Stresses In Liner Research Articles

Finite element analysis of the effect of tibial osteotomy on the stress of polyethylene liner in total knee arthroplasty.

To explore the effects of tibial osteotomy varus angle combined with posterior tibial slope (PTS) on the stress of polyethylene liner in total knee arthroplasty (TKA) by building finite element model (FEM). Established the FEM of standard TKA with tibial osteotomy varus angle 0° to 9° were established and divided into 10 groups. Next, each group was created 10 FEMs with 0° to 9° PTS separately. Calculated the stress on polyethylene liner in each group in Abaqus. Finally, the relevancy between tibial osteotomy angle and polyethylene liner stress was statistically analyzed using multiple regression analysis. As the varus angle increased, the area of maximum stress gradually shifted medially on the polyethylene liner. As the PTS increases, the percentage of surface contact forces on the medial and lateral compartmental of the polyethylene liner gradually converge to the same. When the varus angle is between 0° and 3°, the maximum stress of the medial compartmental surfaces of polyethylene liner rises smoothly with the increase of the PTS. When the varus angle is between 4° and 9°, as the increase of the PTS, the maximum stress of polyethylene liner rises first and then falls, forming a trough at PTS 5° and then rises again. Compared to the PTS, the varus angle has a large effect on the maximum stress of the polyethylene liner (p < .001). When the varus angle is 0° to 3°, PTS 0° is recommended, which will result in a more equalized stress distribution of the polyethylene liner in TKA.

Numerical study on the influence of liner geometry and lay-up sequence on the fatigue life of composite hydrogen storage vessel

This study focuses on the effect of liner geometry and lay-up sequence on the fatigue life of composite hydrogen storage vessel (CHSV). The ellipsoidal ratio and the maximum thickness of boundary section are selected as the independent variables for liner geometry and a sequence is determined that can make the vessel have higher fatigue life from 12 different lay-up schemes. The difference of the stress condition of the liner is the decisive factor that leads to the change of the fatigue life of CHSV, and this paper summarizes the influence law of the von Mises stress of liner on the lifetime of the vessel. The results show that stress concentrations in the dome section and excessive amplitude of alternating stress in the cylinder section should be avoided. Finally, a reasonable combination of parameters is determined, which can be a reference for the design of type III CHSV.

3D-printed hemipelvic prosthesis combined with a dual mobility bearing in patients with primary malignant neoplasm involving the acetabulum: clinical outcomes and finite element analysis

BackgroundLimb salvage reconstruction for pelvic tumors, especially periacetabular tumors, is challenging. We combined the use of dual mobility bearing and 3D-printed hemipelvic prosthesis to improve function and reduce the probability of complications after hemi-pelvic resection in patients with primary acetabular malignancy. The purpose of this study was to evaluate the efficacy and safety of this combination.MethodsBetween October 2011 and May 2021, 11 patients with malignancies involving the acetabulum received hemipelvic replacement with a 3D-printed prosthesis and dual mobility bearing. Follow‐up of postoperative survival, complications, and Musculoskeletal Tumor Society 93 (MSTS-93) lower limb functional scores were carried out. A finite element model of the postoperative pelvis was developed and input into the finite element analysis software. The Von Mises equivalent stress formula was used to analyze the stress distribution of each part of the pelvis under one gait cycle and the stress distribution at different angles of the hip joint.ResultsBy the last follow-up, 9 of the 11 patients (81.8%) were still alive, and 2 patients had local tumor recurrence. The complications including 1 deep infection and 1 dislocation of the artificial joint. Excluding 1 amputation patient, the average score of the remaining 8 patients at the last follow-up was 21.4/30 (71.3%) on the MSTS-93. In the reconstructed pelvis, stress distributions were concentrated on the junction between hemipelvic prosthesis and screw and iliac bone on the resected side, and between femoral prosthesis stem and femoral bulb, while the stress of polyethylene lining was small. Before impact, the polyethylene lining will rotate at a small angle, about 3°. The inner stress of polyethylene liner is greater than the outer stress in all conditions. The polyethylene liner has no tendency to slide out.ConclusionPelvic tumor resection and reconstruction using 3D-printed hemipelvic prosthesis combined with dual mobility bearing was an effective treatment for pelvic tumors. Our patients achieved good early postoperative efficacy and functional recovery. The dual mobility bearing is beneficial to prevent dislocation, and the mechanical distribution and wear of the prosthesis are acceptable.

