Compressive Load Bearing Research Articles

Guar Gum, Gellan Gum Biopolymer Soil Stabilization

In civil engineering and construction, soil stabilization is an important aspect. There are diverse conventional techniques to improve soilproperties and for soil stabilization. This study explores the viability of twotypes of biopolymers, Guar gum and Gellan gum, as sustainable and ecofriendly additives for clayey soil stabilization. Compaction, unconfined compression test, permeability, consistency limit, consolidation tests were performed in the study. The sample for the test has been prepared that biopolymer has been mixed with soil in different proportions. These biopolymers forms hydrogels when they get activated, and it enhances the bonding between soil particles thereby increasing the strength. Treating soilwith biopolymer increases dry unit weight and decreases optimum moisturecontent (OMC).Addition of gum solution reduces friction between soil particles, leading to marginal increase in dry unit weight. Higher the biopolymer content lower is the OMC content and soil become more stiff. The compressive strength and load bearing capacity isfound increasing soilbiopolymerspecimen upon different days of curing. For every tested percentage of treatment the percentage reduction factor rises withbiopolymer concentration due to drop in void ratio that results in a drop in the soil's permeability. Guar Gum and Gellan Gum are used as stabilizers in soil treatment, increasing liquid and plastic limits, shrinkage limit, and viscosity. They activate hydrogels, strengthen bonding activity, and increaseshrinkage limit. The addition of Guar Gum and Gellan Gum improves soil biopolymer mix viscosity and adhesion. The findings of this study positivelyimply that adding this material to weak soil would improve the soil’s characteristics.

Tailor-made design, fabrication and validation of SrO doped nanostructured ZTA ceramic Femoral head – Acetabular socket liner assembly

An established commercial grade SrO doped ZTA composition has been considered to design, fabrication through uniaxial pressing followed by sintering and polishing, validation of dimension, 3D surface profile, 3D microstructure, and compressive load bearing capacity of femoral head – acetabular socket liner prototypes for the hip prosthesis. While design and dimensions are concerned, both the steel (HRC60) molds were designed and machined to achieve precious dimensions of femoral head (FH; OD – 30 ± 0.01 mm) and acetabular socket liner (ASL; ID – 30.15 ± 0.01 mm). A close variation in the range of ±0.01 mm was confirmed the precision geometry of polished FH and ASL with consideration of 22 points coordinate measuring method (CMM). 3D surface profile ensures the surface characteristics of Ra = 0.2 ± 0.01 μm and Rq = 0.5 ± 0.01 μm for outer surface of FH and an inner surface of ASL, respectively. Structure integrity and fabrication defects including cracks and pores free bulk structures were confirmed by Micro CT. The compressive load resistance known as burst strength for independent FH and FH-ASL assembly were measured 16.2 KN and 17.6 KN, respectively. The developed ceramic prototypes have an economic advantage and can be adopted as artificial hip prosthesis after extensive in-vitro and in-vivo analysis.

Postfire reliability analysis of axial load bearing capacity of CFRP retrofitted concrete columns

A reliability analysis of the axial compressive load bearing capacity of postfire reinforced concrete (RC) columns strengthened with carbon fiber reinforced polymer (CFRP) sheets was presented. A 3D finite element (FE) model was built for heat transfer analysis using software ABAQUS. Based on the temperature distribution obtained from the FE analysis, the residual axial compressive load bearing capacity of RC columns was worked out using the section method. Formulas for calculating the residual axial compressive load bearing capacity of the columns after fire exposure and the axial compressive load bearing capacity of postfire columns retrofitted with CFRP sheets were developed. Then the Monte Carlo method was used to analyze the reliability of the axial compressive load bearing capacity of the RC columns retrofitted with CFRP sheets using a code developed in MATLAB. The effects of fire exposure time, load ratio, number of CFRP layers, concrete cover thickness, and longitudinal reinforcement ratio on the reliability of the axial compressive load bearing capacity of the columns after fire were investigated. The results show that within 60 minutes of fire exposure time, the reliability index of the RC columns after retrofitting with two layers of CFRPs can meet the requirements of Chinese code GB 50068 (GB 2001) for safety level II. This method is effective and accurate for the reliability analysis of the axial load bearing capacity of postfire reinforced concrete columns retrofitted with CFRP.

