Metal cutting is a thermo-mechanically coupled process in which plasticity induced heating and friction play a critical role. In this paper, we outline a methodology that combines high resolution experiments with numerical simulations. The simulations were performed with a general purpose finite element code. With this code we evaluate the effects of chip-tool interface friction and rake angle on temperature and cutting force and show that results for residual stresses in the workpiece are consistent with experimental data. We hypothesize that by closely coupling simulations to fine scale spatial and temporal experimental measurements of temperature and strain fields, questions related to choice of parameters in FE simulations can be resolved. We have designed and conducted orthogonal cutting experiments to measure temperatures, using IR detectors, with a spatial resolution of 27 × 27 μm and time scale of 200 ns. Experimentally obtained temperature fields are compared with FE results. We also obtain deformation fields with a spatial resolution of 50 × 50 μm.

The objectives of the present study are to develop a material model of a tracheal smooth muscle tissue from experimental data, and to simulate the mechanical response through a three-dimensional nonlinear finite element analysis. The developed material model and simulation models are validated against the experimental data. The results obtained indicate that the approach and the material model developed are useful for describing the length-dependent characteristics of tracheal smooth muscle tissue.

The biological response of bone cells (osteoblasts and/or osteocytes) to mechanical loading is an important basic science topic in the mechanism of mechano-signal transduction in bone adaptation to mechanical loading. The characterization of this mechanism of signal transduction is crucial in the understanding of the etiology of age-related bone loss, bone loss during space flight and the optimal design of implants for total joint replacements. It has been hypothesized that deformation-generated fluid shear stress is one of the major mechanical stimuli that bone cells respond to. Many in vitro experiments utilize a parallel-plate flow chamber by imposing fluid shear stress on cultured osteoblasts. For example, changes in intracellular Ca ++ levels and mitogen-activated protein kinase (MAPK) phosphorylation has been quantified in response to applied shear flow [1,2]. In these studies, the flow shear stress at the wall of the flow chamber τ wall = 6 μ Q w h 2 , where Q is the volumetric flow rate, w and h are the width and height of the flow chamber, respectively, and μ is the media viscosity. However, this wall shear stress may not indicate the actual stress state which bone cells experience, which depends on the details of the flow-cell interaction, including the mechanical properties of the cell, the attachment condition of the cell to the wall as well as the cell density. In order to obtain a quantitative relationship between the biological response of bone cells to applied shear flow, it is necessary to quantify in detail the flow-cell interaction in a typical shear flow experiment. The objective of this study was to quantify the shear stress within the cell under applied shear flow, incorporating fully coupled flow and solid deformation analyses using the finite element technique. Specifically, we examined the influence of the elastic modulus of the cell and the spacing distance between cells on the shear stress within the cell.

Eighty plus percent of all lower limb amputations performed in the United States each year result from complications of peripheral vascular disease (PVD) [1]. PVD amputees’ vascular systems are significantly compromised and can withstand little extraneous insult. Clinical studies have shown that ill-fitting prosthetic sockets, and/or excessive prosthetics loads can traumatize amputees’ residual limb (RL) tissues [2]. Unfortunately, there are no decisive clinical measures currently available that can be used to ensure prosthesis geometry and applied prosthetics loads are safe and will not compromise limb circulation and cause tissue injury. Minus egregious symptoms of ischemic pain and tissue trauma, it is commonly assumed that the tissue stresses and strains caused by differences between RL and prosthetic socket geometries, and from prosthetics loads incurred during stance and gait, have minimal effect upon RL tissue circulation and health. The objective of this study was to investigate the validity of this assumption by quantitatively measuring the effects prosthetic socket design geometry and applied loads have on transtibial amputee RL tissue circulation, and to determine if tissue circulation sensitivities to variations in socket design were sufficient to enable optimization of prosthesis design parameters.

The stent has been a very effective device for treating vascular disease, such as in the coronary and carotid arteries. Due to the increasingly complex configuration of struts in the stent, it is instructive to investigate the relation between the strut configuration and the force that will result in stent deformation after stent placement. Although it is possible to obtain the same information through experiments or finite element analysis, a simple analytic relation may shed more light on the problem and also indicate new directions when it comes to redesign of existing stents. In our previous study (1), we investigated the drag force on a three dimensional strut structure, and the drag force appeared to be a function of strut configuration. The possible outcome of these drag forces is the focus of our current study.

