Influence of Muscle-Tendon Wrapping on Calculations of Joint Reaction Forces in the Equine Distal Forelimb

The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces between the long bones at each joint. This finding highlighted the importance of taking into account muscle-tendon wrapping when evaluating joint loading in the equine distal forelimb

Sculpturing surfaces with robot manipulators

© 1993 Dr. Colin Reginald BurvillA six freedom robot manipulator can position and orientate a tool anywhere within in its workspace. This enables the manipulator to traverse an oriented cutting tool across surfaces whose topography require the use of all six freedoms. Although the tracing of a general curve within the reachable workspace is theoretically possible, kinematic and control limitations often preclude this. The degree of such limitations may impede the successful generation of a specific surface shape. This research investigated specific surfaces and sculpturing strategies to evaluate the kinematic limitations posed by manipulators. In the assessment of whether a strategy will be successful or not, the manipulator's structural configuration, cutting tool geometry, location of the surface in the workspace, and the trajectory generation method must be taken into consideration. The range of end-effector orientations possible at a single position within the manipulator's workspace was defined as the orientation envelope and provides a measure of manipulator dexterity. The orientation envelope can be used to predict whether a manipulator based sculpturing system can kinematically complete a sculpturing strategy. Surfaces that cannot be sculptured continuously, either due to orientation envelope or dexterity limitations, may be divided into patches, each involving a different strategy. At a special configuration the rank of a six freedom manipulator's Jacobian is less than six because at least two joints lose their linear independence. Special configurations are likely to be encountered during sculpturing of highly curved surface regions and can prevent continuous sculpturing. To permit continuous sculpturing in a. region which contains special configurations, the trajectory curves for the manipulator are either steered away from singular positions on the surface or made to move smoothly through them by adjusting the trajectory path. A system based interface between the Cincinnati Milacron T3-726 controller and an external host computer was written to test the accuracy of the T3-726 in locating end- effector geometries in its workspace during tracing experiments. The T3-726 controller introduced a substantial systematic error which caused end-effector locational errors that tended to increase as the manipulator actuated its joints away from their home positions. Manipulator based sculpturing can only be performed reliably with external joint space control. A novel method of trajectory curve generation is proposed in which only a surface and an initial surface curve description is needed. The evolution of the initial surface curve is driven by the curvature of the curve and the surface to which it is constrained and subsequently generates a family of intermediate trajectory curves

Fatigue life reduction of GFRP composites due to delamination associated with the introduction of functional discontinuities

This paper reports on an experimental investigation into the fatigue life of Glass Fibre Reinforced Polymer (GFRP) when essential design discontinuities are introduced to a GFRP part to enable correct function. Specifically, the impact of high speed drilled holes on fatigue life is investigated. Fatigue life is a critical mechanical property, in particular, for industrial applications where both minimal weight and high reliability are sought. The paper investigates the impact of high speed drilling parameters on the delamination created around the hole, and subsequently on the static strength and fatigue life of GFRP composite laminates. Delamination damage in GFRP specimens is monitored using novel Acoustic Emission (AE) and image processing techniques. The progress of delamination under fatigue testing is used to predict GFRP mechanical performance and associated GFRP mechanical properties are proposed. What follows is an outline of the experimental method used. First, the extent of delamination after high speed drilling was measured in both unidirectional and woven GFRP specimens under different feed rate and cutting speed parameters. Quasi-static three point bending tests were then performed to investigate the effect of delamination on strength and to assist the determination of appropriate fatigue load magnitudes. Then, three point fatigue bending tests were completed. In this step, Acoustic Emission and image processing techniques were applied simultaneously. Experimental results indicated that drilling parameters have negligible effects on the static strength of GFRP specimens, however, the fatigue life of GFRP specimens varied significantly with the changes of drilling parameters. The experimental results also showed that AE and image processing techniques produced consistent data, offering a validation to the data itself and to indicating that both techniques have merit when completing experiments of this type more generally to determine the mechanical behavior (and associated mechanical properties) of specimens

Mechanical characterization of particulated FRP composite pipes: A comprehensive experimental study

