Principal Tensile Strain Research Articles

Design of porous titanium scaffold for complete mandibular reconstruction: The influence of pore architecture parameters

Patients having a medical history of oral cancer, infectious diseases or trauma are often advised surgical intervention with customized complete mandibular constructs (CMC) made of Titanium (Ti) scaffolds. A numerical framework based on a homogenization technique was developed to investigate the influence of pore architecture parameters on homogenized orthotropic material properties of the scaffolds. A comparative 3D Finite Element (FE) analysis of six CMC models, having homogenized orthotropic material properties, under a mastication cycle, was undertaken to pre-clinically determine the optimal CMC for a patient. Orthotropic material properties of Ti-scaffolds decreased with an increase in the inter-strut distance. Stress and strain distributions of CMC models during right molar bite were investigated. Despite small differences in stress distributions in the ‘body’ region of CMC models, the overall stress distribution (tensile and compressive) of CMC models (30–32 MPa) were well comparable to that of an intact mandible (34.54 MPa). Higher magnitudes of tensile strains were observed for models with 0.2 mm (9884μɛ) and 0.4 mm strut diameter (SD), both having 0.5 mm inter-strut distance (ID), at articular condyle area, body and symphysis equivalent part of the constructs. The maximum principal tensile strains were higher in the CMC models with 0.5 mm ID as compared to those having 0.3 mm ID. Comparatively, the scaffolds with lesser ID (0.3 mm) resulted in higher stiffness, thereby evoking less principal strains in the CMC models. Moreover, considering the weight of the scaffolds, the CMC models having 0.3 mm ID with 0.2 mm SD and 0.5 mm ID with 0.6 mm SD seemed most appropriate for a patient.

Multi-Plane Ultrafast Compound 3D Strain Imaging: Experimental Validation in a Carotid Bifurcation Phantom

Strain imaging of the carotid artery (CA) has demonstrated to be a technique capable of identifying plaque composition. This study assesses the performance of volumetric strain imaging derived from multi-plane acquisitions with a single transducer, with and without displacement compounding. These methods were compared to a reference method using two orthogonally placed transducers. A polyvinyl alcohol phantom was created resembling a stenotic CA bifurcation. A realistic pulsatile flow was imposed on the phantom, resulting in fluid pressures inducing 10% strains. Two orthogonally aligned linear array transducers were connected to two Verasonics systems and fixed in a translation stage. For 120 equally spaced elevational positions, ultrasound series were acquired for a complete cardiac cycle and synchronized using a trigger. Each series consisted of ultrafast plane-wave acquisitions at 3 alternating angles. Inter-frame displacements were estimated using a 3D cross-correlation-based tracking algorithm. Horizontal displacements were acquired using the single probe lateral displacement estimate, the single probe compounded by axial displacement estimates obtained at angles of 19.47 and −19.47 degrees, and the dual probe registered axial displacement estimate. After 3D tracking, least squares strain estimations were performed to compare compressive and tensile principal strains in 3D for all methods. The compounding technique clearly outperformed the zero-degree method for the complete cardiac cycle and resulted in more accurate 3D strain estimates.

EVALUATING THE THEORY OF BONE MECHANOREGULATION IN THE PHYSIOLOGICAL LOADING SCENARIO

In this paper, the theory of bone mechanoregulation under physiological loading was evaluated. The entire right tibiae of wild type (WT, [Formula: see text]) and parathyroid hormone (PTH, [Formula: see text]) treated C57BL/6J female mice were scanned using an in vivo [Formula: see text]CT imaging system at 14, 16, 17, 18, 19, 20, 21, and 22 weeks. The PTH intervention started from week 18 until week 22. Subject-specific finite element (FE) models were created from the [Formula: see text]CT images and physiological loading condition was defined in the FE models. The rates of changes in bone mineral content (BMC), bone mineral density (BMD), and bone tissue density (TMD) were quantified over 40 anatomical compartments across the entire mouse tibia. The resulting values were then correlated to the average 1st principal tensile strain ([Formula: see text]) and the strain energy density (SED) for every compartment at weeks 18, 20, and 22. It was found that: in both groups, [Formula: see text] had a minimal effect on the variability of [Formula: see text]BMC ([Formula: see text]); SED had a significant effect on the variability of [Formula: see text]BMC only in the WT group ([Formula: see text]); [Formula: see text] had a significant effect on the variability of [Formula: see text]BMD only in the PTH group ([Formula: see text]); SED had a significant effect on the variability of [Formula: see text]BMD in both groups ([Formula: see text]); neither SED nor [Formula: see text] had a significant effect on the variability of [Formula: see text]TMD ([Formula: see text]). These results are the first to reveal the mechanism of bone mechanoregulation in the physiological loading scenario.

