Stress Distribution

The main objective of this work is the evaluation, by means of the finite element method (FEM) of the mechanical stability and long-term microstructural modifications in bone induced to three different kinds of fractures of the distal femur by three types of implants: the Condyle Plate, the less invasive stabilization system plate (LISS) and the distal femur nail (DFN). The displacement and the stress distributions both in bone and implants and the internal bone remodelling process after fracture and fixation are obtained and analysed by computational simulation. The main conclusions of this work are that distal femoral fractures can be treated correctly with the Condyle Plate, the LISS plate and the DFN. The stresses both in LISS and DFN implant are high especially around the screws. When respect to remodelling, the LISS produces an important resorption in the fractured region, while the other two implants do not strongly modify bone tissue microstructure.

Physiological studies have shown that focal articular surface defects in the human knee may progress to degenerative arthritis. Although the risk of this evolutive process is multifactorial, defect size is one of the most important factors. In order to determine the influence of osteochondral defect size and location on the stress and strain concentrations around the defect rim, a finite element model of the human knee was developed. From our results, it became clear that the size and location of cartilage defects drastically affect to those variables. No stress concentration appeared around the rim of small defects, being the stress distribution mainly controlled by the meniscus contact. On the contrary, important rim stress concentration was found for large osteochondral defects. This alteration of the stress distribution has important clinical implications regarding the long-term integrity of the cartilage adjacent to osteochondral defects. ᭧ (E. Peña), bcalvo@unizar.es (B. Calvo), miguelam@unizar.es (M. Martínez), mdoblare@unizar.es (M. Doblaré). 0010-4825/$ -see front matter ᭧

The model of inclined seam excavation is established acc ording to the deformation characteristics of inclined seam and the principles of FEA. It carried out numerical s imulation method to research rock mass movement, surface subsidence and distribution of stress, which simulated excavat ion with the ANSYS software, at the same time the basi c characteristics of rock movement and the correlative par ameters of surface subsidence are obtained. The ANSYS software can not only compute the deformation mechanism of surface subsidence, but also draw up the distribution contours of stress, the distribution contours of horizontal displace and vertical subsidence. The computing model visuall y displays the deformation and stress distribution of the o verburden rock board, coal strata and lower rock board. The deformation mechanism of surface subsidence provides a refe rence for inclined seam excavation under the building. The underground excavation of mine is the huge and complex system eng...

Metamorphic segregation is defined here as rhe formation and growth of bands or domains of different bulk compositions within an originally unbanded rock. It can result from an instability arising in some deforming rocks when diffusion transfer is significant. The nature of this instability is demonstrated separately for a differentiation associated with a crenulation (Type C) and for one without crenulation (Type L). However, the continuous gradation between the two types observed in nature is also expected from the models.

In the prediction of bone remodelling processes after total hip replacement (THR), modelling of the subject-specific geometry is now state-of-the-art. In this study, we demonstrate that inclusion of subject-specific loading conditions drastically influences the calculated stress distribution, and hence influences the correlation between calculated stress distributions and changes in bone mineral density (BMD) after THR.For two patients who received cementless THR, personalized finite element (FE) models of the proximal femur were generated representing the pre- and post-operative geometry. FE analyses were performed by imposing subject-specific three-dimensional hip joint contact forces as well as muscle forces calculated based on gait analysis data. Average values of the von Mises stress were calculated for relevant zones of the proximal femur. Subsequently, the load cases were interchanged and the effect on the stress distribution was evaluated. Finally, the subject-specific stress distribution was correlated to the changes in BMD at 3 and 6 months after THR.We found subject-specific differences in the stress distribution induced by specific loading conditions, as interchanging of the loading also interchanged the patterns of the stress distribution. The correlation between the calculated stress distribution and the changes in BMD were affected by the two-dimensional nature of the BMD measurement.Our results confirm the hypothesis that inclusion of subject-specific hip contact forces and muscle forces drastically influences the stress distribution in the proximal femur. In addition to patient-specific geometry, inclusion of patient-specific loading is, therefore, essential to obtain accurate input for the analysis of stress distribution after THR.

