Stephan Heyns is professor in the Department of Mechanical and Aeronautical Engineering at the University of Pretoria in South Africa, as well as director of the Centre for Asset Integrity Management (C-AIM) at this university. He was awarded a Bachelor’s degree in mechanical engineering at the University of Pretoria in 1977, his master’s degree in 1982 and his PhD in 1988, also from the University of Pretoria in South Africa.His personal research focuses on machine and structural health monitoring using vibration measurement and analysis techniques including optical measurement techniques, and physical asset integrity management, and the use of machine learning and statistical analysis techniques in these applications. His current work includes structural integrity monitoring in turbomachinery using non-contact measurement, gearbox condition monitoring, and the use of optical measurement techniques for structural integrity assessment.He is the author and co-author of more than 90 peer reviewed journal articles and more than 120 national and international conference papers. He acts as reviewer for various international scientific journals.Prof Heyns has supervised or co-supervised 17 doctoral students and 64 master’s degree students. He has acted as external examiner for master’s and PhD degrees in various universities in Australia, India, South Africa and Sweden.He is a member of scientific committees of various international conferences. These include the International Conference on Structural Engineering, The British Institute of Non-Destructive Testing Condition Monitoring conference, and the International Conference on Condition Monitoring in Non-Stationary Operations.He is an accredited researcher with the National Research Foundation in South Africa, a registered professional engineer in South Africa, as well as a fellow of the South African Academy of Engineering, a honorary fellow of the South African Institution of Mechanical Engineers, a fellow of the Southern African Acoustics Institute and a fellow of the International Society of Engineering Asset Management.
The effect of the rotational speed and axial torque on the diagnostics of tapered rolling element... more The effect of the rotational speed and axial torque on the diagnostics of tapered rolling element bearing defects was investigated. The accelerometer was mounted on the bearing housing and connected to Sound and Vibration Analyzer (SVAN 958) and was used to measure the accelerations from the bearing housing. The data obtained from the bearing was processed to detect damage of the bearing using statistical tools and the results were subsequently analyzed to see if bearing damage had been captured. From this study it can be seen that damage is more evident when the bearing is loaded. Also, at the incipient stage of damage the crest factor and kurtosis values are high but as time progresses the crest factors and kurtosis values decrease whereas the peak and RMS values are low at the incipient stage but increase with damage.
Blade tip timing (BTT) is a noncontact method for measuring turbomachinery blade vibration. Proxi... more Blade tip timing (BTT) is a noncontact method for measuring turbomachinery blade vibration. Proximity sensors are mounted circumferentially around the turbomachine casing and used to measure the tip displacements of blades during operation. Tip deflection data processing is nontrivial due to complications such as aliasing and high levels of noise. Specialized BTT algorithms have been developed to extract the utmost amount of information from the signals. The effectiveness of these algorithms is, however, influenced by the circumferential spacing between the proximity sensors. If the spacing is suboptimal, an algorithm can fail to measure dangerous blade vibration. This paper presents a novel optimization approach that determines the optimal spacing between proximity sensors.
Shot peening (SP) is a controlled and systematic process of surface treatment that has a large nu... more Shot peening (SP) is a controlled and systematic process of surface treatment that has a large number of controllable process parameters that make its application highly challenging. It involves the shooting of small and hard metallic balls at a targeted surface, with the aim of enhancing the fatigue strength of the workpiece under unfavorable service conditions. The compressive residual stress (CRS) induced by this application is expensive to evaluate experimentally. This paper presents a numerical model of the impact of a single-shot on a metallic surface, with the aim to set the stage for a realistic multiple shots peening simulation. The approach proposed herein is a sequential Discrete Element-Finite Element (DE-FE) coupled simulation, based on the use of different types of coefficients of restitution (CoRs) with emphasis on the energetic CoR. The energetic CoR relates the shot/target contact forces to the fractional strain energy needed for localized plastic deformation of the...
International Journal of Mechanical Engineering Education
The conventional single-degree-of-freedom approach to isolator design dealt with in most undergra... more The conventional single-degree-of-freedom approach to isolator design dealt with in most undergraduate curricula, is not always adequate for the design of practical isolator systems. In this article, an optimization approach to the design problem is presented and the viability of the approach demonstrated. It is, however, also shown that multiple local minima may exist and that due care should be exercised in the application of the method.
Transportation Research Record Journal of the Transportation Research Board, 2007
Page 1. 254 surface mine, any savings generated from improved road mainte-nance benefit the minin... more Page 1. 254 surface mine, any savings generated from improved road mainte-nance benefit the mining company directly as a reduced cost per ton of material hauled. A maintenance management system (MMS) approach provides ...