Investigation of mechanical properties of corroded concrete pipes after cured-in-place-pipe (CIPP) rehabilitation under multi-field coupling

The pipeline is mainly subjected to soil load, fluid load and traffic load, the mechanical properties of corroded concrete pipes after cured-in-place-pipe (CIPP) rehabilitation under multi-field coupling have not been revealed. In this paper, a 3D numerical model of buried concrete pipes after CIPP rehabilitation under the coupled effects of the soil load, traffic load and fluid load were established based on the results of the full-scale test. The influence of cover depth, traffic load and fluid load on the maximum principal stress of the pipeline, vertical displacement of the pipeline, the von Mises stress of the CIPP liner and the circumferential bending moment of pipe-liner composite structure were analyzed. Results showed that the cover depth and traffic load have a greater influence on the crown, invert, and springline of the pipe and has a lesser influence on the shoulder and haunch of the pipe; The stress and the circumferential bending moment of the pipeline is mainly caused by the soil load, the vertical displacement of the pipeline and the von Mises stress of CIPP liner is mainly caused by the traffic load, and the fluid load has little effect on the pipe-liner composite structure.

An analysis model for the temperature and residual stress of tunnel liner exposed to fire

An analysis model for the temperature and residual stress of tunnel liner exposed to fire

Response of a polymer liner passing across a pressure pipeline joint opening under axial ground movements

A closed form solution is developed to quantify the stresses that develop in polymer liners installed within pressure pipes, where the liner spans across a joint or ring fracture in the ‘host’ pipeline that is subjected to axial extension as a result of ground movements. The solution considers the zones of slip between liner and host pipe on either side of the joint that is opening. The expression derived indicates that maximum axial liner stress is proportional to the square root of the product of the gap that opens across the joint, liner modulus, internal fluid pressure, coefficient of friction between liner and host pipe, and inverse of liner thickness. Calculations are presented for a typical liner installed within a cast iron water pipe, though research is needed to quantify liner-host pipe friction. Comparisons to finite element calculations demonstrated that the new solution characterises the liner as having higher stiffness than numerical analysis using thick shell elements. Initially the two solutions match, but the new closed form solution becomes more conservative with increasing gap size. FEA was then used to show that temporary reductions in water pressure decrease axial liner stresses significantly.

Numerical simulation of suction cavitation in hydrodynamic journal bearings

AbstractThe prediction of cavitation in journal bearings is one of the current challenges in the field of computational fluid dynamics. Hydrodynamic journal bearings are used in a wide range of technical and industrial applications because they provide low friction and minimal wear. A failure of the bearing system during operation can be caused by suction cavitation. Cavitation describes the phase change from liquid to vapour of a fluid caused by a decrease in pressure below the fluid's vapour pressure at an approximately constant temperature. The implosion of vapour cavities adjacent to the surface of the bearing liner stresses the liner material which in turn can lead to material erosion. The particular case of suction cavitation can be observed, if the bearing is operated under high loads resulting in high eccentricity between shaft and bushing combined with a significant increase in gap width. Suchlike operating conditions are not uncommon for internal combustion engines with a power of 0.1 to 1.0 MW per cylinder. As a result of the transient shaft displacement a suction effect builds up within in the lubricating film accompanied with a strong pressure gradient. Due to the fluid dynamics of the lubricant film flow at the given pressure gradient, the liquid can only equalize the void caused by the shaft displacement until the fluid pressure reaches the vapor pressure and then vapor is generated. The vapor forms a three‐dimensional layer across the lubricating film. Whereas, current flow calculations for hydrodynamic journal bearings are carried out by means of 2D methods which are limited to analyze the three‐dimensional and transient flow in those areas of the journal bearing where cavitation occurs. This work presents the application of a transient, 3D numerical simulation of the two‐phase fluid flow in a journal bearing under conditions of cavitation. The numerical simulations were performed using the code OpenFOAM, which is based on the finite volume method and uses time‐dependent three‐dimensional, incompressible Navier‐Stokes equations. The study on hand discusses the influence of minimal film thickness and displacement velocity vs. the structure of the vapour distribution. The numerical results include images of complex three‐dimensional flow structures and vapor distributions inside the lubricating film.

