Design of a knee joint mechanism that adapts to individual physiology.

PubMed

Jiun-Yih Kuan; Pasch, Kenneth A; Herr, Hugh M

2014-01-01

This paper describes the design of a new knee joint mechanism, called the Adaptive Coupling Joint (ACJ). The new mechanism has an adaptive trajectory of the center of rotations (COR) that automatically matches those of the attached biological joint. The detailed design is presented as well as characterization results of the ACJ. Conventional exoskeleton and assistive devices usually consider limb joints as a one to three degrees of freedom (DOFs) joint synthesized by multiple one-DOF hinge joints in a single plane. However, the biological joints are complex and usually rotate with respect to a changing COR. As a result, the mismatch between limb joint motion and mechanical interface motion can lead to forces that cause undesired ligament and muscle length changes and internal mechanical changes. These undesired changes contribute to discomfort, as well as to the slippage and sluggish interaction between humans and devices. It is shown that the ACJ can transmit planetary torques from either active or passive devices to the limbs without altering the normal biological joint motion.

Recent advances in computational mechanics of the human knee joint.

PubMed

Kazemi, M; Dabiri, Y; Li, L P

2013-01-01

Computational mechanics has been advanced in every area of orthopedic biomechanics. The objective of this paper is to provide a general review of the computational models used in the analysis of the mechanical function of the knee joint in different loading and pathological conditions. Major review articles published in related areas are summarized first. The constitutive models for soft tissues of the knee are briefly discussed to facilitate understanding the joint modeling. A detailed review of the tibiofemoral joint models is presented thereafter. The geometry reconstruction procedures as well as some critical issues in finite element modeling are also discussed. Computational modeling can be a reliable and effective method for the study of mechanical behavior of the knee joint, if the model is constructed correctly. Single-phase material models have been used to predict the instantaneous load response for the healthy knees and repaired joints, such as total and partial meniscectomies, ACL and PCL reconstructions, and joint replacements. Recently, poromechanical models accounting for fluid pressurization in soft tissues have been proposed to study the viscoelastic response of the healthy and impaired knee joints. While the constitutive modeling has been considerably advanced at the tissue level, many challenges still exist in applying a good material model to three-dimensional joint simulations. A complete model validation at the joint level seems impossible presently, because only simple data can be obtained experimentally. Therefore, model validation may be concentrated on the constitutive laws using multiple mechanical tests of the tissues. Extensive model verifications at the joint level are still crucial for the accuracy of the modeling.

In Vivo Talocrural Joint Contact Mechanics With Functional Ankle Instability.

PubMed

Kobayashi, Takumi; Suzuki, Eiichi; Yamazaki, Naohito; Suzukawa, Makoto; Akaike, Atsushi; Shimizu, Kuniaki; Gamada, Kazuyoshi

2015-12-01

Functional ankle instability (FAI) may involve abnormal kinematics and contact mechanics during ankle internal rotation. Understanding of these abnormalities is important to prevent secondary problems in patients with FAI. However, there are no in vivo studies that have investigated talocrural joint contact mechanics during weightbearing ankle internal rotation. The objective of this study to determine talocrural contact mechanics during weightbearing ankle internal rotation in patients with FAI. Twelve male subjects with unilateral FAI (age range, 18-26 years) were enrolled. Computed tomography and fluoroscopic imaging of both lower extremities were obtained during weightbearing passive ankle joint complex rotation. Three-dimensional bone models created from the computed tomographic images were matched to the fluoroscopic images to compute 6 degrees of freedom for talocrural joint kinematics. The closest contact area in the talocrural joint in ankle neutral rotation and maximum internal rotation during either dorsiflexion or plantar flexion was determined using geometric bone models and talocrural joint kinematics data. The closest contact area in the talus shifted anteromedially during ankle dorsiflexion-internal rotation, whereas it shifted posteromedially during ankle plantar flexion-internal rotation. The closest contact area in FAI joints was significantly more medial than that in healthy joints during maximum ankle internal rotation and was associated with excessive talocrural internal rotation or inversion. This study demonstrated abnormal talocrural kinematics and contact mechanics in FAI subjects. Such abnormal kinematics may contribute to abnormal contact mechanics and may increase cartilage stress in FAI joints. Therapeutic, Level IV: cross-sectional case-control study. © 2015 The Author(s).

32 CFR 553.22 - Visitors' rules for the Arlington National Cemetery.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 3 2014-07-01 2014-07-01 false Visitors' rules for the Arlington National Cemetery. 553.22 Section 553.22 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY... authority from the Administrator, General Services Administration, the Secretary of Defense, and the...

Recent Advances in Computational Mechanics of the Human Knee Joint

PubMed Central

Kazemi, M.; Dabiri, Y.; Li, L. P.

2013-01-01

Computational mechanics has been advanced in every area of orthopedic biomechanics. The objective of this paper is to provide a general review of the computational models used in the analysis of the mechanical function of the knee joint in different loading and pathological conditions. Major review articles published in related areas are summarized first. The constitutive models for soft tissues of the knee are briefly discussed to facilitate understanding the joint modeling. A detailed review of the tibiofemoral joint models is presented thereafter. The geometry reconstruction procedures as well as some critical issues in finite element modeling are also discussed. Computational modeling can be a reliable and effective method for the study of mechanical behavior of the knee joint, if the model is constructed correctly. Single-phase material models have been used to predict the instantaneous load response for the healthy knees and repaired joints, such as total and partial meniscectomies, ACL and PCL reconstructions, and joint replacements. Recently, poromechanical models accounting for fluid pressurization in soft tissues have been proposed to study the viscoelastic response of the healthy and impaired knee joints. While the constitutive modeling has been considerably advanced at the tissue level, many challenges still exist in applying a good material model to three-dimensional joint simulations. A complete model validation at the joint level seems impossible presently, because only simple data can be obtained experimentally. Therefore, model validation may be concentrated on the constitutive laws using multiple mechanical tests of the tissues. Extensive model verifications at the joint level are still crucial for the accuracy of the modeling. PMID:23509602

Wnt signalling controls the response to mechanical loading during zebrafish joint development

PubMed Central

Brunt, Lucy H.; Begg, Katie; Kague, Erika; Cross, Stephen

2017-01-01

Joint morphogenesis requires mechanical activity during development. Loss of mechanical strain causes abnormal joint development, which can impact long-term joint health. Although cell orientation and proliferation are known to shape the joint, dynamic imaging of developing joints in vivo has not been possible in other species. Using genetic labelling techniques in zebrafish we were able, for the first time, to dynamically track cell behaviours in intact moving joints. We identify that proliferation and migration, which contribute to joint morphogenesis, are mechanically controlled and are significantly reduced in immobilised larvae. By comparison with strain maps of the developing skeleton, we identify canonical Wnt signalling as a candidate for transducing mechanical forces into joint cell behaviours. We show that, in the jaw, Wnt signalling is reduced specifically in regions of high strain in response to loss of muscle activity. By pharmacological manipulation of canonical Wnt signalling, we demonstrate that Wnt acts downstream of mechanical activity and is required for joint patterning and chondrocyte maturation. Wnt16, which is also downstream of muscle activity, controls proliferation and migration, but plays no role in chondrocyte intercalation. PMID:28684625

Space station rotary joint mechanisms

NASA Technical Reports Server (NTRS)

Driskill, Glen W.

1986-01-01

The mechanism which will be used on the space station to position the solar arrays and radiator panels for Sun pointing and Sun avoidance is described. The unique design features will be demonstrated on advanced development models of two of the joints being fabricated under contract to NASA-MSFC.

The Demise of School Board Collective Bargaining: Arlington, Virginia, 1976-7.

ERIC Educational Resources Information Center

Henderson, Diane D.

1980-01-01

In January 1977 the Virginia Supreme Court ruled local governing bodies did not have the power to enter into collective agreements with public employee groups. This paper traces the background of the lawsuit and examines the aftereffects of the decision on the Arlington School Board's organized employees. (Author/IRT)

46 CFR 154.506 - Mechanical expansion joint: Limits in a piping system.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Mechanical expansion joint: Limits in a piping system..., Construction and Equipment Cargo and Process Piping Systems § 154.506 Mechanical expansion joint: Limits in a piping system. Mechanical expansion joints in a piping system outside of a cargo tank: (a) May be...

46 CFR 154.506 - Mechanical expansion joint: Limits in a piping system.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Mechanical expansion joint: Limits in a piping system..., Construction and Equipment Cargo and Process Piping Systems § 154.506 Mechanical expansion joint: Limits in a piping system. Mechanical expansion joints in a piping system outside of a cargo tank: (a) May be...

46 CFR 154.506 - Mechanical expansion joint: Limits in a piping system.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Mechanical expansion joint: Limits in a piping system..., Construction and Equipment Cargo and Process Piping Systems § 154.506 Mechanical expansion joint: Limits in a piping system. Mechanical expansion joints in a piping system outside of a cargo tank: (a) May be...

46 CFR 154.506 - Mechanical expansion joint: Limits in a piping system.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Mechanical expansion joint: Limits in a piping system..., Construction and Equipment Cargo and Process Piping Systems § 154.506 Mechanical expansion joint: Limits in a piping system. Mechanical expansion joints in a piping system outside of a cargo tank: (a) May be...

46 CFR 154.506 - Mechanical expansion joint: Limits in a piping system.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Mechanical expansion joint: Limits in a piping system..., Construction and Equipment Cargo and Process Piping Systems § 154.506 Mechanical expansion joint: Limits in a piping system. Mechanical expansion joints in a piping system outside of a cargo tank: (a) May be...

Identification of Nonlinear Micron-Level Mechanics for a Precision Deployable Joint

NASA Technical Reports Server (NTRS)

Bullock, S. J.; Peterson, L. D.

1994-01-01

The experimental identification of micron-level nonlinear joint mechanics and dynamics for a pin-clevis joint used in a precision, adaptive, deployable space structure are investigated. The force-state mapping method is used to identify the behavior of the joint under a preload. The results of applying a single tension-compression cycle to the joint under a tensile preload are presented. The observed micron-level behavior is highly nonlinear and involves all six rigid body motion degrees-of-freedom of the joint. it is also suggests that at micron levels of motion modelling of the joint mechanics and dynamics must include the interactions between all internal components, such as the pin, bushings, and the joint node.

The Controllable Ball Joint Mechanism

NASA Astrophysics Data System (ADS)

Tung, Yung Cheng; Chieng, Wei-Hua; Ho, Shrwai

A controllable ball joint mechanism with three rotational degrees of freedom is proposed in this paper. The mechanism is composed of three bevel gears, one of which rotates with respect to a fixed frame and the others rotate with respect to individual floating frames. The output is the resultant motion of the differential motions by the motors that rotates the bevel gears at the fixed frame and the floating frames. The mechanism is capable of a large rotation, and the structure is potentially compact. The necessary inverse and forward kinematic analyses as well as the derivation of kinematic singularity are provided according to the kinematical equivalent structure described in this paper.

Polarity effect of electromigration on mechanical properties of lead-free solder joints

NASA Astrophysics Data System (ADS)

Ren, Fei

The trend of electronic packaging is to package the chips and the associated interconnections in a compact way that allows high speed operation; that allows for sufficient heat removal; that can withstand the thermal cycling associated with the turning on and turning off of the circuits; and that protects the circuits from environmental attack. These goals require that flip chip solder joints have higher resistance to electromigration, stronger mechanical property to sustain thermal mechanical stress, and are lead-free materials to satisfy environment and health concern. With lots of work on chemical reaction, electromigration and mechanical study in flip chip solder joints, however, the interaction between different driving forces is still little known. As a matter of fact, the combination study of chemical, electrical and mechanical is more and more significant to the understanding of the behavior of flip chip solder joints. In this dissertation, I developed one dimensional Cu (wire)-eutectic SnAgCu(ball)-Cu(wire) structure to investigate the interaction between electrical and mechanical force in lead-free solder joints. Electromigration was first conducted. The mechanical behaviors of solder joints before, after, and during electromigration were examined. Electrical current and mechanical stress were applied either in serial or in parallel to the solder joints. Tensile, creep, and drop tests, combined with different electrical current densities (1˜5x10 3A/cm2) and different stressing time (3˜144 hours), have been performed to study the effect of electromigration on the mechanical behavior of solder joints. Nano-indentation test was conducted to study the localized mechanical property of IMC at both interfaces in nanometer scale. Fracture images help analyze the failure mechanism of solder joints driven by both electrical and mechanical forces. The combination study shows a strain build-up during electromigration. Furthermore, a ductile-to-brittle transition in

Design and Evaluation of a Prosthetic Knee Joint Using the Geared Five-Bar Mechanism.

PubMed

Sun, Yuanxi; Ge, Wenjie; Zheng, Jia; Dong, Dianbiao

2015-11-01

This paper presents the mechanical design, dynamics analysis and ankle trajectory analysis of a prosthetic knee joint using the geared five-bar mechanism. Compared with traditional four-bar or six-bar mechanisms, the geared five-bar mechanism is better at performing diverse movements and is easy to control. This prosthetic knee joint with the geared five-bar mechanism is capable of fine-tuning its relative instantaneous center of rotation and ankle trajectory. The centrode of this prosthetic knee joint, which is mechanically optimized according to the centrode of human knee joint, is better in the bionic performance than that of a prosthetic knee joint using the four-bar mechanism. Additionally, the stability control of this prosthetic knee joint during the swing and stance phase is achieved by a motor. By adjusting the gear ratio of this prosthetic knee joint, the ankle trajectories of both unilateral and bilateral amputees show less deviations from expected than that of the four-bar knee joint.

Energy savings opportunity survey, Fort Myer, Arlington, Virginia, summer steam shut-down study: Volume 1 - executive summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-03-01

Fort Myer is a permanent United States Army installation located in Arlington County, Virginia, on a site backing Arlington National Cemetery and overlooking the Potomac River and Washington, D.C. The installation consists of offices, family housing, Army Band facilities, supporting facilities, and barracks buildings including those known as the `Old Guard Barracks` which house soldiers that provide services at Arlington National Cemetery. This report consists of the Summer Steam Shut Down Study of an Energy Savings Opportunity Survey (ESOS) at Fort Myer. The purpose of this study is to improve energy efficiency at Fort Myer by analyzing the effects andmore » benefits of closing the central steam producing boiler facility, Building 447, during the non-heating months from mid-May to mid-October. Currently, the central steam plant operates through this period to provide steam for domestic hot water, steam driven laundry presses, air conditioning system reheat, food preparation and dishwashing demands of twenty-two buildings on the base.« less

Arlington/Alexandria 1990-1991 REEP Workplace Literacy Training Project. Final Evaluation Report.

ERIC Educational Resources Information Center

Peterson, Morris

As part of the National Workplace Literacy Program, the 1990-1991 Arlington Education and Employment Program (REEP) served 333 functionally illiterate limited English proficient (LEP) adults working in Virginia hotels at entry level jobs in housekeeping, food and beverage service, and maintenance. Training in workplace literacy and…

32 CFR 553.15 - Persons eligible for burial in Arlington National Cemetery.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 3 2014-07-01 2014-07-01 false Persons eligible for burial in Arlington National Cemetery. 553.15 Section 553.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY MILITARY RESERVATIONS AND NATIONAL CEMETERIES ARMY NATIONAL CEMETERIES § 553.15 Persons...

Mechanical flexible joint design document

NASA Technical Reports Server (NTRS)

Daily, Vic

1993-01-01

The purpose of this report is to document the status of the Mechanical Flexible Joint (MFJ) Design Subtask with the intent of halting work on the design. Recommendations for future work is included in the case that the task is to be resumed. The MFJ is designed to eliminate two failure points from the current flex joint configuration, the inner 'tripod configuration' and the outer containment jacket. The MFJ will also be designed to flex 13.5 degrees and have three degrees of freedom. By having three degrees of freedom, the MFJ will allow the Low Pressure Fuel Duct to twist and remove the necessity to angulate the full 11 degrees currently required. The current flex joints are very labor intensive and very costly and a simple alternative is being sought. The MFJ is designed with a greater angular displacement, with three degrees of freedom, to reside in the same overall envelope, to meet weight constraints of the current bellows, to be compatible with cryogenic fuel and oxidizers, and also to be man-rated.

Functional joint regeneration is achieved using reintegration mechanism in Xenopus laevis

PubMed Central

Yamada, Shigehito

2016-01-01

Abstract A functional joint requires integration of multiple tissues: the apposing skeletal elements should form an interlocking structure, and muscles should insert into skeletal tissues via tendons across the joint. Whereas newts can regenerate functional joints after amputation, Xenopus laevis regenerates a cartilaginous rod without joints, a “spike.” Previously we reported that the reintegration mechanism between the remaining and regenerated tissues has a significant effect on regenerating joint morphogenesis during elbow joint regeneration in newt. Based on this insight into the importance of reintegration, we amputated frogs’ limbs at the elbow joint and found that frogs could regenerate a functional elbow joint between the remaining tissues and regenerated spike. During regeneration, the regenerating cartilage was partially connected to the remaining articular cartilage to reform the interlocking structure of the elbow joint at the proximal end of the spike. Furthermore, the muscles of the remaining part inserted into the regenerated spike cartilage via tendons. This study might open up an avenue for analyzing molecular and cellular mechanisms of joint regeneration using Xenopus. PMID:27499877

Comments on the Yule Marble Haines block: potential replacement, Tomb of the Unknown Soldier, Arlington National Cemetery

USGS Publications Warehouse

Mossotti, Victor G.

2014-01-01

Marble for the Tomb of the Unknown Soldier at Arlington National Cemetery was cut from the Colorado Yule Marble Quarry in 1931. Although anecdotal reports suggest that cracks were noticed in the main section of the monument shortly after its installation at the Arlington National Cemetery in Arlington, Virginia, detailed documentation of the extent of cracking did not appear until 1963. Although debate continues as to whether the main section of the Tomb of the Unknowns monument should be repaired or replaced, Mr. John S. Haines of Glenwood Springs, Colorado, in anticipation of the permanent closing of the Yule Quarry, donated a 58-ton block of Yule Marble, the so-called Haines block, as a potential backup. The brief study reported here was conducted during mid-summer 2009 at the behest of the superintendent of Arlington National Cemetery. The field team entered the subterranean Yule Marble Quarry with the Chief Extraction Engineer in order to contrast the method used for extraction of the Haines block with the method that was probably used to extract the marble block that is now cracked. Based on surficial inspection and shallow coring of the Haines block, and on the nature of crack propagation in Yule Marble as judged by close inspection of a large collection of surrogate Yule Marble blocks, the team found the block to be structurally sound and cosmetically equivalent to the marble used for the current monument. If the Haines block were needed, it would be an appropriate replacement for the existing cracked section of the Tomb of the Unknown Soldier Monument.

Novel knee joint mechanism of transfemoral prosthesis for stair ascent.

PubMed

Inoue, Koh; Wada, Takahiro; Harada, Ryuchi; Tachiwana, Shinichi

2013-06-01

The stability of a transfemoral prosthesis when walking on flat ground has been established by recent advances in knee joint mechanisms and their control methods. It is, however, difficult for users of a transfemoral prosthesis to ascend stairs. This difficulty is mainly due to insufficient generation of extension moment around the knee joint of the prosthesis to lift the body to the next step on the staircase and prevent any unexpected flexion of the knee joint in the stance phase. Only a prosthesis with an actuator has facilitated stair ascent using a step-over-step gait (1 foot is placed per step). However, its use has issues associated with the durability, cost, maintenance, and usage environment. Therefore, the purpose of this research is to develop a novel knee joint mechanism for a prosthesis that generates an extension moment around the knee joint in the stance phase during stair ascent, without the use of any actuators. The proposed mechanism is based on the knowledge that the ground reaction force increases during the stance phase when the knee flexion occurs. Stair ascent experiments with the prosthesis showed that the proposed prosthesis can realize stair ascent without any undesirable knee flexion. In addition, the prosthesis is able to generate a positive knee joint moment power in the stance phase even without any power source.

Monitoring of Airport Revenues at Arlington Municipal Airport; Federal Aviation Administration Northwest Mountain Region

DOT National Transportation Integrated Search

1997-01-15

The objectives of our audit were to determine whether Federal Aviation : Administration (FAA) monitoring of Arlington Municipal Airport (Airport) was : adequate to ensure (i) a fee and rental structure was maintained which made the : Airport as self-...

Mechanical model of suture joints with fibrous connective layer

NASA Astrophysics Data System (ADS)

Miroshnichenko, Kateryna; Liu, Lei; Tsukrov, Igor; Li, Yaning

2018-02-01

A composite model for suture joints with a connective layer of aligned fibers embedded in soft matrix is proposed. Based on the principle of complementary virtual work, composite cylinder assemblage (CCA) approach and generalized self-consistent micro-mechanical models, a hierarchical homogenization methodology is developed to systematically quantify the synergistic effects of suture morphology and fiber orientation on the overall mechanical properties of sutures. Suture joints with regular triangular wave-form serve as an example material system to apply this methodology. Both theoretical and finite element mechanical models are developed and compared to evaluate the overall normal stiffness of sutures as a function of wavy morphology of sutures, fiber orientation, fiber volume fraction, and the mechanical properties of fibers and matrix in the interfacial layer. It is found that generally due to the anisotropy-induced coupling effects between tensile and shear deformation, the effective normal stiffness of sutures is highly dependent on the fiber orientation in the connective layer. Also, the effective shear modulus of the connective layer and the stiffness ratio between the fiber and matrix significantly influence the effects of fiber orientation. In addition, optimal fiber orientations are found to maximize the stiffness of suture joints.

Adjustable-Torque Truss-Joint Mechanism

NASA Technical Reports Server (NTRS)

Bush, Harold G.; Wallsom, Richard E.

1993-01-01

Threaded pin tightened or loosened; tedious trial-and-error procedure shortened. Mechanism joining strut and node in truss structure preloaded to desired stress to ensure tight, compressive fit preventing motion of strut during loading or vibration. Preload stress on stack of Belleville spring washers adjusted by tightening or loosening threaded Belleville-washer-alignment pin. Pin turned, by use of allen wrench, to adjust compression preload on Belleville washers and adjusts joint-operating torque.

Mechanical Behavior of Dowel-Type Joints Made of Wood Scrimber Composite

PubMed Central

He, Minjuan; Tao, Duo; Li, Zheng; Li, Maolin

2016-01-01

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research. PMID:28773703

Mechanical Behavior of Dowel-Type Joints Made of Wood Scrimber Composite.

PubMed

He, Minjuan; Tao, Duo; Li, Zheng; Li, Maolin

2016-07-15

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research.

Orthotic arm joint. [for use in mechanical arms

NASA Technical Reports Server (NTRS)

Dane, D. H. (Inventor)

1974-01-01

An improved orthopedic (orthotic) arm joint that can be used in various joint of mechanical arms is described. The arm joints includes a worm, which is coupled to an electric motor for rotating a worm gear carried within a rotatable housing. The worm gear is supported on a thrust bearing and the rotatable housing is supported on a radial thrust bearing. A bolt extends through the housing, bearings, and worm gear for securing the device together. A potentiometer extends through the bolt, and is coupled to the rotatable housing for rotating therewith, so as to produce an electrical signal indicating the angular position of the rotatable housing.

32 CFR Appendix A to Part 553 - Specifications for Tributes in Arlington National Cemetery

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 3 2014-07-01 2014-07-01 false Specifications for Tributes in Arlington National Cemetery A Appendix A to Part 553 National Defense Department of Defense (Continued) DEPARTMENT OF... Organizations and State Department of Veterans Organizations published annually by the Veterans Administration...

Experimental analysis of mechanical joints strength by means of energy dissipation

NASA Astrophysics Data System (ADS)

Wolf, Alexander; Lafarge, Remi; Kühn, Tino; Brosius, Alexander

2018-05-01

Designing complex structures with the demand for weight reduction leads directly to a multi-material concept. This mixture has to be joined securely and welding, mechanical joining and the usage of adhesives are commonly used for that purpose. Sometimes also a mix of at least two materials is useful to combine the individual advantages. The challenge is the non-destructive testing of these connections because destructive testing requires a lot of preparation and expensive testing equipment. The authors show a testing method by measuring and analysing the energy dissipation in mechanical joints. Known methods are radiography, thermography and ultrasound testing. Unfortunately, the usage of these methods is difficult and often not usable in fibre-reinforced-plastics. The presented approach measures the propagation of the elastic strain wave through the joint. A defined impact strain is detected with by strain-gauges whereby the transmitter is located on one side of the joint and the receiver on the other, respectively. Because of different mechanisms, energy dissipates by passing the joint areas. Main reasons are damping caused by friction and material specific damping. Insufficient performed joints lead to an effect especially in the friction damping. By the measurement of the different strains and the resulting energy loss a statement to the connection quality is given. The possible defect during the execution of the joint can be identified by the energy loss and strain vs. time curve. After the description of the method, the authors present the results of energy dissipation measurements at a bolted assembly with different locking torques. By the adjustable tightening torques for the screw connections easily a variation of the contact pressure can be applied and analysed afterwards. The outlook will give a statement for the usability for other mechanical joints and fibre-reinforced-plastics.

Failure mechanisms in wood joints bonded with urea-formaldehyde adhesives

Treesearch

B.H. River; R.O. Ebewele; G.E. Myers

1994-01-01

Wood joints bonded with urea-formaldehyde (UF) are weakened by cyclic swelling and shrinking. To study the failure mechanisms in UF-bonded joints, specimens were bonded with unmodified, modified (amine), or phenol formaldehyde adhesive and subjected to accelerated aging. Modification of the adhesive properties increased the cleavage fracture toughness and shear...

Muscle-Specific Effective Mechanical Advantage and Joint Impulse in Weightlifting.

PubMed

Kipp, Kristof; Harris, Chad

2017-07-01

Kipp, K, and Harris, C. Muscle-specific effective mechanical advantage and joint impulse in weightlifting. J Strength Cond Res 31(7): 1905-1910, 2017-Lifting greater loads during weightlifting exercises may theoretically be achieved through increasing the magnitudes of net joint impulses or manipulating the joints' effective mechanical advantage (EMA). The purpose of this study was to investigate muscle-specific EMA and joint impulse as well as impulse-momentum characteristics of the lifter-barbell system across a range of external loads during the execution of the clean. Collegiate-level weightlifters performed submaximal cleans at 65, 75, and 85% of their 1-repetition maximum (1-RM), whereas data from a motion analysis system and a force plate were used to calculate lifter-barbell system impulse and velocity, as well as net extensor impulse generated at the hip, knee, and ankle joints and the EMA of the gluteus maximus, hamstrings, quadriceps, and triceps surae muscles. The results indicated that the lifter-barbell system impulse did not change as load increased, whereas the velocity of the lifter-barbell system decreased with greater load. In addition, the net extensor impulse at all joints increased as load increased. The EMA of all muscles did not, however, change as load increased. The load-dependent effects on the impulse-velocity characteristics of the lifter-barbell system may reflect musculoskeletal force-velocity behaviors, and may further indicate that the weightlifting performance is limited by the magnitude of ground reaction force impulse. In turn, the load-dependent effects observed at the joint level indicated that lifting greater loads were due to greater net extensor impulses generated at the joints of the lower extremity and not greater EMAs of the respective extensor muscles. In combination, these results suggest that lifting greater external loads during the clean is due to the ability to generate large extensor joint impulses, rather than

The effects of load carriage and muscle fatigue on lower-extremity joint mechanics.

PubMed

Wang, He; Frame, Jeff; Ozimek, Elicia; Leib, Daniel; Dugan, Eric L

2013-09-01

Military personnel are commonly afflicted by lower-extremity overuse injuries. Load carriage and muscular fatigue are major stressors during military basic training. To examine effects of load carriage and muscular fatigue on lower-extremity joint mechanics during walking. Eighteen men performed the following tasks: unloaded walking, walking with a 32-kg load, fatigued walking with a 32-kg load, and fatigued walking. After the second walking task, muscle fatigue was elicited through a fatiguing protocol consisting of metered step-ups and heel raises with a 16-kg load. Each walking task was performed at 1.67 m x s(-1) for 5 min. Walking movement was tracked by a VICON motion capture system at 120 Hz. Ground reaction forces were collected by a tandem force instrumented treadmill (AMTI) at 2,400 Hz. Lower-extremity joint mechanics were calculated in Visual 3D. There was no interaction between load carriage and fatigue on lower-extremity joint mechanics (p > .05). Both load carriage and fatigue led to pronounced alterations of lower-extremity joint mechanics (p < .05). Load carriage resulted in increases of pelvis anterior tilt, hip and knee flexion at heel contact, and increases of hip, knee, and ankle joint moments and powers during weight acceptance. Muscle fatigue led to decreases of ankle dorsiflexion at heel contact, dorsiflexor moment, and joint power at weight acceptance. In addition, muscle fatigue increased demand for hip extensor moment and power at weight acceptance. Statistically significant changes in lower-extremity joint mechanics during loaded and fatigued walking may expose military personnel to increased risk for overuse injuries.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

PubMed

Bezci, Semih E; Eleswarapu, Ananth; Klineberg, Eric O; O'Connell, Grace D

2018-02-12

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Effect of Nd:YAG laser beam welding on weld morphology and mechanical properties of Ti-6Al-4V butt joints and T-joints

NASA Astrophysics Data System (ADS)

Kashaev, Nikolai; Ventzke, Volker; Fomichev, Vadim; Fomin, Fedor; Riekehr, Stefan

2016-11-01

A Nd:YAG single-sided laser beam welding process study for Ti-6Al-4V butt joints and T-joints was performed to investigate joining techniques with regard to the process-weld morphology relationship. An alloy compatible filler wire was used to avoid underfills and undercuts. The quality of the butt joints and T-joints was characterized in terms of weld morphology, microstructure and mechanical properties. Joints with regular shapes, without visible cracks, pores, and geometrical defects were achieved. Tensile tests revealed high joint integrity in terms of strength and ductility for both the butt joint and T-joint geometries. Both the butt joints and T-joints showed base material levels of strength. The mechanical performance of T-joints was also investigated using pull-out tests. The performance of the T-joints in such tests was sensitive to the shape and morphology of the welds. Fracture always occurred in the weld without any plastic deformation in the base material outside the weld.

Village of Arlington Heights et al. v. Metropolitan Housing Development Corp. et al. Certiorari to the United States Court of Appeals for the Seventh Circuit. Syllabus.

ERIC Educational Resources Information Center

Supreme Court of the U. S., Washington, DC.

This document presents the Supreme Court decision in the law suit between the Village of Arlington Heights, Illinois, and the Metropolitan Housing Development Corporation (MHDC). MHDC, a nonprofit developer contracted to purchase a tract within the boundaries of the Village of Arlington Heights, Illinois in order to build racially integrated low…

32 CFR Appendix A to Part 553 - Specifications for Tributes in Arlington National Cemetery

Code of Federal Regulations, 2012 CFR

2012-07-01

... inscription of a tribute already presented in Memory of the Unknown Soldier (World War I) may be reworded by... of World War II —The Unknown of the Korean War —The Unknown American of World War II —The Unknown... 553—Specifications for Tributes in Arlington National Cemetery 1. Purpose. The appendix provides...

32 CFR Appendix A to Part 553 - Specifications for Tributes in Arlington National Cemetery

Code of Federal Regulations, 2011 CFR

2011-07-01

... inscription of a tribute already presented in Memory of the Unknown Soldier (World War I) may be reworded by... of World War II —The Unknown of the Korean War —The Unknown American of World War II —The Unknown... 553—Specifications for Tributes in Arlington National Cemetery 1. Purpose. The appendix provides...

Mechanical instability destabilises the ankle joint directly in the ankle-sprain mechanism.

PubMed

Gehring, Dominic; Faschian, Katrin; Lauber, Benedikt; Lohrer, Heinz; Nauck, Tanja; Gollhofer, Albert

2014-03-01

Despite massive research efforts, it remains unclear how mechanical ankle instability (MAI) and functional ankle instability (FAI) affect joint control in the situation of ankle sprain. Thus, the purpose of this study was to evaluate whether individuals with MAI have deficits in stabilising their ankle joint in a close-to-injury situation compared with those with FAI and healthy controls. Ankle-joint control was assessed by means of three-dimensional motion analysis and electromyography in participants with FAI and MAI (n=19), in participants with pure FAI (n=9) and in healthy controls (n=18). Close-to-injury situations were simulated during standing, walking and jumping by means of a custom-made tilt platform. Individuals with FAI and MAI displayed significantly greater maximum ankle inversion angles (+5°) and inversion velocities (+50°/s) in the walking and jumping conditions compared to those with pure FAI and controls. Furthermore, individuals in the FAI and MAI group showed a significantly decreased pre-activation of the peroneus longus muscle during jumping compared to those with FAI. No differences between groups were found for plantar flexion and internal rotation, or for muscle activities following tilting of the platform. The present study demonstrates that MAI is characterised by impairments of ankle-joint control in close-to-injury situations. This could make these individuals more prone to recurrent ankle sprains, and suggests the need for additional mechanical support such as braces or even surgery. In addition, the study highlights the fact that dynamic experimental test conditions in the acting participant are needed to further unravel the mystery of chronic ankle instability.

Atlantic white cedar: ecology, restoration, and management: Proceedings of the Arlington Echo symposium

Treesearch

Philip Sheridan

2005-01-01

A symposium was held on the globally threatened and coastally restricted tree species, Atlantic white-cedar (Chamaecyparis thyoides (L) B.S.P.) at the Arlington Echo Outdoor Education Center, Millersville, MD, in June 2003. The theme of the symposium was “Uniting Forces for Action,” and participants in the symposium came from throughout the range of this species, from...

The University of Texas at Arlington's Virtual Reference Service: An Evaluation by the Reference Staff

ERIC Educational Resources Information Center

Casebier, Katherine D.

2006-01-01

The University of Texas at Arlington's Library began using an online chat reference in 2002. The service, called Collaborative Digital Reference Service, later became "Ask a Librarian." Slightly over one year later, the library joined the University of Texas System's "Ask a Librarian" service. Both services are powered by…

32 CFR Appendix A to Part 553 - Specifications for Tributes in Arlington National Cemetery

Code of Federal Regulations, 2013 CFR

2013-07-01

... —The Unknown Soldier —The Unknown of World War II —The Unknown of the Korean War —The Unknown American of World War II —The Unknown American of the Korean War The identity of the donor/Date of... Appendix A to Part 553—Specifications for Tributes in Arlington National Cemetery 1. Purpose. The appendix...

77 FR 41873 - In the Matter of Alternative Energy Sources, Inc., Arlington Hospitality, Inc., Consolidated Oil...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-16

... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] In the Matter of Alternative Energy Sources, Inc., Arlington Hospitality, Inc., Consolidated Oil & Gas, Inc., CSMG Technologies, Inc., Dakotah... Alternative Energy Sources, Inc. because it has not filed any periodic reports since the period ended...

Intensity-level assessment of lower body plyometric exercises based on mechanical output of lower limb joints.

PubMed

Sugisaki, Norihide; Okada, Junichi; Kanehisa, Hiroaki

2013-01-01

The present study aimed to quantify the intensity of lower extremity plyometric exercises by determining joint mechanical output. Ten men (age, 27.3 ± 4.1 years; height, 173.6 ± 5.4 cm; weight, 69.4 ± 6.0 kg; 1-repetition maximum [1RM] load in back squat 118.5 ± 12.0 kg) performed the following seven plyometric exercises: two-foot ankle hop, repeated squat jump, double-leg hop, depth jumps from 30 and 60 cm, and single-leg and double-leg tuck jumps. Mechanical output variables (torque, angular impulse, power, and work) at the lower limb joints were determined using inverse-dynamics analysis. For all measured variables, ANOVA revealed significant main effects of exercise type for all joints (P < 0.05) along with significant interactions between joint and exercise (P < 0.01), indicating that the influence of exercise type on mechanical output varied among joints. Paired comparisons revealed that there were marked differences in mechanical output at the ankle and hip joints; most of the variables at the ankle joint were greatest for two-foot ankle hop and tuck jumps, while most hip joint variables were greatest for repeated squat jump or double-leg hop. The present results indicate the necessity for determining mechanical output for each joint when evaluating the intensity of plyometric exercises.

Behavior of stress generated in semiconductor chips with high-temperature joints: Influence of mechanical properties of joint materials

NASA Astrophysics Data System (ADS)

Ito, H.; Kuwahara, M.; Ohta, R.; Usui, M.

2018-04-01

High-temperature joint materials are indispensable to realizing next-generation power modules with high-output performance. However, crack initiation resulting from stress concentration in semiconductor chips joined with high-temperature joint materials remains a critical problem in high-temperature operation. Therefore, clarifying the quantitative influence of joint materials on the stress generated in chips is essential. This study investigates the stress behavior of chips joined by Ni-Sn solid-liquid interdiffusion (SLID), which results in a high-temperature joint material likely to generate cracks after joining or when under thermal cycling. The results are compared with those fabricated using three types of solders, Pb-10%Sn, Sn-0.7%Cu, and Sn-10%Sb (mass %), which are conventional joint materials with different melting points and mechanical properties. Using Ni-Sn SLID results in the generation of high compressive stress (500 MPa) without stress relaxation after the joining process in contrast to the case of solders in which the compressive stresses are low (<300 MPa) and decrease to still lower levels (<250 MPa). In addition, no stress relaxation occurs during thermal cycling when using Ni-Sn SLID, whereas stress relaxation is clearly observed during heating to 200 °C using solders. Different stress behaviors between Ni-Sn SLID and other joint materials are illustrated by their mechanical strength and resistance against plastic and creep deformation. These results suggest that stress relaxation in a chip is key in suppressing crack initiation in highly reliable modules during high-temperature operation.

Interfacial microstructure and mechanical properties of brazed aluminum / stainless steel - joints

NASA Astrophysics Data System (ADS)

Fedorov, V.; Elßner, M.; Uhlig, T.; Wagner, G.

2017-03-01

Due to the demand of mass and cost reduction, joints based on dissimilar metals become more and more interesting. Especially there is a high interest for joints between stainless steel and aluminum, often necessary for example for automotive heat exchangers. Brazing offers the possibilities to manufacture several joints in one step at, in comparison to fusion welding, lower temperatures. In the recent work, aluminum / stainless steel - joints are produced by induction brazing using an AlSi10 filler and a non-corrosive flux. The mechanical properties are determined by tensile shear tests as well as fatigue tests at ambient and elevated temperatures. The microstructure of the brazed joints and the fracture surfaces of the tested samples are investigated by SEM.

Mechanical Behavior of CFRP Lattice Core Sandwich Bolted Corner Joints

NASA Astrophysics Data System (ADS)

Zhu, Xiaolei; Liu, Yang; Wang, Yana; Lu, Xiaofeng; Zhu, Lingxue

2017-12-01

The lattice core sandwich structures have drawn more attention for the integration of load capacity and multifunctional applications. However, the connection of carbon fibers reinforced polymer composite (CFRP) lattice core sandwich structure hinders its application. In this paper, a typical connection of two lattice core sandwich panels, named as corner joint or L-joint, was investigated by experiment and finite element method (FEM). The mechanical behavior and failure mode of the corner joints were discussed. The results showed that the main deformation pattern and failure mode of the lattice core sandwich bolted corner joints structure were the deformation of metal connector and indentation of the face sheet in the bolt holes. The metal connectors played an important role in bolted corner joints structure. In order to save the calculation resource, a continuum model of pyramid lattice core was used to replace the exact structure. The computation results were consistent with experiment, and the maximum error was 19%. The FEM demonstrated the deflection process of the bolted corner joints structure visually. So the simplified FEM can be used for further analysis of the bolted corner joints structure in engineering.

Mechanical Behaviour of Bolted Joints Under Impact Rates of Loading

DTIC Science & Technology

2012-01-01

Joints in Glass Fibre / Epoxy Laminates. Composites, Volume 16. No 2. Kolsky, H. (1949). An Investigation of the Mechanical Properties of Materials at...and equations 2.1 and 2, Figures 2.3, 2.4, and 2.5 were constructed to determine optimal specimen properties for later testing of bolted joints of...9.5 l/d=11.5 UNCLASSIFIED UNCLASSIFIED 2.5 Discussion Ideal specimen properties are high total equilibrium times, low equilibrium start times and

Altered Tibiofemoral Joint Contact Mechanics and Kinematics in Patients with Knee Osteoarthritis and Episodic Complaints of Joint Instability

PubMed Central

Farrokhi, Shawn; Voycheck, Carrie A.; Klatt, Brian A.; Gustafson, Jonathan A.; Tashman, Scott; Fitzgerald, G. Kelley

2014-01-01

Background To evaluate knee joint contact mechanics and kinematics during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. Methods Forty-three subjects, 11 with medial compartment knee osteoarthritis and self-reported instability (unstable), 7 with medial compartment knee osteoarthritis but no reports of instability (stable), and 25 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a downhill gait task on a treadmill. Findings The medial compartment contact point excursions were longer in the unstable group compared to the stable (p=0.046) and the control groups (p=0.016). The peak medial compartment contact point velocity was also greater for the unstable group compared to the stable (p=0.047) and control groups (p=0.022). Additionally, the unstable group demonstrated a coupled movement pattern of knee extension and external rotation after heel contact which was different than the coupled motion of knee flexion and internal rotation demonstrated by stable and control groups. Interpretation Our findings suggest that knee joint contact mechanics and kinematics are altered during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. The observed longer medial compartment contact point excursions and higher velocities represent objective signs of mechanical instability that may place the arthritic knee joint at increased risk for disease progression. Further research is indicated to explore the clinical relevance of altered contact mechanics and kinematics during other common daily activities and to assess the efficacy of rehabilitation programs to improve altered joint biomechanics in knee osteoarthritis patients with self-reported instability. PMID:24856791

An investigation into the mechanism for enhanced mechanical properties in friction stir welded AA2024-T3 joints coated with cold spraying

NASA Astrophysics Data System (ADS)

Li, N.; Li, W. Y.; Yang, X. W.; Feng, Y.; Vairis, A.

2018-05-01

Using cold spraying (CS), a surface layer with a modified microstructure and enhanced mechanical properties was formed on a 3.2 mm thick friction stir welded (FSWed) AA2024-T3 joint. The combined effect of "shot peening effect (SPE)" and "heat flow effect (HFE)" during CS were used to enhance joint mechanical properties. The microstructure evolution of the FSWed AA2024-T3 joints in the surface layer following CS coatings and their effect on mechanical properties were systematically characterized with electron back-scattered diffraction, transmission electron microscopy, differential scanning calorimetry and mechanical tests. Based on these experiments, a grain refinement, finer and more S phases, and improved amount of Guinier-Preston-Bagaryatsky (GPB) zones produced by CS treatments are proposed. The deposition of aluminum coating on the joint, lead to hardness recovery in the stir zone and the development of two low hardness zones as the density of GPB increased. The tensile properties of FSWed AA2024-T3 joints improved with the application of the aluminum coatings. Experiments and analysis of the enhanced mechanical properties mechanism indicate that SPE with a high plastic deformation and HFE with an intensive heat flow are necessary for the production of refined grains and increased numbers of GPB zones.

Design optimization of dual-axis driving mechanism for satellite antenna with two planar revolute clearance joints

NASA Astrophysics Data System (ADS)

Bai, Zheng Feng; Zhao, Ji Jun; Chen, Jun; Zhao, Yang

2018-03-01

In the dynamic analysis of satellite antenna dual-axis driving mechanism, it is usually assumed that the joints are ideal or perfect without clearances. However, in reality, clearances in joints are unavoidable due to assemblage, manufacturing errors and wear. When clearance is introduced to the mechanism, it will lead to poor dynamic performances and undesirable vibrations due to impact forces in clearance joint. In this paper, a design optimization method is presented to reduce the undesirable vibrations of satellite antenna considering clearance joints in dual-axis driving mechanism. The contact force model in clearance joint is established using a nonlinear spring-damper model and the friction effect is considered using a modified Coulomb friction model. Firstly, the effects of clearances on dynamic responses of satellite antenna are investigated. Then the optimization method for dynamic design of the dual-axis driving mechanism with clearance is presented. The objective of the optimization is to minimize the maximum absolute vibration peak of antenna acceleration by reducing the impact forces in clearance joint. The main consideration here is to optimize the contact parameters of the joint elements. The contact stiffness coefficient, damping coefficient and the dynamic friction coefficient for clearance joint elements are taken as the optimization variables. A Generalized Reduced Gradient (GRG) algorithm is used to solve this highly nonlinear optimization problem for dual-axis driving mechanism with clearance joints. The results show that the acceleration peaks of satellite antenna and contact forces in clearance joints are reduced obviously after design optimization, which contributes to a better performance of the satellite antenna. Also, the application and limitation of the proposed optimization method are discussed.

Mechanical and Functional Properties of Nickel Titanium Adhesively Bonded Joints

NASA Astrophysics Data System (ADS)

Niccoli, F.; Alfano, M.; Bruno, L.; Furgiuele, F.; Maletta, C.

2014-07-01

In this study, adhesive joints made up of commercial NiTi sheets with shape memory capabilities are analyzed. Suitable surface pre-treatments, i.e., degreasing, sandblasting, and chemical etching, are preliminary compared in terms of surface roughness, surface energy, and substrate thinning. Results indicate that chemical etching induces marked substrate thinning without substantial gains in terms of surface roughness and free energy. Therefore, adhesive joints with degreased and sandblasted substrates are prepared and tested under both static and cyclic conditions, and damage development within the adhesive layer is monitored in situ using a CCD camera. Sandblasted specimens have a significantly higher mechanical static strength with respect to degreased ones, although they essentially fail in similar fashion, i.e., formation of microcracks followed by decohesion along the adhesive/substrate interface. In addition, the joints show a good functional response with almost complete shape memory recovery after thermo-mechanical cycling, i.e., a small accumulation of residual deformations occurs. The present results show that adhesive bonding is a viable joining technique for NiTi alloys.

Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures

DTIC Science & Technology

1988-03-01

Safety Factors for Use When Designing bolted Joints In GRP," Composites , April 1979, pp. M376. 93. Dastln, S., "Joining and Machining Techniques... MACHINE SPACER LOCKmm STEEL PLATE FASTENER 203 mm OR DOWEL FiN EXTENSOMETER EXTENSOMETER TGAUGE LENGTH ATTACHMENT COMPOSITE - PLATE 31 mm p NOTE: NOT TO...No.427 Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures DTIC CXVTflUTION STATEME~r £ELECTE Approved fm Vubhc sIlam l JUL

Literature Review on the Design of Composite Mechanically Fastened Joints (Revue de la Documentation sur la Conception des Joints a Liaison Mecanique en Composites),

DTIC Science & Technology

1986-02-01

mechanics Eisenmann (32) established a bolted joint static strength prediction model based on fracture mechanics for composite materials. The failure...34 Composite Materials, Volume 2, Academic Press, 1974, pp. 353-431. 32. Eisenmann , J.R., "Bolted Joint Static Strength Model for Composite Materials," NASA

Review of the Third Year of the Partial Immersion Program at Key Elementary School, Arlington, Virginia.

ERIC Educational Resources Information Center

Rhodes, Nancy C.

The third year of the partial immersion program in grades one through three at Key Elementary School (Arlington, Virginia), where half the day is taught in English and half in Spanish, is reported. The review includes classroom observations, student and teacher interviews, student assessment, and parent and staff interviews. Student assessments…

An analysis of secondary road maintenance payments to Henrico and Arlington counties with the December 2001 update.

DOT National Transportation Integrated Search

2002-01-01

In 1986, 33.1-23.5:1 of the Code of Virginia established new rates for payments to Henrico and Arlington counties to maintain their secondary roads and specified how the rates were to be adjusted annually. The rates specified for 1986 maintenance pay...

Experimental Investigation of the Influence of Joint Geometric Configurations on the Mechanical Properties of Intermittent Jointed Rock Models Under Cyclic Uniaxial Compression

NASA Astrophysics Data System (ADS)

Liu, Yi; Dai, Feng; Fan, Pengxian; Xu, Nuwen; Dong, Lu

2017-06-01

Intermittent joints in rock mass are quite sensitive to cyclic loading conditions. Understanding the fatigue mechanical properties of jointed rocks is beneficial for rational design and stability analysis of rock engineering projects. This study experimentally investigated the influences of joint geometry (i.e., dip angle, persistency, density and spacing) on the fatigue mechanism of synthetic jointed rock models. Our results revealed that the stress-strain curve of jointed rock under cyclic loadings is dominated by its curve under monotonic uniaxial loadings; the terminal strain in fatigue curve is equal to the post-peak strain corresponding to the maximum cyclic stress in the monotonic stress-strain curve. The four joint geometrical parameters studied significantly affect the fatigue properties of jointed rocks, including the irreversible strains, the fatigue deformation modulus, the energy evolution, the damage variable and the crack coalescence patterns. The higher the values of the geometrical parameters, the lower the elastic energy stores in this jointed rock, the higher the fatigue damage accumulates in the first few cycles, and the lower the fatigue life. The elastic energy has certain storage limitation, at which the fatigue failure occurs. Two basic micro-cracks, i.e., tensile wing crack and shear crack, are observed in cyclic loading and unloading tests, which are controlled principally by joint dip angle and persistency. In general, shear cracks only occur in the jointed rock with higher dip angle or higher persistency, and the jointed rock is characterized by lower fatigue strength, larger damage variable and lower fatigue life.

