A dynamic finite element model of a shod running footstrike was developed and driven with six deg... more A dynamic finite element model of a shod running footstrike was developed and driven with six degree of freedom foot segment kinematics determined from a motion capture running trial. Quadratic tetrahedral elements were used to mesh the footwear components with material models determined from appropriate mechanical tests. Model outputs were compared to experimental high speed video (HSV) footage, vertical ground reaction force (GRF) and centre of pressure (COP) excursion to determine whether such an approach is appropriate for the development of athletic footwear. Although unquantified, good visual agreement to the HSV footage was observed but significant discrepancies were found between the model and experimental GRF and COP readings (9% and 61% of model readings outside of the mean experimental reading ± 2 standard deviations respectively). Model output was also found to be highly sensitive to input kinematics with a 120% increase in maximum GRF observed when translating the force...
ABSTRACT Carbon fibre-reinforced polymer (CFRP) composites used in sports products can be exposed... more ABSTRACT Carbon fibre-reinforced polymer (CFRP) composites used in sports products can be exposed to different in-service conditions such as large dynamic bending deformations caused by impact loading. Composite materials subjected to such loads demonstrate various damage modes such as matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution affects both in-service properties and performance of CFRP that can deteriorate with time. These failure modes need adequate means of analysis and investigation, the major approaches being experimental characterisation and numerical simulations. This research deals with a deformation behaviour and damage in composite laminates due to dynamic bending. Experimental tests are carried out to characterise the behaviour of a woven CFRP material under large-deflection dynamic bending in impact tests carried out to obtain the force-time and absorbed energy profiles for CFRP laminates. Damage in the impacted laminates is analysed using optical microscopy. Numerical simulations are performed to study the deformation behaviour and damage in CFRP for cases of large-deflection bending based on three-dimensional finite-element models implemented in the commercial code Abaqus/Explicit. Multiple layers of bilinear cohesive-zone elements are employed to model the initiation and progression of inter-ply delamination observed in the microscopy studies. The obtained results of simulations show good agreement with experimental data.
ABSTRACT The aim of this paper was to examine differences in delivery characteristics and the res... more ABSTRACT The aim of this paper was to examine differences in delivery characteristics and the resulting response exhibited by ten elite cricket batsmen when hitting repeated front foot drives against three different ball delivery methods; a bowling machine, a Sidearm™ ball thrower and a bowler. Synchronous three-dimensional Vicon motion capture technology and high-speed video were used to track batsman, bat and ball motion, and a range of discrete timing and kinematic variables were extracted from the resulting biomechanical model. Results showed significant differences in speed and ball release-to-impact time between the three delivery methods, thus questioning the validity of the bowling machine and Sidearm™ in the way they are currently used as true representations of batting against a real life bowler. Findings from the timing and kinematics of the subjects’ movements suggest a different technical response is also exhibited when facing the different delivery methods; for example batters were found to initiate movement earlier and have a lower maximum bat speed against the bowling machine, but initiate and complete their front foot stride earlier as well as moving their COM further forward in the Sidearm™ trials.
Volume 1: Advanced Computational Mechanics; Advanced Simulation-Based Engineering Sciences; Virtual and Augmented Reality; Applied Solid Mechanics and Material Processing; Dynamical Systems and Control, 2012
ABSTRACT In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is s... more ABSTRACT In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is studied using a combination of experimental material characterisation, microscopic damage analysis and numerical simulations. Mechanical behaviour of these materials was quantified by carrying out tensile and large-deflection bending tests. A substantial difference was found between the materials’ tensile and flexural properties due to a size effect and stress stiffening of thin laminates. A digital image-correlation technique capable of full-field strain-measurement was used to determine in-plane shear properties of the studied materials. Optical microscopy and micro-computed tomography were employed to investigate deformation and damage mechanisms in the specimens fractured in bending. Various damage modes such as matrix cracking, delaminations, tow debonding and fibre fracture were observed in these microstructural studies. A two-dimensional finite-element (FE) model was developed to analyse the onset and propagation of inter-ply delamination and intra-ply fabric fracture as well as their coupling in the fractured specimen. The developed FE model provided a correct prediction of the material’s flexural response and successfully simulated the sequence and interaction of damage modes observed experimentally.
