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G P Adams - One of the best experts on this subject based on the ideXlab platform.
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Compression LOAD TRANSMISSION IN SCREW COMPRESSORS
Journal of Sound and Vibration, 1997Co-Authors: G P AdamsAbstract:Abstract In the current investigations of the bearing forces in screw compressors, the supports at the bearings are basically treated as ideal, simply supported boundary conditions. By using statics theory, the Loads on the rotors are converted to the bearings at the suction and discharge ends. Some studies on rotor dynamics have shown that the behaviors of a rotor bearing system are, to some extent, controlled by the bearings that support the rotor. Therefore, it is important to study the dynamic performance of the rotor bearing system in screw compressors so that the bearing forces can be more accurately described. In this paper, a numerical method is presented for computing the Compression Loads by integrating the pressure over the rotor surface. Vector calculus and numerical integration methods are implemented to calculate the Compression Loads in order to obtain a robust procedure that can be applied to arbitrary rotor profiles. In addition, a dynamic model of a rigid compressor rotor supported by two cylindrical roller bearings and a four point contact ball bearing is developed from basic principles. This model simulates the dynamic responses of a typical screw compressor configuration. It includes five degrees of freedom of rotor motion interacting with the bearings of non-linear characteristics. Under the Compression Loads, the resulting bearing forces in the screw compressor are compared with those obtained by assuming ideal, simply supported boundary conditions at the bearings. It is shown that the interactions between the rotor and bearings are quite different by coupling the global rotor motion with the local dynamics of the bearings.
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An approach for the calculation of Compression Loads in helical twin screw compressors
1996Co-Authors: G P AdamsAbstract:The main components of a twin screw compressor are two helical rotors. Its complicated geometry makes it difficult to compute the forces and moments induced on each rotor due to the Compression process, the Compression Loads. However, the Compression Loads are an important consideration in the design and analysis of twin screw compressors. In this paper, a numerical method is presented for computing the Compression Loads by integrating the pressure over the rotor surface. Vector calculus and numerical integration schemes are implemented to calculate the Compression Loads in order to obtain a robust procedure that can be applied to arbitrary rotor profiles. The calculated results are given for a specific compressor configuration in terms of the Compression Loads as a function of the rotor angular position. It is shown that the rate of change of the profile radius as a function of the angular coordinate is an important factor affecting the accuracy of the integrations.
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Computation of Compression Loads in Twin Screw Compressors
Journal of Mechanical Design, 1995Co-Authors: G P Adams, Werner SoedelAbstract:The Compression mechanism in a twin screw compressor consists of two helical rotors. In this work, a method is presented for computing the forces and moments induced on each rotor due to gas Compression. These are defined as the Compression Loads. The helical rotor surfaces are defined by the end profiles, wrap angle and rotor length. The 3D surface of each rotor is mapped to 2D integration regions. These regions correspond to the surfaces associated with individual Compression chambers. The Compression Loads are computed by integrating the chamber pressure over the rotor surfaces. The integrals are evaluated at incremental values of the rotor angular position. The method is presented and implemented for a specific compressor configuration. The Compression Loads are resolved to forces at the bearing locations. These bearing forces are presented for operating pressures which represent an under-pressure condition. A frequency analysis demonstrates the rich frequency content of the bearing forces due to the sharpness of the Compression Loads as a function of the rotor angular position. In addition, it is demonstrated that the moment load about the axis of rotation induced on the female is approximately 12 percent of that induced on the male. Therefore, the female rotor motion approaches that of an idler gear.