Thermo-structural Analysis of Solid Rocket Scarfed Nozzle with Composite Ablative Liners for Crew Escape Solid Motor

Crew escape system (CES) is one of the most critical sub-systems in a human-rated launch vehicle. CES has four different types of solid motors. One is the high-altitude escape motor (HEM). This motor has the scarfed nozzle region at the divergent aft-end side which is different from conventional nozzle to accommodate the nozzle inside the envelope of the crew module shroud. The composite ablative phenolic liners are bonded to the nozzle metallic hardware by means of adhesive. The structural integrity of this scarfed nozzle region due to temperature and pressure plays an important role for the success of the motor. The nozzle hardware of this motor comprises of three subassemblies connected together by flanged joint. Composite ablative liners are primarily designed to satisfy the thermal and internal ballistics constraint requirements. Though metallic nozzle hardware is designed to bear the complete internal pressure loads, liners share a substantial part during operation due to its stiffness which is comparable with that of the metallic backup. In addition, the high thermal gradient also results in stresses near the inner surface of the liner. These stresses cannot be estimated by closed-form solutions considering the complexity in geometry, direction-dependent material property, and arbitrary temperature distribution arising during operation. The temperature of the liner at its inner surface is the highest due to its direct contact with hot gases. The temperature within the liner decreases across thickness. It is required to be ensured that the temperature at the liner–hardware interface does not exceed the safe-operating temperature. Thermo-structural analysis of composite ablative liners is essential to estimate the complete stress state in liners and to arrive at the minimum available structural margins. The temperature and scarfed geometry make the analysis all the more complicated. Challenges in modelling liners with the 3D contact surface elements are highlighted. Varying pressure load along the inner surface of the liners is simulated in an exclusive load step, and in addition, temperature data estimated from transient thermal analysis are applied in another load step. Temperature-dependent thermo-physical and structural properties are used for the analysis. The temperature distribution across the liner thickness and stresses in the liner and metallic nozzle are reported at different cross sections and their criticality is analysed. This paper highlights the integrated 3D finite-element modelling and analysis of composite liners of solid rocket scarfed nozzle and also covers the comparison of the mechanical strain and thermal parameters with post-static test values.

A Numerical Analysis of the Stress-strain Behavior of Anchorage Elements and Steel Liner of a Prestressed Concrete Containment Wall

The paper presents a numerical analysis of the stress-strain behavior of the steel liner of a prestressed concrete containment wall and the anchorage elements between the liner and the wall. Models of a block segment of the wall were created and loaded by prestress, operation temperature, creep and shrinkage, loss of coolant accident (LOCA) temperature and LOCA pressure. The purpose of the block models was to observe the stress-strain behavior of the steel liner plate in the course of service life of the structure and to obtain boundary conditions for the detailed models of anchorage elements connecting the liner to the concrete wall. There were two different types of anchorage studied – headed studs and L-profiles. The detailed models of anchorage elements were loaded by displacements calculated in the block models and exploited for the determination of extreme stresses in the steel liner and widths of cracks in the concrete wall. The importance of initial geometry imperfections of the steel liner plate was appraised as well. According to the results, there is no risk of buckling of the liner or failure of the liner and anchorage elements during operation conditions and LOCA. There is also no substantial difference between the stress-strain behavior of the liners connected by headed studs or by L-profiles. However, the initial imperfections of the liner plate were found to be very important for the distribution of stresses in the liner and crack pattern in concrete.

Design and Analysis of Cushioning Packaging for Home Appliances

This research addresses the problem of studying how to design the packing liner of the flat TV and do safety inspection. According to the five step of cushion packaging design method to Select appropriate cushion liner. The finite element software ABAQUS is used to establish the simulation model and Element mesh is divided, combined with the explicit dynamics theory and elastic potential energy and time of flat panel TV striking the ground, to buffer gasket stress analysis and strength check. Through the simulation analysis, flat TV landing impact stress is far less than the maximum stress of liner can bear. The liner in the delivery process has a better protective effect and is able to reuse. This study can solve the problem of waste corrugated paperboard of the past and improve resource utilization.

