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David A Hills - One of the best experts on this subject based on the ideXlab platform.
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the steady state partial slip problem for half plane contacts subject to a Constant Normal Load using glide dislocations
arXiv: Soft Condensed Matter, 2019Co-Authors: Hendrik Andrese, David A Hills, M R MooreAbstract:A new solution for general half-plane contact problems subject to a Constant Normal Load together with alternating shear Loads and tension in the steady state is presented. The method uses a formulation where a displacement correction is made to the fully stuck contact solution. There will be two outer regions of slip and a central permanent stick zone, which is explicitly established. Thereby, the maximum extent of the slip zones is effectively specified. Cases of small and large tension are studied, that is when the direction of slip is the same or opposing at the ends of the contact, respectively.
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methods to solve half plane partial slip contact problems
International Journal of Solids and Structures, 2018Co-Authors: David A Hills, R Ramesh, J R Barber, M R MooreAbstract:Abstract There exists a family of methods for finding the extent of partial slip in contact problems between elastically similar bodies, capable of idealisation by half-planes. Closed form solutions are given to problems subject to a Constant Normal Load and subsequent application of either an increasing shear force or differential bulk tension parallel with the surface. The starting point may be either a sliding contact (as is customary), or a fully adhered contact. The corrections required to impose a point-wise interpretation of Coulomb’s law of friction may be either in the form of a shear traction distribution or as dislocation arrays. The latter, when applied to the fully adhered contact, has the merit of automatically preserving the locked-in relative surface strains.
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half plane partial slip contact problems with a Constant Normal Load subject to a shear force and differential bulk tension
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: M R Moore, R Ramesh, David A Hills, J R BarberAbstract:Abstract This article provides a new form of solution to half-plane contact problems in partial slip where a Normal Load has been applied, held Constant and is subsequently Loaded with both a shear force and differential bulk tension. It uses a formulation where a displacement correction is made to the fully stuck solution. An approximate solution is used to study an isolated contact edge, which employs an asymptotic solution to each edge of the contact. A comparison of the approximation with the exact solution is given to show the range of Loading where the asymptotic solution gives good results.
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plane incomplete contact problems subject to bulk stress with a varying Normal Load
International Journal of Mechanical Sciences, 2017Co-Authors: R Ramesh, J R Barber, David A HillsAbstract:Abstract In the case of a general symmetric incomplete contact, if we can deduce the partial slip solution when it is subjected first to a Normal Load (held Constant) and then to a monotonically increasing bulk tension, we show, here, how to obtain the solution when the Normal Load and bulk tension vary with time in an arbitrary manner. The procedure is demonstrated for a Hertzian contact where the Constant Normal Load solution is known in closed form. It reveals the extent of slip and the shear traction distribution at all points within the contact at any instant. It was discovered that the size of the permanent stick zone, for a given cyclic Loading trajectory, is unique in the steady state. The steady state is established after one cycle of Loading: it is independent of the transient Loading prior to reaching the steady state cycle, which is also observed in the case of varying Normal and shear Loading ( P − Q ). An example is given to illustrate the type of behaviour that is to be expected.
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partial slip incomplete contacts under Constant Normal Load and subject to periodic Loading
International Journal of Mechanical Sciences, 2016Co-Authors: David A Hills, R M N Fleury, Daniele DiniAbstract:Abstract We present a general formulation for the stick slip behaviour of incomplete contact under oscillating Loading, but with a Constant Normal Load. An asymptotic description of the contact traction very close to the contact edges is used. The slip zones present in the steady state with cyclically varying bulk tension and shear force (with an arbitrary phase shift) are found. The range of the variation of the state of stress near both of the contact edges and the respective slip zone sizes are defined in terms of the Loading parameters, including the phase angle. The quality of the approximations used by the asymptotic approach and the range of applicability of the method is also analysed in detail in this paper.
M R Moore - One of the best experts on this subject based on the ideXlab platform.
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the steady state partial slip problem for half plane contacts subject to a Constant Normal Load using glide dislocations
arXiv: Soft Condensed Matter, 2019Co-Authors: Hendrik Andrese, David A Hills, M R MooreAbstract:A new solution for general half-plane contact problems subject to a Constant Normal Load together with alternating shear Loads and tension in the steady state is presented. The method uses a formulation where a displacement correction is made to the fully stuck contact solution. There will be two outer regions of slip and a central permanent stick zone, which is explicitly established. Thereby, the maximum extent of the slip zones is effectively specified. Cases of small and large tension are studied, that is when the direction of slip is the same or opposing at the ends of the contact, respectively.
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methods to solve half plane partial slip contact problems
International Journal of Solids and Structures, 2018Co-Authors: David A Hills, R Ramesh, J R Barber, M R MooreAbstract:Abstract There exists a family of methods for finding the extent of partial slip in contact problems between elastically similar bodies, capable of idealisation by half-planes. Closed form solutions are given to problems subject to a Constant Normal Load and subsequent application of either an increasing shear force or differential bulk tension parallel with the surface. The starting point may be either a sliding contact (as is customary), or a fully adhered contact. The corrections required to impose a point-wise interpretation of Coulomb’s law of friction may be either in the form of a shear traction distribution or as dislocation arrays. The latter, when applied to the fully adhered contact, has the merit of automatically preserving the locked-in relative surface strains.
