Cold Forming Research Articles

Texture Evolution During Cold Forming of Rectangular Hollow Section

This work aims to study the effect of cold forming on the texture evolution during the manufacturing of rectangular hollow sections. Conventional TMCP steel and a direct-quenched steel in 420 MPa strength level are compared. The texture was characterized at the centerline (S=0) and both surfaces (S=0.8) for base material, four flat side and one corner samples of the rectangular hollow section. The results show that the flat sides of both steels have the minor intensity of ∼{554}<225> and ∼{112}<110> texture components and an intense texture component of ∼{001}<110> in the centerline. Generally, any significant difference between four flat size samples was not found and texture intensities of the conventional TMCP steel were slightly sharper compared to direct-quenched steel. The most important change is observed with the inner corner samples, where the randomly oriented texture in the base material and flat side samples changes to the {110}<111>/<112> shear texture components.

Experiment Study on Hardening Behavior of Slab Cold Roll-Beating Forming

New production technologies have been developed over these last few years as answers in response to new market needs, such as higher production flexibility, lower volume batches, more complex shapes for final pieces and new materials. Cold roll-beating is an advanced precision plastic forming technology to better meet the current requirements. To investigate a material’s behavior in cold roll-beating forming operations, in this paper the principal of slab cold roll-beating was briefly introduced and slab cold roll-beating experiments were carried out, and results of the analysis conducted on the produced pieces in terms of metallographic structure and hardness distributions were reported. Our results show that the cold roll-beating forming can cause the metal surface to harden while improving the mechanical properties of the material, which is interesting in order to understand a material’s behavior when it is subjected to this peculiar deformation process; furthermore, it is of great guiding significance for further applications of the new forming technology.

Elbow의 인장 특성에 미치는 성형 방법의 영향

This study carried out the evaluation and comparison the microstructure and tensile properties of elbow, which is manufactured by the cold and hot forming using STS304L. Hot-formed specimen shows the austenite single-phase, while the cold-formed specimen shows some martensite in austenite structure. Heat treated elbows after the cold- and the hot-forming also show the austenite single-phase. It is well known that the martensite produced by cold forming is inverse transformation into austenite by heat treatment. The cold formed specimen shows higher strength but lower elongation than hot-forming specimen. This is a cause of transformation of some austenite into martensite, dislocation, and precipitate generated during cold-forming. The strength of the cold-formed elbow increased by about 15% and the elongation decreased by about 38%, whereas the hot-formed elbow had no significant change in strength and elongation.

Automotive Steel with a High Product of Strength and Elongation used for Cold and Hot Forming Simultaneously.

A low-cost and easy-to-produce C–Mn–Cr automotive steel for both cold and hot forming is presented in this paper. The alloying element Cr was used to replace Mn in medium-Mn steel and instead of B in hot-formed steel, in order to achieve microstructure control and hardenability improvement, replacing the residual austenite-enhanced plasticization with multidimensional enhanced plasticization through multiphase microstructure design, grain refinement, and dispersion enhancement of second-phase particles. The products of strength and elongation for the cold-formed and hot-formed steel were 20 GPa·% and 18 GPa·%, respectively, while the tensile strengths were more than 1000 MPa and 1500 MPa, respectively. This new automotive steel was also characterized by good oxidation resistance. The mechanisms of strength and plasticization of the experimental automotive steel were analyzed.

Development of optimal modelling of thin-walled elements in the form of a shell made of composite materials

The paper presents the research of the stress-strain state of a multilayer composite shell. The optimal construction of a multilayer shell made of composite materials (CM) in the ANSYS system is determined. The optimal construction of a multilayer composite shell provides maximum strength and rigidity at specified loads. An automated procedure developed for choose the angle of fiber laying in the layer. According to the calculations and constructed models, an experimental model of a multilayer shell made of laminated fiberglass manufactured. For the experimental manufacture of a multilayer shell by cold forming, the working drawings of the press-form made. We manually put the layers of shell made of fiberglass T-25 (BM) TU 6-11-380-76. We made layer-by-layer laying of layers in strict accordance with the calculation model, while observing the sizes of elements and reinforcement angles along the base in each layer. The surface of each layer is an ED-20 epoxy resin with a hardener. This approach can be widely used in the engineering and manufacture of structural elements and products from composite materials.

