Hollow Parts Research Articles

МОДЕЛЮВАННЯ ПРОЦЕСІВ КОМБІНОВАНОГО РАДІАЛЬНО-ПРЯМОГО ВИДАВЛЮВАННЯ СКЛАДНОПРОФІЛЬОВАНИХ ПОРОЖНИСТИХ ДЕТАЛЕЙ ІЗ ВИКОРИСТАННЯМ МЕТОДУ КІНЕМАТИЧНИХ МОДУЛІВ

Expanding the capabilities of the kinematic modules method to determine the value of the relative deformation pressure and shaping of a semi-finished product in the processes of combined radial-forward extrusion such as hollow parts with a complex profile. Obtaining calculated dependencies that will allow predicting compliance with the required dimensions of the part and assessing the possibility of defect formation. Upper bound method based on the method of kinematic modules is defined investigation of the main factors, affecting the power mode of deformation and features in the shaping of a semi-finished product in the processes of combined extrusion with several degrees of metal flow freedom Based on the upper bound method by using a kinematic module with two degrees of metal flow freedom is determined the value of the relative deformation pressure for make scheme of combined radial-forward extrusion such as hollow parts with a complex profile. The dependences of the increments in the semi-finished product that make it possible to analyze the influence of technological factors in the process of shaping and possible defect formation in the form of dimple are determined. The possibilities of the upper bound method by using kinematic modules with several degrees of metal flow freedom to assess the power mode and shaping of a semi-finished product in the processes of combined extrusion are determined. Significant influence of friction conditions and geometric parameters of the process the appearance of dimple in combined radial-forward extrusion such as hollow parts with a complex profile are considered. Mathematical relationships for calculating the value of the relative deformation pressure and increments of the semi-finished product in combined radial-forward extrusion such as hollow parts with a complex profile that will contribute to a more active introduction of combined extrusion processes in production are determined.

Designing Hierarchical Honeycombs to Mimic the Mechanical Behaviour of Composites

Honeycombs are used ubiquitously in engineering applications as they have excellent out-of-plane strength and stiffness properties with respect to weight. This paper considers the properties of honeycombs in the in-plane direction, a direction that is significantly weaker and less stiff than the out-of-plane direction. We assess how judiciously locating structural hierarchy within a honeycomb array can be a geometric design principle with direct consequences on the mechanical behaviour of the honeycomb. Here, we use finite element methods to design reinforced honeycomb mechanical metamaterials that mimic the mechanical behaviour of unidirectional fibre reinforced composites. We specifically incorporate structural hierarchy within hollow honeycomb cells to create mechanical metamaterial pseudo-composites, where the hierarchical parts are pseudo-fibres, and the hollow parts are the pseudo-matrix. We find that pseudo-fibre contribution coefficients are higher than the fibre contribution coefficient of carbon fibre reinforced plastics (CFRP). We also find that the elastic modulus of unidirectional pseudo-composites can be predicted using the (Voigt model) rule of mixtures with a good level of accuracy.

Numerical analysis of a two-stage forming process for a hollow part with external flange

This paper presents the results of a numerical analysis of a two-stage forging process for producing a hollow part with an external flange. The numerical analysis was performed via the finite element method using Deform-2D/3D. The analysed case included a cold forming process. The billet was a tube made of a low alloy steel grade 42CrMo4 with its flow curve described by a constitutive equation. The forming process involved the use of two operations: extrusion and forging in a tapered die cavity. The objective of the study was to determine whether the proposed forming technique could be used for production of hollow flanged parts. The kinematics of material flow, distributions of effective strains and the Cockcroft–Latham ductile fracture criterion, as well as force parameters were examined. The conducted research confirmed the correctness of the proposed method.

3Pa4-7 Study of longitudinal–torsional vibration source using stepped horn with hollow part

3Pa4-7 Study of longitudinal–torsional vibration source using stepped horn with hollow part

Comparative analysis of methods for improving the quality of hardened pipe and bar stock for agricultural machinery parts

