Mandrel Diameter Research Articles

Experimental investigation of effective parameters in the tube rotary draw bending process

The rotary draw bending (RDB) process is one of the complex forming processes which is widely used for tube bending. There are different parameters in this process that incorrect selection of them cause the happening of some defects such as thinning and tube ovality. In the present study, the effects of main parameters of the RDB process is investigated on the thinning and ovality of BS 3059 steel tube using the experimental tests. Therefore, a design of experiment (DOE) base on the Taguchi method is used to investigate the effect of mandrel diameter, pressure of pressure die and mandrel position on the thinning of tube outer wall and the tube ovality. Four different values of 7 MPa, 10 MPa, 12 MPa, and 15 MPa are considered for the pressure of pressure die and four values of 7 mm, 15 mm, 20 mm and 34 mm for the mandrel position. The mandrel position is the distance between the mandrel and bending center. Two different chain link mandrels are used with balls diameter of 33.5 mm and 34.5 mm. The results showed that the mandrel position had the most significant effect on the thinning and tube ovality. Although the increase of mandrel position improved the thinning defect in the tube outer wall, the tube ovality increased by the increase of mandrel position from 20 mm to 34 mm. The results showed that the pressure of 7 MPa, mandrel position of 15 mm and the mandrel diameter of 33.5 mm were the best parameters for RDB of BS 3059 steel tube.

Partial replacement of melamine by benzoguanamine in MUF resins towards improved flexibility of agglomerated cork panels

Melamine-urea-formaldehyde (MUF) resins are highly effective adhesives for lignocellulosic materials. However, their high stiffness hinders applications where flexibility is desired. In this work, MUF resins were modified with benzoguanamine by partially replacing melamine in two different steps of the synthesis. The purpose was to obtain a less densely crosslinked, and hence more flexible, structure after cure. All modified MUF resins were characterized using gel permeation chromatography (GPC). Results suggest that benzoguanamine and its derivatives were integrated into the polymer structure. FTIR and 13C-NMR analysis confirmed the presence of benzoguanamine in the modified resins. The addition of benzoguanamine to the MUF resin synthesis significantly improved the flexibility of agglomerated cork panels bound with modified resins. The minimum mandrel diameter on which the panels could be bent by 180° without failure decreased from 18 mm to 12 mm diameter, while the remaining key properties of the panels were maintained (tensile strength and boiling water resistance). The formaldehyde content of the panels (determined according to EN120) corresponds to E1 class.

Experimental study on wrinkle suppressing in multi-pass drawing spinning of 304 stainless steel cylinder

Cylinder shell parts are widely used in industrial and civil areas, and 304 stainless steel cylinders were attempted to be formed by multi-pass drawing spinning. But wrinkling failure occurs in the spinning process. In order to suppress it, two comparative experiments with 206 mm and 245 mm mandrel diameters are carried out to reveal the wrinkling mechanism of multi-pass drawing spinning of 304 stainless steel cylinders. It is found that a thicker mandrel diameter is conducive to the wrinkle suppressing due to the larger instantaneous contacting zone caused by the bigger mandrel. The restraining mechanism of the wrinkling failure is due to the fact that a larger contacting zone can accommodate more circumferentially squeezed metal resulting in smaller tangential compressive stress. This is further proved by the spinning experiment with roller path amendment. The roller path is amended by increasing the curvature of the roller path arc and removing the backward arcs to reduce the tangential compressive stress. Almost no wrinkling failure occurs in the new 304 stainless steel cylinder spinning process.

The impact of bending stress on magnetic properties of Finemet type microwires and ribbons

In our research we studied the influence of bending on the total magnetic losses, the coercivity of minor hysteresis loops and the virgin magnetization curves of amorphous ribbons and microwires prepared from Finemet-type alloy wound on a mandrel of different diameters. The impact of various factors contributing on static and dynamic magnetic properties through bending stress are discussed. The factors pertain to contribution of the magnetoelastic anisotropy, the onset of the strain-induced magnetization, the changes of domain structure and the mobility of domain walls. The major contribution of hysteresis losses as-compared to the eddy-current losses have been observed on changing the mandrel diameter in wound ribbons and wires. The total specific losses of the Finemet-type ribbons are lower than that of microwires at the frequencies ranging from 50 to 400 Hz. Observed difference in the magnetic properties is attributed to different magnetization processes of amorphous microwires and ribbons. A different geometry and magnetoelastic anisotropy of studied materials are most likely to influence the formation of different domain structures.