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
ABSTRACT This paper reports the performance of an ANN-based road profile reconstruction methodolo... more ABSTRACT This paper reports the performance of an ANN-based road profile reconstruction methodology on measured data. The methodology was previously verified on numerical data and it was shown that road profiles and their associated defects could be reconstructed to within a 20% error at a minimum correlation value of 94%. The data used in the present paper were measured on a Land Rover Defender 110 using an eDAC-lite measurement system. The measurements were carried out under different test conditions, namely, different road surface profiles, different vehicle suspension settings, and different vehicle speeds. The neural network was trained with data extracted from 20 m length of a typical test run for each road profile. The results confirm the findings of the numerical study with the methodology achieving a maximum error of about 25 % and correlation of above 90 %. The methodology performs relatively much better in reconstructing bumps than the Belgian pave. KeywordsRoad profile reconstruction-Bayesian regularized NARX neural network-road-vehicle interaction-Road damage identification
The effect of the rotational speed and axial torque on the diagnostics of tapered rolling element... more The effect of the rotational speed and axial torque on the diagnostics of tapered rolling element bearing defects was investigated. The accelerometer was mounted on the bearing housing and connected to Sound and Vibration Analyzer (SVAN 958) and was used to measure the accelerations from the bearing housing. The data obtained from the bearing was processed to detect damage of the bearing using statistical tools and the results were subsequently analyzed to see if bearing damage had been captured. From this study it can be seen that damage is more evident when the bearing is loaded. Also, at the incipient stage of damage the crest factor and kurtosis values are high but as time progresses the crest factors and kurtosis values decrease whereas the peak and RMS values are low at the incipient stage but increase with damage.
Blade tip timing (BTT) is a noncontact method for measuring turbomachinery blade vibration. Proxi... more Blade tip timing (BTT) is a noncontact method for measuring turbomachinery blade vibration. Proximity sensors are mounted circumferentially around the turbomachine casing and used to measure the tip displacements of blades during operation. Tip deflection data processing is nontrivial due to complications such as aliasing and high levels of noise. Specialized BTT algorithms have been developed to extract the utmost amount of information from the signals. The effectiveness of these algorithms is, however, influenced by the circumferential spacing between the proximity sensors. If the spacing is suboptimal, an algorithm can fail to measure dangerous blade vibration. This paper presents a novel optimization approach that determines the optimal spacing between proximity sensors.
Shot peening (SP) is a controlled and systematic process of surface treatment that has a large nu... more Shot peening (SP) is a controlled and systematic process of surface treatment that has a large number of controllable process parameters that make its application highly challenging. It involves the shooting of small and hard metallic balls at a targeted surface, with the aim of enhancing the fatigue strength of the workpiece under unfavorable service conditions. The compressive residual stress (CRS) induced by this application is expensive to evaluate experimentally. This paper presents a numerical model of the impact of a single-shot on a metallic surface, with the aim to set the stage for a realistic multiple shots peening simulation. The approach proposed herein is a sequential Discrete Element-Finite Element (DE-FE) coupled simulation, based on the use of different types of coefficients of restitution (CoRs) with emphasis on the energetic CoR. The energetic CoR relates the shot/target contact forces to the fractional strain energy needed for localized plastic deformation of the...
International Journal of Mechanical Engineering Education
The conventional single-degree-of-freedom approach to isolator design dealt with in most undergra... more The conventional single-degree-of-freedom approach to isolator design dealt with in most undergraduate curricula, is not always adequate for the design of practical isolator systems. In this article, an optimization approach to the design problem is presented and the viability of the approach demonstrated. It is, however, also shown that multiple local minima may exist and that due care should be exercised in the application of the method.
Transportation Research Record Journal of the Transportation Research Board, 2007
Page 1. 254 surface mine, any savings generated from improved road mainte-nance benefit the minin... more Page 1. 254 surface mine, any savings generated from improved road mainte-nance benefit the mining company directly as a reduced cost per ton of material hauled. A maintenance management system (MMS) approach provides ...
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
ABSTRACT This paper reports the performance of an ANN-based road profile reconstruction methodolo... more ABSTRACT This paper reports the performance of an ANN-based road profile reconstruction methodology on measured data. The methodology was previously verified on numerical data and it was shown that road profiles and their associated defects could be reconstructed to within a 20% error at a minimum correlation value of 94%. The data used in the present paper were measured on a Land Rover Defender 110 using an eDAC-lite measurement system. The measurements were carried out under different test conditions, namely, different road surface profiles, different vehicle suspension settings, and different vehicle speeds. The neural network was trained with data extracted from 20 m length of a typical test run for each road profile. The results confirm the findings of the numerical study with the methodology achieving a maximum error of about 25 % and correlation of above 90 %. The methodology performs relatively much better in reconstructing bumps than the Belgian pave. KeywordsRoad profile reconstruction-Bayesian regularized NARX neural network-road-vehicle interaction-Road damage identification
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Papers by Stephan Heyns