Structure and Properties of Ca and Zr Containing Heat Resistant Wire Aluminum Alloy Manufactured by Electromagnetic Casting

Experimental aluminum alloy containing 0.8% Ca, 0.5% Zr, 0.5% Fe and 0.25% Si (wt.%), in the form of a long-length rod 12 mm in diameter was manufactured using an electromagnetic casting (EMC) technique. The extremely high cooling rate during alloy solidification (≈104 K/s) caused the formation of a favorable microstructure in the ingot characterized by a small size of the dendritic cells, fine eutectic particles of Ca-containing phases and full dissolution of Zr in Al the solid solution. Due to the microstructure obtained the ingots possess high manufacturability during cold forming (both drawing and rolling). Analysis of the electrical conductivity (EC) and microhardness of the cold rolled strip and cold drawn wire revealed that their temperature dependences are very close. The best combination of hardness and EC in the cold rolled strip was reached after annealing at 450 °C. TEM study of structure evolution revealed that the annealing mode used leads to the formation of L12 type Al3Zr phase precipitates with an average diameter of 10 nm and a high number density. Experimental wire alloy has the best combination of ultimate tensile strength (UTS), electrical conductivity (EC) (200 MPa and 54.8% IACS, respectively) and thermal stability (up to 450 °C) as compared with alloys based on the Al–Zr and Al– rare-earth metal (REM) systems. In addition, it is shown that the presence of calcium in the model alloy increases the electrical conductivity after cold forming operations (both drawing and rolling).

Web crippling of cold-formed carbon steel, stainless steel, and aluminium channels: Investigation and design

Cold-Formed (CF) structural members have recently drawn significant attention in light gauge steel construction. The employment of the different materials, for example CF carbon steel, stainless steel and aluminium, are becoming more common. These structural members are often subjected to concentrated loading conditions, which ultimately leads to failure through web crippling. A plethora of experimental and numerical studies have investigated the web crippling strength and behaviour of CF carbon steel lipped channel sections. However, only limited studies are available for CF stainless steel and aluminium members.This paper presents the investigation of the web crippling strength of CF lipped channel beams under End Two Flange (ETF) loadings and aims to propose a unified equation considering strength factor. Finite Element (FE) models of CF carbon steel, aluminium, and stainless steel lipped channel beams were developed and validated against the available web crippling ETF load case experimental data. Subsequently, a detailed parametric study was performed based on the validated FE models, to establish a wide-ranging data set. New ETF load case web crippling unified design guidelines were proposed for the CF lipped sections made of carbon steel, stainless steel, and aluminium.

Estimation of fatigue life for clinched joints with the Local Strain Approach incorporating the impact of cold forming to cyclic material properties

Joining by forming is a commonly applied technique in the automotive industry to assemble parts of thin metal sheets to meet the demands of lightweight design. The joining operation induces changes in material behaviour due to cold forming, that can be observed in increased hardness in the area close to the joint neck compared to the base material. Complex geometrical features of clinched joints on a small scale and the lack of non-destructive methods to track local stresses and strains require a combined approach utilizing numerical and experimental techniques. Numerical process and loading simulation are performed utilizing commercial finite element software LS-Dyna®. Hardness measurements in the joint are carried out to assess the impact of forming operation. Cyclic material properties are derived from Vickers hardness to estimate fatigue life with the Local Strain Approach using the damage parameter PSWT. Fatigue life estimation with failure criterion crack initiation obtained from simulation results is compared to those from experiments. The results obtained indicate that the Local Strain Approach is suitable for fatigue life estimations of clinched joints under constant amplitude loading as long as the influence of the forming process is considered.