Study on the microstructure evolution during radial-axial ring rolling of IN718 using a unified internal state variable material model

Microstructure control during radial-axial ring rolling (RARR) of IN718 is important for increasing the performance in service of IN718 rings. However, RARR is an extremely complex dynamic rolling process with non-uniform local deformation and non-uniform temperature distribution, making the microstructure control difficult. This paper presented an internal state variable (ISV) material model which enables the unified prediction of flow behavior and microstructure evolution during dynamic and post dynamic regime. Based on user defined subroutine, a multiscale finite element (FE) model with adaptive motion control of rolls was established to study the evolution of dislocation density, recrystallized fraction and grain size during RARR of IN718. RARR experiment was conducted to verify the multiscale FE model. The predicted outer diameter of the ring and the radial rolling force as well as the microstructure distribution on the ring cross section were in good agreement with the measured results. The evolution and distribution of ISVs were discussed, and the effect of mandrel diameter, main roll diameter, initial temperature, and rolling ratio on the microstructure evolution of the ring was analyzed. Sensitivity analysis of rolling parameters was conducted. The initial temperature is the most sensitive parameter and the initial temperature should be as high as possible with the pinning of δ phase particle to promote the recrystallization process. It should be careful to increase the rolling ratio when the rolling ratio is higher than 1.667. Because the refine effect of grain structure decreases and the rolling force may increase dramatically due to the low temperature.

Sequential multi-objective optimization of thin-walled aluminum alloy tube bending under various uncertainties

Combining the design of experiments (DOE) and three-dimensional finite element (3D-FE) method, a sequential multi-objective optimization of larger diameter thin-walled (LDTW) Al-alloy tube bending under uncertainties was proposed and implemented based on the deterministic design results. Via the fractional factorial design, the significant noise factors are obtained, viz, variations of tube properties, fluctuations of tube geometries and friction. Using the virtual Taguchi's DOE of inner and outer arrays, considering three major defects, the robust optimization of LDTW Al-alloy tube bending is achieved and validated. For the bending tools, the robust design of mandrel diameter was conducted under the fluctuations of tube properties, friction and tube geometry. For the processing parameters, considering the variations of friction, material properties and manufacture deviation of mandrel, the robust design of mandrel extension length and boosting ratio is realized.

Laboratory determination of smear and transition zones due to prefabricated vertical drain installation

ABSTRACTThe smear zone, which develops during the placement of the prefabricated vertical drain (PVD) in the ground using a steel mandrel, is a significant factor that influences the performance of PVDs. The determination of the width and hydraulic conductivity of smear zone is an important consideration in designing ground improvement by preloading with PVDs. Thus, the extent and hydraulic conductivity of the PVD smear zone have received significant attention; however, there is still uncertainty and the topic remains discrepant among investigators. There is limited or no smear zone hydraulic conductivity data that is directly produced by laboratory or field tests. In this study, a laboratory smear zone model experiment that was developed as a performance test for determining the extent of the smear zone and measuring directly its hydraulic conductivity was used. Based on the findings obtained from two different materials (Craney Island dredgings and Hydrite R kaolinite soil), it is indicated that the disturbed zone is made up of two areas, namely smear zone and transition zone, and that the hydraulic conductivity in these areas is lower than the undisturbed soil. The ratio of the hydraulic conductivity of the smear and transition zones to that of the undisturbed soil was found to vary between 0.32 and 0.50 and between 0.57 and 0.82, respectively in different soils. The diameter of the smear zone was found to be 2.3–3.3 times higher than the equivalent diameter of the mandrel depending on the soil. The diameter of the transition zone extended 5.2–7.3 times the equivalent diameter of mandrel again depending on the soil. These directly measured values, in general, are supportive of the published values based on indirect means and the test device can be used to study the impact of mandrels of different size and shape and other factors by minor modification.

