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Mechanical properties considerably reduce in wood-plastic composites (WPCs) due to the use of wood particles, so the structural applications of these composites are scarce. Thus, embedding continuous fibers is considered the most reliable method for increasing mechanical properties, although there are still challenges in employing this method on a large scale. In this study, an elaborated, special modular die with the capability of adjusting 14 rovings of continuous fibers was designed, manufactured, and implemented to simultaneously embed continuous glass fibers into the extruded WPC profile. More precisely, it was aimed to investigate the arrangement of fiber rovings into the desired positions in a WPC profile of 70 wt% wood content. Also, the effect of the glass bundle tex (at three level, 1200,2400 and 4800) and the fiber position (at four levels, 0, 2, 4, and 6 mm of relative movement of the guides) on the mechanical properties of WPCs was evaluated. According to the results, the flexural strength of reinforced specimens for 1200, 2400, and 4800 texes increased by 85.8, 107, and 159.7%, respectively, compared with the non-reinforced composite. Theoretical values were calculated and compared with experimental outcomes. Based on the results, The failure mode was non-catastrophic, which means the specimens were able to carry partial loading; a desirable characteristic for the structural applications.

In spite of product quality increase in the cold roll forming process by previous practical researches for defects prevention, there are some ill-considered defects such as over-bending, which diminished the product quality in the open section products of this process. This defect which happens by superfluous bending of sheet in the forming stand not only lead to defective products, but also trigger other defects such as edge wrinkling. Since in an elaborate process such as cold roll forming, forming parameters play an active role in defect prevention, the effect of some important parameters is investigated on the over-bending defect and product bending angle by doing 68 experimental tests and numerical simulations in the present study. The list of parameters which are investigated includes bend angle increment, flange width, strip thickness, radius of bend, strength of the materials, and inter-distance between successive stands. In addition, the reason behind the effect of each parameter on the accuracy of the bending angle is laid out. Results show that over-bending defect can be compensated or even eliminated by decreasing the bending angle in each stand, a technique called bending angle increment. Increasing the number of forming stands from two to five causes the over-bending to decrease from 6° to 0°. With bending angle increment being the most impactful factor, bending radius, flange width, and strip thickness have a decreasing impact on over-bending. This study also brings forward a reverse relationship between the strength of the material and the intensity of over-bending. The inter-distance between successive stands was found to have the least effect on over-bending. Results highlight the importance of pre-form rolls at the beginning of the roll forming line. Without the usage of pre-form rolls, the folding of strips on a 60° angle, cannot be done in one stand.

This research is focused on the modeling of the deformation behavior of thin austenitic stainless steel sheets to consider size effect in microscale. First, the material with two different thicknesses is heat treated to obtain different grain sizes, and then they are characterized by the uniaxial tensile tests. The experimental results show that flow stress decreases with the reduction of the sheet thickness and the increase of the grain size. The decline of the flow stress curve is associated with the decrease of the strength coefficient and increase of the hardening exponent as the plastic deformation is scaled down to the microscale. To better model the behavior of the material in the microscale, a new constitutive model is proposed based on the Swift equation to take into account the geometry and grain size effect. This model is also defined in the finite element model of the uniaxial tensile test. It is found that the flow stress curve predicted by the proposed constitutive model shifts down by the decrease of the number of grains across the thickness, which are consistent with the experimental results. In addition, the finite element model with the proposed constitutive model predicts accurately the deformation load in the uniaxial tensile tests. It can be concluded that the proposed constitutive model can provide a good description of the flow stress by considering the interactive effect of specimen and grain sizes and can be used in the modeling of material behavior in microforming processes.

