This page has only limited features, please log in for full access.
Bernard Rolfe is currently a Professor (Advanced Manufacturing) in the School of Engineering. He was the Associate Head of School (Research) from 2014-2018, and during his leadership the School tripled its quality journal outputs, and doubled income and PhD numbers. He is on the Academic Advisory Board for the International Federation of Automotive Engineering. Bernard's current research focus is the design and forming of light weight structures. Bernard has received four Vice Chancellor awards and has been part of over fifteen successful nationally competitive large research grants, totalling over AUD $24 million in awarded funds. He has published over 170 refereed articles.
This paper presents a method for four-dimensional (4D) printing of soft pneumatic actuator robot (SPA)s, using nonlinear machine learning (ML) and finite element model (FEM). A FEM is developed to accurately simulate experimental actuation to obtain training data for the ML modeling. More than a thousand data training samples from the hyperelastic material FEM model generated to use as training data for the ML model, which was developed to predict the geometrical requirements of the 4D-printed SPA to realize the bending required for specific tasks. The ML model accurately predicted FEM and experimental data and proved to be a viable solution for 4D printing of soft robots and dynamic structures. This work helps to understand how to develop geometrical soft robots’ designs for nonlinear 4D printing problems using ML and FEM.
Ali Zolfagharian; Lorena Durran; Saleh Gharaie; Bernard Rolfe; Akif Kaynak; Mahdi Bodaghi. 4D printing soft robots guided by machine learning and finite element models. Sensors and Actuators A: Physical 2021, 328, 112774 .
AMA StyleAli Zolfagharian, Lorena Durran, Saleh Gharaie, Bernard Rolfe, Akif Kaynak, Mahdi Bodaghi. 4D printing soft robots guided by machine learning and finite element models. Sensors and Actuators A: Physical. 2021; 328 ():112774.
Chicago/Turabian StyleAli Zolfagharian; Lorena Durran; Saleh Gharaie; Bernard Rolfe; Akif Kaynak; Mahdi Bodaghi. 2021. "4D printing soft robots guided by machine learning and finite element models." Sensors and Actuators A: Physical 328, no. : 112774.
The smooth design of self-supporting topologies has attracted great attention in the design for additive manufacturing (DfAM) field as it cannot only enhance the manufacturability of optimized designs but can obtain light-weight designs that satisfy specific performance requirements. This paper integrates Langelaar’s AM filter into the Smooth-Edged Material Distribution for Optimizing Topology (SEMDOT) algorithm—a new element-based topology optimization method capable of forming smooth boundaries—to obtain print-ready designs without introducing post-processing methods for smoothing boundaries before fabrication and adding extra support structures during fabrication. The effects of different build orientations and critical overhang angles on self-supporting topologies are demonstrated by solving several compliance minimization (stiffness maximization) problems. In addition, a typical compliant mechanism design problem—the force inverter design—is solved to further demonstrate the effectiveness of the combination between SEMDOT and Langelaar’s AM filter.
Yun-Fei Fu; Kazem Ghabraie; Bernard Rolfe; Yanan Wang; Louis N. S. Chiu. Smooth Design of 3D Self-Supporting Topologies Using Additive Manufacturing Filter and SEMDOT. Applied Sciences 2020, 11, 238 .
AMA StyleYun-Fei Fu, Kazem Ghabraie, Bernard Rolfe, Yanan Wang, Louis N. S. Chiu. Smooth Design of 3D Self-Supporting Topologies Using Additive Manufacturing Filter and SEMDOT. Applied Sciences. 2020; 11 (1):238.
Chicago/Turabian StyleYun-Fei Fu; Kazem Ghabraie; Bernard Rolfe; Yanan Wang; Louis N. S. Chiu. 2020. "Smooth Design of 3D Self-Supporting Topologies Using Additive Manufacturing Filter and SEMDOT." Applied Sciences 11, no. 1: 238.
This study investigates the effect of grain size and composition on the material properties and forming limits of commercially supplied stainless steel foil for bipolar plate manufacture via tensile, stretch forming and micro-stamping trials. It is shown that in commercially supplied stainless steel the grain size can vary significantly and that ‘size effects’ can be influenced by prior steel processing and composition effects. While the forming limits in micro-stamping appear to be directly linked to the plane strain forming limits of the individual stainless steel alloys, there was a clear effect of the tensile anisotropy. In contrast to previous studies, forming severity and the likelihood of material failure did not increase with a decreasing channel profile radius. This was related to inaccuracies of the forming tool profile shape.