Upon examination of failed total knee replacements, it has been concluded that it is the performance of the ultra high molecular weight polyethylene (UHMWPE) tibial component that governs the useful lifespan of such a joint. Severe wear of UHMWPE is associated more with tibial components of the knee than with the acetabular cups of total hip replacements. This is due to a notable lack of congruity between the articulating surfaces which leads to the presence of significant localised stresses in the femoro-tibial interface.

A general and practical approach is presented for optimizing structural additions to a base structure for broadband dynamic objectives when the base structure is excited by an arbitrary forcing function. The mode shapes and natural frequencies of the base structure are first found using a commercial finite element code or an experimental modal analysis. The mode shapes are used as basis shapes to reduce the size of the equations. The structural additions are then added as impedances into the reduced modal model. An efficient analysis algorithm is presented to reduce the computational burden for broadband analysis and optimization loops. The power transferred into a Broadband Vibration Absorber (BBVA) from a base structure is maximized as an example application. The numerical results are experimentally verified demonstrating the practical design capabilities of the method.

This paper presents a rib-stiffener pattern design method for reducing vibration energy and/or radiated acoustic power from a vibrating structure. Structural dynamics, acoustics and optimization are programmed in a unified code. To avoid difficulties in defining proper design variables such as the location, the number and the size of stiffeners to be attached on a structure, this paper adopts the idea of “topology optimization”, based on finite elements. This approach enables one to find an optimal rib-stiffener pattern by using a simple design variable, e.g., the density of finite elements. To illustrate this method, a rectangular plate with clamped edges is optimized to reduce the radiated sound power/kinetic energy and the results are compared to that the same plate but without rib-stiffeners.

A formulation that accounts for manufacturing variability in the analysis of structural/acoustic systems is presented. The methodology incorporates the concept of fast probability integration with finite element (FEA) and boundary element analysis (BEA) for producing the probabilistic acoustic response of a structural/acoustic system. The advanced mean value method is used for integrating the system probability density function. FEA and BEA are combined for producing the acoustic response that constitutes the performance function. The probabilistic acoustic response is calculated in terms of a cumulative distribution function. The new methodology is used to illustrate the difference between the results from a probabilistic analysis that accounts for manufacturing uncertainty, and an equivalent deterministic simulation through applications. The probabilistic computations are validated by comparison to Monte Carlo simulations. Based on its computational efficiency and its accuracy the new methodology is concluded to be a viable method of calculating numerically the probabilistic response of structural/acoustic systems due to manufacturing variability.

A solution methodology is introduced for the efficient computation of the acoustic field over restricted domains and for a frequency window. Typically, such partial field solutions include, for example, surfaces enclosing the radiating structure or even single points in the computational domain. The multiple-frequency partial-field (MFPF) method starts out by reformulating the finite element matrix system into a suitable shifted form. The DtN map is used as a radiation boundary condition and is interpreted as a low rank update of the matrix problem. The shifted standard form is then approximated by a rational matrix-valued Padé approximant and solved simultaneously over a frequency range. To obtain the Padé approximation, a banded unsymmetric Lanczos process is applied on the standard shifted form exploiting the matrix Padé-via-Lanczos connection. Numerical examples show the feasibility of the outlined procedure.

The vibroacoustic behavior of an advanced grid-stiffened (AGS) composite structure which is reminiscent of a mock-scale fairing has been investigated. Both finite element analysis (FEA) and experimental modal analysis have been performed and the results corroborated. The lightly-coupled structurally-dominant modes and acoustically-dominant modes can be used to determine the structural acoustic coupling coefficients for the fairing. In addition, the certain critical structural acoustic frequencies have been computed. These results can be assimilated in order to provide insight into the theoretical performance limits of various potential transmission control mechanisms, including geometry or property tuning, the inclusion of passive control materials, or the addition of secondary structural and/or acoustic control inputs.