A Coupled Damage‐Permeability Constitutive Model for Brittle Rocks Subjected to Explosive Loading

A dynamic constitutive model considering coupled damage‐permeability effect is developed for rocks under explosion. The main purpose of this model is to provide reference to in situ leaching mining (include uranium ore, gold ore, etc.) to improve the permeability of rocks using blasting. The damage is induced and described by the summation of all principal tensile strains. This method does not need to determine (distinguish) the stress state of the material and thus does not need to consider the damage induced by differential stresses. A corresponding relation between the damage status and rock permeability is established through a logarithm function. Based on the theoretical foundation, this model is embedded in a three‐dimensional code of ABAQUS, and its applicability is verified through simulating the experiments under the condition of explosive load, the results from numerical simulation are consistent with the experimental results. Moreover, the obvious advantage of the numerical constitutive model is that it can clearly distinguish permeability variation that cannot be done in laboratory test.

Quantification of shear cracking in reinforced concrete beams

This paper presents an experimental work and analysis of test results on diagonal cracking behavior of reinforced concrete (RC) beams that failed in shear. The strain distributions of transverse reinforcement, obtained by closely spaced strain gauges mounted inside transverse reinforcement without disturbing bond, are presented in a form of contour lines at different load levels. The diagonal crack width, average principal and shear strain fields of the shear span were obtained by using the digital image correlation (DIC). Based on the strains of transverse reinforcement along the path of the critical diagonal crack, the shear strength contribution of the transverse reinforcement (Vs) is isolated from the shear strength contribution of concrete (Vc). The value of Vs calculated in this way is generally larger than that obtained from the strains measured at mid-height of stirrups in the case of strong bond, while the difference is insignificant in the case of weak bond. With the full and detailed pictures of internal and external strain fields of the beams, important shear characteristics such as inclination of the principal compression strain and its correlation with principal compression stress, variation of Vc and Vs with respect to crack width and member deflection, relationships between crack width, shear force, principal tensile strain of concrete, and strain of transverse reinforcement, etc. are studied in this work. These relationships shed light on further study of the shear behavior of RC beams.

Biomechanical analysis of immediately loaded implants according to the “All-on-Four” concept

PurposeThe purpose of this study was to investigate the biomechanical behavior of immediately loaded implants in an edentulous mandible according to the “All-on-Four” concept. MethodsA 3D-finite element model of an edentulous mandible was constructed. Four implants were placed between the bilateral mental foramen according to “All-on-Four” concept. A framework made of titanium or acrylic resin between the bilateral first molars was modeled. Immediate loading and a delayed loading protocol were simulated. A vertical load of 200N was applied at the cantilever or on the abutments region of the distal implants, simulating the absence of a cantilever. ResultsThe peak principal compressive strains in the immediate loading models resulted in 24.0–35.8% and 26.4–39.0% increases compared with the delayed loading models under non-cantilever loading and cantilever loading, respectively. The loading position greatly affected the principal compressive and tensile strain values. The peak principal compressive strains in non-cantilever loading resulted in a 45.3–52.6% reduction compared with those in cantilever loading. The framework material did not influence the peak compressive and tensile strain. The maximum micromotion at the bone–implant interface in the immediate loading models was 7.5–14.4μm. ConclusionsMandibular fixed full-arch prostheses without cantilevers may result in a favorable reduction of the peri-implant bone strain during the healing period, compared with cantilevers. The maximum micromotion was within the acceptable limits for uneventful implant osseointegration in the immediate loading models. Framework material did not play an important role in reducing the peri-implant bone strain and micromotion at the bone–implant interface.