Matthias Weiss; Peng Zhang; Michael P. Pereira; Bernard F. Rolfe; Daniel E. Wilkosz; Peter D. Hodgson. Understanding Size Effects and Forming Limits in the Micro-Stamping of Industrial Stainless Steel Foils. Metals 2020, 11, 38 .
AMA StyleMatthias Weiss, Peng Zhang, Michael P. Pereira, Bernard F. Rolfe, Daniel E. Wilkosz, Peter D. Hodgson. Understanding Size Effects and Forming Limits in the Micro-Stamping of Industrial Stainless Steel Foils. Metals. 2020; 11 (1):38.
Chicago/Turabian StyleMatthias Weiss; Peng Zhang; Michael P. Pereira; Bernard F. Rolfe; Daniel E. Wilkosz; Peter D. Hodgson. 2020. "Understanding Size Effects and Forming Limits in the Micro-Stamping of Industrial Stainless Steel Foils." Metals 11, no. 1: 38.
This study investigates the effect of position on build-plate on the dimensional deviations for stainless steel 316L samples made by laser powder-bed fusion. To understand the effect of sample position on the build-plate (substrate) with respect to shrinkage and dimensional deviation, 36 samples in a 6 × 6 array were printed with three repetitions. The value of the diameter was measured at 10 points along the vertical axis in the perpendicular and parallel directions to the flow of the assisted gas. The results of the experiment show that there is shrinkage in both directions with respect to the gas flow. However, the extent of deviation in the perpendicular direction to the gas flow is greater compared to the parallel diameters for the samples. This can be related to the pressure of assisted gas and the difference in cooling rate corresponding to the position of the samples on the building substrate. The hypothesis is proved by conducting further experiments regulating the amount of gas flow by adjusting the individual nozzle for the gas flow to the build chamber. The reason for these deviations is speculated to be related to the rheology of the melt pool. This research could lay a solid foundation for the future development of a compensation strategy to nullify the effect of shrinkage and dimensional deviations on parts made using the laser powder-bed fusion technique. The results of shrinkage of the columns appear to suggest that there is an effect on the circularity from the assisting gas.
Jithin Kozhuthala Veetil; Mahyar Khorasani; Amirhossein Ghasemi; Bernard Rolfe; Ivo Vrooijink; Karin Van Beurden; Sebastiaan Moes; Ian Gibson. Build position-based dimensional deviations of laser powder-bed fusion of stainless steel 316L. Precision Engineering 2020, 67, 1 .
AMA StyleJithin Kozhuthala Veetil, Mahyar Khorasani, Amirhossein Ghasemi, Bernard Rolfe, Ivo Vrooijink, Karin Van Beurden, Sebastiaan Moes, Ian Gibson. Build position-based dimensional deviations of laser powder-bed fusion of stainless steel 316L. Precision Engineering. 2020; 67 ():1.
Chicago/Turabian StyleJithin Kozhuthala Veetil; Mahyar Khorasani; Amirhossein Ghasemi; Bernard Rolfe; Ivo Vrooijink; Karin Van Beurden; Sebastiaan Moes; Ian Gibson. 2020. "Build position-based dimensional deviations of laser powder-bed fusion of stainless steel 316L." Precision Engineering 67, no. : 1.
A new approach was used to characterise the hardening, instability and fracture behaviour of ultra-thin (0.1 mm) stainless steel sheets under stress triaxiality ranging from 0.37 to 0.66. The Swift and the linear hardening laws were used to capture the stress–strain relationship for the complete level of plastic deformation that exceeds that achievable by a uniaxial tensile test. For this, the Virtual Field Method (VFM) was applied, which uses the strain field measured on the surface of the notched samples, to output the material hardening parameters. To determine one set of hardening parameters that fits all conditions of stress triaxiality, an upper bound of major strain was selected for the VFM fitting that optimises a single set of hardening parameters across all of the stress triaxiality conditions. The void coalescence parameter in a Gurson-Tvergaard-Needleman (GTN) fracture model was calibrated and the model results for fracture initiation were validated experimentally with a quasi-biaxial stretching test.
Peng Zhang; Michael P. Pereira; Buddhika Abeyrathna; Bernard F. Rolfe; Daniel E. Wilkosz; Peter Hodgson; Matthias Weiss. Plastic instability and fracture of ultra-thin stainless-steel sheet. International Journal of Solids and Structures 2020, 202, 699 -716.
AMA StylePeng Zhang, Michael P. Pereira, Buddhika Abeyrathna, Bernard F. Rolfe, Daniel E. Wilkosz, Peter Hodgson, Matthias Weiss. Plastic instability and fracture of ultra-thin stainless-steel sheet. International Journal of Solids and Structures. 2020; 202 ():699-716.
