Ideal Stiffness Research Articles

Lightweight design of cannon frame considering dimension and topology coupling

Abstract The cannon frame is a primary load-bearing component of the firepower system, and lightweight design plays an important role improving the artillery’s manoeuvrability. However, the present lightweight design methods don’t consider the interdependency between dimension and topology, hindering the cannon frame from achieving the ideal stiffness to mass ratio. To tackle this issue, a novel lightweight design methodology considering dimension and topology coupling is proposed. By means of orthogonal experiment and topology optimization, various topologies of cannon frame with distinct dimensions are generated. Then the response surface method (RSM) is implemented to devise surrogate models that embody dimension, topologies, stiffness and mass mapping. Finally, global optimization is performed using particle swarm optimization (PSO) algorithm to achieve the concurrent lightweight design of dimension and topology. Compared with the original scheme, the proposed design method reduces the weight by 12.7%.

Multi‐objective optimization design of concrete outriggers based on Genetic–HookeJeeves algorithm: Reducing lateral deflection, differential axial shortening, and construction cost of the structure

SummaryIn the context of tall concrete structures, it is crucial to not only control the lateral displacement of the building but also address the issue of differential axial shortenings in its vertical elements. Concrete outriggers, commonly resembling relatively stiff beams spanning one to two floors, connect the central core to exterior columns. The strategic placement and appropriate stiffness of these outriggers at different heights of the structure can significantly influence the overall behavior of the entire structure. This study focuses on optimizing the location, depth, and thickness of concrete outriggers, along with the dimensions of beams and columns, as well as the thickness of the core shear wall with the objective of minimizing construction costs and mitigating the occurrence of lateral displacement and differential axial shortenings within the structure. To achieve this, a combined approach of the Genetic–HookeJeeves algorithm has been employed. In this research, we have integrated HookeJeeves, a local search algorithm, with the genetic algorithm to create a hybrid approach that demonstrates high convergence performance. The structural modeling and analysis were conducted using ETABS finite element software, while a Euro‐International Concrete Committee model (CEB model) was utilized to assess the magnitude of differential axial shortenings, enabling us to approximate the long‐term behavior of concrete. The findings of this study highlight the significant impact of the location and stiffness of outriggers on mitigating both lateral displacement and differential axial shortenings within the structure. Optimal placement of an outrigger resulted in a 16% reduction in lateral displacement, and this value could reach up to 25% when the outrigger possessed the ideal stiffness. Additionally, such an arrangement led to a remarkable 36% decrease in the maximum differential axial shortening observed in the structure. These outcomes demonstrate that meeting the design requirements of the intended structure not only improves its performance but also reduces construction costs by 31%.

Current Concepts in Management of Distal Femur Fractures

Recent studies report the overall incidence of distal femur fractures as 8.7/100,000/year. This incidence is expected to rise with high energy motor vehicle collisions and elderly osteoporotic fractures in native and prosthetic knees keep increasing. These fractures are more common in males in the younger age spectrum while females predominate for elderly osteoporotic fractures. Surgical treatment is recommended for these fractures to maintain articular congruity, enable early joint motion and assisted ambulation. Over the last two decades, development of minimally invasive and quadriceps sparing surgical approaches, availability of angle stable implants have helped achieve predictable healing and early return to function in these patients. Currently, laterally positioned locked plate is the implant of choice across all fracture patterns. Retrograde with capital implantation of intramedullary nails with provision for multiplanar distal locking is preferred for extra-articular and partial articular fractures. Even with these advancements, nonunion after distal femur fracture fixation can be as high as 19%. Further recent research has helped us understand the biomechanical limitations and healing problems with lateral locked plate fixation and intramedullary nails. This has lead to development of more robust constructs such as nail-plate and double plate constructs aiming for improved construct strength and to minimise failures. Early results with these combination constructs have shown promise in high risk situations such as fractures with extensive metaphyseal fragmentation, osteoporosis and periprosthetic fractures. These constructs however, run the risk of being over stiff and can inhibit healing if not kept balanced. The ideal stiffness that is needed for fracture healing is not clearly known and current research in this domain has lead to the development of smart implants which are expected to evolve and may help improve clinical results in future.

