Liner Thickness Research Articles

Large articulations do not increase wear rates of thin second-generation highly cross-linked polyethylene liners at ten years.

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA. We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point. The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years. The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material.

Fragility analysis of nuclear containment under inner pressure based on a simplified method and program (NCMC)

In order to solve the shortcomings of fragility analysis by finite element method, this paper proposes a method for calculating the structural fragility of nuclear containment under the loading of inner pressure (which is abbreviated as “inner pressure fragility”) based on a simplified calculation method and related program (coded by Python) named as NCMC. This enables direct preliminary screening to delete unsuitable nuclear containment types that cannot meet the required failure probability. In addition, this paper conducts a detailed parameter analysis on factors such as concrete thickness and material type, liner thickness, and the numbers of tendons and rebars in the hoop and vertical directions. By analyzing the changes in failure probability due to parameter changes, based on confirming the safety margin and load bearing capacity of the original nuclear containment type, suggestions for parameter choices are provided for a certain containment. The same method and analyzing routine can also be used for realizing fast parameter selection for other structures.

Cylinder Liner Velocity Calculation under Dynamic Condition in the Pursuit of Liner Cavitation Investigation of an Internal Combustion Engine

<div>An analytical method for nonlinear three-dimensional (3D) multi-body flexible dynamic time-domain analysis for a single-cylinder internal combustion (IC) engine consisting of piston, connecting rod, crank pin, and liner is developed. This piston is modeled as a 3D piston that collides with the liner as in a real engine. The goal is to investigate the piston slap force and subsequent liner vibration. Liner vibrational velocity is directly responsible for pressure fluctuations in the coolant region resulting in bubble formation and subsequent collapse. If the bubble collapse is closer to the liner surface, cavitation erosion in the liner might occur. The mechanism of liner cavitation is briefly explained, which would take a full computational fluid dynamics (CFD) model to develop, which is out of scope for the present work. However, as a first step, the present method focused on a comprehensive and accurate estimation of the highest inward and outward liner velocities, which are directly related to the bubble formation and collapse, respectively. Sensitivity of liner velocity to different engine-operating conditions (warm and hot, with highest skirt temperatures of 178 and 130°C), piston pin bore offsets (thrust side, anti-thrust side directions in the amounts of 0.6 mm, and the nominal no offset case), and liner thicknesses are determined. Piston thermal growth is considered as part of the analysis resulting in interference condition between piston skirt and liner under the hot operating condition and low minimum clearance under the warm condition. Correlation of liner velocity contour plots with real engine liner cavitation erosion is presented. Analytical model showed a maximum liner inward velocity of 55 mm/s with no piston pin offset under nominal engine-operating configuration. A correlation has been found between location of this highest liner velocity and location of the actual cavitation erosion in the field.</div>

The impact of the nonlinear concrete behaviour on the required liner thicknesses of spray-repaired concrete pipes

Buried reinforced concrete pipes (including sewers, stormwater pipes and other gravity flow structures) that experience unsafe levels of deterioration are commonly rehabilitated using trenchless solutions, such as the application of cementitious liners. Cementitious liners are centrifugally cast onto the inner surface of the damaged pipes with a spinning head that travels along the length of the pipe. Once cured, the liner increases the strength of the damaged pipe to resist applied earth and surface loads. A design method previously proposed by the authors provides guidance for selecting the required liner thickness to rehabilitate deteriorated concrete pipes situated at deep burials. However, this design method considers the linear elastic behaviour of the soil and pipe materials. Neglecting the nonlinear effects of crushing concrete within the host pipe may impact the predicted liner thicknesses for repair. Thus, the current study evaluates the impact of incorporating nonlinear compressive material behaviour on the required liner thicknesses to repair damaged concrete pipes. The required liner thicknesses obtained from the nonlinear version of the design method for rehabilitations of several pipes selected from the ASTM C76-11 Standard experiencing varying levels of deterioration are compared to thicknesses obtained using the authors' linear elastic solutions. The comparisons indicated that considering the nonlinear material response of the concrete generates slightly larger estimates of required liner thickness. The discrepancies between the estimated liner thicknesses were observed to be insignificant for pipes experiencing cracking and losses of concrete cover, demonstrating that the linear elastic model is suitable for design purposes. However, for damaged pipes situated at deep burials experiencing losses of tensile reinforcement, the discrepancies between the liner and nonlinear calculations become more significant. It is recommended that the results of the linear elastic model be checked with the nonlinear model for the repair of pipes experiencing loss of tensile reinforcement, or for deeply buried pipes.

