Hole Flanging Research Articles

Cyclic Behavior of Variously Drilled Flange Beam Connected to Box Column

Moment frame system is used as lateral load resisting system against seismic loads. So far, a large body of research has been conducted on steel connections and various types of connections including Reduced Beam Section (RBS) and Drilled Flange Connection (DFC). Using RBS results in formation of inelastic deformation in a part of the beam far from the column flange. They have studied the seismic performance of the recently developed DFC as a simple and efficient alternative to mostly used conventional RBS. In this research, the beam flange was drilled in different patterns in terms of the hole diameter. After simulating the models in Abaqus program, the moment-rotation curves were extracted and analyzed numerically. Having obtained the results of the current research regarding the moment connection where beam flanges are drilled, it is evident that drilling holes in the beam flange with clock pattern can better satisfy the flexibility expectations. Moreover, this pattern had higher capability for plastic hinge transfer from the column face compared to the direct pattern. Additionally, this pattern can reduce the bending stress in penetration weld of direct beam to column connection. Thus, the clock pattern of beam flange holes performed better than the straight one.

Hybrid manufacturing of sheet metals and functionalizing for joining applications via hole flanging

Efficient lightweight solutions are of great interest in many industries (aviation, automotive) particularly regarding the limitation of CO_2-emissions and material waste. An innovative strategy to address these challenges is the use of hybrid manufacturing. Additive manufacturing (laser metal deposition, LMD) and conventional forming methods (hole-flanging) are used to optimize and functionalize AA 6016 sheet metal parts, which are widely used in the manufacturing of car body parts. First of all, the effects of the additive reinforcements on the mechanical and microstructural properties are investigated using tensile and microstructural tests. After manufacturing reinforced blanks and performing subsequent forming operations, the parts are investigated regarding damages and functionalized through threading. This allows the application of a bolt connection, which is tested through rip-off tests to evaluate the effect of the reinforcements on the fracture forces. It can be shown, that reinforcements can be manufactured without defects and virtually no porosity and the formability is only slightly reduced compared to conventional materials. At the same time, the performance of the reinforced bolt joint can be enhanced while the increase in weight can be limited to relatively small amounts.

The effect of strain hardening on the limit forming ratio on the single-step incremental hole flanging process on aluminium plates

Hole-flanging is the process of forming a plate to produce a collar around the hole. This formed collar has several important functions to increase the bonding surface area, as a supporting medium for other components, as a guide, increase construction rigidity, etc. This collar is generally formed through conventional hole flanging which involves making the initial hole in the plate, then punch with a certain profile and a larger diameter pressing the plate in one step of the forming process. This forming process will cause the deformation of the plate so that a collar is formed around the hole. In recent studies, it can be found that the collar can be formed not only with one stage of the conventional hole flanging process, but can also be achieved by a multi-stage incremental hole flanging process using a punch with a multi-purpose general profile. In this research, an experimental study was carried out on the effect of ‘strain hardening’ on the limit forming ratio (LFR) in the single-step incremental hole flanging process on aluminium plates using conical punch. The research hypothesis shows the influence of ‘strain hardening’ on the limit forming ratio (LFR) in the single-step incremental hole flanging process.

Effect of pre-cut hole diameter on deformation mechanics in multi-stage incremental hole flanging of deep drawing quality steel

Incremental hole flanging (IHF) is a relatively new sheet metal forming process to produce intricate shapes without using dedicated punches and dies. The present work focuses on understanding the mechanics of the multi-stage IHF process through experimental studies and the finite element approach. The IHF experiments were performed on deep drawing quality steel sheets with a pre-cut hole diameter of 45 mm, 50 mm, 60 mm, and 70 mm. The cylindrical flanges were formed in four stages with an initial wall angle of 60° to a final angle 90° with an angle increment of 10° in each stage. The maximum and minimum hole expansion ratio was found to be 2.06 and 1.17 respectively. The fracture was observed in a blank of 45 mm pre-cut hole diameter in the third stage at 40 mm depth. The fracture forming limit diagram (FFLD) was determined from incrementally formed varying wall angle conical and pyramidal frustums. Consequently, six different ductile damage models incorporating Hill48 anisotropy plastic theory were successfully calibrated. The Ayyada model showed good agreement with experimental FFLD as compared to all other models. The fracture limit determined experimentally and using the Ayyada model was implemented in the finite element simulation of the IHF process to predict the formability in terms of in-plane strain distribution, forming forces, and thickness distribution. The predicted results matched accurately with the experimental data within a 6% error for all investigated conditions. Noticeably, the strain path in IHF had three deformation modes viz. plane strain, bi-axial stretching, and uni-axial tension, which was comprehended using texture analyses. Finally, irrespective of the initial pre-cut hole diameter, the surface roughness was found to decrease with the number of stages of the IHF process.