In 16 th century, a football found its way into the rafters of a room of Stirling Castle in the h... more In 16 th century, a football found its way into the rafters of a room of Stirling Castle in the heart of Scotland. Roughly 450 years later, the ball was discovered undisturbed and it remains the oldest known object of its kind in the world. The distinctive leather panels and stitching surround and protect an inflated pig's bladder in a construction with clear ancestral ties to the current football. Modern footballs, especially those used for elite level competition, must pass a series of tests relating to performance and durability to ensure that the style and level of play remain consistent through a match and from year to year around the world. A study was undertaken to assess the 16 th c. football based on modern metrics, specifically those outlined by FIFA (circumference, sphericity, COR, water absorption, weight, pressure loss, shape/size retention). A modern FIFA-Approved football was compared with the historically accurate replica (including pig's bladders when possible), which was constructed and provided by the custodians of the original 16 th c. football. The 16 th c. ball was also configured with a modern latex bladder for a separate series of trials to explore the benefits of synthetic materials over a completely organic football. Based on the results, inferences were made about the style of play, supporting some of what is known about the game once banned by King Henry VIII.
The need for efficient and cost effective methods of recording the structural response of running... more The need for efficient and cost effective methods of recording the structural response of running shoes under simple mechanical testing was identified in order to allow virtual prototyping. Digital video was chosen over other methods due to its availability and relatively low cost. Two complementary experiments were set up to test the performance of the data collection methods: (1) Quasi-static, uni-axial loading was applied up to 1.5 kN (+/-1N) over a period of 30 seconds and the 3D structural response recorded using two 50 Hz video cameras, (2) Dynamic, uni-axial loading to 1.5 kN (+/-200N) was performed using a drop-test rig. Shoe deformation was recorded using a highspeed video system operating at 4 kHz. Testing was performed on two shoe types with no uppers, one with a foam midsole, one with a TPU structure midsole. Analysis of the video data was done using ImageJ in conjunction with Visual Basic routines. Results showed a resolution of 0.68 mm for the quasi-static tests (in the plane of the camera) and 0.46 mm for the dynamic testing. These results were acceptable for use, although the resolution of depth using the two 50 Hz camera was only 6.81 mm, so use of another 3D method is recommended.
This paper reports a methodology that employs a three dimensional (3D) digital image correlation ... more This paper reports a methodology that employs a three dimensional (3D) digital image correlation (DIC) system to measure dynamic foot shape during running. DIC is a non-contact optical measurement system, capable of high resolution surface deformation measurements derived from digital images captured of a surface undergoing a deformation. The methodology presented in this paper uses a plurality of synchronised high speed cameras to capture images of the stance phase of the gait cycle, from which surface shape and deformation measurements can be made. Results related to foot morphology are presented which show the merit of the method and potential for future use.
This study took time-stamped ball-related event descriptions and coordinates from Prozone Sports ... more This study took time-stamped ball-related event descriptions and coordinates from Prozone Sports to build a summary of the football's motion. Aerodynamic data from wind tunnel testing and rolling resistance information from FIFA tests were applied to specific scenarios from the dataset to better understand individual events. Slow, short events were found to be the most frequent by far and most of those were intercepted before rolling to a stop. The corner-cross to a header scenario was chosen as an easily-defined event and a flight trajectory was determined. The data could potentially be used to quantify what happens during a kick and in some situations, provide medical researchers with a better idea of what cranial accelerations are present in a header.
The bowling delivery has been recognized as an important factor in cricket. The batsman faces eac... more The bowling delivery has been recognized as an important factor in cricket. The batsman faces each delivery and attempts to read the bowler's actions to predict the type of delivery and to avoid making an error in judgment which could cost the game. Numerous studies have been carried out to investigate factors such as the biomechanic and kinematic aspects of the bowling delivery and what information the batsman is able to pick up from the delivery sequence. However the factors which constitute the bowling delivery, the mechanisms ...
ABSTRACT For the past century, football boots have constantly changed, with new designs and mater... more ABSTRACT For the past century, football boots have constantly changed, with new designs and materials being developed by sporting goods manufacturers to meet player demands. Investigating the effect of such changes on performance was important to further develop football boots. Bending stiffness has been demonstrated as an important performance parameter in running footwear; a concept with potential to investigate football footwear. As football boots consisted of an upper and an outsole, with the latter being manufactured from a far stiffer material than the upper, it could be speculated that the outsole limits the boot's flexibility. The aim of this paper was to create a testing device to quantify whether the whole shoe needed to be considered when designing football boots. The test device consisted of a simplified foot based on biomechanical factors linked to an Instron machine to quantify the load during bending. The bending stiffness of the uppers and boots were found to be non-linear, highlighting the need to specify the angle at which the stiffness was recorded. The upper was shown to have a significant effect on the bending stiffness of the overall boot construction, whilst different upper constructions were shown to affect the bending stiffness. With regard to the findings in this paper, it was concluded that the upper was an important consideration in boot design.
