Tolerance Analysis of Parallel Assemblies Using Tolerance-Maps® and a Functional Map Derived From Induced Deformations

2013 ◽  
Author(s):  
Lupin Niranjan Jaishankar ◽  
Joseph K. Davidson ◽  
Jami J. Shah
Keyword(s):  
Tolerance Analysis ◽  
Tolerance Allocation ◽  
Von Mises Stress ◽  
Target Feature ◽  
Math Model ◽  
Von Mises ◽  
Von Mises Stresses ◽  
Geometric Variation ◽  
Tolerance Accumulation ◽  
The Relationship

This paper concerns about modeling tolerance accumulation in parallel assemblies using a spatial math model, the T-Map. In this paper, a specific case in 3D is discussed where an Accumulation Tolerance-Map is modeled when two parts arranged in parallel support a target part between the datum and the functional target feature. By understanding how much of variation from the supporting parts contribute to variations of the target feature, a designer can better utilize the tolerance budget when assigning values to individual tolerances. When the parts are flexible, deformations are induced when parts in parallel are clamped together during assembly. The amount of deformations on the target part depends on the geometric manufacturing variations on the support parts in parallel assemblies. When parts are clamped stresses are induced in more than one direction depending on the type and amount of geometric variation on the supports. The next part of this paper relates the limit on the largest von Mises stress in the target part to the functional limits in tolerance allocation that must be set at the beginning of a tolerance analysis of parts in such an assembly by the designer. The last part of the paper shows the construction of a Functional Tolerance Map from the tolerance limits obtained from the relationship between von Mises stresses and tolerances on individual parts.

Statistical Tolerance Analysis With Sensitivities Established With Tolerance-Maps

2018 ◽  
Author(s):  
Aniket N. Chitale ◽  
Joseph K. Davidson ◽  
Jami J. Shah
Keyword(s):  
Tolerance Analysis ◽  
Minkowski Sum ◽  
Coordinate Frame ◽  
Target Feature ◽  
Functional Feature ◽  
Design Function ◽  
Statistical Tolerance ◽  
The One ◽  
The Relationship ◽  
Statistical Tolerance Analysis

The purpose of math models for tolerances is to aid a designer in assessing relationships between tolerances that contribute to variations of a dependent dimension that must be controlled to achieve some design function and which identifies a target (functional) feature. The T-Maps model for representing limits to allowable manufacturing variations is applied to identify the sensitivity of a dependent dimension to each of the contributing tolerances to the relationship. The method is to choose from a library of T-Maps the one that represents, in its own local (canonical) reference frame, each contributing feature and the tolerances specified on it; transform this T-Map to a coordinate frame centered at the target feature; obtain the accumulation T-Map for the assembly with the Minkowski sum; and fit a circumscribing functional T-Map to it. The fitting is accomplished numerically to determine the associated functional tolerance value. The sensitivity for each contributing tolerance-and-feature combination is determined by perturbing the tolerance, refitting the functional map to the accumulation map, and forming a ratio of incremental tolerance values from the two functional T-Maps. Perturbing the tolerance-feature combinations one at a time, the sensitivities for an entire stack of contributing tolerances can be built. For certain classes of loop equations, the same sensitivities result by fitting the functional T-Map to the T-Map for each feature, one-by-one, and forming the overall result as a scalar sum. Sensitivities help a designer to optimize tolerance assignments by identifying those tolerances that most strongly influence the dependent dimension at the target feature. Since the fitting of the functional T-Map is accomplished by intersection of geometric shapes, all the T-Maps are constructed with linear half-spaces.

Analysis of Loads and Stresses for a Sewing Needle

2002 ◽  
Author(s):  
Yuan Mao Huang
Keyword(s):  
Shear Stress ◽  
Personal Computer ◽  
Failure Modes ◽  
Von Mises Stress ◽  
Bending Stress ◽  
Principal Stresses ◽  
Acceptable Accuracy ◽  
Von Mises ◽  
Von Mises Stresses ◽  
The Cost

This study analyzes the loads of a needle by using singularity functions and determines the Von-Mises stresses to predict the failure modes of needles by using a personal computer. After principal stresses are calculated from the bending stress, compressive stress and shear stress, predicted failure modes of needles based on the Von-Mises stress coincide with practical existing failure modes reported by a manufacturer. These calculated stresses are also compared with the results obtained by using the software ABAQUS in the mainframe, and the deviation between the results calculated by these two methods is also investigated. Using this methodology can obtain loads, stresses and failure modes of a needle with acceptable accuracy while reducing the cost of using the commercial software in the mainframe.