Polyethylene thickness does not influence aseptic revision rate with highly cross-linked liners in THA with 36-mm femoral heads.

To reduce the risk of dislocation, larger head size can be used in total hip arthroplasty (THA). However, larger head size leads to thinner acetabular liners. With conventional polyethylene, thickness of >8 mm has been advocated to reduce stress and wear rate of the polyethylene. Modern polyethylene has become more wear-resistant. In this study, we investigated if the thickness of sequentially cross-linked polyethylene (XLPE) liners is associated with failure of THA in the medium term. 3654 THAs were included (2009-2016), in which THA was performed with a XLPE liner in combination with a 36-mm femoral head. Patient and surgical characteristics were collected. We compared implant survival of THA with thin liners (<7.9 mm) and thick liners (⩾7.9 mm) with a Kaplan Meier survival analysis at 5 years, median follow-up and 10 years of follow-up with and point aseptic loosening and performed a multivariate analysis to estimate hazard ratios (HR). Median follow-up was 7.7 years (IQR 5.6-9.8). In total, 179 revision procedures were performed, where 82 revisions (46%) were performed for aseptic loosening. The survival rate at 5 years, median and 10 years of follow-up showed no statistically significant difference in implant survival. The survival rate at 10 years follow-up was for thin liners 97.1% (95% CI, 96.3-97.9) and for thick liners 98.2% (95% CI, 97.4-99.0) in the aseptic loosening group (chi-square 2.55; p = 0.11).The adjusted HR for thick liners (⩾7.9 mm) was 0.65 (95% CI, 0.38-1.08) compared with the thin liners (<7.9 mm), which was not significantly different. From this single-centre retrospective study it appears that thinner polyethylene liners are well tolerated when using second-generation highly cross-linked polyethylene. Thickness of the XLPE liners did not influence the risk of aseptic loosening of the implants in the medium term.

Study on jet formation and penetration performance of shaped charge with untypical double-cone titanium liner

Based on the platform of AUTODYN-2D code, the shaped charge with untypical double-cone titanium liner penetrating concrete targets are investigated. The influence of the titanium liner thickness and the height ratio of top cone on the jet tip-velocity and jet characteristics are analyzed. The titanium liner thickness, the height ratio of top cone, and the standoff affecting on the penetration performance of the concrete targets are also conducted. The numerical simulations indicated that, with increasing the titanium liner thickness, the jet tip-velocity gradually decreased, and the penetration depth of the concrete targets first increased and then decreased. When the height ratio of top cone was 0.5, the shaped charge with untypical double-cone titanium liner can combine the advantage of the small cone-angle liner and the large cone-angle liner, which will ensure the sufficient penetration depth and hole diameter. Furthermore, the shaped charge with untypical double-cone titanium liner can penetrate the concrete with a thickness of 1000mm at the standoff within a region between 2.0 CD and 2.5 CD.

NONLINEAR BUCKLING SENSITIVITY ANALYSIS OF THIN-WALLED LINED COMPOSITE PIPE LINER

In order to study the buckling failure of lining delamination of thin-walled lined composite pipe, a numerical analysis model was established by using bilinear cohesion relationship, the buckling mode and critical load of the composite pipe obtained by linear buckling are taken as reference values, the interlayer initial defects were introduced to carry out the nonlinear buckling analysis on the composite pipe lining structure with thin wall lining. The relative displacement curve and deformation morphology of the relative displacement of the lining with the change of external pressure were obtained, and the results are consistent with the existing test results. Based on this model, the buckling sensitivity of lining pipe was analyzed. The results show that the size of interlayer initial defect is the main factor that affects the critical buckling pressure of liner, but it has little influence on the propagation pressure after buckling; However, the increase of interlayer bonding effect significantly improves the buckling resistance and propagation pressure of lining pipe; The ratio of outer tube wall diameter to thickness and liner thickness have significant effects on the critical buckling pressure of liner. The research results provide a reference for determining the interlayer bonding effect and the optimal design of the minimum thickness of the inner liner.