Flexible roll forming process is an advanced manufacturing process, for producing complex and lightweight profiles with variable cross-section. One of the major observed defects in this process is the flange wrinkling of the profiles, which has limited its development especially for the automotive industry. In this paper, the deformation mechanics of the flexible roll forming process is revisited, and the methodology for predicting the onset of wrinkling, which had previously been developed based on the wrinkling limit curve in the space of effective strain versus stress triaxiality, is improved. Then, a new criterion based on the wrinkling limit curve is proposed to predict the possibility of wrinkling in finite element analysis. The criterion is applied to analyze the influence of geometric parameters of the variable cross-section profile and material properties of the sheet on the occurrence of wrinkling. The prediction accuracy is evaluated by performing experiments with different profile shapes. Results show that the new proposed criterion can successfully predict the onset of wrinkling in the flexible roll forming process, and its utilization is recommended for predicting wrinkling in the finite element analysis of sheet metal forming processes.

Fracture is one of the limiting factors of sheet metal forming processes. For this reason, finite element simulations are widely used for providing suitable forming approaches. However, the success of these approaches depends on the correct modeling of fracture in the simulations. In this paper, the fracture behavior of the Aluminum 6061-T6 sheet in the U-bending process is investigated by applying the Gurson–Tvergaard–Needleman model. For this purpose, the Gurson–Tvergaard–Needleman model is defined in the ABAQUS software by means of a proper subroutine. The Gurson–Tvergaard–Needleman model is also modified to take into account the anisotropy effect on the yield surface and the damage evolution due to shear stresses. Then, the proposed models are calibrated using the inverse analysis method based on tension tests with different stress states. The deformation mechanics analysis reveals that considering the normalized Lode angle parameter in the damage function increases the accuracy of fracture prediction, especially in low-stress triaxiality. Comparing the predicted fracture displacements with the experimental value in the U-bending process shows that the modified Gurson–Tvergaard–Needleman model calibrated by the uniaxial tension and in-plane shear tension tests can predict the onset of fracture with acceptable accuracy in the bending process while the original Gurson–Tvergaard–Needleman should be calibrated by a test with stress state close to that in the bending area to have such a result.

In this paper, the modified Mohr-Coulomb (MMC) ductile fracture criterion was adopted to analyze the fracture behavior of the AA6061-T6 aluminum alloy sheet during the U-bending process. Appropriate calibration procedures were employed using various tension tests. A finite element (FE) model was built using the commercial FE code Abaqus/Explicit incorporating the calibrated MMC fracture criterion. It was found that the MMC criterion calibrated by the uniaxial, plane strain, notched, and modified in-plane shear tension tests can predict the onset of fracture in the U-bending process with reasonable accuracy. The error of the predicted fracture displacement was about 2% as compared to experiments. Due to the dependency of the fracture prediction accuracy on the stress state, the effects of process parameters on stress triaxiality and normalized Lode angle parameter were investigated. The negligible effect of process parameters on the stress state confirmed that the calibrated fracture criterion (MMC) was able to predict fracture in different forming conditions with equal accuracy. Also, the proportional stress and strain state in the U-bending process indicate that, besides the high fracture prediction accuracy of the MMC’s damage accumulation function, the fracture forming limit diagram (under proportional loading assumption) can serve as a reliable tool for estimating the onset of fracture in the U-bending process. Therefore, a series of studies were also conducted on damage evolution, crack propagation, principal strains, and fracture displacement during the U-bending process under various forming conditions.

Exact estimates of the power required in manufacturing processes prevent machines from being designed with capacities that are several times greater than those required. Owing to the high energy consumption in the manufacture of tubes and profiles, in this study and considering the effects of some input parameters (including the bend angle increment at each stand, internal distance between the stands, strip thickness, channel flange width, and corner radius) in the production of a symmetrical channel section, the energy consumption and required torque were investigated and optimized using the full factorial method. The results showed that an increase in the bend angle increment at each stand increases the required torque and changes the energy consumption, so an increase in the bend angle increment at each stand from 30° to 60° could save 1 kJ energy for each meter of the product. Moreover, reductions in the flange width and strip thickness reduce the torque and energy for each unit length. The effects of the distance between stands on the energy and the torque depend on the bend angle increment at each stand. Consequently, at lower angle increments, the reduced distance between stands increases the energy consumption and required torque.