scholarly journals Aerodynamic and Structural Characteristics of a Centrifugal Compressor Impeller

2019 ◽  
Vol 9 (16) ◽  
pp. 3416 ◽  
Author(s):  
T R Jebieshia ◽  
Senthil Kumar Raman ◽  
Heuy Dong Kim
Keyword(s):  
Centrifugal Compressor ◽  
Structural Characteristics ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Impeller Blade ◽  
Compressor Impeller ◽  
The One ◽  
Von Mises ◽  
Von Mises Stresses

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. The performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of the compressor under centrifugal force and pressure load from the aerodynamic analysis are applied to the impeller blade and hub to perform the one-way Fluid–Structure Interaction (FSI). For the stress assessment, maximum equivalent von Mises stresses in the impeller blades are compared with the maximum allowable stress of the impeller material. The effects of varying the pressure field on the deformation and stress of the impeller are also calculated. The aerodynamic and structural performance of the centrifugal compressor at 73,000 rpm are investigated in terms of the efficiency, pressure ratio, equivalent von Mises stress, and total deformation of the impeller.

THE BIOMECHANICAL EFFECTS OF CEMENT AUGMENTATION AND PARTIAL VERTEBRAL HEIGHT RESTORATION ON THE LOAD TRANSFER CHANGE OF ADJACENT VERTEBRAE IN VERTEBROPLASTY

2015 ◽  
Vol 15 (03) ◽  
pp. 1550025 ◽  
Author(s):  
CHIEN-YU LIN ◽  
WENG-PIN CHEN ◽  
PO-LIANG LAI ◽  
SHIH-YOUENG CHUANG ◽  
DA-TONG JU ◽  
...  
Keyword(s):  
Load Transfer ◽  
Cement Augmentation ◽  
Erector Spinae ◽  
Von Mises Stress ◽  
Fe Model ◽  
Vertebral Height ◽  
Adjacent Disc ◽  
Before And After ◽  
Von Mises ◽  
Von Mises Stresses

Vertebroplasty is commonly used to treat vertebral wedge fractures (VWFs). However, differing degrees of vertebral height restoration (VHR) have been reported after vertebroplasty, and little is known about how grades (steepness) of VWF deformities affect loadings on the fractured and adjacent unfractured vertebrae. Therefore, the goal of this study was to create a non-linear finite element (FE) model of the T10–L2 thoracolumbar segments. With this model, we aimed to evaluate the biomechanical outcomes of three different collapse models (25%, 50%, and 75%) at the T12 vertebra before and after cement augmentation (CA) and with and without VHR. In these VWF simulations, the forces of the erector spinae, the intradiscal pressure, and the maximum von Mises stresses in the endplates and vertebral bodies increased as vertebral deformation increased. Performing CA alone, without restoring vertebral height for the fractured vertebra, did not change the stiffness of multiple spinal segments or the pressures on the adjacent disc, but it did decrease stresses on the endplates and the vertebral bone. A 10% restoration of vertebral height after CA reduced the maximum von Mises stress in the endplates and bone structures more than when CA did not restore vertebral height (no VHR). These results suggest that achieving partial VHR during vertebroplasty may help prevent postvertebroplasty fractures in the fractured and adjacent vertebrae.

MECHANICAL STRESS MAY CAUSE THE TEAR OF THE LABRUM IN ACETABULAR DYSPLASIA

2004 ◽  
Vol 08 (01) ◽  
pp. 35-41
Author(s):  
Hirotaka Sano ◽  
Norikazu Yamada ◽  
Shingo Maeda
Keyword(s):  
Stress Concentration ◽  
Mechanical Stress ◽  
Acetabular Dysplasia ◽  
The Body ◽  
Von Mises Stress ◽  
Center Edge ◽  
Dimensional Finite Element ◽  
Von Mises ◽  
Distal Border ◽  
The Relationship

In the current study, using the arthrogram, we developed two-dimensional finite element (FE) models of the human hip joint. To clarify the relationship between the stress distribution and the degree of acetabular dysplasia, three FE models were established and analyzed. The models varied only in the degree of the bony covering of the femoral head; i.e. the center-edge (CE) angle=20, 10, 0 degrees. An edge load (x=0 N, y=600 N) was then applied on the distal border of the femur to simulate the bearing of the body weight. In the CE=20 degree model, no definite stress concentration was seen at the site of the labrum. On the other hand, the stress concentration was seen from the attachment of the labrum to the superior aspect of the acetabulum in the CE=0 degree model. The site of stress concentration clearly corresponded to the lesions where the acetabular rim pathologies were seen in the clinical practice. Moreover, we found that the Von Mises stress increases dramatically with decreasing the CE angle at the attachment of the labrum. In the dysplastic hip, the mechanical stress increases significantly at the supero-lateral aspect of the acetabulum, which eventually leads to the tearing or detachment of the labrum.