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Dynamic Simulation of Rotor Contact Forces in Twin Screw Compressors
1994Co-Authors: G P Adams, Werner SoedelAbstract:Werner Soedel Purdue University 1077 Herrick Laboratories West Lafayette, IN 47907 A model is presented for computing the rotor contact forces in twin screw compressors. The objective is to incorporate the contact forces, along with the Compression Loads, in determining the beating forces. The model allows only a rotational degree of freedom for each rotor. A backlash type clearance is modelled between contact points in the rotor meshing zone. This results in a piecewise linear model in which two separate system modes are possible. Separate systems of equations of motion are used to represent each mode. In addition, methods for computing the motion due to transitions between the states are also presented. The system of equations is solved using a Runge-Kutta integration algorithm with time as the independent variable and the rotor angular positions and velocities as the dependent variables. For each rotor, the moment about the rotor axis due to the Compression process is input as a function of the rotor angular position. The simulation is implemented for a typical set of compressor parameters and the resulting bearing forces are computed. The results indicate that the Compression Loads, as compared to the contact force, dominate the bearing forces. OVERVIEW OF MODEL This model is based on research conducted by the authors while at Purdue University [1]. An overview of the model is presented here. Basic Assumptions Utilized The following basic assumptions are applied in developing the model of the rotor interaction. 1. The rotors are assumed to be rigid bodies. The flexibility of the male lobes and female flutes is neglected. 2. The rotor shafts are assumed to be rigid, with no torsional or lateral flexibility. 3. The bearing mounts are assumed to be rigid, with no lateral displacements. These assumptions result in a 2-degree-of-freedom model, each rotor having only a smgle rotational degree of freedom about its central axis. The state of the system is defined by the angular position and velocity of each of the rotors. Rotor Contact The contact between the rotors is modelled using points on the rotor pitch circles, as seen 111 Figure 1. The pitch circles define the kinematic relationship between the rotors. The radii of the pitch circles are assumed to remain constant. A backlash type of clearance is modelled by allowing only one contact point, C, to exist on the male rotor pitch circle, while two contact points, A and B, exist on the female pitch circle. The clearance region is then specified as the angle between points A and B. The contact mode is defined when point C is in contact with either point A or B. The independent mode is defined when point Cis in the clearancf! region.
A Shiraziadl - One of the best experts on this subject based on the ideXlab platform.
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analysis of large Compression Loads on lumbar spine in flexion and in torsion using a novel wrapping element
Journal of Biomechanics, 2006Co-Authors: A ShiraziadlAbstract:Abstract Axial Compression on the spine could reach large values especially in lifting tasks which also involve large rotations. Experimental and numerical investigations on the spinal multi motion segments in presence of physiological Compression Loads cannot adequately be carried out due to the structural instability and artefact Loads. To circumvent these problems, a novel wrapping cable element is used in a nonlinear finite element model of the lumbosacral spine (L1–S1) to investigate the role of moderate to large Compression Loads on the lumbar stiffness in flexion and axial moments/rotations. The Compression Loads up to 2700 N was applied with no instability or artefact Loads. The lumbar stiffness substantially increased under Compression force, flexion moment, and axial torque when applied alone. The presence of Compression preLoads significantly stiffened the load-displacement response under flexion and axial moments/rotations. This stiffening effect was much more pronounced under larger preLoads and smaller moments/rotations. Compression preLoads also increased intradiscal pressure, facet contact forces, and maximum disc fibre strain at different levels. Forces in posterior ligaments were, however, diminished with Compression preload. The significant increase in spinal stiffness, hence, should be considered in biomechanical studies for accurate investigation of the load partitioning, system stability, and fixation systems/disc prostheses.