The most important step in designing the roll-forming processes is to design of a flower pattern. Currently, this is mostly done based on trial and error and the designer's experience. Using an optimized flower pattern, products with the intended dimensional- and geometrical-tolerance limits could be produced by a minimal number of forming stands. Twisting, which is a common defect in roll-formed asymmetrical-channel sections, affects the appearance and functionality of the product. In this research, the twist defect was studied by finite-element analysis for asymmetrical channels with different flange lengths. Some experiments were also performed on an industrial roll-forming machine to verify the accuracy of the finite-element model. The twist defect was observed to result from a torsional torque produced due to different forming forces applied to long and short flanges. Furthermore, in the roll-forming process of asymmetrical-channel sections, the strip is not deformed symmetrically and the long flange edge touches the roll before the short one. Therefore, the long flange is subjected to a forming force before the short flange. Since predicting the twist angle without costly trial and error in a workshop, or time-consuming finite-element simulations is desirable for the roll-forming industries, a simple relation was introduced considering the geometrical properties of asymmetrical-channel sections. Thereby, asymmetrical forming rolls were presented to form both flanges more symmetrically; a smaller twist defect is achieved.

Flexible roll forming is an advanced process for continuous production of variable cross section profiles. In common practice, the cross section width changes in the transition zone by two tangent circular arcs, one of them is stretched and the other is compressed during the forming operation. Web warping is one of the most common defects in variable cross section flexible roll formed profiles. In this paper, the effect of the bend curve on the web warping is investigated to find a cost-effective method for reducing the web warping. For this purpose, different bend curves (circular, quintic, linear, fractional, and Bezier) are designed for a specific variable cross section profile. Finite element simulations are carried out in Abaqus software, and the longitudinal edge strain and the web warping are obtained in the transition zone. An analytical approach is also utilized to calculate the desirable longitudinal edge strain in this zone. The results show that a higher difference between the imposed and desirable longitudinal edge strains leads to a more web warping. Moreover, at each point of the bend curve, this strain difference rises with the increase of the bend curve concavity. For this reason, the profile with linear bend curve has the lowest web warping and is therefore proposed for the variable cross section profiles. Experiments with different bend curves are performed in a flexible roll forming set-up and the history of the longitudinal edge strain and the web warping are measured. The results confirm the accuracy of the finite element model and the capability of the linear bend curve in reducing the web warping.

Because of the high complexity of the cold roll forming process, an accurate estimate of the torque required at each stand is not possible and, in many cases, the designs of cold roll forming lines are based on trial and error. This study experimentally investigated the fold angle increment at each stand, internal distance between the stands, strip thickness, flange width, and channel corner radius to determine their effects on the required torque. Also, using finite element simulation, the effect of plastic strain distributions in flange and bend zones on the required torque was studied. Then, a regression method was used to categorize each studied variable based on its effect on the required torque to produce a channel section in the roll forming process. The microstructure of the bend zone was also studied to see its relation with strain distribution. Experimental results indicate that the strip thickness, fold angle increment, and flange width have the greatest impacts on the required torque, in order of decreasing impact. Numerical results indicate that, unlike the flange width, any variable which increases the longitudinal edge strain will increase the required torque. The findings are expected to help designers and researchers to optimize the torque required for the roll forming lines. This can consequently lead to an optimized energy consumption.

In this work, the effects of processing parameters including temperature, time, and pressure on the properties of amorphous polyvinyl chloride (PVC)/fiberglass thermoplastic composite laminates were evaluated. The film stacking and hot pressing procedure was used to produce the composite laminates, and samples with [0/90]10 layup and thickness of 3 mm were produced. Flexural strength and modulus of the samples were measured using three-point bending test (according to ASTM D790 standard test method), and microscopic images were used to evaluate the failure mechanisms and impregnation quality. The effects of the parameters on the strength were studied using analysis of variance (ANOVA), and it was found that processing temperature has the maximum effect on the products strength and increase of the temperature up to 230°C increases the flexural strength while more increase of temperature results in the matrix degradation and strength reduction. Also, processing time improves the wetting and impregnation quality; however, more increase of the processing time results in the matrix degradation and excessive reduction of the strength.

