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EDITORIAL

J. Mech. Des. 1980;102(4):641. doi:10.1115/1.3254797.
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Abstract
Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Mech. Des. 1980;102(4):644. doi:10.1115/1.3254798.
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Abstract
Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):644-645. doi:10.1115/1.3254799.
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Abstract
Topics: Vibration
Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):645. doi:10.1115/1.3254800.
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Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Medical Devices and Sporting Equipment

J. Mech. Des. 1980;102(4):646-654. doi:10.1115/1.3254801.

Due to better ski equipment, instruction, slope management and increased safety awareness on the part of the skiing public, ski injuries appear to be declining. Ski equipment is incorporating computerized design procedures along with possible applications of microprocessor controlled hardware. Ski instruction has graduated from the maneuver oriented to skills development methods. Biomechanics researchers have obtained experimental loading data during skiing and are utilizing finite element methods to model the skier. Infrared thermography is being utilized on ski clothing design, environmental safety and rescue. Standards are being developed to assure consistent terminology, compatibility between ski equipment, and safety.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):655-662. doi:10.1115/1.3254802.

The Medical Device Amendments to the Food, Drug, and Cosmetics Act mandates that substantially new devices be subjected to study and testing prior to the commencement of clinical trials. The proposed outline for preclinical analysis, testing, and evaluation of orthopaedic implants is intended to guide the designer in defining what the limits of understanding are and, within those limits, to minimize the risk to implant recipient. The process of design qualification and verification is broken down into seven major steps: Problem Definition, Underlying Assumptions, Material Selection, Engineering Analysis, Correlation of Demand to Capabilities, Analytical Estimate of Performance and Experimental Verification of Performance. The discussion of each of these topics focuses on the type of information needed for each activity. Thus, these guidelines present a framework for the rational innovation and design of orthopaedic implants which minimizes the risk to patients involved in clinical trials.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):663-671. doi:10.1115/1.3254803.
Abstract
Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):672-676. doi:10.1115/1.3254804.

This paper describes the design of a new type of forearm crutch that features a conservative form of energy storage. Energy stored by the crutch during an early portion of the gait cycle is returned to the user later in the gait cycle. The results of experimental tests of the new crutch by children ages 7-12 years are presented, and evaluative conclusions are presented.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):677-682. doi:10.1115/1.3254805.

A ski release binding releases the ski boot from the ski for loading environments potentially injurious to the lower extremity. The concept of using a model reference adaptive control system to control ski binding release is explored. Model reference oscillators simulate torsion about the longitudinal leg axis and anterior-posterior bending of the lower extremity. The model oscillator coefficients are adjusted depending upon processed EMG signal levels from lower extremity muscle groups, which serve as state estimators. Background on release binding design, binding circuit diagrams and the results of preliminary tests on a binding are presented in this paper.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):683-687. doi:10.1115/1.3254806.

In a number of studies associated with the deformities of the foot in general and the occurance of plantar ulcer in particular it is required to have an accurate estimate of the average normal and shear pressure variation arising from ground reaction during the walking cycle. This necessitates the measurement of the instantanious area of contact between foot and ground along with the forces. The present paper describes for the first time such a system in which quantitative out-put of the following parameters can be monitored during the walking cycle. (1) Instantanious component forces of the foot-ground reaction (Fv , Fh and Fi ) (2) Instantanious area of contact between foot and ground during the walking cycle (A) (3) Instantanious average normal and shear stress on the underside of foot during the walking cycle.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):688-694. doi:10.1115/1.3254807.

The design of a continuous fiber composite surface femoral shell having the same elastic properties as bone is presented. Contact between the femoral ball and acetabular cup was modeled as an elastic spherical ball loaded on an elastic semi-infinite body. The elastic constants of the composite were obtained by using empirically modified and experimentally verified rule-of-mixture equations relating the elastic properties of bone to those of both the fibers and matrix. The stresses were calculated for the contact problem and applied to a cross-ply laminate made up of orthotropic lamina. An interactive tensor failure criterion was used to select a safe design for polyimide, ultra-high molecular weight (U.H.M.W.), high density polyethylene, acrylic bone cement and epoxy composites using either glass or kevlar fibers. The safest composite design appears to be that made with a polyimide or epoxy matrix and glass or kevlar fibers.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):695-700. doi:10.1115/1.3254808.

The relative translation and rotation of a snow ski and boot under lateral impact of the ski is critical to the function of the ski release binding. The binding couples the ski and ski boot during skiing and releases them under potentially excessive loading of the skier’s leg. A displacement transducer was developed to measure the general, two dimensional translation and rotation of the boot relative to the ski during laboratory impact tests of bindings. The requirement that the boot and ski separate upon release of the binding complicates the transducer design. Lateral impacts were applied with a pendulum at the “ski tip”, at the “ski tail” and at the “boot toe” positions on the ski. The model leg, ankle and ski response were recorded. Significant differences in leg-ski-binding system response were observed with two commercial bindings and with the impact locations on the ski.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):701-710. doi:10.1115/1.3254809.