OPTIMAL FEED RATE CONTROL STRATEGIES FOR FRICTION DRILLING

The presented paper contains the results of research aimed at developing optimal strategies for controlling the feed rate in the friction drilling process. In particular, the use of linear variable feed rate for individual drilling stages and adaptive feed rate control have been tested. The experiments were carried out with the use of a CNC machine tool equipped with an axial force and torque sensor. Correlation between thrust force and torque was shown, respectively, in relation to the feed drive load and the drive of machine tool spindle. Based on this, a feed rate sensorless control strategy was created to protect against excessive and long-term overload both of the tool and the drives. The following assessment criteria were considered: drilling cycle time, maximum values of thrust and torque, maximum values of feed drive load and drive of machine tool spindle, maximum power and energy effect in the form of work necessary to perform during the drilling process and forming the hole flange. The obtained test results, made for low-carbon steel with a tungsten carbide tool, indicate the advantage of the approach based on the linear variable feed rate and adaptive control over the traditional drilling process based on the step change of the feed rate, according to the recommendations given by the tool manufacturers.

Effect of feed and step depth in hole flanging using single point incremental forming

Single Point Incremental Forming can be used to form hole flanges in automobile and aerospace applications. In hole flanging using single point incremental forming, a study on effect of feed and step depth on formability has been carried out. Hole flange thickness is taken as formability criterion. Moreover, effect of those parameters on surface roughness has also been studied to understand effect of Single Point Incremental Forming. The results obtained by experimental work were analyzed and are presented here.

Numerical and experimental study on the behavior of drilled flange steel beam to CFT column connections

Numerous studies conducted on different types of rigid connections such as reduced beam section (RBS) and drilled flange (DF) showed their ductile behavior. This paper evaluates the seismic performance of moment resisting connections with drilled flange (DF) beams as a simple and efficient alternative for RBS connected to concrete-filled steel tube CFT columns. Different patterns are proposed and the shear capacity of panel zone and ductility of connection are assessed to obtain the optimum case. For this purpose, the finite element Abaqus version 6.14 is used for the numerical models with the thickness ratio of beam flange to web, the type of hole and the number of holes in beam flange as the main parameters. The best arrangement of zigzag hole pattern is first determined by cyclic loading and then experimentally validated. Based on the obtained results, the type and number of holes significantly affect the ductility of connection and decrease stress concentration in the area of beam to column connection. In addition, the idea results in changing plastic hinge from the area of beam-to-column connection and panel zone to the beam in its drilled flange region and reducing the possibility of brittle failure at connection. Further, the arrangement can decrease flexural stress in the groove weld of direct beam-to-CFT column connection by 41% and increase the flexural capacity of panel zone by 31%. Furthermore, a 35% enhancement was observed in the shear capacity of panel zone by increasing the flange to web thickness ratio.

Torna Tezgâhı İle Delikli Flanş Üretiminde Yüzey Pürüzlülüğü Optimizasyonu

Aerospace, automotive, etc. many areas are needed hole flanged parts. The production of hole flange on metal sheets is generally done on CNC milling machine. In this study, unlike literature, the production of hole flanges was made on CNC lathe. DKP 37 sheet with thickness of 1 mm was used as material. Within the scope of the study, 65 mm diameter hole flange was successfully produced and surface roughness was optimized. With signal/noise analysis, it is determined that the most important parameter in the production of hole flanges on CNC lathe is the revolution of the part.