Modeling surface water and groundwater interactions for seepage losses estimation from unlined and lined canals

ABSTRACT This study utilized the Slide2 model to simulate surface water and groundwater interactions and estimate seepage losses from unlined and lined irrigation canals. Firstly, it was validated for an unlined canal passing through an unconfined, homogenous, and isotropic infinitely porous depth. Results revealed that the Slide2 model accurately simulated the seepage flow and estimated the seepage losses with R 2 = 0.99 and MAPE = 3.6%. Accordingly, the Slide2 model runs 54 scenarios to explore the effect of different groundwater table (GWT) locations below the canal berm, canal berm widths, and liner properties, such as liner hydraulic conductivity and thickness on the seepage losses from unlined and lined irrigation canals. The results concluded that when the GWT was above the canal surface water level (CSWL), the seepage losses tended to be lower, ensuing an inflow to the canal bed and inner side slope. Conversely, when the GWT was below the CSWL, the seepage losses tended to be higher, ensuing an outflow to the surrounding unsaturated soil. In contrast, the GWT did not affect seepage losses from lined canals. Also, a wider berm resulted in fewer seepage losses, while the canal berm was less effective for lined canals. In addition, the results proved the lining ability to reduce seepage losses. Thus, the average reduction percentage of the seepage losses for lined canal scenarios was 99.87%. Also, a thick liner could decrease the seepage losses maximally by 48.52%, regardless of the GWT location below the canal berm.

Scattering of plane compressional waves by a variable thickness circular lined tunnel

The determination of the dynamic stress concentration factor (DSCF) associated to a circular lined tunnel with variable thickness liner incident upon by compressional P-waves is of particular interest. Due to the lack of symmetry, the treatment of such a problem via the traditional wave-function expansion method is not possible. To circumvent this dilemma it is proposed to employ the dynamic equivalent inclusion method (DEIM). As it will be shown, this method which is based on the notions of the eigenstress and eigenbody-force fields provides an accurate solution for the problem under consideration. In the simple special case where a tunnel with a concentric liner is subjected to plane compressional P-waves the exact wave-function expansion solution given in the literature is recovered. The effect of liner thickness variability on the static and dynamic stress concentration along the interior surface of the liner and along the liner-matrix interface is studied in detail through numerical examples. The maximum value of the DSCF for the concrete and steel liners with positive and negative values of eccentricity is obtained and compared with those of the corresponding concentric cases. It is observed that the eccentricity of the liner results in different behaviors of the stress concentration for the hard (steel) and soft (concrete) liners.

The effect of three-layer liner on the jet formation and penetration capability of shaped charge jet

In order to solve the problem of insufficient penetration ability of common liner, a new three-layer liner was proposed. AUTODYN software was used to simulate the efflux forming process of three-layer liner. The influence of four different impact impedance liner materials and different thickness ratio of three-layer liner on efflux performance was studied. In order to study the penetration ability of shaped charge to semi-infinite target plate, the penetration calculation of the target plate was carried out by taking several standoff under different thickness ratios. The optimal thickness ratio of three-layer liner was determined by studying the penetration depth and opening size of the target plate. The results show: By comparing the matching of liner materials with different impact impedances, the head velocity, effective length, total energy, total kinetic energy and effective jet mass of the jet formed when the three-layer liner material is AL 2024, copper and nickel from the outside to the inside are the best. In the analysis of the matching of the thickness ratio of the three-layer liner, the key to the jet forming is the thickness ratio of the outer liner. Within a certain range, the greater the proportion of the thickness of the outer liner, the better the jet forming; when the material of the three-layer liner is AL 2024-copper-nickel from outside to inside, the thickness ratio of the liner is 4/1/1 from outside to inside, and the jet forming is the best. The maximum penetration depth of the shaped charge with a thickness ratio of 1/1/4 from the outside to the inside of the three-layer liner is 395.5 mm, which is 52.3% higher than that of the shaped charge with a double-layer liner. Compared with the shaped charge with single-layer liner, the penetration depth is increased by 62.6%. When the thickness ratio of the three-layer liner is 1/1/4 from the outside to the inside, the maximum entrance diameter of the target plate is 14.3 mm, which is the same as that of the shaped charge with the double-layer liner. Compared with the shaped charge with single-layer liner, the entrance diameter is in-creased by 14.4%.

Development of Composite Ablative Liners for Solid Rocket Motor Flex Nozzles

Solid Rocket Motor generates high thrust by accelerating high pressure gases to supersonic velocities in convergent divergent nozzle, thus converting pressure energy to kinetic energy of propulsion. As exhaust gas from chamber is of high temperature, the structural steel members of nozzle should be protected from hot gases by highly erosion resistant thermal liners. For this purpose, ablative composite liners made up of Phenolic resin matrix based combined with reinforcement material like carbon fabric is extensively used [1]. Divergent being largest component and contributes more to nozzle weight, the thickness of liner should be as least as possible at the same time; it should be more erosion resistant. The erosion resistant due to hot gases can be increased by fabricating the liner in such a way that the flame only touches the edge of the composite ply of liner and liner has more density. This can be achieved by tape winding of composite prepreg tapes at Zero degrees on tapered metal mandrel using tape winding machine followed by Autoclave curing [2]. This paper gives the details of prepreg, Tape winding, Autoclave Curing and NDT of ablative liner.