Rotational Stiffening Performance of Roof Folded Plates in Torsion Tests and the Stiffening Effect of Roof Folded Plates on the Lateral Buckling of H Beams in Steel Structures

Non-structural members, such as roofs and ceilings, become affixed to main beams that are known as structural members. When such main beams experience bending or compressive forces that lead to lateral buckling, non-structural members may act to restrain the resulting lateral buckling deformation. Nevertheless, neither Japanese nor European guidelines advocate for the utilization of non-structural members as lateral buckling stiffeners for beams. Additionally, local buckling ensues near the bolt apertures in the beam–roof folded plate connection due to the torsional deformation induced by the lateral buckling of the H beam, thereby reducing the rotational stiffness of the roof folded plate to a percentage of its ideal stiffness. This paper conducts torsional experiments on roof folded plates, and with various connection methods between these plates and the beams, to comprehend the deformation mechanism of roof folded plates and the relationship between their rotational stiffness and the torsional moment. Then, the relationship between the demand values against restraining the lateral buckling of the main beam and the experimentally determined bearing capacity of the roof folded plate is elucidated. Results indicate the efficacy of utilizing the roof folded plate as a continuous brace. The lateral buckling design capacity of H beams that are continuously stiffened by roof folded plates is elucidated via application of a connection method that ensures joint stiffness between the roof folded plate and the beam while using Japanese and European design codes.

Ferrite-doped rare-earth nanoparticles for enhanced β-phase formation in electroactive PVDF nanocomposites.

This study offers a novel method for improving the piezoelectric characteristics of polyvinylidene fluoride (PVDF) by adding lanthanated CoFe2O4 nanoparticles (CLFO), thereby addressing the critical need for effective renewable energy solutions. The novelty of this work lies in the synthesis of CLFO nanoparticles and their integration into the PVDF matrix, with polyvinylpyrrolidone (PVP) employed to ensure uniform dispersion. This was accomplished by a special co-precipitation and heat treatment procedure. Nanocomposite films were created using solvent casting with a range of CLFO concentrations (1, 3, 5, and 7 wt%). The structural, morphological, mechanical, and thermal properties of these films were all thoroughly assessed. A remarkable improvement over conventional techniques was found using X-ray diffraction and Fourier transform infrared spectroscopy, which showed up to 80% β-phase development with 3 wt% CLFO. While thermogravimetric studies showed enhanced thermal stability, scanning electron microscopy verified homogeneous nanoparticle dispersion. Mechanical tests revealed ideal stiffness, strength, and ductility at 3 wt% CLFO. Significant advances in electronics and energy harvesting are anticipated from this novel combination of PVDF's piezoelectric properties and CLFO reinforcement. By minimally influencing the environment, these advancements not only tackle the world's energy problems but also present prospective uses for renewable energy technologies.

DESIGN OF VISCO-ELASTIC SUPPORTS FOR TIMOSHENKO CANTILEVER BEAMS

The appropriate design of supports, upon which beams are usually placed as structural components in many engineering scenarios, has substantial significance in terms of both structural efficacy and cost factors. When beams experience various dynamic vibration effects, it is crucial to contemplate appropriate support systems that will effectively adapt to these vibrations. The present work investigates the most suitable support configuration for a cantilever beam, including viscoelastic supports across different vibration modes. Within this particular framework, a cantilever beam is simulated using beam finite elements. The beam is positioned on viscoelastic supports, which are represented by simple springs and damping elements. These supports are then included in the overall structural model. The equation of motion for the beam is first formulated in the temporal domain and then converted to the frequency domain via the use of the Fourier Transform. The basic equations used in the frequency domain are utilized to establish the dynamic characteristics of the beam by means of transfer functions. The determination of the ideal stiffness and damping coefficients of the viscoelastic components is achieved by minimizing the absolute acceleration at the free end of the beam. In order to minimize the objective function associated with acceleration, the nonlinear equations derived from Lagrange multipliers are solved using a gradient-based technique. The governing equations of the approach need partial derivatives with respect to design variables. Consequently, analytical derivative equations are formulated for both the stiffness and damping parameters. The present work introduces a concurrent optimization approach for both stiffness and damping. Passive constraints are established inside the optimization problem to impose restrictions on the lower and higher boundaries of the stiffness and damping coefficients. On the other hand, active constraints are used to ascertain the specific values of the overall stiffness and damping coefficients. The efficacy of the established approach in estimating the ideal spring and damping coefficients of viscoelastic supports and its ability to provide optimal support solutions for various vibration modes have been shown via comparative experiments with prior research.