Gun Barrel Refurbishing Using a Shrink-Fitted Autofrettaged Liner

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
J. Perry ◽  
M. Perl
Keyword(s):  
Cross Sections ◽  
Cost Effective ◽  
Von Mises Stress ◽  
Maximum Pressure ◽  
Internal Diameter ◽  
Original Performance ◽  
Gun Barrel ◽  
Von Mises ◽  
Von Mises Stresses ◽  
The Cost

During the firing of guns, the barrel undergoes two major damaging processes: wear of its inner surface and internal cracking. Barrel's are condemned based on either the increase of their internal diameter due to wear or the severity of their internal cracking. The cost of replacing such a damaged gun barrel runs in the tenth of thousands of U.S.$. Therefore, cost effective methods are sought for restoring such gun barrels. In the present analysis, a new method is proposed for refurbishing vintage gun barrels by machining their inner damaged layer and replacing it by an intact, autofrettaged, shrink-fit liner that will restore the barrel to its original performance. The design of the shrink-fitted liner is based on two design principles. First, the von-Mises residual stress distribution through the thickness of the barrel at each of its cross sections along the inserted liner should be at least equal in magnitude to von Mises stress, which prevailed in the original barrel. Second, once the maximum pressure is applied to the compound barrel, the von-Mises stresses at the inner surfaces of the liner machined barrel should be equal to their respective yield stresses. The preliminary results demonstrate the ability of this process to mend such barrels and bringing them back to their initial safe maximum pressure (SMP) and their intact conditions, rather than condemn them. Furthermore, from the authors' experience, based on a preliminary rough estimate, such an alternative seems to be cost effective.

Statistical Tolerance Analysis With Sensitivities Established From Tolerance-Maps and Deviation Spaces

2019 ◽  
Vol 19 (4) ◽  
Author(s):  
Aniket N. Chitale ◽  
J. K. Davidson ◽  
Jami J. Shah
Keyword(s):  
Tolerance Analysis ◽  
Minkowski Sum ◽  
Coordinate Frame ◽  
Target Feature ◽  
Functional Feature ◽  
Local Reference ◽  
Design Function ◽  
Statistical Tolerance ◽  
The Relationship ◽  
Statistical Tolerance Analysis

Math models aid designers in assessing relationships between tolerances that contribute to variations of a dependent dimension that must be controlled to achieve some design function at a target (functional) feature. The Tolerance-Maps© (T-Maps©) model for representing limits to allowable manufacturing variations is applied to identify the sensitivity of a dependent dimension to each contributing tolerance of the relationship. For each contributing feature and tolerances specified on it, the appropriate T-Map is chosen from a library of T-Maps, each represented in its own respective local reference frame. Each chosen T-Map is then transformed to the coordinate frame at the target feature, and the accumulation T-Map of these is formed with the Minkowski sum. The shape of a functional T-Map/deviation space is circumscribed (fitted) to this accumulation map. Since fitting is accomplished numerically by intersecting geometric shapes, T-Maps/deviation spaces are constructed with linear half-spaces. The sensitivity for each tolerance-and-feature combination is determined by perturbing the tolerance, refitting the functional shape to the modified accumulation map, and forming a ratio of the increment of functional tolerance to the perturbation. Taking tolerance-feature combinations one by one, sensitivities for an entire stack can be built. For certain loop equations, the same sensitivities result by fitting the functional shape to the T-Map/deviation space for each feature, without a Minkowski sum, and forming the overall result as a scalar sum. Sensitivities are used to optimize tolerance assignments by identifying the tolerances that most strongly influence the dependent dimension at the target feature. Form variations are not included in the analysis.