Research on the influences of motion characteristics of jetting projectile charge under water

Shaped charge warhead is important for enhancing the damage performance of underwater weapons. This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters (wall thickness, material), charge aspect ratio, and stand-off distance on the movement characteristics of JPC in water. The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water, the effective length of the JPC in water undergoes two distinct phases: a growth phase and a decrease phase, with the velocity of the JPC decaying exponentially. Increasing the liner thickness, stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC. The optimal ranges for liner thickness and stand-off distance are 0.0363Dk to 0.0545Dk (Dk is the charge diameter), the stand-off distance should be within 1.0Dk. After the charge aspect ratio higher than 1.25, the charge structure exerts minimal influence the movement characteristics of the JPC in water. Material density plays a crucial role in the velocity decay pattern of the JPC during penetration. JPC with higher densities exhibit superior velocity retention capabilities in water, with the velocity decay pattern converging if the densities are similar. Consequently, copper, tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead. Finally, the results will provide an important reference for the design of underwater shaped charge warhead.

In vivo creep and wear performance of vitamin-E-diffused highly crosslinked polyethylene in total hip arthroplasty.

An acetabular liner thickness of around 6mm remains the "gold standard" in total hip arthroplasty. Some surgeons have been recommending the use of the thickest possible liner because contact stress and strain in articulating surfaces decrease with increasing the wall thickness. The purpose of this study was to determine whether in vivo creep and wear performance could be enhanced using a thicker liner over the standard thickness in vitamin-E-diffused highly crosslinked polyethylene (HXLPE). One hundred and twenty-two hips were allocated to age-matched, sex-matched, and body mass index-matched two subgroups implanted either with a 6.8- or 8.9-mm-thick vitamin-E-diffused HXLPE liner against 28-mm cobalt-chrome femoral head, and followed-up for 7years. Linear and volumetric penetration of femoral head into the liners attributed to creep and wear were analyzed for each group. Compressive creep strain generated at the initial 6months was significantly larger in the 6.8-mm group (2.6%) than in the 8.9-mm group (2.2%). The linear steady-state wear observed after 2years was 0.0019 and 0.0015mm/year, whereas the volumetric steady-state wear was 0.54 and 0.45 mm3/years in the 6.8- and 8.9-mm-thick groups, respectively. Although less strain in the thicker group resulted in a slightly less wear, it did not reach significant differences in the steady-state wear rates between the groups. No clinical significance for using a thicker liner over the standard thickness (6.8mm → 8.9mm) was confirmed in the vitamin-E-diffused HXLPE according to the 7-year follow-up. The wear rates for both thicknesses were very low enough to prevent osteolysis, and no mechanical failure was observed at any follow-up interval. Nevertheless, since the significantly higher strain was seen in the thinner liner, further follow-up is needed to compare the longer term wear and the incidence of osteolysis and component fracture.

Formation behavior of hypervelocity reactive compostite jet

A kind of hypervelocity reactive composite liner shaped charge(HRCLSC) structure is designed by combining tungsten additional liner and reactive cooper composite liner. The formation behavior of hypervelocity reactive composite jet (HRCJ) is studied by numerical simulation method. The velocity distribution and detonation wave propagation of HRCJ are compared with that of normal reactive composite jet (NRCJ), which proves that HRCJ has better formation performance. The influence of liner structure on the formation performance of HRCJ is investigated by changing the cone angle of the composite liner and the thickness of the additional liner, the results show that the cone angle of the liner has little effect on jet head velocity while the thickness of the additional liner has great effect on jet velocity. When the thickness of the additional liner is 5mm and the cone angle of the composite liner is 60°, the effective mass utilization rate of the jet is better, and the head velocity reaches maximum.

Study on Formation of EFP with Fins of Hexagonal Liner

In order to further improve the flight stability of explosively formed projectile, the formation method of tail EFP was studied based on the polygonal liner. Under the hexagonal charge structure, the tail fins EFP can be formed when the structural parameters are matched. Through the numerical simulation of LS-DYNA, the influence of the structural parameters of the liner (curvature radius, linear thickness), charge height and shell thickness on the velocity, length-diameter ratio, compactness and wing-diameter ratio of the tail fins EFP was analyzed. In order to make the tail fins EFP performance better, the optimal range of radius of curvature R of hexagon liner is 0.75D ~ 0.85D, liner thickness t is 0.05D ~ 0.06D, charge height L is 0.8D ~ 1.0D, and the optimal range of shell thickness h is 0.06D ~ 0.1D.