The problem of obtaining a high-quality surface is acute in thermal, chemical-thermal and thermomechanical processing of products of rolling production. But, due to the fact that many metallurgical plants are insufficiently equipped with cleaning tools for these types of processing, the required surface quality of metal products is not ensured. Operations related to the removal of defects in the surface of rolled products employ from 30 to 60% of the workers in rolling shops. The need for cleaning leads to a rupture of the production flow, since the metal must be pre-cooled for inspection and cleaning of defects. As a result, the total cost of cleaning is 2 - 3 times higher than the cost of performing the main technological operations - heating and deformation of the metal. In this regard, the combined methods of hot rolling with simultaneous hardening and elimination of surface defects are of particular interest, which gives significant energy savings and excludes etching operations in solutions of sulfuric and hydrochloric acids. The paper considers new methods for stripping rolled stock before deformation in the high-temperature thermomechanical treatment (HTMT) mode of cylindrical hot-rolled solid and hollow billets with screw compression (SC) deformation, combining, along with a high-performance method of shaping and strengthening of rolled products, environmentally friendly (acid-free) methods of surface cleaning, as well as methods of removing surface layer defects combined with mechanical processing. At the same time, simultaneously with cleaning the surface and increasing the accuracy of rolled products, the structure of the surface layer is formed by the mechanism of phase transformations during thermomechanical processing. The type of fracture changes at low-temperature destruction from brittle to ductile. It should also be noted, that there is the need for further development of such well-proven cleaning methods as blade and waterjet processing, which allow, when cleaning rolled products from any steel grades from scale, to implement the most reliable cleaning system, ensure effective removal of surface and deeper defects, increase yield, reduce energy consumption and fit well into the continuous rolling mill line. According to recent studies, waterjet treatment increases the fatigue life of hollow cylindrical parts by up to 15%.

Design of Hydraulic Bulging Die for Automobile Torsion Beam and Optimization of Forming Process Parameters

The hydraulic bulging technology of tubes can provide hollow parts with special‐shaped cross sections. Its manufacturing process can effectively improve material utilization and product accuracy and reduce the number and cost of molds. However, the hydraulic bulging process of parts is very complicated. The size of the tube blank, the design of the loading route, and the forming process parameters will have an effect on the molding quality. Closed tubular torsion automobile beam is considered as the research object to study hydraulic bulging die design and optimize forming process parameters. CATIA software is used to design torsion beam product structure and hydraulic bulging die. AMESim software is employed to design hydraulic synchronous control system for cylinders on both sides of the hydraulic bulging die. Mathematical control model is established and verified in Simulink software. DYNAFORM software is applied to conduct numerical simulation of hydraulic expansion. The supporting pressure, molding pressure, friction coefficient, and feeding quantity are taken as orthogonal experiment level factors. Maximum thinning and maximum thickening rates are taken as hydraulic pressure expansion evaluation indexes to complete the orthogonal experiments. Main molding process parameters are analyzed via orthogonal experiment results and optimized by employing the Taguchi method. Optimal hydraulic bulging parameters are obtained as follows: supporting pressure of 20 MPa, molding pressure of 150 MPa, feeding quantity of 25 mm, and friction coefficient of 0.075. Simulation analysis results indicate that the maximum thinning rate is equal to 9.013%, while the maximum thickening rate is equal to 16.523%. Finally, the design of hydraulic bulging die for torsion beam was completed, and its forming process parameters were optimized.

Installation of screw reduction UVO 20-50 for hardening and calibration of cylindrical parts and billets of agricultural machinery

A screw reduction unit UVO 20-50 (diameter of hardened products from 20 mm to 55 mm) with a closed cooling system for hardened rolled products with the ability to integrate equipment into a production line for manufacturing parts was developed. The UVO unit is intended for shaping and hardening of cylindrical parts by high-temperature thermomechanical treatment (HTMT) with metal deformation by screw compression (VO), ensuring the technical characteristics of products. It is known that some thermomechanical methods of hardening and production of rolled products, for example, steels HTMT, in comparison with conventional types of hardening heat treatment, provide a set of higher properties: strength, ductility and fracture resistance. Evaluating the efficiency of using the hardening thermomechanical treatment of long products for highly loaded parts, it is necessary to use the criteria of fracture mechanics, to study the resistance to brittle and cyclic fracture of steel under the action of stress concentrators, negative temperatures and other difficult test and operating conditions. Taking into account the increased properties of steels with HTMT, it becomes possible to use hollow sections instead of solid billets. The investigated materials and the revealed patterns allow authors to conclude that thick-walled hollow parts, which are used to save metal and lighten the weight of structures, should be considered not only as full-fledged substitutes for solid ones, but also as having an advantage over the latter, mainly due to their better hardenability at surface cold working and less sensitivity to stress concentration at cyclic loads, which makes them more reliable in operation. These research results substantiate the wider use of hollow profiles for such parts of agricultural machinery as track pins, shafts, axles, torsion bars and other parts for various purposes.