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half plane partial slip contact problems with a Constant Normal Load subject to a shear force and differential bulk tension
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: M R Moore, R Ramesh, David A Hills, J R BarberAbstract:Abstract This article provides a new form of solution to half-plane contact problems in partial slip where a Normal Load has been applied, held Constant and is subsequently Loaded with both a shear force and differential bulk tension. It uses a formulation where a displacement correction is made to the fully stuck solution. An approximate solution is used to study an isolated contact edge, which employs an asymptotic solution to each edge of the contact. A comparison of the approximation with the exact solution is given to show the range of Loading where the asymptotic solution gives good results.
J R Barber - One of the best experts on this subject based on the ideXlab platform.
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methods to solve half plane partial slip contact problems
International Journal of Solids and Structures, 2018Co-Authors: David A Hills, R Ramesh, J R Barber, M R MooreAbstract:Abstract There exists a family of methods for finding the extent of partial slip in contact problems between elastically similar bodies, capable of idealisation by half-planes. Closed form solutions are given to problems subject to a Constant Normal Load and subsequent application of either an increasing shear force or differential bulk tension parallel with the surface. The starting point may be either a sliding contact (as is customary), or a fully adhered contact. The corrections required to impose a point-wise interpretation of Coulomb’s law of friction may be either in the form of a shear traction distribution or as dislocation arrays. The latter, when applied to the fully adhered contact, has the merit of automatically preserving the locked-in relative surface strains.
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half plane partial slip contact problems with a Constant Normal Load subject to a shear force and differential bulk tension
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: M R Moore, R Ramesh, David A Hills, J R BarberAbstract:Abstract This article provides a new form of solution to half-plane contact problems in partial slip where a Normal Load has been applied, held Constant and is subsequently Loaded with both a shear force and differential bulk tension. It uses a formulation where a displacement correction is made to the fully stuck solution. An approximate solution is used to study an isolated contact edge, which employs an asymptotic solution to each edge of the contact. A comparison of the approximation with the exact solution is given to show the range of Loading where the asymptotic solution gives good results.
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plane incomplete contact problems subject to bulk stress with a varying Normal Load
International Journal of Mechanical Sciences, 2017Co-Authors: R Ramesh, J R Barber, David A HillsAbstract:Abstract In the case of a general symmetric incomplete contact, if we can deduce the partial slip solution when it is subjected first to a Normal Load (held Constant) and then to a monotonically increasing bulk tension, we show, here, how to obtain the solution when the Normal Load and bulk tension vary with time in an arbitrary manner. The procedure is demonstrated for a Hertzian contact where the Constant Normal Load solution is known in closed form. It reveals the extent of slip and the shear traction distribution at all points within the contact at any instant. It was discovered that the size of the permanent stick zone, for a given cyclic Loading trajectory, is unique in the steady state. The steady state is established after one cycle of Loading: it is independent of the transient Loading prior to reaching the steady state cycle, which is also observed in the case of varying Normal and shear Loading ( P − Q ). An example is given to illustrate the type of behaviour that is to be expected.
R Ramesh - One of the best experts on this subject based on the ideXlab platform.
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methods to solve half plane partial slip contact problems
International Journal of Solids and Structures, 2018Co-Authors: David A Hills, R Ramesh, J R Barber, M R MooreAbstract:Abstract There exists a family of methods for finding the extent of partial slip in contact problems between elastically similar bodies, capable of idealisation by half-planes. Closed form solutions are given to problems subject to a Constant Normal Load and subsequent application of either an increasing shear force or differential bulk tension parallel with the surface. The starting point may be either a sliding contact (as is customary), or a fully adhered contact. The corrections required to impose a point-wise interpretation of Coulomb’s law of friction may be either in the form of a shear traction distribution or as dislocation arrays. The latter, when applied to the fully adhered contact, has the merit of automatically preserving the locked-in relative surface strains.
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half plane partial slip contact problems with a Constant Normal Load subject to a shear force and differential bulk tension
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: M R Moore, R Ramesh, David A Hills, J R BarberAbstract:Abstract This article provides a new form of solution to half-plane contact problems in partial slip where a Normal Load has been applied, held Constant and is subsequently Loaded with both a shear force and differential bulk tension. It uses a formulation where a displacement correction is made to the fully stuck solution. An approximate solution is used to study an isolated contact edge, which employs an asymptotic solution to each edge of the contact. A comparison of the approximation with the exact solution is given to show the range of Loading where the asymptotic solution gives good results.