Effect of mandrel diameter on non-circularity of hollow shafts in cross wedge rolling

Abstract Because of the need for lightweight design, the application of hollow shaft parts rapidly increases. The mandrel plays an important role in the process of forming hollow shafts using cross wedge rolling (CWR). This paper presents the experimental and numerical analysis on the effect of the mandrel diameter on non-circularity in CWR for the hollow shafts with mandrel. A thermomechanical finite element (FE) model was developed to simulate the CWR process of hollow shaft. The experiments and numerical analysis suggest that the diameter of mandrel has a great effect on the non-circularity of hollow shafts. During the CWR process, because of the effect of the mandrel, the workpiece is compressed in radial direction and extended along the circumferential direction, which lead to the increase of the non-circularity. With increasing diameters, the workpieces show larger non-circularity. The non-circularity slowly increases when mandrel diameter is small. However, when the mandrel diameter exceeds a certain value, the non-circularity increases rapidly. Besides, the non-circularity of the inner hole is larger than that of the outer circle. According to the strain curves during the forming process, it can be found that circumferential compressive strain plays an important role in the rounding forming stage. Larger compressive strains decrease the non-circularity of the rolled pieces.

Prediction for multi-index constrained forming limit in shear bending process of Ti-alloy thin-walled tube under differential temperature fields

Predictions for multi-index constrained forming limits and forming limits of Ti-alloy thin-walled tubes have become key problems urgently in need of solutions in order to improve forming potential in their shear bending processes under differential temperature fields. To address this, a method for predicting this type of forming limits was presented by coupling a thermal-mechanical-coupled finite element model for simulating these bending processes, with an energy model for the tubes’ shear-enforced plastic wrinkling predictions and utilizing the response surface designs. Reliable multi-index response surface models corresponding to the wrinkling, the thinning, and the flattening were developed for these TA2 Ti-alloy tubes’ shear bending processes, and their multi-index constrained forming limits were predicted. This found that forming limits, i.e., the maximum moving die displacements depend on the over-thinning or over-flattening for the present conditions. The smaller the values of the outer corner radius, the smaller both the feasible region ranges of the bending die cavity radius and/or the mandrel diameter and these forming limits. When the value of the outer corner radius is a half of the mandrel diameter and the values of the inner corner radius are from 4 to 6 mm; their feasible region ranges are the maximum. The effects of the feasible region of the bending die cavity radius on these forming limits are larger than the mandrel diameter. The moving die displacements located in the vertexes of their feasible regions are the maximum.

A new method for manufacturing hollow valves via cross wedge rolling and forging: Numerical analysis and experiment validation

Cross wedge rolling-forging (CWR-forging) is an innovative process for local plastic deformation that is suitable for forming hollow valves. This paper presents the numerical and experimental results of hollow valve production using this new method. The most popular production methods are described. Then, this study examines the formation of such valves through CWR-forging. A numerical model of CWR-forging using the finite element method (FEM) is developed to estimate the technological viability of this process. The distributions of effective strain, temperature, metal flow, force, and torque are analyzed as well. In this study, changing the stretching angle (β) can effectively avoid swollen holes. therefore, the forming quality of the workpiece can be greatly improved when the forming angle (α) is equal to 35° and the stretching angle (β) is equal to 5° and 4° in the knifing and stretching zones and the mandrel diameter is 4mm, respectively. Numerical results are then verified under laboratory conditions. Experimental results are consistent with the FEM results, thus confirming that hollow valves can be produced through CWR-forging.