Laboratory testing of rectangular beams using a synthetic rock was used to investigate the onset of dilation and spalling. The beams are axially compressed and subjected to 4-point bending to provide non-uniform compressive stresses. The maximum tangential stress occurs at the top of the beam and rapidly decreases with distance from the top of the beam. This stress distribution was used to simulate the maximum tangential stress distribution found around circular excavations. The results showed using this beam test configuration that the onset of dilation based on beam displacement and visually observed spalling began at approximately the same stress level. Discrete element numerical analyses (particle flow code) were used to evaluate the stress path at various locations in the beams. The analyses revealed that spalling and dilation in the beams occurred well below the peak strength failure envelope determined from conventional laboratory tests. The findings suggest that the onset of dilation in laboratory tests appears to be a good indicator for assessing the stress magnitudes required to initiate spalling.

SUMMARY Disc-shaped specimens are frequently tested in order to establish an understanding of the properties of ceramic material. In this study three-dimensional finite element stress analysis has been used to investigate the loading characteristics of this shape of specimen and the effect of incorporating scratches and voids into its structure. The results indicated that stress increased as loading was carried out nearer to the centre of the specimen. The presence of cracks did not affect these stresses whereas the presence of a void resulted in a very high stress concentration.

The Brazilian test is the most used test to determine the indirect tensile strength for brittle materials like concrete. ... ........ The results showed that to obtain a meaningful and validated test with the most accurate indirect tensile strength, it is recommended to take a loading arch 2 alfa >= 20° for the concrete and 2 alfa >= 10° for the mortar.

The fatigue crack initiation from a surface defect is analysed by means of a new attempt based on multiscale reduction of the stress distribution along the potential crack initiation plane. The reduction is performed by averaging process for shear and normal stresses over two critical areas (multiscale concept). The Matake multiaxial fatigue failure criterion was used to combine the effect of the reduced shear and normal stresses and to calculate the equivalent fatigue strength. The results were verified on defective material subjected to proportional loading. Elastic-plastic numerical simulations were performed for each defect geometry and type of loading (tension, torsion, and tension-torsion) to determine stress distribution. The analysis reveals that the proper calculation of the fatigue limit for defective materials requires performing the averaging process for shear and normal stresses separately.

In this work a qualitative analysis of the stress distribution of a cross section of the medial condyle of a human femur by photoelasticity is presented. A model of the cross section was obtained by plaster casting, carefully maintaining the internal architecture of the porous bone. Here the displacement and load curves reported at the ISO -14243-1 are used. The load tests started from total extension at 0° to a complete flexion at 56°. The fringe patterns observed in the porous bone model showed that the maximum stress concentration is shifted from the surface to the interior of the bone, allowing the damping of external forces and diffused them towards the interior of the bone tissue, thus reducing the contact stresses at the surface of the knee joint.

The horizontal compressive stress orientations for Mandapeta field in Krishna-Godavari (K-G) basin had been calculated from borehole breakout data using four-arm dipmeter caliper logs. The minimum horizontal stress magnitude for Mandapeta field was calculated from pore pressure data using poroelastic equation. Threedimensional (3-D) stress modeling using finite element analyses has been carried out for layered sediments and faulted layered sediments in the Mandapeta sub-basin. The length and width of the models are chosen as 5 km and 2 km respectively. Vertical depths of models are considered for sediments at depth 2 km to 5 km. This paper presents a numerical study of stress distributions (contours and trajectories) around fault models of layered geometries, submitted to overburden and unequal horizontal compressive loads. Reorientation and magnitude variation of in-situ stresses near faults and stress discontinuities across faults are observed. Changes in the stress patterns are observed at the interfaces between sediments due to faulting and sedimentbasement layers due to contrast in elastic constants. Remarkable stress gradients are observed between the sediment and basement. Magnitudes of normal component of stress decrease near the faulting whereas shear stress magnitudes increase at the faulting site. There is increase of horizontal principal stresses in the downthrown faulted layers. The maximum horizontal principal stress rotates about 90°just adjacent to the fault. Fluid flow at depth of oil reservoir could be indirectly influenced by the stress contours and by geometries of the stress trajectories. Fluid migration in low permeability reservoir may occur in response to mean stress gradients induced by the tectonic loading. The areas of high mean stress gradient are located at the interface between sediment and basement whereas the areas of low mean stress gradient is exactly coinciding with the areas of upper sediments.