Posture optimization in robotic machining based on comprehensive deformation index considering spindle weight and cutting force

Industrial robot has been considered to be the most promising choice to replace traditional CNC machine tool due to its low cost, high flexibility, versatility and large workspace. However, insufficient stiffness of the robot often leads to deformations and vibrations during the machining process. To improve the machining performance of robot, a posture optimization method through controlling the functional redundancy of robot is proposed. First, considering the spindle weight-induced deformation and cutting force-induced deformation simultaneously, a comprehensive deformation index is proposed to evaluate the stiffness performance of robot posture along the robot milling trajectory. Then, ideal stiffness interval at each cutter location point is calculated by minimizing the proposed deformation index in consideration of the constraints of joint and joint velocity. Next, the kinematics performance index is taken as the optimization target, and the postures of the entire milling trajectory are optimized collaboratively within the ideal stiffness intervals. In order to approximate the global optimal solution, the genetic algorithm is used to solve the optimal robot posture. Finally, a series of simulations and experiments are carried out to verify the proposed index and robot trajectory optimization method, and the results show that the machining accuracy can be efficiently improved by the proposed method.

Finding the globally optimal correlation of cranes drive mechanisms

Optimization of a multi-drive machine, i.e., a tower crane with a pivoting boom, needs to take into account the interactions between cooperating mechanisms. This article outlines a methodology of selecting optimal mechanism structure from a set of possible solutions. By introducing a certain quality criterion, a set of parameters optimized for the full range of motion is determined for each structure. Thus, obtained parameters can be regarded as optimal and guarantee the best mutual adjustment of interacting mechanisms. Accordingly, each structure is assigned the optimum quality index value. Obviously, this index is associated with the type of involved mechanisms and their interactions, allowing us to find the best out of the sets of optimized cranes mechanisms. The method was illustrated for a one-link crane with lever mechanisms, and comparison was made with rope mechanisms. Optimization tasks were formulated assuming the ideal stiffness of the structure in quasi-static conditions. Effectiveness of the optimization was verified under the dynamic conditions, taking into account rope flexibility. Finding globally optimal design solution will yield the best combination of different mechanisms structures such that the dynamic overload values should be significantly reduced at the stage of design of the steel structure.

Mechanical Properties of Interface Layers in SiC/TiAl Composite

Although metal matrix composites (MMC) for the high temperature structural material have been investigated extensively for many years, applications of MMC have been still limited. Among many combinations between the ceramic fibers and the matrix materials, combination of SiC fiber and TiAl based intermetallic compounds has been expected to be one of the best combination, since both SiC fiber and TiAl have demonstrated the capabilities of the low density heat resistant materials. SiC fiber reinforced TiAl composites have been successfully fabricated using hot press method. Optimum temperature and pressure have been determined. SiC/TiAl composite having relatively low fiber volume fraction shows nearly an ideal elastic property applying the law of mixture. Effects of interface layers on the mechanical properties of composites have been studied in detail. Micro-indentation on a single fiber was carried out to examine the pull out strength of SiC fiber quantitatively. Estimated shear stress on the interface was 145-195MPa, those values are quite reasonable since the tensile strength of TiAl matrix was 420MPa and the maximum shear stress would be the half of tensile strength according to Schmid law. Three-point bending tests have been carried out to evaluate the mechanical properties of composites. Fiber volume fraction 8.9% specimen shows ideal bending stiffness compare with the calculated values based on the low of mixture. Reaction layers and the interface between SiC fiber and TiAl have been analyzed by SEM-EDS and XRD. At least two or more reaction layers have been identified. These reaction layers can be explained based on the Si-Ti-C ternary equilibrium phase diagram at 1373K. Optimum conditions of interface structure will be discussed