Chicago/Turabian StylePeng Zhang; Michael P. Pereira; Buddhika Abeyrathna; Bernard F. Rolfe; Daniel E. Wilkosz; Peter Hodgson; Matthias Weiss. 2020. "Plastic instability and fracture of ultra-thin stainless-steel sheet." International Journal of Solids and Structures 202, no. : 699-716.
In the sheet metal stamping process, during sliding contact between the tool and sheet, it is expected that severe events such as tool wear or fracture on the sheet generate acoustic emission (AE) burst waveforms. Attempts have been made in the literature to correlate the AE burst waveform with the wear mechanisms. However, there is a need for additional studies to understand the frequency characteristics of the AE burst waveform due to the severity and progression of the galling wear. This paper will determine the AE frequency characteristics that can be used to monitor galling wear, independent of the experimental process examined. The AE burst waveforms generated during the stamping and scratch tests are analysed in this paper to understand the change in the AE frequency characteristics with the galling severity. These AE burst waveforms were investigated using the Hilbert Huang Transform (HHT) time-frequency technique, band power, and mean-frequency. Subsequently, these AE frequency features are correlated with the wear behaviour observed via high-resolution profilometer images of the stamped parts and scratch surfaces. Initially, the HHT technique is applied to the AE burst waveform to understand the influence of wear severity in the power distribution over the wide AE frequency range. Later, the AE bandpower feature is used to quantitatively analyse the power in each frequency interval during the unworn and worn tool conditions. Finally, the mean-frequency of AE signal is identified to be able to determine the onset of galling wear. The new knowledge defined in this paper is the AE frequency features and wear measurement feature that can be used to indicate the onset of galling wear, irrespective of the processes examined.
Vignesh. V. Shanbhag; Bernard. F. Rolfe; Michael. P. Pereira. Investigation of Galling Wear Using Acoustic Emission Frequency Characteristics. Lubricants 2020, 8, 25 .
AMA StyleVignesh. V. Shanbhag, Bernard. F. Rolfe, Michael. P. Pereira. Investigation of Galling Wear Using Acoustic Emission Frequency Characteristics. Lubricants. 2020; 8 (3):25.
Chicago/Turabian StyleVignesh. V. Shanbhag; Bernard. F. Rolfe; Michael. P. Pereira. 2020. "Investigation of Galling Wear Using Acoustic Emission Frequency Characteristics." Lubricants 8, no. 3: 25.
Background and purpose Radiotherapy is one of the most effective cancer treatment techniques, however, delivering the optimal radiation dosage is challenging due to movements of the patient during treatment. Immobilisation devices are typically used to minimise motion. This paper reviews published research investigating the use of 3D printing (additive manufacturing) to produce patient-specific immobilisation devices, and compares these to traditional devices. Materials and methods A systematic review was conducted across thirty-eight databases, with results limited to those published between January 2000 and January 2019. A total of eighteen papers suitably detailed the use of 3D printing to manufacture and test immobilisers, and were included in this review. This included ten journal papers, five posters, two conference papers and one thesis. Results 61% of relevant studies featured human subjects, 22% focussed on animal subjects, 11% used phantoms, and one study utilised experimental test methods. Advantages of 3D printed immobilisers reported in literature included improved patient experience and comfort over traditional methods, as well as high levels of accuracy between immobiliser and patient, repeatable setup, and similar beam attenuation properties to thermoformed immobilisers. Disadvantages included the slow 3D printing process and the potential for inaccuracies in the digitisation of patient geometry. Conclusion It was found that a lack of technical knowledge, combined with disparate studies with small patient samples, required further research in order to validate claims supporting the benefits of 3D printing to improve patient comfort or treatment accuracy.
Amirhossein Asfia; James Novak; Mazher Iqbal Mohammed; Bernard Rolfe; Tomas Kron. A review of 3D printed patient specific immobilisation devices in radiotherapy. Physics and Imaging in Radiation Oncology 2020, 13, 30 -35.
AMA StyleAmirhossein Asfia, James Novak, Mazher Iqbal Mohammed, Bernard Rolfe, Tomas Kron. A review of 3D printed patient specific immobilisation devices in radiotherapy. Physics and Imaging in Radiation Oncology. 2020; 13 ():30-35.
Chicago/Turabian StyleAmirhossein Asfia; James Novak; Mazher Iqbal Mohammed; Bernard Rolfe; Tomas Kron. 2020. "A review of 3D printed patient specific immobilisation devices in radiotherapy." Physics and Imaging in Radiation Oncology 13, no. : 30-35.