Given the global spread of football (soccer) there are substantial differences in the playing sur... more Given the global spread of football (soccer) there are substantial differences in the playing surfaces used between FIFA member associations. This paper contains results from the second part of a study on elite football players' perceptions of playing surfaces from across the globe. Using a questionnaire, which was developed based on an initial qualitative study, elite players' perceptions of differences in surface properties between natural and artificial (football) turf were examined. In total, 1129 elite footballers, representing 43 countries across six FIFA confederations completed the questionnaire. Exploratory analysis of overall responses revealed that the players had strong opinions with regards to surface properties when directly comparing natural and football turf. In particular, a higher proportion of players stated that football turf was "Too hard/Harder", "More level", "More abrasive" and had "Less grip" compared to natural grass. The results also showed that overall players' perceptions of surface properties, between natural grass and football turf were dependent on their experience of different playing surfaces during their junior and senior careers, in particular, the variability within football turf pitches.
... Christopher Holmes, Roy Jones, Andy Harland and Jon Petzing Loughborough University, ceholmes... more ... Christopher Holmes, Roy Jones, Andy Harland and Jon Petzing Loughborough University, ceholmes@lboro.ac.uk Abstract. ... The objective of this study was to determine the launch characteristics of a place kick, drop kick, spiral kick (kick to touch) and spin pass. ...
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2012
ABSTRACT This paper demonstrates the value of using a flight model in the analysis of the flight ... more ABSTRACT This paper demonstrates the value of using a flight model in the analysis of the flight of a football, and explores the complexity of the model required to produce useful results. Two specific aspects of the simulation are addressed: the need to include a model of spin decay and the requirement to include a full aerodynamic drag profile as a function of Reynolds number rather than a single indicative value. Both are aspects of the ball performance that are experimentally intensive to obtain. The simulated flights show that the inclusion of spin degradation is important if flight validation is the objective, but that it may be unnecessary in a comparative study. The simple analytical model of spin degradation is shown to overestimate the reduction in lateral deviation when compared to experimentally acquired data. Therefore, the experimental method is preferred. The analysis of the shape of the drag profile (drag coefficient against Reynolds number) is explored, and it is shown from the simulated flights that post-critical coefficients of drag have the greatest effect on trajectories, and an average drag value is sufficient for most modelled scenarios.
A dynamic finite element model of a shod running footstrike was developed and driven with six deg... more A dynamic finite element model of a shod running footstrike was developed and driven with six degree of freedom foot segment kinematics determined from a motion capture running trial. Quadratic tetrahedral elements were used to mesh the footwear components with material models determined from appropriate mechanical tests. Model outputs were compared to experimental high speed video (HSV) footage, vertical ground reaction force (GRF) and centre of pressure (COP) excursion to determine whether such an approach is appropriate for the development of athletic footwear. Although unquantified, good visual agreement to the HSV footage was observed but significant discrepancies were found between the model and experimental GRF and COP readings (9% and 61% of model readings outside of the mean experimental reading ± 2 standard deviations respectively). Model output was also found to be highly sensitive to input kinematics with a 120% increase in maximum GRF observed when translating the force...
ABSTRACT Carbon fibre-reinforced polymer (CFRP) composites used in sports products can be exposed... more ABSTRACT Carbon fibre-reinforced polymer (CFRP) composites used in sports products can be exposed to different in-service conditions such as large dynamic bending deformations caused by impact loading. Composite materials subjected to such loads demonstrate various damage modes such as matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution affects both in-service properties and performance of CFRP that can deteriorate with time. These failure modes need adequate means of analysis and investigation, the major approaches being experimental characterisation and numerical simulations. This research deals with a deformation behaviour and damage in composite laminates due to dynamic bending. Experimental tests are carried out to characterise the behaviour of a woven CFRP material under large-deflection dynamic bending in impact tests carried out to obtain the force-time and absorbed energy profiles for CFRP laminates. Damage in the impacted laminates is analysed using optical microscopy. Numerical simulations are performed to study the deformation behaviour and damage in CFRP for cases of large-deflection bending based on three-dimensional finite-element models implemented in the commercial code Abaqus/Explicit. Multiple layers of bilinear cohesive-zone elements are employed to model the initiation and progression of inter-ply delamination observed in the microscopy studies. The obtained results of simulations show good agreement with experimental data.