Evaluation of Ductile Fracture Criteria in Cold Forging of Hollow Parts

Evaluation of Ductile Fracture Criteria in Cold Forging of Hollow Parts

Analiza parametara snage pri kombinovanoj trosmernoj deformaciji kod delova sa prirubnicom

The upper bound power method is used to simulate the process of combined radial-backward-forward extrusion of hollow parts of the "cup with flange and branch pieces" type from a continuous workpiece. The calculation scheme with autonomous deformation zones is used, which contains modules with an inclined boundary and the condition for the equality of powers acting on both sides of the intermediate hard zone is accepted. This made it possible to more accurately determine the power regime and the prevailing direction of the metal flow, which is necessary to assess the character of the forming of the part. The comparison of theoretical and experimental values of the deformation pressures and the flow velocities with each other, as well as with the results obtained by the finite element method shows the feasibility of using the obtained functions for technological calculations of power parameters and evaluating of part forming.

Reflection mode photoacoustic/thermoacoustic dual modality imaging based on hollow concave array

Photoacoustic (PA) and thermoacoustic (TA) imaging can share a set of data acquisition and data processing system, in addition to different excitation sources. In this paper, a reflection mode PA/TA dual modality imaging based on a hollow concave array is proposed. The PA/TA signals are excited through the holes in the hollow array by using optical fiber and dipole antenna, respectively. The excited light, microwave and received ultrasonic signals are coaxial, forming a PA/TA dual modality imaging mode. Through the compensation and calibration of the transducer crystal phase and amplitude of the hollow part of the array, a 3-mm-diameter plastic tube filled with 0.9 wt.% salt water, safflower oil, human arm, back of hand and instep are successfully imaged, separately. These experimental results show that the spatial resolution of the PA/TA dual modality imaging system is 0.33 mm, and this technology has a potential to provide the optical and microwave absorption distribution of tissues at the same time by using the same hollow concave array, which is helpful in accurately detecting tumor, diabetic foot and other diseases, and has a wide range of clinical application prospects.

Experimental Study of the Dynamic Behavior of Thin-Walled Tubular Workpieces in Turning Cutting Process

Nowadays, industrialists, especially those in the automobile and aeronautical transport fields, seek to lighten the weight of different product components by developing new materials lighter than those usually used or by replacing some massive parts with thin-walled hollow parts. This lightening operation is carried out in order to reduce the energy consumption of the manufactured products while guaranteeing optimal mechanical properties of the components and increasing quality and productivity. To achieve these objectives, some research centers have focused their work on the development and characterization of new light materials and some other centers have focused their work on the analysis and understanding of the encountered problems during the machining operation of thin-walled parts. Indeed, various studies have shown that the machining process of thin-walled parts differs from that of rigid parts. This difference comes from the dynamic behavior of the thin-walled parts which is different from that of the massive parts. Therefore, the purpose of this paper is to first highlight some of these problems through the measurement and analysis of the cutting forces and vibrations of tubular parts with different thicknesses in AU4G1T351 aluminum alloy during the turning process. The experimental results highlight that the dynamic behavior of turning process is governed by large radial deformations of the thin-walled workpieces and the influence of this behavior on the variations of the chip thickness and cutting forces is assumed to be preponderant. The second objective is to provide manufacturers with a practical solution to the encountered vibration problems by improving the structural damping of thin-walled parts by additional damping. It is found that the additional structural damping increases the stability of the cutting process and reduces considerably the vibrations amplitudes.

A Rotary Compression Process for Producing Hollow Gear Shafts.

This paper presents selected numerical and experimental results of a study investigating the process of forming hollow stepped gear shafts from tubes by rotary compression. The objective of the study was to determine whether the rotary compression process is an effective method of producing hollow stepped gear shafts and to identify limitations of this manufacturing method. A theoretical analysis involved the numerical modeling of the proposed process by the finite element method (FEM). 3D simulations were performed using the commercial simulation software package Simufact Forming. The analysis involved examining the material flow pattern along with thermal and force parameters of the process. The FEM results were verified with experimental tests conducted under laboratory conditions. The experiments were performed on a machine specially designed for the rotary compression of hollow parts. Results demonstrate that it is difficult to form a stepped gear shaft in one operation. For this reason, such parts should be formed in two operations. The first operation involves the forming of a hollow stepped shaft by rotary compression, while in the second operation, a gear is formed on one of the steps of the shaft.