Incorporating additive manufacturing (AM) constraints in topology optimisation can lead to performance optimality while ensuring manufacturability of designs. Numerical techniques have been previously proposed to obtain support-free designs in AM, however, few works have verified the manufacturability of their solutions. Physical verification of manufacturability becomes more critical recalling that the conventional density-based topology optimisation methods will inevitably require post-processing to smooth the boundaries before sending the results to a 3D printer. This paper presents the smooth design of self-supporting topologies using the combination of a new Solid Isotropic Microstructure with Penalisation method (SIMP) developed based on elemental volume fractions and an existing AM filter. Manufacturability of selected simulation results are verified with Fused Deposition Modeling (FDM) technology. It is illustrated that the proposed method is able to generate convergent self-supporting topologies which are printable using FDM.
Yun-Fei Fu; Bernard Rolfe; Louis N. S. Chiu; Yanan Wang; Xiaodong Huang; Kazem Ghabraie. Design and experimental validation of self-supporting topologies for additive manufacturing. Virtual and Physical Prototyping 2019, 14, 382 -394.
AMA StyleYun-Fei Fu, Bernard Rolfe, Louis N. S. Chiu, Yanan Wang, Xiaodong Huang, Kazem Ghabraie. Design and experimental validation of self-supporting topologies for additive manufacturing. Virtual and Physical Prototyping. 2019; 14 (4):382-394.
Chicago/Turabian StyleYun-Fei Fu; Bernard Rolfe; Louis N. S. Chiu; Yanan Wang; Xiaodong Huang; Kazem Ghabraie. 2019. "Design and experimental validation of self-supporting topologies for additive manufacturing." Virtual and Physical Prototyping 14, no. 4: 382-394.
This paper aims to explore the effects of optimisation parameters (the filter radius, mesh size, and target volume fraction) on the compliance and manufacturability of smooth self-supporting topologies for additive manufacturing (AM); and conduct manufacturability experiments of selected simulation results with the Selective Laser Melting (SLM) technology. In this study, smooth self-supporting topologies are obtained with a combined method of the Solid Isotropic Microstructure with Penalization method (SIMP) with the smooth boundary representation and Langelaar's AM filter. Numerical examples illustrate that a higher filter radius can lead to simpler smooth self-supporting topologies, but curved top corners that violate the critical overhang angle of 45° are inevitably generated. Additionally, the mesh size is found to be not as an important factor as the filter radius in affecting the manufacturability and performance. As a result of the self-supporting constraint, a small volume fraction can easily result in structural discontinuity. The experimental results demonstrate that the self-supporting topologies obtained are all printable in SLM.
Yun-Fei Fu; Bernard Rolfe; Louis N. S. Chiu; Yanan Wang; Xiaodong Huang; Kazem Ghabraie. Parametric studies and manufacturability experiments on smooth self-supporting topologies. Virtual and Physical Prototyping 2019, 15, 22 -34.
AMA StyleYun-Fei Fu, Bernard Rolfe, Louis N. S. Chiu, Yanan Wang, Xiaodong Huang, Kazem Ghabraie. Parametric studies and manufacturability experiments on smooth self-supporting topologies. Virtual and Physical Prototyping. 2019; 15 (1):22-34.
Chicago/Turabian StyleYun-Fei Fu; Bernard Rolfe; Louis N. S. Chiu; Yanan Wang; Xiaodong Huang; Kazem Ghabraie. 2019. "Parametric studies and manufacturability experiments on smooth self-supporting topologies." Virtual and Physical Prototyping 15, no. 1: 22-34.
Stamping tools are prone to wear due to the increased use of advanced high strength steels in the automotive industry. For active monitoring of the wear state of stamping tools using acoustic emission, it is important to establish a correlation between specific wear mechanisms and the acoustic emission signals. An adhesive wear mode (galling), which is commonly observed on the stamping tool, can occur in combination with multiple abrasive wear modes on the workpiece, such as ploughing and cutting. This study will establish a correlation between the sources of the acoustic emission signal to the specific surface wear mechanism observed in the stamping process. Therefore, to investigate the source of acoustic emission signal, sheet metal stamping wear tests were conducted using un-worn and worn tool steel dies (AISI D2) and advanced high strength steel sheet (DP780). Accelerated tribology tests were also conducted using a scratch tester with the same material combination, where galling, cutting and ploughing wear mechanisms were observed. By correlating the acoustic emission features, such as power spectral density from the stamping test and the scratch test, it was observed that the change in the acoustic emission signal observed in the stamping process could be attributed to the galling wear mechanismsThis study contributes to the fundamental understanding of different wear mechanisms in sheet metal forming process, the resulting acoustic emissions, and how these can be utilized to develop active monitoring of the tools in the future.