Development and Investigation of Mechanical Properties of Date Palm Fibre Reinforced Polyester Composites

The present work is devoted to investigate mechanical properties viz. compressive and impact properties of date palm Fibre Reinforced Polyester (FRP). Date palm fibre is found around date fruits and at the bottom of each leaf, that is used as fuel in rural areas. Premier grade industrial Isophthalic polyester resin is used as the matrix. Date Palm Fibre is chemically treated with sodium hydroxide (NaOH) for better adhesion. Results reveal that with an addition of fibre content, the compressive load bearing capacity increases. However, impact strength is not significantly increased with fibre content. Low to medium impact composites can be developed by date palm FRP. This investigation is expected to assist making FRP commodity with reduced cost utilizing agricultural waste.

Scalable MSC-derived bone tissue modules: In vitro assessment of differentiation, matrix deposition, and compressive load bearing

Enhancements to the mechanical properties of modular designs for bone tissue engineering could increase their clinical applications. In this study, bone marrow mesenchymal stem cells (MSCs) and hydroxyapatite (HAP) microgranules were encapsulated in polyelectrolyte complex membranes composed of chondroitin 4-sulfate (C4S), carboxymethyl cellulose (CMC) and chitosan. Microcapsules were formed with and without HAP microgranules, and cultured in either osteoinduction medium (Osteo) or expansion medium (Exp) to produce four microcapsule conditions: Osteo, Osteo+HAP, Exp, and Exp+HAP. Microcapsules facilitated alkaline phosphatase secretion and deposition of bone specific proteins (osteocalcin and osteopontin) by encapsulated MSCs over 28 days of osteogenic culture. SEM and micro-CT analysis showed cell-deposited mineral covering the surfaces of the HAP microgranules and interior of the microcapsule membrane. The mineralized microcapsules could be combined and fused into cylindrical constructs (4 × 5 mm, W × H), and uniaxial compression tests confirmed that microcapsule mineralization greatly enhanced the yield stresses of Osteo and Osteo+HAP fused constructs (10.4 ± 4.4 MPa and 6.4 ± 2.8 MPa), compared to only HAP microgranules (Exp+HAP, 0.5 ± 0.3 MPa). The C4S/CMC/Chitosan microcapsules provide a platform allowing pre-mineralization of microcapsules in vitro for later assembly of larger load-bearing constructs, or for use as an injectable bone regeneration strategy. Statement of SignificanceClinical translation of bone tissue engineering is limited by the difficulty of generating space filling implants that both resist compressive loading, and simultaneously deliver cells throughout the bone defect. Here, we present the design of a microcapsule system containing both stem cells capable of rebuilding bone tissue, and a mechanically tough bone-like mineral, that imparts compression resistance to the microcapsules. The microcapsules support stem cell differentiation to an osteogenic phenotype, that can mineralize the microcapsule membrane and interior. The mineralized microcapsules can be assembled into larger bone constructs, and have mechanical properties on par with trabecular bone.