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plane incomplete contact problems subject to bulk stress with a varying Normal Load
International Journal of Mechanical Sciences, 2017Co-Authors: R Ramesh, J R Barber, David A HillsAbstract:Abstract In the case of a general symmetric incomplete contact, if we can deduce the partial slip solution when it is subjected first to a Normal Load (held Constant) and then to a monotonically increasing bulk tension, we show, here, how to obtain the solution when the Normal Load and bulk tension vary with time in an arbitrary manner. The procedure is demonstrated for a Hertzian contact where the Constant Normal Load solution is known in closed form. It reveals the extent of slip and the shear traction distribution at all points within the contact at any instant. It was discovered that the size of the permanent stick zone, for a given cyclic Loading trajectory, is unique in the steady state. The steady state is established after one cycle of Loading: it is independent of the transient Loading prior to reaching the steady state cycle, which is also observed in the case of varying Normal and shear Loading ( P − Q ). An example is given to illustrate the type of behaviour that is to be expected.
Giovanni Grasselli - One of the best experts on this subject based on the ideXlab platform.
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manuel rocha medal recipient shear strength of rock joints based on quantified surface description
Rock Mechanics and Rock Engineering, 2006Co-Authors: Giovanni GrasselliAbstract:One of the primary objectives of this work is to improve the understanding of the frictional behaviour of rough rock joints under shear Loads, and to relate its shear strength to the “shape” of the joint interface (roughness). Discontinuities have, indeed, an important influence on the deformational behaviour of rock systems. The choice of a general criterion to determine the shear strength of rough rock joints is a problem that has been investigated for many years. Numerous shear models have been proposed to relate shear-strength to measurable joint parameters, but their limitations have to be recognized. The main problem is how to measure and quantify the roughness in order to introduce the morphological aspect of the joint into a shear strength criterion. The first part of this work focuses on the measurement and description of how roughness influences the size and distribution of contact areas during shearing. It has been found that the variation of the contact area can be expressed as a function of the local dip of the surface, measured along the shear direction. The close agreement between this empirical description of the potential contact area and surface measurements permits one to predict the real contact area involved in the phenomenon. In the second part of the work, a new shear strength criterion is proposed to model the shear resistance of joints under Constant Normal Load conditions. It is based on the proposed empirical estimation of rock joint roughness, and on the results from more than fifty Constant-Normal-Load direct-shear tests performed on replicas of tensile joints and on induced tensile fractures for seven rock types. The proposed model is able to describe experimental shear tests conducted in the laboratory, and the required parameters can be easily measured through standard laboratory tests.
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constitutive law for the shear strength of rock joints based on three dimensional surface parameters
International Journal of Rock Mechanics and Mining Sciences, 2003Co-Authors: Giovanni Grasselli, P EggerAbstract:A new constitutive criterion, relating stress and displacements, is proposed to model the shear resistance of joints under Constant Normal Load conditions. It is based on an empirical description of the surface, and on the results from more than 50 Constant-Normal-Load direct-shear tests performed on replicas of tensile joints and on induced tensile fractures for seven rock types. This constitutive model is able to describe experimental shear tests conducted in the laboratory. Moreover, the parameters required in the model can be easily measured through standard laboratory tests. The proposed criterion was also used to estimate the joint roughness coefficient (JRC) value. The predicting values were successfully correlated with JRC values obtained by back analysis of shear tests.
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shear strength of rock joints based on quantified surface description
Rock Mechanics and Rock Engineering, 2001Co-Authors: Giovanni GrasselliAbstract:One of the primary objectives of this work is to better understand the frictional behavior of joints under shear Loads, including the creation of damage zones. Discontinuities have an important influence on the deformational behavior of rock systems. The choice of a general criterion to determine the shear strength of rough rock joints is a general problem that has been investigated for many years. Numerous shear models have been proposed in the last decades to relate shear-strength to measurable joint parameters, but their limitations have to be recognized. The problem is how to measure and then to express the roughness with a number (e.g. JRC) or a mathematical expression in order to introduce the morphology of the joint into a shear strength criterion. In the frame of this work it has been pointed out that the geometry of roughness influences the size and distribution of contact areas during shearing. In order to locate and estimate the contact area during the shearing, it was argued that only the zones of the surface faced to the shear direction, and steeper than a threshold inclination are involved in the shearing. An empirical relation between the potential contact area and the minimal apparent dip inclination of the surface is proposed. The close agreement between this empirical description of the potential contact area, and experimental points permits to predict the real contact area involved in the phenomena. A new constitutive law, relating stress and displacements, is proposed to model the shear resistance of joints under Constant Normal Load conditions. It is based on the empirical surface description, and on the results from more than fifty Constant-Normal-Load direct-shear tests performed on both replicas of tensile joints, and induced tensile fractures for seven rock types. It is shown that this constitutive model is able to describe experimental shear tests realized in laboratory. Moreover, the parameters required in the model can be easily obtained through standard laboratory tests. The proposed model was also used to estimate the JRC value. The expression obtained to evaluate the joint roughness coefficient is capable of predicting the JRC. It was successfully compared with JRC values obtained by back analysis of shear tests. In the current research no attention was paid to investigate the influence of the scale on the shearing. The results have been validated only in the range of the samples tested in laboratory. Further studies are needed to explore the applicability of the proposed model in field conditions.