Load-carrying capacity degradation of reinforced concrete piers due to corrosion of wrapped steel plates

Two-dimensional elastoplastic finite element formulation is employed to investigate the load- carrying capacity degradation of reinforced concrete piers wrapped with steel plates due to occurrence of corrosion at the pier base. By comparing with experimental results, the employed finite element analysis method is verified to be accurate. After that, a series of parametric studies are conducted to investigate the effect of corrosion ratio and corrosion mode of steel plates located near the base of in-service pier P2 on load-carrying capacity of the piers. It is observed that the load-carrying capacity of the piers decreases with the increase in corrosion ratio of steel plates. There exists an obvious linear relationship between the load-carrying capacity and the corrosion ratio in the case of even corrosion mode. The degradation of load-carrying capacity resulted from the web\'s uneven corrosion mode is more serious than that under even corrosion mode, and the former case is more liable to occur than the latter case in actual engineering application. Finally, the failure modes of the piers under different corrosion state are discussed. It is found that the principal tensile strain of concrete and yield range of steel plates are distributed within a wide range in the case of slight corrosion, and they are concentrated on the column base when complete corrosion occurs. The findings obtained from the present study can provide a useful reference for the maintenance and strengthening of the in-service piers.

Comparison of Mechanical Properties ofFiber-Reinforced Sand under Triaxial Compressionand Direct Shear

AbstractThis research investigates the behavior of sandreinforced with polypropylene fiber. To do this, 40 directshear tests and 40 triaxial tests were performed on thecoastal beaches of Babolsar, a city in the North of Iran. Theeffect of parameters such as fiber content, length of fiberand normal or confining pressure on the behavior of Babolsarsand have been studied. In this study, four various fibercontents (0, 0.25, 0.5 and 1 percent), three different lengthsof fiber (6, 12 and 18 mm) and four normal or confiningpressures (50, 100, 200 and 400 kPa) have been employed.The test results show that fiber inclusion has a significanteffect on the behavior of sand. In both direct shear and triaxialtests, the addition of fibers improved shear strengthparameters (C, '), increased peak shear strength and axialstrain at failure, and also limited the amount of post-peakreduction in shear resistance. The comparison of the testresults revealed that due to better fiber orientation towardthe direction of principal tensile strain in triaxial test ascompared to direct shear tests, the fiber efficiency and itseffect on soil behavior is much more significant in triaxialspecimens.

Refinement of Strut-and-Tie Model for Reinforced Concrete Deep Beams.

Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted.

Characterization of cancellous and cortical bone strain in the in vivo mouse tibial loading model using microCT-based finite element analysis

The in vivo mouse tibial loading model has been increasingly used to understand the mechanisms governing the mechanobiological responses of cancellous and cortical bone tissues to physical stimuli. Accurate characterization of the strain environment throughout the tibia is fundamental in relating localized mechanobiological processes to specific strain stimuli in the skeleton. MicroCT-based finite element analysis, together with diaphyseal strain gauge measures, was conducted to quantify the strain field in the tibiae of 16-wk-old female C57Bl/6 mice during in vivo dynamic compressive loading. Despite a strong correlation between the experimentally-measured and computationally-modeled strains at the gauge site, no correlations existed between the strain at the gauge site and the peak strains in the proximal cancellous and midshaft cortical bone, indicating the limitations of using a single diaphyseal strain gauge to estimate strain in the entire tibia. The peak compressive and tensile principal strain magnitudes in the proximal cancellous bone were 10% and 34% lower than those in the midshaft cortical bone. Sensitivity analyses showed that modeling bone tissue as a heterogeneous material had a strong effect on cancellous strain characterization while cortical strain and whole-bone stiffness were primarily affected by the presence of the fibula and the proximal boundary conditions. These results show that microCT-based finite element analysis combined with strain gauge measures provides detailed resolution of the tissue-level strain in both the cancellous and cortical bones of the mouse tibia during in vivo compression loading, which is necessary for interpreting localized patterns of modeling/remodeling and, potentially, gene and protein expression in skeletal mechanobiology studies.

