Assessment of Nominal Contact Area Parameters by Means of Ultrasonic Waves

2004 ◽  
Vol 126 (4) ◽  
pp. 639-645 ◽  
Author(s):  
Francesco Aymerich ◽  
Massimiliano Pau
Keyword(s):  
Contact Area ◽  
Ultrasonic Method ◽  
Ultrasonic Waves ◽  
Contact Interface ◽  
Ultrasonic Beam ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Pressure Sensitive Film ◽  
Blurring Effect ◽  
Nominal Contact Area

In this paper the application of an ultrasonic method to evaluate size and shape of the nominal contact area between two contacting bodies is studied. The technique is based on the analysis of the quota of the ultrasonic wave reflected by the interface, which may be related to the level of contact between the surfaces. A simple deconvolution procedure is applied to the raw ultrasonic data so as to remove the blurring effect introduced by the ultrasonic beam size. The ultrasonic data acquired on a simple sphere-plane contact interface are compared with those obtained by means of a commercial pressure sensitive film and the results are discussed to evaluate the capability of the ultrasonic technique to capture the main contact patch features correctly.

Contact Stress and Linearized Modal Predictions of As-Built Preloaded Assembly

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Adam R. Brink ◽  
Robert J. Kuether ◽  
Matthew D. Fronk ◽  
Bryan L. Witt ◽  
Brendan L. Nation
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Contact Area ◽  
Element Model ◽  
High Fidelity ◽  
Vibration Modes ◽  
Low Level ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Pressure Sensitive Film

Abstract The member stiffness and pressure distribution in a bolted joint is significantly influenced by the contact area of the mechanical interface under a prescribed preload force. This research explores the influence of as-built surface profiles for nominally flat interfaces of a C-Beam assembly with two well-defined contact regions. A high-fidelity finite element model is created such that the model uncertainty is minimized by updating and calibrating the piece parts prior to the preload assembly procedure. The model is then assembled and preloaded to evaluate the contact stresses and contact area for both nominally flat and perturbed non-flat surfaces based on three-dimensional surface topography measurements. The predicted pressures are validated with digitized pressure-sensitive film measurements. The high-fidelity modeling reveals how the compliance and thickness of the pressure-sensitive film alter the measured pressures, leading to incorrect evaluations of the stresses and contact area in the joint. The resulting low-level dynamic behavior of the preloaded assembly is shown to be sensitive to the true contact area by linearizing the nonlinear finite element model about the preloaded equilibrium and performing a computational modal analysis. The resonant frequencies are validated with experimental measurements to demonstrate the effect of the contact area on the modal characteristics of the bolted assembly. Vibration modes and loading patterns exhibit varying levels of sensitivity to the contact area in the joint, leading to an improved physical understanding of the influence of contact mechanics on the low-level linear vibration modes of jointed assemblies.

Validation of a Finite Element Humeroradial Joint Model of Contact Pressure Using Fuji Pressure Sensitive Film

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Sunghwan Kim ◽  
Mark Carl Miller
Keyword(s):  
Finite Element ◽  
Contact Stress ◽  
Contact Area ◽  
Axial Loads ◽  
Contact Areas ◽  
Pressure Sensitive ◽  
Maximum Contact Stress ◽  
Sensitive Film ◽  
Pressure Sensitive Film ◽  
Maximum Contact

A finite element (FE) elbow model was developed to predict the contact stress and contact area of the native humeroradial joint. The model was validated using Fuji pressure sensitive film with cadaveric elbows for which axial loads of 50, 100, and 200 N were applied through the radial head. Maximum contact stresses ranged from 1.7 to 4.32 MPa by FE predictions and from 1.34 to 3.84 MPa by pressure sensitive film measurement while contact areas extended from 39.33 to 77.86 mm2 and 29.73 to 83.34 mm2 by FE prediction and experimental measurement, respectively. Measurements from cadaveric testing and FE predictions showed the same patterns in both the maximum contact stress and contact area, as another demonstration of agreement. While measured contact pressures and contact areas validated the FE predictions, computed maximum stresses and contact area tended to overestimate the maximum contact stress and contact area.