Blanking is one of the high speed processes to produce flat products from sheets economically. In order to expand this process to new materials, the blanking of polyvinyl chloride (PVC)/fiberglass thermoplastic composite laminates and composite/aluminum hybrid laminates was investigated. The laminates were produced by the film stacking procedure and then blanked by circular die and punches. The blanking process was done in two levels of clearance including 4% and 8% of the laminates thickness, two levels of punch speed including 40 mm/min and 200 mm/min and at two levels of temperature (room temperature and 80 °C) for both composite and hybrid laminates. The effects of the parameters on the maximum blanking force, cutting energy, and quality and precision of sheared edges were studied. Cutting mechanism for blanking in different conditions was explained. It was concluded that at room temperature, blanked composite and hybrid laminates had a high quality of sheared edges but at elevated temperature, although the maximum blanking force was reduced, the quality of sheared edge was reduced significantly.

A study on new materials usage to produce fiber metal laminates is presented in this work. Amorphous polyvinyl chloride thermoplastic and aluminum 3550 sheets are used to fabricate the fiber metal laminates. Different surface treatments were carried out on the aluminum sheets and the fiber metal laminates were produced using the film stacking procedure. Flexural strength and modulus of the products and also shear strength of bonding were measured using three-point bending test, and their failure mechanisms were evaluated using optical microscope images. Also, the effects of aluminum layer and aluminum/composite laminates bonding on the dynamic properties of the fiber metal laminates were studied using Dynamic Mechanical Thermal Analysis. It was concluded that mechanical roughening of the aluminum sheet has the maximum effect on the aluminum/matrix bonding strength such that simultaneous fracture of composite laminates and aluminum layer in the bending condition was observed in the produced fiber metal laminates without any delamination.

Semi-crystalline thermoplastic-based composite laminates and fiber metal laminates have a narrow forming temperature window, which limits formability of these products. The intention of this study was investigation of non-melting amorphous polyvinyl chloride as a proper matrix to increase the formability and forming temperature window of these products. For this, [45/−45] and [0/90] layups of polyvinyl chloride-based composite laminates and fiber metal laminates were produced using the film-stacking procedure and later press formed into channel sections at six temperatures in the range of 80 to 200 °C. The effects of the layups and forming temperatures on the forming loads and spring back of the formed profiles were measured, and their effects on the fiber buckling, wrinkling, and delamination of the profiles were evaluated using optical microscope images. The effects of layups and forming temperatures on the deformation mechanisms were also analyzed using the grid strain analysis method. Of the fiber metal laminates, 160 °C was found as the minimum forming temperature, and for the composite laminates, 120 and 160 °C were found as the minimum proper forming temperatures of [45/−45] and [0/90] layups, respectively. Finally, the forming temperature windows and formability of polyvinyl chloride matrix composite laminates and fiber metal laminates were found higher than semi-crystalline matrices.

In this study, the factors influencing bowing defects, which reduce quality in the cold roll forming of pre-notched products, are investigated by conducting experimental cold roll forming tests to produce symmetrical channel sections from pre-notched strips. The input parameters influencing bowing comprise factors that are related to the geometric characteristics of roll-formed products (including the distance between holes, distance between holes and strip edge, hole diameter, web and flange channel width, and strip thickness) and factors that are related to the cold roll forming line (including the forming angle increment or flower pattern, uphill and downhill strategies, horizontal distance between stands, and lubrication condition). Through a non-linear regression method, all the input factors were compared with each other to find the ones that are most and least influential on bowing. The obtained results showed that the forming angle increment and distance between holes had the greatest effects on bowing, so that increasing the number of forming stands from two to six reduced bowing more than five times. The results also showed that compared with other factors, the horizontal distance between stands, lubrication condition, and strip thickness have the least effects on bowing.