Two-step method to improve geometry accuracy of elongated hole flanging by electromagnetic forming

Electromagnetic forming (EMF) was used to conduct elongated hole flanging in this work. The investigation showed that the low geometry accuracy around the elongated hole flanging attributed from an uncoordinated deformation occurred, including unequal flanging heights and different rebound amounts between the straight edges and the circular edges. The uncoordinated flanging height resulted from different strain distribution. The strain distribution of the circular edges was similar to circular hole flanging, while the strain distribution of the straight edge regions was similar to sheet stretch bending. The uncoordinated rebound amount resulted from different deformation mechanisms, stress distribution, and structural stiffness within the forming regions. To improve the geometry accuracy of the elongated hole flanging, a two-step method combined geometric compensation electromagnetic forming (GC-EMF) and electromagnetic calibration (EM calibration) was proposed. GC-EMF was used to achieve equal flanging height by optimizing the prefabricated hole, while EM calibration after GC-EMF was used to improve the forming accuracy by reducing the amount of rebound. The difference in the flanging heights between the straight edges and the circular edges was only 0.1 mm after the GC-EMF process, when the compensation dimension on both sides of the straight edges of a prefabricated hole was 3.4 mm. The gap between the die and the straight edges was 0.2 mm, the gap between the die and the circular edges was 0.1 mm, after EM calibration. Therefore, the improved geometry accuracy of the elongated hole flanging was achieved by combining the GC-EMF with EM calibration. The results obtained and the method proposed in this work present significant guidance for the process of elongated hole flanging or other irregular hole flanging by EMF.

Hole-flanging of AA7075-O sheets: conventional process versus SPIF

Recently, the research interest in hole-flanging for small and medium-sized batches has turned from conventional press-working to SPIF due to the advantages of incremental forming, such as flexibility and cost of tools. Both technologies have been studied separately using different approaches and, therefore, most studies cannot be easily compared. The aim of this work is to provide a better understanding of the deformation process and the material formability in hole-flanging by critically comparing both forming processes. To this end, a series of experimental tests by press-working and a SPIF process in a single stage, using forming tools with same profile radii, are analysed. The material is AA7075-O sheet of 1.6-mm thickness. The deformation process is analysed by measuring circumferential and meridional strains along the flange using Digital Image Correlation techniques. The process limits are evaluated by using the traditional Limiting Forming Ratio (LFR), which defines the maximum reachable diameter of the flange related to the initial pre-cut hole performed, as well as two additional parameters based on either the flange height or the average thickness reduction. Results conclude that the LFR is not an appropriate measurement of flangeability in processes other than conventional press-working and that SPIF is the preferred process to perform hole flanges with more flexibility in shape

Effect of Process Parameters and Preheating Temperature on Surface Roughness and Thickness Distribution in Hole Flanging using Incremental Sheet Metal Forming

Incremental Sheet metal forming is a die less method of forming which offers high formability. In this research work; effect of step depth, tool rotation speed and preheating temperature on surface roughness and thinning of flange wall is investigated in hole flanging using incremental forming. The parameter optimization is carried out by Taguchi method. Grey relational analysis is carried out to obtain best parameter combination.

Effect of process parameters and preheating temperature on surface roughness and thickness distribution in hole flanging using Incremental Sheet metal Forming

Incremental Sheet metal forming is a die less method of forming which offers high formability. In this research work; effect of step depth, tool rotation speed and preheating temperature on surface roughness and thinning of flange wall is investigated in hole flanging using incremental forming. The parameter optimization is carried out by Taguchi method. Grey relational analysis is carried out to obtain best parameter combination.

Influence of Spiral Tool Path Strategy Towards Incremental Backward Hole-flanging process using Curved Shoulder Forming Tool on Copper Sheet