Mechanical characteristics of welded joints between different stainless steels grades

NASA Astrophysics Data System (ADS)

Topolska, S.; Łabanowski, J.

2017-08-01

Investigation of mechanical characteristics of welded joints is one of the most important tasks that allow determining their functional properties. Due to the very high, still rising, cost of some stainless steels it is justified, on economic grounds, welding austenitic stainless steel with steels that are corrosion-resistant like duplex ones. According to forecasts the price of corrosion resistant steels stil can increase by 26 ÷ 30%. For technical reasons welded joints require appropriate mechanical properties such as: tensile strength, bending, ductility, toughness, and resistance to aggressive media. Such joints are applied in the construction of chemical tankers, apparatus and chemical plants and power steam stations. Using the proper binder makes possible the welds directly between the elements of austenitic stainless steels and duplex ones. It causes that such joits behave satisfactorily in service in such areas like maritime constructions and steam and chemical plants. These steels have high mechanical properties such as: the yield strength, the tensile strength and the ductility as well as the resistance to general corrosion media. They are resistant to both pitting and stress corrosions. The relatively low cost of production of duplex steels, in comparison with standard austenitic steels, is inter alia, the result of a reduced amount of scarce and expensive Nickel, which is seen as a further advantage of these steels.

A Study of Knee Joint Kinematics and Mechanics using a Human FE Model.

PubMed

Kitagawa, Yuichi; Hasegawa, Junji; Yasuki, Tsuyoshi; Iwamoto, Masami; Miki, Kazuo

2005-11-01

Posterior translation of the tibia with respect to the femur can stretch the posterior cruciate ligament (PCL). Fifteen millimeters of relative displacement between the femur and tibia is known as the Injury Assessment Reference Value (IARV) for the PCL injury. Since the anterior protuberance of the tibial plateau can be the first site of contact when the knee is flexed, the knee bolster is generally designed with an inclined surface so as not to directly load the projection in frontal crashes. It should be noted, however, that the initial flexion angle of the occupant knee can vary among individuals and the knee flexion angle can change due to the occupant motion. The behavior of the tibial protuberance related to the knee flexion angle has not been described yet. The instantaneous angle of the knee joint at the timing of restraining the knee should be known to manage the geometry and functions of knee restraint devices. The purposes of this study are first to understand the kinematics of the knee joint during flexion, and second to characterize the mechanics of the knee joint under anterior-posterior loading. A finite element model of the knee joint, extracted from the Total Human Model for Safety (THUMS), was used to analyze the mechanism. The model was validated against kinematics and mechanical responses of the human knee joint. By tracking the relative positions and angles between the patella and the tibia in a knee flexing simulation, the magnitude of the tibial anterior protuberance was described as a function of the knee joint angle. The model revealed that the mechanics of the knee joint was characterized as a combination of stiffness of the patella-femur structure and the PCL It was also found that the magnitude of the tibial anterior protuberance determined the amount of initial stretch of the PCL in anterior-posterior loading. Based on the knee joint kinematics and mechanics, an interference boundary was proposed for different knee flexion angles, so

Robust control of multi-jointed arm with a decentralized autonomous control mechanism

NASA Technical Reports Server (NTRS)

Kimura, Shinichi; Miyazaki, Ken; Suzuki, Yoshiaki

1994-01-01

A decentralized autonomous control mechanism applied to the control of three dimensional manipulators and its robustness to partial damage was assessed by computer simulation. Decentralized control structures are believed to be quite robust to time delay between the operator and the target system. A 10-jointed manipulator based on our control mechanism was able to continue its positioning task in three-dimensional space without revision of the control program, even after some of its joints were damaged. These results suggest that this control mechanism can be effectively applied to space telerobots, which are associated with serious time delay between the operator and the target system, and which cannot be easily repaired after being partially damaged.

Microstructure and Mechanical Properties of Friction Stir Welded Aluminum Alloy/Stainless Steel Lap Joints

NASA Astrophysics Data System (ADS)

Ogura, Tomo; Nishida, Taichi; Nishida, Hidehito; Yoshikawa, Syuhei; Yoshida, Takumi; Omichi, Noriko; Fujimoto, Mitsuo; Hirose, Akio

The mechanical properties and interfacial microstructure of an aluminum alloy/stainless steel dissimilar lap joint using friction stir welding (FSW) were characterized. In an FSWed A3003 aluminum alloy-SUS304 steel lap joint, the strength on the advancing side was larger than that at the retreating side. TEM observation indicated that a sound joint can be obtained from the stage of the formation of the amorphous layer owing to the mechanical alloying effects before the formation of intermetallic compounds. This lap joining technique was also successfully applied to A6061-T6 aluminum alloy-grooved SUS304 plates. The maximum tensile strength of the lap joint was approximately the same as that of the base alloy, however, the proof stress of the joint decreased with the dissolution of the β″ phase in the A6061 aluminium alloy, which is caused by the generation of heat during friction stir welding.

Safety assessment of Cracked K-joint Structure Based on Fracture Mechanics

NASA Astrophysics Data System (ADS)

Wang, Xin; Pengyu, Yan; Jianwei, Du; Fuhai, Cai

2017-05-01

The K-joint is the main bearing structure of lattice jib crane. During frequent operation of the crane, surface cracks often occur at its weld toe, and then continue to expand until failure. The safety of the weak structure K-joint of the crane jib can be evaluated by BS7910 failure assessment standard in order to improve its utilization. The finite element model of K-joint structure with cracks is established, and its mechanical properties is analyzed by ABAQUS software, the results show that the crack depth has a great influence on the bearing capacity of the structure compared with the crack length. It is assumed that the K-joint with the semi-elliptical surface crack under the action of the tension propagate stably under the condition that the c/a (ratio of short axis to long axis of ellipse) is about 0.3. The safety assessment of K-joint with different lengths crack is presented according to the 2A failure assessment diagram of BS7910, and the critical crack of K-joint under different loads can be obtained.

Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.

PubMed

Wu, Yue; Nan, Bo; Chen, Liang

2014-01-01

3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N.

Microstructure and Mechanical Properties of Resistance Spot Welding Joints of Carbonitrided Low-Carbon Steels

NASA Astrophysics Data System (ADS)

Taweejun, Nipon; Poapongsakorn, Piyamon; Kanchanomai, Chaosuan

2017-04-01

Carbonitrided low-carbon steels are resistance welded in various engineering components. However, there are no reports on the microstructure and mechanical properties of their resistance spot welding (RSW) joints. Therefore, various carbonitridings were performed on the low-carbon steel sheets, and then various RSWs were applied to these carbonitrided sheets. The metallurgical and mechanical properties of the welding joint were investigated and discussed. The peak load and failure energy increased with the increases of welding current and fusion zone (FZ) size. At 11 kA welding current, the carbonitrided steel joint had the failure energy of 16 J, i.e., approximately 84 pct of untreated steel joint. FZ of carbonitrided steel joint consisted of ferrite, Widmanstatten ferrite, and untempered martensite, i.e., the solid-state transformation products, while the microstructure at the outer surfaces consisted of untempered martensite and retained austenite. The surface hardening of carbonitrided steel after RSW could be maintained, i.e., approximately 810 HV. The results can be applied to carbonitriding and RSW to achieve a good welding joint.

The mechanics and energetics of human walking and running: a joint level perspective.

PubMed

Farris, Dominic James; Sawicki, Gregory S

2012-01-07

Humans walk and run at a range of speeds. While steady locomotion at a given speed requires no net mechanical work, moving faster does demand both more positive and negative mechanical work per stride. Is this increased demand met by increasing power output at all lower limb joints or just some of them? Does running rely on different joints for power output than walking? How does this contribute to the metabolic cost of locomotion? This study examined the effects of walking and running speed on lower limb joint mechanics and metabolic cost of transport in humans. Kinematic and kinetic data for 10 participants were collected for a range of walking (0.75, 1.25, 1.75, 2.0 m s(-1)) and running (2.0, 2.25, 2.75, 3.25 m s(-1)) speeds. Net metabolic power was measured by indirect calorimetry. Within each gait, there was no difference in the proportion of power contributed by each joint (hip, knee, ankle) to total power across speeds. Changing from walking to running resulted in a significant (p = 0.02) shift in power production from the hip to the ankle which may explain the higher efficiency of running at speeds above 2.0 m s(-1) and shed light on a potential mechanism behind the walk-run transition.

The Influence of Processing on Strengthening Mechanisms in Pb-Free Solder Joints

NASA Astrophysics Data System (ADS)

Mutuku, Francis; Arfaei, Babak; Cotts, Eric J.

2017-04-01

The number, and the spacing, of Ag3Sn precipitates in Sn-Ag-Cu/Cu solder joints were related to separate processing parameters. The mechanical properties of an individual solder joint were directly related to the resulting distribution of different dispersoids in the joint. As the number of Ag3Sn precipitates increased, so did solder joint strength and shear fatigue lifetime. The room-temperature shear fatigue lifetime was inversely correlated with the separation between Ag3Sn precipitates. Bi and Sb solid solution strengthening was found to result in significantly larger values of shear strength and shear fatigue lifetime for one Pb-free solder. Room-temperature shear fatigue lifetime tests were identified as a relatively straightforward, yet sensitive means to gain insight into the reliability of Sn-Ag-Cu (SAC) solder joints.

Intra-articular pressures and joint mechanics: should we pay attention to effusion in knee osteoarthritis?

PubMed

Rutherford, Derek James

2014-09-01

What factors play a role to ensure a knee joint does what it should given the demands of moving through the physical environment? This paper aims to probe the hypothesis that intra-articular joint pressures, once a topic of interest, have been left aside in contemporary frameworks in which we now view knee joint function. The focus on ligamentous deficiencies and the chondrocentric view of osteoarthritis, while important, have left little attention to the consideration of other factors that can impair joint function across the lifespan. Dynamic knee stability is required during every step we take. While there is much known about the role that passive structures and muscular activation play in maintaining a healthy knee joint, this framework does not account for the role that intra-articular joint pressures may have in providing joint stability during motion and how these factors interact. Joint injuries invariably result in some form of intra-articular fluid accumulation. Ultimately, it may be how the knee mechanically responds to this fluid, of which pressure plays a significant role that provides the mechanisms for continued function. Do joint pressures provide an important foundation for maintaining knee function? This hypothesis is unique and argues that we are missing an important piece of the puzzle when attempting to understand implications that joint injury and disease have for joint function. Copyright © 2014 Elsevier Ltd. All rights reserved.

32 CFR 553.15a - Persons eligible for inurnment of cremated remains in Columbarium in Arlington National Cemetery.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 3 2014-07-01 2014-07-01 false Persons eligible for inurnment of cremated remains in Columbarium in Arlington National Cemetery. 553.15a Section 553.15a National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY MILITARY RESERVATIONS AND NATIONAL CEMETERIES ARMY...

Effect of Multiple Local Repairs on Microstructure and Mechanical Properties of T24 Steel Welded Joint

NASA Astrophysics Data System (ADS)

Chaus, Alexander S.; Kuhajdová, Andrea; Marônek, Milan; Dománková, Mária

2018-05-01

The effect of multiple local repairs on the microstructure and mechanical properties of the T24 steel welded joints was studied. T24 steel tubes were butt-welded by the GTAW method. Peripheral welded joints were made in four locations of the tube. In order to simulate the repair procedure, the welds were cut off from the root and the first local repair was performed. Other two local repairs were carried out in the same way. After each local repair, the microstructure and mechanical properties of the joints were evaluated. The results of the mechanical tests demonstrate that only two local repairs can be performed on the T24 steel peripheral welded joint. After the third local repair, impact energy of the welded joint was lower than required value, which is attributed to the coarser martensite and the coarser carbide precipitates formed in the heat-affected zone, compared with the weld metal.

Study on Joint Interface and Mechanical Properties of Cu/Pb-Sn/Cu Lap Joint Produced by Friction Stir Soldering Process

NASA Astrophysics Data System (ADS)

Sarkari Khorrami, Mahmoud; Kokabi, Amir Hossein; Movahedi, Mojtaba

2015-05-01

In this work, friction stir soldering (FSS) as a new approach for fabrication of copper/copper lap joints was introduced. This process is principally based on the friction stir processing (FSP) that can be performed using FSP tools with and without pin on the top sheet. In the present study, Pb-Sn foil was used as a solder which would be melted and then extruded in the area between the copper sheets during FSS process. This process was carried out using tools with and without pin at various rotation speeds of 1200, 1400, and 1600 rpm and traverse speed of 32 mm/min. Also, the same joint was fabricated using furnace soldering to compare the mechanical properties obtained with FSS and furnace soldering processes. It was observed that FSS possesses some advantages over the conventional furnace soldering process including the formation of more bond area at the interface corresponding to the higher fracture load of FSS joints compared with furnace soldering one. Moreover, it was concluded that the thickness of intermetallic compounds (IMCs) and the formation of voids at the joint interface were the predominant factor determining the mechanical properties of the FSS joints produced by FSS tool with and without pin, respectively. The microstructural examinations revealed that Cu-Sn IMCs of Cu3Sn and Cu6Sn5 were formed at the joint interface. It was observed that the FSS joint produced by tool with pin experienced the more peak temperature in comparison with that produced by pin-free tool. This may lead to the formation of thicker IMCs at the interface. Of course, the thickness of IMCs can be controlled by choosing proper FSS parameters, especially the rotation speed of the tool.

33 CFR 334.783 - Arlington Channel, U.S. Coast Guard Base Mobile, Mobile, Alabama, Coast Guard restricted area.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Guard Base Mobile, Mobile, Alabama, Coast Guard restricted area. 334.783 Section 334.783 Navigation and... RESTRICTED AREA REGULATIONS § 334.783 Arlington Channel, U.S. Coast Guard Base Mobile, Mobile, Alabama, Coast... without prior approval from the Commanding Officer, U.S. Coast Guard Group Mobile or his designated...

Remote controlled vacuum joint closure mechanism

DOEpatents

Doll, David W.; Hager, E. Randolph

1986-01-01

A remotely operable and maintainable vacuum joint closure mechanism for a noncircular aperture is disclosed. The closure mechanism includes an extendible bellows coupled at one end to a noncircular duct and at its other end to a flange assembly having sealed grooves for establishing a high vacuum seal with the abutting surface of a facing flange which includes an aperture forming part of the system to be evacuated. A plurality of generally linear arrangements of pivotally coupled linkages and piston combinations are mounted around the outer surface of the duct and aligned along the length thereof. Each of the piston/linkage assemblies is adapted to engage the flange assembly by means of a respective piston and is further coupled to a remote controlled piston drive shaft to permit each of the linkages positioned on a respective flat outer surface of the duct to simultaneously and uniformly displace a corresponding piston and the flange assembly with which it is in contact along the length of the duct in extending the bellows to provide a high vacuum seal between the movable flange and the facing flange. A plurality of latch mechanisms are also pivotally mounted on the outside of the duct. A first end of each of the latch mechanisms is coupled to a remotely controlled latch control shaft for displacing the latch mechanism about its pivot point. In response to the pivoting displacement of the latch mechanism, a second end thereof is displaced so as to securely engage the facing flange.

Exploring New Concepts for Joint Urban Operations

DTIC Science & Technology

2003-08-01

Services, and Department of Defense organizations. We would like to ex- press our appreciation to the following: Mr. Mike Collins, Arlington County ...Larry D. Budge, USA (Ret.), JAWP–IDA MG Waldo Freeman, USA (Ret.), Strategy, Forces & Research Division, IDA COL Michael Barron, USA, JAWP–IDA Lt Col...Adaptive Red Team (DART) from Science Applica- tions International Corporation. The Arlington County (Virginia) Police, Fire, and Utilities De

Failure Mechanisms of SAC/Fe-Ni Solder Joints During Thermal Cycling

NASA Astrophysics Data System (ADS)

Gao, Li-Yin; Liu, Zhi-Quan; Li, Cai-Fu

2017-08-01

Thermal cycling tests have been conducted on Sn-Ag-Cu/Fe- xNi ( x = 73 wt.% or 45 wt.%) and Sn-Ag-Cu/Cu solder joints according to the Joint Electron Device Engineering Council industrial standard to study their interfacial reliability under thermal stress. The interfacial intermetallic compounds formed for solder joints on Cu, Fe-73Ni, and Fe-45Ni were 4.5 μm, 1.7 μm, and 1.4 μm thick, respectively, after 3000 cycles, demonstrating excellent diffusion barrier effect of Fe-Ni under bump metallization (UBM). Also, two deformation modes, viz. solder extrusion and fatigue crack formation, were observed by scanning electron microscopy and three-dimensional x-ray microscopy. Solder extrusion dominated for solder joints on Cu, while fatigue cracks dominated for solder joints on Fe-45Ni and both modes were detected for those on Fe-73Ni. Solder joints on Fe-Ni presented inferior reliability during thermal cycling compared with those on Cu, with characteristic lifetime of 3441 h, 3190 h, and 1247 h for Cu, Fe-73Ni, and Fe-45Ni UBM, respectively. This degradation of the interfacial reliability for solder joints on Fe-Ni is attributed to the mismatch in coefficient of thermal expansion (CTE) at interconnection level. The CTE mismatch at microstructure level was also analyzed by electron backscatter diffraction for clearer identification of recrystallization-related deformation mechanisms.

Columnar jointing - the mechanics of thermal contraction in cooling lavas

NASA Astrophysics Data System (ADS)

Lavallée, Y.; Iddon, F.; Hornby, A. J.; Kendrick, J. E.; von Aulock, F. W.; Wadsworth, F. B.

2014-12-01

Columnar joints are spectacular features of volcanic rocks, which form by cracking during cooling-induced contraction of lava. The process, and resultant geometry, manifests a complex interplay between heat dissipation, contraction and tensile strength, yet the formation temperature of such joints remains elusive. Here, we present results from a combination of field survey, thermo-analytical characterisation and mechanical investigation to constrain conditions favourable for columnar jointing. Columnar joints at Seljavellir, a basaltic lava flow at the base of Eyjafjallajökull volcano (Iceland) produce quadratic to heptagonal cross sectional patterns with column widths ranging from 20 to 70 cm in size. The fracture surfaces are characterised by striae with spacing (between 1 to 6 cm) that shares a positive linear relationship to the joint spacing. The striae exhibit both a rough and smooth portion, interpreted to express a change in deformation regime from a ductile response as stress builds up to a fully brittle, mode-I fracture propagation at high stress accumulation. To test the thermo-mechanics of columnar joints we developed an experimental setup to investigate the stress, strain-to-failure and temperature at which basalts undergo tensile failure during cooling from the solidus temperature of 980 °C. We find that fractures initiate at ~800 °C, revealed by a change in stress accumulation (i.e., Young modulus), and complete failure completes after some 0.4% strain at ~670 °C. We interpret the two-stage fracture dynamics as the cause for the change in fracture surface roughness observed in nature. We coupled this dataset with Brazil tensile tests at 30, 400, 600, 800 and 1000 °C. We note that the strain to failure decrease from 1% (>800 °C) to 0.4% (<800 °C). Complementary dilatometric measurements (at 3mN of normal stress and a rate of 2 C/min) constrain the expansion coefficient to be linear and equal to 10-5/°C below the solid temperature. Simple ratio

Spatial variation of fixed charge density in knee joint cartilage from sodium MRI - Implication on knee joint mechanics under static loading.

PubMed

Räsänen, Lasse P; Tanska, Petri; Mononen, Mika E; Lammentausta, Eveliina; Zbýň, Štefan; Venäläinen, Mikko S; Szomolanyi, Pavol; van Donkelaar, Corrinus C; Jurvelin, Jukka S; Trattnig, Siegfried; Nieminen, Miika T; Korhonen, Rami K

2016-10-03

The effects of fixed charge density (FCD) and cartilage swelling have not been demonstrated on cartilage mechanics on knee joint level before. In this study, we present how the spatial and local variations of FCD affects the mechanical response of the knee joint cartilage during standing (half of the body weight, 13 minutes) using finite element (FE) modeling. The FCD distribution of tibial cartilage of an asymptomatic subject was determined using sodium ( 23 Na) MRI at 7T and implemented into a 3-D FE-model of the knee joint (Subject-specific model, FCD: 0.18±0.08 mEq/ml). Tissue deformation in the Subject-specific model was validated against experimental, in vivo loading of the joint conducted with a MR-compatible compression device. For comparison, models with homogeneous FCD distribution (homogeneous model) and FCD distribution obtained from literature (literature model) were created. Immediately after application of the load (dynamic response), the variations in FCD had minor effects on cartilage stresses and strains. After 13 minutes of standing, the spatial and local variations in FCD had most influence on axial strains. In the superficial tibial cartilage in the Subject-specific model, axial strains were increased up to +13% due to smaller FCD (mean -11%), as compared to the homogeneous model. Compared to the literature model, those were decreased up to -18% due to greater FCD (mean +7%). The findings demonstrate that the spatial and local FCD variations in cartilage modulates strains in knee joint cartilage. Thereby, the results highlight the mechanical importance of site-specific content of proteoglycans in cartilage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental Studies on the Mechanical Behaviour of Rock Joints with Various Openings

NASA Astrophysics Data System (ADS)

Li, Y.; Oh, J.; Mitra, R.; Hebblewhite, B.

2016-03-01

The mechanical behaviour of rough joints is markedly affected by the degree of joint opening. A systematic experimental study was conducted to investigate the effect of the initial opening on both normal and shear deformations of rock joints. Two types of joints with triangular asperities were produced in the laboratory and subjected to compression tests and direct shear tests with different initial opening values. The results showed that opened rock joints allow much greater normal closure and result in much lower normal stiffness. A semi-logarithmic law incorporating the degree of interlocking is proposed to describe the normal deformation of opened rock joints. The proposed equation agrees well with the experimental results. Additionally, the results of direct shear tests demonstrated that shear strength and dilation are reduced because of reduced involvement of and increased damage to asperities in the process of shearing. The results indicate that constitutive models of rock joints that consider the true asperity contact area can be used to predict shear resistance along opened rock joints. Because rock masses are loosened and rock joints become open after excavation, the model suggested in this study can be incorporated into numerical procedures such as finite-element or discrete-element methods. Use of the model could then increase the accuracy and reliability of stability predictions for rock masses under excavation.

Models for selecting GMA Welding Parameters for Improving Mechanical Properties of Weld Joints

NASA Astrophysics Data System (ADS)

Srinivasa Rao, P.; Ramachandran, Pragash; Jebaraj, S.

2016-02-01

During the process of Gas Metal Arc (GMAW) welding, the weld joints mechanical properties are influenced by the welding parameters such as welding current and arc voltage. These parameters directly will influence the quality of the weld in terms of mechanical properties. Even small variation in any of the cited parameters may have an important effect on depth of penetration and on joint strength. In this study, S45C Constructional Steel is taken as the base metal to be tested using the parameters wire feed rate, voltage and type of shielding gas. Physical properties considered in the present study are tensile strength and hardness. The testing of weld specimen is carried out as per ASTM Standards. Mathematical models to predict the tensile strength and depth of penetration of weld joint have been developed by regression analysis using the experimental results.

Remote controlled vacuum joint closure mechanism

DOEpatents

Doll, D.W.; Hager, E.R.

1984-02-22

A remotely operable and maintainable vacuum joint closure mechanism for a noncircular aperture is disclosed. The closure mechanism includes an extendible bellows coupled at one end to a noncircular duct and at its other end to a flange assembly having sealed grooves for establishing a high vacuum seal with the abutting surface of a facing flange which includes an aperture forming part of the system to be evacuated. A plurality of generally linear arrangements of pivotally coupled linkages and piston combinations are mounted around the outer surface of the duct and aligned along the length thereof. Each of the piston/linkage assemblies is adapted to engage the flange assembly by means of a respective piston and is further coupled to a remote controlled piston drive shaft to permit each of the linkages positioned on a respective flat outer surface of the duct to simultaneously and uniformly displace a corresponding piston and the flange assembly with which it is in contact along the length of the duct in extending the bellows to provide a high vacuum seal between the movable flange and the facing flange. A plurality of latch mechanisms are also pivotally mounted on the outside of the duct. A first end of each of the latch mechanisms is coupled to a remotely controlled latch control shaft for displacing the latch mechanism about its pivot point. In response to the pivoting displacement of the latch mechanism, a second end thereof is displaced so as to securely engage the facing flange and maintain the high vacuum seal established by the displacement of the flange assembly and extension of the bellows without displacing the entire duct.

Joint Instability and Osteoarthritis

PubMed Central

Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

2015-01-01

Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

Joint instability and osteoarthritis.

PubMed

Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

2015-01-01

Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

Microstructure Evolution and Mechanical Properties of High-Speed Friction Stir Welded Aluminum Alloy Thin Plate Joints

NASA Astrophysics Data System (ADS)

Liu, Fenjun; Fu, Li; Chen, Haiyan

2018-06-01

Sound friction stir welded (FSW) joints of 6061-T6 aluminum alloy sheets with an 0.8 mm thickness were obtained at conventional speed (2000 rpm, 300 mm/min) and high speed (11,000 rpm, 1500 mm/min). The recrystallization mechanism, precipitate evolution, mechanical properties and fracture behavior were investigated in detail. Microstructure analyses revealed that the grain structure evolution in the nugget zone (NZ) was dominated by continuous dynamic recrystallization. In the process of FSW, high speed facilitates the formation of finer equiaxed recrystallized grains, higher density of dislocations and substructures, and a larger number of precipitates in the NZ compared to the conventional speed, which further significantly improves the hardness and tensile strength of the joints. The maximum tensile strength was obtained with 292.6 MPa, 83.2% for the 6061-T6 aluminum alloy and 122.6% for the conventional-speed FSW joints. This work provides an effective method for preparing FSW aluminum alloy thin plate joints with excellent mechanical properties.

Impact of mechanism vibration characteristics by joint clearance and optimization design of its multi-objective robustness

NASA Astrophysics Data System (ADS)

Zeng, Baoping; Wang, Chao; Zhang, Yu; Gong, Yajun; Hu, Sanbao

2017-12-01

Joint clearances and friction characteristics significantly influence the mechanism vibration characteristics; for example: as for joint clearances, the shaft and bearing of its clearance joint collide to bring about the dynamic normal contact force and tangential coulomb friction force while the mechanism works; thus, the whole system may vibrate; moreover, the mechanism is under contact-impact with impact force constraint from free movement under action of the above dynamic forces; in addition, the mechanism topology structure also changes. The constraint relationship between joints may be established by a repeated complex nonlinear dynamic process (idle stroke - contact-impact - elastic compression - rebound - impact relief - idle stroke movement - contact-impact). Analysis of vibration characteristics of joint parts is still a challenging open task by far. The dynamic equations for any mechanism with clearance is often a set of strong coupling, high-dimensional and complex time-varying nonlinear differential equations which are solved very difficultly. Moreover, complicated chaotic motions very sensitive to initial values in impact and vibration due to clearance let high-precision simulation and prediction of their dynamic behaviors be more difficult; on the other hand, their subsequent wearing necessarily leads to some certain fluctuation of structure clearance parameters, which acts as one primary factor for vibration of the mechanical system. A dynamic model was established to the device for opening the deepwater robot cabin door with joint clearance by utilizing the finite element method and analysis was carried out to its vibration characteristics in this study. Moreover, its response model was carried out by utilizing the DOE method and then the robust optimization design was performed to sizes of the joint clearance and the friction coefficient change range so that the optimization design results may be regarded as reference data for selecting bearings

Influences of Shear History and Infilling on the Mechanical Characteristics and Acoustic Emissions of Joints

NASA Astrophysics Data System (ADS)

Meng, Fanzhen; Zhou, Hui; Wang, Zaiquan; Zhang, Liming; Kong, Liang; Li, Shaojun; Zhang, Chuanqing

2017-08-01

Filled joints, which are characterized by high deformability and low shear strength, are among the most critical discontinuities in rock mass and may be sheared repeatedly when subject to cyclic loading. Shear tests were carried out on tension splitting joints, with soil and granular cement mortar particles used as infillings, and the effects of the shear history on the mechanical behavior and acoustic emission (AE) of clean and filled joints were studied. The maximum strength in the subsequent shears was approximately 60% of the peak strength of the first shear for a clean joint, and the friction angle degraded from 63° to 45° after the first shear. The maximum shear strength of the filled joints was lower than 35% of the peak strength of the clean joint under the same normal stress. The change in the shear strength of filled joints with the number of shearing cycles was closely related to the transformation of the shear medium. Rolling friction occurred and the shear strength was low for the granular particle-filled joint, but the strength was elevated when the particles were crushed and sliding friction occurred. The AEs were significantly reduced during the second shear for the clean joint, and the peak AEs were mainly obtained at or near the turning point of the shear stress curve for the filled joint. The AEs were the highest for the cement particle-filled joint and lowest for the dry soil-filled joint; when subjected to repeated shears, the AEs were more complex because of the continuous changes to the shear medium. The evolution of the AEs with the shear displacement can accurately reflect the shear failure mechanism during a single shear process.

Effect of process parameters on microstructure and mechanical properties of friction stir welded joints: A review

NASA Astrophysics Data System (ADS)

Wanare, S. P.; Kalyankar, V. D.

2018-04-01

Friction stir welding is emerging as a promising technique for joining of lighter metal alloys due to its several advantages over conventional fusion welding processes such as low thermal distortion, good mechanical properties, fine weld joint microstructure, etc. This review article mainly focuses on analysis of microstructure and mechanical properties of friction stir welded joints. Various microstructure characterization techniques used by previous researchers such as optical microscopes, x-ray diffraction, electron probe microscope, transmission electron microscope, scanning electron microscopes with electron back scattered diffraction, electron dispersive microscopy, etc. are thoroughly overviewed and their results are discussed. The effects of friction stir welding process parameters such as tool rotational speed, welding speed, tool plunge depth, axial force, tool shoulder diameter to tool pin diameter ratio, tool geometry etc. on microstructure and mechanical properties of welded joints are studied and critical observations are noted down. The microstructure examination carried out by previous researchers on various zones of welded joints such as weld zone, heat affected zone and base metal are studied and critical remarks have been presented. Mechanical performances of friction stir welded joints based on tensile test, micro-hardness test, etc. are discussed. This article includes exhaustive literature review of standard research articles which may become ready information for subsequent researchers to establish their line of action.

Former NASA Astronaut, U.S. Senator John Glenn laid to rest in Arlington Cemetery

NASA Image and Video Library

2017-04-05

On April 6, former astronaut and U.S. Senator John Glenn was interred at Arlington National Cemetery in Virginia. Glenn, who passed away Dec. 8, 2016 at the age of 95, served four terms as a U.S. senator from Ohio, and was one of NASA's original seven Mercury astronauts. His flight on Friendship 7 on Feb. 20, 1962, made him the first American to orbit Earth. The riveting flight united our nation, launched America to the forefront of the space race and secured for him a unique place in the annals of history.

Assesment of influncing factors on mechanical and electrical properties of Al/Cu joints

NASA Astrophysics Data System (ADS)

Selvaraj, R. Meby; Hynes, N. Rajesh Jesudoss

2018-05-01

Joining of dissimilar materials opens up challenging opportunities in todays technology. Al/Cu weldments are used in applications that demands corrosion resistance, thermal and electrical conducting properties. In dissimilar joining mechanical and thermal properties result in large stress gradients during heating. The Al-Cu joints are lighter, cheaper and have conductivity equal to copper alloy. The main scope of this study is to assess the influencing factors of Al/Cu joints in mechanical and electrical properties. It includes the influence of the dilution between the base metals, influence of physical properties, influence of welding parameters, influence of filler metal, influence of heat treatment, and influence of electrical properties

Optimum design of bolted composite lap joints under mechanical and thermal loading

NASA Astrophysics Data System (ADS)

Kradinov, Vladimir Yurievich

A new approach is developed for the analysis and design of mechanically fastened composite lap joints under mechanical and thermal loading. Based on the combined complex potential and variational formulation, the solution method satisfies the equilibrium equations exactly while the boundary conditions are satisfied by minimizing the total potential. This approach is capable of modeling finite laminate planform dimensions, uniform and variable laminate thickness, laminate lay-up, interaction among bolts, bolt torque, bolt flexibility, bolt size, bolt-hole clearance and interference, insert dimensions and insert material properties. Comparing to the finite element analysis, the robustness of the method does not decrease when modeling the interaction of many bolts; also, the method is more suitable for parametric study and design optimization. The Genetic Algorithm (GA), a powerful optimization technique for multiple extrema functions in multiple dimensions search spaces, is applied in conjunction with the complex potential and variational formulation to achieve optimum designs of bolted composite lap joints. The objective of the optimization is to acquire such a design that ensures the highest strength of the joint. The fitness function for the GA optimization is based on the average stress failure criterion predicting net-section, shear-out, and bearing failure modes in bolted lap joints. The criterion accounts for the stress distribution in the thickness direction at the bolt location by applying an approach utilizing a beam on an elastic foundation formulation.

76 FR 24065 - Board Workshop: June 6-7, 2011-Arlington, Virginia; the U.S. Nuclear Waste Technical Review Board...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-29

... NUCLEAR WASTE TECHNICAL REVIEW BOARD Board Workshop: June 6-7, 2011--Arlington, Virginia; the U.S. Nuclear Waste Technical Review Board Will Hold a Workshop on Methods for Evaluating Nuclear Waste Streams... 1987, the U.S. Nuclear Waste Technical Review Board will hold a workshop on Monday, June 6, and Tuesday...

Joint Inversion of Source Location and Source Mechanism of Induced Microseismics

NASA Astrophysics Data System (ADS)

Liang, C.

2014-12-01

Seismic source mechanism is a useful property to indicate the source physics and stress and strain distribution in regional, local and micro scales. In this study we jointly invert source mechanisms and locations for microseismics induced in fluid fracturing treatment in the oil and gas industry. For the events that are big enough to see waveforms, there are quite a few techniques can be applied to invert the source mechanism including waveform inversion, first polarity inversion and many other methods and variants based on these methods. However, for events that are too small to identify in seismic traces such as the microseismics induced by the fluid fracturing in the Oil and Gas industry, a source scanning algorithms (SSA for short) with waveform stacking are usually applied. At the same time, a joint inversion of location and source mechanism are possible but at a cost of high computation budget. The algorithm is thereby called Source Location and Mechanism Scanning Algorithm, SLMSA for short. In this case, for given velocity structure, all possible combinations of source locations (X,Y and Z) and source mechanism (Strike, Dip and Rake) are used to compute travel-times and polarities of waveforms. Correcting Normal moveout times and polarities, and stacking all waveforms, the (X, Y, Z , strike, dip, rake) combination that gives the strongest stacking waveform is identified as the solution. To solve the problem of high computation problem, CPU-GPU programing is applied. Numerical datasets are used to test the algorithm. The SLMSA has also been applied to a fluid fracturing datasets and reveal several advantages against the location only method: (1) for shear sources, the source only program can hardly locate them because of the canceling out of positive and negative polarized traces, but the SLMSA method can successfully pick up those events; (2) microseismic locations alone may not be enough to indicate the directionality of micro-fractures. The statistics of

Improving Mechanical Properties of PVPPA Welded Joints of 7075 Aluminum Alloy by PWHT

PubMed Central

Li, Guowei; Chen, Furong; Han, Yongquan; Liang, Yahong

2018-01-01

In this study, 7075 aluminum alloy with a thickness of 10 mm was successfully welded with no obvious defects by pulsed variable polarity plasma arc (PVPPA) welding. The mechanical properties of PVPPA welded joints have been researched by post weld heat treatment (PWHT). The results indicate that the heat treatment strongly affects the mechanical properties of the welded joints. The tensile strength and the microhardness of the welded joints gradually improved with the increase of the solution temperature. With the increase of the solution time, the tensile strength, and microhardness first dramatically increased and then decreased slightly. The best tensile strength of 537.5 MPa and the microhardness of 143.7 HV were obtained after 490 °C × 80 min + 120 °C × 24 h, and the strength was nearly 91.2% of that of the parent metal, and increased about 35% compared with as-welded. The improvement of strength and microhardness was mainly due to the precipitation of η′ phase. PMID:29510551

Mechanical Prophylaxis after Lower Extremity Total Joint Arthroplasty: A Review.

PubMed

Chughtai, Morad; Newman, Jared M; Solow, Max; Davidson, Iyooh U; Sodhi, Nipun; Gaal, Benjamin; Khlopas, Anton; Sultan, Assem A; Mont, Michael A

2017-12-22

Venous thromboembolism (VTE) is a serious complication that can occur after total hip and knee arthroplasty, and can potentially lead to significant morbidity and even mortality. While various modalities have been used to prevent VTE development, the medications can be associated with a number of adverse events. Therefore, mechanical prophylaxis with pumps and compressive devices has been used more frequently alone, or in combination, with medications. Therefore, the purpose of this study was to review the current literature on mechanical prophylaxis for VTEs after lower extremity total joint arthroplasty. Specifically, we reviewed mechanical prophylaxis after: 1) total hip arthroplasty and 2) total knee arthroplasty.

Static Strength Characteristics of Mechanically Fastened Composite Joints

NASA Technical Reports Server (NTRS)

Fox, D. E.; Swaim, K. W.

1999-01-01

The analysis of mechanically fastened composite joints presents a great challenge to structural analysts because of the large number of parameters that influence strength. These parameters include edge distance, width, bolt diameter, laminate thickness, ply orientation, and bolt torque. The research presented in this report investigates the influence of some of these parameters through testing and analysis. A methodology is presented for estimating the strength of the bolt-hole based on classical lamination theory using the Tsai-Hill failure criteria and typical bolthole bearing analytical methods.

Combustion Mechanisms of Solids

DTIC Science & Technology

1992-02-24

ELEMENT NO. NO NO ACCESSION NO Arlington, VA 22217-5000 11 TITLE (include Security Classification) COMBUSTION MECHANISMS OF SOLIDS 12. PERSONAL AUTHOR(S...FIELD GROUP I SUB-GROUP COMBUSTION , SOLID PROPELLANT 19 ABSTRACT (Continue on reverse if necessary and identify by block number) This report...ingredients tested (AP, AN, PBAN, NMMO and BAMO-THF). Ingredient combustion behavior was studied by the edge burning sandwich method using sandwiches

Recent advances in jointed quantum mechanics and molecular mechanics calculations of biological macromolecules: schemes and applications coupled to ab initio calculations.

PubMed

Hagiwara, Yohsuke; Tateno, Masaru

2010-10-20

We review the recent research on the functional mechanisms of biological macromolecules using theoretical methodologies coupled to ab initio quantum mechanical (QM) treatments of reaction centers in proteins and nucleic acids. Since in most cases such biological molecules are large, the computational costs of performing ab initio calculations for the entire structures are prohibitive. Instead, simulations that are jointed with molecular mechanics (MM) calculations are crucial to evaluate the long-range electrostatic interactions, which significantly affect the electronic structures of biological macromolecules. Thus, we focus our attention on the methodologies/schemes and applications of jointed QM/MM calculations, and discuss the critical issues to be elucidated in biological macromolecular systems. © 2010 IOP Publishing Ltd

Effects of laser power density on static and dynamic mechanical properties of dissimilar stainless steel welded joints

NASA Astrophysics Data System (ADS)

Wei, Yan-Peng; Li, Mao-Hui; Yu, Gang; Wu, Xian-Qian; Huang, Chen-Guang; Duan, Zhu-Ping

2012-10-01

The mechanical properties of laser welded joints under impact loadings such as explosion and car crash etc. are critical for the engineering designs. The hardness, static and dynamic mechanical properties of AISI304 and AISI316 L dissimilar stainless steel welded joints by CO2 laser were experimentally studied. The dynamic strain-stress curves at the strain rate around 103 s-1 were obtained by the split Hopkinson tensile bar (SHTB). The static mechanical properties of the welded joints have little changes with the laser power density and all fracture occurs at 316 L side. However, the strain rate sensitivity has a strong dependence on laser power density. The value of strain rate factor decreases with the increase of laser power density. The welded joint which may be applied for the impact loading can be obtained by reducing the laser power density in the case of welding quality assurance.

Self-reported knee joint instability is related to passive mechanical stiffness in medial knee osteoarthritis.

PubMed

Creaby, Mark W; Wrigley, Tim V; Lim, Boon-Whatt; Hinman, Rana S; Bryant, Adam L; Bennell, Kim L

2013-11-20

Self-reported knee joint instability compromises function in individuals with medial knee osteoarthritis and may be related to impaired joint mechanics. The purpose of this study was to evaluate the relationship between self-reported instability and the passive varus-valgus mechanical behaviour of the medial osteoarthritis knee. Passive varus-valgus angular laxity and stiffness were assessed using a modified isokinetic dynamometer in 73 participants with medial tibiofemoral osteoarthritis. All participants self-reported the absence or presence of knee instability symptoms and the degree to which instability affected daily activity on a 6-point likert scale. Forward linear regression modelling identified a significant inverse relationship between passive mid-range knee stiffness and symptoms of knee instability (r = 0.27; P < 0.05): reduced stiffness was indicative of more severe instability symptoms. Angular laxity and end-range stiffness were not related to instability symptoms (P > 0.05). Conceivably, a stiffer passive system may contribute toward greater joint stability during functional activities. Importantly however, net joint stiffness is influenced by both active and passive stiffness, and thus the active neuromuscular system may compensate for reduced passive stiffness in order to maintain joint stability. Future work is merited to examine the role of active stiffness in symptomatic joint stability.

Self-reported knee joint instability is related to passive mechanical stiffness in medial knee osteoarthritis

PubMed Central

2013-01-01

Background Self-reported knee joint instability compromises function in individuals with medial knee osteoarthritis and may be related to impaired joint mechanics. The purpose of this study was to evaluate the relationship between self-reported instability and the passive varus-valgus mechanical behaviour of the medial osteoarthritis knee. Methods Passive varus-valgus angular laxity and stiffness were assessed using a modified isokinetic dynamometer in 73 participants with medial tibiofemoral osteoarthritis. All participants self-reported the absence or presence of knee instability symptoms and the degree to which instability affected daily activity on a 6-point likert scale. Results Forward linear regression modelling identified a significant inverse relationship between passive mid-range knee stiffness and symptoms of knee instability (r = 0.27; P < 0.05): reduced stiffness was indicative of more severe instability symptoms. Angular laxity and end-range stiffness were not related to instability symptoms (P > 0.05). Conclusions Conceivably, a stiffer passive system may contribute toward greater joint stability during functional activities. Importantly however, net joint stiffness is influenced by both active and passive stiffness, and thus the active neuromuscular system may compensate for reduced passive stiffness in order to maintain joint stability. Future work is merited to examine the role of active stiffness in symptomatic joint stability. PMID:24252592

Post-Traumatic Osteoarthritis in Mice Following Mechanical Injury to the Synovial Joint

PubMed Central

Rai, Muhammad Farooq; Duan, Xin; Quirk, James D.; Holguin, Nilsson; Schmidt, Eric J.; Chinzei, Nobuaki; Silva, Matthew J.; Sandell, Linda J.

2017-01-01

We investigated the spectrum of lesions characteristic of post-traumatic osteoarthritis (PTOA) across the knee joint in response to mechanical injury. We hypothesized that alteration in knee joint stability in mice reproduces molecular and structural features of PTOA that would suggest potential therapeutic targets in humans. The right knees of eight-week old male mice from two recombinant inbred lines (LGXSM-6 and LGXSM-33) were subjected to axial tibial compression. Three separate loading magnitudes were applied: 6N, 9N, and 12N. Left knees served as non-loaded controls. Mice were sacrificed at 5, 9, 14, 28, and 56 days post-loading and whole knee joint changes were assessed by histology, immunostaining, micro-CT, and magnetic resonance imaging. We observed that tibial compression disrupted joint stability by rupturing the anterior cruciate ligament (except for 6N) and instigated a cascade of temporal and topographical features of PTOA. These features included cartilage extracellular matrix loss without proteoglycan replacement, chondrocyte apoptosis at day 5, synovitis present at day 14, osteophytes, ectopic calcification, and meniscus pathology. These findings provide a plausible model and a whole-joint approach for how joint injury in humans leads to PTOA. Chondrocyte apoptosis, synovitis, and ectopic calcification appear to be targets for potential therapeutic intervention. PMID:28345597

Emergence of Joint Attention through Bootstrap Learning based on the Mechanisms of Visual Attention and Learning with Self-evaluation

NASA Astrophysics Data System (ADS)

Nagai, Yukie; Hosoda, Koh; Morita, Akio; Asada, Minoru

This study argues how human infants acquire the ability of joint attention through interactions with their caregivers from a viewpoint of cognitive developmental robotics. In this paper, a mechanism by which a robot acquires sensorimotor coordination for joint attention through bootstrap learning is described. Bootstrap learning is a process by which a learner acquires higher capabilities through interactions with its environment based on embedded lower capabilities even if the learner does not receive any external evaluation nor the environment is controlled. The proposed mechanism for bootstrap learning of joint attention consists of the robot's embedded mechanisms: visual attention and learning with self-evaluation. The former is to find and attend to a salient object in the field of the robot's view, and the latter is to evaluate the success of visual attention, not joint attention, and then to learn the sensorimotor coordination. Since the object which the robot looks at based on visual attention does not always correspond to the object which the caregiver is looking at in an environment including multiple objects, the robot may have incorrect learning situations for joint attention as well as correct ones. However, the robot is expected to statistically lose the learning data of the incorrect ones as outliers because of its weaker correlation between the sensor input and the motor output than that of the correct ones, and consequently to acquire appropriate sensorimotor coordination for joint attention even if the caregiver does not provide any task evaluation to the robot. The experimental results show the validity of the proposed mechanism. It is suggested that the proposed mechanism could explain the developmental mechanism of infants' joint attention because the learning process of the robot's joint attention can be regarded as equivalent to the developmental process of infants' one.

Microstructure and Mechanical Properties of Reaction-Formed Joints in Reaction Bonded Silicon Carbide Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

A reaction-bonded silicon carbide (RB-SiC) ceramic material (Carborundum's Cerastar RB-SIC) has been joined using a reaction forming approach. Microstructure and mechanical properties of three types of reaction-formed joints (350 micron, 50-55 micron, and 20-25 micron thick) have been evaluated. Thick (approximately 350 micron) joints consist mainly of silicon with a small amount of silicon carbide. The flexural strength of thick joints is about 44 plus or minus 2 MPa, and fracture always occurs at the joints. The microscopic examination of fracture surfaces of specimens with thick joints tested at room temperature revealed the failure mode to be typically brittle. Thin joints (<50-55 micron) consist of silicon carbide and silicon phases. The room and high temperature flexural strengths of thin (<50-55 micron) reaction-formed joints have been found to be at least equal to that of the bulk Cerastar RB-SIC materials because the flexure bars fracture away from the joint regions. In this case, the fracture origins appear to be inhomogeneities inside the parent material. This was always found to be the case for thin joints tested at temperatures up to 1350C in air. This observation suggests that the strength of Cerastar RB-SIC material containing a thin joint is not limited by the joint strength but by the strength of the bulk (parent) materials.

Wafer-level Cu-Sn micro-joints with high mechanical strength and low Sn overflow

NASA Astrophysics Data System (ADS)

Duan, Ani; Luu, Thi-Thuy; Wang, Kaiying; Aasmundtveit, Knut; Hoivik, Nils

2015-09-01

In this paper, we report wafer-level bonding using solid-liquid inter-diffusion (SLID) processes for fabricating micro-joints Cu-Sn at low temperature (270 °C). The evolution of multilayer Cu/Sn to micro-joint alloys has been characterized by optical microscopy and mechanical die-shear testing. The Cu-Sn joints with line width from 80 to 200 μm prove to be reliable packaging materials for bonding vacuum micro-cavities with controllable Sn overflow, as well as high mechanical strength (>70 MPa). A thermodynamic model has been performed to further understand the formation of Cu-Sn intermetallic alloys. There are two important findings for this work: 1) Using a two-step temperature profile may significantly reduce the amount of Sn overflow; 2) for packaging, a bond frame width greater than 80 μm will result in high yield.