Sub-horizontal reinforcement of weathered granite before tunneling beneath a spillway

Sub-horizontal jet-grouted columns and pipe roof are usually adopted to reinforce weak ground ahead of tunnel excavation face, but they bear a low tensile strength and poor waterproof capacity, respectively. A combination of sub-horizontal jet-grouted columns and pipe roof was proposed to reinforce weak ground before Jiangmen tunnel passed beneath a spillway for drainage of Yu-long Reservoir. Due to the pipe roof added below the jet-grouted columns, numerical simulation demonstrates that stress in the jet-grouted columns, ground surface settlement, convergence and stress of primary liner are reduced, and the stability of the excavation face is increased substantially. The umbrella formed by jet-grouted columns works as a shell, and the pipes in the pipe roof behave as beams in the longitudinal direction of the tunnel. Due to their respective features in the working mechanism, Jiangmen tunnel stayed safe when it passed beneath the spillway. The field measurements are comparable to the numerical results, although there are some differences in their values due to some influence factors.

Study of Effect of Interface Pressure on the Stress Analysis of Ceramic Lined Pressure Vessels

The present work deals with the effect of interface pressure on the stress and fracture analysis of carbon-epoxy dual jacketed pressure vessels at elevated temperatures. Pre-stress and firing stress is determined for an initial residual interface pressure applied between liner and jacket. The effect of a uniform 100℃ temperature rises above ambient had mixed results for a carbon-epoxy jacketed vessel, due to the differential thermal expansion. While jacket stresses increased moderately and further exceeded typical material strengths, liner stresses decreased significantly and improved structural integrity. The effect of a temperature rise for a steel jacketed vessel was deleterious. Jacket stresses decreased, but with no effect on structural integrity, while liner stresses increased, to the detriment of integrity.

Stress-displacement solution for a lined vertical borehole due to non-axisymmetric in situ stresses

By using the semi-inverse method, an elastic plane stress solution of a lined vertical borehole in an isotropic ground due to non-axisymmetric in situ loads is presented. As two extreme cases, pure bond and pure slip boundary conditions, along the liner/ground interfaces have been implemented. The effect of elastic modulus of liner and ground and thickness of liner upon the stresses and displacements are analyzed. The result indicates that soft liner may alleviate the normal stress and shear stress acting on the liner outer surface. The maximum tangential compressive stresses and tensile stresses in liner for two extreme boundary cases occur on the inner and outer boundaries of liner. The shear stress reaches the maximum value at θ=45° and the harder the liner is, the greater the maximum value is.

Fracture analysis of Carbon-epoxy dual jacketed pressure vessels

The present project deals with the stress analysis of single and dual jacketed vessel at room temperature and stress variation in ceramic lined-composite or steel jacketed vessel at higher temperatures. Fracture analysis of carbon-epoxy dual jacketed pressure vessels is carried out, for a Si3N4 or SiC liner and A723 steel or carbon-epoxy jacket, by calculating the different crack thickness values for different material combinations of liner and jacket materials. An initial residual interface pressure applied between liner and jacket and pressure applied to the bore predicts the stresses developed at the contact region. Pre-stress and firing stresses are determined at room temperature for a steel jacketed ceramic vessels and carbon-epoxy jacketed vessels. Elevated temperature liner stresses are reduced for a carbon-epoxy jacket, due to the effective increase in interface pressure caused by differential thermal expansion.

Liner shipping industry sets sail with full speed

The article presents the past and current trends in liner shipping and stresses that in a near future, the market will benefit from five main factors: the robust shipping surrounding from international trade; the structural change in industrial relocation; the China factor; the increase in ship-owners’ profitability and lastly the liberalisation of markets and of the shipping industry that will generate new opportunities. At the same time, the article also sheds light on factors that could put limits to the growth in the short run: the expected decrease in freight rate, the increase in bunker costs and in port dues combined with the strengthening of imbalance in trades are identified as the main elements that could put limits on the vitality of liner shipping business.

Liner stresses in deep tunnels below the water table

The primary support of a tunnel must be designed to sustain the loads that are transferred from the surrounding ground during excavation. The loads are originated from the ground itself and from the groundwater, if any. For deep circular tunnels, assuming that both ground and support remain within their elastic regime, the load on the primary support does not change with drainage conditions; it is the same whether there is flow towards the tunnel (drained tunnel) or the pore pressure behind the support is hydrostatic (no-drainage tunnel). Stresses and deformations in the ground, however, are quite different, with larger stresses and deformations occurring for the drainage case. In tunnels where there is an impermeable layer between the primary and secondary supports, as the secondary support is placed there is a load transfer from the primary to the secondary support. The primary support unloads and moves outwards, while the secondary support takes load and moves inwards. In tunnels where there is a drainage layer between the primary and secondary supports, the pressure behind the support depends on the discharge capacity of the drainage system relative to the water inflow from the ground. Within the range of cases investigated, the relative permeability factor, r 0 K g/ t f K f, can be used to evaluate the magnitude of the pore pressure buildup behind the secondary support. Numerical experiments combined with analytical solutions provide a rational approach for a preliminary design of the primary and secondary supports in deep tunnels below the water table, and contribute to identify the load-transfer mechanisms between ground, water, and support.