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load bearing and stress analysis of the human spine under a novel wrapping Compression loading
Clinical Biomechanics, 2000Co-Authors: A Shiraziadl, Mohamad ParnianpourAbstract:Objective. To examine biomechanics of the human spine under a novel Compression loading that follows the curvature of the spine. Design. The detailed response of the spine is predicted and compared under various types of Compression loading at different postures. Background. The posture and loading configuration could be so adjusted as to increase load-bearing capacity and stability of the spine in Compression while minimizing the muscle activity and risk of tissue injury. Methods. The nonlinear finite element formulation of wrapping elements sliding over solid body edges is developed and used to study the load-bearing capacity of simplified beam-rigid body thoracolumbar (T1–S1) and lumbosacral (L1–S1) spines under a wrapping Compression force. The load-bearing and stress analysis of a detailed model of the lumbar spine, L1–S1, is also investigated under five wrapping Loads resulting in differential Compression forces at various levels. Follower load at L1, axially fixed Compression at L1, and combined axially fixed Compression and moments load are also considered for comparison. For the detailed model, the effect of changes in the position of wrapping elements and in the lumbar curvature on results are considered. Results. The idealized wrapping loading stiffens the spine, allowing it to carry very large Compression Loads without hypermobility. It diminishes local segmental shear forces and moments as well as tissue stresses. Conclusions. In comparison to fixed axial Compression, the Compression loading by wrapping elements that follow the spinal curvatures increases the load-bearing capacity in Compression and provides a greater margin of safety against both instability and tissue injury. Relevance These findings suggest a plausible mechanism in which postural changes and muscle activation patterns could be exploited to yield a loading configuration somewhat similar to that of the wrapping loading, i.e., the net reaction force at various levels passes through discs nearly normal to their mid-height plane. To alleviate hypermobility in Compression, the wrapping loading could also allow for the application of meaningful Compression Loads in experimental as well as model studies of the multi-segmental spinal biomechanics.
Daining Fang - One of the best experts on this subject based on the ideXlab platform.
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Compression twist deformation of novel tetrachiral architected cylindrical tube inspired by towel gourd tendrils
Extreme Mechanics Letters, 2018Co-Authors: Wenwang Wu, Luchao Geng, Dexing Qi, Daining FangAbstract:Abstract Inspired by the coupling geometrical relations of left-hand (LH) and right-hand (RH) climbing towel gourd tendrils within single branch, innovative chiral architected cylindrical tube is proposed, which can convert axial Compression Loads into angular rotation deformation. Firstly, two series of tetrachiral cylindrical tube samples with rotation disk on the mirror plane (middle cross-section) are designed, where the numbers of unit cells and tetrachiral nodes radius are different. Secondly, the cylindrical tetrachiral tubes are fabricated with Selective Laser Sintering (SLS) nylon sintering techniques, and in-situ Compression tests are performed for studying the relation between axial Compression strain and rotation angle of the spinning disk. It is found that the proposed innovative tetrachiral cylindrical tube is able to generate lateral rotation, and linear relation between rotation angle and Compression force can be harvested. With the progress of micro- and nano-manufacturing techniques, the proposed tetrachiral cylindrical tube with Compression-twist deformation mechanism demonstrates robust mechanical performances for future industrial applications, such as: shape memory morphing structures in aerospace engineering, smart actuators and propellers, smart flexible microelectronics and biomechanical devices.
Sergio Oller - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Matrix Reinforced Composite Materials Subjected to Compression Loads
Archives of Computational Methods in Engineering, 2009Co-Authors: Xavier Martinez, Sergio OllerAbstract:This paper reviews the most common formulations to obtain the Compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965 ) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite. Once having described the different approaches used, and the parameters on which they depend, this paper describes a new formulation capable of obtaining the Compression strength of composites taking into account the fiber buckling phenomenon. This formulation uses the serial/parallel mixing theory developed by Rastellini et al. (Comput. Struct. 86(9):879–896, 2008 ) to simulate the composite, and takes advantage of knowing the mechanical performance of the composite constituents to simulate the fiber buckling phenomenon. This is done with an homogenization procedure. It consists in introducing the interaction between fibers and matrix into their respective constitutive equations. The interaction between fiber and matrix takes into account fiber initial misalignments, its volumetric participation and the mechanical properties of both constituents. The new formulation proposed is implemented in a finite element code, taking into account that fibers can have different misalignment levels, and that the composite behaves differently if it is under tensile or Compression forces. The mechanical performance of the formulation proposed is studied with several finite element simulations of compressed composites. Finally, the correctness of the formulation is proved by comparing the numerical results with the experimental tests provided by Barbero and Tomblin (Int. J. Solids Struct. 33(29):4379–4393, 1996 ), Tomblin et al. (Int. J. Solids Struct. 34(13):1667–1679, 1997 ).