The present study evaluates the fracture behavior of the AA6061-T6 aluminum alloy during the roll forming process using ductile fracture criteria. Three criteria including Ayada, Rice-Tracey, and normalized Cockroft-Latham were utilized to develop an accurate fracture model for predicting fracture onset during the roll forming process. To this end, the fracture criteria were calibrated using uniaxial, plane-strain, and notched tension tests. The model was developed by integrating the calibrated fracture criteria into the numerical analysis (commercial finite element code Abaqus/Explicit) through an appropriate user subroutine. Based on the results, the damage weighting function and calibration procedures had a significant effect on the accuracy of the fracture prediction during the process. When the uniaxial tension test was used as the calibration test, the normalized Cockroft-Latham and Rice-Tracey ductile fracture criteria were not able to predict the fracture onset during the roll forming process and the Ayada fracture criterion could only predict the bending angle of the forming station where the fracture initiated. On the other hand, calibrating ductile fracture criteria using the plane-strain tension test led to higher accuracy in predicting fracture. The most accurate prediction was obtained using the Ayada fracture criterion calibrated by the plane-strain tension test with an error of 7.85%. Overall, the Ayada fracture criterion and plane-strain tension test can be considered as the most appropriate ductile fracture criterion and calibration method for predicting fracture in the roll forming process, respectively.

In this study, the modified Mohr-Coulomb (MMC) ductile fracture criterion was employed to investigate the ductile fracture during the roll forming process of the AA6061-T6 aluminum alloy. To this aim, the MMC fracture criterion was calibrated based on the tension tests and was integrated into the commercial finite element (FE) Abaqus/Explicit using an appropriate user subroutine. The experimental procedures were designed based on two distinct forming strategies, namely single-stage and multi-stage roll forming processes. The results indicate that the calibrated fracture model based on tension tests is capable to predict the fracture initiation in the single-stage roll forming process at an error rate of 4.47%. Meanwhile, the numerically predicted fracture initiation during the multi-stage roll forming process is inconsistent with the experiments. Hence, a nonlinear damage accumulation rule together with the additional test (multi-stage L-bending) was utilized to predict the onset of fracture throughout the multi-stage roll forming process, considering the effect of deformation mechanics and nonlinear loading path during the process. The results reveal that the fracture onset during the multi-stage roll forming process can be accurately predicted when the MMC fracture criterion with the nonlinear damage accumulation rule is used in the numerical fracture model (with an error of about 9%).

In this study, three ductile fracture criteria were used to investigate the fracture in U-bending of AA6061-T6 aluminum alloy sheets. Considering the importance of the calibration procedure, three different tension tests including the uniaxial, plane strain, and notched tensions were conducted based on the stress state analysis. The Ayada, Rice-Tracey, and normalized Cockroft-Latham fracture criteria were calibrated through a hybrid experimental-numerical method to determine their critical damage values. Fracture envelopes (i.e., the locus of fracture strains) were constructed for the investigated fracture criteria based on the results of various tension tests in their calibration procedure. The calibrated fracture criteria were implemented in the commercial finite element (FE) code Abaqus/Explicit using an appropriate user subroutine. The numerical simulation of the bending process was performed and validated by relevant experiments. The accuracy of the fracture criteria was investigated by comparing fracture displacements predicted using the FE model with those measured by experiments. According to the obtained results, variations of damage function (fracture criteria) and the type of the calibration test utilized for a certain fracture criterion have significant effects on the critical damage value, the fracture envelope, and the accuracy of the fracture prediction. For all investigated criteria, the prediction is reasonable when the critical damage value was calibrated under the plane-strain tension. Thus, the plane strain tension is the best calibration method for predicting fracture in the U-bending process. The most accurate fracture prediction is obtained by normalized Cockroft-Latham fracture criterion, which was calibrated by the plane strain tension test with 2.52% error in fracture prediction. However, the prediction of fracture displacement in U-bending process is very imprecise and strongly overestimated, when the uniaxial tension was used as the calibration test. The Ayada criterion has the lowest error of 11.83% for predicting the fracture displacement when the uniaxial tension test was used as a calibration method. Also, the maximum prediction error (the lowest accuracy) was found to be 51.97% by the normalized Cockroft-Latham criterion calibrated under the uniaxial tension test. Globally, for the U-bending process, it is recommended to calibrate the critical damage values under the plane strain condition. But, when only the uniaxial tension test is available, the Ayada fracture criterion gives the best prediction.