Stress and Fracture Analysis of Ceramic Lined, Composite or Steel Jacketed Pressure Vessels

Stress and fracture analysis of ceramic-lined cannon pressure vessels is described, for a Si3N4 or SiC liner and A723 steel or carbon-epoxy jacket and with an initial residual interface pressure between liner and jacket and pressure applied to the bore. Room temperature stresses for a steel jacket over ceramic are similar to those for a carbon-epoxy jacket, but both radial and hoop jacket stresses can exceed typical carbon-epoxy strength values. Elevated temperature liner stresses are reduced for a carbon-epoxy jacket, due to the effective increase in interface pressure caused by differential thermal expansion. Critical crack sizes for brittle fracture are generally very small, albeit larger for Si3N4 than SiC due to lower liner stresses and higher fracture toughness for Si3N4.

Analytical Solutions for Shallow Tunnels in Saturated Ground

Estimates of ground deformations and liner stresses in a tunnel are usually obtained from empirical correlations or from past experience on similar tunnels. These correlations account for only a few of the significant factors, and extrapolation to other cases is questionable because similitude conditions are not generally fulfilled. In this paper, complete analytical solutions for a shallow tunnel in saturated ground are obtained. Two different drainage conditions have been considered: full drainage at the ground-liner interface, and no drainage. The solutions cover different construction processes and soil conditions: (1) dry ground; (2) saturated ground with and without air pressure; (3) with and without a gap between the ground and the liner; and (4) applicability for short term analysis (i.e., undrained excavation and liner installation) and for long term analysis. Since the ground and the liner are assumed to behave elastically, the solutions obtained are restricted to cases where ground deformations are small, such as stiff clays and rocks, or when the excavation method prevents large deformations of the ground.

Recent advances in dem modelling of tumbling mills

In this paper we focus on recent developments in DEM modelling of tumbling mills. Examples of 3D models of SAG mills are presented along with detailed predictions of power draw, liner wear rates, liner stresses and energy spectra. Comparisons of simulation results with photographs of charge motion in a scale model SAG mill demonstrate a high degree of accuracy. The inclusion of particle breakage in the DEM is demonstrated as is the methodology for predicting breakage rates, mill throughput, and equilibrium particle size distribution of the charge. Finally, the variation of power draw with liner shape throughout the lifter life cycle is illustrated.

Mechanical Response of Lined and Unlined Heated Drifts

Approximate relations are developed to determine the steady stresses and displacements that may develop in unlined and lined drifts heated above ambient, as representative of conditions in a nuclear waste repository. For a series of parallel, unlined drifts, radial convergence due solely to thermal effects is everywhere null at early-times; at late times it is a maximum inward at springline, and an equivalent maximum outward at crown and invert. Support pressures and hoop stresses are evaluated for a flexible liner placed in intimate contact with the drift wall, following excavation, where a full slip condition is applied at the drift-liner interface. For rock mass moduli of similar order to, or smaller than, the liner modulus, hoop stresses and support pressures are shown insensitive to rock mass parameters. Surprisingly, liner stresses are strongly controlled by liner modulus, liner Poisson ratio, liner thermal expansion coefficient, and instantaneous liner temperature, and only weakly by rock mass modulus. Response is shown independent of thermal expansion coefficient of the rock mass, and temperature distribution beyond the drift wall. The “misfit” expansion of the liner in the drift cavity controls liner stresses that rise linearly with the temperature of the liner, alone. Importantly, the results demonstrate the potential to control magnitudes of thermal stresses by the incorporation of compressible elements within the liner, or within the blocking or backfill behind the liner. Although the results are partly conditioned by the assumptions of a fully flexible liner and full slip conditions at the drift-liner interface, they serve to define the important parametric dependencies in the mechanical response of heated drifts.