Fluid-Structure Interaction Analysis of Flow-Induced Deformation in a Two-Phase, Neo-Hookean Marine Egg

2006 ◽  
Vol 128 (4) ◽  
pp. 519-526 ◽  
Author(s):  
T. Kim ◽  
C W. Wang ◽  
F. I. M. Thomas ◽  
A. M. Sastry
Keyword(s):  
Interaction Analysis ◽  
Von Mises Stress ◽  
Finite Element Analyses ◽  
Two Phase ◽  
Shear Moduli ◽  
Arbacia Punctulata ◽  
Structure Interaction ◽  
Material Parameters ◽  
Von Mises ◽  
Von Mises Stresses

Coupled computational fluid dynamics and finite element analyses were used to determine the material properties of the egg and jelly layer of the sea urchin Arbacia punctulata. Prior experimental shear flow results were used to provide material parameters for these simulations. A Neo-Hookean model was used to model the hyperelastic behaviors of the jelly layer and egg. A simple compressive simulation was then performed, to compare the maximum von Mises stresses within eggs, with and without jelly layers. Results of this study showed that (1) shear moduli range from ∼100to160Pa, and ∼40to140Pa for an egg without a jelly layer, and jelly layer itself, respectively; and (2) the presence of the jelly layer significantly reduces maximum von Mises stress in an egg undergoing compression.

Trans-Thrombus Blood Pressure Effects in Abdominal Aortic Aneurysms

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Clark A. Meyer ◽  
Carine Guivier-Curien ◽  
James E. Moore
Keyword(s):  
Wall Stress ◽  
Aortic Aneurysms ◽  
Pressure Effects ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Histopathological Studies ◽  
Von Mises ◽  
Von Mises Stresses

How much and how the thrombus supports the wall of an abdominal aortic aneurysm (AAA) is unclear. While some previous studies have indicated that thrombus lacks the mechanical integrity to support much load compared with the aneurysm wall, others have shown that removing thrombus in computational AAA models drastically changes aneurysm wall stress. Histopathological studies have shown that thrombus properties vary through the thickness and it can be porous. The goal of this study is to explore the variations in thrombus properties, including the ability to isolate pressure from the aneurysm wall, incomplete attachment, and their effects on aneurysm wall stress, an important parameter in determining risk for rupture. An analytical model comprised of cylinders and two patient specific models were constructed with pressurization boundary conditions applied at the lumen or the thrombus/aneurysm wall interface (to simulate complete transmission of pressure through porous thrombus). Aneurysm wall stress was also calculated in the absence of thrombus. The potential importance of partial thrombus attachment was also analyzed. Pressurizing at either surface (lumen versus interface) made little difference to mean von Mises aneurysm wall stress values with thrombus completely attached (3.1% analytic, 1.2% patient specific) while thrombus presence reduced mean von Mises stress considerably (79% analytic, 40–46% patient specific) in comparison to models without it. Peak von Mises stresses were similarly influenced with pressurization surface differing slightly (3.1% analytic, 1.4% patient specific) and reductions in stress by thrombus presence (80% analytic, 28–37% patient specific). The case of partial thrombus attachment was investigated using a cylindrical model in which there was no attachment between the thrombus and aneurysm wall in a small area (10 deg). Applying pressure at the lumen resulted in a similar stress field to fully attached thrombus, whereas applying pressure at the interface resulted in a 42% increase in peak aneurysm wall stress. Taken together, these results show that the thrombus can have a wall stress reducing role even if it does not shield the aneurysm wall from direct pressurization—as long as the thrombus is fully attached to the aneurysm wall. Furthermore, the potential for porous thrombus to transmit pressure to the interface can result in a considerable increase in aneurysm wall stress in cases of partial attachment. In the search for models capable of accurately assessing the risk for rupture, the nature of the thrombus and its attachment to the aneurysm wall must be carefully assessed.

scholarly journals Design and Analysis of AC14 Ship Anchor

2021 ◽  
Vol 2070 (1) ◽  
pp. 012235
Author(s):  
Ramu Kandregula ◽  
B Hemanth ◽  
A Harikishan
Keyword(s):  
Modal Analysis ◽  
Solid Modeling ◽  
Von Mises Stress ◽  
Test Load ◽  
Maximum Deformation ◽  
Rest Position ◽  
Different Types ◽  
Von Mises ◽  
Relationship Of ◽  
The Relationship

Abstract A Ship’s anchor makes a ship to be at a fixed location against currents and winds when ship is in rest position. Purpose of anchor is to restrict the drifting of ship, which is occurs due to the currents. Even though there are many different types of anchor, present paper intended to do design and analysis on stockless anchor AC14 type. Project aims to determine the equivalent von-mises stress and maximum deformation in anchor when subjected to proof test. Proof test load is decided based on the mass of the anchor. (Reference is taken for the relationship of proof test load and mass of the anchor. Solid modeling of Stockless ship anchor model is carried out on NX 11.0 and modal analysis of ship anchor is carried out using ANSYS 16.0

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