Primary cilium mechanotransduction of tensile strain in 3D culture: Finite element analyses of strain amplification caused by tensile strain applied to a primary cilium embedded in a collagen matrix

Human adipose-derived stem cells (hASC) exhibit multilineage differentiation potential with lineage specification that is dictated by both the chemical and mechanical stimuli to which they are exposed. We have previously shown that 10% cyclic tensile strain increases hASC osteogenesis and cell-mediated calcium accretion. We have also recently shown that primary cilia are present on hASC and that chemically-induced lineage specification of hASC concurrently results in length and conformation changes of the primary cilia. Further, we have observed cilia length changes in hASC cultured within a collagen I gel in response to 10% cyclic tensile strain. We therefore hypothesize that primary cilia may play a key mechanotransduction role for hASC exposed to tensile strain. The goal of this study was to use finite element analysis (FEA) to determine strains occurring within the ciliary membrane in response to 10% tensile strain applied parallel, or perpendicular, to cilia orientation. To elucidate the mechanical environment experienced by the cilium, several lengths were modeled and evaluated based on cilia lengths measured on hASC grown under varied culture conditions. Principal tensile strains in both hASC and ciliary membranes were calculated using FEA, and the magnitude and location of maximum principal tensile strain determined. We found that maximum principal tensile strain was concentrated at the base of the cilium. In the linear elastic model, applying strain perpendicular to the cilium resulted in maximum strains within the ciliary membrane from 150% to 200%, while applying strain parallel to the cilium resulted in much higher strains, approximately 400%. In the hyperelastic model, applying strain perpendicular to the cilium resulted in maximum strains within the ciliary membrane around 30%, while applying strain parallel to the cilium resulted in much higher strains ranging from 50% to 70%. Interestingly, FEA results indicated that primary cilium length was not directly related to ciliary membrane strain. Rather, it appears that cilium orientation may be more important than cilium length in determining sensitivity of hASC to tensile strain. This is the first study to model the effects of tensile strain on the primary cilium and provides newfound insight into the potential role of the primary cilium as a mechanosensor, particularly in tensile strain and potentially a multitude of other mechanical stimuli beyond fluid shear.

Modification of strut effectiveness factor for reinforced concrete deep beams strengthened with CFRP laminates

This paper proposes a method to modify the strut effectiveness factor in the strut-and-tie model for CFRP-strengthened reinforced concrete deep beams. Two groups of deep beams comprising six ordinary reinforced concrete deep beams and six CFRP-strengthened reinforced concrete deep beams were experimentally tested under the four-point bending configuration. The shear span-to-effective depth ratio of the beams in each group was 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00. The theoretical principal tensile strain in CFRP-strengthened struts was modified based on a proposed empirical relationship, based on two ratios: the experimental to the theoretical value of principal tensile strain and the shear span-to-effective depth of deep beams.

Evaluation of the shear capacity of precast-prestressed hollow core slabs: numerical and experimental comparisons

Since eighties, 400 and 500 mm thick precast-prestressed concrete hollow core slabs, characterized by increasingly optimized cross-sections with non-circular voids, became very common. However, deeper slabs with long spans, which have to resist high line loads acting close to the supports, are subjected to initial web shear cracking and may fail at loads less than those predicted by traditional codes prescriptions. The shear strength capacity of these members without transverse reinforcement is evaluated through a campaign of detailed nonlinear finite element analyses, matching experimental test data collected from past programs. Constitutive models, based on nonlinear fracture mechanisms, are considered to numerically reproduce the experimental response of single span, simply supported, isolated hollow core units, highlighting web-shear failure mechanism, due to short development length and lack of transverse reinforcement. The adopted diffuse smeared fixed cracking constitutive model allows a reliable prediction of shear stress distributions and crack patterns for these members in their inelastic branch. The presence of a variable inclined strut is clearly evident. Peak shear stress is localized at the bottom side of the cross-section, rather than at the level of the centroid. The experienced brittle web-shear failure mechanism is governed by hollow core shapes with circular or non-circular voids, as evidenced by the evolution of the principal tensile strain distributions. Typically, less inclined, more rounded, diagonal crack, controlled by the smooth web width variation along depth, is opposed to a fairly constant variation of the fracture angle inclination, governed by the abrupt and irregular web width drop.