Vignesh V Shanbhag; Bernard F Rolfe; N Arunachalam; Michael P Pereira. Understanding the source of acoustic emission signals during the wear of stamping tools. IOP Conference Series: Materials Science and Engineering 2018, 418, 012098 .
AMA StyleVignesh V Shanbhag, Bernard F Rolfe, N Arunachalam, Michael P Pereira. Understanding the source of acoustic emission signals during the wear of stamping tools. IOP Conference Series: Materials Science and Engineering. 2018; 418 (1):012098.
Chicago/Turabian StyleVignesh V Shanbhag; Bernard F Rolfe; N Arunachalam; Michael P Pereira. 2018. "Understanding the source of acoustic emission signals during the wear of stamping tools." IOP Conference Series: Materials Science and Engineering 418, no. 1: 012098.
Additive manufacturing has been receiving attention as it is capable of producing complex geometries previously unmanufacturable, particularly those resulting from topology optimisation. However, additive manufacturing processes like Selective Laser Melting result in materials that have varying ratios of anisotropy. Currently, the majority of topology optimisation algorithms utilise an isotropic assumption. Through a case study, the present study confirms the hypothesis that anisotropy in the stiffness of the material has a significant detrimental effect on the optimisation outcome where (1) increasing ratio of anisotropy; and/or (2) increasing deviation of the building angle away from being parallel or perpendicular to the principal loading direction results in the decrease of volume reduction achievable through topology optimisation. Material with an out-of-plane shear modulus which is very different from the “near isotropic” value also performed poorly. Compared with the 50% weight reduction of an isotropic case, the worst anisotropic case only managed approximately 27% weight saving. However, in the cases where both the building angle is small (<30°) and the degree of anisotropy is low (≤±10%), the impact on resultant volume reduction was small (<10%). This study indicates that, in general, material anisotropy should be considered in topology optimisation for additive manufacturing.
Louis N.S. Chiu; Bernard Rolfe; Xinhua Wu; Wenyi Yan. Effect of stiffness anisotropy on topology optimisation of additively manufactured structures. Engineering Structures 2018, 171, 842 -848.
AMA StyleLouis N.S. Chiu, Bernard Rolfe, Xinhua Wu, Wenyi Yan. Effect of stiffness anisotropy on topology optimisation of additively manufactured structures. Engineering Structures. 2018; 171 ():842-848.
Chicago/Turabian StyleLouis N.S. Chiu; Bernard Rolfe; Xinhua Wu; Wenyi Yan. 2018. "Effect of stiffness anisotropy on topology optimisation of additively manufactured structures." Engineering Structures 171, no. : 842-848.
Ossama Mamdouh Badr; Bernard Rolfe; Peng Zhang; Matthias Weiss. Applying a new constitutive model to analyse the springback behaviour of titanium in bending and roll forming. International Journal of Mechanical Sciences 2017, 128-129, 389 -400.
AMA StyleOssama Mamdouh Badr, Bernard Rolfe, Peng Zhang, Matthias Weiss. Applying a new constitutive model to analyse the springback behaviour of titanium in bending and roll forming. International Journal of Mechanical Sciences. 2017; 128-129 ():389-400.
Chicago/Turabian StyleOssama Mamdouh Badr; Bernard Rolfe; Peng Zhang; Matthias Weiss. 2017. "Applying a new constitutive model to analyse the springback behaviour of titanium in bending and roll forming." International Journal of Mechanical Sciences 128-129, no. : 389-400.
Blind source extraction (BSE) aims to extract the source of interest (SOI) from the outputs of a mixing system, which is a challenging problem. A property existing in many signals is cyclostationarity and this property has been widely exploited in BSE. While various cyclostationarity-based BSE methods have been reported in the literature, they usually require the mixing system to be instantaneous. In this paper, we address BSE in the context that the mixing system is convolutional. Specifically, a new BSE method is developed to extract cyclostationary source signal from the outputs of a multiple-input-multiple-output finite-impulse-response mixing system. It is shown that if the SOI has a unique cyclostationary frequency, it can be recovered from the measured data. The effectiveness of the proposed BSE method is demonstrated by simulation results.
Yong Xiang; Dezhong Peng; Indivarie Ubhayaratne; Bernard Rolfe; Michael Pereira. Second-Order Cyclostationary Statistics Based Blind Source Extraction from Convolutional Mixtures. IEEE Access 2017, 5, 1 -1.
AMA StyleYong Xiang, Dezhong Peng, Indivarie Ubhayaratne, Bernard Rolfe, Michael Pereira. Second-Order Cyclostationary Statistics Based Blind Source Extraction from Convolutional Mixtures. IEEE Access. 2017; 5 ():1-1.