Pore pressure based method to quantify smear around a vertical drain

Radial consolidation testing of Ballina clay (New South Wales, Australia) was carried out using a large-scale consolidometer 650 mm in diameter. In this study, the characteristics of the smear zone were evaluated on the basis of hydraulic gradient changes derived from the measured excess pore pressure data in the radial direction. The extent of the smear zone determined using this technique is compared with past approaches, where the variations in water content and lateral permeability were adopted to evaluate smear. The approach proposed herein based on the change of hydraulic gradient coincides with the previous two methods, and the smear zone could be established at almost 2·5 times the effective mandrel diameter. A good agreement is also found between the theoretical radial consolidation predictions, after incorporating the smear zone characteristics and the measured time–settlement curve. The proposed method for the determination of smear zone extent can be carried out during consolidation with minimum disturbance to soil, provided a sufficient number of pore pressure transducers are installed. It also eliminates the need for a number of soil samples and high-quality soil sampling technique after the installation of the drain.

Analyzing Bending Stresses on Lithium‐Ion Battery Cathodes induced by the Assembly Process

AbstractThe industrialized winding of electrode–separator composites (ESCs; “jelly rolls”) applies bending stress to the winding mandrel. This affects the mechanical integrity of the substrate's coating and adhesion and may reduce the cycle stability and the battery life. Even though this motivates strong interest in the minimization of bending stress during production, there is no testing method available yet to characterize the composite such that process parameters can be derived. This article introduces a test method and apparatus for the effect of bending stress of electrodes. In this test method, electrodes are pulled over defined radii while the coating adhesion is observed continuously. This resembles the variation of the mandrel diameter and gives detailed insight into the limits of the allowed production parameter window. In a case study, a cathode material with Li(LiMnAl)2O4 (LMO) as active material is selected as an example to show the effectiveness of the method.

International round robin test of the retained critical current after double bending at room temperature of Ag-sheathed Bi-2223 superconducting wires

An international round robin test was carried out in order to establish a test method for retained critical current after double bending at room temperature of Ag-sheathed Bi-2223 superconducting wires. Tests for commercial Bi-2223 tape were conducted by six laboratories using the same guidelines. The standard uncertainties (SUs) of measurands were evaluated for these four quantities: IC0, IC/IC080, IC/IC060, IC/IC050, where, IC0 is initial critical current and IC /IC0XX is critical current after XX mm bending. Using an F test to determine where the most scatter was generated in the test results it was found that the greatest scatter in the normalized critical current measurements came from inter-laboratory scatter. In a type-B uncertainty evaluation, the major contribution was from the bending diameter and measuring temperature. The relative SU tended to increase as the bending diameter decreased. A specific mandrel diameter corresponding to a retained critical current of 95% could be determined with a relative SU of 1.3%. In order to reduce the overall scatter, the temperature difference between the critical current measurements before and after bending should be small.

Improving formability of tube bending for a copper material using finite element simulation

Bending tubes are key products in many industries. The geometric parameters of the bending process are considered according to Taguchi’s orthogonal array and then coupled with finite element simulation to predict and improve the formability of the tube bending process for copper JIS25A material. Three parameters, namely, mandrel diameter, distance between mandrel rings, and distance from the tip of the mandrel bar to the center of the base die, are selected to study their effects on the quality of the bending process. The variance analysis shows that the effect distribution of each parameter to bending quality is determined, and optimal conditions are adopted to conduct experiments.

Numerical analysis of tool geometry effect on the wear characteristics in a radial forward extrusion

The finite element analysis has been performed to investigate the tool wear characteristics in forming a central hub component with radial protrusion by a radial forward extrusion process. The main objective of this study is to investigate the influence of tool geometries on the wear characteristics of the mandrel and container surfaces. Two major process parameters such as annular gap height and mandrel diameter were adopted to examine the wear characteristics. SCM415H steel was selected as a model material in simulation by adopting the Archard’s wear model, which was verified by comparing with experimental results in the literatures. The results of present study were summarized quantitatively in terms of wear profiles on the tool surfaces such as container and mandrel in terms of wear depth, contact pressure and sliding velocity. The localized wear depth is more sensitive to the variation of annular gap height with increase in mandrel diameter.