Piezoelectric Fiber Composites with Interdigitated Electrodes (PFCIDE) were previously introduced as an alternative to monolithic wafers with conventional electrodes for applications of structural actuation. This paper is an investigation into the performance improvement of piezoelectric fiber composite actuators by changing the matrix material. This paper presents a modified micro-electromechanical model and numerical analyses of piezoelectric fiber/piezopolymer matrix composite actuator with interdigitated electrodes (PFPMIDE). Various concepts from different backgrounds including three-dimensional linear elastic and dielectric theories have been incorporated into the present linear piezoelectric model. The rule of mixture and the modified method to calculate effective properties of fiber composites were extended to apply to the PFPMIDE model. The new model was validated comparing with available experimental data and other analytical results. To see the structural responses of a composite plate integrated with the PFPMIDE, three-dimensional finite element formulations were derived. Numerical analyses show that the shape of the graphite/epoxy composite plate with the PFPMIDE may be controlled by judicious choice of voltages, piezoelectric fiber angles, and elastic tailoring of the composite plate.

Compliant mechanisms are elastic continua used to transmit or transform force and motion mechanically. The topology optimization methods developed for compliant mechanisms also give the shape for a chosen parameterization of the design domain with a fixed mesh. However, in these methods, the shapes of the flexible segments in the resulting optimal solutions are restricted either by the type or the resolution of the design parameterization. This limitation is overcome here by focusing on optimizing the skeletal shape of the compliant segments in a given topology. It is accomplished by identifying such segments in the topology and representing them using Bezier curves. The vertices of the Bezier control polygon are used to parameterize the shape-design space . Uniform parameter steps of the Bezier curves naturally enable adaptive finite element discretization of the segments as their shapes change. Practical constraints such as avoiding intersections with other segments and self-intersections, and restrictions on the available space and material, are incorporated into the formulation. A multi-criteria function from our prior work is used as the objective. Analytical sensitivity analysis for the objective and constraints is presented and is used in the numerical optimization. Examples are included to illustrate the shape optimization method.

The present work examines the effectiveness of the experimental, analytical and finite element methods in modeling smart structures. Three modeling approaches are applied to some flexible structures with bonded piezoelectric sensors and actuators. The theoretical approach is limited to simple geometrical structures, the experimental approach is not cost effective for complex geometrical structures, but FEM is very attractive. Overall, the comparisons between the three approaches are fairly good. The good accuracy of FE results are also validated through the two examples selected from the literature (Crawley, 1987; Yousefi-Koma, 1997).

In general, active damping actuators are sized to induce a prescribed level of damping in the structure in the presence of specified disturbance. Unfortunately, structural disturbances cannot be measured directly. Instead, the effect of disturbances on structural response (e.g. deflection, strain, acceleration, etc.) are quantified either in a stochasitic (i.e. spectral data such as autospectrum) or deterministic (i.e. time history data). In this paper, a technique for sizing actuators based on stochastic disturbance information is presented. From the power spectral density of the response, the peak disturbance at each structural mode of interest can be computed as well as the total RMS of the response. A structural dynamic model is synthesized using either finite element analysis or Rayleigh-Ritz formulation. Based on this information, the disturbances can be estimated which is later used to determine whether the actuator size and configuration are sufficient to introduce the prescribed level of damping. The above algorithm is used to design and compare actuators configuration to reduce the vibration on F18 tail model. A comparison between active fiber composite (AFC) actuators and regular d31 actuators is presented. Simulation results show that the AFCs have more authority than the regular d31 actuator.