Many studies have been done as hole flanges have important functional elements in many lightweight construction parts such as to provide sufficient fastening area, stiffness, bearing support, and allow for positioning, etc. Advancement of CAD/CAM software integrated to CNC machines technology has opened a new technology to enable pre-cut hole on sheet metal formed incrementally into required flange profile and height on its periphery known as incremental hole-flanging (IHF). Unlike conventional hole-flanging, the forming of the flange in the IHF process was using a simple tool pressed incrementally into a pre-cut hole with motion path performed by the NC programs on CNC machine. Hence, low volume production and rapid prototyping to reduce initial cost can be achieved to meet today’s production flexibility. There have not been many types of research to study the forming of flanges in incremental backward hole-flanging (IBHF) of closed or semi-closed profiles. By employing full factorial experimental design, this research focused on whether curved shoulder flange forming tool, process variables, and tool geometry of IBHF on copper plate through a spiral tool path strategy affect the produced flange height. The research yielded the results that the curved shoulder flange forming tool was successfully produced flange height through the spiral path strategy. From the data processing, it is shown that the variable of horizontally forming step, the forming rate, the forming tool rotation, and the tool shoulder radius significantly affects the flange height resulted from the IBHF process.

Performance Assessment of Steel Moment Connections Retrofitted with Various Reduced Section Patterns

It is of high importance in seismic retrofitting of lateral load-bearing systems to increase the connections performance. The crucial point in the steel frame retrofitting process is to create plastic hinges in these types of frames. The formation of plastic hinges in beams and near columns generates large strains on column flanges as well as welding metal and heated surroundings, which can lead to brittle failure. The connection should be designed in such a way as to allow plastic hinge formation at certain points of the beam. One such method suggested for retrofit connections is to reduce the beam section locally away from the connection zone. There are various patterns available to locally reduce the beam section, such as circular, elliptical, and symmetric/asymmetric. In recent years, different proposals have been presented to design these connections which vary from older instructions. For this study, radiused cuts in the flange and slotted holes in the web of connection beams were selected for retrofitting analysis. Cyclic behavior, energy damping levels, and ductility of these connections were studied and compared before and after the retrofit by using nonlinear dynamic analysis. The results showed that the symmetrical circular hole pattern in the beam flanges demonstrated reliable performance.

Parametric modeling at defining technological axisymmetric flanging parameters from sheet blanks

The object of the research of the presented article is the internal axisymmetric cylindrical flanging. This work is intended to improve the quality and accelerate the development of technology for flanging round holes from sheet blanks and designing tooling by improving the accuracy of calculating the diameter of the flanging holes in the automated mode for constructing three-dimensional models of a blank and a flanged product. Formulas are proposed that increase the accuracy of calculating the diameter of the hole for flanging. The accuracy of calculating the diameter of the flange hole according to the proposed formulas is determined by comparing the mass of the workpiece with the mass of the flanged part. The algorithm for the automated construction of a sketch of a flanged part and the determination of technological parameters is implemented in KOMPAS-3D. The constructed models allow making changes to their parameters and to provide automatic presentation of the calculation results, as well as their correct graphical interpretation. A discussion of the results of the work allows drawing conclusions about the correctness of the proposed mathematical model and its applicability to the automated construction of three-dimensional models of flanged parts, which will simplify the development of technological and design documentation with a simultaneous increase in their accuracy and reduce the cost of preparing the production.

Experimental studies on incremental hole flanging of steel sheets

ABSTRACTIncremental Hole-Flanging (IHF) process has various applications in rapid prototyping and low volume production of conical and vertical flanges in sheet metal parts. Therefore, understanding mechanics and failure strategies in IHF is very important for successful forming without cracks. In this paper, Deep Drawing (DD) steel blanks with pre-cut hole of 40 and 70 mm diameter are used for multistage conical hole flanging. Conical hole flanges are formed on CNC milling machine with starting angle 60° to final angle 90° with an increment of 10°. The experimental results showed a crack at 80° flange angle with the blank of 40 mm pre-cut hole. The blank with 70 mm-pre-cut hole has no such crack behaviour even at 90° flange angle. The paper also discusses the variation of flange height, surface roughness and forming forces in IHF of DD steel sheets.