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numerical simulation of matrix reinforced composite materials subjected to Compression Loads
Archives of Computational Methods in Engineering, 2009Co-Authors: Xavier Martinez, Sergio OllerAbstract:This paper reviews the most common formulations to obtain the Compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite.
Werner Soedel - One of the best experts on this subject based on the ideXlab platform.
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Computation of Compression Loads in Twin Screw Compressors
Journal of Mechanical Design, 1995Co-Authors: G P Adams, Werner SoedelAbstract:The Compression mechanism in a twin screw compressor consists of two helical rotors. In this work, a method is presented for computing the forces and moments induced on each rotor due to gas Compression. These are defined as the Compression Loads. The helical rotor surfaces are defined by the end profiles, wrap angle and rotor length. The 3D surface of each rotor is mapped to 2D integration regions. These regions correspond to the surfaces associated with individual Compression chambers. The Compression Loads are computed by integrating the chamber pressure over the rotor surfaces. The integrals are evaluated at incremental values of the rotor angular position. The method is presented and implemented for a specific compressor configuration. The Compression Loads are resolved to forces at the bearing locations. These bearing forces are presented for operating pressures which represent an under-pressure condition. A frequency analysis demonstrates the rich frequency content of the bearing forces due to the sharpness of the Compression Loads as a function of the rotor angular position. In addition, it is demonstrated that the moment load about the axis of rotation induced on the female is approximately 12 percent of that induced on the male. Therefore, the female rotor motion approaches that of an idler gear.
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Dynamic Simulation of Rotor Contact Forces in Twin Screw Compressors
1994Co-Authors: G P Adams, Werner SoedelAbstract:Werner Soedel Purdue University 1077 Herrick Laboratories West Lafayette, IN 47907 A model is presented for computing the rotor contact forces in twin screw compressors. The objective is to incorporate the contact forces, along with the Compression Loads, in determining the beating forces. The model allows only a rotational degree of freedom for each rotor. A backlash type clearance is modelled between contact points in the rotor meshing zone. This results in a piecewise linear model in which two separate system modes are possible. Separate systems of equations of motion are used to represent each mode. In addition, methods for computing the motion due to transitions between the states are also presented. The system of equations is solved using a Runge-Kutta integration algorithm with time as the independent variable and the rotor angular positions and velocities as the dependent variables. For each rotor, the moment about the rotor axis due to the Compression process is input as a function of the rotor angular position. The simulation is implemented for a typical set of compressor parameters and the resulting bearing forces are computed. The results indicate that the Compression Loads, as compared to the contact force, dominate the bearing forces. OVERVIEW OF MODEL This model is based on research conducted by the authors while at Purdue University [1]. An overview of the model is presented here. Basic Assumptions Utilized The following basic assumptions are applied in developing the model of the rotor interaction. 1. The rotors are assumed to be rigid bodies. The flexibility of the male lobes and female flutes is neglected. 2. The rotor shafts are assumed to be rigid, with no torsional or lateral flexibility. 3. The bearing mounts are assumed to be rigid, with no lateral displacements. These assumptions result in a 2-degree-of-freedom model, each rotor having only a smgle rotational degree of freedom about its central axis. The state of the system is defined by the angular position and velocity of each of the rotors. Rotor Contact The contact between the rotors is modelled using points on the rotor pitch circles, as seen 111 Figure 1. The pitch circles define the kinematic relationship between the rotors. The radii of the pitch circles are assumed to remain constant. A backlash type of clearance is modelled by allowing only one contact point, C, to exist on the male rotor pitch circle, while two contact points, A and B, exist on the female pitch circle. The clearance region is then specified as the angle between points A and B. The contact mode is defined when point C is in contact with either point A or B. The independent mode is defined when point Cis in the clearancf! region.