Influence of solder joint length to the mechanical aspect during the thermal stress analysis

NASA Astrophysics Data System (ADS)

Tan, J. S.; Khor, C. Y.; Rahim, Wan Mohd Faizal Wan Abd; Ishak, Muhammad Ikman; Rosli, M. U.; Jamalludin, Mohd Riduan; Zakaria, M. S.; Nawi, M. A. M.; Aziz, M. S. Abdul; Ani, F. Che

2017-09-01

Solder joint is an important interconnector in surface mount technology (SMT) assembly process. The real time stress, strain and displacement of the solder joint is difficult to observe and assess the experiment. To tackle these problems, simulation analysis was employed to study the von Mises stress, strain and displacement in the thermal stress analysis by using Finite element based software. In this study, a model of leadless electronic package was considered. The thermal stress analysis was performed to investigate the effect of the solder length to those mechanical aspects. The simulation results revealed that solder length gives significant effect to the maximum von Mises stress to the solder joint. Besides, changes in solder length also influence the displacement of the solder joint in the thermal environment. The increment of the solder length significantly reduces the von Mises stress and strain on the solder joint. Thus, the understanding of the physical parameter for solder joint is important for engineer prior to designing the solder joint of the electronic component.

Effect of Complete Syndesmotic Disruption and Deltoid Injuries and Different Reduction Methods on Ankle Joint Contact Mechanics.

PubMed

LaMothe, Jeremy; Baxter, Josh R; Gilbert, Susannah; Murphy, Conor I; Karnovsky, Sydney C; Drakos, Mark C

2017-06-01

Syndesmotic injuries can be associated with poor patient outcomes and posttraumatic ankle arthritis, particularly in the case of malreduction. However, ankle joint contact mechanics following a syndesmotic injury and reduction remains poorly understood. The purpose of this study was to characterize the effects of a syndesmotic injury and reduction techniques on ankle joint contact mechanics in a biomechanical model. Ten cadaveric whole lower leg specimens with undisturbed proximal tibiofibular joints were prepared and tested in this study. Contact area, contact force, and peak contact pressure were measured in the ankle joint during simulated standing in the intact, injured, and 3 reduction conditions: screw fixation with a clamp, screw fixation without a clamp (thumb technique), and a suture-button construct. Differences in these ankle contact parameters were detected between conditions using repeated-measures analysis of variance. Syndesmotic disruption decreased tibial plafond contact area and force. Syndesmotic reduction did not restore ankle loading mechanics to values measured in the intact condition. Reduction with the thumb technique was able to restore significantly more joint contact area and force than the reduction clamp or suture-button construct. Syndesmotic disruption decreased joint contact area and force. Although the thumb technique performed significantly better than the reduction clamp and suture-button construct, syndesmotic reduction did not restore contact mechanics to intact levels. Decreased contact area and force with disruption imply that other structures are likely receiving more loads (eg, medial and lateral gutters), which may have clinical implications such as the development of posttraumatic arthritis.

Hyaluronan supplementation as a mechanical regulator of cartilage tissue development under joint-kinematic-mimicking loading.

PubMed

Wu, Yabin; Stoddart, Martin J; Wuertz-Kozak, Karin; Grad, Sibylle; Alini, Mauro; Ferguson, Stephen J

2017-08-01

Articular cartilage plays an essential role in joint lubrication and impact absorption. Through this, the mechanical signals are coupled to the tissue's physiological response. Healthy synovial fluid has been shown to reduce and homogenize the shear stress acting on the cartilage surfaces due to its unique shear-thinning viscosity. As cartilage tissues are sensitive to mechanical changes in articulation, it was hypothesized that replacing the traditional culture medium with a healthy non-Newtonian lubricant could enhance tissue development in a cartilage engineering model, where joint-kinematic-mimicking mechanical loading is applied. Different amounts of hyaluronic acid were added to the culture medium to replicate the viscosities of synovial fluid at different health states. Hyaluronic acid supplementation, especially at a physiologically healthy concentration (2.0 mg ml -1 ), promoted a better preservation of chondrocyte phenotype. The ratio of collagen II to collagen I mRNA was 4.5 times that of the control group, implying better tissue development (however, with no significant difference of measured collagen II content), with a good retention of collagen II and proteoglycan in the mechanically active region. Simulating synovial fluid properties by hyaluronic acid supplementation created a favourable mechanical environment for mechanically loaded constructs. These findings may help in understanding the influence of joint articulation on tissue homeostasis, and moreover, improve methods for functional cartilage tissue engineering. © 2017 The Author(s).

Rhythm in joint action: psychological and neurophysiological mechanisms for real-time interpersonal coordination

PubMed Central

Keller, Peter E.; Novembre, Giacomo; Hove, Michael J.

2014-01-01

Human interaction often requires simultaneous precision and flexibility in the coordination of rhythmic behaviour between individuals engaged in joint activity, for example, playing a musical duet or dancing with a partner. This review article addresses the psychological processes and brain mechanisms that enable such rhythmic interpersonal coordination. First, an overview is given of research on the cognitive-motor processes that enable individuals to represent joint action goals and to anticipate, attend and adapt to other's actions in real time. Second, the neurophysiological mechanisms that underpin rhythmic interpersonal coordination are sought in studies of sensorimotor and cognitive processes that play a role in the representation and integration of self- and other-related actions within and between individuals' brains. Finally, relationships between social–psychological factors and rhythmic interpersonal coordination are considered from two perspectives, one concerning how social-cognitive tendencies (e.g. empathy) affect coordination, and the other concerning how coordination affects interpersonal affiliation, trust and prosocial behaviour. Our review highlights musical ensemble performance as an ecologically valid yet readily controlled domain for investigating rhythm in joint action. PMID:25385772

Active Joint Mechanism Driven by Multiple Actuators Made of Flexible Bags: A Proposal of Dual Structural Actuator

PubMed Central

Inou, Norio

2013-01-01

An actuator is required to change its speed and force depending on the situation. Using multiple actuators for one driving axis is one of the possible solutions; however, there is an associated problem of output power matching. This study proposes a new active joint mechanism using multiple actuators. Because the actuator is made of a flexible bag, it does not interfere with other actuators when it is depressurized. The proposed joint achieved coordinated motion of multiple actuators. This report also discusses a new actuator which has dual cylindrical structure. The cylinders are composed of flexible bags with different diameters. The joint torque is estimated based on the following factors: empirical formula for the flexible actuator torque, geometric relationship between the joint and the actuator, and the principle of virtual work. The prototype joint mechanism achieves coordinated motion of multiple actuators for one axis. With this motion, small inner actuator contributes high speed motion, whereas large outer actuator generates high torque. The performance of the prototype joint is examined by speed and torque measurements. The joint showed about 30% efficiency at 2.0 Nm load torque under 0.15 MPa air input. PMID:24385868

Active joint mechanism driven by multiple actuators made of flexible bags: a proposal of dual structural actuator.

PubMed

Kimura, Hitoshi; Matsuzaki, Takuya; Kataoka, Mokutaro; Inou, Norio

2013-01-01

An actuator is required to change its speed and force depending on the situation. Using multiple actuators for one driving axis is one of the possible solutions; however, there is an associated problem of output power matching. This study proposes a new active joint mechanism using multiple actuators. Because the actuator is made of a flexible bag, it does not interfere with other actuators when it is depressurized. The proposed joint achieved coordinated motion of multiple actuators. This report also discusses a new actuator which has dual cylindrical structure. The cylinders are composed of flexible bags with different diameters. The joint torque is estimated based on the following factors: empirical formula for the flexible actuator torque, geometric relationship between the joint and the actuator, and the principle of virtual work. The prototype joint mechanism achieves coordinated motion of multiple actuators for one axis. With this motion, small inner actuator contributes high speed motion, whereas large outer actuator generates high torque. The performance of the prototype joint is examined by speed and torque measurements. The joint showed about 30% efficiency at 2.0 Nm load torque under 0.15 MPa air input.

The Effect of Tool Profiles on Mechanical Properties of Friction Stir Welded Al5052 T-Joints.

PubMed

Kim, Byeong-Jin; Bang, Hee-Seon; Bang, Han-Sur

2018-03-01

Al5052 T butt joints with two skins (5 mm) and one stringer (3 mm) has been successfully welded by friction stir welding (FSW). Notably, this paper has been investigated the effect of tool shape on welded formation mechanism and mechanical properties. The used shapes of tool pin are two types which are cylinder (type 1) and frustum (type 2). Dimension on two types of tool pin shape is respectively pin length of 4.7 mm and pin diameter of frustum type of top (5 mm) and bottom (3 mm). The results of experiment show that inner defects in FSWed T-joints increase significantly in accordance with traverse speed. The maximum tensile strength of welded joint fabricated using type 1 is equivalent to 85% that of the base metal, which is approximately 10% higher than that of type 2. Because welded joint of type 1 has more smoothly plastic flow in comparison with type 2. Consequently, the results show that type 1 is better appropriate for friction stir welded Al5052 T butt joints than type 2.

Experimental Investigation on the Fatigue Mechanical Properties of Intermittently Jointed Rock Models Under Cyclic Uniaxial Compression with Different Loading Parameters

NASA Astrophysics Data System (ADS)

Liu, Yi; Dai, Feng; Dong, Lu; Xu, Nuwen; Feng, Peng

2018-01-01

Intermittently jointed rocks, widely existing in many mining and civil engineering structures, are quite susceptible to cyclic loading. Understanding the fatigue mechanism of jointed rocks is vital to the rational design and the long-term stability analysis of rock structures. In this study, the fatigue mechanical properties of synthetic jointed rock models under different cyclic conditions are systematically investigated in the laboratory, including four loading frequencies, four maximum stresses, and four amplitudes. Our experimental results reveal the influence of the three cyclic loading parameters on the mechanical properties of jointed rock models, regarding the fatigue deformation characteristics, the fatigue energy and damage evolution, and the fatigue failure and progressive failure behavior. Under lower loading frequency or higher maximum stress and amplitude, the jointed specimen is characterized by higher fatigue deformation moduli and higher dissipated hysteresis energy, resulting in higher cumulative damage and lower fatigue life. However, the fatigue failure modes of jointed specimens are independent of cyclic loading parameters; all tested jointed specimens exhibit a prominent tensile splitting failure mode. Three different crack coalescence patterns are classified between two adjacent joints. Furthermore, different from the progressive failure under static monotonic loading, the jointed rock specimens under cyclic compression fail more abruptly without evident preceding signs. The tensile cracks on the front surface of jointed specimens always initiate from the joint tips and then propagate at a certain angle with the joints toward the direction of maximum compression.

Tribology and total hip joint replacement: current concepts in mechanical simulation.

PubMed

Affatato, S; Spinelli, M; Zavalloni, M; Mazzega-Fabbro, C; Viceconti, M

2008-12-01

Interest in the rheology and effects of interacting surfaces is as ancient as man. This subject can be represented by a recently coined word: tribology. This term is derived from the Greek word "tribos" and means the "science of rubbing". Friction, lubrication, and wear mechanism in the common English language means the precise field of interest of tribology. Wear of total hip prosthesis is a significant clinical problem that involves, nowadays, a too high a number of patients. In order to acquire further knowledge on the tribological phenomena that involve hip prosthesis wear tests are conducted on employed materials to extend lifetime of orthopaedic implants. The most basic type of test device is the material wear machine, however, a more advanced one may more accurately reproduce some of the in vivo conditions. Typically, these apparatus are called simulators, and, while there is no absolute definition of a joint simulator, its description as a mechanical rig used to test a joint replacement, under conditions approximating those occurring in the human body, is acceptable. Simulator tests, moreover, can be used to conduct accelerated protocols that replicate/simulate particularly extreme conditions, thus establishing the limits of performance for the material. Simulators vary in their level of sophistication and the international literature reveals many interpretations of the design of machines used for joint replacement testing. This paper aims to review the current state of the art of the hip joint simulators worldwide. This is specified through a schematic overview by describing, in particular, constructive solutions adopted to reproduce in vivo conditions. An exhaustive commentary on the evolution and actually existing simulation standards is proposed by the authors. The need of a shared protocol among research laboratories all over the world could lead to a consensus conference.

The estimated mechanical advantage of the prosimian ankle joint musculature, and implications for locomotor adaptation.

PubMed

Goto, Ryosuke; Kumakura, Hiroo

2013-05-01

In this study we compared the power arm lengths and mechanical advantages attributed to 12 lower leg muscles across three prosimian species. The origins and insertions of the lower leg muscles in Garnett's galago, the ring-tailed lemur, and the slow loris were quantified and correlated with positional behaviour. The ankle joint of the galago has a speed-oriented mechanical system, in contrast to that of the slow loris, which exhibits more power-oriented mechanics. The lemur ankle joint exhibited intermediate power arm lengths and an intermediate mechanical advantage relative to the other primates. This result suggests that the mechanical differences in the ankle between the galago and the lemur, taxa that exhibit similar locomotory repertoires, reflect a difference in the kinematics and kinetics of leaping (i.e. generalised vs. specialised leapers). In contrast to leaping primates, lorises have developed a more power-oriented mechanical system as a foot adaptation for positional behaviours such as bridging or cantilevering in their arboreal habitat. © 2013 Anatomical Society.

Effect of Post-Weld Heat Treatment on Microstructure and Mechanical Properties of X52 Linepipe HFIW Joints

NASA Astrophysics Data System (ADS)

Kavousi Sisi, A.; Mirsalehi, S. E.

2015-04-01

In the present paper, influences of normalization heat treatment on microstructural and mechanical properties of high-frequency induction welded (HFIW) joints of X52 steel have been investigated. HFIW joints were post-weld heat treated at different times and temperatures. The microstructure and mechanical properties of the heat treated joints were then comprehensively investigated. Based on the results, a proper normalization of the primary fine grain steel caused the grain size to increase; but because of converting brittle microstructure into ductile microstructure, it caused the toughness to increase also. In addition, the ductility of the joints was enhanced. Nevertheless, tensile strength, yield strength, and hardness were reduced. The results showed that 950 °C was the optimum normalization temperature from the standpoint of fracture toughness for the X52 steel joints. At 1050 °C, the carbides and/or nitrides in the steel dissolved, and excessive grain growth occurred. Hence, the maximum allowable temperature for normalization was found to be 1000 °C.

The associations between quadriceps muscle strength, power, and knee joint mechanics in knee osteoarthritis: A cross-sectional study.

PubMed

Murray, Amanda M; Thomas, Abbey C; Armstrong, Charles W; Pietrosimone, Brian G; Tevald, Michael A

2015-12-01

Abnormal knee joint mechanics have been implicated in the pathogenesis and progression of knee osteoarthritis. Deficits in muscle function (i.e., strength and power) may contribute to abnormal knee joint loading. The associations between quadriceps strength, power and knee joint mechanics remain unclear in knee osteoarthritis. Three-dimensional motion analysis was used to collect peak knee joint angles and moments during the first 50% of stance phase of gait in 33 participants with knee osteoarthritis. Quadriceps strength and power were assessed using a knee extension machine. Strength was quantified as the one repetition maximum. Power was quantified as the peak power produced at 40-90% of the one repetition maximum. Quadriceps strength accounted for 15% of the variance in peak knee flexion angle (P=0.016). Quadriceps power accounted for 20-29% of the variance in peak knee flexion angle (P<0.05). Quadriceps power at 90% of one repetition maximum accounted for 9% of the variance in peak knee adduction moment (P=0.05). These data suggest that quadriceps power explains more variance in knee flexion angle and knee adduction moment during gait in knee osteoarthritis than quadriceps strength. Additionally, quadriceps power at multiple loads is associated with knee joint mechanics and therefore should be assessed at a variety of loads. Taken together, these results indicate that quadriceps power may be a potential target for interventions aimed at changing knee joint mechanics in knee osteoarthritis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Relationship between mechanical ankle joint laxity and subjective function.

PubMed

Hubbard-Turner, Tricia

2012-10-01

An increase in ankle joint laxity has been reported in patients with chronic ankle instability (CAI). However, it is not known if this increase in joint laxity is responsible for the subjective level of functional deficits also reported in these patients. One hundred twenty subjects with unilateral CAI (55 males, 65 females; age, 20.6 ± 1.5 years; mass, 74.5 ± 13.6 kg; height, 174.2 ± 9.7 cm) participated in the study. Mechanical joint stability was measured with an instrumented ankle arthrometer. The arthrometer measured ankle joint motion for anterior/posterior translation and inversion/eversion angular displacement. Subjective level of function was assessed with the foot and ankle disability index (FADI) and foot and ankle disability index sport (FADIS). Bivariate correlations using Pearson Product Moments were made between all dependent variables taken on the unstable ankles. The strongest relationship was between anterior laxity and the FADIS (r = -0.88, p < 0.0001). As scores on the FADIS decreased, anterior laxity increased. Similar significant results were reported for anterior laxity and the FADI (r = -0.65, p = 0.013), as well as inversion laxity and the FADI (r = -0.53, p = 0.017) and FADIS (r = -0.45, p = 0.013). These data demonstrate that there appears to be a relationship between anterior and inversion ankle laxity and subjective function in those with CAI. Although numerous insufficiencies develop after an ankle sprain, increased laxity may cause some of the subjective functional deficits reported in those with CAI. Strategies to prevent increased laxity following ankle sprain may improve the patient's subjective level of function.

The Effects of Fluid Absorption on the Mechanical Properties of Joint Prostheses Components

NASA Astrophysics Data System (ADS)

Yarbrough, David; Viano, Ann

2010-02-01

Ultra-high-molecular-weight polyethylene (UHMWPE) is the material playing the role of cartilage in human prosthetic joints. Wear debris from UHMWPE is a common reason for joint arthroplasty failure, and the exact mechanism responsible for wear remains an area of investigation. In this study, the microstructure of UHMWPE was examined as a function of fluid absorption. Samples with varying exposure to e-beam radiation (as part of the manufacturing process) were soaked for forty days in saline or artificial synovial fluid, under zero or 100 lbs load. Samples were then tensile-tested according to ASTM D-3895. The post-stressed material was then examined by transmission electron microscopy to evaluate the molecular response to stress, which correlates with macroscopic mechanical properties. Three parameters of the crystalline lamellae were measured: thickness, stacking ratio, and alignment to stress direction. Results indicate that fluid absorption does affect the mechanical properties of UHMWPE at both the microscopic and microscopic levels. )

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-04-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-05-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Characterization of Mechanical Properties and Residual Stress in API 5L X80 Steel Welded Joints

NASA Astrophysics Data System (ADS)

de Sousa Lins, Amilton; de Souza, Luís Felipe Guimarães; Fonseca, Maria Cindra

2018-01-01

The use of high-strength and low-alloy steels, high design factors and increasingly stringent safety requirements have increased the operating pressure levels and, consequently, the need for further studies to avoid and prevent premature pipe failure. To evaluate the possibility of improving productivity in manual arc welding of this type of steel, this work characterizes the mechanical properties and residual stresses in API 5L X80 steel welded joints using the SMAW and FCAW processes. The residual stresses were analyzed using x-ray diffraction with the sin2 ψ method at the top and root of the welded joints in the longitudinal and transverse directions of the weld bead. The mechanical properties of the welded joints by both processes were characterized in terms of tensile strength, impact toughness and Vickers microhardness in the welded and shot peening conditions. A predominantly compressive residual stress was found, and shot peening increased the tensile strength and impact toughness in both welded joints.

Microstructures and Mechanical Properties of 12Cr1MoVG Tube Welded Joints With/Without Post-weld Heat Treatment

NASA Astrophysics Data System (ADS)

Wang, Jingjing; Sun, Jian; Yu, Xinhai; Chen, Guohong; Fu, Qiuhua; Gao, Chao; Tang, Wenming

2017-10-01

Small-caliber, thick-wall 12Cr1MoVG seamless steel tube welded joints were fabricated in this study by gas tungsten arc welding and shielded metal arc welding techniques, then the microstructures, mechanical properties, and residual stress distributions of the joints with or without post-weld heat treatment (PWHT) were compared. The welded joints are mainly composed of bcc ferrite (F), Fe3C, and M7C3 carbides. PWHT did not cause an apparent microstructure evolution in the joints, but promoted granular pearlite decomposition and growth of F grains and carbides, therefore decreasing the yield, tensile strength, and hardness while increasing the impact toughness and elongation of the welded joints. PWHT also released the circumferential residual stress and altered the stress state in the joint from tensile to compressive. Although the mechanical properties and bending performance of the small-caliber, thick-wall 12Cr1MoVG seamless welded joints without PWHT are acceptable, our results show that the joints with PWHT are more reliable.

Mechanical Influences on Morphogenesis of the Knee Joint Revealed through Morphological, Molecular and Computational Analysis of Immobilised Embryos

PubMed Central

Roddy, Karen A.; Prendergast, Patrick J.; Murphy, Paula

2011-01-01

Very little is known about the regulation of morphogenesis in synovial joints. Mechanical forces generated from muscle contractions are required for normal development of several aspects of normal skeletogenesis. Here we show that biophysical stimuli generated by muscle contractions impact multiple events during chick knee joint morphogenesis influencing differential growth of the skeletal rudiment epiphyses and patterning of the emerging tissues in the joint interzone. Immobilisation of chick embryos was achieved through treatment with the neuromuscular blocking agent Decamethonium Bromide. The effects on development of the knee joint were examined using a combination of computational modelling to predict alterations in biophysical stimuli, detailed morphometric analysis of 3D digital representations, cell proliferation assays and in situ hybridisation to examine the expression of a selected panel of genes known to regulate joint development. This work revealed the precise changes to shape, particularly in the distal femur, that occur in an altered mechanical environment, corresponding to predicted changes in the spatial and dynamic patterns of mechanical stimuli and region specific changes in cell proliferation rates. In addition, we show altered patterning of the emerging tissues of the joint interzone with the loss of clearly defined and organised cell territories revealed by loss of characteristic interzone gene expression and abnormal expression of cartilage markers. This work shows that local dynamic patterns of biophysical stimuli generated from muscle contractions in the embryo act as a source of positional information guiding patterning and morphogenesis of the developing knee joint. PMID:21386908

The mechanism of joint capsule thermal modification in an in-vitro sheep model.

PubMed

Hayashi, K; Peters, D M; Thabit, G; Hecht, P; Vanderby, R; Fanton, G S; Markel, M D

2000-01-01

The purpose of this study was to understand the mechanism responsible for joint capsule shrinkage after nonablative laser application in an in-vitro sheep model. Femoropatellar joint capsular tissue specimens harvested from 20 adult sheep were treated with one of three power settings of a holmium:yttrium-aluminum-garnet laser or served as a control. Laser treatment significantly shortened the tissue and decreased tissue stiffness in all three laser groups, whereas failure strength was not altered significantly by laser treatment. Transmission electron microscopic examination showed swollen collagen fibrils and loss of membrane integrity of fibroblasts. A thermometric study revealed nonablative laser energy caused tissue temperature to rise in the range of 64 degrees C to 100 degrees C. Electrophoresis after trypsin digestion of the tissue revealed significant loss of distinct alpha bands of Type I collagen in laser treated samples, whereas alpha bands were present in laser treated tissue without trypsin digestion. The results of this study support the concept that the primary mechanism responsible for the effect of nonablative laser energy is thermal denaturation of collagen in joint capsular tissue associated with unwinding of the triple helical structure of the collagen molecule.

Rhythm in joint action: psychological and neurophysiological mechanisms for real-time interpersonal coordination.

PubMed

Keller, Peter E; Novembre, Giacomo; Hove, Michael J

2014-12-19

Human interaction often requires simultaneous precision and flexibility in the coordination of rhythmic behaviour between individuals engaged in joint activity, for example, playing a musical duet or dancing with a partner. This review article addresses the psychological processes and brain mechanisms that enable such rhythmic interpersonal coordination. First, an overview is given of research on the cognitive-motor processes that enable individuals to represent joint action goals and to anticipate, attend and adapt to other's actions in real time. Second, the neurophysiological mechanisms that underpin rhythmic interpersonal coordination are sought in studies of sensorimotor and cognitive processes that play a role in the representation and integration of self- and other-related actions within and between individuals' brains. Finally, relationships between social-psychological factors and rhythmic interpersonal coordination are considered from two perspectives, one concerning how social-cognitive tendencies (e.g. empathy) affect coordination, and the other concerning how coordination affects interpersonal affiliation, trust and prosocial behaviour. Our review highlights musical ensemble performance as an ecologically valid yet readily controlled domain for investigating rhythm in joint action. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Effect of post weld impact treatment (PWIT) on mechanical properties of spot-welded joint

NASA Astrophysics Data System (ADS)

Ghazali, F. A.; Salleh, Z.; Hyie, K. M.; Rozlin, N. M. Nik; Hamidi, S. H. Ahmad; Padzi, M. M.

2017-12-01

This paper focuses on the study of improvement for spot welding on the tensile shear and hardness by applying post weld impact treatment (PWIT) on the welded joint. The main objective of the research is to characterize and improve the mechanical properties of the joint. The method of PWIT used on the welded joint was Pneumatic Impact Treatment (PIT). The concept of PIT on spot welding is that it improves the mechanical properties of the welded zone. The working sample was undergoing a resistance spot welding of joining two similar in dimension and material of a steel plate before treated. The dimension of both plate are 110 mm × 45 mm × 1.2 mm and the material used were low carbon steel (LCS). All the welded samples were tested for its mechanical properties by performing the tensile-shear and hardness test. Tensile-shear test was conducted on the spot welded, both treated and as-welded samples using crosshead speed of 2 mm/min, while hardness test was performed using 1kgf load via Vickers hardness indenter. The effects of PIT on tensile-shear properties and hardness were evaluated and found that the implementation of PIT has increased tensile shear and hardness significantly.

Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer

The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted formore » by the glass transition temperature, T g, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, T ref, by the same amount as the T g depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive T g depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.« less

Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

DOE PAGES

Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer; ...

2015-08-06

The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted formore » by the glass transition temperature, T g, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, T ref, by the same amount as the T g depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive T g depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.« less

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

2016-04-01

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

Impact of multiple joint impairments on the energetics and mechanics of walking in patients with haemophilia.

PubMed

Lobet, S; Detrembleur, C; Hermans, C

2013-03-01

Few studies have assessed the changes produced by multiple joint impairments (MJI) of the lower limbs on gait in patients with haemophilia (PWH). In patients with MJI, quantifiable outcome measures are necessary if treatment benefits are to be compared. This study was aimed at observing the metabolic cost, mechanical work and efficiency of walking among PWH with MJI and to investigate the relationship between joint damage and any changes in mechanical and energetic variables. This study used three-dimensional gait analysis to investigate the kinematics, cost, mechanical work and efficiency of walking in 31 PWH with MJI, with the results being compared with speed-matched values from a database of healthy subjects. Regarding energetics, the mass-specific net cost of transport (C(net)) was significantly higher for PWH with MJI compared with control and directly related to a loss in dynamic joint range of motion. Surprisingly, however, there was no substantial increase in mechanical work, with PWH being able to adopt a walking strategy to improve energy recovery via the pendulum mechanism. This probable compensatory mechanism to economize energy likely counterbalances the supplementary work associated with an increased vertical excursion of centre of mass (CoM) and lower muscle efficiency of locomotion. Metabolic variables were probably the most representative variables of gait disability for these subjects with complex orthopaedic degenerative disorders. © 2012 Blackwell Publishing Ltd.

Size effects in tin-based lead-free solder joints: Kinetics of bond formation and mechanical characteristics

NASA Astrophysics Data System (ADS)

Abdelhadi, Ousama Mohamed Omer

Continuous miniaturization of microelectronic interconnects demands smaller joints with comparable microstructural and structural sizes. As the size of joints become smaller, the volume of intermetallics (IMCs) becomes comparable with the joint size. As a result, the kinetics of bond formation changes and the types and thicknesses of IMC phases that form within the constrained region of the bond varies. This dissertation focuses on investigating combination effects of process parameters and size on kinetics of bond formation, resulting microstructure and the mechanical properties of joints that are formed under structurally constrained conditions. An experiment is designed where several process parameters such as time of bonding, temperature, and pressure, and bond thickness as structural chracteristic, are varied at multiple levels. The experiment is then implemented on the process. Scanning electron microscope (SEM) is then utilized to determine the bond thickness, IMC phases and their thicknesses, and morphology of the bonds. Electron backscatter diffraction (EBSD) is used to determine the grain size in different regions, including the bulk solder, and different IMC phases. Physics-based analytical models have been developed for growth kinetics of IMC compounds and are verified using the experimental results. Nanoindentation is used to determine the mechanical behavior of IMC phases in joints in different scales. Four-point bending notched multilayer specimen and four-point bending technique were used to determine fracture toughness of the bonds containing IMCs. Analytical modeling of peeling and shear stresses and fracture toughness in tri-layer four-point bend specimen containing intermetallic layer was developed and was verified and validated using finite element simulation and experimental results. The experiment is used in conjunction with the model to calculate and verify the fracture toughness of Cu6Sn5 IMC materials. As expected two different IMC phases

Effect of joint mechanism on vehicle redirectional capability of water-filled road safety barrier systems.

PubMed

Thiyahuddin, M I; Thambiratnam, D P; Gu, Y T

2014-10-01

Portable water-filled barriers (PWFBs) are roadside appurtenances that prevent vehicles from penetrating into temporary construction zones on roadways. PWFBs are required to satisfy the strict regulations for vehicle re-direction in tests. However, many of the current PWFBs fail to re-direct the vehicle at high speeds due to the inability of the joints to provide appropriate stiffness. The joint mechanism hence plays a crucial role in the performance of a PWFB system at high speed impacts. This paper investigates the desired features of the joint mechanism in a PWFB system that can re-direct vehicles at high speeds, while limiting the lateral displacement to acceptable limits. A rectangular "wall" representative of a 30m long barrier system was modeled and a novel method of joining adjacent road barriers was introduced through appropriate pin-joint connections. The impact response of the barrier "wall" and the vehicle was obtained and the results show that a rotational stiffness of 3000kNm/rad at the joints seems to provide the desired features of the PWFB system to re-direct impacting vehicles and restrict the lateral deflection. These research findings will be useful to safety engineers and road barrier designers in developing a new generation of PWFBs for increased road safety. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mechanical Properties of Steel P92 Welded Joints Obtained By TIG Technology

NASA Astrophysics Data System (ADS)

Mohyla, P.; Havelka, L.; Schmidová, E.; Vontorová, J.

2017-11-01

Mechanical properties of P92 steel welded joints obtained using the TIG (141) technology have been studied upon post-welding heat treatment (PWHT). The microhardness, tensile strength, and impact toughness of metal in the weld and heat-affected zone are determined. The PWHT is shown to be obligatory.

Effects of step rate manipulation on joint mechanics during running.

PubMed

Heiderscheit, Bryan C; Chumanov, Elizabeth S; Michalski, Max P; Wille, Christa M; Ryan, Michael B

2011-02-01

the objective of this study was to characterize the biomechanical effects of step rate modification during running on the hip, knee, and ankle joints so as to evaluate a potential strategy to reduce lower extremity loading and risk for injury. three-dimensional kinematics and kinetics were recorded from 45 healthy recreational runners during treadmill running at constant speed under various step rate conditions (preferred, ± 5%, and ± 10%). We tested our primary hypothesis that a reduction in energy absorption by the lower extremity joints during the loading response would occur, primarily at the knee, when step rate was increased. less mechanical energy was absorbed at the knee (P < 0.01) during the +5% and +10% step rate conditions, whereas the hip (P < 0.01) absorbed less energy during the +10% condition only. All joints displayed substantially (P < 0.01) more energy absorption when preferred step rate was reduced by 10%. Step length (P < 0.01), center of mass vertical excursion (P < 0.01), braking impulse (P < 0.01), and peak knee flexion angle (P < 0.01) were observed to decrease with increasing step rate. When step rate was increased 10% above preferred, peak hip adduction angle (P < 0.01) and peak hip adduction (P < 0.01) and internal rotation (P < 0.01) moments were found to decrease. we conclude that subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries.

Effects of Step Rate Manipulation on Joint Mechanics during Running

PubMed Central

Heiderscheit, Bryan C.; Chumanov, Elizabeth S.; Michalski, Max P.; Wille, Christa M.; Ryan, Michael B.

2010-01-01

Purpose The objective of this study was to characterize the biomechanical effects of step rate modification during running on the hip, knee and ankle joints, so as to evaluate a potential strategy to reduce lower extremity loading and risk for injury. Methods Three-dimensional kinematics and kinetics were recorded from 45 healthy recreational runners during treadmill running at constant speed under various step rate conditions (preferred, ± 5% and ± 10%). We tested our primary hypothesis that a reduction in energy absorption by the lower extremity joints during the loading response would occur, primarily at the knee, when step rate was increased. Results Less mechanical energy was absorbed at the knee (p<0.01) during the +5% and +10% step rate conditions, while the hip (p<0.01) absorbed less energy during the +10% condition only. All joints displayed substantially (p<0.01) more energy absorption when preferred step rate was reduced by 10. Step length (p<0.01), center of mass vertical excursion (p<0.01), breaking impulse (p<0.01) and peak knee flexion angle (p<0.01) were observed to decrease with increasing step rate. When step rate was increased 10% above preferred, peak hip adduction angle (p<0.01), as well as peak hip adduction (p<0.01) and internal rotation (p<0.01) moments, were found to decrease. Conclusion We conclude that subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries. PMID:20581720

Finite element analysis of mechanical behavior of human dysplastic hip joints: a systematic review.

PubMed

Vafaeian, B; Zonoobi, D; Mabee, M; Hareendranathan, A R; El-Rich, M; Adeeb, S; Jaremko, J L

2017-04-01

Developmental dysplasia of the hip (DDH) is a common condition predisposing to osteoarthritis (OA). Especially since DDH is best identified and treated in infancy before bones ossify, there is surprisingly a near-complete absence of literature examining mechanical behavior of infant dysplastic hips. We sought to identify current practice in finite element modeling (FEM) of DDH, to inform future modeling of infant dysplastic hips. We performed multi-database systematic review using PRISMA criteria. Abstracts (n = 126) fulfilling inclusion criteria were screened for methodological quality, and results were analyzed and summarized for eligible articles (n = 12). The majority of the studies modeled human adult dysplastic hips. Two studies focused on etiology of DDH through simulating mechanobiological growth of prenatal hips; we found no FEM-based studies in infants or children. Finite element models used either patient-specific geometry or idealized average geometry. Diversities in choice of material properties, boundary conditions, and loading scenarios were found in the finite-element models. FEM of adult dysplastic hips demonstrated generally smaller cartilage contact area in dysplastic hips than in normal joints. Contact pressure (CP) may be higher or lower in dysplastic hips depending on joint geometry and mechanical contribution of labrum (Lb). FEM of mechanobiological growth of prenatal hip joints revealed evidence for effects of the joint mechanical environment on formation of coxa valga, asymmetrically shallow acetabulum and malformed femoral head associated with DDH. Future modeling informed by the results of this review may yield valuable insights into optimal treatment of DDH, and into how and why OA develops early in DDH. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Influence of groove size and reinforcements addition on mechanical properties and microstructure of friction stir welded joints

NASA Astrophysics Data System (ADS)

Reddy Baridula, Ravinder; Ibrahim, Abdullah Bin; Yahya, Che Ku Mohammad Faizal Bin Che Ku; Kulkarni, Ratnakar; Varma Ramaraju, Ramgopal

2018-03-01

The butt joints fabricated by friction stir welding were found to have more strength than the joints obtained by conventional joining process. The important outcome of this process is the successful fabrication of surface composites with improved properties. Thus in order to further enhance the strength of the dissimilar alloy joints the reinforcements can be deposited in to the aluminium matrix during the process of friction stir welding. In the present study the multi-walled carbon nanotubes were embedded in to the groove by varying the width during joining of dissimilar alloys AA2024 and AA7075. Four widths were selected with constant depth and optimum process parameters were selected to fabricate the sound welded joints. The results show that the mechanical properties of the fabricated butt joints were influenced by the size of the groove, due to variation in the deposition of reinforcement in the stir zone. The microstructural study and identification of the elements of the welded joints show that the reinforcements deposition is influenced by the size of the groove. It has also been observed that the groove with minimum width is more effective than higher width. The mechanical properties are found to be improved due to the pinning of grain boundaries.

Joint Contact Stress

PubMed Central

Brand, Richard A

2005-01-01

A joint's normal mechanical history contributes to the maintenance of articular cartilage and underlying bone. Loading facilitates the flow of nutrients into cartilage and waste products away, and additionally provides the mechanical signals essential for normal cell and tissue maintenance. Deleteriously low or high contact stresses have been presumed to result in joint deterioration, and particular aspects of the mechanical environment may facilitate repair of damaged cartilage. For decades, investigators have explored static joint contact stresses (under some more or less arbitrary condition) as a surrogate of the relevant mechanical history. Contact stresses have been estimated in vitro in many joints and in a number of species, although only rarely in vivo. Despite a number of widely varying techniques (and spatial resolutions) to measure these contact stresses, reported ranges of static peak normal stresses are relatively similar from joint to joint across species, and in the range of 0.5 to 5.0 MPa. This suggests vertebrate diarthrodial joints have evolved to achieve similar mechanical design criteria. Available evidence also suggests some disorders of cartilage deterioration are associated with somewhat higher peak pressures ranging from 1-20 MPa, but overlapping the range of normal pressures. Some evidence and considerable logic suggests static contact stresses per se do not predict cartilage responses, but rather temporal aspects of the contact stress history. Static contact stresses may therefore not be a reasonable surrogate for biomechanical studies. Rather, temporal and spatial aspects of the loading history undoubtedly induce beneficial and deleterious biological responses. Finally, since all articular cartilage experiences similar stresses, the concept of a "weight-bearing" versus a "non-weight-bearing" joint seems flawed, and should be abandoned. PMID:16089079

Concept for a fast analysis method of the energy dissipation at mechanical joints

NASA Astrophysics Data System (ADS)

Wolf, Alexander; Brosius, Alexander

2017-10-01

When designing hybrid parts and structures one major challenge is the design, production and quality assessment of the joining points. While the polymeric composites themselves have excellent material properties, the necessary joints are often the weak link in assembled structures. This paper presents a method of measuring and analysing the energy dissipation at mechanical joining points of hybrid parts. A simplified model is applied based on the characteristic response to different excitation frequencies and amplitudes. The dissipation from damage is the result of relative moments between joining partners und damaged fibres within the composite, whereas the visco-elastic material behaviour causes the intrinsic dissipation. The ambition is to transfer these research findings to the characterisation of mechanical joints in order to quickly assess the general quality of the joint with this non-destructive testing method. The inherent challenge for realising this method is the correct interpretation of the measured energy dissipation and its attribution to either a bad joining point or intrinsic material properties. In this paper the authors present the concept for energy dissipation measurements at different joining points. By inverse analysis a simplified fast semi-analytical model will be developed that allows for a quick basic quality assessment of a given joining point.

Effect of Board Thickness on Sn-Ag-Cu Joint Interconnect Mechanical Shock Performance

NASA Astrophysics Data System (ADS)

Lee, Tae-Kyu; Xie, Weidong

2014-12-01

The mechanical stability of solder joints with Sn-Ag-Cu alloy joints on various board thicknesses was investigated with a high G level shock environment. A test vehicle with three different board thicknesses was used for board drop shock performance tests. These vehicles have three different strain and shock level condition couples per board, and are used to identify the joint stability and failure modes based on the board responses. The results revealed that joint stability is sensitive to board thickness. The board drop shock test showed that the first failure location shifts from the corner location near the standoff to the center with increased board thickness due to the shock wave response. From analysis of the thickness variation and failure cycle number, the strain rate during the pulse strain cycle is the dominant factor, which defines the life cycle number per board thickness, and not the maximum strain value. The failure location shift and the shock performance differentiation are discussed from the perspective of maximum principal strain, cycle frequency and strain rate per cycle.

Musclelike joint mechanism driven by dielectric elastomer actuator for robotic applications

NASA Astrophysics Data System (ADS)

Jung, Ho Sang; Cho, Kyeong Ho; Park, Jae Hyeong; Yang, Sang Yul; Kim, Youngeun; Kim, Kihyeon; Nguyen, Canh Toan; Phung, Hoa; Tien Hoang, Phi; Moon, Hyungpil; Koo, Ja Choon; Ryeol Choi, Hyouk

2018-07-01

The purpose of this study is to develop an artificial muscle actuator suitable for robotic applications, and to demonstrate the feasibility of applying this actuator to an arm mechanism, and controlling it delicately and smoothly like a human being. To accomplish this, we perform the procedures that integrate the soft actuator, called the single body dielectric elastomer actuator, which is very flexible and capable of high speed operation, and the displacement amplification mechanism called the sliding filament joint mechanism, which mimics the sliding filament model of human muscles. In this paper, we describe the characteristics and control method of the actuation system that consists of actuator, mechanism, and embedded controller, and show the experimental results of the closed-loop position and static stiffness control of the robotic arm application. Finally, based on the results, we evaluate the performance of this application.

Joint Mobilization Enhances Mechanisms of Conditioned Pain Modulation in Individuals With Osteoarthritis of the Knee.

PubMed

Courtney, Carol A; Steffen, Alana D; Fernández-de-Las-Peñas, César; Kim, John; Chmell, Samuel J

2016-03-01

An experimental laboratory study with a repeated-measures crossover design. Treatment effects of joint mobilization may occur in part by decreasing excitability of central nociceptive pathways. Impaired conditioned pain modulation (CPM) has been found experimentally in persons with knee and hip osteoarthritis, indicating impaired inhibition of central nociceptive pathways. We hypothesized increased effectiveness of CPM following application of joint mobilization, determined via measures of deep tissue hyperalgesia. To examine the effect of joint mobilization on impaired CPM. An examination of 40 individuals with moderate/severe knee osteoarthritis identified 29 (73%) with impaired CPM. The subjects were randomized to receive 6 minutes of knee joint mobilization (intervention) or manual cutaneous input only, 1 week apart. Deep tissue hyperalgesia was examined via pressure pain thresholds bilaterally at the knee medial joint line and the hand at baseline, postintervention, and post-CPM testing. Further, vibration perception threshold was measured at the medial knee epicondyle at baseline and post-CPM testing. Joint mobilization, but not cutaneous input intervention, resulted in a global increase in pressure pain threshold, indicated by diminished hyperalgesic responses to pressure stimulus. Further, CPM was significantly enhanced following joint mobilization. Diminished baseline vibration perception threshold acuity was enhanced following joint mobilization at the knee that received intervention, but not at the contralateral knee. Resting pain was also significantly lower following the joint intervention. Conditioned pain modulation was enhanced following joint mobilization, demonstrated by a global decrease in deep tissue pressure sensitivity. Joint mobilization may act via enhancement of descending pain mechanisms in patients with painful knee osteoarthritis.

The Influence of the Heat-Affected Zone Mechanical Properties on the Behaviour of the Welding in Transverse Plate-to-Tube Joints.

PubMed

Lozano, Miguel; Serrano, Miguel A; López-Colina, Carlos; Gayarre, Fernando L; Suárez, Jesús

2018-02-09

Eurocode 3 establishes the component method to analytically characterize the structural joints between beam and columns. When one of the members involved in the joint is a hollow section (i.e., a tube) there is a lack of information for the specific components present in the joint. There are two different ways to bridge the gap: experimental testing on the actual beam column joints involving tubular sections; or numerical modelization, typically by means of finite element analysis. For this second option, it is necessary to know the actual mechanical properties of the material. As long as the joint implies a welding process, there is a concern related to how the mechanical properties in the heat-affected zone (HAZ) influence the behavior of the joint. In this work, some coupons were extracted from the HAZ of the beam-column joint. The coupons were tested and the results were implemented in the numerical model of the joint, in an attempt to bring it closer to the experimental results of the tested joints.

Effect of Multipass TIG and Activated TIG Welding Process on the Thermo-Mechanical Behavior of 316LN Stainless Steel Weld Joints

NASA Astrophysics Data System (ADS)

Ganesh, K. C.; Balasubramanian, K. R.; Vasudevan, M.; Vasantharaja, P.; Chandrasekhar, N.

2016-04-01

The primary objective of this work was to develop a finite element model to predict the thermo-mechanical behavior of an activated tungsten inert gas (ATIG)-welded joint. The ATIG-welded joint was fabricated using 10 mm thickness of 316LN stainless steel plates in a single pass. To distinguish the merits of ATIG welding process, it was compared with manual multipass tungsten inert gas (MPTIG)-welded joint. The ATIG-welded joint was fabricated with square butt edge configuration using an activating flux developed in-house. The MPTIG-welded joint was fabricated in thirteen passes with V-groove edge configuration. The finite element model was developed to predict the transient temperature, residual stress, and distortion of the welded joints. Also, microhardness, impact toughness, tensile strength, ferrite measurement, and microstructure were characterized. Since most of the recent publications of ATIG-welded joint was focused on the molten weld pool dynamics, this research work gives an insight on the thermo-mechanical behavior of ATIG-welded joint over MPTIG-welded joint.

Prediction of elbow joint contact mechanics in the multibody framework.

PubMed

Rahman, Munsur; Cil, Akin; Stylianou, Antonis P

2016-03-01

Computational multibody musculoskeletal models of the elbow joint that are capable of simultaneous and accurate predictions of muscle and ligament forces, along with cartilage contact mechanics can be immensely useful in clinical practice. As a step towards producing a musculoskeletal model that includes the interaction between cartilage and muscle loading, the goal of this study was to develop subject-specific multibody models of the elbow joint with discretized humerus cartilage representation interacting with the radius and ulna cartilages through deformable contacts. The contact parameters for the compliant contact law were derived using simplified elastic foundation contact theory. The models were then validated by placing the model in a virtual mechanical tester for flexion-extension motion similar to a cadaver experiment, and the resulting kinematics were compared. Two cadaveric upper limbs were used in this study. The humeral heads were subjected to axial motion in a mechanical tester and the resulting kinematics from three bones were recorded for model validation. The maximum RMS error between the predicted and measured kinematics during the complete testing cycle was 2.7 mm medial-lateral translation and 9.7° varus-valgus rotation of radius relative to humerus (for elbow 2). After model validation, a lateral ulnar collateral ligament (LUCL) deficient condition was simulated and, contact pressures and kinematics were compared to the intact elbow model. A noticeable difference in kinematics, contact area, and contact pressure were observed for LUCL deficient condition. LUCL deficiency induced higher internal rotations for both the radius and ulna during flexion and an associated medial shift of the articular contact area. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Knee Joint Contact Mechanics during Downhill Gait and its Relationship with Varus/Valgus Motion and Muscle Strength in Patients with Knee Osteoarthritis

PubMed Central

Farrokhi, Shawn; Voycheck, Carrie A.; Gustafson, Jonathan A.; Fitzgerald, G. Kelley; Tashman, Scott

2015-01-01

Objective The objective of this exploratory study was to evaluate tibiofemoral joint contact point excursions and velocities during downhill gait and assess the relationship between tibiofemoral joint contact mechanics with frontal-plane knee joint motion and lower extremity muscle weakness in patients with knee osteoarthritis (OA). Methods Dynamic stereo X-ray was used to quantify tibiofemoral joint contact mechanics and frontal-plane motion during the loading response phase of downhill gait in 11 patients with knee OA and 11 control volunteers. Quantitative testing of the quadriceps and the hip abductor muscles was also performed. Group differences in contact mechanics and frontal-plane motion excursions were compared using analysis of covariance with adjustments for body mass index. Differences in strength were compared using independent sample t-tests. Additionally, linear associations between contact mechanics with frontal-plane knee motion and muscle strength were evaluated using Pearson's correlation coefficients. Results Patients with knee OA demonstrated larger medial/lateral joint contact point excursions (p<0.02) and greater heel-strike joint contact point velocities (p<0.05) for the medial and lateral compartments compared to the control group. The peak medial/lateral joint contact point velocity of the medial compartment was also greater for patients with knee OA compared to their control counterparts (p=0.02). Additionally, patients with knee OA demonstrated significantly increased frontal-plane varus motion excursions (p<0.01) and greater quadriceps and hip abductor muscle weakness (p=0.03). In general, increased joint contact point excursions and velocities in patients with knee OA were linearly associated with greater frontal-plane varus motion excursions (p<0.04) but not with quadriceps or hip abductor strength. Conclusion Altered contact mechanics in patients with knee OA may be related to compromised frontal-plane joint stability but not with

Adjustable bias column end joint assembly

NASA Technical Reports Server (NTRS)

Wallsom, Richard E. (Inventor); Bush, Harold G. (Inventor)

1994-01-01

An adjustable mechanical end joint system for connecting structural column elements and eliminating the possibility of free movement between joint halves during loading or vibration has a node joint body having a cylindrical engaging end and a column end body having a cylindrical engaging end. The column end joint body has a compressible preload mechanism and plunger means housed therein. The compressible preload mechanism may be adjusted from the exterior of the column end joint body through a port.

The Effects of Load Carriage and Muscle Fatigue on Lower-Extremity Joint Mechanics

ERIC Educational Resources Information Center

Wang, He; Frame, Jeff; Ozimek, Elicia; Leib, Daniel; Dugan, Eric L.

2013-01-01

Military personnel are commonly afflicted by lower-extremity overuse injuries. Load carriage and muscular fatigue are major stressors during military basic training. Purpose: To examine effects of load carriage and muscular fatigue on lower-extremity joint mechanics during walking. Method: Eighteen men performed the following tasks: unloaded…

Structural and mechanical properties of welded joints of reduced activation martensitic steels

NASA Astrophysics Data System (ADS)

Filacchioni, G.; Montanari, R.; Tata, M. E.; Pilloni, L.