Chicago/Turabian StyleYong Xiang; Dezhong Peng; Indivarie Ubhayaratne; Bernard Rolfe; Michael Pereira. 2017. "Second-Order Cyclostationary Statistics Based Blind Source Extraction from Convolutional Mixtures." IEEE Access 5, no. : 1-1.
Coil set is a phenomenon occurring in industrial sheet metal in which the strip retains a residual curvature as it comes off the coil. The roll forming of two coils exhibiting coil set is studied; each coil has similar tensile and bending properties. It is shown that there are significant differences in shape defects in the industrial roll forming of a particular channel section depending on whether the strip is fed in with the convex side upwards or downwards. The properties in bending in the longitudinal direction were determined using a free bending test and found to depend on the direction of bending; when bending so that the curvature increased in the direction of the residual curvature, the bending yield stress was almost 50% lower compared with bending in the direction opposite to the residual curvature, i.e. in straightening the strip. In the transverse direction, bending properties were independent of the direction of bending. The defects measured in the roll formed product were twist and flare and the magnitude of both were greatest when the strip was formed with the residual curvature convex upwards in the roll forming line. The process was simulated using the commercial software package Copra FEA; two sets of material property data were used − both were derived by an inverse method from the bending tests. One case used bend test data from tests in which the curvature increased in the same direction as the residual curvature, and the other set for curvature in the opposite direction. The defects predicted by the numerical analyses reproduced the trends observed in the industrial trials regarding twist and end flare even though the levels predicted were too high. Comparison of the bending test results with other work suggests that the strip is subjected to plastic deformation (straightening) as it comes off the coil resulting in an asymmetric longitudinal residual stress distribution through the thickness. Both the experiments and the results of the simulation strengthen the view that differences in the mechanical behaviour in bending near the elastic plastic transition indicate the presence of residual stresses that influence final shape in the roll forming process.
Matthias Weiss; Buddhika Abeyrathna; Bernard Rolfe; André Abee; Henry Wolfkamp. Effect of coil set on shape defects in roll forming steel strip. Journal of Manufacturing Processes 2017, 25, 8 -15.
AMA StyleMatthias Weiss, Buddhika Abeyrathna, Bernard Rolfe, André Abee, Henry Wolfkamp. Effect of coil set on shape defects in roll forming steel strip. Journal of Manufacturing Processes. 2017; 25 ():8-15.
Chicago/Turabian StyleMatthias Weiss; Buddhika Abeyrathna; Bernard Rolfe; André Abee; Henry Wolfkamp. 2017. "Effect of coil set on shape defects in roll forming steel strip." Journal of Manufacturing Processes 25, no. : 8-15.
Stamping tool wear can significantly degrade product quality, and hence, online tool condition monitoring is a timely need in many manufacturing industries. Even though a large amount of research has been conducted employing different sensor signals, there is still an unmet demand for a low-cost easy to set up condition monitoring system. Audio signal analysis is a simple method that has the potential to meet this demand, but has not been previously used for stamping process monitoring. Hence, this paper studies the existence and the significance of the correlation between emitted sound signals and the wear state of sheet metal stamping tools. The corrupting sources generated by the tooling of the stamping press and surrounding machinery have higher amplitudes compared to that of the sound emitted by the stamping operation itself. Therefore, a newly developed semi-blind signal extraction technique was employed as a pre-processing technique to mitigate the contribution of these corrupting sources. The spectral analysis results of the raw and extracted signals demonstrate a significant qualitative relationship between wear progression and the emitted sound signature. This study lays the basis for employing low-cost audio signal analysis in the development of a real-time industrial tool condition monitoring system.
Indivarie Ubhayaratne; Michael P. Pereira; Yong Xiang; Bernard F. Rolfe. Audio signal analysis for tool wear monitoring in sheet metal stamping. Mechanical Systems and Signal Processing 2016, 85, 809 -826.
AMA StyleIndivarie Ubhayaratne, Michael P. Pereira, Yong Xiang, Bernard F. Rolfe. Audio signal analysis for tool wear monitoring in sheet metal stamping. Mechanical Systems and Signal Processing. 2016; 85 ():809-826.
Chicago/Turabian StyleIndivarie Ubhayaratne; Michael P. Pereira; Yong Xiang; Bernard F. Rolfe. 2016. "Audio signal analysis for tool wear monitoring in sheet metal stamping." Mechanical Systems and Signal Processing 85, no. : 809-826.