Squatting-related tibiofemoral shear reaction forces and a biomechanical rationale for femoral component loosening.

Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.

Statistical Damage Constitutive Model for Concrete under Biaxial Tension

Based on the statistical damage theory and the experimental phenomena, the statistical damage constitutive model for concrete under biaxial tension is proposed. The two meso-scale damage modes, rupture and yield are considered, and the whole damage evolution process is driven by the principal tensile damage strain. The results show that the proposed statistical damage model can accurately predict the constitutive behavior in the uniform damage phase for concrete under biaxial tension. The damage mechanism is discussed in the view point of biaxial strength and deformation properties.

Age-related changes in human peripapillary scleral strain

To test the hypothesis that mechanical strain in the posterior human sclera is altered with age, 20 pairs of normal eyes from human donors aged 20 to 90 years old were inflation tested within 48-h postmortem. The intact posterior scleral shells were pressurized from 5 to 45 mmHg, while the full-field three-dimensional displacements of the scleral surface were measured using laser speckle interferometry. The full strain tensor of the outer scleral surface was calculated directly from the displacement field. Mean maximum principal (tensile) strain was computed for eight circumferential sectors (45° wide) within the peripapillary and mid-peripheral regions surrounding the optic nerve head (ONH). To estimate the age-related changes in scleral strain, results were fit using a functional mixed effects model that accounts for intradonor variability and spatial autocorrelation. Mechanical tensile strain in the peripapillary sclera is significantly higher than the strain in the sclera farther away from the ONH. Overall, strains in the peripapillary sclera decrease significantly with age. Sectorially, peripapillary scleral tensile strains in the nasal sectors are significantly higher than the temporal sectors at younger ages, but the sectorial strain pattern reverses with age, and the temporal sectors exhibited the highest tensile strains in the elderly. Overall, peripapillary scleral structural stiffness increases significantly with age. The sectorial pattern of peripapillary scleral strain reverses with age, which may predispose adjacent regions of the lamina cribrosa to biomechanical insult. The pattern and age-related changes in sectorial peripapillary scleral strain closely match those seen in disk hemorrhages and neuroretinal rim area measurement change rates reported in previous studies of normal human subjects.

Fabrication of Miniature Shell Structures of Stainless Steel Foil and Their Forming Limit in Single Point Incremental Microforming

Single Point Incremental Microforming (SPIMF) using neither dies nor a backing plate is applied to the fabrication of miniature shell structures of stainless steel foil in meso-scale. A piece of 8 µm-thick blank, which is held in a blank holder on a desktop forming machine, is incrementally formed with a thin, round-tip tool. Three kinds of polygonal pyramids are formed, and their forming limits are compared to those when 12 µm-thick aluminum foil is used. It is found that the forming limit of stainless steel foil in forming pyramids depends only on the tensile strain of a triangular lateral face, whereas that of aluminum foil depends on the sum of two principal tensile strains on the surface of a rounded lateral edge. It is also found that the forming limit of stainless steel foil can be drastically increased by SPIMF.

The Importance of Intrinsic Damage Properties to Bone Fragility: A Finite Element Study