Ultrasonic Measurements of Contact Area and Pressure Distribution of a Pneumatic Tire on a Rigid Surface3

2008 ◽  
Vol 36 (1) ◽  
pp. 43-62 ◽  
Author(s):  
Massimiliano Pau ◽  
Bruno Leban ◽  
Antonio Baldi
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Contact Area ◽  
Ultrasonic Method ◽  
Quantitative Information ◽  
Ultrasonic Waves ◽  
Contact Pressure Distribution ◽  
Reflection Data ◽  
Novel Approach ◽  
Pressure Sensitive Film

Abstract Contact phenomena which occur at the tire-ground interface play a crucial role in most issues related to optimal performances of the vehicle, safety, comfort, and energy consumption. Thus, it is essential to have available experimental tools capable of supplying detailed information about the main contact parameters (size and shape of nominal contact area and contact pressure distribution), especially when unknown or unpredictable external conditions make it difficult to use numerical tools in assessing them. Although a number of laboratory techniques have been devised to address this problem, here we propose a novel approach that exploits the property of ultrasonic waves to be differently reflected by a contact interface depending on its stress state. This noninvasive method is capable of supplying in real-time detailed maps of contact conditions as well as quantitative information with regard to geometric features of the contact area and contact pressure distribution values after suitable postprocessing procedures. This study reports the results of the application of the ultrasonic method in the case of contact of a motor-bicycle tire on a rigid surface. A number of tests were carried out under different conditions with regard to inflation pressure and applied load. In each case, the raw reflection data were converted into graphic maps that display the contact area features and contain information about contact pressure. Moreover, to assess the quantitative reliability of the technique, ultrasonic data were compared with those obtained by means of a commercial pressure-sensitive film. The results are discussed to evaluate the capability of the ultrasonic method to correctly capture contact patch features.

A Pressure Sensitive Film Study on the Effect of Screw Omission on Bone-plate Interface Mechanics in Cadaveric Bone

1997 ◽  
Vol 10 (04) ◽  
pp. 205-209 ◽  
Author(s):  
T. C. Hearn ◽  
C. B. Caldwell ◽  
H. Tornkvist ◽  
J. R. Field
Keyword(s):  
Contact Area ◽  
Bone Plate ◽  
Bone Strain ◽  
Average Force ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Metacarpal Bones ◽  
Interface Mechanics ◽  
Pressure Sensitive Film ◽  
Interface Contact

SummaryMinimalising surgical exposure and the amount of hardware implanted has become the aim in promoting the biological healing of fractures. Increased spacing of fewer bone screws can increase the mechanical strength of fracture fixation without jeopardizing the stability of the construction. The omission of selective screws has also been shown to increase bone strain and has been suggested as a means of treating bone plate induced osteoporosis.Using Fuji prescale pressure sensitive film we evaluated the effect of selective screw omission on the platebone interface mechanics. Testing was performed using 10-hole, 4.5 mm DCP applied to equine cadaveric third metacarpal bones. Film was interposed between the bone and the bone plate which were applied to a constant level of screw torque. The resultant digitized bone plate patterns enabled computation of the interface contact area (%) and the average force (Newtons-N) at the interface and a qualitative assessment of the pattern of pressure distribution.The symmetrical omission of 40% of the total screw number resulted in significant differences between the control (10 screws) and each treatment for both interface contact area (p <0.05) and average force (p <0.02). In one pattern of screw omission there was a marginally non-significant difference between the control and treatment interface contact area (p = 0.0518).The results suggest that a dramatic reduction in the number of screws applied to a given plate (40%) evokes significant changes in the interface mechanics. Of interest is the effect the pattern of screw omission had on the interface mechanical features; certain screw omission patterns induced a reduction in contact area and force of the same magnitude as the number of screws omitted (40%), whilst in other patterns of screw omission the effect on interface mechanical features was much less than expected (20%).A number of implications can be postulated from these findings;1. Subsequent to the omission of screws the level interface friction may remain at a level sufficient as to not alter the ability of the fixation, to maintain fracture reduction and stability.2. The interface bone will benefit from a reduction in interface contact presumably resulting in less impairment to blood outflow through the cortex.3. The use of fewer screws in a given construction may augment the inherent bone strain.The effect on plate-bone interface mechanics of the symmetrical omission of screws was evaluated. This was accomplished using Fuji pressure sensitive film and provided an indication of interface contact area and average force. It was found that the omission of 40% of screws from a given plate significantly altered the interface contact area and the average force, however, the extent of these changes was influenced by the pattern of screw omission. This suggests that the selective omission of screws from a plate-bone construction may provide a means of limiting plate-induced osteopaenia during fracture healing, through a reduction in contact area and improved inherent bone strain.