Roll forming is a continuous process in which a flat strip is incrementally bent to a desired profile. This process is increasingly used in automotive industry to form High Strength Steel (HSS) and Advanced High Strength Steel (AHSS) for structural components. Because of the large variety of applications of roll forming in the industry, Finite Element Analysis (FEA) is increasingly employed for roll forming process design. Formability and springback are two major concerns in the roll forming AHSS materials. Previous studies have shown that the elastic modulus (Young’s modulus) of AHSS materials can change when the material undergoes plastic deformation and the main goal of this study is to investigate the effect of a change in elastic modulus during forming on springback in roll forming. FEA has been applied for the roll forming simulation of a V-section using material data determined by experimental loading-unloading tests performed on mild, XF400, and DP780 steel. The results show that the reduction of the elastic modulus with pre-strain significantly influences springback in the roll forming of high strength steel while its effect is less when a softer steel is formed.
A. Abvabi; J. Mendiguren; Andreas Kupke; B. Rolfe; M. Weiss. Evolution of elastic modulus in roll forming. International Journal of Material Forming 2016, 10, 463 -471.
AMA StyleA. Abvabi, J. Mendiguren, Andreas Kupke, B. Rolfe, M. Weiss. Evolution of elastic modulus in roll forming. International Journal of Material Forming. 2016; 10 (3):463-471.
Chicago/Turabian StyleA. Abvabi; J. Mendiguren; Andreas Kupke; B. Rolfe; M. Weiss. 2016. "Evolution of elastic modulus in roll forming." International Journal of Material Forming 10, no. 3: 463-471.
The final mechanical properties of hot stamped components are affected by many process and material parameters due to the multidisciplinary nature of this thermal-mechanical-metallurgical process. The phase transformation, which depends on the temperature field and history, determines the final microstructure and consequently the final mechanical properties. Tailored hot stamping parts - where the cooling rates are locally chosen to achieve structures with graded properties - has been increasingly adopted in the automotive industry. In this case, the robustness of final part properties is more critical than in the conventional hot stamping parts, where the part is fully quenched. In this study, a wide range of input parameters in a generalized hot stamping model have been investigated, examining the effect on the temperature history and resulting final material properties. A generic thermo-mechanical finite element model of hot stamping was created and a modified phase transformation model, based on Scheil\u27s additive principle, has been applied. The comparison between modeling and experiments shows that the modified phase transformation model coupled with the incubation time provides higher accuracy on the simulation of transformation kinetics history. The robustness of four conditions relevant to tailored hot stamping was investigated: heated tooling (with low and high tool conductance), air cooling, and conventional hot stamping. The results show the high robustness of the conventional hot stamping compared to tailored hot stamping, with respect to the stamped component\u27s final material properties (i.e. phase fraction and hardness). Furthermore, tailored hot stamping showed higher robustness when low conductivity tools are used relative to high conductivity tools
Amir Abdollahpoor; Xiangjun Chen; Michael P. Pereira; Namin Xiao; Bernard F. Rolfe. Sensitivity of the final properties of tailored hot stamping components to the process and material parameters. Journal of Materials Processing Technology 2016, 228, 125 -136.
AMA StyleAmir Abdollahpoor, Xiangjun Chen, Michael P. Pereira, Namin Xiao, Bernard F. Rolfe. Sensitivity of the final properties of tailored hot stamping components to the process and material parameters. Journal of Materials Processing Technology. 2016; 228 ():125-136.
Chicago/Turabian StyleAmir Abdollahpoor; Xiangjun Chen; Michael P. Pereira; Namin Xiao; Bernard F. Rolfe. 2016. "Sensitivity of the final properties of tailored hot stamping components to the process and material parameters." Journal of Materials Processing Technology 228, no. : 125-136.
The development of ultra/advanced high strength steels (U/AHSS) has challenged traditional forming methods due to their higher strength and reduced formability. An alternative method is flexible roll forming, which allows the manufacture of sheet metal of high strength and limited ductility into complex and weight-optimized components. However, one major problem in flexible roll forming is the web-warping defect, which is the deviation in height of the web over the length of the profile. The authors’ previous work developed an analytical model to predict the magnitude of web-warping. That model was purely geometric and neglected the effect of material properties. This work develops an analytical solution for the prediction of web-warping that considers both geometric and material parameters. The model results were validated by comparison with numerical and experimental results. The impact of this new model will be the ability to provide a rapid initial design assessment before an intensive numerical analysis of flexible roll forming is conducted.
Jingsi Jiao; Bernard Rolfe; Joseba Mendiguren; Matthias Weiss. An analytical model for web-warping in variable width flexible roll forming. The International Journal of Advanced Manufacturing Technology 2016, 86, 1541 -1555.