Experimental testing on mechanical properties of sandwich structured carbon fibers reinforced composites

The various types of structural sandwich composites panels available are based either in the method of preparation or on the basis of the core material used in between the skin material. The core material is used to increase the stiffness and strength of the entire panel and can be used according to the application or the area of use. For example the various core materials available for preparing a sandwich composite are Aluminum Honeycomb, Balsa wood, High Density Polyurethane Foam, Rohacell Foam or Nomex Core. In this work carbon fiber is a reinforcement phase with various core materials such as Aluminum Honeycomb, Rohacell and HDPU Foam and epoxy resin is used as a matrix to produce various sandwich-structured composites by Vacuum bag manufacturing process. Various tests Three point bending test, tensile and compressive tests carried out in order to validate the design. After the tests are conducted the obtained results and values are compared and graphs were plotted to compare the various Bending, Tensile and Compressive Load bearing capacity of the various sandwich panels prepared with varying core materials. Foam based sandwich panels tend to have better tensile and compressive load bearing capacity as compared to Aluminium Honeycomb due to their structure and Aluminium has better flexural properties because of its core line up which can undertake bending easily.

In vitro assessment of strength, fatigue durability, and disassembly of Ti6Al4V and CoCrMo necks in modular total hip replacements

Modularity in total hip replacement offers advantages with regard to biomechanical adjustments and leg lengths. Recently, modular femoral necks were introduced as an added advantage to head modularity permitting further adjustments in femoral version as well as offset and ease of revision. Currently, most necks are made of Ti6Al4V for which cases of in vivo fractures and inseparable neck-stem junctions have been reported. Therefore, we investigated CoCrMo head-Ti6Al4V stem hip replacements with necks made of CoCrMo as an alternative to Ti6Al4V. We compared the two materials with respect to (1) compressive load bearing capacity; (2) fatigue durability; and (3) component distraction. We performed in vitro fatigue-pull-off, microscopy, fatigue durability and compression investigations. The CoCrMo neck showed a load bearing capacity of 18 kN, 38% higher than 13 kN for the Ti6Al4V neck. A fatigue load of 11.2 kN for 1 million cycle failure was achieved with CoCrMo translating into nearly 1000 times longer fatigue life compared to Ti6Al4V necks. The neck-stem distraction force showed large statistical variation and was similar for both neck materials. Overall, the results suggest a superiority of CoCrMo over Ti6Al4V as neck material with regard to mechanical behavior. However, the corrosion behavior was not appropriately assessed and necessitates additional investigations.

Age- and sex-related regional compressive strength characteristics of human lumbar vertebrae in osteoporosis

To obtain the compressive load bearing and energy absorption capacity of lumbar vertebrae of osteoporotic elderly for the everyday medical praxis in terms of the simple diagnostic data, like computed tomography (CT), densitometry, age, and sex. Compressive test of 54 osteoporotic cadaver vertebrae L1 and L2, 16 males and 38 females (age range 43-93, mean age 71.6 ± 13.3 years, mean bone mineral density (BMD) 0.377 ± 0.089 g/cm(2), mean T-score -5.57 ± 0.79, Z-score -4.05 ± 0.77) was investigated. Based on the load-displacement diagrams and the measured geometrical parameters of vertebral bodies, proportional, ultimate and yield stresses and strains, Young's modulus, ductility and energy absorption capacity were determined. Three vertebral regions were distinguished: superior, central and inferior regions, but certain parameters were calculated for the upper/ lower intermediate layers, as well. Cross-sectional areas, and certain bone tissue parameters were determined by image analysis of CT pictures of vertebrae. Sex- and age-related decline functions and trends of strength characteristics were determined. Size-corrected failure load was 15%-25% smaller in women, proportional and ultimate stresses were about 30%-35% smaller for women in any region, and 20%-25% higher in central regions for both sexes. Young's moduli were about 30% smaller in women in any region, and 20%-25% smaller in the central region for both sexes. Small strains were higher in males, large strains were higher in females, namely, proportional strains were about 25% larger in men, yield and ultimate strains were quasi equal for sexes, break strains were 10% higher in women. Ultimate energy absorption capacity was 10%-20% higher in men; the final ductile energy absorption capacity was quasi equal for sexes in all levels. Age-dependence was stronger for men, mainly in central regions (ultimate load, male: r = -0.66, p < 0.01, female: r = -0.52, p < 0.005; ultimate stress, male: r = -0.69, p < 0.01, female: r = -0.50, p < 0.005; Young's modulus, male: r = -0.55, p < 0.05, female: r = -0.52, p < 0.005, ultimate stiffness, male: r = -0.58, p < 0.05, female: r = -0.35, p < 0.03, central ultimate absorbed energy density, male: r = -0.59, p < 0.015, female: r = -0.29, p < 0.08). For the strongly osteoporotic population (BMD < 0.4 g/cm(2), T-score < -4) the statical variables (loads, stresses) showed significant correlation; mixed variables (stiffness, Young's modulus, energy) showed moderate correlation; kinematical variables (displacements, strains) showed no correlation with age. The strong correlation of men between BMD and aging (r = -0.82, p < 0.001) and betwen BMD and strength parameters (r = 0.8-0.9, p < 0.001) indicated linear trends in age-related strength loss for men; however, the moderate correlation of women between BMD and aging (r = -0.47, p < 0.005) and between BMD and strength parameters (r = 0.4-0.5, p < 0.005) suggested the need of nonlinear (quadratic) approximation that provided the better fit in age-related strength functions of females modelling postmenopausal disproportionalities.