A free bulge test and ductile fracture criteria were used to obtain the forming limit diagrams (FLD) of aluminum alloy AA6063 tubes at high temperatures. Ductile fracture criteria were calibrated using the results of uniaxial tension tests at various elevated temperatures and different strain rates through adjusting the Zener-Holloman parameter. High temperature free bulge test of tubes was simulated in finite element software Abaqus, and tube bursting was predicted using ductile fracture criteria under different loading paths. FLDs which were obtained from finite element simulation were compared to experimental results to select the most accurate criterion for prediction of forming limit diagram. According to the results, all studied ductile fracture criteria predict similarly when forming condition is close to the uniaxial tension, while Ayada criterion predicts the FLD at 473 K and 573 K very well.

Many industrial problems need to be optimized several responses simultaneously. These problems are named multiple response optimization (MRO) and they can have different objectives such as Target, Minimization or Maximization. Committee machine (CM) as a set of some experts such as some artificial neural networks (ANNs) in combination with genetic algorithm (GA) is applied for modeling and optimization of MRO problems. In addition, optimization usually is done on Global Desirability (GD) function. Current article is a development for recent authors' work to determine economic run number for application of CM and GA in MRO problem solving. This study includes a committee machine with four different ANNs. The CM weights are determined with GA which its fitness function is minimizing the RMSE. Then, another GA specifies the final solution with object maximizing the global desirability. This algorithm was implemented on five case studies and the results represent the algorithm can get higher global desirability by repeating the runs and economic run number (ERN) depends on the MRO problem objective. ERN is ten for objective “Target”. This number for objectives which are mixture of minimization and maximization ERN is five. The repetition are continued until these ERN values have considerable increased in maximum GD with respect to average value of GD. More repetition from these ERN to forty five numbers cause a slight raise in maximum GD.

Flexible roll forming is an advanced sheet metal forming process for producing variable cross section profiles. Flange wrinkling at the transition zone where the cross section changes is a major defect in the flexible roll forming process. In this paper, the flange wrinkling at the transition zone is studied using finite element analysis. The results showed that the strip deformation at the transition zone can be considered as a combination of two strip deformations observed in the conventional roll forming process and the flanging process. According to finite element analysis results, when the flange wrinkling occurs, compressive longitudinal strain is smaller than the necessary compressive longitudinal strain calculated by mathematical modeling to obtain the intended profile geometry in the compression zone. Therefore, comparison of compressive longitudinal strain obtained from the finite element analysis and the necessary compressive longitudinal strain is a good criterion to predict the flange wrinkling occurrence. A flexible roll forming setup was developed. Longitudinal strain history is obtained from the finite element simulation and is compared with the experimental data from the flexible roll forming setup. Results show a good agreement and confirm the finite element analysis.

In this paper, the uniaxial loading&ndash, unloading&ndash, reloading (LUR) tensile test was conducted to determine the elastic modulus depending on the plastic pre-strain. To obtain the material parameters and parameter of Yoshida-Uemori&rsquo, s kinematic hardening models, tension&ndash, compression experiments were carried out. The experimental results of the cyclic loading tests together with the numerically predicted response of the plastic behavior were utilized to determine the parameters using the Ls-opt optimization tool. The springback phenomenon is a critical issue in industrial sheet metal forming processes, which could affect the quality of the product. Therefore, it is necessary to represent a method to predict the springback. To achieve this aim, the calibrated plasticity models based on appropriate tests (cyclic loading) were implemented in commercial finite element (FE) code Ls-dyna to predict the springback in the roll forming process. Moreover, appropriate experimental tests were performed to validate the numerical results, which were obtained by the proposed model. The results showed that the hardening models and the variation of elastic modulus have significant impact on springback accuracy. The Yoshida-Uemori&rsquo, s hardening represents more accurate prediction of the springback during the roll forming process when compared to isotropic hardening. Using the chord modulus to determine the reduction in elastic modulus gave more accurate results to predict springback when compared with the unloading and loading modulus to both hardening models.