Fibre-reinforced plates and shells are finding an increasing interest in engineering applications. Consequently, efficient and robust computational tools are required for the analysis of such structural models. As a matter of fact, a large amount of laminate finite elements have been developed and incorporated in most commercial codes for structural analysis. In this paper a new laminate hybrid assumed-strain plate element is derived within the framework of the Firstorder Shear Deformation Theory (i.e. assuming that particles of the plate originally lying along a straight line which is normal to the undeformed middle surface remain aligned along a straight line during the deformation process) and assuming perfect bonding between laminae. The in-plane components of the (infinitesimal) strain tensor are interpolated and by making use of the constitutive law, the corresponding in-plane stress distribution is deduced for each layer. Out-of-plane shear stresses are then computed by integrating the equilibrium equations in each lamina, account taken of their continuity requirements. Out-of-plane shear strains are finally obtained via the inverse constitutive law. The resulting global strain field depends on a fixed number of parameters, regardless of the total number of layers; 12 degrees of freedom are for instance assumed for the developed rectangular element. The proposed model does not suffer locking phenomena even in the thin plate limit and provides an accurate description of inter-laminar stresses. Results are compared with both analytical and other finite element solutions.

Laboratory experiments on undisturbed specimens of a large number of soft clay deposits, as well as previous measurements on clays and granular soils, were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest, K0: (i) after sedimentation – primary consolidation, (ii) during secondary-compression aging, (iii) after active or passive preshearing away from the laterally constrained condition, (iv) during a decrease in effective vertical stress, and (v) during an increase in effective vertical stress in the recompression or compression range, in terms of [Formula: see text], the slope of the effective horizontal [Formula: see text] versus effective vertical[Formula: see text] stress path. The behavior of K0 is explained using the concept of mobilized angle of friction in laterally constrained deformation condition. The Jaky equation provides, in terms of the angle of internal friction, a good estimate of K0 of sedimented, normally consolida...

The prediction of refractories thermal shock behavior can be estimated on two basis: heat transfer conditions andror Ž fracture mechanics concept. Materials considered in our analysis were alumina based refractories with different Al O q 2 3

In this paper, the numerical solution of the hypersingular integral equation using the body force method in cucved crack problems is presented. In the body force method, the stress fields induced by two kinds of standard set of force doublets are used as fundamental solutions. Then, the problem is formulated as a system of integral equations with the singularity of the form r-2. In the numerical calculation, two kinds of unknown functions are approximated by the products of the fundamental density functions and power series. The calculation shows that the present method gives rapidly converging numerical results for curved cracks under various geometrical conditions, In addition, a method of evaluation of the stress intensity factors for arbitrary shaped curved cracks is proposed using the approximate replacement to a simple straight crack.

This paper presents an investigation into the sharpness of a surgical scalpel blade. An experiment was carried out in which a surgical scalpel blade was pushed through an elastomeric substrate at a constant velocity. The force-displacement characteristics were examined by plotting the stiffness as a function of blade displacement and it was found that this curve could clearly identify the point where the material separates to form a cut. A blade sharpness measurement was defined as the energy required to initiate an opening or cut in the substrate. A finite element model was developed to examine the stress state in the substrate at the point where the opening initiates. The development of this model is described. The model was validated against the experiment and close agreement was obtained. The von-Mises stress distribution under the blade tip was plotted and it was shown that the peak stress actually occurs away from the blade tip, suggesting that material separation would initiate away from the substrate surface.

A set of constitutive laws for describing functionally graded materials behaviour during entire sintering process was developed. It can be used to get stress distribution arising during sintering and cooling as well as to check various parameters on sintering of FGM (particle size, density and graded profile of concentration) to optimise the process. It was implemented in ABAQUS code as user subroutine UMAT and fully coupled with heat transfer. Examples of WC-Co functionally graded cone were simulated. The numerical results show that the stresses in functionally graded cone during heating, isothermal holding and cooling have significant differences. Those mismatch stresses caused by differences in densification kinetics and physical properties could contribute to cracks formation at the different location of FGM part and at different sintering stages. This simulation results could be used for a better understanding of the reason of sintering defects such as cracks, and for optimisation of sintering process.

In the design of concrete structures, estimation of the deflection of the structural members under the service loads is often a critical factor. Strains and displacements are linked to the tension stiffening effect, which is not quantified in the standards. The CEB-FIP model code proposes an interesting simplified method for evaluating the concrete tension stiffening effect on reinforced concrete behavior. One of the parameters which enables the mechanical contribution of the concrete to be quantified is the effective tensile active section of the reinforced concrete beams. In this paper, a new method for calculating the effective tensile active section A ct.ef is proposed. The calculation is based on an analytical model of stress distribution in the full depth of the concrete section. An experimental study on several reinforced concrete beams is reported. The results show that the new proposed model enhances the accuracy of the beam deflection predictions significantly.