As the average age of the population has increased, the incidence of age-related bone fracture has also increased. While some of the increase of fracture incidence with age is related to loss of bone mass, a significant part of the risk is unexplained and may be caused by changes in intrinsic material properties of the hard tissue. This investigation focused on understanding how changes to the intrinsic damage properties affect bone fragility. We hypothesized that the intrinsic (μm) damage properties of bone tissue strongly and nonlinearly affect mechanical behavior at the apparent (whole tissue, cm) level. The importance of intrinsic properties on the apparent level behavior of trabecular bone tissue was investigated using voxel based finite element analysis. Trabecular bone cores from human T12 vertebrae were scanned using microcomputed tomography (μCT) and the images used to build nonlinear finite element models. Isotropic and initially homogenous material properties were used for all elements. The elastic modulus (E(i)) of individual elements was reduced with a secant damage rule relating only principal tensile tissue strain to modulus damage. Apparent level resistance to fracture as a function of changes in the intrinsic damage properties was measured using the mechanical energy to failure per unit volume (apparent toughness modulus, W(a)) and the apparent yield strength (σ(ay), calculated using the 0.2% offset). Intrinsic damage properties had a profound nonlinear effect on the apparent tissue level mechanical response. Intrinsic level failure occurs prior to apparent yield strength (σ(ay)). Apparent yield strength (σ(ay)) and toughness vary strongly (1200% and 400%, respectively) with relatively small changes in the intrinsic damage behavior. The range of apparent maximum stresses predicted by the models was consistent with those measured experimentally for these trabecular bone cores from the experimental axial compressive loading (experimental: σ(max) = 3.0-4.3 MPa; modeling: σ(max) = 2-16 MPa). This finding differs significantly from previous studies based on nondamaging intrinsic material models. Further observations were that this intrinsic damage model reproduced important experimental apparent level behaviors including softening after peak load, microdamage accumulation before apparent yield (0.2% offset), unload softening, and sensitivity of the apparent level mechanical properties to variability of the intrinsic properties.

In Vitro Quantification of Strain Patterns in the Craniofacial Skeleton Due to Masseter and Temporalis Activities

Many complications in craniofacial surgery can be attributed to a lack of characterization of facial skeletal strain patterns. This study aimed to delineate human midfacial strain patterns under uniform muscle loading. The left sides of 5 fresh-frozen human cadaveric heads were dissected of all soft tissues except the temporalis and masseter muscles. Tensile forces were applied to the free mandibular ends of the muscles. Maxillary alveolar arches were used to restrain the skulls. Eight strain gauges were bonded to the surface of the midface to measure the strain under single muscle loading conditions (100 N). Maxillary strain gauges revealed a biaxial load state for both muscles. Thin antral bone experienced high maximum principal tensile strains (maximum of 685.5 με) and high minimum principal compressive strains (maximum of -722.44 με). Similar biaxial patterns of lower magnitude were measured on the zygoma (maximum of 208.59 με for maximum principal strains and -78.11 με for minimum principal strains). Results, consistent for all specimens and counter to previously accepted concepts of biomechanical behavior of the midface under masticatory muscle loading, included high strain in the thin maxillary antral wall, rotational bending through the maxilla and zygoma, and a previously underestimated contribution of the temporalis muscle. This experimental model produced repeatable strain patterns quantifying the mechanics of the facial skeleton. These new counterintuitive findings underscore the need for accurate characterization of craniofacial strain patterns to address problems in the current treatment methods and develop robust design criteria.

Regional Variations in Mechanical Strain in the Posterior Human Sclera

The goal of this study was to establish sectorial and regional variability in the mechanical strain of peripapillary and mid-peripheral sclera in normal eyes from elderly human donors. Ten pairs of normal eyes from human donors aged 57 to 90 years old were mechanically inflation-tested within 48 hours post mortem. The intact posterior scleral shells were pressurized from 5 to 45 mm Hg while the full-field three-dimensional displacements of the scleral surface were measured using laser speckle interferometry. The displacement field was fit to continuous and differentiable analytical functions, from which the full strain tensor of the outer scleral surface was calculated. Mean maximum principal (tensile) strain was computed for eight circumferential sectors (45° wide) within the peripapillary and mid-peripheral regions surrounding the optic nerve head (ONH). Overall, the peripapillary sclera exhibited significantly higher tensile strain (1.2%) than mid-peripheral sclera (0.95%) for a 40 mm Hg IOP elevation (P < 0.00001). In the peripapillary region, the inferotemporal sector exhibited the highest tensile strain (1.45%) while the superior sector had the lowest (1.19%; P < 0.00001). Mid-peripheral scleral strains were lower but exhibited a similar sectorial pattern. Human posterior sclera exhibits complex regional mechanical behavior in response to acute IOP elevations from 5 to 45 mm Hg. Results indicate 1) the peripapillary sclera is subjected to significantly higher tensile strain than the adjacent mid-peripheral sclera, and 2) strains are significantly higher in the temporal and inferior quadrants of the peripapillary sclera, which may contribute to the increased prevalence of glaucomatous damage associated with these regions of the ONH.