ABSTRACT The aim of this paper was to examine differences in delivery characteristics and the res... more ABSTRACT The aim of this paper was to examine differences in delivery characteristics and the resulting response exhibited by ten elite cricket batsmen when hitting repeated front foot drives against three different ball delivery methods; a bowling machine, a Sidearm™ ball thrower and a bowler. Synchronous three-dimensional Vicon motion capture technology and high-speed video were used to track batsman, bat and ball motion, and a range of discrete timing and kinematic variables were extracted from the resulting biomechanical model. Results showed significant differences in speed and ball release-to-impact time between the three delivery methods, thus questioning the validity of the bowling machine and Sidearm™ in the way they are currently used as true representations of batting against a real life bowler. Findings from the timing and kinematics of the subjects’ movements suggest a different technical response is also exhibited when facing the different delivery methods; for example batters were found to initiate movement earlier and have a lower maximum bat speed against the bowling machine, but initiate and complete their front foot stride earlier as well as moving their COM further forward in the Sidearm™ trials.
Volume 1: Advanced Computational Mechanics; Advanced Simulation-Based Engineering Sciences; Virtual and Augmented Reality; Applied Solid Mechanics and Material Processing; Dynamical Systems and Control, 2012
ABSTRACT In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is s... more ABSTRACT In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is studied using a combination of experimental material characterisation, microscopic damage analysis and numerical simulations. Mechanical behaviour of these materials was quantified by carrying out tensile and large-deflection bending tests. A substantial difference was found between the materials’ tensile and flexural properties due to a size effect and stress stiffening of thin laminates. A digital image-correlation technique capable of full-field strain-measurement was used to determine in-plane shear properties of the studied materials. Optical microscopy and micro-computed tomography were employed to investigate deformation and damage mechanisms in the specimens fractured in bending. Various damage modes such as matrix cracking, delaminations, tow debonding and fibre fracture were observed in these microstructural studies. A two-dimensional finite-element (FE) model was developed to analyse the onset and propagation of inter-ply delamination and intra-ply fabric fracture as well as their coupling in the fractured specimen. The developed FE model provided a correct prediction of the material’s flexural response and successfully simulated the sequence and interaction of damage modes observed experimentally.
In 16 th century, a football found its way into the rafters of a room of Stirling Castle in the h... more In 16 th century, a football found its way into the rafters of a room of Stirling Castle in the heart of Scotland. Roughly 450 years later, the ball was discovered undisturbed and it remains the oldest known object of its kind in the world. The distinctive leather panels and stitching surround and protect an inflated pig's bladder in a construction with clear ancestral ties to the current football. Modern footballs, especially those used for elite level competition, must pass a series of tests relating to performance and durability to ensure that the style and level of play remain consistent through a match and from year to year around the world. A study was undertaken to assess the 16 th c. football based on modern metrics, specifically those outlined by FIFA (circumference, sphericity, COR, water absorption, weight, pressure loss, shape/size retention). A modern FIFA-Approved football was compared with the historically accurate replica (including pig's bladders when possible), which was constructed and provided by the custodians of the original 16 th c. football. The 16 th c. ball was also configured with a modern latex bladder for a separate series of trials to explore the benefits of synthetic materials over a completely organic football. Based on the results, inferences were made about the style of play, supporting some of what is known about the game once banned by King Henry VIII.
The need for efficient and cost effective methods of recording the structural response of running... more The need for efficient and cost effective methods of recording the structural response of running shoes under simple mechanical testing was identified in order to allow virtual prototyping. Digital video was chosen over other methods due to its availability and relatively low cost. Two complementary experiments were set up to test the performance of the data collection methods: (1) Quasi-static, uni-axial loading was applied up to 1.5 kN (+/-1N) over a period of 30 seconds and the 3D structural response recorded using two 50 Hz video cameras, (2) Dynamic, uni-axial loading to 1.5 kN (+/-200N) was performed using a drop-test rig. Shoe deformation was recorded using a highspeed video system operating at 4 kHz. Testing was performed on two shoe types with no uppers, one with a foam midsole, one with a TPU structure midsole. Analysis of the video data was done using ImageJ in conjunction with Visual Basic routines. Results showed a resolution of 0.68 mm for the quasi-static tests (in the plane of the camera) and 0.46 mm for the dynamic testing. These results were acceptable for use, although the resolution of depth using the two 50 Hz camera was only 6.81 mm, so use of another 3D method is recommended.
This paper reports a methodology that employs a three dimensional (3D) digital image correlation ... more This paper reports a methodology that employs a three dimensional (3D) digital image correlation (DIC) system to measure dynamic foot shape during running. DIC is a non-contact optical measurement system, capable of high resolution surface deformation measurements derived from digital images captured of a surface undergoing a deformation. The methodology presented in this paper uses a plurality of synchronised high speed cameras to capture images of the stance phase of the gait cycle, from which surface shape and deformation measurements can be made. Results related to foot morphology are presented which show the merit of the method and potential for future use.