A method for determining equivalent hardening responses to approximate sheet metal viscoplasticity

Recently developed elevated temperature metal forming technologies improve material formability and address the springback issues of cold forming. However, the behaviour of alloys at elevated temperatures is viscoplastic and therefore considerably more complex than under cold forming conditions. This complex behaviour creates a barrier for industrial designers when designing for elevated temperature processes, and therefore leads to these processes often being overlooked. To overcome this barrier, a new method is proposed here to determine simpler strain hardening responses that are equivalent to the viscoplastic responses of alloys at elevated temperatures. The equivalent hardening responses are expressed by single material hardening curves and their hardening exponents are taken as parameters to approximate sheet metal viscoplasticity. This method therefore makes it possible to develop early-stage design guidelines that consider different materials and stamping processes. The method was successfully applied to two viscoplastic alloys under hot stamping conditions to determine equivalent hardening responses. The feasibility of the method has been assessed through comparing finite element simulations using the determined equivalent material models with ones using viscoplastic models. The result showed that the thinning distributions obtained were consistent in both cases, providing evidence that the method can be applied to a range of component designs.•The proposed equivalent material models are simpler than existing viscoplastic material models and can be derived directly from experimental stress-strain data.•Creating design guidelines from equivalent hardening exponents enables a straightforward way to compare between cold and hot stamping capabilities. This comparison makes it possible to make manufacturing process and material selection decisions quickly and effectively at the onset of a design process.•Design guidelines enabled by the proposed method are critical resources to encourage the uptake of new elevated temperature metal forming technologies that facilitate lightweighting and improved environmental efficiency.

Bortezomib in autoimmune hemolytic anemia and beyond.

Bortezomib is a first-in-class, potent, selective and reversible proteasome inhibitor approved for the treatment of multiple myeloma (MM) and relapsed/refractory mantle cell lymphoma. In these diseases, bortezomib targets plasma cells and lymphocytes reducing tumor burden. Recently, preclinical evidence highlighted its efficacy in reducing long-lived plasma cells responsible of autoantibodies production in several models of autoimmune conditions. These findings paved the way to a number of experiences of bortezomib use in patients with various autoimmune conditions, including autoimmune hemolytic anemia (AIHA). The latter is a nice model of autoimmunity in hematology and is caused by the production of autoantibodies against erythrocytes resulting in various degrees of hemolytic anemia. AIHA is classified in warm and cold forms according to the thermal characteristics of the autoantibody, and first-line treatment mainly relies on steroids for warm cases and the anti-CD20 rituximab for cold ones. Relapsed/refractory cases are still an unmet need, and bortezomib has been proposed in this setting with intriguing efficacy. In this review, we collected available literature on bortezomib use in AIHA and in other immune-mediated hematologic and non-hematologic diseases. Overall, most experiences highlight bortezomib efficacy even in multi-relapsed/refractory patients and suggest to consider its use in AIHA after rituximab failure.

Adapted Process Strategies in Front Face Flow Drilling and Thread Forming of Lightweight Casting Materials

By using modern technologies to produce detachable joints in lightweight components, it is possible to reduce material consumption and manufacturing times. By front face flow drilling of lightweight cast materials, expanded bore walls are formed into thin-walled profiles, which are used as core holes for internal threads. The flow drilling process has to be adapted to the specific properties of the regarded materials AZ91 and AlSi10Mg. Thus, enhanced adjustments make it possible to increase the bore qualities significantly. Particularly in order to improve the roundness of the holes, the influence of decreased feed rates on the shape of the flow-drilled holes is analysed. Furthermore, this paper deals with the influence of the process temperature during flow drilling. By varying the predrilling diameter as well as the peripheral speed, the friction between the tool and the workpiece can be significantly influenced. This directly affects the thermally induced formability of the lightweight alloys. In order to produce high strength threads, cold forming is used instead of conventional tapping. In particular, in the context of the adapted flow drilling strategies, the surface qualities and the threads profiles are investigated in detail. Finally, continuous load increase tests were conducted to evaluate the fatigue properties of the formed internal threads using various strategies.

Numerical simulation and experimental study on cold extrusion process for clutch outer gear hub with inner tooth shapes

In this study, the clutch outer gear hub with inner tooth shapes was formed in five steps associated with three processes to pre-form the cup-shaped blank and two extrusion processes to perform the inner tooth shapes. The extrusion processes were the focus of this investigation because the dimensional accuracy of the inner tooth was the primary consideration to control the automobile transmission functionality. The cold extrusion process of the clutch outer gear hub was simulated by the finite element software DEFORM-3D, and the influences of process parameters such as the entrance angle of extruding punch, the thickness of initial blank, and the length of calibration band on forming load, tooth filling, and stress distribution were investigated. The simulation results show that the rounded corner of inner tooth in the clutch outer gear hub is fully filled, the effective stress and the forming load are relatively small with the entrance angle of extruding punch of 30°, the thickness of initial blank of 6.0 mm, and the length of calibration band of 10 mm. Finally, the experiments were carried out by the cold extrusion forming of the clutch outer gear hub. The results prove the feasibility of the cold extrusion process and the correctness of the numerical simulation results.