This paper describes techniques developed to permit the evaluation of loadings on the forearm of a tennis player immediately prior to ball/racket impact. Kinematic data were obtained using high-speed three-dimensional cinematography. A specially instrumented racket permitted the quantification of finger gripping forces. Relative magnitudes of the various sources of forearm loading (inertial effects, gripping forces, etc.) were evaluated. Optimization techniques were used to estimate individual muscle forces in the forearm. The results correlate reasonably well with observed patterns of muscle electromyographic activity. Limitations of the current analytical model and experimental techniques are discussed along with planned improvements.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):711-717. doi:10.1115/1.3254810.

This paper describes a technique for generating a chain drive capable of allowing a desired varying angular velocity function on the driving shaft while maintaining constant angular velocity of the driven shaft. The technique is closely related to the synthesis of cams with flat faced oscillating followers. The technique is illustrated by the synthesis of a drive train for increasing the power applied to the rear wheel of a bicycle. The synthesized drive train shows a theoretical 12.6 percent increase in delivered power. Comparisons with published experimental results, as well as a discussion of the assumptions used in the synthesis procedure are included.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):718-722. doi:10.1115/1.3254811.

This paper describes the design of a low-cost wheelchair dynamometer used to evaluate patient performance while using their own wheelchairs. Specifications are listed and details of the overall system including controlling schemes are given. Representative clinical research is listed. The multiple uses of the dynamometer system are discussed.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):723-726. doi:10.1115/1.3254812.

The use of surface treated high tensile carbon fibers as reinforcing in acrylic bone cement is discussed. This reinforcement is shown to have certain advantages over untreated high modulus fibers as previously advocated in that much smaller proportions of fiber produce a similar improvement in fatigue life. The use of smaller fiber proportion also has the beneficial side effect of retaining the good viscosity properties of the unreinforced acrylic cement.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):727-731. doi:10.1115/1.3254813.

The paper begins with a panoramic view of the state of the art embracing the spectrum of methods employed by different designers to account for all stress concentration effects in calculations for use in the design of machine elements and components subjected to combined/fatigue loadings. Then, on the basis of the widely accepted von Mises-Goodman approach, and the method deemed the best for incorporating combined stress concentration effects, a general expression is derived for the combined fatigue stress concentration factor which is applicable to any machine element or component subjected to any combination of fatigue loadings. Various load combinations are considered not only to illustrate the use of the derived expression, but also to demonstrate other methods which may lead to calculations which are incorrect depending upon the nature and magnitude of the parameters involved. The specific machine component, that of a stepped shaft subjected to combined fatigue loadings, is selected for particular, detailed and further demonstration. Demonstrative tables and a curve plot are also included.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):734-741. doi:10.1115/1.3254815.

The split nut, invented by Commander P. Y. Williams, is easier to fit than the conventional nut and has a higher inherent strength. The two halves of the nut, which is coned at both ends, fit into a conical washer that forces them tightly onto the bolt. The positive clamping action increases the radial load on the threads, which reduces the tensile bending stress at the root of the thread. The load distribution in the threads is also improved, because the change in thread pitch caused by the axial deformation of the nut and bolt is partly compensated by a rotation of the nut halves about an axis normal to that of the bolt. These two effects reduce the maximum tensile stress at the root of the thread to about half of that in the conventional nut.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):742-748. doi:10.1115/1.3254816.

A strength-of-materials approach is used to develop an approximate stiffness matrix for a uniformly-pretwisted beam segment. The beam element is a 12 degree-of-freedom member that includes shear effects, eccentric loading effects, axial-torsional and bending-torsional coupling, and the torsional stiffening effect of the natural pretwist. The current formulation can be employed as an inexpensive preliminary design tool for pretwisted blading that is suitable for implementation on low-core computer graphics systems. After obtaining a workable geometry, final design optimization can be performed by utilizing more sophisticated, and expensive, three-dimensional finite element models.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):749-756. doi:10.1115/1.3254817.

This paper proposes a method of systematically generating the failure criteria of truss structures by using Matrix Method. The resulting criterion for a statically determinate truss is simple and its failure probability is easily evaluated. In case of a statically indeterminate truss, however, there are many possible modes or paths to complete failure of the structure and it is impossible in practice to generate all of them. Hence, the failure probability is estimated by evaluating its lower and upper bounds. The lower bound is evaluated by selecting the dominant modes of failure and calculating their probabilities. The upper bound is evaluated by assuming that the redundant truss behaves itself like a statically determinate truss, i.e., the structure fails if any one member is subject to failure. Numerical examples are provided to demonstrate the applicability of the propsed methods.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):757-760. doi:10.1115/1.3254818.