Designing sandwich polymer matrix composite panels for structural integrity in fire

This is the continuation of our published paper [Gu P, Asaro RJ. Designing polymer matrix composite panels for structural integrity in fire. Compos Struct 2008;84:300–9]. This paper addresses the compressive mechanical load bearing capacity of sandwich polymer matrix composite panels under transverse thermal gradients caused by fire. An example of such combined loading condition is that of panels in ship and vessel structures under transverse thermal gradients caused by fire. Specifically, we discuss the mechanical design considerations, failure modes that lead the panels to fail in the combined thermal–mechanical condition. An approach to assess critical load among the failure modes is discussed for design purpose. A computer program is developed based on the approach to evaluate sandwich panel’s load bearing capacity in fire. Examples are presented to design the panel for given thermal and mechanical requirements. Due to the core’s low bending stiffness, there is a large decrease of the panel’s load bearing capacity when the fire-exposed skin is degradated.

Intervertebral Disc Degeneration Can Predispose to Anterior Vertebral Fractures in the Thoracolumbar Spine

Mechanical experiments on cadaveric thoracolumbar spine specimens showed that intervertebral disc degeneration was associated with reduced loading of the anterior vertebral body in upright postures. Reduced load bearing corresponded to locally reduced BMD and inferior trabecular architecture as measured by histomorphometry. Flexed postures concentrated loading on the weakened anterior vertebral body, leading to compressive failure at reduced load. Osteoporotic fractures are usually attributed to age-related hormonal changes and inactivity. However, why should the anterior vertebral body be affected so often? We hypothesized that degenerative changes in the adjacent intervertebral discs can alter load bearing by the anterior vertebral body in a manner that makes it vulnerable to fracture. Forty-one thoracolumbar spine "motion segments" (two vertebrae and the intervertebral disc) were obtained from cadavers 62-94 years of age. Specimens were loaded to simulate upright standing and flexed postures. A pressure transducer was used to measure the distribution of compressive "stress" inside the disc, and stress data were used to calculate how compressive loading was distributed between the anterior and posterior halves of the vertebral body and the neural arch. The compressive strength of each specimen was measured in flexed posture. Regional volumetric BMD and histomorphometric parameters were measured. In the upright posture, compressive load bearing by the neural arch increased with disc degeneration, averaging 63 +/- 22% (SD) of applied load in specimens with severely degenerated discs. In these specimens, the anterior half of the vertebral body resisted only 10 +/- 8%. The anterior third of the vertebral body had a 20% lower trabecular volume fraction, 16% fewer trabeculae, and 28% greater intertrabecular spacing compared with the posterior third (p < 0.001). In the flexed posture, flexion transferred 53-59% of compressive load bearing to the anterior half of the vertebral body, regardless of disc degeneration. Compressive strength measured in this posture was proportional to BMD in the anterior vertebral body (r2 = 0.51, p < 0.001) and inversely proportional to neural arch load bearing in the upright posture (r2 = 0.28, p < 0.001). Disc degeneration transfers compressive load bearing from the anterior vertebral body to the neural arch in upright postures, reducing BMD and trabecular architecture anteriorly. This predisposes to anterior fracture when the spine is flexed.