Time-lapse traveltime shifts of reflection events recorded above hydrocarbon reservoirs can be used to monitor production-related compaction and pore-pressure changes. Existing methodology, however, is limited to zero-offset rays and cannot be applied to traveltime shifts measured on prestack seismic data. We give an analytic 3D description of stress-related traveltime shifts for rays propagating along arbitrary trajectories in heterogeneous anisotropic media. The nonlinear theory of elasticity helps to express the velocity changes in and around the reservoir through the excess stresses associated with reservoir compaction. Because this stress-induced velocity field is both heterogeneous and anisotropic, it should be studied using prestack traveltimes or amplitudes. Then we obtain the traveltime shifts by first-order perturbation of traveltimes that accounts not only for the velocity changes but also for 3D deformation of reflectors. The resulting closed-form expression can be used efficiently for numerical modeling of traveltime shifts and, ultimately, for reconstructing the stress distribution around compacting reservoirs. The analytic results are applied to a 2D model of a compacting rectangular reservoir embedded in an initially homogeneous and isotropic medium. The computed velocity changes around the reservoir are caused primarily by deviatoric stresses and produce a transversely isotropic medium with a variable orientation of the symmetry axis and substantial values of the Thomsen parameters and ␦ . The offset dependence of the traveltime shifts should play a crucial role in estimating the anisotropy parameters and compaction-related deviatoric stress components.

The aim of this study was to evaluate the effect of endodontic and restorative treatment on the fracture resistance of posterior teeth. Materials and Methods: Fifty intact premolars were selected and randomly placed into five groups (n = 10): G1, intact teeth (control); G2, mesial-occlusal-distal (MOD) preparation; G3, MOD preparation restored with composite resin (Z-250, 3M ESPE); G4, MOD preparation and endodontic treatment; and G5, MOD preparation, endodontic treatment, and composite resin restoration. The specimens were submitted to an axial compression load in a mechanical test machine (EMIC), at a speed of 0.5 mm/min. Fracture patterns were analyzed at four levels. Five 2D numerical models were created by Ansys 10.0 for finite element analysis (FEA). Results: Mean values of compressive strength for all groups were (Kgf): G1 (83.6 ± 25.4); G2 (52.7 ± 20.2); G3 (82.1 ± 24.9); G4 (40.2 ± 14.2); G5 (64.5 ± 18.1). Statistical analysis (ANOVA and Tukey's test) showed that fracture resistance of G1 was significantly higher than that of G5, G2, and G4. Resistance of G3 was also higher than that of G2 and G4. Results showed that the tooth resistance is completely maintained when MOD preparation is restored with composite resin and partially recovered when MOD preparation associated with an endodontic access is restored in the same way. The endodontic treatment and composite resin restoration influenced stress distribution in the dental structure. Conclusions: Composite resin restoration plays an important role in recovering tooth strength. With regard to fracture mode, restoration and endodontic treatment increased the incidence of periodontal involvement, which was demonstrated by association with the finite element mechanical test method.

The ability of the microbond technique to characterise changes in the physico-chemical structure of the interface between ®bre and matrix has been checked using eight epoxyde/glass ®bre systems differing by their matrix chemistry, ®bre surface treatments, and ®bre diameter. It has been shown that the widely used average IFSS method can lead to biased results. The test is now considered as giving mode I or mixedmode properties of the interface and not only a mode II interfacial toughness or interfacial shear strength (IFSS). Energy approaches are thus be preferred to stress criterion models. The suitability of six theoretical models was checked. Dif®culties were found in determining a parameter or method effectively representative of the physico-chemical structure of the interface. The model providing the most reliable results was that of Scheer and Nairn. Signi®cant plastic¯ow of the polymeric droplet was observed, leading to a questioning of the hypotheses of ideal elastic components. q

An overview is presented of the development of residual stresses in thermal spray coatings and their effects on interfacial debonding. The main experimental techniques for measurement of residual stresses are briefly described, with particular attention given to the method of continuous curvature monitoring. Boundary conditions satisfied by all residual stress distributions are identified and expressions derived for the curvatures and stress distributions arising from a uniform misfit strain between coating and substrate. It is noted that stress distributions in thick coatings rarely correspond to the imposition of such a uniform misfit strain, so that recourse to numerical methods becomes essential for quantitative prediction of stress distributions. Relationships are presented between residual stresses and corresponding strain energy release rates during interfacial debonding. The effect on this of superimposing stresses from an externally applied load is outlined. The initiation of debonding is then considered, covering edge effects and other geometrical considerations. Finally, some specific case histories are briefly outlined to illustrate how the various theoretical concepts involved relate to industrial practice.