The Use of Contact Biomechanics to Study the Intact, Proximal Row Carpectomy and Scaphoid Excision, Four Bone Fusion Wrist

2020 ◽  
Vol 16 (3) ◽  
pp. 189-193
Author(s):  
David H. Wei ◽  
Peter Tang
Keyword(s):  
Proximal Row Carpectomy ◽  
Scapholunate Ligament ◽  
Bone Fusion ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Radiocarpal Joint ◽  
Pressure Sensitive Film ◽  
Number Of Authors

The study of contact biomechanics of the wrist is a challenge. This is partly due to the relatively small size of the joint as well as the lack of space in the radiocarpal joint which makes the delivery of investigative materials such as pressure sensitive film without causing artifact, difficult. Fortunately, a number of authors have studied the intact wrist, the scapholunate ligament injured wrist, the proximal row carpectomy and the scaphoid excision, four bone fusion. Despite some contrasting findings, there are some general concepts that we understand about wrist mechanics.

A Technique for Measuring Absolute Toe Pressures: Evaluation of Pressure-Sensitive Film Techniques

Foot & Ankle ◽  
1992 ◽  
Vol 13 (4) ◽  
pp. 220-223 ◽  
Author(s):  
Alan S. Tuckman ◽  
Frederick W. Werner ◽  
Maria D. Fortino ◽  
Joseph A. Spadaro
Keyword(s):  
Soft Tissues ◽  
Flat Surface ◽  
Imaging System ◽  
Accurate Method ◽  
Total Force ◽  
Confined Space ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Pressure Sensitive Film ◽  
Deforming Forces

Although a number of pathologies of the forefoot in ballet dancers on pointe have been described, pressures and deforming forces have not been adequately measured. To evaluate the possible use of pressure-sensitive film (PSF) in measuring the pressures on the external soft tissues in such a confined space as the dancer's toe shoe, it was tested and calibrated with 20 cadaver toes. Each cadaver toe was internally stabilized and loaded longitudinally against PSF on a flat surface. The resultant films were analyzed with a video imaging system and the pressures and total forces were determined. Results showed that the linearity of the PSF to pressure had a regression value of 0.98. By using two sensitivity ranges of films, the total force measured by the PSF was found to be within 10% of the known applied force on each toe. The PSF, therefore, may very well be a useful and accurate method of measuring external soft tissue pressures on the forefoot.

Biomechanics of the wrist after proximal row carpectomy in cadavers

2009 ◽  
Vol 35 (1) ◽  
pp. 43-45 ◽  
Author(s):  
Y.-L. Zhu ◽  
Y.-Q. Xu ◽  
J. Ding ◽  
J. Li ◽  
B. Chen ◽  
...  
Keyword(s):  
Sharp Decrease ◽  
Material Testing ◽  
Testing System ◽  
Average Pressure ◽  
Proximal Row Carpectomy ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Fresh Frozen ◽  
Pressure Sensitive Film ◽  
Lunate Fossa

We investigated the biomechanics of the radiocapitate joint after a proximal row carpectomy in six fresh-frozen cadaver wrists using super-low-pressure-sensitive film on a material testing system. The average pressure within the lunate fossa increased significantly from 23.2 to 136.4 N/cm2 with a sharp decrease in the contact area from 2.08 to 0.30 cm2 after a proximal row carpectomy. The cartilage of the proximal capitate had four sub-facets and therefore was not as smooth as the normal proximal lunate. We found that the wrist was overloaded after a proximal row carpectomy and the main cause was the anatomical mismatch of the radiocapitate articulation.

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