This paper provides the designer with design formulations, tables and curve plots which may be employed in the design of uniformly loaded, ductile, elastic annular diaphragms clamped at the other edge and free at the inner edge. An exact solution of basic theoretical equations is employed along with the application of the well known and documented distortion energy theory of failure which results in a useful stress vs. strength relationship. An exact solution of the related deflections is also presented for concurrent stiffness (deflection) calculations.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):761-768. doi:10.1115/1.3254819.

The paper presents an approach to obtaining reliability and optimal replacement policies at different operating conditions, based on limited data at one operating condition. Guidelines for the choice of a distribution based on the behavior of sample functions of deterioration processes such as wear and fatigue are provided. The importance of the coefficient of variation is delineated to show how it provides a dimensionless format of the distributions and optimal replacement strategies. Simple graphical solutions of the otherwise complicated optimal replacement equations are illustrated by numerical examples based on experimental data in diverse forms from the areas of cutting tools and fatigue failures.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):769-775. doi:10.1115/1.3254820.

The paper presents an analysis of the elastic response of a simply supported, imperfect, rectangular plate subjected to an in-plane supercritical shear force, suddenly applied at one of the edges in the form of a square pulse. The influence of the initial plate irregularities on the overall response during both loading and postloading period is investigated. The averaged in-plane inertia forces are taken into account. The analysis is an extension of the studies of the response to in-plane normal forces of plates of infinite width and finite length given in [1], and of a finite plate given in [2]. The results indicate that the frequency spectra of free vibrations during the post-loading regime are controlled by the initial irregularities distribution, plate geometry and the load levels.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):776-780. doi:10.1115/1.3254821.

When an expression is known for the curvature of a beam as a function of a bending moment, it is a simple matter to determine the deflected shape. It is a bigger problem to obtain such an explicit expression using a realistic stress-strain curve. This paper begins with a Ramberg-Osgood type of stress-strain formula, that is characterized by a continuous slope change typical of metals in elevated temperatures. A moment-curvature equation of a similar form is then developed and its accuracy is verified for several basic cross-sections. The advantage of this approach is to improve the accuracy and efficiency of deflection analysis compared with the existing manual methods.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):781-786. doi:10.1115/1.3254822.

The unit load method, which is also known as a virtual work method, as well as by several other names, is a widely used tool for calculating deflections of linear structures. A procedure is developed here, which consists of similar steps and can be used when nonlinear material is involved. The formulae are developed based on the concept of complementary energy and the Castigliano theorem extended to nonlinear systems. A few simple examples are solved using this method and the results are compared with those obtained by a finite-element program. It appears that a blend of both types of analysis may be the optimal tool in many situations.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):787-792. doi:10.1115/1.3254823.

Ellipsoids are frequently used for end closure of cylindrical pressure shells. Toroids of elliptic or circular cross-section, are widely used, e.g., for connecting two parallel legs in a U-shape. This paper presents equations for the means and standard deviations of stresses developed in ellipsoids and toroids with internal pressure. Inherent in these equations are the facts that: (a) design variables are generally characterized by spectra of values, rather than by unique values, and (b) a small, but finite, probability of failure must be recognized in any design. By coupling the stresses due to the applied loading as calculated by the equations given in the paper with the strength available in a material, reliability (or the alternative probability of failure) can be calculated. Conversely, for a given reliability the appropriate size can be determined. Appropriate illustrations of application of these equations are provided through tables and figures. The difficulty of relying on a factor of safety is demonstrated.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):793-803. doi:10.1115/1.3254824.

The use of finite elements for simulation of rotor systems has received considerable attention within the last few years. The published works have included the study of the effects of rotatory inertia, gyroscopic moments, axial load, and internal damping; but have not included shear deformation or axial torque effects. This paper generalizes the previous works by utilizing Timoshenko beam theory for establishing the shape functions and, thereby including transverse shear effects. Internal damping is not included but the extension is straight forward. Comparison is made of the finite element analysis with classical dosed form Timoshenko beam theory analysis for nonrotating and rotating shafts.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):804-806. doi:10.1115/1.3254825.

Minimizing solute carry-over into the product is the central object in the design of Radioactive Waste Concentration Systems. Two Stage Evaporators are intrinsically superior to single stage designs in achieving this objective. An analysis of two stage system to optimize its performance is herein developed. A numerical example is employed to illustrate major conclusions.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):807-817. doi:10.1115/1.3254826.