AMA StyleJingsi Jiao, Bernard Rolfe, Joseba Mendiguren, Matthias Weiss. An analytical model for web-warping in variable width flexible roll forming. The International Journal of Advanced Manufacturing Technology. 2016; 86 (5-8):1541-1555.
Chicago/Turabian StyleJingsi Jiao; Bernard Rolfe; Joseba Mendiguren; Matthias Weiss. 2016. "An analytical model for web-warping in variable width flexible roll forming." The International Journal of Advanced Manufacturing Technology 86, no. 5-8: 1541-1555.
A method is presented to determine residual stress distribution in sheet material from data collected in a free bending test. It may be used where the residual stress distribution is symmetrical about the mid-surface as it is usually the case for frequently-used sheet metal post-processing techniques such as skin-pass or temper rolling, tension- and roller leveling. An existing inverse technique is used to obtain a residual stress profile and material constants that provide the best fit in a finite element analysis of bending with the experimentally derived moment–curvature relation. The method is verified for bending of a low-carbon stainless steel using measurement of residual stress by X-ray diffraction. The residual stresses were induced in the sheet by cold rolling. The technique described here can be used industrially as a rapid method of investigating residual stresses in incoming sheet. In processes where the deformation is principally one of bending, such as cold roll forming, it is known that residual stresses have an influence on shape defects and springback and the method presented here can be used to determine whether incoming sheet is suitable for further processing and also as a means of obtaining improved material data input for numerical simulation.
A. Abvabi; B. Rolfe; P.D. Hodgson; M. Weiss. An inverse routine to predict residual stress in sheet material. Materials Science and Engineering: A 2015, 652, 99 -104.
AMA StyleA. Abvabi, B. Rolfe, P.D. Hodgson, M. Weiss. An inverse routine to predict residual stress in sheet material. Materials Science and Engineering: A. 2015; 652 ():99-104.
Chicago/Turabian StyleA. Abvabi; B. Rolfe; P.D. Hodgson; M. Weiss. 2015. "An inverse routine to predict residual stress in sheet material." Materials Science and Engineering: A 652, no. : 99-104.
To enable the design and optimisation of forming processes at room temperature the material behaviour of Ti-6Al-4 V needs to be accurately represented in numerical analysis and this requires an advanced material model. In particular, an accurate representation of the shape and size of the yield locus as well as its evolution during forming is important. In this study a rigorous set of experiments on the quasi-static deformation behaviour of a Ti-6Al-4 V alloy sheet sample at room temperature was conducted for various loading conditions and a constitutive material model developed. To quantify the anisotropy and asymmetry properties, tensile and compression tests were carried out for different specimen orientations. To examine the Bauschinger effect and the transient hardening behaviour in – plane tensile – compression and compression – tensile tests were performed. Balanced biaxial and plane strain tension tests were conducted to construct and validate the yield surface of the Ti-6Al-4 V alloy sheet sample at room temperature. A recently proposed anisotropic elastic-plastic constitutive material model, so-called HAH, was employed to describe the behaviour, in particular for load reversals. The HAH yield surface is composed of a stable component, which includes plastic anisotropy and is distorted by a fluctuating component. The key of the formulation is the use of a suitable yield function that reproduces the experimental observations well for the stable component. Meanwhile, the rapid evolution of the material structure must be captured at the macro - scale level by the fluctuating component embedded in the HAH model. Compared to conventional hardening equations, the proposed model leads to higher accuracy in predicting the Bauschinger effect and the transient hardening behaviour for the Ti-6Al-4 V sheet sample tested at room temperature.
Ossama Mamdouh Badr; Frederic Barlat; Bernard Rolfe; Myoung-Gyu Lee; Peter Hodgson; Matthias Weiss. Constitutive modelling of high strength titanium alloy Ti-6Al-4 V for sheet forming applications at room temperature. International Journal of Solids and Structures 2015, 80, 334 -347.
AMA StyleOssama Mamdouh Badr, Frederic Barlat, Bernard Rolfe, Myoung-Gyu Lee, Peter Hodgson, Matthias Weiss. Constitutive modelling of high strength titanium alloy Ti-6Al-4 V for sheet forming applications at room temperature. International Journal of Solids and Structures. 2015; 80 ():334-347.
Chicago/Turabian StyleOssama Mamdouh Badr; Frederic Barlat; Bernard Rolfe; Myoung-Gyu Lee; Peter Hodgson; Matthias Weiss. 2015. "Constitutive modelling of high strength titanium alloy Ti-6Al-4 V for sheet forming applications at room temperature." International Journal of Solids and Structures 80, no. : 334-347.