Residual stress of typical parts in laser powder bed fusion

Laser powder bed fusion (LPBF) can be directly used to fabricate the metal components with complex structures and high performances. However, the extremely high temperature gradient induces the high residual stress, which leads to deformation or even cracking during the process. A layer-by-layer model was developed to investigate the residual stress of the typical part fabricated by LPBF. The maximum stress was found at the position where the part corner joined with the substrate. The second-largest stress occurred at the top center for the solid parts while occurred at the top center of the long side for the hollow and semi-hollow parts. The residual stress levels of the hollow and semi-hollow parts were obviously less than that of the solid parts, and the residual stress at the middle of the inclined-wall part is lower than that of the thin-walled part. Using the rounded corner instead of the sharp corner and using the arc structure instead of the straight-line structure were helpful in reducing the residual stress in LPBF. The simulated results were in good agreement with the experimental data obtained by the hole-drilling method. The investigated results of this paper can be used to reduce the residual stress in LPBF.

Effects of fabrication method of composite yarn intermediate material and resin melt viscosity on the impregnation properties and mechanical properties of PA66 fiber and glass fiber composites

Continuous fiber-reinforced thermoplastic (c-FRTP) has received attention for reducing automobile weight. Hollow molded parts made by pultrusion molding of braided composites may improve the performance and reduce the weight of automotive parts. However, pultrusion molding of braided composites suffers from productivity problems. This research aimed to increase the productivity of pultrusion molding of braided fabrics to facilitate its practical application. The effects of the fiber intermediate fabrication method and the resin melt viscosity on the impregnation and mechanical properties of the composite were investigated. Glass fiber and polyamide 66 (PA66) were used as the fiber intermediates. Two types of fiber intermediates were used, one with interlace processing and one with the fibers lined up. PA66 fibers with high and low viscosity were used. A correlation was found between impregnation properties and mechanical properties of the molded products, which improved as the unimpregnated ratio decreased. Detailed observations revealed that impregnation of PA66 resin into glass fiber bundles started from interlaced points in the fiber intermediates introduced by interlace processing. Furthermore, low-viscosity PA66 resin had higher fluidity, which better promoted impregnation into glass fiber bundles. These results clarify design guidelines for fiber intermediates to realize better mechanical properties and shorter molding cycles.

Crash Characteristics of Partially Quenched Curved Products by Three-Dimensional Hot Bending and Direct Quench

Recently, improvement of hybrid and electric vehicle technologies, equipped with batteries, continues to solve energy and environmental problems. Lighter weight and crash safety are required in these vehicles body. In order to meet these requirements, three-dimensional hot bending and direct quench (3DQ) technology, which enables to form hollow tubular automotive parts with a tensile strength of 1470 MPa or over, has been developed. In addition, this technology enables to produce partially quenched automotive parts. In this study, the crash characteristics of 3DQ partially quenched products were investigated as the fundamental research of the design for improving the energy absorption. Main results are as follows: (1) for partially quenched straight products in axial crash test, buckling that occurs at nonquenched portion can be controlled; (2) for the nonquenched conventional and overall-quenched curved products, buckling occurs at the bent portion at the initial stage in axial crash tests, and its energy absorption is low; (3) by optimizing partially quench conditions, buckling occurrence can be controlled; and (4) In this study, the largest energy absorption was obtained from the partially quenched curved product, which was 84.6% larger than the energy absorption of the conventional nonquenched bent product in crash test.

Theoretical and Experimental Analysis of a New Process for Forming Flanges on Hollow Parts.

The paper presented a new method for forming flanges on hollow parts by incremental radial extrusion. In the classic process of radial extrusion, additional rings were used to limit the free flow of material in the radial direction. The flange was formed progressively, using rings of increasing diameters. The proposed method was verified by numerical analysis and experimental tests. The numerical calculations were performed by the finite element method using the Deform-3D software package. Tubes made of aluminum alloy EN AW 6060 were used as billets. Laboratory tests were carried out using the Instron 1000 HDX testing machine. The objective of the study was to determine the validity of the proposed flange extrusion method. Results demonstrated that the new method made it possible to produce flanges with a relatively large diameter and uniform thickness, confirming the effectiveness of the proposed forming technique.