Improved Strength and Stiffness Characteristics of Cross-laminated Poplar Timber Columns

Timber apart from being a cheap construction material possesses numerous environmental advantages, which makes it one of the highly sought construction material, particularly for moderately loaded residential structures. Timber due to the easy cultivation of timber trees can be made available in abundance. Thus, can serve as an efficient and sustainable building material, provided its structural potential is tapped fully. In this study, various performance improvement techniques have been used for enhancing the axial strength characteristics of a timber specie (Poplar), that is available in abundance, in the northern part of India. Different binding/wrapping techniques have been adopted to utilize Poplar in a laminated form, known as cross-laminated timber (CLT). It has been found that a strength improvement of about 20% can be achieved in CLT short columns by simply bolting the laminates together, while as this improvement can be as high as 32%, provided cold form steel (CFS) sheets are used for strengthening these CLT timber columns. Similarly, in the case of long CLT columns, a strength improvement of 50% is attained when a double cross helix of fibre reinforced polymer (FRP) cloth is adopted for the strengthening purpose. Furthermore, this study is aimed at utilizing small unused, otherwise, waste timber logs/pieces in columns with strength improvement techniques for improved axial strength performance.

ANALYTICAL STUDY OF FLEXURAL BEHAVIOR OF COLD FORMED STEEL SECTIONS WITH AND WITHOUT PERFORATION

This work is about the investigation of flexural behavior cold formed steel member of different cross sections with and without perforation under similar cross sectional area. This work gives idea about the performance of different sections under same loading condition among selected sections and highlights the increasing the flexural strength of member by using stiffener arrangement. In this work three different cross sectional shapes are selected which are C – section, Z – section and Hat shaped section of same cross sectional area analyzed with and without lip under same loading and end condition as well as with perforation. The selected specimens were analyzed analytically using ANSYS Workbench software which shown better comparison among analyzed different geometries of members. Effectiveness of providing edge stiffener to different perforated sections also determined in this work.

Application of preliminary low-temperature heating for cold forming of complex parts on cold former

The results of experimental studies of flow curves of 32CrB4, 20G2R and 1.4034 (analogue of 40Kh13 steel) steels at different heating temperature of workpieces are presented. Rational intervals of preliminary lowtemperature heating of workpieces made of studied steels are obtained. It allows to decrease forces during cold forging, loads on the working tool and to increase of tool life time up to 2 times.

Structural Performance of Cold Form Steel Truss and its Comparison with Hot Rolled Steel

Structural Performance of Cold Form Steel Truss and its Comparison with Hot Rolled Steel

Methodology for managing quality indicators of hardware products with elements of robust design

Production of metalware is characterized with a great variety of shapes and sizes, originality of each product and a multiple-stage process. Various techniques used to process steel sections (such as cold and hot forming, machining, heat treatment, etc.) make it significantly more difficult to tackle product quality problems. Modern product quality management methodologies are based on a wide use of economical, organizational, technical and other methods. This paper describes a production-related quality control method involving certain elements of robust design. This method is based on the definition of noise factors and control parameters, as well as the conduction of noise and principal experiments. The noise experiment will help estimate the impact of disturbing factors (environmental or industrial) on product quality indicators, whereas the principal experiment will help identify the optimum production mode that can deliver the best quality and, at the same time, minimize the production losses. Robust design techniques can be effectively utilized to control the quality of metalware when developing new and optimizing the existing processes. The paper gives an example of how the quality of S10S steel bars can be controlled through the application of efficient production modes enabling to minimize quality-related costs.