Particulated fiber reinforced polymer (FRP) composite pipes encompass unidirectional continuous glass fibers (hoop glass), resin (thermoset polymer vinylester) matrix, chop glass (discontinuous short fibers), and particulate reinforcement (sand) impregnated into resin. They are categorized based on their nominal diameter, pressure class, and stiffness class. Mechanical characteristics of this class of composite materials have not, to date, been comprehensively studied. As such, this paper presents a systematic approach toward comprehensive experimental investigation into their mechanical characterizations in terms of the axial and hoop tensile strengths. The particulated FRP composite pipes used in the current study have glass fibers reinforced along the hoop direction at approximately 89° angle. To assure the experimental data accuracy and reliability, three batches associated with each pipe category were selected which slightly differ in the composition of their constituents. Three specimens per batch were selected and two types of tests were conducted on each specimen. 18 tests (2 × 3 batches × 3 specimens)) were conducted per pipe category (9 tests for hoop and 9 tests for axial). Therefore, 648 tests were conducted in total on 36 pipe categories. Instron 5569A and Instron 8801 universal testing machines were utilized for the axial tensile tests and a split disc hydraulic testing machine for the hoop tensile tests. The mean tensile and the hoop axial stresses and their associated standard deviations were calculated based on the Population Standard Deviation (PSD) equation and then plotted against the material constituents. The results demonstrated that an increase in the composition of particulate reinforcement results in a decrease in the axial and the hoop tensile strengths. However, increasing the ratio of resin, chop glass, and glass fibers contributes to the enhancement of the axial and the hoop tensile strengths. This study provides comprehensive design guidelines for engineers and manufacturing industries

Higher-order trigonometric series-based analytical solution to free transverse vibration of suspended laminated composite slabs

Suspended floors can be designed as effective pendulum seismic isolators for high-rise buildings. However, research studies on the free vibration of suspended laminated composite slabs are relatively limited. This paper presents a comprehensive analytical solution to the free vibration problem of suspended laminated composite slabs. The equations of elasticity are used to establish the equation of motion. The critical factors influencing free vibration are explicitly considered, including the material anisotropy, number of layers, elastic properties, rotatory inertia, and transverse shear of plates. The higher-order trigonometric series are utilized to solve the dynamic equations. The developed analytical solution is a complete and realistic form of the existing analytical solutions in literature and has the capability of converging fast. The proposed analytical solution does not have a dependency on the shape function as well as separate-of-variable forms unlike the Finite Element Method (FEM). Moreover, the FEM requires an in-depth mesh convergence analysis, particularly for higher-magnitude natural frequencies, which is not the case for the proposed analytical solution for any infinite range of eigenfrequencies. The proposed solution procedure is first verified by the simplified problems available in the literature. For more complex problems, the finite element analysis results obtained from Abaqus are employed to validate the analytical solution. The comparison demonstrates that the proposed analytical solution is accurate and reliable for a wide range of case-study examples. It is found that the natural frequencies of suspended laminated composite slabs are significantly influenced by the crucial factors under investigation

Fatigue test data applicability for additive manufacture: A method for quantifying the uncertainty of AM fatigue data

Additive manufactured (AM) components are increasingly being applied to fatigue-limited applications and are often safety–critical, necessitating confidence in the predicted fatigue response. The fatigue failure mode is highly sensitive to variations in loading, materials and geometry; therefore, published AM fatigue data must be accompanied by robust supporting documentation for confident adoption. International standards provide robust guidance on these documentation requirements; however, there are currently no formal methods for quantifying the uncertainty within published AM fatigue test data. A set of documentation criteria are proposed based on the core requirements of recognised standards for fatigue and AM test reporting. These documentation criteria form the basis for applicability indices proposed to quantify the uncertainty of reported AM fatigue test data. The applicability indices offer a new way to evaluate the suitability of fatigue data for specific applications and are demonstrated for publicly available Powder Bed Fusion Ti-6Al-4V fatigue data. This large number of datasets are examined in terms of the influence of process variables on the observed fatigue response. These observations provide a reference for AM fatigue designers to be aware of the influence of relevant variables on fatigue response, as well as for AM fatigue researchers to identify strategic opportunities for novel contributions