Assessment of possibilities of strawberry jam reformulation

The prevalence of excessive weight gain, obesity, and associated diseases are permanently increasing. Therefore, the interest in food products with a composition suitable for people with the aforementioned health problems is also on the rise. The changes in food composition, nowadays often called reformulation, are mainly focused on reducing the amount of salt, sugar, or fat. Strawberry spreads with different sugar (10 – 40%) and strawberry (20 – 50%) content were prepared and the influence of strawberry jam composition on gel stiffness, colour, and sensory parameters was studied. This study aimed to determine the sensorial and technological limits (sugar and strawberry content) of strawberry jam reformulation. Carrageenan was chosen as a suitable gelling agent for the preparation of these reformulated strawberry products. strawberry spreads. The applicable concentration of carrageenan for the ideal stiffness of strawberry spreads was 2%. The results of the maximum compression force show a statistically significant increase of gel stiffness with increasing addition of strawberry puree, the effect of sugar content was also statistically significant (p = 0.05). This study showed that strawberry spreads with low strawberry and/or sugar content are sensorially acceptable.

Analysis of silo supporting ring beams resting on discrete supports

Elevated cylindrical metal silos are often supported on a ring beam which rests on discrete column supports. The ring beam plays an important role in redistributing the majority of the discrete forces from the column supports into a more uniform stress state in the cylindrical wall, which is necessary to reduce the potential for buckling of the shell wall.Traditional design treatments assumed that the discrete support forces can be fully redistributed by the ring beam, producing circumferentially uniform axial membrane stresses in the silo shell. But it has previously been shown that only a very stiff ring beam can produce even relatively uniform axial membrane stresses in the shell. The ring beam stiffness must be evaluated relative to the stiffness of the silo shell in compatible deformation, since even a thin shell is extremely stiff in its own plane. A test for the ring beam to shell stiffness ratio was previously devised by the authors to determine the ring beam stiffness needed to achieve uniform membrane stresses. This new study assesses ring beams of practical dimensions and stiffness, to evaluate their effectiveness in smoothing the shell axial membrane stresses towards the uniform condition and then to find their effect on the buckling resistance of the shell.This study explores the stress resultants in a closed section ring beam of practical dimensions that is less stiff than the ideal stiffness using a finite element parametric study of the flexible ring beam and connected silo shell. The results show that the ring beam stress resultants, relative to those in an isolated ring beam under the same loading, can be directly related to the established shell to ring beam stiffness ratio (ψ). This treatment may be used to significantly enhance current design practice which, according to the Eurocode EN 1993-4-1 for silos, assumes that the shell applies the full uniform transverse loading onto an isolated ring beam.

Soft Nanohydrogels Based on Laponite Nanodiscs: A Versatile Drug Delivery Platform for Theranostics and Drug Cocktails

A new nanohydrogel drug delivery platform based on Laponite nanodiscs, polyacrylate, and sodium phosphate salts is described. The hybrid nanohydrogel is tailored to obtain soft and flexible nanohydrogels with G' around 3 kPa, which has been proposed as the ideal stiffness for drug delivery applications. In vitro studies demonstrate that the new nanohydrogels are biocompatible, biodegradable, nonswellable, pH-responsive, and noncytotoxic and are able to deliver antineoplastic drugs into cancer cells. The IC50 of nanohydrogels containing cisplatin, 4-fluorouracil, and cyclophosphamide is significantly lower than the IC50 of the free drugs. In vivo experiments suggest that the new nanomaterials are biocompatible and do not accumulate in crucial organs. The simple formulation procedure enables encapsulation of virtually any water-soluble molecule, without the need for chemical modification of the guests. These nanohydrogels are a versatile platform that enables the simultaneous encapsulation of several cancer drugs, yielding an efficient drug cocktail delivery system, which for instance presents a positive synergistic effect against MCF-7 cells.