Analysis of formability in conventional hole flanging of AA7075-O sheets: punch edge radius effect and limitations of the FLC

Hole flanges are commonly manufactured in mass production by conventional press-working. In an industrial context, the process limits are usually evaluated by means of the Limiting Forming Ratio (LFR), which defines the maximum attainable diameter of the flange related to the initial pre-cut hole. Nevertheless, the LFR does not provide enough information about material deformation, thickness distribution or the expected onset and type of failure. In this sense, a systematic investigation using the Forming Limit Diagram (FLD) is needed. Under these circumstances, the aim of this work is to provide a better understanding of the deformation process in conventional hole flanging, analysing the effect of the punch edge radius as well as the influence of the strain distribution along the hole flange on formability. An experimental campaign on 1.6 mm thickness AA7075 annealed sheet was completed using cylindrical punches with different profile radii. In addition, numerical modelling of the process using finite elements was developed. The results allow better understanding of the physical mechanisms governing material deformation and process formability in very ductile materials. In this regard, this research work contributes to the current state of the art in conventional hole flanging by establishing the modes of failure that prevail in the process and the influence of the bending induced by the tool radius in the flange formability. In addition, the limitations of using conventional FLD for providing a limiting threshold for the strain states attained in the flanges deformed with different punch profiles are also identified.

Analytical modeling and experimental validation of the forming force in several typical incremental sheet forming processes

Abstract Incremental sheet forming (ISF) is recognized as an advanced forming process which is highly flexible in cost-effectively producing small batched sheet metal parts. The forming force is dramatically reduced due to the local deformation and successive forming characteristics compared with traditional stamping process, and has vital impact on forming quality. It may however, be noted, that the forming force prediction models widely used are empirical ones, which needs further improvement for wider applicability. Besides, the force fluctuation in ISF has impact on the geometric accuracy, which has been less studied so far. In the present work, the analytical models for predicting the forming force for single-pass single point incremental forming (SPIF), multi-pass incremental forming (MPIF) and incremental hole flanging (IHF) processes are developed based on the new analytical models used to calculate the contact area and the through-thickness stress. A series of experiments of typical sheet metal parts in different geometries for different materials with varied process parameters including wall angle, step depth, tool radius and sheet metal thickness are used to validate the proposed analytical models. The new prediction models are proved to calculate the forming force and force components along the axial, tangential and radial directions with high accuracy for SPIF, MPISF and IHF processes. Moreover, the mechanism of force fluctuation is also investigated, and it's proved that the force fluctuation is caused by varied elastic deflection of the deforming sheet metal.

Experimental investigation of surface integrity during abrasive edge profiling of nickel-based alloy

Component edge profiling is a novel, complex, labor intensive process that is performed on highly stressed features on aerospace parts such as turbine rotor discs employed in aero-engines. This paper is the first of its kind in this area of research. A novel experimental investigation carried out on surface integrity of Inconel 718 during automated abrasive edge profiling process is presented. Edge profiling tests were conducted using compliant Flexhone™ and Novoflex™globular abrasives on turbine bolt and flange holes to the required aerospace part drawing standard. According to the developed globular brush selection criterion, for a given hole size and edge profile geometry and size, the key process variables that impacted the component life were identified. Nylon impregnated silicon carbide globular brushes (320 grit size) showed a satisfactory abrasive performance between cutting and polishing action on tough class 5 extruded burrs. The optimized abrasive edge profiling parameters were used to manufacture 34 center hole specimens which were tested under low cycle fatigue conditions to confirm the ability of abrasive edge profiling process. Fatigue test results demonstrated that automated abrasive edge profiling does not cause fatigue life deficit compared to manual dressing. Both 2-body and 3-body wear mechanisms were observed. Higher the brushed surface Rv (deepest valley on brushed surface profile), lower the fatigue life of the part.

Determination of the Hole-flangeability for thin Sheets

Sheet metal stretching is one of the most frequently applied sheets forming operation in the industry. Hole flanging is a common sheet forming operation to produce structural sheet metal components. Flanges are used for appearance, rigidity, hidden joints, and strengthening of the edge of sheet metal parts. Trial-end-error is the most common approach for tooling and process design in flanging operations. This paper presents some experimental results of hole-flanging process performed on flat deep drawing steel sheets with circular hole drilled or punched in the centre of blank. Three punches of different geometry i.e. cylindrical, hemispherical and conical were used in this experiment. The effect of both the punch geometry and material mechanical parameters (especially strain hardening and plastic anisotropy) on the limit expansion of the hole, limit strain dependence on hole performing technology as well as sheet thickness distribution along collar formed was determined.