Foot problems are quite common. Epidemiological studies have shown as many as 86% of elderly individuals report having problems with their feet, ranging from calluses, cracking and ingrown nails to inflammation, swelling, ischemia, ulceration, and gangrenous necrosis [1]. Persons suffering chronic Diabetes Mellitus are at particular risk of trauma to their feet because of peripheral neuropathy, plantar fat pad and muscle atrophy, and vascular insufficiency. Half of all lower limb amputations each year in the United States are performed on diabetics because of foot and ankle injuries that fail to heal [2]. At the very least, podalgia and pedal trauma restrict person’s mobility and limit their independence, impacting their fiscal as well as their physical well-being. With the exception of memorable catastrophic events, the etiopathogenesis of podalgia and other problems contributing to pedal trauma are generally not well understood. In work with Hansen’s disease and diabetic patients, Brand et al. [3] showed that stresses as small as 1/2 psi could produce trauma in the foot fat pads of even healthy animals, if chronically and repetitively applied without adequate time for tissues to recover and rest, Pedorthic insoles (often with orthopedic shoes) are prescribed for curative as well as prophylactic treatment of podalgia and pedal trauma, especially for diabetic patients with peripheral vascular disease, and arthritic patients with osseous deformity. There are hundreds of such devices commercially available, that range in composition and mechanical characteristics from extremely soft silicone elastomers to stiff plastic and metal plates. They maybe thin or thick, flat or custom milled with precision CAD/CAM systems using 3D laser scans of the individual’s feet to match their pedal contours. Although numerous studies [4, 5, 6] have been conducted, measuring pedal plantar interface stresses, no general quantitative principles for design, performance assessment, or prescription have been developed. These procedures remain highly subjective, and quite variable, depending upon the training, experience, and skill of the patient’s pedorthotist, podiatrist, and/or physcian. The objective of this study was to investigate the stresses and strains incurred in the soft plantar tissues of the foot as a function of insole material and design geometry to enhance understanding of footwear biomechanics and contribute to development of quantitative criteria for prescription, design, and performance assessment of pedorthic footwear.

The effect of graft materials on knee kinematics after ACL reconstruction was investigated parametrically using a 3D finite element knee joint model. The results demonstrated that a stiff graft, such as the current BPTB graft, may overcorrect the kinematics of an ACL deficient knee. A less stiff graft, under appropriate initial tension, may better restore the intact kinematics.

Infants and young children sustain head injury during falls and motor vehicle crashes. A better biomechanical understanding assists to mitigate the head injury in the pediatric population. A three-dimensional finite element model of an infant head was developed. The model included the cranial bone, sutures, fontanelles, brain and foramen magnum. The infant head was impacted with a stationary wall structure. Three types of walls (padded and unpadded flat walls, and unpadded cavity/edge wall) were used. The polypropylene and rigid materials were defined for the wall. Each analysis was conducted at an impact velocity of 6.7 and 8.9 m/sec. The cranial bone of the infant head sustained lower strain during the impact with the padded flat wall. The strain in the cranial bone increased considerably when the padding was removed. A further increase in the strain was observed during the impact with the unpadded cavity/edge wall. While the strain in the cranial bone was diffused under the padded flat wall impact, it was more concentrated under the unpadded cavity/edge wall impact condition.

In this paper a finite element model of a rotating paper machine roll for nip unit rolling contact analyses is discussed. This work presented here is based on the earlier work of the authors presented in [1] and [2]. The major motivations for developing a tailored FE-model including the large spin rotation are firstly to include the complex vibration phenomena as the shell vibrations of the roll structure in the analyses and secondly to reduce the computational costs of the numerical simulations due to the large number of degrees of freedom. The approach used is the use of the modal analysis i.e. to express the dynamics of the roll in terms of the lowest eigenmodes. The equations of motion are at first written in the rotating coordinates and then in addition to this the equations are expressed by using the modal coordinates. Numerical tests executed show that this modeling technique reduces computational costs significantly. Furthermore, use of the (semidefinite) eigenmode basis maintains the vibration characteristics of the roll structure. For verification purposes a test model was constructed and these simulation results were compared to the standard geometrically non-linear finite element analysis.

The influence of geometry on the pressure field within the confined, water-filled annulus between a central, vibrating cylinder and an outer, rigid enclosure is determined. A two dimensional model is constructed using the finite element (FE) method and parameters are identified to characterize the eccentricity of the nominal cylinder position, the size of the annulus relative to the inner cylinder and the degree to which the annulus is not circular (i.e. it is elliptic). The FE solution is verified using a closed form solution for the special case of a concentric cylinder and annulus. It is shown that the system acts as a force multiplier. Analyses of the asymmetrical geometries indicate that while the pressure field on the surface of the cylinder and enclosure can be highly asymmetric, the system is relatively insensitive to minor variations in annulus shape except when the vibrating cylinder is not centrally located within the fluid region or the annulus size itself is small.