2002-12-01

Gas tungsten arc welding and electron beam welding methods were used to realise welding pools on plates of reduced activation martensitic steels. Structural and mechanical features of these simulated joints have been investigated in as-welded and post-welding heat-treated conditions. The research allowed to assess how each welding technique affects the original mechanical properties of materials and to find suitable post-welding heat treatments. This paper reports results from experimental activities on BATMAN II and F82H mod. steels carried out in the frame of the European Blanket Project - Structural Materials Program.

Kinematic evaluation of the finger's interphalangeal joints coupling mechanism--variability, flexion-extension differences, triggers, locking swanneck deformities, anthropometric correlations.

PubMed

Leijnse, J N A L; Quesada, P M; Spoor, C W

2010-08-26

The human finger contains tendon/ligament mechanisms essential for proper control. One mechanism couples the movements of the interphalangeal joints when the (unloaded) finger is flexed with active deep flexor. This study's aim was to accurately determine in a large finger sample the kinematics and variability of the coupled interphalangeal joint motions, for potential clinical and finger model validation applications. The data could also be applied to humanoid robotic hands. Sixty-eight fingers were measured in seventeen hands in nine subjects. Fingers exhibited great joint mobility variability, with passive proximal interphalangeal hyperextension ranging from zero to almost fifty degrees. Increased measurement accuracy was obtained by using marker frames to amplify finger segment motions. Gravitational forces on the marker frames were not found to invalidate measurements. The recorded interphalangeal joint trajectories were highly consistent, demonstrating the underlying coupling mechanism. The increased accuracy and large sample size allowed for evaluation of detailed trajectory variability, systematic differences between flexion and extension trajectories, and three trigger types, distinct from flexor tendon triggers, involving initial flexion deficits in either proximal or distal interphalangeal joint. The experimental methods, data and analysis should advance insight into normal and pathological finger biomechanics (e.g., swanneck deformities), and could help improve clinical differential diagnostics of trigger finger causes. The marker frame measuring method may be useful to quantify interphalangeal joints trajectories in surgical/rehabilitative outcome studies. The data as a whole provide the most comprehensive collection of interphalangeal joint trajectories for clinical reference and model validation known to us to date. 2010 Elsevier Ltd. All rights reserved.

Modeling and simulating the neuromuscular mechanisms regulating ankle and knee joint stiffness during human locomotion.

PubMed

Sartori, Massimo; Maculan, Marco; Pizzolato, Claudio; Reggiani, Monica; Farina, Dario

2015-10-01

This work presents an electrophysiologically and dynamically consistent musculoskeletal model to predict stiffness in the human ankle and knee joints as derived from the joints constituent biological tissues (i.e., the spanning musculotendon units). The modeling method we propose uses electromyography (EMG) recordings from 13 muscle groups to drive forward dynamic simulations of the human leg in five healthy subjects during overground walking and running. The EMG-driven musculoskeletal model estimates musculotendon and resulting joint stiffness that is consistent with experimental EMG data as well as with the experimental joint moments. This provides a framework that allows for the first time observing 1) the elastic interplay between the knee and ankle joints, 2) the individual muscle contribution to joint stiffness, and 3) the underlying co-contraction strategies. It provides a theoretical description of how stiffness modulates as a function of muscle activation, fiber contraction, and interacting tendon dynamics. Furthermore, it describes how this differs from currently available stiffness definitions, including quasi-stiffness and short-range stiffness. This work offers a theoretical and computational basis for describing and investigating the neuromuscular mechanisms underlying human locomotion. Copyright © 2015 the American Physiological Society.

Microstructure and Mechanical Properties of Hybrid Welded Joints with Laser and CO2-Shielded Arc

NASA Astrophysics Data System (ADS)

Wahba, M.; Mizutani, M.; Katayama, S.

2016-07-01

With the objective of reducing the operating costs, argon-rich shielding gas was replaced by 100% CO2 gas in hybrid laser-arc welding of shipbuilding steel. The welding parameters were optimized to obtain buried-arc transfer in order to mitigate spatter formation. Sound butt joints could be successfully produced for plates of 14 and 17 mm thickness in one welding pass. Subsequently, the welded joints were subjected to different tests to evaluate the influence of CO2 shielding gas on the mechanical properties of the welded joints. All tensile-tested specimens failed in the base material, indicating the higher strength of the welded joints. The impact toughness of the welded joints, measured at -20 °C, reached approximately 76% of that of the base material, which was well above the limit set by the relevant standard. The microstructure of the fusion zone consisted of grain boundary ferrite and acicular ferrite uniformly over the plate thickness except for the joint root where the microstructure was chiefly ferrite with an aligned second phase. This resulted in higher hardness in the root region compared with the top and middle parts of the fusion zone.

Modeling and simulating the neuromuscular mechanisms regulating ankle and knee joint stiffness during human locomotion

PubMed Central

Maculan, Marco; Pizzolato, Claudio; Reggiani, Monica; Farina, Dario

2015-01-01

This work presents an electrophysiologically and dynamically consistent musculoskeletal model to predict stiffness in the human ankle and knee joints as derived from the joints constituent biological tissues (i.e., the spanning musculotendon units). The modeling method we propose uses electromyography (EMG) recordings from 13 muscle groups to drive forward dynamic simulations of the human leg in five healthy subjects during overground walking and running. The EMG-driven musculoskeletal model estimates musculotendon and resulting joint stiffness that is consistent with experimental EMG data as well as with the experimental joint moments. This provides a framework that allows for the first time observing 1) the elastic interplay between the knee and ankle joints, 2) the individual muscle contribution to joint stiffness, and 3) the underlying co-contraction strategies. It provides a theoretical description of how stiffness modulates as a function of muscle activation, fiber contraction, and interacting tendon dynamics. Furthermore, it describes how this differs from currently available stiffness definitions, including quasi-stiffness and short-range stiffness. This work offers a theoretical and computational basis for describing and investigating the neuromuscular mechanisms underlying human locomotion. PMID:26245321

Incorporation of Interfacial Intermetallic Morphology in Fracture Mechanism Map for Sn-Ag-Cu Solder Joints

NASA Astrophysics Data System (ADS)

Huang, Z.; Kumar, P.; Dutta, I.; Sidhu, R.; Renavikar, M.; Mahajan, R.

2014-01-01

A fracture mechanism map (FMM) is a powerful tool which correlates the fracture behavior of a material to its microstructural characteristics in an explicit and convenient way. In the FMM for solder joints, an effective thickness of the interfacial intermetallic compound (IMC) layer ( t eff) and the solder yield strength ( σ ys,eff) are used as abscissa and ordinate axes, respectively, as these two predominantly affect the fracture behavior of solder joints. Earlier, a definition of t eff, based on the uniform thickness of IMC ( t u) and the average height of the IMC scallops ( t s), was proposed and shown to aptly explain the fracture behavior of solder joints on Cu. This paper presents a more general definition of t eff that is more widely applicable to a range of metallizations, including Cu and electroless nickel immersion gold (ENIG). Using this new definition of t eff, mode I FMM for SAC387/Cu joints has been updated and its validity was confirmed. A preliminary FMM for SAC387/Cu joints with ENIG metallization is also presented.

Neuro-cognitive mechanisms of decision making in joint action: a human-robot interaction study.

PubMed

Bicho, Estela; Erlhagen, Wolfram; Louro, Luis; e Silva, Eliana Costa

2011-10-01

In this paper we present a model for action preparation and decision making in cooperative tasks that is inspired by recent experimental findings about the neuro-cognitive mechanisms supporting joint action in humans. It implements the coordination of actions and goals among the partners as a dynamic process that integrates contextual cues, shared task knowledge and predicted outcome of others' motor behavior. The control architecture is formalized by a system of coupled dynamic neural fields representing a distributed network of local but connected neural populations. Different pools of neurons encode task-relevant information about action means, task goals and context in the form of self-sustained activation patterns. These patterns are triggered by input from connected populations and evolve continuously in time under the influence of recurrent interactions. The dynamic model of joint action is evaluated in a task in which a robot and a human jointly construct a toy object. We show that the highly context sensitive mapping from action observation onto appropriate complementary actions allows coping with dynamically changing joint action situations. Copyright © 2010 Elsevier B.V. All rights reserved.

Mechanical Reliability of the Epoxy Sn-58wt.%Bi Solder Joints with Different Surface Finishes Under Thermal Shock

NASA Astrophysics Data System (ADS)

Sung, Yong-Gue; Myung, Woo-Ram; Jeong, Haksan; Ko, Min-Kwan; Moon, Jeonghoon; Jung, Seung-Boo

2018-04-01

The effect of thermal shock on the mechanical reliability of epoxy Sn-58wt.%Bi composite (epoxy Sn-58wt.%Bi) solder joints was investigated with different surface-finished substrates. Sn-58wt.%Bi-based solder has been considered as a promising candidate for low-temperature solder among various lead-free solders. However, Sn-58wt.%Bi solder joints can be easily broken under impact conditions such as mechanical shock, drop tests, and bending tests because of their poor ductility. Therefore, previous researchers have tried to improve the mechanical property of Sn-58wt.%Bi solder by additional elements and mixtures of metal powder and epoxy resin. Epoxy Sn-58wt.%Bi solder paste was fabricated by mixing epoxy resin and Sn-58wt.%Bi solder powder to enhance the mechanical reliability of Sn-58wt.%Bi solder joints. The epoxy Sn-58wt.%Bi solder paste was screen-printed onto various printed circuit board surfaces finished with organic solder preservatives (OSP), electroless nickel immersion gold (ENIG), and electroless nickel electroless palladium immersion gold (ENEPIG). The test components were prepared by a reflow process at a peak temperature of 190°C. The thermal shock test was carried out under the temperature range of - 40 to 125°C to evaluate the reliability of Sn-58wt.%Bi and epoxy Sn-58wt.%Bi solder joints. The OSP-finished sample showed a relatively higher mechanical property than those of ENIG and ENEPIG after thermal shock. The average number of cycles for epoxy Sn-58wt.%Bi solder with the OSP surface finish were 6 times higher than that for Sn-58wt.%Bi solder with the same finish. The microstructures of the solder joints were investigated by scanning electron microscopy, and the composition of the intermetallic compound (IMC) layer was analyzed by using energy dispersive spectrometry. Cu6Sn5 IMC was formed by the reaction between Sn-58wt.%Bi solder and a OSP surface-finished Cu after the reflow process. Ni3Sn4 IMC and (Ni, Pd)3Sn4 IMC were formed at the solder

Mechanical Reliability of the Epoxy Sn-58wt.%Bi Solder Joints with Different Surface Finishes Under Thermal Shock

NASA Astrophysics Data System (ADS)

Sung, Yong-Gue; Myung, Woo-Ram; Jeong, Haksan; Ko, Min-Kwan; Moon, Jeonghoon; Jung, Seung-Boo

2018-07-01

The effect of thermal shock on the mechanical reliability of epoxy Sn-58wt.%Bi composite (epoxy Sn-58wt.%Bi) solder joints was investigated with different surface-finished substrates. Sn-58wt.%Bi-based solder has been considered as a promising candidate for low-temperature solder among various lead-free solders. However, Sn-58wt.%Bi solder joints can be easily broken under impact conditions such as mechanical shock, drop tests, and bending tests because of their poor ductility. Therefore, previous researchers have tried to improve the mechanical property of Sn-58wt.%Bi solder by additional elements and mixtures of metal powder and epoxy resin. Epoxy Sn-58wt.%Bi solder paste was fabricated by mixing epoxy resin and Sn-58wt.%Bi solder powder to enhance the mechanical reliability of Sn-58wt.%Bi solder joints. The epoxy Sn-58wt.%Bi solder paste was screen-printed onto various printed circuit board surfaces finished with organic solder preservatives (OSP), electroless nickel immersion gold (ENIG), and electroless nickel electroless palladium immersion gold (ENEPIG). The test components were prepared by a reflow process at a peak temperature of 190°C. The thermal shock test was carried out under the temperature range of - 40 to 125°C to evaluate the reliability of Sn-58wt.%Bi and epoxy Sn-58wt.%Bi solder joints. The OSP-finished sample showed a relatively higher mechanical property than those of ENIG and ENEPIG after thermal shock. The average number of cycles for epoxy Sn-58wt.%Bi solder with the OSP surface finish were 6 times higher than that for Sn-58wt.%Bi solder with the same finish. The microstructures of the solder joints were investigated by scanning electron microscopy, and the composition of the intermetallic compound (IMC) layer was analyzed by using energy dispersive spectrometry. Cu6Sn5 IMC was formed by the reaction between Sn-58wt.%Bi solder and a OSP surface-finished Cu after the reflow process. Ni3Sn4 IMC and (Ni, Pd)3Sn4 IMC were formed at the solder

Knee joint contact mechanics during downhill gait and its relationship with varus/valgus motion and muscle strength in patients with knee osteoarthritis.

PubMed

Farrokhi, Shawn; Voycheck, Carrie A; Gustafson, Jonathan A; Fitzgerald, G Kelley; Tashman, Scott

2016-01-01

The objective of this exploratory study was to evaluate tibiofemoral joint contact point excursions and velocities during downhill gait and assess the relationship between tibiofemoral joint contact mechanics with frontal-plane knee joint motion and lower extremity muscle weakness in patients with knee osteoarthritis (OA). Dynamic stereo X-ray was used to quantify tibiofemoral joint contact mechanics and frontal-plane motion during the loading response phase of downhill gait in 11 patients with knee OA and 11 control volunteers. Quantitative testing of the quadriceps and the hip abductor muscles was also performed. Patients with knee OA demonstrated larger medial/lateral joint contact point excursions (p < 0.02) and greater heel-strike joint contact point velocities (p < 0.05) for the medial and lateral compartments compared to the control group. The peak medial/lateral joint contact point velocity of the medial compartment was also greater for patients with knee OA compared to their control counterparts (p = 0.02). Additionally, patients with knee OA demonstrated significantly increased frontal-plane varus motion excursions (p < 0.01) and greater quadriceps and hip abductor muscle weakness (p = 0.03). In general, increased joint contact point excursions and velocities in patients with knee OA were linearly associated with greater frontal-plane varus motion excursions (p < 0.04) but not with quadriceps or hip abductor strength. Altered contact mechanics in patients with knee OA may be related to compromised frontal-plane joint stability but not with deficits in muscle strength.

Ablating spinal NK1-bearing neurons eliminates the development of pain & reduces spinal neuronal hyperexcitability & inflammation from mechanical joint injury in the rat

PubMed Central

Weisshaar, Christine L.; Winkelstein, Beth A.

2014-01-01

The facet joint is a common source of pain especially from mechanical injury. Although chronic pain is associated with altered spinal glial and neuronal responses, the contribution of specific spinal cells to joint pain are not understood. This study used the neurotoxin [Sar9,Met(O2)11]-substance P-saporin (SSP-SAP) to selectively eliminate spinal cells expressing neurokinin-1 receptor (NK1R) in a rat model of painful facet joint injury to determine the role of those spinal neurons in pain from facet injury. Following spinal administration of SSP-SAP or its control (blank-SAP), a cervical facet injury was imposed and behavioral sensitivity assessed. Spinal extracellular recordings were made on day 7 to classify neurons and quantify evoked firing. Spinal glial activation and IL1α expression also were evaluated. SSP-SAP prevented the development of mechanical hyperalgesia that is induced by joint injury and reduced NK1R expression and mechanically-evoked neuronal firing in the dorsal horn. SSP-SAP also prevented a shift toward wide dynamic range neurons that is seen after injury. Spinal astrocytic activation and IL1α expression were reduced to sham levels with SSP-SAP treatment. These results suggest that spinal NK1R-bearing cells are critical in initiating spinal nociception and inflammation associated with a painful mechanical joint injury. Perspective Results demonstrate that cells expressing NK1R in the spinal cord are critical for the development of joint pain and spinal neuroplasticity and inflammation after trauma to the joint. These findings have utility for understanding mechanisms of joint pain and developing potential targets to treat pain. PMID:24389017

Mechanical and interfacial characterization of laser welded Co-Cr alloy with different joint configurations

PubMed Central

Kokolis, John; Chakmakchi, Makdad; Theocharopoulos, Antonios; Prombonas, Anthony

2015-01-01

PURPOSE The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs. MATERIALS AND METHODS Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a 45° bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (ε) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (α=.05) and Weibull analysis where Weibull modulus m and characteristic strength σο were identified. Fractured surfaces were imaged by a SEM. RESULTS SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, ε, m and σο) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups. CONCLUSION The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability. PMID:25722836

Gap compression/extension mechanism of bacterial flagellar hook as the molecular universal joint.

PubMed

Furuta, Tadaomi; Samatey, Fadel A; Matsunami, Hideyuki; Imada, Katsumi; Namba, Keiichi; Kitao, Akio

2007-03-01

Bacterial flagellar hook acts as a molecular universal joint, transmitting torque produced by the flagellar basal body, a rotary motor, to the flagellar filament. The hook forms polymorphic supercoil structures and can be considered as an assembly of 11 circularly arranged protofilaments. We investigated the molecular mechanism of the universal joint function of the hook by a approximately two-million-atom molecular dynamics simulation. On the inner side of the supercoil, protein subunits are highly packed along the protofilament and no gaps remain for further compression, whereas subunits are slightly separated and are hydrogen bonded through one layer of water molecules on the outer side. As for the intersubunit interactions between protofilaments, subunits are packed along the 6-start helix in a left-handed supercoil whereas they are highly packed along the 5-start helix in a right-handed supercoil. We conclude that the supercoiled structures of the hook in the left- and right-handed forms make maximal use of the gaps between subunits, which we call "gap compression/extension mechanism". Mutual sliding of subunits at the subunit interface accompanying rearrangements of intersubunit hydrogen bonds is interpreted as a mechanism to allow continuous structural change of the hook during flagellar rotation at low energy cost.

High pressure ceramic joint

DOEpatents

Ward, Michael E.; Harkins, Bruce D.

1993-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

Effect of Mg and Cu on mechanical properties of high-strength welded joints of aluminum alloys obtained by laser welding

NASA Astrophysics Data System (ADS)

Annin, B. D.; Fomin, V. M.; Karpov, E. V.; Malikov, A. G.; Orishich, A. M.

2017-09-01

Results of experimental investigations of welded joints of high-strength aluminum-lithium alloys of the Al-Cu-Li and Al-Mg-Li systems are reported. The welded joints are obtained by means of laser welding and are subjected to various types of processing for obtaining high-strength welded joints. A microstructural analysis is performed. The phase composition and mechanical properties of the welded joints before and after heat treatment are studied. It is found that combined heat treatment of the welded joint (annealing, quenching, and artificial ageing) increases the joint strength, but appreciably decreases the alloy strength outside the region thermally affected by the welding process.

A Comprehensive Specimen-Specific Multiscale Data Set for Anatomical and Mechanical Characterization of the Tibiofemoral Joint

PubMed Central

Chokhandre, Snehal; Colbrunn, Robb; Bennetts, Craig; Erdemir, Ahmet

2015-01-01

Understanding of tibiofemoral joint mechanics at multiple spatial scales is essential for developing effective preventive measures and treatments for both pathology and injury management. Currently, there is a distinct lack of specimen-specific biomechanical data at multiple spatial scales, e.g., joint, tissue, and cell scales. Comprehensive multiscale data may improve the understanding of the relationship between biomechanical and anatomical markers across various scales. Furthermore, specimen-specific multiscale data for the tibiofemoral joint may assist development and validation of specimen-specific computational models that may be useful for more thorough analyses of the biomechanical behavior of the joint. This study describes an aggregation of procedures for acquisition of multiscale anatomical and biomechanical data for the tibiofemoral joint. Magnetic resonance imaging was used to acquire anatomical morphology at the joint scale. A robotic testing system was used to quantify joint level biomechanical response under various loading scenarios. Tissue level material properties were obtained from the same specimen for the femoral and tibial articular cartilage, medial and lateral menisci, anterior and posterior cruciate ligaments, and medial and lateral collateral ligaments. Histology data were also obtained for all tissue types to measure specimen-specific cell scale information, e.g., cellular distribution. This study is the first of its kind to establish a comprehensive multiscale data set for a musculoskeletal joint and the presented data collection approach can be used as a general template to guide acquisition of specimen-specific comprehensive multiscale data for musculoskeletal joints. PMID:26381404

U.S. Department of Energy Hydrogen and Fuel Cells Program 2012 Annual Merit Review and Peer Evaluation Report: May 14-18, 2012, Arlington, VA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

2012-09-01

This document summarizes the comments provided by peer reviewers on hydrogen and fuel cell projects presented at the fiscal year (FY) 2012 U.S. Department of Energy (DOE) Hydrogen and Fuel Cells Program and Vehicle Technologies Program Annual Merit Review and Peer Evaluation Meeting (AMR), held May 14-18, 2012, in Arlington, VA.

Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

NASA Astrophysics Data System (ADS)

Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

2014-10-01

To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

NASA Astrophysics Data System (ADS)

Peng, Dong; Shen, Jun; Tang, Qin; Wu, Cui-ping; Zhou, Yan-bing

2013-03-01

Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

Structure and Mechanical Properties of Friction Stir Weld Joints of Magnesium Alloy AZ31

NASA Astrophysics Data System (ADS)

Nagasawa, T.; Otsuka, M.; Yokota, T.; Ueki, T.

The applicability of friction stir welding to hot rolled sheet of commercial magnesium alloy AZ31 plates has been investigated. Friction stir weld joint showed mechanical strength comparable to that of base material, though the ductility remained at one half of that of the latter. The results are consistent with the microstructure which is characterized by a fine grained bond layer bounded by-intermediate grained base metals. It is found that both anodizing treatment and insertion of aluminum foil between batting faces do not degrade the joint properties at all. The results suggest that friction stir welding can be potentially applied to magnesium alloy.

[Effects of exercise on joints.

PubMed

Moriyama, Hideki

Joints are composed of several different tissues(cartilage, capsule, meniscus, and ligament), and articular cartilage plays an important role in maintaining mechanical competence during exercise. Weight-bearing exercise has several benefit, including improved blood and synovial fluid circulation in a given joint. Consistent moderate activities facilitate cycles of anabolism and catabolism. Mechanical stresses are crucial for the maintenance of the morphologic and functional integrity of articular cartilage. Healthy cartilage is exposed by hydrostatic pressure and tensile strain, when cartilage degeneration develops, abnormal cartilage is exposed by shear stress. Moderate(physiological)exercise is characterized by a range of equilibrium between matrix anabolic and catabolic processes, or anabolism beyond catabolism. Joints are susceptible to insufficient or excessive activities, leading to joint degeneration. Lack of exercise is known to induce joint contracture seen clinically as a consequence of disuse changes, and excess mechanical stresses induce joint destruction such as osteoarthritis. Joint diseases resulting from insufficient or excessive activities are new and major challenging issues with our aging population. Thus, it is highly desirable to have an effective and efficient treatment to improve and protect against these joint diseases, and thereby to solve these clearly unanswered issues.

High pressure ceramic joint

DOEpatents

Ward, M.E.; Harkins, B.D.

1993-11-30

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 4 figures.

Evaluation of the cryogenic mechanical properties of the insulation material for ITER Feeder superconducting joint

NASA Astrophysics Data System (ADS)

Wu, Zhixiong; Huang, Rongjin; Huang, ChuanJun; Yang, Yanfang; Huang, Xiongyi; Li, Laifeng

2017-12-01

The Glass-fiber reinforced plastic (GFRP) fabricated by the vacuum bag process was selected as the high voltage electrical insulation and mechanical support for the superconducting joints and the current leads for the ITER Feeder system. To evaluate the cryogenic mechanical properties of the GFRP, the mechanical properties such as the short beam strength (SBS), the tensile strength and the fatigue fracture strength after 30,000 cycles, were measured at 77K in this study. The results demonstrated that the GFRP met the design requirements of ITER.

Bolted Double-Lap Composite Joints Under Mechanical and Thermal Loading

NASA Technical Reports Server (NTRS)

Kradinov, V.; Barut, A.; Madenci, E.; Walker, Sandra P. (Technical Monitor)

2000-01-01

This study concerns the determination of the contact stresses and contact region around bolt holes and the bolt load distribution in single- and double-lap joints of composite laminates with arbitrarily located bolts under general mechanical loading conditions and uniform temperature change. The unknown contact stress distribution and contact region between the bolt and laminates and the interaction among the bolts require the bolt load distribution, as well as the contact stresses, to be as part of the solution. The present method is based on the complex potential theory and the variational formulation in order to account for bolt stiffness, bolt-hole clearance, and finite geometry of the composite laminates.

Microstructure and Mechanical Properties of Stainless Steel/Brass Joints Brazed by Sn-Electroplated Ag Brazing Filler Metals

NASA Astrophysics Data System (ADS)

Wang, Xingxing; Peng, Jin; Cui, Datian

2018-05-01

To develop a high-Sn-content AgCuZnSn brazing filler metal, the BAg50CuZn was used as the base filler metal and a Sn layer was electroplated upon it. Then, the 304 stainless steel and the H62 brass were induction-brazed with the Sn-plated brazing filler metals. The microstructures of the joints were examined with an optical microscope, a scanning electron microscope and an x-ray diffractometer. The corresponding mechanical properties were obtained with a universal tensile testing machine. The results indicated that the induction brazed joints consisted of the Ag phase, the Cu phase and the CuZn phase. When the content of Sn in the Sn-plated Ag brazing filler metal was 6.0 or 7.2 wt.%, the Cu5Zn8, the Cu41Sn11 and the Ag3Sn phases appeared in the brazed joint. The tensile strength of the joints brazed with the Sn-plated filler metal was higher compared to the joints with the base filler metal. When the content of Sn was 6.0 wt.%, the highest tensile strength of the joint reached to 395 MPa. The joint fractures presented a brittle mode, mixed with a low amount of ductile fracture, when the content of Sn exceeded 6.0 wt.%.

Microstructure and Mechanical Properties of 316L Stainless Steel Filling Friction Stir-Welded Joints

NASA Astrophysics Data System (ADS)

Zhou, L.; Nakata, K.; Tsumura, T.; Fujii, H.; Ikeuchi, K.; Michishita, Y.; Fujiya, Y.; Morimoto, M.

2014-10-01

Keyhole left at 316L stainless steel friction stir welding/friction stir processing seam was repaired by filling friction stir welding (FFSW). Both metallurgical and mechanical bonding characteristics were obtained by the combined plastic deformation and flow between the consumable filling tool and the wall of the keyhole. Two ways based on the original conical and modified spherical keyholes, together with corresponding filling tools and process parameters were investigated. Microstructure and mechanical properties of 316L stainless steel FFSW joints were evaluated. The results showed that void defects existed at the bottom of the refilled original conical keyhole, while excellent bonding interface was obtained on the refilled modified spherical keyhole. The FFSW joint with defect-free interface obtained on the modified spherical keyhole fractured at the base metal side during the tensile test due to microstructural refinement and hardness increase in the refilled keyhole. Moreover, no σ phase but few Cr carbides were formed in the refilled zone, which would not result in obvious corrosion resistance degradation of 316L stainless steel.

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints.

PubMed

Borba, Natascha Z; Afonso, Conrado R M; Blaga, Lucian; Dos Santos, Jorge F; Canto, Leonardo B; Amancio-Filho, Sergio T

2017-02-15

In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α' martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined.

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints

PubMed Central

Borba, Natascha Z.; Afonso, Conrado R. M.; Blaga, Lucian; dos Santos, Jorge F.; Canto, Leonardo B.; Amancio-Filho, Sergio T.

2017-01-01

In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α′ martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined. PMID:28772545

Thermal-mechanical fatigue test apparatus for metal matrix composites and joint attachments

NASA Technical Reports Server (NTRS)

Westfall, L. J.; Petrasek, D. W.

1985-01-01

Two thermal-mechanical fatigue (TMF) test facilities were designed and developed, one to test tungsten fiber reinforced metal matrix composite specimens at temperature up to 1430C (2600F) and another to test composite/metal attachment bond joints at temperatures up to 760C (1400 F). The TMF facility designed for testing tungsten fiber reinforced metal matrix composites permits test specimen temperature excursions from room temperature to 1430C (2600F) with controlled heating and loading rates. A strain-measuring device measures the strain in the test section of the specimen during each heating and cooling cycle with superimposed loads. Data is collected and recorded by a computer. The second facility is designed to test composite/metal attachment bond joints and to permit heating to a maximum temperature of 760C (1400F) within 10 min and cooling to 150C (300F) within 3 min. A computer controls specimen temperature and load cycling.

Thermal-mechanical fatigue test apparatus for metal matrix composites and joint attachments

NASA Technical Reports Server (NTRS)

Westfall, Leonard J.; Petrasek, Donald W.

1988-01-01

Two thermal-mechanical fatigue (TMF) test facilities were designed and developed, one to test tungsten fiber reinforced metal matrix composite specimens at temperature up to 1430C (2600F) and another to test composite/metal attachment bond joints at temperatures up to 760F (1400F). The TMF facility designed for testing tungsten fiber reinforced metal matrix composites permits test specimen temperature excursions from room temperature to 1430C (2600F) with controlled heating and loading rates. A strain-measuring device measures the strain in the test section of the specimen during each heating and cooling cycle with superimposed loads. Data is collected and recorded by a computer. The second facility is designed to test composite/metal attachment bond joints and to permit heating to a maximum temperature of 760C (1400F) within 10 min and cooling to 150C (300F) within 3 min. A computer controls specimen temperature and load cycling.

Structural Mechanics Solutions for Butt Joint Seals in Cold Climates

DOT National Transportation Integrated Search

1996-08-01

An effective, formed-in-place joint seal will respond with elastic or viscoelastic behavior over a reasonable design life to any large movement of the joint without adhesive or cohesive failure. For a given joint movement, seals with lower stiffness ...

Predictive and postdictive mechanisms jointly contribute to visual awareness.

PubMed

Soga, Ryosuke; Akaishi, Rei; Sakai, Katsuyuki

2009-09-01

One of the fundamental issues in visual awareness is how we are able to perceive the scene in front of our eyes on time despite the delay in processing visual information. The prediction theory postulates that our visual system predicts the future to compensate for such delays. On the other hand, the postdiction theory postulates that our visual awareness is inevitably a delayed product. In the present study we used flash-lag paradigms in motion and color domains and examined how the perception of visual information at the time of flash is influenced by prior and subsequent visual events. We found that both types of event additively influence the perception of the present visual image, suggesting that our visual awareness results from joint contribution of predictive and postdictive mechanisms.

Glenoid labrum ossification and mechanical restriction of joint motion: extraosseous manifestations of melorheostosis.

PubMed

Subhas, N; Sundaram, M; Bauer, T W; Seitz, W H; Recht, M P

2008-02-01

We report a case of a 47-year-old man who presented with progressive loss of motion and pain in the right shoulder. Radiographs of the shoulder demonstrated dense ossification in the glenoid and humeral head with extension into the periarticular soft tissues. CT and MRI scans confirmed the radiographic findings and also revealed ossification of the glenoid labrum. A radiographic diagnosis of melorheostosis, an uncommon benign sclerosing bone dysplasia, was made. Because of the patient's severe symptomatology, he underwent total shoulder arthroplasty. Histological analysis of the resected masses was consistent with melorheostosis with a few areas covered by a cartilage cap. This case illustrates several uncommon but important features of melorheostosis, including mechanical obstruction of joint motion requiring joint replacement, ossification of the glenoid labrum, and cartilage-covering portions of the intra-articular masses, not to be confused with cartilage-producing tumors.

Expecting ankle tilts and wearing an ankle brace influence joint control in an imitated ankle sprain mechanism during walking.

PubMed

Gehring, Dominic; Wissler, Sabrina; Lohrer, Heinz; Nauck, Tanja; Gollhofer, Albert

2014-03-01

A thorough understanding of the functional aspects of ankle joint control is essential to developing effective injury prevention. It is of special interest to understand how neuromuscular control mechanisms and mechanical constraints stabilize the ankle joint. Therefore, the aim of the present study was to determine how expecting ankle tilts and the application of an ankle brace influence ankle joint control when imitating the ankle sprain mechanism during walking. Ankle kinematics and muscle activity were assessed in 17 healthy men. During gait rapid perturbations were applied using a trapdoor (tilting with 24° inversion and 15° plantarflexion). The subjects either knew that a perturbation would definitely occur (expected tilts) or there was only the possibility that a perturbation would occur (potential tilts). Both conditions were conducted with and without a semi-rigid ankle brace. Expecting perturbations led to an increased ankle eversion at foot contact, which was mediated by an altered muscle preactivation pattern. Moreover, the maximal inversion angle (-7%) and velocity (-4%), as well as the reactive muscle response were significantly reduced when the perturbation was expected. While wearing an ankle brace did not influence muscle preactivation nor the ankle kinematics before ground contact, it significantly reduced the maximal ankle inversion angle (-14%) and velocity (-11%) as well as reactive neuromuscular responses. The present findings reveal that expecting ankle inversion modifies neuromuscular joint control prior to landing. Although such motor control strategies are weaker in their magnitude compared with braces, they seem to assist ankle joint stabilization in a close-to-injury situation. Copyright © 2013 Elsevier B.V. All rights reserved.

Inhibition of prostaglandin biosynthesis as the mechanism of analgesia of aspirin-like drugs in the dog knee joint.

PubMed

Moncada, S; Ferreira, S H; Vane, J R

1975-04-01

A method has been developed to measure the analgesic action of aspirin-like drugs in knee joints of anaesthetized dogs. Bradykinin, injected into the joint cavity, induced a reflex rise in blood pressure which was dose-dependent; this was used as a measure of nociceptive activity. The joint cavity became more sensitive to bradykinin as the experiment proceeded, or when a low concentration of prostaglandin E1 or E2 was infused locally. The increase in sensitivity with time was prevented by local injection of aspirin or indomethacin, but that induced by exogenous prostaglandin infusion was not. Injections of carrageenin into dog knee joints increased the prostaglandin E2 content of synovial fluid by up to 160 ng per joint; indomethacin prevented this increase. These experiments support our previous conclusion that local biosynthesis of a prostaglandin (induced by mild trauma) sensitizes pain receptors to mechanical or chemical stimuli. Aspirin-like drugs are analgesic because they prevent prostaglandin biosynthesis, thereby preventing this sensitization.

Body mass index affects knee joint mechanics during gait differently with and without moderate knee osteoarthritis.

PubMed

Harding, Graeme T; Hubley-Kozey, Cheryl L; Dunbar, Michael J; Stanish, William D; Astephen Wilson, Janie L

2012-11-01

Obesity is a highly cited risk factor for knee osteoarthritis (OA), but its role in knee OA pathogenesis and progression is not as clear. Excess weight may contribute to an increased mechanical burden and altered dynamic movement and loading patterns at the knee. The objective of this study was to examine the interacting role of moderate knee OA disease presence and obesity on knee joint mechanics during gait. Gait analysis was performed on 104 asymptomatic and 140 individuals with moderate knee OA. Each subject group was divided into three body mass categories based on body mass index (BMI): healthy weight (BMI<25), overweight (25≤BMI≤30), and obese (BMI>30). Three-dimensional knee joint angles and net external knee joint moments were calculated and waveform principal component analysis (PCA) was applied to extract major patterns of variability from each. PC scores for major patterns were compared between groups using a two-factor ANOVA. Significant BMI main effects were found in the pattern of the knee adduction moment, the knee flexion moment, and the knee rotation moment during gait. Two interaction effects between moderate OA disease presence and BMI were also found that described different changes in the knee flexion moment and the knee flexion angle with increased BMI with and without knee OA. Our results suggest that increased BMI is associated with different changes in biomechanical patterns of the knee joint during gait depending on the presence of moderate knee OA. Copyright © 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Numerical Analysis Study of the Failure Mechanism of Transparent Materials During Low Velocity Impact Used in Protective Systems

DTIC Science & Technology

2011-07-01

UCRL -50694 (Lawrence Rad.Lab. 1969) 9 Wilkins M.L., ’Ballistic materials and penetration mechanics’ ed. Laib1e.R.C. (Elsevier Sci.Publ.1980) pp.225...ORGANIZATION COPIES ORGANIZATION 2 DARPA L CHRISTODOULOU J GOLDWASSER 3701 N FAIRFAX DR ARLINGTON VA 22217-5600 2 DIRECTED

Skeletal muscle contraction in protecting joints and bones by absorbing mechanical impacts

NASA Astrophysics Data System (ADS)

Rudenko, O. V.; Tsyuryupa, S.; Sarvazyan, A.

2016-09-01

We have previously hypothesized that the dissipation of mechanical energy of external impact is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In this paper, a mathematical justification of this hypothesis is presented. First, a simple mechanical model, in which the muscle is considered as a simple Hookean spring, is considered. This analysis serves as an introduction to the consideration of a biomechanical model taking into account the molecular mechanism of muscle contraction, kinetics of myosin bridges, sarcomere dynamics, and tension of muscle fibers. It is shown that a muscle behaves like a nonlinear and adaptive spring tempering the force of impact and increasing the duration of the collision. The temporal profiles of muscle reaction to the impact as functions of the levels of muscle contraction, durations of the impact front, and the time constants of myosin bridges closing, are obtained. The absorption of mechanical shock energy is achieved due to the increased viscoelasticity of the contracting skeletal muscle. Controlling the contraction level allows for the optimization of the stiffness and viscosity of the muscle necessary for the protection of the joints and bones.

People’s Republic of China Scientific Abstracts, Number 170

DTIC Science & Technology

1977-06-30

Distribution Unlimited 20000324 188 U. S. JOINT PUBLICATIONS RESEARCH SERVICE REPRODUCED BY NATIONAL TECHNICAL INFORMATION SERVICE Reproduced From Best...Road, Wooster, Ohio, 44691. Correspondence pertaining to matters other than procurement may be addressed to Joint Publications Research Service...Performing Organization Name and Addreaa Joint Publications Research Service 1000 North Glebe Road Arlington, Virginia 22201 10. Project/Task/Work

Wrist joint assembly

NASA Technical Reports Server (NTRS)

Kersten, L.; Johnson, J. D. (Inventor)

1978-01-01

A wrist joint assembly is provided for use with a mechanical manipulator arm for finely positioning an end-effector carried by the wrist joint on the terminal end of the manipulator arm. The wrist joint assembly is pivotable about a first axis to produce a yaw motion, a second axis is to produce a pitch motion, and a third axis to produce a roll motion. The wrist joint assembly includes a disk segment affixed to the terminal end of the manipulator arm and a first housing member, a second housing member, and a third housing member. The third housing member and the mechanical end-effector are moved in the yaw, pitch, and roll motion. Drive means are provided for rotating each of the housings about their respective axis which includes a cluster of miniature motors having spur gears carried on the output drive shaft which mesh with a center drive gear affixed on the housing to be rotated.

Joint attention and language evolution

NASA Astrophysics Data System (ADS)

Kwisthout, Johan; Vogt, Paul; Haselager, Pim; Dijkstra, Ton

2008-06-01

This study investigates how more advanced joint attentional mechanisms, rather than only shared attention between two agents and an object, can be implemented and how they influence the results of language games played by these agents. We present computer simulations with language games showing that adding constructs that mimic the three stages of joint attention identified in children's early development (checking attention, following attention, and directing attention) substantially increase the performance of agents in these language games. In particular, the rates of improved performance for the individual attentional mechanisms have the same ordering as that of the emergence of these mechanisms in infants' development. These results suggest that language evolution and joint attentional mechanisms have developed in a co-evolutionary way, and that the evolutionary emergence of the individual attentional mechanisms is ordered just like their developmental emergence.

Effect of Mechanical Heterogeneity on the Crack Driving Force of a Reactor Pressure Vessel Outlet Nozzle DMW Joint

NASA Astrophysics Data System (ADS)

Lingyan, Zhao; Yinghao, Cui; He, Xue

2017-12-01

The welding mechanical heterogeneity, load complexity, material and geometrical structure makes it very difficult to assess the structural integrity of dissimilar metal weld (DMW) joints. Based on a numerical simulated approach of the continuous change of material mechanical property in the buttering layer, a reactor pressure vessel (RPV) outlet nozzle DMW joint with service loads is studied, effect of mechanical heterogeneity on the stress-strain field and stress triaxiality at the semi-elliptical surface crack front are discussed. The analyses show that once the crack extends into the high hardness zone of Alloy 182 buttering, the strain decreases sharply, the strain gradient increases and the crack propagation slows down. The influence of strength mismatch on the stress triaxiality at the shallow crack front is greater than that at the deep crack front. The interaction between strength mismatch and crack depth directly affects the crack growth direction.

Progressive Damage Analysis of Bonded Composite Joints

NASA Technical Reports Server (NTRS)

Leone, Frank A., Jr.; Girolamo, Donato; Davila, Carlos G.

2012-01-01

The present work is related to the development and application of progressive damage modeling techniques to bonded joint technology. The joint designs studied in this work include a conventional composite splice joint and a NASA-patented durable redundant joint. Both designs involve honeycomb sandwich structures with carbon/epoxy facesheets joined using adhesively bonded doublers.Progressive damage modeling allows for the prediction of the initiation and evolution of damage within a structure. For structures that include multiple material systems, such as the joint designs under consideration, the number of potential failure mechanisms that must be accounted for drastically increases the complexity of the analyses. Potential failure mechanisms include fiber fracture, intraply matrix cracking, delamination, core crushing, adhesive failure, and their interactions. The bonded joints were modeled using highly parametric, explicitly solved finite element models, with damage modeling implemented via custom user-written subroutines. Each ply was discretely meshed using three-dimensional solid elements. Layers of cohesive elements were included between each ply to account for the possibility of delaminations and were used to model the adhesive layers forming the joint. Good correlation with experimental results was achieved both in terms of load-displacement history and the predicted failure mechanism(s).

Comparing the effects of mechanical perturbation training with a compliant surface and manual perturbation training on joints kinematics after ACL-rupture.

PubMed

Nawasreh, Zakariya; Failla, Mathew; Marmon, Adam; Logerstedt, David; Snyder-Mackler, Lynn

2018-05-23

Performing physical activities on a compliant surface alters joint kinematics and increases joints stiffness. However, the effect of compliant surface on joint kinematics after ACL-rupture is yet unknown. To compare the effects of mechanical perturbation training with a compliant surface to manual perturbation training on joint kinematics after ACL-rupture. Sixteen level I/II athletes with ACL-rupture participated in this preliminary study. Eight patients received mechanical perturbation with compliant surface (Mechanical) and 8 patients received manual perturbation training (Manual). Patients completed standard gait analysis before (Pre) and after (Post) training. Significant group-by-time interactions were found for knee flexion angle at initial contact (IC) and peak knee flexion (PKF) (p<0.004), with manual group significantly increased knee flexion angle at IC and PKF (p<0.03). Main effects of group were found for hip flexion angle at IC (Manual:34.34+3.51°, Mechanical:27.68+4.08°, p = 0.011), hip rotation angle at PKE (Manual:-3.40+4.78°, Mechanical:5.43+4.78°, p < 0.0001), and knee adduction angle at PKE (Manual:-2.00+2.23°, Mechanical:0.55+2.23°, p = 0.039). Main effects of time were found for hip adduction angle at PKE (Pre:6.98+4.48°, Post:8.41+4.91°, p = 0.04), knee adduction angle at IC (Pre:-2.90+3.50°, Post:-0.62+2.58°, p = 0.03), ankle adduction angle at IC (Pre:2.16+3.54, Post:3.8+3.68, p = 0.008), and ankle flexion angle at PKF (Pre:-4.55+2.77°, Post:-2.39+3.48°, p = 0.01). Training on a compliant surface induces different effects on joint kinematics compared to manual perturbation training after ACL-rupture. Manual perturbation improved hip alignment and increased knee flexion angles, while mechanical training decreased knee flexion angles throughout the stance phase. Administering training on a compliant surface after ACL-rupture may help improving dynamic knee stability, however, long-term effects on knee

Definition of large components assembled on-orbit and robot compatible mechanical joints

NASA Technical Reports Server (NTRS)

Williamsen, J.; Thomas, F.; Finckenor, J.; Spiegel, B.

1990-01-01

One of four major areas of project Pathfinder is in-space assembly and construction. The task of in-space assembly and construction is to develop the requirements and the technology needed to build elements in space. A 120-ft diameter tetrahedral aerobrake truss is identified as the focus element. A heavily loaded mechanical joint is designed to robotically assemble the defined aerobrake element. Also, typical large components such as habitation modules, storage tanks, etc., are defined, and attachment concepts of these components to the tetrahedral truss are developed.

Microstructure and mechanical properties of diffusion bonded W/steel joint using V/Ni composite interlayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, W.S.; Cai, Q.S., E-mail: cai2009pm@163.com; Ma, Y.Z.

2013-12-15

Diffusion bonding between W and steel using V/Ni composite interlayer was carried out in vacuum at 1050 °C and 10 MPa for 1 h. The microstructural examination and mechanical property evaluation of the joints show that the bonding of W to steel was successful. No intermetallic compound was observed at the steel/Ni and V/W interfaces for the joints bonded. The electron probe microanalysis and X-ray diffraction analysis revealed that Ni{sub 3}V, Ni{sub 2}V, Ni{sub 2}V{sub 3} and NiV{sub 3} were formed at the Ni/V interface. The tensile strength of about 362 MPa was obtained for as-bonded W/steel joint and themore » failure occurred at W near the V/W interface. The nano-indentation test across the joining interfaces demonstrated the effect of solid solution strengthening and intermetallic compound formation in the diffusion zone. - Highlights: • Diffusion bonding of W to steel was realized using V/Ni composite interlayer. • The interfacial microstructure of the joint was clarified. • Several V–Ni intermetallic compounds were formed in the interface region. • The application of V/Ni composite interlayer improved the joining quality.« less

A cortically-inspired model for inverse kinematics computation of a humanoid finger with mechanically coupled joints.

PubMed

Gentili, Rodolphe J; Oh, Hyuk; Kregling, Alissa V; Reggia, James A

2016-05-19

The human hand's versatility allows for robust and flexible grasping. To obtain such efficiency, many robotic hands include human biomechanical features such as fingers having their two last joints mechanically coupled. Although such coupling enables human-like grasping, controlling the inverse kinematics of such mechanical systems is challenging. Here we propose a cortical model for fine motor control of a humanoid finger, having its two last joints coupled, that learns the inverse kinematics of the effector. This neural model functionally mimics the population vector coding as well as sensorimotor prediction processes of the brain's motor/premotor and parietal regions, respectively. After learning, this neural architecture could both overtly (actual execution) and covertly (mental execution or motor imagery) perform accurate, robust and flexible finger movements while reproducing the main human finger kinematic states. This work contributes to developing neuro-mimetic controllers for dexterous humanoid robotic/prosthetic upper-extremities, and has the potential to promote human-robot interactions.

Microstructure and mechanical properties of friction stir lap welded Mg/Al joint assisted by stationary shoulder

NASA Astrophysics Data System (ADS)

Ji, Shude; Li, Zhengwei

2017-11-01

Using magnesium alloy as upper sheet, 3 mm-thick AZ31 magnesium alloy and 6061 aluminum alloy were joined using friction stir lap welding assisted by stationary shoulder. The effects of tool rotating speed on cross-sections, microstructure and mechanical properties of Mg/Al lap joints were mainly discussed. Results showed that stationary shoulder contributed to joint formation, by which stir zones (SZ) were characterized by big onion rings after welding. Because of the big forging force exerted by stationary shoulder, the upper region of hook was well bonded. SZ showed much higher hardness because of intermetallic compounds (IMCs). The bonding conditions at the base material (BM)/SZ interface at advancing side and the hook region played important roles on joint lap shear properties. The X-ray diffraction pattern analysis revealed that the main IMCs were Al3Mg2 and Al12Mg17.

U.S. Department of Energy Hydrogen and Fuel Cells Program 2015 Annual Merit Review and Peer Evaluation Report: June 8-12, 2015, Arlington, Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popovich, Neil

The fiscal year 2015 U.S. Department of Energy (DOE) Hydrogen and Fuel Cells Program Annual Merit Review and Peer Evaluation Meeting (AMR), in conjunction with DOE's Vehicle Technologies Office AMR, was held from June 8-12, 2015, in Arlington, Virginia. This report is a summary of comments by AMR peer reviewers about the hydrogen and fuel cell projects funded by DOE's Office of Energy Efficiency and Renewable Energy.

Influence of PC-GTAW Parameters on the Microstructural and Mechanical Properties of Thin AISI 1008 Steel Joints

NASA Astrophysics Data System (ADS)

Kumar, Ravindra; Anant, Ramkishor; Ghosh, P. K.; Kumar, Ankit; Agrawal, B. P.