Reduction of weight and increase of corrosion resistance are among the advantageous applications of aluminum alloys in automotive industry. Producing complicated components with several parts as a uniform part not only increases their strength but also decreases the production sequences and costs. However, achieving this purpose requires sufficient formability of the material. Tube hydroforming is an alternative process to produce complex products. In this process, the higher the material formability the more uniform will be the thickness distribution. In this research, tube hydroforming of aluminum alloy (AA1050) at various temperatures has been investigated numerically to study temperature effect on thickness distribution of final product. Also a warm hydroforming set-up has been designed and manufactured to evaluate numerical results. According to numerical and experimental results in the case of free bulging, unlike the constrained bulging, increase of the process temperature causes more uniform thickness distribution and therefore increases the material formability.

The forming limit diagram (FLD) is a useful method for characterizing the formability of sheet metals. In this article, different numerical models were used to investigate the FLD of tailor-welded blank (TWB). TWBs were CO2 laser-welded samples of interstitial-free (IF) steel sheets with difference in thickness. The results of the numerical models were compared with the experimental FLD as well as with the empirical model proposed by the North American Deep Drawing Research Group. The emphasis of this investigation is to determine the performance of these different approaches in predicting the FLD. These numerical models for FLD are: second derivative of thinning (SDT), effective strain rate (ESR), major strain rate (MSR), thickness strain rate (TSR), and thickness gradient (TG). Results of this research show necking will be happened, when the value of MSR, TSR, ESR criteria is maximum, TG ≤ 0.78 and SDT criterion has the first peak in forming process time. The value of dome height of TWB samples at failure was predicted based on the numerical models for samples with different widths. These numerical predictions were compared with the experimental results. The SDT model indicates a better agreement with experimental results in prediction of both the FLD and the limit dome height (LDH) in comparison to the other numerical models. Both numerical and experimental results show that minimum of LDH is happened in plane strain condition.

Tailor Welded Blanks (TWB) are blanks in which two or more sheets of similar or dissimilar materials, thicknesses, coatings etc. are welded together to form a single sheet before forming. Forming behavior of TWBs is affected by thickness ratio, strength ratio, weld conditions such as weld properties, weld orientation, weld location etc. In this work, Nd:YAG laser welding will be use to weld TWB with different thickness in experimental test. Nd:YAG laser welding parameters such as pulse duration, welding velocity, frequency and peak power will affect formability of TWBs. Taguchis design of experiments methodology is followed to design of experiment and obtain the percentage contribution of factors considered. Erichsen formability test and uniaxial tensile test (ASTM-E8) will be use in experiment setup to compare result of different welding parameters on formability quality of TWBs.

Hydroforming is an advanced process in automotive and aerospace industries to form metal tubes into desired shapes by high pressure fluid. The formation of a two layered tubes has been investigated both numerically and experimentally by a pressurized fluid fed into the internal tube through a nonlinear path with no axial feeding. The experimental setup including two units of die clamping system and pressure intensification system has been designed and built in Tarbiat Modares University. The internal and external layers of hydroformed tubes are used aluminum and copper alloys respectively. Effects of different friction conditions on tubes formability have been investigated. Finite element simulation is performed with LS-Dyna FE explicit code using ETA/Dynaform as the preprocessor. The simulation results show that the part can be formed successfully with the internal pressure of 61 MPa. The finite element results are in agreement with experimental results. It is also shown that imposing high friction condition for external tube and low friction condition for internal tube both will fail more likely.

Considering the necessity of using light weight, high strength and corrosion resistant materials, automotive and aerospace industries need to use advanced production technologies. Hydroforming has been regarded as one of the new technologies in forming of aluminium and magnesium alloys. These alloys have very low formability at room temperature which will be improved at elevated temperatures. In this paper, AA1050 aluminium alloy tube is numerically and experimentally investigated at different temperatures. Thickness distribution in forming zone is studied under different thermal conditions. Numerical results have been verified by experiments and there is a good agreement.