Analysis of underwater acoustic scattering problems using stable node-based smoothed finite element method

A stable node-based smoothed finite element method (SNS-FEM) is presented that cures the “overly-soft” property of the original node-based smoothed finite element method for the analysis of underwater acoustic scattering problems. In the SNS-FEM model, the node-based smoothed gradient field is enhanced by additional stabilization term related to the gradient variance items. It is demonstrated that SNS-FEM provides an ideal stiffness of the continuous system and improves the performance of the NS-FEM and FEM. In order to handle the acoustic scattering problems in unbounded domain, the well known Dirichlet-to-Neumann (DtN) boundary condition is combined with the present SNS-FEM to give a SNS-FEM-DtN model for exterior acoustic problems. Several numerical examples are investigated and the results show that the SNS-FEM-DtN model can achieve more accurate solutions compared to the NS-FEM and FEM.

Effect of Stiffness of Cement on Stress Distribution in Ceramic Crowns.

To analyse the stress distribution in monolithic- and bilayer-structured ceramic crowns by means of the finite element method (FEM), as a function of elastic modulus of the core ceramic, Ecor, and that of the cement used to lute the crown, Ecem, with a view to identifying an ideal stiffness for the cement. A two-dimensional axisymmetric FEM model was created to represent tooth structure with a cemented ceramic crown in place. The value of Ecor was set at 70, 100, 150 and 200 GPa representative of the range of commercially available materials. For the veneer, Even, it was set at 70 GPa, while that of the cement, Ecem, was varied from 0.2 to 200 GPa, in a 1-2-5 sequence. The tensile stress along the x-direction was calculated as an indication of the local sensitivity of the model to failure at a given load. The stiffness of both the core ceramic and of the cement strongly affected the tensile stress distribution. With an increase in Ecor, the stress was increased for low Ecem. Also, the stress in the cement tended to increase with an increase in Ecem. However, the stress in the dentine varied little over the ranges studied here. For Ecor > Ecem, the stress in the core for low Ecem was higher than for high Ecem. It is suggested that the modulus of elasticity for the cement used to lute the ceramic crown plays a critical role in improving the fracture resistance of ceramic restorations.

A stable node-based smoothed finite element method for acoustic problems

It is well-known that the classical “overly-soft” node-based smoothed finite element method (NS-FEM) fails to provide reliable results to the Helmholtz equation due to the “temporal instability”. To cure the fatal drawback of NS-FEM and reduce the dispersion error in computational acoustics, this paper proposed a stable node-based smoothed finite element method (SNS-FEM) for analyzing acoustic problems using linear triangular (for 2D space) and tetrahedral (for 3D space) elements that can be generated automatically for any complicated configurations. In the present formulation, the system stiffness matrix is computed using the smoothed acoustic pressure gradients together with the gradient variance items over the smoothing domains associated with nodes of element mesh. It turns out the addition of stabilization term makes the SNS-FEM possess an ideal stiffness, thus successfully cures the temporal instability and significantly reduces the dispersion error in acoustic problems. Numerical examples, including both benchmark cases and practical engineering problems, demonstrate that the SNS-FEM possesses the following important properties: (1) temporal stability; (2) super accuracy and super convergence; (3) higher computational efficiency; (4) insensitive to mesh distortion.

Design and Performance Evaluation of a Self-Controlled Magneto-Rheological Damper

Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require an isolated power supply and dynamic sensor, which requires large space. This paper presents the achievability and accuracy of a self-controlled, i.e., self-powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed. Another important part of this paper is the increased yield stress of the Magneto-rheological Fluids. Magneto-rheological fluids that use replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. The permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper’s vibration mitigating capacity, an Engine Mount System using the MR damper is simulated with the help of ANSYS software. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self-sensing MR damper is theoretically calculated and evaluated in the frequency domain.

Calculation of reaction forces in the boiler supports using the method of equivalent stiffness of membrane wall.