Field tests were conducted to determine the pump characteristics at four pumping plants on the Southern Nevada Water Project. Each pump tested was instrumented to measure speed, torque, and pressure head as functions of time. Records were obtained for pump startup, normal operation, and power failure. The Southern Nevada system was modeled for these same operations on a master computer program, TAHS. Using TAHS, the pump characteristics were adjusted by an iterative process until the computer results were in agreement with the field test records.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):818-822. doi:10.1115/1.3254827.

The equations of motion of a free swinging compound (physical) pendulum were integrated to obtain a general solution for the elapsed time in the form of a trigonometric integral. The latter was reduced to Jacobian elliptic functions of the first kind, which were then solved by conventional techniques for complete and incomplete integrals. Applying the method developed to a generalized pendulum described by its degree of compounding, the period of its oscillation whilst in frictionless motion for any angle of launch was determined. The degree of compounding of the pendulum had a significant effect on its period of oscillation. This was shown graphically in the form of the variation of a dimensionless time ratio with change in angle of launch for various degrees of compounding. Five specific cases of the time intervals of motion of a compound pendulum were analyzed and solutions obtained. The general equation for the elapsed time of free swinging motion of a simple (mathematical) pendulun, launched from any position and its period of oscillation were also determined.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):823-828. doi:10.1115/1.3254828.

Plastics offer cost, maintenance, and density advantages over metals for many lowstrength applications. Low electrical and thermal conductivities, however, are major deficiencies for some applications. The addition of conductive fillers to the polymer will improve these deficiencies. The two filler parameters which most significantly affect the conductivity of the composite are volume loading and the shape. This paper discusses the effects of various filler types and shapes on the conducitivity of plastics.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):829-834. doi:10.1115/1.3254829.

The natural frequencies and normal modes of a uniform beam depend upon support conditions. The effect of translation and rotation springs at the base is examined in this presentation. This is done in terms of non-dimensional variables and parameters to enhance the utility of the results. The paper also develops the mode participation and dynamic load factors for subsequent application.

Topics: Rotation , Stress , Springs
Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):835-841. doi:10.1115/1.3254830.

The paper presents the use of dimensional analysis as an aid in the design of dynamic systems. Basic theory of dimensional analysis is discussed. Two examples are given: (1) a two degree of freedom vibrating system and (2) a flexible rotor which is flexibly supported at its ends. Choice of suitable non-dimensional parameters is discussed. A digitial computer program is described which generates all of the possible sets of non-dimensional parameters for a given problem.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):842-850. doi:10.1115/1.3254831.

The response of a flexible rotor mounted in six bearing sets has been experimentally determined. One set of axial groove bearings and five sets of pressure dam bearings were tested. Conventional synchronous tracking was used in the analysis and other techniques utilizing an FFT analyzer were developed. The stability of the system was seen to strongly depend on the design of the step bearings. The dam bearings were also noted to lock into subsynchronous whip during deceleration after the system went unstable. The response of the system with varying degrees of unbalance is also analyzed and several structural resonances of the rotor system are discussed.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):851-857. doi:10.1115/1.3254832.

Bolted and riveted connections are quite commonly encountered in various design problems. Many trials have been carried out recently to determine the stress distribution in bolted and riveted joints which is of extreme importance in the design of such joints. Effect of many parameters has been investigated, however effect of thickness ratio of the joint plates did not take too much attention. In this analytic work the effect of various plate thickness on the load and stress distribution in cylindrical bolted joints has been investigated using the finite element technique. Computed results show that the load as well as the stress or pressure distribution under bolt-head or nut are not constant nor uniform. Whatever the thickness ratio of the two plates (I1 /L2 ), constant load and stress occurred across the joint under the bolt-head end. Maximum stress on surface and up to the mid plane level showed an increase with the thickness ratio. However the maximum stress on interface decreases with the thickness ratio to reach its lowest at L1 /L2 = 1. End of loading on surface or at mid plane increases with the increase in thickness ratio, and tends to approach a constant value at L1 /L2 equals 10 or more—on interface the opening position—represented by diameter of joint to bolt diameter D/d, reaches a maximum value of 3.5 then decreases rapidly to reach a constant value of about 2.5 for L1 /L2 = 10 or more. Also the thickness of the plate (L1 ) has a pronounced effect on the opening position.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 1980;102(4):858-864. doi:10.1115/1.3254833.

An experimental investigation of hydrodynamic lubrication of journal bearings was conducted using a polymer melt as the lubricating fluid. The test apparatus monitored the pressure profile, eccentricity ratio, axial flow rate and frictional power loss for a bearing with L/D = 1.5. Due to the non-Newtonian viscosity/shear-rate relation of the polymer, it was necessary to define a generalized Sommerfeld number in order to plot the data. The results provide a tool for the design of polymer lubricated bearings.

Commentary by Dr. Valentin Fuster

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