Influence of design parameters on the mechanical behavior and porosity of braided fibrous stents

Abstract In spite of all innovations in stent design, commonly used metallic stents present several problems such as corrosion, infection and restenosis, leading to health complications or even death of patients. In this context, the present paper reports a systematic investigation on designing and development of 100% fiber based stents, which can eliminate or minimize the problems with existing metallic stents. For this purpose, braided stents were produced by varying different materials, structural and process parameters such as mono-filament type and diameter, braiding angle and mandrel diameter. The influence of these design parameters on mechanical behavior as well as stent's porosity was thoroughly investigated, and suitable parameters were selected for developing a stent with mechanical characteristics and porosity matching with the commercial stents. According to the experimental results, the best performance was achieved with a polyester stent designed with 0.27 mm monofilament diameter, braiding angle of 35° and mandrel diameter of 6 mm, providing similar properties to commercial Nitinol stents.

Fatigue life enhancement of welded stiffened S355 steel plates with noncircular openings

The paper is devoted to fatigue life enhancement of S355 steel welded stiffened plate containing T-shaped stiffeners and girders with non-circular openings. Its rounded corners are natural stress concentrators and potential places for initiation and growth of first-mode fatigue cracks. To slow down this process, beneficial residual compressive stresses are introduced around the non-circular opening corners through mandrel cold working of preliminarily drilled round holes in the corners' zone. The creation through cutting of the non-circular openings and subsequent welding of the T-shaped girders generates residual stress redistribution. The latter is studied both experimentally and numerically. X-ray diffraction method has been employed for residual stress analysis. The mandrel cold working process and subsequent cutting to form the non-circular opening have been simulated through a nonlinear finite element method (FEM) analysis. In order to simulate the residual stress redistribution due to welding of the T-shaped girders with non-circular openings, a sequentially coupled thermal-stress FEM analysis has been carried out. In order to identify the optimal value of the mandrel cold working interference fit (the difference between the mandrel diameter and the initial hole diameter) and welding sequence, a multi-objective optimization task is set and solved. The optimization has been based on a planned numerical experiment. The optimal value of the interference fit and the welding sequence have been found, which ensure high intensity and homogeneity of the residual compressive field around the opening roundings.

Development of braided fiber-based stents.

The mechanical behavior of stents is one of the important factors involved in ensuring their function in maintaining an open blood vessel. This study aims to study the development of different kinds of fiber-based stents, using braiding technology. Moreover, the impact of braiding angle and mandrel's diameter in the mechanical behavior of the stent is also analyzed. Furthermore, stent's mechanical properties like radial and longitudinal compression, bending and porosity will be measured and discuss. The results show that fibrous stents present suitable mechanical properties, when compared to those of commercial ones, and may reduce the disadvantages of commercial metallic stents.

Design and Analysis of Adjustable Inside Diameter Mandrel for Induction Pipe Bender

Pipes are bended to various radius in pipe bending machine (COJAFEX PB 600R). When the pipe length is insufficient mandrel is used. For various diameter pipes various mandrels are used which increases the cost and time of operation in order to avoid this difficulty a mechanism is designed by us in SOLIDWORKS to adjust the diameter of the inside mandrel to suit various diameters of the pipe. The existing mandrel is compared with the designed mandrel and analyzed in ANSYS WORKBENCH.

Coupled Thermo-mechanical FE Simulation of Unloading Cooling Springback in NC Heating Bending of Large Diameter Thin-walled Commercial Pure Titanium Tube

A new FE model of unloading cooling springback in the NC heating bending of large diameter thin-walled commercial pure titanium tube was developed by combination of stress-strain field and temperature field. With the commercial pure titanium tube of Ф50.8×t0.508×R101.6mm as a representative component, the springback behaviours under different processing conditions were investigated. The results show that: 1) The springback angle increases slowly along with temperature increasing. With the temperature at 180-250°C, the springback angle is least. 2) The heating temperature has certain influence on the cross section distortion. With temperature at 180-300°C, forming quality is better. 3) The mandrel diameter has important influence on the cross section distortion. With the increasing of the mandrel's diameter, cross section distortion rate and outside deformation is more uniform.