This study took time-stamped ball-related event descriptions and coordinates from Prozone Sports ... more This study took time-stamped ball-related event descriptions and coordinates from Prozone Sports to build a summary of the football's motion. Aerodynamic data from wind tunnel testing and rolling resistance information from FIFA tests were applied to specific scenarios from the dataset to better understand individual events. Slow, short events were found to be the most frequent by far and most of those were intercepted before rolling to a stop. The corner-cross to a header scenario was chosen as an easily-defined event and a flight trajectory was determined. The data could potentially be used to quantify what happens during a kick and in some situations, provide medical researchers with a better idea of what cranial accelerations are present in a header.
The bowling delivery has been recognized as an important factor in cricket. The batsman faces eac... more The bowling delivery has been recognized as an important factor in cricket. The batsman faces each delivery and attempts to read the bowler's actions to predict the type of delivery and to avoid making an error in judgment which could cost the game. Numerous studies have been carried out to investigate factors such as the biomechanic and kinematic aspects of the bowling delivery and what information the batsman is able to pick up from the delivery sequence. However the factors which constitute the bowling delivery, the mechanisms ...
ABSTRACT For the past century, football boots have constantly changed, with new designs and mater... more ABSTRACT For the past century, football boots have constantly changed, with new designs and materials being developed by sporting goods manufacturers to meet player demands. Investigating the effect of such changes on performance was important to further develop football boots. Bending stiffness has been demonstrated as an important performance parameter in running footwear; a concept with potential to investigate football footwear. As football boots consisted of an upper and an outsole, with the latter being manufactured from a far stiffer material than the upper, it could be speculated that the outsole limits the boot's flexibility. The aim of this paper was to create a testing device to quantify whether the whole shoe needed to be considered when designing football boots. The test device consisted of a simplified foot based on biomechanical factors linked to an Instron machine to quantify the load during bending. The bending stiffness of the uppers and boots were found to be non-linear, highlighting the need to specify the angle at which the stiffness was recorded. The upper was shown to have a significant effect on the bending stiffness of the overall boot construction, whilst different upper constructions were shown to affect the bending stiffness. With regard to the findings in this paper, it was concluded that the upper was an important consideration in boot design.
Given the global spread of football (soccer) there are substantial differences in the playing sur... more Given the global spread of football (soccer) there are substantial differences in the playing surfaces used between FIFA member associations. This paper contains results from the second part of a study on elite football players' perceptions of playing surfaces from across the globe. Using a questionnaire, which was developed based on an initial qualitative study, elite players' perceptions of differences in surface properties between natural and artificial (football) turf were examined. In total, 1129 elite footballers, representing 43 countries across six FIFA confederations completed the questionnaire. Exploratory analysis of overall responses revealed that the players had strong opinions with regards to surface properties when directly comparing natural and football turf. In particular, a higher proportion of players stated that football turf was "Too hard/Harder", "More level", "More abrasive" and had "Less grip" compared to natural grass. The results also showed that overall players' perceptions of surface properties, between natural grass and football turf were dependent on their experience of different playing surfaces during their junior and senior careers, in particular, the variability within football turf pitches.
... Christopher Holmes, Roy Jones, Andy Harland and Jon Petzing Loughborough University, ceholmes... more ... Christopher Holmes, Roy Jones, Andy Harland and Jon Petzing Loughborough University, ceholmes@lboro.ac.uk Abstract. ... The objective of this study was to determine the launch characteristics of a place kick, drop kick, spiral kick (kick to touch) and spin pass. ...
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2012
ABSTRACT This paper demonstrates the value of using a flight model in the analysis of the flight ... more ABSTRACT This paper demonstrates the value of using a flight model in the analysis of the flight of a football, and explores the complexity of the model required to produce useful results. Two specific aspects of the simulation are addressed: the need to include a model of spin decay and the requirement to include a full aerodynamic drag profile as a function of Reynolds number rather than a single indicative value. Both are aspects of the ball performance that are experimentally intensive to obtain. The simulated flights show that the inclusion of spin degradation is important if flight validation is the objective, but that it may be unnecessary in a comparative study. The simple analytical model of spin degradation is shown to overestimate the reduction in lateral deviation when compared to experimentally acquired data. Therefore, the experimental method is preferred. The analysis of the shape of the drag profile (drag coefficient against Reynolds number) is explored, and it is shown from the simulated flights that post-critical coefficients of drag have the greatest effect on trajectories, and an average drag value is sufficient for most modelled scenarios.
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Papers by Andy Harland