The values of reaction forces in the boiler supports are the basis for the dimensioning of bearing steel structure of steam boiler. In this paper, the application of the method of equivalent stiffness of membrane wall is proposed for the calculation of reaction forces. The method of equalizing displacement, as the method of homogenization of membrane wall stiffness, was applied. On the example of “Milano” boiler, using the finite element method, the calculation of reactions in the supports for the real geometry discretized by the shell finite element was made. The second calculation was performed with the assumption of ideal stiffness of membrane walls and the third using the method of equivalent stiffness of membrane wall. In the third case, the membrane walls are approximated by the equivalent orthotropic plate. The approximation of membrane wall stiffness is achieved using the elasticity matrix of equivalent orthotropic plate at the level of finite element. The obtained results were compared, and the advantages of using the method of equivalent stiffness of membrane wall for the calculation of reactions in the boiler supports were emphasized.

Novel design of a self powered and self sensing magneto-rheological damper

Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.

Less rigid stable fracture fixation in osteoporotic bone using locked plates with near cortical slots

Introduction Locked plating leads to improved fixation in osteoporotic bone. In addition, experimental data suggest that overall construct stiffness is increased. Ideal stiffness may be significantly less than that achieved with these locked constructs, and overly stiff constructs may lead to impaired fracture healing and stress concentration at the ends of the plate. In osteoporotic bone, this stiffness mismatch can be even more pronounced. We hypothesized that substituting slots for holes in the near cortex under a locked plate would lead to predictably lower stiffness without diminishing implant stability. Methods Osteoporotic bone substitute segments were used. Locking screws and plates were applied to each specimen using either standard holes or near cortical slots. The slots were designed to allow axial displacement of the screw in the near cortex only, while continuing to provide some torsional stability. Mechanical testing was performed using a progressive dynamic displacement load protocol to determine failure and stiffness. Next, cyclic axial loading was performed with a physiologic load for 10,000 cycles to determine change in stiffness with cycling. Outcomes were compared between groups using Mann–Whitney U tests. Results In the dynamic displacement tests, the slotted specimens reached both maximum load and failure load at a significantly greater displacement than the non-slot group ( p = 0.008), indicating later failure. The magnitude of the maximum load achieved was no different between groups. In the cyclic loading tests, the axial stiffness in the slotted group was significantly lower (1199 N/mm) than the non-slotted group (3538 N/mm; p < 0.05 at all cycles). Stiffness did not change significantly in either group over the course of cycling. Discussion The ability to predictably adjust the axial stiffness of locked plating constructs is critical, particularly in osteoporotic bone. The use of near cortical slots decreases axial stiffness of locking plates, while maintaining fixation stability. This may allow the surgeon to more closely tailor the construct stiffness to the clinical situation to minimize stiffness mismatches and complications.

Substrate Stiffness Affects the Functional Maturation of Neonatal Rat Ventricular Myocytes

Cardiac cells mature in the first postnatal week, concurrent with altered extracellular mechanical properties. To investigate the effects of extracellular stiffness on cardiomyocyte maturation, we plated neonatal rat ventricular myocytes for 7 days on collagen-coated polyacrylamide gels with varying elastic moduli. Cells on 10 kPa substrates developed aligned sarcomeres, whereas cells on stiffer substrates had unaligned sarcomeres and stress fibers, which are not observed in vivo. We found that cells generated greater mechanical force on gels with stiffness similar to the native myocardium, 10 kPa, than on stiffer or softer substrates. Cardiomyocytes on 10 kPa gels also had the largest calcium transients, sarcoplasmic calcium stores, and sarcoplasmic/endoplasmic reticular calcium ATPase2a expression, but no difference in contractile protein. We hypothesized that inhibition of stress fiber formation might allow myocyte maturation on stiffer substrates. Treatment of maturing cardiomyocytes with hydroxyfasudil, an inhibitor of RhoA kinase and stress fiber-formation, resulted in enhanced force generation on the stiffest gels. We conclude that extracellular stiffness near that of native myocardium significantly enhances neonatal rat ventricular myocytes maturation. Deviations from ideal stiffness result in lower expression of sarcoplasmic/endoplasmic reticular calcium ATPase, less stored calcium, smaller calcium transients, and lower force. On very stiff substrates, this adaptation seems to involve RhoA kinase.