Predicting the shape formation of hollow parts with a flange in the process of combined radial-reverse extrusion

The simulation of the process of combined radial reverse extrusion of hollow parts with a flange has established two fundamentally different, in terms of the components of the kinematic modules, calculation schemes CDZ-1.i and CDZ-2.j, taking into consideration the possible shape of the boundary of the section of a metal flow inside a workpiece. The comparison of the dependences of the optimal relative rate of metal outflow in the opposite direction for different schemes indicates significant differences in the resulting values in the course of the deformation process. The relevance of this study is due to making it easier to evaluate the use of the combined extrusion process to produce hollow parts with a flange while maintaining the required dimensions compared to simple deformation schemes. We have identified the lack of detailed studies into the technologies for the introduction of combined extrusion schemes, as well as the absence of technological recommendations for determining the force regime and the shape formation of a semi-finished article. The process of the combined extrusion of hollow parts with a flange was investigated, thereby selecting different types based on the nature of the metal flow depending on the geometric ratios of the deformation process. We have obtained experimental data on the gradual shape formation of a semi-finished product in the process of deformation at different geometric ratios. The limits of using estimation schemes of the process have been defined to obtain data on the increments in a semi-finished product, including in terms of predicting the formation of a shrinkage cavity in the bottom part. It is recommended that a condition of selecting the appropriate scheme should be the condition for a minimum value of the reduced pressure of deformation p i < p j . The resulting recommendations make it easier to predict the shape formation and the force mode of extrusion (a deviation from experimentally obtained data can be reduced to 10 %), which would contribute to evaluating the rationality of the combined extrusion processes while ensuring the required dimensions of a part

Braid-press forming for manufacturing thermoplastic CFRP tube

Braid-press forming was developed for manufacturing hollow tube parts made of carbon fiber reinforced thermoplastic (CFRTP) tape. The CFRTP tapes were braided to make a tube, which was consolidated under pressure and heat in the press forming process. Internal pressure was applied to the braided CFRTP tube by a silicone rubber rod inserted in the tube using axial compression. The reason for using a silicone rubber rod was to apply a high internal pressure until the molten resin solidified, which cannot be achieved in bladder molding and pultrusion, and to obtain good consolidation quality and high mechanical properties. As a result, up to 7 MPa press pressure was successfully applied and the tube made contained no voids and had good flexural properties. The study of the pressure showed that the higher press pressure (from 4.1 MPa) produced tubes with higher flexural properties. The estimation of wall thickness after press forming using the braiding architecture agreed with the measured value. Subjects to be addressed in future studies are productivity improvements and continuous tube manufacturing by the serial joining of braiding and press forming. It can be concluded that braid-press forming is a desirable method for the manufacturing of tubes for structural applications and can be used in future mass-production.

Numerical prediction of deflection of a cylindrical hollow structure due to steady wind loads

A raising population and to meet the raising needs there is an increasing demand for tall structure both for commercial use and industrial purpose. Wind behaviour is a key design parameter for such structures and need to be assessed accurately in the preliminary and secondary design stages. This study is aimed at prediction and analysis of deflection of hollow structure due to steady wind loads. Hollow structures typically represent chimneys that are used in the coal fired stream power plant. A hollow cylindrical part with base diameter of 6 cm is fabricated and tested in wind tunnel at constant speeds of 10, 15 and 20 m/s. An accelerometer is mounted on top of body to measure the deflection. Next, the deflection of the body is predicted numerically using commercial ANSYS software. Initially Computational Fluid Dynamics (CFD) simulations are performed to predict the flow field and associated wind force acting on the body. The wind load is transferred to the structural solver to predict the deflection of the body. The predicted deflection compared well with the wind tunnel experiments. Further FSI simulations are performed by changing the thickness of the hollow structure. The results are analysed to study the effect of wind speed and thickness on the deflection. A cubic polynomial curve-fit for the deflection, as a function of the wind speed is developed.

Development and research of a gas stamping device for making hollow products from a pipe billet

It is advisable to produce hollow thin-walled parts widely used in machine designs from tubular blanks. In existing methods cold forming of the tubular billet takes place for the production of hollow products. In this case, due to the contained plasticity of the blank, parts of complex shape are produced in several transitions. This raises the cost of their production. We have developed a new device for forming hollow products by heating a tubular billet. The device contains a combustion chamber and a working cylinder, separated by a piston. Heating and shaping of the workpiece is carried out under the pressure of the combustion products of compressed fuel mixture supplied to the cavity of the workpiece from the working cylinder. The study was conducted on the basis of well-known equations of thermodynamics and the equations of the heat balance of the process of gaseous fuel combustion. It was found that the ratio of the volumes in the combustion chamber and the working cylinder should range within 2.5...5, and the ratio of the volumes of the working cylinder and the cavity of the pipe billet within 2...2.5. This ensures an increase in gas pressure in the blank cavity by a factor of 25...32, as a result of which the gas pressure reaches 50...65 MPa, and its temperature 2300 C. Due to this, the stamping process is carried out in the temperature range of hot processing, which makes it possible to stamp parts of complex shape in one operation.