Tube hydroforming technology is still considered a new technique growing fast in automotive and aircraft industries. Many researches on all aspects of this process are still required. Contact friction is one of the most effective parameters on tube wall thinning. To successfully fulfill the process without any common defects, it is very important to determine the proper internal pressure and axial feeding loading paths. In this paper, the effect of lubrication on tube wall thinning on ASTM C11000 copper alloy is discussed as well as the effect of internal pressure and axial feeding. An axisymmetric bulged tube is investigated using theoretical, numerical and experimental methods. Improved linear and non-linear pressure and feeding loading paths are applied and the predicted results are experimentally proved. It is observed that non-linear pressure application gives smoother results. Also proper lubrication plays an important role in success of the process.

Metal forming by a laser source is an efficient and economical method for forming sheet metal into straight bend and doubly curved shape. It can be most useful in the automation of sheet metal forming. This paper presents an FEM model for three dimensional thermo-mechanical simulation of the laser forming. The aim of this simulation and experimental study is to identify the response related to deformation and characterize the effects of process parameters such as laser power, beam diameter, scans velocity and pulse duration, in terms of bending angle for a square sheet part. Extensive experimentation, including a design of experiments, is performed to address the above-mentioned aims. From these experiments it has been determined that laser forming using Nd:YAG laser is a flexible manufacturing process for steel sheet bending.

Based on the concept of Tensor Code a numerical method is presented for analysis of the plastic deformation process of circular sheet metals subjected to transverse impact loading. In the solution process, the equation of motion is solved explicitly with finite difference method in a series of small time steps over a Lagrangian mesh of zones. Using this method, a code has been developed and utilized for investigation of the deformation behavior of an explosively loaded circular sheet metal under various conditions. Deformation characteristics of a sheet under rectangular and triangular pressure distributions are discussed. It is shown that when these simple distributions are combined with each other, their individual effects on the deformation behavior are also combined in the deformation process. Effects of shape and duration of pressure pulse as well as boundary conditions have been explored. Moreover, results of the numerical simulation have been compared with those of theoretical solution and experiments reported by other researchers. Good agreements between them show the validity of the developed code.

Multiple response optimization (MRO) problems are usually solved in three phases that include experiment design, modeling, and optimization. Committee machine (CM) as a set of some experts such as some artificial neural networks (ANNs) is used for modeling phase. Also, the optimization phase is done with different optimization techniques such as genetic algorithm (GA). The current paper is a development of recent authors' work on application of CM in MRO problem solving. In the modeling phase, the CM weights are determined with GA in which its fitness function is minimizing the RMSE. Then, in the optimization phase, the GA specifies the final response with the object to maximize the global desirability. Due to the fact that GA has a stochastic nature, it usually finds the response points near to optimum. Therefore, the performance the algorithm for several times will yield different responses with different GD values. This study includes a committee machine with four different ANNs. The algorithm was implemented on five case studies and the results represent for selected cases, when number of performances is equal to five, increasing in maximum GD with respect to average value of GD will be eleven percent. Increasing repeat number from five to forty-five will raise the maximum GD by only about three percent more. Consequently, the economic run number of the algorithm is five.

In this paper, the Young’s modulus and the yield strength of the strip are considered in order to modify the deformation length analysis proposed by Bhattacharyya et al. New analytical equations are developed assuming an elastic-perfectly plastic material behaviour and the deformation length analysed for the simple case of roll forming a U-channel; the analytical results are verified by comparison with experimental data found in the literature. The proposed elastic-plastic deformation length is shorter than Bhattacharyya’s which is rigid-perfectly plastic. It is observed that the influence of elastic properties on the deformation length is not as significant as the plastic properties; however, the authors believe that the elastic effects become more important under conditions where a major area of the strip is under elastic deformation such as when the flange length is long.