Domain structure in aggregating proteoglycans from cartilage

Cartilage is a specialized connective tissue with a biomechanical function which is particularly suited to compressive load bearing, such as in the articular surface of diarthrodial joints. The properties of the tissue depend upon a highly organized extracellular matrix, which contains a dense network of fine collagen fibres embedded in a high concentration of large aggregating proteoglycans. It is the balance between the high osmotic swelling pressure created by the proteoglycans and the tension in the collagen network that results in the compressive properties characteristic of the tissue [ 1 1. The maintenance of the tissue depends on the continued activity of the chondrocytes that produce the components of the matrix. Proteoglycans are constantly turned over even in mature tissue and they are continuously synthesized and secreted by the chondrocytes [ 11. The large aggregating proteoglycan (Fig. 1 ) contains a high molecular mass protein core (230 kDa), t o which is attached, during post-translational processing (mainly in the Golgi), a large number of chondroitin sulphate and keratan sulphate chains which make up 90% of the total mass of the secreted proteoglycan 121. There are also some N-linked and many Winked oligosaccharides attached to the protein core. Link protein is also synthesized by the chondrocytes along the same pathways as proteoglycan [ 3 ] , but the hyaluronan with which they aggregate does not share this pathway as it is synthesized at the chondrocyte plasma membrane and is therefore only available for aggregation after secretion. The extracellular assembly of aggregates, in which proteoglycans bind to hyaluronate, and are stabilized by link protein, provides a mechanism for immobilizing the proteoglycans in the matrix. Investigation of the protein core structure has shown a single gene product which contains several distinct domains (Fig. 1; Table I ) [2, 41. By rotary-shadowing electron microscopy, these appear as two extended and three globular regions (51. The N-terminal region of the protein core contains two globular domains G1 and G2 separated by a 21 nm extended segment. The major extended region bearing much of the keratan sulphate and all of the chondroitin

Load Transfer Characteristics of a Noncemented Total Knee Arthroplasty

This study evaluated load transfer characteristics of femoral and tibial components of a total knee prosthesis that was designed to achieve distal femoral and proximal tibial compressive load-bearing. Strain gauge readings were highest on the cortex of the tibial metaphyseal flare. Roentgenograms of 110 patients with noncemented total knee arthroplasty (TKA) with follow-up periods of 12-24 months were evaluated. Cancellous bone hypertrophy bridging from the undersurface of the tibial component to the metaphyseal cortical bone was noted on all roentgenograms at six months, suggesting stress transfer through cancellous bone to this area. Anterolateral sinking was noted in six of the first 46 patients but was not seen again in the series after a design change was made to more rigidly fix the stem in the bone of the upper tibia. Roentgenograms of the femoral components demonstrated distal bone hypertrophy suggesting compressive load bearing. None of the femoral components migrated or sank.

Load bearing capacity in total ankle joint replacement.

The influence of some simple design variations on the compressive load bearing capacity of tibial and talar prosthetic components in total ankle joint replacement were investigated in an attempt to suggest improvements to current prosthetic designs. Eighteen paired ankle joint preparations were fitted with three types of tibial components and two types of talar components. The tibial component with an intramedullary peg tolerated significantly higher loads before mechanical failure than the two other designs that were equal in load bearing capacity. The mean value of ultimate force was 40 per cent higher and the mean value of yield force was 15 per cent higher. However, for the coefficient of stiffness there was a significant fall of 18 per cent in the mean value. The talar components were equal in load bearing capacity and stiffness.