Density distribution characteristics of the explosively formed reactive material jet

The density evolution behaviour and distribution characteristics of the explosively formed reactive material jet were studied based on the SPH algorithm. Numerical simulations show that the reactive material jet has obvious expansion phenomenon under the shaped charge effect. Especially, the expansion and divergence of the jet head are obvious. In general, the density deficit occurs in the whole reactive material jet, and the density increases from the jet head to the tail. Compared with the initial density of the reactive liner material, the density of jet head decreases by about 30%. In addition, the effect laws of the reactive liner thickness, the liner cone angle, and the type of explosive on the jet density distribution were investigated. With increasing of the reactive liner thickness, increasing of the liner cone angle, and decreasing of the explosive detonation pressure, the proportion of the high-density area on the reactive jet and the average density of the jet head increase.

Numerical simulation of penetration behavior of RHA target with biconical liner

The AUTODYN-2D simulation software was used to study the jet formation of single-cone and biconical shaped charge liner and the damage influence on the RHA target. The numerical simulation results show that compared with the typical single-cone shaped charge structure, the jet head formed by the biconical liner is faster and has better penetration performance on the RHA target. On this basis, the influence of standoff, liner cone angle and line thickness on the penetration characteristics of RHA target under biconical shaped charge was studied. The simulation results show that when the standoff increases from 2.0CD to 3.0CD, the penetration depth increases gradually. When the upper cone angle is 30° and the lower cone angle increases from 40° to 60°, the penetration depth of the formed jet to the target decreases gradually. When the liner thickness increases from 5mm to 6mm, the penetration depth is obviously improved.

Enhanced borehole stability analysis for geological waste disposal under conditions of in-situ stress uncertainty: The case of Yamin Plain, Israel

This work presents a comprehensive parametric study of unsupported and supported vertical boreholes in deep geological deposits. The parametric study is demonstrated for the case of Yamin Plain area, which is the designated site for radioactive waste disposal in Israel, where uncertainty exists regarding the in-situ stresses. The Yamin case is suitable for this study as the target rock layers are of marginal stability under the applied stresses, and therefore a detailed analysis is called for. A parametric factor of safety analysis is utilized for the evaluation of the borehole stability, with and without structural support. To this aim, the estimated stress field is evaluated using both analytical calculations and advanced numerical analyses, incorporating a new spring-boundary condition that yields far greater accuracy than with the commonly used boundary conditions. The parametric study for the borehole stability problem is examined with respect to the in-situ stresses and the structural support. We find that a steel liner is safe under any in-situ stress scenario; HDPE liner is found to be insensitive to liner thickness for the stress scenarios examined, because of the compatibility between the stiffnesses of the rock mass and the liner material; because of the relatively high difference between compressive and tensile strengths of concrete, we find that beyond a certain liner thickness the stability of a concrete liner in fact decreases.

Lubrication behaviors of a novel bearing with fluid-solid-thermal (FST) approach: Experimental and theoretical investigation

The paper investigates the mechanisms of the lubrication performances of a novel water-lubricated bearing considering thermal effect. A revised thermos-dynamic lubrication model comprising FSI and thermal methodology with optimization is built. The static characteristic parameters of water-film and the variation laws of the liner are studied. The influences of rotational speeds and eccentricity ratios on the thermal performances are analyzed. The influences of the liner thickness on the heat dissipation are explored. The internal mechanisms of the large temperature difference are revealed. The variation laws of deformation, stress and strain of the liner are investigated. Results enrich the theoretical systems of lubrication regime, and provide a theoretical support for the design and application of such novel bearings.

Research on the formation behavior of PTFE/Al reactive explosively formed projectile

Based on AUTODYN-3D finite element analysis platform, the SPH algorithm is used to simulate the forming characteristics of Al/PTFE reactive Explosively Formed Projectile (EFP). The evolution behaviors and distribution of morphology, velocity, density, and temperature field during the reactive EFP were analyzed. Numerical simulation results show that Al/PTFE reactive shaped charge can form stable reactive EFP, and the overall density of reactive EFP decreases with the extension of the forming time, and the density of reactive EFP is much lower than the initial density of reactive liner. When the reactive EFP is in the state of freely flying, the high temperature region mainly concentrates on the tail of the reactive EFP, the bottom of the reactive liner and the fracture flying zone, and the high temperature region proportion is significantly affected by the explosive type, the curvature radius of the reactive liner and the wall thickness of the reactive liner.