ANALYSIS OF METHODS OF MAGNETIC PROCESSING OF OSCE DIES FOR COLD AND BOLT FORMING OF BOLTS AND NUTS

Nowadays, in theoretical works and practice of mechanical engineering the issues related to technological strengthening of tool surface layers and change of their properties in the right direction are being developed. The proposed work is devoted to the study of the issues related to the improvement of operating properties of tools made of fast-cutting steels by magnetic pulse processing, which is a combination of electromagnetic and thermodynamic methods to control the unbalanced structure of the substance. Existing methods of magnetic processing are analyzed, on the one hand, as methods to increase tool resistance by overlaying the magnetic field on the processing area and on the other hand, the influence of the magnetic field on the material from which the tool is made. It is shown that methods related to processing of the tool material itself in constant, alternating and pulsed magnetic fields most stably increase tool stability and quality. With increasing intensity of magnetic field, in which the tool was processed, the value of hardness and heat resistance of steel P6M5K5 increased. Tool holding time during magnetic processing is an important element of the magnetic processing mode. Thus, for P6M5 steel the time of magnetic field exposure during 60 seconds is enough to achieve the greatest increase in the hardness of the material. It is noted that the increase in tool resistance is not due to the disadvantages of heat treatment, but due to improved properties of the tool material, and primarily such operational properties as hardness and heat resistance.

Local hydrogen accumulation after cold forming and heat treatment in punched advanced high strength steel sheets

Hydrogen embrittlement is one of the most crucial problems in the application of advanced high strength steel (AHSS) sheets for the automotive industry. Especially, the severe plastic deformation in punched edges makes the components susceptible to hydrogen assisted cracking (HAC). While small amounts of hydrogen are measured in the bulk material, hydrogen concentration increases in the micrometer-sized shear affected zone many times, along with severe plastic deformation. To contribute to the understanding of local microstructure and local stress states on the hydrogen accumulation in the shear affected zone, two industrial AHSS were investigated. Both steels had the same ultimate tensile strength of 1200 MPa, but different uniform elongations. High-pressure torsion (HPT) deformed samples were used to represent the material state in the shear affected zone. Thermal desorption spectroscopy (TDS), X-ray diffraction (XRD), magnetic retained austenite measurements and electron backscattering diffraction (EBSD) in a high resolution secondary electron microscopy (SEM) were applied among other techniques to gain more insights with microstructural resolution. The hydrogen analysis results of the HPT samples were correlated with the local hydrogen trapping capacity in punched edges. Finally, a simplified “two-zone” model considering the bulk and punched edge as separate zones was developed in order to estimate the local hydrogen concentration of punched AHSS sheets as a function of hydrogen bulk concentration. In a concluding remark it is shown, that the effect of the hydrostatic stress field as trap site is negligibly small compared to other traps.

Key manufacturing technologies of the CFETR 1/8 vacuum vessel sector mockup

• Key technology types involved in CFETR 1/8 V V sector model. • Methods and routes of key technologies of CFETR 1/8 V V sector model. • Current manufacturing progress of CFETR 1/8 V V sector model. This paper introduces key technologies and main advances in the development of the 1/8 vacuum vessel (VV) sector mockup of China fusion engineering test reactor (CFETR). The contour accuracy of each VV shell is controlled within ±2 mm through hot forming, solution treatment, and correction of each hyperboloid shell, and cold forming of the single-curved shell. The welding structure between the 1/8 sectors of CFETR VV on site is simulated by using the welding structure between two 1/16 VV sectors as a model. The narrow-gap TIG (NG-TIG) welding process is designed and explored in the sector welding of the 1/32 VV sector. Electron beam (EB) welding of the port stub is completed, and the weld quality meets the design requirement. The results of phased array ultrasonic testing (PAUT) technology reveal that the testing process meets RCC-MR technical requirements and solves the problems of full volume coverage (i.e., missed detection) and signal-to-noise ratio (i.e., misjudgment) of austenitic stainless steel welds. The automatic ray film arrangement trolley can achieve the automatic arrangement of the X-ray film between double shells when the VV is welded on-site. The measurement solution of three-dimensional complex space solves the problem of collimation positioning measurement during the welding, machining, and assembly of the 1/8 VV sector. The results of the study on the virtual assembly and reverse machining technology provide guidance for the actual assembly of the 1/8 VV sector. Finally, measurement and machining of the allowance are realized to solve the problem of numerical control machining of workpieces without a machining datum.