The blanking of thin sheet (0.1±1 mm) of mild steel has been analysed using an elastic±plastic ®nite element method based on the incremental theory of plasticity. The blank diameters are considered in the range 1±4 mm. The study has helped to evaluate the in¯uence of tool clearance, friction, sheet thickness, punch/die size and blanking layout on the sheet deformation. The punch load variation with tool travel and stress distribution in the sheet have been obtained. The results indicate that a reduction in the tool clearance increases the blanking load. The blanking load increases with an increase in the coef®cient of friction. These observations are very similar to the case of blanking of component of large size. Further, these effects are very similar in the case of both single and double blanking. An interblanking site distance of about twice the sheet thickness is good to reduce the thinning of sheet at the intermediate regions between the two blanking sites. For a particular sheet thickness, the blanking load requirement reduces as the blank diameter increases. # 2000 Elsevier Science S.A. All rights reserved.

The aim of this study was to assess the influence of cusp inclination on stress distribution in implant-supported prostheses by 3D finite element method. Materials and Methods: Three-dimensional models were created to simulate a mandibular bone section with an implant (3.75 mm diameter × 10 mm length) and crown by means of a 3D scanner and 3D CAD software. A screw-retained single crown was simulated using three cusp inclinations (10 • , 20 • , 30 • ). The 3D models (model 10d, model 20d, and model 30d) were transferred to the finite element program NeiNastran 9.0 to generate a mesh and perform the stress analysis. An oblique load of 200 N was applied on the internal vestibular face of the metal ceramic crown. Results: The results were visualized by means of von Mises stress maps. Maximum stress concentration was located at the point of application. The implant showed higher stress values in model 30d (160.68 MPa). Cortical bone showed higher stress values in model 10d (28.23 MPa). Conclusion: Stresses on the implant and implant/abutment interface increased with increasing cusp inclination, and stresses on the cortical bone decreased with increasing cusp inclination.

The paper deals with the modelling of riveted joints in aircraft structures with Finite Element Method. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints, which will lead to an increase of the aircraft service life, a smaller number of inspections and lower operation costs of an aircraft. The project assumed FEM modelling of the operating aircraft 's structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various models, at global and local level, were presented and usefulness of them was discussed, influence of the following simplification was analysed; • neglection of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglection of contact phenomenon • neglection of secondary bending • neglection of residual stresses after riveting process The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analysed as well. The method of modelling residual stresses with temperature and thermal coefficient was used. In the second part, the example of analysis of riveted joint was demonstrated for a wing of PZL M28 Skytruck aircraft. It 's is a twin-engine, high-wing, cantilever monoplane of all-metal structure with maximum take-off and landing weight 7500 kg. A submodeling technique was used there. At first, part of the wing model, based on a CAD model, was built. It includes 7 ribs and 6 bulkheads between them. Dimensions of the model eliminate stress perturbation, connected with boundary conditions, in the area near the middle rib. It was a shell model. The boundary conditions were taken on a basis of operation data. Presence of rivets wasn't taken into account. Instead of this, parts were connected continuously (nodes were merged). The Linear model of material was used. The purpose of the part of the wing model was to gain accurate boundary conditions for next model of riveted joint on the middle rib. The behaviour of whole model is correct but stress distribution around rivets is not correct. A shell model of riveted joint was build. A boundary conditions were set on a basis of result from previous analysis. Forces, instead of displacements, were used, as boundary conditions, on account of a large stiffness difference between part models (part of wing and riveted joint model). The nonlinear model of material was used. A contact effect and secondary bending were taken into account. Thanks to that, phenomena around rivets were represented considerably better. Results from this analysis could be used as boundary conditions in a detailed calculation of one or few rivets with solid elements. Such a model was considered as well. The presented method allows to analyse phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN, NASTRAN and MARC software.

d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 83-90 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a A critical view on biaxial and short-beam uniaxial flexural strength tests applied to resin composites using Weibull, fractographic and finite element analyses Composite resin Flexural strength Weibull analysis Fractography Finite element analysis a b s t r a c t Objective. To evaluate the biaxial and short-beam uniaxial strength tests applied to resin composites based upon their Weibull parameters, fractographic features and stress distribution.