2016-09-01

Butt weld joints are prepared using pulse current gas tungsten arc welding out of thin sheets of AISI 1008 steel using various combinations of pulse parameters. During welding, the welding speed was kept high, but with the increase of welding speed the mean current was also increased to get the required weld joint at the constant heat input. The use of pulse current has led to improvement in mechanical and metallurgical properties of weld joints. It has resulted in less development of humping which is a common problem with high-speed welding. The undercut or dipped weld face is not observed severe. The tensile strength and hardness are enhanced by 12.5 and 12%. The increase of tensile strength and hardness is justified through TEM micrograph showing the presence of dislocation.

Joint torques in a freely walking insect reveal distinct functions of leg joints in propulsion and posture control

PubMed Central

2016-01-01

Determining the mechanical output of limb joints is critical for understanding the control of complex motor behaviours such as walking. In the case of insect walking, the neural infrastructure for single-joint control is well described. However, a detailed description of the motor output in form of time-varying joint torques is lacking. Here, we determine joint torques in the stick insect to identify leg joint function in the control of body height and propulsion. Torques were determined by measuring whole-body kinematics and ground reaction forces in freely walking animals. We demonstrate that despite strong differences in morphology and posture, stick insects show a functional division of joints similar to other insect model systems. Propulsion was generated by strong depression torques about the coxa–trochanter joint, not by retraction or flexion/extension torques. Torques about the respective thorax–coxa and femur–tibia joints were often directed opposite to fore–aft forces and joint movements. This suggests a posture-dependent mechanism that counteracts collapse of the leg under body load and directs the resultant force vector such that strong depression torques can control both body height and propulsion. Our findings parallel propulsive mechanisms described in other walking, jumping and flying insects, and challenge current control models of insect walking. PMID:26791608

Effects of the Heterogeneity in the Electron Beam Welded Joint on Mechanical Properties of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Liu, Jing; Gao, Xiao-Long; Zhang, Lin-Jie; Zhang, Jian-Xun

2015-01-01

The aim of this investigation was to evaluate the effect of microstructure heterogeneity on the tensile and low cycle fatigue properties of electron beam welded (EBW) Ti6Al4V sheets. To achieve this goal, the tensile and low cycle fatigue property in the EBW joints and base metal (BM) specimens is compared. During the tensile testing, digital image correlation technology was used to measure the plastic strain field evolution within the specimens. The experimental results showed that the tensile ductility and low cycle fatigue strength of EBW joints are lower than that of BM specimens, mainly because of the effect of microstructure heterogeneity of the welded joint. Moreover, the EBW joints exhibit the cyclic hardening behavior during low fatigue process, while BM specimens exhibit the cyclic softening behavior. Compared with the BM specimens with uniform microstructure, the heterogeneity of microstructure in the EBW joint is found to decrease the mechanical properties of welded joint.

Effect of Stretching Combined With Ultrashort Wave Diathermy on Joint Function and Its Possible Mechanism in a Rabbit Knee Contracture Model.

PubMed

Zhang, Quan Bing; Zhou, Yun; Zhong, Hua Zhang; Liu, Yi

2018-05-01

The aim of this study was to investigate the therapeutic effect of stretching combined with ultrashort wave on joint contracture and explore its possible mechanism. Thirty-two rabbits underwent unilateral immobilization of a knee joint at full extension to cause joint contracture. At 6 wks after immobilization, the rabbits were randomly divided into the following four groups: natural recovery group, stretching treatment group, ultrashort wave treatment group, and combined treatment group. For comparison, eight control group animals of corresponding age were also examined. The effect of stretching and ultrashort wave treatment on joint contracture was assessed by measuring the joint range of motion, evaluating the collagen deposition of joint capsule and assessing the mRNA and protein levels for transforming growth factor β1 in the joint capsule. The combined treatment group led to the best recovery of joint function. The combined treatment with stretching and ultrashort wave was more effective than stretching or ultrashort wave treatment alone against the synovial thickening of suprapatellar joint capsule, the collagen deposition of anterior joint capsule, and the elevated expression of transforming growth factor β1 in the joint capsule. Stretching combined with ultrashort wave treatment was effective in improving joint range of motion, reducing the biomechanical, histological, and molecular manifestations of joint capsule fibrosis in a rabbit model of extending joint contracture.

A self-aligning knee joint for walking assistance devices.

PubMed

Byungjune Choi; Younbaek Lee; Jeonghun Kim; Minhyung Lee; Jongwon Lee; Se-Gon Roh; Hyundo Choi; Yong-Jae Kim; Jung-Yun Choi

2016-08-01

This paper presents a novel self-aligning knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. Self-aligning knee joints can assist in flexion/extension motions of the knee joint and compensate the knee's transitional movements in the sagittal plane. In order to compensate the center of rotation, which moves with the flexion/extension motion of the human knee joint, a self-aligning knee joint is proposed that adds redundant degrees of freedom (i.e., 2-DoF) to the 1-DoF revolute joint. The key idea of the proposed mechanism is to decouple joint rotations and translations for use in lower-extremity wearable devices. This paper describes the mechanical design of this self-aligning knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism is verified by simulations and experiments.

Electromagnetic wave scattering from a forest or vegetation canopy - Ongoing research at the University of Texas at Arlington

NASA Technical Reports Server (NTRS)

Karam, Mostafa A.; Amar, Faouzi; Fung, Adrian K.

1993-01-01

The Wave Scattering Research Center at the University of Texas at Arlington has developed a scattering model for forest or vegetation, based on the theory of electromagnetic-wave scattering in random media. The model generalizes the assumptions imposed by earlier models, and compares well with measurements from several forest canopies. This paper gives a description of the model. It also indicates how the model elements are integrated to obtain the scattering characteristics of different forest canopies. The scattering characteristics may be displayed in the form of polarimetric signatures, represented by like- and cross-polarized scattering coefficients, for an elliptically-polarized wave, or in the form of signal-distribution curves. Results illustrating both types of scattering characteristics are given.

Effect of Epoxy on Mechanical Property of SAC305 Solder Joint with Various Surface Finishes Under 3-Point Bend Test.

PubMed

Jeong, Haksan; Myung, Woo-Ram; Sung, Yong-Gue; Kim, Kyung-Yeol; Jung, Seung-Boo

2018-09-01

Microstructures and mechanical property of Sn-3.0Ag-0.5Cu (SAC305) and epoxy Sn-3.0Ag-0.5Cu (epoxy SAC) solder joints were investigated with various surface finishes; organic solderability preservative (OSP), electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). Bending property of solder joints was evaluated by 3-point bend test method. Microstructure and chemical composition of solder joints was characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. Epoxy did not effect on intermetallic compound (IMC) morphology. Scalloped shaped Cu6Sn5 IMC was observed at OSP surface finish. Chunky-like shaped and needle-like shaped (Ni,Cu)6Sn5 IMC were observed at the solder/ENIG joint and solder/ENEPIG joint, respectively. The bending cycles of SAC305/OSP joint, SAC305/ENIG joints and SAC305/ENEPIG joints were 720, 440 and 481 cycle numbers. The bending cycles of epoxy SAC and three types surface finished solder joints were over 1000 bending cycles. Under OSP surface finish, bending cycles of epoxy SAC solder was approximately 1.5 times higher than those of SAC305 solder joint. Bending cycles of epoxy SAC solder was over twice times higher than those of SAC305 solder with ENIG and ENEPIG surface finishes. The bending property of epoxy solder joint was enhanced due to epoxy fillet held the solder joint.

Assessing Cultural Change in the United States Army Recruiting Command

DTIC Science & Technology

2008-11-10

September 2008) 10Joint Advertising, Marketing Research Studies, 2008 Recruiter Quality of Life Survey: Preliminary Topline Findings, (Arlington, VA...Joint Advertising, Marketing Research Studies), http://www.dmren.org/jamrs/execute/mrs/studies/recruiter-study/2008, (accessed on 10 November 2008...October 2008, (Fort Knox, Kentucky, 17 October 2008), 19. 13 Ibid. 14 Joint Advertising, Marketing Research Studies, 2005 Recruiter Quality of Life

Double slotted socket spherical joint

DOEpatents

Bieg, Lothar F.; Benavides, Gilbert L.

2001-05-22

A new class of spherical joints is disclosed. These spherical joints are capable of extremely large angular displacements (full cone angles in excess of 270.degree.), while exhibiting no singularities or dead spots in their range of motion. These joints can improve or simplify a wide range of mechanical devices.

Lateral Ligament Repair and Reconstruction Restore Neither Contact Mechanics of the Ankle Joint nor Motion Patterns of the Hindfoot

PubMed Central

Prisk, Victor R.; Imhauser, Carl W.; O'Loughlin, Padhraig F.; Kennedy, John G.

2010-01-01

Background: Ankle sprains may damage both the lateral ligaments of the hindfoot and the osteochondral tissue of the ankle joint. When nonoperative treatment fails, operative approaches are indicated to restore both native motion patterns at the hindfoot and ankle joint contact mechanics. The goal of the present study was to determine the effect of lateral ligament injury, repair, and reconstruction on ankle joint contact mechanics and hindfoot motion patterns. Methods: Eight cadaveric specimens were tested with use of robotic technology to apply combined compressive (200-N) and inversion (4.5-Nm) loads to the hindfoot at 0° and 20° of plantar flexion. Contact mechanics at the ankle joint were simultaneously measured. A repeated-measures experiment was designed with use of the intact condition as control, with the other conditions including sectioned anterior talofibular and calcaneofibular ligaments, the Broström and Broström-Gould repairs, and graft reconstruction. Results: Ligament sectioning decreased contact area and caused a medial and anterior shift in the center of pressure with inversion loads relative to those with the intact condition. There were no significant differences in inversion or coupled axial rotation with inversion between the Broström repair and the intact condition; however, medial translation of the center of pressure remained elevated after the Broström repair relative to the intact condition. The Gould modification of the Broström procedure provided additional support to the hindfoot relative to the Broström repair, reducing inversion and axial rotation with inversion beyond that of intact ligaments. There were no significant differences in center-of-pressure excursion patterns between the Broström-Gould repair and the intact ligament condition, but this repair increased contact area beyond that with the ligaments intact. Graft reconstruction more closely restored inversion motion than did the Broström-Gould repair at 20° of

The extraordinary joint material of an articulated coralline alga. II. Modeling the structural basis of its mechanical properties.

PubMed

Denny, Mark W; King, Felicia A

2016-06-15

By incorporating joints into their otherwise rigid fronds, erect coralline algae have evolved to be as flexible as other seaweeds, which allows them to thrive - and even dominate space - on wave-washed shores around the globe. However, to provide the required flexibility, the joint tissue of Calliarthron cheilosporioides, a representative articulated coralline alga, relies on an extraordinary tissue that is stronger, more extensible and more fatigue resistant than that of other algae. Here, we used the results from recent experiments to parameterize a conceptual model that links the microscale architecture of cell walls to the adaptive mechanical properties of joint tissue. Our analysis suggests that the theory of discontinuous fiber-wound composite materials (with cellulose fibrils as the fibers and galactan gel as the matrix) can explain key aspects of the material's mechanics. In particular, its adaptive viscoelastic behavior can be characterized by two, widely separated time constants. We speculate that the short time constant (∼14 s) results from the viscous response of the matrix to the change in cell-wall shape as a joint is stretched, a response that allows the material both to remain flexible and to dissipate energy as a frond is lashed by waves. We propose that the long time constant (∼35 h), is governed by the shearing of the matrix between cellulose fibrils. The resulting high apparent viscosity ensures that joints avoid accumulating lethal deformation in the course of a frond's lifetime. Our synthesis of experimental measurements allows us to draw a chain of mechanistic inference from molecules to cell walls to fronds and community ecology. © 2016. Published by The Company of Biologists Ltd.

Probabilistic joint inversion of waveforms and polarity data for double-couple focal mechanisms of local earthquakes

NASA Astrophysics Data System (ADS)

Wéber, Zoltán

2018-06-01

Estimating the mechanisms of small (M < 4) earthquakes is quite challenging. A common scenario is that neither the available polarity data alone nor the well predictable near-station seismograms alone are sufficient to obtain reliable focal mechanism solutions for weak events. To handle this situation we introduce here a new method that jointly inverts waveforms and polarity data following a probabilistic approach. The procedure called joint waveform and polarity (JOWAPO) inversion maps the posterior probability density of the model parameters and estimates the maximum likelihood double-couple mechanism, the optimal source depth and the scalar seismic moment of the investigated event. The uncertainties of the solution are described by confidence regions. We have validated the method on two earthquakes for which well-determined focal mechanisms are available. The validation tests show that including waveforms in the inversion considerably reduces the uncertainties of the usually poorly constrained polarity solutions. The JOWAPO method performs best when it applies waveforms from at least two seismic stations. If the number of the polarity data is large enough, even single-station JOWAPO inversion can produce usable solutions. When only a few polarities are available, however, single-station inversion may result in biased mechanisms. In this case some caution must be taken when interpreting the results. We have successfully applied the JOWAPO method to an earthquake in North Hungary, whose mechanism could not be estimated by long-period waveform inversion. Using 17 P-wave polarities and waveforms at two nearby stations, the JOWAPO method produced a well-constrained focal mechanism. The solution is very similar to those obtained previously for four other events that occurred in the same earthquake sequence. The analysed event has a strike-slip mechanism with a P axis oriented approximately along an NE-SW direction.

Joint Services Electronics Program.

DTIC Science & Technology

1985-12-01

NavyOffice of Naval Research 800 Ouincy Street Arlington, Virginia -*i. I. This document has been approved I-- for pjiblic release and salo; its C=3...Type of Report & Period Covered.- Department of the Navy Annual Report - Office of Naval Research Oct. 1984- Sept. 1985 . 800 Quincy Street 14...TECHNOLOGY TRANSITION 1 III. RESEARCH SUMMARY 10 A. DIFFRACTION STUDIES/ 10 - - 4.4 1. Diffraction by Non-Conducting Surfaces 10 (a) Diffraction by a

Lateral ligament repair and reconstruction restore neither contact mechanics of the ankle joint nor motion patterns of the hindfoot.

PubMed

Prisk, Victor R; Imhauser, Carl W; O'Loughlin, Padhraig F; Kennedy, John G

2010-10-20

Ankle sprains may damage both the lateral ligaments of the hindfoot and the osteochondral tissue of the ankle joint. When nonoperative treatment fails, operative approaches are indicated to restore both native motion patterns at the hindfoot and ankle joint contact mechanics. The goal of the present study was to determine the effect of lateral ligament injury, repair, and reconstruction on ankle joint contact mechanics and hindfoot motion patterns. Eight cadaveric specimens were tested with use of robotic technology to apply combined compressive (200-N) and inversion (4.5-Nm) loads to the hindfoot at 0° and 20° of plantar flexion. Contact mechanics at the ankle joint were simultaneously measured. A repeated-measures experiment was designed with use of the intact condition as control, with the other conditions including sectioned anterior talofibular and calcaneofibular ligaments, the Broström and Broström-Gould repairs, and graft reconstruction. Ligament sectioning decreased contact area and caused a medial and anterior shift in the center of pressure with inversion loads relative to those with the intact condition. There were no significant differences in inversion or coupled axial rotation with inversion between the Broström repair and the intact condition; however, medial translation of the center of pressure remained elevated after the Broström repair relative to the intact condition. The Gould modification of the Broström procedure provided additional support to the hindfoot relative to the Broström repair, reducing inversion and axial rotation with inversion beyond that of intact ligaments. There were no significant differences in center-of-pressure excursion patterns between the Broström-Gould repair and the intact ligament condition, but this repair increased contact area beyond that with the ligaments intact. Graft reconstruction more closely restored inversion motion than did the Broström-Gould repair at 20° of plantar flexion but limited

Microstructure and mechanical properties of China low activation martensitic steel joint by TIG multi-pass welding with a new filler wire

NASA Astrophysics Data System (ADS)

Huang, Bo; Zhang, Junyu; Wu, Qingsheng

2017-07-01

Tungsten Inner Gas (TIG) welding is employed for joining of China low activation martensitic (CLAM) steel. A new filler wire was proposed, and the investigation on welding with various heat input and welding passes were conducted to lower the tendency towards the residual of δ ferrite in the joint. With the optimized welding parameters, a butt joint by multi-pass welding with the new filler wire was prepared to investigate the microstructure and mechanical properties. The microstructure of the joint was observed by optical microscope (OM) and scanning electron microscope (SEM). The hardness, Charpy impact and tensile tests of the joint were implemented at room temperature (25 °C). The results revealed that almost full martensite free from ferrite in the joints were obtained by multipass welding with the heat input of 2.26 kJ/mm. A certain degree of softening occurred at the heat affected zone of the joint according to the results of tensile and hardness tests. The as welded joints showed brittle fracture in the impact tests. However, the joints showed toughness fracture after tempering and relatively better comprehensive performance were achieved when the joints were tempered at 740 °C for 2 h.

Impact extractive fracture of jointed steel plates of a bolted joint

NASA Astrophysics Data System (ADS)

Daimaruya, M.; Fujiki, H.; Ambarita, H.

2012-08-01

This study is concerned with the development of a fracture criterion for the impact fracture of jointed steel plates of a bolted joint used in a car body. For the accurate prediction of crash characteristics of car bodies by computer-aided engineering (CAE), it is also necessary to examine the behavior and fracture of jointed steel plates subjected to impact loads. Although the actual impact fracture of jointed steel plates of a bolted joint used in cars is complicated, for simplifying the problem it might be classified into the shear fracture and the extractive fracture of jointed steel plates. Attention is given to the extractive fracture of jointed steel plates in this study. The extractive behavior and fracture of three kinds of steel plates used for cars are examined in experiments and numerical simulations. The impact extraction test of steel plates jointed by a bolt is performed using the one-bar method, together with the static test. In order to understand the mechanism of extractive fracture process of jointed steel plates, numerical simulations by a FEM code LS-DYNA are also carried out. The obtained results suggest that a stress-based fracture criterion may be developed for the impact extractive fracture of jointed steel plates of a bolted joint used in a car body.

Musculoskeletal multibody dynamics simulation of the contact mechanics and kinematics of a natural knee joint during a walking cycle.

PubMed

Hu, Jiayu; Chen, Zhenxian; Xin, Hua; Zhang, Qida; Jin, Zhongmin

2018-05-01

Detailed knowledge of the in vivo loading and kinematics in the knee joint is essential to understand its normal functions and the aetiology of osteoarthritis. Computer models provide a viable non-invasive solution for estimating joint loading and kinematics during different physiological activities. However, the joint loading and kinematics of the tibiofemoral and patellofemoral joints during a gait cycle were not typically investigated concurrently in previous computational simulations. In this study, a natural knee architecture was incorporated into a lower extremity musculoskeletal multibody dynamics model based on a force-dependent kinematics approach to investigate the contact mechanics and kinematics of a natural knee joint during a walking cycle. Specifically, the contact forces between the femoral/tibial articular cartilages and menisci and between the femoral and tibial/patellar articular cartilages were quantified. The contact forces and kinematics of the tibiofemoral and patellofemoral joints and the muscle activations and ligament forces were predicted simultaneously with a reasonable level of accuracy. The developed musculoskeletal multibody dynamics model with a natural knee architecture can serve as a potential platform for assisting clinical decision-making and postoperative rehabilitation planning.

Swivel Joint For Liquid Nitrogen

NASA Technical Reports Server (NTRS)

Milner, James F.

1988-01-01

Swivel joint allows liquid-nitrogen pipe to rotate through angle of 100 degree with respect to mating pipe. Functions without cracking hard foam insulation on lines. Pipe joint rotates on disks so mechanical stress not transmitted to thick insulation on pipes. Inner disks ride on fixed outer disks. Disks help to seal pressurized liquid nitrogen flowing through joint.

Altered lower extremity joint mechanics occur during the star excursion balance test and single leg hop after ACL-reconstruction in a collegiate athlete.

PubMed

Samaan, Michael A; Ringleb, Stacie I; Bawab, Sebastian Y; Greska, Eric K; Weinhandl, Joshua T

2018-03-01

The effects of ACL-reconstruction on lower extremity joint mechanics during performance of the Star Excursion Balance Test (SEBT) and Single Leg Hop (SLH) are limited. The purpose of this study was to determine if altered lower extremity mechanics occur during the SEBT and SLH after ACL-reconstruction. One female Division I collegiate athlete performed the SEBT and SLH tasks, bilaterally, both before ACL injury and 27 months after ACL-reconstruction. Maximal reach, hop distances, lower extremity joint kinematics and moments were compared between both time points. Musculoskeletal simulations were used to assess muscle force production during the SEBT and SLH at both time points. Compared to the pre-injury time point, SEBT reach distances were similar in both limbs after ACL-reconstruction except for the max anterior reach distance in the ipsilateral limb. The athlete demonstrated similar hop distances, bilaterally, after ACL-reconstruction compared to the pre-injury time point. Despite normal functional performance during the SEBT and SLH, the athlete exhibited altered lower extremity joint mechanics during both of these tasks. These results suggest that measuring the maximal reach and hop distances for these tasks, in combination with an analysis of the lower extremity joint mechanics that occur after ACL-reconstruction, may help clinicians and researchers to better understand the effects of ACL-reconstruction on the neuromuscular system during the SEBT and SLH.

An Analysis of Pathological Activities of CCN Proteins in Joint Disorders: Mechanical Stretch-Mediated CCN2 Expression in Cultured Meniscus Cells.

PubMed

Furumatsu, Takayuki; Ozaki, Toshifumi

2017-01-01

The multifunctional growth factor CYR61/CTGF/NOV (CCN) 2, also known as connective tissue growth factor, regulates cellular proliferation, differentiation, and tissue regeneration. Recent literatures have described important roles of CCN2 in the meniscus metabolism. However, the mechanical stress-mediated transcriptional regulation of CCN2 in the meniscus remains unclear. The meniscus is a fibrocartilaginous tissue that controls complex biomechanics of the knee joint. Therefore, the injured unstable meniscus has a poor healing potential especially in the avascular inner region. In addition, dysfunction of the meniscus correlates with the progression of degenerative knee joint disorders and joint space narrowing. Here, we describe an experimental approach that investigates the distinct cellular behavior of inner and outer meniscus cells in response to mechanical stretch. Our experimental model can analyze the relationships between stretch-induced CCN2 expression and its functional role in the meniscus homeostasis.

Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

NASA Astrophysics Data System (ADS)

Gao, Qiong; Wang, Kehong

2016-03-01

This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

The evolution of microstructures, corrosion resistance and mechanical properties of AZ80 joints using ultrasonic vibration assisted welding process

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Jiansheng

2017-12-01

The evolution of microstructures, corrosion resistance and mechanical properties of AZ80 joints using an ultrasonic vibration assisted welding process is investigated. The results show that, with ultrasonic vibration treatment, a reliable AZ80 joint without defects is obtained. The coarsening α-Mg grains are refined to about 83.5  ±  3.3 µm and the continuous β-Mg17Al12 phases are broken to granular morphology, owing to the acoustic streaming effect and the cavitation effect evoked by ultrasonic vibration. Both immersion and electrochemical test results indicate that the corrosion resistance of the AZ80 joint welded with ultrasonic vibration is improved, attributed to microstructure evolution. With ultrasonic power of 900 W, the maximum tensile strength of an AZ80 specimen is 261  ±  7.5 MPa and fracture occurs near the heat affected zone of the joint.

The impact of posture and prolonged cyclic compressive loading on vertebral joint mechanics.

PubMed

Gooyers, Chad E; McMillan, Robert D; Howarth, Samuel J; Callaghan, Jack P

2012-08-01

An in vitro biomechanics investigation exposing porcine functional spinal units (FSUs) to submaximal cyclic or static compressive forces while in a flexed, neutral, or extended posture. To investigate the combined effect of cyclically applied compressive force (e.g., vibration) and postural deviation on intervertebral joint mechanics. Independently, prolonged vibration exposure and non-neutral postures are known risk factors for development of low back pain and injury. However, there is limited basic scientific evidence to explain how the risk of low back injury from vibration exposure is modified by other mechanical factors. This work examined the influence of static postural deviation on vertebral joint height loss and compressive stiffness under cyclically applied compressive force. Forty-eight FSUs, consisting of 2 adjacent vertebrae, ligaments, and the intervening intervertebral disc were included in the study. Each specimen was randomized to 1 of 3 experimental posture conditions (neutral, flexed, or extended) and assigned to 1 of 2 loading protocols, consisting of (1) cyclic (1500 ± 1200 N applied at 5 Hz using a sinusoidal waveform, resulting in 0.2 g rms acceleration) or (2) 1500 N of static compressive force. RESULTS.: As expected, FSU height loss followed a typical first-order response in both the static and cyclic loading protocols, with the majority (~50%) of the loss occurring in the first 20 minutes of testing. A significant interaction between posture and loading protocol (P < 0.001) was noted in the magnitude of FSU height loss. Subsequent analysis of simple effects revealed significant differences between cyclic and static loading protocols in both a neutral (P = 0.016) and a flexed posture (P < 0.0001). No significant differences (P = 0.320) were noted between pre/postmeasurements of FSU compressive stiffness. Posture is an important mechanical factor to consider when assessing the risk of injury from cyclic loading to the lumbar spine.

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel

PubMed Central

Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-01

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint. PMID:29361743

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel.

PubMed

Shi, Yonghua; Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-22

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint.

Mechanical properties of friction stir welded butt joint of steel/aluminium alloys: effect of tool geometry

NASA Astrophysics Data System (ADS)

Syafiq, W. M.; Afendi, M.; Daud, R.; Mazlee, M. N.; Majid, M. S. Abdul; Lee, Y. S.

2017-10-01

This paper described the mechanical properties from hardness testing and tensile testing of Friction Stir Welded (FSW) materials. In this project, two materials of aluminium and steel are welded using conventional milling machine and tool designed with different profile and shoulder size. During welding the temperature along the weld line is collected using thermocouples. Threaded pins was found to produce stronger joints than cylindrical pins. 20 mm diameter shoulder tool welded a slightly stronger joint than 18 mm diameter one, as well as softer nugget zone due to higher heat input. Threaded pins also contributed to higher weld temperature than cylindrical pins due to increase in pin contact surface. Generally, higher temperatures were recorded in aluminium side due to pin offset away from steel.

Structure of the bacterial flagellar hook and implication for the molecular universal joint mechanism.

PubMed

Samatey, Fadel A; Matsunami, Hideyuki; Imada, Katsumi; Nagashima, Shigehiro; Shaikh, Tanvir R; Thomas, Dennis R; Chen, James Z; Derosier, David J; Kitao, Akio; Namba, Keiichi

2004-10-28

The bacterial flagellum is a motile organelle, and the flagellar hook is a short, highly curved tubular structure that connects the flagellar motor to the long filament acting as a helical propeller. The hook is made of about 120 copies of a single protein, FlgE, and its function as a nano-sized universal joint is essential for dynamic and efficient bacterial motility and taxis. It transmits the motor torque to the helical propeller over a wide range of its orientation for swimming and tumbling. Here we report a partial atomic model of the hook obtained by X-ray crystallography of FlgE31, a major proteolytic fragment of FlgE lacking unfolded terminal regions, and by electron cryomicroscopy and three-dimensional helical image reconstruction of the hook. The model reveals the intricate molecular interactions and a plausible switching mechanism for the hook to be flexible in bending but rigid against twisting for its universal joint function.

Tensile Shear Properties of the Friction Stir Lap Welded Joints and Material Flow Mechanism Under Pulsatile Revolutions

NASA Astrophysics Data System (ADS)

Hu, Yanying; Liu, Huijie; Du, Shuaishuai

2018-06-01

The aim of the present article is to offer insight into the effects of pin profiles on interface defects, tensile shear properties, microstructures, and the material flow of friction stir lap welded joints. The results indicate that, compared to the lap joints welded by the single threaded plane pin, the three-plane threaded pin, and the triangle threaded pin, the lap joint obtained by the conventional conical threaded pin is characterized by the minimum interface defect. The alternate threads and planes on the pin provide periodical stress, leading to pulsatile material flow patterns. Under the effect of pulsatile revolutions, an asymmetrical flow field is formed around the tool. The threads on the pin force the surrounding material to flow downward. The planes cannot only promote the horizontal flow of the material by scraping, but also provide extra space for the material vertical flow. A heuristic model is established to describe the material flow mechanism during friction stir lap welding under the effect of pulsatile revolutions.

Strength and Mechanics of Bonded Scarf Joints for Repair of Composite Materials

NASA Technical Reports Server (NTRS)

Pipes, R. B.; Adkins, D. W.

1982-01-01

Experimental and analytical investigations of scarf joints indicate that slight bluntness of adherend tips induces adhesive stress concentrations which significantly reduce joint strength, and the stress distribution through the adhesive thickness is non-uniform and has significant stress concentrations at the ends of the joint. The laminate stacking sequence can have important effects on the adhesive stress distribution. A significant improvement in joint strength is possible by increasing overlap at the expense of raising the repair slightly above the original surface. Although a surface grinder was used to make most experimental specimens, a hand held rotary bur can make a surprisingly good scarf. Scarf joints wit doublers on one side, such as might be used for repair, bend under tensile loads and may actually be weaker than joints without doublers.

Neuromuscular properties of different spastic human joints vary systematically.

PubMed

Mirbagheri, M M; Settle, K

2010-01-01

We quantified the mechanical abnormalities of the spastic wrist in chronic stroke survivors, and determined whether these findings were representative of those recorded at the elbow and ankle joints. System identification techniques were used to characterize the mechanical abnormalities of these joints and to identify the contribution of intrinsic and reflex stiffness to these abnormalities. Modulation of intrinsic and reflex stiffness with the joint angle was studied by applying PRBS perturbations to the joints at different joint angles over the range of motion. Age-matched healthy subjects were used as control.

Pain from intra-articular NGF or joint injury in the rat requires contributions from peptidergic joint afferents.

PubMed

Kras, Jeffrey V; Weisshaar, Christine L; Pall, Parul S; Winkelstein, Beth A

2015-09-14

Non-physiological stretch of the cervical facet joint's capsular ligament induces persistent behavioral hypersensitivity and spinal neuronal hyperexcitability via an intra-articular NGF-dependent mechanism. Although that ligament is innervated by nociceptors, it is unknown if a subpopulation is exclusively responsible for the behavioral and spinal neuronal responses to intra-articular NGF and/or facet joint injury. This study ablated joint afferents using the neurotoxin saporin targeted to neurons involved in either peptidergic ([Sar(9),Met (O2)(11)]-substance P-saporin (SSP-Sap)) or non-peptidergic (isolectin B4-saporin (IB4-Sap)) signaling to investigate the contributions of those neuronal populations to facet-mediated pain. SSP-Sap, but not IB4-Sap, injected into the bilateral C6/C7 facet joints 14 days prior to an intra- articular NGF injection prevents NGF-induced mechanical and thermal hypersensitivity in the forepaws. Similarly, only SSP- Sap prevents the increase in mechanical forepaw stimulation- induced firing of spinal neurons after intra-articular NGF. In addition, intra-articular SSP-Sap prevents both behavioral hypersensitivity and upregulation of NGF in the dorsal root ganglion after a facet joint distraction that normally induces pain. These findings collectively suggest that disruption of peptidergic signaling within the joint may be a potential treatment for facet pain, as well as other painful joint conditions associated with elevated NGF, such as osteoarthritis. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effect of Welding Processes on the Microstructure, Mechanical Properties and Residual Stresses of Plain 9Cr-1Mo Steel Weld Joints

NASA Astrophysics Data System (ADS)

Nagaraju, S.; Vasantharaja, P.; Brahadees, G.; Vasudevan, M.; Mahadevan, S.

2017-12-01

9Cr-1Mo steel designated as P9 is widely used in the construction of power plants and high-temperature applications. It is chosen for fabricating hexcan fuel subassembly wrapper components of fast breeder reactors. Arc welding processes are generally used for fabricating 9Cr-1Mo steel weld joints. A-TIG welding process is increasingly being adopted by the industries. In the present study, shielded metal arc (SMA), tungsten inert gas (TIG) and A-TIG welding processes are used for fabricating the 9Cr-1Mo steel weld joints of 10 mm thickness. Effect of the above welding processes on the microstructure evolution, mechanical properties and residual stresses of the weld joints has been studied in detail. All the three weld joints exhibited comparable strength and ductility values. 9Cr-1Mo steel weld joint fabricated by SMAW process exhibited lower impact toughness values caused by coarser grain size and inclusions. 9Cr-1Mo steel weld joint fabricated by TIG welding exhibited higher toughness due to finer grain size, while the weld joint fabricated by A-TIG welding process exhibited adequate toughness values. SMA steel weld joint exhibited compressive residual stresses in the weld metal and HAZ, while TIG and A-TIG weld joint exhibited tensile residual stresses in the weld metal and HAZ.

Torque Limit for Bolted Joint For Composites. Part B; Experimentation

NASA Technical Reports Server (NTRS)

Kostreva, Kristian M.

2003-01-01

Today, aerospace quality composite parts are generally made from either a unidirectional tape or a fabric prepreg form depending on the application. The matrix material, typically epoxy because of it dimensional stability, is pre-impregnated onto the fibers to ensure uniform distribution. Both of these composite forms are finding themselves used in applications where a joint is required. Two widely used joint methods are the classic mechanically fastened joint, and the contemporary bonded joint; however, the mechanically fastened joint is most commonly used by design engineers. A major portion of the research up-to-date about bolted composite joints has dealt with the inplane static load capacity. This work has helped to spawn standards dealing with filled-hole static joint strength. Other research has clearly shown that the clamp-up load in the mechanical fastener significantly affects the joint strength in a beneficial manner by reducing the bearing strength dependence of the composite laminate. One author reported a maximum increase in joint strength of 28%. This finding has helped to improve the reliability and efficiency of the joint in a composite structure.

Regional Security in the Gulf of Guinea; A Vital Interest of the United States

DTIC Science & Technology

2010-03-18

Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law , no person shall be...A paper submitted to the Faculty of the Joint Advanced Warfighting School in partial satisfaction of the requirements of a Master of Science...Degree in Joint Campaign Planning and Strategy. The contents of this paper reflect my personal views and are not necessarily endorsed by the Joint

Central sensitization as the mechanism underlying pain in joint hypermobility syndrome/Ehlers-Danlos syndrome, hypermobility type.

PubMed

Di Stefano, G; Celletti, C; Baron, R; Castori, M; Di Franco, M; La Cesa, S; Leone, C; Pepe, A; Cruccu, G; Truini, A; Camerota, F

2016-09-01

Patients with joint hypermobility syndrome/Ehlers-Danlos syndrome, hypermobility type (JHS/EDS-HT) commonly suffer from pain. How this hereditary connective tissue disorder causes pain remains unclear although previous studies suggested it shares similar mechanisms with neuropathic pain and fibromyalgia. In this prospective study seeking information on the mechanisms underlying pain in patients with JHS/EDS-HT, we enrolled 27 consecutive patients with this connective tissue disorder. Patients underwent a detailed clinical examination, including the neuropathic pain questionnaire DN4 and the fibromyalgia rapid screening tool. As quantitative sensory testing methods, we included thermal-pain perceptive thresholds and the wind-up ratio and recorded a standard nerve conduction study to assess non-nociceptive fibres and laser-evoked potentials, assessing nociceptive fibres. Clinical examination and diagnostic tests disclosed no somatosensory nervous system damage. Conversely, most patients suffered from widespread pain, the fibromyalgia rapid screening tool elicited positive findings, and quantitative sensory testing showed lowered cold and heat pain thresholds and an increased wind-up ratio. While the lack of somatosensory nervous system damage is incompatible with neuropathic pain as the mechanism underlying pain in JHS/EDS-HT, the lowered cold and heat pain thresholds and increased wind-up ratio imply that pain in JHS/EDS-HT might arise through central sensitization. Hence, this connective tissue disorder and fibromyalgia share similar pain mechanisms. WHAT DOES THIS STUDY ADD?: In patients with JHS/EDS-HT, the persistent nociceptive input due to joint abnormalities probably triggers central sensitization in the dorsal horn neurons and causes widespread pain. © 2016 European Pain Federation - EFIC®

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints

PubMed Central

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-01-01

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed. PMID:28772553

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints.

PubMed

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-02-16

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed.

PAIN FROM INTRA-ARTICULAR NGF OR JOINT INJURY IN THE RAT REQUIRES CONTRIBUTIONS FROM PEPTIDERGIC JOINT AFFERENTS

PubMed Central

Kras, Jeffrey V.; Weisshaar, Christine L.; Pall, Parul S.; Winkelstein, Beth A.

2015-01-01

Non-physiological stretch of the cervical facet joint’s capsular ligament induces persistent behavioral hypersensitivity and spinal neuronal hyperexcitability via an intra-articular NGF-dependent mechanism. Although that ligament is innervated by nociceptors, it is unknown if a subpopulation is exclusively responsible for the behavioral and spinal neuronal responses to intra-articular NGF and/or facet joint injury. This study ablated joint afferents using the neurotoxin saporin targeted to neurons involved in either peptidergic ([Sar9,Met(O2)11]-substance P-saporin (SSP-Sap)) or non-peptidergic (isolectin B4-saporin (IB4-Sap)) signaling to investigate the contributions of those neuronal populations to facet-mediated pain. SSP-Sap, but not IB4-Sap, injected into the bilateral C6/C7 facet joints 14 days prior to an intra-articular NGF injection prevents NGF-induced mechanical and thermal hypersensitivity in the forepaws. Similarly, only SSP-Sap prevents the increase in mechanical forepaw stimulation-induced firing of spinal neurons after intra-articular NGF. In addition, intra-articular SSP-Sap prevents both behavioral hypersensitivity and upregulation of NGF in the dorsal root ganglion after a facet joint distraction that normally induces pain. These findings collectively suggest that disruption of peptidergic signaling within the joint may be a potential treatment for facet pain, as well as other painful joint conditions associated with elevated NGF, such as osteoarthritis. PMID:26240991

Mechanical characterization and validation of poly (methyl methacrylate)/multi walled carbon nanotube composite for the polycentric knee joint.

PubMed

Arun, S; Kanagaraj, S

2015-10-01

Trans femoral amputation is one of the most uncomfortable surgeries in patient׳s life, where the prosthesis consisting of a socket, knee joint, pylon and foot is used to do the walking activities. The artificial prosthetic knee joint imitates the functions of human knee to achieve the flexion-extension for the above knee amputee. The objective of present work is to develop a light weight composite material for the knee joint to reduce the metabolic cost of an amputee. Hence, an attempt was made to study the mechanical properties of multi walled carbon nanotubes (MWCNT) reinforced Poly (methyl methacrylate) (PMMA) prepared through melt mixing technique and optimize the concentration of reinforcement. The PMMA nanocomposites were prepared by reinforcing 0, 0.1, 0.2, 0.25, 0.3 and 0.4 wt% of MWCNT using injection moulding machine via twin screw extruder. It is observed that the tensile and flexural strength of PMMA, which were studied as per ASTM D638 and D790, respectively, were increased by 32.9% and 26.3% till 0.25 wt% reinforcement of MWCNT. The experimental results of strength and modulus were compared with theoretical prediction, where a good correlation was noted. It is concluded that the mechanical properties of PMMA were found to be increased to maximum at 0.25 wt% reinforcement of MWCNT, where the Pukanszky model and modified Halpin-Tsai model are suggested to predict the strength and modulus, respectively, of the PMMA/MWCNT composite, which can be opted as a suitable materiel for the development of polycentric knee joint. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of various tool pin profiles on mechanical and metallurgical properties of friction stir welded joints of cryorolled AA2219 aluminium alloy

NASA Astrophysics Data System (ADS)

Kamal Babu, Karupannan; Panneerselvam, Kavan; Sathiya, Paulraj; Noorul Haq, Abdul Haq; Sundarrajan, Srinivasan; Mastanaiah, Potta; Srinivasa Murthy, Chunduri Venkata

2018-02-01

Friction stir welding (FSW) process was conducted on cryorolled (CR) AA2219 plate using different tool pin profiles such as cylindrical pin, threaded cylindrical pin, square pin and hexagonal pin profiles. The FSW was carried out with pairs of 6 mm thick CR aluminium plates with different tool pin profiles. The different tool pin profile weld portions' behaviors like mechanical (tensile strength, impact and hardness) and metallurgical characteristics were analyzed. The results of the mechanical analysis revealed that the joint made by the hexagonal pin tool had good strength compared to other pin profiles. This was due to the pulsating action and material flow of the tool resulting in dynamic recrystallization in the weld zone. This was confirmed by the ultra fine grain structure formation in Weld Nugget (WN) of hexagonal pin tool joint with a higher percentage of precipitate dissolution. The fractograph of the hexagonal tool pin weld portion confirmed the finer dimple structure morphology without having any interior defect compared to other tool pin profiles. The lowest weld joint strength was obtained from cylindrical pin profile weld joint due to insufficient material flow during welding. The Transmission Electron Microscope and EDX analysis showed the dissolution of the metastable θ″, θ' (Al2Cu) partial precipitates in the WN and proved the influence of metastable precipitates on enhancement of mechanical behavior of weld. The XRD results also confirmed the Al2Cu precipitation dissolution in the weld zone.

Defense Acquisition and the Case of the Joint Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a Mechanism for Adaptive Change

DTIC Science & Technology

2013-10-01

pmlkploba=obmloq=pbofbp= Defense Acquisition and the Case of the Joint Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a...of the Joint Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a Mechanism for Adaptive Change 5a. CONTRACT NUMBER 5b. GRANT...findings of our study exploring what drives successful organizational adaptation in the context of technology transition and acquisition within the

Kinematically aligned TKA can align knee joint line to horizontal.

PubMed

Ji, Hyung-Min; Han, Jun; Jin, Dong San; Seo, Hyunseok; Won, Ye-Yeon

2016-08-01

The joint line of the native knee is horizontal to the floor and perpendicular to the vertical weight-bearing axis of the patient in a bipedal stance. The purposes of this study were as follows: (1) to find out the distribution of the native joint line in a population of normal patients with normal knees; (2) to compare the native joint line orientation between patients receiving conventional mechanically aligned total knee arthroplasty (TKA), navigated mechanically aligned TKA, and kinematically aligned TKA; and (3) to determine which of the three TKA methods aligns the postoperative knee joint perpendicular to the weight-bearing axis of the limb in bipedal stance. To determine the joint line orientation of a native knee, 50 full-length standing hip-to-ankle digital radiographs were obtained in 50 young, healthy individuals. The angle between knee joint line and the line parallel to the floor was measured and defined as joint line orientation angle (JLOA). JLOA was also measured prior to and after conventional mechanically aligned TKA (65 knees), mechanically aligned TKA using imageless navigation (65 knees), and kinematically aligned TKA (65 knees). The proportion of the knees similar to the native joint line was calculated for each group. The mean JLOA in healthy individuals was parallel to the floor (0.2° ± 1.1°). The pre-operative JLOA of all treatment groups slanted down to the lateral side. Postoperative JLOA slanted down to the lateral side in conventional mechanically aligned TKA (-3.3° ± 2.2°) and in navigation mechanically aligned TKA (-2.6° ± 1.8°), while it was horizontal to the floor in kinematically aligned TKA (0.6° ± 1.7°). Only 6.9 % of the conventional mechanically aligned TKA and 16.9 % of the navigation mechanically aligned TKA were within one SD of the mean JLOA of the native knee, while the proportion was significantly higher (50.8 %) in kinematically aligned TKA. The portion was statistically greater in mechanically

Detailed Microstructural Characterization and Restoration Mechanisms of Duplex and Superduplex Stainless Steel Friction-Stir-Welded Joints

NASA Astrophysics Data System (ADS)

Santos, T. F. A.; Torres, E. A.; Lippold, J. C.; Ramirez, A. J.

2016-12-01

Duplex stainless steels are successfully used in a wide variety of applications in areas such as the food industry, petrochemical installations, and sea water desalination plants, where high corrosion resistance and high mechanical strength are required. However, during fusion welding operations, there can be changes to the favorable microstructure of these materials that compromise their performance. Friction stir welding with a non-consumable pin enables welded joints to be obtained in the solid state, which avoids typical problems associated with solidification of the molten pool, such as segregation of alloying elements and the formation of solidification and liquefaction cracks. In the case of superduplex stainless steels, use of the technique can avoid unbalanced proportions of ferrite and austenite, formation of deleterious second phases, or growth of ferritic grains in the heat-affected zone. Consolidated joints with full penetration were obtained for 6-mm-thick plates of UNS S32101 and S32205 duplex stainless steels, and S32750 and S32760 superduplex steels. The welding heat cycles employed avoided the conditions required for formation of deleterious phases, except in the case of the welded joint of the S32760 steel, where SEM images indicated the formation of secondary phases, as corroborated by decreased mechanical performance. Analysis using EBSD and transmission electron microscopy revealed continuous dynamic recrystallization by the formation of cellular arrays of dislocations in the ferrite and discontinuous dynamic recrystallization in the austenite. Microtexture evaluation indicated the presence of fibers typical of shear in the thermomechanically affected zone. These fibers were not obviously present in the stir zone, probably due to the intensity of microstructural reformulation to which this region was subjected.

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints

PubMed Central

Avgoulas, Evangelos I.; Sutcliffe, Michael P. F.

2016-01-01

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints. PMID:28773688

A Review of Natural Joint Systems and Numerical Investigation of Bio-Inspired GFRP-to-Steel Joints.

PubMed

Avgoulas, Evangelos I; Sutcliffe, Michael P F

2016-07-12

There are a great variety of joint types used in nature which can inspire engineering joints. In order to design such biomimetic joints, it is at first important to understand how biological joints work. A comprehensive literature review, considering natural joints from a mechanical point of view, was undertaken. This was used to develop a taxonomy based on the different methods/functions that nature successfully uses to attach dissimilar tissues. One of the key methods that nature uses to join dissimilar materials is a transitional zone of stiffness at the insertion site. This method was used to propose bio-inspired solutions with a transitional zone of stiffness at the joint site for several glass fibre reinforced plastic (GFRP) to steel adhesively bonded joint configurations. The transition zone was used to reduce the material stiffness mismatch of the joint parts. A numerical finite element model was used to identify the optimum variation in material stiffness that minimises potential failure of the joint. The best bio-inspired joints showed a 118% increase of joint strength compared to the standard joints.

Microstructure and Mechanical Properties of Laser Welded Joints of DZ125L and IN718 Nickel Base Superalloys

NASA Astrophysics Data System (ADS)

Liang, Taosha; Wang, Lei; Liu, Yang; Song, Xiu

2018-05-01

The microstructure and mechanical properties of the laser welded joint of DZ125L and IN718 nickel base superalloys were investigated. The results show that the fusion zone (FZ) mainly consists of fine dendrite structure with fine γ', Laves phases and MC carbides inhomogeneously distributed. The high welding temperature induces the partial dissolution of γ' in the heat-affected zone (HAZ) of DZ125L and liquation of grain boundaries in both of the HAZs. After post-weld heat treatment (PWHT), fine γ″ and γ' phases precipitate in the FZ, IN718 HAZ and IN718 base metal (BM), and fine γ' precipitate in the γ channel of the HAZ and BM of DZ125L. With tensile testing, the joints after PWHT show higher strengths than that of the weaker DZ125L alloy. Plastic deformation mainly concentrates in the weaker DZ125L and the joint finally fails in the DZ125L BM.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints.

PubMed

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-09-15

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints

PubMed Central

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-01-01

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding. PMID:28914825

Effect of Composite Substrates on the Mechanical Behavior of Brazed Joints in Metal-Composite System

NASA Technical Reports Server (NTRS)

Singh, M.; Morscher, Gregory N.; Shpargel, Tarah; Asthana, Rajiv

2006-01-01

Advanced composite components are being considered for a wide variety of demanding applications in aerospace, space exploration, and ground based systems. A number of these applications require robust integration technologies to join dissimilar materials (metalcomposites) into complex structural components. In this study, three types of composites (C-C, C-SiC, and SiC-SiC) were vacuum brazed to commercially pure Ti using the active metal braze alloy Cusil-ABA (63Ag-35.3Cu-1.75Ti). Composite substrates with as fabricated and polished surfaces were used for brazing. The microstructure and composition of the joint, examined using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), showed sound metallurgical bonding in all systems. The butt strap tensile (BST) test was performed on bonded specimens at room and elevated temperatures. Effect of substrate composition, interlaminar properties, and surface roughness on the mechanical properties and failure behavior of joints will be discussed.

Experimental and numerical study of the failure process and energy mechanisms of rock-like materials containing cross un-persistent joints under uniaxial compression.

