained from the L-PMS was experimentally correlated with the actual preload measured by a washer-type load cell. Since the variation of the distance is related to the stiffness of the bolt and clamped parts, a finite element analysis was also conducted to predict the sensitivity of L-PMS. There was a strong linear relationship between the distance and bolt preload after the bolt and nut were fully snugged. However, a logarithm-shaped nonlinear relationship was irregularly observed before getting snugged, making it difficult to define a clear relationship. In order to tackle this issue, an arc-shaped conductive line was screen-printed onto the surface of the clamped parts using a conductive carbon paste. The results show that a resistance variation of the conductive line during fastening enables to determine the snug point, so the L-PMS combined with resistance measurement results in an approximately ±6% error in the measurement of bolt preload. The proposed L-PMS offers a simple but highly reliable way for measuring bolt preload during fastening, which could be utilized in a heavy-truck production line.

Dynamic properties of bolted joints in laminated composites evaluated using flexural wave propagation

In this study, a method to evaluate the dynamic properties of bolted joints in laminated composites is proposed. The propagation of flexural waves through the joint was used to identify the joint stiffness. Experiments were performed by using carbon fiber/epoxy specimens. The specimens were fastened by a single-lap bolted joint. Vibration responses were measured for specimens fastened using different clamping forces. The dynamic properties of the joint were evaluated using translational and rotational complex joint stiffnesses. The predicted effects of the joint on the system vibration properties were compared to the measurements. A numerical method was proposed to calculate the dynamic properties. The stiffness and loss factor were derived to find the effects of the clamping forces. The evaluated stiffness was close to the predicted static stiffness. The joint loss factor was larger than that of the composite itself. With the increasing clamping forces, the stiffness increased and the loss factor decreased. The proposed method allows non-destructive continuous monitoring of a clamped part with additional information about the vibration reduction capability.

Estimation of Conditions in Exchangeable Jaws Design of Pneumatics Gripper

Abstract The paper deals with the design of replaceable jaws on pneumatics gripper of the CNC milling machine EMCO Concept MILL 105, which is part of the iCIM 3000 manufacturing and assembly system. When designing replaceable jaws to allow firm and safe clamping of rotating and non-rotating parts, it was based on limiting factors such as parameters of the pneumatics gripper, dimensions, shape and material of the clamped parts and the like.