In general the stress calculations in interference-fit designs are estimated by using conventional equations. In the event that the parts show an elastic-plastic behaviour the process becomes more complicated. In this study, the stress distribution in interference fitted shaft-hub assembly was investigated in relation to the ratio of contact length-shaft diameter using the finite element method. During heating and cooling the transient conduction heat transfer state was considered in which the boundary conditions of the system are continuously changed. In such interference fitted connections the occurrence of plastic deformation zone and its distribution was evaluated. It was shown that the current results will certainly help the designer in force in transferring assemblies such as shaft-hub fitting coupled with pulley and gear systems in terms of dimensional analysis, tolerance and controlling the cooling conditions.

A finite element analysis model for the post-local buckling behaviour of cold-formed steel (CFS) members subjected to axial compression has been developed. The finite element model consists of a Total Lagrangian nonlinear 9-node “assumed strain” shell finite element, and experimental-based material properties models to represent the body of the CFS sections. Experimentally derived residual stress variations, and initial geometric imperfections have also been incorporated. A special loading technique and a displacement solution algorithm were employed to obtain a uniform displacement condition at the loading edges. Details of a test program involving 20 non-perforated, and perforated cold-formed stub-column steel sections have been presented in the second part of the paper. The comparison between the test results, and the finite element results was performed for axial and lateral displacement behaviour, buckling loads, ultimate loads, and axial stress distribution. The comparison forms the basis for the evaluation of the efficiency, and the accuracy of the finite element model, and it indicated that the finite element analysis model constructed herein gives accurate and consistent results for the behaviour of the cold-formed steel members subjected to axial compression.

Reduction of the recoil forces on shotgun parts and even effects on the human body are a considerable importance during design of the semi-automatic shotgun parts. These forces are strongly affected by the dynamics of motion of rifle parts upon firing. Therefore, managing of these recoil forces would be crucial issue to produce functional, ergonomic, safe, reliable, and robust designs. In the literature, many researchers have investigated static, dynamic, and fatigue behaviors of most mechanical parts which especially take a role under the dynamic loads. However, shotgun parts have not been investigated formally yet. Therefore, in this study we particularly focused on investigating static, dynamic, and fatigue behaviors of a semi-automatic shotgun's locking block, which is an integral part of the shotgun mechanism during firing. In this study, techniques such as hardness measurements, analysis of the recoil forces of a semi-automatic shotgun, and finite element analysis were performed. Pro/Engineer Wildfire 3.0 series software was used to model the locking block and the other parts of the gun. Moreover, the finite element code ANSYS/LS-DYNA, and ANSYS Workbench were used to determine the stress distribution, and fatigue behaviors of the locking block, based on the Morrow Theorem.

This paper describes the design, kineostatic and safety analysis of a two legged mobile robot that can climb from one surface to another surface by using suction cups. Three artificial constraint equations are derived to create the working Jacobin matrix, and then a progam is written to calculate the reaction and actuator force (moment), based on which, the most dangerous position of the robot is found. Also, we study the amount of the stress distribution on the deformable suction cup due to the exertion of the gravitational force, as well as load distribution of the robot. Copyright 0 1996 Elsevier Science Ltd

Mohr-Coulomb soil model 3D finite element models Capacity of laterally loaded piles Efficiency of fins a b s t r a c t A three-dimensional analysis of laterally loaded fin piles is presented. The behaviour of fin piles is difficult to explain using simple pile-soil theories or two dimensional numerical analyses because of the complicated geometry of the piles. In this study, a nonlinear 3D analysis with an elastic plastic soil model, an elastic pile material and interface elements are used to model the pile-soil interaction. Experimental data confirmed that the predicted behaviour of a monopile was acceptable leading to a more detailed study of the impact of fins upon the lateral resistance. The stress distribution within the pile and the deformation of the fin pile are presented. The increase in resistance gained by placing fins on a pile is illustrated by plotting the lateral resistance against displacement of the pile head for various geometries of the pile. This is expressed as the efficiency of the fins which is the ratio of the lateral resistance of a fin pile to that of a monopile with the same core diameter where the lateral resistance is defined as the resistance at a displacement of 10% of the pile diameter. The efficiency of the piles increases as the length of the fins; the increase is independent of the loading direction relative to the fins.