PubMed

Cao, Rihong; Cao, Ping; Lin, Hang; Fan, Xiang

2017-01-01

Joints and fissures in natural rocks have a significant influence on the stability of the rock mass, and it is often necessary to evaluate strength failure and crack evolution behavior. In this paper, based on experimental tests and numerical simulation (PFC2D), the macro-mechanical behavior and energy mechanism of jointed rock-like specimens with cross non-persistent joints under uniaxial loading were investigated. The focus was to study the effect of joint dip angle α and intersection angle γ on the characteristic stress, the coalescence modes and the energy release of jointed rock-like specimens. For specimens with γ = 30° and 45°, the UCS (uniaxial compression strength), CIS (crack initiation stress) and CDiS (critical dilatancy stress) increase as α increases from 0° to 75°. When γ = 60° and 75°, the UCS, CIS and CDiS increase as α increases from 0° to 60° and decrease when α is over 60°. Both the inclination angle α and intersection angle γ have great influence on the failure pattern of pre-cracked specimens. With different α and γ, specimens exhibit 4 kinds of failure patterns. Both the experimental and numerical results show that the energy of a specimen has similar trends with characteristic stress as α increases.

Generalized Models for Rock Joint Surface Shapes

PubMed Central

Du, Shigui; Hu, Yunjin; Hu, Xiaofei

2014-01-01

Generalized models of joint surface shapes are the foundation for mechanism studies on the mechanical effects of rock joint surface shapes. Based on extensive field investigations of rock joint surface shapes, generalized models for three level shapes named macroscopic outline, surface undulating shape, and microcosmic roughness were established through statistical analyses of 20,078 rock joint surface profiles. The relative amplitude of profile curves was used as a borderline for the division of different level shapes. The study results show that the macroscopic outline has three basic features such as planar, arc-shaped, and stepped; the surface undulating shape has three basic features such as planar, undulating, and stepped; and the microcosmic roughness has two basic features such as smooth and rough. PMID:25152901

Joint Source Location and Focal Mechanism Inversion: efficiency, accuracy and applications

NASA Astrophysics Data System (ADS)

Liang, C.; Yu, Y.

2017-12-01

The analysis of induced seismicity has become a common practice to evaluate the results of hydraulic fracturing treatment. Liang et al (2016) proposed a joint Source Scanning Algorithms (jSSA for short) to obtain microseismic events and focal mechanisms simultaneously. The jSSA is superior over traditional SSA in many aspects, but the computation cost is too significant to be applied in real time monitoring. In this study, we have developed several scanning schemas to reduce computation time. A multi-stage scanning schema is proved to be able to improve the efficiency significantly while also retain its accuracy. A series of tests have been carried out by using both real field data and synthetic data to evaluate the accuracy of the method and its dependence on noise level, source depths, focal mechanisms and other factors. The surface-based arrays have better constraints on horizontal location errors (<20m) and angular errors of P axes (within 10 degree, for S/N>0.5). For sources with varying rakes, dips, strikes and depths, the errors are mostly controlled by the partition of positive and negative polarities in different quadrants. More evenly partitioned polarities in different quadrants yield better results in both locations and focal mechanisms. Nevertheless, even with bad resolutions for some FMs, the optimized jSSA method can still improve location accuracies significantly. Based on much more densely distributed events and focal mechanisms, a gridded stress inversion is conducted to get a evenly distributed stress field. The full potential of the jSSA has yet to be explored in different directions, especially in earthquake seismology as seismic array becoming incleasingly dense.

Conjugate Heat Transfer and Thermo-Structural Analysis of the Actively Cooled Multi-Stage Conical Nozzle and Hypersonic Low-Reynolds Diffuser of the New Arc-Heated Wind Tunnel (AWHT-II) of the University of Texas at Arlington

NASA Astrophysics Data System (ADS)

Campbell, David R.

Arc-heated wind tunnels are the primary test facility for screening and qualification of candidate materials for hypersonic thermal protection systems (TPS). Via an electric arc that largely augments the enthalpy (by tens of MJ/kg) of the working fluid (Air, Nitrogen, CO2 in case of Mars-entry studies) passed through a converging-diverging nozzle at specific stagnation conditions, different regimes encountered in entry and re-entry hypersonic aerothermodynamics can be simulated. Because of the high-enthalpies (and associated temperatures that generally exceed the limits required by the thermo-structural integrity of the facility) the active cooling of the arc-heated wind tunnel's parts exposed to the working gas is critical. This criticality is particularly severe in these facilities due to the time scales associated with their continuous operation capabilities (order of minutes). This research focuses on the design and the conjugate heat transfer and resultant thermo-structural analysis of a multi-segment nozzle and low-Reynolds, hypersonic diffuser for the new arc-heated wind tunnel (AHWT-II) of the University of Texas at Arlington. Nozzles and hypersonic diffusers are critical components that experience highly complex flows (non-equilibrium aerothermochemistry) and high (local and distributed) heat-flux loads which significantly augment the complexity of the problems associated with their thermal management. The proper design and thermo-mechanical analysis of these components are crucial elements for the operability of the new facility. This work is centered on the design considerations, methodologies and the detailed analysis of the aforementioned components which resulted in the definition of final parts and assemblies that are under manufacturing at this writing. The project is jointly sponsored by the Office of Naval Research (ONR) and the Defense Advanced Research Project Agency (DARPA).

Low-Friction, Low-Profile, High-Moment Two-Axis Joint

NASA Technical Reports Server (NTRS)

Lewis, James L.; Le, Thang; Carroll, Monty B.

2010-01-01

The two-axis joint is a mechanical device that provides two-degrees-of-freedom motion between connected components. A compact, moment-resistant, two-axis joint is used to connect an electromechanical actuator to its driven structural members. Due to the requirements of the overall mechanism, the joint has a low profile to fit within the allowable space, low friction, and high moment-reacting capability. The mechanical arrangement of this joint can withstand high moments when loads are applied. These features allow the joint to be used in tight spaces where a high load capability is required, as well as in applications where penetrating the mounting surface is not an option or where surface mounting is required. The joint consists of one base, one clevis, one cap, two needle bearings, and a circular shim. The base of the joint is the housing (the base and the cap together), and is connected to the grounding structure via fasteners and a bolt pattern. Captive within the housing, between the base and the cap, are the rotating clevis and the needle bearings. The clevis is attached to the mechanical system (linear actuator) via a pin. This pin, and the rotational movement of the clevis with respect to the housing, provides two rotational degrees of freedom. The larger diameter flange of the clevis is sandwiched between a pair of needle bearings, one on each side of the flange. During the assembly of the two-axis joint, the circular shims are used to adjust the amount of preload that is applied to the needle bearings. The above arrangement enables the joint to handle high moments with minimal friction. To achieve the high-moment capability within a low-profile joint, the use of depth of engagement (like that of a conventional rotating shaft) to react moment is replaced with planar engagement parallel to the mounting surface. The needle bearings with the clevis flange provide the surface area to react the clevis loads/moments into the joint housing while providing minimal

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Haiyan

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electronmore » backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.« less

Regenerative Medicine and Restoration of Joint Function

DTIC Science & Technology

2014-12-01

to resist fracture and excessive deformation under antici- pated mechanical loading conditions both during the early healing process and for longer...per sample type), the results sug- gest a correlation between percent fractured sinter neck area and mechanical properties with the lowest bending...joint replacement are used to treat a joint with an intra-articular fracture or destroyed by a combat injury. Generation of personalized, anatomically

Combined chemical and mechanical effects on free radicals in UHMWPE joints during implantation.

PubMed

Jahan, M S; Wang, C; Schwartz, G; Davidson, J A

1991-08-01

An electron spin resonance (ESR) technique is employed to determine the free radical distribution in the articulating surfaces of retrieved acetabular cups and knee-joint plateaus (retrieved after more than 6 years of implantation). Similar measurements made on samples prepared from cyclically stressed and unstressed cups, and on samples following oxidations in nitric acid and intralipid solutions provided sufficient data to gain more knowledge about the combined chemical and mechanical effects on PE free radicals during implantation. In UHMWPE free radicals are primarily initiated by gamma-ray sterilization; however, during implantation, peroxy (scission type) free radicals are formed and reach a maximum concentration level (equilibrium state) due to oxidation by chemical (hemoglobin and/or synovial fluids) environment of the joints. Subsequently, due to frictional heating and stress in the loading zones, free radical reaction is accelerated and their number is reduced only in those areas. This is consistent with the observations of a temperature rise in acetabular cups during in vitro frictional wear stress tests and in vivo telemetry observations, as reported by others. Compared with the previously reported SEM micrographs the low-free-radical regions are correlated with high-wear areas and the high-free-radical regions with the low-wear areas.

Interfacial Reaction and Mechanical Properties of Sn-Bi Solder joints

PubMed Central

Huang, Ying; Zhang, Zhijie

2017-01-01

Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi and Sn-15Bi solid solution, Sn-30Bi and Sn-45Bi hypoeutectic and Sn-58Bi eutectic were selected in this work. The microstructure, interfacial reaction under soldering and subsequent aging and the shear properties of Sn-Bi solder joints were studied. Bi content in Sn-Bi solder had an obvious effect on the microstructure and the distribution of Bi phases. Solid solution Sn-Bi solder was composed of the β-Sn phases embedded with fine Bi particles, while hypoeutectic Sn-Bi solder was composed of the primary β-Sn phases and Sn-Bi eutectic structure from networked Sn and Bi phases, and eutectic Sn-Bi solder was mainly composed of a eutectic structure from short striped Sn and Bi phases. During soldering with Cu, the increase on Bi content in Sn-Bi solder slightly increased the interfacial Cu6Sn5 intermetallic compound (IMC)thickness, gradually flattened the IMC morphology, and promoted the accumulation of more Bi atoms to interfacial Cu6Sn5 IMC. During the subsequent aging, the growth rate of the IMC layer at the interface of Sn-Bi solder/Cu rapidly increased from solid solution Sn-Bi solder to hypoeutectic Sn-Bi solder, and then slightly decreased for Sn-58Bi solder joints. The accumulation of Bi atoms at the interface promoted the rapid growth of interfacial Cu6Sn5 IMC layer in hypoeutectic or eutectic Sn-Bi solder through blocking the formation of Cu6Sn5 in solder matrix and the transition from Cu6Sn5 to Cu3Sn. Ball shear tests on Sn-Bi as-soldered joints showed that the increase of Bi content in Sn-Bi deteriorated the shear strength of solder joints. The addition of Bi into Sn solder was also inclined to produce brittle morphology with interfacial fracture, which suggests that the

Cu-Sn Intermetallic Compound Joints for High-Temperature Power Electronics Applications

NASA Astrophysics Data System (ADS)

Lee, Byung-Suk; Yoon, Jeong-Won

2018-01-01

Cu-Sn solid-liquid interdiffusion (SLID) bonded joints were fabricated using a Sn-Cu solder paste and Cu for high-temperature power electronics applications. The interfacial reaction behaviors and the mechanical properties of Cu6Sn5 and Cu3Sn SLID-bonded joints were compared. The intermetallic compounds formed at the interfaces in the Cu-Sn SLID-bonded joints significantly affected the die shear strength of the joint. In terms of thermal and mechanical properties, the Cu3Sn SLID-bonded joint was superior to the conventional solder and the Cu6Sn5 SLID-bonded joints.

Effect of Moisture Cycling on Mechanical Response of Metal-Plate Connector Joints With and Without an Adhesive Interface

Treesearch

Leslie H. Groom

1995-01-01

Wood trusses are frequently located in light-frame structures where they are subjected to significant shifts in moisture conditions. However, little is known about the effects of moisture cycling of the wood members on the mechanical behavior of metal-plate connector (MPC) joints. Thus, the primary objective of this study was to quantify the effect of wood moisture...

Report of a workshop on human-automation interaction in NGATS

DOT National Transportation Integrated Search

2006-10-01

This report reviews the findings of a workshop held in Arlington, VA may 10 and 11, 2006 to consider needs for research on human-automation interaction to support NASA/FAA Joint Planning and Development Office. Participants included representatives f...

Fluid load support and contact mechanics of hemiarthroplasty in the natural hip joint.

PubMed

Pawaskar, Sainath Shrikant; Ingham, Eileen; Fisher, John; Jin, Zhongmin

2011-01-01

The articular cartilage covering the ends of the bones of diarthrodial synovial joints is thought to have evolved so that the loads are transferred under different and complex conditions, with a very high degree of efficiency and without compromising the structural integrity of the tissue for the life of an individual. These loading conditions stem from different activities such as walking, and standing. The integrity of cartilage may however become compromised due to congenital disease, arthritis or trauma. Hemiarthroplasty is a potentially conservative treatment when only the femoral cartilage is affected as in case of femoral neck fractures. In hemiarthroplasty, a metallic femoral prosthesis is used to articulate against the natural acetabular cartilage. It has also been hypothesized that biphasic lubrication is the predominant mechanism protecting the cartilage through a very high fluid load support which lowers friction. This may be altered due to hemiarthroplasty and have a direct effect on the frictional shear stresses and potentially cartilage degradation and wear. This study modelled nine activities of daily living and investigated the contact mechanics of a hip joint with a hemiarthroplasty, focussing particularly on the role of the fluid phase. It was shown that in most of the activities studied the peak contact stresses and peak fluid pressures were in the superior dome or lateral roof of the acetabulum. Total fluid load support was very high (~90%) in most of the activities which would shield the solid phase from being subjected to very high contact stresses. This was dependent not only on the load magnitude but also the direction and hence on the location of the contact area with respect to the cartilage coverage. Lower fluid load support was found when the contact area was nearer the edges where the fluid drained easily. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Optimizing the DoD Supply Chain for the Future Joint Force

DTIC Science & Technology

2013-05-01

4 Sunil Chopra and Peter Meindl, Supply Chain Management: Strategy, Planning, and Operation, 5th ed. (Boston: Pearson Education, Inc., 2013), 339...Arlington, VA: Lexington Institute, 2005. Chopra, Sunil and Peter Meindl. Supply Chain Management: Strategy, Planning, and Operation. 5th ed. Boston

Disclosing the temperature of columnar jointing in lavas.

PubMed

Lamur, Anthony; Lavallée, Yan; Iddon, Fiona E; Hornby, Adrian J; Kendrick, Jackie E; von Aulock, Felix W; Wadsworth, Fabian B

2018-04-12

Columnar joints form by cracking during cooling-induced contraction of lava, allowing hydrothermal fluid circulation. A lack of direct observations of their formation has led to ambiguity about the temperature window of jointing and its impact on fluid flow. Here we develop a novel thermo-mechanical experiment to disclose the temperature of columnar jointing in lavas. Using basalts from Eyjafjallajökull volcano (Iceland) we show that contraction during cooling induces stress build-up below the solidus temperature (980 °C), resulting in localised macroscopic failure between 890 and 840 °C. This temperature window for incipient columnar jointing is supported by modelling informed by mechanical testing and thermal expansivity measurements. We demonstrate that columnar jointing takes place well within the solid state of volcanic rocks, and is followed by a nonlinear increase in system permeability of <9 orders of magnitude during cooling. Columnar jointing may promote advective cooling in magmatic-hydrothermal environments and fluid loss during geothermal drilling and thermal stimulation.

Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

NASA Astrophysics Data System (ADS)

Maduraimuthu, V.; Vasudevan, M.; Muthupandi, V.; Bhaduri, A. K.; Jayakumar, T.

2012-02-01

A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

Progressive Damage Modeling of Durable Bonded Joint Technology

NASA Technical Reports Server (NTRS)

Leone, Frank A.; Davila, Carlos G.; Lin, Shih-Yung; Smeltzer, Stan; Girolamo, Donato; Ghose, Sayata; Guzman, Juan C.; McCarville, Duglas A.

2013-01-01

The development of durable bonded joint technology for assembling composite structures for launch vehicles is being pursued for the U.S. Space Launch System. The present work is related to the development and application of progressive damage modeling techniques to bonded joint technology applicable to a wide range of sandwich structures for a Heavy Lift Launch Vehicle. The joint designs studied in this work include a conventional composite splice joint and a NASA-patented Durable Redundant Joint. Both designs involve a honeycomb sandwich with carbon/epoxy facesheets joined with adhesively bonded doublers. Progressive damage modeling allows for the prediction of the initiation and evolution of damage. For structures that include multiple materials, the number of potential failure mechanisms that must be considered increases the complexity of the analyses. Potential failure mechanisms include fiber fracture, matrix cracking, delamination, core crushing, adhesive failure, and their interactions. The joints were modeled using Abaqus parametric finite element models, in which damage was modeled with user-written subroutines. Each ply was meshed discretely, and layers of cohesive elements were used to account for delaminations and to model the adhesive layers. Good correlation with experimental results was achieved both in terms of load-displacement history and predicted failure mechanisms.

Defense.gov Special Report: Medal of Honor

Science.gov Websites

Recipients Joint Chiefs of Staff, USO Salute Medal of Honor Recipients At an awards dinner, members of the the USO-Metro's 33rd Annual Awards Dinner in Arlington, Va., March 24, 2015, where they shared their

Exercise following a short immobilization period is detrimental to tendon properties and joint mechanics in a rat rotator cuff injury model.

PubMed

Peltz, Cathryn D; Sarver, Joseph J; Dourte, Leann M; Würgler-Hauri, Carola C; Williams, Gerald R; Soslowsky, Louis J

2010-07-01

Rotator cuff tears are a common clinical problem that can result in pain and disability. Previous studies in a rat model showed enhanced tendon to bone healing with postoperative immobilization. The objective of this study was to determine the effect of postimmobilization activity level on insertion site properties and joint mechanics in a rat model. Our hypothesis was that exercise following a short period of immobilization will cause detrimental changes in insertion site properties compared to cage activity following the same period of immobilization, but that passive shoulder mechanics will not be affected. We detached and repaired the supraspinatus tendon of 22 Sprague-Dawley rats, and the injured shoulder was immobilized postoperatively for 2 weeks. Following immobilization, rats were prescribed cage activity or exercise for 12 weeks. Passive shoulder mechanics were determined, and following euthanasia, tendon cross-sectional area and mechanical properties were measured. Exercise following immobilization resulted in significant decreases compared to cage activity in range of motion, tendon stiffness, modulus, percent relaxation, and several parameters from both a structurally based elastic model and a quasi-linear viscoelastic model. Therefore, we conclude that after a short period of immobilization, increased activity is detrimental to both tendon mechanical properties and shoulder joint mechanics, presumably due to increased scar production. (c) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc

Mechanical properties of welded joints of the reduced-activation ferritic steel: 8% Cr-2% W-0.2% V-0.04% Ta-Fe

NASA Astrophysics Data System (ADS)

Hayakawa, H.; Yoshitake, A.; Tamura, M.; Natsume, S.; Gotoh, A.; Hishinuma, A.

1991-03-01

A reduced-activation ferritic steel, 8Cr-2W-0.2V-0.04Ta-Fe (F-82H) has been developed by JAERI and NKK to improve creep properties and toughness as compared with HT9. The mechanical properties and phase stability of the steel were reported at the previous conferences, ICFRM-2 and 3. This paper is concerned with the mechanical properties of weld metal and welded joints using a newly-developed filler wire of F-82H which contains less C and Ta than the base metal. The design concept of chemical composition of the filler wire was based on as much reduction of activity after irradiation as possible and considerations of the hardenability and toughness of the weld metal. Mechanical properties, such as tensile strength and toughness, of the weld metal and welded joints produced by GTAW after stress-relieving heat treatment were investigated. The results showed that this welding material has almost the same properties as the base metal.

Increased leaf angle1, a Raf-like MAPKKK that interacts with a nuclear protein family, regulates mechanical tissue formation in the Lamina joint of rice.

PubMed

Ning, Jing; Zhang, Baocai; Wang, Nili; Zhou, Yihua; Xiong, Lizhong

2011-12-01

Mitogen-activated protein kinase kinase kinases (MAPKKKs), which function at the top level of mitogen-activated protein kinase cascades, are clustered into three groups. However, no Group C Raf-like MAPKKKs have yet been functionally identified. We report here the characterization of a rice (Oryza sativa) mutant, increased leaf angle1 (ila1), resulting from a T-DNA insertion in a Group C MAPKKK gene. The increased leaf angle in ila1 is caused by abnormal vascular bundle formation and cell wall composition in the leaf lamina joint, as distinct from the mechanism observed in brassinosteroid-related mutants. Phosphorylation assays revealed that ILA1 is a functional kinase with Ser/Thr kinase activity. ILA1 is predominantly resident in the nucleus and expressed in the vascular bundles of leaf lamina joints. Yeast two-hybrid screening identified six closely related ILA1 interacting proteins (IIPs) of unknown function. Using representative IIPs, the interaction of ILA1 and IIPs was confirmed in vivo. IIPs were localized in the nucleus and showed transactivation activity. Furthermore, ILA1 could phosphorylate IIP4, indicating that IIPs may be the downstream substrates of ILA1. Microarray analyses of leaf lamina joints provided additional evidence for alterations in mechanical strength in ila1. ILA1 is thus a key factor regulating mechanical tissue formation at the leaf lamina joint.

Robotic joint experiments under ultravacuum

NASA Technical Reports Server (NTRS)

Borrien, A.; Petitjean, L.

1988-01-01

First, various aspects of a robotic joint development program, including gearbox technology, electromechanical components, lubrication, and test results, are discussed. Secondly, a test prototype of the joint allowing simulation of robotic arm dynamic effects is presented. This prototype is tested under vacuum with different types of motors and sensors to characterize the functional parameters: angular position error, mechanical backlash, gearbox efficiency, and lifetime.

Development of a Joint Hydrogen and Syngas Combustion Mechanism Based on an Optimization Approach.

PubMed

Varga, Tamás; Olm, Carsten; Nagy, Tibor; Zsély, István Gy; Valkó, Éva; Pálvölgyi, Róbert; Curran, Henry J; Turányi, Tamás

2016-08-01

A comprehensive and hierarchical optimization of a joint hydrogen and syngas combustion mechanism has been carried out. The Kéromnès et al. ( Combust Flame , 2013, 160, 995-1011) mechanism for syngas combustion was updated with our recently optimized hydrogen combustion mechanism (Varga et al., Proc Combust Inst , 2015, 35, 589-596) and optimized using a comprehensive set of direct and indirect experimental data relevant to hydrogen and syngas combustion. The collection of experimental data consisted of ignition measurements in shock tubes and rapid compression machines, burning velocity measurements, and species profiles measured using shock tubes, flow reactors, and jet-stirred reactors. The experimental conditions covered wide ranges of temperatures (800-2500 K), pressures (0.5-50 bar), equivalence ratios ( ϕ = 0.3-5.0), and C/H ratios (0-3). In total, 48 Arrhenius parameters and 5 third-body collision efficiency parameters of 18 elementary reactions were optimized using these experimental data. A large number of directly measured rate coefficient values belonging to 15 of the reaction steps were also utilized. The optimization has resulted in a H 2 /CO combustion mechanism, which is applicable to a wide range of conditions. Moreover, new recommended rate parameters with their covariance matrix and temperature-dependent uncertainty ranges of the optimized rate coefficients are provided. The optimized mechanism was compared to 19 recent hydrogen and syngas combustion mechanisms and is shown to provide the best reproduction of the experimental data.

Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammadi, J.; Behnamian, Y.; Mostafaei, A., E-mail: amir.mostafaei@gmail.com

2015-03-15

Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560–1400 r/min and 16–40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) were used to investigatemore » the microstructures of the joints welded. Intermetallic phases including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β) were detected in the weld zone (WZ). For different tool rotation speeds, the morphology of the microstructure in the stir zone changed significantly with travel speed. Lap shear tensile test results indicated that by simultaneously increasing the tool rotation and travel speeds to 1400 r/min and 40 mm/min, the joint tensile strength and ductility reached a maximum. Microhardness measurements and tensile stress–strain curves indicated that mechanical properties were affected by FSW parameters and mainly depended on the formation of intermetallic compounds in the weld zone. In addition, a debonding failure mode in the Al/Mg dissimilar weld nugget was investigated by SEM and surface fracture studies indicated that the presence of intermetallic compounds in the weld zone controlled the failure mode. XRD analysis of the fracture surface indicated the presence of brittle intermetallic compounds including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β). - Highlights: • Dissimilar Al/Mg joint was obtained by lap friction stir welding technique. • Effect of rotation and travel speeds on the formation of intermetallic

Effect of Joint Scale and Processing on the Fracture of Sn-3Ag-0.5Cu Solder Joints: Application to Micro-bumps in 3D Packages

NASA Astrophysics Data System (ADS)

Talebanpour, B.; Huang, Z.; Chen, Z.; Dutta, I.

2016-01-01

In 3-dimensional (3D) packages, a stack of dies is vertically connected to each other using through-silicon vias and very thin solder micro-bumps. The thinness of the micro-bumps results in joints with a very high volumetric proportion of intermetallic compounds (IMCs), rendering them much more brittle compared to conventional joints. Because of this, the reliability of micro-bumps, and the dependence thereof on the proportion of IMC in the joint, is of substantial concern. In this paper, the growth kinetics of IMCs in thin Sn-3Ag-0.5Cu joints attached to Cu substrates were analyzed, and empirical kinetic laws for the growth of Cu6Sn5 and Cu3Sn in thin joints were obtained. Modified compact mixed mode fracture mechanics samples, with adhesive solder joints between massive Cu substrates, having similar thickness and IMC content as actual micro-bumps, were produced. The effects of IMC proportion and strain rate on fracture toughness and mechanisms were investigated. It was found that the fracture toughness G C decreased with decreasing joint thickness ( h Joint). In addition, the fracture toughness decreased with increasing strain rate. Aging also promoted alternation of the crack path between the two joint-substrate interfaces, possibly proffering a mechanism to enhance fracture toughness.

Defense Acquisition and the Case of the Joint Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a Mechanism for Adaptive Change

DTIC Science & Technology

2013-04-01

Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a Mechanism for Adaptive Change Kathryn Aten and John T. Dillard Naval...Defense Acquisition and the Case of the Joint Capabilities Technology Demonstration Office: Ad Hoc Problem Solving as a Mechanism for Adaptive Change...describes the preliminary analysis and findings of our study exploring what drives successful organizational adaptation in the context of technology

Effects of medially wedged foot orthoses on knee and hip joint running mechanics in females with and without patellofemoral pain syndrome.

PubMed

Boldt, Andrew R; Willson, John D; Barrios, Joaquin A; Kernozek, Thomas W

2013-02-01

We examined the effects of medially wedged foot orthoses on knee and hip joint mechanics during running in females with and without patellofemoral pain syndrome (PFPS). We also tested if these effects depend on standing calcaneal eversion angle. Twenty female runners with and without PFPS participated. Knee and hip joint transverse and frontal plane peak angle, excursion, and peak internal knee and hip abduction moment were calculated while running with and without a 6° full-length medially wedged foot orthoses. Separate 3-factor mixed ANOVAs (group [PFPS, control] x condition [medial wedge, no medial wedge] x standing calcaneal angle [everted, neutral, inverted]) were used to test the effect of medially wedged orthoses on each dependent variable. Knee abduction moment increased 3% (P = .03) and hip adduction excursion decreased 0.6° (P < .01) using medially wedged foot orthoses. No significant group x condition or calcaneal angle x condition effects were observed. The addition of medially wedged foot orthoses to standardized running shoes had minimal effect on knee and hip joint mechanics during running thought to be associated with the etiology or exacerbation of PFPS symptoms. These effects did not appear to depend on injury status or standing calcaneal posture.

Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running

PubMed Central

Wunsch, Tobias; Alexander, Nathalie; Kröll, Josef; Stöggl, Thomas; Schwameder, Hermann

2017-01-01

To enhance running performance in heel-toe running, a leaf spring structured midsole shoe (LEAF) has recently been introduced. The purpose of this study was to investigate the effect of a LEAF compared to a standard foam midsole shoe (FOAM) on joint mechanics and lower limb muscle forces in overground running. Nine male long-distance heel strike runners ran on an indoor track at 3.0 ± 0.2 m/s with LEAF and FOAM shoes. Running kinematics and kinetics were recorded during the stance phase. Absorbed and generated energy (negative and positive work) of the hip, knee and ankle joint as well as muscle forces of selected lower limb muscles were determined using a musculoskeletal model. A significant reduction in energy absorption at the hip joint as well as energy generation at the ankle joint was found for LEAF compared to FOAM. The mean lower limb muscle forces of the m. soleus, m. gastrocnemius lateralis and m. gastrocnemius medialis were significantly reduced for LEAF compared to FOAM. Furthermore, m. biceps femoris showed a trend of reduction in running with LEAF. The remaining lower limb muscles analyzed (m. gluteus maximus, m. rectus femoris, m. vastus medialis, m. vastus lateralis, m. tibialis anterior) did not reveal significant differences between the shoe conditions. The findings of this study indicate that LEAF positively influenced the energy balance in running by reducing lower limb muscle forces compared to FOAM. In this way, LEAF could contribute to an overall increased running performance in heel-toe running. PMID:28234946

Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running.

PubMed

Wunsch, Tobias; Alexander, Nathalie; Kröll, Josef; Stöggl, Thomas; Schwameder, Hermann

2017-01-01

To enhance running performance in heel-toe running, a leaf spring structured midsole shoe (LEAF) has recently been introduced. The purpose of this study was to investigate the effect of a LEAF compared to a standard foam midsole shoe (FOAM) on joint mechanics and lower limb muscle forces in overground running. Nine male long-distance heel strike runners ran on an indoor track at 3.0 ± 0.2 m/s with LEAF and FOAM shoes. Running kinematics and kinetics were recorded during the stance phase. Absorbed and generated energy (negative and positive work) of the hip, knee and ankle joint as well as muscle forces of selected lower limb muscles were determined using a musculoskeletal model. A significant reduction in energy absorption at the hip joint as well as energy generation at the ankle joint was found for LEAF compared to FOAM. The mean lower limb muscle forces of the m. soleus, m. gastrocnemius lateralis and m. gastrocnemius medialis were significantly reduced for LEAF compared to FOAM. Furthermore, m. biceps femoris showed a trend of reduction in running with LEAF. The remaining lower limb muscles analyzed (m. gluteus maximus, m. rectus femoris, m. vastus medialis, m. vastus lateralis, m. tibialis anterior) did not reveal significant differences between the shoe conditions. The findings of this study indicate that LEAF positively influenced the energy balance in running by reducing lower limb muscle forces compared to FOAM. In this way, LEAF could contribute to an overall increased running performance in heel-toe running.

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing.

PubMed

Villegas, Irene F; Palardy, Genevieve

2016-02-11

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

PubMed Central

Villegas, Irene F.; Palardy, Genevieve

2016-01-01

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints. PMID:26890931

Failure Mechanisms of Thermomechanically Loaded SnAgCu/Plastic Core Solder Ball Composite Joints in Low-Temperature Co-Fired Ceramic/Printed Wiring Board Assemblies

NASA Astrophysics Data System (ADS)

Nousiainen, O.; Putaala, J.; Kangasvieri, T.; Rautioaho, R.; Vähäkangas, J.

2007-03-01

The thermal fatigue endurance of completely lead-free 95.5Sn4Ag0.7Cu/plastic core solder ball (PCSB) composite joint structures in low-temperature Co-fired ceramic/printed wiring board (LTCC/PWB) assemblies was investigated using thermal cycling tests over the temperature ranges of -40°C 125°C and 0°C 100°C. Two separate creep/fatigue failures initiated and propagated in the joints during the tests: (1) a crack along the intermetallic compound (IMC)/solder interface on the LTCC side of the joint, which formed at the high-temperature extremes; and (2) a crack in the solder near the LTCC solder land, which formed at the low-temperature extremes. Moreover, localized recrystallization was detected at the outer edge of the joints that were tested in the harsh (-40°C 125°C) test conditions. The failure mechanism was creep/fatigue-induced mixed intergranular and transgranular cracking in the recrystallized zone, but it was dominated by transgranular thermal fatigue failure beyond the recrystallized zone. The change in the failure mechanism increased the rate of crack growth. When the lower temperature extreme was raised from -40°C to 0°C, no recrystallized zone was detected and the failure was due to intergranular cracks.

Development of a Joint Hydrogen and Syngas Combustion Mechanism Based on an Optimization Approach

PubMed Central

Varga, Tamás; Olm, Carsten; Nagy, Tibor; Zsély, István Gy.; Valkó, Éva; Pálvölgyi, Róbert; Curran, Henry. J.

2016-01-01

ABSTRACT A comprehensive and hierarchical optimization of a joint hydrogen and syngas combustion mechanism has been carried out. The Kéromnès et al. (Combust Flame, 2013, 160, 995–1011) mechanism for syngas combustion was updated with our recently optimized hydrogen combustion mechanism (Varga et al., Proc Combust Inst, 2015, 35, 589–596) and optimized using a comprehensive set of direct and indirect experimental data relevant to hydrogen and syngas combustion. The collection of experimental data consisted of ignition measurements in shock tubes and rapid compression machines, burning velocity measurements, and species profiles measured using shock tubes, flow reactors, and jet‐stirred reactors. The experimental conditions covered wide ranges of temperatures (800–2500 K), pressures (0.5–50 bar), equivalence ratios (ϕ = 0.3–5.0), and C/H ratios (0–3). In total, 48 Arrhenius parameters and 5 third‐body collision efficiency parameters of 18 elementary reactions were optimized using these experimental data. A large number of directly measured rate coefficient values belonging to 15 of the reaction steps were also utilized. The optimization has resulted in a H2/CO combustion mechanism, which is applicable to a wide range of conditions. Moreover, new recommended rate parameters with their covariance matrix and temperature‐dependent uncertainty ranges of the optimized rate coefficients are provided. The optimized mechanism was compared to 19 recent hydrogen and syngas combustion mechanisms and is shown to provide the best reproduction of the experimental data. PMID:27840549

Flaw Tolerance In Lap Shear Brazed Joints. Part 2

NASA Technical Reports Server (NTRS)

Wang, Len; Flom, Yury

2003-01-01

This paper presents results of the second part of an on-going effort to gain better understanding of defect tolerance in braze joints. In the first part of this three-part series, we mechanically tested and modeled the strength of the lap joints as a function of the overlap distance. A failure criterion was established based on the zone damage theory, which predicts the dependence of the lap joint shear strength on the overlap distance, based on the critical size of a finite damage zone or an overloaded region in the joint. In this second part of the study, we experimentally verified the applicability of the damage zone criterion on prediction of the shear strength of the lap joint and introduced controlled flaws into the lap joints. The purpose of the study was to evaluate the lap joint strength as a function of flaw size and its location through mechanical testing and nonlinear finite element analysis (FEA) employing damage zone criterion for definition of failure. The results obtained from the second part of the investigation confirmed that the failure of the ductile lap shear brazed joints occurs when the damage zone reaches approximately 10% of the overlap width. The same failure criterion was applicable to the lap joints containing flaws.

77 FR 37060 - Critical Infrastructure and Key Resources (CIKR) Asset Protection Technical Assistance Program...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-20

...), National Protection and Programs Directorate (NPPD), Office of Infrastructure Protection (IP.../IP/IICD, 245 Murray Lane SW., Mailstop 0602, Arlington, VA 20598-0602. Email requests should go to... Technical Assistance Program (CAPTAP) is offered jointly by the NPPD/IP and the Federal Emergency Management...

Effect of Tool Offset and Tool Rotational Speed on Enhancing Mechanical Property of Al/Mg Dissimilar FSW Joints

NASA Astrophysics Data System (ADS)

Liang, Zhiyuan; Chen, Ke; Wang, Xiaona; Yao, Junshan; Yang, Qi; Zhang, Lanting; Shan, Aidang

2013-08-01

Friction stir welding (FSW) is a promising solid-state joining technique for producing effective welds between Al alloy and Mg alloy. However, previously reported Al/Mg dissimilar FSW joints generally have limited strength or barely any ductility with relatively high strength, which was blamed on the brittle intermetallics formed during welding. In this study, effective joints with comparably high strength (163 MPa) and large elongation (~6 pct) were obtained. Three crucial/weak zones were identified in the welds: (1) Al/Mg bottom interface (BI) zone that resulted from the insufficient materials' intermixing and interdiffusion; (2) banded structure (BS) zone which contains intermetallic particles possibly formed by constitutional liquation; and (3) softened Al alloy to the retreating side (SAA-RS) zone due to the dissolution and coarsening of the strengthening precipitates. Three fracture modes observed in the tensile specimens perpendicular to the weld seam were found closely related to these zones. Their microstructure evolution with the change of tool rotational speed and tool offset was characterized and the consequent effect on the fracture mode alteration was studied. It turned out that enhancing the strengths of all these zones, but keeping the strength of the SAA lowest, is an effective way for enhancing ductility while keeping comparatively high strength in Al/Mg FSW joints. Also, suggestions for further improving the mechanical property of the Al/Mg dissimilar FSW joints were made accordingly for practical applications.

Neural mechanisms and models underlying joint action.

PubMed

Chersi, Fabian

2011-06-01

Humans, in particular, and to a lesser extent also other species of animals, possess the impressive capability of smoothly coordinating their actions with those of others. The great amount of work done in recent years in neuroscience has provided new insights into the processes involved in joint action, intention understanding, and task sharing. In particular, the discovery of mirror neurons, which fire both when animals execute actions and when they observe the same actions done by other individuals, has shed light on the intimate relationship between perception and action elucidating the direct contribution of motor knowledge to action understanding. Up to date, however, a detailed description of the neural processes involved in these phenomena is still mostly lacking. Building upon data from single neuron recordings in monkeys observing the actions of a demonstrator and then executing the same or a complementary action, this paper describes the functioning of a biologically constraint neural network model of the motor and mirror systems during joint action. In this model, motor sequences are encoded as independent neuronal chains that represent concatenations of elementary motor acts leading to a specific goal. Action execution and recognition are achieved through the propagation of activity within specific chains. Due to the dual property of mirror neurons, the same architecture is capable of smoothly integrating and switching between observed and self-generated action sequences, thus allowing to evaluate multiple hypotheses simultaneously, understand actions done by others, and to respond in an appropriate way.

Mechanical characteristics and microstructure of weld joint of high-temperature martensitic steel containing 9% Cr

NASA Astrophysics Data System (ADS)

Shakhova, Ya. E.; Belyakov, A. N.; Kaibyshev, R. O.

2016-04-01

The structure and mechanical characteristics of a weld joint of 10Kh9K3V2MFBR steel (0.097 C, 0.17.Si, 0.54 Mn, 8.75 Cr, 0.21 Ni, 0.51 Mo, 0.07 Nb, 0.23 V, 0.004 N, 0.003 B, 1.6 W, 0.15 Cu, and Fe for balance, wt %) have been studied; the joint was produced by hand welding in an argon atmosphere using 03Kh20N45M7G6B welding wire (0.3 C, 20 Cr, 45 Ni, 7 Mo, 6 Mn, and 1 Nb, wt %). The weld joint is divided into the zone of the base metal, a thermal effect zone, which consists of zones that contain fine and coarse original austenitic grains, and the zone of seam metal. It has been shown that the weld joint of 10Kh9K3V2MFBR steel possesses high strength characteristics at the room temperature under static loading and a satisfactorily impact toughness, which has the minimum value of 30 J/cm2 in the zone of the seam metal and does not depend on the temperature. With a decrease in the temperature from the room temperature to 253 K, a ductile-brittle transition occurs in the thermal effect zone. Creep tests carried out at the temperature of 923 K have shown that the long-term strength of the weld seam is lower than that of the base material in the entire stress range being tested. At stresses of 140 MPa or higher, the acceleration of creep in the weld seam is observed, while at low stresses of about 120 MPa, the rates of creep in the weld seam and in the base metal remain similar until the transition to the stage of accelerated fracture occurs. The difference in the values of the long-term strength is due to premature fracture, which occurs in the thermal effect zone with the finegrained structure.

Hybrid FSWeld-bonded joint fatigue behaviour

NASA Astrophysics Data System (ADS)

Lertora, Enrico; Mandolfino, Chiara; Gambaro, Carla; Pizzorni, Marco

2018-05-01

Aluminium alloys, widely used in aeronautics, are increasingly involved in the automotive industry due to the good relationship between mechanical strength and specific weight. The lightening of the structures is the first objective, which allows the decreasing in the weight in motion. The use of aluminium alloys has also seen the introduction of the Friction Stir Welding (FSW) technique for the production of structural overlapping joints. FSW allows us to weld overlap joints free from defects, but with the presence of a structural notch further aggravated by the presence of a "hook" defect near the edge of the weld. Furthermore, FSW presents a weld penetration area connected to the tool geometry and penetration. The experimental activity will be focused on the combination of two different joining techniques, which can synergistically improve the final joint resistance. In particular, the welding and bonding process most commonly known as weld-bonding is defined as a hybrid process, as it combines two different junction processes. In this paper we analyse FSWelded AA6082 aluminium alloy overlapped joint with the aim of quantitatively evaluating the improvement provided by the presence of an epoxy adhesive between the plates. After optimising the weld-bonding process, the mechanical behaviour of welded joints will be analysed by static and dynamic tests. The presence of the adhesive should limit the negative effect of the structural notch inevitable in a FSW overlapped joint.

[Arthrodesis (with/without correction) of the ankle and subtalar joint: A3 nail fixation with triple bending and mechanical navigation].

PubMed

Richter, M

2014-08-01

Restoration of a stable and plantigrade foot in deformities of the ankle and/or hindfoot and concomitant degenerative changes at the ankle and subtalar joints. Deformities at the ankle and/or hindfoot and concomitant degenerative changes at the ankle and subtalar joint. Failed (corrective) arthrodesis of the ankle and subtalar joints. Fused ankle and degeneration of the subtalar joint. Failed total ankle replacement with insufficient substance of talar body and/or degeneration of subtalar joint. Massive hindfoot instability. Active local infection or relevant vascular insufficiency, possible preservation of the ankle or subtalar joint (relative contraindication). Prone position and posterolateral approach to ankle and subtalar joints (alternative supine position/anterior approach; lateral position/lateral approach). Exposition of ankle and subtalar joints and removal of remaining cartilage. Optional corrective osteotomies and/or bone grafting. Correction and optional fixation of the corrected position with 2.0 mm K-wires. Mechanically navigated insertion of a retrograde guide wire in projection of the tibial axis and insertion of a second guide wire through the entry point of the nail lateral and dorsal to the tibial axis. Reaming and insertion of the A3 nail with a distal double bend; one posterior and one lateral, and a proximal bend corresponding to a slight recurvatum. Insertion of locking screws into the calcaneus, talus and tibia (twice with optional static or dynamic locking). Optional compression between calcaneus and talus, and between tibia and talus. Insertion of a drainage and layer-wise closure. For the first 6 weeks 15 kg partial weight bearing in an orthosis, followed by full weight bearing in a stable standard shoe. In October 2010 (n = 2) and from 15 October 2011 to 13 April 2012 (n = 26) 28 arthrodeses (with/without correction) with A3 fixation were performed. In all cases, exact nail placement was achieved. Thirteen cases completed

A Revolute Joint With Linear Load-Displacement Response for Precision Deployable Structures

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Warren, Peter A.; Peterson, Lee D.

1996-01-01

NASA Langley Research center is developing key structures and mechanisms technologies for micron-accuracy, in-space deployment of future space instruments. Achieving micron-accuracy deployment requires significant advancements in deployment mechanism design such as the revolute joint presented herein. The joint presented herein exhibits a load-cycling response that is essentially linear with less than two percent hysteresis, and the joint rotates with less than one in.-oz. of resistance. A prototype reflector metering truss incorporating the joint exhibits only a few microns of kinematic error under repeated deployment and impulse loading. No other mechanically deployable structure found in literature has been demonstrated to be this kinematically accurate.

Effect of Plasma Surface Finish on Wettability and Mechanical Properties of SAC305 Solder Joints

NASA Astrophysics Data System (ADS)

Kim, Kyoung-Ho; Koike, Junichi; Yoon, Jeong-Won; Yoo, Sehoon

2016-12-01

The wetting behavior, interfacial reactions, and mechanical reliability of Sn-Ag-Cu solder on a plasma-coated printed circuit board (PCB) substrate were evaluated under multiple heat-treatments. Conventional organic solderability preservative (OSP) finished PCBs were used as a reference. The plasma process created a dense and highly cross-linked polymer coating on the Cu substrates. The plasma finished samples had higher wetting forces and shorter zero-cross times than those with OSP surface finish. The OSP sample was degraded after sequential multiple heat treatments and reflow processes, whereas the solderability of the plasma finished sample was retained after multiple heat treatments. After the soldering process, similar microstructures were observed at the interfaces of the two solder joints, where the development of intermetallic compounds was observed. From ball shear tests, it was found that the shear force for the plasma substrate was consistently higher than that for the OSP substrate. Deterioration of the OSP surface finish was observed after multiple heat treatments. Overall, the plasma surface finish was superior to the conventional OSP finish with respect to wettability and joint reliability, indicating that it is a suitable material for the fabrication of complex electronic devices.

The joint in psoriatic arthritis.

PubMed

Mortezavi, Mahta; Thiele, Ralph; Ritchlin, Christopher

2015-01-01

Psoriatic arthritis (PsA), a chronic inflammatory joint disease associated with psoriasis, is notable for diversity in disease presentation, course and response to treatment. Equally varied are the types of musculoskeletal involvement which include peripheral and axial joint disease, dactylitis and enthesitis. In this review, we focus on the psoriatic joint and discuss pathways that underlie synovial, cartilage and bone inflammation and highlight key histopathologic features. The pivotal inflammatory mechanisms and pathobiology of PsA parallel findings in other forms of spondyloarthritis but are distinct from disease pathways described in rheumatoid synovitis and bone disease. The diagnosis of PsA from both a clinical and imaging perspective is also discussed.

The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints.

PubMed

Al-Ezzi, Salih; Quan, Gaofeng; Elrayah, Adil

2018-05-07

This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties.

The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints

PubMed Central

Quan, Gaofeng

2018-01-01

This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties. PMID:29735894

The Joint Strength and Fracture Mechanisms of TC4/TC4 and TA0/TA0 Brazed with Ti-25Cu-15Ni Braze Alloy

NASA Astrophysics Data System (ADS)

Zou, Zhihuan; Zeng, Fanhao; Wu, Haobo; Liu, Jian; Li, Yi; Gu, Yi; Yuan, Tiechui; Zhang, Fuqin

2017-05-01

In this paper, Ti-25Cu-15Ni (mass ratio) braze alloys were prepared by vacuum arc melting. Additionally, the TA0 pure titanium and TC4 titanium alloy were brazed with the Ti-25Cu-15Ni braze alloy at 960, 980, 1000, 1020, and 1040 °C. The effects of the braze temperature on the tensile strength of the TA0 and TC4 joints and their fracture mechanisms were studied. The maximum tensile strength of the TA0 joints of 219.9 ± 0.1 MPa was achieved at a brazing temperature of 980 °C, and the maximum tensile strength of the TC4 joints of 832.9 ± 0.1 MPa was achieved at the same brazing temperature. These results indicate that their ideal joint strength is comparable. According to the fractography results of the TA0 joints, a mixed fracture morphology is indicated. The TA0 fracture surface is dominated by cleavage fracture with a small contribution from ductile fracture. The TC4 joint fracture arises from cleavage.

A Comparative Study on the Microstructure and Mechanical Properties of Cu6Sn5 and Cu3Sn Joints Formed by TLP Soldering With/Without the Assistance of Ultrasonic Waves

NASA Astrophysics Data System (ADS)

Zhao, H. Y.; Liu, J. H.; Li, Z. L.; Song, X. G.; Zhao, Y. X.; Niu, H. W.; Tian, H.; Dong, H. J.; Feng, J. C.

2018-07-01

In this study, the microstructure and mechanical properties of Cu6Sn5 and Cu3Sn intermetallic joints, formed by the transient liquid phase (TLP) soldering process with and without the assistance of ultrasonic waves (USWs), were compared. After the application of USWs in the TLP soldering process, Cu-Sn intermetallic compounds (IMCs) exhibited a novel noninterfacial growth pattern in the molten solder interlayer. The resulting Cu6Sn5 and Cu3Sn joints consisted of refined equiaxed IMC grains with average sizes of 3 and 2.3 µm, respectively. The Cu6Sn5 grains in the ultrasonically soldered intermetallic joints demonstrated uniform mechanical properties with elastic modulus and hardness values of 123.0 and 5.98 GPa, respectively, while those of Cu3Sn grains were 133.9 and 5.08 GPa, respectively. The shear strengths of ultrasonically soldered Cu6Sn5 and Cu3Sn joints were measured to be 60 and 65 MPa, respectively, higher than that for reflow-soldered intermetallic joints. Ultrasonically soldered Cu6Sn5 and Cu3Sn joints both exhibited a combination of transgranular and intergranular fractures during shear testing.

A Comparative Study on the Microstructure and Mechanical Properties of Cu6Sn5 and Cu3Sn Joints Formed by TLP Soldering With/Without the Assistance of Ultrasonic Waves

NASA Astrophysics Data System (ADS)

Zhao, H. Y.; Liu, J. H.; Li, Z. L.; Song, X. G.; Zhao, Y. X.; Niu, H. W.; Tian, H.; Dong, H. J.; Feng, J. C.

2018-05-01

In this study, the microstructure and mechanical properties of Cu6Sn5 and Cu3Sn intermetallic joints, formed by the transient liquid phase (TLP) soldering process with and without the assistance of ultrasonic waves (USWs), were compared. After the application of USWs in the TLP soldering process, Cu-Sn intermetallic compounds (IMCs) exhibited a novel noninterfacial growth pattern in the molten solder interlayer. The resulting Cu6Sn5 and Cu3Sn joints consisted of refined equiaxed IMC grains with average sizes of 3 and 2.3 µm, respectively. The Cu6Sn5 grains in the ultrasonically soldered intermetallic joints demonstrated uniform mechanical properties with elastic modulus and hardness values of 123.0 and 5.98 GPa, respectively, while those of Cu3Sn grains were 133.9 and 5.08 GPa, respectively. The shear strengths of ultrasonically soldered Cu6Sn5 and Cu3Sn joints were measured to be 60 and 65 MPa, respectively, higher than that for reflow-soldered intermetallic joints. Ultrasonically soldered Cu6Sn5 and Cu3Sn joints both exhibited a combination of transgranular and intergranular fractures during shear testing.

Preloaded joint analysis methodology for space flight systems

NASA Technical Reports Server (NTRS)

Chambers, Jeffrey A.

1995-01-01

This report contains a compilation of some of the most basic equations governing simple preloaded joint systems and discusses the more common modes of failure associated with such hardware. It is intended to provide the mechanical designer with the tools necessary for designing a basic bolted joint. Although the information presented is intended to aid in the engineering of space flight structures, the fundamentals are equally applicable to other forms of mechanical design.

Influence of clamp-up force on the strength of bolted composite joints

NASA Astrophysics Data System (ADS)

Horn, Walter J.; Schmitt, Ron R.

1994-03-01

Composite materials offer the potential for a reduction in the number of individual parts and joints in a structure because large one-piece components can replace multipart assemblies. Nevertheless, there are many situations where composite parts must be joined and often mechanical fasteners provide the only practical method of joining those parts. The long-term strength of mechanically fastened joints of composite members can be directly affected by the clamp-up force of the fastener and thus perhaps by the relaxation of this force due to the viscoelastic character of the composite materials of the joint. Methods for predicting the effect of bolt clamp-up force relaxation on the strength of mechanically fastened joints of thermoplastic composite materials were investigated during the present study. A test program, using two thermoplastic composite materials, was conducted to determine the influence of clamp-up force on joint strength, to measure the relaxation of the joint clamp-up force with time, and to measure the change of joint strength as a function of time.

Foot structure is significantly associated to subtalar joint kinetics and mechanical energetics.

PubMed

Maharaj, Jayishni N; Cresswell, Andrew G; Lichtwark, Glen A

2017-10-01

Foot structure has been implicated as a risk factor of numerous overuse injuries, however, the mechanism linking foot structure and the development of soft-tissue overuse injuries are not well understood. The aim of this study was to identify factors that could predict foot function during walking. A total of eleven variables (including measures of foot structure, anthropometry and spatiotemporal gait characteristics) were investigated for their predictive ability on identifying kinematic, kinetic and energetic components of the foot. Three-dimensional motion capture and force data were collected at preferred walking speed on an instrumented treadmill. Mechanical measures were subsequently assessed using a custom multi-segment foot model in Opensim. Factors with significant univariate associations were entered into multiple linear regression models to identify a group of factors independently associated with the mechanical measures. Although no model could be created for any of the kinematic measures analysed, approximately 46% and 37% of the variance in the kinetic and energetic measures were associated with three or two factors respectively. Arch-height ratio, foot length and step width were associated with peak subtalar joint (STJ) moment, while greater STJ negative work was correlated to a low arch-height ratio and greater foot mobility. The models presented in this study suggest that the soft-tissue structures of a flat-arched, mobile foot are at a greater risk of injury as they have greater requirements to absorb energy and generate larger forces. However, as these associations are only moderate, other measures may also have an influence. Copyright © 2017. Published by Elsevier B.V.

Effect of Filler and Heat Treatment on the Physical and Mechanical Properties of the Brazed Joint between Carbide Tip and Steel

NASA Astrophysics Data System (ADS)

Winardi, Y.; Triyono; Wijayanta, A. T.

2017-02-01

In this study, the effect of filler and heat treatment on the physical and mechanical properties of the brazed joint carbide tip and steel was investigated. Tip carbide YG6 and low carbon steel (SS400) is joining by torch brazing with two filler metals, silver, and copper filler. Heat treatment was performed in induction furnace. Microstructure and shear strength of the brazed joint have been investigated. Many silver filler layer are formed on the surface of the base metal rather then using copper filler. The highest shear strength is achieved using a silver filler metal at temperatur 725°C. The highest shear load is 18.62 kN.

Regeneration of limb joints in the axolotl (Ambystoma mexicanum).

PubMed

Lee, Jangwoo; Gardiner, David M

2012-01-01

In spite of numerous investigations of regenerating salamander limbs, little attention has been paid to the details of how joints are reformed. An understanding of the process and mechanisms of joint regeneration in this model system for tetrapod limb regeneration would provide insights into developing novel therapies for inducing joint regeneration in humans. To this end, we have used the axolotl (Mexican Salamander) model of limb regeneration to describe the morphology and the expression patterns of marker genes during joint regeneration in response to limb amputation. These data are consistent with the hypothesis that the mechanisms of joint formation whether it be development or regeneration are conserved. We also have determined that defects in the epiphyseal region of both forelimbs and hind limbs in the axolotl are regenerated only when the defect is small. As is the case with defects in the diaphysis, there is a critical size above which the endogenous regenerative response is not sufficient to regenerate the joint. This non-regenerative response in an animal that has the ability to regenerate perfectly provides the opportunity to screen for the signaling pathways to induce regeneration of articular cartilage and joints.

Regeneration of Limb Joints in the Axolotl (Ambystoma mexicanum)

PubMed Central

Lee, Jangwoo; Gardiner, David M.

2012-01-01

In spite of numerous investigations of regenerating salamander limbs, little attention has been paid to the details of how joints are reformed. An understanding of the process and mechanisms of joint regeneration in this model system for tetrapod limb regeneration would provide insights into developing novel therapies for inducing joint regeneration in humans. To this end, we have used the axolotl (Mexican Salamander) model of limb regeneration to describe the morphology and the expression patterns of marker genes during joint regeneration in response to limb amputation. These data are consistent with the hypothesis that the mechanisms of joint formation whether it be development or regeneration are conserved. We also have determined that defects in the epiphyseal region of both forelimbs and hind limbs in the axolotl are regenerated only when the defect is small. As is the case with defects in the diaphysis, there is a critical size above which the endogenous regenerative response is not sufficient to regenerate the joint. This non-regenerative response in an animal that has the ability to regenerate perfectly provides the opportunity to screen for the signaling pathways to induce regeneration of articular cartilage and joints. PMID:23185640

Friction stir welding of T joints of dissimilar aluminum alloy: A review

NASA Astrophysics Data System (ADS)

Thakare, Shrikant B.; Kalyankar, Vivek D.

2018-04-01

Aluminum alloys are preferred in the mechanical design due to their advantages like high strength, good corrosion resistance, low density and good weldability. In various industrial applications T joints configuration of aluminum alloys are used. In different fields, T joints having skin (horizontal sheet) strengthen by stringers (vertical sheets) were used to increase the strength of structure without increasing the weight. T joints are usually carried out by fusion welding which has limitations in joining of aluminum alloy due to significant distortion and metallurgical defects. Some aluminum alloys are even non weldable by fusion welding. The friction stir welding (FSW) has an excellent replacement of conventional fusion welding for T joints. In this article, FSW of T joints is reviewed by considering aluminum alloy and various joint geometries for defect analysis. The previous experiments carried out on T joints shows the factors such as tool geometry, fixturing device and joint configurations plays significant role in defect free joints. It is essential to investigate the material flow during FSW to know joining mechanism and the formation of joint. In this study the defect occurred in the FSW are studied for various joint configurations and parameters. Also the effect of the parameters and defects occurs on the tensile strength are studied. It is concluded that the T-joints of different joint configurations can be pretended successfully. Comparing to base metal some loss in tensile strength was observed in the weldments as well as overall reduction of the hardness in the thermos mechanically affected zone also observed.

Unloading joints to treat osteoarthritis, including joint distraction.

PubMed

Lafeber, Floris P J G; Intema, Femke; Van Roermund, Peter M; Marijnissen, Anne C A

2006-09-01

Patients are increasingly becoming interested in nonpharmacologic approaches to manage their osteoarthritis. This review examines the recent literature on the potential beneficial effects of unloading joints in the treatment of osteoarthritis, with a focus on joint distraction. Mechanical factors are involved in the development and progression of osteoarthritis. If "loading" is a major cause in development and progression of osteoarthritis, then "unloading" may be able to prevent progression. There is evidence that unloading may be effective in reducing pain and slowing down structural damage. This review describes unloading by footwear and bracing (nonsurgical), unloading by osteotomy (surgical), and has a focus on unloading by joint distraction. Excellent reviews in all these three fields have been published over the past few years. Recent studies argue for the usefulness of a biomechanical approach to improve function and possibly reduce disease progression in osteoarthritis. To improve patient function and possibly reduce disease progression, a biomechanical approach should be considered in treating patients with osteoarthritis. Further research (appropriate high-quality clinical trials) and analysis (clinical as well as preclinical and fundamental) are still necessary, however, to understand, validate, and refine the different approaches of unloading to treat osteoarthritis.

Adhesive-bonded scarf and stepped-lap joints

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1973-01-01

Continuum mechanics solutions are derived for the static load-carrying capacity of scarf and stepped-lap adhesive-bonded joints. The analyses account for adhesive plasticity and adherend stiffness imbalance and thermal mismatch. The scarf joint solutions include a simple algebraic formula which serves as a close lower bound, within a small fraction of a per cent of the true answer for most practical geometries and materials. Digital computer programs were developed and, for the stepped-lap joints, the critical adherend and adhesive stresses are computed for each step. The scarf joint solutions exhibit grossly different behavior from that for double-lap joints for long overlaps inasmuch as that the potential bond shear strength continues to increase with indefinitely long overlaps on the scarf joints. The stepped-lap joint solutions exhibit some characteristics of both the scarf and double-lap joints. The stepped-lap computer program handles arbitrary (different) step lengths and thickness and the solutions obtained have clarified potentially weak design details and the remedies. The program has been used effectively to optimize the joint proportions.

Heavily loaded joints for assembling aerobrake support trusses

NASA Technical Reports Server (NTRS)

Bandel, Hannskarl; Olsson, Nils; Levintov, Boris

1990-01-01

The major emphasis was to develop erectable joints for large aerobrake support trusses. The truss joints must be able to withstand the large forces experienced by the truss during the aero-pass, as well as be easily assembled and disassembled on orbit by astronauts or robots. Other important design considerations include; strength, stiffness, and allowable error in strut length. Six mechanical joint designs, as well as a seventh joint design, where a high strength epoxy is injected to make the connection rigid, are presented.

The in vivo plantar soft tissue mechanical property under the metatarsal head: implications of tissues׳ joint-angle dependent response in foot finite element modeling.

PubMed

Chen, Wen-Ming; Lee, Sung-Jae; Lee, Peter Vee Sin

2014-12-01

Material properties of the plantar soft tissue have not been well quantified in vivo (i.e., from life subjects) nor for areas other than the heel pad. This study explored an in vivo investigation of the plantar soft tissue material behavior under the metatarsal head (MTH). We used a novel device collecting indentation data at controlled metatarsophalangeal joint angles. Combined with inverse analysis, tissues׳ joint-angle dependent material properties were identified. The results showed that the soft tissue under MTH exhibited joint-angle dependent material responses, and the computed parameters using the Ogden material model were 51.3% and 30.9% larger in the dorsiflexed than in the neutral positions, respectively. Using derived parameters in subject-specific foot finite element models revealed only those models that used tissues׳ joint-dependent responses could reproduce the known plantar pressure pattern under the MTH. It is suggested that, to further improve specificity of the personalized foot finite element models, quantitative mechanical properties of the tissue inclusive of the effects of metatarsophalangeal joint dorsiflexion are needed. Copyright © 2014 Elsevier Ltd. All rights reserved.

The International Space Station (ISS) Solar Alpha Rotary Joint (SARJ): Materials & Processes (M&P) Lessons Learned for a Large, Rotating Spacecraft Mechanism

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

2016-01-01

The International Space Station (ISS) utilizes two large rotating mechanisms, the solar alpha rotary joints (SARJs), as part of the solar arrays' alignment system for more efficient power generation. Each SARJ is a 10.3m circumference, nitrided 15-5PH steel race ring of triangular cross-section, with 12 sets of trundle bearing assemblies transferring load across the rolling joint. The SARJ mechanism rotates continuously and slowly - once every orbit, or every 90 minutes. In 2007, the starboard SARJ suffered a lubrication failure, resulting in severe damage (spalling) to one of the race ring surfaces. Extensive effort was conducted to prevent the port SARJ from suffering the same failure, and fortunately that effort was ultimately successful in also recovering the functionality of the starboard SARJ. The M&P engineering function was key in determining the cause of failure and the means for mechanism recovery. From a M&P lessons-learned perspective, observations are made concerning the original SARJ design parameters (boundary conditions), the perceived need for nitriding the race ring, the test conditions employed during qualification, the environmental controls used for the hardware preflight, and the lubrication robustness necessary for complex kinematic mechanisms expecting high-reliability and long-life.

Improved Ball-and-Socket Docking Mechanism

NASA Technical Reports Server (NTRS)

Cloyd, Richard; Bryan, Tom

2004-01-01

A proposed docking mechanism would form a ball-and-socket joint in the docked condition. The mechanism could tolerate significant initial misalignment because it would include an alignment cone that would guide the ball into the socket. Like other ball-and-socket joints, the joint would have three rotational degrees of freedom. This docking mechanism would be a successor to the one described in Passive Capture Joint With Three Degrees of Freedom (MFS-31146), NASA Tech Briefs, Vol. 22, No. 7 (July 1998), page 65. It would contain most of the components of the prior mechanism, plus some additional components that would expand its capabilities.

Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings

PubMed Central

Ali, Murat; Al-Hajjar, Mazen; Partridge, Susan; Williams, Sophie; Fisher, John; Jennings, Louise M

2016-01-01

Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing. PMID:27160559

Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings.

PubMed

Ali, Murat; Al-Hajjar, Mazen; Partridge, Susan; Williams, Sophie; Fisher, John; Jennings, Louise M

2016-05-01

Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing. © IMechE 2016.

Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip joint disease patients.

PubMed

Sakamoto, Junya; Manabe, Yoshitaka; Oyamada, Joichi; Kataoka, Hideki; Nakano, Jiro; Saiki, Kazunobu; Okamoto, Keishi; Tsurumoto, Toshiyuki; Okita, Minoru

2018-07-01

Referred pain in the anterior knee joint is the most common symptom in hip disease patients. The development of referred pain is considered to be related to dichotomizing peripheral sensory fibers. However, no gross anatomical findings identify any dichotomizing fibers innervating both the hip and knee joints. We dissected the femoral and obturator nerves in human cadavers to investigate the distribution of the articular branches in the hip and knee joints. Fourteen embalmed left lower limbs from 14 Japanese adult cadavers (five from females, nine from males, average age 73.8 ± 14.1 years) were observed macroscopically. The articular branches of the femoral and obturator nerves were dissected at the anterior margin of the groin toward the thigh region. After dissections of the articular nerves of the hip joints, the femoral and obturator nerves were exposed from proximally to distally to identify the articular nerves of the knee joints. The branching pattern of the articular branches in the hip and knee joints was recorded. In six of 14 limbs (42.9%), the femoral nerve supplied articular branches to the anteromedial aspect of both the hip and knee joints. These articular branches were derived from the same bundle of femoral nerve. These gross anatomical findings suggested that dichotomizing peripheral sensory fibers innervate the hip and knee joints and these could relate to the referred pain confirmed in the anterior knee joints of patients with hip disease. Clin. Anat. 31:705-709, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Arch structure is associated with unique joint work, relative joint contributions and stiffness during landing.

PubMed

Powell, Douglas W; Queen, Robin M; Williams, D S Blaise

2016-10-01

To examine lower extremity joint contributions to a landing task in high-(HA) and low-arched (LA) female athletes by quantifying vertical stiffness, joint work and relative joint contributions to landing. Twenty healthy female recreational athletes (10 HA and 10 LA) performed five barefoot drop landings from a height of 30cm. Three-dimensional kinematics (240Hz) and ground reaction forces (960Hz) were recorded simultaneously. Vertical stiffness, joint work values and relative joint work values were calculated using Visual 3D and MatLab. HA athletes had significantly greater vertical stiffness compared to LA athletes (p=0.013). Though no differences in ankle joint work were observed (p=0.252), HA athletes had smaller magnitudes of knee (p=0.046), hip (p=0.019) and total lower extremity joint work values (p=0.016) compared to LA athletes. HA athletes had greater relative contributions of the ankle (p=0.032) and smaller relative contributions of the hip (p=0.049) compared to LA athletes. No differences in relative contributions of the knee were observed (p=0.255). These findings demonstrate that aberrant foot structure is associated with unique contributions of lower extremity joints to load attenuation during landing. These data may provide insight into the unique injury mechanisms associated with arch height in female athletes. Copyright © 2016 Elsevier B.V. All rights reserved.

Experiments and kinematics analysis of a hand rehabilitation exoskeleton with circuitous joints.

PubMed

Zhang, Fuhai; Fu, Yili; Zhang, Qinchao; Wang, Shuguo

2015-01-01

Aiming at the hand rehabilitation of stroke patients, a wearable hand exoskeleton with circuitous joint is proposed. The circuitous joint adopts the symmetric pinion and rack mechanism (SPRM) with the parallel mechanism. The exoskeleton finger is a serial mechanism composed of three closed-chain SPRM joints in series. The kinematic equations of the open chain of the finger and the closed chains of the SPRM joints were built to analyze the kinematics of the hand rehabilitation exoskeleton. The experimental setup of the hand rehabilitation exoskeleton was built and the continuous passive motion (CPM) rehabilitation experiment and the test of human-robot interaction force measurement were conducted. Experiment results show that the mechanical design of the hand rehabilitation robot is reasonable and that the kinematic analysis is correct, thus the exoskeleton can be used for the hand rehabilitation of stroke patients.

The porosity formation mechanism in the laser-MIG hybrid welded joint of Invar alloy

NASA Astrophysics Data System (ADS)

Zhan, Xiaohong; Gao, Qiyu; Gu, Cheng; Sun, Weihua; Chen, Jicheng; Wei, Yanhong

2017-10-01

The porosity formation mechanism in the laser-metal inter gas (MIG) multi-layer hybrid welded (HW) joint of 19.05 mm thick Invar alloy is investigated. The microstructure characteristics and energy dispersive spectroscopy (EDS) are analyzed. The phase identification was conducted by the X-ray diffractometer (XRD). Experimental results show that the generation of porosity is caused by the relatively low laser power in the root pass and low current in the cover pass. It is also indicated that the microstructures of the welded joints are mainly observed to be columnar crystal and equiaxial crystal, which are closely related to the porosity formation. The EDS results show that oxygen content is significantly high in the inner wall of the porosity. The XRD results indicate that the BM and the WB of laser-MIG HW all are composed of Fe0.64Ni0.36 and γ-(Fe,Ni). When the weld pool is cooled quickly, [NiO] [FeO] and [MnO] are formed that react on C to generate CO/CO2 gases. The porosity of laser-MIG HW for Invar alloy is oxygen pore. The root source of metallurgy porosity formation is that the dissolved gases are hard to escape sufficiently and thus exist in the weld pool. Furthermore, 99.99% pure Argon is recommended as protective gas in the laser-MIG HW of Invar alloy.

Application of Bionic Design to FRP T-Joints

NASA Astrophysics Data System (ADS)

Luo, Guang-Min; Kuo, Chia-Hung

2017-09-01

We applied the concepts of bionics to enhance the mechanical strength of fiberglass reinforced plastic T-joints. The failure modes of the designed arthrosis-like and gum-like joints were determined using three-point bending tests and numerical simulations and compared with those of normal T-joints bonded using structural adhesives. In the simulation, we used cohesive elements to simulate the adhesive interface of the structural adhesive. The experimental and simulation results show that the arthrosis-like joint can effectively delay the failure progress and enhance the bonding strength of T-joints, thus confirming that an appropriate bionic design can effectively control the bonding properties of structural adhesives.

The interface microstructure, mechanical properties and corrosion resistance of dissimilar joints during multipass laser welding for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2018-05-01

This study presents the interface microstructure, mechanical properties and corrosion resistance of dissimilar joints between Inconel 52M overlays and 316L stainless steel during multipass laser welding for nuclear power plants. The results indicate that the microstructure at the interface beside 316L stainless steel consists of cellular with the width of 30-40 μm, which also exhibits numerous Cr and Mo-rich precipitates like flocculent structure and in chains along grain boundaries as a mixed chemical solution for etching. Many dendritic structure with local melting characteristics and Nb-rich precipitates are exhibited at the interface beside Inconel 52M overlays. Such Nb-rich precipitates at the interface beside Inconel 52M overlays deteriorate the tensile strength and toughness of dissimilar joints at room temperature. The tensile strength of 316L stainless steel at 350 °C significantly decreases with the result that dissimilar joints are fractured in 316L stainless steel. The correlation between corrosion behavior and microstructure of weld metals is also discussed. The difference in high corrosion potential between Nb-rich precipitates and the matrix could result in establishing effective galvanic couples, and thus accelerating the corrosion of weld metals.

Sacroiliac joint luxation after pedicle subtraction osteotomy: report of two cases and analysis of failure mechanism.

PubMed

Charles, Yann Philippe; Yu, Bo; Steib, Jean-Paul

2016-05-01

Sagittal decompensation after pedicle subtraction osteotomy (PSO) is considered as late onset complication. Several mechanisms have been suggested, but little attention has been paid to the caudal end of lumbar instrumented fusion, especially sacral iliac joint (SIJ) deterioration. Clinical histories and radiographic sagittal parameters of two patients with SIJ luxation after PSO are presented. The biomechanical failure mechanism and risk factors are analysed. Two patients underwent correction of fixed anterior sagittal imbalance by PSO, followed by pseudarthrosis revision surgery. Both of them sustained persistent sacroiliac pain, progressive recurrence of anterior imbalance and progressive pelvic incidence (PI) increase around 10°. An acute bilateral SIJ luxation occurred in both patients leading to sharp increase or PI around 20°. One patient was treated by SIJ fusion and the other patient was placed on non-weight-bearing crutch ambulation for 1 year. Both patients had a high preoperative PI (95° and 78°). A theoretical match between lumbar lordosis (LL) and PI was not achieved by PSO. Osteopenia was present in both patients. Computed tomography evidenced L5-S1 pseudarthrosis and sacroiliac joint violation by pelvic or sacral ala screws. Patients with high PI might seek for further compensation at their SIJ when lacking LL after PSO. Chronic anterior imbalance might lead to progressive weakening of sacroiliac ligaments. Initial circumferential lumbosacral fusion and accurate iliac screw fixation might reduce stress on implants, risk for pseudarthrosis, implant failure and finally SIJ deterioration. Bone mineral density should further be investigated preoperatively.

The Changing Role of School Leadership Preparation.

ERIC Educational Resources Information Center

Wilmore, Elaine

2000-01-01

Many U.S. universities are restructuring their administrator-education programs to produce a new breed of principal. The University of Texas at Arlington, Texas A&M, Tarleton State, a Texas A&M-Commerce joint venture, and a regional alternative certification program offer five examples. (Contains 41 references.) (MLH)

Light Satellites - A Dilemma for the U.S. Army

DTIC Science & Technology

1988-12-01

current systems would be siqnificantly overburdened by the need of our national leadeship to qain intelliqence over wide areas of the globe very...January 1988. Contract MDA 903-85-C-0049. ANSER, Arlington, Va. 3. Boutacoff, David A. "Army Banks on Joint STARS for Airland Battle Management

Computational modeling to predict mechanical function of joints: application to the lower leg with simulation of two cadaver studies.

PubMed

Liacouras, Peter C; Wayne, Jennifer S

2007-12-01

Computational models of musculoskeletal joints and limbs can provide useful information about joint mechanics. Validated models can be used as predictive devices for understanding joint function and serve as clinical tools for predicting the outcome of surgical procedures. A new computational modeling approach was developed for simulating joint kinematics that are dictated by bone/joint anatomy, ligamentous constraints, and applied loading. Three-dimensional computational models of the lower leg were created to illustrate the application of this new approach. Model development began with generating three-dimensional surfaces of each bone from CT images and then importing into the three-dimensional solid modeling software SOLIDWORKS and motion simulation package COSMOSMOTION. Through SOLIDWORKS and COSMOSMOTION, each bone surface file was filled to create a solid object and positioned necessary components added, and simulations executed. Three-dimensional contacts were added to inhibit intersection of the bones during motion. Ligaments were represented as linear springs. Model predictions were then validated by comparison to two different cadaver studies, syndesmotic injury and repair and ankle inversion following ligament transection. The syndesmotic injury model was able to predict tibial rotation, fibular rotation, and anterior/posterior displacement. In the inversion simulation, calcaneofibular ligament extension and angles of inversion compared well. Some experimental data proved harder to simulate accurately, due to certain software limitations and lack of complete experimental data. Other parameters that could not be easily obtained experimentally can be predicted and analyzed by the computational simulations. In the syndesmotic injury study, the force generated in the tibionavicular and calcaneofibular ligaments reduced with the insertion of the staple, indicating how this repair technique changes joint function. After transection of the calcaneofibular

Flaw Tolerance in Lap Shear Brazed Joints. Part 1

NASA Technical Reports Server (NTRS)

Flom, Yury; Wang, Li-Qin

2003-01-01

Furnace brazing is a joining process used in the aerospace and other industries to produce strong permanent and hermetic structural joints. As in any joining process, brazed joints have various imperfections and defects. At the present time, our understanding of the influence of the internal defects on the strength of the brazed joints is not adequate. The goal of this 3-part investigation is to better understand the properties and failure mechanisms of the brazed joints containing defects. This study focuses on the behavior of the brazed lap shear joints because of their importance in manufacturing aerospace structures. In Part 1, an average shear strength capability and failure modes of the single lap joints are explored. Stainless steel specimens brazed with pure silver are tested in accordance with the AWS C3.2 standard. Comparison of the failure loads and the ultimate shear strength with the Finite Element Analysis (FEA) of the same specimens as a function of the overlap widths shows excellent correlation between the experimental and calculated values for the defect-free lap joints. A damage zone criterion is shown to work quite well in understanding the failure of the braze joints. In Part 2, the findings of the Part 1 will be verified on the larger test specimens. Also, various flaws will be introduced in the test specimens to simulate lack of braze coverage in the lap joints. Mechanical testing and FEA will be performed on these joints to verify that behavior of the flawed ductile lap joints is similar to joints with a reduced braze area. Finally, in Part 3, the results obtained in Parts 1 and 2 will be applied to the actual brazed structure to evaluate the load-carrying capability of a structural lap joint containing discontinuities. In addition, a simplified engineering procedure will be offered for the laboratory testing of the lap shear specimens.

An investigation on mechanical properties of steel fibre reinforced for underwater welded joint

NASA Astrophysics Data System (ADS)

Navin, K.; Zakaria, M. S.; Zairi, S.

2017-09-01

Underwater pipelines are always exposed to water and have a high tendency to have corrosion especially on the welded joint. This research is about using fiber glass as steel fiber to coat the welded joint to determine the effectiveness in corrosion prevention of the welded joint. Number of coating is varied to determine the better number coating to coat the pipeline. Few samples were left without immersion in salt water and few samples are immersed into salt water with same salinity as sea water. The material sample is prepared in dog bone shape to enable to be used in Universal Tensile Machine (UTM). The material prepared is left immersed for recommended time and tested in Universal Tensile Machine. Upon analyzing the result, the result is used to determine the breakage point whether broken on the welded joint or different place and also the suitable number of coating to be used.

Microstructure evolution in dissimilar AA6060/copper friction stir welded joints

NASA Astrophysics Data System (ADS)

Kalashnikova, T. A.; Shvedov, M. A.; Vasilyev, P. A.

2017-12-01

Friction stir welding process has been applied for making a dissimilar copper/aluminum alloy joint. The grain microstructure and mechanical properties of the obtained joint were studied. The structure of the cross-section of the FSW compound was analyzed. The microstructural evolution of the joint was examined using optical microscopy. The mechanical properties of the intermetallic particles were evaluated by measuring the microhardness according to the Vickers method. The microhardness of the intermetallic particles was by a factor of 4 lower than that of the particles obtained by fusion welding. The results of the investigations enable using friction stir welding for making dissimilar joints.

The influence of size, clearance, cartilage properties, thickness and hemiarthroplasty on the contact mechanics of the hip joint with biphasic layers.

PubMed

Li, Junyan; Stewart, Todd D; Jin, Zhongmin; Wilcox, Ruth K; Fisher, John

2013-06-21

Computational models of the natural hip joint are needed to examine and optimise tissue sparing interventions where the natural cartilage remains part of the bearing surfaces. Although the importance of interstitial fluid pressurisation in the performance of cartilage has long been recognized, few studies have investigated the time dependent interstitial fluid pressurisation in a three dimensional natural hip joint model. The primary aim of this study was to develop a finite element model of the natural hip incorporating the biphasic cartilage layers that was capable of simulating the joint response over a prolonged physiological loading period. An initial set of sensitivity studies were also undertaken to investigate the influence of hip size, clearance, cartilage properties, thickness and hemiarthroplasty on the contact mechanics of the joint. The contact stress, contact area, fluid pressure and fluid support ratio were calculated and cross-compared between models with different parameters to evaluate their influence. It was found that the model predictions for the period soon after loading were sensitive to the hip size, clearance, cartilage aggregate modulus, thickness and hemiarthroplasty, while the time dependent behaviour over 3000s was influenced by the hip clearance and cartilage aggregate modulus, permeability, thickness and hemiarthroplasty. The modelling methods developed in this study provide a basic platform for biphasic simulation of the whole hip joint onto which more sophisticated material models or other input parameters could be added in the future. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

The influence of size, clearance, cartilage properties, thickness and hemiarthroplasty on the contact mechanics of the hip joint with biphasic layers☆

PubMed Central

Li, Junyan; Stewart, Todd D.; Jin, Zhongmin; Wilcox, Ruth K.; Fisher, John

2013-01-01

Computational models of the natural hip joint are needed to examine and optimise tissue sparing interventions where the natural cartilage remains part of the bearing surfaces. Although the importance of interstitial fluid pressurisation in the performance of cartilage has long been recognized, few studies have investigated the time dependent interstitial fluid pressurisation in a three dimensional natural hip joint model. The primary aim of this study was to develop a finite element model of the natural hip incorporating the biphasic cartilage layers that was capable of simulating the joint response over a prolonged physiological loading period. An initial set of sensitivity studies were also undertaken to investigate the influence of hip size, clearance, cartilage properties, thickness and hemiarthroplasty on the contact mechanics of the joint. The contact stress, contact area, fluid pressure and fluid support ratio were calculated and cross-compared between models with different parameters to evaluate their influence. It was found that the model predictions for the period soon after loading were sensitive to the hip size, clearance, cartilage aggregate modulus, thickness and hemiarthroplasty, while the time dependent behaviour over 3000 s was influenced by the hip clearance and cartilage aggregate modulus, permeability, thickness and hemiarthroplasty. The modelling methods developed in this study provide a basic platform for biphasic simulation of the whole hip joint onto which more sophisticated material models or other input parameters could be added in the future. PMID:23664238

An Open-Source Toolbox for Surrogate Modeling of Joint Contact Mechanics

PubMed Central

Eskinazi, Ilan

2016-01-01

Goal Incorporation of elastic joint contact models into simulations of human movement could facilitate studying the interactions between muscles, ligaments, and bones. Unfortunately, elastic joint contact models are often too expensive computationally to be used within iterative simulation frameworks. This limitation can be overcome by using fast and accurate surrogate contact models that fit or interpolate input-output data sampled from existing elastic contact models. However, construction of surrogate contact models remains an arduous task. The aim of this paper is to introduce an open-source program called Surrogate Contact Modeling Toolbox (SCMT) that facilitates surrogate contact model creation, evaluation, and use. Methods SCMT interacts with the third party software FEBio to perform elastic contact analyses of finite element models and uses Matlab to train neural networks that fit the input-output contact data. SCMT features sample point generation for multiple domains, automated sampling, sample point filtering, and surrogate model training and testing. Results An overview of the software is presented along with two example applications. The first example demonstrates creation of surrogate contact models of artificial tibiofemoral and patellofemoral joints and evaluates their computational speed and accuracy, while the second demonstrates the use of surrogate contact models in a forward dynamic simulation of an open-chain leg extension-flexion motion. Conclusion SCMT facilitates the creation of computationally fast and accurate surrogate contact models. Additionally, it serves as a bridge between FEBio and OpenSim musculoskeletal modeling software. Significance Researchers may now create and deploy surrogate models of elastic joint contact with minimal effort. PMID:26186761

Gender differences exist in the hip joint moments of healthy older walkers.

PubMed

Boyer, Katherine A; Beaupre, Gary S; Andriacchi, Thomas P

2008-12-05

Gender differences in the incidence of symptomatic hip osteoarthritis (OA), changes in hip cartilage volume and hip joint space and rates hip arthroplasty of older people are reported in the literature. As the rate of progression of OA is in part mechanically modulated it is possible that this gender bias may be related to inherent differences (if they exist) in walking mechanics between older males and females. The purpose of this study was to examine potential mechanisms for gender differences in hip joint mechanics during walking by testing the hypotheses that females would exhibit higher hip flexion, adduction and internal rotation moments but not significantly greater normalized ground reaction forces (GRFs). Forty-two healthy subjects (21 male, 21 female), ages 50-79yr were recruited for gait analysis. In support of the hypotheses, greater external hip adduction and internal rotation along with hip extension moments were found for females compared to males after normalizing for body size for all self-selected walking speeds. Differences in walking style (kinematics) were the main determinants in the joint kinetic differences as no differences in the normalized GRFs were found. As external joint moments are surrogate measures of the joint contact forces, the results of this study suggest the hip joint stress for the female population is higher compared to male population. This is in favor of a hypothesis that the increased joint contact stress in a female population could contribute to a greater joint degeneration at the hip in females as compared with males.

Fabrication and Assembly of High-Precision Hinge and Latch Joints for Deployable Optical Instruments

NASA Technical Reports Server (NTRS)

Phelps, James E.

1999-01-01

Descriptions are presented of high-precision hinge and latch joints that have been co-developed, for application to deployable optical instruments, by NASA Langley Research Center and Nyma/ADF. Page-sized versions of engineering drawings are included in two appendices to describe all mechanical components of both joints. Procedures for assembling the mechanical components of both joints are also presented. The information herein is intended to facilitate the fabrication and assembly of the high-precision hinge and latch joints, and enable the incorporation of these joints into the design of deployable optical instrument systems.

Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

NASA Astrophysics Data System (ADS)

Wang, Dan; Shen, Jun; Wang, Lin-Zhi

2012-03-01

The effects of the types of overlap on the mechanical properties of the friction stir spot welding (FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations, microhardness tests, and tensile tests. The results show that the microstructure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet. The average distance D between the longitudinal segment of the curved interface and the keyhole periphery, the tensile shear force, and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples. During FSSW of AZ31 and AZ61 dissimilar magnesium alloys, the irregular deformation of the longitudinal segment of the curved interface appears, while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet. Moreover, the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.

In Vivo Measurement of Glenohumeral Joint Contact Patterns

NASA Astrophysics Data System (ADS)

Bey, Michael J.; Kline, Stephanie K.; Zauel, Roger; Kolowich, Patricia A.; Lock, Terrence R.

2009-12-01

The objectives of this study were to describe a technique for measuring in-vivo glenohumeral joint contact patterns during dynamic activities and to demonstrate application of this technique. The experimental technique calculated joint contact patterns by combining CT-based 3D bone models with joint motion data that were accurately measured from biplane x-ray images. Joint contact patterns were calculated for the repaired and contralateral shoulders of 20 patients who had undergone rotator cuff repair. Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition (i.e., repaired versus contralateral). Abduction angle had a significant effect on the superior/inferior contact center position, with the average joint contact center of the repaired shoulder 12.1% higher on the glenoid than the contralateral shoulder. This technique provides clinically relevant information by calculating in-vivo joint contact patterns during dynamic conditions and overcomes many limitations associated with conventional techniques for quantifying joint mechanics.

A revolute joint with linear load-displacement response for a deployable lidar telescope

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Warren, Peter A.; Peterson, Lee D.

1996-01-01

NASA Langley Research Center is developing concepts for an advanced spacecraft, called LidarTechSat, to demonstrate key structures and mechanisms technologies necessary to deploy a segmented telescope reflector. Achieving micron-accuracy deployment requires significant advancements in deployment mechanism design, such as the revolute joint presented herein. The joint exhibits load-cycling response that is essentially linear with less than 2% hysteresis, and the joint rotates with less than 7 mN-m (1 in-oz) of resistance. A prototype reflector metering truss incorporating the joint exhibits only a few microns of kinematic error under repected deployment and impulse loading. No other mechanically deployment structure found in the literature has been demonstrated to be this kinematically accurate.

Adaptive plasticity in mammalian masticatory joints

NASA Astrophysics Data System (ADS)

Ravosa, Matthew J.; Kunwar, Ravinder; Nicholson, Elisabeth K.; Klopp, Emily B.; Pinchoff, Jessie; Stock, Stuart R.; Stack, M. Sharon; Hamrick, Mark W.

2006-08-01

Genetically similar white rabbits raised on diets of different mechanical properties, as well as wild-type and myostatin-deficient mice raised on similar diets, were compared to assess the postweaning effects of elevated masticatory loads due to increased jaw-adductor muscle and bite forces on the proportions and properties of the mandibular symphysis and temporomandibular joint (TMJ). Microcomputed tomography (microCT) was used to quantify bone structure at a series of equidistant external and internal sites in coronal sections for a series of joint locations. Discriminant function analyses and non-parametric ANOVAs were used to characterize variation in biomineralization within and between loading cohorts. In both species, long-term excessive loading results in larger joint proportions, thicker articular and cortical bone, and increased biomineralization of hard tissues. Such adaptive plasticity appears designed to maintain the postnatal integrity of masticatory joint systems for a primary loading environment(s). This behavioral signal may be increasingly mitigated in older organisms by the interplay between adaptive and degradative joint tissue responses.

Robotic Joints Support Horses and Humans

NASA Technical Reports Server (NTRS)

2008-01-01

A rehabilitative device first featured in Spinoff 2003 is not only helping human patients regain the ability to walk, but is now helping our four-legged friends as well. The late James Kerley, a prominent Goddard Space Flight Center researcher, developed cable-compliant mechanisms in the 1980s to enable sounding rocket assemblies and robots to grip or join objects. In cable-compliant joints (CCJs), short segments of cable connect structural elements, allowing for six directions of movement, twisting, alignment, and energy damping. Kerley later worked with Goddard s Wayne Eklund and Allen Crane to incorporate the cable-compliant mechanisms into a walker for human patients to support the pelvis and imitate hip joint movement.

Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control.

PubMed

Daley, M A; Felix, G; Biewener, A A

2007-02-01

We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle-tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor

Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control

PubMed Central

Daley, M. A.; Felix, G.; Biewener, A. A.

2008-01-01

Summary We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle–tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance

Effect of Exchanging Advancing and Retreating Side Materials on Mechanical Properties and Electrochemical Corrosion Resistance of Dissimilar 6013-T4 and 7003 Aluminum Alloys FSW Joints

NASA Astrophysics Data System (ADS)

Zhao, Zhixia; Liang, Haimei; Zhao, Yong; Yan, Keng

2018-03-01

Friction stir welding (FSW) was used to weld dissimilar joints between Al 6013-T4 and Al7003 alloys in this work. The effect of exchanging advancing (AS) and retreating (RS) side material on microstructure, mechanical behaviors and electrochemical corrosion resistance was discussed. Results showed that different joint cross sections were obtained when exchanging AS and RS materials. The material on the AS would be more deformed during the welding process. When the Al6013 placed on the AS, the plastic flow of weld is more sufficient. Whether on the AS or RS, the Al6013-T4 side is the weak region for both tensile specimens and hardness samples. The fracture position corresponds to the minimum hardness position. Also, more strengthening phase can be retained in the joint, and the joint of A6R7 has better corrosion resistance.

A reduced Iwan model that includes pinning for bolted joint mechanics

DOE PAGES

Brake, M. R. W.

2016-10-28

Bolted joints are prevalent in most assembled structures; however, predictive models for their behavior do not exist. Calibrated models, such as the Iwan model, are able to predict the response of a jointed structure over a range of excitations once calibrated at a nominal load. The Iwan model, though, is not widely adopted due to the high computational expense of implementation. To address this, an analytical solution of the Iwan model is derived under the hypothesis that for an arbitrary load reversal, there is a new distribution of dry friction elements, which are now stuck, that approximately resemble a scaledmore » version of the original distribution of dry friction elements. The dry friction elements internal to the Iwan model do not have a uniform set of parameters and are described by a distribution of parameters, i.e., which internal dry friction elements are stuck or slipping at a given load, that ultimately governs the behavior of the joint as it transitions from microslip to macroslip. This hypothesis allows the model to require no information from previous loading cycles. Additionally, the model is extended to include the pinning behavior inherent in a bolted joint. Modifications of the resulting framework are discussed to highlight how the constitutive model for friction can be changed (in the case of an Iwan–Stribeck formulation) or how the distribution of dry friction elements can be changed (as is the case for the Iwan plasticity model). Finally, the reduced Iwan plus pinning model is then applied to the Brake–Reuß beam in order to discuss methods to deduce model parameters from experimental data.« less

[Study on schistosomiasis control measures in mobile boat fishermen. III. Construction and application of regional joint mechanism for schistosomiasis examination and treatment in boatmen].

PubMed

Yang, Gao; Le-Ping, Sun; Yin-Ping, Zuo; Yu-Hui, Xu; Zheng-Qiu, Zhang; Yu-Cai, Ma; Jin-Bin, Gao; Xi-Guang, Zhu; Bo, Zheng; Guo-Jing, Yang; Qing-Biao, Hong; Kun, Yang; You-Sheng, Liang

2011-10-01

To construct the regional joint mechanism for schistosomiasis examination and treatment and the examination protocol among mobile boatmen, so as to provide effective measures for control of mobile infectious sources of schistosomiasis in the Yangtze River basin. According to the characteristics of the cargo frequent mobility of ships with fixed anchor points, the health, maritime and transport sections were jointly cooperated to set up sites for schistosomiasis examination and treatment in ship locks, wharfs and harbors. The infection of schistosomiasis was detected by means of rapid immunological screening and stool examination, and the regional joint mechanism was constructed. The sero-positives were traced for further parasitological examinations and treatment by using the regional joint network for schistosomiasis examination and treatment. The schistosome infections in boatmen were analyzed and compared between different examination and treatment sites and among different navigation coverage. A total of 16 sites for examination and treatment of schistosomiasis, including 5 fixed sites and 11 mobile sites, were set up in 12 townships of 6 districts (counties) of Yangzhou City. During a period between June and August, the examination of schistosomiasis was conducted in 40 sites, and of the 1 225 boatmen from 967 boats detected, 19 cases were sero-positive, with a positive rate of 1.55%. Among the 14 sero-positives examined, no stool positive patients were found. Among the 1 225 boatmen detected, 820 were from fixed sites and 405 from mobile sites, and 4 and 15 cases were found, respectively, with positive rates of 0.49% and 3.70%, respectively, and the sero-positive rate was higher in mobile sites and that in fixed sites. A total of 898 boatmen from the Yangtze River basin and 305 from the local inland rivers were examined, and 3 and 16 sero-positive cases were detected, respectively, with positive rates of 0.33% and 5.25%, respectively, and the sero

[Advances on biomechanics and kinematics of sprain of ankle joint].

PubMed

Zhao, Yong; Wang, Gang

2015-04-01

Ankle sprains are orthopedic clinical common disease, accounting for joint ligament sprain of the first place. If treatment is not timely or appropriate, the joint pain and instability maybe develop, and even bone arthritis maybe develop. The mechanism of injury of ankle joint, anatomical basis has been fully study at present, and the diagnostic problem is very clear. Along with the development of science and technology, biological modeling and three-dimensional finite element, three-dimensional motion capture system,digital technology study, electromyographic signal study were used for the basic research of sprain of ankle. Biomechanical and kinematic study of ankle sprain has received adequate attention, combined with the mechanism research of ankle sprain,and to explore the the biomechanics and kinematics research progress of the sprain of ankle joint.

Joint dynamics of rear- and fore-foot unplanned sidestepping.

PubMed

Donnelly, Cyril J; Chinnasee, Chamnan; Weir, Gillian; Sasimontonkul, Siriporn; Alderson, Jacqueline

2017-01-01

Compare the lower-limb mechanics and anterior cruciate ligament (ACL) injury risk of athletes using a habitual rear-foot (RF) and fore-foot (FF) fall pattern during unplanned sidestepping (UnSS). Experimental cross-sectional. Nineteen elite female field hockey players attended one biomechanical motion capture testing session, which consisted of a random series of pre-planned and unplanned sidestepping sport tasks. Following data collection, participants were classified as possessing a habitual RF or FF fall pattern during UnSS. Hip, knee and ankle joint angles, moments, instantaneous powers and net joint work were calculated during weight acceptance. Between group differences were evaluated using independent sample t-tests (α=0.05). Athletes using a habitual RF fall pattern during UnSS absorbed significantly more work and power through their knee joint (p<0.001), which was coupled with significantly elevated externally applied peak non-sagittal plane peak ankle moments (p<0.05) as well as peak flexion and abduction knee moments (p<0.005). Athletes using a habitual FF fall pattern during UnSS absorbed more power through their ankle joint (p<0.001). A RF fall pattern during UnSS places a large mechanical demand on the knee joint, which is associated with elevated ACL injury risk. Conversely, a FF fall pattern placed a large mechanical demand on the ankle joint. Modifying an athlete's foot fall pattern during UnSS may be viable technique recommendation when returning from knee or ankle injury. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints

PubMed Central

Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

2017-01-01

Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = −1) = 1.68 HV (σa is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints. PMID:28772543

Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints.

PubMed

Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

2017-02-15

Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σ a ( R = -1) = 1.68 HV ( σ a is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints.

The effects of welded joint characteristics on its properties in HDPE thermal fusion welding

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Peng, Jun

2017-05-01

In this paper, PE100 pipes with the diameter of 200 mm and the thickness of 11.9 mm were used as material. The welded joints were obtained in different welding pressures with the optimal welding temperature of 220∘C. Reheating process on the welded joints with the temperature of 130∘C was carried out. The joints exhibited X-type, and the cause of X-type joints was discussed. The temperature field in the forming process of welded joints was measured, and tensile and bending tests on welded joints were carried out. The fracture surface of welded joints was observed by scanning electron microscopy (SEM), and crystallinity calculation was taken by X-ray diffraction (XRD). The mechanism of X-type weld profile effects on welded joints properties was analyzed. It was concluded that the mechanical properties of welded joints decrease with the reduced X distance between lines.

An algorithm for continuum modeling of rocks with multiple embedded nonlinearly-compliant joints [Continuum modeling of elasto-plastic media with multiple embedded nonlinearly-compliant joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurley, R. C.; Vorobiev, O. Y.; Ezzedine, S. M.

Here, we present a numerical method for modeling the mechanical effects of nonlinearly-compliant joints in elasto-plastic media. The method uses a series of strain-rate and stress update algorithms to determine joint closure, slip, and solid stress within computational cells containing multiple “embedded” joints. This work facilitates efficient modeling of nonlinear wave propagation in large spatial domains containing a large number of joints that affect bulk mechanical properties. We implement the method within the massively parallel Lagrangian code GEODYN-L and provide verification and examples. We highlight the ability of our algorithms to capture joint interactions and multiple weakness planes within individualmore » computational cells, as well as its computational efficiency. We also discuss the motivation for developing the proposed technique: to simulate large-scale wave propagation during the Source Physics Experiments (SPE), a series of underground explosions conducted at the Nevada National Security Site (NNSS).« less

An algorithm for continuum modeling of rocks with multiple embedded nonlinearly-compliant joints [Continuum modeling of elasto-plastic media with multiple embedded nonlinearly-compliant joints

DOE PAGES

Hurley, R. C.; Vorobiev, O. Y.; Ezzedine, S. M.