This paper reviews the design and application of paste backfill in underground hard rock mines used as ground support for pillars and walls, to help prevent caving and roof falls, and to enhance pillar recovery for improved productivity. Arching after stope filling reduces vertical stress and increases horizontal stress distribution within the fill mass. It is therefore important to determine horizontal stress on stope sidewalls using various predictive models in the design of paste backfill. Required uniaxial compressive strength (UCS) for paste backfill depends on the intended function, such as vertical roof support, development opening within the backfill, pillar recovery, ground or pillar support, and working platform. UCS design models for these functions are given. Laboratory and backfill plant scale designs for paste backfill mix design and optimization are presented, with emphasis on initial tailings density control to prevent under-proportioning of binder content. Once prepared, paste backfill is transported (or pumped) and placed underground by pipeline reticulation. The governing elements of paste backfill transport are rheological factors such as shear yield stress, viscosity, and slump height (consistency). Different models (analytical, semi-empirical, and empirical) are given to predict the rheological factors of paste backfill (shear yield stress and viscosity). Following backfill placement underground, selfweight consolidation settlement, internal pressure build-up, the arching effect, shrinkage, stope volume, and wall convergence against backfill affect mechanical integrity.

This paper reviews the design and application of paste backfill in underground hard rock mines used as ground support for pillars and walls, to help prevent caving and roof falls, and to enhance pillar recovery for improved productivity. Arching after stope filling reduces vertical stress and increases horizontal stress distribution within the fill mass. It is therefore important to determine horizontal stress on stope sidewalls using various predictive models in the design of paste backfill. Required uniaxial compressive strength (UCS) for paste backfill depends on the intended function, such as vertical roof support, development opening within the backfill, pillar recovery, ground or pillar support, and working platform. UCS design models for these functions are given. Laboratory and backfill plant scale designs for paste backfill mix design and optimization are presented, with emphasis on initial tailings density control to prevent under-proportioning of binder content. Once prepared, paste backfill is transported (or pumped) and placed underground by pipeline reticulation. The governing elements of paste backfill transport are rheological factors such as shear yield stress, viscosity, and slump height (consistency). Different models (analytical, semi-empirical, and empirical) are given to predict the rheological factors of paste backfill (shear yield stress and viscosity). Following backfill placement underground, selfweight consolidation settlement, internal pressure build-up, the arching effect, shrinkage, stope volume, and wall convergence against backfill affect mechanical integrity.

Ridge-buckle defects in cold rolled thin strip originate from the formation of ridges in hot rolled coil and corresponding ridges left in the strip following annealing, cold rolling and tempering. A numerical solution was developed to calculate three-dimensional stress distribution in a wound coil built up wrap-by-wrap and subsequent flatness change in the uncoiled product. The model takes into account both nonlinear compressible characteristic of interwrap layer and uneven strip profile, especially ridges, on the stress evolution during the coiling process. The sensitivity of ridge-buckle defects in cold rolled thin strip to ridges in hot rolled coil profile has been investigated in details. The results show that the ridge-buckle defects in tin plate are much dependent on the height, width and location of ridges in hot coil profile. The permissible tolerance of ridges in hot rolled coil, below which does not produce the ridge-buckle defects in subsequent cold rolling of thin strip, are recommended for different steel grades.

A numerical analysis of ®lament-reinforced internally pressurized cylindrical vessels with over-wrapped metallic liner is presented. The method uses the load-bearing liner approach and leak-before-rupture as design criteria. The structure is modeled as an elastic, ideally plastic liner-reinforced with a quasi-isotropic elastic composite. Based on a balanced stress condition in the pressure vessel, the head shape is obtained by a numerical solution of an elliptic integral. The winding process creates a variable thickness in dome area and results in considerable changes in the on-axis stress distribution incorporated in this study. A 3-D, 2-node interface element is also used to model contact at discrete points between the metallic liner and its surrounded composite shell. Numerical results are reported for the eects of dierent head shapes and the superiority of optimum geodesic head shapes in reducing the maximum stresses is also investigated.