2017-04-06

Here, we present a numerical method for modeling the mechanical effects of nonlinearly-compliant joints in elasto-plastic media. The method uses a series of strain-rate and stress update algorithms to determine joint closure, slip, and solid stress within computational cells containing multiple “embedded” joints. This work facilitates efficient modeling of nonlinear wave propagation in large spatial domains containing a large number of joints that affect bulk mechanical properties. We implement the method within the massively parallel Lagrangian code GEODYN-L and provide verification and examples. We highlight the ability of our algorithms to capture joint interactions and multiple weakness planes within individualmore » computational cells, as well as its computational efficiency. We also discuss the motivation for developing the proposed technique: to simulate large-scale wave propagation during the Source Physics Experiments (SPE), a series of underground explosions conducted at the Nevada National Security Site (NNSS).« less

46 CFR 56.30-3 - Piping joints (reproduces 110).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Piping joints (reproduces 110). 56.30-3 Section 56.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... joint tightness, mechanical strength and the nature of the fluid handled. ...

46 CFR 56.30-3 - Piping joints (reproduces 110).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Piping joints (reproduces 110). 56.30-3 Section 56.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... joint tightness, mechanical strength and the nature of the fluid handled. ...

46 CFR 56.30-3 - Piping joints (reproduces 110).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Piping joints (reproduces 110). 56.30-3 Section 56.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... joint tightness, mechanical strength and the nature of the fluid handled. ...

46 CFR 56.30-3 - Piping joints (reproduces 110).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Piping joints (reproduces 110). 56.30-3 Section 56.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... joint tightness, mechanical strength and the nature of the fluid handled. ...

46 CFR 56.30-3 - Piping joints (reproduces 110).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Piping joints (reproduces 110). 56.30-3 Section 56.30-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND... joint tightness, mechanical strength and the nature of the fluid handled. ...

Assessment of DoD Wounded Warrior Matters -- Joint Base Lewis-McChord

DTIC Science & Technology

2013-05-31

Report No. DODIG-2013-087 May 31, 2013 Special Plans and Operations Assessment of DoD Wounded Warrior... Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other...integrity, efficiency, and effectiveness of the Department of Defense programs and operations . Mission Promote integrity, accountability, and

Characterization of the bending stiffness of large space structure joints

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey

1989-01-01

A technique for estimating the bending stiffness of large space structure joints is developed and demonstrated for an erectable joint concept. Experimental load-deflection data from a three-point bending test was used as input to solve a closed-form expression for the joint bending stiffness which was derived from linear beam theory. Potential error sources in both the experimental and analytical procedures are identified and discussed. The bending stiffness of a mechanically preloaded erectable joint is studied at three applied moments and seven joint orientations. Using this technique, the joint bending stiffness was bounded between 6 and 17 percent of the bending stiffness of the graphite/epoxy strut member.

REEP/Hotel Workplace Literacy Project. Final Performance. October 1, 1988-March 31, 1990.

ERIC Educational Resources Information Center

Arlington County Public Schools, VA.

A 1-year workplace literacy program was a joint effort of the Chamber of Commerce, public schools, and seven hotels in Arlington, Virginia. Participants were employees with limited English proficiency. The project resulted in the production of a manual, a video, curricula for housekeeping and food and beverage workers, curricula for more advanced…

Reflex Responses to Ligament Loading: Implications for Knee Joint Stability

DTIC Science & Technology

2001-10-25

white noise approach", Prentice-Hall".:, 1978. [15] B. Grenfield and B. Wyke, "Reflex innervation of the temporo - mandibular joint .". Nature. 211(52...selective, depending on the magnitude of the angular perturbation. Keywords - Reflex, Periarticular tissue afferents, Joint stability I...INTRODUCTION Traditionally, joint stability has been considered to be purely mechanical in origin, with little or no consideration of neuromuscular

The effect of fixed charge density and cartilage swelling on mechanics of knee joint cartilage during simulated gait.

PubMed

Räsänen, Lasse P; Tanska, Petri; Zbýň, Štefan; van Donkelaar, Corrinus C; Trattnig, Siegfried; Nieminen, Miika T; Korhonen, Rami K

2017-08-16

The effect of swelling of articular cartilage, caused by the fixed charge density (FCD) of proteoglycans, has not been demonstrated on knee joint mechanics during simulated walking before. In this study, the influence of the depth-wise variation of FCD was investigated on the internal collagen fibril strains and the mechanical response of the knee joint cartilage during gait using finite element (FE) analysis. The FCD distribution of tibial cartilage was implemented from sodium ( 23 Na) MRI into a 3-D FE-model of the knee joint ("Healthy model"). For comparison, models with decreased FCD values were created according to the decrease in FCD associated with the progression of osteoarthritis (OA) ("Early OA" and "Advanced OA" models). In addition, a model without FCD was created ("No FCD" model). The effect of FCD was studied with five different collagen fibril network moduli of cartilage. Using the reference fibril network moduli, the decrease in FCD from "Healthy model" to "Early OA" and "Advanced OA" models resulted in increased axial strains (by +2 and +6%) and decreased fibril strains (by -3 and -13%) throughout the stance, respectively, calculated as mean values through cartilage depth in the tibiofemoral contact regions. Correspondingly, compared to the "Healthy model", the removal of the FCD altogether in "NoFCD model" resulted in increased mean axial strains by +16% and decreased mean fibril strains by -24%. This effect was amplified as the fibril network moduli were decreased by 80% from the reference. Then mean axial strains increased by +6, +19 and +49% and mean fibril strains decreased by -9, -20 and -32%, respectively. Our results suggest that the FCD in articular cartilage has influence on cartilage responses in the knee during walking. Furthermore, the FCD is suggested to have larger impact on cartilage function as the collagen network degenerates e.g. in OA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Increased expression of damage-associated molecular patterns (DAMPs) in osteoarthritis of human knee joint compared to hip joint.

PubMed

Rosenberg, John H; Rai, Vikrant; Dilisio, Matthew F; Sekundiak, Todd D; Agrawal, Devendra K

2017-12-01

Osteoarthritis (OA) is a degenerative disease characterized by the destruction of cartilage. The greatest risk factors for the development of OA include age and obesity. Recent studies suggest the role of inflammation in the pathogenesis of OA. The two most common locations for OA to occur are in the knee and hip joints. The knee joint experiences more mechanical stress, cartilage degeneration, and inflammation than the hip joint. This could contribute to the increased incidence of OA in the knee joint. Damage-associated molecular patterns (DAMPs), including high-mobility group box-1, receptor for advanced glycation end products, and alarmins (S100A8 and S100A9), are released in the joint in response to stress-mediated chondrocyte and cartilage damage. This facilitates increased cartilage degradation and inflammation in the joint. Studies have documented the role of DAMPs in the pathogenesis of OA; however, the comparison of DAMPs and its influence on OA has not been discussed. In this study, we compared the DAMPs between OA knee and hip joints and found a significant difference in the levels of DAMPs expressed in the knee joint compared to the hip joint. The increased levels of DAMPs suggest a difference in the underlying pathogenesis of OA in the knee and the hip and highlights DAMPs as potential therapeutic targets for OA in the future.

Mechanical testing and development of the helical field coil joint for the Advanced Toroidal Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, B.E.; Bryan, W.E.; Goranson, P.L.

1985-01-01

The helical field (HF) coil set for the Advanced Toroidal Facility (ATF) is an M = 12, l = 2, constant-ratio torsatron winding consisting of 2 coils, each with 14 turns of heavy copper conductor. The coils are divided into 24 identical segments to facilitate fabrication and minimize the assembly schedule. The segments are connected across through-bolted lap joints that must carry up to 124,000 A per turn for 5 s or 62,500 A steady-state. In addition, the joints must carry the high magnetic and thermal loads induced in the conductor and still fit within the basic 140- by 30-mmmore » copper envelope. Extensive testing and development were undertaken to verify and refine the basic joint design. Tests included assembly force and clamping force for various types of misalignment; joint resistance as a function of clamping force; clamp bolt relaxation due to thermal cycling; fatigue testing of full-size, multiturn joint prototypes; and low-cycle fatigue and tensile tests of annealed CDA102 copper. The required performance parameters and actual test results, as well as the final joint configuration, are presented. 2 refs., 9 figs., 4 tabs.« less

Effects of toe-out and toe-in gait with varying walking speeds on knee joint mechanics and lower limb energetics.

PubMed

Khan, Soobia Saad; Khan, Saad Jawaid; Usman, Juliana

2017-03-01

Toe-out/-in gait has been prescribed in reducing knee joint load to medial knee osteoarthritis patients. This study focused on the effects of toe-out/-in at different walking speeds on first peak knee adduction moment (fKAM), second peak KAM (sKAM), knee adduction angular impulse (KAAI), net mechanical work by lower limb as well as joint-level contribution to the total limb work during level walking. Gait analysis of 20 healthy young adults was done walking at pre-defined normal (1.18m/s), slow (0.85m/s) and fast (1.43m/s) walking speeds with straight-toe (natural), toe-out (15°>natural) and toe-in (15°joints were found to be major energy contributors for toe-in and toe-out respectively. At higher walking speeds, these contributions were switched. The ankle joint remained unaffected by changing walking speeds and foot progression angles. Toe-out/-in gait modifications affected knee joint kinetics and lower limb energetics at all walking speeds. However, their effects were inconsistent at different speeds. Therefore, walking speed should be taken into account when prescribing toe-out/-in gait. Copyright © 2017 Elsevier B.V. All rights reserved.

Design, Static Analysis And Fabrication Of Composite Joints

NASA Astrophysics Data System (ADS)

Mathiselvan, G.; Gobinath, R.; Yuvaraja, S.; Raja, T.

2017-05-01

The Bonded joints will be having one of the important issues in the composite technology is the repairing of aging in aircraft applications. In these applications and also for joining various composite material parts together, the composite materials fastened together either using adhesives or mechanical fasteners. In this paper, we have carried out design, static analysis of 3-D models and fabrication of the composite joints (bonded, riveted and hybrid). The 3-D model of the composite structure will be fabricated by using the materials such as epoxy resin, glass fibre material and aluminium rivet for preparing the joints. The static analysis was carried out with different joint by using ANSYS software. After fabrication, parametric study was also conducted to compare the performance of the hybrid joint with varying adherent width, adhesive thickness and overlap length. Different joint and its materials tensile test result have compared.

Optimizing Marine Corps Maintenance Personnel Conversion to the Joint Strike Fighter

DTIC Science & Technology

2012-03-01

experience levels, retention, fix rates, operations tempo, spare parts issues, and aircraft systems reliability and maintainability are as well related to...manning requirements. The initial phase, which starts six months before the squadron stands up, is called RFO (Ready For Operation ). The second phase...Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget

Global-Local Finite Element Analysis for Thermo-Mechanical Stresses in Bonded Joints

NASA Technical Reports Server (NTRS)

Shkarayev, S.; Madenci, Erdogan; Camarda, C. J.

1997-01-01

An analysis of adhesively bonded joints using conventional finite elements does not capture the singular behavior of the stress field in regions where two or three dissimilar materials form a junction with or without free edges. However, these regions are characteristic of the bonded joints and are prone to failure initiation. This study presents a method to capture the singular stress field arising from the geometric and material discontinuities in bonded composites. It is achieved by coupling the local (conventional) elements with global (special) elements whose interpolation functions are constructed from the asymptotic solution.

Real-Time Visualization of Joint Cavitation

PubMed Central

Rowe, Lindsay

2015-01-01

Cracking sounds emitted from human synovial joints have been attributed historically to the sudden collapse of a cavitation bubble formed as articular surfaces are separated. Unfortunately, bubble collapse as the source of joint cracking is inconsistent with many physical phenomena that define the joint cracking phenomenon. Here we present direct evidence from real-time magnetic resonance imaging that the mechanism of joint cracking is related to cavity formation rather than bubble collapse. In this study, ten metacarpophalangeal joints were studied by inserting the finger of interest into a flexible tube tightened around a length of cable used to provide long-axis traction. Before and after traction, static 3D T1-weighted magnetic resonance images were acquired. During traction, rapid cine magnetic resonance images were obtained from the joint midline at a rate of 3.2 frames per second until the cracking event occurred. As traction forces increased, real-time cine magnetic resonance imaging demonstrated rapid cavity inception at the time of joint separation and sound production after which the resulting cavity remained visible. Our results offer direct experimental evidence that joint cracking is associated with cavity inception rather than collapse of a pre-existing bubble. These observations are consistent with tribonucleation, a known process where opposing surfaces resist separation until a critical point where they then separate rapidly creating sustained gas cavities. Observed previously in vitro, this is the first in-vivo macroscopic demonstration of tribonucleation and as such, provides a new theoretical framework to investigate health outcomes associated with joint cracking. PMID:25875374

Muscle as a molecular machine for protecting joints and bones by absorbing mechanical impacts

PubMed Central

Sarvazyan, Armen; Rudenko, Oleg; Aglyamov, Salavat; Emelianov, Stanislav

2014-01-01

We hypothesize that dissipation of mechanical energy of external impact to absorb mechanical shock is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In physical systems, the common mechanism for absorbing mechanical shock is achieved with the use of both elastic and viscous elements and we hypothesize that the viscosity of the skeletal muscle is a variable parameter which can be voluntarily controlled by changing the tension of the contracting muscle. We further hypothesize that an ability of muscle to absorb shock has been an important factor in biological evolution, allowing the life to move from the ocean to land, from hydrodynamic to aerodynamic environment with dramatically different loading conditions for musculoskeletal system. The ability of muscle to redistribute the energy of mechanical shock in time and space and unload skeletal joints is of key importance in physical activities. We developed a mathematical model explaining the absorption of mechanical shock energy due to the increased viscosity of contracting skeletal muscles. The developed model, based on the classical theory of sliding filaments, demonstrates that the increased muscle viscosity is a result of the time delay (or phase shift) between the mechanical impact and the attachment/detachment of myosin heads to binding sites on the actin filaments. The increase in the contracted muscle's viscosity is time dependent. Since the forward and backward rate constants for binding the myosin heads to the actin filaments are on the order of 100 s-1, the viscosity of the contracted muscle starts to significantly increase with an impact time greater than 0.01 s. The impact time is one of the key parameters in generating destructive stress in the colliding objects. In order to successfully dampen a short high power impact, muscles must first slow it down to engage the molecular mechanism of muscle viscosity. Muscle carries

75 FR 45201 - Agency Information Collection Activities: Submission for OMB Review; Joint Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-02

..., Office of the Comptroller of the Currency, Public Information Room, Mailstop 2-3, Attention: 1557-0081..., 3501 Fairfax Drive, Arlington, VA 22226, between 9 a.m. and 5 p.m. on business days. OTS: You may..., Office of Thrift Supervision, 1700 G Street, NW., Washington, DC 20552, Attention: ``1550-0023 (TFR...

Design, Fabrication and Characterization of High Temperature Joints in Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic joining has been recognized as one of the enabling technologies for the successful utilization of ceramic components in a number of demanding, high temperature applications. Various joint design philosophies and design issues have been discussed along with an affordable, robust ceramic joining technology (ARCJoinT). A wide variety of silicon carbide-based composite materials, in different shapes and sizes, have been joined using this technology. This technique is capable of producing joints with tailorable thickness and composition. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. These joints maintain their mechanical strength up to 1200 C in air. This technology is suitable for the joining of large and complex shaped ceramic composite components and with certain modifications, can be applied to repair of ceramic components damaged in service.

Design, Fabrication, and Characterization of High Temperature Joints in Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic joining has been recognized as one of the enabling technologies for the successful utilization of ceramic components in a number of demanding, high temperature applications. Various joint design philosophies and design issues have been discussed along with an affordable, robust ceramic joining technology (ARCJoinT). A wide variety of silicon carbide-based composite materials, in different shapes and sizes, have been joined using this technology. This technique is capable of producing joints with tailorable thickness and composition. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. These joints maintain their mechanical strength up to 1200C in air. This technology is suitable for the joining of large and complex shaped ceramic composite components and with certain modifications, can be applied to repair of ceramic components damaged in service.

Analytical magmatic source modelling from a joint inversion of ground deformation and focal mechanisms data

NASA Astrophysics Data System (ADS)

Cannavo', Flavio; Scandura, Danila; Palano, Mimmo; Musumeci, Carla

2014-05-01

Seismicity and ground deformation represent the principal geophysical methods for volcano monitoring and provide important constraints on subsurface magma movements. The occurrence of migrating seismic swarms, as observed at several volcanoes worldwide, are commonly associated with dike intrusions. In addition, on active volcanoes, (de)pressurization and/or intrusion of magmatic bodies stress and deform the surrounding crustal rocks, often causing earthquakes randomly distributed in time within a volume extending about 5-10 km from the wall of the magmatic bodies. Despite advances in space-based, geodetic and seismic networks have significantly improved volcano monitoring in the last decades on an increasing worldwide number of volcanoes, quantitative models relating deformation and seismicity are not common. The observation of several episodes of volcanic unrest throughout the world, where the movement of magma through the shallow crust was able to produce local rotation of the ambient stress field, introduces an opportunity to improve the estimate of the parameters of a deformation source. In particular, during these episodes of volcanic unrest a radial pattern of P-axes of the focal mechanism solutions, similar to that of ground deformation, has been observed. Therefore, taking into account additional information from focal mechanisms data, we propose a novel approach to volcanic source modeling based on the joint inversion of deformation and focal plane solutions assuming that both observations are due to the same source. The methodology is first verified against a synthetic dataset of surface deformation and strain within the medium, and then applied to real data from an unrest episode occurred before the May 13th 2008 eruption at Mt. Etna (Italy). The main results clearly indicate as the joint inversion improves the accuracy of the estimated source parameters of about 70%. The statistical tests indicate that the source depth is the parameter with the highest

Thermal Cycling Fatigue in DIPs Mounted with Eutectic Tin-Lead Solder Joints in Stub and Gullwing Geometries

NASA Technical Reports Server (NTRS)

Winslow, J. W.; Silveira, C. de

1993-01-01

It has long been known that solder joints under mechanical stress are subject to failure. In early electronic systems, such failures were avoided primarily by avoiding the use of solder as a mechanical structural component. The rule was first to make sound wire connections that did not depend mechanically on solder, and only then to solder them. Careful design and miniaturization in modern electronic systems limits the mechanical stresses exerted on solder joints to values less than their yield points, and these joints have become integral parts of the mechanical structures. Unfortunately, while these joints are strong enough when new, they have proven vulnerable to fatigue failures as they age. Details of the fatigue process are poorly understood, making predictions of expected lifetimes difficult.

Mechanical Model of Dexterous Continuum Manipulators with Compliant Joints and Tendon/External Force Interactions

PubMed Central

Murphy, Ryan J.; Liu, Hao; Iordachita, Iulian I.; Armand, Mehran

2017-01-01

Dexterous continuum manipulators (DCMs) have been widely adopted for minimally- and less-invasive surgery. During the operation, these DCMs interact with surrounding anatomy actively or passively. The interaction force will inevitably affect the tip position and shape of DCMs, leading to potentially inaccurate control near critical anatomy. In this paper, we demonstrated a 2D mechanical model for a tendon actuated, notched DCM with compliant joints. The model predicted deformation of the DCM accurately in the presence of tendon force, friction force, and external force. A partition approach was proposed to describe the DCM as a series of interconnected rigid and flexible links. Beam mechanics, taking into consideration tendon interaction and external force on the tip and the body, was applied to obtain the deformation of each flexible link of the DCM. The model results were compared with experiments for free bending as well as bending in the presence of external forces acting at either the tip or body of the DCM. The overall mean error of tip position between model predictions and all of the experimental results was 0.62±0.41mm. The results suggest that the proposed model can effectively predict the shape of the DCM. PMID:28989273

Cyclic Behavior of Mortarless Brick Joints with Different Interlocking Shapes

PubMed Central

Liu, Hongjun; Liu, Peng; Lin, Kun; Zhao, Sai

2016-01-01

The framed structure infilled with a mortarless brick (MB) panel exhibits considerable in-plane energy dissipation because of the relative sliding between bricks and good out-of-plane stability resulting from the use of interlocking mechanisms. The cyclic behaviors of MB are investigated experimentally in this study. Two different types of bricks, namely non-interlocking mortarless brick (N-IMB) and interlocking mortarless brick (IMB), are examined experimentally. The cyclic behavior of all of the joints (N-IMB and IMB) are investigated in consideration of the effects of interlocking shapes, loading compression stress levels and loading cycles. The hysteretic loops of N-IMB and IMB joints are obtained, according to which a mechanical model is developed. The Mohr–Coulomb failure criterion is employed to describe the shear failure modes of all of the investigated joints. A typical frictional behavior is observed for the N-IMB joints, and a significant stiffening effect is observed for the IMB joints during their sliding stage. The friction coefficients of all of the researched joints increase with the augmentation of the compression stress level and improvement of the smoothness of the interlocking surfaces. An increase in the loading cycle results in a decrease in the friction coefficients of all of the joints. The degradation rate (DR) of the friction coefficients increases with the reduction in the smoothness of the interlocking surface. PMID:28773291

Estimation of Time-Varying, Intrinsic and Reflex Dynamic Joint Stiffness during Movement. Application to the Ankle Joint

PubMed Central

Guarín, Diego L.; Kearney, Robert E.

2017-01-01

Dynamic joint stiffness determines the relation between joint position and torque, and plays a vital role in the control of posture and movement. Dynamic joint stiffness can be quantified during quasi-stationary conditions using disturbance experiments, where small position perturbations are applied to the joint and the torque response is recorded. Dynamic joint stiffness is composed of intrinsic and reflex mechanisms that act and change together, so that nonlinear, mathematical models and specialized system identification techniques are necessary to estimate their relative contributions to overall joint stiffness. Quasi-stationary experiments have demonstrated that dynamic joint stiffness is heavily modulated by joint position and voluntary torque. Consequently, during movement, when joint position and torque change rapidly, dynamic joint stiffness will be Time-Varying (TV). This paper introduces a new method to quantify the TV intrinsic and reflex components of dynamic joint stiffness during movement. The algorithm combines ensemble and deterministic approaches for estimation of TV systems; and uses a TV, parallel-cascade, nonlinear system identification technique to separate overall dynamic joint stiffness into intrinsic and reflex components from position and torque records. Simulation studies of a stiffness model, whose parameters varied with time as is expected during walking, demonstrated that the new algorithm accurately tracked the changes in dynamic joint stiffness using as little as 40 gait cycles. The method was also used to estimate the intrinsic and reflex dynamic ankle stiffness from an experiment with a healthy subject during which ankle movements were imposed while the subject maintained a constant muscle contraction. The method identified TV stiffness model parameters that predicted the measured torque very well, accounting for more than 95% of its variance. Moreover, both intrinsic and reflex dynamic stiffness were heavily modulated through the

A low cost wearable optical-based goniometer for human joint monitoring

NASA Astrophysics Data System (ADS)

Lim, Chee Kian; Luo, Zhiqiang; Chen, I.-Ming; Yeo, Song Huat

2011-03-01

Widely used in the fields of physical and occupational therapy, goniometers are indispensible when it comes to angular measurement of the human joint. In both fields, there is a need to measure the range of motion associated with various joints and muscle groups. For example, a goniometer may be used to help determine the current status of the range of motion in bend the arm at the elbow, bending the knee, or bending at the waist. The device can help to establish the range of motion at the beginning of the treatment series, and also allow the therapist to monitor progress during subsequent sessions. Most commonly found are the mechanical goniometers which are inexpensive but bulky. As the parts are mechanically linked, accuracy and resolution are largely limited. On the other hand, electronic and optical fiberbased goniometers promise better performance over its mechanical counterpart but due to higher cost and setup requirements does not make it an attractive proposition as well. In this paper, we present a reliable and non-intrusive design of an optical-based goniometer for human joint measurement. This device will allow continuous and longterm monitoring of human joint motion in everyday setting. The proposed device was benchmarked against mechanical goniometer and optical based motion capture system to validate its performance. From the empirical results, it has been proven that this design can be use as a robust and effective wearable joint monitoring device.

The contribution of collagen fibers to the mechanical compressive properties of the temporomandibular joint disc.

PubMed

Fazaeli, S; Ghazanfari, S; Everts, V; Smit, T H; Koolstra, J H

2016-07-01

The Temporomandibular Joint (TMJ) disc is a fibrocartilaginous structure located between the mandibular condyle and the temporal bone, facilitating smooth movements of the jaw. The load-bearing properties of its anisotropic collagenous network have been well characterized under tensile loading conditions. However, recently it has also been speculated that the collagen fibers may contribute dominantly in reinforcing the disc under compression. Therefore, in this study, the structural-functional role of collagen fibers in mechanical compressive properties of TMJ disc was investigated. Intact porcine TMJ discs were enzymatically digested with collagenase to disrupt the collagenous network of the cartilage. The digested and non-digested articular discs were analyzed mechanically, biochemically and histologically in five various regions. These tests included: (1) cyclic compression tests, (2) biochemical quantification of collagen and glycosaminoglycan (GAG) content and (3) visualization of collagen fibers' alignment by polarized light microscopy (PLM). The instantaneous compressive moduli of the articular discs were reduced by as much as 50-90% depending on the region after the collagenase treatment. The energy dissipation properties of the digested discs showed a similar tendency. Biochemical analysis of the digested samples demonstrated an average of 14% and 35% loss in collagen and GAG, respectively. Despite the low reduction of collagen content the PLM images showed considerable perturbation of the collagenous network of the TMJ disc. The results indicated that even mild disruption of collagen fibers can lead to substantial mechanical softening of TMJ disc undermining its reinforcement and mechanical stability under compression. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Mechanical Characteristics of Welded Joints of Aluminum Alloy 6061 T6 Formed by Arc and Friction Stir Welding

NASA Astrophysics Data System (ADS)

Astarita, A.; Squillace, A.; Nele, L.

2016-01-01

Butt welds formed by arc welding in inert gas with nonconsumable electrode (tungsten inert gas (TIG) welding) and by friction stir welding (FSW) from aluminum alloy AA6061 T6 are studied. Comparative analysis of the structures and mechanical properties of the welded joints is performed using the results of optical and electron microscopy, tensile tests, tests for residual bending ductility, and measurements of microhardness. The changes in the microstructure in different zones and the degrees of degradation of the mechanical properties after the welding are determined. It is shown that the size of the tool for the friction stir welding affects the properties of the welds. Quantitative results showing the relation between the microscopic behavior of the alloy and the welding-induced changes in the microstructure are obtained. Friction stir welding is shown to provide higher properties of the welds.

Improving the fatigue resistance of adhesive joints in laminated wood structures

NASA Technical Reports Server (NTRS)

Laufenberg, Theodore L.; River, Bryan H.; Murmanis, Lidija L.; Christiansen, Alfred W.

1988-01-01

The premature fatigue failure of a laminated wood/epoxy test beam containing a cross section finger joint was the subject of a multi-disciplinary investigation. The primary objectives were to identify the failure mechanisms which occurred during the finger joint test and to provide avenues for general improvements in the design and fabrication of adhesive joints in laminated wood structures.

Dynamic properties of human incudostapedial joint-Experimental measurement and finite element modeling.

PubMed

Jiang, Shangyuan; Gan, Rong Z

2018-04-01

The incudostapedial joint (ISJ) is a synovial joint connecting the incus and stapes in the middle ear. Mechanical properties of the ISJ directly affect sound transmission from the tympanic membrane to the cochlea. However, how ISJ properties change with frequency has not been investigated. In this paper, we report the dynamic properties of the human ISJ measured in eight samples using a dynamic mechanical analyzer (DMA) for frequencies from 1 to 80 Hz at three temperatures of 5, 25 and 37 °C. The frequency-temperature superposition (FTS) principle was used to extrapolate the results to 8 kHz. The complex modulus of ISJ was measured with a mean storage modulus of 1.14 MPa at 1 Hz that increased to 3.01 MPa at 8 kHz, and a loss modulus that increased from 0.07 to 0.47 MPa. A 3-dimensional finite element (FE) model consisting of the articular cartilage, joint capsule and synovial fluid was then constructed to derive mechanical properties of ISJ components by matching the model results to experimental data. Modeling results showed that mechanical properties of the joint capsule and synovial fluid affected the dynamic behavior of the joint. This study contributes to a better understanding of the structure-function relationship of the ISJ for sound transmission. Copyright © 2018. Published by Elsevier Ltd.

Effect of moisture cycling on truss-plate joint behavior

Treesearch

Leslie H. Groom

1994-01-01

The structural performance of wood trusses, which are now commonplace in light-frame construction, is dictated in part by the mechanical properties of the truss-plate joints. However, little information exists quantifying the effect of environmental conditions on truss-plate joint properties. The main objective of this paper was to quantify the effect of moisture...

Design of a telerobotic controller with joint torque sensors

NASA Technical Reports Server (NTRS)

Jansen, J. F.; Herndon, J. N.

1990-01-01

The purpose was to analytically show how to design a joint controller for a telerobotic system when joint torque sensors are available. Other sensors such as actuator position, actuator velocity, joint position, and joint velocity are assumed to be accessible; however, the results will also be useful when only partial measurements are available. The controller presented can be applied to either mode of operation of a manipulator (i.e., teleoperation or robotic). Mechanical manipulators with high levels of friction are assumed. The results are applied to a telerobotic system built for NASA. Very high levels of friction have been reduced using high-gain feedback while avoiding limit cycles.

Physicochemical and microscopic characterization of implant–abutment joints

PubMed Central

Lopes, Patricia A.; Carreiro, Adriana F. P.; Nascimento, Rubens M.; Vahey, Brendan R.; Henriques, Bruno; Souza, Júlio C. M.

2018-01-01

Objective: The purpose of this study was to investigate Morse taper implant–abutment joints by chemical, mechanical, and microscopic analysis. Materials and Methods: Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant–abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant–abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant–abutment joints. Statistics: Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Results: Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant–abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Conclusions: Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant–abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication. PMID:29657532

Physicochemical and microscopic characterization of implant-abutment joints.

PubMed

Lopes, Patricia A; Carreiro, Adriana F P; Nascimento, Rubens M; Vahey, Brendan R; Henriques, Bruno; Souza, Júlio C M

2018-01-01

The purpose of this study was to investigate Morse taper implant-abutment joints by chemical, mechanical, and microscopic analysis. Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant-abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant-abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant-abutment joints. Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant-abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant-abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication.

76 FR 24486 - Agency Information Collection Activities; Submission for OMB Review; Joint Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-02

...) on business days between 7 a.m. and 5 p.m. Public Inspection: All comments received will be posted... Fairfax Drive, Arlington, VA 22226, between 9 a.m. and 5 p.m. on business days. OTS: You may submit....m. to 4 p.m. on business days, Attention: Information Collection Comments, Chief Counsel's Office...

Strength of laser welded joints of polypropylene composites

NASA Astrophysics Data System (ADS)

Votrubec, V.; Hisem, P.; Vinšová, L.; Lukášová, V.

2017-11-01

This paper deals with experimental tests of laser welded polypropylene composites. Polymers, such as polypropylene, are often filled with fibres in order to increase their mechanical properties. The welding procedure can also influence material properties nearby weld joints. Therefore the strength of weld joints is lower than strength of primary materials. This effect is proved by realized shear tests. Polymer specimens were filled with 20 % and 40 % of glass fibres and all possible combinations of specimens were welded for experiments. There is also discussed influence of volume fraction of glass fibres in polypropylene on the strength of weld joint.

Kinematics of Hooke universal joint robot wrists

NASA Technical Reports Server (NTRS)

Mckinney, William S., Jr.

1988-01-01

The singularity problem associated with wrist mechanisms commonly found on industrial manipulators can be alleviated by redesigning the wrist so that it functions as a three-axis gimbal system. This paper discussess the kinematics of gimbal robot wrists made of one and two Hooke universal joints. Derivations of the resolved rate motion control equations for the single and double Hooke universal joint wrists are presented using the three-axis gimbal system as a theoretical wrist model.

Multi-Scale Computational Modeling of Ni-Base Superalloy Brazed Joints for Gas Turbine Applications

NASA Astrophysics Data System (ADS)

Riggs, Bryan

Brazed joints are commonly used in the manufacture and repair of aerospace components including high temperature gas turbine components made of Ni-base superalloys. For such critical applications, it is becoming increasingly important to account for the mechanical strength and reliability of the brazed joint. However, material properties of brazed joints are not readily available and methods for evaluating joint strength such as those listed in AWS C3.2 have inherent challenges compared with testing bulk materials. In addition, joint strength can be strongly influenced by the degree of interaction between the filler metal (FM) and the base metal (BM), the joint design, and presence of flaws or defects. As a result, there is interest in the development of a multi-scale computational model to predict the overall mechanical behavior and fitness-for-service of brazed joints. Therefore, the aim of this investigation was to generate data and methodology to support such a model for Ni-base superalloy brazed joints with conventional Ni-Cr-B based FMs. Based on a review of the technical literature a multi-scale modeling approach was proposed to predict the overall performance of brazed joints by relating mechanical properties to the brazed joint microstructure. This approach incorporates metallurgical characterization, thermodynamic/kinetic simulations, mechanical testing, fracture mechanics and finite element analysis (FEA) modeling to estimate joint properties based on the initial BM/FM composition and brazing process parameters. Experimental work was carried out in each of these areas to validate the multi-scale approach and develop improved techniques for quantifying brazed joint properties. Two Ni-base superalloys often used in gas turbine applications, Inconel 718 and CMSX-4, were selected for study and vacuum furnace brazed using two common FMs, BNi-2 and BNi-9. Metallurgical characterization of these brazed joints showed two primary microstructural regions; a soft

Interfacial Microstructure and Mechanical Strength of 93W/Ta Diffusion-Bonded Joints with Ni Interlayer

NASA Astrophysics Data System (ADS)

Luo, Guoqiang; Zhang, Jian; Li, Meijuan; Wei, Qinqin; Shen, Qiang; Zhang, Lianmeng

2013-02-01

93W alloy and Ta metal were successfully diffusion bonded using a Ni interlayer. Ni4W was found at the W-Ni interface, and Ni3Ta and Ni2Ta were formed at the Ni-Ta interface. The shear strength of the joints increases with increasing holding time, reaching a value of 202 MPa for a joint prepared using a 90-minute holding time at 1103 K (830 °C) and 20 MPa. The fracture of this joint occurred within the Ni/Ta interface.

Impact of Acid Attack on the Shear Behaviour of a Carbonate Rock Joint

NASA Astrophysics Data System (ADS)

Nouailletas, O.; Perlot, C.; Rivard, P.; Ballivy, G.; La Borderie, C.

2017-06-01

The mechanical behaviour of structural discontinuities in rock mass is a key element of the stability analysis in civil engineering, petroleum engineering and mining engineering. In this paper, the mechanical analysis is coupled with the acidic attack of a rock joint associated with leakage of CO2 through a geological fault in the context of carbon sequestration. Experiments were conducted at the laboratory scale to assess the shear behaviour of degraded joint: direct shear tests were performed on rock joints that have been previously immersed into water or into an acidic solution (pH 0.2). The shear behaviour of joints is governed by the roughness of its walls: the parameters Z2, Z3, Z4 and RL characterize the rough surfaces. They are calculated from the scans of joint surfaces after and before immersion. Their comparison pointed out a slight impact of the acidic attack. However, the results of the direct shear tests show significant modifications in the shear behaviour for the degraded joints: the tangential stress peak disappears, the tangential stiffness decreases in the stress/displacement curve, and the contraction increases, the dilation angle decreases in the dilation curve. Acid attack has a greater impact on the mechanical properties of the asperities than their geometric characteristics. The results of this study will be used to improve chemo-mechanical modelling to better simulate with higher accuracy the fault stability in different cases of civil engineering, petroleum engineering and mining engineering.

On the generation of tangential ground motion by underground explosions in jointed rocks

NASA Astrophysics Data System (ADS)

Vorobiev, Oleg; Ezzedine, Souheil; Antoun, Tarabay; Glenn, Lewis

2015-03-01

This paper describes computational studies of tangential ground motions generated by spherical explosions in a heavily jointed granite formation. Various factors affecting the shear wave generation are considered, including joint spacing, orientation and frictional properties. Simulations are performed both in 2-D for a single joint set to elucidate the basic response mechanisms, and in 3-D for multiple joint sets to realistically represent in situ conditions in a realistic geological setting. The joints are modelled explicitly using both contact elements and weakness planes in the material. Simulations are performed both deterministically and stochastically to quantify the effects of geological uncertainties on near field ground motions. The mechanical properties of the rock and the joints as well as the joint spacing and orientation are taken from experimental test data and geophysical logs corresponding to the Climax Stock granitic outcrop, which is the geological setting of the source physics experiment (SPE). Agreement between simulation results and near field wave motion data from SPE enables newfound understanding of the origin and extent of non-spherical motions associated with underground explosions in fractured geological media.

Reoperations following proximal interphalangeal joint nonconstrained arthroplasties.

PubMed

Pritsch, Tamir; Rizzo, Marco

2011-09-01

To retrospectively analyze the reasons for reoperations following primary nonconstrained proximal interphalangeal (PIP) joint arthroplasty and review clinical outcomes in this group of patients with 1 or more reoperations. Between 2001 and 2009, 294 nonconstrained (203 pyrocarbon and 91 metal-plastic) PIP joint replacements were performed in our institution. A total of 76 fingers (59 patients) required reoperation (50 pyrocarbon and 26 metal-plastic). There were 40 women and 19 men with an average age of 51 years (range, 19-83 y). Primary diagnoses included osteoarthritis in 35, posttraumatic arthritis in 24, and inflammatory arthritis in 17 patients. There were 21 index, 27 middle, 18 ring, and 10 small fingers. The average number of reoperations per PIP joint was 1.6 (range, 1-4). A total of 45 joints had 1 reoperation, 19 had 2, 11 had 3, and 1 had 4. Extensor mechanism dysfunction was the most common reason for reoperation; it involved 51 of 76 fingers and was associated with Chamay or tendon-reflecting surgical approaches. Additional etiologies included component loosening in 17, collateral ligament failure in 10, and volar plate contracture in 8 cases. Inflammatory arthritis was associated with collateral ligament failure. Six fingers were eventually amputated, 9 had PIP joint arthrodeses, and 2 had resection arthroplasties. The arthrodesis and amputation rates correlated with the increased number of reoperations per finger. Clinically, most patients had no or mild pain at the most recent follow-up, and the PIP joint range-of-motion was not significantly different from preoperative values. Pain levels improved with longer follow-up. Reoperations following primary nonconstrained PIP joint arthroplasties are common. Extensor mechanism dysfunction was the most common reason for reoperation. The average reoperation rate was 1.6, and arthrodesis and amputation are associated with an increasing number of operations. Overall clinical outcomes demonstrated no

[The effects of different welding wires on the mechanical properties of laser welding joints].

PubMed

Huang, Qing-feng; Zhang, Jian-zhong; Jiang, Wei-dong; Li, Quan; Yu, Jin-xing

2006-08-01

To evaluate the mechanical properties and microstructure of laser-welded joints with different welding wires for clinical use of welding wire. The standard tensile test and three-point bending test rods were made from Co-Cr and Ni-Cr alloy, and were laser-welded with different welding wire (commercially welding wire and casting wire). Then the tensile rods were tested for the ultimate tensile strength (UTS), and the bending rods for the ultimate bending strength (UBS). The results was analyzed by one-way ANOVA. The tensile fracture surface were examined by scanning electron microscopy (SEM). Metallurgical analysis were also performed on polished longitudinal sectioned samples. For Co-Cr alloy, the UTS of casting wire group and commercially welding wire group was respectively (606.40+/-82.53)MPa and (693.61+/-47.68)MPa; the UBS was respectively (997.95+/-88.89)MPa and (1160.76+/-91.59)MPa. ANOVA showed a significant difference of UTS and UBS between the two groups at the 0.05 level (P<0.05). For Ni-Cr alloy, the UTS of casting wire group and commercially welding wire group was respectively (558.14+/-46.75)MPa and (582.32+/-35.43)MPa; the UBS was respectively (1084.75+/-46.02)MPa and (1078.29+/-36.25)MPa. There was no significant difference between the two groups (P>0.05). SEM and metallurgical examination showed the welded zone exhibiting more cracks in the casting wire group than in the commercially welding wire group. It would be advisable to work with commercially welding wire for the joints that need better strength.

Subspace methods for identification of human ankle joint stiffness.

PubMed

Zhao, Y; Westwick, D T; Kearney, R E

2011-11-01

Joint stiffness, the dynamic relationship between the angular position of a joint and the torque acting about it, describes the dynamic, mechanical behavior of a joint during posture and movement. Joint stiffness arises from both intrinsic and reflex mechanisms, but the torques due to these mechanisms cannot be measured separately experimentally, since they appear and change together. Therefore, the direct estimation of the intrinsic and reflex stiffnesses is difficult. In this paper, we present a new, two-step procedure to estimate the intrinsic and reflex components of ankle stiffness. In the first step, a discrete-time, subspace-based method is used to estimate a state-space model for overall stiffness from the measured overall torque and then predict the intrinsic and reflex torques. In the second step, continuous-time models for the intrinsic and reflex stiffnesses are estimated from the predicted intrinsic and reflex torques. Simulations and experimental results demonstrate that the algorithm estimates the intrinsic and reflex stiffnesses accurately. The new subspace-based algorithm has three advantages over previous algorithms: 1) It does not require iteration, and therefore, will always converge to an optimal solution; 2) it provides better estimates for data with high noise or short sample lengths; and 3) it provides much more accurate results for data acquired under the closed-loop conditions, that prevail when subjects interact with compliant loads.

The Rationale for Joint Mobilization.

ERIC Educational Resources Information Center

Burkhardt, Sandy

This paper presents an overview of the functions of connective tissue and the mechanisms of joint injury and contracture formation in relation to therapeutic exercise. The components of connective tissue operation are explained, including fibroblasts, macrophages, plasma cells, and collagen. An examination of the histology of connective tissue as…

Plating To Reinforce Welded Joints

NASA Technical Reports Server (NTRS)

Otousa, J. E.

1982-01-01

Electrodeposition used to strengthen welded joints gouged, nicked, or suffered other mechanical damage. Plating cell, typically of acrylic plastic such as poly (Methylmetacrylate), is assembled around part to be plated. Areas not to be plated are masked with plater's tape. Weld area is plated in standard nickel-plating process.

Influence of Laser Power on the Microstructure and Mechanical Properties of a Laser Welded-Brazed Mg Alloy/Ni-Coated Steel Dissimilar Joint

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Xiao, Liyuan; Liu, Fuyun; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai

2017-05-01

In this work, we describe a method to improve the bonding of an immiscible Mg/steel system using Ni as an interlayer by coating it on the steel surface. Laser welding-brazing of AZ31B Mg alloy to Ni-coated Q235 steel using Mg-based filler was performed in a lap configuration. The influence of laser power on the weld characteristics, including joint appearance, formation of interfacial reaction layers and mechanical properties was investigated. The results indicated that the presence of the Ni-coating promoted the wetting of the liquid filler metal on the steel surface. A thermal gradient along the interface led to the formation of heterogeneous interfacial reaction layers. When using a low laser power of 1600 W, the reaction products were an FeAl phase in the direct laser irradiation zone, an AlNi phase close to the intermediate zone and mixtures of AlNi phase and an (α-Mg + Mg2Ni) eutectic structure near the interface at the seam head zone. For high powers of more than 2000 W, the FeAl phase grew thicker in the direct laser irradiation zone and a new Fe(Ni) transition layer formed at the interface of the intermediate zone and the seam head zone. However, the AlNi phase and (α-Mg + Mg2Ni) eutectic structure were scattered at the Mg seam. All the joints fractured at the fusion zone, indicating that the improved interface was not the weakest joint region. The maximum tensile-shear strength of the Mg/Ni-coated steel joint reached 190 N/mm, and the joint efficiency was 70% with respect to the Mg alloy base metal.

Bio-inspired flexible joints with passive feathering for robotic fish pectoral fins.

PubMed

Behbahani, Sanaz Bazaz; Tan, Xiaobo

2016-05-04

In this paper a novel flexible joint is proposed for robotic fish pectoral fins, which enables a swimming behavior emulating the fin motions of many aquatic animals. In particular, the pectoral fin operates primarily in the rowing mode, while undergoing passive feathering during the recovery stroke to reduce hydrodynamic drag on the fin. The latter enables effective locomotion even with symmetric base actuation during power and recovery strokes. A dynamic model is developed to facilitate the understanding and design of the joint, where blade element theory is used to calculate the hydrodynamic forces on the pectoral fins, and the joint is modeled as a paired torsion spring and damper. Experimental results on a robotic fish prototype are presented to illustrate the effectiveness of the joint mechanism, validate the proposed model, and indicate the utility of the proposed model for the optimal design of joint depth and stiffness in achieving the trade-off between swimming speed and mechanical efficiency.

Redistribution of Mechanical Work at the Knee and Ankle Joints During Fast Running in Minimalist Shoes.

PubMed

Fuller, Joel T; Buckley, Jonathan D; Tsiros, Margarita D; Brown, Nicholas A T; Thewlis, Dominic

2016-10-01

Minimalist shoes have been suggested as a way to alter running biomechanics to improve running performance and reduce injuries. However, to date, researchers have only considered the effect of minimalist shoes at slow running speeds. To determine if runners change foot-strike pattern and alter the distribution of mechanical work at the knee and ankle joints when running at a fast speed in minimalist shoes compared with conventional running shoes. Crossover study. Research laboratory. Twenty-six trained runners (age = 30.0 ± 7.9 years [age range, 18-40 years], height = 1.79 ± 0.06 m, mass = 75.3 ± 8.2 kg, weekly training distance = 27 ± 15 km) who ran with a habitual rearfoot foot-strike pattern and had no experience running in minimalist shoes. Participants completed overground running trials at 18 km/h in minimalist and conventional shoes. Sagittal-plane kinematics and joint work at the knee and ankle joints were computed using 3-dimensional kinematic and ground reaction force data. Foot-strike pattern was classified as rearfoot, midfoot, or forefoot strike based on strike index and ankle angle at initial contact. We observed no difference in foot-strike classification between shoes (χ 2 1 = 2.29, P = .13). Ankle angle at initial contact was less (2.46° versus 7.43°; t 25 = 3.34, P = .003) and strike index was greater (35.97% versus 29.04%; t 25 = 2.38, P = .03) when running in minimalist shoes compared with conventional shoes. We observed greater negative (52.87 J versus 42.46 J; t 24 = 2.29, P = .03) and positive work (68.91 J versus 59.08 J; t 24 = 2.65, P = .01) at the ankle but less negative (59.01 J versus 67.02 J; t 24 = 2.25, P = .03) and positive work (40.37 J versus 47.09 J; t 24 = 2.11, P = .046) at the knee with minimalist shoes compared with conventional shoes. Running in minimalist shoes at a fast speed caused a redistribution of work from the knee to the ankle joint. This finding suggests that runners changing from conventional to minimalist

Redistribution of Mechanical Work at the Knee and Ankle Joints During Fast Running in Minimalist Shoes

PubMed Central

Fuller, Joel T.; Buckley, Jonathan D.; Tsiros, Margarita D.; Brown, Nicholas A. T.; Thewlis, Dominic

2016-01-01

Context: Minimalist shoes have been suggested as a way to alter running biomechanics to improve running performance and reduce injuries. However, to date, researchers have only considered the effect of minimalist shoes at slow running speeds. Objective: To determine if runners change foot-strike pattern and alter the distribution of mechanical work at the knee and ankle joints when running at a fast speed in minimalist shoes compared with conventional running shoes. Design: Crossover study. Setting: Research laboratory. Patients or Other Participants: Twenty-six trained runners (age = 30.0 ± 7.9 years [age range, 18−40 years], height = 1.79 ± 0.06 m, mass = 75.3 ± 8.2 kg, weekly training distance = 27 ± 15 km) who ran with a habitual rearfoot foot-strike pattern and had no experience running in minimalist shoes. Intervention(s): Participants completed overground running trials at 18 km/h in minimalist and conventional shoes. Main Outcome Measure(s): Sagittal-plane kinematics and joint work at the knee and ankle joints were computed using 3-dimensional kinematic and ground reaction force data. Foot-strike pattern was classified as rearfoot, midfoot, or forefoot strike based on strike index and ankle angle at initial contact. Results: We observed no difference in foot-strike classification between shoes (χ21 = 2.29, P = .13). Ankle angle at initial contact was less (2.46° versus 7.43°; t25 = 3.34, P = .003) and strike index was greater (35.97% versus 29.04%; t25 = 2.38, P = .03) when running in minimalist shoes compared with conventional shoes. We observed greater negative (52.87 J versus 42.46 J; t24 = 2.29, P = .03) and positive work (68.91 J versus 59.08 J; t24 = 2.65, P = .01) at the ankle but less negative (59.01 J versus 67.02 J; t24 = 2.25, P = .03) and positive work (40.37 J versus 47.09 J; t24 = 2.11, P = .046) at the knee with minimalist shoes compared with conventional shoes. Conclusions: Running in minimalist shoes at a fast speed caused a

Investigation of gold embrittlement in connector solder joints

NASA Technical Reports Server (NTRS)

Lane, F. L.